常壓下在Si(100)基材上選擇性沈積銅膜之研究

Abstract

選擇性沉積各種薄膜在不同基材上是重要的微細加工技術之一，用以製造具有三度空間結構之電子元件，本研究使用Cu（hfac）2為反應物，Ar+3%H2和乙醇當作還原劑，並以汞燈為光源，使用光分解化學氣相沉積法，將銅膜選擇性的沉積在Si(100)面基材的特定位置上。結果顯示，在常壓下，欲利用汞燈照射達到銅膜選擇性沉積之目的，必須控制基材在200~250°C範圍內，跟還原劑的種類無關。至於反應速率則取決於乙醇或Ar+3%H2的加入。還原劑依反應速率快慢，依序為：乙醇>Ar+3%H2+乙醇>Ar+3%H2>無添加。在無添加還原劑的情況之下，除非提高反應溫度，否則沉積速率太慢，不切實際，但溫度太高則不具選擇性沉積的效果。 在只添加乙醇做為還原劑的情況之下，反應物的濃度越高，或汞燈光源的功率越高，則沉積速率越快，但沉積之銅膜的純度降低，亦即銅膜的電阻係數增加。銅膜之純度亦跟基材的溫度有關，溫度在240°C左右，顯示銅膜具最高純度，亦即電阻係數最小。

Selective deposition of various films on different substrates is one of the important micromachining techniques to build a three dimensional structure of an electronic device. the copper films could be selectively deposited on the desired locations of (100) Si wafer by a photo-assisted chemical vapor deposition method with Cu(hfac)2 as the reactant, ethanol or Ar+3%H2 as the reducing agent and Hg lamp as the light source. In order to achieve the purpose of selective deposition of Cu at ambient pressure by hg lamp, the substrate temperature must be controlled in the range of 200~250℃,indeopendent of the type or concentration of the reducing agents. However, the deposition rate deopends on the type and concentration of the reducing agents. By comparing different reducing agents, the order in deposition rate is : ethanol>Ar +3%H2 + ethanol > Ar + 3%H2>no reducing agent. For the case of without adding reducing agent, the deoposition rate is too slow to be acceptable without rising the substrate temoperature. However, if the substrate temperature is too high, selective deposition of Cu can not be achieved. For the case of adding only ethanol as reducing agent, the results also show that a higher reactant concentrtion or a higher lamp power can give rise to a higher deposition rate but will result in a decrease in the purity of copper films, i.e. an increase in resistivity of the films. Furthermore, the purity of Cu films is also a function of timperature; the Cu films show a maximum purity, or a minimum resistivvity at 240°C.