JP3534247B2 - Method of forming resist pattern, method of forming impurity added region, and method of forming fine pattern - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a resist pattern, and more particularly to a method for forming a resist pattern having a periodic repeating pattern in a two-dimensional direction.

[0002]

2. Description of the Related Art A conventional method of forming a resist pattern by X-ray lithography will be described with reference to FIG.

As shown in FIG. 6A, an X-ray mask 1
00 is a support film 100 made of SiC and having a thickness of about 2 μm.
a, and a plurality of X-ray absorption patterns 100b made of Ta, W or the like formed on the surface thereof. Each of the X-ray absorption patterns 100b extends in the direction perpendicular to the paper surface and is arranged at equal intervals in the lateral direction of FIG. For example, the width of each X-ray absorption pattern 100b is 100 nm, the pitch is 200 nm, and the thickness is 300 to 400 nm.

On the surface of the substrate 101, a thickness of about 300-4
A negative type X-ray resist film 102 of 00 nm is formed. The X-ray absorption pattern 100b side surface of the mask 100 and the resist film 102 side surface of the substrate 101 face each other with a minute gap therebetween. This gap is, for example, 20 μm.

Through the mask 100, the resist film 102
Then, the first X-ray exposure is performed. An example of the absorbed dose of the resist film 102 is represented by the curve 110. When the line width and the pitch are reduced, the absorbed dose distribution does not have a rectangular shape and the curve 11
As shown by 0, the shape is close to a triangular wave having a wavelength of 200 nm. After the first exposure, the mask 100 is shifted by a half pitch of the X-ray absorption pattern 100b, and the second exposure is performed.

FIG. 6B shows the distribution of absorbed dose after the second exposure. The dotted line 110a represents the absorbed dose distribution by the first exposure, and the dotted line 110b represents the absorbed dose distribution by the second exposure. The solid line 110s represents the total absorbed dose distribution. The total absorbed dose distribution 110s has a triangular wave shape with a wavelength of 100 nm. The resist film 102 is developed under the condition that the threshold value of the absorbed dose which becomes insoluble in the developing solution becomes the size of the broken line 104.

FIG. 6C shows a sectional view of the resist pattern 105 after development. The resist pattern 105 is composed of a plurality of linear patterns extending in a direction perpendicular to the paper surface, and these linear patterns are arranged at equal intervals in the lateral direction of the drawing. The pitch is half the pitch 200 nm of the X-ray absorption pattern 100b shown in FIG. Further, the width of each linear pattern is smaller than the width of the X-ray transmissive region between the X-ray absorption patterns 100b shown in FIG. In this way, it is possible to form a resist pattern that is narrower in width and narrower in pitch than the width of the X-ray transmission region formed in the X-ray mask.

[0008]

In the method according to the conventional example shown in FIG. 6, a striped pattern in which thin linear patterns are arranged in a one-dimensional direction at a narrow pitch can be formed relatively easily. However, a new problem arises in order to form a regular pattern distributed in a two-dimensional plane.

An object of the present invention is to provide a resist pattern forming method capable of forming a regular pattern distributed in a two-dimensional plane relatively easily.

Another object of the present invention is to provide a method for forming a resist pattern, which allows closely arranged patterns to be arranged.

Another object of the present invention is to provide a method for forming a fine pattern using these resist patterns.

[0012]

According to one aspect of the present invention, a light-shielding pattern is formed on a support film, and a region where the light-shielding pattern is not arranged defines at least a plurality of first and second transmission regions. A plurality of first transmissive regions each having a first shape are regularly distributed at a first pitch in a first direction and at a second pitch in a second direction. A step of preparing a mask in which each of the plurality of second transmissive regions having a shape is regularly distributed corresponding to each of the first transmissive regions; and a substrate on which a photosensitive resist film is formed A step of arranging the mask on the surface of the substrate opposite to each other with a minute gap therebetween, a first exposure step of partially exposing the photosensitive resist film on the substrate through the mask, the mask and the substrate From one to the other in the first direction A second exposure step of moving a distance shorter than the first pitch to partially expose the photosensitive resist film on the substrate through the mask, and a step of developing the exposed photosensitive resist film. Has and
The first transmissive region and the second transmissive region corresponding to each other are
The pattern in which the first transmissive area is transferred and the pattern in which the second transmissive area is transferred are arranged so as to partially overlap or contact each other in the second direction,
The first pattern formed by being exposed in the first exposure step and the second pattern formed by being exposed in the second exposure step are arranged to be continuous with each other. There is provided a resist pattern forming method in which the distribution of absorbed dose of the photosensitive resist film in the exposure step and the second exposure step and the developing sensitivity in the developing step are set.

[0013]

[0014]

Generally, when a polygonal pattern having inwardly convex corners is formed, the corners are easily collapsed.
When the first pattern and the second pattern do not have inwardly convex corners, the first and second patterns can be transferred relatively accurately. Even if the pattern in which both patterns are continuously formed has a convex corner inward, this corner collapse can be prevented.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An X-ray exposure apparatus used in a resist pattern forming method according to an embodiment of the present invention will be described with reference to FIG.

The X-ray exposure apparatus comprises a synchrotron radiation (SR light) generator 1, an SR light propagator 10, and an X-ray stepper 70.

The SR light generator 1 comprises a vacuum container 2 and an electron beam orbit 3 formed therein. SR light is emitted from the electrons that orbit along the orbit 3. This SR light is extracted to the outside through the beam extraction port 4 provided in the vacuum container 2.

The SR light propagating section 10 comprises an incident side vacuum duct 1
1, a mirror housing case 50, and an exit-side vacuum duct 56. An SR light entrance hole 51 and an SR light exit hole 52 are provided in the mirror housing case 50. The incident-side vacuum duct 11 hermetically connects the beam outlet 4 of the SR light generator 1 and the incident hole 51 of the mirror housing 50. Inside the vacuum duct 11, a vacuum shutoff valve, a shutter (not shown) for shutting off radiated light, and the like are arranged. The entrance end of the exit-side vacuum duct 56 is hermetically connected to the exit hole 52.

A reflection mirror 54 is provided in the mirror housing case 50.
Is stored and held by the mirror swing mechanism 53. The SR light entering from the entrance hole 51 is reflected by the mirror 54, passes through the exit hole 52, and the exit side vacuum duct 56.
Incident on the inside. In the mirror 54, the incident surface including the central optical axis of the incident SR light and the normal line of the reflecting surface at the reflection point is vertical, and the angle formed by the incident central optical axis and the reflecting surface is about 1 to 2 °, that is, the incident light The corners are arranged at about 89-88 °.

The swing mechanism 53 swings the mirror 54 about a swing axis perpendicular to a vertical plane including the incident center optical axis as the swing center. The optical axis of the reflected SR light is vertically swung by the swing of the mirror 54. The swing center may be placed at the reflection point of the SR light or at a position different from the reflection point.

An emission window 57 containing a beryllium thin film is attached to the emission end of the emission side vacuum duct 56. The beryllium thin film maintains the airtightness in the emission side vacuum duct 56. The SR light incident on the exit side vacuum duct 56 is
The light is transmitted to the outside through the beryllium thin film in the emission window 57. An X-ray stepper 70 is arranged at a position facing the emission window 57. The X-ray stepper 70 includes a substrate holding means 71.
A and mask holding means 72A are included. The substrate holding means 71A holds the semiconductor substrate 71 at a position where the SR light emitted from the emission window 57 is irradiated. The mask holding means 72A is provided on the front side of the semiconductor substrate 71 so that the X-ray mask 7
Hold 2

SR light is emitted in all directions with respect to the horizontal direction, but spreads only about ± 1 mrad in the vertical direction. By swinging the mirror 54 and swinging the optical axis of the SR light up and down, the SR light can be irradiated onto a wide area of the surface of the semiconductor substrate 71.

Referring to FIG. 2, a plurality of rectangular patterns regularly arranged in mutually orthogonal x-axis and y-axis directions
Problems when the conventional method described in FIG. 6 is used will be described. The exposure apparatus used is, for example, the X-ray exposure apparatus shown in FIG.

FIG. 2A shows a partial plan view of the X-ray mask. A plurality of rectangular X-ray transmissive regions 20 are arranged on the x-axis and the y-axis.
It is regularly arranged in the axial direction. Each X-ray transmission area 20
Is arranged in parallel with the x-axis. The length Lx of the short side (side parallel to the x-axis) is 60 nm, and the length Ly of the long side (side parallel to the y-axis) is 125 nm. The pitch Px in the x-axis direction is 100 nm, and the pitch Py in the y-axis direction is 150 nm.

The X-ray mask shown in FIG. 2A is placed in parallel with the substrate on which the resist film is formed at an interval of 20 μm, and the absorbed dose of the resist film when X-ray exposure is performed is performed. A two-dimensional distribution is shown. A sharp peak appears at a position corresponding to the X-ray transmission region 20.

FIG. 2 (C) shows a graph obtained by cutting the distribution of absorbed dose shown in FIG. 2 (B) at a half height of the peak. The upper half of the sharp peak is cut out to obtain a plate-like two-dimensional distribution. When the resist film is developed under the condition that the development sensitivity is half the peak of the absorbed dose, when a negative resist is used, a resist pattern having a shape corresponding to the upper surface 21 of the plate-like portion remains.

The width of the remaining resist pattern in the x-axis direction is about 22 nm. Therefore, by shifting the mask by a half pitch in the x-axis direction and performing the second exposure, as in the conventional example described with reference to FIG. 6, Px / 2,
That is, a resist pattern having a width of about 22 nm arranged at a pitch of 50 nm can be formed.

However, although the length Ly of the long side of the X-ray transmissive region 20 of the mask is 125 nm, the length of the remaining resist pattern in the y-axis direction is about 65 nm. The X-ray transmissive regions 20 of the mask shown in FIG. 2A are separated by 25 nm in the y-axis direction.
On the other hand, the interval separated in the y-axis direction of the formed resist pattern expands to about 85 nm. In the traditional way,
It is difficult to narrow the space separated in the y-axis direction.

Next, a resist pattern forming method according to the first embodiment of the present invention will be described with reference to FIG. The resist used is a negative type resist. That is, it becomes insoluble in the developer by absorbing X-rays.

FIG. 3A shows a partial plan view of the X-ray mask. A plurality of rectangular X-ray transmissive regions 22 are regularly arranged in the x-axis direction and the y-axis direction. The side of each X-ray transmission region 22 is parallel to the x-axis or the y-axis, the length Lx of the side parallel to the x-axis is 60 nm, and the length L of the side parallel to the y-axis.
y is 125 nm. The pitch Px in the x-axis direction is 100 nm, and the pitch Py in the y-axis direction is 150 nm.
Is.

FIG. 3B shows the distribution of the region N ₁ which became insoluble when X-ray exposure was performed using the mask shown in FIG. 3A. As described with reference to FIG. 2, the insoluble region N
The length of each ₁ in the x-axis direction is about 22 nm, and the length in the y-axis direction is about 65 nm.

Next, the substrate is translated by about 65 nm in the negative direction of the y-axis with respect to the mask. In this state, the second X-ray exposure is performed. By the second exposure, FIG.
As shown in, the region N _{2 obtained} by translating the region N ₁ by 65 nm in the positive direction of the y-axis becomes insoluble. Regions N ₁ and N ₂
And are continuous in the y-axis direction, and both form a rectangular pattern having a short side of 22 nm and a long side of about 130 nm.

Next, the substrate is translated by 50 nm in the negative direction of the x-axis with respect to the mask, and further translated by 10 nm in the negative direction of the y-axis. In this state, the third X-ray exposure is performed. By the third exposure, the region N ₃ becomes insoluble as shown in FIG. The region N ₃ is arranged in the center of the regions N ₂ adjacent to each other in the x-axis direction. Further, with respect to the y-axis direction, the area N ₃ is equal to the area N ₂ .
It is arranged at a position shifted by 0 nm in the positive direction of the y-axis.

Next, the substrate is translated by 65 nm in the negative direction of the y-axis with respect to the mask. In this state, the fourth X-ray exposure is performed. As a result of the fourth X-ray exposure, FIG.
As shown in (E), the region N ₃ is moved in the positive direction of the y-axis by 65
The region N ₄ translated by nm becomes insoluble. Area N ₃
And N ₄ are continuous in the y-axis direction.
A rectangular pattern with m and a long side of about 130 nm is formed.

As shown in FIG. 3E, the width of each of the plurality of insoluble regions in the x-axis direction is 22 nm, and the pitch in the x-axis direction is 50 nm. Further, the length of each insoluble region in the y-axis direction is about 130 nm, and the pitch in the y-axis direction is 15 nm.
It becomes 0 nm. Further, in the rows of insoluble regions that are adjacent to each other in the x-axis direction, the insoluble regions are displaced from each other in the y-axis direction by a half pitch.

After the fourth exposure, when the developing process is performed,
A resist pattern composed of insoluble regions N _{1 to} N ₄ is obtained.

As described above, in the x-axis direction, that is, in the direction parallel to the short side of the X-ray transmissive region 22 of the mask, the pattern width is narrower and the pitch is narrower than that of the X-ray transmissive region 22 of the mask. be able to. Further, in the y-axis direction, that is, in the direction parallel to the long side of the X-ray transmissive region 22 of the mask, it becomes possible to narrow the interval between the patterns adjacent to each other. For example, in the example described with reference to FIG. 2, the distance between the resist patterns has expanded to 85 nm, even though the distance between the X-ray transmission regions of the mask in the y-axis direction is 25 nm. On the other hand, in the case of the first embodiment, the distance separated in the y-axis direction is about 20 nm.

In the first embodiment, in the first exposure step shown in FIG. 3B, the alignment of the mask and the substrate is adjusted while observing the alignment marks. From the second exposure shown in FIG. 3C to FIG.
In each step of the fourth exposure shown in (4), it is not necessary to perform alignment while observing the alignment mark. Since the relative moving distance between the mask and the substrate has already been determined, the substrate holder may be moved in translation by a predetermined distance.

In the first embodiment, the substrate was moved parallel to the mask by 65 nm in the y-axis direction in the step described with reference to FIG. Due to this parallel movement, the insoluble regions N ₁ and N ₂ are in contact with each other and are continuous with each other. If the condition that the insoluble regions N ₁ and N ₂ are continuous is satisfied, both may be partially overlapped. This condition is defined by the distribution of absorbed dose of the resist film and the developing sensitivity.

Further, in the first embodiment described above, the case of forming a plurality of discretely distributed resist patterns by using the negative type resist has been described. Using a positive resist,
By the same method, it is possible to form a resist pattern having a plurality of discretely distributed openings.

The step of moving the substrate in the first embodiment is carried out until the mirror 54 shown in FIG. 1 reaches the top dead center or the bottom dead center of the swing and the next swing starts.
This makes it possible to reduce the processing time.

A technique is known in which SR light is reflected by a convex mirror and diffused in the vertical direction, and the entire exposed surface is exposed simultaneously using the diffused SR light. In this case, the first
After the exposure of the second time is completed, the SR light is blocked by the shutter,
The substrate may be moved. As described with reference to FIGS. 3C and 3E, when the substrate is moved in the y-axis direction, the substrate may be moved while being exposed to SR light. When moved at a constant speed, the absorbed dose in the central portion of the pattern composed of the insoluble regions N ₁ and N ₂ increases. In order to make the absorbed dose evenly close, the moving speed is gradually increased from the start of the movement, and from the time when it passes the center of the area to be exposed,
It is preferable to reduce the moving speed.

Next, a resist pattern forming method according to the second embodiment will be described with reference to FIG.

FIG. 4 shows the in-plane distribution of the insoluble regions N _{1 to} N ₄ of the resist film formed by the method according to the second embodiment.
The insoluble regions N ₁ and N ₄ are arranged at the same position in the y-axis direction, and the insoluble regions N ₂ and N ₃ are arranged at the same position in the y-axis direction. Such a pattern is formed by changing the movement process of the substrate in the y-axis direction described with reference to FIGS. 3D and 3E of the first embodiment. In the second embodiment, a plurality of rectangular patterns arranged in a matrix are formed.

Next, a method of forming a resist pattern according to the third embodiment will be described with reference to FIG.

FIG. 5A shows a partial plan view of an X-ray mask used in the method according to the third embodiment. A plurality of first X-ray transmissive regions 30 each having a rectangular shape are regularly distributed in the x-axis direction and the y-axis direction. Each short side of the first X-ray transparent region 30 is parallel to the x-axis, and the long side is parallel to the y-axis. The pitch in the x-axis direction of the first X-ray transmissive region is Px, and the pitch in the y-axis direction is Py. First X
A region which becomes insoluble when the negative resist film is exposed through the line transparent region 30 is indicated by a broken line 30a. The first insoluble region 30a is located inside the first X-ray transparent region 30.

A plurality of second X-ray transmissive regions 31 each having a square shape are regularly distributed corresponding to each of the first X-ray transmissive regions 30. The length of one side of the second X-ray transmission region 31 is shorter than the long side of the first X-ray transmission region 30. A region which becomes insoluble when the negative resist film is exposed through the second X-ray transmitting region 31 is shown by a broken line 31a.
The second insoluble region 31a is located inside the second X-ray transparent region 31.

Each of the second X-ray transmissive regions 31 is located at a position where the corresponding first X-ray transmissive region 30 is moved in the positive direction of the x-axis by a distance shorter than the pitch Px in the x-axis direction. Will be placed. More precisely, the first insoluble region 30a
The first and second X-ray transmissive regions 30 and 31 are arranged so that and the corresponding second insoluble region 31a partially overlap or contact with each other in the x-axis direction.
With respect to the y-axis direction, the second X-ray transmissive region 31 is arranged at the center of the two first X-ray transmissive regions 30 adjacent to each other in the y-axis direction.

This mask is arranged in parallel to the substrate on which the negative resist film is formed with a certain gap.
The mask and the substrate are aligned, and the first X-ray exposure is performed. After the exposure, the substrate is moved with respect to the mask in the y-axis direction by 1/2 of the pitch Py. In this state, the second exposure is performed. Development is performed after the second exposure.

FIG. 5B shows the shape and distribution of the insoluble region 35 after the second exposure, that is, the resist pattern after development. The insoluble region 35 is in the x-axis direction and y.
They are regularly arranged in the axial direction, the pitch in the x-axis direction is equal to Px, and the pitch in the y-axis direction is 1/2 of Py.

The insoluble region 35 is exposed by the X-rays transmitted through the first X-ray transmissive region 30 and becomes insoluble, and the insoluble region 35 is exposed by the X-rays transmitted through the second X-ray transmissive region 31. And the insoluble region 33. In the case of the third embodiment, the insoluble region 35 has a shape in which a square insoluble region 33 is connected to the rectangular insoluble region 32 at substantially the center of its long side. That is, the insoluble region 35 is
It has a polygonal shape including inwardly convex corners, in other words, corners whose interior angles are greater than 180 °. In reality, the corners of the resist pattern are microscopically rounded to some extent, but macroscopically considered to be polygonal.

Generally, when an attempt is made to form a polygonal pattern having inwardly convex corners by one exposure, the inwardly convex corners are often crushed. Particularly, in the case of a polygonal pattern having an inside angle of 270 °, this corner is easily collapsed.

In the third embodiment, one pattern is formed by exposing a plurality of times. The pattern formed by one exposure does not include a corner that is convex toward the inside. For this reason,
It is possible to prevent collapse of a corner having an interior angle larger than 180 °.

Furthermore, in the third embodiment, the distance for moving the substrate in the y-axis direction after performing the first exposure and before performing the second exposure is 1/2 of the pitch Py. Is generally considered to be about several tens nm to several tens of μm. Since the moving distance is short as described above, it is not necessary to perform the alignment again using the alignment mark before the second exposure, and the alignment is completed only by the mechanical accuracy of the XY stage.

In the third embodiment described above, one pattern is formed with two types of transmission regions, the first X-ray transmission region 30 and the second X-ray transmission region 31, but three or more types of transmission regions are transmitted. One pattern may be formed in the area. In this case, three or more types of transmissive regions are arranged in the y-axis direction. The transparent area is n
If there is a type, the substrate is Py / n
The exposure may be performed n times by moving only in the y-axis direction.

In the third embodiment, the substrate was moved only in the y-axis direction after the first exposure and before the second exposure, but in both the x-axis direction and the y-axis direction. You may move it.

Next, a method for forming a fine pattern using the resist pattern formed by the method according to the first to third embodiments will be described.

First, a resist pattern is formed on the main surface of a substrate having a main surface by the method according to the first to third embodiments. This substrate is, for example, a semiconductor substrate on which a dielectric film such as silicon oxide, a conductive film such as metal, or another semiconductor layer is formed. The substrate is etched to a certain depth using this resist pattern as a mask.
By this etching, the dielectric film, the conductive film, other semiconductor layers, etc. are patterned.

It is also possible to form a fine pattern by lift-off. First, a resist pattern is formed on the main surface of a substrate having a main surface by the method according to the first to third embodiments. A thin film such as a metal film is deposited on the main surface so as to cover this resist pattern. The resist pattern is removed along with the thin film deposited on it. As a result, a fine pattern made of a thin film remains.

It is also possible to perform ion implantation into the semiconductor substrate using the resist pattern formed by the method according to the first to third embodiments as a mask.

The present invention has been described above with reference to the embodiments.
The present invention is not limited to these. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0063]

As described above, according to the present invention,
It is possible to make the intervals of the patterns arranged periodically close. Further, it becomes possible to easily form a pattern having convex corners toward the inside.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an X-ray exposure apparatus used in an embodiment of the present invention.

FIG. 2 is a plan view of a mask used in an exposure method according to a reference example and a graph showing a distribution of absorbed dose of a resist film.

FIG. 3 is a plan view of a mask used in the first embodiment and a plan view showing an arrangement of exposed portions in an exposure process.

FIG. 4 is a plan view showing the arrangement of exposed portions in the exposure process of the second embodiment.

FIG. 5 is a plan view of a mask used in a third embodiment and a plan view showing the arrangement of exposed portions after exposure.

FIG. 6 is a cross-sectional view of a mask and a substrate, a graph showing a distribution of absorbed dose of a resist film, and a cross-sectional view of a formed resist pattern, for explaining a conventional exposure method.

[Explanation of symbols]

1 SR light generator 2 vacuum container 3 orbits 4 Beam outlet 11 vacuum duct 20, 30, 31 X-ray transmission area 21,22 Upper surface of plateau 32, 33, 35 Insoluble area 50 mirror housing 51 entrance hole 52 exit hole 53 Swing mechanism 54 Reflector 56 Output side vacuum duct 57 Exit window 70 X-ray stepper 71 Semiconductor substrate 71A Substrate holding means 72 Mask 72A mask holding means

Front page continuation (51) Int.Cl. ⁷ identification code FI H01L 21/30 502G 531E (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21/027 G03F 7/20 G03F 1/08

Claims (8)

(57) [Claims] 1. A light-shielding pattern is formed on a support film, and a region where the light-shielding pattern is not arranged defines at least a plurality of first and second transmissive regions, each of which has a first shape. One transmissive region is regularly distributed at a first pitch in the first direction and at a second pitch in the second direction, and each of the plurality of second transmissive regions has a second shape. A step of preparing a mask which is regularly distributed corresponding to each of the first transmission regions, and a step of forming a mask with a fine gap on the surface of the substrate on which a photosensitive resist film is formed. And a first exposure step of partially exposing the photosensitive resist film on the substrate through the mask, and one of the mask and the substrate with respect to the other. In a direction by a distance shorter than the first pitch Let
A second exposure step of partially exposing the photosensitive resist film on the substrate through the mask; and a step of developing the exposed photosensitive resist film, the first transmission steps corresponding to each other. The area and the second transmissive area are arranged such that the pattern in which the first transmissive area is transferred and the pattern in which the second transmissive area is transferred partially overlap or contact each other in the second direction. The first pattern formed by being exposed in the first exposure step and the second pattern formed by being exposed in the second exposure step are arranged so as to be continuous with each other. The resist pattern forming method, wherein the distribution of absorbed dose of the photosensitive resist film in the first exposure step and the second exposure step, and the development sensitivity in the development step are set. 2. The method for forming a resist pattern according to claim 1, wherein the pattern in which the first pattern and the second pattern are continuous has an angle having an interior angle of about 270 °. 3. The method of forming a resist pattern according to claim 1, wherein the photosensitive resist film is a film that is exposed to X-rays and is exposed to X-rays in the first and second exposure steps. 4. The method for forming a resist pattern according to claim 1, wherein the photosensitive resist film is a negative type. 5. The resist pattern according to claim 1, wherein in the second exposure step, one of the mask and the substrate is moved with respect to the other by ½ of the first pitch. Forming method. 6. A step of forming a resist pattern on the main surface of a substrate having a main surface by the method according to claim 1, wherein the resist pattern is used as a mask to etch the substrate to a certain depth. And a fine pattern forming method. 7. A step of forming a resist pattern on the main surface of a substrate having a main surface by the method according to any one of claims 1 to 5, and using the resist pattern as a mask, ions are formed in a surface layer of the substrate. And a step of removing the resist pattern. 8. A step of forming a resist pattern on the main surface of a substrate having a main surface by the method according to claim 1, and a thin film on the main surface so as to cover the resist pattern. And a step of removing the resist pattern together with the thin film deposited on the resist pattern.