電漿製程環境中雙極性靜電吸盤的量測與開發

Abstract

雙極性靜電吸盤(Electrostatic Chuck,ESC)已經在一系列的電漿製程環境中被研發使用，它的優勢是在於它不需加入電漿即可以有吸附能力，所以在業界逐漸廣泛運用。而雙極性ESC之上下電極比例、電極材料、表面粗糙度、表面紋路、結合膠的選用、晶圓與雙極性ESC之間的氦氣壓力分佈以及雙極性ESC的背後水冷設計都對雙極性ESC性能優劣有決定性的影響。實驗過程中，我們以鋁金屬作為雙極性ESC的重要材料，並將鋁表面作硬陽極處理來形成第一層介電層，上下電極的面積比例也以互補的靜電吸力作有效的均勻分配，結合膠的選用乃採用熱膨脹係數低、介電常數低、熱傳係數大與結合力強的Epoxy系列結合膠作為第二層介電層。我們利用所建構的高密度電漿環境測試平台，以VB為軟體介面、高感度感測器為硬體介面和RS-232為通訊介面，來測試我們所設計的雙極性ESC之吸附晶片、釋放晶片及晶片散熱的能力。從實驗中發現，在工作電壓未達崩潰電壓情形下，ESC的吸附能力與工作電壓成正比關係。ESC介電層的電阻率降得越低，則ESC吸附與釋放的時間越短，而表面粗糙度越好有助於雙極性ESC的熱傳效率的改善與介電層電阻率的下降。藉由此實驗所得到的數據可以提供設計雙極性ESC上有一個較完善的設計準則，並提供研發廠商一個雙極性ESC的測試平台，對於往後掌握雙極性ESC製程良率有很大的助益。

The bipolar electrostatic chuck for silicon wafers has been developed for used in serial plasma process. The advantage of the bipolar electrostatic chuck is that attractions appear without plasma, so we take advantage of it in industry gradually. The bipolar electrostatic chuck’s proper proportion between the top plate and the bottom plate, material of plates, roughness of plate’s surface, marking of plate’s surface, the choice of the gelatin, the disposal of helium’s pressure between the wafer and the bipolar electrostatic chuck and the rear of the bipolar electrostatic chuck’s cooling water design affect the quality of the bipolar electrostatic chuck importantly. In the experiment, the aluminum material is used for the bipolar electrostatic chuck , and hard anodizing is applied to aluminum to build the first dielectric layer. The proper proportion between the top plate and the bottom plate of the bipolar electrostatic chuck is effectively uniformly distributed by the reciprocative electrostatic attraction. The low dilation coefficient, the low dielectric coefficient, the high thermal coefficient and the strong binding are the main factors in the choice of the gelatin. The gelatin, which is a kind of Epoxy is used to build the second dielectric layer. We build the high density plasma’s test stage which is built by Visual Basic that is a software interface, high sensitivity sensor that is a hardware interface and RS-232 that is a message interface. The stage tests the bipolar electrostatic chuck’s abilities of suction, delivery and cooling. We can find some key points in the experiment. When the working voltage is less than the breakdown voltage, there is a direct proportion between suction and working voltage. When the resistivity of the bipolar electrostatic chuck’s dielectric layer is lower, the time of suction and the time of dechucking is shorter. Better roughness of surface yields better thermal efficiency and lower resistivity of dielectric layers. From the data of the experiments, we can give the bipolar electrostatic chuck a better design principle, and we can also provide manufacturers a test stage that can be used to produce better quality products.