JP3022896B2 - Manufacturing method of exposure mask - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photomask and a photo reticle (hereinafter, referred to as a photo reticle) used for manufacturing a semiconductor device.
In particular, the present invention relates to a method for making the dimensions of a pattern formed on a light-shielding film on a mask uniform in a plane.

[0002]

2. Description of the Related Art Due to the high integration and fine dimensions of semiconductor devices, the demand for dimensional uniformity of masks used for manufacturing the semiconductor devices has been increasing in recent years. For this reason, in the mask manufacturing process, highly anisotropic dry etching, particularly reactive ion etching, is used. However, due to the recent tendency to miniaturization, it is difficult to meet the demand alone, and higher in-plane A manufacturing method capable of realizing uniformity has been required.

FIG. 9 is a sectional view in the order of steps for explaining a conventional mask manufacturing method. First, a mask substrate 1 having a light-shielding film 3 made of Cr or the like formed on a quartz substrate 2 is prepared, a resist for electron beam exposure is spin-coated, and prebaked to form a resist film 4 [FIG.
(A)]. Next, electron beam exposure is performed to draw a desired pattern. Next, development is performed to pattern the resist film 4 (FIG. 9B). Hereinafter, the opening size of the resist film pattern obtained in this step is referred to as a resist film opening size 101.

Next, the light shielding film 3 is selectively removed by reactive ion etching using the patterned resist film 4 as a mask, and a resist film pattern is transferred to the light shielding film 3 (FIG. 9C). Hereinafter, the opening size of the light-shielding film pattern obtained in this step is referred to as a light-shielding film opening size 102. Finally, the resist film is removed and removed to obtain a mask having a desired light-shielding film pattern [FIG. 9 (d)].

FIG. 10 shows the in-plane distribution of the opening 101 of the resist film after the development process, and FIG. 11 shows the in-plane distribution of the opening 102 of the light-shielding film.
In the prior art, the resist film opening size 101 after the development process is used.
In the plane (a value obtained by subtracting the size of the central portion from the size of the peripheral portion), thereby reducing the light-shielding film opening size 102
(To reduce the in-plane dimensional difference). Here, since FIG. 10 shows the experimental result, an in-plane dimensional difference of the resist film opening dimension 101 is generated. The in-plane dimensional difference of the light-shielding film opening dimension 102 shown in FIG.

The experimental results shown in FIGS. 10 and 11 have been obtained under the following conditions. In addition, each dimension measurement was performed at 25 points within a range of 80 mm square on the substrate. Quartz substrate 2: 5 inch (12.7 cm) square substrate with a thickness of 0.09 inch (0.229 cm) Shielding film 3: CrxOy / Cr two-layer structure with a total film thickness of about 1000Å Resist film 4: 5000 塗布Resist for electron beam exposure Pre-bake: hot plate used, bake temperature = 20
Approximately 0 ° C. Electron beam exposure: Using a variable rectangular electron beam exposure apparatus, acceleration voltage = 20 kV, exposure amount = approximately 12 μC / cm 2, drawing a hole pattern with a design dimension of 2.5 μm Developer: Organic solvent-based mixed development Liquid post-development treatment: After rinsing treatment using isopropyl alcohol and spin drying treatment, post baking (using a hot plate, baking temperature = about 110 ° C.) and descum treatment (etching of resist film 4 using oxygen gas plasma (etching) Amount = about 400 °)) Etching gas in reactive ion etching: Cl ₂ /
O ₂ mixed gas

[0007]

In the conventional method of forming a mask pattern, the opening size of the resist film after the developing step is 10 mm.
1 is relatively uniform in the plane as shown in FIG. 10, but the aperture 102 of the light-shielding film greatly varies as shown in FIG. In particular, the opening size is formed large in the peripheral portion. This is because, in the reactive ion etching of the light-shielding film, the etching rate of the peripheral portion is likely to be higher than the etching speed of the central portion, and the opening size of the peripheral portion is transferred larger than the opening size of the central portion in the etching process,
This is because the in-plane dimensional difference of the light-shielding film opening dimension 102 increases in the etching process.

The reason why the etching rate of the peripheral portion is higher than that of the central portion in the reactive ion etching of the light shielding film will be described below. FIGS. 12A and 12B
3A and 3B are a top view and a sectional view showing a schematic configuration of a lower electrode portion of a reactive ion etching apparatus for manufacturing a mask. The surface of the lower electrode 32 is covered with the quartz cover 31 except for the portion where the mask substrate 1 is mounted. Here, the quartz cover 31 is necessary for protecting the lower electrode portion and preventing abnormal discharge during the etching process, and is made of a material that is difficult to be etched by an etching gas.

In the reactive ion etching, it is general that the etching rate of a portion where the consumption of the etching gas species is small becomes relatively high. Since the quartz cover 31 which is hard to be etched is adjacent to the portion, the consumption of the etching gas species in the peripheral portion is smaller than in the central portion, and the etching in the peripheral portion tends to be faster than in the central portion. Therefore, in the etching step, the opening size of the peripheral portion is transferred to be larger than the opening size of the central portion, and the in-plane dimensional difference of the light shielding film opening size 102 increases. Therefore, a problem to be solved by the present invention is to make the size of the light-shielding film pattern on the mask uniform in the plane.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problem that the difference in the opening size in the plane of the light shielding film formed by etching is offset by the difference in the opening size in the plane of the resist film formed by development. This can be solved.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The method of manufacturing an exposure mask according to the present invention comprises the steps of (1) applying a resist on a transparent substrate having a light-shielding film formed on the surface thereof and exposing the same; and (2) performing development. A step of forming a patterned resist film on the light-shielding film; and (3) a step of forming a pattern of the light-shielding film by etching using the resist film formed in the step as a mask. The in-plane difference in the opening size of the resist film generated in the step (2) and the in-plane difference in the opening size of the light-shielding film generated in the step (3) are calculated by :
By changing the flow rate of the developer and measuring in advance, the above (2)
In the step, the flow rate of the developer is determined in advance.
The basis of the measurement result of the in-plane dimensional difference, is developed with the second (3) of the generated in step shielding film opening size plane dimension difference generates a plane dimension difference of the resist film aperture size to offset the condition of It is characterized by being performed.

More preferably, the development is performed by a spray method. At this time, the in-plane resist film opening dimension which cancels the in-plane dimension difference of the light-shielding film opening dimension generated in the third step. The condition for generating the dimensional difference is determined by selecting the set flow rate value of the developer. Preferably, the exposure in the (1) step is performed by electron beam exposure, and the etching in the (3) step is performed by reactive ion etching. Further, if necessary, when estimating the in-plane dimensional difference or the in-plane dimensional distribution of the opening dimensions of the resist film formed by the development, the thickness of the resist film before and after the development is measured by measuring the thickness of the resist film. The in-plane distribution of the amount of film reduction is observed, and thereby, the in-plane dimensional difference or the in-plane dimensional distribution of the opening dimensions of the resist film formed by development is estimated.

[Operation] In the present invention, in the development step of the resist, the development is performed under the condition that the in-plane difference in the opening size of the resist film cancels out the in-plane difference in the opening size of the light-shielding film generated in the etching step. Is performed. For example, when the etching rate at the time of etching the light-shielding film is higher in the peripheral part than in the central part and the opening size of the light-shielding film in the peripheral part is formed larger than that in the central part, the resist film opening in the peripheral part is formed. Development is performed under conditions where the dimensions are smaller than that of the central part. As a result, the in-plane dimensional difference of the development and the in-plane dimensional difference of the etching cancel each other, and the opening dimension of the light-shielding film after the etching is made uniform in the plane. The condition for generating the in-plane dimensional difference in the resist film opening dimension that cancels out the in-plane dimensional difference in the light-shielding film opening dimension generated in the etching step at the time of development is performed, for example, by setting the flow rate value of the developer.

In carrying out the invention of the present application, it is necessary to appropriately measure the in-plane dimensional difference of the resist film opening. By the way, when the flow rate value of the developing solution is changed, both the in-plane dimensional difference of the opening size of the resist film and the in-plane difference of the film reduction amount of the resist film in the developing process change.
There is a high correlation between the in-plane dimensional difference resulting from the development and the in-plane difference in the amount of film reduction. Therefore, in the embodiment of the present invention, this is used to estimate the in-plane dimensional difference of the opening size of the resist film from the in-plane difference in the amount of reduction of the resist film in the developing step. In general, it is easier to measure the film thickness than to measure the opening size of the resist film. Therefore, this method makes it possible to grasp the in-plane dimensional difference of the resist film with high accuracy by a simple method.

[0015]

Next, embodiments of the present invention will be described with reference to the drawings. [First Embodiment] FIG. 1 is a flow chart showing a flow of a manufacturing process according to a first embodiment of the present invention, and FIG. 2 is a sectional view of the first embodiment in the order of steps. In step S1, a mask substrate 1 having a light shielding film 3 formed on a quartz substrate 2 is prepared. Then, in step S2, on the mask substrate 1,
A resist for electron beam exposure is spin-coated, dried, and prebaked to form a resist film 4 [FIG.
(A)]. Next, in step S3, a desired pattern is drawn by electron beam exposure. Then, by spray method,
A development process is performed to form a resist pattern on the resist film 4 (FIG. 2B). The opening size of the resist pattern obtained in this step is referred to as a resist film opening size 101.

The above-described developing step is performed using a developing device shown in FIG. FIG. 3A is a cross-sectional view of the developing chamber, and FIG. 3B is a configuration diagram of a developing solution supply system. First, the mask substrate 1 is transported into the developing device and fixed on the support 21. Next, the support 21 starts rotating, and then pressurization by the pressurizer 22 starts, and the developer 10 from the developer nozzle 20 is radiated onto the mask substrate 1. As shown in FIG. 3B, the developer 10 is stored in the sealed outer container 23, and the flow controller 2
Reference numeral 4 indicates a predetermined flow value of the developer according to the present invention. The flow controller 24 monitors the developer flowing through the flow controller, sends a control signal to the pressurizer 22, and changes the pressure applied to the external container 23 of the pressurizer 22, thereby reducing the flow rate of the developer. Control to set value. The developer 10 emitted from the developer nozzle 20 becomes mist,
Further, it is supplied on the resist film of the mask substrate 1 while spreading in a fan shape. After a lapse of a predetermined time, the pressurization from the pressurizer 22 is stopped, and the emission of the developer 10 is stopped. Next, after rinsing and spin drying, the mask substrate 1
Is stopped, and the mask substrate 1 is carried out of the developing device to complete the developing process.

Returning to FIGS. 1 and 2, in step S5, the light shielding film 3 is selectively removed by reactive ion etching using the resist film 4 as a mask to form a light shielding film pattern to which the resist film pattern has been transferred. [Figure 2
(C)]. Hereinafter, the opening size of the light-shielding film pattern obtained in this step is referred to as a light-shielding film opening size 102. Next, in step S6, the resist film 4 is peeled and removed to complete the mask manufacturing process according to the present embodiment [FIG.
(D)].

FIG. 4 shows the relationship between the set flow rate of the developer 10 and the difference between the in-plane dimension of the resist film opening 101 and the in-plane difference of the light shielding film opening 102. 6 is a graph showing an experimental result of obtaining. Here, the in-plane distribution on the mask substrate 1 is indicated by the in-plane dimensional difference of each dimension (a value obtained by subtracting the size of the central portion from the size of the peripheral portion).

FIGS. 5 and 6 show the in-plane distribution of the resist film opening size 101 and the light shielding film opening size 102 at a set flow rate of 80 cc / min in FIG. 5 and 6, the horizontal and depth directions indicate in-plane positions, and the height direction indicates each dimension value at each position. As shown in FIG. 4, there is a correlation between the set flow rate value of the developer and the in-plane dimensional difference of the resist film opening dimension 101, and the in-plane dimensional difference changes from a positive value to a negative value. Here, the fact that the in-plane dimensional difference of the resist film opening dimension 101 is a positive value means that the peripheral portion has a larger in-plane distribution than the central portion, and that the in-plane dimensional difference is a negative value. This indicates that the size of the central portion has a larger in-plane distribution than the size of the peripheral portion.

Therefore, the experimental results shown in FIG. 4 show that the resist film opening size 101
It is shown that the in-plane dimensional difference (in-plane distribution) can be changed, and the size relationship between the central portion and the peripheral portion can also be changed. Further, the experimental result shown in FIG.
The in-plane dimensional difference of No. 1 and the in-plane dimensional difference of the light-shielding film opening dimension 102 also have a correlation. It is also shown that the value is larger by a substantially constant value (about 0.03 μm). The reason for this is that, as described above, when reactive ion etching is performed using the etching apparatus shown in FIG. 12, the etching rate in the peripheral portion becomes higher than the etching rate in the central portion, and the etching process is performed. This is because the size of the opening in the peripheral portion is larger than the size of the opening in the central portion, and the in-plane dimensional difference increases in the etching process.

From these, an in-plane dimensional difference that cancels out the in-plane dimensional difference of the light-shielding film opening dimension 102 generated in the etching step is generated in the resist film opening dimension 101 by setting the flow rate of the developer 10. Shielding film aperture size 10
It can be seen that the in-plane dimensional difference of No. 2 can be reduced. Note that the in-plane dimensional difference includes a dimensional variation that occurs due to factors other than the above-described reasons, and thus the actual in-plane dimensional difference of the light-shielding film opening dimension 102 does not become zero.

By changing the flow rate of the developer,
The reason why the in-plane dimensional difference (in-plane distribution) of the resist film opening dimension 101 changes can be considered as follows. In a spray type developing device, when the flow rate value of the developing solution changes, the spreading angle of the developing solution fan-shaped on the mask substrate from the developing solution nozzle changes, and the developing distance between the peripheral portion and the central portion on the mask substrate changes. The supply amount of the liquid relatively changes (see FIG. 3). That is, when the supply amount of the developer increases, the spread angle from the developer nozzle 20 increases, and the supply amount of the developer to the peripheral portion becomes larger than that in the central portion, so that the peripheral portion is more developed than the central portion. As a result, the opening size of the resist film at the peripheral portion becomes larger than that at the central portion. Conversely, when the supply amount of the developer decreases, the spread angle of the developer from the developer nozzle 20 also decreases, and the supply of the developer to the peripheral portion is relatively reduced as compared with the central portion. As a result, the progress of development in the peripheral portion is slowed, and the opening size of the resist film in the peripheral portion is smaller than that in the central portion.
The in-plane opening dimensional difference of the resist film caused by this is
It can be changed by changing the flow rate of the developer. Therefore, by setting the flow rate of the developer so that the in-plane opening dimension difference of the resist film caused by the development cancels the in-plane dimension difference of the light shielding film caused by the etching, the light shielding film in the exposure mask to be formed is set. It is possible to make the opening size in the plane uniform. The experimental results shown in FIGS. 4 to 6 were obtained under the same conditions as those in the conventional example described in paragraph [0006].

[Second Embodiment] In implementing the first embodiment, the process management is performed by appropriately measuring the opening size of the resist film. In the second embodiment, a method of observing a change in an in-plane dimensional difference of a resist film opening dimension caused by a set flow rate of a developer by an indirect method without directly measuring a dimension value of a resist film opening dimension. According to. FIG. 7 is a flowchart showing the steps of the main part of the second embodiment of the present invention. Steps S11 and S12 are the same as steps S1 and S2 of the first embodiment. After pre-baking the resist film in step S12, step S12 is performed.
At 12, the resist film thickness is measured at a plurality of locations. The film thickness value at that time is denoted by B. Next, step S1
In step 4, development is performed. The conditions for development are the same as in the first embodiment. After the Descum process in the developing process is completed, in step S15, the resist film thickness is measured at the same position as the measurement position in step S13.
The film thickness value at that time is assumed to be A. Then, for each position in the plane, the amount of reduction in the resist film in the developing process (film thickness B
-Obtain the film thickness value A) and calculate the in-plane difference (in-plane distribution) of the amount of film reduction of the resist film in the developing step. If the thickness of the spin-coated resist film has a high uniformity in the plane, the measurement of the film thickness in step S13 can be replaced with the measurement at one location. . Thereafter, the mask manufacturing process according to the second embodiment is completed through processes corresponding to step S5 (etching process) and step S6 (resist stripping process) in the first embodiment.

[Operation and Effect of Second Embodiment] When the set flow rate value of the developing solution is changed, the in-plane difference in the amount of reduction in the resist film in the developing process and the in-plane difference in the opening size of the resist film are different. To
As shown in FIG. FIG. 8 shows that there is a correlation between the opening size of the resist film when the set flow rate value of the developing solution is changed and the in-plane difference of the amount of reduction of the resist film in the developing process. FIG. 8 also shows that the positive value and the negative value of the in-plane dimensional difference of the opening size of the resist film coincide with the positive value and the negative value of the in-plane difference of the film thickness of the resist film. Therefore, using the correlation between the set flow rate value of the developing solution, the in-plane difference in the opening size of the resist film, and the in-plane difference in the amount of reduction in the resist film in the developing process shown in FIG. It is possible to calculate the in-plane dimensional difference of the opening size of the resist film.

As shown in FIG. 8, the set flow rate of the developer 10 and the in-plane difference in the resist film opening dimension 101 and the in-plane difference in the amount of reduction in the resist film 4 in the developing step are correlated. For some reason, it is considered as follows. In the present invention, the in-plane difference in the opening size of the resist film is generated by changing the set flow rate value of the developing solution. However, as described in the previous embodiment, this difference is caused by the peripheral portion on the mask substrate. This is to cause a difference in the supply amount of the developer between the and the central part, thereby causing a difference in the progress of the development. On the other hand, the decrease in the thickness of the resist film in the developing process is a phenomenon that occurs because the resist film has a property of being slightly dissolved in the developer even when the resist film is not exposed. Depends on the amount of Therefore, when the above-described difference in the development progress occurs between the peripheral portion and the central portion on the mask substrate, the in-plane difference (in-plane distribution) ), And the in-plane difference (in-plane distribution) is considered to be similar in tendency to the in-plane dimensional difference in the opening size of the resist film. Note that the experimental results of FIG. 8 used in the description of the second embodiment are the same as those of the experiments in which the results of FIGS. However, since the developing devices used in the first embodiment and the second embodiment are different, each value for the set flow rate of the developing solution is different between experiments. As described above, according to the second embodiment, it is possible to observe a change in the in-plane difference in the opening size of the resist film by a simpler method. The management of the in-plane dimensional difference of the opening size of the resist film can be simplified.

[0026]

As described above, in the method of manufacturing an exposure mask according to the present invention, an in-plane difference in the opening size of a resist film that cancels out the in-plane difference in opening size of a light-shielding film generated in an etching step is generated. Since the development of the resist film is performed under the conditions, the in-plane dimension of the light-shielding film opening dimension can be made uniform. Thus, according to the present invention,
It is possible to form an exposure mask with high accuracy,
It is possible to provide an exposure mask that can cope with higher integration and finer dimensions of a semiconductor integrated circuit. Further, according to the embodiment in which the in-plane dimensional difference of the opening size of the resist film caused by the development is estimated from the in-plane difference (in-plane distribution) of the amount of reduction in the resist film in the developing step, the manufacturing process of the exposure mask Can be further simplified.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a procedure of a first embodiment of the present invention.

FIG. 2 is a process sectional view of the first embodiment of the present invention.

FIG. 3 is a configuration diagram of a developing device used in an embodiment of the present invention.

FIG. 4 is a graph showing a relationship between a set flow rate of a developer, an in-plane dimensional difference of a resist film opening dimension, and an in-plane dimensional difference of a light shielding film opening dimension in the first embodiment of the present invention.

5 is a view showing an in-plane distribution of a resist film opening dimension at a set flow rate of a developer of 80 cc / min in FIG. 4 in the first embodiment of the present invention.

FIG. 6 is a diagram showing the in-plane distribution of the light-shielding film opening dimension at a set flow rate of the developer of 80 cc / min in FIG. 4 in the first embodiment of the present invention.

FIG. 7 is a flowchart showing a procedure of a second embodiment of the present invention.

FIG. 8 is a view showing a relationship between a set flow rate of a developer, an in-plane dimensional difference of a resist film opening dimension, and an in-plane difference of a resist film reduction amount in the second embodiment of the present invention.

FIG. 9 is a process sectional view of a conventional example.

FIG. 10 is a diagram showing an in-plane distribution of a resist film opening dimension in a conventional example.

FIG. 11 is a view showing the in-plane distribution of the opening size of a light-shielding film in a conventional example.

FIG. 12 is a configuration diagram of a lower electrode portion of a reactive ion etching apparatus for manufacturing a mask.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 mask substrate 2 quartz substrate 3 light shielding film 4 resist film 10 developer 20 developer nozzle 21 support base 22 pressurizer 23 outer container 24 flow controller 31 quartz cover 32 lower electrode 101 resist film opening dimension 102 light shielding film opening dimension

Continued on the front page (51) Int.Cl. ⁷ Identification code FI H01L 21/302 A

Claims (5)

(57) [Claims] 1. A step of applying and exposing a resist on a transparent substrate having a light-shielding film formed on its surface, and (2) forming a patterned resist film on the light-shielding film by performing development. And (3) a step of forming a pattern of a light-shielding film by performing etching using the resist film formed in the step as a mask, the method comprising the steps of: The in-plane difference in the opening size of the resist film and the in-plane difference in the opening size of the light-shielding film generated in the step (3) are measured in advance by changing the flow rate of the developing solution. In the step (3), based on the measurement result of the in-plane dimensional difference between the resist film opening dimension and the light shielding film opening dimension for each flow rate of the developing solution previously determined, the light shielding film opening dimension generated in the step (3) is determined. A method for producing an exposure mask, wherein development is performed under conditions that generate an in-plane dimensional difference in resist film opening dimensions that cancels out in-plane dimensional differences in the method. 2. The exposure according to claim 1, wherein the development in the step (2) is performed by a spray method, and the condition is determined by selecting a set flow rate value of the developer. Manufacturing method for masks. 3. The method of manufacturing an exposure mask according to claim 1, wherein the exposure in the step (1) is performed by electron beam exposure. 4. The method according to claim 1, wherein the etching in the step (3) is performed by reactive ion etching. 5. A step of applying and exposing a resist on a transparent substrate having a light-shielding film formed on its surface, and (2) forming a patterned resist film on the light-shielding film by performing development. And (3) a step of forming a pattern of a light-shielding film by performing etching using the resist film formed in the step as a mask, the method comprising the steps of: The in-plane dimensional difference of the opening size of the resist film to be changed is changed in advance by changing the flow rate of the developing solution.
It is calculated from the in-plane dimensional difference of the amount of film reduction due to the image, and the in-plane dimensional difference of the light-shielding film opening dimension generated in the step (3) is measured in advance with respect to the developer flow rate. In the step (2), the difference between the in-plane dimensional differences of the opening size of the resist film for each of the flow rates of the developing solution obtained in advance is determined .
Based on the calculation result and the measurement result of the in-plane difference in the light-shielding film opening size, the in-plane size difference in the resist film opening size that cancels out the in-plane size difference in the light-shielding film opening size generated in the above (3) step. A method for producing an exposure mask, wherein development is performed under conditions that occur.