- 學位論文
六氟化硫電漿對氮化矽蝕刻之參數優化研究及光譜分析
Parametric Study and Spectral Analysis of SF6 Plasma for SiNx Etching
摘要
本研究探討SF6電漿蝕刻SiNx製程，包括改變電漿功率、SF6/He的氣體配比並加入陰電性氣體O2，探討其對TFT之元件保護層SiNx的蝕刻速率之影響，並利用電漿放射光譜儀對SF6/He、SF6/He/O2電漿中各物種濃度變化及SF6解離率進行分析，探討SiNx蝕刻速率之變化與電漿物種濃度之關連性。 研究發現，提高電漿功率時，蝕刻速率隨之上升；若增加電漿中SF6的流量，則F原子濃度增加且與蝕刻速率成正相關。另在總流量固定下添加陰電性氣體O2後，則會產生增加蝕刻速率的效果，但在不同的O2/ SF6流量配比下，則會有不同的反應機構，可分成三部分：(1) O2/ SF6流量配比值很小時，O2可幫助SF6的解離，此時蝕刻速率比未添加O2時為大。(2)當O2/ SF6流量配比值大於0.2到趨近於1的區間時，此時因SF6大量解離形成F原子，故蝕刻速率是最高的；但同時電漿中O原子也在增加且易與SiNx膜面形成SiOx or SiNxO(y-x)，而O原子增加愈多則使F原子愈不易進行蝕刻反應，故O2/ SF6比值接近1時蝕刻速率開始趨緩。(3) 當O2/SF6配比值大於1時，蝕刻速率下降。因O2大量增加，解離的F原子與O2發生碰撞並形成OF，降低F原子濃度，而導致蝕刻速率的降低。由此中可知，當添加O2後，O2/SF6的流量比值= 0.2 ~ 0.8之間，可得到最佳的蝕刻速率。
並列摘要
In this study, we will research into the etching process of the SF6 plasma on SiNx, including how the changes in the plasma power and the SF6/ He flow ratio values, as well as the addition of the electronegative gases O2 would affect the etching rate of the TFT components protective layer, SiNx. By using the Optical Emission Spectroscopy, the concentration variations of all the elements in SF6/ He and SF6/He/O2 plasma as well as the dissociation of SF6 could be analyzed, so as to further study the changes of the SiNx etching rate and its correlation with the concentrations of the plasma elements. According to the study, when the plasma power increases, the etching rate goes up, too. If the flow rate of SF6 in the plasma increases, the concentration of the F atoms rise and so in the proportion to its etching rate. If electronegative gases O2 are added into the plasma, it will speed up the etching rate. However, under different O2/ SF6 flow ratio values, the reactions will be varied and can be divided into three parts: (1) When the O2/ SF6 flow ratio value is small, O2 can help the dissociation of SF6 and the etching rate is greater than it was when O2 wasn’t added. (2) When the O2/ SF6 flow ratio value is greater that 0.2 and close to 1, and more F atoms are formed due to a large number of SF6 dissociation, the etching rate is the highest; in the meantime, the O atoms in the plasma also increase and may react with the SiNx film to form SiOx or SiNyO(y-x). The more the O atoms are, the more difficult the F atoms are able to carry out the etching reaction. Consequently, it can be inferred when the flow ratio value is close to 1, the etching rate starts to slow down. (3) When the O2/ SF6 flow ratio value is greater than 1, the etching rate goes down. Due to a significant increase in O2, and the formation of OF resulting from the dissociation of the F atoms colliding with O2, the concentration of the F atoms lowers down and leads to a lower etching rate. Thus, the conclusion can be drawn. When O2 is added, and the flow ratio value of O2/SF6 is between 0.2 and 0.8, the best etching rate can be obtained.