In-situ plasma chamber monitoring for feedforward process control

This paper examines the effects of polymer buildup in plasma etching systems and describes a micromachined sensor for in-situ polymer thickness measurement. Using gas flows of 45 sccm CHF3CHF3 and 15 sccm CF4CF4 at 50 mTorr and 1000 W, the oxide:polysilicon selectivity ranges from 2.6 to 8.5 as the polymer thickness on the tool walls varies from 0 to 240 nm. The polymer sensor is based on an electrothermal oscillator that measures the thermal mass change as polymer builds up on a stress-compensated dielectric window. The change in the thermal mass of the window can be detected as a variation in the pulse width (cooling time) of the oscillation. The device operates with a typical cooling time of 2.7 msec and has a measurement resolution of better than 1 nm. The device is flush-mounted in the chamber wall with the exposed window area protected by a thin film of iridium against damage by the plasma. © 1998 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87553/2/427_1.pd

A self-controlled microcontrolled microvalve

Integrated microvalves are needed for a broad range of semiconductor-processing-related applications. These include precision mass microflow controllers (μFCs) for dry etch systems, miniature gas chromatography systems for real-time monitoring, point-of-use semiconductor process reactant generators, and compact control systems for mini-environments. This paper reports a pneumatically actuated, integrated silicon microvalve, which was developed as a forerunner to an 8b μFC intended for the precision control of semiconductor process gases in the range from 0.1 to 10 sccm. The structure was designed to be batch-fabricated and compatible with on-chip thermopneumatic actuation. Assembled single-bit μFC devices achieve the targeted flow rate of 5 sccm (determined by an in-line flow channel) at 20 psid (1034 torr). The valve alone may achieve significantly higher flow rates. The leak rate is 0.08 sccm under 26.1 psig actuation pressure, and the valve can seal against pressures greater than 29 psid (1500 torr). © 1998 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87556/2/937_1.pd

A Microinstrumentation System for Remote Environmental Monitoring

This paper reports on a hybrid micro-instrumentation system that includes a embedded micro-controller, transducers for monitoring environmental parameters, interface/readout electronics for linking the controller and the transducers, and custom circuitry for system power management. Sensors for measuring temperature, pressure, humidity, and acceleration are included in the initial system, which operates for more than 180 days and dissipates less than 700 microW from a 6V battery supply. The sensor scan rate is adaptive and can be event triggered. The system communicates internally over a 1 MHz, nine-line intramodule sensor bus and outputs data over a hard-wired serial interface or a 315MHz wireless link. The use of folding platform packaging allows an internal system volume as small as 5 cc

A high-performance microflowmeter with built-in self test

This paper reports the development of a high-performance readout scheme based on a switched-capacitor circuit and intended for use with an ultrasensitive microflowmeter. The microflow transducer improves significantly on the resolution of current flow devices and uses a differential capacitive pressure sensor to measure the flow. The readout electronics feature a clocking speed of 100 kHz and can drive loads as high as 35 pF. The high d.c. gain of the circuit topology (75 dB) is relatively insensitive to stray input capacitance and is ideally suited for a multichip sensor realization. The uncompensated linearity of the overall readout circuit is 10 bits and the pressure/flow resolution is 12 bits. Since ultrasensitive membranes respond to electrostatic forces, the output is characterized as a function of the duty cycle and pulse width of the readout clocking waveforms. The membrane does not respond to these waveforms for high frequencies ( > 50 kHz), but for lower frequencies the diaphragm deflects in response to the time-average voltage applied across the device. A self-test mode can therefore be implemented simply by changing the duty cycle of this pulse. By modifying the amplitude of the waveform, the device can be autocalibrated over a limited pressure range. The transducer and circuitry have been integrated into a flow package, and the multichip device has been tested versus a calibrated gas flow.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30918/1/0000588.pd

A scaled electronically-configurable multichannel recording array

This paper describes a multichannel microelectrode array capable of recording single-unit neural activity in the central nervous system. The probe features 32 recording sites on a scaled shank less than 50,[mu]m wide. On-chip CMOS circuitry implements signal amplification, multiplexing, and selftesting on eight active channels selected from among the 32 sites. The circuitry has a power dissipation of 3 mW, an active area of 2.5 mm2, and requires only three external leads. It utilizes bidirectional signal transmission over the output data lead for signal output and for channel selection.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27927/1/0000351.pd

Flexible miniature ribbon cables for long-term connection to implantable sensors

This paper describes the development of miniature, multi-lead ribbon cables for connecting implantable sensors to host electronics, either implanted or in the external world. The cables are flexible, electrically stable and biocompatible. Two technologies have been developed: one using polyimide (DuPont PI-2555) and the other using silicon as the support material. The present cables are less than 200 [mu]m wide, are 10 to 20 [mu]m thick and can be of arbitrary length (typically 1-2 cm). They can support as many leads as desired and can be bonded to the sensor substrate using flip-chip bonding techniques.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28664/1/0000481.pd

Active positioning device for a perimodiolar cochlear electrode array

The authors report on an actuated positioning device for a cochlear prosthesis insertion procedure. The device consists of multiple high-aspect ratio fluidic actuator chambers integrated with a high-density silicon cochlear electrode array and manufactured in a tapered-helix form. Actuation chambers with cross-sectional sizes as small as 40 × 200 μm and lengths of 30 mm have been fabricated using flexible polymers. The device will allow for low-resistance basilar insertion of a stimulating electrode array into the cochlea providing for deep, perimodiolar position considered most beneficial for auditory nerve stimulation, while minimizing intracochlear trauma. Experimental measurements, FEA analysis, and modeling demonstrate a viable and appropriate actuation method for a cochlear implant procedure.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47852/1/542_2004_Article_376.pd

A low-power pressure-and temperature-programmed separation system for a micro gas chromatograph.

This thesis presents the theory, design, fabrication and testing of the microvalves and columns necessary in a pressure- and temperature-programmed micro gas chromatograph ({micro}GC). Two microcolumn designs are investigated: a bonded Si-glass column having a rectangular cross section and a vapor-deposited silicon oxynitride (Sion) column having a roughly circular cross section. Both microcolumns contain integrated heaters and sensors for rapid, controlled heating. The 3.2 cm x 3.2 cm, 3 m-long silicon-glass column, coated with a non-polar polydimethylsiloxane (PDMS) stationary phase, separates 30 volatile organic compounds (VOCs) in less than 6 min. This is the most efficient micromachined column reported to date, producing greater than 4000 plates/m. The 2.7 mm x 1.4 mm Sion column eliminates the glass sealing plate and silicon substrate using deposited dielectrics and is the lowest power and fastest GC column reported to date; it requires only 11 mW to raise the column temperature by 100 C and has a response time of 11s and natural temperature ramp rate of 580 C/min. A 1 m-long PDMS-coated Sion microcolumn separates 10 VOCs in 52s. A system-based design approach was used for both columns