Photolithography Technology and Application

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    Photolithography Technologyand Application

    Jeff TsaiDirector, Graduate Institute of Electro-Optical

    Engineering Tatung University

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    Art or Science?

    HP processor, 1977.

    Lind width = 100 to 5micron meter!!

    Resolution = ~ 3 micron

    Can you image the latest

    transistor size? 22nm,

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    Human fine art

    magnified 500x, top metal(M2) is covering DUAL 2-Input AND gate

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    Intel 32 nm technology from the

    Core i5 660 Microprocessor

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    How it works

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    Wiki say Photolithography (or "optical lithography")

    is a process used in microfabrication toselectively remove parts of a thin film orthe bulk of a substrate. It uses light to

    transfer a geometric pattern from a photomask to a light-sensitive chemical photoresist, or simply "resist," on the substrate.

    A series of chemical treatments thenengraves the exposure pattern into thematerial underneath the photo resist.

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    Function of photolithography Generate all layers of patterns

    Transistor

    Define STI, well implant mask,, define gate

    W/L, generate LDD, BPSG via, W plug tosource/drain,

    Interconnections

    Contact hole, island, dualdamascene, metalline

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    Process flow Singe and Prime: 150C, hexamethyldisilazane (HMDS).

    Spin coat: solvent dispensed on the wafer backside, in order to ensurethe wafer backside is clear of resist, and on the frontside wafer edge,to remove resist on the edge (Edge Bead Removal or EBR).

    Pre-bake: drives off excess solvent and turns the resist from a liquidinto a film.

    Expose/Align: patterned by exposure to UV illumination. Exposure isperformed through a "mask",

    Post-expose bake: finer features and smoother vertical-wall profiles

    achieved

    Develop:

    Post-develop bake:

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    Spin coating Coater, Track,

    http://www.apexicindia.com/SpinCoatingTheory.htm

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    Photoresist Spin Coater

    Vacuum

    PR

    EBR

    Wafer

    Chuck

    WaterSleeve

    Drain Exhaust

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    Relationship of Photoresist Thickness to Spin Rate

    and Viscosity

    Thickness

    (mm)

    Spin Rate (rpm)

    07k2k 3k 4k 5k 6k

    0.5

    1.0

    1.5

    2.0

    2.5

    3.0

    3.5100 cst

    50 cst

    27 cst

    20 cst

    10 cst

    5 cst

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    Exposure

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    I-line? G-line? DUV?? Light source vs. resolution

    Wavelength improvement

    436nm365nm248nm193nm

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    Spectrum of the Mercury Lamp

    G-line

    (436)

    H-line

    (405)

    I-line

    (365)

    300 400 500 600

    Wavelength (nm)

    Inten

    sity(a.u

    )

    Deep UV

    (

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    Photolithography Light

    SourcesName Wavelength (nm) Application feature

    size ( m)

    G-line 436 0.50

    Mercury Lamp H-line 405

    I-line 365 0.35 to 0.25

    XeF 351

    XeCl 308

    Excimer Laser KrF (DUV) 248 0.25 to 0.15

    ArF 193 0.18 to 0.13

    Fluorine Laser F2 157 0.13 to 0.1

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    Mask design

    Computed intensity patterns at the wafer for themasks (NAo = 0.6, M= 1/5, s = 0.7). (a) BIM, (b)PSM, (c) cross-sections of the intensity patterns inthe images of the BIM (dashed) and the PSM(solid).

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    Comparison of exposure systems

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    Development

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    Development: Immersion

    Spin DrySpin DryDevelop Rinse

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    Development Profiles

    PR PR

    Substrate Substrate

    PR

    Substrate

    PR

    Substrate

    Normal Development

    Under Development Over Development

    Incomplete Development

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    Pattern Inspection Inspection, stripped PR and rework

    Photoresist pattern is temporary Etch or ion implantation pattern is permanent.

    Photolithography process can rework

    Cant rework after etch or implantation.

    Scanning electron microscope (SEM) for

    small feature size (< 0.5 um) Optical microscope for large feature size

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    Pattern Inspection Overlay or alignment

    run-out, run-in, reticle rotation, wafer rotation,misplacement in X-direction, andmisplacement in Y-direction

    Critical dimension (CD) loss

    Surface irregularities such as scratches,

    pin holes, stains, contamination, etc.

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    Other nanolithography AFM

    Ink print

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    Electron Beam Lithography

    System

    Wafer

    Blanking Plate

    Lens

    Lens

    Lens

    Electron Gun

    Deflection

    Coils

    Stigmator

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    Thank you for your attention