Semiconductor Protective Sheet for Bump Conformity and Clean Peeling
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Solution Overview
Problem
Existing protective sheets for semiconductor processing fail to accurately conform to the uneven surfaces of semiconductor chips with bumps, exhibit poor heat resistance, and leave adhesive residue during high-temperature processes such as reflow and sputtering, leading to issues like lifting and contamination.
Innovation Solution
A protective sheet comprising a substrate with an intermediate layer made from a cured ethylenically unsaturated group-free (meth)acrylic resin and an adhesive layer made from a cured ethylenically unsaturated group-containing (meth)acrylic resin, which is photocurable and forms a three-dimensional crosslinked structure upon active energy ray irradiation, reducing adhesive force and enabling residue-free peeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective sheet is used to protect semiconductor chips with bumps during processing, then surface protection is achieved, but the sheet cannot accurately conform to the uneven bump surfaces
Solution Approach 1:
The protective sheet is divided into multiple layers: a base sheet providing overall protection, a conforming layer with specific viscosity (100-10000 Pa·s at 25°C) that flows to match bump contours, and an adhesive layer for bonding. This segmentation allows each layer to perform its specific function - the conforming layer adapts to uneven surfaces while the base sheet provides structural protection.
Solution Approach 2:
The conforming layer's viscosity is carefully controlled within 100-10000 Pa·s at 25°C to enable it to flow and conform to bump surfaces while maintaining stability. The gel fraction is optimized at 20-80% to balance flexibility for conforming with structural integrity for protection, resolving the contradiction between adaptability and protective reliability.
2Reliability
If the protective sheet is made with strong adhesive to prevent lifting during high-temperature treatment, then heat resistance is improved, but adhesive residue remains on the adherend when peeled off
Solution Approach 1:
The adhesive layer uses a photopolymerization initiator that activates at specific wavelengths (300-400nm) to control the timing and extent of curing. By adjusting the initiator concentration (0.1-10 wt%) and exposure conditions, the adhesive achieves sufficient bonding strength for high-temperature processes while maintaining controlled peelability to prevent residue formation.
Solution Approach 2:
The adhesive layer transitions from a uncured state during application to a cured state during photopolymerization, providing strong adhesion for heat resistance. The controlled crosslinking density through photopolymerization allows the adhesive to maintain strength during processing but enable clean peeling afterward, eliminating residue while preserving heat resistance.
3Reliability
If the protective sheet undergoes high-temperature treatment during reflow or sputtering processes, then semiconductor bonding is achieved, but the protective sheet generates outgas causing lifting
Solution Approach 1:
The base sheet material is selected with specific thermal properties including heat resistance above 200°C and controlled thermal expansion coefficient to match semiconductor substrates. These parameter optimizations allow the sheet to withstand reflow and sputtering temperatures without degrading or generating excessive outgas, maintaining bonding capability while preventing lifting.
4Ease of operation
If the protective sheet is designed to be easily peeled off, then removal is simplified, but surface protection during processing is insufficient
Solution Approach 1:
The protective sheet is segmented into a robust base sheet for surface protection and a separate adhesive layer for bonding and peeling. The base sheet maintains strong protective properties throughout processing, while the adhesive layer's photopolymerization characteristics enable controlled bonding strength that facilitates easy peeling without compromising the base sheet's protective function.
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 protective sheet effectively conforms to uneven surfaces, withstands high temperatures, and can be peeled off without leaving residue, ensuring reliable semiconductor device manufacturing.
Implementation Method 1
an adhesive layer and an intermediate layer in this order on one main surface of the substrate, the intermediate layer being a cured product of a resin composition containing an ethylenically unsaturated group-free (meth)acrylic resin (A1) and a crosslinking agent (B1), and the adhesive layer being a cured product of an adhesive composition containing an ethylenically unsaturated group-containing (meth)acrylic resin (A2), a crosslinking agent (B2), and a photopolymerization initiator (C)
Data Source
AI summary
A protective sheet for semiconductor processing includes a substrate, and an intermediate layer and an adhesive layer in this order on one main surface of the substrate. The intermediate layer is a cured product of a resin composition comprising a (meth)acrylic resin (A1) not containing an ethylenically unsaturated group, and a crosslinking agent (B1), and the adhesive layer is a cured product of an adhesive composition comprising a specific ethylenically unsaturated group-containing (meth)acrylic resin (A2), a crosslinking agent (B2), and a photopolymerization initiator (C). The (meth)acrylic resin (A1) not containing an ethylenically unsaturated group has a plurality of functional groups that react with functional groups of the crosslinking agent (B1), and the ethylenically unsaturated group-containing (meth)acrylic resin (A2) has a plurality of functional groups that react with functional groups of the crosslinking agent (B2).