Diffusion Barrier Layers in Nanosheet Transistors
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Solution Overview
Problem
In semiconductor device fabrication, unwanted diffusion of semiconductor materials, such as germanium, between sacrificial and channel nanosheets occurs due to high thermal budgets, leading to performance issues like shifted gate threshold voltage and poor spacer formation, which existing low thermal budget processes attempt to mitigate but result in low-quality STI oxides.
Innovation Solution
The implementation of selectively formed diffusion barrier layers with controlled diffusion coefficients and thicknesses, using rare earth oxide materials, to prevent semiconductor material diffusion between sacrificial and channel nanosheets, and the formation of multi-segmented inner spacers for additional protection against downstream fabrication processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high thermal budget processes are used for nanosheet fabrication, then device performance is improved, but unwanted diffusion of semiconductor materials between sacrificial and channel nanosheets occurs
Solution Approach 1:
A buffer layer is introduced as an intermediary between the sacrificial nanosheet and the channel nanosheet. This buffer layer acts as a mediator that prevents direct unwanted diffusion of semiconductor materials while allowing the high thermal budget processes needed for device performance. The buffer layer is selectively removed later to release the channel nanosheet.
Solution Approach 2:
The buffer layer is formed in advance before the high thermal budget fabrication processes. This preliminary action establishes a protective barrier that prevents unwanted diffusion during subsequent processing steps, allowing the device to achieve desired performance without material contamination.
2Object-generated harmful factors
If low thermal budget processes are used to prevent diffusion, then unwanted diffusion is reduced, but STI oxide quality deteriorates
Solution Approach 1:
The buffer layer serves as a protective intermediary that enables high thermal budget processes to proceed without causing unwanted diffusion. This allows STI oxide formation and other high-temperature processes to complete with high quality, as the buffer layer prevents material diffusion even at elevated temperatures.
3Object-generated harmful factors
If diffusion barrier layers are formed between sacrificial and channel nanosheets, then material diffusion is prevented, but device structure complexity increases
Solution Approach 1:
The nanosheet structure is segmented into distinct functional layers: sacrificial nanosheet, buffer layer, and channel nanosheet. This segmentation allows the buffer layer to be selectively positioned and removed, preventing material diffusion while maintaining a relatively simple overall device structure that can be fabricated using standard semiconductor processes.
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 effectively prevents unwanted diffusion, maintaining desired performance characteristics and preventing channel voids that could lead to shorts, thereby ensuring reliable and efficient semiconductor device operation.
Implementation Method 1
forming a diffusion barrier layer between the sacrificial nanosheet and the channel nanosheet, wherein a diffusion coefficient of the diffusion barrier layer is selected to substantially prevent a predetermined semiconductor material from diffusing through the diffusion barrier layer
Data Source
AI summary
Embodiments of the invention are directed to a method of fabricating a semiconductor device. A non-limiting example of the method includes performing fabrication operations to form a nanosheet field effect transistor device. The fabrication operations include forming a sacrificial nanosheet and a channel nanosheet over a substrate, forming a diffusion barrier layer between the sacrificial nanosheet and the channel nanosheet, wherein a diffusion coefficient of the diffusion barrier layer is selected to substantially prevent a predetermined semiconductor material from diffusing through the diffusion barrier layer.