JP2011002639A - Susceptor and flash irradiation method using the same, and method for producing photomask blank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical film having a low stress and excellent in-plane uniformity of optical characteristics.SOLUTION: A susceptor is provided, which includes a high reflectance (R1) region and a low reflectance (R2) region in a region to mount a substrate (with a thickness L) that is chamfered by a length of D inwardly from an intersection between a plane including the major face of the substrate and a plane including an end face of the substrate, along the plane including the major face. The low reflectance region (30L) includes a region (30H) interposed between a rectangle c which is present inside a contour obtained by perpendicularly projecting the outermost end of the substrate onto the major face of the susceptor 30, spaced at a distance of (L-D×tanθ)×tanθ from the contour, and a rectangle d inside the contour, spaced at a distance of (D+L×tanθ). The high reflectance region (30H) includes an inner region of a rectangle e which is present inside the contour obtained by perpendicularly projecting the outermost end of the substrate onto the major face of the susceptor 30, spaced at a distance of {D+L×tanθ+α(L×tanθ)} (0<α≤1), and the outer rim of the high reflectance region is present inside the contour, spaced at a distance of (D+L×tanθ), wherein θ represents an angle of the chamfered face with respect to the major face of the substrate.

Description

  The present invention relates to a susceptor, a flash irradiation method using the susceptor, and a method for manufacturing a photomask blank, and more particularly to a technique for providing an optical film having low stress and excellent in-plane uniformity of optical characteristics. .

  In order to form a fine structure of a semiconductor device or the like, patterning is performed by overlaying a plurality of photomasks with high accuracy, but a thin film (optical film) already formed on a substrate in a photomask blank state. If stress is accumulated in the film, the stress accumulated in the film is partially released during the photolithography process, causing “distortion” in the photomask. If there is such a distortion, the overlay accuracy of the photomask is lowered, causing a defect in a circuit pattern drawn.

  If the thin film is formed under such a condition that the stress of each thin film (optical film) is substantially zero, the above-mentioned problems will not occur, but film formation for ensuring various characteristics that the thin film as an optical film should have. It is extremely difficult and practically impossible to find manufacturing process conditions that are also conditions for forming a low-stress thin film at the same time. For this reason, it is necessary to separate the process of forming a film under conditions capable of ensuring desired film characteristics and the process of reducing the stress of the thin film after film formation as independent processes.

  By the way, generally, in the photomask blank manufacturing process, a thin film such as a phase shift film is formed by a sputtering method. However, there is a problem in that stress is generated in the film during the film forming process, and the substrate itself is distorted by the stress to cause warping of the photomask blank. As a method for solving this problem, light from a flash lamp is irradiated to a light-absorbing thin film such as a phase shift film at a predetermined energy density to control film stress, thereby reducing warpage of the photomask blank. Technology has been proposed (Patent Document 1).

  However, when light irradiation is performed using a flash lamp, the light reflected by the irradiation device housing is incident from the chamfered surface or the end surface of the substrate, and the incident light is reflected by the susceptor surface on which the substrate is placed and is reflected on the optical film. Re-incidence results in partial application of excess energy to the optical film, which may cause a phenomenon that the in-plane uniformity of the optical characteristics is reduced.

  An effective method for reducing such reflected light has already been proposed by the present inventors (Patent Document 2), but the reflected light cannot be completely suppressed by these methods. A new technique for obtaining an optical film excellent in in-plane uniformity is desired.

JP 2004-199035 A JP 2008-076994 A

  The present invention has been made in view of such problems, and an object of the present invention is to provide a susceptor suitable for providing an optical film having low stress and excellent in-plane uniformity of optical characteristics, and An object is to provide a flash irradiation method using a susceptor and a photomask blank manufacturing method.

  In order to solve the above-described problem, a susceptor according to a first aspect of the present invention is a susceptor used when irradiating an optical film provided on a transparent substrate with flash light, and the substrate is placed on the susceptor. In this case, the region of the susceptor on which the substrate is placed includes a region having a high reflectance and a region having a low reflectance, and the region having a high reflectance is a region having a small amount of irradiated light reaching when the flash is irradiated. In addition, the low reflectance region is a susceptor which is a region where a large amount of light reaches when the flash light is irradiated.

  A susceptor according to a second aspect of the invention is a susceptor used when irradiating a flash on an optical film provided on a transparent substrate having a chamfered surface between a main surface and an end surface. When the substrate is placed, a quadrilateral band which is a region where the irradiation light incident from the chamfered surface on the upper side of the substrate reaches the substrate placement region in the rectangular region where the substrate of the susceptor is placed. The reflectance of the region is R2, and the reflectance R1 of the region inside the four-sided belt-shaped region is a susceptor higher than the reflectance R2.

  A susceptor according to a third aspect of the present invention is a susceptor used when irradiating an optical film provided on a transparent substrate having a thickness of L with flash light, wherein the transparent substrate has a space between a main surface and an end surface. The chamfered surface has an angle θ (0 <θ <90 °) with respect to the main surface, and the plane including the main surface and the end surface on the plane including the main surface. The surface of the susceptor is chamfered to the inner side by a length D from the intersecting line with the plane including the surface, and the susceptor is relative to the region having a relatively high reflectance (R1) in the region where the substrate is placed. A region having a low reflectivity (R2) is provided, and the high reflectivity region is a rectangle obtained by vertically projecting the extreme end of the substrate onto the surface of the susceptor on which the substrate is placed. {D + L · tan θ + α (L · tan θ)} (where 0 <α ≦ 1) A rectangular inner region on the side, and an outer edge is provided inside the inner rectangle by (D + L · tan θ), and the low-reflectance region has an end of the substrate at the end of the susceptor. An area sandwiched between an inner rectangle of (LD · tanθ) · tanθ and an inner rectangle of (D + L · tanθ) with reference to a rectangular contour obtained by vertical projection onto the surface on which the substrate is placed It is a susceptor provided so that it may contain.

  Preferably, the reflectance R1 is 40% or more with respect to light having a wavelength of 200 to 600 nm.

  For example, the high reflectance region having the reflectance of R1 is made of opaque quartz glass, and the low reflectance region having the reflectance of R2 is made of transparent quartz glass.

  In this case, for example, the opaque quartz glass is quartz glass containing bubbles.

  Further, for example, the high reflectance region having the reflectance of R1 and the low reflectance region having the reflectance of R2 are both made of opaque quartz glass containing bubbles, and the bubble content of the high reflectance region is Is greater than the bubble content in the low reflectivity region.

  Further, for example, the high reflectance region having the reflectance of R1 is made of aluminum, and the low reflectance region having the reflectance of R2 is made of opaque quartz glass.

  The flash irradiation method and the photomask blank manufacturing method according to the present invention include a step of placing a substrate provided with an optical film on the susceptor and irradiating the optical film with light from a flash lamp.

  According to the present invention, since regions having different reflectivities are provided in the surface of the susceptor, in-plane non-uniformity of the amount of light irradiated to the optical film is suppressed, and as a result, the surface has low stress and optical characteristics. An optical film excellent in internal uniformity can be obtained. Such a method of performing flash irradiation using a susceptor is useful for manufacturing a photomask blank or the like.

A quartz substrate equipped with a MoSiON film functioning as a halftone phase shift film for ArF as an optical film is placed on a flat plate susceptor having a white opaque layer (made of foamed quartz) on the entire surface, and flash irradiation is performed. It is the figure which showed the result of having measured the transmittance | permeability of the said optical film along the board | substrate diagonal from the board | substrate center after giving. It is a cross section (partial) figure of the quartz substrate which has the chamfering surface which makes an angle of 45 degrees with the main surface in the edge part. It is a figure for calculating | requiring the area | region where the light incident amount on the surface of a susceptor increases with the light which injected from the chamfering surface 1, and at least the area | region which makes a reflectance high. It is a top view of the example of a susceptor concerning the present invention. The figure which shows the in-plane distribution of the transmittance | permeability of the optical film after performing flash irradiation using the susceptor (A) which made only 130 mm square an opaque area | region, and the other area | region transparent, and the susceptor (B) of a whole opaque area | region. is there.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  First, the inventors' interpretation of the cause of in-plane non-uniformity of the optical film characteristics due to flash irradiation will be described.

  In FIG. 1, a quartz substrate having a MoSiON film functioning as a halftone phase shift film for ArF as an optical film is placed on a flat plate susceptor having a white opaque layer (made of foamed quartz) on the entire surface. FIG. 5 is a diagram showing the result of measuring the transmittance of the optical film along the diagonal of the substrate from the center of the substrate after flash irradiation.

  As shown in FIG. 2, the quartz substrate 10 (a square with a side of 152 mm and a thickness of about 6 mm) has a chamfered surface 11 at an angle of 45 ° with the main surface at the end. .

  As shown in FIG. 1, the transmittance of the optical film is substantially uniform from the diagonal center of the substrate to around 60 mm, while showing a significant increase in transmittance around 90 mm from the center, and as it approaches the edge of the substrate. It has dropped rapidly.

  This is because the light emitted from the flash lamp is reflected by the housing wall or the inner wall of the chamber made of a material that reflects the light, enters from the chamfered surface 11, and further reflects by the substrate mounting surface of the susceptor 30. It is understood that the reflected light is applied to the optical film 20. Such reflected light tends to concentrate about 90 mm from the center of the substrate when viewed on the diagonal line of the substrate 10, so that the transmittance of the optical film at that position is larger than the transmittance at other positions. The result will be different.

  This point will be further described. In general, the end portion of the substrate 10 is chamfered in a tapered shape so that, for example, cracks and the like are unlikely to occur during the manufacturing process of the photomask blank and the use of the photomask. Further, since the optical film 20 is not formed on the entire main surface of the substrate 10, the chamfered surface 11 of the substrate is exposed. In general, the chamfered surface 11 has an angle of 45 ° with respect to the main surface of the substrate, and is formed from the end surface of the substrate to about 0.5 mm inside.

  In the substrate 10 having the chamfered surface 11 as described above, light reflected by the housing wall and the chamber inner wall is likely to enter from the chamfered surface 11. Such incident light travels straight through the substrate 10 and is reflected by the white opaque layer of the susceptor 30, and the reflected light is absorbed by the optical film 20. That is, the amount of flash light applied to the optical film is effectively increased at a specific location in the plane, and as a result, the in-plane uniformity of the optical characteristics is deteriorated.

  At this time, the light irradiated onto the chamfered surface 11 may have a large number of incident angle components. However, the present inventors have introduced the chamfered surface 11 into the substrate 10 from the viewpoint of influence on the optical film 20. Of the incident light, it is considered that the contribution of light that is nearly perpendicular to the chamfered surface 11 is large, and particularly attention is paid to the contribution of a light component having a perpendicular incident angle.

  FIG. 3 is a diagram for obtaining a position where the amount of light incident on the surface of the susceptor 30 is increased by the light incident from the chamfered surface 11 under the above assumption. In the example of this figure, the thickness of the substrate 10 is L, and the chamfered surface 11 is provided at an angle θ (0 <θ <90 °) with respect to the main surface from the end surface of the substrate 10 to the inside by a length D. . In this case, the light from the right end portion of the chamfered surface 11 is inward from the contour (a) obtained by vertically projecting the outermost end portion of the substrate 10 onto the main surface of the susceptor 30 by (LD · tan θ) · tan θ. Incident to (b). In addition, light from the left end portion of the chamfered surface 11 is incident on the inner side (c) by (D + Ltanθ) from a contour (a) obtained by vertically projecting the outermost end portion of the substrate 10 onto the main surface of the susceptor 30.

  That is, the light incident perpendicularly to the chamfered surface 11 is inward by (LD · tanθ) · tanθ in the contour (a) obtained by vertically projecting the endmost portion of the substrate 10 onto the main surface of the susceptor 30. The amount of light incident on the region (d) that is the region (b) and does not include the inner (c) region by (D + Ltanθ) is locally increased.

  Such light is reflected by the surface of the susceptor 30, reaches the optical film region, and gives excessive energy to the region.

  As described above, the generally used substrate has a thickness of 6.4 mm, an angle of the chamfered surface of 45 °, and a length on the main surface of the chamfer of 0.5, respectively. A region inside 12.3 mm and outside 13.3 mm from the endmost surface is irradiated with excess energy.

  Based on this understanding, the present inventors have conceived that the amount of flash light irradiated on the optical film is made uniform by providing different reflectances in a region with a small amount of incident light and a region with a large amount of light on the susceptor surface. did.

  The “reflectance” mentioned here is not the micro-reflectance of the micro area of the material, but the incident light quantity when the vertically incident light is divided into a reflection component, a transmission component, and an absorption component. Means the ratio of the reflection component to. For this reason, the said reflectance does not say a local number further, but means the average reflectance of the area | region.

  For example, as the susceptor material, a material having a very high reflectance such as aluminum or a material having almost no absorption component such as quartz is used. Quartz with a rough surface or inside becomes a highly reflective material due to the contribution of reflection components due to irregular reflection. That is, according to the above definition, transparent quartz is a material having a lower reflectance than foamed quartz or the like, and a material having a higher reflectance as the irregular reflection component increases. Also, opaque quartz becomes a material having a high reflectance as the opacity increases.

  FIG. 4 is a top view of an example of a susceptor according to the present invention. This susceptor 30 has a circular flat plate shape and has a rectangular area on which a substrate is placed. The substrate mounting region (30H) has a region (4 side belt-shaped region: 30L) having a reflectance (R2) lower than the reflectance (R1). Further, the reflectance of the peripheral region outside (30H) (region having four sides of a band: 30X) may be equal to or greater than (R2).

  In the substrate mounting region of the susceptor, for example, a substrate having a chamfered portion at the end as shown in FIG. 3 is placed, and the optical film provided on the main surface is irradiated with light from a flash lamp. A photomask blank or the like is manufactured.

  In this case, the low reflectance region (30L) having the reflectance R2 described above is (LD−tanθ) · tanθ within the contour obtained by vertically projecting the endmost portion of the substrate onto the main surface of the susceptor 30. It is provided so as to necessarily include a region sandwiched between the inner rectangle c and the inner rectangle d by (D + L · tan θ). In addition, the high reflectance region (30H) having the reflectance R1 described above is the rectangle e inside (D · L · tan θ) by α (L · tan θ) from the above (D + L · tan θ), that is, the outermost end of the substrate is the main surface of the susceptor 30. It always includes the inner area of the rectangle e inside by {D + L · tan θ + α (L · tan θ)} from the outline obtained by vertical projection on the inside, and the outer edge is inside the rectangle d inside (D + L · tan θ) above. Is provided. Note that the value of α is positive, and if it is 1 or less, it is possible to give a substantially uniform light irradiation amount to the irradiated film, and if it is 0.66 or less, it is possible to give a more uniform light irradiation amount. .

  The reflectance R1 described above is preferably 40% or more for light with a wavelength of 200 to 600 nm.

  As a combination of the susceptor materials used for the high reflection region and the low reflection region, for example, the high reflectance region is opaque quartz glass, the low reflectance region is transparent quartz glass, and the like. In this case, quartz glass containing bubbles can be used as the opaque quartz glass. The quartz material made opaque by including bubbles with a diameter smaller than 1 mm and larger than 0.8 μm can increase the reflectance to about 40% by increasing the bubble content while maintaining the mechanical strength.

  Other susceptor material combinations include opaque quartz glass containing bubbles in both the high reflectivity region and the low reflectivity region, and the bubble content in the high reflectivity region is higher than the bubble content in the low reflectivity region. You may make it be many.

  Further, the high reflectance region may be made of aluminum, and the low reflectance region may be made of opaque quartz glass.

  The design of the low reflectance region is because the component perpendicularly incident from the chamfered surface makes the largest contribution as described above, but the position indicated by d in FIG. 3 (perpendicular to the chamfered surface). The width of S shown in FIG. 3, that is, α (L · tan θ) does not need to be exactly matched to the innermost position where the incident light reaches) and does not deviate from the gist of the present invention, for example, in the substrate inner direction. ), The area may be included. This is because there is a light component that is incident non-perpendicularly on the chamfered surface, and the width that is affected by the component that is incident non-perpendicularly is a function of the thickness of the substrate and the angle of the chamfered surface. As described above, if α is designed to be 1 or less, a considerable effect can be obtained, and if it is 0.66 or less, a sufficient effect can be obtained.

  Taking the susceptor of the present invention as an example in which the high reflectance region is made of opaque quartz glass made opaque by including bubbles, and the low reflectance region is made of transparent quartz glass, the light incident on the low reflectance region is taken as an example. Most of the light is not reflected by the susceptor but escapes to the back surface, while reflection is caused by the bottom of the device housing where the susceptor is placed, but the light that is reflected back returns to the highly reflective area of the susceptor. For this reason, energy supply to the optical film as the irradiated material is extremely small.

  On the other hand, most of the light incident on the high reflectivity region is light that has once passed through the optical film and has already been attenuated, but this attenuated light is reflected at a relatively high rate. Re-enter the optical film.

  Accordingly, the amount of flash light irradiation can be made uniform between the optical film portion corresponding to the high reflectance region and the optical film portion corresponding to the low reflectance region, and as a result, the in-plane uniformity of the optical film characteristics can be achieved. Become. In addition, by making the reflectance of the high reflectance region sufficiently high, the energy of the re-incident light is effectively used, and the light irradiation energy amount can be set low.

  Note that a peripheral region (region 30X in FIG. 4) having a higher reflectance than the above (30L) may be provided outside the point indicated by c in FIG. Even if the peripheral region (30X) has the reflectivity of R2, the minimum object of averaging the dose of the present invention can be achieved, but the irradiation at the edge of the substrate shown in FIG. It is effective to increase the reflectivity of this (30X) region in order to average the region considered to have a small amount. Further, in the case of increasing the reflectance of the region (30X), as in the case of the boundary between (30H) and (30L), a width of β (L · tan θ) is provided outside the point c in FIG. A boundary between (30L) and (30X) may be provided, and the value of β is preferably 0.66 or less.

  The design of the susceptor described above is based on an apparatus that has one flash irradiation lamp in the center as a flash lamp light irradiation device and irradiates a single irradiated object with flash light. May be an apparatus that irradiates two or more irradiated objects, and it is more complicated to average the amount of energy incident on the optical film that is the irradiated object when irradiation is performed using such an apparatus. Design is required. In such a case, when the flash lamp irradiation is performed, the amount of irradiation light reaching each part of the region on which the substrate is placed may be obtained, and a portion with a large amount of reaching light may be set as the low reflectance region. Note that the amount of irradiated light reached is measured by using the principle of change in transmittance of the inorganic film shown in FIG. 1 and placing a semi-permeable inorganic film on the irradiated object mounting portion and measuring the change in transmittance. can do.

  When the flash lamp light irradiation treatment is performed using the susceptor of the present invention and the stress reduction in the optical film is executed, the flash light irradiation amount can be made uniform, so that the in-plane uniformity of the characteristics of the optical film is maintained. Thus, the stress of the optical film can be reduced. For example, after forming an optical film (for example, a phase shift film) capable of absorbing light irradiated from a flash lamp on a transparent substrate such as synthetic quartz glass or calcium fluoride, the substrate is formed into a susceptor having the above-described configuration. After the optical film is irradiated with flash light to reduce the stress in the film, if necessary, another optical film or the like is formed on the optical film to form a photomask blank.

Examples of the optical film that receives the flash irradiation include a phase shift film, a light shielding film, and an antireflection film formed on the photomask blank. The flash irradiation method of the present invention is a flash lamp used in the present invention. However, in general, considering that the flash light is irradiated with an energy of about 20 J / cm ^{2 in} about 1 to 10 milliseconds, it is special if the light absorption capacity at that wavelength is too high. If no dimming means is used, the film may be destroyed.

  The flash lamp is a light source having a short light emission time and a wide wavelength range with high illuminance, for example, a xenon flash lamp. For this reason, unlike the case of using a laser light source, the light absorption film does not need to be a film that exhibits large absorption with respect to light of a specific wavelength. Therefore, the restrictions on the film composition and the like that can control the stress by the flash irradiation method are extremely loose, and the application range is wide. Further, it is not necessary to scan the irradiation light on the substrate, and the entire surface of the substrate can be irradiated with light (given energy) in a short time. Furthermore, since it has a spectrum over a wide wavelength region, it is possible to simultaneously obtain irradiation effects of light of various wavelengths.

  When such a flash is applied to an optical film (flash absorption film) such as a halftone phase shift film, the film composition, atomic bonding state, etc. change due to absorption of the irradiation light or a sudden temperature change, resulting in stress. A reduction is believed to occur.

  First, a synthetic quartz transparent having a thickness of 6.35 mm and a length of four sides of 152 mm each, and a chamfered surface with an angle of 45 ° with respect to the main surface, extending from the edge of the substrate to a length of 0.50 mm in the main surface direction. A substrate was prepared, and a halftone phase shift film made of MoSiON was formed on the substrate with a film thickness of 760 mm by reactive DC sputtering.

  This phase shift film is a film having a phase difference of about 180 ° and a transmittance of about 5% when an ArF excimer laser (193 nm) is used as exposure light. And after heating this board | substrate (namely, board | substrate with a phase shift film) to the temperature of 80 degreeC, it mounted in the state which faced the phase shift film on the susceptor, and irradiated energy using the xenon flash lamp light from the upper part. At this time, the opaque region of the susceptor was processed as a 130 mm square smaller than the substrate.

  FIG. 5 shows a susceptor (A) in which only the 130 mm square is an opaque region and the other regions are transparent, and a susceptor (B) in the entire opaque region, and a substrate on which an optical film is provided on each susceptor. It is a figure which shows the in-plane distribution of the transmittance | permeability of the optical film after performing flash irradiation. In addition, the reflectance of the said opaque area | region is 40% or more with respect to the light with a wavelength of 200-600 nm.

  From this figure, the transmittance peak at about 90 mm from the center, which was generated when flashing was performed using the susceptor (B) in the entire opaque region, was a susceptor in which only the 130 mm square was an opaque region and the other regions were transparent. It can be seen that it is suppressed when flash irradiation is performed using A).

  This is because the light incident from the chamfered surface passes without being reflected by the opaque region of the susceptor A, as described above, and the amount of flash irradiation to the optical film portion corresponding to the position is suppressed. is there.

  In this embodiment, “foamed glass” made of quartz glass is used as the opaque material of the susceptor, but the material is not limited to this. In addition, the susceptor can have various forms, and the susceptor can be made of an opaque material, or a structure in which a plurality of opaque layers and transparent layers are stacked.

  In order to make it easier to control the amount of strain (stress amount) accumulated in an optical film such as a phase shift film, the amount of flash irradiation is controlled to a predetermined amount or less of light energy. This is because if the amount of flash irradiation is too high, the film quality of the optical film is impaired and the film may be destroyed by excessive irradiation. The “predetermined amount” of the energy of flash irradiation light depends on the optical characteristics of the optical film provided in the photomask blank to be manufactured. For example, in the case of a phase shift mask, it depends on the thickness and transmittance of the phase shift film. It will be.

  Examples of the phase shift film include an amorphous silicon film, a metal compound film containing oxygen, nitrogen, carbon, and the like, and in particular, one or more selected from metals other than silicon and silicon, and oxygen, nitrogen, and carbon. The phase shift film including a single layer or a multilayer containing the above is a film having excellent optical property controllability. Examples of metals other than silicon contained in the phase shift film include W, Mo, Ti, Ta, Zr, Hf, Nb, V, Co, Cr, and Ni. From the viewpoint of reduction and improvement in chemical resistance, those based on Mo are preferred.

  As the phase shift film having such a composition, molybdenum silicide oxide (MoSiO), molybdenum silicide nitride (MoSiN), molybdenum silicide carbide (MoSiC), molybdenum silicide oxynitride (MoSiON), molybdenum silicide oxycarbide (MoSiOC) Alternatively, there is molybdenum silicide oxynitride carbide (MoSiONC) or the like, and such a molybdenum silicide phase shift film can be formed by a reactive sputtering method using MoSi or the like as a target.

When the phase shift film is irradiated with flash light is a film of molybdenum silicide system such as described above, KrF as film specifications, ArF, although there may be a F ₂ laser exposure, the transmittance wavelength range of 200~1100nm in is higher for KrF, for ArF, in order for _{F 2.} That is, since the absorption efficiency of light varies depending on the film quality, there is respectively appropriate region on the irradiation energy by the flash lamp, comprising KrF, ArF, and needs to be larger in the order of F _2.

Specifically, for a phase shift film having a transmittance of 5 to 7% with respect to light having a wavelength of KrF laser (248 nm), the flash irradiation energy is 21.5 J / cm ² as measured by a calorimeter. The following predetermined amount is used. For the phase shift film having a transmittance of 5 to 7% with respect to the light of the ArF laser wavelength (193 nm), the flash irradiation energy is a predetermined amount of 32.5 J / cm ² or less. Further, for the phase shift film having a transmittance of 5 to 7% with respect to the light of the wavelength (157 nm) of the F ₂ laser, the flash irradiation energy is set to a predetermined amount of 41.5 J / cm ² or less. According to observation with a Nomarski microscope, it has been confirmed that a part of the phase shift film on the substrate surface is destroyed when the phase shift film is irradiated with flash light with light energy higher than the above value.

  In the present invention, the unit light emission time (time required for one light emission) of the flash lamp is generally set in the range of 100 μsec to 1 sec. When the irradiation time of the flash lamp is short, the irradiation wavelength tends to shift to the short wavelength side, and when the irradiation time of the flash lamp is long, the irradiation wavelength tends to shift to the long wavelength side. For this reason, in this embodiment, the unit light emission time of the flash lamp is set within the range of 0.1 msec to 100 msec, specifically, the irradiation time is about 1 to 10 msec.

  As described above, the flash irradiation using the susceptor of the present invention has been described by way of examples. However, the above examples are merely examples for carrying out the present invention, and the present invention is not limited to these examples. It is apparent from the above description that various modifications of these embodiments are within the scope of the present invention, and that various other embodiments are possible within the scope of the present invention.

  According to the present invention, it is possible to provide an optical film having low stress and excellent in-plane uniformity of optical characteristics.

10 Substrate 11 Chamfered surface 20 Optical film 30 Susceptor 30L Low reflectance region 30H High reflectance region

Claims (10)

A susceptor used when irradiating an optical film provided on a transparent substrate with a flash,
When the substrate is placed on the susceptor, the region of the susceptor where the substrate is placed includes a region having a high reflectance and a region having a low reflectance.
The susceptor in which the region having a high reflectance is a region having a small amount of irradiated light reaching when the flash is irradiated, and the region having a low reflectance is a region having a large amount of irradiated light reaching when the flash is irradiated. A susceptor used when flashing an optical film provided on a transparent substrate having a chamfered surface between a main surface and an end surface,
When the substrate is placed on the susceptor, within a rectangular region where the substrate of the susceptor is placed, an irradiation area of the irradiation light incident from the chamfered surface on the upper side of the substrate reaches the substrate placement region. A susceptor in which a reflectance of a certain four-sided belt-shaped region is R2, and a reflectance R1 of a region inside the four-sided belt-shaped region is higher than the reflectance R2. A susceptor used when irradiating a flash on an optical film provided on a transparent substrate having a thickness of L,
The transparent substrate is provided with a chamfered surface between a main surface and an end surface,
The chamfered surface has an angle θ (0 <θ <90 °) with respect to the main surface and is long from an intersection line of the plane including the main surface and the plane including the end surface on the plane including the main surface. It is a surface that is chamfered to the inside by a length of D,
The susceptor is provided with a relatively high reflectance (R1) region and a relatively low reflectance (R2) region in a region where the substrate is placed,
The high reflectivity region is defined as {D + L · tan θ + α (L · tan θ)} with reference to a rectangular outline obtained by vertically projecting the extreme end of the substrate onto the surface of the susceptor on which the substrate is placed. (Provided that the inner region of the inner rectangle is necessarily included only by 0 <α ≦ 1), and the outer edge is located inside the inner rectangle by (D + L · tan θ),
The low reflectivity region is (LD−tanθ) · tanθ by using a rectangular outline obtained by vertically projecting the extreme end of the substrate on the surface of the susceptor on which the substrate is placed. A susceptor provided to include an inner rectangle and a region sandwiched between the inner rectangle by (D + L · tan θ).   The susceptor according to claim 2 or 3, wherein the reflectance R1 is 40% or more with respect to light having a wavelength of 200 to 600 nm.   5. The susceptor according to claim 2, wherein the high reflectivity region having the reflectivity of R <b> 1 is made of opaque quartz glass, and the low reflectivity region having the reflectivity of R <b> 2 is made of transparent quartz glass. .   The susceptor according to claim 5, wherein the opaque quartz glass is a quartz glass containing bubbles.   Both the high reflectance region having the reflectance of R1 and the low reflectance region having the reflectance of R2 are made of opaque quartz glass containing bubbles, and the bubble content in the high reflectance region is the low reflectance. The susceptor according to any one of claims 2 to 4, wherein the susceptor is larger than a bubble content in the rate region.   5. The susceptor according to claim 2, wherein the high reflectivity region having the reflectivity of R <b> 1 is made of aluminum, and the low reflectivity region having the reflectivity of R <b> 2 is made of opaque quartz glass.   A flash irradiation method comprising a step of placing a substrate on which an optical film is provided on the susceptor according to claim 1 and irradiating the optical film with light from a flash lamp.   9. A photomask blank manufacturing method comprising a step of placing a substrate provided with an optical film on the susceptor according to claim 1 and irradiating the optical film with light from a flash lamp. Method.