JP2002303510A - Thin film formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin film formation device having a film thickness measurement device equipped with a light receiving optical system capable of measuring a thickness in a desired position of a film body formed on a film formed body. SOLUTION: In this thin film formation device, a thin film is formed on the surface while the film thickness is measured by an optical method, while the film formed body is turned in a vacuum film formation camber. A light emitting optical system and a light receiving optical system of the thickness measurement device are made movable respectively. The light receiving optical system can be moved in a film formation range on the film formed body. The light emitting optical system is made movable corresponding to the movement of the light receiving optical system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film forming apparatus used for forming a multilayer film or the like constituting a band pass filter or the like for optical communication.

[0002]

2. Description of the Related Art In the field of optical communication, DWDM (De
nse Wavelength Division M
A so-called DWDM filter, which is used as a wavelength division filter in a multiplexing (high-density wavelength division multiplexing) communication system, is a multilayer film in which dielectric thin films having different refractive indices are formed on a glass substrate whose surface is polished with high precision. It becomes. This DWDM filter is
It is necessary that the refractive index and the thickness of each thin film constituting the multilayer film exactly match the design values.

The thickness of each thin film considered here is an effective thickness (optical thickness) determined by both the composition and the physical thickness of the actually formed film. When manufacturing this DWDM filter using a thin film forming apparatus such as a vacuum evaporation apparatus, both the composition control of the film forming material for controlling the film thickness and the physical film thickness control are extremely important.
Here, the composition control is performed by selecting an evaporation source material (target) for obtaining a deposition material, and the film thickness control needs to be performed while monitoring the thickness of the thin film to be formed every moment.

In order to monitor the film thickness, the thin film forming apparatus is provided with a film thickness measuring device. As this film thickness measuring apparatus, there is an apparatus utilizing a phenomenon in which, when a thin film is irradiated with light such as a laser beam, reflected light or transmitted light causes an intensity change depending on the film thickness. That is, when light is applied to the thin film, the interference state of the reflected light from the front and back surfaces changes according to the film thickness, and this utilizes the fact that the intensity of reflected light or transmitted light changes.

This film thickness apparatus includes a light irradiation optical system for irradiating light to a thin film, and a signal light generated by transmitting or reflecting the light irradiated through the light irradiation optical system to the thin film, and receiving the signal light to the outside. It has a light receiving optical system for guiding, and a signal processing device for processing the signal light guided to the outside and calculating a physical quantity corresponding to the film thickness.

The light irradiating optical system introduces light from a light source provided outside the vacuum film forming chamber into a vacuum film forming chamber through a transparent window provided on a vacuum partition of the vacuum film forming chamber. The light is condensed and irradiated on the measurement point of the thin film on the glass substrate through the system. In addition, the light receiving optical system is introduced into a light guide device such as an optical fiber device through a lens system designed such that the focal point is located at a measurement point which is a converging point of the irradiation light, and is transmitted to a signal processing device. Lead.

[0007]

When a DWDM filter is manufactured, a film is formed while rotating a glass substrate at a high speed. This is because even if the amount of evaporated particles flying on the surface of the glass substrate is not uniform depending on the location on the substrate, the rotation direction on the glass substrate (the location of the same radius)
In order to obtain a uniform film thickness by making the positions uniform at each position.

[0008] The characteristics of the DWDM filter largely depend on the thickness of each thin film to be laminated. Therefore, it is necessary to control the film formation process while measuring the film thickness distribution in the radial direction of the region formed on the glass substrate.

However, the thickness of the thin film formed on the glass substrate can be uniform in the rotation direction as described above, but is not necessarily uniform in the radial direction. That is, the distance from the evaporation source to each point on the substrate slightly increases as the distance from the center of the substrate to the peripheral point of the substrate increases, and the area also increases. There is a problem that the film thickness changes gradually in the direction and a uniform film thickness cannot be obtained.

On the other hand, in the conventional film thickness monitoring method, the film is not formed while monitoring the entire substrate. For this reason, on the substrate after film formation, not all of the deposited portion can be used, but only a portion (sweet spot) whose film thickness is strictly controlled by a monitor can be used. For example, in the case of forming a multilayer film for a 100 GHz band-pass filter, even if a substrate having a diameter of 100 mm is used, only a region having a diameter of only about 20 mm out of the substrate satisfies the specification.
For this reason, the low yield inevitably increases the price as a product or causes a reduction in product supply capability.

Further, as a conventional film thickness monitoring method, a film formation monitor plate is arranged near a substrate on which a film is formed, and the film thickness of the monitor thin film formed on the film formation monitor plate is measured. Although a method of controlling a film formation process based on the method is known, in such a method, the film formation monitor substrate is disposed at a position different from the actual film formation substrate, The film thickness does not always match the actual film thickness formed on the glass substrate, and sufficient film thickness measurement accuracy cannot be obtained for each thin film. There has been a problem that it is necessary to determine in advance the correction conditions for the calculation.

SUMMARY OF THE INVENTION The present invention has been made under the above-mentioned background, and directly measures the thickness of a thin film formed on a glass substrate and detects light in the radial direction of the substrate. It is an object of the present invention to provide a thin film forming apparatus having a film thickness measuring device having an optical system.

[0013]

In order to solve the above-mentioned problems, a thin film forming apparatus of the present invention comprises: a film forming apparatus for forming a thin film on a surface while rotating a film to be formed in a vacuum film forming chamber; A film thickness measuring device for measuring a film thickness of a thin film formed on the film-forming object by an optical method, wherein the film thickness measuring device is configured to irradiate light to the thin film. An irradiation optical system, a light receiving optical system for receiving signal light generated by transmitting or reflecting the light irradiated through the light irradiation optical system through the thin film and guiding the signal light to the outside, and processing the signal light guided to the outside. A signal processing device for calculating a physical quantity corresponding to the film thickness, wherein the light-receiving optical system has a light-receiving section movable in a range where a thin film is formed on the film-forming body; The system has a light irradiation unit that moves according to the amount of movement of the light receiving unit. It is characterized in.

Preferably, in the thin film forming apparatus according to the present invention, when the film forming apparatus deposits a substance for forming a thin film on the surface of the object to be deposited, the film forming apparatus irradiates the substance to be deposited with ions. Evaporation method (Ion Assist
ed Deposition).

Preferably, in the thin film forming apparatus of the present invention, the thin film formed on the object to be formed is a multilayer film,
The film forming apparatus is capable of forming a thin film of a different material on the object to be formed by stacking the thin films. The film thickness measuring apparatus measures each film thickness, and sequentially forms desired materials and film thicknesses. It is characterized by the fact that

Still preferably, in a thin film forming apparatus according to the present invention, the object to be deposited is a glass substrate, and the multilayer film is
It is formed by laminating dielectric thin films having different refractive indexes in multiple layers, and is formed by DWDM (Dense Wavelength).
h Division Multiplexing (Dense Wavelength Division Multiplexing) It is characterized in that it can be used as a wavelength division filter in a communication system.

[0017]

FIG. 1 is a view showing the entire structure of a thin film forming apparatus according to an embodiment of the present invention.

In FIG. 1, a thin film forming apparatus according to this embodiment comprises a vacuum film forming chamber 2 supported on a base 1 by columns 1a and 1b, and a signal processing apparatus 3 installed at an appropriate place. Having. The vacuum film forming chamber 2 includes a vacuum partition 2a.
The inside and the outside are partitioned by the vacuum pump 2b, so that the inside can be maintained at a high vacuum by the vacuum pump 2b.

In a partial area of the inner bottom surface of the vacuum film forming chamber 2,
A vapor deposition device 21, an ion gun 22, and the like are provided. Further, a transparent window 24 is provided in another area of the inner bottom surface of the vacuum film forming chamber 2. Further, a motor 25 is provided outside the upper center of the vacuum film forming chamber 2, and a rotation shaft 25 a of the motor 25 extends through the vacuum partition 2 a while vacuum sealing the inside of the vacuum film forming chamber 2. The substrate holding device 25b is attached to the tip. This substrate holding device 2
5b is inserted into the through-hole of the glass substrate 100 having a through-hole at the center and holds it, so that the glass substrate 100 can be rotated by the motor 25.

A light receiving optical system 4 is arranged above the glass substrate 100. The light receiving optical system 4 has an optical fiber device 41 and a light receiving lens 42,
The light-receiving end of the optical fiber device 41 and the light-receiving lens 42 are held by the light-receiving block 43 in a predetermined arrangement relationship. The light receiving block 43 is attached to a moving rod 44, and the moving rod 44 can be moved in a horizontal direction by a driving mechanism 45 provided outside.

Here, when a vacuum flexible tube is used for the optical fiber device 41, sufficient flexibility of the tube cannot necessarily be ensured due to the restriction of maintaining the vacuum by the tube itself. A problem arises in that the smooth movement of the light receiving block 43 moved by driving cannot be ensured. Therefore, a flexible tube for the atmosphere is used for the optical fiber device.

An example of the structure of the optical fiber device 41 and the vacuum seal unit 5 will be described with reference to FIGS.
The optical fiber device 41 has a large number of optical fiber wires 41b accommodated in a flexible tube 41a. The flexible tube 41a is formed in a tubular shape by spirally winding two stainless steel strips whose both ends in the width direction are bent, and fitting the bent portions.

The flexible tube 41a is not particularly sealed between the inside and the outside, and can effectively protect the inside optical fiber 41b while ensuring excellent flexibility.

The vacuum seal portion 5 is one in which an optical fiber device 41 is passed through a flange hole 51a of a flange portion 51 fitted into a through hole of the vacuum partition 2a, and an adhesive 52 is filled in the flange hole 51a. In this case, the adhesive 52 not only completely fills the gap between the inner peripheral wall of the flange hole 51a and the optical fiber device 41, but also enters the inside of the flexible tube 41a,
The inside of the flexible tube 41a is also completely filled.

That is, in the section perpendicular to the longitudinal direction of the optical fiber device 41, the flexible tube 41
The gap formed between the inner wall of the optical fiber a and the optical fiber 41b and the gap formed between the optical fiber 41b are completely filled with the adhesive 52. Thereby, the optical fiber device 41 is bonded and fixed to the flange portion 51, and at the same time, the inside and the outside of the vacuum partition 2a are vacuum-sealed. With such a vacuum seal, the leak level in the vacuum film formation chamber is kept at 1.3 × 10 ⁻⁶ Pa · m ³ / sec. Here, a vacuum adhesive is used as the adhesive, and at the time of bonding, defoaming (venting of air in the adhesive) is sufficiently performed, and pressure filling is performed.

As described above, since the flexible tube used for the optical fiber device 41 is a flexible tube for the atmosphere, sufficient flexibility can be ensured. The light receiving position can be freely and accurately selected in the 100 radial directions.

The optical fiber device 41 is extended outside through the vacuum seal portion 5 and is joined to the signal processing device 3. Thus, the signal light L caused by the irradiation of the irradiation light L ₀ from the light source to be described later is adapted to be guided is introduced into the optical fiber 41 to the signal processing device 3 by the light receiving lens 42. The signal processing device 3 changes the interference between the reflected lights on the front and back surfaces caused by the phase difference of the reflected light generated on the front and back surfaces of the thin film when the irradiation light passes through the thin film, resulting from the change in the film thickness. As a result, the film thickness is calculated using the fact that the signal light intensity changes depending on the film thickness.

The irradiation light L ₀ is light from the light irradiation optical system 6 provided outside the transparent window 24 is used. The light irradiation optical system 6 guides the light from the light source 60 by the optical fiber device 61 and irradiates the measurement point on the glass substrate 100 through the emission lens 62. This optical fiber device 6
Reference numeral 1 denotes a large number of optical fiber wires housed in a protection tube (not shown).

In this case, the light emitting end of the optical fiber device 61 and the emitting lens 62 are maintained in a predetermined positional relationship by the emitting block 63.
Is fixed to a moving rod 64, and the moving rod 64 is horizontally movable by a driving mechanism 65. Accordingly, the irradiation point of the irradiation light L ₀ to the glass substrate 100 (the measuring point), it is possible to set an arbitrary position in the radial direction of the glass substrate 100.

The light irradiating section of the light irradiating optical system is set so as to move in accordance with the amount of movement of the light receiving section of the light receiving optical system, so that it is emitted from the light irradiating section and transmitted through the glass substrate. The signal light is always guided to the optical fiber device 41, and the film thickness can be measured at an arbitrary position in the radial direction of the glass substrate 100.

On the base 1, necessary devices such as a power source 210 of the vapor deposition device 21 and a power source 220 of the ion gun 22 are provided.

Next, the DW is formed by the thin film forming apparatus described above.
An example of manufacturing a DM filter will be described. The DWDM filter is formed, for example, on an optical glass substrate such as quartz glass having a thickness of about 10 mm by using Ta ₂ O having a thickness of 220 to 235 nm.
_{5 and} a thin film of SiO ₂ having a thickness of 250 to 260 nm are alternately stacked to form about 80 to 260 layers. In this case, the accuracy of the thickness of each thin film layer is required to keep the error from the design value at 0.1% or less.

Although the thickness of the thin film formed on the glass substrate can be made uniform in the rotational direction as described above, it is not always uniform in the radial direction. That is, the distance from the evaporation source to each point on the substrate becomes slightly longer as the distance from the center point of the substrate to the peripheral point of the substrate increases, and the area also increases. It changes gradually in the direction.

For example, as shown in FIG. 4, compared with the film thickness D1 of the film formed near the center of the substrate (point of radius R1 from the center of the substrate), it is closer to the periphery of the substrate (radius R2 from the center of the substrate). The point D) becomes thicker. As a result, the laminated film after film formation has a so-called “mortar-shaped” film thickness distribution, and there is a problem that a uniform film thickness cannot be obtained over the entire surface of the substrate. On the other hand, in order to form a film that satisfies the specifications required for a DWDM filter with a good yield, it is required to suppress the film thickness unevenness in the substrate to 0.3% or less.

Hereinafter, a procedure for forming a multilayer film on the glass substrate by the thin film forming apparatus according to the present embodiment will be described. First, the vapor deposition device 21 in the vacuum film formation chamber 2 receives T
installing a ₂ O ₅ evaporation source serving the target 211 and the SiO ₂ deposition source serving the target 212 for thin film deposition for thin film deposition.

Next, the quartz glass substrate 100 is held by the substrate holding device 25b. Next, the inside of the vacuum film forming chamber 2 is evacuated to 1 × 10 ⁻⁵ Pa or less by the vacuum pump 2b. Next, the glass substrate 100 is moved 1000 r by the motor 25.
While rotating at a rotation speed of pm, the vapor deposition device 21 and the ion gun 22 are operated to form a thin film on the glass substrate 100. The vapor deposition apparatus 21 irradiates and heats the target 211 or 212 with an electron beam to vapor-deposit a vapor-deposited substance and fly vapor-deposited particles toward the glass substrate 100. The ion gun 22 converts O ⁺ ions into a glass substrate 100.
The glass substrate 1
The thin film formed on the substrate is made firm. When the thickness of one thin film reaches a predetermined thickness, a predetermined operation is performed on the vapor deposition device 21 to switch a target to be vapor-deposited, and a next thin film is formed in the same manner. This operation is repeated to form a multilayer film having a predetermined number of layers.

[0037] In conjunction with the above film formation, the irradiation light L ₀ of the wavelength 1550nm vicinity irradiating the substrate 100 on which a thin film is formed, and receiving the transmitted light L by the light receiving optical system 4, processing by the signal processing device 3 By doing so, the film thickness of the formed thin film is measured, and the film is formed while monitoring the film thickness. That is, the films are formed while controlling the film thickness of each of the thin films stacked in multiple layers with ultra-high accuracy so that the error is 0.1% or less with respect to the design value.

Further, by having a light receiving optical system movable in a range where a thin film is formed on the substrate and a light irradiation optical system movable corresponding to the movement of the light receiving optical system, Since the film formation is performed while monitoring the film thickness in the above step, the film formation is performed while controlling the film thickness unevenness in the substrate to 0.3% or less. In general, the DWDM filter is formed by forming the multilayer film on an optical glass substrate such as a quartz glass disk having a diameter of about 250 mm, and then cutting the glass substrate to form a 1.4 × 1.4 mm ² . It is manufactured by a method of forming a large number of square chips.

In the thin film forming apparatus according to the above-described embodiment, the optical fiber having the light receiving end disposed in the vacuum film forming chamber is directly extended into the vacuum film forming chamber and guided to the signal processing device. The signal light can be guided to the signal processing device without loss. As a result, measurement with good S / N is enabled.

In the thin film forming apparatus according to the above-described embodiment, since the film thickness of the thin film formed on the substrate is monitored while monitoring the film thickness over the entire film forming region, the film thickness can be monitored. The area of the strictly controlled portion (sweet spot) expands as compared with the conventional film thickness monitoring method. Therefore, the area usable as a DWDM filter having desired characteristics can be widened.
It is possible to provide a product at a low cost while improving the yield and the product supply capacity.

[0041]

As described in detail above, the present invention relates to a thin film forming apparatus for forming a thin film on a surface while measuring a film thickness by an optical method while rotating an object in a vacuum film forming chamber. Each of the light irradiation optical system and the light receiving optical system of the film thickness measuring device is movable, and the light receiving optical system capable of moving the range in which the thin film is formed on the film-forming object and the movement of the light receiving optical system are supported. And a light irradiation optical system that is movable by using the thin film forming apparatus having a film thickness measuring apparatus capable of measuring the film thickness in the radial direction of the film formation object. It is.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an overall configuration of a thin film forming apparatus according to an embodiment of the present invention.

FIG. 2 is a partially cutaway sectional view showing a vacuum seal portion of the thin film forming apparatus according to the embodiment of the present invention.

FIG. 3 is a partially enlarged view of FIG. 2;

FIG. 4 is a diagram illustrating a state of a film thickness distribution in a substrate surface when a film is formed by an ion assisted vapor deposition method.

[Explanation of symbols]

 Reference Signs List 2 vacuum film forming chamber 2a vacuum partition 3 signal processing device 4 light receiving optical system 41 optical fiber device 41a flexible tube 41b optical fiber wire 5 vacuum seal part 6 light irradiation optical system 100 glass substrate

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F065 AA30 BB01 BB17 BB22 FF51 LL02 UU02 4K029 AA09 AA24 BB02 BC07 BD00 CA09 EA00 EA01

Claims (4)

[Claims] 1. A film forming apparatus for forming a thin film on a surface while rotating a film-forming object in a vacuum film-forming chamber, and measuring a film thickness of the thin film formed on the film-forming object by an optical method. A thin film forming apparatus comprising: a light irradiation optical system that irradiates light to the thin film; and light irradiated through the light irradiation optical system transmits through the thin film. A light receiving optical system that receives the reflected signal light and guides the signal light to the outside of the film forming apparatus, and a signal processing apparatus that processes the signal light guided to the outside of the film forming apparatus to calculate the film thickness. The light receiving optical system has a light receiving unit that can move in a range where a thin film is formed on the object to be deposited, and the light irradiation optical system has light that moves according to the amount of movement of the light receiving unit. An apparatus for forming a thin film, comprising: an irradiation unit. 2. An ion-assisted vapor deposition method (Io) in which the film forming apparatus deposits a substance for forming a thin film on the surface of the object to be deposited while irradiating the substance with ions with ions.
2. The thin film forming apparatus according to claim 1, wherein the apparatus uses an n-assisted deposition. 3. A thin film formed on the object to be deposited is a multilayer film, and the film forming apparatus is capable of forming thin films of different materials on the object to be deposited in an overlapping manner. 3. The thin film according to claim 1, wherein the thickness of each thin film is measured by a measuring device, and thin films of a desired material and thickness are formed one after another. Forming equipment. 4. A DWDM (Dense Wave) wherein the object to be deposited is a glass substrate, and the multilayer film is formed by laminating dielectric thin films having different refractive indices in multiple layers.
angle Division Multiplexi
4. The thin film forming apparatus according to claim 1, wherein the thin film forming apparatus can be used as a wavelength division filter in a communication system (ng; high-density wavelength division multiplexing).