Innovation and Development of Study Field. nano.tul.cz

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1 Innovation and Development of Study Field Nanomaterials at the Technical University of Liberec nano.tul.cz These materials have been developed within the ESF project: Innovation and development of study field Nanomaterials at the Technical University of Liberec

2 Studijní program:nanotechnologie Studijní obor: Nanomateriály (organizuje prof. J. Šedlbauer, FPP TU v Liberci) Preparation of semiconductor nanomaterials (koordinuje prof. E. Hulicius, FZÚ AV ČR, v.v.i.)

3 8. Supporting techniques: a) Electron beam lithography (EBL); b) Evaporation and sputtering. Explanation of basic principles of these methods. Parameters of the FZU machine. Interesting, modern, expensive and for devices very important machines, but not principal for this lecture.

4 Electron Beam Lithography (EBL) for nanotechnology Fyzikální ústav AV ČR, v.v.i. Institute of Physics AS CR, v.v.i.

5 Photolithography Laboratory (from ) Environment: 3-step air filtration, recirculation of DI water Photolithography: Photoresist processing, wet etching processes, optical equipment e w Dry (plasma) etching (PE), deposition of some layers Individual processing

6 KAN New material properties and materials for nanoelectronics Structures for spintronics and kvantum efects at nanoelectronics created by EBL

7 Conditions for EBL instalation: EBL producer Fulfill: Build adekquate laboratory air temperature stability (± 0,5 C) antivibration bed (< 0,5 16 Hz) suppress acoustic noise (< Hz) suppress mag. disturbance (< Hz) specification of installation and media parameters Users clean rooms => air-conditioning preparation and distribution of DEMI-water gas distribution (N 2, technical gases) technological equipments (vacuum, air, cooling) work organization

8 EBL ve FZÚ AV ČR, v. v. i. - Cukrovarnická E Čisté prostory: 10 m 2 nejčistší část : tř. 100 (zóny: EBL, rezisty) 42 m 2 třída 1000 (sál: expozice/sesazování) 22 m 2 třída (sál: mokré a suché leptání)

9 Parameters measuring výběr r umíst stění nanolitografu proměření lokality (TESCAN) doporučení, upřesnění řešení vyhodnocení postaveného pracoviště proměření parametrů (RAITH) pracoviště způsobilé k instalaci nanolitografu zprovoznění pracoviště povolení zkušebního provozu kolaudace E

10 New EBL equipmentl e_line 1 Raith, BRD 1 - laserově-interferometricky řízený stolek (4 pojezd, 2nm přesnost) - průměr rozlišení el. SEM: svazku: 2nm 1,5nm (20keV), (20keV), resp. resp. 4 nm 3 (1keV) nm (1keV) - nejmenší šířka exponované exponovaný čáry motiv při EBL: při EBL: 2015 nm nm - přesnost: napojování: 20 nm, soukrytu: 40 nm Possibility of partial photolithography masks preparation

11 Kvalifikační testy nanolitografu test u výrobcev za účasti pracovníků FZÚ v. v. i. (Dortmund) dosaženy specifikované parametry po instalaci ve FZÚ v nové laboratoři testy pracovníků výrobce (Cukrovarnická) instalace a oživení nanolitografu úspěšné

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20 Contacts for electrical measurements of semiconductors Transport properties of semiconductors: we study using charge transport between samples and external circuits usually. Interface is electrical contact. We need enough quality metal contacts (definite, reproducible). Schottky barrier (rectifying, spatial charge space) Ohmic contact (negligible decrease of potential, without injection) Methods of contact creation: evaporation, sputtering, CVD, welding, electrolytic spread, (+ annealing for ohmic contacts)

21 Transport studies of insulating layers Capacity (C-V, DLTS ) measurements of MIS structures of samples on which is not able to prepare quality Schottkyho barriers. Longitudinal transport in two dimensional systems and thin films field effect MISFET structures of new materials and structures application of field effect for density of states studies Modification of surface states and study of them stability - diamante, hydrogenated diamante.

22 Equipment conception Basic methods of preparation: Resistive evaporation Evaporation by Electron Beam RF sputtering + substrate cleaning One vacuum system enable in-situ combination of single processes and maximal control of deposition parameters.

23 Why more purpose vacuum system? Advantages of (resistive) evaporation: Simple definition of shape of contact (mask) Combination of different contact materials (more layer ohmic contacts) Elemental technology, relatively cheap, operative Advantages of evaporation by electro beam: Deposition of metals with high melting point (Mo, Ta, Nb, ) High speed of deposition + more precise controlling of speed of evaporation Cooling of the crucible minimalise contamination.

24 Why more purpose vacuum system? Advantages of sputtering: Exact controlling of thickness of layers. Large areas of layers with homogenous thickness. Deposition of compounds and keeping of stechiometry. Deposition isolators (RF sputtering) gate layers, optical applications, piezoelectric layers. Deposition of amorphous and polycristalic layers. Reactive sputtering (target+gas) e.g. SiN x Substrate can be used as a target sputtering of the sample surface cleaning

25 Why more purpose vacuum system? Advantages of combination of sputtering, evaporation and in-situ cleaning Common elements (vacuum system, thickness measurement, controlling of the substrate temperature, ) lower running costs. Deposition of special sequences of materials defined MIS structure preparation. in-situ cleaning (etching) remove undesirable surface layers (oxides) contact quality improvement.

26 Influence of in-situ etching on the ohmic contact resistivity for Ti/Pt on n-inp W. C. Dautremont-Smith et al, J.Vac. Sci. Technol. B 2 (1984) 620

27 Using of multi-purpose vacuum system Ohmic contact, Schottky barer and MIS structure preparation for III-V semiconductor characterisation (MOVPE, E. Hulicius). Optimisation of contacts for III-V structures with wide forbidden gap -(Al)GaN (M. Leys, Leuven). Schottky barrier preparation for defect study in 3D and 2D semiconductors by transient spectroscopy (MAV, CNR). Optimisation contacts for detectors of ionised radiation, including of 2D structures with lateral collecting.

28 Using of multi-purpose vacuum system Preparation of gate structures for study of surface conductivity of the hydrogenated diamond (L. Ley, Erlangen) Development and preparation of low resistivity contacts for diamond structures and nanodiamond (M. Nesládek, M. Vaněček) Development of ohmic contacts for materials with one-dimensional systems (diamond, ZnO,, nanorods), (D. Gruen, ANL, R. Mosca, MASPEC)

29 Multi-purpose vacuum system Auto 500 (producer BOC Edwards) Modular system, adapted for different techniques and experiments. 1. Vacuum system: turbomolecular pump 550 l/s. Rotation pump. LN 2 cryo-trap. oil filters. Limit pressure: 7x10-7 mbar. Time for start at 10-6 mbar: ~60 min. Prevention against power supply failure. Stainless steel vacuum chamber in-front income. Automated valve system.

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31 Multi-purpose vacuum system Auto Evaporation source: Resistance heating, rotation (4 positions) for depositing of different materials under the vacuum. Automatic shutters 3. Sputtering: RF magnetron (3 ), source 600 W for depositing of different materials under the vacuum. Substrate holder Rotation (20-60 per/min) - increase of layer homogeneity.

32 Multi-purpose vacuum system Auto Optical heating of the substrate (Quartz lamp) and measurement of temperature 6. Measurement and controlling of deposited layers. Change of frequency of the quartz crystal Controlling of shutters 7. Testing, personal training.

33 Multi-purpose vacuum system Auto 500

34 Multi-purpose vacuum system Auto Vacuum chamber Stainless steal ø 500 mm, high 500 mm Bushing for additional experiments) Windows for visual controlling of the depositional procedure + periscope 3. Substrate holder rotational (20-60 rot/min) increase of the layer homogeneity electrical isolation (etching, sputtering)

35 Multi-purpose vacuum system Auto Electron beam evaporation source compact, water cooled. Cu crucible, 1 cm 3 5,5 kv, 3kW. 4. Resistive source of evaporation Rotation(4 positions) for depositing of different materials under the vacuum. Automatic shutter closing. 5. Sputtering equipment RF magnetron (3 ), source 600 W. Substrate bias. Etching (cleaning) of substrates by sputtering. Gas flow controlling.

36 Multi-purpose vacuum system Auto Optical heating of substrate (quartz lamp 500 W) and its temperature measurement. 7. Measurement and controlling of layer thickness Quartz crystal frequency changes, material database. Flexible crystal holder, water cooled. Shutter controlling. Testing, personal training. Price of our modification = 7 MKč ( simple 500 = 5 MKč, 306 = 2MKč; minimal equipped 600 = 10 MKč)

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40 Barrier remove. Contact melting (ohmic) Melting in vacuum. Melting in hydrogen (or other gases N 2 Ar). Temperature time controlling.

41 Realisation inlet (ohmic) Electrical contact quality, heat collection. Soldering. Thermocompresion. Ultrasound. Other. Questions of lifetime and reliability!

42 Dielectric (nano) layer preparation Base for lithography Functional materials for device structures Evaporation Sputtering Plasma discharge Other methods

43 Introduction Thin films Why do we need to control the growth at nanometer scale? Thin films deposition methods Substrates: nature, preparation Thin films characterizations

44 Dielectrics LaAlO3, SrTiO3 Ferroelectrics BaTiO3, PbTiO3 Pyroelectrics LiNbO3 Ferromagnets SrRuO3, La0.7Sr0.3MnO3 Conductors SrRuO3, LaNiO3 Magnetoresistive La0.7Sr0.3MnO3 Semiconductors Nb-doped SrTiO3 Superconductors YBa2Cu3O7, (La,Sr)2CuO4

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53 1960: T.H. Maiman constructed the first optical maser using a rod of ruby as the lasing medium 1962: Breech and Cross used ruby laser to vaporize and excite atoms from a solid surface 1965: Smith and Turner used a ruby laser to deposit thin films -> very beginning of PLD technique development However, the deposited films were still inferior to those obtained by other techniques such as chemical vapor deposition and molecular beam epitaxy. Early 1980 s: a few research groups (mainly in the former USSR) achieved remarkable results on manufacturing of thin film structures utilizing laser technology. 1987: Dijkkamp and Venkatesan prepared thin films of YBa2Cu3O7 by PLD In the 1990 s: development of new laser technology, such as lasers with high repetition rate and short pulse durations, made PLD a very competitive tool for the growth of thinfilms with complex stoichiometry. Pulsed laser deposition

54 PVD process whereby atoms in a solid target material are ejected into the gas phase due to bombardment of the material by energetic ions. Sputtered atoms ejected into the gas phase are not in their thermodynamic equilibrium state, and tend to deposit on all surfaces in the vacuum chamber. --> A substrate (such as a wafer) placed in the chamber will be coated with a thin film. Sputtering usually uses an argon plasma.

55 Standard physical sputtering is driven by momentum exchange between the ions and atoms in the material, due to collisions (Behrisch 1981, Sigmund 1987). Analogy with atomic billiards: the ion (cue ball) strikes a large cluster of closepacked atoms (billiard balls). Energy of impinging ions: < 10 ev: elastic backscatting of the ions 10 à 1000 ev: sputtering of the target > 1000eV: ions implantation The number of atoms ejected from the surface per incident particle is called the sputter yield and is an important measure of the efficiency of the sputtering process. Sputter yield depends on: - the energy of the incident ions (>> 10 ev), which depends on target gun s bias voltage Ar gas pressure - the masses of the ions and of target atoms - the binding energy of atoms in the solid

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57 Than you for your attention

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61 Than you for your attention