Semiconductor Substrate Removal Layers to Prevent Epitaxial Bonding
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Solution Overview
Problem
Conventional methods for separating semiconductor epitaxial layers from GaAs substrates often result in the surface of the substrate becoming bonded to the bottom surface of the epitaxial layer, preventing successful separation due to similar etching rates and resulting flat surfaces.
Innovation Solution
A semiconductor substrate configuration with a base substrate, a first removal layer of AlxGa1-xAs (0.6<x≤0.8), and a second removal layer of AlyGa1-yAs (0.7x) with a higher etching rate than the first, allowing the epitaxial layer to be separated by etching the second removal layer, which has a larger etching rate than the first, preventing bonding between the substrate and epitaxial layer surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single removal layer is used and etching is performed to separate the semiconductor epitaxial layer from the base substrate, then the semiconductor epitaxial layer can be separated, but the surface of the base substrate and the bottom surface of the separated epitaxial layer become very flat and may bond to each other, preventing successful separation
Solution Approach 1:
The removal layer is divided into two distinct layers: a first removal layer with lower etching rate and a second removal layer with higher etching rate. This segmentation allows differential etching where the second layer is removed faster, creating surface roughness that prevents bonding between the base substrate and the separated epitaxial layer.
Solution Approach 2:
Different regions of the removal layer structure are assigned different etching rates through compositional variation. The first removal layer (AlxGa1-xAs with 0.6<x≤0.8) has lower etching rate while the second removal layer (AlyGa1-yAs with 0.7<y≤0.9) has higher etching rate, creating localized quality differences that prevent surface bonding.
2Productivity
If the etching rate of the removal layer is made significantly higher than the base substrate and epitaxial layer, then the removal layer can be effectively removed, but it becomes difficult to prevent surface bonding between the base substrate and epitaxial layer due to flat surfaces
Solution Approach 1:
The removal layer is segmented into two layers with different etching rates. The second removal layer provides high etching efficiency for rapid removal, while the first removal layer with lower etching rate remains to create surface roughness that prevents bonding, thus maintaining both productivity and reliability.
Solution Approach 2:
The etching rate parameter is varied across different layers by changing the aluminum composition ratio. The first removal layer has aluminum composition x where 0.6<x≤0.8, while the second removal layer has aluminum composition y where 0.7<y≤0.9, creating controlled parameter differences that achieve both fast removal and bonding prevention.
3Reliability
If a two-layer removal structure with different etching rates is used, then surface bonding can be prevented, but the device complexity increases
Solution Approach 1:
Instead of creating complex multi-layer structures, the invention uses parameter changes within a two-layer framework. By varying the aluminum composition ratio (x and y values) in AlxGa1-xAs and AlyGa1-yAs layers, different etching rates are achieved, maintaining structural simplicity while ensuring reliable separation.
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
Ensures the semiconductor epitaxial layer can be properly separated from the base substrate without bonding, enabling efficient transfer and manufacturing of semiconductor devices with a flat epitaxial surface.
Implementation Method 1
removing the second removal layer by performing etching using a predetermined etching material
Data Source
AI summary
To prevent the surface of a base substrate and the bottom surface of a separated semiconductor epitaxial layer from being bonded to each other even after a removal layer is removed, the semiconductor substrate includes a base substrate, a first removal layer provided on the base substrate, a second removal layer provided above the first removal layer, and a semiconductor epitaxial layer provided above the second removal layer, and an etching rate of the second removal layer for a predetermined etching material is larger than the etching rate of the first removal layer for the predetermined etching material.