Method and apparatus for pattern generation

Abstract

A method of rasterization of a pattern having periodic components for an SLM is presented, the method comprising obtaining (S10) an original pattern having periodicity. A first pattern principal period is determined (S21). An image area of an imaging element and a first pitch are obtained (S31). The original pattern is scaled (S41) with a first raster scaling factor. The scaled pattern is cropped (S51) to include a first integer number of repetitions of pattern items exhibiting periodicity in a first direction covered by the image area, thereby providing a rasterized pattern adapted to an intended pattern generator. The rasterized pattern is associated with data representative of the first scaling factor. A method of writing is also disclosed, the method comprising obtaining the rasterized pattern. Elements of the SLM falling outside the rasterized pattern in the pattern generator are set to be disabled. The rasterized pattern is written to a target surface with an optical scaling factor.

Description

Technical Field

[0001] The present invention generally relates to rasterizing and writing patterns using a pattern generator based on a spatial light modulator, and more particularly to a method and apparatus for rasterizing and writing patterns with periodic components. Background Technology

[0002] Today, pattern generators are used for a variety of purposes. Pattern generators used in lithography systems or photomask lithography systems need to exhibit very precise printing characteristics. One method to achieve high-quality pattern printing is to use spatial light modulators (SLMs), such as digital micromirror devices (DMDs), liquid crystal displays (LCDs), grating light valves (GLVs), planar light valves (PLVs), micro shutter arrays (MSAs), analog spatial light modulators (ASLMs), and / or liquid crystal on silicon (LCSs). An SLM has an array of independently controllable elements arranged to generate an array of imaging elements within an image region on a target surface. The illumination of each individual imaging element is controlled by a corresponding element.

[0003] SLMs inherently possess periodicity, and in applications where the pattern to be printed also exhibits periodicity, various types of interference effects may occur. These effects may remain in the final product (e.g., different types of screens) and are perceptible to the human eye. Very small changes, if systematic, are more easily observed; such changes are often referred to as the Mura effect. SLMs used in pattern generators often have fixed physical dimensions and a fixed field of view aperture, and may have decreasing margins. This makes it difficult to adapt to subtle trends or variations in pattern characteristics. Therefore, it is difficult to mitigate interference phenomena arising from periodic patterns. Summary of the Invention

[0004] Therefore, the overall objective of this technology is to provide a method and apparatus based on SLM that is suitable for avoiding interference effects when printing repeating patterns.

[0005] The above-mentioned objective is achieved by the method and apparatus as described in the independent claim. Preferred embodiments are defined in the dependent claims.

[0006] In general, in a first aspect, a rasterization method for a pattern with periodic components is proposed. This method is intended for use in an SLM-based pattern generator. An SLM has an array of independently controllable elements arranged to generate an array of imaging elements within an image region on a target surface. Illumination of each independent imaging element is controlled by a corresponding such element. The rasterization method includes obtaining an original pattern having periodic pattern items. Determining a first pattern principal period in a first direction of the original pattern. Obtaining information about the image region and a first spacing of the imaging elements in the first direction of the intended pattern generator. Scaling the original pattern in the first direction with a first raster scaling factor to produce a scaled pattern. The first raster scaling factor is equal to a first integer multiplied by the first spacing of the pattern generator in the first direction divided by the first pattern principal period. Clipping the scaled pattern to include a first integer number of repetitions of the periodic pattern items in the first direction and including overlapping decreasing margins (if any) covered by the image region in the first direction of the intended pattern generator, thereby producing a rasterized pattern suitable for the intended pattern generator. This rasterized pattern is associated with data representing the first scaling factor.

[0007] In a second aspect, a method for writing a pattern with a periodic component for an SLM-based pattern generator is proposed. The SLM has an array of independently controllable elements arranged to generate an array of imaging elements in an image region on a target surface. Illumination of each independent imaging element is controlled by a corresponding element. The writing method includes obtaining a rasterized pattern having relevant data representing a first raster scaling factor, thereby defining scaling of the rasterized pattern in a first direction. Elements of the SLM that fall outside the rasterized pattern in the first direction in the pattern generator are disabled. The rasterized pattern is written into the image region on the target surface. The writing includes scaling in the first direction with a first optical scaling factor. The first optical scaling factor is not one.

[0008] In a third aspect, a rasterization module for an SLM-based pattern generator is proposed. The SLM has an array of independently controllable elements arranged to generate an array of imaging elements within an image region on a target surface. Illumination of each independent imaging element is controlled by a corresponding element. The rasterization module includes a processor and a memory. The memory includes instructions executable by the processor, thereby configuring the rasterization module to obtain an original pattern with pattern items exhibiting periodicity. The rasterization module is also configured to determine a first pattern principal period in a first direction of the original pattern. The rasterization module is further configured to obtain information about the image region and a first spacing D1 of the imaging elements in the first direction of the intended pattern generator to be used. The rasterization module is further configured to scale the original pattern in the first direction with a first raster scaling factor, thereby producing a scaled pattern. The first raster scaling factor is equal to a first integer multiplied by the first spacing of the pattern generator in the first direction divided by the first pattern principal period. The rasterization module is further configured to clip and scale the pattern, including a first integer number of repetitions of a periodic pattern item in a first direction, and including overlapping decreasing margins (if any) covered by the image region in the first direction of the intended pattern generator, thereby producing a rasterized pattern suitable for the intended pattern generator. This rasterized pattern is associated with data representing a first raster scaling factor.

[0009] In a fourth aspect, a pattern generator includes a control module and an imaging module. The imaging module is arranged to write a pattern into an image region using a surface-mount laser (SLM). The SLM has an array of independently controllable elements arranged to generate an array of imaging elements within an image region on a target surface. Illumination of each independent imaging element is controlled by a corresponding element. The control module is configured to obtain a rasterized pattern having associated data representing a first raster scaling factor, which defines scaling of the rasterized pattern in a first direction. The control module is also configured to disable elements of the SLM that fall outside the rasterized pattern in the first direction within the pattern generator apparatus. The imaging module includes an optical device controlled by the control module for scaling the rasterized pattern in the first direction with a first optical scaling factor before the rasterized pattern is written into the image region. The first optical scaling factor is not one.

[0010] One advantage of the proposed technique is that the performance of the SLM can be adapted to any periodic pattern. Other advantages will be understood when reading the detailed description. Attached Figure Description

[0011] The invention and its other objects and advantages can be best understood by referring to the following description in conjunction with the accompanying drawings, in which:

[0012] Figure 1 A pattern generator based on SLM is illustrated schematically;

[0013] Figure 2 A portion of the target surface is schematically shown;

[0014] Figure 3 A portion of another target surface is shown;

[0015] Figure 4 This is a flowchart of a method for an embodiment of a conventional method for pattern generation;

[0016] Figure 5 A portion of a scaled pattern is shown at the target surface;

[0017] Figure 6 A portion of the scaling and clipping pattern at the target surface is shown;

[0018] Figure 7 The decreasing margin in an SLM-based pattern generator is illustrated schematically.

[0019] Figure 8 This is a flowchart of the steps of an embodiment of a rasterization method for a pattern with periodic components for an SLM-based pattern generator;

[0020] Figure 9 An SLM array covered with a rasterized pattern is shown;

[0021] Figure 10 An embodiment of optical scaling of a pattern between an SLM and a target area is schematically illustrated;

[0022] Figure 11 This is a flowchart of the steps of an embodiment of a method for writing a pattern with periodic components for an SLM-based pattern generator;

[0023] Figure 12 An embodiment of an SLM array with non-orthogonal principal symmetry axes is schematically illustrated;

[0024] Figure 13 An embodiment of an unaligned SLM is schematically illustrated;

[0025] Figure 14 An embodiment of the multiple exposure principle is illustrated schematically;

[0026] Figure 15 An embodiment of a rasterization module is schematically illustrated;

[0027] Figure 16 An embodiment of the pattern generation system is illustrated schematically;

[0028] Figure 17An embodiment of a pattern generator is schematically illustrated; and

[0029] Figure 18 An embodiment of an optical device for optical scaling in two directions is illustrated schematically. Detailed Implementation

[0030] In all the accompanying drawings, the same reference numerals are used for similar or corresponding elements.

[0031] To better understand the proposed technique, it may be helpful to begin with a brief overview of geometric considerations in an SLM-based pattern generator.

[0032] Figure 1 A pattern generator 1 based on an SLM 2 is schematically shown. The SLM 2 is shown herein as an array 3 of independently controllable elements 4, which in this embodiment are radiation-reflecting elements. Light 5 incident on the array 3 is reflected toward a target surface 10 as a set of exposure beams 6. The target surface 10 is typically supported by a target support 12. The individual elements 4 of the SLM 2 are controllable to allow or suppress reflection. The elements 4 of the SLM 2 can also be set to be disabled, thereby reducing the active portion of the array 3.

[0033] Light exiting the active portion of the SLM 2 is directed to the target surface 10, where it forms an array 20 of imaging elements 22. The imaging elements 22 collectively form the imaging region 14. Thus, the illumination of each individual imaging element 22 is controlled by the corresponding element 4 of the SLM 2. Typically, the imaging region 14 has a nominal optical scaling relative to the SLM array 20. This nominal scaling is a consistent scaling determined by different design parameters (e.g., different distances) and common optics. Arrangements for achieving this nominal scaling are well known to any person skilled in the art and will not be discussed further.

[0034] As described in the Background section, the SLM 2 can be configured in many different ways. The operational details of the SLM 2 are not important to this invention, as long as independent control of the element 4 is achieved and the SLM 2 generates an array 20 of imaging elements 22 in the imaging region 14 on the target surface 10.

[0035] After the imaging area 14 is exposed independently according to the element 4 of the SLM 2, the imaging area 14 can be moved. This can typically be done by mechanically moving the SLM 2 relative to the target support 12, by moving the target support 12, the SLM 2, or both. The movement of the imaging area 14 can also be at least partially performed by the optical device.

[0036] Figure 2A portion of the target surface 10 is schematically shown. The imaging region 14 of the current position of the SLM is depicted as an array 20 of imaging elements 22. The imaging elements 22 have a first spacing D1 in a first direction 101 and a second spacing D2 in a second direction 102. In this illustration, the number of imaging elements is small for illustrative purposes. In this case, some elements of the SLM allow radiation to be directed to the imaging region 14 and are marked in black. The selection of the elements of the SLM is based on printing data representing the pattern 30 to be printed. The intended pattern 30, shown in dashed lines, is for reference only and does not actually exist in the imaging region 14. However, it is easy to see that the imaging elements 22 corresponding to items in the pattern 30 are illuminated, while the imaging elements 22 corresponding to the areas between items in the pattern 30 are not illuminated. Areas of the intended pattern 30 that fall outside the current imaging region 14 are marked as shaded areas and will be processed by previous or subsequent printing steps.

[0037] It should be noted that in some applications, the illumination may correspond to the opposite of pattern 30, that is, only the imaging element 22 outside the intended pattern is illuminated. However, this would resemble a “negative” pattern 30.

[0038] See Figure 2 Once imaging region 14 has been illuminated, it can be moved before the next exposure. An example of the next position is shown in the figure with a dashed line 14”. Another portion of pattern 30 can then be exposed onto the target surface 10. In this way, the entire surface of the target surface 10 can be covered.

[0039] It should be noted here that the displacement of imaging region 14 can also have a small overlap. Thus, each pattern intended to correspond to imaging region 14 can include decreasing margins to avoid edge effects between different imaging regions. This will be discussed further later. Another possibility is to use multiple exposures, where imaging region 14 is moved by only a small fraction of its width, resulting in each point on the target surface 10 being exposed multiple times. Such embodiments will be discussed further below. It is also possible to expose the same imaging region 14 more than once, i.e., without any movement between exposures.

[0040] Figure 3A portion of another target surface 10 is shown. A pattern 30 to be exposed onto the target surface 10 is also shown, but for reference only. This pattern 30 is a periodic pattern with periodic items 32. Pattern 30 exhibits a first main pattern period PM1 in a first direction 101 and a second main period PM2 in a second direction 102. It can be seen that the items 32 of pattern 30 are positioned somewhat differently relative to the imaging element 22 they cover. This is because the first main pattern period PM1 is not a multiple of the first spacing D1 of the imaging element 22, and the second main pattern period PM1 is not a multiple of the second spacing D1 of the imaging element 22. Therefore, the lower left corner of the items 32 has a different position relative to the lower left corner of the imaging element 22. Consequently, the items 32 are typically displaced a small distance in both the horizontal and vertical directions between each repetition. As discussed in the Background section, this small repetitive displacement causes different interference effects, resulting in the Mura problem.

[0041] To mitigate this effect, the concept of this invention is proposed. The basic idea is to use a two-part method. In the first part, the printing data of the pattern to be printed is modified to have a periodicity consistent with the periodicity of the SLM. Therefore, this is a recalculation of the data that forms the basis of the subsequent printing. In the second part, the actual printing is performed based on the recalculated printing data. However, in order to achieve the required absolute and relative dimensions, this writing is performed by scaling in the corresponding direction using an optical scaling factor.

[0042] Figure 4 A flowchart illustrating this relationship is shown. Partial method M1 is a rasterization method for a pattern with periodic components used in an SLM-based pattern generator. Partial method M2 is a writing method for a pattern with periodic components used in an SLM-based pattern generator. These methods can be executed in combination with each other, or even utilize the same processing device. However, these methods can also be executed separately, connected only by transmitting the rasterized pattern and related information of partial method M1 that will be used in partial method M2.

[0043] The effects of the first part of the method will now be explained with reference to a series of accompanying figures. These figures depict hypothetical patterns of the imaging area on the target surface corresponding to operations performed on the printing data of the pattern. However, in this first part of the method, no actual writing is performed, and all operations are performed only on the representation of the printing data of the pattern.

[0044] exist Figure 3 In this study, differences can be observed between repetitive items and the imaging element array. Figure 5In this process, the same pattern is scaled into a scaled pattern 31. The pattern is scaled in the first direction 101 by a first raster scaling factor F1. In this particular instance, F1 is slightly less than 1, causing the scaled pattern 31 to be slightly narrower than the original pattern. This scaling changes the first pattern principal period PM1 to the first scaled pattern principal period PM1' to match a first integer n1 times the first spacing D1 of the SLM in the first direction 101.

[0045] If the original first pattern principal period PM1, the first spacing D1 of the SLM, and the appropriate first integer n1 are known, then the first raster scaling factor F1 can be calculated by the following formula:

[0046] F1 = PM1' / PM1 = n1 * D1 / PM1.

[0047] In the second direction 102, the pattern is scaled by a second raster scaling factor F2. In this particular instance, F2 is slightly greater than 1, such that the scaled pattern 31 is slightly taller than the original pattern. This scaling changes the second pattern principal period PM2 to the second scaled pattern principal period PM2' to match a second integer n2 times the second spacing D2 of the SLM in the second direction 102.

[0048] If the original first pattern principal period PM1, the first spacing D1 of the SLM, and the appropriate first integer n1 are known, then the first raster scaling factor F1 can be calculated by the following formula:

[0049] F2 = PM2' / PM2 = n2 * D2 / PM2.

[0050] The scaled pattern 31 now perfectly matches the SLM's grating. Each part of the repeated item 32 appears in the same relationship as the imaging element 22. For example, the lower left corner of the shown item 32 now coincides with the corner of the imaging element 22 at other locations within the imaging area 14.

[0051] Imaging region 14 includes a total of k1 imaging elements 22 in the first direction 101. Imaging region 14 also includes a total of k2 imaging elements 22 in the second direction 102. However, in most cases, when the number of imaging elements 22 k1 in the first direction 101 is not a multiple of the first integer n1, items of the scaled pattern 31 may partially fall outside imaging region 14. Similarly, in most cases, when the number of imaging elements 22 k2 in the second direction 102 is not a multiple of the second integer n2, items of the scaled pattern 31 may also partially fall outside imaging region 14.

[0052] To avoid this type of partially covered project, the pattern is cropped. This is in Figure 6The diagram illustrates this schematically. A number of k1 imaging elements 22 in the first direction 101 are cropped by a first difference Δk1, leaving k1' imaging elements 22 in the first direction 101. The number k1' of imaging elements 22 in the first direction 101 is selected as a multiple of the main period PM1' of the first scaling pattern. In other words:

[0053] K1' = L1 * PM1',

[0054] Where L1 is an integer.

[0055] Similarly, the number k2 imaging elements 22 in the second direction 102 is clipped by a second difference Δk2, leaving k2' imaging elements 22 in the second direction 102. The number k2' of imaging elements 22 in the second direction 102 is selected as a multiple of the main period PM2' of the second scaling pattern. In other words:

[0056] K2'=L2*PM2',

[0057] Where L2 is an integer.

[0058] This produces a rasterized pattern 33. This rasterized pattern is adapted to the intended pattern generator. The rasterized pattern is also associated with data representing a first scaling factor and a second scaling factor so that the original size and shape can be recovered.

[0059] As mentioned above, when the pattern generator uses a method with overlapping decreasing margins, these margins must be included in the rasterized pattern. Figure 7 The decreasing margin in an SLM-based pattern generator is schematically illustrated. The current imaging region 14 shown has a central region 15, shown as a black area, which has a regular rasterization pattern. In the decreasing region 13, a rasterization pattern is also included in one or two directions around the central region 15, but typically with reduced intensity. In one embodiment, the intensity decreases from full intensity at the boundary of the central region 15 to zero intensity at the outer boundary. In the example shown, the width of the decreasing region is T1 in the first direction 101 and T2 in the second direction 102. The next imaging region 14' is indicated by dashed lines. The next imaging region 14' is moved a distance 17 relative to the current imaging region 14 in the first direction. It can be seen that the decreasing regions 13 and 13' of the current image 14 and the next image 14' overlap, which means that another exposure of these regions is performed on the next image region 14'. This double exposure together produces a pattern in the imaging element similar to the pattern produced by the imaging element in the central region. The use of decreasing margins is believed to reduce edge effects in the imaging region 14, 14'.

[0060] If used, the clipping according to this idea must be adapted to the decreasing region. Therefore, one embodiment of the rasterization method further includes the step of reducing the overlap intensity of the edges of the rasterization pattern.

[0061] In this case, the cutting should be performed according to the following formula:

[0062] K1' = L1 * PM1' + T1, and

[0063] K2' = L2 * PM2' + T2,

[0064] Where T1 and T2 are the widths (spacings) of the overlapping decreasing margins in the first direction 101 and the second direction 102, respectively.

[0065] In the example given above, the periodic pattern has already been processed in two directions. However, in some applications, such as those where the periodicity of the pattern exists only in one direction, it is certainly possible to process it in only one direction.

[0066] Figure 8 A flowchart illustrating the steps of an embodiment of a rasterization method for a pattern with periodic components for an SLM-based pattern generator is shown. The SLM has an array of independently controllable elements arranged to generate an array of imaging elements within an image region on a target surface, wherein the illumination of each independent imaging element is controlled by a corresponding element. In step S10, the original pattern is obtained.

[0067] The original pattern has periodic pattern items. In step S21, the first main pattern period P in the first direction of the original pattern is determined. M1 In step S31, information about the image region and first spacing D1 of the imaging element in the first direction of the intended pattern generator is obtained. In step S40, the original pattern is scaled. In part of step S41, the original pattern is scaled in the first direction by a first raster scaling factor to provide a scaled pattern. The first raster scaling factor is equal to a first integer multiplied by the first spacing of the pattern generator in the first direction divided by the first pattern principal period. In step S50, trimming is performed. In part of step S51, the scaled pattern is trimmed to include a first integer number of repetitions of pattern items that present periodicity in the first direction, and includes overlapping decreasing margins (if any) that cover the image region in the first direction of the intended pattern generator. This provides a rasterized pattern suitable for the intended pattern generator in one direction. This rasterized pattern is associated with data representing the first scaling factor.

[0068] The steps given above take into account the original pattern that repeats in (at least) one direction. In embodiments where the pattern repeats in only one direction, these steps are sufficient to mitigate different Mura effects.

[0069] In the example above, a two-dimensional SLM was assumed. However, this idea also applies to one-dimensional SLMs. In this case, the above steps will mitigate the Mura effect in the array direction of the SLM, while any possible Mura effect in the orthogonal direction must be handled by other means, which is outside the scope of this invention.

[0070] If the original pattern also has periodicity in the second direction and the SLM is a two-dimensional SLM, additional steps can be performed. In step S22, the second pattern principal period P in the second direction of the original pattern is determined. M2 The second direction is orthogonal to or at least laterally positioned relative to the first direction. In step S32, information about the image region and second spacing D2 of the imaging element in the second direction of the intended pattern generator is obtained. In step S40, which scales the original pattern, another step S42 further includes scaling the original pattern in the second direction by a second raster scaling factor, thereby providing a scaled pattern. The second raster scaling factor is equal to a second integer multiplied by the second spacing of the pattern generator in the second direction divided by the second pattern principal period. The clipping step S50 further includes step S52, in which the scaled pattern is further clipped to include pattern items that are periodically presented in the second direction and repeat a second integer number of times, and includes overlapping decreasing margins (if any) that will be covered by the image region in the second direction of the intended pattern generator, thereby providing a rasterized pattern. Thus, the rasterized pattern is also associated with data representing the second raster scaling factor.

[0071] This method yields a rasterized pattern, or more precisely, a definition of the rasterized pattern, which is used as printing data. Associated with this rasterized pattern is the raster scaling factor.

[0072] During the actual write operation, the rasterization pattern and its associated raster scaling factor are obtained. If the write is to be performed by the same entity responsible for rasterization, all data is already available, and the rasterization pattern can usually be obtained by simple retrieval from memory. If the write is to be performed by another entity, the pattern must be obtained by transferring the data representing the rasterization pattern and its associated raster scaling factor to the entity performing the write.

[0073] Figure 9The resulting rasterized pattern 35, overlaid on an array 3 of elements 4 in the SLM to be used, is schematically shown. As mentioned above, clipping may result in the rasterized pattern 35 not utilizing all elements 4 of the SLM. In other words, some elements of the SLM will be useless during printing. Therefore, it is first checked which portion of the SLM's elements fall outside the rasterized pattern in the pattern generator. These elements, denoted as 4', are then set to disabled and are shown in shaded lines in the figure. In other words, the optical clipping is performed similarly to the clipping in the rasterization stage.

[0074] In the case shown, the disabled element is indicated as being located at one edge of the SLM. However, elements on both sides of the remaining pattern can also be disabled in one or both directions.

[0075] The rasterized pattern may be somewhat distorted compared to the original pattern provided as input to the rasterization method. In most embodiments, the goal is to recover this distortion. To this end, the pattern generator has an imaging module arranged to write the pattern into an image region. This imaging module includes optical means configured to perform optical scaling of the pattern as it is written into the image region. This scaling can be controlled to vary in different directions.

[0076] By using this optical scaling, optical scaling can be controlled during pattern writing using a scaling factor associated with the rasterized pattern. In the case of restoring the original shape of items in the pattern, the optical scaling factor used is selected to be equal to the reciprocal of the corresponding raster scaling factor.

[0077] Optical scaling is performed between the SLM and the target area, and is provided as an adjustment or overlay of the nominal optical scaling between the SLM and the target surface in the pattern generator, as discussed further above. In this way, the SLM acts on a rasterized pattern suitable for dividing the SLM into an array of elements. Simultaneously, through optical scaling, the radiation reaching the target area is recovered to reconstruct the original shape.

[0078] Figure 10 This optical scaling is illustrated schematically. Radiation passing through the SLM is... Figure 10 The upper part indicates that the pattern still presents the shape of a rasterized pattern. Figure 10 The lower part shows the pattern written on the target area, i.e., after optical scaling by the imaging module. Imaging element 22' is rescaled according to the optical scaling ratio and covers the scaled imaging area 14', which is different from the nominal area. However, the shape of item 32 is restored to the originally intended shape.

[0079] In the example given above, actions affecting the written pattern have been performed in two directions. However, similar to what was discussed in the rasterization section, in some applications, such as those where the periodicity of the pattern exists only in one direction, it is of course possible to perform the corresponding actions only in one direction.

[0080] In some applications, there is no explicit requirement to maintain an accurate shape during writing. In some such applications, it may even be desirable to obtain some residual shape change of the written pattern. In such applications, the applied optical scaling may differ from the reciprocal of the corresponding raster scaling factor.

[0081] Figure 11 This is a flowchart of the steps of an embodiment of a method for writing a pattern with periodic components for a pattern generator based on an SLM. The SLM has an array of independently controllable elements arranged to generate an array of imaging elements in an image region on a target surface, wherein the illumination of each independent imaging element is controlled by a corresponding element. In step S60, a rasterized pattern is obtained. In part of step S61, data representing a first raster scaling factor associated with the rasterized pattern is obtained. This first raster scaling factor defines scaling of the rasterized pattern in a first direction. In step S70, elements of the SLM are set to be disabled. In part of step S71, elements of the SLM in the pattern generator that fall outside the rasterized pattern in the first direction are set to be disabled. In step S80, the rasterized pattern is written into the image region on the target surface. In part of step S81, the writing includes scaling in the first direction using a first optical scaling factor. The first optical scaling factor is not one.

[0082] In one particular embodiment, the first optical scaling factor is equal to the reciprocal of the first grating scaling factor.

[0083] If the original pattern is also periodic in the second direction, additional steps can be performed. The step of obtaining the rasterized pattern S60 may include a portion of step S62, in which the rasterized pattern is also associated with data representing a second raster scaling factor. This second raster scaling factor defines scaling of the rasterized pattern in the second direction. The second direction is orthogonal to or at least laterally relative to the first direction. The step of disabling elements of the SLM S70 also includes step S72, in which elements of the SLM in the pattern generator that fall outside the rasterized pattern in the second direction are disabled. The writing step S80 also includes step S82, in which scaling in the second direction with a second optical scaling factor is performed.

[0084] In one particular embodiment, neither the first optical scaling factor nor the second optical scaling factor is one.

[0085] In one particular embodiment, the second optical scaling factor is equal to the reciprocal of the second grating scaling factor.

[0086] In the examples given above, both the repeating pattern and the array of elements in the SLM exhibit orthogonal principal axes of symmetry. The array of imaging elements at the target surface is also assumed to be parallel to the intended direction of the periodic pattern. However, in other embodiments, other relationships and geometries can be utilized.

[0087] A simple example is an SLM array with a rectangular geometry, where the distance between two adjacent elements differs in two orthogonal directions. This is easy to use because the two directions are processed separately regardless, and different spacing values ​​can be input.

[0088] In one embodiment, the element array of an SLM can be arranged with non-orthogonal axes. An example is the use of a hexagonally symmetric SLM. In this case, the principal axes of symmetry of the element array point at 60° relative to each other. The imaging elements also exhibit hexagonal symmetry. One of the axes of the imaging element array can, for example, coincide with a first direction of the periodic pattern array. The spacing in this direction will be the distance between two consecutive imaging elements in that direction. However, the spacing in the orthogonal direction will become the distance between two lines in the first direction of the imaging elements in a second direction, i.e., the distance between rows of imaging elements. In this example, the spacing in the second direction will depend on the distance between two adjacent imaging elements and the angle 60°. This is in... Figure 12 The diagram is schematically shown. In the principal symmetry direction, the distances between adjacent imaging elements are d1 and d2, respectively. The spacing D1 in the first direction is equal to d1, while the spacing D2 in the second direction becomes a distance d2 that depends on the angle between the second principal symmetry axis and the second direction.

[0089] Another example of a usable relative geometry is an SLM array that uses an array of imaging elements that results in misalignment with the axis of symmetry of the periodic pattern. This is as follows: Figure 13 As shown, a current imaging region 14 and the next imaging region 14' (dashed line) are shown together. The axes of symmetry of the imaging element are rotated clockwise by angles α1 and α2 relative to the first and second directions, respectively. In most cases, angle α1 is equal to angle α2.

[0090] In other words, in one embodiment, the first main axis of the imaging element array is rotated by a first angle relative to a first direction, whereby the first spacing depends on the distance between two consecutive imaging elements along the first main axis and on the first angle.

[0091] In another embodiment, the second main axis of the imaging element array is rotated by a second angle relative to the second direction, whereby the second spacing depends on the distance between two consecutive imaging elements along the second main axis and on the second angle.

[0092] In some pattern generators, multiple exposures can be utilized. One way to arrange multiple exposures on a target surface is to shift the image region of the SLM on the target surface between two exposures by an amount smaller than the full width of the image region. A typical arrangement is to make the shift between two exposures correspond to an integer fraction of the image region width. For example, if the image region is shifted by 1 / 4 of its width between each exposure, then each point on the target surface will be exposed 4 times. This is in... Figure 14 The diagram is schematically shown. The imaging element array (i.e., imaging region 14) in this example is 16 imaging elements 22 wide. Between each exposure, imaging region 14 moves a distance corresponding to 4 imaging elements, as shown by the dashed line indicating the next imaging region 14'. Twelve rows of imaging elements will expose points on the target surface that have already been exposed, while four rows of imaging elements will expose new portions of the target surface.

[0093] Those skilled in the art will understand that the multiple exposure method can be performed at any integer fraction of the image area. However, it is easier to control the entire writing process if the width of the imaging area includes a number of imaging elements such that the integer fraction covers an integer number of imaging elements. In other words, it is preferable that the number of imaging elements in the direction of movement is an integer multiple of the number of multiple exposures.

[0094] In a system designed according to the above main ideas, the number of imaging elements in the imaging region may depend on the raster scaling factor and the subsequent cropping of the SLM region in the movement direction of the imaging region. Therefore, the final number of imaging elements used in the movement direction may vary depending on the pattern. However, since the scaling factor can be freely chosen in principle, at least within certain limits, it is possible to select the scaling factor in a manner that satisfies preferred multiple exposure conditions.

[0095] For example, to use six overlapping exposures, the total imaging area generated by the SLM must include a number of imaging elements that are divisible by six in the direction of movement. Furthermore, assume the entire SLM width includes 50 imaging elements. Meanwhile, if the periodic pattern has a periodicity corresponding to 6.7 times the spacing between imaging elements, then, ignoring the limitations of multiple exposures, the natural scaling choice would be to enlarge the periodic pattern to 7 times the spacing between imaging elements and crop the width of the imaging area to 7 repetitions of the pattern, i.e., 49 imaging elements. However, 49 is not divisible by 6, making multiple exposures difficult to perform. Conversely, if the periodic pattern is scaled down to 6 times the spacing between imaging elements, it is possible to crop 8 repetitions of the pattern to 48 imaging elements, which is also compatible with the multiple exposure method.

[0096] In other words, in one embodiment, the rasterization method further includes the step of obtaining data regarding a first number of partially overlapping exposures with equidistant displacement in a first direction of the intended pattern generator. A first raster scaling factor in the scaling step and a first integer repetition number in the clipping step are selected such that the ratio between the first integer repetition number multiplied by the first integer and the first number of partially overlapping exposures is an integer. Preferably, the first raster scaling factor is selected as close as possible to 1, taking into account constraints in selecting the first integer and the first integer repetition number (if any).

[0097] In a more refined version of multiple exposure, multiple exposures can be performed in both a first and a second direction. The same argument above can also be applied to the second direction.

[0098] In other words, in another embodiment, the rasterization method further includes a step of obtaining data regarding a second number of partially overlapping exposures with equidistant displacement in a second direction of the intended pattern generator. Then, a second raster scaling factor in the scaling step and a second integer repetition number in the clipping step are selected such that the ratio between the second repetition number multiplied by the second integer and the second number of partially overlapping exposures becomes an integer. Preferably, the second raster scaling factor is chosen to be as close as possible to 1, taking into account constraints in selecting the second integer and the second integer repetition number (if any).

[0099] This idea is applicable to all types of writing methods; however, the initial target technical field is its application to photolithography systems or photomask lithography systems. Therefore, in a preferred embodiment, the pattern generator is a photolithography system or a photomask lithography system.

[0100] exist Figure 15The image shows an embodiment of a rasterization module 60 for an SLM-based pattern generator. As described above, the SLM has an array of independently controllable elements arranged to generate an array of imaging elements within an image region on a target surface, wherein the illumination of each independent imaging element is controlled by a corresponding element. The rasterization module includes a processor 62 and a memory 64. The memory 64 contains instructions executable by the processor 62. Thus, the rasterization module is configured to obtain an original pattern with pattern items exhibiting periodicity, to determine a first pattern principal period in a first direction of the original pattern, and to obtain information about the image region and a first spacing of the imaging elements in the first direction of the intended pattern generator to be used. The instructions also enable the processor 62 to scale the original pattern in the first direction with a first raster scaling factor, thereby providing a scaled pattern. The first raster scaling factor is equal to a first integer multiplied by the first spacing of the pattern generator in the first direction divided by the first pattern principal period. The instructions also enable the processor 62 to trim and scale the pattern, including a first integer number of repetitions of periodic pattern items in a first direction, and including overlapping decreasing margins (if any) covered by the image region in the first direction of the intended pattern generator, thereby producing a rasterized pattern suitable for the intended pattern generator. This rasterized pattern is associated with data representing a first raster scaling factor.

[0101] In a preferred embodiment, memory 64 further includes instructions executable by processor 62, whereby the rasterization module is further configured to determine a second pattern principal period in a second direction of the original pattern, the second direction being orthogonal to the first direction. The instructions also enable processor 62 to obtain information about the image region and second spacing of the imaging element in the second direction of the intended pattern generator, and to scale the original pattern in the second direction with a second raster scaling factor, thereby providing a scaled pattern. The second raster scaling factor is equal to a second integer multiplied by the second spacing of the pattern generator in the second direction divided by the second pattern principal period. The instructions also enable processor 62 to clip the scaled pattern to include a second integer number of repetitions of periodic pattern items in the second direction, and to include overlapping decreasing margins (if any) covered by the image region in the second direction of the intended pattern generator, thereby producing a rasterized pattern suitable for the intended pattern generator. This rasterized pattern is also associated with data representing the second raster scaling factor.

[0102] Figure 16An embodiment of a pattern generation system 70 is shown, which includes a rasterization module 60 and a pattern generator 80. In this embodiment, the rasterization module 60 provides data representing a rasterized pattern and related data representing a scaling factor. In this embodiment, the rasterization module 60 is shown as a separate unit. The rasterized pattern can then be transmitted to the pattern generator 80 via a communication connection 62 or via an alternative wireless means. Alternatively, the data representing the rasterized pattern can be provided by the rasterization module 60 in a data storage device that is physically brought to the pattern generator 80 for access.

[0103] However, in other embodiments, the rasterization module 60 may be provided as part of the pattern generator 80, as shown by the dashed line, wherein processing power is preferably shared by the pattern generator 80 and the rasterization module 60. In this case, the rasterized pattern is transferred from the rasterization module 60 to the pattern generator 80 via internal means.

[0104] Figure 17 An embodiment of a pattern generator 80 is schematically illustrated. The pattern generator 80 includes a control module 82 and an imaging module 84. The imaging module 84 is arranged to write a pattern onto an image region. The imaging module includes an SLM 2. The SLM 2 has an array 3 of independently controllable elements 4 arranged to generate an array of imaging elements in an image region on a target surface 10. The illumination of each independent imaging element is controlled by the corresponding element 4 based on instructions from the control module 84.

[0105] The control module 82 is configured to obtain a rasterized pattern having relevant data representing a first raster scaling factor, which defines the scaling of the rasterized pattern in a first direction. As described above, the rasterized pattern can be provided from an internal or external source in different ways.

[0106] The control module 82 is also configured to disable the element 4 of the SLM 2 that falls outside the rasterized pattern in the first direction in the pattern generator device.

[0107] Imaging module 84 includes an optical device 88 controlled by control module 82, which is used to scale the rasterized pattern in a first direction with a first optical scaling factor before the rasterized pattern is written into the image area. The first optical scaling factor is not one.

[0108] In one embodiment, the first optical scaling factor is equal to the reciprocal of the first grating scaling factor.

[0109] In one embodiment, the control module 84 is further configured to obtain a rasterized pattern having additional data representing a second raster scaling factor, which defines scaling of the rasterized pattern in a second direction. The second direction is orthogonal to the first direction.

[0110] The control module 82 is also configured to disable the element 4 of the SLM 2 that falls outside the rasterized pattern in the second direction in the pattern generator device 80.

[0111] The imaging module includes an optical device 88 controlled by a control module 82, which is used to further scale the rasterized pattern in a second direction with a second optical scaling factor before the rasterized pattern is written into the image area.

[0112] In one embodiment, neither the first optical scaling factor nor the second optical scaling factor is one.

[0113] In one embodiment, the second optical scaling factor is equal to the reciprocal of the second grating scaling factor.

[0114] Figure 18 An embodiment of an optical device 88 for scaling an exposure beam representing a rasterized pattern is shown. Before being written into an image area, the rasterized pattern is scaled in a first direction with a first optical scaling factor, and optionally in a second direction with a second optical scaling factor.

[0115] In the upper part of the figure, a schematic diagram of the second direction is shown. Six lens elements 91-96 are provided, with lens elements 91, 93, and 95 responsible for optical scaling in the first direction. Lens elements 91, 93, and 95 are cylindrical lenses with a center of curvature along an axis perpendicular to the view shown. Lens elements 91 and 93 are movable along the optical axis to provide different optical scaling. Lens element 95 is fixed.

[0116] The lower part of the figure shows a schematic diagram in the first direction. Six lens elements 91-96 are provided, with lens elements 92, 94, and 96 responsible for optical scaling in the second direction. Lens elements 92, 94, and 96 are cylindrical lenses with a center of curvature along an axis perpendicular to the view shown. Lens elements 92 and 94 are movable along the optical axis to provide different optical scaling. Lens element 96 is fixed.

[0117] The embodiment of the optical device 88 described above is merely one example of how optical scaling can be adjusted differently in different directions. Anyone skilled in the art will recognize that similar arrangements with different numbers and types of lenses, as well as other optical arrangements that allow for different adjustments of scaling in different directions, can be used.

[0118] In various embodiments, the SLM 2 may include a digital micromirror device, a liquid crystal display, a grating light valve, a planar light valve, a micro shutter array, an analog spatial light modulator, and / or liquid crystal on silicon.

[0119] In one embodiment, the pattern generator is a photolithography system or a photomask photolithography system.

[0120] In one embodiment, the pattern generator 80 includes more than one SLM 2. The control module 84 is thus configured to independently control each SLM 2 according to the obtained rasterized pattern.

[0121] The above embodiments should be understood as several exemplary examples of the present invention. Those skilled in the art will understand that various modifications, combinations, and changes can be made to these embodiments without departing from the scope of the invention. Specifically, where technically possible, different partial solutions from different embodiments can be combined in other configurations. However, the scope of the invention is limited only by the appended claims.

Claims

1. A rasterization method for a pattern with periodic components based on a pattern generator of a spatial light modulator (2), the spatial light modulator (2) having an array (3) of independently controllable elements (4) arranged to generate an array (20) of imaging elements (22) within an image region (14) on a target surface (10), wherein the illumination of each independent imaging element (22) is controlled by the corresponding element (4), the rasterization method comprising the following steps: - Obtain (S10) the original pattern (30) having a pattern item (32) exhibiting periodicity; - Determine (S21) the first pattern main period (PM1) in the first direction (101) of the original pattern (30); - Obtain (S31) information about the image region (14) and the first spacing (D1) of the imaging element (22) in the first direction (101) of the intended pattern generator to be used; - The original pattern (30) is scaled (S41) in the first direction (101) by a first grating scaling factor to provide a scaled pattern (31); The first grating scaling factor is equal to a first integer multiplied by the first spacing (D1) of the pattern generator in the first direction (101) divided by the first pattern principal period (PM1); - Trim (S51) the scaled pattern (31) to include a first integer number of repetitions of the pattern item (32) that presents periodicity in the first direction (101), and if any, to include overlapping decreasing margins covered by the image region (14) in the first direction (101) of the intended pattern generator, thereby providing a rasterized pattern (33) suitable for the intended pattern generator; The rasterization pattern (33) is associated with data representing the first raster scaling factor.

2. The rasterization method as described in claim 1, characterized in that, The first main axis of the array (20) of the imaging elements (22) is rotated by a first angle (α1) relative to the first direction (101), whereby the first spacing (D1) depends on the distance (d1) between two consecutive imaging elements (22) along the first main axis and depends on the first angle (α1).

3. The rasterization method as described in claim 1 or 2, characterized in that, It also includes the following steps: - Determine (S22) the second pattern principal period (PM2) on the second direction (102) of the original pattern (30), wherein the second direction (102) is orthogonal to the first direction (101); - Obtain (S32) information about the image region (14) and the second spacing (D2) of the imaging element (22) in the second direction (102) of the expected pattern generator to be used; Therefore, the step of scaling the original pattern further includes: scaling the original pattern (30) in the second direction (102) by a second raster scaling factor (S42) to provide the scaled pattern (31); The second grating scaling factor is equal to a second integer multiplied by the second spacing (D2) of the pattern generator in the second direction (102) divided by the second pattern principal period (PM2); Thus, the cropping step further includes cropping (S42) the scaled pattern (31) to include a second integer number of repetitions of the pattern items (32) that are periodic in the second direction (102), and, if any, to include overlapping decreasing margins covered by the image region (14) in the second direction (102) of the intended pattern generator, thereby providing the rasterized pattern (33); The rasterization pattern (33) is thus associated with data representing the second raster scaling factor.

4. The rasterization method as described in claim 3, characterized in that, The second main axis of the array (20) of the imaging elements (22) is rotated by a second angle (α2) relative to the second direction (102), thereby the second spacing (D2) depends on the distance (d2) between two consecutive imaging elements (22) along the second main axis and depends on the second angle (α2).

5. The rasterization method as described in claim 1 or 2, characterized in that... It also includes another step: obtaining data on the first number of partially overlapping exposures with equidistant displacement in the first direction (101) of the expected pattern generator, thereby selecting the first raster scaling factor in the scaling step (S41) and the first integer repetition number in the clipping step (S51) such that the first integer repetition number multiplied by the ratio between the first integer and the first number of partially overlapping exposures becomes an integer.

6. The rasterization method as described in claim 3, characterized in that... It also includes another step: obtaining data on a second number of partially overlapping exposures with equidistant displacement in the second direction (102) of the expected pattern generator, thereby selecting the second raster scaling factor in the scaling step (S42) and the second integer repetition number in the clipping step (S52) such that the second integer repetition number multiplied by the ratio between the second integer and the second number of partially overlapping exposures becomes an integer.

7. The rasterization method as described in claim 3, characterized in that at least one of the following features: If applicable, considering the constraints of selecting the first integer and the number of repetitions of the first integer, the first raster scaling factor should be selected to be as close as possible to 1. If applicable, taking into account the constraints of selecting the second integer and the number of repetitions of the second integer, the second raster scaling factor should be selected as close to 1 as possible.

8. A method for writing a pattern with periodic components for a pattern generator based on a spatial light modulator (2), the spatial light modulator (2) having an array (3) of independently controllable elements (4) arranged to generate an array (20) of imaging elements (22) within an image region (14) on a target surface (10), wherein the illumination of each independent imaging element (22) is controlled by the corresponding element (4), the writing method comprising the following steps: - Obtain (S61) a rasterized pattern having relevant data representing a first raster scaling factor, the first raster scaling factor defining the scaling of the rasterized pattern (33) in a first direction (101); - The element (4) of the spatial light modulator (2) in the pattern generator that falls outside the rasterized pattern in the first direction (101) is set (S62) to be disabled; - Write the rasterized pattern into the image area (14) on the target surface (10) (S80); The writing (S80) includes scaling (S81) in the first direction (101) with a first optical scaling factor; Therefore, the first optical scaling factor is not one.

9. The writing method as described in claim 8, characterized in that, The first optical scaling factor is equal to the reciprocal of the first grating scaling factor.

10. The writing method as described in claim 8 or 9, characterized in that, The rasterization pattern is also associated with data representing a second raster scaling factor, which defines the scaling of the rasterization pattern (33) in a second direction (102) orthogonal to the first direction (101); The step of setting the element (4) of the spatial light modulator (2) to disable further includes setting (S72) the element (4) of the spatial light modulator (2) in the pattern generator that falls outside the rasterization pattern in the second direction (102) to disable; The writing (S80) thus also includes scaling (S82) in the second direction (102) with a second optical scaling factor.

11. The writing method as described in claim 10, characterized in that, Neither the first optical scaling factor nor the second optical scaling factor is the same for realizing the image region.

12. The writing method as described in claim 10, characterized in that, The second optical scaling factor is equal to the reciprocal of the second grating scaling factor.

13. A rasterization module (60) for a pattern generator based on a spatial light modulator (2), the spatial light modulator (2) having an array (3) of independently controllable elements (4) arranged to generate an array (20) of imaging elements (22) within an image region (14) on a target surface (10), wherein the illumination of each independent imaging element (22) is controlled by the corresponding element (4), the rasterization module (60) comprising: - Processor (62); and -Memory (64); The memory (64) contains instructions executable by the processor (62), thereby configuring the rasterization module (60) to: - Obtain the original pattern (30) with a pattern item (32) exhibiting periodicity; - Determine the first pattern principal period (PM1) in the first direction (101) of the original pattern (30); - Obtain information about the image region (14) and the first spacing (D1) of the imaging element (22) in the first direction (101) of the intended pattern generator to be used; - Scale the original pattern (30) in the first direction (101) with a first raster scaling factor to provide a scaled pattern (31); The first grating scaling factor is equal to a first integer multiplied by the first spacing (D1) of the pattern generator in the first direction (101) divided by the first pattern principal period (PM1); - Trim the scaled pattern (31) to include a first integer number of repetitions of the pattern item (32) that presents periodicity in the first direction (101), and if any, include overlapping decreasing margins covered by the image region (14) in the first direction (101) of the intended pattern generator, thereby providing a rasterized pattern (33) suitable for the intended pattern generator. The rasterization pattern (33) is associated with data representing the first raster scaling factor.

14. The rasterization module as described in claim 13, characterized in that, The memory (64) contains additional instructions executable by the processor (62), thereby further configuring the rasterization module (60) to: - Determine the second pattern principal period (PM2) in the second direction (102) of the original pattern (30), wherein the second direction (102) is orthogonal to the first direction (101); - Obtain information about the image region (14) and the second spacing (D2) of the imaging element (22) in the second direction (102) of the intended pattern generator to be used; - The original pattern (30) is scaled in the second direction (102) by a second raster scaling factor to provide the scaled pattern (31); The second grating scaling factor is equal to a second integer multiplied by the second spacing (D2) of the pattern generator in the second direction (102) divided by the second pattern principal period (PM2); - Trim the scaled pattern (31) to include a second integer number of repetitions of the pattern item (32) that presents periodicity in the second direction (102), and if any, include overlapping decreasing margins covered by the image region (14) in the second direction (102) of the intended pattern generator, thereby providing the rasterized pattern (33) suitable for the intended pattern generator. The rasterization pattern (33) is also associated with data representing the second raster scaling factor.

15. A pattern generator (80), comprising: Control module (82); as well as An imaging module (84) is arranged to write a pattern into an image region by means of a spatial light modulator (2), the spatial light modulator (2) having an array (3) of independently controllable elements (4), the array (3) of independently controllable elements (4) being arranged to generate an array (20) of imaging elements (22) in an image region (14) on a target surface (10), wherein the illumination of each independent imaging element (22) is controlled by the corresponding element (4); The control module (82) is configured to obtain a rasterized pattern (33) having relevant data representing a first raster scaling factor, the first raster scaling factor defining the scaling of the rasterized pattern (33) in a first direction (101); - The control module (82) is also configured to disable the element (4) of the spatial light modulator (2) in the imaging module (84) that falls outside the rasterization pattern (33) in the first direction (101); - The imaging module (84) includes an optical device (88) controlled by the control module (82), the optical device (88) being used to scale the rasterization pattern (33) in the first direction (101) with a first optical scaling factor before writing to the image region (14); Therefore, the first optical scaling factor is not one.

16. The pattern generator as claimed in claim 15, characterized in that, The control module (82) is further configured to obtain the rasterization pattern (33) having some other relevant data representing a second raster scaling factor, the second raster scaling factor defining scaling of the rasterization pattern (33) in a second direction (102) orthogonal to the first direction (101); The control module (82) is also configured to disable the elements (4) of the spatial light modulator (2) in the imaging module (84) that fall outside the rasterization pattern in the second direction (102); - The imaging module (84) includes an optical device (88) controlled by the control module (82), which is used to further scale the raster pattern (33) in the second direction (102) with a second optical scaling factor before writing to the image area (14).

Images