This paper summarizes our recent work on high-speed photonic analog-to-digital conversion (A/D) technologies, where picosecond pulses generated by a 10 GHz mode-locked laser source were used to accomplish low-jitter photonic sampling. In addition, we describe our progress in the generation of 40 GHz wavelength-coded pulses for time-interleaved A/D, and the demonstration of photonic bandpass (at 1.6 GHz) Δ-∑ quantizers clocked at 10 GHz.
Chemically-amplified resists show promise as patterning materials in many advanced lithography systems including optical, electron-beam and ion-beam systems. In this study, four such resists including IBM APEX-E, IBM ENR, Shipley UVIIHS, and Shipley SAL-601 (ion-beam and electron-beam exposure only) were characterized for the three methods of exposure to determine relative sensitivities, fundamental resolution limits, and diffusivity for each of the above mentioned exposure methods. It was discovered that volumetric exposure doses for ion-beam and electron-beam were roughly equivalent but all resists were more sensitive to optical exposure. This is most likely due to a difference in transfer of energy to the photoacid generator during the exposure. Resolution tests were conducted in ion-beam exposure with simple line/space array patterns. All resists demonstrated patterning capability with resolution limits of 150 nm, 70 nm, 70 nm, and 50 nm for APEX-E, SAL-601, UVIIHS, and ENR respectively. Evidence of a competing cross-linking mechanism in the positive tone resists was discovered from the resolution tests. From a simple electron-beam `post/hole' experiment with varying post-exposure bake times, it was determined that SAL-601 and APEX-E demonstrated the highest level of diffusivity while UVIIHS and ENR exhibited negligible levels of diffusion. The characterization tests demonstrated the suitability of all four resists as good ion-beam patterning materials in addition to their suitability for electron-beam and optical exposure.
The technique of direct aerial image measurements (AIM) is applied to the evaluation of the mid-spatial frequency scatter produced form an extreme ultraviolet (EUV) laser plasma based microlithography testbed at Sandia National Laboratories in Livermore, Calif. AIM provides an at-wavelength technique for the in-situ characterization of the EUV images produced from the Scharzchild 10X reduction camera. The AIM technique measures the aerial images of the system by sampling the light intensity that passes through a narrow scanning slit (90 nm) and impinges upon a silicon photodiode designed to have a high quantum efficiency at EUV wavelengths. The measurements scan the slit artifact at the image plane across a step-function aerial image generated by the 10X reduction camera. The results of these measurements produce a measurement of the baseline scattered light and the modulation transfer function (MTF). Comparison of the measured MTF with simulated MTFs produces a measure of the combined multi-layer surface roughness variance ((sigma) rms2).
The technique of direct aerial image metrology (AIM) has been applied to characterize the performance of a microlithographic lens. AIM is potentially faster and more reproducible than measurements obtained by scanning electron microscopy. Direct measurement of the aerial image eliminates both the process variations associated with resist processing as well as the subjective nature of evaluating resist profiles. We have used AIM to evaluate some of the primary aberrations of a 248 nm stepper lens. We compare the results to those obtained with latent image scatterometry, a proven technique for measuring lens performance. We found that AIM, while providing qualitatively good results, contained some slight systematic errors that reduced the accuracy of the data. The sources of error and their remedies are discussed.
A new method of testing high numerical aperture microlithographic lenses involves measuring the aerial image produced by the lens rather than using developed resist profiles. Direct measurement of the aerial image eliminates any process variations associated with the resist processing and also removes the subjective nature of evaluating resist profiles. The means of characterizing the aerial image is to measure the image intensity from grating patterns positioned at the image plane. Our image monitor used an artifact mask cover with 2-D scanning pinholes placed over a photodetector. This pinhole cover was fabricated in an 800 angstrom thick layer of amorphous silicon. The size of the pinholes is 0.2 micrometers and the pitch of the pinholes is 6.0 micrometers . This system of Aerial Image Measurement (AIM) has been successfully implemented on a 0.53 NA, deep-UV (DUV) microlithography stepper. In this paper we present the results of various direct aerial images such as elbows, contacts and isolated lines and space patterns measured with this technique. These images are produced from conventional chrome DUV masks.
We explore the use of amorphous silicon as an alternative to chrome for deep UV masks. The primary advantage is that patterns may be dry etched. As masks' feature sizes continue to shrink, this dry etch capability of amorphous silicon can be a significant factor. Amorphous silicon has a further advantage of high absorbtivity over the 190 - 350 nm region. We have characterized the reflectivity and absorption of amorphous silicon, polysilicon, and chrome in the deep UV range from 190 nm to 365 nm. The optical properties of amorphous and polysilicon are very similar, but the superior homogeneity of amorphous silicon for etching suggests it as the preferred form. The absorbtivity of silicon exceeds that of chrome in this region (by about 20%); consequently a 700 A film is adequate to insure transmission of less than .01%. We have examined both optical and e-beam mask making processes. The amorphous silicon is deposited on quartz blanks by means of LPCVD. After removing the backside film, the pattern is transferred to the silicon using e-beam or optical exposure. The pattern is then developed by a dry plasma etch.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.