Vibration Element Etching with Variable Protective Film Thickness
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Solution Overview
Problem
Existing methods for manufacturing vibration elements, such as tuning-fork type vibrators, face challenges in simultaneously forming the outer shape and groove without positional deviations and with limited design freedom due to separate wet and dry etching steps or restrictive micro-loading effects.
Innovation Solution
A method involving a crystal substrate with a protective film of varying thicknesses is used for dry etching, allowing simultaneous formation of the outer shape and groove without relying on micro-loading effects, thereby enhancing design freedom and reducing manufacturing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If separate wet etching and dry etching steps are used to form the outer shape and groove, then the manufacturing process can be performed, but the manufacturing step becomes complicated and positional deviation of the groove with respect to the outer shape is likely to occur
Solution Approach 1:
The patent combines the formation of the outer shape and groove into a single dry etching step by using a protective film with varying thickness. The protective film is formed with different thicknesses in different regions (thinner in groove regions, thicker in vibration arm regions), allowing the etching process to simultaneously create both the outer shape and the groove structure without requiring separate wet and dry etching steps. This merging of operations eliminates positional deviation between the groove and outer shape while simplifying the manufacturing process.
Solution Approach 2:
The protective film is designed with non-uniform thickness distribution across the substrate surface. Specifically, the film thickness is set to be thinner in the groove forming regions and thicker in the vibration arm forming regions. This local variation in film quality enables selective etching depths in different areas during a single dry etching process, achieving both the outer shape and groove formation with precise positional alignment.
2Device complexity
If the outer shape and groove are collectively formed by using the micro-loading effect in dry etching, then the manufacturing step is simplified, but setting of dimensions such as the width of the vibration arm and the width and depth of the groove is restricted, and the degree of freedom in design is low
Solution Approach 1:
The protective film thickness is independently controlled in different regions to achieve desired dimensional parameters. By adjusting the film thickness in groove regions versus vibration arm regions, the design can specify different widths and depths for grooves and vibration arms without being constrained by micro-loading effects. This local quality control provides full design freedom while maintaining process simplicity.
Solution Approach 2:
The invention changes the parameter of protective film thickness to control etching depth and resulting dimensions. By varying the film thickness parameter across different regions of the substrate, the design can independently specify groove width, groove depth, vibration arm width, and other dimensional parameters. This parameter control mechanism eliminates the dimensional restrictions inherent in micro-loading effect-based methods.
3Ease of manufacture
If a uniform thickness protective film is used in dry etching, then the process is simple, but the etching depth cannot be differentiated between groove regions and vibration arm regions
Solution Approach 1:
The protective film is manufactured with non-uniform thickness distribution, being thinner in groove regions and thicker in vibration arm regions. This local quality variation enables the simple single-step dry etching process to achieve differentiated etching depths: areas with thinner film etch deeper to form grooves, while areas with thicker film etch less to form the vibration arm outer shape. This resolves the contradiction by incorporating thickness variation into the film formation step rather than requiring complex process 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
This approach improves the accuracy and flexibility in designing vibration elements by controlling etching depths and preventing unnecessary vibrations, while simplifying the manufacturing process and reducing costs.
Implementation Method 1
a dry etching step of dry-etching the crystal substrate from a side on the first substrate surface via the protective film to form the first surface, the groove, and outer shapes of the first vibration arm and the second vibration arm
Data Source
AI summary
A method of manufacturing a vibration element includes: a protective film forming step of forming a protective film on a first substrate surface of a crystal substrate; and a dry etching step of dry-etching the crystal substrate via the protective film. The protective film satisfies a relationship of T1<T2<T3, in which T1 is a thickness of the protective film in an inter-arm region positioned between a first vibration arm forming region in which a first vibration arm is formed and a second vibration arm forming region in which a second vibration arm is formed, T2 is a thickness of the protective film in a groove forming region in which a groove is formed, and T3 is a thickness of the protective film in a region of the first vibration arm forming region and the second vibration arm forming region excluding the groove forming region.