Combination CVD/ALD method, source and pulse profile modification
The present invention relates generally to methods and apparatus for the controlled growing of material on substrates. According to embodiments of the present invention, a precursor feed is controlled in order to provide an optimal pulse profile. This may be accomplished by splitting the feed into two paths. One of the paths is restricted in a continuous manner. The other path is restricted in a periodic manner. The output of the two paths converges at a point prior to entry of the reactor. Therefore, a single precursor source is able to fed precursor in to a reactor under two different conditions, one which can be seen as mimicking ALD conditions and one which can be seen as mimicking CVD conditions. This allows for an otherwise single mode reactor to be operated in a plurality of modes including one or more ALD/CVD combination modes. Additionally, the pulse profile of each pulse can be modified. The pulse profile can be modified to create a low or very low partial pressure pulse profile at the beginning of a pulse.
1. A method of operating a system having a reactor configured to deposit a thin film, said method comprising:
providing a first amount of a reactant from a reactant source vessel to a reaction space of the reactor at a first volumetric flow rate,
subsequently providing a pulse flow of a second amount of the reactant to the reaction space at a second volumetric flow rate which is greater than said first volumetric flow rate, the pulsed flow comprising a pulse time duration,
removing at least a portion of the second amount of the reactant from the reaction space via delivery of a purge gas to the reaction space,
wherein the providing a first amount of a reactant, providing a pulsed flow of the second amount of the reactant, and removing a portion of the second amount of the reactant are repeated multiple times to deposit the thin film, and
wherein each pulsed flow of the second amount of the reactant entering the reaction space includes less than half of a total amount of the second reactant within a first half of the pulse time duration, thereby initially providing a low partial pressure pulsed flow of the second reactant to the reaction space during each pulsed flow.
2. The method according to claim 1 , wherein the first amount of reactant and the second amount of the reactant are provided from a common reactant source vessel.
3. The method according to claim 1 , wherein the first amount of reactant is at most 50% of the second amount of reactant.
4. The method according to claim 1 , wherein the first volumetric flow rate is controlled by a needle valve or a mass flow controller.
5. The method according to claim 1 , wherein the second reactant is provided to the reaction space as an atomic layer deposition (ALD) process.
6. The method according to claim 1 , wherein the method deposits thin films on silicon wafers.
7. The method according to claim 1 , wherein the second amount of reactant is provided to the reaction space after providing the first amount of reactant to the reaction space.
8. The method according to claim 7 , wherein the providing of the second amount of reactant is repeated until a desired thickness of the film is achieved.
9. The method according to claim 1 , wherein the second reactant is pulsed to the reaction space while the first reactant is continuously delivered to the reaction space.
10. The method according to claim 1 , wherein the first reactant and the second amount of the reactant are provided within a first path and a second path, respectively, and wherein either or both of the first or second paths are substantially restricted.
11. The method according to claim 10 , wherein when either or both of the first or second paths are substantially restricted, and wherein there is no flow of reactant from said corresponding path entering the reaction space.
12. The method according to claim 10 , wherein a time period in restricting a flow of the first path in a periodic manner comprises a purge step.
13. The method of claim 1 , wherein the first half of the pulse time duration is 1.0 second, and wherein each pulsed flow of the second reactant entering the reaction space includes less than half of a total amount of the second reactant within the 1.0 second.
14. The method of claim 13 , wherein each pulsed flow of the second reactant entering the reaction space includes less than 30% of a total amount of the second reactant within the 1.0 second.
15. A method of operating a system having a reactor configured to deposit thin films, said method comprising:
delivering a plurality of pulsed flows of a reactant from a reactant source vessel to a reaction space of the reactor at spaced apart time intervals, each pulsed flow having a pulse time duration,
between selected intervals of the pulsed flows, delivering a purge gas to the reaction space to remove a portion of said reactant from the reaction space, and
wherein each pulsed flow entering the reaction space includes less than 50% of a maximum partial pressure of the reactant for the pulsed flow within a first half of the pulse time duration, thereby initially providing a low partial pressure pulsed flow of the second reactant to the reaction space during each pulse flow.
16. The method according to claim 15 , wherein the partial pressure of the reactant introduced during the first half of the pulse time duration is less than 25% of the maximum partial pressure.
17. The method according to claim 16 , wherein the partial pressure of reactant introduced during the first half of the pulse time duration is less than 10% of the maximum partial pressure.
18. The method according to claim 15 , wherein the method comprises an atomic layer deposition (ALD) process.
19. The method according to claim 15 , wherein the method deposits thin films on silicon wafers.
20. A method of operating a system having a reactor configured to deposit thin films, said method comprising:
delivering a plurality of pulsed flows of a reactant from a reactant source vessel to a reaction space of the reactor at spaced apart time intervals, each pulsed flow having a pulse time duration,
between selected intervals of the pulsed flows, delivering a purge gas to the reaction space to remove a portion of said reactant from the reaction space, and
wherein each pulsed flow entering the reaction space includes less than 50% of a maximum partial pressure of the reactant for the pulsed flow within a first 1.0 second of the pulsed flow, thereby initially providing a low partial pressure pulsed flow of the second reactant to the reaction space during each pulsed flow wherein the 1.0 second is within the first half of the pulse duration.