Non-volatile Memory Mobile Charge Collector for Threshold Stability
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Solution Overview
Problem
Conventional non-volatile semiconductor memory devices experience significant fluctuations in cell threshold voltage due to mobile charges collected near the floating gate from the insulation layer, leading to reliability issues and reduced high-speed performance, especially in miniaturized devices with small active regions.
Innovation Solution
A non-volatile semiconductor memory device design that includes a mobile charge collector to attract and reduce mobile charges from the insulation layer in between-column and between-row regions, thereby minimizing their collection near the floating gate, without increasing the active region area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the area of active regions is increased to reduce mobile charge collection near the floating gate, then fluctuations in cell threshold voltage are reduced, but junction capacity increases and high-speed performance deteriorates
Solution Approach 1:
A dedicated mobile charge collector structure is introduced as an intermediary component between the insulation layer and the floating gate. This collector actively attracts and removes mobile charges from regions near the floating gate, preventing them from causing threshold voltage fluctuations. The collector acts as a mediator that solves the reliability problem without requiring enlargement of the active region, thus preserving high-speed performance.
Solution Approach 2:
The harmful mobile charges are extracted from the critical region near the floating gate by the mobile charge collector. The collector selectively removes positive mobile charges from the insulation layer in the between-column and between-row regions, preventing their accumulation and subsequent attraction to the floating gate. This extraction mechanism stabilizes threshold voltage without affecting active region dimensions or junction capacity.
2Area of stationary object
If miniaturization is pursued to increase memory density, then device size is reduced, but mobile charge collection effects become more significant causing larger threshold voltage fluctuations
Solution Approach 1:
The mobile charge collector serves as a protective intermediary that becomes increasingly important as device dimensions are reduced. In miniaturized devices, the collector is strategically positioned to cover the floating gate and surrounding insulation regions, actively managing mobile charges in the limited space available. This ensures that even as device size decreases, the collector effectively prevents mobile charge-induced threshold voltage fluctuations.
Solution Approach 2:
The mobile charge collector extends into the vertical dimension above the floating gate and insulation layer, creating a three-dimensional charge management structure. By utilizing the vertical space rather than expanding lateral dimensions, the collector effectively manages mobile charges in miniaturized devices without increasing the device footprint, thus maintaining high memory density while improving threshold voltage stability.
3Ease of manufacture
If the floating gate is exposed to the insulation layer between wirings to simplify structure, then manufacturing is easier, but mobile charges are readily collected near the floating gate causing reliability issues
Solution Approach 1:
The mobile charge collector acts as a protective intermediary between the exposed floating gate and the mobile charges in the insulation layer. Even though the floating gate remains exposed to simplify the structure, the collector positioned above and around it actively attracts and removes mobile charges, preventing their accumulation and subsequent attraction to the floating gate. This maintains both structural simplicity and information storage reliability.
Solution Approach 2:
The mobile charge collector converts the potentially harmful mobile charges in the insulation layer into a beneficial effect. By actively attracting mobile charges to the collector rather than allowing them to accumulate near the floating gate, the collector utilizes the mobile charges' natural movement to stabilize threshold voltage. The same mobile charges that would cause reliability issues are instead harnessed to improve device performance.
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 reduces fluctuations in cell threshold voltage while maintaining high-speed performance by efficiently collecting mobile charges from the insulation layer, enhancing the reliability and efficiency of the memory device.
Implementation Method 1
a mobile charge collector configured to attract mobile charges from the insulation layer to at least one of a between-column region and a between-row region and reducing collection of the mobile charges near the floating gate
Data Source
AI summary
In the non-volatile semiconductor memory device, a mobile charge collector layer, a mobile charge collecting contact, a mobile charge collecting first wiring layer, an in-between contact between the mobile charge collector layers, and a mobile charge collecting second wiring layer are disposed adjacent to a floating gate. Thereby, without increasing areas of active regions in the non-volatile semiconductor memory device, the number of mobile charges collected near the floating gate is reduced. The non-volatile semiconductor memory device allows high-speed operation of a memory cell while reducing fluctuations in a threshold voltage of the memory cell caused by collection of the mobile charges, which are attracted from an insulation layer, near the floating gate.