| Summary: | 碩士 === 國立交通大學 === 材料科學與工程學研究所 === 86 ===
Effects of processing parameters on diamond deposition in the etched trenches of Si wafer were studied by the Takuchi method (an orthogonal experimental analysis method). Diamond films were deposited by a microwave plasma chemical vapor deposition (MRCVD) system with CH4 and H2 as the source gases. The trenches of the Si wafer were obtained by a photolithography process plus a wet etching process with SiO2 as the mask and KOH+Isopropanol as the etchant. Morphologies and diamond quality (or diamond content) of the films were characterized by SEM and Raman spectroscopy, respectively. The residual stresses of the films were evaluated by Raman shift method. The preferrd orientations of the films were determined by XRD. The experimental results show the following conclusions.:
(A) By comparing the deposition behaviors on the flat surface of Si wafers with and without the etched trenches at the sides, the results show: (1) Except the residual stress, the main parameters with the greater contributions to the film deposition rate and the diamond quality are almost the same. (2) The main parameter for the residual stress is deposition time (about 53% contribution) and microwave power (32% contribution), respectively. (3) In terms of film morhologies at the same deposition conditions, the films for the former case show more faceted crystals and better diamond quality. (4) For the flat surface, the contributions of the main parameter to I(111)/I(400) of the films are interaction between system pressure and CH4/H2 ratio(66%), CH4/H2 ratio (21%) and system pressure (12%). In other words, the favor conditions for a greater I(111)/I(400) value are in the order of : (CH4/H2 ratio=low) + (system pressure=low) > (CH4/H2 ratio=high) + (sytem pressure=high) > other cases.
(B) By comparing the deposition behaviors on the flat surface and in the trenches of Si wafer, the results show that the contributions of the main parameters: (1) to the deposition rate are CH4/H2 ratio (41%, 52%), system pressure (29%, 24%) and microwave power (or deposition temperature) (26%, 21%), respectively. (2) to diamond content in the films are microwave power (69%, 52%) and CH4/H2 ratio (17%, 38%), respectively. (3) The favor conditions for a greater deposition rate are a higher CH4/H2 ratio and pressure, and a lower microwave power. (4) The favor conditions for a higher diamond quality are opposite of the favor condition for a greater deposition rate. (5) A greater diamond content in the films will give rise to a smaller compressive stress.
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