Tungsten Capping Layer for Low Contact Resistance in IC Fabrication
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Solution Overview
Problem
Existing IC fabrication methods are inadequate in developing improved dielectric and metal interconnection processes and structures, particularly in reducing contact resistance and optimizing the use of tungsten layers, which affects the complexity and efficiency of IC manufacturing.
Innovation Solution
A method involving the use of a non-fluorine-containing tungsten capping layer formed by metal-organic chemical vapor deposition (MOCVD) as a barrier and capping layer for subsequent bulk tungsten layer formation, along with a pre-silicide metal layer and annealing processes to reduce contact resistance and enhance device reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional tungsten deposition methods are used, then contact resistance is reduced, but manufacturing complexity increases due to multiple process steps
Solution Approach 1:
The patent combines the tungsten capping layer formation and bulk tungsten deposition into a single continuous MOCVD process step. The tungsten capping layer is formed first, then bulk tungsten is deposited over it without breaking the vacuum or changing the deposition method, merging two separate process steps into one integrated operation that reduces manufacturing complexity while maintaining low contact resistance
Solution Approach 2:
The tungsten capping layer is formed as a preliminary step before bulk tungsten deposition. This pre-formed capping layer serves as a foundation that enables subsequent bulk tungsten to be deposited with better adhesion and lower contact resistance, preparing the surface in advance to achieve improved electrical properties
2Productivity
If fluorine-containing gases are used in tungsten deposition, then deposition speed increases, but contact resistance increases and device reliability decreases
Solution Approach 1:
The patent changes the chemical composition parameter of the deposition gas from fluorine-containing to non-fluorine-containing gases in the MOCVD process. This parameter change enables the formation of a tungsten capping layer with lower contact resistance while maintaining acceptable deposition speeds through optimized process conditions
Solution Approach 2:
The patent creates a composite structure with a tungsten capping layer formed from non-fluorine-containing gases over the conductive feature. This composite material approach, where the tungsten layer has a specific composition achieved through controlled deposition, provides both adequate deposition speed and reduced contact resistance
3Productivity
If bulk tungsten volume is minimized, then manufacturing efficiency improves, but contact resistance may increase
Solution Approach 1:
The patent applies local quality by creating a tungsten capping layer with specific properties (low contact resistance) at the critical interface region where it contacts the conductive feature. The bulk tungsten volume is minimized elsewhere, but the localized quality of the capping layer at the contact point ensures low contact resistance is maintained
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 reduces contact resistance, minimizes the volume of tungsten used, and simplifies the integration process while providing self-alignment during metal etching and improving device reliability through the formation of a metal feature with an Al-C alloy.
Implementation Method 1
forming a tungsten (W) capping layer by metal-organic chemical vapor deposition (MOCVD)
Implementation Method 2
applying an annealing to form a silicide region in the conductive feature
Data Source
AI summary
A method of fabricating an integrated circuit (IC) is disclosed. The method includes providing a substrate having a conductive feature. A dielectric layer is formed over the substrate, having an opening to expose the conductive feature. A tungsten (W) capping layer is formed over the conductive feature in the opening without using fluorine-containing gases. A bulk W layer is formed over the W capping layer.