JP5938732B2 - Method for manufacturing optical film or optical sheet - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device, a method for producing a pattern forming substrate used for an optical film, a pattern forming substrate, and an optical film or an optical sheet, and particularly, over a very large area compared to a pattern pitch in which unit patterns are repeated several hundred thousand to million times. The present invention relates to a method for producing a pattern forming substrate having a uniform shape, a pattern forming substrate, and an optical film or optical sheet.

  In recent years, research on fine structures having a wavelength level period of light such as a wire grid polarizer has been actively conducted. Such a member or product having a microstructure pattern with a very narrow period is widely useful not only in the semiconductor field but also in the optical field. In general, as a technique for forming such a fine structure pattern, a semiconductor processing technique such as electron beam drawing and a stepper and a laser interference exposure method are widely known.

  However, it is not practical to directly form a fine structure using these techniques because it takes much time and cost. Therefore, by forming a fine concavo-convex pattern on a glass substrate or Si substrate and transferring the pattern-formed substrate with the pattern formed on the surface as a mold (stamper) to the resist (embossing technique), it is fine at low cost and high efficiency. A method of manufacturing a structure has been proposed (for example, Patent Document 1). Even in the case of using the embossing technique, a processing technique such as electron beam drawing is used in forming the mold.

  In the embossing technique, increasing the area of the pattern forming substrate to be a mold is very important for improving productivity. For example, in electron beam writing, the partition area that can be drawn at a time is several mm square or less. Since drawing takes time, considering temperature changes during processing time, etc., a uniform pattern can be created by joining each section over a large area with high accuracy on a Si wafer with a diameter of 20 cm or more. It is difficult.

  In exposure using a stepper, unit patterns can be transferred continuously by repeating step and repeat. In general, pattern transfer is performed on a chip basis, and line and space patterns ( It is required to have a high accuracy in order to form a continuous pattern by closely joining unit patterns each having a concavo-convex lattice shape such as (L / S pattern) in a large area. In addition, since the uniformity of the shape at the nanometer level was not evaluated non-destructively in a wide area of several tens of centimeters, the nano pattern (the pitch of the L / S pattern is 1 μm or less) in which uniformity was ensured It was difficult to manufacture. The laser interference exposure method is suitable for forming uniform and fine patterns over a relatively large area. However, as the exposure area increases, the exposure time increases, and the phase stability of the laser beam and the temperature change of the resist substrate It was difficult to maintain the dimensional stability due to, and it was difficult to form nanopatterns with excellent uniformity.

  Further, in order to obtain a large-area mold, a method of forming a large second mold using the first mold after forming a first mold having a small area has been proposed (for example, a patent). Reference 2).

  However, when the method of Patent Document 2 is used, a unit pattern (a pattern formed on the first mold) is contacted because the resist is partially heated or irradiated when the first mold is transferred. It is difficult to make a continuous pattern together. In particular, as the pitch of the line and space pattern becomes narrower, there is a higher possibility that a defect will occur at the joint portion.

JP 2006-84776 A JP 2005-203797 A

  This invention is made | formed in view of this point, and provides the manufacturing method of a pattern formation board | substrate which has a uniform and continuous pattern shape over a large area compared with a pattern pitch, a pattern formation board | substrate, and an optical film or an optical sheet. One of the purposes.

The manufacturing method of the optical film or optical sheet of the present invention is composed of a continuous concavo-convex lattice pattern having a pitch of 300 nm or less and a height of 50 nm or more and 200 nm or less, and the diameter of the minimum circumscribed circle of the portion where the continuous concavo-convex lattice pattern is formed The continuous concavo-convex grid pattern has a variation width of the reflected light wavelength of the visible light region from the continuous concavo-convex grid pattern within 25 nm, and the continuous concavo-convex grid pattern repeats a fine pattern with a unit area. The pattern forming substrate formed by bonding is made of silicon or silicon oxide, and the pattern on the pattern forming substrate, its replication pattern or reverse pattern is used to form a concavo-convex lattice structure on the film or sheet base material with a transfer resin. It is characterized by transferring.

Further, the method for producing an optical film or optical sheet of the present invention is composed of a continuous concavo-convex lattice pattern having a pitch of 300 nm or less and a height of 50 nm or more and 200 nm or less, and a minimum circumcircle of the portion where the continuous concavo-convex lattice pattern is formed. The diameter is 20 cm or more, and in the continuous concavo-convex lattice pattern, the variation width of the reflectance of the visible light region from the continuous concavo-convex lattice pattern is within 2%, and the continuous concavo-convex lattice pattern repeats a fine pattern of a unit area. The pattern forming substrate bonded and formed by the exposure method is made of silicon or silicon oxide. Using the pattern on the pattern forming substrate, its replication pattern or its reversal pattern, a concavo-convex lattice is formed on the film or sheet substrate by a transfer resin. It is characterized by transferring the structure.

  According to the present invention, a pattern forming substrate having a uniform and continuous pattern shape over a larger area than the pattern pitch can be obtained.

Schematic showing an example of the exposure method of the present invention Measurement results of wavelength and reflectance of the embodiment according to the present invention Measurement results of wavelength and reflectance of comparative example according to the present invention

  The present inventor has intensively studied a method for nondestructively evaluating the uniformity of the shape at the nanometer level in a wide area of several tens of centimeters, and a simple and highly accurate evaluation method using white light or monochromatic light. I found. As a result, it was possible to evaluate the non-uniform portion of the shape, and it was possible to eliminate the non-uniform portion by optimizing the pattern joining condition.

  And while using such an evaluation method, in recent years, applying stepper and interference exposure technology with significantly improved accuracy, and as a result of intensive studies on masks and exposure methods, the seam is visually recognized over a much larger area than the pattern pitch. It came to obtain the pattern formation board | substrate which has the uniform shape which cannot be performed. Hereinafter, an example of a pattern forming substrate on which a nanometer unit pattern is formed in a large area and a method for manufacturing the same will be described.

  First, a substrate is prepared. As the substrate, silicon (Si), silicon oxide, glass, gallium nitride, gallium arsenide, aluminum oxide, silicon carbide, or the like can be used.

  Next, after a resist film is formed on the substrate, the resist film on the substrate is exposed using a step-and-repeat type exposure apparatus (stepper) (see FIGS. 1A and 1B). In FIG. 1B, a region surrounded by a dotted line on the substrate 100 is a region where the resist is exposed by one-time (one-shot) irradiation, and corresponds to a unit pattern obtained by reducing the pattern of the reticle 101.

  In this embodiment, shots are repeated so that a line and space pattern (unit line and space pattern, fine pattern of unit area), which is a fine pattern formed on the reticle, is joined (bonded), The upper resist is exposed (bonded by repeated exposure). Therefore, a continuous line and space pattern (continuous concavo-convex lattice pattern, continuous fine pattern) formed by joining unit line and space patterns is transferred to the resist. In each shot, the amount of overlap between the shots (the amount of the portion where the number of exposures becomes plural) can be arbitrarily set so that the joining is uniform. After the resist film on the substrate is exposed, development is performed by a method suitable for the resist, and then the substrate is etched to form an uneven lattice pattern.

  Here, the fine pattern is composed of a continuous concavo-convex lattice pattern having a pitch of 300 nm or less and a height of 50 nm or more and 200 nm or less, and the area of the portion where the continuous concavo-convex lattice pattern is formed is applied to various uses The diameter is preferably as large as possible, and the diameter of the minimum circumscribed circle of the portion where the concavo-convex lattice pattern is formed is preferably 20 cm or more, more preferably 25 cm or more, and most preferably 30 cm or more. If it is this size, the possibility that it can be applied to optical components such as a wire grid polarizing plate, an antireflection film, and a retardation plate is widened. On the other hand, there is no technical limitation on the upper limit of the size, and according to the interference exposure method, although it depends on the pattern shape, it is possible to form a uniform fine pattern over an area of 100 cm square or more. The diameter of the circle is about 150 cm.

  Next, the uniformity of the joint portion of the unit concavo-convex lattice shape is evaluated for the continuous concavo-convex lattice shape of the obtained pattern forming substrate.

  The uniformity of the joint portion of the unit concavo-convex lattice shape can be evaluated by the optical characteristics of the boundary portion (joint portion) where, for example, four shots are adjacent in the continuous concavo-convex lattice shape.

  The evaluation of the optical characteristics of the joint can be performed by measuring the reflected light in the vicinity of the joint, comparing the reflected light, and evaluating the variation width. Specifically, after defining a predetermined area including the joint portion, a plurality of points are set in the area, and the amount and spectrum (wavelength) of reflected light at the plurality of points when light is irradiated from a predetermined direction. Compare each. The measurement of the reflected light is preferably performed from a plurality of directions, for example, by irradiating light from the X-axis direction which is the extending direction of the continuous uneven lattice shape and the Y-axis direction perpendicular to the X-axis direction, It is preferable to evaluate the variation width of reflected light at a plurality of points in each direction. In the case of the concavo-convex lattice shape produced by the interference exposure method, it is sufficient to set 10 points or more so as to include the point at which the variation width of the reflected light in the visible light (380 to 780 nm) becomes maximum. Preferably, about 20 to 100 points may be set. In the case of a concavo-convex lattice shape produced using a stepper, it is only necessary to set 10 points or more including points and not including joints. Preferably, about 20 to 100 points may be set for each.

  As an example, after setting a plurality of points in the region including the joint, by irradiating the region with light in a predetermined range of wavelengths (for example, 380 nm to 780 nm), and comparing the reflected light at each point, The variation width of the reflected light amount and the reflected light wavelength is evaluated. The variation width of the reflected light wavelength is a fluctuation width (variation width) from an average value of wavelengths at a specific reflectance in a spectrum obtained by overwriting a reflection spectrum of each point in a wavelength region of 380 nm to 780 nm. ). By irradiating light from the X-axis direction and measuring and comparing the reflected light at each point, the amount of reflected light and the variation width of the reflected light wavelength are evaluated. Further, the same evaluation can be performed for the Y-axis direction. Here, the size of the measurement point may be appropriately set according to the color unevenness. For example, when the measurement point is manufactured using a stepper, the diameter is about several μm to 1 mm.

  In the present embodiment, the variation width of the reflected light wavelength in the vicinity of the junction is within 25 nm, or the variation width of the reflectance (the ratio of the incident light amount to the reflected light amount) is within 2%. If it is this range, it can be said that the joint part of unit uneven | corrugated lattice shape has practically sufficient uniformity. Further, the unit-concave-lattice-shaped joint portion has a variation width of the reflected light wavelength in the vicinity of the joint portion within 25 nm and a variation width of the reflectance (ratio of incident light amount to reflected light amount) within 2%. It is more preferable from the viewpoint of uniformity. The variation width of the reflectance is the fluctuation width (variation width) from the average value of the reflectance at a specific wavelength in the spectrum obtained by overwriting the reflection spectrum of each point in the wavelength region of 380 nm to 780 nm. I'll show you. In optimizing the variation width of the reflected light wavelength to 25 nm or less, the height and width of the concavo-convex grid and the pitch variation of the concavo-convex grid should be adjusted to 10 nm or less, preferably 5 nm or less, more preferably 2 nm or less. Is important. In order to optimize the variation width of the reflectance within 2%, the height of the concavo-convex grid and the variation of the pitch of the concavo-convex grid are adjusted to 10 nm or less, preferably 5 nm or less, more preferably 2 nm or less. It is important to do. The variation width of the reflection wavelength is more preferably within 20 nm.

  Thereafter, based on the obtained evaluation results, the pattern forming substrate having a uniform joint can be manufactured by optimizing and setting the joining conditions (exposure conditions and the like) by trial and error.

  The comparative evaluation of the reflectance and the variation width of the reflected light wavelength based on the measurement of the reflected light as described above can be simplified, and visual evaluation can also be easily used. For example, visible light is incident on the substrate surface at an incident angle of 45 degrees or more from a parallel direction or a right angle of the continuous concave-convex lattice pattern, and the reflected light is observed. In this method, it is preferable that the joint portion of the unit cell uneven lattice pattern is not visually recognized.

  When the substrate is made of a transparent material such as silicon oxide, it is preferable to observe and evaluate the reflected light by the same method after coating the surface of the substrate with a light shielding material such as metal on the average of about 20 nm.

  Thus, by using the above evaluation method, it becomes possible to evaluate the uniformity of the pattern over a very large area compared to the pattern pitch, and by optimizing the pattern formation method, the pattern having a uniform shape can be evaluated. A forming substrate can be obtained.

  Moreover, in the evaluation of the joint portion of the unit concavo-convex lattice pattern, a plurality of concavo-convex lattice shapes having a plurality of conditions can be produced on a single substrate by changing the exposure conditions for the resist formed on the single substrate. It is also possible to evaluate the uniformity of the pattern joint with respect to the above exposure conditions.

  Hereinafter, the present invention will be described in detail by way of examples.

  In this example, a stepper shot area of 5 × 20 mm, a pitch of 130 nm, a line-and-space pattern with a line-to-space ratio (L / S ratio) of 6/4, and a pattern with a height of 150 nm are continuously provided. After obtaining a silicon substrate having a diameter of 30 cm formed over a wide area, the reflected light was measured in the vicinity of the boundary where four shots are adjacent to form a cross.

  The reflected light was measured using a reflective spectral film thickness meter FE3000 (automatic stage specification) manufactured by Otsuka Electronics Co., Ltd. The measurement conditions are absolute reflectance measurement, the measurement mode is manual, the objective lens is multiplied by 25 times, the baseline is adjusted with reference to aluminum, and the reflectance of BK7 with known reflectance is also measured as another reference. Confirmed that it was normal.

  Next, a silicon substrate was placed so that the Y-axis of the sample stage of the reflection spectral film thickness meter and the axis direction of the concavo-convex lattice shape were parallel, and the height was adjusted so that the measurement focus coincided with the substrate surface. A silicon substrate was installed, and the height was adjusted so that the measurement focus coincided with the substrate surface. The measurement incident angle at this time was 10 ° to 22 ° with respect to the sample, and the measurement area was 8 μmφ.

  Next, using the measurement mode as a mapping, the measurement points are set in a range of 3 × 3 mm so that four shots are adjacent to each other and include a cross, and a total of 1600 points each of 40 points on the X axis and 40 points on the Y axis are set. The reflected light was measured at intervals.

  First, the result of measuring the reflectance by installing the concavo-convex lattice shape parallel to the Y axis of the automatic stage of the measuring instrument is shown (FIG. 2). This is a comparative example which will be described later, and was produced by optimizing the shot joining conditions with respect to the conditions for producing the concavo-convex lattice shape. When the reflectance of the silicon substrate was measured, the reflectance of the silicon substrate of Condition 1 (Example) was within a variation range of 10 nm in wavelength and 0.7% in reflectance in the wavelength range of 380 to 780 nm. .

  As a comparative example, an uneven lattice shape having a similar shape was formed on a silicon substrate under different joining conditions, and the reflectance was measured. As a result of measuring the reflectance by installing the concave and convex lattice shape in parallel with the Y axis of the automatic stage of the measuring instrument (FIG. 3), the reflectance of the silicon substrate in condition 2 (comparative example) is 27 nm in wavelength, There was a portion with a variation width of 2.1% or more in reflectance.

  Furthermore, the concavo-convex lattice structure was transferred onto the PET film using an ultraviolet curable resin using these two types of silicon substrates. The transferred film was inclined at 30 ° and Al was coated on the concavo-convex structure surface by vacuum deposition with an average thickness of 50 nm.

  Next, Table 1 shows the results when the transmitted light was observed through the white light source on the wire grid film coated with Al.

  In the sample produced under Condition 1, the shot spot of the transmitted light was not visible and the transmitted light was uniform. However, in the sample produced from the silicon substrate of Condition 2, the transmission spots corresponding to the shot spots visible on the silicon substrate were easily visible.

  The pattern forming substrate of the present invention has a uniform and continuous pattern shape with a large area, and can be applied to optical components such as a wire grid polarizing plate, an antireflection structure, and a retardation plate.

100 substrate 101 reticle

Claims (2)

It is composed of a continuous concavo-convex lattice pattern having a pitch of 300 nm or less and a height of 50 nm to 200 nm,
The diameter of the minimum circumscribed circle of the portion where the continuous uneven lattice pattern is formed is 20 cm or more,
In the continuous concavo-convex lattice pattern, the variation width of the reflected light wavelength in the visible light region from the continuous concavo-convex lattice pattern is within 25 nm,
A pattern forming substrate in which the continuous concavo-convex lattice pattern is formed by repeatedly bonding a fine pattern of a unit area by an exposure method is made of silicon or silicon oxide,
A method for producing an optical film or optical sheet , comprising transferring a concavo-convex lattice structure onto a film or sheet substrate by a transfer resin using a pattern on the pattern forming substrate, a replication pattern or an inverted pattern thereof. It is composed of a continuous concavo-convex lattice pattern having a pitch of 300 nm or less and a height of 50 nm to 200 nm,
The diameter of the minimum circumscribed circle of the portion where the continuous uneven lattice pattern is formed is 20 cm or more,
In the continuous concavo-convex grid pattern, the variation width of the reflectance of the visible light region from the continuous concavo-convex grid pattern is within 2%,
A pattern forming substrate in which the continuous concavo-convex lattice pattern is formed by repeatedly bonding a fine pattern of a unit area by an exposure method is made of silicon or silicon oxide,
A method for producing an optical film or optical sheet , comprising transferring a concavo-convex lattice structure onto a film or sheet substrate by a transfer resin using a pattern on the pattern forming substrate, a replication pattern or an inverted pattern thereof.