A simple mask aligner and printing frame for conformable photomask lithography

Conformable photomask lithography allows submicrometer lines to be replicated by contact printing. Surface acoustic wave devices with 0.4-µm lines have been produced using this technique. A mask aligner and printing frame have been designed which feature micrometer controlledXandYmotion, rotation about the center of the viewing field, and both top and bottom illumination of mask and substrate. The construction and use of the apparatus, which is based on a toolmaker's microscope, is fully described.     

A novel offset gated polysilicon thin film transistor without anadditional offset mask

We have proposed a novel offset gated polysilicon TFT fabricated without an offset mask in order to reduce leakage current and suppress the kink effect. The photolithographic process steps of the new TFT device are identical to those of conventional non-offset structure TFT's and an additional mask to fabricate an offset structure is not required in our device. The new device has demonstrated a lower leakage current and a better ON/OFF current ratio compared with the conventional non-offset device. The novel TFT also exhibits a considerable reduction in the kink effect because a very thin film TFT may be easily fabricated due to the elimination of the contact over-etch problem     

Reduction of CD variance by using optical proximity correction for patterning with DUV phase shift mask

Critical dimension (CD) variation with the use of attenuated phase shift mask (PSM) at 248nm wavelength has been simulated and analyzed. Optical proximity effect was found to be severe and can take up the whole CD error budget for 0.25μm process. PSM/OPC conversion rules were developed for a test pattern. Two rules-based automated PSM/OPC conversion programs, one of them with hierarchy management, were used. Bias between isolated and nested features was significantly reduced with the correction. Issues concerning computation time and data multiplication are also discussed.     

A new photoreceiver concept using InGaAs-transferred-electrondevices

A new optical receiver is proposed incorporating an InGaAs-transferred-electron device with Schottky gate-electrode (STED) and an InGaAs-metal-semiconductor-metal detector (MSM). This photoreceiver is applicable to the detection of digital, intensity modulated signals and can be integrated on an InP-substrate. The monolithically integrated circuit has been fabricated. Both the integrated STED and the MSM detector has been characterized. From the measurements the receiver can be expected to offer high current gain and inherent pulse shaping. Based on experiments the sensitivity and the gain of the photoreceiver as a function of the bit-rate has been calculated     

A vertical submicron polysilicon thin-film transistor using a lowtemperature process

This letter presents a submicron (0.5 μ) vertical N-channel MOS thin-film transistor (TFT) fabricated in Polycrystalline Si using a simple low temperature process (⩽600°C). The channel length is determined by the thickness of an SiO₂ film. As a result, submicron vertical polysilicon TFT's can be fabricated without submicron lithographic equipment that is not yet available for large area active matrix liquid crystal display (AMLCD) applications. The device has a dynamic range of greater than five orders of magnitude after hydrogenation     

A new MOS-gate bipolar transistor for power switches

A new monolithic integrated power device, the MOS-gate transistor (MGT), which consists of a bipolar transistor for an output stage and two MOSFET's for a driver stage, has been investigated. The purpose of the study was to obtain a power switch having characteristics of an easy drive, a short turn-off time, and a high current density. The developed device structure featured the integration of three elements into a small cell from a large number of which the MGT chip was constructed. This device had no parasitic thyristor, making it free from the latchup phenomenon. Unit MGT devices with a blocking voltage of 400-500 V were fabricated. A high current density of 90 A/cm²at a collector-emitter voltage of 2 V and a short turn-off time of less than 1 µs were obtained. The MGT devices, which contained 36 cells, were fabricated with chip sizes of 5 × 5 mm. They exhibited a blocking voltage of 500 V, on-state voltage of 2.3 V at a current of 10 A, and turn-off time of 0.5 µs at 150°C.     

A new trench bipolar transistor for RF applications

A new vertical trench SiGe heterojunction bipolar transistor (HBT) is proposed that improves the tradeoff between the cutoff frequency (f/sub T/) and the off-state collector-base breakdown voltage (BV/sub cbo/). Extensive device simulations show that a record f/sub T//spl middot/BV/sub cbo/ product of about 2375 GHz/spl middot/V can be obtained for an HBT having a trench field plate connected to the emitter and a linearly graded doping profile in the collector drift region, while about 700 GHz/spl middot/V can be obtained for a standard optimized HBT. This large improvement is explained mainly by the suppression of the base-widening effect.     

用灰阶编码掩模进行邻近效应校正的实验研究

利用灰阶编码掩模实现光学邻近效应精细校正是改善光刻图形质量的有效方法,设计并利用电子束直写系统加工了实现邻近效应校正的灰阶编码掩模,首次在投影光刻系统上用这一方法实现了光学邻近效应校正,获得了满意的实验结果,在可加工０．７微米的Ｉ线曝光装置上获得了经邻近效应校正的０．５微米光刻线条。     

Novel process for emitter-base-collector self-aligned heterojunction bipolar transistor using a pattern-inversion method

A process for base-emitter-collector self-aligned HBTs using a pattern-inversion method is presented. A fabricated HBT has an emitter with a size of 1.5 × 10?m2 realised by employing a dry-etching method. Typical current gain for the fabricated HBT is 26.     

A four-vacuum-cycle lift-off process for the polycrystalline CdSe thin-film transistor

A photolithographic process is described for the fabrication of the polycrystalline CdSe thin-film transistor (TFT). This process only uses four vacuum cycles and four lift-off masks, without the need of sputter cleaning to prevent contamination. The devices made have a stability similar to the ones made by the single-vacuum process.     

A new fault-management method using congestion-avoidance routing for optical burst-switched networks

Optical burst switching (OBS) has been proposed as a promising technique to support high-bandwidth, bursty data traffic in the next-generation optical Internet. This study investigates a new fault-management framework for an OBS network. In an OBS network, burst-loss performance is a critical concern. In OBS, the data-burst transmission is delayed by an offset time (relative to its burst control packet (BCP), or header), and the burst follows its header without waiting for an acknowledgment for resource reservation. Thus, a burst may be lost at an intermediate node due to contention, which is generally resolved according to the local routing and bandwidth information. The routing table maintained in each OBS node is generally pre-computed and fixed to forward the data bursts. Such a static forwarding feature might have limited efficiency to resolve contentions. Moreover, a burst may be lost and the network may be congested when a network element (e.g., fiber link) fails. Therefore, for reliable burst transport, we develop dynamic routing approaches for preplanned congestion avoidance. Our goal is to proactively avoid congestion during the route-computation process, and our approach employs wavelength-channel utilization, traffic distribution, and link-distance information in the proposed objective functions for routing. Two update mechanisms for maintaining a dynamic routing table are presented to accommodate bursty data traffic. Based on our routing mechanisms, we also propose a new congestion-avoidance-and-protection (CAP) approach, which employs a primary route and a group of backup routes for each node pair against failures and congestion. The performance of the proposed protection strategy using congestion-avoidance routing is demonstrated to be promising through illustrative numerical examples.

A new modulation scheme using asymmetric erorr-correcting codesembedded in optical orthogonal codes for optical CDMA

An embedded-modulation scheme is proposed for optical code division multiple access (CDMA). In this scheme, codewords in an asymmetric error-correcting (AEC) code is embedded in a signature sequence in an optical orthogonal code (OOC) used for identification. We classify the codewords of the AEC code according to the number of "1"s in each codeword, and then derive the bit error rate (BER) of the embedded-modulation scheme. Numerical results show that although the performance has the error floor, for achieving the floor value, the embedded-modulation scheme requires less optical energy per bit than the traditional modulation scheme with the correlation and chip-level receivers. The error floor is primarily due to multiaccess interference (MAI), we furthermore apply Reed-Solomon (RS) coding to the embedded-modulation scheme. Consequently, RS coding reduces the floor value to be negligibly small     

A stripe-geometry InGaAsP/InP heterojunction bipolar transistor suitable for optical integration

A stripe-geometry InGaAsP/InP heterojunction bipolar transistor (HBT) was fabricated for the first time. High current gain (β > 500) and high collector current (Ic> 200 mA) were obtained in devices with an emitter-down configuration. The HBT was successfully integrated with a double-heterostructure (DH) laser, resulting in the first realization of laser operation in a vertical integration.     

A new concept for supermodular alignment network

A technique is described for making alignment networks more reliable and cost effective. The proposed technique envisages minimizing the external links and reducing the propagation delay. The VLSI implementation of the network is based on the modularization concept, achieving a simple layout, flexible design, increased computational speed and high circuit, density. The dual tree topology which allows a smaller pin count for the chip is considered for the realization of the modularized network.     

A new concept for wireless reconfigurable receivers

In this article we present the Self-Adaptive Universal Receiver (SAUR), a novel wireless reconfigurable receiver architecture. This scheme is based on blind recognition of the system in use, operating on a new radio interface comprising two functional phases. The first phase performs a wideband analysis (WBA) on the received signal to determine its standard. The second phase corresponds to demodulation. Here we only focus on the WBA phase, which consists of an iterative process to find the bandwidth compatible with the associated signal processing techniques. The blind standard recognition performed in the last iteration step of this process uses radial basis function neural networks. This allows a strong analogy between our approach and conventional pattern recognition problems. The efficiency of this type of blind recognition is illustrated with the results of extensive simulations performed in our laboratory using true data of received signals.     

A new concept for microstrip-integrated GaAs Schottky-diodes

A new concept for integrated planar Schottky-diodes has been developed. It meets the two important requirements in the design of microwave diodes: high cutoff frequency and low parasitics. Only one epitaxial layer is needed. The Schottky contact is deposited on the slope of a mesa in order to obtain both low series resistance and low capacitance, Up to now, a Zero-bias cutoff frequency of 150 GHz has been achieved. The advantage of this type of diodes as compared to planar diodes produced by double selective epitaxy is the use of standard technology, resulting in good reproducibility and yield.     

A new low-temperature bonding technology between large-area,high-power devices and Mo electrodes using Au-Al films

In order to realize large-area, high-power devices with high-performance, low-temperature diffusion, bonding technology between Al electrodes on both cathode and anode sides of Si devices and Mo electrode foils has been investigated, The 100 mm diameter power devices and the same size Mo foils could be joined by the formation of Au-Al intermetallic compounds below 573 K. The compounds were formed by solid state diffusion with activation energy of about 1.0 eV. Substantial reduction of the mounting force while keeping uniform contact was possible after low-temperature bonding. Reliability of the bonded large area, high-power device was predicted to be sufficient from a metallurgical viewpoint     

DWDM optical millimeter-wave generation for radio-over-fiber using an optical phase modulator and an optical interleaver

We have proposed and experimentally demonstrated a novel scheme to generate a dense wavelength-division multiplexing (DWDM) optical millimeter-wave source by using an optical phase modulator and an optical interleaver. The stability of the DWDM optical millimeter wave generation is largely improved because we use an optical phase modulator without a dc-bias controller and an optical interleaver is subsequently employed to suppress the optical carrier of the DWDM source, which is not as temperature sensitive as a fiber Bragg grating. Moreover, the limitation of chromatic dispersion is greatly reduced due to avoiding the generation of higher order sidebands via driving the phase modulator with optimized RF signal.     

A new approach for optical colored image compression using the JPEG standards

Image compression consists in reducing information volume representing an image. Elimination of redundancies and non-pertinent information enables memory space minimization and thus faster data transmission. The present work aims to improve the quality of the compressed image while minimizing the time required for compression by using the principle of coherent optics. We present an optical adaptation of the method of JPEG compression technique for binary, gray-level and color images. Illustrative simulations will be given at the end to validate our architecture and to evaluate the performance on different types of images (binary, gray and color). An optical implementation setup is proposed and validated experimentally.     

All-optical cross-connect using feed-forward optical buffers with and without QoS: an analysis

An analytical model is derived to evaluate the performance of an optical switch using a feed-forward fiber delay line (FDL) per output for contention resolution. Two different forwarding algorithms for the switch are presented and evaluated: a simple forwarding algorithm (SFA) that is easier to implement, and an enhanced algorithm that provides better performance in terms of both packet loss probability and packet delay. The analytical model can be utilized with both packet and burst switching schemes to characterize the performance of the proposed architecture. Results show that the proposed architecture reduces the packet loss probability compared to that without FDLs. Finally, the same architecture is shown to be capable of supporting Quality of Service (QOS).