Kei Ikeda

Ion Current Density and Ion Energy Distributions at the Electron Cyclotron Resonance Position in the Electron Cyclotron Resonance Plasma

Extremely highly selective phosphorus-doped polycrystalline silicon etching is achieved at the electron cyclotron resonance (ECR) position in a newly developed ECR plasma etching system. To characterize these etching results, the ion current density and the ion energy distribution in a ECR plasma are measured. Microwave power is absorbed completely at the ECR position. Therefore, the ECR position has maximum ion current density in an ECR plasma. Moreover, the mean ion energy and the width of ion energy distribution has minimum values at the ECR position. The ECR position in the ECR plasma can satisfy a high ion current density and a low ion energy at the same time. These characteristics correspond to the etching results.

A scalable time-domain biosensor array using logarithmic cyclic time-attenuation-based TDC for high-resolution and large-scale bio-imaging

This paper presents a time-domain biosensor array that uses a capacitor-less current-mode analog-to-time converter (CMATC) and logarithmic cyclic time-attenuation-based TDC with discharging acceleration. Combining the exponential function of the CMATC and logarithmic function of the proposed TDC offers linear input-output characteristics. The time-domain property enables bio-imaging at a high spatial resolution and large scale while maintaining scalability. Measurement results with a 0.25-μm test chip successfully demonstrated linear input-output characteristics.

Energy-efficient and low-voltage design methodology for a supply-sensing CMOS biosensor using biofuel cells for energy-autonomous healthcare applications

The power sources of wearable sensors play a key role in sensing-system architecture. As potential power sources for sensors monitoring physiological signals near the human body, biofuel cells, which generate energy from the biological environment through chemical methods, have attracted much attention. However, the insufficient open-circuit voltage of biofuel cells owing to thermodynamic limitation is a basic issue. Thus, the use of biofuel cells as a power supply for a sensor imposes a strict limitation upon the power budget. In this report, we propose a design methodology for a low-voltage supply-sensing CMOS biosensor using biofuel cells. To explore the design methodology for performance optimization, a SPICE simulation was conducted. The simulated results reveal an optimum energy-efficient point in the biosensor design parameters. A fabricated 250 nm CMOS test chip was used to verify the validity of the design methodology and the measurement results matched the simulated results.

Design, experimental verification, and analysis of a 1.8-V-input-range voltage-to-current converter using source degeneration for low-noise multimodal CMOS biosensor array

A multimodal complementary metal–oxide semiconductor (CMOS) biosensor array manufactured using measurement methods such as potentiometry, amperometry, and impedimetry improves its cost competitiveness and measurement accuracy. In addition, it provides a wider range of application because it can obtain signals from multiple aspects. To develop high-signal-to-noise ratio (SNR) multimodal biosensor arrays, time-domain current integration was proposed in the literature and found to be effective. In addition to amperometry and impedimetry, it is possible to perform current integration using the potentiometry output by employing a voltage-to-current converter (VCC). However, a conventional VCC with a fixed transconductance mode does not provide a sufficient input range (<0.6 V) and its noise property has not been investigated. In this work, we investigate the design and noise property of a newly proposed VCC with source degeneration that enhances the input range. For evaluating the proposed method, a test chip was fabricated in a 0.6 µm CMOS. The measured results successfully demonstrate that the input range was enhanced from 0.6 to 1.8 V. Autonomous current limitation was also confirmed. The measured total input-referred noise was 0.445 mV (from 10 Hz to 10 kHz, assuming current integration at every 1 ms).

Ion Energy Distributions at the Electron Cyclotron Resonance Position in Electron Cyclotron Resonance Plasma

The extremely high selective phosphorus-doped polycrystalline silicon etching is achieved at the electron cyclotron resonance (ECR) position in a new developed ECR plasma etching system. To characterize these etching results, the ion energy distribution in an ECR plasma is measured. The mean ion energy and the width of ion energy distribution decrease as they near the ECR position. The ECR position in the ECR plasma has a high ion current density and low ion energy at the same time. These characteristics correspond to the etching results.

Design of an energy-autonomous bio-sensing system using a biofuel cell and 0.19V 53μW integrated supply-sensing sensor with a supply-insensitive temperature sensor and inductive-coupling transmitter

This paper presents an energy-autonomous bio-sensing system with the capability of wireless communication. The proposed system includes a biofuel cell as a power source and sensing frontend associated with the integrated supply-sensing sensor. The sensor consists of a digital-based gate leakage timer, supply-insensitive time-domain temperature sensor, and inductive-coupling transmitter. A test chip using 65-nm CMOS technology was operated with a supply of 0.19 V and consumed 53 μW to successfully demonstrate wireless communication with an asynchronous receiver.

A current-mode analog-to-time converter with short-pulse output capability using local intra-cell activation for high-speed time-domain biosensor array

This study demonstrates a current-mode analog-to-time converter (CMATC) enabling short-pulse output capability by using the newly-proposed local intra-cell activation technique, which contributes to the development of high-speed time-domain biosensor array. In the conventional CMATC, the activation pulse is generated globally at the periphery. This limits the output pulse width because of the considerable parasitic word-line capacitance. In this study, a shorter pulse output was achieved by generating the activation pulse locally by using intra-cell configuration without being affected by word-line capacitances. In 1024 × 1024 configuration, 77% pulse width reduction was confirmed using SPICE simulation. A test chip was fabricated using a 0.6 μm standard CMOS process. The measurement results obtained using a sensor chip demonstrate the expected input-output characteristic and 3.36 ns pulse output.

An energy-autonomous bio-sensing system using a biofuel cell and 0.19V 53μW 65nm-CMOS integrated supply-sensing sensor with a supply-insensitive temperature sensor and inductive-coupling transmitter

This paper presents an energy-autonomous bio-sensing system with the capability of proximity communication. The proposed biosensor includes a bio-fuel cell as a power source and sensing front-end associated with the integrated supply-sensing sensor. The sensor consists of a digital-based gate leakage timer, supply-insensitive time-domain temperature sensor, and current-driven inductive-coupling transmitter and achieves low-voltage operation. The timer converts the output supply-voltage from a bio-fuel cell to period output. The supply-insensitive temperature sensor provides PWM output without dependency of the supply voltage. The following inductive-coupling transmitter enables proximity communication. A test chip using 65-nm CMOS technology was operated with a supply of 0.19 V and consumed 53 μW to successfully demonstrate proximity communication with an asynchronous receiver. The measurement results show the possibility of energy-autonomous operation using bio-fuel cells.

Live demonstration: Current-mode analog-to-time converter for a large scale CMOS biosensor array

A real-time quantitative biosensing system that anyone can use anywhere is a key technology for the development of a point-of-care testing (POCT) system for health-care and biochemical research applications. There are two methods for emerging real-time quantitative biosensing: optical and electrical methods. Electrical methods do not require fluorescent labeling, and thus, it is cheaper, faster, smaller, and more accurate than optical methods. In particular, on-chip measurement using a large-scale biosensor array exploits the advantages of highly-integrated CMOS circuits, realizes multi-biomolecular detection and improves the accuracy statistically.