Sequential infiltration synthesis for advanced lithography
A plasma etch resist material modified by an inorganic protective component via sequential infiltration synthesis (SIS) and methods of preparing the modified resist material. The modified resist material is characterized by an improved resistance to a plasma etching or related process relative to the unmodified resist material, thereby allowing formation of patterned features into a substrate material, which may be high-aspect ratio features. The SIS process forms the protective component within the bulk resist material through a plurality of alternating exposures to gas phase precursors which infiltrate the resist material. The plasma etch resist material may be initially patterned using photolithography, electron-beam lithography or a block copolymer self-assembly process.
1. A method of preparing an organic resist mask by sequential infiltration synthesis (SIS) for use in forming at least one patterned feature in a substrate material by an etching or milling process, comprising:
applying an organic resist mask layer to a substrate, the organic resist mask layer characterized by an etch resistance;
patterning the organic resist mask layer with at least one patterned feature; and
forming an inorganic protective etch component within the organic resist mask layer by exposing the organic resist mask layer to a plurality of SIS cycles comprising alternating cycles of:
reacting a first precursor reactive with the organic resist;
reacting a second precursor with the first precursor within the organic resist;
thereby increasing the etch resistance of the organic resist mask layer with respect to the etching or milling process, wherein the etch resistance of the organic resist mask layer is selectively controllable by establishing an infiltration depth of the inorganic protective etch component such that the at least one patterned feature has an aspect ratio of at least 1:1.
2. The method of claim 1 , wherein the first precursor and the second precursor comprise gas phase precursors.
3. The method of claim 2 , wherein the first precursor comprises a metal or metal containing compound, and wherein the inorganic protective etch component comprises a metal oxide or a metal.
4. The method of claim 3 , wherein the inorganic protective etch component comprises metal oxide is selected from the group consisting of Al 2 O 3 , ZnO, SiO 2 , HfO 2 , ZrO 2 and TiO 2 .
5. The method of claim 1 , wherein the organic resist mask layer comprises at least one of poly(methyl methacrylate) (PMMA), ZEP520A, poly(methyl glutarimide) (PMGI), phenol formaldehyde resin (DNQ/Novolac), polyhydroxystyrene-based polymers, polyimides and SU-8.
6. The method of claim 1 , further comprising forming the at least one patterned feature in the substrate material by performing a plasma etching or ion milling process following modification of the etch resistance of the organic resist mask layer.
7. The method of claim 6 , wherein the plasma etching process is defined by a plurality of etching steps performed in order, comprising:
a first etching step configured to break through the protective etch component;
a second etching step configured to break through a layer comprising an oxide of the substrate material; and
a third etching step configured to etch the at least one patterned feature in the substrate.
8. The method of claim 1 , wherein the patterned feature of the organic resist mask layer is prepared by photolithography.
9. The method of claim 1 , wherein the patterned feature of the organic resist mask layer is prepared by electron beam lithography.
10. A method of plasma etching a patterned feature in a substrate material without a hard mask using an organic resist mask layer modified by sequential infiltration synthesis (SIS), comprising:
providing a substrate material;
applying the organic resist mask layer over a surface of the substrate material, the organic resist mask layer having a layer thickness and comprising a first organic material;
forming the patterned feature in the organic resist mask layer by lithography;
modifying the plasma etch or ion milling resistance of the organic resist mask layer having the patterned feature by performing a plurality of SIS cycles, comprising:
exposing the organic resist mask layer to a first precursor reactive with the first organic material; and
exposing the organic resist mask layer to a second precursor to form a protective etch component within at least a portion of the first organic material; and
performing a plasma etching or ion milling process that etches the patterned feature in the substrate material to a feature depth,
wherein the modified organic resist mask layer is characterized by a modified plasma etch or ion milling resistance greater than the initial plasma etch or ion milling resistance.
11. The method of claim 10 , wherein the first organic material comprises PMMA or ZEP520A and the protective etch component comprises a metal oxide.
12. The method of claim 11 , wherein the substrate material comprises Si.
13. The method of claim 11 , wherein the modified plasma etch resistance is selectively controllable by performing a predetermined number of SIS cycles.
14. The method of claim 10 , wherein the patterned feature on the organic resist mask layer is prepared by photolithography.
15. The method of claim 10 , wherein the patterned feature of the organic resist mask layer is prepared by electron beam lithography.
16. The method of claim 10 , wherein the feature depth is between about 5and 10 times the layer thickness.
17. The method of claim 10 , wherein the organic resist mask layer comprises a block copolymer, and wherein the first precursor is substantially non-reactive with at least one block of the block copolymer.
18. The method of claim 17 , wherein the block copolymer comprises nanostructured polystyrene-block-poly (methyl methacrylate) (PS-b-PMMA).
19. The method of claim 10 , wherein the plasma etching process is defined by a plurality of etching steps performed in order, comprising:
a first etching step configured to break through the protective etch component;
a second etching step configured to break through a layer comprising an oxide of the substrate material; and
a third etching step configured to etch the patterned feature in the substrate material to the feature depth.
20. The method of claim 19 , further comprising removing a remaining portion of the organic resist mask layer from the surface of the substrate material.