Differential thermal budget in laser processing: application to formation of titanium silicide

Verma, Gaurav; Talwar, S.; Bravman, J. C.

doi:10.1109/55.870608

Cited by 6 publications

(1 citation statement)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Owing to this unique characteristic, laser irradiation has been proposed to be used as an annealing technique to form thin silicided films with desirable electrical properties. [11][12][13][14] Talwar et al 14 have reported that laser annealing (with an additional RTA step) can form low resistivity TiSi 2 films on polysilicon gates with linewidths as small as 0.07 m and suggested that fine TiSi 2 grains can be formed after laser processing. However, detailed results of grain size analysis were not shown.…”

Section: Introductionmentioning

confidence: 99%

Laser-induced titanium disilicide formation for submicron technologies

Chong

Pey

Wee

et al. 2001

Journal of Elec Materi

View full text Add to dashboard Cite

A great deal of studies on thin-film silicides have been conducted over the past 15 years due to their applications in the fabrication of complementary metal oxide semiconductor devices. 1-7 Silicides can significantly reduce the contact resistance of the gate electrode and the source/drain regions as compared to nonsilicided structures. In particular, titanium disilicide (TiSi 2 ) has been used extensively as a contact material in ultra-large-scale integration technology because of its low electrical resistivity and good thermal stability. 2,3 TiSi 2 is a polymorphic material and may exist either as a high resistivity (ϳ60-90 ⍀cm) base-centered orthorhombic C49 phase or a low resistivity (ϳ15-20 ⍀cm) face-centered orthorhombic C54 phase. 2-4 When titanium reacts with silicon, the high resistivity C49 phase forms at temperatures ranging between 550 and 650°C and then transforms into the low resistivity C54 phase at annealing temperatures greater than 650°C. The C49 structure usually forms first due to a lower barrier to nucleation that has been attributed to a lower surface energy of this phase. On the other hand, the subsequent transformation from the C49 to the C54 phase is limited by a low driving force and a high activation energy. 3,4 Currently, a two-step anneal process is employed for the silicidation of titanium. The first rapid thermal anneal (RTA) step is to achieve the C49 TiSi 2 phase, and the second step is to form the low resistivity C54 TiSi 2 . However, as the width of the polysilicon line decreases to sub-0.25 m, conversion of C49 TiSi 2 to C54 phase becomes increasingly difficult. This is because the C49 to C54 phase transformation nucleates only at locations where three C49 grains intersect and the number of such intersection points (triple grain boundaries) is reduced as the gate length/polysilicon linewidth decreases. 5-7 As a consequence, the TiSi 2 films will be composed of a mixture of C49 and C54 phase and have a higher resistivity than if they are completely in the C54 phase. The need to completely form the C54 phase in submicron structures has encouraged numerous efforts to increase the density of C54 nucleation sites. They include rapid thermal processing, refractory metal ion implantation, and preamorphization of the silicon substrate prior to titanium deposition. [6][7][8] Pulsed laser beams are known to offer the advantage of rapidly heating and cooling localized areas near the top surface regions, while the underlying substrate remains at a much lower temperature. 9,10 Currently, a two-step anneal is employed for the formation of titanium selfaligned silicide (Salicide). The first rapid thermal anneal (RTA) step is to achieve the C49 TiSi 2 phase, and the second step is to form the low resistivity C54 phase. However, as the width of the polysilicon line decreases, conversion of C49 to C54 TiSi 2 becomes increasingly difficult. This is because the C49 to C54 phase transformation nucleates only at locations where three C49 grains intersect and the number of such intersection points i...

show abstract

Section: Introductionmentioning

confidence: 99%