Stacked GAA Gate Dielectrics for Independent nMOS/pMOS Thresholds
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Solution Overview
Problem
Conventional semiconductor device scaling techniques face challenges in creating stacked transistors with different threshold voltages, particularly for complementary field effect transistors, where forming distinct gate dielectrics for n-channel and p-channel MOSFETs is difficult.
Innovation Solution
A method involving a substrate with a gap, where a first layer is formed on nanosheets, encapsulated in a gap filling fluid, and selectively etched to protect it from etching, allowing a second layer with different composition to be formed on exposed nanosheets, followed by removal of the fluid and annealing to form distinct gate dielectrics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional scaling techniques are used to create stacked transistors, then device density and speed are improved, but the ability to form distinct gate dielectrics for different threshold voltages deteriorates
Solution Approach 1:
The gap filling fluid is segmented into two distinct regions: a first region containing the first gap filling fluid and a second region containing the second gap filling fluid. This spatial segmentation allows each region to be selectively removed to form different gate dielectric structures, enabling independent threshold voltage control while maintaining the stacked transistor configuration for high device density
Solution Approach 2:
The gap filling fluids act as intermediary materials that temporarily occupy the gaps between nanosheets during fabrication. These intermediaries are selectively removed to reveal underlying structures or form desired gate dielectric configurations, enabling precise control over threshold voltages without compromising the overall device scaling and density
2Manufacturing precision
If gap filling fluid is used to protect first layer during selective etching, then manufacturing precision is improved, but process complexity increases
Solution Approach 1:
The gap filling fluids are deposited in advance before the selective etching process. The first gap filling fluid is deposited to fill a portion of the gaps, then the second gap filling fluid is deposited to fill remaining gaps. This preliminary action creates a protective mask that enables precise selective removal of the first layer in specific regions, achieving high manufacturing precision while the multi-step deposition is managed through standardized process sequences
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 formation of complementary field effect transistors with independently controlled threshold voltages by creating distinct gate dielectrics for nMOS and pMOS parts, facilitating improved device performance and scalability.
Implementation Method 1
selectively etching the first layer with respect to the gap filling fluid. Thus, the first layer is removed from the second set of nanosheets
Implementation Method 2
the substrate can be annealed. Thus, a first gate dielectric is formed from the first layer and the high-k dielectric and a second gate dielectric is formed from the second layer and the high-k dielectric
Data Source
AI summary
Disclosed are methods and related systems for forming a structure. Embodiments of presently described methods comprise employing a sacrificial gap filling fluid for selectively forming a first layer on one or more first surfaces in a lower part of a gap, and forming a second layer on one or more second surfaces in an upper part of a gap.