JPH0534898A - Phase difference exposing method and phase difference mask for this method - Google Patents

Abstract

PURPOSE:To provide the phase difference mask and phase difference exposing method which can pattern a wafer having steps. CONSTITUTION:First and second phase shifters 112 and 114 for increasing the contrast of the projected light of the mask and first and 2nd sub-phase shifters 116 and 118 for determining the imaging position of the projected light are combined and provided in the phase difference exposing method region 106 of a common mask substrate 110. The one sub-phase shifter 130 may be used in place of using the two sub-phase shifters 116 and 118. The light shielding part 120 may not be provided. The first and 2nd phase shifters are formed to 90 deg. + or -10 deg. phase difference in the directions opposite from each other with respect to direct transmitted light. The first and 2nd sub-phase shifters are formed to the phase difference of either of (360 deg. + or -10 deg.), (180 deg. + or -10 deg.) or (0 deg. and 180 deg. + or -10 deg.) with respect to the direct transmitted light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase difference exposure method for forming a fine pattern on a wafer by using light exposure and a phase difference mask used therefor.

[0002]

2. Description of the Related Art A method using a photomask with a phase shifter has been proposed as one method for finely processing a wafer by using a technique of reducing and transferring a photomask pattern onto a photosensitive layer provided on a wafer, for example, a resist layer. (Japanese Patent Application No. Hei 2-161239). First, prior to the description of the present invention, the proposed phase difference exposure technique will be described with reference to the drawings.

This method is a technique in which a resist layer provided on a wafer is subjected to a phase difference exposure using phase-shifted light that is phase-shifted with respect to the phase of light directly transmitted from a mask substrate which constitutes a photomask. The photomask used for this phase difference exposure is called a phase difference mask, and its constituent parts are patterned on the mask substrate 10 transparent to the light used, as shown in the main part of FIG. A plurality of light shielding parts 12
a, 12b, 12c, and 12d (represented by 12 as a representative, and the light-shielding portion is also referred to as a light-shielding pattern) are arranged at appropriate intervals so as to be adjacent to the light-shielding portion 12 and both outsides thereof. Two types of patterned phase shifters 14
a, 14b, 14c, (representatively indicated by 14) and 16
a and 16b (representatively indicated by 16) are alternately arranged. Of course, a photomask portion (not shown) may be formed with a portion for exposing the resist layer by a normal exposure method, but the description thereof is omitted here. The photomask used in the normal exposure method has, for example, a configuration in which only the light shielding portion is arranged on the mask substrate, or a configuration in which the light shielding portion and one type of phase shifter are combined and arranged,
Alternatively, one type of phase shifter is arranged. 2B is a sectional view taken along line I-I of FIG. 2A.
Shown in.

The photomask 10 will be described. The light transmitted through the mask substrate 10 itself is referred to as direct transmitted light here. When the photomask is illuminated with light,
Light is transmitted through a region of the mask substrate 10 where the light shielding portion 12 is not provided (this region is referred to as a transparent region), and is directly transmitted light in a region where the phase shifters 14 and 16 are not provided. Hereinafter, the phase of this directly transmitted light will be considered as a reference. In the region of the photomask where the phase shifter is provided, the directly transmitted light that has passed through the mask substrate subsequently passes through this phase shifter. The light transmitted through the phase shifters 14 and 16 is shifted in phase with respect to the directly transmitted light. In this case, both the phase shifters 14 and 16 are formed of the same transparent material in a film shape, and the respective film thicknesses thereof cause a relative phase difference (shift amount) of 90 ° with respect to the directly transmitted light. And phase shifter 1
The relative phase difference between 4 and 16 is set to 180 ° to enable high resolution phase difference exposure. In this specification, a unit of an angle such as a phase, a phase difference or a phase amount is represented by "degree".

Further, in the photomask structure shown in FIG. 2A, the shifter edges of the phase shifters 14 and 16 provided between the adjacent light shielding portions 12 selectively provided on the mask substrate 10 serve as transparent portions of the mask substrate 10. It is provided. The light intensity profile of the portion corresponding to the line AA of this photomask is shown in FIG. Also understood from this profile I haven't. Therefore, even if the phase shifter edge is arranged on the transparent portion of the mask substrate other than the light-shielding portion, unnecessary transfer of the shifter edge does not occur, so this photomask is suitable for forming a complicated pattern.

FIG. 3A shows a case where a resist layer having a step on the wafer surface is exposed to form a fine pattern by using the photomask having such a structure.
A brief description will be given with reference to (B) and (C).

FIG. 3A shows a retardation mask having a structure similar to that shown in FIG. 2B. Therefore, the same components are designated by the same reference numerals.
The light intensity distribution when projected using this phase difference mask in an i-line reduction optical system having a numerical aperture NA = 0.50 and σ = 0.50 is as shown in FIG. 3B. Distribution. In the figure, the horizontal axis corresponds to the position of the phase difference mask, and the vertical axis represents the light intensity. At the so-called in-focus position where the focus is not shifted, the distribution shown by the solid line a has a sufficient contrast for pattern formation. However, when there is a defocus in the direction orthogonal to the wafer surface, that is, at a position deviated from the in-focus position, the contrast deteriorates as shown by a broken line b.

In general, the wafer surface on which the pattern is to be formed may be a flat surface or may be an uneven surface due to the already formed circuit components. An example of such a step on the surface is shown in FIG.
In the figure, 20 is a substrate, 22 is a patterned first layer wiring, and 24 is an intermediate insulating film 26 is a phase difference exposure using a phase difference mask for forming a second layer wiring. Is a metal layer to be patterned by utilizing.
Reference numeral 28 denotes a resist pattern obtained by developing after performing the phase difference exposure with the phase difference mask of FIG.

[0009]

When there is a step in the resist layer 28 which is a photosensitive layer, if the image forming position of the projection light of the retardation mask is aligned with the lower surface of the step, the resist layer 26 The areas corresponding to the phase shifters 14a and 16a are illuminated with the light intensity indicated by the solid line a. Therefore, in this region, it is sufficiently resolved and patterned neatly. However, when the depth of focus of the reduction optical system becomes smaller with the miniaturization of the pattern, the upper surface of the step existing in the region exceeding the depth of focus is illuminated with the light intensity indicated by the broken line b. , 14b, 16c, respectively, the resist layer portions are not sufficiently resolved. Therefore, pattern separation is impossible.

An object of the present invention is to perform simultaneous exposure on a photosensitive layer having a step using the same photomask to form a fine pattern of the photosensitive layer on a wafer having a step with high resolution.
(EN) A phase difference exposure method capable of forming a fine pattern on a wafer, and a phase difference mask used for the method.

[0011]

To achieve this object, according to the method of the present invention, a photosensitive layer is formed by using phase-shifted light that is phase-shifted with respect to the phase of light directly transmitted from a mask substrate. In performing the phase difference exposure, the phase shift light is combined with the first and second phase shift light and the first and second phase shift light.
The sub-phase-shifted light is separated into (a) the first and second phase-shifted light by 90 ° ± 10 ° in the opposite directions to the above directly transmitted light.
(B) one of the first and second sub-phase-shifted lights described above has the same phase as the directly transmitted light, and the other directly transmits this directly transmitted light. It is characterized by performing an appropriate phase difference within a range of 180 ° ± 10 ° to light in either direction.

In implementing the present invention, preferably, the above-mentioned separation of the phase-shifted light is performed by (a) the first and second phase-shifted lights are separated by 90 ° ± in opposite directions to the directly transmitted light. Give an appropriate phase difference within the range of 10 °,
(B) Both the first and second sub-phase-shifted lights are provided by giving an appropriate, same amount of phase difference within a range of 180 ° ± 10 ° to either of the direct transmitted lights. May be.

Further, in carrying out the present invention, the above-mentioned phase shift light is separated into first and second phase shift lights and sub phase shift light, and the phase shift light is separated by
(A) The first and second phase-shifted lights are given an appropriate phase difference within the range of 90 ° ± 10 ° in the opposite directions to the directly transmitted light, and (b) the sub-phase shift described above. The light may be provided by giving the directly transmitted light a phase difference of a different amount from that of the above-described first and second phase-shifted lights.

According to the first aspect of the phase difference mask of the present invention, the phase difference mask comprises at least a mask substrate and a phase shifter formed in a pattern on the mask substrate. In a phase difference mask for projecting a mask onto a photosensitive layer with projection light to perform a phase difference exposure on the photosensitive layer, the phase shifter includes first and second phase shifters for increasing the contrast of the projection light. Of the first and second phase shifters, or one or two sub-phase shifters for determining the image formation position of the above-mentioned projected light on the photosensitive layer. Characterize.

The second phase difference mask according to the present invention can also be used.
According to the gist of the invention, at least a mask substrate and a phase shifter provided in a pattern on the mask substrate are provided, and phase shift light that gives a phase difference to the phase of the direct transmitted light from the mask substrate is used. A phase difference mask for performing a phase difference exposure of a resist layer which has been exposed to light, (a) comprises first and second phase shifters and first and second sub-phase shifters, and (b) a second phase shifter. The 1-phase shifter
The first phase-shifted light that has passed through this is configured as a phase shifter that gives an appropriate phase difference within the range of 90 ° ± 10 ° to the above-mentioned directly transmitted light. Is configured as a phase shifter that gives an appropriate phase difference within the range of 270 ° ± 10 ° to the above-mentioned directly transmitted light to the second phase-shifted light transmitted therethrough, (d)
The first sub-phase shifter described above has 0 ° ± 10 with respect to the directly transmitted light as the first sub-phase shift light transmitted through the first sub-phase shifter.
Or a second phase shifter for providing an appropriate phase difference within a range of 360 ° ± 10 °, and (e) the second
The sub-phase shifter is configured as a phase shifter that gives an appropriate amount of phase difference within a range of 180 ° ± 10 ° to the directly transmitted light for the second sub-phase-shifted light transmitted therethrough. And

In implementing the retardation mask of the second aspect, preferably, (a) a plurality of light shielding portions are sequentially arranged in a pattern on the mask substrate, and (b) successively. The first phase shifter described above is provided in one of the two adjacent transparent sections between the light-shielding sections, and the first phase shifter sandwiched between the first phase shifters is disposed in the central region of the transparent section. One sub-phase shifter is provided, and (c) the second phase shifter is sandwiched between the other transparent part of the two adjacent transparent parts and the second phase shifter, and the sub-phase shifter is arranged in the central region of the transparent part. It is preferable to provide the above-mentioned second sub-phase shifter provided.

In implementing the retardation mask according to the second aspect, preferably, (a) the mask substrate is provided with the first phase shifter and the second phase shifter arranged alternately adjacent to each other, and (b) It is preferable that the first sub-phase shifter is provided at the center of the first phase shifter, and (c) the second sub-phase shifter is provided at the center of the second phase shifter.

In implementing the phase difference mask of the second aspect, preferably, the first sub-phase mask and the second sub-phase mask may be replaced with each other.

In implementing the retardation mask according to the second aspect, it is preferable that (a) the pattern widths of the first and second phase masks taken in the direction along the sequential arrangement direction be the same width. (B) The pattern widths of the first and second sub-phase masks taken in the direction along the arrangement direction may have different widths.

In implementing the retardation mask according to the second aspect, preferably, (a) the pattern widths of the first and second sub-phase masks taken in the direction along the arrangement direction are the same width. , (B) the relative phase difference between the first and second sub-phase-shifted lights is held at an appropriate value within the range of 180 ° ± 10 °, and (C) the height of the first and second sub-phase masks described above. It is good to have different heights.

According to the third aspect of the phase difference shifter of the present invention, at least a mask substrate and a phase shifter provided in a pattern on the mask substrate are provided, and the phase of the direct transmitted light from the mask substrate is provided. In a phase difference mask for performing a phase difference exposure on a photosensitive layer using a phase shift light having a phase difference with respect to, a (a) phase shifter includes first and second phase shifters and a sub phase shifter. , (B)
The first phase shifter is configured as a phase shifter that gives an appropriate phase difference within a range of 90 ° ± 10 ° to the above-mentioned directly transmitted light, to the first phase shift light that has passed through the first phase shifter, (C) The second phase shifter converts the second phase shift light that has been transmitted through the second phase shifter by 270 ° ±.
It is configured as a phase shifter that gives an appropriate phase difference within the range of 10 °, and (d) the sub-phase shifter transmits (180 ° ±± It is characterized in that it is configured as a phase shifter that gives an appropriate amount of phase difference within the range of (10 °) or (360 ° ± 10 °).

In implementing the phase difference mask according to the third aspect, preferably, (a) a plurality of light-shielding portions are sequentially arranged in a pattern on the mask substrate, and (b) successive light-shielding portions are sequentially arranged. A first phase shifter and a sub-phase shifter disposed in the central region of the transparent portion and sandwiched by the first phase shifter are provided on one of the two transparent portions adjacent to each other between the transparent portions, (C) A second phase shifter is provided on the other transparent portion of the two adjacent transparent portions, and the sub-phase shifter is sandwiched between the second phase shifters and disposed in the central region of the transparent portion. It is good to provide.

In implementing the phase difference mask according to the third aspect, it is preferable that (a) the mask substrate described above be provided with the first phase shifter and the second phase shifter arranged alternately adjacent to each other. , (B) the first sub-phase shifter is preferably provided at the center of the first phase shifter, and (c) the second sub-phase shifter is provided at the center of the second phase shifter.

In implementing the phase difference mask of the third aspect, preferably, the pattern width of the sub phase shifter taken in the direction along the sequential arrangement direction of the first and second phase masks described above is used. It is preferable that the width is different from the widths of the first and second phase masks described above.

In implementing the retardation mask of the third aspect, preferably, (a) the above-mentioned mask substrate,
Providing a plurality of light-shielding parts arranged in sequence in a pattern,
(B) The first phase shifter described above is disposed on one transparent part of two adjacent transparent parts between successive light-shielding parts.
(C) The above-mentioned second phase shifter is disposed on the other transparent portion of the two adjacent transparent portions, and (d) the above-mentioned first or second transparent portion.
It is preferable to dispose the above-mentioned sub-phase shifters at the transparent portions on both sides of the phase shifter.

In implementing the retardation mask of the third aspect, preferably, (a) the above-mentioned mask substrate,
The first phase shifter and the second phase shifter are alternately arranged so as to be adjacent to each other, and (b) the sub-phase shifter is provided at the center of either one of the first and second phase shifters. good.

In implementing the phase difference mask of the third aspect, preferably, the pattern widths of the sub-phase shifter taken in the direction along the sequential arrangement direction of the first and second phase shifters are The width may be different from the widths of the first and second phase shifters.

In implementing the phase difference mask according to the third aspect, preferably, the sub-phase shifter described above is used.
When using a phase shifter that produces a phase difference of 0 ° ± 10 °,
It is preferable that the sub-phase shifter has a plurality of dot-shaped rectangular patterns that are separated from each other.

According to a fourth aspect of the phase difference mask of the present invention, the phase difference of the direct transmitted light from the mask substrate is provided by including at least a mask substrate and a phase shifter provided in a pattern on the mask substrate. In a phase difference mask for performing a phase difference exposure on a resist layer of a wafer by using a phase shift light having a phase difference with respect to (a), as a phase shifter, first and second phase shifters and a sub phase shifter are provided. (B) the first phase shifter transmits the first phase shift light by 90 ° ± 1 with respect to the direct transmission light described above.
The second phase shifter is configured as a phase shifter that gives an appropriate phase difference within the range of 0 °.
It is configured as a phase shifter that gives an appropriate phase difference within a range of 70 ° ± 10 °, and (d) the sub-phase shifter described above converts the sub-phase shift light transmitted therethrough into the directly transmitted light described above. On the other hand, it is characterized in that it is configured as a phase shifter that gives an appropriate amount of phase difference (excluding 0 °) within a range of 0 ° ± (180 ° ± 10 °).

[0030]

The above-described retardation mask of the present invention itself has the first and second phase shifters (herein, the first and second phase shifters are collectively referred to as the general term, which are collectively referred to as "the first and second phase shifters"). (Referred to as a phase shifter or a main shifter), and a first and a second that determine an image forming position.
Both or one of the sub phase shifters is provided in combination with each other. Therefore, the projection light transmitted through the phase difference mask can be imaged at a position different from the image formation position in the normal exposure method. The image forming position can be changed by appropriately combining the main phase shifter and the sub phase shifter according to the design. Therefore, depending on the height difference of the unevenness of the wafer having the step, a photomask is prepared on the same photomask in which the region of the retardation mask of the present invention and the region of the mask constituent portion of the normal exposure method are mixed. . Then, the photosensitive layer is patterned by performing predetermined processing steps such as collectively exposing the mask pattern of this photomask onto the photosensitive layer, and using this photosensitive layer pattern, a fine pattern is formed on a wafer having a step. Can be built with precision.

[0031]

Embodiments of the present invention will now be described with reference to the drawings. It should be noted that the drawings only schematically show the dimensions, shapes, and positional relationships of the respective constituent components to the extent that the present invention can be understood. Further, it should be understood that the materials, dimensions, shapes, and other required conditions described in the following examples are merely preferable examples, and the present invention is not limited to these conditions. .. Also,
Each cross-sectional view shows a cross section, and hatching and the like representing the cross section are omitted in some cross-sectional areas.

In the following description, the phase difference mask of the present invention and the phase difference exposure method using the same will be described together. Moreover, in the following description, particularly, the description will focus on the components of the phase difference mask.

FIG. 1 is a sectional view of an essential part shown in the direction orthogonal to the substrate surface for explaining the main features of the retardation mask of the present invention.

The retardation mask 100 of the present invention shown in FIG.
Are two areas 102 and 104 of the normal exposure method,
And a region 106 of the phase difference exposure method according to the present invention. The phase difference mask 100 includes a mask substrate 110 formed of a material transparent to light for projecting the phase difference mask, for example, glass. In the phase difference exposure method region 106, the first phase shifters 112 (112a, 1a) formed in a pattern on the mask substrate 110, respectively.
12b) and the second phase shifter 114 (114a, 11).
4b) and one or two sub-phase shifters 116
And / or 118 and the light shielding part 120 are provided. The embodiment shown in FIG. 1 has a configuration including two types, that is, first and second sub-phase shifters 116 and 118. The first and second phase shifters 112 and 114 have the function of increasing the contrast of the projected light. The first and second sub-phase shifters 116 and 118 are used in combination with either or both of the first and second phase shifters 112 and 114, and determine the image formation position of the above-mentioned projection light on the wafer. Has an effect. In the following description, the first and second phase shifters may be collectively referred to as a main shifter, and the first and second sub shifters may be collectively referred to as a sub shifter. These main shifters and sub shifters It is formed by using a normal method such as vapor deposition or the like. Further, the light shielding portions 120 are provided on the mask substrate 110 so as to be separated from each other and sequentially arranged. This light shielding portion 120
Is also referred to as a light shielding pattern. The light-shielding portions 120 are arranged in a pattern so that the projection lights transmitted through the transparent portions on both sides adjacent to the light-shielding portion 120 interfere with each other.

In the embodiment of the phase difference mask structure shown in FIG. 1, in the phase difference exposure method area 106, the light shielding portion 120 is formed in a rectangular stripe shape, for example, chromium (Cr).
The materials are arranged at equal intervals by a conventional forming method. Then, the first and second phase shifters 112 (112a, 112b) and 114 (11) are provided on the transparent portions sequentially positioned between the light-shielding portions 120 adjacent to each other.
4a, 114b) are arranged alternately. The first phase shifter 112 is divided into central portions 112a and 112b, and the first sub-phase shifter 116 is arranged in the gap. Similarly, the second phase shifter 1
The second sub-shifter 118 is provided in the gap between 14a and 114b.
Is provided.

On the other hand, in the normal exposure method area 102, the mask structure is formed by sequentially arranging the light shielding portions 120 on the mask substrate 110 at appropriate intervals, and in the area 104, between the light shielding portions 120, The mask structure has the same type of phase mask 122. In the figure, this light shield 1
20 is shown with hatching.

Next, the phase difference mask structure in the phase difference exposure method region and the phase difference exposure method thereof will be specifically described.

[Embodiment 1] FIG. 4A is a plan view of a main part showing an embodiment of a mask structure in a phase difference exposure method region of a phase difference mask of the present invention, viewed from the mask substrate side. 4B is a cross-sectional view taken along the line II-II in FIG. Further, FIG. 5 is an explanatory diagram for explaining the phase amount shifted by each phase shifter.
According to this embodiment, the mask structure has the same structure as that shown in FIG. Therefore, here, each component is denoted by the same number as that given in FIG. In FIG. 4A, the main shifter 11
2 and 114 and the sub-shifters 116 and 118 are indicated by broken lines, and the light shielding portion 120 is indicated by solid lines.

In this embodiment, the phase amount on the mask substrate 110 is 0 ° or 360 ° (indicated by P1 in FIG. 5). The first phase shifter 112 transmits the first phase shifter 112 through the first phase shifter 112.
A phase shifter that gives the phase shift light an appropriate phase difference (shown by P2 in FIG. 5) within the range of 90 ° ± 10 ° with respect to the light just transmitted through the mask substrate 110, that is, the directly transmitted light. Configure as. Then, the second phase shifter 1
Reference numeral 14 is a phase shifter that gives the second phase-shifted light that has passed through this an appropriate phase difference (indicated by P3 in FIG. 5) within the range of 270 ° ± 10 ° with respect to the directly transmitted light. . Therefore, the relative phase difference between the first and second phase shifters 112 and 114 is 180 °. Further, the first sub-phase shifter 116 transmits the first sub-phase shifter 116 through the first sub-phase shifter 116.
For sub-phase shift light, 0 ° ± 10 ° to direct transmitted light
Or an appropriate phase difference within the range of 360 ° ± 10 ° (see P
4 shows. ) Is provided as a phase shifter, and the second sub phase shifter transmits the second sub phase shift light to an appropriate amount within a range of 180 ° ± 10 ° with respect to the directly transmitted light. It is configured as a phase shifter that gives a phase difference (indicated by P5 in FIG. 5). In this case, the relative phase difference between these sub shifters 116 and 118 is 180 °.
Keep it at ± 10 °. Although the maximum allowable range of the phase difference shifted by each shifter described above is ± 10 °,
This is because if it exceeds this range, the mask pattern cannot be separated.

Image forming characteristics when the phase difference mask 100 is used will be described. When light is projected on the mask 100, as described above, the projection lights transmitted through the adjacent transparent portions interfere with each other. The first on the adjacent transparent part
And between the second phase shifters 112 and 114, and
Since the phase difference between the first and second sub-shifters 116 and 118 is substantially 180 °, the phase difference of the projected light between the adjacent transparent portions is 180 °. Therefore, the light intensity of the light-shielding portion is greatly reduced, so that a transferred image with high contrast can be obtained.

Further, in the phase difference mask structure of the present invention, sub shifters 116 and 118 are provided in the middle of the main shifters 112 and 114, respectively, and the lights transmitted through these sub shifters 116 and 118 interfere with each other. To meet each other. As described above, in this mask structure, since the optical interference is caused by a phase other than 180 °, the interference effect of this sub-mask is added to the interference effect of the main mask, and as a result, the defocus position in the normal exposure method is deviated. Maximum contrast can be obtained in the image plane. Further, in addition to this, since the relative phase difference between the main shifter and the sub shifter is 180 °, the symmetry of the light intensity distribution of the adjacent transmitting portions is always kept equal. Therefore, as compared with the related art, it becomes easier to control the dimensions of the pattern to be formed on the wafer, and moreover, the positioning accuracy can be improved.

Hereinafter, this point will be described more specifically. In the mask structure of FIG. 4, the light shielding part 120 is formed of a chromium vapor deposition film. The pattern width in the arrangement direction is 0.75 μm, the distance between the adjacent light shields 120 is 1.5 μm, and the film thickness is 1000 A ° (angstrom is indicated by A °). First phase shifter 112a Then, the film thickness is set to 2000 A ° and the phase difference from the directly transmitted light is set to 90 °. First The width in the column direction is set to 0.5 μm, and the film thickness is appropriately set so as to give the same phase amount of 360 ° as the mask substrate 110. Therefore, the substantial width of the first phase shifter 112 formed between the light shields 120 is 1.0 μm. Also, the second phase shifters 114a and 114b
Like the first phase shifter And the phase amount is 270 °. Second sub phase shifter 1
18 is 0.5 μ as in the first sub phase shifter 116.
The film is formed with a width of m, but its film thickness is set to about 4000 A ° to give a phase amount of 180 °. Therefore, the substantial width of the second phase shifter 114 formed between the light shields 120 is 1.0 μm.

Such a phase difference mask has a numerical aperture (N
1) using i-line with A) of 0.50 and σ of 0.50
Experimental data of the light intensity distribution when the mask pattern is projected by the / 5 reduction optical system are shown in FIGS. 6 (A) and 6 (B). 6A is on the minus (−) side, and (B) is
Shows the light intensity distribution when the focus position is shifted to the plus side. In these figures, the horizontal axis indicates the position of the light projection pattern corresponding to the direction along the line II-II on the left and right with the line CC of FIG. 4A as the center, and the vertical axis indicates the light intensity. Is shown. In FIG. 6A, a thick curve a indicates a light intensity profile in the case where there is no shift in the focus position by the normal exposure method shown for comparison. Dashed curve b
Indicates that the focus position is on the + side (away from the optical system)
It is a light intensity profile at a position shifted by 0.5 μm. A thin curve c is an optical profile at a position where the focal point position is deviated to the + side by 1.0 μm. As can be understood from this figure, when there is a shift in the focus position of the curves b and c, the main shifters 112 and 114 and the sub shifter 116.
It can be seen that the decrease in contrast hardly occurs due to the optical interference effect with 118 and 118.

Further, in FIG. 6B, a thick curve a shows a light intensity profile in the case where there is no shift of the focus position by the ordinary exposure method shown for comparison. Dashed curve d
Indicates that the focal position is 0.5 on the negative side (in the direction toward the optical system).
It is a light intensity profile at a position deviated by μm. Further, a thin curve e is an optical profile at a position where the focus position is shifted to the − side by 1.0 μm. As can be understood from this figure, when there is a focus position shift of the curve d, the maximum light intensity is maximized and the contrast is increased by the optical interference action between the main shifters 112 and 114 and the sub shifters 116 and 118. I understand.

FIG. 7 shows a shift from the focus position, contrast and maximum light when the phase difference masks shown in FIGS. 4A and 4B are projected using the above-mentioned optical system. It is an experimental data figure for explaining the relation with intensity. The center point of the horizontal axis in the figure is the position of the best image forming surface in the normal exposure method using the mask provided with only the light-shielding pattern, and this position is the reference position where there is no focus shift. Then, the shift amounts of the respective focal positions of minus on the left side and plus on the right side of the horizontal axis are shown in units of μm. The left vertical axis shows the contrast (% unit), and the right vertical axis shows the maximum light intensity (% unit). In the figure, the solid line a is the contrast curve, and the broken line b is the light intensity curve. The contrast and the maximum light intensity are shown with the maximum contrast and the maximum light intensity at the reference position in the normal exposure method as a reference of 100%.

As can be understood from this figure, the change in the contrast is small in the region where the focal position shift is 0 μm to +0.5 μm, and the maximum light intensity is also the same.
Maximum (approx. +0.5
It can be seen that it has a characteristic of being shifted by μm). From this fact, the phase difference mask of the present invention moves the image plane where the maximum light intensity, which is the best for pattern formation, is moved from the best image plane in the ordinary exposure method using the mask having only the light shielding pattern described above. It can be understood that it has the characteristics that make it. Therefore, when patterning a wafer having a step such as an integrated circuit, a phase difference mask is prepared in advance so that the best image forming position corresponds to the step on the wafer, and the resist layer is exposed using this phase difference mask. If it is performed, it becomes possible to form a pattern with high accuracy.

[Embodiment 2] In the retardation mask structure of Embodiment 1 described above, the example in which the light shielding portion 120 is provided in the retardation exposure method area has been described, but in the case of the retardation mask of the present invention, this The light shield 120 may not be provided in the region. This embodiment is shown in FIGS. 8A and 8B. In the configuration example shown in FIG. 8A, the main shifters 112 and 114
The point that the sub-shifters 116 and 118 are arranged at the center of each is the same as that of the first embodiment. However, in the case of the second embodiment, the first and second phase shifters 112 and 114 are arranged alternately adjacent to each other, and the first sub-phase shifter 1 is provided between the first phase shifters 112a and 112b.
16 is provided, and the second sub-phase shifter 118 is provided between the second phase shifters 114a and 114b.

[Embodiment 3] Further, in the retardation mask structure of the present invention, the first and second structures in the structure of Embodiment 2 are added.
The sub-phase difference shifter may be replaced with another structure in which the combination of the main shifter and the sub-shifter is changed. The retardation mask structure in that case is shown in FIG. In this case, the direction of the image plane changes. The first phase shifter 112 is a shifter for shifting the phase by 90 °, and
If the sub-phase shifter 116 is a shifter that shifts the phase by 180 °, the second phase shifter 114 is a shifter that shifts the phase by 270 °, and the second sub-phase shifter 118 is a shifter that shifts the phase by 360 °, the characteristics with respect to the focus position shift are: The sign at defocus is reversed, and as a result, the image plane is best on the minus side. In particular, the maximum light intensity can be obtained at the position where the focus position is deviated by about −0.5 μm.

As described above, like the phase difference masks shown in the second and third embodiments, the phase difference exposure method area of the photomask has four phase shifters 112, 114, 116, in total.
The effect of the present invention can be achieved by the 4-shifter structure constituted by 118.

[Embodiment 4] In the retardation mask structure of the present invention, the structure of Embodiment 1 shown in FIGS. 1
Alternatively, the second sub-phase difference shifter may be replaced with another structure in which the combination of the main shifter and the sub-shifter is changed. The retardation mask structure in that case is shown in FIG. In this case, the structure includes the light shielding portion 120, but like the structures of the second and third embodiments,
An image plane having the maximum light intensity is obtained at a position where the focal point is shifted by about −0.5 μm.

[Embodiment 5] Further, as described above, in the phase difference exposure method region, as in the case of the structures of the respective embodiments already described, the respective mask patterns are arranged side by side without any gap. In the case of the structure, the pattern width of the sub shifters 116 and 118 may be changed for each area in the phase difference exposure area. The retardation mask structure is shown in FIG.

In this structure, the pattern widths of the first and second phase shifters 112 and 114 taken along the direction in which they are sequentially arranged are the same across the entire phase difference exposure method region. Then, the first and second sub-phase shifters 1
The pattern widths of 16 and 118 taken in the direction along the arrangement direction are set to different widths depending on the zones Z1 and Z2 of the phase difference exposure method region. Of course, in the same area, the widths of both sub-shifters I16 and 118 are the same. In the figure, both sub-shifters 116a and 11 in the zone Z1 are
8a and both sub-shifters in zone Z2 are
Shown at 6b and 118b. In this structure, the phase amount to be shifted by each phase shifter does not change the phase amount (thus, the film thickness) determined for each phase shift exposure method region.

Even with such a phase difference mask structure,
As in the case of the above-described embodiment, the operational effects of the present invention can be layered. In particular, the position of the best image plane of the mask pattern can be individually set within the same phase difference exposure method area, so that the mask pattern of the phase difference mask can be finely corresponded to the uneven surface of the wafer with many steps. If formed, the pattern can be formed on the wafer with high accuracy.

[Embodiment 6] Further, in the case of a structure in which the mask patterns are arranged side by side without a gap,
The position of the best image plane can be set by changing the film thickness of the sub shifters 116 and 118. The retardation mask structure in this case is shown in FIG. In this structure, the pattern widths of the first and second sub-phase shifters 112 and 114 taken in the direction along the arrangement direction are made the same width over the entire phase difference exposure method region.
Further, the relative phase difference between the first and second sub-phase shift lights is maintained at an appropriate value within the range of 180 ° ± 10 ° throughout the phase difference exposure method region. Then, the film thicknesses of the first and second sub-phase shifters 116 and 118 are set to different heights depending on the entire area of the phase difference exposure method area or a specific area.

[Embodiment 7] Next, an embodiment of another gist of the phase difference mask of the present invention will be described. FIG. 10 (A)
FIG. 4 is a sectional view showing a mask structure in a phase difference exposure method area of this embodiment. FIG. 11 is an explanatory diagram showing the relationship between the phase amounts of the phase shifters provided in this mask structure.
The feature of the structure of this embodiment is that it has first and second phase shifters 112 and 114 and one type of sub-phase shifter 130 as a phase shifter, and has a three-shifter structure.

The first phase shifter 112 converts the first phase-shifted light that has been transmitted through the first phase-shifted light 112 into the directly transmitted light described above.
It is constructed as a phase shifter which gives an appropriate phase difference within the range of 90 ° ± 10 °. Also, the second phase shifter 114
The second phase-shifted light that has passed through this is configured as a phase shifter that gives an appropriate phase difference within the range of 270 ° ± 10 ° to the directly transmitted light described above. Then, the sub-phase shifter 130 receives
It is configured as a phase shifter that gives an appropriate amount of phase difference within the range of (180 ° ± 10 °) or (360 ° ± 10 °) to the directly transmitted light. In FIG. 11, the phase amount of the mask substrate 110 is 0 °, and this is indicated by P1.
The phase amount of the first phase shifter 112 is indicated by P2, the phase amount of the second phase shifter 114 is indicated by P3, and the sub phase shifter 1
The phase amount of 30 is indicated by P4. Even in the case of the structure of this embodiment, as already described in the first embodiment, the maximum allowable range of the phase difference shifted by each shifter described above is ± 10 °.
However, if it exceeds this range, the mask pattern cannot be separated.

In the embodiment shown in FIGS. 10A and 10B, as in the case of the first embodiment shown in FIG. 4, the light-shielding portions 120 are sequentially arranged on the mask substrate 110 at regular intervals, The structure is such that a main shifter and a sub shifter are provided in the transparent portion between these light shielding portions 120. Further, preferably, the main shifters 112 and 114 are alternately provided in the transparent portion between the adjacent light shielding portions 120. The sub shifter 130 is preferably arranged between the main shifters 112a and 112b as shown in FIG.
It is provided between 14a and 114b.

Imaging characteristics when the retardation mask 100 having this structure is used will be described. When light is projected on the mask 100, as described above, the projection lights transmitted through the adjacent transparent portions interfere with each other. Since the phase difference between the first and second phase shifters 112 and 114 provided on the adjacent transparent portions is substantially 180 °, the phase difference of the projection light between the adjacent transparent portions is 180 °. Therefore, the light intensity of the light-shielding portion is greatly reduced, so that a transferred image with high contrast can be obtained.

Further, in the phase difference mask structure of the present invention, sub shifters 130 are provided in addition to the main shifters 112 and 114, and the lights transmitted through the respective shifters interfere with each other. Thus, in this mask structure, 1
In order to cause optical interference due to phases other than 80 °, the interference effect of this sub-mask is added to the interference effect of the main mask,
Therefore, the best image formation position can be obtained at a position deviated from the focus position in the normal exposure method, and the maximum contrast can be obtained on the image formation surface.

This point will be described more specifically below. In the mask structure of FIG. 10A, the light blocking portion 1
20 is formed by a vapor deposition film of chromium. The pattern width in the arrangement direction is 1.0 μm, the distance between the adjacent light shielding portions 120 is 1.5 μm, and the film thickness is 1000 A °.
The first phase shifters 112a and 112b are sputtered. Then, the phase difference from the directly transmitted light is set to 90 °. Also,
Second phase shifter 114a (Silicon dioxide) film with a thickness of about 6000 A ° and a phase amount of 270 The width of the light pattern 120 in the arrangement direction is 0.5 μm, the film thickness thereof is about 4000 A °, and a phase amount of 180 ° is provided. Therefore, the substantial width formed between the light shielding portions 120 of the first phase shifter 112 and the second phase shifter 114 is 1.0 μm.

Such a retardation mask has a numerical aperture (NA) of 0. 0 as in the case of the first embodiment.
Part (A) and (B) of FIG. 12 show part of the experimental data of the light intensity distribution when a mask pattern is projected by a 1/5 reduction optical system using i-line with 50 and σ of 0.50. In these figures, the horizontal axis represents the light projection position similar to the case of FIGS. 6A and 6B, and the vertical axis represents the light intensity. In FIG. 12A, a thick curve a indicates a light intensity profile in the case where there is no shift in the focus position by the normal exposure method shown for comparison. A broken line curve b is a light intensity profile at a position where the focal position is deviated to the − side (in the direction closer to the optical system) by 0.5 μm. Also, the thin curve c has a focus position of 1.0 on the negative side.
It is an optical profile at a position displaced by μm. As can be understood from this figure, when there is a focus position shift of the curves b and c, the contrast is hardly reduced by the optical interference action between the main shifters 112 and 114 and the sub shifters 116 and 118. . As can be understood from FIG. 12A, the focal length is −
The light intensity distribution at a position shifted by 0.5 μm is such that the 180 ° sub-shifter 130 is provided between the 270 ° second phase shifters 114a and 114b, and the light intensity of the transparent portion (curve b in FIG. 12A). Will increase.

On the other hand, in FIG. 12B, the thick curve a is
The light intensity profile when there is no shift of the focus position by the normal exposure method shown for comparison is shown. Further, a broken line curve d is a light intensity profile at a position where the focal position is shifted to the + side (away from the optical system) by 0.5 μm. The thin curve e has a focus position of 1.0 on the + side.
It is an optical profile at a position displaced by μm. As can be understood from this figure, the 90 ° first phase shifters 112a and 112b at the position where the focus position is shifted by 0.5 μm on the + side.
The light intensity (curve d in FIG. 12B) of the transparent portion where the 180 ° sub-shifter 130 is provided between and increases. Therefore, the retardation mask of this embodiment has a characteristic that the maximum light intensities of the transparent portions which are successively adjacent to each other are obtained at positions different by 1.0 μm. Thus, according to this mask structure,
It is possible to design so that the position of the image plane having the maximum contrast is changed for each transparent portion between the successive light shielding portions 120.

FIGS. 13A and 13B are explanatory views in the case of patterning by the exposure method using the retardation mask of the mask structure of the seventh embodiment described above. This (A) figure is a figure which shows the light intensity distribution by the phase difference mask of this Example. The horizontal axis represents the pattern position of the projection light corresponding to the array direction of the shifters of the phase difference mask, and the vertical axis represents the light intensity. Also, this (B) is applied to a wafer having a step,
FIG. 7 is a cross-sectional view showing a state obtained by exposing and developing with this projection pattern, in which a lower wiring 142 is partially formed on the upper surface of the substrate 140, and an intermediate insulating film 144 is formed on the entire surface including the lower wiring 142. Form. The surface of the intermediate insulating film 144 becomes an uneven surface, and the step between the lower surface and the upper surface of the uneven surface is, for example, about 1 μm. This intermediate insulating film 14
A photosensitive layer such as a resist layer is provided on the surface 4, and a phase difference exposure method is performed on the resist layer having a step on the surface by using this phase difference mask.

As described above, in the above-described phase difference mask of this embodiment, the first shifter group including the combination of the first phase difference shifter 112 having a phase amount of 90 ° and the sub shifter 130 having a phase amount of 180 °. And a second group of shifters, which is a combination of the second phase difference shifter 114 having a phase amount of 270 ° and the sub-shifter 130 having a phase amount of 180 °, are alternately arranged. In FIG. 13A, a region Q1 is a pattern region of the projection light by the first shifter group, and the light intensity distribution is a curve q1. Also, the area Q2
Is a pattern region of the projected light by the second shifter group, and the light intensity distribution is a curve q2. The maximum light intensity by the second shifter group is plus (+) from the image formation position in the normal exposure method.
The maximum light intensity obtained by the first shifter group is 0.5 μm on the minus (−) side.
Obtained at offset positions. Therefore, the distance between the ⅕ reduction projection optical system and the wafer surface is adjusted so that the image forming surface in the normal exposure method is adjusted to an appropriate intermediate position between the upper and lower surfaces of the step of the resist layer. In this way, the lower layer of the step of the resist layer is exposed with the maximum light intensity by the second shifter group, and the upper layer of the step is exposed with the maximum light intensity by the first shifter group. Therefore, even if the resist layer has irregularities, the upper and lower layers of the irregularities are exposed with optimum light intensity. Subsequently, the exposed resist can be appropriately developed and patterned according to a usual technique to form resist patterns 146a and 146b. As described above, according to the phase difference exposure using the phase difference mask of the present invention, it is possible to simultaneously expose a resist layer having a step difference using a single phase difference mask, and further, to form the pattern thereof. The dimensional control of is also greatly improved over the conventional one.

[Embodiment 8] In the retardation mask structure of Embodiment 7 described above, an example in which the light shielding portion 120 is provided in the retardation exposure method area has been described. However, in the case of the retardation mask of the present invention, this The light shield 120 may not be provided in the region. This embodiment is shown in FIG. In the configuration example shown in FIG. 10B, the sub shifter 130 is arranged at the center of each of the main shifters 112 and 114, which is the same as that of the seventh embodiment. However, in the case of the eighth embodiment, the first and second phase shifters 112 and 114 are alternately arranged adjacent to each other, and the first phase shifters 112a and 112b are arranged.
And the sub-phase shifter 130 is provided between the second phase shifter 114a and the second phase shifter 114b. Even with this structure, the effect of the three-shifter structure can be achieved.

[Embodiment 9] The retardation mask having the three-shifter structure described above has a structure in which a sub-shifter is provided so as to be sandwiched between the central portions of the main shifter. Instead of such a structure, the main shifter 112 is used. And 1 on both sides of 114
Even if the structure of arranging 30 (130a, 130b) is 3
The effect of the shifter structure can be achieved. Figure 10
The retardation mask shown in (C) is provided with the light shielding part 120, and the sub shifter 130 is provided in the transparent part between the successive light shielding parts 120, as in the case of the seventh embodiment described in FIG.
a, the second phase difference shifter 114 and the sub shifter 130b
The second shifter group consisting of and is provided, and the transparent part next to
It has a structure in which a first shifter group including the sub shifter 130a, the first phase difference shifter 112, and the sub shifter 130b is provided.

[Embodiment 10] The structure of this embodiment is a structure in which the light shielding portion 120 is not provided, and this is shown in FIG. In this case, the sub shifter 130, the second
Phase shifter 114, sub shifter 130, first phase difference shifter 112, sub shifter 130, second phase difference shifter 11
4, the sub shifter 130 and the first phase difference shifter 112 have a structure in which the main shifter and the sub shifter are sequentially combined and arranged. Even in the case of this retardation mask, it is possible to achieve the above-described effects of the three-shifter structure.

[Embodiment 11] In the retardation masks of Embodiments 7 to 10 described above, the sub phase shifter 130 has a relative phase difference of 180 ° with the directly transmitted light, but a sub phase difference of 360 ° is obtained. A phase shifter may be used. For this purpose, the film thickness of the sub shifter 130 may be changed. Even in the case of this phase difference mask, the position of the best image forming surface in the phase difference exposure method region of the photomask is set to the best image forming surface in the normal exposure method, as in the case of Examples 7 to 10. The structure can be shifted to a desired position. These structures are the structures shown in FIGS. 10A to 10D, and the phase difference of the sub-shifter 130 is 180 ° to 360 °.
However, the illustration of each structure of this embodiment is omitted. Even in this case, the maximum allowable error is ± 1
It is good to set it to 0 °.

[Embodiment 12] As described above, in the phase difference exposure method area, each of Embodiments 7 to 1 already described.
In the case of the structure in which the mask patterns are continuously arranged side by side without a gap like the structure of No. 1, the pattern width of the sub-shifter in the phase difference exposure region can be changed. The retardation mask structure is shown in FIG.

In this structure, the pattern widths of the first and second phase shifters 112 and 114 taken in the direction along the sequential arrangement direction are made the same width over the entire area of the phase difference exposure method. Then, the pattern width of the sub-phase shifter taken in the direction along the arrangement direction is selectively made different within the phase difference exposure method region. This sub shifter is shown by 132 and 134, respectively. In this structure, the phase amount to be shifted by each phase shifter does not change the phase amount (thus, the film thickness) determined for each phase shift exposure method region.

Even with such a phase difference mask structure,
Similar to the above-described Embodiments 7 to 11, the effects of the present invention can be layered. In particular, the position of the best image plane of the mask pattern can be individually set within the same phase difference exposure method area, so that the mask pattern of the phase difference mask can be finely corresponded to the uneven surface of the wafer with many steps. If formed, the pattern can be formed on the wafer with high accuracy.

[Embodiment 13] Further, in the case of the structure in which the mask patterns are arranged side by side without any gap, the width of the sub shifter and the relative phase difference (film thickness) are made constant,
Further, by keeping the relative phase difference between the main shifters 112 and 114 constant and appropriately changing the width of all or a required part of the main shifters 112 and 114, the best image plane of each mask pattern can be obtained. It is also possible to set the position of according to the step of the wafer. Since the phase difference mask structure in this case is clear without exemplifying it, illustration of the structure is omitted.

[Embodiment 14] Next, an embodiment of still another gist of the phase difference mask of the present invention will be described. Figure 15
(A) is a plan view of the main part of the mask structure in the phase difference exposure method region of this embodiment as seen from the mask substrate side, and
FIG. 15B is a sectional view taken along line III-III in FIG. In FIG. 15 (A),
The main shifters 112 and 114 and the sub shifter 150 are shown by broken lines, and the light shielding part 120 is shown by solid lines. The feature of the structure of this embodiment is that the first and second phase shifters are used.
Although the phase shifters 112 and 114 and one type of sub-phase shifter 150 are provided and the structure is a three-shifter structure, which is common to the cases of Examples 7 to 13, one of the main shifters 112 and 114 is used. Sub-shifter 15 on both sides of
0 (150a, 150b) is provided. The phase amounts of the first and second phase shifters 112 and 114 for the above-mentioned directly transmitted light and the phase amounts of the sub-phase shifter 150 for the above-mentioned directly transmitted light are the same as those in the seventh to seventh embodiments.
The same as in the case of No. 13, and therefore, it is assumed that the phase relationship shown in FIG.

In the embodiment shown in FIGS. 15A and 15B, as in the case of the first embodiment shown in FIG. 4, the light shielding portions 120 are sequentially arranged on the mask substrate 110 at regular intervals, The structure is such that a main shifter and a sub shifter are provided in the transparent portion between these light shielding portions 120. Further, preferably, the main shifters 112 and 114 are alternately provided in the transparent portion between the adjacent light shielding portions 120. In this embodiment, the sub shifter 150 is replaced with the main shifter 112,
Or, divide it on both sides of 114 (150, 150b)
Set up. In the embodiment shown in FIGS. 15A and 15B, the sub shifter 150 is provided in combination with the first phase difference shifter 112.

Imaging characteristics when the retardation mask 100 having this structure is used will be described. When the light is projected onto the mask 100, the projection lights transmitted through the first and second phase shifters 112 and 114 of the adjacent transparent portions interfere with each other, as described above. Since the phase difference between the first and second phase shifters 112 and 114 provided on the adjacent transparent portions is substantially 180 °, the phase difference of the projection light between the adjacent transparent portions is 180 °. Therefore, the light intensity of the light-shielding portion is greatly reduced, so that a transferred image with high contrast can be obtained.

Further, in the retardation mask structure of the present invention, the sub shifters 130 are provided on both sides of the main shifter 112.
The interference of the light that has passed through is added, and the lights that have passed through these shifters interfere with each other. As described above, in this mask structure, since the optical interference is caused by a phase other than 180 °, the interference effect of this sub-mask is added to the interference effect of the main mask, so that the position deviated from the focus position in the normal exposure method is used. It is possible to obtain the best image forming position and obtain the maximum light intensity and the maximum contrast on the image forming plane. Therefore, the light intensity between adjacent transparent portions of the mask pattern can be changed.

This point will be described more specifically below. In the mask structure of FIGS. 15A and 15B, the light shielding portion 120 is formed of a chromium vapor deposition film. The pattern width in the arrangement direction is 1.0 μm, the distance between the adjacent light shields 120 is 1.5 μm, and the film thickness is 1000 μm.
A °. Set the first phase shifter 112 to And the phase difference from the directly transmitted light is set to 90 °. Also, the second
The phase shifter 114 also has And the film thickness is about 6000 A ° and the phase amount is 27
0 °, and 1. The width of each light-shielding pattern 120 in the arrangement direction is 0.25 μm, and the total width occupied by one transparent portion is 0.5 μm. Further, the film thickness of each sub-shifter 150 is set to about 4000 A ° so as to give a phase amount of 180 °. Therefore,
The substantial width of the first phase shifter 112 formed between the light shields 120 is 1.0 μm.

Such a phase difference mask is provided with a numerical aperture (N) in the same manner as that described in the first and seventh embodiments.
1) using i-line with A) of 0.50 and σ of 0.50
16A and 16B show a part of the experimental data of the light intensity distribution when the mask pattern is projected by the / 5 reduction optical system. In these figures, the horizontal axis represents the light projection pattern position in the direction corresponding to the arrangement direction of the mask patterns on the left and right with the CC line in FIGS. 15A and 15B as the center, and the vertical axis. The axis shows the light intensity. 16A shows a change in the light intensity when the focus position is shifted to the minus (−) side, and FIG. 16B shows a change in the light intensity when the focus position is shifted to the plus (+) side. ing. Figure 1
In (A) of 6, a thick curve a shows a light intensity profile in the case where there is no shift of the focus position by the normal exposure method shown for comparison. A broken line curve b is a light intensity profile at a position where the focal position is deviated to the − side (in the direction closer to the optical system) by 0.5 μm. Further, a thin curve c is an optical profile at a position where the focal position is deviated to the − side by 1.0 μm. As can be understood from FIG. 16A, the light intensity of the light projection pattern corresponding to the portion of the second phase difference shifter 114 is on the minus (−) side of the image plane in the image passing exposure method. Although the maximum light intensity distribution is obtained, the first phase difference shifter 112 and the sub phase difference shifter 1 adjacent to this can be obtained.
It can be seen that the light intensity of the light projection pattern corresponding to the portion of the shifter group composed of the combination with 50 is slightly lowered.

On the other hand, in FIG. 16B, the thick curve a is
The light intensity profile when there is no shift of the focus position by the normal exposure method shown for comparison is shown. Further, a broken line curve d is a light intensity profile at a position where the focal point position is deviated to the plus (+) side by 0.5 μm (away from the optical system). Further, a thin curve e is an optical profile at a position where the focal position is deviated to the plus (+) side by 1.0 μm. As you can see from this figure,
At the position shifted to the side, the light intensity of the light projection pattern corresponding to the portion of the second phase difference shifter 114 is maximum when deviated by +0.5 μm and +1.0 μm from the image plane in the normal exposure method. Although the light intensity distribution is reduced, the light intensity of the light projection pattern corresponding to the portion of the shifter group formed by the combination of the first phase difference shifter 112 and the sub phase difference shifter 150 adjacent to this is the same as in the case of the normal exposure method. It can be seen that they are almost the same. Further, it can be seen that in each case, the light intensity of 60% or more required for exposing the photosensitive layer was obtained. By utilizing such characteristics, the mask structure in the phase difference exposure method region can be designed in advance so as to change the position of the image surface having the maximum contrast for each transparent portion between the successive light shielding portions 120. Then, this phase difference mask may be used so that the best image plane can be formed on the plus side (the direction away from the reduction projection optical system) and the minus side (the direction closer to the reduction projection optical system).

FIGS. 17A and 17B are explanatory views of patterning by the exposure method using the retardation mask having the mask structure of the above-described fourteenth embodiment. This (A) figure is a figure which shows the light intensity distribution by the phase difference mask of this Example. The horizontal axis represents the pattern position of the projection light corresponding to the array direction of the shifters of the phase difference mask, and the vertical axis represents the light intensity. 13B is a cross-sectional view showing a state similar to that shown in FIG. 13B, showing a state obtained by exposing and developing a wafer having steps with this projection pattern, The lower wiring 142 is partially formed on the upper surface of 140.
Then, an intermediate insulating film 144 is formed on the entire surface including the lower wiring 142. A conductive layer 145 such as a metal layer for forming an upper wiring is provided above the intermediate insulating film 144. The surface of the lightning layer 145 becomes an uneven surface, and the step between the lower surface and the upper surface of the uneven surface is, for example, about 1 μm. A photosensitive layer, for example, a resist layer is provided on the conductive layer 145, and a retardation exposure method is performed using the retardation mask on the resist having a step on the surface.

In FIG. 17A, a region Q3 is a pattern region of the projection light by the shifter group (112, 150), and the light intensity distribution is a curve q3. The area Q4 is a pattern area of the projection light by the second phase difference shifter 144,
The light intensity distribution becomes a curve q4. Shifter group (112, 15
0), the maximum light intensity (curves d and q3) is 0.5 on the plus (+) side from the imaging position in the normal exposure method.
The second phase difference shifter 14 is obtained at a position shifted by μm.
The maximum light intensity according to 4 (curves b and q4) is obtained at a position shifted by 0.5 μm to the minus (−) side. Therefore,
Also in this case, the distance between the ⅕ reduction projection optical system and the wafer surface is adjusted so that the image forming surface in the normal exposure method is adjusted to an appropriate intermediate position between the upper and lower surfaces of the step of the resist layer. . In this way, the lower layer of the step of the resist layer is
The shifter group (112, 150) is exposed with the maximum light intensity, and the upper layer of the step is exposed with the maximum light intensity by the second phase difference shifter 144. Therefore, even if the resist layer has irregularities, the upper and lower layers of the irregularities are exposed with optimum light intensity. Then, the exposed resist can be appropriately developed and patterned according to a usual technique to form resist patterns 148a and 148b. As described above, according to the phase difference exposure using the phase difference mask of the present invention, it is possible to simultaneously expose a resist layer having a step difference using a single phase difference mask, and further, to form the pattern thereof. The dimensional control of is also significantly improved as compared with the conventional one, and the pattern can be formed with high accuracy.

[Embodiment 15] In Embodiment 14 described above,
The sub shifters 150 are provided only on both sides of the first phase difference shifter 112.
The example in which the sub phase difference shifter 150 (150a, 150b) is provided only on both sides of the second phase difference shifter 114 may be adopted instead of the above. Such a structure is shown in FIG. Even with this configuration, the above-described effects of the present invention can be achieved.

[Embodiment 16] In the retardation mask structures of Embodiments 14 and 15 described above, an example in which the light shielding portion 120 is provided in the phase difference exposure method area has been described, but in the case of the retardation mask of the present invention, The light-shielding portion 120 may not be provided in this region, and the light-shielding portion 120 may be formed as a three-shifter structure including the shifters 112, 114 and 150 used in the fourteenth embodiment.
The structure of this embodiment is shown in FIG. However, the method of combining these shifters may be appropriately performed according to the design. In the configuration example shown in FIG. 18B, the sub shifter 150 is arranged at the center of the main shifter 112.
Therefore, in this case, the first and second phase shifters 11
2 and 114 are arranged alternately adjacent to each other, the first
The sub phase shifter 150 is provided between the phase shifters 112a and 112b. Even with this structure, the effect of the three-shifter structure can be achieved.

[Embodiment 17] In the retardation mask of the three-shifter structure of Embodiments 14 and 15 described above, the sub-shifter 150 (150a, 150b) is provided so that any one of the main shifters 122 or 144 is sandwiched in the central portion. However, instead of having such a configuration, a structure in which the sub shifter 150 (150a, 150b) is arranged in the middle of either one of the main shifters 112 and 114,
The effect of the 3-shifter structure can be achieved. Figure 1
In the retardation mask shown in FIG. 9A, the light shielding portion 120 is provided and the transparent portions between the light shielding portions 120 are provided in the same manner as in the case of the fourteenth embodiment described in FIGS. 15A and 15B. To
The second phase shifter 114a, the sub shifter 150, and the second
A structure is provided in which a shifter group including the phase shifter 114b is provided, and only the first phase difference shifter 112 is provided in the sequentially adjacent transparent portions. With this structure, it is possible to shift the best image forming planes vertically with respect to the wafer surface for each mask pattern corresponding to the adjacent transparent portion.
And even with this structure, as in the above-described embodiment,
The effect of the 3-shifter structure can be achieved.

[Embodiment 18] In Example 17, the sub shifter 150 is provided only in the middle of the second phase shifter 114, but the sub shifter 15 is provided only in the middle of the first phase shifter 114.
A structure in which 0 is provided may be used. The structure of this embodiment is shown in FIG. With this structure, it is possible to shift the best image forming planes vertically with respect to the wafer surface for each mask pattern corresponding to the adjacent transparent portion. Even with this structure, it is possible to achieve the operational effects of the three-shifter structure as in the above-described embodiment.

[Embodiment 19] Embodiments 14 to 18 described above.
In the above retardation mask, the sub-phase shifter 150 has a relative phase difference of 180 ° with the directly transmitted light, but a sub-phase shifter having a relative phase difference of 360 ° may be used. For this purpose, the film thickness of the sub shifter 130 may be changed. Even in the case of this phase difference mask, the position of the best image forming surface in the phase difference exposure method region of the photomask is set to the best image forming surface in the normal exposure method as in the case of Examples 14 to 18. The structure can be shifted to a desired position. Note that these structures are shown in FIG. 15 (A) and FIG. 18 (A).
And (B) and the structure shown in (A) and (B) of FIG.
Since it is only changed to 0 °, the illustration of each structure of this embodiment is omitted. Even in this case, the maximum allowable error is ±
It is good to set it to 10 °.

[Embodiment 20] Further, the intervals of the light-shielding portions provided on the mask substrate 110 are not made constant but are changed as required, and the relative phase difference (film thickness) of the main shifters 112 and 114 is made constant, Further, the width of the sub shifter and the relative phase difference (film thickness) are kept constant, and the main shifter 112 is
It is also possible to set the position of the best image forming surface of each mask pattern according to the step of the wafer by appropriately changing the width of all or a required part of 114 and 114. An example of the retardation mask structure in this case is shown in FIG.
Shown in. First phase difference shifters 112c, 112d, 112
The width of e is changed, and the second phase difference shifter 114
The widths of c, 114d and 114e are changed.

[Embodiment 21] Embodiments 14 to 20 described above
In the above, the example in which the sub-shifter is provided in the middle or both sides of the main shifter with the same length in the direction orthogonal to the arrangement direction of the sub-shifter and the main shifter has been described. It may be a pattern. An example of the configuration in this case is shown in FIGS. FIG. 1A is a cross-sectional view, and FIG. 1B is a plan view of relevant parts. In this embodiment, the dot type patterns 160 and 162 are provided in the adjacent second phase shifters 114.
Are alternately arranged. The planar shape of this dot type sub shifter is not limited to the above-mentioned example, and may be provided in any suitable combination with the main shifter of Examples 14 to 20 described above. Even in the case of this structure, it is possible to exhibit the above-described effects of the three-shifter structure.

[Embodiment 22] In addition, Embodiment 14 described above
In (22) to (22), the phase shift amount of the sub-phase shifter 150 is set to (180 ° ± 10 °) (360 ° ± 1).
However, the sub-phase shift light transmitted through the sub-phase shifter 150 is (0 °) different from the direct transmission light described above.
Within the range of (± 10 °) to (180 ° ± 10 °),
The phase shifter may be configured to provide a phase difference of any appropriate amount (however, preferably 0 ° is excluded) in either the + side or the − side. An example of the configuration is shown in FIG.
In the cross-sectional view of. According to the structure of this phase difference shifter,
The relative phase difference and width of the main shifters 112 and 114 are kept constant, and the widths of the sub shifters 150a and 150b are kept constant. It has a different structure. Sub-shifters having different film thicknesses are indicated by 150c, 150d, 150e and 150f, respectively. Even with this configuration, as in the case of each of the above-described embodiments,
The best image plane can be moved in the vertical direction with respect to the wafer so as to match the uneven surface of the wafer.

[Other Embodiments] It is obvious to those skilled in the art that the present invention is not limited to the above-described embodiments, and many modifications and changes can be made. For example, the mask patterns of the phase difference exposure method area of the photomask may be formed by arbitrarily and appropriately combining the configurations of the above-described embodiments. Further, the retardation mask of the present invention may be configured by providing the mask structure of the above-mentioned embodiment of the present invention and the mask structure of the US on the same mask substrate. It is obvious that how to combine the main shifter and the sub shifter depends on the position of the step of the wafer on which the pattern is to be formed, the height of the unevenness of the step surface, and the like. Further, it is apparent that the planar shapes of the main shifter and the sub shifter depend on the planar shape of the pattern to be formed. The material of the main shifter and / or the sub-shifter can be formed of a translucent material other than the above-mentioned silicon dioxide. Further, the phase shift by the main shifter and the sub shifter may be performed by changing the respective film thicknesses, or by forming the shifters by individually changing the respective refractive indexes.

[0091]

As is apparent from the above description, according to the structure of the phase difference mask of the present invention, the contrast of the projection light which is reflected by the phase difference mask is increased in the phase difference exposure method region of the mask substrate. The first and second phase shifters and the first and / or second sub-phase shifters that determine the image formation position of the projected light are provided in any suitable combination. Therefore, by arranging and arranging the combination of the main shifter and the sub shifter in accordance with the position and height of the step difference of the wafer on which the pattern is to be formed, the best connection to the upper and lower layers of the step difference of the photosensitive layer is achieved. It can be brought to the image plane. Therefore, by simultaneously exposing the photosensitive layer using the retardation mask of the present invention, the upper and lower layers of the photosensitive layer having a step can be exposed with optimum light intensity and contrast. Therefore, a wafer having a step can be patterned with high accuracy.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part for explaining the features of a phase difference mask of the present invention.

2A to 2C are explanatory views of a conventionally proposed retardation mask.

3A to 3C are explanatory views of a conventional exposure method which has been conventionally proposed.

4A and 4B are cross-sectional views showing the structure of the first embodiment of the present invention.

5 is an explanatory diagram of a phase amount of each shifter provided in the retardation mask having the structure shown in FIG.

FIG. 6 is a light intensity distribution chart for explaining a change in light intensity with respect to a focus position shift when performing phase difference exposure by a reduction optical system using the phase difference mask having the structure shown in FIG.

7 is an explanatory diagram of the relationship between defocus, contrast, and maximum light intensity when exposure is performed using the phase difference mask having the structure shown in FIG.

8A to 8C are cross-sectional views for explaining the structure of another embodiment of the retardation mask of the present invention.

9A and 9B are cross-sectional views for explaining the structure of another embodiment of the retardation mask of the present invention, respectively.

10A to 10D are cross-sectional views for respectively explaining the structure of another embodiment of the retardation mask of the present invention.

11 is an explanatory diagram of a phase amount of each shifter provided in the retardation mask shown in FIG. 10 (A).

12 (A) and 12 (B) are changes in light intensity with respect to a focal position shift when phase difference exposure is performed by a reduction optical system using the phase difference mask having the structure shown in FIG. 10 (A). FIG. 3 is a light intensity distribution diagram used for the explanation of FIG.

13 (A) and 13 (B) illustrate an example in which phase difference exposure is performed by a 1/5 reduction optical system using the phase difference mask of FIG. 10 (A) to pattern a photosensitive layer. FIG.

FIG. 14 is a sectional view showing the structure of another embodiment of the retardation mask of the present invention.

15 (A) and 15 (B) are a plan view and a cross-sectional view of an essential part for explaining another embodiment of the present invention.

16 (A) and (B) are light with respect to a focal position shift when phase difference exposure is performed by a reduction optical system using the phase difference mask having the structure of (A) and (B) of FIG. It is a light intensity distribution chart for explaining the intensity change.

17A and 17B are patterning of a photosensitive layer by performing phase difference exposure with a 1/5 reduction optical system using the phase difference masks of FIGS. 15A and 15B. It is explanatory drawing explaining an example.

18 (A) and (B) are sectional views for explaining another embodiment of the present invention.

19 (A) and 19 (B) are cross-sectional views provided for explaining another embodiment of the present invention.

FIG. 20 is a cross-sectional view provided for explaining another embodiment of the present invention.

FIG. 21 is a cross-sectional view provided for explaining another embodiment of the present invention.

22 (A) and (B) are sectional views for explaining another embodiment of the present invention.

[Explanation of symbols]

100: Phase difference mask, 102, 10
4: Normal exposure method area 106: Phase difference exposure method area, 110: Mask substrate 112 (112a, 112b), 122 (122a, 1)
22b, 122c, 122d, 122e, 122f):
First phase shifter (main shifter) 114 (114a, 114b), 124 (124a, 1)
24b, 124c): second phase shifter (main shifter) 116 (116a, 116b): first sub-phase shifter (sub-shifter) 118 (118a, 118b): second sub-phase shifter (sub-shifter) 120: light-shielding layer (light-shielding pattern) ) 130, 132, 134, 150 (150a, 150
b): Sub phase shifter (sub shifter) 140: Substrate, 142: Lower wiring 144: Intermediate insulating films 146 (146a, 146b), 148 (148a, 1)
48b): resist pattern

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] August 9, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

Title: Phase difference exposure method and phase difference mask used therefor

[Claims]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase difference exposure method for forming a fine pattern on a wafer by using light exposure and a phase difference mask used therefor.

[0002]

2. Description of the Related Art A method using a photomask with a phase shifter has been proposed as one method for finely processing a wafer by using a technique of reducing and transferring a photomask pattern onto a photosensitive layer provided on a wafer, for example, a resist layer. (Japanese Patent Application No. Hei 2-161239). First, prior to the description of the present invention, the proposed phase difference exposure technique will be described with reference to the drawings.

This method is a technique in which a resist layer provided on a wafer is subjected to a phase difference exposure using phase-shifted light that is phase-shifted with respect to the phase of light directly transmitted from a mask substrate which constitutes a photomask. The photomask used for this phase difference exposure is called a phase difference mask, and its constituent parts are patterned on the mask substrate 10 transparent to the light used, as shown in the main part of FIG. A plurality of light shielding parts 12
a, 12b, 12c, and 12d (represented by 12 as a representative, and the light-shielding portion is also referred to as a light-shielding pattern) are spaced apart at appropriate intervals, and are abutted between these light-shielding portions 12 and both outsides thereof. Two types of patterned phase shifters 14
a, 14b, 14c, (representatively indicated by 14) and 16
a and 16b (representatively indicated by 16) are alternately arranged. Of course, a photomask portion (not shown) may be formed with a portion for exposing the resist layer by a normal exposure method, but the description thereof is omitted here. The photomask used in the normal exposure method has, for example, a configuration in which only the light shielding portion is arranged on the mask substrate, or a configuration in which the light shielding portion and one type of phase shifter are combined and arranged,
Alternatively, one type of phase shifter is arranged. 2B is a sectional view taken along line I-I of FIG. 2A.
Shown in.

The photomask 10 will be described. The light transmitted through the mask substrate 10 itself is referred to as direct transmitted light here. When the photomask is illuminated with light,
Light is transmitted through a region of the mask substrate 10 where the light shielding portion 12 is not provided (this region is referred to as a transparent region), and is directly transmitted light in a region where the phase shifters 14 and 16 are not provided. Hereinafter, the phase of this directly transmitted light will be considered as a reference. In the region of the photomask where the phase shifter is provided, the directly transmitted light that has passed through the mask substrate subsequently passes through this phase shifter. The light transmitted through the phase shifters 14 and 16 is shifted in phase with respect to the directly transmitted light. In this case, both the phase shifters 14 and 16 are formed of the same transparent material in a film shape, and the respective film thicknesses thereof cause a relative phase difference (shift amount) of 90 ° with respect to the directly transmitted light. And phase shifter 1
The relative phase difference between 4 and 16 is set to 180 ° to enable high resolution phase difference exposure. In this specification, a unit of an angle such as a phase, a phase difference or a phase amount is represented by "degree". Further, in this phase difference pattern, the phase shifter 14 is provided without providing the light shielding pattern.
It is possible to obtain the same high contrast by arranging and 16 adjacently.

Further, in the photomask structure shown in FIG. 2A, the shifter edges of the phase shifters 14 and 16 provided between the adjacent light shielding portions 12 selectively provided on the mask substrate 10 serve as transparent portions of the mask substrate 10. It is provided. The light intensity profile of the portion corresponding to the line AA of this photomask is shown in FIG. As can be understood from this profile, the light intensity does not extremely decrease at points B ₁ and B ₂ of the shifter edge. Therefore, even if the phase shifter edge is arranged on the transparent portion of the mask substrate other than the light-shielding portion, unnecessary transfer of the shifter edge does not occur, so this photomask is suitable for forming a complicated pattern.

FIG. 3A shows a case where a resist layer having a step on the wafer surface is exposed to form a fine pattern by using the photomask having such a structure.
A brief description will be given with reference to (B) and (C).

FIG. 3A shows a retardation mask having a structure similar to that shown in FIG. 2B. Therefore, the same components are designated by the same reference numerals.
The light intensity distribution when projected using this phase difference mask in an i-line reduction optical system having a numerical aperture NA = 0.50 and σ = 0.50 is as shown in FIG. 3B. Distribution. In the figure, the horizontal axis corresponds to the position of the phase difference mask, and the vertical axis represents the light intensity. At the so-called in-focus position where the focus is not shifted, the distribution shown by the solid line a has a sufficient contrast for pattern formation. However, when there is a defocus in the direction orthogonal to the wafer surface, that is, at a position deviated from the in-focus position, the contrast deteriorates as shown by a broken line b.

In general, the wafer surface on which the pattern is to be formed may be a flat surface or may be an uneven surface due to the already formed circuit components. An example of such a step on the surface is shown in FIG.
In the figure, 20 is a substrate, 22 is a patterned first layer wiring, and 24 is an intermediate insulating film 26 is a phase difference exposure using a phase difference mask for forming a second layer wiring. Is a metal layer to be patterned by utilizing.
Reference numeral 28 denotes a resist pattern obtained by developing after performing the phase difference exposure with the phase difference mask of FIG.

[0009]

When there is a step in the resist layer 28 which is a photosensitive layer, if the image forming position of the projection light of the retardation mask is aligned with the lower surface of the step, the resist layer 26 The areas corresponding to the phase shifters 14a and 16a are illuminated with the light intensity indicated by the solid line a. Therefore, in this region, it is sufficiently resolved and patterned neatly. However, when the depth of focus of the reduction optical system becomes smaller with the miniaturization of the pattern, the upper surface of the step existing in the region exceeding the depth of focus is illuminated with the light intensity indicated by the broken line b. , 14b, 16c, respectively, the resist layer portions are not sufficiently resolved. Therefore, pattern separation is impossible.

An object of the present invention is to perform simultaneous exposure on a photosensitive layer having a step using the same photomask to form a fine pattern of the photosensitive layer on a wafer having a step with high resolution.
(EN) A phase difference exposure method capable of forming a fine pattern on a wafer, and a phase difference mask used for the method.

[0011]

To achieve this object, according to the method of the present invention, a photosensitive layer is formed by using phase-shifted light that is phase-shifted with respect to the phase of light directly transmitted from a mask substrate. In performing the phase difference exposure, the phase shift light is combined with the first and second phase shift light and the first and second phase shift light.
The sub-phase-shifted light is separated into (a) the first and second phase-shifted light by 90 ° ± 10 ° in the opposite directions to the above directly transmitted light.
(B) one of the above-mentioned first and second sub-phase-shifted lights has the same phase as the above-mentioned directly transmitted light, and the other directly transmits this directly-transmitted light. It is characterized by performing an appropriate phase difference within a range of 180 ° ± 10 ° to light in either direction.

In carrying out the present invention, preferably, the above-mentioned separation of the phase shift light is performed by (a) the first and second phase shift lights are separated by 90 ° ±, in opposite directions to the directly transmitted light. Give an appropriate phase difference within the range of 10 °,
(B) Both the first and second sub-phase-shifted lights are provided by giving an appropriate, same amount of phase difference within a range of 180 ° ± 10 ° to either of the direct transmitted lights. May be.

Further, in carrying out the present invention, the above-mentioned phase shift light is separated into first and second phase shift lights and sub phase shift light, and the phase shift light is separated by
(A) The first and second phase-shifted lights are given an appropriate phase difference within the range of 90 ° ± 10 ° in the opposite directions to the directly transmitted light, and (b) the sub-phase shift described above. The light may be provided by giving the directly transmitted light a phase difference of a different amount from that of the above-described first and second phase-shifted lights.

According to the first aspect of the phase difference mask of the present invention, the phase difference mask comprises at least a mask substrate and a phase shifter formed in a pattern on the mask substrate. In a phase difference mask for projecting a mask onto a photosensitive layer with projection light to perform a phase difference exposure on the photosensitive layer, the phase shifter includes first and second phase shifters for increasing the contrast of the projection light. Of the first and second phase shifters, or one or two sub-phase shifters for determining the image formation position of the above-mentioned projected light on the photosensitive layer. Characterize.

The second phase difference mask according to the present invention can also be used.
According to the gist of the invention, at least a mask substrate and a phase shifter provided in a pattern on the mask substrate are provided, and phase shift light that gives a phase difference to the phase of the direct transmitted light from the mask substrate is used. In a retardation mask for subjecting a resist layer of a photosensitive layer to a phase difference exposure, (a) a phase shifter includes first and second phase shifters, and first and second sub-phase shifters, and (b) a second phase shifter. The 1-phase shifter
It is configured as a phase shifter that gives an appropriate phase difference within the range of 90 ° ± 10 ° to the above-mentioned directly transmitted light, to the first phase-shifted light transmitted therethrough, and (c) the second phase shifter. Is configured as a phase shifter that gives an appropriate phase difference within the range of 270 ° ± 10 ° to the above-mentioned directly transmitted light to the second phase-shifted light transmitted therethrough, (d)
The first sub-phase shifter described above has 0 ° ± 10 with respect to the directly transmitted light as the first sub-phase shift light transmitted through the first sub-phase shifter.
Or a second phase shifter for providing an appropriate phase difference within a range of 360 ° ± 10 °, and (e) the second
The sub-phase shifter is configured as a phase shifter that gives an appropriate amount of phase difference within a range of 180 ° ± 10 ° to the directly transmitted light for the second sub-phase-shifted light transmitted therethrough. And

In implementing the retardation mask of the second aspect, preferably, (a) a plurality of light shielding portions are sequentially arranged in a pattern on the mask substrate, and (b) successively. The first phase shifter described above is provided in one of the two adjacent transparent sections between the light-shielding sections, and the first phase shifter sandwiched between the first phase shifters is disposed in the central region of the transparent section. One sub-phase shifter is provided, and (c) the second phase shifter is sandwiched between the other transparent part of the two adjacent transparent parts and the second phase shifter, and the sub-phase shifter is arranged in the central region of the transparent part. It is preferable to provide the above-mentioned second sub-phase shifter provided.

In implementing the retardation mask according to the second aspect, preferably, (a) the mask substrate is provided with the first phase shifter and the second phase shifter arranged alternately adjacent to each other, and (b) It is preferable that the first sub-phase shifter is provided at the center of the first phase shifter, and (c) the second sub-phase shifter is provided at the center of the second phase shifter.

In implementing the phase difference mask of the second aspect, preferably, the first sub-phase mask and the second sub-phase mask may be replaced with each other.

In implementing the retardation mask according to the second aspect, it is preferable that (a) the pattern widths of the first and second phase masks taken in the direction along the sequential arrangement direction be the same width. (B) The pattern widths of the first and second sub-phase masks taken in the direction along the arrangement direction may have different widths.

In implementing the retardation mask according to the second aspect, preferably, (a) the pattern widths of the first and second sub-phase masks taken in the direction along the arrangement direction are the same width. , (B) holding the relative phase difference between the first and second sub-phase-shifted lights at an appropriate value within the range of 180 ° ± 10 °, and (c) the film thickness of the first and second sub-phase masks described above. It is better to have different film thicknesses.

According to the third aspect of the phase difference shifter of the present invention, at least a mask substrate and a phase shifter provided in a pattern on the mask substrate are provided, and the phase of the direct transmitted light from the mask substrate is provided. In a phase difference mask for performing a phase difference exposure on a photosensitive layer using a phase shift light having a phase difference with respect to, a (a) phase shifter includes first and second phase shifters and a sub phase shifter. , (B)
The first phase shifter is configured as a phase shifter that gives an appropriate phase difference within the range of 90 ° ± 10 ° to the above-mentioned directly transmitted light, to the first phase shift light that has passed through the first phase shifter, (C) The second phase shifter converts the second phase shift light transmitted through the second phase shifter by 270 ° ±.
It is configured as a phase shifter that gives an appropriate phase difference within the range of 10 °, and (d) the sub-phase shifter transmits (180 ° ±± It is characterized in that it is configured as a phase shifter that gives an appropriate amount of phase difference within the range of (10 °) or (360 ° ± 10 °).

In implementing the phase difference mask according to the third aspect, preferably, (a) a plurality of light-shielding portions are sequentially arranged in a pattern on the mask substrate, and (b) successive light-shielding portions are sequentially arranged. A first phase shifter and a sub-phase shifter disposed in the central region of the transparent portion and sandwiched by the first phase shifter are provided on one of the two transparent portions adjacent to each other between the transparent portions, (C) A second phase shifter is provided on the other transparent portion of the two adjacent transparent portions, and the sub-phase shifter is sandwiched between the second phase shifters and disposed in the central region of the transparent portion. It is good to provide.

In implementing the phase difference mask according to the third aspect, it is preferable that (a) the mask substrate described above be provided with the first phase shifter and the second phase shifter arranged alternately adjacent to each other. , (B) it is preferable to provide the sub-phase shifter in the central portion of the first phase shifter, and (c) provide the sub-phase shifter in the central portion of the second phase shifter.

In implementing the phase difference mask of the third aspect, it is preferable that the pattern width of the sub-phase shifter taken in the direction along the sequential arrangement direction of the above-mentioned first and second phase shifters be used. It is preferable that the width is different from the widths of the first and second phase shifters described above.

In implementing the retardation mask of the third aspect, preferably, (a) the above-mentioned mask substrate,
Providing a plurality of light-shielding parts arranged in sequence in a pattern,
(B) The first phase shifter described above is disposed on one transparent part of two adjacent transparent parts between successive light-shielding parts.
(C) The above-mentioned second phase shifter is disposed on the other transparent portion of the two adjacent transparent portions, and (d) the above-mentioned first or second transparent portion.
It is preferable to dispose the above-mentioned sub-phase shifters at the transparent portions on both sides of the phase shifter.

In implementing the retardation mask of the third aspect, preferably, (a) the above-mentioned mask substrate,
The first phase shifter and the second phase shifter are alternately arranged so as to be adjacent to each other, and (b) the sub-phase shifter is provided at the center of either one of the first and second phase shifters. good.

In implementing the phase difference mask of the third aspect, preferably, the pattern widths of the sub-phase shifter taken in the direction along the sequential arrangement direction of the first and second phase shifters are The width may be different from the widths of the first and second phase shifters.

In implementing the phase difference mask according to the third aspect, preferably, the sub-phase shifter described above is used.
When using a phase shifter that produces a phase difference of 0 ° ± 10 °,
It is preferable that the sub-phase shifter has a plurality of dot-shaped rectangular patterns that are separated from each other.

According to a fourth aspect of the phase difference mask of the present invention, the phase difference of the direct transmitted light from the mask substrate is provided by including at least a mask substrate and a phase shifter provided in a pattern on the mask substrate. In a phase difference mask for performing a phase difference exposure on a resist layer of a wafer by using a phase shift light having a phase difference with respect to (a), as a phase shifter, first and second phase shifters and a sub phase shifter are provided. (B) the first phase shifter transmits the first phase shift light by 90 ° ± 1 with respect to the direct transmission light described above.
The second phase shifter is configured as a phase shifter that gives an appropriate phase difference within the range of 0 °, and (c) the second phase shifter transmits the second phase shifted light to the above directly transmitted light by 2
It is configured as a phase shifter that gives an appropriate phase difference within the range of 70 ° ± 10 °. On the other hand, it is characterized in that it is configured as a phase shifter which gives an appropriate amount of phase difference (excluding 0 °) within a range of 0 ° ± (180 ° ± 10 °).

[0030]

The above-described retardation mask of the present invention itself has the first and second phase shifters (herein, the first and second phase shifters are collectively referred to as the general term, which are collectively referred to as "the first and second phase shifters"). (Referred to as a phase shifter or a main shifter), and a first and a second that determine an image forming position.
Both or one of the sub phase shifters is provided in combination with each other. Therefore, the projection light transmitted through the phase difference mask can be imaged at a position different from the image formation position in the normal exposure method. The image forming position can be changed by appropriately combining the main phase shifter and the sub phase shifter according to the design. Therefore, depending on the height difference of the unevenness of the wafer having the step, a photomask is prepared on the same photomask in which the region of the retardation mask of the present invention and the region of the mask constituent portion of the normal exposure method are mixed. . Then, the photosensitive layer is patterned by performing a predetermined processing step such as collectively exposing the mask layer of the photomask onto the photosensitive layer, and using this photosensitive layer pattern, a fine pattern is formed on a wafer having a step. It can be built with high precision.

[0031]

Embodiments of the present invention will now be described with reference to the drawings. It should be noted that the drawings only schematically show the dimensions, shapes, and positional relationships of the respective constituent components so that the present invention can be understood. Further, it should be understood that the materials, dimensions, shapes, and other required conditions described in the following examples are merely preferable examples, and the present invention is not limited to these conditions. .. Also,
Each cross-sectional view shows a cross section, and hatching and the like representing the cross section are omitted in some cross-sectional areas.

In the following description, the phase difference mask of the present invention and the phase difference exposure method using the same will be described together. Moreover, in the following description, particularly, the description will focus on the components of the phase difference mask.

FIG. 1 is a sectional view of an essential part shown in the direction orthogonal to the substrate surface for explaining the main features of the retardation mask of the present invention.

The retardation mask 100 of the present invention shown in FIG.
Are two areas 102 and 104 of the normal exposure method,
And a region 106 of the phase difference exposure method according to the present invention. The phase difference mask 100 includes a mask substrate 110 formed of a material transparent to light for projecting the phase difference mask, for example, glass. In the phase difference exposure method region 106, the first phase shifter 112 (112a, 112a,
112b) and the second phase shifter 114 (114a, 1
14b) and one or two types of sub-phase shifters 11
6 and / or 118 and a light shielding portion 120 are provided.
The embodiment shown in FIG. 1 has a configuration including two types, that is, first and second sub-phase shifters 116 and 118. The first and second phase shifters 112 and 114 have the function of increasing the contrast of the projected light. In addition, the first and second sub-phase shifters 116 and 118 have the first and second sub-phase shifters 116 and 118, respectively.
It is used in combination with either or both of the phase shifters 112 and 114, and has the function of determining the image formation position of the above-mentioned projection light on the wafer. In the following description, the first and second phase shifters may be collectively referred to as a main shifter, and the first and second sub shifters may be collectively referred to as a sub shifter. These main shifter and sub shifter are made of a suitable material transparent to the projected light,
For example, SiO 2 (silicon dioxide) is formed by using a normal method such as vapor deposition. Further, the light shielding unit 120
Are provided on the mask substrate 110 so as to be separated from each other and sequentially arranged. This light blocking portion 120 is also referred to as a light blocking pattern. The light-shielding portion 12 is arranged so that the projection lights transmitted through the transparent portions on both sides adjacent to the light-shielding portion 120 interfere with each other.
0s are arranged in a pattern.

In the embodiment of the phase difference mask structure shown in FIG. 1, in the phase difference exposure method area 106, the light shielding portion 120 is formed in a rectangular stripe shape, for example, chromium (Cr).
The materials are arranged at equal intervals by a conventional forming method. Then, the first and second phase shifters 112 (112a, 112b) and 114 (11) are provided on the transparent portions sequentially positioned between the light-shielding portions 120 adjacent to each other.
4a, 114b) are arranged alternately. The first phase shifter 112 is divided into central portions 112a and 112b, and the first sub-phase shifter 116 is arranged in the gap. Similarly, the second phase shifter 1
The second sub-shifter 118 is provided in the gap between 14a and 114b.
Is provided.

On the other hand, in the normal exposure method area 102, the mask structure is formed by sequentially arranging the light shielding portions 120 on the mask substrate 110 at appropriate intervals, and in the area 104, between the light shielding portions 120, The mask structure has the same type of phase mask 122. In the figure, this light shield 1
20 is shown with hatching.

Next, the phase difference mask structure in the phase difference exposure method region and the phase difference exposure method thereof will be specifically described.

[Embodiment 1] FIG. 4A is a plan view of a main part showing one embodiment of a mask structure in a phase difference exposure method region of a phase difference mask of the present invention, viewed from the mask substrate side. 4B is a cross-sectional view taken along the line II-II of FIG. Further, FIG. 5 is an explanatory diagram for explaining the phase amount shifted by each phase shifter. According to this embodiment, the mask structure has the same structure as that shown in FIG. Therefore, here
Each component is shown with the same number as that given in FIG. In FIG. 4A, both the main shifters 112 and 114 and the sub-shifters 116 and 118 are indicated by broken lines, and the light shielding portion 120 is indicated by solid lines.

In this embodiment, the phase amount on the mask substrate 110 is 0 ° or 360 ° (indicated by P1 in FIG. 5). The first phase shifter 112 transmits the first phase shifter 112 through the first phase shifter 112.
A phase shifter that gives the phase shift light an appropriate phase difference (shown by P2 in FIG. 5) within the range of 90 ° ± 10 ° with respect to the light just transmitted through the mask substrate 110, that is, the directly transmitted light. Configure as. Then, the second phase shifter 1
Reference numeral 14 is a phase shifter that gives the second phase-shifted light that has passed through this an appropriate phase difference (indicated by P3 in FIG. 5) within the range of 270 ° ± 10 ° with respect to the directly transmitted light. . Therefore, the relative phase difference between the first and second phase shifters 112 and 114 is 180 °. Further, the first sub-phase shifter 116 transmits the first sub-phase shifter 116 through the first sub-phase shifter 116.
For sub-phase shift light, 0 ° ± 10 ° to direct transmitted light
Or an appropriate phase difference within the range of 360 ° ± 10 ° (see P
4 shows. ) Is provided as a phase shifter, and the second sub phase shifter transmits the second sub phase shift light to an appropriate amount within a range of 180 ° ± 10 ° with respect to the directly transmitted light. It is configured as a phase shifter that gives a phase difference (indicated by P5 in FIG. 5). In this case, the relative phase difference between these sub shifters 116 and 118 is 180 °.
Keep it at ± 10 °. Although the maximum allowable range of the phase difference shifted by each shifter described above is ± 10 °,
This is because if the range is exceeded, the separation characteristics of the mask pattern with respect to the focus shift will exceed the allowable limit.

Image forming characteristics when the phase difference mask 100 is used will be described. When light is projected on the mask 100, as described above, the projection lights transmitted through the adjacent transparent portions interfere with each other. The first on the adjacent transparent part
And between the second phase shifters 112 and 114, and
Since the phase difference between the first and second sub-shifters 116 and 118 is substantially 180 °, the phase difference of the projected light between the adjacent transparent portions is 180 °. Therefore, the light intensity of the light-shielding portion is greatly reduced, so that a transferred image with high contrast can be obtained.

Further, in the phase difference mask structure of the present invention, sub shifters 116 and 118 are provided in the middle of the main shifters 112 and 114, respectively, and the lights transmitted through these sub shifters 116 and 118 interfere with each other. To meet each other. As described above, in this mask structure, since the optical interference due to the phase other than 180 ° is caused, the interference effect of this sub-mask is added to the interference effect of the main mask, and as a result, the result is deviated from the focus position in the normal exposure method. Maximum contrast can be obtained in the image plane. In addition to this, since the relative phase difference between the main shifter and the sub shifter is 90 °, the symmetry of the light intensity distributions of the adjacent transmitting portions is always kept equal. Therefore, as compared with the related art, it becomes easier to control the dimensions of the pattern to be formed on the wafer, and moreover, the positioning accuracy can be improved.

Hereinafter, this point will be described more specifically. In the mask structure of FIG. 4, the light shielding part 120 is formed of a chromium vapor deposition film. The pattern width in the arrangement direction is 0.75 μm, the distance between the adjacent light shielding portions 120 is 3.5 μm, and the film thickness is 1000 A ° (angstrom is indicated by A °). First phase shifter 112a
And 112b are SiO ₂ formed by sputtering.
A (silicon dioxide) film is formed, the film thickness thereof is set to about 2000 A °, and the phase difference from the directly transmitted light is set to 90 °. First
The sub-phase shifter 116 is formed of a SiO ₂ (silicon dioxide) film, the width of the light-shielding film in the arrangement direction is 0.5 μm, and the film thickness is appropriately set to, for example, 0 or 8000 A ° and the same as the mask substrate 110. A phase amount of 360 ° is applied. Therefore, the substantial width of the first phase shifter 112 formed between the light shields 120 is 3.0 μm. In addition, the second phase shifters 114a and 11
4b is also a SiO ₂ (silicon dioxide) film formed by sputtering similarly to the first phase shifter, and its film thickness is 6
The phase amount is set to 270 ° with about 000 A °. Similarly to the first sub-phase shifter 116, the second sub-phase shifter 118 is also formed with a width of 0.5 μm, but its film thickness is 4000.
A phase amount of 180 ° is given as about A °.
Therefore, the substantial width of the second phase shifter 114 formed between the light shields 120 is 1.0 μm.

Such a phase difference mask has a numerical aperture (N
1) using i-line with A) of 0.50 and σ of 0.50
Experimental data of the light intensity distribution when the mask pattern is projected by the / 5 reduction optical system are shown in FIGS. 6 (A) and 6 (B). 6A is on the minus (−) side, and (B) is
Shows the light intensity distribution when the focus position is shifted to the plus side. In these figures, the horizontal axis indicates the position of the light projection pattern corresponding to the direction along the line II-II on the left and right with the line CC of FIG. 4A as the center, and the vertical axis indicates the light intensity. Is shown. In FIG. 6A, a thick curve a shows a light intensity profile at a position where there is no focal point shift by the normal exposure method shown for comparison. Dashed curve b
Indicates that the focus position is on the + side (away from the optical system)
It is a light intensity profile at a position shifted by 0.5 μm. A thin curve c is an optical profile at a position where the focal point position is deviated to the + side by 1.0 μm. As can be understood from this figure, when there is a shift in the focus position of the curves b and c, the main shifters 112 and 114 and the sub shifter 116.
It can be seen that the decrease in contrast hardly occurs due to the optical interference effect with 118 and 118.

Further, in FIG. 6B, a thick curve a indicates a light intensity profile at a position where there is no focal point shift by the ordinary exposure method shown for comparison. The broken line curve d indicates that the focus position is on the − side (in the direction approaching the optical system).
It is a light intensity profile at a position shifted by 5 μm.
Further, a thin curve e is an optical profile at a position where the focus position is shifted to the − side by 1.0 μm. As can be understood from this figure, when there is a focus position shift of the curve d, the main shifters 112 and 114 and the sub shifters 116 and 118 are.
It can be seen that the maximum light intensity is maximized and the contrast is increased due to the light interference action with.

FIG. 7 shows a shift from the focus position, contrast and maximum light when the phase difference masks shown in FIGS. 4A and 4B are projected using the above-mentioned optical system. It is an experimental data figure for explaining the relation with intensity. The center point of the horizontal axis in the figure is the position of the best image forming surface in the normal exposure method using the mask provided with only the light-shielding pattern, and this position is the reference position where there is no focus shift. Then, the shift amounts of the respective focal positions of minus on the left side and plus on the right side of the horizontal axis are shown in units of μm. The left vertical axis shows the contrast (% unit), and the right vertical axis shows the maximum light intensity (% unit). In the figure, the solid line a is the contrast curve, and the broken line b is the light intensity curve. The contrast and the maximum light intensity are shown with the maximum contrast and the maximum light intensity at the reference position in the normal exposure method as a reference of 100%.

As can be understood from this figure, the change in the contrast is small in the region where the focal position shift is 0 μm to +0.5 μm, and the maximum light intensity is also the same.
Maximum (approx. +0.5
It can be seen that it has a characteristic of being shifted by μm). From this fact, the phase difference mask of the present invention moves the image plane where the maximum light intensity, which is the best for pattern formation, is moved from the best image plane in the ordinary exposure method using the mask having only the light shielding pattern described above. It can be understood that it has the characteristics that make it. Therefore, when patterning a wafer having a step such as an integrated circuit, a phase difference mask is prepared in advance so that the best image forming position corresponds to the step on the wafer, and the resist layer is exposed using this phase difference mask. If it is performed, it becomes possible to form a pattern with high accuracy.

[Embodiment 2] In the retardation mask structure of Embodiment 1 described above, the example in which the light shielding portion 120 is provided in the retardation exposure method area has been described, but in the case of the retardation mask of the present invention, this The light shield 120 may not be provided in the region. This embodiment is shown in FIGS. 8A and 8B. In the configuration example shown in FIG. 8A, the main shifters 112 and 114
The point that the sub-shifters 116 and 118 are arranged at the center of each is the same as that of the first embodiment. However, in the case of the second embodiment, the first and second phase shifters 112 and 114 are arranged alternately adjacent to each other, and the first sub-phase shifter 1 is provided between the first phase shifters 112a and 112b.
16 is provided, and the second sub-phase shifter 118 is provided between the second phase shifters 114a and 114b.

[Embodiment 3] Further, in the retardation mask structure of the present invention, the first and second structures in the structure of Embodiment 2 are added.
The sub-phase difference shifter may be replaced with another structure in which the combination of the main shifter and the sub-shifter is changed. The retardation mask structure in that case is shown in FIG. In this case, the direction of the image plane changes. The first phase shifter 112 is a shifter for shifting the phase by 90 °, and
The sub-phase shifter 116 is a shifter for shifting the phase by 180 °, the second phase shifter 114 is a shifter for shifting the phase by 270 °, and the second sub-phase shifter 118 is a shifter of 360 °.
When the shifter is used to shift the phase, the characteristic with respect to the focal position shift is reversed in sign at the defocus, and as a result, the image plane becomes the best on the minus side. In particular, the maximum light intensity can be obtained at the position where the focus position is deviated by about −0.5 μm.

As described above, like the phase difference masks shown in the second and third embodiments, the phase difference exposure method area of the photomask has four phase shifters 112, 114, 116, in total.
The effect of the present invention can be achieved by the 4-shifter structure constituted by 118.

[Embodiment 4] In the retardation mask structure of the present invention, the structure of Embodiment 1 shown in FIGS. 1
Alternatively, the second sub-phase difference shifter may be replaced with another structure in which the combination of the main shifter and the sub-shifter is changed. The retardation mask structure in that case is shown in FIG. In this case, the structure includes the light shielding portion 120, but like the structures of the second and third embodiments,
An image plane having the maximum light intensity is obtained at a position where the focal point is shifted by about −0.5 μm.

[Embodiment 5] Further, as described above, in the phase difference exposure method region, as in the case of the structures of the respective embodiments already described, the respective mask patterns are arranged side by side without any gap. In the case of the structure, the pattern width of the sub shifters 116 and 118 may be changed for each area in the phase difference exposure area. The retardation mask structure is shown in FIG.

In this structure, the pattern widths of the first and second phase shifters 112 and 114 taken along the direction in which they are sequentially arranged are the same across the entire phase difference exposure method region. Then, the first and second sub-phase shifters 1
The pattern widths of 16 and 118 taken in the direction along the arrangement direction are set to different widths depending on the zones Z1 and Z2 of the phase difference exposure method region. In the figure, both sub-shifters within zone Z1 are shown at 116a and 118a,
Both subshifters within 2 are shown at 116b and 118b. In this structure, the phase amount to be shifted by each phase shifter does not change the phase amount (thus, the film thickness) determined for each phase shift exposure method region.

Even with such a phase difference mask structure,
As in the case of the above-described embodiment, the operational effects of the present invention can be layered. In particular, the position of the best image plane of the mask pattern can be individually set within the same phase difference exposure method area, so that the mask pattern of the phase difference mask can be finely corresponded to the uneven surface of the wafer with many steps. If formed, the pattern can be formed on the wafer with high accuracy.

[Embodiment 6] Further, in the case of a structure in which the mask patterns are arranged side by side without a gap,
The position of the best image plane can be set by changing the film thickness of the sub shifters 116 and 118. The retardation mask structure in this case is shown in FIG. In this structure, the pattern widths of the first and second sub-phase shifters 112 and 114 taken in the direction along the arrangement direction are made the same width over the entire phase difference exposure method region.
Further, the relative phase difference between the first and second sub-phase shift lights is maintained at an appropriate value within the range of 180 ° ± 10 ° throughout the phase difference exposure method region. The film thicknesses of the first and second sub-phase shifters 116 and 118 are made different depending on the entire area of the phase difference exposure method area or a specific area.

[Embodiment 7] Next, an embodiment of another gist of the phase difference mask of the present invention will be described. FIG. 10 (A)
FIG. 4 is a sectional view showing a mask structure in a phase difference exposure method area of this embodiment. FIG. 11 is an explanatory diagram showing the relationship between the phase amounts of the phase shifters provided in this mask structure.
The feature of the structure of this embodiment is that it has first and second phase shifters 112 and 114 and one type of sub-phase shifter 130 as a phase shifter, and has a three-shifter structure.

The first phase shifter 112 converts the first phase-shifted light that has been transmitted through the first phase-shifted light 112 into the directly transmitted light described above.
It is configured as a phase shifter that gives an appropriate phase difference within the range of 90 ° ± 10 °. Also, the second phase shifter 114
The second phase-shifted light that has passed through this is configured as a phase shifter that gives an appropriate phase difference within the range of 270 ° ± 10 ° to the directly transmitted light described above. Then, the sub-phase shifter 130 receives
It is configured as a phase shifter that gives an appropriate amount of phase difference within the range of (180 ° ± 10 °) or (360 ° ± 10 °) to the directly transmitted light. In FIG. 11, the phase amount of the mask substrate 110 is 0 °, and this is indicated by P1.
The phase amount of the first phase shifter 112 is indicated by P2, the phase amount of the second phase shifter 114 is indicated by P3, and the sub phase shifter 1
The phase amount of 30 is indicated by P4. Even in the case of the structure of this embodiment, as already described in the first embodiment, the maximum allowable range of the phase difference shifted by each shifter described above is ± 10 °.
However, if it exceeds this range, the deterioration of the separation characteristics of the mask pattern with respect to the focus deviation exceeds the allowable limit.

In the embodiment shown in FIGS. 10A and 10B, as in the case of the first embodiment shown in FIG. 4, the light-shielding portions 120 are sequentially arranged on the mask substrate 110 at regular intervals, The structure is such that a main shifter and a sub shifter are provided in the transparent portion between these light shielding portions 120. Further, preferably, the main shifters 112 and 114 are alternately provided in the transparent portion between the adjacent light shielding portions 120. The sub shifter 130 is preferably arranged between the main shifters 112a and 112b as shown in FIG.
It is provided between 14a and 114b.

Imaging characteristics when the retardation mask 100 having this structure is used will be described. When light is projected on the mask 100, as described above, the projection lights transmitted through the adjacent transparent portions interfere with each other. Since the phase difference between the first and second phase shifters 112 and 114 provided on the adjacent transparent portions is substantially 180 °, the phase difference of the projection light between the adjacent transparent portions is 180 °. Therefore, the light intensity of the light-shielding portion is greatly reduced, so that a transferred image with high contrast can be obtained.

Further, in the phase difference mask structure of the present invention, sub shifters 130 are provided in addition to the main shifters 112 and 114, and the lights transmitted through the respective shifters interfere with each other. Thus, in this mask structure, 1
In order to cause optical interference due to phases other than 80 °, the interference effect of this sub-mask is added to the interference effect of the main mask,
Therefore, the best image formation position can be obtained at a position deviated from the focus position in the normal exposure method, and the maximum contrast can be obtained on the image formation surface.

This point will be described more specifically below. In the mask structure of FIG. 10A, the light blocking portion 1
20 is formed by a vapor deposition film of chromium. The pattern width in the arrangement direction is 1.0 μm, the distance between the adjacent light shields 120 is 2.0 μm, and the film thickness is 1000 A °.
The first phase shifters 112a and 112b are SiO ₂ (silicon dioxide) films formed by sputtering, the film thickness thereof is 2000 A °, and the phase difference with the direct transmitted light is 90 °. Also, the second phase shifters 114a and 114a
14b is also a SiO ₂ (silicon dioxide) film formed by sputtering similarly to the first phase shifter, and its film thickness is about 6000 A ° and the phase amount is 270 °. The sub phase shifter 130 is formed of a SiO ₂ (silicon dioxide) film, and the width of the light shielding pattern 120 in the arrangement direction is 0.5 μm.
Then, the film thickness is set to about 4000 A ° and a phase amount of 180 ° is given. Therefore, the first phase shifter 1
The substantial width formed between the light shielding part 120 of the 12 and the second phase shifter 114 is 1.5 μm.

Such a retardation mask has a numerical aperture (NA) of 0. 0 as in the case of the first embodiment.
Part (A) and (B) of FIG. 12 show part of the experimental data of the light intensity distribution when a mask pattern is projected by a 1/5 reduction optical system using i-line with 50 and σ of 0.50. In these figures, the horizontal axis represents the light projection position similar to the case of FIGS. 6A and 6B, and the vertical axis represents the light intensity. In FIG. 12A, a thick curve a indicates a light intensity profile at a position when there is no shift of the focus position by the normal exposure method shown for comparison. A broken line curve b is a light intensity profile at a position where the focal position is deviated to the − side (in the direction closer to the optical system) by 0.5 μm. Also, the thin curve C has a focus position of −
It is an optical profile at a position deviated to the side by 1.0 μm.
As can be understood from this figure, when there is a focus position shift of the curves b and c, the contrast is hardly reduced by the optical interference action between the main shifters 112 and 114 and the sub shifters 116 and 118. . As can be understood from FIG. 12A, the light intensity distribution at the position where the focal length is shifted by −0.5 μm is
A 180 ° sub-shifter 130 is provided between the 270 ° second phase shifters 114a and 114b to increase the light intensity (curve b in FIG. 12A) of the transparent portion.

On the other hand, in FIG. 12B, the thick curve a is
The light intensity profile in the position when there is no shift of the focus position by the normal exposure method shown for comparison is shown. Further, a broken line curve d is a light intensity profile at a position where the focal position is shifted to the + side (away from the optical system) by 0.5 μm. Further, a thin curve e is an optical profile at a position where the focal position is deviated to the + side by 1.0 μm. As can be understood from this figure, the focus position is set to +.
At the position shifted by 5 μm, the first phase shifter 11 of 90 °
The light intensity (curve d in FIG. 12B) of the transparent portion where the 180 ° sub-shifter 130 is provided between 2a and 112b increases. Therefore, the retardation mask of this embodiment has a characteristic that the maximum light intensities of the transparent portions which are successively adjacent to each other are obtained at positions different by 1.0 μm. As described above, according to this mask structure, it is possible to design so that the position of the image plane having the maximum contrast is changed for each transparent portion between the light-shielding portions 120 in sequence.

FIGS. 13A and 13B are explanatory views in the case of patterning by the exposure method using the retardation mask of the mask structure of the seventh embodiment described above. This (A) figure is a figure which shows the light intensity distribution by the phase difference mask of this Example. The horizontal axis represents the pattern position of the projection light corresponding to the array direction of the shifters of the phase difference mask, and the vertical axis represents the light intensity. Also, this (B) is applied to a wafer having a step,
FIG. 7 is a cross-sectional view showing a state obtained by exposing and developing with this projection pattern, in which a lower wiring 142 is partially formed on the upper surface of the substrate 140, and an intermediate insulating film 144 is formed on the entire surface including the lower wiring 142. Form. The surface of the intermediate insulating film 144 becomes an uneven surface, and the step between the lower surface and the upper surface of the uneven surface is, for example, about 1 μm. This intermediate insulating film 14
A photosensitive layer such as a resist layer is provided on the surface 4, and a phase difference exposure method is performed on the resist layer having a step on the surface by using this phase difference mask.

As described above, in the above-described phase difference mask of this embodiment, the first shifter group including the combination of the first phase difference shifter 112 having a phase amount of 90 ° and the sub shifter 130 having a phase amount of 180 °. And a second shifter group composed of a combination of the second phase difference shifter 114 having a phase amount of 270 ° and the sub shifter 130 having a phase amount of 180 ° are alternately arranged. In FIG. 13A, a region Q1 is a pattern region of the projection light by the first shifter group, and the light intensity distribution is a curve q1. Also, the area Q2
Is a pattern region of the projected light by the second shifter group, and the light intensity distribution is a curve q2. The maximum light intensity by the second shifter group is plus (+) from the image formation position in the normal exposure method.
The maximum light intensity obtained by the first shifter group is 0.5 μm on the minus (−) side.
Obtained at offset positions. Therefore, the distance between the ⅕ reduction projection optical system and the wafer surface is adjusted so that the image forming surface in the normal exposure method is adjusted to an appropriate intermediate position between the upper and lower surfaces of the step of the resist layer. In this way, the lower layer of the step of the resist layer is exposed with the maximum light intensity by the second shifter group, and the upper layer of the step is exposed with the maximum light intensity by the first shifter group. Therefore, even if the resist layer has irregularities, the upper and lower layers of the irregularities are exposed with optimum light intensity. Subsequently, the exposed resist can be appropriately developed and patterned according to a usual technique to form resist patterns 146a and 146b. As described above, according to the phase difference exposure using the phase difference mask of the present invention, it is possible to simultaneously expose a resist layer having a step difference using a single phase difference mask, and further, to form the pattern thereof. The dimensional control of is also greatly improved over the conventional one.

[Embodiment 8] In the retardation mask structure of Embodiment 7 described above, an example in which the light shielding portion 120 is provided in the retardation exposure method area has been described. However, in the case of the retardation mask of the present invention, this The light shield 120 may not be provided in the region. This embodiment is shown in FIG. In the configuration example shown in FIG. 10B, the sub shifter 130 is arranged at the center of each of the main shifters 112 and 114, which is the same as that of the seventh embodiment. However, in the case of the eighth embodiment, the first and second phase shifters 112 and 114 are alternately arranged adjacent to each other, and the first phase shifters 112a and 112b are arranged.
And the sub-phase shifter 130 is provided between the second phase shifter 114a and the second phase shifter 114b. Even with this structure, the effect of the three-shifter structure can be achieved.

[Embodiment 9] In the retardation mask having the above-mentioned three-shifter structure, the sub-shifter is provided so as to be sandwiched in the central portion of the main shifter, but instead of such a structure, the main shifter 112 and Subshifter 1 on both sides of 114
Even if the structure of arranging 30 (130a, 130b) is 3
The effect of the shifter structure can be achieved. Figure 10
The retardation mask shown in (C) is provided with the light shielding part 120, and the sub shifter 130 is provided in the transparent part between the successive light shielding parts 120, as in the case of the seventh embodiment described in FIG.
a, the second phase difference shifter 114 and the sub shifter 130b
The second shifter group consisting of and is provided, and the transparent part next to
It has a structure in which a first shifter group including a sub-shifter 130a, a first retardation shifter 112, and a sub-shifter 130b is provided.

[Embodiment 10] The structure of this embodiment is a structure in which the light shielding portion 120 is not provided, and this is shown in FIG. In this case, the sub shifter 130, the second
Phase shifter 114, sub shifter 130, first phase difference shifter 112, sub shifter 130, second phase difference shifter 11
4, the sub shifter 130 and the first phase difference shifter 112 have a structure in which the main shifter and the sub shifter are sequentially combined and arranged. Even in the case of this retardation mask, it is possible to achieve the above-described effects of the three-shifter structure.

[Embodiment 11] In the retardation masks of Embodiments 7 to 10 described above, the sub phase shifter 130 has a relative phase difference of 180 ° with the directly transmitted light, but a sub phase difference of 360 °. A phase shifter may be used. For this purpose, the film thickness of the sub shifter 130 may be changed. Even in the case of this phase difference mask, the position of the best image forming surface in the phase difference exposure method region of the photomask is set to the best image forming surface in the normal exposure method, as in the case of Examples 7 to 10. The structure can be shifted to a desired position. Note that these structures are the structures shown in FIGS. 10A to 10D, and the phase difference of the sub shifter 130 is 180 ° to 360 °.
However, the illustration of each structure of this embodiment is omitted. Even in this case, the maximum allowable error is ± 1
It is good to set it to 0 °.

[Embodiment 12] As described above, in the phase difference exposure method area, each of Embodiments 7 to 1 already described.
In the case of the structure in which the mask patterns are continuously arranged side by side without a gap like the structure of No. 1, the pattern width of the sub-shifter in the phase difference exposure region can be changed. The retardation mask structure is shown in FIG.

In this structure, the pattern widths of the first and second phase shifters 112 and 114 taken in the direction along the sequential arrangement direction are made the same width over the entire area of the phase difference exposure method. Then, the pattern width of the sub-phase shifter taken in the direction along the arrangement direction is selectively made different within the phase difference exposure method region. This sub shifter is shown by 132 and 134, respectively. In this structure, the phase amount to be shifted by each phase shifter does not change the phase amount (thus, the film thickness) determined for each phase shift exposure method region.

Even with such a phase difference mask structure,
Similar to the above-described Embodiments 7 to 11, the effects of the present invention can be layered. In particular, the position of the best image plane of the mask pattern can be individually set within the same phase difference exposure method area, so that the mask pattern of the phase difference mask can be finely corresponded to the uneven surface of the wafer with many steps. If formed, the pattern can be formed on the wafer with high accuracy.

[Embodiment 13] Further, in the case of the structure in which the mask patterns are arranged side by side without any gap, the width of the sub shifter and the relative phase difference (film thickness) are made constant,
Further, by keeping the relative phase difference between the main shifters 112 and 114 constant and appropriately changing the width of all or a required part of the main shifters 112 and 114, the best image plane of each mask pattern can be obtained. The position of can be set according to the step of the wafer. Since the phase difference mask structure in this case is clear without exemplifying it, illustration of the structure is omitted.

[Embodiment 14] Next, an embodiment of still another gist of the phase difference mask of the present invention will be described. Figure 15
(A) is a plan view of the main part of the mask structure in the phase difference exposure method region of this embodiment as seen from the mask substrate side, and
FIG. 15B is a sectional view taken along line III-III in FIG. In FIG. 15 (A),
The main shifters 112 and 114 and the sub shifter 150 are shown by broken lines, and the light shielding part 120 is shown by solid lines. The feature of the structure of this embodiment is that the first and second phase shifters are used.
Although the phase shifters 112 and 114 and one type of sub-phase shifter 150 are provided and the structure is a three-shifter structure, which is common to the cases of Examples 7 to 13, one of the main shifters 112 and 114 is used. Sub-shifter 15 on both sides of
0 (150a, 150b) is provided. The phase amounts of the first and second phase shifters 112 and 114 for the above-mentioned directly transmitted light and the phase amounts of the sub-phase shifter 150 for the above-mentioned directly transmitted light are the same as those in the seventh to seventh embodiments.
The same as in the case of No. 13, and therefore, it is assumed that the phase relationship shown in FIG.

In the embodiment shown in FIGS. 15A and 15B, as in the case of the first embodiment shown in FIG. 4, the light shielding portions 120 are sequentially arranged on the mask substrate 110 at regular intervals, The structure is such that a main shifter and a sub shifter are provided in the transparent portion between these light shielding portions 120. Further, preferably, the main shifters 112 and 114 are alternately provided in the transparent portion between the adjacent light shielding portions 120. In this embodiment, the sub shifter 150 is replaced with the main shifter 112,
Or, divide it on both sides of 114 (150, 150b)
Set up. In the embodiment shown in FIGS. 15A and 15B, the sub shifter 150 is provided in combination with the first phase difference shifter 112.

Imaging characteristics when the retardation mask 100 having this structure is used will be described. When the light is projected onto the mask 100, the projection lights transmitted through the first and second phase shifters 112 and 114 of the adjacent transparent portions interfere with each other, as described above. Since the phase difference between the first and second phase shifters 112 and 114 provided on the adjacent transparent portions is substantially 180 °, the phase difference of the projection light between the adjacent transparent portions is 180 °. Therefore, the light intensity of the light-shielding portion is greatly reduced, so that a transferred image with high contrast can be obtained.

Further, in the retardation mask structure of the present invention, the sub shifters 130 are provided on both sides of the main shifter 112.
The interference of the light that has passed through is added, and the lights that have passed through these shifters interfere with each other. As described above, in this mask structure, since the optical interference is caused by a phase other than 180 °, the interference effect of this sub-mask is added to the interference effect of the main mask, and therefore, the position deviated from the focus position in the normal exposure method is used. The best image forming position can be obtained, and the maximum light intensity and the maximum contrast can be obtained on the image forming surface. Therefore, the light intensity between adjacent transparent portions of the mask pattern can be changed.

This point will be described more specifically below. In the mask structure of FIGS. 15A and 15B, the light shielding portion 120 is formed of a chromium vapor deposition film. The pattern width in the arrangement direction is 1.0 μm, the distance between the adjacent light shields 120 is 1.5 μm, and the film thickness is 1000 μm.
Set to A °. The first phase shifter 112 is a SiO ₂ (silicon dioxide) film formed by sputtering, the film thickness thereof is 2000 A °, and the phase difference with the direct transmitted light is 90.
Let be °. The second phase shifter 114 is also a SiO ₂ (silicon dioxide) film formed by sputtering similarly to the first phase shifter, and its film thickness is about 6000 A ° and the phase amount is 270 °, and the transparent portion has a thickness of 1.5 μm. Provide the entire width of. S the sub phase shifters 150a and 150b
iO ₂ (silicon dioxide) film, light-shielding pattern 1
The width of each of the 20 in the array direction is set to 0.25 μm, and the entire width occupied by one transparent portion is set to 0.5 μm. Also,
The film thickness of each sub-shifter 150 is set to about 4000 A ° so as to give a phase amount of 180 °.
Therefore, the substantial width of the first phase shifter 112 formed between the light shields 120 is 1.0 μm.

Such a phase difference mask is provided with a numerical aperture (N) in the same manner as that described in the first and seventh embodiments.
A) with 0.50 and 0.50 with i line 1
16A and 16B show a part of the experimental data of the light intensity distribution when the mask pattern is projected by the / 5 reduction optical system. In these figures, the horizontal axis represents the light projection pattern position in the direction corresponding to the arrangement direction of the mask patterns on the left and right with the CC line in FIGS. 15A and 15B as the center, and the vertical axis. The axis shows the light intensity. 16A shows a change in the light intensity when the focus position is shifted to the minus (−) side, and FIG. 16B shows a change in the light intensity when the focus position is shifted to the plus (+) side. ing. Figure 1
In (A) of 6, a thick curve a shows a light intensity profile at a position when there is no focus position shift by the normal exposure method shown for comparison. A broken line curve b is a light intensity profile at a position where the focal position is deviated to the − side (in the direction closer to the optical system) by 0.5 μm. Further, a thin curve c is a light intensity profile at a position where the focus position is shifted to the − side by 1.0 μm. As can be understood from FIG. 16A, the light intensity of the light projection pattern corresponding to the portion of the second phase difference shifter 114 is on the minus (−) side of the image plane in the image passing exposure method. Although the maximum light intensity distribution is obtained, the light intensity of the light projection pattern corresponding to the portion of the shifter group formed by the combination of the first phase difference shifter 112 and the sub phase difference shifter 150 adjacent to this is slightly lowered. I understand.

On the other hand, in FIG. 16B, the thick curve a is
The light intensity profile in the position when there is no focus position shift by the normal exposure method shown for comparison is shown.
Further, a broken line curve d is a light intensity profile at a position where the focal point position is deviated to the plus (+) side by 0.5 μm (away from the optical system). Further, a thin curve e is a light intensity profile at a position where the focal position is deviated to the plus (+) side by 1.0 μm. As you can see from this figure,
At the position where the focal position is shifted to the + side, the light intensity of the light projection pattern corresponding to the portion of the second phase difference shifter 114 is +0.5 μm and +1.
The maximum light intensity distribution when it is deviated by 0 μm is reduced. It can be seen that it is almost the same as in the case of the normal exposure method. Further, it can be seen that in each case, the light intensity of 60% or more required for exposing the photosensitive layer was obtained. By utilizing such characteristics, the mask structure in the phase difference exposure method region can be designed in advance so as to change the position of the image surface having the maximum contrast for each transparent portion between the successive light shielding portions 120. Then, this phase difference mask may be used so that the best image plane can be formed on the plus side (the direction away from the reduction projection optical system) and the minus side (the direction closer to the reduction projection optical system).

FIGS. 17A and 17B are explanatory views of patterning by the exposure method using the retardation mask having the mask structure of the above-described fourteenth embodiment. This (A) figure is a figure which shows the light intensity distribution by the phase difference mask of this Example. The horizontal axis represents the pattern position of the projection light corresponding to the array direction of the shifters of the phase difference mask, and the vertical axis represents the light intensity. 13B is a cross-sectional view showing a state similar to that shown in FIG. 13B, showing a state obtained by exposing and developing a wafer having steps with this projection pattern, The lower wiring 142 is partially formed on the upper surface of 140.
Then, an intermediate insulating film 144 is formed on the entire surface including the lower wiring 142. A conductive layer 145 such as a metal layer for forming an upper wiring is provided above the intermediate insulating film 144. The surface of the conductive layer 145 becomes an uneven surface, and the step between the lower surface and the upper surface of the uneven surface is, for example, about 1 μm. A photosensitive layer such as a resist layer is provided on the conductive layer 145, and a phase difference exposure method is performed on the resist layer having a step on the surface by using this phase difference mask.

In FIG. 17A, a region Q3 is a pattern region of the projection light by the shifter group (112, 150), and the light intensity distribution is a curve q3. The area Q4 is a pattern area of the projection light by the second phase difference shifter 144,
The light intensity distribution becomes a curve q4. Shifter group (112, 15
0), the maximum light intensity (curves d and q3) is 0.5 on the plus (+) side from the imaging position in the normal exposure method.
The second phase difference shifter 14 is obtained at a position shifted by μm.
The maximum light intensity according to 4 (curves b and q4) is obtained at a position shifted by 0.5 μm to the minus (−) side. Therefore,
Also in this case, the distance between the ⅕ reduction projection optical system and the wafer surface is adjusted so that the image forming surface in the normal exposure method is adjusted to an appropriate intermediate position between the upper and lower surfaces of the step of the resist layer. . In this way, the lower layer of the step of the resist layer is
The shifter group (112, 150) is exposed with the maximum light intensity, and the upper layer of the step is exposed with the maximum light intensity by the second phase difference shifter 144. Therefore, even if the resist layer has irregularities, the upper and lower layers of the irregularities are exposed with optimum light intensity. Then, the exposed resist can be appropriately developed and patterned according to a usual technique to form resist patterns 148a and 148b. As described above, according to the phase difference exposure using the phase difference mask of the present invention, it is possible to simultaneously expose a resist layer having a step difference using a single phase difference mask, and further, to form the pattern thereof. The dimensional control of is also significantly improved as compared with the conventional one, and the pattern can be formed with high accuracy.

[Embodiment 15] In Embodiment 14 described above,
The sub shifters 150 are provided only on both sides of the first phase difference shifter 112.
The example in which the sub phase difference shifter 150 (150a, 150b) is provided only on both sides of the second phase difference shifter 114 may be adopted instead of the above. Such a structure is shown in FIG. Even with this configuration, the above-described effects of the present invention can be achieved.

[Embodiment 16] In the retardation mask structures of Embodiments 14 and 15 described above, an example in which the light shielding portion 120 is provided in the phase difference exposure method area has been described, but in the case of the retardation mask of the present invention, The light-shielding portion 120 may not be provided in this region, and the light-shielding portion 120 may be formed as a three-shifter structure including the shifters 112, 114 and 150 used in the fourteenth embodiment.
The structure of this embodiment is shown in FIG. However, the method of combining these shifters may be appropriately performed according to the design. In the configuration example shown in FIG. 18B, the sub shifter 150 is arranged at the center of the main shifter 112.
Therefore, in this case, the first and second phase shifters 11
2 and 114 are arranged alternately adjacent to each other, the first
The sub phase shifter 150 is provided between the phase shifters 112a and 112b. Even with this structure, the effect of the three-shifter structure can be achieved.

[Embodiment 17] In the retardation mask of the three-shifter structure of Embodiments 14 and 15 described above, the sub-shifter 150 (150a, 150b) is provided so that any one of the main shifters 122 or 144 is sandwiched in the central portion. However, instead of having such a configuration, a structure in which the sub shifter 150 (150a, 150b) is arranged in the middle of either one of the main shifters 112 and 114,
The effect of the 3-shifter structure can be achieved. Figure 1
In the retardation mask shown in FIG. 9A, the light shielding portion 120 is provided and the transparent portions between the light shielding portions 120 are provided in the same manner as in the case of the fourteenth embodiment described in FIGS. 15A and 15B. To
The second phase shifter 114a, the sub shifter 150, and the second
A structure is provided in which a shifter group including the phase shifter 114b is provided, and only the first phase difference shifter 112 is provided in the sequentially adjacent transparent portions. With this structure, it is possible to shift the best image forming planes vertically with respect to the wafer surface for each mask pattern corresponding to the adjacent transparent portion.
And even with this structure, as in the above-described embodiment,
The effect of the 3-shifter structure can be achieved.

[Embodiment 18] In Embodiment 17, the sub shifter 150 is provided only in the middle of the second phase shifter 114, but the sub shifter 15 is provided only in the middle of the first phase shifter 114.
A structure in which 0 is provided may be used. The structure of this embodiment is shown in FIG. With this structure, it is possible to shift the best image forming planes vertically with respect to the wafer surface for each mask pattern corresponding to the adjacent transparent portion. Even with this structure, it is possible to achieve the operational effects of the three-shifter structure as in the above-described embodiment.

[Embodiment 19] Embodiments 14 to 18 described above.
In the above phase difference mask, the sub-phase shifter 150 has a relative phase difference of 180 ° with the directly transmitted light, but a sub-phase shifter having a relative phase difference of 360 ° may be used. For this purpose, the film thickness of the sub shifter 130 may be changed. Even in the case of this phase difference mask, the position of the best image forming surface in the phase difference exposure method region of the photomask is set to the best image forming surface in the normal exposure method as in the case of Examples 14 to 18. The structure can be shifted to a desired position. Note that these structures are shown in FIG. 15 (A) and FIG. 18 (A).
And (B) and the structure shown in (A) and (B) of FIG.
Since it is only changed to 0 °, the illustration of each structure of this embodiment is omitted. Even in this case, the maximum allowable error is ±
It is good to set it to 10 °.

[Embodiment 20] Further, the intervals of the light-shielding portions provided on the mask substrate 110 are not made constant but are changed as required, and the relative phase difference (film thickness) of the main shifters 112 and 114 is made constant, Further, the width of the sub shifter and the relative phase difference (film thickness) are kept constant, and the main shifter 112 is
It is also possible to set the position of the best image forming surface of each mask pattern according to the step of the wafer by appropriately changing the width of all or a required part of 114 and 114. An example of the retardation mask structure in this case is shown in FIG.
Shown in. First phase difference shifters 112c, 112d, 112
The width of e is changed, and the second phase difference shifter 114
The widths of c, 114d and 114e are changed.

[Embodiment 21] Embodiments 14 to 20 described above
In the above, the example in which the sub-shifter is provided in the middle or both sides of the main shifter with the same length in the direction orthogonal to the arrangement direction of the sub-shifter and the main shifter has been described. It may be a pattern. An example of the configuration in this case is shown in FIGS. FIG. 1A is a cross-sectional view, and FIG. 1B is a plan view of relevant parts. In this embodiment, the dot type patterns 160 and 162 are provided in the adjacent second phase shifters 114.
Are alternately arranged. The planar shape of this dot type sub shifter is not limited to the above-mentioned example, and may be provided in any suitable combination with the main shifter of Examples 14 to 20 described above. Even in the case of this structure, it is possible to exhibit the above-described effects of the three-shifter structure.

[Embodiment 22] In addition, Embodiment 14 described above
22 to 22, the phase amount shifted by the sub-phase shifter 150 is (180 ° ± 10 °) (360 ° ± 1)
However, the sub-phase shift light transmitted through the sub-phase shifter 150 is (0 °) different from the direct transmission light described above.
Within the range of (± 10 °) to (180 ° ± 10 °),
The phase shifter may be configured to provide a phase difference of any appropriate amount (however, preferably 0 ° is excluded) in either the + side or the − side. An example of the configuration is shown in FIG.
In the cross-sectional view of. According to the structure of this phase difference shifter,
The relative phase difference and width of the main shifters 112 and 114 are kept constant, and the widths of the sub shifters 150a and 150b are kept constant. It has a different structure. Sub-shifters having different film thicknesses are indicated by 150c, 150d, 150e and 150f, respectively. Even with this configuration, as in the case of each of the above-described embodiments,
The best image plane can be moved in the vertical direction with respect to the wafer so as to match the uneven surface of the wafer.

[Other Embodiments] It is obvious to those skilled in the art that the present invention is not limited to the above-described embodiments, and many modifications and changes can be made. For example, the mask patterns of the phase difference exposure method area of the photomask may be formed by arbitrarily and appropriately combining the configurations of the above-described embodiments. Further, the retardation mask of the present invention may be configured by providing the mask structure of the above-described embodiment of the present invention and the conventional mask structure on the same mask substrate. It is obvious that how to combine the main shifter and the sub shifter depends on the position of the step of the wafer on which the pattern is to be formed, the height of the unevenness of the step surface, and the like. Further, it is clear that the planar shape of the main shifter and the sub shifter depends on the planar shape of the pattern to be formed. The material of the main shifter and / or the sub-shifter can be formed of a translucent material other than the above-mentioned silicon dioxide. Further, the phase shift by the main shifter and the sub shifter may be performed by changing the respective film thicknesses, or by forming the shifters by individually changing the respective refractive indexes.

[0091]

As is apparent from the above description, according to the structure of the phase difference mask of the present invention, the contrast of the projection light which is reflected by the phase difference mask is increased in the phase difference exposure method region of the mask substrate. The first and second phase shifters and the first and / or second sub-phase shifters that determine the image formation position of the projected light are provided in any suitable combination. Therefore, by arranging and arranging the combination of the main shifter and the sub shifter in accordance with the position and height of the step difference of the wafer on which the pattern is to be formed, the best connection to the upper and lower layers of the step difference of the photosensitive layer is achieved. It can be brought to the image plane. Therefore, by simultaneously exposing the photosensitive layer using the retardation mask of the present invention, the upper and lower layers of the photosensitive layer having a step can be exposed with optimum light intensity and contrast. Therefore, a wafer having a step can be patterned with high accuracy.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part for explaining the features of a phase difference mask of the present invention.

2A to 2C are explanatory views of a conventionally proposed retardation mask.

3A to 3C are explanatory views of a conventional exposure method which has been conventionally proposed.

4A and 4B are cross-sectional views showing the structure of the first embodiment of the present invention.

5 is an explanatory diagram of a phase amount of each shifter provided in the retardation mask having the structure shown in FIG.

FIG. 6 is a light intensity distribution chart for explaining a change in light intensity with respect to a focus position shift when performing phase difference exposure by a reduction optical system using the phase difference mask having the structure shown in FIG.

7 is an explanatory diagram of the relationship between defocus, contrast, and maximum light intensity when exposure is performed using the phase difference mask having the structure shown in FIG.

8A to 8C are cross-sectional views for explaining the structure of another embodiment of the retardation mask of the present invention.

9A and 9B are cross-sectional views for explaining the structure of another embodiment of the retardation mask of the present invention, respectively.

10A to 10D are cross-sectional views for respectively explaining the structure of another embodiment of the retardation mask of the present invention.

11 is an explanatory diagram of a phase amount of each shifter provided in the retardation mask shown in FIG. 10 (A).

12 (A) and 12 (B) are changes in light intensity with respect to a focal position shift when phase difference exposure is performed by a reduction optical system using the phase difference mask having the structure shown in FIG. 10 (A). FIG. 3 is a light intensity distribution diagram used for the explanation of FIG.

13 (A) and 13 (B) illustrate an example in which phase difference exposure is performed by a 1/5 reduction optical system using the phase difference mask of FIG. 10 (A) to pattern a photosensitive layer. FIG.

FIG. 14 is a sectional view showing the structure of another embodiment of the retardation mask of the present invention.

15 (A) and 15 (B) are a plan view and a cross-sectional view of an essential part for explaining another embodiment of the present invention.

16 (A) and (B) are light with respect to a focal position shift when phase difference exposure is performed by a reduction optical system using the phase difference mask having the structure of (A) and (B) of FIG. It is a light intensity distribution chart for explaining the intensity change.

17A and 17B are patterning of a photosensitive layer by performing phase difference exposure with a 1/5 reduction optical system using the phase difference masks of FIGS. 15A and 15B. It is explanatory drawing explaining an example.

18 (A) and (B) are sectional views for explaining another embodiment of the present invention.

19 (A) and 19 (B) are cross-sectional views provided for explaining another embodiment of the present invention.

FIG. 20 is a cross-sectional view provided for explaining another embodiment of the present invention.

FIG. 21 is a cross-sectional view provided for explaining another embodiment of the present invention.

22 (A) and (B) are sectional views for explaining another embodiment of the present invention.

[Explanation of reference numerals] 100: phase difference mask, 102, 10
4: Normal exposure method area 106: Phase difference exposure method area, 110: Mask substrate 112 (112a, 112b), 122 (122a, 1)
22b, 122c, 122d, 122e, 122f):
First phase shifter (main shifter) 114 (114a, 114b), 124 (124a, 1)
24b, 124c): second phase shifter (main shifter) 116 (116a, 116b): first sub-phase shifter (sub-shifter) 118 (118a, 118b): second sub-phase shifter (sub-shifter) 120: light-shielding layer (light-shielding pattern) ) 130, 132, 134, 150 (150a, 150
b): Sub phase shifter (sub shifter) 140: Substrate, 142: Lower wiring 144: Intermediate insulating films 146 (146a, 146b), 148 (148a, 1)
48b): resist pattern

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01L 21/027

Claims (19)

[Claims] 1. When the photosensitive layer is subjected to phase difference exposure using phase-shifted light that is phase-shifted with respect to the phase of light directly transmitted from a mask substrate, the phase-shifted light is converted into first and second phase-shifted lights. When,
The first and second sub-phase-shifted lights are separated into: (a) the first and second phase-shifted lights are separated by 90 An appropriate phase difference within the range of ± 10 ° is provided, and (b) one of the first and second sub-phase-shifted lights has the same phase as the directly transmitted light, and the other has 180 ° ± 1 in either direction for direct transmitted light
A phase difference exposure method which is performed by giving an appropriate phase difference within a range of 0 °. 2. When the photosensitive layer is subjected to phase difference exposure using phase-shifted light that is phase-shifted with respect to the phase of the direct transmitted light from the mask substrate, the phase-shifted light is converted into first and second phase-shifted lights. When,
The first and second sub-phase-shifted lights are separated into: (a) the first and second phase-shifted lights are separated by 90 Giving an appropriate phase difference within a range of ± 10 °, and (b) both the first and second sub-phase-shifted lights,
180 ° ± 10 ° in either direction with respect to the direct transmitted light
The phase difference exposure method is performed by giving an appropriate phase difference of the same amount within the range. 3. When the photosensitive layer is subjected to phase difference exposure using phase-shifted light that is phase-shifted with respect to the phase of direct transmitted light from the mask substrate, the phase-shifted light is converted into first and second phase-shifted lights. When,
The sub-phase-shifted light is separated into (a) the first and second phase-shifted lights are separated by 90 ° ± 10 ° in opposite directions to the directly transmitted light. An appropriate phase difference within the range is given, and (b) the sub-phase shift light is given a phase difference of an amount different from that of the first and second phase shift lights with respect to the direct transmission light. Characteristic phase difference exposure method. 4. A phase difference mask comprising at least a mask substrate and a phase shifter formed in a pattern on the mask substrate, wherein the phase difference mask is projected onto the photosensitive layer with projection light to form the photosensitive layer. In a phase difference mask for performing phase difference exposure, the phase shifter includes first and second phase shifters for increasing the contrast of the projection light, and either or both of the first and second phase shifters. 2. A retardation mask which is used in combination with one or two sub-phase shifters for determining an image forming position of the projection light on the photosensitive layer. 5. A photosensitizer using at least a mask substrate and a phase shifter provided in a pattern on the mask substrate, using a phase-shifted light having a phase difference with respect to a phase of light directly transmitted from the mask substrate. A phase difference mask for phase difference exposing a layer, comprising: (a) first and second phase shifters and first and second sub-phase shifters as the phase shifter, and (b) the first phase shifter. Is 90 ° ± 10 ° with respect to the directly transmitted light with respect to the first phase-shifted light transmitted therethrough.
Is configured as a phase shifter that gives an appropriate phase difference within the range of (c), and (c) the second phase shifter transmits the second phase shift light to the direct transmission light by 270 ° ± 10. It is configured as a phase shifter that gives an appropriate phase difference within the range of (°), and (d) the first sub-phase shifter transmits the first sub-phase shifter.
The sub phase shift light is configured as a phase shifter that gives an appropriate phase difference within the range of 360 ° ± 10 ° to the directly transmitted light, and (e) the second sub phase shifter transmits the light. The phase difference mask, wherein the second sub-phase-shifted light is configured as a phase shifter that gives an appropriate amount of phase difference within a range of 180 ° ± 10 ° to the directly transmitted light. 6. The retardation mask according to claim 5, wherein: (a) a plurality of light-shielding portions are sequentially arranged in a pattern on the mask substrate, and (b) between successive light-shielding portions. , The first phase shifter and the first sub-phase shifter disposed in the central region of the transparent portion sandwiched by the first phase shifter in one of the transparent portions of two adjacent transparent portions. And (c) the second phase shifter on the other transparent portion of the two adjacent transparent portions, and the second sub disposed between the second phase shifters and disposed in the central region of the transparent portion. A phase difference mask provided with a phase shifter. 7. The retardation mask according to claim 5, wherein (a) the mask substrate is provided with the first phase shifter and the second phase shifter alternately adjacent to each other, and (b) A phase difference mask characterized in that the first sub-phase shifter is provided in the center of the first phase shifter, and (c) the second sub-phase shifter is provided in the center of the second phase shifter. 8. The retardation mask according to claim 6, wherein the first sub-phase shifter and the second sub-phase shifter are replaced with each other. 9. The retardation mask according to claim 5, wherein: (a) the pattern widths of the first and second phase shifters taken in the direction along the sequential arrangement direction are the same width; ) A retardation mask, wherein the pattern widths of the first and second sub-phase shifters taken in the direction along the arrangement direction are different. 10. The retardation mask according to claim 5, wherein (a) the pattern widths of the first and second sub-phase shifters taken in the direction along the arrangement direction are the same width, and (b) The relative phase difference between the first and second sub-phase shift lights is maintained at an appropriate value within a range of 180 ° ± 10 °, and (C) the heights of the first and second sub-phase shifters are different from each other. A phase difference mask characterized in that 11. A photosensitizer using at least a mask substrate and a phase shifter provided in a pattern on the mask substrate, using phase-shifted light having a phase difference with respect to the phase of light directly transmitted from the mask substrate. A phase difference mask for phase difference exposing a layer, comprising: (a) first and second phase shifters and a sub phase shifter as the phase shifter, and (b) the first phase shifter transmits the phase shifter. The first phase-shifted light is 90 ° ± 10 ° with respect to the directly transmitted light.
(C) The second phase shifter provides the second phase shift light transmitted through the second phase shifter with 270 ° ± 10 with respect to the directly transmitted light. It is configured as a phase shifter that gives an appropriate phase difference within the range of (°), and (d) the sub-phase shifter transmits the sub-phase-shifted light to the directly transmitted light (180 ° ± 10 °). )
Alternatively, the phase difference mask is configured as a phase shifter which gives an appropriate amount of phase difference within a range of (360 ° ± 10 °). 12. The retardation mask according to claim 11, wherein: (a) a plurality of light-shielding portions are sequentially arranged in a pattern on the mask substrate, and (b) between successive light-shielding portions. The first phase shifter and the sub-phase shifter disposed in the central region of the transparent portion, sandwiched by the first phase shifter, are provided in one transparent portion of two adjacent transparent portions, (C) The second phase shifter and the sub-phase shifter disposed in the central region of the transparent portion sandwiched by the second phase shifter are provided on the other transparent portion of the two adjacent transparent portions. A phase difference mask characterized by being provided. 13. The retardation mask according to claim 11, wherein: (a) the mask substrate is provided with the first phase shifter and the second phase shifter alternately adjacent to each other, and (b) A phase difference mask characterized in that the first sub-phase shifter is provided in the center of the first phase shifter, and (c) the second sub-phase shifter is provided in the center of the second phase shifter. 14. The phase difference mask according to claim 11, 12 or 13, wherein a pattern width of a sub-phase shifter taken in a direction along a sequential arrangement direction of the first and second phase masks is A phase difference shifter having a width different from that of the first and second phase masks. 15. A mask substrate and at least a phase shifter provided in a pattern on the mask substrate, and exposed using a phase-shifted light having a phase difference with respect to the phase of the direct transmitted light from the mask substrate. A phase difference mask for phase difference exposing a layer, comprising: (a) first and second phase shifters and a sub phase shifter as the phase shifter, and (b) the first phase shifter transmits the phase shifter. 90 ° ± 10 ° with respect to the directly transmitted light
Is configured as a phase shifter that gives an appropriate phase difference within the range of (c), and (c) the second phase shifter transmits the second phase shift light to the direct transmission light by 270 ° ± 10. It is configured as a phase shifter that gives an appropriate phase difference within a range of (°), and (d) the sub-phase shifter transmits the sub-phase-shifted light to 0 ° ± (180 ° ± 1
A phase difference mask, characterized in that it is configured as a phase shifter for giving an appropriate amount of phase difference (excluding 0 °) within a range of 0 °. 16. The retardation mask according to claim 11, wherein: (a) a plurality of light-shielding portions are sequentially arranged in a pattern on the mask substrate, and (b) between successive light-shielding portions. Of the two adjacent transparent parts, the first phase shifter is provided on one transparent part, and (c) the second phase shifter is provided on the other transparent part of the two adjacent transparent parts. (D) on both sides of the first or second phase shifter,
A retardation mask characterized in that the sub-phase shifter is provided at a transparent portion. 17. The retardation mask according to claim 16, wherein (a) the mask substrate is provided with the first phase shifter and the second phase shifter alternately adjacent to each other, and (b) A phase difference mask, wherein the sub-phase shifter is provided at the center of either one of the first and second phase shifters. 18. The phase difference mask according to claim 16 or 17, wherein the pattern width of the sub-phase shifter taken in the direction along the sequential arrangement direction of the first and second phase shifters is the first And a width different from the width of the second phase shifter. 19. The retardation mask according to claim 11, wherein when the sub-phase shifter is a phase shifter that produces a phase difference of 180 ° ± 10 °, the sub-phase shifter has a plurality of dots separated from each other. Retardation mask characterized by having a rectangular pattern.