JP2003188087A - Aligning method and aligner and method for manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To conquer the difficulty of mask production while enhancing resolution in the exposure of a gate line, or the like, of a severe dimensional rule when a desired pattern is obtained by projection mapping using a phase shift mask. <P>SOLUTION: In an aligner arranged to obtain a desired pattern by projection mapping using a phase shift mask 10, a polarization condition selecting unit 20 for selecting the polarization direction of illumination light with respect to the phase shift mask 10 is provided in parallel with the direction of the compositional side of a pattern formed on the phase shift mask 10 at the time of projection mapping. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure method and an exposure apparatus used in a lithography process in a semiconductor device manufacturing process, and a semiconductor device manufacturing method including the lithography process.

[0002]

2. Description of the Related Art In recent years, in a lithography process in a manufacturing process of a semiconductor device, a high resolution exceeding a resolution limit determined by a wavelength of light is required with miniaturization of a pattern to be formed. 2. Description of the Related Art Phase shift masks (reticles) that enable formation of fine patterns with an exposure wavelength or less are widely used. The phase shift mask obtains high resolution by utilizing the phase difference of transmitted light, and for example, a Levenson type mask is known.

When such a phase shift mask is used, non-polarized light is usually used as illumination light for the mask in order to avoid azimuth dependence of pattern resolution. On the other hand, it is known that the image quality of the transferred image is improved if the illumination light for the mask is polarized in the direction parallel to the constituent sides of the pattern formed on the mask. As disclosed in Japanese Patent No. 88356, a technique combining this with a phase shift mask is also proposed.

[0004]

However, in order to make the polarized light in the azimuth parallel to the pattern-constituting side on the mask, each shifter for generating a phase difference of light in the phase shift mask is changed in accordance with the azimuth. For example, TE (transver
se electric) transparent or TM (transverse magnetic)
It is necessary to install a transmission polarization element. That is, a polarizing element that polarizes transmitted light must be locally provided. However, it is very difficult to make a phase shift mask having such a complicated structure. The difference between TE transmission and TM transmission here is due to the difference between the vibration direction of light in the y direction or the x direction on the incident surface.

Therefore, the present invention makes it possible to enhance the resolution in exposure of a gate line or the like having a strict dimensional rule when obtaining a desired pattern by projection mapping using a phase shift mask, and at the same time, polarization By making the arrangement of the elements a simple structure, it is possible to overcome the difficulty of mask manufacturing, and it is not necessary to consider the azimuth dependence for exposure according to a less strict rule,
An object is to provide an exposure method, an exposure apparatus, and a method for manufacturing a semiconductor device.

[0006]

In order to achieve the above object, the exposure method of the present invention is such that during projection mapping using a phase shift mask, the constituent edges of the pattern formed on the phase shift mask are The polarization direction of the illumination light with respect to the phase shift mask is selected so as to be parallel to the direction.

Further, the exposure apparatus of the present invention is such that, in the projection mapping using the phase shift mask, the phase shift mask is arranged so as to be parallel to the direction of the constituent side of the pattern formed on the phase shift mask. Selection means is provided for selecting the polarization direction of the illumination light with respect to.

Further, in the method for manufacturing a semiconductor device of the present invention, the projection mapping using the phase shift mask is performed so that it becomes parallel to the direction of the constituent side of the pattern formed on the phase shift mask. The polarization direction of the illumination light with respect to the phase shift mask is selected.

According to the exposure method of the above procedure, the exposure apparatus of the above configuration, and the method of manufacturing the semiconductor device of the above procedure, depending on the selection of the polarization direction of the illumination light, for example, when the resolution in exposure is increased. It is possible to make the pattern constituent sides on the phase shift mask parallel to the polarization direction of the illumination light, and in other cases, that is, not to consider the azimuth dependency regarding exposure in the transfer of the mask used for trimming. The trimming mask mentioned here is composed of an arbitrary azimuth pattern, and in order to avoid the azimuth dependence of the transfer pattern dimension, it is necessary to illuminate the mask without polarization. In addition, since the polarization direction can be made parallel to the pattern configuration side by selecting the polarization direction of the illumination light, for example, a phase shift mask in which a pattern including only the configuration side in a specific direction is formed is different for each direction of the configuration side. If used properly, it is not necessary to provide a local polarizing element on the phase shift mask.

Further, the exposure apparatus of the present invention uses at least two phase shift masks each having a pattern formed of only constituent edges in a specific direction depending on the direction of the constituent edges. It is characterized in that a polarizing element for polarizing the illumination light with respect to the phase shift mask is provided so as to be parallel to the direction of the constituent sides of the pattern formed on the mask.

In the exposure apparatus having the above-mentioned structure, since the polarization element corresponding to the direction of the pattern forming side is attached to each phase shift mask, a desired pattern can be obtained by projection mapping using each of these phase shift masks. Then, even if the illumination light for each phase shift mask is unpolarized,
Even if a local polarization element is not provided on each phase shift mask, the polarization direction of the illumination light for each phase shift mask is made parallel to the pattern configuration side of the phase shift mask by the polarization element attached to each phase shift mask. It will be selected.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An exposure method, an exposure apparatus and a semiconductor device manufacturing method according to the present invention will be described below with reference to the drawings.

The exposure method and exposure apparatus described here are used in a semiconductor device manufacturing process. More specifically, it is used for forming a desired pattern on a wafer substrate by projection mapping using a phase shift mask in a lithography step in a semiconductor device manufacturing process.

First, a schematic structure of the exposure apparatus will be described. FIG. 1 is an explanatory diagram showing an example of a schematic configuration of an exposure apparatus according to the present invention. As shown in the figure, the exposure apparatus described here has at least the phase shift mask 10
And a light source (not shown) of illumination light for the phase shift mask 10 and a polarization state selection unit 20 located between them.

Of these, the phase shift mask 10 is arbitrarily selected according to the pattern to be formed on the wafer substrate.
It shall be exchangeable. However, in the present embodiment, as will be described later in detail, as the types of the phase shift mask 10, three types corresponding to V (vertical) azimuth, H (horizontal) azimuth, and non-polarized light are selectively used. .

Further, the light source is adapted to emit illumination light in a non-polarized state in order to avoid the azimuth dependence of the image forming performance of the pattern. That is, when a laser such as KrF or ArF is used as the light source, the light source itself has a strong linear polarization state, but the depolarization element in the exposure apparatus makes it non-polarized at the mask incidence stage, and thus the polarization state selection is performed. It suffices that the unit transmits the light in the unpolarized state.

The polarization state selection unit 20 is a unit for realizing a polarization state in accordance with the pattern orientation on the phase shift mask 10. That is, it is for selecting the polarization direction of the illumination light with respect to the phase shift mask 10. Therefore, the polarization state selection unit 20
Has a disc-shaped revolver 21 rotatably provided. Then, a first polarization section 22, a second polarization section 23, and a non-polarization section 24 are provided on the revolver 21.

The first polarizing portion 22 is a portion formed of a polarizing element that transmits only the polarized component in the V direction (the y direction on the incident surface of the light entering the phase shift mask 10), that is, the illumination light from the light source is transmitted through TE. It is what makes me. The second polarization unit 23 is a portion formed of a polarization element that transmits only the polarization component in the H direction (the x direction on the incident surface of the light to the phase shift mask 10), that is, the illumination light from the light source is TM transmitted. is there. The non-polarization part 24 is a part that transmits the illumination light from the light source as it is unpolarized. It should be noted that, as the polarization elements forming the first polarization section 22 and the second polarization section 23, known polarization elements may be used, and therefore description thereof will be omitted here. In addition, the non-polarization part 24
For example, it may be considered that the above is constituted by a simple aperture.

With such a configuration, in the polarization state selection unit 20, the polarization direction of the illumination light from the light source is the V line direction whose vibration direction corresponds to TE transmission and the H line whose vibration direction corresponds to TM transmission. Choose to be either directional or unpolarized. This polarization state selection unit 20
It is conceivable that the position where is provided is directly above the phase shift mask 10. This is because considering the change in the polarization state after passing through the lens system, it is desirable to select the polarization direction of the illumination light immediately before the incident surface of the phase shift mask 10.

Next, an example of processing operation in the exposure apparatus having the above configuration, that is, the procedure of the exposure method in this embodiment will be described.

Here, it is assumed that the pattern exposure as shown in FIG. 2 is performed. The pattern shown in the figure shows a specific example of a pattern to be formed on a wafer substrate, and includes a gate line 31 extending in the V direction (hereinafter referred to as “V line”) 31 and a gate line extending in the H direction (hereinafter referred to as “V line”). (Referred to as “H line”) 32, and a non-oriented trim portion 33 arranged around them.

In this embodiment, such a pattern is formed using a mask divided into three as shown in FIG. The mask in the illustrated example shows a specific example of the mask used for forming the pattern in FIG. 2, and includes a V line phase shift mask (hereinafter referred to as “V mask”) 11 and an H line phase shift mask. (Hereinafter referred to as "H mask") 12
And a trim mask 13 for forming the trim portion 33 other than those. The V mask 11 is for forming only the V line 31, and has a pattern including only constituent sides extending in the V direction. The mask 12 for H is H
This is for forming only the line 32, and has a pattern consisting of only constituent sides extending in the H direction. Further, since the trim mask 13 forms the trim portion 33, the constituent sides of the pattern have no direction dependency.

That is, in forming the pattern of FIG. 2, first, the V mask 11, the H mask 12, and the trim mask 13 as shown in FIG. 3 are prepared. Then, after the masks 11, 12, and 3 are prepared, they are sequentially set in the exposure device and exposed to form the pattern shown in FIG. 2 on the wafer substrate. At this time, a total of three divided exposures are performed, but the polarization state selection unit 20 selects the polarization direction of the illumination light according to the mask to be used for each exposure.

Specifically, when exposure is performed using the V mask 11, only the V line 31 is formed by this mask 11, and TE is used to increase the line resolution in this direction. Since the exposure by polarized light is desirable, the rotation stop position of the revolver 21 is selected so that the illumination light from the light source passes through the first polarization unit 22. As a result, the polarization state of the illumination light from the light source becomes TE polarized light, and the polarization direction thereof is parallel to the direction of the constituent side of the pattern formed on the V mask 11.

When the exposure using the V mask 11 is completed, the mask 11 is exchanged for the H mask 12, and the exposure using the H mask 12 is performed. In this case, only the H line 32 is formed by the mask 12, and it is desirable to use the TM polarized light for increasing the line resolution in this direction. Therefore, the rotation stop position of the revolver 21 is set to the illumination light from the light source. Select to transmit through the second polarization unit 23. As a result, the polarization state of the illumination light from the light source becomes TM polarization, and the polarization direction and the H mask 12 are used.
The direction of the constituent side of the pattern formed above is parallel.

The two exposures up to this point form the gate lines 31 and 32 in the V direction and the H direction, respectively. After that, in order to form a pattern other than the V line 31 and the H line 32, the H mask 12 is replaced with a trim mask 13, and the trim mask 13 is used for exposure. In this case, as compared with the case where the gate lines 31 and 32 are formed, the resolution is not so required, and therefore it is not necessary to use the phase shift mask. However, in the trim mask 13, component sides extending in the V direction and component sides extending in the H direction are mixed. Therefore, it is desirable that the polarization state is non-polarized (random) in order to avoid a line width difference between VHs. Therefore, the rotation stop position of the revolver 21 is selected so that the illumination light from the light source passes through the non-polarization part 24. As a result, the polarization state of the illumination light from the light source becomes non-polarized, and it becomes possible to perform exposure without direction dependency.

By these three exposures, the pattern as shown in FIG. 2 is projected and imaged on the wafer substrate. That is, by at least three divided exposures,
Projection mapping using the phase shift masks 11 and 12 is performed on the gate lines 31 and 32 having strict size rules, and the V lines 31 are used as the phase shift masks 11 and 12 at that time.
Another H line 32 is used. Then, depending on the orientation (V or H) of the mask pattern, the polarization direction of the illumination light is selected to be parallel to the pattern longitudinal direction. Further, the exposure of the trim mask 13 is an unpolarized exposure.
By doing so, each pattern is exposed in an optimal polarization state.

FIG. 4 is an explanatory diagram showing a specific example of the simulation evaluation result of the difference in the image forming characteristics due to the difference in the polarization state. In the figure, y-axis NILS (Normalized I
mageLog Slope) is an index representing the steepness of the image represented by the following equation (1) when the intensity distribution of the image is I (x), and the higher the value, the wider the process margin. can get. In the formula (1), W represents the pattern width.

[0029]

[Equation 1]

According to the simulation evaluation result of the example shown in the figure, it can be confirmed that, for example, when the V-line 31 is formed, the image quality obtained can be improved by performing the projection mapping with the TE polarized light. That is, V line 31, H line 32
The phase shift mask is divided into two according to, and the polarization state of the illumination light with respect to each of the phase shift masks 11 and 12 is selected to be parallel to the orientation of the mask pattern. It can be said that the image quality can be improved and the process margin can be expanded as compared with the case of irradiating.

As described above, according to this embodiment, during projection mapping, the phase shift mask 11 is arranged so as to be parallel to the direction of the constituent side of the pattern formed on the phase shift masks 11 and 12. , 12, the polarization direction of the illumination light is selected, so that the image quality of the transferred image can be improved and the gate lines 31, 32 with strict size rules can be selected.
It is possible to increase the resolution of. Moreover,
Since the polarization direction can be selected and changed at the mask incidence stage, it is not necessary to previously provide a local polarization element on the phase shift masks 11 and 12, and it is possible to overcome the conventional difficulty of mask manufacturing. .

In particular, in this embodiment, two phase shift masks 11 and 12 for each direction, for V line and H line, are used.
And the selection of the polarization direction of the illumination light corresponding to the switching of the phase shift masks 11 and 12, the improvement of the image quality of the transferred image and the facilitation of the mask manufacturing are surely performed. Can be one.

Further, in the present embodiment, in addition to the two phase shift masks 11 and 12, a trim mask 13 having no direction dependency on the constituent edges of the pattern is prepared, and the projection mapping using the trim mask 13 is performed. In this case, the illumination light is not polarized.
Unlike 1 and 32, it is possible not to consider the azimuth dependency for exposure according to a less strict rule. That is, with respect to the trim portion 33 and the like other than the gate lines 31 and 32, it is not necessary to consider the orientation dependency. Further, the trim section 33 and the like can be formed by one exposure while avoiding a line width difference between VHs.

The azimuths to which the phase shift masks 11 and 12 correspond are not limited to the two directions V and H as described in the present embodiment, but may be three or more and may be arbitrary. The orientation may be In that case, it is assumed that the polarization state selection unit 20 can select the polarization direction of the illumination light in accordance with three or more directions or any direction.

Further, in this embodiment, two polarization element portions such as the first polarization portion 22 and the second polarization portion 23 are provided on the revolver 21, and the revolver 21 is rotated to select the polarization direction. Although described as an example, it may be considered that the polarization direction is selected by only one polarization element section on the revolver. FIG. 5 is an explanatory diagram showing another configuration example of the polarization state selection unit. In the polarization state selection unit 20a of the illustrated example, only one polarization part 22a is provided on the revolver 21a in addition to the non-polarization part 24, but the polarization part 22a itself is at least 90.
It is provided so that it can rotate. Then, the polarization section 22a is rotated according to the pattern orientation of the phase shift masks 11 and 12, thereby selecting the polarization direction of the illumination light. The polarization state selection unit 20 having such a configuration
Even when a is used, the improvement in the image quality of the transferred image and the facilitation of the mask manufacturing can be realized in exactly the same manner as in the above-described embodiment.

Further, it is possible to select the polarization direction as described below. FIG. 6 is an explanatory diagram showing a configuration example of a main part of another embodiment of the exposure apparatus. In the case of the illustrated example, a polarizing plate is fixedly installed on the mask as a polarization state selection unit. That is, a TE transparent polarizing plate 25 is provided on the V mask 11, a TM transparent polarizing plate (not shown) is provided on the H mask 12, and nothing is attached to the trim mask 13. do not do. By performing exposure using such a mask having three polarization state selecting functions, even if the above-mentioned polarization state selecting units 20 and 20a are not provided, the pattern forming sides on each mask are parallel to each other. It becomes possible to select the polarization direction as described above, and it is possible to realize the improvement of the image quality of the transferred image and the facilitation of the mask manufacturing, just as in the case described above. In addition, since the polarizing plate is fixedly installed on the mask and only one kind of polarizing plate is installed in one mask, it is expected that the phase shift mask can be easily manufactured and the exposure apparatus can be simplified.

[0037]

As described above, according to the exposure method, the exposure apparatus, and the semiconductor device manufacturing method of the present invention, the direction of the constituent side of the pattern formed on the phase shift mask during projection mapping. Since the polarization direction of the illumination light with respect to the phase shift mask is selected so that it becomes parallel to, it is possible to improve the image quality of the transferred image and the resolution for gate lines with strict size rules. Can be increased. Moreover, since the polarization direction can be selected, it is not necessary to previously provide a local polarization element on the phase shift mask, and the conventional difficulty of mask manufacturing can be overcome. Further, by selecting the polarization direction of the illumination light, it is possible to realize that the azimuth dependence is not considered for the exposure according to the less strict rule.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of a schematic configuration of an exposure apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing a specific example of a pattern to be formed on a wafer substrate.

FIG. 3 is an explanatory diagram showing a specific example of a mask used for forming the pattern of FIG.

FIG. 4 is an explanatory diagram showing a specific example of a simulation evaluation result of a difference in imaging characteristics due to a difference in polarization state.

FIG. 5 is an explanatory diagram showing another configuration example of the polarization state selection unit in the exposure apparatus according to the present invention.

FIG. 6 is an explanatory diagram showing a configuration example of a main part of another embodiment of the exposure apparatus according to the present invention.

[Explanation of symbols]

10 ... Phase shift mask, 11 ... V mask, 12 ... H
Mask, 13 ... Trim mask, 20, 20a ... Polarization state selection unit 21, 21a ... Revolver, 22 ... First polarization part, 22a ... Polarization part, 23 ... Second polarization part, 24 ... Non-polarization part, 25 ... Polarizing plate, 31 ... V line, 32 ... H line, 33
… Trim part

Claims (8)

[Claims] 1. An exposure method for obtaining a desired pattern by projection mapping using a phase shift mask, wherein the projection mapping is parallel to the direction of the constituent side of the pattern formed on the phase shift mask. So that the polarization direction of the illumination light with respect to the phase shift mask is selected. 2. At least two phase shift masks each having a pattern formed of only constituent edges in a specific direction are prepared for each direction of the constituent edges, and the desired pattern is obtained by projection mapping using each phase shift mask. 2. The exposure method according to claim 1, wherein the polarization direction of the illumination light is selected in correspondence with the switching of the at least two phase shift masks. 3. In addition to the at least two phase shift masks, a non-azimuth mask having no direction dependence on the constituent edges of the pattern is prepared, and the desired pattern is obtained by projection mapping using each of these masks. At the time of the projection mapping using any one of the at least two phase shift masks, the polarization direction of the illumination light is selected corresponding to the switching of the phase shift mask, and the projection mapping using the non-azimuth mask is performed. The exposure method according to claim 2, wherein the illumination light is non-polarized. 4. An exposure apparatus configured to obtain a desired pattern by projection mapping using a phase shift mask, wherein the constituent sides of the pattern formed on the phase shift mask at the time of the projection mapping. An exposure apparatus comprising: a selection unit that selects a polarization direction of illumination light with respect to the phase shift mask so as to be parallel to the direction. 5. At least two phase shift masks each having a pattern formed of only constituent edges in a specific direction are used for each direction of the constituent edges, and the selecting means is capable of switching between the at least two phase shift masks. The exposure apparatus according to claim 4, wherein the polarization direction of the illumination light is selected. 6. In addition to the at least two phase shift masks, a non-azimuth mask having no direction dependence on the constituent edges of the pattern is used, and the selecting means uses one of the at least two phase shift masks. In the case of the projection mapping, the polarization direction of the illumination light is selected corresponding to the switching of the phase shift mask, and the illumination light is non-polarized in the projection mapping using the non-azimuth mask. The exposure apparatus according to claim 5. 7. An exposure apparatus configured to obtain a desired pattern by projection mapping using a phase shift mask, wherein a phase shift mask having a pattern formed of only the constituent edges in a specific direction is formed on the constituent edges. At least two are used for each direction, and each phase shift mask is provided with a polarization element that polarizes the illumination light for the phase shift mask so that it is parallel to the direction of the constituent side of the pattern formed on the phase shift mask. An exposure apparatus, which is characterized by being processed. 8. A method of manufacturing a semiconductor device, wherein a desired pattern is formed on a wafer substrate by projection mapping using a phase shift mask, wherein the pattern formed on the phase shift mask is formed during the projection mapping. A method for manufacturing a semiconductor device, characterized in that the polarization direction of illumination light with respect to the phase shift mask is selected so as to be parallel to the direction of the constituent sides.