Laser Processing Single Crystal Silicon Shield Tunnels
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing laser processing methods fail to form proper shield tunnels in single crystal silicon wafers, as demonstrated by tests using conditions from Japanese Patent Laid-Open No. 2014-221483, which were ineffective for this material.
Innovation Solution
A laser processing apparatus and method utilizing a pulsed laser beam with a wavelength of 1950 nm or more in the transmission wavelength region, combined with a focusing lens numerical aperture setting that ensures the value obtained by dividing the numerical aperture by the refractive index of single crystal silicon falls within the range of 0.05 to 0.2, to form shield tunnels composed of a fine hole and an amorphous region extending from the front to the back surface of the wafer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a laser beam with wavelength of 1030 nm is applied to single crystal silicon wafer using conventional focusing conditions, then the processing can be performed, but proper shield tunnels cannot be formed
Solution Approach 1:
The patent changes the laser beam wavelength parameter from 1030 nm to 1950 nm or more, which is in the transmission wavelength region of single crystal silicon. This parameter change enables the laser beam to properly form shield tunnels in single crystal silicon wafers while maintaining the numerical aperture conditions (NA/n between 0.05 to 0.2).
Solution Approach 2:
Instead of using a wavelength that is absorbed by single crystal silicon (1030 nm), the patent inverts the approach by using a wavelength that is transmitted through the material (1950 nm or more). This inversion allows the laser energy to reach the focal point inside the wafer and form proper shield tunnels.
2Manufacturing precision
If the numerical aperture of the focusing lens is set according to conventional conditions (NA/n between 0.05 to 0.2), then the shield tunnel formation should be proper, but this condition is insufficient when using wrong wavelength with single crystal silicon
Solution Approach 1:
The patent maintains the numerical aperture condition (NA/n between 0.05 to 0.2) but combines it with a critical parameter change in laser wavelength (1950 nm or more). This combination ensures both proper shield tunnel formation and reliable processing results for single crystal silicon wafers.
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 approach enables the proper formation of shield tunnels in single crystal silicon wafers, as evidenced by successful test results showing improved tunnel quality with the specified wavelength and numerical aperture settings.
Implementation Method 1
A pulsed laser beam having a wavelength of 1950 nm or more in a transmission wavelength region to single crystal silicon is applied to single crystal silicon as a workpiece
Implementation Method 2
thereby forming a plurality of shield tunnels arranged along each division line, each shield tunnel being composed of a fine hole and an amorphous region formed around the fine hole
Data Source
AI summary
A laser processing method includes holding a single crystal silicon wafer as a workpiece, selecting a laser beam having a wavelength of 1950 nm or more in a transmission wavelength region to the single crystal silicon wafer, and applying the laser beam to the single crystal silicon wafer along a predetermined area with the focal point of the laser beam set inside the wafer, thereby forming a plurality of shield tunnels arranged along the predetermined area. Each shield tunnel is composed of a fine hole and an amorphous region formed around the fine hole for shielding the fine hole. The fine hole extends from a beam applied surface of the wafer where the laser beam is applied to the other surface opposite to the beam applied surface.