Stewart Smith

Serial-data computation

1: Introduction.- The case for serial-data techniques.- The case against serial-data techniques.- Historical overview of bit-serial techniques.- Final comments.- 2: The First Generation.- FIRST.- The FIRST primitive set.- Bit-serial systems design.- Case study.- FFT subsystem design.- Filterbank subsystem design.- System specifications.- Initial design issues and decisions.- Functional design - the soft model.- Physical design - the hard model.- Test strategy and confidence levels.- A critical appraisal of FIRST.- 3: Rudiments.- Issues of space and time.- Control.- Twos complement integer coding.- Fundamental building blocks - the atoms.- Numerical principles of serial-data additive operations.- Partitioning issues.- 4: Twos Complement Multiplication.- Derivation from bit-parallel architectures.- Scrutiny of two serial-data multipliers.- Word-level equivalent architectures.- Comparison of the S/P and Lyon multipliers.- Serial/parallel multiplier environments.- Other approaches.- 5: Area-Saving Techniques.- Overview of vector computation.- Symmetric-coded serial/parallel muiltiplier.- Serial/parallel inner-product computer.- Architectural case studies.- Architectural synthesis.- Distributed arithmetic in context.- Cascading DA modules.- Incremental computation of squares/sums of squares.- Final comments.- 6: Throughput Enhancement.- Twin-pipe.- Radix-4.- Multi-precision.- Interfacing between operational domains.- The automultiplier.- Final comments.- 7: The Second Generation.- Process-independence.- Overview of SECOND.- PRIMITIVE specification (design capture).- PRIMITIVE verification (behavioural simulation).- Semi-custom PRIMITIVE implementation.- Custom PRIMITIVE implementation.- Other approaches.- Final comments.- 8: Concluding Remarks.- References.- Appendix A - Complex Multiplier.- Appendix B - Logic Synthesis.

Sheet resistance measurement of non-standard cleanroom materials using suspended Greek cross test structures

This paper presents work on the development, fabrication and characterization of a suspended Greek cross measurement platform that can be used to determine the sheet resistance of materials that would contaminate Complementary Metal Oxide Semiconductor (CMOS) processing lines. The arms of the test structures are made of polysilicon/silicon nitride (Si/sub 3/N/sub 4/) to provide a carrier for the film to be evaluated and thick aluminum (Al) probe pads for multiple probing. The film to be evaluated is simply blanket deposited onto the structures and because of its design automatically forms a Greek cross structure with (Al) probe pads. To demonstrate its use, 1) gold (Au), 2) copper (Cu), and 3) silver(Ag) loaded chalcogenide glass Ag/sub y/(Ge/sub 30/Se/sub 70/)/sub 1-y/ have been blanket evaporated in various thicknesses onto the platform in the last processing step and autopatterned by the predefined shape of the Greek crosses. The suspension of the platform ensured electrical isolation between the test structure and the surrounding silicon (Si) substrate. The extracted effective resistivity for Au (5.1/spl times/10/sup -8/ /spl Omega//spl middot/m), Cu (1.8- 2.5/spl times/10/sup -8//spl bsol/ /spl Omega//spl middot/m) and Ag/sub y/(Ge/sub 30/Se/sub 70/)/sub 1-y/ (2.27/spl times/10/sup -5/ /spl Omega//spl middot/m-1.88 /spl Omega//spl middot/m) agree with values found in articles in the Journal of Applied Physics (1963), the Journalof Physics D: Applied Physics (1976), and the Journalof Non-Crystalline Solids (2003). These results demonstrate that the proposed Greek cross platform is fully capable to measure the sheet resistance of low (Au, Cu) and high Ag/sub y/(Ge/sub 30/Se/sub 70/)/sub 1-y/ resistive materials.

A microfluidic system for studying ageing and dynamic single-cell responses in budding yeast.

Recognition of the importance of cell-to-cell variability in cellular decision-making and a growing interest in stochastic modeling of cellular processes has led to an increased demand for high density, reproducible, single-cell measurements in time-varying surroundings. We present ALCATRAS (A Long-term Culturing And TRApping System), a microfluidic device that can quantitatively monitor up to 1000 cells of budding yeast in a well-defined and controlled environment. Daughter cells are removed by fluid flow to avoid crowding allowing experiments to run for over 60 hours, and the extracellular media may be changed repeatedly and in seconds. We illustrate use of the device by measuring ageing through replicative life span curves, following the dynamics of the cell cycle, and examining history-dependent behaviour in the general stress response.

Evaluation of sheet resistance and electrical linewidth measurement techniques for copper damascene interconnect

The effects of the barrier layer and dishing in copper interconnects lead to extra difficulties in measuring sheet resistance (R/sub S/) and linewidth when compared with equivalent measurements on nondamascene tracks. This paper examines these issues and presents the results of simulations that quantify the effects of diffusion barrier layers and dishing on the extraction of R/sub S/ from cross type test structures and the effect this has on linewidth measurement.

The First Generation

Serial-data computational techniques have exciting implementation potential in the light of recent advances in technology for the fabrication of VLSI integrated circuits. There now exists the possibility to realise complex real-time computational algorithms which were previously of only theoretical interest [50]. Many of these algorithms are suitable for execution by dedicated pipelines of serial-data processors in compact VLSI architectures. However with the integration of hundreds of thousands of devices on a single silicon surface arises the considerable likelihood of implementation errors — a ‘complexity crisis’ confronts VLSI designers [113]. To combat complexity, structured design styles and software tools [63, 109] have emerged, culminating in the structural silicon compiler [10, 50]. Structural silicon compilers guarantee working parts from high-level structural descriptions, through automatic assembly of known-good modules by known-good techniques. Low-level design errors are avoided by forcing the designer to follow this route.

Dielectrophoresis based discrimination of human embryonic stem cells from differentiating derivatives

Assessment of the dielectrophoresis (DEP) cross-over frequency (f xo), cell diameter, and derivative membrane capacitance (C m) values for a group of undifferentiated human embryonic stem cell (hESC) lines (H1, H9, RCM1, RH1), and for a transgenic subclone of H1 (T8) revealed that hESC lines could not be discriminated on their mean f xo and C m values, the latter of which ranged from 14 to 20 mF/m(2). Differentiation of H1 and H9 to a mesenchymal stem cell-like phenotype resulted in similar significant increases in mean C m values to 41-49 mF/m(2) in both lines (p < 0.0001). BMP4-induced differentiation of RCM1 to a trophoblast cell-like phenotype also resulted in a distinct and significant increase in mean C m value to 28 mF/m(2) (p < 0.0001). The progressive transition to a higher membrane capacitance was also evident after each passage of cell culture as H9 cells transitioned to a mesenchymal stem cell-like state induced by growth on a substrate of hyaluronan. These findings confirm the existence of distinctive parameters between undifferentiated and differentiating cells on which future application of dielectrophoresis in the context of hESC manufacturing can be based.

Implementation of wireless power transfer and communications for an implantable ocular drug delivery system

A wireless power transfer and communication system based on near-field inductive coupling has been designed and implemented. The feasibility of using such a system to remotely control drug release from an implantable drug delivery system is addressed. The architecture of the wireless system is described and the signal attenuation over distance in both water and phosphate buffered saline is studied. Additionally, the health risk due to exposure to radio frequency (RF) radiation is examined using a biological model. The experimental results demonstrate that the system can trigger the release of drug within 5 s, and that such short exposure to RF radiation does not produce any significant (<or= 1 degrees C) heating in the biological model. The conclusion of the work is that this system could replace a chemical battery in an implantable system, eliminating the risks associated with battery failure and leakage and also allowing more compact designs for applications such as drug delivery.

Comparison of electrical and SEM CD measurements on binary and alternating aperture phase-shifting masks

Many of the recent advances in optical lithography have been driven by the utilization of complex photomasks using optical proximity correction (OPC) or phase-shifting technologies. These masks are difficult and expensive to manufacture so the ability to test and characterize the mask making process is very important. This paper examines the issues involved in the use of relatively low-cost electrical critical dimension (ECD) measurement of mask features. Modified cross-bridge test structures have been designed to allow the on-mask measurement of dense and isolated, binary and phase-shifted layouts. The results of electrical and critical dimension scanning electron microscope (CD-SEM) testing of these structures are presented and indicate the lower variability associated with ECD measurements. In particular the adverse effect of phase-shifting elements on the accuracy of SEM measurements is highlighted.

Techniques to increase the computational throughput of bit-serial architectures

Three architectural techniques are reported, which accelerate bit-serial computation without compromising its favourable advantages. In essence these techniques rely on multi-wire representations of serial data - a step towards bit-parallelism. Interfacing techniques are developed to support the existence of domains of different throughput within a system, thereby enhancing the range of bandwidth-matching techniques available to the systems designer. These techniques also realise the potential to mix processing wordlengths within a serial-data system.

Dielectrophoretic Characterisation of Mammalian Cells above 100 MHz

Abstract Dielectrophoresis (DEP) is a label-free technique for the characterization and manipulation of biological particles - such as cells, bacteria and viruses. Many studies have focused on the DEP cross-over frequency fxo1, where cells in a non-uniform electric field undergo a transition from negative to positive DEP. Determination of fxo1 provides a value for the membrane capacitance from the cell diameter, the means to monitor changes in cell morphology and viability, and the information required when devising DEP cell separation protocols. In this paper we describe the first systematic measurements of the second DEP cross-over frequency fxo2 that occurs at much higher frequencies. Theory indicates that fxo2 is sensitive to the internal dielectric properties of a cell, and our experiments on murine myeloma cells reveal that these properties exhibit temporal changes that are sensitive to both the osmolality and temperature of the cell suspending medium.