A novel evaluation of piezoelectric coefficient of PZT thin film

論文發表人： 鍾添淦 (加州大學洛杉磯分校機械工程研究所博士班)

 

http://spie.org/smart-structures-nde.xml

 

在此篇論文中, 我們提出了一個新的估算壓電薄膜的壓電係數(d₃₁)的方法.  藉由修改傳統的標準製程, 我們可以製造出大面積無裂痕的溶膠凝膠系的鋯鈦酸鉛薄膜.  鋯鈦酸鉛薄膜是以旋轉鍍膜的方式鍍於鉑/鈦/氧化矽/矽晶圓基材上, 而此多結晶型的薄膜具有傾向(111)的結晶方向.  估算此薄膜的壓電係數(d₃₁)的方法乃是基於薄膜應力量測法.  當外加電場於晶圓上的鋯鈦酸鉛薄膜時, 會使該薄膜產生變形.  藉由薄膜應力量測設備(Tencor FLX-2320), 便可量測出整個薄膜/晶圓的曲率變化,  再藉由該曲率變化可計算出薄膜中的應力.  最後, 已知薄膜應力與外加電場, 透過壓電材料的基本行為方程式, 便可估算出壓電薄膜的壓電係數(d₃₁).

　　

In this paper, we demonstrate a new method to evaluate the piezoelectric coefficient (d₃₁) of piezoelectric thin film. The sol-gel driven lead zirconate titanate (PZT) thin film with large crack-free area is obtained by using a modified fabrication process. The polycrystalline film is spin-coated on Pt/Ti/SiO₂/Si substrate and has a preferential (111) orientation. The method to evaluate the piezoelectric coefficient (d₃₁) of the PZT thin film is based on thin film stress measurement technique. Tencor FLX-2320 film stress measurement system which is a very sample and cheap equipment is used to obtain the wafer curvature information when voltage is applied to PZT thin film on wafer. The stress in thin film is calculated by the obtained wafer curvature. By using the constitutive equation of polarized piezoelectric material, the d₃₁ coefficient can be determined from calculated thin film stress and applied voltage input.