Wafer Laser Processing UV Protective Film
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Solution Overview
Problem
The existing wafer processing methods, such as grinding with a protective tape on the front face and using dicing tape on the back face, often result in contamination of device chips due to grinding water penetration and adhesive film scattering, degrading the quality of the chips.
Innovation Solution
A method involving the application of a protective film formed by coating liquid-state resin hardened by ultraviolet rays on the wafer's front face, followed by a modified layer creation using a laser beam, and subsequent back face grinding with controlled water supply to separate individual device chips, along with adhesive film handling to prevent contamination and scattering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a protective tape is adhered to the front face of the wafer and grinding water is supplied during back face grinding, then the wafer can be divided into individual device chips, but the grinding water penetrates from between the divided chips and contaminates the side face and front face of the device chips
Solution Approach 1:
A repulsive liquid layer is introduced as an intermediary substance between the grinding water and the device chips. This repulsive liquid, which has different wetting properties than grinding water, forms a barrier that prevents grinding water from penetrating and contaminating the chip surfaces during the grinding and division process
Solution Approach 2:
A protective film is formed on the front face of the wafer before grinding. This thin film acts as a physical barrier that prevents grinding water from reaching and contaminating the device chips during the grinding process, while still allowing the grinding operation to proceed effectively
2Reliability
If the scheduled division lines have a width of approximately 50 μm to accommodate a 20 μm thick cutting blade, then the cutting can be performed effectively, but the area ratio of the scheduled division lines occupying in the area of the wafer is high and the productivity is low
Solution Approach 1:
The mechanical cutting blade system is replaced with a laser-based internal processing system. The laser creates a modified layer inside the wafer material without requiring a physical blade, eliminating the need for wide division lines and allowing much narrower scribe lines that do not significantly reduce wafer area utilization
Solution Approach 2:
The cutting process transitions from a surface-level mechanical operation to a volumetric internal process. By creating a modified layer within the bulk material rather than removing material from the surface, the process enables narrower division lines and higher wafer area utilization while maintaining cutting effectiveness
3Strength
If adhesive film is used to hold the wafer on the chuck table, then the wafer can be secured during processing, but the adhesive film may scatter and adhere to the front face of device chips causing contamination
Solution Approach 1:
A release film is introduced as an intermediary layer between the adhesive film and the device chips. This release film allows the adhesive to hold the wafer securely during processing while preventing direct contact between the adhesive and the chip surfaces, thereby eliminating adhesive contamination
Solution Approach 2:
A release film is placed over the adhesive film to create a non-stick barrier. This thin film allows the adhesive to perform its holding function while preventing adhesive material from scattering and adhering to the device chips during subsequent processing steps
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 effectively prevents contamination of device chips by containing grinding water and dust, maintains chip quality by suppressing movement and penetration, and ensures clean separation of device chips without adhering debris to their surfaces.
Implementation Method 1
coating liquid-state resin, which is hardened by irradiation of ultraviolet rays thereon, on the front face of the wafer to form a protective film
Implementation Method 2
irradiating a laser beam of a wavelength having a transparency to the wafer along the scheduled division lines with a focal point thereof positioned in the inside of the wafer to form a modified layer along the scheduled division lines in the inside of the wafer
Data Source
AI summary
A wafer is divided into individual device chips along a plurality of scheduled division lines. A protective film is formed by coating liquid-state resin, which is hardened by irradiation of ultraviolet rays thereon, on the front face of the wafer. The protective film is hardened by irradiating ultraviolet rays upon the protective film. A protective tape is adhered on a front face of the hardened protective film. A modified layer is formed by irradiating a laser beam of a wavelength having a transparency to the wafer along the scheduled division lines with a focal point thereof positioned in the inside of the wafer. A back face of the wafer is ground while grinding water is supplied to thin the wafer to a given thickness and divide the wafer into the individual device chips along the scheduled division lines using the modified layer as a start point of the break.