Wafer Dividing via Laser Deteriorated Layer and UV Tape
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Solution Overview
Problem
The existing methods for dividing wafers along lattice patterned dividing lines often result in fine cracks on the rear surfaces of devices due to the soft adhesive used, and dust scattering, which reduces the quality of the devices.
Innovation Solution
A method involving the formation of a deteriorated layer inside the wafer along the dividing lines using a laser beam, combined with reduced adhesive strength on the adhesive tape and the application of a protective tape to prevent bouncing and dust adherence, allowing for controlled division without chipping or dust contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a soft adhesive is applied to the adhesive tape for supporting the wafer during division, then the wafer can be securely held, but the wafer bounces due to the soft adhesive influence, producing fine cracks (chippings) on the rear surfaces of devices
Solution Approach 1:
The adhesive strength is reduced in advance by applying ultraviolet radiation before the division process. This preliminary action ensures that when external force is applied during division, the adhesive will not cause bouncing that leads to chippings, while still maintaining sufficient holding capability.
Solution Approach 2:
The adhesive strength parameter is dynamically adjusted by controlling the degree of ultraviolet radiation application. By changing the adhesive strength from its initial state to a reduced state, the system achieves optimal balance between holding the wafer securely and preventing bouncing during division.
2Productivity
If the wafer is divided along the dividing lines where the deteriorated layer has been formed, then the division can be achieved, but dust is scattered and adheres onto the surfaces of devices, reducing the qualities of the devices
Solution Approach 1:
A protective tape is introduced as an intermediary element between the external environment and the wafer surface during division. This protective tape prevents dust generated during the division process from adhering to the device surfaces, while allowing the division to proceed efficiently.
Solution Approach 2:
The harmful dust particles are effectively removed from the interaction zone by the protective tape barrier. The protective tape captures and isolates the dust that would otherwise contaminate the device surfaces during the division process.
3Manufacturing precision
If the adhesive strength is reduced by applying ultraviolet radiation to the adhesive tape, then the wafer does not bounce during division, but the adhesive strength becomes too weak to hold the wafer securely
Solution Approach 1:
The adhesive strength parameter is precisely controlled by adjusting the intensity and duration of ultraviolet radiation. This parameter change transforms the adhesive from a state that causes bouncing to a state that provides optimal holding without excessive strength, achieving the desired balance.
Solution Approach 2:
The ultraviolet radiation application process provides feedback control for adhesive strength adjustment. By monitoring the division process and wafer stability, the ultraviolet radiation parameters can be adjusted to achieve the optimal adhesive strength that prevents bouncing while maintaining secure holding.
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 effectively prevents chipping on the rear surfaces of devices and prevents dust from adhering to the devices during division, enhancing the quality and integrity of the divided devices.
Implementation Method 1
forming a deteriorated layer inside the wafer along the dividing lines by irradiating with a laser beam of a wavelength having permeability for the wafer
Implementation Method 2
reducing the adhesive strength of the adhesive tape by irradiating with ultraviolet the adhesive tape affixing to the wafer
Data Source
AI summary
A method of dividing a wafer having devices which are formed in a plurality of areas sectioned by a plurality of dividing lines formed in a lattice pattern on the front surface, into individual devices along the dividing lines, comprising: a deteriorated layer forming step for forming a deteriorated layer in the inside of the wafer along the dividing lines by applying a laser beam of a wavelength having permeability for the wafer along the dividing lines; a wafer supporting step for putting the rear surface of the wafer on the surface of an adhesive tape which is mounted on an annular frame and whose adhesive strength is reduced by applying ultraviolet radiation thereto; an adhesive strength reducing step for reducing the adhesive strength of the adhesive tape by applying ultraviolet radiation to the adhesive tape to which the wafer has been affixed; and a dividing step for dividing the wafer into individual devices along the dividing lines where the deteriorated layer has been formed by exerting external force to the wafer affixed to the adhesive tape whose adhesive strength has been reduced after the adhesive strength reducing step.