Part

1

:

Lithography

1 Introduction 1-1. Lithography Roadmap 1-2. Lithography History 1-3. Lithography Strategies 2 The Lithographic Process : Physics 2-1. Optical physics 2-2. Illumination Optics 2-3. E-beam Lithography 2-4. X-Ray Lithography 2-5. Ion Beam Lithography 3 Resist Materials 3-1. Resist 3-2. DUV Resist(KrF & ArF) 4 Resist Process 4-1. Performance Creteria 4-2. Processing Steps 4-3. TLR Process 4-4. TIPS Process

5 Mask Technology 5-1. Lithography Simulation 5-2. Mask Making 5-3. Binary Intensity Mask 5-4. (Phase Shift Mask) 6 Metrology 6-1. CD 6-2. Overlay 1 1-1. Lithography Roadmap DRAM Lithography . DRAM(Dynamic Random Access Memory) 3 4 Memory Logic 2-3 . Design Rule(Minimum pattern size) 4Mb DRAM 0.8 1Gb DRAM 0.18 Non Optical Lithography . Optical Lithography "Step and Repeat" Stepper 436(g-line) 365(i-line) 248(KrF Excimer Laser) DUV Light Stepper Scanner Type .

Introduction

Optical Lithography 0.6 High NA(Numerical Aperture : ) Lens Hardware, Aperture, Stage, Alignment, Reticle Management System CAR(Chemically Amplified Resist) Type Resist Material Process TLR(Tri Layer Resist), TSI(Top Surface Imaging), ARC(Anti Reflective Coating), Mask PSM(Phase Shift Mask) OPC(Optical Proximity Correction) . 248 DUV Lithography Time Delay Effect, Substrate Dependency 0.18 Design Rule . Design Rule

193(ArF Excimer Laser) DUV Lithography . DUV Lithography 0.1 Patterning Light Source Lithography . Electron Beam X-Ray Source , EUV(Extream Ultra-violet) Ion Beam Source . Lithography 3 4 . 1 Photo Lithography Road Map .

1-2. Lithography History Lithography Patterning Photo Etch . Lithography Photo Light Source Optical Non-Optical Lithography . Lithography Wafer Circuit Pattern Substrate Resist Polymer Pattern Mask Resist Resist Pattern , Resist Barrier Substrate Etching Pattern . 2 Process Scheme .

UV Light Source Submicron Patterning 16Mb DRAM , DUV Light Source Sub-quartermicron 256Mb 1Gb DRAM . Optical Lithography Non-Optical Lithography .

1-3. Lithography Strategies 1-3-1. Optical Lithography Contact Printer Wafer Mask Visual Align . Mask Wafer Gap Gap Soft Contact, Hard Contact(1020 ) Vacuum Contact Proximity Printer . 1970 Optical System Projection Type Mask Wafer Size . 1970 Photo Lithography Stepper . Stepper "Step and Repeater" Alignment Accuracy . Stepper Mask Pattern Wafer Pattern 1:1 5:1 10:1 Mask Patterning Size 5:1 . 1990 "Step and Scan" Type Scanner 4:1 Mask

Patterning Chip Size . Light Source g-line(=436) 0.5 Patterning i-Line(=365) 0.4 Patterning . light source OAI(Off Axis Illumination), PSM(Phase Shift Mask) . KrF Laser(=248) Source Resist 0.25 Patterning . ArF Laser(=193) Source 0.13 Patterning .

1-3-2. Electron Beam Lithography Electron Beam Patterning 1960 . ETEC( Perkin-Elmer ) 70 . 80 MOS DRAM Stepper Lithography Tool . , 90 Optical Stepper Lithography Electron Beam Exposure Tool Lithography Exposure Tool .

Electron Beam Lithography Density Chip Size Stepper Scanner Mask Feedback Mask Revision , . Stepper Exposure Tool , Overlay Stitching Accuracy , Electron Beam Exposure MOS Transistor Vth . Electron Beam System Upgrade Mask Cell Projection Aperture Multi-Column System

, High Acceleration Voltage Fiducial Mark Overlay Stitching Accuracy .

1-3-3. X-Ray Lithography X-Ray Lithography optic 0.1 Patterning 20 Proximity Printer . X-Ray Electron Impact Source Power Pulsed Laser X-Ray Power . Mask, Alignment, Resist . Patterning X-Ray System .

1-3-4. Ion Beam Lithography Ion Beam Lithography Electron Beam X-Ray Lithography Group Low Sensitive Resist . Optical Lithography Stepper Type Reflective Mask .

2 The Lithographic Process : Physics2-1. Optical Physics Lithography . Mask(Cr ) , Lens 1,000 Lens . Sub-micron order( 1/1000 ) Photoresist . Lithography Issue Resolution( Pattern ) DOF(Depth of Focus). Rayleigh (1), (2) .

3 +/- 1 . slit P sin1 = , P 1 1 . , 1 0 1 . . 1 . , 1 . , ( ) 1 , 1 . (1) . k1 . (2) DOF k2 * / NA2 k3*(Res)2/ . DRAM , (Res) , (2) Res DOF . (1), (2) DOF .

2-2. Illumination Optics 2-2-1 Uniform illumination Optic . (1) Projector Kohler illumination (2) Critical illumination . Lithography DRAM chip Kohler illumination . Kohler 4 Projection lens Entrance pupil , Reticle . Aperture Mask layer .

4. Aperture Layout 2-2-2 (Off-Axis Illumination) 5 (a) Aperture Projection lens , Conventional illumination . Reticle , . 5 Conventional . 2-1

Reticle Pattern Define Pattern 1 Lens . Conventional Reticle Pattern size Reticle Lens Reticle (1 ) . Reticle Wafer . Reticle Lens , 0 Reticle Reticle (Size ) 1 Lens , .

2-3. Electron Beam Lihography 2-3-1. E-Beam Exposure Tool E-Beam Exposure Tool . CAD Pattern Data System Format Pattern Data Electron Beam On/Off Hardware Electron Gun Electron Beam Electromagnetic Lens Wafer Stage . Electron Beam Stage , Stage Laser Interferometer

, Electron Beam Deflector Feedback . Electron Gun Electron Beam Crossover Gaussian Beam Beam Source Aperture Beam Path ( ) . Variable Shaped Beam Type . Beam Gaussian Beam Type High Resolution VSB Type Throughput . Gaussian Beam Type Deflection Pattern Beam On Raster Scan Type Pattern Beam Address Vector Scan Type . Raster Scan Scanning Positioning Deflection Error Stitching Accuracy Error . Vector Scan Throughput Positioning Error . 90 Vector Scan Stage Moving Accuracy Beam Deflector Raster Scan .

Wafer Deflection Stage Step and Repeat Type Stage Continuous Type . Continuous Type Electron Beam Current Density , Electromagnetic Field Column Design Control .

2-3-2. HL-800D Electron beam lithography density chip size , stepper scanner mask feedback mask revision , . stepper exposure tool , overlay stitching accuracy , electron beam exposure MOS transistor Vth . electron beam system mask cell projection aperture

multi-column

system

,

high

acceleration voltage fiducial mark overlay stitching accuracy . Electron Beam Hitachi HL-800D Acceleration Voltage 50KeV Beam Type VSB(Variable Shaped Beam) CPM(Cell Projection Mask) Throughput . Column 6 .

2-3-3. CPM CPM E-Beam Lithography System Throughput Optic Exposure Tool Mask 7 E-Beam Exposure Tool . E-Beam Exposure Tool Throughput Mask Hitachi CPM IBM SCALPEL , EBeam Column Multi-Column System ETEC JEOL

. E-Beam Exposure Tool Advantest . Mask Mask , Multi-Column Column Synchronization .

2-4. X-Ray Lithogaphy 2-4-1. X-Ray Lithgoraphy Tool X-Ray Lithography Proximity Printer . X-Ray Electron Impact Source Power Pulsed Laser X-Ray Power . 8 XRay Proximity Printer . X-Ray 1:1 Proximity Type Mask Mask Stress Wafer Pattern Replacement Error . Reduction Projection Type X-ray stepper .

2-4-2. X-Ray Mask

Stencil Mask ( Transmission Mask ) . 9 Stencil Mask . .

Absorber : Energy Resist Pattern . Membrane : Stress Energy . Frame : Mask Process Defect Control .

Absorber Membrane Material 10 .

2-5. Ion Beam Lithography 11 Ion Beam Lithography . H He Patterning Stepper . 10-5 Mask Stencil Mask . 12 Ion Beam Mask Top Carbon Layer Absober Damage Protection Si Layer Absorber Membrane .

3 Resist Materials3-1. Resist(microlithography) 1 . LSI . . , . . 1. (positive), (negative) , , ,

1 , 2 , 3 g-line(436nm), KrF(248nm), i-line(365nm),

ArF(193nm), EUV(13nm), E-beam, Ion Beam, X-ray ,

Positive resist , resist etching mask , negative . (Dissolution Inhibition Resist) PAC(Photo Active Compound) physical image polymer 2 solvent, (dye) . g-line, i-line resist . (Chemically Amplified Resist) (acid)

PAG(photo acid generator), physical image polymer resin . 2 3 DUV, VUV resist . (Chain Scission Resist) polymer polymer chain (molecular weight) . 1 mask E-beam resist .

3-1-1. Novolac resin(polymer) physical image organic solvent aqueous base solution , . PAC(Sensitizer) latent image PAC aqueous base solution inhibitor 1520wt . 13 , .O N 2 L ight O C OH

R Bas e I nsoluble Sensitizer (I nh b tor) i i

R Bas e Soluble Photoproduct (Acid )

13. .

Base insoluble sensitizer N2 gas Ketene . Ketene resist , aqueous base solution carboxylic acid latent image . R(Aryl Sulfonate) sensitizer molecule . Develop photo-product Acid Resin PAC+Resin compound . resist Dill's A, B, C parameter , PAC (A), resin (B), PAC decomposition rate(C) resist light intensity PAC latent image contrast photo . , i-line resist A=0.9(um-1), B=0.08(um-1), C=0.12(mJ/cm2) .

3-1-2. PAG(Photo Acid Generator) (H+) PEB(Post Exposure Bake) , resin .

Negative

resist

polymer

(Co-

polymerization) . 2 PEB (latent image) sensitive .

14.

3-1-3. Carbon polymer main chain (h) radical 1 acylcarbon-oxygen , decarbonylation . solvent-base .

15. PMMA radical

3-2. DUV Resist(KrF & ArF) DUV i-line resolution DOF , . . standing wave effect CD swing substrate topology notching . CD swing substrate film Line width . DUV sensitivity , PED(Post Exposure Delay) stability, substrate dependency . i-line , (acid) tail footing . lithography bay bay chemical filter , Track/Scanner cluster chemical filter , Resist polymer overcoating , amine . clean room ammonia room , 10 - 50ppb , chemical filter , 1ppb . Ammonia 5 -10 ppb 5 3 PED stability .

KrF ArF . ArF ArF resist . KrF , ArF resist benzene .

Benzene dry etching i-line KrF resist . , ArF resist ArF laser 193nm resist . , Benzene dry etching , adhesion 2.38% TMAH . R& CTL ARF resist , Performance Lithography .

4 Resist Processing4-1. Performance Creteria sensitivity, DOF margin PED stability, Substrate dependency . Design rule , 0.6um - 0.8um global 0.25um Design Rule device , 2 . 2. KrF

Item

Target - TMAH(2.38%) developable Overcoating Free - Nontoxic

Test Condition Compatable production for mass

1. Chemistry

2. Thickness 3. Sensitivity 4. CD linearity

- 0.7 um - 20% Latitude

- ( Emax - Emin)/Eop - Within a 0.175um L/S +-105 Bias of

6. D.O.F

- Group > 1.2um Conventional(0.60NA, 0.60sigma) Isolated > - Within a +-10% Bias of 1.0um 0.175um L/S - Wall angle >85 - Resist Loss < 10%

7. CD Swing 8. IG Bias 9. PED stability

- < 30% - < 0.01um - > 2 hours

- (Peak Eth - Valley Eth) / Peak Eth - 0.175um L/S - Within 1 0.175um L/S +-105 Bias of

- Ammonium concentration of 20 ppb 10. Sub. - Scum free Dependency - No foot 11. PEB - 120 Stability 13. Resistance Etch Same Novolac - > 6months - Nitride, TiN, BPSG

- 0.175um L/S - 0.30um L/S - Hot plate as - Reactive Ion Etching - Room temperature(20-25 )

14. Shelf Life

4-2. Processing Steps Lithography layout (specification)wafer 1 . , (develop)

. O2 . , , . PSM , modified (TIPS) (TLR) , (defect) . cost-down, , , defect , topology bulk effect, notching , standing wave effect . 3. SLR process -150 / 1-2 , Hot plate

1. HMDS prime 2. P/R coating 3. SOB(Soft Bake) 4. Exposure

0.4-1.6um thickness 90-110 /1-2 , Hot plate best focus ,

Overlay parameter 5. PEB(Post 90-130 /1-2 , Hot plate oven Exposure Bake) 6. Develop 7. Inspection-150 / 1-2

CD, Overlay, Patttern fidelity

HMDS(Hexamethyldisilazane)prime : (CH3)3Si-NH-Si(CH3)3 Si (O) Photoresist . Resist coating : Spin photoresist . Soft bake : Photoresist 80-90% solvent .

Exposure : Mask photoresist , (overlay accuracy) . Post exposure bake : i-line Exposure photoresist (PAC) . DUV (H+) resin . Develop : (TMAH 2.38% : Tetramethyl-Ammonium Hydroxide) . Inspection : Patterning CD, Overlay accuracy, resist

pattern profile defect . 4-3. TLR process SLR resolution DOF , topology pattern profile TLR . TLR(Tri Layer Resist) DOF , Notching , defect cost-up .Adhesion Bottom P/R coating Oxide layer formation Top P/R coating

(1.2 1.6m) (300 ) (0.4m) Exposure Top P/R developing Oxide layer etching Bottom P/R etching

(Alkali solution) (Flourine RIE) (O2 RIE)

16. TLR process Bottom resist coating : Topology mask image , 150 bake resist O2 plasma . Interlayer : SOG, PECVD oxide resist etching mask .

Top resist : Exposure image , topology resist image 0.4m .

4-4 TIPS Process Photo substrate , Notching, Standing wave effect, Pattern collapse, CD Uniformity , CD Linearity , IG(Isolated & Grouped) Bias . TIPS . TIPS (Shallow exposure) , latent image , Silylation mask non-silylation O2 plasma dry develop . , resist , O2 plasma . TIPS , , Notching , DOF . , CD , , P/R strip , silylation SiO2 desilylation , Etching vertical , O2 plasma .P/R coating Exposure PSB(Pre-Silylation Bake) Silylation Dry devolopment

17. TIPS

Silylation source HMDS(Hexa-Methyl-DiSilazane), TMDS(Tetra-Methyl-DiSilazane), B(DMA)MS(Bis-Di-Methyl-Amino-Methyl-silane), B(DMA)DS

[CH3-H-Si(NCH3)2] . Source vapor liquid . Polymer OH site , 1 Si gourp , OH group H Si group dangling . (H2O) Si group out-diffusion, desilylation silylation dry develop cluster .

5 Mask Technology5-1. Lithography Simulation5-1-1. Simulation() model . model . simulation computer , computer program simulation program simulation tool .

Simulation split . simulation .

5-1-2. Lithography Simulation wafer photo resist . Soft bake, exposure, post exposure bake develop simulation simulation parameter simulation . simulation aerial image , resist aerial image level contour simulation . simulation simulation model . diffused aerial image method(DAIM) Simulation tool .

5-1-3. Lithography Simulation Tool lithography simulation tool SOLID-C, DEPICT, PROLITH/2, FAIM, IC WorkBench . HANOL . Tool simulation speed . 3D mask structure simulation, 3D wafer topology simulation, vector simulation simulation . full chip simulation simulation . simulation computer memory .

5-1-4. Simulation Tool Simulation `` . simulation model . , model simulation . Simulation tool model . . model approximation . Simulation , simulation pattern simulation .

5-2. Mask Making5-2-1. Mask(reticle)

5-2-2. Mask (1) Blank Mask

Quartz 1000 chrome , resist coating. resist coating thickness uniformity mask CD uniformity .

(2) Writing MEBES(electron beam), ALTA(laser) CAD data mask resist . resist develop . writing , MEBES resolution writing , ALTA writing defect resolution .

(3) Chrome Wet Etching Develop resist chrome wet etching . chrome dry etch . (4) Inspection / Cr repair

Resist strip cleaning defect repair . Defect mask .

(5) Clean / Pellicle / Inspection Repair cleaning chrome particle pellicle , .

5-3. Binary Intensity Mask 19 quartz chrome . binary , . . chrome chrome OPC(Optical proximity correction) .

5-4. (Phase Shift Mask) 5-4-1. ( ), contrast ( ). , exposure latitude DOF .

. . 21 Qz a, b . .

rm OPD &= (n_Qz - n_air ) d# DELTA phi &= {2pi rm OPD }over lambda# rm&={2pi(n_Qz - n_air ) d } over lambda, ( ) Qz (d) .

rm d = lambda over {2 ( n_Qz - n_air ) } 5-4-2.

(1) Alternating PSM 80 PSM binary intensity mask shifter 22 (a) . (Shifter) E-field 180 pattern binary pattern contrast patterning .

(2) Chromeless PSM

aerial image quality PSM . (1) 0 .

(3) Outrigger PSM PSM contact hole clear line 22 (c) . image contrast .

(4) Rim PSM PSM (3) .

(5) Attenuated PSM PSM . Embedded PSM, Half Tone PSM . dark .[ 22 (e)] ( ) image contrast , . strong PSM, weak PSM , (1)(4) (5) .

5-4-3. Patterning small sigma . Coma aberration pattern Non-linear .

(1) Strong PSM 1) Defect . PSM production . shifter

defect detect repair .

2) . Qz etch , etch uniformity .

3) Qz etch transmittance . Qz dry etch Qz wet etch Qz transmittance error .

4) low , . (stepper scanner)

low . 5) phase conflict 23 (b) . [ 23 (c)] [ 23 (d)] .

(a) (b) (c) (d)

23. (a) standard layout(b) two-phase alternating shifter PSM (c) multi-phase alternating shifter PSM (d) second exposure mask (2) Weak PSM

1) Background 0 secondary lobes . secondary lobes .

2) Low phase error .

phase .

3) Die 4 P/R loss . Scribe lane opaque ring .

contact hole array . DUV PSM chrome .

4) reticle align fail . Reticle align mark chrome .

6 Metrology Lithography . Inspection .

6-1. CD(Critical Dimension) 6-1-1. CD CD layer pattern patterning . 6-1-2. CD SEM(Scanning Electron Microscope) electron gun 1 8001000V anode magnetic lens wafer wafer 2 . CD SEM 10nm , 2 wafer , .

6-2. Overlay 6-2-1. Overlay

layer layer . cell layout 30% . wafer point layer mean+3 sigma .

6-2-2. Overlay - Mask(Reticle) error - +-Optic : aberration(coma,distortion), magnification, ... +-Stage : stepping accuracy, stage accuracy - Process : layer mark . 6-2-3. Misregistration error Overlay error Misregistration 1 .

+-Shot term : shot scale, shot rotation, shot offset +-Wafer term : wafer scale, wafer rotation, wafer offset 6-2-4. mark . type box in box, frame in box, frame in frame optic . mark chip . 5nm .

1. David J. Elliot, 'Microlithography Process Technology for IC Fabrication', Mcgraw-Hill book Company, 1986 2. David J. Elliot, 'Integrated Circuit Fabrication Technology', Mcgraw-Hill book Company, 1982

3. R. S. Longhust, 'Geometrical and Physics Optics' (1981) p. 331333 4. R. Newman, 'Fine Line Lithography' (1980) p. 157163 5. : ` ' (1991) p. 291380 6. Donald W. Johnson, et. al., "I-line, DUV, VUV or X-Ray?" Proc. SPIE 1674, 486 (1992) 7. L. F. Thompson, et. al., "Introduction to Microlithography", American Chemical Society, 1983 8. , , 1992 9. (), , 1993, p. 195227 10. "Intra Field Critical Dimension Variation Using KrF Scanner System For 0.18 Lithography", SPIE (1998) 12. "Tailoring of Isolation Structures with Top Surface Imaging Process by Silylation", SPIE (1998) 13. "A Novel Approximate Model for Resist Process", SPIE (1998) 14. "Design Lithography", SPIE (1998) of Cycloolefin-maleic Anhydride Resist for ArF