Burgess R. Johnson

Development of a MEMS gyroscope for northfinding applications

We report progress toward a MEMS gyroscope suitable for northfinding in pointing and targeting applications. In-run bias stability of 0.03 deg/hr and ARW of 0.002 deg/rt(hr) have been achieved. Gyro performance was measured on tuning-fork type MEMS gyroscopes using DSP-based breadboard electronics. These bias stability and ARW results are within about 6X and 2X, respectively, of meeting the typical gyrocompass requirements for pointing and targeting applications (1 milliradian azimuth precision at 65 degrees latitude with 5 minute integration time). A MEMS gyrocompass meeting these requirements would substantially reduce the size, weight and power of pointing and targeting instruments. The test methodology will be presented, as well as test data on carouseling the sensor to reduce the effects of long-term bias drift.

YBa/sub 2/Cu/sub 3/O/sub 7/ superconductor microbolometer arrays fabricated by silicon micromachining

Linear arrays of YBa/sub 2/Cu/sub 3/O/sub 7/ transition edge microbolometers have been fabricated on silicon substrates using silicon micromachining to produce microbolometer structures with good thermal isolation. These bolometers, which are 85 mu m*115 mu m*1 mu m, have a noise equivalent power (NEP) of 9*10/sup -13/ W/Hz/sup 1/2/. (neglecting contact noise) and a thermal time constant of 24 ms. With contact noise, the NEP is 9*10/sup -12/ W/Hz/sup 1/2/. This performance indicates that a 2-D staring focal plane array of superconductor microbolometers could have a performance comparable to that of HgCdTe staring arrays without further improvements in the sharpness of the superconducting transition or reductions in the YBa/sub 2/Cu/sub 3/O/sub 7/ electrical noise. The use of silicon processing technology to fabricate the superconductor microbolometers results in a significant cost advantage over HgCdTe, and there is no long wavelength cutoff dependence in the sensitivity of a superconductor microbolometer.<<ETX>>

Epitaxial YBa2Cu3O7 superconducting infrared microbolometers on silicon

Superconducting transition-edge infrared microbolometers have been fabricated by silicon micromachining using an epitaxial YLa.05Ba1.95Cu3O7-x (YBCO) film on a epitaxial yttria-stabilized zirconia buffer layer on silicon. The low thermal conductance of the micromachined structures combined with the sharp resistance change at the superconducting transition results in very sensitive infrared detectors. The broadband response of these thermal detectors makes them particularly useful at wavelengths longer than the typical operating range of semiconductor detectors ((lambda) greater than about 20 micrometers ) at moderately high temperatures (T approximately 70 K and higher). The use of standard silicon processing promises low-cost monolithic integration of the readout electronics for arrays of these devices. Preliminary measurements are reported here on a device 140 micrometers X 105 micrometers in size with a detectivity, D*, of 8 +/- 2 X 109 cm Hz1/2/Watt, and NEP of 1.5 X 10-12 Watts/Hz1/2 at 2 Hz and 80.7 K. This value of D* exceeds the highest previously reported D* for a YBCO transition-edge bolometer, and is comparable to the highest reported D* for a thermal detector operating at greater than about 70 K. The thermal time constant for this device was 105 +/- 20 msec.

Transition Edge YBa 2 Cu 3 O 7-x Microbolometers for Infrared Staring Arrays

High-temperature superconducting staring arrays are potentially important for both space and terrestrial applications which require the combination of high sensitivity over a broad wavelength range and relatively high temperature operation. In many such array applications sensitivity is more important than speed of response. Thus, it is desirable to design low- thermal-mass pixels that are thermally isolated from the substrate. To this end, Johnson, et al. at Honeywell have fabricated meander lines of YBa2Cu3O7-x (YBCO) sandwiched between layers of silicon nitride on silicon substrates. The silicon was etched out from under each YBCO meander line to form low-thermal-mass, thermally isolated microbolometers. These 125 micrometers X 125 micrometers devices are estimated to have a noise equivalent power of 1.1 X 10-12 W/Hz1/2 near 5 Hz with a 5 (mu) A bias (neglecting contact noise). A drawback of this original Honeywell design is that the YBCO is grown on an amorphous silicon nitride underlayer, which precludes the possibility of epitaxial YBCO growth. The YBCO therefore has a broad resistive transition, which limits the bolometer response, and the grain boundaries lead to excess noise. We discuss the potential performance improvement that could be achieved by using epitaxial YBCO films grown on epitaxial yttria-stabilized zirconia buffer layers on silicon. This analysis shows a significant signal to noise improvement at all frequencies in devices incorporating epitaxial YBCO films. Progress toward fabricating such devices is discussed.

Innovations in IR projector arrays

In the past year, Honeywell has developed a 512 X 512 snapshot scene projector containing pixels with very high radiance efficiency. The array can operate in both snapshot and raster mode. The array pixels have near black body characteristics, high radiance outputs, broad band performance, and high speed. IR measurements and performance of these pixels will be described. In addition, a vacuum probe station that makes it possible to select the best die for packaging and delivery based on wafer level radiance screening, has been developed and is in operation. This system, as well as other improvements, will be described. Finally, a review of the status of the present projectors and plans for future arrays is included.

High performance infrared detector arrays using thin film microstructures

Honeywell has developed a unique uncooled thermal detector technology based on fabricating thin film structures with temperature sensitive detector materials. High TCR resistive materials such as VOx and YBaCuO, and pyroelectric PbTiO/sub 3/ have been used. Two dimensional imaging arrays of sizes up to 240/spl times/336 have been integrated with Si substrate electronics to achieve temperature sensitivities of less than .04 C operating at room temperature. The thin film detector materials are deposited on microstructure thin film pixels of 2 mil sizes which are subsequently thermally isolated from the substrate by etching away the underlying substrate. The thermal isolation of the microstructure pixel provides the temperature rise and the detector material provides the conversion to an electrical signal.

MEMS sensing and control : An aerospace perspective

Future advanced fixed- and rotary-wing aircraft, launch vehicles, and spacecraft will incorporate smart microsensors to monitor flight integrity and provide flight control inputs. This paper provides an overview of Honeywells MEMS technologies for aerospace applications of sensing and control. A unique second-generation polysilicon resonant microbeam sensor design is described. It incorporates a micron-level vacuum-encapsulated microbeam to optically sense aerodynamic parameters and to optically excite the sensor pick off: optically excited self-resonant microbeams form the basis for a new class of versatile, high- performance, low-cost MEMS sensors that uniquely combine silicon microfabrication technology with optoelectronic technology that can sense dynamic pressure, acceleration forces, acoustic emission, and many other aerospace parameters of interest. Honeywells recent work in MEMS tuning fork gyros for inertial sensing and a MEMS free- piston engine are also described.

Silicon-microstructure superconducting microbolometer infrared arrays

High-temperature superconducting microbolometer silicon microstructure infrared arrays offer the potential of lowest possible production cost combined with high performance for use in infrared imaging systems. Linear arrays employing thin films of yttrium barium copper oxide have been prepared. Small two-dimensional arrays are under development. A 240 X 336 array of 50 micrometers X 50 micrometers pixels operating at 85 K at 30 frames per second with f/1 optics has a theoretical noise equivalent temperature difference of 2.0 X 10-3 deg K.

Toroidal resonators with small frequency mismatch for rate integrating gyroscopes

This paper reports an order of magnitude reduction in frequency mismatch (ΔF) in polycrystalline diamond half-toroid resonators under development for use as microscale rate-integrating gyroscopes. The reduction in ΔF was achieved by eliminating the lip at the perimeter of the resonator. Measurements of resonance decay time as a function of frequency, temperature, and pressure are also reported.

Honeywell resistor array development and future directions

In 1991 the Honeywell Technology Center began the development of large area 2D microemitter arrays for IR scene projection. Since then, 5 different types of 512 X 512 or larger arrays have been fabricated, all in current use. This paper will review the status, properties, and applications of these arrays. Pixel and array improvements which will lead to ultralow power consumption, very high performance, very fast 1024 square arrays are under development. A number of these efforts are described.