具線上放電銳化技術之晶粒分割系統開發與矽晶圓基板晶粒分割研究

Abstract

本研究旨在開發一「具線上放電銳化技術之晶粒分割系統」，並應用於矽晶圓基板晶粒分割研究。傳統電鑄鑽石輪刀，鑽石顆粒含量低，且基材剛性較低，填塞後便須直接拋棄處理，導致刀具成本高。本研究嘗試以含硼聚晶鑽石輪刀取代傳統電鑄鑽石輪刀，聚晶鑽石鑽石含量高達95%以上，且剛性高，可提高鑽石輪刀使用壽命。為避免鑽石輪刀於晶粒分割期間，發生填塞，本研究提出一種線上放電銳化的方法，藉由所設計的「線上放電銳化機構」與「脈衝寬度調變放電電源」，開發出線上放電銳化技術，鑽石輪刀在不拆卸情況下，可於短時間內，完成線上銳化工作。脈衝寬度調變放電電源可輸出高頻、高峰值且窄脈衝寬度的放電波形，可使鑽石輪刀表面快速形成高密度火花熔蝕坑(屑袋)，並裸露出銳利的鑽石切刃。此外，以脈衝寬度調變電源進行線上放電銳化，鑽石輪刀亦可獲得薄化效果及降低輪刀表面的石墨化層。實驗結果顯示，線上放電銳化技術能快速實現刃厚30 μm、刃長400 μm，長寬比達13：1的聚晶鑽石輪刀，表面具高密度且分佈均勻的鑽石切刃與屑袋。為比較晶粒分割實驗的切割道品質，本研究提出「溝崩比」，以便採用「類脆性研削」模式，以較快的進給率和類脆性研削深度，進行晶粒分割，符合商用切割道的容許崩裂量及減少加工所耗時間。實驗結果證實，經線上放電銳化後的聚晶鑽石輪刀，著實可改善傳統電鑄鑽石輪刀切割晶圓所發生的崩裂、蛇行與歪斜等問題。研究也藉由「智能化研削力感測機制」對矽晶圓基板進行10×10陣列的晶粒分割驗證，發現晶圓正面及背面之溝崩比，分別達3.26及1.87，優於商用的溝崩比(1.34)(溝崩比愈大，溝緣崩裂量愈少)，且切割道具高筆直度，晶粒邊壁垂直平整，對半導體產業有實質幫助，深具商業化價值。This study presents the development of a die separation system with an in-situ w-EDD (Electro discharge dressing) technology and study of die separation on silicon wafer substrate. Traditional electroformed diamond wheel tool has a low content of diamond abrasives and low rigidity of the substrate, which must be directly discarded after clogging leading to a high cost of tool. In this study, a BD-PCD (Boron-doped Polycrystalline Composite Diamond) in which possesses a content of diamond abrasive more than 95% and high rigidity is employed to instead of the traditional electroformed diamond wheel tool to improve the tool lifetime. To avoid clogging happened during working, an in-situ discharge dressing technology by which combines the designed "in-situ dressing mechanism" with the "PWM (Pulse-Width Modulation) power source" is developed. The diamond tool can be in-situ dressed in a short time without unloading. The PWM power source readily generates a current train with high-frequency, high-peak and shot-pulse time, which facilitates quickly form a high density spark erosion crater (chip-pocket) on the surface of the diamond wheel and expose the sharp cutting edge. In addition, a thin diamond wheel tool with lower graphitization layer can also be readily obtained. Experimental results show that the developed in-situ discharge dressing technology can quickly finish a diamond wheel tool with a thickness of 30 μm, a length of 400 μm and an aspect ratio of 13: 1. A high density and uniformly distributed diamond cutting edges and chip pockets has been revealed on the wheel surface. To compare the kerf quality, A KCR (Kerf Chipping Ratio) is proposed to perform a die separation at a faster feed-rate and brittle-like grinding depth under a brittle-like regime grinding, which meets the allowable chipping of commercial scribe line and reduces processing time. Experimental results confirm that the chipping, wavy cutting and slant cutting of the traditional electroformed diamond wheel can be improved by using the dressed BD-PCD wheel tool. By applying the mechanism of intellectualized grinding force feedback, a die separation with an array of 10×10 on silicon wafer substrate is verified, it was found that the KCR on the front and back of the wafer reached 3.26 and 1.87, respectively, which were better than the commercial KCR (the larger the KCR, the smaller the chipping at groove edge). Moreover, a scribe line with high-straightness and -wall verticality can be achieved, which is helpful in the semiconductor industry and great commercial value.