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Basic Technologies for High-Performance Solid-State Image Sensors

Objective

The objective of this project was to conduct basic research in the field of high-resolution optical sensors for CIM applications, eg robotics, pattern recognition and optical character recognition. The project provided fundamental technologies which will permit the development of the next generation of image sensors with more than 1 million pixels per chip.
The objective of this project was to conduct basic research in the field of high resolution optical sensors for computer integrated manufacture (CIM) applications (eg robotics, pattern recognition and optical character recognition). The project provided fundamental technologies which will permit the development of the next generation of image sensors with more than 1 million pixels per chip.
With the use of transparent conductive electrodes made out of indium tin oxide layers, instead of polycrystalline silicon electrodes, the loss in light sensitivity due to area reduction of the pixels can now be completely compensated for. The results of working devices show that the overall sensitivity can be increased by a factor of 2 or more for blue light by replacing 3 levels of polysilicon with 2 levels of indium tin oxide.
A complete system for the automatic functional testing of image sensors with respect to the most important operating parameters has been developed.
By optimizing the output stage onchip as a buried channel N-channel metal oxide semiconductor (NMOS) source, followed by 2 or 3 amplification stage for 1.5 micron NMOS technology, and using correlated double sampling of the charge coupled device (CCD) signal, an operation has been realised at 20 MHz driving frequency.
Differentstructures for 1.5 micron NMOS technology have been analyzed by computer simulation. Horizontal antiblooming structures with buried channel and with surface channel diode drains were realized with good spectral response in the whole visible and near infrared spectrum.
An imaging architecture has been proposed with a bus system where the data addresses and control are freely communicated between the sensor, the buffer and the associated processors, realizing the suite of specific functionalities.
The following results were obtained:
-Improved sensitivity: with the use of transparent conductive electrodes made out of indium-tin-oxide layers, instead of polycrystalline silicon electrodes, the loss in light sensitivity due to area reduction of the pixels can now be completely compensat ed for. All processing steps have been worked out, and the results of working devices show that the overall sensitivity can be increased by a factor of two or more for blue light by replacing three levels of polysilicon with two levels of indium-tin-oxide.
-Automated functional test: a complete system for the automatic functional testing of image sensors with respect to the most important operating parameters has been developed. It is suitable for laboratory applications and gains further improvement withan increased address space of the computer and larger capacity of the image-processing system for use in a production environment.
-Reduction of amplifier noise: high-resolution image sensors require high speed and low noise output amplifiers. By optimising the output stage on-chip as a buried channel NMOS source, followed by two or three amplification stages for 1.5 micron NMOS tec hnology, and using correlated double sampling of the CCD signal, an operation has been realised at 20 MHz driving frequency.
-Suppression of blooming: different structures for 1.5 micron NMOS technology have been analysed by computer simulation. Horizontal anti-blooming structures with buried channel and with surface channel diode drains were realised with good spectral respon se in the whole visible and near-infrared spectrum.
-Study of image-processing systems: an imaging architecture has been proposed with a bus system where data addresses and control are freely communicated between the sensor, the buffer and the associated processors, realising the suite of specific functio nalities.
Exploitation
The results of this project will be used in further high-resolution sensor developments, with industrial exploitation expected in the early 1990s.

Coordinator

Valvo Unternehmensbereich
Address
Burchardstraße 19
20095 Hamburg
Germany

Participants (1)

Thomson CSF
France
Address
Centre De Saint-égreve
38521 Saint-égreve