Profiled Sputtering Target Geometry for Uniform Thin Film Deposition
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Solution Overview
Problem
Existing sputtering systems face challenges in achieving uniform thin film deposition and extending target life due to non-uniform erosion profiles and subsequent changes in target surface geometry, leading to issues like redeposition of atoms and altered trajectories of sputtered atoms.
Innovation Solution
A sputtering target with a non-planar sputtering surface featuring a central axis region with a concave curvature feature, designed to reduce shadowing and modify the erosion profile, thereby optimizing the trajectory of sputtered atoms and enhancing film uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a planar sputtering target surface is used, then the target structure is simple and easy to manufacture, but the erosion profile becomes non-uniform during use, leading to non-uniform film deposition and reduced target life
Solution Approach 1:
The target surface is pre-profiled with a concave central axis region and convex surrounding region before sputtering begins. This preliminary geometric configuration compensates for the non-uniform erosion that occurs during sputtering, ensuring that the target erodes uniformly throughout its operational life and produces uniform film deposition.
Solution Approach 2:
The target surface incorporates curved geometric features including a concave curvature in the central axis region and a convex curvature in the surrounding region. These curved profiles modify the erosion pattern during sputtering, preventing the formation of deep grooves and maintaining uniform atom ejection across the target surface.
2Duration of action of stationary object
If the target surface erodes uniformly, then film deposition is uniform, but the target life is limited due to the development of insulating layers and arcing on poorly eroding race tracks
Solution Approach 1:
Different regions of the target surface are given different geometric properties: the central axis region has a concave curvature while the surrounding region has a convex curvature. This local differentiation ensures that each region erodes at an optimal rate, preventing the formation of insulating layers and arcing conditions that would otherwise limit target life.
Solution Approach 2:
The pre-profiled target geometry anticipates and counteracts the development of insulating layers and arcing by establishing an erosion profile that promotes uniform material removal from the outset. The concave-convex profile configuration prevents the formation of poorly eroding race tracks before they can develop into reliability issues.
3Manufacturing precision
If the central axis region has a protruding convex curvature feature, then the target structure is straightforward, but it causes shadowing that blocks sputtered atoms and redirects their trajectories, reducing deposition uniformity
Solution Approach 1:
Instead of using a protruding convex curvature feature in the central axis region, the invention inverts the approach by using a concave curvature. This inversion eliminates the shadowing effect that would block sputtered atoms, allowing uniform atom distribution and deposition across the substrate while maintaining a relatively simple target structure.
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
The modified sputtering target design results in improved film uniformity and extended target life by reducing shadowing and altering the slope of the wear surfaces, allowing more atoms to reach the wafer center and promoting consistent deposition.
Implementation Method 1
when depositing a layer of metal onto a surface or substrate by sputtering a target comprising that metal, the atoms and molecules being deflected or liberated from the target must travel a path to the substrate or other surface
Data Source
AI summary
A sputtering target comprising a sputtering material and having a non-planar sputtering surface prior to erosion by use in a sputtering system, the non-planar sputtering surface having a circular shape and comprising a central axis region including a concave curvature feature at the central axis region. The central axis region having a wear profile after erosion by use in a sputtering system for at least 1000 kWhrs including a protuberance including a first outer circumferential wear surface having a first slope. A reference, protruding convex curvature feature for a reference target after sputtering use for the same time includes a second outer circumferential wear surface having a second slope. The protuberance provides a sputtered target having reduced shadowing relative to the reference, protruding convex curvature feature, wherein the first slope is less steep than a second slope.