Selective Etching of Unreacted Metal Layers in Semiconductor Source/Drain Structures

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Solution Overview

Problem

Existing semiconductor manufacturing processes are inadequate for effectively forming semiconductor structures with precise dimensions and high integration levels, particularly in scaling down device sizes, due to limitations in etching selectivity and process efficiency.

Innovation Solution

A method for forming semiconductor structures involves forming a source/drain structure, depositing a metal layer, annealing it to create a metallic layer, and using an etchant with a high selectivity ratio of HF to propylene carbonate to remove unreacted metal layers, ensuring precise control and integration while maintaining the metallic layer's integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If existing semiconductor manufacturing processes are used, then general fabrication is adequate, but device scaling-down and manufacturing precision deteriorate

Engineering Contradiction:

Improvedevice scaling precisionVSAvoidprocess adequacy

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent changes the chemical parameters of the etching process by using a specific etchant composition (NH4F and HF in a volume ratio of 95:5 to 5:95) to achieve high etching selectivity. This parameter change enables precise removal of unreacted metal layers while preserving the metallic layer and source/drain structure, thereby improving device scaling precision without compromising manufacturability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces an intermediary chemical system (the etchant solution) that mediates between the unreacted metal layer and the metallic layer. The etchant acts as a selective intermediary that differentiates between unreacted metal and reacted metallic layer, enabling precise removal of one while preserving the other, thus resolving the scaling precision issue

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If metal layer is deposited and annealed to form metallic layer, then desired metallic structure is created, but unreacted metal layer remains and must be removed

Engineering Contradiction:

Improvemetallic layer integrityVSAvoidprocess steps

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies a self-service principle where the annealing process itself creates a differentiation between reacted and unreacted metal layers. The annealing treatment causes the metal layer to react with the source/drain structure, forming a metallic layer with distinct chemical properties. This self-differentiation enables subsequent selective removal of unreacted metal without affecting the metallic layer, maintaining reliability while managing complexity

Inventive Principle:

Principle #25Self-service

3Manufacturing precision

If conventional etching is used to remove unreacted metal layer, then metal removal is achieved, but dielectric materials are damaged

Engineering Contradiction:

Improvemetal layer removal precisionVSAvoiddielectric damage

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by creating a chemically differentiated structure where the unreacted metal layer and metallic layer have distinct etching susceptibilities. The etchant is formulated to selectively attack only the unreacted metal layer while being inert to the metallic layer and dielectric materials. This local chemical differentiation enables precise removal of the unreacted metal layer without damaging surrounding dielectric structures

Inventive Principle:

Principle #3Local quality

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 enables efficient removal of unreacted metal layers with high selectivity, allowing for precise semiconductor structure formation, improved integration, and reduced damage to dielectric materials, thus enhancing semiconductor performance and manufacturing efficiency.

Implementation Method 1

annealing the metal layer to react with the source/drain structure to form the metallic layer

Methodology Applied

Scientific EffectAnnealing: Annealing

Implementation Method 2

react with the source/drain structure to form a metallic layer

Methodology Applied

Scientific EffectChemical reaction: Chemical Bonding

Implementation Method 3

removing the unreacted metal layer by using an etchant including HF and propylene carbonate

Methodology Applied

Scientific EffectEtching:

Data Source

PatentUS9324820B1Method for forming semiconductor structure with metallic layer over source/drain structure

Publication Date: 2016.04.26 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A semiconductor structure and a method for forming the same are provided. The method for manufacturing a semiconductor structure includes forming a source/drain structure over a substrate and forming a metal layer on the source/drain structure. The method for manufacturing a semiconductor structure further includes reacting a portion of the metal layer with the source/drain structure to form a metallic layer on the source/drain structure. The method for manufacturing a semiconductor structure further includes removing an unreacted portion of the metal layer on the metallic layer by an etching process. In addition, the etching process includes using an etchant including HF and propylene carbonate, and the volume ratio of HF to propylene carbonate in the etchant is in a range from about 1:10 to about 1:10000.