JP2012151189A - Formation method of fine pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a formation method of a fine pattern capable of forming a line pattern having a narrower line width than a resolution limit of an exposure device.SOLUTION: Disclosed is a formation method of a fine pattern comprising: a step of forming a negative-type photoresist film on the thin film to be etched; a step of drying the photoresist film under a reduced-pressure atmosphere; a step of exposing the dried photoresist film by irradiating the photoresist film with an exposure light using a photomask having an exposure light transmission part having a narrower width than a resolution limit of the exposure device to be used; a step of forming an etching mask from the exposed photoresist film by developing the photoresist film; and a step of etching the thin film using the etching mask.

Description

  The present invention relates to a pattern forming method capable of miniaturizing a circuit pattern of a flat panel display (FPD).

  When manufacturing an FPD, a circuit pattern including various circuit elements and wirings is formed on a glass substrate. The circuit pattern is formed by repeating a procedure of forming a thin film on a glass substrate, forming an etching mask by a photolithography technique, and etching the thin film using the etching mask (for example, Patent Document 1). For example, the width of a line in the current circuit pattern is about 3 μm, but in the future, miniaturization to about 1.5 μm is desired.

JP 2002-341525 A (paragraphs 0002 to 0009)

In order to miniaturize the circuit pattern, it is indispensable to shorten the wavelength of exposure light used in the photolithography process. However, since a large glass substrate with a side length of 1 m is used for manufacturing an FPD, it is difficult to develop and manufacture a short-wavelength light source that can handle such a glass substrate.
The applicant of the present invention has studied a method of realizing a space width of about 2 μm by devising a circuit pattern forming method while using a current exposure apparatus having a resolution of about 3 μm.

  Hereinafter, this method will be described with reference to FIG. First, as shown in FIG. 1A, a photoresist film 13 is formed on a thin film 11 to be etched on a glass substrate S using a positive photoresist.

  Next, as shown in FIG. 1B, exposure light L having a wavelength of 436 nm (g line), 405 nm (h line), or 365 nm (i line) is irradiated to the photoresist film 13 through the photomask 15. The photoresist film 13 is exposed. Here, the illustrated portion of the photomask 15 corresponds to a portion forming a line and space in the circuit pattern, and a plurality of slits 15s are formed at a predetermined pitch. The width SW1 of the slit 15s is, for example, about 1.7 μm while the exposure limit of the exposure apparatus to be used is about 2.5 μm to 3 μm.

  In this case, since the exposure light transmitted through the slit 15s of the photomask 15 spreads due to the diffraction phenomenon, the intensity curve of the transmitted exposure light has a width SW1 of the slit 15s as indicated by reference symbol A in FIG. It will pull the hem beyond. Therefore, in the photoresist film 13, not only the region equal to the width SW1 of the slit 15s exposed when it is assumed that there is no diffraction phenomenon, but also the region P2 outside this can be exposed. That is, if the exposure time is appropriately adjusted (overexposed), a region P2 wider than the region P1 corresponding to the width of the slit 15s (about 1.7 μm), for example, a region P2 having a width of about 2 μm is exposed. It becomes possible. Therefore, after that, when the photoresist film 13 is over-developed, an etching mask M1 having a space S having a width SW2 of about 2 μm is formed (FIG. 1C).

  According to the above method, overexposure is performed using the diffraction phenomenon by the slit 15s having a width smaller than the exposure limit, and a width SW2 of about 2 μm that is larger than the width SW1 of the slit 15s and smaller than the exposure limit is obtained by overdevelopment. It is possible to realize the space S that is included.

However, when this method is applied to the formation of a line, as shown in FIG. 2A, the region P3 to be left in the photoresist film 13 is exposed by the diffraction of exposure light, and etching after development is performed. There is a possibility that the film thickness of the mask M2 becomes too small (FIG. 2B) and cannot be used as an etching mask. Thus, it is difficult to form a line having a width of about 2 μm by the above method. In addition, because of exposure using diffracted light, it is difficult to obtain the uniformity of the width of each line after development.
In view of the above circumstances, the present invention provides a fine pattern forming method capable of forming a line pattern having a line width narrower than the resolution limit of an exposure apparatus.

  According to one aspect of the present invention, a step of forming a negative photoresist film on a thin film to be etched, a step of drying the photoresist film in a reduced-pressure atmosphere, and an exposure apparatus used Using a photomask having an exposure light transmission portion whose width is smaller than the resolution limit in the step of irradiating the dried photoresist film with the exposure light to expose the photoresist film; There is provided a fine pattern forming method including a step of developing the photoresist film to form an etching mask from the photoresist film, and a step of etching the thin film using the etching mask.

  According to the embodiment of the present invention, there is provided a fine pattern forming method capable of forming a line pattern having a line width narrower than the resolution limit of an exposure apparatus.

It is a figure explaining the method of forming the space which has a width | variety below a resolution limit. It is a figure explaining the problem in the case of forming the line which has the width | variety below a resolution limit with the method of FIG. 3 is a flowchart illustrating a fine pattern forming method according to an embodiment of the present invention. It is a schematic diagram which shows each process of the fine pattern formation method by embodiment of this invention. FIG. 5 is a schematic diagram illustrating each step of the fine pattern forming method according to the embodiment of the present invention, following FIG. 4. It is a figure explaining the coating unit and reduced pressure drying unit suitable for the drying in the reduced pressure atmosphere of the photoresist film in the fine pattern formation method by embodiment of this invention. FIG. 5 is a diagram showing a gas flow when a photoresist film is dried in a reduced-pressure atmosphere by the reduced-pressure drying unit of FIG. 4.

  Hereinafter, a fine pattern forming method according to an embodiment of the present invention will be described with reference to FIGS. In the following description, the same or corresponding parts or members are denoted by the same or corresponding reference numerals, and redundant description is omitted.

  First, a thin film (hereinafter referred to as an etching target film) 11 to be etched is formed on a glass substrate (hereinafter simply referred to as a substrate) S. The etching target film 11 is not limited to these, but may be a polysilicon film deposited by a chemical vapor deposition (CVD) method and a metal film deposited by a sputtering method.

  Next, the substrate S on which the etching target film 11 is formed is carried into a predetermined photoresist coating and developing apparatus (hereinafter referred to as a coating and developing apparatus). In the coating and developing apparatus, first, a predetermined process before the formation of the photoresist film 13, such as a hydrophobizing process, is performed. Next, the substrate S is transferred to the photoresist coating unit of the coating and developing apparatus, and as shown in FIG. 4A, a photoresist film 13 is formed on the etching target film 11 (step S1 in FIG. 3). . In the fine pattern forming method according to the embodiment of the present invention, the photoresist film 13 is formed using a negative photoresist (liquid). The negative photoresist is not particularly limited as long as it has sensitivity to the wavelength of the exposure light of the used exposure apparatus. The film thickness of the photoresist film 13 may be in the range from about 0.5 μm to about 3 μm.

  After the photoresist film 13 is formed, as shown in FIG. 4B, the substrate S is transported into a vacuum drying unit 46 provided in the coating and developing apparatus. The vacuum drying unit 46 is configured to be airtight with respect to the external atmosphere, and the inside is exhausted to a reduced pressure by an exhaust device (not shown). As a result, the solvent of the photoresist contained in the photoresist film 13 in the reduced pressure drying unit 46 is evaporated, and the photoresist film 13 is dried (step S2 in FIG. 3). Here, it is desirable that the inside of the reduced-pressure drying unit 46 is reduced to a pressure lower than the vapor pressure of the photoresist solvent at the temperature of the substrate S (for example, 23 ° C.) in the reduced-pressure drying unit 46. When the solvent of the photoresist (liquid) contains, for example, a plurality of solvents, it is desirable that the inside of the vacuum drying unit 46 be depressurized more than the vapor pressure of any of the solvents, preferably the solvent having the largest content. Further, the inside of the vacuum drying unit 46 may be depressurized to a pressure lower than the lowest vapor pressure among the vapor pressures of the plurality of solvents.

  The time required to reach a pressure lower than the vapor pressure of the photoresist solvent is preferably in the range of 5 sec to 40 sec, for example. According to the study of the inventor of the present invention, when the photoresist film 13 is rapidly dried in such a time, the surface layer of the photoresist film 13 is further cured, so that the exposure resistance becomes high (hard to be exposed). ) I know that there is a tendency.

Further, when the photoresist film 13 is dried in a reduced-pressure atmosphere in the reduced-pressure drying unit 46, an inert gas G such as nitrogen gas or a rare gas is allowed to flow above the substrate S, thereby causing the photoresist film 13 to flow. It is preferable to promote the drying of. Thereby, the hardening of the photoresist film 13 and the acceleration of the exposure resistance are expected.
A coating unit suitable for forming the photoresist film 13 and a reduced pressure drying unit 46 suitable for drying under a reduced pressure atmosphere will be described later.

  After the photoresist film 13 is dried in a reduced-pressure atmosphere, the substrate S is heated and further cooled to room temperature (for example, 23 ° C.) for further drying in the coating and developing apparatus. Thereafter, the substrate S is transferred to an exposure apparatus, and the photoresist film 13 is exposed through the photomask 15 as shown in FIG. 4C (step S3 in FIG. 3). Here, the wavelength of the exposure light is, for example, a mixed wavelength of a wavelength of 405 nm (h line) and a wavelength of 365 nm (i line), and the exposure limit is about 2.5 μm to 3.0 μm. Moreover, the exposure amount of exposure light may be 30-40 mJ, for example. Further, the photoresist film 13 may be overexposed with an exposure amount of about 100 mJ.

  In this embodiment, the width SW1 of the slit 15s (exposure light transmitting portion) of the photomask 15 is, for example, about 1.8 μm, which is smaller than the exposure limit. Since the exposure light L is diffracted by the slit 15s, the light intensity curve A of the exposure light L that passes through the slit 15s is traced to the outside of the width SW1 of the slit 15s. For this reason, as shown in FIG. 4C, in addition to exposing the region P4 substantially corresponding to the width SW1 of the slit 15s, the exposure light can be irradiated to the region P5 outside the region P4.

Subsequently, the substrate S is transported to the developing unit of the developing and coating apparatus, and the exposed photoresist film 13 is developed (step S4 in FIG. 3). In the embodiment of the present invention, since the photoresist film 13 is a negative type, the regions P4 and P5 remain after development. However, since the surface layer of the photoresist film 13 is rapidly dried in a reduced-pressure atmosphere in step S2 and is difficult to be exposed, the region P5 that is only irradiated with the diffraction component of the exposure light is sufficiently exposed. It is removed by development. As a result, as shown in FIG. 5D, an etching mask M in which only the region P4 remains is obtained.
In order to surely remove the region P5, the photoresist film 13 is exposed to the developer for a predetermined time after the portion of the photoresist film 13 that is not irradiated with the exposure light is sufficiently dissolved in the developer. It is also possible to perform over-development.

  Here, focusing on the cross-sectional shape of the etching mask M, it can be seen that the width of the etching mask M (region P4) is wide at the upper end and narrows toward the lower end (so-called T-top shape). Moreover, the width of the etching mask M (region P4) at the upper end is substantially equal to the width of the slit 15s of the photomask 15. This is presumably because the photoresist film 13 was dried in a reduced-pressure atmosphere, so that the surface layer of the photoresist film 13 was dried and cured to improve the exposure resistance. Further, it is also an effect of promoting drying by flowing an inert gas G (FIG. 4B) above the photoresist film 13 during drying in a reduced pressure atmosphere.

Subsequently, as shown in FIG. 5E, the etching target film 11 is etched using the etching mask M (step S5 in FIG. 3). This etching is preferably performed, for example, under a pressure lower than 100 mTorr, using an etching gas containing chlorine or an etching gas containing fluorine, depending on the properties of the etching target film 11. Examples of the etching gas containing chlorine include chlorine (Cl ₂ ) gas, a mixed gas of Cl ₂ and sulfur hexafluoride (SF ₆ ), a mixed gas of Cl ₂ and carbon tetrafluoride (CF ₄ ), Cl _There is a mixed gas of ₂ and boron trichloride (BCl ₃ ), and a mixed gas of Cl ₂ and oxygen (O ₂ ). Etching gas containing fluorine includes a mixed gas of SF ₆ and O ₂ , a mixed gas of SF ₆ and nitrogen (N ₂ ), a mixed gas of CF ₄ and O ₂ , and CF ₄ and N ₂ There is a mixed gas. According to these, the etching object film 11 is anisotropically etched. That is, as shown in FIG. 5E, the width of the upper end portion of the etching mask M is transferred to the etching target film 11, and a line 11 L is formed on the substrate S from the etching target film 11.

  As described above, according to the embodiment of the present invention, the negative photoresist film 13 is formed on the etching target film 11, and the photoresist film 13 is dried in a reduced-pressure atmosphere, so that the width smaller than the exposure limit is obtained. Even when the photoresist film 13 is exposed using the slits 15 s, the etching mask M having a width smaller than the exposure limit can be obtained. By anisotropic etching using this etching mask M, a line having a width smaller than the exposure limit can be formed. Further, since the exposure resistance of the surface layer of the photoresist film 13 is improved, the region irradiated with the exposure light remains more reliably, and the uniformity of each line width can be improved.

  Further, as described above, since the surface layer of the photoresist film 13 is not easily exposed by rapidly drying the surface layer of the photoresist film 13 in a reduced-pressure atmosphere, the exposure light diffracted by the slits 15s in the photoresist film 13 is reduced. The irradiated region P5 can be removed by over development. Therefore, the width of the etching mask M (region P4) obtained by development is substantially equal to the width SW1 of the slit 15s. That is, by setting the width SW1 of the slit 15s to be smaller than the exposure limit, a line having a width smaller than the exposure limit can be formed. In addition, the uniformity of the line width can be further improved.

  Further, according to the fine pattern forming method according to the embodiment of the present invention, the resolution limit can be reduced, and without waiting for the development of an exposure apparatus equipped with a short wavelength light source capable of handling a large substrate, the resolution limit is exceeded. Can be formed with a small width and excellent line width uniformity. That is, since it is not necessary to develop and introduce a new exposure apparatus, there is an advantage that miniaturization is possible without an increase in manufacturing cost.

Next, a coating unit suitable for forming the photoresist film 13 and a reduced pressure drying unit 46 suitable for drying in a reduced pressure atmosphere will be described.
FIG. 6 is a side view showing the coating unit 30 and the vacuum drying unit 46 combined therewith. As shown in the figure, the coating unit 30 includes a guide rail 81 disposed on the support base 80, a transfer arm 82 that can hold the substrate S and can be translated along the guide rail 81, and the coating unit 30. And a resist coating unit 44 including a nozzle 84 disposed between the vacuum drying unit 46. The nozzle 84 is connected to a photoresist solution supply source (not shown), and an upper portion of the gate 83 fixed to the support base 80 so as to discharge the photoresist solution supplied from the photoresist solution supply source downward. It is hung from.

  As shown in FIGS. 6 and 7, the vacuum drying unit 46 includes a bowl-shaped lower chamber 85 having an upper surface opened and a lid-shaped upper chamber 86 having a lower surface opened. The upper chamber 86 can be moved up and down by a lifting mechanism (not shown). When the upper chamber 86 is placed on the upper surface of the lower chamber 85 by the elevating mechanism, the upper chamber 86 and the lower chamber 85 are tightly adhered to each other by a seal member (not shown).

  The lower chamber 85 is provided with a stage 88 on which the substrate S is placed. When the upper chamber 86 is lifted upward, the substrate S is loaded and placed on the stage 88. An exhaust port 89 is formed at the bottom of the lower chamber 85. One end of a pipe 90 is connected to the exhaust port 89, and a vacuum pump 91 is connected to the other end of the pipe 90. Furthermore, a supply port 92 for supplying an inert gas such as nitrogen gas or a rare gas is formed at the bottom of the lower chamber 85, and one end of a pipe 96 is connected to the supply port 92, and the other end of the pipe 96 is not connected. An active gas supply source 97 is connected. A rectifying plate 93 is provided between the supply port 92 and the exhaust port 89 so as to close the space between the bottom surface of the lower chamber 85 and the stage 88. As a result, an air flow path is formed from the supply port 92 through the upper side of the substrate S placed on the stage 88 to the back side of the substrate S to reach the intake port 89.

By the coating unit 30 and the reduced pressure drying unit 46 having the above-described configuration, the photoresist film 13 is formed as follows, and this photoresist film 13 is dried in a reduced pressure atmosphere.
First, when the substrate S is placed on the transfer arm 82, the transfer arm 82 moves on the rail 81 toward the gate 83 of the resist coating unit 44. When the front end of the substrate S on the transfer arm 82 reaches below the nozzle 84 suspended from the gate 83, the photoresist solution R is discharged from the nozzle 84 to the substrate S, and the substrate S further moves. Then, a photoresist solution is applied to the upper surface of the substrate S. At this time, the upper chamber 86 of the vacuum drying unit 46 is lifted from the lower unit 85, and the substrate S moves from its front end to the space between the upper chamber 86 and the lower chamber 85. When the rear end of the substrate S passes under the nozzle 84 and the photoresist liquid is applied to the entire upper surface of the substrate S, the substrate S reaches the upper side of the stage 88 as it is and is placed on the stage 88.

Next, the upper unit 86 is placed on the lower unit 85, and the space formed by the upper unit 86 and the lower unit 85 in an airtight manner is decompressed by the vacuum pump 91. Further, when an inert gas is supplied from the inert gas supply source 97 through the pipe 96 and the supply port 92, an inert gas stream flowing on the surface of the photoresist film 13 on the substrate S is formed.
The pressure in the reduced pressure drying unit 46 at this time may be, for example, 100 Pa, and the flow rate of the inert gas may be, for example, about 11 liters / minute.

  Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above-described embodiments, and can be variously changed or modified in light of the appended claims.

  DESCRIPTION OF SYMBOLS 11 ... Etching object film, 13 ... Negative photoresist film, 15 ... Photomask, 11L ... Line, 30 ... Coating unit, 82 ... Transfer arm, 84 ... (Photoresist solution supply) Nozzle, 46 ... Low pressure drying unit, 85 ... Lower unit, 86 ... Upper unit, 88 ... Stage, 91 ... Vacuum pump, 89 ... Exhaust port, 92 ... Inlet port, 97 ... Inert gas supply source, A ... Exposure light intensity curve, M ... Etching mask.

Claims (6)

Forming a negative photoresist film on the thin film to be etched; and
Drying the photoresist film in a reduced pressure atmosphere;
A step of exposing the photoresist film by irradiating the dried photoresist film with the exposure light using a photomask having an exposure light transmission portion having a width smaller than a resolution limit in an exposure apparatus to be used; ,
Developing the exposed photoresist film to form an etching mask from the photoresist film;
And a step of etching the thin film using the etching mask.   2. The fine film according to claim 1, wherein in the drying step, the photoresist film is exposed to an atmosphere reduced to a pressure lower than a vapor pressure of at least one of the plurality of solvents contained in the photoresist film. Pattern forming method.   The fine pattern forming method according to claim 1, wherein an inert gas is flowed above the photoresist film in the drying step.   4. The fine pattern forming method according to claim 1, wherein in the step of exposing the photoresist film, the photoresist film is overexposed. 5.   The method for forming a fine pattern according to claim 1, wherein the photoresist film is over-developed in the step of forming an etching mask.   6. The fine pattern forming method according to claim 1, wherein, in the etching step, the thin film is anisotropically etched under a reduced-pressure atmosphere using a gas containing chlorine or a gas containing fluorine. .

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