Distributed axis electron-beam system for lithography and inspection—preliminary experimental results

Pickard, D. S.; Campbell, C.; Crane, T.; Cruz-Rivera, L. J.; Davenport, Aaron; Meisburger, W. D.; Pease, R. F. W.; Groves, Timothy R.

doi:10.1116/1.1520566

Cited by 10 publications

(4 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The need for a high performance electron source (high current density, low energy spread and long lifetime) in electron beam lithography [1] and microscopy [2] is well established. High current density photocathodes also have very important applications in future ultra fast X-ray laser sources [3,4].…”

mentioning

confidence: 99%

CsBr photocathode at 257nm: A rugged high current density electron source

Liu

Maldonado

Sun

et al. 2006

Applied Physics Letters

Self Cite

View full text Add to dashboard Cite

There is a continuing need for high intensity electron sources that will operate in demountable vacuum and can be externally modulated. Materials with wide bandgap, e.g. diamond, are rugged but need photon energies exceeding the bandgap to emit efficiently and this rules out the use of CW lasers. We have found that a photocathode of CsBr is both adequately intense(>150A/cm 2 ) and rugged and can be excited with photons of energy of 4.8eV(257nm). This is below the energy gap of CsBr(7.3eV) but such operation can be explained by the presence of intraband states about 4eV below the conduction band minimum. SLAC-PUB-12108September 2006 Submitted to Applied Physics LettersThe need for a high performance electron source (high current density, low thick Cr film is deposited on a single crystal sapphire substrate patterned with Cr bars (15 um wide, 80 um spacing, 80 nm thick) to provide electrical contact. This is followed by a 15nm thick CsBr film deposited using an MBE high temperature effusion cell at 400°C.The thickness of the Cr and CsBr films is monitored in-situ with a crystal oscillator. The cathode is then transferred from the deposition chamber to the analysis chamber under vacuum where the photocurrent can be measured in both transmission and reflection modes. As shown in Fig. 1 for the transmission mode, a quartz UV lens focuses the expanded laser beam on the sample substrate to a minimum spot size of about 1.25umutilizing a shear plate. An Ocean Optics (USB2000) spectrophotometer is utilized to collect the photoluminescence signal (180nm-870nm). The electron collector (+1kV) is about 1mm away from the sample. Furthermore, the cathode holder is mounted on a piezoelectric driven flexure stage. This enables scanning the cathode surface across the laser beam, thus a photocurrent map (up to 80um x 80um) can be obtained. In the future, we should be able to engineer the position and density of the absoption states by doping the CsBr film. For example, a series of absorption bands are formed if Au is added in the CsBr film [13,14]. With the proper doping, it may be possible to reduce the excitation photon energy and increase the photoyield.The performance of CsBr under different vacuum conditions is also investigated. Comparing the cross-section intensity profiles, we find that the photocurrent of the activated region drops from 1.6uA to 1.4uA. However, the photocurrents of the other adjacent regions are not affected. These results demonstrate that the surface contamination caused by the pressure increase is localized at the activated region, and the unactivated region is not affected by the pressure burst. This is consistent with the fact that only the activated spot is Cs rich [8], and therefore it is more vulnerable than the unactivated surface. Unlike GaAs and other NEA photoemitters, in which the 5 degradation due to poor vacuum will cause an irreversible damage to the whole cathode, the photocurrent of the activated CsBr region gradually recovers after the vacuum burst.This behavior is consistent with photoly...

show abstract

mentioning

confidence: 99%

CsBr photocathode at 257nm: A rugged high current density electron source

Liu

Maldonado

Sun

et al. 2006

Applied Physics Letters

Self Cite

View full text Add to dashboard Cite

show abstract

“…SEBL is widely used in research and has been used for decades to make masks for the semiconductor industry. Since a single-beam system suffers from extremely slow writing speeds, multi-axis electron-beam lithography (MAEBL) has been proposed [20][21][22][23] . However, experimental results with such systems have been limited and commercial availability is uncertain.…”

Section: Comparison To Other Forms Of Maskless Lithographymentioning

confidence: 99%

Maskless optical lithography using MEMS-based spatial light modulators

2005

View full text Add to dashboard Cite

The semiconductor industry has been driven by significant improvements in optical-lithographic capability. As feature sizes on the wafer shrink faster than the wavelength of the exposing illumination, increasingly complex and expensive steps such as immersion, resolution-enhancement techniques, and optical-proximity correction (OPC) are required. Traditionally, high costs have been amortized over large volumes of chips, and by progressive technological maturity. Optical lithography using MEMs-based spatial-light modulators provides an alternative means of lithography. Significantly lower costs-of-ownership coupled with throughputs acceptable for mask manufacturing, mask prototyping, and low-volume-chip manufacturing are the enabling attributes of such techniques. At MIT, we have pursued a unique version of this technology, which we call Zone-Plate-Array Lithography (ZPAL). In ZPAL, an array of high-numericalaperture diffractive lenses (for example, zone plates) is used to create an array of tightly focused spots on the surface of a photoresist-coated substrate. Light directed to each zone plate is modulated in intensity by one pixel on an upstream spatial-light modulator. The substrate is scanned, and patterns of arbitrary geometry are written in a "dot-matrix" fashion. In this paper, we describe results from our proof-of-concept ZPAL system and its future potential. Lithography using distributed, tightly focused spots presents a different set of advantages and challenges compared to traditional optical-projection lithography. We discuss some of these issues and how they bear on practical system designs.

show abstract

“…A distributed-axis, fixed-aperture (DIFA) system is a simplified version of DiVa in that a beam-defining aperture plate forms fixed Gaussian shaped primary beamlets. 2) As with DiVa, the primary beamlets remain separate throughout their paths in DIFA, which is advantageous, because a significant increase in total current without the increase in Coulomb blurring is enabled, because of the absence of crossover. A resolution less than 50 nm has already been demonstrated by using a test bed.…”

Section: Introductionmentioning

confidence: 99%

Demonstration of Secondary Electron Detection using Monolithic Multi-Channel Electron Detector

Tanimoto

Pickard

Kenney

et al. 2008

jjap

View full text Add to dashboard Cite

In this paper we discuss some topics on the geometry of type II superstring backgrounds with D-branes, in particular on the geometrical meaning of the D-brane charge, the Ramond-Ramond fields and the Wess-Zumino action. We see that, depending on the behaviour of the D-brane on the four non-compact space-time directions, we need different notions of homology and cohomology to discuss the associated fields and charge: we give a mathematical definition of such notions and show their physical applications. We then discuss the problem of corretly defining Wess-Zumino action using the theory of p-gerbes. Finally, we recall the so-called * -problem and make some brief remarks about it. Conclusions and perspectives 24A p-Gerbes 24 B Hodge- * with Minkowskian signature 25 C Direct sum and direct product 26 JHEP11(2009)012of homology and cohomology in the same way it is used for electromagnetism, so that the theory of D-branes becomes actually a generalized version of electromagnetism with higher dimensional sources. In particular, one considers D-branes as sources for violation of Bianchi identity for the Ramond-Ramond fields, so that a Dp-brane charge is the analogue of the magnetic charge for the associated Ramond-Ramond field G 8−p and of the electric charge for its Hodge-dual G p+2 , assuming the democratic formulation of supergravity. Moreover, the Wess-Zumino action, i.e. the minimal coupling of a Dp-brane to the Ramond-Ramond potential C p+1 , is the analogue of the Wilson line for a charged particle moving in a background electromagnetic field. In order to describe D-brane charges, we can consider D-branes which cover part or all of the non-compact space directions. In this case, the brane cannot be seen as an ordinary homology cycle since, by definition of homology, all cycles have compact support. Thus, in order to correctly describe a theory of electromagnetism with non-compact sources, we are forced to consider a different version of homology, called Borel-Moore homology, which takes into account also non-compact cycles. We will also introduce some modified versions of Borel-Moore homology, in order to describe the possible kinds of D-branes. Moreover, we deal with the problem of giving a correct definition of Wess-Zumino action. The potential C p+1 is a connection on a p-gerbe, so that we briefly recall the theory of gerbes with connection, using the language ofČech hypercohomology, in order to explain the meaning of the integral and, if necessary, of its conditions at infinity.As is well known, this picture is affected by some problems: in particular, magnetic charge is quantized by Dirac quantization condition, and this implies that both a Ramond-Ramond field and its Hodge-dual are quantized, while in general Hodge duality does not preserve quantization. In particular, in type IIB theory the field G 5 is self-dual, being a D3-brane both electric and magnetic charge with respect to it: but there is not a good lagrangian description of a theory with a source which is at the same time magnetic and electric, an...

show abstract

Distributed axis electron-beam system for lithography and inspection—preliminary experimental results

Cited by 10 publications

References 6 publications

CsBr photocathode at 257nm: A rugged high current density electron source

CsBr photocathode at 257nm: A rugged high current density electron source

Maskless optical lithography using MEMS-based spatial light modulators

Demonstration of Secondary Electron Detection using Monolithic Multi-Channel Electron Detector

Contact Info

Product

Resources

About