Circular Pattern Formation via Charged Particle Beam Lithography
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Solution Overview
Problem
Manufacturing contacts and vias with square patterns on semiconductor wafers becomes impractical and expensive at technology nodes smaller than 80 nm half pitch, due to corner rounding and high Mask Error Enhancement Factor (MEEF) issues in optical lithography, making it difficult to form accurate circular or near-circular patterns.
Innovation Solution
A method using charged particle beam lithography with circular apertures and varying shot dosages to form circular patterns on a surface, employing either variable shaped beam (VSB) shots or character projection (CP) technology, allowing for the creation of multiple circular patterns with fewer shots and optimizing shot placement and dosage to reduce errors and costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If square patterns are used for contacts and vias in optical lithography, then manufacturing process is simpler, but manufacturing precision deteriorates due to corner rounding and high MEEF at technology nodes smaller than 80 nm
Solution Approach 1:
The patent changes the fundamental parameter of pattern geometry from square to circular. This parameter change eliminates corner rounding issues inherent in square patterns and reduces the Mask Error Enhancement Factor (MEEF), thereby improving manufacturing precision at advanced technology nodes while maintaining process compatibility
Solution Approach 2:
Instead of trying to achieve circular patterns through square apertures with complex proximity effect corrections, the patent inverts the approach by using circular apertures directly. This inversion simplifies the manufacturing process while achieving the desired circular contact and via patterns with superior precision
2Manufacturing precision
If circular apertures are used in charged particle beam lithography, then manufacturing precision of circular patterns improves, but device complexity increases due to need for variable shaped beam shots or character projection technology
Solution Approach 1:
The patent makes the charged particle beam lithography system universal by implementing variable shaped beam (VSB) capability that can dynamically create circular apertures in addition to rectangular shots. This multi-functionality allows the same system to achieve both simple rectangular patterning and precise circular patterning without requiring separate dedicated equipment
Solution Approach 2:
The patent introduces dynamic aperture shaping capability where the beam shape can be changed on-the-fly between rectangular and circular configurations. This dynamic adaptation allows precise circular pattern formation while maintaining the flexibility to use simpler rectangular shots when appropriate, balancing precision needs with system complexity
3Manufacturing precision
If multiple shots are used to form circular patterns, then manufacturing precision improves, but productivity decreases due to increased number of shots required
Solution Approach 1:
The patent performs preliminary action by pre-calculating and optimizing the shot placement and dosage distribution for circular patterns. This includes determining the optimal number and positioning of VSB shots or character projection elements before writing, which enables precise circular pattern formation while minimizing the total number of shots required, thus maintaining productivity
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 reduces the number of shots required to form circular patterns, lowers the Mask Error Enhancement Factor, and makes it more practical to manufacture near-circular contacts and vias, improving the efficiency and accuracy of semiconductor device production.
Implementation Method 1
maskless direct write is a printing process in which charged particle beam lithography is used to transfer patterns to a substrate
Implementation Method 2
a lithographic mask or photomask manufactured from a reticle is used to transfer patterns to a substrate such as a semiconductor or silicon wafer to create the integrated circuit
Data Source
AI summary
A method for fracturing or mask data preparation is disclosed, in which a set of shots is determined, where each shot will direct a circular or nearly-circular dosage pattern to a surface, where each shot comprises a shot dosage, and in which the set of shots is output. A method for forming patterns on a surface using charged particle beam lithography is also disclosed, in which a stencil is provided comprising one or more circular apertures, and where a plurality of circular patterns of different sizes are formed on the surface using a single aperture, by varying the shot dosage.