Thermocompression Wafer Bonding via Polymer Sheet
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Solution Overview
Problem
The existing methods for supporting wafers during processing, such as using liquid resin, double-sided adhesive tape, or wax, result in insufficient supporting force, leading to potential damage and quality degradation of device chips, especially when grinding thin wafers with bumps, and require additional steps for residue removal, reducing productivity.
Innovation Solution
A wafer processing method involving a thermoplastic polymer sheet for thermocompression bonding with a substrate, providing a sufficient supporting force and preventing residue issues, where the wafer is placed on a thermoplastic polymer sheet, evacuated, and heated under pressure to bond securely with the substrate, allowing for stable grinding and easy separation without leaving adhesives on the wafer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If liquid resin or double-sided adhesive tape is used to unite the wafer to the substrate, then the wafer can be supported to the substrate, but the supporting force is insufficient causing possible damage to the wafer
Solution Approach 1:
The patent changes the physical and chemical parameters of the bonding material from liquid resin/adhesive tape to thermoplastic polymer sheet. The thermoplastic polymer sheet provides sufficient mechanical strength and bonding force through thermal compression, resolving the insufficient supporting force issue while maintaining wafer stability during grinding.
Solution Approach 2:
The thermoplastic polymer sheet is designed as a disposable supporting layer that is removed after grinding. This eliminates the need for complex residue removal processes associated with liquid resins and adhesives, while providing adequate supporting force during the critical grinding operation.
2Strength
If liquid resin, adhesive, or wax is used to unite the wafer and substrate, then the wafer can be supported, but residue is left on the front side of the wafer causing quality degradation
Solution Approach 1:
The thermoplastic polymer sheet is designed as a disposable component that is completely removed after grinding. Unlike liquid resins and adhesives that leave residues, the sheet is peeled off cleanly, preventing any contamination of the device front side and maintaining manufacturing precision.
Solution Approach 2:
The patent extracts the bonding function from permanent adhesives to a temporary thermoplastic polymer sheet that can be completely removed. This extraction eliminates the residue problem entirely, as the sheet is peeled off after serving its supporting purpose during grinding.
3Strength
If liquid resin or adhesive is used to support the wafer, then the wafer can be held on the substrate, but additional steps for residue removal are required reducing productivity
Solution Approach 1:
The thermoplastic polymer sheet is designed as a disposable supporting layer that is simply peeled off after grinding. This eliminates the complex residue removal steps required when using liquid resins or adhesives, thereby improving productivity without compromising the supporting force during 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
This method ensures stable support for thin wafers during processing, disperses stress on bumps, prevents damage, and avoids residue on devices, maintaining quality and productivity by using thermocompression bonding with a thermoplastic polymer sheet.
Implementation Method 1
heating the polymer sheet as applying a pressure to the wafer, thereby uniting the wafer through the polymer sheet to the substrate by thermocompression bonding
Implementation Method 2
heating the polymer sheet as applying a pressure to the wafer, thereby uniting the wafer through the polymer sheet to the substrate by thermocompression bonding
Implementation Method 3
evacuating the enclosed environment
Data Source
AI summary
A wafer processing method includes a wafer providing step of placing a polyolefin or polyester sheet on an upper surface of a substrate for supporting a wafer and placing the wafer on an upper surface of the sheet in a condition where a back side of the wafer is exposed upward, a thermocompression bonding step of setting the wafer placed through the sheet on the substrate in an enclosed environment, next evacuating the enclosed environment, and next heating the sheet as applying a pressure to the wafer, thereby uniting the wafer through the sheet to the substrate by thermocompression bonding, a back processing step of processing the back side of the wafer supported through the sheet to the substrate, and a separating step of separating the wafer from the sheet bonded to the substrate.