Workpiece Grinding Method for Sapphire Wafer Thinning
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Thinning semiconductor or optical device wafers, such as sapphire or SiC substrates, is challenging due to their hardness, leading to defects like breaking, cracking, or chipping during grinding, and peeling issues arise when the workpiece thickness reaches 100 μm or less, causing warping and separation from the support substrate.
Innovation Solution
A workpiece grinding method involving surface protection steps with adhesive tapes and a liquid resin adhesive that spreads over the side surface of the workpiece to securely attach it to a support substrate, preventing peeling during grinding and facilitating easy peeling post-processing, using a chuck table with a rotating grinding stone to achieve the desired thickness while preventing warping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the workpiece is fixed to a hard support substrate with strong adhesive force to prevent breakage during grinding, then the workpiece can be protected from breaking, cracking, or chipping, but the workpiece cannot be easily peeled off from the support substrate after grinding
Solution Approach 1:
The adhesive application is segmented into two distinct zones: a first adhesive application area that contacts the support substrate to provide strong fixation during grinding, and a second adhesive application area on the side surface of the outer peripheral portion that provides enhanced grip for peeling. This segmentation allows the adhesive to serve dual functions with different strength requirements in different locations.
Solution Approach 2:
Different regions of the adhesive application have different properties tailored to their specific functions. The adhesive in the first application area is optimized for strong bonding to the support substrate, while the adhesive in the second application area is optimized for providing grip during the peeling process. This local differentiation resolves the contradiction between strong fixation and easy peeling.
2Manufacturing precision
If the workpiece is thinned to 100 μm or less to achieve desired thickness, then the workpiece meets the thickness requirement, but the workpiece warps and the outer peripheral portion separates from the support substrate during grinding
Solution Approach 1:
The adhesive is applied to the side surface of the outer peripheral portion of the workpiece before the grinding process begins. This preliminary action ensures that when the workpiece is thinned and warping occurs, the adhesive already in place on the side surface provides immediate resistance to separation, preventing the outer peripheral portion from detaching from the support substrate.
Solution Approach 2:
The adhesive acts as an intermediary substance between the workpiece and the support substrate. By applying the adhesive to the side surface of the outer peripheral portion, it creates an additional bonding interface that mediates the stress and prevents separation when the workpiece warps during thinning to 100 μm or less.
3Reliability
If adhesive is applied to fix the workpiece to the support substrate, then the workpiece is secured during grinding, but adhesive residue remains on the front surface of the workpiece after peeling
Solution Approach 1:
The adhesive application is extracted and limited to specific areas: the first adhesive application area for fixation and the second adhesive application area on the side surface for peeling grip. By not applying adhesive to the entire surface including the front surface, the method eliminates the source of adhesive residue contamination while maintaining reliable fixation and enabling easy peeling.
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 method effectively prevents defects like breaking, cracking, or chipping by securely fixing the workpiece's outer peripheral portion to the support substrate, allowing for successful peeling and achieving the desired thinness without warping, even for hard materials like sapphire wafers.
Implementation Method 1
causing the adhesive to spread over a side surface of an outer peripheral portion of the workpiece and to fix the side surface of the outer peripheral portion to the support substrate
Implementation Method 2
grinding the back surface of the workpiece with a grinding stone which rotates by a rotation shaft orthogonal to the holding face, and thinning the workpiece to a flexible thickness
Data Source
AI summary
A workpiece grinding method including a first surface protection step of covering a front surface of a workpiece with a workpiece protective member, a second surface protection step of covering front surface of a support substrate with a support substrate protective member, a workpiece unit formation step of causing an adhesive to spread over a side surface of an outer peripheral portion of the workpiece to fix the side surface to the support substrate, and forming a workpiece unit, a grinding step of thinning the workpiece, a first peeling step of peeling off the workpiece after thinning, the workpiece protective member, the adhesive, and the support substrate protective member from the support substrate as one unit in such a manner to turn them over, and a second peeling step of peeling off the workpiece protective member, the adhesive, and the support substrate protective member as one unit from the workpiece.