JPH11283920A - Resist pattern formation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a resist pattern with high accuracy. SOLUTION: In this resist pattern formation method, a desired pattern is formed on a resist film 4 on a substrate 5 to be worked, by using a photomask where at least two kinds of the pattern groups of different pattern dimensions or pattern densities are formed. The formation method is provided with a process for respectively deciding resist film thickness corresponding to the pattern group, corresponding to each exposure required for forming the pattern group into a desired dimension respectively and forming the resist film 4 by the decided film thickness in an area which corresponds to the pattern group on the substrate 5 to be worked, the process for exposing the pattern group to the resist film 4 on the substrate 5 to be worked by the use of the photomask next, and then the process for developing the resist film 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a resist pattern used in the manufacture of semiconductor devices and the like. Here, the resist refers to a photoresist.

[0002]

2. Description of the Related Art In a photolithography process, in order to form a fine pattern with a width smaller than the wavelength of exposure light, it is essential to apply a super-resolution exposure technique using a phase shift mask or the like.

The Levenson-type phase shift masks are, for example, disposed on a transparent substrate, light shields arranged in parallel on the transparent substrate with a predetermined gap therebetween, and every other light shield in a gap between adjacent light shields. And a phase shifter.
Further, the phase shift mask of the Levenson type has a phase difference between the exposure light transmitted through the transmission portion having no phase shifter and the exposure light transmitted through the transmission portion having the adjacent phase shifter. It is formed to be 180 °.

The above-mentioned Levenson-type phase shift mask makes it possible to form a high-density and periodic resist pattern with higher resolution among the phase shift masks. Further, when the Levenson-type phase shift mask is used, a further enlarged depth of focus (DOF) can be obtained.

[0005] However, when a Levenson-type phase shift mask is used to form, for example, a core of a semiconductor device, the core has a complicated pattern shape.
The transmission parts having the phase shifter or the transmission parts having no phase shifter may be partially adjacent to each other. As described above, the above-mentioned phase difference cannot be formed at a place where the same kind of transmission portions are adjacent to each other. Therefore, in such a place, the effect of improving the resolution can no longer be obtained. Therefore, the pattern of the cell part is usually formed in the smallest possible size,
The pattern of the core portion is formed in a relatively large size.

In general, exposure light transmitted through a photomask causes diffraction and interference, and thus varies in intensity and the like. That is, the intensity of the exposure light applied to the resist film is not uniform in all the irradiated portions, but has a distribution. Such an intensity distribution (image intensity distribution) depends on diffraction and interference conditions, that is, the pattern size and pattern density (duty ratio) of the light transmitting portion formed on the photomask.
Depending on the variety. Therefore, the conditions for exposing the resist film formed on the substrate, for example, the optimal value of the exposure amount differ depending on the size and density. Therefore, when forming the core portion and the cell portion at the same time, it may be difficult to expose both of them under optimal conditions.

[0007] Such a problem is not limited to the case where the Levenson type phase shift mask is used, and the same applies to the case where a general photomask is used. Therefore, in the manufacture of a semiconductor device, it is required to further increase a margin of an exposure condition such as an exposure amount in order to form a pattern with higher accuracy.

Prior to the exposure, it is necessary to form a resist film on the substrate. According to the spin coating method, which is a conventional resist coating method, a resist film is formed on the entire coated surface of the substrate. Therefore, the resist film covers even the alignment marks used for aligning the substrate with the photomask or the like at the time of exposure.
As a result, there is a problem that the alignment accuracy is reduced and a resist pattern cannot be formed with high accuracy.

Further, when a resist film is formed on a region where a resist film does not need to be formed like the alignment mark, it is necessary to use more resist. Therefore, there is a problem that the cost increases.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of forming a resist pattern which can form a resist pattern with high precision. Another object of the present invention is to provide a resist pattern forming method capable of further expanding a margin of exposure conditions and simultaneously improving a throughput in simultaneously forming regions having different pattern sizes and pattern densities. It is in.

Still another object of the present invention is to provide a method of forming a resist pattern capable of improving alignment accuracy at the time of exposure. Still another object of the present invention is to provide a method for forming a resist pattern which can contribute to cost reduction.

[0012]

In order to solve the above-mentioned problems, the present invention provides a method for forming a resist on a substrate to be processed by using a photomask on which at least two types of patterns having different pattern dimensions or pattern densities are formed. In a resist pattern forming method for forming a desired pattern on a film, a resist film thickness corresponding to the pattern group is determined according to each exposure amount required to form the pattern group to a desired size, and A step of forming a resist film with the determined thickness in a region corresponding to the pattern group on the substrate, and then exposing the pattern group to a resist film on the substrate to be processed using the photomask, And a step of developing the resist film.

Preferred embodiments of the above resist pattern forming method will be described below. (1) The resist film is formed by a spot coating method. (2) The photomask is formed of a light-shielding portion and an opening, and a phase shift portion in which a phase difference of light transmitted through an adjacent opening is approximately 180 degrees;
When a group of patterns having a small pattern size formed by a non-phase shift portion having a large pattern size is exposed by the phase shift portion, and a pattern group having a large pattern size is exposed by the non-phase shift portion, the resist film thickness relative to the phase shift portion is Is set to be thicker than the resist film thickness for the non-phase shift portion.

(3) The photomask is a halftone mask using a translucent phase shifter instead of a light-shielding film. The photomask for a pattern group having a small pattern size is a resist for a pattern group having a large pattern size. Set thinner than film thickness.

(4) An area where a resist having a thickness of 0 is not applied in the step of forming the resist film is formed on the alignment mark of the substrate to be processed used for alignment in the step of exposing.

(5) In the step of forming the resist film, a region where the resist having a thickness of 0 is not applied is formed in a non-exposed area of the substrate to be processed in the exposing step.

Further, the present invention provides a resist pattern forming method for forming a desired pattern on a resist film on a substrate to be processed by using a photomask on which at least two types of patterns having different pattern dimensions or pattern densities are formed. In, using a positive resist as the resist,
An area where the amount of exposure reaching the pattern is substantially equal to the square of the magnification of the amount of exposure applied to the photomask is extracted, the thickness of the resist film in that area is set to 0, and the other portions are adjusted according to the amount of exposure. Determining the resist film thickness, forming the resist film under the determined conditions, and then exposing the pattern group to a resist film on the substrate to be processed using the photomask; and And a step of developing the resist film.

In the above resist pattern forming method,
It is preferable that a region where the thickness of the resist film is set to 0 is determined in consideration of an error generated at the time of alignment.
The present invention also provides a resist pattern forming method for forming a desired pattern on a resist on a substrate to be processed using a photomask on which at least two types of pattern groups having different pattern dimensions or pattern densities are formed. Using a negative resist as a mask, the region where the exposure amount reaching the pattern is substantially zero is extracted, the thickness of the resist film in that region is set to 0, and the resist film thickness is determined according to the exposure amount in other portions. Forming the resist film under the determined conditions, exposing the pattern group to a resist film on the substrate to be processed using the photomask, and then developing the resist film And a method for forming a resist pattern.

In the above resist pattern forming method,
It is preferable that a region where the thickness of the resist film is set to 0 is determined in consideration of an error generated at the time of alignment.
Further, the present invention provides a step of forming a resist film on one main surface of the substrate, irradiating the resist film with exposure light through a photomask, exposing the resist film, and Including a step of developing the resist film,
The photomask includes a first pattern portion having a light transmitting portion, and a second pattern portion having a light transmitting portion in which at least one of a pattern size and a pattern density is different from the first pattern portion, The step of forming a resist film includes forming first and second regions respectively corresponding to the first and second pattern portions of the resist film to have different thicknesses. Provide a way.

Preferred embodiments of the above resist pattern forming method are described below. (1) The thicknesses of the first and second regions are determined by the intensity of the exposure light observed at a position on the first region corresponding to the light transmitting portion of the first pattern portion, and the thickness of the first and second regions. 2 is determined on the basis of the intensity observed at the position corresponding to the light transmitting portion of the second pattern portion on the second area.

(2) The resist film is formed by a spot coating method. (3) The first pattern portion has a Levenson-type structure, the second pattern portion has a non-Levenson-type structure, and the light transmitting portion of the first pattern portion has a pattern size of the second The second region is smaller than that of the pattern portion, and is formed thinner than the first region.

(4) The pattern size of the light transmitting portion of the first pattern portion is smaller than that of the second pattern portion, and the first region is formed thinner than the second region. To do.

Further, the present invention provides a step of selectively forming a resist film on a part of one main surface of a substrate to form a coating region and a non-coating region on one main surface of the substrate. ,
Exposing the resist film using a photomask,
And a method of forming a resist pattern comprising a step of developing the exposed resist film.

Preferred embodiments of the above resist pattern forming method will be described below. (1) The resist film is formed by a spot coating method. (2) The non-application region is surrounded by the application region.

(3) The substrate has, on one main surface, an alignment mark used for alignment in the exposing step, and the non-coating area includes the alignment mark.

(4) The application area is surrounded by the non-application area. (5) The application area is partitioned by the non-application area. (6) The substrate is a semiconductor wafer, and the application region includes a region corresponding to a plurality of semiconductor chips formed from the semiconductor wafer.

Further, the present invention provides a step of forming a resist film on one main surface of a substrate, a step of irradiating the resist film with exposure light through a photomask to expose the resist film, Including a step of developing the exposed resist film, wherein the resist film is formed using a positive resist, and one main surface of the substrate has substantially the same intensity as the intensity of exposure light applied to the photomask. The step of forming the resist film includes a first region where the same intensity is observed and a second region which is another region. The step of applying the resist on at least a part of the first region A method for forming a resist pattern including applying the resist on the second region without performing the method.

In the above resist pattern forming method,
Preferably, the resist film is formed by a spot coating method. The present invention also provides a step of forming a resist film on one main surface of the substrate, irradiating the resist film with exposure light through a photomask, exposing the resist film, and exposing the resist film to light. Developing a resist film, wherein the resist film is formed using a negative resist, and one main surface of the substrate is a first region where the observed intensity of exposure light is substantially zero. And forming a resist film on the first region without applying the resist on at least a part of the second region. And a method for forming a resist pattern, comprising applying the resist to a substrate. In the resist pattern forming method, it is preferable that the resist film is formed by a spot coating method.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. First, a first embodiment of the present invention will be described. In the first embodiment, the margin of the exposure condition is controlled by making the thickness of the resist film different between some regions and other regions according to the pattern size or pattern density of the photomask.

FIGS. 1A to 1C show an example of a method for forming a resist pattern according to the first embodiment of the present invention.
1A to 1C are cross-sectional views.
FIG. 1A shows a photomask. This photomask is a Levenson-type phase shift mask, and has a non-Levenson part (non-phase shift part) 6 and a Levenson part (phase shift part) 7.

The non-Levenson part 6 is composed of a transparent substrate 1 made of quartz or the like, and a light shielding film 2 formed on the transparent substrate 1. Further, the Levenson part 7 is provided on the transparent substrate 1.
It has a structure in which a light shielding film 2 and a phase shifter 3 are formed thereon.

In FIG. 1A, each light shielding film 2
Are formed in a band shape and are arranged in parallel with a predetermined gap. In addition, every other phase shifter 3 is arranged on the light transmitting portion between the adjacent light shielding films 2.

The Levenson part 7 is so arranged that the phase of the exposure light transmitted through the light transmission part where the phase shifter 3 is formed and the phase of the exposure light transmitted through the light transmission part where the phase shifter 3 is not formed are 180 ° different. Is formed.

Normally, the width of the light shielding film 2 in the Levenson part 7 and the gap between the respective light shielding films 2 are set to be smaller than those in the non-Levenson part 6. That is, the pattern size in the Levenson section 7 is set smaller than that in the non-Levenson section 6.

As described above, since the non-Levenson part 6 and the Levenson part 7 have different structures and pattern sizes, the conditions for diffraction or interference of exposure light are different. Therefore, the exposure light transmitted through the non-Levenson part 6 and the exposure light transmitted through the Levenson part 7 have different intensity profiles. Therefore, the optimal value of the exposure condition such as the exposure amount differs between the non-Levenson part 6 and the Levenson part 7. In other words, in the non-Levenson part 6 and the Levenson part 7,
The range of allowable exposure conditions is different.

In such a case, as shown in FIG. 1B, the resist film 4 formed on the semiconductor substrate 5 is divided into a region corresponding to the non-Levenson portion 6 and a region corresponding to the Levenson portion 7. What is necessary is just to make thickness different. As a result, it is possible to further increase the overlap of the range of the exposure condition that can be permitted in each region. this is,
This is because the optimal exposure condition or the range of the allowable exposure condition varies depending on the thickness of the resist film 4.

The thickness of one of the region corresponding to the non-Levenson portion 6 and the region corresponding to the Levenson portion 7 of the resist film 4 depends on the wavelength of the exposure light, the numerical aperture of the projection optical system, and the coherence factor. The intensity may be determined in advance based on at least one of the intensity of exposure light observed on the resist film, the optical constant of the resist, the dissolution characteristics of the resist, and the development time of the resist.

Exposure is performed under the above conditions, and further development processing is performed to obtain a resist pattern 4 having a rectangular cross section and a desired size, as shown in FIG.
Can be formed.

Here, as shown in FIG. 1B, it is extremely difficult to form a resist film 4 having a partially different film thickness by a conventional spin coating method. Therefore, in order to form the resist film 4, it is necessary to adopt a resist coating method different from a conventional general spin coating method.

As a resist coating method other than the conventional general spin coating method, the following method is known.
For example, Japanese Unexamined Patent Publication No. 7-3299 discloses a method and an apparatus for forming a coating film for making the thickness of the coating film uniform and reducing the amount of the coating liquid used. According to this, the thickness of a coating film is made uniform by spin-coating a solvent and a coating liquid (resist) on a substrate separately and under different rotation speeds. Further, by setting the amount of the coating liquid in accordance with the number of rotations, the amount of the coating liquid used is reduced.

Japanese Patent Application Laid-Open No. 7-321001 discloses a resist coating apparatus having a spray head in which a number of spray holes are arranged. The application of the resist by this apparatus is performed by spraying the resist from each spray hole toward the substrate while moving the spray head in parallel to the substrate surface of the substrate located therebelow. According to this apparatus, the amount of resist used can be reduced.

However, these disclosures aim at equalizing the thickness of the resist film or reducing the amount of the resist used, and form the resist film 4 having a partially different film thickness. It does not disclose a method.

A resist coating method for realizing this is as follows.
A spot coating method can be used. Here, the spot coating method is a coating method capable of locally applying a resist. For example, it refers to a method in which a resist is sprayed in a spot form from a large number of micropores arranged in a matrix and the amount of resist sprayed is controlled for each micropore to form a resist film.

The application of the resist using the spot application method can be performed using, for example, an apparatus shown in FIG. FIG. 2 schematically shows an example of a resist coating apparatus used in the resist pattern forming method according to the first to third embodiments of the present invention. In FIG. 2, a semiconductor substrate 21 as a substrate to be processed is placed on a stage 22. The stage 22 can move the substrate 21 in the X direction (the direction of the front and back of the paper). This movement is controlled by a stage controller 23 connected to the stage 22.

Above the stage 22, a spray head 24 in which a number of spray holes are arranged in a line is provided. The spray head 24 is connected via a dust filter 27 to a container 26 for storing a resist.
Therefore, the resist contained in the container 26 is subjected to a dust filter to remove impurities, and then the spray head 24 is removed.
And sprayed in the form of spots toward the substrate 21 from the spray holes.

The spray amount controller 25 is connected to the spray head 24 and controls the amount of resist spray from the spray holes for each spray hole. Further, the data input unit 29 is connected to the stage controller 23 and the spray amount controller 25. The data input unit 29 supplies these controllers 23 and 25 with data necessary for forming a resist film having a desired shape.

According to the resist coating apparatus described above,
The resist film can be formed on the substrate 21 by spraying the resist from each spray hole while moving the substrate 21 in the X direction. Here, by controlling the moving speed of the substrate 21, the spray amount of the resist from each spray hole, or both of them based on data supplied from the data input unit 29 to the controllers 23 and 25, the desired speed of the substrate 21 is controlled. A resist film can be formed selectively and at a desired thickness on the region.

In forming a resist film using the above apparatus, the dependence of the relationship between the pattern size and pattern density of the resist film to be formed and the exposure conditions on the thickness of the resist film is considered. It is desirable to strictly check in advance by performing a simulation, an experiment, or the like. It is desirable that the relationship between the moving speed of the substrate 21, the spray amount of the resist, and the thickness of the resist film be strictly checked in advance by performing a simulation, an experiment, or the like.

Using the apparatus described above, a resist film was formed by the following method. First, the Levenson-type phase shift mask shown in FIG.
And the line and space (L & S) of the Levenson part 7 is set to a width of 0.15 μm.
It was formed to have a thickness of μm. Note that these sizes are conversion values obtained when the image is transferred onto the substrate 5. next,
Using a device shown in FIG. 2, a resist film 4 was formed on a semiconductor substrate 5 as shown in FIG. The thickness of the resist film 4 is 0.35 μm in the area corresponding to the non-Levenson part 6.
m, and the area corresponding to the Levenson part 7 was 0.5 μm. In addition, as the resist, a chemically amplified negative resist (TDUR-N9 manufactured by Tokyo Ohka Co., Ltd.) was used.

With respect to the resist film 4 formed as described above, the relationship between the exposure conditions (exposure amount and focus) and the pattern data (pattern size) of the mask was examined under the following conditions. That is, KrF laser light (wavelength: 248 nm) is used as exposure light, the numerical aperture (NA) of the projection optical system is 0.55, the coherence factor (σ) is 0.4, and the development time of the resist film 4 is 60 seconds. And

FIG. 3A shows an ED (Exposure Defocus) diagram obtained as described above. As a conventional example, a resist film having a thickness of 0.5 μm
The relationship between the exposure conditions and the pattern data was examined in the same manner, except that the pattern was formed so as to be as follows. FIG. 3B shows an ED diagram obtained when a conventional resist pattern forming method is used.

3A and 3B, the horizontal axis indicates the defocus position, and the vertical axis indicates log ₁₀ (exposure amount). In these figures, a region surrounded by two solid lines indicates a range of exposure conditions where a deviation of a line width of a resist pattern formed using the Levenson portion 7 from a target value is within ± 10%. A region surrounded by two broken lines indicates a range of exposure conditions in which a deviation of a line width of a resist pattern formed using the non-Levenson portion 6 from a target value is within ± 10%.

In FIG. 3B, the Levenson part (L
The range of the exposure condition allowable for the & S width is 0.15 μm each and the range of the exposure condition allowable for the non-Levenson portion (the L & S width is 0.21 μm each) is small. That is, when a pattern corresponding to the Levenson portion and a pattern corresponding to the non-Levenson portion are simultaneously exposed on the resist film, the allowable exposure conditions are only the shaded regions.

On the other hand, in FIG. 3A, the range of the exposure condition allowable for the non-Levenson portion shifts to the right (because a negative resist is used as the resist),
And it is stretched in the vertical axis direction. As a result, the shaded area was greatly expanded. That is, the exposure amount and the focus margin were greatly expanded.

FIG. 4 is a graph showing the margin of the exposure condition. FIG. 4 shows the relationship between the exposure margin and the focus margin obtained from the shaded areas in FIGS. 3A and 3B. In the figure, the horizontal axis indicates the exposure amount margin, and the vertical axis indicates the focus margin.
The curve shown by the solid line shows the data obtained from FIG. 3A, and the curve shown by the broken line shows the data obtained from FIG. 3B.

As is apparent from FIG. 4, according to the present embodiment, the exposure amount margin and the focus margin are greatly improved as compared with the case where the conventional method is used. For example, when the exposure amount margin is 5%, according to this embodiment, the focus margin is improved to 4.2 times as compared with the conventional example.

As described above, the pattern size is different between the non-Levenson part 6 and the Levenson part 7, and by forming the resist film 4 with different thicknesses between the above-mentioned regions, the exposure amount and the focus margin can be expanded. . this is,
The same applies when the pattern density is different between the non-Levenson part 6 and the Levenson part 7.

As described above, a Levenson-type phase shift mask having a Levenson part and a non-Levenson part was used as a photomask, and a negative resist was used as a resist. In this case, the resist film is formed so that the region corresponding to the non-Levenson portion is thinner than the region corresponding to the Levenson portion. Thereby, compared with the case where the resist film is formed to have a uniform thickness, the exposure conditions (exposure amount and focus) required for exposing both regions simultaneously.
Is expanded. Therefore, it is possible to improve the throughput.

Although the case where the Levenson type phase shift mask is used as the photomask has been described above, a halftone type phase shift mask may be used. Hereinafter, a method of forming a resist pattern using a halftone phase shift mask will be described with reference to FIGS. Note that the description of the case where the Levenson-type phase shift mask is used, which overlaps with the above description, is omitted.

FIGS. 5A to 5C show another example of a resist pattern forming method according to the first embodiment of the present invention. FIGS. 5A to 5C are cross-sectional views. FIG. 5A shows a photomask. This photomask is a halftone type phase shift mask,
It has a structure in which a band-shaped halftone film 8 is arranged on a transparent substrate 1 such as quartz with a predetermined gap. Note that the pattern portions 10, 11, and 12 have different pattern sizes and pattern densities.

The halftone type phase shift mask shown in FIG.
L & S of the pattern portion 11 is 0.21 μm in width.
m and the line width and the space width of the pattern portion 12 are 0.21 μm and 0.19 μm, respectively. Note that these sizes are conversion values obtained when the image is transferred onto the substrate 5. Next, using the apparatus shown in FIG. 2, a resist film 9 was formed on the semiconductor substrate 5 as shown in FIG. 5B by a method similar to that described in the first embodiment. The thickness of the resist film 9 is set to 0.6 μm in a region corresponding to the pattern portion 10,
The area corresponding to the pattern section 11 was 0.3 μm, and the area corresponding to the pattern section 12 was 0.1 μm. In addition,
As the resist, a chemically amplified positive resist (wavelength 24
An optical constant at 8 nm of n = 1.78 and k = 0.02) was used.

With respect to the resist film 9 formed as described above, a resist pattern shown in FIG. 5C is formed, and the exposure conditions (exposure amount and focus) and the pattern data (pattern size and pattern density) of the mask are formed. ) Were examined under the following conditions. That is, Kr is used as the exposure light.
F laser light (wavelength: 248 nm) and NA = 0.
6, σ = 0.75, and the development time of the resist film 4 was 90 seconds.

FIG. 6A shows an ED (Exposure Defocus) diagram obtained as described above. Further, as a conventional example, a resist film having a thickness of 0.6 μm
The relationship between the exposure conditions and the pattern data was examined in the same manner, except that the pattern was formed so as to be as follows. FIG. 6B shows an ED diagram obtained when a conventional resist pattern forming method is used.

6A and 6B, the horizontal axis indicates the defocus position, and the vertical axis indicates log ₁₀ (exposure amount). In these figures, a region surrounded by two solid lines indicates a range of exposure conditions in which a deviation of a line width of a resist pattern formed using the pattern unit 10 from a target value is within ± 10%. The area surrounded by two shorter broken lines in which the individual dashes are shorter is the pattern portion 1
1 shows a range of exposure conditions in which the deviation of the line width of the resist pattern formed using No. 1 from the target value is within ± 10%. A region surrounded by two longer dashed lines in which individual dashes are longer defines an exposure condition range in which a deviation of a line width of a resist pattern formed using the pattern unit 12 from a target value is within ± 10%. Is shown.

In FIG. 6B, the pattern portion 10
(The width of the L & S is 0.25 μm) and the allowable range of the exposure condition for the pattern portion 11 (the width of the L & S is 0.21 μm) and the pattern portion 12 (the line width is 0.21 μm). 0.21μ
m, the space width is 0.19 μm), and the overlap with the range of the exposure conditions that can be accepted is slight. That is, when simultaneously exposing the resist films to the patterns corresponding to the pattern portions 10, 11, and 12, respectively, the allowable exposure conditions are only the shaded regions.

On the other hand, in FIG.
Since 1 and 12 are formed thinner, the range of allowable exposure conditions for the pattern portions 11 and 12 is shifted to the left and stretched in the vertical axis direction. As a result, the shaded area was greatly expanded. That is, the exposure amount and the focus margin were greatly expanded.

FIG. 7 is a graph showing the exposure margin and the focus margin. FIG. 7 shows the relationship between the exposure margin and the focus margin obtained from the hatched areas in FIGS. 6A and 6B,
The horizontal axis indicates the exposure amount margin, and the vertical axis indicates the focus margin. The curve shown by the solid line shows the data obtained from FIG. 6A, and the curve shown by the broken line shows the data obtained by FIG.
Shows the data obtained from.

As is apparent from FIG. 7, according to the present embodiment, the exposure amount margin and the focus margin are greatly improved as compared with the case where the conventional method is used. For example, when the exposure margin is 5%, the focus margin is 0 according to the conventional example. In contrast, according to the present embodiment, a focus margin of about 0.4 μm was obtained.

As described above, a halftone phase shift mask having a plurality of pattern portions having different pattern sizes or pattern densities was used as a photomask, and a positive resist was used as a resist. In this case, the resist film
The region corresponding to the pattern portion having the smaller size or the lower ratio of removing the resist film is thinner than the region corresponding to the pattern portion having the larger size or the higher ratio of removing the resist film. It is formed as follows. As a result, the margin of the exposure conditions (exposure amount and focus) required for simultaneously exposing the above three regions can be expanded as compared with the case where the resist film is formed to have a uniform thickness. That is, it is possible to improve the throughput.

As described above, the Levenson type phase shift mask or the halftone type phase shift mask is used as the photomask, but other general photomasks used for forming a resist pattern can also be used. For example, a phase shift mask such as a self-alignment type phase shift mask or an edge light shielding type phase shift mask can be used. Alternatively, a light-blocking mask or the like can be used.

Next, a second embodiment of the present invention will be described. In the second embodiment, a resist film is selectively applied to a part of the substrate by applying the resist on a part of the substrate and applying the resist to the other region without applying the resist. Is formed.

FIG. 8 is a view schematically showing an example of a method for forming a resist pattern according to the second embodiment of the present invention. FIG. 8 is a plan view. In FIG. 8, reference numeral 15 indicates an alignment mark area of the semiconductor wafer, and reference numeral 16 indicates a pattern area of the semiconductor wafer. Conventionally, when a resist film is formed on the pattern region 16, the resist film is also formed on the alignment mark region 15. Alignment mark area 15
If a resist film is formed thereon, an error occurs in measuring the position of the alignment mark. Therefore, a resist pattern cannot be formed with high accuracy.

In this embodiment, the resist is applied only to a part of the wafer. That is, here
The resist is applied on the pattern area 16 without applying the resist on the alignment mark area 15. Therefore, the resist film 17 is selectively formed on the pattern region 16.

When the resist film 17 is selectively formed on the pattern region 16 as described above, the alignment between the wafer and the photomask can be performed with high accuracy. Therefore, by performing exposure and development processing,
A resist pattern can be formed at a desired position in the pattern region 16.

The apparatus shown in FIG. 2 can be used to selectively apply a resist only on a partial area of a wafer. That is, the resist may be sprayed on the pattern area 16 without spraying the resist on the alignment mark area 15 using the apparatus shown in FIG.

As described below, the alignment accuracy was compared between the method for forming a resist pattern according to the second embodiment of the present invention and the conventional method. FIG. 9 (a)
FIG. 9B is a plan view showing an alignment mark arranged in the alignment mark area, and FIG.
9A is a cross-sectional view of the alignment mark shown in FIG.

In the alignment mark area 15 shown in FIG. 8, rectangular alignment marks 18 of 4 μm × 2 μm are actually arranged in a line as shown in FIG. 9A. This alignment mark 18 is a convex part having a height of 0.5 μm, as shown in FIG.

A resist was applied to the wafer except for the alignment mark 18 and its vicinity by the above-described method, and a resist film 17 was selectively formed on the pattern region 17 as shown in FIG.

Next, the wafer having the resist film 17 formed thereon was placed on a stage of an exposure apparatus. Further, while moving the stage, the alignment mark 18 is irradiated with a laser beam having a wavelength of 633 nm, and the scattered light is
Alignment was performed by detecting with.

According to the conventional resist pattern forming method, when the resist film 17 is formed on the pattern region 16, the resist film is also formed on the alignment mark region 15. In this case, ideally, FIG.
As shown in FIG.
8 should be formed conformally. However, it is extremely difficult to form the resist film 17 conformally. That is, the resist film 17
It is formed asymmetrically with respect to the center line of the alignment mark 18 shown by the broken line.

According to the LSA (Laser Scan Alignment) method, the alignment with the base is performed by analyzing the profile of the scattered light from the alignment mark 18. When the resist film 17 was formed by a conventional method, the resist film 17 was formed asymmetrically with respect to the center line of the alignment mark 18. Therefore, FIG.
As shown in the figure, the profile 31 to be detected is significantly displaced from the profile 32 to be originally detected and has a distorted shape. Therefore, according to the conventional method, alignment cannot be performed with high accuracy, and a resist pattern cannot be formed with high accuracy.

On the other hand, as shown in FIG.
When a resist film is selectively formed on a pattern region (not shown) without applying a resist on the alignment mark 18 and its vicinity, scattered light from the alignment mark 18 is affected by the resist film. There was nothing. That is, as shown in FIG. 10D, the detected profile 33 coincides with the profile to be detected. Therefore, according to the above method, alignment can be performed with high accuracy, and as a result, a resist pattern can be formed with high accuracy.

As described above, it has been described that the alignment accuracy can be improved by selectively applying a resist on a part of the substrate, but it is also possible to reduce the cost. .

The above method is not limited to the formation of a resist pattern. The above method can be applied to the formation of other types of films, for example, an antireflection film, and the same effects as described above can be obtained.

FIG. 11A schematically shows a plan view of a semiconductor wafer on which a resist film has been formed using a conventional resist pattern forming method. FIG. 11B schematically shows a plan view of a semiconductor wafer on which a resist film has been formed using the method for forming a resist pattern according to the second embodiment of the present invention.

In FIGS. 11A and 11B, reference numeral 35 indicates a semiconductor wafer.
A resist film 36 is formed thereon. Note that FIG.
In (a) and (b), reference numeral 37 indicates an exposure shot area. The exposure shot areas 37 are arranged as shown in FIGS. 11A and 11B so that the maximum number of semiconductor chips can be obtained from the semiconductor wafer 35. The exposure of the resist film 36 is performed by sequentially exposing each exposure shot area 37.

According to the conventional method, as shown in FIG. 11A, the resist film 36 is formed on an area other than the exposure shot area 37. On the other hand, according to the method according to the second embodiment of the present invention, the resist film 36 can be selectively formed on the exposure shot region 37 as shown in FIG. That is, according to the second embodiment of the present invention, it is possible to reduce the amount of the resist used.

The apparatus shown in FIG. 2 can be used to selectively apply the resist only on the exposure shot area 37. That is, using the apparatus shown in FIG.
The resist may be sprayed on the exposure shot area 37 without spraying the resist on an area other than the exposure shot area 37.

Next, a third embodiment of the present invention will be described. In the third embodiment, a resist film is selectively formed on a part of a substrate based on the intensity distribution of exposure light observed on the resist film.

FIG. 12 schematically shows an example of a method for forming a resist pattern according to the third embodiment of the present invention. In FIG. 12, the photomask 41, the resist pattern 54, and the resist film 58 are each illustrated as a cross-sectional view.

The photomask 41 has a structure in which a light shielding pattern 43 is formed on a transparent substrate 42. Further, the photomask 41 is constituted by a pattern portion R _A, a large pattern portion R _B of the pattern size than the pattern portion R _A.

Reference numeral 50 is a graph showing the intensity distribution of the exposure light observed on the resist film when the resist film is irradiated with the exposure light via the photomask 41. In the figure, the light intensity I on the vertical axis is shown as a relative value. Note that the light intensity is set to 1 when the amount of exposure light observed on the resist film is substantially equal to the amount of exposure light observed on the photomask 41.

[0093] As shown in the graph 50, the intensity profile 51 of the exposure light which is observed in the region corresponding to the pattern portion R _A of the resist film, exposure light is observed in a region corresponding to the pattern portion R _B of the resist film Strength profile 52
Is very different.

According to this embodiment, the resist pattern 54 is formed by the following method. Here, a case where the resist pattern 54 is formed using a positive resist will be described as an example.

First, a resist film 5 is formed on a substrate (not shown).
8 is formed. Here, the resist film 58 is, in the region corresponding to the pattern portion R _B, not formed in a region equal to the intensity I is approximately 1. The width of the opening of the resist film 58 B 'is set narrowly than the width B of the opening corresponding to the pattern portion R _B of the resist pattern 54. This allows
The effect of the alignment error can be reduced.

Next, the resist film 58 is exposed using the photomask 41. Further, the exposed resist film 58
Is developed to obtain a resist pattern 54.
According to the method described above, the resist pattern corresponding to the pattern portion _RA having the smaller pattern size is formed by forming a resist film having a uniform thickness on the entire surface of the substrate corresponding to the pattern portion _RA . On the other hand, the pattern size resist pattern corresponding to the larger pattern portion R _B is formed by forming a selectively resist film on a portion of the area on the substrate. Therefore, according to the above-described method, the amount of the resist used can be reduced.

According to the above-described method, a resist is applied to the entire surface of the region where a finer resist pattern is to be formed. Therefore, the resist pattern shape is unlikely to be deteriorated by using the spot coating method.
That is, according to the above-described method, it is possible to form a resist pattern with high accuracy and reduce costs.

[0098] The case where a positive resist is used as the resist has been described as an example, but a negative resist can also be used. In this case, a region that does not form a resist film 58, in the region corresponding to the pattern portion R _B, may be equal area to the intensity I is approximately 0.

In the above-described method, a region corresponding to the pattern portion _RA of the resist film 58 may be formed to have different thicknesses in a part of the region and another part. This makes it possible to expose both portions under optimal exposure conditions, and to form a resist pattern with high accuracy.

In the method according to the third embodiment, an apparatus shown in FIG. 2 can be used for forming a resist film. The method of forming a resist film using this apparatus is the same as that described in the first and second embodiments. Therefore, the description is omitted.

In the first to third embodiments described above, the apparatus shown in FIG. 2 was used for forming the resist film.
Other devices can be used. That is, any resist coating apparatus can be used as long as the resist film can be formed with a desired thickness and a desired pattern.

[0102]

As described above, according to the resist pattern forming method of the present invention, the thickness of the resist film is different between some regions and other regions according to the pattern size or pattern density of the photomask. Formed. The optimum exposure conditions (exposure amount and focus) or the range of allowable exposure conditions vary depending on the thickness of the resist film. Therefore, it is possible to expose both regions under optimal conditions. Alternatively, it is possible to further increase the overlap of the range of the exposure condition that can be permitted in each region.

Therefore, according to the resist pattern forming method of the present invention, a resist pattern can be formed with high accuracy. Further, it is possible to improve the throughput.

Further, according to the method of forming a resist pattern of the present invention, a resist is applied on a partial area of a substrate without applying a resist on another area, thereby forming a resist on the partial area. On the other hand, a resist film is selectively formed. Therefore, by forming the resist film without applying the resist on the alignment mark, the alignment accuracy at the time of exposure can be improved.
Further, by selectively forming the resist film on the exposure shot region, the amount of the resist used can be reduced, and as a result, the cost can be reduced.

Further, according to the resist pattern forming method of the present invention, a resist film is selectively formed on a part of the substrate based on the intensity distribution of exposure light observed on the resist film. Therefore, the amount of the resist used can be reduced, and as a result, the cost can be reduced. Further, according to the method for forming a resist pattern of the present invention, a resist is applied to the entire surface on a region where a finer resist pattern is formed. Therefore, the resist pattern shape is unlikely to be deteriorated by using the spot coating method. That is, a resist pattern can be formed with high accuracy.

[Brief description of the drawings]

FIGS. 1A to 1C are cross-sectional views schematically showing an example of a method for forming a resist pattern according to a first embodiment of the present invention.

FIG. 2 is a view schematically showing an example of a resist coating apparatus used in a resist pattern forming method according to the first to third embodiments of the present invention.

FIG. 3A is a view showing E obtained by using an example of a method for forming a resist pattern according to the first embodiment of the present invention;
FIG. 3D is an ED diagram obtained when a conventional resist pattern forming method is used.

FIG. 4 is a graph showing a relationship between an exposure amount margin and a focus margin obtained when an example of the method for forming a resist pattern according to the first embodiment of the present invention is used.

FIGS. 5A to 5C are cross-sectional views schematically showing another example of the method for forming a resist pattern according to the first embodiment of the present invention.

FIG. 6A is an ED diagram obtained when another example of the method for forming a resist pattern according to the first embodiment of the present invention is used, and FIG. 6B is a diagram using a conventional method for forming a resist pattern. ED figure obtained when there is.

FIG. 7 is a graph showing a relationship between an exposure amount margin and a focus margin obtained when another example of the resist pattern forming method according to the first embodiment of the present invention is used.

FIG. 8 is a plan view schematically showing an example of a method for forming a resist pattern according to a second embodiment of the present invention.

FIG. 9A is a plan view showing an alignment mark arranged in an alignment mark area of a substrate used in a resist pattern forming method according to a second embodiment of the present invention, and FIG. 9) of alignment mark shown in a)
The figure which shows roughly the cross-section along the B-9B line.

10A is a cross-sectional view schematically illustrating an alignment mark when a conventional and ideal resist pattern forming method is used, and FIG. 10B is a cross-sectional view when a conventional resist pattern forming method is used. A diagram schematically showing a scattered light profile from the detected alignment mark,
(C) is a cross-sectional view schematically showing an alignment mark when the resist pattern forming method according to the second embodiment of the present invention is used, and (d) is a resist according to the second embodiment of the present invention. The figure which shows schematically the scattered light profile from the alignment mark detected when the pattern formation method is used.

FIG. 11A is a front view schematically showing a semiconductor wafer on which a resist film has been formed by using a conventional resist pattern forming method, and FIG. 11B is a resist pattern according to a second embodiment of the present invention; FIG. 2 is a front view schematically showing a semiconductor wafer on which a resist film has been formed by using a forming method.

FIG. 12 is a view schematically showing an example of a method for forming a resist pattern according to a third embodiment of the present invention.

[Explanation of symbols]

 1, 42: Transparent substrate 2: Light-shielding film 3: Phase shifter 4, 9, 17, 36, 58: Resist film 5: Substrate 6: Non-phase shift portion 7: Phase shift portion 8: Halftone film 10-12: Pattern Unit 21 Semiconductor substrate 22 Stage 23 Stage controller 24 Spray head 26 Container 27 Dust filter 25 Spray amount controller 29 Data input unit 15 Alignment mark area 16 Pattern area 18 Alignment marks 31 to 33 51, 52: Profile 35: Semiconductor wafer 37: Exposure shot area 41: Photomask 43: Light shielding pattern 50: Graph 54: Resist pattern

Claims (9)

[Claims] 1. A resist pattern forming method for forming a desired pattern on a resist film on a substrate to be processed using a photomask on which at least two types of pattern groups having different pattern dimensions or different pattern densities is formed. A resist film thickness corresponding to the pattern group is determined in accordance with each exposure amount required to form each group to a desired size, and the determined film thickness is determined in an area corresponding to the pattern group on the substrate to be processed. Forming a resist film on the substrate, exposing the pattern group to a resist film on the substrate to be processed using the photomask, and then developing the resist film. A method for forming a resist pattern. 2. The method according to claim 1, wherein the resist film is formed by a spot coating method. 3. A phase shift section in which the photomask is formed of a light-shielding section and an opening, and a phase difference of light transmitted through an adjacent opening is substantially 180 degrees, and the phase difference is substantially 0 degrees. When a pattern group having a small pattern dimension is exposed at the phase shift section, and a pattern group having a large pattern dimension is exposed at the non-phase shift section,
2. The method according to claim 1, wherein the thickness of the resist for the phase shift portion is set to be larger than the thickness of the resist for the non-phase shift portion. 4. The photomask is a halftone mask using a translucent phase shifter instead of a light-shielding film. The photomask is a resist film for a pattern group having a small pattern dimension and a resist film for a pattern group having a large pattern dimension. 2. The method according to claim 1, wherein the thickness is set smaller than the thickness. 5. A process according to claim 1, wherein an area of the resist film is formed on the alignment mark of the substrate to be used for alignment in the exposing step, where the resist is not applied in the step of forming the resist film. 5. The method for forming a resist pattern according to any one of 1 to 4. 6. The step of forming the resist film,
The method according to claim 1, wherein, in the exposing step, a region where a resist having a thickness of 0 is not applied is formed in a non-exposed area of the substrate to be processed. 7. A resist pattern forming method for forming a desired pattern on a resist film on a substrate to be processed by using a photomask on which at least two types of pattern groups having different pattern dimensions or different pattern densities is formed. A region where the exposure amount reaching the pattern is substantially equal to the square of the magnification of the exposure amount irradiated on the photomask, and the resist film thickness in that region is set to 0, The step of determining the resist film thickness in accordance with the exposure amount, forming the resist film under the determined conditions, and then exposing the pattern group to the resist film on the substrate to be processed using the photomask Forming a resist pattern, and then developing the resist film. 8. A resist pattern forming method for forming a desired pattern on a resist on a substrate to be processed using a photomask on which at least two types of patterns having different pattern dimensions or different pattern densities are formed, Using a negative resist, a region where the exposure amount reaching the pattern is substantially zero is extracted, the thickness of the resist film in that region is set to zero, and the resist film thickness is determined for other parts according to the exposure amount. Forming the resist film under the determined conditions, and then exposing the pattern group to a resist film on the substrate to be processed using the photomask, and then developing the resist film. A method for forming a resist pattern, comprising: 9. A region where the thickness of the resist film is set to 0,
9. The method according to claim 7, wherein the determination is performed in consideration of an error generated during alignment.