Multibeam Writer Dose Correction for Pattern Clarity
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Solution Overview
Problem
Multibeam-writing systems face challenges in achieving high clarity and precision due to issues like image blurring, substripes, and current density variations, which affect the accuracy of pattern creation on substrates, particularly at the nanometer level.
Innovation Solution
The system employs a method to calculate corrected dose amounts for each pixel by determining available current density and applying correction factors, which account for overlapping exposure stripes and current density variations, using multiplicative renormalization and ordered dithering to optimize dose distribution and pattern clarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If overlapping exposure stripes are used to cover the entire exposure region, then productivity is improved by reducing writing time, but manufacturing precision deteriorates due to image blurring and substripes at stripe boundaries
Solution Approach 1:
The patent applies preliminary action by pre-calculating correction factors for each pixel based on its position relative to overlapping stripe boundaries. The dose correction map is computed before actual writing, anticipating and compensating for the blurring and substripe effects that will occur during overlapping exposure. This allows the system to maintain high writing speed while pre-correcting for precision issues.
Solution Approach 2:
The patent changes the dose parameter spatially by applying position-dependent correction factors to each pixel. The correction factor varies depending on the pixel's location relative to stripe boundaries, with pixels near boundaries receiving adjusted doses to compensate for the overlapping exposure effects. This parameter change resolves the contradiction by maintaining both speed and precision.
2Manufacturing precision
If current density variations across the beam array are corrected by applying individual correction factors to each pixel, then manufacturing precision is improved, but device complexity increases due to additional calculation and control requirements
Solution Approach 1:
The patent reduces device complexity by performing the complex dose correction calculations in advance, before the actual writing process. The correction factors are pre-computed based on measured current density variations and stored in a correction map. During writing, the system simply applies these pre-calculated factors without real-time computation, thus maintaining precision while minimizing operational complexity.
Solution Approach 2:
The patent creates a simplified copy or representation of the current density variations in the form of a correction map. Instead of directly measuring and adjusting each beamlet's current in real-time, the system creates a digital correction map that replicates the necessary adjustments. This copying approach simplifies the control system while maintaining dose uniformity.
3Device complexity
If the beam is moved along a predetermined path to create patterns, then device complexity is reduced by using simple beam steering, but manufacturing precision deteriorates due to substripes and edge definition issues
Solution Approach 1:
The patent maintains simple beam steering while improving line edge accuracy through preliminary calculation of position-dependent correction factors. The system pre-determines the exact dose adjustments needed for each pixel based on its location relative to the scanning path and overlapping stripes. This allows simple mechanical beam movement to achieve high precision through intelligent dose modulation.
Solution Approach 2:
The patent changes the dose parameter as a function of position along the scanning path. By modulating the dose delivered to each pixel based on its location relative to stripe boundaries and overlapping regions, the system compensates for the limitations of simple beam steering. This parameter change enables high precision pattern writing without complex beam control mechanisms.
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 enhances the clarity and precision of pattern creation by correcting for blurring and substripes, achieving improved Local and Global Critical Dimension Uniformity and allowing for finer adjustments in line edge positions, thereby improving the overall accuracy and resolution of the multibeam-writing process.
Implementation Method 1
a multibeam-writing system which projects a charged particle beam through a series of apertures onto a target area
Data Source
AI summary
In a charged-particle multi-beam writing method a desired pattern is written on a target using a beam of energetic electrically charged particles, by imaging apertures of a pattern definition device onto the target, as a pattern image which is moved over the target. Thus, exposure stripes are formed which cover the region to be exposed in sequential exposures, and the exposure stripes are mutually overlapping, such that each area of said region is exposed by at least two different areas of the pattern image at different transversal offsets (Y1). For each pixel, a corrected dose amount is calculated by dividing the value of the nominal dose amount by a correction factor (q), wherein the same correction factor (q) is used with pixels located at positions which differ only by said transversal offsets (Y1) of overlapping stripes.