Enhanced formation of the C54 phase of TiSi2 by an interposed layer of molybdenum

Shen

See³

et al. 2001

J. Electrochem. Soc.

We report on the formation of a new material, C40 TiSi 2 , using pulsed laser annealing. On the basis of this laser-induced C40 TiSi 2 , the growth of the technologically important C54 phase is significantly promoted and can be accomplished with a subsequent rapid thermal anneal or furnace annealing at temperatures far below that for the normal C54 formation. The undesirable C49 TiSi 2 is completely bypassed. C40 TiSi 2 can also be easily transformed to the C54 phase with thermal treatments and result in the formation of a pure C54 TiSi 2 layer. The synthesis of C40 phase without the additional refractory metals and its promotion effect on the C54 phase formation have great potential for applications in the integrated circuit industry for 0.10 m technology node and beyond.Titanium disilicide ͑TiSi 2 ) has been widely applied as contact and gate electrodes for complementary metal-oxide-semiconductor ͑CMOS͒ transistor in ultralarge-scale integration ͑ULSI͒ technology. 1 In the current semiconductor industry, rapid thermal annealing ͑RTA͒ is used to fabricate TiSi 2 from Ti/Si wafers. The high resistivity ͑60-70 ⍀ cm͒ metastable C49 phase forms first at RTA temperatures of 550-700°C and transforms to the lowresistivity ͑15-20 ⍀ cm͒ stable C54 phase at higher temperatures of 750-850°C. C54 TiSi 2 is the preferred phase for integrated circuit ͑IC͒ fabrication due to its lower resistivity and better thermal stability as compared with C49 phase. Therefore, a complete C49 to C54 phase transition is important for IC fabrication. However, due to the ''fine line effect'', 1 the transformation to C54 phase on narrow polysilicon lines requires very high annealing temperature, which causes severe problems such as agglomeration 2 and ''punch through'' 3 and results in device failure. Promoting C54 phase formation at low annealing temperatures is essential in terms of both industrial requirements and scientific interests.The conventional preamorphization implantation ͑PAI͒ 4 and implantation through metal ͑ITM͒ 5 methods were usually used to enhance the C54 phase formation by using implantation to create an amorphous Si surface. In recent studies, refractory metals were found to facilitate the C54 phase formation and three approaches were developed to lower the C54 phase formation temperature. A group of IBM researchers first demonstrated that ion implantation of a small dose of refractory metals into the Si substrate prior to Ti deposition could reduce the C54 TiSi 2 formation temperature by 100-150°C. 6 Cabral et al. from the same group later revealed that codeposition of Ti alloyed with refractory metals could serve the same purpose. 7 Mouroux et al. 8 used a different approach in which a thin layer of refractory metal was deposited between Ti capping layer and Si substrate, and the C54 phase was obtained at 100°C lower than the normal C54 formation temperature. 8 Here we demonstrate a different approach to enhance the C54 phase growth and to effectively lower its formation temperature, using laser processing as the first ann...

Section: Discussionmentioning

confidence: 98%

Enhancement Effect of C40 TiSi[sub 2] on the C54 Phase Formation

Shen

See³

et al. 2001

J. Electrochem. Soc.

European Workshop Materials for Advanced Metallization,

“…but Rsqr increases considerably with decreasing linewidth presumably because of the uncompleted C49 to C54 phase transformation. With MO, R, is not only lower but also much less sensitive to linewidth, which is a consequence of the direct formation of the C54 phase already at 700°C [2,3]. For the samples with the silicide formed from the TiMo bilayers at 800"C, a constant value of R, around 2 0 per square is obtained down to 0.35 pm linewidth.…”

mentioning

confidence: 86%

“…Important advances in this specific subject have been made recently : The temperature needed for the formation of the C54 phase of TiSi2 is shown to be lowered by 100-150", either by ion implantation of MO or W into Si prior to Ti sputter-deposition [l], or by deposition of a thin MO layer between Ti films and Si substrates [2]. It has hrther been demonstrated [2,3] that a template mechanism is operative, at least for the case with the interposition of a thin MO layer.…”

Section: *Kth-electrum Solid State Electronics Box E229 S-164 40 Kmentioning

confidence: 99%

A self-aligned silicide technology with the Mo/Ti bilayer system

Kaplan

Mouroux

Zhang

1998

Self Cite

Self-aligned silicide (SALICIDE) with TiSi2 is the most widely used metallisation process that is based on the utilisation of metal silicides in the Si VLSI technology. One important issue with the TiSi;! SALICIDE process is the ever increased difficulties in phase formation on polycrystalline Si (poly-Si) lines, as the line width is scaling down continuously. It is more so on heavily doped poly-Si lines below 0.5 pm width.Despite numerous studies, the formation of TiSi2 remains as a technological challenge. Important advances in this specific subject have been made recently : The temperature needed for the formation of the C54 phase of TiSi2 is shown to be lowered by 100-150", either by ion implantation of MO or W into Si prior to Ti sputter-deposition [l], or by deposition of a thin MO layer between Ti films and Si substrates [2]. It has hrther been demonstrated [2,3] that a template mechanism is operative, at least for the case with the interposition of a thin MO layer.In this work, the formation of Ti& from the T M o bilayers on both blanket and patterned poly-Si substrates during rapid thermal annealing (RTA) was first studied by means of electrical measurements on van der Pauw test structures. Then, ohmic contacts between the silicide and both p-and n-type Si, as well as electrical shorts between the gate and sourceldrain electrodes were investigated. The MO layer was 0.5 nm thick (nominal), and the Ti layer 60 nm. The silicide formation was camed out in N? atmosphere at 700" or 800°C for 30 seconds. Sheet resistance ( R , )measurements of the TiSi2 films formed on blanket substrates show that the presence of MO enhances the formation of the C54 phase resulting in lower R, values at 7OOOC fig. l), in accordance with our previous results on Si and poly-Si substrates [2.3]. On submicron lines, the comparison between the silicide formed from the TiMo bilayers and that from pure Ti (reference) is presented infigure 2. Generally, R, is lower and the spreading in R, is smaller for the samples with MO, under otherwise the same conditions for silicide formation. For the TiSiz formed without MO, it is mainly the C49 phase that is formed at 700°C. Increasing the formation temperature to 800°C reduces R, substatially. but Rsqr increases considerably with decreasing linewidth presumably because of the uncompleted C49 to C54 phase transformation. With MO, R, is not only lower but also much less sensitive to linewidth, which is a consequence of the direct formation of the C54 phase already at 700°C [2,3]. For the samples with the silicide formed from the TiMo bilayers at 800"C, a constant value of R, around 2 0 per square is obtained down to 0.35 pm linewidth. Additional results on contact resistance measurement with Kelvin structures and bridging test with long gates will be presented, showing, probably for the first time, an approach towards the SALICIDE technology using TiMo bilayers. MAM'97 -Materials for Avanced Metallization 116

“…The C49 TiSi 2 is a high-resistivity (60-70 µ Ðcm) metastable phase, whereas C54 TiSi 2 is a stable phase with low resistivity (15-20 µ Ðcm) transformed from the C49 phase. 3 Currently, the rapid thermal annealing (RTA) process is used for silicidation of Ti on Si substrates. The C49 phase is formed first by low-temperature annealing at 600-700°C.…”

Section: Introductionmentioning

confidence: 99%

Laser-induced formation of titanium silicides

Shen

et al. 1999

Surf. Interface Anal.

In this article, we report on the laser‐induced formation of both C49 and C54 TiSi2 films with fine grains using Q‐switched Nd : YAG laser irradiation from Ti/Si samples. The films formed were characterized with micro‐Raman spectroscopy, high‐resolution transmission electron microscopy, energy‐dispersive spectrometry and atomic force microscopy. The TiSi2 films synthesized are single‐phased and thin, with fine grains and a smooth film/substrate interface on the atomic scale. The process is likely to proceed via a solid‐state reaction rather than liquid‐phase intermixing. Our results demonstrate the unique advantages of a laser annealing technique and its potential in deep submicron semiconductor technology. Copyright © 1999 John Wiley & Sons, Ltd.