Ultrathin atomic layer deposition film accuracy thickness control

1. A method for depositing silicon oxide films by plasma-enhanced atomic layer deposition on semiconductor substrates, the method comprising:

(a) inserting a first semiconductor substrate into a chamber;

(b) after inserting the first semiconductor substrate into the chamber and prior to performing a first cycle of plasma-enhanced atomic layer deposition (PEALD) at a deposition temperature, raising the first semiconductor substrate's temperature to about the deposition temperature by exposing the first semiconductor substrate to a helium-free soak gas for a duration of about 500 seconds or less to reduce wafer-to-wafer variation compared to semiconductor substrates processed using a helium-containing soak gas prior to performing the PEALD on a first semiconductor substrate;

(c) performing the PEALD to deposit a first silicon oxide film on the first semiconductor substrate; and

(d) after depositing the first silicon oxide film on the first semiconductor substrate, performing the PEALD in one or more cycles to deposit a second silicon oxide film on a second semiconductor substrate,

wherein a cycle of the PEALD comprises

exposing the substrate to a silicon-containing precursor in a non-plasma environment for a duration sufficient to substantially adsorb the silicon-containing precursor to a surface of the substrate and

exposing the substrate to reactant gases comprising an inert gas and an oxidant in a plasma environment to form at least a portion of the silicon oxide film,

wherein the soak gas contains the reactant gases,

wherein the inert gas is selected from the group consisting of nitrogen, argon, and combinations thereof,

wherein the oxidant selected from the group consisting of oxygen and nitrous oxide, and combinations thereof, and

wherein the first silicon oxide film is deposited to a thickness of less than about 5 nm.

2. The method of claim 1 , wherein proportion of gases in the soak gas is substantially the same as proportion of the gases during the exposing of the substrate to the reactant gases in the cycle of PEALD.

3. The method of claim 1 , wherein flow rate of the soak gas in (b) is within about 10% of a maximum flow rate achievable by the chamber.

4. The method of claim 3 , wherein flow rate of the soak gas in (b) is at least about 15 slm.

5. The method of claim 1 , wherein flow rate of the soak gas in (b) is at least about 25% to about 200% of flow rate of the reactant gases.

6. The method of claim 1 , wherein wafer-to-wafer variation between average thickness of the first silicon oxide film and the second silicon oxide film is less than about ±2 Å.

7. The method of claim 1 , wherein between two and about fifty cycles of the PEALD are performed on each semiconductor substrate.

8. The method of claim 1 , wherein the first semiconductor substrate is exposed to the soak gas for a duration between about 5 seconds and about 60 seconds.

9. The method of claim 1 , wherein the soak gas is a temperature-stabilizing soak gas that stabilizes the first semiconductor substrate's temperature.

10. The method of claim 1 , wherein the wafer-to-wafer variation between average thickness of the first silicon oxide film and the second silicon oxide film is less than about ±2 Å.

11. A method for depositing a film by plasma-enhanced atomic layer deposition on semiconductor substrates, the method comprising:

(a) inserting a first semiconductor substrate into a chamber; and

(b) after inserting the first semiconductor substrate into the chamber and prior to performing a first cycle of plasma-enhanced atomic layer deposition (PEALD) at a deposition temperature, raising the first semiconductor substrate's temperature to about the deposition temperature by exposing the first semiconductor substrate to a helium-free soak gas for a duration of about 500 seconds or less to reduce wafer-to-wafer variation compared to semiconductor substrates processed using a helium-containing soak gas prior to performing the PEALD on a first semiconductor substrate;

(c) performing the PEALD to deposit a first film on the first semiconductor substrate; and

(d) after depositing the first film on the first semiconductor substrate, performing the PEALD in one or more cycles to deposit a second film on a second semiconductor substrate,

wherein a cycle of the PEALD comprises

exposing the substrate to a precursor in a non-plasma environment for a duration sufficient to substantially adsorb the precursor to a surface of the substrate,

exposing the substrate to a second reactant comprising an inert gas and oxygen-containing gas in a plasma environment to form at least a portion of the film,

wherein the soak gas contains the second reactant

wherein the inert gas is selected from the group consisting of nitrogen, argon, and combinations thereof,

wherein the oxygen-containing gas is selected from the group consisting of oxygen and nitrous oxide, and combinations thereof, and

wherein the first film is deposited to a thickness of less than about 5 nm.

12. The method of claim 11 , wherein the proportion of gases in the soak gas is substantially the same as the proportion of gases in the second reactant during the exposing of the substrate to the second reactant in the cycle of PEALD.

13. The method of claim 11 , wherein flow rate of the soak gas in (b) is within 10% of a maximum flow rate achievable by the chamber.

14. The method of claim 13 , wherein the flow rate of the soak gas in (b) is at least about 15 slm.

15. The method of claim 11 , wherein flow rate of the soak gas in (b) is at least about 25% to about 200% of the flow rate of the second reactant used when exposing the first semiconductor substrate to the second reactant in the plasma environment during the cycle of the PEALD.

16. The method of claim 11 , wherein the wafer-to-wafer variation of an average thickness of the first and second films deposited on at least the first and the second semiconductor substrates is less than about ±2 Å.

17. The method of claim 11 , wherein the soak gas is a temperature-stabilizing soak gas that stabilizes the first semiconductor substrate's temperature.

18. A method for depositing silicon oxide films by plasma-enhanced atomic layer deposition on three or more semiconductor substrates, the method comprising:

(a) inserting a first semiconductor substrate into a chamber;

(b) after inserting the first semiconductor substrate into the chamber and prior to performing a first cycle of plasma-enhanced atomic layer deposition (PEALD) on the first semiconductor substrate at a deposition temperature, raising the first semiconductor substrate's temperature to about the deposition temperature by exposing the first semiconductor substrate to a helium-free soak gas for a duration of about 500 seconds or less;

(c) performing n cycles of the PEALD to deposit a first silicon oxide film on the first semiconductor substrate;

(d) after removing the first semiconductor substrate having the first silicon oxide film from the chamber and inserting a second semiconductor substrate into the chamber, performing the n cycles of the PEALD on the second semiconductor substrate to deposit a second silicon oxide film; and

(f) after removing the second semiconductor substrate having the second silicon oxide film from the chamber and inserting a third semiconductor substrate into the chamber, performing the n cycles of the PEALD on the third semiconductor substrate to deposit a third silicon oxide film,

wherein each of the n cycles of the PEALD comprises

exposing the semiconductor substrate to a silicon-containing precursor in a non-plasma environment for a duration sufficient to substantially adsorb the silicon-containing precursor to a surface of the semiconductor substrate and

exposing the semiconductor substrate to an oxidant in a plasma environment to form at least a portion of the silicon oxide film,

wherein the helium-free soak gas contains one or more gases of the oxidant used when exposing the first semiconductor substrate to the oxidant in the plasma environment during the cycle of the PEALD,

wherein the n cycles of PEALD are performed to deposit less than about 5 nm of silicon oxide on the second and third semiconductor substrates, and

wherein wafer-to-wafer variation of an average thickness of the first, second, and third silicon oxide films deposited on the three or more semiconductor substrates is less than about ±2 Å.

19. The method of claim 18 , wherein the helium-free soak gas is a temperature-stabilizing soak gas that stabilizes the first semiconductor substrate's temperature.