• Journal of Sensor Science and Technology
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• v.10 no.3
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• pp.148-155
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• 2001

A pressure sensor on the tip of a catheter which is utilized to measure the in-vivo pressure in a human body was fabricated and the characteristic of the pressure sensor as measured. To fit into a catheter with 1 mm caliber, samples of $150\;{\mu}m$(thickness) ${\times}$ (600, 700, 800, 900, 1000) ${\mu}m$(width) ${\times}2\;mm$(length) was fabricated. The thicker face with $450\;{\mu}m$ thickness of SDB wafer was made thin to $134\;{\mu}m$ thickness using KOH etchant and it made possible to fabricate sensor cell with the width shorter than 1 mm. Different to the whitstone bridge sensor, we formed one piezoresistor and one reference resistor in sensor. Therefore there are possibilities of reduction of the sensitivity, then by using the simulation tool ANSYS 5.5.1, the location and the type of the piezoresistor was optimized. Another piezoresistor type of sensor which contain one longitudinal and one transverse piezoresistor was fabricated at the same time, but the sensitivity was not improved very much. To get the output versus the pressure, a constant current source and a implementation amplifier was used. As a result, the maximum sensitivity of the sensor with one piezoresistor was $1.6\;{\mu}V/V/mmHg$.

• Journal of Sensor Science and Technology
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• v.6 no.3
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• pp.172-179
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• 1997

This paper describes a multiplexed-multivariate fiber-optic interferometric sensor system with remote sensing capability. Signal processor of the implemented sensor system is designed as a digital fringe counter that is well adapted to the signal processing of the remote fiber-optic Fabry-Perot interferometric sensor array. By summing up the reported optical data of the optical fiber, a guideline for choosing the optical effect suitable for a specific measurand is presented. As an example, a pressure sensing device that utilizes the strain-optic effect of the optical fiber by attaching it onto a stainless steel diaphragm of which diameter is 4.3 cm, is built and attached to the sensor system. The changes in optical phase difference of the fiber-optic Fabry-Perot interferometric press ure sensor while filling a water tank 2 meters high, was counted by the half-fringe counting signal processor. Test results showed that the measurement error is less than ${\pm}3.6\;cm$ over the measured range of 2 meters.

• Journal of Sensor Science and Technology
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• v.2 no.1
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• pp.19-27
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• 1993

Capacitive pressure sensor for low pressure measurements has been fabricated by using $n^{+}$ epitaxial layer electrochemical etching stop and glass-to-silicon electrostatic bonding technique. The sensor had hybrid configuration of a sensor chip, which consists of sensor capacitor and reference capacitor, and two output signal detection IC chips. A fabricated sensor, with a $1.0{\times}1.0 mm^{2}$ square size and a $10{\mu}m$ thick flat diaphragm, showed a 7.1 pF zero pressure capacitance, and 5.2 % F.S, sensitivity in 10 KPa pressure range. By using a capacitance to voltage converter, the thermal zero shift of 0.051 %F.S./$^{\circ}C$ and the thermal sensitivity shift of 0.12 %F.S./$^{\circ}C$ for temperature range of $5{\sim}45^{\circ}C$ were obtained.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.1
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• pp.19-24
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• 2005

In this paper, the fabrication process of Si pressure sensors utilizing piezoresistive effect was optimized. The efficiency(yield) of the fabrication process for Si piezoresistive pressure sensors was improved by conducting Si anisotrophic etching process after processes of piezoresistors and AI circuit patterns. The position and process parameters for piezoresistors were determined by ANSYS and SUPREM simulators, respectively. The measured thickness of p-type Si piezoresistors from the boron depth-profile measurement was in good agreement with the simulated one from SUPREM simulation. The Si anisotrohic etching process for diaphragm was optimized by adding ammonium persulfate(AP) to tetramethyl ammonium hydroxide (TMAH) solution.

• Journal of Sensor Science and Technology
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• v.7 no.3
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• pp.171-178
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• 1998

Silicon piezoresistive absolute pressure sensor for gas leakage alarm system was developed. This sensor must operate normally in the range of $0{\sim}600\;mmH_{2}O$ pressure, and $0{\sim}100^{\circ}C$ temperature. To make the most of this sensor for gas leakage alarm system, gas must not leak from the sensor itself when the diaphragm of the sensor fractures. Thus, the sealed diaphragm cavity was anodically bonded to pyrex 7740 glass under the condition of $10^{-4}$ torr, at $400^{\circ}C$. The sensitivity of developed sensor was $4.06{\mu}V/VmmH_{2}O$ for $600\;mmH_{2}O$ full-scale pressure range. And temperature compensation method of this sensor is to change bridge-in put-voltage linearly in proportion to the temperature variation by using diode(PXIN4001) or Al thin film resistor. By these methods the temperature effect in the range of $0{\sim}100^{\circ}C$ was compensated over 80 % for offset drift, 95 % for sensitivity.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.11
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• pp.62-68
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• 1990

On the basis of standard Si processing, the miniaturized piezoresistive-type Si pressure sensor with a chip size of $1.7{\times}1.7{mm^2}$ was fabricated and its operating characteristics were investigated. The sensor chip has a full-bridge type of 4 boron-diffused resistors which is formed on an $1.0{\times}1.0{mm^2}$ area, $20{\mu}m$ thick n-type Si diaphragm and finally, encapsulated under room temperature, 1 atm in order to measure a gauge pressure. The operating characteristics of this sensor were determined as a pressure sensitivity of $14.2{\mu}$V/VmmHg, a rated pressure range of 0~760 mmHg, and a maximum nonlinearity of $1.0{\%}$ FS at room temperature.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.790-793
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• 2005

In these days, the piezoresistive material has been applied to various sensors in order to measure the change of physical quantities. But the relationship between the sensitivity of a sensor and the position and size of piezoresistor has rarely been studied. Therefore, this paper was focused on the effect of residual stress induced in piezoresistor on the distribution of resistance change ratio and supposed the feasible position of piezoresistor. The resulting are following; The tensile residual stress in the vicinity of piezoresistor decreased the value of resistance change ratio and could not effect on all the area of diaphragm but local area around the piezoresistor. Also, the piezoresistor in the diaphragm type pressure sensor with boss should fabricate in the edge of boss in order to increase the sensitivity of pressure sensor.

• Journal of the Semiconductor & Display Technology
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• v.2 no.4
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• pp.19-22
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• 2003

In this paper, Si anisotropic etching characteristics of tetramethylammonium hydroxide (TMAH)/ammonium persulfate (AP) solutions were investigated to realize the optimum structure of a diaphragm for the piezoresistive pressure sensor application. Due to its low toxicity and its high compatibility with the CMOS processing, TMAH was used as Si anisotropic etchants. The variations of Si etch rate on the etching temperature, TMAH concentration, and etching time were obtained. With increasing the etching temperature and decreasing TMAH concentrations, the Si etch rate is increased while a significant non-uniformity exists on the etched surface because of formation of hillocks on the <100> surface. With the addition of AP to TMAH solution, the Si etch rate is increased and an improvement in flatness on the etching front is observed. The Si etch rate is also maximized with increasing the number of addition of AP to TMAH solution per one hour. The Si square diaphragms of 20$\mu\textrm{m}$ thickness and 100-400 $\mu\textrm{m}$ one-side length were fabricated successfully by adding AP of (5/6)g to 800 ml TMAH solution every 10 minutes.