Wafer Backside Recess Processing to Suppress Thin-Wafer Deflection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Wafers with circular recesses tend to deflect when thinned to 100 μm or below, making them difficult to handle and increasing the risk of breakage due to the formation of a circular recess.
Innovation Solution
A wafer processing method that includes forming a circular recess and an annular projection on the back surface, followed by applying a laser beam of a specific wavelength to the annular projection to create a modified layer before or after the recess formation, which helps in suppressing wafer deflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the wafer is ground to thin the wafer to a thickness of 100 μm or below to form a circular recess, then the wafer can be divided into individual devices, but the wafer at a part corresponding to the circular recess may be deflected and the risk of breakage is enhanced
Solution Approach 1:
A modified layer is formed in the annular projection before the wafer is divided into individual devices. This preliminary action strengthens the annular projection that supports the circular recess, preventing wafer deflection and breakage during subsequent handling and dicing operations.
Solution Approach 2:
The laser beam is applied selectively to the annular projection surrounding the circular recess, creating a modified layer only in this specific region. This local modification enhances the mechanical properties where needed most - at the support structure - without affecting the overall wafer or device regions.
2Ease of operation
If a circular recess is formed in the center of the back surface of the wafer to facilitate handling, then the wafer can be accommodated in a cassette, but the wafer may deflect and become difficult to accommodate
Solution Approach 1:
The modified layer is formed in the annular projection before the wafer is placed in the cassette. This preliminary strengthening ensures that the wafer maintains its flatness and structural integrity during the handling and loading process, enabling easy accommodation in the cassette without deflection issues.
Solution Approach 2:
The laser processing creates a modified layer with altered material properties in the annular projection. This modified layer acts as a composite structure with enhanced mechanical strength, providing local reinforcement that maintains wafer flatness while preserving ease of handling.
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 wafer deflection and facilitates handling by creating a modified layer that reduces stress and enhances mechanical properties, thereby minimizing the risk of breakage during the thinning process.
Implementation Method 1
applying a laser beam of such a wavelength as to be transmitted through the wafer to the annular projection to thereby form a modified layer
Data Source
AI summary
A wafer processing method includes a circular recess forming step of forming a circular recess in a center of a back surface of a wafer to thereby form an annular projection surrounding the circular recess, and a modified layer forming step of applying a laser beam of such a wavelength as to be transmitted through the wafer to the annular projection to thereby form a modified layer.