Steven A. Lis

Air-turbulence-compensated interferometer for IC manufacturing

SPARTA has developed a novel dual wavelength interferometer which is directly aimed at stepper stage control and general IC metrology. It utilizes an existing HeNe based dual frequency interferometric system and couples it directly to a second system which provides the real time air turbulence compensation. The optical design provides for colinear optical beam paths for the two systems over the measurement path. Compensated position measurements are provided at a rate of 30 Hz which is sufficient to permit high throughput stage positioning for all modern steppers. Stage position accuracy is determined to 4 nm 3(sigma) and stage precision (which is a two pass operation) can be 5.6 nm 3(sigma) . Future improvements in performance can be expected since the present design is not near fundamental limits. The interferometric system design has a form factor compatible with existing stepper systems. Testing of this system has been carried out in a laboratory environment under a variety of conditions, including those which would simulate a clean room environment. Test results are used in detail and conclusions will be presented which define the impact this system can have on stepper overlay performance and IC metrology. Because the interferometer is the basic ruler upon which much of the stepper metrology, setup, and operation is based, an improvement in performance of this system provides numerous benefits in the areas of stage precision, alignment, lens metrology, and reticle qualification and fabrication. Furthermore, the elimination of air turbulence as a stepper design concern can permit improvements in stepper performance and throughput with fewer engineering compromises.

Experimental demonstration of ultradense 4D holographic mass storage

This paper presents the results of a two-year Phase II SBIR program investigating a number of the key aspects of the use of Spectral Hole Burning media in a high capacity holographic optical digital computer memory. Factors which were experimentally examined include data longevity and unintentional erasure, and fundamental capacity issues relating to data densities and crosstalk. An experimental memory system was constructed and tested which had all the key elements of a digital memory system. Our experimental results confirm our previous analyses which indicate useful storage densities of 1012 bytes/cm3.

Experimental implementation of an optical neural network scalable to very large size

This paper describes recent results obtained during the experimental development of a holographic optical neural network based upon the spectrally selective recording properties of spectral hole burning materials. This general architecture has been initially tested as a bi- directional associative memory system (a subclass of neural networks). The results obtained clearly demonstrate the fundamental ability to fully connect two 2D planes of digital information. Expectations are that this architecture can be extended to capacities of 1012 interconnects or greater in a modest form factor system.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A high capacity content addressable memory architecture-experimental demonstration of a 4D optical neural network

This paper describes the construction and operation of a 4-dimensional neural network computer. This demonstration system uses holographic interconnects recorded in a volume spectral hole burning medium. The paper provides an overview of the demonstration system and includes experimental details of components: the tunable laser, the detector arrays, the spatial light modulators, and preparation and cooling of the spectral hole burning medium. Experimental results showing association of image patterns and a bidirectional associative memory experiment are presented and discussed.<<ETX>>

Experimental demonstration of a 4D optical neural network

This paper describes the construction and operation of a 4D neural network computer. This demonstration system uses holographic interconnects recorded in a volume spectral hole burning medium. The paper provides an overview of the demonstration system and includes experimental details of components: the tunable laser, the detector arrays, the spatial light modulators, and preparation and cooling of the spectral hole burning medium. Experimental results showing association of image patterns and a bidirectional associative memory experiment are presented and discussed.

High-capacity content-addressable memory architecture

This paper describes a new hardware architecture for searching and accessing data. This Content Addressable Memory (CAM) can be implemented using holographic storage in spectral hole burning media. The use of laser wavelength as a fourth dimension for volume holographic recording provides an additional addressing variable which can be used to advantage in a CAM architecture. This paper consists of three parts: definition of a CAM, presentation of two CAM concepts for digital data string and analog function search, and a discussion of architecture issues.