Showing papers on "Microheater published in 1996"

A polysilicon flow sensor for gas flow meters

Abstract: 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.

Low-power micro gas sensor

Abstract: The stable and low-power heating characteristics of a microheater are very important for the micro gas sensor. Membrane-type gas sensors have been fabricated by silicon IC technology. Steady-state thermal analysis by the finite-element method is performed to optimize the thermal properties of the gas sensor. From the analysis, the desirable size of the microheater for low power consumption is determined. The heating properties of fabricated poly-Si and Pt microheaters have been tested. The sensing characteristics of the packaged microsensor are also examined.

Micro heating apparatus for synthetic fibers and related methods

Abstract: This invention provides an improved method and apparatus for non-contact quantum mechanical heating of thermoplastic fibers by resonant energy absorption of laser energy by the fiber. In one embodied form, the unique method for continuous heating of thermoplastic fibers comprises the steps of: a) preparing a thermoplastic synthetic fiber for heat treatment; b) illuminating the fiber with a beam of radiation from a carbon monoxide continuous wave laser beam of resonant frequency for the prescribed fiber being treated; c) traversing the fiber to be treated across the path of the laser beam in a direction perpendicular to the beam of radiation from the laser source; d) adjusting the rate of traversement of the fiber to maintain the temperature of the thermoplastic fiber within a temperature range of about five percent below the melting point of the thermoplastic fiber to continuously heat the fiber by resonant energy absorption of the laser beam. In a presently preferred embodiment, the unique microheater apparatus is provided comprising a laser heater furnished with a collimator and back reflector, to enhance the heating efficiency of the non-contact quantum mechanical process. The unique microheater apparatus accordingly provides a source of non-contact heat before, after or during a false twisting process or fiber stretching process.

Characteristics analysis of wavelength-division-multiplexing fiber couplers fabricated with a microheater

Abstract: Optical properties and taper profiles of 1.31/1.55-μm wavelength-division-multiplexing (WDM) fiber couplers have been experimentally analyzed. A newly developed microheater was used for the fabrication in air. The elongation lengths were controlled so that the fourth coupling peak would reach the 1.55-μm wavelength. The wavelength difference Δλ between the peak coupling wavelength of 1.55 μm and that around 1.31 μm decreased linearly at each fusion temperature with the fusion time. At each fusion temperature, the Δλ value decreased linearly with the elongation length and decreased exponentially with the neck width. The Δλ value and the taper shape at the minimum limit of the degree of fusion were estimated. The fabrication condition and the taper shape for 1.31-μm and 1.55-μm WDM coupling were also analyzed.

Microheater, its manufacture, and gas sensor

Abstract: PURPOSE: To provide a microheater with excellent insulating property and good heating efficiency, a method for manufacturing it, and a gas sensor using this microheater. CONSTITUTION: In a microheater provided with a base, a thin plate part formed on the base, and a heating electrode, the base 2 has a cavity part 3, and the heating electrode 5 is formed in the cavity part 3 inner part which is the reverse side of the thin plate part 4. The heating electrode 5 is formed by ion implantation to the base 2 and etching. Further, the microheater 1 is preferably provided with a gas sensing material on the surface of the thin plate part 4.

Thermodynamic analysis of WDM fiber couplers fabricated by using a microheater

Abstract: The activation energy for the silica glass fusion reaction which occurs during the fabrication of a fiber coupler was determined by using a microheater. The coupling peak wavelength around 1.31 μm was determined by fusion temperature and time. The effective fusion time is determined from the dependence of the coupling properties on the set fusion time at each temperature. Moreover, the effective fusion time for 1.31 1.55 μ m wavelength-division-multiplexing (WDM) coupling was determined for each fusion temperature. This relation indicates that the glass deformation during fusion is expressed by a simple Arrhenius formula. The apparent activation energy estimated from this relation is 135 kcal/mol and this agrees with the value for the melt viscosity of silica glass. The increase in the hydroxyl content of the fabricated couplers is identified by a slight increase in the excess loss of less than 0.1 dB at 1.38 μm, and can be largely attributed to the elongation process.

Phase-sensitive techniques applied to a micromachined vacuum sensor

Abstract: Phase sensitive AC measurement techniques are particularly applicable to micromachined sensors detecting temperature changes at a sensor caused by a microheater. The small mass produces rapid thermal response to AC signals which are easily detectable with lock-in amplifiers. Phase sensitive measurements were applied to a CMOS compatible micromachined pressure sensor consisting a polysilicon sense line, 760 microns long, on an oxide microbridge separated by 6 microns on each horizontal side from similar polysilicon heaters, all over a micromachined cavity. Sinusoidal heater signals at 32 Hz induced temperature caused sense line resistance changes at 64 Hz. The lock-in detected this as a first harmonic sense resistor voltage from a DC constant sense current. By observing the first harmonic the lock-in rejects all AC coupling of noise by capacitance or inductance, by measuring only those signals at the 64 Hz frequency and with a fixed phase relationship to the heater driver signals. This sensor produces large signals near atmospheric pressure, declining to 7 (mu) V below 0.1 mTorr. Phase measurements between 760 and 100 Torr where the air's thermal conductivity changes little, combined with amplitude changes at low pressure generate a pressure measurement accurate at 5 percent from 760 Torr to 10 mTorr, sensing of induced temperature changes of 0.001 degree C.

Design, fabrication, and testing of polysilicon microheaters in silicon

Abstract: We report the technology for the design, fabrication and testing of polysilicon microheaters in silicon using a standard 2 micrometers n-well CMOS technology. The polysilicon microheaters are realized in two steps: layout design for CMOS process and post processing etching. An additional layer in CMOS technology called `open' was incorporated. The `open' layer creates a direct opening to the substrate. Post processing is done on the fabricated CMOS chips using isotropic etchant like xenon difluoride (XeF2) or anisotropic etchant like ethylenediamine pyrocatechol (EDP) to create a `cavity' in the silicon substrate. The cavity provides thermal isolation from the polysilicon microheaters to the circuits and other devices. These microheaters can reach incandescence at very low power. Several test devices incorporating arrays of polysilicon microheaters were designed and fabricated. Measurements are presented that verify the design and performance of the microheater.