Integrating a first contact structure in a gate last process
A method is provided that includes providing a substrate; forming a transistor in the substrate, the transistor having a dummy gate; forming a dielectric layer over the substrate and transistor; forming a contact feature in the dielectric layer; and after forming the contact feature, replacing the dummy gate of the transistor with a metal gate. An exemplary contact feature is a dual contact.
1. A method comprising:
providing a substrate;
forming a transistor that includes a gate dielectric layer disposed over the substrate and a metal gate disposed over the gate dielectric layer;
forming a dual contact structure that is coupled to a doped region of the transistor, wherein the forming the dual contact structure includes:
before forming the metal gate of the transistor, forming a first contact feature coupled to the doped region of the transistor, and
after forming the metal gate of the transistor, forming a second contact feature coupled to the first contact feature; and
forming a dummy dual contact structure in a first region of the substrate that is less dense than a second region of the substrate in which the transistor is disposed.
2. The method of claim 1 wherein the first contact feature and the second contact feature have a substantially same width.
3. The method of claim 1 wherein:
the forming the first contact feature coupled to the doped region of the transistor includes:
forming a first interlevel dielectric layer over the substrate and the transistor,
forming a first trench in the first interlevel dielectric layer, wherein the first trench exposes the doped region of the transistor, and
forming a first contact plug in the first trench, the first contact plug being coupled to the exposed doped region; and
the forming the second contact feature coupled to the first contact feature includes:
forming a second interlevel dielectric layer over the first interlevel dielectric layer and the transistor,
forming a second trench in the second interlevel dielectric layer, wherein the second trench exposes the first contact plug, and
forming a second contact plug in the second trench, the second contact plug being coupled to the exposed first contact plug.
4. The method of claim 3 wherein the forming the metal gate of the transistor includes:
performing a chemical mechanical polishing process on the first interlevel dielectric layer until a dummy gate of the transistor is exposed;
removing the dummy gate, thereby forming a trench; and
forming a work function metal layer and a filler metal layer in the trench, thereby forming the metal gate.
5. The method of claim 1 further including forming a metal interconnect layer over the dual contact structure, wherein the metal interconnect layer is coupled to the second contact feature.
6. The method of claim 1 further including:
forming a first interlevel dielectric layer over the substrate and the transistor;
forming the dummy dual contact structure in the first interlevel dielectric layer when forming the dual contact structure.
7. The method of claim 6 wherein the forming the dummy dual contact structure when forming the dual contact structure includes:
forming a first dummy contact feature when forming the first contact feature; and
forming a second dummy contact feature when forming the second contact feature, wherein the second dummy contact feature is coupled to the first dummy contact feature.
8. A method comprising:
providing a substrate having a first region and a second region, wherein the second region has a pattern density that is substantially less than a pattern density of the first region;
forming a first transistor and a second transistor in the first region, wherein the first transistor and the second transistor each include a gate dielectric layer and a metal gate disposed over the gate dielectric layer;
forming a dual contact structure in the first region between the first transistor and the second transistor, wherein the forming the dual contact structure includes:
before forming the metal gate of the first transistor and the second transistor, forming a first contact feature coupled to a doped region of one of the first transistor and the second transistor, and
after forming the metal gate of the first transistor and the second transistor, forming a second contact feature coupled to the first contact feature; and
forming a dummy dual contact structure in the second region.
9. The method of claim 8 wherein the first contact feature and the second contact feature have a substantially same width.
10. A method comprising:
providing a substrate having a first region and a second region, wherein the second region has a pattern density that is substantially less than a pattern density of the first region;
forming a first transistor and a second transistor in the first region, wherein the first transistor and the second transistor each include a gate dielectric layer and a metal gate disposed over the gate dielectric layer;
forming a dual contact structure in the first region between the first transistor and the second transistor, wherein the forming the dual contact structure includes:
before forming the metal gate of the first transistor and the second transistor, forming a first contact feature coupled to a doped region of one of the first transistor and the second transistor, and
after forming the metal gate of the first transistor and the second transistor, forming a second contact feature coupled to the first contact feature; and
forming a dummy dual contact structure in the second region, wherein the forming the dummy dual contact structure includes:
forming a first dummy contact feature; and
forming a second dummy contact feature coupled to the second contact feature.
11. The method of claim 10 further including:
forming the first dummy contact feature at the same time as forming the first contact feature; and
forming the second dummy contact feature at the same time as forming the second contact feature.