8/13/2019 Alternate Lithograph Techniques

1/20

Lecture 21 Alternative Lithography Techniques

EECS 598-002 Winter 2006

Nanophotonics and Nano-scale Fabrication

P.C.Ku

8/13/2019 Alternate Lithograph Techniques

2/20

2EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.Ku

Overview

Immersion lithography

EUV lithography

Interference lithography Imprint lithography

Maskless lithography (ML2)

8/13/2019 Alternate Lithograph Techniques

3/20

3EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.Ku

Trends in lithography

Resolution limit = k1/NA and NA = nsin

8/13/2019 Alternate Lithograph Techniques

4/20

4EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.Ku

8/13/2019 Alternate Lithograph Techniques

5/20

5EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.Ku

Immersion lithography

Resolution limit = /2NA and NA = nsin

Conventional lithography: n = 1

Immersion lithography: n = 1.44 (pure water) Current projected limit = 35 nm half pitch.

Issues need to be taken care of:

Possible bubbling of water

Water temperature control to keep the refractive index constant

Water-resist interaction resist needs to be water resistant

Metrology (e.g. registration) can be a challenge if done throughwater

8/13/2019 Alternate Lithograph Techniques

6/20

6EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.Ku

How to introduce water?

Swimming pool design

Entire stage under water

Bathtub design

Entire wafer under water

Shower design Water is injected to the part of the wafer thats going to be

exposed.

8/13/2019 Alternate Lithograph Techniques

7/20

7EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.Ku

Shower design

Wafer edge

exposure

may bean issue.

8/13/2019 Alternate Lithograph Techniques

8/20

8EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.Ku

First generation of immersion tools

NA < 1. But DOF is improved.

8/13/2019 Alternate Lithograph Techniques

9/20

9EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.Ku

Extreme UV lithography (EUVL)

At wavelength of 13-14 nm: no refractive optics. Need to

use reflection optics. Reflectors are made of Mo/Si Bragg

reflectors.

EUVL mask

8/13/2019 Alternate Lithograph Techniques

10/20

10EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.Ku

EUVL system schematic

From Nanoelectronics and Information Technology

8/13/2019 Alternate Lithograph Techniques

11/20

11EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.Ku

Interference lithography

8/13/2019 Alternate Lithograph Techniques

12/20

12EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.Ku

Extension from conventional lithography

-1-1

-2

-3

1

-4

-2

Add intensities from exposures with different illumination

angles.

Add in zero order through a separate optical path whenneeded.

8/13/2019 Alternate Lithograph Techniques

13/20

13EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.Ku

Why do we need the zero-th order

Conventional

Exposure

High Spatial

Frequencies Only

High Spatial

Frequencies

Plus Zero Order

Printed

Resist

Calculated

Image

8/13/2019 Alternate Lithograph Techniques

14/20

14EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.Ku

Implementation of IIL

Zero order light follows the

path on the right.

The movable mirror M1 selects

the diffraction orders that willadd with zero order at the wafer.

The effective NA approaches

sin(U+sin-1NAobj).

8/13/2019 Alternate Lithograph Techniques

15/20

15EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.Ku

IIL with i-line lithography

8/13/2019 Alternate Lithograph Techniques

16/20

16EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.Ku

Multiple beam interference

8/13/2019 Alternate Lithograph Techniques

17/20

17EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.Ku

Imprint lithography

Nice tutorial on the web: link

http://www.molecularimprints.com/Technology/technology

2.html

8/13/2019 Alternate Lithograph Techniques

18/20

18EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.Ku

Maskless lithography (ML2)

SCAPAL (scattering with angular limitation in projection

electron beam lithography)

8/13/2019 Alternate Lithograph Techniques

19/20

19EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.Ku

Proximity effect in e-beam lithography

Resolution limit is not determined by electron wavelength

but rather by backscattered electrons (proximity effect.)

8/13/2019 Alternate Lithograph Techniques

20/20

20EECS 598-002 Nanophotonics and Nanoscale Fabrication by P.C.Ku

Schedule for the rest of the semester

Etching

Thin film deposition

Self-assembly and hybrid nanofabrication Miscellaneous e.g. VLS nanowire growth,

Summary of the course and outlook

+ guest lecture on photonic crystals (time TBA)