Angled Silicon MEMS Resonator for Temperature-Stable Frequency
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Solution Overview
Problem
Microelectromechanical systems (MEMS) resonant elements exhibit significant temperature sensitivity, leading to variations in resonant frequency due to thermal changes in Young's modulus, which complicates maintaining stable frequency output across temperature ranges.
Innovation Solution
The implementation of MEMS resonant elements with specific dopant concentrations and structural designs, such as non-uniform doping and angled beam configurations, combined with integrated circuits for temperature compensation, allows for minimized temperature sensitivity and stable frequency output across a range of temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional MEMS resonant elements are used, then manufacturing is simplified, but temperature sensitivity causes significant frequency variation
Solution Approach 1:
The patent applies parameter changes by precisely controlling the doping concentration (e.g., 1e19 to 1e21 atoms/cm³) and crystal orientation angles (e.g., <110> ± 5 degrees) of the silicon resonant element to achieve minimal temperature sensitivity and stable frequency output across temperature ranges
Solution Approach 2:
The patent implements local quality by creating non-uniform doping profiles within the silicon resonant element, where different regions have different doping concentrations to optimize temperature compensation and frequency stability in specific areas of the resonator structure
2Ease of manufacture
If beam segments are aligned with silicon crystal orientation, then manufacturing is easier, but temperature-induced Young's modulus changes cause frequency drift
Solution Approach 1:
The patent applies asymmetry by deliberately misaligning the beam segments at specific angles (e.g., 45 degrees) relative to the silicon crystal orientation, creating an asymmetric configuration that compensates for temperature-induced frequency drift while maintaining manufacturability through defined angular relationships
3Reliability
If dopant concentration is increased to compensate temperature sensitivity, then frequency stability improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes the doping concentration parameter within a specific range (1e19 to 1e21 atoms/cm³) to achieve effective temperature compensation while maintaining practical manufacturing precision, avoiding excessively high doping levels that would require ultra-precise fabrication control
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
These designs achieve stable frequency output by minimizing temperature-induced frequency variations, enabling MEMS devices to maintain a predetermined frequency stability even as ambient temperatures change, with the potential for zero or near-zero frequency change over temperature ranges.
Implementation Method 1
a doped silicon resonant element having a dopant concentration that minimizes a temperature sensitivity of the Young's modulus of the doped silicon resonant element
Implementation Method 2
thermally induced changes to the Young's modulus (or other variables) tend to change the mechanical stiffness of the structure
Data Source
AI summary
The present inventions, in one aspect, are directed to micromachined resonator comprising: a first resonant structure extending along a first axis, wherein the first axis is different from a crystal axis of silicon, a second resonant structure extending along a second axis, wherein the second axis is different from the first axis and the crystal axis of silicon and wherein the first resonant structure is coupled to the second resonant structure, and wherein the first and second resonant structures are comprised of silicon (for example, substantially monocrystalline) and include an impurity dopant (for example, phosphorus) having a concentrations which is greater than 1019 cm−3, and preferably between 1019 cm−3 and 1021 cm−3.