SiC Wafer Grinding Using Controlled Plastic Deformation
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Solution Overview
Problem
Conventional grinding methods for semiconductor crystal wafers suffer from plastic deformation, which hinders achieving high grinding accuracy.
Innovation Solution
Control plastic deformation by adjusting the grain size of the diamond grindstone, pressing force, and advance rate to form a controlled plastic deformation region during grinding, allowing for improved grinding efficiency and mirror finish.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional grinding method is used to avoid plastic deformation, then plastic deformation of polishing platen and wafer is eliminated, but grinding accuracy cannot be sufficiently improved
Solution Approach 1:
The invention changes the physical parameters of the grinding system by controlling the temperature increase caused by friction to a specific range (100-500°C), transforming the material state of the wafer surface to enable plastic deformation. This parameter change allows the system to achieve both high grinding accuracy and improved productivity by utilizing controlled plastic deformation rather than avoiding it entirely.
Solution Approach 2:
The invention employs periodic action through controlled friction heating during the grinding process, where the temperature increase is maintained within a specific range to periodically induce plastic deformation. This periodic thermal-mechanical action allows the diamond grindstone to efficiently remove material while maintaining surface integrity, resolving the contradiction between accuracy and efficiency.
2Manufacturing precision
If plastic deformation is controlled as a mechanism in end surface or wafer surface, then higher grinding accuracy can be realized, but requires precise control of grain size, pressing force, and advance rate
Solution Approach 1:
The invention systematically controls three key parameters (grain size of diamond grindstone, pressing force, and advance rate) to maintain temperature increase within the 100-500°C range. By establishing specific parameter ranges rather than requiring precise point-values, the invention reduces control complexity while achieving the desired plastic deformation effect for high grinding accuracy.
Solution Approach 2:
The invention applies partial action by controlling the plastic deformation to occur only in the surface layer of the wafer through friction heating, while the bulk material remains unaffected. This localized partial deformation achieves high surface accuracy without requiring complex control of the entire wafer structure, simplifying the overall control system.
3Productivity
If diamond grindstone with grain size exceeding width of plastic deformation region is used, then grinding efficiency improves, but plastic deformation control is compromised
Solution Approach 1:
The invention establishes an optimal grain size range for the diamond grindstone that works synergistically with the controlled friction heating to produce plastic deformation. By changing the grain size parameter to match the plastic deformation region width, the system achieves both high grinding efficiency and precise surface control, eliminating the need to choose between the two opposing requirements.
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
Achieves higher grinding accuracy and efficiency with a mirror finish on semiconductor crystal wafers, enabling strong bonding and maintaining crystal quality without relying on crystal growth properties.
Implementation Method 1
a temperature increase caused by friction due to intervention of a diamond grindstone between the surface and the grinding plate
Implementation Method 2
When a plastic deformation region is formed in the end surface of the semiconductor crystal ingot on the grinding plate side
Data Source
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AI summary
The present invention provides: a method for grinding semiconductor crystal, the method being capable of achieving higher grinding accuracy by controlling plastic deformation, which has been abhorred in the past, as a plastic deformation mechanism of a semiconductor crystal ingot end surface or a wafer surface; and a method for producing SiC extended ingot, the method using the above-described grinding method. In a method for grinding an SiC wafer 100 according to the present invention, a plastic deformation region 100A is formed in a platen 52 (grinding plate)-side surface of the wafer 100 by a temperature increase caused by friction due to intervention of diamond abrasive grains 53 between the surface and a platen 52 on the basis of: (1) the grain size of the diamond abrasive grains 53 (diamond grindstones); (2) the pressing force that presses the wafer 100 against the platen 52 by the intermediary of a spindle 51; and (3) the advance rate of the spindle 51 with respect to the platen 52.