Mo-Cu Composite Backing Plate for Sputtering Warpage and Corrosion
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Solution Overview
Problem
Large-diameter sputtering targets made from low thermal expansion materials face warpage issues due to thermal expansion differences with conventional backing plates, leading to non-uniform film deposition and contamination from corrosion of molybdenum backing plates during high-power sputtering.
Innovation Solution
A Mo or Mo alloy backing plate with a thin anticorrosive metal layer, formed by diffusion-bonding Cu, Al, or Ti alloys on the cooling surface, reduces thermal expansion mismatch and corrosion, enhancing bonding strength and cooling efficiency while preventing contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a copper backing plate is used for cooling, then cooling efficiency is improved, but thermal expansion difference causes warpage during cooling
Solution Approach 1:
The invention uses a composite backing plate structure consisting of a molybdenum base layer (providing low thermal expansion) and a copper coating layer (providing high thermal conductivity for cooling). This composite structure combines the advantages of both materials while mitigating their individual disadvantages, resolving the contradiction between cooling efficiency and warpage prevention.
2Shape
If molybdenum backing plate is used to reduce thermal expansion difference, then warpage is reduced, but corrosion occurs during high-power sputtering
Solution Approach 1:
The molybdenum-copper composite backing plate combines molybdenum's low thermal expansion properties with copper's excellent corrosion resistance. The copper coating layer protects the molybdenum base from corrosion during high-power sputtering while the molybdenum base maintains dimensional stability, thus resolving both contradictions simultaneously.
3Strength
If brazing is used to bond target and backing plate, then bonding is achieved, but warpage and bonding strength deterioration occur due to shrinkage difference
Solution Approach 1:
The molybdenum-copper composite backing plate reduces warpage during brazing due to molybdenum's low thermal expansion, maintaining better bonding strength. The copper layer provides a bonding interface while the molybdenum base minimizes dimensional changes during heating and cooling cycles.
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 solution significantly reduces warpage and particle generation, ensures uniform film deposition, and maintains equipment cleanliness by minimizing corrosion and improving thermal conductivity and strength of the backing plate.
Implementation Method 1
a layer formed from an anticorrosive metal obtained by diffusion-bonding one or more types of metals selected from among Cu, Al and Ti
Implementation Method 2
Issues that become problematic during this kind of high power sputtering are the strength and cooling capacity (favorable thermal conductivity) of the backing plate itself
Implementation Method 3
the difference in the thermal expansion between the target material and the backing plate material increases, and the target is prone to warpage
Data Source
AI summary
Provided is a backing plate obtaining by bonding an anticorrosive metal and Mo or a Mo alloy, wherein the backing plate comprises, on a surface of the Mo or Mo alloy backing plate to be cooled (cooling surface side), a layer having a thickness corresponding to 1/40 to ⅛ of a total thickness of the backing plate and formed from an anticorrosive metal obtained by bonding one or more types of metals selected from among Cu, Al and Ti, or an alloy thereof. Additionally provided is a sputtering target-backing plate assembly obtained by bonding the foregoing Mo or Mo alloy backing plate and a target formed from a low thermal expansion material.Particularly in semiconductor applications, reductions in size have progressed and control of particles during sputtering has become stricter. The present invention aims to resolve the problem of warpage of sputtering targets formed from low thermal expansion materials and problems occurring with respect to the anticorrosive properties of Mo or Mo alloy backing plates.