Pressure-Sensitive Adhesive Sheet for Semiconductor Wafer Grinding
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Solution Overview
Problem
Existing surface protection sheets for semiconductor wafers with bumps fail to prevent collapse of bumps during back surface grinding, leading to dimples or cracks, due to inadequate viscoelasticity and residual stress issues.
Innovation Solution
A pressure-sensitive adhesive sheet with a base film composed of a cured polyether polyol urethane(meth)acrylate oligomer layer and a thermoplastic resin layer, providing specific viscoelasticity to moderate height differences and prevent bump collapse during grinding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the pressure-sensitive adhesive layer is increased to moderate height differences and resolve pressure differences, then the cushioning property improves, but the pressure-sensitive adhesives easily wraparound base parts of the bumps causing attachment to the circuit side
Solution Approach 1:
The invention changes the physical and chemical parameters of the pressure-sensitive adhesive by specifying molecular weight ranges (5,000-50,000), functional group ratios (0.01-1.0 mmol/g), and composition ratios with inert fillers (90:10 to 50:50). These parameter changes optimize the adhesive's viscosity and flow characteristics to prevent wraparound while maintaining cushioning effectiveness.
Solution Approach 2:
The invention uses composite materials by combining the pressure-sensitive adhesive with inert fillers (such as silica, alumina, or titanium oxide) in specific ratios. This composite structure provides both the cushioning property needed to moderate height differences and the controlled flow characteristics that prevent excessive wraparound and attachment to the circuit side.
2Reliability
If the flowability of the pressure-sensitive adhesives is increased to resolve pressure differences, then the pressure difference due to level difference of bumps is resolved, but the pressure-sensitive adhesives easily wraparound base parts of the bumps
Solution Approach 1:
The invention optimizes the flowability parameter by controlling the molecular weight (5,000-50,000) and functional group ratio (0.01-1.0 mmol/g) of the pressure-sensitive adhesive. This balanced flowability allows the adhesive to adequately fill and resolve pressure differences caused by bump height variations without becoming too fluid to cause wraparound.
Solution Approach 2:
The invention applies local quality by using inert fillers that provide different local properties within the adhesive composition. The filler particles provide structural support and control flow behavior in high-stress areas, allowing the adhesive to resolve pressure differences without excessive wraparound.
3Object-generated harmful factors
If a surface protection sheet with opening part is used to prevent adhesive attachment to bumps, then adhesive wraparound is prevented, but the protection coverage is reduced and handling becomes more complex
Solution Approach 1:
Instead of modifying the sheet structure with opening parts, the invention changes the chemical and physical parameters of the pressure-sensitive adhesive itself. By controlling molecular weight, functional group ratio, and adding inert fillers, the adhesive's flow and adhesion properties are optimized to prevent wraparound naturally, maintaining a simple continuous sheet structure.
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 solution effectively prevents bump collapse and dimple/crack formation during wafer grinding, ensuring stable wafer integrity and smoothness, with adjustable compression stress and improved handling properties.
Implementation Method 1
a layer of a cured product in which a composition including a polyether polyol urethan(meth)acrylate oligomer and an energy ray curable monomer is cured by energy ray irradiation
Data Source
AI summary
The base film of the invention is a base film of a pressure-sensitive adhesive sheet for laminating onto a semiconductor wafer composed of: (A) a layer of a cured product in which a composition including a polyether polyol urethan(meth)acrylate oligomer and an energy ray curable monomer is cured by energy ray irradiation, and (B) a thermoplastic resin layer. The present invention, by using a surface protection sheet, protects a circuit side of a wafer with bumps, prevents collapse of bumps on the circuit side when grinding the back surface, and prevents generation of dimples or cracks on the grinding surface.