Method for forming source/drain contacts
A method includes providing a structure that includes a substrate, a gate structure over the substrate, and a source/drain (S/D) feature including silicon germanium (SiGe) adjacent to the gate structure. The method further includes implanting gallium (Ga) into the S/D feature; performing a first annealing process at a first temperature to recrystallize the SiGe; depositing a conductive material including a metal over the S/D feature after the first annealing process; performing a second annealing process at a second temperature to cause reaction between the metal and the S/D feature; and performing a third annealing process at a third temperature to activate dopants including Ga in the S/D feature.
1. A method, comprising:
providing a structure that includes:
a substrate;
a gate structure over the substrate; and
a source/drain (S/D) feature including silicon germanium (SiGe) adjacent to the gate structure;
implanting gallium (Ga) into the S/D feature;
performing a first annealing process at a first temperature to recrystallize the SiGe;
depositing a conductive material including a metal over the S/D feature after the first annealing process;
performing a second annealing process at a second temperature to cause reaction between the metal and the S/D feature; and
performing a third annealing process at a third temperature to activate dopants including Ga in the S/D feature.
2. The method of claim 1 , wherein the third temperature is higher than the first and second temperatures.
3. The method of claim 1 , wherein the first temperature is in a range from about 400 degrees Celsius to about 600 degrees Celsius.
4. The method of claim 1 , wherein both the first and the second temperatures are in a range from about 400 degrees Celsius to about 600 degrees Celsius.
5. The method of claim 1 , wherein a ratio of Ge:Si in the SiGe is greater than 1.
6. The method of claim 1 , wherein Ge concentration in the SiGe ranges from about 55% to about 75%.
7. The method of claim 1 , wherein the implanting of Ga applies a Ga ion dose ranging from about 5E14 cm −2 to about 1E15 cm −2 .
8. The method of claim 1 , further comprising:
implanting boron (B) into the S/D feature simultaneously with the implanting of Ga.
9. The method of claim 1 , wherein the metal includes titanium.
10. The method of claim 1 , wherein the gate structure includes a high-k dielectric layer and a metal gate electrode.
11. The method of claim 1 , after the second annealing process and before the third annealing process, further comprising:
removing unreacted portions of the conductive material.
12. The method of claim 11 , after the third annealing process, further comprising:
depositing another conductive material over the S/D feature.
13. A method, comprising:
providing a structure that includes:
a substrate;
a gate structure over the substrate;
a source/drain (S/D) feature including silicon germanium (SiGe) adjacent to the gate structure; and
one or more dielectric layers over sidewalls of the gate structure and over the S/D feature;
etching the one or more dielectric layers to form an opening exposing the S/D feature;
implanting gallium (Ga) ions into the S/D feature through the opening;
performing a first annealing process at a recrystallization temperature of the SiGe;
depositing a material including a metal over the S/D feature after the first annealing process;
performing a second annealing process to form a compound having Si and the metal over the S/D feature;
performing a third annealing process to activate dopants including Ga in the S/D feature; and
forming an S/D contact plug over the compound.
14. The method of claim 13 , wherein the recrystallization temperature of the SiGe is in a range from about 525 degrees Celsius to about 575 degrees Celsius.
15. The method of claim 13 , wherein Ge concentration in the SiGe ranges from about 55% to about 75%.
16. The method of claim 13 , wherein the first annealing process causes Ga ions to segregate and to move to a top portion of the S/D feature.
17. The method of claim 13 , wherein the first and second annealing processes are performed at about a same temperature that is lower than a temperature of the third annealing process.
18. A method, comprising:
providing a structure that includes:
a substrate;
a high-k metal gate structure over the substrate; and
a source/drain (S/D) feature including silicon germanium (SiGe) adjacent to the high-k metal gate structure;
implanting gallium (Ga) ions and boron (B) ions into the S/D feature;
performing a first annealing process at a recrystallization temperature of the SiGe;
depositing a conductive material including a metal over the S/D feature after the first annealing process;
performing a second annealing process to form one or more compounds having Si and the metal over the S/D feature;
performing a third annealing process to activate dopants including Ga and B in the S/D feature; and
forming an S/D contact plug over the one or more compounds.
19. The method of claim 18 , wherein Ge concentration in the SiGe ranges from about 55% to about 75%.
20. The method of claim 18 , wherein the third annealing process is performed at a temperature higher than the recrystallization temperature.