Tokuhiko Tamaki

Quantitative Evaluation of Gate Oxide Damage during Plasma Processing Using Antenna-Structure Capacitors

Plasma-induced damage of gate oxides is evaluated from the difference between the intrinsic charge-to-breakdown (Q BD) and the residual Q BD. This difference, ΔQ BD, corresponds to the plasma-induced damage to the oxide and to the accumulation of conduction current from the plasma into the oxide. It is shown experimentally that the plasma-induced damage ΔQ BD increases in proportion to the antenna ratio (exposed antenna area/gate area). The ΔQ BD of the antenna capacitor depends not on the device structures such as the gate oxide thickness, but on the plasma process conditions.

New SOI CMOS process with selective oxidation

Both NMOSand PMOS-transistors have been fabricated on the silicon islands based on the conventional polysilicon-gate CMOS process technique (Fig. 4). Subthreshold leakage current for the W/L = 1.5pd0.8pm n-channel transistor is less than O.lpA (Fig. 5-a). Transistors fabricated on poorly planarized structures show a hump in an Id-Vg curve (Fig. 5-b), that is ascribable to the threshold lowering at the MOSFET channel edge3). Effective inversion mobility of electrons is about 600cm2/Vsec and that of holes is about 300cm2/Vsec. These values are comparable with those of bulk CMOS transistors. Both 25-stage CMOS ring oscillators and 1/2 frequency dividers can successfully be fabricated, and their excellent characteristics are confirmed. Each stage comprises NMOSand PMOS-transistors with same size of W/Leff = 1.5!,1m/1.3pm. The delay time per stage at Vdd = 5 V is 360 psec with 0.033pJ per stage power dissipation.

6.1 An over 120dB simultaneous-capture wide-dynamic-range 1.6e− ultra-low-reset-noise organic-photoconductive-film CMOS image sensor

Image sensors are increasingly becoming key devices for various applications (in-vehicle, surveillance, medical, and so on). To realize the best possible imaging and sensing performance, there is growing demand for extended dynamic range that can precisely reproduce color tone. Several conventional papers have described methods for enhancing dynamic range, such as multiple exposures in a frame [1] and a lateral overflow integration capacitor [2,3]. However, all these techniques realize a 100-to-200dB dynamic range by synthesizing multiple exposures, with asynchronism between multiple exposures causing time distortion. Thus, a simultaneous-capture wide dynamic range (SCWDR) over 100dB is desired.

First demonstration of 0.9 μm pixel global shutter operation by novel charge control in organic photoconductive film

Organic photoconductive film (OPF) image sensor is the strong candidate to extend image sensor application and create new image sensor world. This paper introduces new charge generation and extraction operation in OPF sensor. By spatial and temporal control of electric field in OPF, high speed global shutter operation in sub-micron pixel, electrical iris control without ND filter, phase difference detective autofocusing are demonstrated.

6.2 210ke− Saturation signal 3µm-pixel variable-sensitivity global-shutter organic photoconductive image sensor for motion capture

Image sensors for applications such as machine vision, in-vehicle cameras, and surveillance cameras require a global shutter (GS) function. GS functions are an increasingly powerful technology driver, not only for solving imaging problems caused by rolling shutter distortion or flash bands, but also for use in sensing applications [1]. Conventional CMOS image sensors (CIS) with GS functions require storage located near the photoelectric conversion area [2-3], and the two-stage transferring pixel structures required to suppress kT/C noise need two storage nodes and extra transistors. This makes it difficult, in GS pixels, to simultaneously shrink the pixel size and enlarge the saturation signal.

Lensfree on-chip high-resolution imaging using two-way lighting, and its limitations

A high-magnification image of a biological sample can generally be obtained by an optical microscope with an objective lens, moving the image sensor with a sub-pixel shift and the subsequent image processing for super-resolution. However, to obtain a high-resolution image, a large number of images will be required for the super-resolution, and thus it is difficult to achieve real-time operation, and the field-of-view (FOV) is not sufficiently wide. The currently proposed digital holography technique places a sample on the image sensor and captures the interference fringe (hologram) to reconstruct a 3D high-resolution image in a computer. This technique ensures the features of a wide FOV, whereas the high resolution obtained by image processing cannot ensure real-time operation, because it requires recursive calculations of light propagation and adequate computer resources. To realize wide FOV and the real-time operation at the same time, we have developed a new technique: Lensfree on-chip high-resolution imaging using two-way lighting. High-resolution image is immediately obtained by image processing of the low-resolution images of the samples. This makes it possible to ensure a wide FOV, a deep depth of focus without the need for focus adjustment, and a continuously expanding operation. We also discuss the limitations of the high resolution.

ClF/sub 3/ gas compound for particle free contact hole etching

We propose a novel contact hole etching process using gas phase reaction of ClF/sub 3/. Particle free etching can be achieved by suppressing polymer deposition on the chamber wall while maintaining high oxide/silicon selectivity. ClF/sub 3/ can simultaneously etch oxide and clean the chamber wall. The same chamber can be used to remove the damaged silicon layer after contact hole formation and additional plasma apparatus, which has been necessary in conventional etching, is eliminated. This technology ensures high yield and cost-effective contact hole etching.<<ETX>>

Damage-free metal etching using Lissajous electron plasma

Requirements for metal etching in sub-half micron devices include precise profile and dimension control along with low charge related damage for gate oxides thinner than 10 nm. Lissajous Electron Plasma (LEP) is a new plasma generation method which provides a uniform low pressure plasma using a rotating electric field. Due to its low operating pressure, LEP achieves excellent profile control and high selectivity without using polymer forming gases. In addition, generation of a low pressure plasma with a non-magnetic configuration, which is a distinctive feature of LEP, results in damage-free etching in CMOS devices.<<ETX>>