Insulating Alignment Marks for Semiconductor Optical Devices
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for forming alignment marks on compound semiconductor substrates either fail to detect marks well with electron beam exposure apparatuses or degrade the reliability of semiconductor optical devices, particularly when using wet-etching or dry-etching processes.
Innovation Solution
A method involving the formation of insulating structures on a primary surface of a group III-V semiconductor region, followed by growing a second group III-V semiconductor region to create an epitaxial wafer, which includes forming depressions or using the edges of insulating structures for alignment during electron beam exposure to accurately pattern a diffraction grating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wet-etching is used to form alignment marks on compound semiconductor substrate, then alignment marks can be formed easily, but electron beam exposure apparatuses cannot detect them very well
Solution Approach 1:
The invention changes the material parameter of the alignment mark from etched semiconductor material to insulating material (such as silicon oxide or silicon nitride). This material parameter change enables the alignment marks to have different etching selectivity and detection properties, allowing them to be both easily formed and well-detected by electron beam exposure apparatuses.
2Measurement precision
If dry-etching is used to form alignment marks on compound semiconductor substrate, then alignment marks can be formed with good detection, but this process may degrade the reliability of the semiconductor optical devices
Solution Approach 1:
The invention introduces an insulating layer as an intermediary material between the semiconductor substrate and the alignment mark formation process. This insulating layer serves as a mediator that can be easily etched to form alignment marks without exposing the underlying semiconductor structure to harmful dry-etching processes, thus protecting device reliability while enabling good mark detection.
3Manufacturing precision
If insulating structures are formed before growing the second group III-V semiconductor region, then excellent alignment is achieved during electron beam exposure, but the process complexity increases
Solution Approach 1:
The invention performs preliminary action by forming the insulating layer and etching alignment marks on the substrate before growing the semiconductor layers. This preliminary formation of alignment marks ensures that accurate alignment can be performed during electron beam exposure in subsequent steps, while the insulating layer is later removed to avoid interfering with device operation.
Solution Approach 2:
The insulating layer serves as a temporary structure used only for alignment purposes. After serving its function as alignment marks, the insulating layer is selectively removed (discarded) through etching, leaving no harmful residues in the final device. This temporary use and subsequent removal resolves the complexity issue while maintaining alignment precision.
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 enables excellent alignment and accurate pattern formation for semiconductor optical devices, enhancing the reliability and detection capabilities during electron beam exposure without degrading the semiconductor devices.
Implementation Method 1
growing a second group III-V semiconductor region on the first group III-V semiconductor region to form an epitaxial wafer
Data Source
AI summary
In a method of fabricating a semiconductor optical device, insulating structures for an alignment mark for use in electron beam exposure are formed on a primary surface of a first group III-V semiconductor region. After forming the insulating structures, a second group III-V semiconductor region is grown on the first group III-V semiconductor region to form an epitaxial wafer. The height of the insulating structures is larger than thickness of the second group III-V semiconductor region. After forming the second group III-V semiconductor region, alignment for the electron beam exposure is performed. After the alignment, a resist is exposed to an electron beam to form a resist mask. The resist mask has a pattern for a diffraction grating, and the resist is on the epitaxial wafer.