Carbon-Doped Polysilicon Bottom Gate for Nonvolatile Memory

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Solution Overview

Problem

Nonvolatile memory devices face challenges in improving reliability, particularly in preventing oxidation of the floating gate electrode and maintaining uniformity of the tunnel insulation layer thickness, which affects data storage and erasure efficiency.

Innovation Solution

Incorporating a carbon-doped polysilicon layer for the bottom gate electrode, with a concentration range of 0.1% to 20%, to reduce grain size and suppress oxidation, and using a gate interlayer insulation layer to enhance coupling between the control and floating gate electrodes, while maintaining a recessed structure to prevent interference and oxidation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional polysilicon layer is used for the bottom gate electrode, then the device structure is simple and easy to manufacture, but oxidation occurs at the interface with the tunnel insulation layer, degrading reliability

Engineering Contradiction:

Improveoxidation resistance of bottom gate electrodeVSAvoidgate electrode structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Carbon is doped into the polysilicon layer of the bottom gate electrode at a concentration of 0.1% to 20%, which fundamentally changes the material properties. This parameter change suppresses oxidation reactions at the interface with the tunnel insulation layer while maintaining the electrical functionality of the gate electrode, thereby improving reliability without requiring a completely different material system

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The bottom gate electrode is constructed as a composite material by combining carbon-doped polysilicon. This composite approach leverages the beneficial properties of both carbon (oxidation resistance) and polysilicon (electrical conductivity and compatibility with existing semiconductor processes), achieving improved oxidation resistance while maintaining device functionality

Inventive Principle:

Principle #40Composite materials

2Productivity

If the bottom gate electrode is positioned close to the tunnel insulation layer for compact design, then device density increases, but phosphorus diffusion occurs, degrading electrical properties

Engineering Contradiction:

Improvedevice densityVSAvoidelectrical property stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

Carbon doping in the bottom gate electrode changes the diffusion characteristics of the polysilicon material. The carbon atoms modify the crystal structure and bonding properties, creating a barrier that suppresses phosphorus diffusion even when the gate electrode is positioned in close proximity to the tunnel insulation layer, thus maintaining electrical property stability while achieving high device density

Inventive Principle:

Principle #35Parameter changes

3Reliability

If carbon doping concentration is increased to suppress oxidation, then oxidation resistance improves, but manufacturing precision becomes more difficult to control

Engineering Contradiction:

Improveoxidation resistanceVSAvoidcarbon doping concentration control

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

Instead of requiring precise control of carbon doping at very low concentrations, the invention employs a broader doping range of 0.1% to 20%. This partial or excessive action approach ensures sufficient oxidation resistance is achieved across the entire range, making the process more robust and easier to control in manufacturing while still preventing excessive oxidation that would degrade device performance

Inventive Principle:

Principle #16Partial or excessive action

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 improves the reliability and electrical properties of nonvolatile memory devices by reducing phosphorus diffusion, maintaining thermal stability, and preventing excessive oxidation, thereby enhancing charge maintenance and data storage efficiency.

Implementation Method 1

Incorporating a carbon-doped polysilicon layer for the bottom gate electrode, with a concentration range of 0.1% to 20%, to reduce grain size and suppress oxidation

Methodology Applied

Scientific EffectOxidation suppression: Oxidation

Implementation Method 2

This approach improves the reliability and electrical properties of nonvolatile memory devices by reducing phosphorus diffusion, maintaining thermal stability

Methodology Applied

Scientific EffectPhosphorus diffusion: Diffusion

Implementation Method 3

using a gate interlayer insulation layer to enhance coupling between the control and floating gate electrodes

Methodology Applied

Scientific EffectCapacitive coupling: Capacitance

Data Source

PatentUS8232590B2Nonvolatile memory devices

Publication Date: 2012.07.31 SAMSUNG ELECTRONICS CO LTD

AI summary

Provided is a nonvolatile memory device. The nonvolatile memory device includes: a tunnel insulation layer on a semiconductor substrate; a floating gate electrode including a bottom gate electrode doped with carbon and contacting the tunnel insulation layer and a top gate electrode on the bottom gate electrode; a gate interlayer insulation layer on the floating gate electrode; and a control gate electrode on the gate interlayer insulation layer.