以矽甲烷/氨氣/氮氣電漿沉積氮化矽薄膜之二維模型研究

本研究建立氮化矽之電漿化學氣相沉積反應機制，先以零維反應器模型求解，接著再導入二維軟體中，建立最佳化之二維模型，探討不同操作參數對製程之影響。首先利用本實驗室先前所建立之SiH4/NH3電漿反應機制進行求解，發現在進料添加氮氣後與實驗結果之趨勢有所誤差，故簡化並精進原始模型，建立一套SiH4/NH3/N2電漿反應機制，包含38項氣相反應與17項表面反應，使模型預測與實驗結果之趨勢吻合。接著利用物種生成速率分析(Rate-of-production Analysis)探討影響鍍膜速率之因素，主要由4種鍍膜物種(SiH3、SiH2NH2、SiHNH2及Si(NH2)3)來控制氮化矽之鍍膜速率與膜材之氮矽比。最後將上述所建立之氮化矽反應機制匯入商業軟體CFD-ACE+，以二維模型求解。研究發現，在單一RF周期內，電子溫度受電場的經時變化影響甚巨，但電子密度及各物種濃度不隨時間而變；進料加入氮氣後電漿鞘層厚度由0.5公分降至0.2公分，電子溫度降低但電子密度提高，因氮氣稀釋了鍍膜物種濃度而使鍍膜速率降低，但有助於提升鍍膜的均勻性；改變SiH4的進料方面主要對鍍率有很大的影響，而增加NH3的進料流量對於氮矽比則有明顯的提升。提高功率或壓力皆可提升鍍膜速率，但不影響氮矽比，對鍍膜均勻性亦無太大影響。

關鍵字

電漿化學氣相沉積；氮化矽；鍍膜均勻性

並列摘要

This study established the reaction mechanism of plasma enhance chemical vapor deposition (PECVD) of silicon nitride (SiNx). First, a zero-dimensional reactor model was used to refine the reaction steps and rate constants, then the refined reaction mechanism was used to establish an optimized two-dimensional model and explore the influence of various operating parameters on the SiNx film deposition process. This refined mechanism for SiNx deposition by SiH4/NH3/N2 plasma includes 38 gaseous reactions and 17 surface reactions. It is found that the zero-dimensional model predictions are consistent with the experimental results. The Rate-of-Production analysis shows that four main deposition precursors (SiH3、SiH2NH2、SiHNH2 and Si(NH2)3) control the growth rate and the N/Si atomic ratio of the deposited film. Finally, the silicon nitride reaction mechanism established above was incorporated into the commercial software CFD-ACE+ and solved by a two-dimensional model with 4026 total mesh. It is found out that in one RF cycle, the temperature of electrons is greatly affected by the changes in the electric field over time, but the electron density and the concentration of each species do not change with time. When nitrogen is added in the feed gas, the thickness of the plasma sheath is reduced from 0.5 cm to 0.2 cm. The electron temperature decreases but the electron density increases. Although the deposition rate decreases due to the dilution of the deposition species by nitrogen addition, but the uniformity of the film improves significantly; Changing the feed of SiH4 mainly impacts the deposition rate, while increasing the feed flow of NH3 has a significant increase in the N/Si atomic ratio. Increasing the power or pressure can increase the film deposition rate, but it does not affect the N/Si atomic ratio. And it does not have much effect on the uniformity of the growth.