Silicon Cavity Etching with Retarding Mask Structures
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Solution Overview
Problem
Current methods for producing cavities in silicon substrates for semiconductor components, such as angled cavities for optical elements, face challenges in achieving precise angular orientations, low geometrical tolerances, and high surface quality, particularly in terms of surface roughness and cost-effectiveness.
Innovation Solution
An anisotropic etching method is employed, where a silicon substrate with a tilted {111} plane is etched using a mask with specific retarding structures and projection regions, allowing for the formation of cavities with inclined side surfaces and rectangular openings, optimizing etching duration to create a smooth floor surface and minimize undercutting, thus enhancing precision and reducing processing time and costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If mechanical processing methods are used to produce cavities in silicon substrates, then the production process is simple, but the surface quality (surface roughness, angular precision, geometrical tolerances) deteriorates
Solution Approach 1:
The patent replaces mechanical processing methods with chemical etching processes. Specifically, it uses anisotropic etching with tailored etching masks that have retarding structures and projection regions, allowing precise cavity formation through chemical means rather than mechanical tools, thereby achieving superior surface quality and angular precision without mechanical contact
Solution Approach 2:
The patent employs controlled etching parameters including etching duration, etching solution composition, and mask structure geometry to precisely control the cavity formation process. By adjusting these parameters, the method achieves high manufacturing precision for angular orientation and surface quality while maintaining processability
2Manufacturing precision
If anisotropic etching is used to achieve high surface quality, then surface roughness and angular precision improve, but processing time increases
Solution Approach 1:
The patent applies preliminary structuring to the etching mask by incorporating retarding structures and projection regions before the etching process begins. These pre-designed mask features control the etching progression, allowing high-precision cavity formation to be achieved more efficiently by guiding the chemical etching process from the outset rather than requiring multiple adjustment steps
Solution Approach 2:
The patent uses the etching mask as a precise template or copy of the desired cavity geometry. The mask structures (retarding structures and projection regions) are designed to replicate the final cavity shape, enabling direct transfer of the precise geometric pattern to the silicon substrate through etching, thereby reducing processing time while maintaining high precision
3Manufacturing precision
If conventional etching masks are used, then the process is simple, but the ability to control cavity geometry and achieve rectangular openings with precise angles deteriorates
Solution Approach 1:
The patent divides the etching mask into functional segments: retarding structures that control etching progression in specific regions, projection regions that define cavity boundaries, and opening regions that determine cavity aperture. This segmentation allows independent optimization of each mask region to achieve precise control over the three-dimensional cavity geometry
Solution Approach 2:
The patent uses the etching mask as an intermediary tool that translates the desired cavity geometry into the actual etched structure. The mask structures (retarding structures and projection regions) mediate the etching process by selectively protecting and exposing substrate regions, enabling precise geometric control without directly forming the cavity itself
4Productivity
If batch processing is implemented to improve productivity, then production efficiency increases, but process control and quality consistency become more difficult
Solution Approach 1:
The patent designs the etching mask with universal features that can be replicated across multiple substrates in a batch. The retarding structures and projection regions are configured to provide consistent geometric control for all cavities formed in the batch, ensuring quality consistency while enabling simultaneous processing of multiple substrates to improve 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
This method results in cavities with high angular precision, low surface roughness, and reduced geometrical tolerances, offering significant improvements in surface quality and process efficiency compared to mechanical processing, while being compatible with semiconductor technology and allowing for batch processing of multiple cavities.
Implementation Method 1
an anisotropic etching of the silicon substrate during a defined etching duration. Here, an etching rate in the <100> directions of the silicon substrate is lower than in other spatial directions
Data Source
AI summary
A method for forming a cavity in a silicon substrate, a surface of the silicon substrate having a tilting angle relative to a first plane of the silicon substrate, and the first plane being a {111} plane of the silicon substrate, and situation of an etching mask on the surface of the silicon substrate. The etching mask has a retarding structure that protrudes into the mask opening, and a first etching projection region. All further edges of the mask opening outside the first etching projection region are situated essentially parallel to {111} planes of the silicon substrate. The method includes an anisotropic etching of the silicon substrate during a defined etching duration. An etching rate in the <111> directions of the silicon substrate is lower than in other spatial directions, and the first retarding structure is undercut in a first undercut direction going out from the first etching projection region.