晶圓在快速熱程序爐中之熱傳及熱應力分析

Abstract

本文主要探討在快速熱程序爐（RTP）中，晶圓受燈源輻射加熱的熱傳過與熱應力分析。晶圓由於邊緣散熱效應的影響，因而造成溫度的不均勻，並引起熱應力而造成晶圓的塑性變形。因此必須先瞭解晶圓的熱傳行為方能進而探討晶圓的熱應力。 本文分析晶圓受熱之物理模式而建立出在此模式下的熱統御方程與應力統御方程，並利用有限差分的數值方式求得晶圓之溫度的分佈與應力場。文中先就均勻輻射加熱與高斯曲線輻射加熱來說明晶圓因本身輻射性質而產生的邊緣效應。並討論不同的均勻輻加熱量造成的邊緣效應影響與熱應力行為。依據邊緣效應所展現出的特性，本文提供一均溫模式輻射加熱曲線，以達到在任何時刻晶圓均不會發生塑性變形的要求。最後就晶圓尺寸之不同來做溫度與應力的分析。 結果顯示由晶圓邊緣散出的能量，將導致靠近晶圓邊緣附近的區域的溫度明顯降低。由高斯分佈與均勻加熱曲線之比較可知晶圓表面的熱通量形式會對晶圓表面的溫度分佈造成很大的影響。最後的結果顯示邊緣效應對晶圓厚度尺寸的影響較半徑尺寸來的大。

This surdy investigates heat transfer and thermal stress of wafer in a rapid thermal processing -type oven used for semiconductor processes. Thermal st11resses that are induced by temperature nonuniformity due to a heat loss at the edge of the wafer are calculated and compared to yield stress of silicon at the appropriate temperature and strain rate. The model in this study includes radiant heat transfer to the wafer from the lamps, heat conduction within the wafer, adn emission of radiation from the wafer. The finite-difference scheme was employed to solve the two-dimensional heat conduction equation, from which the radial temperature profile could be simulated . The uniform and Gaussian distribution heat flux were also used to demonstrate the edge effect and discuss the relation between the temperature profile and stress field . In this study, the uniform-temperature model was proposed to improve the temperature uniformity and reduce thermal stresses of the wafers in the transient behavior. Finally, the temperature vand thermal stress of wafers in different sizes are also studied. The results show that there is a heat loss at the edge of the wafer which produces a dcrease in temperature toward the edge. Comparison between Gaussian distribution and uniform heat flux show that the effect of the radiant heat flux distribution over the wafer in temperature uniformity is important. Edge effect of wafer thickness is more pronounced than that of wafer radius.