Semiconductor Strain Gage Fabrication via Deep Reactive Ion Etching
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Solution Overview
Problem
Conventional semiconductor strain gage manufacturing is labor-intensive and limited to low-volume production, resulting in poor control over device performance and high costs due to manual processes and wide variation in gage temperature-resistance characteristics.
Innovation Solution
The use of semiconductor-on-insulator substrates for high-volume production of strain gages, where the main structural members are sculpted from the device layer using deep reactive ion etching, allowing for precise control over gage resistance and performance characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional manual manufacturing methods are used, then labor flexibility is maintained, but manufacturing precision and productivity are severely limited
Solution Approach 1:
The patent replaces manual mechanical manufacturing processes with automated semiconductor fabrication equipment. Photolithography patterns define gage geometries with sub-micron precision, and reactive ion etching removes material with atomic-layer control, eliminating the precision limits of manual techniques while enabling high-volume wafer-scale production.
Solution Approach 2:
The invention changes the fundamental manufacturing parameters by transitioning from discrete manual operations to continuous automated processes. By controlling etch time, temperature, and chemistry parameters across entire wafers simultaneously, the system achieves uniform gage resistance across hundreds of devices, resolving the contradiction between precision and productivity.
2Manufacturing precision
If conventional wet chemistry and plasma etching methods are used, then process simplicity is maintained, but manufacturing precision and uniformity deteriorate
Solution Approach 1:
The patent applies preliminary action by forming a sacrificial oxide layer before etching the gage bodies. This oxide layer serves as a protective mask during subsequent processing steps and is selectively removed to release the gage structures. The preliminary oxidation step enables precise geometric control while maintaining overall process manageability through systematic sequencing.
3Productivity
If manual gage resistance trimming is performed, then individual gage adjustment is possible, but productivity and cost efficiency deteriorate
Solution Approach 1:
The invention segments the gage resistance control function into two parts: (1) precise geometric definition through photolithography that establishes baseline resistance values, and (2) selective removal of sacrificial material that fine-tunes resistance. This segmentation eliminates the need for manual trimming while achieving both high productivity and precise resistance control through parallel wafer-scale processing.
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 the production of strain gages with tightly controlled performance specifications, reducing production costs and improving sensor performance by achieving higher reproducibility and uniformity in gage resistance.
Implementation Method 1
deep reactive ion etching
Implementation Method 2
A timed acid etch is used to remove the excess silicon material holding the individual gages together
Data Source
AI summary
Strain gages in accordance with the present disclosure are sculpted from a device layer of a semiconductor-on-insulator wafer using deep reactive ion etching, yielding very good control over the electrical properties and physical dimensions of the strain gages. In some embodiments, groups of fully fabricated strain gages are physically connected to handling frames via sprues, which eases handling, enables automated assembly, and facilitates tracing of individual gages from the beginning of fabrication through final packaging. In some embodiments, sprues are configured to mitigate accidental separation of the gages from their frames while simultaneously easing their removal in response to specific forces applied by a handling tool.