JP2834468B2 - Method of forming resist pattern - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a lithography technique used for manufacturing a semiconductor device and the like, and more particularly, to a technique using an electron beam as an exposure means.
The present invention relates to a method for forming a highly accurate resist pattern.

(Prior Art) Conventional resist pattern forming techniques mainly use light as exposure means. However, with the increase in the density of semiconductor integrated circuits, for example, even with an optical exposure means using far ultraviolet rays having a short wavelength, there is a limit to miniaturization of a resist pattern. Therefore, development of exposure means capable of realizing fine drawing dimensions such as X-rays and electron beams has been promoted.

Among them, when a resist pattern is formed using an electron beam, optimum development conditions differ depending on a desired resist pattern area, pattern shape, and pattern density (distance between adjacent resist patterns). Such a phenomenon is caused by a so-called proximity effect. In general, the proximity effect is roughly classified into two types: a solid-state proximity effect generated in each resist pattern and an inter-graphic proximity effect generated between a plurality of adjacent resist patterns.

Prior to the description of the present invention, these proximity effects will be described with reference to the drawings, exemplifying a case where a resist pattern is formed using a positive resist.

First, FIGS. 5A to 5D are diagrams for explaining the proximity effect in a figure. 5 (A), 5 (C) and 5 (D) are schematic cross-sectional views, in which hatching or the like showing the cross section is partially omitted.

First, as shown in FIG. 5 (A), a positive resist is applied to the surface of the substrate 11 to be processed to form a resist film 13. This resist film 13 is irradiated with electron beam are denoted a series of arrow a at a predetermined acceleration voltage, performing exposure regions P ₁ and P ₃ to be removed for patterning.

Here, a relatively large width in the cross section of the removal pattern regions P _1, which is referred to as pattern width d _1. Moreover, the relatively small width d ₃ of the pattern width of the removal pattern region P _3.
Here, as shown in FIG. 5 (A), an unexposed area (remaining pattern area) P ₂ to be left as a pattern, sandwiched between two removed pattern areas P ₁ and P _{3 which} are exposed areas. Is d ₂ .

FIG. 5 (B) is a characteristic curve diagram schematically showing the energy absorbed by the resist width 13 as an electron beam irradiation intensity distribution, paying attention to the plane on which the film 13 extends. In this figure, paying attention to the resist cross section shown in FIG.
In order to correspond to the positional relationship between the _two regions P ₁ , P ₂ , and P ₃ , the horizontal axis represents the distance, and the vertical axis represents the irradiation intensity of the resist film in arbitrary units.

As can be understood from FIG. 5B, the resist film 13
Even when the same amount of electron beam irradiation over the entire surface, resulting in a difference in the radiation intensity between the removal pattern region P ₁ and the removal pattern region P _3. This is called a proximity effect in a figure. In general, the irradiated intensity of pattern width in a large removal pattern regions P ₁ y _P1, when the pattern width is the irradiated intensity of a small removal pattern region P ₃ and y _P3, the magnitude relation between these two irradiation intensity _yP1 > _yP3 .

FIG. 5C is a diagram schematically showing a cross section of the resist pattern 15 obtained by developing after the above-described electron beam irradiation that causes the in-figure proximity effect. As shown in this figure, as a relatively large removal pattern region P ₁ is developed and removed over the pattern width d ₁ in accordance with the design, optimizing the development conditions to suit the irradiation intensity y _P1 described above If it is, the under-development with a relatively small removal pattern region P _3. Therefore, the removal pattern region _{P 3, (d 3 -d 4} ) over a corresponding pattern width, the irradiation portion electron beam remained to.

On the other hand, when the development conditions are set in accordance with the irradiation intensity y _P3 (see FIG. 5B), as shown in FIG. 5D, the removal pattern area P ₃ has a pattern width d according to the design. although that may be developed and removed over the _3, remove the pattern region P ₁ is the over-development. Therefore, the removal pattern area P ₁
(D ₅ -d ₁₎ over the corresponding pattern width, thus being excessively removed.

By the way, when forming P ₁ and P ₃ of the removal pattern area by electron beam irradiation, dispersion occurs in the electron beam at the boundary of the area, and therefore, from the center to the end of each area,
The irradiation intensity gradually decreases. Hereinafter, such a dispersion, the distance between which the irradiation intensity is substantially zero from the maximum value, corresponding to the removal pattern regions P ₁ and P ₃ in x _P1
And the x _P3, in the following description, there are cases where the respective areas, referred to the dispersion or the dispersion x _P1 and dispersion x _P3 the unit (FIG. 5 (B)). The above-mentioned proximity effect in a figure is
Each pattern area P ₁ and P ₃ formed by electron beam irradiation
The distance d ₂ between the occurs when sufficiently larger than the sum of the variances (x _P1 + x _P3).

On the other hand, in forming a resist pattern, if the distance between adjacent removal pattern regions is smaller than the sum of the above variances, in addition to the above-described intra-graphic proximity effect, the variances of the respective removal pattern regions overlap with each other. The proximity effect between figures occurs.

FIG. 6 (A) is an explanatory diagram similar to FIG. 5 (A) for explaining the inter-graphic proximity effect. In this figure, remove the pattern region P ₁ and the removal pattern region P ₃ as described above
DOO hitting the forming by electron beam irradiation, instead of the remaining pattern area P ₂ in FIG. 5 (A), shows a case of forming a remaining pattern region P ₄ pattern width is small d ₆ sufficiently is there.

In this case, FIG. 6B is a characteristic curve diagram of the electron beam irradiation intensity distribution shown in the same manner as FIG. 5B, and in this case, it is understood from FIG. 6B. as it can be, in the portion corresponding to the remaining pattern area P _4, remove the pattern region
The dispersion x _P1 and dispersion x _P3 occurs at the boundary of the P ₁ and P ₃ overlap each other, dispersion region will continuously. The distance of this dispersion area is _xP4, and here, this area is simply referred to as dispersion or dispersion _xP4 . Thus, figure between proximity effect occurs when the distance between the removal pattern region P ₁ and the removal pattern region P ₃ is small, therefore, the dispersion x _P4 above two removal pattern regions P ₁ and pattern width P ₃ (A resist pattern shape after development is omitted).

In the above description, two proximity effects have been described by focusing on the plane on which the resist film 13 extends. However, the actual resist film has a predetermined thickness according to the design.

FIG. 7 (A) is a diagram showing the distribution of the intensity of irradiation of the electron beam in the resist film. The vertical axis represents the thickness of the resist film in arbitrary units, and the horizontal axis represents the distance in the plane of the resist film. FIG. 9 is a schematic isoenergy curve diagram taken as (μm).

As can be understood from this figure, the irradiation intensity distribution becomes wider as the electron beam progresses from the resist film surface in the film thickness direction due to scattering of the electron beam. Therefore, even if each of the pattern widths d ₁ , d ₂ , and d _{3 of} the resist pattern 15 is formed in accordance with the design, as shown in the cross-sectional view of FIG. boundary between the residual pattern region P ₂ and removal pattern regions P ₁ and P ₃ becomes curved.

The influence of the proximity effect on the resist pattern described above hinders the realization of fine pattern dimensions, and various correction techniques have been conventionally proposed.

Conventional correction techniques can be broadly divided into two types, calculation correction and process correction. Further, process correction can be divided into each correction technique in a resist film formation process, a development process, or an electron beam irradiation process. .

Calculation Correction The calculation correction corrects the information on the electron beam irradiation intensity in advance according to the area, pattern shape, and pattern density of the resist pattern, and optimizes the irradiation intensity distribution on the resist film. In this technique, optimization is performed by changing the pattern width in each pattern area unit, and each pattern area is further subdivided into elementary pattern areas, and the irradiation intensity in one elementary pattern area is corrected and optimized. Is known.

Process Correction (I) Resist Film Forming Process Multilayer Resist This correction technique reduces the influence of electron beam scattering by forming a resist film in a multilayer structure. For example, forward scattering is reduced by reducing the thickness of a layer sensitive to an electron beam. Further, a layer having a low electron beam reflectivity can be employed as a layer serving as a base of the resist film, so that backscattering can be reduced.

Improvement of resist characteristics This technique aims to suppress the proximity effect by improving a resist as a material, and is known to improve contrast characteristics and the like.

(II) Development Process For example, by using a developer (weak solvent) having a relatively small developing ability, selectivity in the development process is improved.

(III) Electron Beam Irradiation Process Electron Beam Irradiation with High Acceleration Voltage This technology reduces the backscattering by increasing the acceleration voltage from the normally used 20 (kV) to a high acceleration voltage of 50 (kV) or more. is there.

Double exposure method (i) Ghost exposure method This correction technique is disclosed in Reference I: Japanese Patent Application Laid-Open No. 59-921.

The ghost lightning method, in addition to the electron beam irradiation (see FIG. 5 (A)) according to the removal pattern regions P ₁ and P _3, with respect to the remaining pattern region P ₂ corresponding to the inverted pattern, FIG. 8 As shown in FIG. 3A, the irradiation intensity of the electron beam b serving as a background is lower than that of the irradiation of the electron beam a.

FIG. 8 (B) is a characteristic curve diagram showing the above-described background electron beam irradiation in the same manner as FIG. 5 (B). As can be understood from FIG. In the part where the irradiation intensity is smaller than the design,
To compensate drives out the irradiation intensity y _a.

Here, FIG. 8 (C) shows the fifth example except that the total irradiation intensity by the two electron beam irradiations is plotted on the vertical axis.
It is a figure shown similarly to figure (B). As can be understood from this figure, in this technique, in the removal pattern region P ₁ and the removal pattern region P ₃ Prefecture, performs electron beam irradiation as _{y P1 ≒ y P3 + y a} , yet as a uniform background
It is possible to get y _BG .

(Ii) Fog exposure method This correction technique is described in Document II: “Proximity Effect Reduction Method by Fog Exposure” (Semiconductor World, May 1986,
85-91).

The fogging exposure method, in addition to the irradiation of the electron beam a in accordance with a fifth diagram removal pattern regions P ₁ and P ₃ has been described with reference to (A), as shown in FIG. 9 (A), the resist film 13 is configured to irradiate the electron beam c over the entire surface. At this time, the entire surface irradiation is performed as shown in FIG. 9 (B) similar to FIG. 8 (B).
As shown in, carried out in the irradiation intensity y _s.

Here, FIG. 9 (C) is a diagram showing the total irradiation intensity on the vertical axis, similarly to FIG. 8 (C). According to this fogging exposure method, the relative ratio of the total irradiation intensity between the two removal pattern regions described above becomes small as shown in the following equation, so that the proximity effect in the figure can be reduced. It is.

(Problems to be Solved by the Invention) However, with the above-described conventional correction technology, it is difficult to simultaneously improve the workability related to the design of the resist pattern and suppress the intra-graphic proximity effect and the inter-graphic proximity effect. There was a problem.

Hereinafter, this point will be described in detail for each correction technique. First, the calculation correction substantially suppresses the above-described two proximity effects, and a large correction effect can be obtained. However, calculating information on the irradiation intensity (hereinafter, referred to as pattern data) requires a complicated calculation for each combination of adjacent pattern regions. For this reason, computer processing for the purpose of creating pattern data takes a long time, and a TAT (Turn Around Time: time required to manufacture one product) is delayed.

In addition, among the process corrections, the prior arts relating to the resist film forming process and the developing process all have insufficient suppression of the proximity effect, and are difficult to apply to the manufacture of various types of semiconductor devices.

Further, among the conventional correction techniques related to the electron beam irradiation process, the electron beam irradiation with a high acceleration voltage makes it difficult to manufacture an exposure machine capable of drawing at high speed and with high accuracy, and is not practical. In addition, the use of an electron beam having a high energy has a bad influence on a semiconductor material, and sometimes deteriorates the operating characteristics of a semiconductor device.

The double exposure method such as the ghost exposure method and the fogging exposure method, which are conventionally known, is effective for suppressing the proximity effect in a figure, but the proximity effect between figures described with reference to FIG. It is difficult to achieve the control. Further, the entire surface of the resist film including the remaining pattern region needs to be irradiated with an electron beam, as well as a portion necessary for forming a substantial resist pattern, such as a removed pattern region when a positive resist is used. For this reason, it is difficult to reduce TAT. Further, when a positive resist is used, the above-described irradiation of the entire surface reduces the thickness of a resist pattern remaining after development, and may cause a pattern defect on a substrate to be processed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a resist pattern forming technique capable of simultaneously improving the workability of resist pattern design and suppressing the intra-graphic proximity effect and the inter-graphic proximity effect, in view of the above-described conventional problems. It is in providing.

(Means for Solving the Problems) In order to achieve this object, according to the method for forming a resist pattern of the present invention, a region to be removed, which is to be removed, is formed on a layer to be processed, and A method of forming a resist pattern by removing an area to be removed by performing an electron beam irradiation and a developing process on a positive type resist film having an adjacent area to be left in a positive resist film, Applying a resist film;
Irradiating a predetermined dose of the electron beam to the area to be removed, irradiating the predetermined area with an electron beam having a dose higher than the predetermined dose to the remaining area, and setting the remaining area to have a negative type characteristic; Performing a process to remove an area to be removed.

In the method of forming a resist pattern according to the present invention, preferably, the positive resist film is a novolak-based positive resist film, and the above-described predetermined dose is 50 to 50.
It is good to set it to 500 (μC / cm ² ).

In the method of forming a resist pattern according to the present invention, the positive resist film is preferably a positive resist film containing polymethyl methacrylate.

(Action) According to the method of forming a resist pattern of the present invention, in addition to the electron beam irradiation at a predetermined dose to the region to be removed such that the positive resist exhibits positive characteristics, the above-described method is performed in the region to remain. The electron beam irradiation is performed at a dose higher than the predetermined dose, so that the above-mentioned positive resist exhibits negative characteristics. Therefore, the variance that occurs between the expected remaining area and the expected removal area is substantially canceled. Therefore, it is possible to achieve suppression of the two proximity effects that occur between the region to be removed and the region to remain, and to form a resist pattern with high accuracy.

(Example) Hereinafter, an example of a method for forming a resist pattern according to the present invention will be described with reference to the drawings. It should be understood that the drawings referred to in the following description are only schematically shown to the extent that the present invention can be understood, and that the present invention is not limited to only the illustrated examples.

In this embodiment, as a positive resist suitable for carrying out the present invention, a novolak-based positive resist "AZ
−2400 ”(Shipley, trade name).

FIG. 2 shows the normalized film thickness on the vertical axis and the electron beam dose (μC / cm) on the horizontal axis in order to explain the relationship between the dose of the electron beam and the resist characteristics for the positive resist described above.
FIG. 2 is a characteristic curve diagram showing ² ) on a logarithmic scale.

As can be understood from this figure, the positive resist described above, positive characteristic is made larger as increasing the dose of the electron beam from 1 (μC / cm ^2), in the figure, the values indicated as I _P ( At about 50 (μC / cm ² ), the normalized film thickness becomes zero.
Such positive type characteristics even further by increasing the dose of the electron beam, in the figure, the values indicated as I _n (about 500 ([mu] C / c
m ² )).

Furthermore, negative characteristics increases according to increase the dose from such I _n, normalized film thickness gradually increases.

As described above, as the positive resist which changes from the positive type characteristic to the negative type characteristic by increasing the dose of the electron beam, a series of novolak-based resists and those containing polymethyl methacrylate (PMMA) are known. ing.

Next, FIG. 1 (A) is a diagram schematically showing a cross section corresponding to FIG. 5 (A) described above for explaining the embodiment of the present invention. In the figure, hatching indicating a cross section and the like are partially omitted, and detailed explanations of components having the same functions as the components already described are omitted.

First, as in the conventional case, the above-described positive resist is applied to the surface of the substrate 11 to be processed, and a resist film 13 is formed. Thereafter, the the removal pattern P ₃ having a removal pattern region P ₁ and the pattern width d ₃ having a pattern width d ₁ performing electron beam irradiation of a low dose (shown denoted by the series of arrows D ₁₎ .

In the present invention, for example, a region of the remaining pattern region as shown by P _2, removing the pattern region P ₁ and the above-described
For each of the edge region P _e in contact with P ₃ and the boundary pattern width
The d ₇ than performing electron beam irradiation at a high dose (shown denoted by the series of arrows D _2).

Such an edge region that contacts the boundary is formed around the island region when the removal pattern region is an island region, and is formed when the removal pattern region is a stripe region when the removal pattern region is an island region. The regions on both sides of the stripe may be set as edge regions.

Such two types of doses of electron beam irradiation use various conventionally known techniques such as a combination of a beam shape such as a variable beam or a spot beam and a scanning method such as a vector scan method or a raster scan method. can do.

In this embodiment, regardless of the pattern width of each removal pattern regions P ₁ and P _3, the pattern width d ₇ of the edge area P _e 0.5
(Μm).

The electron beam irradiation described above, a low dose of D ₁ as shown a positive characteristic 200 (μC / cm ^2), and a high dose D ₂ shown a negative characteristic 1200 (μC / cm ² ), Respectively (see FIG. 2).

FIG. 1 (B) shows the energy absorbed by the resist film 13 when the electron beam is irradiated at two doses under the conditions of the present embodiment, as an electron beam irradiation intensity distribution. FIG. 5 is a characteristic curve diagram similar to FIG.

As can be understood from this diagram and the conditions regarding the high dose and the low dose described above, each of the remaining pattern regions (P _{2 in} FIG. 1 (A)) has a high dose that exhibits a negative type characteristic. An edge region (pattern width d ₇ ) irradiated with the electron beam is formed. Therefore, considering that performing development with an alkali developer according to the above-described positive resist, the residual pattern regions P ₁ and P ₃ become variable dissolution zone, the edge region P _e
Shows a negative type characteristic, and thus becomes an insoluble region. further,
Of the remaining pattern regions P _2, the portion excluding the edge region P _e described above because it is the unexposed portion is insoluble region. Therefore, if the resulting shapes in proximity effect that the irradiation intensity is different according to the width of each of the removal pattern region, be subjected to positive development process example according to a small removal pattern area P ₃ of the irradiation intensity, remaining edge area of the pattern region P ₂
Since P _e is insoluble, the removal pattern area P _{1 having} a large pattern width
It is not removed in the design width d ₁ or more.

Thus, according to the method of the present invention may be a value d ₂ in accordance with the design pattern width of the remaining pattern region P _2.

Among the dispersing portion caused by forming the edge region, the portion of the distributed x _B1 and x _B2 occurring removing the pattern region is a region adjacent regions remains together. Further, as in this embodiment, the pattern width of the edge region is set to 0.5
(Μm), the width of the variances x _B1 and x _B2 is
It is about 0.05 (μm). Therefore, since the width corresponding to such dispersion is equal to or less than the resolution limit of the resist pattern,
The progress of the development in the above-mentioned dispersed portion is slowed down, and no substantial defect occurs in the resist pattern.

FIG. 3 is a schematic sectional view showing a resist pattern after development, similar to FIG. 7 (B). As can be understood from the figure, the cross-sectional shape of the resist pattern 17 formed by applying the method of the present invention can be substantially rectangular. Such an effect is obtained by the positive-type characteristic (see FIG. 7A) relating to the removal pattern region caused by the scattering of the electron beam and the similar scattering of the electron beam in the thickness direction of the resist film 13. It is considered that the negative characteristics related to the edge region cancel each other. Thereby, the resolution characteristic of the resist pattern in the thickness direction is also improved. By performing dry etching using the resist pattern as a mask, it is possible to suppress variations in pattern dimensions on the substrate to be processed.

Further, FIG. 4 is a diagram showing the resist pattern 17 after development by a schematic plane. As can be understood from this figure, the majority of the remaining pattern area P ₂ excluding the edge region P _e may be formed without the electron beam irradiation. Therefore, the time required for electron beam irradiation can be expected to be reduced as compared with the above-described conventional double exposure method.

At this time, it was subjected to resist patterning by setting 0.5 to uniformly pattern width d ₇ of the edge area P _e (μm) in this embodiment. However, the pattern width d ₇ is and minimum resolution in accordance with the characteristics of the positive resist is used, any suitably be designed in accordance with the pattern density of the resist pattern to be desired.

In addition, as described above, setting the pattern width d ₇ of the edge area P _e uniformly, because it can be highly accurate resist pattern formation, without requiring complicated operations, the pattern data The time required for creation can be reduced.

As described above, the embodiments of the present invention have been described in detail. However, it is obvious that the present invention is not limited to the above-described embodiments.

As an example of a positive resist suitable for practicing the present invention, the case of using a novolak-based resist has been described in the above embodiment. However, the present invention is not limited to this, as long as the resist exhibits a positive type characteristic at a low dose and a negative type characteristic at a high dose. As a resist exhibiting such characteristics, two types of novolak-based positive resists or PMMA-based positive resists can be used in place of "AZ-2400" used in the above-described embodiment. By setting the dose appropriately, the same effect as described above can be obtained.

(Effects of the Invention) As is clear from the above description, according to the method for forming a resist pattern of the present invention, electrons with a predetermined dose amount with respect to a region to be removed such that the positive resist exhibits positive characteristics are obtained. In addition to the line irradiation, an electron beam irradiation with a dose higher than the above-mentioned predetermined dose is performed in the remaining area to cause the above-mentioned positive resist to exhibit the negative type characteristics. For this reason, even when the pattern density and the pattern width of a plurality of resist patterns formed on the same layer to be processed are variously different, a region where a negative pattern characteristic is exhibited in a region where a predetermined pattern width is expected to remain in a predetermined region. , The intra-graphic proximity effect and the inter-graphic proximity effect can be substantially suppressed.

Therefore, by applying the method of forming a resist pattern according to the present invention, it is possible to simultaneously improve both the workability in designing the resist pattern and the suppression of the intra-graphic proximity effect and the inter-graphic proximity effect.

[Brief description of the drawings]

FIG. 1A is an explanatory view showing a schematic cross section for explaining the conditions of electron beam irradiation performed in the example, and FIG. 1B is a diagram illustrating the conditions of electron beam irradiation performed in the example. For the sake of explanation, the irradiation intensity is plotted on the vertical axis and the first intensity is plotted on the horizontal axis.
FIG. 2A is a characteristic curve diagram in which distances are taken in accordance with the arrangement relationship of the cross sections shown in FIG. 2A. FIG. 2 is a graph showing characteristics of the positive resist used in the embodiment of the resist pattern forming method of the present invention. A characteristic curve diagram showing the normalized film thickness on the vertical axis and the dose of the electron beam on the horizontal axis. FIG. 3 is a schematic diagram of a resist pattern obtained by applying the present invention to explain the embodiment. FIG. 4 is an explanatory view showing a schematic plane of a resist pattern corresponding to FIG. 3, and FIGS. 5 (A) to 5 (D) are diagrams showing the principle of the proximity effect in a figure. FIGS. 6A and 6B are diagrams for explaining the principle of the inter-graphic proximity effect, and FIGS. 7A and 7B are diagrams for explaining the prior art.
Iso-energy curve over the cross-sectional direction of the resist pattern,
8 (A) to 8 (C) illustrate a ghost exposure method as a conventional technique, and FIGS. 9 (A) to 9 (C) illustrate a conventional resist pattern after development. It is a figure for explaining a fog exposure method as a technique. 11 ...... substrate to be processed, 13 ...... resist films 15 and 17 ...... resist pattern P _1, P ₃ ...... removal pattern regions P _2, P ₄ ...... residual pattern region P _e ...... edge area, d ₁ ~ d ₇ … Pattern width D ₁ … Low dose electron beam D ₂ … High dose electron beam.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-190931 (JP, A) JP-A-2-143516 (JP, A) JP-A-1-292824 (JP, A) JP-A-62-1987 245630 (JP, A) JP-A-57-112020 (JP, A) JP-A-63-104329 (JP, A) JP-A-63-58829 (JP, A) JP-A-62-257724 (JP, A) JP-A-2-87617 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01L 21/027

Claims (3)

(57) [Claims] An electron beam irradiation and a development process are performed on a positive resist film formed on a layer to be processed and having a region to be removed to be removed and a region to be left adjacent to the region to be removed. A method of forming the resist pattern by removing the to-be-removed region, performing a step of applying the positive resist film on the layer to be processed, and applying a predetermined dose of an electron beam to the to-be-removed region. Irradiating the predetermined area with an electron beam having a dose higher than the predetermined dose to irradiate the remaining area with a negative characteristic; and performing a developing process to remove the area to be removed. Forming a resist pattern. 2. The method of forming a resist pattern according to claim 1, wherein said positive resist film is a novolak-based positive resist film, and said predetermined dose is 50 to 500 (μC / cm ² ).
A method of forming a resist pattern. 3. The method for forming a resist pattern according to claim 1, wherein the positive resist film is a positive resist film containing polymethyl methacrylate.