本實驗主要目的為以電漿輔助化學氣象沉積系統(Plasma Enhanced Chemical Vapor Deposition : PECVD)在矽基板上成長低應力氮化矽薄膜(low stress silicon nitride film)並研究探討低應力氮化矽薄膜的物理特性，並進一步將低應力氮化矽薄膜應用於微光機電系統，製作一種靜電控制的光衰減器。在我們的實驗中，薄膜應力可隨著成長工作壓力(working pressure)作微調，工作壓力越大，應力朝張應力(tensile stress)發展。利用這個關係，我們成功的調製出應力值為+170MPa與折射率為1.8的氮化矽薄膜。利用矽基板經過KOH溶液於背面開孔蝕刻移除後，厚度1um與面積5 x 5 mm²的平整氮化矽鼓膜(membrane)能成功的編製，並成功的在薄膜上製作光柵(grating)。除此之外，研究比較電漿輔助化學氣象沉積與低壓化學氣相沉積(Low Pressure Chemical Vapor Deposition : LPCVD)兩種低應力氮化矽薄膜的材料特性差異，發現電漿輔助化學氣象沉積的氮化矽鼓膜在紫外光UV波段有極佳的穿透效率，在240nm波段仍有50%的穿透效益，低壓化學氣相沉積的氮化矽鼓膜在400nm以下的短波長光幾乎被收，所以電漿輔助化學氣象沉積的氮化矽鼓膜較適合應用於紫外光波段。 Silicon nitride is one of the most common dielectric materials because it can be synthesized by various methods. In this work, SiNx films deposited on silicon by a Plasma Enhanced Chemical Vapor Deposition (PECVD) reactor was investigated as an alternative method for low stress membrane fabrication. In our experiments, the stress of silicon nitride film is as a decreased function of working pressure. The low tensile stress 170 MPa and refractive index 1.8 of the film can be obtained at working pressure 750 mTorr. After KOH wet etching from backside of silicon substrate, a 5 x 5 mm² flat square membrane with thickness of 1µm was successfully fabricated. The UV transmittance of the free standing membrane was measured, which showed that UV light is transmissible down to 200nm wavelength. The chemical composition of the film analyzed by using X-ray photoelectron spectroscopy ( XPS ) and Fourier Transform Infrared Spectroscopy ( FTIR) showed it is a SiNxHy film.
