鑽石線鋸碳化矽方法之研究

Abstract

單晶碳化矽(Silicon Carbide, SiC)相較於其他半導體材料，有著能承受高電壓、高電流和高溫的特性，在現今高功率、高耗能的設備中有不可或缺的地位。由於其僅次於鑽石的極高硬度及耐磨耗性，在加工上有極度耗時和高成本的問題。而晶圓基板大多以固定鑽石線鋸作為主要切片製程，而所使用的鑽石線材佔了加工成本很大的比例，且切片品質對於後續製程所需時間和成本的影響也很大。 本研究將超音波輔助加工和電化學輔助加工應用於線鋸切片製程，超音波輔助加工(UAWS)是利用超音波振動破壞工件表面使材料容易移除，以及空化作用移除線材上的黏屑。電化學輔助加工(ECWS)則是利用陽極氧化反應，使碳化矽表面生成較軟的二氧化矽氧化層，降低切削難度，並和傳統線鋸加工(CWS)做比較，接著再加上工件旋轉機構組合加工，。 經實驗結果發現，在無旋轉機構的加工模式中，UAWS可以降低42 %翹曲度以及5 %表面粗糙度，ECWS則因為氧化層生成速度較進給速度慢很多，無法得到改善的效果。CWS在加入工件旋轉機構後，可以降低64 %的翹曲度以及53 %的表面粗糙度。而相較於同樣有旋轉機構的CWS，UAWS可以降低40 %的翹曲度以及13 %的表面粗糙度，ECWS在加入旋轉機構後，工件在非切削區進行反應，使氧化層厚度大於切削區前進的距離，提高被移除材料中氧化層所佔比例，降低切削難度，相較於有旋轉機構的CWS，翹曲度下降約51 %，表面粗糙度下降約13 %。兩種加工方式在切片品質方面具有相近的表現，而ECWS在加工後磨粒維持較突出的狀態，加工後期的切削力也較小，顯示在工件旋轉的狀態下，ECWS應用於線鋸加工優勢。

Compared to other semi-conductor materials, single crystalline silicon carbide has the characteristics of bearing high voltage, high current, and high temperature. It has an indispensable status in modern equipment with high power and high energy consumption. Because of its high hardness and resistance to wear that second only to diamond, there is a problem of high time consumption and high cost during the SiC wafer manufacturing. Wafer substrate is mainly sliced by fixed diamond wire saw process. The diamond wire used for the process accounts for a huge proportion of the process cost, and the quality of the sliced wafer also has an influence on the manufacturing time and cost of the follow-up process. This study apply ultrasonic-assisted machining and electrochemical machining to wire saw process. The ultrasonic-assisted wire saw(UAWS) uses ultrasonic vibration to destroy the surface of the workpiece. The electrochemical assisted wire saw(ECWS) grows a softer silicon dioxide on the SiC surface by electro-chemical oxidation which can lower the cutting difficulty. And then adding two processes to workpiece-rotating mechanism to do a combination processing. In no workpiece-rotating mechanism experiment, UAWS can get a warp reduction rate of 42 % and a roughness reduction rate of 5 %. ECWS cannot enhance the wafer quality because the oxide layer growing rate is much slower than the feed rate. After adding the mechanism, CWS can get a warp reduction rate of 64 % and a roughness reduction rate of 53 % compared to no workpiece-rotating mechanism. UAWS can get a warp reduction rate of 40 % and a roughness reduction rate of 13 % compared to CWS which has added the mechanism. After adding the mechanism, workpiece can react at no-cutting area, making the oxide layer thickness bigger than the moving distance in the cutting area. As a result, compared to CWS which has added the mechanism, ECWS can get a warp reduction rate of 51 % and a roughness reduction rate of 13 %. The wire also decreases the wear rate by 1.5 %. Two processing have a similar performance on wafer quality, but ECWS can get a better wire condition and lower cutting force, which shows that ECWS has the advantage when applying to the wire saw process with workpiece-rotating mechanism.