VCSEL Fabrication Using Dielectric Etch-Stop Layer
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Solution Overview
Problem
Existing methods for fabricating VCSELs with micro/nano-structured mode selective layers face challenges in achieving precise control over etch depth, leading to variations in production yield due to the dependence on etch rate and time, especially in wet chemistry etching processes.
Innovation Solution
The introduction of a dielectric etch-stop layer on top of a partial semiconductor top-mirror, allowing for precise control of etch depth by using etch techniques with different rates in dielectric and semiconductor materials, reducing the dependence on etch rate and time, and enabling high precision in layer thickness control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If etch depth is determined by timing the etch process based on estimated etch rate, then fabrication can be completed, but etch depth control precision deteriorates due to dependence on etch rate and time parameters
Solution Approach 1:
An etch-stop layer is introduced as an intermediary between the micro/nano-structured mode selective layer and the underlying layer. This etch-stop layer has a significantly lower etch rate compared to the mode selective layer, causing the etch process to automatically stop when reaching the etch-stop layer interface. This intermediary layer eliminates the need for precise timing control and provides inherent etch depth precision, directly resolving the contradiction between manufacturing precision and production yield.
2Adaptability or versatility
If multiple fabrication steps including resist deposition, exposure, development, and etching are added to create micro/nano-structured mode selective layer, then mode control capability is improved, but process complexity increases
Solution Approach 1:
The etch-stop layer is deposited in advance during the standard VCSEL fabrication process, before the micro/nano-structured mode selective layer is formed. This preliminary action ensures that when subsequent etching is performed to create the mode selective structure, the etch process will automatically self-limit at the predetermined depth defined by the etch-stop layer position. This eliminates the need for complex real-time depth monitoring and control during etching, reducing overall process complexity while maintaining mode control capability.
3Measurement precision
If shallow etching of less than 100 nm is performed in partial semiconductor top-mirror to control wavelength, then wavelength control is improved, but etch depth precision deteriorates due to lack of etch stop mechanism
Solution Approach 1:
The etch-stop layer serves as a precise depth marker that automatically terminates the etch process at the desired shallow depth. By positioning the etch-stop layer interface at the target etch depth (less than 100 nm into the top-mirror), the etch process inherently achieves both the shallow depth requirement for wavelength control and the precision needed for manufacturing, eliminating the trade-off between these two parameters.
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 significantly reduces etch depth variations, improving the reproducibility and yield of VCSELs by allowing precise control of the micro/nano-structured layer thickness, enabling high-power, single-mode operation with reduced uncertainty in the etch process.
Implementation Method 1
The etch technique has a first etch rate in the dielectric micro/nano-structured mode selective layer and a second etch rate in the layer on which the dielectric micro/nano-structured mode selective layer is formed, the first etch rate being higher than the second etch rate.
Data Source
AI summary
The invention relates to fabrication of VCSELs. It provides a method for fabricating a VCSEL that contains a micro/nano-structured mode selective lateral layer, where the micro/nano-structured layer is obtained by well controlled local etching. The invention enables control of the micro/nano-structured layer thickness with very high precision. In particular, the invention relates to a method for fabricating a VCSEL with a micro/nano-structured mode selective layer for controlling the VCSELs transverse electromagnetic modes.