Gapfill of variable aspect ratio features with a composite PEALD and PECVD method
Provided herein are methods and apparatus for filling one or more gaps on a semiconductor substrate. The disclosed embodiments are especially useful for forming seam-free, void-free fill in both narrow and wide features. The methods may be performed without any intervening etching operations to achieve a single step deposition. In various implementations, a first operation is performed using a novel PEALD fill mechanism to fill narrow gaps and line wide gaps. A second operation may be performed using PECVD methods to continue filling the wide gaps.
1. A method of filling a gap on a substrate surface, the method comprising:
(a) introducing a first reactant in vapor phase into a reaction chamber having the substrate therein, and allowing the first reactant to adsorb onto the substrate surface;
(b) introducing a second reactant in vapor phase into the reaction chamber;
(c) exposing the substrate surface to plasma to drive a surface reaction between the first and second reactants on the substrate surface to form a film lining the gap;
(d) sweeping or purging the reaction chamber;
(e) introducing at least a third reactant in vapor phase into the reaction chamber; and
(f) generating a plasma from at least the third reactant to drive a gas phase reaction, wherein the gas phase reaction produces a gap-filling material, and wherein the gap-filling material partially or completely fills the gap on the substrate surface.
2. The method of claim 1 , wherein the plasma in operation (f) is a capacitively coupled plasma.
3. The method of claim 1 , wherein at least one of the first and second reactants is the same as the third reactant.
4. The method of claim 3 , wherein operation (e) further comprises introducing a fourth reactant in vapor phase into the reaction chamber while introducing the third reactant into the reaction chamber.
5. The method of claim 1 , wherein the film formed in (c) comprises the same material as the gap-filling material formed in (f).
6. The method of claim 1 , wherein operations (a) through (c) are repeated before operations (e) through (f), and wherein no pumpdown occurs after each iteration of operation (c).
7. The method of claim 1 , wherein the method is performed without any intervening etching operations.
8. The method of claim 1 , wherein the first reactant is a silicon-containing reactant and the second reactant is an oxidizing reactant.
9. The method of claim 8 , wherein the first reactant comprises BTBAS.
10. The method of claim 8 , wherein the second reactant comprises oxygen and/or nitrous oxide.
11. The method of claim 10 , wherein the second reactant comprises oxygen and nitrous oxide, and wherein a volumetric flow rate of oxygen and a volumetric flow rate of nitrous oxide do not differ by more than about 20%.
12. The method of claim 1 , wherein the third reactant is TEOS or silane.
13. The method of claim 1 , wherein the substrate is not removed from the reaction chamber during or between any of operations (a) through (f).
14. The method of claim 1 , wherein operations (a)-(c) comprise forming a conformal film that is thicker at the bottom of the gap than on the upper sidewalls of the gap.
15. The method of claim 1 , wherein operation (c) comprises preferentially densifying the film near the top of the gap compared to the film near the bottom of the gap.
16. The method of claim 1 , wherein operation (c) comprises preferentially burying ligands in the film near the bottom of the gap compared to the film near the upper sidewalls of the gap.