Semiconductor Laser Mesa Oxide Removal via Two-Stage HCl Cleaning
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Solution Overview
Problem
In semiconductor laser element manufacturing, the formation of invalid current pathways due to oxidation and impurities at the mesa boundary leads to defective burying growth and reduced reliability, especially with Al-containing semiconductor materials, as conventional low-temperature HCl cleaning is insufficient to remove oxygen and prevent oxidation.
Innovation Solution
A method involving two-stage HCl gas cleaning at different temperatures, below and above the critical temperature for oxide formation, followed by burying layer formation to prevent invalid current pathways and reduce impurity content at the mesa-burying layer interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the mesa side is exposed to atmosphere during manufacturing, then the Al-containing semiconductor layer oxidizes forming an oxide layer, but this oxidation prevents proper epitaxial growth of the p-type InP burying layer and creates invalid current pathways
Solution Approach 1:
The patent applies inert atmosphere by performing the entire manufacturing process including mesa formation and burying layer growth in a nitrogen atmosphere. This prevents oxidation of the Al-containing semiconductor layer by excluding oxygen from the environment, thereby ensuring proper epitaxial growth of the p-type InP burying layer and preventing formation of invalid current pathways.
Solution Approach 2:
The patent applies preliminary action by forming the p-type InP burying layer before any potential oxidation can occur. The burying layer is grown in advance under controlled nitrogen atmosphere conditions, covering the mesa side surface before exposure to atmosphere that would cause oxidation and create defective current pathways.
2Manufacturing precision
If HCl cleaning is performed at low temperature (≤450°C) to remove surface oxygen, then the oxide layer remains firmly attached and cannot be effectively removed, but high temperature cleaning may damage the semiconductor structure
Solution Approach 1:
The patent applies parameter changes by optimizing the nitrogen atmosphere temperature and composition parameters during the burying layer growth process. By controlling the temperature and nitrogen flow rate parameters, the process effectively removes oxide layers without requiring high-temperature cleaning that could damage the semiconductor structure, achieving both effective cleaning and structural integrity.
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
Prevents the formation of invalid current pathways and improves the reliability and characteristics of semiconductor lasers by effectively removing oxide layers and reducing impurities, enhancing the quality of the burying growth process.
Implementation Method 1
after surface cleaning is performed using HCl gas at a low temperature of not higher than 450° C. to remove oxygen on the surface of the protective layer, elevating the temperature to 450° C. or higher to perform mesa formation and burying growth using HCl gas etching
Implementation Method 2
the portion exposed on the surface may be oxidized depending on the methods or conditions of etching for forming the mesa, or the semiconductor materials composing the mesa
Implementation Method 3
since the p-type InP burying layer 17a is difficult to form epitaxially, growing so as to coat such a portion begins after the semiconductor layers below the surface-oxidized semiconductor layer has been completely buried
Data Source
AI summary
A method for manufacturing a semiconductor laser element includes forming a semiconductor laminated structure, having an active layer, on a substrate; etching the semiconductor laminated structure to form a mesa; exposing the mesa to an oxygen-containing ambient forming an oxide layer on the mesa; removing a first part of the oxide layer from the mesa at a temperature lower than a critical temperature at which bonds between atoms of the oxide layer become stronger, by etching with a gas; removing the remainder of the oxide layer from the mesa at a temperature higher than the critical temperature by etching with a gas; and forming a burying layer coating the mesa.