MEMS Gyroscope Quality Factor Testing at Wafer Probe

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Solution Overview

Problem

Conventional MEMS devices face challenges in improving performance, reducing size, and decreasing cost, while also requiring more complex microsystems with greater computational power, which are not adequately addressed by existing technologies.

Innovation Solution

A method for testing MEMS devices by applying driving signals at specific resonant frequencies and phases to determine a quality characteristic, allowing for assessment and binning of devices based on their performance, which includes measuring the quality factor Q to evaluate the hermetic/vacuum seal and screen out sub-par devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional MEMS fabrication technologies are used, then manufacturing simplicity is maintained, but performance improvement and quality control are limited

Engineering Contradiction:

Improvequality factor measurement precisionVSAvoidtesting process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent replaces complex mechanical quality assessment methods with automated electrical signal-based measurement. By applying driving signals and measuring resonant frequencies and phase shifts, the system automatically determines quality factors without manual intervention, thereby improving measurement precision while maintaining process simplicity

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The MEMS device itself provides the measurement data through its resonant response. The device's natural vibration characteristics at different frequencies reveal quality information about the hermetic seal, eliminating the need for separate complex testing equipment and enabling self-diagnostic capability

Inventive Principle:

Principle #25Self-service

2Reliability

If hermetic/vacuum seal quality is improved, then device performance is enhanced, but manufacturing complexity and cost increase

Engineering Contradiction:

Improvehermetic seal qualityVSAvoidmanufacturing simplicity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent performs quality factor measurement at wafer-level chip probe before final packaging. This preliminary testing identifies devices with sub-par vacuum levels early in the manufacturing process, allowing for early rejection or rework without complicating the final hermetic sealing process

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Instead of using complex physical inspection methods to assess hermetic seal quality, the patent employs automated electrical measurement of resonant frequencies. This substitution simplifies the manufacturing process by using standard electrical testing equipment rather than specialized hermeticity testing apparatus

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Productivity

If device performance screening is enhanced, then yield of good devices increases, but testing time and process complexity increase

Engineering Contradiction:

Improvedevice yieldVSAvoidtesting time

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The patent applies periodic driving signals at multiple specific frequencies to the MEMS device to excite resonant modes. By measuring the phase shift and amplitude response at these periodic intervals, the system efficiently extracts quality factor information in a systematic and time-efficient manner

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent performs comprehensive quality assessment at wafer-level chip probe before final device completion. This preliminary screening identifies and separates high-yield devices from defective ones early in the manufacturing flow, preventing waste of time on subsequent processing of poor-quality devices

Inventive Principle:

Principle #10Preliminary action

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 enables easy-to-use processes that rely on conventional fabrication technologies, providing automated Q measurement for higher yields of better-performing MEMS devices and reducing production costs by identifying and discarding devices with sub-par vacuum levels.

Implementation Method 1

Each of the driving signals causes the MEMS device to resonate at a first and second resonant frequency, respectively

Methodology Applied

Scientific EffectResonance: Resonance

Data Source

PatentUS10267636B1Method to test the quality factor of a MEMS gyroscope at chip probe

Publication Date: 2019.04.23 MCUBE INC

AI summary

A method for a MEMS device comprises determining in a computer system, a first driving signal for the MEMS device in response to a first time delay and to a base driving signal, applying the first driving signal to the MEMS device to induce the MEMS device to operate at a first frequency, determining a second driving signal for the MEMS device in response to a second time delay and to the base driving signal, applying the second driving signal to the MEMS device to induce the MEMS device to operate at a second frequency, determining a first quality factor associated with the MEMS device in response to the first frequency and the second frequency, determining a quality factor associated with the MEMS device in response to the first quality factor, and determining whether the quality factor associated with the MEMS device, exceeds a threshold quality factor.