氮電漿處理低介材HSQ應用於銅金屬製程之薄膜特性研究

Abstract

摘要 本論文重點在於探討銅金屬製程與低介材HSQ（Hydrogen Silsesquioxane）薄膜之間的交互影響。研究結果發現： 1.旋塗完成之HSQ薄膜經高溫爐管熱固化一小時候，厚度會提昇至6542 Å，這是因為HSQ的多孔性結構之形成所致。折射率方面，也因為熱固化程序改變了HSQ薄膜的結構，使其重新鍵結，形成多孔性結構，由剛塗佈時的2.32降為1.75。 2.經過400℃熱固化處理後，在1050 ㎝-1處的Si-O鍵結收峰有增強之勢。此時為HSQ薄膜由熱固化前之籠狀結構（Cage-like）變為網狀結構（Network）。 3.經電漿處理之HSQ薄膜： （1) N2電漿處理直接於薄膜表面取代形成含氮之薄膜表面比原本具多孔性的HSQ薄膜更為緻密，而造成厚度稍有減少。 （2) 經N2電漿處理的薄膜表面，確實有防止HSQ與外界水氣作用之效果。 （3） 四個參數（溫度、時間、功率、壓力）對表面粗糙度之影響並不是非常顯著。 （4） 隨著電漿處理時間增加，推測含氮鍵結之成分比例亦越大，因而造成薄膜本身應力增加，基材對薄膜本身之拉伸應力則相對提高。 （5） 由XPS分析發現於Binding Energy約400 eV時，有氮成份的鍵結，而且根據文獻判斷應為SiNx鍵結無誤，並且配合XRD觀察，於2θ＝27度及33度可觀察到氮矽化合物之繞射峰，證明N2電漿確實與HSQ薄膜表面產生化學作用。 4. Cu／HSQ（N2， Plasma）／Si 之結構特性探討： （1）經400℃回火程序銅薄膜表面大致上可維持相當良好的表面性質，並無明顯折出物或局部破裂之現象。 （2）回火溫度400℃處理後之試片，片電阻均有大幅下降的現象，此推測為熱回火處理程序，而引發銅膜之再結晶，使得銅膜趨於較佳之Cu （111）晶面結構而提高其導電度。 （3）為N2電漿處理之HSQ薄膜之XRD圖，觀察結果顯示，繞射峰相當平緩代表結晶粒非常細微，且有許多非結晶成分（Amorphous Component）。

Abstract The interaction between copper metallization process and low-k material HSQ was studied. The results were as follows: 1. Because of the forming of HSQ porous structure, the thickness of the HSQ increased from to Ǻ by curing process. The index of refraction also decreased from 2.32 to 1.75 (under 633 nm). 2. After the curing at 400℃, Si-O peak（FTIR）at 1050 cm-1 increased. This is an indication that HSQ structure changed from cage-like to network。 3. HSQ after nitrogen plasma treatment 1. Because of the nitrogen-content surface, HSQ became more dense, therefore, the thickness decreased. 2. The nitrogen-content surface retarded HSQ from reacting with the moisture surrounding. 3. The influence of four parameters (temperature, time, power, and pressure) to the roughness of the surface is not obvious. 4. With the increasing of plasma treatment time, the proportion of Si-N bond increased, which caused the increasing of the stress of the HSQ itself. 5. From the ESCA, Binding Energy at 400 eV (N, 1s), according to the documents, it belongs to SiNx bonding. Assisted by the observation of XRD, there are diffraction peaks at 2θ＝27 and 33 degree, which proved N2 plasma really has a chemical reaction with HSQ film. 4. The characteristics of Cu/ HSQ (N2, Plasma)/ Si structure: 1.By the procedure of 400℃ curing, the surface of the copper maintained the quite good quality and didn’t have any obvious defects or cracks. 2.After 400℃ curing, the sheet resistance of this muti-level structure substantially lowered. It is suggested that re-crystallization of copper formed a better crystal structure, therefore, raised its electrical conductivity. 3.From the observation of the XRD graphies, the HSQ after N2 plasma treatment showed the flatten diffraction peak which is a indication of the existence of small crystalline grain and a large amount of amorphous component.