Field effect transistors with dual silicide contact structures
The structure of a semiconductor device with dual silicide contact structures and a method of fabricating the semiconductor device are disclosed. A method of fabricating the semiconductor device includes forming first and second fin structures on a substrate, forming first and second epitaxial regions on the first and second fin structures, respectively, forming first and second contact openings on the first and second epitaxial regions, respectively, selectively forming an oxide capping layer on exposed surfaces of the second epitaxial region, selectively forming a first metal silicide layer on exposed surfaces of the first epitaxial region, removing the oxide capping layer, and forming first and second conductive regions on the metal silicide layer and on the exposed surfaces of the second epitaxial region, respectively. The first metal silicide layer includes a first metal. The first and second conductive regions includes a second metal different from the first metal.
1. A method, comprising:
forming first and second fin structures on a substrate;
forming first and second source/drain (S/D) regions on the first and second fin structures, respectively;
forming first and second contact openings simultaneously on the first and second S/D regions, respectively, to expose surfaces of the first and second S/D regions;
selectively forming an oxide capping layer on the exposed surfaces of the second S/D region within the second contact opening;
forming a metal silicide layer on the exposed surfaces of the first S/D region within the first contact opening;
removing the oxide capping layer; and
forming a conductive region on the exposed surfaces of the second S/D region within the second contact opening.
2. The method of claim 1 , wherein the selectively forming the oxide capping layer comprises:
forming first and second oxide layers on the exposed surfaces of the first and second S/D regions; and
etching the first and second oxide layers with a cleaning process to remove the first oxide layer.
3. The method of claim 2 , wherein the forming the first and second oxide layers comprises simultaneously oxidizing the exposed surfaces of the first and second S/D regions within the first and second contact openings.
4. The method of claim 2 , wherein the forming the first and second oxide layers comprises:
growing the first oxide layer on the exposed surface of the first S/D region at a first growth rate; and
growing the second oxide layer on the exposed surface of the second S/D region at a second growth rate, wherein a ratio of the second growth rate to the first growth rate ranges from about 3 to about 10.
5. The method of claim 2 , wherein the forming the first and second oxide layers comprises growing the second oxide layer thicker than the first oxide layer.
6. The method of claim 2 , wherein the etching the first and second oxide layers comprises:
removing the first oxide layer; and
thinning down the second oxide layer to form the oxide capping layer.
7. The method of claim 1 , wherein the forming the metal silicide layer comprises selectively depositing a layer of a first metal on the exposed surfaces of the first S/D region within the first contact opening, wherein the first metal has a work function value lower than a work function value of a second metal in the conductive region.
8. The method of claim 7 , wherein the forming the metal silicide layer comprises rapid thermal annealing the layer of the first metal on the exposed surfaces of the first S/D region.
9. The method of claim 1 , further comprising forming an additional metal silicide layer between the conductive region and the second S/D region, wherein the additional metal silicide layer and the conductive region comprise a same metal.
10. The method of claim 9 , wherein the forming the additional metal silicide layer comprises rapid thermal annealing the conductive region.
11. A method, comprising:
forming first and second source/drain (S/D) regions on a substrate;
forming first and second contact openings on the first and second S/D regions to expose surfaces of the first and second S/D regions, respectively;
simultaneously oxidizing exposed surfaces of the first and second S/D regions at different oxidation rates;
selectively removing the oxidized surface of the first S/D region to form an oxide capping layer on the exposed surfaces of the second S/D region;
forming a metal silicide layer on the exposed surfaces of the first S/D region within the first contact opening;
forming a metal capping layer on the metal silicide layer;
removing the oxide capping layer; and
forming first and second conductive regions on the metal capping layer and on the exposed surfaces of the second S/D region within the second contact opening, respectively.
12. The method of claim 11 , wherein the forming the metal silicide layer and the forming the metal capping layer comprise:
depositing a metal layer on the exposed surfaces of the first S/D region within the first contact opening;
depositing a layer of metal nitride or metal silicon nitride on the metal layer; and
rapid thermal annealing the metal layer and the layer of metal nitride or metal silicon nitride.
13. The method of claim 11 , wherein the simultaneously oxidizing exposed surfaces of the first and second S/D regions comprises growing a first oxide layer on the first S/D region and a second oxide layer on the second S/D region, the second oxide layer being thicker than the first oxide layer.
14. The method of claim 11 , wherein the selectively removing the oxidized surface of the first S/D region comprises:
performing a cleaning process on the oxidized surfaces of the first and second S/D regions to etch the oxidized surfaces on the first and second S/D regions at a substantially same etching rate.
15. The method of claim 11 , wherein the forming the second conductive region comprises depositing a metal layer within the second contact opening in direct contact with the second S/D region and sidewalls of the second contact opening.
16. A method, comprising:
forming first and second fin structures on a substrate;
forming first and second source/drain (S/D) regions on the first and second fin structures, respectively;
forming first and second contact openings simultaneously on the first and second S/D regions, respectively, wherein the first and second S/D regions are exposed;
selectively forming an oxide capping layer on exposed surfaces of the second S/D region within the second contact opening;
forming a first metal silicide layer on exposed surfaces of the first S/D region within the first contact opening, wherein the first metal silicide layer comprises a first metal;
forming a metal capping layer on the first metal silicide layer;
removing the oxide capping layer; and
depositing a second metal on the metal capping layer, the exposed surfaces of the second S/D region, and sidewalls of the second contact opening.
17. The method of claim 16 , wherein the forming the metal capping layer comprises:
selectively depositing a layer of the first metal on the exposed surfaces of the first S/D region within the first contact opening, wherein the first metal has a work function value lower than a work function value of the second metal;
selectively depositing a layer of metal nitride or metal silicon nitride on the layer of the first metal; and
rapid thermal annealing the layer of the first metal and the layer of metal nitride or metal silicon nitride.
18. The method of claim 16 , wherein the selectively forming the oxide capping layer comprises:
forming first and second oxide layers in contact with the exposed surfaces of the first and second S/D regions, wherein the second oxide layer is thicker than the first oxide layer; and
performing a cleaning process on the first and second oxide layers to remove the first oxide layer and a portion of the second oxide layer.
19. The method of claim 18 , wherein the forming the first and second oxide layers comprises oxidizing the exposed surfaces of the second S/D region within the second contact opening at a higher oxidation rate than that of the exposed surfaces of the first S/D region within the first contact opening.
20. The method of claim 16 , further comprising annealing the second metal on the exposed surfaces of the second S/D region to form a second metal silicide layer.