1. DONE BY,
A.POOJA SHUKLA
ECE ‘B’ (190912066)
SAVEETHA UNIVERSITY

2. • To fabricate PHOTONIC CRYSTAL in SOI.
• To use 248-nm deep UV Lithography for
fabrication.
• To use metal-oxide-semiconductor process.

3.  Demonstration of wavelength-scale photonic
nanostructures, including PHOTONIC
CRYSTALS.
 Fabrication of silicon on insulator using deep
UV Lithography.
 Comparing UV lithography with E-BEAM
lithography.

4. 1. Overview of photonic crystals, using deep UV
Lithography.
2. Use in optical waveguides.
3. Current Lithography techniques for
fabrication of PICs.

5. 1. PHOTONIC CRYSTALS
2. SOI FOR INTEGRATED OPTICS
3. LITHOGRAPHY FOR PHOTONIC CRYSTALS
4. FABRICATION
5. LITHOGRAPHY ISSUES

6.  PHOTONIC CRYSTALS are periodic optical
nanostructures that are designed to affect the
motion of photons in a similar way that
periodicity of a semiconductor crystal affects
the motion of electrons.
 They have separate high dielectric and low
dielectric regions.
 Periodic – spacing for relevant light frequency.

7. • Reduce Band Gap
• Reduce defects
example: if there
is a LINE DEFECT in
structure, it will act as
a waveguide
• Avoids Propagation
of a Material

8. The fabrication method depends upon the
number of dimensions that the photonic band
gap must exist in.
 1-D Photonic Crystals
 2-D Photonic Crystals
 3-D Photonic Crystals

9. • Any type of
dimension can be
used.
• High refractive
index contrast
gives high
diffractive
property.
• PBG bounds
defects in crystal.
• Completely lossless and allows short bends
without radiation loss.

10.  SOI was first used in CMOS application to
reduce the parasitary capacitance to the silicon
substrate.
 The top layer of SI acts as an optical waveguide
due to high vertical index contrast.
 SOI uses large cores i.e., top SI layers of upto
10um thick but we use 205nm.
 SOI wafer bonding of a buried oxide is 400nm.
 Due to leakage slab waveguide remains single
mode for a silicon thickness upto 268nm.
 The minimum loss of 6 db/mm.

11. 12
Loss due to substrate leakage (cm)
10
8
100 nm
6 150 nm
200 nm
4 250 nm
500 nm
2
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Thickness silica layer (um)

12. Photolithography (or "optical lithography") is a
process used in microfabrication to selectively
remove parts of a thin film or the bulk of a
substrate.
It uses light to transfer a geometric pattern from
a photomask to a light-sensitive chemical
"photoresist", or simply "resist," on the
substrate.
For example, in complex integrated circuits, a
modern CMOS wafer will go through the
photolithographic cycle up to 50 times

13.  Size within 10nm.  Size of any illuminated
wavelength.
 Most used for research  Widely used for CMOS
purpose. fabrication.
 Structure is not  Mostly used for
defined. structure defining.
 Defines extremely  Reduced wavelength
small features. become fuzzy.
 Not suitable for large  High end deep
volume because the lithography
process is very slow.

14. Steps involved in the fabrication of the PHOTONIC
CRYSTALS are given below,




16. o The deep uv lithography facilities we use 5500/300
deep uv stepper with an illumination wavelength of
248 nm.
o The stepper uses 200 nm wafers.
o It is used in resist coating, baking, and
development.
o Steps for lithography,
1. Wafer illuminated in stepper
2. Post exposure bake – resist impurity is
removed
3. Development

17. The etching of the SOI wafer is done using a double
etch, in different chambers

18.  No air is exposed
when two chambers
are etched.
 The top layer of
silicon is etched
using LOW
PRESSURE and HIGH
DENSITY.
 The top layer of
silicon can be
replaced by
AMORPHOUS
SILICON.

20.  The first lithography test were carried out using a
CMOS process evaluation mask with dense contact
holes.
 For perfect crystal we expose LARGER HOLES but
SAME PITCH (400 to 600 nm), ratio is (0.25 to 0.35).
 Vertical sidewalls show roughness in square lattices
so we prefer SUPERDENSE TRIANGULAR LATTICES

22.  The triangular lattice provides various pitch and hole
size, both in top-down and cross-section view.
 Holes are very uniform through out the lattice.
 There is an strong effect of side lobes from the crystal
wall.

23. A common problem in dense structures are,
1. The size and shape of a structure is changed with the
presence of a neighboring structures.
2. The various structures on photonic Ics each require
different lithography conditions.
3. The effects are,
(a) Optical Proximity Effects
(b) Line Hole Bias

24.  Photonic crystals are superdense periodic structures
with feature sizes close to the illumination
wavelength.
 During lithography, neighboring holes interfere with
eachother.
 Due to this the holes get larger or smaller during the
print.
 This phenomenon is called as OPTICAL PROXIMITY
EFFECTS (OPE).

25.  The denser the structures and the smaller the
pitch, the stronger the OPE becomes

26.  The border holes are smaller than the holes in the
bulks.
 The hole in the inner corner prints more smaller than
the border holes.
 EXAMPLE:
When the OPE of the lattice with a
relatively large pitch of 530 nm, but with holes targeted
at 420 nm.

27. 18
16
14
12
10
design print
8
6 target print
4
2
0
200 400 600 800
 Different geometrics are on the same level of the
chip, and preferably printed together.
 Small holes needs a much higher illumination than the
larger holes i.e, a few hundreds of nm in width.

28.  The new mask structures should be included to study
the effect of OPE in photonic crystals.
 The lithography should target the features with the
highest exposure.
 The bias should be applied on the mask to the
features that need less energy to print on target.

29. 1. Deep uv lithography has potential for the mass
fabrication of ultra compact photonic Ics based on
photonic crystal.
2. SOI shows well defined holes with very little edge
roughness.
3. The neighboring of the holes can be avoided by using
OPTICAL PROXIMITY CORRECTION (OPC) method.
4. Thus, deep uv lithography is suitable for providing
mass-manufacturing capabilities to the ultracompact
photonic Ics.

30. • Fabrication of photonic crystals in SOI using 248 nm
deep uv lithography, IEEE.
• SOI Photonic Crystal Fabrication Using Deep UV
Lithography, IEEE.
• www.google.com
• www.wikipedia.com