外文翻譯---微型半導(dǎo)體流量傳感器的發(fā)展（英文）

1、Measurement 33 (2003) 109–119www.elsevier.com/locate/measurementDevelopment of miniaturized semiconductor flow sensorsa , b b b b * F. Kohl , R. Fasching , F. Keplinger , R. Chabicovsky , A. Jachimowicz , c G. Urbana

2、68; Ludwig Boltzmann Institut fur Biomedizinische Mikrotechnik, Wien, Austria b ¨ Institut fur Industrielle Elektronik und Materialwissenschaften, Vienna University of Technology, Gusshausstrasse 27–29, A-1040 Wien,

3、 Austria c ¨ ¨ ¨ Institut fur Mikrosystemtechnik, Albert-Ludwigs-Universitat Freiburg, George Kohler Allee 103, D-79110 Freiburg, GermanyAccepted 8 October 2002AbstractMiniaturized flow sensors based on th

4、in film germanium thermistors were developed offering high flow sensitivities and short response times. The thermistors are placed on a silicon nitride diaphragm carried by a silicon frame. Using the 3 controlled overtem

5、perature scheme the measurable airflow rate ranges from 0.6 to 150 000 cm /h. In this paper we mainly report on the dynamic properties of the sensor. The response of the sensor to step changes of the heater power will be

6、 compared with its response to shock waves for both the constant power mode and the constant overtemperature operating mode. A simple arrangement for the generation of acoustic shock waves will be presented. ? 2002 Elsev

7、ier Science Ltd. All rights reserved.Keywords: Electrocalorimetric flow measurement; Thin film germanium thermistors; Micromachined flow sensor1. Introduction the engine’s fuel consumption and the pollution of the enviro

8、nment. For the development of such en- There is a growing demand of micro-flow sensors gines a wide velocity measuring range and high for industrial, automotive, domestic and medical resolution monitoring of the time cou

9、rse of the air applications. The measuring principle can be based velocity is desirable. on thermistors, thermopiles, pyroelectric elements, The electrocalorimetric flow sensor presented here pn-junctions, resonating mic

10、robridges, Prandtl tubes is based on a heat transfer principle in which a and several other effects [1–10]. Micromachining is heated body is cooled by a passing flow and the local adopted to achieve high sensitivity, qui

11、ck response rate of cooling depends on the flow velocity [11]. and low power consumption. The sensor is based on the so-called ‘hot film’ flow One important application of flow sensors is the measurement method. A very t

12、hin silicon nitride measuring of the instantaneous air intake of combus- diaphragm supported by a micromachined silicon tion engines. Knowledge of this combustion process frame is mounted flush with the wall of a flow pa

13、rameter is essential if one tries to minimize both channel as shown in Fig. 1. A thin film heating resistor is embedded in the diaphragm to obtain a*Corresponding author. symmetric surface temperature distribution. Two02

14、63-2241/02/$ – see front matter ? 2002 Elsevier Science Ltd. All rights reserved. PII: S0263-2241(02)00058-1F. Kohl et al. / Measurement 33 (2003) 109–119 111Both silicon nitride layers form the diaphragm of the micromac

15、hined sensor. Silicon nitride exhibits a low thermal conductivity resulting in high flow sensitivi- ty. The thermal conductivity of silicon nitride is about 2.3 W/m ? K as compared to 150 W/m ? K for silicon. A further a

16、dvantage of the silicon nitride diaphragm is its small thickness resulting in a small thermal conduction. The 800-nm thick diaphragm used in our sensor has been proved to be very stable in a tangential flow (Fig. 2). Amo

17、rphous germanium exhibits high values of Fig. 3. Schematic top view of the thin film structures on the sensor diaphragm. Two layouts with interdistances between heater both the resistivity and its temperature coefficient

18、. and diaphragm temperature sensors of 35 and 100 mm were The temperature coefficient of resistance (TCR) is realized. approximately 2 2%/K and the resistivity is about 5 V m at room temperature. Measurements of the temp

19、erature dependence of the thermistor resistance power is about 4 mW, which corresponds to a heater between 77 and 330 K revealed, that the electrical voltage of 3 V . Both platinum and nichrome have conductivity of amorp

20、hous germanium is governed been applied as the heater material. by a variable range hopping process [14]. At room Furthermore, narrow pair tolerances of the ther- temperature the TCR varies only slightly with tem- mistor

21、 characteristics are important to achieve high perature, which eases appreciable the burden for resolution in temperature difference measurements. compensating of changes of the ambient temperature. Nonetheless a high pr

22、ecision of the sensor geometry A layout as shown in Fig. 3 and a 250-nm thick is necessary for an offset free bi-directional sensor germanium film result in a resistance of 70 kV at characteristic. 20 8C. It has been pro

23、ved that the long-term stability Both the heater and the thermistors exhibit small of this characteristic is better than 0.5% per year. A dimensions in the nominal flow direction and large noise equivalent temperature di

24、fference of 10 mK for extents perpendicular to this direction. These ex- a bandwidth of 10 Hz is achieved with this thermis- treme aspect ratios of heater and thermistor area tor technology [10]. For comparison, Johnson

25、noise were chosen for four reasons: (a) to achieve a only would limit the resolution to 4.75 mK. pronounced directional characteristic for the flow sensitivity, (b) to avoid delay of response due to thermal propagation t

26、imes, (c) to achieve suitable resistance values of the thermistor and the heater, 3. Experimental and (d) to ensure a uniform local temperature throughout the amorphous germanium area under 3.1. Sensor mounting static an

27、d dynamic heat transport conditions. Furthermore, due to the high aspect ratio a one- To study the sensor properties in situations that are dimensional modeling of heat conduction in the typical for various applications

28、the chip was attached diaphragm and two-dimensional models for heat to different carrier constructions. convection are sufficient for basic considerations. For free field calibration in a wind tunnel and The thin film st

29、ructures were produced on a wafer, other experimental measurements the sensor chip is which has first been covered by a silicon nitride glued to a 0.15-mm thick printed circuit board (PCB) layer. Then a low stress silico

30、n nitride protective film flush fitted with the board surface (Fig. 4). For this is deposited nearly at room temperature using a purpose the flexible PCB was formed using an PECVD process. The low deposition temperature