石英、氮化矽與碳化矽基板上長晶之觀測研究

Abstract

Kerf-less矽晶片鑄造技術是一種使用矽晶直接接觸不同基板的方法，由於此方法比起其他非傳統鑄造技術有更高的潛能突破晶片品質和產量的限制，所以是一項相當重要的研究主題。使用基板作為鑄造晶片的方法讓人能更好控制鑄造出的晶片型態和晶體特性，同時也具有更好控制溫度分布的能力，因此能有較好的晶片輸出。在這份研究裡，我們使用固向觀測及測量溫度的方法，來更加了解矽晶片在不同基板上的長晶機制。研究氮化矽、石英板和碳化矽在5 K/min 到 100 K/min的冷卻速度下的變化。在使用固向觀測方法下，我們發現根據不同基板和冷卻速度矽晶片長晶由帶狀成核變化為圓形狀成核。帶狀成核一開始在軸向快速長晶，之後再向側向長晶，例如樹枝狀生長，而圓形狀成核有著更加穩定的徑向長晶。目前的文章討論了帶狀成核和圓形狀成核的長晶模式和觀察趨勢。在長晶模式中，冷卻速度和過冷現象被發現是一個重要的因素，因為它們影響了成核頻率和回火現象。在帶狀成核時，增加冷卻速度和過冷皆被發現能增加成核傾向和晶粒生長頻率，是因為他們對過冷和局部溫度梯度的影響。但是，在圓形成核模式時，即使在低過冷狀態下成核能得到較高的晶粒頻率。臨界成核半徑和回火速度被用來解釋長晶模式和那些引起圓形狀長晶需要的參數。電子背向散射繞射分析被用於進行晶向和晶粒大小分布測量，測量結果和固向觀測及溫度測量方法一致。

Kerf-less silicon casting technologies utilizing direct contact on a foreign substrate remains an important research topic due to its potential in overcoming the quality and production output limitations present in other non-conventional silicon casting technologies. The use of substrate as a casting surface provides the system better control over the casted wafer’s morphological and crystallographic characteristics, and it also grants better control over the temperature distribution to achieve higher throughput. In this study, in situ observations and temperature measurements were carried out to better understand the nucleation and growth behavior of silicon thin-sheets on various substrates. Silicon nitride, quartz, and silicon carbide substrates at cooling rates ranging from 5 K/min to 100 K/min were considered. Visual observations revealed variations in the growth mode of silicon wafers from strips growth to circular growth due to substrate and the cooling parameters effects to the underlying driving force for solidification. The nucleation of solid strips, i.e., dendrites, initially grew axially at high rates before expanding laterally, whereas circular nucleations grew radially at a relatively slower and stable pace. Furnace cooling parameters and the extent to which the substrate can sustain the undercooling were found to dictate the ensuing mode of growth and the trends experienced therein. Undercooling estimates, recalescence rates, solidification densities, and growth kinetics were discussed to discern their interrelation and explain their effects to the resulting nucleation and wafer growth behavior. Increasing cooling rate and undercooling for nucleation were found to consistently increase grain frequency as confirmed by electron backscatter diffraction analysis. Prevalence of certain grain orientation and the consequent increase in Σ3 grain boundaries was also discerned due to the preference of dendritic strips growth.