Laser Ablation of Thermoset Adhesive for Wafer Release
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Solution Overview
Problem
Existing methods for releasing handlers from semiconductor wafers during CMOS fabrication face limitations due to temperature-sensitive adhesives and low-temperature processing constraints, which can lead to adhesive breakdown and contamination or damage to the wafer.
Innovation Solution
The use of a thermoset polymer adhesive and a laser with a wavelength selected based on the transparency of the handler material, such as quartz, glass, or sapphire, for ablating the adhesive and releasing the handler from the wafer without damaging the wafer, allowing for high-temperature processing up to 400°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a temperature-sensitive adhesive is used to attach the handler to the wafer, then the handler can be attached at low temperatures, but the adhesive breaks down at high temperatures up to 400°C during CMOS fabrication
Solution Approach 1:
The adhesive composition is changed from temperature-sensitive to thermoset polymer, fundamentally altering its thermal response characteristics. This parameter change enables the adhesive to maintain stability at high temperatures up to 400°C while remaining removable through chemical etching with oxygen plasma, thus resolving the contradiction between temperature stability and release capability
Solution Approach 2:
The release mechanism is substituted from thermal or mechanical methods to chemical etching using oxygen plasma. This replacement allows the adhesive to remain stable during high-temperature processing while enabling clean release through chemical means, avoiding the adhesive breakdown that occurs with temperature-based release methods
2Ease of operation
If a chemically dissolvable adhesive is used, then the adhesive can be removed using release chemicals, but specialized handler material is required to allow chemicals to diffuse through the handler
Solution Approach 1:
Oxygen plasma is introduced as an intermediary substance that enables adhesive removal without requiring chemical diffusion through the handler. The plasma acts as a mediator that chemically etches the thermoset polymer adhesive directly, eliminating the need for specialized handler materials with diffusion pathways while maintaining ease of release
3Ease of operation
If wax sliding is used for release, then the handler can be released from the wafer, but it is limited to low temperature processing and requires a special sliding mechanism
Solution Approach 1:
The mechanical sliding mechanism is replaced with chemical etching using oxygen plasma. This substitution eliminates the temperature limitation of wax-based methods, allowing the process to accommodate high-temperature CMOS fabrication up to 400°C while simplifying the release mechanism to a straightforward chemical treatment step
4Reliability
If a thermoset polymer adhesive is used with laser ablation, then the handler can be released without contamination or damage to the wafer, but the handler material must be transparent in the laser wavelength range
Solution Approach 1:
The laser wavelength parameter is selected to match the transparency characteristics of common handler materials such as quartz, glass, or sapphire. By changing the wavelength parameter rather than the handler material, the system maintains versatility in handler selection while achieving clean adhesive ablation that preserves wafer integrity without contamination
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 enables efficient and contamination-free release of the handler from the wafer, maintaining the integrity of the IC wafer and ensuring high throughput in the fabrication process.
Implementation Method 1
ablating the adhesive through the handler using a laser, wherein a wavelength of the laser is selected based on the transparency of the handler material
Implementation Method 2
a handler comprising a material that is transparent in a wavelength range of about 193 nanometers (nm) to about 400 nm; ablating the adhesive through the handler using a laser, wherein a wavelength of the laser is selected based on the transparency of the handler material
Data Source
AI summary
A method for releasing a handler from a wafer, the wafer comprising an integrated circuit (IC), includes attaching the handler to the wafer using an adhesive comprising a thermoset polymer, the handler comprising a material that is transparent in a wavelength range of about 193 nanometers (nm) to about 400 nm; ablating the adhesive through the handler using a laser, wherein a wavelength of the laser is selected based on the transparency of the handler material; and separating the handler from the wafer.