berlin Nanoscale Resolution Options for Optical Localization Techniques C. Boit TU Berlin Chair of Semiconductor Devices EUFANET Workshop on Optical Localization Techniques Toulouse, Jan 26, 2009
Jan 26, 2009 EUFANET 09 Toulouse 2 Nanoprobing of Identified Node Resolution < 50nm Parallel lapping down to contact layer Isolated devices Low ohmic contact Destructive to circuit AFM Feedback Tip Detector Probe Tip Piezo AFP needles tungsten contacts Laser Additonal Signals IMD W PW bulk-si NW bulk Silicon
Jan 26, 2009 EUFANET 09 Toulouse 3 Optical Backside Circuit Analysis GHz regime managed by most dynamic techniques Feature Size Resolution: 2 levels of analysis Level 1: IR + SIL to identify critical area Level 2: Nanoprobing to verify critical node prep circuit destructive increasing need for a high resolution optical localization technique Laser Stimulated Electrical Signal LVP Laser CCD Photon Emission
Trench Floor Planarity Jan 26, 2009 EUFANET 09 Toulouse 4 Global navigation through silicon with co-axial IR and ion column IR-Microscope Ion Beam DCG Systems - OptiFIB ΔZ 130nm Co-planarity check of trench bottom to chip levels with interference rings (fringes)
Jan 26, 2009 EUFANET 09 Toulouse 5 FIB Ultra Thin Back Surface Procedure mechanical thinning localized FIB trench -1 st endpoint on n-wells voltage image contrast -2 nd endpoint on STI material image contrast < 400nm remaining Si local high precision alignment actives 150µm STI n wells poly p-diff n-diff ARC 4-40000µm 2 STI
frontside AFP backside TUB Research @ ISTFA 07 parallel lapping down to contact layer isolated devices low ohmic contact Destructive to circuit FIB backside process devices not isolated creation of new circuit nodes Circuit fully functional AFP needles tungsten contacts IMD W FIB Pt D S G PW bulk-si NW bulk Silicon Jan 26, 2009 EUFANET 09 Toulouse 6
UltraThin Si - Ideal Platform for NanoAnalysis Jan 26, 2009 EUFANET 09 Toulouse 7 Ultra Thin Backside Technique Visible or UV Laser Stimulation Nanoprobing, C-AFM IR Technique LADA, Dyn. LS TUB Research E-Beam Techniques: - Voltage probing LVP, TRE - E Beam induced photocurrent LADA, Dyn. LS STI e - Light Nano Probes M1 M2 350nm n-well
Dual Gates: Ultra Thin Body not to scale etc M2 M2 Cu M1 W CoSi ILD p-poly n-poly p + NW STI STI n + PW p-poly 0,3µm BOX = Buried Oxide n-poly 100µm 1,5µm SX SX Jan 26, 2009 EUFANET 09 Toulouse 8
Jan 26, 2009 EUFANET 09 Toulouse 9 Interaction Dimensions Gate length Technology UTS (SOI PD) UTB (SOI FD / Dual Gate etc) 100nm 100nm 40nm 50nm 40nm 50nm
Backside Access: Transmission of Light in Silicon Jan 26, 2009 EUFANET 09 Toulouse 10 Spectral Absorption in Silicon Soref et al., IEEE J. of Quant. Elec., Vol. QE-23, No.1, January 1987 10 5 10 4 Concentration of free electrons N [x 10 18 cm -3 ] UTS: 350nm α (cm -1 ) Blue Light 430nm (2.8 ev): α 350nm -1 10 3 10 2 10 1 24 6 40 0.32 undoped T = 300 K 10 0 0.0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 Photon Energy (ev) UTB: UV? EBeam?
Jan 26, 2009 EUFANET 09 Toulouse 11 SNOM on UTB Resolution = f (tip geometry, working distance) but independent of wavelength! Photon Emission III-V Ge STI
Jan 26, 2009 EUFANET 09 Toulouse 12 SNOM on UTB Photon Emission Laser Stimulation - transferred power? LVP - SNR? III-V Ge STI
Jan 26, 2009 EUFANET 09 Toulouse 13 Resolution = f (tip geometry, working distance) but independent of wavelength! SNOM on UTB III-V Ge STI
Jan 26, 2009 EUFANET 09 Toulouse 14 Photon Emission LVP - SNR? Laser Stimulation - transferred power? Thermal LS when tip is scanning over STI SNOM on UTB III-V Ge STI
Jan 26, 2009 EUFANET 09 Toulouse 15 FET Delay Variation on Defined Node shorter wave length absorption depth 100nm optical confinement by FIB trench - waveguide - impact only on exposed transistor hν Resolution of stimulation by confinement
FIB Guided SNOM on UTB Jan 26, 2009 EUFANET 09 Toulouse 16 Adaption of Sidewalls to Fiber? Better thermal management: Narrow FIB Trench to UTS Trench as waveguide? or for Fiber probing? Ge STI III-V
FIBbed SIL Jan 26, 2009 EUFANET 09 Toulouse 17 Solid Immersion Lens (SIL) created out of the bulk silicon material perpendicular transition Si / air, no refraction sample surface (chip backside) removed material object plane
Results Jan 26, 2009 EUFANET 09 Toulouse 18 Images of the SIL (r 91 µm, t 34 µm) using a laser scanning microscope at wavelength λ = 1064 nm 30µm 30µm focused on SIL focused on background
Jan 26, 2009 EUFANET 09 Toulouse 19 Nanoscale Potential TUB Research Technique Resolution Potential Comment Optical through 500nm 100nm Limited bulk Si (IR) (SIL) resolution Nanoprobing 50nm 10nm Limited dynamics E Beam 100nm Material degradation? Optical through 300nm < 100nm Realization ultra thin Silicon (SIL) complex UV through ultra 150nm < 50nm Material thin silicon degradation?
Jan 26, 2009 EUFANET 09 Toulouse 20
Ultra Thin Body UTB Jan 26, 2009 EUFANET 09 Toulouse 21 SOI: Partially depleted = PD Fully Depleted FD V GS = 0 Poly Gate Depleted Si BOX Si V GS > V T Conductive Channel Subthreshold Slope 60mV / dec FD active layer => UTB