Fabrication of multilayered carbon MEMS devices
The various technologies presented herein relate to formation of carbon micromechanical systems (CMEMS), wherein the CMEMS comprise multiple layers of carbon structures and are formed using a plurality of photoresist precursors that are processed to form carbon. The various embodiments can be utilized in producing a plurality of CMEMS with full production level fabrication, e.g., 6 inch wafers can be processed. A pyrolyzed layer of carbon is lithographically defined after pyrolysis, wherein the post-pyrolysis etch process can produce carbon structures having repeatable and accurate device geometries, with straight sidewalls. A sacrificial layer can be applied to facilitate separation of a first carbon layer from a second carbon layer, wherein, upon pyrolysis to form the second carbon layer and lithography thereof, the sacrificial layer is removed to form a CMEMS comprising a first carbon layer (e.g., comprising bottom contacts) located beneath a second carbon layer (e.g., a mechanical layer).
1. A method for forming a carbon micromechanical system (CMEMS), the method comprising:
forming a sacrificial layer over a patterned first carbon layer, wherein the first carbon layer is formed by pyrolyzing a first photoresist layer causing material in the first photoresist layer to decompose to form the first carbon layer, wherein the first carbon layer is patterned after pyrolysis of the first photoresist layer;
subsequent to forming the sacrificial layer over the patterned first carbon layer, patterning the sacrificial layer;
depositing a second photoresist layer over the patterned sacrificial layer;
subsequent to depositing the second photoresist layer, pyrolyzing the second photoresist layer to form a second carbon layer;
after pyrolyzing the second photoresist layer, patterning the second carbon layer; and
removing the sacrificial layer leaving the patterned second carbon layer located over the patterned first carbon layer, wherein removal of the sacrificial layer causes a region that was previously filled with the sacrificial layer to form an opening between the patterned first carbon layer and the patterned second carbon layer.
2. The method of claim 1 , wherein the sacrificial layer comprises polysilicon, silicon dioxide, silicon nitride, a metal, or any other material that can be removed with suitable etching technologies such as dry etch or aqueous dissolution.
3. The method of claim 1 , wherein the sacrificial layer is removed with any of a vapor pressure system utilizing xenon difluoride (XeF 2 ), an isotropic dry etch, or an isotropic wet etch.
4. The method of claim 1 , wherein the sacrificial layer is formed on the first carbon layer by one of low-pressure chemical vapor deposition (LPCVD), physical vapor deposition, CVD, sputtering, electroplating, or evaporation deposition.
5. The method of claim 1 , wherein the first carbon layer and the second carbon layer are patterned through use of a photoresist or a hard mask.
6. The method of claim 5 , wherein the hard mask comprises one of silicon dioxide (SiO 2 ), a high-density plasma SiO 2 , a silane-based material, SiH 4 /Ar/O 2 high-density plasma oxide, SiH 4 /N 2 O/N 2 based CVD oxide, an alumina-based material (Al 2 O 3 ), or physical vapor deposited Al 2 O 3 .
7. The method of claim 1 , wherein the first carbon layer and the second carbon layer are patterned through use of an inductively reactive ion plasma (ICP) with O 2 /Ar/SF 6 chemistry.
8. The method of claim 1 , wherein the first carbon layer is patterned to form bottom contacts.
9. The method of claim 1 , wherein the second carbon layer is a mechanical layer.
10. The method of claim 1 , wherein the first carbon layer and the second carbon layer are formed by pyrolysis at about 1150° C.
11. The method of claim 1 , wherein the first carbon layer is formed on a substrate.
12. The method of claim 1 , wherein the first carbon layer and the second carbon layer comprise at least one of sp 2 -hybrid orbital carbon or sp 3 -hybrid orbital carbon.
13. The method of claim 1 , wherein the CMEMS is formed on a 6 inch wafer.
14. The method of claim 1 , further comprising:
forming a second sacrificial layer over the patterned second carbon layer;
subsequent to forming the second sacrificial layer over the patterned second carbon layer, patterning the second sacrificial layer;
depositing a third layer of photoresist material over the patterned second sacrificial layer;
subsequent to depositing the third photoresist layer, pyrolyzing the third photoresist layer to form a third carbon layer;
after pyrolyzing the third photoresist layer, patterning the third carbon layer; and
removing the second sacrificial layer leaving the patterned third carbon layer located over the patterned second carbon layer, wherein removal of the second sacrificial layer causes a second region that was previously filled with the second sacrificial layer to form a second opening between the patterned second carbon layer and the patterned third carbon layer.
15. A method for fabricating a carbon micromechanical system (CMEMS), the method comprising:
forming a first layer of photoresist material on a substrate, wherein the substrate is a 6 inch silicon wafer;
subsequent to forming the first photoresist layer on the substrate, pyrolyzing the first photoresist layer to form a first carbon layer;
after pyrolyzing the first photoresist layer, patterning the first carbon layer;
forming a sacrificial layer over the patterned first carbon layer;
after forming the sacrificial layer over the patterned first carbon layer, patterning the sacrificial layer;
depositing a second layer of photoresist material over the patterned sacrificial layer;
subsequent to depositing the second photoresist layer, pyrolyzing the second photoresist layer to form a second carbon layer;
after pyrolyzing the second photoresist layer, patterning the second carbon layer; and
removing the sacrificial layer leaving the patterned second carbon layer located over the patterned first carbon layer, wherein removal of the sacrificial layer causes a region that was previously filled with the sacrificial layer to form an opening between the patterned first carbon layer and the patterned second carbon layer.