光電化學蝕刻製作矽質微米連續壁結構

Formation of Macro-wall Array on Silicon by Photo Electrochemical Etching

本研究之目的乃在n-型（100）矽單晶上利用光電化學方法，蝕刻出微米級連續壁結構。為了增進蝕刻效果，分別就預蝕刻結構、氫氟酸蝕刻液濃度、酒精添加劑等參數，探討其對電化學陽極極化曲線輪廓之影響，以及對蝕刻外觀之效應，找出最佳蝕刻參數。
研究結果顯示：n-型（100）矽單晶在150W鹵素燈照光下，在含5～10 M酒精之氫氟酸（濃度範圍在1～6 M）溶液中，在低於特性蝕孔電位之外加偏壓之下，均可成功製作微米級連續壁結構。若增加氫氟酸濃度則不僅蝕刻速率降低，並且蝕孔形貌比較粗糙；添加酒精雖可促進連續壁形貌之平滑度，但濃度過高會使蝕刻速率下降。

The purpose of this study is to fabricate arrays of macro-walls on the surface of n-type silicon (100) by photo-electrochemical etching. Techniques such as dc-potentiodynamic polarization and potentiostatic etching were employed to explore the anodic dissolution behavior of silicon in HF solution. The anodic etching behavior and the etching morphology of n-type silicon (100) were found to be governed by the depth of pre-etched pits, the kind of etching solution, the concentration of etchants and the additives involved.
Arrays of macro-walls were fabricated at potentials less than the porous characteristic potential on n-type silicon (100), which was illuminated with a 150 w halogen lamp and etched in HF solutions (with concentration ranging from 1 to 6 M) containing 5-10 M ethanol. The etching rate in pore-etching decreases as the HF concentration increases from 1 M to 6 M. Optimal addition of ethanol (5-10 M) in 2 M HF not only accelerates the etching rate but also enhances the surface smoothness of the pore-walls. However, excessive addition of ethanol (16 M) results in decrease of the etching rate.