question 1

(*)Which of the following are advantages of using a narrow bandwidth lamp for photolithography?

A allows getting standing waves
B it requires less cleaning
C it does not require any postbake
D allows achieving better resolution

question 2

(*)Which of the following improves adhesion of photoresist?

A Surface contamination
B Smooth surface
C Photoresist primers
D Adsorbed layer of water

question 3

(*)What factors affect photoresist adhesion?

A Surface smoothness
B The length of time of the post bake
C Wetting characteristics of resist
D Incorrect alignment

question 4

(*)For projection printing, which option(s) can give improved resolution?

A Thinner photoresist
B Usage of phase-shifting mask
C Shorter wavelength
D Smaller numerical aperture
E Larger numerical aperture

question 5

(*)Postbake is not needed for

A Wet Etching
B Ar-Ion Etching
C Lift off

question 6

(*)Resist thickness right after spinning depends on

A resist viscosity
B wafer-holder design
C post-bake temperature and time
D spinning velocity

question 7

(*2)Which force(s) act on a photoresist section during spin coating?

A Centripetal Force
B Earth's Gravitational Force
C Centrifugal Force
D Lorentz Force
E Surface Energy Cohesive Force

question 8

(*)Which of the following statements are true?

A Prebake is used to evaporate the solvent from the resist after spin coating
B In negative photoresist exposed areas become insolvable in the developer
C Postbake is needed for liftoff processes
D Longer and hotter postbake makes subsequent resist removal more difficult

question 9

(*2) Which of the following methods can be useful in reducing the effects of standing waves in photoresists?

A using thinner photoresists
B using thicker photoresists
C using monochromatic incident light
D decreasing the numerical aperture of the optical system involved
E de-focussing the optical system
F using a broadband illuminations
G using immersion photolithography

question 10

(*3)Which light wavelength(s) can safely be used for making grating with period of 1.3 µm if a contact mode mask aligner and a photoresist with typical thickness of 1.3 µm are employed?
Hint:Use equation 2b_min = 3 sqrt(l(a+d/2))

A 193 nm
B 248 nm
C 335 nm
D 365 nm
E 405 nm

question 11

(*2) How to increase photolithography resolution? Use:

A thicker photoresist and shorter wavelength
B thicker photoresist and longer wavelength
C thinner photoresist and shorter wavelength
D thinner photoresist and larger aperture
E more sensitive photoresist and shorter exposure time
F more sensitive photoresist and shorter developing time

question 12

Why is prebaking in a convection oven longer than on a hot plate?

A It takes longer time to heat the whole wafer uniformly
B Crust on the surface prevents evaporation of solvent
C Solvent vapors cannot escape the oven thereby building saturated vapor atmosphere around the wafer
D Cracks at the surface

question 13

Can you make photolithography without pre-bake in principle?

A Yes, but results can be irreproducible
B Yes, but exposure time can depend on how long it takes to align a pattern/mask
C Yes, but the wafer can stick to the mask if a contact printing is used
D No, the pre-bake is absolutely essential step of photolithography and cannot be avoided
E No, because photoresist is not photosensitive enough without pre-baking

question 14

Which of the following steps in Photolithography should not be used for the liftoff method?

A Soft Bake
B Developing
C Hard Bake
D Post processing cleaning
E Exposure

question 15

The temperature is a measure of

A the number density of gas molecules
B the kinetic energy of gas molecules
C the potential energy of gas molecules
D the mean-free path of molecules
E the interatomic forces

question 16

(*2)Why does immersion photolithography give higher resolution?

A Because the incident light has shorter wavelength
B Because the mask alignment is better
C Because of no dust particles in the liquid
D Because of a larger numerical aperture that can be used without decrease of the depth of focus, thanks to a larger refractive index of the liquid between the objective and photoresist
E Because of lenses with larger diameter
F Because of smaller mechanical vibrations due to high viscosity of liquid

question 17

(*2)Is it possible to use photoresist pattern with an undercut for the etch processing?

A No, the undercut is meant for the lift-off processing only
B Yes, but the resulting thin-film pattern will most likely be smaller than intended
C No, because the photoresist pattern is "negative" relative to the pattern of the mask
D No, because the photoresist pattern is the same as the pattern of the mask

question 18

(*)The photolithography resolution depends on:

A Diffraction of light
B Density of photoresist
C Thickness of photoresist
D Mask-to-photoresist distance

question 19

(*6)Taking the amplitude of a quartz-crystal oscillations at f = 6 MHz to be 35 nm,
calculate the maximum acceleration of a 10-nm gold thin film deposited on the surface of the crystal. It is roughly ... [m/s^2]

A 1E-1
B 3E+0
C 1E+2
D 3E+3
E 5E+4
F 1E+5
G 3E+7
H 5E+7
I 1E+8