Liquid Phase Epitaxy (LPE) Formation of Localized High Quality and Mobility Ge & SiGe by High Dose Ge-Implantation with Laser Melt Annealing for 10nm and 7nm Node CMOS Technology

Localized Ge and SiGe high quality/mobility device surface material region on bulk-Si and SOI wafers are needed for 10nm and 7nm node CMOS technology.  Traditionally SiGe and Ge device surface material on bulk-Si or SOI wafers are realized by CVD epitaxial growth or Vapor Phase Epi (VPE) at elevated temperatures.  Selective deposition can be achieved with hard mask.  To reduce defects strain relaxed buffer (SRB) or aspect ratio trapping (ART) have been employed with bulk-Si or layer transfer wafer bonding for SiGeOI or GeOI.  An alternative to VPE is to use either SPE (solid phase epitaxy) or LPE (liquid phase epitaxy) to form SiGe or Ge epitaxial surface layers.  

Using high dose Ge implantation >E16/cm² with photoresist soft mask as proposed in 2004 by Borland et al [1,2].  Localized amorphous Ge surface regions can be formed after Ge-infusion doping by Gas Cluster Ion Beam (GCIB) technique followed by low temperature SPE to form single crystal thin surface Ge epitaxial layers but residual end-of-range (EOR) damage remained.  Today, laser melt annealing of implanted junctions are currently being used in production for high quality back-side illuminated CMOS image sensors used in smart phone cameras by several IC and foundry semiconductor manufacturers to completely eliminate any residual implant damage/defects with 100% dopant activation provided the melt depth exceeds the implant damage depth [3]. 

Last year at IWJT-2013 Borland et al [4] reported using Ge-plasma ion implantation at 1E16/cm² and 1E17/cm² doses with laser melt annealing to realize up to 55% SiGe by LPE with >4x higher mobility at 160cm²/Vs.  One limitation they noted with plasma implantation was poor retained dose due to surface sputtering at low energies which limited the Ge content to <55% for 1E17/cm² dose.  Therefore to overcome this retained dose problem we investigated Ge beamline ion implantation in this paper which should give 100% retained dose. 

                The Ge surface amorphous layer thickness measured by elipsometry was 15nm while the Ge-SIMS depth profile measures 7nm Ge at 100%.  Therma-wave analysis was used to monitor the Ge-implant damage recovery and Ge or SiGe recrystallized epitaxial surface layer after various laser melt annealing conditions of varying power level and pulse duration.  The Ge-SIMS depth profiles shows we could vary the melt depth for  LPE Ge layer from 10nm to >400nm and the Ge layer content from 97% down to 2% respectively.   We will also show X-TEM of the Ge-LPE regions.

                Sb implantation was used to investigate n-type dopant activation in Ge at low and high doses of 3E13/cm² and 3E15/cm².  Rs measurements were done using a special Hx 4 point probe and SRP (spreading resistance profile) depth profiles.

                In summary, using high dose beam-line Ge-implantation we realized >7nm amorphous Ge deposition.  Epitaxial growth of Ge was achieved by liquid phase epitaxy using shallow laser melt annealing between 10nm and >400nm melt depths.

References

[1] J. Borland et al., ECS Oct 2004 meeting, PV 2004-07, p.769.

[2] J. Borland et al., US Patent #7,259,036 Aug 2007.

[3] S. Wuu et al., IEDM-2010, paper 14.1.

[4] J. Borland et al., IWJT-2013 meeting, paper S4-4, page 49.