GaN Laser Diode Electrode Contact via Sacrificial Resist
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Solution Overview
Problem
Conventional methods for manufacturing semiconductor optical devices with waveguide ridges face challenges in maintaining a sufficient contact area between the electrode and the top semiconductor layer, leading to increased contact resistance and operating voltage, especially in blue-violet lasers where GaN-based materials have high resistance, and often result in damaged semiconductor layers during etching processes.
Innovation Solution
A method involving the formation of a dielectric film on a laminated semiconductor structure, followed by photolithography to create resist patterns that expose the semiconductor layer, allowing for dry etching to form concave portions and waveguide ridges, and subsequent wet etching to remove the dielectric film and form a metal electrode layer in full contact with the semiconductor layer, avoiding reduction in contact area and damage to the semiconductor layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If lift-off process is used to form insulating film with opening, then insulating film can be formed covering waveguide ridge, but contact area between electrode layer and contact layer is reduced
Solution Approach 1:
The method performs preliminary actions by forming the electrode layer and opening in the contact layer before forming the insulating film. This sequence ensures the electrode has full contact area with the contact layer initially, and the insulating film is subsequently formed to cover the waveguide ridge without compromising the already-established electrode contact.
2Manufacturing precision
If conventional etching process is used to form opening in dielectric film, then dielectric film can be removed to expose semiconductor layer, but semiconductor layer is damaged
Solution Approach 1:
The method introduces a sacrificial organic layer as an intermediary between the electrode layer and the dielectric film during the opening formation process. This organic layer protects the underlying semiconductor layer from damage during etching, allowing precise opening formation while preventing harmful effects on the semiconductor material.
Solution Approach 2:
The organic layer serves multiple functions: it acts as a mask during opening formation, protects the semiconductor layer from damage, and is subsequently removed without requiring additional complex processing steps. The layer essentially serves itself by being consumed in the process to protect the semiconductor.
3Productivity
If contact area is reduced, then lift-off process can be completed, but contact resistance increases
Solution Approach 1:
The electrode layer and its contact opening are formed before the insulating film deposition. This preliminary formation ensures maximum contact area between the electrode and contact layer is achieved while the contact resistance is still critical, and subsequent insulating film formation does not reduce this contact 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 ensures a high yield in manufacturing semiconductor optical devices with reliable contact between the electrode and the semiconductor layer, preventing increased contact resistance and maintaining device performance by avoiding damage to the semiconductor layer during the etching process.
Implementation Method 1
forming by a photolithography process a first resist pattern of a resist film disposed on a surface of the dielectric film
Implementation Method 2
removing portions of the upper surface side of the second semiconductor layer by dry etching using the first resist pattern as a mask
Implementation Method 3
removing the dielectric film and the deposited SiO2 film by etching including wet etching using the second resist pattern as a mask
Data Source
AI summary
A method for manufacturing an laser diode includes: providing a wafer having thereon a semiconductor structure; depositing an SiO2 film; forming channels and a waveguide ridge between the channels in the wafer; forming an SiO2 film over the wafer; forming a resist pattern covering the SiO2 film in the channels such that the top surfaces of the resist pattern are lower than the top surface of the deposited SiO2 film on the top of the waveguide ridge, the resist pattern exposing the SiO2 film on the top of the waveguide ridge; removing the SiO2 film and the deposited SiO2 film by wet etching, using the resist pattern as a mask, to expose a p-GaN layer in the waveguide ridge; and forming an electrode layer on the top surface of the p-GaN layer.