Method of manufacturing an integrated circuit with buried power rail

1. A method of manufacturing an integrated circuit having buried power rails, the method comprising:

forming a first dielectric layer on an upper surface of a first semiconductor substrate;

forming a plurality of power rail trenches in an upper surface of the first dielectric layer;

forming the buried power rails in the plurality of power rail trenches;

forming a second dielectric layer on the upper surface of the first dielectric layer and upper surfaces of the buried power rails;

forming a third dielectric layer on a donor wafer;

bonding the third dielectric layer to the second dielectric layer after the forming of the third dielectric layer on the donor wafer; and

forming a plurality of semiconductor devices, vias, and metal interconnects on or in the donor wafer,

wherein the buried power rails are encapsulated by the first dielectric layer and the second dielectric layer, and

wherein the buried power rails are below the plurality of semiconductor devices.

2. A method of manufacturing an integrated circuit having buried power rails, the method comprising:

forming a first dielectric layer on an upper surface of a first semiconductor substrate;

forming a plurality of power rail trenches in an upper surface of the first dielectric layer;

forming the buried power rails in the plurality of power rail trenches;

forming a second dielectric layer on the upper surface of the first dielectric layer and upper surfaces of the buried power rails;

forming a third dielectric layer on a donor wafer;

bonding the third dielectric layer to the second dielectric layer; and

forming a plurality of semiconductor devices, vias, and metal interconnects on or in the donor wafer,

wherein the buried power rails are encapsulated by the first dielectric layer and the second dielectric layer,

wherein the buried power rails are below the plurality of semiconductor devices, and

wherein the forming the first dielectric layer comprises thermal oxidation of the upper surface of the first semiconductor substrate.

3. The method of claim 1 , wherein the forming the first dielectric layer comprises depositing the first dielectric layer on the upper surface of the first semiconductor substrate.

4. The method of claim 1 , wherein the forming the buried power rails comprises:

depositing a liner in each of the plurality of power rail trenches;

depositing a conductive material on the liner in each of the plurality of power rail trenches; and

performing chemical mechanical planarization.

5. A method of manufacturing an integrated circuit having buried power rails, the method comprising:

forming a first dielectric layer on an upper surface of a first semiconductor substrate;

forming a plurality of power rail trenches in an upper surface of the first dielectric layer;

forming the buried power rails in the plurality of power rail trenches;

forming a second dielectric layer on the upper surface of the first dielectric layer and upper surfaces of the buried power rails;

forming a third dielectric layer on a donor wafer;

bonding the third dielectric layer to the second dielectric layer; and

forming a plurality of semiconductor devices, vias, and metal interconnects on or in the donor wafer,

wherein the buried power rails are encapsulated by the first dielectric layer and the second dielectric layer,

wherein the buried power rails are below the plurality of semiconductor devices,

wherein the forming the buried power rails comprises:

depositing a liner in each of the plurality of power rail trenches;

depositing a conductive material on the liner in each of the plurality of power rail trenches; and

performing chemical mechanical planarization, and

wherein the conductive material has a thermal stability of at least approximately 700° C.

6. The method of claim 5 , further comprising annealing the second dielectric layer at a temperature of at least approximately 700° C.

7. The method of claim 4 , wherein the conductive material is a refractive metal.

8. The method of claim 7 , wherein the refractive metal is tungsten or ruthenium.

9. A method of manufacturing an integrated circuit having buried power rails, the method comprising:

forming a first dielectric layer on an upper surface of a first semiconductor substrate;

forming a plurality of power rail trenches in an upper surface of the first dielectric layer;

forming the buried power rails in the plurality of power rail trenches;

forming a second dielectric layer on the upper surface of the first dielectric layer and upper surfaces of the buried power rails;

forming a third dielectric layer on a donor wafer;

bonding the third dielectric layer to the second dielectric layer; and

forming a plurality of semiconductor devices, vias, and metal interconnects on or in the donor wafer,

wherein:

the buried power rails are encapsulated by the first dielectric layer and the second dielectric layer,

the buried power rails are below the plurality of semiconductor devices,

the first dielectric layer is a thermal oxide layer have a thickness in a range from approximately 0.05 μm to approximately 9.8 μm,

the second dielectric layer is a deposited oxide layer having a thickness in a range from approximately 0.05 μm to approximately 0.1 μm, and

the third dielectric layer is a thermal oxide layer having a thickness in a range from approximately 0.05 μm to approximately 0.1 μm.

10. The method of claim 1 , further comprising:

depositing a liner on each of the buried power rails; and

performing chemical mechanical planarization, the performing mechanical planarization removing the liner along an upper surface of each of the buried power rails.