JP3322837B2 - Mask, manufacturing method thereof and pattern forming method using mask - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a mask, a method of manufacturing the same, and a pattern forming method using the mask, and more particularly to a mask using a phase shift of light, a method of manufacturing the same, and a pattern forming method using the mask.

[0002]

2. Description of the Related Art In the process of manufacturing a semiconductor device, when a pattern such as an element or a circuit is formed on a semiconductor wafer, a pattern transfer exposure method using ultraviolet light is usually used.
The pattern transferred to the semiconductor wafer is formed by the presence or absence of a light shielding metal thin film provided on a light transmitting glass substrate. Of the glass substrate having a transfer pattern formed thereon, the one provided with a pattern having the same size and number as the chip pattern to be transferred onto the wafer is called a full-size mask or simply a mask, and is enlarged, for example, 5 to 10 times. A chip on which a smaller number of chip patterns than the number of chips formed on a wafer are provided is called an enlarged mask or reticle. And, in the case of a mask,
In the case of a reticle, transfer exposure of a pattern is performed on a wafer through a resist film by reduction projection using a reduction lens system. In this case, it is necessary to increase the light contrast at the edge of the exposure area in order to increase the resolution when transferring a pattern that is miniaturized and highly integrated. FIG. 70 shows a conventional mask formed of an opaque layer and a transparent substrate layer having a predetermined shape, and FIG. 71 shows a case where a pattern is formed on a wafer. FIG. 70 shows a conventional photomask 45.
It is a block diagram showing 0. In FIG. 70, reference numeral 451 denotes an opaque layer made of a material such as metallic chromium (Cr), which is a transparent substrate layer.
A predetermined pattern is formed by lithography and etching as described above. Also, in FIG. 71, light C emitted from an exposure apparatus (not shown) is applied to an opaque layer of the photomask 450.
451 does not transmit, but transmits through the transparent substrate layer 452 where the opaque layer 451 is not formed. The transmitted light passes through the imaging lens system 45
3, the resist material 455 such as OFPR (trade name, Tokyo Ohka Kogyo Co., Ltd.) applied on the wafer 454 is exposed. Thus, the same pattern as that of the photomask 450 is formed on the wafer 454 by etching.

When a pattern is formed using an optical lens system, the pattern is formed on the wafer 454 based on data of only the contrast due to the presence or absence of an opaque layer.
Therefore, pattern formation has a physical resolution limit due to the wavelength of light from the optical lens system, and it is difficult to form a pattern narrower than the wavelength of light used. In the conventional photolithography process, an opaque layer such as a chromium (Cr) film is formed on a transparent substrate such as glass or quartz, and a patterned reticle is used. Figure 72
(A) and (B) show examples of such a conventional pattern forming method.

In FIG. 72A, a light source 461 is composed of a mercury lamp or an excimer laser provided with filters for i-line and g-line. The reticle 464 is being irradiated. The illumination system lens 462 has, for example, partial coherency σ
= 0.50 is used. The reticle 464 is formed of an opaque pattern 469 such as a Cr film on a transparent substrate 468 such as glass.
Is formed. The opaque pattern 469 on the reticle 464 is
6 An image is formed on the upper photoresist layer 467. Imaging lens
For 465, for example, one with a numerical aperture NA = 0.50 is used. In the case of the above-described pattern forming method, the resolution is K1 · λ / NA. Here, K1 is a process coefficient, usually 0.6
Take a value of ~ 0.8. λ is the light wavelength, and NA is the numerical aperture of the imaging lens. Wavelength λ of light 463 emitted from light source 461
Is, for example, about 365 nm for the i-line of a mercury lamp,
In the case of an excimer laser, the wavelength is, for example, 248 nm or 198 nm.
The numerical aperture NA depends on the imaging lens system, but is, for example, about 0.5. To improve the resolution, reduce K1 or λ, and
A needs to be increased, but K1 and NA cannot be freely selected. The wavelength λ is also limited by the light source and the optical system. When the wavelength λ of the light used for exposure, the numerical aperture NA, and the process coefficient K1 are determined, the resolution is determined, and a pattern having a resolution lower than the resolution cannot be formed.

The light 463 emitted from the light source 461 is a reticle 464
The entire surface of the opaque pattern 469 is illuminated, and the portion of the light that illuminates the opaque pattern 469 is blocked by the opaque pattern 469. For this reason, as shown in the lower part of FIG. 72A, only the light irradiated to the portion having no opaque pattern passes through the reticle 464 and is irradiated on the photoresist layer 467 by the imaging lens 465. On the photoresist layer 467, a pattern having a light intensity distribution proportional to the square of the amplitude of the irradiated light is formed, and the photoresist layer 467 is selectively exposed.

FIG. 72B shows an enlarged opaque mask having an opaque pattern. Transparent substrates such as glass and quartz
An opaque pattern 469 of a Cr pattern is formed on 468 to form a mask or reticle 464. The minimum width W of the pattern that can be exposed is limited by the resolution determined by the imaging lens 465. FIG. 73 (A) to FIG. 73 (A) show how the light intensity distribution when a line pattern thinned beyond the resolving power is exposed by such a conventional technique is exposed.
This will be described below with reference to FIG. FIG. 73 (A)
(D), the wavelength of the light used is 365 nm, the numerical aperture NA is 0.50, and the partial coherency σ is about 0.50.

FIG. 73A shows a light intensity distribution when a pattern having a width of 0.35 μm is formed. The light intensity distribution approaches “0” at the center position (0.0), and gradually rises on both sides. Line width approx.1.0 μ at the position where the light intensity is maximum
m or more. If the photoresist layer is developed with a light intensity of about 0.2 as a development threshold, a pattern having a designed width of about 0.35 μm can be developed.

FIG. 73 (B) shows a light intensity distribution when a pattern having a width of 0.30 μm is imaged. The width of FIG.
Compared to the case of 35 μm, the only thing that changes clearly is
This is an increase in the minimum light intensity at the center position (0, 0). There is no significant change in the width of the light intensity distribution itself. FIG.
3C and 3D show light intensity distributions when a pattern having a width of 0.25 μm and a pattern having a width of 0.20 μm are formed, respectively. Figure 73
As in the case of (B), the minimum value of the light intensity at the center of the pattern gradually increases, but the pattern width itself does not show much change. That is, even if the pattern width is reduced beyond the resolving power, the pattern width of the obtained light intensity distribution does not decrease, but rather the minimum value of the light intensity at the pattern center increases. In this case, not only cannot the exposure line width be reduced, but also the black level is raised to gray. Thus, an image having a resolution lower than the resolution cannot be formed.

[0009] To this end, IBM Corporation first issued the IEEE
TRANSACTIONS ON ELECTRON DEVICES, VOL.ED-29, NO.12,
DECEMBER 1982, Improving Resolution in Photol
entitled ithography with a Phase-Shifting Mask ”, the transmitted light is obtained by setting the predetermined pattern part on the mask to have an optical path length different from that of the remaining part having other patterns. Phase of light on both wafers
A method of shifting the degree has been announced. in this way,
The interference of light between the patterns is eliminated to improve the light contrast on the wafer, and the resolution in the same exposure apparatus is improved.

However, there is a problem that it is difficult to apply the method to a mask or a reticle having a fine pattern by the conventional method disclosed in this publication, and the trouble of creating pattern data unique to the phase shift pattern increases.
Therefore, there is a demand for a phase shift pattern that can be more easily applied to a mask or a reticle having a fine pattern and does not cause an increase in the number of steps such as pattern data creation.

In the above-described conventional phase shift mask, the phase shift pattern is formed by forming an auxiliary light transmitting pattern having a narrower width than the designed light transmitting pattern (white pattern) near the designed pattern. An organic pattern such as a resist formed through coating, exposure and development steps or an inorganic pattern formed through chemical vapor deposition and lithography steps is mounted on the auxiliary pattern as a phase shifter. For example, a phase shift mask using a negative resist pattern for a phase shifter is formed by a method described below with reference to FIGS.

First, as shown in FIG. 74A, a light-shielding film 552 is provided on a glass substrate 551, and an aperture pattern having a width of, for example, about 1.5 μm, that is, a light-transmitting film is formed by lithography using electron beam (EB) exposure. A design pattern (transfer pattern) 553 composed of a region and a design pattern 553
Fine patterns 554A and 554B, each of which is an opening pattern having a width of, for example, about 0.5 μm, which is narrower than the design pattern, are formed in the vicinity area separated by about 0.5 μm as auxiliary patterns.

Next, as shown in FIG. 74 (b), on the surface of the glass substrate 551 including the inner surfaces of the opening patterns 553, 554A and 554B, a transparent thin conductive film for preventing charge-up during EB exposure. Form 555. Next, as shown in FIG. 74 (c), the phase of the light transmitted on the glass
A negative EB resist film 656 having a thickness shifted by 0 degrees is applied and formed, and after prebaking as necessary, EB exposure of a phase shift pattern is performed on the fine patterns 554A and 554B.

Here, the thickness D of the resist film 656 is obtained by the following equation (1). D = λ / 2 (n−1) (1) λ: Wavelength of Light Used for Exposure n: Refractive Index of Shifter Material When the i-line having a wavelength of 365 nm is used for exposure, for example, refraction of resist film 656 Since the ratio is about 1.6, the thickness D of the resist film 656 is about 304 μm.

Next, as shown in FIG. 74 (d), a phase shifter comprising a negative EB resist film 656 having a film thickness of D is selectively developed on the fine patterns 554A and 554B comprising the light-transmitting regions, ie, as shown in FIG. The phase shift patterns 556A and 556B are formed. FIG. 75 is a profile diagram of the phase corresponding to the pattern position of the i-line transmitted through the mask when exposure is performed with the i-line using the phase shift mask having the configuration shown in FIG. 74 (d).

On the other hand, when a positive resist is used, through the same steps as in the case of using the negative resist, as shown in FIG. 557 is formed. Note that each reference numeral in the figure indicates the same object as in FIG. FIG. 77 is a phase profile diagram of transmitted light (i-line) corresponding to the phase shift mask shown in FIG.

In the phase shift masks shown in FIGS. 74 (d) and 76, as shown in the phase profile diagrams of FIGS. 75 and 77, the i-line (ia) penetrates the design pattern 553 of each mask. And ic) and the i-line (ib and id) transmitted through the auxiliary patterns 554A and 554B are 180 degrees out of phase. For this reason, the i-line (ia, ic) scattered laterally from the region directly below the design pattern of the resist film to be exposed is shifted 180 degrees out of phase from the region immediately below the adjacent auxiliary pattern. I
The lines are canceled by the lines (ib, id), the contrast of the end face of the exposed area is increased, and the resolution is improved.

The aperture width of the auxiliary pattern is formed to be narrow enough that the amount of light for exposing to the bottom of the resist film is not obtained in the standard exposure. No pattern is transferred onto the wafer. The prior art shown in FIGS. 74 to 77 has been proposed in, for example, JP-A-61-292643, JP-A-62-67514, and JP-A-62-18946.

[0019]

However, the conventional phase shift mask has the following problems. First, in the case of a mask that does not use a phase shift, it is difficult to form a pattern smaller than the wavelength of light due to the physical resolution limit of the optical system. In order to realize a thin line width, it is necessary to make a structural change such as reducing a light wavelength to be used or increasing a numerical aperture. Therefore, a fine pattern required by a future IC or the like cannot be formed by an optical method.

Second, in the case of a mask using a phase shift, it can be applied only to a pattern having a regularity such as a so-called line and space, and cannot be applied to the manufacture of an IC including various patterns. In addition, since an opaque layer is always required, a fine pattern cannot be formed. Third, in the case of a mask using a phase shift, an auxiliary pattern that is finer than the design pattern must be patterned using an exposure technique. Is limited.

Fourth, in the case of a mask using a phase shift, pattern data including unique auxiliary pattern data, phase shift pattern data, etc. must be created in addition to the design pattern data. Man-hours increase. Fifth, in the case of a mask using a phase shift, when an organic substance such as a resist is used for a phase shifter, it is difficult to control the film quality and thickness which affect the refractive index, so that the phase shift amount is accurate and uniform. It is difficult to form a shift pattern.

Sixth, in the case of a mask using a phase shift, since the phase shifter is made of a different material from the glass substrate, reflection occurs at the boundary between the phase shifter and the glass substrate, and the exposure efficiency is reduced. Therefore, the present invention provides a mask capable of forming a narrow pattern exceeding the resolution of the related art, forming a fine pattern with improved resolution, and simplifying the pattern data, and a method of manufacturing the same. It is another object of the present invention to provide a pattern forming method using a mask.

[0023]

FIG. 1 is a diagram illustrating the principle of the present invention. 1 includes a transparent substrate layer 2 transparent to light used for exposure and a mask pattern layer 5 formed on the transparent substrate layer 2. The mask pattern layer 5
The pattern includes a transmission thin film layer 3a that transmits light waves from a light source.

As shown in FIG. 1, the mask 1 has a mask pattern layer 5 formed of a phase shift layer 3a. Accordingly, the phase of the wavelength of light passing through the portion where the mask pattern layer 5 exists and the portion where the mask pattern layer 5 does not exist is shifted.
At the boundary between the light whose phase is shifted and the light which is not shifted, the light intensity is reduced due to interference. Thereby, the mask 1
When a pattern is formed on a wafer through an imaging lens system in (1), the light intensity is reduced due to interference at the boundary between the phase-shifted light and the light that is not converted. That is, an interference pattern smaller than the wavelength of light is obtained on the wafer, and a fine pattern can be formed. In addition, the resolution can be improved by adjusting the thickness of the mask pattern layer 5 to change the phase to be shifted.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a first embodiment of a mask according to the present invention. The mask 1 includes a transparent substrate layer 2 transparent to light L used for exposure, and a mask pattern layer 5 formed on the transparent substrate layer 2. The mask pattern layer 5 is composed of a phase shift layer 3a through which light L can pass.

Among the light transmitted through the mask 1, the light transmitted through the phase shift layer 3a and the light transmitted only through the transparent substrate 2 are out of phase with each other. Therefore, at the boundary between the light transmitted only through the transparent substrate 2 and the light transmitted through the phase shift layer 3a and causing a phase shift, the light intensity is reduced due to interference. Thereby, at the time of exposure, an interference pattern smaller than the wavelength of the light L used for exposure can be formed on a wafer (not shown). Further, by adjusting the thickness of the mask pattern layer 5, the amount of phase shift of light can be adjusted to improve the resolution of the exposure pattern.

FIG. 2 shows one of the phase shift layers 3 a of the mask 1.
FIG. 4 is a diagram for explaining light intensity at one edge portion.
In FIG. 5A, the phase of light between the light transmitted through the transparent substrate 2 and the phase shift layer 3a and the light transmitted only through the transparent substrate 2 is shifted, for example, by approximately 180 degrees. Accordingly, the electric vector E and the light intensity P of the light transmitted through the mask 1 are as shown in FIGS. As is apparent from FIG. 3C, the line pattern can be exposed by utilizing the change in the light intensity at the edge of the phase shift layer 3a.

FIG. 3 is a diagram for explaining the light intensity at both edge portions of the phase shift layer 3a of the mask 1. FIG. 2, the same parts as those of FIG. 2 are denoted by the same reference numerals, and the description thereof will be omitted. In this case, when the width W of the phase shift layer 3a is sufficiently small, the light intensity P of the light transmitted through the mask 1 becomes as shown in FIG. Thus, the width of the line pattern can be controlled by controlling the width W.

FIG. 4 schematically shows an optical system used for exposure using the mask 1. The light source 6 is composed of, for example, a mercury lamp, and the mercury lamp is provided with a filter (not shown) that allows only the i-line (wavelength: 365 nm) to pass. Light from the light source 6 reaches the mask 1 located at the focal length of the lens system 8 as light L via the illumination lens system 8. Here, partial coherence (partial coherency) σ of light L
Is 0.5, but σ may be in the range of 0.3 ≦ σ ≦ 0.7.

The light transmitted through the mask 1 forms an image on a wafer 11 on which a photoresist layer 10 is applied, via an imaging lens system 9. Here, the imaging lens system 9 comprises a 1/5 reduction lens, and the numerical aperture NA is 0.5. The wafer 11 is vacuum-sucked by a flat chuck (not shown) to keep the wafer flat. Next, a first embodiment of a pattern forming method using a mask according to the present invention will be described with reference to FIG. 5 showing an exposure state in FIG. The light passing through the illumination lens system 8 in FIG. 4 becomes a light 7a transmitted through the mask pattern layer 5 of the mask 1 and a light 7b transmitted through a portion without the mask pattern layer 5, and has a phase difference of 180 degrees.

These lights 7a and 7b are transmitted to the imaging lens system 9
Is formed on the photoresist layer 10 on the wafer 11 through the interface, but a sharp change in light intensity occurs at a portion corresponding to the edge portion of the phase shift layer 3a due to interference. Therefore, a pattern smaller than the wavelength of light can be formed on the wafer 11. Next, first and second embodiments of the method of manufacturing the mask 1 according to the present invention will be described with reference to FIGS. 6 and 7, respectively. 6 and 7, substantially the same parts as those in FIG. 1 are denoted by the same reference numerals.

In FIG. 6A, the transparent substrate layer 2 is formed of a material that transmits i-rays such as quartz and glass. A resist material 3 is applied on the transparent substrate layer 2 as shown in FIG. As the resist material 3, materials such as an EB (electron beam) resist, a photo resist, and an ion resist are used. When an EB resist is used as the resist material 3, the resist pattern 4 is formed as shown in FIG. 6C by drawing and developing with an electron beam. Then, as shown in FIG. 6D, a silicon oxide constituting the phase shift layer 3a is formed on the surface of the resist pattern 4.
Sputter with a thickness of 0.388 μm. Thereafter, the EB resist is stripped with a resist stripping agent, whereby a mask pattern layer 5 of a phase shift layer (silicon oxide layer) 3a is formed on the transparent substrate layer 2 as shown in FIG.

In the embodiment shown in FIG. 7, a thin film layer 12 of aluminum oxide is formed on a transparent substrate layer 2 shown in FIG. 7A and similar to FIG. 6, as shown in FIG. 7B. On the aluminum oxide thin film layer 12, silicon oxide to be the phase shift layer 3a shown in FIG.
Form 0.388 μm. Further, a resist material 3 is applied on the phase shift layer 3a as shown in FIG. And
By drawing and developing by electron beam,
A resist pattern 4 shown in (E) is formed. Thereafter, plasma etching or reactive ion etching of the phase shift layer 3a is performed using carbon tetrafluoride (CF ₄ ) gas. The resist material 3 is peeled off by ashing (ashing) using oxygen plasma to form a mask pattern layer 5 of the phase shift layer (silicon oxide layer) 3a shown in FIG. Here, the aluminum oxide thin film layer 1
Since 2 is not etched with carbon tetrafluoride, it becomes an etching stopper, and a mask pattern layer 5 of a 0.388 μm phase shift layer (silicon oxide layer) 3a can be obtained accurately.

The thickness of the phase shift layer 3a is 0.388 μm.
Is a thickness that shifts the wavelength of i-line 365 nm by 180 degrees (opposite phase). The phase shift amount and the thickness of the phase shift layer 3a are represented by the following general formula (2). (N · t / λ) − (t / λ) = S (2) In the equation (2), n is the bending rate of the phase shift layer 3a for shifting the phase, λ is the wavelength of the used light L, and S is the phase. Shift amount / 2π
(1/2 for the opposite phase), and t is the thickness of the phase shift layer 3a.

In the embodiment shown in FIGS. 6 and 7, the bending ratio of the phase shift layer (silicon oxide layer) 3a is n = 1.47, the wavelength of the used light L is λ = 0.365 nm, and the phase shift amount is S.
= 1/2, the equation (2) becomes the following equation (3). (1.47t / 0.365)-(t / 0.365) = 1/2 (3) Thus, the thickness t of the phase shift layer 3a becomes 0.388 μm. Here, the reason why the phase shift amount is set to 1/2 (180 degrees) is that the phase shift amount is optimal for pattern formation due to interference.

FIG. 8 is a plan view of the mask pattern layer 5 formed on the mask 1 as described above. When forming a 0.35 μm line and space pattern with a 1/5 reduction lens system, the width b should be 0.15 μm (reticle size 0.75 μm)
And the width a of the region 13 without the phase shift layer 3a is 0.55 μm.
m (reticle size 2.75 μm), the light intensity on the wafer 11 can be obtained as shown in FIG. 9B.

FIG. 9B is compared with the conventional case shown in FIG. 9A. For convenience of explanation, the conventional method uses an opaque layer
451 (FIG. 71) is made of chrome having a thickness of 50 to 80 nm and a width of 0.35 μm (reticle size 1.75 μm), and the width of the interval between the opaque film patterns is set to 0.35 μm (reticle size 1.75 μm).
As shown in FIG. 9A, the light intensity is about 50 in the conventional method.
%, And the contrast is clearly low.
In this state, a photoresist layer 455 (FIG.
It is impossible to form a pattern in 2). On the other hand, in this embodiment, as shown in FIG. 9B, the light intensity on the wafer 11 is about 80%. Therefore, it is clear that the light intensity is greatly improved, and there is no change in the dark part.
Has also improved significantly.

Next, a description will be given of a second embodiment of the pattern forming method using the mask according to the present invention, by referring to FIG. FIGS. 10A and 10B are a plan view and a cross-sectional view of a mask 1 for forming a pattern in which a large pattern and a fine pattern are mixed on a wafer, respectively. Shaded area 14
Is an opaque layer made of, for example, chrome having a thickness of 50 to 80 nm. A white background is a portion where the transparent substrate layer 2 is exposed, and is divided into a large pattern region 15 and a fine pattern region 16. The phase shift layer 3a has a fine pattern area 1
6 is formed. The large pattern region 15 is patterned by a conventional method, and the fine pattern region 16 uses the phase shift layer 3a of the present invention. As for patterns such as ICs, large patterns and fine patterns are mixed,
This embodiment is suitable for IC patterning. FIG. 10C shows a pattern formed on the wafer 11 by the mask 1 in this manner. According to this embodiment, even a pattern including a fine pattern can be formed in a small number of steps, and the resolution can be sufficiently improved.

Next, a second embodiment of the mask according to the present invention will be described with reference to FIG. In a mask 1A shown in FIG. 11, a phase shift layer 3a is formed at an edge portion of an opaque film layer 14 formed on a transparent substrate layer 2. Opaque film layer 14
Is made of, for example, chromium having a thickness of 50 nm to 80 nm. For convenience, it is assumed that the fine pattern is isolated on the left part of the transparent substrate layer 2 in the drawing, and the fine pattern is adjacent to the right part of the drawing on the transparent substrate layer 2. 3b comprises only a phase shift layer 3a for forming a fine pattern,
A pattern is formed on the wafer 11 as described later by the effect of light interference due to the phase shift. Note that a, b, and
c will be described later.

FIG. 12 shows the phase shift layer 3a of the mask 1A.
FIG. 4 is a diagram for explaining light intensity at an edge portion of FIG. In FIG. 2A, the phase of light between the light transmitted through the transparent substrate 2 and the phase shift layer 3a and the light transmitted only through the transparent substrate 2 is shifted, for example, by approximately 180 degrees. Accordingly, the light intensity P of the light transmitted through the mask 1 is as shown in FIG. As is clear from FIG. 7B, the line pattern can be exposed by utilizing the change in light intensity at the edge of the phase shift layer 3a.

FIG. 13 shows the phase shift layer 3a of the mask 1A.
FIG. 4 is a diagram for explaining light intensity at both edge portions of FIG.
In the figure, the same parts as those in FIG. In this case, the light intensity P of the light transmitted through the mask 1A is as shown in FIG. This allows
By controlling the width W, the width of the line pattern can be controlled.

Next, a description will be given of a third embodiment of the pattern forming method using the mask according to the present invention, by referring to FIG. 14 showing an outline of an optical system used for exposure using the mask 1A. In this figure, substantially the same parts as those in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 14, light L entering the mask 1A from the light source 6 via the illumination lens system 8 does not pass through the opaque layer 14. The phase of the light 7a transmitted through the phase shift layer 3a is shifted, and the phase is inverted with respect to the light 7b transmitted only through the transparent substrate layer 2. Lights 7a and 7b are
An image is formed on the photoresist layer 10 on the wafer 11 via the imaging lens system 9. In this case, the light 7b transmitted only through the transparent substrate layer 2 and the light 7a transmitted through the phase shift layer 3a and phase-converted interfere with each other, causing a rapid change in light intensity. Therefore, the portion where the opaque layer 14 is provided and the opaque layer 1
The contrast with the portion where 4 is not provided is improved. Here, the conditions of the optical system in FIG. 14 are the same as those in FIG. Therefore, the thickness of the phase shift layer 3a is set to 0.388 μm and the amount of phase shift is set to 180 degrees (inversion angle) according to the above equation (3).

Here, the effect obtained by forming the phase shift layer 3a on the edge of the opaque layer 14 will be described with reference to FIGS. FIG. 15A shows a case where the phase shift layer 3a is not provided at the edge of the opaque layer 14, and FIG. 15B shows a case where the phase shift layer 3a has a width b = 0.15 μm.
Shows the case where m is provided. The light intensity distribution in this case is shown in FIG.
Are shown correspondingly to In the case of FIG. 16B, it can be seen that the change in the light intensity distribution is sharp at the portion of the phase shift layer 3a (around 0.0 μm on the X axis). That is, FIG.
The case (B) indicates that the ability to form a fine pattern is large. In this case, the boundary between the phase shift layer 3a and the exposed portion of the transparent substrate layer 2 is 0.0 μm on the X coordinate, and the boundary between the opaque layer 14 and the phase shift layer 3a is −0.15 μm on the X coordinate. Then, the boundary between the white background and the black character of the formed pattern is +0.1 μm, which is obtained from the light intensity distribution in FIG.

Accordingly, i-line (wavelength 365 nm), numerical aperture NA
In the case of a lens of 0.5, the exposed portion of the transparent substrate layer 2 is made 0.2 μm (0.1 μm on one side) larger than the design dimension of the pattern to be finally obtained (1.0 μm for the 5 × reticle size)
(0.5 μm on one side)) and the phase shift layer 3a
When formed at 0.15 μm (reticle size 0.75 μm), a resist pattern can be formed with design dimensions. In the following description, it is assumed that a reticle is made in accordance with these rules for convenience.

It should be noted that this rule is such that when the wavelength of light or the numerical aperture of the lens changes, the amount of dimensional conversion at the exposed portion of the transparent substrate layer 2 and the width of the phase shift layer 3a formed around the edge of the opaque layer 14 Needs to be changed. For example, K
When using a rF (krypton fluoride) laser (wavelength 248 nm) and a lens having a numerical aperture NA = 0.48, the exposed portion of the transparent substrate layer 2 is set to 0.13 μm (0.065 μm on one side) from the design dimensions.
) (5x reticle size 0.65μm (0.3 on one side)
Optimum results can be obtained by setting the width of the phase shift layer 3a around the edge of the opaque substrate layer 14 to 0.06 μm. In this case, when the white patterns approach each other, the region of the opaque layer 14 between the white patterns disappears, and the white patterns are separated only by the phase shift layer 3a on the mask.

Since it is empirically known that the resolution is improved by 20% according to the phase shift method, the amount of dimensional conversion in the exposed portion of the transparent substrate layer 2 and the width of the phase shift layer 3a are determined on the premise of this. Required. That is, when the numerical aperture NA of the lens is i = 0.5 at the i-line, the resolution limit when no phase shift is performed is represented by 0.6 × (λ / NA). Accordingly, the resolution limit when performing the phase shift is 0.6 × (λ / NA) × 0.8. When the numerical value is substituted, the width of the phase shift layer 3a becomes 0.35.
μm.

FIG. 17 shows a case where the present embodiment is applied to a so-called line-and-space pattern. In the figure,
The phase shift layer 3a is formed on the edge of the opaque layer 14, and the phase shift layer 3a is also formed between the four spaces where the transparent substrate layer 2 is exposed. Light intensity distribution when the dimension conversion amount a in the exposed portion of the transparent substrate layer 2 and the width b of the phase shift layer 3a are changed in a line and space pattern having a resolution limit of 0.35 μm when the phase shift is performed. Is shown in FIG. FIG. 18A shows that a = 0.45 μm and b = 0.2
FIG. 18B shows the light intensity distribution in the case of 5 μm.
FIG. 18C shows the light intensity distribution when 0.50 μm and b = 0.20 μm, FIG. 18C shows the light intensity distribution when a = 0.55 μm and b = 0.15 μm, and FIG. 18D shows a = 0.60 μm , B = 0.10
The light intensity distribution of μm is shown. In order to form a line and space pattern, it is necessary to set a + b = 0.70 μm. As shown in FIGS. 18A to 18D, when the width b of the phase shift layer 3a is large, the peak of the light intensity decreases. Further, when the width b of the phase shift layer 3a is small, the light intensity in the space part is increased, and the contrast is reduced. The contrast is optimum when b = 0.15 μm, and then a = 0.55 μm. Since the boundary between the phase shift layer 3a and the exposed portion of the transparent substrate layer 2 is shifted so as to make the exposed portion of the transparent substrate layer 2 larger than the designed dimension of 0.10 μm on one side, it corresponds to the above-described example of the edge of the large pattern. Here, when the phase shift is performed, the width b of the phase shift layer 3a is 30 to 60 (%) of the resolution limit, that is, 0.144 to 0.22.
Must be 8 μm.

In particular, a high contrast can be obtained by setting b at 40 to 50% of the resolution limit. On the other hand, the width of the exposed portion of the transparent substrate layer 452 is 0.35 μm (reticle size 1.75 μm), and the width of the opaque layer 451 is 0.35 μm.
FIG. 19 shows the light intensity distribution when the reticle size is 1.75 μm. In FIG. 19, the light intensity of this embodiment is
The light intensity of the related art is about 55% while the light intensity in the case of (C) is about 80%, which indicates that the contrast in this embodiment is improved.

The width b of the phase shift layer 3a is 30 which is the resolution limit.
To be 60% means that the shifter pattern needs to be smaller than the design pattern by 20 to 35% (one side) of the resolution limit. For i-line lenses with NA = 0.5, 0.
070 to 0.123 μ (one side) smaller than the design pattern.
Further, when the pattern of the phase shift layer is arranged between the opaque layer and the exposed portion of the transparent substrate, the phase shift layer pattern width is 1.0 to less than the reduction width of 20 to 35% (one side).
Experience has shown that 1.5 times is better. This width is
In the case of an i-line lens with NA = 0.5, the value is 0.070 to 0.185 μm.

For example, a KrF excimer laser (wavelength 24
8 nm) and a lens with a numerical aperture NA = 0.48,
The resolution limit when performing a phase shift is 0.25 μm.
In this case, the dimension conversion amount a at the exposed portion of the transparent substrate layer 2
FIGS. 20B to 20F show light intensity distributions when the width b of the phase shift layer 3a is changed. Note that FIG.
Indicates a case where no phase shift is performed. FIG. 20 (B) shows a
= 0.35 μm, b = 0.15 μm.
FIG. 20C shows the light intensity distribution when a = 0.36 μm and b = 0.14 μm, and FIG. 20D shows the light intensity distribution when a = 0.38 μm and b
FIG. 20 (E) shows the light intensity distribution when a = 0.40 μm and b = 0.10 μm, and FIG. 20 (F) shows the light intensity distribution when a = 0.42 μm and b = 0.08. The light intensity distribution in the case of μm is shown. As shown in FIG.
When the width b of the phase shift layer 3a is 0.12 μm, an optimum contrast can be obtained. FIG. 20 shows that the width b of the phase shift layer 3a is
Is 30 to 60% of the resolution limit when the phase shift is performed.
It can be understood that it is only necessary to be within the range.

FIG. 21 (A) shows a part of FIG. 11, in which the phase shift layer 3a is provided on both edges of the opaque layer 14.
Is formed, and the transparent substrate layer 2 is exposed between the phase shift layers 3a. FIG. 21B shows a conventional photomask 450.
And an opaque layer 451 on the transparent substrate layer 452.
In this case, a mask pattern composed of only the mask pattern is formed.

First, the width a of the transparent substrate layer 2 exposed in FIG. 21A is set to 0.55 μm (reticle size 2.75 μm) and the width b of the phase shift layer 3a is set to 0.15 μm.
m (reticle size 0.75μm). FIG. 21 (B)
The width d where the transparent substrate layer 452 is exposed is 0.35 μm (1.75 μm on the reticle). FIG. 22 shows the light intensity distributions in these cases. As shown in FIG. 22A, the light intensity in the present embodiment is about 100%, while the light intensity in the conventional example is about 65% as shown in FIG.
It can be seen that the contrast is improved in this embodiment. Therefore, as described above, a good result can be obtained by forming the portion where the transparent substrate layer 2 is exposed to be larger than the pattern to be obtained and arranging the phase shift layer 3a on the outer side of the pattern.

FIG. 23 shows an example in which a black pattern is formed on a white background. FIG. 23A shows a mask for forming a 0.35 μm black pattern by using a phase shift. According to the above rules, for example, the width c is 0.15μ
m (reticle size 0.75 μm) becomes a mask pattern composed of only the phase shift layer 3a. FIG. 24A shows the light intensity of the light imaged on the wafer in this case. On the other hand, FIG.
3 (B) shows a mask when no phase shift is performed. The mask shown in FIG. 23B is made of an opaque layer 14 having a width of 0.35 μm (reticle size 1.75 μm), and the light intensity to be imaged is shown in FIG. As shown in FIG. 24, when the phase shift is performed, the fall of the light intensity is sharper, and the resolution of the black pattern is improved.

FIG. 25 shows a case where this embodiment is applied to an IC pattern. FIG. 25A is a plan view showing the shape of a part of the mask 1A. FIG. 25B is a plan view showing a pattern formed on the wafer 11. In FIG. 3A, a phase shift layer 3a is formed in a fine pattern portion adjacent to a pattern at an edge portion of the opaque layer 14 and a portion where the transparent substrate layer 2 is exposed. That is, in FIG.
Indicates an isolated pattern area, and 16 indicates a pattern adjacent area.

Next, a pattern formed on the wafer 11 using the mask 1A is shown in FIG. 26A, and the state of light interference by the mask 1A is verified. In FIG. 26A, the pattern width g is fixed at 0.35 μm, and h is 0.35 μm, 0.4 μm.
, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 1.0 μm
Should be changed to In this case, according to the rule described above, when the patterns having the pattern widths h of 0.35 μm, 0.4 μm, and 0.5 μm are close to each other, the white pattern is separated only by the phase shift layer 3a as shown in FIG. . When the pattern width h is 0.6 μm, 0.7 μm, 0.8 μm
When the patterns of m and 1.0 μm are separated to some extent, as shown in FIG. 26C, the opaque layer 14 exists between the white patterns in the mask pattern.

Here, the pattern width h on the wafer is 0.35 μm.
m. First, the mask dimension a of FIG.
m (reticle size 2.75μm), b 0.15μm (reticle size 0.75μm), c 0.15μm (reticle size 0.75μm)
FIG. 27A shows the light intensity distribution in the case of m). On the other hand, the conventional mask dimension e in FIG.
FIG. 27B shows the light intensity distribution when m (reticle size 1.75 μm) and f is 0.35 μm (reticle size 1.75 μm). Comparing the two, the light intensity obtained in the present example is about 85%, while the light intensity in the related art is about 55%.
%, Which indicates that the contrast is improved in this embodiment.

FIG. 28 shows the light intensity distribution when the pattern width h is 0.4 μm, FIG. 29 shows the light intensity distribution when h is 0.5 μm, and FIG. 30 shows the light intensity distribution when h is 0.6 μm.
FIG. 31 shows the light intensity distribution when h is 0.7 μm.
The light intensity distribution at 0.8 μm is shown in FIG.
FIG. 33 shows the light intensity distribution at the time of. FIG. 28-
As is clear from FIG. 33, according to the present embodiment, the light intensity is increased and the contrast is improved as compared with the conventional example.

The table shows the pattern dimensions of the isolated pattern 15 shown in FIG. 25A with respect to the pattern width h.

[0059]

[Table 1]

As is clear from the table, the pattern size change of the isolated pattern 15 due to the influence of light interference is ± 0.01 μm.
Within. Therefore, it is possible to control the pattern size, but to control the pattern size more accurately, the pattern widths a, b, and b in FIGS.
What is necessary is just to change the values of c and i. Next, an example in which the present embodiment is applied to a contact hole pattern will be described. FIG. 34A shows a mask 1A when a 0.35 μm contact hole is formed. According to the above rule, the width a of the exposed portion of the transparent substrate layer 2 is 0.55 μm,
The width b of the phase shift layer 3a is 0.15 μm. The light intensity in this case is shown in FIG. On the other hand, FIG. 34B shows a mask in which no phase shift is performed. Transparent substrate layer 2
The size l of the exposed portion is 0.35 μm. The light intensity in this case is shown in FIG. As shown in FIG. 35, the contrast of the contact hole can be greatly improved by applying this embodiment.

Next, the third and fourth embodiments of the mask manufacturing method according to the present invention will be described with reference to FIGS. 36 and 37, respectively. In FIGS. 36 and 37, substantially the same parts as those in FIGS. 6 and 7 are denoted by the same reference numerals, and description thereof will be omitted. FIG.
The transparent substrate layer 2 shown in (A) is made of, for example, quartz. An opaque layer 14 made of, for example, 50 to 80 nm chromium is formed on the transparent substrate layer 2 as shown in FIG. Then, a resist material 3 made of, for example, an EB resist is applied on the opaque layer 14, and a normal mask manufacturing process (not shown) including EB drawing, development, etching, and resist peeling is performed. Thereafter, a pattern 20 of the opaque layer 14 is formed as shown in FIG. A resist material 3 made of an EB resist is applied again on the pattern 20, and a resist pattern 4 shown in FIG. 36D is formed by EB drawing and developing steps. Further, a phase shift layer 3a made of, for example, silicon oxide having a thickness of 0.388 μm is formed on the resist pattern 4 as shown in FIG. Next, the opaque layer 14 and the mask pattern layer 5 of the phase shift layer 3a are formed as shown in FIG.

In the embodiment of FIG. 37, FIG.
By the same process as (C), a thickness of 50 to 50 mm is formed on the transparent substrate layer 2.
Pattern 20 of opaque layer 14 of 80 nm chromium
Are formed as shown in FIG. Then, a stopper layer 21 serving as a stopper when performing a plasma etching of an oxide film described later is formed on the pattern 20 as shown in FIG.
It is formed as shown in FIG.

The stopper layer 21 is obtained by forming a thin film of aluminum oxide, which is resistant to plasma etching with carbon tetrafluoride (CF ₄ ), on the pattern 20 by sputtering or the like. On this stopper layer 21, a phase shift layer 3a made of, for example, silicon oxide is formed to a desired thickness by sputtering or the like as shown in FIG. This desired thickness is set to 0.388 μm (Equation (3)) to cause a 180 ° phase shift. On this phase shift layer 3a, a resist material 3 made of, for example, an EB resist is applied, and a resist pattern 4 shown in FIG. 37D is formed by EB drawing and development processes. Then, the phase shift layer 3 exposed by the CF ₄ plasma
a, and the phase shift layer 3 is removed by peeling the resist.
FIG. 37 shows a mask pattern layer 5 for phase shift according to FIG.
It is formed as shown in FIG.

Next, a fifth embodiment of the method of manufacturing a mask according to the present invention will be described with reference to FIG. In this embodiment, FIG.
A third embodiment of the mask according to the present invention shown in FIG. The third embodiment of the mask has a configuration in which the region corresponding to the phase shift pattern of the glass substrate is dug deeper than the design pattern to be transferred to shift the phase of light.
It has a design (transfer) pattern of μm width.

In FIG. 38A, a chromium (Cr) layer 32 having a thickness of about 500 to 1000 ° is formed as an opaque layer on a glass substrate 31 made of synthetic quartz and having a thickness of about 2 to 3 mm by sputtering or the like. . The Cr layer 32 may have a thickness of, for example, 0.35 μm by lithography using normal EB exposure.
In the case of a design pattern having an m width, an opening pattern 33 having a width of 0.85 μm is formed.

Next, in FIG. 38B, a conductive layer for preventing charge-up during EB exposure is formed on the substrate 31.
Form 34. The conductive layer 34 is made of, for example, molybdenum silicide (MoSi ₂ ) by sputtering or the like for 200 to 30 minutes.
It is obtained by forming to a thickness of about 0 mm. Then, the substrate 3
After applying a negative type EB resist layer 35 on the substrate 1 and performing pre-baking, a pattern having a width of 0.55 μm is EB-exposed almost at the center of the opening pattern 33 of the Cr 32. 35
A indicates an exposed resist layer.

Next, the resist layer 35A exposed to the design pattern formation region by performing normal development is removed as shown in FIG.
And the resist layer 35A
The exposed conductive layer (MoSi ₂ layer) 34 is selectively removed by dry etching using a mixed gas of carbon tetrachloride (CCl ₄ ) and oxygen (O ₂ ) using the mask as a mask. FIG.
8 (D), using the resist layer 35A and the Cr layer 32 as a mask, the upper surface of the glass substrate 31 that is exposed corresponding to the phase shift pattern is made of carbon tetrafluoride (CF ₄ ) and O _2.
Reactive ion etching (R
Etching by IE) process. On both sides of a 0.55 μm-wide pattern 36 having the same surface as the upper surface of the glass substrate 31, 0.15 μm-wide phase shift patterns 37A and 37B having lower upper surfaces are formed. Note that the phase of the transmitted light of the phase shift patterns 37A and 37B is
The etching depth D for shifting by 180 degrees with respect to the light passing through the mask is determined by the fact that this mask has a wavelength λ = 365 nm.
It is used in line exposure, and since the refractive index of glass is n = 1.54, it becomes about 0.36 μm according to the above equation (1).

Next, in FIG. 38 (E), the resist layer 35A is removed by a normal ashing process, and the MoSi ₂ layer 34 under the resist layer 35A is removed by a dry etching process using a mixed gas of CCl ₄ and O _2. The mask 1C according to the third embodiment of the present invention is completed. FIG. 39 shows FIG.
The phase profile of the light transmitted through the mask 1C is shown corresponding to the mask 1C shown in FIG. In the figure, ia is the transmitted light of the central pattern 36, ib is the phase shift pattern 3
7A and 7B show transmitted light.

The mask 1C has a structure in which the phase shift pattern is dug deep by using a negative resist when patterning the phase shift pattern. However, when a positive resist is used,
A mask according to a fourth embodiment of the present invention in which the central portion is dug deeper than the phase shift pattern in contrast to the present embodiment is shown in FIG.
It is formed by substantially the same process.

Next, a sixth embodiment of the mask manufacturing method according to the present invention will be described with reference to FIG. In this embodiment, FIG.
A mask 1D shown in FIG. In FIG. 40, FIG.
The same parts as in FIG. 8 are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 40 (A), Cr formed on glass substrate 31
An opening pattern 33 having a width of 0.85 μm is formed in the layer 32. On this substrate 31, a MoSi ₂ layer 3 for preventing charge-up
After the formation of the substrate 4, a positive EB resist layer 38 is formed on the substrate 31. Next, EB exposure of a design pattern is performed on the central portion of the opening pattern 33 of the Cr layer 32 of the resist layer 38. 38A indicates an exposure area.

Next, in FIG. 40B, the exposed region 38A of the resist layer 38 is removed by development, and the resist layer 3 is removed.
The exposed MoSi ₂ layer 34 is removed by dry etching with a mixed gas of CCl ₄ and O ₂ through the opening 39 of No. 8. RIE using a mixed gas of CF ₄ and O ₂
The upper surface of the glass substrate 31 exposed in the opening 39 by the processing is etched to a depth D of about 0.36 μm as in the case of FIG.

In FIG. 40C, the resist layer 38 is removed by ashing, and then the MoSi ₂ layer 34 under the resist layer 38 is removed by dry etching using a mixed gas of CCl ₄ and O _2. . Thereby, the mask 1D is completed. FIG. 41 shows the state shown in FIG.
5 shows a phase profile of light transmitted through the mask 1D corresponding to the mask 1D shown in FIG. In the figure, Ic is the transmitted light of the central pattern 40, id is the phase shift pattern 41A,
41B shows the transmitted light of FIG.

Next, a seventh embodiment of the method of manufacturing a mask according to the present invention will be described with reference to FIG. FIG. 1A shows a transparent substrate 51 made of, for example, glass or fused quartz. As shown in FIG. 1B, a phase shift layer 52, for example, a silicon oxide film is formed on a transparent substrate 51. The phase shift layer 52 is formed by a vapor deposition (CVD) method,
It is formed by an on-glass (SOG) method. In the present embodiment, the phase shift layer 52 is used to invert the phase of light.
It has a thickness of 00 °.

In FIG. 42C, an opaque layer 53 is formed on the phase shift layer 52. The opaque layer 53 is made of, for example, chromium (Cr). When Cr is used, the thickness of the Cr is, for example, 700 to 1000 °. Next, application of EB resist, E
By performing B drawing, development and etching of the opaque layer 53, an opaque layer pattern 53a shown in FIG. 42D is formed.

The pattern 53a of the opaque layer is used as a mask, and the phase shift layer 52 is removed by etching as shown in FIG. In this embodiment, since the phase shift layer 52 is an oxide film, RIE using a mixed gas of CF ₄ and CHF ₃ is used for etching. next,
As shown in FIG. 42F, application of the EB resist layer 54,
Unnecessary portions 53b of the opaque layer 53 are exposed by performing a B drawing process and a developing process.

Finally, the EB resist layer 54 is removed,
By removing unnecessary portions 53b of the opaque layer 53 by etching, a mask 1E which is a fifth embodiment of the mask according to the present invention shown in FIG. 42G is completed. FIG.
FIG. 42H is a plan view of the mask 1 </ b> E corresponding to FIG. Next, an eighth embodiment of the method for manufacturing a mask according to the present invention will be described with reference to FIG. 42, those parts which are substantially the same as those corresponding parts in FIG. 42 are designated by the same reference numerals, and a description thereof will be omitted. The steps of FIGS. 43A, 43B and 43C are respectively shown in FIG.
It corresponds to steps (A), (C) and (D),
In this embodiment, the phase shift layer 52 is omitted.

In FIG. 43D, the opaque layer pattern 53a is used as a mask, and the transparent substrate 51 is removed by etching. As the etching, for example, C
Using RIE using a mixed gas of F ₄ and CHF _3, the transparent substrate 51 is etched to a predetermined depth. In the case of inverting the phase of light, the predetermined depth is 3900 ° in this embodiment.

In FIG. 43 (E), an unnecessary portion 53b of the opaque layer 53 is exposed by applying an EB resist layer 54, performing EB drawing and developing. Finally, the EB resist layer 54 is removed, and unnecessary portions 53b of the opaque layer 53 are removed by etching, thereby completing the mask 1C shown in FIG. FIG. 43 (G) shows the state shown in FIG.
FIG. 9 is a plan view of a mask 1C corresponding to FIG.

According to the seventh and eighth embodiments of the method of manufacturing the mask, the opaque layer is used as a phase shift layer or a mask for etching the transparent substrate. Can be prevented from shifting. Next, a ninth embodiment of the mask manufacturing method according to the present invention will be described with reference to FIG. 43, those parts which are substantially the same as those corresponding parts in FIG. 43 are designated by the same reference numerals, and a description thereof will be omitted.

In FIG. 44A, an opaque layer 53 is formed on a transparent substrate 51, an EB resist layer (not shown) is applied on the opaque layer 53, and a pattern is formed by EB drawing. The pattern is developed and the opaque layer 53 is patterned by etching. The opaque layer 53 is made of, for example, Cr, and is formed on the transparent substrate 51 by sputtering. After patterning, the EB resist is removed.

In FIG. 44B, the transparent substrate 51 is etched to a predetermined depth by using the pattern 53c of the opaque layer 53 as a mask. The etching condition is such that the exposed transparent substrate 51 is etched by a parallel plate electrode type high frequency excitation (13.56 MHz) RIE apparatus. The etching is performed, for example, at a power of about 0.1 W / cm ² and a pressure of 0.1 to 0.05 Torr using a mixed gas of CF ₄ or CHF ₃ and O ₂ as an etchant gas. Control is performed while detecting with an end point detector so that the etching depth becomes λ / 2 (n−1). When λ = 0.365 μm, λ / 2 (n−1) = 0.39 μ
m.

In FIG. 44 (C), after etching the transparent substrate 51, a positive resist layer 55 (eg, OFPR-800) is applied to a thickness of about 1.0 μm on the transparent substrate 51 and the pattern 53c, and prebaked at 100 ° C. I do. FIG. 44 (D)
Then, the light in the resist photosensitive area from the back surface of the transparent substrate 51,
For example, the entire surface is irradiated with monochromatic light having a wavelength of 436 nm and 40 to 60 mJ / cm ² to expose only the resist layer 55 on the transparent substrate 51. Thereafter, the transparent substrate 51 is immersed in a 2.38% aqueous solution of TMAH for 40 seconds to perform a developing process, so that the resist layer 55 remains only on the pattern 53c. Further, a rinsing process and a drying process are performed.

After forming the resist pattern, the opaque layer 5
The pattern 53c of FIG.
Partial removal as shown in (E). The amount of side etching is controlled by the etching time so that about 0.4 to 0.8 μm of the opaque layer 53 is removed on one side. Finally, in FIG. 44 (F), the resist layer 55 remaining on the opaque layer 53 is ashed and removed by O ₂ ashing to complete a mask substantially the same as the mask 1D shown in FIG. 40 (C).

Next, a tenth embodiment of the mask manufacturing method according to the present invention will be described with reference to FIG. 44, those parts which are substantially the same as those corresponding parts in FIG. 44 are designated by the same reference numerals, and a description thereof will be omitted. The steps shown in FIGS. 45A to 45C correspond to the steps shown in FIG.
It may be the same as the steps shown in (A) to (C). However,
In FIG. 45B, the transparent substrate 51 is etched to a depth of λ / 2 (n−1). When λ = 0.365 μm, λ /
2 (n−1) = 0.39 μm.

In FIG. 45 (D), as described with reference to FIG. 45 (D), the entire surface of the transparent substrate 51 is irradiated with light in the resist-sensitive region from the rear surface to expose only the resist layer 55 on the transparent substrate 51. Removed by development. In this embodiment, the opaque layer 53 is partially exposed by over-exposure, over-development, or short-time ashing after development and drying.

Next, as shown in FIG. 45E, the exposed opaque layer 53 is removed by etching using the resist layer 55 as an etching mask. In FIG. 45 (F), the resist layer 55 remaining on the opaque layer 53 is ashed and removed by O ₂ ashing to complete a mask substantially the same as the mask 1D. Next, an eleventh embodiment of the mask manufacturing method according to the present invention will be described with reference to FIG. 44, those parts which are substantially the same as those corresponding parts in FIG. 44 are designated by the same reference numerals, and a description thereof will be omitted.

The steps shown in FIG.
In this embodiment, the resist layer 55 is formed on the transparent substrate 51 without etching the transparent substrate 51 as shown in FIG.
In FIG. 46C, only the resist layer 55 on the transparent substrate 51 is removed in the same manner as in the step of FIG. After that, in this embodiment, the transparent substrate 51 is etched to a depth of λ / 2 (n−1) using the resist layer 55 as a mask. When λ = 0.365 μm, λ / 2 (n−1) = 0.
39 μm.

In FIG. 46D, a part of the pattern 53c of the opaque layer 53 is removed by side etching. The steps in FIG. 46 (E) may be the same as the steps in FIG. 44 (F). According to the embodiment shown in FIGS. 44 to 46, it is not necessary to align the pattern of the opaque layer and the pattern of the phase shift layer. Therefore, it is possible to manufacture a highly accurate mask having no pattern displacement. Further, depending on the material of the phase shift layer, it is conceivable that problems such as adhesion to the substrate and cleaning may occur. However, in these embodiments, since a part of the transparent substrate functions as the phase shift layer, the material of the phase shift layer is Does not matter. Therefore, there is no need to consider the stability and durability of the material of the phase shift layer, and a fine pattern exceeding the resolution limit of the exposure apparatus can be easily formed.

Next, the pattern forming method using the mask according to the present invention will be described in more detail. FIG. 47 is a diagram for explaining a pattern forming method using the edge of the phase shift layer of the mask, and corresponds to FIG. In FIG. 47, substantially the same parts as those in FIG.
The description is omitted. Refractive index n, thickness t on transparent substrate 2
Are formed to constitute the mask 1. The pattern of the mask 1 is imaged on a photoresist layer 10 on a semiconductor substrate (wafer) 11 by an imaging lens system 9. At this time, a desired pattern is imaged by the edge of the phase shift layer 3a.

The phase shift layer 3a transmits incident light, but imparts a phase shift to transmitted light by having a refractive index n different from that of air or vacuum. The phase shift amount S is S = (n−1) t / λ (2π (n−1) t / λ in the case of radian display). The following description is based on the assumption that the phase shift amount S is π (opposite phase).

As shown in the middle part of FIG. 47, the light transmitted through the mask 1 has its electric vector E changed in phase to the opposite phase corresponding to the pattern of the phase shift layer 3a. When light having such a distribution of the electric vector E of light is incident on the photoresist layer 10 and absorbed, the light intensity distribution at that time is proportional to E ^2, and therefore, as shown in the lower part of FIG. To form a black pattern PB having a small width. That is,
As shown in the middle of the figure, when the sign of the electric vector E of light is inverted, there is a point where the electric vector E becomes zero. Since the distribution of the obtained light intensity P is proportional to the square of the electric vector E, the minimum value of P becomes 0 at the point of E = 0. Therefore, a clear black pattern is obtained.

Generally, when the phase shift layer 3a changes the phase of transmitted light, a pattern in which the phase change is spatially distributed is obtained. When the phase change is in the opposite phase, the light intensity P at the position where the phase changes is always 0, and even when integrated over time. Therefore, the light intensity becomes 0 at the edge of the phase shift layer 3a. When the phase change is other than the opposite phase, the electric vector E has the same sign or the opposite sign depending on time, and the light intensity obtained by time integration does not become zero.

An example of image formation using such an edge portion of the phase shift layer will be described with reference to FIGS. FIG. 48A shows a light intensity distribution when the phase shift layer gives a phase shift of π (opposite phase). In the figure, the region of the phase shift π corresponds to the region to the left of 0.0 on the horizontal axis, and is in contact with the opening of the right phase shift 0 at the position of 0.0. FIG. 48A shows the light intensity distribution at one edge portion of such a phase shift layer. At the center of the pattern corresponding to the end of the phase shift layer, the light intensity decreases to almost zero. According to such an imaging principle, it is possible to obtain a line pattern exceeding the conventional resolution. When the phase difference at the edge of the phase shift layer is 180 ° ± 30 °, the same effect can be obtained.

FIG. 48B shows the light intensity distribution when the phase shift layer gives a phase shift of π / 2. When the phase shift is π / 2, there is a case where the phase of the light transmitted through the phase shift layer and a phase of the light transmitted through the opening become opposite to each other, and when the light is integrated over time. The minimum value of the light intensity does not become zero. In the case shown in the figure, the minimum value of the light intensity is about 0.5 or more, which is about half of the light intensity of about 1.0 in the uniform portion. If the development level is set to be equal to or less than the minimum value of the light intensity, the development in which the pattern in the figure is ignored can be performed. The phase difference at the edge of the phase shift layer is 90 ± 15.
°, the pattern is ignored and not formed under normal development conditions (development level 35%). If the development level is set between the minimum value and the uniform value of the light intensity, the pattern is developed at the central portion.

Next, a fourth embodiment of a pattern forming method using a mask according to the present invention will be described with reference to FIG. FIG.
FIGS. 9A and 9B are diagrams for explaining the formation of a loop-shaped pattern according to the present embodiment. FIG. 49A shows a mask pattern. Opening 6 formed from transparent substrate
The mask 61 is formed on the mask 0. The mask 61
It has a phase shift amount corresponding to a half-wavelength optical path difference of incident light, and gives a π phase shift to transmitted light. The result of imaging such a mask pattern is as shown in FIG. The portion where only the opening 60 or the phase shift layer 61 is imaged has a constant light intensity and becomes white on the screen.
A black pattern 62 is formed at the boundary between the opening 60 and the phase shift layer 61. That is, when the light transmitted through the opening 60 and the light transmitted through the phase shift layer 61 are mixed by interference, the opposite phases cancel each other, so that the light intensity becomes 0 and a black pattern is formed.

When the phase shift layer 61 is formed of a silicon oxide film and the i-line of the mercury lamp is used as light, the refractive index of the phase shift layer 61 is about 1.47, and the refractive index of air having a refractive index of about 1.00 is about 1.47. It has a refractive index difference of 0.47. The thickness of the silicon oxide film forming the half-wavelength optical path difference is about 0.388 μm. The opposite phase is most effective for canceling the amplitude of the combined light due to the interference. However, even if the phase is not the opposite phase, an effective decrease in the light intensity can be obtained within a range of, for example, ± 30%. .

When the phase shift layer 61 having the phase shift π is formed on the opening having no phase shift as in the mask pattern shown in FIG. 49, a black pattern is formed at a portion corresponding to the edge of the phase shift layer 61 Is done. In this case, the black pattern has a closed loop shape. FIG. 50 (A),
(B) shows a mask pattern for forming an open shape (line segment) and its imaging pattern.

FIG. 50A shows the shape of a mask pattern. A phase shift layer 61 whose one side forms a target line segment is formed on the opening 60.
Adjacent to the remaining (unwanted) edge of
2 is formed. That is, one side 61 out of four sides of the phase shift layer 61 having a phase shift of π
“a” forms a boundary with the region where the phase shift is 0, and forms a black pattern 65 as shown in FIG.
Generate. The other sides 61b, 61c, 61d are
Since it is in contact with the phase shift layer 64 having a phase shift of π / 2, the phase change when traversing the edge is π / 2, and the decrease in light intensity at the edge is small. The amount of phase shift on the side around the phase shift layer 64 is also π / 2, and similarly, the decrease in light intensity is small. By adjusting the development level, only the black pattern 65 can be left. Although the case where one gray level is formed between the white and black levels has been described, two or more halftone levels may be used.

As described above, by using a plurality of types of phase shift layers having different amounts of phase shift, a pattern such as an open line segment can be formed. FIG.
(A) and (B) show a mask pattern and an imaging pattern for forming a dot pattern. In FIG. 51A, a phase shift layer 61 having a phase shift of π is formed over the opening 60, and a phase shift layer 64 having a phase shift of π / 2 is surrounded except for one apex. In. That is, the phase shift layer 61 is in contact with the opening 60 only at one vertex thereof. When such a mask pattern is imaged, a black pattern 66 can be formed only in a portion where the phase shift layer 61 and the opening 60 are in contact with each other, as shown in FIG. Phase shift layer 61
Between the phase shift layer 64 and the phase shift layer 64 has a phase shift amount of π / 2.
Therefore, the decrease in light intensity is smaller than that of the black pattern 66. The phase shift amount of the outer peripheral portion of the phase shift layer 64 is also π / 2, and the decrease in light intensity is similarly small. Therefore, only the black pattern 66 can be developed as a pattern, and the other halftone patterns can be treated as white patterns.

The case where one linear pattern is formed has been described above. The formation of a pattern having an intersection will be described below. FIGS. 52 (A), (B) and (C)
3A and 3B show a mask pattern and an imaging pattern that form a pattern of intersecting lines. FIG. 52A shows a first mask pattern. The plane is divided into four quadrants corresponding to the area divided by the intersecting lines, and an opening 60 without a phase shift is provided in the first quadrant. A π phase shift layer 61 is provided, and another phase shift layer 67 having a phase shift of 2π is provided in the other quadrant. That is, the boundaries between the quadrants are
With a phase shift π.

FIG. 52B shows a second mask pattern. As in FIG. 52 (A), the plane is divided into four quadrants, and an opening 60 having no phase shift in the first quadrant and a phase shift layer 61 having a phase shift of π in two quadrants adjacent thereto are provided. 0 phase shift in the remaining quadrant
Another opening 68 is provided. Also in this case, a phase shift π occurs between adjacent quadrants.

When such a mask pattern is imaged, an image pattern as shown in FIG. 52 (C) is obtained. That is, a portion having a uniform phase is imaged as a white pattern, and a portion having a phase shift of π is a black pattern.
The image is formed as Although the case where the straight lines intersect is illustrated and described, the intersecting line is not limited to a straight line and may be any curve.

FIGS. 53A and 53B show a mask pattern and an image forming pattern in the case of forming a T-shaped pattern in which one straight line hits another straight line and ends there. In FIG. 53A, phase shift layers 61a and 61b having a phase shift of π are formed adjacent to the opening 60 having a phase shift of 0. Also, the phase shift layer 61a
Is provided above the aperture 68 to form a boundary having a phase shift of π therebetween. Since these boundaries are accompanied by a phase shift of π, a black pattern is formed when an image is formed as shown in FIG. When the phase shift layers 61b and 68 are directly adjacent to each other, the boundary is imaged as a black pattern with a phase shift of π, so that a phase shift layer 71 having a phase shift of π / 2 is formed between them. . That is, since only a phase shift of π / 2 occurs at the boundary of the phase shift layer 71, the decrease in light intensity is relatively small. By adjusting the development threshold, such a decrease in light intensity can be developed as a white pattern. As a result, a black pattern 72 is formed as shown in FIG.

In the mask pattern of FIG. 53A, a case is shown in which there is a gap between the opening 68 and the phase shift layer 61b, but such a gap may be smaller than a certain value. In semiconductor devices, etc.,
For example, a wide area for making a contact is provided in the middle of the wiring pattern. FIG. 54 shows a mask pattern and an imaging pattern for forming such a wiring pattern.
(A) to (D).

In FIG. 54 (A), an opening 60 having a phase shift of 0 and a phase shift layer 61 having a phase shift of π are in contact with each other to form a linear boundary. An opening 74 having a phase shift of 0 is formed in the phase shift layers 75 and 61 having the shift π. Both the opening 74 and the phase shift layer 75 have a rectangular shape, and the boundary between the opening 74 and the phase shift layer 61 is linearly arranged together with the boundary between the opening 60 and the phase shift layer 61. All the boundaries shown by solid lines in the figure are boundaries accompanied by a phase change of π.

In FIG. 54B, boundaries defining each region are formed in the same manner as in FIG. 54A. However,
The portion that was the opening 74 in FIG. 54A is replaced with a phase shift layer 76 having a phase shift of 2π. FIG.
As in FIG. 4A, a phase shift of π is formed between the upper and lower regions of the horizontal straight line. Further, a rectangular boundary of phase shift π is formed at the center.

FIG. 54C shows another mask pattern. It is largely separated into two regions by a horizontal straight line. At the upper part, an opening 60 without phase shift is arranged on the right side, and a phase shift layer 61 with a phase shift π is formed on the left side. Are in contact with each other at different lengths. Further, a phase shift layer 77 having an intermediate phase shift π / 2 between both regions is formed in the upper part in the drawing. A structure symmetrical to the upper part is formed below the center line. That is, a phase shift layer 61 having a phase shift of π is formed below the opening 60, and an opening 68 without a phase shift is formed below the phase shift layer 61, and is in contact with each other for a limited length. I have. Intermediate phase shift π / 2
The phase shift layer 77 having these regions 61 and 68
Is formed in the middle. As a whole, a boundary with a phase shift of π is formed along a horizontal straight line, and also at a central vertical line segment.

FIG. 54 (D) shows FIGS. 54 (A), (B),
FIG. 4 shows an image forming pattern when a mask pattern as shown in FIG. That is, a black pattern 78 having a region whose width is increased at the center is formed. FIG.
2 (A), (B), FIG. 53 (A), FIG. 54 (A),
In the case where the lengths of the lines in the mask patterns (B) and (C) are set to a finite length, a region having an intermediate level phase shift such as π / 2 may be formed in an unnecessary portion.

The mask patterns for forming various image forming patterns have been described above. The following describes what light intensity profiles can be obtained by numerical calculations for some of them. In the calculation, light having a wavelength of 365 nm was used, and an imaging lens having a numerical aperture NA = 0.50 and an illumination lens having a partial coherency σ = 0.50 were used.

FIGS. 55A to 55C show examples of crossing line patterns. FIG. 55 (A) is a schematic diagram showing a pattern of intersecting lines and a sample link area thereof. The mask pattern shown in FIG. 52B is adopted, and the coordinates of the X, Y, and Z axes are used in the direction shown on the right side in the figure. The region indicated by the broken line was set as a sampling region, and the light intensity in the region was calculated according to the model. FIG. 55 (B)
5 is a graph showing a light intensity profile in a sampling region shown in FIG. As can be clearly understood from the figure, a deep valley is formed at the boundary with the phase shift π, the lower half shown in FIG. 55 (A) is not shown, but has a symmetric structure. That will be obvious to those skilled in the art. When such a light intensity profile is represented by a contour line with respect to the light intensity, FIG.
As shown in FIG. That is, a region having the lowest light intensity is formed in the lower side extending in the X direction and a central portion extending in the Y direction in the drawing, and a portion where the light intensity gradually increases is formed adjacent to these regions.

Next, the light intensity of the example of the wiring pattern shown in FIG. FIG. 56A shows a mask pattern of the type shown in FIG. 54A, and its sampling region is indicated by a broken line. Also, as shown in the right part of the figure, the coordinates of the X, Y, and Z axes are used. FIG. 56B shows the light intensity profile in the sampling area. A narrow valley is formed along the X direction, and the valley is widened near the region where X = 0. When this profile is projected on the XY plane, FIG.
As shown in FIG. It can be clearly seen from the figure that a wide valley is formed at the center.

FIGS. 57A to 57C are diagrams showing a case where the wiring mask pattern shown in FIG. 54C is used. FIG. 57A shows a mask pattern and its sampling region. A phase shift of 0 is shown on the horizontal axis in the center of the figure.
Opening 60 and a phase shift layer 61 having a phase shift of π are formed in contact with each other, and a phase shift of π / 2
Is formed. Also, the opening 60
Has an angle θ ₁ with the horizontal direction. Two sides of the phase shift layer (intermediate region) 77 form an angle θ ₂ . Further, the upper side of the phase shift layer 61 forms an angle θ ₃ with the horizontal direction. A phase shift layer 61 having a phase shift of π is formed symmetrically in contact with the opening 60 below the horizontal axis, and an opening 68 having a phase shift of 0 is formed below the phase shift layer 61.
Are formed. Further, another phase shift layer 77 is formed at a position symmetrical to the phase shift layer 77. The width of a narrow region where the central openings 60 and 68 and the phase shift layer 61 are in contact is W1. In this sample, θ1 =
θ2 = θ3 = 60 degrees and W1 = 0.2 μm. FIGS. 57B and 57C show an image forming pattern formed by using such a mask pattern. The area indicated by the broken line is the sampling area.

FIG. 57B shows the light intensity profile in the sampling area. In the figure, it can be seen that a deep valley is formed in the X direction, a valley extends in the Y direction at the center, and a shallow valley that branches further is formed. When the light intensity profile of FIG. 57 (B) is projected on the XY plane, it becomes as shown in FIG. 57 (C).

FIGS. 58A to 58C show examples of a mask pattern having a configuration similar to that of the mask pattern shown in FIG. 51A. In the figure, the opening 6 having a phase shift of 0 is shown on the right side.
0 is formed, and a phase shift layer 61 having a phase shift of π with a triangular tip on the left side is disposed, and a width W2 is provided between the two.
Contact is formed. A phase shift layer 64 having a phase shift of π / 2 is formed in an intermediate region between the opening 60 and the phase shift layer 61. The light intensity distribution was calculated for a sampling area surrounded by a broken line in the figure. Note that W
As for 2, a gap of 0.08 μm is set, and the angle formed by the two boundary lines formed by the phase shift layers 61 and 64 is 6
0 degrees.

FIG. 58 (B) shows the light intensity profile in the sampling area, and FIG. 58 (C) shows its projection on the XY plane. It will be understood that an elliptical minimum light intensity region is formed near (0.0). Figure 59
(A), (B) is a figure for demonstrating a line and space pattern.

FIG. 59A shows a line-and-space mask pattern. Open area 80 with zero phase shift
And a phase shift layer 81 having a phase shift of π are alternately formed to form a line and space pattern.
For example, when the light intensity profile formed in the imaging pattern is calculated on the assumption that the opening region 80 and the phase shift layer 81 have a width of 0.5 μm, the result is as shown in FIG. 59B. A minimum light intensity is formed in a portion corresponding to a boundary between the opening region 80 and the phase shift layer 81. The light wavelength was 365 μm, the numerical aperture NA = 0.53, and the partial coherency σ = 0.50.

FIGS. 60A and 60B show the case where mixed patterns of various sizes are formed. FIG. 60A shows a mask pattern. On the upper stage, an opaque layer (Cr layer) 85 and a phase shift layer 86 for forming a large black pattern
A phase shift layer 87 for forming an image of the phase shift layer itself is formed in an intermediate portion, and a phase shift layer 87 for forming an image pattern in a side (edge) portion is formed in a lower portion. A shift layer 88 is formed. Around the phase shift layer 88, a phase shift layer 8 having an intermediate phase shift for preventing an unnecessary side from being imaged.
9 are formed. Phase shift layers 86, 87, 88
Gives a phase shift π, and the phase shift layer 89 gives, for example, a phase shift π / 2. Numerical aperture NA for i-line = 0.4
In the case of using a lens of .about.0.6, a pattern of 0.5 .mu.m or more is formed by arranging a region 86 having a phase shift .pi. 0.3-0.
In order to form a 5 μm black pattern, as shown in the middle part, a mask is formed with a pattern of only the phase shift layer 87 having a phase shift of π. The pattern of 0.25 μm or less is formed by the boundary between the phase shift layer 88 having a phase shift of π and the opening region having a phase shift of 0. At this time, the unnecessary side of the phase shift layer 88 is surrounded by the phase shift layer 89 showing an intermediate phase shift so that an image is not formed by adjusting the development level.

FIG. 60B shows an example of an image forming pattern.
A black pattern 91 corresponding to the mask formed by the opaque layer 85 and the phase shift layer 86 is formed at the upper part, a black pattern 92 corresponding to the phase shift layer 67 is formed at the intermediate part, and a black pattern 91 is formed at the lower part. A thin black pattern 93 corresponding to the boundary between the phase shift layer 88 and the opening region 90 is formed. When an IC is manufactured using photolithography, an image of a reticle pattern is formed on a wafer using an imaging lens system. With the miniaturization of the IC pattern, the numerical aperture NA of the imaging lens system is increased to improve the resolving power, thereby coping with the miniaturization of the IC pattern. However, if the numerical aperture NA of the imaging lens system is increased in order to improve the resolution,
The depth of focus FD becomes smaller according to the following equation (4).

[0119]

(Equation 1)

Here, K ₂ is a process coefficient. Therefore, a pattern cannot be accurately formed on a surface having irregularities. Therefore, a description will be given of an embodiment in which a pattern can be favorably formed even on a surface having irregularities. FIG. 61 shows a sixth embodiment of the mask according to the present invention. In the figure, substantially the same parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In this embodiment, the phase shift layer 3a includes a shifter portion 3a1 having a thickness D1 and a shifter portion 3a2 having a thickness D2 (D2> D1). By providing the shifter portions having different thicknesses as described above, it is possible to arbitrarily control the focal position of the image at the time of exposure.

Next, a description will be given of a fifth embodiment of the pattern forming method using the mask according to the present invention. In this embodiment, the thickness of the phase shift layer of the mask is partially varied as needed. For convenience of explanation, it is assumed that a pattern is formed using the mask 1A shown in FIG. 11 and the optical system shown in FIG. 14, and the relationship between the thickness of the phase shift layer 3a and the shift of the focal position (hereinafter referred to as defocus) will be described. I do. Light to use,
The material and the like of the phase shift layer 3a are the same as those in the embodiment described above. When the thickness t of the phase shift layer 3a when the phase shift amounts S of 180, 120 and 240 degrees are obtained using the equation (2), they are 0.388, 0.259 and 0.517 μm, respectively.

First, when t = 0.388 μm and S = 180 degrees, if the defocus amount is 0, the light intensity distribution becomes as shown in FIG.
The result is as shown in FIG. However, if the direction approaching the wafer 11 along the optical axis of the lens system 9 is set to the plus (+) direction and the defocus amounts are set to +1.0 and +0.5 μm,
The light intensity distribution is as shown in FIGS. 62 (A) and (B), respectively. On the other hand, when the defocus amounts are set to -0.5 and -1.0 μm, the light intensity distributions are as shown in FIGS. 62 (D) and (E), respectively. From FIG. 62, it can be seen that the light intensity distribution changes in the same manner regardless of whether the focal position shifts in the plus direction or the minus (-) direction.

Next, when t = 0.259 μm and S = 120 degrees, the light intensity distributions obtained by setting the defocus amounts to +1.0, +0.5, 0, and −0.5 μm are shown in FIG. 63 (A). ),
(B), (C), and (D) show. FIG. 63 shows that the maximum contrast is obtained when the defocus amount is +0.5 μm. When t = 0.517 μm and S = 240 °, the light intensity distributions obtained by setting the defocus amounts to +0.5, 0, −0.5, and −1.0 μm are shown in FIG.
(B), (C), and (D) show. FIG. 64 indicates that the maximum contrast is obtained when the defocus amount is -0.5 μm.

Therefore, in this embodiment, the focal position can be controlled within a range of 0.5 μm by appropriately setting the thickness t of the phase shift layer. In the IC manufacturing process, IC
May be higher than some other areas. For example, in a dynamic random access memory (DRAM), when a stacked capacitor is used, the memory cell part is 0.5 to 1.
0 μm higher. In such a case, if a pattern is formed to the resolution limit using a lens having a large numerical aperture, the depth of focus becomes shallow as described above, and the
It is difficult to apply to manufacturing.

However, according to this embodiment, application to a DRAM using a stacked capacitor as shown in FIG. 65 is also possible. In FIG. 65, substantially the same parts as those in FIGS. 14 and 61 are denoted by the same reference numerals, and description thereof will be omitted. In this case, a lower portion on the IC surface, such as a peripheral portion of the DRAM, is patterned using the thinner shifter portion 3a1 of the phase shift layer 3a. Therefore, D1 is made thinner than 0.388 μm. For example, the cell portion of the DRAM and the peripheral circuit portion are 1
If there is a step of about μm, set D1 = 0.259 μm. On the other hand, a high portion on the IC surface, such as a cell portion of a DRAM using a stacked capacitor, is a phase shift layer 3a.
The pattern is formed using the thicker shifter portion 3a2. Therefore, D2 is made thicker than 0.388 μm. For example, if the cell portion is about 1 μm higher than the peripheral circuit portion, D2
= 0.517 μm.

As described above, by controlling the thickness of the phase shift layer in accordance with the irregularities on the surface of the IC, it is possible to form a pattern by focusing on all the parts on the surface of the IC. As described above, in the present invention, a pattern is formed using a phase shift layer. Therefore, an arbitrary fine pattern can be formed by using a mask in which a phase shift layer is appropriately arranged. FIGS. 66 to 69 show a mask in each figure (A) and a corresponding pattern in each figure (B).
66 to 69, 90 is an opaque layer, 91 is a phase shift layer, and 92 is a window.

In the above embodiment, the partial coherency σ is set to 0.5. However, the present invention is not limited to this, and may be in the range of 0.3 ≦ σ ≦ 0.7. Light used for exposure using a mask is not limited to i-line. Further, the light may be irradiated from the side of the transparent substrate on which the phase shift layer is provided or from the opposite side. The materials of the transparent substrate and the phase shift layer are not limited to those of the embodiment. For example, the transparent substrate may be transparent to light used for exposure. The phase shift layer is made of, for example, SiO ₂ , Al ₂ O ₃ , MgF ₂ or the like.

Further, the mask in each embodiment includes a reticle. Therefore, it goes without saying that the pattern forming method using the mask according to the present invention is not limited to pattern formation of a semiconductor device, but can also be applied to pattern formation of a mask or a reticle. Although the present invention has been described with reference to the embodiments, the present invention can be variously modified in accordance with the gist of the present invention, and these are not excluded from the present invention.

[0129]

According to the present invention, a pattern having a narrow width exceeding the conventional resolution can be formed by effectively using a phase shift layer, and a fine pattern can be formed with improved resolution. This is very useful in practice because the pattern data can be simplified.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a diagram for explaining light intensity at one edge portion of a phase shift layer.

FIG. 3 is a diagram for explaining light intensity at both edge portions of a phase shift layer.

FIG. 4 is a schematic configuration diagram of an optical system used for exposure using a first embodiment of a mask.

FIG. 5 is a diagram for explaining a first embodiment of a pattern forming method using a mask.

FIG. 6 is a process chart illustrating a first example of a method for manufacturing a mask.

FIG. 7 is a process chart illustrating a second embodiment of the method of manufacturing a mask.

FIG. 8 is a plan view of a mask pattern.

9 is a diagram illustrating the light intensity distribution of FIG.

FIG. 10 is a diagram for explaining a second embodiment of the pattern forming method using the mask. .

FIG. 11 is a sectional view showing a second embodiment of the mask.

FIG. 12 is a diagram for explaining light intensity at one edge portion of a phase shift layer.

FIG. 13 is a diagram for explaining light intensity at both edge portions of a phase shift layer.

FIG. 14 is a diagram for explaining a third embodiment of the pattern forming method using the mask.

FIG. 15 is a diagram for explaining the pattern in FIG. 11;

16 is a diagram illustrating the light intensity distribution in FIG.

FIG. 17 is an explanatory diagram when the second embodiment of the mask is applied to a line and space pattern.

FIG. 18 is a diagram illustrating a light intensity distribution when the dimension conversion amount a and the width b of the phase shift layer are changed.

19 is a diagram illustrating a conventional light intensity distribution corresponding to FIG.

FIG. 20 is a diagram illustrating a light intensity distribution when a KrF excimer laser is used in FIG.

FIG. 21 is a diagram showing a part of FIG. 11;

FIG. 22 is a diagram illustrating the light intensity distribution in FIG.

FIG. 23 is an explanatory diagram when a black pattern is formed on a white background.

24 is a diagram illustrating the light intensity distribution in FIG.

FIG. 25 is an explanatory diagram in the case where the second embodiment of the mask is applied to an IC pattern format.

FIG. 26 is a diagram showing a part of the pattern in FIG. 11;

FIG. 27: Pattern width h is 0.3, 0.4, 0.5, 0.6, 0.
It is a figure explaining the light intensity distribution in the case of 7, 0.8, and 1.0 micrometer.

FIG. 28: Pattern width h is 0.3, 0.4, 0.5, 0.6, 0.
It is a figure explaining the light intensity distribution in the case of 7, 0.8, and 1.0 micrometer.

FIG. 29: Pattern width h is 0.3, 0.4, 0.5, 0.6, 0.
It is a figure explaining the light intensity distribution in the case of 7, 0.8, and 1.0 micrometer.

FIG. 30: Pattern width h is 0.3, 0.4, 0.5, 0.6, 0.
It is a figure explaining the light intensity distribution in the case of 7, 0.8, and 1.0 micrometer.

FIG. 31: Pattern width h is 0.3, 0.4, 0.5, 0.6, 0.
It is a figure explaining the light intensity distribution in the case of 7, 0.8, and 1.0 micrometer.

FIG. 32: Pattern width h is 0.3, 0.4, 0.5, 0.6, 0.
It is a figure explaining the light intensity distribution in the case of 7, 0.8, and 1.0 micrometer.

FIG. 33: Pattern width h is 0.3, 0.4, 0.5, 0.6, 0.
It is a figure explaining the light intensity distribution in the case of 7, 0.8, and 1.0 micrometer.

FIG. 34 is an explanatory diagram in the case where the second embodiment of the mask is applied to the formation of a contact hole pattern.

FIG. 35 is a diagram illustrating the light intensity distribution of FIG.

FIG. 36 is a process diagram illustrating a third example of the method for manufacturing a mask.

FIG. 37 is a process diagram illustrating a fourth example of the method for manufacturing a mask.

FIG. 38 is a process diagram illustrating a fifth example of the method for manufacturing a mask.

39 is a diagram showing a phase profile of light transmitted through the mask shown in FIG.

FIG. 40 is a process chart illustrating a sixth example of the method for manufacturing a mask.

FIG. 41 is a diagram showing a phase profile of light transmitted through the mask shown in FIG.

FIG. 42 is a process diagram illustrating a seventh embodiment of the method of manufacturing a mask.

FIG. 43 is a process diagram illustrating an eighth example of the method for manufacturing a mask.

FIG. 44 is a process diagram illustrating a ninth embodiment of a method for manufacturing a mask.

FIG. 45 is a process diagram illustrating a tenth embodiment of the method of manufacturing a mask.

FIG. 46 is a process diagram illustrating an eleventh embodiment of the method for manufacturing a mask.

FIG. 47 is a diagram illustrating a pattern forming method using a mask.

FIG. 48 is a light intensity distribution diagram illustrating imaging using an edge portion of a phase shift layer.

FIG. 49 is a diagram for explaining a fourth embodiment of the pattern forming method using the mask, and is a diagram for explaining a loop-shaped pattern.

FIG. 50 is a view for explaining a fourth embodiment of a pattern forming method using a mask, and is a view for explaining an open pattern;

FIG. 51 is a diagram for explaining a fourth embodiment of the pattern forming method using the mask, and is a diagram for explaining a dot pattern.

FIG. 52 is a view for explaining the fourth embodiment of the pattern forming method using the mask, and is a view for explaining a pattern of intersecting lines.

FIG. 53 is a view for explaining a fourth embodiment of the pattern forming method using the mask, and is a view for explaining a T-shaped pattern.

FIG. 54 is a diagram for explaining a fourth embodiment of the pattern forming method using a mask, and is a diagram for explaining a wiring pattern.

FIG. 55 is a view for explaining a fourth embodiment of the pattern forming method using the mask, and is a view for explaining an intersecting pattern.

FIG. 56 is a diagram for explaining a fourth embodiment of the pattern forming method using the mask, and is a diagram for explaining a wiring pattern.

FIG. 57 is a diagram for explaining a fourth embodiment of the pattern forming method using the mask, and is a diagram for explaining a wiring pattern.

FIG. 58 is a view for explaining the fourth embodiment of the pattern forming method using the mask, and is a view for explaining an oval pattern.

FIG. 59 is a diagram for explaining a fourth embodiment of the pattern forming method using the mask, and is a diagram for explaining a line-and-space pattern.

FIG. 60 is a view for explaining a fourth embodiment of a pattern forming method using a mask, and is a view for explaining mixed patterns of various sizes.

FIG. 61 is a sectional view showing a sixth embodiment of the mask.

FIG. 62 is a diagram illustrating a light intensity distribution when phase shift layers having different thicknesses are provided.

FIG. 63 is a diagram illustrating a light intensity distribution when phase shift layers having different thicknesses are provided.

FIG. 64 is a diagram illustrating a light intensity distribution when phase shift layers having different thicknesses are provided.

FIG. 65 is a diagram illustrating a fifth embodiment of the pattern forming method using the mask.

FIG. 66 is a diagram showing an example of a pattern that can be formed according to the present invention.

FIG. 67 is a diagram showing an example of a pattern that can be formed by the present invention.

FIG. 68 is a diagram showing an example of a pattern that can be formed according to the present invention.

FIG. 69 is a diagram showing an example of a pattern that can be formed by the present invention.

FIG. 70 is a cross-sectional view showing a conventional mask provided with an opaque layer.

71 is a configuration diagram of an optical system that performs pattern formation using the mask of FIG. 70.

FIG. 72 is a diagram illustrating a conventional pattern forming method.

FIG. 73 is a diagram illustrating a light intensity distribution in a conventional example.

FIG. 74 is a process chart of a conventional mask manufacturing method using a negative resist having a phase shift layer.

75 is a diagram showing a phase profile of light transmitted through the mask shown in FIG. 74 (d).

FIG. 76 is a cross-sectional view of a mask having a phase shift layer manufactured using a positive resist.

FIG. 77 is a diagram showing a phase profile of light transmitted through the mask shown in FIG. 76.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 mask 2,51 transparent substrate 3a, 52 phase shift 3 resist material 4 resist pattern 5 mask pattern layer 6 light source 8 lens system 9 imaging lens system 10 photoresist 11 wafer 12 aluminum thin film layer 13 region 14,53 opaque layer 15 large pattern Region 16 Fine pattern region 20 Pattern 21 Stopper layer 31 Glass substrate 32 Cr layer 33 Opening pattern 34 MOSI layer 35 Negative EB resist layer 36, 40 Design pattern 37A, 37B, 41A, 41B Phase shift pattern 38 Positive EB resist layer 39 Opening 53a Pattern 54 EB resist layer 55 Resist 60,68 Opening layer 61 Mask 62,65,66,69,72,78 Black pattern 64,67,71,75,76,77 Phase shift 80 Opening area 81 Phase shift layer 85 chrome mask 86,87,88,89 phase shift layer 90 openings 91, 92 black pattern

Continued on the front page (72) Inventor Masao Taguchi 1015 Uedanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Co., Ltd. Person Yuichiro Yanagishita 1015 Uedanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Limited (56) References JP-A-2-210250 (JP, A) JP-A-63-10162 (JP, A) JP-A-1-147458 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03F 1/00-1/16

Claims (7)

(57) [Claims] 1. A mask comprising a transparent substrate layer transparent to light used for exposure and a mask pattern layer formed on the transparent substrate layer, wherein at least a part of the mask pattern layer transmits the light. A predetermined phase shift occurs between the phase of light transmitted through the phase shift layer and the phase of light transmitted through a portion of the mask where the phase shift layer is not provided, The shift layer is provided alongside the first edge and the first edge
With a second edge that has occurred and occurred at two of said edges
One pattern on the wafer by phase shift
A mask formed on a dist layer . 2. The phase shift layer comprises a part of the transparent substrate layer, and a thickness of a part of the transparent substrate layer constituting the phase shift layer is different from a thickness of another part of the transparent substrate layer. This
The mask according to claim 1 , wherein : Wherein the phase shift layer is characterized by having a plurality of different portions thicknesses from each other, according to claim 1 or 2
The mask as described. 4. The light transmitted through the mask is passed through a lens system.
The pattern is formed by forming an image on a photoresist layer on the wafer.
Pattern formation using a mask formed on the photoresist layer
In the method, the mask comprises a transparent substrate layer transparent to light used for exposure.
And a mask pattern layer formed on the transparent substrate layer.
At least a part of the mask pattern transmits the light.
Only the phase shift layer to be transmitted, and the light transmitted through the phase shift layer and the phase shift
Specified with the light transmitted through the part without the soft layer
And the phase shift layer is provided side by side with the first edge and the first edge.
With a second edge that has occurred and occurred at two of said edges
One pattern on the wafer is transferred by the phase shift
Characterized by including a step of forming a photoresist layer,
A pattern forming method using a mask. 5. The phase shift layers have different thicknesses.
The method according to claim 4, further comprising a plurality of parts.
A pattern forming method using a mask. 6. The phase shift layers having different thicknesses.
According to the unevenness of the photoresist layer using a plurality of portions
The method includes a step of imaging a pattern at a focal length.
A pattern forming method using the mask according to claim 5.
Law. 7. A transparent substrate transparent to light used for exposure.
And a mask pattern layer formed on the transparent substrate layer.
A mask pattern layer comprising: an opaque layer; and an end of the opaque layer.
And a phase shift layer that transmits the light.
Is, the phase shift 30% pattern width of the resolution limit of the layer 6
0%, and the phase of light transmitted through the phase shift layer and the phase of the mask
The position of light transmitted through the part where the phase shift layer is not provided
A predetermined phase shift occurs between the first edge and the first edge.
With a second edge that has occurred and occurred at two of said edges
Photo-resist pattern on wafer by phase shift
A mask, which is formed in a layer.