Sensor Device Leakage Current Suppression via Barrier Layers
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Solution Overview
Problem
Miniaturization of sensor chips leads to narrowed gaps between piezoresistors and wiring, increasing the likelihood of parasitic MOS structures and resulting leakage currents, which degrade the output characteristics of force sensors.
Innovation Solution
A sensor device with a piezoresistive element and diffusion wirings of opposite polarity, and barrier layers of the same polarity as the semiconductor substrate, are used to suppress leakage currents by forming a first barrier layer between adjacent diffusion wirings and a second barrier layer on the surface of piezoresistive elements and diffusion wirings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If sensor chips are miniaturized, then the sensor size is reduced, but gaps between piezoresistors and wiring are narrowed causing leakage currents
Solution Approach 1:
An insulating film is introduced as an intermediary layer between adjacent piezoresistors and between piezoresistors and wiring. This mediator prevents direct electrical contact that would cause leakage currents, while allowing the sensor chip to maintain miniaturized dimensions. The insulating film acts as a physical barrier that eliminates the harmful electrical interaction without requiring larger spacing between components.
2Productivity
If gaps between piezoresistors and wiring are narrowed, then device integration is improved, but parasitic MOS structures occur causing leakage currents
Solution Approach 1:
The insulating film transforms the potential harm of narrow gaps (which create parasitic MOS structures) into a beneficial configuration. By covering the gaps with the insulating film, the design accepts tight spacing for high integration but converts the harmful electrical interaction into a controlled structure where the insulating film prevents parasitic MOS formation while maintaining the integrated layout.
3Ease of manufacture
If leakage current occurs, then manufacturing complexity is reduced, but output characteristics are degraded
Solution Approach 1:
The insulating film is formed preliminarily during the manufacturing process, before final assembly and operation. This preliminary action of creating the insulating barrier prevents leakage currents from occurring in the first place, rather than attempting to correct output characteristic degradation after the sensor is manufactured. The prevention is built into the structure during fabrication.
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 effectively suppresses leakage currents, improving the offset and noise characteristics of the sensor output, thereby enhancing detection accuracy, especially in 6-axis detection systems where leakage current impact is significant.
Implementation Method 1
a force sensor has been known which detects force in multi-axis directions by attaching a sensor element to an initiating strain element made of metal and detecting an elastic deformation of the initiating strain element caused by applying external force
Implementation Method 2
a first barrier layer formed between the adjacent diffusion wirings in the semiconductor substrate and has a same polarity as the polarity of the semiconductor substrate
Data Source
AI summary
A sensor device includes a piezoresistive element that is formed in a semiconductor substrate and has a polarity opposite to a polarity of the semiconductor substrate, diffusion wirings that are formed in the semiconductor substrate and have a polarity opposite to the polarity of the semiconductor substrate, a first barrier layer formed between the adjacent diffusion wirings in the semiconductor substrate and has a same polarity as the polarity of the semiconductor substrate, and a second barrier layer that is formed on surface layers of the piezoresistive element and the diffusion wirings and have a same polarity as the polarity of the first barrier layer.