Lithography – Basic Concept. Overview of photolithography (ctnd.) Lithography consists of...

Lithography ndash Basic Concept

Overview of photolithography (ctnd)

bull 1048708 Lithography consists of patterning substrate by employing the interaction of beams of photons or particles with materialsbull 1048708 Photolithography is widely used in the integrated circuits (ICs) manufacturingbull 1048708 The process of IC manufacturing consists of a series of 10-20 steps or more called mask layers where layers of materials coated with resists are patterned then transferred onto the material layer


bull 1048708 A photolithography system consists of a light source a mask and a optical projection systembull 1048708 Photoresists are radiation sensitive materials that usually consist of a photo-sensitive compound a polymeric backbone and a solventbull 1048708 Resists can be classified upon their solubility af

ter exposure into positive resists (solubility of exposed area increases) and negative resists (solubility of exposed area decreases)

Lithography

bull I Basic lithography processes

bull II Types of lithography

Basic Photo-Lithography Processes

bull Resist Coatingbull Surface preparationbull Spin coatingbull Soft bake (pre-bake)bull Exposurebull Alignmentbull Exposurebull Developmentbull Developmentbull Hard bake (post-bake)bull Strippingbull Pattern Transferbull Etchingbull Lift offdeposition

Substrate Cleaningbull Particularly troublesome grease oil or wax stainsbull 2-5 min ultrasonic bath in trichloroethylene (TCE)bull or trichloroethane (TCA) 65-75ordmC (carcinogenic)bull Standard grease removalbull 2-5 min ultrasonic bath in acetonebull 2-5 min ultrasonic bath in methanolbull 2-5 min ultrasonic bath in DI H2Obull Repeat the first three steps 3 timesbull 30 sec rinse under free flowing DI H2Obull Oxide and other material removalbull 5 min H2OH2O2NH3OH 411 70-80ordmC (cleaning Ge)bull 30 sec 50 HF (Glass or SiO2)bull DI H2O 3 rinsesbull 5 min H2OH2O2HCl 511 70-80ordmCbull DI H2O 3 rinsesbull Spin dry (wafer) N2 blow dry

Sp

in C

oatin

g -A

Softbake

bull Remove the resist solventbull Convection Oven 90-100 ordmC 15-20 min removal starts at surface solvent trappingbull Conduction (hotplate) 75-85ordmC 40-60 sec removal starts at bottom uniform heating

Continue

bull R = k1λNA

bull where λ is wavelength employed NA is numerical aperture of lense and NA = sin α k1 is a constant typically k = 06 - 08

bull DOF = plusmnk2 λ(NA)2

Hardbake

bull Stabilize the developed resist for subsequent processes

bull Can make removal very difficult

bull Remove residual solvent

bull Not necessary for lift-off

bull Temperaturetime can change the profile

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bull 1048708 Lithography consists of patterning substrate by employing the interaction of beams of photons or particles with materialsbull 1048708 Photolithography is widely used in the integrated circuits (ICs) manufacturingbull 1048708 The process of IC manufacturing consists of a series of 10-20 steps or more called mask layers where layers of materials coated with resists are patterned then transferred onto the material layer




Lithography






Sp

in C

oatin

g -A

Softbake


Continue

bull R = k1λNA



Hardbake






Phase Shifter

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Lithography






Sp

in C

oatin

g -A

Softbake


Continue

bull R = k1λNA



Hardbake






Phase Shifter

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Sp

in C

oatin

g -A

Softbake


Continue

bull R = k1λNA



Hardbake






Phase Shifter

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Softbake


Continue

bull R = k1λNA



Hardbake






Phase Shifter

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Continue

bull R = k1λNA



Hardbake






Phase Shifter

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Hardbake






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Phase Shifter

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Lithography – Basic Concept. Overview of photolithography (ctnd.) Lithography consists of...

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Transcript of Lithography – Basic Concept. Overview of photolithography (ctnd.) Lithography consists of...