MOCVD之氮化鎵/p型氮化鎵薄膜沉積製程化學反應場模擬分析

Abstract

在金屬有機化學氣相沉積法磊晶氮化鎵以及p型氮化鎵的過程中，三甲基鎵、二茂鎂以及氨氣等在一系列的氣相化學反應以及表面化學反應均對薄膜成長速率以及均勻性有相當的影響。為了成長出高品質薄膜，了解其中的熱流場以及化學場機制是必要的。本研究將利用Ansys-Fluent進行數值模擬分析，以了解各項製程控制因素對薄膜成長速度及薄膜均勻性之影響。本研究先利用2D模擬腔壓100torr~760torr，轉速100~500rpm操作環境下腔體內熱流場情形，發現操作壓力在100torr以上流場較為混亂。而過高的轉速亦會造成流場混亂。接著在3D模擬中將操作環境參數縮小至100torr下，0~200rpm。由結果顯示，在低壓下腔體內的流場較為均勻，而適當提高轉速可增加氣體擴散性，增加沉積速率。

In the metalorganic chemical vapor deposition (MOCVD) process to grow GaN and p-GaN thin film on silicon wafer, a sequence of gas-phase and surface-phase reactions between Ga(CH3)3, Cp2Mg, and NH3 precursors occurred, which have a great influence on the film uniformity, composition and growth efficiency. To grow high-quality films on a substrate in MOCVD chamber, it is crucial to understand the basic mechanism of gas flow, thermal distribution, and chemical reactions. The simulation process in this paper was worked with Ansys-Fluent to understand the influence of each growth epaxity factor on the growth rate and uniformity. This study first simulates the thermal and gas flow field distribution in the chamber with 100 torr~760 torr atmosphere and 0~500 rpm rotational speed. Simulation results showed that gas flow field distribution under 100 torr is more chaotic than other conditions. Next, in 3D simulation, we reduce the interval of operational condition to 100 torr atmosphere and 0~200 rpm rotational speed. The results indicated that gas flow field distribution in the chamber is more uniform under low pressure. In conclusion, by raising rotational speed appropriately, it may enhance the diffusion of gas flow in the chamber and increase growth rate.