The temperature dependence of the resistivities of rc-type silicon inversion layers at liquid helium temperatures was studied in detail. The temperature dependence was found to be correlated to the mobility of the sample. Our results can be explained by Coulomb scattering, with possible contributions by surface-roughness scattering in high-mobility samples.The role of the local-field effect in differential reflectance spectroscopy is studied within a classical model for an ordered over layer of a weakly adsorbed species on a metal substrate. Results for Ar on Al at two coverages strongly indicate the importance of the local-field effect in such optical studies.

A set of test structures designed to characterize and compare the performance of CMOS passive and active pixel image sensors is presented. The test structures are designed so that they can be rapidly ported from one process to another. They are also designed so that individual photodetectors and pixel circuits as well as entire image sensor arrays can be characterized and compared based on: quantum efficiency, spectral response, fixed pattern noise, sensitivity, blooming, input referred read noise, reduction of quantum efficiency caused by silicide/salicide, lag, digital switching noise sensitivity, impact ionization noise sensitivity, dynamic range, and temperature dependency of all measured parameters. Four test chips that include a variety of these structures have been built in two different O.35m CMOS processes. The test chips include nineteen types of individual photodetectors and thirty eight types of 64 x 64 pixel arrays. The test methodology and preliminary test results from these chips will be presented.keywords: CMOS imaging, APS, quantum efficiency, dark current, spectral response 2. INTRODUCTION CMOS image sensors are being actively researched as an alternative to CCDs for digital imaging applications.The main advantage of using CMOS is the ability to integrate most or all of a digital imaging system on a single chip, thus reducing cost and power dissipation. Remarkable results have been published showing that certain CMOS sensors compare favorably to CCDs in dynamic range, and fixed pattern noise.7'1 In spite of these reported results we believe that the know-how required to build such integrated CMOS sensors especially in advanced (O.35jm and below) processes is still lacking. Issues such as image sensor noise , quantum efficiency and dark current are not well understood for advanced CMOS processes. Most published work is concerned with the implementation of a specific sensor architecture in a specific process. For example Denyer8 reports on passive pixel sensor built in a 1.5gm process, Forchheimer2 reports on passive pixel sensor built in a 1.6tm process, Fossum4 reports on an active pixel sensor built in a 2.Opm process, Dickinson' reports on an active pixel sensor built in a O.9pm process, and Fowler3 and Yang" report on sensors with pixel level A/D conversion built in 1.21um and O.8pm processes respectively. As a result it is difficult to objectively compare the characteristics of different sensor designs. Additionally, the reported results do not provide designers the predictive knowledge necessary to select the best image sensor architecture for the given process or to optimize the design of the selected architecture.In this paper we describe a set of test structures that can be used to characterize a CMOS process for image sensor applications. The goal of designing the test structures is to be able to characterize and compare the performance of different photodetectors, pixel circuits, and sensor architectures built in the same process and across different processes. The results obt...

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The time dependence of hot carrier degradation of n-channel MOSFETs and the methodology of accelerated stress have been investigated in detail. The time (T) dependence is foLund to be inconsistent with the simple expression of TN (N 0.25 ), but rather slhow a slow-down of the degradation rate. The slope of the degradation curve is also found to be dependent on the stress bias voltage. The projection of device lifetime by accelerated stress based on the TN law and the assumption of constant slope independent of stress bias is unreliable.