Fluorine-free tungsten deposition process employing in-situ oxidation and apparatuses for effecting the same

1. A method of depositing tungsten over a substrate, comprising:

disposing the substrate into a vacuum enclosure of a tungsten deposition apparatus;

performing a first tungsten deposition process that deposits a first tungsten layer on a physically exposed surface of the substrate by forming a vacuum and flowing a fluorine-containing tungsten precursor gas into the vacuum enclosure;

performing an in-situ oxidation process by exposing the first tungsten layer to an oxidation agent gas while the substrate remains within the vacuum enclosure without breaking the vacuum and forming a tungsten oxyfluoride gas which is pumped out of the vacuum enclosure; and

performing a second tungsten deposition process that deposits a second tungsten layer on the first tungsten layer by flowing the fluorine-containing tungsten precursor gas into the vacuum enclosure in the second tungsten deposition process after the in-situ oxidation process.

2. The method of claim 1 , wherein:

the vacuum enclosure comprises a process chamber containing a plurality of substrate pockets;

a plurality of substrates including the substrate are loaded into the plurality of substrate pockets;

the first tungsten deposition process is performed at a first process position in the process chamber; and

the second tungsten deposition process is performed at a second process position in the process chamber.

3. The method of claim 2 , wherein:

the process chamber comprises a first showerhead overlying the first process position and a second showerhead overlying the second process position;

the first tungsten deposition process is performed when the substrate located in a first substrate pocket of the plurality of substrate pockets is located in the first process position and the fluorine-containing tungsten precursor gas is flowed through the first showerhead;

the in-situ oxidation process is performed by flowing the oxidation agent gas through the first showerhead while the substrate located in the first substrate pocket is located in the first process position; and

the second tungsten deposition process is performed when the substrate located in the first substrate pocket is located in the second process position and the fluorine-containing tungsten precursor gas is flowed through the second showerhead.

4. The method of claim 3 , further comprising lifting the substrate above a pedestal of the first substrate pocket during the in-situ oxidation process, and lowering the substrate onto the pedestal of the first substrate pocket during the second tungsten deposition process.

5. The method of claim 2 , wherein:

the process chamber comprises a first showerhead overlying the first process position, a second showerhead overlying the second process position, and an oxidation region located between the first process position and the second process position;

the first tungsten deposition process is performed when the substrate located in a first substrate pocket of the plurality of substrate pockets is located in the first process position and the fluorine-containing tungsten precursor gas is flowed through the first showerhead;

the in-situ oxidation process is performed by flowing the oxidation agent gas into the oxidation region while the substrate located in the first substrate pocket is moving from the first process position to the second process position; and

the second tungsten deposition process is performed when the substrate located in the first substrate pocket is located in the second process position and the fluorine-containing tungsten precursor gas is flowed through the second showerhead.

6. The method of claim 5 , wherein the process chamber comprises a plurality of showerheads and a plurality of oxidation regions which alternate along an azimuthal direction around a vertical axis passing through a geometrical center of an entire volume of the process chamber.

7. The method of claim 6 , further comprising rotating the plurality of substrate pockets around the vertical axis in one or two directions while performing the in-situ oxidation process.

8. The method of claim 1 , wherein:

the vacuum enclosure comprises an oxidation chamber that is connected to a process chamber through a transfer region that is under vacuum; and

the in-situ oxidation process is performed after transferring the substrate from the process chamber in which the first tungsten layer is deposited into the oxidation chamber and flowing the oxidation agent gas into the oxidation chamber.

9. The method of claim 1 , wherein performing the in-situ oxidation process comprises:

exposing the first tungsten layer to the oxidation agent gas to form a tungsten oxyfluoride layer on the first tungsten layer;

preheating the substrate to at least 110 degrees Celsius to sublimate the tungsten oxyfluoride layer to the tungsten oxyfluoride gas; and

pumping the tungsten oxyfluoride gas out of the vacuum enclosure.

10. The method of claim 1 , wherein:

the tungsten-containing precursor gas comprises tungsten hexafluoride; and

each of the first tungsten deposition process and the second tungsten deposition process comprise a respective thermal chemical vapor deposition or atomic layer deposition process that is performed at an elevated temperature in a range from 380 degrees Celsius to 480 degrees Celsius.

11. The method of claim 1 , wherein:

the substrate comprises a semiconductor substrate including a vertically alternating stack of insulating layers and laterally-extending cavities thereupon, wherein the insulating layers are supported by vertically-extending structures that extend through each of the insulating layers within the vertically alternating stack; and

the first tungsten layer and the second tungsten layer are deposited within volumes of the laterally-extending cavities.

12. The method of claim 11 , wherein the vertically-extending structures comprise memory opening fill structures each including a respective vertical semiconductor channel and a respective memory film.

13. The method of claim 11 , wherein:

each of the laterally-extending cavities are partly filled with the first tungsten layer after the first tungsten deposition process; and

the tungsten oxyfluoride gas which is pumped out of the vacuum enclosure through remaining unfilled volumes of the laterally-extending cavities.