Monolithic three-dimensional structures
View Patent ↗Three-dimensional structures of arbitrary shape are fabricated on the surface of a substrate through a series of processing steps wherein a monolithic structure is fabricated in successive layers. A first layer of photoresist material is spun onto a substrate surface and is exposed in a desired pattern corresponding to the shape of a final structure, at a corresponding cross-sectional level in the structure. The layer is not developed after exposure; instead, a second layer of photoresist material is deposited and is also exposed in a desired pattern. Subsequent layers are spun onto the top surface of prior layers and exposed, and upon completion of the succession of layers each defining corresponding levels of the desired structure, the layers are all developed at the same time leaving the three-dimensional structure.
1. A monolithic optical coupler integrally fabricated on an optical chip and having a solid, void-free, multilevel three-dimensional shape comprising:
a first layer of lithographically definable material on a top surface of said chip, said first layer being individually and at least partially exposed lithographically to define an arbitrary first layer pattern corresponding to the shape of a first level of the multilevel optical coupler;
multiple additional layers of lithographically definable material, each additional layer being on a top surface of a preceding layer, each additional layer being individually and at least partially exposed lithographically to define vertically aligned arbitrary patterns corresponding to the shapes of respective additional levels of the multilevel optical coupler;
a barrier between each of said layers of lithographically definable material;
said layers, upon development, each being of a selected arbitrary shape and being vertically aligned and stacked to form said solid, three-dimensional, multilevel monolithic optical coupler for connecting an optical device on said chip to another optical device either on the chip or external to it.
2. The monolithic optical coupler of claim 1 , wherein said lithographically definable material is a positive photoresist material, wherein said exposed pattern in each of said first and additional layers is removed by development and unexposed portions of each of said layers form said optical device.
3. The monolithic optical device coupler of claim 1 , wherein said lithographically definable material is a negative photoresist material, whereby said exposed pattern in each of said first and additional layers forms said optical device upon development of said photoresist material.
4. The monolithic optical coupler of claim 1 , wherein lithographically definable material of at least one of said first and additional layers is a first photoresist material and the lithographically definable material of at least a second of said first and additional layers is a second photoresist material.
5. The monolithic optical coupler of claim 1 , wherein each of said barrier layers is a photosensitive material.
6. The monolithic optical coupler of claim 1 , wherein the pattern formed in each of said first and additional lithographically definable layers is of a different shape.
7. The monolithic optical coupler of claim 6 , wherein each of said first and additional lithographically definable and barrier layers is optically transparent.
8. A monolithic, multilevel, three-dimensional structure integrally fabricated on a chip, comprising:
a first layer of lithographically definable material on a top surface of said chip, said first layer being individually and at least partially exposed lithographically to define an arbitrary first layer pattern corresponding to the shape of a first level of the multilevel structure;
multiple additional layers of lithographically definable material, each additional layer being located on and supported by the top surface of a preceding layer, each additional layer being individually and at least partially exposed lithographically to define a corresponding arbitrary pattern in each additional layer, the patterns in said first and additional layers defining vertically aligned and at least partially overlapping layers, the pattern of each lithographically-defined layer corresponding to the shape of a corresponding level of the multilevel structure;
a barrier between each of said lithographically-defined layers of lithographically definable material; and
said lithographically-defined layers, upon development, being of such arbitrary shape and vertical alignment as to form a solid, three-dimensional, multilevel monolithic structure on said chip.
9. The structure of claim 8 , wherein said lithographically-defined layers are of arbitrary thickness.
10. The structure of claim 8 , wherein the pattern in at least one of said lithographically-defined first and additional layers defines a nonperiodic level in said structure.
11. The structure of claim 8 , wherein said structure is an optical coupler for connecting an optical device on said chip to another optical device either on the chip or external to it.
12. The structure of claim 8 , wherein said lithographically definable material is a positive photoresist material, wherein said exposed pattern in each of said first and additional levers is removed by development, and wherein unexposed portions of said layers form said levels of said structure.
13. The structure of claim 8 , wherein said lithographically definable material is a negative photoresist material, wherein said exposed pattern in each of said first and additional layers forms a corresponding level of said structure upon development of said photoresist material.
14. The structure of claim 8 , wherein the lithographically definable material of at least one of said first and additional layers is a first photoresist material and the lithographically definable material of at least a second of said first and additional layers is a second photoresist material.
15. The structure of claim 8 , wherein the pattern formed in each of said lithographically-defined layers is of a different shape.
16. The structure of claim 8 , wherein each of said lithographically-defined layers is optically transparent.
17. The structure of claim 8 , wherein the lithographically definable material of each layer is selected from a group consisting of optically transmissive polymer and positive or negative photoresist materials.
18. The structure of claim 8 , wherein the pattern of at least one of said lithographically-defined layers defines a periodic level in said structure.
19. The structure of claim 8 , wherein said structure comprises at least three levels, each level having an arbitrary size and shape.
20. The structure of claim 8 , wherein said barrier is a photosensitive material.
21. The structure of claim 8 , wherein said barrier is a photosensitive material comprising a lithographically definable material and a water soluble material.