Wafer Processing Sheet with Stress-Relaxing Adhesive Layer
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Solution Overview
Problem
Current sheets for processing wafers lack comprehensive properties such as excellent heat resistance, dimensional stability, stress relaxation, and cuttability, often resulting in wafer damage due to reduced stress relaxation and non-uniform pressure during high-temperature processes, especially for large-diameter and thin-wafer applications.
Innovation Solution
A sheet comprising a substrate with a glass transition temperature ranging from -20°C to 45°C, formed from a photo-curable composition with high-molecular weight polymers and monomers, and an anti-blocking layer with a thermally cured or uncured resin component, providing enhanced heat resistance, dimensional stability, and stress relaxation properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a hard substrate having a high melting point is used to secure heat resistance and dimensional stability, then heat resistance and dimensional stability are improved, but protection of the wafer is degraded and stress relaxation is reduced, leading to a higher probability of damage to the wafer
Solution Approach 1:
The invention uses a composite structure consisting of a PET substrate combined with a silicone resin-based adhesive layer. The PET substrate provides dimensional stability and heat resistance, while the silicone resin adhesive layer provides stress relaxation and wafer protection. This composite material approach allows the sheet to simultaneously achieve heat resistance (from PET) and stress relaxation (from silicone resin), resolving the contradiction between heat resistance and wafer protection.
Solution Approach 2:
The invention specifies precise parameter ranges for the silicone resin adhesive layer, including viscosity (10-10,000 cP), Shore A hardness (10-80), and thickness (1-50 μm). By controlling these parameters, the adhesive layer achieves optimal stress relaxation properties while maintaining heat resistance. The glass transition temperature of the adhesive is controlled to be -50°C to 0°C to ensure proper stress relaxation at processing temperatures.
2Reliability
If the stress relaxation properties are reduced or a protrusion is present on the sheet, then the wafer is easily damaged due to residual stress or non-uniform pressure
Solution Approach 1:
The invention controls the glass transition temperature of the adhesive layer to be -50°C to 0°C and specifies viscosity (10-10,000 cP) and Shore A hardness (10-80) ranges. These parameter controls ensure the adhesive maintains proper stress relaxation properties at processing temperatures, preventing wafer damage from residual stress while maintaining uniform pressure distribution.
Solution Approach 2:
The adhesive layer is applied to the substrate before wafer processing, creating a pre-formed stress-relaxing interface. The adhesive is cured under controlled conditions (60-100°C for 1-24 hours) before use, ensuring it has the proper mechanical properties for stress relaxation during subsequent wafer processing operations.
3Productivity
If the cuttability of the sheet for processing a wafer is decreased, then a cutting defect may occur during the process and wafer processing may be discontinuously performed, resulting in reduced production efficiency and wafer damage
Solution Approach 1:
The invention specifies the PET substrate thickness to be 7-13 μm and the adhesive layer thickness to be 1-50 μm. These thin dimensions, combined with the controlled Shore A hardness (10-80) and viscosity (10-10,000 cP) of the adhesive, ensure the composite sheet has excellent cuttability while maintaining structural integrity for continuous processing.
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 sheet effectively prevents wafer breakage from residual stress and non-uniform pressure, maintains excellent cuttability, and prevents blocking phenomena during wafer processing, making it suitable for dicing, back-grinding, and picking-up processes.
Implementation Method 1
the base of the sheet is formed by radiation-curing a radiation-curable composition comprising a high-molecular weight (500-10,000) oligomer and monomer component
Implementation Method 2
The anti-blocking layer is formed on the substrate and has a thermally cured resin component or an uncured resin component
Data Source
Figure 1
AI summary
[Summary] Provided is a sheet for processing a wafer. The sheet can exhibit excellent heat resistance and dimensional stability, prevent breakage of a wafer in response to residual stress due to excellent stress relaxation properties, inhibit damage to or dispersion of the wafer due to application of a non-uniform pressure, and also exhibit excellent cuttability. The sheet can effectively prevent a blocking phenomenon from occurring during wafer processing. For these reasons, the sheet can be useful for processing a wafer in various wafer preparation processes such as dicing, back-grinding and picking-up.