US-12622247-B2 - Manufacturing method of semiconductor structure

Abstract

The present disclosure provides a manufacturing method of a semiconductor structure including the following steps. A trench is formed between bit lines. A seed layer is deposited in the trench, and a first contact layer is deposited on the seed layer in the trench. A second contact layer is deposited on the first contact layer to fill the trench, in which a second doping concentration of the second contact layer is lower than a first doping concentration of the first contact layer. An annealing process is performed on the first contact layer and the second contact layer, such that dopants in the first contact layer diffuse into the second contact layer to form a contact plug including the first contact layer and the second contact layer.

Inventors

• Cheng Yan JI

Assignees

• NANYA TECHNOLOGY CORPORATION

Dates

Publication Date

20260505

Application Date

20230517

Claims (19)

1. 1 . A manufacturing method of a semiconductor structure, comprising: forming a trench between bit lines; depositing a seed layer in the trench; depositing a first contact layer on the seed layer in the trench; depositing a second contact layer on the first contact layer to fill the trench, wherein a second doping concentration of the second contact layer is lower than a first doping concentration of the first contact layer; depositing a capping layer on the second contact layer after depositing the second contact layer, wherein a third doping concentration of the capping layer is lower than the second doping concentration of the second contact layer; and performing an annealing process on the first contact layer and the second contact layer, such that dopants in the first contact layer diffuse into the second contact layer to form a contact plug comprising the first contact layer and the second contact layer.
2. 2 . The manufacturing method of claim 1 , wherein the first doping concentration of the first contact layer before performing the annealing process is higher than a doping concentration of the contact plug after performing the annealing process.
3. 3 . The manufacturing method of claim 1 , wherein the seed layer is undoped before performing the annealing process.
4. 4 . The manufacturing method of claim 3 , wherein after performing the annealing process, the dopants in the first contact layer diffuse into the seed layer to form the contact plug comprising the seed layer.
5. 5 . The manufacturing method of claim 1 , wherein the seed layer, the first contact layer, and the second contact layer have a uniform doping concentration after performing the annealing process.
6. 6 . The manufacturing method of claim 1 , wherein a thickness of the first contact layer is larger than a thickness of the seed layer, and wherein a thickness of the second contact layer is larger than the thickness of the first contact layer.
7. 7 . The manufacturing method of claim 1 , wherein a ratio of a thickness of the second contact layer to a thickness of the first contact layer is in a range of 1.3 to 3.1.
8. 8 . The manufacturing method of claim 1 , wherein the seed layer, the first contact layer, and the second contact layer are formed of a same polysilicon material.
9. 9 . The manufacturing method of claim 1 , wherein the second contact layer comprises a recessed portion at a top surface of the second contact layer, and wherein the capping layer fills the recessed portion.
10. 10 . The manufacturing method of claim 1 , wherein the capping layer has a flat top surface after depositing the capping layer.
11. 11 . The manufacturing method of claim 1 , wherein a thickness of the capping layer is larger than a thickness of the second contact layer.
12. 12 . The manufacturing method of claim 1 , further comprising: performing a planarization process after performing the annealing process to make a top surface of the contact plug levelled with top surfaces of the bit lines.
13. 13 . A manufacturing method of a semiconductor structure, comprising: forming a trench between bit lines; delivering a first source gas of SiH 4 and PH 3 to the trench to form a first contact layer; delivering a second source gas of SiH 4 and PH 3 to the trench to form a second contact layer on the first contact layer, wherein a first ratio of PH 3 to SiH 4 of the first source gas is higher than a second ratio of PH 3 to SiH 4 of the second source gas; delivering a third source gas of SiH 4 and PH 3 to the trench to form a capping layer on the second contact layer; and performing an annealing process to form a contact plug from the first contact layer and the second contact layer.
14. 14 . The manufacturing method of claim 13 , wherein the first ratio of PH 3 to SiH 4 of the first source gas is higher than 0.3.
15. 15 . The manufacturing method of claim 13 , wherein a flow rate of the second source gas is higher than a flow rate of the first source gas.
16. 16 . The manufacturing method of claim 13 , wherein a third ratio of PH 3 to SiH 4 of the third source gas is lower than the second ratio of PH 3 to SiH 4 of the second source gas.
17. 17 . The manufacturing method of claim 13 , wherein a third ratio of PH 3 to SiH 4 of the third source gas is lower than 0.05.
18. 18 . The manufacturing method of claim 13 , wherein a flow rate of the second source gas is higher than a flow rate of the third source gas.
19. 19 . The manufacturing method of claim 13 , wherein forming the first contact layer, forming the second contact layer, and forming the capping layer are performed in-situ.

Description

BACKGROUND Field of Invention The present disclosure relates to a manufacturing method of a semiconductor structure. More particularly, the present disclosure relates to the manufacturing method of a contact plug of the semiconductor structure. Description of Related Art With the advancement of semiconductor techniques, the size of semiconductor structure has become smaller, which has led to an increase in the integration of semiconductor devices. In this case, the critical dimension of the semiconductor structure is also reduced, so that the electronic product may be more compact. However, as the critical dimension of the semiconductor structure gets smaller, the process techniques for manufacturing the semiconductor structure will face many challenges. For example, since the semiconductor structures have become smaller, the requirement for fewer voids therein became higher to achieve the expected yield and performance. SUMMARY According to an embodiment of the present disclosure, a manufacturing method of a semiconductor structure is provided. A trench is formed between bit lines. A seed layer is deposited in the trench, and a first contact layer is deposited on the seed layer in the trench. A second contact layer is deposited on the first contact layer to fill the trench, in which a second doping concentration of the second contact layer is lower than a first doping concentration of the first contact layer. An annealing process is performed on the first contact layer and the second contact layer, such that dopants in the first contact layer diffuse into the second contact layer to form a contact plug including the first contact layer and the second contact layer. In some embodiments, the first doping concentration of the first contact layer before performing the annealing process is higher than a doping concentration of the contact plug after performing the annealing process. In some embodiments, the seed layer is undoped before performing the annealing process. In some embodiments, after performing the annealing process, the dopants in the first contact layer diffuse into the seed layer to form the contact plug including the seed layer. In some embodiments, the seed layer, the first contact layer, and the second contact layer have a uniform doping concentration after performing the annealing process. In some embodiments, a thickness of the first contact layer is larger than a thickness of the seed layer, and a thickness of the second contact layer is larger than the thickness of the first contact layer. In some embodiments, a ratio of a thickness of the second contact layer to a thickness of the first contact layer is in a range of 1.3 to 3.1. In some embodiments, the seed layer, the first contact layer, and the second contact layer are formed of a same polysilicon material. In some embodiments, the manufacturing method further includes depositing a capping layer on the second contact layer after depositing the second contact layer and before performing the annealing process. A third doping concentration of the capping layer is lower than the second doping concentration of the second contact layer. In some embodiments, the second contact layer includes a recessed portion at a top surface of the second contact layer, and the capping layer fills the recessed portion. In some embodiments, the capping layer has a flat top surface after depositing the capping layer. In some embodiments, a thickness of the capping layer is larger than a thickness of the second contact layer. In some embodiments, the manufacturing method further includes performing a planarization process after performing the annealing process to make a top surface of the contact plug levelled with top surfaces of the bit lines. According to another embodiment of the present disclosure, a manufacturing method of a semiconductor structure is provided. A trench is formed between bit lines. A first source gas of SiH4 and PH3 is delivered to the trench to form a first contact layer. A second source gas of SiH4 and PH3 is delivered to the trench to form a second contact layer on the first contact layer, in which a first ratio of PH3 to SiH4 of the first source gas is higher than a second ratio of PH3 to SiH4 of the second source gas. A third source gas of SiH4 and PH3 is delivered to the trench to form a capping layer on the second contact layer. An annealing process is performed to form a contact plug from the first contact layer and the second contact layer. In some embodiments, the first ratio of PH3 to SiH4 of the first source gas is higher than 0.3. In some embodiments, a flow rate of the second source gas is higher than a flow rate of the first source gas. In some embodiments, a third ratio of PH3 to SiH4 of the third source gas is lower than the second ratio of PH3 to SiH4 of the second source gas. In some embodiments, the third ratio of PH3 to SiH4 of the third source gas is lower than 0.05. In some embodiments, a flow rate of the second so