Processes for preparing integrated circuits with improved source/drain contact structures and integrated circuits prepared according to such processes

1. A process for preparing an integrated circuit, the process comprising: providing a semiconductor structure comprising a transistor with a gate electrode structure, sidewall spacers disposed on opposite sides of the gate electrode structure to insulate the gate electrode structure and to align ion implantation into the semiconductor substrate, and source and drain regions, wherein at least one of the source and drain regions comprises a shaped contact structure overlaid with a contact etch stop layer and a pre-metal dielectric material, wherein the shaped contact structure has a substantially diamond-shaped cross-sectional shape; overlaying the shaped contact structure with a contact etch stop layer and a pre-metal dielectric material; removing a first portion of the pre-metal dielectric material overlaying the shaped contact structure with a first anisotropic etch such that a second portion of the pre-metal dielectric material remains overlaying the shaped contact structure; removing the second portion of the pre-metal dielectric material overlaying the shaped contact structure with a second anisotropic etch, wherein the second anisotropic etch is capable of etching the pre-metal dielectric material while being substantially ineffective against the contact etch stop layer; removing the contact etch stop layer overlaying the shaped contact structure with a third anisotropic etch to expose the shaped contact structure, wherein the third anisotropic etch is capable of etching the contact etch stop layer while being substantially ineffective against the shaped contact structure so as to preserve the substantially diamond-shaped cross-sectional shape of the shaped contact structure after exposure to the third anisotropic etch.

2. The process of claim 1 , wherein the shaped contact structure comprises an epitaxially deposited semiconductor material.

3. The process of claim 1 , wherein the shaped contact structure comprises an epitaxially deposited semiconductor material selected from the group consisting of silicon, silicon germanium (SiGe), germanium (Ge), gallium arsenide (GaAs), or indium phosphide (InP).

4. The process of claim 1 , wherein the contact etch stop layer comprises a nitride material.

5. The process of claim 1 , wherein the pre-metal dielectric material, including both the first portion and the second portion, comprises an oxide material.

6. The process of claim 1 , wherein the first anisotropic etch is timed to stop before reaching the contact etch stop layer.

7. The process of claim 1 , wherein the second anisotropic etch uses NH 3 /NF 3 or SF 6 /H 2 O.

8. The process of claim 1 , wherein the second anisotropic etch is a chemical oxide removal cleaning step.

9. The process of claim 1 , wherein the third anisotropic etch is a nitride dry etch.

10. A process for fabricating an integrated circuit, the process comprising: providing a semiconductor substrate; forming a transistor with a gate electrode structure, sidewall spacers disposed on opposite sides of the gate electrode structure to insulate the gate electrode structure and to align ion implantation into the semiconductor substrate, and source and drain regions in and on the semiconductor substrate, wherein at least one of the source and drain regions comprises a shaped contact structure, wherein the shaped contact structure has a substantially diamond-shaped cross-sectional shape; overlaying the shaped contact structure with a contact etch stop layer and a pre-metal dielectric material; removing a first portion of the pre-metal dielectric material overlaying the shaped contact structure with a first anisotropic etch such that a second portion of the pre-metal dielectric material remains overlaying the shaped contact structure; removing the second portion of the pre-metal dielectric material overlaying the shaped contact structure with a second anisotropic etch, wherein the second anisotropic etch is capable of etching the pre-metal dielectric material while being substantially ineffective against the contact etch stop layer; removing the contact etch stop layer overlaying the shaped contact structure with a third anisotropic etch to expose the shaped contact structure, wherein the third anisotropic etch is capable of etching the contact etch stop layer while being substantially ineffective against the shaped contact structure so as to preserve the substantially diamond-shaped cross-sectional shape of the shaped contact structure after exposure to the third anisotropic etch; applying an electrical contact material to the exposed shaped contact structure.

11. The process of claim 10 , wherein the shaped contact structure comprises an epitaxially deposited semiconductor material.

12. The process of claim 10 , wherein the shaped contact structure comprises an epitaxially deposited semiconductor material selected from the group consisting of silicon, silicon germanium (SiGe), germanium (Ge), gallium arsenide (GaAs), or indium phosphide (InP).

13. The process of claim 10 , wherein the contact etch stop layer comprises a nitride material.

14. The process of claim 10 , wherein the pre-metal dielectric material comprises an oxide material.

15. The process of claim 10 , wherein the first anisotropic etch is timed to stop before reaching the contact etch stop layer.

16. The process of claim 10 , wherein the second anisotropic etch NH 3 /NF 3 or SF 6 /H 2 O.

17. The process of claim 10 , wherein the second anisotropic etch is a chemical oxide removal cleaning step.

18. The process of claim 10 , wherein the third anisotropic etch is a nitride dry etch.