Selective dual silicide formation using a maskless fabrication process flow
A first dielectric layer is selectively formed such that the first dielectric layer is formed over a source/drain region of a first type of transistor but not over a source/drain region of a second type of transistor. The first type of transistor and the second type of transistor have different types of conductivity. A first silicide layer is selectively formed such that the first silicide layer is formed over the source/drain region of the second type of transistor but not over the source/drain region of the first type of transistor. The first dielectric layer is removed. A second silicide layer is formed over the source/drain region of the first type of transistor.
1. A semiconductor device, comprising:
a first transistor having a first type of conductivity, wherein the first transistor includes: a first source/drain, a first silicide formed in a vertical direction over the first source/drain, a first contact formed in the vertical direction over the first silicide, and a first nitride material formed between the first silicide and the first contact in the vertical direction; and
a second transistor having a second type of conductivity that is different from the first type of conductivity, wherein the second transistor includes: a second source/drain, a second silicide formed over the second source/drain, a conductive layer formed over the second silicide, a second nitride material formed over the conductive layer, and a second contact formed over the second nitride material, wherein the first silicide and the second silicide have different work functions, and wherein the conductive layer includes a metal layer and a metal silicide layer.
2. The semiconductor device of claim 1 , wherein the first transistor is an N-type transistor, and wherein the second transistor is a P-type transistor.
3. The semiconductor device of claim 1 , wherein a work function of the second silicide is greater than a work function of the first silicide.
4. The semiconductor device of claim 1 , wherein:
the first silicide contains: TiSi x , AlSi x , HfSi x , LiSi x , ErSi x , YbSi x , YSi x , or LaSi x ; and
the second silicide contains WSi x , MoSi x , RuSi x , NiSi x , or CoSi x .
5. The semiconductor device of claim 1 , wherein the first nitride material or the second nitride material contains titanium nitride, hafnium nitride, lanthanum nitride, erbium nitride, ytterbium nitride, or yttrium nitride.
6. The semiconductor device of claim 1 , wherein the second contact is formed directly on the second nitride material.
7. The semiconductor device of claim 1 , wherein a bottom surface of the first silicide and a bottom surface of the second silicide have different shapes in a cross-sectional view.
8. The semiconductor device of claim 1 , wherein a bottom surface of the first silicide is at least partially curved.
9. The semiconductor device of claim 1 , wherein the first source/drain includes an epitaxial layer.
10. A semiconductor device, comprising:
an NFET that includes:
a first source/drain region;
a first silicide layer disposed over the first source/drain region, the first silicide layer having a first work function; and
a first conductive contact disposed over the first silicide layer; and
a PFET that includes:
a second source/drain region;
a second silicide layer disposed over the second source/drain region, the second silicide layer having a second work function that is higher than the first work function;
a metal layer disposed over the second silicide layer;
a metal silicide layer disposed over the metal layer;
a nitride layer disposed over the metal silicide layer; and
a second conductive contact disposed over the nitride layer
wherein the first silicide layer and the second silicide layer have different geometric profiles in a cross-sectional side view.
11. The semiconductor device of claim 10 , wherein a lower surface of the first silicide layer is more curved than a lower surface of the second silicide layer in the cross-sectional side view.
12. The semiconductor device of claim 10 , wherein the second silicide layer is recessed into the second source/drain region in the cross-sectional side view.
13. The semiconductor device of claim 10 , wherein the NFET further includes a nitride layer disposed between the first silicide layer and the first conductive contact.
14. The semiconductor device of claim 10 , wherein an upper surface of the first source/drain region has a lower vertical elevation than an upper surface of the first silicide layer in the cross-sectional side view.
15. A semiconductor device, comprising:
an NFET that includes:
a first source/drain region;
a first silicide layer disposed over the first source/drain region, the first silicide layer having a first work function;
a first nitride layer disposed over the first silicide layer; and
a first conductive contact disposed over the first nitride layer; and
a PFET that includes:
a second source/drain region;
a second silicide layer disposed over the second source/drain region, the second silicide layer having a second work function that is greater than the first work function;
a conductive layer disposed over the second silicide layer, wherein the conductive layer includes a metal layer and a metal silicide layer;
a second nitride layer disposed over the conductive layer; and
a second conductive contact disposed over the second nitride layer.
16. The semiconductor device of claim 15 , wherein the first silicide layer is in direct contact with the first nitride layer.
17. The semiconductor device of claim 15 , wherein a bottom surface of the second conductive contact has a more elevated position vertically than a bottom surface of the first conductive contact.
18. The semiconductor device of claim 15 , wherein the first silicide layer and the second silicide layer have different geometric profiles.
19. The semiconductor device of claim 1 , wherein a bottom surface of the first silicide is more curved than a bottom surface of the second silicide.
20. The semiconductor device of claim 15 , wherein an upper surface of the first silicide layer is more elevated vertically than an upper surface of the second silicide layer.