Hard Mask Linewidth Control via Sidewall Spacer Doping
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Solution Overview
Problem
Current double patterning technologies for semiconductor fabrication are limited in achieving varied linewidths on a single chip, particularly in applications like NAND flash memory where peripheral and core portions require different linewidths, with the maximum achievable linewidth being only twice the minimum linewidth.
Innovation Solution
A method involving the formation of first and second patterned material layers, where the second layer acts as a mask to change the properties of the exposed top and side portions of the first layer, allowing for the creation of hard masks with arbitrary linewidths by removing portions with unchanged properties between the property-changed sidewalls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If double patterning technology is used to achieve smaller critical dimension, then lithographic resolution is improved, but the ability to provide varied linewidths on a single chip is limited
Solution Approach 1:
The patent divides the patterning process into multiple stages: first forming initial patterns, then creating sidewall spacers, and finally performing selective removal to generate varied linewidths. This segmentation allows different regions to have different linewidths while maintaining the precision benefits of double patterning.
Solution Approach 2:
The patent applies local quality by selectively removing material in different regions to create varied linewidths. Specifically, it removes a portion of the first patterned material layer between adjacent sidewall spacers in first regions, while preserving material in second regions, thereby creating different linewidths in different locations on the same chip.
2Manufacturing precision
If sidewall doping is used to double pattern density, then minimum linewidth is achieved, but maximum linewidth is limited to only twice the minimum linewidth
Solution Approach 1:
The patent performs preliminary actions by forming sidewall spacers and selectively removing portions of the first patterned material layer before final etching. This preliminary structuring enables the creation of varied linewidths beyond the simple twice-minimum limitation, as the selective removal creates intermediate structures that define different linewidth regions.
Solution Approach 2:
The patent introduces an additional dimensional control by using vertical sidewall spacers and controlling the thickness and positioning of the first patterned material layer. This dimensional approach allows linewidths to be controlled not just by horizontal spacing but also by vertical layer thickness, expanding the achievable linewidth range.
3Ease of manufacture
If cap layer is used as mask for sidewall doping, then doped portions are formed, but the method cannot provide more varied linewidths
Solution Approach 1:
The patent extracts the masking function from a simple cap layer and replaces it with sidewall spacers formed through selective etching. By removing (taking out) the material between sidewall spacers in specific regions, the patent creates varied linewidths while maintaining the ease of doping process in other regions.
Solution Approach 2:
The patent introduces sidewall spacers as intermediary structures that mediate between the doping process and the final linewidth variation. These spacers serve as temporary structures that define regions for selective removal, enabling both the ease of doping and the capability for varied linewidths.
Data Source
AI summary
A method for forming a hard mask in semiconductor device fabrication comprises: forming first and second patterned material layers on a third material layer, the second patterned material layer only covering the top of predetermined regions of the first patterned material layer; changing a property of exposed top and side portions of the first patterned material layer using the second patterned material layer as a mask, forming property-changed roofs at the exposed top portions of the first patterned material layer and forming property-changed sidewalls with a predetermined width at the exposed side portions of the first patterned material layer; removing the second patterned material layer and portions of the first patterned material layer with exposed tops and an unchanged property located between the property-changed sidewalls, to form the hard mask.