Pulsed-electron-beam annealing of ion-implantation damage

Abstract

Short-duration high-intensity pulsed electron beams have been used to anneal ionimplantation damage in silicon and to electrically activate the dopant species. Lattice regrowth and dopant activation were determined using 4He+ backscattering, SEM, TEM, and device performance characteristics as diagnostic techniques. The annealing mechanism is believed to be liquid-phase epitaxial regrowth initiating from the substrate. The high-temperature transient pulse produced by the electron beam causes the dopant to diffuse rapidly in the region where the liquid state is achieved.

Demonstration of Pulsed Electron Beam Applications (PEBA) for Fabricating Small Geometry Semiconductor Devices

“…In addition, the liquid phase epitaxy technique was shown to reduce dislocation density in the annealed, implanted regions compared to furnace processing. 4 PEBA affected only the near surface region, and did not diffuse junctions below the implants, about 1 micron…”

“…( 4 ) Through control of'fluence and particle energy, electron beams were used to heat silicon to a depth of one micron, allowing temperature in the bulk of the wafer to rise no more than 100C. Brief thermal gradients caused epitaxial crystal growth in the heated surface material to anneal ion implantation damage, and to recrystallize low temperature deposited polycrystalline or amorphous silicon films.…”

“…Liquid phase epitaxy uses the electron beam to melt the silicon to some desired depth, below the implant, and restores perfect crystal structure upon cooling. (4 ) Solid phase epitaxy is a two step anneal, with a low temperature thermal treatment (e.g., 550 0 C for 2 hours) restoring the crystal structure, (7 ) and a pulse at non-melting fluence levels activating the dopant. Each process has different applications.…”

Large area electron beam annealing

“…1 Annealing via electron beams has also been achieved using point/ line/ and broad area sources. 4 The previous electron beam annealing worku employed high voltage ( > 20 k V) beams of small area that were focused to reach the required energy density. The broad area source used previously 4 was a high voltage (20-100 kV) high current (10-50 kA) field emission discharge that provides a 100-ns pulsed electron beam.…”

“…In annealing applications it caused liquid phase regrowth of the implant damaged layer of the semiconductor substrate thereby causing undesired redistribution of the as-implanted dopant profile. 4 More recently, an electron beam generated by a glow discharge was used to anneal ion implanted silicon. 5 In this experiment a 10-cm-diam aluminum cathode operating in pure helium produced a maximum discharge current of 80 rnA at 9 k V (unfocused electron beam power density was -9 W / cm 2 ) .…”