Methods of fabricating semiconductor devices and semiconductor devices including a contact plug processed by rapid thermal annealing

1. A method of fabricating a semiconductor device, comprising:

depositing tungsten on an insulating layer in which a contact hole is formed by chemical vapor deposition (CVD);

performing chemical mechanical planarization (CMP) on the tungsten to expose the insulating layer and form a tungsten contact plug;

performing rapid thermal oxidation (RTO) on the tungsten contact plug in an oxygen atmosphere such that the tungsten expands volumetrically into tungsten oxide,

after performing the RTO, removing a part of the tungsten oxide that has volumetrically expanded upward from a surface of the insulating layer by buffing CMP, wherein removing a part of the tungsten oxide includes flattening a surface of the tungsten oxide to be at a same level as the surface of the insulating layer; and

after the buffing CMP, reducing the tungsten oxide and transforming the tungsten oxide to metallic tungsten by performing rapid thermal hydrogenation (RTH) or rapid thermal ammoniation (RTNH) on the contact plug in a hydrogen or ammonia atmosphere.

2. The method as claimed in claim 1 , wherein the RTO includes a heating process of heating the tungsten at a high temperature of 400° C. or more for one minute or more and/or a plasma process of heating the tungsten at a power of 20 watts or more for one minute or more.

3. The method as claimed in claim 1 , wherein:

the insulating layer includes an oxide, and

the CMP performed before performing the RTO is a single step process during which a ratio of oxygenated water used as a slurry to a total content is 2% or more, and the tungsten has a higher etch selectivity than the oxide of the insulating layer, such that the tungsten contact plug is dished while a part of the tungsten having the higher etch selectivity is recessed, and

the dished tungsten contact plug expands volumetrically in random directions during the RTO.

4. The method as claimed in claim 1 , wherein:

the insulating layer includes an oxide, and

the CMP performed before performing the RTO includes two steps, such that:

during a first step, a ratio of oxygenated water used as a slurry to a total content is 2% or more, the tungsten has a higher etch selectivity than the oxide of the insulating layer, and a part of the tungsten having the higher etch selectivity is recessed, and

during a second step, a ratio of oxygenated water used as a slurry to a total content is 0.5% or less, the tungsten has a lower etch selectivity than the oxide of the insulating layer, and the tungsten contact plug protrudes while the oxide having the higher etch selectivity is removed such that a surface of the tungsten protrudes, and

the protruding tungsten contact plug expands uniformly and volumetrically in vertical directions during the RTO.

5. The method as claimed in claim 1 , wherein the RTH or RTNH includes a heating process during which heating method is performed on the tungsten oxide at a high temperature of 400° C. or more.

6. The method as claimed in claim 1 , wherein a speed at which the tungsten oxide is reduced to the metallic tungsten when hydrogen or ammonia molecules react with the tungsten oxide is proportional to a hydrogen pressure, a reaction temperature, and a reaction time.

7. The method as claimed in claim 1 , wherein the RTH or RTNH includes a plasma process.

8. A method of fabricating a semiconductor device including a semiconductor substrate on which an oxide insulating layer is formed and includes at least one contact hole formed therein, the method comprising:

depositing tungsten on the semiconductor substrate including the contact hole until the contact hole is overfilled;

forming a tungsten contact plug by planarizing the semiconductor substrate including the tungsten using a chemical mechanical planarization (CMP) process until the insulating layer is exposed;

performing rapid thermal oxidation (RTO) on the tungsten contact plug in an oxygen atmosphere and oxidizing the tungsten to tungsten oxide;

removing a part of the tungsten oxide that has volumetrically expanded upward from the surface of the insulating layer when the tungsten is oxidized to the tungsten oxide by buffing CMP, wherein removing a part of the tungsten oxide includes flattening a surface of the tungsten oxide to be at a same level as the surface of the insulating layer, and

reducing the tungsten oxide into metallic tungsten.

9. The method as claimed in claim 8 , wherein reducing the tungsten oxide to metallic tungsten includes reducing the tungsten oxide into metallic tungsten by performing rapid thermal hydrogenation (RTH) or rapid thermal ammoniation (RTNH) on the contact plug in a hydrogen or ammonia atmosphere.

10. The method as claimed in claim 8 , wherein reducing the tungsten oxide into metallic tungsten includes reducing the tungsten oxide into metallic tungsten by performing rapid thermal nitridation (WIN) on the tungsten oxide in a nitrogen atmosphere and nitriding the tungsten oxide.

11. A method of fabricating a semiconductor device, the method comprising:

forming a tungsten contact plug in a contact hole of an insulating layer using a chemical vapor deposition (CVD) process and a chemical mechanical planarization (CMP) process;

oxidizing the tungsten contact plug using rapid thermal annealing (RTA) in an oxygen atmosphere;

flattening a surface of the oxidized tungsten contact plug using a buffing CMP process, wherein flattening the surface of the oxidized tungsten contact plug using the buffing CMP process includes flattening the surface of the oxidized tungsten contact plug to be at a same level as a surface of the insulating layer, and

reducing the oxidized tungsten contact plug by performing rapid thermal hydrogenation (RTH) or rapid thermal ammoniation (RTNH) in a hydrogen or ammonia atmosphere.

12. The method as claimed in claim 11 , wherein flattening the surface of the oxidized tungsten contact plug using the buffing CMP process further includes removing a part of an oxidized region of the tungsten contact plug formed by oxidizing the tungsten contact plug.

13. The method as claimed in claim 11 , wherein oxidizing the tungsten contact plug includes oxidizing a surface of the tungsten contact plug.