Technique to deposit sidewall passivation for high aspect ratio cylinder etch
Various embodiments herein relate to methods, apparatus and systems for forming a recessed feature in dielectric material on a substrate. Separate etching and deposition operations are employed in a cyclic manner. Each etching operation partially etches the feature. Each deposition operation forms a protective coating on the sidewalls of the feature to prevent lateral etch of the dielectric material during the etching operations. The protective coating may be deposited using methods that result in substantial preservation of a mask layer on the substrate. The protective coating may be deposited using particular reactants and/or reaction conditions that are unlikely to damage the mask layer. The protective coating may also be deposited using particular reaction mechanisms that result in substantially complete sidewall coating. In some cases the protective coating is deposited using plasma assisted atomic layer deposition, a modified plasma assisted atomic layer deposition, or plasma assisted chemical vapor deposition.
1. An apparatus for forming an etched feature in dielectric material on a substrate, the apparatus comprising:
one or more reaction chambers, wherein at least one reaction chamber is designed or configured to perform etching, and wherein at least one reaction chamber is designed or configured to perform deposition, each reaction chamber comprising:
an inlet for introducing process gases to the reaction chamber,
an outlet for removing material from the reaction chamber, and
a plasma source; and
a controller having instructions for:
(a) generating an etching plasma comprising an etching reactant, exposing the substrate to the etching plasma, and partially etching the feature in the dielectric material, wherein the substrate comprises a mask layer;
(b) after (a), depositing a protective film on sidewalls of the feature, wherein the protective film is deposited along substantially the entire depth of the feature, wherein the mask layer is substantially preserved during (b), wherein depositing the protective film comprises the following steps performed in a cyclic manner:
(i) flowing a first deposition reactant into a reaction chamber and allowing the first deposition reactant to adsorb onto the substrate surface, wherein the first deposition reactant is a silicon-containing reactant; and
(ii) flowing a second deposition reactant into the reaction chamber, wherein the first and second deposition reactants react to form the protective film; and
(c) repeating (a)-(b) until the feature is etched to a final depth, wherein the protective film deposited in (b) substantially prevents lateral etch of the feature during (a), and wherein the feature has an aspect ratio of about 5 or greater at its final depth.
2. The apparatus of claim 1 , wherein the reaction chamber designed or configured to perform etching is the same reaction chamber designed or configured to perform deposition, such that both (a) and (b) occur in the same reaction chamber.
3. The apparatus of claim 1 , wherein the reaction chamber designed or configured to perform etching is different from the reaction chamber designed or configured to perform deposition, and wherein the controller further comprises instructions to transfer the substrate between the reaction chamber designed or configured to perform etching and the reaction chamber designed or configured to perform deposition.
4. The apparatus of claim 1 , wherein the second deposition reactant comprises carbonyl sulfide (COS).
5. The apparatus of claim 1 , wherein both the first and second deposition reactants are provided in a plasma, and wherein a composition of the plasma changes over the course of (i) and (ii).
6. An apparatus for depositing a silicon-containing film on a substrate, the apparatus comprising:
a reaction chamber comprising:
an inlet for introducing process gases to the reaction chamber,
an outlet for removing material from the reaction chamber, and
a plasma source; and
a controller having instructions for:
(a) flowing a first reactant into the reaction chamber and exposing the substrate to the first reactant, wherein the first reactant comprises a silicon-containing reactant;
(b) flowing a second reactant into the reaction chamber and exposing the substrate to the second reactant, wherein the second reactant comprises carbonyl sulfide (COS); and
(c) reacting the first and second reactant to thereby deposit the silicon-containing film on the substrate.
7. The apparatus of claim 6 , wherein the controller further comprises instructions for generating plasma and exposing the substrate to plasma, wherein a composition of the plasma changes over time such that during a first stage the plasma comprises the first reactant but not the second reactant, during a second stage the plasma comprises inert gas and neither the first nor second reactant, and during a third stage the plasma comprises the second reactant but not the first reactant, the first, second, and third stages occurring in that order, and
cyclically repeating the first, second, and third stages until the silicon-containing film reaches a final thickness.
8. The apparatus of claim 7 , wherein the controller further comprises instructions for extinguishing the plasma in a fourth stage, the fourth stage occurring after the third stage, wherein the first, second, third, and fourth stages are cyclically repeated until the silicon-containing film reaches the final thickness.
9. The apparatus of claim 6 , wherein the controller comprises instructions for performing (a) while no plasma is present in the reaction chamber.
10. The apparatus of claim 6 , wherein the first and second reactants react with one another in a chemical vapor deposition reaction.
11. The apparatus of claim 6 , wherein the first and second reactants react with one another in an adsorption-limited reaction.