ALD Reactor Temperature Cycling for Memory Sidewall Film Coverage
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Solution Overview
Problem
The challenge of depositing high-quality films on structurally enervated regions, such as high aspect ratio trenches and overhanging layers in memory cell stacks, is exacerbated by the miniaturization of memory devices, leading to issues like weak spots, voids, and poor adhesion in the sidewalls.
Innovation Solution
A method involving sequential cyclic supply of reactive gases in a vacuum chamber, with controlled temperature changes and substrate motion, to form conformal films on these challenging regions using atomic layer deposition (ALD), employing a reactor with temperature and gas distribution control, and optionally plasma enhancement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional ALD is used to deposit films on high aspect ratio trenches and overhanging layers, then the self-limiting growth mechanism is maintained, but poor film coverage and weak spots occur in enervated regions
Solution Approach 1:
The substrate is rotated during the ALD process to dynamically change the deposition geometry. This rotation enables the reactive gases to access enervated regions like high aspect ratio trenches and overhanging layers from multiple angles, achieving uniform film coverage that static substrates cannot provide, while preserving the self-limiting ALD growth mechanism
Solution Approach 2:
The ALD process employs periodic pulsing of reactive gases alternating with purge steps. This periodic action allows sequential monolayer deposition that maintains self-limiting growth while the substrate rotation between pulses ensures comprehensive coverage of difficult-to-reach regions, eliminating weak spots and voids
2Productivity
If memory devices are miniaturized to increase density, then device capacity is improved, but film deposition quality on sidewalls deteriorates due to increased aspect ratios
Solution Approach 1:
Substrate rotation transforms the static high aspect ratio geometry into a dynamically accessible structure. By rotating the substrate during gas pulsing, the reactive species can reach sidewalls and enervated regions that would otherwise be shadowed or inaccessible in miniaturized high-density structures, maintaining film quality despite increased device density
Solution Approach 2:
The invention introduces rotational motion as a new dimension to the deposition process. Instead of relying solely on gas flow direction, the substrate rotation adds temporal and spatial variability, allowing reactive gases to access three-dimensional enervated regions from multiple angles throughout the deposition cycle
3Productivity
If purge steps are shortened to increase deposition speed, then productivity is improved, but vapor phase reactant mixing is not prevented, risking CVD reactions
Solution Approach 1:
Substrate rotation during the purge interval creates enhanced gas flow dynamics and prevents reactant mixing through continuous motion. The rotation ensures that even with shorter purge times, vapor phase reactants remain separated by the moving substrate geometry, preventing unwanted CVD reactions while maintaining high deposition rates
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 reliable manufacturing of memory devices with improved film quality and coverage in enervated areas, eliminating weak spots and voids, thereby enhancing the mechanical strength and reliability of memory arrays.
Implementation Method 1
a first reactant is provided into the chamber so that a condensed portion of the first reactant is absorbed on the substrate
Implementation Method 2
the temperature is controlled to a second temperature, the second temperature being greater than the first temperature, after the condensed portion of the first reactant is absorbed on the substrate, such that the condensed portion of the first reactant is partially vaporized
Implementation Method 3
a second reactant is provided into the chamber, and the second reactant reacts with the first reactant to form a reaction product
Data Source
AI summary
Apparatus and methods related to forming films on sidewalls of memory cell stacks in memory and logic devices. In one approach, a silicon wafer is held in a chamber of an atomic layer deposition (ALD) reactor. A temperature in the reactor is controlled to a first temperature (e.g., room temperature or below) where a first gas reactant that is provided into the chamber condenses and is adsorbed on the target wafer or substrate. The first reactant or precursor is partly vaporized at a second temperature in the reactor that is greater than the first temperature. A second gas reactant is provided into the chamber. The second gas reactant reacts with the adsorbed portion of the first gas reactant in its activated state. The reaction product is a film on the sidewall of a memory cell stack or logic devices. The foregoing steps are repeated to form a desired thickness of the film.