Exposure light frequency enhancement device, photomask and method of manufacturing the same

Abstract

The application provides an exposure light frequency enhancement device, a photomask and a preparation method thereof. The device comprises a light-transmitting substrate and a surface plasmon layer. The surface plasmon layer comprises a plurality of nano-unit structures. The plurality of nano-unit structures are arranged periodically and spacedly in a first direction and a second direction of the surface plasmon layer plane, and can match the wavelength of the exposure light to generate a sum frequency effect. The sum frequency effect can form sum frequency light passing through the light-transmitting substrate. The power of the sum frequency light accounts for less than or equal to 30% of the total power of the exposure light passing through the surface plasmon layer. The exposure light contains less than 30% of higher frequency sum frequency light. The resolution and contrast of the projection photolithography process can be improved, and the original frequency light source is still largely used. The photolithography assembly basically does not need to be adjusted, and the energy loss is less.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of semiconductor manufacturing, and particularly relates to an exposure light frequency enhancement device for projection photolithography, a photomask and a preparation method thereof. BACKGROUND

[0002] With the continuous progress of integrated circuit manufacturing methods and the continuous reduction of line width, the area of semiconductor devices is becoming smaller and smaller, and the layout of semiconductors has evolved from ordinary single-function discrete devices to integrated high-density multi-function integrated circuits. From the initial IC (integrated circuit) to LSI (large-scale integrated circuit), VLSI (very large-scale integrated circuit), and today's ULSI (ultra large-scale integrated circuit), the area of devices is further reduced. Considering the complexity, long-term nature and high cost of process research and development, how to further improve the integration density of devices on the basis of existing technology to obtain as many effective chip numbers as possible on the same silicon wafer and thus improve the overall benefit will be paid more and more attention by chip manufacturers. Among them, the projection photolithography process plays a key role. For the photolithography technology in this paper, the projection photolithography equipment, process and mask plate technology are the most important.

[0003] The simplest binary mask (BIM) or phase shift mask (PSM) has a mask layer Cr with a thickness of about 50-100 nm. The phase shift of the phase shift mask can be provided by the groove depth on the patterned quartz substrate.

[0004] The double-layer phase shift mask can include a light-shielding Cr layer and a MoSiON layer, and the thickness of the MoSiON layer is about 50-150 nm to ensure its phase shift and attenuation function. After the pattern of the double-layer phase shift mask is completed, the phase shift and attenuation of the double-layer phase shift mask are determined by the thickness of the MoSiON layer. The phase shift mask can also include a multi-layer structure to obtain better photomask performance.

[0005] However, the above-mentioned photomask still has the problems of insufficient resolution and contrast of the pattern on the silicon wafer.

[0006] It should be noted that the above introduction to the technical background is only to facilitate a clear and complete description of the technical solutions of the present application, and to facilitate the understanding of those skilled in the art. The above technical solutions cannot be considered as known to those skilled in the art merely because they are described in the background section of the present application. SUMMARY

[0007] In view of the above-mentioned shortcomings of the prior art, the present application aims to provide an exposure light frequency enhancement device, a photomask and a preparation method thereof, which are used to solve the problems of insufficient resolution and contrast of the photomask in the existing projection technology.

[0008] To achieve the above-mentioned objects and other related objects, the present application provides an exposure light frequency enhancement device for projection photolithography, which comprises: a light-transmitting substrate comprising opposite first and second surfaces; and a surface plasmon layer located on the first surface of the light-transmitting substrate, wherein the surface plasmon layer comprises a plurality of nano-unit structures arranged in a periodic and spaced manner in a first direction and a second direction of the surface plasmon layer plane, respectively, and the nano-unit structures are arranged to generate sum-frequency effect matched with the wavelength of the exposure light, and the sum-frequency effect can form sum-frequency light passing through the light-transmitting substrate, and the proportion of the power of the sum-frequency light to the total power of the exposure light passing through the surface plasmon layer is less than or equal to 30%.

[0009] Optionally, the exposure light comprises two polarized lights polarized parallel to the row direction and the column direction, respectively.

[0010] Optionally, the period size of the nano-unit structures arranged in the first direction and the second direction is an integer multiple of 1 to 5 times the wavelength of the exposure light, respectively.

[0011] Optionally, the surface plasmon layer can generate surface plasmons under the action of the exposure light, a part of the surface plasmons passes through the surface plasmon layer to enhance the field strength of the near-field light, and the near-field of another part of the surface plasmons can resonate with a first light wave polarized parallel to the first direction and a second light wave polarized parallel to the second direction based on the periodic and spaced arrangement to generate sum-frequency effect and form a third light wave perpendicular to the surface plasmon layer, and the third light wave is the sum-frequency light.

[0012] Optionally, the resonance frequencies of the near-field light waves of the surface plasmons in the first direction and the second direction are the same as or an integral multiple of the light frequencies of the first light wave and the second light wave polarized in the same direction, respectively.

[0013] Optionally, the period size of the nano-unit structures arranged in the first direction is an integer multiple of 1 to 5 times the wavelength of the exposure light, so that the resonance frequency in the first direction is 1 to 0.2 times the frequency of the first light wave, and the period size of the nano-unit structures arranged in the second direction is an integer multiple of 1 to 5 times the wavelength of the exposure light, so that the resonance frequency in the second direction is 1 to 0.2 times the frequency of the second light wave.

[0014] Optionally, the resonance frequency f1 and wavelength λ1 of the first direction, the resonance frequency f2 and wavelength λ2 of the second direction, the frequency f3 and wavelength λ3 of the third light wave satisfy the following formula: f3=f1+f2, λ3=λ1*λ2 / (λ1+λ2).

[0015] Optionally, the thickness of the surface plasmon layer is between one half and three times the wavelength of the exposure light.

[0016] Optionally, the first direction and the second direction are perpendicular.

[0017] Optionally, the material of the surface plasmon layer includes a semi-transparent metal or a transparent conductive oxide to ultraviolet light.

[0018] Optionally, the material of the surface plasmon layer has a direct transmittance of greater than or equal to 40% to the exposure light.

[0019] Optionally, the material of the surface plasmon layer includes a semi-transparent metal, the semi-transparent metal includes one of Al, Au, Ag and Pd, and the thickness of the semi-transparent metal is less than or equal to 20 nanometers.

[0020] Optionally, the material of the surface plasmon layer includes a transparent conductive oxide to ultraviolet light, the transparent conductive oxide includes one of indium oxide, tin oxide, indium tin oxide and zinc oxide, and the thickness of the transparent conductive oxide is less than or equal to 30 nanometers.

[0021] Optionally, the direct transmittance of the semi-transparent conductive object to the exposure light is greater than 50%, and the direct transmittance of the transparent conductive object to the exposure light is greater than 80%.

[0022] Optionally, the power of the sum frequency light accounts for 10%-20% of the total power of the exposure light passing through the surface plasmon layer.

[0023] Optionally, the wavelength of the third light wave is 15%-25% less than the wavelength of the exposure light.

[0024] Optionally, the size of the nano-unit structure is equal to the spacing of two adjacent nano-unit structures.

[0025] Optionally, the shape of the nano-unit structure includes one of a square, a rectangle, a circle and an ellipse.

[0026] The application also provides a preparation method of the exposure light frequency enhancement device for projection lithography as described in any one of the above embodiments, comprising the steps of: providing a light-transmitting substrate; and forming a surface plasmon layer on the light-transmitting substrate.

[0027] The present invention also provides a photomask for projection lithography, the photomask comprising: an exposure light frequency enhancement device for projection lithography as described in any of the above embodiments; a transparent substrate having opposing first and second surfaces, the second surface being bonded to the second surface of the light-transmitting substrate of the enhancement device; and a light-shielding layer covering the first surface of the transparent substrate, the light-shielding layer having an exposure window that penetrates the light-shielding layer.

[0028] Optionally, the photomask further includes a phase-shifting material layer located between the transparent substrate and the light-shielding layer, and the exposure window stops at the top surface of the phase-shifting material layer.

[0029] Optionally, the transparent substrate is made of synthetic quartz glass, the light-shielding layer is made of chromium, chromium oxide, and chromium nitride, and the phase-shifting material layer is made of molybdenum silicon oxide, molybdenum silicon oxynitride, molybdenum silicon carbide, chromium silicon oxide, chromium silicon oxynitride, and chromium silicon carbide.

[0030] The present invention also provides a method for fabricating a photomask for projection lithography as described in any of the above embodiments, the method comprising the steps of: providing a light-transmitting substrate having opposing first and second surfaces; forming a surface plasmon resonance layer on the first surface of the light-transmitting substrate; providing a transparent substrate having opposing first and second surfaces, forming a light-shielding layer on the first surface of the transparent substrate, and forming an exposure window in the light-shielding layer; and bonding the second surface of the light-transmitting substrate and the second surface of the transparent substrate.

[0031] The present invention also provides a photomask for projection lithography, the photomask comprising: an exposure light frequency enhancement device for projection lithography as described in any of the above embodiments; and a light-shielding layer covering a second side of the light-transmitting substrate, the light-shielding layer having an exposure window that penetrates the light-shielding layer.

[0032] Optionally, the photomask further includes a phase-shifting material layer located between the light-transmitting substrate and the light-shielding layer, with the exposure window ending at the top surface of the phase-shifting material layer.

[0033] Optionally, the material of the light-shielding layer includes one of chromium, chromium oxide, and chromium nitride, and the material of the phase-shifting material layer includes one of molybdenum silicon oxide, molybdenum silicon oxynitride, molybdenum silicon carbide, chromium silicon oxide, chromium silicon oxynitride, and chromium silicon carbide.

[0034] The present invention also provides a method for fabricating a photomask for projection lithography as described in any of the above embodiments, the method comprising the steps of: providing a light-transmitting substrate having a first surface and a second surface opposite to each other; forming a surface plasmon resonance layer on the first surface of the light-transmitting substrate; forming a light-shielding layer on the second surface of the light-transmitting substrate, and forming an exposure window in the light-shielding layer.

[0035] As described above, the exposure light frequency enhancement device, photomask, and preparation method of the present invention have the following beneficial effects:

[0036] The exposure light frequency enhancement device provided by this invention involves depositing a surface plasmon polariton layer on the surface of a light-transmitting substrate. The surface plasmon polariton layer comprises multiple nanounit structures, and the material of the surface plasmon polariton layer includes a semi-transparent conductive material or a conductive material transparent to ultraviolet light. These nanounit structures are arranged in a periodic interval along a first and second direction on the plane of the surface plasmon polariton layer, respectively, to generate a sum-frequency effect by matching the wavelength of the exposure light (such as 365nm i-line light, 248nm ultraviolet light UV, 193nm deep ultraviolet light DUV, etc.). This sum-frequency effect forms sum-frequency light that passes through the light-transmitting substrate, and the power of this sum-frequency light accounts for less than or equal to 30% of the total power of the exposure light passing through the surface plasmon polariton layer. This solution is based on the sum-frequency effect, where a portion of the surface plasmon polariton... The near-field of the plasmon polariton interacts with a first light wave polarized in a first direction parallel to the surface and a second light wave polarized in a second direction. If the resonant frequencies of the near-field light waves of the surface plasmon polariton in the first and second directions are the same as or integer fractional multiples of the frequencies of the first and second light waves polarized in the same direction, a third light wave (sum-frequency light) perpendicular to the surface with a sum-frequency effect will be formed. The frequency of the third light wave is the sum of the resonant frequencies of the first and second directions, and the wavelength of the third light wave is shorter than the wavelength of both the first and second light waves. This results in the exposed light passing through the surface plasmon polariton layer having a first part with a constant wavelength and a second part with a shortened wavelength, thereby greatly improving the resolution and contrast of the photolithography process. Furthermore, this scheme largely utilizes the original frequency light source, requiring minimal or no adjustment to the original light source wavelength in the photolithography components, while ensuring high light transmittance and minimal energy loss.

[0037] The surface plasmon polariton layer of the present invention is a semi-transparent or transparent conductive material. On the one hand, it can generate surface plasmon polaritons to enhance the exposure light. On the other hand, it can effectively reduce the shading of the exposure light and improve the transmittance of the exposure light, thereby ensuring the final light intensity of the photolithography process. Attached Figure Description

[0038] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the embodiments of this application and to illustrate the implementation of this application, together with the textual description, to explain the principles of this application. Obviously, the drawings described below are merely some embodiments of this application.

[0039] Figures 1-4 The diagram shows the structure of each step in the preparation method of the exposure light frequency enhancement device according to Embodiment 1 of the present invention, wherein, Figure 3 The diagram shown is a cross-sectional structural schematic of the exposure light frequency enhancement device according to Embodiment 1 of the present invention. Figure 4 The diagram shown is a top view of the exposure light frequency enhancement device according to Embodiment 1 of the present invention.

[0040] Figures 5-9 The diagram shows the structure presented in each step of the photomask fabrication method according to Embodiment 2 of the present invention, wherein, Figure 8 and Figure 9 The diagrams show the structures of the two photomasks in Embodiment 2 of the present invention.

[0041] Figure 10 and Figure 11 The diagram shows the structural schematics of two photomasks according to Embodiment 3 of the present invention.

[0042] Component designation explanation

[0043] 101 Transparent substrate

[0044] 102 Surface Plasmon Layer

[0045] 201 Transparent substrate

[0046] 202 Light-shielding layer

[0047] 203 Phase-shifting material layer Detailed Implementation

[0048] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0049] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, whole, step, or component, but does not exclude the presence or addition of one or more other features, wholes, steps, or components.

[0050] Features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, combined with features in other embodiments, or substituted for features in other embodiments.

[0051] In the detailed description of embodiments of the present invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged and not to scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. In actual fabrication, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0052] For ease of description, spatial relation terms such as “below,” “under,” “lower than,” “below,” “above,” and “upper” may be used herein to describe the relationship between one element or feature shown in the accompanying drawings and other elements or features. It will be understood that these spatial relation terms are intended to include directions other than those depicted in the drawings for devices in use or operation. Furthermore, when a layer is referred to as being “between” two layers, it may be the only layer between the two layers, or there may be one or more layers in between.

[0053] In the context of this application, the structure described above the first feature may include embodiments in which the first and second features are formed in direct contact, or embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

[0054] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention 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.

[0055] Example 1

[0056] like Figure 3 and Figure 4As shown, this embodiment provides an exposure light frequency enhancement device for projection lithography. The enhancement device includes: a light-transmitting substrate 101, including a first surface and a second surface facing each other; a surface plasmon polariton layer 102 located on the first surface of the light-transmitting substrate 101. The surface plasmon polariton layer 102 includes multiple nanounit structures, which are arranged in a periodic interval in the row and column directions to generate a sum-frequency effect. The surface plasmon polariton layer 102 is used to generate surface plasmon polaritons under the action of the exposure light. Some of the surface plasmon polaritons pass through the surface plasmon polariton layer 102 to enhance the field strength of the near-field light. The near-field of another part of the surface plasmon polaritons, based on the periodic interval arrangement, can resonate and match with a first light wave polarized parallel to the first direction of the surface and a second light wave polarized in the second direction to generate a sum-frequency effect and form a third light wave perpendicular to the surface plasmon polariton layer. The exposure light includes two polarized beams, one polarized parallel to the row direction and the other polarized parallel to the column direction. The wavelength of the third light wave can be designed to be smaller than the wavelength of the first light wave and smaller than the wavelength of the second light wave. The exposure light frequency enhancement device provided by this invention, by depositing a surface plasmon polariton layer on the surface of a transparent substrate, includes multiple nanounit structures arranged periodically at intervals in the row direction and in the column direction. The surface plasmon polariton layer can generate surface plasmon polaritons under the action of exposure light (the wavelength of the exposure light can be 365nm, 248nm, 193nm, etc.). Some surface plasmon polaritons pass through the surface plasmon polariton layer to enhance the field strength of the exposure light, while another part of the surface plasmon polaritons is polarized into a first light wave in a first direction and a second light wave in a second direction. After passing through the surface plasmon polariton layer, the first and second light waves undergo a sum-frequency effect to form a third light wave. The wavelength of the third light wave is smaller than the wavelength of both the first and second light waves, so that the exposure light after passing through the surface plasmon polariton layer has a first part with a constant wavelength and a second part with a shortened wavelength, thereby greatly improving the resolution and contrast of the photolithography process.

[0057] In one embodiment, the resonant frequencies of the near-field light waves of the surface plasmon polaritons in the first and second directions are the same as or integer multiples of the light frequencies of the first and second light waves polarized in the same direction.

[0058] In one embodiment, the light-transmitting substrate 101 has a light transmittance greater than 80%. The light-transmitting substrate 101 may include synthetic quartz glass, soda glass, etc., but is preferably synthetic quartz glass. The thickness of the light-transmitting substrate 101 can be a conventional thickness or thinner. As an example, the thickness of the light-transmitting substrate 101 can be between 2 mm and 8 mm. For example, the thickness of the light-transmitting substrate 101 can be 6 mm.

[0059] In one embodiment, the exposure light includes, for example, 365nm i-line light, 248nm ultraviolet light (UV), 193nm deep ultraviolet light (DUV), etc.

[0060] In one embodiment, surface plasmon polaritons are generated when the exposure light irradiates the surface plasmon layer 102. In this embodiment, the surface plasmon polaritons, as electromagnetic field surface wave modes propagating at the interface between the conductor (such as metal) and the medium, are formed by the collective oscillation of high-density free electron gas in the conductor under the excitation of the electromagnetic field of the exposure light. They have a high near-field enhancement effect and super-diffraction-limited optical field localization, thereby effectively enhancing the field strength of the exposure light on the surface of the mask substrate.

[0061] In one embodiment, the material of the surface plasmon resonance layer 102 has a direct transmittance of 40% or more to the exposure light, in order to minimize the obstruction of the exposure light by the surface plasmon resonance layer 102.

[0062] In one embodiment, the surface plasmon resonance layer 102 comprises a translucent or transparent conductive material to minimize the obstruction of exposure light by the surface plasmon resonance layer 102.

[0063] In one embodiment, the translucent conductive material has a transmittance of more than 50% to the exposed light, and the transparent conductive material has a transmittance of more than 80% to the exposed light.

[0064] In one embodiment, the surface plasmon layer 102 is made of a translucent metal, which includes one of Al, Au, Ag, and Pd, and the thickness h of the translucent metal is less than or equal to 20 nanometers. In this embodiment, the surface plasmon layer 102 is made of gold (Au), and the thickness of the gold is 15 nanometers. By adjusting the thickness of the metal, it can be made translucent with a certain light transmittance. At the same time, it is necessary to ensure that the metal has a certain thickness to ensure the amount of surface plasmon excitation. In a preferred embodiment, the thickness h of the translucent metal is preferably 10 nanometers to 20 nanometers.

[0065] In one embodiment, the surface plasmon layer 102 is made of a transparent conductive oxide, which includes one of indium oxide, tin oxide, indium tin oxide, and zinc oxide, and the thickness of the transparent conductive oxide is less than or equal to 30 nanometers. When the surface plasmon layer 102 is a transparent conductive oxide, the surface plasmon layer 102 can be set to a larger thickness to increase the amount of excited surface plasmons. At the same time, increasing the thickness of the transparent conductive oxide will not significantly reduce the transmittance of the exposed light. Preferably, the thickness of the surface plasmon layer 102 can be 20 nanometers to 30 nanometers.

[0066] The surface plasmon polariton layer of the present invention is a semi-transparent or transparent conductive material. On the one hand, it can generate surface plasmon polaritons to enhance the exposure light. On the other hand, it can effectively reduce the shading of the exposure light and improve the transmittance of the exposure light, thereby ensuring the final light intensity of the photolithography process.

[0067] In this embodiment, the first direction is perpendicular to the second direction. The resonant frequency of the surface plasmon resonance layer in the first direction is positively correlated with the wavelength of the first light wave and the structural periodicity of the nanounit structure arranged in the first direction. Similarly, the resonant frequency of the surface plasmon resonance layer in the second direction is positively correlated with the wavelength of the second light wave and the structural periodicity of the nanounit structure arranged in the second direction. By designing and controlling the periodicity of the nanounit structure arranged in the first and second directions, so that the resonant frequencies of the plasmon resonance in the first and second directions are the same as or integer fractional multiples of the frequencies of the first and second light waves, a sum-frequency effect will be formed, generating a third light wave perpendicular to the surface. The frequency of the third light wave is the sum of the resonant frequencies of the first and second directions.

[0068] In one embodiment, the resonant frequency f1 and wavelength λ1 in the first direction, the resonant frequency f2 and wavelength λ2 in the second direction, and the frequency f3 and wavelength λ3 of the third light wave satisfy the following formulas: f3=f1+f2, λ3=λ1*λ2 / (λ1+λ2).

[0069] In one embodiment, the periodic size of the nanounit structures arranged in the first direction is one to five times the wavelength of the exposure light, such that the resonant frequency in the first direction is 1 to 0.2 times the frequency of the first light wave; and the periodic size of the nanounit structures arranged in the second direction is one to five times the wavelength of the exposure light, such that the resonant frequency in the second direction is 1 to 0.2 times the frequency of the second light wave.

[0070] For example, when the exposure light is the same light source, and the periodic size of the nano-unit structures arranged in the first direction is equal to the wavelength of the exposure light, and the periodic size of the nano-unit structures arranged in the second direction is equal to the wavelength of the exposure light, the frequencies of the first and second light waves are f and the wavelength is λ, then the frequency of the third light wave is 2f and the wavelength is λ / 2. However, for exposure light with a shorter wavelength λ (such as 193nm deep ultraviolet light DUV), the periodic size of the nano-unit structures arranged in the first direction can be equal to the wavelength of the exposure light, and the wavelength of the first light wave obtained by polarization is equal to the wavelength of the exposure light, both being λ. The periodic size of the nano-unit structures arranged in the second direction is three times the wavelength of the exposure light, which can increase the polarized second wavelength to 3λ, and the wavelength of the third light wave is 3 / 4λ. This way, on the one hand, a third light wave with a shortened wavelength can be obtained, and on the other hand, the wavelength of the third light wave is not too short, causing it to be easily absorbed by the light-transmitting substrate 101, thereby ensuring that the third light wave has a certain intensity. According to the above setting rules, preferably, the wavelength of the third light wave is set to be 15% to 25% smaller than the wavelength of the exposure light.

[0071] Because the third light wave has a shorter wavelength, its ability to penetrate the light-transmitting substrate 101 is weaker than that of the exposure light of the original wavelength. Therefore, during photolithography exposure, it is preferable to ensure a certain amount of exposure light of the original wavelength and a portion of the shorter-wavelength third light wave to maintain exposure intensity while improving the resolution and contrast of the photolithography process. Based on this, in one embodiment, the power of the third light wave accounts for less than or equal to 20% of the total power of the exposure light passing through the surface plasmon resonance layer 102. For example, the power of the third light wave is preferably 10% to 20% of the total power of the exposure light passing through the surface plasmon resonance layer 102.

[0072] In one embodiment, the size of the nanounit structure and the spacing between two adjacent nanounit structures are equal.

[0073] In one embodiment, the shape of the nanounit structure includes one of square, rectangular, circular, and elliptical shapes.

[0074] The exposure light frequency enhancement device provided by this invention, by setting a surface plasmon polariton layer on the surface of a light-transmitting substrate, includes multiple nano-unit structures arranged periodically at intervals in the row direction and in the column direction. The surface plasmon polariton layer can generate surface plasmon polaritons under the action of exposure light (the wavelength of the exposure light can be 365nm, 248nm, 193nm, etc.). Some surface plasmon polaritons pass through the surface plasmon polariton layer to enhance the field strength of the exposure light, while other surface plasmon polaritons are polarized into a first light wave in a first direction and a second light wave in a second direction. After passing through the surface plasmon polariton layer, the first light wave and the second light wave form a third light wave through a sum-frequency effect. The wavelength of the third light wave is smaller than the wavelength of the first light wave and smaller than the wavelength of the second light wave, so that the exposure light after passing through the surface plasmon polariton layer has a first part with a constant wavelength and a second part with a shortened wavelength, thereby greatly improving the resolution and contrast of the photolithography process.

[0075] like Figures 1-4 As shown, this embodiment also provides a method for fabricating an exposure light frequency enhancement device for projection lithography as described in any of the above schemes, including the steps of: 1) providing a light-transmitting substrate 101, such as... Figure 1 As shown; 2) A surface plasmon resonance layer 102 is formed on the light-transmitting substrate 101 by sputtering and photolithography-etching processes, such as... Figure 2 and Figure 3 As shown.

[0076] Example 2

[0077] like Figure 8 and Figure 9 As shown, this embodiment provides a photomask for projection lithography, the photomask comprising:

[0078] The exposure light frequency enhancement device, transparent substrate 201, and light-shielding layer 202 used for projection lithography are described in Embodiment 1, and will not be repeated here.

[0079] The transparent substrate 201 has a first side and a second side facing each other, and the second side is bonded to the second side of the light-transmitting substrate 101 of the enhancement device.

[0080] The light-shielding layer 202 covers the first side of the transparent substrate 201, and the light-shielding layer 202 has an exposure window that penetrates the light-shielding layer 202.

[0081] In one embodiment, the transparent substrate 201 is made of synthetic quartz glass, and the light-shielding layer 202 is made of one of chromium, chromium oxide, and chromium nitride.

[0082] In one embodiment, such asFigure 9 As shown, the photomask further includes a phase-shifting material layer 203, which is located between the transparent substrate 201 and the light-shielding layer 202. The exposure window stops at the top surface of the phase-shifting material layer 203. The material of the phase-shifting material layer 203 includes one of molybdenum oxide silicon, molybdenum oxynitride silicon, molybdenum oxynitride silicon carbide, chromium oxide silicon, chromium oxynitride silicon, and chromium oxynitride silicon carbide.

[0083] like Figures 1-9 As shown, this embodiment also provides a method for fabricating a photomask for projection lithography. The fabrication method includes the following steps: 1) providing a light-transmitting substrate 101, the light-transmitting substrate 101 having opposing first and second surfaces, such as... Figure 1 As shown; 2) A surface plasmon resonance layer 102 is formed on the first surface of the light-transmitting substrate 101 by sputtering and photolithography-etching processes, as shown. Figure 2 and Figure 3 As shown; 3) A transparent substrate 201 is provided, the transparent substrate 201 having opposing first and second surfaces, a light-shielding layer 202 is formed on the first surface of the transparent substrate 201, and an exposure window is formed in the light-shielding layer 202, as shown. Figures 5-7 As shown; 4) Bond the second surface of the light-transmitting substrate 101 and the second surface of the transparent substrate 201, as shown. Figure 8 As shown.

[0084] In this embodiment, a photomask for projection lithography with an integrated exposure light frequency enhancement device is formed by bonding. The surface plasmon resonance layer 102 and the light-shielding layer 202 can be fabricated on different substrates, so that the surface plasmon resonance layer 102 and the light-shielding layer 202 will not interfere with each other. Finally, the two substrates only need to be bonded by bonding process, which can effectively ensure the stability and yield of photomask fabrication.

[0085] Example 3

[0086] like Figure 10 and Figure 11 As shown, this embodiment provides a photomask for projection lithography. The photomask includes an exposure light frequency enhancement device for projection lithography and a light-shielding layer 202. The structure of the exposure light frequency enhancement device is as described in Embodiment 1, and will not be repeated here.

[0087] The light-shielding layer 202 covers the second side of the light-transmitting substrate 101, and the light-shielding layer 202 has an exposure window that penetrates the light-shielding layer 202. The material of the light-shielding layer 202 includes one of chromium, chromium oxide, and chromium nitride.

[0088] In one embodiment, such as Figure 11As shown, the photomask further includes a phase-shifting material layer 203, which is located between the light-transmitting substrate 101 and the light-shielding layer 202. The exposure window stops at the top surface of the phase-shifting material layer 203. The material of the phase-shifting material layer 203 includes one of molybdenum oxide silicon, molybdenum oxynitride silicon, molybdenum oxynitride silicon carbide, chromium oxide silicon, chromium oxynitride silicon, and chromium oxynitride silicon carbide.

[0089] like Figures 1-3 and Figure 10 , Figure 11 As shown, this embodiment also provides a method for fabricating a photomask for projection lithography. The fabrication method includes the following steps: 1) providing a light-transmitting substrate 101, the light-transmitting substrate 101 having opposing first and second surfaces, such as... Figure 1 As shown; 2) A surface plasmon resonance layer 102 is formed on the first surface of the light-transmitting substrate 101 by sputtering and photolithography-etching processes, as shown. Figure 2 and Figure 3 As shown; 3) A light-shielding layer 202 is formed on the second surface of the light-transmitting substrate 101, and an exposure window is formed in the light-shielding layer 202, as shown. Figure 10 As shown.

[0090] In this embodiment, the surface plasmon resonance layer 102 and the light-shielding layer 202 are fabricated on the same substrate, which can save one substrate and one bonding process, thereby effectively reducing the cost of the fabrication process. Furthermore, compared with bonding two substrates, using the same substrate can effectively reduce the overall thickness of the photomask and improve the transmittance of the exposed light.

[0091] As described above, the exposure light frequency enhancement device, photomask, and preparation method of the present invention have the following beneficial effects:

[0092] The exposure light frequency enhancement device provided by this invention involves depositing a surface plasmon polariton layer on the surface of a light-transmitting substrate. This layer comprises multiple nanounit structures arranged periodically at intervals in both the row and column directions. Under the influence of exposure light (wavelengths can be 365nm, 248nm, 193nm, etc.), the surface plasmon polariton layer generates surface plasmon polaritons. Some of these surface plasmon polaritons penetrate the surface plasmon polariton layer, enhancing the field intensity of the exposure light. The near-field of another portion of the surface plasmon polaritons interacts with a first light wave polarized parallel to the first direction of the surface and a second light wave polarized in the second direction. The interaction between the second and third light waves of the surface plasmon polaritons, and the resonant frequencies of the near-field light waves in the first and second directions, respectively, and the light frequencies of the first and second light waves polarized in the same direction, will form a third light wave with a sum-frequency effect and perpendicular to the surface. The frequency of the third light wave is the sum of the resonant frequencies in the first and second directions. The wavelength of the third light wave is shorter than the wavelength of the first light wave and shorter than the wavelength of the second light wave. This results in the exposed light after passing through the surface plasmon polariton layer having a first part with a constant wavelength and a second part with a shortened wavelength, thereby greatly improving the resolution and contrast of the photolithography process.

[0093] The surface plasmon polariton layer of the present invention is a semi-transparent or transparent conductive material. On the one hand, it can generate surface plasmon polaritons to enhance the exposure light. On the other hand, it can effectively reduce the shading of the exposure light and improve the transmittance of the exposure light, thereby ensuring the final light intensity of the photolithography process.

[0094] Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0095] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. An exposure light ray frequency enhancement device for projection photolithography, characterized by, The frequency enhancement device comprises: A light-transmitting substrate comprising opposite first and second faces; A surface plasmon layer on the first face of the light-transmitting substrate, the surface plasmon layer comprising a plurality of nano-unit structures arranged periodically and spaced apart in a first direction and a second direction of the surface plasmon layer plane to generate a sum-frequency effect that can match the wavelength of the exposure light, the sum-frequency effect forming sum-frequency light that passes through the light-transmitting substrate, the power of the sum-frequency light accounting for less than or equal to 30% of the total power of the exposure light that passes through the surface plasmon layer; The surface plasmon layer can generate surface plasmons under the action of the exposure light, a part of the surface plasmons passing through the surface plasmon layer to enhance the field strength of the near-field light, and another part of the surface plasmons generating a sum-frequency effect to form third light that is perpendicular to the surface plasmon layer based on the periodic and spaced arrangement to resonate with first light polarized parallel to the surface first direction and second light polarized parallel to the surface second direction, the third light being the sum-frequency light; The period size of the nano-unit structures arranged in the first direction is an integer multiple of 1-5 times the wavelength of the exposure light, so that the resonance frequency in the first direction is 1-0.2 times the frequency of the first light, and the period size of the nano-unit structures arranged in the second direction is an integer multiple of 1-5 times the wavelength of the exposure light, so that the resonance frequency in the second direction is 1-0.2 times the frequency of the second light; The resonance frequency f1 and wavelength λ1 in the first direction, the resonance frequency f2 and wavelength λ2 in the second direction, and the frequency f3 and wavelength λ3 of the third light satisfy the following formula: f3=f1+f2, λ3=λ1*λ2 / (λ1+λ2).

2. The exposure light ray frequency enhancement device for projection photolithography of claim 1, wherein: The exposure light comprises two polarized lights polarized parallel to the first direction and the second direction.

3. The exposure light ray frequency enhancement device for projection photolithography of claim 1, wherein: The resonance frequencies of the near-field light waves of the surface plasmons in the first direction and the second direction are the same as or an integral multiple of the light frequencies of the first light and the second light polarized in the same direction.

4. The exposure light ray frequency enhancement device for projection photolithography of claim 1, wherein: The thickness of the surface plasmon layer is between one-half and three times the wavelength of the exposure light.

5. The exposure light ray frequency enhancement device for projection photolithography of claim 1, wherein: The first direction and the second direction are perpendicular.

6. The exposure light ray frequency enhancement device for projection photolithography of claim 1, wherein: The power of the sum-frequency light accounts for 10%-20% of the total power of the exposure light that passes through the surface plasmon layer.

7. The exposure light ray frequency enhancement device for projection photolithography of claim 1, wherein: The direct transmittance of the material of the surface plasmon layer to the exposure light is greater than or equal to 40%.

8. The exposure light ray frequency enhancement device for projection photolithography of claim 1, wherein: The material of the surface plasmon layer comprises a semi-transparent metal or a transparent conductive oxide.

9. The exposure light ray frequency enhancement device for projection photolithography of claim 8, wherein: The semi-transparent metal comprises one of Al, Au, Ag, and Pd, and the thickness of the semi-transparent metal is less than or equal to 20 nanometers; the transparent conductive oxide comprises one of indium oxide, tin oxide, indium tin oxide, and zinc oxide, and the thickness of the transparent conductive oxide is less than or equal to 30 nanometers.

10. The exposure light ray frequency enhancement device for projection photolithography of claim 8, wherein: The direct transmittance of the semi-transparent conductive object to the exposure light is 50% or more.

11. A method of manufacturing an exposure light frequency enhancement device for projection photolithography according to any one of claims 1 to 10, characterized by, The method comprises the steps of: Providing a light-transmitting substrate; forming a surface plasmon layer on the light-transmitting substrate.

12. A photomask for projection lithography, characterized in that The photomask comprises: The exposure light frequency enhancement device for projection photolithography according to any one of claims 1-10; A transparent substrate having opposite first and second faces, the second face being bonded to the second face of the light-transmitting substrate of the enhancement device; A light-blocking layer covering the first face of the transparent substrate, the light-blocking layer having an exposure window penetrating the light-blocking layer.

13. The photomask for projection photolithography of claim 12, wherein: The photomask further comprises a phase-shifting material layer between the transparent substrate and the light-blocking layer, the exposure window stopping at the top surface of the phase-shifting material layer.

14. A method of producing a photomask for projection lithography as claimed in any one of claims 12-13, characterized in that, The method comprises the steps of: providing a light-transmitting substrate having opposite first and second faces; forming a surface plasmon layer on the first face of the light-transmitting substrate; providing a transparent substrate having opposite first and second faces, forming a light-blocking layer on the first face of the transparent substrate, and forming an exposure window in the light-blocking layer; bonding the second face of the light-transmitting substrate and the second face of the transparent substrate.

15. A photomask for projection lithography, characterized in that The photomask comprises: The exposure light frequency enhancement device for projection photolithography according to any one of claims 1-10; A light-blocking layer covering the second face of the light-transmitting substrate, the light-blocking layer having an exposure window penetrating the light-blocking layer.

16. The photomask for projection photolithography of claim 15, wherein: The photomask further comprises a phase-shifting material layer between the transparent substrate and the light-blocking layer, the exposure window stopping at the top surface of the phase-shifting material layer.

17. A method of producing a photomask for projection lithography as claimed in any one of claims 15-16, characterized in that, The method comprises the steps of: providing a light-transmitting substrate having opposite first and second faces; forming a surface plasmon layer on the first face of the light-transmitting substrate; forming a light-blocking layer on the second face of the light-transmitting substrate, and forming an exposure window in the light-blocking layer.

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