Floating-Body DRAM Leakage Shielding Patterns

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Solution Overview

Problem

Conventional single transistor DRAM cells with floating bodies have poor data retention characteristics due to rapid recombination of holes stored in the bulk region with electrons in the source and drain regions, leading to increased junction capacitances and decreased data sensing margin and operating speed.

Innovation Solution

Incorporating leakage shielding patterns between the floating body and source and drain regions, which can be made of silicon oxide, silicon nitride, or silicon oxynitride layers, to minimize the contact surface and block leakage paths of excess holes, thereby extending the retention time of excess carriers in the excess carrier storage region.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the source and drain regions are made shallower than the bulk region to maximize hole storage, then the data storage capacity is improved, but the recombination of holes with electrons increases, leading to poor data retention

Engineering Contradiction:

Improvehole storage capacityVSAvoiddata retention characteristics

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

An insulating layer is introduced as an intermediary between the source/drain regions and the bulk region. This insulating layer acts as a mediator that prevents direct contact and recombination between holes in the bulk region and electrons in the source/drain regions, thereby improving data retention while maintaining high hole storage capacity

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent segments the contact interface between source/drain regions and bulk region by introducing an insulating layer. This segmentation separates the electrical contact function from the storage function, allowing holes to be stored in the bulk region while preventing recombination at the junction interfaces

Inventive Principle:

Principle #1Segmentation

2Ease of operation

If the junction area of source and drain regions is increased, then the electrical contact is improved, but the junction capacitance increases, leading to decreased data sensing margin and operating speed

Engineering Contradiction:

Improveelectrical contact qualityVSAvoidoperating speed

Core Design Contradiction:

Ease of operationVSSpeed

Solution Approach 1:

The insulating layer serves as an intermediary that enables electrical contact between source/drain regions and the bulk region through the floating body structure while minimizing direct junction area. This reduces junction capacitance and improves operating speed while maintaining adequate electrical contact for device operation

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS7851859B2Single transistor memory device having source and drain insulating regions and method of fabricating the same

Publication Date: 2010.12.14 SAMSUNG ELECTRONICS CO LTD

AI summary

A single transistor floating-body dynamic random access memory (DRAM) device includes a floating body located on a semiconductor substrate and a gate electrode located on the floating body, the floating body including an excess carrier storage region. The DRAM device further includes source and drain regions respectively located at both sides of the gate electrode, and leakage shielding patterns located between the floating body and the source and drain regions. Each of the source and drain regions contact the floating body, which may be positioned between the source and drain regions. The floating body may also laterally extend under the leakage shielding patterns, which may be arranged at outer sides of the gate electrode.