| 摘要: | 太陽能電池製程中影響產量的主因在於晶圓切割階段，而現今切割方式以線鋸加工為主流，其優點為可複線式加工，加工效率高。但此方式為接觸式加工，過程中易產生加工應力進而造成晶圓破裂損壞，及磨粒無法完全使用，且磨粒回收過程複雜並造成環境污染。因此，近年來相關文獻中提出以線切割放電加工方式切割矽晶圓，使用此法可有效改善線鋸加工之缺點，但因目前仍以加工單晶矽材料為主，而多晶矽材料加工方面的文獻甚少，主要原因為相較於單晶矽材料，多晶矽因具有晶界多變、電阻大等特性導致無法順利加工，故本研究嘗試採用線切割放電加工加工多晶矽晶圓，並對其加工特性做一探討。 本研究主要分成二大部份，第一部份採用純水作為加工液，對於加工可行性進行探討，過程中以不同製程參數進行實驗，並了解加工特性之影響趨勢。第二部份則為前一部份所得之結果進行製程改善，於加工液中添加焦磷酸鈉粉末，主要目的為利用磷元素的高導電性以提升加工效率，並藉由放電時所產生的高溫特性，迫使加工液中之磷元素擴散至矽晶圓表面進而達到P-N接合之效果。若相較於傳統太陽能電池製程，則可省略離子佈植階段，獲得製程簡化之效益。由本研究結果可知，以焦磷酸鈉溶液為加工液時，於脈衝時間6.5μs及電流10A可得加工速度0.528㎜/min，在相同加工參數比較下，純水加工速度為0.216㎜/min，其加工速度提升2.4倍。因在高溫下加工液產生電解效果進而改善表面粗糙度，並藉由本研究可證實含磷加工液可改善加工效率並可同時獲得表面摻雜之效果。 During solar cell processing, wafer cutting is an import procedure for yield, nowadays wire saw is the main cutting process, it has multi-wire with high efficiency, but has produced stress while cutting, it may let wafer break, and the particle can not be used fully, the particle will contaminate environment. Therefore, wire electrical discharge machining was investigated to improve wire saw processing, but most of research of material is single-crystal silicon, the poly-crystal investigate is few, because poly-crystal silicon with higher resistance, it is hard to machine for wire electrical discharge machining. This research is mainly divided into two major parts, the first part adopts pure water as dielectric in order to know the possibly of machinine, and investigate the influence of characteristic of each processing parameter The second part is according to the previous part results to improve the machining efficiency, we add sodium pyrophosphate powder in pure water, we want use phosphorous’ high electric conductivity to improve the efficiency, and use high temperature let phosphorous doping into wafer’s surface by wire electrical discharge machining to achieve p-n junction. Comparing with conventional solar cell processing, can save ion implantation, let the processing simply. Form the experiment results, using sodium pyrophosphate as dielectric can get fast feed ratio is 0.528 mm per second while pulse on time is 6.5μs, ampere is 10A, and comparing in the same parameter, the feed ratio increase 2.4 magnification, and improve surface roughness by electrolysis at high temperature, as previous results corroborating that dielectric with phosphorous can improve machining efficiency and dopping phosphorous into surface simultaneously. |
