Solid solubility limited dopant activation of group III dopants (B, Ga & In) in Ge targeting sub-7nm node low p+ contact resistance

Low contact resistance (Rc) is key to boost device performance for sub-10nm node. At VLSI Technology Symposium 2016 Samsung reported they reduced Rc by 10% from 14nm to 10nm bulk FinFET technology [1]. TSMC in their beyond 10nm node FinFET paper reported reducing S/D (source/drain) parasitic resistance and enhanced contact process [2] and at IEDM-2016 reported 7nm FinFET reduced S/D parasitic resistance and developed a novel contact process [3]. A complete session #7 was dedicated to “Contact Resistance Innovations for Sub 10nm Scaling” with 4 papers at the VLSI Technology Symposium 2016 [4-7]. To achieve Rc in the low E-9 Ωcm
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requires active dopant carrier concentration >5E20/cm
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to low E21/cm
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. For SiP n+ S/D contacts P >1E21/cm
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active dopant carrier concentration is realized with laser melt annealing resulting in Rc <1E-9 Ωcm
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[6]. For 70%-SiGe p+ S/D contacts IMEC reported using pre and post Ge amorphous implants to boost the B-implant activation with nsec laser melt annealing to reduce Rc from 1.2E-8 Ωcm
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to 2.1E-9 Ωcm
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[4]. IBM/GF on the other hand reported reducing SiGe p+ S/D Rc from 1.3E-8 Ωcm
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to 1.9E-9 Ωcm
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by using a thin 12nm 100%-Ge trench-epi and switching from a p+ Ge:B to a p+ Ge:B:group-III metastable alloy for surface interface doping [8]. The group-III Me-alloy in Ge boosted p+ dopant activation from ∼1E19/cm
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with B to ∼8E20/cm
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with Ge+Me-alloy. They mentioned no difference between msec non-melt and nsec melt laser annealing.