JPS62245201A - Chemical phase synthesizing method for crystal stock having curvature - Google Patents

Abstract

PURPOSE:To obtain a crystal stock which has curvature by a direct CVD method and to decrease a grinding allowance by heating a substrate disposed with circular conical or pyramidal crystals having the same compsn. as the compsn. to be synthesized and introducing a gaseous raw material thereto to deposit the resulted product of decomposition and reaction thereon. CONSTITUTION:The metallic vapor transported by a reactive gas and carrier gas spreads to the substrate 9 surface, the steps between the substrate 9 surface and the circular conical or pyramidal crystals 21 or the surfaces, etc. of the circular conical or polycrystals 21 and deposits on all thereof in the case of disposing the circular conical crystal 21 on the surface of, for example, the substrate 9 and executing CVD synthesis. The growing surfaces of the growing crystals 21 become gradually gentle when the deposition progresses. The growing surface of the polycrystal 11 deposited on the substrate 9 has the convex spherical faces approximately the same as the convex spherical faces of the lenses to be formed if the height of the circular conical crystals 21, the diameter of the base thereof and/or the disposing position on the substrate 9 surface are adequately selected. The grinding allowance 27 is thereby extremely decreased in the case of grinding the lenses 13 having the convex spherical faces from the polycrystal stock 23.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for vapor phase synthesis of crystalline materials. More specifically, suitable for producing a crystal material with curvature,
This invention relates to a chemical vapor phase synthesis method capable of producing crystals having a surface shape with curvature.

Conventional optical devices such as lasers and photodetectors require optical components such as mirrors that reflect light, lenses that transmit light, and optical windows.

Optical glass is the most widely used material for transmission-type optical components in the visible region. However, with the development of optical equipment, the range of properties required of optical materials has gradually expanded and become more diverse.

For example, some optical devices require optical materials that transmit light in the infrared or ultraviolet wavelength range. Further, when a lens with a higher refractive index and lower dispersion is required, the above-mentioned optical glass may not be able to meet the requirement.

Crystals are used as a material that satisfies the optical properties described above that cannot be achieved with optical glasses.

Crystals: i) have high transmittance for light in a wide wavelength range and can be used for a wide wavelength range of 0.11 to 70 μ by selecting an appropriate crystal; ii) the relationship between transmittance, refractive index, and dispersion is unique. It has optical characteristics such as birefringence and optical rotation, which are not found in glass. These characteristics vary depending on the type of crystal, and are selected depending on the intended use.

In addition to the above optical properties, when selecting optical materials,
Issues include the crystal's melting point, hardness, cleavability, elastic constant, density, strength against thermal shock, coefficient of thermal expansion, thermal conductivity, solubility in water, and the size of the crystal that can be used. Crystals have better resistance to thermal shock than optical glasses, and are particularly suitable as optical components for high-output lasers such as CO□ lasers.

However, in many cases, there is a limit to the size of single crystal materials, and polycrystal materials may be used instead. Optical materials using polycrystals are
It is stable, resistant to thermal shock, can be easily obtained in large sizes, and has optical properties that are comparable to single crystals.

Examples of methods for producing polycrystalline optical materials include a method of press-molding crystal powder at high temperature, a chemical vapor phase synthesis method (CVD synthesis method), and the like. Among these, the CVD synthesis method is an excellent method in terms of raw material yield and control of crystal grain size.
CV is an optical component for high output lasers such as O□ lasers.
Zn5e, ZnS, etc. obtained by the D synthesis method are used.

Currently, the production of polycrystalline optical components using the CVD synthesis method is
A disc-shaped or cylindrical material is hollowed out from a flat polycrystalline material obtained by CVD synthesis, the outer periphery and both sides are ground, and the material is then lapped and polished to achieve the desired shape and surface accuracy. .

Here, we will explain how to manufacture crystalline optical components using a general CVD synthesis method using polycrystalline materials as an example, as shown in the attached Figures 3 and 4.
This will be explained in more detail with reference to FIG. 4(a) and FIG. 4(5).

The attached FIG. 3 is a schematic cross-sectional view for explaining a general vertical CVD apparatus. As shown in the figure, the vertical CVD equipment is
The upright reaction vessel 1, the heater 3 provided outside the reaction vessel 1, and the outside and inside of the reaction vessel 1 are communicated with each other, and H2
A reaction gas introduction pipe 5 for introducing a reaction gas such as Se into the reaction vessel 1, a carrier gas such as an inert gas, and the vapor of the molten metal carried by the carrier gas from the surface of the molten metal such as 2n into the reaction vessel 1. A carrier gas introduction pipe 7 is provided to introduce the carrier gas into the inside of the carrier gas.

When performing vapor phase synthesis, first the substrate 9 is placed on a suitable support (
(not shown), the substrate 9 is placed inside the reaction vessel 1, and then the substrate 9 is heated by the heater 3 to a temperature suitable for growing polycrystals. Thereafter, the reaction gas and the carrier gas containing molten metal vapor are introduced into the reaction vessel 1 through the introduction pipe 5.7.
Introduce it in the direction of the arrow inside. The molten metal vapor carried by the reaction gas and carrier gas decomposes and reacts on the substrate heated to an appropriate temperature, and the polycrystal 11 that is the decomposition and reaction product is deposited on the surface of the substrate 9. Ru. For example, H2Se as the reactant gas and Zn as the molten metal vapor.
When steam is used, 2nSe polycrystals are deposited on the surface of the substrate 9.

The substrate 9 is generally assembled into a polygonal tube having a square cross section as shown in FIG. 4(a), or a hexagonal cross section as shown in FIG. 4(a). The polycrystalline materials 11 deposited on these substrates 9 are removed from the substrates 9 and disassembled into flat plates.

A disc-shaped or cylindrical optical component material is cut out from the plate-shaped polycrystal obtained in this way, and is ground into a predetermined shape.
Furthermore, a polycrystalline optical component can be obtained by finishing the surface with precision by lapping, polishing, etc.

However, the method for manufacturing polycrystalline optical components described above has the following problems.

Problems to be Solved by the Invention As already mentioned, when polycrystals formed by the conventional CVD method are used as materials, optical components are obtained from flat polycrystals deposited on flat substrates. Therefore, when manufacturing a convex lens in which one surface is a convex spherical surface, there are drawbacks such as not only a large amount of grinding allowance but also a long working time is required.

That is, in the CVD synthesis method, when a flat substrate 9 as shown in attached FIG. 2(a) is used, the polycrystalline ll deposited on the substrate 9 is as shown in FIG. 2(b). , is plate-like. As a result, as is clear from FIG. 2(C), when manufacturing a convex lens 13 having a convex spherical surface from the obtained flat polycrystalline material 12, first a disk,
Since a cylindrical material is cut out and processed, a large grinding allowance 15 is required, which lengthens the working time and greatly reduces the raw material yield.

The conventional techniques and their problems have been explained above using polycrystalline materials as an example. However, the above problems are caused by CVD
This also exists in the production of single-crystal optical components by the method. That is, manufacturing a single crystal convex lens is still carried out by cutting out a convex lens from a flat single crystal material, and the large cutting allowance inevitably increases the working time and reduces the raw material yield.

Therefore, an object of the present invention is to solve the problems of the conventional method of synthesizing crystals for optical components using the CVD method, and to synthesize crystals for optical components with a high raw material yield using the CVD method.

Means for Solving the Problems As a result of various studies in order to solve the problems of the above-mentioned prior art, the inventor of the present invention found that the present invention can directly form a crystalline material having a convex spherical surface by a CVD synthesis method. The present invention was completed based on the finding that it is very advantageous in achieving the objective.

That is, in the chemical vapor phase synthesis method of the present invention, a conical or polygonal pyramidal crystal having the same composition as the crystal to be synthesized is placed on the surface of a substrate, and then the substrate is heated to a predetermined temperature. It is characterized by introducing a raw material gas onto a substrate and depositing decomposition and reaction products to synthesize crystals.

In the present invention, the conical or polygonal pyramidal crystal disposed on the substrate may be either single crystal or polycrystal. Also, there is no need to make the tip so thin.
Therefore, it can be easily manufactured by grinding using a normal diamond tool or the like.

Further, it is preferable to appropriately select the height of the conical or polygonal pyramidal crystal, the shape of the bottom surface, and the arrangement interval thereof, depending on the curvature and diameter of the convex lens to be manufactured.

For example, when manufacturing a polycrystalline convex lens with a large curvature, it is preferable to obtain a polycrystalline material having a convex spherical surface with a large curvature that is almost the same as the curvature of the convex lens. It can be obtained by using conical or polygonal pyramidal polycrystals or single crystals. In addition, when manufacturing a convex lens with a larger diameter, it is preferable to obtain a polycrystalline material having a convex or spherical surface with a large diameter to match the diameter of the convex lens, and the arrangement interval on the substrate of conical or polygonal pyramidal polycrystals. It is obtained by expanding .

In addition, when obtaining a polycrystalline material having a convex spherical surface with a large diameter, in order to reduce the amount of deposited polycrystals and obtain a desired spherical surface, it is necessary to create a step on the growth surface during the growth process of the polycrystalline material. It is preferable to make it difficult to do so. Therefore, it is preferable to use a conical or polygonal pyramidal crystal with a larger base area.

In the present invention, as described above, the height, bottom shape, dimensions, or spacing of the conical or polygonal pyramidal crystal placed on the substrate, and the shape of the crystal material deposited on the substrate, such as the crystal There is a close relationship between the curvature of the convex spherical surface of the material, the radius of the base, etc. Therefore, under various crystal synthesis conditions in advance, the surface shape of the crystal material, that is, 11 curvature,
It is preferable to determine the relationship between the radius, etc., the height of the conical or polygonal pyramidal crystal disposed on the substrate, the maximum radius of the base, or the ratio of both, and create a calibration curve from the results.

According to the present invention, the method for supporting and fixing the conical or polygonal pyramidal crystal on the surface of the substrate may be any method as long as it does not cause the problem of contamination of the deposited crystals and can be reliably supported and fixed, and there are no particular limitations. do not. For example, a preferred example is to provide a recess with a cross-sectional shape corresponding to the substrate surface or a circumscribed circular cross-section, and to fit the conical or polygonal pyramidal crystal into the recess. Further, in order to more securely fit the crystal and the substrate, the crystal should have a fitting part at its bottom that has the same shape as the recessed part and has slightly smaller dimensions. You can also do it.

Furthermore, in order to prevent contaminants from being mixed into the manufactured crystal, foreign matter on the surface of the conical or polygonal pyramidal crystal placed on the substrate is removed by dry etching such as plasma etching or chemical etching. It is preferable to leave it there. For example, in Zn5eSZnS, HCI
Chemical etching can be performed by immersion in a 50% solution of for several minutes.

This process produces conical or polygonal pyramidal polycrystals,
Inclusions are incorporated between the crystals that were later synthesized in the vapor phase,
The produced crystals are not contaminated.

The CVD synthesis method of the present invention using the thus obtained substrate can be performed using various CVD synthesis methods, such as halide CVD method, photochemical
VD method, MOCVD method (meta organ 1c
CVD method) or PCVD method (Plasma CVD method)
law).

Furthermore, the chemical vapor phase synthesis method of the present invention can provide a convex spherical surface to various polycrystalline and single crystalline materials.
2nS, etc., NaCl, K suitable as an infrared optical material
Crystal materials having convex spherical surfaces such as Br, Ge5Si, etc. and 5102, Ca F 2, A I 203, etc., which are suitable as ultraviolet optical materials, can be advantageously obtained.

Effect It is advantageous to improve the CVD method as described above in order to solve the problems of the conventional CVD method and obtain a polycrystalline material suitable for manufacturing polycrystalline members with curvature such as convex lenses. be.

That is, Zn5e SZn obtained by the conventional CVD method
A crystal material such as S has a flat plate shape, and a convex lens is manufactured by processing a disc or columnar material cut out from it into a predetermined curvature by grinding or the like, which requires a large amount of grinding allowance.

In the method of the present invention, by using a substrate on which conical or polygonal pyramidal crystals are arranged, a crystal material having a surface shape with curvature can be directly obtained. Therefore, by manufacturing a convex lens using a portion having this curvature, it is possible to significantly reduce the grinding allowance.

In order to produce a material for optical components having a spherical surface close to a predetermined curvature in advance, it is important to use the CVD method, which is excellent in terms of wrap-around ability and feed-through ability, and this point is addressed by the present invention. This is an essential requirement in the method.

That is, for example, if we take a polycrystalline material as an example, the attached Figure 1 (
When a conical crystal 21 is arranged on the surface of the substrate 9 and CVD synthesis is performed as shown in a), the metal vapor carried by the reaction gas and the carrier gas flows between the surface of the substrate 9, the surface of the substrate 9, and the conical crystal. or a step with the polygonal pyramidal crystal 21,
It wraps around the surface of the conical or polycrystalline 21 and is deposited on all of them.

As this deposition progresses, the growth surface of the growing crystal 21 gradually becomes gentler.

Thus, by appropriately selecting the height of the conical crystal 21, the diameter of its bottom surface, and/or its placement position on the surface of the substrate 9, the polygons deposited on the substrate 9 can be reduced as shown in FIG. The growth surface of the crystal 11 has a convex spherical surface that is almost the same as the lens to be manufactured.

As a result, when a lens 13 having a convex spherical surface is obtained by grinding or the like from the polycrystalline material 23 obtained as shown in FIG. 1(C), the grinding allowance 27 becomes extremely small.

This makes it possible to significantly shorten the working time and greatly improve the manufacturing yield of optical components, thereby making it possible to reduce product costs.

Although the explanation has been given above mainly using a polycrystalline material as an example, the above crystal growth process, its effects, etc. are the same for a single-crystalline material.

Examples Hereinafter, the CVD synthesis method according to the present invention will be explained in more detail with reference to Examples. However, this example does not limit the scope of the invention in any way.

As shown in the attached FIG. 2(a), a hole was made on the substrate 9, and a 2nSe polycrystal 27 formed by a diamond tool into a conical shape with a height of 3 mm and a bottom diameter of 2 mm was fitted into the hole. The holes were placed 50 mm apart from each other.

Furthermore, before fitting, the conical Zn5e polycrystal 27 was chemically etched by immersing it in a 50% HCI aqueous solution for 5 minutes.

On the thus obtained substrate 9, the CV shown in the attached FIG.
Zn5eGCV D was synthesized using D equipment. That is, the substrate 9 according to the present invention is assembled into an appropriate shape and placed inside the reaction tube 1, and the internal pressure is adjusted to 5Q'l'orr.
A carrier gas Ar containing Zn vapor is introduced through the carrier gas introduction pipe 5, and a reaction gas 1 is introduced through the reaction gas introduction pipe 7.
(2Se with a flow rate of 0.5N1/min and 2.ON
It was introduced at I/min. At this time, the temperature of the substrate 9 was set to 700° C., and under these conditions, Zn5e polycrystals were synthesized on the substrate 9 according to the CVD method at a growth rate of 50 μm for 200 hours.

The Zn5e polycrystal 21 thus formed on the substrate 9 is
The deposition distribution was as shown in the attached FIG. 1(b), and each had convex spherical portions with a radius of 2 Q mm and a curvature of 5 Q mm, with their centers spaced apart by 50 mm.

When a convex lens with a diameter of 38.1 mm and having a convex spherical surface with a radius of 19.95 mm and a curvature of 60 mm was manufactured from this polycrystal 2, the grinding allowance was extremely small. Furthermore, the obtained convex spherical lens was optically no different from that obtained by the conventional method.

Effects of the Invention As explained above, when manufacturing a lens having a convex spherical surface using a polycrystal synthesized by CVD synthesis, it is advantageous to obtain a crystalline material having curvature by direct CVD according to the method of the present invention. .

According to the conventional method, the crystal material obtained by the CVD synthesis method has a flat plate shape, and manufacturing a lens having a convex spherical surface from this crystal requires a large grinding allowance.

However, according to the present invention, by arranging conical or polygonal pyramidal crystals similar to the crystals to be synthesized on the substrate, the deposition distribution can be controlled and polycrystals and single crystals having convex spherical parts can be synthesized. It became possible to obtain. Therefore, by using this convex spherical surface portion to manufacture convex lenses having approximately the same radius of curvature, it becomes possible to significantly reduce the grinding allowance.

Furthermore, by changing the height of the conical crystal, the diameter of its base, the arrangement on the substrate, etc., the radius, curvature, etc. of the convex spherical surface that can be used can be changed.
By using the VD synthesis method, various convex lenses can be manufactured with a small amount of grinding allowance, and it is extremely economical.

[Brief explanation of drawings]

Attached FIG. 1(a) is a cross-sectional view of a substrate used in the CVD synthesis method according to the present invention, and attached FIG. 1(b) is a cross-sectional view showing the shape of polycrystals deposited on the substrate of the present invention. , Attached FIG. 1(C) shows the polycrystal,
FIG. 2(a) is a cross-sectional view of a substrate used in the conventional CVD synthesis method, and FIG. 2(b) is a diagram showing the relationship between a convex lens and a grinding allowance. FIG. 2(C) is a cross-sectional view of a polycrystalline material deposited on a substrate by CVD synthesis method, and attached FIG. This is a diagram showing the relationship between a convex lens and a grinding allowance. Attached Figure 3 is a schematic sectional view showing a general vertical CVD device, and attached Figures 4 (a) and (b) are a general vertical type CVD
FIG. 3 is a diagram showing the cross-sectional shape of a substrate used in the device and the cross-sectional shape of polycrystal deposited on the substrate. (Main reference numbers) ■... Reaction chamber, 3... Heater, 5... Reaction gas introduction tube, 7... Carrier gas introduction tube, 9... Substrate, 11... Polycrystal, 12... Flat polycrystalline Crystal material, 13. Convex lens, 15. Grinding allowance, 21. Conical or polygonal pyramidal crystal, 23. Polycrystalline material.

Claims (4)

[Claims] (1) After placing a conical or polygonal pyramidal crystal having the same composition as the crystal to be synthesized on the surface of a substrate, heating the substrate to a predetermined temperature and introducing a source gas onto the substrate. A chemical vapor phase synthesis method for crystalline materials with a curvature on the surface, which is characterized by the deposition of decomposition and reaction products. (2) In advance, under various crystal synthesis conditions, the height, bottom shape, or arrangement on the substrate surface of the conical or polygonal pyramidal crystal, and the curvature of the crystal layer obtained by chemical vapor phase synthesis, 2. The chemical vapor phase synthesis method according to claim 1, wherein a relationship between diameter or thickness is determined and a crystal material having a predetermined shape is synthesized according to the obtained calibration curve. (3) Claim 1, wherein the substrate has a recess on the surface of the substrate, and the conical or polygonal pyramidal crystal is fitted and fixed in the recess. Or the chemical vapor phase synthesis method described in Section 2. (4) Claim 3, characterized in that the conical or polygonal pyramidal crystal has a fitting part at its lower part that has the same shape as the recessed part and has slightly smaller dimensions. Chemical vapor phase synthesis method described in Section.