Wafer Alignment via Laser Ablation of Insulating Film
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Solution Overview
Problem
The challenge is to accurately align a semiconductor wafer with an insulating film on its processed surface during laser beam processing, as the insulating film prevents detection of alignment marks, hindering precise positioning on the chuck table.
Innovation Solution
An alignment method for a laser beam processing machine that involves storing design coordinates based on crystal orientation marks, removing the insulating film at alignment mark positions using a laser beam, and adjusting coordinates for precise positioning, allowing accurate alignment despite the insulating film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an insulating film is coated on the processed surface of the wafer, then the quality of the via holes is improved by preventing metal diffusion into the substrate, but the alignment marks cannot be detected, making accurate positioning difficult
Solution Approach 1:
The insulating film is selectively removed only at the alignment mark positions, creating localized exposed regions while maintaining the film's protective function in other areas. This segmentation allows simultaneous achievement of mark detection and via hole quality protection
Solution Approach 2:
The insulating film is extracted (removed) specifically at the alignment mark locations to enable detection. This selective extraction resolves the contradiction by removing the film only where it obstructs the detection function, while preserving it where it provides protective function
2Ease of manufacture
If a drill is used to form via holes in the substrate, then the process is simple, but the drill must be controlled extremely accurately to avoid damaging the bonding pads, and productivity is reduced
Solution Approach 1:
The mechanical drilling process is replaced with a laser beam processing system. The laser beam can be precisely controlled to form via holes without physical contact, eliminating the accuracy-control issues of mechanical drills and enabling higher productivity through automated laser scanning and processing
3Measurement precision
If the insulating film is completely removed to enable alignment mark detection, then accurate positioning is achieved, but the protective function against metal diffusion is lost
Solution Approach 1:
The insulating film coverage is changed from uniform (complete) to non-uniform (selective removal at alignment marks). This local quality change allows the film to provide protection in most areas while enabling detection at specific locations, resolving the contradiction between protection and detection
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
Enables accurate positioning of the wafer on the chuck table, ensuring precise alignment and processing even with an insulating film on the surface, thereby improving the efficiency of laser beam processing.
Implementation Method 1
a laser beam application means having a condenser for applying a laser beam to the workpiece held on the chuck table
Data Source
AI summary
An alignment method of a laser beam processing machine comprising a chuck table, a laser beam application means having a condenser for applying a laser beam to the workpiece held on the chuck table, an image pick-up means for picking up an image of the workpiece held on the chuck table and a control means having a memory for storing the specifications of the workpiece, the method comprising the steps of storing the design coordinates of a processing position set based on the mark indicating the crystal orientation of a wafer and alignment marks; picking up an image of the periphery of the wafer with the image pick-up means and locating the mark indicating the crystal orientation of the wafer at a predetermined position; positioning the design coordinate position of each of the alignment marks set based on the mark indicating the crystal orientation of the wafer right below the condenser and applying a laser beam from the condenser so as to remove the insulating film in the alignment mark areas; and picking up an image of the alignment marks with the image pick-up means and adjusting the coordinates of the processing position of the wafer on the chuck table based on the image of the alignment marks.