半導體金屬蝕刻機台於預防維修時之污染物逸散控制

Abstract

半導體金屬蝕刻製程主要使用Cl2(氯氣)、BCl3(氯化硼)等氣體，以高能電漿(plasma)離子化產生自由基(free radicals)後使其與晶圓表面之鋁反應將多餘之鋁蝕刻而產生溝槽。為維持晶圓生產良率須定期進行腔體的預防維修保養，主要清除反應腔壁所附著製程副產物。在打開密閉反應腔及擦拭腔壁時會產生極刺鼻味道且含有HCl、HCN、CNCl等毒性氣體，會逸散至潔淨室，所造成勞工健康危害。 本實驗主要目的在研究金屬蝕刻預防維修保養擦拭反應腔時，建立良 好反應腔(內徑30.5cm x 21.5cm)污染物逸散控制方法與探討其控制效率。實驗以固定流量的1000 ppm追蹤氣體SF6在腔底連續釋放，以了解反應腔的氣罩效率或反應腔上方全開，在側邊視窗孔抽氣時對污染物逸散的控制效率。在氣罩的控制效率實驗時，在反應腔底SF6流量為5 LPM釋放，腔面外加上本實驗所設計氣罩並與潔淨室內低真空抽氣軟管銜接抽氣控制；利用反應腔側邊抽氣的控制效率實驗時，反應腔底的SF6以1 lpm、5 lpm、8 lpm、10 lpm釋放。以上兩種實驗的氣罩或側邊抽氣流率均為3130±68 lpm。污染物量測儀器為FTIR，量測點包含呼吸帶與低真空抽氣軟管末端。抽氣效率定義為SF6於腔底部釋放與低真空軟管前段釋放時，兩者在低真空抽氣軟管末端SF6平均濃度之比值。 實驗結果顯示在反應腔於進行定期預防保養維修擦拭時，於反應腔視窗孔處進行抽氣，可有效的控制危害性的氣體逸散控制，在呼吸帶測得的追蹤氣體SF6濃度均低於FTIR之偵測下限。反應腔全開之抽氣控制效率最高98.8 %，與使用氣罩時之控制效率97.5 %不相上下。因此在反應腔全開之情況下，在側邊的視窗孔抽氣，可有效的控制氣體污染物逸散，此方法可以廣泛的應用至半導體金屬乾蝕刻機台的預防保養作業。

The main gases in metal etching are hydrogen trichloride and boron chloride in semiconductor manufacturing processes. The process gases are ionized to form free radicals by plasma, which etch off aluminum film of the wafer surface. To increase product yield, the by-product deposited on the reactor chamber must be cleaned during preventive maintenance. When we open and clean the chamber, odor as well as toxic gases(e.g., hydrogen chloride, cyanogen chloride, hydrogen cyanide, etc.) are released. These toxic gases are diffused into the clean room and pose heath threat to workers. The main purposes of this study are to develop a method to control pollutant dispersion and to measure the control efficiency during the chamber preventative maintenance of a metal etcher. The research method is to release a 1000ppm SF6 tracer gas at the bottom of the chamber. The hood control efficiency was measured when the SF6 flow rate was 5 LPM and the total venting flow rate of 3130±60 LPM. The control efficiency by side drafting near the opening of the chamber was measured at the SF6 flow rate of 1,5,8,10 LPM. The venting flow rate was also 3130±60 LPM. The SF6 concentrations at the breathing zone and the end point of the venting pipe were measured by an extractive FTIR. The control efficiency is defined as the ratio of the measured SF6 concentrations at the end point of venting pipe to that in the chamber. The results show that the toxic gases dispersion can be controlled effectively by venting air at the window of the chamber. The SF6 concentration at the breathing zone was found to be lower than the detective limit of the FTIR. The measured control efficiency by side vacuuming of a fully opened chamber is 98.8%, which is comparable to 97.5% by using a hood. Therefore, the side vacuuming method is an effective pollution dispersion control method during the preventive maintenance of the metal dry etcher in the semiconductor factory.