無塵室空氣酸鹼污染物的分析及其對元件缺陷影響之研究

Analyses and Effects of Acids and Bases Airborne Contaminants in Cleanroom on the Defects of Wafer Devices

曾麗玲(Li-Lin tseng)

指導教授 ： 林錕松

元智大學/工程學院/化學工程與材料科學學系/碩士(2007年)

https://doi.org/10.6838/YZU.2007.00276

摘要

國際半導體技術藍圖(ITRS)預估至2010年關鍵尺寸將朝45nm邁進，而氣態分子污染(Airborne molecular contamination, AMC)控制為關鍵技術之一。本研究針對四大類無塵室氣態分子污染物中之酸類及鹼類污染物進行研究探討，藉由離子層析儀(IC)、離子移動式光譜儀(IMS)及傅立葉轉換紅外線光譜(FTIR)於晶圓代工廠的無塵室環境測試，探討無塵室空氣中的酸鹼性分子污染物之濃度分佈與污染的來源。應用場發掃描式電子顯微鏡(FE-SEM)、穿透式電子顯微鏡(TEM)進行產品測試，期望進一步了解酸鹼性分子污染物對製程產品的影響。
以超純水為採樣介質、700 mL/min之取樣流速，再使用離子層析儀進行分析，藉由微量標準氣體產生器比較驗證，此方法之氟離子與氨的回收率均可達75~125%。研究發現9.4%的蝕刻機台在機台維護保養時酸性污染物的濃度偏高是四大模組中污染比例最高的。製程晶圓污染測試，則發現有47.8%的蝕刻機台所產出的晶圓產品會逸散高濃度的腐蝕氣體於環境當中，沉積高濃度酸性污染物的晶圓暴露於環境中，酸性污染物會隨無塵室的氣流方向擴散，擴散的面積約為150 × 30 cm2。此外機台水洗塔、管路洩漏及製程粉末副產物等污染源也不容忽視。
在無塵室酸鹼性污染物的影響部份，研究發現無塵室環境的氟離子濃度在5~10 ppb左右的環境下6 h，晶圓金屬層會造成數百個腐蝕的缺陷，隨著暴露時間增加，腐蝕的缺陷同時上升。研究發現半導體廠F-濃度嚴格管制，低濃度的氟離子對硼矽玻璃纖維威脅性不大，然而，蝕刻殘留去除液也會使玻璃纖維劣化，引發掺雜類的硼污染，並且擴散至全廠，使用鹼性化學濾網可暫時性降低硼濃度，以鐵氟龍取代硼矽玻璃纖維濾網後，全廠硼污染之污染區及爐管區的狀況可以明顯改善分別為60-70及80-90%。
在污染源的控制部份研究發現，使用局部抽氣管、開啟反應室前使用氣體清除反應室殘留物、零件隔離等方式，可有效降低機台維護保養時環境的腐蝕性氣體濃度。在晶圓出口處加裝一聚氯乙烯材質的隔離裝置，並安裝抽氣管路導入中央處理系統，可減少盛裝的晶圓盒吸附過高的腐蝕性氣體，降低交叉污染機率。無塵室內部氨氣洩露時，利用稀釋控制概念於洩露發生源最近的位置，使用除煙裝置，加速置換無塵室的污染空氣，可酸短無塵室環境污染約1/2的時間。選擇適當的化學過濾器並安裝於適當的位置可有效去除氣態分子污染物，另對於水溶性的氣態分子污染物可選擇空氣洗滌器(Air washer)去除污染，其平均去除效率約80%。

關鍵字

無塵室 ； 酸鹼性氣態分子污染物 ； 硼污染 ； 金屬線腐蝕 ； 超高效率濾網 ； 化學濾網 ； 空氣洗滌器 ； 玻璃纖維濾網。

並列摘要

International Technology Roadmap of Semiconductor (ITRS) predicts the critical dimension will go to 45nm in 2010 and airborne molecular contamination (AMC) control is a critical technology. Therefore, the main objectives of the present study were molecular acids (MA) and molecular bases (MB) in the 4 type’s contaminants. Contamination distribution and their contaminative source in the cleanroom were investigated by ion chromatography (IC); ion mobility spectroscopy (IMS) and fourier transform infrared spectroscopy (FTIR). The deleterious effects on production were measured by field emission microscopy (FE-SEM) and transmission electron microscope (TEM).
The flow rate was 700 mL/min and sampling medium carried out by ultrapure water then used ion chromatography to measure the contamination. The analytic method of contaminates was verified with standard permeation tube. The recovery rates were 75~125% in the floride and ammonia. Etch of equipments were showed highest contaminated rate after the investigation in 4 modules. 9.4% of equipments outgased high concentration acids from equipment during the engineer implemented performance maintain (PM) in etch module. 47.8% equipment of etch produced high concentration of corrosive gas with wafer and outgased to environment during production wafer. Acidic contaminants diffused with air flow after deposited high acidic concentration wafer exposed to environment. Diffusion area was around 150 × 30 cm2. In addition byproduct and leakage from scrubber, piping could be neglected.
In the effects of acids and bases contaminants section, the metal layer of product was caused more than hundreds corrosive defects after production exposed 6 h in the cleanroom environment with fluoride concentration around 5-10 ppb. The corrosive defects raised with increasing the production exposed time. Low concentration F- could not attack glass fiber since F- concentration control within narrow range in the semiconductor factory. Glass fiber was damaged by stripper and caused boron contamination around the fab. Boron concentration was decreased temporarily after used cation chemical filter. Boron contaminated was improved obviously after used PTFE filter to replace glass fiber. The boron improved rate in source and diffusion areas were 60-70 and 80-90%.

並列關鍵字

Cleanroom ； Airborne molecular contamination ； Boron contamination ； Metal corrosion ； ULPA ； Chemical filter ； Air washer ； Glass fiber.

參考文獻

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