Self-Aligned Metal Gate Patterning for Stacked Multi-Gate Channels
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The semiconductor industry faces challenges in selectively depositing work function metal layers for stacked multi-gate devices without damaging surrounding structures, particularly in sub-10 nanometer technology nodes where precise control is required for optimal threshold voltages and device performance.
Innovation Solution
A method involving the formation of a gate dielectric layer, dielectric plug layers, and a titanium-containing dummy liner, followed by a self-assembled blocking layer to selectively deposit work function metal layers around nanosheet/nanowire transistors, reducing the need for etching back and minimizing exposure to the top channel members.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional gate formation processes are used for stacked devices, then the process is generally adequate for intended purposes, but selective formation of different work function layers causes undesirable damages to surrounding structures
Solution Approach 1:
A titanium-containing dummy liner is introduced as an intermediary layer between the channel members and the work function metal layers. This dummy liner selectively binds the first work function metal layer, preventing it from depositing on the top active region. The dummy liner acts as a mediator that enables selective deposition without requiring aggressive etch-back processes that would damage surrounding structures.
Solution Approach 2:
The titanium-containing dummy liner is formed in advance before the work function metal layer deposition. This preliminary action creates a protective pattern that guides the subsequent selective deposition process, ensuring that the first work function metal layer only forms where needed (bottom active region) and does not damage the top active region or surrounding structures.
2Manufacturing precision
If etch-back processes are used to remove excess work function metal layer, then the first work function metal layer can be removed from the top active region, but surrounding structures suffer undesirable damage
Solution Approach 1:
The titanium-containing dummy liner serves as a selective binding agent that prevents the first work function metal layer from depositing on the top active region in the first place. This eliminates the need for etch-back processes entirely, as the selective deposition is achieved through the dummy liner's selective binding properties rather than through selective removal of excess material.
Solution Approach 2:
The dummy liner is formed beforehand to establish the selective deposition pattern. This preliminary patterning action prevents the formation of excess work function metal layer on the top active region, thereby eliminating the need for subsequent etch-back processes that would cause damage to surrounding structures.
3Ease of manufacture
If the top active region is not protected during deposition of the first work function metal layer, then the deposition process is simpler, but the top active region suffers undesirable damage
Solution Approach 1:
The titanium-containing dummy liner acts as a protective intermediary that is selectively present only on the bottom active region. This allows the first work function metal layer to be deposited over the entire structure without requiring separate protection steps for the top active region. The dummy liner's selective binding properties automatically prevent deposition on the top active region, simplifying the overall process while protecting the top active region from damage.
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 allows for precise and selective deposition of work function metal layers, enhancing the optimization of threshold voltages and reducing manufacturing complexities, thereby improving device performance and reliability in stacked multi-gate devices.
Implementation Method 1
a self-assembled precursor is used to form a blocking layer over the dummy liner
Implementation Method 2
the self-assembled precursor is configured to bind to titanium on the dummy liner such that the blocking layer is only formed on surfaces of the dummy liner
Data Source
AI summary
Methods of forming a metal gate structure of a stacked multi-gate device are provided. A method according to the present disclosure includes depositing a titanium nitride (TiN) layer over a channel region that includes bottom channel layers and top channel layers, depositing a dummy fill layer to cover sidewalls of the bottom channel layers, after the depositing of the dummy fill layer, selectively forming a blocking layer over the TiN layer along sidewalls of the top channel layers, selectively removing the dummy fill layer to release the bottom channel layers, selectively depositing a first work function metal layer to wrap around each of the bottom channel layers, forming a gate isolation layer over a top surface of the first work function metal layer, removing the blocking layer, releasing the top channel layers, and selectively depositing a second work function metal layer to wrap around each of the top channel layers.