JP2011181548A - Imprinting method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imprinting method which has superior mold-releasing characteristics between a mold and a resin, reduces pattern defects due to the resin and has a high-precision pattern formed at a low cost, and also to provide an imprinting device using the imprinting method. <P>SOLUTION: In the imprinting method, the mold having a pattern formed is pressed against the photosetting resin on a substrate to be processed and exposed to light emitted by a light source in each shot to cure the photosetting resin, and the mold is released from the cured photosetting resin. An exposure amount adjusting part which adjusts an exposure amount of light to cure the photosetting resin, is provided between the light source and mold, and is used to make an exposure amount in a region where the mold is released from the photosetting resin finally, smaller than that of other regions in a pattern formation region in each shot. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an imprint method that forms fine concavo-convex patterns and is excellent in releasability by reducing pattern defects due to resin, and an imprint apparatus using the imprint method.

  In recent years, especially for semiconductor devices, high speed operation and low power consumption operation are required due to further progress in miniaturization, and high technology such as integration of functions called system LSIs is required. Under such circumstances, the lithography technology that is necessary for producing the pattern of the semiconductor device has become very expensive as the exposure apparatus and the like as the pattern becomes finer, and the price of the mask used therefor also becomes expensive. Yes.

  In contrast, the nanoimprint method (hereinafter referred to as imprint method) proposed by Chou et al. In Princeton University in 1995 forms a fine pattern having a high resolution of about 10 nm while the apparatus price and the material used are low. It is attracting attention as a technology (see Patent Document 1).

  In the imprint method, a mold (also referred to as a template, stamper, or mold) in which a nanometer-sized uneven pattern is formed on the surface in advance is pressed against a transfer material such as a resin formed on the substrate surface that is the workpiece. This is a technology that mechanically deforms and precisely transfers a fine pattern, and processes the workpiece using the patterned resin as a resist mask. Once the mold is made, the nanostructure can be easily and repeatedly molded, resulting in high throughput and economics, and because it is a nano-processing technology with little harmful waste, not only semiconductor devices in recent years, Application to various fields is expected.

  Such imprinting methods include a thermal imprinting method in which a concavo-convex pattern is transferred by heat using a thermoplastic resin, or a photoimprinting method in which a concavo-convex pattern is transferred by ultraviolet rays using a photocurable resin (for example, patents). Document 2) is known. As the resin as the transfer material, a thermoplastic resin is used in the thermal imprint method, and a photocurable resin is used in the photoimprint method. The optical imprint method can transfer a pattern at a low applied pressure at room temperature, and does not require a heating / cooling cycle like the thermal imprint method and does not cause dimensional changes due to mold or resin heat. It is said that it is excellent in terms of productivity.

  FIG. 7 is a process cross-sectional view showing pattern formation by a conventional optical imprint method. As shown in FIG. 7A, first, a mold 70 having a pattern to be transferred is prepared. On the other hand, a low-viscosity photocurable resin 72 is applied on the substrate 71 to be processed.

  Next, the concavo-convex pattern of the mold 70 is brought into contact with the photo-curable resin 72 on the substrate 71 to be pressed, and light (ultraviolet rays) 73 is applied while the mold 70 is pressed, as shown in FIG. 7B. Irradiation is performed to cure the photocurable resin to obtain a cured photocurable resin 74.

  Next, as shown in FIG. 7C, the mold 70 is released from the cured photocurable resin 74. The example shown in FIG. 7C shows a state where the mold is released by applying a release force F from the two opposite ends of the mold to the upper side of the sheet. After the mold release, a transfer pattern is formed by the photocurable resin 74 on the substrate 71 to be processed.

  In the imprint method, a portion of the photocurable resin 74 corresponding to the convex portion of the mold 70 remains as a thin residual film on the substrate 71 to be processed. As shown in FIG. 7D, the remaining film is removed by ion etching using oxygen gas.

  Molds used in the imprint method are required to have pattern dimension stability, chemical resistance, processing characteristics, and the like. Taking the case of the photoimprint method as an example, generally, quartz glass that transmits ultraviolet rays used for photocuring is used. In the imprint method, the pattern shape of the mold must be faithfully transferred to a resin that is a transfer material. For this purpose, it is necessary to transfer the mold shape to the resin and then release the mold without changing the shape when the mold is released.

  However, usually, a mold made of quartz glass or the like has a low releasability from a resin that is a pattern transfer material, and a part of the resin adheres to the mold side when the mold is released from the resin on which the transfer pattern is formed. Therefore, there is a problem in that chipped defects are generated in the concavo-convex pattern of the transferred resin, and the pattern accuracy tends to be lowered. Further, there is a problem that the mold having the resin adhered to the pattern cannot be used for subsequent pattern transfer unless the adhered resin is removed. For this reason, as a method for improving the mold releasability between the mold and the resin, for example, a method for improving the releasability by applying and forming a thin film of a release agent such as a fluororesin on the surface of the concave and convex pattern of the mold has been proposed. .

  However, even when a mold release agent is used, when imprinting is performed using a mold continuously, the applied mold release agent is gradually lost from the surface of the concavo-convex pattern, resulting in a decrease in mold release property. There is a problem in that the resin sometimes adheres to the mold and accurate pattern transfer cannot be performed. In general, it is known that the curing of the resin causes a resin contraction to generate a stress, and the defect of the concavo-convex pattern due to the resin is generated at a location where the stress is easily concentrated at the time of mold release.

  For this reason, in order to improve the mold releasability between the mold and the resin in the photoimprint method, the mold having a phase displacement layer is used and the exposure intensity is controlled to cure the photocurable resin at a specific site. A method has been proposed in which the degree of resin pattern defects is selectively uncured by selectively reducing the degree of shrinkage and reducing the shrinkage stress, thereby suppressing the occurrence of defects in the transfer pattern (Patent Document 3). reference).

JP-T-2004-504718 JP 2002-93748 A JP 2008-201020 A

  However, the optical imprint method described in Patent Document 3 requires the use of coherent light as exposure light, and there is a problem that the light source and the apparatus are complicated. Complex processes such as film formation of the displacement layer, alignment of the pattern on the front and back of the mold, and etching processing on the front and back are required, and there is a problem that the pattern of the phase displacement layer must be changed for each mold. In addition, there is a problem that the imprint apparatus becomes expensive and deviates from the original purpose of forming a high-precision pattern at a low cost by the imprint method.

  Therefore, the present invention has been made in view of the above problems. That is, an object of the present invention is an imprint method for forming a fine concavo-convex pattern, which is excellent in releasability between a mold and a resin, reduces pattern defects due to the resin, and forms a high-precision pattern at low cost. And an imprint apparatus using the imprint method.

  In order to solve the above problems, an imprint method according to the invention of claim 1 of the present invention presses a mold having a pattern against a photocurable resin on a substrate to be processed, and emits light emitted from a light source, An imprint method in which the photocurable resin is cured by exposing the photocurable resin to each shot through the mold, and then the mold is released from the cured photocurable resin. An exposure amount adjustment unit that adjusts an exposure amount of light for curing the photocurable resin is provided between the light source and the mold, and the exposure amount adjustment unit is used to form a pattern formation region for each shot. In the above, the exposure amount of the region where the mold is finally released from the cured photocurable resin is made smaller than the exposure amount of other regions.

  The imprint method according to claim 2 of the present invention is the imprint method according to claim 1, wherein a region where the mold is finally released from the cured photocurable resin is in the pattern forming region. It is the center part of this.

  In the imprinting method according to the third aspect of the present invention, the mold having a pattern formed is pressed against a photocurable resin on a substrate to be processed, and light emitted from a light source is transmitted through the mold to the photocuring. An imprint method in which the photocurable resin is cured by exposing the photocurable resin to each shot, and then the mold is released from the cured photocurable resin, between the light source and the mold. An exposure amount adjusting unit that adjusts an exposure amount of light for curing the photocurable resin, and using the exposure amount adjusting unit, an area having a high pattern density in the pattern forming region for each shot. The exposure amount is made smaller than the exposure amount in the region having a low pattern density.

  The imprint method according to claim 4 of the present invention is the imprint method according to any one of claims 1 to 3, wherein the exposure amount adjusting unit cures the photocurable resin. It has a transmittance distribution or a reflectance distribution of light to be generated.

  The imprint method according to claim 5 of the present invention is the imprint method according to any one of claims 1 to 4, wherein the exposure amount adjustment is performed in a pattern formation region for each shot. The light transmittance and transmittance distribution of the part, or the reflectance and reflectance distribution are variable.

  The imprint method according to a sixth aspect of the present invention is the imprint method according to any one of the first to fifth aspects, wherein the exposure amount adjusting unit has two levels of light transmittance. The gradation mask has a transmittance region that changes as described above.

  An imprint apparatus according to a seventh aspect of the present invention is characterized by using the imprint method according to any one of the first to sixth aspects.

  The imprint method of the present invention is provided with an exposure amount adjusting unit that adjusts an exposure amount of light for curing the photocurable resin in accordance with a method of applying a release force to the mold or a pattern density of the mold. By using the amount adjustment part, in the pattern formation area for each shot, the degree of cure of the photocurable resin in the area where defects during mold release are likely to occur is reduced, and the mold and resin have excellent mold release properties. It is possible to suppress or reduce the occurrence of pattern defects due to the resin and to form a highly accurate pattern at low cost.

  The imprint apparatus using the imprint method of the present invention is excellent in releasability between the mold and the resin by providing an exposure amount adjusting unit that adjusts the exposure amount of light for curing the photocurable resin. Generation of pattern defects can be suppressed or reduced, and an inexpensive imprint apparatus that can form a highly accurate pattern can be obtained.

It is a schematic block diagram which shows an example of the imprint apparatus using the imprint method of this invention. It is a schematic block diagram which shows the other example of the imprint apparatus using the imprint method of this invention. It is the top view and sectional drawing which show the example of the gradation mask used for the exposure amount adjustment part in the 1st Embodiment of this invention. It is the top view and sectional drawing which show the other example of the gradation mask used for the exposure amount adjustment part in the 1st Embodiment of this invention. It is a top view which shows the example of the gradation mask used for the exposure amount adjustment part in the 2nd Embodiment of this invention. It is the top view and sectional drawing which show the example of the gradation mask used for the exposure amount adjustment part in the 3rd Embodiment of this invention. It is process sectional drawing which shows an example of the pattern formation by the conventional optical imprint method.

  The present inventor found that the defects when releasing the imprint mold and the photocurable resin tend to be distributed in the pattern formation region for each shot, and the mold is the last from the cured photocurable resin. It has been found that defects are likely to occur in the area where the mold is released. Here, the defect at the time of releasing means a defect such as a chip generated on the photocurable resin side, and corresponds to a defect caused by part of the photocurable resin adhering to the mold side. .

  Further, the defect at the time of mold release is more likely to occur in the central portion than in the peripheral portion of the pattern forming region in the pattern forming region for each shot. Defects at the time of mold release are likely to occur at the center of the shot when the mold and the photocurable resin are released from the mold, as shown in FIG. In many cases, the mold release is started from both ends, so that the peeling progresses from the periphery to the center of the mold transfer area, and the release speed increases particularly in the center of the shot, and the area corresponding to the center of the shot. It is presumed that a larger release force than the shot peripheral part acts on the photo-curable resin, and the resin is torn and becomes a defect.

  Further, defects at the time of mold release are likely to occur in a region having a high pattern density in a pattern formation region for each shot. In areas where the pattern density is high, the contact area between the concavo-convex pattern of the mold and the photo-curing resin is large. Interpreted to be easier.

(Imprint method)
Therefore, the imprinting method of the present invention presses the mold having a concavo-convex pattern against the photocurable resin on the substrate to be processed, and transmits light emitted from the light source to the photocurable resin through the mold for each shot. In the imprint method in which the photocurable resin is cured by exposing to a mold, the pattern is transferred, and then the mold is released from the cured photocurable resin, the light exposure amount for curing the photocurable resin is adjusted. By using the exposure amount adjustment unit, within the pattern formation region for each shot, by making the exposure amount of the photocurable resin in the region where defects at the time of release are likely to occur smaller than the region where normal exposure is performed, By reducing the crosslink density of the resin, the degree of cure of the resin is lowered to facilitate release, and the occurrence of defects during release is suppressed or reduced.
Hereinafter, embodiments will be described.

(First embodiment)
In the imprint method in the present embodiment, an exposure amount adjustment unit that adjusts an exposure amount of light (ultraviolet rays) that cures the photocurable resin is provided between the light source and the mold, and the exposure amount adjustment unit is used. Within the pattern formation area for each shot, the exposure amount of the area that is finally released from the photo-curing resin in which the mold is cured is changed, and the exposure amount of the area that is finally released is smaller than the exposure amount of other areas. Is. Finally, by reducing the exposure amount of the region to be released, the degree of curing of the photocurable resin in the region is reduced, and the release property of the region is improved.

  Hereinafter, the imprint method of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an example of an imprint apparatus 100 using the imprint method of the present invention. In the description of the present embodiment, the region that is finally released from the photo-curing resin that has been cured by the mold is the central portion in the pattern formation region, and another region that is different from the region that is finally released is in the pattern formation region. A description will be given by taking as an example a region excluding the central portion. As described with reference to FIG. 7, when the mold is released from the cured photocurable resin, the mold is usually released by applying a release force from both opposite ends of the mold. In this case, the region to be released last is the central portion in the pattern formation region.

  An imprint apparatus 100 as an example shown in FIG. 1 includes a light source 101, a contact lens 103 that forms an optical system that guides light (ultraviolet rays) 102 from the light source, a diffusion plate 104 that uniformizes unevenness of the light source, and exposure. An amount adjusting unit 105; a field lens 107 that is in an optical path that guides light to the condenser lens 109; and an aperture stop that controls the illumination light incident angle range; and a light distribution according to the exposure amount adjusting unit 105. A condenser lens 109, a mold 110, and a substrate to be processed 111 coated with a photocurable resin on the surface of a wafer or the like, a mold driving unit, a substrate driving unit to be processed, and other mechanisms Have

  The light source 101 includes a high-pressure mercury lamp or a halogen lamp that generates light (ultraviolet rays) 102 for curing the photocurable resin, and includes a shutter (not shown) for switching between irradiation and light shielding.

  Since the mold 110 has a concave / convex pattern to be transferred facing toward the substrate 111 to be processed and transmits exposure light for photocuring the photocurable resin, it is generally made of a transparent member such as synthetic quartz. It has been.

  The mold driving unit includes a mold holding unit (not shown) for holding the mold 110 in the imprint apparatus 100 and an imprint mechanism unit (not shown) as a driving unit for pressing the mold 110 downward. The imprint mechanism unit also includes a vertical movement mechanism, a pressure mechanism, a posture control mechanism, and a rotational alignment mechanism so that the mold 110 transfer surface and the substrate to be processed 111 are in close contact with each other.

  The processed substrate driving unit includes a substrate holding unit 112 that holds the processed substrate 111 and a substrate moving stage 113 for adjusting the position and posture of the substrate holding unit 112. The substrate movement stage 113 can be moved in the x and y plane directions by the substrate movement drive unit 114, and the entire surface of the substrate 111 to be processed can be transferred. The substrate moving stage 113 can be positioned with high precision. Further, the substrate moving stage 113 has not only positioning but also means for adjusting the posture of the surface of the substrate to be processed 111, and has a function of adjusting the posture of the surface of the substrate to be processed 111.

  Other mechanisms include a surface plate, a vibration isolator, a frame, an alignment scope (not shown), and the like. The surface plate supports the entire imprint apparatus 100 and forms a reference plane for moving the substrate moving stage 113. The vibration isolator has a function of removing vibration from the floor and supports the surface plate. The frame supports components from the light source 101 to the mold 110 located above the workpiece substrate 111. The alignment scope measures the position of the alignment mark on the workpiece substrate 111 and positions the substrate moving stage 113 based on the result.

(Exposure adjustment part)
In the present invention, the exposure amount adjusting unit 105 is a member having a function of changing the exposure amount of a predetermined region of the substrate 111 to be exposed by changing the exposure amount of light (ultraviolet rays) 102 emitted from the light source 101. This means that it has a transmittance distribution or a reflectance distribution for adjusting the exposure amount of light (ultraviolet rays) for curing the photocurable resin. In the example of this embodiment shown in FIG. 1, light (ultraviolet light) 102 emitted from the light source 101 passes through an exposure amount adjusting unit 105 in which the transmittance of the central region is changed, so that the central portion where the light intensity is attenuated. Light 102 a and peripheral light 102 b whose light intensity is substantially maintained, and reaches the mold 110 through the condenser lens 109. Therefore, the exposure amount of the photocurable resin applied on the substrate 111 to be processed by the light transmitted through the mold 110 is smaller in the central portion than in the peripheral portion, and the degree of cure of the central portion of the photocurable resin is the peripheral portion. Smaller than. As a result, when the mold and the cured photocurable resin are released, the shot center part is easily released, and the occurrence of pattern defects due to the resin in imprinting is suppressed.

  In the imprint apparatus 100 illustrated in FIG. 1, the case where the exposure amount adjustment unit 105 is above the field lens 107 has been described as an example. However, the position of the exposure amount adjustment unit 105 is not limited to the above example. The exposure amount adjusting unit 105 is provided so as to irradiate a predetermined region of the mold 110 with light (ultraviolet light) 102 emitted from the light source 101, so that it is in the optical path between the light source 101 and the mold 110. In this case, it may be provided so as to be located in any conjugate with the mold pattern surface.

  The imprint apparatus 100 illustrated in FIG. 1 illustrates a case where the light transmittance is adjusted by the exposure amount adjusting unit 105 and the exposure amount of the light 102 that cures the photocurable resin is adjusted using the transmitted light. In the present invention, as will be described later, it is also possible to adjust the light reflectance by the exposure amount adjusting unit, and to adjust the exposure amount of light for curing the photocurable resin using the reflected light.

  In the present invention, when adjusting the exposure amount using the light emitted from the light source 101 as the transmitted light, the exposure amount adjustment unit 105 uses the transmittance distribution of the light (ultraviolet rays) 102 for curing the photocurable resin. A member having a transmittance region in which the transmittance of light (ultraviolet rays) 102 changes in two or more steps is used. As the transmittance region, a region where the transmittance of light (ultraviolet rays) 102 is substantially 100% may be included. As the exposure amount adjusting unit 105 that adjusts the light transmittance, for example, a photomask called a gradation mask having a light (ultraviolet) transmittance distribution, a diffractive optical element (DOE), or the like. Is mentioned. As the diffractive optical element, a diffraction grating, a holographic optical element, or a computer generated hologram (CGH) element can be applied. The computer generated hologram element is designed in advance to generate a light pattern having a desired light intensity distribution, A transparent synthetic quartz substrate can be fabricated by etching in multiple steps in a stepped manner.

  Further, in the present invention, the exposure amount adjusting unit 105 in the case where the exposure amount is adjusted using light emitted from the light source as transmitted light has a transmittance distribution of light (ultraviolet rays) for curing the photocurable resin. The gradation mask is more preferable because it is relatively easy to manufacture. The gradation mask that can be used in the present invention includes a mask called a gray tone mask or a slit mask. The gradation mask can adjust the light transmittance for curing the photocurable resin by forming a region having a transmittance distribution on one main surface of the synthetic quartz substrate. The gradation mask is formed by using a mask blank provided with a predetermined thin film, applying a photoresist or an electron beam resist, exposing with ultraviolet rays, a laser, or an electron beam, and etching the thin film to form a pattern.

  Hereinafter, a typical example in the case where a gradation mask is used as the exposure amount adjustment unit 105 for adjusting the light transmittance will be described in detail.

  FIG. 3 is a plan view and a cross-sectional view of a gradation mask used in the exposure adjustment unit 105 of the present invention, and shows three types of examples. Each of the masks is an example in which the transmittance at the center of the mask is small, and is an example of a gradation mask having a transmittance region that changes in at least three stages including a region where the light transmittance is substantially 100%. .

  3A is a gradation mask 30A having two layers of thin films having different transmittances, FIG. 3A-1 is a plan view, and FIG. 3B-1 is FIG. 3A-1. It is sectional drawing in the AA of. The mask 30A includes a transparent substrate portion 31a having substantially 100% light transmittance and semi-transparent regions 32a and 33a having different transmittances. The thin films constituting the two layers may be thin films made of the same material, or thin films made of different materials. This gradation mask can be prepared by, for example, a method disclosed in Japanese Patent Laid-Open No. 7-49410. The magnitude of the transmittance is 33a <32a <31a. As described above, the region 31a is a region having a high transmittance substantially including 100%, and the region 32a is less than 100% and smaller than the region 31a. In the medium transmittance region, the region 33a can be provided as a predetermined low transmittance region that is smaller than the region 32a and exceeds 0%.

  3B is a one-layer gradation mask 30B made of a semi-transparent film. FIG. 3B-1 is a plan view, and FIG. 3B-2 is B in FIG. 3B-1. It is sectional drawing in the -B line. The mask 30B includes a transparent substrate portion 31b having substantially 100% light transmittance and semi-transparent regions 32b and 33b having different transmittances. The region 32b is a region where a rectangular or circular dot pattern having a size that cannot be resolved by exposure light exists. This gradation mask can be created by, for example, a method disclosed in JP-A-2004-70087. The magnitude of the transmittance is 33b <32b <31b. As described above, the region 31b is a region having a high transmittance substantially including 100%, and the region 32b is a region having a predetermined medium transmittance that is less than 100% and smaller than the region 31b. By adjusting, it is possible to display multiple gradations. The region 33b can be provided as a region having a predetermined low transmittance that is smaller than the region 32b and exceeds 0%.

  FIG. 3C is a one-layer gradation mask 30C made of a translucent film, which is a mask called a slit mask or a gray tone mask. FIG. 3C-1 is a plan view, and FIG. c) -2 is a cross-sectional view taken along line CC of FIG. 3 (c) -1. The mask 30C includes a transparent substrate portion 31c having substantially 100% light transmittance and semi-transparent regions 32c and 33c having different transmittances. The region 32c is a region where there exists a slit pattern having a size that cannot be resolved by exposure light. This gradation mask can be created by, for example, a method disclosed in JP-A-2002-189280. The magnitude of the transmittance is 33c <32c <31c. As described above, the region 31c is a region having a high transmittance substantially including 100%, and the region 32c is less than 100% and smaller than the region 31c. In the medium transmittance region, the region 33c can be provided as a predetermined low transmittance region that is smaller than the region 32c and exceeds 0%.

  By using any one of the above-illustrated gradation masks as the exposure amount adjusting unit 105, the exposure amount of the photocurable resin applied on the substrate 111 by the light transmitted through the mold 110 is shot. The central part is smaller than the peripheral part, the degree of curing of the photocurable resin corresponding to the mold central part is reduced, and when the mold is released from the cured photocurable resin, the shot central part is released. It becomes easy and there exists an effect that generation | occurrence | production of the pattern defect by the resin in an imprint is suppressed.

  In the above embodiment, the case where the region where the mold is finally released from the cured photocurable resin is the central portion of the pattern formation region has been described as an example, but the mold release force is applied from one end side of the mold. There is also a case of releasing. In this case, the region to be released last is an end portion of the mold on the opposite side to the side where the release force is applied in the pattern formation region. FIGS. 4A and 4B are a plan view and a cross-sectional view showing an example of a gradation mask used in the exposure amount adjusting unit 105 when a mold release force is applied from one end side of the mold, and the light transmittance is as shown in FIG. This is an example of a gradation mask having a transmittance region that changes in three stages including a substantially 100% region.

  4A and 4B are two-layer gradation masks 40 having different transmittances. FIG. 4A-1 is a plan view, and FIG. 4A-2 is a line DD in FIG. 4A-1. It is sectional drawing. The mask 40 includes a transparent substrate portion 41 having substantially 100% light transmittance and semi-transparent regions 42 and 43 having different transmittances. The thin films constituting the two layers may be thin films made of the same material, or thin films made of different materials. The size of the transmittance is 43 <42 <41. As described above, the region 41 is a region having a high transmittance substantially including 100%, and is a region in which the mold end on the side to which the release force is applied is exposed. Yes, the region 42 is a region having a predetermined medium transmittance that is less than 100% and smaller than the region 41, the region 43 is a region having a predetermined low transmittance that is smaller than the region 42 and exceeds 0%, and is a region to be finally released. Can be provided as a region to be exposed.

  In the example of the gradation mask used as the exposure amount adjustment unit 105, a rectangular shape including a square is shown as an area having a different transmittance on the mask, but it is not limited to a rectangular shape. In the pattern formation region for each shot by the mold, at least depending on the shape of the region where the mold is finally released from the cured photocurable resin, the region having different transmittance may be any shape such as a circle, an ellipse, and an indeterminate shape. The shape can be set. Further, although the case where the transmittance area of the gradation mask changes to three stages including a substantially 100% area is illustrated, it is not limited to three stages from the beginning, but changes to two stages or four stages. It may be a transmittance region.

(Second Embodiment)
Next, an imprint method according to the second embodiment of the present invention will be described. The imprint method in the present embodiment is provided with an exposure amount adjustment unit that adjusts an exposure amount of light (ultraviolet rays) for curing the photocurable resin between the light source and the mold, and using the exposure amount adjustment unit, In the pattern formation region for each shot, the exposure amount is changed depending on the density of the pattern, and the exposure amount in the high pattern density region is made smaller than the exposure amount in the low pattern density region. As the imprint apparatus, the imprint apparatus 100 shown in FIG. 1 described in the first embodiment or the imprint apparatus 200 shown in FIG. 2 described later is used. Hereinafter, in the present embodiment, a case where the imprint apparatus 100 illustrated in FIG. 1 is used will be described.

  As in the first embodiment, the exposure amount adjusting unit 105 in this embodiment has a transmittance distribution of light (ultraviolet rays) 102 for curing the photocurable resin shown in FIG. A member having a transmittance region that changes in two or more steps is used.

  FIG. 5 is an example in which a gradation mask is used for the exposure adjustment unit 105 in the present embodiment, and is a schematic plan view of the gradation mask 50. The light transmittance of the gradation mask 50 corresponds to the pattern density of the mold, and a region 51 having a high light transmittance of exposure light is provided in a region where the pattern density of the mold is low, and the region where the pattern density is intermediate is exposed. A semi-transparent region 52 having an intermediate light transmittance is provided, and a semi-transparent region 53 having a low exposure light transmittance is provided in a region having a high pattern density. Information on the pattern density of the mold can be obtained by analyzing layout pattern data at the time of forming the concave / convex pattern of the mold.

  As the gradation mask of this embodiment, any of the gradation masks shown in FIGS. 3A to 3C described in the first embodiment can be used. The transmittance is 53 <52 <51, the region 51 is a region having a high transmittance substantially including 100%, and the region 52 has a predetermined medium transmittance that is less than 100% and smaller than the region 51. In the region, the region 53 can be provided as a region having a predetermined low transmittance that is smaller than the region 52 and exceeds 0%.

  The gradation mask of this embodiment is used as the exposure amount adjustment unit 105, and is exposed onto the substrate 111 to be processed by the light transmitted through the mold 110 by exposure with the imprint apparatus 100 described in the first embodiment. The exposure amount of the photo-curing resin is changed depending on the pattern density in the pattern formation region for each shot, and the exposure amount in the high pattern density region is smaller than the exposure amount in the low pattern density region. Therefore, the degree of cure of the photocurable resin corresponding to the high pattern density region is reduced, and when the mold and the cured photocurable resin are released, the release of the high pattern density region is facilitated. There is an effect that generation of pattern defects due to resin in printing is suppressed.

(Third embodiment)
In the third embodiment, in the pattern formation region for each shot in the first embodiment or the second embodiment, light (ultraviolet rays) transmittance and transmittance distribution of the exposure amount adjusting unit, or This is an imprint method in which the reflectance and the reflectance distribution are variable. Hereinafter, in the present embodiment, an example in which a gradation mask for adjusting the transmittance is used for the exposure adjustment unit 105 in the case of using the imprint apparatus 100 illustrated in FIG. 1 will be described. For example, by using the gradation mask 40 shown in FIG. 4 described above, the exposure adjustment unit 105 is provided with a movement mechanism (not shown) in the DD direction of FIG. The transmittance distribution can be made variable.

  In the present embodiment, the light transmittance on both opposite sides of the mold can be made variable by providing two or more gradation masks provided in the exposure adjustment unit 105. FIG. 6 shows an example of the exposure amount adjusting unit 105 having two gradation masks shown in FIG.

  In FIG. 6, the exposure adjustment unit 105 is composed of two gradation masks 60A and 60B having different transmittances. FIGS. 6 (a) -1 and 6 (b) -1 are plan views, and FIG. ) -2 is a cross-sectional view taken along line E1-E1 in FIG. 6 (a) -1, and FIG. 6 (b) -2 is a cross-sectional view taken along line E2-E2 in FIG. 6 (b) -1. Each of the masks 60A and 60B includes a transparent substrate portion 61 having substantially 100% light transmittance and semi-transparent regions 62 and 63 having different transmittances. The thin films constituting the translucent region may be thin films made of the same material, or thin films made of different materials. The transmittance is 63 <62 <61. As described above, the region 61 is a region having a high transmittance substantially including 100%, and is a region in which the mold end portion on the side where the release force is applied is exposed. Yes, the region 62 is a region with a predetermined medium transmittance less than 100% and smaller than the region 61, the region 63 is a region with a predetermined low transmittance smaller than the region 62 and exceeds 0%, and the region to be finally released Can be provided as a region to be exposed. Note that the region 63 can be used as a single translucent region or as a transmittance region overlapped with the region 62.

  The gradation masks 60A and 60B described above are used as a two-sheet exposure amount adjustment unit 105 as shown in FIG. 6C, and each is independently in the direction of the arrow in FIG. With the moving mechanism, the light transmittance of the exposure amount adjusting unit 105 can be varied within a predetermined range. If the mechanism is capable of moving in the direction (y direction) perpendicular to the x direction in addition to the x direction, a more complicated variable exposure amount adjustment unit 105 can be obtained.

  The gradation mask with variable light transmittance and transmittance distribution according to the present embodiment is used as the exposure amount adjusting unit 105, and exposure is performed by the imprint apparatus 100 described in the first embodiment, whereby the mold 110 is transmitted. The exposure amount of the photocurable resin applied on the substrate 111 to be processed by the light is gradually reduced from the other end side where the one end side of the shot is opposed, and the photocurable resin corresponding to the one end side of the mold The degree of cure is reduced, and when the mold and the cured photo-curing resin are released from the other end of the mold, it is easier to release the shot from one end of the shot, which is the final release area, and defects are generated. Is suppressed. Further, by adjusting the light transmittance and transmittance distribution by moving the position of the exposure amount adjusting unit 105, the mold release property between the photocurable resin and the mold can be improved more precisely, and the resin in imprinting Occurrence of pattern defects due to is suppressed.

(Fourth embodiment)
In the above embodiment, the case where the light transmittance is adjusted as the exposure amount adjustment unit has been described. However, in the present invention, the light reflectance for each region of the exposure amount adjustment unit is adjusted, and the exposure amount adjustment unit It is also possible to adjust the exposure amount of light for curing the photocurable resin using the reflected light. FIG. 2 is a schematic configuration diagram illustrating an example of an imprint apparatus 200 using a reflection optical system using the imprint method of the present invention.

  An imprint apparatus 200 as an example shown in FIG. 2 includes a light source 201, a contact lens 203 that forms an optical system that guides light (ultraviolet rays) 202 from the light source, a diffusion plate 204 that uniformizes unevenness of the light source, and exposure. In accordance with an amount adjustment unit 205, a mirror 206, a field lens 207 that is in the optical path that guides light to the condenser lens 209, changes the direction of the light beam, an aperture stop 208 that controls the illumination light incident angle range, and an exposure amount adjustment unit 205. A condenser lens 209 that forms an image of the distribution of light, a mold 210, and a substrate to be processed 211 in which a photocurable resin is applied to the surface of a wafer or the like, a mold driving unit, a processing substrate driving unit, And other mechanisms.

  The imprint apparatus 200 shown in FIG. 2 adjusts the light reflectivity by the exposure amount adjusting unit 205 and adjusts the exposure amount for curing the photocurable resin using the reflected light. In FIG. 2, the mirror 206 has a function of reflecting the light 202 from the light source toward the exposure amount adjusting unit 205 and reflecting the reflected light from the exposure amount adjusting unit 205 again toward the field lens 207. The exposure adjustment unit 205 will be described below, but other members constituting the imprint apparatus 200 are the same as those described in FIG.

  In the example of the present embodiment shown in FIG. 2, the light (ultraviolet light) 202 emitted from the light source 201 passes through the exposure amount adjustment unit 205 in which the reflectance in the central region is lowered, so that the central portion where the light intensity is attenuated. Light 202 a and peripheral light 202 b whose light intensity is substantially maintained, and reaches the mold 210 through the condenser lens 209. Therefore, the exposure amount of the photocurable resin applied onto the substrate to be processed 211 by the light transmitted through the mold 210 is smaller in the central portion than in the peripheral portion, and the degree of cure of the central portion of the photocurable resin is the peripheral portion. Smaller than. As a result, when the mold and the cured photocurable resin are released, the shot center part is easily released, and the occurrence of pattern defects due to the resin in imprinting is suppressed.

  In the present invention, the exposure amount adjusting unit 205 has a reflectance distribution of light (ultraviolet rays) for curing the photocurable resin, and has a reflectance region in which the reflectance of light (ultraviolet rays) changes in two or more stages. A member is used. The reflectance region may include a region where the reflectance of light (ultraviolet rays) 202 is substantially 100%. As the exposure amount adjusting unit 205, for example, a reflective photomask having a reflectance distribution of light (ultraviolet rays) or a DMD (digital micromirror device: Texas In) in which a number of micromirrors are two-dimensionally arranged. The exposure amount can be adjusted by forming an on / off state using a mirror array such as a trademark of Strument Corporation.

  In the present embodiment using reflected light, the reflectance and reflectance distribution of the light for curing the photocurable resin can be arbitrarily changed by using a reflective photomask or DMD for the exposure amount adjusting unit 205. It is also possible to make it variable.

  In the present invention shown in each of the above embodiments, the degree of cure of the resin in the region where the exposure amount of the transfer pattern by the photocurable resin formed on the substrate to be processed is reduced after the mold is released is the transfer pattern. When it is assumed that it is not sufficient in the post-process after the formation, the formed transfer pattern is subjected to a full exposure or partial exposure treatment with light (ultraviolet rays) for curing the resin, or the substrate to be processed is heated at a predetermined temperature. By performing the treatment, the degree of cure of the resin of the transferred pattern can be improved and made uniform while maintaining the transfer pattern accuracy.

Example 1
A synthetic quartz substrate having an outer shape of 6 inches square and a thickness of 0.25 inches is used as a mold substrate. An electron beam resist is applied to a thickness of 200 nm on one main surface of the synthetic quartz substrate, and electron beam drawing is performed. After development, dry etching was performed to form a mold having an uneven pattern. The concavo-convex pattern on the mold is obtained by forming a 6-chip pattern in which a line / space pattern having a width of 70 nm and a pitch of 140 nm is provided in one chip in the pattern formation region for each shot.

Next, as an exposure adjustment unit, a mask is formed by depositing silicon oxynitride (SiON) and chromium nitride (CrN) in this order on one main surface of a synthetic quartz substrate having an outer shape of 6 inches square and a thickness of 0.25 inches. Blanks were produced. Next, after applying a photoresist on the above mask blanks, pattern exposure and development, chromium nitride is mixed with chlorine and oxygen mixed gas, silicon oxynitride is pattern etched with CF ₄ , and the resist is peeled off. Then, an exposure amount adjustment unit made of a gradation mask was produced. As shown in FIG. 3 (a), the exposure amount adjusting unit has a square shape with an outer shape of 90 × 90 mm inside a region where the transmittance of exposure light made of a quartz substrate with an outer shape of 152 × 152 mm is substantially 100%. An exposure light transmittance region of 75% made of a silicon oxynitride film is formed, and an exposure light transmittance region of 50% outer shape made of chrome nitride oxynitride having an outer shape of 40 × 40 mm is formed at the inner central portion. .

  Next, a photocurable resin PAK-01 (manufactured by Toyo Gosei Kogyo Co., Ltd.) is spin-coated on a silicon wafer having a diameter of 200 mm to form a coating film, and then the above-described exposure amount adjustment is performed on the imprint apparatus shown in FIG. The mold was pressed against the resin and irradiated with ultraviolet light having a wavelength of 320 nm to cure the photocurable resin. Next, a mold release force was applied upward from two opposite end faces of the mold, and the mold was released from the cured resin. At the time of mold release, the mold area finally released is the center of the mold. A pattern having a width of 70 nm, a pitch of 140 nm, and a depth of 70 nm was transferred onto the wafer by release. No defects due to mold release occurred in the pattern of the photocurable resin on the wafer and the pattern of the mold.

(Comparative Example 1)
Using the mold used in Example 1, without providing an exposure adjustment section, the imprint apparatus shown in FIG. 1 imprints under the same conditions as in Example 1, and after curing the photocurable resin, When mold release force is applied upward from two opposing end faces and the mold is released from the cured resin, pattern defects of the photocurable resin due to release occur in several places in the center of the shot on the wafer. Was.

(Example 2)
A synthetic quartz substrate similar to that in Example 1 was used as a mold, and a mold having a concavo-convex pattern was formed. The concavo-convex pattern on the mold is obtained by forming a 6-chip pattern by providing a contact hole pattern with a diameter of 80 nm and a pitch of 160 nm in one chip in the pattern formation region for each shot.

Next, as an exposure adjustment unit, a molybdenum silicide (MoSi) thin film and a chromium oxynitride (CrON) thin film are formed in this order on one main surface of a synthetic quartz substrate having an outer shape of 6 inches square and a thickness of 0.25 inches. Then, after applying a photoresist thereon, pattern exposure, development, etching of chromium oxynitride with a mixed gas of chlorine and oxygen and etching of silicon oxynitride with CF ₄ , the resist is peeled off, The exposure amount adjustment part which becomes is obtained. As shown in FIG. 4A-1, the exposure amount adjusting unit is in contact with a region where the transmittance of exposure light made of a quartz substrate having an outer shape of 152 × 52 mm is substantially 100%, and the region where the transmittance is 100%. Exposure light consisting of a rectangular silicon oxynitride film having an outer shape of 90 × 50 mm and an exposure light consisting of a rectangular chromium oxynitride having an outer shape of 40 × 50 mm in contact with the 75% transmittance region. A region having a transmittance of 50% is formed.

  Next, the exposure amount adjusting unit was installed in the imprint apparatus shown in FIG. 1, the mold was pressed against the resin, and the photocurable resin was cured by irradiating ultraviolet rays. Next, the mold was released from the cured resin by applying a release force upward from the end face of the mold on the side of the region where the transmittance of ultraviolet rays became substantially 100%. At the time of mold release, the mold area finally released is the end opposite to the side where the mold release force is applied to the mold, and corresponds to an area where the transmittance of the exposure adjustment section is 50%. A contact hole pattern with a diameter of 80 nm and a pitch of 160 nm was transferred onto the wafer by release. No defects due to mold release occurred in the pattern of the photocurable resin on the wafer and the pattern of the mold.

(Example 3)
As the mold, the same synthetic quartz substrate as in Example 1 is used. As shown in FIG. 5, in the pattern formation region for each shot, a region having a high pattern density, a middle region of the pattern density, and a pattern density A mold having a low region was produced.

  Next, using mask blanks similar to those in Example 1, as shown in FIG. 5 corresponding to the pattern density of the mold, a region having a high pattern density in the pattern formation region for each shot is divided into a chromium nitride film and an acid. A two-layer silicon nitride film is used, the light transmittance is reduced to 50%, the middle region of the pattern density is a silicon oxynitride film, the light transmittance is 75%, and the light in the region where the pattern density is low The exposure amount adjustment part which consists of the gradation mask which made the transmittance | permeability of 100% substantially 100% and exposed the transparent substrate was obtained.

  Next, the exposure amount adjusting unit was installed in the imprint apparatus shown in FIG. 1, the mold was pressed against the resin, and the photocurable resin was cured by irradiating ultraviolet rays. Next, a mold release force was applied upward from two opposite end faces of the mold, and the mold was released from the cured resin. No defects due to mold release occurred in the pattern of the photocurable resin on the wafer and the pattern of the mold.

(Comparative Example 2)
The mold used in Example 3 was imprinted under the same conditions as in Example 3 using the imprint apparatus shown in FIG. 1 without providing the exposure amount adjusting unit, and after curing the photocurable resin, When the mold was released from the cured resin by applying a release force upward from the two end faces facing each other, a pattern defect of the photocurable resin due to the release occurred in a high pattern density region. .

Example 4
In this example, the mold used in Example 2 was used.

  As the exposure adjustment unit, a two-layer gradation mask is used instead of the two-layer gradation mask used in Example 2, and one gradation mask is formed on a synthetic quartz substrate as shown in FIG. Further, the molybdenum silicide thin film was patterned as a transmission film having a transmittance of 75%, and the other gradation mask was patterned using a chromium oxynitride thin film as a transmission film having a transmittance of 50%.

  Next, an exposure amount adjusting unit made of the above-described two gradation masks is installed in the imprint apparatus shown in FIG. 1, and the position of the gradation mask made of the chromium oxynitride thin film is adjusted. The photo-curing resin was cured by irradiating with UV light. Next, the mold was released from the cured resin by applying a release force upward from the end face of the mold on the side of the region where the transmittance of ultraviolet rays became substantially 100%. At the time of mold release, the mold area finally released is the end opposite to the side where the mold release force is applied to the mold, and corresponds to an area where the transmittance of the exposure adjustment section is 50%. A contact hole pattern with a diameter of 80 nm and a pitch of 160 nm was transferred onto the wafer by release. No defects due to mold release occurred in the pattern of the photocurable resin on the wafer and the pattern of the mold.

(Example 5)
In this example, the mold used in Example 1 was used.

  Next, as an exposure adjustment unit, a chromium (Cr) film and a chromium oxide (CrO) film are sequentially formed on one main surface of a synthetic quartz substrate having an outer shape of 6 inches square and a thickness of 0.25 inches. A mask blank having a layer structure was produced. Next, after applying a photoresist on the above mask blanks, pattern exposure and development, the chromium oxide film is subjected to pattern etching with a mixed gas of chlorine and oxygen, and the resist is formed with the lower chromium film remaining. It peeled and the exposure amount adjustment part by the reflection type photomask which consists of a chromium high reflection film and a chromium oxide low reflection film was produced. This exposure amount adjusting unit has an exposure light reflectivity of 15% made of chromium oxide having an outer shape of 90 × 90 mm at the center, and an exposure light reflectivity made of a square chrome film having an outer shape of 152 × 152 mm on the outer side. 60% of the area is formed.

  Next, a photocurable resin PAK-01 (manufactured by Toyo Gosei Kogyo Co., Ltd.) is spin-coated on a silicon wafer having a diameter of 200 mm to form a coating film, and then the above-described exposure amount adjustment is performed on the imprint apparatus shown in FIG. The mold was pressed against the resin and irradiated with ultraviolet light having a wavelength of 320 nm to cure the photocurable resin. Next, a mold release force was applied upward from two opposite end faces of the mold, and the mold was released from the cured resin. At the time of mold release, the mold area finally released is the center of the mold. A pattern having a width of 70 nm, a pitch of 140 nm, and a depth of 70 nm was transferred onto the wafer by release. No defects due to mold release occurred in the pattern of the photocurable resin on the wafer and the pattern of the mold.

100, 200 Imprint apparatus 101, 201 Light source 102, 202 Light (ultraviolet light)
102a, 202a Center light 102b, 202b with attenuated intensity Peripheral light 103, 203 Contact lens 104, 204 Diffusing plate 105, 205 Exposure intensity adjusting unit 206 Mirror 107, 207 Field lens 108, 208 Aperture Diaphragm 109, 209 Condenser lens 110, 210 Mold 111, 211 Substrate 112, 212 Substrate holding part 113, 213 Substrate movement stage 114, 214 Substrate movement drive part 30A, 30B, 30C, 40, 50, 60A, 60B Gradation Masks 31a, 31b, 31c, 41, 51, 61 High transmittance regions 32a, 32b, 32c, 42, 52, 62 Medium transmittance regions 33a, 33b, 33c, 43, 53, 63 Low transmittance regions 70 Mold 71 Cover Processed substrate 72 Photocurable resin 73 Light (purple Outside line)
74 Cured photo-curing resin

Claims (7)

The mold with the pattern formed is pressed against the photocurable resin on the substrate to be processed, and light emitted from a light source is exposed to the photocurable resin for each shot through the mold. Is an imprint method in which the mold is released from the cured photocurable resin after curing,
Between the light source and the mold, an exposure amount adjustment unit that adjusts an exposure amount of light for curing the photocurable resin is provided, and the exposure amount adjustment unit is used.
An imprinting method, wherein an exposure amount of a region where the mold is finally released from the cured photocurable resin is made smaller than an exposure amount of other regions in a pattern formation region for each shot.   The imprint method according to claim 1, wherein a region where the mold is finally released from the cured photocurable resin is a central portion in the pattern formation region. The mold with the pattern formed is pressed against the photocurable resin on the substrate to be processed, and light emitted from a light source is exposed to the photocurable resin for each shot through the mold. Is an imprint method in which the mold is released from the cured photocurable resin after curing,
Between the light source and the mold, an exposure amount adjustment unit that adjusts an exposure amount of light for curing the photocurable resin is provided, and the exposure amount adjustment unit is used.
An imprint method characterized in that, in a pattern formation region for each shot, an exposure amount in a region having a high pattern density is made smaller than an exposure amount in a region having a low pattern density.   The imprint according to any one of claims 1 to 3, wherein the exposure amount adjusting unit has a light transmittance distribution or a reflectance distribution for curing the photocurable resin. Method.   5. The light transmittance and transmittance distribution, or the reflectance and reflectance distribution of the exposure amount adjusting unit are variable in the pattern formation region for each shot. The imprint method according to any one of the above.   6. The input according to claim 1, wherein the exposure amount adjustment unit is a gradation mask having a transmittance region in which light transmittance changes in two or more steps. How to print.   An imprint apparatus using the imprint method according to any one of claims 1 to 6.

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