Reverse tone self-aligned contact
Some embodiments of the present disclosure relate to a method to form a source/drain self-aligned contact to a transistor or other semiconductor device. The method comprises forming a pair of gate structures over a substrate, and forming a source/drain region between the pair of gate structures. The method further comprises forming a sacrificial source/drain contact which is arranged over the source/drain region and which is arranged laterally between neighboring sidewalls of the pair of gate structures. The method further comprises forming a dielectric layer which extends over the sacrificial source/drain contact and over the pair of gate structures. The dielectric layer differs from the sacrificial source/drain contact. The method further comprises removing a portion of the dielectric layer over the sacrificial source/drain contact and subsequently removing the sacrificial source/drain contact to form a recess, and filling the recess with a conductive material to form a source/drain contact.
1. A method, comprising:
forming a sacrificial material around and above a pair of gate structures, wherein a source/drain region is arranged between the pair of gate structures;
removing the pair of gate structures to form a pair of cavities within the sacrificial material;
filling the pair of cavities with a gate material to form a pair of replacement gate structures;
forming a sacrificial source/drain contact between the pair of replacement gate structures;
forming a dielectric layer over the sacrificial source/drain contact and over the pair of replacement gate structures;
sequentially etching both the sacrificial source/drain contact and the dielectric layer to form a recess that extends through the sacrificial material; and
filling the recess with a conductive material to form a source/drain contact that is electrically coupled to the source/drain region.
2. The method of claim 1 , wherein the removing the sacrificial source/drain contact and dielectric layer to form the recess comprises:
forming a mask to expose a portion of the dielectric layer over the source/drain region and to cover other portions of the dielectric layer;
performing a first etch with the mask in place to remove the exposed portion of the dielectric layer and create a recess within the dielectric layer, wherein the recess terminates at an upper surface of the sacrificial source/drain contact; and
performing a second etch of the recess to remove the sacrificial source/drain contact and to extend the recess so that it terminates at an upper surface of the source/drain region.
3. The method of claim 1 , wherein the removing the pair of gate structures and forming the pair of replacement gate structures comprise:
forming insulating sidewall spacers arranged about opposing sidewalls of a sacrificial gate electrode of each of the pair of gate structures;
forming an etch stop material over the sacrificial gate electrode and sidewall spacers prior to forming the sacrificial source/drain contact;
recessing the sacrificial gate electrode to form cavities within vertical surfaces of the sidewall spacers; and
forming the replacement gate structures by filing the cavities with metal.
4. The method of claim 3 , further comprising forming a strained source/drain region between the pair of gate structures prior to forming the etch stop material.
5. A method of forming a conductive contact, comprising:
forming a source/drain region within a substrate;
forming a first sacrificial gate structure over the substrate at a location laterally offset from the source/drain region;
depositing amorphous silicon vertically over the source/drain region and latterly adjacent to the first sacrificial gate structure;
forming a second sacrificial gate structure over the substrate at a location laterally separated from the first sacrificial gate structure by the amorphous silicon;
replacing the first sacrificial gate structure with a first metal gate structure;
replacing the second sacrificial gate structure with a second metal gate structure;
forming a dielectric layer over the amorphous silicon and the first metal gate structure;
sequentially etching both the dielectric layer and the amorphous silicon to form a recess; and
filling the recess with a conductive material to form a source/drain contact.
6. The method of claim 5 , further comprising:
forming a second sacrificial gate structure over the substrate at a location laterally separated from the first sacrificial gate structure by the amorphous silicon; and
replacing the second sacrificial gate structure with a second metal gate structure.
7. The method of claim 5 , further comprising:
forming a layer of etch stop material over the first sacrificial gate structure and the source/drain region; and
performing a first planarization process that forms a first planar surface comprising the layer of etch stop material and the amorphous silicon.
8. The method of claim 7 , further comprising:
recessing the amorphous silicon below the layer of etch stop material after performing the first planarization process;
depositing the dielectric layer onto the amorphous silicon after recessing the amorphous silicon, wherein the dielectric layer contacts sidewalls of the layer of etch stop material; and
performing a second planarization process that forms a second planar surface comprising the layer of etch stop material, the dielectric layer, and the first sacrificial gate structure.
9. A method of forming a conductive contact, comprising:
forming a pair of sacrificial gate structures over a substrate;
forming a source/drain region between the pair of sacrificial gate structures;
forming a sacrificial source/drain contact over the source/drain region and laterally between the pair of sacrificial gate structures;
replacing the pair of sacrificial gate structures with a pair of metal gate structures;
forming a dielectric layer over the sacrificial source/drain contact and the pair of metal gate structures, wherein the dielectric layer is laterally offset from the pair of metal gate structures and overlaps the pair of metal gate structures along a vertical direction normal to an upper surface of the substrate;
etching a portion of the dielectric layer over the sacrificial source/drain contact and subsequently etching the sacrificial source/drain contact to form a recess; and
filling the recess with a conductive material to form a source/drain contact.
10. The method of claim 9 , wherein the removing the sacrificial source/drain contact comprises:
performing a first etch process to etch dielectric layer according to a masking layer to form a opening within the dielectric layer that extends to an upper surface of the sacrificial source/drain contact; and
performing a second etch process to etch the sacrificial source/drain contact according to the opening to form the recess, which extends to at an upper surface of the source/drain region.
11. The method of claim 10 , wherein the second etch process has an etching selectivity configured to etch the sacrificial source/drain contact faster than the pair of metal gate structures.
12. The method of claim 9 , wherein the pair of metal gate structures respectively comprise:
a gate electrode;
insulating sidewall spacers arranged about opposing sidewalls of the gate electrode; and
a capping layer overlying an upper surface of the gate electrode.
13. The method of claim 12 , wherein the capping layer comprises silicon nitride (SiN).
14. The method of claim 9 , wherein the forming the sacrificial source/drain contact comprises:
forming a sacrificial material over the pair of sacrificial gate structures, wherein the sacrificial material fills a lateral region over the source/drain region between neighboring sidewalls of the pair of sacrificial gate structures; and
forming the sacrificial source/drain contact by removing the sacrificial material outside the lateral region such that remaining sacrificial material forms the sacrificial source/drain contact.
15. The method of claim 9 , wherein the sacrificial source/drain contact and the dielectric layer meet at an interface that lies on a plane, which intersects upper sidewall portions of the pair of metal gate structures.
16. The method of claim 9 , wherein the sacrificial source/drain contact comprises amorphous silicon.
17. The method of claim 1 , wherein the sacrificial material comprises a ‘U’ shape that extends along sidewalls of the pair of gate structures.
18. The method of claim 1 , further comprising:
removing the pair of gate structures to form the pair of cavities, which contact the sacrificial material.
19. The method of claim 9 , further comprising:
forming a sacrificial material around and above the pair of sacrificial gate structures; and
wherein the dielectric layer contacts sidewalls of the sacrificial material.
20. The method of claim 19 , wherein the dielectric layer has an upper surface aligned with an upper surface of the sacrificial material.