Metal Silicide Layer Thermal Stability in DRAM Capacitor

Solution Overview

Problem

Conventional semiconductor manufacturing processes face challenges with the thermal stability of metal silicide layers in DRAM devices, leading to agglomeration and increased sheet resistance, which affects device performance and yield.

Innovation Solution

A method involving a combination of rapid thermal processing and millisecond annealing is used to form a metal silicide layer with improved thermal stability, preventing agglomeration and maintaining low electrical resistance, by performing consecutive heat treatments at different temperatures, including a high-temperature millisecond annealing process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a high-temperature nitride process is performed on the metal silicide, then the lower electrode can be formed, but the metal silicide layer is partially agglomerated and sheet resistance rapidly increases

Engineering Contradiction:

Improvelower electrode formationVSAvoidmetal silicide layer stability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

A protective oxide layer is formed on the metal silicide layer before the nitride process. This preliminary protective layer prevents direct exposure of the metal silicide to high-temperature nitride processing conditions, thereby preventing agglomeration and sheet resistance increase while still allowing the lower electrode to be formed

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

An oxide layer is introduced as an intermediary between the metal silicide layer and the nitride processing environment. This intermediate layer acts as a barrier that protects the metal silicide from direct high-temperature nitride exposure, preventing harmful effects while enabling the necessary electrode formation process

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If a high-temperature nitride process is performed on the metal silicide, then the lower electrode can be formed, but the metal silicide layer is partially broken and electrical shorting occurs

Engineering Contradiction:

Improvelower electrode formationVSAvoidmetal silicide layer integrity

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

A protective oxide layer is formed on the metal silicide layer before the nitride process. This preliminary protective layer prevents direct exposure of the metal silicide to high-temperature nitride processing conditions, thereby preventing agglomeration and sheet resistance increase while still allowing the lower electrode to be formed

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

An oxide layer is introduced as an intermediary between the metal silicide layer and the nitride processing environment. This intermediate layer acts as a barrier that protects the metal silicide from direct high-temperature nitride exposure, preventing harmful effects while enabling the necessary electrode formation process

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of manufacture

If a high-temperature nitride process is performed, then the lower electrode can be formed, but the dopants of the source/drain regions are prevented from activating and channel resistance increases

Engineering Contradiction:

Improvelower electrode formationVSAvoiddopant activation

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

A protective oxide layer is formed on the metal silicide layer before the nitride process. This preliminary protective layer prevents direct exposure of the metal silicide to high-temperature nitride processing conditions, thereby preventing agglomeration and sheet resistance increase while still allowing the lower electrode to be formed

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

An oxide layer is introduced as an intermediary between the metal silicide layer and the nitride processing environment. This intermediate layer acts as a barrier that protects the metal silicide from direct high-temperature nitride exposure, preventing harmful effects while enabling the necessary electrode formation process

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 approach enhances the thermal stability and reduces sheet resistance of the metal silicide layer, ensuring reliable operation and increased manufacturing yield by preventing agglomeration and maintaining low contact resistance.

Implementation Method 1

the metal of the metal layer and the polysilicon of the buried contact react with each other by a consecutive thermal process to thereby form a metal silicide layer on the buried contact

Methodology Applied

Scientific EffectDiffusion: Diffusion

Implementation Method 2

A method involving a combination of rapid thermal processing and millisecond annealing is used to form a metal silicide layer with improved thermal stability

Methodology Applied

Scientific EffectAnnealing: Annealing

Data Source

PatentUS8877583B2Method of manufacturing a semiconductor device

Publication Date: 2014.11.04 SAMSUNG ELECTRONICS CO LTD

AI summary

In a method of forming an ohmic layer of a DRAM device, the metal silicide layer between the storage node contact plug and the lower electrode of a capacitor is formed as the ohmic layer by a first heat treatment under a first temperature and an instantaneous second heat treatment under a second temperature higher than the first temperature. Thus, the metal silicide layer has a thermo-stable crystal structure and little or no agglomeration occurs on the metal silicide layer in the high temperature process. Accordingly, the sheet resistance of the ohmic layer may not increase in spite of the subsequent high temperature process.