3D NAND Layer Stack Overlay Improvement
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Solution Overview
Problem
3D NAND memory cells face challenges in creating high-capacity devices due to in-plane distortion (IPD) and lithographic overlay errors in oxide/nitride (ON) layer stacks, which affect the manufacturing of densely-packed memory devices.
Innovation Solution
A method involving plasma-enhanced chemical vapor deposition (PECVD) processes to form silicon dioxide (SiO2) and silicon nitride (Si3N4) layers with symmetric RF power application and controlled gas flow rates, repeated to create layer stacks with minimized IPD and improved lithographic overlay, using a showerhead with a symmetric RF circuit to ensure uniform plasma deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional PECVD processes are used to form ON layer stacks, then deposition can be achieved, but in-plane distortion and lithographic overlay errors occur due to non-uniform plasma distribution
Solution Approach 1:
The patent applies asymmetric RF power coupling to a symmetric showerhead structure, where RF power is applied to only one port of the showerhead rather than both ports symmetrically. This asymmetric power application creates a controlled plasma distribution pattern that compensates for inherent chamber non-uniformities, thereby reducing in-plane distortion and improving lithographic overlay precision in the deposited ON layer stacks
Solution Approach 2:
The patent modifies the RF power application parameters by coupling RF power to a single port rather than using symmetric dual-port coupling. This parameter change alters the plasma generation characteristics, creating a non-uniform plasma distribution that compensates for chamber-induced distortions and improves the uniformity of the deposited layers
2Quantity of substance
If the number of ON layer pairs is increased to achieve high capacity, then storage capacity improves, but accumulation of IPD and overlay errors worsens
Solution Approach 1:
By using asymmetric RF power coupling, the patent achieves improved uniformity in each individual layer deposition. This reduced per-layer distortion allows for the stacking of many more layer pairs (64 or more) while keeping the cumulative overlay error within acceptable limits, thereby enabling high-capacity storage
3Stability of the object's composition
If symmetric RF power is applied to increase deposition uniformity, then layer uniformity improves, but in-plane distortion persists due to chamber non-uniformities
Solution Approach 1:
The patent resolves this contradiction by intentionally applying asymmetric RF power to compensate for the symmetric chamber non-uniformities. The asymmetric power distribution creates a plasma pattern that counteracts the chamber-induced distortions, achieving both layer uniformity and reduced in-plane distortion simultaneously
Solution Approach 2:
The asymmetric RF power coupling is designed to pre-compensate for the expected chamber non-uniformities. By applying power asymmetrically from the start of deposition, the process counteracts the distorting effects that would otherwise accumulate during the formation of multiple layers
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 reduces in-plane distortion by 10-50% and improves lithographic overlay, enabling the production of high-capacity 3D NAND memory devices with enhanced performance and reliability.
Implementation Method 1
A method of forming a layer stack of oxide/nitride (ON) layers is provided. The method includes transferring a substrate to a process chamber, heating a pedestal retaining the substrate to a deposition temperature, and flowing a first silicon-containing gas... A first radio frequency (RF) power is symmetrically applied to the first silicon-containing gas... to form a first material layer of silicon dioxide (SiO2)
Implementation Method 2
A first radio frequency (RF) power is symmetrically applied to the first silicon-containing gas, the oxygen-containing gas, and the first dilution gas to form a first material layer of silicon dioxide (SiO2)
Data Source
AI summary
Embodiments described herein relate to manufacturing layer stacks of oxide/nitride (ON) layers with minimized in-plane distortion (IPD) and lithographic overlay errors. A method of forming a layer stack ON layers includes flowing a first silicon-containing gas, an oxygen-containing gas, and a first dilution gas. A RF power is symmetrically applied to form a first material layer of SiO2. A second silicon-containing gas, a nitrogen-containing gas, and a second dilution gas are flowed. A second RF power is symmetrically applied to form a second material layer of Si3N4. The flowing the first silicon-containing gas, the oxygen-containing gas, and the first dilution gas, the symmetrically applying the first RF power, the flowing the second silicon-containing gas, the nitrogen-containing gas, and the second dilution gas, and the symmetrically applying the second RF power is repeated until a desired number of first material layers and second material layers make up a layer stack.