In situ application of etch back for improved deposition into high-aspect-ratio features
A continuous in situ process of deposition, etching, and deposition is provided for forming a film on a substrate using a plasma process. The etch-back may be performed without separate plasma activation of the etchant gas. The sequence of deposition, etching, and deposition permits features with high aspect ratios to be filled, while the continuity of the process results in improved uniformity.
1. A method for depositing a film on a substrate wafer disposed within a process chamber, the method comprising:
providing a first gaseous mixture to the process chamber;
generating a plasma from the first gaseous mixture to deposit a first portion of the film on the substrate wafer;
thereafter, flowing a fluorine-based etchant gas into the process chamber without terminating the plasma;
applying an electrical bias to the substrate wafer while flowing the fluorine-based etchant gas to provide a net etching back of part of the first portion of the film; and
thereafter, providing a second gaseous mixture to the process chamber without terminating the plasma to deposit a second portion of the film on the substrate wafer.
2. The method recited in claim 1 wherein the bias has a power density approximately between 0.9 W/cm 2 and 3.2 W/cm 2 .
3. The method recited in claim 1 wherein the second gaseous mixture is substantially the same as the first gaseous mixture.
4. The method recited in claim 1 wherein the first and second gaseous mixtures each include a silicon-containing gas and an oxygen-containing gas.
5. The method recited in claim 1 wherein:
providing the first gaseous mixture to the process chamber comprises providing a flow of a source gas and a flow of a fluent gas to the process chamber; and
flowing the fluorine-based etchant gas into the process chamber without terminating the plasma comprises:
terminating the flow of the source gas without terminating the flow of the fluent gas; and
thereafter, providing a flow of the fluorine-based etchant.
6. The method recited in claim 5 wherein the fluent gas comprises an inert gas.
7. The method recited in claim 1 wherein:
providing the first gaseous mixture to the process chamber comprises providing a flow of a source gas to the process chamber; and
flowing the fluorine-based etchant gas into the process chamber without terminating the plasma comprises:
providing a flow of the fluorine-based etchant to the process chamber; and
thereafter, terminating the flow of the source gas.