Lithography Technology on Nano-Structure Printing

Transcription

1 Lithography Technology on Nano-Structure Printing The Optical and Non-Optical Methods Tsann-Bim Chiou ( 邱燦賓 ) TDC Taiwan, ASML Oct. 15, 2002

2 Outline Lithography in IC Manufacturing Optical Lithography MIntroduction MExposure Systems MProcess MCritical Component- the Lens MOthers T. B.

3 Outline (contd.) Electron-Beam Lithography MIntroduction MExposure Systems MProcess MApplications MCritical Issues T. B.

4 Lithography in IC Manufacturing IC example- CMOS and NMOS T. B.

5 Litho- The art of imaging 2D 3D 人力 工具 ( 電子 )

6 Requirement in critical layer- for DRAM Year of Introduction Half Pitch (nm) Contacts (nm) CD Control (nm, 3σ) Overlay (nm) Minimum Field Size (mm 2 ) Wafer Size (mm, diameter) Source: ITRS 2001

7 Requirement in critical layer- for MPU Year of Introduction Gate (resist, nm) Half Pitch (nm) Contacts (resist, nm) CD Control (nm, 3σ) Minimum Field Size (mm 2 ) Wafer Size (mm, diameter) Source: ITRS 2001

8 Optical Lithography T. B.

9 Optical Lithography Introduction Light Source ( 光源 ) Condenser ( 聚光鏡 ) Mask, Reticle ( 光罩 ) Projection Lens ( 投影透鏡 ) Photoresist ( 光阻劑 ) Wafer ( 晶圓 )

10 The important requirements Throughput( 產能 ) Speed Imaging( 成像 ) Quality Overlay( 疊對 ) Accuracy

11 Imaging Isolated line Dense line Projection Lens 0.18um 0.13um

12 Imaging- optical diffraction λ α Under the same λ, when feature pitch gets smaller, the diffraction angle becomes larger λ α

13 Imaging- diffraction Isolated space mask Equal lines and spaces 1 0 m(x) M(fx) M(fx) M(f x ) M ( f ) = x fx [1/w] ( π w f ) sin π f x x M ( f x ) = n= ( 2πi( f x f y ) dx dy M ( f x, f y ) m( x, y) exp x + y ) = fx [1/w] ( π w f ) sin π f x x δ f x n p T. B.

14 Imaging- diffraction Pitch 1:1 Pitch 1: an n (or n/p for fx) an an Pitch 1:5 n (or n/p for fn) ~Iso 0.02 an n (or n/p for fn) n (or n/p for fn) T. B.

15 Optical Lithography Exposure Systems 光罩轉換裝置 照光器 Light Source ( 光源 ) Condenser ( 聚光鏡 ) Mask, Reticle ( 光罩 ) Projection Lens ( 投影透鏡 ) Photoresist ( 光阻劑 ) Wafer ( 晶圓 ) 光罩平台 投影透鏡 感應器平板 光源 Light Source 晶圓平台 晶圓轉換裝置

16 How does it work? T. B.

17 Light source- ArF spec NanoLith 7000, Cymer Inc. Wavelength: 193 nm Repetition Rate: 4000 Hz Pulse Energy: 5 mj Average Output Power: 20 W Integrated Energy Stability: ±0.3%

18 Illuminator ASML system (I-Line) T. B.

19 Illuminator T. B.

20 Stepper and scanner systems Stepper full field bucket model 曝光前 shutter closed 曝光中 shutter open shutter closed 將曝光晶粒 劑量 位置 曝光晶粒 Scanner slit sized hour glass model Prior to exposure Scanning Exposure (laser) pulses Unexposed, scanning die 劑量 位置 曝光晶粒

21 The stepper action T. B.

22 The scanner action T. B.

23 The action T. B.

24 Optical Lithography Process Substrate 清洗 Cleaning 底材 Spin 旋轉塗佈 Coat Pre-Bake 預烘烤 (Soft ( 軟烤 Bake) ) Development 顯影 Post-Exposure 曝後烘烤 Bake (PEB) Exposure 曝光 ADI Plasma 電漿 Descum 去渣 Post-Bake 顯後烘烤 (Hard ( 硬烤 Bake) ) PR 光阻劑 Strip 去除 Etching 蝕刻 Rework AEI

25 Resist process- the track T. B.

26 Optical Lithography Critical component- the lens Lens is a low pass filter

27 Lens gathers part of diffraction orders, NA NA (Numerical Aperture)

28 Resolution Examples of KrF source (NA=0.68) 200nm 180nm 160nm 150nm k 1 Res=k 1 λ / NA Res NA = λ = nm 130nm

29 Depth Of Focus (DOF) -0.4µm -0.3µm DOF = k 2 λ ( NA ) 2-0.2µm For NA=0.68, KrF -0.1µm 0 µm k 2 = = DOF NA λ µm +0.2µm

30 Isolated line through focus -0.6u -0.5u -0.4u -0.3u -0.2u 180nm isolated line 248nm 0.53NA 0.74σ -0.1u 0.5u 0.4u 0.3u 0.2u 0.1u 0.0u 187 image CD (microns) focus (microns) T. B.

31 Lens aberration W ( ρ, θ ) = Z n fn( ρ, θ ) n Z n : weighting factor, called Zernike coefficient f n (ρ,θ): basic aberration mode, called Zernike polynomial

32 Zernike polynomials, f n (ρ,θ) 1 0θ 2 1θ θ θ θ θ foil 4-foil 3-foil astigmatism coma spherical T. B.

33 The impact of lens aberration Ideal aerial image Coma-type image Spherical-type image Coma: Z7/Z8, Z14/15, Z23/Z24, Z34/35 3-foil: Z10/Z11, Z19/Z20, Z30/Z31 5-foil: Z26/Z27 M Lead to horizontal asymmetry parameter Spherical: Z9, Z16, Z25, Z36, Z37(49) 4-foil: Z17/Z18, Z28/Z29 Astigmatism: Z12/Z13, Z21/22, Z32/33 M Lead to vertical asymmetry parameter

34 The impact of lens aberration- even terms M Impact on lithographic performance: Z9 spherical iso-dense bias iso-focal tilt Z5/Z6 astigmatism HV CD difference T. B.

35 The impact of lens aberration- odd terms M Impact on lithographic performance: 170 nm 190 nm Z7/Z8 coma LR CD difference, L1-L2 (2-bar) Z10/Z11 3-foil image degradation of hexagonal stru. such as brickwall, honeycomb c d no 3-foil 0.1λ Z11 0.2λ Z11

36 Flare (light scattering) contamination (salts) multiple (back-) reflections inhomogeneity (quality) of of lens material (especially with with new new materials, like like CaF2 CaF2 in in and and nm nm systems) lens surface roughness errors (dominant straylight source source in in EUV EUV systems) contamination (salts)

37 Impact of flare Dense BE BE changes Dose [mj/cm2] EL EL reduces 70 dense, no flare dense, 5% Eff. flare Focus [um]

38 Optical Lithography Others F F F 0.0 F F F nm 1:1 pitch 193 scanner F F nm 1:1 pitch 193 scanner F F F F F 0.0 F F F+ 0.3

39 Preliminary results of 157 scanner Bilayer-resist process BIM dense Alt-PSM dense Alt-PSM 1:2

40 The dual-stage scanner T. B.

41 The NGL (next generation lithography) LOptical 光學 LExtreme UV (EUV) 極紫外光 LElectron-Beam (E-Beam) 電子束 ME-Beam Direct Writing ME-Beam Projection Lithography(EPL) LX-ray Lithography (XRL) X 光 LIon-Beam Projection Lithography (IPL) 投影式離子束 T. B.

42 Electron-Beam Lithography T. B.

43 Electron-Beam Lithography Introduction Mask Making Optical Square Transparent Plate, ex., Qz EUV Wafer Process SCALPEL Wafer Process XRL Wafer Process IPL Wafer Process T. B.

44 Direct writing Direct Write Patterning of ultra small feature size ASIC Special device manufacture, ex., Single Electron Transistor (SET, SED), optical devices Research and development for studying device physics T. B.

45 Features Short wavelength λ<1 Å, depending on accelerating voltage High resolution <0.1 µm (be not limited by diffraction) Accurate registration over small areas of a wafer Large Depth Of Focus (DOF) with very small numerical aperture Low defect density High-resolution patterning of special devices Low throughput Electron scattering effects

46 Electron-Beam Lithography Exposure Systems Constitution : Electron source : Electron optical column : Vacuum chamber : Mechanical stage : Control computers

47 Writing categories E-Beam System Scanning Beam Projection Gaussian Beam Shaped Beam Proximity Raster Scan Vector Scan Fixed Shape Beam Variably Shaped Beam 1:1 Photocathode Reduction Vector Scan

48 Schematic of Gaussian and shape beams Gaussian Beam Fixed Shape Beam

49 Schematic of vector scan and raster scan T. B.

50 Variably shaped beam T. B.

51 Comparison of the writing strategies Gaussian beam Variably shaped beam

52 Example of diaphragm (mini-reticle) T. B.

53 Electron-Beam Lithography Process Similar to standard process of the optical lithography... Kinds of E-Beam Resist: Poly(methyl methacrylate)- PMMA, 甲基丙烯酸酯 Poly(olefin sulfones) Epoxy resists, 環氧物 Styrene resists, 聚苯乙烯 Polyimide Chemically amplified resists, 化學倍增型光阻

54 Electron-Beam Lithography Applications IC structure printing 100 nm 100 nm

55 Mask making General mask used in optical lithography Open area (quartz substrate) Chrome border MoSi attpsm material

56 Source: Bell Labs T. B. Mask making- for the NGLs

57 3D profiles Blazed elliptical grating (variable dose) Blazed elliptical grating (variable energy) T. B.

58 Nano-device printing Single Electron Transistors (SET) Quantum wire (QW) lasers 30 nm InGaAs/GaAs quantum dot arrays T. B.

59 Micro machining Source: Sandia Labs

60 Electron-Beam Lithography The critical Issues Butting- subfield and shot Notches Subfield Shot Overlaps T. B.

61 Electron scattering- proximity effect Intraproximity Effect 10 kev After correction Interproximity Effect 25 kev 50 kev

62 Electron charging with conductive bottom layer

63 Data handling Year Data Volume (GB) Data Volume (GB) Year T. B.

64 The End Thank you...

65 Backup materials T. B.

66 Comparison of the writing strategies T. B.