Controlling Film Thickness Distribution by Magnetron Sputtering with Rotation and Revolution

Handan Huang,Zhong Zhang,Zhanshan Wang,Yiyun Yao,Li Jiang,Runze Qi

doi:10.3390/coatings11050599

Abstract

The laterally graded multilayer collimator is a vital part of a high-precision diffractometer. It is applied as condensing reflectors to convert divergent X-rays from laboratory X-ray sources into a parallel beam. The thickness of the multilayer film varies with the angle of incidence to guarantee every position on the mirror satisfies the Bragg reflection. In principle, the accuracy of the parameters of the sputtering conditions is essential for achieving a reliable result. In this paper, we proposed a precise method for the fabrication of the laterally graded multilayer based on a planetary motion magnetron sputtering system for film thickness control. This method uses the fast and slow particle model to obtain the particle transport process, and then combines it with the planetary motion magnetron sputtering system to establish the film thickness distribution model. Moreover, the parameters of the sputtering conditions in the model are derived from experimental inversion to improve accuracy. The revolution and rotation of the substrate holder during the final deposition process are achieved by the speed curve calculated according to the model. Measurement results from the X-ray reflection test (XRR) show that the thickness error of the laterally graded multilayer film, coated on a parabolic cylinder Si substrate, is less than 1%, demonstrating the effectiveness of the optimized method for obtaining accurate film thickness distribution.

Highlights

Since Gobel successfully applied the laterally graded multilayer collimator in X-ray diffraction to modulate the divergence X-ray beam into a parallel X-ray beam [1,2], this type of collimator has had an important role in X-ray diffractometry for realizing high-resolution diffraction, powder diffraction, protein crystallography, and other measurements requiring high-intensity and parallel X-ray beams
Film with a periodic thickness of about 3–6 nm was coated on a 240 mm-long substrate, and the film thickness error was less than 1% [6]
We proposed a speed curve design for the substrate based on a planetary motion magnetron sputtering coating system to modulate the speed of the substrate passing through the target

Summary

Introduction

Since Gobel successfully applied the laterally graded multilayer collimator in X-ray diffraction to modulate the divergence X-ray beam into a parallel X-ray beam [1,2], this type of collimator has had an important role in X-ray diffractometry for realizing high-resolution diffraction, powder diffraction, protein crystallography, and other measurements requiring high-intensity and parallel X-ray beams. The key difficulty in coating laterally graded multilayer films by magnetron sputtering is controlling the deposition rate at different positions on the substrate efficiently and accurately [3,4,5,6]. Villa designed a variety of masks for plane substrates, spherical substrates, and vertical cylindrical substrates [8] This method can be used to deposit multilayer films with different gradients in two dimensions, the mask reduces the sputtering efficiency of the target material, and the coating cycle is extended.

Particle Transport Model

Assumptions of the Model

Results