We have developed a one-wire-type thermal flow sensor that has a polysilicon microheater. It has a very wide flow-measurement range of 0.005–35 m s−1 and very short response time of 0.14 ms (90%). The size of the flow-sensor chip is 1 mm × 1 mm × 0.3 mm. The sensitivity is above 22 mV (m s−1) −1 2 when it is operated in constant-resistance mode. The electric power consumed to keep the temperature rise of the microheater at 80 K in windless air at 22 °C under atmospheric pressure is about 6 mW. To minimize the power consumption the shape of the microheater should be a straight line and its length should be a specific value. As polysilicon has large resistivity, large output signals can be obtained without amplifiers. It can be applied to household gas flow meters and other systems.

A polysilicon flow sensor for gas flow meters

It is an object to obtain a calorimeter characterized by excellent mechanical strength, and a manufacturing method thereof, when a plurality of calorimeters are arranged inside a single substrate The calorimeter has an absorbent for converting energy of radioactive rays into heat and a resistor for converting heat into an electrical signal using superconductive transition are arranged on a membrane for determining thermal conductivity with the membrane being attached to a substrate, the substrate having a tri-layer structure comprising an etching layer, an etching stop layer and a support substrate, the membrane being arranged separated by the thickness of the etching stop layer and the etching layer

Calorimeter and manufacturing method thereof

We have developed a one-wire type thermal flow sensor that has a polysilicon microheater. It has very wide flow measurement range of 0.005-35m/s and very short response time of 0.14ms (90%). The size of the flow sensor chip is 1mm x 1mm x O.3mm. The sensitivity is above 22mV/(m/s)/sup 1/2/ when it is operated by constant resistance mode. Consuming electric power to keep the temperature rise of the microheater 80K in windless air at 22/spl deg/C under atmospheric pressure is about 6mW. As the polysilicon has large resistivity, large output signals can be gotten without amplifiers. It can be applied to household gas flowmeters and other systems.

A Polysilicon Flow Sensor For Gas Flowmeters

We have newly developed a single crystal silicon micromachined pulsed infrared light source, with a microbridge. The chip size is 2/spl times/1/spl times/0.35 mm/sup 3/. The microbridge size is 365/spl times/85/spl times/1.5 /spl mu/m/sup 3/. We can easily control the temperature of silicon microbridge by pulsed electric signal up to the frequency range of 2 kHz. The modulated temperature is more than 700/spl deg/C at 100 Hz and 100/spl deg/C at 2 kHz. The thermal time constant is 0.4 msec. We measured transient temperature distribution of microbridge. We estimate performance of infrared light source from these results.

Single crystal silicon micromachined pulsed infrared light source

In order to manufacture a high performance infrared emitting device which has high speed thermal response characteristics and a high infrared emissivity, a bridge part (heating part) having an isolation space is formed in a silicon substrate. After boron ions are implanted as impurities such that the peak value of the impurity concentration distribution is not less than 5 x 1019/cm3, the substrate is annealed under predetermined conditions to activate the impurity layer which is a bridge part to adjust its thickness not larger than 5 νm. Even if the thickness of the bridge part is reduced in order to improve the thermal response characteristics, since the impurity concentration is high, the infrared emissivity is not lowered and, further, a large temperature modulation width can be obtained. The dosage of the boron ions is preferably not less than 3.0 x 1014/cm2. In order to activate the impurity layer after the boron ion doping, if the substrate is annealed, for instance, at a temperature of 1100 °C - 1200 °C in a nitrogen gas atmosphere for 5 - 40 minutes and, further, in a wet oxygen atmosphere for 25 - 40 minutes, the concentration of the boron ions and the activation of the impurity layer can be improved stably.

Process for producing infrared emitting device and infrared emitting device produced by the process

Microheater made of heavily Boron doped single crystal Si beam covered with SiO 2 film, 1000×300×3 μm, is fabricated on the n type Si substrate by the anisotropic etching technique. As this microheater has an air bridge structure of low resistivity semiconductor material with positive but small temperature coefficient of resistance, a broad heating area up to 800 °C is easily obtained and it has quick response with the thermal time constant t of about 4 ms and has small power consumption. Since this heating area is made of p type layer in the n type substrate,this area can be electrically isolated from the substrate because of the formation of p-n junction.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S1946427400320334

Mitsuteru Kimura

Papers

Microheater Made of Heavily Boron Doped Single Crystal Silicon Beam