Mask-Free Gate Formation for Dissimilar Threshold Voltages
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Solution Overview
Problem
Conventional semiconductor fabrication methods for creating multiple gate electrodes with different threshold voltages are costly due to the use of photolithographic technologies and masks, which are undesirable in a competitive business environment.
Innovation Solution
A method involving the formation of first and second cavities in a dielectric structure with selective isotropic etches to create retained portions of material layers, allowing for the formation of gate structures with varying channel lengths and work-function materials without the need for additional photolithography masks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If photolithographic technologies and masks are used to create multiple gate electrodes with different threshold voltages, then manufacturing precision is improved, but device complexity and fabrication cost increase
Solution Approach 1:
The gate electrode is segmented into multiple portions (first gate electrode portion, second gate electrode portion) with different work-function materials deposited in different regions. This segmentation allows different threshold voltages to be achieved through selective material deposition rather than using complex photolithographic masking processes.
Solution Approach 2:
Different work-function materials are deposited in different local regions of the gate electrode structure. The first work-function material is deposited in a first region and the second work-function material in a second region, creating local variations in threshold voltage without requiring global photolithographic patterning.
2Manufacturing precision
If photolithographic masks are used to adjust gate electrode characteristics, then manufacturing precision is improved, but fabrication cost increases
Solution Approach 1:
The mechanical photolithographic masking system is replaced with a vapor deposition system that can selectively deposit work-function materials in different regions. This substitution eliminates the need for expensive masks and photolithographic tools while maintaining precise control over gate electrode characteristics.
Solution Approach 2:
The approach changes from using photolithographic parameters (mask patterns, exposure conditions) to controlling deposition parameters (material selection, deposition location, layer thickness) to achieve the desired gate electrode characteristics. This parameter change enables cost-effective fabrication while maintaining manufacturing precision.
3Adaptability or versatility
If multiple gate electrodes with different threshold voltages are formed using conventional methods, then device functionality is improved, but productivity decreases due to additional processing steps
Solution Approach 1:
The formation of multiple gate electrodes with different threshold voltages is merged into a single continuous process flow. The first and second work-function materials are deposited sequentially in different regions without requiring intermediate masking, alignment, or etching steps, thereby maintaining device functionality while improving fabrication throughput.
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
Enables the fabrication of semiconductor devices with multiple gate electrodes having dissimilar threshold voltages without the use of photolithography masks, reducing fabrication costs and allowing for the formation of gate electrodes with varying work-function components.
Implementation Method 1
performing a first isotropic etch on the protective layer to selectively remove a portion of the protective layer and form a retained portion of the protective layer
Implementation Method 2
performing a second isotropic etch on the first material layer to selectively remove a portion of the first material layer and form a retained portion of the first material layer
Data Source
AI summary
The present disclosure generally relates to semiconductor device fabrication and integrated circuits. More particularly, the present disclosure relates to replacement metal gate processes and structures for transistor devices having a short channel and a long channel component. The present disclosure also relates to processes and structures for multi-gates with dissimilar threshold voltages. The present disclosure further provides a method of forming structures in a semiconductor device by forming a first and second cavities having sidewalls and bottom surfaces in a dielectric structure, where the first cavity has a narrower opening than the second cavity, forming a first material layer in the first and second cavities, forming a protective layer over the first material layer, where the protective layer fills the first cavity and conformally covers the sidewall and the bottom surfaces of the second cavity, performing a first isotropic etch on the protective layer to selectively remove a portion of the protective layer and form a retained portion of the protective layer, performing a second isotropic etch on the first material layer to selectively remove a portion of the first material layer and form a retained portion of the first material layer, removing the retained portion of the protective layer, and forming a second material layer in the first and second cavities, the second material layer being formed on the retained portion of the first material layer.