These materials have been developed within the ESF project: Innovation and development of study field Nanomaterials at the Technical University of Liberec
Innovation and Development of Study Field Nanomaterials at the Technical University of Liberec
nano.tul.cz
Studijní program: Nanotechnologie
Studijní obor: Nanomateriály (organizuje prof. J. Šedlbauer, FPP TU v Liberci)
Preparation of semiconductor
nanomaterials
2013/2014
(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)
http://www.fzu.cz/oddeleni/povrchy/litografie/tour.html
3-step air filtration,
recirculation of DI water
Photolithography:
Environment:
Photoresist processing,
wet etching processes,
optical equipment
Dry (plasma) etching (PE),
deposition of some layers
Individual processing
e w
KAN400100652 4 – 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 laboratory
Conditions 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. - Cukrovarnická
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 measuring
E
výběr umístění nanolitografu
proměření lokality (TESCAN)
doporučení, upřesnění řešení
vyhodnocení postaveného pracoviště
proměření parametrů (RAITH)
pracoviště způsobilé k instalaci nanolitografu
zprovoznění pracoviště
povolení zkušebního provozu
kolaudace
New 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 nanolitografu
test u výrobce
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
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 lithography
Functional 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 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
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
