Lateral Oxidation Process for Sub-Lithographic Pitch Reduction
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Solution Overview
Problem
Photolithographic techniques have a minimum pitch limit that restricts feature size reduction in integrated circuits, and existing self-aligned double patterning methods face challenges in achieving uniformity and yield due to issues like rounding, footing, and residue on features.
Innovation Solution
The method involves laterally oxidizing patterned features on a substrate using a capping layer to confine oxidation, forming oxidation spacers around unoxidized cores, and removing the cores to achieve a reduced pitch without anisotropic etching, using a sacrificial structural material like silicon-containing layers and oxygen-containing precursors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If photolithography techniques are used to pattern features, then features can be formed with standard processes, but the minimum pitch limit restricts feature size reduction
Solution Approach 1:
The patent applies segmentation by dividing the patterning process into multiple stages: first forming initial features at a relaxed pitch, then using those features as templates to create additional features in the spaces between them. This multi-step approach effectively segments the overall pitch reduction goal into manageable steps, achieving sub-lithographic pitch without requiring a single high-resolution lithography step.
Solution Approach 2:
The patent uses preliminary action by first forming sacrificial features (mandrels) that serve as templates for subsequent feature formation. These preliminary features are formed at a pitch that is achievable with standard photolithography, then used to guide the formation of final features at a smaller pitch. The preliminary features are later removed, having served their templating purpose.
2Manufacturing precision
If self-aligned double patterning (SADP) is used to extend photolithography capabilities, then pitch can be reduced below optical resolution, but uniformity and yield are compromised due to rounding, footing, and residue
Solution Approach 1:
The patent extracts the problematic steps from the traditional SADP process. Specifically, it removes the anisotropic etching step that causes rounding and footing, and eliminates the need for spacer formation that leads to residue. The invention achieves pitch multiplication through a simpler sequence: form mandrels, deposit conformal layer, perform isotropic etch, remove mandrels. This extraction of problematic elements maintains pitch reduction capability while improving uniformity and yield.
Solution Approach 2:
The patent substitutes the mechanical/anisotropic etching process with a chemical/isotropic etching approach. Instead of using directional physical etching that creates rounding and footing at feature corners, the invention employs isotropic etching that uniformly removes material in all directions, eliminating the mechanical effects that cause non-uniformity. This substitution replaces a process prone to defects with one that achieves cleaner, more uniform feature formation.
3Manufacturing precision
If anisotropic etching is used in SADP to form spacers, then pitch can be reduced, but rounding, footing, and residue are introduced on features
Solution Approach 1:
The patent substitutes anisotropic etching with isotropic etching. The isotropic etch process removes material uniformly in all directions through chemical reaction, avoiding the directional mechanical removal that causes rounding at corners and footing at bases. This substitution eliminates the harmful mechanical effects while achieving the desired pitch reduction through the conformal layer deposition and subsequent mandrel removal.
Solution Approach 2:
The patent changes the etching parameters from anisotropic (directional, physical) to isotropic (non-directional, chemical). This parameter change fundamentally alters the etching mechanism to eliminate rounding and footing. Additionally, the process parameters are optimized to ensure complete mandrel removal without leaving residue, achieving clean feature formation at reduced pitch.
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 enhances the uniformity and yield of feature formation by eliminating rounding, footing, and residue, allowing for smaller pitch and improved integrated circuit performance.
Implementation Method 1
A capping layer may be disposed above lateral features to laterally confine the oxidation
Implementation Method 2
laterally oxidizing the plurality of cores to form a plurality of oxidation spacers
Data Source
AI summary
Methods of laterally oxidizing features of a patterned substrate are described. A capping layer may be disposed above lateral features to laterally confine the oxidation. The oxidizable features may be material patterned near the optical resolution of a photolithography system using a high-resolution photomask. The oxidizable features may be wider than the spaces between the oxidizable features and may be about three times the width of the spaces. Oxidized portions may be formed on either side of repeated oxidizable features. The unoxidized portions may then be removed as part of a self-aligned double patterning (SADP) process. A gapfill layer deposited thereon may be etched or polished back to form alternating fill and non-sacrificial features.