KR100501247B1 - Etching mask using azobenzene compounds - Google Patents

Abstract

The present invention adopts the principle of photophysical mass transfer of azobenzene compounds, rather than conventional photochemical reactions depending on the properties of photosensitive materials, to obtain a mask manufacturing technique with high selectivity in a large area, and to shrink and expand materials by photoreaction. It provides a etching mask fabrication process by a single exposure process that does not cause deformation problems such as the like, but does not require a post-processing step, such as a developing step, which is a step of removing the stray light reaction portion, and also provides a simple lattice structure on a conventional plane. While it was possible to control the spacing and depth of the grating, the microsurface irregularities of various shapes can be formed by using the superposition principle of the microstructure pattern, so that the optical device, the semiconductor device, and the micro electro mechanical system can be formed. Improved to make it easy to manufacture devices that require fine surface irregularities Intended to provide a mask.

Description

Etching mask using azobenzene compounds

The present invention relates to an etching mask having a structure in which a surface of a material containing azobenzene is irradiated with a predetermined light beam and a fine surface irregularities are formed on the surface thereof. By using the fine surface irregularities formed on the surface as an etching mask according to the principle, the mask is not exposed to the deformation of the material due to the photoreaction and the mask is exposed by a single exposure process that does not require a post-process step such as a development step. It can be fabricated, and the superficial uneven structure of various shapes can be formed by using the superposition principle of the microstructure pattern, so the device which requires the microsurface uneven structure such as optical device, semiconductor device and micro electro mechanical system It is related with the etching mask improved by making it easy to manufacture.

The most commonly used technique for fabricating the etching mask was an optical interferometric lithography method using a photochemical reaction of a photosensitive material.

1 is a schematic diagram of a typical optical experimental apparatus for optical interference lithography, in which wavelength light from a single wavelength light source 10 is passed through a first lens 12, and the extended wavelength light is again converted into a second lens 14; Pass through to convert into parallel light.

At this time, the parallel light is divided into a light beam directly reaching the surface of the sample 16 and a light beam reflected by the mirror 18, and complementary and destructive interference with each other to form a periodicity of the light intensity.

Accordingly, the periodic photochemical or crosslinking reaction occurs on the sample 16, which is a photosensitive material, and the portion where the photochemical reaction does not occur is dissolved and removed using a developer such as an aqueous alkaline solution, thereby providing a regular lattice structure. Can be formed and used as an etching mask.

Conventional optical interference lithography techniques using photochemical reactions of photosensitive materials have been developed based on light source wavelengths and types of photosensitive materials. The light source wavelength has been advanced in the direction of using a light source having a short wavelength to form a narrower diffraction structure. In the early 1970s, 436 nm g-rays were used, and from the late 1970s, they began to use 365 nm I-rays from Mercury lamps.

Recently, as a semiconductor memory, shorter light source capable of lithography below 300 nm is needed to realize 64 MDRAM, KrF laser light source with 248 nm wavelength has been commercialized and studies using 193 nm ArF laser light source have been actively reported. It is becoming.

Currently, as the photosensitive material, diazonaphthoquinone (DNQ) and novolak resin are mainly used.

Fabrication of the etching mask as described above requires a technique of precisely controlling the photochemical reaction of the material as a method using a photochemical or photocuring reaction of the photosensitive material.

That is, the photosensitive material of the above purpose has to have high photosensitivity, high resolution, and thermal stability, and furthermore, it is necessary to develop a more suitable material because no material deformation such as shrinkage or swelling occurs during the photoreaction.

In addition, since the fabricated mask can provide only a fine lattice structure on a two-dimensional plane, there is a need for a technique capable of forming various fine surface structures, and a process of removing chemicals in a portion where photoreaction does not occur after exposure. do.

To this end, most of the wet development process (wet developing), there is a problem that can cause severe deformation of the pattern formed according to the process conditions.

Accordingly, the present inventors formed on the surface of the azobenzene compound when exposed to the azobenzene compound by the principle of photophysical material movement of the azobenzene compound, rather than the photochemical reaction of the photosensitive polymer, which is dependent on the characteristics of the existing photosensitive material. The present invention was completed by transferring the microstructure to the lower layer by using the resulting fine surface asperity structure as an etching mask.

Accordingly, the present invention introduces the photophysical mass transfer principle of azobenzene compounds rather than conventional photochemical reactions depending on the properties of the photosensitive material, thereby obtaining a mask manufacturing technique having high selectivity in a large area, and shrinking of the material by photoreaction. It provides a etching mask fabrication process by a single exposure process that does not cause deformation problems such as swelling, expansion, etc., and does not require a post-processing step such as a developing step, which is a step of removing stray light reaction parts, and also provides a simple grating on a conventional plane. While it was possible to control the spacing and depth of the grating in the structure, the microsurface irregularities of various shapes can be formed by using the superposition principle of the microstructure pattern. Easily manufacture devices that require surface relief grating (SRG) It is an object of the present invention to provide an etching mask that can be improved.

The present invention for achieving this object

An etching mask is provided, which is achieved by exposing a predetermined ray of light to a surface of a material having an azobenzene group, thereby forming a fine surface concavo-convex structure on the surface of which waves are curved.

In a preferred embodiment, when exposing the surface of the azobenzene material, the light beam used is characterized by using one or more of linearly polarized light, circularly polarized light, and elliptical polarized light.

In another embodiment, when exposing the surface of the azobenzene material, it is characterized in that the use of interference light of different polarization and wavelength combination of the respective light sources.

In particular, the azobenzene material is an organic or inorganic monomolecule or polymer in which an azobenzene functional group is chemically bonded, or an organic or inorganic material in which an azobenzene compound is doped in a chemically unbound state. The azobenzene compound used in the present invention is a compound having an azobenzene group, and the azobenzene group has a chemical structure in which two benzene groups are connected by two nitrogen atoms. The nitrogen atoms connecting the two benzene groups each have one unbonded electron pair, and photoisomerization occurs between the trans structure and the cis structure isomer by the light energy. Incident light when exposed to light The characteristics of a vertically oriented with respect to the linear polarization direction are widely known. The chemical structure of the azobenzene group used in the present invention are represented as follows: Formula 1: [Formula 1] The azobenzene group represented by Chemical Formula 1 is a structure in which -N = N- group connects two aromatic rings, and it is a general fact that hydrogen of each aromatic ring may be substituted with a different kind of element. However, the substituents X and Y may be -H, -O-, -NR ₂ , -NO ₂ , -S-, -SO-, -CO-, or an aliphatic or aromatic substituent connected with a halogen group. The azobenzene group compound is added to the organic or inorganic material in a chemically bonded state or a non-chemically bonded state (non-bonded state), characterized in that the organic or inorganic materials are commonly used in the art There is no need to specifically limit the type since it can be used. Specifically, the organic material may be polymethylmethacrylate, polystyrene, polyamide, polyepoxide, or the like. May use the same polymer material, an inorganic material as may be used by mixing at the sole or need by selecting a metal oxide such as _{SiO 2, TiO 2, SnO 2} . In other words, the present invention is gwanggeo dynamics of azobenzene compound molecule It is not performed alone, but uses the principle of forming a microsurface diffraction structure by moving together azobenzene groups and chemically unbonded peripheral materials. When the azobenzene compound and an organic or inorganic material are added in an unbonded state as described above, It was conceived that similar optical behavior can be observed although the efficiency is lower than that of using azobenzene compound and organic or inorganic substance in a chemically bonded state.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described.

First, the optical characteristics of the azobenzene used in the present invention will be described in more detail as follows.

An azobenzene group has a chemical structure in which two benzene groups are connected by two nitrogen atoms, and is an aromatic compound in which electrons are delocalized throughout the molecule by side overlap of an electron orbit.

In the nitrogen atom connecting two benzene groups, there is one unpaired electron pair, and photoisomerization reaction occurs between the trans structure and the cis structure isomer by the light energy.

If the azobenzene compound is exposed to linearly polarized light, the property of orienting perpendicularly to the linear polarization direction of incident light is widely known.

Figure 2 schematically shows the light guide linear alignment described above.

The azobenzene material, that is, the organic polymer, the monomolecule, and the liquid crystalline material including the azobenzene may form a fine concavo-convex structure on the surface of the film when exposed to light of the wavelength of the light absorption region of the azobenzene.

The optical device is the same as the optical device of the optical interference lithography of the conventional photosensitive material shown in FIG. 1, wherein the light source typically uses a laser beam of 488 nm or 514 nm of an argon laser.

In addition, the diffraction structure to be formed is closely dependent on the diffraction efficiency depending on the polarization direction of the incident light, p polarized light more effectively than the s polarized light to form a fine surface irregularities structure, 45 ° linearly polarized or circularly polarized light is more effectively fine It is known that surface irregularities are formed.

Therefore, λ / 2 waveplate optical material capable of rotating the linear polarization plane of the laser beam within the range of 0 to 90 ° in conventional optical devices, or λ / 4 capable of converting linear polarization to circular polarization It is necessary to further install the wave surface at a position between the single wavelength light source 10 and the first lens 12 shown in FIG.

The microsurface irregularities formed at this time are not due to photochemical reactions but to the movement of photophysical materials. Therefore, various mechanisms have been proposed to elucidate this phenomenon in detail. The theory (mean field theory), the theory introduced by introducing the hydrodynamic concept has been proposed.

The spacing of the surface lattice structure of the azobenzene material formed by the interference light can be controlled by Scheme 1 in the same manner as the conventional optical interference lithography.

nλ = 2d sinθ

Where λ is the wavelength of the laser beam used, d is the periodic spacing of the surface grating structure to be formed, and θ is the angle of incidence satisfying this condition and refers to the angle at which the ray is incident on the normal of the film.

In addition, the depth of the grating increases in proportion to the incident light intensity and exposure time, and the wavelength of the light source used, the maximum absorption wavelength of the azobenzene material, the polarization characteristics of the light source, the thickness of the material film, the glass transition temperature and the chemical structure of the material Closely related to

The formation of the fine surface irregularities formed by the mass transfer of azobenzene is possible by overlapping the light source of various waves due to the property of overlapping, or after the surface microstructures are formed. It is possible to form a fine surface irregularities structure.

In order to measure in real time the formation of the fine surface irregularities structure, the diffraction efficiency was measured using a laser beam existing outside the absorption wavelength of azobenzene, for example, a helium-neon laser having a wavelength of 633 nm. It should not affect the formation of the structure.

The microstructure of the structure can be analyzed using atomic force microscopy (AFM) or scanning electrom microscopy (SEM).

The structural transition to the lower layer using the fine surface uneven structure of the azobenzene material formed by the above-described method as an etching mask will be described in more detail as follows.

Fig. 3 is a schematic diagram of transferring the surface structure to the film of the lower layer using the prepared fine surface asperity structure as an etching mask.

The etching using the mask of the present invention proceeds to a film manufacturing step of Figure 3 (a), Figure 3 (b) forming a fine surface uneven structure on the azobenzene material layer, Figure 3 (c) plasma etching step as a whole three steps (d) shows the structure finally obtained.

Adding a detailed description of the material layer constituting each manufacturing step, as shown in Figure 3 (a), first forming the first film 24, which is a material necessary for the operation of the device on the substrate 22, On the upper layer, a second film 26, which is a material layer requiring a fine surface uneven structure, is formed.

Examples of the material of the film 26 include a low loss material for light absorption in an optical waveguide, a conductive material for a semiconductor device or a photoelectric device, and a material with high transparency for an antireflection film.

Finally, a film of the azobenzene material 28 is formed, and then the surface of the azobenzene material 28 is exposed to light by the method described above, so that a plasma etching mask of the fine surface irregularities structure 30 is shown in Fig. 3 (b). Shaped as shown.

When the etching mask of the fine surface irregularities structure 30 is etched to the second film 26 by the plasma etching method as shown in FIG. 3 (c), the thickness difference of the fine surface irregularities structure 30 is different. Due to this concave-convex structure can be transferred to the second film 26, the finally obtained structure is as shown in Figure 3 (d).

The micro surface irregularities transition by simple etching requires that the second film 26 can be etched by the same kind of plasma source as the azobenzene material layer, and the selectivity ratio of the irregularities structure is changed to the azobenzene layer by changing the etching conditions. The fine surface irregularities can be adjusted to be larger or smaller.

FIG. 4 schematically illustrates the use of a surface lattice structure of azobenzene material as a mask for selective multi-step etching. In this case, the layer to which the structure is to be transferred is a layer that can be etched by a different kind of plasma from the azobenzene material layer, and the inorganic material 32 mainly corresponds to this.

The etching step includes a one step process (FIG. 4A) of etching the azobenzene material layer in which the fine surface uneven structure 30 is formed, and a two step etching process of the material layer 32 to which the uneven structure is to be transferred (FIG. 4B). It is configured and the type of plasma source and etching conditions must be adjusted between the two etching steps.

When the upper end of the remaining fine surface concave-convex structure 30 in the obtained structure is removed by the plasma source used in the one-step etching, for example, the oxygen plasma source, finally, the microstructure as shown in Fig. 4G can be obtained.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by Examples.

Example 1

The structure was transferred to cyclotine (CYCLOTENE * 3022 Resins) through a reactive ion etchin (RIE) process using a fine surface asperity structure of the azobenzene material prepared as described above as a mask.

The etching was performed by mixing a tetrafluoromethane (CF ₄ ) gas and oxygen (O ₂ ) gas in a ratio of 5:20 at a vacuum of 10 W and 200 mTorr, and etching was performed at an etching rate of 76 nm / min for 6 minutes. Was carried out.

The results of this embodiment are shown in FIG. 5. FIG. 5A shows the shape of the fine surface irregularities formed on the azobenzene film before etching, and on the CYCLOTENE * 3022 Resins resin film after etching. As a result, it was confirmed that the microsurface lattice structure of the azobenzene material was transferred to the lower cyclotine as shown in FIG. 5B.

Example 2

In order to realize a practical device using a microsurface irregularities structure of the azobenzene material prepared as described above as a mask, a lattice structure was formed on the core layer of the planar waveguide optical filter, that is, the optical waveguide.

The detailed manufacturing process is a six-step manufacturing process, as shown in the accompanying Figures 6a to 6f, when the manufacturing process of each step in order as follows.

(a) A process of forming the lower cladding layer 101 and the core layer 102 on the substrate 100 is performed (FIG. 6A).

(b) After the step (a), an azobenzene material is formed on the core layer 102 and exposed to form a fine surface asperity structure 103 (FIG. 6B).

(c) After the step (b), a reaction ion etching process was performed while using the fine surface uneven structure 103 as a mask to form the same uneven structure in the core layer 102 (FIG. 6C). Proceed.

(d) After the step (c), the SiN layer 104 is applied onto the core layer 102 having an uneven structure by using a plasma chemical vapor deposition process (PECVD), and a lithography process in a direction perpendicular to the center portion thereof. The process (FIG. 6D) of manufacturing the photoresist pattern 105 using the above is advanced.

(e) After the step (d), a reaction ion etching process is performed to remove the SiN layer 104 and the core layer 102 except for the area covered by the photoresist pattern 105, thereby removing the lower cladding layer ( Proceed with the process to expose the surface of 101).

(f) Next, the process of removing the remaining photoresist pattern 105 and the SiN layer 104 to form a channel optical waveguide 106 in which the core layer having the fine surface roughness structure remaining thereon is formed (FIG. 6e) proceeds.

(g) Finally, the upper cladding layer 107 is spin-coated on the lower cladding layer 101 including the channel optical waveguide 106 to produce a planar waveguide grating optical filter 200 (FIG. 6F). This is going on.

The measurement results of the transmission characteristics of the planar optical waveguide grating optical filter manufactured by the above process are as shown in FIG. 7.

As described above, according to the etching mask using the azobenzene material according to the present invention, the process is simpler than the conventional method using the photosensitive material, does not require wet development (wet developing) of the material by the light reaction Deformation problems such as shrinkage and expansion do not occur, and not only a simple lattice structure but also a variety of fine surface irregularities can be formed and a curved fine structure can be formed, so that optical devices, electronic devices, and micromechanics in various materials can be formed. It can be usefully applied to the lithography method of implementing the system.

Since the etching mask pattern of the present invention can form complex fine surface structures using not only a simple lattice structure that is a linear lattice structure regularly arranged, but also a superimposed principle of the pattern, an optical element requiring various fine surface irregularities structures, It can be applied to technical fields such as semiconductor devices, optical communication devices, display devices, and microelectromechanical systems.

In particular, since the etching mask forming process of the present invention is a process that is not limited to the substrate to be applied, the substrate type (Si, silica (SiO 2), GaAs, InP, InGaAs, InGaAsP, conductive polymer, light emitting polymer, low light loss polymer, transparent It is applicable to all kinds of organic and inorganic materials such as polymers.

1 is a schematic diagram of an exemplary optical experiment for optical interference lithography,

2 is a schematic view showing a photoisomerization reaction of an azobenzene group,

3 is a plan view showing a state in which the structure transition to the lower layer using a fine surface irregularities structure of the azobenzene material as an etching mask,

4 is a plan view showing a state in which a fine surface irregularities structure of an azobenzene material is used as a mask for selective multi-step etching;

Figure 5a, 5b is a photograph showing the microstructure of the surface irregularities of the azobenzene material and the microstructure transferred to the lower layer by plasma etching with a scanning electron microscope (SEM),

6A to 6G are schematic diagrams sequentially showing a manufacturing process of the planar waveguide grating optical filter according to the embodiment;

7 is a transmission spectrum of the optical filter manufactured by the method of the above embodiment.

<Explanation of symbols for the main parts of the drawings>

10: wavelength light source 12: first lens

14 second lens 16 sample

18: mirror 22: substrate

24: first film 26: second film

28: azobenzene material 30: fine surface irregularities

100 substrate 101 lower cladding layer

102 core layer 103 fine surface irregularities

104 SiN layer 105 Photoresist pattern

106: channel optical waveguide 107: upper cladding layer

200: planar waveguide grating optical filter

Claims (4)

Etching mask using an azobenzene material, characterized in that a predetermined light beam is exposed to the surface of the material having azobenzene groups, thereby forming a fine surface irregularities structure on the surface The etching mask according to claim 1, wherein when exposing the surface of the azobenzene material, one or more linearly polarized light, circularly polarized light, or elliptical polarized light is used. The etching mask according to claim 2, wherein when exposing the surface of the azobenzene material, interference light having different polarizations and wavelengths of the respective light sources are used. The azobenzene material according to claim 1, wherein the azobenzene material is an organic or inorganic monomolecule or a polymer in which an azobenzene functional group is chemically bonded, or an organic or inorganic material in which an azobenzene compound is doped in a chemically unbound state. An etching mask using an azobenzene substance.