**2. Production principle of conventional capacitively coupled plasma**

In order to perform the high-speed processing of the LSI semiconductor, high-density plasma is needed for CCP. The power balance of CCP in the form of a global model [17] is expressed as the following equation:

$$P\_{ab} = \epsilon \boldsymbol{\nu}\_{\epsilon} \boldsymbol{\mu}\_{\p} S(\boldsymbol{\varepsilon}\_{\epsilon} + \boldsymbol{\varepsilon}\_{\cdot} + \boldsymbol{\varepsilon}\_{\cdot}).\tag{1}$$

Here, *P*ab, *e*, *u*B, and *S* are the total absorbed power, the electronic charge, the Bohm velocity, and the surface area, respectively. *ε*<sup>e</sup> and *ε*<sup>i</sup> are the averaged energy loss per electron and ion lost to the electrodes. *ε*<sup>c</sup> denotes the collisional energy loss per electron-ion pair created. The plasma density, *n*<sup>e</sup> , can be determined from Eq. (1)

In the dry-etching processing, the silicon wafer patterned by the photoresist mask for LSI

of these gases, the fluorine atoms dissociated by an electron impact collision with the mol-

silicon wafer is etched with assistance of energetic ions produced in the plasma. For example, a high-density plasma sources have been developed to challenge patterning features less than

The plasma deposition has a sputtering deposition and a plasma-enhanced chemical vapor deposition (PECVD) method. The sputtering deposition is to impinge ions to the material target biased by a negative potential so as to sputter atoms from the target. The functional thin films such as transparent conductive oxide used in tableted computer and smartphone are deposited by sputtering method [9]. The sputtering depositions are prepared by DC magnetron and radio frequency (RF) magnetron plasma sources [10]. Various typed sputtering sources have been developed for the synthesis of high-quality thin films [10]. Especially, RF magnetron plasma source has an advantage that the insulated films can be deposited on the various substrates compared with DC magnetron plasma source. The PECVD is to dissociate

In these plasma-processing techniques, capacitively coupled plasma (CCP) with parallel plates was widely utilized. The physics of CCP has been studied by many researchers [11–16]. The sustaining mechanism of CCP is the electron heating process that the oscillating radio frequency sheath near the powered electrode plays an important role in electron acceleration as well as the collisional heating in the presence of electric fields and the emission process of secondary electrons from the electrode [11–16]. However, the electron heating process cannot

The requirement of these semiconductor devices with high-speed operation and high performance is increasing annually. In order to perform the demand, high-speed plasma processing, that is, a high-density plasma production, is important. However, CCP does not attain high-density plasma. Thus, the high-density CCP is required. In this chapter, the production principle of conventional CCP and the special CCP with various electrodes and

**2. Production principle of conventional capacitively coupled plasma**

In order to perform the high-speed processing of the LSI semiconductor, high-density plasma is needed for CCP. The power balance of CCP in the form of a global model [17] is expressed

*Pab* = *ene uB S*(*ε<sup>e</sup>* + *ε<sup>i</sup>* + *εc*). (1)

Here, *P*ab, *e*, *u*B, and *S* are the total absorbed power, the electronic charge, the Bohm velocity,

are the averaged energy loss per electron and ion

and *ε*<sup>i</sup>

ecules react with the silicon surface to generate a volatile etch product like SiF<sup>4</sup>

, CHF<sup>3</sup>

, SF<sup>6</sup>

) [3–7]. In the case

so that the

is exposed in plasma containing halogen molecules (e.g., CF<sup>4</sup>

210 Plasma Science and Technology - Basic Fundamentals and Modern Applications

molecule by electron impact so as to deposit radicals [8].

0.25 μm with high aspect ratios [8].

produce high-density plasma.

magnets is reviewed.

as the following equation:

and the surface area, respectively. *ε*<sup>e</sup>

$$m\_{\varepsilon} = \frac{P\_{ab}}{en\_{\varepsilon}S(\varepsilon\_{\varepsilon} + \varepsilon\_{\varepsilon} + \varepsilon\_{\varepsilon})}.\tag{2}$$

When only thermal electrons are lost to the boundary surfaces [18], *ε*<sup>e</sup> will be negligible. In general, the electron temperature decreases with increasing gas pressure [17]. Then, *ε*<sup>c</sup> increases, while *ε*<sup>i</sup> regularly decreases with increasing gas pressure, because the sheath is more collisional. For a fixed absorbed power, the increase in the plasma density is resulted with increasing gas pressure. Even for a relatively high-gas pressure of 50 Pa used in RF PECVD, however, the plasma density at a conventional driving frequency of 13.56 MHz is less than 1010 cm−3.

In order to increase the plasma density at the typical frequency of 13.56 MHz, ingenious device is required. In the next section, the various ingenuities will be introduced.
