**2. Experimental and discussion**

Since the limitation of the space of this chapter, anodized aluminum and boron carbide coating as chamber materials will be demonstrated and discussed in details.

All the ceramic and CVD test coupons (except anodized aluminum coupons) are polished to mirror surface finish with the average surface roughness less than 1.0 -in in Ra. The anodized aluminum coupons are anodized with the surface roughness less than 32 -in (asreceived). The thermal spray coatings keep the as-coated surface. Ceramic and CVD coated coupons weigh the pre-test weight. Anodized aluminum and thermal spray coating coupons were measured to obtain the average coating layer thickness before test. All the test coupons were soaked in IPA for 5 minutes, wiped by both IPA and acetone, rinsed by deionized water (DIW) for 1 minute and baked at 110oC for 30 minutes. A special thermal conductive tape was used to mount the test coupons on locations in the etching chamber. Three locations were selected to mount the test coupons. Test coupons are mounted on chamber top window, chamber wall, and electrostatic chuck surface, respectively. Etching systems used in this study include Applied Materials 200mm and 300mm etching tools and Lam 2300 etching tools. During materials characterization on chamber wall, on chamber top window and on electrostatic chuck, a dummy aluminum wafer was used to cover the electrostatic ceramic surface. The etching process recipe keeps running for three minutes, followed by a cooling down process for about two minutes, than repeat the etching recipe. The minimum process time (RF hours) cycled is 120 RF hours and the longest process time cycled is 200 RF hours.

A typical process recipe under a 200mm etch tool is shown below [21, 22, 25, 30]:

**Step 1.** Plasma Etching & Dechuck Steps


Repeat process recipe (step 1 and step 2) until the accumulated RF hours achieve 120 RF hours or 200 RF hours, respectively.

After plasma etching processes, all the test coupons were removed from the chamber. A post wet cleaning was carried out to remove polymer, etch by-products, and other contaminants. All the coupons were then DIW rinsed and baked at 110oC for 30 minutes. Post weight measurements were carried out to obtain the average thickness loss per RF hour. For anodized aluminum and spray coating coupons, post thickness measurements were carried out in order to obtain the coating thickness loss per RF hour.

All the coupons are studied by SEM before and after plasma etching process. The corrosion/erosion rates of different test coupons are recorded and compared as mils per RF hour. Test coupons on etch chamber top window, chamber wall and on electrostatic chuck surfaces are shown in Fig. 9.

Since the limitation of the space of this chapter, anodized aluminum, boron carbide, and

Since the limitation of the space of this chapter, anodized aluminum and boron carbide

All the ceramic and CVD test coupons (except anodized aluminum coupons) are polished to mirror surface finish with the average surface roughness less than 1.0 -in in Ra. The anodized aluminum coupons are anodized with the surface roughness less than 32 -in (asreceived). The thermal spray coatings keep the as-coated surface. Ceramic and CVD coated coupons weigh the pre-test weight. Anodized aluminum and thermal spray coating coupons were measured to obtain the average coating layer thickness before test. All the test coupons were soaked in IPA for 5 minutes, wiped by both IPA and acetone, rinsed by deionized water (DIW) for 1 minute and baked at 110oC for 30 minutes. A special thermal conductive tape was used to mount the test coupons on locations in the etching chamber. Three locations were selected to mount the test coupons. Test coupons are mounted on chamber top window, chamber wall, and electrostatic chuck surface, respectively. Etching systems used in this study include Applied Materials 200mm and 300mm etching tools and Lam 2300 etching tools. During materials characterization on chamber wall, on chamber top window and on electrostatic chuck, a dummy aluminum wafer was used to cover the electrostatic ceramic surface. The etching process recipe keeps running for three minutes, followed by a cooling down process for about two minutes, than repeat the etching recipe. The minimum process time (RF hours) cycled is 120 RF hours and the longest process time

coating as chamber materials will be demonstrated and discussed in details.

A typical process recipe under a 200mm etch tool is shown below [21, 22, 25, 30]:


were carried out in order to obtain the coating thickness loss per RF hour.


Repeat process recipe (step 1 and step 2) until the accumulated RF hours achieve 120 RF

After plasma etching processes, all the test coupons were removed from the chamber. A post wet cleaning was carried out to remove polymer, etch by-products, and other contaminants. All the coupons were then DIW rinsed and baked at 110oC for 30 minutes. Post weight measurements were carried out to obtain the average thickness loss per RF hour. For anodized aluminum and spray coating coupons, post thickness measurements

All the coupons are studied by SEM before and after plasma etching process. The corrosion/erosion rates of different test coupons are recorded and compared as mils per RF hour. Test coupons on etch chamber top window, chamber wall and on electrostatic chuck

Y2O3 as chamber materials will be demonstrated.

**2. Experimental and discussion** 

cycled is 200 RF hours.

**Step 1.** Plasma Etching & Dechuck Steps

Torr He flow/180 seconds. - 100Ar/TFO/500Ws/100Wb/5sec.

hours or 200 RF hours, respectively.

**Step 2.** Cooling Down Step

surfaces are shown in Fig. 9.

Fig. 9. Test coupons in etching chamber are mounted on chamber top window (left) and on chamber wall (right) and on the dummy aluminum wafer on an electrostatic chuck surface (right, white surface).

Fig. 10 shows the test results of various materials obtained from worldwide suppliers. The letters of A, B, C, D et al represent the suppliers and their materials. Agreements were signed for not allowing to release the names of the worldwide suppliers and their materials. The plasma etching rate is in the unit of mils (1 mil = 25.4 m). It is obvious that either YAG (solid solution of Al2O3 and Y2O3) and solid Y2O3 can reduce the plasma etching rate at the order of 40-50 times in comparison with the previously used chamber materials such as high purity alumina. That is the reason why Y2O3 has been as one of the leading chamber materials in plasma etching tools in the past 10 years for the leading semiconductor etching equipment companies.

Fig. 10. Test results of new and old chamber materials in plasma etching on chamber top window. The etch rate reduction of new chamber materials can reduce the etching rate by 40 to 50 times.

A Systematic Study and Characterization of Advanced Corrosion Resistance Materials

best corrosion resistance among the four configurations as shown in Fig. 11 [25].

**"A" Coating Al Alloy**

**5 Min. 1.5 - 36 Hr.**

**9 - 31 Hr. 29 - 268 Hr.** 

**"A" Coating + Sealing Al Alloy**

The test sequence is shown in Fig. 12 [25].

and Their Applications for Plasma Etching Processes in Semiconductor Silicon Wafer Fabrication 11

and fast in comparison with ASTM standard salt spray test method [45, 46]. The test results show that boron carbide coating on anodized aluminum and sealed with HL126 provide the

**HCl + AL HCl + Al2O3**

Fig. 11. After plasma etching for 200 RF hours, Boron carbide coated anodized aluminum

The wet cleaning compatibility of four configurations is also tested by soaking the large size B4C coated rings in saturated AlCl3 solution at pH=0 for 90 minutes, then put the rings in an environmental chamber to monitor the time when boron carbide coating starts to peel off.

Fig. 12. Wet cleaning compatibility test of four configurations of boron carbide coated rings.

sealed with HL126 sealant provides the best corrosion in all configuration.

**"A" Coating Anodization Al Alloy**

**"A" Coating + Sealing Anodization Al Alloy**

**peel**

**peel**

For test results on chamber wall, the etching rate of anodized aluminum from various suppliers w/wo hot DI water seal is between 0.050 to 0.070 mils / RF hour. For boron carbide coating through a thermal spray method, the etching rate is below 0.001 mils/RF hour. For sintered or hot pressed boron carbide, the etching rate is between 0.0001 to 0.0007 mils/RF hours. It is also obvious that the plasma etching resistance of boron carbide can improve the plasma resistance by 50 times or higher. In fact, boron carbide coated chamber has been using at worldwide wafer fabrication customer sites since 1998. 50 to 100 times chamber life improvement has been demonstrated since 1998 up to today [21, 22, 25, 30, 41].

In order to select the best configuration of surface coatings such as B4C (boron carbide), three configurations are considered. Configuration 1 is the coating of B4C on bare aluminum surface. Configuration 2 is the B4C coating on anodized aluminum surface. Configuration 3 is the B4C coating on anodized aluminum surface and then HL126 sealant is used to seal the pores in the spray coating layer. HL126 contains methacrylate esters and it can fill very tiny pores. The metal contamination levels of HL126 is pretty low. All metal levels are below 1 ppm except the sodium level at 57 ppm. Permabond HL126 is a high strength and low viscosity anaerobic threadlocker. Its properties are listed in the attached table below:

#### **PHYSICAL PROPERTIES OF THE UNCURED ADHESIVE \***


Table 1. Properties of HL126 sealant

The corrosion resistance of boron carbide coated coupons after plasma etching is tested by HCl bubble test method which was first proposed by Shih in 1992 and was used as a standard technique in anodization study for IC industry in 1994 [42]. The fundamental concept of the defined HCl bubble test method can be explained as follows. The dilute HCl solution can go through the pores and micro-cracks on coating and anodized aluminum layer to react with bare aluminum under the coating or under the anodized aluminum. When HCl reacts with aluminum alloy, hydrogen bubbles will generate. Streams of hydrogen bubbles can be observed and the time to start the continuous hydrogen bubbles can be recorded and compared for different coating configuration and different types of anodized aluminum before and after plasma etching processes. Shih [43, 44] has set up the method at two major semiconductor equipment companies since 1994 and the method has been widely accepted by worldwide anodization suppliers. The method is simple, low cost

For test results on chamber wall, the etching rate of anodized aluminum from various suppliers w/wo hot DI water seal is between 0.050 to 0.070 mils / RF hour. For boron carbide coating through a thermal spray method, the etching rate is below 0.001 mils/RF hour. For sintered or hot pressed boron carbide, the etching rate is between 0.0001 to 0.0007 mils/RF hours. It is also obvious that the plasma etching resistance of boron carbide can improve the plasma resistance by 50 times or higher. In fact, boron carbide coated chamber has been using at worldwide wafer fabrication customer sites since 1998. 50 to 100 times chamber life improvement has been demonstrated since 1998 up to today [21, 22, 25, 30, 41]. In order to select the best configuration of surface coatings such as B4C (boron carbide), three configurations are considered. Configuration 1 is the coating of B4C on bare aluminum surface. Configuration 2 is the B4C coating on anodized aluminum surface. Configuration 3 is the B4C coating on anodized aluminum surface and then HL126 sealant is used to seal the pores in the spray coating layer. HL126 contains methacrylate esters and it can fill very tiny pores. The metal contamination levels of HL126 is pretty low. All metal levels are below 1 ppm except the sodium level at 57 ppm. Permabond HL126 is a high strength and low

viscosity anaerobic threadlocker. Its properties are listed in the attached table below:

Base Resin, Methacrylate Esters

**PHYSICAL PROPERTIES OF THE UNCURED ADHESIVE \***

Solid, % 100 Color Green Viscosity, cP, 25°C (77°F) 20 Consistency Liquid Gap Filling, in 0.005 Specific Gravity 1.09 Flash Point, °C (°F) >110(230) Shelf Life stored at or below 27°C (80°F), months 12

Dielectric strength, MV/m 11 Electric Resistance, ohm-cm 1015

Operating temperature oC (oF) 150 (300)

The corrosion resistance of boron carbide coated coupons after plasma etching is tested by HCl bubble test method which was first proposed by Shih in 1992 and was used as a standard technique in anodization study for IC industry in 1994 [42]. The fundamental concept of the defined HCl bubble test method can be explained as follows. The dilute HCl solution can go through the pores and micro-cracks on coating and anodized aluminum layer to react with bare aluminum under the coating or under the anodized aluminum. When HCl reacts with aluminum alloy, hydrogen bubbles will generate. Streams of hydrogen bubbles can be observed and the time to start the continuous hydrogen bubbles can be recorded and compared for different coating configuration and different types of anodized aluminum before and after plasma etching processes. Shih [43, 44] has set up the method at two major semiconductor equipment companies since 1994 and the method has been widely accepted by worldwide anodization suppliers. The method is simple, low cost

**Performance properties of the cured sealant**

Table 1. Properties of HL126 sealant

Properties

**Electric Properties**

and fast in comparison with ASTM standard salt spray test method [45, 46]. The test results show that boron carbide coating on anodized aluminum and sealed with HL126 provide the best corrosion resistance among the four configurations as shown in Fig. 11 [25].

Fig. 11. After plasma etching for 200 RF hours, Boron carbide coated anodized aluminum sealed with HL126 sealant provides the best corrosion in all configuration.

The wet cleaning compatibility of four configurations is also tested by soaking the large size B4C coated rings in saturated AlCl3 solution at pH=0 for 90 minutes, then put the rings in an environmental chamber to monitor the time when boron carbide coating starts to peel off. The test sequence is shown in Fig. 12 [25].

Fig. 12. Wet cleaning compatibility test of four configurations of boron carbide coated rings.

A Systematic Study and Characterization of Advanced Corrosion Resistance Materials






gate oxide when a born carbide coated chamber is used.

introduced as the new chamber wall coating.

shown in Fig. 17 [48].

and Zn in 1,000, 2,000, and 3,000 wafer marathons, respectively.

and Their Applications for Plasma Etching Processes in Semiconductor Silicon Wafer Fabrication 13





Fig. 14. The leakage current of gate oxide in log scale indicates that there is no damage to

The metal contamination using a boron carbide coated chamber has shown meeting the specification of metal contaminations such as Ca, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, Ti,

There is no metal contamination introduced when a high purity boron carbide coating is

The monitoring data of on-wafer aluminum etch rate, etch rate non-uniformity, defect and particle performance, and thickness measurements of boron carbide coating before and after plasma etching processes are shown in the following figures and tables. In Fig. 15, the particle data during a 3,000 wafer marathon are provided and compared with the specification requested by customers. It is obvious that new B4C coated chamber wall can meet the requirement of particles. In this study, particles at and larger than 0.2 m are recorded. The B4C coated chamber wall can also provide excellent aluminum etch rate and etch rate non-uniformity through the entire 3,000 wafer marathon as shown in Fig.16 [47]. The boron carbide coated chamber is also qualified through a 2,000 wafer marathon for etching of 0.15 m feature size. Excellent aluminum etching performance is demonstrated as

On a 300mm etch tool, boron carbide coated chamber was also used in a 1,000 wafer marathon. The boron carbide coated chamber meets all the requirements including aluminum etch rate and etch rate non-uniformity, etch profiles, defects and particles, metal contamination [49]. The particle performance at 0.12 m or larger is the critical requirement. It is obvious that the boron carbide coated chamber can meet the requirement. The up limit

After plasma etching O2/Cl2 for 120 RF hours, the thickness of pre and post boron carbide

of particle allowance at 0.12 m or larger is defined as 50 adders/per wafer.

coating on anodized aluminum is measured and the data are listed in Table 2








For coating on bare aluminum alloy, the entire coating layer peeled off during immersion in the saturated AlCl3 solution at pH=0.0. The coating on anodized aluminum can hold 45 hours in the environmental chamber and the coating layer peeled off completely at 47 hours. Both coating on bare aluminum alloy and on anodized aluminum with the use of HL126 sealant can hold up to 114 hours in the environmental chamber without any failure. At 114 hours, the environmental chamber test was stopped. From the test results of HCl bubble test and wet cleaning compatibility test, coating on anodized aluminum with the use of HL 126 sealant can provide the best corrosion resistance. This configuration is selected as the final configuration as the new chamber wall material.

In order to qualify boron carbide coating as a new chamber material, many aspects have to be considered. One of the concerns is the impact to ICF (ion current flux). Three configurations are considered and compared in the etching chamber. The ICF of anodized aluminum chamber is used as the baseline. Boron carbide coatings on bare aluminum or on anodized aluminum are studied through ICF measurements. The results showed that the three configurations have the compatible ICF. The results of ICF measurements are shown in Fig. 13 [21, 22, 25, 30].

Fig. 13. ICF measurements on the wafer during the use of three configuration chambers.

Another concern is the potential damage to gate oxide. The leakage current measurements on the gate oxide show that born carbide coating does not introduce damage to gate oxide.

The measurements of leakage current of gate oxide are shown in Fig. 14 [21, 22, 25, 30].

For coating on bare aluminum alloy, the entire coating layer peeled off during immersion in the saturated AlCl3 solution at pH=0.0. The coating on anodized aluminum can hold 45 hours in the environmental chamber and the coating layer peeled off completely at 47 hours. Both coating on bare aluminum alloy and on anodized aluminum with the use of HL126 sealant can hold up to 114 hours in the environmental chamber without any failure. At 114 hours, the environmental chamber test was stopped. From the test results of HCl bubble test and wet cleaning compatibility test, coating on anodized aluminum with the use of HL 126 sealant can provide the best corrosion resistance. This configuration is selected as the final

In order to qualify boron carbide coating as a new chamber material, many aspects have to be considered. One of the concerns is the impact to ICF (ion current flux). Three configurations are considered and compared in the etching chamber. The ICF of anodized aluminum chamber is used as the baseline. Boron carbide coatings on bare aluminum or on anodized aluminum are studied through ICF measurements. The results showed that the three configurations have the compatible ICF. The results of ICF measurements are shown

Fig. 13. ICF measurements on the wafer during the use of three configuration chambers.

The measurements of leakage current of gate oxide are shown in Fig. 14 [21, 22, 25, 30].

Another concern is the potential damage to gate oxide. The leakage current measurements on the gate oxide show that born carbide coating does not introduce damage to gate oxide.

configuration as the new chamber wall material.

in Fig. 13 [21, 22, 25, 30].

Fig. 14. The leakage current of gate oxide in log scale indicates that there is no damage to gate oxide when a born carbide coated chamber is used.

The metal contamination using a boron carbide coated chamber has shown meeting the specification of metal contaminations such as Ca, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, Ti, and Zn in 1,000, 2,000, and 3,000 wafer marathons, respectively.

There is no metal contamination introduced when a high purity boron carbide coating is introduced as the new chamber wall coating.

The monitoring data of on-wafer aluminum etch rate, etch rate non-uniformity, defect and particle performance, and thickness measurements of boron carbide coating before and after plasma etching processes are shown in the following figures and tables. In Fig. 15, the particle data during a 3,000 wafer marathon are provided and compared with the specification requested by customers. It is obvious that new B4C coated chamber wall can meet the requirement of particles. In this study, particles at and larger than 0.2 m are recorded. The B4C coated chamber wall can also provide excellent aluminum etch rate and etch rate non-uniformity through the entire 3,000 wafer marathon as shown in Fig.16 [47].

The boron carbide coated chamber is also qualified through a 2,000 wafer marathon for etching of 0.15 m feature size. Excellent aluminum etching performance is demonstrated as shown in Fig. 17 [48].

On a 300mm etch tool, boron carbide coated chamber was also used in a 1,000 wafer marathon. The boron carbide coated chamber meets all the requirements including aluminum etch rate and etch rate non-uniformity, etch profiles, defects and particles, metal contamination [49]. The particle performance at 0.12 m or larger is the critical requirement. It is obvious that the boron carbide coated chamber can meet the requirement. The up limit of particle allowance at 0.12 m or larger is defined as 50 adders/per wafer.

After plasma etching O2/Cl2 for 120 RF hours, the thickness of pre and post boron carbide coating on anodized aluminum is measured and the data are listed in Table 2

A Systematic Study and Characterization of Advanced Corrosion Resistance Materials

and Their Applications for Plasma Etching Processes in Semiconductor Silicon Wafer Fabrication 15

Fig. 17. The boron carbide coated chamber shows an excellent aluminum etch performance

Pre 0 (Post) 200 400 600 800 1000 WCR

Location Pre (mils) STD(mils) Post (mils) STD(mils) Delta A (10 data) 17.60 0.413 17.98 0.236 +0.38 B (10 data) 17.55 0.363 17.52 0.225 - 0.03 C (10 data) 18.76 0.287 18.56 0.201 - 0.20 **30 data 17.97 (average) 18.02 (average) +0.05** 

**Wafer Count**

Fig. 18. Particle adders as of ≥ 0.12 m size in a 1,000 wafer marathon on a 300mm etch tool. The boron carbide coating on anodized aluminum with HL126 sealant is used as the

Table 2. The overall coating thickness before and after plasma etching under O2/Cl2 plasma

(pressn)

RF On Gas Only

1025 (postssn)

1050

on a feature size as of 0.15 m through a 2,000 wafer marathon.

0

for 120 RF hours.

chamber coating to replace anodized aluminum.

10

20

30

**Particle Adders**

40

50

**DPS CHAMBER PARTICLE DATA**

Fig. 15. Gas-only and RF-on particles during a 3,000 wafer marathon. The up limit of allowance of defect and particles is defined as 50 adders/ per wafer.

**Al Etch Rate and Nonuniformity**

Fig. 16. Al etch rate and etch rate non-uniformity during a 3,000 wafer marathon.

**DPS CHAMBER PARTICLE DATA**

**Gas-only average = 9 adders/wafer (or < 0.03 /cm2) RF-on average = 3 adders/wafer (or < 0.012 /cm2)**

**Wf 1 Gas Wf 2 Gas Gas Only Avg Wf 1 RF Wf 2 RF RF-On Avg**

**Nonunif. (% max/min)**

0.00% 2.00% 4.00% 6.00% 8.00% 10.00% 12.00% 14.00% 16.00% 18.00% 20.00%

0 500 1000 1500 2000 2500 3000 **Wafer Count**

**Al Etch Rate and Nonuniformity**

Al E/R

Al Unif(max-min)

0 500 1000 1500 2000 2500 3000 **Wafer Count**

Fig. 16. Al etch rate and etch rate non-uniformity during a 3,000 wafer marathon.

Fig. 15. Gas-only and RF-on particles during a 3,000 wafer marathon. The up limit of

allowance of defect and particles is defined as 50 adders/ per wafer.

0

0

**Etch Rate (A/min)**

50

100

150

**Particle Adders >0.2 m**

200

250

300

Fig. 17. The boron carbide coated chamber shows an excellent aluminum etch performance on a feature size as of 0.15 m through a 2,000 wafer marathon.

**Wafer Count** Fig. 18. Particle adders as of ≥ 0.12 m size in a 1,000 wafer marathon on a 300mm etch tool. The boron carbide coating on anodized aluminum with HL126 sealant is used as the

chamber coating to replace anodized aluminum.


Table 2. The overall coating thickness before and after plasma etching under O2/Cl2 plasma for 120 RF hours.

A Systematic Study and Characterization of Advanced Corrosion Resistance Materials

times [41].

and Their Applications for Plasma Etching Processes in Semiconductor Silicon Wafer Fabrication 17

About 7% production yield is reported in comparison with the old chamber configuration. The lifetime of chamber of chamber wall and chamber top window can improve about 50

The new boron carbide coating has been introducing to worldwide wafer fabrication for over 10 years with over 1,000 chambers introduced to wafer fabrication in IC industry. The chamber lifetime has demonstrated to improve from the worse case as of 60 RF hours (1,800 wafers) under BCl3/Cl2 etching plasma to over 4,000 RF hours or longer in semiconductor wafer fabrication in the world. It also demonstrates that the chamber materials play a critical role in semiconductor etching equipment, particularly, for the cost reduction. A short comparison of

anodized aluminum and born carbide coating is highlighted in Table 4 [21, 22, 25, 30].

Particle performance normal\* better Metal contamination normal better

Surface roughness normal higher Polymer adhesion normal better Wet cleaning recovery normal normal Process performance normal normal Production yield normal better Gate oxide damage no no Water adsorption normal normal Micro-hardness (100g) 360-450 3,000

Etch process window normal normal

Table 4. Comparison of Anodized Aluminum and Boron Carbide Coating

(5wt% HCl solution) 30 minutes to 24 hours

Effect of base aluminum alloys to coating quality

Items Anodized aluminum Boron Carbide Coating Maximum etch rate 0.07 mils/RF hour 0.001 mils/RF hour Mininum lifetime 1,800 wafers 120,000 wafers

Micro-cracks yes no, but with coating pores Coating bonding very high less than anodized Al

Localized attack yes, through cracks no, with HL126 sealant.

Risk of undercut corrosion no no, with HL126 sealant HCl bubble time ≤ 10 minutes (non hot DIW seal) > 50 hours, with HL126

yes, large impact no

Anodized aluminum has been using as the major etching tools surface coatings since 1980. It still received a lot of applications in plasma etching tools because of its low cost, easy to manufacture, easy to make large or small sizes of the parts, wide applications, easy to refurbish, and achieving good quality control at different suppliers in the world. Therefore, the study of anodized aluminum has always been a major task for the major semiconductor etching tool manufacturers. For high purity Y2O3 thermal spray coating, it has been qualified and applied as one of the major chamber components in plasma etching tools in the past 10 years. It is still one of the major materials as coating or as a solid sintered material which is used in plasma etching tools. At Lam Research Corporation, great attentions have been paid in the improvements and the new development of anodized aluminum and Y2O3 coatings.

sealant

(after hot DIW seal)

It is obvious that there is little coating thickness loss after 120 RF hours under O2/Cl2 plasma. The main purpose of O2/Cl2 plasma is to test the performance of HL126 sealant under O2/Cl2 plasma condition.

After the detail study through a thorough process qualification, the new boron carbide coated chamber wall is used to replace the previously anodized aluminum surface. The new ceramic material such as YAG or Y2O3 is used to replace original high purity alumina. This configuration was introduced to semiconductor wafer fabrication for evaluation. Excellent etch performance, enhanced defect and particle reduction, and 50 to 100 times chamber lifetime improvement are reported. The production yield of the wafer fabrication also improved about 7% in production at the customer site (see Fig.19) [41]. The following data provide some of the information. The sequence of the data collection is as follows:

Baseline configuration using the old chamber hard ware submitted to gas-only and RF-on particle measurements without seasoning. After 1st RF-on particle measurement, five oxide wafers were used for seasoning the chamber, then RF-on particles were measured again. Two PR wafers were used to seasoning the chamber before final RF-on particle measurement. The test data are shown in Table 3 [41].


\*: Unit in particle counts/wafer and particle adders at 0.2 m or larger are recorded.

Table 3. Gas-only and RF-on particles of old and new chamber configurations

Fig. 19. Production yield improvement at wafer fabrication when new chamber material, hardware and best-known method are implemented.

It is obvious that there is little coating thickness loss after 120 RF hours under O2/Cl2 plasma. The main purpose of O2/Cl2 plasma is to test the performance of HL126 sealant

After the detail study through a thorough process qualification, the new boron carbide coated chamber wall is used to replace the previously anodized aluminum surface. The new ceramic material such as YAG or Y2O3 is used to replace original high purity alumina. This configuration was introduced to semiconductor wafer fabrication for evaluation. Excellent etch performance, enhanced defect and particle reduction, and 50 to 100 times chamber lifetime improvement are reported. The production yield of the wafer fabrication also improved about 7% in production at the customer site (see Fig.19) [41]. The following data

Baseline configuration using the old chamber hard ware submitted to gas-only and RF-on particle measurements without seasoning. After 1st RF-on particle measurement, five oxide wafers were used for seasoning the chamber, then RF-on particles were measured again. Two PR wafers were used to seasoning the chamber before final RF-on particle

10 34 53 48

2 56 5

Fig. 19. Production yield improvement at wafer fabrication when new chamber material,

w/o seasoning w/o seasoning 5 ox seasoning 2 PR seasoning

provide some of the information. The sequence of the data collection is as follows:

Condition Gas-only RF-on(1) RF-on(2) RF-on(3)

\*: Unit in particle counts/wafer and particle adders at 0.2 m or larger are recorded. Table 3. Gas-only and RF-on particles of old and new chamber configurations

measurement. The test data are shown in Table 3 [41].

hardware and best-known method are implemented.

under O2/Cl2 plasma condition.

Old chamber configuration

New chamber Configuration About 7% production yield is reported in comparison with the old chamber configuration. The lifetime of chamber of chamber wall and chamber top window can improve about 50 times [41].

The new boron carbide coating has been introducing to worldwide wafer fabrication for over 10 years with over 1,000 chambers introduced to wafer fabrication in IC industry. The chamber lifetime has demonstrated to improve from the worse case as of 60 RF hours (1,800 wafers) under BCl3/Cl2 etching plasma to over 4,000 RF hours or longer in semiconductor wafer fabrication in the world. It also demonstrates that the chamber materials play a critical role in semiconductor etching equipment, particularly, for the cost reduction. A short comparison of anodized aluminum and born carbide coating is highlighted in Table 4 [21, 22, 25, 30].


Table 4. Comparison of Anodized Aluminum and Boron Carbide Coating

Anodized aluminum has been using as the major etching tools surface coatings since 1980. It still received a lot of applications in plasma etching tools because of its low cost, easy to manufacture, easy to make large or small sizes of the parts, wide applications, easy to refurbish, and achieving good quality control at different suppliers in the world. Therefore, the study of anodized aluminum has always been a major task for the major semiconductor etching tool manufacturers. For high purity Y2O3 thermal spray coating, it has been qualified and applied as one of the major chamber components in plasma etching tools in the past 10 years. It is still one of the major materials as coating or as a solid sintered material which is used in plasma etching tools. At Lam Research Corporation, great attentions have been paid in the improvements and the new development of anodized aluminum and Y2O3 coatings.

A Systematic Study and Characterization of Advanced Corrosion Resistance Materials

(1) m + VMx' = MM + Vm + Xe- (3) MM = Mx+ + Vmx' (2) m = MM + (x/2) Vo'' + Xe- (4) Vo'' + H2O = Oo + 2H

anodized aluminum systems are shown as follows:

Kendig, Shih and others [61- 72] as shown in Fig.20.

Z() = Rs + Rb/{1+(jCbRb)

2- and Mi

interstitials: Oi

and Their Applications for Plasma Etching Processes in Semiconductor Silicon Wafer Fabrication 19

Outer film grows via precipitation of Al3+ due to hydrolysis. The fundamental reactions for

Metal film Environment

The principal crystallographic defects are (1) vacancies: Vo''and VMx' for MOx/2; (2)

semiconductor junctions. The fundamentals and process optimization of anodized aluminum have been studied thoroughly by Brace, Thompson, Wood, Mansfeld, and recent years by Shih through the comprehensive studies of anodization of different aluminum alloys, different anodization processes, and different manufacturing processes [51 – 60]. The interface model of anodized aluminum with hot DIW seal has been described by Mansfeld,

Fig. 20. The typical interface model of anodized aluminum with a hot DI water seal.

in 3.5wt% NaCl (similar to seawater) for 365 days as shown in Fig. 21 [28, 38].

where Cb = obA/Db; Cpo = opoA/Dpo and CPE = k(j)n

o = 8.854 x 10-14 F/cm and is the permittivity of free space. In Fig.20, Cb and Rb are barrier layer capacitance and resistance, respectively. Rpo and CPE are the total impedance of the porous layer defined as Zpo which equals to Rpo + CPE. Cpo is the capacitance of the porous layer. CPE represents the constant phase element (CPE). A two-time constant interface model and suitable values of Rb and Zpo indicate a good quality of anodized aluminum. Zpo values highly depend on the quality control of hot DI water sealing process and it is very important for the improvement of the corrosion resistance of anodized aluminum [73-82]. Rb values depend on the voltage applied during anodization as well as the overall process control during anodization. A uniform and thick barrier layer helps to improve the dielectric voltage breakdown of the anodized aluminum. Mansfeld and Shih [63-69] developed a software package specially for the analysis of electrochemical impedance spectroscopy (EIS) data of anodized aluminum and the software has been widely applied for EIS data analysis. The EIS data of the new anodized aluminum developed and qualified at Lam Research Corporation show that the anodized aluminum has no corrosion

x+. In fact, oxide films can be described as exponentially-doped

2}+(Rpo+CPE)/{1+(jCpo(Rpo+CPE))1}

These studied have been highlighted in John and Hong's presentation [28, 31-33, 35-39] and the publications of the new anodized aluminum study with Mansfeld et al [38, 39].

The study and characterization of anodized aluminum and the methodology are shown below. But the techniques are not limited to the techniques listed below:


Although there are so many techniques used in the anodized aluminum study, there are only key techniques which are selected as a routine quality monitoring of worldwide anodization suppliers. The basic techniques are surface roughness, thickness of anodic film, color and color uniformity, dielectric voltage breakdown, acidic corrosion resistance through HCl bubble test, electrochemical impedance in 3.5wt% NaCl solution, surface micro-hardness, SEM cross section to observe the anodic layer micro-cracks, and admittance under 3.5wt% K2SO4 solution at 1000 Hz. For the surface cleanliness of anodization, ICPMS analysis of post precision wet cleaning has been used as a standard technique for metal contamination control. Since the requirements to anodized aluminum quality, corrosion resistance, and surface cleanliness for plasma etching tools are much strict and higher than the traditional industry applications, improvements of corrosion resistance and surface cleanliness are always the tasks. Lam Research has defined the surface cleanliness and the corrosion resistance of anodized aluminum specification for a standard type III and advanced anodized aluminum [28, 31-33, 35-39, 44].

The reaction mechanism of aluminum oxidation is summarized by Macdonald [50] as a reasonable model. The oxides grow as bilayer structures with an inner layer due to movement of oxygen vacancies from metal/film interface and an outer layer due to the movement of cations outward from the film/environmental interface. The vacancy concentrations vary exponentially with distance. The cathode consumes electrons by evoloving hydrogen and reducing oxygen. Barrier layer grows into metal phase via reaction. Outer film grows via precipitation of Al3+ due to hydrolysis. The fundamental reactions for anodized aluminum systems are shown as follows:


18 Corrosion Resistance

These studied have been highlighted in John and Hong's presentation [28, 31-33, 35-39] and

The study and characterization of anodized aluminum and the methodology are shown

the publications of the new anodized aluminum study with Mansfeld et al [38, 39].






Although there are so many techniques used in the anodized aluminum study, there are only key techniques which are selected as a routine quality monitoring of worldwide anodization suppliers. The basic techniques are surface roughness, thickness of anodic film, color and color uniformity, dielectric voltage breakdown, acidic corrosion resistance through HCl bubble test, electrochemical impedance in 3.5wt% NaCl solution, surface micro-hardness, SEM cross section to observe the anodic layer micro-cracks, and admittance under 3.5wt% K2SO4 solution at 1000 Hz. For the surface cleanliness of anodization, ICPMS analysis of post precision wet cleaning has been used as a standard technique for metal contamination control. Since the requirements to anodized aluminum quality, corrosion resistance, and surface cleanliness for plasma etching tools are much strict and higher than the traditional industry applications, improvements of corrosion resistance and surface cleanliness are always the tasks. Lam Research has defined the surface cleanliness and the corrosion resistance of anodized aluminum specification for a standard type III and

The reaction mechanism of aluminum oxidation is summarized by Macdonald [50] as a reasonable model. The oxides grow as bilayer structures with an inner layer due to movement of oxygen vacancies from metal/film interface and an outer layer due to the movement of cations outward from the film/environmental interface. The vacancy concentrations vary exponentially with distance. The cathode consumes electrons by evoloving hydrogen and reducing oxygen. Barrier layer grows into metal phase via reaction.


below. But the techniques are not limited to the techniques listed below:






advanced anodized aluminum [28, 31-33, 35-39, 44].


The principal crystallographic defects are (1) vacancies: Vo''and VMx' for MOx/2; (2) interstitials: Oi 2- and Mi x+. In fact, oxide films can be described as exponentially-doped semiconductor junctions. The fundamentals and process optimization of anodized aluminum have been studied thoroughly by Brace, Thompson, Wood, Mansfeld, and recent years by Shih through the comprehensive studies of anodization of different aluminum alloys, different anodization processes, and different manufacturing processes [51 – 60]. The interface model of anodized aluminum with hot DIW seal has been described by Mansfeld, Kendig, Shih and others [61- 72] as shown in Fig.20.

Fig. 20. The typical interface model of anodized aluminum with a hot DI water seal.

Z() = Rs + Rb/{1+(jCbRb) 2}+(Rpo+CPE)/{1+(jCpo(Rpo+CPE))1} where Cb = obA/Db; Cpo = opoA/Dpo and CPE = k(j)n

o = 8.854 x 10-14 F/cm and is the permittivity of free space.

In Fig.20, Cb and Rb are barrier layer capacitance and resistance, respectively. Rpo and CPE are the total impedance of the porous layer defined as Zpo which equals to Rpo + CPE. Cpo is the capacitance of the porous layer. CPE represents the constant phase element (CPE). A two-time constant interface model and suitable values of Rb and Zpo indicate a good quality of anodized aluminum. Zpo values highly depend on the quality control of hot DI water sealing process and it is very important for the improvement of the corrosion resistance of anodized aluminum [73-82]. Rb values depend on the voltage applied during anodization as well as the overall process control during anodization. A uniform and thick barrier layer helps to improve the dielectric voltage breakdown of the anodized aluminum. Mansfeld and Shih [63-69] developed a software package specially for the analysis of electrochemical impedance spectroscopy (EIS) data of anodized aluminum and the software has been widely applied for EIS data analysis. The EIS data of the new anodized aluminum developed and qualified at Lam Research Corporation show that the anodized aluminum has no corrosion in 3.5wt% NaCl (similar to seawater) for 365 days as shown in Fig. 21 [28, 38].

A Systematic Study and Characterization of Advanced Corrosion Resistance Materials


for 365 days. Black – 365D005; Red – 365D107; Blue – 365D073.

Parameters D005 D107 D073 Cpo (nF) 9.15 9.20 9.33 Cb (F) 8.45 9.19 8.97 Zpo (Mohm) 0.731 0.784 0.698 Rb (Mohm) 628.4 820.5 681.5 n 0.1814 0.1733 0.1733 <sup>1</sup> 0.887 0.900 0.887 <sup>2</sup> 0.958 0.930 0.940 A (area in cm2) 20.0 20.0 20.0 Chi-sq 2.785x10-3 3.761x10-3 2.775x10-3 Zpo (ohm-cm2) 1.462x107 1.568x107 1.396x107 Rb (ohm-cm2) 1.257x1010 1.641x1010 1.363x1010

theta

Immersion in 3.5wt% NaCl Solution


and Their Applications for Plasma Etching Processes in Semiconductor Silicon Wafer Fabrication 21

10-4 10-3 10-2 10-1 100 101 102 103 104 105 106

Frequency (Hz)

10-4 10-3 10-2 10-1 100 101 102 103 104 105 106

Frequency (Hz)

Fig. 22. EIS Bode-plots of advanced anodized aluminum coupons in 3.5wt% NaCl solution

Table 6. Detailed of EIS Data Analysis of test Samples D005, D107 and D073 after 365 Day's

In Table 6, is called frequency dispersion which is related to surface inhomogeneties with different dimensions [83]. Chi-sq is the fitting error between the experimental data and fitted data at each frequency. The detailed calculation is shown as below [84] and is the sum of the fitting error at each frequency multiplying 100 and dividing the total data points.

Chi-sq = (100/N) {[ Zexp(fi) – Zfit(fi)]/Zexp(fi)} TEM is also used to obtain the barrier layer thickness of different types of anodized aluminum [80]. In Fig. 23, a standard type III anodization achieves about 50nm thickness of the barrier layer. The thickness of a new anodization can be as thick as 100nm due to the higher voltage applied in the anodization process. The thicker barrier layer can provide a

Fig. 21. EIS data of anodized aluminum in 3.5wt% NaCl solution for 365 days.

The overall impedance and HCl bubble test results are shown in Table 5. EIS data of three test coupons after immersion in 365 days in 3.5wt% NaCl solution are analyzed using the software written by Shih and Mansfeld called "ANODAL" [63-69].


Table 5. The overall impedance and HCl Bubble Time of Test Coupons After Immersion in 3.5wt% NaCl solution for 365 days (coupons were prepared in three different batches of anodization processes) [78].

The Bode-plots of the three EIS data after 365 day's immersion in 3.5wt% NaCl solution is shown in Fig. 22. The anodized aluminum shows an excellent corrosion resistance and high quality of process control.

The complete EIS data analysis of the three test anodized aluminum samples is listed in Table 6 below. It is obvious that a consistent and an excellent corrosion resistance on both porous layer and barrier layer have been demonstrated. It is very important to improve the overall corrosion resistance of anodized aluminum through a well-controlled hot DI water sealing process. The parameters of hot DI water sealing tank water purity level, temperature range, sealing time, hot DI water pH value, and the pre-cleaning of the anodized aluminum before loading to the hot DI water tank will impact the quality of the sealing quality. The anodized anodization as a chamber coating for semiconductor IC industry moved from previously used non-sealed type III anodization or other types of non-sealed anodization to a well-controlled hot DI water sealed anodization for over 15 years because the hot DI water sealed anodized aluminum has demonstrated much better overall corrosion resistance in plasma etching chamber.

Fig. 21. EIS data of anodized aluminum in 3.5wt% NaCl solution for 365 days.

software written by Shih and Mansfeld called "ANODAL" [63-69].

365D005 1.462x107 1.257x1010 > 24 365D107 1.568x107 1.641x1010 > 24 365D073 1.396x107 1.363x1010 > 24

anodization processes) [78].

quality of process control.

plasma etching chamber.

The overall impedance and HCl bubble test results are shown in Table 5. EIS data of three test coupons after immersion in 365 days in 3.5wt% NaCl solution are analyzed using the

Coupon ID Zpo (ohm-cm2) Rb (ohm-cm2) HCl bubble time in hours

Table 5. The overall impedance and HCl Bubble Time of Test Coupons After Immersion in 3.5wt% NaCl solution for 365 days (coupons were prepared in three different batches of

The Bode-plots of the three EIS data after 365 day's immersion in 3.5wt% NaCl solution is shown in Fig. 22. The anodized aluminum shows an excellent corrosion resistance and high

The complete EIS data analysis of the three test anodized aluminum samples is listed in Table 6 below. It is obvious that a consistent and an excellent corrosion resistance on both porous layer and barrier layer have been demonstrated. It is very important to improve the overall corrosion resistance of anodized aluminum through a well-controlled hot DI water sealing process. The parameters of hot DI water sealing tank water purity level, temperature range, sealing time, hot DI water pH value, and the pre-cleaning of the anodized aluminum before loading to the hot DI water tank will impact the quality of the sealing quality. The anodized anodization as a chamber coating for semiconductor IC industry moved from previously used non-sealed type III anodization or other types of non-sealed anodization to a well-controlled hot DI water sealed anodization for over 15 years because the hot DI water sealed anodized aluminum has demonstrated much better overall corrosion resistance in

Fig. 22. EIS Bode-plots of advanced anodized aluminum coupons in 3.5wt% NaCl solution for 365 days. Black – 365D005; Red – 365D107; Blue – 365D073.


Table 6. Detailed of EIS Data Analysis of test Samples D005, D107 and D073 after 365 Day's Immersion in 3.5wt% NaCl Solution

In Table 6, is called frequency dispersion which is related to surface inhomogeneties with different dimensions [83]. Chi-sq is the fitting error between the experimental data and fitted data at each frequency. The detailed calculation is shown as below [84] and is the sum of the fitting error at each frequency multiplying 100 and dividing the total data points.

$$\text{Chi-sq} = \text{(100/N)} \,\, \Sigma \,\, \{ [\, |Z\_{\text{exp}}(\mathbf{f}\_{\text{i}}) - Z\_{\text{fit}}(\mathbf{f}\_{\text{i}})| ]\} / \,\, \Sigma\_{\text{exp}}(\mathbf{f}\_{\text{i}}) $$

TEM is also used to obtain the barrier layer thickness of different types of anodized aluminum [80]. In Fig. 23, a standard type III anodization achieves about 50nm thickness of the barrier layer. The thickness of a new anodization can be as thick as 100nm due to the higher voltage applied in the anodization process. The thicker barrier layer can provide a

A Systematic Study and Characterization of Advanced Corrosion Resistance Materials

resistance study of anodized aluminum.

locations are selected to run the HCl bubble test [76].

different thickness in a thick aluminum block [77].

are as follows:

and Their Applications for Plasma Etching Processes in Semiconductor Silicon Wafer Fabrication 23

The HCl bubble test can be processed at any position of etching chamber before and after etching process. In Fig. 25, one process chamber is studied on its corrosion resistance in 5.0wt% HCl solution [76]. This method has received a wide application for the corrosion

Fig. 25. HCl bubble test on a used process chamber after 12,000 wafers processing. Six

shown in Fig. 26. Eleven different test methods are applied to the study.

A systematic study of anodized aluminum made of Al6061-T6 11" thick block was carried out. It is obvious that HCl bubble test can be studied at different thickness positions to compare the differences of corrosion resistance [77]. The detail positions of different tests are

HCl bubble test can be carried at different thickness to evaluate the corrosion resistance at

The thermal properties of anodized aluminum have also been studied. One of the typical studies was published in the work with Mansfeld [39]. A lot of studied have been carried out at Lam through the years [39, 73-82]. All these studies show that anodized aluminum film can be degraded through the use at a relatively high temperature. Both porous layer and barrier layer can be impacted depending on the operation temperature. Radii before anodizing on aluminum parts have to be controlled and the micro-cracks at corners and

High purity Y2O3 has advantages in comparison with anodized aluminum and ceramic such as high purity alumina in many aspects. First of all, it can reduce the plasma etching rate for both metal etch and silicon etch by a factor of 40 times. It can bring cost saving in etch tools for semiconductor wafer fabrication. It can also reduce metal contamination too. The comparison of anodized aluminum and thermal spray coating of high purity Y2O3 are summarized by John and Shih [28, 31]. The advantages of Y2O3 coated anodized aluminum

edges depend on the type of anodized aluminum and final thickness of anodic layer.




higher barrier layer resistance during the EIS study as shown in Table 5 and Table 6. By combining both an excellent hot DI water seal processing to obtain an excellent corrosion resistance of the porous layer and a thicker barrier layer of the anodic film, the anodic film can hold 365 days in seawater without corrosion.

Fig. 23. TEM pictures of a standard type III hard anodization (left) and a mixed acid anodization (right) [80]

For acidic corrosion resistance of anodized aluminum, HCl bubble test is an easy and very effective method to obtain the corrosion resistance. From Fig. 24 below, one can see the good and poor anodized aluminum under the solution of 5wt% HCl solution (28, 31-33, 44, 78]. On the left of Fig.24, there is no any hydrogen bubble generated under the attack of a strong acid within 2 hours immersion. It indicates a high quality of anodized aluminum. On the right of Fig. 24, anodized aluminum generates a lot of hydrogen bubbles in 5wt% HCl solution only after 10 minutes immersion in the acid. It indicates a poor anodized aluminum.

Fig. 24. Acidic corrosion resistance of two test coupons of anodized aluminum. On the left, anodized aluminum does not show any acidic corrosion in two hours and on the right, anodized aluminum shows severe acidic corrosion after only 10 minutes immersion in the acid.

higher barrier layer resistance during the EIS study as shown in Table 5 and Table 6. By combining both an excellent hot DI water seal processing to obtain an excellent corrosion resistance of the porous layer and a thicker barrier layer of the anodic film, the anodic film

Fig. 23. TEM pictures of a standard type III hard anodization (left) and a mixed acid

For acidic corrosion resistance of anodized aluminum, HCl bubble test is an easy and very effective method to obtain the corrosion resistance. From Fig. 24 below, one can see the good and poor anodized aluminum under the solution of 5wt% HCl solution (28, 31-33, 44, 78]. On the left of Fig.24, there is no any hydrogen bubble generated under the attack of a strong acid within 2 hours immersion. It indicates a high quality of anodized aluminum. On the right of Fig. 24, anodized aluminum generates a lot of hydrogen bubbles in 5wt% HCl solution only after 10 minutes immersion in the acid. It indicates a poor anodized

Fig. 24. Acidic corrosion resistance of two test coupons of anodized aluminum. On the left, anodized aluminum does not show any acidic corrosion in two hours and on the right, anodized aluminum shows severe acidic corrosion after only 10 minutes immersion in the

can hold 365 days in seawater without corrosion.

anodization (right) [80]

aluminum.

acid.

The HCl bubble test can be processed at any position of etching chamber before and after etching process. In Fig. 25, one process chamber is studied on its corrosion resistance in 5.0wt% HCl solution [76]. This method has received a wide application for the corrosion resistance study of anodized aluminum.

Fig. 25. HCl bubble test on a used process chamber after 12,000 wafers processing. Six locations are selected to run the HCl bubble test [76].

A systematic study of anodized aluminum made of Al6061-T6 11" thick block was carried out. It is obvious that HCl bubble test can be studied at different thickness positions to compare the differences of corrosion resistance [77]. The detail positions of different tests are shown in Fig. 26. Eleven different test methods are applied to the study.

HCl bubble test can be carried at different thickness to evaluate the corrosion resistance at different thickness in a thick aluminum block [77].

The thermal properties of anodized aluminum have also been studied. One of the typical studies was published in the work with Mansfeld [39]. A lot of studied have been carried out at Lam through the years [39, 73-82]. All these studies show that anodized aluminum film can be degraded through the use at a relatively high temperature. Both porous layer and barrier layer can be impacted depending on the operation temperature. Radii before anodizing on aluminum parts have to be controlled and the micro-cracks at corners and edges depend on the type of anodized aluminum and final thickness of anodic layer.

High purity Y2O3 has advantages in comparison with anodized aluminum and ceramic such as high purity alumina in many aspects. First of all, it can reduce the plasma etching rate for both metal etch and silicon etch by a factor of 40 times. It can bring cost saving in etch tools for semiconductor wafer fabrication. It can also reduce metal contamination too. The comparison of anodized aluminum and thermal spray coating of high purity Y2O3 are summarized by John and Shih [28, 31]. The advantages of Y2O3 coated anodized aluminum are as follows:


A Systematic Study and Characterization of Advanced Corrosion Resistance Materials

samples or parts as shown in Fig. 27 [28, 78].

aluminum in 3.5wt% NaCl solution [78].

Z() = Rb/{1+(jCbRb)

and Their Applications for Plasma Etching Processes in Semiconductor Silicon Wafer Fabrication 25

In order to study Y2O3 coating on anodized aluminum, the following electrochemical cell configuration is used to study the overall impedance and interface model of the coated

Fig. 27. Electrochemical cell configuration during EIS study of Y2O3 coated anodized

Fig. 28. The proposed interface model of Y2O3 coated anodized aluminum in EIS study

monitored. The interface model can be described as the following equation [28, 78].

Assuming that Cc, Cpo and Cb are capacitances which represent the capacitances of Y2O3 coating layer, porous layer of anodized aluminum and barrier layer of anodized aluminum, respectively. The interface parameters can be obtained and the coating quality can be

3} + (Rp + CPE)/{1+(jCpo(Rp+CPE))2} + Rc/{1+(jCcRc)

1} + Rs

barrier layer of anodized aluminum as shown in Fig. 28 [28, 78]

An interface model of Y2O3 coated anodize aluminum shows a three-time constant interface model indicating a Y2O3 coated layer, the porous layer of anodized aluminum, and the

Fig. 26. A systematic study the anodized aluminum of Al6061-T6 11" thick block.

Although thermal spray and sintered Y2O3 has been widely using as one of the chamber materials in wafer fabrication, the study of this material as well as its coating has never been stopped because of the challenges. These studies for semiconductor IC wafer fabrication contain the following studies, but not limit to these techniques [28, 78].


**Total test locations**

**TH Thickness 7 C Color 7 R Ra roughness 3 A Admittance 20 H HCl bubble test 13 V Breakdown voltage 20 E EIS 2 T Taber abrasion 1 W Coating weight 1 M Microhardness 1 S SEM/EDX 5**

**Legend**

Fig. 26. A systematic study the anodized aluminum of Al6061-T6 11" thick block.

contain the following studies, but not limit to these techniques [28, 78].















Although thermal spray and sintered Y2O3 has been widely using as one of the chamber materials in wafer fabrication, the study of this material as well as its coating has never been stopped because of the challenges. These studies for semiconductor IC wafer fabrication



In order to study Y2O3 coating on anodized aluminum, the following electrochemical cell configuration is used to study the overall impedance and interface model of the coated samples or parts as shown in Fig. 27 [28, 78].

Fig. 27. Electrochemical cell configuration during EIS study of Y2O3 coated anodized aluminum in 3.5wt% NaCl solution [78].

An interface model of Y2O3 coated anodize aluminum shows a three-time constant interface model indicating a Y2O3 coated layer, the porous layer of anodized aluminum, and the barrier layer of anodized aluminum as shown in Fig. 28 [28, 78]

Fig. 28. The proposed interface model of Y2O3 coated anodized aluminum in EIS study

Assuming that Cc, Cpo and Cb are capacitances which represent the capacitances of Y2O3 coating layer, porous layer of anodized aluminum and barrier layer of anodized aluminum, respectively. The interface parameters can be obtained and the coating quality can be monitored. The interface model can be described as the following equation [28, 78].

$$\mathcal{Z}(\alpha) = \mathcal{R}\_b / \{1 + (\text{j}\alpha \text{C}\_\text{c} \text{R}\_\text{b})^{a\_3}\} + (\mathcal{R}\_p + \text{CPE}) / \{1 + (\text{j}\alpha \text{C}\_\text{po} (\text{R}\_p + \text{CPE}))^{a\_2}\} + \mathcal{R}\_c / \{1 + (\text{j}\alpha \text{C}\_\text{c} \text{R}\_\text{c})^{a\_1}\} + \mathcal{R}\_s$$

A Systematic Study and Characterization of Advanced Corrosion Resistance Materials

characterization, development and application.

chamber coating of the current plasma etching tools.

next generation plasma etching feature size applications.

and yttrium oxide (YAG).

**3. Conclusions** 

365 days.

today.

**4. Acknowledgement** 

and Their Applications for Plasma Etching Processes in Semiconductor Silicon Wafer Fabrication 27







The author would like to express great thanks to Professor H. W. Pickering and Professor D. D. Macdonald for their guidance during author's Ph.D. study at the Pennsylvania State University between 1981 and 1986. Great thanks to Professor F. B. Mansfeld for author's post doctor and research work at University of Southern California between 1986 and 1990. Thanks to Dr. M. W. Kendig and Professor W. J. Lorenz. Many thanks to Dr. Richard Gottscho, Dr. John Daugherty, and Dr. Vahid Vahedi at Lam Research Corporation. Both Lam Research Corporation and Applied Materials provided the author the opportunity to carry on the systematic study of advanced materials under high density plasma on plasma etching tools. The author would like to express thanks to many individuals during the study of chamber materials through the past 18 years. There have been hundreds of individuals who gave support and encouragement to the author. Due to the limitation of space, the author cannot list all the individuals. Some of the individuals are Dr. Duane Outka, Dr. Tuochuan Huang, Chris Chang, Patrick Barber, Declan Hayes, Dr. Shun Wu, Dr. Harmeet Singh, Dr. Yan Fang, Dr. Armen Avoyan, Dr. Siwen Li, Shenjian Liu, Dr. Qian Fu, Dr. Steve Lin, Nianci Han, Dr. Peter Loewenhardt, Dr. Diana Ma, Mike Morita, Tom Stevenson, Sivakami Ramanathan, John Mike Kerns, Dean Larson, Alan Ronne, Hilary Haruff, David

Where Z is the total impedance, Rb is the barrier layer resistance of anodization, Rp is the porous layer resistance of porous layer of anodized aluminum, CPE is the constant phase element of the porous layer, Rc is the coating resistance, and Rs is the solution resistance.

Soaking three spraycoated Y2O3 on anodized aluminum in 3.5wt% NaCl solution for 7 days, the EIS data are shown in Fig.29. The EIS data indicate that samples coated at different time have the similar overall impedance and the quality control of coating process is consistent. The complete analysis of the EIS data using a three-time constant interface model is shown below (Table 7).


Table 7. Interface parameters of three spraycoated Y2O3 on anodized aluminum

Fig. 29. EIS data of three spraycoated Y2O3 on anodized aluminum in 3.5wt% NaCl solution for 7 days. Excellent coating quality control is observed through the EIS study [28, 78].
