Isolated capacitors within shallow trench isolation
View Patent ↗A semiconductor process and apparatus provide a shallow trench isolation capacitor structure that is integrated in an integrated circuit and includes a bottom capacitor plate that is formed in a substrate layer ( 10 ) below a trench opening, a capacitor dielectric layer ( 22 ) and a recessed top capacitor plate ( 28 ) that is covered by an STI region ( 30 ) and isolated from cross talk by a sidewall dielectric layer ( 23 ).
1. A method for fabricating a capacitor, comprising:
providing a semiconductor substrate structure;
forming a trench opening in the semiconductor substrate structure to define bottom and sidewall surfaces of the trench opening where the bottom surface exposes a bottom capacitor plate semiconductor region in the semiconductor substrate structure;
forming a capacitor dielectric layer on the bottom surface of the trench opening and an insulating dielectric sidewall layer on the sidewall surface of the trench opening, where the insulating dielectric sidewall layer is thicker than the capacitor dielectric layer; and
forming a conductive top capacitor plate layer on the capacitor dielectric layer in the trench opening.
2. The method of claim 1 , further comprising forming a shallow trench isolation region on the conductive top capacitor plate layer.
3. The method of claim 1 , where forming the insulating dielectric sidewall layer on the sidewall surface of the trench opening comprises forming a dielectric liner in the trench opening comprising a sidewall surface liner layer at a thickness that provides electrical isolation for the capacitor.
4. The method of claim 1 , where forming the capacitor dielectric layer and the insulating dielectric sidewall layer comprises:
forming a dielectric layer on the bottom and sidewall surfaces in the trench opening;
anisotropically etching the dielectric layer in the trench opening to remove the dielectric layer from the bottom of the trench opening while retaining dielectric layer on the sidewall surface of the trench opening; and
forming a dielectric layer on the bottom of the trench opening which forms a capacitor dielectric layer for the capacitor.
5. The method of claim 1 , where forming the capacitor dielectric layer and the insulating dielectric sidewall layer comprises growing the capacitor dielectric layer and the insulating dielectric sidewall layer on the trench opening with a thermal oxidation process.
6. The method of claim 1 , where forming the capacitor dielectric layer and the insulating dielectric sidewall layer comprises:
forming a dielectric layer on the bottom and sidewall surfaces in the trench opening; and
anisotropically etching the dielectric layer in the trench opening to leave insulating dielectric sidewall layer that is at least twice as thick as the capacitor dielectric layer.
7. The method of claim 1 , where forming the conductive top capacitor plate layer comprises:
depositing a conductive layer on at least the capacitor dielectric layer on the bottom surface of the trench opening; and
anisotropically etching the conductive layer in the trench opening to form sidewall top capacitor plate structures in the trench opening without removing the capacitor dielectric layer on the bottom surface of the trench opening.
8. The method of claim 1 , where forming the conductive top capacitor plate layer comprises forming a metal-based material on the capacitor dielectric layer on the bottom surface of the trench opening as a top capacitor plate having a top surface which is below a top surface of the semiconductor substrate structure.
9. The method of claim 1 , where forming the conductive top capacitor plate layer comprises forming a silicide material on the capacitor dielectric layer on the bottom surface of the trench opening as a top capacitor plate having a top surface which is below a top surface of the semiconductor substrate structure.
10. The method of claim 1 , where forming the shallow trench isolation region comprises:
depositing an insulating material to cover the conductive top capacitor plate layer and fill the trench opening; and
planarizing the insulating material in the trench opening.
11. A method for fabricating a capacitor, comprising:
providing a semiconductor substrate structure having a top surface;
forming a trench opening in the semiconductor substrate structure by selectively removing a portion of the semiconductor substrate structure in a first region to define bottom and sidewall surfaces where the bottom surface exposes a semiconductor region in the semiconductor substrate structure which forms a bottom capacitor plate;
forming a dielectric liner in the trench opening comprising a sidewall surface liner layer that is thicker than a bottom surface liner layer; and
forming a conductive layer on the bottom surface liner layer in the trench opening as a top capacitor plate.
12. The method of claim 11 , where forming the dielectric liner comprises:
forming a dielectric layer on the bottom and sidewall surfaces in the trench opening; and
anisotropically etching the dielectric layer in the trench opening to partially etch the dielectric layer to form the dielectric liner having a sidewall surface liner layer that is thicker than a bottom surface liner layer which forms a capacitor dielectric layer for the capacitor.
13. The method of claim 11 , where forming the dielectric liner comprises:
forming a dielectric layer on the bottom and sidewall surfaces in the trench opening;
anisotropically etching the dielectric layer in the trench opening to remove the dielectric layer from the bottom of the trench opening while retaining dielectric layer on the sidewall surface of the trench opening; and
forming a dielectric layer on the bottom of the trench opening which forms a capacitor dielectric layer for the capacitor.
14. The method of claim 11 , where forming the conductive layer comprises:
depositing a metal-based conductive layer having a thickness on at least the bottom surface liner layer in the trench opening; and
reducing the thickness of the metal-based conductive layer in the trench opening to form the top capacitor plate having a top surface which is recessed below the top surface of the semiconductor substrate structure.
15. The method of claim 11 , where forming the conductive layer comprises:
depositing a conductive layer on at least the bottom surface liner layer in the trench opening; and
anisotropically etching the conductive layer in the trench opening to form sidewall top capacitor plate structures in the trench opening without removing the bottom surface liner layer.
16. The method of claim 11 , where forming the conductive layer comprises forming a silicide material on the bottom surface liner layer in the trench opening as a top capacitor plate.
17. The method of claim 11 , where forming the dielectric liner comprises forming a dielectric liner in the trench opening comprising a sidewall surface liner layer that is at least twice as thick as the bottom surface liner layer to provide electrical isolation for the capacitor.
18. The method of claim 11 , further comprising forming an isolation layer over the top capacitor plate.
19. An integrated circuit trench capacitor structure, comprising:
a first capacitor plate formed from a semiconductor layer located below a trench formed in a substrate;
a capacitor dielectric layer located on the first capacitor plate and in the trench; and
a second capacitor plate located on the capacitor dielectric layer from a conductive material that is located in the trench, where the second capacitor plate is electrically isolated from adjacent semiconductor material by a sidewall dielectric layer that is located on a sidewall of the trench and that is thicker than the capacitor dielectric layer.
20. The integrated circuit trench capacitor structure of claim 19 , where the second capacitor plate comprises a recessed second capacitor plate located on the capacitor dielectric layer and formed with a conductive material located in the trench, where the recessed second capacitor plate has a top surface which is below a top surface of the substrate and which is covered by a dielectric material.
21. The integrated circuit trench capacitor structure of claim 19 , where the second capacitor plate is formed in a trench that separates a first active area in which is formed one or more first transistors of a first conductivity type from a second active area in which is formed one or more second transistors of a second different conductivity type.