Conductive Elastomeric Seal Shorting Prevention on Pressure Sensor Die Edges
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Solution Overview
Problem
Conductive elastomeric seals in semiconductor pressure sensors can short circuit due to improper alignment, causing errors or failures, especially when wrapping over the die edge, which is exacerbated by manufacturing tolerances and exposure to higher pressures.
Innovation Solution
Creating a P-type edge on the die with a back-biased PN junction using P-type doping material around the edge of the sensor die to prevent shorting by establishing an isolation region, which breaks the electrical path if the seal contacts the edge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conductive elastomeric seals are used to connect signals from the pressure sensing element to electrical leads, then electrical connection is achieved, but shorting occurs when the seal wraps around the die edge
Solution Approach 1:
A non-conductive barrier layer is introduced as an intermediary between the conductive elastomeric seal and the die edge. This barrier layer prevents direct electrical contact between the seal and the N-type epi region, eliminating the shorting hazard while preserving the electrical connection function of the seal to the metallization pads.
Solution Approach 2:
The harmful conductive property is extracted from the seal at the critical die edge region by placing a non-conductive barrier layer, while the useful conductive connection function is maintained in the intended signal path areas where the seal contacts the metallization pads.
2Ease of manufacture
If the silicon pressure die is made slightly smaller than the package housing to accommodate manufacturing tolerances, then assembly is enabled, but the conductive seal can wrap over the die edge and cause shorting
Solution Approach 1:
The non-conductive barrier layer serves as a mediator that allows the die to be positioned within the housing with standard manufacturing tolerances without creating shorting hazards. The barrier layer compensates for the size difference and prevents seal wraparound contact.
Solution Approach 2:
The non-conductive barrier layer is placed beforehand on the die edge to cushion against the potential harmful effect of seal wraparound, preventing shorting before it can occur during assembly or operation.
3Adaptability or versatility
If higher pressure sensing capability is implemented, then measurement range is extended, but shorting from conductive seals becomes more pronounced
Solution Approach 1:
The non-conductive barrier layer provides consistent electrical isolation regardless of the pressure sensing capability, preventing shorting hazards across the entire extended pressure measurement range.
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
Prevents adverse effects on sensor function by eliminating shorting issues with conductive elastomeric seals, ensuring reliable operation across various pressure ranges by using a P-type edge as an isolation region.
Implementation Method 1
the P-type diffusion creates a back biased PN junction at the edge of the sensor die such that if one of the signal pads shorts to the die edge it will not have an electrical path and not cause any adverse effect on the sensor function
Data Source
AI summary
A pressure sensor includes a sensing element fabricated on an N-type epitaxial layer grown on a P-type substrate, a P-type isolation region located around the edge of the sensing element die and in contact with the P-type substrate, and a conductive elastomeric seal engaging the P-type isolation region prevents shorting of the conductive elastomeric seal with the N-type epitaxial layer of the sensing element die. A method of making a pressure sensor comprises growing an n-type epitaxy layer on a p-type substrate wafer, resulting in a pressure sensor die and substrate having an edge, obtaining a mask adapted for fabricating an isolation diffusion layer around the edge using P-type material, and creating an isolation layer diffusion using P-type doping material around the edge using the mask. A conductive elastomeric seal can then be placed over the sensor die to make electrical contact to the package.