Semiconductors. SEM and EDAX images of an integrated circuit. SEM EDAX: Si EDAX: Al. Institut für Werkstoffe der ElektrotechnikIWE

Transcription

1 SEM and EDAX images of an integrated circuit SEM EDAX: Si EDAX: Al source: [Cal 99 / 605] M&D-.PPT, slide: 1,

2 Classification semiconductors electronic semiconductors mixed conductors ionic conductors intrinsic semiconductors n-typ extrinsic extrinsic semiconductors p-type extrinsic requirements requirements for for technical technical applications: applications: band band gap gap 0, ,1...3 ev ev n- n- or or p-type p-type conduction conduction no no ionic ionic conduction conduction chemical chemical and and thermal thermal stability stability solubility solubility of of dopants dopants in in the the host host lattice lattice covalent bonding source: [Hahn 73 / 78] M&D-.PPT, slide: 2,

3 Elemental and Dopants period group band gap E g / ev of different semiconductors II III IV V VI VII T = 0 K T = 300 K 2 3 Be Mg B Al C Si N P O S F Cl Si Ge GaAs 1,17 0,74 1,52 1,11 0,68 1,38 4 Ca Zn Ga Ge As Se Br InAs 0,36 0,35 5 Sr Cd In Sn Sb Te I InSb 0,23 0,18 CdS 2,58 2,42 p-type n-type CdTe 1,61 1,45 - dopants for Si and Ge ZnO 3,44 3,20 source: [Hahn73 / 78] M&D-.PPT, slide: 3,

4 Elemental and Compound elemental s. compound s. IV - IV bonding III - V bonding II - VI bonding number of electrons per unit C SiC Si GeSi Ge Sn AlP AlAs, GaP AlSb, GaAs, InP GaSb,InAs InSb ZnS ZnSe, CdS ZnTe, CdSe, HgS CdTe, HgSe HgTe atomic bonding forces become more ionic source: [Hey 76 / 31] M&D-.PPT, slide: 4,

5 Properties of Elemental and Compound source: [Cal 99 / 617] M&D-.PPT, slide: 5,

6 Electrical Conduction in Intrinsic Silicon at T = 0 K Si Si Si Si Si band band structure structure conduction band Si Si Si Si Si E C E g = 1,11 ev (Si) Si Si Si Si Si E V Si Si Si Si Si valence band * T = 0 K Si Si (Ge (Ge ): ): 4 outer outer electrons electrons (sp (sp 3 3 -hybride) -hybride) no no electrons electrons in in the the conduction conduction band* band* source: IWE M&D-.PPT, slide: 6,

7 Electrical Conduction in Intrinsic Silicon at T > 0 K Si Si Si Si Si band band structure structure conduction band Si Si Si Si Si E C Si Si Si Si Si Si Si Si Si Si valence band E V source: IWE charge carriers at T > 0 K (mobile) (mobile) electrons electrons in in the the conduction conduction band band (mobile) (mobile) holes holes in in the the valence valence band band M&D-.PPT, slide: 7,

8 Charge Carriers in Intrinsic E C E Fi T = 0 K f ( E) = 1 1+ e E E kt Fi E V 0 1 f(e) E Fi : fermi-level for intrinsic semiconductor thermal equilibrium generation 0 e - + h + n(t) = p(t) recombination intrinsic charge carrier concentration n i n i = n = p n: (mobile) electrons in the conduction band p: (mobile) holes in the valence band source: IWE M&D-.PPT, slide: 8,

9 Charge Carrier Concentration and Fermi Level electron concentration n (conduction band) n = N C e ( EC E kt hole concentration p (valence band) p = N V e Fi ( EFi E kt V ) ) N N C V * 2 2π m ² n kt = h * 2π mp kt = 2 h² intrinsic charge carrier concentration n i Eg 2kT ni Neff e = Neff = NC NV fermi level in an intrinsic semiconductor E E Fi Fi m = E + with for = E V V + * 1 3 p * * Eg + kt ln Eg = EC EV mp = m * n 2 4 mn 1 2 E g source: IWE M&D-.PPT, slide: 9,

10 Intrinsic Conductivity intrinsic conductivity by excitation of free electron-hole-pairs σi = ni e0 ( µ n + µ p ) mobility of free electrons and holes e τ 0 n 0 p µ n = * µ p = * mn mp e τ temperature dependence of electron and hole mobility µ n = T β n µ p = T β p source: IWE M&D-.PPT, slide: 10,

11 Fermi Distribution Function, Density of States and filled Electron States f(e), z(e) fermi fermi -- level level E Fi Fi fermi-distribution function f(e) density of states z(e) empty states in valence band E C kt E Fi filled states in conduction band E g E V E C E Fi E T > 0 K E V source: [Heime / 3-40] M&D-.PPT, slide: 11,

12 Band Gap E g and Concentration of Charge Carriers as f(t) T / K 1, band gap E g / ev 1,4 1,2 1,0 0,8 Ge Si GaAs intrinsic charge carrier concentration n i / cm GaAs Ge Si 0, T / K K / T source: [Heime 3-25, 26] M&D-.PPT, slide: 12,

13 Intrinsic and Extrinsic (n- and p-type) intrinsic intrinsic semiconductor semiconductor extrinsic extrinsic n-type n-type (donor-doped) (donor-doped) extrinsic extrinsic p-type p-type (acceptor-doped) (acceptor-doped) Si 4+ Si 4+ Si 4+ Si 4+ Si 4+ Si 4+ Si 4+ Si 4+ Si 4+ Si 4+ Si 4+ Si 4+ As 5+ Si 4+ Si 4+ Si 4+ Si 4+ Si 4+ Si 4+ Si 4+ Si 4+ Si 4+ Si 4+ Si 4+ Ga 3+ Si 4+ Si 4+ source: [Hahn 73 / 98] n = p = n i n >> p n << p conduction band conduction band conduction band E C E C E g =1,11eV + valence band E Fi E V donor state + valence band E F E V acceptor state valence band E C E F E V M&D-.PPT, slide: 13,

14 Donors and Acceptors donors donors excitation from a donor state generates an electron in the conduction band ionisation energy*: E D = 4 0 * mn e 2 (4π ε ε D) r 0 2 in Si: P E D = 45 mev Sb E D = 39 mev As E D = 54 mev acceptors acceptors excitation from an acceptor state generates a hole in the valence band ionisation energy*: E A = m * p e (4π ε ε D) r 0 2 in Si: B E A = 45 mev Al E A = 67 mev Ga E A = 72 mev m * calculation using the hydrogen model H H + + e - e 0 0 E Ion = = 13, 6eV 2 2 (4π ε D) 0 4 source: IWE M&D-.PPT, slide: 14,

15 Distribution Function f(e), Density of States z(e) and filled Electron States intrinsic intrinsic n = p n-type n-type (donor-doped) (donor-doped) n >> >> p p-type p-type (acceptor-doped) (acceptor-doped) p >> >> n E E E n z C n z C n z C E C E Fi E V p f E C E D E F E V N z D D p f E D E C E F E A E V p f N A z A E A z V z V z V z,f,n,p z,f,n,p z,f,n,p source: [Heime 3-77] M&D-.PPT, slide: 15,

16 Electrical Conductivity vs. Temperature For intrinsic semiconduction: lnσ C E g 2kT C - a temperature-independent constant E g - the band gap k - Boltzmann s constant source: [Cal 99 / 624] M&D-.PPT, slide: 16,

17 Charge Carrier Concentration vs. Reciprocal Temperature For intrinsic semiconduction: ln n = ln p C' E g 2kT ln p ln n E g = 2k / = 2k ( 1/ T ) ( 1 T ) source: [Cal 99 / 625] M&D-.PPT, slide: 17,

18 Extrinsic, Saturation and Intrinsic Behavior vs. Reciprocal Temperature p-type extrinsic semiconductor source: [Cal 99 / 626] M&D-.PPT, slide: 18,

19 Intrinsic and Extrinsic Conduction intrinsic conductivity (n = p = n i ) σ = n e µ + µ ) = n e ( µ + µ ) = p e ( µ + µ ) i i 0 ( n p 0 n p 0 n p n-type intrinsic conductivity (n >> p, n p = n i ²) σ 0 n e µ n p-type intrinsic conductivity (n << p, n p = n i ²) σ p e µ 0 p source: IWE M&D-.PPT, slide: 19,

20 Hall Effect Experiment V H : Hall voltage, depends on: I x : current B z : magnetic field d: the specimen thickness V H = R H I d x B z R H : Hall coefficient (constant for a given material) R H = 1/ne 0, µ n = R H σ, (n-type) R H = -1/pe 0, µ p = R H σ, (p-type) Determination Determination of of majority majority charge charge carrier carrier type, type, concentration concentration and and mobility mobility source: [Cal 99 / 629] M&D-.PPT, slide: 20,

21 : Devices p-n Rectifying Junction electron /hole distribution for: no electrical potential forward bias reverse bias source: [Cal 99 / 631] M&D-.PPT, slide: 21,

22 : Devices p-n Rectifying Junction current current -- voltage voltage characteristics characteristics voltage voltage vs. vs. time time current current vs. vs. time time source: [Cal 99 / 632] M&D-.PPT, slide: 22,

23 : Devices p-n-p Junction Transistor circuitry circuitry Input Input // output output voltage voltage vs. vs. time time source: [Cal 99 / 633] M&D-.PPT, slide: 23,

24 : Devices p-n-p Junction Transistor no no potential potential applied applied bias bias applied applied source: [Cal 99 / 634] M&D-.PPT, slide: 24,

25 : Devices MOSFET-Transistor source: [Cal 99 / 634] M&D-.PPT, slide: 25,

26 Development of Microelectronics 1959: 1 st planar transistor 764 µm 1995: transistor structures between 0,4 and 1,3 µm source: [ Spekd4 / 52 ] M&D-.PPT, slide: 26,

27 Development of Lithography Technology capacity of memory-chips / Mbit ultraviolet light (wavelength: 365 nm) ultraviolet light (wavelength: 248 and 365 nm) ultraviolet light (wavelength: 248 nm) ultraviolet light (wavelength: 193 and 248 nm) x-rays ultraviolet light (wavelength: 193 nm) hard and soft x-rays, electron beam hard and soft x-rays, electron beam research pilot plants production mass production source: [ Spekd4 / 53 ] M&D-.PPT, slide: 27,

28 Photolithography System optical alignment system controller mask Hgarclamp mask exposure reduction lens position measurement positioning unit robot controlled wafer handling source: [ Spekd4 / 55 ] M&D-.PPT, slide: 28,

29 communication technology information technology entertainment electronics medical technology energy and and environmental technologies microelectronics automotive electronics home electronics industrial electronics source: Siemens M&D-.PPT, slide: 29,

30 Sales 1996 gross national product 3540 Mrd. DM electronic devices 80 Mrd. DM electronic components 20 Mrd. DM microelectronics 12 Mrd. DM *compared to microelectronics mechanical engineering electrical and electronic engineering precision mechanics, optics automotive office equipment, IT source: Siemens M&D-.PPT, slide: 30,

31 Developement of Integration elements/chip structures µm sub-circuit year of introduction source: Siemens M&D-.PPT, slide: 31,