**4. Low-***k* **plasma damage**

The induced plasma damage on low-*k* dielectrics during the fabrication of Cu/low-*k* intercon-

After processing of Metal-1 (M-1), the etching stop layer (Cu barrier dielectric layer) is firstly deposited by PECVD method. The used material can be SiN, SiC, or SiCN. Before deposition,

ment [36, 37]. Both these two steps would damage the underlying low-*k* dielectric. Then, a PECVD SiCOH low-*k* dielectric film is deposited for the Via-1 (V-1)/Metal-2 (M-2) patterning. Due to the presence of the etching stop layer, the plasma damage is seldom occurred in this step. Next, Via-1 and Metal-2 trench are subsequently patterned. Via-1 patterning is stopping on the etching layer. Then, before Metal-2 trench patterning, the plug is filled into the Via-1 to avoid etching during Metal-2 trench etching. Finally, resist removal and etching stop layer

In the Via-1 and Metal-2 trench patterning, the etching process induces plasma damage not

The damaged layer on the horizontal surfaces can be removed as the etching proceeds. Therefore, the resulted damage on the low-*k* dielectric is the result of a competition between the etching rate and the diffusion rate of active species causing the damage. The non-damaging process can be achieved by using higher etching rate process. However, for vertical surfaces, the damage is still remained after etch. The damage is more minor due to the absence of ion

**Figure 1.** Via-first dual-damascene process flow for Cu/low-*k* interconnects. (A) Etching stopping layer deposition

Photoresist ashing or stripping. (F) Via-1 ARC plug and M-2 trench lithography. (G) M-2 trench etching. (H) ARC plug removal, photoresist ashing, and stripping etching stop layer opening. (I) Cu metal barrier and seed layer deposition. (J)

Cu ECP deposition. (K) Cu CMP. (L) Etching stopping layer deposition (repeated (A)).

). (B) Low-*k* dielectric (SiCOH) deposition. (C) Via-1 lithography. (D) Via-1 etching. (E)

) for adhesion improve-

nects by the use of via-first dual-damascene process is described below:

296 Plasma Science and Technology - Basic Fundamentals and Modern Applications

plasma clean is performed to remove copper oxide (CuOx

opening are subsequently performed to complete the dual-damascene patterning.

only on the horizontal surfaces but also on the vertical surfaces (sidewall).

NH3

or H2

(SiN, SiC, SiCN, SiCOH, SiO2
