PECVD Nitride Films With Oxidizer Tuning for 3D NAND Etch Selectivity
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Solution Overview
Problem
The fabrication of 3D NAND memory structures faces challenges due to nitride films with high hydrogen content, leading to issues such as striations, pillar holes, and stress changes during processing, which affect dry etch rates and in-plane displacement, ultimately impacting device performance and integration.
Innovation Solution
The introduction of a controlled amount of an oxidizer, such as oxygen, during the deposition of nitride films in a PECVD reactor, which reduces hydrogen content and improves dry etch selectivity and in-plane displacement, while maintaining the fundamental properties of the nitride layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If nitride films are deposited with silane, ammonia and nitrogen in a PECVD reactor, then the films achieve high density and good conformality, but the films contain high hydrogen content leading to outgassing, stress changes, and poor dry etch selectivity
Solution Approach 1:
The patent changes the chemical composition parameters of the nitride film by introducing oxygen during deposition. This is achieved by adding oxygen-containing gases (such as O2, CO, or CO2) to the PECVD reactor along with silane, ammonia, and nitrogen. The oxygen incorporation modifies the film's hydrogen content and bonding structure, reducing hydrogen outgassing and stabilizing stress while maintaining film density and conformality.
Solution Approach 2:
The patent creates a composite nitride film with incorporated oxygen, forming a new material composition that combines the benefits of high-density nitride with reduced hydrogen content. This composite approach allows the film to exhibit improved dry etch selectivity and thermal stability while maintaining the desired physical properties for 3D NAND fabrication.
2Ease of manufacture
If nitride films have high hydrogen content, then the deposition process is simpler, but dry etch rates are affected and striations and pillar holes occur
Solution Approach 1:
The patent modifies the deposition parameters by introducing oxygen into the PECVD process, which changes the film's chemical composition and reduces hydrogen content. This parameter change improves dry etch uniformity and eliminates striations and pillar holes while maintaining reasonable process complexity through automated gas flow control.
3Reliability
If oxidizer is added to reduce hydrogen content and improve etch selectivity, then dry etch performance and IPD improve, but the fundamental properties of the nitride layer must be maintained
Solution Approach 1:
The patent carefully controls the oxygen addition parameters to achieve the desired hydrogen reduction and etch selectivity improvement while maintaining nitride layer properties. By adjusting oxygen flow rate, deposition temperature, and gas ratios, the process optimizes film composition to preserve electrical and physical characteristics essential for device performance.
Solution Approach 2:
The patent employs process monitoring and control mechanisms to ensure that oxygen incorporation does not compromise fundamental nitride layer properties. Through real-time measurement of film characteristics and adjustment of deposition parameters, the process maintains the necessary electrical properties while achieving improved etch selectivity and reduced hydrogen content.
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 dry etch selectivity, reduces non-uniformity, and improves thermal stability, resulting in better control over gate length and threshold voltage, with increased throughput and reduced stress shifts in the nitride films.
Implementation Method 1
supplying an inert gas to a plasma enhanced chemical vapor deposition (PECVD) reactor that supports a substrate having said oxide layer; providing power to an electrode of the PECVD reactor, where the power is configured to strike a plasma; flowing reactant gases into the PECVD reactor
Implementation Method 2
The improvement relates to a way of uniquely tuning the nitride film during the deposition process. Broadly speaking, the turning of the nitride film is accomplished by adding a controlled amount of an oxidizer to the reactants used in forming the nitride layer
Data Source
AI summary
A method for depositing a nitride layer over an oxide layer to form an oxide-nitride stack is provided. The method includes supplying an inert gas to a plasma enhanced chemical vapor deposition (PECVD) reactor that supports a substrate having said oxide layer. Then, providing power to an electrode of the PECVD reactor, where the power is configured to strike a plasma. Then, flowing reactant gases into the PECVD reactor. The reactant gases include a first percentage by volume of ammonia (NH3), a second percentage by volume of nitrogen (N2), a third percentage by volume of silane (SiH4) and a fourth percentage by volume of an oxidizer. The fourth percentage by volume of said oxidizer is at least 0.5 percent by volume and less than about 8 percent by volume. Then, continuing to flow the reactant gases into the PECVD reactor until the nitride layer is determined to achieve a target thickness over the oxide layer.