Control of transient enhanced diffusion of boron after laser thermal processing of preamorphized silicon

Abstract

In this article we report the role of excess interstitials in the end-of-range region in transient enhanced diffusion of boron during annealing of laser-processed samples. The results show that although the amorphous layer in preamorphized silicon can be completely annealed by laser irradiation, the end-of-range damages were not sufficiently annealed. The end-of-range region contains a supersaturation of interstitial defects that enhance the diffusion of boron during a post-laser processing anneal. It is found that the transient enhanced diffusion is significantly suppressed when the melt depth is extended beyond the amorphous layer such that the interstitial dose in the region adjacent to the laser-melted layer is minimized. In this way, the abruptness of laser-processed ultrashallow junctions can be maintained upon further annealing at moderately high temperatures. Cross-sectional transmission electron microscopy shows that a virtually defect-free regrown layer is obtained by overmelting beyond the amorphous layer into the substrate.

Electrical activation phenomena induced by excimer laser annealingin B-implanted silicon

“…Excimer laser annealing (ELA) of ion implanted Si, thoroughly investigated in the early 1980s, 4-6 has recently received renewed interest within the semiconductor community for its possible application to the formation of ultrashallow junctions in Si. [7][8][9][10][11][12] The technique offers many advantages compared to conventional rapid thermal anneal (RTA) procedures, such as control over the junction depth and a higher dopant activation efficiency. [7][8][9][10][11][12] When performing ELA to form shallow junction, the junction depth is normally determined by the melt depth induced by the laser irradiation, as long as the implanted region is shallower than the melted one.…”

“…[7][8][9][10][11][12] The technique offers many advantages compared to conventional rapid thermal anneal (RTA) procedures, such as control over the junction depth and a higher dopant activation efficiency. [7][8][9][10][11][12] When performing ELA to form shallow junction, the junction depth is normally determined by the melt depth induced by the laser irradiation, as long as the implanted region is shallower than the melted one. 8,9,12 Indeed, this is the most commonly studied condition in the original works on laser annealing of B-implanted samples [4][5][6] and also represents the situation of more recent ULE implanted samples.…”

“…8,9,12 Indeed, this is the most commonly studied condition in the original works on laser annealing of B-implanted samples [4][5][6] and also represents the situation of more recent ULE implanted samples. 8,9,12 We showed that in ULE ͑1000-250 eV͒ B-implanted Si, the junction depth can be easily controlled by the energy density, irrespectively of the implantation energy. 8 In fact, the profile depth was approximately the same for different implant energies ͑1000-250 eV͒ and defined by the laser fluence only, as melt depth was exceeding the projected range of the implanted ions.…”

“…[7][8][9][10][11][12] When performing ELA to form shallow junction, the junction depth is normally determined by the melt depth induced by the laser irradiation, as long as the implanted region is shallower than the melted one. 8,9,12 Indeed, this is the most commonly studied condition in the original works on laser annealing of B-implanted samples [4][5][6] and also represents the situation of more recent ULE implanted samples. 8,9,12 We showed that in ULE ͑1000-250 eV͒ B-implanted Si, the junction depth can be easily controlled by the energy density, irrespectively of the implantation energy.…”

Role of low temperature rapid thermal annealing in post-laser-annealed p-channel metal-oxide-semiconductor field effect transistor

“…[6][7][8] However, a high temperature RTA above 800°C could cause undesirable boron deactivation and enhanced boron diffusion. [9][10][11] Furthermore, the effects of post-LA RTA are not decoupled from subsequent thermal cycles, such as silicidation, in the reported articles. 6,7 In this letter, we report that a post-LA RTA with an annealing temperature as low as 600°C can be used in reducing the crystalline defects unannealed out by LA during the formation of laser annealed ultrashallow p + / n junctions, leading to a good electrical performance of p-channel metaloxide-semiconductor field effect transistor ͑p-MOSFET͒.…”