Hydrogenation and Nitridization for Metal Layer Oxygen Reduction
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Solution Overview
Problem
In semiconductor devices, the presence of oxygen in titanium and titanium nitride layers increases electrical resistance due to the formation of titanium oxides, which are insulating and lead to poor adhesion between layers, resulting in increased electrical resistance and voids in contact structures.
Innovation Solution
A method involving a sequential hydrogenation and nitridization process is applied to reduce bulk and interfacial oxygen in metal layers, using a nonoxidizing plasma with hydrogen and nitrogen, followed by a thermal anneal, to minimize oxygen content and enhance adhesion between layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermal anneal silicidation process is performed after deposition of Ti and TiN layers, then electrical resistance is reduced through silicide formation, but titanium oxides (TiOx) form due to air exposure, increasing electrical resistance and creating adhesion problems
Solution Approach 1:
A titanium nitride layer is deposited over the Ti/TiN stack before thermal anneal silicidation to prevent air exposure and TiOx formation during subsequent processing steps. This preliminary protective action eliminates the harmful oxidation that would otherwise occur during the anneal process and subsequent handling.
Solution Approach 2:
The titanium nitride capping layer creates an inert barrier environment that prevents oxygen from reaching the Ti and TiN layers during thermal anneal and storage. This inert protective environment maintains the low electrical resistance by preventing the formation of insulating titanium oxides.
2Strength
If TiOx is present in contact structure, then adhesion between TiN and Co capping layer deteriorates, but removing TiOx requires additional processing steps
Solution Approach 1:
The titanium nitride capping layer is deposited in advance to prevent TiOx formation before adhesion issues can occur. This preliminary protective measure ensures good adhesion between the TiN layer and subsequent Co capping layer without requiring additional removal or treatment steps.
Solution Approach 2:
The titanium nitride capping layer extracts or removes the need for TiOx removal steps by preventing oxidation in the first place. Instead of adding steps to remove harmful TiOx, the capping layer approach eliminates the problem at its source.
3Adaptability or versatility
If air break occurs between Ti/TiN deposition and thermal anneal, then processing flexibility is improved, but TiOx formation increases due to oxygen exposure
Solution Approach 1:
The titanium nitride capping layer is deposited as a preliminary protective measure before any air breaks occur in the process flow. This allows processing flexibility with multiple air breaks while the capping layer continuously prevents oxygen exposure and TiOx formation during all subsequent steps.
Solution Approach 2:
The titanium nitride capping layer creates a permanent inert barrier that maintains protection against oxygen exposure even when air breaks occur between processing steps. This enables processing flexibility while continuously preventing harmful oxidation.
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 process effectively decreases electrical resistance by reducing oxygen concentrations in the metal layers, improving adhesion and conductivity, and preventing oxidation during subsequent processing steps.
Implementation Method 1
exposing a surface of the metal layer to a nonoxidizing plasma including hydrogen
Implementation Method 2
exposing the exposed surface of the substrate to a plasma including nitrogen
Implementation Method 3
performing a thermal anneal process on the metal layer for a particular time and at a particular temperature
Data Source
AI summary
Embodiments described herein generally relate to a sequential hydrogenation and nitridization process for reducing interfacial and bulk O atoms in a conductive structure in a semiconductor device. A hydrogenation and plasma nitridization process is performed on a metal nitride layer in a conductive structure prior to deposition of a second metal layer, thereby reducing interfacial oxygen atoms formed on a surface of the metal nitride and oxygen atoms present in the bulk metal layers of the conductive structure. As a result, adhesion of the second metal layer to the metal nitride layer is improved and the electrical resistance of the contact structure is reduced.