Protective Film Thickness Control for High Aspect Ratio Recesses
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Solution Overview
Problem
Conventional etching processes face challenges in forming recesses with high aspect ratios, particularly due to sidewall bowing and clogging issues caused by the formation of protective films, which affect the uniformity and consistency of critical dimensions in semiconductor substrates.
Innovation Solution
A method involving the use of a precursor and a modification gas in a reaction chamber to form a protective film on the sidewalls of recesses, with controlled thickness distribution, using an inhibitor gas to suppress film formation at the mask opening and reduce clogging, while maintaining film thickness uniformity throughout the etching process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective film is formed with uniform thickness to suppress lateral etching, then sidewall protection is improved, but the mask opening decreases in size which leads to clogging
Solution Approach 1:
The patent applies local quality by forming a protective film with non-uniform thickness distribution, where the film is thicker at the lower portion of the sidewall and thinner at the upper portion near the mask opening. This localized variation in film thickness allows sufficient protection where lateral etching occurs while maintaining adequate mask opening size to prevent clogging.
Solution Approach 2:
The patent utilizes parameter changes by controlling the ALD process conditions, including precursor exposure time, reaction gas flow rates, and temperature profiles, to achieve the desired non-uniform film thickness distribution. By adjusting these process parameters, the film thickness is optimized to provide protection without causing mask opening reduction.
2Reliability
If a sub-conformal ALD process is used to form thicker film at the upper portion, then sidewall protection is improved, but the mask opening decreases in size which leads to clogging
Solution Approach 1:
The patent reverses the conventional sub-conformal approach by implementing a protective film with thicker concentration at the lower sidewall region and thinner concentration at the upper region near the mask opening. This inverted local quality distribution addresses the specific etching challenges while avoiding mask clogging.
Solution Approach 2:
The patent inverts the traditional sub-conformal ALD strategy by deliberately forming a thinner film at the upper portion and thicker film at the lower portion of the sidewall. This inversion resolves the contradiction by providing protection where needed (lower sidewall) while preserving mask opening integrity (upper region).
3Productivity
If etching depth increases to form high aspect ratio recesses, then device density is improved, but sidewall bowing increases due to lateral etching
Solution Approach 1:
The patent applies preliminary action by forming the protective film on the sidewall before conducting the deep etching process. This pre-formed protective layer prevents lateral etching and sidewall bowing during the subsequent high-aspect-ratio etching, enabling increased device density without compromising sidewall uniformity.
Solution Approach 2:
The protective film acts as an intermediary layer between the etching plasma and the sidewall surface. This intermediary protective film prevents direct interaction between the etching species and the sidewall, thereby preventing lateral etching and maintaining sidewall shape uniformity during deep etching processes.
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 approach allows for the formation of recesses with improved etching quality by preventing sidewall bowing and maintaining the integrity of critical dimensions, enabling broader diameters at the recess bottom while suppressing bowing in the upper portion, thus enhancing the consistency and performance of memory cells.
Implementation Method 1
supplying an inhibitor gas and a modification gas to the reaction chamber to generate a plasma
Data Source
AI summary
A plasma processing apparatus includes a reaction chamber having a gas inlet and a gas outlet; a gas supply connected to the gas inlet; a substrate support disposed in the reaction chamber; a plasma generator that forms a plasma in the reaction chamber; and processing circuitry. The processing circuitry controls provision of a substrate on the substrate support, the substrate including an etching layer and a mask on the etching layer; controls provision of a Si-containing gas to the reaction chamber to deposit a Si-containing film on at least a sidewall of a recess in the etching layer; controls the gas supply to supply a gas mixture to the reaction chamber; and controls the plasma generator to generate a first plasma from the gas mixture, thereby modifying the Si-containing film to form a protective film on the sidewall of the recess.