Buried Gate Trench Structure for Threshold Voltage Modulation

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

The increasing demand for higher integration and high-speed semiconductor devices poses challenges such as decreased process margins in exposure processes and difficulties in defining fine patterns, necessitating improved electrical characteristics and fabrication methods.

Innovation Solution

A semiconductor device with a buried gate structure comprising a gate trench, gate dielectric layer, high and low work function layers, and a capping layer, where the high work function layer shifts the flat band voltage positively and the low work function layer shifts it negatively, allowing for modulation of the threshold voltage without channel doping, and improving gate-induced drain leakage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If higher integration is pursued, then device functionality and capacity improve, but process margin decreases and fine pattern definition becomes difficult

Engineering Contradiction:

Improveintegration capabilityVSAvoidprocess margin

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The gate electrode is divided into multiple segments (first gate electrode and second gate electrode) with different work functions, allowing independent optimization of each segment's electrical characteristics without affecting the entire gate structure, thus enabling higher integration while maintaining process margins

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the gate electrode are assigned different work function values (high work function in first region, low work function in second region) to locally optimize electrical characteristics for specific functional requirements, enabling fine pattern definition and high integration simultaneously

Inventive Principle:

Principle #3Local quality

2Ease of manufacture

If conventional gate structures are used, then fabrication is simpler, but electrical characteristics and threshold voltage control are insufficient

Engineering Contradiction:

Improvefabrication simplicityVSAvoidelectrical characteristics

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The work function parameter of the gate electrode is changed by forming regions with different work functions (high and low) within the same gate structure, enabling precise threshold voltage control and improved electrical characteristics while maintaining compatibility with conventional fabrication processes

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The gate electrode is formed as a composite structure combining materials or regions with different work functions (such as metal nitride with different doping levels or composite metal layers), achieving superior electrical characteristics and threshold voltage modulation capability

Inventive Principle:

Principle #40Composite materials

3Reliability

If channel doping is used to modulate threshold voltage, then threshold voltage control is achieved, but gate-induced drain leakage increases

Engineering Contradiction:

Improvethreshold voltage controlVSAvoidgate-induced drain leakage

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The threshold voltage control function is extracted from the channel region (by removing the need for channel doping) and transferred to the gate electrode itself through the creation of high and low work function regions, which directly modulate the electric field at the gate-channel interface without introducing harmful doping effects into the channel

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The gate dielectric layer serves as an intermediary that transmits the electric field modulation from the high/low work function gate regions to the channel, enabling threshold voltage control without direct doping of the channel, thereby preventing gate-induced drain leakage

Inventive Principle:

Principle #24Intermediary (Mediator)

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

The solution enhances electrical characteristics by modulating the threshold voltage and reducing gate-induced drain leakage, improving the semiconductor device's performance and integration capabilities.

Implementation Method 1

a high work function layer and a lower gate electrode that fill a bottom portion of the gate trench over the gate dielectric layer; an upper gate electrode including a low work function adjusting element over the lower gate electrode and including the same metal nitride as a material of the lower gate electrode

Methodology Applied

Scientific EffectWork function modulation:

Implementation Method 2

a capping layer that gap-fills the other portion of the gate trench over the upper gate electrode

Methodology Applied

Scientific EffectGap-filling deposition: Deposition (physical)

Data Source

PatentUS20230290848A1Semiconductor device and method for fabricating the same

Publication Date: 2023.09.14 SK HYNIX INC

AI summary

A semiconductor device includes: a substrate including a gate trench; a gate dielectric layer formed along sidewalls and bottom surfaces of the gate trench; a high work function layer and a lower gate electrode that fill a bottom portion of the gate trench over the gate dielectric layer; an upper gate electrode including a low work function adjusting element over the lower gate electrode and including the same metal nitride as a material of the lower gate electrode; and a capping layer that gap-fills the other portion of the gate trench over the upper gate electrode.