Multicolor photolithography materials and methods
The present invention relates to photoresist compositions comprising a base resin such as a monomer capable of radical polymerization upon photoinitiation, and photoinitiator molecules such as a diketone, and multicolor photolithography methods. Photoresist compositions comprise photoinitiator molecules that are exposed to a first radiation source, thereby exciting the photoinitiator molecules from a ground state to a pre-activated state. The pre-activated state molecules are then exposed to a second radiation source in selected locations, thereby deactivating the pre-activated state molecules in the selected locations. Any remaining pre-activated state molecules are exposed to a third radiation source, exciting such remaining pre-activated state photoinitiator molecules to an activated state. Polymerization of the base resin is then initiated.
1. A multicolor photolithography method, comprising the steps of:
providing a substrate at least partially coated with a layer of a photoresist composition comprising a reactive monomer and photoinitiator (PI) molecules;
exposing said PI molecules to a first radiation source, thereby exciting said PI molecules from a ground state to a pre-activated state;
exposing said pre-activated state PI molecules to a second radiation source in selected locations, thereby deactivating said pre-activated state PI molecules in said selected locations; and
exposing any of said pre-activated state PI molecules remaining to a third radiation source, thereby exciting said remaining pre-activated state PI molecules to an activated state, and initiating polymerization of said reactive monomer in said photoresist composition.
2. The method of claim 1 , wherein said first radiation source is a pulsed laser.
3. The method of claim 1 , wherein said second radiation source is a continuous-wave laser.
4. The method of claim 1 , wherein said third radiation source is a pulsed laser.
5. The method of claim 1 , wherein at least one of said first, second or third radiation source emits visible light.
6. The method of claim 1 , wherein said photoinitiator molecules are a diketone having substituent groups R 1 and R 2 , wherein at least one of R 1 or R 2 is selected from the group consisting of an alkyl substituent, an aryl substituent, a substituted aryl substituent, a heterocyclic aryl substituent, a cycloalkene substituent, and a heterocyclic cycloalkene substituent.
7. The method of claim 1 , wherein said photoinitiator molecules are selected from the group consisting of biacetyl (C 4 H 6 O 2 ), benzil (C 6 H 5 CO 2 ), 2.2′-pyridil (C 12 H 8 N 2 O 2 ), α-naphthil (C 22 H 14 O 2 ), β-naphthil (C 22 H 14 O 2 ), and furil (C 10 H 6 O 4 ).