MEMS Resonator Beam Cross-Section for Uniform Etching
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Solution Overview
Problem
Conventional MEMS resonators face challenges in achieving accurate electrode shaping due to irregularities and uneven etching rates caused by temperature distribution during the resist etch back process, leading to potential short circuits between input and output electrodes.
Innovation Solution
The resonator design features a beam and support portion with equal sectional areas perpendicular to the longitudinal direction, maintaining uniform etching rates and preventing temperature gradients, thus ensuring accurate electrode patterning and preventing short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a resist is formed to a desired height to expose only the apex of the triangular beam, then the electrode height can be controlled, but the resist accumulates at the skirt portion of the beam causing poor controllability of the opening portion
Solution Approach 1:
The patent applies an etch back process to the resist after it has been formed to the desired height. This preliminary removal of excess resist material eliminates the accumulation at the skirt portion of the beam, allowing for precise control of the opening portion width while maintaining the required electrode height coverage.
2Manufacturing precision
If an etch back is applied to the resist to planarize the projecting portion, then the opening portion can be formed, but temperature distribution causes uneven etching rates and curved opening portions
Solution Approach 1:
The patent modifies the beam cross-sectional shape from a triangular prism to a shape with a flat top surface. This local geometric modification eliminates the temperature distribution problem during resist etch back, as the flat top provides uniform heat dissipation. Consequently, the etching rate becomes uniform across the beam width, producing straight, parallel electrode edges with high patterning accuracy.
3Ease of manufacture
If the beam has a triangular cross section, then the anisotropic etching process can form the beam and support portion, but irregularities are large making photolithography difficult
Solution Approach 1:
The patent transitions from a symmetric triangular prism cross-section to an asymmetric cross-section with a flat top surface. This asymmetric modification maintains the advantages of anisotropic etching for beam formation while eliminating the large surface irregularities at the apex, thereby enabling successful photolithography and precise electrode patterning.
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 improves the accuracy of electrode shaping, enhances the reliability of the resonator by preventing short circuits and maintaining uniform etching rates, thereby increasing the resonator's reliability.
Implementation Method 1
a beam and a support portion which are made of a single-crystal silicon are formed by patterning the single-crystal silicon layer through anisotropic etching
Implementation Method 2
applying an etch back to the resist 807 formed so as to cause only an apex of a triangle to be exposed
Data Source
AI summary
A resonator using the MEMS technology is provided which improves the accuracy of a shape of electrodes so as avoid a short circuit that would otherwise be caused between input and output electrodes to thereby increase the reliability thereof. A resonator includes a substrate 101, an insulation layer 102 formed selectively on the substrate 101 as a sacrificial surface, a beam 103 formed on the substrate 101 via a space, a first support portion 104A formed on the insulation layer 102 of the same material as that of the beam 103, and electrodes formed with a space defined between the beam 103 and themselves for signals to be inputted thereinto and outputted therefrom. A sectional area of the beam 103 and a sectional area of the first support portion 104A are substantially equal in a section which is perpendicular to a longitudinal direction of the beam 103.