High-Purity Copper Sputtering Target Warpage Reduction
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Solution Overview
Problem
Conventional high-purity copper sputtering targets require a backing plate to prevent deformation during sputtering, which reduces utilization efficiency and affects film thickness uniformity, with existing solutions either compromising on strength or introducing strain that worsens film uniformity.
Innovation Solution
A high-purity copper sputtering target is developed without a backing plate, enhancing the strength and hardness of the flange part through heat treatment and cold working, while adjusting the (111) orientation ratio to minimize warpage and improve film uniformity, allowing for easier recycling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a backing plate is used to prevent deformation during sputtering, then the target strength is improved, but the utilization efficiency deteriorates
Solution Approach 1:
The invention merges the target and backing plate into a single integrated structure made of high-purity copper. The backing plate is not a separate component but an integral part of the target itself, eliminating the need for separate attachment while maintaining structural strength during sputtering.
Solution Approach 2:
The invention changes the material parameters by using high-purity copper (99.99% or higher) with specific physical properties for both the target and backing plate portions. The copper's inherent strength and thermal conductivity are leveraged to eliminate deformation without requiring additional materials or components.
2Shape
If a backing plate is used to prevent deformation, then the warpage is reduced, but the film thickness uniformity deteriorates
Solution Approach 1:
The invention applies homogeneity by using the same high-purity copper material throughout the entire integrated structure. This uniform material composition ensures consistent physical properties across the target and backing plate, preventing differential thermal expansion or contraction that would cause warpage and affect film uniformity.
Solution Approach 2:
While the target and backing plate are integrated, the invention functionally segments the structure into a target portion (for sputtering) and a backing plate portion (for support and cooling). This functional segmentation allows each part to perform its specific role optimally while maintaining overall structural integrity and film uniformity.
3Strength
If strain is introduced based on ECAE to increase strength, then the target strength is improved, but the film thickness uniformity deteriorates
Solution Approach 1:
The invention changes the material parameters by selecting high-purity copper with specific purity (99.99% or higher) and controlling its physical properties. Instead of introducing strain through ECAE, the invention relies on the inherent strength and controlled microstructure of the high-purity copper material to achieve both strength and 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 target achieves reduced warpage and improved film uniformity, enhancing the yield and reliability of semiconductor products, and facilitating easier recycling by eliminating the need for a backing plate.
Implementation Method 1
enhancing the strength and hardness of the flange part through heat treatment and cold working
Implementation Method 2
a method of forming a diffusion barrier layer made of Ta or TaN on a wiring or a wiring groove, and thereafter subjecting copper to sputter deposition
Implementation Method 3
enhancing the strength and hardness of the flange part through heat treatment and cold working
Data Source
Figure 1
AI summary
A high-purity copper sputtering target, wherein a Vickers hardness of a flange part of the target is in a range of 90 to 100 Hv, a Vickers hardness of an erosion part in the central area of the target is in a range of 55 to 70 Hv, and a crystal grain size of the erosion part is 80 µm or less. This invention relates to a high-purity copper sputtering target that does not need to be bonded to a backing plate (BP), and aims to provide a high-purity copper sputtering target capable of forming a thin film having superior uniformity by enhancing a strength (hardness) of the flange part of the target, and reducing an amount of warpage of the target. Moreover, the uniformity of the film thickness is improved by adjusting the (111) orientation ratio of the erosion part and the flange part in the target. The present invention thereby aims to provide a high-purity copper sputtering target, which is capable of improving the yield and reliability of semiconductor products that are being subject to further miniaturization and higher integration, and useful for forming a copper alloy wiring for semiconductors.