Auger Electron Spectroscopy, AES ......

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  • 1

    歐 傑 電 子 能 譜 儀

    化 學 分 析 電 子 儀

    Electron Spectroscopy for Chemical Analysis, ESCA

    Auger Electron Spectroscopy, AES

    材料系 徐雍鎣

  • 2

    當原子內層電子受激游離,產生一電洞,上層電子會填補此一電洞以降低原子之位能,此

    一降低的能量若大於同層或上層能階某電子的束縛能時,該電子將有機會被游離出原子,

    經此過程被游離的電子依發現者(Pierre Auger)的姓氏命名為Auger電子。

    The kinetic energy of the Auger electron (XYZ)

    is

    Ek(XYZ) = Ex - Ey - Ez

    where Ex, Ey and Ez are respective binding

    energies for electrons in level X, Y and Z.真空態

    E xyz= EX -EY -EZ

    歐傑電子動能

    自由原子

    EZ

    X

    Z

    Y

    EY EX

    歐傑電子

    游離電子

    激發探束 No Auger transition can be observed for hydrogen

    and helium because 3 electrons are required to

    complete the Auger transition process .

    歐傑電子能譜儀 (Auger Electron Spectroscopy, AES)

    An Auger transition can be expressed as the

    following general form, XpYqZr, where X, Y and Z

    are principle levels, and subscripts, p, q and r, are

    subshells of X, Y and Z, respectively

  • 3

    L2,3

    3p

    2p

    Vacuum level

    3s

    2sL1

    M2,3

    M1

    3d/4s/4p

    Free atom

    K 1s

    29Cu

    14Si

    KLL

    原子序越大, 外層電子越多, 束縛能越大 !

  • 4

    For a solid sample, EB = hν - KE - φ;

    φ: 試品功函數(Work function)

     φ

    電子能量分析器電子束

    試片 電子訊號

    X-ray

    一般AES分析係利用一電子束(2 - 30 KeV)照射在試品表面上以激發帶特性動能的Auger電

    子,經由Auger電子的動能,試驗者可判斷試片表面的元素成份或化學態。

  • 5

    Electrons emitting form

    an Ag surface irradiated

    with an electron beam of

    1 keV.

    Auger electrons

    Elastic peak

    Plasma loss Secondary electrons

    A u

    g e r

    in te

    n s it

    y (

    c n

    ts /s

    e c )

    A u

    g e r In

    te n

    s ity

    (d I/d

    E )

    Kinetic Energy (eV)

    AES spectrum of Si(100);

    differential spectrum (above) and

    integrated spectrum.

    一次電子

    背向散射電子

    穿透電子

    X光 二次電子

    Auger電子

  • 6

    MNN

    LMM Triplet

  • 7

    AES spectra of the first row of transition metals

    第 一 列 過 渡 金 屬 A E S 能 譜

  • 8

    992

    842 850

    862

    942

    801734 770 778

    721

    66

    110 48

  • 9

    Si3N4

    SiO2

    Si

    Si(LMM) Si(KLL)

    Chemical State Analysis by AES

    Differential spectrum

    Differential spectrum

  • 10

    AES Analyses of Diamond,

    Graphite and a-carbon

    200 225 250 275 d

    N (E

    )/ d

    E

    Electron Energy (eV)

    a-Carbon

    Graphite

    Diamond

    235 245

    256

    268

    Ao (KV1V1)A1

    (KV2V3)

    Ao-wsAo-wp

  • 11

    500 1000 1500 2000

    C(KLL)

    Fe(LMM)

    Kinetic Energy (ev)

    SURVEY AES

    Catalyst: Fe,

    Gas source: CH4/H2,

    Growth by MPCVD

    SEM image of the capping

    layer on Fe nanoparticles

    Carbon capping layer analysis for iron nanoparticles by AES

    AES survey spectrum

  • 12

    500 1000 1500 2000

    C

    Fe

    Kinetic Energy (ev)

    SURVEY CNPs(Fe)

    200 220 240 260 280

    E d

    N (E

    )/ d E

    Kinetic Energy(ev)

    CNPs(Fe)-C

    Damond

    Graphite

    crystal

    Poly-

    Graphite

    a-Carbon

  • 13

    1. Ultra-high Vacuum system

    2. Electron gun

    3. Electron energy analyzer

    4. Detection system

    5. Data acquisition system

    歐 傑 電 子 儀 系 統 示 意 圖

    電子訊號

    電子能量分析器

    電子槍

    試片

    二次電子 檢測器

    Ultra-high Vacuum

  • E1 Eo

    E2

    Excitation Source

    Sample

    Signal

    Transfer Lens

    R1

    R2

    Ro

    (V1)

    Vo

    (V2)

    Hemispherical analyzer (HSA)

    (球扇電子能量分析器)

    電 子 能 量 分 析 器

    V2 - V1 = Vo [(R2/R1) - (R1/R2)]

    Vo = K(V2 –V1)

    K is called the spectrometer constant.

    Feaures of HSA

    * Low transmission without a transfer lens. * High energy resolution.

    DE / E = Constant

    DE : Energy resolution

  • 15

    X-ray or e-beam radiation

    Sample

    E-gun Deflected Electrons

    SignalR1

    R2

    V

    a

    E = [Ke V/ ln(R2/R1) ]

    E = K’eV

    Features of CMA: * high transmission * relatively low energy resolution * sensitive to sample position

    Cylindrical mirror analyzer (CMA)

    (筒鏡電子能量分析器)

    電 子 能 量 分 析 器

    K’ is again the spectrometer constant.

  • 16

    Analysis Methods using AES

    由於低能電子(1 - 3 KeV)在固態材料之平均自由行徑(Inelastic mean free path)很短(5 Å - 20

    Å ),AES檢測的深度大致上在50 Å 以內;當電子束直徑很小時,SAM技術可得取SEM

    及表面元素之Auger影像,如果利用離子束濺射試樣表面,並檢測產生之新表面的Auger

    訊號,便可得到試樣自表面到內部的元素成份縱深分佈(Depth Profiling),因此適合分析

    薄膜及披覆材料。

    Mapping

    E-beam

    Survey scan

    E-beam

    d N

    /d E

    E(eV)

    Depth profiling

    Ion beam E-beam

    Depth (nm)

    A t.

    C o

    n c.

  • 17

    Aluminum oxide defect on poly-Si

    SEM image of the bridge defect

    on poly-Si gate pattern

    The Al(KLL) Auger map (green)

    overlapped on the SEM image.

  • 18

    Red: N, Green Al, Blue: Si

    Submicron defect analysis by Auger electron microscope

    Source : PHI

    The top of the dot off the patterned oxynitride

    feature is Al according to Auger analysis.

    A dot (0.25 mm)was found after

    the deposition of the blanket

    silicon oxynitride film and after

    the plasma etch of the film.

  • 19

    縱深成份分佈分析 (Depth Profiling)

    Surface Analysis techniques can be used to study the atomic composition as a function of

    depth from the surface of solid materials. This technique is called depth profiling. For

    destructive depth profiling, an ion beam is used to erode the sample surface. The newly

    created surface after ion sputtering is then analyzed with AES or ESCA. Thus, atomic

    compositions at various depths below the sample surface can be derived from the

    successive sputtering and measurement cycles.

    原 子 濃 度

    縱深 (濺蝕深度)

    A

    B

    2 3

    能量分析器 (AES, ESCA)

    1

    離子束

    電子束

    1 2 3

  • 20

    AES depth profiles for Ni(50 nm)/Cr(50 nm) multilayer.

    (a) static sample, (b) rotating sample.

    Ni Cr

  • 21

    AES depth profiles for the interface between

    TaSix and Poly-Si films.

    ? TaSix

    Si

  • 22

    Thin gate oxidation with N2O

    Si SiOxNy

    SiO2

    Raw data

    Depth

    profiles

  • 23

    K

    M L

    N XPS (X-ray Photoelectron Spectroscopy)

    X光光電子儀

    X光 XPS光電子

    UPS光電子

    UV光

    Ek = hn - EB  EB = hn - Ek

    where h: Planck constant, n: the photon frequency, and EB : the binding energy of the photoelectron.

    UPS (Ultra-violet photoelectron spectroscopy)

    UV光光電子儀

    For a solid sample, EB = hν - KE - φ;

    φ: 試品功函數(Work function)

     φ

    化 學 分 析 電 子 儀

    ESCA (Electron Spectroscopy for Chemical Analysis)

  • 24

    球扇形能量分析器

    檢測器

    數具擷取 系統

    Ultra-high Vacuum

    X光光源

    表面~5 nm

    X-光

    光電子

  • 25

    Light source for Photoelectron spectroscopy

    1. Core Level Excitation

    2. Deacceleration of Electrons

    (Bremsstrahlung)

    X -r

    a y

    I n

    te n

    si ty

    Filter Cutoff

    Energy

    Ka

    Flux distribution

    of a typical x-ray source

    電子束

    X光

    Al 窗

    Twin-Anode X-ray Source

    HV

    冷卻水 陽極

    燈絲

    X-ray photoelectron excitation source

    Y Mz 132.3 0.44

    Zr Mz 151.4 0.77

    Na Ka 1041.4 0.4

    Mg Ka 1253.6 0.7

    Al Ka 1486.6 0.8

    Si K