A method for preparing a multi-layer EUV photoresist

Abstract

The application relates to a preparation method of a multilayer EUV photoresist, and relates to the technical field of photoresist, which comprises an EUV photoresist and a covering structure or an interlayer structure formed by at least one antireflection film, the covering structure is that one or more antireflection films cover the EUV photoresist to form a single-layer or multi-layer film covering structure, and the interlayer structure is that one or more antireflection films are inserted into the EUV photoresist to form a multilayer film structure in which the antireflection film layer and the photoresist are stacked with each other. The technical effect of the application is that the obtained photoresist has higher exposure efficiency for extreme ultraviolet light of a certain wavelength or a certain wave band, and has higher thermal stability, chemical stability and mechanical stability, is less prone to cracking and defects, is more resistant to thermal expansion, and is less prone to reaction with water in the air.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photoresist, and particularly relates to a preparation method of a multilayer EUV photoresist. BACKGROUND

[0002] Photoresist is an important photosensitive material used in semiconductor manufacturing and micro-nano processing. Its key role is to achieve high-resolution and high-precision pattern transfer, thereby manufacturing complex micro-nano structures. When exposed to a specific wavelength of light source, the chemical properties of photoresist will change, allowing fine patterns to be formed on its surface. These patterns are then transferred to the substrate material to generate the required microelectronic structures through subsequent etching or deposition processes. Photoresist is widely used in the fields of semiconductor manufacturing, micro-electro-mechanical systems, optoelectronic devices, display manufacturing, etc.

[0003] With the continuous advancement of integrated circuit manufacturing technology, the critical dimension of the lithography process is continuously shrinking. The current leading technology of lithography is deep ultraviolet (DUV) and extreme ultraviolet (EUV) lithography technology. EUV lithography technology is bound to replace DUV lithography technology. Because the wavelength of EUV lithography is shorter, its resolution is higher. EUV does not need to use multiple patterning like DUV lithography technology, and can achieve the same line width with fewer process steps and lower cost. Therefore, EUV lithography is crucial for advanced nodes (such as 5 nanometers, 3 nanometers) production.

[0004] EUV lithography technology also has higher requirements for photoresist. The number of EUV light photons with a wavelength of 13.5 nanometers is less than that of DUV light, and the penetration depth in photoresist material is short. In thick photoresist, most of the extreme ultraviolet photons are absorbed at the surface, and the absorbed EUV light will produce scattering in the lower layer, resulting in incomplete or uneven exposure of the photoresist depth. This uneven exposure will cause a decrease in pattern fidelity, and the exposure at the top of the resist layer will be more than at the bottom. Therefore, the use of thick resist will cause the pattern to be unclear, blurred or thin, which is not suitable for high-resolution feature requirements. And the photon dose of EUV is low, and random effects occur. These reasons will increase the line edge roughness (LER) and line width roughness (LWR). High-resolution EUV lithography of advanced nodes (such as 7 nanometers, 5 nanometers and below) requires extremely precise control of pattern edges and line widths. Thinner resist can reduce line edge roughness (LER) and line width roughness (LWR), thereby helping to improve the accuracy of small feature patterns. And thinner resist can reduce the amount of outgassing material, reduce the risk of contamination, and better meet the high requirements of EUV tool maintenance.

[0005] Therefore, the thickness of EUV photoresist is typically between 20 nm and 50 nm. This is much thinner than the traditional resist used in deep ultraviolet (DUV) lithography, which has a thickness typically between 80 nm and 100 nm. It is foreseeable that the future EUV photoresist thickness should be controlled below 20 nm or even below 10 nm.

[0006] Photosensitivity refers to the degree of sensitivity of a photoresist to light, i.e., the ability to undergo a chemical reaction under the irradiation of light of a specific wavelength. If the photosensitivity of the photoresist is low, a higher light intensity or longer exposure time is required during the lithography process to achieve the desired exposure effect. Different photoresists have different photosensitivity to different wavelengths of light. For example, some photoresists have higher photosensitivity under deep ultraviolet light (DUV, 193 nm), while they may have lower photosensitivity under extreme ultraviolet light (EUV, 13.5 nm). This poses a challenge for photoresist technology in driving semiconductor manufacturing towards smaller sizes and higher densities.

[0007] The development and optimization of photoresists have always been an important research direction in the field of materials science and engineering. By improving the photosensitivity, heat resistance and resolution of photoresists, the performance and integration of microelectronic devices can be further improved.

[0008] One disadvantage of ultra-thin EUV photoresist is that the volume available for exposure reaction is much smaller than DUV due to the thinness of the photoresist, which requires improving the absorption rate of EUV photoresist.

[0009] Reflection of light on the surface and inside of the photoresist will cause a part of the light energy to be lost. The reflected light cannot effectively participate in the exposure process, thereby reducing the utilization rate of light energy. These factors jointly affect the efficiency and accuracy of the lithography process, so in the design and optimization of photoresist, how to reduce reflection and improve light absorption is an important research direction.

[0010] EUV photoresist also requires higher thermal stability, chemical stability and mechanical stability. The high energy of EUV light can cause local heating, which requires the photoresist to withstand these conditions without reducing or losing resolution. They must also resist chemical expansion during development to maintain the authenticity of fine patterns. If the mechanical properties of the photoresist are poor, it may produce defects during coating or cracking or peeling during development. SUMMARY

[0011] The purpose of the present application is to solve the technical problem of low absorption efficiency of ultra-thin EUV photoresist, and to improve the stability of EUV photoresist. A preparation method of multi-layer EUV photoresist is proposed. By covering one or more layers of antireflection film on the EUV photoresist, the light intensity acting on the photoresist is increased, thereby improving the light source utilization rate of the photoresist. Or insert one or more layers of antireflection film in the photoresist, increase the absorption rate of the photoresist to the exposure light. The photoresist prepared by the method solves the technical problem of low absorption efficiency of the existing photoresist to the photoetching light source, and improves the stability of the photoresist.

[0012] In order to solve the above technical problems, the technical solution adopted by the present application is:

[0013] A preparation method of multi-layer EUV photoresist, comprising EUV photoresist, and at least one antireflection film forming a covering structure or an intercalation structure, the covering structure is one or more antireflection films covering on the EUV photoresist, forming a single-layer or multi-layer film covering structure; the intercalation structure is one or more antireflection films inserted into the EUV photoresist, forming a multi-layer film structure in which the antireflection film layer and the photoresist are superimposed.

[0014] Further, in the single-layer or multi-layer film covering structure, the single-layer film is prepared by alternately introducing trimethylaluminum and water as precursors, using inert gas as carrier gas, and performing atomic layer deposition at room temperature or below 100 DEG C, the trimethylaluminum is introduced for 50 milliseconds, and the purge time is 30 seconds; the water is introduced for 50 milliseconds, and the purge time is 30 seconds.

[0015] Further, in the single-layer or multi-layer film covering structure, the multi-layer film is first grown by atomic layer deposition technology to form an aluminum oxide layer with an optical thickness of half wavelength, atomic layer deposition is performed at room temperature or below 100 DEG C, trimethylaluminum is introduced for 50 milliseconds, and the purge time is 30 seconds, water is introduced for 50 milliseconds, and the purge time is 30 seconds; then a half wavelength thick hafnium oxide layer is grown, using tetrakis(dimethylamine) hafnium and ozone as precursors, alternately introducing inert gas as carrier gas, and performing atomic layer deposition at room temperature or below 100 DEG C, wherein tetrakis(dimethylamine) hafnium is introduced for 50 milliseconds, and the purge time is 30 seconds, ozone is introduced for 50 milliseconds, and the purge time is 30 seconds.

[0016] Further, the antireflection film layer and the photoresist are superimposed into the multilayer film structure, one or more antireflection films are inserted into the EUV photoresist, wherein the single layer film is grown by atomic layer deposition using trimethylaluminum and water as precursors, inert gas as carrier gas, at room temperature or below 100 DEG C, the trimethylaluminum is introduced for 50 milliseconds, and the purge time is 30 seconds; the water is introduced for 50 milliseconds, and the purge time is 30 seconds; the multilayer film is first grown by atomic layer deposition to form an aluminum oxide layer with an optical thickness of half wavelength, at room temperature or below 100 DEG C, trimethylaluminum is introduced for 50 milliseconds, and the purge time is 30 seconds, water is introduced for 50 milliseconds, and the purge time is 30 seconds; then a hafnium oxide layer with a thickness of half wavelength is grown, using hafnium tetrakis(dimethylamide) and ozone as precursors, inert gas as carrier gas, at room temperature or below 100 DEG C, wherein the hafnium tetrakis(dimethylamide) is introduced for 50 milliseconds, and the purge time is 30 seconds, the ozone is introduced for 50 milliseconds, and the purge time is 30 seconds.

[0017] Further, the inert gas is nitrogen or argon.

[0018] Further, the thickness of the aluminum oxide film layer is 2.1+4.1k nanometers, k=0, 1, 2, 3.

[0019] A multilayer EUV photoresist is prepared by the above method, and the photoresist has a cover structure or an interlayer structure formed by at least one antireflection film.

[0020] The principle of the present application is:

[0021] The emergence of EUV technology requires that the thickness of the photoresist be controlled below 50 nanometers, and in the future it may be developed to below 10 nanometers. Therefore, the reaction volume of the photoresist in EUV lithography is much smaller than that in DUV lithography, and it is urgent to improve the exposure sensitivity of the EUV photoresist.

[0022] When light passes through the interface of different media, partial reflection occurs due to the difference in refractive index. By designing an antireflection film with appropriate material and thickness, the reflected light at the interface between the antireflection film layer and the photoresist and the reflected light at the surface of the antireflection film layer can be made to have opposite phases, thereby interfering with each other and canceling out, reducing the intensity of the reflected light. Since the reflected light is reduced, more light can pass through the antireflection film layer into the photoresist, thereby increasing the intensity of the transmitted light. Therefore, the antireflection film layer optimizes the distribution of light, so that more light can be effectively utilized by the photoresist.

[0023] The metal oxide covering layer is very dense, which can effectively enhance the stability of the photoresist, so that the photoresist is isolated from air during exposure, so as to avoid unnecessary chemical reactions of the photoresist in contact with air during non-exposure process (such as during wafer transfer). The metal oxide covering layer has a small thermal expansion coefficient, which can offset the thermal expansion during the photoetch process.

[0024] The material of the antireflection film layer can be selected from oxides, photoresists of different materials, etc. The antireflection film layer can be grown by spin coating, chemical vapor deposition (MOCVD, ALD, etc.), molecular layer deposition (MLD). The thickness of the antireflection film layer needs to be determined according to the refractive index of the antireflection film layer and the wavelength of the exposure light source.

[0025] The technical effects of the present application are:

[0026] 1. The photoresist with the antireflection film layer has higher exposure efficiency for extreme ultraviolet light of a certain wavelength or a certain waveband than the photoresist without the film layer.

[0027] 2. The photoresist with the antireflection film layer has higher thermal stability, chemical stability and mechanical stability than the photoresist without the film layer: it is less prone to cracking and defects; it is more resistant to thermal expansion; it is less prone to reaction with water in air. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 Figure 1 is a schematic diagram of the photoresist with the multilayer antireflection film layer of embodiment 1 of the present application;

[0029] Figure 2 Figure 2 is a schematic diagram of the photoresist with the intercalated antireflection film layer of embodiment 2 of the present application.

[0030] Figure 3 Figure 3 is a schematic diagram of the photoresist with and without a covering layer.

[0031] In the figure: 1, exposure light; 2, antireflection film layer; 3, photoresist; 4, reflected light. DETAILED DESCRIPTION

[0032] The technical solutions of the present application will be further described below in combination with the drawings. The high-stability photoresist described in the present application is as shown in Figure 1. Figures 1-2

[0033] As a first embodiment, the covering layer adopts a multilayer film scheme and an intercalation scheme to form the photoresist structure shown in embodiments 1 and 2. The multilayer film scheme is to cover one or more antireflection film layers on the surface of the photoresist. The intercalation scheme is to stack the antireflection film layer and the photoresist into a multilayer film structure.

[0034] Embodiment 1

[0035] ​Multi-layer film solution: one or more layers of antireflection film are coated on the surface of the photoresist.

[0036] In the current chip manufacturing process, the photoresist is coated on the wafer by spin coating before exposure. Taking EUV light source as an example, the wavelength of the exposure light source is 13.5 nm. Spin coating cannot meet the needs of EUV photoresist because it is prone to defects and breakage when coating photoresist with a thickness of tens of nanometers. Currently, some people are trying to use molecular layer deposition to deposit EUV photoresist. The present application can cooperate with this method to improve the absorption efficiency of EUV photoresist. After the photoresist is deposited by molecular layer deposition, in-situ atomic layer deposition (ALD) can be performed. According to the idea of the present application, an aluminum oxide layer can be grown on the surface of the photoresist by ALD process as an antireflection film. The specific growth process is as follows: trimethylaluminum and water are used as precursors and are alternately introduced, and inert gas (nitrogen, argon) is used as carrier gas. In order to prevent the photoresist from denaturing due to temperature rise, atomic layer deposition can be performed at room temperature or below 100℃. The trimethylaluminum is introduced for 50 milliseconds, and the purge time is 30 seconds; the water is introduced for 50 milliseconds, and the purge time is 30 seconds. Atomic layer deposition technology can accurately control the thickness of the grown film layer, providing the possibility of controlling the thickness of the aluminum oxide film layer to the nanometer level. The refractive index of aluminum oxide is n = 1.63. According to the antireflection film formula D = (2k + 1) λ / 4n, it can be known that when the thickness of the aluminum oxide film layer is 2.1 + 4.1k (k = 0, 1, 2, 3) nanometers, it has the effect of increasing the transmission of light. Due to the existence of the antireflection film, on the one hand, the exposure efficiency of the photoresist can be increased, and on the other hand, the dense aluminum oxide film layer can enhance the stability of the photoresist, prevent the wafer from cracking and defects due to shaking, thermal expansion, etc., and can isolate water and oxygen in the air.

[0037] The selection of the single-layer film can also be a mixed type of graded refractive index film, which is realized based on metal chemical vapor deposition (MOCVD). Two types of films, one with low refractive index and one with high refractive index, are deposited simultaneously in the MOCVD deposition process. By controlling the deposition rates of the two types of films, any refractive index film between the high and low refractive index values can be theoretically obtained.

[0038] If the exposure light source has a wide spread, the single layer film can only increase the transmittance of light at a certain wavelength, and the energy of other wavebands is wasted. In this case, a multilayer film scheme can be used, such as the λ / 4-λ / 2W type film and the λ / 4-λ / 4V type film and the variants of these two film systems. For example, on the surface of the photoresist, a layer of aluminum oxide with an optical thickness of half a wavelength is first grown using atomic layer deposition technology (using trimethylaluminum and water as precursors, and inert gas (nitrogen, argon) as carrier gas. To prevent the photoresist from being denatured by elevated temperature, atomic layer deposition can be performed at room temperature or below 100°C. Trimethylaluminum is introduced for 50 milliseconds, and the purge time is 30 seconds; water is introduced for 50 milliseconds, and the purge time is 30 seconds.), and then a half-wavelength thick layer of hafnium oxide is grown (using tetrakis(dimethylamine) hafnium and ozone as precursors, and inert gas (nitrogen, argon) as carrier gas. To prevent the photoresist from being denatured by elevated temperature, atomic layer deposition can be performed at room temperature or below 100°C. Tetrakis(dimethylamine) hafnium is introduced for 50 milliseconds, and the purge time is 30 seconds; ozone is introduced for 50 milliseconds, and the purge time is 30 seconds.). The refractive indices of aluminum oxide and hafnium oxide are different, and the combination can achieve transmittance of the entire waveband. This multilayer film scheme improves the exposure efficiency of the photoresist.

[0039] Example 2

[0040] Interlayer scheme: The antireflection film layer and the photoresist are stacked on each other to form a multilayer film structure.

[0041] If two photoresists are both sensitive to a certain wavelength of UV light, they are photoresist A and photoresist B, and their compositions and refractive indices are different. Compared with single photoresist A and photoresist B, photoresist A and photoresist B can be cross-covered on the wafer, from top to bottom: photoresist A-photoresist B-photoresist A. Therefore, photoresist A acts as an antireflection film for photoresist B, and photoresist A + photoresist B can act as an antireflection film for the bottom photoresist A, thereby achieving performance improvement of the overall photoresist.

[0042] The preparation method of the embodiment is the same as that of Embodiment 1, except that the embodiment uses an intercalated structure, specifically, one or more antireflection films are inserted into the EUV photoresist, wherein the single-layer film is obtained by alternately introducing trimethylaluminum and water as precursors, using an inert gas as a carrier gas, and performing atomic layer deposition at room temperature or below 100 DEG C, the trimethylaluminum is introduced for 50 milliseconds and purged for 30 seconds, the water is introduced for 50 milliseconds and purged for 30 seconds; the multi-layer film is first grown by atomic layer deposition to form an aluminum oxide layer with an optical thickness of half a wavelength, trimethylaluminum is introduced for 50 milliseconds and purged for 30 seconds, water is introduced for 50 milliseconds and purged for 30 seconds, and atomic layer deposition is performed at room temperature or below 100 DEG C; then a half-wavelength-thick hafnium oxide layer is grown by alternately introducing tetrakis(dimethylamine) hafnium and ozone as precursors, using an inert gas as a carrier gas, and performing atomic layer deposition at room temperature or below 100 DEG C, wherein the tetrakis(dimethylamine) hafnium is introduced for 50 milliseconds and purged for 30 seconds, and the ozone is introduced for 50 milliseconds and purged for 30 seconds.

[0043] EUV lithography requires the thickness of the photoresist to be in the order of tens of nanometers. When the exposure light is incident on the photoresist, part of the light enters the interior of the photoresist and participates in the lithography reaction, and another part of the light is reflected. Since the reflected light does not participate in the lithography reaction, it is wasted. The embodiment inserts one or more antireflection film layers into the photoresist to increase the absorption rate of the exposure light by the photoresist.

[0044] Referring to FIG. 1, Figure 3 When light passes through the interface between different media, part of the light is reflected due to the difference in refractive index. By designing an antireflection film with appropriate material and thickness, the reflected light at the interface between the antireflection film layer and the photoresist and the reflected light at the surface of the antireflection film layer can have opposite phases, thereby interfering with and canceling each other, reducing the intensity of the reflected light. Since the reflected light is reduced, more light can pass through the antireflection film layer into the photoresist, thereby increasing the intensity of the transmitted light. Therefore, the antireflection film layer optimizes the distribution of light, allowing more light to be effectively utilized by the photoresist.

[0045] The present application proposes covering one or more antireflection film layers on the photoresist. The thickness of the antireflection film layer is determined according to the refractive index of the antireflection film layer and the wavelength of the exposure light source. The antireflection film can make the reflected light interfere and cancel each other out, thereby allowing more light to pass through the antireflection film layer into the photoresist. This increases the utilization rate of the photoresist for the exposure light source. In addition, the presence of the antireflection film layer enhances the transmission of light of a specific wavelength and weakens the effect of light sources other than the specific wavelength, thereby avoiding unnecessary photochemical reactions during the non-exposure process, thereby increasing the exposure accuracy.

[0046] The multilayer antireflection film of the present application is composed of multiple layers of thin films with different refractive indexes and thicknesses to achieve antireflection effect on multiple wavelengths of light. Since the refractive indexes of different wavelengths of light in a medium are different, a single layer of antireflection film can only achieve the best antireflection effect on a certain specific wavelength of light. The multilayer antireflection film, however, can achieve better antireflection effect in a wider wavelength range through the interaction of different layers of film, thus reducing the requirements of the photolithography process on the light source. Therefore, the photolithography efficiency can be greatly improved. In addition, the antireflection film layer is not limited to being coated on the surface of the photoresist, but can also be inserted into the photoresist. The design of the multilayer film structure of the present application can significantly improve the efficiency and accuracy of the photolithography process.

[0047] The presence of the cover layer can also increase the mechanical stability of the photoresist. The photoresist needs to be uniformly coated on the substrate, and if the coating is not uniform or has defects, it will affect the photolithography effect. After the surface of the photoresist is covered with a cover layer, the photoresist needs to overcome the tension of the cover layer to break, so a dense cover layer (such as oxide) can increase the mechanical stability and thermal stability of the photoresist.

[0048] It should be further pointed out that the above embodiments are only used to understand the technical solutions of the present application, and are not used to limit the protection scope of the present application. Any obvious adjustments and modifications made to the above technical solutions that belong to the technical concept of the present application should also belong to the protection scope of the present application.

Claims

1. A method for preparing a multilayer EUV photoresist, characterized by: The intercalated structure comprises EUV photoresist and at least one antireflection film layer, and the intercalated structure is a multilayer film structure in which one or more antireflection film layers are inserted into the EUV photoresist, and the antireflection film layer and the photoresist are stacked on each other. In the multilayer film structure in which the antireflection film layer and the photoresist are stacked on each other, one or more antireflection film layers are inserted into the EUV photoresist, wherein the single layer film is deposited by atomic layer deposition at a temperature below 100 ℃ using trimethylaluminum and water as precursors, with the trimethylaluminum being introduced for 50 milliseconds and purged for 30 seconds, and the water being introduced for 50 milliseconds and purged for 30 seconds; and the multilayer film is first grown by atomic layer deposition at a temperature below 100 ℃ to form an aluminum oxide layer with an optical thickness of half a wavelength, with the trimethylaluminum being introduced for 50 milliseconds and purged for 30 seconds, and the water being introduced for 50 milliseconds and purged for 30 seconds, and then grown by atomic layer deposition at a temperature below 100 ℃ to form a hafnium oxide layer with an optical thickness of half a wavelength, with the hafnium tetrakis(dimethylamide) being introduced for 50 milliseconds and purged for 30 seconds, and the ozone being introduced for 50 milliseconds and purged for 30 seconds.

2. The method of claim 1, wherein the multilayer EUV resist is prepared by: The inert gas is nitrogen or argon.

3. The method of claim 1, wherein the multilayer EUV resist is prepared by: The thickness of the aluminum oxide film layer is 2.1+4.1k nanometers, and k=0, 1, 2 or 3.

4. A multilayer EUV photoresist prepared by any one of the methods of claims 1-3.

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