Lowell L. Wood

X‐ray lasers

One of the great barriers to improving our understanding of the molecular basis of life is that we do not yet have any way of examining individual macromolecules in living tissue. The progress made so far in unravelling the structures of biological macromolecules is based on painstaking chemical and x‐ray crystallographic analyses of pure, crystalline samples of a given macromolecule.1 This situation could, however, be completely revolutionized if a source of coherent x rays were available. Although, as we shall show below, the realizaton of this goal is beset with difficulties, experiments aimed towards its accomplishments are under way, as shown in figure 1.

Wafer‐scale laser pantography: Fabrication of n‐metal‐oxide‐semiconductor transistors and small‐scale integrated circuits by direct‐write laser‐induced pyrolytic reactions

A complete set of processes sufficient for manufacture of n‐metal‐oxide‐semiconductor (n‐MOS) transistors by a laser‐induced direct‐write process has been demonstrated separately, and integrated to yield functional transistors. Gates and interconnects were fabricated of various combinations of n‐doped and intrinsic polysilicon, tungsten, and tungsten silicide compounds. Both 0.1‐μm and 1‐μm‐thick gate oxides were micromachined with and without etchant gas, and the exposed p‐Si [100] substrate was cleaned and, at times, etched. Diffusion regions were doped by laser‐induced pyrolytic decomposition of phosphine followed by laser annealing. Along with the successful manufacture of working n‐MOS transistors and a set of elementary digital logic gates, this letter reports the successful use of several laser‐induced surface reactions that have not been reported previously.

CHEMICAL QUENCHING OF THE TRIPLET STATE IN FLASHLAMP‐EXCITED LIQUID ORGANIC LASERS

Greatly improved lasing of flashlamp‐excited organic dyes has been achieved by collisionally deexciting the triplet state of dye molecules with newly discovered chemical additives. Experimental results show the quantitative improvement of several principal organic lasing compounds when they are placed in solution with chemical additives. An explanation of the deexcitation mechanism is offered; the criteria for selecting proper chemical additives are listed.

Laser‐induced thermonuclear fusion

Laser‐induced fusion has recently joined magnetic‐confinement fusion as a prime prospect for generating controlled thermonuclear power. During the past three years, the Atomic Energy Commission has accelerated the national laser‐fusion program more than tenfold, to about

Separation of isotopes by laser deflection of atomic beam. I. Barium

30 million annually, and the Soviet Union has a program of comparable size.

Wafer-Scale Laser Lithography: I. Pyrolytic Deposition Of Metal Microstructures

Spatial separation of isotopes of barium in an atomic beam has been demonstrated, using radiation pressure of light from a tunable dye laser which resolved the unusually narrow isotopic hyperfine structure of the Ba (I) 5535.7‐A resonance line. Observations of the deflected monoisotopic beam indicate an average of 25 photons scattered per atom in the deflected beam.

Multifrequency radiation pressure laser, isotope separation

Mechanisms for laser-driven pyrolytic deposition of micron-scale metal structures on crystalline silicon have been studied. Models have been developed to predict temporal and spatial properties of laser-induced pyrolytic deposition processes. An argon ion laser-based apparatus has been used to deposit metal by pyrolytic decomposition of metal alkyl and carbonyl compounds, in order to evaluate the models. These results of these studies are discussed, along with their implications for the high-speed creation of micron-scale metal structures in ULSI systems.

Wafer-Scale Laser Pantography: IV. Physics of Direct Laser-Writing Micron-Dimension Transistors

Abstract Isotope separation by laser deflection of an atomic beam is limited in its efficiency by the accumulation of atoms in metastable states. This restriction can be removed with the use of lasers which excite metastable atoms to states from which spontaneous decay to the ground state is allowed. This is demonstrated in the separation of barium isotopes, where efficiency was improved from a lower limit of 70% to at least 83% using a second laser. Efficiency approaching 100% can be achieved in barium with a second laser but the required wavelength is not available.

High resolution spectroscopy using photodeflection

The processes involved in the fabrication of micron-dimension transistors and small-scale integrated circuits using only the technique of direct laser-writing by localized pyrolytic surface reactions are discussed. New experimental findings in the deposition of tungsten by silicon. surface reduction of tungsten hexafluoride and doped polysilicon are presented. The techniques used to fabricate laser beam-written n-MOSFETs are being extended to make unipolar JFETs and bipolar lateral pnp transistors.

Oscillator strength of the barium 6s6p 1 P 1 –6s5d 1 D 2 transition inferred from photodeflection efficiency*

Abstract Isotope separation by laser deflection of an atomic beam, combined with simultaneous mass spectroscopy, has been used to determine optical frequency shifts and to assign mass numbers to all components of the Ba 6s 2 1 S 0 −6s6p 1 P 1 5536 A resonance. Several components which cannot be resolved optically without the use of enriched samples, were resolved with the technique described. They are 135 Ba (F= 5 2 ) at 120 MHz, 136Ba at 128 MHz and 134Ba at 138 MHz.