Device with ground plane for high frequency signal transmission and method therefor
A method for forming a semiconductor structure includes forming an isolation region in a semiconductor substrate; forming a conductive layer over the isolation region; forming a first dielectric layer over the conductive layer; forming a plurality of conductive vias extending through the first dielectric layer to the conductive layer and electrically contacting the conductive layer; forming a second dielectric layer over the first dielectric layer; and forming a conductive ground plane in the second dielectric layer. Each of the plurality of conductive vias is in electrical contact with the conductive ground plane, and the conductive ground plane includes an opening, wherein the opening is located directly over the conductive layer. At least one interconnect layer may be formed over the second dielectric layer and may include a transmission line which transmits a signal having a frequency of at least 30 gigahertz.
1. A method for forming a semiconductor structure, the method comprising:
forming a first isolation region and a second isolation region in a semiconductor substrate;
forming a first conductive layer over the first isolation region and a second conductive layer over the second isolation region;
forming a first dielectric layer over the first conductive layer and the second conductive layer;
forming a first plurality of conductive vias extending through the first dielectric layer to the first conductive layer and electrically contacting the first conductive layer and a second plurality of conductive vias extending through the first dielectric layer to the second conductive layer and electrically contacting the second conductive layer;
forming a second dielectric layer over the first dielectric layer;
removing portions of the second dielectric layer to leave a first portion of the second dielectric layer over the first conductive layer and a second portion of the second dielectric layer over second conductive layer; and
forming a conductive ground plane from a third conductive layer, using chemical mechanical processing (CMP), around the first portion of the second dielectric layer, around the second portion of the second dielectric layer, on and in electrical contact with the first plurality of conductive vias, and on and in electrical contact with the second plurality of conductive vias, wherein the CMP removes all of the third conductive layer that is over the first portion of the second dielectric layer and all of the third conductive layer that is over the second portion of the second dielectric layer and provides a planar top surface of the ground plane.
2. The method of claim 1 , wherein the conductive ground plane comprises a metal and the first conductive layer comprises polysilicon.
3. The method of claim 1 , further comprising:
forming at least one interconnect layer over the second dielectric layer and conductive ground plane, wherein the at least one interconnect layer, wherein the signal has a frequency of at least 30 gigahertz.
4. The method of claim 1 , further comprising:
forming a transistor in and over the semiconductor substrate, between the first isolation region and the second isolation region, wherein the transistor comprises a gate over the semiconductor substrate, a first source/drain region in the semiconductor substrate and adjacent the gate electrode, and a second source/drain region in the semiconductor substrate and adjacent the gate electrode.
5. The method of claim 4 , wherein the forming the transistor comprises:
forming the gate electrode simultaneously with the conductive layer.
6. The method of claim 5 , wherein the first conductive layer and the gate electrode each comprises polysilicon.
7. The method of claim 4 , further comprising:
forming a first silicide region over the first conductive layer, wherein the first plurality of conductive vias are in electrical contact with the first conductive layer via the first silicide region; and
forming a second silicide region over the first and second source/drain regions and the gate electrode, wherein the first silicide region and the second silicide region are formed simultaneously.
8. The method of claim 4 , further comprising:
forming at least one interconnect layer over the second dielectric layer and conductive ground plane; and
forming a contact which electrically contacts at least one of the gate electrode, the first source/drain region, or the second source/drain region, wherein the contact extends through a third portion of the second dielectric layer to electrically contact the at least one interconnect layer.
9. The method of claim 1 , further comprising:
forming a silicide region over the first conductive layer, wherein the first plurality of conductive vias are in electrical contact with the first conductive layer via the silicide region.
10. A method for forming a semiconductor structure, the method comprising:
forming a first isolation region and a second isolation region in a semiconductor substrate;
forming a first conductive layer over the first isolation region and a second conductive layer over the second isolation region, wherein the first conductive layer comprises a first polysilicon-containing layer over the first isolation region and a first silicide layer over the first polysilicon-containing layer and the second conductive layer comprises a second polysilicon-containing layer over the second isolation region and a second silicide layer over the second polysilicon-containing layer;
forming a first dielectric layer over the first conductive layer and the second conductive layer;
forming a first plurality of conductive vias extending through the first dielectric layer to the second silicide layer and a second plurality of vias extending through the first dielectric layer to the second silicide layer;
forming a second dielectric layer over the first dielectric layer;
removing portions of the second dielectric layer to leave a first portion of the second dielectric layer over the first conductive layer and a second portion of the second dielectric layer over second conductive layer and to expose the first plurality of conductive vias and the second plurality of conductive vias; and
forming a metal-containing conductive ground plane from a third conductive layer around the first portion of the second dielectric layer and the second portion of the second dielectric layer using chemical mechanical polishing (CMP), wherein:
the metal-containing conductive ground plane is continuous and has a planar top surface; and
the first plurality of conductive vias and the second plurality of conductive vias are in electrical contact with the metal-containing conductive ground plane by the metal-containing conductive ground plane being on the first plurality of conductive vias and the second plurality of conductive vias.
11. The method of claim 10 , further comprising:
forming a transistor in and over the semiconductor substrate, between the first isolation region and the second isolation region, wherein the transistor comprises a polysilicon-containing gate over the semiconductor substrate, a first source/drain region in the semiconductor substrate and adjacent the polysilicon-containing gate, and a second source/drain region in the semiconductor substrate and adjacent the polysilicon-containing gate.
12. The method of claim 11 , wherein the forming the transistor comprises:
forming the polysilicon-containing gate simultaneously with the polysilicon-containing layer of the conductive layer.
13. The method of claim 11 , further comprising:
forming silicide regions over the first and second source/drain regions and the polysilicon-containing gate, wherein the silicide regions are formed simultaneously with the silicide layer of the conductive layer.
14. The method of claim 11 , comprising:
forming at least one interconnect layer over the second dielectric layer and metal-containing conductive ground plane; and
forming a contact which electrically contacts at least one of the gate electrode, the first source/drain region, or the second source/drain region, wherein the contact extends through the second dielectric layer to electrically contact the at least one interconnect layer.
15. The method of claim 10 , further comprising:
forming at least one interconnect layer over the second dielectric layer and metal-containing conductive ground plane, wherein the at least one interconnect layer transmits a signal, wherein the signal has a frequency of a least 30 gigahertz.