JP2000097610A - Pinhole - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pinhole (e.g. microscopic pinhole with the dimension of 1 μm or less) which achieves an easier making and a higher durability. SOLUTION: There are arranged a transparent substrate 2 and a metal light shielding film 1 which comprises metal having the melting point of 1,800 deg.C or higher provided on the substrate 2 and has a microscopic opening 3 formed by removing a part of the film. The metal is preferably chromium, molybdenum, tungsten, tantalum, ruthenium, niobium, rhenium, rhodium, osmium, iridium, hafnium, vanadium or zirconium or an alloy or a compound containing those of the metals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pinhole used in an optical apparatus, and more particularly to an interferometer for measuring the surface shape of an optical element and the wavefront aberration of an optical system with high accuracy. It relates to a pinhole suitable for use.

[0002]

2. Description of the Related Art Conventionally, a Fizeau interferometer or a Twyman-Green interferometer has been used for measuring a spherical shape and a wavefront aberration. However, these interferometers require a reference surface, and measure the spherical shape and the wavefront aberration by comparison with the reference surface. Therefore, the measurement accuracy cannot exceed the surface accuracy of the reference surface.

Further, as an interferometer that does not require a reference plane, a Point Diff based on a wavefront diffracted by a pinhole is used.
A raction interferometer (hereinafter, referred to as PDI) is known (see Japanese Patent Application Laid-Open No. 2-228505). In this interferometer, the spherical shape and wavefront aberration are determined by using an ideal spherical wave generated by pinhole diffraction as a reference wavefront. High-accuracy measurement.

Conventionally, as such a pinhole for PDI, a thin plate made of metal (such as copper or stainless steel) provided with a through hole has been used.

[0005]

However, in the above-mentioned prior art, the thickness of the metal thin plate is required to be about 10 μm in order to maintain mechanical strength.
A through hole having a size of μm or less has a problem that it is difficult to manufacture the through hole because the aspect ratio of the hole (hole depth / hole diameter) becomes too large.

When a pinhole composed of a through hole having a small hole diameter is used for performing high-precision PDI measurement, the light spot diameter of the light is condensed small in accordance with the pinhole. There is a problem that the energy input per area increases and the pinhole is damaged. The present invention has been made in view of such a problem, and is easier to manufacture than before, and has a pinhole (for example, having a size of 1
It is intended to provide a fine pinhole of μm or less.

[0007]

Therefore, the present invention firstly provides a transparent substrate and a metal light shielding film provided on the substrate and having a melting point of 1800 ° C. or higher, and a part of the light shielding film is removed. And a metal light-shielding film in which a fine opening is formed as a pinhole portion.

[0008] The present invention also relates to a second aspect of the present invention wherein "the metal is chromium, molybdenum, tungsten, tantalum, ruthenium, niobium, rhenium, rhodium, osmium, iridium, hafnium, vanadium or zirconium, or And a pinhole according to claim 1 (claim 2).

The third aspect of the present invention is that the pinhole according to claim 1 or 2 further comprises a transparent protective film covering the light-shielding film and the fine opening.
I will provide a. The present invention also relates to a fourth aspect, wherein the surface of the protective film is flat, or at least the surface portion of the protective film covering the fine opening is flat. Claim 4) "is provided.

In a fifth aspect of the present invention, the material of the protective film is silicon oxide, tantalum oxide, alumina, boron nitride, carbon, silicon nitride, silicon carbide, or boron carbide. The pinhole according to 3 or 4 (claim 5) "is provided. In a sixth aspect of the present invention, “a heat conductive layer made of a material having high thermal conductivity is further provided between the light shielding film and the protective film or between the substrate and the light shielding film. The pinhole according to any one of claims 3 to 5 (claim 6) is provided.

[0011] The present invention is also directed to a seventh aspect, wherein the "thermally conductive layer comprises:
The pinhole (Claim 7) according to Claim 6, which has an opening larger than the fine opening formed in the light shielding film. Eighth, the present invention provides a pinhole according to claim 6 or claim 7, wherein the material of the heat conductive layer is copper, aluminum, gold, or silver. .

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a pinhole according to the present invention (claims 1 to 8), a part of a metal light-shielding film (a metal light-shielding film having a melting point of 1800 ° C. or more) on a transparent substrate is partially removed. A fine opening which is a part is formed. Therefore,
The pinhole according to the present invention (claims 1 to 8) is easier to manufacture than conventional and has higher durability than before.

An embodiment (one example) of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing an example of a pinhole according to the present invention. In this pinhole, a metal light-shielding film 1 is formed on the surface of a transparent substrate 2 made of glass or the like, and a part thereof is removed to form a pinhole portion (fine opening) 3.

The thickness of the light-shielding film 1 may be a thickness that shields (not transmits) light of a used wavelength, and is usually 50 to 200 nm.
It is about. Here, for reference, FIG.
1 shows a conventional pinhole provided with a through hole 3. The metal thin plate 4 needs to have a thickness of at least about 10 μm in order to maintain its mechanical strength.

When forming a pinhole 3 having a diameter of 1 μm or less, the conventional pinhole (FIG. 2) requires an aspect ratio of the hole of 10 or more, and the processing becomes extremely difficult. In the pinhole according to the present invention, the aspect ratio of the pinhole portion (fine opening) 3 provided in the light shielding film 1 is 0.05.
Processing is easy because it may be about 0.2. For forming the light shielding film 1 according to the present invention, a thin film forming method such as vacuum deposition, sputtering, chemical vapor deposition (CVD), and ion plating can be used.

As a method for forming the pinholes (fine openings) 3 in the light-shielding film 1, a lift-off method, a dry etching method, or the like can be used. As the diameter of the pinhole portion (fine opening) 3 becomes smaller, the spot diameter of the light condensed on the pinhole portion 3 also becomes smaller.

In a conventional pinhole as shown in FIG.
Since the metal thin plate 4 in which the through-hole 3 is formed is made of copper, stainless steel, or the like having a relatively low melting point, there is a problem that the metal thin plate 4 is melted, scattered, and broken by a temperature rise due to light absorption. . Such a phenomenon is called laser ablation. Originally, in the conventional pinhole as shown in FIG. 2,
Since the processing for forming the fine through-holes 3 in the metal thin plate 4 is performed by using laser ablation, the durability thereof is essentially limited.

On the other hand, in the pinhole according to the present invention as shown in FIG. 1, since the light shielding film 1 is made of a metal material having a high melting point of 1800 ° C. or more, the condensed spot diameter becomes small and the light energy density becomes small. Does not cause destruction of the pinhole portion 3 due to melting of the light shielding film 1. Therefore, it has higher durability than the conventional pinhole. Examples of the material of the light shielding film 1 according to the present invention include chromium, molybdenum, tungsten, tantalum, ruthenium, niobium,
Rhenium, rhodium, osmium, iridium, hafnium, vanadium or zirconium can be used. Alternatively, an alloy or a compound containing these metals may be used (claim 2).

FIG. 3 is a structural view showing an example of a pinhole according to the present invention (claim 3) with further improved durability. In this pinhole, a metal light-shielding film 1 is provided on the surface of a transparent substrate 2 made of glass or the like, and a part thereof is removed to form a pinhole portion (fine opening) 3. The pinhole further includes a transparent protective film 5 covering the light-shielding film 1 and the pinhole portion (fine opening) 3.

In the pinhole according to the present invention (claim 3), even if the condensing spot diameter becomes small and the energy density of light becomes high and melting of the light shielding film 1 starts, the thick protective film 5 is formed.
Since it is covered with, the destruction of the pinhole portion 3 can be prevented (further improvement in durability). Since a material transparent to the wavelength to be used is used for the protective film 5, the thickness can be increased. For example, the thickness may be about 0.5 to 5 μm.

A protective film 5 is formed on the pinhole 3 of the light shielding film 1.
Is formed, dents corresponding to the pinholes (fine openings) 3 of the light shielding film 1 are formed on the surface of the protective film 5. Although the size of the dent depends on the method of forming the protective film 5, the wavefront of the transmitted light causes a disturbance due to refraction, which causes a measurement error when used for PDI. Therefore, in order to prevent this, it is preferable that the surface of the protective film 5 is polished and flattened.

In other words, it is preferable that the surface of the protective film according to the present invention is flat, or at least the surface portion of the protective film according to the present invention which covers the pinholes (fine openings) is flat. 4). The material of the protective film according to the present invention includes silicon oxide (SiO ₂ ), tantalum oxide (Ta).
₂ O ₅ ), alumina (Al ₂ O ₃ ), boron nitride (BN), carbon (C), silicon nitride (SiN), silicon carbide (SiC), boron carbide (B ₄ C), and the like can be used ( Claim 5).

Further, the protective film according to the present invention can be formed by a thin film forming method such as sputtering, chemical vapor deposition (CVD), or ion plating. FIG. 4 is a diagram showing an example of a pinhole in which a rise in temperature according to the present invention (claim 6) is suppressed. In this pinhole, a metal light-shielding film 1 is provided on the surface of a transparent substrate 2 made of glass or the like, and a part thereof is removed to form a pinhole portion (fine opening).
3 are formed. In this pinhole, a heat conductive layer 6 made of a material having high heat conductivity is provided above or below the light shielding film 1, and further covers the heat conductive layer 6, the light shielding film 1 and the pinhole portion (fine opening) 3. A transparent protective film 5 is provided.

The heat conductive layer 6 is formed on the pinhole 3 of the light shielding film 1.
It is provided so as to have a larger opening (specifically, an opening larger than the diameter of the converging spot on the pinhole portion). When light is condensed in the vicinity of the pinhole portion 3, the temperature of this portion tends to rise locally, but the heat is transmitted to the heat conducting layer 6 and quickly conducted to the peripheral portion. The temperature rise in the vicinity of the portion 3 can be suppressed (further improvement in durability).

Copper, aluminum, gold, silver or the like can be used as the material having high thermal conductivity used for the thermal conductive layer 6 according to the present invention (claim 8). Such a high heat conductive material generally has a low melting point, but since the heat conductive layer 6 has a large opening so that the condensed light does not directly hit,
The temperature rise due to light absorption is small.

Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples.

[0027]

Embodiment 1 In a pinhole according to the present embodiment, a metal light-shielding film 1 is formed on the surface of a transparent substrate 2 and a part thereof is removed to form a pinhole portion (fine opening) 3 (FIG. 1). (Fig. 1). Substrate 2 has a thickness of 2mm with its front and back polished
And tantalum was used as the material of the light shielding film 1.

Hereinafter, a method for manufacturing a pinhole according to this embodiment will be described. First, a tantalum thin film layer having a thickness of 200 nm was formed on the substrate 2 using a high-frequency magnetron sputtering apparatus. Next, a resist was applied on the tantalum thin film layer, a fine opening having a diameter of 0.5 μm was drawn by an electron beam drawing apparatus, and developed to obtain a resist pattern.

Then, using the resist pattern as a mask, the light shielding film 1 of the tungsten thin film layer is etched by a parallel plate type reactive ion etching apparatus using CF ₄ gas to form a pinhole portion (diameter 0.5 μm). After that, the pinhole of the present example was completed by removing the resist. When the pinhole portion 3 is formed, in the conventional pinhole (FIG. 2), the aspect ratio of the hole needs to be, for example, 10 or more, and the processing becomes extremely difficult. In FIG. 1, the aspect ratio of the pinhole portion (fine opening) 3 provided in the light-shielding film 1 is 0.4, and processing is easy.

In the pinhole according to the present embodiment,
Since the light-shielding film 1 is made of a metal material having a high melting point of 1800 ° C. or more, even if the focused spot diameter becomes smaller and the light energy density becomes higher, the pinhole portion 3 due to the melting of the light-shielding film 1 is destroyed. It does not occur and has higher durability than conventional pinholes. Therefore, the pinhole according to the present embodiment is easier to manufacture than the conventional one and has higher durability than the conventional one.

[0031]

Embodiment 2 In a pinhole (FIG. 3) according to this embodiment, a metal light-shielding film 1 is provided on the surface of a transparent substrate 2, and a part thereof is removed to form a pinhole portion (fine opening) 3. Have been. The pinhole according to the present embodiment further includes a transparent protective film 5 that covers the light-shielding film 1 and the pinhole portion (fine opening) 3.

The substrate 2 has a thickness of 5 m with its front and back surfaces polished.
m of fluorite was used, and molybdenum was used as the material of the light shielding film 1. Hereinafter, a method of manufacturing the pinhole according to the present embodiment will be described. First, a molybdenum thin film layer having a thickness of 100 nm was formed on a substrate by using an ion plating apparatus.

Next, a resist was applied on the molybdenum thin film layer, a fine opening having a diameter of 0.4 μm was drawn by an electron beam drawing apparatus, and developed to obtain a resist pattern. Then, using this resist pattern as a mask, the light shielding film 1 of the molybdenum thin film layer was etched by an ECR (Electron Cyclotron Resonance) plasma dry etching apparatus using SF ₆ gas to form a pinhole portion 3.

Next, after removing the resist, the plasma CV
A protective film 5 was formed by depositing a ₂ μm-thick SiO ₂ thin film layer on the surface by using a D apparatus. Here, the pinhole 3 of the protective film 5
Since a dent corresponding to the thickness of the light-shielding film 1 was formed on the surface portion corresponding to, the surface was polished and flattened until the dent was eliminated. As described above, the pinhole of this example having the pinhole portion (fine opening) 3 having a diameter of 0.4 μm was completed.

As in the first embodiment, the pinhole according to the second embodiment is easier to manufacture than the conventional one, and has higher durability than the conventional one. Further, in the pinhole according to the present embodiment, even if the condensed spot diameter becomes small and the energy density of light becomes high and melting of the light shielding film 1 starts, the pinhole portion is covered with the thick protective film 5 because it is covered. 3 can be prevented (having higher durability).

[0036]

Embodiment 3 In a pinhole (FIG. 4A) according to the present embodiment, a metal light-shielding film 1 is provided on the surface of a transparent substrate 2 and a part thereof is removed to form a pinhole portion (fine opening). 3 are formed. Further, a heat conductive layer 6 made of a material having high heat conductivity is provided on the light shielding film 1, and a transparent protective film 5 covering the heat conductive layer 6, the light shielding film 1 and the pinholes (fine openings) 3 is provided. Have been.

The heat conductive layer 6 is provided so as to have an opening that is larger than the pinhole 3 of the light shielding film 1 (specifically, an opening that is larger than the diameter of the condensing spot on the pinhole). ing. The substrate 2 was made of diamond having a thickness of 0.3 mm whose front and back surfaces were polished, and tungsten was used as the material of the light shielding film 1.

Hereinafter, a method of manufacturing a pinhole according to this embodiment will be described. First, a tungsten thin film layer having a thickness of 120 nm was formed on a substrate using a plasma CVD apparatus. Next, a resist was applied on the tungsten thin film layer, a fine opening having a diameter of 0.3 μm was drawn by an electron beam drawing apparatus, and developed to obtain a resist pattern.

Then, using this resist pattern as a mask, an ICP (inductively coupled plasma) dry etching apparatus using SF ₆ gas is used to form a tungsten thin film light shielding film 1.
Was etched to form a pinhole 3. Next, after the resist is peeled off, the resist is applied again, exposed and developed with ultraviolet rays, and has a diameter of 1 so as to cover the pinhole portion 3.
A μm circular resist pattern was formed.

Next, a thickness is formed on this by using a vacuum deposition apparatus.
By depositing a 1 μm gold thin film layer and removing the resist covering the pinhole portion 3 together with the gold thin film layer adhered thereon (lift-off method), the heat conduction having an opening surrounding the pinhole portion 3 is achieved. Layer 6 was formed. Next, a protective film 5 was formed by depositing a hard carbon thin film layer having a thickness of 5 μm on the surface by a plasma CVD apparatus.

Here, a dent corresponding to the thickness of the light-shielding film 1 was formed on a surface portion of the protective film 5 corresponding to the pinhole 3, and the surface was polished and flattened until the dent was eliminated. As described above, the pinhole of this example having the pinhole portion (fine opening) 3 having a diameter of 0.3 μm was completed. Like the first and second embodiments, the pinhole according to the present embodiment is easier to manufacture than the conventional one and has higher durability than the conventional one.

Further, as in the second embodiment, in the pinhole according to the present embodiment, even if the condensing spot diameter becomes small and the energy density of light becomes high and melting of the light shielding film 1 starts, the thick protective film 5 is formed. Because it is covered with pinhole part 3
Can be prevented (having higher durability). Further, in this embodiment, even if light is condensed near the pinhole portion 3 and the temperature of this portion is going to rise locally, the heat is transmitted to the heat conductive layer 6 and quickly transmitted to the peripheral portion. Therefore, it is possible to suppress a rise in temperature near the pinhole portion 3 (having even higher durability).

[0043]

Embodiment 4 In a pinhole (FIG. 4B) according to the present embodiment, a heat conductive layer 6 made of a material having high heat conductivity is provided on the surface of a transparent substrate 2 and a part thereof is removed. An opening is formed. Further, the metal light-shielding film 1 is provided on the heat conductive layer 6, and a part thereof is removed to form a pinhole portion (fine opening) 3.

Further, a transparent protective film 5 which covers the light-shielding film 1 and the pinhole portion (fine opening) 3 is provided. The opening of the heat conductive layer 6 has a size larger than that of the pin hole 3 of the light shielding film 1, and the pin hole 3 is formed inside the opening of the heat conductive layer 6. The substrate 2 was made of quartz having a thickness of 1 mm whose front and back surfaces were polished, and rhenium was used as the material of the light shielding film 1.

Hereinafter, a method of manufacturing a pinhole according to this embodiment will be described. First, apply resist on the substrate,
It was exposed and developed with ultraviolet rays to form a circular resist pattern having a diameter of 1 μm. Next, on top of this,
After the copper thin film layer having a thickness of 0.8 μm was formed, the circular resist pattern was removed together with the copper thin film layer adhered thereon (lift-off method) to form a heat conductive layer 6 having an opening with a diameter of 1 μm.

Next, a resist was applied on the heat conductive layer 6, exposed to ultraviolet light, and developed to form a circular resist pattern having a diameter of 0.5 μm inside the opening. Next, after forming a rhenium thin film layer with a thickness of 70 nm on this by an ion beam sputtering apparatus, the circular (0.5 μm diameter) resist pattern is removed together with the rhenium thin film layer adhered thereon (lift-off method). As a result, the light shielding film 1 having the pinholes 3 was formed.

Next, a 6 μm-thick alumina thin film layer was deposited on the surface by an ion plating apparatus to form a protective film 5. Here, a dent corresponding to the thickness of the light-shielding film 1 was formed on the surface of the protective film 5 corresponding to the pinhole 3, and the surface was polished and flattened until the dent was eliminated. As described above, the pinhole of this example having the pinhole portion (fine opening) 3 having a diameter of 0.5 μm was completed.

Like the first to third embodiments, the pinhole according to the present embodiment is easier to manufacture than the conventional one and has higher durability than the conventional one. Further, similarly to the second and third embodiments, in the pinhole according to the present embodiment, the condensed spot diameter becomes smaller, the energy density of light becomes higher, and the light shielding film 1 becomes larger.
Even when the melting of the pinhole 3 starts, the pinhole portion 3 can be prevented from being broken (having higher durability) because it is covered with the thick protective film 5.

Further, similarly to the third embodiment, even if light is condensed in the vicinity of the pinhole portion 3 and the temperature of this portion is locally increased, the heat is transmitted to the heat conductive layer 6,
Since the heat is quickly transmitted to the peripheral portion, a temperature rise near the pinhole portion 3 can be suppressed (having even higher durability).

[0050]

As described above, in the pinhole according to the present invention in which the pinhole portion is formed by removing a part of the light-shielding film on the transparent substrate, the thickness of the light-shielding film can be reduced. A pinhole having a large hole diameter can be easily manufactured. In the pinhole according to the present invention,
Since the light-shielding film is made of a metal material with a high melting point of 1800 ° C or higher, even if the focused spot diameter is small and the energy density of light is high, the pinhole may be destroyed due to melting of the light-shielding film. And has higher durability than conventional pinholes.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a pinhole according to a first embodiment.

FIG. 2 is a schematic configuration diagram showing an example of a conventional pinhole.

FIG. 3 is a schematic configuration diagram illustrating a pinhole according to a second embodiment.

FIG. 4 is a schematic configuration diagram showing a pinhole (FIG. 4 (a)) of a third embodiment and a pinhole (FIG. 4 (b)) of a fourth embodiment.

[Explanation of Signs of Main Parts]

 DESCRIPTION OF SYMBOLS 1 ... Light shielding film 2 ... Transparent substrate 3 ... Pinhole part 4 ... Metal substrate 5 ... Protective film 6 ... Thermal conductive layer

Claims (8)

[Claims] 1. A transparent substrate, and 1800 ° C. provided on the substrate.
A metal light-shielding film having a melting point as described above, and a metal light-shielding film formed by removing a part of the light-shielding film to form a fine opening serving as a pinhole portion. 2. The method according to claim 1, wherein the metal is chromium, molybdenum, tungsten, tantalum, ruthenium, niobium, rhenium,
2. The pinhole according to claim 1, wherein the pinhole is rhodium, osmium, iridium, hafnium, vanadium or zirconium, or an alloy or compound containing these metals. 3. The device according to claim 1, further comprising a transparent protective film covering the light shielding film and the fine opening.
Pinhole described. 4. The pinhole according to claim 3, wherein the surface of the protection film is flat, or at least a surface portion of the protection film covering the fine opening is flat. 5. The pin according to claim 3, wherein the material of the protective film is silicon oxide, tantalum oxide, alumina, boron nitride, carbon, silicon nitride, silicon carbide, or boron carbide. hole. 6. A heat conduction layer made of a material having high thermal conductivity is further provided between the light-shielding film and the protective film or between the substrate and the light-shielding film. Pinhole according to any of the above. 7. The pinhole according to claim 6, wherein the heat conduction layer has an opening larger than a fine opening formed in the light shielding film. 8. The pinhole according to claim 6, wherein a material of the heat conductive layer is copper, aluminum, gold, or silver.