Nanosheet Fin Height Control Across Dense and Isolation Regions
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Solution Overview
Problem
Nanosheet-based semiconductor devices face challenges with height variations due to differences in oxide quality, recess rates, and processing depths, particularly in multiple region structures like dense array and isolation regions, leading to inconsistent fin heights.
Innovation Solution
The solution involves forming fin structures composed of stacked nanosheets with a trench isolation region separating dense array and isolation regions, using a selective etch process to maintain uniform fin heights across both regions, and employing a conformal dielectric liner to protect and define the fin structures during etching, ensuring consistent nanosheet heights.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a dense array of fin structures is formed in the array region, then the device density and drive current are improved, but the fin height varies due to differences in oxide quality and recess rates compared to the isolation region
Solution Approach 1:
The substrate is divided into an array region and an isolation region separated by a trench isolation structure. This segmentation allows independent processing and height control for each region, enabling the dense array of fin structures to be formed in the array region while maintaining uniform fin height across both regions by adjusting processing parameters independently for each region.
Solution Approach 2:
Different processing conditions are applied to different regions: the array region receives processing optimized for high device density with selective etching, while the isolation region receives processing optimized for height control. This local quality approach allows the fin height to be uniform across regions while maintaining high device density in the array region.
2Manufacturing precision
If the trench isolation region is formed to separate array and isolation regions, then the fin height uniformity is improved, but the device complexity and processing steps increase
Solution Approach 1:
The trench isolation structure serves multiple functions: it physically separates the array region from the isolation region, provides a reference plane for height control, and enables independent processing of each region. This multi-functionality allows fin height uniformity to be achieved without proportionally increasing device complexity, as the same isolation structure accomplishes multiple objectives.
3Manufacturing precision
If selective etching is used to form fin structures with uniform height, then the nanosheet height control is improved, but the etch process complexity and processing time increase
Solution Approach 1:
A sacrificial layer is formed beforehand on the substrate before forming the fin structures. This preliminary action provides a controlled etch stop layer that enables selective etching to proceed efficiently with uniform depth control. The pre-formed sacrificial layer allows the etch process to terminate automatically at a predetermined depth, improving nanosheet height control while reducing the need for complex real-time process monitoring.
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 ensures precise control over nanosheet active heights, reducing variations and enhancing the uniformity of fin structures, thereby improving the reliability and performance of nanosheet devices.
Implementation Method 1
etching of a base nanosheet in the stack of nanosheets that is in direct contact with the substrate employs an etch process that is selective to the substrate
Implementation Method 2
forming a protective liner on the plurality of fin structures; and forming a second depth trench in the substrate. In some embodiments, the protective liner protects the dense array of fin structures and the isolation fin structures during etch processes
Data Source
AI summary
A semiconductor device including a substrate having a dense array region and an isolation region. The semiconductor device includes plurality of first fin structures of stacked nanosheets is present in the dense array region separated by a single pitch, wherein each fin structure in the first plurality of fin structures has a same first nanosheet height as measured from an upper surface of the substrate in the dense array region. The semiconductor device further includes at least one second fin structure of stacked nanosheets is present in the isolation region, wherein a number of second fin structure in the isolation region is less than a number of first fin structures in the dense array region, the at least one fin structure having a second nano sheet height that is measured from the upper surface of the substrate in the isolation region that is the same as the first nanosheet height.