Ralf Brederlow

A 128 128 CMOS Biosensor Array for Extracellular Recording of Neural Activity

Sensor arrays are a key tool in the field of neuroscience for noninvasive recording of the activity of biological networks, such as dissociated neurons or neural tissue. A high-density sensor array complementary metal–oxide–semiconductor chip is presented with 16 K pixels, a frame rate of 2 kiloframes per second, and a pitch of 7.8 m 7.8 m for imaging of neural activity. The related circuit and system issues as well as process aspects are discussed. A mismatch-canceling calibration circuitry with current mode signal representation is used. Results from first biological experiments are presented, which prove full functionality of the chip.

A 128 /spl times/ 128 CMOS bio-sensor array for extracellular recording of neural activity

A CMOS sensor array for monitoring neural signals of living cells with 128 /spl times/ 128 pixels in a 1 mm/sup 2/ area is described. A standard 0.5 /spl mu/m, 5 V CMOS process extended by top electrodes covered by a relatively thin bio-compatible dielectric is used. Detection circuitry is based on a sensor-MOSFET mismatch-compensating current-mode technique.

A mixed-signal design roadmap

The article presents a roadmap for the 2001 International Technology Roadmap for Semiconductors. It uses performance figures of merit (FoMs) derived from basic circuits critical to mixed-signal design performance. Extrapolations from the FoMs to future performance values establish the device parameters necessary for design progress.

A low-power true random number generator using random telegraph noise of single oxide-traps

A true random number generator is realized by utilizing the noise produced by single oxide traps in small-area MOSFETs in combination with built-in redundancy. The circuit has an area of 0.009mm2 in 0.12mum CMOS and consumes 50muW at 200kb/s random output data. The concept is robust against environmental noise and supply-voltage variations and is thus suitable for operation within security controllers

Biochemical sensors based on bulk acoustic wave resonators

A new general purpose approach for a sensor based on a mass-weighting principle has been developed. This concept offers the advantage to replace a complex and expensive optical system by a low-cost electronic readout system. In contrast to all established sensor principles the system only depends on the availability of specific probe molecules attached at the surface. The biochemical sensor principle is based on a film bulk acoustic wave resonator which detects mass differences on a biochemical prepared surface.

On the degradation of p-MOSFETs in analog and RF circuits under inhomogeneous negative bias temperature stress

The effect of inhomogeneous Negative Bias Temperature Stress (NBTS) applied to p-MOS transistors under analog and RF CMOS operating conditions is investigated. Experimental data of a 0.18 /spl mu/m standard CMOS process are presented and an analytical model is derived to physically explain the effect of stress on the device characteristics. The impact of inhomogeneous NBTS on device lifetime is considered and compared to the homogeneous case.

Device reliability in analog CMOS applications

A comprehensive discussion is performed of MOSFET reliability under analog operation taking into account channel hot-carrier (CHC) stress, bias temperature (BT) instabilities, hard and soft breakdown and SILC. The conditions for the occurrence of these mechanisms and criteria for stress induced malfunction of analog circuits are discussed including the physics behind the behavior of typical analog device parameters after CHC and BT stress.

Low-frequency noise of integrated polysilicon resistors

This paper presents an analytical first principle model for the low-frequency noise current of polysilicon layers used as resistors in analog CMOS applications. The observed noise is much higher than predicted by the models mostly used in circuit simulation. The dependence on specific processing parameters such as doping or deposition techniques are investigated and explained. The model is confirmed by measurement of deviations in the flicker noise behavior of small size resistors. Guidelines for analog circuit design and a noise model for circuit simulation are presented.

AC-only RF ID tags for barcode replacement

An RF ID concept using ac-powered circuits without DC conversion is demonstrated for barcode replacement. A 32b codeword ID tag including an RF front-end, voltage limiter, frequency divider, ROM and power modulator has a 0.02mm/sup 2/ area in a 0.13/spl mu/m CMOS process. A packaging technology uses a sidewall contact to facilitate the assembly process.

Explanation and quantitative model for the matching behaviour of poly-silicon resistors

We investigate the matching behaviour of poly-silicon resistors. Experimental results from an analog CMOS process with three poly-silicon options are discussed and compared with a quantitative model which is developed using fit parameter-free analytical calculations and Monte-Carlo simulations. It is found that mismatch is directly proportional to the grain size. A relation is derived that allows us to optimize devices for low mismatch circuit applications.