Design And Fabrication Of A 2-D Wind Sensor Based On Piezo-resistance

There are many anemometry depends on various methods, from revolving monitoring cup to the ultrasonic anemometer to the new hot wind vane etc. With the development of microelectronics theory and fabrication process, the methods based on different principles are gradually realizing the miniaturization of sensors. Nowadays, with the concept of the Internet of Things (IoT) being proposed, the sensors is increasingry urgent in environmental, economic and durable. The anemograph which is bulky or large consumption is able to meet many limits in applications. The silicon piezoresistive sensor is becoming a main force in the field of pressure and velocity measurement due to its good mechanical and electrical properties.Based on the piezoresistive sensing, a new flow sensor which detect both the flow direction from lm/s to 30m/s and the direction angle of 360° is introduced. It combines Si-sensor with mech-packaging, and has a lot of advantages such as simple process, low-cost, low-power, no heater, no thermal drift, small size, fast response and easy to install and so on. In this study, the theoretical derivation and top-down design method were used to investigate the design and optimize of the structure, the process and fabrication of the chip and the packaging and test of the sensor, which is shown as follows:First of all, the principle of the sensor and measuring method is illustrated:via the deflection of the sensitive cantilever, the fluid pressure can be transformed to the stress of the structure. By measuring the change of the piezoresistance in two orthogonality directions, the flow velocity and direction can be calculated. Each part of the principle is theoretical demonstrated to work out the design parameters. Include:calculating the initial resistance value by the demand of the power consumption, deducing the wind-pressure-stress equation and the stress-resistance change equation according to the fluid mechanics and piezoresistive effect. The length-with ratio of the piezoresistance and the cantilever structure is obtained by SUPREM and ANSYS simulation respectively.Then, the process flow and the masks are designed to process wafers. After die saw, the piezoresistive cantilever beams in different size are tested to verify whether the wind speed-piezoresistance change tendency corresponds with the simulation results. Then get the best structure according to the tests and finish the system packaging. The cantilever beam dimension is 10 X 0.8 X 0.05mm3, initial value of the piezoresistive is about 2200Ω, and the sensor system size is 120mm in diameter and 55mm in height. The test error is less than Im/s in the range of 0-30m/s. The experimental sensitivity △V/v gas is 0.3V/(m·s-1) in minimum between 0-lm/s. And the error of degree is less than 15°.Finally, the measurements and results are discussed in this paper. Aimed at solving the problems of the sensor an improvement measure is proposed.