Epitaxial Growth of Ga-doped SiGe for Reduction of Contact Resistance in finFET Source/Drain Materials

Abstract

Here we evaluate in-situ Ga doping of SiGe as an alternative to ex-situ ion implantation for source/drain contact formation. Si0.5Ge0.5 layers are grown on an ASM Intrepid ES high volume CVD reactor and co-doped with B and Ga. A circular transmission line measurement (CTLM) comparison of SiGe:B and SiGe:B:Ga is presented and we report a statistically significant improvement in contact resistivity with the addition of Ga. The Ti/SiGe contacts formed with the B-doped sample had an average ρc ~ 9 x 10-9 Ω-cm2 while the best Ga/B co-doped sample yielded an average ρc ~ 2.5 x 10-9 Ω-cm2. We also evaluate the epitaxial growth on fin patterned wafers and we are able to demonstrate high crystalline quality SiGe:Ga layers without loss of selectivity on the dielectric areas of the wafer.

Ultralow Contact Resistivity on Ga-Doped Ge with Contact Co-Implantation of Ge and B

“…Note that the samples have already been Gadoped before contact implantation, and such procedure is to mimic the practical contact flow in modern PMOS. [12][13][14][15][16] Fig. 6 shows SIMS Ga and B profiles for the three CT I/Is.…”

“…[5][6][7] Recently, Ga is proposed as a promising p-type dopant for Ge-based materials such as Ge, SiGe, and GeSn due to its high solid solubility of 5 × 10 20 cm −3 in Ge, 4 and as compared with the B-doped counterparts, superior contact performances with sub-10 −9 ρ c have been demonstrated on Ga-doped Ge, 8,9 SiGe, 10 and GeSn. 11 In modern PMOS, Ga is more often used for contact surface doping to booster the metal/SiGe interfacial acceptor concentration, in combination with B for S/D junctions doping [12][13][14][15][16] to further lower ρ c . In, 9 contact surface doping of Ga was also adopted on in situ Gadoped S/D regions for Ge and GeSn, further ρ c improvements were accomplished.…”

B and Ga Co-Doped Si1−xGex for p-Type Source/Drain Contacts

“…p-type Si 1−x Ge x epitaxial layers with a nominal Ge content of 45% were externally grown using chemical vapor deposition (CVD) on blanket 300 mm n-type Si(001) substrates. 19 The samples include a B-doped Si 1−x Ge x reference (sample R) and five Ga and B codoped Si 1−x Ge x epilayers (samples A, B1, B2, C, and D). Samples A, B1, B2, and C were grown targeting an increasing nominal Gacontent from A to C. Sample B1 and B2 have the same nominal Galevel, but different thicknesses, with t B2 > t B1 .…”

Pulsed Laser Annealed Ga HyperdopedPoly‐Si/SiOxPassivating Contacts for High‐Efficiency Monocrystalline Si Solar Cells

“…However, doping concentrations >10 20 cm −3 are desired for various applications, such as shallow p + junction, [38,39] superconducting semiconductors, [40][41][42] and low contact resistivity p-type contacts for solar cells. [32,43] Conventional thermal processes cannot reach a high level of doping concentration, so to overcome the equilibrium solid solubility limit, some early studies in the 1980s based on non-equilibrium processes have shown supersaturated Ga in silicon with a substitutional doping level of 1-8 × 10 20 cm −3 [44][45][46][47][48] as well as an active doping concentration of ∼3.5 × 10 20 cm −3 . [49,50] But in all works reported, Ga was solely studied in single crystalline silicon, and no studies have been shown to investigate Ga hyperdoping in poly-Si or in poly-Si/SiO x passivating contact structures.…”