A Study on Surface Roughness of Curved Silicon Crystal Spectrometer Fabricated by Plasma Chemical Vaporization Machining


Article Preview

We propose the application of open-air type numerically controlled plasma chemical vaporization machining (NC-PCVM) to fabricate a doubly curved crystal (DCC) substrate. Since PCVM utilizes only a chemical reaction to remove the work piece surface, there is no degradation of the crystallographical properties of the work piece material. In our previous study, we succeeded in fabricating a curved Si (111) crystal substrate with a curvature radius error of 0.08 %. Rocking curve measurement results revealed that there was no lattice strain on the processed surface. However, surface roughness degraded after PCVM figuring. To reduce the surface roughness, we modified the structure of the electrode unit, which generates plasma, to be able to supply a shielding gas. By supplying helium with a flow rate of 0.5 L/min as the shielding gas, rms surface roughness of the silicon was reduced from 0.73 nm to 0.42 nm. Excessive supply of helium (> 1 L/min) and/or supply of argon caused deterioration of the surface roughness. These results indicate that appropriate supply of the shielding gas is effective in reducing roughness in the open-air type PCVM process.



Edited by:

W.B. Lee, C.F. Cheung and S. To




Y. Yamamoto et al., "A Study on Surface Roughness of Curved Silicon Crystal Spectrometer Fabricated by Plasma Chemical Vaporization Machining", Key Engineering Materials, Vol. 516, pp. 522-526, 2012

Online since:

June 2012




[1] K. Yamamura, S. Shimada, Y. Mori, Damage-free improvement of thickness uniformity 20 of quartz crystal wafer by plasma chemical vaporization machining, Ann. CIRP 57 (2008) 567-570.

DOI: https://doi.org/10.1016/j.cirp.2008.03.132

[2] M. Hosoda, K. Ueda, M. Nagano, N. Zettsu, S. Shimada, K. Taniguchi, K. Yamamura, Fabrication of damage-free curved silicon crystal substrate for a focusing x-ray spectrometer by plasma chemical vaporization machining, Key Eng. Mater. 447-448 (2010).

DOI: https://doi.org/10.4028/www.scientific.net/kem.447-448.213

[3] C.J. Mogab, A.C. Adams, D. L. Flamm, Plasma etching of Si and SiO2-The effect of oxygen additions to CF4 plasmas, J. Appl. Phys. 49 (1978) 3796-3803.

DOI: https://doi.org/10.1063/1.325382

Fetching data from Crossref.
This may take some time to load.