Reserving spatial light modulator sections to address field non-uniformities

Abstract

To provide improved photolithography systems and methods using a digital micromirror device (DMD).SOLUTION: The DMD comprises columns and rows of micromirrors disposed opposite a substrate. Light beams reflect off the micromirrors onto the substrate, resulting in a patterned substrate. Certain subsets of the columns and rows of micromirrors may be positioned to the "off" position, such that they dump light, in order to correct for uniformity errors, i.e., features larger than desired, in the patterned substrate. Similarly, certain subsets of the columns and rows of micromirrors may be defaulted to the "off" position and selectively allowed to return to their programmed position in order to correct for uniformity errors, i.e., features smaller than desired, in the patterned substrate.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001]

[0001] Embodiments of the present disclosure relate generally to apparatus, systems, and methods for processing one or more substrates, and more particularly to apparatus, systems, and methods for performing photolithography processes. More particularly, embodiments of the present disclosure relate to improved apparatus, systems, and methods for addressing field non-uniformities in a substrate during processing. [Background technology]

[0002]

[0002] Photolithography is widely used in the manufacture of semiconductor devices and display devices such as liquid crystal displays (LCDs). 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 screen devices, personal digital assistants (PDAs), mobile phones, television monitors, and the like. Flat panels typically contain a layer of liquid crystal material forming pixels sandwiched between two plates. When power from a power source is applied across the liquid crystal material, the amount of light that passes through the liquid crystal material is controlled at the location of the pixel, thereby allowing an image to be generated.

[0003]

[0003] Microlithography techniques have been used to create electrical features that are incorporated as part of the liquid crystal material layer that forms the pixels. According to this technique, a light-sensitive photoresist is applied to at least one surface of a substrate. A pattern generator then exposes selected areas of the light-sensitive photoresist to light as part of a pattern, causing chemical changes in the photoresist in the selected areas and preparing those selected areas for subsequent material removal and / or material addition steps to create the electrical features.

[0004]

[0004] In order to continue to provide display devices and other devices at prices that consumers demand, new apparatus and approaches are needed to accurately and cost-effectively produce patterns on substrates, such as large area substrates. Summary of the Invention

[0005]

[0005] Embodiments of the present disclosure generally provide improved photolithography systems and methods that use spatial light modulators such as digital micromirror devices (DMDs). In one embodiment, a DMD device is disclosed. The DMD comprises an array of micromirrors positioned opposite a substrate. A light beam reflects off the micromirrors to the substrate, resulting in a patterned substrate. A particular subset of the array of micromirrors may be placed in an "off" position, which dumps light to correct for uniformity errors (i.e., accumulated exposure in the patterned substrate). Similarly, a particular subset of the array of micromirrors may be defaulted to an "on" position and selectively enabled to return to a programmed position to correct for uniformity errors (i.e., exposed area in the patterned substrate).

[0006] In one embodiment, a method of patterning a substrate using a DMD is disclosed. After the DMD scans the substrate, the substrate is evaluated for uniformity errors. If an area is found to be overexposed, a subset of the columns of the DMD are set to an "off" position, so that the light beam is reflected to a light dump instead of being reflected to the patterned substrate. As a result, the pattern in the designated area of ​​the substrate is attenuated.

[0007]

[0007] In another embodiment, another method of patterning a substrate using a DMD is disclosed. Before the DMD scans a substrate, a subset of the DMD's micromirror rows are set to an "off" position and act as spares. After the DMD scans the substrate, the substrate is evaluated for uniformity errors. If underexposed areas are found, a subset of the spare rows are activated and the micromirrors are positioned as programmed. This results in a assisted pattern (i.e., increased exposures) in designated areas of the substrate.

[0008] So that the above-mentioned features of the present disclosure can be understood in detail, a more particular description of the present disclosure briefly summarized above can be had by reference to embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the present disclosure is open to other equally effective embodiments, and therefore, that the accompanying drawings illustrate only typical embodiments of the present disclosure and should not be considered as limiting the scope of the present disclosure. [Brief description of the drawings]

[0009] [Figure 1A] FIG. 1 is a perspective view of a photolithography system according to an embodiment disclosed herein. [Figure 1B] FIG. 1 is a perspective view of a photolithography system according to an embodiment disclosed herein. [Figure 2A] 1 is a schematic perspective view of an image projection device according to an embodiment disclosed herein. [Figure 2B] 1 is a schematic perspective view of an image projection device according to an embodiment disclosed herein. [Diagram 3] FIG. 1 is a schematic diagram of a digital micromirror device according to an embodiment disclosed herein. [Figure 4] FIG. 1 is a flow diagram of a method for patterning a substrate according to an embodiment disclosed herein. [Diagram 5] FIG. 1 is a flow diagram of a method for patterning a substrate according to an embodiment disclosed herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010]

[0009] To facilitate understanding, wherever possible, like reference numerals have been used to designate like elements common to the figures. Furthermore, elements of one embodiment may be advantageously adapted for use in other embodiments described herein.

[0011]

[0010] The embodiments of the present disclosure generally provide improved photolithography systems and methods using a digital micromirror device (DMD). In one embodiment, a DMD device is disclosed. The DMD comprises an array of micromirrors positioned opposite a substrate. A light beam reflects off the micromirrors to the substrate, resulting in a patterned substrate. A particular subset of the array of micromirrors may be placed in an "off" position, which dumps light by reducing the number of exposures to the patterned substrate to correct for uniformity errors. Similarly, a particular subset of the array of micromirrors may be placed in an "off" position by default and selectively enabled to return to a programmed position by increasing the number of exposures provided to the patterned substrate to correct for uniformity errors.

[0012] 1A is a perspective view of a photolithography system 100 according to an embodiment disclosed herein. The system 100 includes a base frame 110, a slab 120, a stage 130, and a processing device 160. The base frame 110 sits on the floor of a manufacturing facility and supports the slab 120. A passive pneumatic isolator 112 is positioned between the base frame 110 and the slab 120. In one embodiment, the slab 120 is a one-piece piece made of granite, and the stage 130 is placed on the slab 120. A substrate 140 is supported by the stage 130. A number of holes (not shown) are formed in the stage 130, allowing a number of lift pins (not shown) to extend therethrough. In some embodiments, the lift pins rise to an extended position to receive the substrate 140 from one or more transfer robots (not shown), or the like. One or more transfer robots are used to load and unload the substrate 140 onto and from the stage 130 .

[0013]

[0012] The substrate 140 comprises any suitable material, for example, quartz, which is used as part of a flat panel display. In other embodiments, the substrate 140 is made of other materials. In some embodiments, the substrate 140 has a layer of photoresist formed thereon. The photoresist is sensitive to radiation. A positive photoresist includes portions of the photoresist that, when exposed to radiation, are respectively soluble in a photoresist developer. The photoresist developer is applied to the photoresist after a pattern has been written into the photoresist. A negative photoresist includes portions of the photoresist that, when exposed to radiation, are respectively insoluble in a photoresist developer. The photoresist developer is applied to the photoresist after a pattern has been written into the photoresist. 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. In this embodiment, a pattern is generated on the surface of the substrate 140 to form electronic circuits.

[0014]

[0013] The system 100 includes a pair of supports 122 and a pair of tracks 124. The pair of supports 122 is disposed on a slab 120. The slab 120 and the pair of supports 122 are a single piece of material. The pair of tracks 124 are supported by the pair of supports 122, and the stage 130 moves in the X-direction along the tracks 124. In one embodiment, the pair of tracks 124 are a pair of parallel magnetic channels. As shown, each track 124 in the pair of tracks 124 is linear. In other embodiments, one or more of the tracks 124 are non-linear. An encoder 126 is coupled to the stage 130 to provide position information to a controller (not shown).

[0015] The processing device 160 includes a support 162 and a processing unit 164. The support 162 is disposed on the slab 120 and includes an opening 166 for the stage 130 to pass under the processing unit 164. The processing unit 164 is supported by the support 162. In one embodiment, the processing unit 164 is a pattern generator configured to expose a photoresist in a photolithography process. In some embodiments, the pattern generator is configured to perform a maskless lithography process. The processing unit 164 includes a plurality of image projection devices (shown in FIGS. 2A and 2B). In one embodiment, the processing unit 164 includes as many as 84 image projection devices. Each image projection device is disposed in a case 165. The processing device 160 is useful for performing maskless direct patterning.

[0016] In operation, the stage 130 moves in the X direction from a loading position shown in FIG. 1A to a processing position. The processing position is one or more positions of the stage 130 as it passes under the processing units 164. In operation, the stage 130 is lifted by a number of air bearings (not shown) and moves from the loading position to the processing position along the pair of tracks 124. A number of vertical guiding air bearings (not shown) are coupled to the stage 130 and positioned adjacent the inner walls 128 of each support 122 to stabilize the movement of the stage 130. To process and / or index the substrate 140, the stage 130 also moves in the Y direction by moving along the track 150. The stage 130 is capable of independent movement, capable of scanning the substrate 140 in one direction and stepping in the other direction.

[0017]

[0016] The metrology system measures in real time the X and Y lateral position coordinates of each stage 130 so that each of the multiple image projection devices can accurately pinpoint the location of the pattern being written onto the photoresist covered substrate. In addition, the metrology system provides a real-time measurement of the angular position of each stage 130 about the vertical or Z axis. The angular position measurement can be used to keep the angular position constant during a servomechanical scan, or can be used to apply corrections to the position of the pattern being written onto the substrate 140 by the image projection device 270 shown in Figures 2A-2B. These techniques can be used in combination.

[0018] 1B is a perspective view of a photolithography system 200 according to an embodiment disclosed herein. The system 200 is similar to the system 100, but the system 200 includes two stages 130. Each of the two stages 130 is capable of independent operation, scanning the substrate 140 in one direction and advancing in the other direction. In some embodiments, while one of the two stages 130 is scanning the substrate 140, the other of the two stages 130 unloads the exposed substrate and loads the next substrate to be exposed.

[0019] 1A and 1B depict two embodiments of a photolithography system, other systems and configurations are contemplated herein. For example, photolithography systems including any suitable number of stages are contemplated.

[0020]

[0019] Figure 2A is a schematic perspective view of an image projection device 270 according to an embodiment, useful in a photolithography system such as system 100 or system 200. The image projection device 270 includes one or more spatial light modulators 280, an alignment and inspection system 284 including a focus sensor 283 and a camera 285, and a projection optical system 286. The components of the image projection device vary depending on the spatial light modulator used. Spatial light modulators include, but are not limited to, micro LEDs, VCSELs, any solid-state emitter of electromagnetic radiation, digital micromirror devices (DMDs), and liquid crystal displays (LCDs).

[0021] In operation, the spatial light modulator 280 is used to modulate one or more properties of light (e.g., amplitude, phase, or polarization). This light is projected through the image projection device 270 onto a substrate (e.g., substrate 140). The alignment and inspection system 284 is used for alignment and inspection of the components of the image projection device 270. In one embodiment, the focus sensor 283 includes multiple lasers. The multiple lasers are directed through the lens of the camera 285 and back through the lens of the camera 285, and imaged onto a sensor to detect whether the image projection device 270 is in focus. The camera 285 is used to image the substrate (e.g., substrate 140) to ensure that the alignment of the image projection device 270 and the photolithography system 100 or 200 is accurate or within a predetermined tolerance. The projection optics 286 (e.g., one or more lenses) are used to project the light onto the substrate (e.g., substrate 140).

[0022]

[0021] Figure 2B is an image projection device 281 according to an embodiment described herein. In the embodiment shown in Figure 2B, the image projection device 281 uses one or more DMDs 289 as spatial light modulators. The image projection device 281 is part of an image projection system 290, which includes a light source 272, an aperture 274, a lens 276, a frustrated prism assembly 288, one or more DMDs 289 (one shown), and a light dump 282, in addition to an alignment and inspection system 284 and a projection optics 286. The light source 272 is any suitable light source (e.g., a light emitting diode (LED) or a laser) capable of generating light of a predetermined wavelength. In one embodiment, the predetermined wavelength is in the blue range or the near ultraviolet (UV) range (e.g., less than about 450 nm). The frustrated prism assembly 288 includes multiple reflective surfaces. As an example, the projection lens 286 is a 10x objective lens. During operation of the image projection device 281 shown in FIG. 2B, a light beam 273 having a predetermined wavelength (e.g., a wavelength in the blue range) is generated by a light source 272. The light beam 273 is reflected by a frustrated prism assembly 288 to a DMD 289. The DMD 289 includes a plurality of mirrors, the number of which corresponds to the number of pixels to be projected. The plurality of mirrors are individually controllable, and each micromirror of the plurality of mirrors is set to an on or off position based on mask data provided to the DMD 289 by a controller (not shown). When the light beam 273 reaches a mirror of the DMD 289, a mirror in the "on" position reflects the light beam 273 to a projection lens 286 (i.e., forming a plurality of writing beams). The projection lens 286 then projects the writing beam onto the surface of the substrate 140. A mirror in the "off" position reflects the light beam 273 to a light dump 282 instead of the surface of the substrate 140.

[0023]

[0022] In some cases, errors may occur that introduce uniformity errors across the field. For example, the light beam 273 projected onto the mirrors of the DMD 289 may have some errors, resulting in a higher intensity of light being projected onto some areas of the DMD 289 and a lower intensity of light being projected onto another area of ​​the DMD 289. As a result, multiple writing beams projected onto the surface of the substrate 140 may introduce uniformity errors, resulting in more light being projected onto some areas of the surface of the substrate 140 and less light being projected onto other areas of the surface of the substrate 140. The embodiments of the present disclosure improve upon methods and devices to reduce these uniformity errors.

[0024]

[0023] Figure 3 is a schematic diagram of a substrate 140 moving relative to a DMD 289. The mirrors of the DMD 289 are arranged in rows and columns. The total number of columns of mirrors of the DMD 289 is represented by the letter C. The substrate 140 moves at a particular speed relative to the DMD 289. Similarly, a light beam 273 is emitted from the light source 272 at regular intervals. The substrate 140 moves at a speed such that it travels a distance W in the X direction relative to the DMD 289 between flashes of the light beam 273. The distance W corresponds to the number of columns Q of mirrors of the DMD 289. The total number of exposures that the DMD 289 makes in one scan across the substrate 140 is represented by the letter T. The total number of columns C of mirrors of the DMD 280 divided by the total number of exposures T during one scan equals the number of columns Q that the DMD 280 moves in one interval.

[0025]

[0024] Figure 4 is a flow diagram of a method for patterning a substrate to provide attenuation of the light beam in areas of overexposure. At 410, the DMD 289 scans the substrate 140 and patterns the substrate as indicated by the solid-state programming device. At 420, the solid-state programming device evaluates the uniformity of the patterned substrate 140. In one embodiment, evaluating the uniformity of the patterned substrate 140 includes comparing the intensity or dimensions of features of the patterned substrate 140. At 430, the programming device identifies non-uniform areas of the patterned substrate. For example, non-uniform areas may be indicated by features that do not have the correct dimensions (i.e., features that are larger than intended in this embodiment). Features that are larger than intended can be corrected by reducing the number of exposures received in the areas of the patterned substrate 140 where the features appear. At 440, to correct for non-uniformity errors, the programming device designates a subset of the multiple columns and rows of micromirrors for attenuation during the next scan or scans of the DMD. At 450, the columns and rows of micromirrors designated for attenuation are those columns and rows in which the micromirrors are set to the "off" position, i.e., positioned to reflect the light beam 273 into a light dump rather than onto the surface of the substrate 140. At 460, the DMD scans the substrate again with the designated subset of columns and rows of micromirrors set to the "off" position. The period of time that the designated columns and rows of micromirrors are deactivated is the same period of time required for the DMD to scan the area designated for attenuation.

[0026]

[0025] The resulting scan results in an improvement in uniformity errors by reducing the number of exposures received in areas of the patterned substrate 140 where uniformity errors appear. In other words, the area designated for attenuation is exposed to one less pulse of the light beam 273 than the rest of the patterned substrate 140. For example, if the DMD 289 includes 1600 columns and an area of ​​the substrate is set to receive 190 pulses of the light beam 273, the number of columns that are set to the "off" position by default is equal to 1600÷190=8.42, which is rounded up to the nearest integer, or 8. The eight designated columns are set to "off" by default, regardless of the previously programmed pattern. As a result, in one scan of the DMD 289, the corresponding area of ​​the patterned substrate receives one less pulse than the rest of the patterned substrate. The resulting degree of attenuation in that area is 8 / 1600=0.5% attenuation. The uniformity improvement can be further limited to a precise subset of rows in a column designated for attenuation, rather than the entire column.

[0027]

[0026] Those skilled in the art will appreciate the methods used to reveal uniformity errors in a patterned substrate. Uniformity errors can be discovered by comparing features of the patterned substrate to a desired pattern and identifying features that differ from the desired pattern. Uniformity errors can also be discovered using a photodiode. For example, a photodiode or other sensor can record the intensity of light from the DMD 289 as the DMD scans across the substrate. The sensor can read the non-uniformity of the light emitter during the scan. Additionally, uniformity errors may be revealed after further processing of the patterned substrate. For example, if a further processing step causes an area of ​​the substrate to deflect, the deflection may indicate a uniformity error in the patterning of the substrate.

[0028] 5 is a flow diagram of a method of patterning a substrate to provide assistance in areas where uniformity errors appear, which can be corrected by increasing the number of exposures in areas of the patterned substrate 140 where features appear smaller than intended. At 510, the programming device designates a subset of the columns and rows of micromirrors of the DMD 289 to be deactivated and held in reserve for potential assistance. At 520, the programming device sets the designated subset of the columns and rows of micromirrors to an "off" position or deactivates them. At 530, the DMD 289 scans the substrate 140. During this scan, the micromirrors of the designated columns reflect the light beam 273 to a light dump. At 540, the programming device evaluates the uniformity of the patterned substrate 140. In one embodiment, evaluating the uniformity of the patterned substrate 140 includes comparing the intensity or dimensions of features of the patterned substrate 140 to a desired pattern. At 550, the programming device identifies non-uniform regions in the patterned substrate. For example, non-uniform regions may be indicated by features that do not have the correct dimensions (i.e., in this embodiment, features that are smaller than intended). Such features that are smaller than intended can be corrected by increasing the number of exposures over the number of exposures to the surrounding areas of the patterned substrate 140. At 560, to correct the non-uniformity errors, the programming device designates a subset of the multiple columns and rows of micromirrors that were held in reserve at 520 for assistance during the next scan or scans of the DMD 289. At 570, the columns and rows of micromirrors designated for assistance are those columns and rows of micromirrors set to programmed positions, i.e., columns and rows that are arranged according to a pattern, rather than deactivated or defaulted, to reflect the light beam 273 to a light dump. At 580, the DMD 289 scans the substrate again with the designated subset of the columns of micromirrors set to the patterned positions.The time period for activation of a designated column and row of micromirrors is at least the time period required for the DMD to scan the area designated for assistance.

[0029]

[0028] Situations may arise where one or more regions of non-uniformity requiring attenuation and one or more regions of non-uniformity requiring assistance appear on a single patterned substrate 140. In such cases, the DMD can be programmed to accommodate both attenuation and assistance in the appropriate regions.

[0030]

[0029] The embodiments disclosed herein provide methods and devices for improving uniformity errors when patterning a substrate using the DMD 289. These methods are an improvement over other methods that have been considered to address non-uniformity. For example, attempts have been made to randomly attenuate the exposure intensity by randomly selecting micromirrors to direct the light beam 273 to the light dump. However, this method resulted in "clumping," i.e., too many micromirrors being packed together that are programmed to dump the light beam 273. However, the embodiments disclosed herein provide a uniform method to address the problem of increasing or decreasing the exposure intensity without clumping.

[0031] While the above description is directed to embodiments of the disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, the scope of which is determined by the claims that follow.

Claims

1. 1. A method for patterning a substrate using a digital micromirror device including an array of micromirrors arranged in a plurality of columns and rows, comprising: scanning the substrate with the digital micromirror device; assessing the uniformity of the patterned substrate; Identifying non-uniform regions of the patterned substrate; designating a subset of the plurality of columns of micromirrors for attenuation; turning off the designated subset of the plurality of columns of micromirrors; Scanning the substrate with the digital micromirror device. A method comprising:

2. after turning off the designated subset of the plurality of columns of micromirrors; designating a subset of the plurality of rows of micromirrors for attenuation; turning off the designated subset of the plurality of rows of the micromirrors. The method of claim 1 further comprising:

3. Identifying the non-uniform regions of the patterned substrate includes locating areas of difference between the patterned substrate and a desired pattern; 2. The method of claim 1, wherein designating a subset of the plurality of columns of micromirrors for attenuation comprises selecting a subset of the plurality of columns that corresponds to the non-uniform region of the patterned substrate.

4. scanning the substrate with the digital micromirror device; a first exposure of the array of micromirrors to a light beam; a movement of the substrate position by a distance W; a second exposure of the array of micromirrors to the light beam; and The method of claim 1 , comprising:

5. 5. The method of claim 4, wherein the number of columns in the subset of the plurality of columns of micromirrors is equal to the number of columns of micromirrors at the distance W rounded to the nearest integer, and the movement of the distance W is determined by dividing the total number of columns of the digital micromirror device by the total number of exposures in one scan of the digital micromirror device.

6. 1. A method for patterning a substrate using a digital micromirror device including an array of micromirrors arranged in a plurality of columns and rows, comprising: scanning the substrate with the digital micromirror device, wherein a subset of a plurality of rows of the digital micromirror device are turned off during scanning; assessing the uniformity of the patterned substrate; Identifying non-uniform regions of the patterned substrate; designating a subset of the plurality of rows of micromirrors for assistance; and turning on the designated subset of the plurality of columns of micromirrors; Scanning the substrate with the digital micromirror device. A method comprising:

7. The method of claim 6 , wherein the designated subset of the plurality of columns of the micromirrors for assistance includes fewer than all rows in the subset of the plurality of columns.

8. Identifying the non-uniform regions of the patterned substrate includes locating areas of difference between the patterned substrate and a desired pattern; 7. The method of claim 6, wherein designating a subset of the plurality of rows of micromirrors for assistance comprises selecting a subset of the plurality of rows that corresponds to the non-uniform region of the patterned substrate.

9. scanning the substrate with the digital micromirror device; a first exposure of the array of micromirrors to a light beam; A change in distance W in the position of the substrate; and a second exposure of the array of micromirrors to the light beam; and The method of claim 6, comprising:

10. 10. The method of claim 9, wherein the number of columns in the subset of the plurality of columns of micromirrors is equal to the number of columns of micromirrors at the distance W rounded to the nearest integer, and the change in distance W is determined by dividing the total number of columns of the digital micromirror device by the total number of exposures in one scan of the digital micromirror device.

11. 1. A digital micromirror device for patterning a substrate, comprising: An array of micromirrors arranged in a plurality of columns and rows of micromirrors, some of the plurality of columns and rows of micromirrors configured to be activated or deactivated as a unit. Equipped with The digital micromirror device is in communication with a programming device, the programming device comprising: Identifying non-uniform regions of the patterned substrate; Designating some subset of the plurality of columns and rows of micromirrors to be activated or deactivated as a unit; A digital micromirror device configured to:

12. the number of columns and rows of the micromirrors being: Dividing a total number of micromirror rows in the plurality of rows of the micromirror device by a total number of exposures in a scan of the digital micromirror device; Rounding to the nearest integer The digital micromirror device of claim 11 , wherein the digital micromirror device is determined by:

13. The digital micromirror device of claim 11 , wherein some of the subsets of the multiple columns and rows of the micromirrors are activated or deactivated as a unit over a period of time, the period of time including the time required for the digital micromirror device to move across the non-uniform region of the patterned substrate.

14. The programming device, determining whether the non-uniform regions are regions of increased or decreased exposure relative to a surrounding field of the patterned substrate; deactivating some subset of the plurality of rows of micromirrors if the non-uniform regions are regions of increased exposure relative to a surrounding field of the patterned substrate. and further configured to: The digital micromirror device of claim 11.

15. 15. The digital micromirror device of claim 14, wherein the programming device is further configured to activate some subset of the multiple rows of micromirrors when the non-uniform regions are areas of reduced exposure relative to a surrounding field of the patterned substrate.

Images