Concave Sputtering Target for Uniform PVD Film Deposition
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Solution Overview
Problem
In semiconductor fabrication, traditional physical vapor deposition (PVD) methods face challenges in achieving uniform film thickness across the substrate, particularly in high dielectric constant and metal gate applications, where the film at the wafer's central region tends to be thicker than at other locations, leading to non-uniformity issues.
Innovation Solution
A concave sputtering target design with a sloped region between the peripheral edges and a central flat region, where the sloped region is angled between 5 to 30 degrees, and the central region diameter is between 50% to 90% of the overall target diameter, to ensure uniform material deposition across the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a flat or convex sputtering target is used, then the target structure is simple and easy to manufacture, but the film thickness uniformity across the substrate deteriorates
Solution Approach 1:
The sputtering target is designed with different surface profiles in different regions: a flat central region and a concave peripheral region with specific curvature. This local differentiation of surface geometry allows the central region to deposit material uniformly while the concave peripheral region compensates for the natural thickness variation by directing more flux toward the substrate center, thereby achieving improved film thickness uniformity across the entire substrate surface.
Solution Approach 2:
The patent introduces a concave curved surface profile in the peripheral region of the sputtering target, replacing the traditional flat or convex geometry. This curvature is specifically designed with a controlled radius of curvature to modify the angular distribution of sputtered material flux, directing more material toward the substrate center and reducing the characteristic central-thick-edgeč–„ non-uniformity, thus achieving better overall film thickness uniformity.
2Manufacturing precision
If the sputtering target has a complex concave shape to improve uniformity, then film uniformity improves, but the manufacturing difficulty and cost increase
Solution Approach 1:
Rather than creating a completely new complex target geometry, the invention applies a localized concave profile modification only to the peripheral region of the target, while maintaining a flat central region. This localized approach reduces manufacturing complexity compared to fully custom geometries, as it can be achieved through conventional machining or bonding of segmented targets with different profiles.
Solution Approach 2:
The sputtering target can be manufactured as multiple segments or rings with different surface profiles (flat central region, concave peripheral region) that are subsequently bonded together. This segmentation approach simplifies the manufacturing of each individual segment using conventional techniques, while the assembled composite target achieves the desired complex geometry for improved film uniformity.
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 concave target design significantly improves radial uniformity of film thickness, reducing variations by up to 50% compared to traditional flat and frustum targets, and is less sensitive to process parameters like gas flow rate and target-wafer spacing, resulting in more consistent film deposition.
Implementation Method 1
Sputtering is a physical vapor deposition (PVD) process in which high-energy ions impact and erode a solid target and deposit the target material on the surface of a substrate
Implementation Method 2
a gas energizer to energize the process gas
Data Source
AI summary
Target assemblies and PVD chambers including target assemblies are disclosed. The target assembly includes a target that has a concave shaped target. When used in a PVD chamber, the concave target provides more radially uniform deposition on a substrate disposed in the sputtering chamber.