Seamless Metallization Contacts via Segmented TiN Liners
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Solution Overview
Problem
The fabrication of tungsten contacts in semiconductor structures is hindered by the reaction between fluorine and titanium, leading to hollow contact defects, increased contact resistance, and distortion of the contact profile due to the formation of titanium fluoride, which also prevents detection of pinch-off and keyhole defects during the process.
Innovation Solution
A method involving the use of a sacrificial release layer with varying RF power treatments to create a graded etch rate, allowing for the formation of a fluorine-free tungsten layer and a thinner TiN liner, which eliminates residual Ti and reduces tungsten keyholes, enabling seamless metal filling and improved contact resistance by optimizing the profile and reducing voids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a thicker TiN layer is used to mitigate fluorine-titanium reaction, then the harmful reaction is reduced, but contact resistance increases due to increased barrier to electron conduction
Solution Approach 1:
The liner structure is segmented into two distinct parts: a thin TiN barrier layer at the bottom of the contact opening and a thicker TiN layer on the sidewalls. This segmentation allows the bottom TiN layer to minimize electron conduction barrier while still providing sufficient protection against fluorine-titanium reaction, thereby reducing contact resistance while mitigating harmful reactions.
Solution Approach 2:
Different thicknesses of TiN liner are applied to different locations within the contact opening. The bottom portion has a thinner TiN layer optimized for electron conduction, while the sidewalls have a thicker TiN layer optimized for fluorine barrier protection. This local quality differentiation resolves the contradiction by optimizing each region for its primary function.
2Reliability
If a thinner TiN layer is used to reduce contact resistance, then electron conduction improves, but fluorine diffusion increases towards the oxygen getter ion metalized plasma titanium
Solution Approach 1:
The liner is segmented with a thin bottom TiN layer for low contact resistance and thicker sidewall TiN layers for fluorine barrier protection. This segmentation allows the system to achieve both low contact resistance and effective fluorine diffusion prevention simultaneously.
Solution Approach 2:
The TiN layer thickness is optimized locally: thinner at the bottom for electron conduction and thicker on sidewalls for fluorine barrier. This local quality approach allows the thin bottom layer to reduce contact resistance while the thicker sidewall layers prevent fluorine diffusion.
3Object-generated harmful factors
If fluorine-titanium reaction occurs, then titanium fluoride substances are formed, but contact resistance increases and profile distortion occurs
Solution Approach 1:
A TiN barrier layer is deposited at the bottom of the contact opening before tungsten fill to prevent fluorine from reaching and reacting with the Ti contact. This preliminary protective action prevents the formation of titanium fluoride substances that would increase contact resistance and cause profile distortion.
Solution Approach 2:
The TiN barrier layer acts as an intermediary between the fluorine-containing environment and the Ti contact material. It provides a protective interface that prevents direct fluorine-titanium interaction, thereby preventing harmful titanium fluoride formation while maintaining good electrical contact properties.
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 method results in reduced tungsten keyholes, larger openings for deposition, and lower contact resistance due to the elimination of fluorine-related defects, allowing for seamless metal filling and improved inspection capabilities.
Implementation Method 1
depositing a sacrificial release layer on an insulating layer using a multi-cycle CVD process with different RF power treatments at different deposition layers of the sacrificial release layer
Implementation Method 2
forming a fluorine-free tungsten (W) layer on the conductive liners
Data Source
AI summary
The present disclosure relates to semiconductor structures and, more particularly, to seamless metallization structures and methods of manufacture. A structure includes: a contact opening formed in an oxide material and in alignment with an underlying structure; a metal liner lining the sidewalls and bottom of the contact opening, in direct electrical contact with the underlying structure; a conductive liner on the metal liner, within the contact opening; and tungsten fill material on the conductive liner and within the contact opening.