Transitional Silicide Protection During Metal Stripping

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Solution Overview

Problem

Current methods for stripping un-reacted metal from transitional silicide in transistor manufacturing damage the silicide, leading to increased contact resistance and junction leakage due to the lack of selectivity between the stripping agents and the silicide.

Innovation Solution

A surface oxidation process using hydrogen peroxide is performed to form a protective layer on the transitional silicide, followed by a hydrochloric acid hydrogen peroxide mixture stripping process, which selectively removes the un-reacted metal without damaging the silicide, allowing for circular application of these processes to ensure complete removal of remnants.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a hydrochloric acid hydrogen peroxide mixture stripping process is performed to strip un-reacted metal, then the stripping effectiveness is improved, but the transitional silicide is damaged

Engineering Contradiction:

Improvestripping effectivenessVSAvoidsilicide damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A protective layer is formed on the transitional silicide surface before performing the stripping process. This preliminary protective layer prevents the stripping solution from directly contacting and damaging the silicide, while still allowing effective removal of un-reacted metal remnants.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The protective layer acts as an intermediary between the stripping solution and the transitional silicide. It selectively allows the stripping agents to remove un-reacted metal while blocking direct contact with the silicide, thereby preventing damage during the stripping process.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Stability of the object's composition

If thermally stable metal (Pt) is added to the metal layer to prevent silicide agglomeration, then the thermal stability is improved, but the stripping selectivity deteriorates

Engineering Contradiction:

Improvethermal stabilityVSAvoidstripping selectivity

Core Design Contradiction:

Stability of the object's compositionVSManufacturing precision

Solution Approach 1:

The protective layer serves as an intermediary that enables selective stripping. It allows the stripping solution to differentiate between un-reacted metal and transitional silicide, achieving high selectivity even when thermally stable metals like Pt are present in the metal layer.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The protective layer changes the chemical environment at the silicide surface, creating different reaction conditions that enhance the selectivity between stripping un-reacted metal versus attacking the silicide, even in the presence of thermally stable metals.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If multiple stripping processes are performed circularly to ensure complete removal of remnants, then the stripping completeness is improved, but the process complexity increases

Engineering Contradiction:

Improvestripping completenessVSAvoidprocess complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The protective layer is formed once before the stripping process, enabling multiple stripping cycles to be performed without repeatedly protecting the silicide. This preliminary protective measure simplifies the overall process by eliminating the need for repeated protective layer formation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The protective layer remains in place throughout multiple stripping cycles, allowing continuous stripping action to be performed on the un-reacted metal without interrupting to reform protection. This enables complete removal of metal remnants through repeated stripping while maintaining process simplicity.

Inventive Principle:

Principle #20Continuity of useful 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 method effectively strips un-reacted metal from transitional silicide without damaging it, maintaining the integrity and reducing contact resistance, thereby preventing junction leakage and ensuring the stability of the silicide.

Implementation Method 1

A surface oxidation process utilizing hydrogen peroxide is performed on the transitional silicide to form a protective layer on the transitional silicide

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 2

a hydrochloric acid hydrogen peroxide mixture (HPM) stripping process is performed on the substrate to strip the remnant metal

Methodology Applied

Scientific EffectChemical etching:

Data Source

PatentUS7390754B2Method of forming a silicide

Publication Date: 2008.06.24 UNITED MICROELECTRONICS CORP

AI summary

A method of stripping a remnant metal is disclosed. The remnant metal is formed on a transitional silicide of a silicon substrate. Firstly, a surface oxidation process is performed on the transitional silicide, so as to form a protective layer on the transitional silicide. Then, a HPM stripping process is performed on the silicon substrate in order to strip the remnant metal.