Silicon VLSI Technology Research Articles

Silicon-Germanium multi-quantum well photodetectors in the near infrared

Single crystal Silicon-Germanium multi-quantum well layers were epitaxially grown on silicon substrates. Very high quality films were achieved with high level of control utilizing recently developed MHAH epitaxial technique. MHAH growth technique facilitates the monolithic integration of photonic functionality such as modulators and photodetectors with low-cost silicon VLSI technology. Mesa structured p-i-n photodetectors were fabricated with low reverse leakage currents of ~10 mA/cm² and responsivity values exceeding 0.1 A/W. Moreover, the spectral responsivity of fabricated detectors can be tuned by applied voltage.

Bio-inspired vision

Nature still outperforms the most powerful computers in routine functions involving perception, sensing and actuation like vision, audition, and motion control, and is, most strikingly, orders of magnitude more energy-efficient than its artificial competitors. The reasons for the superior performance of biological systems are subject to diverse investigations, but it is clear that the form of hardware and the style of computation in nervous systems are fundamentally different from what is used in artificial synchronous information processing systems. Very generally speaking, biological neural systems rely on a large number of relatively simple, slow and unreliable processing elements and obtain performance and robustness from a massively parallel principle of operation and a high level of redundancy where the failure of single elements usually does not induce any observable system performance degradation. In the late 1980`s, Carver Mead demonstrated that silicon VLSI technology can be employed in implementing ``neuromorphic'' circuits that mimic neural functions and fabricating building blocks that work like their biological role models. Neuromorphic systems, as the biological systems they model, are adaptive, fault-tolerant and scalable, and process information using energy-efficient, asynchronous, event-driven methods.In this paper, some basics of neuromorphic electronic engineering and its impact on recent developments in optical sensing and artificial vision are presented. It is demonstrated that bio-inspired vision systems have the potential to outperform conventional, frame-based vision acquisition and processing systems in many application fields and to establish new benchmarks in terms of redundancy suppression/data compression, dynamic range, temporal resolution and power efficiency to realize advanced functionality like 3D vision, object tracking, motor control, visual feedback loops, etc. in real-time. It is argued that future artificial vision systems, if they are to succeed in demanding applications such as autonomous robot navigation, micro-manipulation or high-speed tracking, must exploit the power of the asynchronous, frame-free, biomimetic approach.

Growth of III/V Materials on Large Area Silicon

The compound semiconductor industry has seen tremen-dous progress in applications ranging from high-power electronics to optoelectronics. However, most of the de-vices being produced today are discrete due to the com-paratively high cost of wafer area and the low level of integration experience compared to the silicon industry. Hence, co-integration with mainstream silicon manufac-turing processes in which the compound semiconductor device is selectively deposited in areas where needed while the rest of the chip is kept in standard silicon VLSI technology is seen as one of the most promising ways to harvest the potential of III-V compounds.

Modeling ion trap thermal noise decoherence

We present a detailed analysis of ion heating caused by thermal fluctuation noise in ion traps. The results of the analysis are used to estimate thermal noise ion heating rates for a variety of trap electrode configurations and materials, including recent scalable multiplexed planar ion trap proposals based on silicon VLSI technology. We find that minimizing thermal noise ion heating places severe constraints on the design and materials used for ion traps.

Improvement of Power Electronic Structure Characteristics Using Sic Technology - Overview

This paper is dedicated to the recent unprecedented boom of SiC electronic technology. The contribution deals with a brief survey of those properties. In particular, the differences (both good and bad) between SiC electronics technology and well-known silicon VLSI technology are highlighted. Projected performance benefits of SiC electronics are given for several large-scale applications at the end of the contribution. The basic properties of SiC material were discussed already at the beginning of 1980's, also in our work place [1].

Material and process limits in silicon VLSI technology

The integrated circuit (IC) industry has followed a steady path of shrinking device geometries for more than 30 years. It is widely believed that this process will continue for at least another ten years. However there are increasingly difficult materials and technology problems to be solved over the next decade if this is to actually occur, and beyond ten years there is great uncertainty about the ability to continue scaling metal-oxide-semiconductor field-effect transistor (MOSFET) structures. This paper describes some of the the most challenging materials and process issues to be faced in the future and where possible solutions are known, describes these potential solutions. The paper is written with the underlying assumption that the basic metal-oxide-semiconductor (MOS) transistor will remain the dominant switching device used in ICs and it further assumes that silicon will remain the dominant substrate material.

Polysilicon Waveguides for Silicon Photonics

AbstractPhotonic integrated circuits in silicon require waveguiding through a material compatible with silicon VLSI technology. Polysilicon (polySi), with a high index of refraction compared to SiO2 and air, is an ideal candidate for use in silicon optical interconnect technology. Inspite of its advantages, the biggest hurdle to this technology is that losses of 350dB/cm have been measured in as-deposited polySi waveguide structures, as against ldB/cm losses measured in waveguides fabricated in crystalline silicon. We report methods for reducing scattering and absorption, which are the main sources of losses in this system. To reduce surface scattering losses we fabricate waveguides in smooth recrystallized amorphous silicon and Chemo-Mechanically Polished (CMP) polySi, both of which reduce losses by about 40dB/cm to 15dB/cm. Atomic Force Microscopy (AFM) and spectrophotometry studies are used to monitor surface roughness which has been reduced from an RMS roughness value of 19–20nm down to about 4–6nm. Bulk absorption/scattering losses can depend on size, structure, and quality of grains and grain boundaries which we investigate by means of Transmission Electron Microscopy (TEM). Although the lowest temperature deposition has twice as large a grain size as the highest temperature deposition, the losses appear to not be greatly dependent on grain size in the 0.1pm to 0.4pm range. Additionally, absorption/scattering at dangling bonds is investigated before and after a low temperature Electron-Cyclotron Resonance (ECR) hydrogenation step. After hydrogenation, we obtain the lowest reported polySi loss values at λ = 1.54μm of about 15dB/cm.

Ion sources for dry etching: Aspects of reactive ion beam etching for Si technology (invited)a)

Aspects of ion beam sources are treated which emerge from their use for reactive ion beam etching (RIBE) in silicon VLSI technology. As a basis for this treatment, the requirements for dry etching for VLSI are elaborated, as well as the consequences of these requirements for ion beam sources to be used for such technology. Practical experience with two types of ion beam sources for this application are highlighted, a classical Kaufman source and a first-generation ECR source. Aspects relevant for microfabrication related to grid optics, and the use of reactive gases, are discussed. Most important in this context are the internal microdivergence of an ion beam and the fragmentation of molecular gases taking place in the source and the ion beam as well. The consequence for potential application of RIBE for micropatterning must be to characterize sources by measuring their energy- and angle-resolved particle fluxes to the wafer.

Ion sources for dry etching: Aspects of reactive ion beam etching for Si technology (invited) (abstract)a)

Aspects of ion beam sources are treated which emerge from their use for reactive ion beam etching (RIBE) in silicon VLSI technology. As a basis for this treatment, the requirements for dry etching for VLSI are elaborated, as well as the consequences of these requirements for ion beam sources to be used for such technology. Practical experience with two types of ion beam sources for this application are highlighted, a classical Kaufman source and a first-generation ECR source. Aspects relevant for microfabrication related to grid optics, and the use of reactive gases, are discussed. Most important in this context are the internal microdivergence of an ion beam and the fragmentation of molecular gases taking place in the source and the ion beam as well. The consequence for potential application of RIBE for micropatterning must be to characterize sources by measuring their energy- and angle-resolved particle fluxes to the wafer.

Trends in ion implantation in silicon VLSI technology

A brief review is presented on the emerging difficulties of implantation in manufacturing small geometry VLSIs of the future. The importance of understanding the physical phenomena associated with the behavior of implanted ions and generated disorders is reflected in the design and fabrication of accurately controlled depth and lateral profiles of shallow and submicron size junctions. As a particular example, the complexity of implantation and mixing involved in a solid phase silicidation reaction is described. New technology fields such as MeV range high-energy implantation, finely focused beam implantation, and heavy dose oxygen or nitrogen ion implantation are also reviewed briefly. Differences between the physical processes involved in the new field of implantation and those of conventional technology are presented with a short description of machine trends in the field.