Sidewall Damage - Silicon

Sidewall Damage - Silicon - Dry Etching

Material Name: Silicon
Record No.: 60
Primary Chemical Element in Material: Si
Sample Type: Wafer
Uses: Etching
Etchant Name: None
Etching Method: Dry etching
Etchant (Electrolyte) Composition: No data
Procedure (Condition): No data
Note: In Figure 1, some obvious sidewall damage can be seen in the trenches etched at a bias power of 35W. As the bias power increases, the uniformity of the ions decreases. This is caused by the fact that some plasmas bombard the sidewall before reaching the bottom during the etching cycle. On the upper side of the trench’s sidewall, the polymer materials of the deposition layer, along with some silicon, are partly removed by the bombardment of the ions, which leads to a rapid expansion of the trench’s width. On the lower parts of the sidewall, the sputtered polymer materials will redeposit onto the sidewall and form new deposition layers, which makes it thicker than the layers on the upper sidewalls. Several intense redeposition functions generated by high bias power may again shrink the width of the lower parts of the trenches, which also facilitates sidewall damage.
Reference: Tiantong Xu, et al., Effects of deep reactive ion etching parameters on etching rate and surface morphology in extremely deep silicon etch process with high aspect ratio, Advances in Mechanical Engineering, 2017, Vol. 9(12) 1–19, DOI: 10.1177/1687814017738152.

Figure 1: (a) SEM cross section of 6-mm-wide trenches, etched by bias power levels of 15 and 35 W, respectively. Sidewall damage can be seen in the 35 W trenches. (b) SEM cross section of 55-mm-wide trenches, etched by bias power levels of 15 and 35 W, respectively. Sidewall damage can be seen in the 35 W trenches. (c) SEM cross section of 110-mm-wide trenches, etched by bias power levels of 15 and 35 W, respectively. Sidewall damage can be seen in the 35 W trenches.