Suppression of parasitic deposition in a substrate processing system by suppressing precursor flow and plasma outside of substrate region

1. A substrate processing system, comprising:

a showerhead that comprises a head portion and a stem portion and that delivers precursor gas to a chamber,

wherein the head portion includes an upper surface, a sidewall, a lower planar surface including a plurality of holes, and a cylindrical cavity defined therebetween,

wherein the head portion extends radially outwardly from one end of the stem portion towards sidewalls of the chamber and defines a cavity between the upper surface of the head portion and an upper surface of the chamber,

wherein the cylindrical cavity of the head portion receives process gas via the stem portion,

wherein the process gas in the cylindrical cavity flows though the plurality of holes in the lower planar surface and is distributed into the chamber; and

a collar that connects the showerhead to the upper surface of the chamber adjacent to an opposite end of the stem portion,

wherein the collar includes a base portion, a stem portion and a plurality of slots, is arranged around the stem portion of the showerhead, and directs purge gas through the plurality of slots into the cavity between the head portion of the showerhead and the upper surface of the chamber and a first plate that includes an opening that receives the stem portion of the showerhead,

wherein the first plate is arranged between (i) a lower edge of the stem portion of the collar, below the plurality of slots and (ii) the head portion of the showerhead.

2. The substrate processing system of claim 1 , wherein:

the stem portion of the collar defines an inner cavity that receives the stem portion of the showerhead.

3. The substrate processing system of claim 2 , wherein:

the collar includes first passages arranged in the base portion of the collar;

the collar includes second passages defined between a surface of the inner cavity of the stem portion of the collar and the stem portion of the showerhead; and

the purge gas flows through the first passages to the second passages and from the second passages through the slots.

4. The substrate processing system of claim 2 , wherein the stem portion of the collar has a circular cross section.

5. The substrate processing system of claim 2 , wherein:

the collar includes first passages arranged in the base portion of the collar;

the collar includes second passages arranged in the stem portion of the collar; and

the purge gas flows through the first passages to the second passages and from the second passages through the slots.

6. The substrate processing system of claim 2 , wherein the cavity defines:

a plurality of first surfaces that are arranged in a spaced apart relationship around a first circumference; and

a plurality of arcuate surfaces that are arranged between the plurality of first surfaces, where the plurality of arcuate surfaces curve radially outwardly relative to the plurality of first surfaces.

7. The substrate processing system of claim 1 , wherein the collar directs the purge gas between the first plate and the stem portion of the showerhead and between the first plate and the head portion of the showerhead.

8. The substrate processing system of claim 1 , wherein one surface of the first plate includes a plurality of first projections to provide uniform spacing between the first plate and the head portion of the showerhead, and wherein the opening includes a plurality of second projections to provide uniform spacing between the first plate and the stem portion of the showerhead.

9. The substrate processing system of claim 1 , further comprising:

N dielectric plates including the first plate, the N dielectric plates arranged around the stem portion of the showerhead between the head portion of the showerhead and the upper surface of the chamber,

wherein the collar directs the purge gas at least one of:

above and below the N dielectric plates; and

between the N dielectric plates,

where N is an integer greater than zero.

10. An atomic layer deposition system comprising the substrate processing system of claim 1 .

11. The substrate processing system of claim 1 , wherein the showerhead is powered by an RF signal to generate plasma in the chamber.

12. The substrate processing system of claim 1 , wherein the chamber is grounded.

13. The substrate processing system of claim 1 , wherein the cylindrical cavity has a diameter that is greater than a diameter of the stem portion.

14. The substrate processing system of claim 1 , wherein the showerhead includes a chandelier showerhead.

15. The substrate processing system of claim 1 , wherein the first plate is arranged such that the purge gas is directed from the plurality of slots across an upper surface of the first plate.

16. The substrate processing system of claim 15 , wherein the collar directs the purge gas downward into the opening of the first plate and into a gap between a lower surface of the first plate and an upper surface of the head portion of the showerhead.