Through-Substrate Laser Focusing With Aberration Correction
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Solution Overview
Problem
Existing laser treatment methods for semiconductor substrates face challenges due to silicon's inability to transmit electromagnetic radiation with wavelengths smaller than 1,100 nm, limiting the use of common infrared lasers, and difficulties in efficiently focusing the laser beam and preventing damage to adjacent regions.
Innovation Solution
A system and method that utilize a laser beam with a wavelength greater than the sum of 500 nm and the substrate's bandgap wavelength, and less than the sum of 2,500 nm and the substrate's bandgap wavelength, combined with an optical device featuring a digital aperture greater than 0.3 and spherical aberration correction, to focus the laser beam through the semiconductor substrate and treat the region adjacent to it without damaging nearby areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a common infrared laser with wavelength smaller than 1,100 nm is used, then the laser can be readily available and cost-effective, but silicon substrate cannot transmit the radiation effectively
Solution Approach 1:
The patent changes the wavelength parameter of the laser beam to be greater than the bandgap wavelength of silicon (approximately 1,100 nm), specifically using wavelengths in the range of 1,100-2,500 nm. This parameter change enables the laser beam to transmit through the silicon substrate effectively while still achieving the desired treatment effect on the target region.
2Manufacturing precision
If the laser beam is focused onto the region to be treated through the substrate, then treatment precision is improved, but non-linear interactions cause difficulty in efficient focusing and potential damage to adjacent regions
Solution Approach 1:
The patent employs pulsed laser delivery with pulse durations in the range of 0.1 ps to 1,000 ps. This periodic action allows the laser energy to be delivered in controlled bursts, enabling precise focusing onto the target region while limiting the total energy exposure time, thereby preventing thermal accumulation and damage to adjacent regions.
Solution Approach 2:
The patent uses pulse durations and peak powers specifically optimized to deliver sufficient energy for effective treatment while avoiding excessive energy that would cause damage. By controlling the pulse parameters within specific ranges, the system achieves the minimum necessary action for treatment without exceeding the threshold for harmful effects.
3Productivity
If the laser pulse duration is very short (0.1 ps to 1,000 ps) with high peak power (300 kW to 100 MW), then treatment efficiency is improved, but controlling the energy delivery becomes more challenging
Solution Approach 1:
The patent incorporates control systems that monitor and regulate the laser pulse parameters in real-time. By implementing feedback control, the system can maintain precise control over the pulse duration and peak power, ensuring that each pulse delivers the optimal energy for treatment while preventing any single pulse from exceeding safe energy thresholds.
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 allows for effective focusing and treatment of the region through the substrate, minimizing non-linear interactions and preventing damage to adjacent regions, thereby overcoming the limitations of previous methods.
Implementation Method 1
the wavelength of the incident laser beam is greater than the sum of 500 nm and of the wavelength associated with the bandgap of the material forming the substrate
Implementation Method 2
an optical device associating a digital aperture greater than 0.3 and means for correcting the spherical aberrations occurring during the crossing of the substrate
Implementation Method 3
the ablation of the seed layer by means of an infrared laser through the substrate
Implementation Method 4
comprising the physical, chemical, or physico-chemical modification or the ablation of said region
Data Source
AI summary
A system for the treatment of a region of an object adjacent to a substrate. The system includes a source of an incident laser beam delivering a focused laser beam. The wavelength of the incident laser beam is greater than the sum of 500 nm and of the wavelength associated with the bandgap of the material forming the substrate and smaller than the sum of 2,500 nm and of this wavelength. The system includes an optical device associating a digital aperture greater than 0.3 and means for correcting the spherical aberrations appearing during the crossing of the substrate for a given thickness of the substrate and a given distance between the substrate and the optical device. The processing being performed on the region through the substrate, and including the physical, chemical, or physico-chemical modification or the ablation of said region.