Protective Conductive Cap on Aluminum Gate Electrodes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In semiconductor device manufacturing, the scaling of transistor gate structures leads to issues with the reliability and predictability of devices due to material interactions during contact formation, causing undesirable shifts in threshold voltage and device reliability problems, particularly with aluminum gate electrodes being vulnerable to etch/clean processes.
Innovation Solution
A method involving the formation of a protective conductive cap on the metal gate electrode, which is selectively grown or deposited in direct contact with the gate electrode, physically separating it from contact structures and preventing material intrusion, thereby maintaining the integrity of the gate structure and reducing threshold voltage shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a replacement metal gate structure is formed using aluminum gate electrode, then device performance and operational characteristics are improved, but the gate electrode becomes vulnerable to etch/clean processes during contact formation, causing material intrusion and threshold voltage shifts
Solution Approach 1:
A protective conductive cap is introduced as an intermediary layer between the aluminum gate electrode and the contact structure. This cap prevents direct interaction between the etch/clean processes and the gate electrode material, blocking harmful factors while maintaining electrical functionality through its conductive properties.
Solution Approach 2:
The protective conductive cap is formed on the gate electrode surface before the contact structure fabrication process. This preliminary protective action ensures the gate electrode is shielded during subsequent etch/clean operations, preventing material intrusion and threshold voltage shifts that would otherwise occur.
2Ease of operation
If contact structures are formed to provide electrical connection to the gate electrode, then device functionality is improved, but contact material enters and partially fills the gate cavity, affecting threshold voltage
Solution Approach 1:
The protective conductive cap serves as a mediator that allows electrical connection to be established while preventing contact material from entering the gate cavity. The cap's surface provides a safe interface for contact formation, maintaining manufacturing precision by blocking material intrusion that would otherwise affect threshold voltage.
Solution Approach 2:
The gate structure is segmented into two functional parts: the aluminum gate electrode for electrical functionality and the protective conductive cap for protection during contact formation. This segmentation allows contact structures to be formed on the cap surface without compromising the integrity or threshold voltage control of the underlying gate electrode.
3Ease of operation
If the gate electrode surface is exposed for contact formation, then electrical connection is enabled, but the exposed surface is susceptible to material intrusion and contamination
Solution Approach 1:
The protective conductive cap acts as an intermediary surface that enables contact formation while preventing material intrusion. Contact structures can be formed on the cap's exposed surface, which is resistant to etch/clean processes, thereby blocking harmful factors from reaching the underlying gate electrode.
Solution Approach 2:
The surface properties of the gate structure are changed by adding the protective conductive cap, which has different chemical and physical properties than the aluminum gate electrode. This parameter change makes the surface resistant to material intrusion during contact formation while maintaining electrical conductivity for contact connection.
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 protective conductive cap effectively prevents contact material from entering the gate electrode, enhancing device reliability and predictability by maintaining the original threshold voltage and reducing defects associated with material interactions during processing.
Implementation Method 1
selectively forming a protective conductive cap on and in direct physical contact with the planarized upper surface of the conductive metal gate electrode
Data Source
AI summary
A replacement gate structure that includes a conductive metal gate electrode is formed in a gate cavity, wherein the gate cavity is formed in a dielectric material formed above an active region of a semiconductor device. An upper surface of the conductive metal gate electrode and an upper surface of the dielectric material are planarized during a common planarization process, and a protective conductive cap is selectively formed on and in direct physical contact with the planarized upper surface of the conductive metal gate electrode. A contact structure is formed in a dielectric insulating layer formed above the replacement gate structure, the contact structure directly contacting the protective conductive cap.