Nonvolatile Memory Through-Hole Etching via Additive Concentration Gradient
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Solution Overview
Problem
In collectively patterned three-dimensionally stacked nonvolatile semiconductor memory devices, tapered through-holes lead to unstable threshold voltage and reduced bit density due to varying diameters along the hole depth, affecting memory cell operations and capacity.
Innovation Solution
The solution involves forming a stacked structural body with alternating electrode and insulating films, where the concentration of additives in the electrode films is varied to control the etching rate, resulting in a through-hole with a perpendicular wall and uniform diameter, ensuring consistent threshold voltage across the memory cell regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the depth of the through-hole is increased to increase memory capacity, then the memory capacity is improved, but the through-hole becomes tapered causing unstable threshold voltage
Solution Approach 1:
The patent applies local quality by varying the additive concentration in different regions of the electrode films. Specifically, the electrode films have different additive concentrations at different heights, which creates different etching rates at different depths of the through-hole. This local variation in material composition enables the formation of a perpendicular sidewall profile while maintaining deep through-holes, thereby increasing memory capacity without compromising threshold voltage stability.
Solution Approach 2:
The patent employs parameter changes by modifying the additive concentration parameter in the electrode films as a function of height. By changing the chemical composition parameter (additive concentration) across different regions, the etching rate parameter is controlled to produce a uniform diameter through-hole. This parameter variation approach allows deep through-holes to be formed with perpendicular sidewalls, resolving the contradiction between increased memory capacity and threshold voltage stability.
2Quantity of substance
If the depth of the through-hole is increased to increase bit density, then the bit density is improved, but the diameter in the lower portion is reduced preventing proper semiconductor pillar formation
Solution Approach 1:
The patent applies local quality by making the additive concentration in the electrode films position-dependent. The electrode films contain different additive concentrations at different heights, which creates spatially varying etching rates. This ensures that the etching process removes material at different rates at different depths, compensating for the natural tapering effect and maintaining a uniform through-hole diameter throughout its depth, thus enabling proper semiconductor pillar formation while increasing bit density.
Solution Approach 2:
The patent uses parameter changes by varying the additive concentration parameter in the electrode films along the vertical direction. This composition gradient causes the etching rate to change with depth, counteracting the tapering that would normally occur in deep holes. The result is a through-hole with uniform diameter despite increased depth, allowing semiconductor pillars to be properly formed and bit density to be increased.
3Quantity of substance
If the through-hole diameter is reduced in the lower portion to increase memory capacity, then the memory capacity is improved, but the semiconductor pillar cannot be filled into the interior
Solution Approach 1:
The patent applies parameter changes by modifying the additive concentration in the electrode films as a function of height. This creates a depth-dependent etching rate that maintains a uniform through-hole diameter from top to bottom. By controlling the etching process through compositional variation, the patent ensures that deep through-holes have sufficient diameter throughout their length to accommodate semiconductor pillars, thereby enabling both high memory capacity and proper pillar formation.
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 stabilizes memory cell operations by maintaining uniform threshold voltage characteristics and enabling higher bit density without the fluctuations associated with tapered holes.
Implementation Method 1
the concentration of additives in the electrode films is varied to control the etching rate, resulting in a through-hole with a perpendicular wall and uniform diameter
Data Source
AI summary
According to one embodiment, a nonvolatile semiconductor memory device includes a substrate, a stacked structural body, a semiconductor pillar, and a memory unit. The stacked structural body is provided on a major surface of the substrate. The stacked structural body includes electrode films alternately stacked with inter-electrode insulating films in a direction perpendicular to the major surface. The pillar pierces the body in the direction. The memory unit is provided at an intersection between the pillar and the electrode films. The electrode films include at least one of amorphous silicon and polysilicon. The stacked structural body includes first and second regions. A distance from the second region to the substrate is greater than a distance from the first region to the substrate. A concentration of an additive included in the electrode film in the first region is different from that included in the electrode film in the second region.