Semiconductor Capacitor Electrodes with Oxide-Nitride Layers

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Solution Overview

Problem

In highly integrated semiconductor devices, such as DRAM, the reduction in cell size leads to reduced effective area of the lower electrode of the cell capacitor, necessitating high dielectric constant materials that often result in increased leakage currents due to reactions with doped polysilicon electrodes.

Innovation Solution

The use of a stacked electrode structure comprising a conductive metal nitride layer, at least part of which is oxidized to form a metal oxide nitride, combined with a doped polysilicon germanium layer, where nitrogen is trapped in interstitial sites or forms N—O bonds, reducing dopant penetration and leakage currents.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If high dielectric constant materials (Al2O3, HfO2, Ta2O5, TiO2) are used to increase cell capacitance in reduced area, then the capacitance per unit area is improved, but leakage current increases due to reactions with doped polysilicon electrodes

Engineering Contradiction:

Improvecell capacitanceVSAvoidleakage current

Core Design Contradiction:

Quantity of substanceVSObject-generated harmful factors

Solution Approach 1:

A stacked electrode structure is introduced as an intermediary between the high dielectric constant material and the doped polysilicon electrode. The stack consists of a conductive metal nitride layer (TiN, WN, or TaN) and a doped polysilicon germanium layer, which together form a barrier that prevents direct reaction between the dielectric material and the electrode, thereby reducing leakage current while maintaining high capacitance

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The electrode is constructed as a composite material system combining conductive metal nitride (TiN, WN, or TaN) with doped polysilicon germanium. This composite structure provides both electrical conductivity and chemical stability, preventing harmful reactions with the high dielectric constant material while maintaining low leakage current

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If doped polysilicon layers are used to form capacitor electrodes, then the electrode formation process is simplified, but reactions with high dielectric constant materials deteriorate electrical characteristics

Engineering Contradiction:

Improveelectrode formationVSAvoidelectrical characteristic

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

Inventive Principle:

Principle #40Composite materials

3Ease of manufacture

If thermal treatment at high temperature (>600°C) is performed to form doped polysilicon layer, then the polysilicon deposition is completed, but leakage current characteristic deteriorates

Engineering Contradiction:

Improvepolysilicon depositionVSAvoidleakage current

Core Design Contradiction:

Ease of manufactureVSObject-generated harmful factors

Solution Approach 1:

The conductive metal nitride layer serves as a protective intermediary between the high dielectric constant material and the doped polysilicon germanium layer during thermal treatment. This intermediary layer prevents dopant diffusion and chemical reactions even at high temperatures, maintaining low leakage current characteristics

Inventive Principle:

Principle #24Intermediary (Mediator)

4Temperature

If doped polysilicon germanium layer is used for low temperature process, then the deposition temperature is reduced, but dopant diffusion into lower layers increases leakage current

Engineering Contradiction:

Improvedeposition temperatureVSAvoidleakage current

Core Design Contradiction:

TemperatureVSObject-generated harmful factors

Solution Approach 1:

The conductive metal nitride layer (TiN, WN, or TaN) acts as a diffusion barrier intermediary between the doped polysilicon germanium layer and the lower capacitor layers. This intermediary prevents dopant diffusion into lower layers, maintaining low leakage current even when using low temperature deposition processes

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

This configuration effectively minimizes leakage currents and improves data retention and refresh characteristics in semiconductor capacitors by reducing dopant penetration into lower layers.

Implementation Method 1

at least part of an upper surface of the conductive metal nitride layer may be oxidized to form TiON

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 2

N2 may be trapped in interstitial sites within the TiON, or nitrogen may form N—O bonds in the TiON

Methodology Applied

Scientific EffectAdsorption: Adsorption

Implementation Method 3

at least part of an upper surface of the dielectric layer may be nitridized to form an oxide nitride layer

Methodology Applied

Scientific EffectNitridization: Nitriding

Data Source

PatentUS7422943B2Semiconductor device capacitors with oxide-nitride layers and methods of fabricating such capacitors

Publication Date: 2008.09.09 SAMSUNG ELECTRONICS CO LTD

AI summary

Capacitors having upper electrodes that include a lower electrode, a dielectric layer and an upper electrode that includes a conductive metal nitride layer and a doped polysilicon germanium layer are provided. At least part of the conductive metal nitride layer is oxidized and/or at least part of the dielectric layer is nitridized.