JPH11172448A - Production of optical parts - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for producing optical parts capable of forming a coating which has excellent in-surface uniformity, has decreased pinholes and local defects and has excellent coatability. SOLUTION: This plasma treatment apparatus has a vessel 101 with which a pressure reduction is possible, a gas supply means 103 for supplying a gas to be converted to a plasma into the vessel and a microwave supply means 111 for supplying microwaves into the vessel and applying surface treatment to a body to be treated for optical parts. The surface to be treated is subjected to the surface treatment by using the plasma treatment apparatus in which the surface of the microwave supply means facing the body to be treated is formed of a microwave permeable dielectric substance in a shape corresponding to the shape of the surface to be treated of the body to be treated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of a method for manufacturing an optical component using a plasma processing apparatus suitable for surface treatment of an optical component having a surface to be processed.

[0002]

2. Description of the Related Art There is a need for a technique for performing a surface treatment such as cleaning or film formation on an object having a non-planar surface.

[0003] A typical example is the formation of an antireflection film or a reflection-enhancing film on a lens, a mirror, or a window material.

Conventionally, as disclosed in JP-A-2-23267, a film is formed by a PVD method such as sputtering.

[0005] Since the PVD method has a large damage to a film to be formed, the present inventors have attempted to form a film by a CVD method.

[0006] Thermal CVD is not suitable in terms of thermal deformation of an object to be processed, and optical CVD is not sufficient in terms of throughput.

In order to obtain a film having a higher transmittance (lower absorptivity) and superior light resistance and environmental resistance than the antireflection film obtained by the PVD method at present, plasma excitation using a 13.56 MHz RF power source is required. CVD (PE-CVD) is also insufficient, and must be PE-CVD that can provide a higher density plasma.

As a PE-CVD capable of obtaining a high-density plasma of 10 ¹⁰ cm ⁻³ or more, there is an electrodeless PE-CVD using microwaves such as electron cyclotron resonance CVD (ECR-PECVD).

FIG. 5 shows a plasma processing apparatus described in JP-A-6-216047.

This apparatus includes a plasma generation chamber 2 and a processing chamber 4, in which microwave power introduction means 5, 6, 8 and a magnetic field application means 10 are installed. An introduction system 20 is connected, a chemical reaction material gas introduction system 22 is connected to the processing chamber 4, and an RF power introduction unit 18 is connected to the sample stage 14. A control device 27 for modulating respective powers is provided for the RF power source 8 and the RF power source 18. The RF power and the microwave power are modulated in synchronization with each other, and the condition in which the film formation is prioritized and the condition in which the sputter etching is prioritized are alternately repeated.
A D film is formed.

[0011]

When a film is formed by the apparatus shown in FIG. 5, a dense film can be formed on average, but the film has poor in-plane uniformity.

Further, there is a high probability that the reaction by-products stay near the surface to be processed, resulting in pinholes in the film or a film having a locally different composition ratio.

An object of the present invention is to provide a method for producing an optical component which is excellent in in-plane uniformity and can form a coating excellent in coverage with few pinholes and local defects.

[0014]

According to the present invention, there is provided a method of manufacturing an optical component, comprising: a container capable of being depressurized; gas supply means for supplying a gas to be converted into plasma into the container; and evacuation of the container. A plasma processing apparatus for performing a surface treatment on an object to be processed for an optical component, the plasma processing apparatus comprising: an exhaust unit for supplying microwave to the container; Surface treatment of the surface to be processed is performed by using a plasma processing apparatus in which a surface facing the object to be processed has a shape corresponding to the surface to be processed of the object to be processed and is formed of a microwave transparent dielectric. Features.

Here, it is preferable that the gas is supplied from a plurality of openings provided on a surface of the microwave supply means facing the object to be processed.

It is preferable that the microwave supply means has an antenna formed of a conductor flat plate having a number of slots.

The distance between the inner surface of the dielectric and the surface of the object to be processed is preferably set within a range of more than 10 mm and 50 mm or less, and the relative density difference of the plasma density in the surface to be processed is substantially reduced. It is desirable to be able to control each within 20%.

It is preferable that a rotation mechanism is provided on the support of the object to be processed.

The surface treatment is the formation of a thin film, and the object is quartz or fluorite, and the surface treatment is a coating for forming a thin film for anti-reflection or enhanced reflection on the object. Can be

According to the present invention, a high-density plasma excited by microwaves can be confined in a narrow discharge space, so that a dense film can be obtained.

Further, since the surface to be processed is located in a region where the plasma density is uniform, it is possible to perform uniform plasma processing on the surface to be processed having a large area.

Since the volume of the discharge space is reduced, the discharge chamber can be easily evacuated even with a vacuum pump having a small exhaust capacity, and even if reaction by-products are generated, they are quickly removed from between the discharge chambers. It is unlikely to cause pinholes and the like. If a large number of gas supply holes are formed in the conductor, uniform gas supply is possible even in a narrow space, and a film in which the composition ratio of the compound is constant in the plane can be formed.

[0023]

FIG. 1 is a schematic sectional view showing an embodiment of a plasma processing apparatus used in the present invention.

Reference numeral 101 denotes a vacuum vessel which can be decompressed. The vacuum vessel is connected to an exhaust port 102 by an exhaust means (not shown).
It is configured so that the pressure can be reduced to about 10 ^-6 Pa to 133 Pa.

The container 101 is provided with a number of gas supply ports 103, and is provided with UHF, SHF, EHF such as microwaves.
A gas which becomes a plasma by the high frequency energy of the band is introduced from here.

Further, a holder 104 for placing and holding the object to be processed W is provided in the container 101, and is vertically movable so that the vertical position thereof can be selected as appropriate. It is spinning. Holder 104
Can be applied with a bias potential. Then, the holder driving mechanism 105 vertically moves and rotates the holder 104.

Reference numeral 106 denotes a non-planar dielectric plate made of a dielectric provided with a large number of gas supply ports 108, and has the function of a shower head for supplying gas.

This dielectric plate is a microwave-permeable dielectric, and is made of alumina, quartz, aluminum nitride (AlN), calcium fluoride, magnesium fluoride, or the like.

The gas introduced from the gas inlet 103 selected for the gas supply system (not shown) is supplied into the plasma process space A via the gas supply passage 108 of the dielectric plate 106.

In this embodiment, it is assumed that a mirror surface on a flat surface is processed as the object to be processed. Reference numeral 115 denotes an O-ring for vacuum sealing.

FIG. 2 is a perspective view of the non-planar dielectric plate 106, in which the lower surface facing the object to be processed is drawn upward. The interval Tg between the gas supply passage 108 of the dielectric plate 106 and the workpiece W is configured to be substantially constant within a certain allowable range.

The introduction of microwaves is as follows.

The microwave supply means has a coaxial tube 110, a conductor plate antenna 111 having a number of slots, and dielectric thin films 112 and 113 serving as microwave supply windows. The inner conductor 110 a of the coaxial tube 110 is connected to the center of the conductor plate antenna 111. 114 is an antenna adapter.

A microwave generated by a microwave oscillator (not shown) propagates through the coaxial tube 110 and passes through the conductor plate antenna 1.
Propagate to 11. Microwaves propagated from a number of slots provided in the antenna 111 are radiated.

FIG. 3 is a plan view of the conductor flat plate antenna 111.

The conductor plate antenna 111 has a number of slots 111S arranged concentrically or spirally. The slot 111S is composed of a pair of notches having a direction crossing each other, and the length and arrangement interval of the notches are appropriately determined according to the microwave wavelength and the required plasma intensity.

Such an antenna is called a radial line slot antenna and is disclosed in Japanese Patent Application Laid-Open No. 1-184923, US Pat. No. 5,034,086, or Japanese Patent Application Laid-Open No. 8-1.
No. 11,297, JP-A-4-48805, and the like.

Next, the operation of forming a thin film on a mirror by the method of the present invention will be described.

The mirror W is placed and fixed on the holder 104 in the apparatus so that the surface to be processed faces upward.

The holder 104 is raised by the driving mechanism 105, and the object-supplying surface 106a of the microwave supply means is
The ascent is stopped at a position where the distance Tg between the workpiece and the processing surface Wa of the processing target is within a range of more than 10 mm and 50 mm or less.

After the pressure inside the container 101 is reduced to about 1.3 × 10 ⁻⁵ Pa by an exhaust pump connected to the exhaust port 102, the processing gas is supplied from a gas supply system connected to the gas inlet 103 to a gas supply passage. It is introduced into the plasma process space A through 108. The pressure in the container is controlled from 13.3 Pa to 1.33 × 10 ³ by controlling the gas supply amount and the exhaust amount.
Maintain an appropriate pressure selected from Pa. Coaxial tube 110
A microwave is supplied to the conductive flat plate antenna 111 through the coaxial tube 110 from the microwave oscillator connected to the antenna.

Thus, a glow discharge is generated in the plasma process space, and a gas plasma is generated. At this time, the plasma density is as high as 10 ¹¹ to 10 ¹³ cm ^-3 , and a dense and high-quality film can be formed.

Further, according to this embodiment, even if microwaves are used, the interval Tg of the process space is 10 cm or less (in this embodiment, 10 g).
cm, which is sufficiently smaller than 50 mm).
The reaction by-product generated in the space A can be exhausted and removed at high speed. Therefore, a high-quality film with few pinholes can be formed. Further, since the interval is 50 mm or less, the reaction by-product can be exhausted sufficiently quickly even with a vacuum pump having a relatively small exhaust capacity.

FIG. 4 is a graph showing the relationship between the distance Tg between the dielectric plate and the object to be processed and the plasma density. Tg is 10mm
If it is less than the above, the plasma density will greatly change even if the interval is slightly different, and if the Tg exceeds 50 mm, the plasma density will rapidly decrease. 10m where the inflection point exists
If m <Tg ≦ 50 mm, the relative density difference of the plasma falls within 20%, and as a result, a uniform film can be formed.

As described above, the method of the present invention can be applied not only to a flat mirror but also to a surface treatment of a spherical lens having a convex surface if the height difference of the unevenness is more than 10 mm and 50 mm or less. It can also be used for surface treatment of a spherical lens.

Examples of the object W to be processed in the present invention include an insulating translucent member made of quartz, fluorite or the like, and a conductive non-translucent member such as aluminum. The former is a convex lens, It is used as a concave lens, a reflection mirror, and a window member, and the latter is used as a reflection mirror.

The surface treatment that can be performed by the method of the present invention includes formation of a thin film, plasma cleaning, and plasma etching. In particular, the method of the present invention is advantageous for forming a thin film, specifically, aluminum oxide, silicon oxide,
The formation of tantalum oxide, magnesium oxide, aluminum fluoride, and magnesium fluoride films.

Since the thin film is formed by plasma CVD,
The source gas used is trimethyl aluminum (TM
A), triisobutylaluminum (TiBA), organic aluminum compounds such as dimethyl aluminum hydride (DMAH), _{or, SiH 4, Si 2 H 6} , S
iF ₄ , a silicon compound such as tetraethylorthosilicate (TEOS), or an organic compound of magnesium such as a tantalum compound or bisethylcyclopentadienyl magnesium. Further, in addition to these source gases, it is desirable to use an oxidizing gas such as oxygen, nitrogen oxide, fluorine, or NF3. You may.

As a microwave oscillator, 2.45 GHz
An ordinary microwave oscillator having a frequency of 5.0 GHz, 8.3 GHz, or the like is used.

[0050]

EXAMPLE A flat mirror made of quartz whose surface was polished was placed and fixed on a holder 104 of the apparatus shown in FIG.

The holder 10 is operated by operating the drive mechanism 105.
4 was raised, and the holder 104 was fixed at a position where Tg was 20 to 30 mm. After the interior of the aluminum container 1 was once evacuated to 1.3 × 10 ⁴ Pa and decompressed, the holder 104 was rotated. TM vaporized as processing gas
A and O ₂ were introduced, the pressure was set to 13.3 Pa, and microwaves were supplied to generate gas plasma. Thus, an aluminum oxide film was formed on the quartz surface.

[0052]

As described above, according to the present invention,
Using a high-density microwave plasma, uniform processing can be performed not only on a flat surface but also on an optical component having a concave or convex surface to be processed.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment of a plasma processing apparatus applicable to the present invention.

FIG. 2 is a plan view of a planar dielectric plate.

FIG. 3 is a plan view of the conductor plate antenna.

FIG. 4 is a diagram showing a relationship between a distance between a dielectric plate and an object to be processed and a plasma density.

FIG. 5 is a sectional view of a conventional plasma processing apparatus.

[Explanation of symbols]

 Reference Signs List 101 vacuum vessel 102 exhaust port 103 gas inlet 104 holder 105 driving mechanism 106 dielectric plate 108 gas supply passage 110 coaxial tube 111 conductor flat plate antenna 111S slot 112, 113 dielectric thin film 115 O-ring A plasma process space W workpiece

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Nobuyoshi Tanaka 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Masaki Hirayama 52 Funacho, Wakabayashi-ku, Sendai City, Miyagi Prefecture 103 Pansion Aihara (72) Inventor Tadahiro Omi 2-1-17- 301 Yonegabukuro, Aoba-ku, Sendai, Miyagi

Claims (8)

[Claims] 1. A container that can be depressurized, gas supply means for supplying a gas to be converted into plasma into the container, exhaust means for exhausting the inside of the container, and microwave supply into the container A microwave supply means for performing a surface treatment on the object to be processed for an optical component, wherein a surface of the microwave supply means facing the object to be processed has a surface facing the object to be processed. A method for manufacturing an optical component, comprising: performing a surface treatment on a surface to be processed using a plasma processing apparatus having a shape corresponding to the surface to be processed and formed of a microwave-permeable dielectric. 2. The method for manufacturing an optical component according to claim 1, wherein the gas is supplied from a plurality of openings provided on a surface of the microwave supply unit facing the object to be processed. 3. The method of manufacturing an optical component according to claim 1, wherein said microwave supply means has an antenna formed of a conductor flat plate having a large number of slots. 4. The optical component according to claim 1, wherein a distance between an inner surface of the dielectric and a surface of the object is set within a range of more than 10 mm and 50 mm or less. Manufacturing method. 5. The method of manufacturing an optical component according to claim 1, wherein a relative density difference between plasma densities in the surface to be processed can be suppressed to approximately 20% or less. 6. The method for manufacturing an optical component according to claim 1, wherein a rotation mechanism is provided on the support of the object to be processed. 7. The method for manufacturing an optical component according to claim 1, wherein said surface treatment is formation of a thin film. 8. The object to be processed is quartz or fluorite,
2. The method according to claim 1, wherein the surface treatment is a coating for forming a thin film for preventing reflection or increasing reflection on the object.