#4 (Oct. 22) Photolithgraphy

-What is photolithgraphy?-Thin-film patterning using phtolithgraphy-Applications of photolithgraphy-Trends in minimum pattern sizes

What Is Photolithgraphy?Photo + LithographTechnologies to replicate patterns on a photomask to substrates or thin films on the substrates by using photo-chemical reaction photoresist

Photomask Thin film on a substrate

What Is Photoresit

A material that changes its solubility to developer by irradiation of light (ultraviolet or X ray) and electron beam

Changes:(1) Non-soluble to solvable (positive-type photoresist)(2) Soluble to non-soluble (negative-type photoresist)

Composition of Photoresist

Sensitizer

Change of Sensitizer by UV Irradiation

Non-soluble Soluble

Purposes and Features of Photolithography

Purposes-Fabrication of electron devices such as LSIs-Fabrication of micromachines-Packaging of LSIs and micromachines

Features-Minimum size of 1 m or less is achievable-Batch process-Pattern repetition

a

Photoresist （ 1 m ）

Chromium thin film（ 50 nm)

Fused-quartz substrate (1 mm)

ba b

Photomask Fabrication (1)Chromium thin film deposition and

photoresist deposition

Electron beam

a ba b

Photomask Fabrication (2)

a ba b

Photomask Fabrication (3)

Development

a ba b

Photomask Fabrication (4)

Etching of chromium thin film

a ba b

Photomask Fabrication (5)

Photoresisit removal

Silicon substrate

a ba b

Phtolithography of Al Thin Film (1)

SiO2thin film(1 m)

a ba b

Phtolithography of Al Thin Film (2)

Al thin film（ 1 m)

a ba b

Phtolithography of Al Thin Film (3)

Photoresist

a ba b

Phtolithography of Al Thin Film (4)

Followed by pre-baking at 120 ℃

Mercury lampPhotomask

a ba b

Phtolithography of Al Thin Film (5)

Wavelength (nm)

Inte

nsi

ty (

rela

tive

)

Emission Spectrum of Mercury Lamp

a ba b

Phtolithography of Al Thin Film (6)

Development

Followed by post-baking at 120~180 ℃

a ba b

Phtolithography of Al Thin Film (7)

Al thin film etching

a ba b

Phtolithography of Al Thin Film (8)

Photoresist removal

a ba

Photoresist

Lift-Off of Al Thin Film (1)

b

(2)

Mercury lampPhotomask

a ba b

Lift-Off of Al Thin Film (2)

a ba b

Lift-Off of Al Thin Film (3)

Development

a ba b

Lift-Off of Al Thin Film (4)

(5)

a ba b

Lift-Off of Al Thin Film (5)

a ba b

Lift-Off of Al Thin Film (6)

Wiring Using Al Thin Films

Contact holes

Cross-Section of CMOS LSI

Electron beam scanner

ReticlePhotomask

Stepper

Pattern generator Stepper

Pattern Size Reduction by Stepper

WaferDesign data

Contact aligner

Projection aligner

Stepper

http://www.tochigi-nikon.co.jp/business/stepper/

Trends in Minimum Pattern Size

http://public.itrs.net/

Inside Clean Room (MIT)

           by Richard P. Feynman

http://www.zyvex.com/nanotech/feynman.html

There's Plenty of Room at the BottomAn Invitation to Enter a New Field of Physics

Homework: Read This Article by 11/4