Structured Polysilicon Cover Layer for Pressure Sensor Shielding
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Solution Overview
Problem
Pressure sensors face challenges in simultaneously optimizing pressure and temperature measurement, with existing solutions either leading to material fatigue, difficulty in diaphragm rupture detection, and interference from temperature fluctuations and external electrical fields, while also struggling to maintain signal stability and accuracy.
Innovation Solution
A pressure sensor design featuring a structured, electrically conductive cover layer with two isolated areas, one for shielding and error detection and the other as a thermistor, allowing for separate optimization of doping levels and reducing mechanical stress on the thermistor, enabling better signal quality and error detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a metallic shield is used to protect against external electrical interference, then shielding effectiveness is improved, but non-reproducible deviations in the measurement signal occur, particularly at high temperatures
Solution Approach 1:
The patent changes the material parameter of the shield from metallic to doped polysilicon, which has different electrical and thermal properties. This material substitution allows the shield to maintain electrical interference protection while exhibiting more stable behavior at high temperatures, eliminating the non-reproducible signal deviations caused by metallic shields
Solution Approach 2:
The patent uses doped polysilicon as a composite material that combines the shielding functionality with improved thermal stability. The doped polysilicon layer integrates both the shielding function and temperature compensation capability in a single material system, resolving the conflict between shielding effectiveness and measurement stability
2Measurement precision
If low doping is used in the cover layer to achieve high resistance for temperature determination, then temperature measurement capability is improved, but the temperature dependency increases generating a signal with insufficient swing
Solution Approach 1:
The patent segments the cover layer into two electrically isolated areas with different doping levels. Area 1 has lower doping for temperature determination with high resistance, while area 2 has higher doping to provide sufficient temperature signal swing. This segmentation allows each area to be optimized for its specific function without compromise
Solution Approach 2:
Different regions of the cover layer are assigned different doping concentrations according to their specific functional requirements. The local doping level is optimized for either temperature measurement or signal generation, resolving the contradiction between high resistance needs and sufficient signal swing requirements
3Reliability
If high doping is used in the sensor elements to achieve lower temperature dependency, then pressure measurement stability is improved, but the cover layer cannot be used for temperature measurement with sufficient signal swing
Solution Approach 1:
The patent divides the cover layer into two separately doped areas, allowing the sensor elements (in the bending plate) to use high doping for stable pressure measurement while the cover layer areas use different doping levels for their respective functions. The segmentation decouples the doping requirements of pressure sensing from temperature measurement
Solution Approach 2:
The doping concentration is locally optimized in different areas: high doping in sensor elements for pressure stability, and varied doping in cover layer areas for temperature measurement and signal generation. This local quality differentiation resolves the contradiction between pressure measurement reliability and temperature measurement capability
4Device complexity
If the cover layer is used for both shielding and temperature determination, then device complexity is reduced, but the doping level cannot be optimized for both functions simultaneously
Solution Approach 1:
The cover layer is segmented into two electrically isolated areas that can be separately doped and optimized for their specific functions. This segmentation maintains the structural simplicity of a single cover layer while enabling independent optimization of doping levels for shielding and temperature determination
Solution Approach 2:
The cover layer is designed as a multi-functional element that simultaneously provides shielding, temperature determination, and error detection capabilities. By segmenting the layer into areas with different functions and doping levels, the patent achieves multiple functions in a single structural component without compromising optimization of each function
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 design enhances the sensor's ability to accurately measure pressure and temperature, reduces mechanical stress on the thermistor, and allows for effective error detection, improving signal quality and stability by enabling separate optimization of the screen and thermistor areas.
Implementation Method 1
The sensor elements are generally designed as piezoresistive elements, in particular as resistors. It is known to produce these elements in silicon with the aid of doping methods such as diffusion or implantation.
Implementation Method 2
a thick layer (4) which is electrically insulating, in particular an oxide or oxide-nitride layer
Implementation Method 3
A material commonly used for electrical shielding is doped polysilicon. These material properties include the coefficient of thermal expansion, hardness, and the moduli of elasticity and shear.
Implementation Method 4
Boron or phosphorus, for example, are used as dopants in the production of polysilicon. The doping takes place, for example, by diffusion, by implantation or by adding a gas during the deposition of the cover layer serving as a shield.
Implementation Method 5
the temperature is determined according to the prior art by measuring the change in resistance, for example that of the measurement elements connected in a Wheatstone bridge
Data Source
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AI summary
The invention relates to a pressure sensor (1) comprising a substrate (2) having a formed measuring membrane (3) and an electrically conductive cover layer (4) which comprises electrical contact elements (5, 6, 7, 8) and which is electrically insulated in relation to the substrate (2) by means of an insulating layer (9). The cover layer (4) is structured such that in two regions (10, 11), that are electrically insulated from one another, two independent measurements of the respective resistance between two contact elements (5, 6, 7, 8) are possible. The regions (10, 11) of the cover layer (4) serve for shielding the sensor elements (12, 13) of the measuring membrane (3) from electromagnetic influences from the outside, for detecting damage to the measuring membrane (3) as well as for the exact temperature determination.