Vertical DRAM Transistor Body Contact Layout for Floating Body Effects

Solution Overview

Problem

Floating body effects in vertical access transistors of Dynamic Random-Access Memory (DRAM) lead to degraded charge retention and power distribution issues, necessitating the development of architectures and methods to alleviate these problems.

Innovation Solution

Integrated assemblies with vertically-displaced source/drain regions and adjacent body contact regions, where the body contact regions are laterally-spaced from the source/drain regions by an insulative region, and methods involving the formation of trenches and bowl regions filled with insulative material to create insulative posts and layers, which help to alleviate floating body effects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of moving object

If vertical access transistors are used in DRAM, then device footprint is reduced and integration density is improved, but floating body effects occur leading to degraded charge retention and power distribution issues

Engineering Contradiction:

Improvedevice footprintVSAvoidcharge retention

Core Design Contradiction:

Area of moving objectVSReliability

Solution Approach 1:

The body region is segmented into multiple body contact regions that are laterally spaced from the source/drain regions by insulative regions. This segmentation allows the body to be electrically divided into isolated sections, preventing floating body effects while maintaining the vertical transistor structure's compact footprint.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Insulative regions are introduced as intermediary elements between the body contact regions and source/drain regions. These insulative regions electrically isolate the body contact regions from the source/drain, preventing harmful floating body effects while allowing the compact vertical transistor design to be maintained.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Area of moving object

If vertical access transistors are used in DRAM, then device footprint is reduced and integration density is improved, but floating body effects occur leading to power distribution problems

Engineering Contradiction:

Improvedevice footprintVSAvoidpower distribution

Core Design Contradiction:

Area of moving objectVSUse of energy by moving object

Solution Approach 1:

The body region is segmented into multiple body contact regions that are laterally spaced from the source/drain regions by insulative regions. This segmentation allows the body to be electrically divided into isolated sections, preventing floating body effects while maintaining the vertical transistor structure's compact footprint.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Multiple body contact regions are established at the same reference voltage potential, creating equipotential regions throughout the body. This ensures uniform voltage distribution across the compact vertical transistor structure, eliminating power distribution problems associated with floating bodies.

Inventive Principle:

Principle #12Equipotentiality

3Device complexity

If body contact regions are placed adjacent to source/drain regions, then compact transistor design is achieved, but floating body effects are exacerbated

Engineering Contradiction:

Improvetransistor design compactnessVSAvoidfloating body effects

Core Design Contradiction:

Device complexityVSObject-generated harmful factors

Solution Approach 1:

Insulative regions are introduced as intermediary elements between the body contact regions and source/drain regions. These insulative regions electrically isolate the body contact regions from the source/drain, preventing harmful floating body effects while allowing the compact vertical transistor design to be maintained.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The insulative regions are locally positioned only between the body contact regions and source/drain regions, providing electrical isolation precisely where needed. This localized approach maintains compactness while eliminating floating body effects in the critical interaction zones.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS12137551B2Integrated assemblies having body contact regions proximate transistor body regions; and methods utilizing bowl etches during fabrication of integrated assemblies

Publication Date: 2024.11.05 MICRON TECHNOLOGY INC

AI summary

Some embodiments include an integrated assembly having a semiconductor-containing structure with a body region vertically between an upper region and a lower region. The upper region includes a first source/drain region. The lower region is split into two legs which are both joined to the body region. One of the legs includes a second source/drain region and the other of the legs includes a body contact region. The first and second source/drain regions are of a first conductivity type, and the body contact region is of a second conductivity type which is opposite to the first conductivity type. An insulative material is adjacent to the body region. A conductive gate is adjacent to the insulative material. A transistor includes the semiconductor-containing structure, the conductive gate and the insulative material. Some embodiments include methods of forming integrated assemblies.