Recessed Micromechanical Etching with Self-Supporting Mask

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Solution Overview

Problem

Existing etching methods for micromechanical device layers require multiple masks and steps to achieve multiple recess depths, which is inefficient and prone to errors, especially when dealing with high aspect ratio structures.

Innovation Solution

A method involving a self-supporting etching mask that protects vertical sidewalls and etch-control areas to control the etch rate, allowing multiple recess depths to be achieved simultaneously without additional masks, by altering the geometry of etch-control areas.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If multiple masks and multiple deep etching steps are used to achieve multiple recess depths, then the manufacturing precision of recess depths is improved, but the device complexity and loss of time increase significantly

Engineering Contradiction:

Improverecess depth precisionVSAvoidetching process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

A self-supporting mask is introduced as an intermediary element that forms on the sidewalls of recessed structures during the etching process. This mask automatically controls the etching depth by providing a physical barrier, eliminating the need for multiple separate masks and etching steps while maintaining precise depth control for multiple recess levels.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The etching process itself generates the depth-control mask through in-situ formation on the sidewalls of recessed structures. The mask forms automatically during etching and self-regulates the etching depth, making the process self-controlling and eliminating the need for external mask management for each depth level.

Inventive Principle:

Principle #25Self-service

2Manufacturing precision

If multiple masks and multiple deep etching steps are used to achieve multiple recess depths, then the manufacturing precision of recess depths is improved, but the loss of time increases significantly

Engineering Contradiction:

Improverecess depth precisionVSAvoidtotal etching process time

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

Multiple etching operations that would traditionally require separate masks and sequential processing are merged into a single integrated etching step. The self-supporting mask enables simultaneous formation of multiple recess depths in one continuous process, dramatically reducing total processing time while maintaining precision.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The etching process continues uninterrupted in a single continuous operation, with the self-supporting mask providing ongoing depth control throughout the etching cycle. This eliminates the stop-start nature of multiple sequential etching steps, maintaining continuous productive action throughout the process.

Inventive Principle:

Principle #20Continuity of useful action

3Manufacturing precision

If additional masks and mask removal steps are used for multiple recess levels, then the manufacturing precision of multiple recess depths is improved, but the ease of manufacture deteriorates

Engineering Contradiction:

Improvemultiple recess depths precisionVSAvoidrecess etching simplicity

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The self-supporting mask serves as an automatic intermediary that forms during etching and provides inherent depth control. This eliminates the need for operators to manage multiple masks and perform repeated mask removal steps, greatly simplifying the manufacturing process while maintaining precise multi-level recess depth control.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 enables the simultaneous recessing of micromechanical structures to multiple depths within a single structural layer without the need for separate masks, improving efficiency and reducing the risk of measurement errors or short-circuits.

Implementation Method 1

protecting the vertical sidewalls formed in a first deep etch with a self-supporting etching mask before the second deep etching step

Methodology Applied

Scientific EffectPhysical barrier protection:

Implementation Method 2

form etch-control areas which extend at regular intervals from a self-supporting vertical mask on one side of a recess area to a self-supporting vertical mas on another side of the recess area. The width and spacing of these etch-control areas influence the vertical etch rate

Methodology Applied

Scientific EffectEtch rate control through geometric configuration:

Implementation Method 3

The second deep etch may be either an isotropic or an anisotropic etching process

Methodology Applied

Scientific EffectIsotropic etching:

Data Source

PatentUS11094552B2Method for etching recessed structures

Publication Date: 2021.08.17 MURATA MFG CO LTD

AI summary

A method for manufacturing recessed micromechanical structures in a wafer. A first etching mask and a second etching mask are patterned on the horizontal face of the wafer. The second etching mask defines at least one recess area and the first etching mask defines at least one etch-control area within the at least one recess area. The placement, number and dimensions of the etch-control areas influence the vertical etch rate of the recessed structure. Adjacent structures can be etched to different recess depths by selecting suitable etch-control areas.