Semiconductor Capacitor Hard Mask Layout for Profile Uniformity
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Solution Overview
Problem
Existing methods for forming semiconductor capacitors face challenges in achieving uniform profiles and balanced capacitance due to variations in etching rates and mask layer thicknesses, leading to misalignment and increased capacitance issues.
Innovation Solution
A method involving the sequential formation of dielectric and sacrificial layers with distinct hard mask layers of varying thicknesses and dopant types, where the first hard mask layer is etched faster than the second, resulting in improved profile control and reduced capacitance variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single hard mask layer is used in existing methods, then the manufacturing process is simpler, but the profile uniformity and capacitance balance deteriorate due to etching rate variations
Solution Approach 1:
The single hard mask layer is segmented into two distinct hard mask layers with different thicknesses and dopant types. The first hard mask layer has a first thickness and first dopants, while the second hard mask layer has a second thickness and second dopants. This segmentation allows differential etching rates that compensate for profile variations and achieve balanced capacitance across capacitors formed in the dielectric stack.
Solution Approach 2:
Different regions of the mask structure are assigned different local properties: the first hard mask layer contains first dopants with specific concentration ranges, while the second hard mask layer contains second dopants with different concentration ranges. This local quality differentiation enables precise control of etching rates in different vertical zones, improving profile uniformity and capacitance balance.
2Reliability
If uniform thickness hard mask layers are used, then the manufacturing process is easier, but capacitance balance deteriorates due to etching rate variations through the dielectric stack
Solution Approach 1:
The hard mask structure employs asymmetric thickness distribution: the first hard mask layer has a first thickness, and the second hard mask layer has a second thickness that differs from the first. This asymmetric design compensates for the varying etching rates encountered when etching through different depths of the dielectric stack, ensuring that all capacitors achieve balanced capacitance values despite the complexity of the asymmetric mask structure.
3Manufacturing precision
If the same dopant type is used in both hard mask layers, then the manufacturing process is simpler, but profile control and capacitance uniformity deteriorate
Solution Approach 1:
The dopant concentration parameter is changed between the two hard mask layers. The first hard mask layer contains first dopants with a first dopant concentration within a first range, while the second hard mask layer contains second dopants with a second dopant concentration within a second range. This parameter change enables differential etching behavior that improves profile control and achieves uniform capacitance across all capacitors formed in the dielectric stack.
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 enhances the uniformity of capacitor profiles and reduces capacitance imbalances, ensuring consistent alignment and performance in subsequent etching and deposition processes.
Implementation Method 1
The first hard mask layer and the second hard mask layer are etched using the patterned mask as an etch mask to form a first hard mask and a second hard mask, in which the first hard mask layer is etched faster than the second hard mask layer
Implementation Method 2
the first hard mask layer includes first dopants having a first conductivity type, and the second hard mask layer includes second dopants having a second conductivity type different from the first conductivity type
Data Source
AI summary
A method of forming a semiconductor structure includes forming a dielectric stack over a substrate, in which forming the dielectric stack includes forming a first support layer, a first sacrificial layer, a second support layer, a second sacrificial layer and a third support layer in sequence. A first hard mask layer is formed over the dielectric stack. A second hard mask layer is formed over the first hard mask layer. A patterned mask is formed over the second hard mask layer. The first and second hard mask layers are etched using the patterned mask as an etch mask to form first and second hard masks, in which the first hard mask layer is etched faster than the second hard mask layer. An opening is formed in the dielectric stack to expose the substrate. A bottom electrode layer is formed in the opening of the dielectric stack.