P-Type Sensor Substrate Stress Reduction
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Solution Overview
Problem
Existing physical quantity sensors, such as acceleration sensors, face challenges with stress concentration at the interface between semiconductor layers and insulation films, leading to reduced device characteristics and mechanical reliability, particularly when using N conductive type substrates without diffusion layers.
Innovation Solution
The use of P conductive type impurity-doped substrates and insulation films, along with P conductive type silicon electrodes, reduces stress concentration and improves mechanical reliability by allowing for wider resistivity ranges without diffusion layers, enabling accurate detection of physical quantities through capacitance changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If N conductive type substrate without diffusion layer is used, then manufacturing process is simplified, but stress concentration occurs at the interface between semiconductor layer and insulation film
Solution Approach 1:
The patent changes the conductive type parameter of the substrate from N-type to P-type, which fundamentally alters the stress characteristics at the interface between the semiconductor layer and insulation film. This parameter change eliminates stress concentration while maintaining the simplified manufacturing process that avoids diffusion layers.
2Device complexity
If N conductive type substrate is used, then device structure is simplified, but resistivity range becomes narrow
Solution Approach 1:
The patent changes the conductive type parameter from N-type to P-type, which expands the achievable resistivity range. P-type substrates allow for a broader spectrum of resistivity values without requiring additional diffusion layers, thus maintaining structural simplicity while improving manufacturing precision.
3Measurement precision
If electrode is formed in semiconductor layer via insulation film with doped N conductive type impurity, then capacitance detection is enabled, but stress concentration occurs at the interface
Solution Approach 1:
The patent changes the impurity type parameter from N-type to P-type in both the insulation film and semiconductor layer. This parameter change maintains the capacitance detection functionality while eliminating the stress concentration that occurs at the interface when N-type impurities are used.
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 approach enhances the accuracy and reliability of physical quantity sensors by reducing stress concentration and improving temperature distortion ratios, while simplifying the manufacturing process and eliminating the need for diffusion layers.
Implementation Method 1
the present inventors study that stress may be concentrated at an interface between a semiconductor layer and an insulation film when the electrode for detecting a capacitance is formed in the semiconductor layer via the insulation film having a doped N conductive type impurity
Implementation Method 2
The acceleration sensor for detecting acceleration of an mobile object such as a vehicle is disclosed in JP-A-H06-88837 corresponding to U.S. Pat. No. 5,561,248. The sensor includes a pair of electrodes, which are spaced apart from each other, so that the sensor detects the acceleration according to capacitance change between the electrodes.
Implementation Method 3
The first electrode is made of P conductive type silicon. The first electrode and the second electrode are separated from each other, and the physical quantity is detected based on a capacitance between the first electrode and the second electrode.
Data Source
AI summary
A physical quantity sensor includes: a sensor substrate including a first support substrate, a first insulation film and a first semiconductor layer, which are stacked in this order; a cap substrate including a second support substrate disposed on the first semiconductor layer, and has a P conductive type; and multiple electrodes, which are separated from each other. The first support substrate, the first insulation film and the first semiconductor layer have the P conductive type. The physical quantity is detected based on a capacitance between the plurality of electrodes, and the electrodes are disposed in the first semiconductor layer.