Plasma Recess Etching with Staged Temperature Control
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Solution Overview
Problem
Existing substrate processing methods face challenges in preventing shape defects, such as bowing, of the side wall of recesses formed during etching due to the adherence of reaction by-products, which can lead to the formation of shoulder portions and non-linear etching.
Innovation Solution
A plasma processing method that involves forming a protective film on the side wall of the recess and etching the bottom in stages, with the first stage suppressing the formation of shoulder portions by controlling the temperature of the substrate support to a higher temperature and the second stage further etching at a lower temperature, typically −40° C. or lower, to prevent bowing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the substrate temperature is lowered to prevent reaction by-products from adhering to the side wall, then the formation of shoulder portions is suppressed, but the etching speed decreases and the recess cannot be etched to the target depth efficiently
Solution Approach 1:
The etching process is divided into multiple stages with different temperature conditions. The first stage uses a higher temperature (−20° C. or higher) to achieve rapid etching, while the second stage uses a lower temperature (−40° C. or lower) to prevent by-product adhesion and form the desired side wall shape. This segmentation allows both high productivity and good shape control to be achieved at different times in the process.
2Productivity
If the substrate temperature is raised to increase etching speed, then the recess can be etched to target depth efficiently, but reaction by-products adhere to the side wall causing shoulder portion formation and shape defects
Solution Approach 1:
The etching process is divided into multiple stages with different temperature conditions. The first stage uses a higher temperature (−20° C. or higher) to achieve rapid etching, while the second stage uses a lower temperature (−40° C. or lower) to prevent by-product adhesion and form the desired side wall shape. This segmentation allows both high productivity and good shape control to be achieved at different times in the process.
Solution Approach 2:
The etching process alternates between different temperature conditions in a periodic manner, switching from a higher temperature phase to a lower temperature phase. This periodic action allows the process to exploit the benefits of both temperature conditions - high etching speed during the warm phase and clean side wall formation during the cold phase.
3Device complexity
If a single stage etching process is used, then the process is simple and fast, but it cannot simultaneously achieve high etching speed and prevent shoulder portion formation
Solution Approach 1:
The etching process is divided into multiple stages with different temperature conditions. The first stage uses a higher temperature (−20° C. or higher) to achieve rapid etching, while the second stage uses a lower temperature (−40° C. or lower) to prevent by-product adhesion and form the desired side wall shape. This segmentation allows both high productivity and good shape control to be achieved at different times in the process.
Solution Approach 2:
The etching process alternates between different temperature conditions in a periodic manner, switching from a higher temperature phase to a lower temperature phase. This periodic action allows the process to exploit the benefits of both temperature conditions - high etching speed during the warm phase and clean side wall formation during the cold phase.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method effectively suppresses the formation of shape defects on the side wall of the recess, ensuring a linear and precise etching process by controlling the temperature and gas ratios, thereby improving the aspect ratio and depth of the recess.
Implementation Method 1
controlling a temperature of the substrate support to −40° C. or lower
Implementation Method 2
generating plasma from a processing gas to etch a bottom of the recess
Implementation Method 3
etch a bottom of the recess
Data Source
AI summary
A plasma processing method includes: (a) providing a substrate having an etching target film with a recess formed therein, on a substrate support; (b) forming a protective film on a side wall of the recess; (c) after (b), generating plasma from a processing gas to etch a bottom of the recess; and (d) performing a sequence including (b) and (c) one or more times. The step (c) includes a first stage of etching the bottom of the recess while suppressing a formation of a shoulder portion caused when reaction by-products produced by the etching adhere to the side wall, and a second stage of further etching the bottom of the recess in a state where a temperature of the substrate support is controlled to −40° C. or lower, after the first stage.