MEMS Cavity Pressure Control via Electrically Activated Getter Seal

Solution Overview

Problem

Existing MEMS devices face challenges in maintaining stable low surrounding pressure across their service life due to thermal activation of getter materials during the bonding process, limiting separate optimization of bonding and getter activation, and requiring thermal activation which is not decoupled from other process steps.

Innovation Solution

A micromechanical device with a first cavity containing an MEMS element and a second cavity connected via an electrically activatable seal, allowing for independent control of internal pressure using a getter material in the second cavity, which is not thermally activated, enabling selective gas sorption and pressure stabilization through electrical activation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a getter material is thermally activated during the bonding process, then the cavity pressure can be adjusted, but the bonding process and getter activation cannot be separately optimized

Engineering Contradiction:

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The device is divided into a first cavity (sensor cavity) and a second cavity (getter cavity) that are hermetically sealed from each other during bonding. The getter material is placed in the second cavity and activated separately after the bonding process, allowing independent optimization of bonding parameters and getter activation parameters.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The getter material is pre-positioned in the second cavity before the bonding process, but its activation is delayed until after bonding is complete. This preliminary placement allows the getter to be ready for activation at the optimal time, separate from the bonding process.

Inventive Principle:

Principle #10Preliminary action

2Productivity

If multiple sensors with different cavity pressures are produced on one chip, then production efficiency is improved, but separate optimization of each sensor's cavity pressure becomes difficult

Engineering Contradiction:

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

Each sensor is assigned its own hermetically sealed cavity (first cavity), while a shared second cavity containing the getter material provides individual pressure control. This segmentation allows multiple sensors to be produced on one chip while maintaining the ability to independently optimize each sensor's cavity pressure through selective getter activation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The hermetic seal acts as an intermediary barrier between the sensor cavity and the getter cavity, enabling independent pressure control. This seal allows the getter material to be activated to adjust pressure in one sensor cavity without affecting other sensor cavities on the same chip.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If the getter material is thermally activated, then gas sorption is achieved, but the activation temperature conflicts with bonding process requirements

Engineering Contradiction:

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The getter material is pre-positioned in the second cavity in its inactive state before the bonding process. This allows the bonding process to proceed at its required temperature without thermal activation of the getter, and the getter is activated later at the optimal time with appropriate electrical stimulation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The thermal activation mechanism is replaced with electrical activation of the getter material. Instead of using heat to activate the getter during or after bonding, an electrical signal is applied to the getter material in the second cavity, allowing activation at lower temperatures and at any time after bonding is complete.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 solution allows for precise adjustment and stabilization of internal pressure in MEMS devices, decoupling getter activation from the bonding process, and enabling selective gas management to maintain optimal sensor performance across the service life without enlarging the device's base area.

Implementation Method 1

the connection channel having a seal by which the first cavity and the second cavity are hermetically sealed from each other

Methodology Applied

Scientific EffectHermetic sealing:

Implementation Method 2

the seal being able to be opened electrically

Methodology Applied

Scientific EffectElectrical activation:

Implementation Method 3

a getter material is introduced into the cavity, in which case the task of the getter is restricted to the adsorption of gas emissions from the sensor and/or the cap

Methodology Applied

Scientific EffectAdsorption: Adsorption

Implementation Method 4

The sorption of gases is advantageously able to be increased in that a suitable getter material is additionally introduced into the second cavity

Methodology Applied

Scientific EffectSorption: Sorption

Data Source

PatentUS10501311B2Micromechanical device having a first cavity and a second cavity

Publication Date: 2019.12.10

AI summary

A micromechanical device having a first cavity, which has a MEMS element, and having a second cavity. The second cavity is connected to the first cavity with a connection channel, the connection channel having a seal by which the first cavity and the second cavity are hermetically sealed from each other, the seal being able to be opened electrically.