Semiconductor Laser Chip Recessed Marks for Stress Distribution
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Solution Overview
Problem
Semiconductor laser chips with long laser cavity lengths experience stress-induced cracks and fractures due to thermal and mechanical stresses, particularly when bonded to heat sinks with different thermal expansion coefficients, leading to reduced thermal reliability and increased manufacturing costs.
Innovation Solution
The semiconductor laser apparatus incorporates recessed marks on the semiconductor laser chip's surface, limited to a predetermined distance from the end faces and sized as a quarter of the chip's width, to distribute stress concentration away from the resonator's center, using materials with matching thermal expansion coefficients to minimize thermal stress and maintain effective heat radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the laser cavity length is increased to expand the optical gain region and achieve high optical output, then the optical output is improved, but stress concentration and crack occurrence increase due to the long and thin chip structure
Solution Approach 1:
The patent applies local quality by creating recessed portions only at specific locations (front and rear end faces) of the semiconductor laser chip, rather than uniformly across the entire chip. This localized modification reduces stress concentration at the ends where it occurs most frequently, while preserving the overall chip structure and optical performance. The recessed portions are strategically positioned to address the specific stress distribution pattern in long-cavity chips without affecting the central gain region.
2Ease of operation
If recessed portions including marks are formed on the surface of the semiconductor laser chip, then assembly and handling are facilitated, but stress concentration occurs at the steps of the recessed portions leading to cracks
Solution Approach 1:
The patent localizes the recessed portions to specific regions (front and rear end faces) away from the central gain region, maintaining their utility for assembly and handling while minimizing their harmful stress concentration effects. The recessed marks are positioned where they provide operational benefits without interfering with the optical path or concentrating stress in critical areas.
Solution Approach 2:
The patent converts the potentially harmful stress concentration at recessed portions into a beneficial arrangement by positioning these recesses at the end faces where stress from bonding processes is naturally directed. The recessed portions at the ends accommodate bonding stresses without compromising the central region's integrity, effectively using the harmful stress concentration mechanism to protect the critical gain region.
3Reliability
If a square die bonding surface is formed to reduce stress, then stress distribution is improved, but the area of the semiconductor laser chip increases and manufacturing cost increases
Solution Approach 1:
Instead of modifying the entire chip surface with a square die bonding surface, the patent applies localized recessed portions only at the front and rear end faces. This selective approach improves stress distribution at the critical bonding regions without increasing the overall chip area, maintaining cost-effectiveness while achieving the stress distribution benefit.
4Speed
If the laser cavity length is increased to improve writing speed, then writing speed is improved, but the chip becomes longer and thinner increasing susceptibility to stress and breakage
Solution Approach 1:
The patent addresses the mechanical weakness of long and thin chips by applying localized recessed portions at the end faces, which are the most vulnerable regions. This localized modification strengthens the chip structure where it is most needed without affecting the overall length required for high-speed operation, maintaining the speed benefit while improving mechanical robustness.
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 design effectively suppresses stress concentration and fracture occurrence, enhancing the semiconductor laser chip's resistance to temperature and mechanical stress while maintaining high power handling capabilities without increasing the chip's area or interfering with heat radiation, thus reducing manufacturing costs.
Implementation Method 1
a heat sink 3 for the semiconductor laser chip 1... The heat sink 3 is used for preventing emission efficiency from decreasing due to a temperature increase on the semiconductor laser chip 1 during a laser operation
Implementation Method 2
a stress is generated by a difference in thermal expansion coefficient between the submount 2 and the heat sink 3 and a tensile stress is generated on the surface of the semiconductor laser chip 1
Data Source
AI summary
A semiconductor laser apparatus of the present invention includes: a semiconductor laser chip 1 having an electrode 11 formed on a surface of the semiconductor laser chip 1; a heat sink 3 for the semiconductor laser chip 1; a submount 2 disposed between the semiconductor laser chip 1 and the heat sink 3 and bonded to the semiconductor laser chip 1 and the heat sink 3; and recessed marks 13 formed on the surface of the semiconductor laser chip 1 by partially removing the electrode 11, wherein the semiconductor laser chip 1 is longer in the resonator direction than in a direction orthogonal to the resonator direction, and the recessed marks 13 are disposed within a predetermined distance from each of the front and rear end faces of the semiconductor laser chip.