JP2011163839A - Method and device for inspecting substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for inspecting a substrate capable of detecting a foreign matter, the refractive index of which is equal or near to that of a substrate with high sensitivity. <P>SOLUTION: A process for irradiating the metal film 15, which is formed on the surface 16a of a prism 16, with light from the interface side of the surface 16a of the prism 16 and the metal film 15 in a state that the uneven pattern formed on the substrate 20 is allowed to approach the metal film 15 formed on the surface 16a of the prism 16 to acquire the reflection characteristics of light is performed with respect to a plurality of substrates 20 to compare the reflection characteristics with each other between a plurality of the substrates 20. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for inspecting a substrate having a concavo-convex pattern and a substrate inspection apparatus.

  For example, an imprint technique and a near-field exposure technique have been proposed as one of fine pattern formation techniques for semiconductor devices, recording media, and the like. In the imprint technology, a substrate (template) with a concavo-convex pattern engraved on it is applied to the imprint material such as a photo-curing resin applied on the object to be patterned, and light is applied to cure the imprint material. And transferring the pattern onto the imprint material.

  In the imprint technique, after transferring the pattern to the imprint material, the template is released from the imprint material. At this time, a part of the imprint material may remain attached to the template.

  For example, the difference in refractive index between a quartz template and a photo-curable resin that is an imprint material is very small, so a very small amount of resin adhering to a minute recess is detected by an optical technique such as an optical microscope. It is difficult.

  For example, Patent Document 1 discloses a contamination detection system using surface plasmon resonance spectroscopy, but this only discloses detection of contaminants adhering to a metal layer.

JP 2007-173786 A

  The present invention provides a substrate inspection method and a substrate inspection apparatus that can detect a foreign substance having a refractive index equal to or close to that of the substrate with high sensitivity.

According to one aspect of the present invention, the metal film is formed from the interface side between the surface of the prism and the metal film in a state in which the uneven pattern formed on the substrate is brought close to the metal film formed on the surface of the prism. A method for inspecting a substrate is provided, wherein the step of irradiating light on a film to acquire the reflection characteristic of the light is performed on the plurality of substrates, and the reflection characteristics are compared among the plurality of substrates.
According to another aspect of the present invention, the prism and the substrate in a state where the prism having the surface on which the metal film is formed and the concavo-convex pattern formed on the substrate are close to the metal film. And irradiating the metal film with light from the interface between the surface of the prism and the metal film, and a holding device that holds the prism and the substrate so as to be relatively movable in the surface direction of the metal film. There is provided a substrate inspection apparatus comprising: a light source; and a measurement device that acquires a reflection characteristic of the light irradiated on the metal film.
According to yet another aspect of the present invention, a prism having a surface on which a metal film is formed, a metal film formed on the surface of the prism, and a substrate formed on the metal film. A holding device that holds the prism and the substrate in a state in which a concavo-convex pattern is brought close; a light source that irradiates light to the metal film from an interface side between the surface of the prism and the metal film; A measuring device that acquires a reflection characteristic of the light irradiated to the metal film, wherein the prism reflects the light incident on the prism a plurality of times at different locations in the metal film. There is provided an inspection apparatus for a substrate, which is capable of guiding in a plane direction.

  ADVANTAGE OF THE INVENTION According to this invention, the inspection method of a board | substrate and the inspection apparatus of a board | substrate which can detect a foreign material with a refractive index equivalent to or close to a board | substrate with high sensitivity are provided.

The schematic diagram which illustrates the composition of the substrate inspection device concerning the embodiment of the present invention. The schematic cross section which shows the pattern formation method using the template in the imprint method. The flowchart which shows the board | substrate inspection method which concerns on embodiment of this invention. The graph which illustrates the reflective characteristic acquired with the apparatus of FIG. The graph which shows an example of the relationship between the reflection angle of the state which surface plasmon resonance was excited, and the refractive index of the substance on a metal film. The flowchart which shows the other specific example of the board | substrate inspection method which concerns on embodiment of this invention. The schematic diagram which shows the other specific example of the board | substrate inspection apparatus which concerns on embodiment of this invention. The schematic diagram which shows the other specific example of the board | substrate inspection apparatus which concerns on embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic view illustrating the configuration of a substrate inspection apparatus according to an embodiment of the invention.

  The substrate inspection apparatus according to this embodiment includes a prism 16 having a surface 16a on which a metal film 15 is formed, a holding device 30 that holds the prism 16 and the substrate 20 to be inspected, a light source 31 such as a laser output device, and the like. An optical system 32 such as a lens, a detection device 33 for detecting reflected light, a measuring device 34 for deriving reflection characteristics based on the detection result of the reflected light, and a comparison device for comparing the reflection characteristics among a plurality of substrates 20 35 and a storage device 36 in which reflection characteristics are stored and held as data.

  The prism 16 is formed in, for example, a hemispherical shape, and the metal film 15 is formed on the flat surface 16a. A concave / convex pattern having a plurality of concave portions 22 and convex portions 21 is formed on the substrate 20, and the metal film 15 is irradiated with inspection light from the light source 31 in a state where the concave / convex pattern is brought close to the metal film 15. The reflected light from the film 15 is detected by the detection device 33.

  The prism 16 and the substrate 20 are held by the holding device 30. FIG. 1 schematically shows a state in which the prism 16 and the substrate 20 held by the holding device 30 are viewed from above the holding device 30. In addition, the holding device 30 holds both the prism 16 and the substrate 20 so that the prism 16 and the substrate 20 can be moved relative to each other in the surface direction (arrow A direction) of the metal film 15 in a state where the uneven pattern of the substrate 20 is brought close to the metal film 15. To do.

  The inspection light output from the light source 31 is incident on the prism 16 through the optical system 32, and is applied to the metal film 15 from the interface side between the metal film 15 and the surface 16a of the prism 16 on which the metal film 15 is formed. Is irradiated.

  The light irradiated and reflected on the metal film 15 is detected by the detection device 33, and the reflection characteristic is acquired from the detection result. As will be described later, the reflection characteristics include a reflection angle, a reflectance, and a reflection intensity of reflected light in a state where surface plasmon resonance is excited on the surface of the metal film 15.

  When the thin metal film 15 is irradiated with light through the prism 16, specific light absorption (attenuation of reflected light) is observed at a certain angle in the total reflection angle region. At this time, an electron wave mode causing coupling with light (evanescent light) occurs on the surface of the metal film 15, and surface plasmon resonance is excited.

The refractive index of the substance existing close to the surface of the metal film 15 within the penetration distance of the evanescent light is n ₁ , the complex dielectric constant of the metal film 15 is ε _m , the speed of irradiation light is c, and the angular frequency is ω. Then, the wave number k _sp satisfying the surface plasmon resonance is expressed by the following formula 1.

The reflection angle θ in the state where the surface plasmon resonance is excited is given by the following equation 2 using the refractive index n _p of the prism 16.

Therefore, according to Equation 2, when the refractive index n ₁ of the substance on the surface of the metal film 15 changes, the reflection angle θ in a state where the surface plasmon resonance is excited changes. Further, if the material on the surface of the metal film 15 is different, the reflectance (or reflection intensity) in a state where the surface plasmon resonance is excited may change depending on the light absorption characteristics of the material.

  In the present embodiment, an imprint template will be described as an example of the substrate 20 to be inspected. The substrate (template) 20 is formed with a concavo-convex pattern having convex portions 21 and concave portions 22.

  A pattern forming method using the substrate (template) 20 will be described with reference to FIG.

  First, as shown in FIG. 2A, an imprint material 11 is supplied on the layer to be processed 10. The processing target layer 10 is, for example, a semiconductor substrate or an insulating layer, a semiconductor layer, a conductive layer, or the like formed on the semiconductor substrate. A liquid imprint material 11 is applied on the layer to be treated 10 by, for example, a spin coating method. The imprint material 11 is, for example, an ultraviolet curable resin.

  Next, as shown in FIG. 2B, the uneven pattern of the substrate (template) 20 is brought into contact with the liquid imprint material 11. The concave / convex pattern of the substrate (template) 20 is pressed against the imprint material 11, and the imprint material 11 is filled in the recess 22. In this state, the imprint material 11 is cured by, for example, irradiating the imprint material 11 with ultraviolet rays.

  The substrate (template) 20 is made of a material (for example, quartz) having transparency to ultraviolet rays. Accordingly, ultraviolet rays are irradiated from above the substrate (template) 20, and the ultraviolet rays pass through the substrate (template) 20 and reach the imprint material 11. Thereby, the imprint material 11 is cured.

  The convex portion 21 of the substrate (template) 20 enters the imprint material 11 so as to push the imprint material 11, and the imprint material 11 is cured while the concave portion 22 is filled with the imprint material 11. . Therefore, after the curing, the imprint material 11 is transferred with a pattern in which the concave / convex pattern of the substrate (template) 20 is reversed.

  Next, as shown in FIG. 2C, the substrate (template) 20 is pulled up from the imprint material 11, and the imprint material 11 is released from the substrate (template) 20.

  Thereafter, various processes such as etching and impurity introduction are performed on the layer to be processed 10 using the imprint material 11 having the concavo-convex pattern transferred thereon as a mask.

  Next, inspection of the substrate (template) 20 using the substrate inspection apparatus illustrated in FIG. 1 will be described. The flow is shown in FIG.

  First, the reflection characteristics of the substrate (template) 20 before being used for imprinting, that is, before being brought into contact with the imprint material 11, are acquired using the apparatus of FIG. 1 (step S1).

  That is, the uneven pattern formed on the substrate 20 before use (not in contact with the imprint material 11) is brought close to the metal film 15 formed on the surface 16a of the prism 16. Here, the distance between the surface of the metal film 15 and the tip of the convex portion 21 in the concavo-convex pattern is made shorter than the wavelength of the irradiation light from the light source 31.

  In this state, the inspection light is applied to the metal film 15 from the interface side between the surface 16 a of the prism 16 and the metal film 15, and the reflected light is detected by the detection device 33. In addition, since surface plasmon resonance is excited only at the time of TM polarized light (p polarized light) irradiation, the polarization of irradiated light is controlled to TM polarized light (p polarized light).

  Then, the measuring device 34 derives the relationship between the reflection angle θ of the reflected light and the reflectance as exemplified in FIG. 4, for example. The characteristic at the time of the above-described inspection with respect to the substrate 20 before use is represented by a solid line. That is, at the reflection angle θ1, light energy is converted into surface plasmon energy, surface plasmon resonance is excited, and the reflectance (or reflection intensity) is greatly reduced. This result is stored in the storage device 36 as standard data or reference data.

  Next, the substrate (template) 20 used for imprinting and in contact with the imprint material 11 is inspected in the same manner as the pre-use substrate (step S2). That is, the uneven pattern formed on the used substrate 20 is brought close to the metal film 15 formed on the surface 16 a of the prism 16, and the metal film 15 is moved from the interface between the surface 16 a of the prism 16 and the metal film 15. On the other hand, the inspection light is irradiated, and the reflected light is detected by the detection device 33.

Here, in the used substrate (template) 20, when the imprint material 11 remains attached in the recess 22, the refractive index of the portion close to the surface of the metal film 15 (n ₁ in the above formula 2). Changes, the reflection angle θ corresponding to the surface plasmon excitation angle (resonance angle) changes.

  The reflection characteristics acquired at the time of inspecting the used substrate 20 are represented by broken lines in FIG. 4, for example. In the used substrate 20, when the reflection angle is θ2, light energy is converted into surface plasmon energy, surface plasmon resonance is excited, and the reflectance (or reflection intensity) is greatly reduced.

For example, a quartz substrate (template) 20 having a refractive index n ₁ of 1.51 is used, the refractive index n ₁ of the imprint material 11 is 1.46, and the surface of the prism 16 having a refractive index n _p of 1.7. FIG. 5 shows the relationship of the above equation 2 in the case where an Au film is formed as the metal film 15 on 16a and a He—Ne laser having a wavelength of 632 nm is irradiated as inspection light.
In the graph of FIG. 5, the horizontal axis is the reflection angle θ in a state where surface plasmon resonance is excited, and the vertical axis is the right side in Equation 2.

Before imprinting, that is, in a state where the imprint material 11 is not attached to the concavo-convex pattern, n ₁ is 1.51, and after imprinting, the imprint material 11 is attached to the concavo-convex pattern, n ₁ is 1.46.

From the graph of FIG. 5, the reflection angle (surface plasmon excitation angle) θ differs by about 5 ° when n ₁ is 1.51 and when n ₁ is 1.46. Therefore, by comparing the surface plasmon excitation angle (θ2 in FIG. 4) of the used substrate 20 with the surface plasmon excitation angle (θ1 in FIG. 4) of the substrate 20 before use, an imprint material is formed on the uneven pattern. It can be determined whether or not a foreign object such as 11 is attached.

  The difference in refractive index between the quartz substrate (refractive index 1.51) and the ultraviolet curable resin (refractive index 1.46) is about 3%. For example, an optical microscope or the like detects a change in the refractive index between the two. It ’s difficult. However, the surface plasmon resonance is sensitive to a change in the refractive index on the surface of the metal film. By monitoring the surface plasmon excitation angle (resonance angle), the difference in the refractive index with the substrate 20 is small. Foreign matter can be detected with high sensitivity.

  For example, the comparison device 35 refers to the surface plasmon excitation angle θ1 for the pre-use substrate 20 stored in the storage device 36 and compares it with the surface plasmon excitation angle θ2 for the used substrate 20 (step S3 in FIG. 3). .

  For example, if the difference Δθ between θ1 and θ2 is greater than or equal to a preset threshold θth, the amount of imprint material 11 adhering to the concavo-convex pattern cannot be allowed, and the substrate (template) at the time of the next imprint When 20 is used, it is determined that a defect may occur in the transfer pattern, and the substrate (template) 20 is supplied to the cleaning process (step S4a).

  If the difference Δθ between θ1 and θ2 is smaller than the threshold θth, the substrate (template) 20 is continuously used for the next imprint as it is (step S4b).

  According to the present embodiment described above, it is not necessary to clean the substrate (template) 20 used for imprinting every time after use, thereby reducing costs and improving productivity. Furthermore, defects on the substrate (template) 20 can be surely removed in advance, and defects such as semiconductor devices and recording media patterned by the imprint method can be reduced and cost can be reduced by improving yield.

  The inspection light may be applied to each concave portion 22 to sequentially determine whether or not a foreign matter such as the imprint material 11 is attached to each concave portion 22, or in a relatively wide range including a plurality of concave portions 22. Irradiation may be performed to evaluate the reflection characteristics of the irradiated region. In any case, when there is a foreign matter such as the imprint material 11 in the irradiation region of the inspection light, a difference in reflection angle at which surface plasmon resonance is excited occurs compared to the case where there is no foreign matter, and the uneven pattern The presence or absence of adhered foreign matter can be determined.

  Further, when the inspection region on the substrate 20 where the uneven pattern is formed is larger than the surface 16a of the prism 16, that is, the planar size of the surface of the metal film 15, the substrate 20 and the prism 16 are arranged in the plane direction of the metal film 15. The entire region to be inspected of the substrate 20 is covered. For example, the substrate 20 is linearly moved in the direction of arrow A in FIG.

  Further, by rotating the substrate 20 and the prism 16 together with the holding device 30 in the θ direction, it is possible to change the incident angle of the inspection light and detect the reflection angle at which the surface plasmon resonance is excited.

As described above, the surface plasmon excitation angle θ changes depending on the refractive index n _{1 of the} substance close to the surface of the metal film 15. Furthermore, depending on the absorption characteristics of the substance, the reflectance (or reflection intensity) in the state where surface plasmon resonance is excited may change.

  Therefore, whether or not foreign matter such as the imprint material 11 is attached to the concave-convex pattern of the substrate 20 can also be determined by a change in reflectance (reflection intensity) in a state where surface plasmon resonance is excited. By evaluating both the reflection angle (surface plasmon excitation angle) and the reflectivity (reflection intensity) at that time, the certainty (reliability) of the presence / absence determination of foreign matter increases.

  For example, by utilizing the fact that the reflectance (reflection intensity) varies depending on the presence or absence of foreign matter, the image data of reflected light can also be used as reflection characteristics for determining the presence or absence of foreign matter. In this case, for example, an imaging device is used as the detection device 33 that detects reflected light.

  In the vicinity of the surface plasmon excitation angle when the inspection light is irradiated over a relatively wide range and there is no foreign matter in the irradiated region, almost no reflected light is observed. That is, the acquired image data is dark. Then, when the inspection light is irradiated with the substrate 20 with foreign matter attached close to the metal film 15 without changing the incident angle of the inspection light, the surface plasmon resonance is not excited at the incident angle, and the reflectance (reflection intensity) ) Is not drastically reduced, and the acquired image data is bright. That is, the pattern portion with the foreign matter becomes brighter and the presence or absence of a defect can be confirmed at high speed.

  In the above-described embodiment, the reflection characteristics are compared between the imprint material 11 and the non-contact substrate 20 before using the imprint, and the imprint material 11 and the contacted substrate 20 after using the imprint. . However, not only the comparison between the substrates 20 before and after use, but also by comparing the reflection characteristics between the plurality of substrates 20 before use, it is possible to specify a substrate including a defect in advance before use. The flow is shown in FIG.

  First, similarly to the above-described embodiment, the irradiation of inspection light and the acquisition of reflection characteristics are performed on a plurality of substrates 20 before use (step S11).

Next, in step S12, the reflection characteristics are compared between the plurality of substrates 20.
For example, the average value of the reflection characteristics between the plurality of substrates 20 is calculated, and if there is something different from the average value by a predetermined threshold or more, it is determined that there is some foreign matter attached and the cleaning process is performed. (Step S13a). A substrate having a reflection characteristic smaller than the threshold value with respect to the average value is used in the imprint process (step S13b). Thereby, the pattern transfer defect in an imprint process can be prevented reliably.

  In order to increase the inspection accuracy for the presence or absence of foreign matter, it is desirable to bring the surface of the metal film 15 and the substrate 20 into close contact. In order to improve the adhesion between the two, it is effective to interpose a medium 18 such as an oil-based liquid or a resin film as an adhesion layer between them as shown in FIG. The medium 18 is transparent to inspection light. As a result, the metal film 15 and the substrate 20 are in close contact with each other via the medium 18, and high inspection accuracy is obtained. At this time, the medium 18 used at the time of inspection is the same between the substrates 20 whose reflection characteristics are compared, or the medium 18 having the same refractive index is used.

  Further, the shape of the prism is not limited to a hemispherical shape, and may be a cone shape, a truncated cone shape, or the like. For example, FIG. 8 shows an example using a prism 40 having a truncated cone or truncated pyramid shape.

  For example, the metal film 15 is formed on the surface 40 a on the upper bottom side, and the substrate 20 is arranged with the concavo-convex pattern in proximity to the surface of the metal film 15. When such a prism 40 is used, the inspection light incident on the prism 40 can be guided in the surface direction of the metal film 15 while being reflected a plurality of times at different locations in the metal film 15.

  As schematically represented by arrows in FIG. 8, the light incident on the prism 40 is totally reflected a plurality of times on the upper bottom side and the lower bottom side where the metal film 15 is formed, and It is guided in the surface direction. Thereby, a comparatively wide area | region in the uneven | corrugated pattern of the board | substrate 20 can be test | inspected at once. In some cases, the entire region of the concavo-convex pattern of the substrate 20 can be inspected without relatively moving the substrate 20 and the prism 40.

  Even in this case, there is a difference in the reflection characteristics in the state where the surface plasmon resonance is excited depending on whether or not there is a foreign substance in the inspection light irradiation region, and the presence or absence of the foreign substance can be determined from the difference.

  The embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to them, and various modifications can be made based on the technical idea of the present invention.

  In the above-described embodiment, the imprint template is exemplified as the substrate to be inspected. However, the present invention is not limited to this, and a photomask generally used for pattern exposure or a contact-type mask used for near-field exposure, etc. The present invention can also be applied to this inspection. Examples of the patterning target using these substrates include semiconductor devices and recording media.

  The detectable foreign matter is not limited to a resin such as an imprint material. The present invention can detect a foreign substance having a refractive index equivalent to or close to that of a substrate with high sensitivity.

  DESCRIPTION OF SYMBOLS 11 ... Imprint material, 15 ... Metal film, 16, 40 ... Prism, 18 ... Medium, 20 ... Substrate, 30 ... Holding device

Claims (7)

  The metal film is irradiated with light from the interface side between the surface of the prism and the metal film in a state where the uneven pattern formed on the substrate is brought close to the metal film formed on the surface of the prism. A method for inspecting a substrate, wherein the step of obtaining the reflection characteristics of the plurality of substrates is performed, and the reflection characteristics are compared between the plurality of substrates. The substrate is an imprint template that transfers the inverted pattern of the concavo-convex pattern to the resin by bringing the concavo-convex pattern into contact with the resin,
Evaluating a template that has been in contact with the resin from a comparison between the reflection characteristic of the template in which the concave / convex pattern is not in contact with the resin and the reflection characteristic of a template in which the concave / convex pattern is in contact with the resin. The substrate inspection method according to claim 1.   Filling the space between the metal film and the concavo-convex pattern with a medium that transmits the light, and irradiating the light with the metal film and the concavo-convex pattern in close contact with each other through the medium, the reflection characteristics are obtained. The substrate inspection method according to claim 1, wherein the substrate inspection method is obtained.   The reflection characteristic is at least one of a reflection angle and a reflectance of the light in a state where surface plasmon resonance is excited on the surface of the metal film. The inspection method of the board | substrate of description.   The distance between the surface of the said metal film and the front-end | tip of the convex part in the said uneven | corrugated pattern is made shorter than the wavelength of the said light, The board | substrate as described in any one of Claims 1-4 characterized by the above-mentioned. Inspection method. A prism having a surface on which a metal film is formed;
A holding device for holding the prism and the substrate so that the prism and the substrate can be moved relative to each other in the surface direction of the metal film in a state in which an uneven pattern formed on the substrate is brought close to the metal film. ,
A light source that irradiates the metal film with light from an interface side between the surface of the prism and the metal film;
A measuring device for obtaining a reflection characteristic of the light irradiated on the metal film;
A board inspection apparatus comprising: A prism having a surface on which a metal film is formed;
A metal film formed on the surface of the prism;
A holding device that holds the prism and the substrate in a state in which the uneven pattern formed on the substrate is brought close to the metal film;
A light source that irradiates the metal film with light from an interface side between the surface of the prism and the metal film;
A measuring device for obtaining a reflection characteristic of the light irradiated on the metal film;
With
The substrate inspection apparatus, wherein the prism is capable of guiding the light incident on the prism in a plane direction of the metal film while reflecting the light multiple times at different locations in the metal film.

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