Korean Chemical Engineering Research

The Korean Institute of Chemical Engineers (한국화학공학회)
권호 표지

Characteristics of Amorphous Silicon Gate Etching in Cl2/HBr/O2 High Density Plasma

Cl2/HBr/O2 고밀도 플라즈마에서 비정질 실리콘 게이트 식각공정 특성

  • Lee, Won Gyu (Deptartment of Chemical Engineering, Kangwon National University)
  • 이원규 (강원대학교 화학공학과)
  • Received : 2008.12.26
  • Accepted : 2009.01.21
  • Published : 2009.02.28
Download PDF
⟨ Previous Next ⟩

Abstract

In this study, the characteristics of amorphous silicon etching for the formation of gate electrodes have been evaluated at the variation of several process parameters. When total flow rates composed of $Cl_2/HBr/O_2$ gas mixtures increased, the etch rate of amorphous silicon layer increased, but critical dimension (CD) bias was not notably changed regardless of total flow rate. As the amount of HBr in the mixture gas became larger, amorphous silicon etch rate was reduced by the low reactivity of Br species. In the case of increasing oxygen flow rate, etch selectivity was increased due to the reduction of oxide etch rate, enhancing the stability of silicon gate etching process. However, gate electrodes became more sloped according to the increase of oxygen flow rate. Higher source power induced the increase of amorphous silicon etch rate and CD bias, and higher bias power had a tendency to increase the etch rate of amorphous silicon and oxide.

본 연구에서 고밀도 플라즈마 식각 장치를 사용한 비정질 실리콘 막의 게이트 전극선 형성공정에서 여러 가지 식각 변수가 치수 제어와 식각 속도 및 식각 선택비 등 식각 특성에 미치는 영향을 분석하였다. $Cl_2/HBr/O_2$로 구성된 식각 기체의 전체 유량을 증가시키면 비정질 실리콘의 식각 속도가 증가하나 식각 전후의 형상치수는 변화없이 거의 일정하였다. 전체 유량을 고정시키고 $Cl_2$와 HBr 간의 유량비를 변화시키면 HBr의 유량이 커질수록 비정질 실리콘의 식각 속도가 감소하였다. $O_2$의 유량을 증가시키면 산화막의 식각 속도가 상대적으로 낮아져 식각 선택비를 증가시켜 식각 공정의 안정성을 높이나 게이트 전극선을 경사지게 하는 특성을 보인다. Source power의 증가는 비정질 실리콘 식각 속도의 증가와 더불어 형상치수의 증가를 가져오며, bias power의 증가는 비정질 실리콘과 산화막의 식각 속도를 증가시키나 식각 선택비를 크게 감소시키는 경향을 보였다.

Keywords

References

  1. Tsou, L. Y., 'Effect of Photoresist on Plasma Etching,' J. Electrochem. Soc., 135, 2354-2356(1989)
  2. Joubert, O. and Bell, F. H., "Polysilicon Gate Etching in High- Density Plasmas: Comparison Between Oxide Hard mask and Resist Mask," J. Electrochem. Soc., 144, 1854-1861(1997) https://doi.org/10.1149/1.1837690
  3. Nakamura, M., Iizuka, K. and Yano, H., "Very High Selectivity n+ poly-Si RIE with Carbon Elimination," Jpn. J. Appl. Phys., 28, 2142-2146(1989) https://doi.org/10.1143/JJAP.28.2142
  4. Guinn, K. V., Cheng, C. C. and Donnelly, V. M., "Quantitative Chemical Topography of Polycrystalline Si Anisotropically Etched in $CI_2/O_2$ High Density Plasmas," J. Vac. Sci. Technol. B, 13, 214-226(1995) https://doi.org/10.1116/1.588355
  5. Bell, F. H. and Joubert, O., "Polysilicon Gate Etching in High Density Plasmas. V. Comparison between Quantitative Chemical Analysis of Photoresist and Oxide Masked Polysilicon Gates Etched in HBr/$CI_2/O_2$ Plasmas," J. Vac. Sci. Technol. B, 15, 88-97 (1997) https://doi.org/10.1116/1.589259
  6. Zau, G. and Sawin, H., "Effect of $O_2$ Feed Gas Impurity on $CI_2$ Based Plasma Etching of Polysilicon," J. Electrochem. Soc., 139, 250-256(1992) https://doi.org/10.1149/1.2069179
  7. Tsou, L. Y., "High Selective Reactive Ion Etching of Polysilicon with Hydrogen Bromide," J. Electrochem. Soc., 136, 3003-3006 (1989) https://doi.org/10.1149/1.2096391
  8. Box, G., Hunter, W. G. and Hunter, J. S., Statistics for Experimenters, John Wiley & Sons, New York, USA(1975)
  9. Wolf, S., Silicon Processing for the VLSI Era Vol3- The Submicron MOSFET, Lattice Press, Sunset Beach, CA(1995)
  10. Low, C. H., Chin, W. S., Zhou, M. S., Zhong, Q. H. and Chan, L. H., 'Characterization of Si(100) Surfaces after High Density Plasma HBr/$CI_2/O_2$ Etching by AFM and XPS,' 44th National Symposium of American Vacuum Society, San Jose(1997)