Etch Front Metal Catalyst for Uniform High-Aspect-Ratio Memory Profiles
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Solution Overview
Problem
High aspect ratio etching in semiconductor devices results in tapered features that are wider at the top than the bottom, leading to increased device failure, limited device density, and reduced performance, especially in 3D NAND and DRAM manufacturing.
Innovation Solution
A method involving a halogen-containing etch gas plasma followed by a metal catalyst deposition and subsequent fluorine-containing etch gas plasma is used to etch silicon-containing stacks, selectively depositing the metal catalyst on the etch front and bottoms of features, enhancing isotropic etching to achieve uniform feature widths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If high aspect ratio etching is performed using conventional methods, then etching depth is achieved, but feature tapering occurs resulting in wider top than bottom dimensions
Solution Approach 1:
A metal catalyst layer is deposited on the etch front and bottom surfaces of the features before the main etching process. This preliminary deposition of catalyst material on specific surfaces (etch front and bottom) enables selective enhancement of etching rate at these locations during subsequent etching steps, counteracting the tapering effect and achieving uniform feature widths from top to bottom while maintaining high etching depth
Solution Approach 2:
The metal catalyst is selectively deposited only on the etch front and bottom surfaces of the features, creating localized regions with enhanced etching activity. This local concentration of catalyst material on specific surfaces (rather than uniform distribution) enables precise control over the etching profile, achieving straight sidewalls and uniform width by enhancing etching at the front and bottom while leaving sidewalls relatively unaffected
2Length of stationary object
If high aspect ratio etching is performed to achieve deep features, then device depth is improved, but device failure rate increases due to tapered features
Solution Approach 1:
The metal catalyst layer is deposited on the etch front and bottom surfaces before the main etching process begins. This preliminary action ensures that when deep etching is performed, the catalyst-enhanced regions maintain uniform width throughout the etching process, preventing the tapered geometry that leads to device failure. The uniform straight sidewalls resulting from this approach maintain structural integrity at high aspect ratios, thereby improving device reliability
Solution Approach 2:
The introduction of metal catalyst material changes the chemical reactivity parameters of the etch front and bottom surfaces. This parameter change (adding catalytic material) selectively increases the etching rate at these locations, enabling the formation of deep features with uniform cross-sectional area. The modified surface chemistry at the etch front and bottom creates conditions for straight sidewalls, preventing the narrowing at the base that would otherwise cause device failure in deep structures
3Device complexity
If conventional etching methods are used for high aspect ratio structures, then process simplicity is maintained, but device density is limited due to tapered features
Solution Approach 1:
A metal catalyst layer is deposited on the etch front and bottom surfaces of the features before the main etching process. This preliminary deposition enables subsequent etching steps to achieve uniform width features with straight sidewalls, maximizing the usable space in high aspect ratio structures. By preventing tapering, more features can be packed into the same area, thereby increasing device density while adding only one deposition step to the process
Solution Approach 2:
The selective deposition of metal catalyst on etch front and bottom surfaces creates localized regions that etch at enhanced rates. This local quality enhancement allows for precise control of the etching profile, producing uniform width features that optimize space utilization. The ability to maintain constant width throughout the feature depth enables higher device density compared to conventional tapered etching, with the added complexity being limited to the catalyst deposition step
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 enables deeper etching with controlled taper angles, reducing feature width variations and allowing for more precise control of high aspect ratio structures, thereby improving device performance and reducing manufacturing complexity.
Implementation Method 1
The stack is partially etched by providing a halogen containing etch gas and forming the halogen containing etch gas into a halogen containing plasma, wherein the halogen containing plasma partially etches features into the stack
Implementation Method 2
A metal catalyst containing layer is deposited on the etch front of the features by providing a metal catalyst containing gas, forming the metal catalyst containing gas into a metal catalyst containing plasma
Implementation Method 3
The features are further etched by providing a fluorine containing etch gas and forming the fluorine containing etch gas into a fluorine containing plasma, wherein the fluorine containing plasma selectively etches sidewalls adjacent to the etch front of the features
Implementation Method 4
the plasma of the metal catalyst containing layer isotropically etches the etch front
Data Source
AI summary
A method for etching features in a silicon containing stack below a patterned mask is provided. The stack is partially etched by providing a halogen containing etch gas and forming the halogen containing etch gas into a halogen containing plasma, wherein the halogen containing plasma partially etches features with an etch front. A metal catalyst containing layer is deposited on the etch front of the features by providing a metal catalyst containing gas, forming the metal catalyst containing gas into a plasma, and selectively depositing more of the metal catalyst containing layer on the etch front and bottoms of the features than tops of the features. The features are further etched by providing a fluorine containing etch gas and forming a fluorine containing plasma, wherein the plasma selectively etches sidewalls adjacent to the etch front of the features with respect to sidewalls adjacent to tops of the features.