ArF光阻在半導體微影製程之缺陷硏究

Abstract

本論文研製的目地在於深次微米時代的來臨後，ArF光阻製程漸成為微影製程的主流，目前一套完整的深次微米半導體製程將包括了40道以上的微影製程，且其中有約一半的製程屬於ArF光阻製程，所以ArF光阻製程的重要性可以說是與日俱增。一般我們可以分為三個階段來處理光阻產生的缺陷，第一個階段為材料製造階段，因未適當的處理材料不純物或材料配方未最佳化而造成的缺陷，我們可由原物料的純度控制及配方比例的調配來改善;第二個階段為缺陷反應生成階段，為顯影過程中光阻與顯影液所產生的副產物，這些副產物也就是後來缺陷的來源；第三階段為缺陷清除階段，就是要將所有不該殘留在晶片表面的雜質清洗乾淨。本論文將針對第一階段及第三階段所產生的問題做探討 當光阻中較大的樹脂聚合物又無法溶於所搭配的溶劑時，就會產生沉澱物而造成光阻的橋接;同時也可能因為不易溶沉澱物在旋轉塗佈時造成光阻槽的污染。實驗結果發現，將小孔徑光阻的濾心預溼加上兩段式的過濾程式及新的光阻溶劑可有效的控制光阻缺陷。比較傳統的顯影方式(顯影頭靜止噴灑+晶片微轉)與(顯影頭掃描噴灑+晶片靜止)到最新的(顯影頭掃描噴灑+晶片快速旋轉)，實驗結果顯示顯影噴灑頭與晶片同時移動轉動，可獲得最佳的缺陷移除效果，且可節省50%以上的顯影液用量。若再加上最新的清洗架構(PDR程式)，清洗效果超乎想像的好，可減少至少2/3以上的清洗時間，且順利的通過產品良率驗證。

Semiconductor had stridden forward to sub-micron generation now, the line & space become smaller and smaller, the fine pitch result will induce some process issue. This paper will probe into ArF process defect, which comes from photo resist material & developer recipe not optimized. Generally we can handle the photo resist relative defects by 3 steps. The first step is material manufacturing stage, we can improve the photo resist quality by optimizing the manufacturing process flow & filtration system; the second step is defect generation stage, the defect comes from the byproduct of resist & developer solution, it’s very difficult to control the byproduct generation; the third step is the defect cleaning stage, we can remove the defect by optimizing clean recipe. This paper will try to resolve the defect issue in step1 & 3. The root cause of ArF resist defect from material is the bad solubility between solvent & polymer, when the large size polymer exists in photo resist and can’t be solved by solvent, the precipitate will be generated and induce pattern bridge defect. In the meantime, the insolubility material will also induce coater cup contamination. Experiment results show the smaller filter pore size, pre-wet filter, 2 step filtration & new resist solvent can efficiently improve the defect. This paper will also introduce a new developer method (Statically dispense developer & high speed wafer rotation), which can efficiently reduce >50% developing volume compared with traditional method. The new developer method can also achieved very low defect level at short developer process time. Almost 2/3 process time is reduced by this new method. We believe this new concept will be the standard format for future developer process recipe.