MEMS Resonator Anchor Heating for Stable Temperature Control

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Solution Overview

Problem

MEMS resonators experience significant temperature drift due to ambient temperature variations, which existing feedback control systems using Wheatstone bridges cannot accurately stabilize, leading to non-uniform temperature profiles and inaccurate control of resonator electrical characteristics.

Innovation Solution

A MEMS resonator design featuring a resistive heating element with ends exposed to ambient temperature and a feedback control system, where the anchor is thermally coupled to a location with minimal ambient temperature dependency, allowing the heating current to pass through the anchor rather than the resonator, maintaining a stable temperature for the resonator body.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If heating current is passed through the resonator in a Wheatstone bridge configuration, then temperature stabilization is achieved, but non-uniform temperature profile is created within the resonator

Engineering Contradiction:

Improvetemperature stabilizationVSAvoidtemperature uniformity

Core Design Contradiction:

TemperatureVSStability of the object's composition

Solution Approach 1:

The heating function is segmented from the resonator body and transferred to the anchor structure. The anchor is divided into a first anchor connected to the resonator and a second anchor extending in a different direction, with the heating current passing through the second anchor to a location with minimal ambient temperature dependency. This segmentation allows the resonator to be heated without the current flowing directly through it, resolving the contradiction between achieving temperature stabilization and maintaining temperature uniformity.

Inventive Principle:

Principle #1Segmentation

2Ease of manufacture

If the resonator is thermally coupled to ambient temperature locations, then ease of manufacturing is improved, but temperature drift increases

Engineering Contradiction:

Improvethermal coupling simplicityVSAvoidtemperature drift

Core Design Contradiction:

Ease of manufactureVSTemperature

Solution Approach 1:

The anchor serves as an intermediary thermal coupling element between the resonator and the substrate. Instead of directly coupling the resonator to ambient temperature locations, the anchor mediates this coupling by providing a thermal path through its structure. The anchor is thermally coupled to a location that has minimal dependency on ambient temperature, allowing the resonator to be indirectly coupled to ambient temperature locations while reducing temperature drift through the anchor's thermal management function.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Measurement precision

If feedback control measures temperature at the resonator location, then temperature control accuracy is improved, but sensitivity to ambient temperature variations increases

Engineering Contradiction:

Improvetemperature measurement accuracyVSAvoidambient temperature sensitivity

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The temperature measurement function is extracted from the resonator body and relocated to the anchor structure. The feedback control system now measures temperature at the anchor location rather than directly at the resonator. This extraction removes the measurement point from the ambient temperature sensitive zone while maintaining its ability to accurately reflect the resonator's temperature through thermal coupling, thereby reducing sensitivity to ambient temperature variations while preserving measurement accuracy.

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 configuration provides a stable temperature for the resonator, reducing its sensitivity to ambient temperature variations and enabling accurate feedback control, as demonstrated by finite element simulations showing minimal temperature fluctuations across the resonator.

Implementation Method 1

a feedback control system for controlling the resistive heating element to provide heating in order to maintain the resonator body at a constant temperature

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

the anchor is thermally coupled to a location of the resistive heating element which has a lowest dependency of its temperature on the ambient temperature

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS8729973B2MEMS resonator

Publication Date: 2014.05.20 STMICROELECTRONICS INT NV

AI summary

A MEMS resonator comprises a resonator body (34), and an anchor (32) which provides a fixed connection between the resonator body (34) and a support body. A resistive heating element (R1,R2) and a feedback control system are used to maintain the resonator body (34) at a constant temperature. A location for thermally coupling the anchor (32) to the resistive heating element (R1,R2) is selected which has a lowest dependency of its temperature on the ambient temperature during the operation of the feedback control.