A device and method for super-resolution lithography based on a dielectric waveguide

Abstract

The application discloses a kind of super-resolution lithography device and method based on dielectric waveguide, its structure includes transparent substrate, mask layer of nanometer grating or cavity array structure, filling layer, waveguide structure layer formed by two layers of dielectric film layer covering photosensitive layer, substrate layer in turn.The waveguide structure arrangement can effectively filter out stray order diffraction wave excited by mask, and high-frequency evanescent wave of specific diffraction order is transmitted to photosensitive layer, forming deep subwavelength grating array pattern with high aspect ratio, high light field intensity characteristics.The method can break through the constraint of diffraction limit, and form super-resolution lithography pattern.It can be used for processing various period patterns, and has important application in integrated circuit and optoelectronic device preparation.

Description

Technical Field

[0001] This invention relates to the field of super-resolution lithography technology, and in particular to a super-resolution lithography device and method based on dielectric waveguide. Background Technology

[0002] With the rapid development of the semiconductor industry, the degree of optical integration is becoming increasingly higher, which requires the size of nanodevices to be continuously reduced. Therefore, the resolution of photolithography fabrication processes must be continuously improved. However, traditional optical systems suffer from the diffraction limit, which greatly restricts the improvement of the resolution of photolithography technology.

[0003] Currently, the most representative super-resolution lithography method is surface plasmon lithography. Because surface plasmons possess unique optical properties, they can couple and amplify evanescent waves, thereby breaking the diffraction limit and bringing new opportunities for research in super-resolution focusing, imaging, and lithography. Even though surface plasmon lithography has significant advantages, its inherent metal losses are relatively high, resulting in low light transmission efficiency and shallow lithographic pattern depth. Furthermore, it is highly susceptible to introducing metal contamination during the lithography process, affecting the actual performance of the devices.

[0004] Therefore, there is a need for a super-resolution lithography device and method that can avoid metal loss and contamination. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a super-resolution lithography device and method based on a dielectric waveguide. The method utilizes a subwavelength dielectric thin film to construct a planar waveguide, forming a dielectric waveguide structure, thereby achieving high-frequency evanescent wave enhancement and selective, efficient transmission, and ultimately forming a deep subwavelength interference pattern on the photosensitive layer.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] The super-resolution lithography device based on dielectric waveguide provided by the present invention comprises, from top to bottom, a transparent substrate layer, a mask layer, a planarization film layer, a transmissive dielectric film layer, a photosensitive layer, a reflective dielectric film layer, and a substrate layer.

[0008] The transmission dielectric film, the photosensitive layer, and the reflection dielectric film constitute a dielectric waveguide structure film layer, forming a resonant cavity;

[0009] The dielectric waveguide structure film is used to filter out stray diffraction waves excited by the mask layer, transmit high-frequency evanescent waves to the photosensitive layer, and enhance the evanescent waves to form a super-resolution lithographic pattern.

[0010] Furthermore, the transmissive medium film layer and the photosensitive layer are vacuum adsorbed.

[0011] Furthermore, the mask layer is a grating pattern mask layer composed of a nano-slit or hole array.

[0012] Furthermore, the pattern arrangement period in the slit or aperture array structure of the nanograting is 40nm to 400nm, and the duty cycle is 0.1 to 0.9.

[0013] Furthermore, the reflective dielectric film and the transmissive dielectric film are dielectric layers made of the same material.

[0014] Furthermore, both the reflective medium film and the transmissive medium film are made of titanium dioxide.

[0015] Furthermore, the thickness of the transmission medium film is 10 nm to 100 nm.

[0016] The method for fabricating a super-resolution photolithography device based on a dielectric waveguide provided by this invention includes the following steps:

[0017] (a) Cleaning the substrate as a transparent base layer;

[0018] (b) Fabrication of mask layer using conventional photolithography;

[0019] (c) Mask layer planarization;

[0020] (d) Preparation of a transmission medium film;

[0021] (e) Clean another substrate to serve as the substrate layer;

[0022] (f) Fabrication of a reflective dielectric film on a substrate layer;

[0023] (g) Prepare a photosensitive layer on a reflective medium film;

[0024] (h) Make close contact between the bottom film layer and the mask layer, and expose the S-polarized illumination light perpendicularly from one side of the mask layer;

[0025] (i) The super-resolution lithographic pattern is finally obtained by developing with a developer.

[0026] Furthermore, the reflective medium film material and the transmissive medium film material are metal oxide layers.

[0027] Furthermore, both the reflective medium film and the transmissive medium film are made of titanium dioxide.

[0028] The beneficial effects of this invention are as follows:

[0029] This invention provides a super-resolution lithography device and method based on a dielectric waveguide. The structure sequentially includes a transparent substrate, a grating mask layer with a nano-slit or hole array structure, a filling layer, a waveguide structure layer formed by two dielectric film layers covering a photosensitive layer (i.e., a transmission dielectric film layer, a reflection dielectric film layer, and a photosensitive layer), and a substrate layer. This waveguide structure arrangement effectively filters out stray diffraction waves excited by the mask and transmits high-frequency evanescent waves of specific diffraction orders to the photosensitive layer, forming a deep subwavelength grating array pattern with high aspect ratio and high optical field intensity. This method can overcome the diffraction limit constraint to form super-resolution lithography patterns. It can be used to process various periodic patterns and has important applications in the fabrication of integrated circuits and optoelectronic devices.

[0030] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0031] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the following figures are provided for illustration:

[0032] Figure 1 This is a schematic diagram of the structure of the present invention.

[0033] Figure 2 This is a schematic diagram of the fabrication process of the super-resolution lithography device of the present invention.

[0034] Figure 3 This is a graph of the optical transfer function (OTF) of the dielectric film.

[0035] Figure 4 This is a simulation image of the photolithographic structure.

[0036] Figure 1 In the middle: 1. Transparent substrate layer; 2. Mask layer; 3. Planarization film layer; 4. Transmitting medium film layer; 5. Photosensitive layer; 6. Reflecting medium film layer; 7. Substrate layer. Detailed Implementation

[0037] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0038] Example 1

[0039] like Figure 1As shown, this embodiment provides a super-resolution lithography device based on a dielectric waveguide, which uses a dielectric film layer instead of a metal film layer to reduce transmission loss and enhance evanescent wave transmission efficiency, and finally forms a deep subwavelength pattern on the photosensitive layer. The structure of the super-resolution lithography device is arranged from top to bottom as follows: transparent substrate layer 1, mask layer 2, planarization film layer 3, transmission dielectric film layer 4, photosensitive layer 5, reflection dielectric film layer 6, and substrate layer 7.

[0040] The waveguide structure arrangement can effectively filter out stray diffraction waves excited by the mask, and transmit high-frequency evanescent waves of specific diffraction orders to the photosensitive layer, forming a deep subwavelength grating array pattern with high aspect ratio and high light field intensity.

[0041] This method can overcome the diffraction limit and form super-resolution lithographic patterns. It can be used to process various periodic patterns and has important applications in the fabrication of integrated circuits and optoelectronic devices.

[0042] In this embodiment, the transmissive dielectric film 4, the photosensitive layer 5, and the reflective dielectric film 6 constitute a dielectric waveguide structure consisting of two dielectric film layers covering the photosensitive layer. The photosensitive layer 5 of the waveguide structure layer is in close contact with the transmissive dielectric film 4 under vacuum adsorption. This close contact minimizes the thickness of the air gap layer, thereby reducing evanescent wave loss and minimizing the influence of other materials on the waveguide performance. Vacuum is used to compress the film layers using atmospheric pressure, reducing the influence of air gaps; alternatively, external forces could be applied to the upper and lower parts for compression. Through simulation optimization, the required materials and thicknesses are obtained. Light incident on the photosensitive layer 5 undergoes multiple total internal reflections, forming a resonant structure. Imaging occurs within the photosensitive layer 5, and the function is only achieved when the dielectric film 4, the photosensitive layer 5, and the bottom reflective dielectric film 6 are all present simultaneously.

[0043] In this embodiment, the transparent substrate layer 1 is inorganic glass, fused silica, plexiglass, or transparent plastic.

[0044] In this embodiment, the mask layer 2 is a nanograting array pattern, such as a periodically arranged nano-slit structure. The material of the mask layer 2 can be metals such as Au, Al, and Cr, or media such as TiO2 and SiO2. The arrangement period of the nano-slit or hole array structure is 40nm to 400nm, and the duty cycle is 0.1 to 0.9.

[0045] In this embodiment, the planarization film layer 3 is made of PMMA or a curing adhesive.

[0046] In this embodiment, the material of the transmission medium film 4 is MgF2, Si3N4, GaN, AlN, Al2O3, TiO2, SiO2, or Ta2O5; the film thickness is 10nm to 100nm. The material of the reflection medium film 6 in this embodiment is MgF2, Si3N4, GaN, AlN, Al2O3, TiO2, SiO2, or Ta2O5. The material of the bottom medium film 6 does not need to be the same as that of the transmission medium film 4, but it is better if the two layers are the same. The thickness of the reflection medium film 6 and the transmission medium film 4 can be within a preset range. The thickness of the reflection medium film 6 can be slightly the same as that of the transmission medium film 4, or the thickness of the reflection medium film 6 and the transmission medium film 4 can be within a preset range.

[0047] In this embodiment, the reflective dielectric film 6 and the transmissive dielectric film 4 are both made of metal oxide layers. The reflective dielectric film 6 and the transmissive dielectric film 4 are both made of titanium dioxide layers.

[0048] In this embodiment, the photosensitive layer 5 is a photoresist with a thickness of 5nm to 500nm;

[0049] In this embodiment, the substrate layer 7 is made of glass, quartz, silicon wafer, or PET.

[0050] The super-resolution lithography method based on dielectric waveguides provided in this embodiment is as follows:

[0051] A transparent substrate is uniformly illuminated by an S-polarized plane wave light source. The plane wave acts on a grating mask layer composed of nano-slits or an array of holes, exciting diffracted waves with different wave vector characteristics. After passing through a planarization film layer, the diffracted waves are transmitted to a dielectric waveguide structure film layer. Utilizing the spatial spectrum filtering function of the dielectric waveguide, high-frequency diffracted waves of the same order are allowed to pass through, and finally a super-resolution interference pattern is formed in the intermediate photosensitive layer.

[0052] like Figure 2 As shown, the main steps of the super-resolution lithography method in this embodiment are as follows:

[0053] (a) Clean the substrate as a transparent substrate layer 1;

[0054] (b) Mask layer 2 was prepared by magnetron sputtering;

[0055] (c) Mask pattern planarization to form film layer 3;

[0056] (d) Preparation of transmission dielectric film by physical vapor deposition 4;

[0057] (e) Clean another substrate to serve as substrate layer 7;

[0058] (f) Prepare a reflective dielectric film 6 on the substrate 7 by physical vapor deposition;

[0059] (g) A photosensitive layer 5 is prepared on the reflective medium film 6 by spin coating;

[0060] (h) Make close contact between the bottom film layer and the mask layer, and expose the S-polarized illumination light perpendicularly from one side of the mask layer;

[0061] (i) The super-resolution lithographic pattern is finally obtained by developing with a developer.

[0062] In this embodiment, both the reflective and transmissive dielectric layers are made of metal oxides. The reflective and transmissive dielectric layers are made of titanium dioxide.

[0063] Metal contamination is a common problem during photolithography processes using pre-fabricated surface plasmon lithography (SPL) devices. Metal contamination occurs because the SPL device itself contains metal layers (such as gold, silver, or aluminum), and during close-contact exposure, metal particles inevitably settle onto the fabricated device's structural pattern, leading to defects and affecting performance. However, in this embodiment, the reflective dielectric layer 6 and the transmissive dielectric layer 4 of the super-resolution lithography device are made of metal oxide layers, while the reflective dielectric layer 6 and the transmissive dielectric layer 4 are made of titanium dioxide layers. Therefore, metal contamination does not occur during photolithography processes using the SPL device provided in this embodiment.

[0064] Example 2

[0065] like Figure 1 As shown, the transparent substrate 1 in this embodiment is made of inorganic glass, fused silica, plexiglass or transparent plastic. The transparent substrate needs to be made of a material with a certain hardness and not easily deformed, and has a high transmittance to ultraviolet light and visible light.

[0066] The mask layer 2 is a periodic mask grating, belonging to a nano-slit or hole array structure. Its material is selected from metals such as Au, Al, and Cr, or dielectrics such as TiO2 and SiO2. The arrangement period of the nano-slit or hole array structure is 40nm to 400nm, and the duty cycle is 0.1 to 0.9. The mask grating is formed by depositing mask material on the transparent substrate layer 1 using physical vapor deposition to form a film layer, and then fabricating the nano-slit or hole array structure using traditional photolithography or electron beam direct writing / focused ion beam direct writing processes.

[0067] The planarization film layer 3 can be made of materials such as PMMA or curing adhesive, and its thickness can be 5nm to 50nm. The function of the planarization film layer is to fill the mask gaps. It is formed by coating PMMA or curing adhesive onto the mask layer 2, curing it by heating or light, and then etching to thin it out.

[0068] The transmission dielectric film 4 is prepared by depositing a dielectric material on the planarized film 3 using a physical vapor deposition method, and its structure is as follows: Figure 1 As shown. The film materials include, but are not limited to, MgF2, Si3N4, GaN, AlN, Al2O3, TiO2, SiO2, Ta2O5, etc., and the thickness of each film layer can be 10nm to 100nm.

[0069] The function of the transmission medium film layer 4 is to selectively transmit the nth order grating diffracted light in each direction when the incident light irradiates the mask layer 2.

[0070] The photosensitive layer 5 is a photoresist that is sensitive to incident light, with a thickness of 5nm to 500nm; the bottom dielectric film layer 6 is made of materials including but not limited to MgF2, Si3N4, GaN, AlN, Al2O3, TiO2, SiO2, Ta2O5, etc., and the thickness of each film layer can be 10nm to 100nm.

[0071] The substrate 7 is made of materials including but not limited to glass, quartz, silicon wafers, PET, etc. The photosensitive layer 5 is directly coated on the reflective medium film layer 6, and the reflective medium film layer 6 is then directly coated on the substrate 7.

[0072] The principle of this invention is:

[0073] When a plane-wave beam illuminates the nano-slit or aperture array grating of mask layer 2, its transverse wave vector is:

[0074] k x =nk0sinθ+m(λ / P)k0,

[0075] Where k0 is the free space wave vector, n is the refractive index of the mask layer substrate, θ is the incident angle, P is the grating period, λ is the incident light wavelength, and m is the diffraction wave order excited by the mask grating.

[0076] The dielectric in the film layer of the dielectric waveguide structure has a filtering transmission function for diffracted waves, so that only diffracted waves within a specific wave vector range can pass through, while other diffraction orders are strongly suppressed.

[0077] The high-frequency evanescent waves that are ultimately transmitted interfere with each other and form a super-resolution pattern on the photosensitive layer. The period of the interference pattern is: p = P / (2m).

[0078] By adjusting the geometric parameters (including film thickness and thickness ratio) and material parameters (including refractive index) of the transmission and reflection media films, selective transmission of evanescent waves in different spatial spectra can be achieved, with a large number of degrees of adjustment freedom.

[0079] In this embodiment, the thickness of the dielectric film layer affects the OTF curve, resulting in differences in the peak value and the corresponding kx / k0. It also affects the contrast and light intensity of the photolithographic pattern in the photosensitive layer 5.

[0080] Furthermore, the dielectric film layer exhibits low transmission loss, resulting in a high light field intensity for the photosensitive layer pattern and enabling shorter exposure times. Additionally, the single-diffraction order filtering transmission reduces the influence of stray waves, leading to higher contrast in the lithographic pattern. This device offers advantages such as simple structure, flexible use, high efficiency, and low cost.

[0081] Example 3

[0082] like Figure 1 As shown: S-polarized light is used, with an incident wavelength of 193 nm and an incident angle of 0°; the transparent substrate 1 is a glass substrate; the mask layer 2 is a one-dimensional slit array Al mask with a period of 88 nm and a thickness of 35 nm; the planarization film layer 3 is made of PMMA and has a thickness of 15 nm; the dielectric film layer 4 is made of TiO2 with a dielectric constant of 7.84 and a thickness of 22 nm; the photosensitive layer 5 is made of photoresist with a dielectric constant of 2.9177+0.1880i and a thickness of 30 nm; the bottom dielectric film layer 6 is made of TiO2 with a dielectric constant of 7.84 and a thickness of 20 nm.

[0083] When an S-polarized plane light wave is perpendicularly incident on a slit grating of a mask layer, it will excite diffraction waves of different orders. If the first-order diffraction wave is limited, the transverse wave vector is 2.208k0.

[0084] like Figure 3 As shown, the filtering and transmission characteristics of the dielectric film can be described by the optical transfer function (OTF) curve. The OTF curve of the overall structure consisting of two dielectric films and photoresist at a wavelength of 193 nm is shown below. Figure 3 The horizontal axis represents the transverse wave vector of the light wave transmitted through the film, and the vertical axis represents the transmission coefficient. According to... Figure 3 The OTF curves show a transmission passband for the transverse wave vector, with the passband interval located between 1.5k0 and 2.5k0 for high-frequency wave vectors. This indicates that only high-frequency evanescent waves with spatial wave vectors within this range can penetrate the dielectric film. Therefore, only the positive and negative first-order diffraction waves (m=1) can pass through the dielectric film, while other diffraction orders will be suppressed. Two coherent plane waves propagate to the photosensitive layer and interfere with each other to form a deep subwavelength one-dimensional periodic pattern. According to p=P / (2m), the period of the interference pattern is 44nm.

[0085] like Figure 4 As shown, Figure 4 This embodiment uses the simulation software COMSOL Multiphysics for verification. The simulated light wave transmission effect is shown, where the horizontal axis (x) represents the length direction of this embodiment, and the vertical axis (z) represents the thickness direction. The z-direction is also the light wave transmission direction. Figure 4 It can be clearly seen that the slit array mask excites the diffraction wave, and after the diffraction wave propagates in the dielectric film layer, the period of the pattern formed in the photosensitive layer is half the period of the mask grating, and the light field covers the entire thickness of the photosensitive layer.

[0086] Example 4

[0087] like Figure 1 As shown: S-polarized light is used, with an incident wavelength of 405nm and an incident angle of 0°; the transparent substrate 1 is a glass substrate; the mask layer 2 is a one-dimensional slit array Al mask with a period of 204nm and a thickness of 30nm; the planarization film layer 3 is made of PMMA and has a thickness of 30nm; the dielectric film layer 4 is made of TiO2 and has a thickness of 44nm; the photosensitive layer 5 is made of photoresist with a refractive index of 2.8583-0.1170i and a thickness of 80nm; the bottom dielectric film layer 6 is made of TiO2 and has a thickness of 50nm.

[0088] When an S-polarized plane wave perpendicularly illuminates the slit grating of the mask layer, it will excite diffraction waves of different orders. If the first-order diffraction wave is limited, the transverse wave vector is k. x =1.974k0; Similarly, only high-frequency evanescent waves with spatial wave vectors in the passband can pass through the dielectric film. Therefore, only the positive and negative first-order diffraction waves (m=1) can pass through the dielectric film, while other diffraction orders will be suppressed. Two coherent plane waves propagate to the photosensitive layer and interfere with each other to form a deep subwavelength one-dimensional periodic pattern. According to p=P / (2m), the period of the interference pattern can be obtained as 102nm.

[0089] The above-described embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. A super-resolution photolithography device based on a dielectric waveguide, characterized in that: The transparent substrate layer (1), mask layer (2), planarization film layer (3), transmission medium film layer (4), photosensitive layer (5), reflection medium film layer (6), and substrate layer (7) are arranged sequentially from top to bottom. The transmissive dielectric film (4), the photosensitive layer (5), and the reflective dielectric film (6) constitute a dielectric waveguide structure film layer, forming a resonant cavity; the photosensitive layer is sandwiched between the transmissive dielectric film layer and the reflective dielectric film layer, and the three together constitute a dielectric waveguide structure film layer in which the photosensitive layer is covered by two dielectric film layers, and form a resonant cavity; light incident on the photosensitive layer undergoes multiple total internal reflections, forming a resonant structure, and an image is formed in the photosensitive layer; The dielectric waveguide structure film is used to filter out stray order diffraction waves excited by the mask layer, enhance high-frequency evanescent waves, and transmit them to the photosensitive layer to form a super-resolution lithographic pattern.

2. The super-resolution lithography device based on dielectric waveguide as described in claim 1, characterized in that: The transmissive medium film (4) and the photosensitive layer (5) are vacuum adsorbed.

3. The super-resolution lithography device based on dielectric waveguide as described in claim 1, characterized in that: The mask layer (2) is a grating pattern mask layer composed of nano-slits or hole arrays.

4. The super-resolution lithography device based on dielectric waveguide as described in claim 3, characterized in that: The pattern arrangement period in the slit or aperture array structure of the nanograting is 40nm~400nm, and the duty cycle is 0.1~0.

9.

5. The super-resolution lithography device based on dielectric waveguide as described in claim 1, characterized in that: The reflective medium film (6) and the transmissive medium film (4) are made of the same material.

6. The super-resolution lithography device based on dielectric waveguide as described in claim 1, characterized in that: The reflective medium film (6) and the transmittance medium film (4) are both made of titanium dioxide.

7. The super-resolution lithography device based on dielectric waveguide as described in claim 1, characterized in that: The thickness of the transmission medium film 4 is 10 nm to 100 nm.

8. A method for fabricating a super-resolution photolithography device based on a dielectric waveguide as described in any one of claims 1-7, characterized in that: Includes the following steps: Clean the substrate as a transparent base layer; Traditional photolithography is used to prepare mask layers; Mask layer planarization; Preparation of transmission dielectric film; Clean another substrate to serve as the substrate layer; A reflective dielectric film layer is prepared on a substrate layer; A photosensitive layer is prepared on a reflective dielectric film; The substrate layer, the reflective medium film layer, and the photosensitive layer are combined to form the bottom film layer; The bottom film layer and the transmission medium film layer are brought into close contact, and S-polarized illumination light is incident perpendicularly from one side of the mask layer for exposure. The super-resolution lithographic pattern is obtained by developing the image with a developer.

9. The fabrication method of the super-resolution photolithography device based on dielectric waveguide as described in claim 8, characterized in that: The reflective medium film material and the transmissive medium film material are both metal oxide layers.

10. The method for fabricating a super-resolution photolithography device based on a dielectric waveguide as described in claim 8, characterized in that: The reflective medium film and the transmissive medium film are both made of titanium dioxide.

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