JP2010045317A - Reflective photomask, holding device, exposure device, and exposure method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflective photomask with a dust removing function for a magnetic material as a non-charged material to remove dust in an exposure process. <P>SOLUTION: In the reflective photomask having a pattern forming region on its surface, a thin-film coil is formed on the backside of the reflective photomask so that an electric current flows in the thin-film coil to prevent dust from depositing on the pattern forming region. Further, a first yoke is located in the whole or part of the outer periphery of the pattern forming region on the surface and a second yoke is located in the whole or part of the sides of the reflective photomask. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a reflective photomask, a gripping apparatus, an exposure apparatus, and an exposure method, and more particularly to a reflective photomask, a gripping apparatus, an exposure apparatus, and an exposure method used in a photolithography process in semiconductor manufacturing.

  With the recent miniaturization and high integration of semiconductor integrated circuits, the pattern dimensions of photomasks (reticles) used in the photolithography process, which is the manufacturing process, are also being miniaturized. When foreign matter adheres to the pattern surface of the photomask, the foreign matter is projected onto the surface of the semiconductor substrate and becomes a defect. For this reason, a dust removal protective film called a pellicle has been conventionally devised to suppress adhesion of foreign matter to the pattern surface.

  A resin material having a high transmittance with respect to the wavelength of an exposure light source used in the photolithography process is used for the pellicle. The pellicle generally has a structure in which a thin film processed is attached to a metal frame. This frame is used by attaching an end surface opposite to the pellicle to the photomask with an adhesive.

  Current exposure light sources are mainly KrF laser (wavelength 248 nm) and ArF laser (wavelength 193 nm). With the recent miniaturization of semiconductor integrated circuits, there has been a demand for further shortening of the exposure wavelength, and development of extreme ultraviolet lithography (hereinafter referred to as “EUV lithography”) (EUV: Extreme Ultraviolet Lithography) The wavelength of the exposure light source is approximately 13.5 nm, and at a wavelength of 13.5 nm, a conventional pellicle made of a resin does not transmit and cannot be used. For this reason, resin materials that generate outgas tend to be avoided for reasons of lowering the degree of vacuum.

For this reason, Patent Document 1 discloses a technique including a mechanism for attaching charged floating particles by generating an electric field in the vicinity of a mask inside an exposure apparatus (see Patent Document 1). Further, Patent Document 2 discloses a technique using a container in which the pellicle function is replaced by duplicating a container for storing an EUV mask (see Patent Document 2).
JP 2006-12076 A JP 2007-141925 A

  However, in Patent Document 1, when a method of generating an electric field is used, there is a problem that it does not act on an uncharged substance. Further, in Patent Document 2, when the container is duplicated, the mask is taken out from the container during the exposure inside the exposure apparatus, so that there is a problem that the dust removing function does not work during the exposure process.

  Accordingly, the present invention has been made to solve the above-described problem, and a reflection type photomask having a dust removal function of a magnetic substance that is an uncharged substance and having a dust removal function in an exposure process is provided. An object of the present invention is to provide a gripping apparatus, an exposure apparatus, and an exposure method.

  According to the first aspect of the present invention, in a reflective photomask having a pattern formation region on the surface, a thin film coil is formed on the back surface of the reflective photomask, and a current is passed through the thin film coil so that dust is generated in the pattern formation region. The reflection type photomask is characterized in that it is configured to prevent adhesion.

  According to a second aspect of the present invention, in the reflective photomask according to the first aspect, the first yoke is disposed on all or part of the outer periphery of the pattern formation region on the surface. This is a photomask.

  According to a third aspect of the present invention, in the reflective photomask according to the first or second aspect, the second yoke is disposed on all or part of the side surface of the reflective photomask. The reflection type photomask.

  According to a fourth aspect of the present invention, a reflective photomask is formed by patterning a substrate, a multilayer reflective film formed on the substrate, a protective film formed on the multilayer reflective film, and a protective film. 4. The reflection-type photo according to claim 1, comprising: a buffer film; an absorption film patterned on the buffer film; and a low-reflection film patterned on the absorption film. It is a mask.

  The invention according to claim 5 of the present invention is the reflective photomask according to claim 4, wherein the thin film coil is made of a conductive nonmagnetic material.

  The invention according to claim 6 of the present invention is the reflective photomask according to any one of claims 1 to 5, wherein the back surface conductive film constituting the thin film coil is larger than the pattern formation region. Is.

  The invention according to claim 7 of the present invention is a gripping device for gripping the reflective photomask according to any one of claims 1 to 6, characterized by comprising means for passing a current through the thin film coil. This is a gripping device.

  According to an eighth aspect of the present invention, in the exposure apparatus for transferring to a desired pattern using exposure light on the reflective photomask according to any one of the first to sixth aspects, the reflective photomask is gripped. The electrostatic chuck is an exposure apparatus including means for passing a current through a thin film coil.

  According to a ninth aspect of the present invention, the reflective photomask according to any one of the first to sixth aspects is arranged, and a current is passed through the thin film coil of the reflective photomask to cause dust in the pattern formation region. The exposure method is characterized in that exposure is performed with extreme ultraviolet rays while preventing adhesion.

  According to the present invention, it is possible to provide a reflective photomask having a dust removal function of a magnetic substance that is an uncharged substance and having a dust removal function in an exposure process.

  Hereinafter, the present invention will be described with reference to the drawings. In the embodiment of the present invention, the same constituent elements are denoted by the same reference numerals, and redundant description among the embodiments is omitted.

  FIG. 1 is a schematic sectional view showing the structure of a reflective photomask 100 according to the present embodiment. Unlike the conventional mask structure using a wavelength of 243 nm (KrF laser) or a wavelength of 193 nm (ArF laser), the reflective photomask 100 is used for the reflective photomask 100 because it uses light having a wavelength of 13.5 nm. Since the quartz material does not transmit light, it has a reflective structure. Note that the general specifications of the reflective photomask are standardized by SEMI standards P37-1102 and P37-1103, which are industry standards.

  As shown in FIG. 1, the reflective photomask 100 according to the present embodiment is formed of a multilayer film, and the low reflection film 10, the absorption film 20, and the buffer from the light incident direction (the arrow direction in the figure). A film 30, a protective film 40, a multilayer reflective film 50, a substrate 60, and a back conductive film 70 are provided.

  The low reflection film 10 according to the present embodiment may use light having a wavelength other than 13.5 nm for pattern shape inspection, and the contrast between the multilayer reflection film 50 and the low reflection film 10 (((Rm-Ra ) / (Rm + Ra)) × 100 (%)). The absorption film 20 according to the present embodiment absorbs irradiated EUV light (extreme ultraviolet light) when a pattern is formed, and is selected from materials having high absorbability with respect to EUV light. The low reflection film 10 and the absorption film 20 are preferably formed using a material containing tantalum (Ta) as a main component and at least one of silicon (Si), oxygen (O), and nitrogen (N).

  The buffer film 30 according to the present embodiment is a sacrificial film that protects the multilayer reflective film 50 (described later) from damage when the reflective photomask 100 is corrected by a physical or chemical reaction. The buffer film 30 is preferably formed using a material containing chromium (Cr) or zirconium (Zr) as a main component and at least one of oxygen (O), nitrogen (N), and silicon (Si).

  The protective film 40 is used to protect the multilayer reflective film 50 from deterioration due to surface oxidation or the like, and functions as an etching stopper that prevents damage to the multilayer reflective film 50 when the buffer film 30 is removed by etching. It is. The protective film 40 is preferably formed using a material such as silicon (silicon) and Ru (ruthenium).

  The multilayer reflective film 50 reflects EUV light that is exposure light, and is composed of a multilayer film made of a combination of materials having significantly different refractive indexes with respect to EUV light. The material of the multilayer reflective film 50 can be formed, for example, by repeatedly laminating a combination of molybdenum (Mo) and silicon (Si) or molybdenum (Mo) and beryllium (Be) for about 40 cycles. The film thickness of each layer of the multilayer reflective film 50 is, for example, 2.8 nm for the Mo film and 4.2 nm for the Si film. Here, the portions that form the optical contrast (brightness and darkness) to be a pattern are the multilayer reflection film 50 and the absorption film 20.

  Quartz is used for the substrate 60, and it is particularly preferable to use synthetic quartz to which titanium (Ti) or titanium oxide (TiO) is added. Synthetic quartz is known to have a lower coefficient of thermal expansion than quartz without addition.

  The back conductive film 70 is formed in order to use a gripping device that uses the electrostatic adsorption principle for mounting in an exposure apparatus. The back conductive film 70 is preferably made of a material containing chromium (Cr) as a main component and at least one of oxygen (O) and nitrogen (N).

  Although not shown, a dual-purpose film serving as both the protective film 40 and the buffer film 30 for protecting the multilayer reflective film 50 can be provided between the absorption film 20 and the multilayer reflective film 50. Ru (ruthenium) is preferably used as the material of the dual-purpose film.

  Hereinafter, the mechanism of the reflective photomask 100 with a dust removal function according to the embodiment of the present invention will be described with reference to FIGS. FIG. 2A is a schematic cross-sectional view showing the structure of a reflective photomask 100 with a dustproof function according to the embodiment of the present invention, and FIG. 2B is a reflection with a dustproof function according to the embodiment of the present invention. 2 is a schematic bottom view showing a structure of a mold photomask 100. FIG.

  The principle of the dustproof function according to the embodiment of the present invention uses a magnetic field, and the generation of the magnetic field is based on Ampere's right-handed screw law. As shown in FIG. 2A, the reflective photomask 100 with a dustproof function according to the embodiment of the present invention has a pattern of the low reflective film 10, the absorption film 20 and the buffer film 30 of the reflective photomask 100 described above. The formed pattern region 160 and the thin film coil 110 are formed on a part of the back surface conductive film 70. Here, the thin film coil 110 can be obtained by patterning a part of the back surface conductive film 70. Further, as shown in FIG. 2B, pads (electrodes) 130 are formed at both ends of the thin film coil 110, and the pads (electrodes) 130 are connected to a power source 140.

  Next, the principle of magnetic field generation in the reflective photomask 100 with a dustproof function according to the embodiment of the present invention will be described. 3A and 3B show the principle of magnetic field generation of the reflective photomask 100 with a dustproof function according to the embodiment of the present invention. As shown in FIGS. 3A and 3B, when a direct current is supplied from a power source 140 to a pad (electrode) 131 with a negative electrode and a pad 132 with a positive electrode, a magnetic field is generated in the thin film coil 110, and the magnetic field lines 150 are generated. It occurs (in the direction of the arrow in the figure). The current flowing from the power supply 140 may be direct current or alternating current, and can be selected as appropriate. The strength of the magnetic field can be adjusted by the current supplied from the power source 140, the number of turns and the line width of the thin film coil 110, etc., and the dust containing the magnetic material as an element is attracted and captured by the magnetic force lines 150 to obtain a dust removing action. Can do. As shown in FIG. 3A, the generated magnetic force lines 150 pass through the pattern region 160 of the reflective photomask 100, and a dust suction effect appears in the pattern region 160 of the reflective photomask 100.

  Therefore, as shown in FIGS. 4A and 4B, the attractive force can be reduced by providing a portion having a higher magnetic force (higher magnetic flux density) than the pattern region 160 of the reflective photomask 100. Give a gradient. As a means for increasing the magnetic flux density, the first yoke 170 using a high magnetic permeability material is provided on all or part of the outer periphery of the reflective photomask 100 rather than the pattern region 160 of the reflective photomask 100. Since the lines of magnetic force converge in the first yoke 170, the attractive force can be made stronger than the pattern region 160 of the reflective photomask 100. Since dust is attracted to the first yoke 170 side, dust adhesion to the pattern region 160 of the reflective photomask 100 can be suppressed. As shown in FIG. 4A, the first yoke 170 is as high as possible from the pattern surface of the reflective photomask 100 with respect to the pattern region 160 of the reflective photomask 100 as long as there is no influence of the exposure optical system. It can be a protective wall against dust flying obliquely. Although not shown, the first yoke 170 may be further provided on the back side of the reflective photomask 100. In this case, the material is limited to a material having the same mechanical strength as the film thickness of the back surface conductive film 70. As will be described later, the reflective photomask 100 has a patterning device 160 in the exposure apparatus with the pattern region 160 of the reflective photomask 100 facing downward, and a back surface conductive film 70 on the opposite side of the backside conductive film 70 utilizing electrostatic attraction. This is because the entire surface is adsorbed by the chuck). The reason why the film thicknesses are the same is to ensure flatness in gripping, and the mechanical strength cannot be ensured to be flat when deformed by a chucking force. For example, an FeNi alloy (permalloy) is preferably used as the material of the first yoke 170.

  4A and 4B, the first yoke 170 is disposed only on the pattern region 160 surface side of the reflective photomask 100. However, as shown in FIGS. The second yoke 180 may be provided on all or part of the side surface of the mask 100. The second yoke 180 can narrow the range in which the magnetic force is applied, and can suppress attraction from the reflective photomask 100 to a foreign object that is spatially far away. When the second yoke 180 is installed, the external dimensions of the reflective photomask 100 are generally set in the above-described industry standards, and thus must be within that range. Examples of means for forming the first and second yokes 170 and 180 as thin films include plating, coating, and sputtering. As an example of the sputtering method, it is preferable to use a magnetic material capable of forming a thin film of several tens of nm, for example. As the magnetic material, it is preferable to use a CoCrTa alloy or a CoCrPt alloy used for a hard disk.

  FIGS. 6A and 6B show the relationship between the deflection of the reflective photomask 100 and the pattern region 160 of the reflective photomask 100 and the back conductive film 70 according to the embodiment of the present invention. The pattern region 160 and the back surface conductive film 70 will be described with reference to FIGS. As shown in FIG. 6A, the reflective photomask 100 according to the embodiment of the present invention has the pattern region 160 of the reflective photomask 100 in the exposure apparatus, and the back conductive film 70 on the opposite surface side. Is attracted to the entire surface by a gripping device 210 (electrostatic chuck) using electrostatic attraction. This is partly due to the purpose of avoiding foreign matter adhering to the pattern area 160 of the reflective photomask 100 due to gravity drop. The region of the back surface conductive film 70 preferably has a larger outer dimension than the pattern region 160 of the reflective photomask 100. In the case of being small, as shown in FIG. 6B, a stress is generated on the reflective photomask 100 by the step A, and there is a possibility that the pattern region 160 may be distorted due to bending.

  The back conductive film 70, the thin film coil 110, and the pad 130 will be described with reference to FIGS. As described above, the back conductive film 70, the thin film coil 110, and the pad 130 are preferably flush with each other so as not to cause bending due to the step A. In addition, conductivity is required for gripping by the electrostatic chuck 210, and conductivity is required because current flows through the thin film coil 110 and the pad 130. As shown in FIG. 1, these members have an advantage that they can be used together because the back conductive film 70 which is the structure of the reflective photomask 100 originally needs conductivity.

  As shown in FIG. 1, the material constituting the reflective photomask 100 and the material of the back surface conductive film 70 (including the thin film coil 110 and the pad 130) include a non-charged substance by using a conductive nonmagnetic material. Dust can be absorbed and captured effectively. Specifically, it is preferable to use chromium nitride (CrN) as the material of the back surface conductive film 70. CrN can form a thin film using a sputtering method and form a pattern using a photolithography method. In the conductive magnetic material, the attraction effect is improved by the electromagnet effect, but the attraction point appears not on the first yoke 170 but also on the surface of the pattern region 160 of the reflective photomask 100. Further, even when no current is passed through the thin film coil 110, as long as at least one is made of a magnetic material, the defect that the magnetic substance adheres to the pattern region 160 of the reflective photomask 100 is unavoidable.

  A case will be described in which the above-described reflective photomask 100 according to the embodiment of the present invention is installed in the exposure apparatus 300 and has a dust removing action during the exposure process. FIGS. 7A and 7B show a mechanism for holding the reflective photomask 100 with a dust removal function according to the embodiment of the present invention on the electrostatic chuck 210 and show that it has a dust removal action during the exposure process. As shown in FIGS. 7A and 7B, the reflective photomask 100 is gripped and mounted on the electrostatic chuck 210 in the transfer exposure process to the semiconductor substrate in the exposure apparatus. 7A and 7B show a part of the inside of the exposure apparatus, but a light source, a condensing optical system for a mask, a projection optical system for a semiconductor substrate, and the like are omitted. The electrostatic chuck 210 has an electrode 220 for supplying a charge to the inside in order to develop electrostatic adsorption. In the current supply to the reflective photomask 100 according to the embodiment of the present invention, the wiring 230 and the contact 240 are provided inside the electrostatic chuck 210 and supplied from here to the pad 130 of the reflective photomask 100. Good.

  Next, a case where the reflective photomask 100 according to the embodiment of the present invention is transported by a robot or the like will be described. FIG. 8 shows that the reflection type photomask 100 with a dust removal function according to the embodiment of the present invention, an exposure apparatus provided with a gripping mechanism, and a dust removal function in a transport process in the exposure apparatus. As shown in FIG. 8, the inside of the exposure apparatus 300 is in a vacuum environment. In FIG. 8, a light source, a condensing optical system for a mask, a projection optical system for a semiconductor substrate, and the like are omitted. The reflective photomask 100 is stored in a mask library 310 inside the exposure apparatus 300. The mask library 310 is also a vacuum environment. Although FIG. 8 shows a multi-stage structure, it may be a single-wafer type and there is no limit on the quantity. In this mask library 310, it is stored in at least the inner case 320 of the double case. From the take-out operation from the inner case 320 of the double case to the electrostatic chuck 210, it is taken out and moved by the transfer robot 330 that performs mechanical operation, and is attached to the electrostatic chuck 210. During this time, the reflective photomask 100 does not receive any protection against dust. Therefore, the arm 340 of the transfer robot 330 is provided with a contact 350 that enables supply of current at a position corresponding to the pad 130 of the reflective photomask 100, and is taken out by flowing current from the power supply 140 through the wiring 360. The exposure apparatus in which the dust removing action of the present invention works also in the moving and mounting processes is realized.

  Next, an exposure method for performing exposure by placing the reflective photomask 100 in the exposure apparatus 300 will be described. In the exposure method according to the embodiment of the present invention, the reflective photomask 100 is disposed on the electrostatic chuck 210 in the exposure apparatus 300. In the exposure apparatus 300, an electric current is passed through the thin film coil 110 of the reflective photomask 100 to perform exposure with extreme ultraviolet rays while preventing dust from adhering to the pattern formation region. Thus, by performing exposure, the yield of semiconductor manufacturing can be improved.

  The reflection type photomask for extreme ultraviolet lithography of the present invention can be expected to improve the yield of semiconductor manufacturing because the dust removing action acts on the reflection type photomask during the exposure process.

It is a schematic sectional drawing which shows the structure of the reflection type photomask which concerns on this Embodiment. (A) is a schematic sectional drawing which shows the structure of the reflective photomask with a dust removal function which concerns on embodiment of this invention, (b) is the reflective photomask with a dust removal function which concerns on embodiment of this invention It is a schematic bottom view which shows the structure of these. (A) is a schematic sectional drawing which shows the principle of the magnetic field generation | occurrence | production of the reflective photomask with a dust removal function which concerns on embodiment of this invention, (b) is a reflection with a dust removal function which concerns on embodiment of this invention. It is a schematic bottom view which shows the principle of the magnetic field generation of a type photomask. (A) is a schematic sectional drawing which shows the structure of the photomask with a dust removal function which concerns on embodiment of this invention, and the convergence effect | action of a magnetic field, (b) is a reflection with dust removal function which concerns on embodiment of this invention It is a schematic bottom view which shows the structure of a type | mold photomask, and the convergence effect | action of a magnetic field. (A) is a figure which shows the structure of the photomask with a dust removal function which concerns on embodiment of this invention, and the convergence effect | action of a magnetic field, (b) is a reflective photo with dust removal function which concerns on embodiment of this invention It is a schematic bottom view which shows the structure of a mask, and the convergence effect | action of a magnetic field. (A) And (b) is a schematic sectional drawing which shows the relationship between the bending of the reflection type photomask which concerns on embodiment of this invention, and the pattern area | region formed on the reflection type photomask. It is a figure which shows the mechanism which hold | grips the reflective photomask with a dust removal function which concerns on embodiment of this invention to an electrostatic chuck. It is a schematic sectional drawing which shows the conveyance process of the exposure apparatus provided with the reflective photomask with a dust removal function which concerns on embodiment of this invention, and a holding mechanism.

Explanation of symbols

10: Low reflection film, 20: Absorption film, 30: Buffer film, 40: Protective film, 50: Multi-layer reflection film, 60: Substrate, 70: Back conductive film, 100: Reflective photomask, 110: Thin film coil, 130 : Pad, 140: Power supply, 150: Magnetic field line, 160: Pattern region, 170: First yoke, 180: Second yoke, 210: Electrostatic chuck, 220: Electrode, 230: Wiring, 240: Contact, 300: Exposure apparatus, 310: mask library, 320: inner case, 330: transfer robot, 340: arm, 350: contact, 360: wiring

Claims (9)

In a reflective photomask having a pattern formation region on the surface,
A reflective photomask, wherein a thin film coil is formed on the back surface of the reflective photomask, and current is passed through the thin film coil to prevent dust from adhering to the pattern formation region. The reflective photomask according to claim 1,
A reflective photomask, wherein a first yoke is disposed on all or part of the outer periphery of the pattern formation region on the surface. The reflective photomask according to claim 1 or 2,
A reflective photomask comprising a second yoke disposed on all or a part of a side surface of the reflective photomask. The reflective photomask is
A substrate,
A multilayer reflective film formed on the substrate;
A protective film formed on the multilayer reflective film;
A buffer film patterned on the protective film;
An absorption film patterned on the buffer film;
The reflective photomask according to claim 1, further comprising a low-reflection film patterned on the absorption film.   5. The reflective photomask according to claim 4, wherein the thin film coil is made of a conductive nonmagnetic material.   6. The reflective photomask according to claim 1, wherein a back surface conductive film constituting the thin film coil is larger than the pattern formation region.   7. A gripping apparatus for gripping the reflective photomask according to claim 1, further comprising means for passing a current through the thin film coil. In the exposure apparatus which transfers to a desired pattern using exposure light to the reflection type photomask in any one of Claims 1 thru | or 6,
An exposure apparatus, wherein the electrostatic chuck for gripping the reflective photomask includes means for causing a current to flow through the thin film coil. The reflective photomask according to any one of claims 1 to 6 is disposed,
An exposure method characterized in that exposure is carried out with extreme ultraviolet rays while current is passed through the thin film coil of the reflective photomask to prevent dust from adhering to the pattern formation region.

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