燈源加熱之八吋矽晶圓快速加熱處理器之熱傳及氣流實驗研究

Abstract

本篇論文係利用自行設計的燈光加熱之快速加熱處理器，藉暫態溫度的量測及流場之觀測來研究一個八吋矽晶圓在快速加熱過程(Rapid Thermal Processing)中處理器爐體內浮力驅動的熱流場特性。 本實驗探討在晶圓下方所加的高傳導係數銅板對晶圓等溫性的影響，以及研究多孔性平板(porous plug)在不同孔洞大小對處理器爐體內流場的影響。本實驗亦對於單管垂直進氣方式之爐內在加溫及降溫過程中不同晶圓溫度、不同噴嘴至晶圓距離、不同進氣流量及不同爐內壓力對流場的影響做了詳細的探討。此外，對一個固定晶圓溫度下對不同進口流量、噴嘴至晶圓距離及處理器壓力對流場形成的暫態過程均作有系統研究。依據我們的實驗結果顯示在晶圓下方加入一塊銅板可以有效地降低其溫度的非均勻性。 當使用一個較細小孔之多孔性平板作為整流板時，在處理器中將產生較佳的流場分佈。對一個單管噴流噴至晶圓表面在近似穩定的昇溫及降溫過程中，浮力使得流體在靠近晶圓表面附近產生一個圍繞爐軸線的漩渦（vortex roll ）。當溫度升高時，較高的浮力與慣性力比值使得漩渦產生扭曲及不對稱。當溫度高到某一階段，高的浮力與慣性力比值使進來的噴流無法碰觸晶圓的表面。

An experimental lamp heated, rapid thermal processor (RTP) for processing an eight-inch single silicon wafer was established in the present study to investigate the buoyancy driven thermal and gas flow characteristics in the processing chamber by combined transient temperature measurement and flow visualization. Air is chosen as the working fluid to replace the insert gases intending to lower the experiment cost. Experiments were carried out to explore the effects of placing a highly conducting copper plate beneath the wafer on the uniformity of the wafer temperature and effects of the hole size in the showerhead on the resulting flow in the processing chamber. Moreover, the changes of the flow pattern in the processor with the gas entering into it through a small pipe and injecting vertically downwards onto the wafer were examined for various wafer temperatures and gas flowrates during the quasi-steady heating and cooling processes. In addition, the transient flow formation for the wafer heated at a given temperature for various flowrates. Results have been obtained and they indicated that adding the copper plate can effectively reduce the nonuniformity of the wafer temperature. Besides, using a showerhead with finer holes in it results in a better flow distribution in the processor. For the gas jet impinging on the wafer during the quasi-steady heating and cooling processes, the buoyancy induces a circular vortex roll surrounding the axis of the chamber right on the wafer when it is at low temperature. At high buoyancy-to-inertia ratio the vortex roll is highly deformed and nonaxisymmetric. As the buoyancy-to-inertia ratio is high enough, the inlet gas jet could not touch the wafer surface and is deflected away. At low buoyancy the generation of new roll by splitting from the original roll was noted during the transient flow formation processes.