Integrated Resonator Mass Bias for Frequency Drift Control

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Solution Overview

Problem

Crystal oscillators used in electronics often experience frequency drift over time due to mass accumulation, which is not effectively addressed by existing technologies.

Innovation Solution

An integrated resonator with a mass bias is introduced within plastic packaging to prevent or reduce frequency drift, featuring a substrate with alternating dielectric layers, a piezoelectric layer, electrodes, and a mass bias over the upper Bragg reflector, encapsulated in plastic to maintain a stable frequency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a crystal oscillator is used for frequency control, then timing stability is initially good, but frequency drift occurs over time due to mass accumulation

Engineering Contradiction:

Improvefrequency stabilityVSAvoidoperational time

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The patent applies preliminary action by pre-loading the resonator with a known mass (mass bias) during manufacturing. This mass is intentionally added to the resonator structure before operation to compensate for future mass accumulation. The mass bias is calculated and positioned to counteract the expected frequency drift that would occur during the device's operational lifetime, thereby maintaining frequency stability over extended periods.

Inventive Principle:

Principle #10Preliminary action

2Ease of manufacture

If the resonator structure is simplified for integration, then manufacturing ease improves, but frequency stability may be compromised

Engineering Contradiction:

Improveintegration easeVSAvoidfrequency stability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent merges the mass bias structure with the existing resonator components, integrating it into the same fabrication process and structural framework. The mass bias is formed using the same material deposition and patterning techniques as the resonator electrodes and dielectric layers, eliminating the need for separate manufacturing steps. This integration maintains frequency stability while preserving manufacturing simplicity and compatibility with standard semiconductor fabrication processes.

Inventive Principle:

Principle #5Merging (Combining)

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

The mass bias stabilizes the resonator's frequency by preloading a known mass, reducing shifts from additional mass accumulation and maintaining frequency stability over time.

Implementation Method 1

A piezoelectric layer is formed between the top and bottom dielectric structures

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

The added mass functions to prevent or at least reduce frequency drift over time of the resonator device

Methodology Applied

Scientific EffectMass loading effect:

Data Source

PatentUS11799436B2Method of forming an integrated resonator with a mass bias

Publication Date: 2023.10.24 TEXAS INSTRUMENTS INC

AI summary

A method of forming a resonator includes forming top and bottom dielectric structures over a substrate. A piezoelectric layer is formed between the top and bottom dielectric structures. A bottom electrode is formed between the piezoelectric layer and the bottom dielectric structure, and a top electrode is formed between the piezoelectric layer and the top dielectric structure. A metal layer is formed over the top dielectric structure and is patterned, thereby forming a first contact pad making electrical contact to the top electrode, a second contact pad making electrical contact with the bottom electrode, and a mass bias located over the top dielectric structure.