Metal Oxide Gate Stack for Ultra-Low Threshold Voltage MOS
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Solution Overview
Problem
Current methods for reducing threshold voltage in transistors are approaching their limits, particularly for advanced technologies beyond the 3 nm node, and face challenges such as shadowing effects from doping, surface oxidation, and loss of conductor characteristics in high-work-function materials, which hinder the achievement of ultra-low threshold voltages without adverse effects on device performance.
Innovation Solution
The formation of ultra-thin metal oxides as the metal gate electrode in p-type MOS devices, involving a deposition process of a p-type work function metal film, an in-situ capping layer, and an ex-situ oxygen plasma treatment to transform the metal film into a metal oxide film, achieving a work function above 4.9-5.1 eV close to the semiconductor substrate's band edge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If existing methods are used to reduce threshold voltage, then threshold voltage is reduced to some extent, but the methods are approaching their limit and cannot achieve ultra-low threshold voltages beyond 3 nm node
Solution Approach 1:
The patent changes the work function parameter of the gate electrode by using metal oxide materials (such as ruthenium oxide, iridium oxide) with work functions above 4.9-5.1 eV, which is a significant increase from conventional gate materials. This parameter change enables ultra-low threshold voltages that cannot be achieved with existing gate materials, thereby resolving the limitation of current threshold voltage reduction methods for advanced technology nodes beyond 3 nm.
2Manufacturing precision
If high-work-function materials are used to reduce threshold voltage, then threshold voltage is reduced, but the materials lose conductor characteristics and suffer from surface oxidation
Solution Approach 1:
The patent employs composite material structures where metal oxide work function layers (such as ruthenium oxide, iridium oxide) are combined with conductive materials. The metal oxide layer provides the high work function necessary for low threshold voltage, while the composite structure maintains conductor characteristics. This composite approach resolves the contradiction between achieving low threshold voltage and maintaining material reliability against oxidation and conductor property loss.
3Manufacturing precision
If doping is used to reduce threshold voltage, then threshold voltage is reduced, but shadowing effects occur that degrade device performance
Solution Approach 1:
The patent extracts and eliminates the doping process from the threshold voltage control mechanism. Instead of using doping to reduce threshold voltage, the invention uses metal oxide work function materials with inherently high work functions (above 4.9-5.1 eV) to achieve ultra-low threshold voltages. This extraction of the doping step removes the source of shadowing effects and associated device performance degradation, while still achieving the desired low threshold voltage.
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 enables the achievement of ultra-low threshold voltages, improves device performance by reducing gate resistance, simplifies fabrication processes, and lowers production costs, while maintaining power efficiency and enhancing material stability against oxidation.
Implementation Method 1
an ex-situ oxygen plasma treatment to transform the metal film into a metal oxide film
Implementation Method 2
a deposition process of a p-type work function metal film
Data Source
AI summary
A method of manufacturing a semiconductor device is provided. A substrate is provided. The substrate has a first region and a second region. An n-type work function layer is formed over the substrate in the first region but not in the second region. A p-type work function layer is formed over the n-type work function layer in the first region, and over the substrate in the second region. The p-type work function layer directly contacts the substrate in the second region. And the p-type work function layer includes a metal oxide.