JP2009237339A - Photomask and method for manufacturing semiconductor device using the photomask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photomask and a method for manufacturing a semiconductor device capable of suppressing a difference in exposure amounts at a boundary between a circuit pattern area and a multiple exposure area when performing a step exposure. <P>SOLUTION: A photomask 1 has a circuit pattern forming area 13 in the central part of a mask substrate 11, and a repetitive pattern in a first area part 15a facing each side of the mask substrate 11 and in a second area parts 15b facing each of the four corners. When using an exposure device with a numerical aperture being NA, a light source wavelength being λ, the incidence angle of exposure light entering the photomask being θ, and the coherence factor being σ, the repetitive pattern satisfies the relationship: T/(1+T)<(a)<2T/(1+T) and p=λ/(1+σ)NA wherein T represents transmissivity or reflectivity of the pattern forming film, and (a) represents the proportion of a pattern space s to a pattern pitch p. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a photomask used in a lithography process for manufacturing a semiconductor device and a method for manufacturing a semiconductor device using the photomask.

  In recent years, in semiconductor devices, for example, large-scale integrated circuit devices, miniaturization of circuit patterns has become increasingly necessary for high integration. Therefore, in the manufacture of large-scale integrated circuit devices, in order to perform projection exposure of finer circuit patterns, a semi-transparent film (half-tone film) has recently been formed on a translucent mask substrate. A circuit pattern is provided by selectively removing the semi-transparent film in the circuit pattern formation region in the central part of the mask substrate, and the phase of the light passing through the semi-transparent film is changed to that of the light passing through the circuit pattern (translucent part). A halftone phase shift mask is used which has a relationship that is substantially inverted with respect to the phase.

  In the halftone phase shift mask, the light that passes through the vicinity of the boundary between the translucent part and the semi-transparent film and wraps around by the diffraction cancels each other, and the contrast of the boundary can be maintained well.

  On the other hand, when a circuit pattern is transferred onto a wafer using a halftone phase shift mask, an exposure method called a step-and-repeat method is used. This step-and-repeat method is a method of repeatedly (repeat) shots of a circuit pattern on a wafer while sequentially moving (stepping) the wafer.

  When exposure is performed by this step-and-repeat method, generally, an adjacent region adjacent to the circuit pattern formation region is also exposed in the peripheral region on the outer periphery of the circuit pattern formation region. Accordingly, among adjacent shot areas on the wafer, an area where adjacent areas overlap (hereinafter referred to as a multiple exposure area) is generated.

  In this multiple exposure area, exposure is performed a plurality of times with exposure light transmitted through the semi-transparent film, so even if the exposure amount does not substantially contribute to exposure in one exposure, the exposure amount is added to the exposure. The amount that contributes may be reached. As a result, there is a problem that an unnecessary pattern is formed in a portion that should not be formed and a pattern defect occurs.

  Therefore, a fine repetitive pattern that forms a multiple exposure region in the peripheral region of the outer periphery of the circuit pattern formation region and does not transmit light to the adjacent region, specifically, a resolution in which the amplitude of transmitted light is zero A method has been proposed in which a dark portion is formed in an adjacent region by periodically arranging minute repetitive patterns below the limit to suppress the generation of unnecessary patterns (for example, see Patent Document 1).

However, in this method, when exposed, the circuit pattern region where light is transmitted by the semi-transparent film does not transmit light at all in the adjacent region. Therefore, the circuit pattern region and adjacent region where light is transmitted by the semi-transparent film. There is a problem that the difference in the exposure amount at the boundary between and the circuit pattern area becomes extremely large, and the circuit pattern resolution may be lowered due to the influence of the adjacent area on the circuit pattern area.
JP-A-7-253651

  The present invention has been made in view of the above-described problems, and a photomask capable of suppressing a difference in exposure amount at a boundary portion between a circuit pattern region and an adjacent region forming a multi-exposure region on the outer periphery thereof at the time of exposure. Another object of the present invention is to provide a method for manufacturing a semiconductor device using the photomask.

In order to achieve the above object, a pattern transfer method according to an aspect of the present invention is a method of manufacturing a semiconductor device by projecting and exposing a circuit pattern formed on a photomask and transferring the circuit pattern onto a wafer. The photomask has a planar rectangular mask substrate whose main surface is covered with a pattern formation film, a circuit pattern provided on the pattern formation film in a circuit pattern formation region in the center of the mask substrate, and the circuit pattern A repetitive pattern for forming a multiple exposure region on the wafer at the time of exposure of the circuit pattern on the outer periphery of the formation region, the transmittance or reflectance of the pattern forming film is T, and the pattern of the repetitive pattern The ratio of the pattern space to the pitch p is a, the numerical aperture NA, the light source wavelength λ, and the exposure light incident on the photomask The incident angle theta, when the coherence factor is used exposure apparatus sigma,
The repeating pattern is
T / (1 + T) <a <2T / (1 + T) and
p <λ / (1 + σ) NA
It is characterized by satisfying the following relationship simultaneously.

In addition, a photomask according to one embodiment of the present invention includes a circuit pattern formation region having a main surface covered with a semi-transparent film or an absorption film, a central portion, and a region adjacent to the outer periphery of the circuit pattern formation region. A planar rectangular mask substrate, a circuit pattern provided in the semi-transparent film or absorption film in the circuit pattern formation region, and a repeating pattern,
The transmissivity or reflectance of the semi-transparent film is T, the ratio of the pattern space to the pattern pitch p of the repetitive pattern is a, the numerical aperture NA, the light source wavelength λ, and the exposure light incident on the mask substrate. When using an exposure apparatus with an angle θ and a coherence factor σ,
The repeating pattern is
T / (1 + T) <a <2T / (1 + T) and
p <λ / (1 + σ) NA
It is characterized by satisfying the following relationship simultaneously.

  According to the present invention, at the time of exposure, a photomask capable of suppressing a difference in exposure amount at a boundary portion between a circuit pattern region and an adjacent region forming an outer peripheral multiple exposure region, and a semiconductor using the photomask An apparatus manufacturing method can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a plan view of a halftone phase shift mask according to the first embodiment of the present invention, FIG. 2 is a cross-sectional view taken along the line AA ′ in FIG. It is an expanded sectional view of the 1st and 2nd repetitive pattern in the adjacent field which forms a multiple exposure field.

  As shown in FIGS. 1 to 3, the halftone phase shift mask 1 of this embodiment includes a mask substrate 11. The mask substrate 11 is a translucent glass substrate and has a square planar shape. A semitranslucent film (halftone film) 12 is provided on the main surface of the mask substrate 11.

  Further, the mask substrate 11 is provided with a circuit pattern forming region 13 and a peripheral region 14. Here, the circuit pattern formation region 13 is provided in the central portion of the mask substrate 11 and is a region for forming a fine circuit pattern 20 (described later) to be transferred onto the wafer, and surrounds the entire circuit pattern 20 in close proximity. Represents the outline.

  The peripheral region 14 is provided around the outer periphery of the circuit pattern formation region 13. Of the peripheral region 14, the adjacent region 15 adjacent to the circuit pattern forming region 13 is irradiated with exposure light when the circuit pattern 20 is transferred onto the wafer, thereby forming a multiple exposure region on the wafer. Hereinafter, the adjacent region 15 is also referred to as a multiple exposure formation region.

  A circuit pattern 20 is provided in the circuit pattern formation region 13 at the center of the mask substrate 11. The circuit pattern 20 is composed of an opening that allows light of an intensity that substantially contributes to exposure to pass through by selectively removing a part of the semi-transparent film 12.

  Here, the circuit pattern 20 improves the resolution of the main circuit pattern 20a that is actually transferred onto the wafer and the main circuit pattern 20a that is disposed adjacent to the main circuit pattern 20a and transferred onto the wafer. Therefore, both auxiliary patterns 20b provided for this purpose are included.

Specifically, the main circuit pattern 20a and the auxiliary pattern 20b have a line shape.

  Further, a light shielding film 17 is provided on the semi-transparent film 12 in the outer peripheral edge portion of the peripheral region 14. The light shielding film 17 is made of, for example, a Cr film.

  In addition, in the peripheral region 14, the adjacent region 15 includes a fine first repetitive pattern 21 having a predetermined period and a second repetitive pattern 22 having a period different from the first repetitive pattern. Yes.

  The first repetitive pattern 21 is arranged in each of the first region portions 15 a facing each side of the mask substrate 11 in the adjacent region 15. In addition, the second repetitive pattern 22 is arranged in each of the second region portions 15 b at the corners facing the four corners of the mask substrate 11 in the adjacent region 15.

  The first repetitive pattern 21 and the second repetitive pattern 22 are configured by selectively removing a part of the semitransparent film 12, and are formed in a line shape here, both of which are AA ′ lines. Are arranged along.

  When step exposure is performed using the halftone phase shift mask 1 configured as described above, a multiple exposure region is formed on the wafer by the adjacent region 15 as shown in FIG.

  FIG. 4 shows the multiple exposure area on the wafer. FIG. 4A assumes the case where the transfer is performed twice adjacent to the wafer, and FIG. 4B assumes the case where the transfer is performed four times adjacent to the wafer. Is.

  As shown in FIG. 4A, when the transfer is performed twice adjacently on the wafer, the first adjacent area 15-1 in the first first shot area 30 and the second second time are transferred. A double exposure region 34 that overlaps with the second adjacent region 15-2 in the shot region 31 and is exposed twice is formed. Further, as shown in FIG. 4B, when four times of transfer are performed adjacent to each other on the wafer, the adjacent first and second shot regions 30, 31, first and third shot regions 30, 32 are adjacent. The second and fourth shot regions 31, 33 and the third and fourth shot regions 32, 33 overlap each other in a double exposure region 34, adjacent first to fourth shot regions 30-33. In a portion where the four shot areas overlap, a quadruple exposure area 35 that is exposed four times is formed.

  In the adjacent region 15, even the exposure light transmitted through the semi-transparent film 12 having low transmittance is exposed multiple times in the multiple exposure regions 34 and 35 such as the double exposure region 34 and the quadruple exposure region 35. For this reason, exposure may be performed that reaches an intensity that substantially contributes to exposure. As a result, unnecessary patterns are formed in the multiple exposure regions 34 and 35 that should not be formed.

  On the other hand, if a dark part that does not transmit light is formed in the adjacent region 15 that forms the multiple exposure regions 34 and 35, the difference in exposure amount at the boundary between the circuit pattern region and the multiple exposure region on the wafer It becomes very large and may adversely affect the resolution of the circuit pattern.

  Therefore, it is necessary to adjust the transmitted light of the adjacent region 15 forming the multiple exposure region to a predetermined intensity, that is, to reduce the difference in the exposure amount at the boundary between the circuit pattern forming region 13 and the adjacent region 15.

  For this purpose, the first and second repetitive patterns 21 and 22 need to be configured so as to weaken the intensity of the 0th-order diffracted light and prevent the 1st-order diffracted light from entering the projection lens and forming an image. Specifically, the first repetitive pattern 21 is configured such that the transmittance of the repetitive pattern 21 is lower than the transmissivity of the semi-transmissive film 12 and larger than 0 at the time of exposure. On the other hand, the second repeating pattern 22 needs to be configured such that the transmittance is lower than ½ of the transmittance of the semi-transparent film 12 and larger than 0.

  Hereinafter, as described above, when the first repetitive pattern 21 and the second repetitive pattern 22 are exposed, the intensity of the 0th-order diffracted light transmitted through the repetitive patterns 21 and 22 is reduced, and the first-order analysis light is transmitted. A description will be given of design conditions for configuring the projector lens so as not to form an image.

First, the pattern pitch of the semi-transparent film 12 in the first repetitive pattern 21 and the second repetitive pattern 22 is p, the space between patterns is s, and the ratio of the pattern space s to the pattern pitch p (duty A) a = s / p (1)
It is defined as When the transmissivity T [%] of the semi-transparent film is used, the amplitude A0 of the 0th-order diffracted light transmitted through the first repetitive pattern 21 and the second repetitive pattern 22 can be expressed by the following equation.

A ₀ = a (1 + T) −T (2)
Here, since the intensity of the 0th-order diffracted light changes depending on the duty ratio a of the repeated patterns 21 and 22, the first repeated pattern 21 is smaller than the transmittance T of the semi-transparent film 12 and the transmittance T is 0. The diffraction efficiency is set so as not to form the dark part of the film. Further, in the second repeated pattern 22, the diffraction efficiency is set so as not to form a dark portion having a transmittance T that is smaller than ½ of the transmittance T of the semi-transmissive film 12.

The condition that the 0th-order diffracted light is smaller than the transmissivity of the semi-transparent film 12 is that from the above equation (2), in the first repetitive pattern 21, as shown in the following equation (3), the second repetitive pattern 21 In pattern 22, as shown in the following equation (4),
0 <a (1 + T) −T <T (3)
0 <a (1 + T) −T <T / 2 (4)
It is. Thus, in the first repeating pattern 21, as shown in the following formula (5), and in the second repeating pattern 22, as shown in the following formula (6),
T / (1 + T) <a <2T / (1 + T) (5)
T / (1 + T) <a <3T / 2 (1 + T) (6)
It becomes.

Here, if the semi-transparent film 12 having an intensity transmittance of 6% is used, the transmittance T is
T = (0.06) ^1/2 = 0.2449 (7)
When the value of equation (7) is substituted into the above equations (5) and (6), 0.1967 <a <0.3935 is obtained in the first repetitive pattern 21, and 0 in the second repetitive pattern 22. 1967 <a <0.2951.

  Next, design conditions for configuring the first repetitive pattern 21 and the second repetitive pattern 22 so that the primary analysis light enters the projection lens and does not form an image at the time of exposure will be described.

  When the incident angle at which the exposure light emitted from the light source part farthest from the numerical aperture NA, the light source wavelength λ, and the optical axis is incident on the halftone phase shift mask is θ, the value defined by sin θ / NA is σ Assuming a (coherence factor) exposure apparatus, the first-order diffracted light does not enter the projection lens when the following condition is satisfied.

p <λ / (1 + σ) NA (8)
Therefore, the first repetitive pattern 21 satisfies the above expressions (5) and (8) at the same time, and the second repetitive pattern 22 satisfies the above expressions (6) and (8) at the same time. The s, p, and T of the first and second repeating patterns 21 and 22 may be determined.

  For example, under an ArF light source with NA = 0.92, wavelength of about 193 nm, and coherent illumination (σ = 0), the pattern pitch of the first and second repetitive patterns 21 and 22 satisfying the above equation (8). p can be determined to be 200 nm, for example. From this condition and the conditions of the 0th-order diffracted light of the above formulas (5) and (6), for example, in the first repetitive pattern 21, the pattern pitch is 200 nm, the line part is about 140 nm, the space part is about 60 nm, The second repeating pattern 22 may be configured as a pattern having a pattern pitch of 200 nm, a line portion of about 160 nm, and a space portion of about 40 nm.

  When σ ≠ 0, it should be considered that the ± 1st-order diffracted light has a spread, but in the case of annular illumination, this σ corresponds to the outer periphery of the annular zone, and the second, fourth, In the case of eye illumination, it corresponds to a circumscribed circle. Therefore, the conditions in this embodiment are generally considered to hold.

  Next, a method for manufacturing the halftone phase shift mask having the above structure will be described with reference to FIGS.

  First, as shown in FIG. 5A, on a transparent substrate, for example, a transparent glass substrate 11, using ~ (formation method), as a pattern forming film, chromium fluoride (CrF), molybdenum silicide (MoSiO). Then, a semi-transparent film (halftone film) 12 made of tungsten silicide (WSiO), zirconium silicide (ZrSiO) or the like is formed. The semi-transparent film is often used with a transmittance of about 2 to 20%. Next, a light shielding film 17 made of chromium (Cr) is formed on the semi-transparent film 12.

  Next, as shown in FIG. 5B, a resist 18 is formed on the light shielding film 17 by using, for example, a coating method, and the resist 18 is patterned by using, for example, a laser, and then developed. Do. This patterning is performed so that the outer peripheral edge portion of the peripheral region 14 is left and the circuit pattern forming region 13 and the adjacent region 15 of the peripheral region 14 have openings 18a. Thereafter, as shown in FIG. 5C, the light shielding film 17 exposed in the opening 18a is etched using the resist 18 as a mask, and then the resist 18 is removed.

  Next, as shown in FIG. 6A, a resist 19 is formed again on the light shielding film 17 and the semi-transparent film 12, and after patterning the resist 19 as shown in FIG. 6B, Perform development processing. In this patterning, a pattern corresponding to the circuit pattern 20 is formed in the circuit pattern formation region 13, and a pattern corresponding to the first repetitive pattern 21 is formed in the first region portion 15 a of the adjacent region 15. A pattern corresponding to the second repetitive pattern 22 is formed in the second region portion 15 b of the adjacent region 15.

  Next, as shown in FIG. 6C, the semi-transparent film 12 is etched using the patterned resist 19 as a mask. As a result, the circuit pattern 20 is formed in the circuit pattern formation region 13, and the first repetitive pattern 21 is formed in the first region portion 15 a of the adjacent region 15. In addition, the second repetitive pattern 22 is formed in the second region portion 15b of the adjacent region 15, respectively. Here, the 1st and 2nd repeating patterns 21 and 22 are formed in a line and space shape. Thereafter, the resist 19 is removed. After the resist 19 is removed, cleaning, inspection, and correction are performed, and a halftone phase shift mask as shown in FIGS. 1 to 3 is completed.

  According to the above-described embodiment, the following effects can be obtained. That is, the first repetitive pattern 21 is configured so that the transmittance of the repetitive pattern is lower than the transmissivity of the semi-transparent film 12 and larger than 0, and the second repetitive pattern 22 is formed as the repetitive pattern. Is configured to be lower than ½ of the transmissivity of the semi-transparent film 12 and larger than 0, so that the next time of transmission through the first and second repetitive patterns 21 and 22 is achieved. Reduce the intensity of the folding light. Further, the first-order diffracted light transmitted through the first and second repetitive patterns 21 and 22 enters the projection lens so as not to form an image. Thereby, the difference of the exposure amount of the boundary part of a circuit pattern area | region and a multiple exposure area | region on a wafer can be suppressed.

  In the above-described embodiment, an example in which a positive resist is used as a resist has been described. However, in the case of a negative resist, it can be used in the same manner by simply replacing the line portion and the space portion in the case of a positive resist. The type of resist to be used can be selected depending on the efficiency of the mask pattern arrangement.

(Second Embodiment)
In recent years, an exposure method using EUV (Extreme Ultra Violet) light has been proposed due to the rapid miniaturization of semiconductor elements. However, in the wavelength region of EUV light, light absorption by a substance is very large, and thus light refraction. In the refraction type optical system using the optical system, since the transmittance of the EUV light to the optical element such as a lens is lowered and the practicality is lost, the reflection type optical system is used.

  The second embodiment is an example in which the present invention is applied to a reflective photomask. FIG. 7 is a plan view of the reflective photomask according to the second embodiment of the present invention, and FIG. 'A cross-sectional view taken along the line and viewed in the direction of the arrow. FIG. 9 is an enlarged cross-sectional view of the first and second repetitive patterns in the adjacent region forming the multiple exposure region.

  As shown in FIGS. 7 to 9, the reflective photomask 40 of this embodiment has a mask substrate 51. As the mask substrate 51, a glass substrate called a low expansion glass having a very small thermal expansion coefficient is used, and has a square planar shape. On the upper surface of the mask substrate 51, a reflective multilayer film 42, a buffer layer 43, and an absorber layer 44 are sequentially stacked.

  Here, the reflective multilayer film 42 has a structure in which a molybdenum (Mo) layer and a silicon (Si) layer are alternately laminated in order to obtain a high reflectance by utilizing multiple reflection in the exposure wavelength region. The buffer layer 43 is made of, for example, tantalum (Ta), chromium (Cr), or the like. The absorber layer 44 is made of, for example, tantalum nitride (TaN).

  The mask substrate 51 is provided with a circuit pattern formation region 53 and a peripheral region 54. Here, the circuit pattern formation region 53 is provided in the central portion of the mask substrate 51 and is a region for forming a fine circuit pattern 60 (described later) to be transferred onto the wafer, and surrounds the entire circuit pattern 60 in close proximity. Represents the outline.

  The peripheral region 54 is provided around the outer periphery of the circuit pattern formation region 53. Of the peripheral region 54, an adjacent region 55 adjacent to the circuit pattern formation region 53 is irradiated with exposure light when the circuit pattern 60 is transferred onto the wafer, thereby forming a multiple exposure region on the wafer. Hereinafter, the adjacent region 55 is also referred to as a multiple exposure formation region.

  A circuit pattern 60 is provided in the circuit pattern formation region 53 at the center of the mask substrate 51. The circuit pattern 60 selectively removes a part of the laminated film of the buffer layer 43 and the absorber layer 44 to transmit light having an intensity that substantially contributes to exposure and reflect the light by the reflective multilayer film 42. It is comprised from such an opening part.

  Here, the circuit pattern 60 improves the resolution of the main circuit pattern 60a that is actually transferred onto the wafer and the main circuit pattern 60a that is arranged adjacent to the main circuit pattern 60a and transferred onto the wafer. Therefore, both auxiliary patterns 60b provided for this purpose are included.

Specifically, the main circuit pattern 60a and the auxiliary pattern 60b have a line shape.

  Further, a light shielding film 57 is provided on the absorber layer 44 in the outer peripheral edge portion of the peripheral region 54. The light shielding film 57 is made of, for example, a Cr film.

  In the peripheral region 54, the adjacent region 55 includes a fine first repeating pattern 61 having a predetermined period and a second repeating pattern 62 having a period different from the first repeating pattern. Yes.

  The first repetitive pattern 61 is disposed in each of the first region portions 55 a facing each side of the mask substrate 51 in the adjacent region 55. Further, the second repetitive pattern 62 is disposed in each of the second region portions 55 b at the corners of the adjacent region 55 facing the four corners of the mask substrate 51.

  The first repetitive pattern 61 and the second repetitive pattern 62 are configured by selectively removing a part of the buffer layer 43 and the absorber layer 44, and are formed in a line shape here. Arranged along the line -B '.

  In the reflection type photomask 40 configured in this way, the exposure light is prevented from being reflected by the absorber layer 44. However, it is known that the absorber layer 44 slightly reflects. . Therefore, as in the case of the halftone phase shift mask, when step exposure is performed, an area that is exposed a plurality of times such as the double exposure area 34 and the quadruple exposure area 35 is formed on the wafer.

  In the adjacent region 55, even if the reflectivity of the absorber layer 44 is low, the multiple exposure region such as the double exposure region 34 and the quadruple exposure region 35 is exposed multiple times, so that it substantially contributes to the exposure. In some cases, exposure is performed to reach the required intensity. As a result, unnecessary patterns are formed in the multiple exposure regions 34 and 35 that should not be formed. On the other hand, on the wafer, the difference in the exposure amount at the boundary between the circuit pattern area and the multiple exposure area becomes extremely large, which may adversely affect the circuit pattern resolution.

  Therefore, the reflected light of the adjacent area 55 that forms the multiple exposure area is adjusted to a predetermined intensity, that is, the difference in the exposure amount at the boundary between the circuit pattern formation area 53 and the adjacent area 55 that forms the multiple exposure area is reduced. is required.

  For this purpose, the first and second repeating patterns 61 and 62 are configured so as to weaken the intensity of the 0th-order diffracted light of the reflected light in the absorber layer 44 and prevent the first-order diffracted light from entering the projection lens and forming an image. There is a need. Specifically, the first repetitive pattern 61 is configured such that the reflectance of the repetitive pattern 61 is lower than the reflectance of the absorber layer 44 and larger than 0 at the time of exposure. On the other hand, the second repetitive pattern 62 needs to be configured so that the reflectance is lower than 1/2 of the reflectance of the absorber layer 44 and larger than 0.

  Next, as described above, when the first repetitive pattern 61 and the second repetitive pattern 62 are exposed, the intensity of the 0th-order diffracted light reflected by these repetitive patterns 61 and 62 is reduced, and the first-order analysis is performed. A description will be given of design conditions for making a configuration in which light enters the projection lens and does not form an image.

  First, the pattern pitch of the absorber layer 44 in the first repetitive pattern 61 and the second repetitive pattern 62 is p, the width between the patterns is s, and the normalized pattern space a is the above formula (1). If the same definition is used, the reflectance of the first repetitive pattern 61 is lower than the reflectance of the absorber layer 44, and the diffraction efficiency is such that no dark portion having a reflectance of 0 is formed. The refraction pattern 62 has a reflectance lower than ½ of the reflectance of the absorber layer 44 and a diffraction efficiency that does not form a dark portion with a reflectance of 0. Similar to the halftone phase shift mask, they can be expressed by the above-described equations (5) and (6), respectively.

  Here, if the absorber layer 44 having an intensity reflectance of 2% is used, 0.1239 <a <0.2478 in the first repetitive pattern 61 and 0.1239 <a <in the second repetitive pattern 62. 0.1858.

  In the first and second repetitive patterns 61 and 62, the condition that the first-order diffracted light does not enter the projection lens is also expressed by the above-described equation (8), as in the case of the halftone phase shift mask of the first embodiment. Can do. Accordingly, the first repetitive pattern 61 satisfies the above expressions (5) and (8) simultaneously, and the second repetitive pattern 62 satisfies the above expressions (6) and (8) simultaneously. S, p, and T of the first and second repeating patterns 61 and 62 may be determined.

  For example, under an EUV light source with NA = 0.25, wavelength of about 13.5 nm, and coherent illumination (σ = 0), the pattern pitch of the first and second repetitive patterns 61 and 62 satisfying Expression (8) p can be determined to be 50 nm, for example. From this condition and the conditions of the 0th-order diffracted light of the above formulas (5) and (6), for example, in the first repetitive pattern 61, the pattern pitch is 50 nm, the line part is about 40 nm, the space part is about 10 nm, The second repeated pattern 62 may be a pattern having a pattern pitch of 50 nm, a line portion of about 42.5 nm, and a space portion of about 7.5 nm.

  When σ ≠ 0, it should be considered that the ± 1st-order diffracted light has a spread, but in the case of annular illumination, this σ corresponds to the outer periphery of the annular zone, and the second, fourth, In the case of lighting, it corresponds to a circumscribed circle. Therefore, the conditions in this embodiment are generally considered to hold.

  Next, a manufacturing method of the reflective photomask having the above structure will be described with reference to FIGS.

  First, as shown in FIG. 10A, a reflective multilayer film 42 is formed on a mask substrate 51 by alternately laminating Mo layers and Si layers by using, for example, a sputtering method. On the reflective multilayer film 42, a buffer layer 43, an absorber layer 44, and a light shielding film 57 are sequentially stacked by sputtering or CVD.

  Next, as shown in FIG. 10B, a resist 48 is formed on the light shielding film 57 by using, for example, a coating method, and the resist 48 is patterned by using, for example, a laser, and then developed. Do. This patterning is performed so as to leave the outer peripheral edge portion of the peripheral region 54 and have the opening 48 a in the circuit pattern forming region 53 and the adjacent region 55 of the peripheral region 54.

Thereafter, as shown in FIG. 10C, the light shielding film 57 exposed in the opening 48a is etched using the resist 48 as a mask, and then the resist 48 is removed.

  Next, as shown in FIG. 11A, a resist 49 is formed again on the light shielding film 57 and the absorber layer 44, and after the resist 49 is patterned as shown in FIG. 11B, development is performed. Process. In this patterning, a pattern corresponding to the circuit pattern 60 is formed in the circuit pattern formation region 53, and a pattern corresponding to the first repetitive pattern 61 is formed in the first region portion 55 a of the adjacent region 55. A pattern corresponding to the second repetitive pattern 62 is formed in the second region portion 55 b of the adjacent region 55.

  Next, as shown in FIG. 11C, the absorber layer 44 and the buffer layer 43 are sequentially etched using the resist 49 as a mask. Thereby, the circuit pattern 60 is formed in the circuit pattern formation region 53, and the first repetitive pattern 61 is formed in the first region portion 55 a of the adjacent region 55. In addition, the second repetitive pattern 62 is formed in the second region portion 55b of the adjacent region 55, respectively. Here, the first and second repeating patterns 61 and 62 are formed in a line-and-space shape.

  Thereafter, the resist 49 is removed. After removing the resist 49, cleaning, inspection, and correction are performed, and a reflective photomask 40 as shown in FIGS. 7 to 9 is completed.

  According to the above-described embodiment, the following effects can be obtained. That is, the first repeating pattern 61 is configured so that the reflectance of the repeating pattern is lower than the reflectance of the absorber layer 44 and larger than 0, and the second repeating pattern 62 is formed of the repeating pattern. By configuring the reflectivity to be lower than 1/2 of the reflectivity of the absorber layer 62 and greater than 0, the zero-order diffracted light reflected by the first and second repetitive patterns 61 and 62 can be reduced. Reduce strength. Further, the first-order diffracted light reflected by the first and second repetitive patterns 61 and 62 is prevented from entering the projection lens and forming an image. Thereby, the difference of the exposure amount of the boundary part of a circuit pattern area | region and a multiple exposure area | region on a wafer can be suppressed.

  In the above-described embodiment, an example in which a positive resist is used as a resist has been described. However, in the case of a negative resist, it can be used in the same manner by simply replacing the line portion and the space portion in the case of a positive resist. The type of resist to be used can be selected depending on the efficiency of the mask pattern arrangement.

(Third embodiment)
A third embodiment of the present invention will be described with reference to FIG. FIG. 12A is a plan view of a halftone phase shift mask according to the third embodiment of the present invention, and FIG. 12B is a diagram showing first and second repetitive patterns in adjacent regions forming a multiple exposure region. It is a top view.

  In this embodiment, the first and second repetitive patterns of the first region portion and the second region portion of the adjacent region forming the multiple exposure region are replaced with the line-and-space shape in the first embodiment, in a lattice shape. It is a thing. Hereinafter, the same parts as those in the first embodiment are denoted by the same reference numerals, description thereof will be omitted, and different parts will be described.

  That is, as shown in FIG. 12, in the halftone phase shift mask 70 of the present embodiment, the circuit pattern 20 is formed in the circuit pattern formation region 13 at the center of the translucent mask substrate 11. A first repetitive pattern 71 and a second repetitive pattern 72 are formed in the adjacent region 15 adjacent to the outer periphery of the circuit pattern forming region 13 and forming a multiple exposure region.

  The first repetitive pattern 71 is formed in the first region portion 15 a facing each side of the mask substrate 11 in the adjacent region 15, and the second repetitive pattern 72 is formed in the mask substrate 11 in the adjacent region 15. Are formed in the second region portion 15b of the corner portion facing the four corner portions. The first and second repetitive patterns 71 and 72 are formed in a hole shape by selectively removing a part of the semi-transmissive film 12 having the transmittance T.

  Next, as in the case of the first embodiment, the first repetitive pattern 71 is configured to be lower than the transmittance of the semi-transmissive film 12 and larger than 0 at the time of exposure. On the other hand, the design condition for configuring the second repetitive pattern 72 to be lower than 1/2 of the transmittance of the semi-transparent film 12 and larger than 0 at the time of exposure will be described. To do.

The pattern pitch of the first repeating pattern 71 and the second repeating pattern 72 in the X-axis direction in FIG. 12 is p _x , the opening dimension is s _x , the pattern pitch in the Y-axis direction is p _y , and the opening dimension is s _y. The ratio of the pattern space s to the pattern pitch p (duty) a _x a _y is expressed as a _x = s _x / p _x (9)
_{a y = s y / p y} ····· (10)
It is defined as When the transmissivity T [%] of the semi-transparent film is used, the amplitudes A _0x and A _0y of the 0th-order diffracted light transmitted through the first repetitive pattern 71 and the second repetitive pattern 72 are expressed by the following equations. Can do.

A _0x = a _x (1 + T) −T (11)
A _0y = a _y (1 + T) −T (12)
Here, since the intensity of the 0th-order diffracted light changes depending on the duty ratio a of the repetitive pattern, in the first repetitive pattern 71, a dark portion having a transmissivity T of 0 that is smaller than the transmissivity T of the semi-transparent film 12 is obtained. The diffraction efficiency is set so as not to form. In the second repeated pattern 72, the diffraction efficiency is set so as not to form a dark portion having a transmittance T that is smaller than ½ of the transmittance T of the semi-transmissive film 12.

The condition that the 0 next-development light becomes smaller than the transmittance T of the semi-transparent film 12 is as follows from the above formulas (9) and (10) to the following formulas (13) and (14) in the first repetitive pattern 71. As shown, in the second repetitive pattern 72, as shown in the following formulas (15) and (16), 0 <a _x (1 + T) −T <T (13)
0 <a _y (1 + T) −T <T (14)
0 <a _x (1 + T) −T <T / 2 (15)
0 <a _y (1 + T) −T <T / 2 (16)
It is. Accordingly, in the first repeating pattern 71, as shown in the following expressions (17) and (18), and in the second repeating pattern 72, as shown in the following expressions (19) and (20), T / (1 + T) <a _x <2T / (1 + T) (17)
T / (1 + T) <a _y <2T / (1 + T) (18)
_{T / (1 + T) <} a x <3T / 2 (1 + T) ····· (19)
T / (1 + T) <a _y <3T / 2 (1 + T) (20)
It becomes.

Here, when the semi-transparent film 12 having an intensity transmittance of 6% is used, the above formulas (7), (17), and (18), and the above formulas (7), (19), and (20) are used. In the first repetitive pattern 71, 0.1967 <a _x and a _y <0.3935, and in the second repetitive pattern 72,
0.1967 <a _x and a _y <0.2951.

  Next, design conditions for configuring the first repetitive pattern 71 and the second repetitive pattern 72 so that the first-order diffracted light enters the projection lens and does not form an image during exposure will be described. As in the first embodiment, when the incident angle at which the exposure light emitted from the light source part farthest from the numerical aperture NA, the light source wavelength λ, and the optical axis enters the halftone phase shift mask is θ, Assuming an exposure apparatus whose value defined by sin θ / NA is σ, the first-order diffracted light does not enter the projection lens when the following expression is satisfied.

p _x <λ / (1 + σ) NA (21)
p _y <λ / (1 + σ) NA (22)
Accordingly, the first repetitive pattern 71 satisfies the expressions (17) and (18) and the expressions (21) and (22) at the same time, and the second repetitive pattern 72 includes the expressions (19) and (20 ) And equations (21) and (22) may be satisfied simultaneously by determining s _x , s _y , p _x , p _y , and T of the first and second repetitive patterns 71 and 72.

For example, under an ArF light source with NA = 0.92, a wavelength of about 193 nm, and under coherent illumination (σ = 0), the first and second repetitive patterns 71 satisfying the above formulas (21) and (22). , 72 and the pattern pitch _p x, _{p y,} for example, can be determined as 200 nm. Based on this condition and the conditions of the 0th-order diffracted light of the above-mentioned formulas (17) to (20), for example, in the first repetitive pattern 71, a hole pattern having an aperture size of about 60 × 60 nm and an aperture interval of about 140 nm, The second repeating pattern 72 may be configured as a hole pattern having an opening size of about 40 × 40 nm and an opening interval of about 160 nm.

  The opening region is not limited to a square shape, and the opening size and the opening interval satisfying the above conditions can be variously modified.

  When σ ≠ 0, it should be considered that the ± 1st-order diffracted light has a spread, but in the case of annular illumination, this σ corresponds to the outer periphery of the annular zone, and the second, fourth, In the case of lighting, it corresponds to a circumscribed circle. Therefore, the conditions in this embodiment are generally considered to hold.

  Note that the halftone phase shift mask in the present embodiment can be produced by a method similar to the manufacturing method in the first embodiment described above.

  Also in the present embodiment described above, similarly to the first embodiment, the transmittance of the first repeated pattern 71 is lower than the transmittance of the semi-transparent film 12 and larger than 0. By configuring the second repetitive pattern 72 so that the transmittance of the repetitive pattern is lower than 1/2 of the transmissivity of the semi-transmissive film 12 and larger than 0, The intensity of the 0th-order diffracted light transmitted through the first and second repeating patterns 71 and 72 is weakened. Further, the first-order diffracted light transmitted through the first and second repetitive patterns 71 and 72 is prevented from entering the projection lens and forming an image. Thereby, the difference of the exposure amount of the boundary part of a circuit pattern area | region and a multiple exposure area | region on a wafer can be suppressed.

(Fourth embodiment)
In the reflective photomask of the second embodiment, the fourth embodiment of the present invention is the first of the line and space shapes of the first region portion 15a and the second region portion 15b of the adjacent region 15 forming the multiple exposure region. Instead of the first and second repetitive patterns 61 and 62, the first and second repetitive patterns 71 and 72 of the lattice-shaped hole pattern of the third embodiment are used. Since the materials and structures of the glass substrate, the reflective multilayer film, the buffer layer, the absorber layer, and the light shielding film in the other reflective photomask are the same as those in the second embodiment, the description thereof is omitted.

  In addition, the reflective photomask in this embodiment can be similarly produced using the manufacturing method of the first embodiment, as in the second embodiment.

  Also in the above-described embodiment, as in the second embodiment, it can be applied to exposure using EUV light, and the exposure amount at the boundary between the circuit pattern region and the multiple exposure region on the wafer can be applied. The difference can be suppressed.

(Fifth embodiment)
Next, a method for manufacturing a semiconductor device according to the fifth embodiment of the present invention will be described with reference to FIGS. FIG. 13 is a flowchart showing the manufacturing process of the semiconductor device.

  First, a gate insulating film made of, for example, a silicon oxide film is formed on the main surface of a semiconductor wafer made of silicon (Si) single crystal by a thermal oxidation method, a radical oxidation method, or the like (step S101). On the gate insulating film, a conductive film made of, for example, low-resistance polycrystalline silicon is formed (step S102). Next, a positive resist is applied on the conductor film by, for example, a spin coating method (step S103).

  Subsequently, the semiconductor wafer is transferred to the exposure apparatus and placed on the wafer stage. Further, the above-described photomask is placed on the mask stage of the exposure apparatus (step S104).

  Next, the exposure light emitted from the light source of the exposure apparatus is irradiated to the resist on the main surface of the semiconductor wafer via the photomask, and the circuit pattern of the photomask is transferred to the resist (step S105). Here, as the exposure light, an ArF light source (wavelength of about 193 nm) is used when a transmission type halftone phase shift mask is used, and an EUV light source (wavelength of about 13.5 nm is used when a reflection type photomask is used. ) Is used.

  Next, the semiconductor wafer is unloaded from the exposure apparatus, and the resist of the semiconductor wafer is subjected to development processing (step S106), thereby forming a resist pattern on the main surface of the semiconductor wafer.

  Then, after processing the conductor film using the resist pattern as an etching mask (step S107), the resist pattern is removed to form a gate electrode made of the conductor film.

  Subsequently, the semiconductor device is completed by providing the source / drain and the wiring electrically connected thereto using a known diffusion technique, wiring technique, and the like (step S108).

  In addition, this invention is not limited to the said embodiment, In the range which does not deviate from the meaning of this invention, it can change and implement variously. For example, in each of the above-described embodiments, the first and second repeating patterns are not limited to the line-and-space pattern and the lattice pattern, but may be a checkered pattern.

The top view which showed typically the halftone type | mold phase shift mask which concerns on the 1st Embodiment of this invention. Sectional drawing of the halftone type phase shift mask cut | disconnected along the A-A 'line | wire of FIG. 1, and looked at the arrow direction. The expanded sectional view of the 1st and 2nd repeating pattern in the adjacent area | region which forms the multiple exposure area | region of FIG. FIG. 4A is a diagram for explaining a multiple exposure area when the wafer is exposed by the halftone phase shift mask of FIG. 1, FIG. 4A is a plan view of a double exposure area, and FIG. The top view which shows an area | region. Sectional drawing which showed typically the manufacturing process of the halftone type phase shift mask which concerns on the 1st Embodiment of this invention. Sectional drawing which showed typically the manufacturing process of the photomask which concerns on the 1st Embodiment of this invention. The top view which showed typically the reflection type photomask which concerns on the 2nd Embodiment of this invention. Sectional drawing of the reflective photomask cut | disconnected along the B-B 'line | wire of FIG. 7, and looked at the arrow direction. The expanded sectional view of the 1st and 2nd repeating pattern in the adjacent area | region which forms the multiple exposure area | region of FIG. Sectional drawing which showed typically the manufacturing process of the reflection type photomask which concerns on the 2nd Embodiment of this invention. Sectional drawing which showed typically the manufacturing process of the reflection type photomask which concerns on the 2nd Embodiment of this invention. FIG. 12 is a diagram schematically showing a halftone phase shift mask according to a third embodiment of the present invention, and FIG. 12 is an enlarged plan view of first and second repetitive patterns in an adjacent region forming a multiple exposure region. 9 is a flowchart showing a method for manufacturing a semiconductor device according to a fifth embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,70 Halftone phase shift mask 11, 51 Mask substrate 12 Semi-transparent film 13, 43 Circuit pattern formation area 14, 54 Peripheral area 15, 55 Adjacent area (multiple exposure formation area)
15a, 55a 1st area | region part 15b, 55b 2nd area | region part 15-1 1st adjacent area 15-2 2nd adjacent area 17, 57 Light shielding film 18, 19, 48, 49 Resist 18a, 48a Opening part 20, 60 Circuit Patterns 20a, 60a Main circuit patterns 20b, 60b Auxiliary patterns 21, 61, 71 First repeating patterns 22, 62, 72 Second repeating pattern 30 First shot area 31 Second shot area 32 Third shot area 33 Fourth Shot area 34 Double exposure area 35 Quad exposure area 40 Reflective photomask 42 Reflective multilayer film 43 Buffer layer 44 Absorber layer p Pattern pitch s Pattern-to-pattern spacing a Ratio of pattern space to pattern pitch

Claims (5)

A method of manufacturing a semiconductor device by projecting and exposing a circuit pattern formed on a photomask and transferring the circuit pattern onto a wafer,
The photomask is a planar rectangular mask substrate whose main surface is covered with a pattern forming film,
A circuit pattern provided in the pattern formation film in a circuit pattern formation region in the center of the mask substrate;
Having a repetitive pattern on the outer periphery of the circuit pattern formation region and forming a multiple exposure region on the wafer when the circuit pattern is exposed;
The transmittance or reflectance of the pattern forming film is T, the ratio of the pattern space to the pattern pitch p of the repetitive pattern is a, the numerical aperture NA, the light source wavelength λ, and the incident angle of the exposure light incident on the photomask. When using an exposure apparatus with θ and coherence factor σ,
The repeating pattern is
T / (1 + T) <a <2T / (1 + T) and
p <λ / (1 + σ) NA
A method for manufacturing a semiconductor device, characterized by simultaneously satisfying the following relationship: The repetitive pattern includes a first repetitive pattern provided on the pattern forming film in a first region portion facing each side of the mask substrate;
A second repetitive pattern provided on the pattern forming film in a second region portion facing each corner of the mask substrate;
The transmittance or reflectance of the pattern forming film is T, the ratio of the pattern space to the pattern pitch p of the first and second repetitive patterns is a, the numerical aperture NA, the light source wavelength λ, and the light incident on the photomask. When using an exposure apparatus in which the incident angle of the exposure light is θ and the coherence factor is σ,
The first repeating pattern is:
T / (1 + T) <a <2T / (1 + T) and
p <λ / (1 + σ) NA
Satisfy the relationship
The second repeating pattern is
T / (1 + T) <a <3T / 2 (1 + T) and
p <λ / (1 + σ) NA
The method of manufacturing a semiconductor device according to claim 1, wherein:   3. The method of manufacturing a semiconductor device according to claim 1, wherein the first and second repeating patterns are line patterns arranged periodically. A planar rectangular mask substrate having a main surface covered with a semi-transparent film or an absorption film and having a circuit pattern forming region provided in the center and a region adjacent to the outer periphery of the circuit pattern forming region;
A circuit pattern provided on the translucent film or absorption film in the circuit pattern formation region;
A repeating pattern,
The transmissivity or reflectance of the semi-transparent film is T, the ratio of the pattern space to the pattern pitch p of the repetitive pattern is a, the numerical aperture NA, the light source wavelength λ, and the exposure light incident on the mask substrate. When using an exposure apparatus with an angle θ and a coherence factor σ,
The repeating pattern is
T / (1 + T) <a <2T / (1 + T) and
p <λ / (1 + σ) NA
A photomask characterized by satisfying the following relationship simultaneously. The repetitive pattern includes a first repetitive pattern provided on the pattern forming film in a first region portion facing each side of the mask substrate;
A second repetitive pattern provided on the pattern forming film in a second region portion facing each corner of the mask substrate;
The transmittance or reflectance of the pattern forming film is T, the ratio of the pattern space to the pattern pitch p of the first and second repetitive patterns is a, the numerical aperture NA, the light source wavelength λ, and the light incident on the photomask. When using an exposure apparatus in which the incident angle of the exposure light is θ and the coherence factor is σ,
The first repeating pattern is:
T / (1 + T) <a <2T / (1 + T) and
p <λ / (1 + σ) NA
Satisfy the relationship
The second repeating pattern is
T / (1 + T) <a <3T / 2 (1 + T) and
p <λ / (1 + σ) NA
The photomask according to claim 4, wherein the following relationship is satisfied simultaneously.

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