Device and method for setting relative laser intensity

Abstract

An apparatus, computer program, computer-readable medium, and method for setting corresponding relative laser intensities for a plurality of pixels representing a lithographic exposure. The plurality of pixels includes: at least one edge pixel located at an edge of a pixel region to be exposed; and at least one adjacent pixel arranged to be spaced apart from the at least one edge pixel by one pixel in a direction perpendicular to the edge towards the pixel region to be exposed. The method includes proportionally reducing the relative laser intensity of each pixel of the plurality of pixels from a previously set corresponding first relative laser intensity to a corresponding second relative laser intensity. The laser dose conversion of the relative laser intensity of the pixel is proportionally adjusted from a previously set first laser dose conversion to a second laser dose conversion such that the corresponding effective exposure laser dose of each pixel is achieved by the second laser dose conversion of the corresponding second relative laser intensity, and the corresponding effective exposure laser dose of each pixel is equal to the corresponding effective exposure laser dose of each pixel generated by the first laser dose conversion of the corresponding first relative laser intensity. The corresponding relative laser intensity of the edge pixel of the at least one edge pixel or the adjacent pixel of the at least one adjacent pixel is increased from the corresponding second relative laser intensity to a corresponding third relative laser intensity.

Description

Technical Field

[0001] The present disclosure relates to pattern generation, and more particularly, to a method for setting corresponding relative laser intensities for a plurality of pixels representative of lithographic exposure. Background Art

[0002] In the field of pattern generation, such as in mask printing, the pattern to be printed is typically transformed relative to a plurality of (grid) pixels, and a corresponding relative laser intensity proportional to the pixel area covered by the pattern to be printed is set for each of the plurality of pixels. For some of the plurality of pixels, all of their respective areas are covered by the pattern, and thus, their respective relative laser intensities are set to 100%. For some of the plurality of pixels (at the edge of the pattern), only a part of their respective areas is covered by the pattern, and thus, a corresponding relative laser intensity proportional to their respective covered areas is set (thus less than 100%). For example, if 50% of the pixel area is covered by the pattern, a 50% relative laser intensity is set for that pixel. The problem with prior art pattern generators is that the edge sharpness and edge roughness of the printed pattern sometimes cannot reach a satisfactory level. Summary of the Invention

[0003] The inventors have realized that the problem of unsatisfactory edge sharpness and edge roughness of the printed pattern in the prior art depends on the relative laser intensities of the pixels at or near the pattern edge. The edge of the pattern is the critical point between the pixels being exposed to a certain extent (i.e., the relative laser intensity is higher than 0%) and the pixels not being exposed at all (i.e., the relative laser intensity is equal to 0%).

[0004] According to a first aspect, there is provided a method for setting corresponding relative laser intensities for a plurality of pixels representative of lithographic exposure. The plurality of pixels includes: at least one edge pixel located on the edge of the pixel area to be exposed; and at least one adjacent pixel arranged to be one pixel away from the at least one edge pixel in a direction perpendicular to the edge towards the pixel area to be exposed. The method proportionally reduces the relative laser intensity of each pixel of the plurality of pixels from a previously set corresponding first relative laser intensity to a corresponding second relative laser intensity; proportionally adjusts the laser dose conversion of the relative laser intensity of the pixel from a previously set first laser dose to a second laser dose conversion such that the corresponding effective exposure laser dose of each pixel is achieved by the second laser dose conversion of the corresponding second relative laser intensity, and the corresponding effective exposure laser dose of each pixel is equal to the corresponding effective exposure laser dose of each pixel generated by the first laser dose conversion of the corresponding first relative laser intensity; and increases the corresponding relative laser intensity of the edge pixel of the at least one edge pixel or the adjacent pixel of the at least one adjacent pixel from the corresponding second relative laser intensity to a corresponding third relative laser intensity by a constant addition term.

[0005] By first proportionally reducing the relative laser intensity of each pixel and then proportionally adjusting the laser dose conversion such that the effective exposure laser dose of each pixel is the same as if there were no proportional reduction of the relative laser intensity and proportional adjustment of the laser dose conversion, the highest relative laser intensity is effectively reduced to less than 100% relative laser intensity. This accommodates an increase in the relative laser intensity of the pixel, regardless of its original (first) relative laser intensity. Accordingly, the corresponding relative laser intensities of edge pixels or adjacent pixels can be increased by a constant additive term, which enables enhancement of edge sharpness and edge roughness.

[0006] Relative laser intensity is a way of indicating the laser intensity associated with a pixel and can be defined, for example, by 100% relative laser intensity, which corresponds to the laser intensity selected to achieve a desired exposure on an adjacent pixel for which 100% of the area of the pixel should be exposed according to the pattern.

[0007] The previously set corresponding first relative laser intensity and previously set first laser dose conversion of each pixel have been preselected (calibrated) such that the previously set first laser dose conversion of the previously set first relative laser intensity of 100% laser intensity will result in 100% exposure, where 100% exposure is the effective exposure laser dose that has been calibrated to give a desired constant exposure on an adjacent pixel for which 100% of the area of the pixel should be exposed according to the pattern.

[0008] An edge pixel can be defined as a pixel for which the corresponding first relative laser intensity is greater than 0% relative laser intensity and is arranged adjacent to at least one pixel for which the corresponding first relative laser intensity is 0% relative laser intensity.

[0009] An adjacent pixel can be defined as a pixel for which the corresponding first relative laser intensity is greater than 0% relative laser intensity and is arranged adjacent to the edge pixel in a direction perpendicular to the edge.

[0010] The corresponding second relative laser intensity can be equal to the corresponding first relative laser intensity multiplied by a factor less than 1. In other words, the corresponding second relative laser intensity of each pixel among a plurality of pixels is the corresponding first relative laser intensity multiplied by a factor less than 1.

[0011] The inventors also recognize that when implemented for edge pixels in some cases, through the first laser dose conversion with respect to the corresponding first relative laser intensity, the laser intensity converted from a relative laser intensity higher than 100% will enhance the edge sharpness and edge roughness, and in some cases will also enhance the edge sharpness and edge roughness for adjacent pixels. Therefore, the corresponding third relative laser intensity can be configured such that the corresponding effective exposure laser dose obtained by the second laser dose conversion of the corresponding third relative laser intensity of at least one edge pixel or at least one adjacent pixel of an adjacent pixel is greater than the corresponding effective exposure laser dose obtained by the first laser dose conversion of 100% relative laser intensity with respect to the corresponding first relative laser intensity. This means that the edge pixel or the adjacent pixel will have a higher effective exposure laser dose than the pixels of the plurality of pixels completely covered by the pattern, and thus, according to the corresponding first relative laser intensity, the edge pixel or the adjacent pixel should have 100% relative laser intensity.

[0012] The method may further include a condition based on which a constant addition term is increased with respect to the edge pixel of at least one edge pixel or the adjacent pixel of at least one adjacent pixel. For example, a threshold may be introduced such that under the condition that the corresponding relative laser intensity of the edge pixel of at least one edge pixel corresponds to a relative laser intensity greater than the threshold, the corresponding second relative laser intensity of the edge pixel of at least one edge pixel is increased to the corresponding third relative laser intensity by the constant addition term. On the other hand, under the condition that the corresponding relative laser intensity of the edge pixel of at least one edge pixel corresponds to a relative laser intensity less than the threshold, the corresponding second relative laser intensity of the adjacent pixel of at least one adjacent pixel is increased to the corresponding third relative laser intensity by the constant addition term.

[0013] The corresponding first relative laser intensity may correspond to the corresponding percentage from 0% to 100% relative laser intensity. Therefore, since the corresponding second relative laser intensity corresponds to a decrease from the corresponding first relative laser intensity, the corresponding second relative laser intensity will correspond to the corresponding percentage from 0% to less than 100% relative laser intensity.

[0014] According to a second aspect, there is provided a computer-readable medium having stored thereon a computer program including computer-readable instructions that, when executed on a processing device, cause the processing component to perform the method of the first aspect.

[0015] The computer-readable medium of the second aspect may further include additional features corresponding to the additional features described with respect to the method of the first aspect.

[0016] The computer-readable medium of the second aspect may be, for example, a non-transitory computer-readable medium. According to the third aspect, there is provided a computer program including computer-readable instructions which, when executed on a processing device, cause the processing device to perform the method of the first aspect.

[0017] The computer program of the third aspect may further include additional features corresponding to the additional features described in relation to the method of the first aspect.

[0018] According to the fourth aspect, there is provided a device for setting respective relative laser intensities for a plurality of pixels. The plurality of pixels includes at least one edge pixel and at least one adjacent pixel, wherein the at least one adjacent pixel is arranged to be one pixel away from the at least one edge pixel in a direction perpendicular to the edge. The device includes a processing component configured to perform the method of the first aspect.

[0019] The device of the fourth aspect may further include additional features corresponding to the additional features described in relation to the method of the first aspect.

[0020] According to the fifth aspect, there is provided a mask writing system including the device according to the fourth aspect.

[0021] The mask writer system of the fifth aspect may further include additional features corresponding to the additional features related to the description of the device of the fourth aspect.

[0022] According to the sixth aspect, there is provided a method for setting an effective exposure laser dose for a plurality of pixels representing a lithographic exposure. The plurality of pixels includes: at least one edge pixel; at least one adjacent pixel arranged to be one pixel away from the at least one edge pixel in a direction perpendicular to the edge; and non-adjacent pixels arranged to be at least a plurality of pixels away from the at least one edge pixel in a direction perpendicular to the edge. The method includes setting respective effective exposure laser doses for each of the plurality of pixels such that the respective effective exposure laser doses of the edge pixels of the at least one edge pixel or the adjacent pixels of the at least one adjacent pixel are higher than the respective effective exposure laser doses of the non-adjacent pixels. Brief Description of the Drawings

[0024] Examples will be described below with reference to the drawings, wherein:

[0025] Figure 1 A schematic diagram showing the setting of respective relative laser intensities for a plurality of pixels representing a lithographic exposure according to the present disclosure, related to a mask writing system according to the prior art;

[0026] Figure 2 A flowchart showing an example of the method according to the present disclosure;

[0027] Figure 3a -d shows an illustration of a part of a pattern to be printed on a photosensitive resist, which is related to the implementation of the method and device of the present disclosure; and

[0028] Figure 4 Shows a schematic diagram of an example of a device according to the present disclosure.

[0029] All the drawings are schematic, and generally only show the parts necessary to clarify each example, while other parts may be omitted or only suggested. Detailed Description

[0030] The method and device of the present disclosure can be advantageously implemented in a pattern generator for printing a pattern onto a photosensitive resist.

[0031] Figure 1 Shows a schematic diagram of setting respective effective exposure laser intensities for a plurality of pixels, where the plurality of pixels represent a lithographic exposure related to a mask writing system (lithographic exposure system) according to the prior art. Block 110 represents the acquisition of an original pattern description, for example, in the form of vector pattern data, which is pattern data for mask exposure in the form of vector data (geometric figures specified by coordinates) in an ideal coordinate system. Then, in block 120, the vector pattern data is used in rasterization to generate pixel data with relative intensities, which can be simplified to be completed by checking the area coverage of the vector data in each pixel. Thus, the respective relative laser intensity of each pixel is proportional to a part of the pixel area covered by the vector pattern data. For pixels completely covered by the vector pattern data, the corresponding relative laser intensity is set to 100%. For pixels at the pattern edge where the vector pattern data only covers a part (such as 50%), the corresponding relative laser intensity of 50% is set. Here, the pixel area covered by the pattern means that this area corresponds to the pattern area to be exposed.

[0032] Then, in block 130, the pixel data with linear area coverage is calibrated for the non-linear response of exposure and chemical image development. Compensation is also made for various aspects of the pixel intensity and size in the exposure beam and scanning direction. In block 140, the respective relative laser intensities of the pixels are proportionally converted into the respective effective exposure laser intensities of the pixels. Given the current intensity from the laser light source and the optics, the respective effective exposure laser intensities of the pixels are calibrated to give an appropriate amount of light, so as to give a uniform exposure level on adjacent fully exposed pixels.

[0033] Then, in block 150, the respective effective exposure laser intensities of the pixels are provided to a mask writing system (lithographic exposure system). The mask writing system includes a laser source 160, a modulator 170, and a deflector 180. The modulator 170 uses the respective exposure laser intensities of the pixels to modulate the laser beam from the laser source 160. The modulated laser beam is projected onto a photosensitive resist (mask) 190 through the deflector 180 so as to expose the photosensitive resist according to a desired pattern, that is, to provide respective effective exposure laser intensities / doses. Additional components such as optical devices (not shown) are included in the mask writing system between the laser source 160 and the modulator 170, between the modulator 170 and the deflector 180, and between the deflector 180 and the mask 190.

[0034] The inventors have recognized that the edge sharpness and edge roughness of a printed pattern depend on the relative laser intensities of the pixels at or near the pattern edge. The edge of a pattern is the boundary between pixels that are exposed to a certain extent (i.e., relative laser intensity higher than 0%) and pixels that are not exposed at all (i.e., relative laser intensity equal to 0%). For example, the edge sharpness and edge roughness will be negatively affected by the relative laser intensities of the edge pixels set within a certain percentage. Relative laser intensities close to 100%, such as 80% and above, will result in satisfactory edge sharpness and edge roughness characteristics. This is because the relative laser intensities of the edge pixels are close enough to 100% to provide edge sharpness and edge roughness with satisfactory characteristics. Similarly, relative laser intensities close to 0%, such as 20% and lower, will form satisfactory characteristics related to edge sharpness and edge roughness. This is because the relative laser intensities of the edge pixels are very small compared to the 100% relative laser intensities of the adjacent pixels, and for the adjacent pixels, the relative laser intensities dominate the appearance of the edge in terms of edge sharpness and edge roughness. In contrast, relative laser intensities close to 50% will generally result in unsatisfactory edge sharpness and edge roughness. The edge sharpness and edge roughness of a printed pattern can be enhanced by increasing the relative laser intensities of the edge pixels or adjacent pixels. Edge pixels are pixels with respective relative laser intensities greater than 0% relative laser intensity and are arranged adjacent to at least one pixel with a respective first relative laser intensity of 0% relative laser intensity. In other words, edge pixels are pixels to be exposed and are adjacent to pixels not to be exposed. Edge pixels are arranged at the edge of the pixel region to be exposed (the region including the pixels). Adjacent pixels are pixels with respective relative laser intensities greater than 0% relative laser intensity and are arranged to be adjacent to the edge pixels in a direction perpendicular to the edge towards the pixel region to be exposed. In other words, adjacent pixels are pixels to be exposed and are adjacent to pixels that are adjacent to the edge pixels and not exposed in the opposite direction.

[0035] Figure 2A flowchart showing an example of method 200 according to the present invention is presented. Method 200 is used to set respective relative laser intensities for a plurality of pixels representing a lithographic exposure. The plurality of pixels includes at least one edge pixel and at least one adjacent pixel. The relative laser intensity of each pixel in the plurality of pixels is preset to a respective first relative laser intensity. This can generally be done relative to the corresponding relative laser intensities that rasterize the description of the original pattern into a plurality of pixels.

[0036] Method 200 includes proportionally reducing 210 the relative laser intensity of each pixel in the plurality of pixels from the previously set respective first relative laser intensity to a respective second relative laser intensity. For example, the respective first laser intensity of each pixel in the plurality of pixels can be multiplied by a factor less than 1. For example, if the factor is 0.8, a pixel with a respective first relative laser intensity of 100% will have a respective second relative laser intensity of 80%.

[0037] Regarding Figure 1 , the reduction 210 of the relative laser intensity is performed for block 120 (before block 130).

[0038] Method 200 further includes proportionally adjusting 220 the conversion of the laser dose of the relative laser intensity of the pixels from the previously set first laser dose to a second laser dose conversion. The proportional adjustment is such that the respective effective exposure laser dose of each pixel in the plurality of pixels is achieved by the second laser dose conversion of the respective second relative laser intensity, and the respective effective exposure laser dose of each pixel in the plurality of pixels is equal to the respective effective exposure laser dose of each pixel in the plurality of pixels that should have been obtained from the first laser dose conversion of the respective first relative laser intensity. For example, if the factor is 0.8, a pixel with a respective first relative laser intensity of 100% will have a respective second relative laser intensity of 80%, and using the second laser dose conversion, for the pixel that now has 80% of the second relative laser intensity, the effective exposure laser dose will be the same as that of the pixel with 100% of the first relative laser intensity using the first laser dose conversion.

[0039] For Figure 1 , the proportional adjustment 220 of the laser dose conversion is performed for block 140 (before block 150).

[0040] The proportional decrease in the relative laser intensity and the proportional adjustment of the laser dose conversion will result in the effective exposure laser dose of each pixel in the plurality of pixels remaining unchanged, but the set relative laser intensities will all decrease. Method 200 further includes increasing 230 the respective relative laser intensity of at least one edge pixel or at least one adjacent pixel of the adjacent pixels from the respective second relative laser intensity to a respective third relative laser intensity. This increase can be achieved, for example, by adding a constant term.

[0041] The corresponding third relative laser intensity can be configured such that the corresponding effective exposure laser dose obtained by second laser dose conversion of the corresponding third relative laser intensity through an edge pixel of at least one edge pixel or an adjacent pixel of at least one adjacent pixel is higher than the corresponding effective exposure laser dose obtained by first laser dose conversion of a relative laser intensity of 100% relative to the corresponding first relative laser intensity. This means that the edge pixel or the adjacent pixel will have a higher effective exposure laser dose than the pixels of the plurality of pixels completely covered by the pattern and should thus have a relative laser intensity of 100% according to the corresponding first relative laser intensity. This is achievable because the proportional decrease in the relative laser intensity and the proportional adjustment of the laser dose conversion will result in an unchanged effective exposure laser dose for each pixel in the plurality of pixels, but the set relative laser intensities will all decrease. For example, the corresponding third laser intensity can be 100% relative laser intensity. Using the second laser dose conversion, this will be converted into an effective exposure laser dose higher than the corresponding effective exposure laser dose obtained by first laser dose conversion of a relative laser intensity of 100% relative to the corresponding first relative laser intensity. This is because the corresponding effective exposure laser dose obtained by first laser dose conversion of a relative laser intensity of 100% relative to the corresponding first relative laser intensity is equal to the corresponding effective exposure laser dose obtained by second laser dose conversion of a relative laser intensity less than 100% relative to the corresponding second relative laser intensity.

[0042] Regarding Figure 1 , increasing the corresponding relative laser intensity of at least one edge pixel or an adjacent pixel of at least one adjacent pixel by 230 is performed with respect to block 120 (before block 130).

[0043] It can be determined based on one or more thresholds whether to add a constant term to an edge pixel or an adjacent pixel. For example, if one threshold is used, say 40%, then under the condition that the corresponding relative laser intensity of the edge pixel of at least one edge pixel corresponds to a relative laser intensity greater than the threshold, a constant addition term is added to the corresponding second relative laser intensity of the edge pixel of at least one edge pixel to the corresponding third relative laser intensity.

[0044] Under the condition that the corresponding relative laser intensity of the edge pixels of the at least one edge pixel corresponds to a relative laser intensity less than a threshold, the corresponding second relative laser intensity of the adjacent pixels of the at least one adjacent pixel is increased to a corresponding third relative laser intensity by a constant addition term. Here, the adjacent pixels are the adjacent pixels corresponding to the edge pixels with a relative laser intensity less than the threshold. Preferably, the threshold is set relative to the corresponding first relative laser intensity, which provides unsatisfactory characteristics in terms of edge sharpness and edge roughness. For example, relative to the corresponding first relative laser intensity, such a threshold can be set to 50%, which for a factor of 0.8 would correspond to 40% relative to the corresponding second relative laser intensity. Regarding Figure 1 , the pixel data with an effective exposure laser dose provided by method 200 includes the unaffected effective exposure laser dose of all pixels that are not edge pixels or adjacent pixels. Generally, in order to convert vector pattern data into an effective exposure laser dose for pattern printing, non-linearity must be considered and complex calibration and compensation are included. Edge pixels or adjacent pixels will receive a higher effective exposure laser dose. The transformation in method 200 is applied to the relative laser intensity (e.g., by multiplying by a factor less than 1), for which the intensity is still linear with respect to the exposure area. Additionally, the laser dose conversion is non-linearly calibrated and compensated, but the level of the laser dose conversion can be adjusted so as to provide an unaffected effective exposure laser dose for all pixels that should be fully exposed. Thus, according to Figure 2 the method 200 for Figure 1 the adjustment of block 120 and block 140 can be independent of Figure 1 block 130.

[0045] Embodiments of the method of the present disclosure will now be described with reference to Figure 3a -d. Figure 3a -d shows an illustration of a part of a pattern to be printed on a photosensitive resist and 36 pixels associated with the photosensitive resist. For the purpose of description, the pixels are designated relative to six columns A - F and six rows 1 - 6, such that the upper left pixel is designated as pixel A1, the next pixel to the right is designated as pixel B1, and so on up to F6.

[0046] It should be noted that Figure 3a -d is only used to illustrate the example principle of printing a pattern onto a photosensitive resist. The number of pixels and the relative size of the pixels and the resulting pattern are not intended to reflect real results, but rather a part of some pixels and a much larger pattern in general.

[0047] In Figure 3aIn it, a part of the pattern is represented as a diagonal stripe area with respect to 36 pixels A1 to F6. All pixels in columns C, D, and E are completely covered by the pattern, and the pixels in columns A and F are outside the pattern. The pixels in column B are partially covered by the pattern, such that the first two pixels B1 and B2 are covered to 40%, and the subsequent four pixels B3, B4, B5, and B6 are covered to 60%. It should be noted that Figure 3a merely for illustrative purposes, the degree to which different pixels are covered is shown.

[0048] In the prior art, the pattern generator has been calibrated to generate a relative laser intensity proportional to the relative area (i.e., percentage of area) of the pixels determined to be covered by the pattern for each pixel, and the relative laser intensity of that pixel is set to that specific percentage. Turning to Figure 3b , this is shown with respect to Figure 3a the pattern portion shown. For the pixels in columns C, D, and F that are 100% covered by the pattern, a 100% relative laser intensity is set as the respective first relative laser intensity for these pixels. This is illustrated by the black pixels representing 100% relative laser intensity. For the two pixels B1 and B2 in column B that are 40% covered by the pattern starting from the top of the column, a 40% relative laser intensity is set as the respective first relative laser intensity for these pixels. This is illustrated by the pixels represented by black dots on a white background, representing 40% relative laser intensity. For the following four pixels B3, B4, B5, and B6 in column B that are 60% covered by the pattern, a 60% relative laser intensity is set as the respective first relative laser intensity for these pixels. This is illustrated by the pixels indicated by black vertical stripes on a white background representing 60% relative laser intensity.

[0049] Since the pixels B1 and B2 with a first relative laser intensity of 40% respectively and the pixels B3, B4, B5, and B6 with a first relative laser intensity of 60% respectively are all in the intermediate range close to 50%, the characteristics of the edge sharpness and edge roughness of the printed pattern will be unfavorable. To enhance the characteristics of the edge sharpness and edge roughness of the printed pattern, the method according to the present invention can be used, such as regarding Figure 1 the method described. Then starting from proportionally reducing the relative laser intensity of each pixel of the pixels from the respective first relative laser intensity to the respective second relative laser intensity. Regarding Figure 3b , the respective first laser intensity of each pixel of a plurality of pixels can be multiplied by a factor of 0.8. Thus, the pixels in columns C, D, and E with a first relative laser intensity of 100% respectively will have a second relative laser intensity of 80% respectively. This is in Figure 3cAs shown, the pixels are represented as white dots on a black background, representing 80% relative laser intensity. Two pixels B1 and B2, each having a first relative laser intensity of 40% starting from the top of column B, will each have a second relative laser intensity of 32%. This is shown in Figure 3c As shown, the pixels are represented as black grids on a white background, representing 32% relative laser intensity. The following four pixels B3, B4, B5, and B6 in column B, each having a first relative laser intensity of 60%, will each have a second relative laser intensity of 48%. This is shown in Figure 3c As shown, the pixels are represented as black horizontal lines representing 48% relative laser intensity. As Figure 3c shown, the reduction in relative laser intensity is then combined with a proportional adjustment of the laser dose that converts the relative laser intensity of the pixels, from a previously set first laser dose to a second laser dose. The proportional adjustment is such that the corresponding effective exposure laser dose for each pixel among the plurality of pixels is achieved by the second laser dose conversion of the corresponding second relative laser intensity, and the corresponding effective exposure laser dose for each pixel among the plurality of pixels is equal to the corresponding effective exposure laser dose that each pixel among the plurality of pixels should have been converted from the first laser dose of the corresponding first relative laser intensity.

[0050] The proportional reduction in relative laser intensity and the proportional adjustment of the laser dose conversion will result in the effective exposure laser dose remaining unchanged for each pixel in the pixels, but the set relative laser intensity will all be reduced. However, by doing so, it accommodates a separate increase in the relative laser intensity with respect to all pixels, since all pixels will now have a corresponding second relative laser intensity of 80% or less.

[0051] To enhance the characteristics of the edge sharpness and edge roughness of the printed pattern, the relative laser intensity of at least one edge pixel of the edge pixels or at least one adjacent pixel of the adjacent pixels can be increased from the corresponding second relative laser intensity to the corresponding third relative laser intensity. This increase can be achieved, for example, by adding a constant term.

[0052] In Figure 3d it is shown the relative laser intensity of each pixel after increasing the relative laser intensity of some pixels. For example, in column E, the relative laser intensity of pixels E1, E2, E3, E4, E5, and E6, which are edge pixels, has been increased by adding a constant addition term corresponding to 20% relative laser intensity to the corresponding second relative laser intensity of 80%, resulting in a corresponding third relative laser intensity of 100%. This is shown in Figure 3dAs shown, pixels E1, E2, E3, E4, E5, and E6 are indicated as black representing 100% relative laser intensity. This means that the edge pixels E1, E2, E3, E4, E5, and E6 in column E will have a higher effective exposure laser dose than the pixels D1, D2, D3, D4, D5, and D6 in column D, where the pixels in column D have 100% relative laser intensity according to their respective first relative laser intensities. This is because the corresponding effective exposure laser dose obtained by converting the first laser dose of 100% relative laser intensity with respect to the corresponding first relative laser intensity is equal to the corresponding effective exposure laser dose obtained by converting the second laser dose of less than 100% relative laser intensity with respect to the corresponding second relative laser intensity.

[0053] Generally, increasing the effective exposure laser dose of edge pixels, for example by increasing the relative laser intensity such that it is higher than the effective exposure laser dose of pixels having 100% relative laser intensity according to the corresponding first relative laser intensity, will enhance the characteristics of the edge sharpness and edge roughness of the printed pattern with respect to that edge pixel. This increase can be referred to as providing an excess with respect to the edge pixel.

[0054] It can be determined whether to add a constant term to the edge pixel or the adjacent pixel based on one or more thresholds. For example, regarding Figure 3b , a threshold of 40% is used with respect to the corresponding relative laser intensity, which corresponds to 50% with respect to the corresponding first relative laser intensity. For edge pixels whose respective second relative laser intensity is higher than the threshold of 40%, the constant addition term is added to the respective second relative laser intensity of the edge pixel, and for edge pixels whose respective second relative laser intensity is lower than 40%, the constant addition term is added to the respective second relative laser intensity of the adjacent pixel of the edge pixel.

[0055] The two pixels B1 and B2 starting from the top of column B have second relative laser intensities of 32% respectively, as Figure 3c shown, the pixels are represented as a black grid on a white background. This is lower than the threshold of 40%, and the constant addition term is added to the respective second relative laser intensities of the adjacent pixels C1 and C2 of the edge pixels B1 and B2 respectively. In this case, the constant addition term corresponding to 20% relative laser intensity is added to the respective second relative laser intensities of the adjacent pixels C1 and C2 of 80%, resulting in the respective third relative laser intensities of the two adjacent pixels C1 and C2 being 100%. This is shown in Figure 3d where the pixels C1 and C2 are indicated as black representing 100% relative laser intensity. This means that the adjacent pixels C1 and C2 will each have a higher effective exposure laser dose than the pixels D1 and D2 in column D, where the pixels in column D have 100% relative laser intensity according to their respective first relative laser intensities.

[0056] Typically, when the corresponding edge pixels have a lower portion in the middle range of approximately 50%, such as a corresponding first relative laser intensity of 50% or lower, the relative laser intensity of adjacent pixels is increased by adding a constant addition term while maintaining the corresponding relative laser intensity of the corresponding edge pixels. This will enhance the characteristics of the edge sharpness and edge roughness of the printed pattern relative to the corresponding edge pixels because it will effectively reduce the relative laser intensity of the edge pixels relative to the relative laser intensity of adjacent pixels. Therefore, the relative laser intensity of adjacent pixels will more dominantly influence the appearance of the edge, which will enhance the characteristics of the edge in terms of edge sharpness and edge roughness.

[0057] The following four pixels B3, B4, B5, and B6 in column B with respective first relative laser intensities of 60% will have respective second relative laser intensities of 48%. This is shown in Figure 3c where the pixels are represented as black horizontal lines representing 48% relative laser intensity. This is above the threshold of 40%, and the constant addition term is added to the respective second relative laser intensities of the edge pixels B3, B4, B5, and B6. In this case, the constant addition term corresponding to 20% relative laser intensity is added to the respective 48% second relative laser intensities of the edge pixels B3, B4, B5, and B6, resulting in respective third relative laser intensities of 68% for the two edge pixels B3, B4, B5, and B6. This is shown in Figure 3d where the edge pixels B3, B4, B5, and B6 are represented by black vertical stripes on a white background, representing 68% relative laser intensity. This means that each of the edge pixels B3, B4, B5, and B6 will have a higher effective exposure laser dose than would be the case based on their respective first relative laser intensities and first laser dose conversion.

[0058] Typically, when the corresponding edge pixels have a corresponding first relative laser intensity in the upper portion of the middle range of approximately 50%, such as 50% or higher, increasing the effective exposure laser dose of the edge pixels, such as by adding a constant addition term to the corresponding second relative laser intensity, will enhance the characteristics of the edge sharpness and edge roughness of the printed pattern associated with the edge pixels. This is because the increased effective exposure laser dose will correspond to the effective exposure laser dose generated by the corresponding first relative laser dose and first dose conversion, where the corresponding first relative laser dose is closer to the higher range, such as 80 - 100%, resulting in satisfactory characteristics regarding edge sharpness and edge roughness.

[0059] The pixels C3, C4, C5, and C6 in column C and the pixels D1, D2, D3, D4, D5, and D6 in column D do not change in terms of their respective relative laser intensities. This is shown in Figure 3d where the pixels are represented by white dots on a black background, representing 80% relative laser intensity, which is the same asFigure 3c Same as in

[0060] Figure 4 FIG. shows a schematic diagram of an example of a device 400 for setting respective relative laser intensities for a plurality of pixels according to the present invention. The plurality of pixels includes at least one edge pixel and at least one adjacent pixel, wherein the at least one adjacent pixel is arranged to be one pixel apart from the at least one edge pixel in a direction perpendicular to the edge. The device includes processing means configured to perform the methods of the present disclosure, such as the methods described with respect to Figure 1 and Figure 3a -d. The processing means may for example be a processor 410 included in the device 400.

[0061] The device 400 may further include a computer-readable medium, for example in the form of a memory 420. The computer-readable medium may include computer-readable instructions 430 which, when executed on a processing device such as the processor 410, cause the processing device to perform the methods of the present disclosure, such as the methods described with respect to Figure 1 and Figure 3a -d. The computer-readable instructions 430 may be included in a computer program. The device 400 may further be included in a mask writing system.

[0062] As described above, the inventors have recognized that the edge sharpness and edge roughness of a printed pattern depend on the relative laser intensity of the pixels at or near the pattern edge. In this regard, the inventors have also recognized that by providing an "overdose" to the edge pixels or adjacent pixels, the edge can be enhanced with respect to edge sharpness and edge roughness.

[0063] A method for setting the effective exposure laser dose of a plurality of pixels representing a lithographic exposure is described below. The plurality of pixels includes: at least one edge pixel arranged at the edge of a pixel region to be exposed; at least one adjacent pixel arranged one pixel apart from the at least one edge pixel in a direction perpendicular to the edge towards the pixel region to be exposed; and non-adjacent pixels arranged at least two pixels apart from the at least one edge pixel in a direction perpendicular to the edge towards the pixel region to be exposed. The method includes setting the respective effective exposure laser dose of each of the plurality of pixels such that the respective effective exposure laser dose of the edge pixel of the at least one edge pixel or the adjacent pixel of the at least one adjacent pixel is higher than the respective effective exposure laser dose of the non-adjacent pixels.

[0064] The non-adjacent pixels are pixels completely covered by the vector pattern data of the pattern to be printed. Since the respective effective exposure laser dose of the edge pixel or adjacent pixel is set to be higher than the respective effective exposure laser dose of the non-adjacent pixels, an "overdose" is provided to the edge pixel or adjacent pixel. The overdose can be achieved, for example, by combiningFigure 2 The described method 200 or any other suitable means may be used to implement it.

[0065] The above description of the examples is considered non - restrictive. Although specific examples have been described, various changes, modifications, or variations can be conceived by those of ordinary skill in the art within the scope defined by the appended claims.

Claims

1. A method for setting corresponding relative laser intensities for a plurality of pixels representing a lithographic exposure, wherein the plurality of pixels includes: At least one edge pixel, located on the edge of the pixel region to be exposed; And at least one adjacent pixel, the at least one adjacent pixel being arranged to be one pixel apart from the at least one edge pixel in a direction perpendicular to the edge towards the pixel region to be exposed, the method comprising the steps of: Proportionally reducing the relative laser intensity of each of the plurality of pixels from a previously set respective first relative laser intensity to a respective second relative laser intensity; Proportionally adjusting the laser dose conversion of the relative laser intensity of the pixels from a previously set first laser dose conversion to a second laser dose conversion such that the respective effective exposure laser dose of each pixel is achieved by the second laser dose conversion of the respective second relative laser intensity, the respective effective exposure laser dose of each pixel being equal to the respective effective exposure laser dose of each pixel produced by the first laser dose conversion of the respective first relative laser intensity; And Increasing the respective relative laser intensity of the edge pixel of the at least one edge pixel or the adjacent pixel of the at least one adjacent pixel from the respective second relative laser intensity to a respective third relative laser intensity by a constant addition term.

2. The method according to claim 1, wherein the respective second relative laser intensity is equal to the respective first relative laser intensity multiplied by a factor less than 1.

3. The method according to claim 1, wherein the respective third relative laser intensity is such that the respective effective exposure laser dose obtained by the second laser dose conversion of the respective third relative laser intensity of the edge pixel of the at least one edge pixel or the adjacent pixel of the at least one adjacent pixel is higher than the respective effective exposure laser dose obtained by the first laser dose conversion of a 100% relative laser intensity relative to the respective first relative laser intensity.

4. The method according to claim 1, further comprising: Under the condition that the respective relative laser intensity of the edge pixel of the at least one edge pixel corresponds to a relative laser intensity greater than a threshold, increasing the respective second relative laser intensity of the edge pixel of the at least one edge pixel to the respective third relative laser intensity by the constant addition term, and under the condition that the respective relative laser intensity of the edge pixel of the at least one edge pixel corresponds to a relative laser intensity less than the threshold, increasing the respective second relative laser intensity of the adjacent pixel of the at least one adjacent pixel to the respective third relative laser intensity by the constant addition term.

5. The method according to claim 1, wherein the respective first relative laser intensity corresponds to a respective percentage from 0 to 100% relative laser intensity.

6. The method according to claim 1, wherein the edge pixel is a pixel with a respective first relative laser intensity greater than 0% relative laser intensity and is arranged adjacent to at least one pixel with a respective first relative laser intensity of 0% relative laser intensity.

7. The method according to claim 6, wherein the adjacent pixels are pixels with the corresponding first relative laser intensity greater than 0% relative laser intensity, and are arranged adjacent to the edge pixels in a direction perpendicular to the edge.

8. A computer-readable medium comprising computer-readable instructions that, when executed on a processing device, cause the processing device to perform the method according to claim 1.

9. A device for setting corresponding relative laser intensities for a plurality of pixels, wherein the plurality of pixels includes at least one edge pixel and at least one adjacent pixel, and wherein the at least one adjacent pixel is arranged to be one pixel apart from the at least one edge pixel in a direction perpendicular to the edge, the device comprising processing means configured to perform the method according to claim 1.

10. A mask writing system comprising the device according to claim 9.

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