Cobalt-Titanium Contact Stack for Lower Resistance at Small Nodes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
As semiconductor sizes shrink, the contact resistance between different conductive materials, such as cobalt and titanium, increases due to smaller contact sizes and higher numbers of contacts, posing a challenge for efficient electron travel in semiconductor circuits.
Innovation Solution
The method involves forming a cobalt-titanium structure by depositing a titanium layer using CVD, followed by a titanium nitride layer via ALD, and then alternating layers of cobalt using PVD and CVD processes. Additionally, treatments like nitridation, hydrogen soak, and silane gas soak are applied to reduce oxidation and enhance adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If semiconductor sizes are shrunk to allow more circuits in the same space, then circuit density is improved, but contact resistance increases
Solution Approach 1:
The contact structure is divided into multiple distinct layers (titanium layer, titanium nitride layer, cobalt layers) with specific functions. The titanium layer provides adhesion, the titanium nitride layer serves as a diffusion barrier and intermediate layer, and the cobalt layers provide conductivity. This segmentation allows each layer to be optimized for its specific function, reducing overall contact resistance despite smaller contact sizes.
Solution Approach 2:
The invention uses a composite structure combining different materials (titanium, titanium nitride, cobalt) with complementary properties. Titanium provides strong adhesion to silicon, titanium nitride offers chemical stability and barrier properties, and cobalt provides low contact resistance and conductivity. This composite approach achieves both low contact resistance and reliable adhesion in miniaturized structures.
2Manufacturing precision
If titanium layer is deposited using CVD process, then film coverage is improved, but oxidation occurs increasing contact resistance
Solution Approach 1:
A titanium nitride layer is deposited immediately after the titanium layer using ALD process, creating a protective barrier before oxidation can occur. This preliminary protective action prevents the titanium from reacting with oxygen, maintaining low contact resistance while preserving the good film coverage achieved by CVD deposition.
Solution Approach 2:
The titanium nitride layer acts as an intermediary between the titanium layer and the environment. It serves as a diffusion barrier that prevents oxygen from reaching the titanium, thereby preventing oxidation. This intermediate layer maintains the beneficial adhesion properties of titanium while protecting it from harmful oxidation.
3Reliability
If multiple deposition processes are used for cobalt layers, then adhesion and film quality are improved, but process complexity increases
Solution Approach 1:
The cobalt deposition is segmented into two distinct processes: PVD for the first cobalt layer and CVD for the second cobalt layer. PVD provides excellent adhesion to the titanium nitride layer, while CVD provides superior film coverage and conformality. This segmentation allows each deposition method to contribute its strengths, achieving both good adhesion and high film quality.
Solution Approach 2:
The invention changes deposition parameters by using two different deposition methods with distinct characteristics. PVD operates with different physical conditions compared to CVD, allowing optimization of each layer for its specific function. The first cobalt layer is optimized for adhesion using PVD parameters, while the second layer is optimized for coverage using CVD parameters.
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 effectively reduces contact resistance, improves cobalt adhesion, and enhances the reliability of semiconductor devices by minimizing oxidation and eliminating the need for certain nitridation steps, thereby maximizing cobalt volume and improving film quality.
Implementation Method 1
depositing a titanium layer using a chemical vapor deposition (CVD) process
Implementation Method 2
depositing a titanium nitride layer on the titanium layer using an atomic layer deposition (ALD) process
Implementation Method 3
depositing a first cobalt layer on the titanium nitride layer using a physical vapor deposition (PVD) process
Implementation Method 4
treating the titanium layer with a nitridation process, wherein the nitridation process is nitrogen and/or hydrogen plasma
Implementation Method 5
treating the titanium layer with a nitridation process
Implementation Method 6
treating the titanium layer with a hydrogen soak and/or plasma process
Implementation Method 7
treating the titanium layer with a hydrogen soak and/or plasma process
Data Source
AI summary
Methods for producing a reduced contact resistance for cobalt-titanium structures. In some embodiments, a method comprises depositing a titanium layer using a chemical vapor deposition (CVD) process, depositing a first cobalt layer on the titanium nitride layer using a physical vapor deposition (PVD) process, and depositing a second cobalt layer on the first cobalt layer using a CVD process.