Maskless lithographic printing method

Abstract

Various embodiments herein relate to methods of using maskless lithography to form layers. In these embodiments, the method implements a dose-varying staircase that divides a geometry into overlay portions. The overlay portions can include different doses for each portion to achieve control of the taper. The taper can be achieved by operating the geometric "mask data" into different dose overlay portions controlled by a pixel blending (PB) exposure technique. To perform the methods described herein, a maskless lithography tool is used. The maskless lithography tool includes a controller that performs software-based "mask data" operations. Because the method is performed masklessly by software without the additional mask cost and manufacturing time, there is greater flexibility to adjust the taper angle and / or photoresist thickness residuals of multi-tone / grey-tone mask features, which is an advantage over traditional lithography methods that use masks.

Description

[0001] background

[0002] field

[0003] The various implementations described herein generally relate to maskless lithography methods, and in particular, to methods for forming layers using maskless lithography.

[0004] Related technical descriptions

[0005] Photolithography is widely used in the manufacture of semiconductor devices and display devices, such as liquid crystal displays (LCDs). Large-area substrates are frequently used in LCD manufacturing. LCDs, or flat panels, are commonly used in active-matrix displays, such as computers, touch panel devices, personal digital assistants (PDAs), mobile phones, television displays, and similar devices. Generally, a flat panel may consist of a layer of liquid crystal material that forms pixels sandwiched between two panels. When energy from a power supply is applied to the entire liquid crystal material, the amount of light passing through the liquid crystal material can be controlled at the pixel location, thereby generating an image.

[0006] Microlithography is typically used to fabricate electrical feature structures incorporated into the liquid crystal material layer that forms pixels. According to this technique, light-sensitive photoresist is usually applied to at least one surface of a substrate. A pattern generator then exposes selected areas of the photoresist as part of a pattern with light, causing a chemical change in the photoresist within the selected areas, thus preparing the selected areas for subsequent material removal and / or material addition processes to fabricate the electrical feature structure.

[0007] Taper control is a well-known technique in the art for controlling the angle of photoresist sidewalls. This technique allows for a smooth taper profile, enabling good step-coverage in thin-film processes and allowing for changes in substrate structure angles to improve out-coupling efficiency in organic light-emitting diodes (OLEDs). Various methods, such as mask-based lithography systems, have been proposed to achieve taper controllability for fabricating intermediate thickness patterns in photoresist. However, mask-based lithography systems can present challenges. For example, fine-tuning the taper angle often requires removing and manipulating the mask to prepare more complex multitone patterns, which is time-consuming and costly. It is difficult to obtain the desired taper due to the difficulty in adjusting the mask's transparency (the concept of a gray-tone mask) or fine grating / slit (the concept of a gray-tone mask) to achieve the appropriate energy often exposed on the photoresist. Mask-based methods also cannot achieve "multitone process and taper control" together in a single printing step. This approach often increases mask complexity and cost. More complex multitone / gray-tone masks reduce mask production yield, thus tightening the process window for lithography. Furthermore, since process variation in lithography also affects taper effects and critical dimension variations, mask production requires extensive experimentation to recreate the mask, which, due to mask lead time, prolongs the entire process validation process.

[0008] Therefore, there is a need in this field to use a method based on maskless lithography to control the sidewall angle of photoresist. Summary of the Invention

[0009] One or more implementations described herein generally relate to methods for forming layers using maskless lithography.

[0010] In one embodiment, a method for forming a photoresist layer using a maskless lithography technique includes the following steps: obtaining a critical dimension of the photoresist layer; inputting a layer thickness and a tapered control angle determined based on the obtained critical dimension; calculating the geometric distance of the photoresist layer using the layer thickness and the tapered control angle; dividing the geometric distance into multiple pluralities of sections; determining the width of each of the multiple sections; and determining the dose size of each of the multiple sections.

[0011] In another embodiment, a method for forming a photoresist layer on a substrate using a maskless lithography technique includes the following steps: obtaining a first critical dimension of a first photoresist layer; inputting a first layer thickness and a first taper control angle determined based on the obtained first critical dimension; calculating a first geometric distance of the first photoresist layer using the first layer thickness and the first taper control angle; dividing the first geometric distance into a first plurality of portions; determining a first width of each of the first plurality of portions; determining a first dose size of each of the first plurality of portions; and forming a second photoresist layer on the first photoresist layer.

[0012] In another embodiment, a method for forming photoresist layers with varying photoresist residual thicknesses having a multi-tone / grayscale mask feature structure using a maskless lithography technique includes the following steps: obtaining a critical dimension of the photoresist layer; inputting a layer thickness and taper control angle determined based on the obtained critical dimension; calculating the geometric distance of the photoresist layer using the layer thickness and taper control angle; dividing the geometric distance into multiple portions; determining the width of each portion; determining the size of the multiple portions by a target photoresist residual thickness; and determining the dose size of each portion. Attached Figure Description

[0013] To gain a detailed understanding of the method with the aforementioned structural features described in this disclosure, a more specific description of the above-briefly presented disclosure can be obtained by referring to various embodiments, some of which are illustrated in the accompanying drawings. However, it should be noted that the drawings only illustrate several typical embodiments of this disclosure and should not be considered as limiting the scope of this disclosure, as this disclosure may acknowledge several other equivalent embodiments.

[0014] Figure 1 This is a perspective view of a system according to at least one embodiment described herein.

[0015] Figure 2This is a schematic diagram of a plurality of image projection systems according to at least one embodiment described herein.

[0016] Figure 3 It is a computing system according to at least one embodiment described herein.

[0017] Figure 4 This is a flowchart of a method according to at least one embodiment described herein.

[0018] Figure 5A and Figure 5B This is a schematic diagram of a layer formed on a substrate according to at least one embodiment described herein.

[0019] Figure 6A and Figure 6B These are top views and cross-sectional views of multiple parts formed using reverse tone printing according to at least one embodiment described herein.

[0020] Figure 7A and Figure 7B These are top views and cross-sectional views of multiple parts formed using positive tone printing according to at least one embodiment described herein.

[0021] Figure 8 This is a schematic diagram showing the relationship between multiple parts and cumulative dose size according to at least one embodiment described herein.

[0022] For ease of understanding, the same reference numerals have been used where possible to indicate common elements in the figures. Elements and features of one embodiment may be advantageously incorporated into several other embodiments without further description. Detailed Implementation

[0023] In the following description, numerous specific details are set forth to provide a more thorough understanding of various embodiments of this disclosure. However, it will be apparent to those skilled in the art that one or more embodiments of this disclosure may be practiced without one or more of these specific details. In other instances, well-known structural features have not been described to avoid obscuring one or more embodiments of this disclosure.

[0024] The various embodiments described herein generally relate to methods for forming layers using maskless lithography. In these embodiments, the method implements ladders of dose change. By overlaying multiple dose changes onto a designated area with a specific pattern design, a tapered profile with fine-tuning tapered angles can be achieved. When implementing ladders of dose change, the geometry can be divided into overlaying sections. These overlaying sections can include different doses for each section, thereby enabling desired tapered control.

[0025] Due to the nature of pixel blending (PB) and the division of multiple exposure levels to create such taper sections, the taper sections can be well controlled. Taper sections can be achieved by manipulating geometric “mask data” to cover portions exposed to various doses, controlled by PB exposure techniques. The cumulative energy magnitude of each distinct portion penetrates the depth of the photoresist, resulting in a smoother taper transition from bottom to top. In several embodiments described herein, this method can be applied to both one-dimensional (1D) and two-dimensional (2D) line space designs. To perform the methods described herein, a maskless lithography tool is used. The maskless lithography tool includes a controller that performs software-based “mask data” manipulation. Therefore, multi-layer taper control can be achieved without any additional steps. Furthermore, because these methods are performed masklessly by software, there is greater flexibility in adjusting taper angles without requiring any additional mask costs and manufacturing time, offering advantages over conventional lithography methods using masks.

[0026] Figure 1This is a perspective view of a system 100 according to at least one embodiment described herein. System 100 includes a base 102, a plate 104, two or more platforms 106, and a processing device 108. In some embodiments, a single platform 106 may be used. The base 102 may be placed on the floor of a manufacturing facility and support the plate 104. A passive air isolator 110 is positioned between the base 102 and the plate 104. The plate 104 may be a single piece of granite, and two or more platforms 106 are disposed on the plate 104. A substrate 112 is supported by each of the two or more platforms 106. A plurality of holes (not shown) are formed in the platforms 106 to allow a plurality of lifting rods (not shown) to extend through the platforms 106. The lifting rods can rise to an extended position to receive the substrate 112, for example, from a transfer robot (not shown). The transfer robot positions the substrate 112 on the lifting rod, which then gently lowers the substrate 112 onto the platform 106.

[0027] The substrate 112 may be made of, for example, quartz and serves as part of a flat panel display. In several other embodiments, the substrate 112 may be made of other materials. In some embodiments, a photoresist layer may be formed on the substrate 112. The photoresist is radiation-sensitive and may be a positive or negative photoresist, meaning that the portion of the photoresist exposed to radiation may be soluble or insoluble in a photoresist developer applied to the photoresist after pattern writing. The chemical composition of the photoresist determines whether it is a positive or negative photoresist. Exemplary photoresist chemical compositions may include at least one of diazonaphthoquinone, phenol formaldehyde resin, poly(methyl methacrylate), poly(methyl glutarimide), and SU-8. In this way, patterns can be formed on the surface of the substrate 112 to form electronic circuitry.

[0028] System 100 includes a pair of supports 114 and a pair of tracks 116. The pair of supports 114 are located on a plate 104, and both the plate 104 and the pair of supports 114 can be made of a single piece of material. The pair of tracks 116 are supported by the pair of supports 114, and two or more platforms 106 can move along the tracks 116 in the X direction. In one embodiment, the pair of tracks 116 are a pair of parallel magnetic channels. As shown, each track 116 of the pair of tracks 116 is linear. In several other embodiments, the tracks 116 may have a non-linear shape. An encoder 118 is coupled to each platform 106 to provide position information to a controller 302 (see [link to controller 302]). Figure 3 ).

[0029] In these embodiments, the processing device 108 includes a support 120 and a processing unit 122. The support 120 is disposed on a plate 104 and includes an opening 124 providing two or more platforms 106 passing beneath the processing unit 122. The processing unit 122 may be supported by the support 120. In some embodiments, the processing unit 122 is a pattern generator configured to expose photoresist in a lithographic printing process. The pattern generator is configured to perform a maskless lithographic printing process. The processing unit 122 may include multiple image projection systems (such as...) disposed in a case 126. Figure 2 (As shown). The processing device 108 can be used to perform maskless direct patterning. During operation, such as Figure 1 As shown, one of two or more platforms 106 moves in the X direction from a loading position to a processing position. The processing position may refer to one or more positions of the platform 106 as it passes under the processing unit 122. During operation, the two or more platforms 106 are lifted by a plurality of air bearings 132 and moved along a pair of tracks 116 from the loading position to the processing position. Each of the two or more platforms 106 can also move in the Y direction by moving along track 130 to process and / or index the substrate 112.

[0030] Figure 2 This is a perspective view of a plurality of image projection systems 200 according to at least one embodiment described herein. In these embodiments, each image projection system 200 generates multiple beams 202 onto a surface 204 of a substrate 112. As the substrate 112 moves in the X and Y directions, the entire surface 204 is patterned by the beams 202. The number of image projection systems 200 may vary depending on the size of the substrate 112 and / or the speed of the platform 106. Figure 1 ).

[0031] In these embodiments, each image projection system 200 includes a light source 206, an aperture 208, a lens 210, a mirror 212, a digital micromirror device (DMD) 214, a light dump 216, a camera 218, and a projection lens 220. The light source 206 may be a light-emitting diode (LED) or a laser, and the light source 206 may be capable of generating light with a predetermined wavelength. In some embodiments, the predetermined wavelength is in the blue or near-ultraviolet (UV) range, for example, less than about 450 nm. The mirror 212 may be a spherical mirror. The projection lens 220 may be a 10x objective lens. The DMD 214 may include multiple mirrors, the number of which may correspond to the resolution of the projected image.

[0032] During operation, a light beam 222 with a predetermined wavelength, such as wavelengths within the blue range, is generated by light source 206. The light beam 222 is reflected by mirror 212 onto DMD 214. DMD 214 includes multiple individually controllable mirrors, each of which can be in an "on" or "off" position based on mask data provided to DMD 214 via controller 302, as will be discussed below. Figure 3 Further description follows. When beam 222 reaches the mirror of DMD 214, the mirror in the "on" position reflects beam 222 (i.e., forming multiple beams 202) to projection lens 220. Then, projection lens 220 projects beam 202 onto surface 204 of substrate 112. The mirror in the "off" position reflects beam 222 to light collector 216 instead of surface 204 of substrate 112.

[0033] Figure 3 A computing system 300 according to at least one embodiment described herein is illustrated. As shown, the computing system 300 includes a plurality of servers 308, a focus-setting application server 310, and a plurality of controllers 302 (only two of the plurality of controllers 302 are shown for clarity), each controller 302 being connected to a communication network 306 (e.g., the Internet). Servers 308 can communicate with a database 312 via a local connection (e.g., a Storage Area Network (SAN) or Network Attached Storage (NAS)) or via the Internet. Servers 308 are configured to directly access data included in the database 312 or to connect to a database manager configured to manage data in the database 312.

[0034] Each controller 302 may include conventional components of a computing device, such as a processor, system memory, hard disk drive, battery, input devices such as a mouse and keyboard, and / or output devices such as a display or graphical user interface, and / or combined input / output devices such as a touch screen that not only receives input but also displays output. Each server 308 and focus setting application server 310 may include a processor and system memory (not shown) and may be configured to use, for example, relational database software and / or a file system to manage content stored in database 312. Server 308 may be programmed to communicate with another server 308, controller 302, and focus setting application server 310 using a network protocol such as TCP / IP. Focus setting application server 310 may communicate directly with controller 302 via communication network 306. Controller 302 is programmed to execute software 304, such as programs and / or other software applications, and access applications managed by server 308.

[0035] In the various embodiments described herein, a user can operate a controller 302 that is connected to a server 308 via a communication network 306. Pages, images, data, files, and similar information can be displayed to the user via the controller 302. Information and images can be displayed via a display device and / or a graphical user interface that communicates with the controller 302.

[0036] It should be noted that controller 302 can be a personal computer, portable mobile computing device, smartphone, video game console, home digital media player, network-connected television, set-top box, and / or other computing device with components suitable for communicating with communication network 306 and / or desired applications or software. Controller 302 is configured to operate method 400 below and can also execute other software applications.

[0037] Figure 4 This is a flowchart of a method 400 according to at least one embodiment described herein. In these embodiments, method 400 uses the above-described... Figures 1 to 3 The method may be performed using the systems and apparatus described herein, but is not limited to these systems and apparatuses; other similar systems and apparatuses may also be used. Method 400 uses a maskless lithography-based technique to form the photoresist layer. Figure 5A and Figure 5B This is a schematic diagram of a layer formed on a substrate according to at least one embodiment described herein. Figure 6A and Figure 6B These are top views and sectional views of multiple parts formed using inverted color printing according to at least one embodiment described herein. Figure 7A and Figure 7BThese are top views and sectional views of multiple parts formed using positive color printing according to at least one embodiment described herein. Figure 8 This is a schematic diagram showing the relationship between multiple portions of a plurality of components and cumulative dose magnitude according to at least one embodiment described herein. Figures 5A to 8 This helps explain method 400.

[0038] In block 402, the critical dimension can be obtained using a critical dimension scanning electron microscope (CD-SEM). In several other embodiments, the critical dimension can be obtained using a scanning electron microscope (SEM), a reflectometer thin film gauge, an ellipsometer thin film gauge, an atomic force microscope (AFM), a focused ion beam (FIB), a white light interferometry (WLI), a contact / non-contact type roughness gauge, or other similar devices. The obtained critical dimension can be... Figure 5A The critical dimension 501 is shown. In frame 404, the layer thickness (e.g., first layer thickness 502) and the taper control angle (e.g.) Figure 5A Angles A and B shown are input to controller 302. The first layer thickness 502 is determined, for example, by the thickness at critical dimension 501. Angles A and B are the angles between the surface of the second layer 510 of the photoresist and the top of critical dimension 501. In box 406, geometric distances are calculated using the first layer thickness 502 and angles A and B, for example... Figure 5A The geometric distances 504 and 505 are shown in the diagram. More specifically, geometric distances 504 and 505 are calculated by dividing the first layer thickness 502 by the tangents of angles A and B. For example, the calculation can be expressed using the following formula:

[0039] Z = X / tan(Y)

[0040] Z is the geometric distance 504 or 505, X is the first layer thickness 502, and Y is angle A or angle B. In some embodiments, the first layer thickness 502 is 4.5 micrometers, but it can also be other thicknesses.

[0041] Within frame 408, the geometric distance between photoresist layer 604 and photoresist layer 704 is divided into multiple portions 602 or 702. Figure 6A and Figure 7A For example, such as Figure 6A and Figure 7A As shown, multiple parts 602 and 702 can be divided into five parts, represented by parts A, B, C, D, and E. In box 410, the width of each of the multiple parts 602 or 702 is determined. In this example, the width of each part from A to E can be found using the following formula. Figure 6B and 7B As shown, the width of each section from A to E is represented by width A, width B, width C, width D, and width E. The formula is as follows:

[0042] Width A = Critical Size

[0043] Width B = A + Z / (N-1)*2

[0044] Width C = A + Z / (N-1)*4

[0045] Width D = A + Z / (N-1)*6

[0046] Width E = A + Z / (N-1)*8

[0047] Z is the geometric distance, and N is the total number of parts. Figure 6A and Figure 7A The example shown is 5).

[0048] In box 412, a linear relationship is used to determine the dosage of each of the multiple sections 602 and 702. First, there is a linear relationship between the layer depth and the layer width. For inverted color printing, such as... Figure 6A and Figure 6B As shown, the width increases linearly with the depth of penetration into the photoresist layer 604. For example, in Figure 6B The width E is greatest at section E. Section E is the deepest part of layer 604. Figure 6B The width A is smallest at part A, which corresponds to the top surface of photoresist layer 604, therefore its depth is zero to its minimum value. The opposite is true for positive tone printing, such as... Figure 7A and Figure 7B As shown. In this embodiment, the width decreases linearly with increasing depth into the photoresist layer 704.

[0049] In addition, such as Figure 8As shown in schematic diagram 802, there is a linear relationship between the depth of the photoresist layer and the dosage. In inverse-tone printing, the dosage increases linearly with increasing photoresist layer depth. Therefore, the dosage also increases linearly with increasing width, just as width increases linearly with increasing depth, as discussed above. For positive-tone printing, the dosage decreases linearly with increasing width because depth decreases linearly with increasing width. Figure 6B The width and depth of each of the multiple portions 602 of the photoresist layer 604 are shown. As illustrated, in reverse-tone printing, the width and depth increase from portion A to portion E. In reverse-tone printing, portion A has the smallest width and depth, while portion E has the largest. As the width and depth decrease, the dose size decreases linearly. Conversely, Figure 7B This shows that in positive-tone printing, the width of each of the multiple portions 702 of the photoresist layer 704 increases as the depth decreases. Portion A has the smallest width but the largest depth, while portion E has the largest width and the smallest depth. Therefore, in reverse-tone printing, portion A has the smallest dose size, while portion E has the largest dose size, and vice versa for positive-tone printing, forming an "overlay dose." In other words, if the first layer 512 of the photoresist ( Figure 5A and Figure 5B The geometry of the object is divided into several covered sections, such as multiple sections 602 and 702, which allows for control of the tapered section. Therefore, depending on the geometry design, an island or line will be created in the case of a reverse color, and a trench or via will be created in the case of a positive color.

[0050] In the five sections of the first layer 512, the basic concept is that the total coverage dose of each layer reaches the dose threshold of the photoresist. Due to the nature of the coverage, the dose of each section can be cumulative. For example, the dose of section E can be 20%, the dose of section D can be 40%, the dose of section C can be 60%, the dose of section B can be 80%, and the dose of section A can be 100%. However, these dose values ​​can vary. In several other embodiments, asymmetric taper sections can be achieved at any desired angle by appropriately adjusting the positions of the sections.

[0051] In some implementations, such as Figure 5B As shown, method 400 produces multi-tone applications. Multi-tones include topography with two or more layers having the same or different thicknesses. Figure 5BThe diagram illustrates a two-layer configuration with contrasting tones, but it can also be applied to positive tones and / or multi-layer configurations. First, a first layer 512 with angles A and B and a first thickness 502 is formed by applying frames 402 to 412 as shown in method 400 above. In frame 414, the substrate 112 can be selectively removed from the processing apparatus. However, in several other embodiments, method 400 can be performed without forming the first layer 512. In frame 416, the same frames 402-412 used to form the first layer 512 can be used to form the second layer 510. Figure 5B As shown, the second layer thickness 503 is determined by the thickness at the critical dimension 506. Geometric distances 507 and 508 are calculated using the second layer thickness 503 and angles C and D, allowing the second layer 510 to be formed on the substrate 112 as intended. It should be noted that when constructing the second layer 510, the cumulative dose can be added from the cumulative dose of the first layer 512. For multi-tone applications, if the desired configuration includes islands and trenches, both inverse and positive tones can be applied simultaneously. Although a positive resist is described in these embodiments, these embodiments can be configured to use a negative resist.

[0052] Method 400 advantageously utilizes a maskless lithographic printing tool to easily achieve taper control. Therefore, multi-layer taper control can be achieved without any additional steps. Furthermore, since Method 400 is performed masklessly by software, it offers greater flexibility in adjusting taper angles, eliminating the need for additional mask costs and manufacturing time. It allows for the partial or overall creation of 3D symmetrical or asymmetrical taper sidewalls of any pattern shape with any desired angle on the substrate, offering advantages over conventional lithographic printing methods using masks.

[0053] By adjusting the number of portions, grayscale exposure of any pattern shape of photoresist residue of any desired thickness (for both positive and negative photoresists) can be achieved locally or entirely on the substrate, and can be freely combined with the aforementioned tapered portions, offering further advantages compared to traditional lithographic printing methods using masks.

[0054] While the foregoing describes several embodiments of the present invention, many other and further embodiments can be designed without departing from the basic scope of the present disclosure, the scope of which is defined by the appended claims.

Claims

1. A method for forming a photoresist layer using a maskless lithography technique, comprising the following steps: To obtain the critical dimension of the photoresist layer; Input the layer thickness and taper control angle determined based on the obtained critical dimensions; The geometric distance of the photoresist layer is calculated using the layer thickness and the taper control angle. The geometric distance is divided into multiple coverage areas; Determine the width of each of the plurality of covering portions, wherein the width increases or decreases linearly with increasing depth into the photoresist layer; and Determine the cumulative dose size for each of the plurality of coverage portions.

2. The method of claim 1, wherein the plurality of covering portions comprises portion A, portion B, portion C, portion D, and portion E.

3. The method of claim 2, wherein the cumulative dose of part B is 20% less than the cumulative dose of part A.

4. The method of claim 3, wherein the cumulative dose of part C is 20% less than the cumulative dose of part B.

5. The method of claim 4, wherein the cumulative dose of part D is 20% less than the cumulative dose of part C, and the cumulative dose of part E is 20% less than the cumulative dose of part D.

6. A method for forming multiple photoresist layers on a substrate using a maskless lithography technique, comprising the following steps: Obtain the first critical dimension of the first photoresist layer; Input the first layer thickness and the first taper control angle determined based on the obtained first critical dimension; The first geometric distance of the first photoresist layer is calculated using the first layer thickness and the first taper control angle. Divide the first geometric distance into a first plurality of coverage portions; A first width is determined for each of the first plurality of covered portions, wherein the first width increases or decreases linearly with increasing depth into the first photoresist layer; Determine a first cumulative dose size for each of the first plurality of coverage portions; and A second photoresist layer is formed on the first photoresist layer.

7. The method of claim 6, further comprising the following steps: Obtain the second critical dimension of the second photoresist layer; Input the second layer thickness and the second taper control angle determined based on the obtained second critical dimension; The second geometric distance of the second photoresist layer is calculated using the second layer thickness and the second taper control angle; Divide the second geometric distance into a second plurality of coverage portions; Determine the second width of each of the second plurality of covering portions; and Determine the second cumulative dose size for each of the second plurality of coverage portions.

8. The method of claim 7, wherein the method is performed without removing the substrate from the processing device.

9. The method of claim 7, wherein the method is performed by removing the substrate from the processing apparatus before forming the second photoresist layer.

10. A method for forming a photoresist layer using a maskless lithography technique, the photoresist layer having a different photoresist residual thickness beyond conventional multi-tone / grayscale mask feature structures, the method comprising the following steps: To obtain the critical dimension of the photoresist layer; Input the layer thickness and taper control angle determined based on the obtained critical dimensions; The geometric distance of the photoresist layer is calculated using the layer thickness and the taper control angle. The geometric distance is divided into multiple coverage areas; The width of each of the plurality of covered portions is determined, wherein the width increases or decreases linearly with increasing depth into the photoresist layer; The size of the plurality of covered portions is determined by the target photoresist residual thickness; and Determine the cumulative dose size for each of the plurality of coverage portions.

11. The method of claim 10, wherein the plurality of covering portions comprises portion A, portion B, portion C, and portion D.

12. The method of claim 11, wherein the cumulative dose of part B is 20% less than the cumulative dose of part A.

13. The method of claim 12, wherein the cumulative dose of part C is 20% less than the cumulative dose of part B.

14. The method of claim 13, wherein the cumulative dose of part D is 20% less than the cumulative dose of part C.

15. The method of claim 10, wherein the photoresist layer is a positive resist or a negative resist.

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