Photolithography is a technique used to transfer geometric patterns from a photomask to a photoresist layer on a substrate. It involves cleaning the substrate, coating it with photoresist, exposing the photoresist to light through a photomask, developing the photoresist to remove either exposed or unexposed areas, etching the substrate where the photoresist was removed, and stripping off the remaining photoresist. Photolithography is widely used in the semiconductor industry to fabricate microelectronic circuits and sensors.

1. A BRIEF DESCRIPTION OF
PHOTOLITHOGRAPHY
Presented By:
Shashi Kant
Roll : 16PH62R13
Solid State Technology
Department of Physics, IIT Kharagpur
M.Tech 1st Year
Email : shashikant754@gmail.com

2. Outline
 History
 Lithography
 Techniques of lithography
 Photolithography
 Process
 Application
 References

3. History of Lithography:
 It was invented in 1796 by German author and actor Alois
Senefelder as a cheap method of publishing theatrical works.
fig : 1
fig : 2
Fig: 3

4. What is lithography ?
 Lithos meaning "stone" and graphein meaning "to write.
 Lithography is the transfer of geometric shapes on a mask to a
smooth surface
Why lithography ?
 Simple layers of thin films do not
make a Device.

5. Techniques of Lithography:
 Photolithography
 E-beam lithography
 X-ray lithography.
 Interference lithography.
 Scanning Probe.

6. Photolithography:
 Photolithography is an optical means for transferring
patterns onto a substrate .
 Photolithography is a technique that is used to define
the shape of micro machined structures on a wafer.

7. Basic Procedure:
 Cleaning
 Photoresist
 Exposure and developing
 Etching
 Photoresist removal

8. Process of Photolithography:
Cleaning-
 Dust from scribing
 Atmospheric Dust
 Bacteria.

9. Photoresist:
Positive photoresist
• Become soluble after
exposure
 When developed , the
exposed parts dissolved
 Better resolution
Negative photoresist
• Becomes insoluble after
exposure
 When developed, the
unexposed parts dissolved
• Cheaper
• cheaper
Two types of photoresist-

10. Exposure and developing:
 Determined by the wavelength of the light and the numerical
aperture of the system. The resolution can be expressed as

11. Etching:
 The act or process of making designs or pictures on a
metal plate , glass, etc.
Photoresist Removal:

12. Application:
Fabrication of microcircuits
Semiconductor Industry
Sensors
Microprocessor

13. References:
 “VLSI Technology” S.M.Sze, Second Edition, 2004, McGraw
Hill Book Company.
 http://www.lithoguru.com
“Nanotechnology; Principles and Practices”, Third
Edition,2015, by Sulabha K. Kulkarni.
“Introduction to Nanotechnology” by Charles P. Poole, and
Frank J. Owens.