Cobalt-Titanium Sputtering Target Assembly with Copper Interlayer
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Solution Overview
Problem
The thermal stress caused by the mismatch in coefficients of thermal expansion (CTE) between cobalt-titanium alloys and copper alloy backing plates leads to debonding or cracking of sputtering targets in high-power sputtering chambers, which are critical for semiconductor fabrication.
Innovation Solution
A cobalt-titanium sputtering target assembly is formed using powder metallurgy, combined with a copper interlayer and a two-step diffusion bonding process to minimize thermal stress, involving vacuum hot pressing and high/low bond temperatures to achieve a strong bond with a copper alloy backing plate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a diffusion-bonded target is used in high-power sputtering chambers, then the sputtering target can withstand high power density, but thermal stress caused by CTE mismatch between cobalt-titanium alloy and copper alloy backing plate leads to debonding or cracking
Solution Approach 1:
A copper interlayer is introduced between the cobalt-titanium sputtering target and the copper alloy backing plate. This interlayer acts as a mediator that accommodates the CTE mismatch between the two materials, reducing thermal stress during high-power sputtering operations and preventing debonding or cracking at the bonding interface.
Solution Approach 2:
The bonding process parameters are optimized by performing diffusion bonding at elevated temperatures (e.g., 700-900°C) followed by controlled cooling. This temperature parameter change enables effective bonding while managing thermal stress, and the hold time is extended (e.g., 1-4 hours) to ensure complete bonding before thermal cycling begins.
2Manufacturing precision
If powder metallurgy is used to form the cobalt-titanium sputtering target, then the target can achieve high density (at least 95%), but the bonding process becomes more complex
Solution Approach 1:
The vacuum hot pressing process is used to simultaneously achieve two objectives: consolidating the powder metallurgy target to at least 95% density and preparing the bonding surface for diffusion bonding to the backing plate. This merged process eliminates the need for separate densification and bonding preparation steps, reducing overall process complexity.
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 assembly withstands high-power sputtering conditions without warping, ensuring reliable operation in semiconductor manufacturing by preventing debonding or cracking, and maintaining structural integrity.
Implementation Method 1
vacuum hot pressing the powder mixture at about 800° C. to about 1150° C. at a hydraulic pressure of about 2 ksi (13.8 MPa) to about 5 ksi (34.5 MPa) and for a hold time of about 2 hours to about 5 hours to form a cobalt-titanium sputtering target
Implementation Method 2
a copper alloy backing plate diffusion bonded to the sputtering target
Data Source
AI summary
A method of making a cobalt-titanium sputtering target is provided in which the sputtering target includes 0.5 atomic percent to 24.9 atomic percent titanium. A sputtering target assembly and a method of making a sputtering target assembly are also provided.