JP2008053666A - Pattern formation method and pattern formation object - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a pattern in a way that a fine pattern on an HSQ film is maintained even at a high temperature and a pattern formation object having the fine pattern fabricated in a way that it is maintained event at a high temperature. <P>SOLUTION: A fine pattern 2a is added by a nano-imprint method which presses a mold 8 to an HSQ film 2 on a substrate 1. After the mold 8 is separated, oxygen is radiated onto a surface of the fine pattern 2a (HSQ film 2) without a heating process for the HSQ film 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The claimed invention is a method for forming a fine pattern (pattern with irregularities in the nm or μm level) on the HSQ film so that the shape is maintained even when used at a high temperature, and thus the fine pattern is formed. The present invention relates to a formed HSQ pattern formed body.

HSQ (hydrogen silsesquioxane polymer) is a sol-gel inorganic polymer material, and is a meaningful transfer material that enables room-temperature nanoimprinting with high accuracy and high throughput that does not require thermal cycling or UV irradiation. Since it consists of a repeating structure of HSiO _3/2 and has a high dry etching resistance equivalent to SiO ₂ , the transferred fine pattern can also be used as a mask for dry etching. The high transparency also brings various advantages.

  A room temperature nanoimprint process using an HSQ film is shown in FIGS. (1) The HSQ film 2 is formed on the substrate 1 by spin-coating HSQ as a transfer material. (2) Next, the mold 8 having a fine pattern formed on the surface (the lower surface in the figure) by electron beam lithography or the like is pressed against the HSQ film 2 at room temperature without applying heat to maintain an appropriate pressure. (3) The mold 8 is peeled from the substrate 1 and the HSQ film 2, and (4) and (5) residues (residual film) 2x and the like on the substrate 1 are removed by etching.

The chemical structure and spectrum measurement result (FTIR) of HSQ are shown in FIG. According to FTIR measurement, the main ^{spectrum, 2260cm -1: Si-H stretching} , 1130-1180cm -1: Si-O, 1130cm -1 among which: Si-O stretching of cage structure , 1080cm -1: Si -O stretching of network structure, and 860-830cm ^-1 : O-Si-H. FTIR results show that HSQ is a polysiloxane that does not contain organic groups such as vinyl groups. When heated to 500 ° C., Si—H decreases and Si—O increases. Further, when heated to 1000 ° C., Si—H is almost lost and only Si—O is obtained, and HSQ becomes SiO ₂ .

The room temperature nanoimprint using the HSQ film is described in the following Patent Document 1, Non-Patent Document 1, and the like.
Japanese Patent Laid-Open No. 2003-100609 S. Matsui, Y. Igaku et al. “J. Vac. Sci. Technol., B19, 2801 (2001)”

The fine pattern formed on the HSQ film has a problem that it is easily deformed when heated to a certain temperature or higher. FIGS. 14A to 14D are cross-sectional SEM images showing this, and when the mold is pressed and peeled to form a fine pattern with a line width of about 200 nm, the sample is heated to each set temperature. It is a photograph of a pattern. As shown in FIG. 14C, it was difficult to maintain the shape when heated to 200 ° C., and the pattern disappeared at a temperature higher than that. As estimated from the fact that the surface hardness increases with the temperature rise and the measurement result of FIG. 13, with heating, the Si-O cage structure opens to become a ladder structure, and the ladder structure forms a network structure. At the same time, it is considered that HSQ is converted into SiO ₂ and hardened by decreasing Si—H.

If the formed fine pattern is not maintained at a certain temperature or higher, the use of such a pattern forming body is greatly limited. For example, a SiO ₂ lamellar grating, which is a diffraction grating used in soft X-ray spectroscopy, needs to be resistant to high heat caused by X-ray irradiation in a vacuum, but is formed of an HSQ film as described above. In such a case, there is no such resistance, and it cannot be used as a lamellar lattice.

  The invention according to claim provides a pattern forming method for maintaining a fine pattern formed on an HSQ film even at a high temperature, and a pattern forming body on which a fine pattern is formed so as to be maintained even at a high temperature. Is.

In order to solve the above problems, the inventors give a fine pattern to the HSQ film, and then perform oxygen irradiation (irradiation of oxygen ions or oxygen plasma) on the surface of the film (surface having the fine pattern). did.
By doing so, the shape of the fine pattern of the HSQ film is maintained even when heated to 200 ° C. or higher (see FIG. 3). When oxygen irradiation is performed on the surface of the HSQ film, it is converted to SiO ₂ (or changes to a composition similar to SiO _{2 in} the very thin range (estimated to be about ₂ to 3 nm in depth)). As a result, the hardness increases, and it is considered that the subsequent pattern can be maintained. The reason why SiO ₂ is formed on the surface of the HSQ film is that, as will be described later (see FIG. 4, Table 1 and FIG. 5), after oxygen irradiation, the ratio of O to Si increases and contact of water droplets occurs. This is because the corners are equivalent to those on the SiO ₂ surface. As described above, the shape tends to collapse when SiO ₂ is formed. However, in the case of oxygen irradiation, there is almost no influence on the shape because it is limited to SiO ₂ in a very thin surface area.

The pattern forming method described above is performed by, for example, applying a fine pattern by pressing a mold (a mold having a fine pattern formed on the surface) against the HSQ film (that is, by a method called nanoimprint), and peeling the mold (HSQ After separation from the film, the surface of the HSQ film may be irradiated with oxygen without interposing the heating process. For example, the procedure of FIG. 1 is followed.
If a mold is used, a fine pattern can be applied to the HSQ film with high accuracy and efficiency. Moreover, when oxygen irradiation is performed without interposing a heating process after peeling off the mold, a fine pattern provided with high accuracy is maintained as it is even at a high temperature. Therefore, this method is suitable for producing a pattern forming body having an accurate pattern and capable of being used at a high temperature (for example, the aforementioned lamellar lattice).

On the other hand, a fine pattern is applied by pressing a mold against the HSQ film, and after peeling the mold, a part of the surface is reflowed by heating the HSQ film, and oxygen irradiation is performed on the surface. Good. For example, it is based on the procedure of FIG.
When a fine pattern is formed with high precision using a mold and the HSQ film is heated to reflow part of the surface, a pattern including a convex curved surface such as a spherical surface as shown in FIGS. 9 (4) and 10 Can be easily formed. The formed body having such a pattern can be used as a microlens array widely used in the field of optical applications such as a liquid crystal projector and an optical communication connector.

The HSQ film may be provided by spin coating on a substrate, or may be provided by a method in which a mold is pressed immediately after applying a droplet as described below. That is, for example, as shown in FIGS. 7 (1) to (4) (or (1) to (3) in FIG. 9), an HSQ film is formed by dropping an HSQ liquid on the substrate. In addition, the mold is pressed against the film before the solvent in the liquid evaporates (and thus the surface of the HSQ film is cured), and after the solvent is evaporated (and thus the surface of the HSQ film is cured), By separating the mold, a fine pattern is applied to the HSQ film. Thereafter, the surface of the film is irradiated with oxygen without sandwiching or interposing the heating process of the HSQ film.
By adopting such a method, a) the pressure required to press the mold (transfer pressure) is lowered to press the mold before the hardness of the HSQ film increases, and b) the transfer depth to the HSQ film. The fine pattern is faithfully transferred to the HSQ film, such as being uniform regardless of the line width of the mold. C) The HSQ residue (residual film) on the substrate after transfer becomes thin and easy to remove. The following advantages are brought about. Thereby, fine patterning in various optical components can be performed with higher accuracy and higher throughput.

In the above pattern forming method, electron beam irradiation or argon ion irradiation may be performed instead of oxygen irradiation.
By performing electron beam irradiation or argon ion irradiation instead of oxygen irradiation, the fine pattern in the HSQ film can be maintained at a high temperature. According to the measurement by the inventors, even when electron beam irradiation was performed, the ratio of O to Si in the HSQ film increased, and the contact angle of water droplets approached that on the surface of SiO ₂ (see Table 3). reference). From this point, it is considered that, as in the case of oxygen irradiation, the fine pattern can be maintained as a result of increasing the hardness by forming SiO _{2 in} the thin area of the surface of the HSQ film.

The pattern forming body having a fine pattern on the surface is preferably formed by any one of the above pattern forming methods.
Such a pattern forming body can be used even in an environment of high temperature (particularly 200 ° C. or higher), used as a mold for thermal nanoimprinting, a mask for high temperature dry etching, or further to a high heat resistant low expansion substrate. Optical components such as blazed diffraction gratings, lamellar gratings, etc. from the possibility of compatibility (wide selection range with a wide coefficient of linear expansion), UV transmission, low wavelength dispersion, transparency, high heat resistance, high chemical resistance, etc. It is suitable for use as a dry etching mask for processing a magnetic thin film of patterned media, which is a high-density recording medium such as a large capacity hard disk.
In particular, a method in which a fine pattern is applied to the HSQ film with a mold, the mold is peeled off, the HSQ film is heated to reflow part of the surface, and oxygen irradiation is performed on the surface (for example, FIG. The pattern forming body formed in 9) is suitable for use as a microlens array (including an intermediate product for manufacturing the microlens array).

  According to the pattern forming method according to the claims, the shape of the fine pattern formed on the HSQ film is maintained even when heated to 200 ° C. or higher. Therefore, the pattern forming body on which a fine pattern is formed in this way can be used as an optical component that is required to withstand high temperatures, such as a mold for thermal nanoimprint, a mask for high temperature dry etching, a lamellar lattice, or patterned media. It becomes. Note that pattern formation can be further improved in accuracy and efficiency, and a microlens array can be obtained.

A first embodiment relating to the implementation of the invention is introduced in FIGS. In this embodiment, a fine pattern is formed on a film of HSQ (for example, “FOX16” of Dow Corning Co. or “OCD T-12” of Tokyo Ohka Kogyo Co., Ltd.) by the procedure of FIGS. That is, the HSQ film 2 is provided on the surface of the substrate 1 by a method such as spin coating (spin coating) (FIG. 1A), and the mold 8 is pressed thereon (FIG. 1B). The mold 8 has a fine concavo-convex pattern 8a on its surface (lower surface in the figure). For example, the mold 8 is made of Si and SiO _2, and the concavo-convex pattern 8a is formed on the SiO ₂ portion by electron beam lithography and dry etching. Is. When the pressed mold 8 is peeled from the HSQ film 2, a fine pattern 2 a to which the uneven pattern 8 a of the mold 8 is transferred is formed on the HSQ film 2 by so-called room temperature nanoimprint (FIG. 1C). The HSQ film 2 having the fine pattern 2a thus formed is subjected to oxygen irradiation (O ₂ RIE, that is, oxygen ion irradiation, but may be oxygen plasma irradiation) using the apparatus 11 shown in FIG. 2 (FIG. 1 (d)). . Then, the HSQ film 2 is placed in a high temperature environment such as 1000 ° C. (FIG. 1E).

The apparatus 11 of FIG. 2 that performs oxygen irradiation of FIG. 1D is for reactive ion etching, and includes a high-frequency electrode and a ground electrode connected to a high-frequency power source 14, an oxygen gas supply path, an exhaust path, and the like. ing. The substrate 1 is placed on the high-frequency electrode in the plasma ion sheath so that the HSQ film 2 (pattern 2a) faces up and faces the ground electrode, and the surface of the HSQ film 2 is irradiated with oxygen ions of several tens eV. The conditions of oxygen irradiation adopted in the experiment are as follows.
Power frequency: 13.56MHz
Oxygen gas pressure: 5Pa
Irradiation time: 10 sec
RF power: 100W

  3A to 3F are cross-sectional SEM images showing states when the HSQ film 2 formed by the procedure of FIG. 1 is left at each set temperature for 10 minutes. The line width of the pattern is about 200 nm. Even when the HSQ subjected to oxygen irradiation is 200 ° C. or less (FIGS. 3A to 3C), each case is heated to 300 ° C., 500 ° C., and 1000 ° C. (FIGS. 3D to 3F). )) Also confirms that the pattern shape is maintained.

FIG. 4 shows the measurement results of the XPS spectrum on the HSQ surface (X-ray source is Mg. 1253.6 eV Kα ray is used), and shows the spectrum for each oxygen pressure when oxygen irradiation is performed for 10 seconds. Table 1 below shows the results of investigating the ratio of O to Si on the HSQ surface (strength ratio; ratio of peak height between O1s and Si2p) based on FIG.

From FIG. 4 and Table 1, it can be seen that when the irradiation time is the same, the ratio of O to Si on the HSQ surface increases as the oxygen pressure increases. In addition, the ratio of O in SiO ₂ (the same intensity ratio as described above) is 4.87 (see Table 3 described later).

Fig. 5 shows the contact angle of water droplets on the HSQ surface irradiated with oxygen. Fig. 5 (a) is a diagram showing the relationship with the oxygen pressure during oxygen irradiation. c) is a side view of a water droplet showing contact angles of 104 ° and 25 °, respectively. The RF power for the oxygen irradiation in FIG. 5A is 100 W, and the irradiation time is 10 seconds. While the contact angle of the untreated HSQ surface is 104 °, the contact angle of the HSQ surface irradiated with oxygen is drastically reduced to about 26 °, approaching the contact angle in SiO ₂ (25 °, see Table 3). It was.
In view of the above, by oxygen irradiation, believed to SiO ₂ of (or change to SiO ₂ and similar composition) have occurred with respect to the surface of the HSQ.

  FIG. 6 is a cross-sectional SEM image showing a fine pattern (line width is about 1 μm) formed on the HSQ film as a lamellar lattice. 6 (a), 6 (b), and 6 (c) are respectively in a state of being heated to 180 ° C. without being irradiated with oxygen immediately after peeling off the mold, and being heated to 1000 ° C. after being irradiated with oxygen. HSQ is shown. When oxygen irradiation is not performed (FIG. 6B), the pattern shape changes at 180 ° C., but with oxygen irradiation (FIG. 6C), the pattern shape is maintained even at 1000 ° C. Yes.

  FIG. 7 shows a form in which a fine pattern is formed by a slightly different procedure. In this embodiment, a fine pattern is imparted to the HSQ film by the nanoimprint technique shown in FIGS. That is, the HSQ film 3 on the substrate 1 is formed not by spin coating but by applying HSQ droplets (FIG. 7 (1)), and promptly, that is, the solvent in HSQ (for example, methyl isobutyl ketone ( Before the MIBK)) evaporates, the mold 8 is pressed against the HSQ film 3 (FIG. 7 (2)). The solvent is evaporated by leaving time with the mold 8 being pressed or heating the substrate 1 to about 90 ° C. (FIG. 7 (3)). Thereafter, the mold 8 is peeled from the substrate 1 and the HSQ film 3 to obtain a pattern 3a on the HSQ film 3 (FIG. 7 (4)). After that, oxygen irradiation is performed on the pattern 3b as described above (FIG. 2 and the like).

  In the method shown in FIG. 7, the transfer pressure can be lowered to about 1 MPa to press the mold 8 while the HSQ film 3 is soft, and a faithful transfer to the pattern of the mold 8 is realized. The HSQ residue on the substrate after the transfer could be made as thin as 10 nm or less. Such a method is expected to be preferable as a patterning technique for producing optical parts such as dry etching masks, patterned media, polarizing plates, and diffraction gratings.

FIG. 8 shows a transfer pattern (FIG. 8A) obtained by pressing a mold against HSQ formed by spin coating, and a pattern (FIG. 8B shown in FIG. )). In the case of FIG. 8A, although the transfer pressure is as high as 22 MPa, the pattern of the mold 8 is not faithfully formed in the transfer depth or the like, and the HSQ residue is as thick as about 200 nm. On the other hand, in the case of FIG. 8B transferred by the procedure of FIG. 7, the transfer pressure is low as described above, the pattern is faithfully formed on the mold, and the residue is thin. The mold 8 used for forming the patterns of FIGS. 8A and 8B and the manufacturing conditions thereof are as shown in Table 2.

  9 (1) to 9 (4) show a fine pattern forming process as still another embodiment. In this process, first, a fine pattern 3b is formed on the substrate 1 by the same nanoimprinting procedure as in FIG. That is, the HSQ film 3 is provided on the substrate 1 by applying droplets rather than by spin coating (FIG. 9 (1)), and the mold 8 is pressed before the solvent in the HSQ evaporates (FIG. 9 (2)). )), The mold 8 is peeled off after evaporating the solvent by waiting for a while or heating the substrate 1 to about 90 ° C. (FIG. 9 (3)). Thereby, as an example, a pattern 3b in which a large number of discontinuous columnar protrusions having a diameter and a height of 0.5 μm are arranged is formed.

The process of FIG. 9 is characteristic in that after the mold 8 is peeled off, the substrate 1 having the pattern 3b is baked to reflow the vicinity of the surface of the pattern 3b (FIG. 9 (4)). . The baking process is performed by heating the substrate 1 at 220 ° C. for 10 minutes, and a pattern 3c having a convex curved surface such as a spherical surface is formed by HSQ reflow.
Then, oxygen irradiation is performed to give the pattern 3c high temperature resistance. In this example, a lens-like pattern 3c having a diameter of 0.5 μm could be obtained. The SEM images for the patterns corresponding to FIGS. 9 (3) and (4) are shown in FIGS. 10 (a) and 10 (b).

  In the embodiment introduced above, oxygen irradiation was performed on the HSQ, but the inventors also conducted an experiment in which an electron beam was irradiated instead of the oxygen irradiation. This is because the surface of the HSQ is expected to be cured by electron beam irradiation.

  FIG. 11 is a cross-sectional SEM image in which a fine pattern having a line width of about 500 nm is formed on the HSQ on the substrate, the surface is irradiated with an electron beam of about 50 eV, and the resulting pattern (and the substrate) is heated. It is. When heated to 100 ° C. and 200 ° C. (FIGS. 11B and 11C), pattern collapse was not observed as compared to the one before heating (FIG. 11A).

For the HSQ before and after the electron beam irradiation, the XPS spectrum and the water droplet contact angle were measured in the same manner as in FIGS. The measurement results are summarized in Table 3 in comparison with the data for oxygen irradiation (oxygen ion irradiation) and the data for SiO ₂ . According to Table 3, it is presumed that the surface of the HSQ (having a depth of about 1 μm) is converted to SiO ₂ even in the case of electron beam irradiation. However, the degree seems to be slightly smaller than in the case of oxygen irradiation.

FIGS. 1A to 1E are diagrams showing a pattern formation procedure for the HSQ film. It is a schematic diagram which shows the method and installation of oxygen irradiation in the process of FIG.1 (d). FIGS. 3A to 3F are cross-sectional SEM images when the HSQ films formed by the procedure of FIG. 1 are each heated to a set temperature. It is a measurement result of the XPS spectrum of the HSQ film | membrane surface, Comprising: It is a figure which shows distribution for every oxygen pressure at the time of oxygen irradiation. FIG. 5 (a) is a diagram showing the relationship between oxygen pressure and contact angle during oxygen irradiation, and FIGS. 5 (b) and 5 (c) show the contact angle measured on the surface of the HSQ film. It is a side view of the water droplet which shows the case of 104 degrees and 25 degrees, respectively. FIGS. 6A to 6C are cross-sectional SEM images showing fine patterns formed on the HSQ film as a lamellar lattice, and FIGS. 6A to 6C are heated immediately after heating the mold to 180 ° C. without oxygen irradiation. An HSQ film in a state and an HSQ film in a state heated to 1000 ° C. after oxygen irradiation are shown. 7 (1) to 7 (4) show a pattern forming procedure for the HSQ film, which is different from FIG. A transfer pattern (FIG. 8 (a)) obtained by pressing a mold against the HSQ film formed by spin coating and a pattern (FIG. 8 (b)) applied by droplet application and transferred according to the procedure of FIG. It is a SEM image shown. 9 (1) to 9 (4) show a pattern forming procedure for the HSQ film, which is different from those shown in FIGS. FIGS. 10A and 10B are SEM images showing changes in the fine pattern before and after reflowing the HSQ. FIGS. 11A to 11C show an example in which the surface of the HSQ film provided with a fine pattern is irradiated with an electron beam, no heating (FIG. 11A), 100 ° C. heating (the same (b)), 200 It is a cross-sectional SEM image of the HSQ film | membrane in each case of a degree-C heating (the same (c)). FIGS. 12 (1) to 12 (4) show a general process of room temperature nanoimprint using an HSQ film. The chemical structure and spectrum measurement results (FTIR) of HSQ are shown. FIGS. 14A to 14D are cross-sectional SEM images showing the change in shape of the fine pattern formed on the HSQ film when heated.

Explanation of symbols

1 Substrate 2/3 HSQ film 2a / 3a / 3b Transfer pattern 8 Mold

Claims (8)

  A pattern forming method comprising: providing a HSQ film with a fine pattern, and then irradiating the surface of the film with oxygen.   The fine pattern is given to the HSQ film by pressing the mold, and after the mold is peeled off, the surface is irradiated with oxygen without interposing the heating process of the HSQ film. Pattern forming method.   It is characterized in that a fine pattern is given to the HSQ film by pressing the mold, and after peeling the mold, a part of the surface is reflowed by heating the HSQ film, and oxygen irradiation is performed on the surface. The pattern forming method according to claim 1.   Drop the HSQ liquid onto the substrate, press the mold against the liquid before the solvent evaporates, evaporate the solvent, and then peel off the mold to give a fine pattern to the HSQ film The pattern formation method according to any one of claims 1 to 3.   The pattern forming method according to claim 1, wherein electron beam irradiation or argon ion irradiation is performed instead of oxygen irradiation.   A pattern forming body formed by the pattern forming method according to claim 1.   It is used as an optical component such as a thermal nanoimprint mold, a high-temperature dry etching mask, a blazed diffraction grating, or a lamellar grating, or used as a dry etching mask for processing a magnetic thin film of patterned media. Item 7. The pattern forming body according to Item 6. A pattern forming body formed by the pattern forming method according to claim 3 and used as a microlens array.