Source alternating MOCVD processes to deposit tungsten nitride thin films as barrier layers for MOCVD copper interconnects
View Patent ↗An alternating source MOCVD process is provided for depositing tungsten nitride thin films for use as barrier layers for copper interconnects. Alternating the tungsten precursor produces fine crystal grain films, or possibly amorphous films. The nitrogen source may also be alternated to form WN/W alternating layer films, as tungsten is deposited during periods where the nitrogen source is removed.
1. A source alternating CVD process for forming tungsten-containing barrier layers comprising:
a) heating a substrate within a CVD chamber;
b) introducing an alternating source of a W(CO) 6 precursor into the CVD chamber;
c) introducing NH 3 gas into the chamber throughout at least one cycle of the alternating source of a W(CO) 6 precursor; whereby the W(CO) 6 and NH 3 react to deposit WN onto the heated substrate; and
d) turning the NH 3 gas on and off to provide for, when the NH 3 gas is off, deposition of a tungsten layer, thereby forming alternating layers of WN/W to produce a low resistance tungsten-containing film.
2. The process of claim 1 , wherein the substrate is heated to a temperature between about 200° C. and 450° C.
3. The process of claim 1 , wherein the substrate is heated to a temperature between about 351° C. and 400° C.
4. The process of claim 1 , wherein the alternating source W(CO) 6 precursor is introduced into the chamber by an alternating source of carrier gas.
5. The process of claim 4 , wherein the alternating source of carrier gas is hydrogen.
6. The process of claim 5 , wherein the hydrogen has an on-state flow rate between about 10 sccm and 200 sccm.
7. The process of claim 6 , wherein the hydrogen has an on/off period that varies from about 25 seconds/5 seconds to 5 seconds/25 seconds.
8. The process of claim 1 , wherein the chamber pressure is between about 200 mtorr and 1,000 mtorr.
9. The process of claim 1 , wherein the NH 3 source has an on-state flow rate of between about 20 sccm and 50 sccm.
10. A source alternating CVD process for forming tungsten-containing barrier layers comprising:
a) heating a substrate to a temperature between about 200° C. and 450° C. within a CVD chamber at a pressure of between about 200 mtorr and 1,000 mtorr;
b) providing an alternating source of a W(CO) 6 precursor into the CVD chamber by sublimating a solid W(CO) 6 precursor and delivering it into the CVD chamber by turning a hydrogen carrier gas having a flow rate of between about 10 sccm and 200 sccm on and off according to a sequence with a on/off period that varies from about 25 seconds/5 seconds to 5 seconds/25 seconds;
c) delivering an NH 3 gas into the CVD chamber at a flow rate of between about 20 sccm and 50 sccm throughout at least one cycle of the W(CO) 6 precursor, whereby the W(CO) 6 and NH 3 react to deposit WN onto the heated substrate; and
d) turning the NH 3 gas on and off to provide for, when the NH 3 gas is off, deposition of a tungsten layer, thereby forming alternating layers of WN/W to produce a low resistance tungsten-containing film.