InGaAs/InP Photodetector Fabrication With Selective Phosphorus Removal
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In the production of light-receiving devices using InGaAs/InP-based materials, phosphorus precipitates on the wafer surface after impurity diffusion treatment, leading to reduced light-receiving sensitivity and increased ohmic resistance, necessitating a method for selective removal of these precipitates without etching the underlying InP and InGaAs layers.
Innovation Solution
A method involving the sequential growth of an InP buffer layer, an InGaAs light absorption layer, and an InP cap layer on an InP substrate, followed by forming an InGaAs contact layer, removing part of it, and diffusing impurities in a phosphorus-containing atmosphere. The method includes selectively removing phosphorus precipitates using a strong aqueous base, such as TMAH, to minimize etching of InP and InGaAs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a rapid temperature falling rate is used during impurity diffusion treatment, then excessive diffusion is prevented and manufacturing efficiency is improved, but phosphorus precipitates form on the wafer surface which degrades light-receiving characteristics and increases ohmic resistance
Solution Approach 1:
A protective film is formed on the wafer surface before impurity diffusion treatment to prevent phosphorus precipitation. This preliminary protective measure allows rapid cooling to be used without the harmful side effect of phosphorus precipitate formation, thus resolving the contradiction between manufacturing efficiency and device reliability
Solution Approach 2:
The patent converts the harmful phosphorus precipitation phenomenon into a removable surface layer by forming a specific protective film structure that incorporates phosphorus in a controllable manner. The protective film is then selectively removed to reveal a clean surface, transforming the potential harm into a controlled process step
2Productivity
If a rapid temperature falling rate is used during impurity diffusion treatment, then excessive diffusion is prevented, but phosphorus precipitates form on the wafer surface which increases ohmic resistance during electrode formation
Solution Approach 1:
The protective film is formed in advance before diffusion treatment to prevent phosphorus precipitation that would later cause high ohmic resistance. This allows the diffusion process to proceed efficiently with rapid cooling without generating the harmful precipitates
3Reliability
If phosphorus precipitates are removed by etching, then light-receiving characteristics are improved, but InP and InGaAs layers are also etched which damages the wafer structure
Solution Approach 1:
The protective film is selectively removed (taken out) from the wafer surface after diffusion treatment, extracting only the phosphorus-containing protective layer while leaving the underlying InP and InGaAs layers intact. This selective removal eliminates phosphorus precipitates without damaging the sensitive semiconductor structure
Solution Approach 2:
The protective film acts as an intermediary layer that can be selectively removed using specific etchants that do not attack the InP and InGaAs layers. This intermediary structure enables selective phosphorus removal while protecting the underlying wafer structure from etching damage
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 method allows for the selective removal of phosphorus precipitates, thereby improving the light-receiving characteristics and reducing ohmic resistance in the light-receiving device, while maintaining the integrity of the InP and InGaAs layers.
Implementation Method 1
selectively removing a phosphorus precipitate adhered to a surface in the step of diffusing the impurity using a strong aqueous base
Implementation Method 2
diffusing an impurity to the opening pattern portion in a phosphorus-containing atmosphere
Implementation Method 3
using an epitaxial wafer in which an InP buffer layer, an InGaAs light absorption layer, and an InP cap layer are epitaxially grown sequentially on an InP substrate
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The present invention is a method for producing a light-receiving device using an epitaxial wafer in which an InP buffer layer, an InGaAs light absorption layer, and an InP cap layer are grown on an InP substrate, the method including the steps of forming an InGaAs contact layer on the InP cap layer, removing a part of the InGaAs contact layer by a photolithography method to form an InGaAs contact portion, forming a protective film so as to coat the InP cap layer and the InGaAs contact portion, forming an opening pattern portion in a part of the protective film, diffusing an impurity to the opening pattern portion in a phosphorus-containing atmosphere, selectively removing a phosphorus precipitate adhered to a surface in the step of diffusing the impurity using a strong aqueous base, and forming an electrode on the InGaAs contact portion and a back surface of the InP substrate. This provides the method for producing a light-receiving device, in which only a phosphorus precipitate precipitated on a wafer surface can be selectively removed.