A 0.18-/spl mu/m CMOS bioluminescence detection lab-on-chip

The paper describes a bioluminescence detection lab-on-chip consisting of a fiber-optic faceplate with immobilized luminescent reporters/probes that is directly coupled to an optical detection and processing CMOS system-on-chip (SoC) fabricated in a 0.18-/spl mu/m process. The lab-on-chip is customized for such applications as determining gene expression using reporter gene assays, determining intracellular ATP, and sequencing DNA. The CMOS detection SoC integrates an 8 /spl times/ 16 pixel array having the same pitch as the assay site array, a 128-channel 13-bit ADC, and column-level DSP, and is fabricated in a 0.18-/spl mu/m image sensor process. The chip is capable of detecting emission rates below 10/sup -6/ lux over 30 s of integration time at room temperature. In addition to directly coupling and matching the assay site array to the photodetector array, this low light detection is achieved by a number of techniques, including the use of very low dark current photodetectors, low-noise differential circuits, high-resolution analog-to-digital conversion, background subtraction, correlated multiple sampling, and multiple digitizations and averaging to reduce read noise. Electrical and optical characterization results as well as preliminary biological testing results are reported.     

Polysilicon base contact in I2L transistors

The extrinsic base diode minority carrier distribution under poly in I2L transistors can be calculated (or computed) in terms of an effective surface recombination velocity Seff at the mono/poly silicon interface similar to the oxide and metal cases. An analytical expression for Seff as a function of polysilicon parameters is given and compared to numerical solutions. Calculated ring speeds show a slight improvement in propagation delay for metal contact compared to poly contact.     

Mechanisms of reactive sputtering of indium I: Growth of InN in mixed Ar-N2 discharges

Optical absorption and emission spectroscopies were used for in situ investigations of process occuring in the plasma and at the electrode-gas interfaces which control the reactive sputter etching of indium targets and the reactive deposition of InN films in mixed Ar-N₂ glow discharges. The sputtering parameters used were a d.c. target voltage of -2.5 kV, a total sputtering pressure P of 30–70 m Torr (4–9.3 Pa), N₂ mol.% C_N2 values of 0–100 and a target-to-substrate separation d of 3–6 cm. Under these conditions no indication of complete nitride formation at the target surface or of sputter ejection of InN molecular species was obtained. Increasing C_N2 at a constant value of P caused a decrease of the target sputtering rate R. This decrease was due primarily to a decrease in the ion current i_T, which was caused by thermalization of low energy electrons in the plasma through excitation of vibrational modes in molecular N₂. Atomic absorption provided a real-time monitor of R over the entire range of sputtering parameters. The optical emission intensity from sputtered indium atoms in the cathode glow was found to increase with C_N2 (even though R decreased) because of enhanced excitation through collisions with N₂ metastable species.The nitrogen concentration in the deposited films, as determined by X-ray photoelectron spectroscopy and X-ray diffraction, was found to depend strongly on C_N2, P_N2 and d. The dependence on d was caused by the position of the growing film surface with respect to the negative glow region where most of the atomic nitrogen was formed through the reaction N₂⁺ + N₂ → N₂ + N⁺ + N In discharges with short mean free paths this is the primary mechanism of nitrogen incorporation since indium does not chemisorb N₂, only atomic nitrogen. InN films grown on glass substrates at about 80°C were found to be polycrystalline n-type semiconductors with a room temperature resistivity of 40 mΩ cm, a carrier concentration of about 5×10¹⁸ cm^-3 and an electron mobility of approximately 20 cm² V^-1 s^-1. The refractive index at a wavelength of 1 μm and the room temperature direct band gap were found to be 2.85 and 1.7 eV respectively.     

Super-Resolution Based on Curvelet Transform and Sparse Representation

Super-resolution techniques are used to reconstruct an image with a high resolution from one or more low-resolution image(s). In this paper, we proposed a single image super-resolution algorithm. It uses the nonlocal mean filter as a prior step to produce a denoised image. The proposed algorithm is based on curvelet transform. It converts the denoised image into low and high frequencies (sub-bands). Then we applied a multi-dimensional interpolation called Lancozos interpolation over both sub-bands. In parallel, we applied sparse representation with over complete dictionary for the denoised image. The proposed algorithm then combines the dictionary learning in the sparse representation and the interpolated sub-bands using inverse curvelet transform to have an image with a higher resolution. The experimental results of the proposed super-resolution algorithm show superior performance and obviously better-recovering images with enhanced edges. The comparison study shows that the proposed super-resolution algorithm outperforms the state-of-the-art. The mean absolute error is 0.021 ± 0.008 and the structural similarity index measure is 0.89 ± 0.08.     

CMOS image sensors

In this article, we provide a basic introduction to CMOS image-sensor technology, design and performance limits and present recent developments and future directions in this area. We also discuss image-sensor operation and describe the most popular CMOS image-sensor architectures. We note the main non-idealities that limit CMOS image sensor performance, and specify several key performance measures. One of the most important advantages of CMOS image sensors over CCDs is the ability to integrate sensing with analog and digital processing down to the pixel level. Finally, we focus on recent developments and future research directions that are enabled by pixel-level processing, the applications of which promise to further improve CMOS image sensor performance and broaden their applicability beyond current markets.     

An efficient method for the analysis of the space-charge region of diffused junctions

An efficient numerical method is presented which gives the solution for electrostatic potential, carrier density and space charge density distribution of an asymetrical junction. This method is based on the numerical solution of Poisson's equation assuming a zero-current approximation. A comparison between the present method and two different methods is made.     

Mechanisms of reactive sputtering of indium II: Growth of indium oxynitride in mixed N2-O2 discharges

The reactive sputtering of indium in mixed N₂-O₂ discharges was investigated using in situ optical absorption and emission spectroscopic analyses of plasma processes. All measured discharge parameters including the target sputtering rate, the target current and the sputtered indium emission intensity and neutral atom density exhibited abrupt changes with oxygen concentration at a critical value C¹. For a total pressure of 50 mTorr C¹ was approximately 2.5 mol.%. The abrupt change was caused by the formation of an indium oxide layer on the target surface over a very narrow range of O₂ partial pressures. The nitrogen coverage on the target was small at all gas compositions because of rapid preferential sputtering.X-ray photoelectron spectroscopy, Auger electron spectroscopy and X-ray diffraction were used to characterize the deposited film chemistry and structure as functions of the growth conditions. All films were n-type semiconductors and could be classified into the following three groups: (1) films grown at 0<C₀₂<2.5 mol.% were InN-based alloys with the wurtzite structure containing oxygen in solid solution; (2) films grown at 2.5 mol.% <C_O2<6 mol.% were two-phase mixtures; (3) films grown at C_O2>6 mol.% were cubic In₂O₃-based alloys with nitrogen in solid solution. Optical band gap measurements showed that E_g ranged from 1.7 to 2.4 eV for films of type (1) and from 2.4 to 3.6 eV for films of type (3).     

Sidewall effects in shallow emitter of small bipolar transistor

The current injected into a shallow emitter is studied using a two-dimensional numerical solution of the transport equations, including the effects of bandgap reduction, lifetime and surface recombination velocity. The present results show clearly the correlation between the injected current and the bowl-shaped emitter area as well as the width of metal contact.