Mask reticle, photomask and method for manufacturing the same

Abstract

The application provides a mask substrate, a photomask and a preparation method thereof, and is applied to the technical field of photolithography machines. The mask substrate comprises a transparent substrate and an up-conversion layer attached to one surface of the transparent substrate. After the mask substrate is applied to a photolithography machine, a main light source of the photolithography machine can irradiate the up-conversion layer, and the mixed light can be emitted from another surface of the transparent substrate opposite to the surface where the up-conversion layer is located after up-conversion of the up-conversion layer, so that the mixed light can be used as a mixed light source for light exposure of the photolithography machine, and the photolithography machine can obtain higher resolution and contrast.

Description

Technical Field

[0001] This application relates to the field of photolithography technology, specifically to a patternless photomask substrate, a patterned photomask, and a method for preparing the same. Background Technology

[0002] Photolithography (also known as mask alignment exposure machine, exposure system, photolithography system, etc.) is the core equipment for manufacturing semiconductor chips. Using a technique similar to photo printing, it transfers the fine pattern on a photomask (also called a photomask) onto a silicon wafer through light exposure projection (and a reduction of 4 times), enabling large-scale, repetitive production of chip circuits. The photomask typically uses a transparent glass substrate (such as a quartz substrate) with good light transmittance as the mask material. A metal layer (such as chromium Cr) is then deposited on the surface of this substrate as a light-shielding layer. The thickness of this metal layer is approximately 50-100 nm. By patterning this metal layer, the fine geometric patterns corresponding to the chip circuit, such as lines and holes, are formed. These patterns are then projected onto the silicon wafer during photolithography exposure, i.e., the circuit pattern is projected onto the photoresist on the silicon wafer.

[0003] In photolithography, higher resolution and contrast in the lithography machine enable narrower lithographic linewidths when using photomasks to manufacture chip circuits, thus increasing chip circuit manufacturing density. Currently, common evolutionary improvement schemes for reducing linewidth include: first, evolving the wavelength of light used in the lithography machine to shorter wavelengths, such as from ultraviolet (UV) lithography to deep ultraviolet (DUV) lithography, or even extreme ultraviolet (EUV) lithography; second, improving the numerical aperture (NA) on the wafer side, such as using new optical designs to increase the aperture, or using immersion lenses to increase the NA of the objective lens. However, these improvement schemes all require fundamental modifications to the lithography machine, making them complex and requiring significant improvements. They are not easily implemented directly on existing lithography machines, and the costs of improvement and implementation are very high.

[0004] Therefore, there is an urgent need for a new technology solution that can be based on existing lithography machines, starting with the mask substrate, and can improve the resolution and contrast of the lithography machine. Summary of the Invention

[0005] In view of this, embodiments of this specification provide a photomask, a photomask, and a method for preparing the same. By amplifying the light from the main light source (i.e., the light source used for exposure) of the lithography machine through the photomask, a new hybrid light source is emitted. The hybrid light source contains light waves from the original main light source (i.e., exposure light) and new light waves with shorter wavelengths (i.e., excitation light). After using this hybrid light source as the irradiation light source for light exposure in the lithography machine, the lithography linewidth of the lithography machine can be reduced, thereby improving the resolution and contrast of the lithography machine.

[0006] The embodiments in this specification provide the following technical solutions:

[0007] This specification provides an embodiment of a patternless mask substrate, the mask substrate comprising: a transparent substrate, including a first side and a second side opposite to each other; a light-shielding layer covering the first side of the transparent substrate; and an upconversion layer covering the second side of the transparent substrate, through which at least a portion of a predetermined exposure light can pass, the upconversion layer comprising a two-step photon upconversion thin layer formed by a heterojunction of a wide bandgap semiconductor layer and a narrow bandgap semiconductor layer;

[0008] Wherein, after the preset exposure light shines on the upconversion layer, at least a portion of the exposure light undergoes upconversion to form excitation light with a wavelength shorter than the exposure light; the mixed light passing through the transparent substrate includes the preset exposure light and the excitation light.

[0009] This specification also provides a patterned photomask, the photomask comprising: a mask substrate as described in any embodiment of this specification; and an exposure window formed on a light-shielding layer of the mask substrate; the exposure window and the light-shielding area on the light-shielding layer form a photomask pattern.

[0010] This specification also provides a method for preparing a mask substrate, the method comprising:

[0011] A first light-transmitting substrate is provided, the first light-transmitting substrate having opposing first and second surfaces;

[0012] A light-shielding layer is formed on the first surface of the first light-transmitting substrate;

[0013] An upconversion layer is formed on the second surface of the first light-transmitting substrate.

[0014] This specification also provides a method for preparing a photomask, the method comprising:

[0015] A first light-transmitting substrate is provided, the first light-transmitting substrate having opposing first and second surfaces;

[0016] A light-shielding layer is formed on a first surface of the first light-transmitting substrate, and an exposure pattern window is formed on the light-shielding layer;

[0017] An upconversion layer is formed on the second surface of the first light-transmitting substrate.

[0018] Compared with the prior art, the beneficial effects that at least one technical solution adopted in the embodiments of this specification can achieve include at least:

[0019] By using an upconversion layer on a photomask substrate to enhance the light from the main light source (i.e., the light source used for photolithography), a hybrid light source is formed. This hybrid light source contains both the light waves from the original main light source (i.e., the exposure light) and new light waves with slightly shorter wavelengths (i.e., the excitation light). This hybrid light source is ideally suited as the illumination source for photolithography exposure, improving lithography resolution and contrast without requiring modifications to the photolithography machine's optical system. Therefore, by applying the photomask substrate provided in this specification to an existing photolithography machine, the main light source can be upconverted to obtain the enhanced hybrid light source, thereby effectively improving lithography resolution and contrast during photolithography exposure. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the structure for obtaining a hybrid light source through upconversion of a mask substrate in this application;

[0022] Figure 2 This is a schematic diagram of the structure of a mask base plate in this application;

[0023] Figure 3 This is a schematic diagram of the structure in this application where upconversion is performed on the mask base plate;

[0024] Figure 4 This is a schematic diagram of the material properties used to form the upconversion layer in a mask substrate according to this application;

[0025] Figure 5 This is a schematic diagram of a process for preparing a mask substrate according to this application;

[0026] Figure 6 This is a schematic diagram of the structure of a photomask in this application;

[0027] Figure 7 This is a schematic diagram of the structure in this application that obtains a narrower linewidth using a photomask;

[0028] Figure 8 This is a schematic diagram of the structure of a photomask in this application;

[0029] Figure 9 This is a schematic diagram of the structure of a photomask in this application;

[0030] Figure 10 This is a schematic diagram of the structure in this application that obtains a narrower linewidth using a photomask;

[0031] Figure 11 This is a schematic diagram of a process for preparing a photomask in this application;

[0032] Figure 12 This is a schematic diagram of a method for fabricating a photomask according to this application;

[0033] Figure 13 This is a schematic diagram of a method for preparing a photomask according to this application. Detailed Implementation

[0034] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0035] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0036] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this application, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0037] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. The drawings only show the components related to this application and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0038] Additionally, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that practice can be carried out without these specific details.

[0039] Currently, narrower lithography linewidths determine that lithography machines (or lithography processes) can achieve higher resolution and contrast, thus enabling the manufacture of higher-density semiconductor chip circuits. Existing improvement schemes for reducing linewidths all involve modifying the lithography machine itself, which is difficult and costly, such as replacing UV lithography machines with DUV lithography machines, or even upgrading to the more advanced EUV lithography machines.

[0040] In view of this, the inventors conducted in-depth research and improvement exploration on lithography machines, light exposure and masks, as well as various improvement schemes for reducing linewidth. Common photomasks include binary photomasks (BM or BIM) and phase-shift masks (PSM). As lithography processes become smaller and smaller, the linewidth (Critical Dimension, CD, also known as critical dimension, etc.) of photomasks (BM, PSM, etc.) has become a bottleneck for advanced ultraviolet (UV) lithography processes in wafer manufacturing. However, if the illumination laser used for light exposure in the lithography machine can include some light with wavelengths slightly shorter than the main laser, the resolution and contrast of the lithography can be improved.

[0041] Based on this, the embodiments of this specification propose a new technical solution for enhancing the main light source of a lithography machine through a mask substrate: such as... Figure 1As shown, a mask substrate is provided that enhances the main light source of a lithography machine using an upconversion layer. Specifically, through this new mask substrate, mixed light is directly generated from the main laser (such as a scanning main ultraviolet laser or a stepping main ultraviolet laser, where the wavelength of the main ultraviolet light can be 193nm, 248nm, or 365nm, etc.). The upconversion layer converts a portion of the incident light from the main laser into new light with a slightly shorter wavelength (i.e., excitation light). For example, when the original incident light wavelength is 193nm, the wavelength of the new light can be shortened by about 20nm; when the original incident light wavelength is 248nm, the wavelength of the new light can be shortened by about 50nm; and when the original incident light wavelength is 365nm, the wavelength of the new light can be shortened by about 70nm. Therefore, the mixed light source contains light of the original wavelength and new light of a shorter wavelength. Thus, when this mixed light source is used as the irradiation source for light exposure in a lithography machine, the resolution and contrast of the lithography can be improved, thereby reducing the linewidth of the lithography and enabling the fabrication of higher-density semiconductor chip circuits.

[0042] It should be noted that the main light source of a lithography machine can be selected according to the actual application requirements. For example, the main light source can be an ultraviolet laser (UV laser), or it can be other light sources used for lithography. For ease of illustration, the following illustration uses the main ultraviolet laser source commonly used in lithography machines.

[0043] The technical solutions provided by the various embodiments of this application are described below with reference to the accompanying drawings.

[0044] like Figure 2 As shown in the figure, this specification provides a mask substrate for use in a projection lithography machine. The mask substrate includes: a transparent substrate 11, a light-shielding layer (not shown in the figure), and an upconversion layer 12. The transparent substrate includes opposing first surfaces (such as...). Figure 2 The lower surface and the second surface (as shown in the image) Figure 2 The upper surface of the transparent substrate 11); the light-shielding layer covers the first surface of the transparent substrate 11, and the upper conversion layer 12 is attached to the second surface of the transparent substrate 11.

[0045] In implementation, the upconversion layer 12 can be a two-step photon upconversion layer (TUP layer), wherein the TUP layer can be a thin, two-layer structure made of upconversion material. Figure 2 (Not shown in the text). The upconversion material is a material that generates shorter wavelength light under longer wavelength excitation, and the upconversion layer includes a heterojunction formed by a wide bandgap semiconductor layer and a narrow bandgap semiconductor layer, which is a double thin layer that can realize two-step photon upconversion.

[0046] like Figure 3As shown in the figure, the two-step photon up-conversion layer is composed of a wide-gap semiconductor layer (WGS) and a narrow-gap semiconductor layer (NGS). Under the irradiation of incident UV laser (with wavelength λ, i.e., Incident UV Laser with λ), the incident laser photon energy (where the photon energy < WGS bandgap) will be absorbed by the NGS, and then two additional photoexcitation processes will be induced, namely from the VB (Valence band) to the IB (intermediate band), and then from the IB to the CB (conduction band), finally achieving the excitation from the VB to the CB of the WGS, that is, under the excitation of a UV laser with a longer wavelength, an output of light with a shorter wavelength (i.e., the excitation light) is generated (such as Output UV in the figure, whose wavelength is slightly shorter than the original wavelength λ, denoted as wavelength λˊ). Therefore, the photons emitted by the WGS (from the CB to the VB) can have higher energy and shorter wavelength than the incident light. Thus, after the incident light passes through the up-conversion layer, the total output is a mixed light composed of the incident light and the excitation light.

[0047] It should be noted that in the up-conversion layer, it can be the WGS that contacts the second surface of the transparent substrate 11, or it can be the NGS that contacts the second surface of the transparent substrate 11, that is, in the up-conversion layer, the stacking order of the WGS and the NGS can be reversed; also, both the WGS layer and the NGS layer should be thin enough to allow the incident light to be partially transparent.

[0048] In implementation, the transparent substrate 11 can be a transparent (transparent), semi-transparent (semi-transparent) glass transparent substrate, and preferably a quartz transparent substrate (Quartz substrate) can be selected, so that the light emitted from the up-conversion layer to the transparent substrate can be transparently transmitted in the transparent substrate without being absorbed and turned into heat energy.

[0049] Based on the aforementioned mask substrate structure, when the preset exposure light irradiates the up-conversion layer, at least part of the exposure light can form excitation light with a wavelength shorter than the exposure light through the up-conversion effect, so the mixed light transmitted through the transparent substrate includes the preset exposure light and the excitation light.

[0050] As described above Figure 1As shown, the schematic process of the main light source of the lithography machine forming a hybrid light source after passing through the mask substrate is as follows: The main light source of the lithography machine can be incident from the space above the upconversion layer 12, that is, the main light source irradiates the upconversion layer 12; since the upconversion layer 12 can be excited and undergo upconversion under the irradiation of the incident light, some photons of the longer wavelength incident light are excited and converted into shorter wavelength outgoing light in the upconversion layer. Both the incident light and the outgoing light are transparently transmitted from one side surface of the transparent substrate 11 to the other side surface, forming a hybrid light. This hybrid light can be used as a hybrid light source for irradiation (exposure) of the lithography machine. The light from the main light source that passes through the upconversion layer and the transparent substrate can be labeled as the first light, and the excitation light obtained by the upconversion layer after being irradiated by the main light source and undergoing upconversion can be labeled as the second light. Therefore, the hybrid light can include the first light and the second light.

[0051] The upconversion layer of the photomask upconverts some photons from the main light source of the lithography machine. The main light source then forms a mixed light after passing through the upconversion layer. This mixed light is emitted through the transparent substrate and can be used as the irradiation light source for light exposure in the lithography machine. This irradiation light source contains light of the original wavelength of the main light source and light of a slightly shorter wavelength obtained after upconversion. Therefore, when the mixed light is used for light exposure, it is equivalent to improving the resolution and contrast of the lithography.

[0052] In some implementations, such as Figure 2 The transparent substrate shown can be a single substrate material or a substrate formed by bonding two substrate materials together. Those skilled in the art should understand that when the transparent substrate 11 is formed by bonding two substrate materials, the two substrates are bonded back-to-back (e.g., silicon oxide-silicon oxide bonding, such as thermo-pressure bonding), with an upconversion layer disposed on one side of one substrate and a light-shielding layer pattern disposed on the other side of the other substrate. Incident light irradiates the upconversion layer, and after the upconversion layer transmits part of the incident light and upconverts the remaining incident light to form excitation light, a mixed light is obtained. This mixed light is then transmitted through the two transparent substrates to the light-shielding layer.

[0053] In some implementations, as described above Figure 2 As shown, the upconversion layer may include a two-step photonic upconversion thin layer formed by a heterojunction of a wide bandgap semiconductor layer (WGS) and a narrow bandgap semiconductor layer (NGS).

[0054] Specifically, WGS is selected as an n-type semiconductor, and NGS is selected as a p-type semiconductor, thus forming a heterojunction structure. Since there is no DC bias on this heterojunction, leakage of the heterojunction does not need to be considered in practical applications, which is beneficial for the adaptability of the mask substrate in different applications.

[0055] In some implementations, the order between WGS and NGS can be set according to the actual application requirements, which helps to improve the adaptability of the mask substrate.

[0056] In one example, the WGS can be on the NGS, i.e., the NGS is in contact with the transparent substrate, where the main ultraviolet light source of the lithography machine is incident on the wide bandgap semiconductor layer.

[0057] In one example, WGS can be in NGS, where a wide bandgap semiconductor layer is in contact with the transparent substrate, and the main ultraviolet light source of the lithography machine is incident on the narrow bandgap semiconductor layer.

[0058] In some implementations, appropriate semiconductor materials can be selected to construct WGS and / or NGS according to the actual application requirements.

[0059] In practice, the materials used to form a wide bandgap semiconductor layer and / or to form a narrow bandgap semiconductor layer may include any of the following materials: silicon (Si), gallium arsenide (GaAs), silicon carbide (SiC, such as βSiC, 4HSiC, etc.), gallium nitride (GaN), aluminum nitride (AlN), aluminum gallium nitride (GaAlN), and diamond.

[0060] like Figure 4 The diagram lists some semiconductor materials that can be used as WGS and NGS and their related properties, which will not be elaborated on here. Furthermore, in specific implementations, appropriate semiconductor materials can be selected to construct WGS and NGS based on actual application needs and the bandgap; no restrictions are placed on the selection criteria here.

[0061] In some implementations, based on the characteristics of the semiconductor material and the required excitation wavelength design requirements, it is possible to select from, for example... Figure 4 Among the material properties shown, materials for the upconversion layer (such as AlN, GaN, etc.) should be selected with the bandgap as the core indicator.

[0062] Specifically, the materials of the wide bandgap semiconductor layer and the narrow bandgap semiconductor layer are selected based on the bandgap width (BG) as the core indicator, according to the preset wavelength of the exposure light, in order to achieve the upconversion function, and to make the wavelength of the excitation light 5%-20% shorter than the preset wavelength of the exposure light.

[0063] In practice, when selecting the upconversion layer material based on the bandgap width, the relationship between the bandgap and the excitation wavelength can be as follows: BG = 1234 / l (nm).

[0064] For example, for a 193nm main light source, a wide bandgap WBG (6.73-7.99eV) is selected, and a narrow bandgap NBG (<6.4eV) is selected.

[0065] For example, for a 248nm main light source, a wide bandgap WBG (5.23 - 6.22eV) is selected, and a narrow bandgap NBG (<4.98eV) is selected;

[0066] For example, for a 365nm main light source, a wide bandgap WBG ~ (3.56 - 4.28eV) is selected, and a narrow bandgap NBG ~ 3.38eV is selected.

[0067] Preferably, the wavelength of the excitation light is 10%-15% shorter than the wavelength of the preset exposure light.

[0068] For example, for a 193nm main light source, a wide bandgap WBG ~ (7.11 - 7.52eV) is preferred, and a narrow bandgap NBG < 6.4eV is preferred;

[0069] For example, for a 248nm main light source, a wide bandgap WBG (5.53 - 5.85eV) is preferred, and a narrow bandgap NBG < 4.98eV is preferred;

[0070] For example, for a 365nm main light source, a wide bandgap WBG ~ (3.75 – 3.98eV) is preferred, and a narrow bandgap NBG ~ 3.38eV is preferred.

[0071] In some embodiments, the excitation light generated by the upconversion layer accounts for no more than 20% of the total power of the mixed light. In practice, this can be determined by the thickness of the upconversion layer and the optical parameters (n, k), where n and k represent the refractive index and extinction coefficient, respectively. The thickness of each of the two thin upconversion layers is approximately 2 nm to 30 nm.

[0072] In some implementations, the upconversion layer is designed to have an overall transmittance of about 80% or more for the exposure light, based on the overall requirements for the exposure light in photolithography. This can also be determined by the thickness and optical parameters (n,k) of the upconversion layer.

[0073] It should be noted that those skilled in the art should understand that the transmittance requirements of the upconversion layer for incident exposure light can be achieved by selecting the material, optical parameters (n,k), and thickness of the upconversion layer (i.e., WGS, NGS).

[0074] In some implementations, both WGS and NGS layers can be deposited as crystalline or non-crystalline structures (such as polycrystalline or even amorphous) depending on the actual application requirements, and can even be quantum dot structures (QD structures).

[0075] In practice, the wide bandgap semiconductor layer may include a material layer deposited with any of the following structures: crystalline structure, amorphous structure, quantum dot nanostructure;

[0076] And / or, the narrow bandgap semiconductor layer includes a material layer deposited in any of the following structures: crystalline structure, amorphous structure, quantum dot nanostructure.

[0077] By depositing WGS and NGS on the surface of a transparent substrate, the two-step photon upconversion in the upconversion layer can still function, which is beneficial for implementation and improvement in practical applications.

[0078] In some implementations, WGS and / or NGS can be made thin enough, such as <30nm, to allow the incident main ultraviolet laser portion to pass transparently through the upconversion layer before exiting.

[0079] In one example, the thickness of the wide bandgap semiconductor layer is less than 30 nm.

[0080] In one example, the thickness of the narrow bandgap semiconductor layer is less than 30 nm.

[0081] In some implementations, most mainstream lithography machines still use ultraviolet lasers as the main light source. In this example, the main light source may include an ultraviolet laser. Therefore, there is no need to modify the main light source; a hybrid light source can be formed directly based on the main light source in the existing lithography machine using a mask substrate.

[0082] In some embodiments, the ultraviolet light wavelength of the ultraviolet laser source includes any one of the following wavelengths: 193nm, 248nm, and 365nm. Therefore, after passing through the mask substrate, the main ultraviolet light source becomes a mixed ultraviolet light source. For example, when the main light source is an ultraviolet laser source with a wavelength of 193nm, the mixed light source emitted from the mask substrate will contain two types of ultraviolet light: one with a wavelength of 193nm and the other with a wavelength slightly shorter than 193nm (within 20nm). Similarly, when the main light source is an ultraviolet laser source with a wavelength of 248nm, the mixed light source emitted from the mask substrate will contain two types of ultraviolet light: one with a wavelength of 248nm and the other with a wavelength slightly shorter than 248nm (within 50nm). And again, when the main light source is an ultraviolet laser source with a wavelength of 365nm, the mixed light source emitted from the mask substrate will contain two types of ultraviolet light: one with a wavelength of 365nm and the other with a wavelength slightly shorter than 365nm (within 70nm).

[0083] It should be noted that in practical applications, a hybrid light source suitable for the actual application scenario can be determined based on the characteristics of the main light source and the upconversion layer of the lithography machine. This is just an example.

[0084] In some embodiments, the mask substrate can be used as a mask substrate in BM (Built-in Mask) or PSM (Pulse-Shrink Mask). Specifically, the mask substrate may further include a phase-shifting material layer located between the transparent substrate and the light-shielding layer. It should be noted that when the mask substrate is used as a mask substrate in BM, the thickness of the phase-shifting material layer is zero. When the mask substrate is used as a mask substrate in PSM, the thickness and material selection of the phase-shifting material layer can be determined according to actual application needs; for example, MoSi may be selected as the phase-shifting material. x O y N z For example, a thickness of 50-150nm, etc.

[0085] Based on the same inventive concept, embodiments of this specification provide a method for preparing a mask substrate, wherein the mask substrate is the mask substrate with an upconversion layer provided in any of the foregoing embodiments of this specification, and the mask substrate can be applied to a lithography machine.

[0086] like Figure 5 As shown, the preparation method includes:

[0087] Step S202: Provide a first light-transmitting substrate, the first light-transmitting substrate having a first surface and a second surface opposite to each other;

[0088] Step S204: Form a light-shielding layer on the first surface of the first light-transmitting substrate;

[0089] Step S206: An upconversion layer is formed on the second surface of the first light-transmitting substrate.

[0090] It should be noted that those skilled in the art should understand that the order of steps S204 and S206 can be determined according to actual preparation needs. For example, step S204 can be performed first, followed by step S206. That is, a light-shielding layer (such as a chromium layer) can be formed on the first surface of the first light-transmitting substrate first, and then an upconversion layer can be formed on the second surface of the first light-transmitting substrate. This illustration does not constitute a limitation.

[0091] In addition, the light-transmitting substrate can preferably be a transparent quartz substrate, and the upconversion layer can include a two-step photon upconversion thin layer formed by a heterojunction of a wide bandgap semiconductor layer and a narrow bandgap semiconductor layer. For relevant descriptions of the mask substrate, please refer to the foregoing examples, which will not be elaborated here.

[0092] It should be noted that the prepared mask substrate can be found in the aforementioned... Figure 1 , Figure 2 I will not go into details.

[0093] In some embodiments, when the transparent substrate of the mask base is formed by bonding multiple substrate materials, the preparation method may further include: providing a second light-transmitting substrate, the second light-transmitting substrate having opposing first and second surfaces;

[0094] At this point, step S206, which involves forming an upconversion layer on the second surface of the first light-transmitting substrate, may include: forming an upconversion layer on the first surface of the second light-transmitting substrate, and bonding the second surface of the first light-transmitting substrate and the second surface of the second light-transmitting substrate together.

[0095] It should be noted that the order of forming the upconversion layer on the first light-transmitting substrate and bonding the first light-transmitting substrate and the second light-transmitting substrate can be determined according to actual preparation needs, and the illustration here does not constitute a limitation.

[0096] Based on the same inventive concept, embodiments of this specification provide a patterned photomask that, when applied to a lithography machine, can improve the resolution and contrast of the lithography machine.

[0097] like Figures 6 to 9 As shown in the embodiments of this specification, a novel photomask is provided, comprising: a mask substrate and an exposure window as described in any of the foregoing embodiments, wherein the exposure window is formed on a light-shielding layer of the mask substrate; the exposure window and the light-shielding area on the light-shielding layer form a mask pattern.

[0098] It should be noted that the photomask pattern corresponds to the photomask pattern used when photolithography is performed on a silicon wafer for chip circuitry. Therefore, in the novel photomask provided in this specification, the photomask pattern can be a pattern formed directly on the photomask substrate, or it can be a pattern already formed on a conventional photomask.

[0099] In other words, the light-shielding layer in the mask substrate can be a light-shielding layer that is independently covering the mask substrate, such as... Figure 8 As shown, the light-shielding layer is formed on the mask substrate, and the light-shielding layer does not form a mask pattern; the light-shielding layer in the mask substrate, such as... Figure 9 This illustrates that the light-shielding layer is a light-shielding layer with a pre-formed mask pattern in a conventional mask, that is, a conventional photomask is used to replace the light-shielding layer of the mask base. In this case, the transparent substrate of the conventional mask and the transparent substrate of the mask base are bonded back to back (such as by bonding).

[0100] In practice, a novel photomask can be formed by bonding a conventional mask without an upconversion layer (i.e., a conventional mask substrate or a patterned photomask) back-to-back with the novel mask substrate provided in this specification. The conventional mask (such as BM, PSM, etc.) is disposed on a target surface, which is the other surface of the transparent substrate of the mask substrate opposite to the surface where the upconversion layer is located.

[0101] like Figure 7 As shown, in a novel photomask, the main light source of the lithography machine (such as a primary UV laser) incident light onto the upper surface of a mask substrate with a two-step upconversion thin layer (a thin layer composed of WGS and NGS), thereby transmitting mixed light (which is a combination of DUV emission from WGS and part of the primary UV laser) into the transparent substrate, thus enhancing the resolution and contrast of the UV pattern during light exposure.

[0102] In some implementations, the conventional mask may be a binary mask or a phase-shifting mask, and the conventional mask is preferably a patterned mask.

[0103] In some implementations, the conventional mask may be disposed on the lower surface of the mask base, depending on the specific form of the conventional mask.

[0104] In one example, as described above Figure 6 As shown, when the binary mask (BM) or phase-shifting mask (PSM) is a mask containing a transparent substrate, the transparent substrate of the binary mask or phase-shifting mask can be bonded to the other surface of the transparent substrate of the mask base plate opposite to the surface where the upconversion layer is located.

[0105] In one example, such as Figure 8 and Figure 9 As shown, when the binary mask or phase-shifting mask is a mask that does not contain a transparent substrate, the binary mask or phase-shifting mask is integrated on the other surface of the transparent substrate of the mask substrate, opposite to the surface where the upconversion layer is located.

[0106] It should be noted that the integrated setup here can refer to depositing the conventional mask layer on the surface of the transparent substrate of the mask slab.

[0107] like Figure 10 As shown, in a novel photomask, the main light source of the lithography machine (such as the primary ultraviolet laser source, i.e., the primary source UV) incident light onto the upper surface of a mask substrate with a two-step upconversion thin layer (a thin layer composed of WGS and NGS), thereby transmitting mixed light (which is UV excited from WGS and part of the primary ultraviolet laser) through the transparent substrate. In the light exposure, after the mixed light passes through the photomask, a UV output with better resolution and contrast is obtained.

[0108] Based on the same inventive concept, embodiments of this specification provide a method for preparing a photomask to produce the novel photomask described in any of the foregoing embodiments of this specification, wherein the photomask can be applied to a photolithography machine.

[0109] In one example, such as Figure 11 As shown, the preparation method may include:

[0110] Step S402: Provide a first light-transmitting substrate, the first light-transmitting substrate having a first surface and a second surface opposite to each other;

[0111] Step S404: A light-shielding layer is formed on the first surface of the first light-transmitting substrate, and an exposure pattern window is formed on the light-shielding layer;

[0112] Step S406: An upconversion layer is formed on the second surface of the first light-transmitting substrate.

[0113] By forming an upconversion layer and a light-shielding layer on a first light-transmitting substrate, and forming an exposure window in the light-shielding layer, wherein the exposure window and the light-shielding area of ​​the light-shielding layer constitute a mask pattern, and then the preset exposure light is incident on the upconversion layer, and mixed light is emitted from the exposure window, wherein the mixed light contains most of the exposure light and a slightly shorter wavelength excitation light (the excitation light is formed by the excitation of part of the exposure light through the upconversion layer), the mixed light emitted from the window contains the original exposure light with a longer wavelength and the excitation light with a slightly shorter wavelength, which can reduce the lithography linewidth and is beneficial to improving the resolution and contrast of the lithography machine.

[0114] In one example, such as Figure 12 As shown, a novel photomask can be prepared through the following steps:

[0115] Step a) Deposit an upconversion layer on a surface of a transparent substrate such that the upconversion layer is attached to a surface of the transparent substrate (the upper surface in the figure) to prepare a mask substrate as described in any of the preceding embodiments, i.e., obtain a mask substrate with an upconversion layer;

[0116] Step b) A conventional mask is disposed on the target surface to form a photomask as described in any of the preceding embodiments, wherein the target surface is another surface of the transparent substrate of the mask base relative to the surface where the upconversion layer is located.

[0117] Specifically, such as Figure 12 As shown, given that traditional masks already have corresponding transparent substrates, in step b), the transparent substrate of the traditional mask (such as a traditional mask base or photomask) can be directly bonded back-to-back with the transparent substrate of the mask base with the conversion layer, thereby forming the structure described above. Figure 6 The novel photomask described above.

[0118] Specifically, such as Figure 13 As shown, since conventional masks do not have a corresponding transparent substrate, in step a), an upconversion layer and a conventional mask layer are deposited on the backside (marked as the upper surface in the figure) and the front side (marked as the lower surface in the figure) of the transparent substrate, respectively, and in step b), a mask pattern is formed.

[0119] It should be noted that the prepared photomask can be found in the aforementioned... Figure 6 , Figure 8 and Figure 9 The diagrams are as shown, and the details will not be elaborated further.

[0120] Based on the same inventive concept, embodiments of this specification provide a lithography machine. The lithography machine includes a mask substrate as described in any of the foregoing embodiments, or a photomask as described in any of the foregoing embodiments; wherein the main ultraviolet light source of the lithography machine irradiates the upconversion layer of the mask substrate.

[0121] By applying the novel mask substrate or photomask provided in the embodiments of this specification in a lithography machine, a narrower lithography linewidth can be obtained without making extensive modifications to the lithography machine, thereby improving the resolution and contrast of the lithography machine.

[0122] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. In particular, the product embodiments described later are relatively simple since they correspond to the methods; relevant parts can be referred to the descriptions in the system embodiments.

[0123] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A mask substrate, characterized in that, The mask base plate includes: A transparent substrate, comprising a first and a second surface facing each other; A light-shielding layer covers the first surface of the transparent substrate; And an upconversion layer covering the second surface of the transparent substrate, through which at least a portion of the predetermined exposure light can pass, the upconversion layer comprising a two-step photon upconversion thin layer forming a heterojunction of a wide bandgap semiconductor layer and a narrow bandgap semiconductor layer; Wherein, after the preset exposure light shines on the upconversion layer, at least a portion of the exposure light undergoes upconversion to form excitation light with a wavelength shorter than the exposure light; the mixed light passing through the transparent substrate includes the preset exposure light and the excitation light; The proportion of the excitation light to the total power of the mixed light is less than or equal to 20%; The thickness of the wide bandgap semiconductor layer is less than 30 nm; And / or, the thickness of the narrow bandgap semiconductor layer is less than 30 nm.

2. The mask substrate according to claim 1, characterized in that, The transparent substrate includes a quartz substrate.

3. The mask substrate according to claim 1, characterized in that, In the upconversion layer, either a wide bandgap semiconductor layer or a narrow bandgap semiconductor layer is in contact with the transparent substrate.

4. The mask substrate according to claim 1, characterized in that, The upconversion layer has an overall transmittance of over 80% for the exposed light.

5. The mask substrate according to claim 1, characterized in that, The materials of the wide bandgap semiconductor layer and the narrow bandgap semiconductor layer are selected based on the bandgap width as the core indicator, according to the preset wavelength of the exposure light, in order to achieve the upconversion function, and to make the wavelength of the excitation light 5%-20% shorter than the preset wavelength of the exposure light.

6. The mask substrate according to claim 5, characterized in that, The wavelength of the excitation light is 10%-15% shorter than the wavelength of the preset exposure light.

7. The mask substrate according to claim 1, characterized in that, The transparent substrate is a single substrate material or is made by bonding two substrate materials together.

8. The mask substrate according to claim 1, characterized in that, Materials used to form wide bandgap semiconductor layers include any one of the following: silicon, gallium arsenide, silicon carbide, gallium nitride, aluminum nitride, aluminum gallium nitride, and diamond. And / or, the materials used to form the narrow bandgap semiconductor layer include any of the following: silicon, gallium arsenide, silicon carbide, gallium nitride, aluminum nitride, aluminum gallium nitride, and diamond.

9. The mask substrate according to claim 1, characterized in that, Wide bandgap semiconductor layers include material layers deposited with any of the following structures: crystalline structure, amorphous structure, quantum dot nanostructure; And / or, the narrow bandgap semiconductor layer includes a material layer deposited in any of the following structures: crystalline structure, amorphous structure, quantum dot nanostructure.

10. The mask substrate according to claim 1, characterized in that, The wavelength of the exposure light includes any of the following wavelengths: 193nm, 248nm, and 365nm.

11. The mask substrate according to claim 1, characterized in that, The mask substrate further includes a phase-shifting material layer, which is located between the transparent substrate and the light-shielding layer.

12. A method for preparing a mask substrate as described in any one of claims 1 to 11, characterized in that, Including the following steps: A first light-transmitting substrate is provided, the first light-transmitting substrate having opposing first and second surfaces; A light-shielding layer is formed on the first surface of the first light-transmitting substrate; An upconversion layer is formed on the second surface of the first light-transmitting substrate.

13. The preparation method according to claim 12, characterized in that, The step of forming an upconversion layer on the second surface of the first light-transmitting substrate specifically includes: forming an upconversion layer on the first surface of the second light-transmitting substrate, and bonding the second surface of the first light-transmitting substrate and the second surface of the second light-transmitting substrate; The preparation method further includes: providing a second light-transmitting substrate, the second light-transmitting substrate having a first side and a second side opposite to each other.

14. A photomask, characterized in that, The photomask includes: The mask base plate as described in any one of claims 1-11; Additionally, an exposure window is formed on the light-shielding layer of the mask substrate; the exposure window and the light-shielding area on the light-shielding layer form a mask pattern.

15. A method for preparing a photomask as described in claim 14, characterized in that, Including the following steps: A first light-transmitting substrate is provided, the first light-transmitting substrate having opposing first and second surfaces; A light-shielding layer is formed on a first surface of the first light-transmitting substrate, and an exposure pattern window is formed on the light-shielding layer; An upconversion layer is formed on the second surface of the first light-transmitting substrate.

16. The preparation method according to claim 15, characterized in that, The step of forming an upconversion layer on the second surface of the first light-transmitting substrate specifically includes: forming an upconversion layer on the first surface of the second light-transmitting substrate, and bonding the second surface of the first light-transmitting substrate and the second surface of the second light-transmitting substrate; The preparation method further includes: providing a second light-transmitting substrate, the second light-transmitting substrate having opposing first and second surfaces.

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