Microsystems technology and bioMEMS (2002-2010)
A robust microfluidic bioMEMS device and packaging technology has been developed which supports leak-free networks, reusable packaging, and connectivity for fluidic, electrical, and optical networks. Spatially selective deposition of chitosan biofunctional sites has been demonstrated, followed by localized protein assembly on the sites within the bioMEMS. The programmable biofunctionality of surface reaction sites and the flexibility of the bioMEMS system design provides an attractive platform for metabolic engineering, biomolecular sensing and synthesis, and cell-based sensing applications. Examples:
“Integrated Fabrication of Polymeric Devices for Biological Applications”, M. J. Kastantin, S. Li, A. P. Gadre, L-Q Wu, W. E. Bentley, G. F. Payne, G. W. Rubloff, and R. Ghodssi, Sensors and Materials (invited) 15 (6), 295-311 (2003).
“A fabrication platform for electrically mediated optically active biofunctionalized sites in BioMEMS”, Michael A. Powers, Stephan T. Koev, Arne Schleunitz, Hyunmin Yi, Vildana Hodzic, William E. Bentley, Gregory F. Payne, Gary W. Rubloff, and Reza Ghodssi, Lab on a Chip 5, 583-586 (2005).
“BioMEMS Device and Package Design for Spatially Selective Biomolecule Assembly”, Jung Jin Park, Theresa M. Valentine, Hyunmin Yi, Xiaolong Luo, Gregory F. Payne, Willliam E. Bentley, Reza Ghodssi, and Gary W. Rubloff, Lab on a Chip (submitted).
“Voltage-Programmable Biofunctionality in MEMS Environments using Electrodeposition of a Reactive Polysaccharide”, Li-Qun Wu, Hyunmin Yi, Sheng Li, David A. Small, Jung Jin Park, Gary W. Rubloff, Reza Ghodssi, William E. Bentley, and Gregory F. Payne, Proc. IEEE Transducers 2003, 1871-1874 (2003).
Surface-controlled biomaterials and biofunctionalization (2002-2010)
Electrodeposition of the polysaccharide chitosan has proven to provide a versatile template for spatially selective biofunctionalization of surfaces for biotechnology applications, where the pH-responsive properties of chitosan (pKa=6.3) enable transport under soluble (acidic) conditions vs. deposition under insoluble (basic) conditions. After depositing an amine-rich chitosan surface, a variety of biospecies can be covalently conjugated to the surface, including proteins, enzymes, nucleic acids, viruses, and cells. These biofunctionalized surfaces demonstrate expected activity, e.g. in sandwich assay applications or in small molecule catalysis promoted by surface enzymes. Examples:
“Biofabrication with Chitosan”, Hyunmin Yi, Li-Qun Wu, William E. Bentley, Reza Ghodssi, Gary W. Rubloff, James N. Culver, and Gregory F. Payne, review paper, Biomacromolecules 6 (6) 2881-2894 (Nov/Dec 2005).
“Signal-Directed Sequential Assembly of Biomolecules onto Patterned Surfaces”, Hyunmin Yi, Li-Qun Wu, Reza Ghodssi, Gary W. Rubloff, Gregory F. Payne, and William E. Bentley, Langmuir 21 (6) 2104-2107 (Mar 15 2005).
“Nature-inspired Creation of Protein-Polysaccharide Conjugate and its Subsequent Assembly onto a Patterned Surface”, Tianhong Chen, David A. Small, Li-Qun Wu, Gary W. Rubloff, Reza Ghodssi, Rafael Vazquez-Duhalt, William E. Bentley, and Gregory F. Payne, Langmuir 19 (22), 9382-86 (2003).
“Patterned Assembly of Genetically Modified Viral Nanotemplates via Nucleic Acid Hybridization”, Hyunmin Yi, Saira Nisar, Sang-Yup Lee, Michael A. Powers, William E. Bentley, Gregory F. Payne, Reza Ghodssi, Gary W. Rubloff, Michael T. Harris, and James N. Culver, Nano Letters (communication, 2005, ASAP article on web).
Direct diagnostics for advanced electronic materials and processes (2001-present)
Thermal processing combined with in-situ and post-process materials characterization directly reveal the thermally-activated nanostructural transformations which occur in fabricating nanoporous low-K dielectrics for use in advanced interconnects, particularly the relative kinetics of polymer cross-linking and porogen decomposition and volatilization.
Integration of real-time chemical sensing into atomic layer deposition (ALD) process equipment elucidates the surface chemistry and kinetics of the half-reactions intrinsic to ALD. Our wafer-scale prototype reactors enable the integration of real-time sensors, the direct observation of surface kinetics, and the optimization of process design, supporting ALD’s move into mainline manufacturing. Examples:
“Thin Film Transformations and Volatile Products in the Formation of Nanoporous Low-K PMSSQ-based Dielectric”, P. Lazzeri, L. Vanzetti, M. Anderle, M. Bersani, J. J. Park, Z. Lin, R. M. Briber, G. W. Rubloff, H. C. Kim, R. D. Miller, J. Vac. Sci. Technol. B 23, 908-917 (May/Jun 2005).
“ToF-SIMS studies of nanoporous PMSSQ materials: kinetics and reactions in the processing of low-K dielectrics for ULSI applications”, P. Lazzeri, G. W. Rubloff, L. Vanzetti, R. M. Briber, M. Anderle, M. Bersani, J. J. Park, H.-C. Kim, W. Volksen, R. D. Miller, and Z. Lin, Surface and Interface Analysis 36, 304-310 (2004).
“Real-Time Observation and Optimization of Tungsten ALD Process Cycle”, Wei Lei, Laurent Henn-Lecordier, Mariano Anderle, Gary W. Rubloff, Mario Barozzi, and Massimo Bersani, J. Vac. Sci. Technol.B (submitted).
Novel approaches to equipment design and combinatorial materials and process development (2001-2005)
Following on equipment innovations for integrated and ultraclean processing, the concept of spatially-programmable process reactor design has been developed and implemented in a prototype for CVD and ALD processes. This strategy enables across-wafer uniformity to be achieved independent of the chosen process design point. It also makes possible the extension of combinatorial materials design to chemical vapor deposition processes, which are important in view of the increasing need for complex new materials needed for new technologies and for their manufacturability by CVD techniques. Pursuit of combinatorial experimentation and materials informatics is carried out within our NSF International Materials Institute. Examples:
“Simulation-Based Design and Experimental Evaluation of a Spatially Controllable Chemical Vapor Deposition Reactor”, Jae-Ouk Choo, Raymond A. Adomaitis, Gary W. Rubloff, Laurent Henn-Lecordier, and Yijun Liu, AIChE J. 51 (2) 572-584 (Feb 2005).
“Development of a Spatially Controllable Chemical Vapor Deposition Reactor with Combinatorial Processing Capabilities”, J. O. Choo, R. A. Adomaitis, L. Henn-Lecordier,Y. Cai, and G. W. Rubloff, Rev. Sci. Instr. 76, 062217-1 to 062217-10 (June 2005).
“Spatially programmable microelectronics process equipment using segmented gas injection showerhead with exhaust gas recirculation”, Raymond A. Adomaitis, John N. Kidder, Jr., and Gary W. Rubloff, U.S. Patent No. 6,821,910, issued Nov. 23, 2004.
“Data Management and Visualization of X-ray Diffraction Spectra from Thin Film Ternary Compound Spreads”, I. Takeuchi, C. J. Long, O. O. Famodu, M. Murakami, J. Hattrick-Simpers, G. W. Rubloff, M. Stukowski, and K. Rajan, Rev. Sci. Instr. 76, 062223-1 to 062223-8 (June 2005).
In-situ chemical sensing and real-time advanced process control (1993-present)
Downstream chemical sensing (mass spectrometry,acoustic) has been applied for the first time to CVD, PECVD, plasma etch, and recently atomic layer deposition (ALD) processes for semiconductor manufacturing. Time-dependent signals through the process cycle show product generation and reactant depletion, leading to a thickness/rate metrology which is now being explored as a driver for advanced process control. The time-dependent signals also reveal process recipe and equipment functionality details important for fault management. These applications are key to the advanced process control needs specified in the International Technology Roadmap for Semiconductors. Examples:
“In-Situ Metrology: the Path to Real-Time Advanced Process Control”, Gary W. Rubloff, Invited Paper, Proc. 2003 International Conference on Characterization and Metrology for ULSI Technology, Austin, TX, March 24-28, 2003, ed. by D. G. Seiler et. al., AIP Conf. Proc. Vol. 683, ISBN 0-7354-0152-7 (AIP, Melville NY, 2003), 583-591.
“Thickness Metrology for SiO2 RTCVD using Real-Time Mass Spectrometry”, G. Lu, L. L. Tedder, and G. W. Rubloff, J. Vac. Sci. Technol. B 17 (4), 1417-23 (Jul/Aug 1999).
“Process Diagnostics and Thickness Metrology for the Chemical Vapor Deposition of W from H2/WF6 using in-situ Mass Spectrometry”, T. Gougousi, Y.Xu, J. N. Kidder, G. W. Rubloff, and C. Tilford, J. Vac. Sci. Technol. B (submitted).
“Real-time, in-situ film thickness metrology in a 10 Torr W chemical vapor deposition process using an acoustic sensor”, L. Henn-Lecordier, J. N. Kidder, Jr., and G. W. Rubloff, J. Vac. Sci. Technol. B 21 (3), 1055-1063 (May/Jun 2003).
“In-situ chemical sensing in AlGaN/GaN high electron mobility transistor metalorganic chemical vapor deposition process for real-time prediction of product crystal quality and advanced process control”, Soon Cho, Gary W. Rubloff, Michael E. Aumer, Darren B. Thomson, Deborah P. Partlow, Rinku Parikh, and Raymond A. Adomaitis, J. Vac. Sci. Technol. B 23 (4), 1386-1397 (Jul/Aug 2005).
“In-situ mass spectrometry in a 10 torr W chemical vapor deposition process for film thickness metrology and real-time advanced process control”, Soon Cho, Laurent Henn-Lecordier, Yijun Liu, and Gary W. Rubloff, J. Vac. Sci. Technol. B 22(3) 880-887 (MayJun 2004).
Simulation-based learning systems (1993-2000)
Working closely with the Human-Computer Interaction Laboratory (HCIL, www.cs.umd.edu/hcil/), we have created a versatile platform for active learning in science and engineering. The platform (SimPLE) couples a rich user environment to a variety of simulation engines (MatLab, VisSim, Excel, etc.) so that learners in semiconductor manufacturing, transportation systems, computer science, hydrology and other domains can explore system behavior at various levels of depth. The environments include powerful learning tools, e.g. a learning historian, active guidance material, animated visualization, etc. Examples:
Center for Engineered Learning Systems (CELS) at www.isr.umd.edu/CELS/
“Simulation Based Learning Environments and the Use of Learning Histories”, A. Rose, R. Salter, S. Keswani, N. Kositsyna, C. Plaisant, G. Rubloff, and B. Shneiderman, Extended Proceedings of the ACM Conference on Human Factors and Computing Systems (CHI’2000), Den Haag, April 2000.
“Some Dynamic-Simulator-Based Control Education Modules”, R. Sreenivasan, W. S. Levine, and G. W. Rubloff, Proc. Of American Control Conference, June 28-30, 2000, Chicago, IL, vol. 5, pp. 3458-3462 (2000).
“Education in Semiconductor Manufacturing Processes through Physically-Based Dynamic Simulation”, G. Brian Lu, Mansour Oveissi, David Eckard, and Gary W. Rubloff, Proc. 1996 Frontiers in Education Conference, Nov. 6-9, 1996, Salt Lake City, Utah (IEEE Service Center, Piscataway, NJ, 1996), ISBN 96CH35946, pp. 250-253.
SemiZone CP1102: Science and Operation of Vacuum Systems, www.semizone.com
Dynamic simulation of process and equipment systems (1993-2000)
A methodology has been developed to capture the physics and chemistry underlying semiconductor process and equipment systems in dynamic simulators, allowing the user to experiment freely with a virtual system whose response is quantitatively and temporally realistic. These simulators have proven to be powerful tools for: analyzing experiments; optimizing process recipes for manufacturing and environmental metrics; and designing equipment, sensor, and control components. They have also been recently integrated with logistics (discrete event) models for factory operations to address process/operations tradeoffs. And they have been integrated into advanced software environments to create self-contained learning modules for manufacturing education and training. Examples:
“Polysilicon RTCVD Process Optimization for Environmentally-Conscious Manufacturing”, G. Lu, M. Bora, and G. W. Rubloff, IEEE Trans. Semicond. Manuf. 10 (3), 390-398 (August 1997).
“Contamination Control for Gas Delivery from a Liquid Source in Semiconductor Manufacturing”, G. Lu, G. W. Rubloff, and J. Durham, IEEE Trans. Semicond. Manuf. 10 (4), 425-432 (Nov., 1997).
“Evaluating the Impact of Process Changes on Cluster Tool Performance”, J. W. Herrmann, N. Chandrasekharan, B. F. Conaghan, M-Q Nguyen, G. W. Rubloff, and R. Z. Shi, IEEE Trans. Semicond. Manuf. 13 (2), 181-192 (May 2000).
Chemical mechanisms and film properties in CVD (1992-1996)
Initial surface or gas phase reaction steps can be critical in determining film properties, particularly topography. For ozone/TEOS CVD, initial gas phase reaction forms a critical deposition precursor which enables high film conformality over submicron 3-D features. Nucleation-controlled growth at surface defects under selective growth conditions permits the formation of rough polysilicon films suitable for use in enhanced surface area capacitors for DRAM applications. And in W CVD on Si from H2/WF6 , initial reaction consumes (etches) surface Si and releases SiF4 product. Examples:
“Role of Gas Phase Reactions in Sub-Atmospheric CVD Ozone/TEOS Processes for Oxide Deposition”, I. Shareef, G. W. Rubloff, and W. N. Gill, J. Vac. Sci. Technol. B 14(2), 772-774 (Mar/Apr 1996).
“CVD Growth of Rough-Morphology Silicon Films over a Broad Temperature Range”, S. S. Dana, M. Anderle, G. W. Rubloff, and A. Acovic, Appl. Phys. Lett. 63 (10), 1387-89 (6 Sept. 1993).
“Apparatus for Directional Low Pressure Chemical Vapor Deposition (DLPCVD)”, G. W. Rubloff and J. J. Hsieh, U.S. Patent No. 5,290,358, issued March 1, 1994.
Multichamber processing and analysis (1978-1994)
A research strategy has been devised and exploited for combining semiconductor process steps with analytical techniques of surface science in UHV-controlled multichamber environments, so that ultraclean process conditions enable a high degree of chemical control of the processes while in-situ surface analysis provides powerful insight into process mechanisms. This work began on metal/Si and silicide/Si interfaces, extended to metal/polymer interfaces, and reached a major milestone in its success with chemical processes (oxidation and CVD) involving gas phase reactants. The approach also served effectively as a research prototype for the dominant industry trend to cluster (multichamber) processing. Examples:
“Integrated Processing for Microelectronics Science and Technology”, G. W. Rubloff and D. T. Bordonaro, IBM J. Res. Devel. 36 (2), 233-276 (1992).
“Motive Structure for Transporting Workpieces”, M. Renier, S. M. Gates, M. Liehr, and G. W. Rubloff, U.S. Patent No. 4,794,863, issued January 3, 1989.
Ultraclean, integrated MOS processing and defect microchemistry(1987-92)
Device quality thermal SiO2 structures have been fabricated under UHV-clean conditions to investigate chemical systematics which affect electrical properties. SiO formation at the surface from trace oxygen species or at the Si/SiO2 interface upon annealing degrades quality, and can be prevented by appropriate surface cleaning/passivation before oxidation and by adding sufficient trace oxygen during the process sequence. This work provides a clear picture and guideline for contamination control strategies in manufacturing. Examples:
“Defect Microchemistry at the SiO2/Si Interface”, G. W. Rubloff, K. Hofmann, M. Liehr, and D. R. Young, Phys. Rev. Lett. 58, 2379 (1987).
“Post-Oxidation Anneal of Silicon Dioxide”, K. Hofmann, G. W. Rubloff, and D. R. Young, U.S. patent no. 4,784,975, issued November 15, 1988.
“Integrated Processing of MOS Gate Dielectric Structures”, G. W. Rubloff, M. Offenberg, and M. Liehr, IEEE Trans. Semi. Manuf. 7 (1), 96-100 (Feb, 1994).
“Surface etching and roughening in integrated processing of thermal oxides”, M. Offenberg, M. Liehr, and G. W. Rubloff, J. Vac. Sci. Technol. A 9 (3), 1058 (1991).
Metal/polymer interfaces and polymer surfaces (1983-86)
Surface analysis, complemented by molecular orbital calculations, revealed for the first time the importance of interfacial diffusion of metal atoms into polymer, competition between metal in-diffusion and strong chemical bonding/reaction at the metal/polymer interface, and the reversible adsorption/absorption/desorption of water at the polymer surface. Examples:
“Chemical Bonding at the Polyimide Surface”, P. Hahn, G. W. Rubloff, and P. S. Ho, J. Vac. Sci. Technol. A 2, 756 (1984).
“Chemical Bonding and Reaction at Polymer Surfaces and Metal/Polymer Interfaces”, P. S. Ho, P. O. Hahn, G. W. Rubloff, F. K. LeGoues, and D. Silverman, J. Vac. Sci. Tech. A 3, 739 (1985).
“Enhanced Adhesion Between Metals and Polymers”, P. S. Ho, P. O. Hahn, H. Lefakis, and G. W. Rubloff, U.S. Patent No. 4,720,401, issued January 19, 1988.
Metal/Si and silicide/Si interfaces (1978-86)
UHV in-situ interface formation and surface analysis provided the first direct identification of interfacial silicide formation on a microscopic/atomic scale, revealing: (i) chemical trends in reactivity across the transition-metal series; (ii) the role of low temperature reactivity at the interface and the competition between other material reactions and silicide formation during growth and at the interface; (iii) the early stages of Schottky barrier formation; (iv) the correlation of initial and final electrical barrier characteristics with interfacial chemistry; (v) the role of controlled interfacial contaminants in modifying interface properties; (vi) the electronic structure of bulk silicide compounds. Examples:
“Chemical Bonding and Reactions at the Pd/Si Interface”, G. W. Rubloff, P. S. Ho, J. L. Freeouf, and J. E. Lewis, Phys. Rev. B15 23, 4183 (1981).
“Interface States at the Pt-Silicide/Si Interface”, G. W. Rubloff, Phys. Rev. B15 25, 4307 (1982).
“Schottky Barrier Formation at Pd/Si(111) and V/Si(111) Interfaces”, R. Purtell, J. G. Clabes, G. W. Rubloff, P. S. Ho, B. Reihl, and F. J. Himpsel, J. Vac. Sci. Technol. 21, 615 (1982).
“Chemical Reactions at Pt/oxide/Si and Ti/oxide/Si Interfaces”, M. Liehr, F. LeGoues, G. W. Rubloff, and P. S. Ho, J. Vac. Sci. Tech. A 3, 983 (1985).
“Low Temperature Material Reaction at the Ti/Si(111) Interface”, R. M. Tromp, G. W. Rubloff, and E. J. van Loenen, J. Vac. Sci. Technol. A 4, 865 (1986).
Novel applications of diagnostics and experimental methods (1986-93)
Positron annihilation spectroscopy (with Brookhaven) has demonstrated the existence of microvoids in thermal oxides in MOS device structures. Picosecond ultrasonic laser techniques (with Brown U.) have revealed technologically important phenomena at buried interfaces, including the formation of silicide compounds and the presence of ultrathin (3-5 Å) fluorocarbon contaminants as present in etch residues. Pulsed gas dosing methods have been demonstrated for time-resolved surface studies at reaction temperatures. Pulsed laser induced photoemission has been proposed for time-resolved voltage/waveform measurements of high speed chips. Examples:
“Microvoids at the SiO2/Si Interface”, B. Nielsen, K. G. Lynn, D. O. Welch, T. C. Leung, and G. W. Rubloff, Phys. Rev. B 40, 1434 (1989).
“Nondestructive detection of titanium disilicide phase transformation by picosecond ultrasonics”, H.-N. Lin, R. J. Stoner, H. J. Maris, J. M. E. Harper, C. Cabral, Jr., J.-M. Halbout, and G. W. Rubloff, Appl. Phys. Lett. 61 (22), 2700 (1992).
“Noninvasive picosecond ultrasonic detection of ultrathin interfacial layers: CFx at the Al/Si interface”, G. Tas, R. J. Stoner, H. J. Maris, G. W. Rubloff, G. S. Oehrlein, and J. M. Halbout, Appl. Phys. Lett. 61 (15), 1787 (1992).
“Photoemission Studies of Time-Resolved Surface Reactions: Isothermal Desorption of CO from Ni(111)”, G. W. Rubloff, Surface Science 89, 566 (1979).
“Fundamentals of Laser Photoemission for Testing High Speed Devices and Circuits”, G. W. Rubloff and H. Beha, Characterization of Very High Speed Semiconductor Devices and Circuits, Ravi Jain, Editor, SPIE Vol. 795, p. 256 (1987).
“Photon Assisted Tunneling Testing of Passivated Integrated Circuits”, H. Beha, R. W. Dreyfus, A. M. Hartstein, and G. W. Rubloff, U.S. Patent No. 4,644,264, issued Feb. 17, 1987.
“Noncontact Dynamic Tester for Integrated Circuits”, H. Beha, R. W. Dreyfus, and G. W. Rubloff, U.S. Patent No. 4,706,018, issued November 10, 1987.
“Full Chip Integrated Circuit Tester”, H. Beha, R. W. Dreyfus, and G. W. Rubloff, U.S. Patent No. 4,703,260, issued October 27, 1987.
Organic molecule reactions on metal and oxide surfaces (1975-78)
These surface spectroscopy studies revealed the patterns of chemical bonding and reaction of small organic molecules on transition-metal and oxide surfaces, including the first such studies on oxide surfaces. Examples:
“Ultraviolet-Photoemission Studies of Formic Acid Decomposition on ZnO Nonpolar Surfaces”, H. Luth, G. W. Rubloff, and W. D. Grobman, Solid State Commun. 18, 1427 (1976).
“Chemisorption of Organic Molecules on ZnO(1100) Surfaces: C5H5N, (CH3)2CO and (CH3)2SO”, H. Luth, G. W. Rubloff, and W. D. Grobman, Surface Science 74, 365 (1978).
“Ultraviolet Photoemission and Flash Desorption Studies of the Chemisorption and Decomposition of Methanol on Ni(111)”, G. W. Rubloff and J. E. Demuth, J. Vac. Sci. Technol. 14, 419 (1977).
“Chemisorption and Decomposition Reactions of Oxygen-Containing Organic Molecules on Clean Pd Surfaces Studied by UV Photoemission”, H. Luth, G. W. Rubloff, and W. D. Grobman, Surface Science 63, 325 (1977).
Optical studies of solids and surfaces (1968-78)
These studies began with high precision reflectometry development and its application to among the first applications of synchrotron radiation to solid state physics, showing core level excitons in ionic materials. They continued to modulation spectroscopy and stress-dependent Raman spectroscopy. The reflectometry methods were then applied to submonolayer chemisorption. Examples:
“Far-Ultraviolet Reflectance Spectra of Ionic Crystals”, G. W. Rubloff, J. Freeouf, H. Fritzsche, and K. Murase, Phys. Rev. Lett. 26, 1317 (1971).
“Piezo-optical Evidence for Transitions at the 3.4 eV Optical Structure of Silicon”, F. H. Pollak and G. W. Rubloff, Phys. Rev. Lett. 29, 789 (1972).
“Resonance Raman Scattering in InAs near the E1 Gap”, G. W. Rubloff, E. Anastassakis, and F. H. Pollak, Solid State Commun. 13, 1755 (1973).
“Optical Reflectance Spectroscopy of Surface States in H2 Chemisorption on W(100)”, G. W. Rubloff, J. Anderson, M. A. Passler, and P. J. Stiles, Phys. Rev. Lett. 32, 667 (1974).