Indium Sputtering Target Surface Roughness Stabilization
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Solution Overview
Problem
Conventional indium sputtering targets experience a significant drop in film deposition rate during initial sputtering, leading to unstable film thickness and prolonged stabilization time, which affects the quality of sputtered films.
Innovation Solution
The surface roughness of indium sputtering targets is intentionally increased to an arithmetic average roughness of 5 μm to 70 μm and ten point average roughness of 100 μm to 400 μm through methods like dry ice particle blasting or using abrasive paper to reduce the initial sputtering rate and achieve a stable deposition rate sooner.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the surface of indium sputtering target is polished to be smooth (Ra ≤ 4 μm, Rzjis ≤ 60 μm), then the initial sputtering rate is high, but the film deposition rate becomes unstable and takes long time to stabilize
Solution Approach 1:
The surface of the indium sputtering target is pre-treated to form nodules before sputtering begins. This preliminary action of creating a rough surface structure (Ra = 5-70 μm, Rzjis = 100-400 μm) ensures that the sputtering process starts with a stable deposition rate from the beginning, eliminating the initial high rate followed by gradual decline observed with smooth surfaces.
2Reliability
If the surface of indium sputtering target is made rough with nodules, then the film deposition rate stabilizes quickly, but the initial sputtering rate is lower
Solution Approach 1:
The surface roughness parameters are deliberately changed from conventional smooth values (Ra ≤ 4 μm) to specific rough values (Ra = 5-70 μm, Rzjis = 100-400 μm). This parameter change in surface topology creates nodules that modify the sputtering process dynamics, allowing stable film deposition from the start while maintaining acceptable deposition rates.
3Shape
If conventional polishing methods are used to smooth the target surface, then the surface appearance is good, but the sputtering efficiency decreases dramatically over time
Solution Approach 1:
Instead of polishing the surface to be smooth as conventionally done, the invention inverts the approach by deliberately creating a rough surface with nodules. This inverted surface preparation method prevents the dramatic decrease in sputtering efficiency that occurs with smooth surfaces, maintaining stable and high deposition rates throughout the sputtering process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach shortens the stable rate attainment time, stabilizing the film deposition rate and reducing variations in film thickness, with a decrease in film deposition rate after ten hours being 30% or less compared to the initial rate, thereby enhancing the quality and consistency of sputtered films.
Implementation Method 1
The surface to be sputtered is treated by dry ice particle blasting or by using abrasive paper
Implementation Method 2
Indium has been used as a sputtering target for forming a light absorbing layer for Cu—In—Ga—Se-based (CIGS-based) thin film solar cells
Data Source
AI summary
An indium sputtering target with a short time to attain a stable film deposition rate once sputtering has begun is provided. An indium sputtering target having a surface to be sputtered with an arithmetic average roughness Ra of from 5 μm to 70 μm prior to sputtering.