High Aspect Ratio Electrode Patterning via Segmented Masking
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Solution Overview
Problem
The increase in aspect ratio of lower electrodes in capacitors poses challenges during the patterning process due to the use of thick or opaque hard mask layers, making alignment and photolithography difficult.
Innovation Solution
A method involving the formation of a sacrificial layer with a transparent material, where first and second mask patterns with opaque materials are created in parallel, allowing for the formation of openings with high aspect ratios through the layer, facilitating electrode formation and capacitor dielectric layer deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a thick or opaque hard mask layer is used to form holes for high aspect ratio lower electrodes, then the aspect ratio of the lower electrode can be increased, but alignment and overlay determination becomes difficult
Solution Approach 1:
The patent divides the mask structure into multiple segments: a transparent sacrificial mask layer and separate opaque hard mask patterns. The opaque hard mask patterns are formed only in specific regions where needed, while the sacrificial mask layer provides the transparent background. This segmentation allows the transparent sacrificial mask to enable precise alignment determination while the opaque hard mask patterns provide the necessary masking function for etching, thus resolving the contradiction between achieving high aspect ratio and maintaining alignment precision.
Solution Approach 2:
The patent introduces a transparent sacrificial mask layer as an intermediary between the substrate and the opaque hard mask patterns. This sacrificial mask layer serves as a mediator that enables precise alignment determination during photolithography due to its transparency, while the opaque hard mask patterns formed on top provide the necessary masking function. The intermediary sacrificial mask layer thus allows both high aspect ratio formation and precise alignment determination to coexist.
2Shape
If a thick hard mask layer is used to form high aspect ratio holes, then the lower electrode aspect ratio increases, but photolithography and etching processes become significantly difficult
Solution Approach 1:
The patent segments the masking function into two parts: a thin transparent sacrificial mask layer that facilitates easy photolithography due to its transparency and thinness, and separate opaque hard mask patterns that provide the necessary etching protection. This segmentation allows photolithography to be performed easily on the transparent sacrificial mask while the opaque hard mask patterns enable precise etching control, thus resolving the contradiction between achieving high aspect ratio and maintaining ease of manufacture.
Solution Approach 2:
The transparent sacrificial mask layer acts as an intermediary that simplifies the photolithography process due to its transparency and thinness, making pattern formation easier. Meanwhile, the opaque hard mask patterns formed on top serve as the actual etching masks. This intermediary structure thus makes both photolithography and etching processes significantly easier while still enabling high aspect ratio lower electrode formation.
3Reliability
If an opaque hard mask layer is used for patterning, then the mask provides good etching protection, but alignment determination with lower layer becomes difficult
Solution Approach 1:
The patent segments the masking functionality into two distinct components: a transparent sacrificial mask layer that enables precise alignment determination due to its transparency, and opaque hard mask patterns that provide reliable etching protection. The opaque hard mask patterns are formed only in the specific regions where etching protection is needed, while the transparent sacrificial mask layer covers the entire area to facilitate alignment. This segmentation thus allows both reliable etching protection and precise alignment determination to coexist.
Solution Approach 2:
The transparent sacrificial mask layer serves as an intermediary between the substrate and the opaque hard mask patterns. It provides a transparent background that enables precise alignment determination with the lower layer, while the opaque hard mask patterns formed on top provide the necessary etching protection. This intermediary structure thus resolves the contradiction between providing good etching protection and enabling easy alignment determination.
Data Source
AI summary
Methods of forming a hard mask capable of implementing an electrode having a high aspect ratio are provided. A molding layer may be formed on a substrate. A sacrificial layer may be formed on the molding layer. First mask patterns may be formed in parallel in the sacrificial layer. After the first mask patterns are formed, second mask patterns, which cross the first mask patterns and are in parallel, may be formed in the sacrificial layer. The first mask patterns and the second mask patterns may have materials more opaque than the sacrificial layer. Upper surfaces of the sacrificial layer, the first mask patterns and the second mask patterns may be exposed at the same horizontal level. The sacrificial layer may be removed. Openings, which pass through the molding layer, may be formed using the first mask patterns and the second mask patterns as etch masks. Electrodes may be formed in the openings.