Research on the difference in etching rates of SiO2 at the top and bottom of high-aspect-ratio trench in C4F8/Ar/O2 plasma etching

Deep trench isolation technology has high isolation and antilatch capabilities and is widely used in high-performance computing, mobile devices, smart wearables, medical, and automotive electronics. This paper focuses on addressing the issue of differential SiO2 etch rates between the top and bottom of high aspect ratio (with a depth-to-width ratio exceeding 20:1) trench during dry etching. This discrepancy arises from the difference in size and depth, leading to varying amounts of plasma exposure for the top and bottom regions. To minimize the etch rate difference between the top and bottom, the following research was conducted. In this study, C4F8 was employed as the primary etchant, while O2/Ar served as the auxiliary gas. The objective was to conduct an in-depth analysis of the specific impacts that key process parameters—including chamber pressure, power, and gas flow rate—have on the etching rates at both the top and bottom of deep trench. Experimental results indicate that the etch rate ratio between the bottom and top correlates positively with bias power, while it correlates negatively with pressure, source power, and the flow rates of C4F8. When the C4F8 flow rate is 7 SCCM or the O2 flow rate is 30 SCCM, the etch rate at the bottom even exceeds that at the top. The findings of this paper provide valuable insights for optimizing etching processes and contribute to the further development of related fields.