JP2006330691A - Method of exposure using half-tone mask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a deep depth of focus which is suitable for the exposure of a resist on a glass base plate for a display panel. <P>SOLUTION: The method of exposure includes using a half-tone mask 24, passing an (i) ray from a light source 12 for exposure to a nonmagnification projection optical system 26 via the half-tone mask 24, and irradiating the resist 30 on the glass base plate 28 with the (i) ray, having passed through the optical system 26. The optical system 26 has a numerical aperture NA2, obtained from NA2=k1×0.365/R, within a specified range. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for exposing a photoresist on a glass substrate using a halftone mask.

  In a crystalline thin film transistor (hereinafter referred to as “TFT”) formed on a glass substrate for a display panel such as a liquid crystal display panel, it is considered to make the TFT finer in order to improve the operation performance.

  The glass substrate on which the TFT is formed has a remarkably large plate thickness deviation in comparison with that of the semiconductor wafer. This glass substrate has a large thickness deviation of about 9 μm (about 9 μm / 100 mm □) per square area with a side of 100 mm (due to the surface roughness and the plate thickness distribution of the substrate itself).

  When forming TFTs on the glass substrate as described above, the exposure of the photoresist on the glass substrate requires a deeper depth of focus than the exposure for manufacturing a semiconductor device on the semiconductor wafer substrate. That is, in order to manufacture a TFT with finer dimensions, it is necessary to increase the resolution of an exposure apparatus used at that time and to prevent the depth of focus from becoming shallow. The resolution of an exposure apparatus for TFT is currently about 1.5 μm or 3 μm. In this exposure apparatus, when the resolution is increased from the above value, the depth of focus becomes shallow.

  When the resolution is higher than, for example, about 0.8 μm, the depth of focus becomes shallower than the thickness deviation of about 9 μm / 100 mm □ of the glass that is the substrate on which the TFT is formed. A desired resist pattern cannot be formed. When exposing a photoresist on a glass substrate having a large plate thickness deviation, the optical system of the exposure apparatus is required to have a deeper focus because the difference in height of the photoresist surface is large. An exposure process for manufacturing a TFT includes a contact hole forming process that requires a deep depth of focus. In this case, since the depth of focus at the time of exposure is usually shallower than that in the case of a line pattern, the photoresist film thickness needs to be devised so as not to be shallow.

  For example, the depth of focus when forming a contact hole of 0.5 μm □ is as very shallow as ± 0.9 μm. When such a contact hole is formed for manufacturing a TFT formed on a glass substrate by an exposure apparatus, a region out of focus depth is wide, so that the photoresist remains at the bottom of the contact hole, , Through holes do not open. As a result, for example, contact with the source region or the drain region cannot be made.

  Further, the contact hole of the exposure mask when forming the TFT generally has a square shape. The contact hole for the TFT formed in the photoresist by exposing the photoresist through such a mask has rounded corners and becomes substantially circular. As a result, in the above exposure method, it is difficult to form a hole penetrating the photoresist.

  Non-Patent Document 1 pages 39 to 40 show that halftone phase shift masks (in this specification, simply referred to as “halftone masks”) improve resolution and depth of focus in exposure technology. ing.

  Further, Patent Document 1 discloses a technique for exposing a resist used in a processing step of a semiconductor wafer for a semiconductor device or a semiconductor thin film formed on a glass substrate for a display panel using a halftone mask. ing.

February 25, 1997, published by Ohm Co., Ltd. “Ultra-fine processing technology”

JP 2003-234285 A

  The numerical aperture NA of the exposure apparatus described on page 40 of Non-Patent Document 1 is 0.5, and the coherence factor σ is 0.2. These values are values for an integrated circuit (LSI) as described in Non-Patent Document 1.

  When forming a TFT on a glass substrate for a display substrate, the exposure area per one time on the photoresist on the glass substrate is determined in consideration of the throughput, and since this exposure area is large, the resolution is also important, The depth of focus is more important. This is because the thickness deviation of the glass substrate is much larger than that of the LSI Si wafer as described above.

  However, Non-Patent Document 1 discloses specifics such as the type of exposure optical system, the numerical aperture NA, and the coherence factor σ for increasing the depth of focus in exposure when a TFT is formed on a glass substrate for a display substrate. Typical values are not listed.

  Patent Document 1 also describes a Si wafer for LSI mainly, but a numerical aperture NA and a coherence factor σ for obtaining a depth of focus necessary for exposure when a TFT is formed on a glass substrate for a display substrate. The specific value of is not described.

  As described above, for exposure of a resist formed on a glass substrate for a display panel, particularly for the production of contact holes for crystalline TFTs, a deeper depth of focus can be obtained. The type of light source, coherence factor σ, type of exposure optical system used, numerical aperture NA, etc. are not yet known.

  An object of the present invention is to use a halftone phase shift mask that obtains a deep focal depth suitable for exposure for manufacturing a TFT formed on a substrate having a large thickness deviation such as a glass substrate for a display panel. It is to provide an exposure method.

  In any of the first to third exposure methods according to the present invention, a light beam from an exposure light source is incident on an optical system through a halftone mask, and the light beam passing through the optical system is exposed to a photosensitive material on a glass substrate. Irradiating a resist layer made of the above, using i-line as the light beam, and using an equal magnification projection optical system having a numerical aperture NA obtained by the equation (1) as the optical system.

  In the first exposure method according to the present invention, the halftone mask has a line pattern to be formed on the resist layer. In Equation (1), k1 is a coefficient having a value of 0.41 to 0.44, and R is the width of a line formed in the resist layer.

  In the second exposure method according to the present invention, the halftone mask has a contact hole pattern to be formed in the resist layer on the glass substrate. In the formula (1), k1 is a coefficient having a value of 0.48 to 0.5, and R is the diameter (or major axis) of the hole formed in the resist layer.

  In the third exposure method according to the present invention, the halftone mask is a contact hole pattern to be formed in the resist layer on the glass substrate, and has a contact hole pattern having a contact hole arrangement pitch of 4 times or more of the contact holes. Have In the formula (1), k1 is a coefficient having a value of 0.48 to 0.5, and R is a hole diameter formed in the resist layer.

  According to the first to third exposure methods according to the present invention, a deep depth suitable for exposure of a resist layer for manufacturing a TFT formed on a substrate having a large thickness deviation such as a glass substrate for a display panel. An exposure method using a halftone phase shift mask capable of obtaining a depth of focus can be obtained.

[Definition of terms]
In the present invention, “rectangular” includes an oval and an ellipse. A contact hole is formed by burying a conductor that is electrically connected between conductor layers provided on the front and back surfaces through an insulating layer, between a conductor and a source region or a drain region, or between gate electrodes. Therefore, it is a hole provided in the insulating layer. In this specification, a hole provided in a photosensitive material film for forming this hole by etching is also defined as a contact hole.
First, an exposure apparatus used in the exposure method of the present invention will be described.
[Example of exposure apparatus]

  Referring to FIG. 1, an exposure apparatus 10 includes, in addition to an exposure light source 12, a reflecting mirror 14 that is disposed in an optical path from the light source 12 and reflects a light beam emitted from the light source 12, and a reflecting mirror. Two kinds of intermediate lenses 16 and 18 for converging the light beam reflected by 14, a reflecting mirror 20 for reflecting the light beam from the intermediate lens 18 toward the halftone mask 24, and a light beam reflected by the reflecting mirror 20 A focusing lens 22 that focuses the light and irradiates the halftone mask 24, and a light beam that has passed through the halftone mask 24 irradiates a photosensitive material layer such as a resist film 30 formed on a substrate to be processed such as a glass substrate 28. Projection optical system 26.

  The light source 12 is a mercury lamp that generates i-line having a wavelength of 365 nm, for example.

  The reflecting mirror 14, the intermediate lenses 16 and 18, the reflecting mirror 20 and the focusing lens 22 are general optical members and form an illumination optical system 23. The light beam from the light source 12 is focused by such an illumination optical system 23 and is incident on the halftone mask 24. The halftone mask 24 is a mask whose light shielding region has a transmittance of 6 to 8%.

  The glass substrate 28 is a glass substrate 28 used for manufacturing a display panel such as a liquid crystal display panel, for example, and a thin film transistor for driving the display panel as described later is provided on a semiconductor thin film provided on the glass substrate 28. It is formed.

  The projection optical system 26 is an equal magnification projection optical system that projects the image of the mask 24 onto the resist film 30 at an equal magnification, for example. In the illustrated example, the projection optical system 26 includes an NA aperture 32, a pupil plane 34, a plurality of lenses 36, and the like. Yes. The light beam that has passed through the halftone mask 24 enters the resist film 30 through the projection optical system 26 at an equal magnification.

  The resist film 30 is made of, for example, a chemically amplified photoresist material for i-line. For example, a photoresist material is applied to the surface of the glass substrate 28 by an appropriate method such as spin coating, and then dried to form the resist film 30.

  NA1 which is the numerical aperture of the illumination optical system 23 including the converging lens 22 and hence the numerical aperture of light incident on the halftone mask 24 from the converging lens 22 is expressed by the following equation (2) when the opening angle of incident light is 2φ. Can be obtained from

  NA1 = sinφ (2)

  Similarly, NA2 which is the numerical aperture of the projection optical system 26 and hence the numerical aperture of the light irradiated from the projection optical system 26 onto the resist film 30 is expressed by the following equation (3) when the opening angle of incident light is 2θ. Obtainable.

  NA2 = sin θ (3)

  [Example of mask]

    As shown in FIG. 2A, for example, the halftone mask 24 used for exposure is a line-and-space with equal intervals and equal pitches in which light transmitting portions 40 and light shielding portions 42 having the same width are formed at equal pitches. A halftone phase shift mask for lines having a pattern can be obtained. FIG. 2 is a view for explaining a halftone mask 24 and an embodiment of a resist pattern exposed and developed by light transmitted through the halftone mask 24. FIG. 2A is a plan view of the halftone mask 24. FIG. (B) is sectional drawing of the to-be-processed substrate for demonstrating the state exposed in relation to the mask pattern obtained along the 2B-2B line in (A).

  Further, as shown in FIG. 3A, the halftone mask 24 is a contact having dense contact hole patterns with equal intervals and equal pitches, in which light transmitting portions 44 having the same width are formed in a matrix at equal pitches. It can also be used as a halftone phase shift mask for holes. In these illustrated examples, the dimension between the light transmission parts 44 (that is, the light shielding part 46) is also the same as the width dimension of the light transmission part 44. FIG. 3 is a view for explaining an embodiment of a halftone mask 24 and a resist pattern exposed and developed by the transmitted light of the halftone mask 24, wherein (A) is a plan view of the halftone mask 24. (B) is sectional drawing of the to-be-processed substrate for demonstrating the state exposed in relation to the mask pattern obtained along the 3B-3B line | wire in (A).

  Even if the halftone mask 24 has any of the above patterns, as the halftone mask 24, the light shielding portions 42 and 46 having a transmittance of 6 to 8% and the phase of the light are rotated by 180 degrees, A light shielding portion having a transmittance of 100%, or a light shielding portion having a transmittance of 6-8% and simultaneously rotating the phase of light by 180 °, and a transmittance of almost 100% Any of the halftone masks 24 having the light transmitting portion may be used.

  Although the material for the light shielding parts 42 and 46 differs depending on which type of the halftone mask 24 is used, a known material that is commercially available can be used. Regardless of which halftone mask 24 is used, the halftone mask 24 having such a pattern is manufactured prior to the exposure of the resist layer 30.

  When the resist layer 30 is exposed to the exposure apparatus 10 shown in FIG. 1 using the halftone mask 24 having the pattern shown in FIG. 2A and the resist layer 30 is developed after the exposure, the resist layer 30 is developed on the glass substrate 28. The resist layer 30 is composed of a portion of the remaining resist layer 30 having an equal interval and an equal pitch as shown in a cross-sectional view in FIG. 10B and a portion from which the resist layer is removed, that is, a space 50. A line and space pattern is formed.

  In the pattern shown in FIG. 2B, the space 50 from which the resist layer 30 has been removed corresponds to the light transmitting portion 40 of the pattern in FIG. 2A, and the portion 52 where the resist layer 30 remains is shown in FIG. Corresponds to the light shielding part 42 of the pattern.

  When the resist layer 30 is exposed to the exposure apparatus 10 using the halftone mask 24 having the mask pattern shown in FIG. 3A, and the resist layer 30 is developed after the exposure, the resist layer 30 on the glass substrate 28 is developed. As shown in FIG. 3B, a dense contact hole pattern having an equal interval and an equal pitch is formed.

  In the exposure pattern shown in FIG. 3B, the space 50 from which the resist layer 30 has been removed corresponds to the light transmitting portion 44 of the pattern in FIG. 2A, and the portion 56 where the resist layer 30 remains is shown in FIG. This corresponds to the light shielding part 46 of the pattern in FIG.

  For example, in the first exposure method according to the present invention, a photoresist having a line-and-space pattern consisting of lines arranged at equal intervals of 0.5 μm width with i-line (wavelength: 365 nm) from an exposure light source When the layer 30 is to be formed (i-line chemically amplified resist), the numerical aperture NA2 is a region 0.3 to 0.32 having a deep focal depth of the equal magnification projection optical system 26 shown by the rectangular dotted line frame in FIG. Thus, the coherence factor σ is about 0.75 to 0.85 having a deep focal depth indicated by the rectangular dotted line frame in FIG. 5 (the same applies to a normal Cr mask). A coherence factor σ of 0.85 or more is a deep depth of focus, but it is very difficult to produce an actual exposure optical system with such a σ. Therefore, the coherence factor σ is set to about 0.75 to 0.85. Further, when R = 0.5 μm in the equation (1), by substituting the range of the numerical aperture NA2 and the double critical value of 0.3 to 0.32 into the equation (1), the corresponding k1 A range of 0.41 to 0.44 is determined.

  Further, for example, an i-line chemically amplified resist having a line-and-space pattern composed of lines arranged at equal intervals of 0.8 μm width with i-line (wavelength: 365 nm) from the exposure light source 12 is formed. In this case, the numerical aperture NA2 is 0.18 to 0.2 from the characteristic of the rectangular dotted line frame in FIG. 4, and the coherence factor σ is about 0.75 to 0.85 from the characteristic of the rectangular dotted line frame in FIG. Become.

  For example, in the second exposure method according to the present invention, contact holes (dense contact holes, i.e., holes having a diameter of 0.5 μm arranged at equal intervals by i-line (wavelength: 365 nm) from the exposure light source 12 are arranged. The hole NA center pitch is 1 .mu.m. When a mask 24 transmitted light image is formed on a resist (i-line chemically amplified resist), the numerical aperture NA2 of the equal magnification projection optical system 26 is 0.35 to .0 from FIG. 365, and the coherence factor σ of the equal-magnification projection optical system 26 is about 0.6 to 0.85 from FIG. 7 (the same is true for a normal Cr mask). Further, when R = 0.5 μm in the equation (1), by substituting the critical value of 0.35 to 0.365 in the numerical aperture NA2 range into the equation (1), the corresponding k1 A range of 0.48 to 0.5 is required.

  Further, for example, a halftone mask 24 having a dense contact hole pattern (having a pitch between hole centers of 1.6 μm) composed of a large number of holes having an aperture of 0.8 μm with i-line (wavelength: 365 nm) from the exposure light source 12. When a transmitted light image is formed on the photoresist film 30 (i-line chemically amplified resist), the numerical aperture NA2 of the equal magnification projection optical system 26 is 0.22 to 0.23, and the coherence of the equal magnification projection optical system 26 is obtained. The factor σ is about 0.6 to 0.85 (same for normal Cr mask). Although the hole shape of the halftone mask 24 is a square, the shape of the resist pattern actually formed is a circle.

  For example, in the third exposure method, when holes having a diameter of 0.5 μm are formed, the pitch between the center of the halftone mask 24 is 1.2 μm or more. The numerical aperture NA2 of the equal magnification projection optical system 26 is 0.35 to 0.365, and the coherence factor σ of the equal magnification projection optical system 26 is about 0.3 to 0.55. In this case, when R = 0.5 μm in the formula (1), the corresponding critical value k1 is obtained by substituting the range of the numerical aperture NA2 and the double critical value of 0.35 to 0.365 into the formula (1). In the range of 0.48 to 0.5.

  According to such an exposure method using the halftone mask 24, the depth of focus of the equal magnification projection optical system 26 becomes deeper than that of a normal Cr mask. As the depth of focus increases, a highly accurate pattern can be formed on the resist film 30 formed on a glass substrate having a large plate thickness deviation. The ability to form a high-definition pattern on the resist film 30 formed on the glass substrate having a large thickness deviation means that a highly integrated TFT circuit can be formed on the glass substrate.

  Further, in the exposure method of the present invention as described above, if the resolution is the same as that of a normal Cr mask, exposure can be performed with a smaller numerical aperture NA2 than that of a normal Cr mask. If the numerical aperture NA2 is reduced in this way, the difficulty of manufacturing the lens decreases (manufacturing of the lens becomes easier).

  In order to form a line-and-space pattern with equal intervals and equal pitches with a line width of 0.5 μm and a line center pitch of 1 μm in the resist pattern, a halftone mask 24 shown in FIG. The resist layer 30 was exposed by the exposure apparatus 10 shown in FIG.

  An i-line having a wavelength of 365 nm was used as the exposure light beam, and a chemically amplified resist agent for i-line was used as the resist layer 30.

  Actually, a plurality of experiments were performed in which the coherence factor σ was fixed at 0.8 and the numerical aperture NA2 corresponding to the convergence angle θ of the equal magnification projection optical system 26 in FIG. 1 was changed.

  FIG. 4 shows the relationship between the depth of focus of the equal magnification projection optical system 26 and the numerical aperture NA2 of the projection optical system 26 obtained as a result of the first embodiment.

  As is clear from FIG. 4, when the numerical aperture NA2 of the equal magnification projection optical system 26 is 0.3, the focal depth of the equal magnification projection optical system 26 is the deepest. When the numerical aperture NA2 is 0.29 and 0.32, the focal depth is almost the same.

  However, considering lens aberration, the depth of focus becomes smaller when the numerical aperture NA is 0.29. Therefore, it is apparent that the numerical aperture NA2 is preferably in the range of 0.3 to 0.32 indicated by a dotted frame in FIG. Such a numerical aperture range shows better characteristics than a normal Cr mask.

  At this time, R is 0.5 μm, λ = 365 nm, numerical aperture NA2 range, and 0.3 to 0.32 are substituted into equation (1) called Rayleigh equation to obtain k1 range. Then, a range of 0.41 to 0.44 is obtained as k1.

  The halftone mask 24 shown in FIG. 2A is used as the halftone mask 24 in order to form a line-and-space pattern with the same interval and the same pitch as in the first embodiment, and the exposure apparatus 10 shown in FIG. Thus, the resist layer 30 was exposed under the same conditions as in Example 1.

  A difference from the first embodiment is that instead of changing the numerical aperture NA2 by fixing the coherence factor σ to 0.8, a plurality of experiments in which the numerical aperture NA2 is fixed to 0.3 and the coherence factor σ is changed are performed. went.

  FIG. 5 shows the relationship between the depth of focus of the equal magnification projection optical system 26 of the exposure apparatus 10 and the coherence factor σ obtained as a result of the second embodiment.

  As is clear from FIG. 5, the focal depth of the equal magnification projection optical system 26 is small in a region where the coherence factor σ is smaller than 0.8, and when the coherence factor σ is smaller than 0.75, the focal depth is significantly smaller than ± 2 μm. However, when the coherence factor σ is larger than 0.8, the depth of focus becomes almost constant.

  The light source manufacturing limit for the coherence factor σ is approximately 0.85 or more. Therefore, it is clear that the coherence factor σ is preferably 0.75 to 0.85 shown by the dotted frame in FIG.

  In order to form a dense contact hole pattern in the resist layer 30 having a plurality of rectangular holes having a side of 0.5 μm in the resist pattern, that is, a plurality of holes having a diameter of 0.5 μm and a pitch between hole centers of 1 μm. Using the mask shown in FIG. 3A as the tone mask 24, the resist layer 30 was exposed by the exposure apparatus 10 shown in FIG.

  An i-line having a wavelength of 365 nm was used as the exposure light beam, and a chemically amplified resist agent for i-line was used as the resist layer 30.

  Actually, a plurality of experiments were performed with the numerical aperture NA2 varied while the coherence factor σ was fixed at 0.8.

  FIG. 6 shows the relationship between the depth of focus of the projection optical system 26 and the numerical aperture NA2 of the projection optical system 26 obtained as a result of the third embodiment.

  As apparent from FIG. 6, the projection optical system 26 has the deepest depth of focus when the numerical aperture NA2 of the projection optical system 26 in the exposure apparatus 10 is 0.35. Further, when the numerical aperture NA2 of the projection optical system 26 is 0.34 and 0.365, substantially the same depth of focus is obtained.

  However, considering the lens aberration, the depth of focus of the projection optical system 26 becomes smaller when the numerical aperture NA2 is 0.34. Therefore, the numerical aperture NA2 ranges from 0.35 to 0 indicated by a dotted frame in FIG. It is clear that .365 is desirable.

  At this time, R is 0.5 μm, λ = 365 nm, numerical aperture NA2 range, 0.35 to 0.365 is substituted into Rayleigh's equation (1) to obtain the range of k1, and k1 is 0. A range of .48 to 0.5 is required.

  In order to form the same dense contact hole pattern as in Example 3 in the resist 30, exposure is performed by the exposure apparatus shown in FIG. 1 using the mask shown in FIG. 3A as the halftone mask 24 under the same conditions as in Example 3. did.

  The difference from Example 3 is that instead of changing the numerical aperture NA2 by fixing the coherence factor σ to 0.8, a plurality of experiments in which the numerical aperture NA2 is fixed to 0.35 and the coherence factor σ is changed are performed. went.

  FIG. 7 shows a simulation result of the relationship between the depth of focus of the projection optical system 26 of the exposure apparatus 10 and the coherence factor σ of the projection optical system 26 in Example 4 when the numerical aperture NA2 is fixed to 0.35. .

  As is apparent from FIG. 7, the depth of focus is small in the region where the coherence factor σ is smaller than 0.8, and the depth of focus is significantly less than ± 1.2 μm below 0.60. However, when the coherence factor σ is larger than 0.8, the depth of focus becomes almost constant.

  As described above, the manufacturing limit of the light source with respect to the coherence factor σ is approximately 0.85. Therefore, it is clear that the coherence factor σ is preferably 0.6 to 0.85 as indicated by a dotted frame in FIG.

  3A as a halftone mask 24 for forming the transmitted light on the resist layer 30 in a halftone mask 24 of a dense contact hole pattern having a plurality of rectangular holes with sides of 0.5 μm in the resist pattern. 24, the resist layer 30 was exposed by the exposure apparatus 10 shown in FIG.

  A wavelength of 365 nm was used as the exposure light beam, i-line was used as the exposure light beam, and a chemically amplified resist agent for i-line was used as the resist layer 30.

  Actually, a plurality of experiments were performed with the numerical aperture NA2 of the exposure apparatus 10 fixed at 0.35 and the coherence factor σ and the hole center-to-center distance (center-to-center pitch) varied. The coherence factor σ was set to 0.8 when the pitch between the hole centers was 1 μm, and was set to 0.4 otherwise.

  FIG. 8 shows the relationship between the hole center pitch of the halftone mask 24 and the depth of focus of the projection optical system 26 obtained as a result of the fifth embodiment.

  As is clear from FIG. 8, when the equal pitch of the light transmitting portions 44 having the same hole width dimension, that is, the diameter of the halftone mask 24 exceeds 1 μm, the depth of focus of the projection optical system 26 is drastically deepened, The pitch is almost constant at 2 μm or more. It is clear that the pitch is desirably 1.2 μm or more so that the depth of focus is ± 2 μm or more. In FIG. 8, “isolated” refers to a case where a single contact hole exists.

  In order to form a dense contact hole pattern in the resist 30 having a plurality of rectangular holes each having a side of 0.5 μm in the resist pattern and a rectangular hole having a center-to-center pitch of 2 μm, a halftone mask 24 is illustrated. Using the mask shown in FIG. 3A, the resist 30 was exposed by the exposure apparatus shown in FIG.

  A wavelength of 365 nm was used as the exposure light, i-line was used as the exposure light, and a chemically amplified resist for i-line was used as the resist 30.

  In practice, a plurality of experiments were performed with the coherence factor σ fixed at 0.4 and the numerical aperture NA2 varied.

  FIG. 9 shows the relationship between the hole center pitch and the depth of focus of the projection optical system 26 obtained as a result of the sixth embodiment.

  As is clear from FIG. 9, the depth of focus of the projection optical system 26 is the deepest when NA2 is 0.35. In FIG. 9, regions having substantially the same depth of focus when the numerical aperture NA2 is 0.34 and 0.365 are indicated by dotted line frames.

  However, in consideration of lens aberration, the depth of focus of the projection optical system 26 when the numerical aperture NA2 is 0.34 becomes shallower. Therefore, the range of the numerical aperture NA2 is preferably 0.35 to 0.365. Is clear. The range of k1 at this time is 0.48 to 0.5, as shown in the third embodiment.

  In order to form in the resist 30 a dense contact hole pattern in which a plurality of rectangular holes with sides of 0.5 μm in the resist pattern are arranged so that the pitch between the centers thereof is 2 μm, a halftone mask 24 shown in FIG. The resist layer 30 was exposed using the exposure apparatus 10 shown in FIG.

  A wavelength of 365 nm was used as the exposure light beam, i-line was used as the exposure light beam, and a chemically amplified resist agent for i-line was used as the resist layer 30.

  Actually, a plurality of experiments were performed with the numerical aperture NA2 fixed at 0.35 and the coherence factor σ varied.

  FIG. 10 shows the relationship between the coherence factor σ obtained as a result of Example 7 and the depth of focus of the projection optical system 26.

  As is apparent from FIG. 10, the depth of focus tends to be maximum at the coherence factor σ0.4. It is clear that the coherence factor σ is desirably 0.3 to 0.55 so that the depth of focus is ± 2 μm or more.

  In the exposure method of the present invention, for example, when the line pattern mask according to the present invention is used in the manufacture of an LCD, a manufacturing portion having a size and shape substantially corresponding to the line pattern of the mask pattern is formed on the LCD. The value of the numerical aperture NA2 and the light source can be specified by each exposure apparatus.

  The present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention.

It is a block diagram which shows one Example of an exposure apparatus suitable for implementing the exposure method which concerns on this invention. It is a figure for demonstrating one Example of the resist pattern exposed and developed by the halftone mask used by the exposure process for demonstrating the exposure method which concerns on this invention, and the transmitted light of this halftone mask, (A) is a plan view of a halftone mask, and (B) is a cross-sectional view of a substrate to be processed for explaining an exposed state in association with a mask pattern obtained along line 10B-10B in (A). It is a figure for demonstrating one Example of the resist pattern exposed and developed by the halftone mask used by the exposure process for demonstrating the exposure method which concerns on this invention, and the transmitted light of this halftone mask, (A) is a plan view of a halftone mask, and (B) is a cross-sectional view of a substrate to be processed for explaining an exposed state in association with a mask pattern obtained along line 3B-3B in (A). It is a characteristic curve figure which shows the relationship between the numerical aperture of the equal magnification projection optical system 26 of the exposure apparatus of FIG. 1 obtained by the 1st Example of this invention, and a depth of focus. It is a characteristic curve figure which shows the relationship between the coherence factor of the 1x projection optical system 26 of the exposure apparatus of FIG. 1 obtained by 2nd Example of this invention, and a focal depth. It is a characteristic curve figure which shows the relationship between the numerical aperture of the equal magnification projection optical system 26 of the exposure apparatus of FIG. 1 obtained by the 3rd Example of this invention, and a focal depth. It is a characteristic curve figure which shows the relationship between the coherence factor of the equal magnification projection optical system 26 of the exposure apparatus of FIG. 1 obtained by 4th Example of this invention, and a focal depth. It is a characteristic curve figure which shows the relationship with a focal depth when changing the equal pitch of the light transmissive part of the halftone mask of FIG. 3 obtained by the 5th Example of this invention. It is a characteristic curve figure which shows the relationship between the numerical aperture of the equal magnification projection optical system 26 of the optical apparatus of FIG. 1 obtained by the 6th Example of this invention, and a depth of focus. It is a characteristic curve figure which shows the relationship between the coherence factor of the equal magnification projection optical system 26 of the exposure apparatus of FIG. 1 obtained by the 7th Example of this invention, and a focal depth.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Exposure apparatus 12 Light source 14,20 Reflector 16,18 Intermediate lens 22 Condensing lens 24 Halftone mask 26 Projection optical system 28 Glass substrate 30 Resist film 40, 44 Light transmission area 42, 46 Mask light shielding area

Claims (6)

An exposure method in which light from an exposure light source is incident on an optical system via a halftone mask, and the resist layer made of a photosensitive material on the glass substrate is irradiated with the light that has passed through the optical system for exposure. ,
The ray is i-line;
The halftone mask has a line pattern;
The optical system is an equal magnification projection optical system, and when k1 is a coefficient having a value of 0.41 to 0.44 and R is the width of a line formed in the resist layer, Having a numerical aperture NA obtained,
NA2 = k1 × 0.365 / R
An exposure method using a halftone phase shift mask.   The exposure method using the halftone phase shift mask according to claim 15, wherein the coherence factor σ of the i-line is 0.75 to 0.85. An exposure method in which light from an exposure light source is incident on an optical system via a halftone mask, and the resist layer made of a photosensitive material on the glass substrate is irradiated with the light that has passed through the optical system for exposure. ,
The ray is i-line;
The halftone mask has a contact hole pattern;
The optical system is an equal magnification projection optical system, and when k1 is a coefficient having a value of 0.48 to 0.5 and R is a diameter of a hole formed in the resist, the following equation is obtained. Having a numerical aperture NA,
NA2 = k1 × 0.365 / R
An exposure method using a halftone mask.   The exposure method using a halftone phase shift mask according to claim 17, wherein the coherence factor σ of the i-line is 0.6 to 0.8. An exposure method in which light from an exposure light source is incident on an optical system via a halftone mask, and the resist layer made of a photosensitive material on the glass substrate is irradiated with the light that has passed through the optical system for exposure. ,
The ray is i-line;
The halftone mask is a contact hole pattern to be formed in the resist on the glass substrate, and has a contact hole pattern having a contact hole arrangement pitch not less than four times the diameter of the contact hole,
The optical system has a numerical aperture NA obtained by the following equation, where k1 is a coefficient having a value of 0.48 to 0.5, and R is a contact hole diameter formed in the resist layer.
NA2 = k1 × 0.365 / R
An exposure method using a halftone mask.   519. The exposure method using a halftone phase shift mask according to claim 519, wherein the coherence factor σ of the i-line is 0.3 to 0.55.

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