Vertical 3D Memory Channel Segmentation for Stability
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Solution Overview
Problem
As semiconductor design rules shrink, there is a challenge in forming memory cells with sufficient space, particularly in DRAM arrays, where the channel stability and threshold voltage stability over time are compromised due to limited space and thermal budget constraints.
Innovation Solution
The introduction of a three-node access device with a channel formed from both channel material and passivation material, which reduces thermal exposure and decreases threshold voltage, enhancing stability and scalability in vertical 3D memory devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If design rules are shrunk to increase memory density, then memory capacity is improved, but channel stability and threshold voltage stability deteriorate due to limited space and thermal budget constraints
Solution Approach 1:
The channel structure is segmented into multiple materials: a first channel material (e.g., silicon) and a second channel material (e.g., germanium) arranged in alternating layers. This segmentation allows each material to contribute its strengths - silicon provides stability while germanium enhances carrier mobility - thereby maintaining channel stability even as design rules shrink and memory capacity increases.
Solution Approach 2:
The patent employs composite channel structures combining different semiconductor materials (silicon-germanium alloys, alternating silicon and germanium layers) to create a channel that simultaneously achieves high carrier mobility and threshold voltage stability. The composite nature allows optimization of electrical properties without sacrificing structural stability, resolving the contradiction between increased density and maintained reliability.
2Quantity of substance
If design rules are shrunk to increase memory density, then memory capacity is improved, but threshold voltage stability over time deteriorates due to thermal budget constraints
Solution Approach 1:
The patent modifies the channel material composition parameters, specifically incorporating germanium-rich regions or alternating layers of silicon and germanium. This parameter change in material composition enables the channel to maintain stable threshold voltage over time even under reduced thermal budgets, as the germanium content can be optimized to control carrier concentration and improve voltage stability without requiring high-temperature processing.
Solution Approach 2:
By creating composite channel structures with silicon and germanium in specific ratios and configurations, the patent achieves threshold voltage stability that persists over time. The composite materials allow the channel to resist degradation from thermal effects while maintaining the high density required by shrunk design rules.
3Ease of manufacture
If channel material is used alone without passivation material, then manufacturing is simpler, but channel stability and threshold voltage control deteriorate
Solution Approach 1:
The second channel material serves multiple functions simultaneously: it acts as an active conduction path like the first channel material, but also provides passivation and stabilization effects. This multi-functionality means that while the structure appears more complex, the second material integrates several roles (conduction, stability, threshold voltage control) that would otherwise require separate components, thereby maintaining ease of manufacture while improving reliability.
Solution Approach 2:
The composite channel structure combines two materials where the second material (e.g., germanium) not only contributes to conduction but also provides stabilizing effects. This composite approach achieves both channel stability and threshold voltage control within the same structural framework, resolving the contradiction between manufacturing simplicity and channel reliability.
Data Source
AI summary
Systems, methods and apparatus are provided for depositing alternating layers of dielectric material and sacrificial material in repeating iterations to form a vertical stack, forming a plurality of vertical openings through the vertical stack to form elongated vertical, pillar columns with sidewalls in the vertical stack, patterning the pillar columns to expose a location to form a channel region, selectively removing a portion of the sacrificial material to form first horizontal openings in the first horizontal direction in the sidewalls of the elongated vertical, pillar columns, and depositing a channel material in the first horizontal openings to form the channel region within the sidewalls for the horizontally oriented access devices.