Celestino Gaeta, Harry Rieger, I. C. Edmond Turcu, Richard Forber, S. Campeau, Kelly Cassidy, Michael Powers, Robert Grygier, Juan Maldonado, G. French, Joe Naunguyan, Charles Kelsy, Peter Hark, James Morris, Richard Foster
A compact laser produced plasma x-ray source radiates 24 Watts average power of 1nm x-rays in 2(pi) steradians. The x-ray power conversion efficiency is 9% from the laser average power focused on the x-ray target. The laser-plasma x-ray source is generated by a 300W compact, diode-pumped, solid-state Nd:YAG laser system. The tabletop laser system is constructed on a 4ft x 8ft optical bench and the laser modules are 1ft high. The total wall-plug power consumption for this laser-produced-plasma x-ray source is 22 kW. The x-ray source is optimized for integration with and x-ray stepper to provide a complete x-ray lithography exposure tool for the manufacture of high speed GaAs devices.
A high power picosecond soft x-ray source is generated by a compact, modular, diode pumped solid state laser BriteLightTM. Three x-ray source version are constructed from laser modules with increasing power. The power of the x-ray sources is tailored to potential applications. The building block of such a modular system is a 3 Watt x-ray power source with 1.1 keV x-ray photon energy. The laser system is very compact with dimensions of 4 ft X 3 ft X 1 fit. It is composed of a laser master oscillator, pre-amplifier and one power amplifier. A four laser amplifier system was also constructed in order to generate 12 W of x-rays for application to x-ray lithography.
I. C. Edmond Turcu, Richard Forber, Robert Grygier, Harry Rieger, Michael Powers, S. Campeau, G. French, Richard Foster, Phillip Mitchell, Celestino Gaeta, Z. Cheng, Jay Burdett, David Gibson, Stephen Lane, Troy Barbee, Stanley Mrowka, Juan Maldonado
An x-ray power of 2.8 Watts at the 1 nm x-ray lithography wavelength was generated by a copper plasma formed by a single laser beam focused to an intensity of greater than 1014 W/cm2 on a copper tape target. The all solid state BritelightTM YAG laser has 700 ps pulse duration, 300 Hz pulse repetition rate, average power of 75 Watts, and less than 2 times diffraction limited beam quality at the fundamental 1.064 micrometer wavelength. The single beam laser system has a master oscillator, a preamplifier and one power amplifier, all diode pumped. Measurements confirmed negligible copper vapor debris at 8 cm from the laser-plasma source with atmospheric pressure He gas and modest gas flow. The point source x-ray radiation was collimated with either a polycapillary or grazing mirror collimator. The near-parallel beam of x-rays has good divergence both globally (0.5 mrad) and locally (less than 3 mrad), good uniformity (2% achievable goal) and large uniform field size (20 mm X 20 mm full field and 25 mm X 36 mm scanning system). High-resolution lithography was performed for the first time with collimated 1 nm point source x-rays. A power scaling system is being built with eight amplified beams in parallel on the x-ray target, and is expected to achieve 24 - 30 Watts of x-rays. A 16 beam laser plasma x-ray lithography system could achieve a throughput of 24 wafer levels per hour using 300 mm diameter wafers.
Collimating of the x-ray beam is essential to point source proximity x-ray lithography for controlling radial magnification and increasing the beam intensity. Polycapillary optic collimators were developed to meet the challenges of point source proximity x-ray lithography. Sophisticated modeling software was developed for design and optimization of polycapillary collimators to meet specific requirements. Using this software, a highly efficient collimator was designed to deliver a well-collimated beam centered at 1.1 keV for a 20 mm X 20 mm field. The collimator was constructed and was tested with both an electron bombardment source and a laser generated plasma source. The design goals of intensity gain and divergence controls have been achieved. The intensity variation within the printing field can be less than 2%.
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