Method to improve reliability of replacement gate device
View Patent ↗A method of fabricating a replacement gate stack for a semiconductor device includes the following steps after removal of a dummy gate: growing a high-k dielectric layer over the area vacated by the dummy gate; depositing a thin metal layer over the high-k dielectric layer; depositing a sacrificial layer over the thin metal layer; performing a first rapid thermal anneal; removing the sacrificial layer; and depositing a metal layer of low resistivity metal for gap fill.
1. A method of fabricating a gate stack for a semiconductor device, said method comprising steps of:
after removal of a dummy gate, providing a replacement gate structure by performing steps of:
growing a high-k dielectric layer over an area vacated by the dummy gate;
depositing a thin metal layer over the high-k dielectric layer;
depositing a sacrificial layer over the thin metal layer;
performing a first rapid thermal anneal of the replacement gate structure at a high temperature of not less than 800° C.;
removing the sacrificial layer from the thin metal layer to expose an entirety of the thin metal layer directly over a channel region of the semiconductor device; and
depositing a metal layer of low resistivity metal directly on an entirety of the thin metal layer in the gate stack.
2. The method of claim 1 further comprising:
performing a second rapid thermal anneal after annealing the structure.
3. The method of claim 2 performing the second rapid thermal anneal comprises performing a millisecond anneal with a laser.
4. The method of claim 2 wherein performing the second rapid thermal anneal comprises performing a millisecond anneal with a flash lamp.
5. The method of claim 1 wherein performing the first rapid thermal anneal comprises annealing at a temperature between 800° C. and 1100° C.
6. The method of claim 5 wherein performing the first rapid thermal anneal further comprises spiking the temperature for a period of time up to five seconds.
7. The method of claim 6 wherein performing the first rapid thermal anneal comprises annealing the structure in ambient nitrogen.
8. The method of claim 1 wherein depositing the metal layer comprises:
depositing a work function metal; and
depositing a gap fill metal of low resistivity.
9. The method of claim 1 wherein depositing the sacrificial layer comprises depositing a layer of polycrystalline silicon.
10. The method of claim 1 wherein depositing the sacrificial layer comprises depositing a layer of amorphous silicon.