Korean Chemical Engineering Research

The Korean Institute of Chemical Engineers (한국화학공학회)
권호 표지

Effects of Bias Voltage and Ion-incident Angle on the Etching of Photoresist in a High-density CHF3 Plasma

고밀도 CHF3 플라즈마에서 바이어스 전압과 이온의 입사각이 Photoresist의 식각에 미치는 영향

  • Kang, Se-Koo (Dept. of Chem. Eng., Seoul National University) ;
  • Min, Jae-Ho (Dept. of Chem. Eng., Seoul National University) ;
  • Lee, Jin-Kwan (Dept. of Chem. Eng., Seoul National University) ;
  • Moon, Sang Heup (Dept. of Chem. Eng., Seoul National University)
  • 강세구 (서울대학교 화학생물공학부) ;
  • 민재호 (서울대학교 화학생물공학부) ;
  • 이진관 (서울대학교 화학생물공학부) ;
  • 문상흡 (서울대학교 화학생물공학부)
  • Received : 2006.02.11
  • Accepted : 2006.07.03
  • Published : 2006.10.31
Download PDF
⟨ Previous Next ⟩

Abstract

The etch rates of photoresist (PR) and the etch selectivity of $SiO_2$ to PR in a high density $CHF_3$ plasma were investigated at different ion-incident angles and bias voltages. A Faraday cage was employed for the accurate control of ion-incident angles. The ion energy was controlled by changing bias voltages. The etch rate of $SiO_2$ continuously decreased with ion-incident angles but the etch rate of PR remained constant up to the middle angle region and decreased afterwards. The etch rates of $SiO_2$ normalized to those at $0^{\circ}$ incident angle changed with the ion-incident angle following a cosine(${\theta}$) curve. On the other hand, the normalized etch rates of the PR changed showing a drastic over-cosine shape in the middle angle region. The etch selectivity of $SiO_2$ to PR decreased with an increase in the ion-incident angle because the etch yields of PR were enhanced by physical sputtering in the middle angle region compared to the case of $SiO_2$ etching. The etch selectivity of $SiO_2$ to PR decreased with an increase in the bias voltage at nearly all ion-incident angles.

고밀도 $CHF_3$ 플라즈마를 이용한 식각에서 photoresist(PR)의 식각속도 및 $SiO_2$의 PR에 대한 식각 선택도가 이온의 입사 각도에 따라 변화하는 특성을 관찰하였다. 플라즈마 내에 파라데이 상자를 설치하여 이온의 입사 각도를 조절하였으며, 바이어스 전압을 변화시켜 이온의 입사 에너지를 조절하였다. 대부분의 바이어스 전압에서 $SiO_2$의 식각속도는 이온입사각도가 증가함에 따라 단조 감소함에 비해 PR의 식각속도는 중간각도 영역까지 일정하다가 그 이후에 감소하기 시작하였다. 이온입사각도가 $0^{\circ}$인 조건에서의 식각속도를 기준으로 정규화된 식각속도(NER)는 $SiO_2$의 경우 cosine함수와 거의 일치하였으나 PR의 경우 중간각도영역에서 over-cosine 형태를 보였다. PR에 대한 $SiO_2$의 식각선택도는 이온입사각도에 따라 점차로 감소하였는데, 이는 PR이 $SiO_2$에 비해 중간각도에서 물리적 스퍼터링에 의해 식각 수율이 크게 증가하였기 때문이다. 또한, 바이어스 전압의 증가에 따라 PR에 대한 식각선택도는 대부분의 이온입사각도에서 감소하였다.

Keywords

References

  1. Samukawa, S. and Mukai, T., 'High-Performance Silicon Dioxide Etching for Less Than 0.1-$\mu$m-high-aspect Contact Holes,' J. Vac. Sci. Technol. B, 18(1), 166-171(2000) https://doi.org/10.1116/1.591169
  2. Cho, B.-O., Hwang, S.-W., Lee, G.-R. and Moon, S. H., 'Angular Dependence of $SiO_{2}$ Etching in Fluorocarbon Plasma,' J. Vac. Sci. Technol. A, 18(6), 2991-2789(2000)
  3. Gray, D. C., Mohindra, V. and Sawin, H. H., 'Redeposition Kinetics in Fluorocarbon Plasma Etching, ' J. Vac. Sci. Technol. A, 12(2), 354-364(1994) https://doi.org/10.1116/1.578879
  4. Lee, R. E., 'Microfabrication by Ion-beam Etching,' J. Vac. Sci. Technol. A, 16(2), 164-179(1979) https://doi.org/10.1116/1.569897
  5. Chen, F. F. and Chang, J. P., 'Lecture Notes on Principles of Plasma Processing,' Kluwer Academic/Plenum Publishers(2003)
  6. Barish, E. L., Vitkavage, D. J. and Mayer, T. M., 'Sputtering of Chlorinated Silicon Surfaces Studied by Secondary ion Mass Spectrometry and ion Scattering Spectroscopy,' J. Appl. Phys., 57(4), 1336-1342(1985) https://doi.org/10.1063/1.334536
  7. Coburn, J. W., 'In Situ Auger Electron Spectroscopy of Si and $SiO_{2}$ Surfaces Plasma Etched in $CF_{4}/H_{2}$ Glow Discharges,' J. Appl. Phys., 50(8), 5210-5213(1979) https://doi.org/10.1063/1.326660
  8. Oehrlein, G. S. and Williams, H. L., 'Silicon Etching Mechanisms in a $CF_{4}/H_{2}$ Glow Discharge,' J. Appl. Phys., 62(2), 662-672 (1987) https://doi.org/10.1063/1.339766
  9. Oehrlein, G. S., Robey, S. W., Lindstrom, J. L., Chan, K. K., Kaso, M. A. and Scilla, G. J., 'Surface Modifications of Electronic Materials Induced by Plasma Etching,' J. Electrochem. Soc., 136(7), 2050-2057(1989) https://doi.org/10.1149/1.2097160
  10. Oehrlein, G. S., Zhang, Y., Vender, D. and Joubert, O., 'Fluorocarbon High-density Plasmas. II. Silicon Dioxide and Silicon Etching Using $CF_{4}$ and $CHF_{3}$,' J. Vac. Sci. Technol. A, 12(2), 333-344 (1994) https://doi.org/10.1116/1.578877
  11. Rueger, N. R., Beulens, J. J., Schaepkens, M., Doemling, M. F., Mirza, J. M., Standaert, T. E. F. M. and Oehrlein, G. S., 'Role of Steady State Fluorocarbon Films in the Etching of Silicon Dioxide Using $CHF_{3}$ in an Inductively Coupled Plasma Reactor,' J. Vac. Sci. Technol. A, 15(4), 1881-1889(1997) https://doi.org/10.1116/1.580655
  12. Standaert, T. E. F. M., Schaepkens, M., Rueger, N. R., Sebel, P. G. M., Oehrlein, G. S. and Cook, J. M., 'Study on the $SiO_{2}$-to- $Si_{3}N_{4}$ Etch Selectivity Mechanism in Inductively Coupled Fluorocarbon Plasmas and a Comparison with $SiO_{2}$-to-Si Mechanism,' J. Vac. Sci. Technol. A, 17(1), 26-37(1999) https://doi.org/10.1116/1.582108
  13. Vender, D., Haverlag, M. and Oehrlein, G. S., 'Ion-induced Fluorination in Electron Cyclotron Resonance Etching of Silicon Studied by X-ray Photoelectron Spectroscopy,' Appl. Phys. Lett., 61(26), 3136-3138(1998)
  14. Standaert, T. E. F. M., Hedlund, C., Joseph, E. A. and Oehrlein, G. S., 'Role of Fluorocarbon Film Formation in the Etching of Silicon, Silicon Dioxide, Silicon Nitride, and Amorphous Hydrogenated Silicon Carbide,' J. Vac. Sci. Technol. A, 22(1), 53-60 (2004) https://doi.org/10.1116/1.1626642
  15. Butterbaugh, J. W., Gray, D. C. and Sawin, H. H., 'Plasma-surface Interactions in Fluorocarbon Etching of Silicon Dioxide,' J. Vac. Sci. Technol. B, 9(3), 1461-1470(1991) https://doi.org/10.1116/1.585451
  16. Ikegami, N., Ozawa, N., Miyakawa, Y., Hirashita, N. and Kanamori, J., 'Mechanism of Surface-reaction in Fluorocarbon Dry Etching of Silicon Dioxide – An Effective of Thermal Excitation,' Jpn. J. Appl. Phys., 31, 2020-2024(1992) https://doi.org/10.1143/JJAP.31.2020
  17. Pelletier, J., 'A Model for the Halogen-based Plasma-etching of Silicon,' J. Phys. D: Appl. Phys., 20(7), 858-869(1987) https://doi.org/10.1088/0022-3727/20/7/007