Homogeneous Silicon MEMS Comb Structures for Capacitive Detection

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Solution Overview

Problem

Existing MEMS devices face challenges in achieving optimal accuracy and efficiency due to non-homogenous materials in comb structures, leading to electrostatic differences and misalignment issues during manufacturing, which affect the precision and effectiveness of capacitive detection.

Innovation Solution

A method involving deep silicon etching of a single homogenous material layer to create self-aligned critical structures, eliminating the need for electrical biasing and ensuring uniform vertical surfaces, allowing for precise and efficient capacitive detection with multi-layer comb structures for fully linear detection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If non-homogenous materials are used in comb structures, then manufacturing flexibility is improved, but electrostatic differences and misalignment issues occur affecting detection precision

Engineering Contradiction:

Improvemanufacturing flexibilityVSAvoidcapacitive detection precision

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent applies homogeneity by using a single homogenous material layer (silicon) for the entire device structure instead of multiple different materials. This eliminates electrostatic differences between materials while maintaining manufacturing flexibility through versatile etching and patterning processes on the homogeneous silicon layer.

Inventive Principle:

Principle #33Homogeneity

2Device complexity

If multiple masks and layers are used for comb structure manufacturing, then structural complexity is improved, but misalignment issues and manufacturing difficulty increase

Engineering Contradiction:

Improvecomb structure capabilityVSAvoidmanufacturing alignment precision

Core Design Contradiction:

Device complexityVSEase of manufacture

Solution Approach 1:

The patent merges multiple functions into a single homogenous material layer, where one silicon layer provides both structural support and comb electrodes. This consolidation eliminates the need for multiple separate material layers and their associated alignment procedures, reducing manufacturing complexity while maintaining device functionality.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent uses a single mask with strategically positioned openings to define multiple distinct structures (comb electrodes, suspension beams, proof mass) simultaneously. This segmentation approach allows complex multi-component structures to be created in one patterning step without requiring sequential alignment of multiple masks.

Inventive Principle:

Principle #1Segmentation

3Measurement precision

If dense comb structures are created, then detection accuracy is improved, but area required for comb structures increases

Engineering Contradiction:

Improvedetection accuracyVSAvoidcomb structure area

Core Design Contradiction:

Measurement precisionVSArea of stationary object

Solution Approach 1:

The patent achieves dense comb structures by utilizing vertical dimension through recessed features and multi-level configurations within the silicon layer. This allows high-density electrode arrangements that provide accurate capacitive detection while minimizing the horizontal footprint of the device.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 highly accurate and dense comb structures with improved material optimization, enabling precise capacitive detection and reducing the area required for comb structures, enhancing the performance of MEMS devices.

Implementation Method 1

First trenches are etched using the first mask, the first trenches defining the lateral dimensions of the at least comb structures

Methodology Applied

Scientific EffectEtching:

Implementation Method 2

The first trenches are filled with a deposit layer

Methodology Applied

Scientific EffectDeposition: Deposition (physical)

Implementation Method 3

A key element in a capacitive MEMS device is a variable capacitor formed between two electrodes... The amount of deflection can be sensed from changes in capacitance from the changes in the gap between the two electrodes

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentEP3294665B1A manufacturing method of a multi-level micromechanical structure

Publication Date: 2023.10.18 MURATA MFG CO LTD

Figure 1a~1d
Figure 1e~1h
Figure 2a~2d

AI summary

A method for manufacturing a micromechanical device layer is performed on a device wafer comprising a single layer of homogenous material. The method comprises patterning a first mask on a first face of the device wafer, the first mask patterning at least lateral dimensions of comb structures and outlines of large device structures. First trenches are etched, the first trenches defining the lateral dimensions of the at least comb structures and outlines of large device structures in a single deep etching process. Recession etching may be used on one or two faces of the device wafer for creating structures at least partially recessed below the respective surfaces of the device wafer. A double mask etching process may be used on one or two faces of the device wafer for creating structures at least partially recessed to mutually varying depths from the respective face of the device wafer.