Controlling light source wavelength for selectable phase shift between pixels in a digital lithography system

Abstract

A digital lithography system can adjust the wavelength of a light source to compensate for tilt errors in a micromirror while maintaining a perpendicular direction for the reflected light. Adjacent pixels can have a phase shift determined by the optical path difference between their respective light rays. This phase shift can be preselected to be any value by generating the corresponding wavelength at the light source based on the optical path difference. To generate a specific wavelength corresponding to a desired phase shift, the light source can produce a plurality of optical components having wavelengths that bracket the wavelength of the selected phase shift. The intensities of these components can then be individually controlled to produce an effect approximating the selected phase shift on the substrate.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Non-Provisional Patent Application No. 17 / 750,751, filed May 23, 2022, entitled "CONTROLLING LIGHT SOURCE WAVELENGTHS FOR SELECTABLE PHASE SHIFTS BETWEEN PIXELS IN DIGITAL LITHOGRAPHY SYSTEMS," which is incorporated herein by reference.

[0002] This disclosure generally describes methods for generating a preselected phase shift between pixels in a digital lithography system. More particularly, this disclosure describes controlling the wavelength output of a light source to generate or approximate the effect of a preselected phase shift on a substrate during a lithography process. [Background technology]

[0003] Spatial light modulators are often used to provide spatially varying modulation to light beams. An example of a spatial light modulator, the digital micromirror device (DMD), is used as a reflective digital light switch in various applications, including digital lithography. In digital lithography, the DMD is generally combined with other image processing components, such as memory, a light source, and optical elements, and used to project a desired pattern onto a photosensitive material on a substrate being processed.

[0004] A DMD typically contains hundreds of thousands of microscopic mirrors ("micromirrors") arranged in a rectangular array. Each micromirror corresponds to a single pixel of the image to be displayed and can be tilted at various angles around a hinge. Depending on the tilt angle of the micromirror, the micromirror is in an "on" or "off" state. In the on state, light is reflected from the DMD to a lens, and the pixel is ultimately projected brightly onto the substrate. In the off state, the light is directed elsewhere, such as to a light dump, and the projected pixel appears dark.

[0005] The phase shift between adjacent micromirrors of a DMD affects the resolution and depth of focus of the projected image. Typically, the phase shift between adjacent micromirrors of a DMD is 0 degrees. A DMD with a 0-degree phase shift between adjacent micromirrors is known as a blazed DMD. Blazed DMDs exhibit good resolution and depth of focus, but as device dimensions decrease, improved resolution and better depth of focus are required, especially for line spacing. In mask-based lithography, hard phase-shift masks have been used to print extremely narrow dark lines. However, hard phase-shift masks are limited by the topology of their design.

[0006] Thus, there is a need in the art for improved spatial light modulators and digital lithography methods for their use that increase image resolution and depth of focus. Summary of the Invention

[0007] In some embodiments, a digital lithography system may include a first spatial light modulator pixel configured to direct a first beam of light onto a substrate during a digital lithography process, a second spatial light modulator pixel configured to direct a second beam of light onto the substrate during the digital lithography process, and a light source configured to generate the first beam of light. The first beam of light may include multiple components, including a first component having a first wavelength that generates a first phase shift greater than a preselected phase shift, and a second component having a second wavelength that generates a second phase shift less than the preselected phase shift. The digital lithography system may include a controller configured to control intensities of the multiple components to generate an effect on the substrate that approximates the preselected phase shift.

[0008] In some embodiments, a method for adjusting a phase shift between pixels in a digital lithography system may include projecting a first light beam onto a first spatial light modulator pixel. The first spatial light modulator pixel may direct the first light beam onto a substrate during a digital lithography process. The first light beam may include multiple components, including a first component having a first wavelength that generates a first phase shift greater than a preselected phase shift and a second component having a second wavelength that generates a second phase shift less than the preselected phase shift. The method may also include projecting a second light beam onto a second spatial light modulator pixel. The second spatial light modulator pixel may direct the second light beam onto the substrate during the digital lithography process. The method may also include controlling intensities of the multiple components to generate an effect on the substrate that approximates the preselected phase shift.

[0009] In some embodiments, a method for adjusting or selecting a phase shift between pixels in a digital lithography system may include projecting a first light beam onto a first spatial light modulator pixel. The first spatial light modulator pixel may direct the first light beam onto a substrate during the digital lithography process. The method may also include projecting a second light beam onto a second spatial light modulator pixel. The second spatial light modulator pixel may direct the second light beam onto the substrate during the digital lithography process. The second spatial light modulator pixel may be adjacent to the first spatial light modulator pixel in an array of spatial light modulator pixels. The method may additionally include controlling the wavelength of the first light beam and / or the wavelength of the second light beam based on an optical path difference between the first light beam and the second light beam to produce a preselected phase shift between the first light beam and the second light beam on the substrate.

[0010] In any embodiment, any and all of the following features may be implemented in any combination, without limitation: The second spatial light modulator pixel may be adjacent to the first spatial light modulator pixel in an array of spatial light modulator pixels in a digital micromirror device. The first spatial light modulator pixel may include a micromirror that adjusts between an on position that reflects light onto the substrate and an off position that reflects light away from the substrate. The light source may also be configured to generate a second light beam, such that the first light beam and the second light beam originate from the light source. The second light beam may be generated from a different light source, and the controller may be further configured to control the intensity of a component in the second light beam to correct for a tilt error in the second spatial light modulator pixel that is different from a tilt error in the first spatial light modulator pixel. The light source may include multiple groups of laser diodes. A first subset of the multiple groups of laser diodes may be configured to output approximately a first wavelength, and a second subset of the multiple groups of laser diodes may be configured to output approximately a second wavelength. The light source may include a homogenizing rod that mixes the first component with the second component to generate a uniform first beam of light. The multiple components may include multiple additional components in addition to the first and second components. The first wavelength may generate a first phase shift that is approximately 20° greater than a preselected phase shift. The second wavelength may generate a second phase shift that is approximately 10° less than the preselected phase shift. The preselected phase shift may be selectable to be between 0° and 359°. Controlling the intensities of the multiple components may include calculating weights for each of the multiple components in a linear combination of deviations between the first and second phase shifts from the preselected phase shift, such that the linear combination is approximately zero. The weights in the linear combination may correspond to the intensities of the multiple components.Approximating the preselected phase shift can generate a pattern of light intensity on the substrate that approximates the pattern of light intensity that would be present on the substrate using a single wavelength corresponding to the preselected phase shift. The first phase shift can be calculated from the first wavelength and the optical path difference between the first and second light beams. The second spatial light modulator pixel can be adjacent to the first spatial light modulator pixel in an array of spatial light modulator pixels in a digital micromirror device, and the second light beam can also include a first component and a second component. Controlling the wavelength of the first light beam can include switching between different laser diodes that generate light having different wavelengths. Controlling the wavelength of the first light beam can include changing the wavelength of the first light beam by controlling the temperature of the light source, mechanically altering the cavity of the light source, or electroacously altering the cavity of the light source.

[0011] A further understanding of the nature and advantages of various embodiments may be realized by reference to the remaining portions of the specification and the drawings, in which like reference numerals are used throughout the several views to refer to like components. In some instances, a sub-label is associated with a reference numeral to indicate one of multiple similar components. When reference is made to a reference numeral without specification to an existing sub-label, it is intended to refer to all such multiple similar components. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view of a system for digital lithography, according to some embodiments. [Figure 2] FIG. 1 illustrates a perspective schematic view of an image projection system of a system, according to some embodiments. [Figure 3] FIG. 1 illustrates a digital micromirror device (DMD), according to some embodiments. [Figure 4A]1A-1C illustrate pairs of adjacent micromirrors directing light rays toward a substrate, according to some embodiments. [Figure 4B] 10A-10C illustrate adjacent micromirrors with tilt angles that differ from the ideal tilt angle, according to some embodiments. [Figure 4C] 10A-10C illustrate how variations in tilt angle can be addressed by changing the angle of the light beam, according to some embodiments. [Figure 5] 1A-1C illustrate how the optical path difference (OPD) between two adjacent micromirrors can result in a phase shift on the substrate, according to some embodiments. [Figure 6] FIG. 1 illustrates a system for adjusting the phase shift between pixels in a digital lithography system, according to some embodiments. [Figure 7] FIG. 1 illustrates a flowchart of a method for adjusting or selecting a phase shift between pixels in a digital lithography system, according to some embodiments. [Figure 8] FIG. 1 illustrates a light source that can be used in a lithography system, according to some embodiments. [Figure 9] FIG. 1 illustrates a system for using a light beam having multiple wavelengths that bracket a preselected wavelength, according to some embodiments. [Figure 10] 10A-10C are graphs illustrating the effect of using a light beam with multiple light components that bracket preselected phase shifts, according to some embodiments. [Figure 11] FIG. 10 illustrates a graph showing how multiple components can be used to approximate and tune to any preselected wavelength, according to some embodiments. [Figure 12] FIG. 1 illustrates a flowchart of a method for selecting or adjusting a phase shift between pixels in a digital lithography system, according to some embodiments. [Figure 13]FIG. 1 illustrates an exemplary computer system in which various embodiments may be implemented. DETAILED DESCRIPTION OF THE INVENTION

[0013] FIG. 1 is a perspective view of a system 100 for digital lithography, according to some embodiments. The system 100 may include a base frame 110, a slab 120, one or more stages 130 (two are shown by way of example), and / or processing equipment 160. The base frame 110 may rest on the floor of a fabrication facility and support the slab 120. A passive pneumatic isolator 112 may be positioned between the base frame 110 and the slab 120. In some embodiments, the slab 120 may comprise a monolithic piece of granite, and the one or more stages 130 may be disposed on the slab 120. A substrate 140 may be supported by each of the one or more stages 130. Multiple holes (not shown) may be formed in the one or more stages 130 to allow multiple lift pins (not shown) to extend therethrough. The lift pins may rise to an extended position to receive the substrate 140, such as from one or more transfer robots (not shown). One or more transfer robots may be used to load and unload substrates 140 from one or more stages 130 .

[0014] Substrate 140 may be made of, for example, glass and used as part of a flat panel display. In some embodiments, substrate 140 may be made of other materials. In some embodiments, substrate 140 may have a photoresist layer formed thereon. The photoresist may be sensitive to radiation and may include positive or negative photoresist, meaning that after a pattern is written into the photoresist, the portions of the photoresist exposed to radiation may be soluble or insoluble, respectively, in a photoresist developer applied to the photoresist. The chemical composition of the photoresist may determine whether the photoresist will be a positive or negative photoresist. For example, the photoresist may include at least one of diazonaphthoquinone, phenol formaldehyde resin, poly(methyl methacrylate), poly(methyl glutarimide), and / or SU-8. In this manner, patterns may be created on the surface of substrate 140 to form electronic circuits.

[0015] The system 100 may further include a pair of supports 122 and a pair of tracks 124. The pair of supports 122 may be disposed on the slab 120, and the slab 120 and the pair of supports 122 may be formed as a single piece of material. The pair of tracks 124 may be supported by the pair of supports 122, and the one or more stages 130 may be movable along the tracks 124 in the X direction. In some embodiments, the pair of tracks 124 may include a pair of parallel magnetic channels. As shown, each track 124 of the pair of tracks 124 may be linear. In some embodiments, the tracks 124 may have a nonlinear shape. An encoder 126 may be coupled to each of the one or more stages 130 to provide location information to a controller (not shown).

[0016] Processing device 160 may include a support 162 and / or processing units 164. Support 162 may be disposed on slab 120 and may include an opening 166 for one or more stages 130 to pass under processing unit 164. Processing unit 164 may be supported by support 162. In some embodiments, processing unit 164 may include a pattern generator configured to expose photoresist in a photolithography process. In some embodiments, the pattern generator may be configured to perform a maskless lithography process. Processing unit 164 may include multiple image projection devices (shown in FIG. 2). In some embodiments, processing unit 164 may include multiple light sources, such as laser diodes. Each image projection device may be disposed in a case 165. Processing device 160 may be used to perform maskless direct patterning.

[0017] During operation, one of the one or more stages 130 may move in the X direction from a loading position shown in FIG. 1 to a processing position. The processing position may refer to one or more positions of the stage 130 as it passes under the processing unit 164. During operation, the one or more stages 130 may be lifted by multiple air bearings (not shown), which may be movable along the pair of tracks 124 from the loading position to the processing position. Multiple vertical guide air bearings (not shown) may be coupled to each of the one or more stages 130 and positioned adjacent the inner wall 128 of each support 122 to stabilize the movement of the stage 130. Each of the one or more stages 130 may also be movable in the Y direction by moving along the track 150 to process and / or index the substrate 140. Each of the one or more stages 130 may be capable of independent movement, scanning the substrate 140 in one direction and stepping it in the other direction. In some embodiments, while one of the one or more stages 130 is scanning a substrate 140, another of the one or more stages 130 may be unloading the exposed substrate and loading the next substrate to be exposed.

[0018] A metrology system may measure the X and Y lateral position coordinates of each of the one or more stages 130 in real time so that each of the multiple image projection devices can accurately place the pattern being written on the photoresist-coated substrate. The metrology system may also provide real-time measurement of the angular position of each of the one or more stages 130 about the vertical or Z axis. The angular position measurement may be used to hold the angular position constant during scanning by a servo mechanism, or the angular position measurement may be used to apply corrections to the position of the pattern being written on the substrate 140 by the image projection device 290, as shown below in FIG. 2. These techniques may be used in any combination, without limitation.

[0019] FIG. 2 illustrates a perspective schematic view of an image projection system 270 of system 100, according to some embodiments. The image projection system may include a spatial light modulator, a focus sensor and / or a camera, and a projection lens. As shown in FIG. 2, the image projection system 270 may include a light source 272, an aperture 274, a lens 276, a frustrated prism assembly 288, one or more digital micromirror devices (DMDs) 280 (one is shown), a light dump 282, a focus sensor and camera 284, and / or a projection lens 286. The frustrated prism assembly 288, the DMD 280, the focus sensor and camera 284, and the projection lens 286 may be part of an image projection device 290. In some embodiments, the light source 272 may include a light emitting diode (LED) or a laser, and the light source 272 may be capable of producing light having a predetermined or tunable wavelength. For example, the predetermined wavelength may be in the blue or near ultraviolet (UV) range, such as less than about 450 nm. The frustrated prism assembly 288 may include multiple reflective surfaces. In one embodiment, the projection lens 286 may include a 6x or 10x objective lens. Other embodiments of the image projection system, which may include one or more spatial light modulators other than a DMD, may include fewer or more components, as needed in the system for that particular spatial light modulator.

[0020] This disclosure may refer to a DMD as an example of a spatial light modulator. However, other spatial light modulators are also contemplated in this disclosure. Other spatial light modulators may include, but are not limited to, arrays of liquid crystals, such as liquid crystal displays (LCDs) and ferroelectric liquid crystal displays (FLCoS), and arrays of microscopic light emitting devices (microLEDs). Each spatial light modulator may include an array of spatial light modulator pixels that can be switched between "on" and "off" so that a pattern of spatial light modulator pixels can modulate light rays to provide a selected level of attenuation. During operation, the spatial light modulator pixels may be controllable so that each pixel can be brightened, darkened, and / or attenuated.

[0021] During operation of the image projection system 270 shown in FIG. 2, a light source 272 may generate light beams 273 having a predetermined or tunable wavelength, such as a wavelength in the blue range. The light beams 273 may be reflected by a frustrated prism assembly 288 to the DMD 280. As shown in FIG. 3, the DMD may include multiple micromirrors, the number of which may correspond to the number of pixels to be projected. The multiple micromirrors may be individually controllable, and each micromirror of the multiple micromirrors may be in an ON or OFF position based on mask data provided to the DMD 280 by a controller (not shown). When the light beams 273 reach the micromirrors of the DMD 280, the micromirrors in the ON position may reflect the light beams 273 to the projection lens 286, which may form multiple writing beams. The projection lens 286 may then project the writing beams onto the surface of the substrate 140. A micromirror in the off position may reflect light ray 273 to a light dump 282 or another location instead of to the surface of substrate 140 .

[0022] FIG. 3 illustrates a DMD 380 according to some embodiments. The DMD 380 can be used in the image projection device 290 and system 100 described above. The DMD 380 can also be useful in any other system or device utilizing a DMD. The DMD 380 can include multiple spatial light modulator pixels, shown as micromirrors 381, arranged in a micromirror array 383. The DMD 380 can be used as a spatial light modulator, where the micromirrors 381 can be tilted at various angles and used to adjust the angle of reflection of an illumination beam on the DMD 380 so that, after reflection, the on-beam is aimed at the center of the image projection device 290 and the image created in the illumination system is centered in the projection system. In one example, the stable position of each micromirror 381 can be plus or minus approximately 12 degrees with an error of approximately ±1.0 degree relative to the surface of the micromirror 381. For example, the first tilt position 389 may correspond to plus 12±1.0 degrees, and the second tilt position 391 may correspond to minus 12.0±1.0 degrees.

[0023] The edges 385 of the micromirrors 381 may be aligned along orthogonal axes, such as the X and Y axes. These axes may coincide with similar axes referenced to the substrate 140 or stage coordinate system after accounting for the 90-degree fold introduced by the frustrated prism assemblies 288. However, hinges 387 on the micromirrors 381 may be located on opposing corners of the micromirrors 381, causing the micromirrors 381 to pivot on axes that are 45 degrees relative to the X and Y axes. As discussed above, these micromirrors 381 may be switched between on and off positions by varying the angle of tilt of the micromirrors.

[0024] In some embodiments, the hinges 387 may be oriented diagonally to tilt each of the micromirrors 381 on an axis that is 45 degrees relative to the X and Y axes of each of the micromirrors 381. In other embodiments, the hinges 387 may be oriented parallel to the edge 385 of each of the micromirrors 381 to tilt each of the micromirrors 381 on an axis that is parallel to the edge 385 of each of the micromirrors 381. In one example, all of the hinges 387 may be oriented diagonally. In another example, all of the hinges 387 may be oriented parallel to the edge 385 of each of the micromirrors 381. In yet another example, a first portion of the hinges 387 may be oriented diagonally and a second portion of the hinges 387 may be oriented parallel to the edge 385 of each of the micromirrors 381.

[0025] In a conventional blazed DMD, the phase shift between adjacent micromirrors can be 0 degrees. A conventional 0-degree phase shift can result in negligible cancellation. However, the phase shift between adjacent micromirrors 381 of a DMD 380, e.g., the first micromirror 381a and the second micromirror 381b, can be equal to or approximately 180 degrees. This configuration is called an anti-blazed DMD. When the phase shift between adjacent spatial light modulator pixels, e.g., the first micromirror 381a and the second micromirror 381b, is 180 degrees, there is exact or nearly exact cancellation between the adjacent micromirrors 381 and symmetrical brightening between adjacent pixels. In one example, each pair of adjacent micromirrors 381 has a 180-degree phase shift.

[0026] 4A illustrates a pair of adjacent micromirrors directing light rays toward a substrate, according to some embodiments. In this example, a first micromirror 402 and a second micromirror 404 may be configured in an "on" position to direct light toward a substrate 451 during a digital lithography process. The angle 424 of the first micromirror 402 may be at an ideal position, such as +12.0°. The angle 426 of the second micromirror 404 may be the same as the angle 424 of the first micromirror 402. When these two angles 424, 426 of the adjacent micromirrors 402, 404 are equal to the ideal values, the light rays reflected from the micromirrors 402, 404 may be reflected directly onto the substrate 451 at an angle of 90° relative to the substrate 451. For example, a first light ray 406 projected from a light source may be reflected from the first micromirror 402 onto the substrate 451 at a right angle. Similarly, the second light ray 408 may also be reflected from the second micromirror 404 at a right angle onto the substrate 451. When the light ray hits the substrate 451 at a right angle, this results in vertical features and accurate layout on the substrate 451.

[0027] In addition to ensuring that light rays are directed orthogonally onto the substrate 451, another important consideration is the optical path difference (OPD) 420 between any two adjacent micromirrors. As illustrated in FIG. 4, the OPD 420 between a first light ray 406 and a second light ray 408 represents the difference in the total distance traveled by these rays. In particular, it can be assumed that the distance between each of the micromirrors 402, 404 and the substrate 451 is the same. However, the distance from the light source that generates the light rays 406, 408 is different because the second micromirror is farther from the light source than the first micromirror. This difference is represented by the OPD 420, which results in a phase shift between the first light ray 406 and the second light ray 408 on the substrate 451.

[0028] FIG. 5 illustrates how an OPD 506 between two adjacent micromirrors can result in a phase shift on the substrate, according to some embodiments. A wave representation 502 of a light ray is represented as a sinusoidal waveform having a wavelength 504. The OPD 506 represents the additional distance traveled by the second light ray 408 in FIG. 4A . Assuming that the first light ray 406 and the second light ray 408 are in phase when the first light ray 406 reflects from the first micromirror 402, the phase shift 508 can be determined by identifying the remainder when dividing the OPD 506 by the wavelength 504. Each wavelength 504 represents a full 360° phase shift (which can be ignored), and the remainder therefore represents the phase shift between the first light ray 406 and the second light ray 408 on the surface of the substrate 451. As explained in more detail below, a phase shift that can be accurately predicted or selected can provide several benefits in lithography processes.

[0029] FIG. 4B illustrates adjacent micromirrors whose tilt angles differ from the ideal tilt angle, according to some embodiments. While FIG. 4A illustrates micromirrors operating in the “on” position to tilt at a precise 12.0° angle, exhibiting tilt angles 424, 426, not all manufactured DMD arrays are this precise. Typically, the tilt angle accuracy in manufactured DMD arrays can vary by as much as 1.0°. To identify manufactured DMD arrays with sufficiently high accuracy (e.g., 12.0°±0.06°), batches of manufactured DMD arrays may need to be analyzed to identify which of the manufactured DMD arrays actually fall within tighter manufacturing tolerances. This significantly reduces the yield at which manufactured DMD arrays can be used for lithography processes requiring extremely precise mirror tilt.

[0030] FIG. 4B illustrates the result of micromirrors 402, 404 having non-ideal tilt angles 440, 442. Assuming the position of the light source remains unchanged, light rays 406, 408 may be reflected from micromirrors 402, 404 such that light rays 406, 408 are no longer perpendicular to substrate 451. This may result in angled sidewalls because light rays 406, 408 penetrate the photoresist layer on substrate 451 at an angle. Additionally, because the layers on substrate 451 have non-negligible thicknesses, the horizontal location where light rays 406, 408 strike substrate 451 may vary depending on the depth of the top layer. Therefore, errors in the tilt angles 440, 442 of micromirrors 402, 404 may cause reflected light rays 406, 408 to no longer be perpendicular to substrate 451, causing errors in the pattern printed on substrate 451.

[0031] Note that the pitch 422 between two adjacent micromirrors 402, 404 can remain relatively constant within or between batches of manufactured DMD arrays. The pitch 422 can be tightly controlled during manufacturing to minimize variation in the distance between micromirrors in the array.

[0032] FIG. 4C illustrates how variations in tilt angles 440, 442 can be addressed by changing the angles of light rays 406, 408, according to some embodiments. When variations in tilt angles 440, 442 of micromirrors 402, 404 cause reflected light rays 406, 408 to no longer be perpendicular to the substrate 451, the angles at which light rays 406, 408 are projected onto the micromirrors 402, 404 can be adjusted to compensate. For example, the position of the light source can be changed relative to the positions of the micromirrors 402, 404. Changing the position of the light source can result in a change in the angle of incidence of light rays 406, 408 as they reflect from the micromirrors 402, 404. As illustrated in FIG. 4C, this position can be adjusted until the light rays 406, 408 are reflected so that they are again perpendicular to the substrate 451.

[0033] Varying the position or angle at which the light source projects light rays 406, 408 can again cause light rays 406, 408 to be normal to substrate 451, but this can also cause the OPD to change between light rays 406, 408. For example, OPD 444 in FIG. 4C is shortened relative to OPD 420 in FIGS. 4A and 4B. As explained above and illustrated in FIG. 5, changing OPD 444 can directly affect the phase shift 508 between light rays 406, 408 on substrate 451.

[0034] Different phase shifts may be desired for different purposes during the lithography process. For example, a 180° phase shift between adjacent micromirrors may create a null at the boundary between the two micromirrors. This allows the lithography pattern to create extremely dense line-space patterns where the line-plus-space pitch is equal to the pitch between two adjacent micromirrors for resolution enhancement. In another example, a 0° phase shift between adjacent micromirrors may reinforce the pattern at the boundary. Other pattern designs may benefit from using a selectable phase shift, such as a 90°, 270°, and / or any other degree phase shift. Therefore, it may be desirable not only to maintain a selected phase shift to compensate for source location or tilt angle errors, but also to select an arbitrary phase shift based on the needs of a particular design.

[0035] To overcome this technical problem, embodiments described herein may tune the wavelength of the light beams 406, 408 using various techniques to select or adjust the desired phase shift. Three variables may affect the phase shift: the pitch 422 between the micromirrors 402, 404, the length of the OPD 444, and the wavelength of the light beams 406, 408. Because the pitch 422 may be assumed to be relatively constant and the OPD 444 may be varied to maintain perpendicular light beams, some embodiments may tune the wavelength of the light beams 406, 408 to achieve a preselected phase shift or to fine-tune that phase shift. As illustrated in FIG. 5 , tuning the wavelength 504 for a given OPD 506 adjusts the phase shift 508 in a manner that can be predicted and calculated.

[0036] 6 illustrates a system 600 for adjusting the phase shift between pixels in a digital lithography system, according to some embodiments. The system 600 may include an array of micromirrors, including the pair of micromirrors illustrated in FIG. 6, referred to simply for purposes of distinction as a first micromirror 402 and a second micromirror 404. As explained above, these micromirrors 402, 404 may be oriented in an “on” position (e.g., approximately 12°) to direct light from a light source 602 toward a substrate 451 to print a pattern on a layer on the substrate 451, such as a photoresist layer.

[0037] The system may include a light source 602. The light source 602 may include one or more laser diodes or other light sources configured to generate light at a preselected frequency. As described above, the light source 602 may be configured to adjust the wavelength of the light during operation to set or adjust the phase shift based on the ODP 444. Such adjustments may be made by selecting different colors of laser diodes in the light source to be operational at different times. Some embodiments may make adjustments to the wavelength by adjusting the temperature of the light source 602 to cause the wavelength to increase / decrease. Some embodiments may include multiple light sources that may be substituted for the light source 602 to generate wavelengths at different frequencies.

[0038] Some embodiments may include a controller 604. By way of example, Figure 13, described below, includes a computer system that may be used as a controller for operating the light source 602 as part of a lithography system. For example, the controller 604 may include one or more microprocessors or microcontrollers, along with one or more non-transitory computer-readable media that store instructions that cause the microprocessors / microcontrollers to perform operations that control the frequency, operation, timing, etc. of the light source 602.

[0039] Note that only a single light source 602 is illustrated in FIG. 6 . This illustration is provided by way of example only and not by way of limitation. The light source 602 may be comprised of multiple laser diodes or other light sources. Other light sources may also be present to generate light for other micromirrors in the array. Furthermore, the light source 602 may be responsible for generating light that is reflected as the first light beam 406 and / or the second light beam 408. For example, the first light beam 406 and the second light beam 408 may originate from, but are not limited to, the same light source 602 or from different light sources.

[0040] FIG. 7 illustrates a flowchart 700 of a method for adjusting or selecting a phase shift between pixels in a digital lithography system, according to some embodiments. The method may include projecting a first light beam onto a first spatial light modulator pixel (702). As described above, the first spatial light modulator pixel may include a digital micromirror. The first spatial light modulator pixel may direct the first light beam onto a substrate during the digital lithography process. The method may also include projecting a second light beam onto a second spatial light modulator pixel (704). The second spatial light modulator pixel may also include a digital micromirror or other similar device, which may similarly direct the second light beam onto a substrate during the digital lithography process. The first and second spatial light modulator pixels may be positioned adjacent to each other in an array of pixels. The first and second light beams may originate from the same light source or from different light sources, such as phase-locked laser diodes or laser diode arrays.

[0041] This method can be used to set or adjust a phase shift between a first beam and a second beam on a substrate. For example, when referring to a "preselected phase shift," this refers to a phase shift between these specific micromirrors that is specifically selected for a particular lithography process. This can be in contrast to simply using micromirrors to generate light at a wavelength that results in OPD based on tilt error and performing the process with the resulting phase shift. Instead, a preselected phase shift can be determined for the process, and the wavelength of light from the light source can be adjusted or selected to produce the preselected phase shift.

[0042] Therefore, the method may further include controlling (706) the wavelength of the first light beam and the wavelength of the second light beam based on the optical path difference between the first light beam and the second light beam. The wavelength may be selected or adjusted to produce a preselected phase shift between the first light beam and the second light beam on the substrate. The wavelength may be selected based on the OPD, as described above with respect to FIG. 5. As described above, the light source may be configured such that the wavelength of light generated by the light source is adjustable. This adjustment may be made by activating a different light source, adjusting the operation of the light source, adjusting the temperature of the light source, mechanically adjusting the cavity length of the laser source, electro-acoustically altering the cavity of the light source, activating or substituting an alternative light source into the lithography system, and / or any other method of adjusting or selecting the wavelength of light to produce a desired phase shift. For example, a first subset of the multiple laser diodes may be configured to produce a wavelength that causes a 180° phase shift. A second subset of the plurality of laser diodes may be configured to produce a wavelength that causes a phase shift of 0°, and another subset of the laser diodes may be configured to produce another wavelength, such as 270°, etc. These subsets may be activated based on the preselected wavelengths.

[0043] It should be appreciated that the specific steps illustrated in FIG. 7 provide a particular method for adjusting or selecting a phase shift between pixels in a digital lithography system according to various embodiments. Other sequences of steps may be performed according to alternative embodiments. For example, alternative embodiments may perform the steps outlined above in a different order. Moreover, the individual steps illustrated in FIG. 7 may include multiple sub-steps that may be performed in various sequences as appropriate for the individual step. Furthermore, additional steps may be added or removed depending on the particular application. Many variations, modifications, and alternatives are within the scope of the present disclosure.

[0044] Next, one particular method for adjusting the effective wavelength of a light source used in a lithography process is described, which involves using multiple light sources with different frequencies and adjusting the intensities of these light sources to produce the effect of a phase shift on the substrate.

[0045] FIG. 8 illustrates a light source 800 that may be used in a lithography system, according to some embodiments. This light source 800 is provided by way of example only and is not limiting. Other light sources having different groupings and configurations of laser diodes or other similar equipment may be used in its place. This light source 800 may include a laser module 802. The laser module 802 may include multiple laser diodes. In some embodiments, the laser diodes may be divided into groups, and the groups may include multiple matched laser diodes driven by corresponding drive circuitry. Each group may be populated with multiple laser diodes having similar wavelengths. Note that FIG. 8 illustrates four groups of four laser diodes each as a simplified example for clarity only. As indicated by the ovals, any number of laser diodes and groups may be used without limitation.

[0046] For embodiments described below, some of the groups may include laser diodes configured to emit light at wavelengths shorter than the preselected wavelength, and some of the groups may include laser diodes configured to emit light at wavelengths longer than the preselected wavelength. For example, a first group 808 may be driven by first drive circuitry 806 and configured to generate light at a higher wavelength, and a second group 838 may be driven by second drive circuitry 833 and configured to generate light at a lower wavelength.

[0047] The system may include a controller 804 configured to control the intensity of the various groups of laser diodes. For example, the controller 804 may be implemented using a microprocessor, microcontroller, and / or computer system, as described below in FIG. 13. The controller 804 may cause the intensity of the first group 808 to be higher than the intensity of the second group 838, or vice versa. The controller 804 may calculate the appropriate intensity for each group in the laser module 802, as described in detail below.

[0048] Each laser diode in the laser module 802 may be coupled to a corresponding optical fiber 814. These optical fibers may be bundled together and aimed into a homogenizing rod 816 or other form of light pipe, which scrambles the light into a uniform illumination beam that can be projected onto the micromirrors in the array. Thus, each of the "light beams" described above may include multiple components from different light laser diode groups that generate light at different wavelengths. For example, a first light component may be generated by the first group of laser diodes 808 at one wavelength, and a second light component may be generated by the second group of laser diodes 838 at another wavelength. The output of the homogenizing rod 816 may be light 818, directed as one or more light beams, as described above. For example, light 818 may be the source of both the first and second light beams in FIGS. 4A-4C and elsewhere in this disclosure.

[0049] FIG. 9 illustrates a system 900 for using a light beam having multiple wavelengths bracketing a preselected wavelength, according to some embodiments. The system 900 is similar to the systems described above, except that a light source 911 can be configured to generate the first light beam 406 having at least two different components. For example, the first component can be generated using a laser diode that outputs light at a wavelength higher than the preselected wavelength, where the preselected wavelength corresponds to a desired phase shift between the first light beam 406 and the second light beam 408 on the substrate 451. Similarly, the second component can be generated using a laser diode that outputs light at a wavelength lower than the preselected wavelength. Alternatively, the first and second components can be characterized based on their corresponding phase shifts relative to the preselected phase shift. The first component can generate a phase shift greater than the preselected phase shift, and the second component can generate a phase shift less than the preselected phase shift. These two components 902, 904 can be mixed together to form the first light beam 406. As explained above, the light source 911 may also generate the second light beam 408 that is projected onto the second micromirror 404, although this is not explicitly shown in Figure 9. Alternatively, a second light source (not shown) may generate the second light beam 408.

[0050] The light source 911 may include the controller described above that controls the intensity of the first component 902 and the intensity of the second component 904. It has been discovered that by bracketing a preselected wavelength or phase shift on the substrate by wavelengths or phase shifts above and below the preselected wavelength or phase shift, the effect of the preselected phase shift can be approximated by the combined light intensity of the two components on the substrate. Furthermore, by adjusting the relative intensities between the first component 902 and the second component 904, the effective phase shift can be tuned or adjusted between the phase shift of the first component 902 and the phase shift of the second component 904 using a weighted combination of the phase shifts.

[0051] FIG. 10 illustrates a graph 1000 of the effect of using a light beam with multiple light components that bracket a preselected phase shift, according to some embodiments. In this example, the preselected phase shift is selected as 0°. This corresponds to a preselected wavelength that can be calculated based on the OPD of a particular micromirror array. Therefore, the preselected phase shift and the preselected wavelength can be used interchangeably, as they are easily derived from each other. Curve 1008 illustrates the intensity of light on the surface of a substrate. The vertical axis of graph 1000 represents the intensity of light on the substrate using a normalized scale of arbitrary units. The horizontal axis of graph 1000 represents the location on the substrate in microns (μm). The 0 μm location corresponds to the center position between a first micromirror and a second micromirror, which may be adjacent in the array. The pitch between these two micromirrors may be approximately 1.26 μm, which roughly corresponds to the peak on the curve in graph 1000. The results of graph 1000 are based on a defocus level of approximately −3 μm.

[0052] Because light sources may not be readily available for a preselected wavelength corresponding to a 0° phase shift, first and second components having phase shifts greater than and less than the preselected phase shift may be used simultaneously. In this example, the first component corresponding to curve 1004 represents a wavelength that produces a phase shift approximately 10° less than the 0° phase shift (e.g., 350°), and the second component corresponding to curve 1002 represents a wavelength that produces a phase shift approximately 20° greater than the 0° phase shift. Note that these curves are individually different from curve 1008, which corresponds to a preselected wavelength that produces a preselected 0° phase shift.

[0053] However, when the first and second components are combined to form a light beam reflected from the micromirror, the overall light intensity on the substrate can be made to approximate the effect of a preselected phase shift at a preselected wavelength. For example, the two components can be combined in a linear combination, where the weight assigned to each component corresponds to the difference in their corresponding phase shifts relative to the preselected phase shift. In this implementation, the weight assigned to each component makes the linear combination of the two components approximately equal to zero. For example, a component with a -10° phase shift relative to a preselected 0° phase shift can be multiplied by 2 / 3, and a component with a +20° phase shift relative to a preselected 0° phase shift can be multiplied by 1 / 3, making the linear combination of these components approximately equal to zero. These weights can then be used to control the brightness or intensity of each component. For example, the intensity of a component with a -10° phase shift can be approximately twice the intensity of a component with a +20° phase shift. The intensity of each component can be dynamically controlled during operation by the controller described above.

[0054] The combination of the two components when the intensity of each component is controlled is shown in graph 1000 as curve 1006. Note that curve 1006 for the combined components closely approximates curve 1008, which corresponds to an ideal phase shift for a preselected wavelength. This illustrates how the effects of a first component and a second component can be used to approximate the effect of a preselected phase shift or wavelength on a substrate by controlling the intensities of these components.

[0055] FIG. 11 illustrates graphs showing how multiple components, according to some embodiments, can be used to approximate and tune to any preselected wavelength. While 0° and 180° are described above as example phase shifts, these embodiments can easily be used to generate any phase shift between any two micromirrors in an array at various defocus levels. By way of example, graph 1100 illustrates approximating a 0° phase shift at a +3 μm defocus length, graph 1102 illustrates approximating a 180° phase shift at a 0 μm defocus length, graph 1106 illustrates approximating a 90° phase shift at a +3 μm defocus length, and graph 1108 illustrates approximating a 280° phase shift at a 0 μm defocus length. These graphs illustrate how any phase shift can be approximated using these techniques.

[0056] In these examples, the phase shifts or wavelengths bracketing the preselected phase shifts or preselected wavelengths were selected such that the higher phase shifts were approximately 20° greater than the preselected phase shifts and the lower phase shifts were approximately 10° less than the preselected phase shifts. While this particular bracketing of preselected phase shifts has been shown to closely approximate the effect of the preselected phase shifts, not all embodiments need use these particular values. For example, other embodiments may use phase shift values ​​for the first component that are greater than between approximately 5° and approximately 10°, greater than between approximately 10° and approximately 15°, greater than between approximately 15° and approximately 20°, greater than between approximately 20° and approximately 25°, greater than between approximately 25° and approximately 30°, etc. Similarly, other embodiments may use phase shift values ​​for the second component that are between approximately 5° and approximately 10° less, between approximately 10° and approximately 15° less, between approximately 15° and approximately 20° less, between approximately 20° and approximately 25° less, between approximately 25° and approximately 30° less, etc. Each of these different ranges may be used in different combinations without limitation and has different advantages depending on the particular lithography pattern, laser diode type, photoresist material, and / or other characteristics of the lithography system.

[0057] The systems described above may use the same mixture of wavelengths in the laser diodes for the DMD as a whole. This allows the system to correct for the average error in the mirror tilt angle of each DMD. However, some embodiments may additionally correct for the individual micromirror tilt error of the DMD array itself. For example, individual wavelengths may be mixed and the angle of incidence may be adjusted across the DMD based on the tilt error of each individual micromirror. These embodiments may vary the light source, intensity, and angle of light to compensate for local variations in the micromirror tilt angle.

[0058] The examples described above illustrate only two components of a light beam by way of example. However, other embodiments may use three or more components of a light beam. For example, a preselected phase shift may be bracketed by three, four, five, etc. components having phase shifts greater than and / or less than the predetermined phase shift. The relative brightness of each of these components may be determined using a weighted combination of the light components described above. In particular, weights corresponding to intensity may be calculated such that the weighted combination of phase shift deviations from the preselected phase shift is approximately zero.

[0059] FIG. 12 illustrates a flowchart 1200 of a method for selecting or adjusting a phase shift between pixels in a digital lithography system, according to some embodiments. The method may include projecting a first light beam onto a first spatial light modulator pixel (1202). As described above, the first spatial light modulator pixel may include a digital micromirror. The first spatial light modulator pixel may direct the first light beam onto a substrate during the digital lithography process. The method may also include projecting a second light beam onto a second spatial light modulator pixel (1204). The second spatial light modulator pixel may also include a digital micromirror or other similar device and may similarly direct the second light beam onto a substrate during the digital lithography process. The first and second spatial light modulator pixels may be positioned adjacent to each other in an array of pixels. The first and second light beams may originate from the same light source or from different light sources, such as a laser diode or laser diode array.

[0060] The first light beam may include multiple components, including a first component having a first wavelength that generates a first phase shift greater than a preselected phase shift. Similarly, the multiple components may also include a second component having a second wavelength that generates a second phase shift less than the preselected phase shift. The preselected phase shift may correspond to a desired phase shift between the light beams reflected by two micromirrors on the substrate. As described above, the multiple components in the first light beam may include other components in addition to the two specific components described above. The same light source that generates the first light beam may also generate the second light beam, and therefore the second light beam may also include these components.

[0061] The method may further include controlling 1206 the intensities of the multiple components to produce an effect on the substrate that approximates a preselected phase shift. The intensity of each component may be controlled based on a linear combination of deviations of the corresponding phase shift from the preselected phase shift. The weight applied to each of these phase shift deviations in the weighted combination may be calculated so that the linear combination is approximately zero. The weighted combination may include any number of components in the light beam. Approximating the preselected phase shift may produce a pattern of light intensity on the substrate that approximates the pattern of light intensity that would exist using a single wavelength corresponding to the preselected phase shift.

[0062] It should be appreciated that the specific steps illustrated in FIG. 12 provide a particular method for selecting or adjusting a phase shift between pixels in a digital lithography system according to various embodiments. Other sequences of steps may be performed according to alternative embodiments. For example, alternative embodiments may perform the steps outlined above in a different order. Moreover, the individual steps illustrated in FIG. 12 may include multiple sub-steps that may be performed in various sequences as appropriate for the individual step. Furthermore, additional steps may be added or deleted depending on the particular application. Many variations, modifications, and alternatives are within the scope of the present disclosure.

[0063] Each of the methods described herein may be implemented by a computer system. Each step of these methods may be performed automatically by the computer system and / or may be provided with input / output involving a user. For example, a user may provide inputs for each step in the method, and each of these inputs may be in response to a particular output requesting such input, where the output is generated by the computer system. Each input may be received in response to a corresponding requested output. Furthermore, inputs may be received from a user, received from another computer system as a data stream, retrieved from a memory location, retrieved over a network, requested from a web service, etc. Similarly, outputs may be provided to a user, provided to another computer system as a data stream, stored in a memory location, sent over a network, provided to a web service, etc. In short, each step of the methods described herein may be performed by a computer system and may involve any number of inputs, outputs, and / or requests to and from the computer system, which may or may not involve a user. Steps that do not involve a user may be said to be performed automatically by the computer system without human intervention. Therefore, in light of this disclosure, it will be understood that each step of each method described herein may be altered to include input and output to and from a user, or may be performed automatically by a computer system without human intervention, with any decisions made by a processor. Additionally, some embodiments of each of the methods described herein may be implemented as a set of instructions stored on a tangible, non-transitory storage medium to form a tangible software product.

[0064] FIG. 13 illustrates an exemplary computer system 1300 on which various embodiments may be implemented. System 1300 may be used to implement any of the computer systems or controllers described above. For example, system 1300 may be used to implement a controller that controls the intensity of components of light projected onto micromirrors and reflected onto a substrate during the lithography process described above. As shown in the figure, computer system 1300 includes a processing unit 1304 that communicates with several peripheral subsystems via a bus subsystem 1302. These peripheral subsystems may include a processing acceleration unit 1306, an I / O subsystem 1308, a storage subsystem 1318, and a communication subsystem 1324. Storage subsystem 1318 includes a tangible computer-readable storage medium 1322 and a system memory 1310.

[0065] The bus subsystem 1302 provides a mechanism for allowing the various components and subsystems of the computer system 1300 to communicate with each other as intended. While the bus subsystem 1302 is shown schematically as a single bus, alternative embodiments of the bus subsystem may utilize multiple buses. The bus subsystem 1302 may be any of several types of bus structures, including a memory bus or memory controller, a peripheral bus, and a local bus using any of a variety of bus architectures. For example, such architectures may include an Industry Standard Architecture (ISA) bus, a Micro Channel Architecture (MCA) bus, an Enhanced ISA (EISA) bus, a Video Electronics Standards Association (VESA) local bus, and a Peripheral Component Interconnect (PCI) bus, which may be implemented as a mezzanine bus manufactured to the IEEE P1386.1 standard.

[0066] Processing unit 1304, which may be implemented as one or more integrated circuits (e.g., conventional microprocessors or microcontrollers), controls the operation of computer system 1300. One or more processors may be included in processing unit 1304. These processors may include single-core or multi-core processors. In some embodiments, processing unit 1304 is implemented as one or more independent processing units 1332 and / or 1334, each of which may include a single or multi-core processor. In other embodiments, processing unit 1304 may be implemented as a quad-core processing unit formed by integrating two dual-core processors into a single chip.

[0067] In various embodiments, processing unit 1304 may execute various programs in response to program code and may maintain multiple simultaneously executing programs or processes. At any given time, some or all of the program code to be executed may reside in processor 1304 and / or in storage subsystem 1318. Through suitable programming, processor 1304 may provide the various functionality described above. Computer system 1300 may additionally include a processing acceleration unit 1306, which may include a digital signal processor (DSP), a special purpose processor, or the like.

[0068] The I / O subsystem 1308 may include user interface input devices and user interface output devices. User interface input devices may include a keyboard, a pointing device such as a mouse or trackball, a touchpad or touchscreen integrated into a display, a scroll wheel, a click wheel, a dial, buttons, switches, a keypad, an audio input device with a voice command recognition system, a microphone, and other types of input devices. User interface input devices may include, for example, a motion-sensing and / or gesture-recognition device such as a Microsoft Kinect® motion sensor that allows a user to control and interact with an input device, such as a Microsoft Xbox® 360 game controller, through a natural user interface using gestures and spoken commands. User interface input devices may also include an eye-gesture recognition device such as a Google Glass® blink detector that detects eye activity from a user (e.g., “blinking” while taking a picture and / or making a menu selection) and translates the eye gesture as input to an input device (e.g., Google Glass®). Additionally, the user interface input devices may include a voice recognition sensing device that allows a user to interact with a voice recognition system (e.g., the Siri® navigator) through voice commands.

[0069] User interface input devices may include, but are not limited to, three-dimensional (3D) mice, joysticks or pointing sticks, gamepads, and graphic tablets, as well as audio / visual devices such as speakers, digital cameras, digital camcorders, portable media players, webcams, image scanners, fingerprint scanners, barcode readers, 3D scanners, 3D printers, laser range finders, and eye-tracking devices. Additionally, user interface input devices may include medical imaging input devices, such as, for example, computed tomography, magnetic resonance imaging, positron emission tomography, and medical ultrasound devices. User interface input devices may also include audio input devices, such as, for example, MIDI keyboards, digital musical instruments, and the like.

[0070] User interface output devices may include display subsystems, indicator lights, or non-visual displays such as audio output devices. The display subsystem may be a flat panel device such as one using a cathode ray tube (CRT), liquid crystal display (LCD), or plasma display, a projection device, a touch screen, etc. In general, use of the term "output device" is intended to include all conceivable types of devices and mechanisms for outputting information from computer system 1300 to a user or to another computer. For example, user interface output devices may include various display devices that visually convey text, graphics, and audio / video information, such as, but not limited to, monitors, printers, speakers, headphones, automobile navigation systems, plotters, voice output devices, and modems.

[0071] Computer system 1300 may include a storage subsystem 1318 that comprises software elements shown as currently residing in system memory 1310. System memory 1310 may store program instructions that are loadable and executable on processing unit 1304, as well as data generated during the execution of these programs.

[0072] Depending on the configuration and type of computer system 1300, system memory 1310 may be volatile (such as random access memory (RAM)) and / or non-volatile (such as read-only memory (ROM), flash memory, etc.). RAM typically contains data and / or program modules that are immediately accessible to and / or presently being operated on and executed by the processing unit 1304. In some implementations, system memory 1310 may include several different types of memory, such as static random access memory (SRAM) or dynamic random access memory (DRAM). In some implementations, a basic input / output system (BIOS), containing the basic routines that help to transfer information between elements within computer system 1300, such as during start-up, may typically be stored in ROM. By way of example and not limitation, system memory 1310 also illustrates application programs 1312, program data 1314, and operating system 1316, which may include client applications, a web browser, a mid-tier application, a relational database management system (RDBMS), etc. By way of example, operating system 1316 may include various versions of Microsoft Windows®, Apple Macintosh®, and / or Linux operating systems, various commercially available UNIX® or UNIX-like operating systems (including, but not limited to, various GNU / Linux operating systems, Google Chrome® OS, etc.), and / or mobile operating systems such as iOS, Windows® Phone, Android® OS, BlackBerry® 10 OS, and Palm® OS operating systems.

[0073] The storage subsystem 1318 may also provide a tangible computer-readable storage medium for storing the basic programming and data constructs that provide the functionality of some embodiments. Software (programs, code modules, instructions) that, when executed by a processor, provide the functionality described above may be stored in the storage subsystem 1318. These software modules or instructions may be executed by the processing unit 1304. The storage subsystem 1318 may also provide a repository for storing data used in accordance with some embodiments.

[0074] Storage subsystem 1300 may also include computer-readable storage medium reader 1320, which may be further connected to computer-readable storage medium 1322. Along with, and optionally in combination with, system memory 1310, computer-readable storage medium 1322 may comprehensively represent storage media for containing, storing, transmitting, and retrieving computer-readable information on a temporary and / or more permanent basis, in addition to remote, local, fixed, and / or removable storage devices.

[0075] The computer-readable storage medium 1322 containing the code or portions of code can also include any suitable medium, including, but not limited to, storage media and communication media, such as volatile and nonvolatile, removable and non-removable media, implemented in any method or technology for information storage and / or transmission. This can include tangible computer-readable storage media, such as RAM, ROM, Electronically Erasable Programmable ROM (EEPROM), flash memory or other memory technology, CD-ROM, digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or other tangible computer-readable media. This can also include non-tangible computer-readable media, such as a data signal, data transmission, or any other medium that can be used to transmit desired information and that can be accessed by computing system 1300.

[0076] By way of example, the computer-readable storage medium 1322 may include a hard disk drive that reads from or writes to non-removable, non-volatile magnetic media, a magnetic disk drive that reads from or writes to removable, non-volatile magnetic disks, and an optical disk drive that reads from or writes to removable, non-volatile optical disks, such as CD-ROMs, DVDs, and Blu-Ray® disks or other optical media. The computer-readable storage medium 1322 may include, but is not limited to, Zip® drives, flash memory cards, Universal Serial Bus (USB) flash drives, Secure Digital (SD) cards, DVD disks, digital video tapes, etc. The computer-readable storage media 1322 may also include flash memory-based solid-state drives (SSDs), enterprise flash drives, SSDs based on non-volatile memory such as solid-state ROM, solid-state RAM, dynamic RAM, static RAM, DRAM-based SSDs, SSDs based on volatile memory such as magnetoresistive RAM (MRAM) SSDs, and hybrid SSDs that use a combination of DRAM-based SSDs and flash memory-based SSDs. Disk drives and their associated computer-readable media may provide non-volatile storage of computer-readable instructions, data structures, program modules, and other data for the computer system 1300.

[0077] The communications subsystem 1324 provides an interface to other computer systems and networks. The communications subsystem 1324 serves as an interface for receiving data from other systems from the computer system 1300 and for transmitting data to other systems from the computer system 1300. For example, the communications subsystem 1324 may enable the computer system 1300 to connect to one or more devices via the Internet. In some embodiments, the communications subsystem 1324 may include radio frequency (RF) transceiver components, global positioning system (GPS) receiver components, and / or other components for accessing wireless voice and / or data networks (e.g., using cellular telephone technology, advanced data network technologies such as 3G, 4G, or EDGE (Enhanced Data Rates for Global Evolution), WiFi (IEEE 802.11 family of standards), or other mobile communications technologies, or any combination thereof). In some embodiments, the communications subsystem 1324 may provide wired network connectivity (e.g., Ethernet) in addition to or instead of a wireless interface.

[0078] In some embodiments, the communications subsystem 1324 may also receive incoming communications in the form of structured and / or unstructured data feeds 1326, event streams 1328, event updates 1330, etc., for one or more users who may be using the computer system 1300.

[0079] By way of example, the communications subsystem 1324 may be configured to receive data feeds 1326 in real time from users of social networks and / or other communications services, such as web feeds such as Twitter® feeds, Facebook® updates, Rich Site Summary (RSS) feeds, and / or real-time updates from one or more third-party sources.

[0080] Additionally, the communications subsystem 1324 may also be configured to receive data in the form of a continuous data stream, which may include an event stream 1328 of real-time events and / or event updates 1330, which may be continuous or infinite in nature without an explicit end. Examples of applications that generate continuous data may include, for example, sensor data applications, financial tickers, network performance measurement tools (e.g., network monitoring and traffic management applications), clickstream analysis tools, automobile traffic monitoring, etc.

[0081] The communications subsystem 1324 may also be configured to output structured and / or unstructured data feeds 1326, event streams 1328, event updates 1330, etc. to one or more databases that may be in communication with one or more streaming data source computers coupled to the computer system 1300.

[0082] The computer system 1300 may be one of a variety of types, including a handheld portable device (e.g., an iPhone® cellular phone, an iPad® computing tablet, a PDA), a wearable device (e.g., a Google Glass® head-mounted display), a PC, a workstation, a mainframe, a kiosk, a server rack, or any other data processing system.

[0083] Due to the ever-changing nature of computers and networks, the description of computer system 1300 shown in the figure is intended as a specific example only. Many other configurations are possible, having more or fewer components than the system shown in the figure. For example, customized hardware could also be used, and / or particular elements could be implemented in hardware, firmware, software (including applets), or a combination. Additionally, connections to other computing devices, such as network input / output devices, could be employed. Based on the disclosure and teachings provided herein, other ways and / or methods for implementing various embodiments should be apparent.

[0084] As used herein, the terms "about" or "approximately" or "substantially" can be interpreted as being within the range that would be expected by a person skilled in the art in light of this specification.

[0085] In the above description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of various embodiments. It will be apparent, however, that some embodiments may be practiced without some of these specific details. In other instances, well-known structures and devices are shown in block diagram form.

[0086] The above description provides only exemplary embodiments and is not intended to limit the scope, applicability, or configuration of the present disclosure. Rather, the above description of various embodiments provides an enabling disclosure for implementing at least one embodiment. It should be understood that various changes may be made in the function and arrangement of elements without departing from the spirit and scope of the several embodiments as set forth in the appended claims.

[0087] Specific details have been given in the above description to provide a thorough understanding of the embodiments. However, it will be understood that the embodiments may be practiced without these specific details. For example, circuits, systems, networks, processes, and other components may be shown as components in block diagram form in order to avoid obscuring the embodiments in unnecessary detail. In other instances, well-known circuits, processes, algorithms, structures, and techniques may be shown without unnecessary detail in order to avoid obscuring the embodiments.

[0088] Also, it should be noted that particular embodiments may be described as a process, which is depicted as a flowchart, a flow diagram, a data flow diagram, a structure diagram, or a block diagram. While a flowchart may describe operations as a sequential process, many of the operations may be performed in parallel or concurrently. Additionally, the order of operations may be rearranged. A process terminates when its operations are completed, but may have additional steps not included in the diagram. A process may correspond to a method, a function, a procedure, a subroutine, a subprogram, etc. When a process corresponds to a function, its termination may correspond to a return of the function to the calling function or the main function.

[0089] The term "computer-readable medium" includes, but is not limited to, portable or fixed storage devices, optical storage devices, wireless channels, and various other media capable of storing, containing, or transporting instructions and / or data. A code segment or machine-executable instruction may represent a procedure, a function, a subprogram, a program, a routine, a subroutine, a module, a software package, a class, or any combination of instructions, data structures, or program statements. A code segment may be coupled to another code segment or a hardware circuit by passing and / or receiving information, data, arguments, parameters, or memory contents. Information, arguments, parameters, data, etc. may be passed, forwarded, or transmitted via any suitable means including memory sharing, message passing, token passing, network transmission, etc.

[0090] Furthermore, the embodiments may be implemented by hardware, software, firmware, middleware, microcode, hardware description languages, or any combination thereof. When implemented in software, firmware, middleware, or microcode, the program code or code segments to perform the necessary tasks may be stored in a machine-readable medium. A processor may perform the necessary tasks.

[0091] In the foregoing specification, features have been described with reference to specific embodiments thereof, but it should be recognized that not all embodiments are limited thereto. Various features and aspects of the several embodiments may be used individually or together. Moreover, the embodiments may be utilized in any number of environments and applications other than those described herein without departing from the broader spirit and scope of the specification. Accordingly, the specification and drawings should be regarded as illustrative rather than restrictive.

[0092] Additionally, for purposes of illustration, the methods have been described in a particular order. It should be appreciated that in alternative embodiments, the methods may be performed in an order different from that described. It should also be appreciated that the methods described above may be performed by hardware components or may be embodied in a sequence of machine-executable instructions that can be used to cause a machine, such as a general-purpose or special-purpose processor or logic circuitry programmed with instructions, to perform the method. These machine-executable instructions may be stored on one or more machine-readable media, such as a CD-ROM or other type of optical disk, a floppy diskette, ROM, RAM, EPROM, EEPROM, magnetic or optical card, flash memory, or other type of machine-readable medium suitable for storing electronic instructions. Alternatively, the methods may be performed by a combination of hardware and software.

Claims

1. a first spatial light modulator pixel configured to direct a first light beam onto a substrate during a digital lithography process; a second spatial light modulator pixel configured to direct a second light beam onto the substrate during the digital lithography process; a light source configured to generate the first light beam, the first light beam comprising: a first component having a first wavelength that produces a first phase shift greater than a preselected phase shift; a second component having a second wavelength that generates a second phase shift less than the preselected phase shift; and a light source comprising a plurality of components comprising: a controller configured to control the intensities of the plurality of components to produce an effect on the substrate that approximates the preselected phase shift; and A digital lithography system comprising:

2. 10. The system of claim 1, wherein the second spatial light modulator pixel is adjacent to the first spatial light modulator pixel in an array of spatial light modulator pixels in a digital micromirror device.

3. 10. The system of claim 1, wherein the first spatial light modulator pixel comprises a micromirror that adjusts between an on position that reflects light onto the substrate and an off position that reflects light away from the substrate.

4. The system of claim 1 , wherein the light source is also configured to generate the second light beam, such that the first light beam and the second light beam originate from the light source.

5. 2. The system of claim 1, wherein the second light beam is generated from a different light source, and the controller is further configured to control the intensity of components in the second light beam to correct for tilt errors in the second spatial light modulator pixels that are different from tilt errors in the first spatial light modulator pixels.

6. 10. The system of claim 1, wherein the light source comprises a plurality of groups of laser diodes, a first subset of the plurality of groups of laser diodes configured to output approximately the first wavelength, and a second subset of the plurality of groups of laser diodes configured to output approximately the second wavelength.

7. The system of claim 1 , wherein the light source comprises a homogenizing rod that mixes the first component with the second component to produce a uniform first light beam.

8. The system of claim 1 , wherein the plurality of components comprises a plurality of additional components in addition to the first component and the second component.

9. 1. A method for adjusting a phase shift between pixels in a digital lithography system, the method comprising: projecting a first light beam onto a first spatial light modulator pixel; the first spatial light modulator pixel directs the first light beam onto a substrate during a digital lithography process, the first light beam comprising: a first component having a first wavelength that produces a first phase shift greater than a preselected phase shift; a second component having a second wavelength that generates a second phase shift less than the preselected phase shift; and projecting a first light beam, the first light beam comprising a plurality of components comprising: projecting a second light beam onto a second spatial light modulator pixel, the second spatial light modulator pixel directing the second light beam onto the substrate during the digital lithography process; controlling the intensities of the plurality of components to produce an effect on the substrate that approximates the preselected phase shift; and A method comprising:

10. 10. The method of claim 9, wherein the first wavelength produces a first phase shift that is approximately 20 degrees greater than the preselected phase shift.

11. 10. The method of claim 9, wherein the second wavelength produces a second phase shift that is approximately 10 degrees less than the preselected phase shift.

12. 10. The method of claim 9, wherein the preselected phase shift is selectable to be a phase shift between 0° and 359°.

13. 10. The method of claim 9, wherein controlling the strengths of the plurality of components comprises calculating a weight for each of the plurality of components in a linear combination of deviations between the first phase shift and the second phase shift from the preselected phase shift, such that the linear combination is approximately zero.

14. The method of claim 13 , wherein the weights in the linear combination correspond to the strengths of the components.

15. 10. The method of claim 9, wherein approximating the preselected phase shift produces a pattern of light intensity on the substrate that approximates a pattern of light intensity that would be present on the substrate using a single wavelength corresponding to the preselected phase shift.

16. 10. The method of claim 9, wherein the first phase shift is calculated from the first wavelength and an optical path difference between the first light beam and the second light beam.

17. 10. The method of claim 9, wherein the second spatial light modulator pixel is adjacent to the first spatial light modulator pixel in an array of spatial light modulator pixels in a digital micromirror device, and the second light beam also comprises the first component and the second component.

18. 1. A method for adjusting or selecting a phase shift between pixels in a digital lithography system, the method comprising: projecting a first light beam onto a first spatial light modulator pixel, the first spatial light modulator pixel directing the first light beam onto a substrate during a digital lithography process; projecting a second light beam onto a second spatial light modulator pixel, the second spatial light modulator pixel directing the second light beam onto the substrate during the digital lithography process, the second spatial light modulator pixel being adjacent to the first spatial light modulator pixel in an array of spatial light modulator pixels; controlling the wavelength of the first light beam and / or the wavelength of the second light beam based on an optical path difference between the first light beam and the second light beam to produce a preselected phase shift between the first light beam and the second light beam on the substrate; A method comprising:

19. 20. The method of claim 18, wherein controlling the wavelength of the first light beam comprises switching between different laser diodes that produce light having different wavelengths.

20. 20. The method of claim 18, wherein controlling the wavelength of the first light beam comprises varying the wavelength of the first light beam by controlling a temperature of a light source, mechanically altering a cavity of the light source, or electro-acoustically altering the cavity of the light source.

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