Selmer Wong

2Kx2K molecular beam epitaxy HgCdTe detectors for the James Webb Space Telescope NIRCam instrument

The NIRCam instrument will fly ten of Rockwell Scientific’s infrared molecular beam epitaxy HgCdTe 2048x2048 element detector arrays, each the largest available with current technology, for a total of 40 Megapixels. The instrument will have two varieties of MBE HgCdTe, a SWIR detector with λco = 2.5 μm, for the shortwave channel of NIRCam (0.6-2.3 μm); and a MWIR detector with λco = 5.3 μm, for the longwave channel of NIRCam (2.4-5.0 μm). Demonstrated mean detector dark currents less than 0.01 electrons per second per pixel at operating temperatures below 42 K for the MWIR and below 80 K for the SWIR, combined with quantum efficiency in excess of 80 percent and read noise below 6 electrons rms, make these detector arrays by far the most sensitive SWIR and MWIR devices in the world today. The unique advantages of molecular beam epitaxy as well as FPA data on noise, dark current, quantum efficiency, and other performance metrics will be discussed. In addition, the focal plane assembly package designs will be presented and discussed.

Mechanism studies of scanning electron microscope measurement effects on 193-nm photoresists and the development of improved line-width measurement methods

The effect of scanning electron microscope (SEM) measurements on the dimensions of resist features was studied for 193nm resist materials. Initial measurements showed that resist lines became smaller as they were repeatedly measured, with size changes of up to 40 to 50 nm after 50 to a 100 measurements. There was a significant size change for the two 193nm resist systems tested, an acrylate based single layer system and a hybrid single layer system, although the magnitude of the effect was different for each system. The total dose per SEM measurement seen locally by the resist was calculated to be on the order of 100 (mu) C/cm

Advanced technology trends for astronomy at Rockwell Scientific

_2), a significant amount by the standards of e-beam induced chemistry. Entire wafers of the hybrid system were cured in an e-beam curing system to enable chemical characterization of irradiated resist. It was found that there was loss of the anhydride functionality when blanket-coated wafers of the hybrid system were cured and a corresponding reduction in film thickness. The remaining material was cross-linked. However, to our surprise, we found that e-beam curing of exposed line and space patterns id not result in any critical dimension (CD) change, any height change, or any profile change. What is more, the cured line and spaces patterns did not show significant line width change when repeatedly measured in a SEM. It is speculated that the resists gets hot while being measured and how hot affects how much shrinkage is seen. Depending on the temperature reached, either cross-linking or annealing will be the fastest process; and the balance between the two will determine how much shrinkage is seen during measurement.

Advanced imaging sensors at Rockwell Scientific Company

This paper discusses the latest technologies for space and ground-based astronomy being pursued by Rockwell Scientific. The discussion covers the latest demonstrated performance of large format NIR (~1.7um cutoff) detectors mated to the HAWAII-2RG readout integrated circuit, our proven readout for large-format arrays for astronomy. Developmental work is presented on the HAWAII-4RG family (consisting of 4k x 4k, 4k x 8k, and 8k x 8k formats), RSC’s newest additions planned to the HAWAII series of astronomy readout integrated circuits. We also present the status of our multifunctional command-and-control ASIC for FPAs, which was first reported at the August 2002 SPIE.

The SIDECAR ASIC — Focal Plane Electronics on a Single Chip

The past 2 to 3 years has been a period of explosive growth in technology development for imaging sensors at Rockwell Scientific Co. (RSC). The state of the art has been advanced significantly, resulting in a number of unique advanced imaging sensor products. A few key examples are: 2048 x 2048 sensor chip assemblies (SCA) for ground and space-based applications, 4096 x 4096 mosaic close-butted mosaic FPA assemblies, a very high performance 10 x 1024 hybridized linear SCA for optical network monitoring and other applications, the revolutionary CMOS ProCam-HD imaging system-on-a-chip for high definition television (HDTV), and RSCs near-infrared emission microscope camera for VLSI defect detection/analysis. This paper provides selected updates of these products and thereby provides an overview of the ongoing highly fertile period of technology and product development at Rockwell Scientific. A view into future directions for advanced imaging sensors is also provided.

Detectors for the James Webb Space Telescope near infrared spectrograph (NIRSpec)

Traditionally, focal plane arrays require extensive external focal plane electronics (FPE) to provide clocks and biases as well as to digitize the analog output signals. The FPE has to be well-designed and is typically large, heavy and powerhungry. Most importantly, the FPE has to be placed some distance away from the FPA, which complicates maintaining low noise performance throughout the complete system. To offer an alternative to the discrete electronics, Rockwell Scientific has developed a new approach known as the SIDECAR application-specific integrated circuit (ASIC). This single chip provides all the functionality necessary to operate an infrared array with the convenience of a pure digital interface to the outside world. This paper will present performance data on the latest generation of the SIDECAR ASIC operating the JWST H2RG detector arrays at cryogenic temperature. The test results demonstrate that an ASIC based FPA system will meet or exceed all performance requirements for the JWST mission. The SIDECAR ASIC has been selected by NASA to become the FPA drive electronics for all shortwave infrared instruments on JWST.

Large format HgCdTe arrays for the James Webb Space Telescope

The Near Infrared Spectrograph (NIRSpec) will be the James Webb Space Telescopes (JWSTs) primary near-infrared spectrograph. NIRSpec is a multi-object spectrograph with fixed-slit and integral field modes. EADS/Astrium is building NIRSpec for the European Space Agency (ESA), with NASA is providing the detector subsystem and programmable multi-aperture mask. In this paper, we summarize recent progress on the detector subsystem including tests demonstrating that JWSTs Rockwell HAWAII-2RG sensor chip assemblies have achieved Technology Readiness Level 6 (TRL-6). Achieving TRL-6 is an important milestone because TRL-6 is required for flight.

Enhancement of photoresist plasma etch resistance via electron beam surface cure

The near infrared spectrograph (NIRSpec) will be the James Webb Space Telescopes (JWSTs) primary near-infrared spectrograph. NIRSpec is a multi-object spectrograph with fixed-slit and integral field modes. EADS/Astrium is building NIRSpec for the European Space Agency (ESA), with NASA providing the detector subsystem and programmable multi-aperture mask. In this presentation we present an overview of the detector subsystem (DS)