Time-divisional Plasma Etch for Micro-loading Control
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Solution Overview
Problem
The challenge in semiconductor fabrication is etching high aspect ratio features with uniform critical dimensions (CDs) and controlling etch rates across regions of varying feature densities, as existing continuous plasma etch processes result in non-uniform profiles, micro-loading, and polymer residue issues, leading to defects and performance degradation in integrated circuits.
Innovation Solution
A time-divisional plasma etch process with alternating cycles of plasma etching and flash processes to remove polymers, eliminating the need for oxidation steps and maintaining uniform CDs, thereby achieving vertical profiles and minimizing micro-loading effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If continuous plasma etch process is used to increase etch rate, then productivity is improved, but manufacturing precision deteriorates due to non-uniform profiles and micro-loading effects
Solution Approach 1:
The patent applies periodic action by implementing time-divisional plasma etching with alternating etch and flash cycles. The process switches between plasma etching mode (for material removal) and flash mode (for polymer removal and surface cleaning) in periodic intervals, enabling both high etch rates and uniform CD control through rhythmic alternation of process conditions
Solution Approach 2:
The continuous etch process is segmented into discrete time-divisional cycles, where each cycle consists of an etch portion followed by a flash portion. This segmentation allows independent optimization of etch rate (during etch portion) and profile uniformity (during flash portion), resolving the contradiction between productivity and precision
2Productivity
If carbon-containing gas is used as etchant to increase etch rate, then productivity is improved, but object-generated harmful factors worsen due to polymer residue formation
Solution Approach 1:
The patent converts the harmful polymer residue into a beneficial protective layer during the etch process, then selectively removes it during the flash portion. The polymer initially formed by carbon-containing gas protects sidewalls during etching, and the subsequent flash step removes excess polymer, transforming the harmful residue into a controlled process mechanism
Solution Approach 2:
Periodic alternation between plasma etching (where polymer forms and protects) and flash mode (where polymer is removed) enables continuous high-rate etching while periodically eliminating harmful residues, maintaining both productivity and surface cleanliness
3Object-generated harmful factors
If oxidation step is added to remove polymer, then object-generated harmful factors are reduced, but device complexity increases
Solution Approach 1:
The patent merges the polymer removal function into the existing plasma etch process by implementing a flash mode within the same chamber and process cycle, eliminating the need for separate oxidation steps or additional process equipment, thus reducing device complexity while maintaining effectiveness
Solution Approach 2:
The plasma process is made universal by enabling it to perform both etching and polymer removal functions through time-divisional operation. The same plasma chamber and gas delivery system execute multiple functions (etching with carbon-containing gas, cleaning with flash mode), reducing overall process complexity
4Manufacturing precision
If etching features with high aspect ratio is performed, then manufacturing precision is improved for deep features, but object-affected harmful factors worsen due to non-uniform spacing and profiles
Solution Approach 1:
The time-divisional periodic action alternates between etching phases (advancing depth) and flash phases (rejuvenating surface conditions). This periodic rejuvenation maintains uniform reactive species distribution and polymer layer thickness along the deep feature sidewalls, preventing non-uniform profiles even at high aspect ratios
Solution Approach 2:
The flash portion performs preliminary cleaning and surface preparation before the next etching cycle begins. This preliminary action ensures uniform surface conditions are established in advance, preventing non-uniform profile development during subsequent deep etching of high aspect ratio features
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 ensures precise control over etch depth and CD uniformity, reducing micro-loading and polymer-related issues, resulting in more vertical feature profiles and improved pattern transfer in high aspect ratio etching.
Implementation Method 1
performing a first time-divisional plasma etch process step within a plasma chamber to a first depth of the plurality of etched features, performing a flash process step to remove any polymers from exposed surfaces of the plurality of etched features
Data Source
AI summary
A method of producing plurality of etched features in an electronic device is disclosed that avoids micro-loading problems thus maintaining more uniform sidewall profiles and more uniform critical dimensions. The method comprises performing a first time-divisional plasma etch process step within a plasma chamber to a first depth of the plurality of etched features, and performing a flash process step to remove any polymers from exposed surfaces of the plurality of etched features without requiring an oxidation step. The flash process step is performed independently of the time-divisional plasma etch step. A second time-divisional plasma etch process step is performed within the plasma chamber to a second depth of the plurality of etched features. The method may be repeated until a desired etch depth is reached.