Semiconductor Buffer Layer Material Differentiation for Substrate Removal
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing methods for forming photonic ICs using silicon face challenges in substrate removal, leading to undercut issues due to the etching of like-kind materials, which complicates the protection of other layers and affects the performance of the chip.
Innovation Solution
A composite device is created by bonding a III-V chip to a silicon platform, where the substrate is removed using a substrate-removal etch, and the buffer layer is made of a different material than the substrate to reduce undercut, employing a multi-quantum well structure with alternating layers and an etch stop to facilitate safe etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a substrate-removal etch is used to remove the substrate after bonding, then electrical contacts can be formed on the chip, but undercut is formed on the chip because the etch also removes like-kind material of the chip
Solution Approach 1:
The buffer layer is made of a different material composition than the substrate (e.g., InGaAsP vs InP), creating local material differentiation. This allows the etch process to selectively remove the substrate while leaving the buffer layer intact, preventing undercut formation while still enabling electrical contact formation.
Solution Approach 2:
The material composition parameter of the buffer layer is changed to be different from the substrate. By adjusting the composition (e.g., using ternary or quaternary semiconductors instead of binary), the etch resistance is modified to prevent undercut during substrate removal.
2Ease of manufacture
If the buffer layer is made of the same material as the substrate, then the etch process is simple, but the buffer layer is etched along with the substrate causing undercut
Solution Approach 1:
The buffer layer uses a different material composition (e.g., InGaAsP) compared to the substrate (e.g., InP), creating local material differentiation. This enables selective etching where the substrate is removed but the buffer layer remains intact, preventing undercut while maintaining manufacturing feasibility.
Solution Approach 2:
The device structure employs composite materials with different etch resistances - the buffer layer uses ternary or quaternary semiconductors while the substrate uses binary semiconductors. This composite approach allows differential etching to achieve precise substrate removal without buffer layer damage.
3Manufacturing precision
If like-kind material is changed to a material that is more etch resistant, then etching of other layers is reduced, but the etch process becomes more complex
Solution Approach 1:
The buffer layer is engineered with different material composition (e.g., InGaAsP with specific ratios) to provide localized etch resistance. This targeted material differentiation protects only the buffer layer during substrate removal, balancing precision requirements with manageable device complexity.
Solution Approach 2:
The composition parameters of the buffer layer are optimized to achieve the desired etch resistance. By controlling the ratios of constituent elements in ternary or quaternary semiconductors, the etch selectivity is tuned to protect the buffer layer while allowing complete substrate removal.
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 allows for the reduction of undercut in the buffer layers, enhancing the structural integrity and optical performance of the photonic device by preventing etchant leakage and maintaining the integrity of the buffer layers during substrate removal.
Implementation Method 1
The etch stop is between the buffer layer and the substrate, to facilitate substrate removal
Implementation Method 2
bonding the first device to a floor of a recess of the second device
Data Source
AI summary
A device for a gain medium for a semiconductor laser has an active region, a buffer layer, a substrate, and an etch stop between the buffer layer and the substrate. The device is bonded to a silicon platform having silicon devices, such as a waveguide and mirror. The substrate is removed, after bonding the device to the platform. The buffer layer is made of different material than the substrate to reduce undercut of the buffer layer during substrate removal compared to a buffer layer made of the same material as the substrate.