Polysilicon Thermopile Research Articles

An Integrated Thermopile-Based Sensor with a Chopper-Stabilized Interface Circuit for Presence Detection.

This paper presents a sensor-readout circuit system suitable for presence detection. The sensor consists of a miniaturized polysilicon thermopile, realized employing MEMS micromachining by STMicroelectronics, featuring a responsivity value equal to 180 V/W, with 13 ms response time. The readout circuit is implemented in a standard 130-nm CMOS process. As the sensor output signal behaves substantially as a DC, the interface circuit employs the chopper technique in order to minimize offset and noise contributions at low frequency, achieving a measured input referred offset standard deviation equal to 1.36 V. Measurements show that the presented system allows successfully detecting the presence of a person in a room standing at 5.5 m from the sensor. Furthermore, the correct operation of the system with moving targets, considering people either walking or running, was also demonstrated.

Temperature calibration and electrical characterization of the differential scanning calorimeter chip UFS1 for the Mettler-Toledo Flash DSC 1

This paper reports on the temperature calibration and electrical characterization of the calorimeter chip UFS1 (internal design XI-400) developed for the new commercially available differential scanning calorimeter (DSC), the Flash DSC 1 of Mettler-Toledo. The chip consists of 2 identical membranes both with a p-type polysilicon microheater in the center of the membrane and a p/n-type polysilicon thermopile for measuring the sample temperature. The temperature calibration of the XI-400 is performed in the temperature range from 208 K to 723 K. An isothermal calibration is first performed to calibrate the heater resistance and the obtained curve is used to calibrate the integrated thermopile. The accuracy of the calibration is then determined by measuring the extrapolated onset temperature ( T e ) of primary standards. A detailed electrical characterization of the device is also reported. The calibration method implemented and the good temperature reproducibility of the device allow to use devices with uncalibrated heater resistance in the temperature range from 208 K to 723 K with a typical maximum error of ±5 K.

Characterization of heavily doped polysilicon films for CMOS-MEMS thermoelectric power generators

This paper presents the material characterization of boron- and phosphorus-doped LPCVD polysilicon films for the application of thermoelectric power generators. Electrical resistivity, Seebeck coefficient and thermal conductivity of polysilicon films doped with doses from 4 × 1015 to 10 × 1015 at cm−2 have been measured at room temperature. Specific contact resistance between polysilicon and aluminum is studied and nickel silicidation is formed to reduce the contact resistance. The overall thermoelectric properties, as characterized by the figure of merit, are reported for polysilicon doped with different doping concentrations. For the most heavily doping dose of 10 × 1015 at cm−2, figure of merit for p- and n-type polysilicon is found as 0.012 and 0.014, respectively. Based on the characterization results, a CMOS compatible thermoelectric power generator composed of boron- and phosphorus-doped polysilicon thermopiles is fabricated. When 5 K temperature difference is maintained across two sides of a device of size of 1 cm2, the output power is 1.3 µW under a matched electrical resistance load.

Characterization of phosphorus and boron heavily doped LPCVD polysilicon films in the temperature range 293-373 K

In this paper, thermal properties of phosphorus and boron-doped low pressure chemical vapor deposition (LPCVD) polysilicon layers with regard to sensor applications are presented. Thermoelectric coefficient and relative resistance variations of polysilicon are investigated within the temperature range of 293-373 K. Test structures and characterization benches have been developed to obtain measurements with precision of 5%. Ion implantation has been experimented to achieve low electrical resistivities and high Seebeck coefficients. It can be seen that the temperature coefficient of resistance of doped polysilicon is negative, approaches zero, or positive depending on the doping concentration. These results are, to our knowledge, the first reported for such dopant concentrations and are important for design and optimization of high sensitivity thermal sensors using n- and p-doped-LPCVD polysilicon thermopile.

Infrared micro-spectrometer based on a diffraction grating

The optical properties of crystalline silicon in the IR spectral range have been used for the realisation of a grating type micro-spectrometer. An aluminium metallisation on a double side polished silicon wafer is used for fabrication of the multi-slit gratings. The dispersed spectrum propagates through this silicon wafer and is projected on an array of polysilicon thermopiles, integrated in a second bulk micromachined silicon wafer. The two wafers are bonded at low temperature. An IR spectrometer results, which is simple to fabricate and remains compatible with standard IC processing.

Low-cost satellite attitude control sensors based on integrated infrared detector arrays

This paper describes attitude control systems (ACS) for satellites and a new, static system based on an integrated infrared (IR) detector array. After a short introduction on the use and control of satellites in general, we explain the advantage of static systems, made possible by the use of integrated IR detector arrays. In particular, the static system is lighter and smaller than the previous systems, and requires less power. The electronics is updated to state-of-the art, increasing the autonomy of the system and thereby reducing its dependence upon the satellite microcontroller. The detectors are based on a bipolar silicon process for the mechanical structure (using electrochemically controlled etching-KOH etching), with an SiN membrane for thermal isolation of the pixels, which have a polymer black coating for transduction of radiation to heat and n-type versus p-type polysilicon thermopiles for heat detection. The pixel pitch is 600 /spl mu/m, the black area is approximately 495 /spl times/ 440 /spl mu/m/sup 2/, and the pixel sensitivity is approximately 55 V/W, at a thermopile resistance of 23 k/spl Omega/. Two types of detectors have been designed: a single-array type with 32 pixels in two staggered arrays, and a chip with four 32-pixel arrays integrated in a cross. This has made it possible to make a family of earth sensors for the different missions in space.

Design and fabrication of infrared detector arrays for satellite attitude control

This paper describes the design, modelling and fabrication of infrared detectors for attitude control systems (ACS) for satellites. After a short introduction on the use and control of satellites in general, we explain the advantages of our integrated arrays of infrared detector units (pixels). Two types of detectors have been manufactured, a staggered array (ISA) with 32 pixels (in two staggered arrays of 16 pixels each) or in a cross of four staggered arrays (FPA) having 128 pixels in total. The choice depends upon the specific application (geostationairy or GEO orbit or low-altitude orbit). The detectors are based on a bipolar silicon process for the mechanical structure (electrochemically controlled etching (ECE)-KOH etching), with a SiN membrane for thermal isolation of the pixels, which have a polymer black coating for transduction of radiation to heat and n-type vs. p-type polysilicon thermopiles for heat detection. The pixel pitch is 600 μm, the black area is about 495×440 μm and the pixel sensitivity is about 55 V/W, at a thermopile resistance of 23.5 kΩ. The ISA measures in its present form 13.5×4 mm, the FPA measures 20.5×20.5 mm.

The role of thin films in integrated solid-state sensors

This paper reviews recent developments in integrated solid-state sensors, with emphasis on the important roles played by thin films in these device structures. Most such sensors employ transducers and custom interface circuits on a common substrate, with fabrication based on the processes associated with integrated circuits. Specific examples are used to illustrate the important electrical, mechanical, thermal, optical, and chemical properties of thin films in integrated sensors. Recently proposed undercut polysilicon film structures are discussed as an alternative to traditional bulk structures for measuring parameters such as pressure and flow. A multielectrode intracortical recording array under development for closed-loop neural prostheses is also described. This microprobe can be realized with high yields, with recording sites spaced as close as a few microns, and with substrate widths of less than 50 μm. A thin-film silicon thermal imager utilizes thin dielectric windows and polysilicon thermopiles to realize a broadband infrared detector which does not require cooling and which can be realized with effective element spacings less than 200 μm.