JPH11119443A - Formation of resist pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a technique for making resist patterns finer without depending on a short-wavelength light, such as ArF light (wavelength 198 nm). SOLUTION: A positive resist 12 is first applied on a film 10 to be formed. Next, the positive resist is exposed by using a prescribed mask 14. The patterns of the mask are transferred to the positive resist by exposing the positive resist via the mask. Next, the positive resist is developed to form temporary resist patterns 12a. Hole patterns 16a are formed in the positions of the temporary resist patterns corresponding to the opening parts b of the mask. The temporary resist patterns are baked after development. The temporary resist patterns are deformed by this baking, by which the resist patterns 12b are formed. The baking of the resist is intrinsically carried out for the purpose of removing the residual solvent and residual moisture but in this embodiment, the baking is executed at a temp. higher than the temp. of the ordinary baking for the purpose described above. The baking is executed at a temp. higher than usual in such a manner to reduce the size of the temporary resist patterns. Consequently, the bore of the hole patterns is reduced and the novel hole patterns 16b are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a resist pattern in a photolithography process in a semiconductor manufacturing process.

[0002]

2. Description of the Related Art In semiconductor manufacturing, a photolithography technique is generally used as a method for forming patterns of elements and wirings. In photolithography, a photoresist applied on a substrate is patterned using an exposure device such as a stepper. With the recent high integration and miniaturization of LSI, it is required to form a finer resist pattern. For this reason, KrF excimer laser deep UV (ultraviolet) light (wavelength 248 nm) has begun to be used as exposure light for forming a resist pattern instead of i-line (wavelength 365 nm) of a mercury lamp. As a result, a finer resist pattern can be formed.

However, a conventional i-line resist is 248 nm.
It does not have high sensitivity around the light wavelength. Therefore, a special resist having high sensitivity in the wavelength region of deep UV light must be used. At present, chemically amplified positive resists are commercially available as resists having relatively high sensitivity in the deep UV wavelength region. The superiority of the sensitivity of this type of resist will not change in the future, and it is considered that the resist will become mainstream.

[0004]

However, there is a demand for further miniaturization of patterns in the future, and it is expected that the above-mentioned pattern forming method using a KrF excimer laser and a chemically amplified positive resist will eventually be limited. Is done. Further, exposure technique using short-wavelength light such as ArF light (wavelength 198 nm), it does not stand prospect of currently commercialized. Therefore, it is necessary to consider a new method of miniaturizing the resist pattern without relying on the shortening of the wavelength of the exposure light.

[0005]

Therefore, according to the method of forming a resist pattern of the present invention, a step of applying a resist on a film to be processed, a step of exposing the resist using a predetermined mask, A step of forming a temporary resist pattern by developing the resist, and performing a post-development bake at a temperature higher than a normal bake for the purpose of removing residual solvent and residual moisture, thereby deforming the temporary resist pattern, And a step of forming

As described above, by performing baking after development, the temporary resist pattern can be deformed.
This is because a resist having poor heat resistance loses heat when it receives heat (this phenomenon is called a heat flow). For example,
In the hole pattern formed in the resist, the resist portion around the hole melts into the hole, and the diameter of the hole is reduced. Thus, the pattern size of the temporary resist pattern can be reduced by the baking. In addition, since the reduction in the pattern size occurs uniformly in each part, it does not depend on the pattern (shape).

[0007] Further, the amount of reduction in the pattern size can be controlled by the baking temperature. As described above, the baking after the development is preferably performed at a higher temperature than the normal baking for removing the residual solvent and the residual moisture.

For example, for a chemically amplified positive resist TDUR-P7 (trade name) manufactured by Tokyo Ohka Kogyo Co., Ltd., normal baking is generally performed at about 90 ° C. However, when the purpose is to reduce the pattern size,
The baking after development is preferably performed at a temperature in the range of 120C to 130C.

According to the method of forming a resist pattern of the present invention, a step of applying a positive resist on a film to be processed, a step of performing a first exposure of the positive resist using a predetermined mask, Developing to remove the exposed portion of the positive resist to form a temporary resist pattern, performing a second exposure to incompletely expose the temporary resist pattern, and performing baking to deform the temporary resist pattern And forming a resist pattern.

As described above, the second exposure is performed on the unexposed portion after the first exposure, that is, the temporary resist pattern. In the second exposure, if the entire surface is exposed with light having an appropriate wavelength and an appropriate exposure amount, the heat resistance of the temporary resist pattern is improved. Therefore, the size reduction amount of the temporary resist pattern with respect to the change in the baking temperature is reduced. Therefore, the pattern size reduction amount can be controlled by the second exposure and baking.

In the method of forming a resist pattern according to the present invention, it is preferable that the second exposure is performed at the time of baking after development.

In this case, since the second exposure is completed within the bake time, the throughput does not decrease.

According to the method of forming a resist pattern of the present invention, a step of applying a positive resist on a film to be processed, a step of performing a first exposure of the positive resist using a predetermined mask, Performing a development to remove the photosensitive portion of the positive resist, forming a temporary resist pattern, and performing a first bake at a higher temperature than a normal bake for the purpose of removing residual solvent and residual moisture, Deforming the temporary resist pattern to form a resist pattern;
The method includes a step of performing a second exposure for completely exposing the resist pattern, and a step of performing a second bake for the purpose of removing residual solvent and residual moisture.

As described above, the first baking is performed for the purpose of pattern size reduction, and then the second exposure is performed. In the second exposure, the resist pattern formed by the first bake is completely exposed, so that the pattern is not deformed in the second bake performed thereafter. That is, in the second baking, the residual solvent and residual moisture contained in the resist pattern can be removed. As described above, the size reduction amount of the pattern can be controlled by the temperature and time of the first baking.

According to the method of forming a resist pattern of the present invention, a step of applying a positive resist on a film to be processed, a step of performing a first exposure of the positive resist using a predetermined mask, Removing the photosensitive portion of the positive resist by performing development, forming a temporary resist pattern, and performing baking at a temperature higher than a normal bake for the purpose of removing residual solvent and residual moisture to form a temporary resist pattern. Forming a resist pattern by performing a second exposure to completely expose the temporary resist pattern during baking, thereby suppressing deformation of the temporary resist pattern. I do.

As described above, the temporary exposure pattern is completely exposed by performing the second exposure during the baking. Therefore, the dimension reduction amount of the temporary resist pattern can be controlled by the baking temperature and the time from the start of baking to the time of performing the second exposure. After the second exposure, baking can be performed continuously for the purpose of removing the residual solvent and residual moisture contained in the resist pattern. Therefore, the throughput does not decrease.

According to the method for forming a resist pattern of the present invention, a step of applying a positive resist on a film to be processed, a step of performing a first exposure of the positive resist using a predetermined mask, Removing the photosensitive portion of the positive resist by performing development, forming a temporary resist pattern, and performing baking at a temperature higher than a normal bake for the purpose of removing residual solvent and residual moisture to form a temporary resist pattern. And performing a second exposure for incompletely exposing the temporary resist pattern and a third exposure for completely exposing the temporary resist pattern during the baking. The resist pattern is formed by suppressing deformation of the temporary resist pattern.

As described above, the temporary resist pattern is incompletely exposed by performing the second exposure in the middle of the baking. As a result, the heat resistance of the temporary resist pattern is improved. Subsequently, the temporary exposure pattern is completely exposed by performing the third exposure during the execution of the baking. Therefore, the size reduction amount of the temporary resist pattern is determined by the baking temperature and
The exposure amount in the second exposure and the third exposure from the start of baking
It can be controlled by the time until the second exposure is performed. Further, after the third exposure, baking can be continuously performed for the purpose of removing the residual solvent and residual moisture contained in the resist pattern. Therefore, the throughput does not decrease.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. It should be noted that the drawings only schematically show the shape and the like so that the present invention can be understood.
Further, the numerical conditions, materials, and the like described below are merely examples. Therefore, the present invention is not limited to this embodiment.

[First Embodiment] In this embodiment, a first method of forming a resist pattern will be described. FIG. 1 is a cross-sectional view for explaining a first method of forming a resist pattern. In this method, first, a positive resist 12 is applied on a film to be processed 10 (FIG. 1A). The processing target film 10 is a film for performing patterning by etching using a resist pattern. This resist pattern is formed by processing the positive resist 12. As the positive resist 12, a chemically amplified positive resist (TDUR-P7 manufactured by Tokyo Ohka Kogyo Co., Ltd.) is used. Positive resist 12
Is formed on the upper surface of the film to be processed 10 by a spin coating method. In this example, a positive resist 12 having a thickness of 10000 (angstrom) is formed.

Next, the positive resist 12 is exposed using a predetermined mask 14 (FIG. 1B). The mask 1 is exposed by exposing the positive resist 12 through the mask 14.
The pattern No. 4 is transferred to the positive resist 12. In this embodiment, this exposure is performed using KrF excimer laser light a. That is, the positive resist 12 is irradiated with laser light having a wavelength of 248 nm through the opening b of the mask 14. As a result, the positive resist 12 irradiated with the laser beam
Is exposed. Therefore, a latent image reflecting the pattern of the mask 14 is formed on the positive resist 12 as an unexposed portion. The positional relationship between the positive resist 12 and the mask 14 and the like may be appropriately set according to various exposure methods.

Next, a temporary resist pattern 12a is formed by developing the positive resist 12 (FIG. 1C). An alkaline aqueous solution such as a TMAH aqueous solution is used as a developer. The exposed film 10 to be processed is immersed in the developing solution to selectively dissolve and remove the photosensitive portion of the positive resist 12. Then, since a pattern corresponding to the latent image of the positive resist 12 remains on the film to be processed 10, a temporary resist pattern 12a having a predetermined pattern is obtained. As shown in FIG. 1C, a hole pattern 16a is formed at the position of the temporary resist pattern 12a corresponding to the opening b of the mask 14.

After the development, the temporary resist pattern 12a is baked. The temporary resist pattern 12a is deformed by this baking to form a resist pattern 12b (FIG. 1).
(D)). Normally, the resist is baked for the purpose of removing the residual solvent and residual moisture. However, in this embodiment, baking is performed at a higher temperature than the above-described normal baking. In this manner, the temporary resist pattern 1 is baked at a higher temperature than usual.
The size of 2a is reduced. That is, the hole pattern 16a
Is reduced to form a new hole pattern 16b.

FIG. 2 is a graph schematically showing the dependence of the pattern size on the baking time. The horizontal axis indicates time, and the vertical axis indicates dimensions. In the figure, time t0 is a bake start time, and time t1 is a bake end time. Also,
Each of the line segments a, b, c, and d shown in FIG. 2 indicates a time change of the pattern dimension value (the aperture value of the hole pattern 16b (16a)) when the baking temperature is varied. A line segment a indicates a dimensional change when a normal baking temperature is set. Line segments b, c, and d show dimensional changes when the temperature is set higher than the normal bake temperature. The line segments b, c and d correspond to the case where the baking temperature is set higher in this order. For example, when the baking temperature during normal baking is 90 ° C., in this embodiment, baking is performed at a temperature of 120 ° C., 125 ° C., or 130 ° C. In this case, the line segment a shows a dimensional change at 90 ° C., the line segment b shows a dimensional change at 120 ° C., and the line segment c
Indicates a dimensional change at 125 ° C., and a line segment d indicates 130 ° C.
The dimensional change at the time of is shown. As shown in FIG. 2, during baking, the pattern size decreases with time. And, as is clear from the comparison of each line segment, the higher the baking temperature is, the larger the reduction ratio of the pattern size is.

FIG. 3 is a graph showing the dependence of the pattern size on the baking temperature. The bake temperature (in units of ° C) is plotted on the horizontal axis, and the range of 80 ° C to 130 ° C is shown in graduations every 10 ° C. In addition, the vertical axis indicates the pattern dimensions (unit: μm), and the range of 0.15 μm to 0.3 μm is shown for every 0.05 μm. In the graph, the measured diameter of the hole pattern 16b is indicated by a white circle symbol corresponding to the baking temperature. The baking time (that is, (t1
−t0). ) Is 60 seconds.

FIG. 4 shows the measured hole pattern 16.
It is a table | surface which shows the aperture value of b. In the first row of the table, the baking temperature and the baking time are described. In the second row of the table, the corresponding measured values are described in μm units. That is, “90 ° C. 60 s” (that is, the baking temperature is 90
° C and a bake time of 60 seconds. )), The aperture value is 0.269 μm, “120 ° C. 60 s” (that is, the bake temperature is 120 ° C., and the bake time is 60 seconds).
When the baking temperature is 125 ° C. and the baking time is 60 seconds, the aperture value is 0.174 μm.

Therefore, as is apparent from FIGS. 3 and 4, the higher the baking temperature is, the higher the speed of reducing the pattern size is. The baking after the development is performed, for example, at 120 ° C. to 13 ° C.
It is preferred to work at a temperature in the range of 0 ° C.

As described above, the amount of reduction in the pattern size can be controlled by the baking temperature. Also,
This dimension reduction amount does not depend on the shape of the hole pattern 16a after development. That is, the reduction amount of the pattern size of the hole pattern 16 b does not depend on the pattern size of the mask 14.

FIG. 5 is a graph showing the relationship between mask dimensions and pattern dimensions. The horizontal axis is the mask dimension (μm unit)
From the range of 0.2 μm to 0.5 μm to 0.05 μm
Each scale is shown. The dimensions of this mask are shown in FIG.
The value of the diameter of the opening b of the mask 14 shown in FIG. The vertical axis indicates the pattern size (μm unit), from 0 μm
The range of 0.6 μm is shown on a scale of 0.1 μm. The measured pattern size is the value of the diameter of the hole pattern 16b shown in FIG.

Further, the relationship between the mask size and the pattern size is obtained for different baking temperatures. In the figure, white circle symbols indicate the measurement results when the baking temperature was 90 ° C. Each white circle symbol is represented by being connected to each other by a line segment a. The square symbols indicate the measurement results when the baking temperature was set to 120 ° C. The square symbols are connected to each other by a line segment b. Triangle symbols indicate the measurement results when the baking temperature was set to 125 ° C. The triangular symbols are shown connected to each other by a line segment c. Also,
The inverted triangle symbol indicates a measurement result when the baking temperature is 130 ° C. The inverted triangle symbols are connected to each other by a line segment d. The baking time for each bake is 60 seconds.

FIG. 6 is a table showing measured values of the diameter of the hole pattern 16b. In the first row of the table, the baking temperature and the baking time are described. Also, in the first column of the table,
The mask dimension value (μm unit) is described. Then, the measured values of the pattern dimensions are described in units of μm in the corresponding columns in the second and subsequent rows and the second and subsequent columns of the table.

Therefore, as shown in FIGS. 5 and 6, it can be seen that the pattern dimension and the mask dimension are almost directly proportional. In addition, the rate of change of the pattern dimension with respect to the mask dimension becomes substantially constant regardless of the baking temperature. Therefore, the reduction amount of the pattern size does not depend on a slight difference in the mask size.

The amount of reduction in the pattern size does not depend much on differences in exposure conditions and the like. For example, the pattern dimension has a small dependence on the focus during exposure (the distance between the focus of the exposure light and the resist). FIG. 7 is a graph showing the relationship between focus and pattern size. Focus (μm unit) on the horizontal axis, -0.5μm ~ 1
The range of μm is graduated every 0.5 μm. The vertical axis indicates the pattern dimension (μm unit), from 0 μm to
The range of 0.3 μm is graduated every 0.05 μm.

The relationship between the focus and the pattern size is obtained for different baking temperatures. In FIG. 7, white circle symbols indicate measurement results when the baking temperature is 90 ° C. Each white circle symbol is represented by being connected to each other by a line segment a. The square symbol indicates a baking temperature of 120 ° C.
This is the measurement result when The square symbols are connected to each other by a line segment b. Triangle symbols indicate the measurement results when the baking temperature was set to 125 ° C. The triangular symbols are shown connected to each other by a line segment c. still,
The baking time for each bake is 60 seconds.

FIG. 8 shows the measured hole pattern 16.
It is a table | surface which shows the aperture value of b. In the first row of the table, the baking temperature and the baking time are described. In the first column of the table, the focus value (in μm) is described. Then, the measured values of the pattern dimensions are described in units of μm in the corresponding columns in the second and subsequent rows and the second and subsequent columns of the table.

Therefore, as shown in FIGS. 7 and 8, the pattern size is almost constant with respect to the change in focus.
That is, the change in the pattern size due to the difference in focus is small. Therefore, according to the method of this embodiment, the pattern size can be reduced without impairing the margin for the focus and the exposure amount in the conventional process. Moreover, in the method of this embodiment, only the setting of the bake temperature is changed with respect to the conventional process, so that it is not necessary to change the apparatus configuration. Therefore, the throughput does not decrease.

[Second Embodiment] Next, a second method for forming a resist pattern will be described. The steps of the second forming method will be described with reference to FIGS. 1A to 1C and FIG. FIG. 9 is a cross-sectional view for explaining the second forming method.

First, a positive resist 1 is formed on the film 10 to be processed.
2 is applied (FIG. 1A). Next, a predetermined mask 14
The first exposure of the positive resist 12 is performed using (FIG. 1B). Next, development is performed to remove the photosensitive portion of the positive resist 12 to form a temporary resist pattern 12a (FIG. 1C). Hole pattern 1 in positive resist 12
6a is formed.

Subsequently, in this embodiment, a second exposure for incompletely exposing the temporary resist pattern 12a is performed (FIG. 9A). For example, normal deep UV
Using a batch exposure machine, the entire surface is exposed by setting an appropriate wavelength and exposure amount so that the temporary resist pattern 12a is not completely exposed. In this example, the entire surface exposure is performed by irradiating light a having a central wavelength of 365 nm. As described above, when the incomplete exposure is performed, the heat resistance of the temporary resist pattern 12a can be improved.

Next, as in the case of the first forming method, baking is performed to deform the temporary resist pattern 12a to form a resist pattern 12b (FIG. 9B). By this baking, the pattern size (diameter) of the hole pattern 16a is reduced, and a new hole pattern 16b is obtained. However,
Since the temporary resist pattern 12a is incompletely exposed in the second exposure process described above, the amount of reduction in the pattern size is smaller than in the case of the first forming method.

FIG. 10 is a graph showing the dependence of the pattern size on the baking time. The horizontal axis indicates time, and the vertical axis indicates dimensions. Line segments a, b, c and d shown in FIG. 10 respectively correspond to line segments a, b, c and d shown in FIG. As shown in FIG. 10, the second exposure is started at a time t2 before the bake start time t0, and is also ended at a time t3 before the bake start time t0. The difference between the first forming method and the second forming method is the presence or absence of the second exposure. According to the second forming method, as is clear from the comparison between FIG. 2 and FIG. 10, the rate of change of the pattern dimension with respect to time is reduced.
Therefore, the dimension reduction amount can be controlled with higher accuracy.

Next, the actual measurement results are shown in FIGS.
It is shown in FIG. FIG. 11 is a graph showing the dependence of the dimension reduction amount on the baking temperature. The bake temperature (in ° C.) is plotted on the horizontal axis, and the range of 120 ° C. to 130 ° C. is graduated every 5 ° C. Also, the vertical axis indicates the dimension reduction amount (μm unit). This dimension reduction amount is an amount expressed on the basis of a pattern dimension when baked at a temperature of 90 ° C. The dimension reduction amount is shown in a range of 0 μm to 0.2 μm in increments of 0.05 μm.

FIG. 11 shows a measurement result of the dimension reduction amount when the second exposure is performed and a measurement result of the dimension reduction amount when the second exposure is not performed. In the drawing, the white circle symbol indicates the measurement result when the second exposure was not performed. Each white circle symbol is represented by being connected to each other by a line segment a. The square symbols indicate the measurement results when the second exposure was performed. The square symbols are connected to each other by a line segment b.

FIG. 12 is a table showing the measured values of the diameter of the hole pattern 16b. The first row of the table describes the bake temperature. In the first column of the table, the presence or absence of the second exposure is described. Then, the measured values of the dimension reduction amount are described in μm units in the corresponding columns in the second row and subsequent columns and the second and subsequent columns of the table.

As shown in FIGS. 11 and 12, when the second exposure is performed, the change in the dimensional reduction amount with respect to the change in the bake temperature is smaller than when no exposure is performed. As described above, since the heat resistance of the resist is appropriately improved by performing the second exposure, the amount of dimensional reduction gradually changes with a change in the baking temperature.

Next, with reference to FIGS. 13 and 14, a description will be given of a change in the pattern size with respect to the exposure amount. FIG.
Is a graph showing the dependence of the pattern size (the diameter of the hole pattern 16b) on the exposure dose. On the horizontal axis is the exposure (mJ / cm
² units) and take 0 mJ / cm ^{2 to} 500 mJ / cm ²
Is scaled every 100 mJ / cm ² . The vertical axis indicates the pattern dimension (μm unit),
The range from [mu] m to 0.3 [mu] m is shown on a scale of 0.05 [mu] m. The measured values of the pattern dimensions are indicated by white circles in the graph, and the white circles are connected by a line segment a.

FIG. 14 shows the measured hole pattern 1.
It is a table | surface which shows the aperture value of 6b. In the first row of the table, the exposure amount is described in mJ / cm ² . Then, in the corresponding columns of the second row of the table, the measured values of
It is described in m units.

The measurement results shown in FIGS. 13 and 14 are obtained when baking is performed at a temperature of 125 ° C. for 60 seconds. As shown in FIGS. 13 and 14, the pattern size increases as the exposure amount increases. That is, the size reduction amount can be reduced as the exposure amount increases.

As described above, according to the second forming method, the dimension reduction amount can be controlled by the baking temperature of the bake after development and the exposure amount of the second exposure. Moreover, similarly to the above-described first forming method, the hole pattern size can be reduced without impairing the margin for the exposure amount and focus in the conventional process.

[Third Embodiment] Next, a third method for forming a resist pattern will be described. Third forming method and second
Compared with the formation method, the third formation method is characterized in that the above-described second exposure is performed at the time of performing the baking after development.

First, a positive resist 1 is formed on the film 10 to be processed.
2 is applied (FIG. 1A). Subsequently, a predetermined mask 1
The first exposure of the positive resist 12 is performed using the resist 4 (FIG. 1B). Next, development is performed to form a positive resist 12
Is removed to form a temporary resist pattern 12a (FIG. 1C).

Next, exposure is performed while performing baking using an exposure apparatus (multipurpose optical unit) having a built-in baking means. In this embodiment, the temporary resist pattern 12a is exposed immediately after the start of baking. This exposure is
Corresponds to the second exposure described in the embodiment. Therefore, in the exposure performed during this baking, the temporary resist pattern 12a is incompletely exposed. Then, this exposure moderately improves the heat resistance of the temporary resist pattern 12a.

FIG. 15 is a graph showing the dependence of the pattern size on the baking time. The horizontal axis indicates time, and the vertical axis indicates dimensions. Line segments a, b, c and d shown in FIG. 15 correspond to line segments a, b, c and d shown in FIG. 2, respectively. As shown in this graph, the second exposure is started at the same time as the bake start time t0.
The second exposure is completed at time t2 before the bake end time t1. As described above, since the exposure is started during the baking step and the exposure is completed during the baking step, the throughput does not decrease.

[Fourth Embodiment] Next, a fourth method of forming a resist pattern will be described with reference to FIG.
FIG. 16 is a cross-sectional view for explaining a fourth method of forming a resist pattern. It should be noted that, up to a point, substantially the same steps as those of the first forming method are included, so that this step will first be briefly described with reference to FIG.

First, a positive resist 1 is formed on the film 10 to be processed.
2 is applied (FIG. 1A). Subsequently, a predetermined mask 1
The first exposure of the positive resist 12 is performed using the resist 4 (FIG. 1B). Next, development is performed to form a positive resist 12
Is removed to form a temporary resist pattern 12a (FIG. 1 (C) and FIG. 16 (A)). Accordingly, a hole pattern 16a is formed in the positive resist 12.

Then, the first baking is performed at a temperature higher than the normal baking for the purpose of removing the residual solvent and the residual moisture, thereby deforming the temporary resist pattern 12a to form the resist pattern 12b (FIG. 16). (B)). This baking is performed, for example, at about 120 ° C. By this baking, the temporary resist pattern 12a having poor heat resistance generates a heat flow and changes its shape. And the hole pattern 16a
Is reduced, and a new hole pattern 16b is formed.

Next, a second exposure for completely exposing the resist pattern 12b is performed (FIG. 16C). That is, the resist pattern 12b is irradiated with a deep UV light having a sufficient exposure amount to completely expose the resist by using a deep UV batch exposure machine. By performing the entire surface exposure in this manner, the heat resistance of the resist pattern 12b is improved.

Then, a second baking is performed for the purpose of removing the residual solvent and residual moisture (FIG. 16D).
In this baking step, the resist pattern 1
No heat flow occurs because 2b has sufficient heat resistance. Therefore, the residual solvent and residual moisture that were insufficient in the first baking step can be removed.

FIG. 17 is a graph showing the dependence of the pattern size on the baking time. The horizontal axis indicates time, and the vertical axis indicates dimensions. Line segments a, b and c shown in FIG.
Respectively correspond to the line segments a, b and c shown in FIG. As shown in FIG. 17, the first baking is started at time t0 and ended at time t1. Subsequently, the second exposure is started at time t2, and this exposure is performed until time t3. Finally, the second baking is performed within the times t4 and t5.

Therefore, in this forming method, the dimension reduction amount of the resist pattern can be controlled by the first baking temperature and the first baking time (t1-t0). The size reduction amount is determined by the hole pattern size after development and the first size.
It does not depend on a slight difference in the shape of the hole pattern caused by variations in the conditions of the second exposure. Therefore, the size of the hole pattern can be reduced without impairing the margin for the exposure amount and the focus in the conventional process.

Since the heat resistance of the resist pattern 12b is greatly improved by the second exposure, the shape does not change even if the second baking is performed at the same baking temperature as the first baking. Therefore, the first bake and the second bake can be performed using the same bake plate, and no additional bake plate is required.

[Fifth Embodiment] Next, a fifth method for forming a resist pattern will be described. In the fifth forming method,
A second exposure is performed during baking after development. In the second exposure, deformation of the temporary resist pattern is stopped by completely exposing the temporary resist pattern.
This fifth forming method will be described with reference to FIGS.

First, the positive resist 1 is formed on the film 10 to be processed.
2 is applied (FIG. 1A). Subsequently, a predetermined mask 1
The first exposure of the positive resist 12 is performed using the resist 4 (FIG. 1B). Next, development is performed to form a positive resist 12
Is removed to form a temporary resist pattern 12a (FIG. 1C). Accordingly, a hole pattern 16a is formed in the positive resist 12.

Next, exposure is performed while performing baking using an exposure apparatus (multipurpose optical unit) having a built-in baking means. This baking is performed at a higher temperature than a normal baking for the purpose of removing the residual solvent and the residual moisture, thereby deforming the temporary resist pattern 12a. Then, after baking is performed for an appropriate time, the temporary resist pattern 12a is exposed. This exposure corresponds to the second exposure described in the fourth embodiment. Therefore, in the exposure performed during this baking, the temporary resist pattern 12a is completely exposed. Then, the temporary resist pattern 12a is exposed by this exposure.
To improve the heat resistance and prevent deformation due to baking.

FIG. 18 is a graph showing the dependence of the pattern size on the baking time. The horizontal axis indicates time, and the vertical axis indicates dimensions. Line segments a, b and c shown in FIG.
Respectively correspond to the line segments a, b and c shown in FIG.

As shown in FIG. 18, baking after development is started at time t0. Then, when the temperature is set higher than during the normal baking (in the case of the line segments b and c in FIG. 18), the pattern size decreases with the passage of time (however, as shown in FIG. 18, the pattern size decreases). Does not necessarily decrease linearly.) Subsequently, at time t1, the second exposure is started. This exposure is performed at time t2.
Continue until By this exposure, the pattern size stops decreasing, and a predetermined resist pattern 12b and a hole pattern 16b are obtained (see FIG. 1 (D); however, FIG. 18).
As shown in (1), the pattern size does not stop decreasing at the same time as the start of exposure. ). After that, the baking is continued, and the baking is ended at an appropriate time t3.

As described above, in the fifth forming method, the pattern size reduction amount is controlled by the temperature of the bake after development and the time (t1-t0) from the start of the bake to the start of the exposure. be able to. Further, the exposure amount at the time of exposure can be controlled by adjusting the time (t2−t1) or the like. Further, the residual solvent and residual moisture contained in the resist pattern 12b can be completely removed by the baking after the completion of the exposure. The second exposure is
Since the process is started during the baking process and ended during the baking process, the throughput does not decrease.

[Sixth Embodiment] Next, a sixth method for forming a resist pattern will be described. In the sixth forming method, exposure is performed twice during baking after development. In the first exposure, the temporary resist pattern 12a is incompletely exposed to light so that the pattern size can be reduced at an appropriate speed by baking. In the next exposure, the temporary resist pattern 12a is completely exposed to light, and the reduction of the pattern size due to the baking is stopped.

First, the positive resist 1 is formed on the film 10 to be processed.
2 is applied (FIG. 1A). Subsequently, a predetermined mask 1
The first exposure of the positive resist 12 is performed using the resist 4 (FIG. 1B). Next, development is performed to form a positive resist 12
Is removed to form a temporary resist pattern 12a (FIG. 1C).

Next, exposure is performed while performing baking using an exposure apparatus (multipurpose optical unit) having a built-in baking means. In this embodiment, the temporary resist pattern 12a is exposed immediately after the start of baking. This exposure is
Corresponds to the second exposure described in the embodiment. Therefore, in the exposure performed during this baking, the temporary resist pattern 12a is incompletely exposed. Then, this exposure moderately improves the heat resistance of the temporary resist pattern 12a.

Next, after baking is continuously performed for an appropriate time, a third exposure for completely exposing the temporary resist pattern 12a is performed. As a result, the deformation of the temporary resist pattern 12a stops, and the resist pattern 12b is obtained. The third exposure is also performed using the same multipurpose light unit as the second exposure. This third exposure is
This corresponds to the second exposure described in the fifth embodiment.

FIG. 19 is a graph showing the dependence of the pattern size on the baking time. The horizontal axis indicates time, and the vertical axis indicates dimensions. Line segments a, b and c shown in FIG.
Respectively correspond to the line segments a, b and c shown in FIG.

As shown in FIG. 19, the second exposure is
It starts at the same time as the bake start time t0 and ends at the time t1. Subsequently, at time t2, the third exposure is started. This exposure is continued until time t3. By this exposure, the pattern size stops decreasing, and a predetermined resist pattern 12b and thus a hole pattern 16b are obtained (FIG. 1D). After that, the baking is continued, and the baking is ended at an appropriate time t4.

As described above, in the sixth forming method, the amount of reduction in the pattern size is determined by the temperature of the bake after development and the time (t2−t) from the start of the bake to the start of the third exposure.
t0) and the exposure amount at the time of the second exposure.
Further, the resist pattern 12 is baked after the completion of the exposure.
The residual solvent and residual water contained in b can be completely removed. Note that the second and third exposures are started during the baking step and ended during the baking step, so that the throughput does not decrease.

[0075]

According to the resist pattern forming method of the present invention, the temporary resist pattern is deformed by performing a post-development bake at a temperature higher than a normal bake for the purpose of removing residual solvent and residual moisture. Then, a resist pattern is formed. Therefore, a resist pattern finer than the conventional KrF can be formed without using short-wavelength light such as ArF light.
It can be formed using a light and chemically amplified resist.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a first method of forming a resist pattern;

FIG. 2 is a diagram showing the dependence of pattern size on baking time.

FIG. 3 is a diagram showing bake temperature dependence of pattern dimensions.

FIG. 4 is a diagram showing bake temperature dependence of pattern dimensions.

FIG. 5 is a diagram showing a relationship between a mask dimension and a pattern dimension.

FIG. 6 is a diagram showing a relationship between a mask dimension and a pattern dimension.

FIG. 7 is a diagram showing the relationship between focus and pattern dimensions.

FIG. 8 is a diagram showing a relationship between focus and pattern dimensions.

FIG. 9 is a diagram provided for explanation of a second method of forming a resist pattern.

FIG. 10 is a diagram showing bake time dependence of pattern dimensions.

FIG. 11 is a diagram showing a bake temperature dependency of a dimension reduction amount.

FIG. 12 is a diagram showing the bake temperature dependence of the dimension reduction amount.

FIG. 13 is a diagram showing the dependence of the pattern size on the exposure dose.

FIG. 14 is a diagram showing the dependence of pattern dimensions on the amount of exposure.

FIG. 15 is a diagram showing bake time dependence of pattern dimensions.

FIG. 16 is a view for explaining a fourth method of forming the resist pattern;

FIG. 17 is a diagram showing bake time dependence of pattern dimensions.

FIG. 18 is a diagram showing bake time dependence of pattern dimensions.

FIG. 19 is a diagram showing the dependence of pattern size on baking time.

[Explanation of symbols]

 10: Film to be processed 12: Positive resist 12a: Temporary resist pattern 12b: Resist pattern 14: Mask 16a, 16b: Hole pattern

Claims (7)

[Claims] 1. a step of applying a resist on a film to be processed; a step of exposing the resist using a predetermined mask; a step of developing the resist to form a temporary resist pattern; Deforming the temporary resist pattern by performing a post-development bake at a temperature higher than a normal bake for the purpose of removing residual moisture, and forming a resist pattern. Forming method. 2. The method of forming a resist pattern according to claim 1, wherein the baking after the development is performed at a temperature in a range of 120 ° C. to 130 ° C. 3. A step of applying a positive resist on the film to be processed, a step of performing a first exposure of the positive resist using a predetermined mask, and a step of developing to expose a photosensitive portion of the positive resist. Removing and forming a temporary resist pattern; performing a second exposure to incompletely expose the temporary resist pattern; and performing a bake to deform the temporary resist pattern to form a resist pattern. And a method for forming a resist pattern. 4. The method for forming a resist pattern according to claim 3, wherein the second exposure is performed at the time of performing the baking after the development. 5. A step of applying a positive resist on a film to be processed, a step of performing a first exposure of the positive resist using a predetermined mask, and a step of performing development to remove a photosensitive portion of the positive resist. Removing, forming a temporary resist pattern; and performing a first bake at a temperature higher than a normal bake for the purpose of removing residual solvent and residual moisture to deform the temporary resist pattern, Forming a second pattern, performing a second exposure for completely exposing the resist pattern, and performing a second bake for the purpose of removing residual solvent and residual moisture. Method of forming a resist pattern. 6. A step of applying a positive resist on a film to be processed, a step of performing a first exposure of the positive resist using a predetermined mask, and a step of developing to expose a photosensitive portion of the positive resist. Removing and forming a temporary resist pattern; and performing a bake at a temperature higher than a normal bake for the purpose of removing residual solvent and residual moisture to deform the temporary resist pattern. Forming a resist pattern by performing a second exposure that completely exposes the temporary resist pattern during the execution of the step, thereby suppressing deformation of the temporary resist pattern. 7. A step of applying a positive resist on a film to be processed, a step of performing a first exposure of the positive resist using a predetermined mask, and a step of developing to expose a photosensitive portion of the positive resist. Removing, forming a temporary resist pattern; and performing a bake at a temperature higher than a normal bake for the purpose of removing residual solvent and residual moisture to deform the temporary resist pattern. During the execution, the second exposure for incompletely exposing the temporary resist pattern is performed, and the third exposure for completely exposing the temporary resist pattern is performed. A method for forming a resist pattern, comprising: forming a resist pattern while suppressing the formation of the resist pattern.