Transmission Electron Microscopy for metrology and characterization of semiconductor devices Bert Freitag, Laurens Kwakman, Ivan Lazic and Frank de Jong FEI / ThermoFisher Scientific, Achtseweg Noord 5, 5651 GG Eindhoven, The Netherlands
Trends in Semiconductors Industry 03/05/2017 Device scaling ( More Moore ), todays technology challenges: New 3D device structures New materials & chemistry +45 Elements (Potential) Complex, marginal processes. Critical dimensions in 3D, < 10 nm 2
Trends in Semiconductors Industry TEM Microscopy for two use cases: analytics & metrology 1 2 Ni2Si NiSi SiGe SiGe CD s Si b b c Co Ti Si Silicide short Cu BEOL FIN CD s LER: LER: Strain Ti SiN Si Metal Barrier Analytics & Defect analysis (EDX, EELS, Diffraction) ONO CD s Metrology : CD s, pitch, LER, OL, 3
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 TEM sample volume Trends in Semiconductors Industry TEM demand explodes to meet 3D transistor and litho challenges Faster TEM data and more TEM data: TEM sample volume trend metrology materials science TEM transition: from Lab to Fab Information source: Intel, SPIE 2016 TEM microscopy needs to be fast, automated and easy to use (and sensitive, accurate & reproducible for metrology) 4
A new STEM metrology workflow TEM microscopy requires a workflow with different tools to Prepare thin TEM lamellas from full wafers Extract TEM lamellas from wafer, return wafers in manufacturing line Measure TEM lamellas in TEM microscope
03/05/2017 FEI s TEM workflow developments in EU projects A TEM metrology box with FEI technology inside What Newly developed Technologies are inside? Phase 1: new METRIOS TEM platform Automated microscope alignements, active drift control Automated image acquisition Automated STEM and TEM metrology Made in The EU Phase 2: extended capabilities Software Embedded spherical aberration Corrector Software Embedded EDX acquisition Phase 3: improved capabilities New EDX detector Automated EDX metrology Improved accuracy: calibration and distortion corrections 6
(STEM) Probe Cs correctors, ease-of-use! Corrector Technology is not new, but the important innovation is that Abberation correction has become a simple push button operation! operators can use it instantaneously, automatically; it works and provides consistent, excellent results Example: 14 nm device using OptiSTEM Starting Point: C1A1 correction at low mag: 1 st order focus + stigmatism 7
(STEM) Probe Cs correctors Corrector Technology is not new, but the important innovation is that Abberation correction has become a simple push button operation! operators can use it instantaneously, automatically; it works and provides consistent, excellent results Example: 14 nm device using OptiSTEM Zoom in on silicon after 1 st order: Once per day, A2B2 correction: 2 nd order Axial coma + 3fold stigmatism 8
Time per Sample (min) The (demonstrated) benefits of automation Manual STEM metrology Automated STEM metrology 120 25 nm High Resolution ( ~ 1.1 A) Accurate (~ 1 %) CD info in 3D Image based, No modeling 100 80 60 40 20 0 Sample Prep Imaging & Metrology Automated Manual Slow No Statistical data Poor precision: (3% 3 s) Automation Fast (~ 10 x faster) 9
The (demonstrated) benefits of automation Manual STEM metrology Automated STEM metrology 25 nm High Resolution ( ~ 1.1 A) Accurate [~ 1 %] CD info in 3D Image based, No modeling 21 samples/wfr 45 devices/sample 5 CD s / device ~ 5000 data /10 hrs Slow No Statistical data Poor precision: (3% 3 s) Automation Fast (~ 10 x faster) Statistical Data (10 x more) 10
STEM Precision 3s (nm) The (demonstrated) benefits of automation Manual STEM metrology Automated STEM metrology 25 nm High Resolution ( ~ 1.1 A) Accurate (~ 1 %) CD info in 3D Image based, No modeling 1 0.8 0.6 0.4 0.2 0 STEM Metrology Dynamic Precision Manual Metrology Automated Metrology TopWidth MiddleWidth BottomWidth HeightSiOC HeightSi Pitch Slow No Statistical data Poor precision: (3% 3s) Automation Fast (~ 10 x faster) Statistical Data (10 x more) Adequate precision (1% 3s, 3x better) Accurate ( ~ 0.4 %, 2x better) 11
Metrios analytical STEM application examples
03/05/2017 EDX based metrology of 3D VNAND memory schematic of 3D VNAND memory Vertical X-section showing ONO stack Plan view STEM imaging of ONO dielectric Difficult (diffraction) contrast in direct STEM images for ONO metrology 13
03/05/2017 EDX based metrology of 3D VNAND memory Plan view EDX map with line scan EDX line scan TiN O N O Al x O y Si SiO2 Si N O N O Al Ti W W Si SiO 2 Si = 12.2 nm NONO = 2.6/4.2/4.3/9.7 nm TiN = 2.5 nm, AlO x = 3.0 nm EDX provides chemical contrast and is well adapted for ONO metrology 14
03/05/2017 Plasma doping of FINFET (damage and profile) Silicon FIN Silicon FIN Silicon FIN Imec s FinFet structure D03 a-silicon layer As precipitates D03 2nm Oxide layer voids SiO2 STI 45 nm HR STEM image showing silicon atoms (dumbells) Plasma doping does not create significant damage in the FIN silicon lattice 15
03/05/2017 Plasma doping of FINFET (damage and profile) a-si SiO 2 Si FIN Top of Fin EDX line scan profiles Si FIN SiO 2 a-si EDX scan stepsize: ~ 0.15 nm! STEM- EDX chemical map: Silicon, Oxygen, Arsenic As Si SiO2 Sidewall of Fin EDX line scan profiles EDX shows As doping accumulation at Si-SiO 2 interfaces 16
idpc a new STEM imaging technique
Imperfection of (S)TEM imaging techniques Ga? N? ABF-STEM GaN 110 (schematic) HAADF-STEM N Ga Ga N? 18
New technique: idpc-stem GaN 110 Ga N Titan FEI: idpc-stem of GaN 110 High tension: 300 kev Opening angle: 21 mrad Cs corrected 19
idpc How does it work? GaN Q1 Q2 Q3 Q4 4 Segment Detector y Beam Q3 Q2 r Q1 θ x I DPC r p = I idpc r p Q4 DPC x = Q 1 Q 3 DPC y = Q 2 Q 4 -E x = V/ x = Q1-Q3 -E y = V/ y = Q2-Q4 F I idpc = 1 2π F ψ in 2 F φ idpc (represents φ) φ = σv Integration (electric field is conservative) Patent: US 9,312,098 B2 Lazić et al. I. Lazić, E.G.T. Bosch, S. Lazar, Ultramicroscopy 160 (2016) 265-280 I idpc r p 20
Why do(n t) we see Nitrogen? GaN 1120 (experiment) ABF [2] idpc (object φ) [1] ADF (object φ 2 ) [2] Periodic system of elements (simulation) Ga 31 N 7 Ga 31 N 7 Ga 31 N 7 [1] I. Lazić, E.G.T. Bosch, S. Lazar, Ultramicroscopy 160 (2016) 265-280 [2] E.G.T Bosch, I. Lazić, Ultramicroscopy 156 (2015) 59 72 21
Examples on GaN[211] zeolite interfaces LiTi2O4 Semicon devices
Ultimate lateral resolution Comparison idpc with HAADF on GaN [211] 63pm 63pm More information accessible Light and heavy elements imaged at the same time with sub Angstrom resolution
Low-dose imaging with idpc: Zeolite Zeolite imaged at 300 kev idpc Dose: 961 e - /Å 2 Sample damages at dose of 5000 e - /Å 2 Not possible to focus using ADF image Zeolite structure: MFI ZSM-5 [010] Imaging of extremely sensitive materials possible 2nm
Interface termination : idpc-stem images of ZrO2/Ni interface HAADF idpc Zr O Sample: courtesy of Prof. Dr. Wayne Kaplan, Israel Institute of Technology Technion High pass filter Titan Themis 300 STEM at 300kV Image size: 512x512 Frame time: 6 s Detector: DF4/iDPC Converg. angle: 21 mrad Imaging of atomic configuration of the interface and the termination of the substrate Confidential 25
Extremely light element imaging Simultaneous ADF-STEM vs. idpc-stem ADF idpc LiTi 2 O 4 LiTi 2 O 4 Li clearly visible within LiTi 2 O 4 using idpc-stem
Extremely light element imaging idpc-stem: Experiment vs. simulation Observation from comparison with simulations: idpc Experiment Simulation t = 19 nm D f = -22.5 nm Li is visible if beam best focus is inside sample t = 19 nm D f = -15 nm In top-right corner Li is visible: Sample is probably thicker than 20 nm t = 8 nm D f = -5 nm Defocus change consistent with thickness change
BF 0 14 mrad Contrast enhancement on semicon devices : STEM EDS DF2 17 32 mrad Confidential DF4 34 89 mrad HAADF 89 210 mrad 28 STEM EELS in Talos 200kV Acquisition: 17 min System mag.: 910 kx Current 250 pa Drift corr.: On Map size: 406x384 Display: Raw counts, smoothed 28
Contrast enhancement on semicon devices STEM & idpc @ low dose Confidential BF 0 14 mrad DF4 34 89 mrad idpc STEM at 200kV Image size: 1024 x 1024 Detector: HAADF, DF4, DF2, BF Frame time: Magnification: Current 40 s 640 Mx 5 pa 29 idpc at 200kV Image size: 1024 x 1024 Detector: Frame time: Magnification: DF4, 1.1m Cl 20 s 640 Mx Current 5 pa, Filter 0 30 Contrast enhancement at only ~1000pe/pixel electron dose 29
Conclusions The newly developed automated Metrios Metrology TEM microscope combines ease of use with excellent metrology capabilities.now adequate for 10 nm device technology: precision ~ 0.2 nm 3s, accuracy ~ 0.4% Automated and sensitive STEM-EDX allows for fast chemical characterization (dopants, stoichiometry,..) but also complements STEM metrology for low contrast materials ( e.g. ONO layer stacks) Statistically relevant (S)TEM data provide new solutions for process control of advanced devices: Line roughness analysis (LWR and LER), Hybrid (reference) metrology for e.g. OCD or CD-SEM idpc-stem is direct and linear imaging electrostatic potential of the sample. It is capable of imaging light and heavy elements together. It is a low dose technique with superior contrast, which enables to handle sensitive materials in metrology applications 30
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