以流體式數值模擬直流磁控電漿濺鍍系統之磁場影響

A Fluid Approach of Numerical Study on the Effect of Magnetic Field in DC Magnetron Discharge

葉家豪(Chia-Haw Yeh)

指導教授 ： 洪銘聰

國立中央大學/工學院/機械工程學系/碩士(2010年)

摘要

隨著半導體工業的發展，電漿製程的開發受到大量關注，在金屬鍍膜製程上，平板式直流濺鍍製程已不足以供應業界在金屬化製程所需之製程速度，需要開發更高的電漿源提升濺鍍率及沉積速度。利用直流磁控式濺鍍系統，以外加磁場大幅增加靶材區之電漿密度，藉由大量離子轟擊提升靶材濺鍍率與沉積率，但由於磁場分佈所導致靶材上離子轟擊分佈不均，會造成靶材使用率不佳與沉積分佈不均等問題，必需藉由磁場之設計與改良來修正。本文主要對直流磁控式濺鍍之開發，磁鐵盤之設計對電漿密度的影響進行研究與探討，利用電漿模擬方式，討論單環及多環磁鐵盤截面上磁鐵排列方式不同，磁力分佈對電漿密度與靶材濺鍍率之影響。
本文採用流體式模擬方法，搭配有限元素分析軟體COMSOL Mutiphysics多重物理偶合模組做為電漿模型之建立。為了使模擬更符合真時物理情況，文中同時也考慮到溫度與氬氣激發態粒子之影響。氣體溫度、電子溫度之上升，使得整體電漿密度下降；電子溫度會隨著磁力線分佈有相同之趨勢，且在40 eV ~ 70 eV有最大之游離產生率發生；而當考慮氬氣激發態之碰撞影響，對電子、離子密度皆有提升之作用。
模擬結果顯示，帶電粒子受到磁力作用下，會在磁力線平行極板處聚集，在單環磁鐵盤模擬中，帶電粒子會在兩磁鐵中間區集中，而衍伸至多環磁鐵盤模擬時，離子集中處會隨著磁鐵盤剖面上磁鐵數之不同而改變。當截面為七個磁鐵時，靶材受離子轟擊之集中處在兩外環中間區；而在六個磁鐵排列下，離子轟擊靶材則轉往兩內環中間區集中。文中最後對靶材濺鍍率及侵蝕剖面進行計算，並探討壁面磁絕緣之模型，分散離子轟擊之峰值數量及位置，提供一改良電漿製程之方法。

關鍵字

磁控式濺鍍 ； 流體式模型 ； 電漿模擬

並列摘要

The plasma fabrication process attracts more and more attentions in the semiconductor industry in recent years. In the metallization process, the sputtering rate and deposition rate of the Planer DC Sputtering process is not enough to satisfy the semiconductor industry. It’s more necessary to develop the high density plasma system to improve the sputtering rate and deposition rate.
In the DC Magnetron Sputtering, an external magnetic field is applied to enhance the plasma density around the target. The sputtering rate and deposition rate will rise by additional ion bombardment, but it still has the problem that the ion bombardment flux distribution is not smooth along the target. It causes the non-uniformity of target erosion and the surface deposition. It is very important to have an appropriate design of the magnetic fields.
In this thesis, we numerically study the discharge phenomena of a DC Magnetron Sputtering system, including the effects of different magnet plate design and how it affects the plasma density. The plasma distributions and the relationships of ion bombardment on the target are discussed for the one-ring magnet plate and the multi-ring magnet plate.
In the plasma simulation, we use the fluid model method to reduce the computational time and make it more convenient to set up the plasma parameters. To make the plasma simulations more close to the reality, we also consider the effects of the gas temperature and the argon metastable atoms. When the gas temperature and the electron temperature increase, it causes the plasma density decreasing. The electron temperature distribution is same as the magnet line of force distribution. When the electron temperature in the region of 40 eV ~ 70 eV, it causes the maximal ionization rate and excitation rate. Considering the argon metastable atoms contribution, it makes the simulation more close to the real situation and causes the plasma density increasing.
In the result of this thesis, we find out that the plasma species follow the magnet lines of force and concentrate near the target surface, where the magnet lines of force are parallel to the electrode in the one-ring magnet situation. In the case of the seven-magnet plasma distribution, there are two concentration picks of ion bombardment near the edge of the target, while in the case of the six-magnet plasma distribution, the ion bombardment picks are located near the center of the target. Finally, we calculate the sputtering rates and the target erosion profiles. A special case with magnetic isolated boundary is discussed, which enhances the plasma density and the uniformity of target erosion.

並列關鍵字

fluid model ； magnetic sputtering ； plasma simulation

參考文獻

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