Multi-Threshold-Voltage Device Fabrication Using Sacrificial Barrier Layers

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Solution Overview

Problem

The existing methods for forming multi threshold-voltage (Vth) semiconductor devices damage the high-k dielectric layer due to repeated etching and re-deposition of titanium nitride (TiN) layers, leading to interface damage.

Innovation Solution

The formation of barrier layers between TiN layers allows for selective etching of each TiN layer, preventing damage to the underlying high-k dielectric layer by using a multi-stack of alternating barrier and TiN layers, which are deposited and etched in a controlled manner to achieve desired thicknesses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If TiN layers are etched all the way down to the high-k dielectric layer to form multi Vth devices, then different TiN thicknesses can be achieved, but the high-k dielectric layer is damaged and exposed to etchants

Engineering Contradiction:

ImproveTiN thickness controlVSAvoidhigh-k dielectric layer damage

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

A sacrificial oxide layer is introduced as an intermediary between the TiN layers and the high-k dielectric layer. This sacrificial layer absorbs the etching damage, preventing direct contact between etchants and the high-k dielectric layer while still allowing precise control of TiN thicknesses through selective etching processes

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The sacrificial oxide layer is deposited beforehand to cushion and protect the high-k dielectric layer from subsequent etching damage. This protective layer is strategically positioned to absorb the full impact of etchants during the TiN thickness adjustment process, ensuring the underlying high-k dielectric remains intact

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Adaptability or versatility

If TiN is deposited and re-deposited multiple times to form multi Vth devices, then different threshold voltages can be achieved, but the process becomes highly complex

Engineering Contradiction:

Improvemulti Vth capabilityVSAvoidfabrication process complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The TiN structure is segmented into multiple discrete layers separated by sacrificial oxide layers. This segmentation allows independent thickness control of each TiN layer through selective etching, enabling multi Vth device formation from a single deposition sequence rather than requiring multiple complete deposition cycles

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

All TiN layers are deposited in advance with uniform thickness before any etching occurs. The subsequent selective removal of sacrificial oxide layers and portions of TiN layers creates the desired thickness variations, eliminating the need for repeated deposition and etching cycles

Inventive Principle:

Principle #10Preliminary 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 enables the formation of multi Vth devices without damaging the high-k dielectric layer, allowing for precise control of TiN thicknesses and improving the integrity of the TiN to high-k dielectric interface, suitable for advanced technology nodes like 14 nm and 10 nm.

Implementation Method 1

removing the third TiN layer in second and third regions, exposing the second barrier layer in the second and third regions

Methodology Applied

Scientific EffectEtching:

Implementation Method 2

removing the first and second masking layers by ashing

Methodology Applied

Scientific EffectAashing:

Implementation Method 3

depositing the TiN and barrier layers by chemical vapor deposition (CVD), atomic layer deposition (ALD), or physical vapor deposition (PVD)

Methodology Applied

Scientific EffectPhysical vapor deposition: Physical Vapour Deposition

Implementation Method 4

depositing the TiN and barrier layers by chemical vapor deposition (CVD), atomic layer deposition (ALD), or physical vapor deposition (PVD)

Methodology Applied

Scientific EffectChemical vapor deposition: Chemical Vapour Deposition

Data Source

PatentUS10020202B2Fabrication of multi threshold-voltage devices

Publication Date: 2018.07.10 GLOBALFOUNDRIES US INC

AI summary

A method of fabricating multi Vth devices and the resulting device are disclosed. Embodiments include forming a high-k dielectric layer over a substrate; forming a first TiN layer, a first barrier layer, a second TiN layer, a second barrier layer, and a third TiN layer consecutively over the high-k dielectric layer; forming a first masking layer over the third TiN layer in a first region; removing the third TiN layer in second and third regions, exposing the second barrier layer in the second and third regions; removing the first masking layer; removing the exposed second barrier layer; forming a second masking layer over the third TiN layer in the first region and the second TiN layer in the second region; removing the second TiN layer in the third region, exposing the first barrier layer in the third region; removing the second masking layer; and removing the exposed first barrier layer.