Photodiode Waveguide Mesa Etching Stopper
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Solution Overview
Problem
Conventional semiconductor photodiodes with waveguide structures experience scattered parasitic resistance due to the stacking sequence of semiconductor layers in the butt-joint, leading to inefficiencies in the optical coupling process.
Innovation Solution
A method involving the growth of a p-type contact layer with aluminum, which serves as an etching stopper, while other waveguide regions and layers are free from or have less aluminum, ensuring the p-type contact layer maintains a consistent thickness during etching, thereby reducing parasitic resistance scattering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching processes are used on photodiode structures with varying aluminum content, then etching can proceed through all layers, but the p-type contact layer thickness becomes scattered leading to parasitic resistance variation
Solution Approach 1:
The patent utilizes the aluminum content parameter difference between the p-type contact layer (high Al) and other layers (low or no Al) to create selective etching behavior. By controlling etching parameters to target aluminum-containing materials, the process achieves selective removal of waveguide and cladding layers while preserving the p-type contact layer thickness, thereby resolving the contradiction between manufacturing precision and reliability
Solution Approach 2:
The patent applies local quality by creating etching stopper regions with distinct aluminum content characteristics. The p-type contact layer is deliberately designed with high aluminum content to provide localized etching resistance, while other layers have low or no aluminum. This local compositional differentiation enables precise control over etching depth and protects the contact layer from thickness variation, simultaneously improving manufacturing precision and parasitic resistance consistency
2Ease of manufacture
If the p-type contact layer contains high aluminum content to serve as etching stopper, then etching selectivity is improved, but the layer becomes more resistant to etching which may affect process control
Solution Approach 1:
The patent exploits the aluminum content parameter to create a stark contrast in etching rates. The p-type contact layer's high aluminum content (50-70%) versus the low or zero aluminum content in other layers creates a parameter-based etching selectivity mechanism. This allows the etching process to automatically stop at the contact layer interface, providing both ease of manufacture through selective etching and precision through self-limited etching depth
Solution Approach 2:
The high aluminum content in the p-type contact layer provides self-service by automatically functioning as an etching stopper during the etching process. The material composition itself creates the stopping mechanism without requiring additional process controls or monitoring, enabling both easy manufacturing and precise depth control through the material's inherent properties
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 effectively suppresses parasitic resistance scattering and enhances the precision of mesa formation, improving the optical coupling and overall performance of the semiconductor photodiode with a waveguide structure.
Implementation Method 1
the p-type contact layer may show the etching rate far less than etching rates for other regions and layers. Accordingly, the p-type contact layer is substantially invariant in a thickness thereof even when the p-type contact layer is exposed in plasma during the etching to form the waveguide mesa and the active mesa
Data Source
AI summary
A process to form a photodiode (PD) with the waveguide structure is disclosed. The PD processes thereby reduces a scattering of the parasitic resistance thereof. The process includes steps to form a PD mesa stripe, to bury the PD mesa stripe by the waveguide region, to etch the PD mesa stripe and the waveguide region to form the waveguide mesa stripe. In the etching, the lower contact layer plays a role of the etching stopper.