Stress Sensor With Slanted Surfaces For Out-Of-Plane Shear Detection
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Solution Overview
Problem
Existing stress sensors in semiconductor components, particularly those using piezoresistive effects, face limitations in detecting out-of-plane shear stress components and normal stress components due to sensitivity issues and temperature compensation challenges, especially on (100) wafer surfaces, which restrict their ability to accurately measure all stress components of the stress tensor.
Innovation Solution
A stress sensor with slanted surfaces and resistive paths at oblique inclination angles relative to the main surface, allowing for the measurement of out-of-plane shear stress and normal stress components, and additional planar resistive paths for temperature-compensated measurement of all stress components, including σxx, σyy, σzz, σxz, σyz, and σxy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If piezoresistive stress sensors are used on (100) wafer surfaces, then temperature compensation can be achieved through resistance shift subtraction, but out-of-plane shear stress components cannot be detected
Solution Approach 1:
The patent introduces slanted surfaces at oblique inclination angles relative to the main wafer surface, creating a third-dimensional measurement capability. This allows the sensor to detect out-of-plane shear stress components (σxz, σyz) in addition to in-plane stress components, thereby resolving the limitation of planar sensors while maintaining temperature compensation capabilities through complementary resistor configurations.
2Measurement precision
If rosette sensors are used to detect stress components, then in-plane stress components can be measured, but out-of-plane stress components cannot be detected
Solution Approach 1:
The patent extends the traditional planar rosette sensor concept by incorporating slanted surfaces that protrude from the main wafer surface at defined inclination angles. This three-dimensional configuration enables the sensor to detect out-of-plane shear stress components while maintaining the ability to measure in-plane stress components through appropriately oriented resistive paths on the slanted surfaces.
3Adaptability or versatility
If non-planar current paths are created below shallow trench isolation, then out-of-plane shear stress can be detected, but de-embedding of stress components becomes very challenging
Solution Approach 1:
The patent changes the geometric parameter of the sensor surface from planar to slanted at a defined oblique inclination angle. This geometric modification creates a direct relationship between the measured resistance changes and the stress components, simplifying the extraction process. The known inclination angle serves as a critical parameter that enables straightforward calculation of out-of-plane shear stress components without complex de-embedding procedures.
4Measurement precision
If (111) surface wafer is used for rosette sensors, then more orientation-dependent piezoresistive coefficients are obtained, but the surface cannot be processed in conventional CMOS technology
Solution Approach 1:
The patent maintains the advantages of (100) wafer surfaces for CMOS compatibility by introducing slanted surfaces through mechanical or chemical means after fabrication. This approach preserves the ease of manufacturing on standard (100) wafers while achieving the orientation-dependent piezoresistive coefficients typically associated with (111) surfaces, as the slanted geometry provides the necessary angular sensitivity without requiring non-CMOS-compatible wafer orientations.
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 sensor provides a straightforward and reliable method to monitor and measure all stress components of the stress tensor, overcoming the limitations of existing technologies by accurately determining out-of-plane and in-plane stress components without the need for complex structural modifications or additional processing steps.
Implementation Method 1
A well-known approach to detecting package-induced stress is based on the piezoresistive effect in diffused resistors or transistors
Data Source
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AI summary
The sensor of the invention is configured to be incorporated in a semiconductor component such as an integrated circuit chip, comprising a semiconductor substrate (50). A stress sensor according to the present invention comprises one or more slanted surfaces (102,102') of the substrate material with a known oblique inclination angle relative to the main surface (100) of the substrate, and resistive paths (103) at least on the slanted surfaces. According to a preferred embodiment, two slanted surfaces are provided with complementary inclination angles relative to the main surface, and one or more pairs of resistive paths are produced on the pair of surfaces, the inclination angles of the paths of each pair being equally complementary. The knowledge of the inclination angle allows to measure or monitor out-of-plane shear stress components based on a measurement of the resistance of the slanted resistive paths.