MOSFET Gate Electrode Composition Control via Selective Silicidation
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Solution Overview
Problem
Conventional methods for manufacturing semiconductor devices with metal gate electrodes face challenges in controlling the work function and threshold voltage of MOSFETs, particularly with fully silicided gates, where the composition changes are limited and difficult to achieve the desired values.
Innovation Solution
A method involving the formation of gate electrodes with different compositions for n-type and p-type MOSFETs using high dielectric insulating films, where a first metal containing layer and a second metal containing layer are selectively removed, and a third metal containing layer is formed to react with the gate electrode layers, resulting in silicide formation through thermal processing, allowing for precise control of the threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a FUSI gate is used to suppress the gate depletion layer, then the MOSFET performance is improved, but the work function and threshold voltage cannot be controlled to a desired value
Solution Approach 1:
The patent changes the composition parameters of the metal gate electrode by using different ratios of Ni and Si, and by controlling the thickness of the silicide layer formed through thermal processing. This allows precise adjustment of the work function and threshold voltage while maintaining the FUSI gate structure for suppressed gate depletion layer
Solution Approach 2:
The patent creates a composite metal gate structure consisting of Ni and Si layers that form NiSi silicide through thermal processing. This composite material approach enables simultaneous achievement of low resistance (from silicided structure) and controllable work function (from adjustable Ni:Si ratio)
2Manufacturing precision
If the composition of the FUSI gate is changed to adjust the threshold voltage, then the threshold voltage can be modified, but the Ni on the polysilicon cannot be adequately removed with the mixture of hydrochloric acid and hydrogen peroxide
Solution Approach 1:
The patent changes the chemical parameters of the etching solution by replacing hydrochloric acid with sulfuric acid in the mixture. This parameter change enables adequate removal of Ni from polysilicon while allowing precise control of threshold voltage through composition adjustment of the metal gate electrode
Solution Approach 2:
The patent introduces a protective film as an intermediary layer during the metal gate formation process. This protective film enables selective removal of Ni in certain regions while preserving Ni in other regions, facilitating both threshold voltage control and complete Ni removal where needed
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 formation of MOSFETs with distinct threshold voltages for n-type and p-type devices, improving the control over the work function and threshold voltage, addressing the limitations of existing methods.
Implementation Method 1
performing a thermal processing, thereby causing reaction between the metal contained in said first metal containing layer and said first gate electrode layer to convert said first gate electrode layer into an alloy
Data Source
AI summary
A method of manufacturing a semiconductor device having a MOSFET of a first conductivity type and a MOSFET of a second conductivity type different from the first conductivity type formed on a semiconductor substrate, the method has: forming a gate insulating film; forming a first gate electrode layer, and forming a second gate electrode layer; forming a first metal containing layer on said first gate electrode layer and said second gate electrode layer; forming a second metal containing layer for preventing diffusion of a metal on said first metal containing layer; forming a third metal containing layer on said second gate electrode layer from which said first metal containing layer and said second metal containing layer are selectively removed, the third metal containing layer having a thickness different from the thickness of said first metal containing layer in a case where the third metal containing layer contains the same metal or alloy as the metal or alloy contained in said first metal containing layer; and performing a thermal processing, thereby causing reaction between the metal contained in said first metal containing layer and said first gate electrode layer to convert said first gate electrode layer into an alloy and causing reaction between the metal contained in said third metal containing layer and said second gate electrode layer to convert said second gate electrode layer into an alloy, thereby forming gate electrodes of different compositions.