Laser interference lithography apparatus and method

Abstract

The present disclosure provides a laser interference lithography method, comprising: performing interference exposure on a wafer coated with photoresist; and performing patterned flood exposure on the interference-exposed wafer, wherein performing the flood exposure comprises: determining a first light field distribution in the interference-exposed wafer; determining a light field distribution of a flood light source for the flood exposure as a second light field distribution based on the first light field distribution, an intended pattern distribution, and parameters of the flood light source for the flood exposure; and patterning the light field distribution of the flood light source based on the second light field distribution, and controlling the flood light source with the patterned light field distribution to perform flood exposure on the interference-exposed wafer, thereby forming the intended pattern distribution in the flood-exposed wafer.

Description

Technical Field

[0001] This invention relates to the field of photolithography. More specifically, this invention relates to laser interference lithography equipment and methods. Background Technology

[0002] Interference lithography is a technique for patterning large-area arrays of submicron structures. It involves recording the interference of two or more coherent light beams onto a photoresist to create various regular periodic patterns, including gratings, holes, pillars, cones, and lattices. When a coherent laser beam is split into two or more beams, then combined and overlapped in a specific area, a regular pattern of light intensity, such as gratings or dots, is formed. The photoresist material is then exposed through these intensity patterns, and the interference pattern is recorded after development. This lithography technique allows for maskless patterning of large-area substrates using shorter exposure times. Interference lithography enables the high-productivity and low-cost production of periodic nanostructures over large areas, thus playing a crucial role in emerging energy, sensing, luminescence, and other applications.

[0003] Typically, interference lithography can generate periodic patterns using two different methods: Lloyd's mirror structures and dual-beam holographic imaging structures. However, when using interference lithography to fabricate periodic nanopatterns, the uneven exposure light field of the light source often leads to uneven duty cycles in the photoresist pattern after exposure, thus reducing the product's process accuracy. Furthermore, many applications require patterns with position-varying duty cycle distributions, such as patterns with linearly varying duty cycles. Such requirements are generally difficult to meet using the exposure light field of interference lithography. Therefore, high-productivity and low-cost interference lithography equipment struggles to meet these demands.

[0004] Therefore, there is a need for a laser interference lithography apparatus and method capable of providing desired lithographic patterns, wherein the laser interference lithography apparatus and method can provide desired lithographic patterns with high precision without significantly increasing the complexity of the apparatus and manufacturing costs. Summary of the Invention

[0005] The purpose of this disclosure is to address at least some or all of the problems described above.

[0006] One aspect of this disclosure provides a laser interference lithography apparatus, comprising: a dual-beam or multi-beam laser interference lithography apparatus configured to perform interference exposure on a wafer coated with photoresist; a floodlight source having a patternable light field distribution and configured to perform patterned floodlight exposure on the interference-exposed wafer; and a controller configured to: determine a first light field distribution in the interference-exposed wafer; determine a second light field distribution of the floodlight source based on the first light field distribution, a desired pattern distribution, and parameters of the floodlight source; and pattern the light field distribution of the floodlight source based on the second light field distribution, and control the floodlight source having the patterned light field distribution to perform patterned floodlight exposure on the interference-exposed wafer, thereby forming the desired pattern distribution in the flood-exposed wafer.

[0007] In one example, the floodlight source further includes a defocusing module configured to defocus the light emitted by the floodlight source to form a generalized blurred spot.

[0008] In another example, the floodlight source also includes a motor configured to form a generalized, blurred spot of light by slightly moving the floodlight source.

[0009] In another example, the floodlight source may further include a light field patterning module, wherein the controller is further configured to pattern the light field distribution of the floodlight source via the light field patterning module to have the second light field distribution.

[0010] In another embodiment, the laser interference lithography apparatus may further include a developing unit configured to develop a wafer that has undergone generalized exposure.

[0011] In another embodiment, a patterned floodlight source is implemented using a grayscale image from a UV projector, wherein different grayscale values ​​in the grayscale image represent different light intensities.

[0012] In another embodiment, the first light field distribution is an ideal interference pattern, and the second light field distribution is a uniform distribution.

[0013] In another embodiment, the first light field distribution is an ideal interference pattern, and the second light field distribution is a stepped distribution.

[0014] Another aspect of this disclosure provides a laser interference lithography method, which may include: performing interference exposure on a wafer coated with photoresist; and performing patterned flood exposure on the interference-exposed wafer, wherein performing patterned flood exposure includes: determining a first light field distribution in the interference-exposed wafer; determining a light field distribution of the flood light source as a second light field distribution based on the first light field distribution, a desired pattern distribution, and parameters of a flood light source for the patterned flood exposure; and patterning the light field distribution of the flood light source based on the second light field distribution, and controlling the flood light source having the patterned light field distribution to perform patterned flood exposure on the interference-exposed wafer, thereby forming the desired pattern distribution in the flood-exposed wafer.

[0015] In one example, the laser interference lithography method may additionally include performing a development process on the overexposed wafer.

[0016] In another example, determining the first light field distribution includes: developing the interferometrically exposed sample; detecting the contour of the developed wafer using a scanning electron microscope; and determining the first light field distribution in the interferometrically exposed wafer based on the detected contour.

[0017] In another example, determining the second light field distribution may include: in response to determining that the expected pattern distribution is a periodic pattern with a uniform duty cycle, determining to apply a higher overexposure dose at locations where the first light field distribution is smaller, and to apply a lower overexposure dose at locations where the first light field distribution is larger.

[0018] In another example, determining the second light field distribution may include: determining the second light field distribution in response to determining that the expected pattern distribution is a pattern distribution with a spatially modulated duty cycle, such that the pattern distribution with the spatially modulated duty cycle is formed in the overexposed wafer.

[0019] In another embodiment, a patterned floodlight source is implemented using a grayscale image from a UV projector, wherein different grayscale values ​​in the grayscale image represent different light intensities.

[0020] In another embodiment, the first light field distribution is an ideal interference pattern, and the second light field distribution is a uniform distribution.

[0021] In another embodiment, the first light field distribution is an ideal interference pattern, and the second light field distribution is a stepped distribution. Attached Figure Description

[0022] Figure 1 The architecture of a fiber-optic dual-beam laser interference lithography apparatus according to an exemplary embodiment of this disclosure is shown;

[0023] Figures 2A to 2C A schematic diagram of a laser interference lithography apparatus according to an exemplary embodiment of the present disclosure is shown;

[0024] Figure 3 An architectural diagram of a laser interference lithography apparatus according to an exemplary embodiment of this disclosure is shown;

[0025] Figure 4 A flowchart of a laser interference lithography method according to an exemplary embodiment of this disclosure is shown;

[0026] Figure 5 A flowchart of a generalized exposure process according to an exemplary embodiment of this disclosure is shown; and

[0027] Figure 6 A grid structure with a period of, for example, 1 μm is shown formed using a laser interference lithography apparatus and method according to an example embodiment of the present disclosure.

[0028] Figure 7 A sample image is shown, illustrating the fabrication of a pattern with a spatially modulated duty cycle on a 3-inch sample using a laser interference lithography apparatus and method according to an exemplary embodiment of the present disclosure.

[0029] Figure 8 An example is shown of obtaining a gate structure with uniform linewidth on a large wafer using the method and apparatus according to an exemplary embodiment of this disclosure.

[0030] Figure 9 An example of spatially modulating the fill rate of a two-dimensional nanostructure is shown by using a method and apparatus according to an exemplary embodiment of the present disclosure. Detailed Implementation

[0031] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0032] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0033] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0034] When expressions such as "making at least one of A, B, and C" are used, they should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, and C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or systems having A, B, and C, etc.). Similarly, when expressions such as "a system having at least one of B or C" are used, they should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, or C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or systems having A, B, and C, etc.).

[0035] In the accompanying drawings, the same or similar reference numerals are used to indicate the same or similar structures.

[0036] Figure 1 The architecture of a fiber-optic dual-beam laser interference lithography apparatus according to an exemplary embodiment of this disclosure is shown.

[0037] Specifically, the fiber-optic dual-beam laser interference lithography apparatus according to an exemplary embodiment of this disclosure includes a laser source 110 and a fiber beam splitter 120. The laser source 110 may be a single-frequency ultraviolet laser that outputs highly coherent single-frequency ultraviolet light. For example, the wavelength of the laser source 110 may be 266 nm, 351 nm, 355 nm, 360 nm, or other ultraviolet or near-ultraviolet wavelengths. The highly coherent single-frequency ultraviolet light is output to the fiber beam splitter 120 via a single-mode polarization-maintaining fiber (PMF). In a preferred embodiment, the fiber beam splitter 120 may also be polarization-maintaining and is used to split the input highly coherent single-frequency ultraviolet light into at least two sub-laser beams. The at least two sub-beams form an interference pattern, thereby performing interference exposure on a wafer located on an operating table and held by a clamp, such as a holder.

[0038] Furthermore, this fiber-optic dual-beam laser interferometry lithography apparatus may additionally include a controller 140, a photodetector 150, an actuator 130, and a sheet-like beam splitter. For example... Figure 1As shown, for example, a piezoelectric ceramic actuator 130 can be located on at least one branch of the fiber optic beam splitter 120, so that the controller 140 can control the actuator 130 to change the phase of the sub-beam on its branch to change the interference pattern based on the detection of the interference pattern by the photodetector 150.

[0039] The following will be based on Figure 1 The fiber-optic dual-beam laser interference lithography apparatus shown is an example of a dual-beam or multi-beam laser interference lithography apparatus; however, it should be clear that the inventive concept is not limited to apparatuses such as... Figure 1 The fiber-optic dual-beam laser interference lithography equipment shown is also adaptable to Lloyd's mirror structures and other dual-beam or multi-beam laser interference lithography equipment.

[0040] Figures 2A to 2C A schematic diagram of a laser interference lithography apparatus according to an exemplary embodiment of the present disclosure is shown. Figures 2A to 2C Taking the use of positive photoresist as an example, a schematic diagram is shown of the periodic patterns generated under an ideal interference pattern, an actual interference pattern without overexposure processing, and a compensated interference pattern after overexposure compensation.

[0041] like Figure 2A As shown, under ideal conditions, the interference pattern exhibits perfect periodicity. In this case, due to the use of positive photoresist, the photoresist is washed away at locations where the light distribution exceeds the photoresist damage threshold. This allows for the construction of a perfectly periodic pattern. However, because the exposure light field is often non-uniform (typically a Gaussian beam), the duty cycle of the photoresist pattern after interference pattern exposure will be non-uniform, such as… Figure 2B As shown.

[0042] To overcome the aforementioned problems, this application proposes using patterned overexposure after interference exposure to compensate for manufacturing errors caused by the non-uniformity of the light field during interference exposure, such as the non-uniform duty cycle of periodic devices. Specifically, this can be achieved by using patterned overexposure after interference exposure. Figure 2B After the interference pattern shown is exposed, patterned flood exposure, or simply flood exposure, is performed using a floodlight source with an emission wavelength within the sensitive wavelength range of the photoresist to compensate for the non-uniformity of the light field during interference exposure. Specifically, the light field distribution of the floodlight source can be designed so that the cumulative exposure dose distribution in the flood-exposed wafer exhibits a pattern with a uniform duty cycle, such as... Figure 2CAs shown. Alternatively, further, the light field distribution of the floodlight source can be designed so that the cumulative exposure dose distribution in the flood-exposed wafer can exhibit the desired light field distribution, thereby obtaining the desired lithographic pattern. In other words, by using patterned flood exposure to compensate for interference exposure, not only can a periodic structure with a uniform duty cycle be obtained, but also a spatially modulated duty cycle distribution can be obtained, such as linear variation of the duty cycle within a certain range, periodic variation of the duty cycle, radial variation of the duty cycle, or even any given pattern. This patterned secondary exposure can be achieved through ultraviolet projection exposure, ultraviolet lithography with a mask, and directional laser writing. It should also be noted that, although Figures 2A to 2C The inventive concept of this application is illustrated using positive photoresist as an example. However, this application is not limited to this. This application can also be applied to various types of photoresists such as negative photoresist and reverse photoresist.

[0043] The following is for reference Figures 3 to 5 This disclosure describes a laser interference lithography apparatus and method according to exemplary embodiments thereof.

[0044] Specifically, Figure 3 An architectural diagram of a laser interference lithography apparatus according to an exemplary embodiment of this disclosure is shown. Figure 3 As shown, the laser interference lithography apparatus according to an exemplary embodiment of this disclosure includes a dual-beam or multi-beam laser interference lithography apparatus 310, a floodlight source 320, and a controller 330. Specifically, the dual-beam or multi-beam laser interference lithography apparatus 310 is used to perform laser interference exposure on a sample wafer coated with photoresist. The controller 330 can determine a first light field distribution in the interference-exposed wafer; determine the light field distribution of the floodlight source as a second light field distribution based on the first light field distribution, a desired pattern distribution, and parameters of the floodlight source 320 (e.g., wavelength, power, etc.); and pattern the light field distribution of the floodlight source based on the second light field distribution, and control the floodlight source having the patterned light field distribution to perform patterned floodlight exposure on the interference-exposed wafer, thereby forming the desired pattern distribution in the flood-exposed wafer.

[0045] The dual-beam or multi-beam laser interference lithography equipment 310 can, for example, employ... Figure 1This is achieved using a fiber-optic dual-beam or multi-beam laser interference lithography apparatus, which can be configured to perform interference exposure on a photoresist-coated wafer. For example, the dual-beam or multi-beam laser interference lithography apparatus 310 may include: a laser source configured to emit highly coherent ultraviolet / near-ultraviolet single-frequency light (e.g., at a wavelength of 405 nm); an input coupling fiber configured to couple the coherent laser beam from the laser source to a fiber beam splitter; and a fiber beam splitter configured to split the coherent laser beam from the input coupling fiber into at least two sub-laser beams, and output the sub-laser beams through two or more output coupling fibers, thereby performing interference exposure on the photoresist-coated wafer.

[0046] The floodlight source 320 may have a patternable light field distribution and be configured to perform patterned flood exposure on an interference-exposed wafer, i.e., to expose the wafer using a patterned generalized light spot. Specifically, the floodlight source 320 may include a defocusing module, which may be implemented by a defocusing optics device configured to defocus the light emitted by the floodlight source to form a generalized blurred light spot. Alternatively, the floodlight source 320 may also optionally include a motor configured to move the floodlight source slightly to form a generalized blurred light spot. Furthermore, the floodlight source 320 may also typically include a light field patterning module, such as a spatial light modulator, for forming a patterned grayscale light field distribution. Since different grayscale values ​​on a digital grayscale image represent different light intensities on a projected pattern, patterned flood exposure can be performed based on the grayscale image. Furthermore, the floodlight source 320 can have the same or different wavelength as the laser source included in the dual-beam or multi-beam laser interference lithography apparatus 310, as long as both are within the sensitive wavelength range of the photoresist. In the example, 405nm or 365nm can be selected as the wavelength of the floodlight source.

[0047] The controller 330 may be implemented as one or more processing modules. These processing modules are capable of determining a first light field distribution in the interferometrically exposed wafer. In one embodiment, determining the first light field distribution may include: developing the interferometrically exposed sample using a developing apparatus; detecting the contours of the developed wafer using an inspection instrument such as a scanning electron microscope; and determining the first light field distribution in the interferometrically exposed wafer based on the detected contours.

[0048] After determining the first light field distribution, the controller 330 can further determine the light field distribution of the floodlight source as a second light field distribution based on the determined first light field distribution, the expected pattern distribution, and the parameters of the floodlight source; and based on the determined second light field distribution, pattern the light field distribution of the floodlight source, and control the floodlight source 320 with the patterned light field distribution to perform patterned flood exposure on the interferometrically exposed wafer, thereby forming the expected pattern distribution in the flood-exposed wafer. For example, as Figures 2A to 2C As shown, if the distribution of the first light field can be determined as follows... Figure 2B The pattern distribution shown is expected to have Figure 2A Given a uniform duty cycle pattern, if the floodlight source and the laser source included in a two-beam or multi-beam laser interference lithography apparatus have the same wavelength, the second light field distribution can be determined based on the differences in the pattern. In one specific embodiment, an empirical table of compensation values ​​can be obtained experimentally, and the floodlight dose distribution required to obtain the target duty cycle distribution can be obtained by looking up the table. Of course, if the two do not have the same wavelength, the second light field distribution is determined by considering the influence of light at that wavelength on the first light field distribution within the interference-exposed wafer. More specifically, for the case where the expected pattern is a periodic pattern with a uniform duty cycle, a higher floodlight dose is applied at locations with a smaller first light field distribution (i.e., a smaller interference exposure dose), and a lower floodlight dose is applied at locations with a larger first light field distribution (i.e., a larger interference exposure dose), such as... Figure 2C As shown.

[0049] Alternatively, the laser interference lithography apparatus according to an exemplary embodiment of this disclosure may further include a developing unit configured to develop a wafer that has undergone generalized exposure.

[0050] The above illustrates a laser interference lithography apparatus according to an exemplary embodiment of this disclosure. This apparatus compensates for interference exposure by employing patterned overexposure, that is, by determining the light field distribution of the overexposure source based on the first light field distribution obtained after interference exposure and performing overexposure compensation accordingly. This allows for the realization of any given lithography pattern, i.e., it can controllably provide the desired lithography pattern with high precision without significantly increasing the complexity of the equipment and manufacturing costs. The formed interference lithography pattern can be a one-dimensional grating structure or a two-dimensional dot matrix, aperture array, or other structure. Applications of the formed pattern include distributed feedback (DFB) lasers, field emission displays (FEDs), liquid crystal displays (LCDs), advanced data storage applications, gratings, metric standards, and moth-eye subwavelength structures (SWS), etc.

[0051] It should be noted that although the components included in the laser interference lithography apparatus according to the exemplary embodiments of this disclosure are described above in a discrete form, these components may be formed discretely or integrated into a system. Furthermore, the components may also be separated into multiple components or combined into one or more components without affecting the implementation of this disclosure.

[0052] Figure 4 A flowchart of a laser interference lithography method according to an exemplary embodiment of the present disclosure is shown. The laser interference lithography method according to an exemplary embodiment of the present disclosure generally includes: in operation S410, performing interference exposure on a wafer coated with photoresist; and in operation S420, performing patterning overexposure on the interference-exposed wafer. In a preferred embodiment, after coating the photoresist, a homogenization process may also be additionally performed to ensure uniform coating of the photoresist. Furthermore, the laser interference lithography method may also include performing a development process, i.e., developing the overexposure wafer, thereby ultimately providing the desired lithographic pattern.

[0053] Figure 5 A flowchart of a generalized exposure process according to an exemplary embodiment of this disclosure is shown. Specifically, the generalized exposure operation S420 may further include operations S421 to S423.

[0054] In operation S421, a first light field distribution in the interferometrically exposed wafer is determined. As described above, determining the first light field distribution may include: developing the interferometrically exposed sample using a developing apparatus; detecting the contour of the developed wafer using an inspection instrument such as a scanning electron microscope; and determining the first light field distribution in the interferometrically exposed wafer based on the detected contour.

[0055] In operation S422, based on the first light field distribution, the expected pattern distribution, and the parameters of the floodlight source used for the flood exposure, the light field distribution of the floodlight source is determined as the second light field distribution. For the case where the expected pattern distribution is a periodic pattern with a uniform duty cycle, determining the second light field distribution involves applying a higher flood exposure dose at locations where the first light field distribution is smaller (i.e., the interference exposure dose is smaller), and applying a lower flood exposure dose at locations where the first light field distribution is larger (i.e., the interference exposure dose is larger). However, for the case where the expected pattern distribution is a pattern distribution with a spatially modulated duty cycle, the second light field distribution can be determined such that the pattern distribution with the spatially modulated duty cycle is formed in the wafer after flood exposure.

[0056] In operation S423, based on the second light field distribution, the light field distribution of the floodlight source is patterned, and the floodlight source having the patterned light field distribution is controlled to perform patterned flood exposure on the interferometrically exposed wafer, thereby forming the desired pattern distribution in the flood-exposed wafer. For example, when the floodlight source is equipped with a light field patterning module such as a spatial light modulator, the light field distribution of the floodlight source can be patterned via the light field patterning module to have the second light field distribution.

[0057] As can be seen, the laser interference lithography method according to the exemplary embodiments of this disclosure compensates for interference exposure by employing generalized exposure. That is, the light field distribution of the generalized light source is determined based on the first light field distribution obtained after interference exposure, and generalized exposure compensation is performed accordingly. This allows for the realization of any given lithography pattern, i.e., it can controllably provide the desired lithography pattern with high precision without significantly increasing the complexity of the equipment and manufacturing costs. The interference lithography pattern formed by employing the equipment and method shown in the exemplary embodiments of this disclosure can be a one-dimensional grating structure or a two-dimensional dot matrix, aperture array, or other structure. Applications of the formed pattern include distributed feedback (DFB) lasers, field emission displays (FEDs), liquid crystal displays (LCDs), advanced data storage applications, gratings, metric standards, and moth-eye subwavelength structures (SWS), etc.

[0058] Figures 6 to 1 Examples of the methods and apparatus used in the exemplary embodiments of this disclosure are shown.

[0059] Figure 6 A gate-like structure with a period of, for example, 1 μm, formed using a laser interference lithography apparatus and method according to an exemplary embodiment of this disclosure is shown. Experimental studies on structures with the same period are also presented. Figure 6 As shown in Figure a, the exposure dose of the interference pattern is 4.6 mJ / cm. 2 The step size is 27.6 mJ / cm 2 Gradually increased to 55.2 mJ / cm 2 And the exposure dose of the floodlight source was reduced from 0 mJ / cm 2 Gradually increased to 13.2 mJ / cm 2 Electron microscopy images of the grating structure were observed under different interferometric and floodlight exposure doses. It was found that increasing the interferometric and / or floodlight exposure doses reduced the linewidth. However, different initial interferometric exposure doses resulted in different linewidth modulation ranges, with lower initial interferometric exposure doses leading to a larger linewidth modulation range, such as... Figure 6 As shown in Figure b. For example, the exposure dose of a floodlight source starts from 0 mJ / cm². 2 Gradually increased to 13.2 mJ / cm2 Able to initially achieve 27.6 mJ / cm 2 The exposed gate structure produces a linewidth variation of approximately 180 nm, while only the initial value of 55.2 mJ / cm² is achieved. 2 The exposed gate structure produces a linewidth variation of approximately 140 nm.

[0060] Figure 7 and Figure 8 A schematic diagram is shown of a dual-beam or multi-beam laser interference lithography apparatus employing an ideal interference pattern and a floodlight source with a patterned distribution performing a secondary exposure.

[0061] Figure 7 This document shows a sample image of a pattern with a spatially modulated duty cycle fabricated on a 3-inch sample using a laser interference lithography apparatus and method according to an exemplary embodiment of this disclosure, and electron micrographs of the 3-inch sample at positions corresponding to the background, the letter "H", the letter "K", and the letter "U", respectively. The grid structures on the wafer all have a period of 600 nm, but exhibit four different linewidths. Specifically, the linewidth of the grid structure in the background is 250 nm, the linewidth of the grid structure at the letter "H" is 190 nm, the linewidth of the grid structure at the letter "K" is 140 nm, and the linewidth of the grid structure at the letter "U" is 110 nm.

[0062] Figure 8 An example is shown of obtaining a gate structure with uniform linewidth on a large wafer using the method and apparatus according to exemplary embodiments of this disclosure. When processing a large wafer with a two-beam or multi-beam laser interference lithography apparatus having an ideal interference pattern, the distribution of the interference pattern on the wafer may deviate from the ideal interference pattern due to various factors such as the large wafer size or the performance of the interference light source. Therefore, the resulting gate structure may have a non-uniform linewidth. Based on the concept of this application, in this case, a secondary exposure can be performed using a patterned floodlight source to compensate for this.

[0063] For example, Figure 8 Figure a illustrates a schematic diagram of photolithography performed on a large-size wafer (e.g., 4-inch) using only the interference holographic method, with its scanning electron microscope (SEM) images ((a1) to (a4)) clearly showing that the width of the fabricated gate structure increases from 127 nm to 270 nm. Conversely, Figure b illustrates a schematic diagram of photolithography performed on a large-size wafer using the photolithography method according to an exemplary embodiment of this disclosure, with its SEM images ((b1) to (b4)) clearly showing that the width of the fabricated gate structure remains substantially at 127 nm. Figures c and d show the variations in linewidth and linewidth roughness of the gate structure on the 4-inch wafer, respectively, as a function of position.

[0064] It can be seen that by using the photolithography method according to the exemplary embodiment of this disclosure, the linewidth deviation of the gate structure can be reduced from 36.2 nm to 3.2 nm. Furthermore, the linewidth roughness is also significantly improved, especially for the gate structure near the wafer edge.

[0065] In addition to patterning large-area and uniformly distributed grating structures, the laser interference lithography apparatus and method of the exemplary embodiments of this disclosure can also spatially modulate the fill rate of two-dimensional nanostructures.

[0066] Figure 9 An example of spatially modulating the fill rate of a two-dimensional nanostructure using a method and apparatus according to an exemplary embodiment of this disclosure is illustrated. A two-dimensional pattern with a 700 nm period is exposed on the back side of a silicon oxide wafer, and then a grayscale image consisting of 25 grayscale values ​​is used to adjust the fill rate, where the 25 grayscale values ​​represent different exposure doses. Figure a shows a photograph of the developing substrate and an electron microscope image of the marked area, where the color gradually changes from brown to gold in a 5×5 cell as the grayscale value used for the secondary exposure increases from 0 to 240. This substrate includes a two-dimensional nanostructure with a 700 nm period and has various fill rates adjusted by secondary exposure of the grayscale pattern. Figure b shows the photoresist fill rate of the 25 areas in Figure a. As can be seen from Figure b, the photoresist fill rate decreases with increasing dose used for the secondary exposure. Figure c shows a schematic of fabricating a fine painting on a 3-inch wafer. It is evident that the apparatus and method according to an exemplary embodiment of this disclosure are capable of effectively spatially modulating the fill rate of two-dimensional nanostructures.

[0067] from Figures 7 to 9 It can be seen that the laser interference lithography apparatus and method according to the exemplary embodiments of this disclosure can be applied to fabricate patterns with spatially modulated duty cycles, overcoming the application limitations of the laser interference lithography apparatus and method. Accordingly, existing interference lithography systems can be improved to produce desired nanostructures with or without periodicity over a large area.

[0068] Furthermore, it should be noted that although this application describes the inventive concept in the order of performing interference exposure followed by patterning overexposure, those skilled in the art will understand that the order of performing interference exposure and patterning exposure can be reversed, i.e., interference exposure can be performed after overexposure. Moreover, the two can also be performed substantially simultaneously. The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of this disclosure. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than those marked in the drawings. For example, two consecutively indicated blocks may actually be performed substantially in parallel, and they may sometimes be performed in reverse order, depending on the functions involved. It should also be noted that each box in a block diagram or flowchart, as well as combinations of boxes in a block diagram or flowchart, can be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0069] Those skilled in the art will understand that although this disclosure has been shown and described with reference to specific exemplary embodiments thereof, they should understand that various changes in form and detail may be made to this disclosure without departing from the spirit and scope of the disclosure as defined by the appended claims and their equivalents. Therefore, the scope of this disclosure should not be limited to the above embodiments, but should be determined not only by the appended claims, but also by their equivalents.

Claims

1. A laser interference lithography apparatus, comprising: a dual-beam or multi-beam laser interference lithography apparatus configured to perform an interference exposure on a wafer coated with photoresist; a flood light source having a light field distribution that can be patterned and configured to perform a patterned flood exposure on the interference-exposed wafer to compensate for the interference exposure; and a controller configured to: - determine a first light field distribution in the interference-exposed wafer; - determine, based on the first light field distribution, an intended pattern distribution, and parameters of the flood light source, a light field distribution of the flood light source as a second light field distribution; and - pattern the light field distribution of the flood light source based on the second light field distribution and control the flood light source having the patterned light field distribution to perform a patterned flood exposure on the interference-exposed wafer to form the intended pattern distribution in the flood-exposed wafer, wherein the flood light source further comprises a light field patterning module, and wherein the controller is further configured to pattern the light field distribution of the flood light source via the light field patterning module to have the second light field distribution, wherein the dual-beam or multi-beam laser interference lithography apparatus comprises: - a laser light source configured to emit ultraviolet / near-ultraviolet single-frequency light with high coherence; - an input-coupling fiber configured to couple the ultraviolet / near-ultraviolet single-frequency light from the laser light source to a fiber beam splitter; and - a fiber beam splitter configured to split the light from the input-coupling fiber into at least two sub-laser beams and output the at least two sub-laser beams through an output-coupling fiber to perform the interference exposure on the wafer.

2. The laser interference lithography apparatus of claim 1, wherein the flood light source further comprises a defocusing module configured to defocus light emitted by the flood light source to form a generalized blurry spot.

3. The laser interference lithography apparatus of claim 1, wherein the flood light source further comprises a motor configured to cause a small movement of the flood light source to form a generalized blurry spot.

4. The laser interference lithography apparatus of claim 1, further comprising a developing unit configured to develop the flood-exposed wafer.

5. The laser interferometric lithography apparatus of claim 1, wherein, The flood light source has the same or different wavelength as the dual-beam or multi-beam laser interference lithography apparatus.

6. The laser interferometric lithography apparatus of claim 1, wherein, The intended pattern distribution comprises a one-dimensional grating structure, a two-dimensional dot array, and a hole array.

7. A laser interference lithography method, comprising: performing an interference exposure on a wafer coated with photoresist via a dual-beam or multi-beam laser interference lithography apparatus; and performing a patterned flood exposure on the interference-exposed wafer via a flood light source having a light field distribution that can be patterned to compensate for the interference exposure, wherein performing the patterned flood exposure comprises: - determining a first light field distribution in the interference-exposed wafer; - determining, based on the first light field distribution, an intended pattern distribution, and parameters of the flood light source for the patterned flood exposure, a light field distribution of the flood light source as a second light field distribution; and - patterning the light field distribution of the flood light source based on the second light field distribution and controlling the flood light source having the patterned light field distribution to perform a patterned flood exposure on the interference-exposed wafer to form the intended pattern distribution in the flood-exposed wafer. - patterning a light field distribution of the flood light source based on the second light field distribution, and controlling the flood light source with the patterned light field distribution to pattern-expose the interfered-exposed wafer, thereby forming the intended pattern distribution in the pattern-exposed wafer, wherein the flood light source further comprises a light field patterning module, and wherein the light field distribution of the flood light source is patterned via the light field patterning module to have the second light field distribution, wherein performing the interfered exposure via the two-beam or multi-beam laser interference lithography apparatus comprises: - emitting high-coherence ultraviolet / near-ultraviolet single-frequency light; - splitting the ultraviolet / near-ultraviolet single-frequency light into at least two sub-beams; and - outputting the at least two sub-beams to interfere-expose the wafer.

8. The laser interferometric lithography method of claim 7, further comprising: performing a developing process on the pattern-exposed wafer.

9. The laser interference lithography method of claim 7, determining the first light field distribution comprises: developing the interfered-exposed sample; detecting a profile of the developed wafer by a scanning electron microscope; and determining the first light field distribution in the interfered-exposed wafer based on the detected profile.

10. The laser-interference lithography method of claim 7, wherein determining the second light-field distribution comprises: in response to determining that the intended pattern distribution is a periodic pattern with a uniform duty cycle, determining to apply a higher pattern-exposure dose at locations where the first light field distribution is smaller, and to apply a lower pattern-exposure dose at locations where the first light field distribution is larger.

11. The laser-interference lithography method of claim 7, wherein determining the second light-field distribution comprises: in response to determining that the intended pattern distribution is a pattern distribution with a spatially modulated duty cycle, determining the second light field distribution such that the pattern distribution with the spatially modulated duty cycle is formed in the pattern-exposed wafer.

12. The laser interferometric lithography method of claim 7, wherein, the flood light source and the two-beam or multi-beam laser interference lithography apparatus have the same or different wavelengths.

13. The laser interferometric lithography method of claim 7, wherein, the intended pattern distribution comprises a one-dimensional grating structure, a two-dimensional dot array, and a hole array.

Images