Wafer Packaging Using UV Temporary Bonding Carrier
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Solution Overview
Problem
Wafer packaging methods face challenges in maintaining wafer integrity and image sensing ability due to the need for optical glass sheets, which can lead to warpage and contamination issues during the dicing process, affecting the yield rate and light transmittance of image sensing chips.
Innovation Solution
A wafer packaging method that uses a light transmissive carrier with an ultraviolet temporary bonding layer to support the wafer without an optical glass sheet, allowing for precise adhesion and removal, and a light transmissive protection sheet with permanent and temporary bonding layers to protect conductive pads from contamination during processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an optical glass sheet is used to cover the wafer surface for protection, then the wafer is protected from dust and warpage is prevented, but the light transmittance of the wafer is reduced and the conductive pads are prone to contamination during dicing
Solution Approach 1:
The patent removes the optical glass sheet from the wafer structure and replaces it with a light transmissive carrier that provides mechanical support without the contamination issues. The carrier is bonded to the wafer backside, allowing the wafer surface to remain exposed and uncontaminated while still providing protection against warpage and dust.
Solution Approach 2:
The light transmissive carrier acts as an intermediary between the wafer and the external environment. It provides the protective functions previously offered by the optical glass sheet (mechanical support, warpage prevention) while being optically transparent and non-contaminating, thus resolving the contradiction between protection and light transmittance.
2Object-affected harmful factors
If the wafer surface is left uncovered to improve light transmittance, then image sensing ability is improved, but the wafer becomes prone to warpage and cracking during handling and dicing
Solution Approach 1:
The light transmissive carrier serves as a mediator that provides structural support to the thin wafer without interfering with light transmission. By bonding the carrier to the wafer backside, the wafer gains mechanical strength to prevent warpage and cracking during handling and dicing, while the front surface remains exposed for optimal light transmittance.
Solution Approach 2:
Instead of placing the protective layer on the front surface of the wafer (where it would block light), the patent moves the protective function to the backside of the wafer. This dimensional change allows the protection mechanism to operate from the opposite side, eliminating the conflict between protection and light transmittance.
3Stability of the object's composition
If the optical glass sheet is bonded to the wafer, then the wafer is stabilized against warpage, but the conductive pads located at the wafer edges are contaminated during subsequent dicing and chemical processing
Solution Approach 1:
The patent extracts the protective function from the optical glass sheet and transfers it to the light transmissive carrier bonded on the wafer backside. This separation removes the source of contamination (the glass sheet) from proximity to the conductive pads, allowing the pads to remain clean during dicing and chemical processing while the carrier continues to provide wafer stabilization.
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 method enhances wafer stability against warpage, improves light transmittance, and increases the yield rate by eliminating the need for optical glass sheets and preventing contamination of conductive pads, thereby improving the image sensing ability of the chips.
Implementation Method 1
An ultraviolet temporary bonding layer is formed on the second surface of the light transmissive carrier or a third surface of the wafer opposite to the first surface. The ultraviolet temporary bonding layer is used to adhere the second surface of the light transmissive carrier to the third surface of the wafer
Implementation Method 2
A fourth surface of the light transmissive carrier opposite to the second surface is exposed to ultraviolet to eliminate adhesion force of the ultraviolet temporary bonding layer
Data Source
AI summary
A wafer packaging method includes the following steps. A wafer having a plurality of integrated circuit units is provided. A first surface of the wafer opposite to the integrated circuit units is ground. A release layer is formed on a second surface of a light transmissive carrier. An ultraviolet temporary bonding layer is formed on the second surface of the light transmissive carrier or a third surface of the wafer. The ultraviolet temporary bonding layer is used to adhere the second surface of the light transmissive carrier to the third surface of the wafer. The first surface of the wafer is adhered to an ultraviolet tape. A fourth surface of the light transmissive carrier is exposed to ultraviolet to eliminate adhesion force of the ultraviolet temporary bonding layer. The light transmissive carrier and the release layer are removed.