Apparatus and method for setting relative laser intensity

Abstract

An apparatus, computer program, computer-readable medium, and method for setting respective relative laser intensities for a plurality of pixels representing a lithography exposure, the plurality of pixels including at least one edge pixel disposed at an edge of the region of the pixel to be exposed and at least one adjacent pixel, the at least one adjacent pixel disposed one pixel away from the at least one edge pixel in a vertical direction away from the edge toward the region of the pixel to be exposed. The method includes proportionally decreasing the relative laser intensity of each pixel of the plurality of pixels from a respective pre-set first relative laser intensity to a respective second relative laser intensity. A laser dose conversion of the relative laser intensity of the pixel is proportionally adjusted from a pre-set first laser dose conversion of the first relative laser intensity to a second laser dose conversion of the second relative laser intensity. The proportional adjustment is an adjustment such that the effective exposure laser dose of each pixel is achieved by a second laser dose transformation of each second relative laser intensity that is equal to the effective exposure laser dose of each pixel resulting from the first laser dose transformation of each first relative laser intensity, and the relative laser intensity of each edge pixel of the at least one edge pixel or adjacent pixel of the at least one adjacent pixel increases from the respective second relative laser intensity to the respective third relative laser intensity by a constant addition term.

Description

Technical Field

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

Background Art

[0002] In the area of pattern generation in mask printing and the like, the pattern to be printed is usually transformed with respect to a plurality (grid) of pixels, and the respective relative laser intensities are set for each pixel of the plurality of pixels in proportion to the area of the pixel covered by the pattern to be printed. For some of the plurality of pixels, all of the area of each pixel is covered by the pattern, and thus, a respective relative laser intensity of 100% is set. For some of the plurality of pixels (at the edge of the pattern), only a part of the area of each pixel is covered by the pattern, and thus, a respective relative laser intensity proportional to each covered area (and thus less than 100%) is set. For example, if 50% of the area of a pixel is covered by the pattern, this means setting a relative laser intensity of 50% for that pixel. The problem associated with prior art pattern generation devices is that the sharpness of the edge and the roughness of the edge of the printed pattern are sometimes insufficient.

Summary of the Invention

[0003] The inventor has noticed that the problem associated with the prior art that the sharpness of the edge and the roughness of the edge of the printed pattern are insufficient is due to the relative laser intensity of the pixel at the edge of the pattern or the pixel close to the edge. The edge of the pattern is the boundary between a place where the pixel is exposed to some extent, that is, a place with a relative laser intensity higher than 0%, and a place where the pixel is not exposed at all, that is, a place with a relative laser intensity equal to 0%.

[0004] According to a first aspect, a method is provided for setting respective relative laser intensities for a plurality of pixels representing lithographic exposure. The plurality of pixels includes at least one edge pixel disposed at an edge of an area of pixels to be exposed and at least one adjacent pixel. The at least one adjacent pixel is disposed one pixel away from the at least one edge pixel in a direction perpendicular to the edge and toward the area of pixels to be exposed. The method includes proportionally decreasing the relative laser intensity of each pixel of the plurality of pixels from each respective first relative laser intensity to each respective second relative laser intensity. The laser dose conversion of the relative laser intensity of the pixels is proportionally adjusted from a first laser dose conversion of the already set first relative laser intensity to a second laser dose conversion of the second relative laser intensity. The proportional adjustment is such that the second laser dose conversion of each respective second relative laser intensity equal to the respective effective exposure laser dose of each pixel due to the first laser dose conversion of each respective first relative laser intensity results in the respective effective exposure laser dose of each pixel being achieved. The relative laser intensity of each of the edge pixels within the at least one edge pixel or of the adjacent pixels of the at least one adjacent pixel is increased from each respective second relative laser intensity to each respective third relative laser intensity by a constant additional term.

[0005] First, the relative laser intensity of each pixel is proportionally decreased, and then the laser dose conversion is proportionally adjusted such that the effective exposure laser dose of each pixel is the same as it would be without the proportional decrease in relative laser intensity and the proportional adjustment of the laser dose conversion. As a result, the highest relative laser intensity is effectively reduced to a relative laser intensity of less than 100%. This corresponds to an increase in the relative laser intensity for the pixels, regardless of the original (first) relative laser intensity of the pixels. Thus, the relative laser intensity of each edge pixel or adjacent pixel can be increased by a constant additional term that enables improvement in the sharpness of the edge and the roughness of the edge.

[0006] Relative laser intensity is a way to indicate laser intensity with respect to a pixel. For example, it can be defined by a relative laser intensity of 100%, and the 100% relative laser intensity corresponds to the laser intensity selected so as to achieve the desired exposure in adjacent pixels where 100% of the area of the pixel should be exposed according to the pattern.

[0007] For each already set first relative laser intensity and already set first laser dose conversion of each pixel, the already set first laser dose conversion of the already set first relative laser intensity of 100% laser intensity has already been selected (calibrated) so as to result in 100% exposure, where 100% exposure is the effective exposure laser dose calibrated so as to give a desired constant exposure in adjacent pixels where 100% of the area of the pixel should be exposed according to the pattern.

[0008] An edge pixel can be defined as a pixel in which each first relative laser intensity is a relative laser intensity greater than 0 percent and which is arranged adjacent to at least one pixel in which each first relative laser intensity is a relative laser intensity of 0 percent.

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

[0010] Each second relative laser intensity may be equal to each first relative laser intensity multiplied by a coefficient less than 1. In other words, for each pixel of a plurality of pixels, each second relative laser intensity is each first relative laser intensity multiplied by a coefficient less than 1.

[0011] The inventor further noticed that higher laser intensities than those obtained by the first laser dose conversion for each first relative laser intensity where 100 percent relative laser intensity is converted can be achieved for edge pixels in some situations and for adjacent pixels in some situations, which improves the sharpness and roughness of the edges. Thus, each effective exposure laser dose achieved by the second laser dose conversion of the third relative laser intensity of each of the edge pixels within at least one edge pixel or of the adjacent pixels of at least one adjacent pixel can be configured to be greater than each effective exposure laser dose achieved by the first laser dose conversion of 100 percent relative laser intensity for each first relative laser intensity. This means that the edge pixels or adjacent pixels have a higher effective exposure laser dose than for the pixels that should have 100 percent relative laser intensity according to each first relative laser intensity, as they are completely covered by the pattern.

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

[0013] Each of the first relative laser intensities may correspond to each percentage of relative laser intensities from 0 percent to 100 percent. As a result, since each of the second relative laser intensities corresponds to the decrease from each of the first relative laser intensities, each of the second relative laser intensities corresponds to each percentage of relative laser intensities from 0 to less than 100 percent.

[0014] According to a second aspect, there is provided a computer-readable medium storing a computer program including computer-readable instructions that, when executed on a processing device, cause the processing means 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.

[0017] According to a third aspect, there is provided a computer program including computer-readable instructions that, when executed on a processing device, cause the processing device to perform the method of the first aspect.

[0018] The computer program of the third aspect may further include additional features corresponding to the additional features described with respect to the method of the first aspect.

[0019] According to a fourth aspect, there is provided an apparatus 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, and at least one adjacent pixel is arranged one pixel away from at least one edge pixel in a direction perpendicular to the edge. The apparatus includes processing means configured to perform the method of the first aspect.

[0020] The apparatus of the fourth aspect may further include additional features corresponding to the additional features described with respect to the method of the first aspect.

[0021] According to a fifth aspect, a mask drawing system including the device according to the fourth aspect is provided.

[0022] The mask drawing system according to the fifth aspect may further include additional features corresponding to the additional features described for the device according to the fourth aspect.

[0023] According to a sixth aspect, a method of setting effective exposure laser doses for a plurality of pixels representing lithographic exposure is provided. The plurality of pixels includes at least one edge pixel, at least one adjacent pixel disposed one pixel away from at least one edge pixel in a direction perpendicular to the edge and away from the edge, and at least one non - adjacent pixel disposed at least a plurality of pixels away from at least one edge pixel in a direction perpendicular to the edge and away from the edge. The method includes setting the effective exposure laser dose for each pixel of the plurality of pixels such that the effective exposure laser dose for each of the edge pixels within at least one edge pixel or each of the adjacent pixels adjacent to at least one adjacent pixel is higher than the effective exposure laser dose for each of the non - adjacent pixels. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Examples will be described below with reference to the accompanying drawings.

[0025]

Figure 1

Figure 2

Figure 3a

Figure 3b

Figure 3c

Figure 3d

Figure 4

[0026] All the diagrams are schematic, and generally, only the parts necessary to clarify each example are shown, while other parts may be omitted or only proposed.

Mode for Carrying Out the Invention

[0027] The methods and apparatuses of the present disclosure can be advantageously implemented in a pattern generation apparatus that prints a pattern on a photosensitive resist.

[0028] FIG. 1 shows a schematic diagram for setting each effective exposure laser intensity for a plurality of pixels representing lithographic exposure with respect to a mask drawing system (lithographic exposure system) according to the prior art. Block 110 represents obtaining an original pattern description in the form of vector pattern data, which is pattern data for mask exposure in the form of vector data of an ideal coordinate system (geometric figure specified by coordinates), for example. Then, the vector pattern data is used in block 120 for rasterization to generate pixel data having relative intensities, which can be done, briefly speaking, by examining the area range of the vector data for each pixel. And the relative laser intensity of each pixel is proportional to the area portion of the pixel covered by the vector pattern data. For pixels completely covered by the vector pattern data, a relative laser intensity of 100% for each is set. For pixels at the edge of a pattern that covers only a part, for example, 50%, of the vector pattern data, a relative laser intensity of 50% for each is set. Here, the area of the pixel covered by the pattern means that the area corresponds to the area of the pattern to be exposed.

[0029] Next, in block 130, the pixel data in the linear region range is calibrated for the non-linear reaction of exposure and chemical image development. Corrections are also made for the pixel intensities and sizes in various aspects in the exposure beam and sweep direction. In block 140, each relative laser intensity for a pixel is proportionally converted into each effective exposure laser intensity for the pixel. Each effective exposure laser intensity for a pixel is calibrated to provide the correct amount of light to give a uniform exposure level to adjacent sufficiently exposed pixels for which the current intensity is provided from the laser light source and optical system.

[0030] Next, in block 150, each effective exposure laser intensity for a pixel is provided to a mask drawing system (lithography exposure system). The mask drawing system includes a laser source 160, a modulator 170, and a deflector 180. Each exposure laser intensity for a pixel is used by the modulator 170 to modulate the laser beam from the laser source 160. The modulated laser beam is projected onto a photosensitive resist (mask) 190 by the deflector 180 to expose the photosensitive resist according to a desired pattern, i.e., to provide each effective exposure laser intensity / dose. Additional components such as an optical system (not shown) are included in the mask drawing 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.

[0031] The inventor noticed that the sharpness and roughness of the edges of a printed pattern are due to the relative laser intensity of the pixels at the edge of the pattern or the pixels close to the edge. The edge of the pattern is the boundary between a location where the pixel is exposed to some extent, i.e., a relative laser intensity higher than 0%, and a location where the pixel is not exposed at all, i.e., a relative laser intensity equal to 0%. For example, the sharpness of the edge and the roughness of the edge are affected by the relative laser intensity of the edge pixels set within a specific ratio. For example, a relative laser intensity close to 100% such as 80% or more results in a sharpness of the edge and a roughness of the edge with sufficient characteristics. This is due to the relative laser intensity of the edge pixels being close enough to 100% to provide sufficient characteristics regarding the sharpness of the edge and the roughness of the edge. Similarly, a relative laser intensity close to 0% such as 20% or less results in sufficient characteristics regarding the sharpness of the edge and the roughness of the edge. This is because the relative laser intensity of the edge pixels is small enough with respect to the relative laser intensity of 100% of the adjacent pixels, and the relative laser intensity of the adjacent pixels affects the appearance of the edge from the perspective of the sharpness of the edge and the roughness of the edge. In contrast, a relative laser intensity closer to 50% generally results in a sharpness of the edge and a roughness of the edge with insufficient characteristics. By increasing the relative laser intensity of the edge pixels or the adjacent pixels, the sharpness of the edge and the roughness of the edge of the printed pattern can be improved. An edge pixel is a pixel arranged adjacent to at least one pixel whose respective relative laser intensity is a relative laser intensity greater than 0% and whose respective first relative laser intensity is a relative laser intensity of 0%. In other words, an edge pixel is a pixel that is exposed and is adjacent to a pixel that is not exposed. An edge pixel is arranged at the edge of the area of the exposed pixels (the area including the pixels). An adjacent pixel is a pixel whose respective relative laser intensity is a relative laser intensity greater than 0% and is arranged adjacent to the edge pixel in a direction perpendicular to the edge and towards the area of the exposed pixels.In other words, an adjacent pixel is a pixel that is exposed and that is adjacent to the edge pixel in a direction opposite to a pixel that is adjacent to the edge pixel and not exposed.

[0032] FIG. 2 shows a flowchart of an example of a method 200 for setting respective relative laser intensities for a plurality of pixels representative of lithographic exposure according to the present disclosure. The plurality of pixels includes at least one edge pixel and at least one adjacent pixel. The relative laser intensity of each pixel of the plurality of pixels has already set respective first relative laser intensities. This can typically be done with respect to the rasterization of the original pattern description to respective relative laser intensities for the plurality of pixels.

[0033] Method 200 includes proportionally decreasing 210 the relative laser intensity of each pixel of the plurality of pixels from the respective already set first relative laser intensities to respective second relative laser intensities. For example, a coefficient less than 1 can be multiplied by each of the first laser intensities of each pixel of the plurality of pixels. For example, when the coefficient is 0.8, a pixel having 100% of each of the first relative laser intensities has 80% of each of the second relative laser intensities.

[0034] With respect to FIG. 1, proportionally decreasing 210 the relative laser intensity is done with respect to block 120 (before block 130).

[0035] Method 200 further includes adjusting the laser dose conversion of the relative laser intensity of pixels proportionally from a previously set first laser dose conversion to a second laser dose conversion 220. The proportional adjustment is such that the effective exposure laser dose of each pixel of a plurality of pixels, equal to the first laser dose conversion of each first relative laser intensity, is achieved by the second laser dose conversion of each second relative laser intensity. For example, when the coefficient is 0.8, pixels having each first relative laser intensity of 100% have each second relative laser intensity of 80%, and using the second laser dose conversion, the effective exposure laser dose for pixels currently having 80% of the second relative laser intensity is the same as the effective exposure laser dose for pixels having 100% of the first relative laser intensity using the first laser dose conversion.

[0036] With respect to FIG. 1, the proportional adjustment 220 of the laser dose conversion is performed with respect to block 140 (before block 150).

[0037] The proportional decrease in the relative laser intensity and the proportional adjustment of the laser dose conversion result in an invariant effective exposure laser dose for each pixel of the plurality of pixels, while all the set relative laser intensities are decreased.

[0038] Method 200 further includes increasing the relative laser intensity of each edge pixel within at least one edge pixel, or each adjacent pixel of at least one adjacent pixel, from each second relative laser intensity to each third relative laser intensity 230. The increase can be, for example, by adding a constant term.

[0039] The respective effective exposure laser doses achieved by the second laser dose conversion of each of the edge pixels within at least one edge pixel, or of each of the adjacent pixels of at least one adjacent pixel, can be configured to be higher than the respective effective exposure laser doses achieved by the first laser dose conversion of 100% relative laser intensity with respect to each of the first relative laser intensities. This means that the edge pixel or adjacent pixel is completely covered by the pattern and thus has a higher effective exposure laser dose than for the pixels of the plurality of pixels that should have a 100% relative laser intensity according to each of the first relative laser intensities. This is achievable because a proportional decrease in relative laser intensity and a proportional adjustment of the laser dose conversion result in an invariant effective exposure laser dose for each pixel of the plurality of pixels, while the set relative laser intensities are all decreased. For example, each of the third laser intensities can be a 100% relative laser intensity. Using the second laser dose conversion, this is converted to an effective exposure laser dose that is higher than the respective effective exposure laser doses achieved by the first laser dose conversion of 100% relative laser intensity with respect to each of the first relative laser intensities. This is because the respective effective exposure laser doses achieved by the first laser dose conversion of 100% relative laser intensity with respect to each of the first relative laser intensities are equal to the respective effective exposure laser doses achieved by the second laser dose conversion of a relative laser intensity of less than 100% with respect to each of the second relative laser intensities.

[0040] With respect to FIG. 1, increasing the relative laser intensity of each of the edge pixels within at least one edge pixel, or of each of the adjacent pixels of at least one adjacent pixel 230 is performed with respect to block 120 (before block 130).

[0041] Whether the constant term is added to the edge pixel or to the adjacent pixel can be determined based on one or more thresholds. For example, when one threshold, for example, 40% is used, a constant addition term is added to the second relative laser intensity of each of the edge pixels within at least one edge pixel, on the condition that the relative laser intensity of each of the edge pixels within at least one edge pixel corresponds to a relative laser intensity greater than the threshold, leading to each third relative laser intensity.

[0042] On the condition that the relative laser intensity of each of the edge pixels among at least one edge pixel corresponds to a relative laser intensity less than a threshold value, the second relative laser intensity of each of the adjacent pixels of at least one adjacent pixel is increased to each third relative laser intensity by a constant addition term. Here, the adjacent pixel is an adjacent pixel corresponding to an edge pixel having a relative laser intensity less than the threshold value. The threshold value is preferably set with respect to each first relative laser intensity that provides insufficient characteristics regarding the sharpness of the edge and the roughness of the edge. For example, the threshold value can be set to 50% with respect to each first relative laser intensity, and a coefficient of 0.8 corresponds to 40% with respect to each second relative laser intensity. Regarding FIG. 1, the pixel data having the effective exposure laser dose provided by method 200 includes an effective exposure laser dose that is not affected for 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, it is necessary to consider non-linearity, which includes complex calibration and correction. Edge pixels or adjacent pixels receive a higher effective exposure laser dose. The conversion of method 200 is applied to the relative laser intensity that is still linear with respect to the exposure area (for example, by multiplication by a coefficient less than 1). Furthermore, although the laser dose conversion is non-linearly calibrated and corrected, the level of the laser dose conversion can be adjusted to provide an effective exposure laser dose that is not affected for all pixels to be sufficiently exposed. Therefore, the adjustment of blocks 120 and 140 of FIG. 1 according to method 200 of FIG. 2 can be performed independently of block 130 of FIG. 1.

[0043] The implementation of the method of the present disclosure is now described with respect to FIGS. 3a to 3d. FIGS. 3a to 3d show a part of a pattern printed on a photosensitive resist and a diagram regarding 36 pixels regarding the photosensitive resist. For the sake of explanation, the pixels are designated with respect to 6 columns A to F and 6 rows 1 to 6. As a result, the upper left pixel is designated as pixel A1, the next pixel on the right is designated as pixel B1, and so on up to F6.

[0044] Note that FIGS. 3a - 3d are provided merely for illustrative purposes of showing the exemplary principle of printing a pattern onto a photosensitive resist. The number of pixels, the relative dimensions of the pixels, and the resulting pattern are not intended to reflect the actual results, but rather are intended to reflect some of the pixels and, typically, a much larger portion of the pattern.

[0045] In FIG. 3a, a portion of the pattern is shown as a diagonal stripe region with respect to 36 pixels A1 - F6. All of the pixels in columns C, D, and E are completely covered by the pattern, and the pixels in columns A and F are outside of the pattern. The pixels in column B are partially covered by the pattern such that the first two pixels B1 and B2 are covered up to 40% and the following four pixels B3, B4, B5, and B6 are covered up to 60%. Note that FIG. 3a is for illustrative purposes only to show the degree to which the various pixels are covered.

[0046] In the prior art, the pattern generation device is calibrated to generate the relative intensity of the laser for each pixel in proportion to the relative area, that is, the ratio of the area, the ratio of the pixels determined to be covered by the pattern, and the relative intensity of the laser for that pixel is set to that specific ratio. Returning to FIG. 3b, this is shown for a part of the pattern shown in FIG. 3a. For the pixels in columns C, D, and F covered up to 100% by the pattern, a relative laser intensity of 100% is set as each first relative laser intensity for that pixel. This is shown by the pixels shown as black representing a relative laser intensity of 100%. For the two pixels B1 and B2 from the top of column B covered up to 40% by the pattern, a relative laser intensity of 40% is set as each first relative laser intensity for that pixel. This is shown by the pixels shown as black dots on a white background representing a relative laser intensity of 40%. For the next four pixels B3, B4, B5, and B6 of column B covered up to 60% by the pattern, a relative laser intensity of 60% is set as each first relative laser intensity for that pixel. This is shown by the pixels shown as vertical black stripes on a white background representing a relative laser intensity of 60%.

[0047] Pixels B1 and B2, each having a first relative laser intensity of 40%, and both pixels B3, B4, B5, and B6, each having a first relative laser intensity of 60%, are both in an intermediate range close to 50%. Therefore, the characteristics of the sharpness and edge roughness of the printed pattern are not favorable. To improve the characteristics of the sharpness and edge roughness of the printed pattern, for example, a method according to the present disclosure, such as that described with respect to FIG. 1, can be used. Next, begin to proportionally decrease the relative laser intensity of each pixel of the pixels from each first relative laser intensity to each second relative laser intensity. With respect to FIG. 3b, a coefficient of 0.8 can be multiplied by each first laser intensity of each pixel of a plurality of pixels. Thus, the pixels in columns C, D, and E, each having a first relative laser intensity of 100%, have a second relative laser intensity of 80% each. This is shown in FIG. 3c by pixels shown as white dots on a black background representing a relative laser intensity of 80%. The two pixels B1 and B2 from the top of column B, each having a first relative laser intensity of 40%, have a second relative laser intensity of 32% each. This is shown in FIG. 3c by pixels shown as black grids on a white background representing a relative laser intensity of 32%. The next four pixels B3, B4, B5, and B6 in column B, each having a first relative laser intensity of 60%, have a second relative laser intensity of 48% each. This is shown in FIG. 3c by pixels shown as black horizontal lines representing a relative laser intensity of 48%.

[0048] Next, the decrease in relative laser intensity as shown in FIG. 3c is combined with 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. The proportional adjustment is such that each effective exposure laser dose of each pixel of a plurality of pixels is achieved by the second laser dose conversion of each second relative laser intensity equal to the each effective exposure laser dose of each pixel of a plurality of pixels due to the first laser dose conversion of each first relative laser intensity.

[0049] The proportional decrease in relative laser intensity and the proportional adjustment of laser dose result in an invariant effective exposure laser dose for each pixel, but the set relative laser intensities all decrease. However, doing this would correspond to an individual increase in relative laser intensity for all pixels because each of the second relative laser intensities for all pixels is currently 80% or less.

[0050] To improve the sharpness of the edges and the roughness characteristics of the printed pattern, the relative laser intensity of the edge pixels within at least one edge pixel or the adjacent pixels of at least one adjacent pixel can be increased from each second relative laser intensity to each third relative laser intensity. The increase can be, for example, by the addition of a constant term.

[0051] Figure 3d shows each relative laser intensity for the pixels after increasing the relative laser intensity for a portion of the pixels. For example, in column E, the relative laser intensity of the edge pixels, pixels E1, E2, E3, E4, E5, and E6, is increased by adding a constant addition term corresponding to 20% relative laser intensity to each second relative laser intensity of 80%, resulting in each third relative laser intensity of 100%. This is shown in Figure 3d by pixels E1, E2, E3, E4, E5, and E6 shown as black representing 100% relative laser intensity. This means that the edge pixels E1, E2, E3, E4, E5, and E6 in column E have a higher effective exposure laser dose than the pixels D1, D2, D3, D4, D5, and D6 in column D, which had 100% relative laser intensity according to each first relative laser intensity. This is because each effective exposure laser dose achieved by the first laser dose conversion of 100% relative laser intensity according to each first relative laser intensity is equal to each effective exposure laser dose achieved by the second laser dose conversion of less than 100% relative laser intensity according to each second relative laser intensity.

[0052] Generally, for example, by increasing the relative laser intensity such that the effective exposure laser dose of an edge pixel is higher than the effective exposure laser dose for a pixel having 100% relative laser intensity corresponding to each first relative laser intensity, the characteristics of the sharpness of the edge and the roughness of the edge of the printed pattern with respect to that edge pixel are improved. This increase can be referred to as providing an overdose with respect to the edge pixel.

[0053] Whether the constant term is added to the edge pixel or to the adjacent pixel can be determined based on one or more threshold values. For example, with respect to FIG. 3b, a threshold value of 40% is used for each relative laser intensity, which corresponds to 50% with respect to each first relative laser intensity. For each edge pixel having a second relative laser intensity exceeding the threshold value of 40%, a constant addition term is added to each second relative laser intensity of the edge pixel, and for each edge pixel having a second relative laser intensity lower than 40%, the constant addition term is added to each second relative laser intensity of the adjacent pixel of the edge pixel.

[0054] Two pixels B1 and B2 from the top of column B, each having a second relative laser intensity of 32%, are shown in FIG. 3c by pixels shown as a black grid on a white background. This is lower than the threshold of 40%, and a constant addition term is added to each of the second relative laser intensities of the adjacent pixels C1 and C2 of the edge pixels B1 and B2, respectively. In this case, a constant addition term corresponding to a relative laser intensity of 20% is added to each of the 80% of the second relative laser intensities of the adjacent pixels C1 and C2, respectively, thereby resulting in a third relative laser intensity of 100% for each of the two adjacent pixels C1 and C2. This is shown in FIG. 3d by pixels C1 and C2 shown as black, representing a relative laser intensity of 100%. This means that the adjacent pixels C1 and C2 have a higher effective exposure laser dose than that for the pixels D1 and D2 of column D, which each had a relative laser intensity of 100% for each of the first relative laser intensities, respectively.

[0055] Generally, while maintaining the relative laser intensity of each of the corresponding edge pixels, by increasing the relative laser intensity of the adjacent pixels by adding a constant addition term, when the corresponding edge pixels have a first relative laser intensity in a lower intermediate range around 50%, such as 50% or less, the characteristics of the sharpness and roughness of the edge of the printed pattern with respect to the corresponding edge pixels are improved. This is because the increase effectively reduces the relative laser intensity of the edge pixels with respect to the relative laser intensity of the adjacent pixels. Therefore, the relative laser intensity of the adjacent pixels has a greater impact on the appearance of the edge, which improves the characteristics of the edge in terms of sharpness and roughness of the edge.

[0056] The next four pixels B3, B4, B5, and B6 in column B, each having a first relative laser intensity of 60%, have a second relative laser intensity of 48% each. This is shown in Figure 3c by the pixels shown as a black horizontal line representing a relative laser intensity of 48%. This is above the threshold of 40%, and a constant addition term is added to the second relative laser intensity of each of the edge pixels B3, B4, B5, and B6. In this case, a constant addition term corresponding to a relative laser intensity of 20% is added to the 48% second relative laser intensity of each of the edge pixels B3, B4, B5, and B6, thereby resulting in a third relative laser intensity of 68% for each of the two edge pixels B3, B4, B5, and B6. This is shown in Figure 3d by the edge pixels B3, B4, B5, and B6 shown as black vertical stripes on a white background representing a relative laser intensity of 68%. This means that the edge pixels B3, B4, B5, and B6 each have a higher effective exposure laser dose than they had based on the first relative laser intensity and the first laser dose conversion of each of the edge pixels B3, B4, B5, and B6.

[0057] Generally, for example, by increasing the effective exposure laser dose of the edge pixels by adding a constant addition term to each of the second relative laser intensities, when the corresponding edge pixels have a first relative laser intensity in the middle range of the higher portion around 50%, such as 50% or more, the characteristics of the sharpness and roughness of the edge of the printed pattern regarding the edge pixels are improved. This is because the increased effective exposure laser dose corresponds to the effective exposure laser dose resulting from each of the first relative laser dose and the first dose conversion, and each of the first relative laser doses is close to a higher range, for example, 80% - 100%, and for this range, sufficient characteristics regarding the sharpness and roughness of the edge occur.

[0058] The pixels C3, C4, C5, and C6 in column C, and the pixels D1, D2, D3, D4, D5, and D6 in column D are invariant in terms of their respective relative laser intensities. This is shown in FIG. 3d by the pixels indicated by white dots on a black background, which represent a relative laser intensity of 80%, the same as in FIG. 3c.

[0059] FIG. 4 shows a schematic diagram of an example of the setting of each relative laser intensity for the device 400 or a plurality of pixels according to the present disclosure. The plurality of pixels includes at least one edge pixel and at least one adjacent pixel, and at least one adjacent pixel is arranged one pixel away from at least one edge pixel in a direction perpendicular to the edge. The device includes processing means configured to perform the method of the present disclosure, such as the method described with respect to FIGS. 1 and 3a-3d. The processing means can be, for example, the processor 410 provided in the device 400.

[0060] The device 400 may further include a computer-readable medium in the form of, for example, a memory 420. The computer-readable medium may include computer-readable instructions 430 that cause a processing device, such as the processor 410, to perform the method of the present disclosure, such as the method described with respect to FIGS. 1 and 3a-3d, when executed on the processing device. The computer-readable instructions 430 may be included in a computer program. The device 400 may be further provided in a mask drawing system.

[0061] As described above, the inventors have noticed that the sharpness and roughness of the edge of the printed pattern are due to the relative laser intensity of the pixels at or near the edge of the pattern. In this regard, the inventors have further noticed that the edge can be improved with respect to edge sharpness and edge roughness by providing an "overdose" to the edge pixels or adjacent pixels.

[0062] A method for setting the effective exposure laser dose of a plurality of pixels representing lithographic exposure is described below. The plurality of pixels includes at least one edge pixel disposed at an edge of the area of the pixel to be exposed, at least one adjacent pixel disposed one pixel away from at least one edge pixel in a vertical direction away from the edge and towards the area of the pixel to be exposed, and at least one non - adjacent pixel disposed at least two pixels away from at least one edge pixel in a vertical direction away from the edge and towards the area of the pixel to be exposed. The method includes setting the effective exposure laser dose of each pixel of the plurality of pixels such that the effective exposure laser dose of each of the edge pixels within at least one edge pixel or each of the adjacent pixels adjacent to at least one adjacent pixel is higher than the effective exposure laser dose of each of the non - adjacent pixels.

[0063] The non - adjacent pixels are pixels that are completely covered by the vector pattern data depicting the pattern to be printed. Since the effective exposure laser dose of each of the edge pixels or adjacent pixels is set higher than the effective exposure laser dose of each of the non - adjacent pixels, an "overdose" is provided to the edge pixels or adjacent pixels. The overdose can be achieved, for example, by method 200 described with respect to FIG. 2 or any other suitable method.

[0064] The description of the above example should be considered non - limiting. Although specific examples have been described, it will be apparent to those skilled in the art that various changes, modifications, or alterations are contemplated within the scope as defined in the appended claims.

Claims

Claim 1 A method for setting respective relative laser intensities for a plurality of pixels representing lithographic exposure, comprising: the plurality of pixels including at least one edge pixel disposed at an edge of an area of pixels to be exposed and at least one adjacent pixel, wherein the at least one adjacent pixel is disposed one pixel away from the at least one edge pixel in a vertical direction away from the edge and toward the area of pixels to be exposed, the method comprising: proportionally decreasing the relative laser intensity of each pixel of the plurality of pixels from each respective first relative laser intensity to each respective second relative laser intensity; proportionally adjusting the laser dose conversion of the relative laser intensity of a pixel from a previously set first laser dose conversion value to a second laser dose conversion value such that each effective exposure laser dose of each pixel is achieved by the second laser dose conversion value of each respective second relative laser intensity equal to the respective effective exposure laser dose of each pixel due to the first laser dose conversion value of each respective first relative laser intensity; and increasing the relative laser intensity of the edge pixel among the at least one edge pixel or the adjacent pixel of the at least one adjacent pixel from each respective second relative laser intensity to each respective third relative laser intensity by a constant addition term. Claim 2 The method according to claim 1, wherein each respective second relative laser intensity is equal to each respective first relative laser intensity multiplied by a factor less than 1. Claim 3 The method according to claim 1 or 2, wherein each respective third relative laser intensity is such that each effective exposure laser dose achieved by the second laser dose conversion value of each respective third relative laser intensity of the edge pixel among the at least one edge pixel or the adjacent pixel of the at least one adjacent pixel is higher than each effective exposure laser dose achieved by the first laser dose conversion value of 100% relative laser intensity with respect to each respective first relative laser intensity. Claim 4 On the condition that the relative laser intensity of each of the edge pixels among the at least one edge pixel corresponds to a relative laser intensity greater than a threshold value, the constant addition term increases the second relative laser intensity of each of the edge pixels among the at least one edge pixel to the third relative laser intensity of each; On the condition that the relative laser intensity of each of the edge pixels among the at least one edge pixel corresponds to a relative laser intensity less than the threshold value, the constant addition term increases the second relative laser intensity of each of the adjacent pixels among the at least one adjacent pixel to the third relative laser intensity of each; The method according to any one of claims 1 to 3, further comprising the above.

5. The method according to any one of claims 1 to 4, wherein each of the first relative laser intensities corresponds to a ratio of relative laser intensities from 0 percent to 100 percent.

6. An edge pixel is a pixel arranged adjacent to at least one pixel having a relative laser intensity greater than 0 percent and a relative laser intensity of 0 percent for each of the first relative laser intensities, according to the method of any one of claims 1 to 5.

7. An adjacent pixel is a pixel arranged adjacent to an edge pixel in a direction perpendicular to the edge, having a relative laser intensity greater than 0 percent for each of the first relative laser intensities, according to the method of claim 6.

8. A computer-readable medium including computer-readable instructions that, when executed on a processing device, cause the processing device to perform the method according to any one of claims 1 to 7.

9. A computer program including computer-readable instructions that, when executed on a processing device, cause the processing device to perform the method according to any one of claims 1 to 7.

10. A device for setting 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 the at least one adjacent pixel is arranged one pixel away from the at least one edge pixel in a direction perpendicular to the edge; The apparatus comprises processing means configured to perform the method according to any one of claims 1 to 7. **Claim 11** A mask drawing system comprising the apparatus according to claim 10.

Images