MOL Contact TiSi Capping for Low-Resistance Semiconductor Contacts
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Solution Overview
Problem
Middle of the line (MOL) contacts in semiconductor structures exhibit high resistance due to the use of titanium silicon nitride (TiSiN) layers, leading to poor connections between front end of the line (FEOL) semiconductor structures and back end of the line (BEOL) interconnects, thereby reducing the performance of packaged semiconductor structures.
Innovation Solution
A method involving selective titanium silicide (TiSi) deposition followed by a fluorine-free metal deposition, such as tungsten or molybdenum, and a plasma vapor deposition (PVD) seed layer to eliminate high resistivity TiSiN layers, enabling bottom-up tungsten fill and conformal deposition to reduce contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a TiSiN layer is used as a capping layer to prevent oxidation of TiSi, then the protection function is improved, but the contact resistance increases significantly
Solution Approach 1:
The patent removes the TiSiN capping layer from the contact structure entirely, extracting the high-resistance element that was causing poor electrical connections. The TiSi layer is left exposed without the nitrided capping layer, eliminating the 300 μohms-cm resistance problem while maintaining oxidation protection through alternative means
Solution Approach 2:
The patent changes the material composition parameter by eliminating nitrogen from the capping layer structure. Instead of using TiSiN (titanium silicon nitride), the invention uses pure TiSi (titanium silicide) with controlled thickness and composition ratios (such as TiSi2 with 50-70 at% Si), fundamentally changing the electrical resistance parameter from high to low
2Reliability
If a bilayer of TiSi and TiSiN is formed to prevent oxidation, then the protection function is improved, but the contact resistance and structural complexity increase
Solution Approach 1:
The patent extracts and removes the TiSiN layer from the bilayer capping structure, simplifying the contact architecture from two layers (TiSi + TiSiN) to a single TiSi layer. This reduction eliminates the interface between layers and reduces overall structural complexity while maintaining the essential protection function
Solution Approach 2:
The patent uses a composite approach by forming TiSi with specific composition ratios (TiSi2 with 50-70 at% Si) that provide both oxidation resistance and low electrical resistance simultaneously, eliminating the need for layered composite structures and achieving dual functionality in a single material system
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 significantly reduces contact resistance from approximately 300 μohms-cm to less than 20 μohms-cm, improving the connectivity and performance of semiconductor structures by eliminating high resistivity TiSiN layers and reducing the thickness of fluorine-free metal deposition processes.
Implementation Method 1
performing a selective titanium silicide (TiSi) deposition process on a middle-of-the-line (MOL) contact structure... where the selective TiSi deposition process is a chemical vapor deposition (CVD) process
Implementation Method 2
where the selective deposition process is a fluorine free metal deposition process of the metal material, where the fluorine free metal deposition process is a halide based atomic layer deposition (ALD) process
Implementation Method 3
or chemical vapor deposition (CVD) process using a metal chloride gas with hydrogen gas
Implementation Method 4
where the seed layer deposition process is a plasma vapor deposition (PVD) process that anneals the metal material deposited by the fluorine free metal deposition process
Implementation Method 5
where the selective etch process is a dry etch process or a wet etch process
Data Source
AI summary
Methods for reducing contact resistance include performing a selective titanium silicide (TiSi) deposition process on a middle of the line (MOL) contact structure that includes a cavity in a substrate of dielectric material. The contact structure also includes a silicon-based connection portion at a bottom of the cavity. The selective TiSi deposition process is selective to silicon-based material over dielectric material. The methods also include performing a selective deposition process of a metal material on the MOL contact structure. The selective deposition process is selective to TiSi material over dielectric material and forms a silicide capping layer on the silicon-based connection portion. The methods further include performing a seed layer deposition process of the metal material on the contact structure.