Wafer Processing Laser Division Fluid Unloading
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Solution Overview
Problem
The existing methods for cutting semiconductor wafers, such as using cutting blades, limit the number of devices that can be obtained and pose a risk of damaging MEMS devices due to water scattering, and are challenging for cutting low-k films without separation, while laser processing can unintentionally crack wafers with modified layers.
Innovation Solution
A wafer processing method involving a wafer unit formed with an adhesive tape and annular frame, where a laser beam is applied along division lines to form modified layers, followed by blowing a fluid to cancel close contact between the tape and holding surface, and then using transfer means to unload and divide the wafer along these lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a cutting blade is used to cut the semiconductor wafer, then the wafer can be divided into separate regions, but the division groove width (20-40 μm) limits the number of devices that can be obtained
Solution Approach 1:
The patent replaces the mechanical cutting blade system with a laser processing system. The laser beam processes the wafer without physical contact, eliminating the need for mechanical division grooves and enabling much narrower division lines, thus increasing the number of devices that can be obtained from a single wafer.
Solution Approach 2:
The patent uses a fluid (gas or liquid) to blow off the adhesive tape from the wafer surface after laser processing. This pneumatic or hydraulic method eliminates the need for mechanical peeling that could damage the processed wafer or devices, providing a gentle separation mechanism.
2Ease of manufacture
If a cutting blade is used to cut the semiconductor wafer, then the wafer can be divided, but cutting water scatters and may damage MEMS devices
Solution Approach 1:
The patent replaces the wet mechanical cutting process with a dry laser processing method. The laser beam performs the cutting without requiring water for cooling or dust removal, thereby eliminating the harmful scattering of cutting water that could damage sensitive MEMS devices.
Solution Approach 2:
The laser processing can be performed in a controlled atmosphere (inert or vacuum environment) that protects the wafer and devices from contamination by water or other harmful substances, while still achieving effective cutting through the laser's thermal and ablation effects.
3Ease of manufacture
If a cutting apparatus is used to cut the semiconductor wafer, then the wafer can be divided, but cutting of low-k film without separation is difficult
Solution Approach 1:
The patent replaces the mechanical cutting apparatus with a laser processing system that can handle low-k films effectively. The laser's concentrated energy allows it to process low-k materials without the mechanical stress and separation issues that plague traditional cutting methods, enabling continuous processing of delicate low-k film structures.
4Ease of operation
If the adhesive tape is forcibly separated from the holding surface after laser processing, then the wafer can be unloaded, but the wafer may be unintentionally cracked
Solution Approach 1:
The patent uses a fluid blow-off method to gently separate the adhesive tape from the wafer surface. The fluid (gas or liquid) is directed at the tape to break the adhesion bond, allowing the tape to be removed without applying mechanical stress or force to the wafer, thereby preventing cracks in the processed structure.
Solution Approach 2:
The patent employs a fluid cushion between the tape and wafer surface during the separation process. This fluid layer acts as a cushion that absorbs the separation energy, preventing direct mechanical contact and forceful separation that could cause cracking. The cushioning effect protects the wafer throughout the unloading process.
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 prevents unintentional cracking of wafers with formed modified layers by reducing the forceful separation and allows for precise division of wafers into individual device chips without damaging them.
Implementation Method 1
applying a laser beam having a transmission wavelength to the wafer held on the holding surface of the chuck table along each division line to thereby form a modified layer inside the wafer along each division line
Implementation Method 2
holding the wafer of the wafer unit through the adhesive tape on a holding surface of a chuck table under suction
Implementation Method 3
blowing a fluid from the holding surface against the adhesive tape after performing the processing step to thereby cancel the close contact between the adhesive tape and the holding surface
Data Source
AI summary
A wafer processing method includes a wafer unit forming step of supporting a wafer through an adhesive tape to an annular frame to thereby form a wafer unit, a wafer unit holding step of holding the wafer through the adhesive tape on a holding surface of a chuck table under suction, a processing step of applying a laser beam to the wafer held on the chuck table to thereby form a modified layer inside the wafer, an unloading step of unloading the wafer unit from the chuck table, and a dividing step of dividing the wafer along the modified layer as a division start point. The wafer processing method further includes a close contact canceling step of blowing a fluid from the holding surface against the adhesive tape after performing the processing step to thereby cancel the close contact between the adhesive tape and the holding surface.