Nitride Semiconductor Substrate Removal via Laser-Chemical Decomposition
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Solution Overview
Problem
The existing methods for removing disparate substrates from nitride semiconductor wafers often result in incomplete decomposition, surface irregularities, and breakage of the nitride semiconductor layer, requiring mechanical polishing and applying mechanical stress, which can lead to unsatisfactory surface conditions.
Innovation Solution
Irradiating the disparate substrate with a laser beam of a wavelength shorter than the band gap wavelength of the nitride semiconductor layer in an acidic or alkaline etching solution, causing thermal decomposition and chemical etching to proceed simultaneously, ensuring uniform removal and a smooth surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser beam irradiation is used to remove the disparate substrate, then the removal process is fast and does not require special materials, but the nitride semiconductor layer may be incompletely decomposed, fused, or broken due to non-uniform laser intensity distribution
Solution Approach 1:
An etching solution is introduced as an intermediary medium between the laser beam and the nitride semiconductor layer. The solution absorbs excess laser energy and facilitates uniform chemical etching, preventing direct thermal damage to the semiconductor layer while maintaining efficient substrate removal.
Solution Approach 2:
The invention changes the physical-chemical parameters of the removal process by introducing chemical etching via etching solution alongside laser irradiation. This combination allows control over the decomposition rate and surface quality, transforming the purely thermal process into a controlled chemo-thermal process.
2Reliability
If mechanical stress is applied to remove the disparate substrate, then complete removal can be achieved, but the nitride semiconductor layer may break and fragments remain on the substrate
Solution Approach 1:
The invention replaces the mechanical stress method with a combination of laser irradiation and chemical etching. This substitution eliminates the need for mechanical force that causes layer breakage, achieving complete substrate removal through chemical decomposition facilitated by the etching solution.
3Shape
If mechanical polishing is performed after substrate removal, then the surface can be smoothed, but the process becomes complex and time-consuming
Solution Approach 1:
The invention merges the substrate removal process with the surface smoothing function. By combining laser irradiation with chemical etching in the etching solution, the process simultaneously removes the substrate and produces a smooth semiconductor layer surface, eliminating the need for separate mechanical polishing steps.
Solution Approach 2:
The etching solution enables the semiconductor layer surface to smooth itself during the substrate removal process. The chemical etching automatically produces a flat, smooth surface as a byproduct of the decomposition reaction, making the surface finishing function self-service rather than requiring additional processing.
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 prevents breakage of the nitride semiconductor layer during substrate removal, achieves a mirror-quality surface with surface roughness not exceeding 10 nm, and simplifies the subsequent device formation by enabling dry etching instead of mechanical polishing.
Implementation Method 1
laser beam of a wavelength that has high absorption rate with the nitride semiconductor is irradiated from the disparate substrate side, so as to decompose the nitride semiconductor located near the interface into nitrogen and metal
Implementation Method 2
remove the disparate substrate by irradiating the interface between the disparate substrate and the nitride semiconductor with laser beam
Implementation Method 3
irradiating the disparate substrate with a laser beam of a wavelength shorter than the band gap wavelength of the nitride semiconductor layer in an acidic or alkaline etching solution, causing thermal decomposition and chemical etching to proceed simultaneously
Data Source
AI summary
To remove the disparate substrate from nitride semiconductor layer grown over the disparate substrate, that is made of a material different from nitride semiconductor, by irradiating the disparate substrate with laser beam having a wavelength shorter than the band gap wavelength of the nitride semiconductor layer, while supplying an acidic or alkaline etching solution to the interface between the disparate substrate and the nitride semiconductor layer.