Monolithic Differential Pressure Sensor with Front-Side Access
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Solution Overview
Problem
Conventional differential pressure sensors have large dimensions and complex, costly manufacturing processes due to the need for backside etching and bonding, which are restrictive in applications requiring economy and simplicity.
Innovation Solution
An integrated differential pressure sensor with a monolithic semiconductor body featuring a buried cavity and flexible membrane, where the access trench is formed through the front side, eliminating the need for backside etching and using a package with fluid-tight insulation to protect the membrane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If backside etching and bonding are used to create the cavity, then the sensor can be manufactured with traditional methods, but the sensor dimensions become large and manufacturing complexity increases
Solution Approach 1:
Instead of etching the cavity from the backside of the substrate, the patent inverts the approach by etching the access trench from the front side of the substrate to reach the buried cavity. This eliminates the need for backside etching and bonding operations, simplifying the manufacturing process while enabling compact sensor dimensions.
Solution Approach 2:
The cavity is formed as a buried structure within the substrate before the access trench is created. This preliminary formation of the cavity allows subsequent front-side processing to complete the sensor fabrication, avoiding complex backside operations and reducing overall sensor size.
2Manufacturing precision
If backside etching and bonding are used, then the cavity can be formed, but the manufacturing process becomes complex and costly
Solution Approach 1:
The patent inverts the conventional approach by forming the access trench from the front side rather than etching from the backside. This inversion eliminates multiple complex steps including backside bonding, alignment, and etching, while maintaining precise cavity formation through front-side process control.
Solution Approach 2:
The patent combines the cavity formation and access trench creation into an integrated front-side process sequence. This merging of operations that were traditionally separate (backside etching and front-side access creation) reduces manufacturing complexity while preserving the required precision for differential pressure sensing.
3Measurement precision
If the membrane is exposed, then pressure differential can be measured, but the membrane lacks mechanical protection
Solution Approach 1:
The patent implements a nested structure where the flexible membrane is positioned within a protected cavity formed in the substrate. The cavity acts as a protective enclosure that shields the membrane from mechanical damage while allowing pressure differential measurement through the access trench, maintaining both measurement precision and mechanical protection.
Solution Approach 2:
The buried cavity serves as an intermediary structure between the exposed membrane and the external environment. It provides mechanical protection to the sensitive membrane while still allowing the pressure differential to be transmitted for accurate measurement, acting as a protective mediator.
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 reduces sensor dimensions, simplifies and cost-reduces the manufacturing process, protects the sensitive membrane, and enhances response times by eliminating the need for complex bonding and backside etching, making it suitable for various applications.
Implementation Method 1
the flexible membrane 4 is deformed as a function of the difference between the first pressure and the second pressure
Implementation Method 2
Piezoresistive elements 5, connected in a Wheatstone-bridge configuration, are diffused in a surface portion of the flexible membrane 4
Data Source
AI summary
An integrated differential pressure sensor includes, in a monolithic body of semiconductor material, a first face and a second face, a cavity extending at a distance from the first face and delimited therewith by a flexible membrane formed in part by epitaxial material from the monolithic body and in part by annealed epitaxial material from the monolithic body, an access passage in fluid communication with the cavity, and in the flexible membrane at least one transduction element configured so as to convert a deformation of the flexible membrane into electrical signals. The cavity is formed in a position set at a distance from the second face and is delimited at the second face with a portion of the monolithic body.