Optical Waveguide Receiver MIM Capacitor Flatness
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Solution Overview
Problem
The formation of metal-insulator-metal (MIM) structures on semiconductor substrates for optical waveguide receivers is hindered by surface roughness, leading to non-uniform breakdown voltage distribution and irregularities, which are exacerbated by the presence of hillocks on the substrate surface.
Innovation Solution
A method involving the growth of stacked semiconductor layers, selective etching to expose a flat core layer, and the formation of an MIM capacitor on this flat surface, using etching rates differences between semiconductor materials to achieve a smooth base for the capacitor, thereby ensuring uniform breakdown voltage distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If MIM structure is directly formed on the semiconductor substrate, then the capacitor can be integrated with the photodiode and optical waveguide, but the surface roughness of the substrate causes non-uniform breakdown voltage distribution
Solution Approach 1:
The patent introduces an intermediary semiconductor layer between the rough substrate surface and the MIM capacitor structure. This intermediate layer serves as a mediator that provides a flat surface for capacitor formation while being grown on the rough substrate, thus resolving the contradiction between integration ease and manufacturing precision.
Solution Approach 2:
The patent performs preliminary action by growing the semiconductor layer on the substrate before forming the MIM capacitor structure. This preliminary growth creates a flat surface in advance, ensuring uniform breakdown voltage distribution while maintaining the integrated structure.
2Ease of manufacture
If the buried layer is removed by etching to form the MIM capacitor region, then the capacitor can be formed, but hillocks remain on the substrate surface causing irregularities
Solution Approach 1:
The patent converts the harmful effect of hillocks into a beneficial process by using them as etching masks. The hillocks protect certain regions during etching, and the etching process itself removes the hillocks while creating the desired capacitor region, thus transforming the surface irregularity problem into a solution.
Solution Approach 2:
The patent changes the physical and chemical parameters of the substrate surface through etching processes. By controlling etching conditions, the hillocks are removed and the surface is flattened, transforming the rough surface into a flat surface suitable for MIM capacitor formation.
3Manufacturing precision
If a semiconductor buffer layer is grown to obtain a flatter surface, then the MIM structure can be formed on a flatter surface, but deposits on the mask impair the flatness and the mask cannot be removed
Solution Approach 1:
The patent changes the material parameters and growth conditions of the semiconductor layer to achieve flatness without masks. By optimizing the epitaxial growth parameters, a flat surface is obtained directly, eliminating the need for masks and avoiding deposit-related problems.
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 results in optical waveguide receivers with uniform breakdown voltage characteristics and high breakdown strength, reducing the impact of substrate irregularities and enhancing manufacturing efficiency and compactness.
Implementation Method 1
A semiconductor layer epitaxially grown on the semiconductor substrate generally has a flatter surface as compared to a surface of the semiconductor substrate.
Data Source
AI summary
A method for manufacturing an optical waveguide receiver includes the steps of growing first and second stacked semiconductor layer sections, the second stacked semiconductor layer section including a core layer and a cladding layer; forming a first mask including first and second portions; etching the first and second stacked semiconductor layer sections by using the first mask, the first and second stacked semiconductor layer sections covered with the first portion being etched in a mesa structure, the second stacked semiconductor layer section covered with the second portion being etched in a terrace-shaped structure; removing the second portion from the first mask with the first portion left; selectively etching the cladding layer until exposing a surface of the core layer; and sequentially forming a first metal layer, an insulating film, and a second metal layer on the core layer exposed in the step of selectively etching the cladding layer.