Method of forming substrate contact for semiconductor on insulator (SOI) substrate
A semiconductor structure is provided that includes a material stack including an epitaxially grown semiconductor layer on a base semiconductor layer, a dielectric layer on the epitaxially grown semiconductor layer, and an upper semiconductor layer present on the dielectric layer. A capacitor is present extending from the upper semiconductor layer through the dielectric layer into contact with the epitaxially grown semiconductor layer. The capacitor includes a node dielectric present on the sidewalls of the trench and an upper electrode filling at least a portion of the trench. A substrate contact is present in a contact trench extending from the upper semiconductor layer through the dielectric layer and the epitaxially semiconductor layer to a doped region of the base semiconductor layer. A substrate contact is also provided that contacts the base semiconductor layer through the sidewall of a trench. Methods for forming the above-described structures are also provided.
1. A method of forming a semiconductor device comprising:
providing a material stack comprising an epitaxially grown semiconductor layer on a base semiconductor layer, a dielectric layer on the epitaxially grown semiconductor layer, and an upper semiconductor layer present on the dielectric layer;
forming an etch mask on an upper surface of the upper semiconductor layer, wherein the etch mask comprises a contact opening, an isolation opening and a capacitor opening;
etching a contact trench into contact with the base semiconductor layer, an isolation trench into contact with the base semiconductor layer, and a capacitor trench having a base portion present in the epitaxially grown semiconductor layer;
forming a conformal dielectric layer on the contact trench, the isolation trench and the capacitor trench;
removing the conformal dielectric layer from a base portion of the contact trench, wherein said removing the conformal dielectric layer comprises forming a block mask over the isolation trench and the capacitor trench, and removing an exposed portion of the conformal dielectric layer that is present at the base portion of the contact trench using an anisotropic etch, wherein the conformal dielectric layer at base portions of the capacitor trench and the isolation trench remain;
forming a dopant region in the base semiconductor layer at the base portion of the contact trench; and
filling the contact trench, the isolation trench and the capacitor trench with a conductive material.
2. The method of claim 1 , wherein the epitaxially grown semiconductor layer has a thickness that is greater than 1.0 micron.
3. The method of claim 1 , wherein the forming of the etch mask comprises depositing at least one pad nitride layer on the upper semiconductor layer, forming a photoresist mask atop the at least one pad nitride layer, and etching the at least one pad nitride layer to provide the etch mask.
4. The method of claim 1 , wherein the capacitor trench has a first width, the contact trench has a second width, and the isolation trench has a third width, wherein the third width is greater than the second width and the second width is greater than the first width.
5. The method of claim 1 , wherein the base semiconductor layer is doped with a p-type dopant, and the epitaxially grown semiconductor layer is doped to an n-type dopant.
6. The method of claim 1 , wherein the etching comprises an anisotropic etch step.
7. The method of claim 1 , wherein the forming of the conformal dielectric layer on the contact trench, the isolation trench and the capacitor trench comprises deposition of a silicon nitride node dielectric layer on sidewalls and base portions of each of the contact trench, the isolation trench and the capacitor trench.
8. The method of claim 1 , wherein the forming of the dopant region in the base semiconductor layer at the base portion of the contact trench comprises ion implantation of a p-type dopant into the base semiconductor layer at the base portion of the contact trench.
9. The method of claim 1 , wherein the filling the contact trench, the isolation trench and the capacitor trench with a conductive material comprises depositing a conformal layer of metal nitride on sidewalls and base portions of the contact trench, the isolation trench and the capacitor trench, and filling the contact trench, the isolation trench and the capacitor trench with a doped semiconductor or a metal.
10. A method of forming a semiconductor device comprising:
providing a material stack comprising an epitaxially grown semiconductor layer on a base semiconductor layer, a dielectric layer on the epitaxially grown semiconductor layer, and an upper semiconductor layer present on the dielectric layer;
forming an etch mask on an upper surface of the upper semiconductor layer, wherein the etch mask comprises a contact opening, an isolation opening and a capacitor opening;
etching a contact trench into contact with the base semiconductor layer, an isolation trench into contact with the base semiconductor layer, and a capacitor trench having a base portion present in the epitaxially grown semiconductor layer;
forming a conformal dielectric layer on the contact trench, the isolation trench and the capacitor trench;
removing the conformal dielectric layer from a base portion of the contact trench;
forming a dopant region in the base semiconductor layer at the base portion of the contact trench; and
filling the contact trench, the isolation trench and the capacitor trench with a conductive material, wherein the filling the contact trench, the isolation trench and the capacitor trench with a conductive material comprises depositing a conformal layer of metal nitride on sidewalls and base portions of the contact trench, the isolation trench and the capacitor trench, and filling the contact trench, the isolation trench and the capacitor trench with a doped semiconductor or a metal.
11. The method of claim 10 , wherein the epitaxially grown semiconductor layer has a thickness that is greater than 1.0 micron.
12. The method of claim 10 , wherein the forming of the etch mask comprises depositing at least one pad nitride layer on the upper semiconductor layer, forming a photoresist mask atop the at least one pad nitride layer, and etching the at least one pad nitride layer to provide the etch mask.
13. The method of claim 10 , wherein the capacitor trench has a first width, the contact trench has a second width, and the isolation trench has a third width, wherein the third width is greater than the second width and the second width is greater than the first width.
14. The method of claim 10 , wherein the base semiconductor layer is doped with a p-type dopant, and the epitaxially grown semiconductor layer is doped to an n-type dopant.
15. The method of claim 10 , wherein the etching comprises an anisotropic etch step.
16. The method of claim 10 , wherein the forming of the conformal dielectric layer on the contact trench, the isolation trench and the capacitor trench comprises deposition of a silicon nitride node dielectric layer on sidewalls and base portions of each of the contact trench, the isolation trench and the capacitor trench.
17. The method of claim 10 , wherein the removing of the conformal dielectric layer from the base portion of the contact trench comprises forming a block mask over the isolation trench and the capacitor trench, and removing an exposed portion of the conformal dielectric layer that is present at the base portion of the contact trench using an anisotropic etch, wherein the conformal dielectric layer at base portions of the capacitor trench and the isolation trench remain.
18. The method of claim 10 , wherein the forming of the dopant region in the base semiconductor layer at the base portion of the contact trench comprises ion implantation of a p-type dopant into the base semiconductor layer at the base portion of the contact trench.