淺溝槽內氧化層蝕刻

Abstract

由於半導體製程廣泛使用光阻覆蓋方式，去定義並獲得所需圖案。在矽槽回填及化學機械研磨製程後，欲在淺溝槽內蝕刻二氧化矽，則須使用一道光罩流程以光阻覆蓋來保護主動區。本論文主要以調配蝕刻參數方式來提高對主動區上氮化矽蝕刻選擇比，進而取代光阻使用。減少一道光罩使用而直接以主動區上氮化矽當作一遮蔽層，此概念可縮短製造流程及生產成本，也是此實驗目標及方向。 本實驗在提高淺溝槽內二氧化矽對主動區上氮化矽之蝕刻選擇比，蝕刻製程參數中，氣體流量比例以及壓力是主要影響實驗因子。在低壓條件下調整CHF3對CF4氣體流量比例，在兩種製程氣體比例為4:1，蝕刻時間固在30秒的條件下，二氧化矽對氮化矽蝕刻選擇比最高，經由實驗試片在電子影像上的驗證，蝕刻淺溝槽內二氧化矽180nm深度的同時，氮化矽厚度仍保有9.2nm高度，表示減少一道光罩使用是可行的。

Due to photo resist is widely used in pattern definition with semiconductor process, we need photo resist to protect active region when silicon dioxide inside the shallow trench isolation etch .The thesis studies the high selectivity in oxide over nitride with different process parameters split. The hard mask layer will use silicon nitride instead of resist material. The concept of mask less will diminish process flow and production cost. To increase the etch selectivity for silicon dioxide inside shallow trench isolation to silicon nitride in active region, the parameters of etch will be properly used and adjusted in the experiment. The key factors are process gas ratio and pressure. To fine tune the gas ratio of CHF3 to CF4 with low pressure condition, it will get the highest etch selectivity when the gas ratio value is 4.The monitor wafers will be used to check remain nitride and oxide loss. From the SEM image, we find the silicon nitride in active region will over 9.2nm and silicon dioxide loss in shallow trench isolation is near 180 nm. No mask used in the experiment is available.