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From exotic implantations to nickel-cobalt alloy for totally silicided gate modulation

Delphine Aimé 1,2Benoit Froment 1Véronique Carron 3Marco Hopstaken 4Frédéric Milési 3

1. STMicroelectronics, 850 rue Jean Monnet, Crolles 38926, France
2. Laboratoire de Physique de la matière (LPM), INSA, 7 avenue capelle, Lyon 69621, France
3. CEA (LETI), 17 rue des Martyrs, Grenoble 38054, France
4. Philips, 850 rue Jean Monnet, Crolles 38926, France

Abstract

In order to obtain a dual metal gate, workfunction tuning by various exotic implantations (F, O, Ga, In, C, Er, Se, Al, Sb,...) has been investigated for a fully silicided NiSi gate. According to electrical data, there is no significant breakthrough observed in the NiSi workfunction. However, it seems that some species like Al, Sb and Ga have special interactions with nickel silicide. TEM and SIMS analysis indicate that silicidation is strongly slowed down with Sb implant (<3e15 dose), and in a less extent with Al implants (>5e15 dose). In both cases, the silicidation has been blocked and the polySi gate has not been entirely silicided. On one hand, a uniform but thin NiSi layer was observed with Sb.On the other hand, Auger mapping clearly showed clusters and evidenced lateral phase segregation into NiSi matrix with poly-Si domains. Moreover, for species like Ga, the surface composition would consist mainly of Ni2Si and NiSi domains with local presence of Ga-precipitates, surrounded by Si-rich halo. This implies that implanted Ga has segregated during/after silicidation anneals, locally affecting silicidation kinetics. The same phenomenon might have appeared for fluorine.

As most exotic species implanted hardly modulate the workfunction, nickel-cobalt alloys formed from bilayers were also investigated for further gate modulation. It was observed that a significant modulation from 4,62eV to 5eV can be achieved, which is interesting for PMOS devices. Thorough electrical and physical characterizations such as SIMS and TEM were used to understand this modulation.

 

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Presentation: Oral at E-MRS Fall Meeting 2006, Symposium A, by Delphine Aimé
See On-line Journal of E-MRS Fall Meeting 2006

Submitted: 2006-05-15 19:11
Revised:   2009-06-07 00:44