TiN Metal Gate Structure for Threshold Voltage Stability
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Solution Overview
Problem
In integrated circuit fabrication, particularly in CMOS technology, the shrinking technology nodes pose challenges in achieving a stable threshold voltage due to atomic diffusion between adjacent metal gates, leading to device instability and failure.
Innovation Solution
A method is introduced to fabricate a metal gate structure using a 'gate last' process, where an oxygen-containing or fluorine-containing TiN layer is formed over the gate dielectric to prevent Al atomic diffusion, maintaining the effective thickness of the gate dielectric and stabilizing the threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a metal gate structure is formed using a gate last process, then the number of subsequent high temperature processing steps is reduced, but atomic diffusion between adjacent gates causes threshold voltage shifts and device instability
Solution Approach 1:
A TiN barrier layer is introduced as an intermediary between adjacent metal gate structures. This TiN layer prevents atomic diffusion of metal atoms between neighboring gates, thereby stabilizing threshold voltage while allowing the gate last process to proceed with reduced subsequent processing steps.
Solution Approach 2:
The harmful atomic diffusion process is extracted and blocked by introducing a separate TiN barrier layer. This layer specifically targets and prevents the diffusion of metal atoms between adjacent gates, separating the gate formation process from the unwanted atomic migration.
2Area of moving object
If technology nodes are shrunk to improve device integration, then device density increases, but atomic diffusion between adjacent gates becomes more significant causing device failure
Solution Approach 1:
The TiN barrier layer serves as a mediator that becomes increasingly critical as technology nodes shrink. With reduced spacing between adjacent gates, the barrier layer's role in preventing atomic diffusion becomes more significant, enabling higher device density without proportionally increasing diffusion-related failures.
Solution Approach 2:
The TiN barrier layer is formed in advance to prevent atomic diffusion before it can occur. By establishing this protective layer prior to metal gate formation, the patent preemptively counteracts the harmful diffusion effect that would otherwise be exacerbated by smaller technology nodes.
3Speed
If the effective thickness of gate dielectric is reduced to improve device performance, then switching speed increases, but threshold voltage becomes more sensitive to process variations
Solution Approach 1:
The TiN barrier layer acts as an intermediary that stabilizes the gate dielectric interface. By preventing metal atom diffusion into the gate dielectric, this layer reduces threshold voltage sensitivity to process variations even when the dielectric thickness is reduced to achieve faster switching speeds.
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 enhances device performance by reducing the sensitivity of threshold voltage to process variations, thereby improving the stability and reliability of CMOS devices.
Implementation Method 1
atomic diffusion between adjacent gates causes shifts in the threshold voltage of CMOS devices
Implementation Method 2
doping a first portion of the TiN layer using an oxygen-containing plasma treatment; doping a second portion of the TiN layer using a nitrogen-containing plasma treatment
Data Source
AI summary
A method of making a semiconductor device includes depositing a TiN layer over a substrate. The method further includes doping a first portion of the TiN layer using an oxygen-containing plasma treatment. The method further includes doping a second portion of the TiN layer using a nitrogen-containing plasma treatment, wherein the second portion of the TiN layer directly contacts the first portion of the TiN layer. The method further includes forming a first metal gate electrode over the first portion of the TiN layer. The method further includes forming a second metal gate electrode over the second portion of the TiN layer, wherein the first metal gate electrode has a different work function from the second metal gate electrode, and the second metal gate electrode directly contacts the first metal gate electrode.