Low temperature tungsten film deposition for small critical dimension contacts and interconnects
Provided are methods of void-free tungsten fill of high aspect ratio features. According to various embodiments, the methods involve a reduced temperature chemical vapor deposition (CVD) process to fill the features with tungsten. In certain embodiments, the process temperature is maintained at less than about 350° C. during the chemical vapor deposition to fill the feature. The reduced-temperature CVD tungsten fill provides improved tungsten fill in high aspect ratio features, provides improved barriers to fluorine migration into underlying layers, while achieving similar thin film resistivity as standard CVD fill. Also provided are methods of depositing thin tungsten films having low-resistivity. According to various embodiments, the methods involve performing a reduced temperature low resistivity treatment on a deposited nucleation layer prior to depositing a tungsten bulk layer and/or depositing a bulk layer via a reduced temperature CVD process followed by a high temperature CVD process.
1. A method of filling a recessed feature on a substrate, the method comprising:
providing a substrate having a field region and a first recessed feature, the first recessed feature being recessed from the field region and comprising sidewalls, a bottom, an opening, and corners;
depositing a tungsten nucleation layer on the sidewalls and bottom of the first recessed feature; and
filling the first recessed feature with a low temperature CVD tungsten bulk layer via a chemical vapor deposition (CVD) process; wherein the substrate temperature during the CVD process is maintained at between about 250° C. and 350° C.
2. The method of claim 1 , wherein the first recessed feature has an aspect ratio of at least 10:1.
3. The method of claim 1 , wherein the first recessed feature has an aspect ratio of at least 20:1.
4. The method of claim 1 , wherein width of the first recessed feature opening is no more than about 100 nm.
5. The method of claim 1 , wherein width of the first recessed feature opening is no more than about 50 nm.
6. The method of claim 1 , wherein the width of the first recessed feature opening is no more than about 40 nm.
7. The method of claim 1 , wherein filling the first recessed feature comprises covering the feature corners with the low temperature CVD bulk layer.
8. The method of claim 1 , wherein the substrate further comprises a second feature recessed from the field region, said second recessed feature having an aspect ratio lower than that of the first recessed feature.
9. The method of claim 1 , wherein filling the first recessed feature with a low temperature CVD tungsten bulk layer comprises introducing a halogenated tungsten-containing precursor and a reducing agent into a reaction station housing the substrate.
10. The method of claim 9 , wherein the halogenated tungsten-containing precursor is tungsten hexafluoride.
11. The method of claim 1 , wherein the feature comprises a liner layer.
12. The method of claim 11 , wherein the liner layer has a thickness of no more than 5 nm.
13. The method of claim 1 , further comprising, after depositing a tungsten nucleation layer on the sidewalls and bottom of the first recessed feature and prior to filling the first recessed feature with a low temperature CVD tungsten bulk layer, soaking the substrate with a tungsten-precursor.
14. The method of claim 1 , wherein substrate temperature during the CVD process is maintained at between about 250° C. and 325° C.
15. The method of claim 1 , wherein the low temperature CVD tungsten bulk layer has no observable volcano defects.