Digital lithography apparatus having an automatic focus position control unit and method of using the same

Abstract

Embodiments of the present disclosure relate to digital lithography systems and associated methods, the system including at least one light source configured to emit a light beam onto a substrate through a lens, at least one image sensor configured to detect a reflected light beam from the substrate through the lens, at least one motor configured to move the lens to focus the light beam on the substrate, and a controller in communication with the at least one light source, the at least one image sensor, and the at least one motor, wherein the controller actuates the at least one motor to move the lens in response to at least one signal from the at least one image sensor.

Description

Technical Field

[0001] Embodiments of the present disclosure relate to a digital lithography apparatus having an autofocus position control unit and a method of using such a digital lithography apparatus.

Background Art

[0002] Photolithography is widely used in the manufacture of semiconductor devices and display devices such as liquid crystal displays (LCDs) and organic light emitting diode displays (OLEDs). Large area substrates are often utilized in the manufacture of LCDs. LCDs or flat panels are commonly used in active matrix displays such as computers, touch panel devices, personal digital assistants (PDAs), mobile phones, and television monitors. Generally, a flat panel may include a liquid crystal material layer that forms pixels sandwiched between two plates. When power from a power source is applied across the entire liquid crystal material, the amount of light passing through the liquid crystal material can be controlled at pixel positions where image generation is possible.

[0003] Digital lithography techniques are generally used to create electrical features incorporated as part of a liquid crystal material layer that forms pixels. According to this technique, a photosensitive photoresist is typically applied to at least one surface of a substrate. A pattern generator then optically exposes selected areas of the photosensitive photoresist as part of a pattern, causing a chemical change in the photoresist in the selected areas and preparing these selected areas for subsequent material removal and / or material addition processes to create electrical features.

[0004] There is a need for new apparatuses, approaches, and systems for creating patterns accurately and cost-effectively on substrates.

Summary of the Invention

[0005] According to various embodiments, a digital lithography system includes at least one light source configured to emit light rays onto a substrate through a lens, at least one image sensor configured to detect reflected light rays from the substrate through the lens, at least one motor configured to move the lens to focus the light rays on the substrate, and a control device in communication with the at least one light source, the at least one image sensor, and the at least one motor, wherein the control device is configured to operate the at least one motor to move the lens in response to at least one signal from the at least one image sensor.

[0006] In a further embodiment, a digital lithography system includes a plurality of light sources each configured to emit light rays onto a substrate through a lens, a plurality of image sensors each configured to detect reflected light rays from the substrate through the lens, wherein each light source is paired with an image sensor, at least one motor configured to move the lens to focus the light rays on the substrate, a plurality of autofocus channels each associated with at least one of the plurality of light sources and at least one of the plurality of image sensors, and a control device in communication with the plurality of light sources, the plurality of image sensors, and the at least one motor, wherein the control device is configured to operate the at least one motor to move the lens in response to one or more signals from the plurality of image sensors.

[0007] Furthermore, embodiments of a method for automatically focusing a light beam in a digital lithography system disclosed herein include directing at least one light beam from at least one light source onto a substrate through a lens, reflecting at least one light beam from the substrate through the lens onto at least one image sensor, receiving at least one signal from the at least one image sensor by a control device, wherein the at least one signal indicates the position of the light beam on the substrate, receiving at least one signal by the control device, and controlling, by the control device, the position of the lens to focus the light beam on the surface of the substrate.

[0008] The present disclosure is shown in the figures of the accompanying drawings with like reference numerals indicating like elements, by way of illustration and not limitation. It should be noted that different references to "an" or "one" embodiment in the present disclosure are not necessarily to the same embodiment, and such references mean at least one.

Brief Description of the Drawings

[0009]

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DETAILED DESCRIPTION OF THE INVENTION

[0010] Embodiments of the present disclosure relate to the control of the position of a lens within a digital lithography tool in a robust and accurate manner to provide precise focus with little or no non-uniformity. By a digital lithography system and method, a device structure is printed onto a substrate (e.g., a glass substrate) using a light source. The digital lithography system and method described herein are used, inter alia, to manufacture displays. For example, assume a customer orders 5,000 telephones and provides a semiconductor manufacturer with patterns for these 5,000 parts. The manufacturer can form hundreds of these patterns per substrate. The same manufacturing process can be repeated, for example, 100 or 200 times. A semiconductor manufacturer typically scans a first substrate as an initial reference scan. However, each substrate (e.g., glass) may be slightly different, and the position can be slightly distorted in one direction or the other with some misalignment in the placement between machines. By tracking the height variations of the substrate, a control device can move the lens to appropriately focus the light source during the scan.

[0011] An autofocus system according to embodiments herein utilizes one or more light rays that pass through a precision lens and are then projected onto a substrate. The light source is then reflected back and measured using an image sensor to determine its position. In some embodiments, the substrate effectively forms a mirror with lines projected onto a transparent surface having a reflective material (e.g., chromium) on the bottom. Due to this reflectivity, it may be difficult to identify the position of the surface of the substrate. In some embodiments, when a material layer is printed on another layer, different types of reflectivities are created on these layers. The light rays may be out of focus due to these varying reflectivities. For example, the lens may drift to one side or the other from the target position. In some embodiments, the substrate includes multiple layers, each layer being transparent. The substrate can be formed from, for example, 5, 6, 7, 8, or 9 transparent layers. When the light rays are directed at the substrate, the signal becomes very noisy and it becomes difficult for the system to determine the height of the surface.

[0012] In some cases, the substrate can be heated and / or cooled, and its height can change, which may, for example, bend the light source over the edge. The systems and methods described herein are configured to focus the light source during such conditions. When the system is not scanning the substrate, the height of the lens with respect to the substrate can change. For example, when a new substrate is placed on the stage, the substrate material has various thicknesses (e.g., on the order of microns), so each individual substrate is slightly different from other substrates with respect to height. Sensors within the system are configured to determine this change in height. Such information can be used as feedback for controlling the focus of the light source. In the case of systems and methods that use a light source to perform a printing operation, it is beneficial to maintain the focus of the light source. The autofocus subsystem described by the embodiments herein functions with improved software control of the autofocus subsystem.

[0013] To obtain an accurate focus in real time, various parameters are considered, including substrate conditions (e.g., topography, reflectivity, pattern structure, etc.), chuck flatness, stage movement, measurement noise, and the effects of heat. The methods and systems according to the embodiments herein collect such parameter data in real time and use the real-time data to control the position of the light source. In some embodiments, historical parameter data (e.g., from previous scanning and lithography processes) may also be used to control the position of the light source.

[0014] The systems and methods described herein improve the focus accuracy of an optical lens in real-time by accurately controlling its position using a control device and a motor unit. The systems and methods according to embodiments herein utilize real-time autofocus signals and empirical reference positions to determine the actual movement during printing. Such systems and methods also utilize some or all of the autofocus signals to drive one or more motors in different use cases. The systems and methods according to various embodiments can minimize non-uniformity and produce improved faithful prints, and optionally, can ignore the underlying layer on the substrate, the orientation / density of the underlying pattern, and / or the scanning speed.

[0015] In the systems and methods described herein, it is beneficial to focus the light source "on-the-fly" to maintain focus, especially during high scanning speeds. To maintain precise focus, various parameters are considered, including substrate conditions (e.g., topography, reflectivity, and pattern structure), chuck flatness, stage movement, measurement noise, and the effects of heat during scanning.

[0016] The embodiments described in this specification utilize positioning control during high-speed scanning. The position can be determined by the following approaches: 1) an approach that uses the signal centroid of autofocus together with proportional-integral-derivative (PID) control, i.e., an approach that uses the PID control loops of all channels and the signal centroid of autofocus as feedback to determine movement; 2) an approach that uses the signal centroid of autofocus together with a Kalman filter, i.e., an approach that uses the Kalman filters of all channels and the signal centroid of autofocus as feedback to determine movement; 3) an approach (similar to 1) that uses the signal centroid of autofocus together with dynamic channel selection, an approach that uses some but not all channels dynamically to determine movement, and / or 4) determined by an approach that uses an empirical reference position together with feedback of a real-time autofocus signal, and this approach in 4) is different from approach 3) in that the position is not always determined by the real-time autofocus signal. Rather, approach 4) uses both a predetermined reference position and the real-time autofocus signal, and the reference position can be obtained from a planar substrate (i.e., no underlying pattern), a first-layer print, a post-processed position generated from other methods. Different approaches can be used depending on whether there is an underlying / underlying pattern and / or the orientation / density of the underlying pattern.

[0017] FIG. 1 shows a schematic diagram of a digital lithography system 100 according to one or more embodiments of the present disclosure. In system 100, a light source 102 is configured to project a light beam 104 onto a substrate 106 via a reflector 108 and a lens 110. The substrate may be formed of a suitable material including, but not limited to, glass, reflective material, metal, chromium, polymer, crystal, or oxide. The lens may be an optical lens, a spherical lens, or an aspherical lens. The light source 102 may be mounted to the system 100 via a mounting substrate 112 configured to stabilize the light source 102 during operation. Suitable light sources include, but are not limited to, lasers, continuous wave (CW) lasers, quality (Q) switched lasers, mode-locked lasers, etc. The reflector 108 may be formed of any suitable material including, but not limited to, mirrors, glass, metal, etc. The lens 110 may be an optical lens formed of any suitable material including, but not limited to, glass, silica, crystal material, nanocrystal material, etc.

[0018] System 100 further includes at least one image sensor 114, and the image sensor 114 may be mounted on a strip board 115. In some embodiments, a plurality of image sensors 114 may be mounted in a row on the strip board. The image sensor 114 may be a linear image sensor, a complementary metal oxide semiconductor (CMOS) or active pixel image sensor, a charge-coupled device (CCD) image sensor, a solid-state device that converts an optical image into an analog signal in a line-by-line manner and the like. The image sensor 114 may be used to detect a light source spot 116 on the substrate 106. As shown in FIG. 1, the light beam 104 is reflected from the substrate 106 at the light source spot 116 and directs the reflected light beam 118 towards a reflector 120. The reflected light beam 118 is reflected from the reflector 120 to a reflector 122, where it is directed towards the image sensor 114 as an autofocus signal.

[0019] In the embodiment shown in FIG. 1, the system 100 has a single autofocus channel 124, but it should be understood that in some embodiments the system 100 may include multiple autofocus channels. For example, the system 100 may include multiple autofocus channels such that each channel is associated with a light source and a linear image sensor pair. In some embodiments, the systems described herein include at least three autofocus channels.

[0020] The system 100 may further include a unit consisting of a control device 126 and one or more motors 128. Suitable control devices 126 include, but are not limited to, proportional control devices, integral control devices, proportional-integral control devices, proportional-derivative control devices, or proportional-integral-derivative (PID) control devices.

[0021] Suitable motors include, but are not limited to, linear motors such as piezoelectric motors, ultrasonic motors, ultrasonic resonance motors, piezo stepper motors, piezo walk motors, piezo stick slip motors, flexure type motors, and inertial motors. The control device 126 is configured to operate one or more linear motors 128. According to an embodiment, one or more linear motors 128 move the lens 110 relative to the substrate 106 to improve and / or optimize the focus of the light source 104 on the substrate 106. The data processing unit 130 transmits signals to and receives signals from at least one image sensor 114, the light source 102, and the control device 126.

[0022] FIG. 2 shows a schematic diagram of the change in the position of the lens 210 relative to the surface 207 of the substrate 206. As the substrate is processed, layers of circuit and device features are built up, making it difficult for the lens 210 to focus light rays onto the surface of the substrate. The systems and methods described herein are configured to detect the position of the surface of the substrate and optimize the focus of light rays onto the surface of the substrate.

[0023] As shown in FIG. 2, when the light beam 204 reaches the substrate 206 through the lens 210 at the spot 215, the light beam 204 is reflected from the substrate 206 and returns to the lens 210 at 211. During subsequent scanning of the substrate 206 using a light source (not shown), the height of the surface of the substrate changes from 207 to 209, as represented by, for example, ΔZ, and the distance between the surface of the substrate and the lens 210 can decrease.

[0024] As shown in FIG. 2, when the height of the surface of the substrate 206 shifts towards the lens 210 as represented by 209, the light beam 213 is reflected from the surface 209 at the spot 217 and returns to the lens 210 at 216. According to an embodiment, the substrate height change (ΔZ) can be captured and measured by the change in the signal centroid of the autofocus. After being reflected at the spot 215, the light beam 204 generates a beam spot 218 on the linear image sensor 214. The centroid of the beam spot 218 is calculated and represents the relative distance between 207 and 210. Similarly, the light beam 213 generates a beam spot 219 (which needs to be added) on the linear image sensor 214. Thus, the shift (ΔL) on the linear image sensor 214 can capture the change in the height (ΔZ) of the substrate.

[0025] The movement of the lens 210 can be determined by the shift (ΔL) on the linear image sensor 214 caused by one or more autofocus channels as described above, for example, the substrate height change (ΔZ) The shift ΔL of 211 to 216 (and the spots 215 to 217) caused by the height of the substrate surface (i.e., 207 to 209) can cause the focus of the light source to shift and / or create non-uniformity. change ΔZ

[0026] The systems and methods according to embodiments of this specification are used to refocus a light source taking into account the height change ΔZ of the surface of a substrate. In some embodiments, there is a correspondence between the incidence of the light source on the surface of the substrate (e.g., spots 215, 217) and the movement of the reflected light rays along the linear sensor 214. For example, the measurement of the linear shift indicates the change in the height of the surface of the substrate relative to the lens. Thus, the system 100 can be calibrated using an autofocus channel to maintain a target focus (e.g., number of pixels) during processing. A planar (uncoated) substrate can be scanned and used for calibration. The height variations are based on variations in the thickness of the substrate material (e.g., glass). The substrate can be pre-scanned during printing and then, when actually printing pixels on the substrate, the printing is scanned in real time. When scanning the substrate, if the actual number of pixels changes, the control device determines that the light rays are a certain number of pixels away from the target. Using a feedback loop, the control device 126 commands the linear motor 128 to move the lens 110 to return the focus of the light rays 104 to the target position.

[0027] Figure 3A shows a substrate height map representing out-of-focus of an optical lens during image scanning. A control device and a motor unit were used to automatically focus the light source within a digital lithography system. This substrate height map shows problems that can occur when the focus is not controlled during processing. During this scan, 70 scans along the y-axis were performed in 12800 frames along the x-axis. The substrate height map shows the topology of the substrate through the lens. The scanned substrate comprised multiple layers of devices, circuit features, and films. The lens focused the light rays on the underlying features rather than on the surface of the substrate, resulting in the horizontal and vertical lines shown. If the linear motor cannot move the lens to track the surface of the substrate, the resulting error will be greater than the depth of focus and the printed pattern will be out of focus.

[0028] In one or more embodiments, the substrate may contain chromium or other metal and non-metal materials, i.e., the substrate may consist of a combination of materials. Similarly, one region of the substrate may have a different combination of materials than another region of the substrate. As the light source scans a substrate having such irregular materials, the lens may be moved to the wrong position, resulting in the lines shown in FIG. 3A, so that the light source is no longer focused. The systems and methods according to one or more embodiments herein are configured to remove the variations resulting from this focus shift. In other words, the light rays reflected from the substrate may reflect from a device or layer in a lower layer within the substrate rather than from the surface of the substrate. Thus, the lens attempts to focus the light rays on the underlying features rather than on the currently printed surface. This causes the motor to move the lens to an unwanted position, shifting the focus of the light rays and resulting in the pattern shown in FIG. 3A. The systems and methods according to one or more embodiments herein, rather than facilitating these incorrect signals, rather correct them. The systems and methods described herein are configured to maintain accurate positioning control during high-speed scanning. Control of the movement of the lens can minimize non-uniformity and improve the fidelity of printing.

[0029] FIG. 3B shows a substrate height map representing a low-contrast, non-uniform luminance region (i.e., non-uniformity) within an image scan. In some cases, inappropriate movement of the lens can result in non-uniformity. As shown in the substrate height map of FIG. 3B, there is non-uniformity in the vicinity of the following (x, y) coordinates: (10 mm, -80 mm).

[0030] According to one or more embodiments, among other things, a method 400 for controlling the position of a lens using a control device and a linear motor together with an image sensor is described herein. In one or more embodiments, the control device is calibrated with respect to the position of the light beam along the image sensor and the height of the surface of the substrate. The control method 400 shown in FIG. 4 uses the signal centroid of the autofocus together with proportional-integral-derivative (PID) control to direct the position of the lens. In block 402, the light source projects a light beam onto the substrate through the lens.

[0031] In block 404, the light beam is reflected from the substrate and returns through the lens. The reflected light beam is irradiated onto an image sensor (e.g., a linear image sensor) configured to receive and detect the light beam at a plurality of positions along the length of the image sensor. As shown in FIG. 2, the reflected light beam can be used to determine the shift ΔL between the predicted position 211 and the actual position 216 of the light beam.

[0032] In block 406, the control device receives from the image sensor a signal indicating the position of the reflected light beam that is reflected back onto the image sensor through the lens. The control device determines the difference between the actual position of the light beam and the target position of the light beam. As shown in FIG. 2, the shift (ΔL) along the length of the reflected light beam corresponds to the height of the surface of the substrate change (ΔZ) corresponds to.

[0033] In block 408, the control device determines the current height of the surface of the substrate. The control device then uses a control method, such as a PID control loop, as feedback along with the centroid of the autofocus signal for one or more channels to determine the movement of the lens for proper focusing with respect to the determined height of the substrate. For example, if the lens focuses the light beam on a lower layer structure below the surface of the substrate, the control device moves the lens to focus the light beam on the surface of the substrate (i.e., to focus at a height above the lower layer structure). In some embodiments, the control device uses dynamic channel selection as feedback along with the centroid of the autofocus signal for one or more channels. For example, the control device uses dynamically some but not all channels to control the movement of the lens. In other embodiments, the control device uses all channels to control the movement of the lens. In one or more embodiments, the autofocus signals are collected from the image sensor, and then the centroid of these signals is determined and used to confirm the position.

[0034] In some embodiments, as an alternative to the PID control loop described above, method 400 combines a Kalman filter (i.e., linear quadratic estimation) as feedback with the centroid of the autofocus signal for one or more channels. In this embodiment, the control device utilizes historical data from the centroid of the autofocus signal for one or more channels combined with the current one or more channel measurements. In this embodiment, the Kalman filter also predicts how the surface height changes and the control device actuates the linear motor to move the lens to focus the light beam on the surface of the substrate. In some embodiments, the Kalman filter is based on the following equation. The Kalman filter model assumes that the true state at time k evolves from the state at (k - 1) according to the following equation. x k =F k x k-1 +B k u k +w k Wherein, ·F k is the previous state xk-1 It is a state transition model applied to ·B k is a control input model applied to the control vector u k ·w k is process noise, which is assumed to be derived from a zero-mean multivariate normal distribution (N) with covariance (Q k ) (w k ~N(0, Q k )) At time k, the observation (or measurement) z k of the true state x k is performed according to the following equation z k =H k x k +v k where ·H k is the observation model, which maps the true state space to the observation space ·v k is the observation noise, which is assumed to be zero-mean Gaussian white noise with covariance (R k ) (v k ~N(0, R k )) The initial state and the noise vectors {x0, w1,..., w k , v1,..., v k} at each step are all assumed to be mutually independent

[0035] ​In some embodiments, instead of the PID control loop described above, method 400 combines an empirical reference position for a substrate (e.g., a reference map of the substrate) with the signal centroid of real-time autofocus for one or more channels as feedback. In some embodiments, each substrate has a reference map that is tracked by an identification code. In this embodiment, the position of the lens is not necessarily determined by real-time autofocus signals from one or more channels. The control device utilizes both the real-time autofocus signal and a predefined reference position of the lens controlled by the control device. The reference position can be obtained from a planar substrate (i.e., without underlying patterns or features), a first layer of printing, a post-processed position generated from other methods, etc. In some embodiments, any of the above control approaches can be used depending on whether there is an underlying layer or pattern, the orientation or density of the underlying pattern. For example, the light rays passing through the lens can be out of focus due to the varying reflectivities of the substrate surface. The systems and methods described herein are configured to measure the actual height of the substrate surface. To do this, previous information regarding the height and / or filtering of the substrate surface is used to move the lens to maintain the focus of the light rays on the substrate surface.

[0036] FIG. 5A shows a substrate height map representing the substrate height measured during scanning when the position is determined using proportional-integral-derivative control with the centroid of autofocus for one or more channels. During this scan, 35 scans along the y-axis were performed with 12,800 frames along the x-axis. The control device collected the autofocus signals and determined the centroid of these signals. This centroid was used by the PID control device to generate the position of the lens. In some embodiments, this method of scanning the substrate can be used on a "blank substrate" (e.g., a complete surface, an uncoated surface).

[0037] FIG. 5B shows a substrate height map representing the substrate height measured during scanning when the position is determined by dynamic channel selection control together with the centroid of the autofocus of one or more channels. This control method is used to dynamically select a specific autofocus channel, and although not all, some channels can be used as feedback to the PID controller to determine movement. During this scanning, three autofocus channels (i.e., pairs of three image sensors and light sources) were used, and the data for each scan was stored in memory and accessible by the controller. Data from the channel with the best signal was used in the control loop. In some embodiments, the controller can dynamically select the number of channels. During scanning, the light beam can land at specific pixel positions. Some positions can be on complex device features, reflective materials, and / or multilayer structures. Scanning at such positions can have relatively more noise (i.e., it is difficult to focus at that pixel position). The system can dynamically increase the number of channels at that position to improve the feedback signal. By using this method to control the position of the lens, lines as shown in FIG. 3A are removed and / or reduced.

[0038] FIG. 6A shows a substrate height map representing the substrate height measured during scanning when the position is determined using PID control together with the centroid of the autofocus. To generate this substrate height map, 57 scans along the y-axis were performed at 6,545 frames along the x-axis. By using this method to control the position of the lens, lines as shown in FIG. 3A are removed and / or reduced.

[0039] FIG. 6B shows a substrate height map representing the substrate height measured during scanning when the position is determined by the centroid of the autofocus together with Kalman filter control. This method is similar to the method of reducing the treble control on a stereo so that only lower frequency signals pass through. In this embodiment, by using this method to control the position of the lens, lines as shown in FIG. 3A are removed and / or reduced.

[0040] FIG. 7A shows a substrate height map representing the substrate height measured during scanning when the position is determined by the center of gravity of the autofocus together with proportional-integral-derivative control. During this scanning, 55 scans were performed along the y-axis for 6,400 frames along the x-axis. The substrate height map resulted in several line patterns.

[0041] FIG. 7B shows a substrate height map representing the substrate height measured during scanning when the position is determined by a reference position together with feedback control of the real-time autofocus signal. During these scans, an empirical reference position was utilized. For example, the systems and methods described herein may store each data scan in memory. Each one or more previous layers may be utilized by the control system as a reference. This reference data (or history data) may utilize the real-time image sensor signal as a feedback signal within the control loop and may be combined. In some embodiments, the real-time signal may include noise as a result of multiple layers within the substrate. Thus, the real-time signal may be ignored due to excessive noise.

[0042] For example, the real-time signal may be utilized when the signal is determined to be reliable. In some embodiments, using the real-time signal for feedback, the control device knows the actual height of the substrate in a specific area (or pixel) of the substrate. This actual height can be compared to the first layer since the reference map is stored in the memory of the system and the height difference can be determined. The control device will apply this difference in the corresponding pixel area. According to one or more embodiments described herein, when this method is utilized by the control device to control the position of the lens by operating the linear motor, the noise or line patterns shown in FIG. 7B are substantially reduced or removed compared to the scan presented in FIG. 3A.

[0043] FIG. 8 illustrates a diagrammatic representation of a machine in an exemplary form of a computer system 800 including a set of instructions executable by a system as described herein to perform any one or more of the methods discussed herein. In one implementation, the system may include instructions to enable execution of the processes and corresponding components shown and described in relation to FIGS. 1, 2, and 4.

[0044] In an alternative implementation, the system may include a machine (e.g., networked) connected to other machines in a LAN, intranet, extranet, or the Internet. The machine may operate as a server machine in a client-server network environment. The machine may be a personal computer (PC), neural computer, set-top box (STB), personal digital assistant (PDA), cellular phone, server, network router, switch, or bridge, or any machine capable of executing a set of instructions (sequential or otherwise) that specify actions to be taken by that machine. Further, while only a single machine is illustrated, the term "machine" shall be construed to include any collection of machines that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methods described herein.

[0045] An exemplary computer system 800 can include a processing device (processor) 802, a main memory 804 (e.g., read-only memory (ROM)), a flash memory, a dynamic random access memory (DRAM) such as synchronous DRAM (SDRAM), a static memory 806 (e.g., flash memory, static random access memory (SRAM)), and a data object storage device 818 that communicate with each other via a bus 830.

[0046] The processing device 802 represents one or more general-purpose processing devices such as a microprocessor, a central processing unit, etc. More specifically, the processing device 802 can be a complex instruction set computing (CISC) microprocessor, a reduced instruction set computing (RISC) microprocessor, a very long instruction word (VLIW) microprocessor, or a processor implementing other instruction sets, or a processor implementing a combination of instruction sets. The processing device 802 can also be one or more dedicated processing devices such as an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a digital signal processor (DSP), a network processor, etc. In various implementations of the present disclosure, the processing device 802 is configured to execute instructions for the devices or systems described herein to perform the operations and processes described herein.

[0047] The computer system 800 may further include a network interface device 808. The computer system 800 may also include a video display unit 810 (e.g., a liquid crystal display (LCD) or a cathode ray tube (CRT)), an alphanumeric input device 812 (e.g., a keyboard), a cursor control device 814 (e.g., a mouse), and a signal generation device 816 (e.g., a speaker).

[0048] The data storage device 818 may include a computer-readable medium 828 on which one or more instruction sets of one or more of the methodologies or functions described herein for implementing any one or more of the methodologies or functions described herein are stored. The instructions may also be fully or at least partially present in the main memory 804 and / or in the processing logic 826 of the processing device 802 during their execution by the computer system 800, the main memory 804, and the processing device 802 also constituting a computer-readable medium.

[0049] The instructions may further be transmitted or received through the network 820 via the network interface device 808. Although the computer-readable storage medium 828 is shown as a single medium in the exemplary implementation, the term "computer-readable storage medium" should be interpreted to include a single medium or multiple media (e.g., a centralized or distributed database and / or associated caches and servers) that store one or more instruction sets. The term "computer-readable storage medium" should also be interpreted to include any medium that can store, encode, or transmit an instruction set for machine execution and cause a machine to execute any one or more of the methodologies of the present disclosure. Accordingly, the term "computer-readable storage medium" should be interpreted to include, without limitation, solid state memory, optical media, and magnetic media.

[0050] The foregoing description sets forth numerous specific details, such as examples of particular systems, components, methods, etc., in order to provide a good understanding of some embodiments of the present disclosure. However, it will be apparent to those skilled in the art that at least some embodiments of the present disclosure may be practiced without these specific details. In other instances, well-known components or methods are not described in detail or are presented in simple block diagram form in order to avoid unnecessarily obscuring the present disclosure. Accordingly, the specific details described are merely illustrative. Particular implementations may vary from these illustrative details and still be contemplated as within the scope of the present disclosure.

[0051] As used herein, the singular forms "a", "an", and "the" include plural references unless the context clearly dictates otherwise. Thus, for example, reference to "a precursor" includes a single precursor as well as a mixture of two or more precursors, and reference to "a reactant" includes a single reactant as well as a mixture of two or more reactants and the like.

[0052] References to "an embodiment" or "embodiments" throughout this specification mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Additionally, the term "or" is intended to mean an inclusive "or" rather than an exclusive "or". The term "about" or "approximately" as used herein is intended to mean that the recited nominal value is accurate within ±10% of the value presented, such that "about 10" would include 9 - 11.

[0053] The term "at least about" in relation to a measured amount refers to the normal variation in the measured amount as would be predicted by one of ordinary skill in the art in making a measurement, exercising a level of care commensurate with the precision of the object of the measurement and the measuring equipment, and any greater amount. In certain embodiments, the term "at least about" includes the amount obtained by subtracting 10% from the recited number, and any greater amount such that "at least about 10" would include 9 and greater than 9. This term can also be expressed as "about 10 or more". Similarly, the term "less than about" typically includes the amount obtained by adding 10% to the recited number, and any lesser amount such that "less than about 10" would include 11 and less than 11. This term can also be expressed as "about 10 or less".

[0054] The description of numerical ranges herein is intended to serve only as a shorthand way of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., "such as") provided herein is intended merely to illustrate particular materials and methods and is not limiting. No language in this specification should be construed as indicating any non-claimed element as essential to the practice of the disclosed materials and methods.

[0055] The operations of the methods herein are shown and described in a particular order, but the order of each method operation can be changed so that a particular operation can be performed in the reverse order, or so that a particular operation can be performed at least partially concurrently with other operations. In another embodiment, the instructions or sub-operations of separate operations can be in an intermittent and / or alternating manner.

[0056] It should be understood that the above specification is exemplary and not intended to be limiting. Many other embodiments will be apparent to those of ordinary skill in the art upon reading and understanding the above specification. Accordingly, the scope of the present disclosure should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

Claims

1. At least one light source configured to emit a light beam onto a substrate through a lens; At least one image sensor configured to detect reflected light rays from the substrate through the lens; At least one motor configured to move the lens to focus the light beam onto the substrate; A control device communicating with the at least one light source, the at least one image sensor, and the at least one motor, wherein the control device is configured to operate the at least one motor to move the lens in response to at least one signal from the at least one image sensor; The control device, a proportional-integral-derivative control method that uses the centroid of the autofocus signal from one or more autofocus channels associated with the at least one light source and the at least one image sensor as a feedback signal, or a Kalman filter control method that uses the centroid of the autofocus signal from one or more autofocus channels associated with the at least one light source and the at least one image sensor as a feedback signal, or a proportional-integral-derivative control method with dynamic channel selection that uses the centroid of the autofocus signal from one or more autofocus channels associated with the at least one light source and the at least one image sensor as a feedback signal, or an empirical reference position control method that uses the centroid of the real-time autofocus signal from one or more autofocus channels associated with the at least one light source and the at least one image sensor as a feedback signal is configured to operate the at least one motor while the light beam scans the substrate using at least one of them; A digital lithography system.

2. The system according to claim 1, wherein the at least one light source comprises at least one of a laser, a continuous wave (CW) laser, a quality (Q) switched laser, or a mode-locked laser.

3. The system according to claim 1, wherein the substrate comprises at least one material of glass, a reflective material, metal, chromium, polymer, crystal, or oxide.

4. The system according to claim 1, wherein the lens comprises at least one of an optical lens, a spherical lens, or an aspherical lens.

5. The system according to claim 1, wherein the at least one image sensor comprises at least one of a linear image sensor, a complementary metal oxide semiconductor (CMOS) or active pixel image sensor, a charge coupled device (CCD) image sensor, or a solid state device.

6. The system according to claim 1, wherein the at least one motor comprises a linear motor comprising at least one of a piezoelectric motor, an ultrasonic motor, an ultrasonic resonance motor, a piezo stepper motor, a piezo walk motor, a piezo stick slip motor, a flexure type motor, or an inertia motor.

7. A plurality of light sources each configured to emit a light beam onto a substrate through a lens, A plurality of image sensors each configured to detect a reflected light beam from the substrate through the lens, wherein each light source is paired with each image sensor, At least one motor configured to move the lens to focus the light beam onto the substrate, A plurality of autofocus channels each associated with at least one of the plurality of light sources and at least one of the plurality of image sensors, A control device in communication with the plurality of light sources, the plurality of image sensors, and the at least one motor, The control device operates the at least one motor to move the lens in response to one or more signals from the plurality of image sensors while the light beam scans the substrate, The control device, while the light beam scans the substrate, Uses a proportional integral derivative control method that uses the signal centroid of autofocus from one or more autofocus channels as a feedback signal, or Uses a Kalman filter control method that uses the signal centroid of autofocus from one or more autofocus channels as a feedback signal, or Uses a proportional integral derivative control method with dynamic channel selection that uses the signal centroid of autofocus from one or more autofocus channels as a feedback signal, or Using an empirical reference position control method that uses the signal centroid of real-time autofocus from the one or more autofocus channels as a feedback signal, actuating the at least one motor, a digital lithography system. **Claim 8** In a digital lithography system, a method for automatically focusing a light beam while the light beam scans a substrate, comprising: directing at least one light beam from at least one light source onto the substrate through a lens; reflecting the at least one light beam from the substrate through the lens onto at least one image sensor; receiving, by a control device, at least one signal from the at least one image sensor, the at least one signal indicating a position of the at least one light beam on the substrate; controlling, by the control device, a position of the lens for focusing the at least one light beam onto a surface of the substrate while the at least one light beam scans the substrate; one or more autofocus channels are associated with the at least one light source and the at least one image sensor; the control device uses a proportional-integral-derivative control method that uses the signal centroid of autofocus from the one or more autofocus channels as a feedback signal, or uses a Kalman filter control method that uses the signal centroid of autofocus from the one or more autofocus channels as a feedback signal, or uses a proportional-integral-derivative control method with dynamic channel selection that uses the signal centroid of autofocus from the one or more autofocus channels as a feedback signal, or uses an empirical reference position control method that uses the signal centroid of real-time autofocus from the one or more autofocus channels as a feedback signal. A method. **Claim 9** The method of claim 8, further comprising calibrating the signal from the at least one image sensor by correlating a change in length (ΔL) of the reflected light beam along the length of the at least one image sensor with a change in height (ΔZ) of the surface of the substrate. **Claim 10** The method according to claim 8, wherein controlling the position of the lens includes operating at least one motor to move the lens. **Claim 11** The method according to claim 10, wherein the at least one motor is a linear motor selected from the group consisting of a piezoelectric motor, an ultrasonic motor, an ultrasonic resonance motor, a piezo stepper motor, a piezo walk motor, a piezo stick slip motor, a flexure type motor, and an inertia motor. **Claim 12** The method according to claim 8, wherein the substrate comprises at least one material selected from the group consisting of glass, a reflective material, metal, chromium, a polymer, a crystal, or an oxide. **Claim 13** The method according to claim 8, wherein the at least one image sensor is selected from the group consisting of a linear image sensor, a complementary metal oxide semiconductor (CMOS) or active pixel image sensor, a charge coupled device (CCD) image sensor, and a solid state device.

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