利用熱儲存層與微結構增進Poly-Si側向結晶的研究與模擬

Abstract

本文主要模擬KrF(248nm)laser施打在a-Si膜表面後，因熱傳所造成的溫度分佈。並定義出潛熱作用時間為結晶時間，在不考慮成核點的影響下，潛熱作用時間越長，結晶成長時間就越長。藉由比較結晶時間來討論加上熱儲存層SiO2與SiNx的優缺點，與增加環境溫度所造成的效應。其中隨著環境溫度的增加，在a-Si蓋上SiO2有最佳值100nm造成最佳結晶時間，此外蓋上SiNx隨著厚度增加，可以得到較長的結晶時間，在較低製程溫度可以得到較長結晶時間。最後引進溝渠定位長晶，模擬其熱流分布，找到其溝渠最小間隔，與最佳溝渠深度，藉由紀錄其固液接面，算出其結晶速度，並估計其結晶大小。

In this thesis we simulate the heat transfer inside the a-Si thin film after KrF laser annealing. And by defining latent heat process region, the temperature distribution among the samples can be successfully measured. Not concerning nucleation effect, the recrystallization time becomes longer with the solidifying duration. We find that the thickness of SiO2 capping layer has an optimized value 100nm with and without trench, and that of SiNx capping layer thicker than 100nm has better performance on solidifying duration compared with the same thickness of SiO2 capping layer. We simulated the trench-assisted ELA. And we find out its optimized trench depth, 300nm, and its smallest separation, 2μm. It is proved that trench-assisted position-control ELA can induce lateral grain growth by observing the isothermal diagram. By recording the movement of the 1350K isothermals, we can calculate the isothermal moving velocity, namely solid-liquid interface velocity. Finally, we can estimate the grain size from a trench to one side is about 3μm for an optimized condition. In a word, utilizing a trench can induce about 6μm lateral grain growth.