燈源加熱之垂直快速加熱爐內流場觀測研究：進氣多孔板之效應

Abstract

本篇論文利用實驗流場觀測方法研究在燈源加熱之垂直快速加熱爐內進氣多孔板對於八吋晶片上方流場之效應。在這次的研究中，我們用厚銅板來取代晶片以便獲得較佳的溫度均勻性，同時，我們也利用乾空氣來替代反應氣體。在這次的研究裡，我們使用了三種不同的進氣多孔板來做比較。首先，我們在一薄石英圓盤上穿了921個大小均一的孔洞，並將之稱為單一進氣多孔板。接下來，第二種多孔板由兩個穿孔的石英圓盤所組成，我們並將之稱為雙進氣多孔板。在上方的多孔板的孔徑由小而大組成，並與下方均一孔徑的多孔板有十公分的間距。最後，第三種多孔板是由一個均一孔徑的多孔板與一個環形塊狀物所組成，我們並將之命名為修正型進氣多孔板。在本實驗中的物理參數包括銅板和入口空氣的溫差與入口空氣的流量。此外，關於在混合爐體內的進氣角度亦做了相關的試驗。 從測試段所拍攝的側視圖顯示三個典型的流場結構。在低浮慣比(buoyancy-to-inertia ratio)時，整個反應爐體被衝擊塞柱流(plug flow)所佔據，此時流體直接衝擊到銅板，因此銅板上方並沒有其他渦流的產生。反之，高浮慣比時，整個反應爐體被一對巨大的浮力驅動流(buoyancy-induced flow)所支配。而當浮慣比處於兩者中間時，一個由衝擊塞柱流和浮力驅動流所組成的混合渦流 將會產生。此外，改變進氣角度對於爐體內流場結構只有輕微的影響。比較上述的三種進氣多孔板，我們發現相對於使用單一進氣多孔板而言，雙進氣多孔板在部分的情況下可以輕微的減少浮力驅動流的強度和尺寸大小。此外，使用修正型進氣多孔板可以明顯的壓制浮力驅動流的產生。在中浮慣比時，浮力驅動流被抑制而產生所謂的衝擊塞柱流。這種有效的流場穩定現象導因於我們置入的環形塊狀物，可以增加進氣氣流的速度以及減少爐體外圍區域的局部雷利數(Rayleigh number

The effects of the showerhead on the recirculating air flow in a model lamp heated vertical rapid thermal processor for an eight-inch wafer is extensively investigated by experimental flow visualization. A thick copper disk is used to simulate the wafer for its better uniformity of surface temperature and air is used to replace the reactant gases in the present study. Three different showerheads are tested in the present study. The first showerhead is a thin circular uniformly perforated quartz plate, designated as the single showerhead. The second showerhead consists of two perforated plates and is designated as the double showerhead. The top plate has nonuniform perforations, while the bottom one has uniform perforations with a separating distance of 10 cm between them. The third showerhead is made up of a uniformly perforated plate and an annular block placed right below the outer edge of the plate, which is named as the modified showerhead. The physical parameters in the experiment include the temperature difference between the copper plate and inlet air and the inlet air flow rate. In addition, the angle of the air injected into the mixing chamber is also tested. The side view flow photos taken from the processor reveal three typical flow patterns. Specifically, at lower buoyancy-to-inertia ratios, the plug flow dominates in the processing chamber and no vortex roll appears above the copper plate. While at high buoyancy-to-inertia ratios the chamber is occupied by a big buoyancy-induced circular vortex roll. A mixed vortex flow consisting of both a plug flow and a buoyancy-induced vortex roll prevails at intermediate buoyancy-to-inertia ratios. Besides, the change of the gas injection angle is found to only slightly affect the recirculating flow in the chamber. Compared with the processor installed with single showerhead, the use of the double showerhead can slightly reduce the strength and size of the buoyancy-induced flow for some cases. Moreover, using the modified showerhead can significantly suppress the buoyancy induced flow. At intermediate buoyancy-to-inertia ratios the buoyancy induced vortex roll can be completely eliminated, resulting in a plug flow. This effective flow stabilization is due to the acceleration of the gas flow as well as the reduction of the local Rayleigh number in the outer zone of the processing chamber by the installation of the annular bloc