Method involving pulsed beam processing of metallic and dielectric materials

#1. Field of Invention

#The present invention relates to thermal processing of metallic and dielectric materials and, more particularly, is directed towards a method and apparatus involving pulsed beam localized thermal processing of metallic and dielectric materials.

#2. Description of the Prior Art

#A fuller understanding of the nature and objects of the present invention will become apparent upon consideration of the following detailed description taken in connection with the accompanying drawings, wherein:

#FIG. 1 is a schematic and block diagram of a system embodying the present invention for pulsed flash lamp processing of metallic and dielectric materials;

#FIG. 2 is a schematic and block diagram of an alternate embodiment for pulsed laser processing of metallic and dielectric materials;

#The present invention provides a method and apparatus for localized thermal processing of specific regions of metallic and dielectric materials by momentarily elevating the temperature, thermal gradient and heating/cooling rate of the surface region. Thermal processing includes mechanical annealing, annealing and electrical activation of ion implanted material, annealing of ion induced radiation damage, sintering for electrical or mechanical characteristic improvement, short range atomic diffusion in the material, formation of arbitrary alloy phases, surface texture modification, and the like. A short duration pulsed beam generated by, for example, an electron beam generator, a laser or flash lamp, is directed towards specific surface regions of the metallic or dielectric material to be processed. The short duration pulse impacts upon the surface region, the pulsed electrons or photons incident upon the surface being absorbed as they penetrate the material, and the deposited energy momentarily elevates the thermal process parameters in the vicinity of the impacted region. The desired thermal effect occurs when the temperature in the region to be processed exceeds specified threshold levels, the threshold levels being related to the particular process effect desired and the specific material involved.

#The parameters that are variable in the pulsed beam processing are: (1) the energy spectrum of the pulsed beam; (2) the duration of the pulses; (3) the total energy per unit area carried to the material surface by the electron beam or photons per pulse; and (4 ) the total number of pulses employed. The energy spectrum, intensity and pulse width are selected so that specific process parameters in the entire region to be processed are raised above minimum process effect levels. Duration of the pulse is sufficiently short so that the deposited energy is not dissipated from the process region during the pulse period, whereby minimum processing temperatures are not presented throughout the region. The total energy deposited per unit area on the metallic or dielectric material by the pulse is determined from consideration of the requirements for achieving minimum thermal processing parameters throughout the implanted region without exceeding thresholds for energy-induced structural damage mechanisms such as vaporization, fracturing, and the like, anywhere in the material. It has been found that single pulses are adequate for annealing particular ion implantation conditions in specific materials, however, multiple pulses are necessary for completion of other pulsed processes under certain conditions.

#Pulsed electrons and photons incident upon the material surface are absorbed as they penetrate the material. The energy of the electrons and photons is converted to heat in the absorbing material, the heating effect being spatially dependent upon rate and position at which the energy is absorbed. The momentary temperature elevation in a region extending from the material surface through an arbitrary selected depth is controlled by varying the pulsed beam parameters. The use of the pulsed beam for processing of metallic and dielectric materials provides localization of thermal treatment at the necessary region, the treatment being performed in time durations of the order of 10.sup.-1 second or less. Temperatures achieved depend upon the material and the deposited energy density, and are controlled by selection of the characteristics of the electron or light pulse. At completion of the pulse period and the achievement of peak temperature, the temperature profile relaxes back to an equilibrium level with a time constant which depends upon geometry and material characteristics.