Research on the Response Characteristic of Capacitive Pressure Sensor

Although semiconductor capacitive pressure sensor is more sensible and less affected by temperature than resistance pressure sensor and thus more often used in pressure measurement in harsh situations, it has the disadvantage due to the nonlinearity of output characteristic. Therefore, in order to improve this nonlinearity, previous studies proposed various complex forms of electrode structures including double electrode, step electrode, complex electrode. However, these generate several difficult problems in device manufacturing process. Also, many assumptions were needed in mathematical analysis of operation characteristic of device due to the complexity in structure and an exact prediction about the operation characteristic was difficult because the error of analytic model is large.

For the enhancement of overload protection capacity and linearity as well as the sensitivity of device, the structure of capacitive pressure sensor operating in the contact mode is proposed and the structure of electrode is designed in the form of curved surfaces, with which micro-machining is possible, on the basis of MEMS technology, which is developing rapidly throughout the world. In this case, the simple structure leads to simple manufacturing process and lower cost.

The virtual radius model, the analytic model used to analyze contact deformation characteristic in previous studies, correspond to the case in which the electrode is plane and the curved surface electrode and contact deformation characteristic of diaphragm cannot be interpreted with this model.

New mathematical model, which is able to interpret the curved surface electrode and the contact deformation characteristic of diaphragm, was proposed on the basis of previous virtual radius model.

Also, the contact deformation characteristic of diaphragm depending on pressure in concave well substrate touch-mode capacitive pressure sensor is interpreted with the new analytic model and on the basis of it, the response characteristic of sensor was interpreted. The correctness of proposed analytic model and the result of interpretation are tested through simulation using finite element interpreter.

The proposed analytic model is new and esteemed to be useful to design various types of capacitive pressure sensor and to predict and estimate the characteristics of them in the future.

This paper is published by Kang Myong Chol, section leader from Semiconductor Institute on the title of “Capacitance response of concave well substrate touch-mode capacitive pressure sensor: mathematical analysis and simulation” in the SCI magazine, “Microelectronics Journal”.