Sputtering Target Gradient Strength Layer Deformation
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Solution Overview
Problem
Hat-type sputtering targets with cylindrical backing plates face deformation due to water pressure and thermal stress, leading to unstable deposition characteristics, as existing bonding methods like mechanical bonding and diffusion bonding introduce electrical resistance and particle size variations.
Innovation Solution
A sputtering target with a plate-shaped target body featuring a gradient strength layer on its cooling surface, which has higher hardness and tensile strength than the sputtering surface, inhibiting deformation and stabilizing deposition characteristics by integrating a cylindrical flange portion for cooling and mechanical bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a cylindrical backing plate is used for hat-type sputtering targets, then the target can be bonded to the outer peripheral portion, but water pressure and thermal stress cause deformation beyond the yield point leading to unstable deposition characteristics
Solution Approach 1:
The invention applies local quality by creating a gradient strength layer with varying tensile strength from the front surface toward the back surface. The front surface maintains low strength (35 N/mm² or less) to preserve crystal orientation and deposition characteristics, while the gradient strength layer progressively increases strength toward the back surface to resist deformation from water pressure and thermal stress, thereby maintaining film thickness distribution stability.
Solution Approach 2:
The invention uses composite materials by creating a target body with non-uniform internal structure - a gradient strength layer that transitions from softer material at the front surface to harder material at the back surface. This composite structure combines the benefits of soft material (good deposition characteristics) with hard material (deformation resistance) within a single target body.
2Strength
If mechanical bonding or diffusion bonding is used to bond the target to the backing plate, then the target can be securely attached, but electrical contact resistance increases and particle size variations occur
Solution Approach 1:
The invention merges the target body and backing plate into an integrated structure where the gradient strength layer is formed as part of the target body itself rather than using separate bonding layers. This eliminates the need for additional bonding materials that would introduce electrical resistance and particle size variations, while the gradient strength layer provides sufficient bonding strength through its progressive strength distribution.
3Manufacturing precision
If the target material is made of high-purity aluminum, then the deposition characteristics are improved, but the tensile strength becomes lower making the target more susceptible to deformation
Solution Approach 1:
The invention applies local quality by creating spatial variation in material properties within the target body. The front surface maintains high-purity aluminum characteristics with low tensile strength (35 N/mm² or less) to ensure good crystal orientation and film thickness uniformity, while the gradient strength layer progressively increases strength toward the back surface to provide mechanical support and deformation resistance.
Solution Approach 2:
The invention uses composite materials by creating a target body that transitions from high-purity aluminum at the front surface to strengthened material in the gradient strength layer. This composite structure allows the target to simultaneously exhibit soft characteristics (good for deposition) at the front and hard characteristics (good for strength) at the back.
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 gradient strength layer effectively suppresses deformation and maintains stable deposition characteristics by distributing stress and maintaining crystal orientation, ensuring consistent film thickness and deposition rate.
Implementation Method 1
the target receives a thermal stress that acts on a sputtering surface and a cooling water pressure that acts on the back surface thereof
Implementation Method 2
a cooling water pressure that acts on the back surface thereof during sputtering
Implementation Method 3
the backing plate is cooled by the cooling water supplied to the inside of the flange portion
Data Source
AI summary
A sputtering target according to an embodiment of the present invention includes: a plate-shaped target body formed of a metal material. The target body includes a target portion and a base portion. The target portion has a sputtering surface. The base portion has a cooling surface and includes a gradient strength layer, the cooling surface being positioned on a side opposite to the sputtering surface and having hardness higher than that of the sputtering surface, the gradient strength layer having tensile strength that gradually decreases from the cooling surface toward the target portion.