JP3115517B2 - Method of forming resist 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 pattern forming method used for manufacturing a semiconductor device or the like.
The present invention relates to a method for forming a resist pattern in a lithography process using an ultraviolet ray having a wavelength of 450 nm or less, an X-ray, a charged beam, an i-ray (365 nm), a KrF excimer laser (248 nm), an ArF excimer laser (193 nm) or the like as an exposure energy source. .

[0002]

2. Description of the Related Art In recent years, the miniaturization of semiconductor devices has been further advanced, and the design rule has become 0.25 μm at the development level. Therefore, the specification of the line width of a resist pattern has become stricter than in the past. ing. Conventionally, measures for actively reducing dimensional variations in a lithography process have been mainly taken for dimensional variations in a chip and dimensional variations in a wafer. The main causes of these dimensional variations are the multiple interference effect in the resist film and the reflected light from the substrate. For these, it is possible to reduce the variance by providing an antireflection film on the front or lower surface of the resist film. And
Further, it can be reduced by using a surface resolution process such as a silylation process.

However, dimensional variations between wafers (including lots) have not received much attention in the past.
As the specifications of the line width of the resist pattern become strict, it has become necessary to reduce the dimensional variation of the line width between wafers, and several reports have been made recently.

The dimensional variation in line width between wafers is caused by variations in the substrate structure, for example, variations in the thickness of a resist film formed on the substrate, or due to an exposure apparatus. The difference between the exposure energy actually absorbed by the resist film and the difference between the intended exposure focus and the exposure focus actually applied to the exposure of the resist film. It is considered that the dimensional variation of the line width between wafers occurs due to the difference in the exposure conditions including the exposure focus and the exposure focus.

As an example of a report on dimensional variations in line width between wafers, recently, IBM's John St.
urvantant et al. (1994 SP
IEVol. 2196 p352-359). this is,
Irradiate the latent image generated on the surface of the resist film with laser light,
The intensity of the diffracted light is detected. The relationship between the intensity of the diffracted light and the line width of the resist pattern is determined in advance, and the desired line width is determined from the intensity of the diffracted light detected during or after the heat treatment (PEB). The development time is calculated so as to obtain the following, and the result is fed forward to the development step, thereby controlling the line width of the resist pattern.

As an example of a report on reduction of dimensional variation in line width between wafers using the above-described surface resolution process, recently, Shoa of the University of New Mexico has been reported.
ibZaidi et al. (1994 SPI
E Vol. 2196 p341-351). By irradiating a laser beam to the latent image formed on the surface of the resist film and detecting the intensity of the diffracted light, predicting the line width of the resist pattern, correcting the process parameters of the surface resolution process, This is to compensate for the line width.

[0007]

However, each of the above methods requires a repetitive pattern because of the use of diffracted light. For this reason, it is necessary to provide a repeating pattern or to use a repeating pattern in the device structure, and in any case, there is a problem that the pattern of the latent image is restricted.

There is also a problem that the intensity of the diffracted light becomes inaccurate due to the influence of the laser light transmitted through the resist film due to the reflected light from the base and the like.

In view of the above, the present invention predicts the line width of a resist pattern without using diffracted light, thereby eliminating dimensional variations in line width between wafers.
An object is to obtain a stable line width of a resist pattern.

[0010]

In order to achieve the above object, according to the first aspect of the present invention, there is a correlation between the line width of a resist pattern and exposure conditions actually applied to exposure of a resist film. Along with focusing on the fact that there is also a correlation between the height of the latent image formed on the resist film after exposure and the exposure conditions actually applied to the exposure of the resist film, the actual exposure conditions are used as parameters. , The line width of the resist pattern is predicted from the latent image height.

[0011] Specifically, a solution taken by the invention of claim 1 includes a resist film forming step of forming a resist film on a substrate, an exposure step of exposing a predetermined pattern to the resist film, A developing step of developing the exposed resist film to form a resist pattern; and a method of forming a resist pattern, the height of a latent image formed on the resist film after exposure and the line width of the resist pattern in the developing step. A first correlation between the line width of the resist pattern at a predetermined value of the parameter affecting the first pattern, and a relationship between the predetermined value of the parameter and the line width of the resist pattern for each exposure condition consisting of exposure energy or exposure focus. Measuring the height of the latent image actually formed on the exposed resist film; And obtaining a latent image height, the first
Calculating a predicted line width that is a line width of a resist pattern corresponding to the latent image height and a predetermined value of the parameter, from the second correlation,
Determining a predicted exposure condition that is the exposure condition corresponding to the predetermined value of the parameter and the predicted line width,
Obtaining a value of the parameter corresponding to a desired line width of the resist pattern and the predicted exposure condition from the second correlation, and forming a resist pattern based on the value of the parameter. Is what you do.

According to the first aspect of the present invention, the height of the latent image formed on the resist film after the exposure and the line width of the resist pattern at a predetermined value of a parameter which influences the line width of the resist pattern in the developing step are set. First
When the predicted line width corresponding to the latent image height and the predetermined value of the parameter is obtained from the first correlation, the line width can be predicted almost exactly.

Next, from a second correlation between the predetermined value of the parameter and the line width of the resist pattern for each exposure condition, a predicted exposure condition corresponding to the predetermined value of the parameter and the predicted line width is obtained. Since the predicted line width is substantially accurate, the exposure conditions actually applied to the exposure of the resist film can be predicted almost accurately.

Therefore, when the values of the parameters corresponding to the desired line width of the resist pattern and the predicted exposure conditions are obtained from the second correlation, the parameters corresponding to the exposure conditions actually applied to the exposure of the resist film are obtained. Can be obtained.

According to a second aspect of the present invention, a limitation is added to the configuration of the first aspect that a parameter affecting the line width of the resist pattern in the developing step is a developing time.

A third aspect of the present invention provides a resist film forming step of forming a resist film on a substrate, an exposing step of exposing a predetermined pattern to the resist film, and a step of exposing the predetermined pattern. A resist pattern forming method including a heat treatment step of performing a heat treatment on a resist film and a resist pattern forming step of developing a resist pattern subjected to the heat treatment to form a resist pattern is formed on the resist film after exposure. The first correlation between the height of the latent image and the line width of the resist pattern at a predetermined value of a parameter that affects the line width of the resist pattern in the heat treatment step, and, for each exposure condition consisting of exposure energy or exposure focus Calculating a second correlation between a predetermined value of the parameter and a line width of the resist pattern; Determining the latent image height by measuring the height of the latent image actually formed on the exposed resist film; and determining the latent image height and the parameter from the first correlation. Calculating a predicted line width which is a line width of the resist pattern corresponding to the predetermined value, and a predicted exposure condition which is the exposure condition corresponding to the predetermined value of the parameter and the predicted line width from the second correlation. Obtaining a value of the parameter corresponding to a desired line width of the resist pattern and the predicted exposure condition from the second correlation, and performing a heat treatment on the resist film based on the value of the parameter. Is provided.

According to the third aspect of the present invention, an effect is obtained in which the parameters affecting the line width of the resist pattern in the developing step of the first aspect are replaced with the parameters affecting the line width of the resist pattern in the heat treatment step. Can be

According to a fourth aspect of the present invention, there is added to the configuration of the third aspect, that a parameter affecting the line width of the resist pattern in the heat treatment step is a processing time or a processing temperature.

A solution taken by the invention of claim 5 includes a resist film forming step of forming a resist film on a substrate, an exposure step of exposing a predetermined pattern to the resist film, and a step of exposing the predetermined pattern. A resist pattern forming method comprising a modified film forming step of forming a surface modified film on the resist film, and a developing step of developing the resist film having the surface modified film formed thereon to form a resist pattern. A first correlation between the height of the latent image formed on the film and the width of the surface modified film at a predetermined value of a parameter affecting the width of the surface modified film in the modified film forming step, and exposure energy or exposure Determining a second correlation between a predetermined value of the parameter and the width of the surface modification film for each exposure condition including a focus; And obtaining a latent image height by measuring the height of a latent image formed on the film, from the first correlation,
Obtaining a predicted modification film width which is a width of the surface modification film corresponding to the latent image height and the predetermined value of the parameter; and, from the second correlation, a predetermined value of the parameter and the predicted modification film width. Calculating a predicted exposure condition that is the exposure condition corresponding to the second correlation; and obtaining a value of the parameter corresponding to the desired width of the surface-modified film and the predicted exposure condition from the second correlation, And forming a surface modification film based on the values.

According to the fifth aspect of the present invention, the distance between the height of the latent image formed on the resist film after the exposure and the line width of the resist pattern at a predetermined value of the parameter affecting the width of the surface modification film in the modification film forming step. Since there is a first correlation, when the predicted modified film width corresponding to the latent image height and the predetermined value of the parameter is obtained from the first correlation, the width of the modified film is almost accurately predicted. be able to.

Next, from the second correlation between the predetermined value of the parameter for each exposure condition and the width of the surface modification film,
When the predicted exposure condition corresponding to the predetermined value of the parameter and the predicted modified film width is obtained, the predicted modified film width is almost accurate, so that the exposure condition actually applied to the exposure of the resist film is almost accurately predicted. be able to.

Therefore, when the value of the parameter corresponding to the desired line width of the resist pattern and the predicted exposure condition is obtained from the second correlation, the parameter corresponding to the exposure condition actually applied to the exposure of the resist film is obtained. Can be obtained.

According to a sixth aspect of the present invention, in addition to the structure of the fifth aspect, there is added a limitation that a parameter affecting the width of the surface modified film in the modified film forming step is a processing time or a processing temperature.

According to a seventh aspect of the present invention, there is added a limitation that the height of the latent image is determined by an atomic force microscope to the constitutions of the first to sixth aspects.

[0025] According to another aspect of the present invention, a resist pattern forming method is obtained by developing the width of a surface modification film formed on a resist film and developing the resist film on which the surface modification film is formed. A step of obtaining a correlation between the line width of the resist pattern, a step of forming an actual resist film on the substrate, a step of exposing a predetermined pattern to the actual resist film, A step of forming an actual surface modification film on the surface of the exposed actual resist film, and measuring the width of the actual surface modification film, and determining the width of the actual surface modification film and the corresponding resist from the correlation. Determining a predicted line width, which is the line width of the pattern, and determining whether the predicted line width is within an allowable range of a desired line width, and when the predicted line width is within an allowable range, While forming a resist pattern by developing the resist film in the when the predicted linewidth is not within the allowable range is to a configuration and a process of removing the actual resist film.

According to the present invention, there is a correlation between the width of the surface modification film formed on the resist film and the line width of the resist pattern obtained by developing the resist film on which the surface modification film is formed. Since there is a relationship, when the line width of the resist pattern corresponding to the actual width of the surface modification film is obtained from the correlation, the line width can be predicted almost accurately.

When the predicted line width is within the allowable range, the actual resist film is developed. On the other hand, when the predicted line width is not within the allowable range, the actual resist film is removed. A defective resist film can be removed without going through an etching step for the resist film.

According to a ninth aspect of the present invention, in the configuration of the fifth, sixth or eighth aspect, the resist film is a resist film that generates an acid when subjected to pattern exposure, and the surface modification film is formed by the pattern exposure. After absorbing water in the exposed portion of the resist film, by supplying water and a metal alkoxide to the surface of the exposed portion that has absorbed the water, it is a metal oxide film formed on the surface of the exposed portion It is to be added.

The invention of claim 10 is the invention of claim 5, 6, or 8.
In the above structure, the surface modification film is a silylated film formed on the surface of the unexposed portion of the resist film that has been subjected to pattern exposure.

[0030] The invention of claim 11 adds the limitation that the width of the surface modification film is determined by an atomic force microscope to the constitution of claims 8 to 10.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a resist pattern forming method according to one embodiment of the present invention will be described with reference to the drawings. In the following embodiments, the exposure condition will be described by taking an exposure energy as an example. However, the exposure condition may include an exposure focus in addition to the exposure energy.

(Embodiment 1) FIG. 1 is a view for explaining an outline of a process sequence of a resist pattern forming method according to a first embodiment of the present invention. As shown in FIG.
After a resist film is formed on a substrate, a predetermined pattern is exposed on the resist film, and a heat treatment (PEB) is performed on the resist film on which the pattern has been exposed. Measure the height. And
A development time is determined from a correlation between a previously obtained latent image shape and a pattern size after development, and the resist film is developed based on the development time to form a resist pattern having high dimensional stability. Is what you do.

Hereinafter, a method for forming a resist pattern according to the first embodiment will be described in detail with reference to FIGS. In the first embodiment, the development time is selected as a parameter that affects the line width of the resist pattern in the development process. However, the parameter is not limited to the development time, and the temperature, concentration, and the like of the developer in the development process are determined. It is also possible to select.

In the first step, a first correlation between the height of the latent image formed on the resist film after exposure and the line width of the resist pattern at a predetermined developing time is determined by the following procedure.

First, exposure energy (exposure intensity × time)
And the height of the latent image.

A resist “ASKA” for KrF excimer laser is deposited on a silicon substrate to a thickness of 0.98 μm to form a resist film.
22 to 38 mJ / using an F excimer laser stepper
Exposure was performed while changing the exposure energy between cm ² . Next, the resist film is subjected to a heat treatment at a temperature of 95 ° C. for 90 seconds, and then the height of the latent image of the 0.25 μmL / S (line and space) pattern formed on the surface of the resist film is measured. The measurement was performed using a force microscope (AFM).

FIG. 2 shows a schematic structure of a cross-sectional shape of the resist film surface observed by AFM. In FIG. 2, Ha indicates the height of the latent image in the exposed portion, and Hb indicates the height of the latent image in the unexposed portion. In FIG. 2, the latent image heights Ha and Hb are emphasized for easy understanding of the latent image height.

FIG. 3 shows the exposure energy and the latent image heights Ha and H.
This shows that there is a certain relationship between the exposure energy and the height of the latent image. In FIG. 3, the relationship between the exposure energy and the latent image height is obtained by using the center line pattern among a plurality of line patterns, but this relationship is the same for other line patterns.

Next, the relationship between the exposure energy and the line width of the resist pattern formed during a predetermined development time is determined.

In the same manner as described above, the resist film exposed by changing the exposure energy is applied to a developing solution: NMD-3 (trade name:
Using TMAH = 2.38%), development was performed for a predetermined development time, for example, a development time of 60 seconds to form a resist pattern, and the line width of the formed 0.25 μmL / S resist pattern was measured.

FIG. 4 shows the relationship between the exposure energy and the line width of the resist pattern when the development is performed for 60 seconds. It can be seen that there is a relationship between the exposure energy and the line width of the resist pattern. .

FIG. 5 shows the relationship between the exposure energy and the latent image height, and the relationship between the exposure energy and the line width of the resist pattern when development is performed for a predetermined development time, for example, 60 seconds. Next, a first correlation between the height of the latent image formed on the resist film after the exposure and the line width of the resist pattern after the development for 60 seconds is obtained.

In the second step, a second correlation between the development time for each exposure energy and the line width of the resist pattern is determined. The second correlation is to control the line width to a predetermined value by changing the development time when the line width of the resist pattern is out of specifications when the line width of the resist pattern is predicted from the measured latent image height. Is necessary for

FIG. 6 shows an example in which the exposure energy is 2
The second correlation between the development time at 6, 30, 34 mJ / cm ² and the line width of the resist pattern is shown.

In the third step, the height of the latent image formed on the resist film when pattern exposure is actually performed is determined to determine the height of the latent image. The method for obtaining the latent image height is the same as that described above, and will not be described here.

In a fourth step, a predicted line width which is a line width of the resist pattern corresponding to the measured latent image height and a predetermined developing time, for example, a developing time of 60 seconds, is obtained from the first correlation. . Hereinafter, a method of calculating a predicted line width corresponding to the measured latent image height and a predetermined development time, for example, a development time of 60 seconds, from the first correlation will be specifically described. That is, the latent image height Ha after PEB
As a result, when the latent image height Ha is 63 nm, the estimated line width of the resist pattern when the development is performed for a development time of 60 seconds is 0.31 μm from the relationship shown in FIG.

As a fifth step, from the second correlation,
A predicted exposure energy (corresponding to exposure energy actually absorbed by the resist film), which is an exposure energy corresponding to a predetermined development time and a predicted line width, is obtained. In other words, based on the second correlation shown in FIG.
It can be seen that a predicted line width of 31 μm is obtained when the exposure energy is 26 J / cm ^2.
/ Cm ² is set as the predicted exposure energy.

As a sixth step, from the second correlation,
A development time corresponding to a desired line width of the resist pattern and the predicted exposure energy is obtained. That is, when a development time corresponding to a curve of exposure energy and a desired line width, for example, a line width of 0.25 μm, is determined for 26 J / cm ² in the second correlation shown in FIG. Since it is known that there is, the actual development is performed in the development time of 80 seconds.

As described above, according to the first embodiment, the height of the latent image formed after the exposure is measured with high accuracy by the AFM, and the developing time is set based on the measured latent image height. Since the resist pattern can be fed forward, the line width of the resist pattern can be obtained without using diffracted light, so that dimensional variations in the line width of the resist pattern between wafers can be greatly reduced.

Hereinafter, a first evaluation test of the method for forming a resist pattern according to the first embodiment will be described.

A method for forming a resist pattern according to the first embodiment, ie, A
When a resist pattern is formed by controlling the developing time based on the latent image height measured using FM, and when a resist pattern is formed by performing development with the original developing time without controlling the developing time The dimensional variation of the line width was verified. FIG. 7 shows the dimensional variation of the line width when the development time was controlled and when the development time was not controlled. As is apparent from FIG. 7, the case where the development time was controlled by the latent image height measured by the AFM was used. Can reduce the dimensional variation.

Hereinafter, a second evaluation test of the method for forming a resist pattern according to the first embodiment will be described.

A method of forming a resist pattern according to the first embodiment, that is, a result of measuring the height of a latent image formed on a resist film on an aluminum substrate using an AFM for 25 continuously processed wafers is described. In the case where the resist pattern is formed by controlling the developing time based on the above, the case where the resist pattern is formed by performing the development with the initial developing time without controlling the developing time, The dimensional variation of the line width between the case where the resist pattern was formed by controlling the developing time based on the light intensity measured using the method was verified. FIG. 8 shows the results of the above verification. When the development time was controlled based on the latent image height measured by the AFM, the development time was controlled using the light diffraction method as well as when the development time was not controlled. It is apparent that the dimensional variation of the line width can be reduced as compared with the case where the control is performed. The reason why the AFM method can reduce the dimensional variation of the line width compared to the light diffraction method is that in the case of the light diffraction method, the detection laser light transmitted through the resist film is irregularly reflected by the grains of the aluminum substrate, and this reflected light is originally In contrast, in the case of the AFM method, the height of the latent image formed on the surface of the resist film is measured without using the diffracted light, whereas the detection accuracy is degraded because the detection accuracy is deteriorated. Therefore, it is thought that high-precision control is possible.

Hereinafter, a third evaluation test of the method for forming a resist pattern according to the first embodiment will be described.

A method of forming a resist pattern according to the first embodiment, that is, the height of a latent image formed in an isolated pattern of 0.25 μm exposed on a resist film on a silicon substrate for 25 continuously processed wafers. The case where the resist pattern is formed by controlling the developing time based on the result measured by using the AFM and the case where the resist pattern is formed by performing the development with the original developing time without controlling the developing time The dimensional variation of the line width was verified. As is clear from FIG. 9, the dimensional variation can be reduced when the development time is controlled by the latent image height measured by the AFM.

In the first embodiment, the difference between the height of the latent image formed on the resist film after exposure and the line width of the resist pattern at a predetermined value of a parameter affecting the line width of the resist pattern in the developing step is described. Instead, the first correlation was determined. Instead, the height of the latent image formed on the resist film after exposure and the value of the resist pattern at a predetermined value of a parameter that affects the line width of the resist pattern in the heat treatment step were determined. It is also possible to obtain a first correlation between a line width and a line width of a resist pattern corresponding to the latent image height and a predetermined value of the parameter from the first correlation. Good. In this case, as a parameter that affects the line width of the resist pattern in the heat treatment step, for example, a heat treatment time or a heat treatment temperature can be given.

(Embodiment 2) FIG. 10 is a view for explaining an outline of a process sequence of a resist pattern forming method according to a second embodiment of the present invention. As shown in FIG. 10, a resist film is formed on a substrate. Is formed, a predetermined pattern is exposed on the resist film, and a heat treatment (PEB) is performed on the resist film on which the pattern has been exposed.
M is used to measure the shape of the latent image, that is, the height of the latent image. Then, the silylation processing time is determined from the correlation between the shape of the latent image obtained in advance and the dimension of the pattern after development,
The silylation process is performed on the surface of the resist film based on the silylation time. Thereafter, dry development is performed to form a resist pattern.

Hereinafter, a method for forming a resist pattern according to the second embodiment will be described in detail with reference to FIGS. In the second embodiment, the processing time of the silylation treatment is selected as a parameter affecting the width of the modification film in the modification film formation step. However, the parameter is not limited to the treatment time of the silylation treatment, and other parameters may be used. It may be the processing time required for forming the type of modified film, or the processing temperature.

In the first step, a first correlation between the height of the latent image formed on the resist film after exposure and the width of the silylated film at a predetermined silylation processing time is determined by the following procedure.

First, the relationship between the exposure energy and the height of the latent image is determined.

SAL6 manufactured by Shipley on a silicon substrate
After forming a resist film by depositing a resist made of 01 to a thickness of 1 μm, the resist film was exposed to light using a KrF excimer laser stepper while changing the exposure energy. Regarding the magnitude of the exposure energy in the second embodiment, different from the first embodiment, a value suitable for the silylation process is selected. Next, 110 to the resist film
After performing the heat treatment at a temperature of 60 ° C. for 60 seconds, the height of the latent image is obtained by the AFM in the same manner as in the first embodiment, thereby obtaining the relationship between the exposure energy and the latent image height.

Next, the relationship between the exposure energy and the width of the silylated film formed by the silylation process for a predetermined time is determined. That is, hexamethylcyclotrisilazane (H) is applied to the resist film exposed by changing the exposure energy.
Using a solution of MCTS), a silylation treatment was performed in a liquid phase at 25 ° C. for a predetermined treatment time to form a silylated film.
FIG. 11 shows the 0.5 μm formed after the silylation treatment.
The cross-sectional shape of the m / L / S silylated film is shown, and the silylated film is selectively formed in the unexposed portions. Since the width of the formed silylated film depends on the exposure energy,
There is a predetermined relationship between the exposure energy and the width of the silylated film. In FIG. 11, reference numeral 1 denotes a silicon substrate, reference numeral 2 denotes a resist film formed on the silicon substrate 1, and reference numeral 3 denotes a silylated film 3 formed on the surface of the resist film 2.

Next, based on the relationship between the exposure energy and the latent image height and the relationship between the exposure energy and the width of the silylated film when the silylation process is performed for a predetermined processing time, the latent image height and the predetermined latent image height are determined. A first correlation between the silylation film width at the time of performing the silylation process for the processing time is obtained.

In the second step, a second correlation between the silylation processing time for each exposure energy and the width of the silylated film is determined. The second correlation is that when the width of the silylation film is out of the specification when the width of the silylation film is predicted from the measured latent image height, the width of the silylation film is changed by changing the silylation processing time. Necessary for controlling to a predetermined value.

FIG. 12 shows that the exposure energy is 110,13.
FIG. 12 shows a second correlation between the silylation time and the width of the silylated film at 0,150 mJ / cm ² .
From this, it is understood that there is a correlation between the silylation processing time and the width of the silylated film for each exposure energy.

As a third step, the height of the latent image formed on the resist film when pattern exposure is actually performed is determined to determine the height of the latent image.

As a fourth step, from the first correlation,
An estimated width of the silylated film, which is a width of the silylated film corresponding to the measured latent image height and a predetermined silylation processing time, is obtained.

As a fifth step, from the second correlation,
Expected exposure energy which is exposure energy corresponding to a predetermined silylation processing time and an estimated width of the silylated film (corresponding to the exposure energy actually absorbed by the resist film).
Ask for.

As a sixth step, from the second correlation,
The silylation processing time corresponding to the desired width of the silylation film and the predicted exposure energy is determined, and after performing the actual silylation processing at the silylation processing time, the resist film on which the silylation film is formed is RIE etching using O ₂ plasma is performed, and thereafter, predetermined development is performed to form a resist pattern.

Since the etching selectivity between the silylated film and the resist film is as high as about 16, the line width of the resist pattern formed after the final dry development greatly depends on the width of the silylated film. Therefore, as shown in the second embodiment, by performing feed-forward control of the silylation processing time, it is possible to reduce dimensional variations in the line width of the resist pattern between wafers. When the continuous processing was actually performed on 25 wafers, the dimensional variation between the wafers of 0.5 μmL / S was ± 0.03 μm to ± 0.015 μm by performing the feedforward control of the silylation processing time. It was confirmed that it could be reduced.

As described above, according to the second embodiment,
The height of the latent image is measured with high accuracy by the AFM, and the silylation processing time obtained based on the measured latent image height can be fed forward to the silylation processing step. It can be greatly reduced. The same effect can be obtained even if the latent image shape is measured by AFM before the heat treatment before the silylation treatment and the processing time of the heat treatment step before the silylation treatment is fed forward.

In the first embodiment, the resist film for the KrF excimer laser “ASK” is used as the resist film.
Although A ″ was used, other resists for KrF excimer laser may be used, or resists for g-line, i-line, ArF excimer laser, X-ray, and charged beam may be used. In the case of using NMD-3 as a developing solution, one corresponding to a resist is used as the exposure light, but other developing solutions may be used instead of wet developing, Alternatively, dry development may be performed.

In the second embodiment, the SAL 601 is used for the resist film.
For rF excimer laser, For ArF excimer laser,
Resists for X-rays and charged beams may be used.

In the first or second embodiment.
The height of the latent image was measured by AFM, but instead,
What can measure the height of the latent image formed on the surface of the resist film in the order of nm can be used as appropriate, and the measurement of the height of the latent image is performed off-line, but may be performed in-line, Control of the development time or control of the processing time for surface modification may be automated.

(Embodiment 3) FIG. 13 is an explanatory view of a process sequence of a method for forming a resist pattern according to a third embodiment of the present invention, as shown in FIG. 13 after a resist film is formed on a substrate. After exposing a predetermined pattern to the resist film, and then selectively forming a surface modification film on an exposed portion or an unexposed portion of the pattern-exposed resist film, the width of the surface modification film is measured by AFM. Then, the pattern size is predicted from the correlation between the width of the surface modification film obtained in advance and the pattern size after development. If the predicted pattern size is within an allowable range, the resist film is developed. On the other hand, if the predicted pattern size is not within the allowable range, the surface modification film and the resist film are removed.

Hereinafter, a method for forming a resist pattern according to the third embodiment will be described in detail with reference to FIGS.

First, as shown in FIG. 14, a resist made of a copolymer of 1,2,3,4-tetrahydronaphthylideneimino p-styrenesulfonate and methyl methacrylate is formed on a silicon substrate 1. After forming the film 2 to a thickness of 1 μm, a predetermined pattern of the resist film 2 is exposed using a KrF excimer laser stepper to generate an acid on the surface of the exposed portion of the resist film 2. Thereafter, the resist film 2 is maintained at a humidity of 95% at a temperature of 30 ° C., and methyltriethoxysilane (MTEOS) as an alkoxysilane gas and water vapor are supplied to the surface of the resist film 2 so that the resist film 2 0.5 μm made of polysiloxane as a metal oxide film selectively on the surface of the exposed portion
After the L / S surface modification film 4 is formed, the surface modification film 4
Is measured by AFM.

Next, the resist film 2 on which the surface modification film 4 was formed was subjected to RIE etching using O ₂ plasma to form a 0.5 μm L / S resist pattern 5 as shown in FIG. Thereafter, the line width W21 of the resist pattern 5 is measured by AFM.

Next, the correlation between the width W20 of the surface modification film 4 and the line width W21 of the developed resist pattern 5 is determined as shown in FIG.

Next, in the same manner as described above, after a predetermined pattern is exposed on the actual resist film, an actual surface modification film is formed on the surface of the actual resist film on which the predetermined pattern has been exposed. Measure the width of the surface-modified film.

Next, the width W of the surface modification film 4 shown in FIG.
From the correlation between 20 and the line width of the resist pattern 5 after development: W21, a predicted line width which is the line width of the resist pattern corresponding to the actual width of the surface modification film is obtained.
In FIG. 16, the vertical axis indicates the width of the surface modification layer and the line width of the resist pattern. Then, it is determined whether or not the predicted line width falls within the allowable range of the line width of the resist pattern. ₂ Perform RIE etching using plasma.

On the other hand, when the predicted line width is not within the allowable range of the line width of the resist pattern, a process as shown in FIG. 17 is performed. That is, as shown in FIG. 17A, an element isolation layer 11 is formed on a silicon substrate 10.
The polysilicon film 12, the silicon oxide film 13, and the resist film 14 are sequentially formed, and the predicted line width corresponding to the width of the surface modification film 15 made of polysiloxane formed on the resist film 14 is an allowable range of the line width of the resist pattern. If not, as shown in FIG. 17B, the surface modification film 15 is removed by CF ₄ plasma, and then, as shown in FIG. 17C, the resist film 14 is removed by O ₂ plasma. After removal, the silicon substrate 10 is regenerated. Thus, the silicon substrate 1 on which the element isolation layer 11, the polysilicon film 12, and the silicon oxide film 13 are formed
0 can be reproduced without damaging it.
Thereafter, a resist film is formed on the regenerated silicon substrate 10 in the same manner as described above, and a resist pattern can be formed. Since the silicon substrate 10 is not damaged as described above, the silicon oxide film 13 and the polysilicon film 1 are again formed by the formed resist pattern.
Even if the gate electrode is formed by etching the substrate 2, for example, problems such as variations in the characteristics of the semiconductor element do not occur.

According to the third embodiment, the width of the surface modification film 15 made of polysiloxane is measured with high precision by AFM, so that the measured surface modification film 15 can be obtained without performing the developing process on the resist film 14. The line width of the resist pattern can be accurately predicted on the basis of the width of the line 15, and when the line width exceeds the allowable range, the silicon substrate 10 can be regenerated without damage, thereby reducing the dimensional variation of the line width of the resist pattern between wafers. can do.

In the third embodiment, if the line width of the resist pattern exceeds the allowable range, the CF
After removing the surface modification film 15 by the plasma of ₄ , the O ₂
The resist film 14 is removed by plasma. Alternatively, the surface modification film 15 may be removed by HF and then the resist film 14 may be removed by an organic solvent such as acetone.

In the third embodiment, the surface modification film is a metal oxide film, but may be the silylation film shown in the second embodiment instead.

[0086]

According to the method for forming a resist pattern according to the first aspect of the present invention, by measuring the height of a latent image formed on the surface of the resist film after exposure, the method is actually applied to the exposure of the resist film. It is possible to obtain a parameter value in a development step corresponding to the exposure condition, and if development is performed based on the parameter value, a desired line width of the resist pattern can be realized. Since the line width of the pattern can be accurately predicted, even if the exposure conditions for pattern exposure vary,
It is possible to obtain a stable resist pattern line width without dimensional variations in line width between wafers.

According to the method for forming a resist pattern according to the second aspect of the present invention, since the parameter is the development time,
Since the development time that greatly affects the line width of the resist pattern can be controlled, the dimensional variation of the line width between wafers can be further reduced.

According to the method for forming a resist pattern according to the third aspect of the present invention, the parameter affecting the line width of the resist pattern in the developing step of the first aspect affects the line width of the resist pattern in the heat treatment step. If the heat treatment is performed based on the value of the parameter in the heat treatment step, a desired line width of the resist pattern can be realized, so that the line width of the resist pattern can be accurately predicted without using diffracted light. Therefore, even if the exposure conditions for pattern exposure vary, it is possible to obtain a stable resist pattern line width without dimensional variations in line width between wafers.

According to the resist pattern forming method of the present invention, since the parameter is the heat treatment time or the heat treatment temperature, the time or temperature of the heat treatment which greatly affects the line width of the resist pattern can be controlled.
The dimensional variation of the line width between wafers can be further reduced.

According to the resist pattern forming method of the present invention, by measuring the height of the latent image formed on the surface of the resist film after the exposure, the exposure conditions actually applied to the exposure of the resist film are measured. When a surface modification film is formed based on the value of the parameter, a surface modification film having a desired width can be formed, and the line width of the resist pattern is formed on the resist film. Depends on the width of the surface modification film
Since the line width of the resist pattern can be accurately controlled without using diffracted light, a stable resist pattern line width can be obtained without dimensional variations in line width between wafers even when pattern exposure conditions vary. .

According to the resist pattern forming method of the present invention, since the parameter is the heat treatment time or the heat treatment temperature, it is possible to control the heat treatment time or temperature which has a large influence on the width of the surface modification film. In this case, the dimensional variation of the line width can be further reduced.

According to the resist pattern forming method of the present invention, since the height of the latent image is obtained by an atomic force microscope capable of measuring the unevenness in the order of nm, the height of the latent image can be measured in the order of nm. Since the value of the parameter in the developing step, the heat treatment step or the surface modification film forming step can be accurately obtained, the desired line width of the resist pattern can be obtained very accurately.

According to the resist pattern forming method of the present invention, by measuring the width of the surface modification film formed on the resist film, it is possible to predict the line width of the resist pattern almost accurately. The resist film is removed when the expected line width is not within the allowable range, so that the defective resist film can be removed without exposing the substrate, so that the damage to the substrate is greatly reduced,
As a result, it is possible to reduce dimensional variations in line width between wafers and variations in characteristics of semiconductor elements and the like.

According to the resist pattern forming method according to the ninth aspect of the present invention, the surface-modifying film is formed such that water is absorbed into the exposed portion of the pattern-exposed resist film, and then water and water are applied to the surface of the exposed portion having absorbed the water. By supplying the metal alkoxide, it is a metal oxide film formed on the surface of the exposed part. Therefore, when forming a metal oxide film as a surface modification film, by measuring the width of the metal oxide film, the resist pattern The line width can be predicted almost exactly.

According to the method for forming a resist pattern according to the tenth aspect of the present invention, since the surface modified film is a silylated film, the width of the silylated film is measured when forming the silylated film as the surface modified film. Accordingly, the line width of the resist pattern can be predicted almost accurately.

According to the method for forming a resist pattern according to the eleventh aspect of the present invention, the width of the surface modified film is measured in the order of nm because the width of the surface modified film is determined by the atomic force microscope capable of measuring the unevenness in the order of nm. can do.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a process sequence of a method for forming a resist pattern according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of a resist film surface observed by AFM in the method of forming a resist pattern according to the first embodiment.

FIG. 3 is a diagram illustrating a relationship between exposure energy and a latent image height in the resist pattern forming method according to the first embodiment.

FIG. 4 is a view showing a relationship between exposure energy and a line width of the resist pattern in the method for forming a resist pattern according to the first embodiment.

FIG. 5 is a diagram showing a first correlation between the height of a latent image and the line width of a resist pattern in the method for forming a resist pattern according to the first embodiment.

FIG. 6 is a diagram showing a second correlation between a development time and a line width of the resist pattern in the method for forming a resist pattern according to the first embodiment.

FIG. 7 is a diagram showing an evaluation test of the method for forming a resist pattern according to the first embodiment, showing a dimensional variation in line width when the development time is controlled and when the development time is not controlled; It is.

FIG. 8 is a view showing an evaluation test of the method for forming a resist pattern according to the first embodiment, in which the development time is controlled, the development time is not controlled, and the development time is measured using the light diffraction method. FIG. 7 is a diagram showing a variation in line width when the control is performed.

FIG. 9 is a diagram showing an evaluation test of the method for forming a resist pattern according to the first embodiment, showing a dimensional variation in line width when the developing time is controlled and when the developing time is not controlled; It is.

FIG. 10 is a schematic view of a process sequence of a method for forming a resist pattern according to a second embodiment of the present invention.

FIG. 11 is a cross-sectional view showing a cross-sectional shape of a silylated film formed after a silylation process in a method for forming a resist pattern according to a second embodiment of the present invention.

FIG. 12 is a view showing a relationship between a silylation processing time and a width of a silylation film in a method for forming a resist pattern according to a second embodiment of the present invention.

FIG. 13 is a schematic diagram of a process sequence of a method for forming a resist pattern according to a third embodiment of the present invention.

FIG. 14 is a cross-sectional view showing one step of a method for forming a resist pattern according to the third embodiment.

FIG. 15 is a cross-sectional view showing one step of a method for forming a resist pattern according to the third embodiment.

FIG. 16 is a view showing a relationship between an exposure amount and a line pattern dimension in the resist pattern forming method according to the third embodiment.

FIG. 17 is a cross-sectional view showing each step of the resist pattern forming method according to the third embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 silicon substrate 2 resist film 3 silylation film 4 surface modification film 5 resist pattern 10 silicon substrate 11 element isolation layer 12 polysilicon film 13 silicon oxide film 14 resist film 15 surface modification film

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-60-249327 (JP, A) JP-A-63-260019 (JP, A) JP-A-64-32623 (JP, A) JP-A-4- 120718 (JP, A) JP-A-4-361525 (JP, A) JP-A-7-212630 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/027 G03F 7 / 20 521

Claims (11)

(57) [Claims] A resist film forming step of forming a resist film on a substrate; an exposure step of exposing a predetermined pattern to the resist film; and a resist pattern formed by developing the resist film having the predetermined pattern exposed A resist pattern forming method comprising: a resist pattern line width at a predetermined value of a parameter that affects a height of a latent image formed on a resist film after exposure and a line width of the resist pattern in the developing step. And determining a second correlation between a predetermined value of the parameter and a line width of the resist pattern for each exposure condition consisting of exposure energy or exposure focus, and Measuring the height of a latent image actually formed on the exposed resist film to determine the height of the latent image; Determining a predicted line width which is a line width of the resist pattern corresponding to the latent image height and the predetermined value of the parameter; and determining the predetermined value of the parameter and the predicted line width from the second correlation. Obtaining a predicted exposure condition, which is the exposure condition corresponding to, and obtaining a value of the parameter corresponding to a desired line width of a resist pattern and the predicted exposure condition from the second correlation, Forming a resist pattern based on the value of (1). 2. The method according to claim 1, wherein a parameter affecting a line width of the resist pattern in the developing step is a developing time. 3. A resist film forming step of forming a resist film on a substrate, an exposure step of exposing a predetermined pattern to the resist film, and a heat treatment step of performing a heat treatment on the resist film having the predetermined pattern exposed. Forming a resist pattern by developing the heat-treated resist film, the resist pattern forming method comprising the steps of: The first correlation between the line width of the resist pattern at a predetermined value of a parameter affecting the line width of the resist pattern, and the predetermined value of the parameter and the line of the resist pattern for each exposure condition consisting of exposure energy or exposure focus Second between width
Determining the latent image height by measuring the height of the latent image actually formed on the exposed resist film; and determining the latent image height from the first correlation. Obtaining a predicted line width which is a line width of the resist pattern corresponding to the height and the predetermined value of the parameter; and the exposure corresponding to the predetermined value of the parameter and the predicted line width from the second correlation. Determining a predicted exposure condition, which is a condition; and determining, from the second correlation, a value of the parameter corresponding to a desired line width of the resist pattern and the predicted exposure condition, and forming a resist film based on the value of the parameter. And a heat treatment step. 4. The method according to claim 3, wherein the parameter affecting the line width of the resist pattern in the heat treatment step is a processing time or a processing temperature. 5. A resist film forming step of forming a resist film on a substrate, an exposure step of exposing a predetermined pattern to the resist film, and a modification of forming a surface modification film on the resist film exposed to the predetermined pattern. A resist pattern forming method comprising: a film forming step; and a developing step of developing a resist film on which a surface modification film is formed to form a resist pattern, wherein a height of a latent image formed on the resist film after exposure is increased. The first correlation between the width of the surface modified film at a predetermined value of the parameter affecting the width of the surface modified film in the modified film forming step, and the parameter of the parameter for each exposure condition consisting of exposure energy or exposure focus Determining a second correlation between the predetermined value and the width of the surface modification film; and measuring a height of a latent image actually formed on the exposed resist film. A step of obtaining a latent image height; a step of obtaining, from the first correlation, a predicted modified film width that is a width of a surface modified film corresponding to the latent image height and a predetermined value of the parameter; Obtaining a predicted exposure condition, which is the exposure condition corresponding to the predetermined value of the parameter and the predicted modified film width, from the correlation of the following, from the second correlation, the desired width of the surface modified film and the Obtaining a value of the parameter corresponding to the predicted exposure condition, and forming a surface modification film based on the value of the parameter. 6. The method according to claim 5, wherein the parameter affecting the width of the surface modification film in the modification film forming step is a processing time or a processing temperature. 7. The method according to claim 1, wherein the latent image height is determined by an atomic force microscope. 8. A step of determining a correlation between a width of a surface modification film formed on the resist film and a line width of a resist pattern obtained by developing the resist film on which the surface modification film is formed. Forming an actual resist film on a substrate; exposing a predetermined pattern to the actual resist film; and forming an actual surface modification film on the surface of the actual resist film having the predetermined pattern exposed. Forming, measuring the width of the actual surface modification film, and obtaining a predicted line width that is the line width of the resist pattern corresponding to the width of the actual surface modification film from the correlation, It is determined whether the line width is within an allowable range of a desired line width, and when the predicted line width is within an allowable range, the actual resist film is developed to form a resist pattern. To contrast, a resist pattern forming method characterized by comprising the step of removing the actual resist film when the predicted linewidth is not within the allowable range. 9. The resist film is formed of a resist that generates an acid when subjected to pattern exposure, and the surface modification film absorbs water in an exposed portion of the pattern-exposed resist film and then absorbs water. 9. The method according to claim 5, wherein the metal oxide film is formed on the surface of the exposed portion by supplying water and a metal alkoxide to the surface of the exposed portion. 10. The resist pattern according to claim 5, wherein the surface modification film is a silylated film formed on a surface of an unexposed portion of the resist film that has been subjected to pattern exposure. Forming method. 11. The method according to claim 8, wherein the width of the surface modification film is determined by using an atomic force microscope.