JP2004235574A - Method of forming resist pattern and method of fabricating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To apply a pattern of a nanometer size onto a resist film. <P>SOLUTION: A resist pattern, which is a circuit pattern transferred to a resist film 22, is formed by irradiating a photomask 13 with a non-resonant light, whose wavelength is longer than that of a light corresponding to the resonance energy between the molecules that constitute the resist film 22, generating a near-field light in a region of a nanometer size based on the circuit pattern drawn on the photomask 13, and sensitizing the photoresist film 22 by the generated near-field light. Microfabrication for a device can be realized based on this resist pattern. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for forming a resist pattern for transferring a circuit pattern drawn on a photomask onto a resist film applied to the surface of a sample, and a method for fabricating a device having such a process, and in particular, realizes nanometer-sized patterning. More particularly, the present invention relates to a method for forming a resist pattern and a method for manufacturing a device.
[0002]
[Prior art]
In recent years, with the advent of integrated circuits (ICs), the degree of integration has been improved to large-scale integrated circuits (LSIs), and further restrictions have been imposed on design dimensions in circuit patterns. It is being actively performed.
[0003]
Optical lithography is one means of such fine processing, in which a resist film is formed on a substrate surface such as a silicon oxide film, and the pattern is transferred by exposing through a mask on which an integrated circuit pattern is drawn. (See, for example, Non-Patent Document 1).
[0004]
FIG. 6 is a diagram for explaining the outline of optical lithography. First, in step S51, an organic photosensitive resin such as a resist is applied on the substrate 71 on which the film to be processed 72 is formed by using a spinner to form a uniform resist film 73. After heating and drying the resist film 73, the process proceeds to step S52, where a mask 74 on which an integrated circuit pattern is drawn is superposed on the substrate 71.
[0005]
Next, the process proceeds to step S53, and the integrated circuit pattern drawn on the photomask 74 is transferred to the resist film 73 on the substrate 71 using an exposure device described later. That is, by performing exposure through a mask on which an integrated circuit pattern is drawn, a photochemical reaction is caused to the resist film 73.
[0006]
Next, the process proceeds to step S54, in which a resist pattern is formed by developing the resist film 73 using a developing solution. When the resist film 73 is a positive resist film in which the photosensitive portion is solubilized in a developing solution composed of an alkaline aqueous solution, the photosensitive portion can be removed using a developing solution.
[0007]
The resist pattern thus formed is etched in the next step S55 as a so-called etching mask on the film to be processed 72, and the resist film 73 is peeled off in step S56, thereby completing a series of lithography steps. Become.
[0008]
FIG. 7 is a diagram showing the basic configuration of an exposure apparatus used for transferring an integrated circuit pattern.
[0009]
The exposure device 8 includes a light source 81 that emits light, an illumination optical system 82 that collects light emitted from the light source 81, a photomask 83 on which an integrated circuit pattern is drawn, and light transmitted through the photomask 83. And a projection optical system 84 for forming an image on the substrate 71.
[0010]
The integrated circuit pattern drawn on the photomask 83 is illuminated via the illumination optical system 82, and only the transmitted light is imaged by the projection optical system 84. As a result, the resist film 74 formed on the substrate 71 is exposed corresponding to the image of the integrated circuit pattern.
[0011]
[Non-patent document 1]
N. Shiraishi, et al. : Proc. SPIE, Vol. 1674, p. 741 (1992)
[0012]
[Problems to be solved by the invention]
By the way, with the recent increase in capacity of optical information communication, it is necessary to form a nanometer-sized integrated circuit pattern in order to further increase the integration and density of semiconductor devices. Usually, in order to realize such ultra-fine patterning, it is necessary to irradiate the resist film 74 with short-wavelength light by using a vacuum ultraviolet light source or an X-ray light source instead of the light source 81 described above. .
[0013]
However, when a vacuum ultraviolet light source or an X-ray light source is used, it is necessary to add a new light source or an optical component to an existing exposure apparatus used for optical lithography, thereby increasing the burden on the user and increasing the overall system. However, there is a problem that the cost cannot be suppressed.
[0014]
Therefore, the present invention has been devised in view of the above-described problems, and in order to eliminate the burden of labor by the user and further reduce the cost of the entire system, the existing exposure apparatus is applied as it is. It is an object of the present invention to provide a method of forming a resist pattern capable of performing nanometer-sized patterning on a resist film, and a method of manufacturing a device having such a step.
[0015]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, a resist pattern forming method to which the present invention is applied is a resist pattern forming method for transferring a circuit pattern drawn on a photomask onto a resist film applied to the surface of a sample. On the other hand, by irradiating light longer than the wavelength based on the resonance energy between the molecules constituting the resist film, near-field light is generated in a local region corresponding to the circuit pattern, and the generated near-field light is applied to the resist film. Expose to light.
[0016]
In this method of forming a resist pattern, a so-called non-resonant light longer than a wavelength of light corresponding to resonance energy between molecules constituting a resist film is irradiated on a photomask, and a circuit pattern drawn on the photomask is irradiated with the so-called nonresonant light. Then, near-field light is generated in a nanometer-sized region, and the generated near-field light is used to expose the resist film.
[0017]
In addition, in order to solve the above-described problem, a device manufacturing method to which the present invention is applied includes a device having a photolithography step of transferring a circuit pattern drawn on a photomask onto a resist film applied to a surface of a material. In the photolithography step, in the photolithography step, near-field light is generated in a local region according to a circuit pattern by irradiating a photomask with light longer than a wavelength based on resonance energy between molecules constituting a resist film. The resist film is exposed to the generated near-field light.
[0018]
In this method for manufacturing a device, a so-called non-resonant light longer than a wavelength of light corresponding to resonance energy between molecules constituting a resist film is irradiated on a photomask, and based on a circuit pattern drawn on the photomask. And a photolithography step of generating near-field light in a nanometer-sized region and exposing the resist film to the generated near-field light.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
First, an exposure system 1 for realizing a resist pattern forming method according to the present invention will be described in detail with reference to FIG.
[0020]
The exposure system 1 includes a light source 11 for emitting light, an illumination optical system 12 for condensing light emitted from the light source 11, and a photomask 13 on which an integrated circuit pattern is drawn. In the exposure system 1, a substrate 21 made of, for example, a silicon oxide film and having a resist film 22 formed on the surface is provided so as to be in contact with the photomask 13.
[0021]
The light source 11 is a pulse light source that emits light having a wavelength of about 684 nm based on control by a driving power supply (not shown). Incidentally, if the wavelength of this light is longer than the wavelength at which the molecules constituting the resist film 22 are exposed, in other words, the so-called non-resonant light is longer than the wavelength of light corresponding to the resonance energy between the molecules constituting the resist film. Should be fine. Incidentally, a cooling medium sent from a cooling device (not shown) may be circulated around the light source 11.
[0022]
The illumination optical system 12 has a polarizing lens and controls the polarization direction of light emitted from the light source 11 based on the coordinates and direction of the integrated circuit pattern. The illumination optical system 12 has a focusing lens, and controls a beam diameter and a beam shape to be irradiated on the photomask 13. The illumination optical system 12 controls the incident angle of light on the photomask 13 in cooperation with the light source 11.
[0023]
The photomask 13 is made of a quartz glass plate in which a Cr thin film for shielding light is formed in accordance with an integrated circuit pattern, and is irradiated with light whose beam diameter or the like is controlled by the above-described illumination optical system 12. In the photomask 13, light applied to the region where the Cr thin film is formed is blocked, and light transmitted through the region where the Cr thin film is not formed illuminates the resist film 22 as it is. That is, by irradiating the photomask 13 on which the integrated circuit pattern is drawn in advance with light as described above, the pattern can be transferred to the resist film 2.
[0024]
In this exposure system 1, in order to easily perform mask alignment between the photomask 13 and the integrated circuit pattern in the previous process, a positioning mechanism using a high-precision stage or an interference system, and an alignment mark reading optical system Etc. may be provided.
[0025]
The resist film 22 is an organic photosensitive resin that causes a chemical reaction in response to light. As the resist film 22, a negative type which becomes insoluble in a developer by polymerization and crosslinking in a region irradiated with light, or a positive type which becomes decomposable in a developer by decomposing the region irradiated with light. Any of the types may be applied.
[0026]
Next, a photolithography process including a method of forming a resist pattern to which the present invention is applied will be described in detail with reference to FIG.
[0027]
First, in step S11, a resist film 22 is formed on the substrate 21. For example, a spinner method may be employed for forming the resist film 22. In this spinner method, a desired film thickness can be obtained by controlling the rotation speed of the spinner while referring to the viscosity of the resist, the solid content, and the evaporation rate of the solvent. Incidentally, after the formation of the resist film 22, pre-baking is performed to remove the solvent contained in the film.
[0028]
Next, the process proceeds to step S12, where the photomask 13 is superimposed on the substrate 21. In this step S12, by bringing the photomask 13 into close contact with the substrate 21 coated with the resist film 22, the generated near-field light reaches the resist film 22. In this step S12, the distance between the photomask 13 and the substrate 21 coated with the resist film 22 may be determined based on the wavelength of the light to be irradiated.
[0029]
Next, the process proceeds to step S13, where light is irradiated from the illumination optical system 12 to the photomask 13. Incidentally, since the light irradiated in this resist pattern forming method is so-called non-resonant light, the resist film 22 does not directly respond to the light transmitted through the photomask 13 and does not chemically change.
[0030]
However, non-resonant near-field light is generated at an edge portion of the integrated circuit pattern by a mechanism described later. Then, as a result of the resist film 22 responding to the near-field light, a chemical reaction proceeds in a local region corresponding to the integrated circuit pattern.
[0031]
Next, the process proceeds to step S14, where the resist film 22 is developed using a developing solution to form a resist pattern. If the resist film 22 is a positive type, the region sensitive to such near-field light can be removed using a developer. Incidentally, after the development is completed, post baking may be performed in order to improve the adhesion between the resist film 22 and the substrate 21.
[0032]
The resist pattern thus formed is etched in the next step S15 as a so-called etching mask on the substrate 21, and the resist film 22 is peeled off in step S16, thereby completing a series of photolithography steps. .
[0033]
FIG. 3 shows the relationship between the distance between atomic nuclei and the potential energy of each molecule constituting the resist film 22. In the normal exposure, the molecules constituting the positive resist film 22 are irradiated with light in a band corresponding to the energy difference Ea between the ground level and the excitation level (hereinafter, this light is referred to as resonance light). By doing so, it is excited to an excited level. Since this excited level exceeds the dissociation energy Eb, the molecules can be photodissociated in the direction indicated by the dotted arrow.
[0034]
Incidentally, in the present invention, the molecules constituting the resist film 22 receive the non-resonant near-field light as described above, and dissociate through excitation (multi-step transition process) by a plurality of times of light absorption. For example, as shown in FIG. 3, the molecules constituting the resist film 22 receive non-resonant light longer than the wavelength of the light corresponding to Ea, excite once to the molecular orbital level, and then move to the molecular orbital level. Excitation to a higher molecular orbital level and excitation to an excited level or molecular dissociation orbital level can be achieved by excitation by light absorption for the third time.
[0035]
The reason that molecular vibrations can be excited in this way is that the irradiation of near-field light breaks the Born-Oppenheimer approximation and causes direct excitation to the vibrational level of molecules. .
[0036]
FIG. 4 is a diagram for explaining such excitation using a harmonic oscillator model. In FIG. 4, molecules B1 and B2 are molecules constituting the resist film 22, and electrons A1 and A2 are electrons that form a pair with each of the molecules B1 and B2.
[0037]
Since the amplitude distribution of the near-field light applied to the resist film 22 is spatially different, the vibration states of the atoms A1 and A2 are also different from each other. For example, when the amplitude of the electron A1 that has received the near-field light is longer than the amplitude of the electron A2, the distance between the electrons is particularly long at the timings t1 and t3 shown in FIG. Become. At this timing, the attractive force between the electrons A1 and the electrons A2 increases, so that the distance between the electrons A1 and the molecules B1 and B2 that form a pair with the electrons A2 also decreases.
[0038]
That is, by irradiating the resist film 22 with such non-resonant near-field light having a spatially different amplitude, the distance of not only the electrons A1 and A2 but also the molecules B1 and B2 is periodically changed. It can be vibrated in the direction of the arrow in the figure. Thus, the molecules B1 and B2 can be decomposed and excited to an excited level or a molecular dissociation orbital level.
[0039]
FIG. 5 shows a substrate 21 that has been patterned through the photolithography process described above. When light is irradiated on the photomask 13 on which the Cr thin film having a width of 10 μm is formed, near-field light is generated at each edge portion of the Cr thin film. As a result, the substrate 21 is selectively etched in the nanometer-sized region where the near-field light is generated, and finally, a groove having a width of about 30 to 50 nm and a depth of about 50 nm is formed.
[0040]
That is, by applying the method of forming a resist pattern according to the present invention, non-resonant near-field light can be generated in a nanometer-sized region corresponding to the integrated circuit pattern. Thus, a nanometer-sized resist pattern can be formed, and ultra-fine processing of the substrate 21 can be performed.
[0041]
In particular, in the present invention, since the existing exposure apparatus used for photolithography can be applied as it is by changing the wavelength of the light source 11, there is no need to replace it with another light source such as a vacuum ultraviolet light source or an X-ray light source. The burden on the user can be reduced, and the cost of the entire system can be significantly reduced.
[0042]
The region where the near-field light is generated is based on the integrated circuit pattern. For this reason, by designing the integrated circuit pattern into a shape in which a near field is easily generated, a resist pattern including a groove having a width of 30 nm or less can be formed on the resist film 22.
[0043]
Note that the present invention is not limited to the above embodiment. Since the region where the near-field light is generated depends on the angle and / or the direction of deflection of the light irradiated on the photomask 13, these may be adjusted by further controlling the illumination optical system 12 and the like. Further, whether or not a chemical reaction is performed in response to near-field light depends on the type of a resist used. Therefore, a resist may be selected in relation to a designed integrated circuit pattern.
[0044]
Further, in the present invention, the contact exposure method in which the substrate 21 and the photomask 13 are brought into contact with each other or the proximity exposure method in which a gap of 10 to 20 μm is provided between the substrate 21 and the photomask 13 has been described as an example. The method is not limited to such a method, and for example, a projection optical system for forming an image of the light transmitted through the photomask 13 on the substrate 21 may be provided.
[0045]
Further, the present invention is not limited to the method of forming a resist pattern in the photolithography process, but may be applied to a method of manufacturing a device having the photolithography process.
[0046]
【The invention's effect】
As described in detail above, in the method for forming a resist pattern and the method for manufacturing a device to which the present invention is applied, a so-called non-resonant light longer than a wavelength of light corresponding to resonance energy between molecules constituting a resist film is used. Irradiation is performed on the mask, and near-field light is generated in a nanometer-sized region based on the circuit pattern drawn on the photomask, and the resist film is exposed to the generated near-field light.
[0047]
Accordingly, in the present invention, a nanometer-sized resist pattern can be formed according to the generated near-field light, and ultra-fine processing of the substrate can be performed. In particular, in the present invention, the existing exposure apparatus used for photolithography can be applied as it is by changing the wavelength of the light source, so that there is no need to replace it with another light source and the burden on the user can be reduced. Thus, the cost of the entire system can be significantly reduced.
[0048]
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an exposure system for realizing a resist pattern forming method according to the present invention.
FIG. 2 is a flowchart showing a lithography process including a method of forming a resist pattern to which the present invention is applied.
FIG. 3 is a diagram illustrating a relationship between potential energy and distance between atoms in each molecule constituting a resist film.
FIG. 4 is a diagram for explaining excitation of molecules constituting a resist film using a harmonic oscillator model.
FIG. 5 is a diagram showing a substrate patterned through a photolithography process.
FIG. 6 is a diagram for explaining the outline of optical lithography.
FIG. 7 is a view showing the principle configuration of an exposure apparatus used for transferring an integrated circuit pattern.
[Explanation of symbols]
Reference Signs List 1 exposure system, 11 light source, 12 illumination optical system, 13 photomask, 21 substrate, 22 resist film

Claims (6)

In a resist pattern forming method for transferring a circuit pattern drawn on a photomask onto a resist film applied to the surface of a sample,
By irradiating the photomask with light longer than the wavelength based on the resonance energy between the molecules constituting the resist film, a near-field light is generated in a local region according to the circuit pattern,
A method of forming a resist pattern, comprising exposing the resist film to the generated near-field light. 2. The method according to claim 1, further comprising irradiating the photomask in contact with the resist film with light. 2. The method according to claim 1, further comprising controlling an incident angle and / or a polarization direction of the irradiation light with respect to the photomask. In a device manufacturing method having a photolithography step of transferring a circuit pattern drawn on a photomask onto a resist film applied to the surface of a material,
In the photolithography step, a near-field light is generated in a local region corresponding to the circuit pattern by irradiating a photomask with light longer than a wavelength based on resonance energy between molecules constituting the resist film. And exposing the resist film to the generated near-field light. 5. The device manufacturing method according to claim 4, wherein light is irradiated to a photomask contacted with the resist film. 5. The device manufacturing method according to claim 4, further comprising controlling an incident angle and / or a polarization direction of the irradiation light with respect to the photomask.

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