噴濺沈積之蒙地卡羅模擬

Abstract

在本研究中，吾人發展完成一種蒙地卡羅模擬程式，可以用來分析噴濺沈積過程中，噴濺的分佈和粒子到達基板時的分佈情形。此模擬程式以近似二元碰撞為基礎，採用萬用原子際的位能模式， 計算原子的散射角度。噴濺產率與入射粒子的方向、能量和質量相依。原子脫離靶板的角度和能量的分佈在此研究中亦曾檢視。沈積層的厚度分佈和幾種條件有關，包括噴濺的入射角度和位置、及氣體的壓力和基板到靶板的距離。在此模擬程式中，為了加速電腦計算速度，我們使用多項式近似法來計算碰撞截面積，而採用”粒子雲團”的構思，來統計沈積分佈。我們的噴濺原子源以環形”跑道”之高氏分佈入射而模擬更符合實際情形。由於入射源不是均勻的，吾人應調整氣體壓力和基靶距離的殊幾得到平坦而有效率的沈積。

In this study, a computer program of Monte Carlo simulation for sputter deposition of atoms from target to substrate is developed. The sputter yield and distribution as well as the arrival flux and thickness distributions are determined. The simulation program is based on the binary collision approximation for both solid target and gas chamber. The scattering and cross-section are calculated based on Biersack's universal screening potential. Calculations are made of the dependence of the sputtering yield on the incident angle and energy. Angular and energy distributions of the ejected atoms are evaluated. The deposition thickness is examined under various conditions of incident angle and location, background pressure, and substrate-to-target distance. In the simulation program, polynomial fitting for scattering collision cross-section and the "particle cloud" scheme for deposited distribution have been employed to accelerate the computation. We use the "racetrack" annulus as the source of the sputtered atoms to simulate the actual magnetron sputtering. Because the sputtered distribution is not uniform, We must adjust the background pressure and substrate-to-target distance to achieve the flat and efficient deposition Chinese Abstract ………………………………………………… i English Abstract ………………………………………………… ii Acknowledgements ………………………………………………… iii Contents …………………………………………………………… iv 1. Introduction …………………………………………………… 1 2. Physical Basics ……………………………………………………4 2.1 General Aspects ……………………………………………… 4 2.2 Scattering Angle …………………………………………… 6 2.3 Screen Potentials …………………………………………… 9 2.4 Nuclear and Electronic Energy Losses …………………… 10 2.5 Surface Binding Energy …………………………………… 11 3. Numerical Computations ………………………………………… 12 3.1 Scattering Cross Section and Mean Free Path ………… 12 3.2 Random Processes ……………………………………………… 15 3.3 Angular Transformation and Three-Dimension Trajectory 20 3.4 Particle Cloud ………………………………………………… 22 3.5 Calculation Procedure………………………………………… 23 4. Results and Discussion ………………………………………… 25 4.1 Sputtered Yields ……………………………………………… 25 4.1.1 Effects of Incident Energy ………………………… 25 4.1.2 Effects of Incident Angle …………………………… 27 4.1.3 Energies Distribution of Sputtered Particles … 28 4.1.4 Angular Distribution of Sputtered Particles …… 30 4.2 Effects of Gas Pressure and Target-Substrate Distance 32 4.3 Deposition distributions …………………………………… 34 4.3.1 Bombarding at the Center of Target ……………… 34 4.3.2 Bombarding at the Gaussian Ring of Target……… 38 4.3.3 Distributions of Arriving Flux …………………… 42 5. Conclusions ………………………………………………………… 44 References ……………………………………………………………… 45