Semiconductor Pressure Sensor Manufacturing via Epitaxial Membrane and Cavity Migration
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Solution Overview
Problem
Current semiconductor pressure sensor manufacturing methods are complex, costly, and not compatible with standard semiconductor industry processes, particularly in creating cavities underneath suspended structures.
Innovation Solution
A method involving a wafer with a bulk semiconductor region, forming a membrane and a closed cavity by digging trenches, epitaxial growth, and heat treatment to migrate semiconductor material, allowing for the transduction of membrane deflection into electrical signals, resulting in a low-cost, reduced-dimension pressure sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional methods (SOI substrates, porous silicon, wet etching) are used to create cavities underneath suspended structures, then pressure sensing functionality is achieved, but the manufacturing process becomes complex and costly
Solution Approach 1:
Instead of creating the cavity first and then forming the membrane above it (conventional approach), this patent inverts the sequence by forming the membrane first on the bulk semiconductor substrate, then creating the cavity underneath. This is achieved by depositing a sacrificial layer, forming the membrane, and finally removing the sacrificial layer to create the cavity. This inversion simplifies the overall manufacturing process and improves compatibility with standard semiconductor fabrication techniques.
Solution Approach 2:
The patent applies preliminary action by forming the membrane structure before creating the cavity underneath it. The membrane is deposited and patterned on the bulk substrate first, establishing the sensing element in advance. Then the cavity is formed by removing sacrificial material that was placed beneath the membrane. This preliminary formation of the membrane simplifies subsequent processing steps and reduces manufacturing complexity.
2Reliability
If conventional cavity formation methods are used, then pressure sensing is enabled, but manufacturing costs increase
Solution Approach 1:
The inverted manufacturing sequence—forming the membrane first, then creating the cavity underneath—reduces manufacturing costs by using simpler, more compatible semiconductor fabrication techniques. The approach avoids complex specialized processes required by conventional methods, utilizing standard deposition, etching, and sacrificial layer removal techniques that are already prevalent in the semiconductor industry.
Solution Approach 2:
The patent uses a sacrificial layer as an intermediary material that is temporarily deposited beneath the membrane, then removed to create the cavity. This intermediary approach simplifies cavity formation compared to direct etching methods, as the sacrificial layer provides a defined structure that can be easily removed through standard dissolution or etching processes, reducing overall manufacturing complexity and cost.
3Reliability
If standard semiconductor fabrication processes are not used, then cavity formation is achieved, but compatibility with industry standards is lost
Solution Approach 1:
By inverting the conventional sequence to form the membrane before the cavity, the patent enables the use of standard semiconductor fabrication processes throughout. The membrane formation uses standard deposition and patterning techniques, and the subsequent cavity creation uses standard sacrificial layer removal methods. This inverted approach maintains full compatibility with industry-standard processes, unlike conventional methods that require specialized non-standard steps.
Solution Approach 2:
The patent employs universal semiconductor fabrication techniques that can be applied throughout the entire manufacturing process—from membrane deposition to cavity formation. The sacrificial layer approach and subsequent removal process are multi-functional, serving both as a structural template during fabrication and as a means to create the final cavity. This universality of approach enhances adaptability to standard industry processes.
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 method enables the production of low-cost, compact semiconductor pressure sensors with efficient signal transduction, suitable for various applications, including the automotive field, where power consumption and size are critical.
Implementation Method 1
epitaxially growing, starting from said first walls, a closing layer of semiconductor material
Implementation Method 2
carrying out a heat treatment, thereby causing migration of the semiconductor material of said first walls and forming a closed cavity
Data Source
AI summary
Method for manufacturing a semiconductor pressure sensor, wherein, in a silicon substrate, trenches are dug and delimit walls; a closing layer is epitaxially grown, that closes the trenches at the top and forms a suspended membrane; a heat treatment is performed so as to cause migration of the silicon of the walls and to form a closed cavity underneath the suspended membrane; and structures are formed for transducing the deflection of the suspended membrane into electrical signals.