Beam Dose Computing for Lithography Line Width Uniformity
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Solution Overview
Problem
Current microlithography technologies face challenges in achieving uniformity of line widths due to proximity, loading, and fogging effects during the writing of ultrafine circuit patterns, leading to inaccuracies in semiconductor device fabrication.
Innovation Solution
A method and apparatus for computing and controlling the charged particle beam dose by dividing the target object's surface into regions of different sizes, calculating corrected doses for fogging and loading effects, and using these to determine proximity effect corrections, thereby optimizing the beam dose at each position to minimize line width variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high-accuracy electron beam photolithographic apparatus is used to generate ultrafine patterns, then the image resolution is improved, but line width uniformity deteriorates due to proximity and loading effects
Solution Approach 1:
The patent applies preliminary correction by calculating and storing proximity effect correction coefficients and loading effect correction values before the actual pattern writing process. The system pre-processes the pattern data to determine the appropriate beam dose adjustments needed for each region, thereby compensating for expected distortions before they occur during lithography.
Solution Approach 2:
The patent implements local quality correction by dividing the pattern into multiple regions and applying different correction coefficients to different areas. The system calculates region-specific proximity effect correction coefficients and loading effect correction values based on local pattern density and geometry, allowing each region to be optimized independently for uniform line width control.
2Manufacturing precision
If the beam dose is increased to improve pattern definition, then the pattern accuracy is improved, but line width variations worsen due to back scattering and fogging effects
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the beam dose parameter based on pattern characteristics. The system calculates the optimal beam dose for each region by considering pattern density, line width, and area, then modifies the dose accordingly to minimize back scattering and fogging effects while maintaining pattern definition.
Solution Approach 2:
The patent implements feedback correction by using measured line width data from test patterns to refine and update the proximity effect correction coefficients and loading effect correction values. The system compares actual measured line widths with target values and adjusts the correction parameters accordingly, creating a closed-loop optimization process.
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 solution effectively corrects for multiple sources of line width deviations, enhancing the uniformity and accuracy of ultrafine pattern writing, allowing for more precise control of the beam dose to achieve consistent line widths across the target surface.
Implementation Method 1
a radiation source for emitting a charged particle beam; a pattern generator having more than one deflector and one or more apertures for guiding the beam toward the object to thereby permit writing of a pattern thereon
Implementation Method 2
a pattern generator having more than one deflector and one or more apertures for guiding the beam toward the object
Data Source
AI summary
A beam dose computing method includes dividing a surface area of a target object into include first, second and third regions of different sizes, the third regions being less in size than the first and second regions, determining first corrected doses of a charged particle beam for correcting fogging effects in the first regions, determining corrected size values for correcting pattern line width deviations occurring due to loading effects in the second regions to create a map of base doses of the beam in respective of said second regions and to prepare a map of proximity effect correction coefficients in respective of said second regions, using the maps to determine second corrected doses of the beam for proximity effect correction in the third regions, and using the first and second corrected doses to determine an actual beam dose at each position on the surface of said object.