Stress-controlled formation of tin hard mask
Disclosed is a method to form a titanium nitride (TiN) hard mask in the Damascene process of forming interconnects during the fabrication of a semiconductor device, while the type and magnitude of stress carried by the TiN hard mask is controlled. The TiN hard mask is formed in a multi-layered structure where each sub-layer is formed successively by repeating a cycle of processes comprising TiN and chlorine PECVD deposition, and N 2 /H 2 plasma gas treatment. During its formation, the stress to be carried by the TiN hard mask is controlled by controlling the number of TiN sub-layers and the plasma gas treatment duration such that the stress may counter-balance predetermined external stress anticipated on a conventionally made TiN hard mask, which causes trench sidewall distortion, trench opening shrinkage, and gap filling problem.
1. A method of fabricating a semiconductor device, the method comprising:
providing a stack of layers comprising a substrate, an etch stop layer formed over the substrate, and an insulating layer formed over the etch stop layer;
determining a number of a titanium nitride (TiN) sub-layers and a duration of a plasma gas treatment to be performed in the formation of each of the TiN sub-layers, wherein the determination is made in such a way that when the TiN hard mask is formed in accordance with the TiN sub-layer number and the duration of the plasma gas treatment, the TiN hard mask will have an internal stress that counter-balances an external stress to be exerted on the TiN hard mask to be formed over the insulating layer; and
forming the TiN hard mask over the insulating layer, wherein the TiN hard mask is formed of TiN sub-layers of the determined TiN sub-layer number, and wherein each of the TiN sub-layers is successively formed by a cycle of processes that includes depositing TiN mixed with chlorine and performing a plasma gas treatment for the determined duration.
2. The method of claim 1 , wherein the TiN mixed with the chlorine is deposited in a TiCl 4 Gas.
3. The method of claim 1 , wherein the cycle of processes includes controlling a concentration of the chlorine between about one and about ten atomic percent.
4. The method of claim 1 , wherein the TiN mixed with the chlorine is deposited by plasma enhanced chemical vapor deposition (PECVD).
5. The method of claim 1 , wherein the plasma gas treatment uses a mixture of nitrogen (N 2 ) and hydrogen (H 2 ) gas.
6. The method of claim 1 , wherein the cycle of processes includes controlling a concentration of the chlorine by controlling a duration of the plasma gas treatment in the each cycle.
7. The method of claim 1 , further comprising determining the number of sub-layers in the TiN hard mask in consideration of the desired type and magnitude of internal stress in the TiN hard mask.
8. The method of claim 1 , further comprising forming a plurality of trenches on the stack of layers, each trench extending into the insulation layer, thereby leaving a plurality of trench sidewalls interweaving the trenches.
9. The method of claim 8 , further comprising forming an anti-diffusion barrier film over the plurality of trenches and the plurality of trench sidewalls.
10. A method of fabricating a semiconductor device, the method comprising:
determining external stress to be exerted on a model TiN hard mask in a model semiconductor structure, the model semiconductor structure including: a model insulating layer and a plurality of model trenches defined into the model insulating layer thereby to define a plurality of interweaving model trench sidewalls, each of the model trench sidewalls including the model insulating layer, the model TiN hard mask formed over the model insulating layer, and a model anti-diffusion barrier film formed over the model TiN hard mask;
determining a number of TiN sub-layers, and a duration of a plasma gas treatment to be performed in the formation of each of the TiN sub-layers, wherein the determination is made in such a way that when a TiN hard mask is formed in accordance with the TiN sub-layer number and the duration of a plasma gas treatment, the TiN hard mask will have an internal stress that counter-balances an external stress;
providing a stack of layers including: a substrate; an etch stop layer formed over the substrate; and an insulating layer formed over the etch stop layer; and
forming a TiN hard mask over the insulation layer, wherein the TiN hard mask comprises TiN sub-layers of the determined TiN sub-layer number, and wherein each of the TiN sub-layers is successively formed by depositing TiN mixed with chlorine, and treating the deposited TiN sub-layer with a plasma gas for the determined duration.
11. The method of claim 10 , wherein the TiN mixed with the chlorine is deposited in a TiCl 4 Gas.
12. The method of claim 10 , wherein the TiN mixed with the chlorine is deposited by plasma enhanced chemical vapor deposition (PECVD).
13. The method of claim 10 , wherein the plasma gas is a mixture of nitrogen (N 2 ) and hydrogen (H 2 ) gas.
14. The method of claim 10 , wherein the external stress is determined in consideration of the width and height of the plurality of model trench sidewalls, and the type and thickness of the model anti-diffusion barrier film.
15. The method of claim 10 , wherein the duration of a plasma gas treatment is determined in consideration of a relation between the internal stress of the TiN hard mask and a concentration of the chlorine.
16. The method of claim 15 , wherein the concentration of the chlorine is controlled to be between about one and about ten atomic percent.
17. The method of claim 10 , wherein the number of TiN sub-layers is determined in consideration of a relation between internal stress of the TiN hard mask and a number of TiN sub-layers.
18. The method of claim 10 , further comprising forming a plurality of trenches defined into the insulation layer, leaving a plurality of trench sidewalls interweaving the trenches and being topped by the TiN hard mask.
19. The method of claim 18 , further comprising forming an anti-diffusion barrier film upon the plurality of trenches and the plurality of trench sidewalls, wherein the anti-diffusion barrier film is made of substantially the same material, and has substantially the same thickness, as the model anti-diffusion barrier film.
20. A method comprising:
determining a number of a titanium nitride (TiN) sub-layers and a duration of a plasma gas treatment to be performed in the formation of each of the TiN sub-layers, wherein the determination is made in such a way that when the TiN hard mask is formed in accordance with the TiN sub-layer number and the duration of the plasma gas treatment, the TiN hard mask will have an internal stress that counter-balances an external stress to be exerted on the TiN hard mask to be formed over a semiconductor substrate; and
forming the TiN hard mask over the semiconductor substrate, wherein the TiN hard mask is formed of the number of determined TiN sub-layers and wherein each of the TiN sub-layers is successively formed by a cycle of processes that includes depositing TiN mixed with chlorine and performing a plasma gas treatment for the determined duration.