MEMS, Micromachining & Sensors: Prof. Glenn H. Chapman

This page contains the paper abstract and full PDF versions of publications on Micromachining and Microsensors. Click on the link to download pdf version.  See also the sensor array papers in the WSI papers section, micromachined systems in the Angular Domain Imaging papers , and grayscale mask 3D structures in the Inorganic Thermal Resist papers.  Papers here are listed in order of publication
Note: These papers are for academic use only and are not available for distribution or publication for other purposes.

Refereed Journal Papers

M. Salomon, J. Armitage, G.H. Chapman, M. Dixit, W. Faszer, J-L. Hamel and G. Oakham, "Passivation of Gas Microstrip Detectors and Long Term Operation Stability", Nuclear Instruments and Methods in Physics, A351, 313-316 (1994)  nimpr94.pdf  256KB
We have studied the long-term operation of gas microstrip detectors which have been passivated with a layer of nickel oxide. We have used as the active gas CF4/isobutane (80: 20) and three different types of substrates: Tedlar, glass and Upilex. In all three cases we found that the detectors are stable after passivation and can operate for a month without changes in gain at rates of MHz. The total accumulated charge was approximately 100 mC.

V. Ward, M.J. Syrzycki, and G.H. Chapman, "CMOS Photodetector with Built-In Light Adaptation Mechanism," Microelectronic Journal, 24, 547-553, (1993).  micro93.pdf  458KB
This paper reports research results on a new class of silicon photodetectors with light adaptation mechanisms. Previously used devices feature a limited dynamic range which is much smaller than a range of light intensity present in our environment. Intelligent vision systems functioning similarly to human vision systems require new photodetectors with abilities not only to cover wider dynamic range, but also able to accomplish background adaptation and dark adaptation mechanisms similar to those existing in human retina. The proposed class of devices uses the same silicon structure operating in two or more operating modes of different sensitivity, with light- controllable switching between different modes. The measurements conducted on CMOS photodetectors fabricated in the 3 micron CMOS technology show that the new photodetectors have a dynamic range increased by at least two orders of magnitude and feature limited power consumption, which is especially attractive for large area transducer systems.

Stoev, I., Surzycki, M., Parameswaran, M., Chapman, G., and Rawicz, A. "Process Optimization for Micromachined Silicon Non-Reverse Valve", Can. Jour. of Physics, 70, 881-885 (1992).  cjp92c.pdf  6960KB
The paper targets the development and optimization of technology for a micromachined silicon nonreverse valve, intended for fluid delivering applications in miniature fluidic systems. Several combinations of valve geometries and semiconductor process parameters were investigated, resulting in fabrication of different structures. Two-dimensional simulations were used to optimize the process parameters necessary to obtain V-grooved silicon membranes of specific thicknesses. The mechanical performance of the valve was also tested. Finally, modifications of valve structure for possible integration with a pressure sensor were proposed.

Refereed Conference Proceedings

J.M. Dykes, D.K. Poon, J. Wang, D. Sameoto, J.T.K. Tsui, C. Choo, G.H. Chapman, A.M. Parameswaren, and B.L. Gray, “Creation of embedded structures in SU-8”, Proc. SPIE Photonics West Microfluidics, BioMEMS, and Medical Microsystems V, v 6465, pp 64650N1-N12, San Jose, Jan 2007. photonw07mems.pdf 2,425KB
Two methods were investigated for the creation of encapsulated micro-fluidic channels and bridges in negative tone SU-8 photoresist.  The first uses two exposures at different wavelengths to create the channel sidewalls and micro-channel encapsulation layer; the other method creates both using a single I-line (365 nm) exposure and a grayscale photomask.  These methods can define structures with vertical dimensions ranging to hundreds of microns and introduces very little extra processing complexity.  For the dual wavelength method, an I-line light source is used to define the channel walls while a non-collimated deep-UV (254 nm) light source provides a large energy dose to the top surface of the SU-8 to produce a membrane over all the channels.  Using the dual wavelength method allows SU-8 to be used as the material for the channels and the encapsulation method is self-limiting avoiding the requirement for precise control over the exposure dose.  The rate of UV dose and the post-exposure baking parameters are critical to the quality and strength of the micro-channels.  Properly designed channels have been successfully developed in lengths up to 1 cm.   Alternatively using a grayscale Zn/Al bimetallic photomask and a single I-line exposure, 3D bridge micro-structures were successfully made on SU-8.  The use of grayscale masks for both techniques also provides the possibility of shaping the channel.  With the ability to create micro-bridges, further research will be performed to investigate how well the single exposure technique can be used to produce micro-channels of various sizes and dimensions.

C. Hu, X. Qu, J.Q.M Wu, and G.H. Chapman, “MOS hydrogen sensor array for 2D gas distribution mapping”, Conf. of Metallurgists 2005, pp 497-504, Calgary, Canada, Aug., 2005. com05.pdf 118KB
A MOS capacitor hydrogen sensor array is reported for hydrogen gas distribution mapping. Si(100) was used as substrate for film deposition. After silicon oxide growing on the silicon surface with dry thermal oxidation, palladium film was sputtered on silicon oxide as hydrogen-sensitive gate material in MOS structure. The 3x3 sensor array was patterned on silicon substrate and packaged in one chip. Sensors’ response was test with impedance analyzer. The sensors in array were calibrated in the hydrogen concentration range from 10ppm to 10000ppm. The 2D hydrogen concentration distribution was obtained with the calibrated sensor array.

G.H. Chapman, N. Sawadsky and P.P.S. Juneja, "Phase sensitive techniques applied to a micromachined vacuum sensor", Proc. SPIE Micromachined Devices and Components Conf., v 2882, pg 266-277, Austin, TX, (Oct. 1996)  micromachined95.pdf  2,294KB
Phase sensitive AC measurement techniques are particularly applicable to micromachined sensors detecting temperature changes at a sensor caused by a microheater. The small mass produces rapid thermal response to AC signals which are easily detectable with lock-in amplifiers. Phase sensitive measurements were applied to a CMOS compatible micromachined pressure sensor consisting a polysilicon sense line, 760 microns long, on an oxide microbridge separated by 6 microns on each horizontal side from similar polysilicon heaters, all over a micromachined cavity. Sinusoidal heater signals at 32 Hz induced temperature caused sense line resistance changes at 64 Hz. The lock-in detected this as a first harmonic sense resistor voltage from a DC constant sense current. By observing the first harmonic the lock-in rejects all AC coupling of noise by capacitance or inductance, by measuring only those signals at the 64 Hz frequency and with a fixed phase relationship to the heater driver signals. This sensor produces large signals near atmospheric pressure, declining to 7 (mu) V below 0.1 mTorr. Phase measurements between 760 and 100 Torr where the air's thermal conductivity changes little, combined with amplitude changes at low pressure generate a pressure measurement accurate at 5 percent from 760 Torr to 10 mTorr, sensing of induced temperature changes of 0.001 degree C.

P.P.S. Juneja and G.H. Chapman, "A Wide-Range Vacuum Sensor using Phase-Sensitive Detection", Proceedings of CCVLSI'93, 3A 7-12, Banff, Alb (1993).  ccvlsi93.pdf 532KB
A CMOS compatible micromachined pressure sensor has been developed with a wide operating range of 760- 1E-4 Torr. It employs a unique design, and measures the pressure dependent heat flow from a thermally isolated microheater across a 6 micron gap to a sense resistor. The sensor’s rapid thermal response allows the application of phase-sensitive AC measurement technique, and enables detection of temperature changes of less than 0.5 millidegree Celsius. The measurement technique also eliminates the various compensations required by Wheatstone- bridge method, widely employed in the existing vacuum gauges.

Back to Prof. Glenn Chapman Home
ENSC Faculty or Engineering Science People or Engineering Science Home Page
Page maintained by: Glenn Chapman
Last updated June 4, 2008