Methods and apparatuses for showerhead backside parasitic plasma suppression in a secondary purge enabled ALD system
Disclosed are methods of depositing films of material on semiconductor substrates employing the use of a secondary purge. The methods may include flowing a film precursor into a processing chamber and adsorbing the film precursor onto a substrate in the processing chamber such that the precursor forms an adsorption-limited layer on the substrate. The methods may further include removing at least some unadsorbed film precursor from the volume surrounding the adsorbed precursor by purging the processing chamber with a primary purge gas, and thereafter reacting adsorbed film precursor while a secondary purge gas is flowed into the processing chamber, resulting in the formation of a film layer on the substrate. The secondary purge gas may include a chemical species having an ionization energy and/or a disassociation energy equal to or greater than that of O 2 . Also disclosed are apparatuses which implement the foregoing processes.
1. An apparatus for depositing a film of material on a semiconductor substrate, the apparatus comprising:
a processing chamber;
a substrate holder in the processing chamber;
a showerhead for flowing film precursor and primary purge gas into the processing chamber;
a showerhead collar for flowing a secondary purge gas into the processing chamber;
one or more primary flow valves for controlling flow of film precursor and flow of primary purge gas through the showerhead;
one or more secondary flow valves for controlling flow of secondary purge gas through the showerhead collar;
a valve-operated vacuum source for removing primary and secondary purge gases from the processing chamber, and for removing film precursor from the volume surrounding the substrate in the processing chamber;
a plasma generator for generating a plasma in the processing chamber; and
one or more controllers comprising machine-readable, non-transitory media containing instructions for operating the one or more valves, vacuum source, and plasma generator to deposit a film of material onto the semiconductor substrate, including instructions for:
(a) operating the primary flow valve(s) to flow a film precursor into the processing chamber;
(b) controlling conditions within the processing chamber such that film precursor adsorbs onto the substrate in the processing chamber forming an adsorption-limited layer;
(c) operating the primary flow valve(s) to flow a primary purge gas into the processing chamber and operating the valve-operated vacuum source to evacuate it thereby removing at least some unadsorbed film precursor from the volume surrounding the adsorbed film precursor; and
(d) operating the plasma generator to form a plasma in the processing chamber, the plasma activating reaction of the adsorbed film precursor to form a film layer on the substrate;
(e) operating the secondary flow valve(s) to flow a secondary purge gas into the processing chamber while activating the reaction in (d), wherein the secondary purge gas comprises a chemical species having an ionization energy and/or a disassociation energy equal to or greater than that of O 2 .
2. The apparatus of claim 1 , wherein:
the showerhead comprises:
a stem portion;
a head portion; and
apertures in the bottom surface of the head portion for flowing film precursor and primary purge gas into the processing chamber; and
the showerhead collar comprises:
a stem portion;
a head portion; and
apertures in the stem portion for flowing a secondary purge gas into the processing chamber.
3. The apparatus of claim 2 , wherein the apertures of the showerhead are holes and the apertures of the showerhead collar are slots.
4. The apparatus of claim 1 , wherein the chemical species comprising the secondary purge gas is O 2 .
5. The apparatus of claim 1 , wherein the primary purge gas comprises an inert gas.
6. The apparatus of claim 5 , wherein the primary purge gas comprises Ar and/or N 2 .
7. The apparatus of claim 1 , wherein the one or more controllers further includes instructions for operating the secondary flow valve(s) to flow the secondary purge gas into the processing chamber during (a)-(d).
8. The apparatus of claim 1 , wherein a flow of carrier gas is used to flow the film precursor into the processing chamber in (a).
9. The apparatus of claim 8 , wherein the carrier gas comprises an inert gas.
10. The apparatus of claim 9 , wherein the carrier gas comprises N 2 and/or Ar.
11. The apparatus of claim 1 , wherein the one or more controllers further includes instructions for repeating (a)-(e) one or more times to deposit additional layer(s) of film on the substrate.
12. The apparatus of claim 1 , wherein the one or more controllers further includes instructions for operating the secondary flow valve(s) to flow the secondary purge gas into the processing chamber for at least a portion of the time during (a).
13. The apparatus of claim 1 , wherein the one or more controllers further includes instructions for operating the secondary flow valve(s) to flow the secondary purge gas into the processing chamber for at least a portion of the time during each of (a), (b), (c), and (d).
14. The apparatus of claim 1 , wherein the showerhead collar is configured to cause the secondary purge gas to flow into the process chamber in a direction substantially parallel to the plane of the substrate.
15. The apparatus of claim 1 , wherein the showerhead is configured to cause the primary purge gas to flow into the process chamber in a direction substantially perpendicular to the plane of the substrate.
16. The apparatus of claim 1 , wherein the primary purge gas in (c) flows into the process chamber at a rate of about 5,000 to 45,000 sccm.
17. The apparatus of claim 1 , wherein the secondary purge gas in (e) flows into the process chamber at a rate of about 1 to 30,000 sccm.