Structured Semiconductor Substrate with Inclined Cavity Walls
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Solution Overview
Problem
Current methods for manufacturing structured semiconductor substrates, such as those used in photodetectors, are complex and difficult to implement industrially, limiting their productivity and optical absorption efficiency across a wide spectrum of wavelengths, including the infrared range.
Innovation Solution
A method for manufacturing a structured semiconductor substrate with cavities having inclined walls, achieved through a process involving the deposition of a sacrificial layer, anisotropic etching, and subsequent removal of the sacrificial layer to create a network of cavities with controlled depth and shape, enhancing optical absorption across visible and infrared wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If laser pulse irradiation is used to create micro-structured substrate, then optical absorption is improved, but manufacturing complexity increases and industrial applicability decreases
Solution Approach 1:
The patent replaces the complex laser pulse irradiation process with a simpler chemical etching process using KOH solution. Instead of using high-energy laser pulses to create the micro-structured cavities, the invention uses chemical reactions between KOH and silicon to form the same cavity structure, thereby substituting a complex physical process with a simpler chemical process that is more suitable for industrial manufacturing.
Solution Approach 2:
The patent changes the manufacturing parameters from laser pulse duration, energy, and frequency to chemical etching parameters such as KOH concentration, temperature, and etching time. This parameter transformation allows the same structural outcome (micro-cavities with inclined walls) to be achieved through a more controllable and industrially friendly chemical process rather than a complex physical process.
2Ease of manufacture
If conventional silicon substrate is used, then manufacturing is simple, but optical absorption efficiency is limited
Solution Approach 1:
The patent segments the flat silicon substrate surface into numerous micro-cavities with inclined walls through chemical etching. This segmentation creates a three-dimensional structure that increases the effective surface area and light-trapping capability, thereby improving optical absorption while maintaining compatibility with standard silicon manufacturing processes.
Solution Approach 2:
The patent transitions from a two-dimensional flat substrate surface to a three-dimensional micro-structured surface with cavities having inclined walls. This dimensional transformation allows light to be trapped and absorbed more effectively through multiple reflections within the cavities, significantly enhancing optical absorption in the infrared range while building upon conventional silicon substrate manufacturing.
3Manufacturing precision
If complex laser processing is used, then cavity structure is achieved, but productivity decreases
Solution Approach 1:
The patent replaces the low-productivity laser processing system with a high-productivity chemical etching system. The chemical etching process using KOH solution can treat large areas of substrate simultaneously and at higher speeds, while the self-organizing nature of the etching process maintains precise cavity structure formation, thereby resolving the contradiction between precision and productivity.
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
The method enables high optical absorption of at least 70% for wavelengths between 600-1000 nm and 10-15% for 1200-2000 nm, improving the substrate's applicability and productivity for industrial-scale production.
Implementation Method 1
a) anisotropic etching of at least part of the semiconductor material in the zones not covered by the sacrificial layer, with an etching speed of the semiconductor material which is at least ten times higher than the etching speed of the sacrificial layer
Implementation Method 2
The etching of step iii consists in removing at least part of the semiconductor material from step ii, not covered by the islands of sacrificial layer: said islands of sacrificial layer thus serve as protection or 'mask' for the parts of semiconductor material that they cover
Implementation Method 3
The structured substrate of the present invention is more particularly a micro-structured substrate, since the fields of application of this type of substrate belong to microelectronics. The depth of the cavities with inclined walls can thus be of the order of a few tens of micrometers, or less than ten micrometers. For wavelengths ranging from 600 nm to 1000 nm, the structured substrate according to the present invention advantageously makes it possible to have an optical absorption of at least 70%
Data Source
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AI summary
The present invention relates to a method for manufacturing a structured semiconductor substrate (100) comprising the following steps: i. depositing, on the surface (1a) of a semiconductor material (1), a sacrificial layer (2), different from the semiconductor material, ii. etching at least partially the sacrificial layer (2) formed in step i, so as to form islands (2a) of sacrificial layer on the surface (1a) of the semiconductor material, iii. etching at least partially the semiconductor material (1) of step ii, at the level of the areas (1c) not protected by said islands (2a), so as to form a structured semiconductor material (10), this step iii being carried out in the presence of oxygen so as to deposit a layer of an oxide (3) on the surface of the semiconductor material, and iv. eliminate the islands (2a) of sacrificial layer and the oxide layer (3), on the surface of the semiconductor material obtained in step iii, to form said structured substrate (100).