ALD Reactor Temperature Cycling for Memory Cell Sidewall Films
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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 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 sidewalls using atomic layer deposition (ALD), employing plasma and thermal processes to enhance film quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional ALD is used to deposit films on high aspect ratio trenches, then the deposition process can be performed, but weak spots and voids form in the sidewalls due to poor film quality in structurally enervated regions
Solution Approach 1:
The substrate is rotated during the ALD deposition process to dynamically change the deposition angle and gas flow distribution. This rotation ensures uniform film deposition on vertical sidewalls of high aspect ratio trenches, preventing weak spots and voids while maintaining conformal coverage throughout the trench structure
Solution Approach 2:
The invention introduces substrate rotation as an additional dimensional parameter to the conventional ALD process. By rotating the substrate around its central axis, the process transforms from a static vertical deposition to a dynamic multi-angle deposition, enabling uniform film growth on previously difficult-to-access sidewall regions
2Manufacturing precision
If the substrate is rotated during deposition, then uniform film coverage is achieved on sidewalls, but the device complexity increases due to additional motion control requirements
Solution Approach 1:
The substrate support structure serves multiple functions: it holds the substrate during deposition, provides the rotation mechanism for uniform coverage, and acts as a heating element. By combining these functions into a single integrated component, the invention avoids adding separate rotation and heating systems, thereby limiting the increase in device complexity
3Manufacturing precision
If sequential cyclic supply of reactants is used, then conformal films are formed on complex structures, but the deposition time increases due to multiple pulses required
Solution Approach 1:
The invention employs periodic pulsing of reactant gases in sequential cycles, with each pulse depositing a controlled amount of material. The substrate rotation is synchronized with these periodic reactant pulses to ensure that each surface region receives uniform exposure during each cycle, achieving conformal coverage while maintaining efficient deposition timing
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 the growth of high-quality conformal films in structurally challenging areas, improving the reliability and mechanical strength of memory devices by eliminating weak spots and voids.
Implementation Method 1
providing a first reactant into the chamber so that a condensed portion of the first reactant is formed on the substrate
Implementation Method 2
the condensed portion of the first reactant is vaporized by heating to a second temperature
Implementation Method 3
providing a second reactant into the chamber, wherein 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.