Stacked Nanosheet Step Configuration With Etch Stop Layer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional nanosheet device processing faces challenges in forming a step region in vertical stacks, leading to tapered profiles, uniform etching issues, and compromised channel width control, which affects the electrical properties of stacked nanosheet devices.
Innovation Solution
Incorporating an etch stop layer in the vertical stack to maintain the height of the top material stack and forming a dielectric oxide structure in proximity to the step region, ensuring precise formation of a step configuration without tapering and maintaining channel width control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If conventional nanosheet device processing is used to form a step region in vertical stacks, then the step region can be formed, but tapered profiles are created and channel width control is compromised
Solution Approach 1:
An etch stop layer is introduced as an intermediary component between the top and bottom material stacks. This layer acts as a mediator that defines the step region boundary while preventing unwanted etching into the top material stack, thereby maintaining vertical profiles and precise channel width control during the formation of the step region
Solution Approach 2:
The etch stop layer is formed in advance before the etching process that creates the step region. By preparing this protective layer beforehand, the subsequent etching can proceed with precise control, forming the step region without compromising the vertical profiles or channel width of the nanosheets
2Shape
If etching is performed to create a step region, then the step configuration is achieved, but the height of the top material stack is compromised due to tapering
Solution Approach 1:
The etch stop layer serves as a protective intermediary that stops the etching process at a precisely defined location. This prevents the etchant from removing material from the top material stack, thereby maintaining its full height and vertical profile while still allowing the step region to be formed in the bottom material stack
Solution Approach 2:
The etch stop layer is deposited beforehand to establish a protective barrier before the etching process begins. This preliminary action ensures that when the etch is performed to create the step region, the top material stack is protected from damage and maintains its intended height
3Ease of manufacture
If uniform etching is applied across the vertical stack, then the etching process is simple, but the step region cannot be precisely formed
Solution Approach 1:
The etch stop layer acts as a mediator that enables selective etching. By providing a layer with different etch selectivity, the process can achieve precise step region formation through controlled etching steps, maintaining relative simplicity while improving precision
Solution Approach 2:
The introduction of the etch stop layer changes the etching parameters by creating distinct etch selectivity zones. This allows the etching process to proceed with different rates or stopping points in different regions, enabling precise step region formation without significantly complicating the overall process
Data Source
AI summary
An etch stop layer is provided in a vertical stack containing a bottom material stack and a top material stack. Notably, the etch stop layer is provided in an area in which a step region is desired and thus during the etch use to provide the step region the etch stops on the etch stop layer without tapering or compromising the height of the top material stack. Also, prior to gate formation, a dielectric oxide is formed in an area in proximity to the nanosheet step region and a portion thereof remains in the structure after nanosheet and functional gate structure formation.