Thermal CVD Dielectric Gapfill With Cyclic Passivation and Densification
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Solution Overview
Problem
Current deposition methods for dielectric materials in semiconductor fabrication face challenges in filling large area gaps and high aspect ratio features, such as those found in 3D-NAND structures, due to issues like cracking, shrinkage, and high costs associated with existing processes like SACVD, PECVD TEOS, and ALD.
Innovation Solution
A method involving thermal CVD combined with densification and passivation operations, where deposition, densification, and passivation are performed in alternating cycles without breaking vacuum, using plasma-free and plasma environments, to form conformal and gap-free dielectric films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional deposition methods (SACVD, PECVD TEOS, ALD) are used to fill large area gaps and high aspect ratio features, then deposition can be achieved, but cracking, shrinkage, and high costs occur
Solution Approach 1:
The deposition process is divided into multiple sequential stages: initial conformal deposition, gapfill deposition, and overburden deposition. Each stage uses optimized deposition conditions and may involve different precursor combinations, allowing the process to adapt to the changing geometry of the feature being filled while maintaining film integrity and reducing defects
Solution Approach 2:
The process dynamically adjusts deposition parameters including temperature, pressure, precursor flow rates, and reaction chemistry throughout the deposition sequence. By changing parameters based on the deposition stage and feature geometry, the process achieves conformal coverage in narrow regions while preventing cracking and shrinkage in filled regions
2Manufacturing precision
If deposition is performed to achieve conformal coverage in high aspect ratio features, then step coverage is improved, but deposition rate decreases and seam formation increases
Solution Approach 1:
The process uses periodic alternation between deposition and etch steps, with multiple cycles of conformal deposition followed by selective etching. This periodic action allows material to be deposited conformally on all surfaces while removing excess material from horizontal surfaces, achieving high step coverage without requiring excessively slow deposition rates
Solution Approach 2:
The total deposition is segmented into multiple thinner layers deposited in separate steps rather than one thick layer. Each layer is deposited conformally and then processed, allowing the cumulative effect to achieve high step coverage while maintaining reasonable deposition rates for each individual layer
3Productivity
If existing deposition processes are used for 3D-NAND structures, then fabrication can proceed, but material waste increases and efficiency decreases
Solution Approach 1:
The process performs preliminary conformal deposition to establish uniform film coverage on all feature surfaces before attempting to fill the feature. This preliminary action ensures that subsequent gapfill material adheres properly and reduces the need for excessive over-deposition and removal, minimizing material waste
Solution Approach 2:
The deposition process applies different material compositions and deposition conditions to different regions of the feature. By tailoring the deposition chemistry and parameters to the local geometry (narrow vs. wide regions), the process achieves efficient filling with minimal material waste while maintaining film quality throughout
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 efficient filling of large area gaps and high aspect ratio features with silicon oxide, achieving high step coverage and reducing film defects, thereby improving the fabrication process efficiency and reducing costs.
Implementation Method 1
introducing a deposition precursor and a reactant to the chamber housing the semiconductor substrate to expose the semiconductor substrate to a plasma free environment including the deposition precursor and the reactant and form the dielectric material
Implementation Method 2
introducing a passivation gas to the chamber and igniting a passivation plasma in a passivation gas ambient
Implementation Method 3
exposing the dielectric material to a densification plasma in the chamber generated in an inert gas ambient
Data Source
AI summary
Methods and apparatuses for depositing dielectric films into features on semiconductor substrates are described herein. Methods involve depositing dielectric films by using controlled thermal chemical vapor deposition, with periodic passivation operations and densification to modulate film properties.