Jan Dziuban

New approach of fabrication and dispensing of micromachined cesium vapor cell

We describe the fabrication of wafer-scale alkali vapor cells based on silicon micromachining and anodic bonding. The principle of the proposed micromachined alkali cell is based on an extremely compact sealed vacuum cavity of a few cubic millimeters containing caesium vapors, illuminated by a high-frequency modulated laser beam. The alkali cells are formed by sealing an etched silicon wafer between two glass wafers. The technique of cell filling involves the use of an alkali dispenser. The activation of cesium vapors is made by local heating of the dispenser below temperature range causing degradations of cesium vapor purity. Thus, the procedure avoids negative effects of cesium chemistry on the quality of cell surfaces and sealing procedure. To demonstrate the clock operation, cesium absorption as well as coherent population trapping resonance was measured in the cells.

Microwave enhanced fast anisotropic etching of monocrystalline silicon

Abstract A wet microwave enhanced selective anisotropic fast etching of single-crystal silicon has been developed. Deep square cavities with flat thin silicon membranes of very good quality were etched in standard (100) n-type substrate. Si3N4 CVD layer served as the mask. For microwaves 2.54 GHz and 100 W of microwave power, etching velocity of (100) plane was increased almost 30 times in comparison to the standard process. The total time of etching process of thin membranes in standard Si substrate was reduced from hours to minutes. Anisotropic etching of Si in deionized water was obtained.

Corrugated silicon nitride membranes as suspensions in micromachined silicon accelerometers

This paper presents some theoretical considerations and experimental results carried out to investigate the potential use of corrugated silicon nitride membranes as a mechanical suspension in micromachined silicon capacitive accelerometers.

Silicon optical pressure sensor

Abstract A novel optical-fiber silicon pressure sensor with a bossed membrane has been fabricated. The pressure deflects the micromachined thin membrane and moves the end of a fiber illuminating the p-n junction fabricated near the edge of the membrane in a standard IC process. A photovoltage proportional to the degree of deflection of the membrane is generated in the junction. A nontypical output voltage versus inlet pressure characteristic has been obtained.

LTCC package for MEMS device

LTCC package of silicon membrane katharometer was made and investigated. The package protects the katharometer against mechanical damage and makes possible an easy connection of electrical signals. Moreover, the heater and temperature sensors allow for obtaining the proper temperature of the element. The basic electrical parameters of the integrated heater and thermistors as well as measured temperature distribution are presented.

Self-compensating piezoresistive pressure sensor

Abstract A double-bridge method of pressure-sensor compensation has been tested. Three types of sensors are produced: standard with a flat, square, thin membrane and single Wheatstone bridge with four diffused piezoresistors in standard configuration and new sensors with ‘cut’ piezoresistors and a flat or bossed square membrane with two identical Wheatstone bridges. One bridge is active, positioned on the membrane, sensitive to pressure and to all types of process- and temperature-induced errors. The other is inert, 100 μm away from the membrane and theoretically not sensitive to pressure. The good quality of new sensors with ‘cut’ piezoresistors has been confirmed. A good sensitivity of 250 mV (100 kPa, 5 V d.c.) has been obtained. Proper connection of the active and inert bridges has compensated the off-set voltage and temperature drift of the off-set voltage from values V off ,=110 mV to 40 mV and TCV off =0.15%/°C to 0.01-0.05%/°C. Tests of die and wafer-scale distributions show that statistical variations of V off may not be self-compensated by the use of the double-bridge method. The unexpectably high sensitivity of the inert bridge shows deep surface-stress penetration in the pressure-sensor die, which may destruct the stability of CMOS on-chip circuits. A modification of the double-bridge compensation method has been proposed.

On-Chip Scanning Confocal Microscope with 3D MEMS Scanner and VCSEL Feedback Detection

We propose an original approach of a miniature scanning confocal microscope that uses two electrostatic scanners with microoptical lenses. For this chip-scale microscope, we demonstrated the use of optical feedback of VCSELs laser as an active detection. The z-axis scanner will provide a vertical motion of the first microlens in the range of 100 mum, controlling the focal length of the objective. Raster scanning (30 mum in both directions) of a specimen by the focused illumination spot will be implemented by actuating of second microlens by x-y-axis scanner.

Mold-type field-emission array fabrication by the use of fast silicon etching

The SiC sharp-emitter field-emission arrays have been produced by a transfer-mold technique. An alternate method of microwave-enhanced wet anisotropic silicon etching has been applied to the fabrication of field-emission arrays. Supporting, back side (100)-oriented, 380 μm thick silicon substrate has been etched away six times faster as compared to the thermally activated, standard KOH etching process. The alternate etching method may be successfully applied to any existing transfer-mold fabrication procedures.

Desorption/ionization mass spectrometry on array of silicon microtips

We have shown that a sample of bio-species deposited onto the spot of the array of protruded metal gated silicon tips (DIOST) may be effectively ionized and evaporated by UV laser pulsed light illumination. This phenomenon has been never observed on flat surface of silicon dioxide or TiW-Au thin film layers the materials which were used in construction of the tips array. Nature of this process is not known; the most intriguing fact is the protonization as well as negative electron ionization of bio-samples. The new DIOST platform was used for TOF MS tests, and clearly readable, low-noised mass spectrograms of LGG and dopamine were observed.

SiC field emitter arrays fabricated by transfer mold technique

The field emission arrays of SiC sharp emitter tips have been produced for the first time by use of the transfer mold technique. The test structures of active gun, containing approximately 3×104 of emitters, were prepared. The field emission current and work function calculations for SiC emitter arrays have been presented.