Studijní program:NanotechnologieStudijní obor: Nanomateriály

(organizuje prof. J. Šedlbauer, FPP TU v Liberci)

Preparation of semiconductor nanomaterials

2014/2015

(prof. E. Hulicius, FZÚ AV ČR, v.v.i.,)

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.

Electron Beam Lithography (EBL) for nanotechnology

Fyzikální ústav AV ČR, v.v.i.Institute of Physics AS CR, v.v.i.

Photolithography Laboratory (from 1999-2000)Photolithography Laboratory (from 1999Photolithography Laboratory (from 1999--2000)2000)

http://www.fzu.cz/oddeleni/povrchy/litografie/tour.html

3-step air filtration, recirculation of DI water

PhotolithographPhotolithographyy:

Environment:

Photoresist processing, wet etching processes,optical equipment

Dry (plasma) etching (PE), deposition of some layers

Individual processing

e w

KAN4001006524 – New material properties and materials for nanoelectronics

KAN4001006524 – New material properties and materials for nanoelectronics

Structures for spintronics and kvantum efects at nanoelectronics created by EBL

1.7.2006 – 31.12.2010

Build adekquate laboratoryBuild adekquate laboratoryConditions for EBL instalation:

Fulfill:

EBL producer

Users

air temperature stability (± 0,5°C) antivibration bed (< 0,5 μm/s @ ≤16 Hz) suppress acoustic noise (< 50 dB @ ≤ 100 Hz) suppress mag. disturbance (< 1 mG @ ≤ 100 Hz) specification of installation and media parameters

clean rooms => air-conditioning preparation and distribution of DEMI-water gas distribution (N2 , technical gases) technological equipments (vacuum, air, cooling) work organization

EBL ve FZÚ AV ČR, v. v. i. - CukrovarnickáEBL ve FZEBL ve FZÚÚ AV AV ČČR, v. v. i. R, v. v. i. -- CukrovarnickCukrovarnickáá

Čisté prostory: 10 m2 … nejčistší část : tř. 100 (zóny: EBL, rezisty)

42 m2 …třída 1000 (sál: expozice/sesazování)

22 m2 … třída 10000 (sál: mokré a suché leptání)

E

Parameters measuringParameters measuringParameters measuring

E

vvýýbběěr umr umííststěěnníí nanolitografunanolitografu

proměření lokality (TESCAN) doporučení, upřesnění řešení

vyhodnocenvyhodnoceníí postavenpostavenéého pracoviho pracoviššttěě

proměření parametrů (RAITH) pracoviště způsobilé k instalaci nanolitografu

zprovoznzprovozněěnníí pracovipracoviššttěě

povolení zkušebního provozu kolaudace

New EBL equipmentLNew EBL equipmentLNew EBL equipmentL

Possibility of partial photolithography masks preparation

1

- laserově-interferometricky řízený stolek (4“ pojezd, 2nm přesnost)- rozlišení SEM: ≤ 2nm (20keV), resp. ≤ 4 nm (1keV)- šířka exponované čáry při EBL: 20 nm- přesnost: napojování: ≤ 20 nm, soukrytu: ≤ 40 nm

e_LiNE

Raith, BRD

- laserově-interferometricky řízený stolek (4“ pojezd, 2nm přesnost)- průměr el. svazku: ≤ 1,5nm (20keV), resp. ≤ 3 nm (1keV)- nejmenší exponovaný motiv při EBL: 15 nm- přesnost: napojování: ≤ 20 nm, soukrytu: ≤ 40 nm

1

Kvalifikační testy nanolitografuKvalifikaKvalifikaččnníí testy nanolitografutesty nanolitografu

test u vtest u výýrobcerobce

za účasti pracovníků FZÚ v. v. i. (Dortmund) dosaženy specifikované parametry

po instalaci ve FZpo instalaci ve FZÚÚ v novv novéé laboratolaboratořřii

testy pracovníků výrobce (Cukrovarnická) instalace a oživení nanolitografu úspěšné

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)

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.

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.

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.

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. SiNx

– Substrate can be used as a target → sputtering of the sample surface → cleaning

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.

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

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.

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)

Multi-purpose vacuum system Auto 500 (producer BOC Edwards)

1. Vacuum system: • turbomolecular pump 550 l/s.• Rotation pump.• LN2 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.

Modular system, adapted for different techniques and experiments.

2. 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.

Multi-purpose vacuum system Auto 500

5. 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.

Multi-purpose vacuum system Auto 500

Multi-purpose vacuum system Auto 500

Multi-purpose vacuum system Auto 500

2. 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)

Multi-purpose vacuum system Auto 500 3. Electron beam evaporation source

• compact, water cooled.• Cu crucible, 1 cm3

• 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.

Multi-purpose vacuum system Auto 500

6. 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)

• Barrier remove.

• Melting in vacuum.

• Melting in hydrogen (or other gases – N2 Ar).

• Temperature time controlling.

Contact melting (ohmic)

Electrical contact quality, heat collection.

• Soldering.• Thermocompresion.• Ultrasound.• Other.

Questions of lifetime and reliability!

Realisation inlet (ohmic)

Base for lithographyFunctional materials for device structures

• Evaporation• Sputtering• Plasma discharge• Other methods

Dielectric (nano) layer preparation

• Introduction• • Thin films• • Why do we need to control the growth at

nanometer scale ?• •Thin films deposition methods• • Substrates: nature, preparation…• • Thin films characterizations

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 …

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 developmentHowever, the deposited films were still inferior to those obtained

by other techniques such aschemical vapor deposition and molecular beam epitaxy.Early 1980’s: a few research groups (mainly in the former USSR)

achieved remarkable resultson manufacturing of thin film structures utilizing laser technology.1987: Dijkkamp and Venkatesan prepared thin films of

YBa2Cu3O7 by PLDIn the 1990’s: development of new laser technology, such as

lasers with high repetition rateand short pulse durations, made PLD a very competitive tool for

the growth of thinfilms withcomplex stoichiometry.Pulsed laser deposition

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.

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 close-packed 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

Than you for your attention

Than you for your attention