Wafer Edge Trimming with Damage Layer Repair Before Grinding
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Solution Overview
Problem
During the chip manufacturing process, the back surface of wafers with beveled outer circumferential regions is prone to cracking and dust generation due to stress concentration and damage layers formed during edge trimming.
Innovation Solution
A processing method that includes a trimming step to annularly cut the beveled outer circumferential region and a cutting surface treatment step where energy is locally supplied to the cutting surface to remove or repair damage layers, thereby preventing breakage and dust generation during grinding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If edge trimming is executed to remove the beveled outer circumferential region, then the wafer shape is improved and stress concentration is reduced, but a damage layer is formed in the cutting surface which causes breakage during grinding and dust generation in subsequent steps
Solution Approach 1:
The patent applies preliminary action by performing surface treatment (such as chemical etching, mechanical polishing, or plasma treatment) on the cutting surface immediately after edge trimming and before grinding. This preliminary treatment removes or repairs the damage layer formed during trimming, preventing it from causing breakage during subsequent grinding operations. The surface treatment step is inserted between trimming and grinding to address the damage layer problem before it causes issues.
2Volume of moving object
If the back surface is ground to thin the wafer, then the chip size is reduced, but cracks occur in the outer circumferential region due to stress concentration
Solution Approach 1:
The patent applies preliminary action by beveling the outer circumferential region before grinding operations. This beveling creates a gradual transition at the edge, preventing stress concentration that would occur with a sharp 90-degree corner. The preliminary beveling modifies the geometry in advance to eliminate the root cause of cracking during subsequent grinding and thinning operations.
Solution Approach 2:
The patent applies local quality by applying different geometric characteristics to different regions of the wafer. The outer circumferential region is given a beveled shape with a specific angle (e.g., 45 degrees), while the central region maintains its original flat geometry. This localized geometric modification addresses stress concentration specifically at the vulnerable edge regions without affecting the overall wafer structure or grinding process.
3Device complexity
If the damage layer is not removed after trimming, then the process is simpler, but breakage occurs during grinding and dust is generated in subsequent steps
Solution Approach 1:
The patent applies preliminary action by incorporating a surface treatment step immediately after trimming to remove the damage layer and prevent dust generation. The surface treatment (chemical etching, mechanical polishing, or plasma treatment) is performed as a preliminary measure before subsequent grinding and processing steps, eliminating the source of dust generation in advance rather than dealing with dust removal later.
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 suppresses breakage of the wafer and generation of dust in subsequent grinding steps by addressing the damage layers and stress concentrations in the outer circumferential region.
Implementation Method 1
a cutting blade cut into the outer circumferential region that is beveled from one surface side of the wafer and annularly cutting the outer circumferential region
Implementation Method 2
locally supplying energy to a cutting surface that is formed in the outer circumferential region in the trimming step
Data Source
AI summary
Energy is locally supplied to a cutting surface that is formed in an outer circumferential region of a wafer in a trimming step, before a grinding step of grinding the wafer. This can remove or repair at least part of a damage layer formed in the outer circumferential region of the wafer due to the trimming step. As a result, breakage of the wafer that originates from the outer circumferential region in the grinding of the wafer which has been subjected to the edge trimming and generation of dust in a step after this grinding can be suppressed.