Christian Keyser

Laboratory calibration of the Extreme-Ultraviolet Imaging Spectrometer for the Solar-B satellite

The laboratory end-to-end testing of the Extreme-Ultraviolet Imaging Spectrometer (EIS) for the Solar-B satellite is reported. A short overview of the EIS, which observes in two bands in the extreme-ultraviolet wavelength range, is given. The calibration apparatus is described, including details of the light sources used. The data reduction and analysis procedure are outlined. The wavelength calibration using a Penning source to illuminate the aperture fully is presented. We discuss the aperture determination using a radiometrically calibrated hollow-cathode-based source. We then give an account of the predicted and measured efficiencies from consideration of the efficiencies of individual optical elements in first order, an account of efficiencies out of band when radiation incident in one band is detected in the other, and efficiencies in multiple orders. The efficiencies measured in first order for in band and out of band are compared with the predictions and the sensitivity, and its uncertainties are derived. Application of the radiometric calibration is discussed.

Optics and mechanisms for the Extreme-Ultraviolet Imaging Spectrometer on the Solar-B satellite.

The Extreme-Ultraviolet Imaging Spectrometer (EIS) is the first of a new generation of normal-incidence, two-optical-element spectroscopic instruments developed for space solar extreme-ultraviolet astronomy. The instrument is currently mounted on the Solar-B satellite for a planned launch in late 2006. The instrument observes in two spectral bands, 170-210 A and 250-290 A. The spectrograph geometry and grating prescription were optimized to obtain excellent imaging while still maintaining readily achievable physical and fabrication tolerances. A refined technique using low ruling density surrogate gratings and optical metrology was developed to align the instrument with visible light. Slit rasters of the solar surface are obtained by mechanically tilting the mirror. A slit exchange mechanism allows selection among four slits at the telescope focal plane. Each slit is precisely located at the focal plane. The spectrograph imaging performance was optically characterized in the laboratory. The resolution was measured using the Mg iii and Ne iii lines in the range of 171-200 A. The He ii line at 256 A and Ne iii lines were used in the range of 251-284 A. The measurements demonstrate an equivalent resolution of ~2 arc sec? on the solar surface, in good agreement with the predicted performance. We describe the EIS optics, mechanisms, and measured performance.

Laser plasma EUVL sources: progress and challenges

The most pressing technical issue for the success of EUV lithography is the provision of a high repetition-rate source having sufficient brightness, lifetime, and with sufficiently low off-band heating and particulate emissions characteristics to be technically and economically viable. We review current laser plasma approaches and achievements, with the objective of projecting future progress and identifying possible limitations and issues requiring further investigation.

Diagnostics for laser plasma EUV sources

A high repetition-rate laser plasma source, possessing distinct radiation and particle emission characteristics, is now a principal candidate light source for the next generation of technology for the fabrication of computer chips. For these sources to satisfy this critical need they will need to meet unprecedented levels of performance, stability and lifetime. We review here some of the principal diagnostics of the EUV radiation that are now being utilized in the metrology, spectroscopy and imaging of these sources.

EUV spectroscopy of mass-limited Sn-doped laser micro-plasmas

The 13 nm emission that results from laser plasmas created from tin targets, results from a milliard of transitions occurring in many ions of tin (Sn6+-Sn13+). Understanding the energy manifolds within these multiple states will further our ability to manipulate energy into the narrow emission band demanded by EUV Lithography. A combined experimental theoretical program is underway to measure and interpret the detailed EUV emission spectra from laser plasmas suitable for EUVL, particularly mass-limited droplet laser plasmas. We employ high resolution spectroscopy in the 2 - 60 nm wavelength regions to characterize the emission from the plasma. This is interpreted with the aid of combined hydrodynamic/ radiation transport computer models. The results of this study will have impact on the in-band EUV conversion efficiency, estimation of the out-of-band short-wavelength emission, and in the development of electron temperature plasma diagnostics.

High-efficiency tin-based EUV sources

We have previously proposed the use of mass-limited, tin-containing laser plasma sources for EUV lithography applications. Here we report advances in measurements of the spectral output, conversion efficiency, and debris emission from these sources. We also report progress in the use of repeller field debris inhibition techniques for this source.

Dynamics of Mass-Limited Laser Plasma Targets as Sources for Extreme Ultraviolet Lithography

The droplet laser plasma source has many attractive features as a continuous, almost debris-free source for extreme ultraviolet (EUV) and X-ray radiation applications. In a combined experimental and theoretical study, we are analyzing the interaction physics between the laser light and microscopic spherical liquid droplet targets over a range of conditions.

Radiation transport modeling for Xe and Sn-doped droplet laser-plasma sources

Detailed understanding of the complex UTA emission from Xe and Sn laser plasmas is imperative to the development of efficient 13.5 nm sources for EUVL. We are developing a comprehensive theoretical modeling approach to these sources, utilizing state-of-the-art hydrodynamic and radiation transport plasma codes. These models are specifically applied to Xe and Sn-doped microscopic droplet targets laser-plasmas irradiated with nanosecond laser pulses. The plasma expansion models are compared to experimental determinations of the plasma electron density distributions. The output of the radiation transport code is used to interpret details of the spectral emission measured from these plasmas over a broad range of parameters.

Dynamics of high-repetition-rate laser plasma extreme ultraviolet sources from droplet targets

As a mass limited target the water droplet laser plasma source has been shown to have many attractive features as a continuous, almost debris-free source for extreme ultraviolet (EUV) and X-ray applications. Through a dual experimental and theoretical study, we analyze the interaction physics between the laser light and the target. The hydrodynamic laser plasma simulation code, Medusa103 is used to model the electron density distribution for comparison to electron density distributions obtained through Abel inversion of plasma interferograms. In addition, flat field EUV spectra are compared to synthetic spectra calculated with the atomic physics code RATION.

Liquid droplet-target laser plasma sources for EUV lithography

Summary form only given. Recently we have reported a new target configuration having >2% conversion efficiency making >60 W possible with diode pumped Nd:laser technology. We are currently undertaking a combined theoretical and experimental investigation of laser plasmas produced in this regime. This includes measurements of the plasma and radiation dynamics with particle, radiation and optical diagnostics. Laser-plasma sources must also meet stringent long-term operation and debris-free conditions for EUV lithography. We are making detailed studies of these issues.