Cyclic Etch Process for FinFET Fin Uniformity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In the semiconductor industry, the fabrication of three-dimensional designs such as FinFET and GAA transistors faces challenges in achieving uniform fin critical dimensions, reduced tapering, and line width roughness due to variations in fin density and pitch across different regions of the semiconductor device.
Innovation Solution
A cyclic etch process is employed, involving a polymer deposition phase and a material removal phase, using varying process gases and plasma parameters to form a second patterned mask that defines fins in the semiconductor layer, thereby reducing fin critical dimension variation, tapering, and line width roughness across different regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional etch process is used to form fins in the semiconductor layer, then the fabrication process is simple and fast, but the fin critical dimensions show high variation, significant tapering, and line width roughness across regions with different fin densities
Solution Approach 1:
The etch process is divided into multiple sequential etch cycles, where each cycle consists of etching a portion of the mandrel and then removing a portion of the mask layer. This segmentation allows progressive formation of fins with controlled critical dimensions, reducing variation and tapering compared to a single-step etch process
Solution Approach 2:
A mask layer is formed over the semiconductor layer before the etch cycles begin, and this mask layer is specifically designed to be removed in portions during the etch cycles. The preliminary formation of this protective mask layer enables precise control over the etching process and final fin dimensions
2Productivity
If the fin density varies across different regions of the semiconductor device, then higher device density is achieved, but the etch loading varies causing non-uniform fin depths and increased critical dimension variation
Solution Approach 1:
The etch process uses periodic etch cycles with alternating deposition and etching steps. This periodic action allows the process to accommodate varying etch loading across different regions by repeatedly adjusting the etch conditions, resulting in more uniform fin depths across high-density and low-density regions
Solution Approach 2:
The etch process parameters are changed between cycles and regions to compensate for varying etch loading. By adjusting parameters such as etch time, power, and gas flow during different cycles, the process maintains uniform fin critical dimensions across regions with different fin densities
3Area of moving object
If the pitch between fins is reduced to increase device density, then more fins fit in the same area, but line width roughness and critical dimension control become more difficult
Solution Approach 1:
The multi-cycle etch process segments the formation of closely-spaced fins into controlled stages, allowing each fin to be formed with precise dimensional control even when pitch is reduced. This prevents line width roughness that would occur in single-step etching of high-density fin structures
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
The cyclic etch process results in more uniform fin depths and reduced etch loading across regions with different densities, leading to improved line width roughness and reduced fin tapering, enhancing the overall semiconductor device performance.
Implementation Method 1
a first phase to form a polymer layer over the first patterned mask
Implementation Method 2
performing a cyclic etch process... using varying process gases and plasma parameters
Data Source
AI summary
A semiconductor device and method for forming the semiconductor device are provided. A first layer is formed over a semiconductor layer, and a first patterned mask is formed over the first layer. A cyclic etch process is then performed to define a second patterned mask in the first layer. The cyclic etch process includes a first phase to form a polymer layer over the first patterned mask and a second phase to remove the polymer layer and to remove a portion of the first layer. A portion of the semiconductor layer is removed using the second patterned mask to define a fin from the semiconductor layer.