U.D. ZeitnerFraunhofer Institut für Angewandte Optik und Feinmechanik

Jena

Micro- and Nano-Technology...... for Optics

Today: 1. Introduction

E. – Bernhard KleyInstitute of Applied Physics Friedrich-Schiller University Jena

and

Fraunhofer Institut für Angewandte Optik und Feinmechanik Jena

Course Content

1. Introduction (today)

2. Basic optical considerations

- discussion of physical effects relevant in micro- and nano-optics

3. Fabrication technologies for micro- and nano-structures

- Coating technologies

- Lithography

- Etching technologies

- Replication

- Ultra-precision micro-machining

4. Characterization techniques

- mechanical profiler

- AFM

- SEM

- optical surface profiler

- interferometer

5. Applications

Additional Information

Literature:

- S. Sinzinger, J. Jahns “Microoptics”, Wiley-VCH

- H.-P. Herzig “Micro-Optics”, Taylor & Francis

- B.C. Kress, P. Meyrueis “Applied Digital Optics”, Wiley

- C. Mack “Fundamental Principles of Optical Lithography”, Wiley

Course material will be uploaded to:

www.iap.uni-jena.de/teaching.html

Lecture “Micro- and Nano-Technology”

Micro-Structured Optics in Nature

2µm

Nano-structures with

anti-reflection

properties on moth‘s-

eyes

Lens-arrays as

insects eyes

100µm

Colors of butterflies

by diffraction

gratings

4µm

Different Approaches

Nature Technology

!?

“Bottom-Up” “Top-Down”

Lithography

Modern and high end optics need

micro- und nanostructures

2 prominent examples

Galaxies are very differentand what about our milky way ?

Vigo Galaxy clusterAbout 150 galaxies visible in the picture

NGC 6744

GAIA (ESA)

launched in Dec. 2013

RVS

230mm

GAIA’s effective medium

grating

Spectrometer grating for the Gaia mission

of European Space Agency

Gaia (Dec. 2011)

-1E9 Stars

- Magnitude: 22.5-20

Distance measurement by read shift measurement

Radial Velocity Spectrometer

Spektral range: 847-874 nm

Grating

Gravitational Waves

Gravitational wave Astronomy

1916 General Theory of Relativity[Einstein, AdP 1916]

[www.nikhef.nl]

relative length deviation:

Reflective Michelson-Interferometer and critical components

[Drever, Proc. 7th M. Grossmann Meeting 1996]

Gravitational Wave Detection

Dl

How to reduce the

thermas noise

Detector

nH

nL

nH

nHnL

Motivation: Cavities for interferometer in gravitational detection and lasers

Low optical and mechanical loss is required

high mechanical Q-factor

low reflectivity

quartz / silicon

nH

nL

Monolithic dielectric mirror

high reflectivity

low mechanical Q-factor

Does a monolithic solution exist?

Monolithic resonant Si-mirror (=1550 nm)

Si

waveguide + grating

grating/effective media

Si

99.8% reflectivity

measured @ 1550nm

Silicon-Pattern for Monolithic Mirrors

huge variety of low and high resolution structures

Examples of micro-structured elements

1mm

1µm

10nm

10µm

100µm

100nm

characteristic

feature size

micro-lenses, micro-prisms

lens-arrays,

refractive beam-shaper

diffractive beam-shaper,

Fresnel-lenses,

diffraction gratings

effective media,

sub--gratings,

photonic crystals,

meta-materials

hybride elements

Size scale of micro-optical effects

Size-Scale of Optical Structures

1Å

1nm

1µm

1mm

1m

law of refraction

and reflection

light diffraction

effective medium

spontaneous and

stimulated emission

astronomic

mirrors

lenses

micro-lenses

antireflection pattern,

polarizers, phase retarder

photonic crystals

miniaturized

lenses

paraxial beam splitters

non paraxial beam splitter

spectroscopic gratingsm

icro

op

tics

(atomic size) light sources

optical elementsoptical effects

Effects of Size-Scaling

1mm 100µm 10µm 1µm 100nm

refraction diffraction

influence of physical effects on optical functions

is changing if characteristic feature sizes are scaled

focus:f=5mm

125µ

m

structure size

artificial

dichroitic

materials

physical effect:effective material-

propertiesdisturbing useful !

diffractive

beam splitter

2µm

wire-

grid-

polarizer

Milestones of optical engineering

Maxwell

1831 - 1879

electromagnetic

wave theory

Fresnel

1788 - 1827

wave theory

of the light

Hertz

1857 - 1894

exp. confirm.

of Maxwell

Fourier

1768 - 1830

Fourier

expansion

Abbe

1840 - 1905

theory of

opt. image

Basics in physics

and mathematicsAnalytical and numerical

evaluation of physical optics

Personal

Computer

Dedicated

micro- and

nanomachining

technologies

18

00

19

00

20

00

Fundamental

understanding

of optics

Zuse

1910 - 1995

1941

1st calculator

Fabrication Technologies for Micro-Optics

common micro-optics fabrication methods are

• lithography (photo-, e-beam-, laser-)

• ultra precision micro-machining

• melting / reflow technology

• more elaborated technologies

different size and functionality

different fabrication methods

for micro-optical components compared to classical (macro) optics

4. Resist exposure

e-beam lithography

or photolithography

Lithography Process Chain for Resist pattern

5. Resist development

resist

(sensitive to light or

electrons)

Substrate

(e.g. Si-wafer)

, e-

1. Substrate preparation

(cleaning, …)

2. Resist coating

(e.g. spin coating)

patterned resist

mask for

subsequent

processes

evaporation of

solvent

3. Baking

High-End Lithography Tool

DUV lithography stepper, =193nm

(ASML)

very low flexibility

EUV lithography stepper, =13.5nm

(ASML)

microelectronic chips

on Si-wafers

Lithography Roadmap (past development)

2010

lithography roadmap

Lithography Roadmap (ongoing)

International Technology Roadmap for Semiconductors (2015)

Lithography for Optical Applications

Lithography tools are developed for micro-electronics fabrication!

Demands of optics on lithography:

• arbitrary lateral contours (often radially symmetric)

• several 100mm size of single elements with sub-micron features

• thick substrates for elements with low wave-front error

• non-planar substrates possible

• …

steady development along

semiconductor road-mapvanishing versatility for

other applications

Typical Optical Surfaces and Contours

Contours Profiles

lens prism beam shaper

binary grating blazed grating

subwavelength gratings

complex surface

profiles

>>

<

>

>>

>

<

characteristic

detail

Courtesy of E.-B. Kley

Demanding Micro Optics Applications

Computer-Generated Holograms

Pulse compression gratings

Spectrometry for Space Applications

Polarizers

1. Resist exposure with

e-beam lithography

Lithography Process Chain for Optics

2. Resist development

3. Chromium etching

(RIE)

4. Deep etching into

substrate (ICP)

resist

Cr-layer

SiO2-Substrate

e-

optional:

multiple iterations

of the process for

multi-level elements

Technology for continuous profiles

variable dose exposure:

development:

resist

substrate

intensity modulated

exposure beam

t1 t2

dose dependent profile depth in

resist after development process

proportional transfer (RIE):

Ions (e.g. CF4)

element profile transferred

into substrate material