Nanotechnology I+II 2006 / 07

Transcription

1 Nanotechnology for engineers Winter semester Nanotechnology I+II 2006 / 07 Juergen Brugger & Patrik Hoffmann & Teams Course agenda (winter semester) Nanotechnology I winter semester ( ) week hour content Presented by responsible 25-Oct 1 Cours objectives, "regles de jeu" JB 1 2 Outlook to the course. Table de matieres. What is nanotechnology? " 1-Nov 1 Basics of Physical Chemistry (Atkins Chapter), PH Martin/Alexandre 2 2 QM for spectroscopy - and chemical bonds " " 8-Nov 1 " " " 3 2 chemical bonds, molecular orbital " " 15-Nov 1 " " " 4 2 " " " 22-Nov 1 Nanomaterials, wet, dry, nanoparticles, security aspect " " 5 2 Nanocharacterization; optical microscopy " " 29-Nov 1 Exercice (1): Phys.Chem basics " " 6 2 Nanocharacterization: SEM, TEM " " 6-Dec 1 Nanocharacterization: SEM, TEM " " 7 2 " " " 13-Dec 1 " " " 8 2 Exercice (2): Opt and electron microscopy " " 20-Dec 1 Electron microscopy " " 9 2 " " " NOEL vacances 10-Jan 1 Physical effects in nanoscale device (Coulomb blockade, tunneling,..) JB Oscar 10 2 Tunnel effect and STM " " 17-Jan 1 Scaling laws, forces at nanoscale " " 11 2 Nanocharacterization: AFM and other SPM " " 24-Jan 1 Exercise (3): Nanoscale effects, STM, AFM " " 12 2 PVD thin film for nanotechnology " Kris 31-Jan 1 Nanolitho (lateral control, materials, DUV, EUV, EBL, challenges, ) " " 13 2 Exercice (4): Ultra-thin films and lithography " " 7-Feb 1 Review of winter semester; outlook of summer semester. " " 14 2 Test 1: 10 multiple choice, 3 simple calcuations, 3 verbal answers (45 min) " " 2 1

2 Nanotechnology for engineers Winter semester (nano)lithography Lithography was originally invented as a method for printing in 1798 by Alois Senefelder, and has been a valuable method for reproducing artwork for centuries. From the Greek lithos (stone) and graphy (writing), lithography literally means writing on rocks. In the context of nanotechnology, the method is widely employed by the semiconductor industry to pattern the surface of silicon wafers. Illumination Light source Optical system Mask Resist CMOS in Nanometric dimensions 10 mm 1 1K 1M 1G 1T Nbr of devices on 1 chip µm MEMS Transistor IC s 1 µm Quantum dots ( nm) neurones Human Brain dendrites 10 nm 1 Ang Nanowires (5nm) Nanotubes ( 1.3 nm) 2004 Limits of matter 2010 Proven Feasibility 4 2

3 Moore s law(s) The Law originated in 1965, when Gordon Moore, then head of R&D at Fairchild Semiconductor Corp. and now chairman emeritus of Intel Corp., Santa Clara, Calif., predicted that the number of transistors on an IC would double every year for the next 10 years [IEEE Spectrum, June 1997, pp ]. At that time, Moore's astute prediction had not yet achieved law hood. It was simply an extension of a straight line through five points on a semi-logarithmic plot of transistor count per year for the first six years of the neonatal IC industry, Moore's Second Law states that the cost of building a semiconductor fab line is doubling every three to four years. According to Dan Hutcheson, the president of VLSI Research, "The price per transistor will bottom out sometime between 2003 and From that point on, there will be no economic point in making transistors smaller. So Moore's Law ends in seven years" (Forbes, 25 March 1995). 5 What are the challenges for NGL? Technical challenges Resolution Throughput ( W/H) CD control (10% of nominal CD) Overlay (30% of the node) Resist issues Pellicles issues Economical challenges Mask cost and fabrication delay Equipment cost Equipment in time to market NGL: Next Generation Lithography 6 3

4 Content Lithography: Brief survey Optical lithography Illumination methods Resolution limits Resolution enhancements Exposure wavelength and light sources Mask materials and optical systems Set-up of the optical path for short wavelength Extreme UV (EUV), X-ray lithography Electron beam lithography Electron direct write Scalpel Photoresist Alignment of several layers 7 Survey Data of micro/nanostructure (CAD) Electron beam writer / laser beam writer DUV nm UV: nm Mask for contact, proximity or projection lithography EUV 11-14nm X-ray <10nm Electron beam projection Ion beam projection Direct writing Resist coated substrate / develop Wet/dry chemical etching Micro/nanostructure on substrate 8 4

5 Illumination methods and resolution limits 3 methods: Contact Proximity projection lithography contact Light source Condenser lens proximity Light source Condenser lens Common point: Condenser lens for parallel beam resist substrate resist substrate gap Key issue: minimum feature size (MFS) Illumination method Illumination wavelength Materials of optical system Resist used projection Light source Condenser lens Optical system resist substrate 9 Illumination methods and resolution limits contact Light source proximity Light source Condenser lens Condenser lens resist substrate resist substrate gap contact MFS = d λ d = thickness( resist) λ = wavelength proximity MFS ( d + g) λ d = thickness( resist) g = gap λ = wavelength Example: d = 1 μm λ = 400 nm MFS ~ 600 nm Example: d = 1 μm λ = 400 nm g = 10 μm MFS ~ 2 μm?? 10 5

6 Illumination methods and resolution limits Projection lithography Mainly used today for IC industry Not shadow projection Picture of the is projected No contact No deterioration Excellent resolution (reduction e.g. 4x, 5x) Reduction of errors Stepper, x-y movement, from field to field projection Light source Condenser lens Optical system MFS = d λ d = thicknessresist ( ) substrate λ = wavelength Rayleigh criterion says: MFS=0.61*λ/NA In microlithography: MFS=k 1 *λ/να k 1 =technology cte ( ) Non-ideal behaviour of equipment Lens error Resist processing, shape, etc. 11 Hg arc emission spectrum I G H Hg-arc lamps: G-line (436 nm), H-line (405 nm), I-line (365 nm) With typical k1 and NA values ~ 400 nm resolution possible Hg/Xe: wavelength λ = 248 nm, resolution ~ 300 nm but low intensity New light sources, high intensity, excimer laser (exited & dimer) Describes a molecule in exited state (KrF, ArF, F2) 248, 193 nm) 12 6

7 Exposure wavelength and light sources Wavelength [nm] ~ 10 ~ 1 Source Hg arc lamp Hg arc lamp Hg arc lamp Hg/Xe arc lamp, KrF excimer laser ArF excimer laser F2 laser Laser-produces plasma sources X-ray tube, syncrotonon Range G-line H-line I-line Deep UV (DUV) DUV Vacuum UV (VUV) Extreme UV (EUV) X-Ray 13 Optical path Two concepts for setting up an optical path: Refractive elements (lenses): here the light passes the and lenses (transparent); transmission depends on wavelength (first: borosilicate glass (limit at 250nm) Reflective elements (mirrors) Classical one-axis micro-lithography lens Design depends strongly on the wavelength used Combined refractive/reflective (catadioptric) Generation of projection lenses 14 7

8 What is catadioptric? Catadioptric sensors are imaging sensors built with combinations of mirrors (catoptrics), and lenses (dioptrics). The main advantage of using mirrors with cameras is that by using a curved mirror a wide field of view can be obtained. Catadioptric sensors are sometimes also known as omnidirectional sensors. The word "catadioptric" alone used to be used often to describe telescope designs that used mirrors. Here is the definition that Google gives, from the Astrosoc Website Glossary : Catadioptric (also spelled catadioptic): Reflecting telescope, so-called because the beam of light is 'folded', i.e. reflected, back through a hole in the main mirror, before reaching the eyepiece. The effect is to increase the telescope's focal length, thus producing a more portable but also costlier instrument. Catadioptrics use a lens-like correcting plate in the front for spherical aberration. The commonest types are the Schmidt- Cassegrain and Maksutov-Cassegrain. So a catadioptric may be a telescope, microscope, projector or an optical device not used for imaging at all. In computer vision, the term catadioptric sensor is used for sensors consisting of cameras and mirrors. Catadioptric sensors are sometimes also known as omnidirectional sensors, although this terminology is misleading, since they rarely are omnidirectional in the sense that they capture an image in all directions. Catadioptric system (combined refraction/reflection) 15 Resolution enhancement of Optical Lithography λ Resolution: R = k 1 NA (Rayleigh) λ Depth of Focus: DOF = k 2 NA 2 to decrease R : need to decrease λ and increase NA (stepper) BUT: DOF decreases too!... need to decrease k1-> k 1 = Optical engineering = f(resist,, illumination) OPC (Optical Proximity correction) PSM (Phase Shift Masks) OAI (Off-Axis Illumination) illumination 16 8

9 Resolution enhancement (by optical engineering) OPC Optical Proximity Correction Design Reticle Wafer Original Anti-Serifs Chrome e Bright (+) Dark (0) Bright (-) i e 2 Etched Quartz (d) Quartz Silicon 17 i PSM Phase Shift Mask d=l/2(n-1) Resist Threshold Mask E-Field Intensity Wafer Immersion lithography NA= n sin α R=k 1 λ/na DOF = k 2 λ/na 2 Lens R=k 1 (λ/n)/sin α DOF = k 2 nλ/na 2 n α> 1 Air n=1 193 nm dry Medium Air n 1.0 λ/n 193 nm Wafer Stage 193 nm immersion 157 nm dry H 2 O N nm 157 nm 157 nm immersion PFPE 1.37 nm 115 nm 18 9

10 Immersion lithography Using an immersion fluid between the wafer and the lens has two benefits. First, it enhances depth of focus or DOF for a given numerical aperture. Second, immersion allows lens designs with numerical apertures significantly larger than 1.0, therefore allowing improved resolution ASML NIKON Resolution = k (process factor) x λ (wavelength of the illumination light)/na NA = n x sinθ 19 Companies A few examples ASML (NL) Intel (US) Motorola (US) Infineon (D) AMD Hitachi (J) EM Microelectronics (CH) 20 10

11 Exposure Tool Cost Projections $100,000, nm 193 nm 13.5 nm 193i Stepper Capital Cost $10,000,000 $1,000,000 $100, Year 21 Reticle set cost for production Mask set cost ($x1000) Node (nm) 22 Data from P. Silverman (Intel Corp.) 11

12 Success story of microelectronics Une réduction des coûts unique dans l histoire de l industrie EVOLUTION DU PRIX DE 1 Million de transistors Cents 6 Cents 0.5 Cents Nanoimprint lithography Mold (Si,SiO2,.) 1. Imprint Polymer Substrat 2. Pattern transfer RIE 200 mm imprinted wafer Interest of this technology : low cost transfert of nano structures (10-20 nm) on large area (200 mm) 24 12

13 Remember Optical lithography is the workhorse of modern semiconductor industry. Performance depends on Illumination methods, optics, resist processing Resolution enhancements to reach sub-wavelength resolution Currently DUV in production (90nm) In future extreme UV (EUV) X-ray lithography? Electron beam lithography? New emerging nanolithography Nanoimprint lithography (ITRS roadmap 2004) 25 What is today strategy? Rayleigh Criteria : R=k1 λ/na Immersion Litho λ λ/n λ CD(nm) nm Optical Litho. With transmission s 193 nm 157 nm (131 nm) EUV Litho. With reflexion s EUV 13,5 nm For low volume (CoO) EPL/Nanoimprint Litho. Maskless E-Beam NGL (96)