Semiconductor Cavity Formation via Dry and Electrochemical Etching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for producing cavities in semiconductor substrates, such as those used in microelectromechanical systems (MEMS), face limitations in achieving high aspect ratios and precise control over cavity depth while minimizing surface area and production costs.
Innovation Solution
A method combining dry etching and electrochemical etching, where dry etching creates provisional cavities with steep sidewalls, followed by protective material deposition and removal to expose the substrate for electrochemical etching, allowing for precise control of cavity depth and reduced surface area requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wet-chemical etching is used to produce cavities, then the etching process is simple and selective, but the aspect ratio is limited and large surface area is required
Solution Approach 1:
The etching process is divided into two distinct stages: first, dry etching creates a provisional cavity with steep sidewalls to achieve high aspect ratio; second, wet-chemical etching is applied selectively to the exposed bottom section to achieve precise depth control. This segmentation allows each method to contribute its strengths without being limited by the other's weaknesses.
Solution Approach 2:
The dry etching step is performed as a preliminary action before wet-chemical etching. This preliminary dry etching creates the provisional cavity structure with the desired high aspect ratio, preparing the substrate for the subsequent selective wet-chemical etching that will achieve the final precise depth without compromising the aspect ratio.
2Manufacturing precision
If electrochemical etching is used, then precise depth control is achieved, but complex doping structures are required
Solution Approach 1:
Instead of using complex electrochemical etching throughout the entire cavity depth, the patent applies wet-chemical etching only partially to the exposed bottom section of the provisional cavity. This partial application achieves the necessary precision for the final depth without requiring the complex doping structures that would be needed for full-depth electrochemical etching.
3Length of stationary object
If dry etching is used alone, then high aspect ratio cavities are produced, but precise depth control is difficult to achieve
Solution Approach 1:
The protective material serves as an intermediary element that enables the transition from dry etching to selective wet-chemical etching. It is deposited on the sidewalls during dry etching, then selectively removed at the bottom to expose the substrate for precise wet-chemical etching, allowing both high aspect ratio and precise depth control to be achieved.
4Area of stationary object
If cavity area is reduced to minimize chip area, then more cavities fit on the chip, but production cost and complexity increase
Solution Approach 1:
The patent changes the etching parameters and methodology by combining two different etching approaches (dry and wet-chemical) with distinct parameter regimes. This allows optimization of both the cavity geometry (high aspect ratio, small footprint) and the production process, achieving area reduction without proportionally increasing complexity.
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 enables the production of cavities with high aspect ratios and precise depth control, reducing the required chip area and production costs while maintaining sensitivity and functionality in MEMS components.
Implementation Method 1
dry etching the semiconductor substrate, wherein the dry etching is effected from a surface of the semiconductor substrate
Implementation Method 2
The protective material is deposited with regard to a subsequent wet-etching process at the surface of the semiconductor substrate and at cavity surfaces
Implementation Method 3
electrochemically etching the semiconductor substrate, wherein the electrochemical etching is effected at the exposed section of the bottom of the at least one provisional cavity
Data Source
AI summary
A method for producing at least one cavity within a semiconductor substrate includes dry etching the semiconductor substrate from a surface of the semiconductor substrate at at least one intended cavity location in order to obtain at least one provisional cavity. The method includes depositing a protective material with regard to a subsequent wet-etching process at the surface of the semiconductor substrate and at cavity surfaces of the at least one provisional cavity. Furthermore, the method includes removing the protective material at least at a section of a bottom of the at least one provisional cavity in order to expose the semiconductor substrate. This is followed by electrochemically etching the semiconductor substrate at the exposed section of the bottom of the at least one provisional cavity. A method for producing a micromechanical sensor system in which this type of cavity formation is used and a corresponding MEMS are also disclosed.