JP2004172339A - Mask for exposure using extreme ultraviolet light - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain the resolution sufficiently coping with the fining tendency in the case of exposing a pattern by using extreme ultraviolet light, and to avoid defects such as a difference from line width and positional deviation of the pattern. <P>SOLUTION: An exposure mask 1 using extreme violet light for exposing a desired pattern on a body to be exposed by using the extreme violet light is configured with a stencil structure provided with an opening region 1a through which the extreme violet light made incident onto a mask surface from its vertical direction passes, and a shade area 1b for shading the extreme violet light. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a mask for exposure to ultra-short ultraviolet light corresponding to so-called ultra-short ultraviolet light, which is used in a lithography process for forming a circuit pattern of a semiconductor device.
[0002]
[Prior art]
In recent years, with the miniaturization of semiconductor devices, a resist pattern obtained by exposing and developing a resist, which is a photosensitive material applied on a wafer substrate, and a circuit pattern obtained by etching using the resist pattern as an etching mask Are tending to shrink. Further, not only the pattern width but also the pitch between patterns or the pitch between memory cells is required to be further reduced.
[0003]
Such a demand for reduction can be met by making the wavelength of light used for exposure of the resist shorter. For example, a semiconductor device having a design rule of 350 nm has a wavelength of 365 nm, a semiconductor device having a design rule of 250 nm and 180 nm has a wavelength of 248 nm, and a semiconductor device having a design rule of 130 nm and 100 nm has a wavelength of 193 nm. As the miniaturization of GaN has progressed, the wavelength of light used for exposure has been shortened, and further, ultraviolet light having a wavelength of 157 nm has been used.
[0004]
In general, it is known that the resolution based on these wavelengths is represented by a Rayleigh equation of w = k1 × (λ / NA). Here, w is the minimum width pattern to be resolved, NA is the numerical aperture of the lens of the projection optical system, and λ is the wavelength of the exposure light. Further, k1 is a process constant determined mainly by the selection of the performance of the resist and the super-resolution technique, and it is known that up to about k1 = 0.35 can be selected by using the optimum resist and the super-resolution technique. Have been. The super-resolution technique is to obtain a pattern smaller than a wavelength by selectively using ± 1st-order diffracted light of light transmitted through a mask and diffracted by a light-shielding pattern on the mask.
[0005]
According to the Rayleigh's formula, for example, the minimum pattern width that can be used when a wavelength of 157 nm is used is w = 61 nm if a lens with NA = 0.9 is used. That is, in order to obtain a pattern width smaller than 61 nm, it is necessary to use ultraviolet light having a wavelength shorter than 157 nm.
[0006]
For this reason, recently, it has been studied to use Extreme Ultra Violet (EUV) light having a wavelength around 13.5 nm as the ultraviolet light having a wavelength shorter than 157 nm. However, ultra-short ultraviolet light is strongly absorbed by any substance and has a refractive index close to 1. Therefore, when using ultra-short ultraviolet light, a reflective mask and a reflective optical system that reflect light are used instead of a light-transmitting mask and an optical system. More specifically, for example, a reflective mask and a mirror in a reflective optical system are configured based on a reflective multilayer substrate (mask blanks) having a structure in which Si (silicon) layers and Mo (molybdenum) layers are alternately laminated. (For example, see Patent Document 1). It is to be noted that the laminated structure of the reflective multilayer substrate generally has a repeating number of 40 layers.
[0007]
[Patent Document 1]
JP-A-2002-222664
[0008]
[Problems to be solved by the invention]
By the way, when a reflective mask is used, the light reflected on the mask surface must be guided to the projection optical system without interfering with the light incident on the mask. Therefore, the light incident on the mask must necessarily be obliquely incident at an angle φ with respect to the normal to the mask surface. This angle is determined by the numerical aperture NA of the lens of the projection optical system, the mask magnification m, and the size σ of the illumination light source. More specifically, for example, when a mask having a reduction magnification of 5 times is used on a wafer, in an exposure apparatus with NA = 0.3 and σ = 0.8, the light is 3.44 ± 2.75 °. It will be incident on the mask with a solid angle. When a mask having a reduction magnification of 4 times is used on a wafer, in an exposure apparatus with NA = 0.25 and σ = 0.7, light has a solid angle of 3.58 ± 2.51 °. Incident on the mask. In consideration of these solid angles, the incident angle of the exposure light incident on the mask is usually set to be around 5 °. Here, the incident angle is defined as an angle formed with a normal to the mask surface.
[0009]
However, if the incident light on the mask is obliquely incident, the direction of the projection vector of the incident light on the mask surface is horizontal to the pattern side on the mask as shown in FIG. (A)) or the image is perpendicular (see (b) in the figure), the transferred images obtained on the wafer differ from each other. Further, not only in the case of horizontal / vertical, but also in the case where the direction of the projection vector has an arbitrary angle with respect to the pattern side, the transferred image on the wafer differs depending on the angle. That is, if the angle between the projection vector and the pattern side is different, the transfer image obtained on the wafer will be different due to the so-called projection effect. The difference in the transferred images generated in this way causes a difference in the pattern contrast of each transferred image, and may cause a problem that the line width in each transferred image is different. Furthermore, the pattern center position of the transferred image is shifted, and as a result, there is a possibility that the pattern position is shifted from a desired position.
[0010]
In addition, if the angle between the projection vector and the pattern side is different, the above-described problem may be caused, and it is necessary to limit the angle of incidence of oblique incidence. This is because the amount of shift of the center of gravity on the pupil plane of the projection optical system of the diffracted light generated by the mask pattern, that is, the so-called telecentricity, is maintained within a desired value. Therefore, in the case of oblique incidence, the NA of the projection optical system must be smaller than the upper limit of about 0.25 due to the limitation of the angle of incidence.
[0011]
However, assuming that k1 = 0.60 assuming that the super-resolution technique is not used, the resolution limit when NA = 0.25 is w = 32 as apparent from the Rayleigh equation described above. .4 nm. Therefore, for example, when a size smaller than 32.4 nm is required in a gate line width requiring a small size due to a rapid progress of miniaturization of a line width, even if the ultra-short ultraviolet light has a short wavelength, It may be difficult to deal with this.
[0012]
Therefore, the present invention solves the above-mentioned drawbacks in the reflective mask when performing exposure using ultra-short ultraviolet light, and does not cause defects such as a difference in line width and a positional shift of a pattern. An object of the present invention is to provide a mask for exposure to ultra-short ultraviolet light, which can obtain a resolution that can sufficiently cope with the progress of image formation.
[0013]
[Means for Solving the Problems]
The present invention is an ultra-short ultraviolet light exposure mask devised to achieve the above object. That is, an exposure mask of ultra-short ultraviolet light for exposing a desired pattern on an object to be exposed using ultra-short ultraviolet light, which transmits ultra-short ultraviolet light incident from a direction perpendicular to the mask surface. The stencil structure includes an opening region and a light-shielding region for shielding the ultrashort ultraviolet light.
[0014]
The present invention also provides an ultra-short ultraviolet light exposure mask for exposing a desired pattern on an object to be exposed using ultra-short ultraviolet light, the ultra-short ultraviolet light being incident on the mask surface in a perpendicular direction. It is characterized by comprising a membrane structure having a transmission region for transmitting light and a light shielding region for shielding the ultrashort ultraviolet light.
[0015]
According to the mask for exposure to ultra-short ultraviolet light having the above configuration, the light-shielding region blocks the ultra-short ultraviolet light, but transmits the ultra-short ultraviolet light in the opening region or the transmission region. Therefore, even when the ultra-short ultraviolet light is incident perpendicularly to the mask surface, the desired pattern on the object is exposed due to the difference in contrast between the transmitted light in the aperture region or the transmission region and the portion shielded by the light-shielding region. Patterning can be performed. In other words, by performing normal incidence on the mask surface, it is possible to prevent the transfer image obtained on the object to be exposed from being affected by the angle of the pattern side on the mask. Furthermore, oblique incidence does not need to be performed as in the case of a reflection type mask, and ultra-short ultraviolet light only needs to be incident perpendicularly to the mask surface, so that the numerical aperture NA of the projection optical system lens is not restricted. . Therefore, for example, by setting a large numerical aperture NA, a transfer image with higher resolution can be obtained as compared with the case of oblique incidence even if the wavelength of the ultrashort ultraviolet light is the same.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an exposure mask for ultrashort ultraviolet light according to the present invention will be described with reference to the drawings.
[0017]
[First Embodiment]
Here, as a first embodiment of the present invention, an ultrashort ultraviolet light exposure mask according to the first and second aspects of the present invention will be described. The exposure mask described in the present embodiment exposes a desired pattern (for example, a circuit pattern) on an object to be exposed such as a wafer in a lithography step, which is one step in a method of manufacturing a semiconductor device, using ultra-short ultraviolet light. It is used for The “extremely short ultraviolet light” here is, for example, a wavelength shorter than the ultraviolet light used in the previous lithography process (for example, 1 nm or more and 100 nm or less) as typified by a wavelength of 13.5 nm. The following are applicable.
[0018]
FIG. 1 is a schematic diagram showing a schematic configuration example of a first embodiment of an exposure mask according to the present invention. As shown in the figure, the exposure mask 1 described in the present embodiment has a stencil structure. The stencil structure refers to a structure including an opening that transmits light and a light-shielding portion that shields light. That is, the exposure mask 1 includes the opening region 1a that transmits the ultra-short ultraviolet light and the light-shielding region 1b that shields the ultra-short ultraviolet light.
[0019]
The light-shielding region 1b has a single-layer structure made of a single material. Specifically, the light-shielding region 1b is formed of, for example, a single-layer structure of SiC (silicon carbide).
[0020]
In the exposure mask 1 configured as described above, even when the ultra-short ultraviolet light is incident perpendicularly to the mask surface, the contrast difference between the transmitted light of the opening region 1a and the portion shielded by the light shielding region 1b causes A desired pattern can be patterned on an object to be exposed such as a wafer. Therefore, it can be said that the opening region 1a transmits ultra-short ultraviolet light incident on the mask surface of the exposure mask 1 in a direction perpendicular to the mask surface. Similarly, it can be said that the light-shielding region 1b shields ultra-short ultraviolet light incident on the mask surface from the vertical direction.
[0021]
By the way, it is generally considered that the optical density in the stencil structure should be about 3 in the SEMI (Semiconductor Equipment and Materials International) standardized standard, for example. Here, the optical density (OD; Optical Density) is the ratio of the amount of transmitted light (To) to the amount of incident light (Ti) expressed as a logarithm with a base of 10 (OD = log). ₁₀ (Ti / To)).
[0022]
FIG. 2 shows a plot of the relationship between the optical density and the film thickness of the main material used for the transmission type mask. Here, Si, SiC (silicon carbide) and TaN (tantalum nitride) are mentioned as the main materials. Note that the relationship between the optical density and the film thickness shown in the figure is uniquely determined for each material.
[0023]
As is clear from the relationship shown in FIG. 2, in the exposure mask 1 in which the light-shielding region 1b has a single-layer structure of SiC, in order to secure the optical density 3, the thickness of the light-shielding region 1b is set to about 1550 nm. Should be set to. That is, the thickness of the light-shielding region 1b is specified based on the type of material forming the light-shielding region 1b and the value of the optical density of the exposure mask 1.
[0024]
Such an exposure mask 1 may be manufactured by the following procedure. For example, a SiC film is formed to a thickness of 1550 nm on a Si substrate prepared in advance by using a normal pressure CVD (chemical vapor deposition) method, a low pressure CVD method, a plasma CVD method, or a sputtering method. Thereafter, the Si substrate is removed by back etching, and a resist is applied on the SiC film. Then, etching is performed after a pattern is formed on the resist using an electron beam or the like. Thereby, the exposure mask 1 having the above-described configuration can be obtained.
[0025]
Next, the light intensity distribution obtained with the exposure mask 1 having the above configuration, that is, the exposure mask 1 having the stencil mask structure in which the light-shielding region 1b has a single-layer structure of SiC will be described. FIG. 3 is an explanatory view showing a specific example of a light intensity distribution when a dense pattern of 120 nm on a 4 × mask (30 nm in coordinates on a wafer) is transferred onto a wafer. FIG. 4 is a diagram illustrating 120 nm on a 4 × mask (coordinates on a wafer). FIG. 5 is an explanatory diagram showing a specific example of light intensity distribution when an isolated space pattern of 30 nm is transferred onto a wafer. FIG. 5 shows a case where a dense pattern of 80 nm (20 nm in coordinates on a wafer) is transferred onto a wafer on a 4 × mask. FIG. 6 is an explanatory diagram showing a specific example of the light intensity distribution when an isolated space pattern of 80 nm (20 nm in coordinates on the wafer) on a 4 × mask is transferred onto a wafer. is there.
[0026]
In each example, the light intensity distribution when NA = 0.25, NA = 0.30, NA = 0.40, NA = 0.50 and NA = 0.6 is illustrated. The reason why the plurality of NAs are illustrated is that, in the exposure mask 1, the optical axis direction of the ultra-short ultraviolet light incident on the mask surface may be vertical. This is because there is no restriction. Note that NA = 0.25 is the same value as the NA used in the case of conventional oblique incidence.
[0027]
According to each of these figures, it can be seen that in each case, the peak value (maximum value) of the light intensity in the light intensity distribution increases as the value of NA increases. That is, as the NA increases, the maximum value of the light intensity also increases.
[0028]
Next, the pattern contrast on the wafer obtained by the above light intensity distribution will be described. FIG. 7 is an explanatory diagram showing a specific example of the pattern contrast when each pattern in FIGS. 3 to 6 is transferred onto a wafer. In the illustrated example, the pattern contrast is represented by using NILS (Normalized Image Log-Slope). NILS is defined as w × ln (I) / dx, where w is the pattern width, I is the light intensity, and x is the pattern coordinates. In the drawing, NILS indicates a value obtained at a pivotal point. The pivot point refers to a point in the light intensity distribution where the line width does not change even when defocused. Taking FIG. 6 as an example, a light intensity of 0.25 corresponds to a pivot point.
[0029]
According to the example shown in FIG. 7, it can be seen that the pattern contrast is significantly improved with an increase in the value of NA. That is, the larger the NA, the better the pattern contrast.
[0030]
As described above, the exposure mask 1 described in the present embodiment has a stencil structure including the opening region 1a and the light-shielding region 1b. Since the desired pattern can be patterned on the wafer by vertical incidence, there is no restriction of NA unlike the case of the conventional oblique incidence, and the maximum value of the light intensity increases as the value of NA increases. It is possible to achieve a resolution of a pattern of 20 nm on a wafer, which was difficult to achieve with a reflective mask. Further, the pattern contrast also increases.
[0031]
Specifically, in the conventional reflection type mask, as described above, if k1 is set to about 0.60 on the assumption that the super-resolution technique is not used, the resolution when NA = 0.25 is set. The limit is w = 32.4 nm. However, in the exposure mask 1 according to the present embodiment, there is no restriction on the NA unlike the case of oblique incidence, so that the NA can be set to be larger than 0.25. That is, since the stencil structure allows the NA to be set large, for example, in the case of k1 = 0.60 without using the super-resolution technique in the Rayleigh equation, if the NA is 0.60, 13. A resolution of 5 nm can be obtained, and as a result, a size smaller than the resolution limit w = 32.4 nm of the reflective mask can be formed.
[0032]
Further, since the exposure mask 1 described in the present embodiment has a stencil structure, even if fine particles, dirt, etc. adhere to the mask surface, the fine particles, dirt, etc. adversely affect the transfer performance. Can be avoided. That is, even if fine particles and dirt adhere to the mask surface, the transfer performance is not affected at all.
[0033]
Further, since the exposure mask 1 described in the present embodiment has a stencil structure, the optical axis direction of the ultra-short ultraviolet light may be perpendicular to the mask surface, and the oblique incidence in the conventional reflective mask may be different. The evil can be eliminated. That is, depending on whether the direction of the projection vector of the incident light is horizontal or vertical with respect to the pattern side on the mask, which is a drawback of the reflection type mask, or whether or not an arbitrary angle is provided, etc., on the wafer. There is no problem that the obtained transfer images are different. Further, there is no problem that the pattern position shifts from a desired position due to the shift of the pattern center position of the transferred image.
[0034]
[Second embodiment]
Next, as a second embodiment of the present invention, an ultrashort ultraviolet light exposure mask according to the first and third aspects of the present invention will be described. Note that, here, the description will be given mainly focusing on the differences from the above-described first embodiment.
[0035]
FIG. 8 is a schematic diagram showing a schematic configuration example of the exposure mask according to the second embodiment of the present invention. As shown in the figure, the exposure mask 2 described in the present embodiment has the opening region 2a that transmits the ultra-short ultraviolet light and the shielding mask for the ultra-short ultraviolet light, as in the case of the above-described first embodiment. Although the light-shielding region 2b has a stencil structure including a light-shielding region 2b, the light-shielding region 2b has a laminated structure made of a plurality of materials, unlike the case of the first embodiment. Specifically, for example, the light shielding region 2b is configured by a laminated structure in which the Si layer 21 and the TaN layer 22 are laminated. Among them, the Si layer 21 mainly functions as a layer for supporting the mask structure. Further, the TaN layer 22 mainly functions as a layer for shielding extremely short ultraviolet light.
[0036]
Also in the exposure mask 2 configured as described above, the opening region 2a and the light shielding region 2b can correspond to the perpendicular incidence of the extremely short ultraviolet light on the mask surface. That is, the opening region 2a transmits the ultra-short ultraviolet light incident on the mask surface of the exposure mask 2 from the vertical direction, and the light-shielding region 2b transmits the ultra-short ultraviolet light incident on the mask surface from the vertical direction. It can be said that it shields the light.
[0037]
Further, as with the first embodiment, the exposure mask 2 only needs to ensure an optical density of about 3 in the stencil structure. In this exposure mask 1, in order to ensure the optical density 3, the thickness of the TaN layer 22 that shields ultrashort ultraviolet light is set to about 240 nm based on the relationship of FIG. 2 described in the first embodiment. Should be set to. On the other hand, the thickness of the Si layer 21 supporting the mask structure may be arbitrarily set without depending on the value of the optical density in the exposure mask 2, but is preferably 500 nm or more in order to maintain the mask structure.
[0038]
Such an exposure mask 2 may be manufactured by the following procedure. For example, an Si layer 21 is formed to a thickness of 500 nm on a glass substrate prepared in advance by using a normal pressure CVD method, a low pressure CVD method, a plasma CVD method, or a sputtering method, and a TaN layer 22 is further formed thereon by 240 nm. Formed with a thickness of Thereafter, the glass substrate is removed by back etching, and a resist is applied on the TaN layer 22. Then, after forming a pattern on the resist using an electron beam or the like, the Si layer 21 and the TaN layer 22 are etched. Thus, the exposure mask 2 having the above-described configuration can be obtained. At this time, the internal stress control in the TaN layer 22 may be performed by controlling the film forming conditions of the TaN layer 22, but may be performed by appropriately combining an annealing method, an ion irradiation method, or the like. Absent.
[0039]
Next, the light intensity distribution obtained by the exposure mask 2 having the above-described configuration, that is, the light intensity distribution obtained by the exposure mask 2 having the stencil mask structure in which the light shielding region 2b has a laminated structure of the Si layer 21 and the TaN layer 22 will be described. FIG. 9 is an explanatory diagram showing a specific example of the light intensity distribution when a dense pattern of 120 nm on a 4 × mask (30 nm in coordinates on a wafer) is transferred onto a wafer, and FIG. 10 is 120 nm on a 4 × mask (coordinates on a wafer). FIG. 11 is an explanatory diagram showing a specific example of light intensity distribution when an isolated space pattern of 30 nm is transferred onto a wafer. FIG. 11 shows a case where a dense pattern of 80 nm (20 nm in coordinates on the wafer) is transferred onto a 4 × mask on the wafer. FIG. 12 is an explanatory diagram showing a specific example of the light intensity distribution when an isolated space pattern of 80 nm (20 nm in coordinates on the wafer) on a 4 × mask is transferred onto a wafer. is there.
[0040]
According to each of these figures, it can be seen that in each case, the peak value (maximum value) of the light intensity in the light intensity distribution increases as the value of NA increases. That is, as the NA increases, the maximum value of the light intensity also increases.
[0041]
Next, the pattern contrast on the wafer obtained by the above light intensity distribution will be described. FIG. 13 is an explanatory diagram showing a specific example of a pattern contrast when each pattern in FIGS. 9 to 12 is transferred onto a wafer. Also in the example of the figure, the pattern contrast is expressed by using NILS, and NILS indicates a value obtained at a pivotal point.
[0042]
According to the example shown in FIG. 13, it can be seen that the pattern contrast is significantly improved with an increase in the value of NA. That is, the larger the NA, the better the pattern contrast.
[0043]
As described above, the exposure mask 2 described in the present embodiment, as in the case of the first embodiment described above, allows vertical incidence on the mask surface even when using ultra-short ultraviolet light. Therefore, there is no restriction on NA, and it is possible to achieve the resolution of a pattern of 20 nm on the wafer, and the pattern contrast is also increased. Furthermore, it is possible to prevent adverse effects on transfer performance even if minute particles, dirt, etc. adhere to the mask surface, and also to eliminate the adverse effects of oblique incidence (such as displacement of a transferred image on a wafer). Become.
[0044]
[Third Embodiment]
Next, as a third embodiment of the present invention, a description will be given of an ultrashort ultraviolet light exposure mask according to the fifth and sixth aspects of the present invention. Note that also here, the description will be focused mainly on the differences from the above-described first or second embodiment.
[0045]
FIG. 14 is a schematic diagram showing a schematic configuration example of the exposure mask according to the third embodiment of the present invention. As shown in the figure, the exposure mask 3 described in the present embodiment has a membrane structure. The membrane structure, unlike the stencil structure described in the first or second embodiment, refers to a structure in which a light transmitting portion is not an opening but a light transmitting film. That is, the exposure mask 3 includes the transmission region 3a that transmits the ultra-short ultraviolet light and the light-shielding region 3b that blocks the ultra-short ultraviolet light.
[0046]
Of these, the transmission region 3a needs to transmit extremely short ultraviolet light. Therefore, as the membrane material forming the transmission region 3a, for example, it is conceivable to use Si having a large transmittance of ultra-short ultraviolet light. On the other hand, since the light-shielding region 3b only needs to shield the ultrashort ultraviolet light, it is conceivable to form the light-shielding region 3b with a single-layer structure made of a single material using, for example, TaN. However, even if the light-shielding region 3b has a single-layer structure, it is assumed that the light-shielding region 3b is laminated on Si forming the transmission region 3a as shown in the example in the state where the exposure mask 3 is formed.
[0047]
Also in the exposure mask 3 configured as described above, the transmission region 3a and the light-shielding region 3b can correspond to the vertical incidence of the extremely short ultraviolet light on the mask surface. That is, the transmissive region 3a transmits the ultra-short ultraviolet light incident on the mask surface of the exposure mask 3 from the perpendicular direction, and the light-shielding region 3b transmits the ultra-short ultraviolet light incident on the mask surface from the perpendicular direction. It can be said that it shields the light.
[0048]
Further, as with the first or second embodiment, the exposure mask 3 only needs to secure an optical density of about 3 in the membrane structure. In this exposure mask 3, in order to secure the optical density 3, the thickness of the TaN layer forming the light shielding region 3b is set to about 240 nm based on the relationship of FIG. 2 described in the first embodiment. do it. On the other hand, the thickness of the Si layer forming the transmission region 3a needs to be a thickness capable of transmitting ultra-short ultraviolet light. However, the thickness of the Si layer may be set to about 500 nm since the Si layer also functions as a layer supporting the mask structure. Conceivable.
[0049]
Such an exposure mask 3 may be manufactured by the following procedure. For example, on a glass substrate prepared in advance, a normal-pressure CVD method, a low-pressure CVD method, a plasma CVD method, or a sputtering method is used to form a 500-nm-thick Si layer serving as a membrane material for forming the transmission region 3a. Further, a TaN layer for forming the light shielding region 3b is formed thereon with a thickness of 240 nm. Thereafter, the glass substrate is removed by back etching, and a resist is applied on the TaN layer. Then, after forming a pattern on the resist using an electron beam or the like, etching is performed only on the TaN layer. Thereby, the exposure mask 3 having the above-described configuration can be obtained. At this time, the internal stress of the TaN layer may be controlled by controlling the film forming conditions of the TaN layer. Alternatively, an annealing method, an ion irradiation method, or the like may be used as appropriate.
[0050]
Next, the light intensity distribution obtained with the exposure mask 3 having the above-described configuration, that is, the exposure mask 3 having the membrane mask structure including the transmission region 3a and the light shielding region 3b will be described. FIG. 15 is an explanatory view showing a specific example of a light intensity distribution in which a dense pattern of 120 nm (30 nm in coordinates on a wafer) is transferred onto a 4 × mask, and FIG. 16 is 120 nm on a 4 × mask (30 nm in coordinates on a wafer). FIG. 17 is an explanatory view showing a specific example of a light intensity distribution in which an isolated space pattern is transferred onto a wafer. FIG. 17 is a diagram showing a light intensity distribution in which an isolated line pattern of 120 nm (30 nm in coordinates on the wafer) is transferred onto a wafer. It is explanatory drawing which shows a specific example. FIG. 18 is an explanatory view showing a specific example of a light intensity distribution in which a dense pattern of 80 nm on a 4 × mask (20 nm in a coordinate on a wafer) is transferred onto a wafer, and FIG. 19 is 80 nm on a 4 × mask (in a coordinate on a wafer). FIG. 20 is an explanatory diagram showing a specific example of a light intensity distribution in which an isolated space pattern of 20 nm is transferred onto a wafer. FIG. 20 is a light intensity in which an isolated line pattern of 80 nm (20 nm in coordinates on a wafer) is transferred onto a wafer on a 4 × mask. It is explanatory drawing which shows the specific example of distribution.
[0051]
According to each of these figures, it can be seen that in each case, the peak value (maximum value) of the light intensity in the light intensity distribution increases as the value of NA increases. That is, as the NA increases, the maximum value of the light intensity also increases.
[0052]
Next, the pattern contrast on the wafer obtained by the above light intensity distribution will be described. FIG. 21 is an explanatory diagram showing a specific example of the pattern contrast when each pattern in FIGS. 15 to 20 is transferred onto a wafer. Also in the example of the figure, the pattern contrast is expressed by using NILS, and NILS indicates a value obtained at a pivotal point.
[0053]
According to the example shown in FIG. 21, it can be seen that the pattern contrast is also significantly improved with an increase in the value of NA. That is, the larger the NA, the better the pattern contrast. Moreover, even with the exposure mask 3 having the membrane structure, the pattern contrast is no different from that of the stencil structure in the first or second embodiment. That is, in the exposure mask 3 having the membrane structure, since the ultra-short ultraviolet light passes through the transmission region 3a, the absorption of the ultra-short ultraviolet light in the transmission region 3a occurs. The increase only has no effect on the pattern transfer performance.
[0054]
As described above, also in the exposure mask 3 described in the present embodiment, similarly to the case of the above-described first or second embodiment, even when the ultra-short ultraviolet light is used, the exposure is performed on the mask surface. Since normal incidence can be performed, there is no restriction on NA, and a 20-nm pattern on the wafer can be resolved, and the pattern contrast also increases. Furthermore, it is possible to prevent adverse effects on transfer performance even if minute particles, dirt, etc. adhere to the mask surface, and also to eliminate the adverse effects of oblique incidence (such as displacement of a transferred image on a wafer). Become.
[0055]
As described above, the exposure masks 1, 2, and 3 of the above-described first to third embodiments are configured with a stencil structure or a membrane structure, so that the case where ultrashort ultraviolet light is used is used. Also, normal incidence can be performed on the mask surface. That is, conventionally, when using ultra-short ultraviolet light, there was only an idea that oblique incidence was performed using a reflective mask and a reflective optical system due to the characteristics of the ultra-short ultraviolet light, The exposure masks 1, 2, and 3 of the first to third embodiments are configured based on a novel idea of applying a stencil structure or a membrane structure even when using ultrashort ultraviolet light. , It is possible to make the ultrashort ultraviolet light incident perpendicular to the mask surface. Therefore, it is possible to increase the value of NA of the projection optical system as compared with the case of performing oblique incidence, and it is possible to sufficiently increase the miniaturization without causing problems such as a difference in line width and a displacement of a pattern. Corresponding resolution can be obtained.
[0056]
Here, the improvement of the resolution will be described with a specific example. FIGS. 22 to 24 show patterns of 120 nm, 80 nm, and 40 nm (30 nm, 20 nm, and 10 nm, respectively, on a wafer) on a 4 × mask using a conventional reflection mask under the condition of NA = 0.25. FIG. 4 is an explanatory diagram showing a specific example of a light intensity distribution when the image is transferred to a spot. According to these examples, the conventional reflection type mask can only resolve a dense pattern and an isolated space pattern up to 120 nm on a 4 × mask (30 nm on a wafer). Further, an isolated line pattern can be resolved only up to 80 nm on a 4 × mask (20 nm on a wafer). In addition, a pattern shift is observed due to the oblique effect caused by the obliquely incident light.
[0057]
On the other hand, in the exposure masks 1, 2, and 3 of the first to third embodiments, the following improvement in resolution can be obtained. FIGS. 25 to 27 show, using the exposure masks 1, 2, and 3 of the first to third embodiments, 40 nm on a quadruple mask (10 nm in coordinates on a wafer) under the condition of NA = 0.6. FIG. 4 is an explanatory diagram showing a specific example of a light intensity distribution when a dense pattern, an isolated space pattern, and an isolated line pattern are transferred onto a wafer. As is clear from these figures, when NA = 0.6, both the dense pattern, the isolated space pattern, and the isolated line pattern are 40 nm (4 nm) on the 4 × mask without using the super-resolution technique. (10 nm) pattern resolution on the wafer can be achieved. In other words, the use of the exposure masks 1, 2, and 3 of the first to third embodiments makes it possible to satisfactorily expose the dense pattern, the isolated space pattern, and the isolated line pattern without using the super-resolution technique. A remarkable effect that a pattern can be formed in the vicinity can be obtained.
[0058]
In the first to third embodiments, the present invention has been described with preferred specific examples. However, it is needless to say that the present invention is not limited to these embodiments. In particular, the materials, film thicknesses, and the like described in the first to third embodiments are merely specific examples.
[0059]
Further, in the first to third embodiments, the case where the material, the film thickness, and the like of the light shielding regions 1b, 2b, 3b are set in order to secure the optical density 3 has been described as an example. It is known that two or more optical densities corresponding to light need to be ensured (for example, three authors such as Pei-Yang Yan, "TNEU Mask Fabrication and Character"). See “TaN EUVL Mask Fabrication and Characterization”, (USA), Proceedings of SPIE, Vol. 4343, 2001, pp. 409-414. Therefore, the material, film thickness and the like of the light-shielding regions 1b, 2b, 3b are not limited to those capable of securing the optical density 3, and the optical density is 2 or more as in the invention according to claim 4 or 7. What is necessary is just to be formed so that it may become.
[0060]
【The invention's effect】
As described above, the exposure mask for ultra-short ultraviolet light according to the present invention has a stencil structure or a membrane structure. Therefore, the value of NA of the projection optical system can be made larger than that of the reflective mask. Therefore, it is possible to realize a resolution that cannot be obtained by the conventional reflection type mask. Moreover, since vertical incidence can be performed, there is no occurrence of pattern displacement which is a drawback of the reflective mask. Furthermore, since the structure is such that ultra-short ultraviolet light is transmitted, even if fine particles and dirt adhere to the mask surface, the transfer performance is not adversely affected.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a schematic configuration example of an exposure mask according to a first embodiment of the present invention.
FIG. 2 is an explanatory diagram showing a relationship between an optical density and a film thickness of a main material used for a transmission mask.
3 is an explanatory diagram of a light intensity distribution by the exposure mask of FIG. 1, and is a specific example of a light intensity distribution when a dense pattern of 120 nm (30 nm in coordinates on a wafer) on a 4 × mask is transferred onto a wafer; FIG.
4 is an explanatory diagram of a light intensity distribution by the exposure mask of FIG. 1, and is a specific example of a light intensity distribution when an isolated space pattern of 120 nm on a 4 × mask (coordinates on a wafer is 30 nm) is transferred onto a wafer; It is a figure showing an example.
5 is an explanatory diagram of a light intensity distribution by the exposure mask of FIG. 1, and is a specific example of a light intensity distribution when a dense pattern of 80 nm (20 nm in coordinates on a wafer) on a 4 × mask is transferred onto a wafer; FIG.
6 is an explanatory diagram of a light intensity distribution by the exposure mask of FIG. 1, and is a specific example of a light intensity distribution when an isolated space pattern of 80 nm (20 nm in coordinates on a wafer) on a 4 × mask is transferred onto a wafer. It is a figure showing an example.
FIG. 7 is an explanatory diagram showing a specific example of a pattern contrast when each pattern in FIGS. 3 to 6 is transferred onto a wafer.
FIG. 8 is a schematic diagram illustrating a schematic configuration example of an exposure mask according to a second embodiment of the present invention.
9 is an explanatory diagram of a light intensity distribution by the exposure mask of FIG. 8, and is a specific example of a light intensity distribution when a dense pattern of 120 nm (30 nm in coordinates on a wafer) on a 4 × mask is transferred onto a wafer; FIG.
10 is an explanatory diagram of a light intensity distribution by the exposure mask of FIG. 8, and is a specific example of a light intensity distribution when an isolated space pattern of 120 nm (30 nm in coordinates on a wafer) on a 4 × mask is transferred onto a wafer. It is a figure showing an example.
11 is an explanatory diagram of a light intensity distribution by the exposure mask of FIG. 8, and is a specific example of a light intensity distribution when a dense pattern of 80 nm (20 nm in coordinates on a wafer) on a 4 × mask is transferred onto a wafer; FIG.
12 is an explanatory diagram of a light intensity distribution by the exposure mask of FIG. 8, and is a specific example of a light intensity distribution when an isolated space pattern of 80 nm (20 nm in coordinates on a wafer) on a 4 × mask is transferred onto a wafer. It is a figure showing an example.
FIG. 13 is an explanatory diagram showing a specific example of a pattern contrast when each pattern in FIGS. 9 to 12 is transferred onto a wafer.
FIG. 14 is a schematic view showing a schematic configuration example of an exposure mask according to a third embodiment of the present invention.
15 is an explanatory diagram of a light intensity distribution by the exposure mask of FIG. 14, and is a specific example of a light intensity distribution when a dense pattern of 120 nm (30 nm in coordinates on a wafer) on a 4 × mask is transferred onto a wafer; FIG.
16 is an explanatory diagram of a light intensity distribution by the exposure mask of FIG. 14, and is a specific example of a light intensity distribution when an isolated space pattern of 120 nm (30 nm in coordinates on a wafer) on a 4 × mask is transferred onto a wafer. It is a figure showing an example.
17 is an explanatory diagram of light intensity distribution by the exposure mask of FIG. 14, and is a specific light intensity distribution when an isolated line pattern of 120 nm (30 nm in coordinates on a wafer) on a 4 × mask is transferred onto a wafer; It is a figure showing an example.
18 is an explanatory diagram of a light intensity distribution by the exposure mask of FIG. 14, and is a specific example of a light intensity distribution when a dense pattern of 80 nm (20 nm in coordinates on a wafer) on a 4 × mask is transferred onto a wafer; FIG.
19 is an explanatory diagram of a light intensity distribution by the exposure mask of FIG. 14, and is a specific example of a light intensity distribution when an isolated space pattern of 80 nm (20 nm in coordinates on a wafer) on a 4 × mask is transferred onto a wafer. It is a figure showing an example.
20 is an explanatory diagram of a light intensity distribution by the exposure mask of FIG. 14, and is a specific example of a light intensity distribution when an isolated line pattern of 80 nm (20 nm in coordinates on a wafer) on a 4 × mask is transferred onto a wafer; It is a figure showing an example.
FIG. 21 is an explanatory diagram showing a specific example of pattern contrast when each pattern in FIGS. 15 to 20 is transferred onto a wafer.
FIG. 22 is a specific example of a light intensity distribution when a 120-nm pattern (30 nm in coordinates on a wafer) is transferred onto a wafer using a conventional reflective mask under the condition of NA = 0.25 on a 4 × mask. FIG.
FIG. 23 shows a specific example of light intensity distribution when a pattern of 80 nm on a 4 × mask (20 nm in coordinates on a wafer) is transferred onto a wafer using a conventional reflective mask under the condition of NA = 0.25. FIG.
FIG. 24 is a specific example of light intensity distribution when a pattern of 40 nm (10 nm in coordinates on a wafer) is transferred onto a 4 × mask under the condition of NA = 0.25 using a conventional reflective mask. FIG.
25 is a view showing a state where NA = 0.6, and a dense pattern of 40 nm (10 nm in coordinates on a wafer) on a 4-times mask was transferred onto a wafer using the exposure masks of FIGS. 1, 8 and 14; FIG. 9 is an explanatory diagram showing a specific example of a light intensity distribution in the case.
FIG. 26 is a view showing an example in which an isolated space pattern of 40 nm (10 nm in coordinates on a wafer) on a 4-fold mask is transferred onto a wafer under the condition of NA = 0.6 using the exposure masks of FIGS. FIG. 7 is an explanatory diagram showing a specific example of a light intensity distribution in the case where the light intensity distribution is performed.
FIG. 27 is a view showing an example in which an isolated line pattern of 40 nm (10 nm in coordinates on a wafer) on a 4 × mask is transferred onto a wafer using the exposure masks of FIGS. 1, 8 and 14 under the condition of NA = 0.6. FIG. 7 is an explanatory diagram showing a specific example of a light intensity distribution in the case where the light intensity distribution is performed.
FIG. 28 is an explanatory diagram showing an example of a relationship between a projection vector and a mask pattern side.
[Explanation of symbols]
1,2,3 ... exposure mask, 1a, 2a ... open area, 1b, 2b, 3b ... light shielding area, 3a ... transmission area

Claims (7)

An ultra-short ultraviolet light exposure mask for exposing a desired pattern on the object to be exposed using ultra-short ultraviolet light,
An ultra-short ultraviolet light characterized by being constituted by a stencil structure including an opening region for transmitting ultra-short ultraviolet light incident on the mask surface from a perpendicular direction and a light-shielding region for shielding the ultra-short ultraviolet light. Light exposure mask. 2. The exposure mask according to claim 1, wherein the light-shielding region has a single-layer structure made of a single material. 2. The mask according to claim 1, wherein the light-shielding region has a laminated structure made of a plurality of materials. 2. The exposure mask according to claim 1, wherein the light-shielding region is formed to have an optical density of 2 or more. An ultra-short ultraviolet light exposure mask for exposing a desired pattern on the object to be exposed using ultra-short ultraviolet light,
An ultra-short ultraviolet light characterized by being constituted by a membrane structure having a transmission region for transmitting ultra-short ultraviolet light incident on the mask surface in a perpendicular direction and a light-shielding region for shielding the ultra-short ultraviolet light. Light exposure mask. The exposure mask according to claim 5, wherein the light-shielding region has a single-layer structure made of a single material. The mask for exposure to ultra-short ultraviolet light according to claim 5, wherein the light shielding region is formed so as to have an optical density of 2 or more.

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