JP2003318094A - Reflector for aligner, aligner, and semiconductor device manufactured by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aligner having a multilayer film reflector in the optical system, with reflectance improved for radiating light in the wavelength domain of UV or less and with resolving power consequently improved in the projection optical system, and to provide a semiconductor device. <P>SOLUTION: A reflector 1 for an aligner is a layered body 50 wherein a periodic structure 100 is layered on a substrate 5 and, in the periodic structure 100, high-refraction layers 10 and low-refraction layers 11 are periodically and alternately arranged in layers, composed of mediums each presenting different refraction to different exposing lights. A period in the periodic structure 100 is a pair of a high-refraction layer 10 and a low-refraction layer 11. The thickness of a period in the periodic structure 100 is so adjusted that it corresponds to an integral multiplication of half (λa/2) the average wavelength λa of an exposing light in each of the mediums constituting the high-refraction layer 10 and the low-refraction layer 11. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflector for an exposure apparatus, an exposure apparatus, and a semiconductor device manufactured by using the same, and particularly for an exposure apparatus suitable for exposure light having a short wavelength in the ultraviolet wavelength range or shorter. The present invention relates to a reflecting mirror, an exposure apparatus, and a semiconductor device manufactured using them.

[0002]

2. Description of the Related Art A technique using an exposure apparatus is generally used as a technique for forming an element pattern corresponding to the device characteristics on a semiconductor element device such as a semiconductor integrated circuit element or an optical integrated circuit element. Further, as the exposure device, a mask pattern of a mask pattern layer, which is mainly composed of a light source, an illumination optical system, a mask stage, a projection optical system, and a wafer stage, which is a prototype of an element pattern formed on the mask stage, A reduction projection type in which reduction transfer is performed on a wafer stage is widely used.

In such an exposure apparatus, it is important to reduce and transfer a sharp mask pattern onto a wafer stage. Therefore, it is required to increase the resolution of the optical system that constitutes the exposure apparatus. Further, with the recent increase in integration and density of semiconductor devices, improvement in resolution is an essential requirement for forming semiconductor devices. Examples of methods for improving the resolution include shortening the wavelength of exposure light obtained from a light source and increasing the numerical aperture of the projection optical system.

However, an increase in the numerical aperture of the projection optical system leads to a decrease in the depth of focus. Therefore, at present, with the numerical aperture set to the extent that a practical depth of focus is secured, it is possible to shorten the wavelength of exposure light. Has been. To shorten the wavelength, the h-line (λ = 405 nm) and i-line (λ = 365n) of a mercury lamp are used.
mF), KrF excimer laser (λ = 248n
m) as a light source has been put to practical use, and further, an ArF excimer laser (λ = 193n) is used.
m) or using soft X-rays (λ to 30 nm) using a laser plasma X-ray source as a light source has been variously studied.

Further, when the wavelength of the exposure light in the near-ultraviolet wavelength region or less is shortened as described above, the decrease in the transmittance of the optical lens poses a problem. Therefore, the illumination optical system and the projection optical system are better than the reflective optical system. Composed. In such a reflection type optical system, a reflection mirror using a metal thin film typified by Al is generally used.

[0006]

However, even in the reflecting mirror using the above-mentioned metal thin film, there is a problem that the reflectance is lowered in the short wavelength region where the wavelength region used for the exposure light is the ultraviolet wavelength region or less. Becomes Therefore, it has been proposed to alternately stack two types of media having different refractive indices with respect to exposure light and use a multilayer film reflecting mirror utilizing multiple reflection. However, even in such a multilayer-film reflective mirror, it is necessary to improve its reflectance.

If the reflectance of the multilayer film reflecting mirror used in the reflection type optical system with respect to the exposure light is not sufficient, the intensity of the exposure light will be excessively attenuated as it propagates through the optical system. As a result, a reduction in throughput occurs when the mask pattern, which is the prototype of the element pattern formed on the mask stage, is transferred to the wafer stage in a reduced size. In addition, it is not possible to increase the number of multilayer film reflecting mirrors that make up the projection optical system, and the increase in the numerical aperture of the projection optical system is suppressed by the design, which in turn improves the resolution of the projection optical system. Will be suppressed. Moreover,
In the multi-layered film reflecting mirror, the energy resulting from the extinction of the exposure light causes a problem of accelerating the deterioration speed of the multi-layered film reflecting mirror. So far, the problems of the multilayer film reflecting mirror used in the reflection type optical system have been described, but the same can be said for the mask pattern layer forming the mask pattern formed on the wafer stage. This is because this mask pattern layer also generally has a laminated structure similar to that of a multilayer-film reflective mirror using multiple reflection in order to improve the reflectance with respect to exposure light.
In the present specification, a laminated structure similar to this multilayer film reflecting mirror is also called a multilayer film reflecting mirror.

As described above, in order to respond to the miniaturization of the element pattern of the semiconductor device, to shorten the exposure light to improve the resolution of the optical system constituting the exposure apparatus,
An issue is to improve the reflectance of the multilayer-film reflective mirror used in the optical system with respect to the exposure light. Further, also in the multilayer-film reflective mirror included in the mask pattern layer forming the mask pattern, improving the reflectance with respect to the exposure light is a problem similarly to the optical system.

The present invention has been made in consideration of the above problems. That is, the present invention provides a mask pattern layer formed on a mask stage constituting an exposure apparatus, a multilayer mirror for an exposure apparatus used in an optical system such as an illumination optical system and a projection optical system, and a reflector for the exposure apparatus. In an exposure apparatus having a reflection mirror for an exposure apparatus, and a semiconductor device in which an element pattern is manufactured using the exposure apparatus, exposure light,
In particular, a reflecting mirror for an exposure apparatus that can improve the reflectance with respect to exposure light in the ultraviolet wavelength region or less, and an exposure apparatus that can improve the resolution in the projection optical system accompanying it.
Moreover, it is an object of the present invention to provide a semiconductor device capable of miniaturizing an element pattern and improving its accuracy.

[0010]

A reflecting mirror for an exposure apparatus of the present invention for solving the above-mentioned problems is a mask forming a mask pattern of exposure light obtained from a light source through an illumination optical system. An exposure apparatus that illuminates a first substrate that serves as a mask stage on which a pattern layer is formed and reduces and transfers an image of the mask pattern onto a second substrate that serves as a wafer stage via a projection optical system. Which is used as a multilayer-film reflective mirror in at least one of the mask pattern layer, the illumination optical system, and the projection optical system, which comprises two or more kinds of media having different refractive indexes with respect to the exposure light. A plurality of periodically arranged periodic structures has a laminated body laminated on a substrate, and the periodic structure has a one-dimensional photonic coupling to the exposure light. As the layer thickness of one cycle is characterized by comprising it has been adjusted.

The reflecting mirror for an exposure apparatus according to the present invention is a multilayer film reflecting mirror used in any one of a mask pattern layer, an illumination optical system and a projection optical system constituting a reduction projection type exposure apparatus. Conventionally, as a multilayer film reflecting mirror used for such an application, two kinds of media having different refractive indices for exposure light are alternately laminated on a substrate, and the exposure light is multiply reflected on the surface of the multilayer film reflecting mirror. As described above, the layer thickness of the layer formed of each medium was adjusted. The multi-layered film reflection mirror utilizing the multiple reflection has an advantage that the reflectance with respect to the exposure light is increased as compared with the case where the substrate is coated with a single layer of a metal thin film. However, with the shortening of the exposure light wavelength in the near-ultraviolet wavelength region (about 500 nm) or less, the reflectance due to the multiple reflection is caused by the decrease in the reflectance of each medium constituting the multilayer-film reflective mirror with respect to the exposure light. It drops sharply.

Therefore, the reflecting mirror for an exposure apparatus according to the present invention has an exposure light, as compared with a conventional multi-layer film reflecting mirror using multiple reflection.
In particular, from the viewpoint of increasing the reflectance with respect to exposure light in the near-ultraviolet wavelength region or less, it has the following constituent requirements. First, the reflecting mirror for an exposure apparatus of the present invention has a laminated body in which a plurality of periodic structure bodies in which two or more kinds of media having different refractive indexes are periodically arranged are laminated on a substrate. Secondly, the periodic structure has a layer thickness of one period adjusted so as to be a one-dimensional photonic crystal with respect to exposure light.

FIG. 5 shows an example of the periodic structure which the reflecting mirror for an exposure apparatus of the present invention has. The periodic structure 100 in FIG. 5 is a case where two types of media having different refractive indexes, which are exposed to exposure light, are stacked so as to be alternately and periodically arranged. By stacking in this manner, the high refractive index layer 10 and the low refractive index layer 11 are cyclically stacked, and the pair of the high refractive index layer 10 and the low refractive index layer 11 corresponds to one cycle. I will do it. Further, the layer thickness of the one period corresponds to an integral multiple of a half wavelength (λa / 2) of the in-medium average wavelength λa obtained by averaging the in-medium wavelengths of the exposure light in the high refractive index layer 10 and the low refractive index layer 11, respectively. It is adjusted so that

The periodic structure 100 having the above structure
In Fig. 4, the refractive index periodically changes in the stacking direction as shown in the schematic view of Fig. 4. The length of one cycle in the periodic change of the refractive index is the periodic structure 100.
When the half wavelength of the propagating light propagating in the inside in the stacking direction, that is, an integral multiple of the half wavelength (λa / 2) of the average wavelength in the medium, corresponds to such propagating light, the periodic structure 10
It cannot propagate in 0 and is reflected in a form close to perfect reflection (reflectance is 1). As described above, the phenomenon of reflecting light in a certain wavelength range is generally called a photonic bandgap because it has the same concept as the bandgap explained by the dispersion relation of electrons in a solid crystal in a semiconductor or the like. . In particular, the periodic structure 100 having a photonic band gap only for light propagating in the stacking direction is called a one-dimensional photonic crystal.

In FIG. 5, two kinds of media having different refractive indexes for the exposure light are used, but by periodically stacking three or more kinds of media having different refractive indexes for the exposure light, the periodicity can be improved. Of course, the structure may be a one-dimensional photonic crystal for exposure light. FIG. 7 as an example thereof
The periodic structure 100 has a different refractive index with respect to the exposure light.
This is the case when a seed medium is used. A pair of the high-refractive index layer 10, the medium-refractive index layer 12 and the low-refractive index layer 11 is set as one cycle, and the layer thicknesses of the one cycle are the high-refractive index layer 10, the middle-refractive index layer 12 and the low-refractive index of the exposure light, respectively. It is adjusted so as to correspond to an integral multiple of a half wavelength (λa / 2) of the medium average wavelength λa of the medium wavelength in the index layer 11. With such a configuration, as shown in FIG. 6, the refractive index changes periodically with respect to the stacking direction, and the length of one cycle is an integral multiple of a half wavelength of the in-medium average wavelength λa. Corresponding to. As a result, the periodic structure 100 shown in FIG. 7 can be used as a one-dimensional photonic crystal for exposure light.

As described above, in the periodic structure provided in the reflecting mirror for an exposure apparatus of the present invention, the one-dimensional photonic region in which the wavelength region reflected by the photonic bandgap corresponds to the region including the wavelength region of the exposure light. It is regarded as a crystal. As a result, in the reflecting mirror for an exposure apparatus of the present invention, it is possible to significantly improve the reflectance with respect to the exposure light as compared with the conventional multilayer film reflecting mirror using multiple reflection. Also,
The layer thickness of one period in the periodic structure may be adjusted so as to correspond to an integral multiple of a half wavelength of the average wavelength in the medium.
As the period layer thickness increases, the light attenuation rate increases. Therefore, in particular, by adjusting the layer thickness of one period in the periodic structure so as to correspond to one wavelength or half wavelength of the average wavelength in the medium, the reflection of the exposure light of the reflecting mirror for the exposure apparatus of the present invention is further improved. It is possible to improve the rate. From such a viewpoint, when the layer thickness of one period in the periodic structure is adjusted so as to correspond to a half wavelength of the average wavelength in the medium, the reflection of the exposure light of the exposure apparatus reflection mirror of the present invention is most likely. It is possible to improve the rate.

However, as the exposure light has a shorter wavelength, it is naturally necessary to reduce the layer thickness of one period in the periodic structure. Therefore, in an actual system, it may be difficult to control the uniformity of the layer thickness when stacking the respective media forming one cycle. If the layer thickness is not uniform, the reflectance of the periodic structure with respect to the exposure light is reduced. Therefore, considering such contents,
It is necessary to adjust the layer thickness of one period in the periodic structure according to one wavelength or half wavelength of the wavelength in the medium.

The wavelength of the exposure light in each medium in each medium constituting one cycle of the periodic structure is a value obtained by dividing the wavelength of the exposure light by the refractive index of each medium with respect to the exposure light. Therefore, the larger the refractive index for the exposure light, the shorter the wavelength in the medium. This means that the higher the refractive index of the exposure light, the higher the light density of the exposure light propagating in the medium in the stacking direction, and the higher the probability of light scattering or light absorption. means. Therefore, in each medium forming one cycle of the periodic structure, the layer thickness of the layer having the maximum refractive index for the exposure light (hereinafter, also referred to as a high refractive index layer) is set to the layer having the minimum refractive index for the exposure light. By making it at least smaller than the layer thickness (hereinafter, also referred to as a low refractive index layer), it is possible to reduce the probability of light scattering or light absorption in the high refractive index layer. As a result, it is possible to further increase the reflectance of the periodic structure and thus the reflecting mirror for the exposure apparatus. Further, if the layer thickness of the high refractive index layer is made excessively smaller than the layer thickness of the low refractive index layer, conversely, the probability of occurrence of light scattering or light absorption in the low refractive index layer may increase. Therefore, in particular, the layer thickness of the high refractive index layer is adjusted so that the propagation lengths of the exposure light corresponding to the in-medium wavelength in the high refractive index layer and the low refractive index layer become equal. That is, when the layer thickness of the high refractive index layer is t1, the refractive index for the exposure light is n1, the layer thickness of the low refractive index layer is t2, and the refractive index for the exposure light is n2, then t1 × n1 = t2 × The layer thickness of the high refractive index layer is adjusted so as to be n2. As a result, without increasing the probability of occurrence of defects such as light scattering and light absorption in the low refractive index layer, it is possible to reduce the probability of occurrence of such defects even in the high refractive index layer.

Next, the wavelength width of the exposure light reflected by the reflecting mirror for the exposure apparatus of the present invention will be described. The wavelength width is
It depends on the refractive index of each medium constituting one period of the periodic structure to the exposure light. Specifically, it depends on the refractive index difference Δn between the maximum refractive index and the minimum refractive index of the exposure light in each medium forming one cycle. As this Δn increases, the wavelength width of the reflected exposure light, that is, the wavelength region of the reflected exposure light, increases. Therefore, in the case of reflecting the exposure light in a certain specific wavelength region, it is possible to use a plurality of periodic structure bodies or a single periodic structure body. The schematic diagram of FIG. 8 shows a case where two periodic structure bodies are combined as an example using a plurality of periodic structure bodies. The first periodic structure body 101 and the second periodic structure body 102 have different wavelength regions to be reflected, one layer thickness of one period reflects exposure light having a center wavelength λ1, and the other has a center wavelength. It is adjusted so as to reflect the exposure light of λ2. By combining two such periodic structure bodies, the wavelength width Δλ of the exposure light reflected as a whole is the wavelength width of the exposure light reflected by the first periodic structure body 101 and the second periodic structure body 102, respectively. Δ
It is a combination of λ1 and Δλ2. On the other hand, it is also possible to reflect the exposure light in the wavelength region having the same wavelength width Δλ by a single periodic structure. In that case, the refractive index difference Δn within one period of the periodic structure is calculated as 1 of the first periodic structure 101 and the second periodic structure 102 in FIG.
The material of each medium forming one cycle may be appropriately selected so that the respective refractive index differences Δn in the cycle are increased to the extent that they are added.

As described above, the reflecting mirror for an exposure apparatus of the present invention can effectively reflect the exposure light in a certain specific wavelength range regardless of whether a plurality of or a single periodic structure is used. It is possible. However, along with the shortening of the wavelength of the exposure light, it may be difficult to obtain a large difference in refractive index within one period of the periodic structure. In such a case, in particular, it can be said that it is an effective means to widen the wavelength region to be reflected by using a plurality of periodic structure bodies. On the other hand, when it is possible to sufficiently reflect the exposure light with a single periodic structure, it is particularly preferable to use a single periodic structure. A single periodic structure requires less total number of stacked layers than a plurality of periodic structures. By reducing the number of stacked layers in this way, the attenuation rate of the exposure light propagating in the periodic structure can be suppressed. As a result, the reflectance for the exposure light can be further increased by using the reflecting mirror for an exposure apparatus that uses a single periodic structure. Further, since the periodic structure is laminated on the substrate, when a single periodic structure is used, stress such as strain stress concentrated on the substrate can be reduced. As a result, the substrate and the periodic structure are formed. It is possible to reduce the deformation that occurs in the body.

Next, regarding the number of media constituting the periodic structure, one period of the periodic structure is constituted by two or more kinds of media as described above, so that the periodic structure is subjected to one-dimensional photo with respect to exposure light. It can be a nick crystal. However, as the number of media forming one cycle increases, it becomes necessary to relatively reduce the layer thickness of each layer composed of each medium. When the layer thickness of each layer made of each medium is reduced in this way, it becomes difficult to control the uniformity of the layer thickness as the layer thickness decreases. When the layer thickness uniformity of each layer made of each medium is deteriorated, uniformization of the refractive index in each layer is suppressed,
As a result, the reflectance of the periodic structure with respect to the exposure light is reduced. Therefore, it is desirable to reduce the number of media forming the periodic structure as much as possible. In particular, by forming one period of the periodic structure body from two kinds of media, it is possible to further improve the reflectance of the periodic structure body, and by extension, the exposure light of the reflecting mirror for an exposure apparatus of the present invention.
In addition, reducing the number of media forming one cycle of the periodic structure can also suppress light scattering at the laminated interface between adjacent layers of the media. This is
This leads to an improvement in the reflectance of the periodic structure with respect to the exposure light.

As described above, the exposure apparatus reflector using the photonic bandgap according to the present invention has a significantly improved reflectance with respect to exposure light as compared with the conventional multi-layer film reflector utilizing multiple reflection. It is possible to By using such a reflection mirror for an exposure apparatus of the present invention as a multi-layered film reflection mirror in at least one of a mask pattern layer, an illumination optical system and a projection optical system constituting the exposure apparatus, a conventional multi-layered film reflection mirror is provided. It is possible to suppress the deterioration speed as compared with. In the illumination optical system, since the exposure light is first propagated, there is an advantage that the deterioration speed of the multilayer mirror used is suppressed. Further, in the projection optical system, by using the exposure apparatus reflecting mirror of the present invention as a multilayer film reflecting mirror, it is possible to increase the number of multilayer film reflecting mirrors constituting the projection optical system. As a result, the numerical aperture of the projection optical system can be improved, which in turn can improve the resolution of the projection optical system. Further, by using the reflective mirror for an exposure apparatus of the present invention as the multilayer film reflective mirror included in the mask pattern layer, the exposure light propagated from the illumination optical system can be efficiently propagated to the projection optical system, and thus the mask. It is possible to sharply reduce and transfer the pattern image of the pattern layer onto the wafer stage.

When the reflecting mirror for an exposure apparatus according to the present invention is used as a multilayer film reflecting mirror in a mask pattern layer, an illumination optical system and a projection optical system which constitute the exposure apparatus, the effect of the present invention is most exerted. . That is, it is possible to further reduce the attenuation rate of the intensity of the exposure light propagating in the order of the illumination optical system, the mask pattern layer, and the projection optical system, as compared with the case of using the conventional multilayer-film reflective mirror. As a result, it is possible to further improve the numerical aperture of the projection optical system and further improve the resolution of the projection optical system.

As described above, the wavelength width of the exposure light reflected by the reflecting mirror for the exposure apparatus of the present invention increases as the refractive index difference Δn in one period of the periodic structure increases. Therefore, by increasing the refractive index difference Δn, it is possible to more reliably reflect the exposure light in the exposure apparatus reflecting mirror of the present invention. Further, the refractive index of each medium constituting one cycle of the periodic structure body with respect to the exposure light, the refractive index changes depending on the wavelength region of the exposure light used.
Therefore, the material of each medium constituting one cycle of the periodic structure is appropriately selected so that the refractive index difference within the one cycle becomes large depending on the wavelength region of the exposure light used.

As described above, the refractive index of each medium constituting one cycle of the periodic structure with respect to the exposure light varies depending on the wavelength region of the exposure light to be used. The high refractive index material group of the medium and the low refractive index material group of the medium which forms the low refractive index layer can be exemplified below. High-refractive index material group Si, Ge, Be, Sb, Cr, Mn and other single elements, and 6h-SiC, 3c-SiC, BP, AlP, AlA
Compounds such as s, AlSb, GaP, and TiO ₂ .・ Low refractive index material group Mg, Ca, Sr, Ba, Ni, Cu, Mo, Al, A
u, Ag, and other single elements, and SiO ₂ , CeO ₂ , Z
rO ₂ , MgO, Sb ₂ O ₃ , BN, AlN, Al ₂ O
Compounds such as ₃ , Si ₃ N ₄ and CN.

Regardless of the above-mentioned medium, the medium changes so that the refractive index thereof becomes close to 1 toward the limit where the wavelength becomes 0. Therefore, due to the shape of the changing curve, the material of the high refractive index material group may have a smaller refractive index than the material of the low refractive index material group in the short wavelength region such as the soft X-ray region. That is, the material group of the medium described above is merely an example, and does not give a guideline to all wavelength regions.

From the high refractive index material group and the low refractive index material group, etc., according to the wavelength range of the exposure light to be used,
It is desirable to select a combination that causes a large difference in refractive index. Further, in each of the high refractive index material group and the low refractive index material group, such as a compound in which a single element is combined, one or more materials may be selected as a material forming one medium.

In the above description, attention was paid only to the refractive index of each medium constituting the periodic structure with respect to the exposure light, but the following points should be noted regarding the selection of the material for each medium. This is the degree of translucency of light that has propagated to the periodic structure that is a one-dimensional photonic crystal, that is, exposure light. That is, it is desirable to select a material that does not absorb the light in the wavelength range of the exposure light used as much as possible. For example, in terms of semiconductor materials, it is desirable to select an indirect transition type semiconductor such as Si rather than a direct transition type semiconductor.

In the medium constituting the layers other than the high refractive index layer and the low refractive index layer, which is necessary when one period of the periodic structure is constituted by three or more kinds of mediums, the above high refractive index material group and It may be appropriately selected from the low refractive index material group.
In particular, it is desirable to select a material having a low absorptance for exposure light.

Further, in the conventional multi-layered film reflecting mirror constituting the exposure apparatus, as a substrate on which the multi-layered film is laminated, Si having a small expansion coefficient is usually used from the viewpoint of heat resistance and the like.
And SiO ₂ are used. When considering stacking a periodic structure on a substrate made of such a material,
In particular, by selecting at least Si from the material group serving as the high refractive index medium and at least SiO ₂ from the material group serving as the low refractive index medium, it is possible to stack a periodic structure having excellent layer thickness uniformity. Becomes In addition, one cycle of the periodic structure is 2
In the case of using the medium of the seed, there is also an advantage that the layer made of SiO ₂ can be easily formed by thermally oxidizing the layer made of Si.

As described above, the exposure apparatus reflection mirror of the present invention can improve the reflectance with respect to the exposure light, as compared with the conventional multilayer film reflection mirror utilizing multiple reflection. In addition, in a conventional multi-layered film reflection mirror using multiple reflection, in order to increase the reflectance with respect to exposure light, two adjacent layers having different refractive indices with respect to exposure light are set as one cycle, and the number of cycles is the near ultraviolet wavelength. Even in the region, for example, it is set to about 30 cycles, and if it is a shorter wavelength region than the near-ultraviolet wavelength region, the period is longer than that. However, in the reflecting mirror for an exposure apparatus of the present invention, it is possible to maintain a high reflectance with respect to exposure light even when the number of periods is reduced as compared with the conventional multilayer film reflecting mirror. . Also in the present invention, the required number of periods increases in the ultraviolet wavelength region and below as the exposure light has a shorter wavelength. For example, if the wavelength of the exposure light is 100 nm or more, 15 periods, particularly It is possible to sufficiently reflect the exposure light with the number of cycles of about 10 cycles. Furthermore, for exposure light in the near-ultraviolet wavelength region, about 4 cycles are sufficient. On the other hand, for example, the exposure light is transmitted through the soft X-ray wavelength region (λ to 3
0 nm), the required number of cycles increases, but the number of cycles is still about 30. As described above, in the present invention, it is possible to reduce the number of periods in the periodic structure. As a result, it is possible to reduce stress such as strain stress concentrated on the substrate, and it is possible to reduce deformation occurring in the substrate and the periodic structure.

Up to this point, the constituent features of the reflecting mirror for an exposure apparatus of the present invention which can improve the reflectance with respect to exposure light as compared with the conventional multilayer film reflecting mirror have been described. In such a reflection mirror for an exposure apparatus, the wavelength range of the exposure light to be targeted is not particularly limited. However, in order to cope with the recent miniaturization of element patterns in semiconductor devices, there is a need for a multilayer-film reflective mirror capable of improving the reflectance with respect to exposure light in the near-ultraviolet wavelength region or less. Therefore, the reflecting mirror for an exposure apparatus of the present invention has a wavelength of 5
By using it for exposure light having a wavelength of near-ultraviolet wavelength of 00 nm or less, its usefulness can be particularly enhanced. In the exposure light in the near-ultraviolet wavelength region of 500 nm or less, the lower limit value of the wavelength region depends on the light source of the exposure light that can be used. For example, a laser plasma X-ray source or the like is used as the light source. When a light source in the soft X-ray wavelength range is used, the wavelength of the exposure light is about 10 nm.

As described above, the reflecting mirror for an exposure apparatus according to the present invention is applied as a multilayer film reflecting mirror to a mask pattern layer, an illumination optical system, a projection optical system, and the like that constitute a reduction projection type exposure apparatus. The idea is to do it.
With such an application, in the exposure apparatus having the exposure apparatus reflection mirror of the present invention, it is possible to effectively suppress the attenuation of the exposure light intensity in the mask pattern layer and the optical system. As a result, it is possible to reduce the transfer of the mask pattern of the mask pattern layer formed on the mask stage onto the wafer stage and improve the throughput when forming the element pattern on the wafer. This means that work efficiency when forming an element pattern on a semiconductor device is improved. Further, since the exposure time when forming the element pattern on the semiconductor device is shortened as described above, it is possible to suppress the deterioration of the positional accuracy that occurs when the element pattern is formed. Furthermore, as described above, since it is possible to improve the numerical aperture in the projection optical system, it is possible to improve the resolution for forming the element pattern. As described above, by using the exposure apparatus having the exposure apparatus reflection mirror of the present invention, the apparatus performance related to the element pattern formation can be improved.

Further, in a semiconductor device in which an element pattern is formed by using the exposure apparatus having the above-described exposure apparatus reflection mirror of the present invention, since the formation accuracy of the element pattern is improved, a device having excellent element characteristics is obtained. It becomes possible to Furthermore, in such an exposure apparatus,
It is possible to shorten the exposure light to be used in the near-ultraviolet wavelength region or less while maintaining the device performance related to the element pattern formation. As a result, in the semiconductor device, it is possible to increase the fineness of the element pattern and further improve the element characteristics.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a schematic sectional view showing an embodiment of a reflecting mirror for an exposure apparatus of the present invention.
The exposure apparatus reflecting mirror 1 which is a multilayer film reflecting mirror for exposure light has a laminated body 50 in which the periodic structure 100 is laminated on the base 5, and the periodic structure 100 is exposed to the exposure light. On the other hand, high refractive index layers 10 and low refractive index layers 11 made of a medium having different refractive indexes are alternately arranged periodically and laminated. Further, one cycle in the periodic structure 100 is a pair of the high refractive index layer 10 and the low refractive index layer 11. Further, the layer thickness for one period is a half wavelength (λa / 2) of the in-medium average wavelength λa obtained by averaging the in-medium wavelengths of the exposure light in the respective media forming the high refractive index layer 10 and the low refractive index layer 11, respectively. ) Is adjusted to correspond to an integer multiple. The periodic structure 100 that satisfies the above structural requirements is called a one-dimensional photonic crystal for exposure light. As a result, the exposure apparatus reflection mirror 1
It is possible to improve the reflectance with respect to the exposure light as compared with the conventional multilayer-film reflective mirror using multiple reflection.

Further, by making the layer thickness of one period in the periodic structure 100 correspond to one wavelength (λa) or half wavelength (λa / 2) of the average wavelength λa in the medium, the reflecting mirror for the exposure apparatus The reflectance with respect to the exposure light of No. 1 can be further increased. One period of the periodic structure 100 in FIG. 3 is
This is a case where two kinds of mediums having different refractive indexes with respect to the exposure light are used. However, as shown in FIG. On the other hand, it is also possible to form a periodic structure that becomes a one-dimensional photonic crystal. Further, in FIG. 3, the periodic structure 10
One cycle of the periodic structure 100 is configured such that the uppermost layer of 0 (the uppermost layer in the drawing) is the low refractive index layer 11, but the uppermost layer may be the high refractive index layer 10 as a matter of course. Good. As described above, it is important that the reflecting mirror for an exposure apparatus of the present invention has a periodic structure that becomes a one-dimensional photonic crystal with respect to exposure light.

Further, in the periodic structure, it is important to increase the difference in the refractive index between the medium having the maximum refractive index and the minimum refractive index with respect to the exposure light in each medium forming one period. Is. However, increasing the difference in the refractive index becomes difficult as the exposure light has a short wavelength in the near ultraviolet region, particularly in the ultraviolet wavelength region or less. Therefore, by using a medium forming a layer located at the uppermost layer of the periodic structure, if the refractive index for the exposure light is larger than 1, on the other hand, if it is smaller than 1, a smaller medium is used, It is also possible to improve the reflectance of the periodic structure for exposure light. However, even in this case, it is desirable that the medium forming the uppermost layer has a smaller absorptance with respect to the exposure light.

Not only the above-mentioned medium constituting the uppermost layer of the periodic structure but also the medium constituting one cycle of the periodic structure is desired to have a smaller absorptance with respect to the exposure light. Be done. In consideration of such light absorption effect, according to the wavelength range of the exposure light used,
Each medium is appropriately selected so that the difference between the maximum refractive index of each medium and the minimum refractive index of the exposure light becomes large.

As shown in FIG. 9, a first periodic structure 101 and a second periodic structure 10 are formed on a substrate 5 as one-dimensional photonic crystals for exposure lights having different wavelength regions.
It is also possible to form the reflecting mirror 1 for an exposure apparatus from a laminated body 50 in which 2 and 2 are laminated. In this case, it is possible to reflect the exposure light reflected by each of the first periodic structure 101 and the second periodic structure 102 in the wavelength width of the exposure light, by the reflecting mirror 1 for the exposure apparatus. Becomes For example, using only a single periodic structure as shown in Figure 3,
If the exposure mirror 1 cannot sufficiently reflect the exposure light, the exposure mirror 1 can sufficiently reflect the exposure light by using a plurality of periodic structures as shown in FIG. It will be possible. In FIG. 9, the laminated body 50 is composed of two types of periodic structures 100, but it is of course possible to use three or more types of periodic structures.

The material of the substrate in the reflecting mirror for an exposure apparatus of the present invention, including the substrate 5 in FIGS. 3 and 9, depends on each medium constituting the periodic structure, but Si, Si
O ₂ , SiC, CeO ₂ , ZrO ₂ , TiO ₂ , Mg
It is possible to use O, BN, AlN, Si ₃ N ₄ , Al ₂ O ₃ or the like, and the same kind as any one of the respective media forming the periodic structure may be used as the material of the substrate. Among the above materials, Si, SiO ₂ , SiC, and BN, which have excellent mechanical strength and heat resistance, are particularly suitable as the material of the substrate.

The periodic structure laminated on the substrate as shown in FIGS. 3 and 9 is formed by CVD (Chemical Vapor Depos).
ition method, MOVPE (Metalorganic Vapor Phase Ep)
It can be formed using a well-known thin film growth method such as an itaxy) method and an MBE (Molecular Beam Epitaxy) method.
In addition, as the exposure light used has a wavelength shorter than the ultraviolet wavelength region, the layer thickness of each layer constituting the periodic structure is set to several nm.
It may be necessary to adjust to about several tens of nm, but in that case, in particular, the MBE method or ALE (Atomic Lay
er epitaxy method, the growth of each layer constituting the periodic structure can be controlled at the atomic layer level, and the layer thickness of each layer of the periodic structure can be laminated with good uniformity.

The reflectance of the periodic structure with respect to the exposure light depends on the uniformity of the layer thickness of each layer. When the uniformity of the layer thickness of each layer deteriorates when the periodic structure is laminated on the substrate,
The refractive index in each layer becomes non-uniform, and as a result,
This leads to a reduction in the reflectance of the periodic structure with respect to the exposure light. Therefore, from the viewpoint of improving the uniformity of the layer thickness of each layer, as shown in FIG. 2, the buffer layer 20 having a laminated interface with the substrate 5 and the periodic structure 100 is provided between the substrate 5 and the periodic structure 100. The layers may be laminated for the purpose of relaxing the difference in lattice constant and the difference in expansion coefficient caused by the difference in constituent material from the lowermost layer (lowermost layer in the drawing).

The exposure apparatus reflecting mirror of the present invention as shown in FIGS. 2, 3 and 9 includes a mask pattern layer, an illumination optical system and a projection optical system which constitute a reduction projection type exposure apparatus. It can be effectively applied to an optical system as a multilayer-film reflective mirror. FIG. 1 shows a schematic configuration diagram of a reduction projection type exposure apparatus. In the exposure apparatus 40 of FIG. 1, the exposure light obtained from the light source 41 is reflected and condensed by the multilayer-film reflective mirror 42 that constitutes the illumination optical system 60, and then illuminates the first substrate 43 that serves as a mask stage. To be done. Next, the exposure light is reflected by the mask pattern layer 44 that forms the mask pattern formed on the first substrate 43, and is sequentially reflected by the convex mirror 45 and the concave mirror 46 that form the projection optical system 61, and then the wafer. The second substrate 47, which is a stage, is reached. By the exposure light propagating through such an optical path, the mask pattern formed in the region of the mask pattern layer 44 illuminated by the exposure light is reduced and transferred onto the wafer 48. Further, by synchronously scanning the first substrate 43 and the second substrate 47 in accordance with the reduction magnification of the projection optical system, all the mask patterns formed on the mask pattern layer 44 can be reduced and transferred onto the wafer 48. it can.

The convex mirror 45 and the concave mirror 46 constituting the projection optical system 61 in FIG. 1 are multilayer film reflecting mirrors in which a multilayer film for reflecting exposure light is formed on a substrate having an aspherical surface shape. Are arranged so that their central axes are coaxial. Such a multilayer-film reflective mirror included in the illumination optical system and the projection optical system forming the exposure apparatus is desired to have high reflectance with respect to exposure light, particularly exposure light in the near-ultraviolet wavelength region or less. Therefore, the exposure apparatus reflecting mirror of the present invention is applied to the multilayer film reflecting mirror in a dominant manner. By applying the reflecting mirror for an exposure apparatus of the present invention to a multilayer film reflecting mirror included in an illumination optical system or a projection optical system that constitutes the exposing apparatus, the deterioration speed is suppressed as compared with a conventional multilayer film reflecting mirror. Is possible. The effect of suppressing the deterioration speed becomes particularly remarkable as the wavelength of the exposure light becomes shorter, that is, the energy becomes higher. Further, in the projection optical system in which the exposure apparatus reflecting mirror of the present invention is applied as a multilayer film reflecting mirror, since the number of the multilayer film reflecting mirrors can be increased, it is possible to improve the resolution in the projection optical system. Become. Further, since it is possible to shorten the exposure time when the mask pattern is reduced and transferred to the wafer, it is possible to improve the accuracy of the formation position when the mask pattern is reduced and transferred to the wafer and to improve the throughput, that is, the work efficiency. .

Further, the mask pattern layer 44 shown in FIG.
Is a reflective mask, and usually has a different refractive index with respect to the exposure light on the substrate in order to increase the reflectance with respect to the exposure light.
The medium of the seed is alternately laminated, and the multi-layered film reflecting mirror is formed in which the layer thickness of each medium is adjusted so as to cause multiple reflection. Therefore, it is also possible to apply the reflecting mirror for an exposure apparatus of the present invention to the multilayer film reflecting mirror of the mask pattern layer,
Of course it is possible. As a result, the reflectance of the mask pattern layer 44 with respect to the exposure light can be improved. The exposure apparatus to which the reflecting mirror for an exposure apparatus of the present invention is applied is not limited to the form shown in FIG. 1, but can be applied to a known exposing apparatus having a multilayer film reflecting mirror.

As described above, in a semiconductor device having a mask pattern, that is, an element pattern formed by using the exposure apparatus having the reflecting mirror for an exposure apparatus of the present invention, the accuracy of forming the element pattern is improved. Therefore, it becomes possible to obtain excellent element characteristics.

The reflectance characteristics of the periodic structure, which is a one-dimensional photonic crystal included in the reflecting mirror for an exposure apparatus of the present invention, with respect to exposure light was verified by theoretical calculation. Further, the theoretical calculation was performed when the periodic structure was composed of two types of media, and the center wavelength of the exposure light, the material of the medium forming the periodic structure, and the number of periods of the periodic structure were changed. The results are shown below.

(Theoretical calculation 1) As shown in FIG. 5, the periodic structure is composed of two kinds of media, the high refractive index layer is made of Si (refractive index 3.5), and the low refractive index layer is made of SiO ₂ ( The case where it is configured to have a refractive index of 1.5) is used. The exposure light has a center wavelength of 400 nm, and the layer thickness of the high-refractive index layer is set to 1 of the in-medium wavelength (center wavelength / 3.5).
/ 4 wavelength, the layer thickness of the low-refractive index layer is set to ¼ wavelength of the in-medium wavelength (center wavelength / 1.5), so that the high-refractive index layer and the low-refractive index layer form a pair. Was set to be a half wavelength of the in-medium average wavelength obtained by averaging the in-medium wavelength with respect to the center wavelength of each layer. Further, the reflectance characteristics were calculated under the condition that the high refractive index layer and the low refractive index layer were one cycle and were stacked for four cycles.

The result of the above theoretical calculation is shown in FIG. Figure 1
As shown in 0, the exposure light in the wavelength range from the near-ultraviolet wavelength range to the ultraviolet wavelength range is reflected by complete reflection having a reflectance of 1. Further, as the result shows, it is possible to sufficiently reflect the exposure light in the vicinity of the near-ultraviolet wavelength region by the periodic structure having a period number of about 4 periods.

(Theoretical calculation 2) Construct one period of the periodic structure
Two kinds of media are used, TiO_Two(Refractive index 3.0) and SiO
_Two(Refractive index 1.5), center wavelength becomes 285 nm
Except that the exposure light was used and the number of cycles was 6
High-refractive-index layer and low-refractive-index layer
The calculation was performed assuming the respective layer thicknesses of. (Theoretical calculation 3) Two kinds of media that make up one cycle of the periodic structure
The quality is Si (refractive index 0.5) and SiO _Two(Refractive index 2.
0), and as the exposure light having a central wavelength of 120 nm,
The same conditions as in theoretical calculation 1 except that the number of cycles is 8
To temporarily set the thickness of each of the high and low refractive index layers.
Then, the calculation was performed.

The results of the above theoretical calculation are shown in FIG. 11 and FIG.
Shown in. The result of theoretical calculation 2 corresponds to FIG. 11, and the result of theoretical calculation 3 corresponds to FIG. As these results show,
The exposure light in the wavelength region of 0 nm or more can be sufficiently reflected by the periodic structure having a period number of about 8 periods. Of course, 100 nm in the periodic structure
In order to ensure the reflectance characteristic with respect to the exposure light in the above wavelength region, it does not prevent the number of cycles from being further increased from about eight cycles. In addition, in consideration of the absorption effect and work efficiency in the actual system, and by analogy from these calculation results, it is considered that about 15 cycles, particularly about 10 cycles is sufficient.

(Theoretical calculation 4) Two kinds of media constituting one period of the periodic structure are made of Si (refractive index 0.98) and SiO ₂
Theoretical calculation 1 except that the exposure light has a refractive index of 0.90, the central wavelength is 30 nm, and the number of periods is 28.
Under the same conditions as above, calculation was performed assuming the respective layer thicknesses of the high refractive index layer and the low refractive index layer. The results are shown in Figure 1.
3 shows. The number of periods required for the periodic structure is 28, which is larger than the other results, but as the calculation result shows, it is possible to sufficiently reflect the exposure light belonging to the soft X-ray region. I understand. In such a short wavelength region as the soft X-ray region, it is difficult to set a large difference in refractive index between the high refractive index layer and the low refractive index layer.
Therefore, as shown by the results in FIG. 13, the wavelength width of the reflected exposure light is smaller than the other results. In such a case, it is particularly effective to use a plurality of periodic structures having different central wavelengths of the exposure light to be reflected.

From the above theoretical calculation results, it is understood that the reflecting mirror for an exposure apparatus of the present invention has better reflectance characteristics with respect to exposure light than the conventional one. Further, the type of each medium constituting the periodic structure is not limited as long as it has the same refractive index as each medium used in the theoretical calculation. However, it is preferable to use a medium having a higher translucency with respect to the exposure light in consideration of the absorption effect in the actual system. As described above, the reflecting mirror for an exposure apparatus of the present invention is not limited to the above-described embodiments and theoretical calculation forms, and is applied to a multilayer film reflecting mirror that is required to have improved reflectance with respect to exposure light. It is possible.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an exposure apparatus to which a reflecting mirror for an exposure apparatus of the present invention is applied.

FIG. 2 is a schematic sectional view showing an embodiment of a reflecting mirror for an exposure apparatus of the present invention.

FIG. 3 is a schematic sectional view showing an embodiment of a reflecting mirror for an exposure apparatus of the present invention.

FIG. 4 is a schematic diagram for explaining constituent requirements of a periodic structure included in a reflecting mirror for an exposure apparatus of the present invention.

FIG. 5 is a schematic cross-sectional view for explaining a periodic structure included in a reflecting mirror for an exposure apparatus of the present invention.

FIG. 6 is a schematic diagram for explaining constituent features of a periodic structure included in a reflecting mirror for an exposure apparatus of the present invention.

FIG. 7 is a schematic cross-sectional view for explaining a periodic structure included in a reflecting mirror for an exposure apparatus of the present invention.

FIG. 8 is a schematic diagram for explaining a periodic structure body included in a reflecting mirror for an exposure apparatus of the present invention.

FIG. 9 is a schematic sectional view showing an embodiment of a reflecting mirror for an exposure apparatus of the present invention.

FIG. 10 is a calculation result obtained by theoretically calculating the reflectance of a periodic structure which is a one-dimensional photonic crystal included in the reflecting mirror for an exposure apparatus of the present invention.

11 is a calculation result of theoretical calculation subsequent to FIG.

FIG. 12 is a calculation result of theoretical calculation subsequent to FIG. 11.

13 is a calculation result of theoretical calculation subsequent to FIG. 12.

[Explanation of symbols]

1 Reflector for exposure equipment 5 base 10 High refractive index layer 11 Low refractive index layer 12 Middle refractive index layer 40 exposure equipment 41 light source 43 First substrate 44 Mask pattern layer 47 Second substrate 60 Illumination optical system 61 Projection optical system 100 periodic structure

Claims (8)

[Claims] 1. An exposure light obtained from a light source is illuminated via an illumination optical system onto a first substrate on which a mask pattern layer forming a mask pattern is formed, and an image of the mask pattern is projected onto a projection optical system. In an exposure apparatus for reducing and transferring onto a second substrate via an exposure apparatus, the exposure apparatus is used as a multilayer film reflection mirror in at least one of the mask pattern layer, the illumination optical system, and the projection optical system that constitute the exposure apparatus. And a plurality of periodic structures in which two or more kinds of media having different refractive indices for the exposure light are periodically arranged, the reflecting mirror having a laminated body laminated on a substrate, and A reflecting mirror for an exposure apparatus, wherein the periodic structure has a layer thickness of one period adjusted so as to be a one-dimensional photonic crystal with respect to the exposure light. 2. The layer thickness of one period of the periodic structure is
The reflecting mirror for an exposure apparatus according to claim 1, wherein the reflecting mirror corresponds to one wavelength or a half wavelength of an in-medium average wavelength obtained by averaging in-medium wavelengths of the exposure light in each medium forming a cycle. 3. In each medium forming one cycle of the periodic structure, the layer thickness of the layer having the maximum refractive index with respect to the exposure light is the minimum refractive index with respect to the exposure light. The layer thickness is adjusted to be at least smaller than the layer thickness of the layer.
A reflecting mirror for an exposure apparatus according to. 4. The exposure light apparatus reflection according to claim 1, wherein the laminated body is a single laminated body of the periodic structure laminated on a substrate. mirror. 5. The periodic structure is formed by periodically arranging two kinds of media having different refractive indexes with respect to the exposure light, according to any one of claims 1 to 4. Reflector for exposure equipment. 6. The wavelength of the exposure light is at least 500.
The reflective mirror for an exposure apparatus according to claim 1, wherein the reflective mirror has a thickness of not more than nm. 7. An exposure apparatus comprising the exposure apparatus reflection mirror according to claim 1. Description: 8. A semiconductor device having an element pattern formed by using the exposure apparatus according to claim 7.