Metal Carbide Gate with Electropositive Element for Threshold Voltage Control
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Solution Overview
Problem
Semiconductor devices with metal gates and high-K gate dielectrics face challenges in achieving low threshold voltage and effective device scaling due to increased effective oxide thickness and complexity in dual-metal gate integration, particularly with the presence of magnesium oxide.
Innovation Solution
A semiconductor device structure featuring a metal carbide gate with a transition metal and an electropositive element, such as tantalum, magnesium, and carbon, directly interfaced with the gate dielectric, which is formed using co-sputtering or other deposition methods to lower the work function and threshold voltage without adverse effects on high-K gate dielectrics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If magnesium oxide is added to the gate dielectric layer to lower threshold voltage, then the threshold voltage is lowered, but the effective oxide thickness increases limiting device scaling
Solution Approach 1:
The patent extracts the threshold voltage control function from the gate dielectric layer and relocates it to the metal gate layer by incorporating electropositive elements. This separation allows the gate dielectric to maintain its original thickness for scaling while the metal gate composition controls the threshold voltage, resolving the contradiction between threshold voltage adjustment and effective oxide thickness minimization.
Solution Approach 2:
The patent changes the compositional parameters of the metal gate layer by incorporating electropositive elements (such as magnesium, calcium, or rare earth elements) to adjust the work function and control threshold voltage. This parameter change in the metal gate composition eliminates the need to change the gate dielectric thickness, thereby maintaining minimal effective oxide thickness while achieving desired threshold voltage.
2Reliability
If magnesium oxide is added to lower threshold voltage, then threshold voltage control is improved, but dual-metal gate integration becomes more challenging
Solution Approach 1:
The patent applies local quality by incorporating electropositive elements specifically in the n-type metal gate layer to achieve n-type threshold voltage characteristics, while the p-type metal gate layer can use different compositions. This localized compositional differentiation enables independent optimization of n-type and p-type device thresholds without requiring complex removal or modification processes, simplifying dual-metal gate integration.
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 solution effectively lowers the threshold voltage of N-channel devices while maintaining minimal effective oxide thickness, facilitating device scaling and simplifying dual-metal gate integration by incorporating an electropositive element in the metal carbide gate.
Implementation Method 1
formed using co-sputtering or other deposition methods
Data Source
AI summary
A semiconductor device structure is formed over a semiconductor substrate and has a gate dielectric over the semiconductor substrate and a gate over the gate dielectric. The gate, at an interface with the gate dielectric, comprises a transition metal, carbon, and an electropositive element. The transition metal comprises one of group consisting of tantalum, titanium, hafnium, zirconium, molybdenum, and tungsten. The electropositive element comprises one of a group consisting of a Group IIA element, a Group IIIB element, and lanthanide series element.