1. NANO-Lithography Name : DEKONG ZENG EE235 Spring 2007
Recent progress in high resolution lithography
Daniel Bratton, Da Yang, Junyan Dai and Christopher K. Ober*
Materials Science and Engineering, Cornell University, Ithaca, NY 14853, USA
All material gathered from Public Domain

2. Outline Photo-Lithography Immersion Lithography EUV Lithography
Two-Photon 3D Lithography
NANO-imprint Lithography
NANO-fabrication with Block Copolymers

3. Roadmap for Lithography

4. Photolithography Abbe (critical) illumination:
---intensity in each location on reticle is determined by corresponding location in light source。
Köhler illumination
---intensity in each location on reticle is integral local source intensities。

5. State of art Lithography

6. Lithography Road Map
Cost of a stepper today: $20M!

7. Liquid immersion lithography

8. Improvement of immersion lithography
At same CD : improvements in DOF
Improvements in resolution
The resolution enhancement from immersion lithography is therefore about 30-40% (depending on materials used), or about one technology node. The depth of focus, is also 40-70% better (proportional to the refractive index of the imaging medium considered) than a corresponding "dry" tool at the same resolution

9. Immersion lithography system
Immersion lithography: $30M!!
Fluid: 193nm water
157nm polyfluoropolyether
high index fluids desired.

10. Immersion lithography system

11. Immersion lithography Defects
Contribution of Defects
Images of Defects

12. Issues with Immersion Lithography
Very big lenses (hence expensive) !!
Field size reduction ?
Mechanical issues and hydrodynamics
Bubble formation disturbing the image
Stage vibrations transferred to lens
Heating of immersion liquid upon exposure
New defect mechanisms at wafer level
Interaction of photo resist with immersion liquid
Fluid contamination
Polarization effects degrading contrast

13. EXTREME ULTRAVIOLET (EUV) Lithography
A laser is directed at a jet of xenon gas. When the laser hits the xenon gas, it heats the gas up and creates a plasma.
Once the plasma is created, electrons begin to come off of it and it radiates light at 13 nanometers, which is too short for the human eye to see.
The light travels into a condenser, which gathers in the light so that it is directed onto the mask.
A representation of one level of a computer chip is patterned onto a mirror by applying an absorber to some parts of the mirror but not to others. This creates the mask.
The pattern on the mask is reflected onto a series of four to six curved mirrors, reducing the size of the image and focusing the image onto the silicon wafer. Each mirror bends the light slightly to form the image that will be transferred onto the wafer.

14. (EUV) Lithography Gas discharged plasma Laser produced plasma
This entire process has to take place in a vacuum because these wavelengths of light are so short that even air would absorb them. Additionally, EUVL uses concave and convex mirrors coated with multiple layers of molybdenum and silicon -- this coating can reflect nearly 70 percent of EUV light at a wavelength of 13.4 nanometers. The other 30 percent is absorbed by the mirror. Without the coating, the light would be almost totally absorbed before reaching the wafer. The mirror surfaces have to be nearly perfect; even small defects in coatings can destroy the shape of the optics and distort the printed circuit pattern, causing problems in chip function.

15. (EUV) Lithography Issues

16. Step-and-Flash IMPRINT Lithography (SFIL)
Commerical nanoimprinter: $ M
Lower forces: 100 kPa 　
No heating, no cooling
Longer lifetime, faster imprint
Sub 5-nm demonstrated
Issues：
Production　of templates
Defect　control
Small throughput
Materials

17. Two-Photon 3D Lithography 双光子三维微细加工

18. NANO-fabrication with BLOCK COPOLYMERS

19. Conclusion ？