VCSEL Mesa Etching Selectivity for Stress and Thermal Management
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Solution Overview
Problem
The existing methods for producing surface emitting semiconductor devices, such as VCSELs, face issues with stress and reliability due to lattice-mismatch-induced strain and inefficient heat dissipation, particularly when removing oxidized regions in the dry etching process, which can lead to excessive etching of other semiconductor regions.
Innovation Solution
A method involving the formation of a semiconductor stacked structure with a current-confinement layer and DBR portions, where the DBR includes layers with different aluminum contents, followed by selective wet etching of oxidized regions and subsequent dry etching of the DBR's peripheral portion to adjust the mesa shape without excessively etching non-oxidized semiconductors, thereby improving stress management and heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If dry etching is used to remove oxidized regions in the DBR portion, then the oxidized regions can be removed, but excessive etching of non-oxidized semiconductor regions occurs leading to poor heat dissipation
Solution Approach 1:
The etching process is divided into two distinct segments: first wet etching to selectively remove oxidized regions, then dry etching to remove peripheral DBR portions. This segmentation allows each etching method to be optimized for its specific purpose, preventing excessive etching of non-oxidized regions while effectively removing oxidized regions.
Solution Approach 2:
Wet etching is introduced as an intermediary step between mesa formation and final DBR removal. This intermediary process selectively removes oxidized regions without significantly etching non-oxidized semiconductor regions, thereby protecting the heat dissipation path while achieving the desired removal of oxidized areas.
2Reliability
If oxidized regions are formed in the DBR portion during current-confinement layer oxidation, then current confinement is achieved, but lattice-mismatch strain increases causing stress and potential cracks
Solution Approach 1:
The harmful oxidized regions in the DBR portion are selectively extracted using wet etching. This removes the source of lattice-mismatch strain while preserving the current-confinement layer's oxidized region that is essential for current confinement. The extraction is selective, targeting only the DBR's oxidized regions.
Solution Approach 2:
The physical-chemical state of the DBR's oxidized regions is changed from solid semiconductor oxide to removed material through selective wet etching. This parameter change eliminates the lattice-mismatch strain caused by the oxidized regions while maintaining the functional oxidized region in the current-confinement layer.
3Stress or pressure
If the mesa portion diameter is reduced to remove oxidized regions, then stress is reduced, but the active area and light output are decreased
Solution Approach 1:
Instead of reducing the overall mesa diameter, the harmful oxidized regions in the DBR are selectively extracted using wet etching. This approach removes the stress源 while maintaining the original mesa dimensions and active area, thereby preserving light output while reducing stress.
Solution Approach 2:
The etching process is made selective to different regions: wet etching targets oxidized regions in the DBR for removal, while dry etching removes peripheral DBR portions. This local quality differentiation allows stress reduction without compromising the active emission area.
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 effectively removes oxidized regions while minimizing stress and heat dissipation issues, enhancing the reliability and thermal characteristics of the semiconductor device by preventing excessive etching and maintaining the integrity of the substrate.
Implementation Method 1
an oxidation step of oxidizing the first semiconductor layer from a side face of the mesa portion toward the inside of the mesa portion, and forming an annular oxidized region inside the first semiconductor layer
Implementation Method 2
a first etching step of selectively etching an oxidized region formed in the DBR portion in the oxidation step by a wet etching
Implementation Method 3
a second etching step of removing a peripheral portion of the DBR portion by etching
Data Source
AI summary
A method for producing a surface emitting semiconductor device includes a step of forming a semiconductor stacked structure including an active layer, a first semiconductor layer containing aluminum on the active layer, and a DBR portion, on the first semiconductor layer, to include alternating stacked second semiconductor layers and third semiconductor layers having different aluminum contents; a step of forming a mesa portion by etching the DBR portion and the first semiconductor layer; an oxidation step of oxidizing the first semiconductor layer from a side face of the mesa portion toward the inside of the mesa portion to form an annular oxidized region inside the first semiconductor layer; a first etching step of selectively etching an oxidized region formed in the DBR portion; and a second etching step of removing a peripheral portion of the DBR portion.