Lithographic apparatus and device manufacturing method utilizing data filtering
First Claim
1. A lithography apparatus, comprising:
- a projection system configured to project a beam of radiation onto a substrate as an array of sub-beams of radiation;
a patterning device configured to modulate the sub-beams of radiation to substantially produce a requested dose pattern on the substrate, the dose pattern being built up from an array of spot exposures in which at least neighboring ones of the spot exposures are imaged incoherently with respect to each other and each of the spot exposures is produced by one of the sub-beams of radiation at a particular time;
a data manipulation device configured to produce a control signal comprising spot exposure intensities to be produced by the patterning device based on a direct algebraic least-squares fit of spot exposure intensities to data derived from the requested dose pattern, wherein the least-squares fit is performed by multiplying a pseudo-inverted form of a point-spread function matrix by a column vector representing the pattern data derived from the requested dose pattern, the point-spread function matrix comprising information about a shape and relative position of the point-spread function of each spot to be exposed on the substrate by one of the sub-beams of radiation at a given time; and
a low-pass filter configured to remove spatial frequency components of a signal above a selected threshold frequency, incorporated offline into the pseudo-inverted form of the point-spread-function matrix, ready for the least-squares fit, by the following operation;
[K]+filtered=Flow-pass filter[K]+,wherein [K]+ and [K]+filtered are the pseudo-inverted form of the point-spread function matrix respectively before and after filtering, andwherein Flow-pass filter is a mathematical definition of the low-pass filter in a spatial domain.
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Abstract
An apparatus and method are used to form patterns on a substrate. The apparatus comprises a projection system, a patterning device, a low-pass filter, and a data manipulation device. The projection system projects a beam of radiation onto the substrate as an array of sub-beams. The patterning device modulates the sub-beams to substantially produce a requested dose pattern on the substrate. The low-pass filter operates on pattern data derived from the requested dose pattern in order to form a frequency-clipped target dose pattern that comprises only spatial frequency components below a selected threshold frequency. The data manipulation device produces a control signal comprising spot exposure intensities to be produced by the patterning device, based on a direct algebraic least-squares fit of the spot exposure intensities to the frequency-clipped target dose pattern. In various examples, filters can also be used.
39 Citations
9 Claims
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1. A lithography apparatus, comprising:
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a projection system configured to project a beam of radiation onto a substrate as an array of sub-beams of radiation; a patterning device configured to modulate the sub-beams of radiation to substantially produce a requested dose pattern on the substrate, the dose pattern being built up from an array of spot exposures in which at least neighboring ones of the spot exposures are imaged incoherently with respect to each other and each of the spot exposures is produced by one of the sub-beams of radiation at a particular time; a data manipulation device configured to produce a control signal comprising spot exposure intensities to be produced by the patterning device based on a direct algebraic least-squares fit of spot exposure intensities to data derived from the requested dose pattern, wherein the least-squares fit is performed by multiplying a pseudo-inverted form of a point-spread function matrix by a column vector representing the pattern data derived from the requested dose pattern, the point-spread function matrix comprising information about a shape and relative position of the point-spread function of each spot to be exposed on the substrate by one of the sub-beams of radiation at a given time; and a low-pass filter configured to remove spatial frequency components of a signal above a selected threshold frequency, incorporated offline into the pseudo-inverted form of the point-spread-function matrix, ready for the least-squares fit, by the following operation;
[K]+filtered=Flow-pass filter[K]+,wherein [K]+ and [K]+filtered are the pseudo-inverted form of the point-spread function matrix respectively before and after filtering, and wherein Flow-pass filter is a mathematical definition of the low-pass filter in a spatial domain. - View Dependent Claims (2, 3, 4)
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5. A lithography apparatus, comprising:
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an illumination system configured to condition a beam of radiation; a projection system configured to project the beam of radiation onto the substrate as an array of sub-beams of radiation; a patterning device configured to modulate the sub-beams of radiation to substantially produce a requested dose pattern on the substrate, the dose pattern being built up from an array of spot exposures, each of the spot exposure being produced by one of the sub-beams of radiation at a particular time, wherein the radiation intensity of a given sub-beam of radiation is controlled according to an activation state of a corresponding portion of the patterning device; a dose sensor configured to measure a source intensity of the beam of radiation and a spot intensity of the sub-beams of radiation on the substrate; and a data manipulation device configured to transform a signal comprising spot exposure radiation doses derived from the requested dose pattern to a control signal representing activation states of the patterning device to produce the requested dose pattern, wherein the transformation corrects for intensity variations measured by the dose sensor as a ratio between the source intensity and the spot intensity and caused by at least one of components of the projection system, components of the illumination system, radiation sources for the illumination system, and components of the patterning device. - View Dependent Claims (6, 7)
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8. A method, comprising:
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projecting a beam of radiation onto a substrate as an array of sub-beams of radiation; modulating the sub-beams of radiation to substantially produce a requested dose pattern on the substrate, the dose pattern being built up from an array of spot exposures in which at least neighboring ones of the spot exposures are imaged incoherently with respect to each other and each of the spot exposures is produced by one of the sub-beams of radiation at a particular time; producing a control signal comprising spot exposure intensities to be produced by the modulating based on a direct algebraic least-squares fit of the spot exposure intensities to data derived from the requested dose pattern, wherein the least-squares fit is performed by multiplying a pseudo-inverted form of a point-spread function matrix by a column vector representing the pattern data derived from the requested dose pattern, the point-spread function matrix comprising information about the shape and relative position of the point-spread function of each spot to be exposed on the substrate by one of the sub-beams of radiation at a given time; and filtering to remove spatial frequency components of a signal above a selected threshold frequency, incorporated offline into the pseudo-inverted form of the point-spread-function matrix, ready for the least-squares fit, by the following operation;
[K]+filtered=Flow-pass filter[K]+,wherein [K]+ and [K]+filtered are the pseudo-inverted form of the point-spread function matrix respectively before and after filtering, and where Flow pass filter represents a mathematical definition of the filtering in the spatial domain.
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9. A method, comprising:
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conditioning a beam of radiation; detecting a source dose intensity of the beam of radiation; projecting the beam of radiation onto the substrate as an array of sub-beams of radiation; detecting a spot dose intensity of the sub-beams of radiation on the substrate; modulating the sub-beams of radiation to substantially produce a requested dose pattern on the substrate, the dose pattern being built up from an array of spot exposures, each of the spot exposures being produced by one of the sub-beams of radiation at a particular time; controlling radiation intensity of a given one of the sub-beams of radiation according to an activation state of a corresponding portion of a patterning device that performs the modulating; transforming a signal comprising spot exposure radiation doses derived from the requested dose pattern to a control signal representing activation states of the patterning device to substantially produce the requested dose pattern; and modifying the transforming step to correct for intensity variations determined by a ratio of the detected source and spot dose intensities and caused by at least one of components of the projection system, components of the illumination system, radiation sources for the illumination system, and components of the patterning device.
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Specification