Vertical FET Uniform Profiles via Dummy Fin Etch Loading
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Solution Overview
Problem
Conventional semiconductor fabrication techniques for vertical FET devices face challenges in achieving uniform structural profiles due to micro-loading effects from etch and planarizing processes, leading to variations in device dimensions and performance.
Innovation Solution
The method involves forming sacrificial vertical semiconductor fins in isolation regions concurrently with device regions, using these fins to minimize etch process micro-loading effects and non-uniform topography, and replacing them with insulating dummy fins to ensure uniform gate lengths and device performance across different regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional etch processes are used to form vertical FET devices, then device fabrication can be completed, but micro-loading effects cause variation in gate length between dense and isolated regions
Solution Approach 1:
The patent forms dummy fins in isolation regions before the main etch process. These dummy fins are etched concurrently with the actual device fins, establishing a consistent etch environment and loading condition across all regions. This preliminary structuring ensures that when the gate material is deposited and recessed, all regions experience identical etch conditions, eliminating micro-loading effects and achieving uniform gate lengths.
Solution Approach 2:
The patent introduces dummy fins specifically in isolation regions where they are needed to match the etch loading of dense device regions. This localized addition of structural elements creates uniform etch conditions only where required, without affecting the device regions. The dummy fins provide local etch loading compensation, ensuring consistent gate length formation across different pattern densities.
2Shape
If CMP process is used to planarize conductive gate material, then surface flatness is improved, but dishing effects cause initial thickness variation
Solution Approach 1:
The patent forms dummy fins before depositing the conductive gate material. These dummy fins provide physical support structures that prevent CMP dishing in isolation regions during the planarization process. By having these fins in place beforehand, the CMP process maintains consistent material removal rates across all regions, preventing the formation of dished surfaces and ensuring uniform initial thickness of the gate material layer.
3Adaptability or versatility
If vertical FET devices are formed with different pattern densities, then device design flexibility is improved, but non-uniform topography causes gate length variation
Solution Approach 1:
The patent adds dummy fins specifically in isolation regions to create uniform etch loading conditions. This localized modification allows the design to maintain different pattern densities in different regions while achieving uniform manufacturing results. The dummy fins are placed only where needed (in isolation regions) to compensate for the lack of natural etch loading, enabling design flexibility without sacrificing gate length consistency.
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 enables the fabrication of vertical FET devices with uniform structural profiles and consistent gate lengths, reducing micro-loading effects and dishing issues, thereby improving device performance and reliability.
Implementation Method 1
a gate length of a metal gate is defined by a timed etching of a layer of conductive gate material, typically performed by a reactive ion etch (RIE)
Implementation Method 2
the initial thickness variation of a planarized layer of conductive gate material (prior to the gate recess), which results from dishing effects that can result from chemical mechanical polishing (CMP)
Data Source
AI summary
Semiconductor devices are fabricated with vertical field effect transistor (FET) devices having uniform structural profiles. Semiconductor fabrication methods for vertical FET devices implement a process flow to fabricate dummy fins within isolation regions to enable the formation of vertical FET devices with uniform structural profiles within device regions. Sacrificial semiconductor fins are formed in the isolation regions concurrently with semiconductor fins in the device regions, to minimize/eliminate micro-loading effects from an etch process used for fin patterning and, thereby, form uniform profile semiconductor fins. The sacrificial semiconductor fins within the isolation regions also serve to minimize/eliminate non-uniform topography and micro-loading effects when planarizing and recessing conductive gate layers and, thereby. form conductive gate structures for vertical FET devices with uniform gate lengths in the device regions. The sacrificial semiconductor fins are subsequently removed and replaced with insulating material to form the dummy fins.