Development of thin-film multijunction thermal converters at NIST

Kinard, J.R.; Novotny, Donald B.; Lipe, Thomas E.; Huang, De-Xiang

doi:10.1109/19.571853

Cited by 22 publications

(3 citation statements)

References 7 publications

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“…The nonlinear electro-thermal differential problem is solved by increasing the thermal time constant of a thermal converter. [13][14][15][16][17][18] A planar cromel-alumel multijunction thermal converter is fabricated on an low pressure chemical vapor deposition (LPCVD) Si 3 N 4 (200 nm)/SiO 2 (400 nm)/Si 3 N 4 (200 nm) diaphragm (5 Â 8 mm 2 ), prepared by silicon bulk micromachining, which thermally isolates a bifilar NiCr heater (93 ) and the hot junctions of cromel-alumel thermopile (at the intervals of 20 mm and 4.66 k) from the silicon substrate. A silicon obelisk thermal integrator under the heater is formed using KOH anisotropic etching from the back surface.…”

Section: Introductionmentioning

confidence: 99%

Fabrication of Low-Frequency AC-DC Thermal Converter with Thermal Mass

Jung¹,

Eon²,

Kim³

et al. 2005

Jpn. J. Appl. Phys.

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The use of a thin film or a planar multijunction thermal converter (PMJTC) for the ac-dc transfer of voltage and current is well established. In general, a three dimensional multijunction thermal converter (MJTC) has the advantage of accuracy and a single junction thermal converter (SJTC) has that of low cost. PMJTCs provide a long-term stability, a high sensitivity and a high-dynamic-frequency range. It is well known that PMJTCs show small ac-dc voltage transfer differences in the audiofrequency range. However, it is difficult to obtain a small ac-dc transfer difference at low frequencies, particularly with thin-film-based thermal converters. The small ac-dc transfer difference at low frequencies is caused by nonlinearities in the heat transport mechanism (in thin films) and in the thermal-to-electric conversion process (in the thermocouples of thin films). This study has been conducteded to achieve a smaller ac-dc transfer difference on thin-film chromel-alumel thermal converters operating at low frequencies. An optional silicon obelisk is formed underneath the thin membrane to minimize ac-dc transfer differences at lower frequencies. The floating obelisk structure enhances the isothermal operation and slows thermal transfer compared with the standard configuration without the obelisk, resulting in a smaller ac-dc transfer difference at low frequencies. Also, it is possible that thin-film thermal converters can be used as the flow sensor and infrared sensor.

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Section: Introductionmentioning

confidence: 99%

Fabrication of Low-Frequency AC-DC Thermal Converter with Thermal Mass

Jung¹,

Eon²,

Kim³

et al. 2005

Jpn. J. Appl. Phys.

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“…The latest advance in thermal transfer devices is the Film Multijunction Thermal Converter (FMJTC) [12,13] which uses thin-film fabrication technology to deposit the heater and thermocouples on a silicon chip. These devices have been fabricated at NIST and elsewhere and have the potential to be used as working standards in place of SJTCs.…”

Section: Introduction To Ac-dc Difference Metrologymentioning

confidence: 99%

Operation and reference manual for the NIST automated AC-DC calibration systems and software

Lipe¹

2004

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Introduction-3 a glass form. In either case, for higher voltages, the resistor makes the dominant contribution to both the ac-dc difference and the uncertainty of a TVC [16,17]. The NIST Automated Systems for Thermal Transfer Standard Calibrations The present generation of NIST automated thermal transfer standard calibration systems was begun by a prototype system designed by Earl S. Williams and assembled in the early part of the 1980s [18,19]. This system was initially intended for the testing and development of solid-state transistor-based sensors. It became obvious that this automated system was also ideal for routine ac-dc difference measurements as part of the regular NIST calibration service for thermal transfer instruments. Accordingly, it was employed for some routine calibrations in early 1984. Because of the success of this system, a second automated system was assembled and used for routine calibrations beginning in 1985. A third automated system, initially intended for current calibrations, was assembled in 1998, and a fourth in 2000. Because of the availability of highperformance transconductance amplifiers, all four automated systems can be used for both voltage and current calibrations. Although these three automated systems differ in their exact details, all automated ac-dc calibration systems have several common attributes, as shown in Figure 1. All must have highlystable and precise sources of ac voltage or current and dc voltage or current, an arrangement for switching between the ac and dc signals, and a method of monitoring the outputs of the thermal converters with adequate precision. In the NIST systems, the ac and dc signals are provided by separate sources, although in principle, a multifunction calibrator might serve as a single signal source, and the switching is accomplished by relays. The millivolt-level output electromotive forces (emfs) of the thermal converters are monitored using sensitive, low-noise digital nanovoltmeters. The systems also have various arrangements of ac and dc voltmeters and frequency counters to monitor the performance of the system. The calibration systems are controlled by Apple eMac [20] running National Instruments' LabVIEW [21] software. LabVIEW is a graphics-oriented system control package, which acts as a "virtual instrument" (VI) during the calibration procedure, displaying data and results in real time as the measurements proceed. This arrangement is a significant improvement over the older BASIC language-based systems, which, although menu-driven and straightforward to use, nevertheless required the operator to proceed through many screens to operate the system. With the "virtual instrument" concept, the same screen is displayed for the entire calibration run (in most cases) and acts as both the input and output stages of the system.

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“…The three-dimensional multijunction thermal converters (3-D MJTC), which exhibit both a higher voltage responsivity and a smaller ac-dc transfer difference than the 3-D SJTC, have been developed and also used as ac standards for a fairly long time in spite of the yet unresolved problems of a tedious fabrication process and a low production yield. In recent years, various attempts have been made to realize planar MJTCs as a more practical ac standard by using well-developed semiconductor process technologies to overcome the problems encountered with the fabrication of 3-D MJTCs [3]- [7].…”

Section: Introductionmentioning

confidence: 99%

A planar Bi-Sb multijunction thermal converter with small ac-dc transfer differences

Kim

Lee²,

Lee

et al. 2002

IEEE Trans. Instrum. Meas.

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A planar Bi-Sb multijunction thermal converter was fabricated on the LPCVD Si 3 N 4 /SiO 2 /Si 3 N 4-diaphragm, prepared by silicon bulk micromachining, which thermally isolated a bifilar Pt-or NiCr-heater and the hot junctions of a Bi-Sb thermopile from the silicon substrate. The voltage responsivity, the ac-dc transfer difference, and the fluctuations of the output thermoelectric voltage and heater resistance were discussed to investigate the design factors of a thermal converter. The respective voltage responsivities in air and in a vacuum of the thermal converter with a built-in NiCr-heater were about 14.0 mV/mW and 54.0 mV/mW. The ac-dc voltage and the current transfer differences in air were about 0.60 ppm and 0.11 ppm in the dc reversing frequency range from 10 Hz to 10 kHz. They are sufficiently small to be used as practical ac standards. Compared to the thermal converter with a built-in Pt-heater, the thermal converter with a built-in NiCr-heater demonstrated a higher voltage responsivity and smaller ac-dc transfer differences, while exhibiting slightly larger fluctuations in output thermoelectric voltage and in heater resistance.

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Development of thin-film multijunction thermal converters at NIST

Cited by 22 publications

References 7 publications

Fabrication of Low-Frequency AC-DC Thermal Converter with Thermal Mass

Fabrication of Low-Frequency AC-DC Thermal Converter with Thermal Mass

Operation and reference manual for the NIST automated AC-DC calibration systems and software

A planar Bi-Sb multijunction thermal converter with small ac-dc transfer differences

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