CN114911141B

CN114911141B - EUV lithography method and EUV lithography apparatus

Info

Publication number: CN114911141B
Application number: CN202210807148.0A
Authority: CN
Inventors: 季明华; 董于虎; 黄早红
Original assignee: Shanghai Chuanxin Semiconductor Co ltd
Current assignee: Shanghai Chuanxin Semiconductor Co ltd
Priority date: 2022-07-11
Filing date: 2022-07-11
Publication date: 2022-09-23
Anticipated expiration: 2042-07-11
Also published as: KR102598196B1; JP7304503B1; CN114911141A; JP2024009753A

Abstract

Before an EUV photoresist layer coated on a wafer is subjected to EUV exposure, DUV exposure is firstly carried out on the surface layer of the EUV photoresist layer, so that the surface layer of the EUV photoresist layer becomes a hydrophilic surface layer, and moisture is further condensed on the hydrophilic surface layer of the EUV photoresist layer to form a thin water film, therefore, in the process of carrying out EUV exposure on the EUV photoresist layer, the effect of shortening the effective wavelength can be realized by utilizing the characteristic that the refractive index of water is greater than that of air, so that the pattern resolution and the contrast after EUV exposure are further enhanced, and the production of a finer structure is facilitated. Compared with the existing EUV lithography equipment, the EUV lithography equipment of the invention can only add a DUV light source and a gas supply system, and the improvement scheme of the equipment is simple.

Description

EUV lithography method and EUV lithography apparatus

Technical Field

The invention relates to the technical field of integrated circuit manufacturing, in particular to an EUV (extreme ultraviolet) photoetching method and EUV photoetching equipment.

Background

A lithographic apparatus is capable of projecting a circuit pattern on a photomask (photo mask) at a magnification or reduction onto a wafer used to manufacture Integrated Circuits (ICs). Furthermore, there is the following relationship (i.e., the rayleigh criterion) between the feature size of the circuit pattern on the wafer and the parameters of the lithographic apparatus: CD = k1 λ/NA. Where λ is the wavelength of the exposure light source used by the lithographic apparatus, NA is the numerical aperture of the projection module in the lithographic apparatus, k1 is an adjustment factor related to the exposure process, also called the rayleigh constant, and CD is the feature size (or critical dimension) of the circuit pattern on the wafer.

With the rapid development of the integrated circuit manufacturing technology, the feature size CD of the integrated circuit is continuously reduced, the integration level is gradually increased, the wavelength λ of the exposure light source used by the lithography equipment is also gradually decreased, and the currently used mainstream lithography technology adopts 193nm to 248nm deep ultraviolet laser (DUV) as the exposure light source. The exposure process (double exposure, multiple exposure, etc.) implemented by DUV lithography equipment also gradually approaches the lithography limit that can be reached by the DUV wavelength, and it is difficult to meet the requirement of further shrinking the feature size CD of the integrated circuit. Therefore, extreme ultraviolet lithography (EUVL) equipment using EUV (extreme ultraviolet) wavelength has come into play, and shows greater competitive advantages, and becomes the first choice for next-generation lithography.

Among them, how to improve the pattern resolution of the EUV lithography method and EUV lithography apparatus and produce finer structures than before is one of the hot spot issues that the technicians in this field pay attention to.

Disclosure of Invention

The invention aims to provide an EUV lithography method and an EUV lithography apparatus, which can improve the pattern resolution of the EUV lithography technology and produce a finer structure than before.

To achieve the above object, the present invention provides an EUV lithography method, comprising the steps of:

providing a wafer, wherein an EUV photoresist layer is formed on the wafer;

performing DUV exposure on the surface layer of the EUV photoresist layer by using a DUV light source to enable the surface layer of the EUV photoresist layer to become a hydrophilic surface layer;

providing water vapor to the hydrophilic surface layer of the EUV photoresist layer, and condensing at least part of the provided water vapor on the hydrophilic surface layer of the EUV photoresist layer to form a water film;

and exposing a pattern on the EUV photomask to the EUV photoresist layer below the hydrophilic surface layer through the water film by utilizing an EUV light source.

Optionally, the hydrophilic surface layer has a thickness of less than 2 nm.

Optionally, the DUV exposure has a wavelength of 193nm to 248nm and an exposure dose of less than 1mJ/cm 2.

Optionally, at least one time of DUV exposure is performed on the surface layer of the EUV photoresist layer, and the time of each time of DUV exposure is 5-10 s.

Optionally, after each of the DUV exposures or after all times of the DUV exposures are completed, a plasma treatment is performed on the surface layer of the EUV photoresist layer to enhance the hydrophilicity of the hydrophilic surface layer.

Optionally, the plasma used for the plasma treatment comprises at least one of N, O, H.

Optionally, the process conditions of the plasma treatment include: the process pressure is 10mTorr to 100 mTorr.

Optionally, the hydrophilic surface of the EUV photoresist layer is provided with water vapor by a flow of a carrier gas of a desired humidity mixed with deionized water.

Optionally, the carrier gas stream comprises nitrogen and/or an inert gas.

Optionally, the required humidity is at least 60%.

Optionally, the thickness of the water film is at least λ/2n nm, where λ is the wavelength of the EUV light source and n is the refractive index of water.

Based on the same inventive concept, the invention also provides EUV lithography equipment, which comprises a DUV exposure system with a DUV light source, an EUV exposure system with an EUV light source and an air supply system arranged at the periphery of the EUV exposure system; the DUV exposure system is used for carrying out DUV exposure on the surface layer of the EUV photoresist layer on the corresponding wafer by using the DUV light source so as to enable the surface layer of the EUV photoresist layer to become a hydrophilic surface layer; the gas supply system is used for supplying water vapor to the hydrophilic surface layer of the EUV light resistance layer, and at least part of the supplied water vapor is condensed on the hydrophilic surface layer of the light resistance layer to form a water film; the EUV exposure system is used for exposing a pattern on an EUV photomask to the EUV photoresist layer below the hydrophilic surface layer through the water film by using the EUV light source.

Optionally, the gas supply system supplies water vapor to the hydrophilic surface layer of the EUV photoresist layer on the wafer placed on the wafer stage through a carrier gas flow mixed with deionized water and requiring humidity; and the gas supply system is closed both during DUV exposure and during EUV exposure.

Optionally, the carrier gas stream provided by the gas supply system comprises nitrogen and/or an inert gas.

Optionally, the required humidity is at least 60%.

Optionally, the EUV lithography apparatus further includes a plasma processing system disposed outside the DUV exposure system or at the periphery of the EUV exposure system, wherein the plasma processing system is configured to perform plasma processing on the hydrophilic surface layer after the DUV light source performs DUV exposure on the surface layer of the EUV photoresist layer and before the gas supply system provides water vapor, so as to enhance the hydrophilicity of the hydrophilic surface layer.

Optionally, the plasma provided by the plasma processing system includes at least one of N, O, H.

Optionally, the DUV exposure system has a DUV wafer stage, the EUV exposure system has an EUV wafer stage, the EUV lithography apparatus is a dual-wafer stage lithography machine, one of the DUV and EUV wafer stages performs an exposure operation while the other performs a non-exposure operation including a loading, alignment or unloading.

Compared with the prior art, the technical scheme of the invention has at least one of the following beneficial effects:

before EUV exposure is carried out on an EUV photoresist layer coated on a wafer, DUV exposure is carried out on the surface layer of the EUV photoresist layer, so that the surface layer of the EUV photoresist layer becomes a hydrophilic surface layer, and moisture is further condensed on the hydrophilic surface layer of the EUV photoresist layer to form a thin-thickness water film.

Drawings

Fig. 1 is a schematic structural diagram of an EUV lithography apparatus of the related art.

FIG. 2 is a flow chart of an EUV lithography method according to an embodiment of the present invention.

Fig. 3 to 7 are cross-sectional views of device structures in the flow of an EUV lithography method according to an embodiment of the present invention.

Fig. 8 is a schematic cross-sectional structure diagram of an EUV photomask used in an EUV lithography method according to an embodiment of the present invention.

FIG. 9 is a schematic structural diagram of an EUV lithographic apparatus according to an embodiment of the present invention.

FIG. 10 is a schematic structural diagram of an EUV lithographic apparatus according to another embodiment of the present invention.

Detailed Description

In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without one or more of these specific details. In other instances, well-known features have not been described in order to avoid obscuring the invention. It is to be understood that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the size and relative sizes of layers and regions may be exaggerated for clarity to indicate like elements throughout.

It will be understood that when an element or layer is referred to as being "on …," other elements or layers, it can be directly on, adjacent, connected, or coupled to the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on …" other elements or layers, there are no intervening elements or layers present. It will be understood that, although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, sections and/or processes, these elements, components, regions, layers, sections and/or processes should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, section and/or process from another element, component, region, layer, section and/or process. Thus, a first element, component, region, layer, section and/or process discussed below could be termed a second element, component, region, layer, section and/or process without departing from the teachings of the present invention.

Spatially relative terms such as "under …," "under …," "below," "under …," "above …," "above," "on top," "on bottom," "front," "back," and the like may be used herein for ease of description to describe one element or feature's relationship to another element or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, then elements or features described as "under" or "beneath" or "under" or "on the bottom surface or" on the back surface of "other elements or features would then be oriented" on "or" top "or" right "the other elements or features. Thus, the exemplary terms "under …," "under …," and "behind …" can include both an upper and a lower orientation. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatial descriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term "and/or" includes any and all combinations of the associated listed items.

As described in the background, how to improve the pattern resolution of EUV lithography apparatuses and EUV lithography methods and produce finer structures than before is one of the hot spot issues that those skilled in the art are concerned with.

The present EUV lithography apparatus is a dry lithography apparatus, and a typical structure thereof is shown in fig. 1, and comprises: an EUV light source 110, an EUV illumination module 111, an EUV mask stage 112 for placing an EUV reticle 20, an EUV projection module 113, and an EUV wafer stage 114 for placing a wafer 30.

In the prior art, in order to improve the pattern resolution of the EUV lithography apparatus and the EUV lithography method thereof, a finer structure is produced than before to meet the requirement of further shrinking the feature size CD of the integrated circuit (for example, below 5 nm), and the EUV lithography apparatus is generally upgraded and replaced by improving the structures of the EUV light source, the EUV illumination module 111, the EUV projection module 113, and the like of the EUV lithography apparatus, for example: the resolution capability of the EUV lithography equipment is further improved by developing a projection module with a higher image-side numerical aperture NA than before. Obviously, this approach is costly.

Based on the above, the present invention provides an EUV lithography method and EUV lithography apparatus, wherein before EUV exposure of an EUV photoresist layer, DUV exposure is performed on a surface layer of the EUV photoresist layer to form a hydrophilic surface layer, and then water vapor is provided on the surface of the hydrophilic surface layer to form a thin water film, so that during EUV exposure, the pattern resolution and contrast of EUV lithography are further enhanced by using the characteristic that the effective wavelength of EUV exposure light in the water film is shortened, thereby achieving the effect of improving the pattern resolution of EUV lithography with a simpler scheme and at a lower cost, and being capable of producing finer structures than before.

The EUV lithography method and EUV lithography apparatus of the present invention are described in detail below with reference to fig. 2 to 10 and a specific embodiment.

Referring to fig. 2, an embodiment of the invention provides an EUV lithography method, and specifically includes the following steps:

s1, providing a wafer, wherein an EUV photoresist layer is formed on the wafer;

s2, performing DUV exposure on the surface layer of the EUV photoresist layer by using a DUV light source to enable the surface layer of the EUV photoresist layer to become a hydrophilic surface layer;

s3, providing water vapor to the hydrophilic surface layer of the EUV photoresist layer, and condensing at least part of the provided water vapor on the hydrophilic surface layer of the EUV photoresist layer to form a water film;

and S4, exposing the pattern on the EUV photomask to the EUV photoresist layer below the hydrophilic surface layer through the water film by using an EUV light source.

Referring to fig. 3, in step S1, the provided wafer 30 may be any suitable wafer, which may be a bare wafer, or a wafer on which a film, a pattern, a circuit or a device has been formed. An EUV photoresist layer 31 is coated on the global top surface of the wafer 30 by a spin-on photoresist method. The material of the EUV photoresist layer 31 is, for example, a positive photoresist or a Chemical Amplified Resist (CAR), and the material composition of the EUV photoresist layer 31 includes: resin (resin/polymer) as a binder for different materials in the photoresist, which imparts mechanical and chemical properties (such as adhesion, film thickness, thermal stability, etc.) to the photoresist; a Solvent (Solvent) for maintaining the liquid state of the photoresist to have good fluidity; additives (Additive) are used to change certain characteristics of the photoresist, such as adding a coloring agent to improve the reflection of the photoresist.

As an example, the EUV photoresist layer 31 is a positive photoresist, the resin of which is novolac formaldehyde, which provides adhesiveness and chemical resistance of the photoresist, when no dissolution inhibitor is present, the novolac resin is dissolved in a developer, the photosensitizer is a photosensitive Compound (PAC), and most commonly Diazonaphthoquinone (DNQ), before exposure, DNQ is a strong dissolution inhibitor, which reduces the dissolution rate of the resin, and after uv exposure, DNQ is chemically decomposed in the photoresist to become a solubility enhancer, which greatly increases the solubility factor in the developer to 100 or more. This exposure reaction produces carboxylic acids in the DNQ, which have high solubility in the developer and good contrast in positive photoresists, so that the resulting patterns have good resolution.

As another example, the EUV light-blocking layer 31 is a chemically amplified resist CAR, the resin of which is polyethylene with chemical group protection (t-BOC) (PHS), water insoluble (hydrophobic), the photosensitizer is a Photo Acid Generator (PAG), and after the photoresist is exposed, the PAG in the exposed area generates a photochemical reaction to generate an Acid, the acid acts as a chemical catalyst to remove the protecting groups on the resin during Post Exposure Bake (PEB), so that the photoresist in the exposed area is converted from the original water-insoluble photoresist into the developer with water (hydrophic) as the main component, the exposure speed of the chemically amplified photoresist is very fast, which is about 10 times that of the DNQ linear phenolic resin photoresist, and has good optical sensitivity to short wavelength light sources, can provide steep sidewall, and has high contrast, such as high resolution with a size of 0.25 μm or less.

In step S2, referring to fig. 3 and 4, the surface layer of the EUV photoresist layer 31 is globally DUV exposed, for example, the surface layer of the EUV photoresist layer 31 is placed under a DUV light source to be flood-irradiated, so that the surface layer of the EUV photoresist layer 31 becomes a hydrophilic surface layer 31a, and the part under the hydrophilic surface layer 31a which is not DUV exposed is marked as 31 b. The principle of the step is that the optical sensitivity of the EUV photoresist layer to the DUV light source is lower than that of the EUV photoresist layer, so that only the shallow surface layer of the EUV photoresist layer 31 can be weakly exposed by using low-dose and short-time DUV exposure, the DUV exposure depth is controllable through DUV exposure parameters, after the DUV exposure, the shallow surface layer of the EUV photoresist layer 31 generates a certain photochemical reaction to generate an acid, and the acid serves as a chemical catalyst and can remove a part of protective groups on resin of the shallow surface layer of the EUV photoresist layer 31, so that the shallow surface layer of the EUV photoresist layer 31 is changed from original hydrophobicity to hydrophilicity.

Obviously, the thickness of the hydrophilic surface layer 31a depends on the material of the EUV photoresist layer 31, the exposure dose and the exposure time of the DUV exposure, and other exposure parameters.

In this step, at least one exposure time (e.g., 5s to 10 s) and exposure dose (e.g., less than 1 mJ/cm) can be performed on the entire surface of the EUV photoresist layer 31 ² ) The lower DUV exposure (e.g., flood irradiation of the surface layer of the EUV photoresist layer 31 with a DUV light source) results in the formation of a hydrophilic surface layer 31a having a thickness of no more than 2nm, e.g., 1 nm. The DUV exposure wavelength is 193nm to 248nm, such as 193nm or 248 nm.

Alternatively, when the DUV exposure is insufficient to achieve the hydrophilic surface layer 31a with the required thickness, that is, the hydrophilic capability of the hydrophilic surface layer 31 formed after the DUV exposure does not meet the requirement of the subsequent step S3, the surface layer of the EUV photoresist layer 31 may be further subjected to a plasma treatment after each of the DUV exposures or after all times of the DUV exposures are completed, so as to enhance the hydrophilicity of the hydrophilic surface layer 31 a. Wherein, as an example, the plasma used for the plasma treatment comprises at least one of N, O, H. The principle that the plasma treatment can enhance the hydrophilicity of the hydrophilic surface layer 31a is: the hydrophilic surface layer combines with atoms such as N, O, H in the corresponding plasma (including chemical reactions such as bonding) to form a thin hydrophilic layer rich in hydrophilic atoms, thereby increasing the hydrophilicity of the original hydrophilic surface layer.

Further optionally, the process pressure of the plasma treatment is lower, for example, 10mTorr to 100mTorr, so as to improve the distribution uniformity of atoms such as N, O, H on the surface of the EUV photoresist layer 31 after the plasma treatment, and further facilitate the formation of a water film with a uniform film thickness in step S3.

In step S3, referring to fig. 4 and 5, water vapor is provided to the hydrophilic surface layer 31a of the EUV photoresist layer 31, and at least a portion of the provided water vapor condenses on the hydrophilic surface layer 31a to form a water film 32. The thickness of the water film 32 depends on the hydrophilic ability of the hydrophilic surface layer 31a of the EUV photoresist layer 31, which is at least half the wavelength of the EUV beam in water, i.e., λ/2n nm. Optionally, water film 32 is formed to have a thickness of at least λ/2n nanometers, where λ is the wavelength of the EUV light source and n is the refractive index of water, and no more than 20 nanometers. Preferably, the thickness of the water film 32 is λ/2n nm or a multiple of the optimal transmittance of the EUV projection module 113. As an example, n =1.33 and λ =13.6 nanometers, the thickness of water film 32 is λ/2n =13.6 nanometers/(2 ≈ 1.33) ≈ 5 nanometers.

It should be noted that the thickness of the formed water film 32 is not too thin (for example, less than λ/2n nm), otherwise, on one hand, under the action of surface tension, there is some water film 32 on the surface of the hydrophilic surface layer 31a and some is not, thereby resulting in non-uniform thickness of the water film 32 formed on the surface of the EUV photoresist layer 31 on the whole of the wafer 30, and not easy to form a complete shorter light wavelength, which affects uniformity of feature size after EUV lithography; on the other hand, insufficient thickness of the water film 32 naturally evaporates a part or all of the film during exposure, thereby affecting the lithography effect.

Meanwhile, the thickness of the formed water film 32 is not too thick (for example, greater than 20 nm), the upper surface of the water film 32 is bounded by air, and the lower surface is bounded by the lower surface of the hydrophilic surface layer 31a, i.e., it is required to ensure that the thickness of the water film 32 is not enough to contact the surface of the last objective lens in the projection module of the EUV lithography apparatus, and an air gap exists between the water film 32 and the projection module. On the one hand, the EUV mask is of a reflective type, and light reflected to the projection module has a large loss relative to light emitted from the EUV light source, so that if the formed water film 32 is too thick, the EUV light is absorbed, and the subsequent EUV exposure of the EUV photoresist layer 31b is insufficient; on the other hand, if the water film 32 on the EUV photoresist layer 31b is too thick, the temperature increases due to excessive absorption of EUV light, which may cause thermal deformation of the EUV photoresist layer 31b, and thus, the subsequent EUV exposure effect of the EUV photoresist layer 31b may be affected.

Alternatively, in step S3, moisture may be supplied to the hydrophilic surface layer 31a by a carrier gas flow of a required humidity mixed with deionized water. The carrier gas stream comprises nitrogen and/or an inert gas (e.g., argon and/or helium), the desired humidity is at least 60%, and the water film 32 has a thickness of at least λ/2n nanometers. λ/2n is the half wavelength of the EUV beam in water, where λ is the wavelength of the EUV light source and n is the refractive index of water. Preferably, the thickness of the water film 32 is λ/2n nm or a multiple of the optimal transmission coefficient of the EUV projection module 113. As an example, n =1.33, λ =13.6 nm, and the thickness λ/2n ≈ 5nm of the water film 32.

In step S4, referring to fig. 5 and 6, the pattern on the corresponding EUV reticle is exposed onto the EUV photoresist layer 31b under the hydrophilic surface layer 31a 'through the water film 32 by using the EUV light source, at which time the EUV photoresist layer 31b becomes the EUV exposed portion 31 b' and the non-EUV exposed portion 31 c.

The EUV light source used in this step may be a synchrotron radiation source such as a Free Electron Laser (FEL) capable of producing coherent radiation with very high spectral brightness. The wavelength lambda of the EUV light source is 5nm to 30nm, for example 11nm to 14 nm. With a wavelength λ of 13.6nm being most commonly used.

Referring to fig. 8, the blank of the EUV photomask used in this step generally has a substrate (such as glass or quartz, etc.) 200, a reflective film stack (such as an alternate stack of Mo and Si, also called a reflective structure) 201, a cap layer 202 (including at least one of ru, ru alloy, and ru oxide, for example), and an absorber layer (which may be a single layer film or a multi-layer film, including at least one of co, te, hf, ni, ta, cr, ta-based material, cr-based material, etc.) 203 (which are stacked in sequence), the reflective film stack 201 is used for reflecting the EUV exposure beam, and the absorber layer 203 is used for absorbing the EUV exposure beam and is etched into a predetermined pattern (i.e., a circuit pattern) 203a required for manufacturing an integrated circuit. The absorber layer 203 has a low EUV reflectivity, for example less than 3-5%. The EUV reticle also has a border pattern 204 that extends through the absorber layer 203, the cap layer 202, and the reflective film stack 201, and a backside conductive layer 205 (e.g., comprising at least one of chromium, chromium-based materials, tantalum, or tantalum-based materials, etc.) on the backside of the substrate 200.

In this embodiment, the water film 32 can achieve a better resolution of the lithography pattern, and the fundamental reason is: the water film 32 is in close contact with the surface of the EUV photoresist layer 31b, the refractive index n is larger than air (the refractive index is 1), when the wavelength of the EUV exposure beam emitted by the EUV light source is λ, the wavelength in the water film becomes λ/n, and further, as can be seen from the rayleigh criterion CD = k1 λ/NA, under the condition that the rayleigh constant k1 and the numerical aperture NA of the projection module are not changed, the wavelength of light in the water film becomes shorter, which results in that the characteristic dimension CD of the pattern formed after the EUV exposure of the EUV photoresist layer 31b becomes smaller, and further defines a finer pattern, thereby adding the water film 32 and achieving a better EUV lithography pattern resolution effect. For example, when the refractive index n =1.33 of water film 32 and the wavelength λ =13.6 nm of the EUV exposure beam emitted from EUV light source 110, the wavelength in water film 32 is 13.6/1.33 ≈ 10 nm.

It should be noted that, in this step, the hydrophilic surface layer 31a of the EUV photoresist layer 31 itself adsorbs water vapor to become a water-rich hydrophilic surface layer 31a ', on which a water film 32 is further condensed due to the adsorption force and surface tension between water molecules, and the water-rich hydrophilic surface layer 31 a' and the water film 32 may actually be solution layers formed by dissolving components of the hydrophilic surface layer in water, wherein the solvent of the solution layer is water, and the solute is a component that can be dissolved in water in the hydrophilic surface layer 31a, so that the refractive index of the solution layer is larger than that of deionized water, thereby further shortening the effective wavelength relative to deionized water, and achieving better EUV lithography pattern resolution compared to a mode in which a deionized water film is formed only on the surface of the EUV photoresist layer.

Subsequently, after the EUV exposure is completed, referring to fig. 7, the wafer 30 may be transferred to a developing system for development, and the EUV exposed portion 31c is removed, and the remaining unexposed portion 31 b' is used as a patterned photoresist layer for etching the wafer 30.

In summary, in the EUV lithography method of the present invention, before EUV exposure is performed on an EUV photoresist layer on a wafer, DUV exposure is performed on a surface layer of the EUV photoresist layer to form a hydrophilic surface layer, and then moisture is condensed on the hydrophilic surface layer to form a thin water film, so that an effective wavelength is shortened by using a characteristic that a refractive index of water is greater than that of air, and thus, a pattern resolution and a contrast of EUV lithography are further enhanced, which is beneficial for producing a finer structure than before, and the method is simple and low in cost.

It should be understood that, when the EUV lithography method of the present invention is applied to a corresponding method for manufacturing a semiconductor device, it may complete an EUV lithography process required for an EUV photoresist layer coated on a wafer, expose a pattern on a corresponding EUV photomask to the EUV photoresist layer on the surface of the wafer with an enhanced pattern resolution and contrast, form a patterned EUV photoresist layer on the wafer after developing the EUV exposed photoresist layer, and then form a corresponding pattern (e.g., a circuit pattern, a frame pattern, etc.) on the wafer after etching a corresponding film layer in the wafer using the patterned EUV photoresist layer as a mask.

In addition, since the EUV lithography method of the present invention is applied to the method for manufacturing a semiconductor device, a finer structure can be advantageously manufactured in a wafer than before.

Referring to fig. 9, an EUV lithography apparatus according to an embodiment of the present invention includes a DUV exposure system 10, an EUV exposure system 11, and a gas supply system 12.

The DUV exposure system 10 includes a DUV light source 100, a DUV illumination module 101, an EUV projection module 102, and a DUV wafer stage 103, which are sequentially arranged along a light path.

The DUV light source 100 is used for generating a DUV exposure beam with a wavelength lambda of 193 nm-248 nm, and DUV exposure is carried out on an EUV photoresist layer (not shown) on a wafer 30 on a DUV silicon wafer stage 103 through the DUV exposure beam, so that the surface layer of the EUV photoresist layer becomes a hydrophilic surface layer.

The DUV illumination module 101 is configured to direct, shape, reflect, transmit, or control the DUV exposure beam emitted by the DUV light source 100 through various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof.

The DUV projection module 102 is configured to adjust an angle, a focal length, an intensity, and the like of a DUV exposure beam emitted by the DUV light source 100, so that the DUV exposure beam emitted by the DUV light source 100 can be transmitted to the wafer 30 placed on the DUV wafer stage 103 after passing through the DUV illumination module 101, and then DUV exposure is performed on a surface layer of the EUV photoresist layer on the wafer 30. Optionally, the DUV projection module 102 disposed corresponding to the DUV light source 100 may irradiate the global surface of the wafer 30 on the DUV wafer stage 103, that is, the size of the exposure field is larger than the size of the wafer 30, so that the surface layer of the EUV photoresist layer on the global surface of the wafer may be exposed by one DUV exposure.

The DUV wafer stage 103 is configured to carry a wafer 30 (i.e., a silicon wafer) to be DUV exposed, which can accurately fix, move, and position the position of the wafer 30 to be DUV exposed in accordance with certain parameters. With further reference to fig. 3 to 6, before the wafer 30 is placed on the DUV wafer stage 103, the EUV photoresist layer 31 is formed on the surface of the wafer 30, and after the DUV exposure system 10 performs the DUV exposure on the wafer 30, the surface layer of the EUV photoresist layer 31 on the surface of the wafer 30 becomes a hydrophilic surface layer.

The EUV exposure system 11 includes an EUV light source 110, an EUV illumination module 111, an EUV mask stage 112, an EUV projection module 113, and an EUV wafer stage 114, which are arranged in this order along an optical path.

The EUV light source 110 is configured to generate an EUV exposure beam having a wavelength λ of 5nm to 30nm (with a wavelength λ of 13.6nm being most commonly used). The EUV light source 110 may be a synchrotron radiation source such as a Free Electron Laser (FEL) capable of producing coherent radiation with very high spectral brightness.

The EUV illumination module 111 is configured to direct, shape, reflect, transmit, or control various types of optical components of the EUV exposure beam emitted from the EUV light source 110, and ultimately transmit the EUV exposure beam emitted from the EUV light source 110 onto the EUV reticle 20 placed on the EUV mask stage 112. The EUV illumination module 111 may be, for example, a refractive, reflective, magnetic, electromagnetic, electrostatic or other type of optical component, or any combination thereof.

The EUV mask stage 112 is configured as a support structure that can support the reflective EUV reticle 20, which can use mechanical, vacuum, electrostatic or other clamping techniques, and precisely fix, move and position the reflective EUV reticle 20 according to certain parameters, ensuring that the reflective EUV reticle 20 is in a desired position relative to the EUV projection module 113. The EUV mask stage 112 bears the weight of the reflective EUV reticle 20 and holds the reflective EUV reticle 20 in a manner that depends on the orientation of the reflective EUV reticle 20, the design of the lithographic apparatus, and other conditions, such as whether the reflective EUV reticle 20 is held in a vacuum environment. The EUV mask stage 112 may be a frame or a stage, which may be fixed or movable as desired. The structure of the reflective EUV photo-mask 20 can be referred to in fig. 7, and will not be described herein.

The EUV wafer stage 114 is configured to carry the wafer 30 after exposure by the DUV exposure system 10, which can accurately fix, move, and position the wafer 30 in accordance with certain parameters. With reference to fig. 3 to 6, before the EUV exposure system performs EUV exposure on the wafer 30, the EUV photoresist layer 31 is formed on the surface of the wafer 30, and the surface layer of the EUV photoresist layer 31 is a hydrophilic surface layer on which a water film is formed, the water film being condensed from water in the air flow of the air supply system.

The EUV projection module 113 is configured to adjust an angle, a focal length, an intensity, and the like of an EUV exposure beam to be reflected by the reflective EUV reticle 20 on the EUV mask stage 112, and transmit the EUV exposure beam onto the wafer 30 placed on the EUV wafer stage 114, thereby subjecting the EUV resist layer 31 to EUV exposure.

The gas supply system 12 is arranged at the periphery of the EUV wafer stage 114 and is configured to supply water vapor to the hydrophilic surface layer of the EUV photoresist layer 31 of the wafer 30 after the DUV-exposed wafer 30 is transferred onto the EUV wafer stage 114 and before the EUV light source 110 performs EUV exposure on the EUV photoresist layer 31 on the wafer 30 on the EUV wafer stage 114, and at least part of the supplied water vapor condenses on the hydrophilic surface layer of the EUV photoresist layer 31 to form a water film 32. The "water vapor" may be gaseous water or may be liquid water of very small size (e.g., liquid mist water) that can be transported by a carrier gas (e.g., nitrogen and/or an inert gas).

Optionally, the gas supply system 12 is opened during movement of the EUV wafer stage 114 and supplies water vapor to the hydrophilic surface layer of the EUV photoresist layer 31 on the wafer 30 carried on the EUV wafer stage 114 by a flow of carrier gas mixed with deionized water at a required humidity (e.g., at least 60%); the gas supply system 12 is turned off during both the DUV exposure period (i.e., the period in which the DUV light source 100 DUV exposes the EUV photoresist layer 31) and the EUV exposure period (i.e., the period in which the EUV light source 110 EUV exposes the EUV photoresist layer 31).

Further alternatively, the carrier gas stream provided by the gas supply system 12 may include nitrogen and/or an inert gas, including, for example, a mixture of one or more of argon, helium, and the like. Wherein, the thickness of the water film formed on the surface of the EUV photoresist layer after the water supply system 12 is opened is controlled by the hydrophilicity level of the hydrophilic surface layer of the EUV photoresist layer (i.e. the hydrophilicity of the surface of the EUV photoresist layer).

It should be understood that, in the present embodiment, the EUV light source 110 and the DUV light source 100 correspond to a set of illumination modules and a set of projection modules respectively, so that the EUV lithography apparatus of the present embodiment is designed for a dual-wafer stage (Twin stage) system. The EUV light source 110 and the DUV light source 100 are used separately, and for the same wafer 30, when EUV lithography needs to be performed on the wafer 30, the DUV light source 100 is used at the DUV wafer stage 103, DUV exposure is performed on the surface of the EUV photoresist layer on the global surface of the wafer to form a required hydrophilic surface layer, and then a water film is formed on the hydrophilic surface layer through the gas supply system, and then the EUV light source 110 is used at the EUV wafer stage 114, so that the overall control of the EUV lithography apparatus can be simplified and the lithography process can be accelerated.

In order to further accelerate the production efficiency of the EUV lithography apparatus, one of the DUV and EUV wafer stages 103, 114 performs an exposure operation while the other performs a non-exposure operation such as loading, alignment, leveling, focusing, and unloading.

In this case, the wafer 30 may be moved to a wafer stage (not shown) in the exposure field of the DUV light source 100, and after the DUV exposure is completed, the wafer 30 may be moved to the EUV wafer stage 114 in the exposure field of the EUV light source 110. Specifically, the working process of the EUV lithography apparatus for performing EUV lithography on a wafer 20 includes:

firstly, fixing an EUV mask 20 with a required pattern on an EUV mask table 112, and fixing a wafer 30 with an EUV photoresist layer on a DUV wafer table 103;

then, the DUV light source 100 is turned on, the DUV exposure light beam emitted by the DUV light source 100 enters the surface layer of the EUV photoresist layer 31 of the wafer 30 of the DUV wafer stage 103 through the DUV illumination module 101 and the DUV projection module 102 corresponding to the DUV light source 100, and then the DUV exposure is performed on the surface layer of the EUV photoresist layer 31 of the wafer 30 globally to form a required hydrophilic surface layer;

next, the DUV light source 100 is turned off, the DUV-exposed wafer 30 is transferred onto the EUV wafer stage 114, the gas supply system 12 is turned on, and water vapor is supplied to the hydrophilic surface layer of the EUV photoresist layer on the DUV-exposed wafer 30 by the carrier gas flow mixed with deionized water and having a required humidity (for example, at least 60%), thereby forming a water film 32 with a uniform thickness on the entire surface of the EUV photoresist layer 31 on the wafer 30 due to moisture adsorption;

then, the gas supply system 12 is closed, the EUV light source 110 is opened, EUV exposure beams emitted by the EUV light source 110 are transmitted through the EUV illumination module 111 corresponding to the EUV light source 110 and then incident on the EUV mask 20 at the EUV mask stage 112, and then are reflected by the EUV mask 20 and then incident into the EUV projection module 113 corresponding to the EUV light source 110, the EUV projection module 113 focuses the beams on the target area of the EUV photoresist layer 31 of the wafer 30 of the EUV wafer stage 114 through the water film 32, so as to complete one EUV exposure, and then the EUV wafer stage 114 is stepped to complete the EUV exposure of each target area of the EUV photoresist layer 31.

It should be understood that, in the EUV lithography apparatus of this embodiment, the DUV light source 100, the DUV illumination module 101, the DUV projection module 102, the DUV silicon wafer stage 103, the EUV light source 110, the EUV illumination module 111, the EUV mask stage 112, the EUV projection module 113, the EUV silicon wafer stage 114, and the gas supply system 12 may be integrated in the same frame housing, or at least one of them may be separately set up from other modules, or at least one of them may be integrated with other systems or modules of the EUV lithography apparatus, for example, the DUV illumination module 101 and the DUV projection module 102 of the DUV exposure system 10 may be shared with another illumination system and projection module for alignment and independent, so as to reduce the volume of the EUV lithography apparatus, so as to accelerate the lithography process (one system is used for alignment, one system is used for exposure, and is not described herein again), which may be adjusted based on the system design of the existing dual silicon wafer stage (Twin stage), and to adapt the exposure requirements of the DUV light source 100.

In addition, the subsystems of the EUV lithography apparatus (i.e., the DUV exposure system 10, the EUV exposure system 11, and the gas supply system 12) described in the present embodiment are merely provided as a specific example, and it is not illustrated that the EUV lithography apparatus of the present invention has only these subsystems, it may also include other subsystems in an existing EUV lithography apparatus, such as at least one of a coating system for forming an EUV photoresist layer on a wafer surface, a measurement system (including sensors and the like) for measuring corresponding parameters in a lithography process, a development system for developing the EUV photoresist layer 31 on an exposed wafer 30, a robot system for handling and replacing the wafer 30 and/or reticle 20, a cleaning system for cleaning the wafer 30 after development, a hydrophilic surface treatment system for hydrophilic surface treatment of the EUV photoresist layer 31, and the like.

For example, referring to FIG. 10, another embodiment of the present invention provides an EUV lithography apparatus having not only a DUV exposure system 10, an EUV exposure system 11, and a gas supply system 12, but also a plasma processing system 13 disposed around the periphery of a DUV wafer stage 103. The plasma treatment system 13 is used to plasma treat the hydrophilic surface layer of the EUV photoresist layer on the wafer 30 after the DUV light source 100 DUV exposes the EUV photoresist layer on the wafer 30 and before the wafer 30 is transferred from the DUV wafer stage 103 onto the EUV wafer stage 114 to enhance the hydrophilicity of the hydrophilic surface layer.

Of course, in other embodiments of the invention, a plasma treatment system 13 may also be arranged at the periphery of the EUV exposure system 11, which is configured to plasma treat the hydrophilic surface layer of the EUV photoresist layer on the wafer 30 after the wafer 30 is transferred from the DUV wafer stage 103 onto the EUV wafer stage 114 and before the gas supply system supplies water vapor to the hydrophilic surface layer of the EUV photoresist layer on the wafer 30 on the EUV wafer stage 114, so as to enhance the hydrophilicity of the hydrophilic surface layer.

Optionally, the plasma processing system 13 is used for performing hydrophilic surface processing on the surface of the EUV photoresist layer at a lower process pressure, for example, 10mTorr to 100mTorr, so as to improve the distribution uniformity of atoms such as N, O, H on the surface of the EUV photoresist layer 31 after the plasma processing, thereby facilitating the formation of a water film with a uniform film thickness.

For another example, referring to fig. 9 or 10, another embodiment of the present invention provides an EUV lithography apparatus having not only the DUV exposure system 10, the EUV exposure system 11, and the gas supply system 12, but also a robot system (not shown) for handling the wafer 30 and a wafer stage that forms a corresponding cascade with the DUV wafer stage 103 and the EUV wafer stage according to process steps, wherein one or more wafer stages (not shown) may be used for steps other than DUV exposure and EUV exposure (e.g., plasma processing, pre-cleaning, developing, post-cleaning, baking, etc.) on the wafer.

In summary, the EUV lithography apparatus of the present invention may add a corresponding DUV exposure system and an air supply system to the original EUV lithography apparatus, and then before exposing the EUV photoresist layer on the wafer, the DUV exposure is performed on the surface layer of the EUV photoresist layer to form a hydrophilic surface layer, and then the water is condensed on the hydrophilic surface layer to form a thin water film, so that the effective wavelength shortening effect is achieved by using the characteristic that the refractive index of water is greater than that of air, and further the pattern resolution and contrast of the EUV lithography are further enhanced.

The above description is only for the purpose of describing the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and any variations and modifications made by those skilled in the art based on the above disclosure are within the scope of the present invention.

Claims

1. An EUV lithography method, characterized by comprising the steps of:

providing a wafer, wherein an EUV light resistance layer is formed on the wafer;

2. The EUV lithography method as claimed in claim 1, characterized in that the hydrophilic surface layer has a thickness of less than 2 nm.

3. The EUV lithography method as claimed in claim 1, wherein the DUV exposure has a wavelength of 193nm to 248nm and an exposure dose of less than 1mJ/cm ² 。

4. The EUV lithography method as claimed in claim 1, wherein at least one DUV exposure is performed on the surface layer of the EUV photoresist layer, and the time for each DUV exposure is 5s to 10 s.

5. The EUV lithography method as claimed in claim 4, characterized in that after each of said DUV exposures or after all times of DUV exposures have been completed, a surface layer of said EUV photoresist layer is subjected to a plasma treatment in order to increase the hydrophilicity of said hydrophilic surface layer.

6. An EUV lithography method as claimed in claim 5, characterized in that the plasma used for the plasma treatment comprises at least one of N, O, H.

7. An EUV lithography method as claimed in claim 5, characterized in that the process conditions of the plasma treatment comprise: the process pressure is 10 mTorr-100 mTorr.

8. The EUV lithography method as claimed in claim 1, characterized in that the hydrophilic surface of the EUV photoresist layer is provided with water vapor by means of a carrier gas flow of a desired humidity mixed with deionized water.

9. The EUV lithography method as claimed in claim 8, characterized in that the carrier gas flow comprises nitrogen and/or an inert gas.

10. The EUV lithography method according to claim 8, wherein the required humidity is at least 60%.

11. The EUV lithography method according to claim 1, wherein the water film has a thickness of at least λ/2n nm, wherein λ is the wavelength of the EUV light source and n is the refractive index of water.

12. An EUV lithography apparatus, comprising a DUV exposure system with a DUV light source, an EUV exposure system with an EUV light source and a gas supply system arranged at the periphery of the EUV exposure system; the DUV exposure system is used for carrying out DUV exposure on the surface layer of the EUV photoresist layer on the corresponding wafer by using the DUV light source so as to enable the surface layer of the EUV photoresist layer to become a hydrophilic surface layer; the gas supply system is used for supplying water vapor to the hydrophilic surface layer of the EUV light resistance layer, and at least part of the supplied water vapor is condensed on the hydrophilic surface layer of the light resistance layer to form a water film; the EUV exposure system is used for exposing a pattern on an EUV photomask to an EUV photoresist layer below the hydrophilic surface layer through the water film by using the EUV light source.

13. The EUV lithographic apparatus according to claim 12, wherein the gas supply system supplies water vapor to the hydrophilic surface layer of the EUV photoresist layer on the wafer by means of a flow of a carrier gas of a required humidity mixed with deionized water; and the gas supply system is closed both during DUV exposure and during EUV exposure.

14. EUV lithography apparatus according to claim 13, wherein the carrier gas flow provided by the gas supply system comprises nitrogen and/or an inert gas.

15. EUV lithography apparatus according to claim 13, wherein the required humidity is at least 60%.

16. EUV lithography apparatus according to one of claims 12 to 15, further comprising a plasma treatment system arranged peripherally to the DUV exposure system or peripherally to the EUV exposure system, for plasma treating the hydrophilic surface layer after DUV exposure of the surface layer of the EUV resist layer by the DUV light source and before the gas supply system supplies water vapor, in order to increase the hydrophilicity of the hydrophilic surface layer.

17. An EUV lithographic apparatus as claimed in claim 16, wherein said plasma provided by said plasma processing system comprises at least one of N, O, H.

18. EUV lithography apparatus according to one of claims 12 to 15 or 17, wherein the DUV exposure system has a DUV wafer stage, the EUV exposure system has an EUV wafer stage, the EUV lithography apparatus is a dual wafer stage lithography machine, one of the DUV and EUV wafer stages being exposed while the other wafer stage is exposed to a non-exposure operation comprising an upper, alignment or lower wafer.