MEMS Cavity Etching via Dual-Layer Liner and Cover

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Solution Overview

Problem

Conventional methods face challenges in producing high-quality cavities for microstructures with sufficient quality and economic efficiency in microelectromechanical systems (MEMS) due to difficulties in removing sacrificial layers with varying etching rates of cover and liner layers.

Innovation Solution

A method involving a liner layer with a high etching rate and a cover layer with a lower etching rate, where the liner layer is used to rapidly access and remove the sacrificial layer, ensuring efficient and clean etching, and the cover layer provides dielectric insulation, facilitating the formation of cavities and improved electrical contacts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a single layer is used for covering the cutout, then the process is simple, but the etching rate is insufficient to rapidly access and remove the sacrificial layer

Engineering Contradiction:

Improveetching rateVSAvoidlayer structure complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The cover layer is divided into two distinct layers: a first cover layer with high etching rate for rapid sacrificial layer access, and a second cover layer with lower etching rate for controlled etching. This segmentation allows each layer to perform its specific function optimally without compromising the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the cover structure have different etching rates tailored to their specific functions. The first cover layer region contacts the sacrificial layer and has high etching rate, while the second cover layer region provides insulation and has lower etching rate, creating local quality variations that optimize overall performance.

Inventive Principle:

Principle #3Local quality

2Reliability

If the liner layer is made thin for better contact, then electrical contact is improved, but the liner layer may not provide sufficient barrier function

Engineering Contradiction:

Improveelectrical contact qualityVSAvoiddiffusion barrier function

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The liner layer thickness is optimized to a specific range (5-50 nm) that balances two competing requirements: thin enough to allow good electrical contact when contact holes are formed, but thick enough to provide adequate diffusion barrier function. This parameter optimization resolves the contradiction between contact quality and barrier function.

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If conventional etching methods are used, then the process is simple, but residue remains after sacrificial layer removal

Engineering Contradiction:

Improvecleanliness of etchingVSAvoidetching time

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The first cover layer is applied preliminarily to create a high etching rate pathway before the final etching process. This preliminary structure enables the etching solution to rapidly access and remove the sacrificial layer completely, preventing residue formation while maintaining controlled etching through the second cover layer.

Inventive Principle:

Principle #10Preliminary action

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 rapid and residue-free removal of sacrificial layers, improving the quality and reliability of MEMS by preventing defects and ensuring efficient etching, thus enhancing the robustness and integrity of microelectromechanical components.

Implementation Method 1

completely removing the liner material and the further material from the cutout by means of wet-chemically etching the liner layer using an etching solution, wherein the etching solution has a greater etching rate for the liner layer than for the cover layer

Methodology Applied

Scientific EffectWet-chemical etching:

Data Source

PatentUS11787686B2Method for processing a layer structure and microelectromechanical component

Publication Date: 2023.10.17 INFINEON TECHNOLOGIES AG

AI summary

In accordance with various embodiments, a method for processing a layer structure is provided, where the layer structure includes a first layer, a sacrificial layer arranged above the first layer, and a second layer arranged above the sacrificial layer, where the second layer includes at least one opening, and the at least one opening extends from a first side of the second layer as far as the sacrificial layer. The method includes forming a liner layer covering at least one inner wall of the at least one opening; forming a cover layer above the liner layer, where the cover layer extends at least in sections into the at least one opening; and wet-chemically etching the cover layer, the liner layer and the sacrificial layer using an etching solution, where the etching solution has a greater etching rate for the liner layer than for the cover layer.