Systems and methods for distributing light delivery

Abstract

A method for improving the sequencing of light transmission in a lithography process includes: determining an intensity sequence of light to be transmitted, including an interval within the intensity sequence in which no light is substantially transmitted to a substrate; and transmitting the light to a substrate according to the intensity sequence using a digital mirror device (DMD) via a light source.

Description

[Technical Field]

[0001] The description herein generally relates to patterning processes. More specifically, the present invention includes apparatus, methods, and computer program products for improving light transmission in lithography processes. [Previous Technology]

[0002] Lithography equipment can be used, for example, in the manufacture of integrated circuits (ICs). A pattern ("design layout") corresponding to an individual layer of the IC can be transferred to a target portion (e.g., containing one or more dies) on a substrate (e.g., a silicon wafer) coated with a radiation-sensitive material ("resist") by methods such as irradiating a target portion with a pattern on a patterning device. Generally, a single substrate contains a plurality of adjacent target portions, and the pattern is sequentially transferred by the lithography equipment to these adjacent target portions, one target portion at a time. In one type of lithography equipment, the entire pattern on the patterning device is transferred to one target portion in a single operation; such equipment may also be called a stepper. In alternative equipment, a stepping scanning device allows a projection beam to scan the patterning device in a given reference direction ("scanning direction") while simultaneously moving the substrate parallel or antiparallel to this reference direction. Different portions of the pattern on the patterning device are progressively transferred to a target portion. Because lithography devices generally have a reduction ratio M (e.g., 4), the substrate moving speed F will be 1 / M time, at which point the projection beam scans the patterning apparatus. Further information about lithography devices can be found, for example, in US 6,046,792, which is incorporated herein by reference.

[0003] Before the pattern is transferred from the patterning apparatus to the substrate, the substrate may undergo various processes, such as primer application, resist coating, and soft baking. After exposure, the substrate may undergo other processes ("post-exposure processes"), such as post-exposure baking (PEB), development, hard baking, and measurement / inspection of the transferred pattern. This array of processes forms the basis for manufacturing individual layers of a device (e.g., an IC). The substrate may then undergo various procedures, such as etching, ion implantation (doping), metallization, oxidation, chemical mechanical polishing, etc., all intended to refine the individual layers of the device. If several layers are required in the device, the entire process or its variations are repeated for each layer. Ultimately, a device will be present in each target portion of the substrate. These devices are then separated from each other by techniques such as cutting or sawing, thereby allowing individual devices to be mounted on a carrier, connected to pins, etc.

[0004] Therefore, manufacturing apparatus (such as semiconductor devices) typically involves processing a substrate (e.g., a semiconductor wafer) using several manufacturing processes to form various features and multiple layers of such devices. These layers and features are typically manufactured and processed using, for example, deposition, lithography, etching, deposition, chemical mechanical polishing, and ion implantation. Multiple devices can be fabricated on multiple dies on a substrate, and then these devices are separated into individual devices. This device manufacturing process can be considered a patterning process. A patterning process involves performing patterning steps (such as optical and / or nanoimprint lithography) using patterning devices in a lithography apparatus to transfer a pattern on the patterning device to the substrate, and the patterning process typically, but as appropriate, involves one or more related patterning processing steps, such as resist development by a developing apparatus, baking the substrate using a baking tool, etching the pattern using an etching apparatus, etc.

[0005] As mentioned, lithography is a central step in the manufacturing of devices such as ICs, in which functional elements of a pattern-defining device, such as microprocessors and memory chips, are formed on a substrate. Similar lithography techniques are also used to form flat panel displays, microelectromechanical systems (MEMS) and other devices, as well as 2D and / or 3D stack-up fabrication.

[0006] As semiconductor manufacturing processes continue to advance, the size of functional components has been continuously reduced over the decades, while the number of functional components, such as transistors, per device has been steadily increasing, following a trend known as "Moore's law." In the current state of technology, layers of devices are manufactured using lithography equipment that uses illumination from a deep ultraviolet light source to project a pattern corresponding to a design layout onto a substrate, thereby producing individual functional components with dimensions much smaller than 100 nm, that is, less than half the wavelength of radiation from the light source (e.g., a 193 nm light source).

[0007] This process, which provides features for printing sizes smaller than the classical resolution limit of lithography equipment, can be called low-k1 lithography according to the resolution formula CD = k1 × λ / NA, where λ is the wavelength of the radiation used (e.g., 248 nm or 193 nm), NA is the numerical aperture of the projection optics in the lithography equipment, CD is the "critical size" (typically the smallest feature size printed), and k1 is an empirical resolution factor. Generally speaking, the smaller k1 is, the more difficult it becomes to reproduce patterns on a substrate that resemble the shape and size planned by the designer to achieve specific electrical functionality and performance. To overcome these difficulties, complex fine-tuning steps are applied to lithography equipment, design layouts, or patterning devices. These steps include, but are not limited to, optimization of NA and optical coherence settings, customized illumination schemes, the use of phase-shift patterning devices, optical proximity correction (OPC, sometimes also called "optical and procedural correction") in the design layout, or other methods generally defined as "resolution enhancement techniques" (RET). As used herein, the term "projection optics" should be broadly interpreted to encompass various types of optical systems, including, for example, refractive optics, reflective optics, aperture and reflective-refractive optics. The term "projection optics" may also include components operating according to any of these design types for collectively or individually guiding, shaping, or controlling a projected radiation beam. The term "projection optics" may include any optical component in a lithography apparatus, regardless of its location within the optical path of the lithography apparatus. Projection optics may include optical components for shaping, adjusting, and / or projecting radiation from a source before it passes through a patterning device, and / or for shaping, adjusting, and / or projecting radiation after it has passed through a patterning device. Projection optics typically exclude the light source and the patterning device. [Summary of the Invention]

[0008] A method, system, and computer program for improving light transmission during a lithography process are disclosed. In one embodiment, a method for improving the sequencing of light transmission in a lithography process includes: determining an intensity sequence of light to be transmitted, including an interval within the intensity sequence in which no light is substantially transmitted to a substrate; and transmitting the light to a substrate according to the intensity sequence using a digital mirror device (DMD) via a light source.

[0009] In some variations, the method may further include determining a target intensity of light transmitted to a point on the substrate. The determined intensity sequence may be transmitted from the digital mirror device (DMD) to the substrate to achieve the target intensity, wherein substantially no light is transmitted to the substrate during the interval. This may include storing a set of instructions for the intensity sequence of light in a physical memory. Thus, in some variations, the presence of the interval may reduce the impact of the upcoming instruction set in the intensity sequence stored in the physical memory on the configuration of the DMD.

[0010] In other variations, the intensity sequence is represented by bits stored in physical memory, and the interval is located after the most significant bit in the sequence. An asymmetric distribution of the intensity sequence can be determined, which reduces the difference between the transmission centroid of one of the sites and the target centroid of the site.

[0011] In one related state, a method for improving the sequencing of light transmission in a lithography process includes: determining a target intensity of light transmitted to a point on a substrate; determining, by means of a digital mirror device (DMD), an intensity sequence of light to be transmitted to the substrate to achieve the target intensity, the intensity sequence including an interval within the intensity sequence in which no light is substantially transmitted to the substrate; storing an instruction set for the intensity sequence of light in a physical memory; and transmitting light to the substrate by means of a light source using the DMD according to the intensity sequence, wherein the presence of the interval reduces the influence of the upcoming instruction set in the intensity sequence stored in the physical memory on the configuration of the DMD.

[0012] In some variations, the intensity sequence may be represented by bits stored in physical memory, and the interval is located after the most significant bit in the sequence. It can be determined that one of the intensity sequences is symmetrically distributed, which reduces the difference between the transmission centroid of one of the sites and the target centroid of one of the sites.

[0013] In other variations, a method may also include modifying the symmetrical distribution into an asymmetric distribution by incorporating an asymmetry into the intensity sequence, the asymmetry further reducing the difference between the transfer centroid and the target centroid. The transfer centroid may be adjusted by changing the position of the intensity sequence or intervals.

[0014] In other variations, the intensity sequence may be an 8-bit intensity distribution, symmetrical, and / or may include skipping light transmission between two light transmission intervals.

[0015] Furthermore, some variations may include determining the intensity sequence individually for each of the mirrors in the DMD.

[0016] In a related configuration, a computer program product includes a non-transitory computer-readable medium having instructions recorded thereon, which, when executed by a computer, perform the method as described in any of the above method configurations.

[0017] In another related embodiment, a system for transmitting light to a substrate includes: a light source; a digital mirror device; a physical memory configured to store instructions for transmitting light from the light source using the digital mirror device; and a non-transitory computer-readable medium having the instructions recorded thereon, the instructions causing operations when executed by a computer, the operations including: determining a target intensity of light transmitted to a point on the substrate; determining, by means of a digital mirror device (DMD), an intensity sequence of light to be transmitted to the substrate to achieve the target intensity, the intensity sequence including an interval within the intensity sequence in which no light is substantially transmitted to the substrate; storing a set of instructions for the intensity sequence of light in the physical memory; and transmitting light to the substrate by means of the light source using the DMD according to the intensity sequence, wherein the presence of the interval reduces the influence of the upcoming instruction set in the intensity sequence stored in the physical memory on the configuration of the DMD.

[0018] In some variations, the physical memory may be positioned close to the DMD such that the charge used to store the sequence in the physical memory causes an angular deviation of the mirrors in the DMD. For example, the physical memory may be located less than 1 mm from the digital mirror device. Furthermore, the system may include a control system configured to actuate the mirrors in the digital mirror device to transmit the intensity sequence of light to the substrate. The system may also include a microlens array (MLA) configured to guide light from the DMD to the substrate. The system may also be configured to manufacture computer chips or flat panel displays.

Implementation Method

[0036] As used herein, the term "substrate" describes a material that can guide light as part of a manufacturing process. For example, a substrate may include photoresist, wafer, flat panel display, photosensitive material having (e.g., metal or other functional material) and abrasive paste containing particles, etc.

[0037] As used herein, the terms "patterning process" or "printing" mean a process, as part of a lithography process, of creating an etched substrate by applying light to a specified pattern. A patterning process may also include any process involving the transfer of light in the manufacture of a flat panel display device or integrated circuitry (e.g., in its development).

[0038] This document describes one or more embodiments of lithography systems and apparatuses, lithography methods, programmable patterning devices, and other apparatuses, articles of manufacture, and methods. In one embodiment, a low-cost and / or flexible maskless lithography apparatus is provided. Because it is maskless, conventional masks are not required to expose patterns, for example, in the manufacture of computer chips (ICs) or flat panel displays. Similarly, packaging applications do not require one or more rings; the programmable patterning device can provide digital edge-processing "rings" for packaging applications to avoid edge projection. Maskless (digital patterning) can also be achieved on flexible substrates. As described herein, various embodiments of the disclosed systems and methods allow for increased tolerance in the alignment / positioning of lens arrays used in lithography.

[0039] FIG1 is a simplified diagram illustrating an exemplary lithography system according to one embodiment. As shown in FIG1, the lithography apparatus 100 may include a patterning device 110 and a projection system 150. The patterning device 110 may include a light source 112 (such as a laser diode as discussed herein) and a mirror array 140. The mirror array 140 may receive light (also referred to herein as a radiated beam or beam 114) from the light source 112 and cause the beam 114 to be laterally displaced in the X and / or Y directions. In one embodiment, the patterning device 110 may include a lens 130 to image the radiated beam 114 from the light source 112 onto the mirror array 140.

[0040] The deflected beam 114 from the mirror array 140 can be received by the projection system 150. The projection system 150 may include an objective lens 152, a lens array 154, and any number of other lenses or lens arrays for performing focusing, magnification, aberration correction, etc. The objective lens 152 may be configured to receive the beam 114 from the patterning device 110. In the example of FIG1, the beam 114 is diverged from the objective lens 152 and received by the lens array 154, which may include any number of individual lenses. The lens array 154 may then focus the beam 114 onto a substrate 160. As further described herein, the substrate 160 may be movable relative to the lithography apparatus 100, as indicated by the arrows.

[0041] By controlling the amplitude of light imaged onto a specific portion of the substrate 160, maskless lithography and methods incorporating greyscaling (described in further detail below) that provide benefits to the lithography process can be performed. Therefore, in one embodiment, a method of performing lithography may include illuminating a mirror array 140 with a beam 114. The mirror array 140 may include a plurality of mirrors that receive light. The light may be imaged onto the substrate 160 to produce a pattern.

[0042] In one embodiment, a single light source 112 may be present for the mirror array 140. In other embodiments, the light source 112 may comprise multiple light sources (e.g., 2, 3, 6, 10, etc.) combined to provide illumination. In one embodiment, the light source 112 may be turned on and off corresponding to a dual-state trigger frequency of the adjustment frequency of the mirror array 140. For example, if the mirror array 140 is capable of changing its configuration 30 times per second (e.g., 1 / 60 second stationary and 1 / 60 second adjustment), the light source 112 may be operated to turn on and off such that the mirror array 140 is not illuminated during its 1 / 60 second adjustment cycle. In another embodiment, one or more laser diodes may serve as the light source 112 and may be controlled to emit light, for example, at a dual-state trigger frequency or in a pattern or continuously.

[0043] In another embodiment, the lithography system may include multiple light sources (collectively illustrated as light source 112 in FIG. 1) configured to generate light having multiple light amplitudes. The light may then be patterned at a mirror array configured to guide the patterned light to a substrate.

[0044] Depending on the circumstances, the lithography apparatus may include a radiation system (not shown) for supplying radiation (e.g., ultraviolet (UV) radiation) to a plurality of light sources 112. If the patterning device is the radiation source itself (e.g., a laser diode array or an LED array), the lithography apparatus may be designed to not have a radiation system (i.e., not have a radiation source other than the patterning device itself), or at least to have a simplified radiation system.

[0045] The radiation system may include an illumination system (illuminator) configured to receive radiation from a radiation source. The illumination system may include one or more of the following elements: a radiation transfer system (e.g., adapted to guide mirrors), a radiation adjustment device (e.g., a beam expander), an adjustment device for setting the angular amplitude distribution of the radiation (generally, at least adjusting the outer and / or inner radial ranges of the amplitude distribution in the pupil plane of the illuminator (which may be referred to as σ_outer and σ_inner, respectively)), a beam concentrator, and / or a condenser. The illumination system may be used to adjust the radiation supplied to the light source 112 to have a desired uniformity and amplitude distribution in its cross-section. The illumination system may be configured to divide the radiation into sub-beams, which may, for example, be associated with one or more of a plurality of light sources 112. For example, a two-dimensional diffraction grating may be used to divide the radiation into sub-beams. In the description of this invention, the terms "beam of radiation / radiation beam" and "beam" cover, but are not limited to, the case where beam 114 comprises a plurality of such sub-beams of radiation.

[0046] In other embodiments, the radiation system may also include a radiation source (e.g., an excimer laser) for generating radiation to supply to or via the light source 112. For example, when the radiation source is an excimer laser, the radiation source and the lithography device 100 may be separate entities. In such cases, the radiation source is not considered part of the lithography device 100, and radiation is transferred from the source to the illuminator. In other cases, such as when the source is a mercury lamp, the radiation source may be an integral part of the lithography device 100. Both in these cases are covered within the scope of the invention.

[0047] In one embodiment, the radiation source (which may be light source 112 in one embodiment) can provide radiation having wavelengths of at least 5 nm, such as at least 10 nm, at least 50 nm, at least 100 nm, at least 150 nm, at least 175 nm, at least 200 nm, at least 250 nm, at least 275 nm, at least 300 nm, at least 325 nm, at least 350 nm, or at least 360 nm. In one embodiment, the radiation has a wavelength of up to 450 nm (e.g., up to 425 nm, up to 375 nm, up to 360 nm, up to 325 nm, up to 275 nm, up to 250 nm, up to 225 nm, up to 200 nm, or up to 175 nm). In one embodiment, the radiation may have wavelengths including 436 nm, 405 nm, 365 nm, 355 nm, 248 nm, 193 nm, 157 nm, 126 nm, and / or 13.5 nm. In one embodiment, the radiation may include a wavelength of about 365 nm or about 355 nm. In one embodiment, the radiation may include a broadband wavelength, such as covering 365 nm, 405 nm, and 436 nm. A 355 nm laser source may also be used. In one embodiment, the radiation may have a wavelength of about 405 nm.

[0048] In one embodiment, radiation may be directed from the illumination system to the patterning device 110 at angles between 0 and 90°, for example, between 5 and 85°, between 15 and 75°, between 25 and 65°, or between 35 and 55°. Radiation from the illumination system may be provided directly to the patterning device 110 (i.e., without relying on the mirror array 140). In an alternative embodiment, radiation may be directed from the illumination system to the patterning device 110 by means of a beam splitter configured such that the radiation is initially reflected by the beam splitter and directed to the patterning device 110. The patterning device 110 may modulate the beam 114 and reflect it back to the beam splitter, which will then transmit the modulated beam toward the substrate 160. However, alternative configurations may be used to direct radiation to the patterning device 110 and subsequently to the substrate 160. In detail, if a transmissive patterning device 110 (e.g., an LCD array) is used or the patterning device 110 is self-emissive (e.g., a laser diode), then an illumination system configuration may not be required.

[0049] Although the lithography apparatus 100 according to an embodiment of the present invention is described herein as being used for exposing a substrate, the lithography apparatus 100 may also be used to expose a resist on a substrate or to project a patterned beam 114 for use in resist-free lithography.

[0050] To process pixels (or more generally, positions) on a substrate requiring exposure, a mirror array 140 can be provided to guide the beam 114 to the desired position. In one embodiment, the beam 114 can be guided by the mirror array 140 to a site on the substrate 160 requiring exposure. In one embodiment, the mirror array 140 can be configured to deflect the beam 114 in both the X and Y directions to position the site on a pixel on the substrate. When a portion of the beam 114 is not needed, that portion can be deflected toward a beam cutoff.

[0051] As discussed above, the mirror array 140 can facilitate the deflection of the light beam 114 from the light source 112 in the X and / or Y directions. In other words, this type of mirror array 140 can direct the light beam 114 toward a specific position on the lens array 154 and thus toward the substrate 160. In one embodiment, the mirror array 140 can deflect radiation only in the Y direction or only in the X direction. In one embodiment, the mirror array 140 can deflect radiation in both the X and Y directions.

[0052] In one embodiment, the mirror array 140 may be a mechanical (i.e., galvanometer type), electro-optic, and / or acousto-optic mirror array. Mechanical mirror arrays tend to provide the largest number of resolvable radiation points (i.e., a resolvable point is defined as the angle by which the beam is deflected equal to its own angular dispersion), but tend to be the slowest in terms of point scanning rate. Electro-optic mirror arrays tend to be the fastest in terms of point scanning rate, but tend to have the smallest number of resolvable radiation points.

[0053] In one embodiment, the mirror array 140 may be an electro-optic mirror array. The electro-optic mirror array can provide a switching speed of up to several nanoseconds. In one embodiment, the electro-optic mirror array can provide a deflection angle of + / -15 degrees. In one embodiment, this can generate approximately 600 radiation sites for an input beam divergence of 0.05 degrees. In one embodiment, the use of an electro-optic mirror array avoids having rapidly moving mechanical parts for radiation deflection. In one embodiment, there may be no moving optical elements between the radiation source 112 and the substrate 160.

[0054] The electro-optic mirror array may include an optically transparent piezoelectric material. Therefore, in one embodiment, the beam 114 can be deflected due to a potential difference applied to the piezoelectric material. For example, when a potential difference is applied throughout the optically transparent material, the refractive index of the material changes, which alters the direction of beam propagation (i.e., deflects the radiated beam). In one embodiment, the material is selected from: LiNbO3, LiTaO3, KH2PO4 (KDP), or NH4H2PO4 (ADP). LiTaO3 is transparent at a wavelength of 405 nm.

[0055] The projection system 150 (e.g., a quartz and / or CaF2 lens system or a hybrid reflection-refraction system comprising lens elements made of such materials, or a mirror system) can be used to project the beam 114 onto the substrate 160. The projection system 150 can project a first grayscale pattern provided by the light source 112 and the mirror array 140 such that the first grayscale pattern is coherently formed on the substrate 160.

[0056] In this regard, the projection system may include one or more focusing elements (generally referred to herein as a mirror array or lens array 154), such as a microlens array 154 (MLA) or a Fresnel lens array 154, to form a secondary source and to image the site onto the substrate 160.

[0057] In one embodiment, light can be imaged onto a lens array 154 including lenses that focus light onto the substrate 160. In another embodiment, the substrate 160 can be illuminated multiple times at one location to transmit the total light amplitude.

[0058] In one embodiment, the lens array 154 (e.g., MLA) may include at least 10 focusing elements, such as at least 100 focusing elements, at least 1,000 focusing elements, at least 10,000 focusing elements, at least 100,000 focusing elements, or at least 1,000,000 focusing elements. In some embodiments, the number of lenses in the lens array 154 may be equal to the number of mirrors in the mirror array 140.

[0059] In one embodiment, the lens array 154 may be moved at least in the direction toward and away from the substrate, for example, when using one or more actuators. The ability to move the lens array 154 toward and away from the substrate allows for, for example, focus adjustment without moving the substrate 160. In one embodiment, individual lens elements in the lens array 154 (e.g., individual lens elements in the lens array 154) may be moved at least in the direction toward and away from the substrate (e.g., for local focus adjustment of a non-flat substrate or to bring each optical column to the same focal length).

[0060] Any of the lenses in the lens array 154 can focus light onto a point on the substrate. As used herein, a "point" means an area on the substrate 160 where light from one or more lenses arrives. The point may be, but is not required to be, the focal point of any particular lens. In some embodiments, the point may correspond to the waist of a Gaussian beam. Due to the distance and angle between the substrate and the beam, the shape of any lens, the beam block with a shaped aperture, etc., the point may be circular, elliptical, or any other shape.

[0061] In one embodiment, the site size may be 10 micrometers or less, 5 micrometers or less, for example, 3 micrometers or less, 2 micrometers or less, 1 micrometer or less, 0.5 micrometers or less, 0.3 micrometers or less, or about 0.1 micrometers. In one embodiment, the site size on the substrate is 0.1 micrometers or greater, 0.2 micrometers or greater, 0.3 micrometers or greater, 0.5 micrometers or greater, 0.7 micrometers or greater, 1 micrometer or greater, 1.5 micrometers or greater, 2 micrometers or greater, or 5 micrometers or greater. In one embodiment, the site size is about 0.1 micrometers. In one embodiment, the site size is about 0.5 micrometers. In one embodiment, the site size is about 1 micrometer. These sizes may apply to the diameter, major axis, or semi-major axis of the site, or other relevant dimensions.

[0062] In some embodiments, the lithography apparatus may include a controller that generates signals at each stage during the exposure process to set the patterning means to a necessary state. The pattern to be formed on the substrate may be provided to the lithography apparatus in a vector-defined format, such as GDSII. To convert design information into control signals, the controller may include one or more data manipulation devices that can be configured to perform processing steps on a data stream representing the pattern. The data manipulation devices may be collectively referred to as a "data path".

[0063] The data manipulation device of the data path can be configured to perform one or more of the following functions: converting vector-based design information into bit-image pattern data; converting bit-image pattern data into a desired radiation dose image (i.e., a desired radiation dose profile covering the substrate); converting the desired radiation dose image into a desired radiation amplitude value for each light source; and converting the desired radiation amplitude value for each light source into a corresponding control signal.

[0064] In one embodiment, control signals can be supplied to the light source 112 and / or one or more other devices (e.g., mirror arrays and / or sensors) via wired or wireless communication. Additionally, signals from the light source 112 and / or from one or more other devices (e.g., mirror arrays and / or sensors) can be transmitted to a controller. Power can be supplied to the light source 112 or one or more other devices (e.g., mirror arrays and / or sensors) via wired or wireless means in a manner similar to that of the control signals. For example, in a wired embodiment, power can be supplied via one or more wires, regardless of whether they are the same as or different from the wires carrying the signals. A sliding contact configuration can be provided for power transmission. In a wireless embodiment, power can be transmitted via RF coupling.

[0065] While the preceding discussion has focused on control signals supplied to the light source 112 and / or one or more other devices (e.g., mirror arrays and / or sensors), it should be understood that it covers additionally or alternatively transmitting signals from the light source 112 and / or from one or more other devices (e.g., mirror arrays and / or sensors) to the controller via appropriate configuration. Thus, communication can be unidirectional (e.g., communication only to or from the light source 112 and / or one or more other devices (e.g., mirror arrays and / or sensors)) or bidirectional (i.e., communication from and to the light source 112 and / or one or more other devices (e.g., mirror arrays and / or sensors)).

[0066] In one embodiment, the control signal used to provide the pattern can be modified to take into account factors that may affect the proper supply and / or display of the pattern on the substrate. For example, correction can be applied to the control signal to take into account the heating of one or more of the light source 112, lenses, etc. This heating can cause changes in the pointing direction of the light source 112, lenses, etc., changes in the uniformity of radiation, etc. In one embodiment, measured temperatures and / or expansion / contraction associated with the light source 112 and / or other elements such as sensors can be used to modify the control signals that have been otherwise provided to form the pattern. Thus, for example, the temperature of the light source 112 can vary during exposure, causing a change in the projected pattern that would be provided at a single constant temperature. Therefore, the control signal can be modified to take into account this variation. Similarly, in one embodiment, results from the alignment sensor and / or the level sensor 150 can be used to modify the pattern provided by the light source 112. The pattern can be modified to correct distortions, such as those caused by optical devices (if present) between the light source 112 and the substrate 160, irregularities in the positioning of the substrate 160, or non-uniformity of the substrate 160.

[0067] The substrate 160 can be accurately moved, for example, to position different target portions within the path of the beam 114, by means of a positioning device (and, depending, a position sensor on the base, such as an interferometric measuring device, a linear encoder, or a capacitive sensor that receives the interferometric beam). In other embodiments, the positioning device for the light source 112 can be used, for example, to accurately correct the position of the light source 112 relative to the path of the beam 114 during scanning. For example, some embodiments may include a control system that controls the scanning of the substrate relative to the MLA or other components of the optical column described herein (e.g., any combination of components in FIG. 1). The control system can therefore provide two-dimensional horizontal translation, vertical translation, or rotation of the substrate in any combination.

[0068] FIG2 is a schematic diagram illustrating an exemplary lithography system and a method for printing a pattern onto a scanned substrate. In one embodiment, the lithography apparatus 100 can project radiation from the light source 112 onto the substrate in a manner that does not form individual pixels projected onto the substrate but actually forms a substantially continuous image projected onto the substrate. The lithography apparatus 100 (specifically, the light source 112) can be configured to provide pixel grid imaging as described in more detail herein. As depicted in the upper figure of FIG2, the site 210 will appear to have an overlap based on the distance between the microlenses in the microlens array. However, by scanning the substrate at certain angles, a printed pattern with sufficient overlap of site size can be produced to avoid gaps in the printing.

[0069] The solid circles in the lower part of Figure 2 represent the array of sites S (or 310 in the side view) projected onto the substrate 160 by the lens array 154 in the projection system 150. The substrate 160 is moved in the X direction relative to the projection system 150 during a series of exposures on the substrate. Hollow circles represent site exposures SE (or 210 in the side view) that may have been previously exposed onto the substrate 160. As shown, each point projected onto the substrate 160 by the lens array 154 within the projection system 150 is exposed in a column R of site exposures on the substrate 160. The complete pattern for the substrate 160 is generated by the sum of all columns R of site exposures SE exposed by each of the sites S. This configuration may be referred to as "pixel grid imaging". It should be understood that Figure 2 is schematic and the sites S can actually overlap, as discussed further herein.

[0070] As can be seen, the array of radiation sites S can be configured at an angle α relative to the substrate scanning direction (the edges of the substrate 160 are parallel to the X and Y directions). This operation is performed such that as the substrate 160 moves in the scanning direction (X direction), each radiation site will traverse different areas of the substrate, thereby allowing the entire substrate to be covered by the array of radiation sites S. In various embodiments, the angle α can be approximately 80°, 75°, 60°, 45°, 30°, 20°, 10°, 5°, 3°, 1°, 0.5°, 0.25°, 0.10°, 0.05°, or 0.01°. In one embodiment, the angle α is at least 0.0001°, for example, at least 0.001°. The tilt angle α and the width of the array in the scanning direction are determined based on the image site size and array spacing in the direction perpendicular to the scanning direction to ensure that the entire surface area of ​​the substrate 160 is processed. In many embodiments further discussed herein, the angle (also referred to as the scanning angle) can be approximately 45° due to the exemplary mirror array presented.

[0071] As used herein, the term “approximately” for scan angles means that the angle may not be exactly a specific angle, but may vary slightly in practice due to the geometric details of the system. Therefore, such figures are given primarily for illustrative purposes, and it should be understood that those skilled in this art will recognize that the precise values ​​will vary.

[0072] In photolithography, a desired feature can be generated on a substrate by selectively exposing a layer of resist on the substrate to radiation. Areas of the resist receiving a minimum radiation dose ("dose threshold") undergo a chemical reaction, while other areas remain unchanged. This chemical difference in the resist layer allows the resist to develop, i.e., selectively removing areas that have received at least the minimum dose or removing areas that have not received the minimum dose. Thus, portions of the substrate remain protected by the resist, while areas of the substrate from which the resist is removed are exposed, allowing for additional processing steps, such as selective etching of the substrate, selective metal deposition, etc., to generate the desired feature. Patterning radiation can be performed by controlling the patterning apparatus 110 such that the radiation transmitted to the resist layer on the substrate within the desired feature is at a sufficiently high amplitude, such that this area receives a radiation dose above the dose threshold during exposure, while other areas on the substrate receive a radiation dose below the dose threshold by providing zero or significantly lower radiation amplitudes.

[0073] In practice, even if the maximum radiation amplitude is provided on one side of the feature boundary and the minimum radiation amplitude is provided on the other side, the radiation dose at the edge of the desired feature does not suddenly change to zero from the given maximum dose. Instead, due to the diffraction effect, the radiation dose level can gradually decrease across the transition zone. The location of the boundary of the desired feature that is finally formed after the resist is developed is then determined by the position where the received dose drops below the radiation dose threshold. The contour of the gradually decreasing radiation dose across the transition zone and therefore the precise location of the feature boundary can be more precisely controlled by providing radiation that reaches not only the maximum or minimum amplitude level but also the amplitude level between the maximum and minimum amplitude levels to points on or near the feature boundary on the substrate. This can be called "grayscale" or "grayscale subdivision".

[0074] Grayscale can provide greater control over the position of feature boundaries than is possible in a lithography system, where the radiation amplitude provided to the substrate can only be set to two values ​​(i.e., exactly the maximum and minimum values). In one embodiment, at least three different radiation amplitude values ​​can be projected, such as at least four, at least eight, at least sixteen, at least 32, at least 64, at least 100, at least 128, or at least 256 radiation amplitude values. If the patterning device is the radiation source itself (e.g., an array of light-emitting diodes or laser diodes), grayscale can be achieved, for example, by controlling the amplitude level of the transmitted radiation. If the patterning device includes a mirror array 140, grayscale can be achieved by controlling the tilt angle of the mirror array 140. Furthermore, grayscale can be performed by grouping a plurality of programmable elements and / or mirror arrays and controlling the number of elements and / or mirror arrays in each group that are turned on or off at a given time.

[0075] In one example, the patterning apparatus (comprising one or more lithography apparatuses providing a sequence of exposures to one or more substrates) may have a series of states, including: (a) a black state, wherein the provided radiation is at its minimum or even has zero proportion for the amplitude distribution of its corresponding pixel; (b) a whitest state, wherein the provided radiation accounts for the maximum proportion; and (c) a plurality of states between the two, wherein the provided radiation accounts for a moderate proportion. All of the plurality of states may be described as a sequence of gray states, selectable between black and white to achieve grayscale printing.

[0076] Figure 3 is a simplified diagram illustrating an exemplary sequence of transmitting light to a substrate with a given centroid according to some embodiments. When printed to a substrate, it is typically necessary to transmit light of a given total intensity or target intensity to specific points or sites. When performing pixel grid imaging, the required intensity can be accumulated from numerous sites having an intensity at a bit-level, such as that described previously in the "grayscale" section. Therefore, transmitting light with a specific intensity requires a combination of "intensity bits". For example, an intensity of 5 (at a certain bit-level, for light intensity that can be transmitted by an optical system) requires transmitting two intensity 1 bits (2 × 2 1) and one intensity 1 bit (1 x 2 0). Depending on how these light pulses are transmitted, the resulting intensity pattern may be off-center. Such off-center sites may therefore cause defects or other problems in the photolithography process. It should be understood that the intensity levels used for patterning can be varied as needed to provide the desired resolution in later transmissions. For example, in some embodiments, the intensity sequence can be transmitted based on a 4, 5, 6, 7, 8-bit intensity distribution to provide different intensity values ​​such as 16, 32, 64, 128, and 256. An 8-bit intensity pattern for providing 256 radiation amplitude values ​​was previously described with reference to FIG2.

[0077] The top portion of Figure 3 depicts the distribution of intensity (vertical coordinate of the plot) transmitted at different times (horizontal coordinate of the plot) and thus to slightly different locations on the substrate. These different times / locations in the distribution are referred to herein as "sequences," with sequence 310 being an example having six light-transmitting "intervals" 312, each with a specific element intensity. While this distribution is controlled by the system to be as symmetrical as possible in some embodiments, it still possesses an asymmetry that could lead to off-center shifting of sites while transmitting the required total intensity. This is visible by comparing the geometric center 314 (e.g., in Figure 3, where three intervals exist on either side), where the "centroid" 316 is the center of the resulting intensity-weighted distribution. As used herein, the term "centroid" (or COG) should be understood as meaning the weighted center of the intensity of light transmitted to the substrate.

[0078] The middle portion of Figure 3 depicts an example of the effect of no light transmission on the center of gravity during two portions of sequence 320. This example is intended to illustrate the effect of intervals including no light transmission to the substrate on the center of gravity. As depicted, the fourth and sixth bits in sequence 320 do not actually transmit to the substrate. In some implementations, cut-off bits (i.e., not transmitting light to the substrate) can be used to modulate the intensity. However, this can cause parasitic shifts in the COG. To avoid transmitting light to the substrate during specific intervals, in some embodiments, specific mirrors of the DMD can be bi-state switched to direct the beam to different locations on the cutoff rather than the substrate. In other implementations, the laser can be gated off, different optics can be manipulated to interrupt beam transmission, etc. As shown, non-transmission during specific intervals in the sequence can cause a shifted center of gravity 326 at the resulting site, which is closer to the geometric center of gravity 314, however, at a reduced intensity.

[0079] The bottom portion of Figure 3 illustrates an alternative solution in which sequence 330 delivers the same intensity as sequence 320 but in a symmetrical pattern. Here, due to symmetry, the geometric center 334 and the centroid 336 are in the same location. However, in this example, to produce the required 13 intervals instead of the symmetrical pattern required in sequence 310, and thus effectively reduce the output by approximately half (due to the doubling of the time required to deliver the required intensity).

[0080] Figure 4A is a simplified diagram illustrating the effect of a next pattern on the mirror position according to some embodiments. Because printed patterns on a substrate often require nanoscale accuracy, even a very small effect on light transmission can cause unacceptable deviations. In many embodiments, when a light pattern is provided to the substrate, there may be a large number of configurations of the DMD that need to be stored and executed as the substrate is scanned through the DMD. In some embodiments, physical memory (e.g., CMOS memory circuitry) may be located close to the DMD such that the charge used to store a sequence (e.g., including the next bit in the sequence) in the physical memory causes a deviation in the angle of the mirror in the DMD. For example, in some embodiments, the physical memory may be located less than 1 mm (e.g., 10 micrometers) from the DMD. Therefore, one technical problem solved by the present invention is that the charge used to store a later configuration can be close enough to affect the transmission of the current configuration. This is referred to herein as the "next pattern effect" (NPE).

[0081] As illustrated in the simplified example of Figure 4A, the physical memory 410 can store the current configuration 422 of the mirror of the DMD in the first location 420. As previously explained, the current configuration can be the position (on / off) of the mirror of the DMD at a given point in time. When scanning the substrate relative to the DMD, the overall (target) intensity of light is transmitted to the substrate via the various configurations of the DMD. The charge distribution of the current configuration 422 in the first location 420 is described by addition (+) and subtraction (-).

[0082] A single instance of a mirror 412 of the DMD is shown in FIG. 4A. The mirror 412 may be configured to have a target position 424 for transmitting light to the substrate. However, a next position 430 in the physical memory 410 may contain a next pattern having a next charge distribution 432 that influences the orientation of the mirror (represented by a desired angle 440). In some embodiments, the disclosed system may include a control system configured to actuate the mirror to have a given orientation in a digital mirror device, thereby transmitting a sequence of light intensity to the substrate. The orientation of the mirror of the DMD may be achieved by the control system providing a specific electrostatic potential to switch the mirror angle between a position that transmits light to the substrate and a position that does not transmit light. A MEMS-based optical switch is one example that can be used with the DMD. Therefore, a very small change in the mirror angle may be caused by the interaction of the electric field from the next charge distribution 432 with the electrostatically positioned mirror. This is depicted by the change in mirror position from target position 424 to new (incorrect) position 434 (exaggerated for illustrative purposes). As further described herein, the influence of this next pattern can be mitigated by modifying the intensity sequence of light transmitted by the pattern stored in physical memory.

[0083] Figures 4B and 4C further illustrate the effects of the next pattern. Figure 4B illustrates a DMD in target position 424 and / or with a desired angle 440, for example, if the next position 430 does not store a pattern, does not store charge, is far from the first position 420, has a self-canceling charge distribution, etc., so that it has essentially no effect on the DMD. Figure 4C illustrates two examples of mirrors in incorrect positions due to different next pattern effects. The top portion of Figure 4C illustrates an exaggerated version of the next pattern effect due to an exemplary next charge distribution 432 having many positive charges or being predominantly positive charges. In this example, the effect is to reduce the angle of the mirror as indicated by the arrow and incorrect position 434. The bottom portion of Figure 4C illustrates the opposite example where the charge in the next charge distribution is predominantly negative. Here, the mirror deflects in the opposite direction, causing the angle to be greater than the desired angle 440.

[0084] In some embodiments, patterns other than the "next" pattern can also have a similar effect on mirror alignment. For example, storing a "previous" pattern close enough to the mirror can also cause such an effect. The previous pattern can be stored in a memory buffer for recording purposes or for efficient reuse later in the sequence. Thus, the present invention anticipates that the effect of storing electronic instructions in physical memory can cause an electrostatic effect that perturbs the mirror from its desired orientation. In this way, the method described herein can generally be used to mitigate the effects of pattern storage, where the pattern can be the "next," "previous," or any other pattern in the sequence, such that its storage affects the DMD.

[0085] Figure 5A is a simplified diagram illustrating a method for mitigating the effects of the next pattern according to some embodiments. The effects of the next pattern can be mitigated by a strategy similar to that previously discussed with reference to Figure 3. As previously mentioned, the effects of the next pattern can slightly alter the position of the transmitted light. This result can be similar to the example in Figure 3 where the center of gravity of the light is changed based on a specific intensity sequence. The effects of the next pattern can be mitigated similarly by introducing intervals in the planned sequence that do not transmit light to the substrate (even if the corresponding bits are still stored in physical memory). Because the NPE is deterministic, its effect on the center of gravity can be accurately predicted in advance for a given sequence.

[0086] The top portion of Figure 5A depicts an exemplary sequence 510 of light transmitted at 11 intervals. This sequence is symmetrical, and therefore one would expect the center of gravity to be the same as the geometric center 516 of the sequence. However, due to the influence of the next pattern, the actual center of gravity 514 is slightly shifted (exaggerated for illustrative purposes).

[0087] The middle portion of Figure 5A illustrates that the NPE can be mitigated by selecting a sequence 520 with certain intervals 528 that are not transmitted to the substrate. In this example, there are five such intervals 528: a central interval and two intervals on each side. This has the effect of reducing the difference between the centroid 524 (attributed to the NPE) and the geometric center 516 (which is the same as in sequence 510). However, by not transmitting all the light in the sequence, this alters the total intensity of the transmitted light to a different intensity than the desired or target intensity.

[0088] The bottom portion of Figure 5A illustrates an example of another method for mitigating the effects of the next pattern. The sequence 530 shown can transmit the desired intensity (e.g., the same intensity in sequence 510), but has intervals skipped between each transmission interval, similar to the example shown in the middle portion of Figure 5A. This method greatly reduces NPE, as is evident from the small difference between the geometric center 534 and the centroid 536, since the "next pattern" for each bit is 0, thus the COG shift for each mirror is the same as for each possible summed intensity. However, this has the cost of requiring up to twice the interval. This method therefore has the cost of reducing the manufacturing output of transmitted light by almost half.

[0089] The skipping of the frame as depicted in sequence 530 differs from having interval 528, where substantially no light is transmitted to the substrate. For example, in sequence 520, the (next) interval 528 still has bits stored in physical memory, and therefore will affect the current position of the mirror. However, because light in this interval is not transmitted to the substrate, the effect is that the resulting centroid of the printed position is actually closer to the geometric (or expected) centroid. In contrast, completely skipping the interval means that no bits are stored in physical memory. Here, the bits stored in memory are fixed bits (e.g., 1 or 0) used for bi-state switching of the mirror position. Therefore, this storage of non-intensity-dependent bits mitigates the effect of the next pattern. This significantly reduces the effect of the next pattern because the "next" bit / interval (which is intensity-dependent) is now a greater distance from the current instruction pattern in physical memory. To reiterate, the electric field from these more distant stored instructions is greatly reduced at the mirror position due to this increased distance, and thus the influence on the next pattern is much smaller.

[0090] Figure 5B illustrates another exemplary embodiment of mitigation of the effects of the next pattern. Sequence 540 is a symmetrical pattern in which COG 544 is almost aligned with the geometric center 546 of the sequence. The modified sequence 550 in the middle portion of Figure 5B has a COG 554 that differs from COG 544, due to the inclusion of a gap that does not transmit light to the substrate. This also has the effect of reducing the total intensity transmitted by the sequence. Sequence 560 in the bottom portion of Figure 5B has an almost correct COG 564. Similar to sequence 530, each cycle also includes a "next" gap in which no light is transmitted to the substrate. Although COG 564 is significantly closer to the geometric center 546, this again increases the number of cycles required.

[0091] Figure 6 is a simplified diagram illustrating a method for mitigating the effects of a next pattern according to some embodiments. The present invention includes a method for improving the sequencing of light transmission in a lithography process. As shown in Figure 6, this may include determining an intensity sequence of light to be transmitted, including intervals within the intensity sequence where substantially no light is transmitted to the substrate (sometimes referred to herein as "non-transmission intervals"). After determining the sequence, the method may include transmitting light to the substrate via a digital mirror device (DMD) according to the intensity sequence using a light source. In some implementations, the presence of this interval may reduce the impact of upcoming instruction sets in the intensity sequence stored in physical memory on the configuration of the DMD.

[0092] Some embodiments may also include determining a target intensity of light to be transmitted to a point on the substrate, such as a target intensity required for processing photoresist. Therefore, in various embodiments, the determined intensity sequence may be transmitted from the digital mirror device (DMD) to the substrate to achieve the target intensity, wherein substantially no light is transmitted to the substrate during the interval. In some embodiments, this may include determining the intensity sequence individually for one or more (or each) of the mirrors in the DMD.

[0093] The example shown in the top portion of Figure 6 of the sequence is similar to those previously described, but has some additional details that facilitate NPE mitigation and deliver the desired intensity with a reduced number of intervals. The distribution of the intervals themselves does not need to be symmetrical, but can actually be determined to deliver the desired intensity but with a reduced number (or, in other embodiments, a minimum number) of intervals. Such embodiments may include determining the target intensity of light delivered to a site on the substrate. By using the various techniques disclosed herein, some methods may further include determining an asymmetric distribution of the intensity sequence that reduces the difference between the center of gravity of the delivery at the site and the target center of gravity at the site. The asymmetry in the optimized sequence may be caused by an optimization process that maintains the total desired power (e.g., represented by the sum of intensity bits) but also has substantially no light delivered to one or more intervals of the substrate.

[0094] The example of FIG6 (top portion) has a sequence 610 with an asymmetrical distribution, which reduces the total number of required intervals. The centroid 616 is depicted with interval 6. Also, the example sequence 610 includes three intervals 618 in which substantially no light is transmitted to the substrate. In some embodiments, because the intensity sequence can be represented by bits stored in physical memory, the effect of mitigating NPE is greatest when the non-transmitting interval follows a transmitting interval with a large intensity or bit value. In this way, the interval substantially following the maximum bit can be determined. Thus, in some embodiments, at least one interval may be located after the most significant bit in the sequence. This is depicted in FIG6 by the most significant bit (MSB) 612 at position 5 and the non-transmitting interval 618 at position 6. Other benefits can be achieved by including other non-transmitting intervals at selected locations in the sequence. For example, in FIG6, similar non-transmitting intervals exist at positions 4 and 8 after the next two most significant bits (positions 3 and 7). However, in some implementations, not every interval needs to have a corresponding non-transferring interval, because typically only the larger intensity bits contribute the most to the influence on the next pattern. As previously mentioned, in the example of Figure 3, including non-transferring intervals between each transfer interval significantly reduces yield. Thus, the return on mitigating the influence on the next pattern by further including non-transferring intervals is reduced. Therefore, in some embodiments, the determination of the intensity sequence and any non-transferring intervals may further include using a cost function that reflects the balance between having an accurate centroid and increasing the number of intervals. Such a cost function can be extremely beneficial in optimizing manufacturing processes as described herein. However, increasing the number of intervals comes at the cost of yield, but some embodiments may sacrifice yield to improve accuracy. Therefore, some embodiments may utilize a sequence of 6, 7, or 8 bits with 1 to 5 additional cycles corresponding to the most significant bit.

[0095] The bottom portion of Figure 6 illustrates one example of an alternative solution that may be used in some embodiments. Here, a symmetrical intensity sequence 620 is determined. This can reduce (or eliminate) the difference between the transmission centroid of the site and the target centroid of the site. This solution also has the advantage of providing a simplified implementation compared to some other embodiments disclosed herein. Sequence 620 is also illustrated, in some embodiments, the intensity sequence may include skipping the transmission of light between two light transmission intervals. However, due to the additional total number of intervals that may be required, the yield may be reduced, as explained in other examples previously herein.

[0096] Figure 7A is a simplified diagram illustrating an exemplary fine-tuning of the center of gravity of a light intensity sequence according to some embodiments. Determining the light intensity sequence and any non-transfer intervals 718 may, in some cases, include placing the non-transfer intervals at different positions in the sequence to optimize the center of gravity. For example, the top portion of Figure 7 is an example sequence 710, in which a transfer interval 712 is present at position 5 and a non-transfer interval 714 is present at position 6. Thus, the overall sequence has a specific center of gravity 716. In some embodiments, the disclosed method may include adjusting the transfer center of gravity by changing the sequence of intensity or the position of the (non-transfer) intervals. Changing the intensity sequence may include making the sequence more symmetrical, less asymmetrical, or any other change by shifting intensity bits from one position to another. In some embodiments, similar manipulation may be performed for the non-transfer intervals. For example, as shown in the bottom portion of Figure 7A, for the modified sequence 720, intervals 712 and 714 are reversed from their positions in sequence 710. As shown, this slightly alters the center of gravity 726. In this way, the system and its associated algorithms can determine and fine-tune the focus required for the application.

[0097] Figure 7B illustrates the calculation of alternative positions for non-transmitting light intervals. Given an intensity pattern (including alternative bit positions), the written intensity, and an NPE value (e.g., in nm), the COG can be calculated. In Figure 7B, an example COG calculation is performed with an NPE of -66 [nm]. For all intensity patterns, alternative bit positions and corresponding COGs can be calculated. In this example, eight possibilities from three alternative positions (8, 16, and 32) are actually used for the calculation, but for illustration purposes, only two possibilities 740 and 750 are shown. The alternative bit positions used can therefore be selected individually for each individual intensity, such that the COG of the intensity sequence has minimal deviation from the midpoint of the intensity pattern (shown by the thick line 760).

[0098] In some implementations, a brute-force approach can be used to find the most suitable periodic pattern. To determine the optimal intensity pattern, we can define a cost function (CF) to determine which intensity pattern yields the best result. One instance of cost can be the RMS value of the COG values ​​calculated for each intensity of the profile, weighted by the intensity itself. This is the RMS value of curve 760 in Figure 7B. Intensity patterns with lower costs are calculated to have lower COG shifts compared to intensity patterns with higher costs, resulting in improved patterning.

[0099] As an example of a brute-force method, the cost of all possible intensity patterns can be determined by identifying all possible intensity patterns for each number of bits to be tested in each number of frames in the test sequence. Next, the possible zero-frame / balance bit positions in each intensity pattern are determined. In some implementations, to reduce the parameter space without unduly affecting the final result, some low-intensity bits can be fixed (i.e., their positions do not change as part of the optimization). For example, the two lowest intensities can be fixed to the outermost positions to reduce the probability. Then, for each possible intensity pattern and possible alternative bit positions, the cost is calculated. This can produce a very large number of configurations. The intensity pattern and alternative bit positions with the lowest cost can be selected.

[0100] In other embodiments, the determined sequence may be symmetrical at the beginning, but the method further includes modifying the symmetrical distribution into an asymmetric distribution (similar to sequence 610) by incorporating asymmetry into the intensity sequence, which further reduces the difference between the transmission centroid and the target centroid. This asymmetry can be generated by replacing one combination of bits with another combination that has different intensity contributions but the same total intensity.

[0101] Figure 8 is a block diagram of an example computer system CS according to an embodiment.

[0102] The computer system CS includes a bus BS or other communication mechanism for transmitting information, and a processor PRO (or multiple processors) coupled to the bus BS to process information. The computer system CS also includes main memory MM, such as random access memory (RAM) or other dynamic storage device, coupled to the bus BS for storing information and instructions to be executed by the processor PRO. The main memory MM can also be used to store temporary variables or other intermediate information during the execution of instructions to be executed by the processor PRO. The computer system CS further includes read-only memory (ROM) or other static storage device coupled to the bus BS for storing static information and instructions for the processor PRO. A storage device SD, such as a magnetic disk or optical disk, is provided and coupled to the bus BS for storing information and instructions.

[0103] The computer system CS can be coupled via bus BS to a display DS for displaying information to the computer user, such as a cathode ray tube (CRT), or a flat panel or touch panel display. Input devices ID, including alphanumeric keys and other keys, are coupled to bus BS to transmit information and command selections to the processor PRO. Another type of user input device is a cursor controller CC, such as a mouse, trackball, or cursor direction keys, used to transmit directional information and command selections to the processor PRO and to control cursor movement on the display DS. This input device typically has two degrees of freedom in two axes (a first axis (e.g., x) and a second axis (e.g., y)), which allow the device to specify a position in a plane. Touch panel (screen) displays can also be used as input devices.

[0104] According to one embodiment, portions of one or more methods described herein can be executed by a computer system CS responding to a processor PRO executing one or more sequences of one or more instructions contained in main memory MM. These instructions can be read from another computer-readable medium (such as a storage device SD) into main memory MM. Execution of the instruction sequence contained in main memory MM causes processor PRO to execute the program steps described herein. One or more processors in a multiprocessor configuration can also be used to execute the instruction sequence contained in main memory MM. In alternative embodiments, hard-wired circuitry can be used instead of or in combination with software instructions. Therefore, the description herein is not limited to any particular combination of hardware circuitry and software.

[0105] As used herein, the term "computer-readable media" means any media that participates in providing instructions to the processor PRO for execution. Such media can take many forms, including (but not limited to) non-volatile media, volatile media, and transmission media. Non-volatile media include, for example, optical discs or magnetic disks, such as storage devices SD. Volatile media include dynamic memory, such as main memory MM. Transmission media include coaxial cables, copper wires, and optical fibers, including conductors containing buses BS. Transmission media can also take the form of sound waves or light waves, such as sound waves or light waves generated during radio frequency (RF) and infrared (IR) data communications. Computer-readable media can be non-transitory, such as floppy disks, flexible magnetic disks, hard disks, magnetic tapes, any other magnetic media, CD-ROMs, DVDs, any other optical media, punch cards, paper tapes, any other physical media with a perforated pattern, RAM, PROMs and EPROMs, FLASH-EPROMs, any other memory chips or cartridges. Non-transitory computer-readable media may have instructions recorded thereon. When executed by a computer, the instructions may perform any of the features described herein. Transitory computer-readable media may include carrier waves or other propagating electromagnetic signals.

[0106] Various forms of computer-readable media may be involved when one or more sequences of instructions are carried to the processor PRO for execution. For example, initially, such instructions may be carried on a disk of a remote computer. The remote computer may load the instructions into its dynamic memory and transmit the instructions via a telephone line using a modem. The modem at the computer system CS local end may receive data on the telephone line and convert the data into an infrared signal using an infrared transmitter. An infrared detector coupled to the bus BS may receive the data carried in the infrared signal and place the data on the bus BS. The bus BS carries the data to the main memory MM, from which the processor PRO fetches and executes the instructions. The instructions received by the main memory MM may be stored on the storage device SD, either before or after execution by the processor PRO, as appropriate.

[0107] The computer system CS may also include a communication interface CI coupled to a bus BS. The communication interface CI provides bidirectional data communication coupling to a network connection NDL connected to a local area network (LAN). For example, the communication interface CI may be an integrated Services Digital Network (ISDN) card or modem to provide data communication connectivity with a corresponding type of telephone line. As another example, the communication interface CI may be a local area network (LAN) card to provide data communication connectivity with a compatible LAN. Wireless connectivity may also be implemented. In any of these implementations, the communication interface CI transmits and receives electrical, electromagnetic, or optical signals carrying digital data streams representing various types of information.

[0108] Network Connectivity (NDL) typically provides data communication with other data devices via one or more networks. For example, a Network Connectivity (NDL) may provide a connection to a host computer (HC) via a Local Area Network (LAN). This may include providing data communication services via a global packet data communication network (now commonly referred to as the "Internet" INT). Local Area Networks (LANs) use electrical, electromagnetic, or optical signals carrying digital data streams. Signals through various networks and signals on the Network Connectivity (NDL) via the Communication Interface (CI) are exemplary carrier forms for transmitting information, carrying digital data to and from the computer system (CS).

[0109] A computer system CS can send and receive messages (including code) via a network, a network data link (NDL), and a communication interface (CI). In an Internet example, a host computer HC can transmit requested code for an application via an Internet INT, a network data link (NDL), a local area network (LAN), and a communication interface (CI). For example, such a downloaded application may provide all or part of the methods described herein. The received code may be executed by the processor PRO upon receipt and / or stored in a storage device SD or other non-volatile storage for later execution. In this way, the computer system CS can obtain application code in carrier form.

[0110] Figure 9 is a schematic diagram of a lithography device according to an embodiment.

[0111] The lithography equipment may include a lighting system IL, a first stage MT, a second stage WT and a projection system PS.

[0112] The lighting system IL can adjust the radiated beam B. In this specific case, the lighting system also includes a radiation source SO.

[0113] The first object stage (e.g., patterning device stage) MT may have a patterning device holder for holding the patterning device MA (e.g., a magnifying mask) and is connected to a first locator for accurately positioning the patterning device relative to the item PS.

[0114] The second object stage (substrate stage) WT may have a substrate holder for holding the substrate W (e.g., a resist-coated silicon wafer) and is connected to a second locator for accurately positioning the substrate relative to the item PS.

[0115] The projection system ("lens") PS (e.g., a refractive, reflective or reflective refractive optical system) can image the irradiated portion of the patterning device MA onto the target portion C (e.g., containing one or more grains) of the substrate W.

[0116] As described herein, the device may be of the transmissive type (i.e., having transmissive patterning devices). However, in general, it may also be of the reflective type, for example (having reflective patterning devices). The device may use patterning devices of a different kind than those of classic masks; examples include programmable mirror arrays or LCD matrices.

[0117] A source SO (e.g., a mercury lamp or excimer laser, LPP (laser-generated plasma) EUV source) generates a radiating beam. For example, this beam is fed directly or after passing through an adjustment device such as a beam expander Ex into an illumination system (illuminator) IL. The illuminator IL may include an adjustment device AD ​​for setting the outer and / or inner radial ranges of the amplitude distribution in the beam (typically referred to as σ outer and σ inner, respectively). Additionally, it will typically include various other components, such as a beam accumulator IN and a condenser CO. In this way, the beam B irradiated onto the patterning device MA has the desired uniformity and amplitude distribution in its cross-section.

[0118] In some embodiments, the source SO may be inside the housing of the lithography device (as is often the case when the source SO is, for example, a mercury lamp), but it may also be located away from the lithography device, with the radiation beam generated by the source SO being guided into the device (e.g., by means of a suitable guide mirror); the latter case may be when the source SO is an excimer laser (e.g., a laser based on KrF, ArF or F2).

[0119] The beam PB then intercepts the patterning device MA held on the patterning device stage MT. Having traversed the patterning device MA, the beam B can pass through the lens PL, which focuses the beam B onto the target portion C of the substrate W. With the aid of the second positioning device (and the interferometric measurement device IF), the substrate stage WT can be accurately moved, for example, to position different target portions C within the path of the beam PB. Similarly, the first positioning device can be used to accurately position the patterning device MA relative to the path of the beam B, for example, after mechanically picking the patterning device MA from the patterning device library or during scanning. Generally, the movement of the stages MT and WT can be achieved by means of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning). However, in the case of a stepper (relative to a stepping scanning tool), the patterning device stage MT may be connected only to the short-stroke actuator, or it may be fixed.

[0120] The drawn tool can be used in two different modes - step mode and scan mode. In step mode, the patterning stage MT is kept substantially stationary, and the entire patterning image is projected at once (i.e., a single "flash") onto the target portion C. The substrate stage WT is shifted in the x and / or y directions so that different target portions C can be illuminated by the beam PB.

[0121] In scanning mode, the same principle applies, except that the given target portion C is not exposed in a single "flash". Instead, the patterning stage MT can move at a speed v in a given direction (the so-called "scanning direction", for example, the y-direction) so that the projection beam B scans the patterning image; simultaneously, the substrate stage WT moves simultaneously in the same or opposite directions at a speed V = Mv, where M is the magnification of the lens PL (usually M = 1 / 4 or 1 / 5). In this way, a relatively large target portion C can be exposed without compromising resolution.

[0122] Figure 10 is a schematic diagram of another lithography device (LPA) according to an embodiment.

[0123] The LPA may include a source collector module SO, an illumination system (illuminator) IL configured to adjust the radiated beam B (e.g., EUV radiation), a support structure MT, a substrate stage WT, and a projection system PS.

[0124] The support structure (e.g., patterning device stage) MT may be constructed to support the patterning device (e.g., mask or magnifying mask) MA and connected to a first positioner PM configured to accurately position the patterning device.

[0125] The substrate stage (e.g., wafer stage) WT may be constructed to hold the substrate (e.g., resist-coated wafer) W and connected to a second positioner PW configured to accurately position the substrate.

[0126] The projection system (e.g., a reflective projection system) PS can be configured to project a pattern applied to the radiation beam B by the patterning device MA onto a target portion C (e.g., containing one or more grains) of the substrate W.

[0127] As described herein, the LPA can be of a reflective type (e.g., using a reflective patterning device). It should be noted that because most materials are absorptive in the EUV wavelength range, the patterning device can have a multilayer reflector comprising, for example, multiple stacks of molybdenum and silicon. In one example, the multi-stack reflector has 40 pairs of molybdenum and silicon layers, each layer being a quarter wavelength thick. X-ray lithography can be used to produce even smaller wavelengths. Because most materials are absorptive at both EUV and X-ray wavelengths, the patterned absorbent material segments (e.g., a TaN absorber on top of a multilayer reflector) defining features on the topography of the patterning device will be either printed (positive resist) or unprinted (negative resist).

[0128] The illuminator IL can receive an extreme ultraviolet (EUV) radiation beam from the source collector module SO. Methods for generating EUV radiation include, but are not limited to, converting a material having at least one element (e.g., xenon, lithium, or tin) into a plasma state using one or more emission spectra within the EUV range. In one such method (often referred to as laser-generated plasma (“LPP”)), plasma can be generated by irradiating fuel (such as droplets, streams, or clusters of material having an emission element within the spectral range) with a laser beam. The source collector module SO may be part of an EUV radiation system including a laser used to provide a laser beam for exciting the fuel. The resulting plasma emits output radiation (e.g., EUV radiation), which is collected using a radiation collector disposed within the source collector module. For example, when a CO2 laser is used to provide a laser beam for fuel excitation, the laser and the source collector module may be separate entities.

[0129] In such cases, the laser lithography apparatus may not be considered part of the laser forming lithography device, and the radiated beam may be transmitted from the laser to the source collector module by means of a beam delivery system including, for example, a suitable guide mirror and / or beam expander. In other cases, for example, when the source is a discharge-generating plasma EUV generator (often referred to as a DPP source), the source may be an integral part of the source collector module.

[0130] The illuminator IL may include an adjuster for adjusting the angular amplitude distribution of the radiated beam. Generally, it can adjust at least the outer radial range and / or inner radial range (typically referred to as σouter and σinner, respectively) of the amplitude distribution in the pupil plane of the illuminator. Additionally, the illuminator IL may include various other components, such as faceted field mirror elements and pupil mirror devices. The illuminator can be used to adjust the radiated beam to have desired uniformity and amplitude distribution in its cross-section.

[0131] A radiation beam B may be incident on a patterning device (e.g., a mask) MA held on a support structure (e.g., a patterning device stage) MT, and patterned by the patterning device. After reflection from the patterning device (e.g., the mask) MA, the radiation beam B passes through a projection system PS, which focuses the radiation beam B onto a target portion C of the substrate W. The substrate stage WT can be precisely moved by means of a second locator PW and a position sensor PS2 (e.g., an interferometric measuring device, a linear encoder, or a capacitive sensor), for example, to position different target portions C in the path of the radiation beam B. Similarly, a first locator PM and another position sensor PS1 can be used to accurately position the patterning device (e.g., the mask) MA relative to the path of the radiation beam B. Patterning device alignment marks M1, M2 and substrate alignment marks P1, P2 can be used to align the patterning device (e.g., the mask) MA and the substrate W.

[0132] The LPA device described can be used in at least one of the following modes: step mode, scan mode and stationary mode.

[0133] In the stepping mode, when the entire pattern to be applied to the radiation beam is projected onto the target portion C in one go, the support structure (e.g., patterning stage) MT and the substrate stage WT are kept substantially stationary (i.e., single static exposure). Then, the substrate stage WT is shifted in the X and / or Y directions so that different target portions C can be exposed.

[0134] In the scanning mode, while the pattern to be applied to the radiation beam is projected onto the target portion C, the support structure (e.g., patterning stage) MT and the substrate stage WT are scanned simultaneously (i.e., single dynamic exposure). The speed and direction of the substrate stage WT relative to the support structure (e.g., patterning stage) MT can be determined by the magnification (reduction) and image inversion characteristics of the projection system PS.

[0135] In static mode, the support structure (e.g., patterning stage) MT is kept substantially stationary to hold the programmable patterning device, while the substrate stage WT is moved or scanned, and the pattern imparted to the radiation beam is projected onto the target portion C. In this mode, a pulsed radiation source is typically used, and the programmable patterning device is updated as needed after each movement of the substrate stage WT or between successive radiation pulses during a scan. This operating mode can be readily applied to maskless lithography using programmable patterning devices (such as programmable mirror arrays of the type mentioned above).

[0136] Figure 11 is a detailed view of a lithography device according to an embodiment.

[0137] As shown, the LPA may include a source collector module SO, an illumination system IL, and a projection system PS. The source collector module SO is constructed and configured such that a vacuum environment can be maintained within the enclosure structure ES of the source collector module SO. An EUV radiation emitting thermoplasm HP can be formed by generating a plasma source through discharge. EUV radiation can be generated by a gas or vapor (e.g., Xe gas, Li vapor, or Sn vapor), wherein the thermoplasm HP is established to emit radiation in the EUV range of the electromagnetic spectrum. For example, the thermoplasm HP is established by a discharge that generates at least a partially ionized plasma. For efficient radiation generation, Xe, Li, Sn vapor, or any other suitable gas or vapor with a partial pressure of 10 Pa may be required. In one embodiment, an excited tin (Sn) plasma is provided to generate EUV radiation.

[0138] Radiation emitted by the thermoplasm HP is transmitted from the source chamber SC to the collector chamber CC via a gas barrier or contaminant trap CT (in some cases, also referred to as a contaminant barrier or foil trap) positioned in or behind an opening in the source chamber SC. The contaminant trap CT may include a channel structure. The contaminant trap CT may also include a gas barrier, or a combination of a gas barrier and a channel structure. As known in the art, the contaminant trap or contaminant barrier CT further indicated herein includes at least a channel structure.

[0139] The collector chamber CC may include a radiation collector CO, which may be a so-called grazing incidence collector. The radiation collector CO has an upstream radiation collector side US and a downstream radiation collector side DS. Radiation traversing the radiation collector CO may be reflected from the grating spectral filter SF to be focused along the optical axis indicated by the dotted line 'O' into a virtual source point IF. The virtual source point IF may be referred to as the intermediate focus, and the source collector module is configured such that the intermediate focus IF is located at or near the opening OP in the enclosure structure ES. The virtual source point IF is an image of the radiative emission plasma HP.

[0140] Subsequently, radiation traverses the illumination system IL, which may include a faceted field mirror device FM and a faceted pupil mirror device pm, which are configured to provide the desired angular distribution of the radiated beam B at the patterning device MA and the desired uniformity of the radiation amplitude at the patterning device MA. After the radiated beam B is reflected at the patterning device MA held by the support structure MT, a patterned beam PB is formed, and the patterned beam PB is imaged onto the substrate W held by the substrate stage WT via the projection system PS and the reflective element RE.

[0141] Additional devices beyond those shown may typically be present in the illumination optics unit IL and the projection system PS. Depending on the type of lithography equipment, a grating spectral filter SF may be present. Furthermore, more mirrors than those shown in the diagram may be present; for example, one to six additional reflective elements may be present in the projection system PS.

[0142] The collector optics CO may be a nested collector with a grazing incidence reflector GR, as an example only of a collector (or collector mirror). The grazing incidence reflector GR is arranged to be axially symmetrical about the optical axis O, and this type of collector optics CO can be used in combination with a discharge plasma source commonly referred to as a DPP source.

[0143] Figure 12 is a detailed view of the source collector module SO of a lithography device LPA according to an embodiment.

[0144] The source-collector module SO can be part of the LPP radiation system. The laser LA can be configured to deposit laser energy into a fuel such as xenon (Xe), tin (Sn), or lithium (Li), thereby generating a highly ionized plasma HP with an electron temperature of tens of eV. The high-energy radiation generated during the de-excitation and recombination of this plasma is emitted from the plasma, collected by the near-normal incident collector optics CO, and focused onto the opening OP in the enclosure structure ES.

[0145] The concepts disclosed herein can be simulated or mathematically modeled for any general imaging system used to image sub-wavelength features, and are particularly applicable to emerging imaging technologies capable of generating increasingly shorter wavelengths. Emerging technologies already in use include extreme ultraviolet (EUV) and DUV lithography, which can generate wavelengths of 193 nm using ArF lasers and even 157 nm using fluorine lasers. Furthermore, EUV lithography can generate wavelengths in the range of 20 nm to 50 nm by using synchrotrons or by bombarding materials (solids or plasmas) with high-energy electrons, thereby generating photons in this range.

[0146] While the concepts disclosed herein can be used for imaging on substrates such as silicon wafers, it should be understood that the disclosed concepts can be used with any type of lithography system, for example, a lithography system for imaging on substrates other than silicon wafers.

[0147] The above description is intended to be illustrative and not restrictive. Therefore, it will be apparent to those skilled in the art that modifications can be made as described without departing from the scope of the claims set forth below.

[0148] Other embodiments are disclosed in the following list of numbered items: 1. A method for improving the sequencing of light transmission in a lithography process, the method comprising: determining an intensity sequence of light to be transmitted, including an interval within the intensity sequence during which substantially no light is transmitted to a substrate; and transmitting the light to a substrate by means of a light source using a digital mirror device (DMD) according to the intensity sequence. 2. The method of any of the preceding items, the method further comprising determining a target intensity of light transmitted to a point on the substrate. 3. The method of any of the preceding items, wherein the determined intensity sequence is to be transmitted to the substrate by the digital mirror device (DMD) to achieve the target intensity, and wherein substantially no light is transmitted to the substrate during the interval. 4. The method of any of the preceding items, the method further comprising storing an instruction set for the intensity sequence of light in a physical memory. 5. The method of any of the preceding clauses, wherein the presence of the interval reduces the impact of an upcoming instruction set in the intensity sequence stored in the physical memory on a configuration of the DMD. 6. The method of any of the preceding clauses, wherein the intensity sequence is represented by bits stored in the physical memory, and the interval is located after a most significant bit in the sequence. 7. The method of any of the preceding clauses, further comprising determining an asymmetric distribution of the intensity sequence, the asymmetric distribution reducing a difference between a transit centroid of the site and a target centroid of the site. 8. A method for improving the sequencing of light transmission in a lithography process, the method comprising: determining a target intensity of light to be transmitted to a point on a substrate; determining, by means of a digital mirror device (DMD), an intensity sequence of light to be transmitted to the substrate to achieve the target intensity, the intensity sequence including an interval within the intensity sequence in which substantially no light is transmitted to the substrate; storing an instruction set for the intensity sequence of light in a physical memory; and transmitting light to the substrate by means of a light source using the DMD according to the intensity sequence, wherein the presence of the interval reduces the influence of an upcoming instruction set in the intensity sequence stored in the physical memory on the configuration of the DMD. 9. The method of any of the preceding claims, wherein the intensity sequence is represented by bits stored in the physical memory, and the interval is located after a most significant bit in the sequence. 10. The method of any of the preceding claims, further comprising determining a symmetrical distribution of the intensity sequence, the symmetrical distribution reducing a difference between a transmission centroid of the point and a target centroid of the point. 11. The method of any of the preceding clauses further comprises modifying the symmetrical distribution into an asymmetric distribution by incorporating an asymmetry into the intensity sequence, the asymmetry further reducing the difference between the transmission centroid and the target centroid.12. The method of any of the preceding clauses, further comprising adjusting a transmission centroid by changing the position of one of the intensity sequence or the interval. 13. The method of any of the preceding clauses, wherein the intensity sequence is an 8-bit intensity distribution. 14. The method of any of the preceding clauses, wherein the intensity sequence is symmetrical. 15. The method of any of the preceding clauses, wherein the intensity sequence includes skipping the transmission of light between two light transmission intervals. 16. The method of any of the preceding clauses, further comprising determining the intensity sequence individually for each of the plurality of mirrors in the DMD. 17. The method of any of the preceding clauses, wherein changing the position of one of the intensity sequence or the interval further comprises: calculating a plurality of alternative bit positions and their corresponding centroids based on the intensity; and selecting the alternative bit position with the smallest deviation from the middle of one of the intensity patterns transmitted by the DMD. 18. The method of any of the preceding clauses, wherein the calculation includes performing a brute-force method to calculate all possible intensity patterns in a parameter space except for at least one low-intensity bit that remains fixed. 19. A computer program product comprising a non-transitory computer-readable medium having instructions recorded thereon, which, when executed by a computer, perform the method of any of the preceding clauses. 20. A system for transmitting light to a substrate, the system comprising: a light source; a digital mirror device; a physical memory configured to store instructions for transmitting light from the light source using the digital mirror device; and a non-transitory computer-readable medium having the instructions recorded thereon, the instructions causing operations when executed by a computer, the operations comprising: determining a target intensity of light transmitted to a point on the substrate; determining, by means of the digital mirror device (DMD), a sequence of intensity of light to be transmitted to the substrate to achieve the target intensity, the sequence of intensity including an interval within the sequence in which substantially no light is transmitted to the substrate; storing a set of instructions for the intensity sequence of light in the physical memory; and transmitting light to the substrate by means of the light source using the DMD according to the intensity sequence, wherein the presence of the interval reduces the influence of an upcoming set of instructions in the intensity sequence stored in the physical memory on the configuration of the DMD. 21. A system as described in any of the preceding system clauses, wherein the physical memory is positioned close to the DMD such that the charge used to store the sequence in the physical memory causes an angular deviation of the mirror in the DMD. 22. A system as described in any of the preceding system clauses, wherein the physical memory is located less than 1 mm from the digital mirror device. 23. A system as described in any of the preceding system clauses, further comprising a control system configured to actuate the mirror in the digital mirror device to transmit the intensity sequence of light to the substrate.24. The system of any of the preceding system items further includes a microlens array (MLA) configured to guide light from the DMD to the substrate. [Simplified Explanation of the Diagram]

[0019] The accompanying drawings, incorporated in and forming part of this specification, illustrate certain aspects of the subject matter disclosed herein and, together with the description, help to explain some principles associated with the disclosed examples. In the drawings:

[0020] Figure 1 is a simplified diagram illustrating an exemplary maskless lithography system according to an embodiment.

[0021] Figure 2 is a simplified diagram illustrating an exemplary substrate and exposure pattern according to an embodiment.

[0022] Figure 3 is a simplified diagram illustrating pixel grid imaging at a substrate according to an embodiment.

[0023] Figure 4A is a simplified diagram illustrating the effect of a pattern on the position of a mirror according to an embodiment.

[0024] Figure 4B is a simplified diagram illustrating a mirror in the correct position according to an embodiment.

[0025] Figure 4C is a simplified diagram illustrating a mirror in an incorrect position according to an embodiment.

[0026] Figure 5A is a simplified diagram illustrating the displacement of a critical dimension according to one embodiment.

[0027] Figure 5B is a simplified diagram illustrating another exemplary embodiment of mitigation of the effect of the next pattern according to one embodiment.

[0028] Figure 6 is a flowchart illustrating the processing of a maskless lithography method according to an embodiment.

[0029] Figure 7A is a simplified diagram illustrating an exemplary fine-tuning of the centroid of a light intensity sequence according to an embodiment.

[0030] Figure 7B illustrates the calculation of the alternating positions of the non-transmitting light intervals according to one embodiment.

[0031] Figure 8 is a block diagram of an example computer system according to an embodiment.

[0032] Figure 9 is a schematic diagram of a lithography device according to an embodiment.

[0033] Figure 10 is a schematic diagram of another lithography device according to one embodiment.

[0034] Figure 11 is a detailed view of a lithography device according to an embodiment.

[0035] Figure 12 is a detailed view of the source collector module of a lithography device according to an embodiment.

Claims

1. A method for improving the sequencing of light transmission in a lithography process, the method comprising: determining a time-based intensity sequence of light to be transmitted to a substrate and a distribution of the determined time-based intensity sequence, wherein the determined time-based intensity sequence includes a plurality of intervals, the plurality of intervals including an interval in the determined time-based intensity sequence in which substantially no light is transmitted to the substrate; and transmitting light to the substrate by means of a light source using a digital mirror device (DMD) according to the plurality of intervals of the determined time-based intensity sequence.

2. The method of claim 1, further comprising determining a target intensity of light transmitted to a point on the substrate.

3. The method of claim 2, wherein the determined time-based intensity sequence is to be transmitted by the digital mirror device (DMD) to the substrate to achieve the target intensity, and wherein during the interval, substantially no light is transmitted to the substrate.

4. The method of claim 3, further comprising storing a set of instructions for the determined time-based intensity sequence of light in a physical memory.

5. The method of claim 4, wherein the presence of the interval reduces the impact of one of the upcoming instruction sets in the determined time-based intensity sequence stored in the entity memory on a configuration of the DMD.

6. The method of claim 1, wherein the determined time-based intensity sequence is represented by bits stored in physical memory, and the interval is located after a most significant bit in the sequence.

7. The method of claim 2, further comprising determining an asymmetric distribution of the determined time-based intensity sequence, the asymmetric distribution reducing a difference between a transmission centroid of the site and a target centroid of the site.

8. A method for improving the sequencing of light delivery in a lithography process, the method comprising: determining a target intensity of light to be delivered to a point on a substrate; determining, by means of a digital mirror device (DMD), an intensity sequence of light to be delivered to the substrate to achieve the target intensity, the intensity sequence including an interval within the intensity sequence in which substantially no light is delivered to the substrate; storing an instruction set for the intensity sequence of light in a physical memory; and delivering light to the substrate by means of a light source using the DMD according to the intensity sequence, wherein the presence of the interval reduces the influence of an upcoming instruction set in the intensity sequence stored in the physical memory on a configuration of the DMD.

9. The method of claim 8, wherein the intensity sequence is represented by bits stored in physical memory, and the interval is located after a most significant bit in the sequence.

10. The method of claim 8, further comprising determining a symmetrical distribution of the intensity sequence, the symmetrical distribution reducing a difference between a transmission centroid of the site and a target centroid of the site.

11. The method of claim 10, further comprising modifying the symmetrical distribution into an asymmetric distribution by including an asymmetry in the intensity sequence, the asymmetry further reducing the difference between the transit centroid and the target centroid.

12. The method of claim 8, further comprising adjusting a transmission center of gravity by changing the position of the sequence or the interval of intensity.

13. The method of claim 8, wherein the intensity sequence includes skipping the transmission of light between two light transmission intervals.

14. The method of claim 8, further comprising determining the intensity sequence individually for each of the plurality of mirrors in the DMD.

15. The method of claim 12, wherein changing the position of the sequence or the interval of the intensities further comprises: calculating a plurality of alternative bit positions and their corresponding centroids based on the intensities; and selecting alternative bit positions such that the COG of the intensity sequence has a minimum deviation from the middle of an intensity pattern transmitted by an optical system including the DMD.

16. A computer program product comprising a non-transitory computer-readable medium having instructions recorded thereon, which, when executed by a system, cause the system to perform the method as described in any one of claims 1 to 15.

17. A system for transmitting light to a substrate, the system comprising: a light source; a digital mirror device; a physical memory configured to store instructions for transmitting light from the light source using the digital mirror device; and a non-transitory computer-readable medium having the instructions recorded thereon, the instructions causing the system to perform operations when executed by one or more processors of the system, the operations comprising: determining a target intensity of light transmitted to a point on the substrate; determining, by means of the digital mirror device (DMD), a sequence of intensity of light to be transmitted to the substrate to achieve the target intensity, the sequence of intensity including an interval within the sequence in which substantially no light is transmitted to the substrate; storing a set of instructions for the intensity sequence of light in the physical memory; and transmitting light to the substrate by means of the light source using the DMD according to the intensity sequence, wherein the presence of the interval reduces the influence of an upcoming set of instructions in the intensity sequence stored in the physical memory on a configuration of the DMD.

18. The system of claim 17, wherein the physical memory is positioned close to the DMD such that the charge used to store the sequence in the physical memory causes an angular deviation of one of the mirrors in the DMD.

19. The system of claim 17, wherein the system is configured to manufacture computer chips.

20. The system of claim 17, wherein the system is configured to manufacture a flat panel display.

Images