Systems, software applications, and methods for improving dose uniformity

Abstract

[0003] Embodiments of the present disclosure relate to a method, system, and apparatus for improving dose uniformity in a photolithography system. The method includes projecting a writing beam from a projection unit onto a mask to generate multiple incident beams, adjusting the projection unit to produce a distribution of incident angles corresponding to the incident beams, using a lens to focus the multiple incident beams onto a photoresist layer disposed above a substrate, removing portions of the photoresist layer to form a device pattern, and forming a structure on the substrate corresponding to the device pattern. The mask has a mask pattern corresponding to the device pattern. By focusing the multiple incident beams onto the photoresist, the swing curves of the incident beams interfere to reduce the amplitude of a composite swing curve of the incident beams, and the photoresist layer is developed with a photoresist pattern corresponding to the device pattern.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate generally to photolithography systems, and more particularly to systems and methods for improving dose uniformity in photolithography systems. [Background technology]

[0002] Photolithography is widely used in semiconductor device manufacturing, e.g., for back-end processing of semiconductor devices, and in display device manufacturing, e.g., for liquid crystal displays (LCDs). For example, large-area substrates are often used in the manufacture of display devices, such as optical chips used in augmented reality or virtual reality (AR / VR) devices. A photolithography system has a projection unit that projects a writing beam toward one or more masks. The one or more masks have patterns corresponding to the patterns to be written into a photoresist layer on the surface of the substrate. However, thickness variations (e.g., thickness non-uniformity) in the photoresist layer affect the light absorption uniformity (e.g., swing effect) of the photoresist layer. The light absorption uniformity of the photoresist affects the dose uniformity (e.g., exposure) of the photolithography system, which in turn affects the critical dimensions and electrical performance of semiconductor devices. Therefore, there is a need in the art for improved methods for lithography to reduce light absorption non-uniformity caused by non-uniform photoresist layers. Summary of the Invention

[0003] In one embodiment, a method is provided that includes projecting a writing beam from a projection unit onto a mask to generate a plurality of incident beams, adjusting the projection unit to produce a distribution of incident angles corresponding to the incident beams, using a lens to focus the plurality of incident beams onto a photoresist layer disposed above a substrate, removing portions of the photoresist layer to form a device pattern, and forming a structure on the substrate corresponding to the device pattern. The mask has a mask pattern corresponding to the device pattern. By focusing the plurality of incident beams onto the photoresist, swing curves of the incident beams interfere to reduce the amplitude of a composite swing curve of the incident beams, and the photoresist layer is developed with a photoresist pattern corresponding to the device pattern.

[0004] In another embodiment, a lithography system is disclosed. The lithography system includes a projection unit, a mask, and a lens. The projection unit is adjustable to change a distribution of incident angles corresponding to one or more incident light beams. The mask is disposed spaced apart from the projection unit in a projection direction. The mask has a mask pattern corresponding to a device pattern. The lens is spaced apart from the mask in the projection direction. The mask generates one or more incident light beams having corresponding swing curves from a writing beam projected from the projection unit. The one or more incident light beams are focused by the lens to reduce the amplitude of the composite swing curves of the incident light beams, and a photoresist layer is developed on a substrate with a photoresist pattern corresponding to the device pattern.

[0005] In another embodiment, a controller storing instructions is disclosed that, when executed by a computer processor, cause the controller to: store one or more mask patterns corresponding to one or more device patterns in a memory; write one of the one or more mask patterns corresponding to one of the one or more device patterns onto a mask; project a writing beam onto the mask using a projection unit to produce one or more incident light beams; calculate an angle of incidence for one of the one or more incident light beams; adjust the size and shape of the projection unit to change the angle of incidence of the incident light and reduce the amplitude of a resultant swing curve of the lithography system; focus the one or more incident light beams onto a photoresist layer disposed on a substrate using a lens; and generate a photoresist pattern on the photoresist layer corresponding to the mask pattern. The angle of incidence is calculated using a thickness of the photoresist layer and a wavelength of the incident light.

[0006] In order that the above-mentioned features of the present disclosure may be understood in detail, a more particular description of the present disclosure briefly summarized above can be made with reference to embodiments, some of which are shown in the accompanying drawings. It should be noted, however, that the accompanying drawings illustrate only typical embodiments of the present disclosure and therefore should not be considered as limiting the scope of the present disclosure, which may also encompass other equally effective embodiments. [Brief explanation of the drawings]

[0007] [Figure 1A] FIG. 1 is a schematic diagram of a lithography system in accordance with some embodiments. [Figure 1B] 1 is a schematic top view of a lens according to some embodiments. [Figure 2] 1 is a schematic diagram of a lithographic environment in accordance with some embodiments. [Figure 3A] 1 illustrates the interaction of a photoresist layer with incident light according to some embodiments. [Figure 3B]FIG. 1 illustrates a swing curve relationship between photoresist layer thickness and photoresist absorptivity, according to some embodiments. [Figure 4A] FIG. 1 illustrates the interaction of a photoresist layer with incident light having two incoherent source points, according to some embodiments. [Figure 4B] FIG. 10 illustrates the swing curve relationship between photoresist layer thickness and photoresist absorptivity for incident light with two incoherent source points, according to some embodiments. [Figure 5] FIG. 10 illustrates average swing curves from zeroth and first order incident light, according to some embodiments. [Figure 6A] 1 is a schematic top view of a circular illumination phase shift lens according to some embodiments. [Figure 6B] FIG. 1 is a schematic top view of a dipole illumination phase shift lens according to some embodiments. [Figure 7] 1 is a flow diagram of a method for a lithography process to reduce swing effects in a photoresist layer, according to some embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0008] To facilitate understanding, the same reference numerals have been used wherever possible to designate identical elements common to the figures, and it is believed that elements disclosed in one embodiment may be beneficially utilized in other embodiments, unless specifically stated otherwise.

[0009] Embodiments of the present disclosure relate to systems, methods, and apparatus for improving dose uniformity in a photolithography system. Some embodiments of the method include projecting a writing beam from a projection unit onto a mask to generate multiple incident beams, adjusting the size and shape of the projection unit to create a distribution of incident angles corresponding to the incident beams, using a lens to focus the multiple incident beams onto a photoresist layer disposed above a substrate, removing portions of the photoresist layer to form a device pattern, and forming a structure on the substrate corresponding to the device pattern. The mask has a mask pattern corresponding to the device pattern. By focusing the multiple incident beams onto the photoresist, swing curves of the incident beams interfere to reduce the amplitude of a composite swing curve of the incident beams, and the photoresist layer is developed with a photoresist pattern corresponding to the device pattern. A controller stores instructions that, when executed by a computer processor, cause the controller to perform operations of the method using the lithography system.

[0010] FIG. 1A is a schematic diagram of a lithography system 100. FIG. 1B is a schematic top view of a second lens 140. It should be understood that the lithography system 100 is an exemplary system, and that other systems may be used with or modified to achieve aspects of the present disclosure. The system includes a projection unit 102 including one or more light sources, such as light-emitting diodes (LEDs) or lasers, capable of projecting a writing beam 105 toward a mask 104. In some embodiments, a first lens 103 directs the writing beam 105 toward the mask 104. The mask 104 is disposed above a substrate 106. The mask 104 has a mask pattern corresponding to a device pattern for forming structures on the substrate 106 and / or a photoresist pattern for developing a photoresist layer 110 disposed above the substrate 106. The second lens 140 is disposed between the substrate 106 and the mask 104. In some embodiments, second lens 140 comprises any suitable material, such as fused silica, calcium fluoride, or other suitable material.

[0011] Substrate 106 may comprise any suitable material used as part of a flat panel display, such as glass. In some embodiments that can be combined with other embodiments described herein, substrate 106 is made of other materials that can be used as part of a flat panel display. In some embodiments that can be combined with other embodiments described herein, substrate 106 may have a surface width of about 300 mm to about 4000 mm, e.g., about 500 mm to about 3000 mm, e.g., about 1000 mm to about 2000 mm. In some embodiments, substrate 106 is a rectangular substrate having dimensions of about 300 x 400 mm to about 3000 x 3500 mm, e.g., about 2940 x 3370 mm.

[0012] In one embodiment, a film layer to be patterned, such as by pattern etching, is formed on the substrate 106, and a photoresist layer 110 sensitive to electromagnetic radiation, such as ultraviolet (UV), extreme ultraviolet (EUV), or deep UV light, is formed on the film layer to be patterned. In another embodiment, the photoresist layer 110 is deposited on the substrate 106, and the photoresist layer 110 is developed to provide a pattern for depositing a structure on the substrate 106. A positive-tone photoresist includes portions of the photoresist layer 110 that, when exposed to radiation, are soluble in a photoresist developer that is applied to the photoresist layer 110 after a pattern has been written into the photoresist layer 110 using electromagnetic radiation (e.g., light). A negative-tone photoresist includes portions of the photoresist layer 110 that, when exposed to radiation, are insoluble in a photoresist developer that is applied to the photoresist layer 110 after a pattern has been written into the photoresist layer 110 using electromagnetic radiation (e.g., light). Negative tone development involves a positive tone photoresist layer 110 being exposed through a bright field mask, where the exposed regions are insoluble in organic solvents (e.g., n-butanol), respectively, and remain on the substrate 106 after development. The chemical composition of the photoresist layer 110 determines whether the photoresist layer 110 is a positive tone photoresist or a negative tone photoresist. The photoresist layer 110 has a thickness t of about 0.5 μm to about 2 μm. In some embodiments, the thickness of the photoresist layer 110 is about 1 to about 4 times the size of the structures to be formed on the substrate 106. However, other thicknesses are contemplated.

[0013] During operation, the projection unit 102 projects a writing beam 105 (e.g., electromagnetic radiation or light) in a projection direction toward the mask 104 to develop the photoresist layer 110. In the illustrated embodiment, a first lens 103 focuses the light from the projection unit 102 toward the mask 104. The mask pattern of the mask 104 corresponds to a device pattern to be written in the photoresist layer 110 when the writing beam 105 is projected toward the mask 104. In some embodiments that can be combined with other embodiments described herein, the device pattern may correspond to a device to be patterned on the substrate 106. In other embodiments that can be combined with other embodiments described herein, the device pattern may correspond to one or more devices to be patterned in a film layer disposed on the substrate 106. The mask 104 generates one or more incident lights 120 from the writing beam 105. An image of the incident light 120 corresponding to the mask pattern may be generated on the second lens 140. An image of the incident light 120 is generated by a Fourier transform of the mask 104. The incident light 120 generates a first image 145A, a second image 145B, and a third image 145C. The second lens 140 focuses electromagnetic radiation (e.g., light) from one or more of the incident lights 120 toward the photoresist layer 110 to pattern the photoresist layer 110 with a photoresist pattern. For ease of illustration, the focusing of the incident light for the first image 145A is shown as first focused incident light 120A, the focusing of the incident light for the second image 145B is shown as second focused incident light 120B, and the focusing of the incident light for the third image 145C is shown as third focused incident light 120C. Nothing in this disclosure should be construed as imposing limitations regarding the manner in which the incident light 120 is focused toward the photoresist layer 110. The photoresist pattern corresponds to a device pattern. Portions of the photoresist layer 110 exposed to the incident light 120 according to the mask pattern are removed, exposing the substrate 106 or a thin film disposed on the substrate 106 .

[0014] In some embodiments, which may be combined with other embodiments described herein, the lithography system 100 is sized to be capable of exposing the entire photoresist layer 110 on the substrate 106. In other embodiments, the lithography system 100 is sized to be capable of exposing a portion of the photoresist layer 110 on the substrate 106. The substrate 106 is supported by a stage 116 operable to position the substrate 106 in a predetermined path under one or more masks 104. Movement of the substrate 106 may be controlled by a controller 108. The controller 108 is generally designed to facilitate control and automation of the lithography process based on a mask pattern file. The mask pattern file includes mask pattern data including instructions for positioning the mask 104 according to embodiments of the method 700 described herein. The controller 108 may be coupled to or in communication with at least the projection unit 102, the stage 116, and the encoder 118. The projection unit 102 and the encoder 118 may provide information regarding substrate processing and substrate alignment to the controller 108. For example, the projection unit 102 may provide information to the controller 108 to alert the controller 108 that substrate processing is complete.

[0015] 2 is a schematic diagram of a lithography environment 200. As shown in FIG. 2, the lithography environment 200 includes, but is not limited to, a virtual design device 202, a mask modeling device 204, a mask manufacturing device 206, a lithography system 100, a controller 108, and multiple communication links 201, as well as a transport system 203. Each lithography environment device is operatively connected to the controller 108 by the communication link 201. Alternatively or additionally, each lithography environment device can communicate indirectly by first communicating with the controller 108, which then communicates with the target lithography environment device. Each lithography environment device in the lithography environment 200 may be located in the same area or manufacturing facility, or in different areas.

[0016] The virtual design device 202 is operable to at least one of create, optimize, verify, and update a design file. The design file corresponds to a device pattern to be written in the photoresist layer 110. The mask modeling device 204 is operable to split the design file and generate a mask pattern file. The mask manufacturing device 206 is operable to receive mask pattern data for the mask 104 transmitted from the mask modeling device 204. According to operations of a method 700 described herein, the mask manufacturing device 206 is operable to manufacture a mask pattern for the mask 104 corresponding to the device pattern to be written in the photoresist layer 110 when the mask 104 is positioned according to embodiments described herein. In some embodiments, the mask 104 may be a conventional mask. In other embodiments, the mask 104 may be a phase-shift mask. In yet other embodiments, the mask 104 may be a digital mask. The lithography system 100 is operable to receive the mask 104 according to operations of the method 700 described herein.

[0017] The virtual design device 202, the mask modeling device 204, the mask making device 206, the lithography system 100, and the controller 108 each include an on-board processor and memory configured to store instructions corresponding to any portion of the method 700 described below. The communication link 201 may include at least one of a wired connection, a wireless connection, a satellite connection, etc. The communication link 201 includes sending and receiving a universal metrology file (UMF) or any other file used to store data, according to embodiments described further herein. The communication link 201 may include temporarily or permanently storing the file or data in a cloud before transferring or copying the file or data to a lithography system tool. The mask making device 206 and the mask modeling device 204 are connected by a transport system 203. The transport system 203 is operable to transport the substrate 106 between the mask making device 206 and the lithography system 100. In one embodiment, which may be combined with other embodiments described herein, the transport system 203 may include a robot or other device connectable to the controller 108 operable to transport the mask 104. In one embodiment, which may be combined with other embodiments described herein, the transport system 203 may be physically manipulated by a user.

[0018] The controller 108 includes a central processing unit (CPU) 212, support circuits 214, and memory 216. The CPU 212 may be one of any type of computer processor that can be used in an industrial environment to control lithography environment devices. The memory 216 is coupled to the CPU 212. The memory 216 may be one or more of readily available memory, such as random access memory (RAM), read-only memory (ROM), a floppy disk, a hard disk, or any other form of digital storage, local or remote. The support circuits 214 are coupled to the CPU 212 to support the processor in a conventional manner. These circuits include cache, power supplies, clock circuits, input / output circuitry, subsystems, etc. The controller 108 may include the CPU 212 coupled to input / output (I / O) devices in the support circuits 214 and the memory 216. For example, a metrology device may measure the thickness of the photoresist layer 110 and input the measurements to determine whether the photoresist layer 110 has been properly developed and patterned into a selected photoresist pattern.

[0019] The memory 216 may include one or more software applications, such as a control software program. The memory 216 may also include stored media data used by the CPU 212 to perform the method 700 described herein. The CPU 212 may be a hardware unit or combination of hardware units capable of executing software applications and processing data. The CPU 212 is generally configured to execute one or more software applications and process stored media data that may be contained within the memory 216. The controller 108 controls the transfer of data and files to and from various lithography environment devices. The memory 216 is configured to store instructions corresponding to any operation of the method 700 according to embodiments described herein. For example, the memory may store a recipe for developing the photoresist layer 110 and instructions for calculating recipe changes in response to input from a metrology device during development of the photoresist layer 110.

[0020] FIG. 3A illustrates the interaction of the photoresist layer 110 with incident light 320. FIG. 3B illustrates a swing curve 325 defined by the relationship between the thickness t of the photoresist layer 110 and the photoresist absorptivity. During development of the photoresist layer 110, as described above, electromagnetic radiation (e.g., incident light 320) is absorbed by the photoresist layer 110 to create a positive-tone or negative-tone photoresist layer 110. The photoresist absorptivity is defined as the ratio of the incident light 320 absorbed by the photoresist layer 110. The incident light 320 that is not absorbed by the photoresist layer 110 is either transmitted to a layer below the photoresist layer 110 (e.g., the substrate 106 or some other material deposited on the substrate 106) as transmitted light 321 or reflected from the surface of the photoresist layer 110 as reflected light 322. The photoresist absorptivity depends on the thickness t of the photoresist layer 110 or other optical properties such as opacity. The swing curve 325 is defined by the relationship curve between the photoresist absorbance and the photoresist thickness t. The amplitude of the swing curve 325 is affected by the thickness t of the photoresist layer 110 (e.g., decreasing the thickness of the photoresist layer 110 increases the amplitude of the swing curve 325). The period of the swing curve (e.g., swing period) is related to the wavelength (λ) of the incident light 320. When the incident light 320 is normal (e.g., perpendicular) to the top surface 324 of the photoresist layer 110, the swing period is λ / 2. When the incident light 320 obliquely exposes the top surface 324 of the photoresist layer 110, the swing period is λ / 2 × cos(α), where α is the angle between the vector V normal (e.g., perpendicular) to the top surface 324 of the photoresist layer 110 and the vector of the transmitted light 321. The swing curve 325 is also affected by the refractive indices of the photoresist layer 110 and the substrate 106; for example, a stronger reflection at the photoresist layer / substrate (PR / S) interface 330 increases the amplitude of the swing curve 325.

[0021] The formation of the photoresist layer 110 can inherently involve variations in thickness t (e.g., thickness non-uniformity) across the substrate 106. Thickness variation is the difference between the maximum and minimum points of the top surface 124 of the photoresist layer 110. Photoresist deposition techniques can result in up to 2-3% variation in the thickness of the photoresist layer 110 across the substrate 106, depending on the size of the substrate 106 and / or the deposition tool. A 1% thickness variation can have a 10%-20% impact on the amount of light absorbed by the photoresist layer 110 during development of the photoresist layer 110. Absorption non-uniformity affects the definition of the development of the photoresist layer and therefore the critical dimension (CD) of the pattern defined by the photoresist layer 110. A poorly defined pattern results in non-uniformity in the critical dimension (CD) of structures formed on the substrate 106, which can affect the electrical characteristics of semiconductor devices. Therefore, reducing the amplitude of the swing curve 325 of the photoresist layer 110 can improve CD consistency for structures formed on the substrate 106 of a semiconductor device.

[0022] 4A illustrates the interaction of a photoresist layer 110 with incident light having two incoherent source points. FIG. 4B illustrates a first swing curve 425A and a second swing curve 425B, which are defined by the relationship between the thickness of the photoresist layer 110 and the photoresist absorbance for incident light having two incoherent source points. In applications where the projection unit 102 for developing the photoresist layer 110 has two incoherent source points (e.g., when using a mask), the writing beam 105 becomes a first incident light 420A and a second incident light 420B. The first incident light 420A that is not absorbed by the photoresist layer 110 is transmitted to a layer below the photoresist layer 110 (e.g., the substrate 106 or some other material deposited on the substrate 106) as transmitted light 421A or is reflected from the surface of the photoresist layer 110 as reflected light 422A. The second incident light 420B that is not absorbed by the photoresist layer 110 is either transmitted to a layer below the photoresist layer 110 (e.g., the substrate 106 or some other material deposited on the substrate 106) as transmitted light 421B or reflected off the surface of the photoresist layer 110 as reflected light 422B. Each incident light 420A, 420B has its own swing curve 425A, 425B, respectively. The swing curves 425A, 425B can interfere with each other constructively or destructively, thus affecting the absorption non-uniformity and, therefore, the CD of the final structure on the substrate 106 of the semiconductor device.

[0023] In one embodiment, the mask 104 is a conventional photomask. The mask 104 generates at least 0th, +1st, and −1st order light from the incident light 120. In other embodiments, + / −nth order light is also possible, where n is an integer greater than or equal to 0. The first image 145A, the second image 145B, and the third image 145C are images of the incident light 120 generated on the second lens 140 by Fourier transforming the mask 104. Because the second lens 140 has finite dimensions, only low-order light (e.g., 0th and + / −1st order light) can pass through the second lens 140. The first focused incident light 120A illuminates the photoresist layer 110 at an angle normal (e.g., perpendicular) to the top surface 124 of the photoresist layer 110. The second and third converging incident beams 120B and 120C are focused toward the photoresist layer 110 and obliquely illuminate the top surface 324 of the photoresist layer 110. Therefore, the second and third converging incident beams 120B and 120C have a smaller swing period than the first converging incident beam 120A. The incidence angles α of the second and third converging incident beams 120B and 120C depend on the pitch (P) of the line-and-space pattern and the optical properties of the mask 104. The period of the line-and-space pattern is determined by the device pattern. The lithography system 100 is optimized to minimize the period of the line-and-space pattern. Because the projection unit 102 has a non-zero radius, the incidence angles may be different within each order (1, 2, ..., n-1, n) of the incident beam (e.g., the size and shape of the projection unit 102 may affect the swing curve of the incident beam). The angle of incidence of the nth order light in the photoresist layer 110 is calculated using Equation 1 below.

[0024]

number

[0025] where n is the order of light, and n PR is the refractive index of the photoresist layer 110.

[0026] 5 shows a composite swing curve 525C from a zero-order swing curve 525A and a + / - first-order swing curve 525B. The first focused incident light 120A, the second focused incident light 120B, and the third focused incident light 120C simultaneously illuminate the photoresist layer 110, producing a composite swing curve with a swing amplitude that is smaller than the individual swing amplitudes. The period (T) of the swing curve is calculated using Equation 2 below:

[0027]

number

[0028] Based on the thickness t of the photoresist layer 110, the light undergoes t / T cycles. The interference (I) between the 0th order swing curve 525A(T) and the + / -1st order swing curves 525B(T') is measured using Equation 3 below:

number

[0029] When interference is an integer, the swing curves interfere constructively. When interference (I) is an integer +0.5, the swing curves interfere destructively. When swing curves interfere destructively, the amplitude of the composite swing curve is reduced.

[0030] The amplitude of the composite swing curve 525C can be reduced by controlling the shape and size of the projection unit 102. By changing the size or shape of the projection unit 102, the first image 145A, the second image 145B, and the third image 145C are generated to correspond to the size and shape of the projection unit 102. The shapes and sizes of the first image 145A, the second image 145B, and the third image 145C create a distribution of incident angles α, which the second lens 140 focuses onto the photoresist layer 110. The difference in incident angle α creates a difference between the 0th order swing curve 525A and the + / −1st order swing curves 525B. For example, a larger projection unit 102 widens the width of the + / −1st order swing curves, where the width of the + / −1st order swing curves corresponds to the size of the projection unit 102. The wider + / −1st order swing curves create more destructive interference, thereby reducing the amplitude of the composite swing curve 525C. Therefore, the size and shape of projection unit 102 can be modified to achieve the angle of incidence required to reduce the amplitude of composite swing curve 525C according to equations 1-3.

[0031] Figure 6A is a schematic top view of a circular illumination phase shift lens 640A. Figure 6B is a schematic top view of a dipole illumination phase shift lens 640B. The phase shift lenses 640A and 640B are used with a phase shift mask 104 that does not have a zero-order incident light.

[0032] In one embodiment, the shape of the projection unit 102 is changed to a single circular projection unit 102. The circular projection unit 102 projects incident light through a phase-shift mask 104. The phase-shift mask 104 generates a first image 645A and a second image 645B on a circular illumination phase-shift lens 640A. The lens 640A focuses the +1st order incident light and the −1st order incident light toward the photoresist layer 110. By controlling the size and shape of the circular projection unit 102, a distribution of incident angles α is created, which are focused by the second lens 140. The distribution of incident angles α creates a difference between the +1st order swing curve and the −1st order swing curve, shifting the phase of the +1st order swing curve and the −1st order swing curve by 180 degrees, thereby reducing the amplitude of the composite swing curve 525C of the lithography system 100. In one embodiment, widening the projection unit 102 can increase the width of the swing curves from the + / -1 order incident light, and therefore interfere more destructively, reducing the amplitude of the resultant swing curve 525C.

[0033] In some embodiments, based on the thickness of the photoresist layer 110 and the wavelength of the incident light, the controller 108 can calculate the shape and size of the projection unit 102 required to produce the distribution of incident angles α needed to reduce the amplitude of the composite swing curve 525C for the lithography system 100 according to Equations 1-3. The controller 108 can further use machine learning to optimize an algorithm for calculating the angles of incidence based on the thickness of the photoresist layer 110 and store instructions in the memory 216 corresponding to the angles of incidence for the photoresist layer development strategy. Additionally, the controller 108 can monitor the development of the photoresist layer 110 using a metrology device and adjust the distribution of angles of incidence α or the wavelength of light to form the photoresist pattern.

[0034] In FIG. 6B, a dipole projection unit 102 is utilized to project incident light through a phase-shift mask 104. The dipole projection unit 102 includes a first projection unit and a second projection unit. In one embodiment, the wavelength of the light from the first projection unit is the same as the wavelength of the light from the second projection unit. In another embodiment, the wavelength of the light from the first projection unit is different from the wavelength of the light from the second projection unit. The dipole illumination phase-shift mask 104 generates a first image 645A, a second image 645B, a third image 645C, and a fourth image 645D on a dipole phase-shift lens 640B. The size and shape of the first projection unit and the second projection unit control the incident angle α of the + / − first-order incident light, thereby creating a distribution of incident angles α. The dipole phase shift lens focuses the + / -1 order incident light of the first projection unit and the + / -1 order incident light of the second projection unit toward the photoresist layer 110. By controlling the size and shape of the first projection unit and the second projection unit, the +1 order swing curves and the -1 order swing curves of the first projection unit and the second projection unit are 180 degrees out of phase, reducing the amplitude of the resultant swing curve 525C of the lithography system 100. In one embodiment, widening the first projection unit and the second projection unit can increase the width of the swing curves from the + / -1 order incident light and reduce the amplitude of the resultant swing curve 525C.

[0035] In some embodiments, based on the thickness of the photoresist layer 110 and the wavelength of the incident light, the controller 108 can calculate the shape and size of the first and second projection units required to produce the distribution of incidence angles α needed to reduce the amplitude of the composite swing curve 525 for the lithography system 100. The controller 108 can further use machine learning to optimize an algorithm for calculating the incidence angle α based on the thickness of the photoresist layer 110 and store instructions in the memory 216 corresponding to the incidence angle for the photoresist layer development strategy. Additionally, the controller 108 can use a metrology device to monitor the development of the photoresist layer 110 and adjust the incidence angle α or the wavelength of the light to form the photoresist pattern.

[0036] In yet another embodiment, the mask 104 is a digital mask 104. The digital mask 104 includes multiple mirrors that can be programmed to be switched "on" (e.g., making the mirrors reflective) or "off" (e.g., making the mirrors transparent / transparent). The mirrors can control the transmission of light through the digital mask toward the second lens 140, allowing for control of the transmission of the 0th order and + / -1st order swing curves. The size and shape of the projection unit 102 can be modified to control the distribution of the incidence angle α of the + / -1st order incident light. By controlling the incidence angle α, the + / -1st order swing curve and the 0th order swing curve of the projection unit 102 are 180 degrees out of phase.

[0037] In some embodiments, based on the thickness of the photoresist layer 110 and the wavelength of the incident light, the controller 108 can calculate the shape and size of the projection unit 102 needed to produce the distribution of incidence angles α needed to reduce the amplitude of the resultant swing curve for the lithography system 100. The controller 108 can further use machine learning to optimize algorithms for calculating the incidence angles and mirror programs based on the thickness of the photoresist layer 110 and store instructions in the memory 216 corresponding to the incidence angles for the photoresist layer development recipe. Additionally, the controller 108 can monitor the development of the photoresist layer 110 using a metrology device and adjust the incidence angles or wavelength of light for the photoresist pattern.

[0038] As a result of reducing the amplitude of the composite swing curve of lithography system 100, the dose uniformity and critical dimension variations may be reduced by about 5% to about 30%, such as by about 10% to about 25%.

[0039] 7 is a flow diagram of a method 700 of a lithography process for reducing swing effects in photoresist layer 110. In optional operation 701, a design file is created by virtual design device 202. The design file corresponds to a device pattern to be written in photoresist layer 110. In some embodiments, which may be combined with other embodiments described herein, the design file is created prior to the operations of method 700 described herein. In operation 702, mask modeling device 204 generates a mask pattern file having mask pattern data.

[0040] In operation 703, the mask manufacturing device 206 manufactures a mask pattern for the mask 104 that corresponds to a device pattern to be written in the photoresist layer 110 when the mask 104 is positioned according to embodiments described herein. The mask may be a conventional mask 104, a phase-shift mask, or a digital mask. In operation 704, the mask 104 is received by the lithography system 100 and positioned between the projection unit 102 and the second lens 140 according to the mask pattern data.

[0041] In operation 705, the projection unit 102 projects a writing beam 105 (e.g., electromagnetic radiation or light) toward the mask 104. In some embodiments, the writing beam 105 passes through a first lens 103 to direct the writing beam 105 toward the mask 104. The mask 104 generates at least one incident light 120, which generates an image 145. The size and shape of the projection unit 102 can vary the angle of incidence α of the at least one incident light 120. In one embodiment, changing the size of the projection unit creates a distribution of angles of incidence α. In one embodiment, the mask 104 is a conventional mask that generates a first image 145A, a second image, and a third image 145C on the second lens 140. In another embodiment, the mask 104 is a phase-shift mask that generates a +1 order image and a −1 order image.

[0042] one perpendicular to the top surface 124 of the substrate 106, a second image 145B obliquely contacting the top surface 124 of the substrate 106, and a third focused incident light 120C obliquely contacting the top surface 124 of the substrate 106. one obliquely contacting the top surface 124 of the substrate 106, and a -1 order incident light obliquely contacting the top surface 124 of the substrate 106.

[0043] In operation 706, second lens 140 focuses incident light 120 toward photoresist layer 110. In embodiments in which a conventional mask 104 is utilized, second lens 140 focuses incident light from first image 145A, second image 145B, and third image 145C toward photoresist layer 110. For ease of illustration, the focusing of incident light for first image 145A is shown as first focused incident light 120A, the focusing of incident light for second image 145B is shown as second focused incident light 120B, and the focusing of incident light for third image 145C is shown as third focused incident light 120C. Nothing in this disclosure should be construed as imposing any limitations regarding the manner in which incident light 120 is focused toward photoresist layer 110. The first focused incident light 120A may correspond to 0th order incident light, and the second focused incident light 120B and the third focused incident light 120C may correspond to + / -1st order incident light directed toward the photoresist layer 110.

[0044] Based on the size and shape of the projection unit, the distribution of the angles of incidence of the incident light 120 causes the swing curves of the +1st and −1st order incident light to be 180 degrees out of phase with each other from the swing curve of the 0th order incident light, thereby reducing the amplitude of the resultant swing curve of the lithography system 100. In embodiments where a phase-shift mask 104 is utilized, the second lens 140 focuses the + / −1st order incident light toward the photoresist. Based on the size and shape of the projection unit, the distribution of the angles of incidence of the incident light causes the swing curves of the +1st and −1st order incident light to be 180 degrees out of phase with each other, thereby reducing the amplitude of the resultant swing curve of the lithography system 100. In embodiments with a digital mask, multiple programmable mirrors can control the transmission of light through the digital mask toward the second lens 140, allowing the second lens 140 to control the 0th and + / −1st order swing curves. Based on the size and shape of the projection unit, the distribution of incident angles of the incident light causes the swing curve of the +1st order incident light and the swing curve of the −1st order incident light to be 180 degrees out of phase with the swing curve of the 0th order incident light, reducing the amplitude of the resultant swing curve of the lithography system 100. In one embodiment, the method includes programming a programmable mirror to be either transparent or reflective to control the transmission of light through the digital mask.

[0045] In operation 707, the focused incident light develops the photoresist layer 110 in a pattern to form a plurality of structures on the substrate 106. After the incident light 120 develops the photoresist layer 110, portions of the photoresist layer 110 are dissolved to form the pattern. In one embodiment, the pattern exposes a film layer disposed on the substrate 106 that can be etched to form structures on the substrate 106. In another embodiment, the pattern exposes the substrate 106 to allow for deposition of structures onto the substrate 106.

[0046] The controller 108, which includes a central processing unit (CPU) 212, support circuits 214, and memory 216, may be coupled to or in communication with at least the projection unit 102, the stage 116, and the encoder 118. The projection unit 102 and encoder 118 may provide information to the controller 108 regarding substrate processing and the angle of incidence. For example, the projection unit 102 may provide information to the controller 108 to alert the controller 108 that substrate processing is complete or that the angle of incidence is not aligned with the photoresist layer development recipe. In some embodiments, the size and shape of the projection unit 102 may be controlled by the controller 108 to control the angle of incidence α of the + / − first order incident light. Based on the thickness of the photoresist layer 110 and the wavelength of the incident light, the controller 108 may calculate the size and shape of the projection unit 102 required to produce the distribution of angles of incidence α required to reduce the amplitude of the resultant swing curve 525 for the lithography system 100. The controller 108 can further use machine learning to optimize an algorithm for calculating the angle of incidence based on the thickness of the photoresist layer 110 and store instructions corresponding to the angle of incidence for the photoresist layer development strategy in the memory 216. Additionally, the controller 108 can use a metrology device to monitor the development of the photoresist layer 110 and adjust the angle of incidence α of the light or the wavelength of the light to form the photoresist pattern.

[0047] In summary, a lithography process method and system are disclosed that provide an improved method for reducing light absorption non-uniformity caused by a non-uniform photoresist layer. The system projects a writing beam from a projection unit toward a mask, generating multiple incident light beams. The incident light beams generate images of the pattern from the mask on a lens, which focuses the incident light beams toward the non-uniform photoresist. By measuring the thickness of the photoresist layer and controlling the size and shape of the projection unit, the necessary angle of incidence can be achieved to reduce the amplitude of the system's resultant swing curve. Reducing the amplitude of the resultant swing curve reduces the light absorption non-uniformity in the photoresist layer. The absorption non-uniformity affects the definition of the development of the photoresist layer and therefore the critical dimension (CD) of the resulting optical device. A controller can optimize the size and shape of the projection unit using machine learning. The controller can monitor the development of the photoresist layer during lithography and adjust the size and shape of the projection unit to optimize the lithography.

[0048] While the foregoing is directed to several embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, the scope of the present invention being determined by the appended claims.

Claims

1. projecting a writing beam from a projection unit onto a mask to form a plurality of incident beams, the mask having a mask pattern corresponding to a device pattern; adjusting the size and shape of the projection unit to produce a distribution of incident angles corresponding to the incident light, whereby swing curves of the incident light interfere to reduce the amplitude of a resultant swing curve of the incident light, and developing a photoresist layer with a photoresist pattern corresponding to the device pattern; focusing the plurality of incident beams toward a photoresist layer disposed above a substrate using a lens; removing a portion of the photoresist layer to form the device pattern; forming a structure on the substrate corresponding to the device pattern; A method comprising:

2. The method of claim 1 , wherein the mask generates a first incident light, a second incident light, and a third incident light.

3. The method of claim 1 , wherein the mask is a digital mask that generates the first incident light, the second incident light, and the third incident light.

4. The method of claim 3 , wherein the digital mask comprises a plurality of mirrors, the method comprising programming the mirrors to be either transparent or reflective.

5. 10. The method of claim 1, wherein the mask comprises a phase shift mask that generates the first incident light and the second incident light.

6. The method of claim 1 , wherein the composite swing curve is an average of the swing curves of the incident light.

7. 2. The method of claim 1, wherein each of the plurality of incident light beams has a swing curve corresponding to a thickness of the photoresist layer, an angle of incidence of the exposure of the incident light to the photoresist layer, and a wavelength of the incident light.

8. a projection unit adjustable to change a distribution of angles of incidence corresponding to one or more incident rays; a mask arranged at a distance from the projection unit in a projection direction and having a mask pattern corresponding to a device pattern; a lens spaced apart from the mask in the projection direction; 1. A lithography system comprising: the mask generates the one or more incident lights having corresponding swing curves from a writing beam projected from the projection unit, the one or more incident lights are focused by the lens to reduce the amplitude of a composite swing curve of the incident lights, and a photoresist layer is developed on a substrate with a photoresist pattern corresponding to the device pattern; Lithography system.

9. The lithography system of claim 8 , wherein the lens focuses the first incident light, the second incident light, and the third incident light.

10. 9. The lithography system of claim 8, wherein the mask is a phase shift mask and the lens focuses the first incident light and the second incident light.

11. 9. The lithography system of claim 8, wherein the projection unit is a dipole projection unit including a first projection unit and a second projection unit, the mask is a phase shift mask, and the lens focuses a first incident light of the first projection unit, a second incident light of the second projection unit, a third incident light of the first projection unit, and a fourth incident light of the second projection unit to reduce an amplitude of a composite swing curve of the incident light.

12. 9. The lithography system of claim 8, wherein the mask is a digital mask, and the lens focuses the first incident light, the second incident light, and the third incident light to reduce an amplitude of a composite swing curve of the incident lights.

13. 9. The lithography system of claim 8, wherein the one or more incident lights each have a swing curve corresponding to a thickness of the photoresist layer, an angle of incidence of exposure of the incident light to the photoresist layer, and a wavelength of the incident light.

14. A controller storing instructions that, when executed by a computer processor, cause the controller to: storing in a memory one or more mask patterns corresponding to one or more device patterns; writing one mask pattern of the one or more mask patterns corresponding to one device pattern of the one or more device patterns onto a mask; projecting a writing beam onto the mask using a projection unit to produce one or more incident beams; calculating an angle of incidence for one of the one or more incident rays; adjusting the size and shape of the projection unit to change the angle of incidence of the incident light and reduce the amplitude of a resultant swing curve of a lithography system; using a lens to focus the one or more incident beams toward a photoresist layer disposed on a substrate; generating a photoresist pattern on the photoresist layer corresponding to the mask pattern; Let them do this, the angle of incidence is calculated using the thickness of the photoresist layer and the wavelength of the incident light; controller.

15. The controller of claim 14 , wherein the controller includes a metrology device for providing input related to the thickness of the photoresist layer to calculate the angle of incidence.

16. The controller of claim 14 , wherein the controller performs the step of moving the substrate based on the angle of incidence to generate the photoresist pattern on the photoresist layer corresponding to the mask pattern.

17. 15. The controller of claim 14, wherein the controller performs the step of varying the wavelength of the incident light based on the angle of incidence to generate the photoresist pattern on the photoresist layer corresponding to the mask pattern.

18. The controller of claim 14 , wherein the composite swing curve is an average of the swing curves of the incident light.

19. 15. The controller of claim 14, wherein the mask comprises a digital mask, the digital mask comprising a plurality of mirrors, and wherein the controller performs the steps of programming the mirrors to be either transparent or reflective based on the angle of incidence to generate the photoresist pattern on the photoresist layer corresponding to the mask pattern.

20. The controller of claim 14 , wherein the mask comprises a phase shift mask.

Images