Generating 3D photoresist profiles using digital lithography

Abstract

The embodiments described herein provide a lithography process system, software application, and method for forming a three-dimensional profile in a single exposure operation. An image projection system of the lithography system provides multiple shots to a photoresist layer. A local shot density of the multiple shots within an exposure field is varied to form a three-dimensional profile in the photoresist layer. The local shot density determines the amount of exposure provided by the image projection system at each subgrid of the exposure field. The exposure dose determines the thickness of the photoresist layer when the multiple shots are projected onto the photoresist layer.

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate generally to lithography systems and, more particularly, to lithography process systems, software applications, and methods for forming three-dimensional profiles in a single exposure operation. [Background technology]

[0002] Photolithography is widely used in the manufacture of semiconductor devices, e.g., back-end processing of semiconductor devices, and display devices, such as liquid crystal displays (LCDs). For example, in the manufacture of LCDs, large area substrates are often utilized. LCDs, or flat panel displays, are commonly used in active matrix displays, such as computers, touch panel devices, personal digital assistants (PDAs), mobile phones, television monitors, and the like. In general, flat panel displays include a layer of liquid crystal material as a phase change material at each pixel, sandwiched between two plates. When power from a power source is applied across or through the liquid crystal material, the amount of light passing through the liquid crystal material can be controlled, i.e., selectively modulated, at the pixel location to generate an image on the display.

[0003] One challenge with lithography is to form three-dimensional profiles that have smooth transitions across the profile. Existing lithography systems lack the desired ability to form three-dimensional profiles in a single exposure operation.

[0004] Therefore, there is a need in the art for lithography processing systems, software applications, and / or methods that have improved capabilities for forming three-dimensional profiles in a single exposure. Summary of the Invention

[0005] In one embodiment, a system is provided. The system includes a slab and a moveable stage positionable above the slab. The moveable stage is configured to support a substrate having a photoresist layer disposed thereon. The system further includes a controller configured to provide mask pattern data to a lithography system. The mask pattern data includes an exposure area having a gray pattern, the gray pattern being defined by a plurality of subgrids. Each subgrid includes a pattern area defined therein. The system further includes a lithography system support coupled to the slab having an opening to allow the moveable stage to pass underneath. The lithography system includes a processing unit having a plurality of image projection systems that receive the mask pattern data, each image projection system including a spatial light modulator having a plurality of spatial light modulator pixels for projecting a plurality of shots. The controller is configured to position a plurality of pattern areas within each of the subgrids to vary a local shot density in each subgrid, the controller configured to instruct each of the spatial light modulators to project a plurality of shots onto a plurality of pattern areas in each subgrid of the gray pattern.

[0006] In another embodiment, a non-transitory computer readable medium is provided. The non-transitory computer readable medium stores instructions that, when executed by a processor, cause the computer system to perform the steps of providing mask pattern data having a plurality of exposure areas to a processing unit of a lithography system. The processing unit has a plurality of image projection systems that receive the mask pattern data, each exposure area including a gray pattern. The gray pattern includes a plurality of sub-grids and a plurality of pattern areas in each sub-grid. The plurality of pattern areas correspond to a local shot density for each sub-grid. In a single scan of a substrate having a photoresist layer disposed thereon under the plurality of image projection systems, the steps further include projecting a plurality of shots onto the photoresist layer into the plurality of pattern areas of the gray pattern, and developing the photoresist layer to form a three-dimensional profile in the photoresist layer. The three-dimensional profile is defined by the local shot density for each sub-grid for each exposure area.

[0007] In yet another embodiment, a method is provided. The method includes providing mask pattern data having a plurality of exposure areas to a processing unit of a lithography system. The processing unit has a plurality of image projection systems that receive the mask pattern data, each exposure area including a gray pattern. The gray pattern includes a plurality of sub-grids and a plurality of pattern areas in each sub-grid. The plurality of pattern areas correspond to a local shot density for each sub-grid. In a single scan of a substrate having a photoresist layer disposed thereon under the plurality of image projection systems, the method further includes projecting a plurality of shots onto the photoresist layer at the plurality of pattern areas of the gray pattern, and developing the photoresist layer to form a three-dimensional profile in the photoresist layer. The three-dimensional profile is defined by the local shot density for each sub-grid for each exposure area.

[0008] So that the above-listed features of the present disclosure may be understood in detail, a more particular description of the present disclosure briefly outlined above may be had by reference to embodiments, some of which are illustrated in the accompanying drawings, it being noted, however, that the accompanying drawings depict merely exemplary embodiments and therefore should not be considered as limiting its scope, which may admit of other equally effective embodiments. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view of a system according to one embodiment. [Figure 2A] FIG. 1 is a schematic cross-sectional view of an image projection system according to an embodiment. [Figure 2B] FIG. 1 is a schematic diagram of a spatial light modulator according to an embodiment. [Figure 2C] FIG. 1 is a schematic diagram of a spatial light modulator according to an embodiment. [Diagram 3] FIG. 1 is a schematic diagram of a computing system according to one embodiment. [Figure 4] FIG. 1 is a schematic diagram of a single exposure lithography application according to an embodiment. [Diagram 5] FIG. 2 is a schematic diagram of a controller according to an embodiment. [Figure 6] 2A-2C are schematic plan views of a portion of a substrate during a digital lithography process according to an embodiment; [Figure 7A] FIG. 2 is a schematic plan view of an exposure area divided into a plurality of sub-grids according to an embodiment; [Figure 7B] FIG. 2 is a schematic plan view of a gray pattern having multiple sub-grids according to an embodiment. [Figure 8A] FIG. 13 is a diagram of local shot density of a gray pattern according to an embodiment. [Figure 8B] 8B is a chart corresponding to the diagram of FIG. 8A according to one embodiment. [Figure 9]1 is a flow diagram of a method for forming a three-dimensional profile in a photoresist layer using a lithographic process according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] For ease of understanding, the same reference numerals have been used, where possible, to designate identical elements that are common to each of the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

[0011] The disclosed embodiments relate to a lithography process system, software application, and method for forming a three-dimensional profile in a single exposure operation. One embodiment of the system includes a controller configured to provide mask pattern data to a lithography system. The mask pattern data includes a gray pattern. The lithography system has a processing unit having a plurality of image projection systems that receive the mask pattern data. Each image projection system includes a spatial light modulator having a plurality of spatial light modulator pixels for projecting a plurality of shots. The controller is configured to vary a local shot density across the substrate.

[0012] FIG. 1 is a perspective view of a system 100, such as a digital lithography system, that may benefit from embodiments described herein. The system 100 includes a stage 114 and a processing device 104. The stage 114 is supported by a pair of tracks 116 disposed on a slab 102. A substrate 120 is supported by the stage 114. The stage 114 is supported by a pair of tracks 116 disposed on the slab 102. The stage 114 moves along the pair of tracks 116 in an X direction as indicated by the coordinate system shown in FIG. 1. In one embodiment, which may be combined with other embodiments described herein, the pair of tracks 116 is a pair of parallel magnetic channels. As shown, each track of the pair of tracks 116 extends in a linear path. An encoder 118 is coupled to the stage 114 to provide information of the position of the stage 114 to a controller 122.

[0013] The controller 122 is generally designed to facilitate control and automation of the processing techniques described herein. The controller 122 may be coupled to or in communication with the processing device 104, the stage 114, and the encoder 118. The processing device 104 and the encoder 118 may provide information to the controller 122 regarding substrate processing and substrate alignment. For example, the processing device 104 may provide information to the controller 122 to inform the controller 122 that substrate processing is complete. The controller 122 facilitates control and automation of methods of lithography processes including varying local shot density during a single exposure. A program (or computer instructions), which may be referred to as an imaging program, readable by the controller 122 determines which tasks can be performed on the substrate 120. The program includes mask pattern data and code for monitoring and controlling processing time and substrate position. The mask pattern data corresponds to a pattern to be imaged in the photoresist using electromagnetic radiation.

[0014] The substrate 120 includes any suitable material used as part of a flat panel display, such as glass. In other embodiments that may be combined with other embodiments described herein, the substrate 120 is made of other materials that can be used as part of a flat panel display. The substrate 120 has a film layer to be patterned formed thereon, such as by etching a pattern into the substrate 120, and a photoresist layer formed on the film layer to be patterned, the photoresist layer being sensitive to electromagnetic radiation, such as ultraviolet (UV) or deep UV "light". A positive photoresist includes a portion of the photoresist that, when exposed to radiation, is soluble in a photoresist developer that is applied to the photoresist after a pattern is drawn into the photoresist using electromagnetic radiation. A negative photoresist includes a portion of the photoresist that, when exposed to radiation, is insoluble in a photoresist developer that is applied to the photoresist after a pattern is drawn into the photoresist using electromagnetic radiation. The chemical composition of the photoresist determines whether the photoresist is a positive or negative photoresist. Examples of photoresists include, but are not limited to, at least one of diazonaphthoquinone, phenol formaldehyde resin, poly(methyl methacrylate), poly(methyl glutarimide), and SU-8. After exposure of the photoresist to electromagnetic radiation, the resist is developed to leave a patterned photoresist on the undercoat layer. The patterned photoresist is then used to transfer etch the undercoat thin film to form a similar pattern on the undercoat layer. The undercoat layer is utilized to form a portion of the electronic circuitry of the display panel.

[0015] The processing device 104 includes a support 108 and a processing unit 106. The processing device 104 straddles a pair of tracks 116 and is disposed on the slab 102, thereby including the pair of tracks 116 and an opening 112 for the stage 114 to pass under the processing unit 106. The processing unit 106 is supported above the slab 102 by the support 108. In one embodiment that may be combined with other embodiments described herein, the processing unit 106 is a pattern generator configured to expose a photoresist in a photolithography process. In some embodiments that may be combined with other embodiments described herein, the pattern generator is configured to perform a maskless lithography process. The processing unit 106 includes a plurality of image projection systems. An example of an image projection system is shown in FIG. 2A. In one embodiment that may be combined with other embodiments described herein, the processing unit 106 includes as many as 84 image projection systems. Each image projection system is disposed in a case 110. Processing unit 106 is useful for performing maskless direct pattern writing into photoresist or other electromagnetic radiation sensitive materials.

[0016] FIG. 2A is a schematic cross-sectional view of an image projection system 200 that may be used in the system 100. The image projection system 200 includes a spatial light modulator 210 and a projection optical system 212. The components of the image projection system 200 vary depending on the spatial light modulator 210 used. The spatial light modulator 210 includes an array of electrically addressable elements. The electrically addressable elements include, but are not limited to, digital micromirrors, liquid crystal displays (LCDs), liquid crystal over silicon (LCoS) devices, ferroelectric liquid crystal on silicon (FLCoS) devices, and microshutters. The spatial light modulator 210 includes a plurality of spatial light modulator pixels. Each spatial light modulator pixel of the plurality of spatial light modulator pixels is individually controllable and configured to project an imaging beam corresponding to one pixel of the plurality of pixels. The collection of the plurality of pixels forms a pattern to be imaged in the photoresist, referred to herein as a mask pattern. The projection optics 212 includes a projection lens, e.g., a 10x objective lens, used to project light onto the substrate 120. In operation, based on mask pattern data provided by the controller 122 to the spatial light modulator 210, each spatial light modular pixel of the plurality of spatial light modulator pixels is in an "on" position or an "off" position. Each spatial light modular pixel in the "on" position forms a writing beam that the projection optics 212 then projects onto the photoresist layer surface of the substrate 120 to form pixels of the mask pattern.

[0017] In one embodiment that may be combined with other embodiments described herein, the spatial light modulator 210 is a DMD. The image projection system 200 includes a light source 202, an aperture 204, a lens 206, a frustrated prism assembly 208, a DMD, and a projection optics 212. The DMD includes a plurality of mirrors, i.e., a plurality of spatial light modulator pixels. Each mirror of the plurality of mirrors corresponds to a pixel that may correspond to a pixel of a mask pattern. In some embodiments that may be combined with other embodiments described herein, the DMD includes more than about 4,000,000 mirrors. The light source 202 is any suitable light source, such as a light emitting diode (LED) or a laser, capable of generating light having a predetermined wavelength. In one embodiment that may be combined with other embodiments described herein, the predetermined wavelength is in the blue or near ultraviolet (UV) range, such as less than about 450 nm. The frustrated prism assembly 208 includes a plurality of reflective surfaces. In operation, a light beam 201 is generated by the light source 202. Light beam 201 is reflected by frustrated prism assembly 208 to the DMD. When light beam 201 reaches the mirrors of the DMD, each mirror in the "on" position reflects light beam 201, forming a lithography beam, also called a "shot," which projection optics 212 then projects as shots onto the photoresist layer surface of substrate 120. Multiple lithography beams 203, also called shots, form multiple pixels of the mask pattern.

[0018] 2B is a schematic diagram of a DMD spatial light modulator 210. A plurality of mirrors 213, also called spatial light modulator pixels, are arranged in a grid having M rows and N columns. Each of the plurality of mirrors 213 is operable to be in an "on" position or an "off" position. A pixel pitch 215 is defined as the distance between the centroids of adjacent spatial light modulator pixels.

[0019] A plurality of spatial light modulator pixels of spatial light modulator 210 are arranged in an aggregated shot pattern 604 (shown in FIG. 6) where each spatial light modulator pixel corresponds to a potential shot 606 (shown in FIG. 6). Each potential shot 606 represents the centroid of a mirror 213. Controller 122 (shown in FIG. 1) provides instructions to spatial light modulator 210 based on mask pattern data. The mask pattern data determines which of the plurality of mirrors 213 are in the "on" position. In an embodiment, if a mirror 213 is in the "on" position, a shot is delivered. In an embodiment, if a mirror 213 is in the "off" position, no shot is delivered.

[0020] 3 is a schematic diagram of a computing system 300 configured to vary local shot density across a substrate, in which embodiments of the present disclosure may be implemented. As shown in FIG. 3, the computing system 300 may include a number of servers 308, a single exposure lithography application 312, and a number of controllers 122 (i.e., computers, personal computers, mobile / wireless devices, only two of which are shown for clarity), each of which is connected to a communication network 306 (e.g., the Internet). The servers 308 may communicate with a database 314 via a local connection (e.g., a storage area network (SAN) or network attached storage (NAS)) or via the Internet. The servers 308 are configured to either directly access the data contained in the database 314 or interface with a database manager configured to manage the data contained in the database 314.

[0021] Each controller 122 may include the components of a computing device, such as a processor, system memory, a hard disk drive, a battery, input devices such as a mouse and keyboard, and / or output devices such as a monitor or graphical user interface, and / or a combination input / output device such as a touch screen that not only receives input but also displays output. Each server 308 and single exposure lithography application 312 may include a processor and system memory (not shown) and may be configured to manage content stored in database 314 using, for example, relational database software and / or a file system. The I / O device interface 408 shown in FIG. 4 may be programmed to communicate with each other, the controller 122, and the single exposure lithography application 312 using a network protocol such as, for example, the TCP / IP protocol. The single exposure lithography application 312 may communicate directly with the controller 122 through the communications network 306. The controller 122 is programmed to execute software 304, such as programs and / or other software applications, and to access applications managed by the server 308.

[0022] In the embodiments described below, each user may operate a controller 122, which may be connected to a server 308 via a communications network 306. Pages, images, data, documents, etc. may be displayed to the user via the controller 122. Information and images may be displayed through a display device and / or a graphical user interface in communication with the controller 122.

[0023] It should be noted that the controller 122 may be a personal computer, a laptop mobile computing device, a smart phone, a video game console, a home digital media player, a network-connected television, a set-top box, and / or other computing device having suitable components for communicating with the communications network 306 and / or the necessary applications or software. The controller 122 may also execute other software applications configured to receive content and information from the single exposure lithography application 312.

[0024] 4 is a schematic diagram of a single exposure lithography application 312. The single exposure lithography application 312 includes, but is not limited to, a central processing unit (CPU) 402, a network interface 404, memory 420, and storage 430 that communicate via an interconnect 406. The single exposure lithography application 312 may include an I / O device interface 408 that connects I / O devices 410 (e.g., keyboard, video, mouse, audio, touch screen, etc.). The single exposure lithography application 312 may further include a network interface 504 (shown in FIG. 5) configured to transmit data over a data communications network.

[0025] CPU 402 retrieves and executes programming instructions stored in memory 420 and generally controls and coordinates the operation of other system components. Similarly, CPU 402 stores and retrieves application data residing in memory 420. CPU 402 is included to represent a single CPU, multiple CPUs, a single CPU with multiple processing cores, etc. Interconnect 406 is used to transmit programming instructions and application data between CPU 402, I / O device interface 408, storage 430, network interface 404, and memory 420.

[0026] Memory 420 is included to generally represent random access memory and stores software applications and data for use by CPU 402 during operation. Storage 430, although shown as a single unit, may be a combination of fixed and / or removable storage devices, such as fixed disk drives, floppy disk drives, hard disk drives, flash memory storage drives, tape drives, removable memory cards, CD-ROMs, DVD-ROMs, Blu-Ray, HD-DVDs, optical storage, network attached storage (NAS), cloud storage, or a storage area network (SAN), configured to store non-volatile data.

[0027] The memory 420 may store instructions and logic for executing an application platform 426, which may include single exposure lithography application software 428. The storage 430 may include a database 432 configured to store data 434 and associated application platform content 436. The database 432 may be any type of storage device.

[0028] A network computer is another type of computer system that may be used in conjunction with the disclosure provided herein. A network computer typically does not include a hard disk or other mass storage, and executable programs are loaded from a network connection into memory 420 for execution by CPU 502 (shown in FIG. 5). A typical computer system typically includes at least a processor, a memory, and an interconnect that couples the memory to the processor.

[0029] 5 is a schematic diagram of the controller 122 used to access the single exposure lithography application 312 and obtain or display data associated with the application platform 426. The controller 122 may include, without limitation, a central processing unit (CPU) 502, a network interface 504, an interconnect 506, memory 520, storage 530, and support circuits 540. The controller 122 may include an I / O device interface 508 that connects I / O devices 510 (e.g., keyboards, displays, touch screens, and mouse devices) to the controller 122.

[0030] Similar to CPU 402, CPU 502 is included to represent a single CPU, multiple CPUs, a single CPU with multiple processing cores, etc., and memory 520 is included to represent random access memory in general. Interconnect 506 may be used to transfer programming instructions and application data between CPU 502, I / O device interface 508, storage 530, network interface 504, and memory 520. Network interface 504 may be configured to transfer data over communication network 306, for example, to transfer content from single exposure lithography application 312. Storage 430, such as a hard disk drive or solid state storage drive (SSD), may store non-volatile data. Storage 530 may include database 531. Database 531 may include data 532, other content 534, and image processing unit 536 having data 538 and control logic 539. Illustratively, memory 520 may include an application interface 522 that may itself display software instructions 524 and / or store or display data 526. The application interface 522 may provide one or more software applications that allow the controller to access data and other content hosted by the single exposure lithography application 312.

[0031] As shown in FIG. 1, the system 100 includes a controller 122. The controller 122 includes a central processing unit (CPU) 502, a memory 520, and support circuits 540 (or I / O 508). The CPU 502 may be one of any form of computer processor used in industrial environments to control various processes and hardware (e.g., pattern generators, motors, and other hardware) and monitor processes (e.g., processing time and substrate position). The memory 520 shown in FIG. 5 is connected to the CPU 502 and may be one or more of readily available memories such as random access memory (RAM), read-only memory (ROM), floppy disk, hard disk, or any other form of digital storage, local or remote. Software instructions and data may be encoded and stored in the memory to instruct the CPU 502. The support circuits 540 are also connected to the CPU 502 to support the processor in a conventional manner. The support circuits 540 may include conventional cache 542, power supplies 544, clock circuits 546, input / output circuits 548, subsystems 550, and the like. A program (or computer instructions) readable by the controller 122 determines what tasks can be performed on the substrate 120. The program may be software readable by the controller 122 and may include, for example, code for monitoring and controlling process time and substrate position.

[0032] It should be recognized, however, that all of these and similar terms should be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise, as will be apparent from the discussion that follows, throughout the description, discussions using terms such as "processing" or "calculating" or "computing" or "determining" or "displaying" and the like will be understood to refer to operations and processes of a computer system or similar electronic computing device that manipulates and converts data represented as physical (electronic) quantities in the computer system's registers and memory into other data that is similarly represented as physical quantities in the computer system's memory or registers or other such information storage, transmission, or display device.

[0033] The present examples also relate to an apparatus for performing the operations herein. This apparatus may be specially constructed for the required purposes or may comprise a general-purpose computer selectively activated or reconfigured by a computer program stored in the computer. Such a computer program may be stored in a computer-readable storage medium such as, but not limited to, a read-only memory (ROM), a random-access memory (RAM), an EPROM, an EEPROM, a flash memory, a magnetic or optical card, a floppy disk, an optical disk, a CD-ROM, and any type of disk including a magneto-optical disk, or any type of medium suitable for storing electronic instructions, each of which is coupled to a computer system interconnect.

[0034] The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Various general-purpose systems may be used with programs in accordance with the teachings herein, or it may prove convenient to construct more specialized apparatus to perform the required method operations. The structure of a variety of these systems will be apparent from the above description. In addition, the examples are not described with reference to any particular programming language, and thus various examples may be implemented using a variety of programming languages.

[0035] As described in more detail herein, embodiments of the present disclosure relate to lithography applications that relate to the ability to apply mask pattern data to a substrate 120 in a single exposure lithography process. The embodiments described herein relate to a software application platform that includes a method for forming a three-dimensional profile in a single exposure.

[0036] FIG. 6 is a schematic plan view of a portion 600 of a substrate 120 during a digital lithography process. The substrate 120 includes a photoresist layer 601 disposed above the substrate 120. In some embodiments, which may be combined with other embodiments described herein, a liner layer is disposed below the photoresist layer. The image projection system 200 (shown in FIG. 2 ) corresponding to the portion 600 of the substrate 120 receives mask pattern data from the controller 122. The mask pattern data defines one or more exposure areas 602 to be superimposed on the substrate 120. The exposure areas 602 define areas of the photoresist layer 601 to be exposed to a writing beam from the image projection system 200. The exposure areas 602 include, but are not limited to, circles, triangles, ellipses, regular polygons, irregular polygons, and / or irregular shapes. The one or more exposure areas 602 may be provided in the mask pattern data.

[0037] A plurality of spatial light modulator pixels of spatial light modulator 210 are arranged in an aggregate shot pattern 604. Aggregate shot pattern 604 is overlaid on substrate 120. Each spatial light modulator pixel of spatial light modulator 210 corresponds to a potential shot 606. Aggregate shot pattern 604 indicates a location where each of the potential shots 606 may be projected onto substrate 120. Mask pattern data determines which of the plurality of spatial light modulator pixels are in an "off" or "on" position. Each potential shot 606 represents the centroid of mirror 213 (shown in FIG. 2B). If a spatial light modulator pixel is in an "on" position, then potential shot 606 is projected onto the corresponding location on substrate 120.

[0038] As shown in FIG. 6, a grid 608 of a plurality of unit areas 610 is overlaid on the substrate 120. Each unit area 610 corresponds to one spatial light modulator pixel of the spatial light modulator 210. In the embodiment shown in FIG. 6, each unit area 610 is operable to receive five separate potential shots 606 (i.e., a first shot 606A, a second shot 606B, a third shot 606C, a fourth shot 606D, and a fifth shot 606E) in response to mask pattern data. Each unit area 610 may include hundreds of shots 606, for example, 50-500 potential shots. For example, each unit area 610 includes 60-150 potential shots 606. Increasing the number of potential shots 606 allows finer control of the collection of light on the photoresist layer 601. A first shot 606A, a second shot 606B, a third shot 606C, a fourth shot 606D, and a fifth shot 606E each across a plurality of spatial light modulator pixels are projected in sequence.

[0039] The aggregate shot pattern 604 has an aggregate shot pitch 612. The aggregate shot pitch 612 is the distance between adjacent potential shots 606. The aggregate shot pitch 612 is determined by the pixel pitch 215 (shown in FIG. 2B ) and the magnification of the image projection system 200. Each of the plurality of potential shots 606 has a shot step 614 between each potential shot 606. The plurality of potential shots 606 are uniformly distributed within each unit area 610 to minimize the distance between each of the potential shots 606. The spatial light modulator 210 is oriented at an angle θ DMD The image projection system 200 is rotated slightly by θ DMD The support 108 may be mounted on the support 108 so as to be rotated by only

[0040] As the substrate 120 scans under the image projection system 200, the processing unit 106 projects a number of shots 606 onto the portion 600 of the substrate 120, which correspond to a number of spatial light modulator pixels in the "on" position. Each shot 606 of the number of shots 606 is projected inside an exposure area 602 as defined according to mask pattern data. The number of shots 606 in the exposure area 602 may overlap. For example, if the number of shots 606 are sufficiently dense within the exposure area 602, a pattern corresponding to the exposure area 602 is exposed in the photoresist layer 601.

[0041] FIG. 7A is a schematic plan view of an exposure area 602 divided into a plurality of sub-grids 702. Each sub-grid 702 has a length L. The gray pattern 700 is provided in the mask pattern data by the controller 122. The gray pattern 700 is determined according to the method 900 described herein. In some embodiments, which may be combined with other embodiments described herein, the area of ​​the sub-grid 702 is smaller than the area of ​​the plurality of mirrors 213 (shown in FIG. 2B). The length L is smaller than the optical resolution of the image projection system 200. The optical resolution is smaller than the pixel pitch 215. In addition, the length L may be reduced to accommodate a three-dimensional profile with a steep gradient. Reducing the length L results in more sub-grids 702 constituting the exposure area 602, resulting in the formation of a steep gradient in the three-dimensional profile.

[0042] 7B is a schematic plan view of a gray pattern 700 having multiple sub-grids 702. The sub-grids 702 are utilized to vary the local shot density of an exposure region 602. The gray pattern 700 may be formed to vary the local shot density within each sub-grid 702 as multiple shots 606 (shown in FIG. 6) corresponding to multiple spatial light modulator pixels in the "on" position are provided in the exposure region 602. Multiple pattern areas 704 are defined within each sub-grid by mask pattern data. The multiple pattern areas 704 may be determined according to the single exposure lithography application 312 described herein.

[0043] The multiple pattern areas 704 are defined to achieve a local shot density. For example, to reduce the local shot density in each subgrid 702 by 50%, the multiple pattern areas 704 in each subgrid 702 are formed with 50% of the area of ​​the subgrid 702. The pattern areas 704 are 50% of the area of ​​the subgrid 702 to achieve a local shot density of 50%. In such an example, only "shots" that fit into the pattern areas 704 are provided to achieve a desired exposure dose during processing. The ratio of the pattern areas 704 to the area of ​​each of the subgrids 702 defines a gray pattern density map. The gray pattern density map is utilized to define the shape and size of the multiple pattern areas 704.

[0044] Pattern field pitch 706 is defined as the distance between the centroids of adjacent pattern fields 704. In some embodiments, which may be combined with other embodiments described herein, the length L and pattern field pitch 706 are matched to improve the resolution of the three-dimensional profile formed.

[0045] In one embodiment, which may be combined with other embodiments described herein, each subgrid 702 includes the same local shot density. In another embodiment, which may be combined with other embodiments described herein, the local shot density is different in at least two adjacent subgrids 702. Potential shots 606 (shown in FIG. 6 ) corresponding to spatial light modulator pixels that overlap with patterned regions 704 of the gray pattern 700 are in the “on” position as instructed by the controller 122 according to the mask pattern data. Thus, the number of shots 606, i.e., the local shot density, matches the ratio of the area of ​​the patterned regions 704 to the area of ​​the subgrid 702. In some embodiments, the local shot density in each subgrid 702 may not perfectly match the ratio of the area of ​​the patterned regions 704 to the area of ​​the subgrid 702 due to the discrete nature of digital lithography.

[0046] FIG. 7C is a schematic plan view of a plurality of pattern regions 704. FIG. 7C shows an example of the pattern regions 704 in each subgrid 702. The plurality of pattern regions 704 are not limited to those shown in FIG. 7C. The shape of the pattern region 704 includes, but is not limited to, a circle, a triangle, an ellipse, a regular polygon, a non-regular polygon, and / or an irregular shape. The shape of the pattern region 704 is determined based on the complexity of the exposure region 602 and imperfections caused by the image projection system 200. For example, the shape of the pattern region 704 may be determined to avoid shapes that induce optical aberrations by the image projection system 200. Each shape of the pattern region 704 may be arranged with a rotation angle in the subgrid 702. Each pattern region 704 may achieve a local shot density of 0% to 100% in each subgrid 702.

[0047] FIG. 8A is a diagram 801 of local shot density of a gray pattern 700. The local shot density varies from 0% to 100% across the exposure area 602. The local shot density is determined by the ratio of the number of pattern areas 704 within the subgrid 702 to the area of ​​the subgrid 702 of the gray pattern 700. FIG. 8B is a chart 802 corresponding to the diagram 801 of FIG. 8A. The X-axis corresponds to the position along the exposure area 602 shown in FIG. 8A. The Y-axis corresponds to the amount of exposure light applied to the exposure area 602. The amount of exposure light corresponds to the percentage of the photoresist layer 601 that is developed and removed due to exposure of the photoresist to the intensity of light emitted from the light source 202.

[0048] In an embodiment where the local shot density is 0% (i.e., the plurality of mirrors 213 are all in the "off" position), the exposure dose is 0% and thus the thickness of the remaining photoresist layer 601 is 100%. In an embodiment where the local shot density is 100% (i.e., the plurality of mirrors 213 are all in the "on" position), the exposure dose is 100% and thus the photoresist layer 601 is completely removed. Thus, by varying the local shot density across the exposure area 602 by defining the pattern area 704, it is possible to form a three-dimensional profile in the photoresist layer 601.

[0049] For example, a sloped profile is formed in photoresist layer 601 (shown in FIG. 6) by varying the local shot density as shown in FIG. 8A. The three-dimensional profile in photoresist layer 601 can be transferred to one or more underlying layers by an etching process (e.g., an anisotropic etching process), thereby allowing the three-dimensional profile to be incorporated into integrated circuits, displays, etc. The three-dimensional profile may be a curved, spherical, non-spherical, concave, convex, tapered, semi-cylindrical, or angular profile.

[0050] The three-dimensional profile may be formed in a single exposure operation of the image projection system 200. By performing the exposure operation in a single pass, the occurrence of multiple exposures can be avoided. A single exposure operation provides increased throughput and reduces alignment challenges. Furthermore, due to the need for only a single exposure, the profile is formed regardless of queue time (the time between exposure and development of the photoresist layer 601). Thus, the gray pattern 700 provides increased throughput, the ability to develop three-dimensional profiles in the photoresist layer 601, and reduces overlay challenges associated with the use of multiple masks.

[0051] 9 is a flow diagram of a method 900 for forming a three-dimensional profile in a photoresist layer 601 using a lithography process. The method 900 enables defining a gray pattern 700 according to a desired photoresist profile to be formed. The controller 122 described herein facilitates the operation of the method 900. The method 900 is performed in a single exposure operation of the image projection system 200. Prior to the method 900, a desired photoresist profile is determined. The desired photoresist profile may be a three-dimensional profile. The method 900 may be at least partially performed by a single exposure lithography application 312.

[0052] In operation 901, a contrast curve of a desired photoresist profile is determined. The contrast curve traces the exposure dose versus the removal thickness of a photoresist layer having a desired photoresist profile. Such a curve may be empirically determined in advance or may be applicable to future operations. In operation 902, a map of removal thickness across the desired photoresist profile is determined. The map indicates the removal thickness of the photoresist at each location. The removal thickness map is determined based on the contrast curve. In operation 903, an exposure dose map is determined. The exposure dose map is determined by referencing the map of removal thickness versus contrast curve. The exposure dose corresponds to the percentage of the photoresist layer 601 that is developed due to the exposure of the photoresist to the intensity of light emitted from the light source 202 of the image projection system 200. For example, by determining the removal thickness at each location, the required exposure dose can be determined at each location.

[0053] In operation 904, a gray pattern density map is determined. The gray pattern density map is derived by determining the ratio of the local exposure dose at each location (i.e., each subgrid 702) to the nominal exposure dose. The gray pattern density map determines the number of shots 606 that need to be projected per subgrid 702 to generate an exposure dose based on the exposure dose map. The gray pattern density map determines the local shot density at each subgrid 702. In operation 905, a gray pattern 700 is generated based on the gray pattern density map. The gray pattern density map defines the ratio of the local exposure dose to the nominal exposure dose. A plurality of pattern areas 704 at each subgrid 702 define the gray pattern 700. The shape and size of the plurality of pattern areas 704 are determined in operation 905 to correspond to the gray pattern density map. The gray pattern 700 is provided to the image projection system 200 by the controller 122 in the form of mask pattern data.

[0054] In operation 906, the gray pattern is printed and measured. As the substrate 120 scans under the image projection system 200 in a single pass, the processing unit 106 projects multiple shots 606 according to the gray pattern 700. The local shot density is varied across multiple sub-grids 702. Since the exposure dose at each sub-grid 702 depends on the local shot density, the thickness of the removed photoresist layer 601 varies across the substrate 120. Thus, the photoresist layer 601 will have a three-dimensional profile. The thickness of the three-dimensional profile may then be measured. In operation 907, the thickness of the desired photoresist profile is compared to the thickness of the three-dimensional profile formed in the photoresist layer 601 in operation 906. In embodiments where the thicknesses do not match, the exposure dose map is adjusted accordingly. For example, the exposure dose at each location can be increased or decreased. As a result, the pattern area 704 will increase or decrease in area in response. Operations 903-907 may then be repeated until the desired photoresist profile thickness equals the thickness of the three-dimensional profile.

[0055] In operation 908, the photoresist layer 601 is smoothed. In some embodiments, the number of shots 606 projected onto each subgrid 702 of the gray pattern 700 does not always result in a smooth thickness transition between adjacent subgrids 702 of the photoresist layer 601. Therefore, to improve the thickness transition in the photoresist layer 601, one of a first smoothing operation, a second smoothing operation, or a third smoothing operation may be performed.

[0056] The first smoothing operation involves broadening the width of the laser pulse of the light source 202 projected onto the substrate 120. Because the stage 114 (shown in FIG. 1) moves at a constant speed during scanning, broadening the width of the laser pulse (i.e., increasing the pulse width) reduces the roughness of the photoresist layer 601 in the direction of movement of the stage 114. Conventionally, the pulse width of the light source 202 multiplied by the speed of the stage 114 is about 40% or less of the pixel pitch 215 (shown in FIG. 2B). However, in the first smoothing operation, the pulse width of the light source 202 multiplied by the speed of the stage 114 is about 100% to about 150% of the pixel pitch 215 to allow blending of the projected shots 606. The blending occurs in the direction of movement of the stage 114.

[0057] The second smoothing operation involves adjusting the image projection system 200 to print the gray pattern 700 slightly out of focus. Thus, the multiple shots 606 projected onto the exposure area 602 will be blurred. Blurring the multiple shots 606 increases the blending of adjacent shots 606. Thus, when the photoresist layer 601 is developed, the thickness transition will be smoother.

[0058] The third smoothing operation includes a baking process. The baking process may be performed on the photoresist layer 601 after exposure (i.e., operation 906). The baking process may be performed on the liner layer after development of the photoresist layer 601. The baking temperature is about 150° C. to about 250° C. Baking has a diffusion effect that allows the photoresist or liner layer to melt slightly. Thus, the photoresist or liner layer is smoothed.

[0059] In summary, a lithography process system, software application, and method for forming a three-dimensional profile in a single exposure operation are provided herein. To form a three-dimensional profile in a photoresist layer, a local shot density of multiple shots in an exposure area is varied. The local shot density determines the exposure dose provided by an image projection system in each subgrid of the exposure area. The exposure dose determines the thickness of the photoresist layer when the multiple shots are projected onto the photoresist layer. By adjusting the local shot density by defining multiple pattern areas in each subgrid of the exposure area where the multiple shots should be projected, the thickness of the photoresist layer can be formed to have a three-dimensional profile. The three-dimensional profile may be formed in a single exposure operation of a lithography system. The utilization of a gray pattern provides increased throughput, the ability to develop a three-dimensional profile in a photoresist layer, and reduces overlay challenges associated with the use of multiple masks.

[0060] While the forgoing is directed to embodiments of the present disclosure, other and further embodiments of the present disclosure may be devised without departing from the basic scope thereof, which scope is determined by the following claims.

Claims

1. Slabs and a movable stage positionable above the slab, the movable stage configured to support a substrate having a layer of photoresist disposed thereon; a controller configured to provide mask pattern data to a lithography system, the mask pattern data having an exposure area having a gray pattern, the gray pattern being defined by a plurality of sub-grids, each sub-grid including a pattern area defined therein; and a lithography system support coupled to the slab, the lithography system support having an opening therebelow to allow the moveable stage to pass therebelow; Equipped with the lithography system includes a processing unit having a plurality of image projection systems for receiving the mask pattern data; Each image projection system includes a spatial light modulator having a plurality of spatial light modulator pixels for projecting a plurality of shots; the controller is configured to place a plurality of pattern regions within each of the subgrids to vary local shot density in each subgrid; the controller is configured to instruct each of the spatial light modulators to project the plurality of shots onto the plurality of pattern areas in each subgrid of the gray pattern. system.

2. The system of claim 1 , wherein the local shot density corresponds to an area ratio of the pattern area to each subgrid.

3. The system of claim 2 , wherein the controller is configured to increase the local shot density to increase a thickness of the photoresist layer to be removed during development.

4. The system of claim 3 , wherein the controller is configured to reduce the local shot density to reduce a thickness of the photoresist layer to be removed during development.

5. 2. The system of claim 1, wherein the controller is configured to command the multiple shots to be projected onto the multiple pattern areas, the multiple shots exposing the photoresist layer to an intensity of light emitted from the image projection system to form a three-dimensional profile in the photoresist layer.

6. The system of claim 5 , wherein the three-dimensional profile is a curved, spherical, aspherical, concave, convex, tapered, semi-cylindrical, or angled profile.

7. The system of claim 1 , wherein each spatial light modulator pixel of the plurality of spatial light modulator pixels of the spatial light modulator is individually controllable by the controller.

8. 2. The system of claim 1, wherein the local shot density defined by each pattern area in one subgrid is different from the local shot density in at least one adjacent subgrid.

9. When executed by a processor, Providing mask pattern data having a plurality of exposure areas to a processing unit of a lithography system, the processing unit having a plurality of image projection systems for receiving the mask pattern data, each exposure area including a gray pattern, the gray patterns comprising: Multiple sub-grids, and A plurality of pattern areas in each subgrid, the plurality of pattern areas corresponding to the local shot density of each subgrid. providing a a single scan of a substrate having a photoresist layer disposed thereon under said multiple image projection systems; projecting a plurality of shots onto the photoresist layer onto the plurality of pattern areas of the gray pattern; developing the photoresist layer to form a three-dimensional profile in the photoresist layer, the three-dimensional profile being defined by the local shot density in each sub-grid of each exposure area; A non-transitory computer-readable medium storing instructions for causing a computer system to execute the method.

10. 10. The non-transitory computer-readable medium of claim 9, wherein each image projection system comprises a spatial light modulator having a plurality of mirrors for projecting the plurality of shots onto the exposure area of ​​an aggregate shot pattern.

11. 10. The non-transitory computer-readable medium of claim 9, wherein a pulse width of a light source in each image projection system multiplied by a speed of the single scan of the substrate is approximately 100% to 150% of a pixel pitch, the pixel pitch being the distance between adjacent centroids of spatial light modulator pixels in the multiple image projection systems.

12. 10. The non-transitory computer readable medium of claim 9, wherein the multiple image projection systems are out of focus and the multiple shots are blurred in the exposure area.

13. 10. The non-transitory computer readable medium of claim 9, further comprising a baking process, wherein the photoresist layer is baked at a temperature of about 150°C to about 250°C.

14. Providing mask pattern data having a plurality of exposure areas to a processing unit of a lithography system, the processing unit having a plurality of image projection systems for receiving the mask pattern data, each exposure area including a gray pattern, the gray patterns comprising: Multiple sub-grids, and A plurality of pattern areas in each subgrid, the plurality of pattern areas corresponding to the local shot density of each subgrid. Providing and providing a single scan of a substrate having a photoresist layer disposed thereon under said multiple image projection systems; projecting a plurality of shots onto the photoresist layer onto the plurality of pattern areas of the gray pattern; developing the photoresist layer to form a three-dimensional profile in the photoresist layer, the three-dimensional profile being defined by the local shot density in each sub-grid of each exposure area; A method comprising:

15. The method of claim 14 , wherein each image projection system comprises a spatial light modulator having a plurality of mirrors for projecting the plurality of shots onto the exposure area of ​​an aggregate shot pattern.

16. 15. The method of claim 14, wherein a pulse width of a light source in each image projection system multiplied by a speed of the single scan of the substrate is about 100% to 150% of a pixel pitch, the pixel pitch being the distance between adjacent centroids of spatial light modulator pixels in the multiple image projection systems.

17. The method of claim 14 , wherein the multiple image projection systems are out of focus and the multiple shots are blurred in the exposure area.

18. 15. The method of claim 14, further comprising a baking process, wherein the photoresist layer is baked at a temperature of about 150°C to about 250°C.

19. The method of claim 14 , wherein the plurality of pattern regions of the gray pattern are derived based on the local shot density desired in each sub-grid.

20. 15. The method of claim 14, further comprising performing an etching process on the photoresist layer such that the three-dimensional profile is transferable to one or more liner layers disposed below the photoresist layer.

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