Sampling rates of high-performance electronic analog-to-digital converters (ADC) are fundamentally limited by the timing jitter of the electronic clock. This limit is overcome in photonic ADC's by taking advantage of the ultra-low timing jitter of femtosecond lasers. We have developed designs and strategies for a photonic ADC that is capable of 40 GSa/s at a resolution of 8 bits. This system requires a femtosecond laser with a repetition rate of 2 GHz and timing jitter less than 20 fs. In addition to a femtosecond laser this system calls for the integration of a number of photonic components including: a broadband modulator, optical filter banks, and photodetectors. Using silicon-on-insulator (SOI) as the platform we have fabricated these individual components. The silicon optical modulator is based on a Mach-Zehnder interferometer architecture and achieves a VπL of 2 Vcm. The filter banks comprise 40 second-order microring-resonator filters with a channel spacing of 80 GHz. For the photodetectors we are exploring ion-bombarded silicon waveguide detectors and germanium films epitaxially grown on silicon utilizing a process that minimizes the defect density.
Photonic Analog-to-Digital Conversion (ADC) has a long history. The premise is that the superior noise performance of
femtosecond lasers working at optical frequencies enables us to overcome the bottleneck set by jitter and bandwidth of
electronic systems and components. We discuss and demonstrate strategies and devices that enable the implementation
of photonic ADC systems with emerging electronic-photonic integrated circuits based on silicon photonics. Devices
include 2-GHz repetition rate low noise femtosecond fiber lasers, Si-Modulators with up to 20 GHz modulation speed,
20 channel SiN-filter banks, and Ge-photodetectors. Results towards a 40GSa/sec sampling system with 8bits resolution
Combining optical and electron beam exposures on the same wafer level is an attractive approach for extending
the usefulness of current generation optical tools. This technique requires high-performance hybrid resists that perform
equally well with optical and e-beam tools. In this paper Rohm and Haas EPICTM 2340, a 193-nm chemically amplified
photoresist, is used in a hybrid exposure role. The e-beam tool was used to pattern 45 nm half-pitch features and a 193-
nm immersion stepper was used to pattern 60-nm half-pitch features in the same resist layer. The effects of processing
parameters and delay times were investigated.
Advances in femtosecond lasers and laser stabilization have led to the development of sources of ultrafast optical pulse
trains that show jitter on the level of a few femtoseconds over tens of milliseconds and over seconds if referenced to
atomic frequency standards. These low jitter sources can be used to perform opto-electronic analog to digital conversion
that overcomes the bottleneck set by electronic jitter when using purely electronic sampling circuits and techniques.
Electronic Photonic Integrated Circuits (EPICs) may enable in the near future to integrate such an opto-electronic
analog-to-digital converters (ADCs) completely. This presentation will give an overview of integrated optical devices
such as low jitter lasers, electro-optical modulators, Si-based filter banks, and high-speed Si-photodetectors that are
compatible with standard CMOS processing and which are necessary for the implementation of EPIC-chips for advanced
The aggressive scaling in critical dimensions, coupled with the increasing use of subresolution features in optical proximity correction (OPC), dictates that maskwriters should have at their disposal electron beam resists capable of printing 100-nm OPC features on 280-nm design rule masks (70-nm features on the wafer). There is a need to survey commercial chemically amplified resists for use as mask making resists, and for completeness, such a survey would require that each resist be compared with an optimized resist process. To accomplish this task in a acceptable time period we have chosen to perform electron beam lithography modeling to quickly identify the resist process combinations that will lead to superior resist performance. We have used the technique of combining electron beam resist modeling with lithography to screen chemically amplified resists for use in electron beam mask making. This was accomplished by comparing experimentally determined resist sensitivities and profiles with those predicted from ProBeam /3D lithography modeling software.
We have surveyed the commercial resist market with the dual purpose of identifying diazoquinone/novolac based resists that have potential for use as e-beam mask making resists and baselining these resists for comparison against future mask making resist candidates. For completeness, this survey would require that each resist be compared with an optimized developer and development process. To accomplish this task in an acceptable time period, e-beam lithography modeling was employed to quickly identify the resist and developer combinations that lead to superior resist performance. We describe the verification of a method to quickly screen commercial i-line resists with different developers, by determining modeling parameters for i-line resists from e-beam exposures, modeling the resist performance, and comparing predicted performance versus actual performance. We determined the lithographic performance of several DNQ/novolac resists whose modeled performance suggests that sensitivities of less than 40 (mu) C/cm2 coupled with less than 10-nm CD change per percent change in dose are possible for target 600-nm features. This was accomplished by performing a series of statistically designed experiments on the leading resists candidates to optimize processing variables, followed by comparing experimentally determined resist sensitivities, latitudes, and profiles of the DNQ/novolac resists a their optimized process.
We have surveyed the commercial resist market with the dual purpose of identifying diazoquinone/novolac based resist that have potential for use as e-beam mask making resists and baselining these resist for comparison against future mask making resist candidates. For completeness, such a survey would require that each resists be compared with an optimized developer and develop process. To accomplish this task in an acceptable time period we have chosen to perform e-beam lithography modeling to quickly identify the resist developer combinations that will lead to superior resists performance. We describe the development and verification of a method to quickly screen commercial i-line resists under e-beam exposure with different developers. This was accomplished by determining modeling parameters for i-line resist from e-beam exposures, modeling the resist performance, and comparing predicted performance versus actual performance. We evaluated whether the technique of combining e-beam resist modeling with lithography can be used to quickly and efficiently screen i-line resists for use in e-beam mask making. This was accomplished by comparing experimentally determined resists sensitivities and profiles with those predicted from ProBeam/3D lithography modeling software.