垂直單晶片 RTP 處理爐內流場觀測及熱傳量測研究

Abstract

本篇論文是在一燈源加熱之八吋垂直式 RTP 處理爐內進行流場觀測及溫度場的量測，藉以了解處理爐內流場之變化及熱傳現象。為了改善晶圓上溫度不均勻的分布，我們設計將一高熱傳導係數之銅板放置於晶圓下方。我們也將改變進氣口到晶圓的距離及在不同流量下來研究銅板對晶圓均溫性的影響。另外，我們也將對單一垂直管進氣 (Single gas jet) 方式，在不同溫度、不同流量的考量下，對流場在升溫及降溫的過程中的變化作詳細的研究。從晶圓上之選定點所量測到的暫態溫度數據可發現在晶圓下方加入一片高熱傳係數的銅板，可改善晶圓上溫度的不均勻分佈；較均勻的流場分佈也可以造就晶圓上較均勻的溫度分佈。在單一垂直管進氣時，升溫及降溫過程中由浮力所造的渦流將於氣柱兩側形成；而在較低溫時，靠近壁面兩側位置亦會形成渦流。此外，在較高浮力比慣性力比(buoyancy-to-inertia ratio)時，氣柱兩側的渦流會變得較不對稱，且會上下擺動並繞著氣柱旋轉。當浮力的效應變得更強時，氣柱本身將發生擺動，甚至到達不了晶圓表面。

Single wafer, rapid thermal processing (RTP) is known to play an important role in the recent microchip manufacturing. In this study a lamp heated vertical RTP processor for an eight-inch wafer is used to investigate the thermal and flow characteristics in the processor by conducting transient temperature measurement and flow visualization. The effects of placing a high thermal conductivity copper plate beneath the wafer to improve the uniformity in the wafer temperature distribution for various jet-to-wafer distances were also studied. Moreover, the changes of the flow patterns in the processor with a gas jet impinging onto the wafer during the quasi-steady heating and cooling processes for various wafer temperatures and gas flow rates were examined in detail. The data from the transient temperature measurement at selected locations on the wafer indicated that adding the copper plate can effectively reduce the nonuniformity of the wafer temperature and a more uniform flow field can result in a more uniform wafer temperature. For the single gas jet impinging on the wafer during the ramp-up and ramp-down processes, the buoyancy induces a circular vortex roll surrounding the gas jet and another vortice forms near the side wall of the processor at low wafer temperature. Besides, at high buoyancy-to-inertia ratio the vortex roll becomes deformed and nonaxisymmetric, and moves up and down and rotates around the gas jet. As the buoyancy force is high enough, the gas jet swings in time and the jet can not even touch the surface of the wafer before it is defleted away.