JP2014033050A - Imprint system and imprint method - Google Patents

Abstract

An object of the present invention is to detect the presence / absence of a pattern defect in a template release process.
An imprint system according to this embodiment includes an application unit that applies a photocurable material on a substrate, a holding unit that holds a template on which a concavo-convex pattern is formed, and moves in a vertical direction. A light irradiating unit that irradiates light in a state where the concavo-convex pattern is in contact with the photocurable material to cure the photocurable material, and the template when the template is released from the cured photocurable material. A first evaluation value of a contact area between the template and the photocurable material is calculated using an imaging unit that images the photocurable material, and an image generated by the imaging unit, and the first evaluation is performed. A calculation unit that calculates a second evaluation value of the mold release operation using the value, and a determination unit that determines whether or not a pattern defect has occurred in the cured photocurable material based on the second evaluation value; Equipped with a.
[Selection] Figure 1

Description

  Embodiments described herein relate generally to an imprint system and an imprint method.

  As a technique for forming a fine pattern at low cost, an optical nanoimprint method is known. This is because the template having irregularities corresponding to the pattern to be formed on the substrate is pressed against the photocurable organic material layer applied on the substrate surface, and this is irradiated with light to cure the organic material layer, thereby In this method, the pattern is transferred by releasing from the material layer.

  In the optical nanoimprint method, the pattern of the organic material layer may be destroyed when the template is released from the organic material layer. Therefore, it is required to detect the presence or absence of pattern defects in the template release process.

US Patent Application Publication No. 2010/074443

  An object of the present invention is to provide an imprint system and an imprint method for detecting whether or not a pattern defect is generated in a template release process.

  According to the present embodiment, the imprint system includes an application unit that applies a photocurable material on a substrate, a holding unit that holds a template on which an uneven pattern is formed, and moves in a vertical direction, and the unevenness of the template. Irradiating light in a state where the pattern is in contact with the photocurable material to cure the photocurable material, the template and the template when releasing the template from the cured photocurable material A first evaluation value of a contact area between the template and the photocurable material is calculated using an imaging unit that images the photocurable material and an image generated by the imaging unit, and the first evaluation value And a determination unit that calculates a second evaluation value of the mold release operation using, and a determination unit that determines presence or absence of pattern defects in the cured photocurable material based on the second evaluation value. .

It is a schematic block diagram of the imprint system which concerns on this embodiment. It is process sectional drawing explaining the imprint method. It is a figure which shows the transition of a contact area. It is a figure which shows the example of a contact area. It is a figure which shows an example of the evaluation value of a contact area. It is a figure which shows the template from which a pattern side wall density differs.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of an imprint system according to the present embodiment. As illustrated in FIG. 1, the imprint system includes a template holding unit 10, a substrate holding unit 20, a light irradiation unit 30, an imaging unit 40, a coating unit 50, and a calculation control unit 60.

  The template holding unit 10 holds the template 11 and can move in the horizontal direction and the vertical direction. The template 11 is, for example, a quartz template having a fine uneven pattern formed on the surface. The template holding unit 10 holds the template 11 so that the uneven pattern of the template 11 faces a substrate 21 described later. A vacuum chuck or an electrostatic chuck can be used for the template holder 10. The template holding unit 10 is divided into a plurality of regions in the in-plane direction of the template 11, and can control the holding timing and holding force of the template 11 for each divided region.

  The substrate holding unit 20 holds a substrate (wafer) 21 to be processed and can move in the horizontal direction. The substrate holding unit 20 may be movable in the vertical direction. A vacuum chuck or an electrostatic chuck can be used for the substrate holding unit 20. The substrate holding unit 20 is divided into a plurality of regions in the in-plane direction of the substrate 21, and the holding timing and holding force of the substrate 21 can be controlled for each divided region.

  The application unit 50 applies the imprint material 22 to the surface of the substrate 21. The imprint material 22 is, for example, a photocurable organic material such as an acrylic monomer.

  The irradiation unit 30 emits light for curing the imprint material 22 on the substrate 21. For example, the irradiation unit 30 irradiates ultraviolet rays. As shown in FIG. 1, the irradiation part 30 is provided above the template holding | maintenance part 10, and the template holding | maintenance part 10 and the template 11 consist of a light transmissive material. The irradiation unit 30 irradiates light with the template 11 in contact with the imprint material 22 on the substrate 21.

  The imaging unit 40 images the template 11 and the imprint material 22 when the template 11 is released from the imprint material 22 on the substrate 21 at a predetermined time interval, and generates an image.

  The arithmetic control unit 60 includes a movement control unit 61, an evaluation value calculation unit 62, and a determination unit 63, and includes a template holding unit 10, a substrate holding unit 20, an irradiation unit 30, an imaging unit 40, and an application unit 50. Control the behavior.

  Alignment marks are respectively formed on the template 11 and the substrate 21. The imprint system is provided with a detection mechanism (not shown) for detecting the position of each alignment mark. For example, a laser interferometer can be used as the detection mechanism. The arithmetic control unit 60 acquires the position of the alignment mark from the detection mechanism, and calculates the amount of movement of the template 11 and / or the substrate 21 so that the template 11 is positioned above a desired region of the substrate 21. The movement control unit 61 controls the template holding unit 10 and / or the substrate holding unit 20 based on the calculated movement amount. As a result, the template 11 moves in the horizontal direction relative to the substrate 21, and alignment (alignment) is performed.

  The movement control unit 61 controls the template holding unit 10 to move the template 11 in the vertical direction so that the template 11 is brought into contact with the imprint material 22 on the substrate 21 or released from the imprint material 22. To do. Further, the movement control unit 61 can control the moving speed and moving distance of the template 11 in the vertical direction.

  The movement of the relative positions of the template 11 and the substrate 21 includes not only moving the template 11 and the substrate 21 but also changing the holding force of the template 11 and the substrate 21 to deform the template 11 and the substrate 21. You may go out.

  The evaluation value calculation unit 62 calculates an evaluation value of a contact area (described later) between the template 11 and the imprint material 22 and an evaluation value of the mold release behavior of the template 11. The determination unit 63 determines whether or not a pattern defect has occurred based on the evaluation value of the mold release behavior calculated by the evaluation value calculation unit 62. The mold release of the template 11 is demonstrated using FIG.

  In the imprint process, as shown in FIG. 2A, the application unit 50 (see FIG. 1) applies the imprint material 22 onto the substrate 21.

  Next, as shown in FIG. 2B, the substrate 21 and the template 11 are aligned (aligned), and the uneven pattern surface of the template 11 is brought into contact with the applied imprint material 22. The liquid imprint material 22 flows into the concavo-convex pattern of the template 11 and enters.

  Next, as shown in FIG. 2C, after the imprint material 22 is filled in the concavo-convex pattern, ultraviolet rays are irradiated from the back side (upper side in the drawing) of the template 11 using the irradiation unit 30. Thereby, the imprint material 22 is cured.

  Next, as shown in FIG. 2D, the template 11 is moved upward, and the template 11 is peeled off from the imprint material 22. This is the release of the template 11.

  FIG. 3 shows an example of the transition of the contact area (shaded portion in the figure) between the template 11 and the imprint material 22 due to the release of the template 11, which is acquired as an image by the imaging unit 40. Image acquisition by the imaging unit 40 is at least 10 frames / second, preferably 20 frames / second, more preferably 25 frames / second. The imaging unit 40 starts imaging with the start of the release operation. For example, the start of the mold release operation can be detected from the movement control signal in the vertical direction of the template 11. As shown in FIG. 3, the release phenomenon occurs from the outer periphery of the contact area between the template 11 and the imprint material 22 on the substrate 21.

  The evaluation value calculation unit 62 recognizes the boundary between the template 11 and the imprint material 22 from the image acquired by the imaging unit 40 and detects a contact area. For example, as shown in FIG. 3, the image includes a substantially rectangular or substantially elliptical line corresponding to the boundary between the contact area and the already released area. As shown in FIG. 4, when there are a plurality of lines in the image due to the influence of the thin film interference effect, etc., the innermost line may be regarded as a boundary line based on a predetermined criterion, or the outermost line and the outermost line may be An intermediate line between the inner peripheral lines may be used as the boundary line.

Then, the evaluation value calculation unit 62 calculates the evaluation value of the contact area. Here, the evaluation value of the contact area is a distance L _{i, j} to the boundary of the contact area in one or more predetermined directions starting from the center of the template 11 as shown in FIG. Here, i indicates a measurement direction, and j indicates that the image is an image after elapse of j · Δt from the start of mold release. Δt is an image acquisition interval (imaging rate of the imaging unit 40). The direction from the center of the template 11 is, for example, the diagonal direction of the rectangular template 11.

In measuring the distance L _{i, j to} the boundary of the contact area, it is preferable to avoid the dicing line. Therefore, the measurement direction of the distance L _{i, j to} the boundary of the contact area preferably does not include a direction parallel to the outer peripheral side of the template 11.

Generally, the template 11 is provided with an uneven pattern corresponding to a plurality of chips. When L _{i, j} is obtained in an oblique direction of the template 11, a plurality of chips in the template 11 are passed in this direction, so that evaluation can be performed with an average pattern density in the template 11.

Thereafter, the evaluation value calculation unit 62 calculates the evaluation value F of the release behavior using the evaluation function represented by the following mathematical formula 1.

Here, a _i is a weight function for each direction, m is the number of images used for the release behavior, and n is the number of evaluation directions. The evaluation value F of the release behavior obtained by this evaluation function is a value indicating variation in the amount of change in the moving speed of the boundary of the contact area. The smaller the evaluation value F of the mold release behavior, the more stable the mold release process, and the smaller the force applied to the pattern made of the cured imprint material 22. Therefore, the release behavior can be quantitatively evaluated by this evaluation function, and the presence or absence of pattern defects can be estimated based on the evaluation value F of the release behavior.

  In the present embodiment, in the mold release step shown in FIG. 2D, the imaging unit 40 images the template 11 and the imprint material 22 a plurality of times at a predetermined imaging rate. Then, after the release processing, the evaluation value calculation unit 62 calculates the evaluation value of the contact area and the evaluation value of the release behavior by the method described above using the image generated by the imaging unit 40. When the calculated evaluation value of the release behavior is equal to or less than a predetermined value, the determination unit 63 determines that no pattern defect has occurred in the mold release process of the template 11 shown in FIG. If it is greater than the value, it is determined that a pattern defect has occurred.

  Thus, according to the present embodiment, it is possible to quantitatively evaluate the mold release behavior of the template 11 and detect the occurrence of pattern defects in the template mold release process.

  In the above embodiment, imprint processing is performed on a plurality of regions of one substrate 21. The imprint system calculates an evaluation value F of the release behavior for the imprint process for at least one region, and if the evaluation value F is out of a predetermined range, an abnormality determination signal for the substrate 21 is produced and managed. It may be sent to the system. A predetermined inspection process or workpiece processing is performed on the substrate 21 on which the abnormality determination has occurred. By using the evaluation value F for production management, production efficiency can be improved.

  In the above-described embodiment, the imprint material 22 is cured by the irradiation unit 30 irradiating the ultraviolet ray. However, when the imprint material 22 is a thermosetting organic material, the irradiation unit 30 irradiates the infrared ray with the infrared ray. The print material 22 may be heated and cured.

(First modification)
In the above embodiment, the distance L _{i, j} from the center of the template 11 to the boundary of the contact region in one or more predetermined directions is used as the evaluation value of the contact region. However, the center of the contact region may be used as the starting point. . Thereby, even when the center of the contact region is shifted from the center of the template 11, the mold release behavior of the template 11 can be quantitatively evaluated more stably.

(Second modification)
In obtaining the distance L _{i, j} to the boundary of the contact region, the center of gravity of the side wall density of the uneven pattern provided on the template 11 may be used as a starting point. The pattern side wall density corresponds to the total area of the side walls of the concavo-convex pattern and is different from the pattern density. For example, the templates 11A and 11B shown in FIGS. 6A and 6B have the same pattern density, but the pattern sidewall density is higher in the template 11B.

  As the center of gravity of the pattern sidewall density, the center of gravity of the convex part of the concave / convex pattern of the template 11, the center of gravity of the concave part of the concave / convex pattern, or the center of gravity of the length of the contour line of the concave / convex pattern can be used. The contour line of the concavo-convex pattern may be divided into two directions along the contour piece direction of the template 11 and calculated for each direction.

  Further, the template 11 is divided into regions of a predetermined size, the average pattern sidewall density of the divided regions is calculated, and the pattern sidewall density of the entire template 11 is calculated based on the center of each divided region and the average pattern sidewall density of each divided region. The center of gravity may be obtained. For these techniques, an area representative method partially used for optical proximity correction of photolithography and flare correction of EUV lithography can be applied.

Since the mold release speed varies depending on the pattern side wall density, it is desirable that the end point of the mold release, that is, the end point of the contact area exists near the center of gravity of the pattern side wall density. By determining the distance L _{i, j} to the boundary of the contact area by such a method, the release behavior can be quantified more accurately.

(Third Modification)
The area of the contact region may be used as the evaluation value of the contact region. The area of the contact area can be represented by the number of pixels of the contact area in the acquired image.

In this case, the evaluation function of the release behavior can be expressed by the following formula 2.

Here, S _j is the contact area in the image after elapse of j · Δt from the start of mold release. The smaller the evaluation value F of the mold release behavior obtained by this evaluation function, the closer the area change rate with time is.

More generally, a difference with respect to a time change function f (mΔt) of a predetermined ideal area may be obtained as shown in Equation 3 below.

  The smaller the evaluation value F of the mold release behavior obtained by Formula 2 or Formula 3, the more stable the mold release process, and the smaller the force applied to the pattern made of the cured imprint material 22. When the calculated evaluation value F is equal to or less than the predetermined value, the determination unit 63 determines that no pattern defect has occurred in the mold release process of the template 11 illustrated in FIG. 2D, and the evaluation value is greater than the predetermined value. It is determined that a pattern defect has occurred.

(Fourth modification)
Whether the predetermined position of the template 11 is included in the contact area may be used as the evaluation value of the contact area. The predetermined position of the template 11 is, for example, the center position of the template 11 or the gravity center position of the pattern side wall density of the template 11.

In this case, the evaluation function of the release behavior can be expressed by the following formulas 4 and 5. In Formula 5, the predetermined position of the template 11 is set as the barycentric position of the pattern side wall density.

  The larger the evaluation value F obtained from this evaluation function, the more stable the mold release processing is, and the smaller the force applied to the pattern made of the cured imprint material 22 is. When the calculated evaluation value F is equal to or greater than a predetermined value, the determination unit 63 determines that no pattern defect has occurred in the mold release process of the template 11 illustrated in FIG. 2D, and the evaluation value F is less than the predetermined value. In this case, it is determined that a pattern defect has occurred.

Further, a shift between the center of the contact area and the center of gravity position of the pattern side wall density may be considered. In this case, the evaluation function of the release behavior can be expressed by the following formulas 6 and 7.

Further, the area of the contact region may be taken into consideration. In this case, the evaluation function of the release behavior can be expressed by the following formulas 8 and 9.

(5th modification)
When the template 11 is released, the contact area may be divided. In such a case, a depression is generated in the outer shape of the contact area. For this reason, you may determine an evaluation function based on the closed space property of a contact | adherence area | region. As an example, evaluation may be performed using a vector sum of outer tangents on the outer periphery of the contact area.

(Sixth Modification)
The imprint system according to the embodiment may further include a storage unit that stores the calculated evaluation value F of the release behavior and the control factor of the release operation in combination. Control factors for the mold release operation include, for example, the vertical movement speed of the template 11, the holding force of the template 11 in each divided region of the template holding unit 10, the holding force of the substrate 21 in each divided region of the substrate holding unit 20, This is the amount of curing energy of the print material 22. Moreover, you may include the stamp position in the board | substrate 21 in a control factor. This is because the deformation amount of the substrate 21 at the time of mold release changes depending on the stamping position in the substrate 21.

  The imprint system further includes an optimum control factor calculation unit that calculates an optimum value of each control factor of the release operation based on the release factor control factor and the release behavior evaluation value stored in the storage unit. It may be provided. The arithmetic control unit 60 may optimize the control factor using the calculated optimum value of the control factor.

  When an imprint apparatus is used during mass production of semiconductor devices, it is necessary to optimize control factors for a plurality of imprint apparatuses. Further, when imprint processing is performed on a plurality of layers of a semiconductor device, it is necessary to optimize a control factor for each layer because the pattern layout is different for each layer. In addition, when the thickness or type of the imprint material is changed, it is necessary to optimize the control factor again. By automating optimization of control factors, the start-up adjustment period of the device can be greatly shortened.

  The optimum value of the control factor may be obtained by correlating information such as the defect density of the pattern formed on the substrate and the yield of the electrical characteristics with the evaluation value of the release behavior.

  Further, in the optimization of the control factor of the mold release operation, other physical quantities detected by the imprint apparatus, for example, the upper limit value of the maximum mold release force and the maximum value of the time required for the mold release operation may be included in the constraint condition. Good.

  When an imprint apparatus is used in mass production of semiconductor devices, the optimum value of the control factor can be changed depending on the long-term stability of the apparatus, the storage stability of the imprint material, the change in the surface state of the template 11, and the like. In the mass production process, the evaluation value F of the mold release behavior is calculated according to a predetermined sampling rule, and the control factor of the mold release operation is periodically optimized, so that the optimal control factor is set in the imprint apparatus as needed. Can do. Thereby, generation | occurrence | production of a defect can be reduced and long-term manufacturing efficiency can be improved.

  At least a part of the arithmetic control unit 60 described in the above-described embodiment may be configured by hardware or software. When configured by software, a program for realizing at least a part of the functions of the arithmetic control unit 60 may be stored in a recording medium such as a flexible disk or a CD-ROM, and read and executed by a computer. The recording medium is not limited to a removable medium such as a magnetic disk or an optical disk, but may be a fixed recording medium such as a hard disk device or a memory.

  Further, a program for realizing at least a part of the functions of the arithmetic control unit 60 may be distributed via a communication line (including wireless communication) such as the Internet. Further, the program may be distributed in a state where the program is encrypted, modulated or compressed, and stored in a recording medium via a wired line such as the Internet or a wireless line.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

DESCRIPTION OF SYMBOLS 10 Template holding | maintenance part 11 Template 20 Substrate holding | maintenance part 21 Substrate 22 Imprint material 30 Light irradiation part 40 Imaging part 50 Application | coating part 60 Operation control part 61 Movement control part 62 Evaluation value calculation part 63 Determination part

Claims (6)

An application part for applying a photocurable material on the substrate;
Holding a template on which a concavo-convex pattern is formed, and a holding part that moves in a vertical direction;
A light irradiation unit for irradiating light in a state where the uneven pattern of the template is in contact with the photocurable material, and curing the photocurable material;
An imaging unit that images the template and the photocurable material when releasing the template from the cured photocurable material;
A first evaluation value of a contact area between the template and the photocurable material is calculated using an image generated by the imaging unit, and a second evaluation value of the mold release operation is calculated using the first evaluation value. A calculation unit for calculating,
Based on the second evaluation value, a determination unit that determines the presence or absence of pattern defects in the cured photocurable material;
With
The first evaluation value is a length of the contact area in a predetermined direction starting from the center of the template,
The second evaluation value is a value indicating a variation in the amount of change in the moving speed of the boundary of the contact area,
The determination unit determines that a pattern defect has not occurred when the second evaluation value is less than or equal to a predetermined value, and determines that a pattern defect has occurred when the second evaluation value is greater than a predetermined value. Characteristic imprint system. An application part for applying a photocurable material on the substrate;
Holding a template on which a concavo-convex pattern is formed, and a holding part that moves in a vertical direction;
A light irradiation unit for irradiating light in a state where the uneven pattern of the template is in contact with the photocurable material, and curing the photocurable material;
An imaging unit that images the template and the photocurable material when releasing the template from the cured photocurable material;
A first evaluation value of a contact area between the template and the photocurable material is calculated using an image generated by the imaging unit, and a second evaluation value of the mold release operation is calculated using the first evaluation value. A calculation unit for calculating,
Based on the second evaluation value, a determination unit that determines the presence or absence of pattern defects in the cured photocurable material;
An imprint system comprising:   The imprint system according to claim 2, wherein the first evaluation value is a distance to a boundary of the contact area in a predetermined direction starting from the center of the template.   The imprint system according to claim 3, wherein the second evaluation value indicates a variation in a change amount of a moving speed of a boundary of the contact area.   The determination unit determines that a pattern defect has not occurred when the second evaluation value is less than or equal to a predetermined value, and determines that a pattern defect has occurred when the second evaluation value is greater than a predetermined value. The imprint system according to claim 4, wherein the system is an imprint system. Apply a photo-curing material on the substrate,
Contact the template on which the concavo-convex pattern is formed with the photocurable material,
Irradiating light to the photocurable material in a state where the template is in contact with the template, curing the photocurable material,
Release the template from the cured photocurable material, and image the template and the photocurable material to generate an image,
Using the image, a first evaluation value of a contact area between the template and the photocurable material is calculated,
A second evaluation value of the mold release operation is calculated using the first evaluation value;
Based on the second evaluation value, the presence or absence of occurrence of pattern defects in the cured photocurable material is determined.
Imprint formation method.

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