Semiconductor Pressure Sensor Tapered Edge Corrosion
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Solution Overview
Problem
Semiconductor pressure sensor devices face corrosion issues in harsh environments like exhaust systems due to exposure to corrosive substances and moisture, leading to adhesion loss and galvanic corrosion between metal layers, particularly with the TiW and Au films used for corrosion resistance.
Innovation Solution
A semiconductor pressure sensor device with a metal wiring layer, an adhesion securing and diffusion preventing layer, and a conductive layer are stacked with a normal tapered edge shape to prevent recess formation and corrosion, using films like Cr, Pt, and Au, and electrostatic bonding of a glass substrate to enhance durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If TiW film and Au film are stacked on aluminium wiring layer for corrosion resistance, then corrosion resistance is improved, but side etching occurs during wet etching process creating minute gaps that lead to corrosion
Solution Approach 1:
The invention changes the edge shape of the stacked metal layer from a rectangular profile to a tapered shape with a specific angle (30-60 degrees). This curvature modification eliminates the horizontal edge portion where minute gaps would form during wet etching, thereby preventing corrosion while maintaining the corrosion-resistant film structure.
Solution Approach 2:
The invention applies different etching rates to different portions of the stacked metal layer by controlling the etching process to create a tapered profile. The edge portion is selectively shaped to have a specific angle, creating local geometric variation that prevents capillary condensation of corrosive substances while preserving the overall film integrity.
2Reliability
If normal tapered edge shape is formed to prevent minute gap formation, then corrosion is suppressed, but manufacturing process complexity increases
Solution Approach 1:
The invention controls the etching process parameters (etching solution composition, etching time, temperature) to achieve the desired tapered edge shape. By adjusting these parameters, the etching rate is controlled to create the specific angle (30-60 degrees) without requiring additional manufacturing steps, thus maintaining process simplicity while achieving corrosion suppression.
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 solution effectively suppresses corrosion and adhesion loss in harsh environments by preventing the formation of minute gaps where corrosive gases can condense and cause corrosion, maintaining the integrity of the sensor device.
Implementation Method 1
a glass substrate (11) electrostatically bonded to the rear surface (1b) of the semiconductor substrate (1)
Implementation Method 2
a TiW film 57 which is an adhesion securing and diffusion preventing layer... to prevent Au atoms of the Au film 58 from diffusing to the aluminium wiring layer 54
Implementation Method 3
The strain gauge resistors 52, being provided on the diaphragm 52a... is such that the larger the strain amount of the diaphragm 52a, the more greatly the resistance value of the strain gauge resistors 52 changes
Implementation Method 4
an amphiphilic substance 27... forms a hydrophobic film 28 on the aluminium wiring layer 4
Data Source
AI summary
Aspects of a semiconductor pressure sensor device can include a semiconductor substrate having a depressed portion which forms a vacuum reference chamber, a diaphragm disposed on the front surface of the semiconductor substrate, and strain gauge resistors. The device can further include an aluminum wiring layer disposed on the semiconductor substrate, an antireflection film which is a TiN film disposed on the aluminum wiring layer, an adhesion securing and diffusion preventing layer which is a film stack of a Cr film and Pt film disposed on the TiN film, and an Au film stacked on the adhesion securing and diffusion preventing layer.