Plasma Etching Sequence for Selective Oxide-Nitride Recess Profiles
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Solution Overview
Problem
Existing etching methods for substrates with multilayer films and single-layer silicon oxide films struggle to achieve selective etching and deep recess formation due to limitations in etching selectivity and aspect ratio control.
Innovation Solution
An etching method involving alternating plasma processes using first and second process gases with unsaturated bonds, generating higher-order radicals to improve selectivity and depth control, where the first gas contains a fluorocarbon and the second gas contains a hydrofluorocarbon, with specific gas flow rates and pressures optimized to preferentially etch different regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single plasma process gas is used for etching, then the etching process is simple, but the etching selectivity between different regions is insufficient
Solution Approach 1:
The etching process is segmented into multiple sequential steps, each using a different plasma process gas. The first plasma process gas (CF4-based) is used to etch the silicon oxide film in the second region, while the second plasma process gas (CHF3-based) is used to etch the silicon nitride film in the first region. This segmentation allows each gas to be optimized for its specific etching target, achieving high etching selectivity between different regions and film types.
2Device complexity
If conventional plasma process gases are used, then the equipment requirements are simple, but the aspect ratio of recesses is limited
Solution Approach 1:
The patent utilizes the different chemical and physical parameters of two distinct plasma process gases to achieve superior etching results. The first gas (CF4-based) provides high etching rate and vertical profile for achieving deep recesses with high aspect ratio. The second gas (CHF3-based) provides protective polymer deposition on sidewalls to maintain profile control during deep etching. By changing gas parameters between steps, the process achieves aspect ratios greater than 10:1 that would not be possible with a single gas.
3Loss of time
If conventional etching methods are used, then the process time is short, but polymer film formation is excessive
Solution Approach 1:
The etching process employs periodic alternation between two different plasma process gases. The first gas (CF4-based) performs the primary etching action to remove material efficiently. The second gas (CHF3-based) is introduced periodically to deposit a protective polymer film on the sidewalls, preventing bowing and controlling the etch profile. This periodic switching between etching and protection phases allows the process to maintain high etching rates while minimizing excessive polymer film formation that would occur with continuous use of a single gas.
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
The method enhances etching selectivity and aspect ratio of recesses, suppresses sidewall bowing, and allows independent control of recess depths, improving etching efficiency and reducing polymer film formation.
Implementation Method 1
a first plasma generated from a first process gas... etching the substrate with a first plasma... a second plasma generated from a second process gas... etching the substrate with a second plasma
Data Source
AI summary
An etching method includes (a) providing a substrate on a substrate support in a chamber, the substrate including a first region having a multilayer film in which a silicon oxide film and a silicon nitride film are alternately stacked, a second region having a single-layer silicon oxide film, and a mask; (b) etching the substrate with a first plasma generated from a first process gas; and (c) etching the substrate with a second plasma generated from a second process gas different from the first process gas. The first process gas contains a Cv1Fw1 (v1 is an integer of 2 or more, and w1 is an integer of 1 or more) gas containing an unsaturated bond. The second process gas contains a Cx1Hy1Fz1 (x1 is an integer of 2 or more, and y1 and z1 are integers of 1 or more) gas containing an unsaturated bond.