Wafer Grinding Method Reducing Chippings
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Solution Overview
Problem
The TAIKO process for wafer thinning results in chippings at the inner circumferential edge of the ring-shaped reinforcing part, leading to wafer breakage, irregular etching, and issues with metal film formation and dicing tape sticking.
Innovation Solution
A grinding method that includes a holding step and two grinding steps to form a thin plate part and a ring-shaped reinforcing part, with specific movements of the grinding wheel to reduce chippings, such as grinding the inner circumferential side surface of the ring-shaped reinforcing part and separating the grinding abrasive stones from the wafer surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the TAIKO process is employed to thin the wafer by grinding the device region, then the strength of the wafer is improved and warpage is suppressed, but chippings are generated at the inner circumferential edge of the ring-shaped reinforcing part
Solution Approach 1:
The invention applies preliminary action by performing a first grinding step that grinds the device region to form the ring-shaped reinforcing part before the second grinding step. This preliminary grinding creates a controlled structure that prevents uncontrolled chipping generation during subsequent processing. The first grinding step establishes the reinforcing part with predetermined geometry, preventing the generation of harmful chippings at the inner circumferential edge.
Solution Approach 2:
The grinding process is segmented into multiple distinct steps: a first grinding step that grinds the device region to form the ring-shaped reinforcing part, and a second grinding step that grinds the inner circumferential side surface. This segmentation allows each step to perform its specific function optimally - the first step creates the reinforcing structure while the second step refines the inner circumferential surface, preventing chipping generation.
2Productivity
If the grinding wheel is vertically lowered to advance the grinding, then the grinding efficiency is improved, but the contact between the outer circumferential side surface of grinding abrasive stones and the inner circumferential side surface of the ring-shaped reinforcing part increases chippings
Solution Approach 1:
The grinding operation is segmented into two separate steps with distinct functions. The first grinding step focuses on forming the ring-shaped reinforcing part by grinding the device region. The second grinding step specifically addresses the inner circumferential side surface. This segmentation prevents the simultaneous occurrence of vertical lowering contact that causes chipping, while maintaining grinding efficiency through optimized step sequences.
Solution Approach 2:
The first grinding step performs preliminary action by forming the ring-shaped reinforcing part with controlled geometry before the second grinding step occurs. This preliminary formation establishes a structure that prevents uncontrolled chipping during the subsequent second grinding step, even when the grinding wheel is vertically lowered for efficiency.
3Reliability
If chippings are formed at the inner circumferential edge, then the wafer structure is compromised leading to breakage, but removing chippings requires additional processing steps
Solution Approach 1:
The first grinding step performs preliminary action by forming the ring-shaped reinforcing part with controlled geometry that prevents chipping generation in the first place. By establishing this structured reinforcing part before subsequent processing, the invention maintains wafer integrity and reliability without requiring additional corrective processing steps to remove chippings.
Solution Approach 2:
The invention converts the potential harm of chipping into a benefit by using the grinding process to deliberately form the ring-shaped reinforcing part with controlled geometry. The grinding action that could potentially cause chipping is instead harnessed to create a beneficial reinforcing structure with smooth, chip-free surfaces that enhance wafer integrity.
4Ease of manufacture
If wet etching is executed after the TAIKO process, then the back surface is processed, but etching at the inner circumferential edge causes the edge to become wave line-shaped with irregular recesses and projections
Solution Approach 1:
The first grinding step performs preliminary action by forming the ring-shaped reinforcing part with a controlled, uniform inner circumferential surface before wet etching occurs. This preliminary formation ensures that when wet etching is subsequently applied to the back surface, the etchant encounters a uniform surface that prevents the formation of wave line-shaped irregularities, maintaining manufacturing precision and edge uniformity.
Solution Approach 2:
The processing is segmented into distinct steps: the first grinding step creates the uniform ring-shaped reinforcing part, and the wet etching step subsequently processes the back surface. This segmentation ensures that the inner circumferential edge is already uniform before etching begins, preventing the propagation of irregularities during the etching process and maintaining edge uniformity.
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 reduces the number and size of chippings at the inner circumferential edge of the ring-shaped reinforcing part, minimizing wafer breakage and improving the subsequent processing steps like etching and tape sticking.
Implementation Method 1
grinding a region on a back surface side corresponding to a device region in the wafer to form a recess part with a circular disc shape
Implementation Method 2
holding the wafer by a chuck table rotatable around a rotating shaft disposed to pass through the center of the chuck table
Data Source
AI summary
A grinding method of a wafer having a circular disc shape includes a first grinding step of forming a ring-shaped reinforcing part by lowering a grinding wheel relative to a chuck table to bring the grinding wheel close to the wafer and grinding the wafer, a second grinding step of grinding the inner circumferential side surface of the ring-shaped reinforcing part by moving the grinding wheel relative to the wafer toward the outside of the wafer in the radial direction, a first separation step of separating the grinding wheel from the inner circumferential side surface of the ring-shaped reinforcing part by moving the grinding wheel relative to the wafer toward the inside of the wafer in the radial direction and a second separation step of separating the grinding wheel from the top surface of a thin plate part by raising the grinding wheel relative to the chuck table.