JP5499668B2 - Imprint mold and pattern forming method using the mold - Google Patents

Description

  The present invention relates to an imprint mold in which a fine uneven pattern is formed and a pattern forming method using the mold.

  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.

  On the other hand, the nanoimprint method (also called imprint method) proposed by Chou et al. In Princeton University in 1995 is a fine pattern formation technology having a high resolution of about 10 nm, although the apparatus price and materials used are low. It is attracting attention (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.

  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.

  Therefore, whether or not the mold unevenness pattern and the transfer material have good releasability is extremely important in determining the quality, yield, and productivity of the imprinted product.

  Various factors are related to the mold release property between the mold and the resin. For example, the mold release speed of the mold gripping part, the mold release angle between the mold and the substrate to be processed, and the mold release temperature should be controlled. Therefore, a method for preventing the occurrence of pattern defects has been proposed (see Patent Document 3). Also, a method of releasing the mold by deforming it when the mold and the resin are released has been proposed (see Patent Document 4).

JP-T-2004-504718 JP 2002-93748 A JP 2008-183731 A US2007 / 0126156A1

  However, the method described in Patent Document 3 is to prevent the occurrence of defects at the time of mold release by controlling the mold release speed and the mold release angle when the mold is released. The relationship between the mold release speed and the number of defects in the graph shows that the mold release speed is a factor related to the occurrence of defects, but the specific part of the mold where defects occur and how to prevent them There was a problem that no solution was disclosed. Further, since Patent Document 4 uses a mold that can be deformed, the molding material and structure are limited, and there is a problem that an error occurs in the positional accuracy of the transferred pattern.

  Therefore, the present invention has been made in view of the above problems. That is, an object of the present invention is to use a mold that controls the mold release speed to reduce the occurrence of defects at the time of mold release and the mold when releasing the mold and the resin on the substrate in imprinting. It is to provide a pattern forming method.

In order to solve the above-described problems, an imprint mold according to the first aspect of the present invention is a method in which a mold having an uneven pattern is pressed against a resin on a substrate to be processed, and then the resin is cured. After imprinting the pattern onto the resin, the imprint mold is used for an imprint method in which the mold is released from the resin, and the pattern on the mold is released from the main pattern to be transferred. And a dummy pattern for adjusting a releasing force that is more difficult to release from the resin than the main pattern .

Imprinting mold according to the invention of claim 2 of the present invention, the imprint mold according to claim 1, wherein the dummy pattern, that is at least formed in a region where the mold is demolded last It is a feature.

  The imprint mold according to the third aspect of the present invention is the imprint mold according to the second aspect, wherein a region where the mold is finally released from the resin is a central portion of the mold. It is characterized by.

  The imprint mold according to claim 4 of the present invention is the imprint mold according to any one of claims 1 to 3, wherein the dummy pattern has a pattern density higher than that of the main pattern. Is characterized by a large value.

  The imprint mold according to claim 5 of the present invention is the imprint mold according to any one of claims 1 to 4, wherein the dummy pattern is surface-modified or the The adhesion between the dummy pattern and the resin is made larger than the adhesion between the main pattern and the resin depending on whether or not surface modification is applied to the main pattern.

  The imprint mold according to claim 6 of the present invention is the imprint mold according to any one of claims 1 to 5, wherein the dummy pattern is first released from the mold. It has a pattern density distribution from the region to be released toward the region to be released last, and the pattern density of the region to be released last is the largest.

  A pattern forming method according to a seventh aspect of the present invention uses the imprint mold according to any one of the first to sixth aspects, and presses the mold against a resin on a substrate to be processed. Next, the resin is cured, and after the pattern of the mold is transferred to the resin, the mold is released from the resin.

  The imprint mold of the present invention uses the mold area that is finally released from the resin to be imprinted as a dummy pattern for adjusting the release force, and the dummy pattern that is difficult to release is supported by the mold and the resin. The mold release speed is controlled, the mold is prevented from being rapidly released from the main pattern portion, and the occurrence of defects at the time of release in the main pattern is suppressed or reduced.

  The pattern forming method of the present invention prevents immature mold release from the main pattern portion by imprinting using an imprint mold provided with a dummy pattern for adjusting the release force. Generation of defects at the time of mold release is prevented or reduced, and a high-quality transfer pattern can be obtained.

It is a top view which shows 1st Embodiment of the mold for imprint which provided the dummy pattern for mold release force adjustment in this invention. It is a top view which shows 2nd Embodiment of the mold for imprint which provided the dummy pattern for mold release force adjustment in this invention. It is a top view which shows 3rd Embodiment of the mold for imprint which provided the dummy pattern for mold release force adjustment in this invention. It is sectional drawing which shows an example when a mold and photocurable resin are mold-released, and a top view which shows the area | region on the mold side which produced the transfer defect by imprint. It is process sectional drawing which shows an example of the pattern formation method of this invention.

  This inventor examined the generation | occurrence | production state of the defect at the time of releasing the mold for imprint, and resin about the case of the optical imprint method. FIG. 4 is a cross-sectional view showing an example when the mold and the photocurable resin are released from the mold, and a plan view showing a region of the mold surface where a transfer defect has occurred due to imprinting. As shown in FIG. 4A, a photocurable resin is applied onto the substrate 43 to be processed, the mold 40 is pressed, and then a photocurable resin 44 cured by irradiation with light is formed. The mold 40 is released from the both ends with a constant release force F. FIG. 4B shows a defect occurrence region (inside the broken line circle) 45 on the surface side of the mold 40 in which a transfer defect after mold release has occurred. Shows the state of concentration. The defect at the time of releasing means a defect caused by a part of the photocurable resin adhering to the mold 40 side, and corresponds to a defect such as a chip generated on the photocurable resin 44 side.

  As shown in FIG. 4, defects at the time of mold release concentrate on the center of the mold 40 when the mold 40 and the photocurable resin 44 are released from the both ends of the mold 40 with a certain force. When the mold is started, peeling progresses from the peripheral part to the central part of the transfer area of the mold 40, the peeling area per time is reduced in the central part of the mold 40, the mold release speed is increased, and the center of the mold 40 is increased. It is presumed that a large release force acts on the photo-curable resin 44 in the region corresponding to the part, and the resin is torn and becomes a defect.

(Imprint mold)
Therefore, the imprint mold of the present invention forms a main pattern to be transferred on the mold, and provides a dummy pattern for adjusting the mold release force in an area where defects are likely to occur at the time of mold release. The mold release speed is controlled to increase, and the occurrence of defects at the time of mold release is suppressed or reduced. Here, the main pattern is a desired pattern to be transferred to the resin on the substrate to be processed among the patterns formed on the mold. The dummy pattern is a pattern that is not used for actual processing of the substrate to be processed among the patterns formed on the mold, and has a function of assisting transfer of the main pattern to the resin on the substrate to be processed. Means a pattern.

The dummy pattern is preferably formed at least in a region where the mold is finally released from the resin on the substrate to be processed, and more preferably more difficult to release from the resin than the main pattern.
Hereinafter, embodiments of the imprint mold of the present invention will be described with reference to the drawings, taking the case of the optical imprint method as an example.

(First embodiment)
The imprint mold of this embodiment is a case where the dummy pattern is in the center of the mold. The planar outer shape on the side where the concave / convex pattern of the mold is formed is usually a rectangular shape including a square corresponding to an imprint shot. FIG. 1 is a plan view of the imprint mold according to the first embodiment as viewed from the pattern side. The pattern on the mold 10 includes a main pattern 11 to be transferred and a mold release force at the time of mold release. And a dummy pattern 12 for adjustment. In the example shown in FIG. 1, the main pattern 11 is provided with six chips, and a dummy pattern 12 is formed between the main patterns 11 at the center of the mold 10.

  Normally, at the time of mold release, as shown in FIG. 4 above, the mold and the photocurable resin are often released from the opposite ends of the mold with a constant force. The area to be released into the mold becomes the mold center, and the mold release speed in the mold center is larger than the mold release speed in other areas. Therefore, as shown in FIG. 1, a dummy pattern 12 is provided at the center of the mold 10, and more preferably, the dummy pattern 12 is more difficult to release than the main pattern 11, and the release speed of the dummy pattern 12 and its surroundings is reduced. Thus, the occurrence of defects in the main pattern 11 at the time of mold release is prevented or reduced.

  As a method of making the above-mentioned dummy pattern harder to release than the main pattern, a method of making the pattern density of the dummy pattern larger than the pattern density of the main pattern, or surface modification of the dummy pattern or making the dummy pattern a main pattern Depending on whether or not the surface modification to be applied is performed, a method of making the adhesiveness between the dummy pattern and the photocurable resin larger than the adhesiveness between the main pattern and the photocurable resin can be applied.

  In order to increase the pattern density of the dummy pattern, for example, by providing a dense pitch hole pattern as the dummy pattern, the pattern density can be increased to increase the surface area of the pattern and make it difficult to release.

  In order to increase the adhesion between the dummy pattern and the photocurable resin depending on the presence or absence of surface treatment, for example, chemical modification treatment with an organic compound such as a fluorine-based silane coupling agent or surface modification with fluorine plasma is performed in a region other than the dummy pattern. It is possible to use a method in which the surface is modified by applying a quality treatment or the like, and the surface is not modified in the dummy pattern region.

(Second Embodiment)
The imprint mold of the present embodiment is a case where the dummy pattern is near one side of the periphery of the mold. FIG. 2 is a plan view of the imprint mold according to the second embodiment as viewed from the pattern side. The pattern on the mold 20 includes a main pattern 21 to be transferred and a mold release force at the time of mold release. And an adjustment dummy pattern 22. In the example shown in FIG. 2, the main pattern 21 is provided with four chips, and a dummy pattern 22 is formed in the vicinity of the outer side of the main pattern 21 at the periphery of the mold 20.

  In the second embodiment, the mold 20 is released from the other end side on the mold 20 opposite to the end where the dummy pattern 22 is located, and the mold 20 is finally released from the photocurable resin. The region is the end of the mold 20 provided with the dummy pattern 22. By providing the dummy pattern 22, the mold release speed around the dummy pattern 22 and its periphery is slowed down, and the occurrence of defects in the main pattern 21 at the time of mold release is prevented or reduced.

(Third embodiment)
In the imprint mold of this embodiment, the dummy pattern has a pattern density distribution from the first mold release area to the last mold release area, and the last pattern release area has the highest pattern density. Is the case. For example, the first mold release area is the mold periphery, the last mold release area is the mold center, and the dummy pattern has a density distribution from the mold periphery to the mold center. This is the case where the pattern density is the highest.

  FIG. 3 is an example of the third embodiment, and is a plan view seen from the pattern side showing the imprint mold. The pattern on the mold 30 is the main pattern 31 to be transferred and when releasing the mold. And a dummy pattern 32 for adjusting the mold release force. The dummy pattern 32 has a density distribution from the periphery of the mold 30 toward the center. In addition, a plurality of dummy patterns 32 are provided.

  In the third embodiment illustrated in FIG. 3, the mold 30 is released from the opposite ends of the mold 30, and the area where the mold 30 is finally released from the photocurable resin is the center of the mold 30. Become. By giving the dummy pattern 32 a density distribution from the periphery to the center of the mold 30, the release speed of the dummy pattern 32 and its periphery is slowed down, and the generation of defects in the main pattern 31 at the time of release is prevented or It is to reduce.

  In each of the above-described embodiments, the area where the dummy pattern is provided is an area where no pattern is required, such as between chips. In general, in the case of imprinting for a semiconductor application, there is an area where a pattern is unnecessary between chips, and a dummy pattern can be arranged. By making the dummy pattern area harder to release than the main pattern and releasing the dummy pattern area last, the release speed of the main pattern is controlled to prevent or reduce the occurrence of defects. . As described above, the region where the dummy pattern is provided need only be formed at least in a region where the mold is finally released from the photocurable resin, and can be provided at one or a plurality of locations on the mold.

  In the present invention, the size of the dummy pattern can be arbitrarily set according to the size of the entire transfer area of the mold, the size of the main pattern, the number and arrangement of patterns, and the like. The pattern used as the dummy pattern is not particularly limited in the type of pattern, but a pattern having a high pattern density such as the hole pattern described above is preferable. This is because increasing the pattern density makes it difficult to peel off the dummy pattern, slows the mold release speed around it, and prevents or reduces the occurrence of defects in the main pattern at the time of mold release.

(Mold material)
As a mold material used in the present invention, a mold used in a conventionally known imprint method can be used. In the case of the photoimprint method, quartz glass that has good pattern stability, chemical resistance, and processing characteristics and transmits ultraviolet rays used for photocuring is preferable. The mold on which the pattern is formed can also be used by being attached to a member that holds the mold.

(Dummy pattern production method)
The dummy pattern in the present invention can be produced by forming on the mold at the same time as the main pattern is produced, and a conventionally known mold manufacturing method can be applied, and the mold of the present invention can be produced easily. .

(Pattern formation method)
The pattern forming method of the present invention uses the imprint mold described in the above embodiment, presses the mold against the resin on the substrate to be processed, then cures the resin and transfers the mold pattern to the resin. The mold is released from the resin.

  FIG. 5 is a process sectional view by the optical imprint method showing an example of the pattern forming method of the present invention. As shown in FIG. 5A, first, the mold 50 of the present invention described above having a main pattern to be transferred and a dummy pattern for adjusting a releasing force when releasing is prepared. On the other hand, a low-viscosity photocurable resin 54 a is applied on the substrate 53 to be processed.

  Next, as shown in FIG. 5 (b), the mold 50 is brought into contact with the photocurable resin 54 a on the substrate 53 to be pressed, and light (ultraviolet light) 56 is irradiated while the mold 54 is pressed. The photocurable resin 54 is cured.

  Next, as shown in FIG. 5C, the mold 50 is released from the cured photocurable resin 54. FIG. 5C shows a state in which the mold is released by applying the release force F from the two opposite ends of the mold to the upper side of the sheet. By using the mold 50 of the present invention, the occurrence of defects at the time of releasing the main pattern is prevented or reduced, and a transfer pattern by the high-quality photo-curable resin 54 having no defects in the main pattern is formed on the substrate 53 to be processed. It is formed.

  In the imprint method, the portion of the photocurable resin 54 corresponding to the convex portion of the mold 50 remains as a thin residual film on the workpiece substrate 53. Therefore, when the surface of the workpiece substrate 53 needs to be exposed, As shown in FIG. 5D, the remaining film is removed by ion etching using oxygen gas.

  The pattern forming method of the present invention prevents immature mold release from the main pattern portion by imprinting using an imprint mold provided with a dummy pattern for adjusting the release force. Generation of defects at the time of mold release is prevented or reduced, and a high-quality transfer pattern can be formed.

  In the pattern forming method of the present invention, a defect at the time of releasing may occur in the dummy pattern portion. However, as long as the occurrence of the releasing defect in the main pattern is suppressed, the defect in the dummy pattern portion is practical. It will not be a hindrance.

  In the above description of the embodiment of the present invention, the case of the optical imprint method has been described. However, the present invention can also be applied to the thermal imprint method. For example, in the thermal imprint method, a thermoplastic resin is applied onto a substrate to be processed, the mold, the substrate, and the resin are heated above the glass transition temperature of the resin, and the resin is deformed by pressing the mold while maintaining this state. The resin is then cooled and cured to transfer the mold pattern to the resin. When the resin is sufficiently cooled and cured, the mold is released from the cured resin. Since the problem of mold release between the mold and the cured resin occurs in the thermal imprint method as in the case of the optical imprint method, the present invention can also be applied in the thermal imprint method.

  As a mold substrate, a synthetic quartz substrate having an external shape of 6 inches in length, 6 inches in width, and 0.25 inches in thickness is used, and an electron beam resist is applied to a thickness of 200 nm on one main surface of the synthetic quartz substrate, After the electron beam was drawn and developed, a mold having a concavo-convex pattern was formed by dry etching. The concavo-convex pattern on the mold is composed of a main pattern to be transferred and a dummy pattern for adjusting the releasing force, and the main pattern is provided with a line / space pattern having a width of 70 nm and a pitch of 140 nm in one chip in the transfer region. The 6-chip pattern is a dummy pattern in which a hole pattern having a diameter of 40 nm and a pitch of 80 nm is provided in a space between chips at the center of the mold in the transfer region.

  Next, a photocurable resin PAK-01 (manufactured by Toyo Gosei Kogyo Co., Ltd.) is formed on a silicon wafer having a diameter of 200 mm by spin coating to form a coating film, and then the above mold is pressed against the resin, and ultraviolet light having a wavelength of 320 nm. Was applied to cure the photocurable resin. Next, a mold release force F was applied upward from two opposite end faces of the mold to release the mold from the cured resin. At the time of mold release, the mold area finally released is a dummy pattern area at the center of the mold. A main pattern and a dummy pattern having a width of 70 nm, a pitch of 140 nm, and a depth of 70 nm were transferred onto the wafer by release. No defects due to mold release occurred in the main pattern of the photocurable resin on the wafer and the main pattern of the mold.

10, 20, 30, 40, 50, 60 Mold 11, 21, 31, 41 Main pattern 12, 22, 32, 42 Dummy pattern 45 Defect generation region 53, 63 Substrate 54, 64 Cured photocurable resin 55 Transfer defect generation region 64a Light curable resin 66 Light (ultraviolet light)

Claims (7)

An imprinting method is used in which an imprint method is formed by pressing a mold having an uneven pattern against a resin on a substrate to be processed, then curing the resin and transferring the pattern to the resin, and then releasing the mold from the resin. A mold for printing,
For imprint, wherein the pattern on the mold has a main pattern to be transferred and a dummy pattern for adjusting a release force that is less likely to release from the resin than the main pattern when releasing the mold. mold. The dummy pattern, imprint mold according to claim 1, characterized in that it is formed at least in a region where the mold is demolded last.   The imprint mold according to claim 2, wherein a region where the mold is finally released from the resin is a central portion of the mold.   The imprint mold according to any one of claims 1 to 3, wherein the dummy pattern has a pattern density larger than that of the main pattern.   Depending on whether the dummy pattern is surface-modified or not subjected to surface modification applied to the main pattern, the adhesion between the dummy pattern and the resin is made larger than the adhesion between the main pattern and the resin. The imprint mold according to claim 1, wherein the mold is an imprint mold.   The dummy pattern has a pattern density distribution from a region where the mold is released first to a region where the mold is released last, and the pattern density of the region where the mold is released last is the largest. The imprint mold according to any one of claims 1 to 5. Using the imprint mold according to any one of claims 1 to 6,
A pattern forming method, wherein the mold is pressed against a resin on a substrate to be processed, the resin is then cured, the pattern of the mold is transferred to the resin, and then the mold is released from the resin.

Images