Circular Connecting Pad Patterning for Uniform Semiconductor Etching
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Solution Overview
Problem
In semiconductor memory device manufacturing, the existing immersion photolithography process results in connecting pads with non-uniform dimensions due to etching load effects, leading to insufficient margins and potential capacitor leakage during the patterning process.
Innovation Solution
A method involving a triple exposure process to form a hexagonal pattern definition structure on a substrate, where three groups of patterns intersect at 120°, allowing for the formation of a columnar structure with a circular bottom, which is then used as a mask to etch a circular connecting pad, ensuring uniformity and preventing leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If two layers of photomasks are used in immersion photolithography to form linear patterns, then the manufacturing process is simplified, but the connecting pad dimensions become non-uniform due to etching load effects
Solution Approach 1:
The patent divides the pattern formation into three separate exposure steps, each creating a set of parallel lines at 120° angles. This segmentation of the photolithography process allows each exposure to be optimized independently, and the cumulative effect of all three exposures creates a hexagonal pattern that resolves the etching load effect problem by distributing the pattern density more uniformly across the substrate.
Solution Approach 2:
The patent transitions from forming simple linear patterns in one or two directions to creating a three-dimensional hexagonal pattern arrangement. By introducing patterns in three different directions (0°, 60°, 120°) that intersect to form hexagons, the solution adds dimensional complexity to the pattern geometry, which in turn creates more uniform etching conditions and circular connecting pads.
2Shape
If the connecting pad is formed with an elliptical shape from pattern transfer, then the original parallelogram pattern is maintained, but the short axis direction has insufficient margin during capacitor patterning
Solution Approach 1:
The patent deliberately designs the pattern to form circular (spheroidal in 2D cross-section) connecting pads rather than elliptical or parallelogram shapes. The three-group parallel line patterns intersecting at 120° create hexagonal openings that, when etched, form circular connecting pads due to the isotropic nature of the etching process. This circular geometry provides equal margins in all directions, eliminating the short axis margin problem.
3Shape
If the connecting pad maintains an oval shape after etching, then the top is shaped by plasma effect but the bottom maintains elliptical shape, but this leads to breakdown and capacitor leakage
Solution Approach 1:
The patent creates a pattern density distribution where the hexagonal arrangement of intersecting parallel lines results in more uniform local pattern density across the entire substrate. This uniformity ensures that the etching load is distributed evenly, allowing both the top and bottom of the connecting pad to be shaped into circles with consistent dimensions, thereby preventing the breakdown and leakage issues caused by dimensional non-uniformity.
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 method ensures the connecting pads are circular, providing a larger margin during capacitor patterning and preventing breakdown, thus avoiding capacitor leakage.
Implementation Method 1
A near-bottom of the hole is primarily subjected to bombardment of an etching gas, causing the bottom of the hole to maintain its original elliptical shape
Implementation Method 2
a top of the hole is constantly subjected to plasma effect and shaped like a relatively regular circle
Data Source
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AI summary
Embodiments provide method for forming a connecting pad. The method includes: providing a substrate; sequentially forming a conductive layer, a first pattern definition layer and a second pattern definition layer on a surface of the substrate; sequentially forming three groups of patterns intersecting with each other at 120° on the second pattern definition layer, an intersection portion of the three groups of patterns forming a hexagonal pattern definition structure on the second pattern definition layer; transferring the pattern definition structure downward, and etching away a portion of the first pattern definition layer, such that the remaining first pattern definition layer forms a columnar structure, wherein a bottom of the columnar structure is circular in shape under an action of an etching load effect; and etching the conductive layer by using the remaining first pattern definition layer as a mask, such that the remaining conductive layer forms a circular connecting pad.