Laser Spike Annealing for sub-20nm Logic Devices Jeff Hebb, Ph.D. July 10, 2014 1 NCCAVS Junction Technology Group Semicon West Meeting July 10, 2014
Outline Introduction Pattern Loading Effects LSA Applications Dopant Activation Ti silicide Summary 2 NCCAVS Junction Technology Group Semicon West Meeting July 10, 2014
LSA Overview v s CO 2 Laser (10.6μm) Power Control Algorithm Temperature Conversion Reflective Optics p-polarized Hot Chuck Scanning Stage Emission Detector Laser Beam V s Dwell time = w v x Silicon Note: Beam is stationary, wafer scans Key Attributes Within-die Uniformity CO2 Laser: λ ~ 10um P-polarized, brewster angle Within-wafer & Wafer-to-wafer Temperature feedback control 3 NCCAVS Junction Technology Group Semicon West Meeting July 10, 2014
Pattern Loading Effects 4 NCCAVS Junction Technology Group Semicon West Meeting July 10, 2014
Pattern Effects and Parametric Yield System-on-a-Chip A B T Low T High Variations in pattern density lead to local variations in the absorbed radiation during RTP or millisecond anneal This can lead to local variations in peak temperature, and variations in performance of devices which are supposed to be matched Device A gets colder during anneal Device B gets hotter during anneal Device Performance Mismatch! Pattern loading effects during millisecond annealing or RTP can cause device performance mismatch within the die parametric yield loss and degraded circuit speed 5 NCCAVS Junction Technology Group Semicon West Meeting July 10, 2014
Pattern Loading Effects in RTP: Equipment Solution Ref 1 Highlights Lots of recent work on how to change RTP equipment solutions to suppress pattern effects: backside heating 1 or Differential Thermal Energy Control 2 These approaches are being implemented in Fabs for critical processes at advanced nodes Current implementations for dummification are not adequate for critical processes Ref 2 1. X. Yu et al, IEDM 2012 2. P. Timans et al., IWJT 2014 6 NCCAVS Junction Technology Group Semicon West Meeting July 10, 2014
Pattern Effects in MSA: Layout Design Solution Pre-dummification Post-dummification ΔT > 100 o C (typical) (yp Simulation showed ΔT < 50 o C SC Lin et al., Using genetic algorithm to optimize the dummy filling problem of the flash lamp anneal process in semiconductor manufacturing, J. Intell. Man. (2012) Difficult to reduce to acceptable levels due to short heat diffusion length (~100um) Difficult to make design rules to cover all layouts in a foundry environment 7 NCCAVS Junction Technology Group Semicon West Meeting July 10, 2014
Pattern Loading Effects: Thin Film Interference PLE: DL > FLA >> LSA Re eflectivity (%) FLA/RTP Diode Laser (λ=0.8um) Re eflectivity (%) 100 80 60 40 CO2 θ Bare Si wafer 340 nm oxideonsi +10% oxide thickness -10% oxide thickness 120 nm poly on oxide +10% poly thickness -10% poly thickness LSA CO 2 (λ =10.6um) P-polarized Brewsters Brewster sangle 20 Wavelength (μm) 0 9.0 9.5 10.0 10.5 11.0 11.5 12.0 Wavelength (μm) PLE caused by thin film interference variations severe at short λ Long λ+p-pol+brewster s angle make LSA insensitive to device film variations 8 NCCAVS Junction Technology Group Semicon West Meeting July 10, 2014
2 5 Pattern Loading Effects in Millisecond Annealing: Equipment Solution (LSA) LSA Flash Anneal / Diode Laser 0 5 1 0 1 5 2 0 Fins θ Long λ Brewsters Angle No shadowing or light trapping by Fins Fins Short λ Near normal incidence Can have light trapping by Fins Silicon Silicon Measured reflectance map Measured reflectance map ΔT ~ 10 o C ΔT > 100 o C LSA provides an equipment solution for PLE in millisecond annealing 9 NCCAVS Junction Technology Group Semicon West Meeting July 10, 2014
Applications 10 NCCAVS Junction Technology Group Semicon West Meeting July 10, 2014
LSA Applications for 14/10nm FinFET Devices Fin Hi-k anneal Extension anneal Ti silicide S/D Anneal & Re-activation Device Applications Source/Drain extension annealing Deep Source/Drain annealing Hi-k anneal Dopant re-activation Ti Silicide LSA enables device performance improvements and leakage reduction for FinFETs 11 NCCAVS Junction Technology Group Semicon West Meeting July 10, 2014
Source/Drain (epi) Activation Post-dep properties of Si:P Epi 1 Post-LSA properties of Si:P Epi 1 As-deposited activation efficiency is low Trade-off between growth rate and activation Activation greatly improves with LSA Further improvement with cryogenic a-si + LSA LSA improves activation and device performance by S/D activation in FinFETs 2 Sources: 1.Itokawa et al., IWJT 2012, 2.Yamashita et al, VLSI 2011 12 NCCAVS Junction Technology Group Semicon West Meeting July 10, 2014
Thermal Profiles of LSA vs. Flash Anneal T1 T2 T2 Active Carr rier Concen ntration ne ear peak (cme Carrier Con ncentration 3) ( De-activation during FLA anneal 1.E+21 10 21 (cm -3 ) Peak Active 1E+20 1.E+20 10 T2=1100C, As 3keV 2e15 Ref: H. Kennel (Intel), RTP 2010 10 20 600 700 800 900 1000 Intermediate Temperature, T1 (C) LSA is a true low thermal budget anneal with no dopant de-activation Extra thermal budget of FLA can cause dopant de-activation slower devices 13 NCCAVS Junction Technology Group Semicon West Meeting July 10, 2014
New Channel Materials 7nm pfet 7nm nfet Me elting Tempe erature (C) 1600 1400 1200 1000 800 600 Si In.5 Ga.5 As InP Ge A. Steegen, Imec Technology Forum, Semicon 2014 New channel materials will suffer damage at much lower thermal budgets than Si Low thermal budget of LSA compatible with new channel materials 14 NCCAVS Junction Technology Group Semicon West Meeting July 10, 2014
Arsenic Activation and Diffusion in Ge SPE Regrowth Thickness for 200usec LSA (calculated) Ge Si Highlights Ge substrates* implanted with As 5keV 2e15 (creates ~10nm self amorphizing layer) Since SPE happens in Ge at much lower temperatures than Si, use low chuck temperatures to reduce thermal budget** Splits: Peak temperature: t 600 to 900C Dwell time: 200 and 800usec Chuck temperature: RT and 200C *Note: Substrates were Ga doped to ~ 6e17cm-2 ** A higher SPE temperature typically results in higher activation * Y. Wang et al., IWJT 2014 15 NCCAVS Junction Technology Group Semicon West Meeting July 10, 2014
Arsenic Activation in Ge: Results Chuck T=200 o C Chuck T=200 o C 200usec 200 and 800 usec Significant diffusion starts above 760C at 200usec Significantly ifi more diffusion i at 800usec than 200usec * Y. Wang et al., IWJT 2014 16 NCCAVS Junction Technology Group Semicon West Meeting July 10, 2014
Arsenic Activation in Ge: Results (cont d) Rs vs. Temperature Rs vs. Xj Significant Rs reduction at 800usec due to extra diffusion Chuck temperature RT vs. 200C did not make significant difference * Y. Wang et al., IWJT 2014 17 NCCAVS Junction Technology Group Semicon West Meeting July 10, 2014
LSA for Titanium Silicide Schottky barrier height Advantages of LSA for Ti silicide φb ρc exp Higher temperature than RTA N D lower contact resistance Dopant concentration Minimal interdiffusion of gate stack layers Process control Minimal pattern effects Closed loop temperature control Becomes critical for Ti silicide where process window is smaller than Ni silicide Refs: D. James, AVS JTG Semicon West (2013) and C. Sohn et al., IEEE Trans. Elec. Dev., Apr. 2013. 18 NCCAVS Junction Technology Group Semicon West Meeting July 10, 2014
LSA for Ti silicide: Phase Transformation Study Y. Wang et al, IWJT 2014 Phases detected by XRD: A1: Ti A2: Ti, Ti 5 Si 3 A3: Ti 5 Si 3, possible Ti 5 Si 4 or TiSi 20nmTi with B2/B3: TiSi 2 (C40) 10nm TiN cap B4/B5: TiSi 2 (C54) Examples of φ B (G. Qttaviani et al, 850-1000 o C Phys. Rev. Lett., 1980): TiSi 2 : 0.6V TiSi: 0.5V NiSi: 0.67V Low Rs not required Low Rc is the goal (low φ B ) No need to anneal at temperatures greater than ~1000C, where gate stack could be compromised 19 NCCAVS Junction Technology Group Semicon West Meeting July 10, 2014
Measured reflectance: LSA (10.6um) Pattern Loading Effects (PLE) For Silicides Within-die temperature distribution: Simulated from measured reflectance maps 40 Measured reflectance: Diode Laser (0.8um) ΔT ~ 10C ensity obability D Pr 30 20 10 Diode laser LSA Ti Silicide Process Window (estimated) ΔT > 100C 0 700 750 800 850 900 950 T ( o C) Severe PLE of diode laser could impact yield for Ti silicide (PLE >100C) PLE of LSA is well within the process window (PLE~10C) 20 NCCAVS Junction Technology Group Semicon West Meeting July 10, 2014
Summary Long-wavelength LSA provides an equipment-design solution for pattern loading effects in millisecond annealing LSA plays a critical role in reducing series resistance and leakage in today s FinFETs through multiple applications As sub-10nm devices migrate to new channel materials, low thermal budget annealing approaches such as LSA will be become more critical 21 NCCAVS Junction Technology Group Semicon West Meeting July 10, 2014