Laser-induced direct formation of C54 TiSi2 films with fine grains on c-Si substrates

Chen, S. Y.; Shen, Zexiang; Chen, Z. D.; Chan, L.; See, A.

doi:10.1063/1.124801

Cited by 14 publications

(8 citation statements)

References 13 publications

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“…However, this may not be the case for a single pulsed laser irradiation because the duration of annealing is in the regime of tens of nanoseconds. Although Chen et al 12 had reported that C54 TiSi 2 can be obtained using laser annealing without prior formation of the C49 phase, it should be mentioned that the laser system (a Q-switched Nd:YAG laser with a wavelength of 1.06 m) that was used in their experiment is different from the 248 nm pulsed excimer laser that was employed in this work. Hence, in our work, the heating mechanism during laser irradiation and duration of anneal (pulse duration) is different from that of Chen et al 12 Furthermore, they 12 postulated that C54 TiSi 2 was formed via a solid-state reaction between Ti and Si and that no melting had occurred during the laser irradiation.…”

Section: Resultsmentioning

confidence: 84%

“…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%

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Laser-induced titanium disilicide formation for submicron technologies

Chong

Pey

Wee

et al. 2001

Journal of Elec Materi

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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...

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Section: Resultsmentioning

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Laser-induced titanium disilicide formation for submicron technologies

Chong

Pey

Wee

et al. 2001

Journal of Elec Materi

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“…Pulsed laser annealing has also been investigated and several important benefits have been demonstrated. First, due to its fast ramping rate and short anneal duration, nanosecond laser annealing (UV-NLA) has been found to enable the formation of smaller grains of C49-TiSi2 than RTA [30][31][32] , increasing the density of C54-TiSi2 nucleation sites. Chen et al 30 have also reported that the transformation temperature into C54-TiSi2 can be significantly reduced by pulsed laser annealing.…”

Section: Introductionmentioning

confidence: 99%

“…Chen et al 30 have also reported that the transformation temperature into C54-TiSi2 can be significantly reduced by pulsed laser annealing. Moreover, the technologically favorable C54-TiSi2 phase has been obtained directly after the laser annealing step 30,32,33 .…”

Section: Introductionmentioning

confidence: 99%

Impact of nanosecond laser energy density on the C40-TiSi2 formation and C54-TiSi2 transformation temperature

Esposito

Kerdilès

Gregoire

et al. 2020

Journal of Applied Physics

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The formation of Ti based contacts in new image sensors CMOS technologies is limited by the requirement of low thermal budget. The objectives for these new 3D-technologies are to promote ohmic, low resistance, repeatable and reliable contacts by keeping the process temperature as low as possible. In this work, UV-nanosecond laser annealing were performed before classical rapid thermal annealing (RTA) to promote the formation at lower RTA temperatures of the low resistivity C54-TiSi2 phase. The laser energy density was varied from 0.30 to 1.00 J/cm² with 3 pulses in order to form the C40-TiSi2 phase and finally to obtain the C54-TiSi2 phase by a subsequent RTA at low temperature. The formed Ti-silicides were characterized by four-point probe measurements, X-Ray Diffraction, Transmission Electron Microscopy and Atom Probe Tomography. A threshold in the laser energy density for the formation of the C40-TiSi2 is observed at an energy density of 0.85 J/cm² for the targeted TiN/Ti stack on blanket wafers. The C40-TiSi2 formation by laser annealing prior to RTA enables to reduce the formation temperature of the C54-TiSi2 phase by 150°C in comparison to a single RTA applied after the Ti/TiN deposition. This specific phase sequence is only observed for a laser energy density close to 0.85 J/cm². At higher energy densities, the presence of C49-TiSi2 or a mix of C49-TiSi2 and C54-TiSi2 is observed. The underlying mechanisms for the phase sequence and formation are discussed in details.

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“…1 Compared to the C54 TiSi 2 phase grown via rapid thermal annealing the grain size of the laser-grown C54 TiSi 2 phase is smaller, 1 which is highly desired for interconnects in the subquarter very large scale integration ͑VLSI͒ technology. Because of the high reactivity and the gettering properties of Ti, 2-6 it is extremely difficult to avoid oxygen contamination during the TiSi 2 fabrication even when the Ti deposition and interface annealing are performed under ultrahigh vacuum ͑UHV͒ conditions.…”

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confidence: 99%