JP2008009117A - Method of forming dielectric multilayer film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming a dielectric multilayer film used for an optical device whereby the characteristics of the dielectric multilayer film is easily and precisely controlled and the optical device having excellent characteristics is obtained. <P>SOLUTION: The method of forming the dielectric multilayer film formed on the optical device is provided with a first step for forming a test dielectric multilayer film simultaneously on the optical device and a reference substrate for a reference arranged in the vicinity of the optical device before regular film-forming and measuring the characteristics of the optical device and the reference substrate on each of which the test dielectric multilayer film is formed and obtaining the difference of the characteristics between them and a second step for regularly forming the dielectric multilayer film simultaneously on the optical device and the reference substrate following the first step, measuring the characteristics of the regularly film-formed reference substrate and obtaining the characteristics of the regularly film-formed optical device based on the characteristics of the regularly film-formed reference substrate and the difference of the characteristics. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a dielectric multilayer film, and more particularly to a method for manufacturing a dielectric multilayer film used for an optical element.

  In recent years, various optical elements such as optical lenses, dichroic mirrors, bandpass filters, and laser mirrors on which a dielectric multilayer film is formed have been developed (see, for example, Patent Document 1 and Patent Document 2).

  A dielectric multilayer film is formed by alternately laminating a plurality of thin films of a high refractive index dielectric material and a low refractive index dielectric material having a predetermined optical film thickness on a substrate. Normally, the material of the high refractive index film and the material of the low refractive index film are evaporated alternately from the evaporation source installed separately in the vacuum chamber, and these materials are vapor deposited on the substrate held in the vacuum chamber. It is manufactured by a method of forming a dielectric multilayer film.

  A dielectric multilayer film having a large number of layers has a large reflection characteristic (transmission characteristic) with respect to a specific wavelength region and incident angle region of light, and has excellent wavelength dependency and angle dependency. Since the change in the thickness (optical thickness) of the thin film with respect to the change in the wavelength of light and the change in the distance (optical thickness) transmitted through the thin film with respect to the change in the incident angle of light are equivalent, the wavelength dependence and the angle dependence It can be said that sex is an equivalent property.

  As described above, the optical element on which the dielectric multilayer film having wavelength dependency (or angle dependency) is formed utilizes, for example, a color filter or angle dependency disclosed in Patent Literature 1 and Patent Literature 2. Not only as an incident surface of an optical system, such as a SIM (Solid Immersion Mirror), but also because it has a composite function, it does not require additional members, and functions only when combined like a SIM. There is an effect that can be.

  By the way, when a dielectric multilayer film having wavelength dependency (angle dependency) changes its optical film thickness at the time of manufacture, the wavelength (angle) shifts and an optical element having desired characteristics cannot be obtained. However, in film formation processes such as vacuum deposition and sputtering, which are usually performed, optical film thickness variations due to repetition called batch-to-batch errors and optical film thickness variations within the same film-forming process called batch errors occur. To do. Therefore, when a dielectric multilayer film is formed on the optical element, it is important to manage its characteristics.

Therefore, as a method for managing the characteristics of the dielectric multilayer film in the film formation process, when forming an optical element as a product, a reference substrate for reference is generally disposed in the vicinity of the optical element. A film is formed together. The obtained optical element and the reference substrate exhibit the same characteristics, and the multilayer dielectric formed on the optical element as the characteristic value of the optical element with the measured value of the reference substrate that can easily measure the characteristic Manage the characteristics of
JP 2005-31390 A JP 2005-134539 A

  Thus, when forming a dielectric multilayer film on an optical element, it is important to control the characteristics with high accuracy. However, the optical lens technology disclosed in Patent Document 1 and Patent Document 2 did not suggest a manufacturing method related to such film formation.

  In addition, in the conventional method for managing the characteristics of the optical element as a product with the characteristics of the reference substrate, the difference in the size and shape of the optical element and the reference substrate, the difference in the holding method during vapor deposition and the distance from the vapor deposition source For example, the characteristics of the optical element and the reference substrate may not match. Therefore, it is considered difficult to manage the characteristics of the optical element by using the characteristics of the optical element as a product with the characteristics of the reference substrate.

  The present invention has been made in view of the above problems, and in the method for producing a dielectric multilayer film used in an optical element, the characteristics of the dielectric multilayer film can be easily and accurately managed, and the optical characteristics of the excellent characteristics It is an object of the present invention to provide a method for producing a dielectric multilayer film capable of obtaining an element.

  The above object is achieved by the invention described in any one of the following items 1 to 4.

1. In the method for producing a dielectric multilayer film formed on an optical element,
Before the main film formation, the dielectric multilayer film is simultaneously formed on the optical element and a reference substrate for reference arranged in the vicinity of the optical element, and the characteristics of the optical element formed on the test film and the reference substrate are measured. A first step of obtaining the characteristic difference;
Subsequent to the first step, the dielectric multilayer film is formed on the optical element and the reference substrate at the same time, the characteristics of the formed reference substrate are measured, and based on the characteristics and the characteristic difference. And a second step of acquiring the characteristics of the optical element formed as a film.

  2. 2. The method for producing a dielectric multilayer film according to 1 above, wherein a surface of the optical element on which the dielectric multilayer film is formed is formed in a curved shape.

3. The optical element is loaded into a film formation holder that holds the optical element and formed into a film,
With the optical element loaded in the film formation holder, the maximum effective length of the surface on which the dielectric multilayer film is deposited is set to D, and the dielectric multilayer film is deposited on the optical element. 3. The dielectric multilayer film according to 1 or 2 above, wherein the ratio of D to T satisfies the following expression, where T is a thickness of a holding portion that determines a region to be held and holds the optical element: Manufacturing method.
Formula: 5 <D / T <100
4). The optical element on which the dielectric multilayer film is formed is a dichroic mirror having a spectral characteristic of a reflectance of approximately 100% in a predetermined wavelength region and a transmittance of approximately 100% in other wavelength regions. 4. The method for producing a dielectric multilayer film according to any one of 1 to 3 above.

  According to the present invention, the characteristics of the optical element formed in the main film are acquired based on the characteristic difference between the optical element obtained in advance by the test film formation and the reference substrate and the characteristics of the reference substrate obtained in the main film formation. I did it. Therefore, as described above, even when the characteristics of the optical element and the reference substrate do not match due to the difference in the size and shape of the optical element and the reference substrate, or the difference in the distance from the deposition method and the holding method during vapor deposition, A dielectric formed on an optical element can be obtained simply by measuring the characteristics of the reference substrate that can be easily measured in this film formation. The characteristics of the multilayer film can be known. By using the characteristic values obtained in this way, the characteristics of the dielectric multilayer film can be managed easily and efficiently with high accuracy without individually measuring optical elements that are difficult to measure. An optical element having excellent characteristics can be obtained.

  The method for producing a dielectric multilayer film according to the present invention is suitable for an optical element in which it is difficult to easily measure the characteristics, for example, the surface on which the dielectric multilayer film is formed is formed in a curved shape. When measuring wavelength-dependent characteristics (spectral characteristics) with a commonly used spectrometer, if the surface to be deposited is formed in a curved surface, the incident angle changes depending on the measurement position, and the influence of the angle-dependent characteristics is affected. It is difficult to measure wavelength-dependent characteristics with high accuracy. Although it is possible to measure using a microspectroscope, it is necessary to accurately measure the apex position of the lens. As a result, it takes a lot of time for measurement and is not suitable as a management method in the manufacturing process. Therefore, the manufacturing method according to the present invention is preferable because the characteristics of the dielectric multilayer film can be easily and efficiently managed with high accuracy.

When mass-producing optical elements, usually, a plurality of optical elements are incorporated into a film formation holder and then placed in a film formation apparatus for film formation. The film formation holder includes a portion (holding portion) for pressing the optical element in order to hold the optical element. A region inside the holding portion is formed. The thickness T of the holding portion (the thickness of the portion that determines the region where the dielectric multilayer film is formed on the optical element) cannot be made zero. For this reason, in the optical element, at least about the thickness T of the holding portion, usually in the range of several times the thickness T around the holding portion, the film is disturbed by a shadow from the evaporation source. To do. As the optical element becomes smaller, this disturbance cannot be ignored, and it becomes difficult to form a uniform multilayer film without disturbance throughout the effective range D of the optical element. Therefore, it is necessary to properly define the relationship between the thickness T of the holding portion and the maximum effective length D of the surface on which the dielectric multilayer film is formed on the optical element. Therefore, in the present invention, the relationship between T and D is defined so as to satisfy the following (Formula 1).
5 <D / T <100 (Formula 1)
If the lower limit of 5 is not reached in (Equation 1), the influence of the disturbance extends to the central portion of the optical element, and an optical element in which a dielectric multilayer film with good characteristics is formed cannot be obtained. On the other hand, when the upper limit value 100 is exceeded, the optical element has such a size that the influence of disturbance can be ignored. Even if the manufacturing method according to the present invention is not used, the characteristics can be measured by a conventional simple method.

  The dielectric multilayer film manufacturing method according to the present invention is a method for manufacturing an optical element such as a dichroic mirror having a spectral characteristic of a reflectance of approximately 100% in a predetermined wavelength region and a transmittance of approximately 100% in other wavelength regions. Suitable for manufacturing method. Such an optical element becomes a high-performance optical element having a composite function by properly using the reflective region and the transmissive region. However, on the other hand, if the boundary between the reflective region and the transmissive region changes, it will sensitively affect the deterioration of the characteristic, so it is usually necessary to strictly manage the characteristic change at the boundary part. Therefore, the manufacturing method according to the present invention is preferable because the characteristics of the dielectric multilayer film can be easily and efficiently managed with high accuracy, and an optical element having good characteristics can be obtained stably at all times. It is.

  Hereinafter, embodiments of a method for producing a dielectric multilayer film according to the present invention will be described with reference to the drawings.

  First, the appearance of the lens 1 and the flat glass 2 corresponding to the optical element and the reference substrate in the present invention will be described with reference to FIG. FIG. 1A is a side view showing the appearance of the lens 1, and FIG. 1B is a side view showing the appearance of the flat glass.

  As shown in FIG. 1A, the first surface 101 of the lens 1 on which the dielectric multilayer film is formed is formed in a curved shape. Moreover, as shown in FIG.1 (b), the front and back surfaces 201 and 202 of the flat glass 2 are formed in flat planar shape.

  Next, an example of the characteristics of the dielectric multilayer film formed on the lens 1 having such a configuration will be described with reference to FIG. FIG. 2A is a graph showing the wavelength dependence characteristics of the dielectric multilayer film, and FIG. 2B is a graph showing the angle dependence characteristics of the dielectric multilayer film.

  A multilayer dielectric multilayer film in which a thin film of a high refractive index dielectric material and a thin film of a low refractive index dielectric material having a predetermined optical film thickness are alternately laminated on the lens 1 is shown in FIG. ) And (b), the reflectance is approximately 100% in a predetermined wavelength region (incident angle region), and the transmittance is approximately 100% in other wavelength regions (incident angle region). Reflection characteristics (transmission characteristics) with respect to a specific wavelength region and incident angle region are large, and it has excellent wavelength dependency and angle dependency.

  Next, the coat holder 3 will be described with reference to FIG. FIG. 3A is a plan view showing a configuration of an example of the coat holder 3, and FIG. 3B is a diagram illustrating a state in which the lens 1 is loaded on the coat holder 3 in FIG. FIG.

  The coat holder 3 corresponds to the film formation holder in the present invention, and holds the lens 1 during film formation. As shown in FIG. 3A, the coat holder 3 is provided with a plurality of holes 301 into which the lens 1 is loaded. When the lens 1 is mass-produced, a plurality of lenses 1 are simultaneously loaded into a plurality of holes 301 provided in the coat holder 3 and then placed in a vacuum vapor deposition apparatus 6 described later to form a film.

As shown in FIG. 3B, the coat holder 3 includes a holding portion 302 that holds the lens 1. A region D inside the holding portion 302 is formed. The thickness T of the holding portion (the thickness of the portion that determines the region where the dielectric multilayer film is formed on the lens 1) cannot be made zero. For this reason, in the lens 1, the peripheral portion 102 of the holding portion 302 is formed as a shadow from the evaporation source at least in the range of the thickness T of the holding portion 302, usually several times the thickness T. Disturbance occurs. As the shape of the lens 1 becomes smaller, this disturbance cannot be ignored, and it becomes difficult to form a uniform multilayer film without any disturbance throughout the effective range D of the lens 1. Therefore, it is necessary to properly define the relationship between the thickness T of the holding portion and the maximum effective length D of the surface on which the dielectric multilayer film is formed on the lens 1. Therefore, in the present invention, the relationship between T and D is defined so as to satisfy the following (Formula 1). Here, for example, D is 2.8 mm and T is 0.15 mm.
5 <D / T <100 (Formula 1)
When D / T is less than the lower limit value 5 in (Expression 1), the influence of film formation disturbance extends to the central portion 103 of the lens 1 to obtain the lens 1 on which a dielectric multilayer film having good characteristics is formed. I can't. On the other hand, when D / T exceeds the upper limit value 100, the lens 1 has such a size that the influence of disturbance can be ignored. In this case, the characteristics can be measured by a conventional simple method without using the manufacturing method according to the present invention.

  Next, the flow of a film forming process for forming a dielectric multilayer film having the above-described characteristics on the lens 1 will be described with reference to FIG. FIG. 5 is a diagram showing a flow of a dielectric multilayer film forming process.

  First, several coat holders 3 are prepared, and the lenses 1 are loaded into the plurality of holes 301 provided in the respective coat holders 3 (step 1). Next, the plurality of coat holders 3 loaded with the lenses 1 are mounted in the plurality of holes 501 provided in the dome jig 5 shown in FIG. 6, and at the same time, the flat glass 2 for reference is mounted on the coat holder 3. For example, it is mounted in the hole 502 adjacent to the hole 501 (step S2). In this case, the flat glass 2 is formed in a disc shape of, for example, φ30 mm or φ60 mm in accordance with the shape of the hole 502 of the dome jig 5. In the case of vacuum deposition, the lens 1 loaded in the coat holder 3 is mounted on the dome jig 5 and formed into a film. The dome jig 5 is for keeping each lens 1 at a certain distance from the vapor deposition source in order to suppress variations in film formation during vapor deposition of the plurality of lenses 1. Next, the dome jig 5 on which the coat holder 3 loaded with the lens 1 and the flat glass 2 are mounted is placed on the coat dome 601 of the vacuum vapor deposition apparatus 6 shown in FIG. 7, and test film formation is performed (step S3). ). In addition, the dome jig 5 and the vacuum evaporation apparatus 6 shown in FIGS.

  When the test film formation is completed, the wavelength-dependent characteristics (spectral characteristics) of the formed lens 1 and flat glass 2 are measured. Since the lens 1 is small and the surface on which the film is formed is formed in a curved surface shape, it is difficult to measure with a commonly used spectrometer. Therefore, the spectral characteristics near the apex of the curved surface of the lens 1 are measured using a microspectroscope. In addition, about flat glass, it can measure easily with the spectrometer used normally.

  Here, an example of each measured spectral characteristic will be described with reference to FIG. FIG. 8 is a graph showing an example of spectral characteristics (wavelength-dependent characteristics) of the lens 1 and the flat glass 2 that have been subjected to test film formation.

  As shown in FIG. 8, the spectral characteristic R of the lens 1 and the spectral characteristic H of the flat glass 2 are different in the wavelength at which the reflectance is 50%, which is a boundary between reflection and transmission. If the wavelengths at which the reflectance of the lens 1 and the flat glass 2 are 50% are λr0 and λh0, respectively, it can be confirmed that λr0 has a longer wavelength by Δλ (for example, 15 nm) than λh0. In this way, the characteristic difference (wavelength difference) Δλ between the lens 1 and the flat glass 2 is acquired (step S4). This characteristic difference (wavelength difference) Δλ is constant in each batch as long as the relative positional relationship between the lens 1 and the flat glass 2 does not change. Thus, steps S1 to S4 correspond to the first step in the present invention.

Next, following the first step, main film formation is performed on the lens 1 and the flat glass 2 in the same manner as in steps S1 to S3 (step S5). When the main film formation is completed, the wavelength dependency characteristic (spectral characteristic) of the formed flat glass 2 is measured (step S6). The wavelength λr1 is the boundary between the reflection and transmission of the measured flat glass 2 and has a reflectance of 50%, and λh1 is the boundary between the reflection and transmission of the formed lens 1 and the reflectance is 50%. Is a value obtained by adding the characteristic difference (wavelength difference) Δλ obtained by the above-described test film formation to λh1, that is, a value obtained by the following (Expression 2). In this way, the wavelength λr1 of the lens 1 can be known (step S7).
λr1 = λr1 + Δλ (Formula 2)
Thus, steps S5 to S7 correspond to the second step in the present invention.

  Thus, according to the method for manufacturing a dielectric multilayer film according to the embodiment of the present invention, the difference in size and shape between the lens 1 and the flat glass 2, and the difference in the holding method during deposition and the distance from the deposition source. Even if the characteristics of the glass 1 and the flat glass 2 do not coincide with each other, the characteristic difference between the lens 1 and the flat glass 2 is grasped in advance in the test film formation, and in this film formation, it can be easily measured. By simply measuring the characteristics of the flat glass 2, the characteristics of the dielectric multilayer film formed on the lens 1 can be known. By using the characteristic values obtained in this way, it is possible to easily and efficiently manage the characteristics of the dielectric multilayer film without performing individual measurement of the lens 1 which is difficult to measure. An optical element having excellent characteristics can be obtained.

  The present invention has been described above with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and can be changed or improved as appropriate. For example, instead of the coat holder 2 described with reference to FIG. 3, the coat holder 4 having the configuration shown in FIG. 4 may be used. FIG. 4 is a plan view showing a configuration of another example of the coat holder.

  As shown in FIG. 4, the coat holder 4 is provided with a hole 402 for loading the flat glass 2 at the center and a plurality of holes 401 for loading the lens 1 at the periphery of the hole 402. Thereby, the relative positional relationship of the lens 1 and the flat glass 2 can be maintained reliably.

It is a side view which shows the external appearance by an example of the lens and flat glass which concern on this invention. It is a graph which shows an example of the wavelength dependence characteristic and angle dependence characteristic of the dielectric multilayer film concerning this invention. It is a schematic diagram which shows the structure by an example of the film-forming holder (coat holder) which concerns on this invention. It is a schematic diagram which shows the structure by another example of the film-forming holder (coat holder) which concerns on this invention. It is a figure which shows the flow of the film-forming process in the manufacturing method of the dielectric multilayer film concerning this invention. It is a schematic diagram which shows the structure of the conventional dome jig. It is a schematic diagram which shows schematic structure of the conventional vacuum evaporation system. It is a graph which shows the spectral characteristic (wavelength dependence characteristic) of the lens and flat glass by test film-forming in the manufacturing method of the dielectric multilayer film concerning this invention.

Explanation of symbols

1 Lens 2 Flat glass 3, 4 Deposition holder (coat holder)
5 Dome jig 6 Vacuum deposition equipment

Claims (4)

In the method for producing a dielectric multilayer film formed on an optical element,
Before the main film formation, the dielectric multilayer film is simultaneously formed on the optical element and a reference substrate for reference arranged in the vicinity of the optical element, and the characteristics of the optical element formed on the test film and the reference substrate are measured. A first step of obtaining the characteristic difference;
Subsequent to the first step, the dielectric multilayer film is formed on the optical element and the reference substrate at the same time, the characteristics of the formed reference substrate are measured, and based on the characteristics and the characteristic difference. And a second step of acquiring the characteristics of the optical element formed as a film. 2. The method for producing a dielectric multilayer film according to claim 1, wherein the surface of the optical element on which the dielectric multilayer film is formed is formed in a curved shape. The optical element is loaded into a film formation holder that holds the optical element and formed into a film,
With the optical element loaded in the film formation holder, the maximum effective length of the surface on which the dielectric multilayer film is deposited is set to D, and the dielectric multilayer film is deposited on the optical element. 3. The dielectric multilayer according to claim 1, wherein a ratio of D to T satisfies the following expression, where T is a thickness of a holding portion that determines a region to be held and holds the optical element. A method for producing a membrane.
Formula: 5 <D / T <100 The optical element on which the dielectric multilayer film is formed is a dichroic mirror having a spectral characteristic of a reflectance of approximately 100% in a predetermined wavelength region and a transmittance of approximately 100% in other wavelength regions. The method for producing a dielectric multilayer film according to any one of claims 1 to 3.

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