Backside Etched Isolation Trenches for MEMS Stress Management

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Solution Overview

Problem

Conventional MEMS device manufacturing techniques using frontside trenches are complex, prone to over etch grooves, and limit structural beam thickness, affecting device performance.

Innovation Solution

The method involves etching isolation trenches from the backside of the substrate, simplifying the process by omitting polysilicon refilling and protection steps, allowing thicker structural beams and reducing manufacturing costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If frontside trenches are used for stress isolation, then stress isolation is achieved, but the manufacturing process becomes complex and over etch grooves occur

Engineering Contradiction:

Improvestress isolationVSAvoidmanufacturing process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent inverts the conventional approach by etching isolation trenches from the backside of the substrate instead of the frontside. This inversion simplifies the manufacturing process by eliminating the need for polysilicon refilling and protection steps, while still achieving effective stress isolation between the MEMS structure and the substrate.

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If frontside trenches are used for stress isolation, then stress isolation is achieved, but structural beam thickness is limited

Engineering Contradiction:

Improvestress isolationVSAvoidstructural beam thickness

Core Design Contradiction:

ReliabilityVSLength of moving object

Solution Approach 1:

By inverting the etching direction to the backside, the patent removes the constraint on structural beam thickness that exists in frontside trench approaches. The backside etching allows thicker structural beams to be formed without interference from trench formation processes.

Inventive Principle:

Principle #13The other way round (Inversion)

3Ease of manufacture

If polysilicon refilling and protection steps are performed, then frontside trenches are formed, but manufacturing cost increases

Engineering Contradiction:

Improvetrench formationVSAvoidmanufacturing cost

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

The patent extracts and eliminates the unnecessary polysilicon refilling and protection steps from the manufacturing process. By using backside etching, only the essential trench formation remains, reducing manufacturing complexity and cost while achieving the same stress isolation function.

Inventive Principle:

Principle #2Taking out (Extraction)

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 a more cost-effective, less complex manufacturing process with reduced over etch grooves and thicker structural beams, enhancing MEMS device performance by minimizing stress-related issues.

Implementation Method 1

etching a trench in the second side of the substrate

Methodology Applied

Scientific EffectEtching:

Data Source

PatentUS20240300808A1MEMS stress isolation technology with backside etched isolation trenches

Publication Date: 2024.09.12 ANALOG DEVICES INC

AI summary

Described herein are manufacturing techniques for achieving stress isolation in microelectromechanical systems (MEMS) devices that involve isolation trenches formed from the backside of the substrate. The techniques described herein involve etching a trench in the bottom side of the substrate subsequent to forming a MEMS platform, and processing the MEMS platform to form a MEMS device on the top side of the substrate subsequent to etching the trench.