GAA Nanostructure Gate Stack for Uniform Source-Drain Current
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Solution Overview
Problem
The semiconductor industry faces challenges in forming reliable semiconductor devices at increasingly smaller sizes due to the complexity and difficulty of fabrication processes as feature sizes decrease, affecting production efficiency and cost.
Innovation Solution
The implementation of a gate all around (GAA) transistor structure formed using a nanostructure stack with a gate stack and spacer structures, along with source/drain layers and contact structures, to improve current uniformity and device performance by ensuring consistent distances between nanostructures and contact structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If feature sizes are decreased to increase functional density, then production efficiency and cost are improved, but fabrication process complexity and difficulty increase
Solution Approach 1:
The fabrication process is divided into multiple patterning steps (e.g., self-aligned double patterning, self-aligned triple patterning) where each step creates a portion of the final pattern. This segmentation allows complex nanoscale features to be formed through simpler, more controllable sequential steps rather than attempting to create all features in a single complex lithography step.
Solution Approach 2:
Mandrel structures and spacer structures are formed in advance before the final pattern transfer. These preliminary structures serve as templates and alignment references for subsequent etching steps, ensuring precise feature placement and dimensions are achieved before the actual device features are created.
2Area of stationary object
If feature sizes are decreased to increase functional density, then chip area utilization is improved, but manufacturing precision requirements increase
Solution Approach 1:
Self-aligned patterning techniques are employed where subsequent pattern layers are automatically aligned to previous layers through physical attachment (spacers formed on mandrels, second mandrels formed on first spacers). This creates an equipotential alignment system where registration errors are minimized because each layer is defined relative to the previous layer rather than requiring absolute position control.
Solution Approach 2:
The patent employs multiple etching selectivities and deposition thicknesses as controllable parameters. By carefully selecting etch chemistry, power, pressure, and spacer deposition thickness, precise control over feature dimensions is achieved. The spacer thickness directly determines the pitch of the final pattern, providing a simple parameter to control feature spacing with high precision.
3Ease of manufacture
If conventional planar transistor structures are used, then fabrication is simpler, but current uniformity and device performance deteriorate
Solution Approach 1:
The patent transitions from planar (2D) gate structures to three-dimensional gate-all-around structures where the gate electrode completely surrounds the channel in multiple dimensions. This dimensional change provides superior electrostatic control over the channel, ensuring uniform current flow through the nanostructures while maintaining compatibility with standard semiconductor fabrication processes.
Solution Approach 2:
The device structure employs nested configurations where gate electrodes are positioned around nanostructures, which are themselves surrounded by dielectric materials and contact structures. This nested arrangement allows the gate to control current flow from multiple directions simultaneously, improving current uniformity while the self-aligned fabrication approach keeps the manufacturing process manageable.
Data Source
AI summary
A semiconductor device structure is provided. The semiconductor device structure includes a substrate. The semiconductor device structure includes a first nanostructure over the substrate. The semiconductor device structure includes a gate stack over the substrate and surrounding the first nanostructure. The gate stack is partially embedded in the first nanostructure. The semiconductor device structure includes a first source/drain layer surrounding the first nanostructure and adjacent to the gate stack. The semiconductor device structure includes a contact structure surrounding the first source/drain layer. A first portion of the contact structure is between the first source/drain layer and the substrate.