Interference exposure system

Abstract

The utility model discloses an interference exposure system, and relates to the field of optics, and the interference exposure system comprises a light source module which is used for outputting a collimated light beam; the prism is arranged in the output direction of the collimated light beam and is used for transmitting the incident collimated light beam; the grating mask and the prism are arranged in an attached mode, the grating mask is used for diffracting collimated light beams which penetrate through the prism and are incident on the prism to generate coherent light beams, and the coherent light beams are emitted to a substrate and form a patterned interference exposure field on the substrate; and the prism is also used for refracting and outputting stray light reflected back to the prism by the grating mask. Therefore, the prism can emit stray light, so that the occurrence of the problem that the contrast ratio of interference fringes and the exposure effect are influenced due to the fact that the stray light falls on the substrate again is reduced, and a patterned interference exposure field with higher definition can be formed on the substrate.

Description

Technical Field

[0001] The present application relates to the field of optical technology, and more specifically, to an interference exposure system. Background Art

[0002] Diffraction gratings are key optical elements in various applications and play a key role in various application fields. In the related art, gratings can generally be prepared based on near-field holography. Near-field holography uses a grating mask as a beam splitting element and generates interference patterns by using the interference between the diffracted light of the phase mask. The pattern of the phase mask can be transferred to a substrate coated with photoresist. Therefore, the light beam has a short propagation length and no phase change occurs. The period of the interference pattern depends only on the mask period, and the exposure device is simple and compact. It is a stable and promising micro-nano pattern production method. However, when using the existing near-field holography for interference exposure, the obtained interference fringes have a serious problem of reduced contrast, and the interference exposure effect is not good. Utility Model Content

[0003] In view of the above problems, the present application proposes an interference exposure system.

[0004] In a first aspect, an embodiment of the present application provides an interference exposure system, characterized in that the interference exposure system includes: a light source module for outputting a collimated light beam; a prism, wherein the prism is arranged in the output direction of the collimated light beam, and is used to transmit the incident collimated light beam; a grating mask, wherein the grating mask and the prism are bonded together, and the grating mask is used to diffract the collimated light beam incident thereon through the prism to generate a coherent light beam, and the coherent light beam is emitted onto a substrate and forms a patterned interference exposure field on the substrate; wherein the prism is also used to refract and output the stray light reflected back to the prism by the grating mask.

[0005] The interference exposure system provided by the present application can be made by a prism that allows a collimated light beam to be incident on a grating mask at a specific angle through one surface of the prism, and the incident light generates diffracted light after hitting the grating mask, and the substrate is subjected to interference exposure by utilizing the mutual interference of the diffracted light, thereby forming a patterned interference exposure field on the substrate; at the same time, the prism can also emit the remaining stray light, thereby reducing the occurrence of problems such as the stray light falling on the substrate again and affecting the contrast of the interference fringes and the exposure effect. In other words, it helps to form a patterned interference exposure field with higher definition on the substrate, thereby reducing the problem of grating deformation on the substrate caused by stray light to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0007] Figure 1 A system architecture diagram of an interference exposure system provided by an embodiment of the present application is shown;

[0008] Figure 2 A schematic diagram of interference exposure at a Littrow angle provided by an embodiment of the present application is shown;

[0009] Figure 3 A system architecture diagram of an interference exposure system provided by another embodiment of the present application is shown;

[0010] Figure 4 A system architecture diagram of an interference exposure system provided by another embodiment of the present application is shown;

[0011] Figure 5 A schematic diagram of an optical path for preparing a volume holographic grating mask provided in an embodiment of the present application is shown;

[0012] Figure 6 A schematic diagram of an optical path for reproducing a volume holographic grating mask provided by an embodiment of the present application is shown;

[0013] Figure 7 A schematic structural diagram of a substrate provided in one embodiment of the present application is shown. DETAILED DESCRIPTION

[0014] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0015] In the description of the present invention, the terms "first", "second", etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0016] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or mutual communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two components or the interaction relationship between two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0017] In the related art, a major problem with the near-field holographic exposure method is how to suppress the interface reflection of each optical element during exposure. The stray light caused by multiple reflections on the interface will cause the contrast of the interference fringes on the photoresist surface to be seriously reduced.

[0018] Therefore, in order to overcome the above-mentioned defects, an embodiment of the present application provides an interference exposure system, which can avoid the influence of stray light on the interference exposure effect to a certain extent.

[0019] See also Figure 1 , Figure 1 1 is a schematic diagram of the system architecture of an interference exposure system provided in an embodiment of the present application. The interference exposure system includes: a light source module 110 , a prism 120 and a grating mask 130 .

[0020] The light source module 110 is used to output a collimated light beam, wherein the collimated light beam can be understood as a parallel light beam.

[0021] The prism 120 is arranged in the output direction of the collimated light beam, and is used to transmit the incident collimated light beam; wherein the transmitted collimated light beam may be a directly transmitted collimated light beam, or a refracted collimated light beam, and the specific transmission mode is determined by the incident angle of the collimated light beam incident on the prism 120, and this embodiment makes a limitation on this. wherein the prism 120 is a polygonal prism, and the polygonal prism includes at least one of a triangular prism, a trapezoidal prism and a square prism, and of course, may also include prisms of other shapes.

[0022] Considering that if holographic exposure is achieved in a normal incidence manner, that is, using the mutual interference of ±1-order diffraction light to form an interference pattern with a diffraction grating period of 1 / 2 of the grating mask period, there will be problems such as the formation of background light due to the 0-order light falling on the exposure substrate, reducing the contrast of the exposure field, and thus affecting the exposure effect. Based on this, the present application can arrange a prism 120 in the output direction of the collimated light beam to transmit the collimated light beam, and make the transmitted collimated light beam as follows Figure 2 The setting angle θ shown i The incident angle is incident on the grating mask, setting the angle θi :

[0023] θ i =arcsin(λ 0 / 2Λ g )

[0024] Among them, λ 0 is the wavelength of the collimated beam, Λ g is the period of the grating mask. That is, through the refraction of the prism, the collimated light beam is refracted at the Littrow angle (i.e., θ i ) is incident, so that there is only the 0th order diffraction beam and the negative 1st order diffraction beam in the grating mask.

[0025] The grating mask 130 is arranged in a bonded manner with the prism 120, and the grating mask is used to fold the collimated light beam incident thereon through the prism to diffract and generate a coherent light beam, and emit the coherent light beam to the substrate to form a patterned interference exposure field on the substrate. Specifically, the first surface of the grating mask 130 is arranged in a bonded manner with the first surface of the prism 120, and the collimated light beam passing through the prism 120 is incident on the first surface of the grating mask 130, and the coherent light beam is emitted from the second surface of the grating mask 130 to the substrate 20. The first surface of the prism 120 is used to refract the stray light reflected back to the first surface of the grating mask 130, and the second surface of the prism 120 is used to output the stray light refracted and emitted from the first surface of the prism 120, and the second surface of the prism 120 is any surface of the multiple surfaces of the prism 120 except the first surface. In this way, since the first surface of the grating mask 130 is arranged in close contact with the first surface of the prism 120, the total reflection angle at the interface between the grating mask and the prism can be changed, so the number of light rays that are totally reflected at the interface between the grating mask and the prism can be reduced, and the stray light that is diffracted and returned to the second surface of the grating mask can be further reduced, so the contrast can be improved. Preferably, the refractive index of the prism 120 is also greater than the refractive index of the grating mask 130, so as to prevent the problem that part of the light beam reflected back to the first surface of the grating mask 130 is totally reflected on the first surface of the grating mask 130, thereby avoiding the problem that this part of the light beam is diffracted and returned to the second surface of the grating mask again to form stray light that falls on the substrate 20 again, affecting the contrast of the interference fringes and the exposure effect.

[0026] The coherent light beam includes the aforementioned 0th order diffraction light beam and the negative 1st order diffraction light beam, and the 0th order diffraction light beam and the negative 1st order diffraction light beam have the same diffraction energy, so that the contrast of the patterned interference exposure field formed on the substrate is the clearest, in other words, the interference fringe pattern with the clearest contrast can be generated on the substrate. The period Λ of the interference fringes generated by the interference of the 0th order diffraction light beam and the negative 1st order diffraction light beam is:

[0027]

[0028] Furthermore, the prism 120 is also used to reflect the stray light (i.e. Figure 1 The light beam represented by the dotted line in the middle is refracted and output.

[0029] In a specific embodiment, by attaching a prism 120 to the first surface of the grating mask 130, and the refractive index of the prism 120 is greater than the refractive index of the grating mask 130, the total reflection condition of the light beam partially reflected to the first surface of the grating mask 130 is broken, and this part of the light beam is refracted through the first surface of the prism 120, and the second surface of the prism 120 outputs this part of the stray light refracted from the first surface. This effectively prevents this part of the light beam from returning to the second surface of the grating mask again, and diffracting to form stray light that falls on the substrate 20 again, affecting the contrast of the interference fringes and the exposure effect.

[0030] See also Figure 3 , a schematic diagram of the system architecture of an interference exposure system 10 provided in another embodiment of the present application. The interference exposure system includes: a light source module 110, a prism 120, a grating mask 130 and a refractive index matching liquid 140. The light source module 110 includes a laser light source 111, a spatial filter 112, a lens 113 and a reflector 114.

[0031] In this embodiment, the first surface of the grating mask 130 is bonded to the first surface of the prism 120, and the refractive index matching liquid 140 is used to fill the gap between the first surface of the grating mask 130 and the first surface of the prism 120, and the refractive index difference between the refractive index of the refractive index matching liquid 140 and the refractive index of the prism 120 is less than a preset threshold. It can be understood that the refractive index of the refractive index matching liquid 120 is preferably the same as the refractive index of the prism 120, but if the refractive indices are different, the refractive index difference between the two needs to be small. Because the main function of the refractive index matching liquid is to fill the air gap between the prism 120 and the grating mask 130, so as to prevent the light on the first surface of the grating mask from being totally reflected. Preferably, the refractive index of the refractive index matching liquid is close to that of the prism 120, and both are greater than that of the grating mask 130, thereby more effectively preventing the problem of the partial light beam reflected back to the first surface of the grating mask 130 being totally reflected on the first surface of the grating mask 130, that is, avoiding the diffraction of the partial light beam back to the second surface of the grating mask to form stray light that falls on the substrate 20 again, affecting the contrast of the interference fringes and the exposure effect. In this way, the problem of grating deformation on the substrate caused by stray light is reduced, which helps to form a patterned interference exposure field with higher definition on the substrate.

[0032] The laser light source 111 is used to output a laser beam; the spatial filter 112 is used to filter the laser beam; the lens 113 is used to collimate the laser beam after beam filtering to obtain the collimated beam; the reflector 114 is used to reflect the collimated beam so that the reflected collimated beam is incident on the prism 120.

[0033] The light source module 110 is used to output a collimated light beam. The prism 120 is arranged in the output direction of the collimated light beam and is used to transmit the incident collimated light beam. After transmission, the incident angle θ of the collimated light beam incident on the grating mask 130 is i The formulas mentioned in the above-mentioned embodiments are still satisfied. The refracted collimated light beam is incident on the first surface of the grating mask 130, and the coherent light beam (i.e., the 0th-order diffraction light beam and the negative 1st-order diffraction light beam) is emitted from the second surface of the grating mask 130 to the substrate to form a patterned interference exposure field on the substrate 20; the second surface of the prism 120 is used to refract and emit the stray light reflected from the second surface of the grating mask 130, and the second surface of the prism 120 is any surface of the multiple surfaces of the prism except the first surface. The second surface of the grating mask 130 can be as follows: Figure 2 The periodic convex structure shown.

[0034] In some embodiments, the substrate 20 may be Figure 3The photoresist layer 202 shown in FIG. 1 includes a top antireflection layer 201, a photoresist layer 202 and a base layer 203. The base layer 203 is a medium to which the photoresist can be attached. That is, the photoresist is attached to the base layer 203 to form the photoresist layer 202, and the material thereof can be selected from glass, polymethylmethacrylate (PMMA), polyethylene (PET), SIO 2 Preferably, a top anti-reflection layer 201 may be attached to the photoresist layer 202 to reduce the reflection of the diffracted light beam, thereby promoting the clarity of the interference pattern and improving the clarity of the fine pattern formed on the substrate 20.

[0035] The photoresist layer 202 may be a positive photoresist. After the interference exposure of the present embodiment, the positive photoresist on the surface of the substrate 20 may be cleaned by a developer, the exposed portion may be dissolved, and the unexposed portion may be left, so that an image of a grating structure is formed on the surface of the substrate 20. Of course, the layer 202 may also be a negative photoresist. After multiple interference exposures, the negative photoresist on the surface of the substrate 20 may be cleaned by a developer, the unexposed portion may be dissolved, and the exposed portion may be left, so that an image of a grating structure may also be formed on the surface of the substrate 20.

[0036] In this embodiment, the prism can make the collimated light beam incident on the grating mask at a specific angle through one surface of the prism, and the incident light generates diffracted light after hitting the grating mask. The mutual interference of the diffracted light is used to perform interference exposure on the substrate, thereby forming a patterned interference exposure field on the substrate; at the same time, the prism can also emit the remaining stray light, thereby reducing the occurrence of problems such as the stray light falling on the substrate again to affect the contrast of the interference fringes and the exposure effect. In addition, the refractive index matching liquid is filled in the gap between the first surface of the grating mask and the first surface of the prism, which more effectively reduces the amount of light that is totally reflected on the first surface of the grating mask 130, and further reduces the amount of light that is diffracted after being totally reflected on the first surface of the grating mask and then returned to the second surface of the grating mask. In this way, the problem of grating deformation on the substrate caused by stray light is reduced, which helps to form a patterned interference exposure field with higher definition on the substrate.

[0037] See also Figure 4, a schematic diagram of the system architecture of an interference exposure system 10 provided in another embodiment of the present application. The interference exposure system includes: a light source module 110, a prism 120 and a volume holographic grating mask 130. The light source module 110 includes a laser light source 111, a spatial filter 112, a lens 113 and a reflector 114; the volume holographic grating mask 130 is a transmission type. Since the two interference light beams of the present application reach the interference plane (i.e., substrate 20) at a very short distance after diffraction, the laser light source does not need a very long coherence length, and a laser light source with low coherence can be used.

[0038] The laser light source 111 is used to output a laser beam; the spatial filter 112 is used to filter the laser beam; the lens 113 is used to collimate the laser beam after beam filtering to obtain the collimated beam; the reflector 114 is used to reflect the collimated beam so that the reflected collimated beam is incident on the prism 120.

[0039] The light source module 110 is used to output a collimated light beam. The prism 120 is arranged in the output direction of the collimated light beam and is used to transmit the incident collimated light beam. After transmission, the incident angle θ of the collimated light beam incident on the grating mask 130 is i The formula mentioned in the above embodiment is still satisfied. The first surface of the volume holographic grating mask 130 is closely arranged with the first surface of the prism 120, and the volume holographic grating mask 130 is used to diffract the incident collimated light beam after refraction to generate a coherent light beam (i.e., a 0th order diffraction light beam and a negative 1st order diffraction light beam), wherein the energy of the 0th order diffraction light beam and the negative 1st order diffraction light beam are equal, and the 0th order diffraction light beam and the negative 1st order diffraction light beam have an overlapping irradiation area on the substrate 20.

[0040] The substrate 20 is composed of a volume holographic film 204 and a base layer 203, wherein the base layer 203 is used to carry the volume holographic film 204, and the base layer 203 can be made of glass, TAC, PET and other materials, which are not limited in this embodiment. The volume holographic film is a photosensitive film, which records the distribution of interference fringes in the form of a refractive index change distribution, and the fringes correspond to the grating structure. It can be understood that since the volume holographic grating mask 130 is essentially a film with a periodic refractive index distribution, the volume holographic grating mask 130 is to attach this film to the first surface of the prism 120 during exposure. The refraction angle of this part of light entering the air has been calculated during exposure, so it will not bring a lot of stray light. Therefore, in this embodiment, there is no need to add a refractive index matching liquid between the volume holographic grating mask 130 and the prism 120.

[0041] In some embodiments, Figure 3As shown, the substrate 20 includes a volume holographic film 204 and a base layer 203. Based on this, the 0th order diffraction beam and the negative 1st order diffraction beam generated by the volume holographic grating mask 130 generate interference fringes on the substrate 20, and the volume holographic film 204 on the substrate 20 records the periodic distribution of the interference fringes. Other stray light except the 0th order diffraction beam and the negative 1st order diffraction beam will be refracted and emitted through the prism 120, and will not fall on the volume holographic film 204 of the substrate 20 to affect the clarity of the interference fringes.

[0042] In this mode, see Figure 5 and Figure 6 , showing the process of preparing and reproducing the grating using the transmission type volume holographic grating mask 130. The preparation of the transmission type volume holographic grating 130 is that the object light and the reference light are incident on the volume holographic film layer on the same side of the volume holographic film layer. The specific angles at which the object light and the reference light are incident on the surface of the film layer can be set according to the diffraction efficiency, diffraction angle and diffraction order. The reproduction process is that the reference light is incident on the film layer at the same angle as when it is exposed. At this time, 0th order and -1st order diffraction light will be diffracted and emitted on the other side of the film layer. Among them, the 0th order diffraction beam is the reference light, and the -1st order diffraction beam is the object light. It can be generally understood that the angle of the object light is reproduced using the reference light.

[0043] In other embodiments, Figure 7 As shown, the prism 120 can also be a trapezoidal prism, and the substrate 20 can include a photoresist layer 202 and a base layer 203, that is, the volume holographic grating mask 130 is used to expose the photoresist layer 202 at a close distance. Specifically, the collimated light beam is emitted from one surface of the trapezoidal prism 120 and incident on the volume holographic grating mask 130. The volume holographic grating mask 130 diffracts to produce a 0th order diffraction beam and a negative 1st order diffraction beam with equal energy, while the stray light will be emitted through the remaining surfaces of the trapezoidal prism 120, reducing the stray light from falling on the photoresist layer 202 again to affect the interference exposure effect. The 0th order diffraction beam and the negative 1st order diffraction beam interfere with each other on the photoresist layer, and the interference pattern generated by the photoresist layer is recorded to form a grating.

[0044] It should be noted that different structures of the substrate 20 can be reused in any embodiment mentioned in the present application, and will not be described in detail here.

[0045] In this embodiment, the use of a volume holographic grating as a grating mask can accurately control the diffraction 0th order and -1st order light efficiency to be equal, and the obtained interference fringes have a high contrast. In addition, this embodiment uses a volume holographic grating mask to expose the photoresist layer to form a surface relief grating. Since the angle selectivity of the volume holographic grating is relatively narrow, the angles of the diffraction 0th order and -1st order light can be accurately controlled, that is, an interference exposure system that can easily control the direction and contrast of the diffracted light is provided. In addition, the prism can also emit the remaining stray light, thereby reducing the occurrence of problems such as stray light falling on the substrate again to affect the contrast of the interference fringes and the exposure effect. In this way, it is helpful to form a patterned interference exposure field with higher clarity on the substrate, thereby reducing the problem of grating deformation obtained on the substrate due to stray light to a certain extent.

Claims

1. An interference exposure system, characterized in that: The interference exposure system comprises: A light source module, used for outputting a collimated light beam; A prism, the prism is arranged in the output direction of the collimated light beam, and is used to transmit the incident collimated light beam; A grating mask, the grating mask and the prism are arranged in affixed relation, the grating mask is used to diffract a collimated light beam incident thereon through the prism to generate a coherent light beam, the coherent light beam is emitted onto a substrate and forms a patterned interference exposure field on the substrate; The prism is also used to output the stray light reflected by the grating mask back to the prism.

2. The interference exposure system according to claim 1, characterized in that: The first surface of the grating mask is arranged in contact with the first surface of the prism, the collimated light beam passing through the prism is incident on the first surface of the grating mask, and the coherent light beam is emitted from the second surface of the grating mask to the substrate; The first surface of the prism is used to refract the stray light reflected back from the first surface of the grating mask, and the second surface of the prism is used to output the stray light refracted from the first surface of the prism. The second surface of the prism is any surface among the multiple surfaces of the prism except the first surface.

3. The interference exposure system according to claim 2, characterized in that: The interference exposure system also includes a refractive index matching liquid, which is used to fill the gap between the first surface of the grating mask and the first surface of the prism, and the refractive index difference between the refractive index of the refractive index matching liquid and the refractive index of the prism is less than a preset threshold.

4. The interference exposure system according to claim 2, characterized in that: The grating mask is a volume holographic grating mask, and a first surface of the volume holographic grating mask is closely arranged to the first surface of the prism.

5. The interference exposure system according to claim 1, characterized in that: The prism is used to transmit the collimated light beam so that the collimated light beam after transmission is at a set angle θ i The incident angle is incident on the grating mask, and the setting angle θ i for: i i =arcsin(λ0 / 2Λ g ) Wherein, λ0 is the wavelength of the collimated light beam, Λ g is the period of the grating mask.

6. The interference exposure system according to claim 5, characterized in that: The coherent light beam includes a zero-order diffraction light beam and a minus-first-order diffraction light beam obtained based on the diffraction of the collimated light beam.

7. The interference exposure system according to any one of claims 1 to 6, characterized in that: The light source module includes a laser light source, a spatial filter, a lens and a reflector; The laser light source is used to output a laser beam; The spatial filter is used to perform beam filtering on the laser beam; The lens is used to collimate the laser beam after beam filtering to obtain the collimated beam; The reflector is used to reflect the collimated light beam so that the reflected collimated light beam is incident on the prism.

8. The interference exposure system according to any one of claims 1 to 6, characterized in that: The prism is a polygonal prism, and the polygonal prism includes at least one of a triangular prism, a trapezoidal prism and a square prism.

9. The interference exposure system according to any one of claims 1 to 6, characterized in that: The refractive index of the prism is greater than the refractive index of the grating mask.

10. The interference exposure system according to any one of claims 1 to 6, characterized in that: The substrate comprises a volume holographic film and a base layer, wherein the base layer is used for carrying the volume holographic film, and the coherent light beam forms the patterned interference exposure field on the volume holographic film.

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