KR101966857B1 - Diamond and cubic boron nitride thin film laminated and method for fabricating the same - Google Patents

Abstract

In order to improve the peeling property of a cubic boron nitride (cBN) thin film layer by depositing a cubic boron nitride (cBN) thin film layer on a diamond thin film layer, a diamond thin film layer having a plate shape grown in a vertical direction as a diamond thin film layer is used, (CBN) thin film layer is deposited on the diamond thin film layer of the structure to induce a structure in which the diamond thin film layer and the cubic boron nitride (cBN) thin film layer are bonded in a wedge shape to improve the peeling property of the cubic boron nitride (cBN) thin film layer The present invention relates to a laminate of a diamond thin film and a cBN thin film and a method of producing the diamond thin film and a cBN thin film by a hot filament chemical vapor deposition (HFCVD) Forming a diamond thin film layer having a planar structure; And depositing a cubic boron nitride (cBN) thin film on the diamond thin film layer, wherein the cubic boron nitride (cBN) thin film is filled in the void space of the vertically grown diamond thin film layer And the cubic diamond boron nitride (cBN) thin film having a plate-like structure grown in the vertical direction is in the form of a wedge engaging with each other.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diamond thin film and a method for fabricating the diamond thin film,

The present invention relates to a laminated body of a diamond thin film and a cBN thin film and a method of manufacturing the same, and more particularly, to a method of manufacturing a laminated body of a diamond thin film and a cBN thin film by depositing a cubic boron nitride (cBN) thin film layer on the diamond thin film layer to improve the peeling property of the cubic boron nitride (CBN) thin film layer is deposited on a diamond thin film layer having a plate-like structure by using a diamond thin film layer having a plate-like structure grown in a vertical direction as a diamond thin film layer so that a diamond thin film layer and a cubic boron nitride (cBN) To a laminated body of a diamond thin film and a cBN thin film capable of improving the peeling property of a cubic boron nitride (cBN) thin film layer and a method for manufacturing the same.

Cubic boron nitride (hereinafter abbreviated as "cBN") has properties similar to those of diamond having the highest hardness and thermal conductivity. In addition, it has superior oxidation resistance, high temperature stability and response stability to iron-based metals It is a material that is very applicable to wear resistant thin films such as cutting tools and molds. The cBN thin film can be deposited by various methods such as chemical vapor deposition or vacuum physical vapor deposition. However, there is a problem in the adhesion of the thin film, so that application is not made. Weak adherence of cBN thin films is due to the large compressive residual stresses of amorphous BN thin films and tBN thin films and films formed at the initial stage in the formation of cBN thin films. In order to solve this problem, efforts have been made to reduce the residual stress of the thin film or to increase adhesion by inserting an artificial interlayer.

Diamond has a lattice constant similar to that of cBN, so cubic boron nitride (cBN) can be grown on diamond at high temperatures above 900 ° C. The possibility of the heteroepitaxial film of cBN / diamond film, which is obtained by growing cubic boron nitride (cBN) thin film without formation of intermediate weak layer such as buried boron nitride (tBN) (US 7645513). In the cBN / diamond composite film proposed in US 7645513, the diamond film corresponds to a microcrystalline diamond film synthesized through a chemical vapor deposition process.

A method has been proposed in which hydrogen is added to a reactive gas in order to reduce the residual stress applied to the cubic boron nitride (cBN) thin film (H.-S. Kim, J.-K. Park, W.-S. Lee and Y.-J. Baik, Variation of residual stress in cubic boronitride film caused by hydrogen addition during unbalanced magnetron sputtering, Thin Solid Films 519 (2011) 7871-7874). This method provides a very simple way to reduce the residual stress and thus provide sufficient adhesion. In addition, when an intermediate layer such as diamond is applied together, it is anticipated that an increase in adhesion and a decrease in residual stress can be expected at the same time, which is a very useful method for applications.

US 7645513

 H.-S. Kim, J.-K. Park, W.-S. Lee and Y.-J. Baik, Variation of residual stress in cubic boronitride film caused by hydrogen addition during unbalanced magnetron sputtering, Thin Solid Films 519 (2011) 7871-7874

In order to improve the peeling property of a cubic boron nitride (cBN) thin film layer by depositing a cubic boron nitride (cBN) thin film layer on a diamond thin film layer, a diamond thin film layer having a plate shape grown in a vertical direction as a diamond thin film layer is used, (CBN) thin film layer is deposited on the diamond thin film layer of the structure to induce a structure in which the diamond thin film layer and the cubic boron nitride (cBN) thin film layer are bonded in a wedge shape to improve the peeling property of the cubic boron nitride (cBN) thin film layer And a cBN thin film laminated thereon, and a method of manufacturing the same.

The present invention also relates to a laminate of a diamond thin film and a cBN thin film which can suppress the residual stress applied to cubic boron nitride (cBN) by controlling the supply timing of hydrogen when depositing a cubic boron nitride (cBN) thin film layer, And the like.

According to another aspect of the present invention, there is provided a method of manufacturing a laminated body of a diamond thin film and a cBN thin film, comprising: forming a diamond thin film layer grown in a vertical direction using a hot filament chemical vapor deposition (HFCVD) method; And depositing a cubic boron nitride (cBN) thin film on the diamond thin film layer, wherein the cubic boron nitride (cBN) thin film is filled in the void space of the vertically grown diamond thin film layer And the cubic diamond boron nitride (cBN) thin film having a plate-like structure grown in the vertical direction is in the form of a wedge engaging with each other.

The HFCVD method uses a mixed gas of hydrogen (H ₂ ) and methane (CH ₄ ), and the ratio of methane (CH ₄ ) is 3 to 5 vol%. Further, the diamond thin film layer having a plate-like structure grown in the vertical direction is a thin film whose surface portion is discontinuous.

The cubic boron nitride (cBN) thin film and the tBN (turbostratic BN) thin film are formed by a sputtering process using a reactive gas or a sputtering process using an ion beam A mixed gas of argon (Ar) and nitrogen (N ₂ ) is supplied as a reactive gas until the tBN thin film is formed, and argon (Ar) is supplied after the tBN thin film is completely grown, , Nitrogen (N ₂ ), and hydrogen (H ₂ ) is supplied to the reaction gas.

The laminate of the diamond thin film and the cBN thin film according to the present invention has a cubic boron nitride (cBN) thin film laminated on a vertically grown diamond thin film layer grown in a vertical direction, and a diamond thin film layer And the cubic boron nitride (cBN) thin film is stacked in an empty space so that the diamond thin film layer grown in the vertical direction and the cubic boron nitride (cBN) thin film are in a wedge shape engaging with each other.

The laminated body of the diamond thin film and the cBN thin film according to the present invention and the manufacturing method thereof have the following effects.

As the diamond thin film and the cBN thin film are bonded in a wedge shape, the mechanical bonding force is improved and the peeling property of the cBN thin film can be improved. Also, by controlling the supply timing of hydrogen when cBN thin film is deposited, the interface characteristics between cBN and diamond thin film can be improved.

1 is a schematic view of a laminate of a diamond thin film and a cBN thin film according to an embodiment of the present invention.
2A to 2C are SEM micrographs showing the surface texture of the diamond thin film according to the mixing ratio of methane (CH ₄ ).
Fig. 3 is a graph showing the residual stress of the cBN thin film according to the hydrogenation amount.

The present invention provides a thin film structure of cubic boron nitride (cBN) with improved delamination properties.

Cubic boron nitride (cBN) thin films are easily peeled off. This is due to the amorphous BN and tBN thin films formed during the deposition of the cubic boron nitride (cBN) thin films and the large residual compressive stresses of the cubic boron nitride (cBN) Also, the cubic boron nitride (cBN) thin film is easily detached.

In order to improve the peeling property of a cubic boron nitride (cBN) thin film, the present invention deposits a cubic boron nitride (cBN) thin film on a diamond thin film layer having a vertically grown plate structure to form a diamond thin film layer and a cubic boron nitride ) Thin - film wedge type is induced to improve the peeling property of the cubic boron nitride (cBN) thin film.

As the cubic boron nitride (cBN) thin film is deposited in the void space of the diamond thin film layer grown in the vertical direction, the vertically grown diamond thin film layer and the cubic boron nitride (cBN) The interlocking wedge shape enhances the mechanical coupling force.

The diamond thin film layer is deposited by using a HFCVD method. In the HFCVD process, the ratio of CH ₄ in the mixed gas of hydrogen (H ₂ ) and methane (CH ₄ ) A diamond thin film layer having a plate-like structure grown in the direction of the surface can be formed.

In the diamond thin film deposition using HFCVD method, the continuous monocrystalline thin film is deposited as the ratio of methane (CH ₄ ) is lowered, and the discontinuous polycrystalline thin film is deposited as the ratio of methane (CH ₄ ) is higher.

Here, the term 'continuous' means that a thin film having a relatively uniform diamond surface is deposited when the diamond thin film layer is deposited on the substrate, and the term 'discontinuous' means that the surface portion of the diamond thin film deposited on the substrate has a non- This implies the same filling rate and growth in the form of an island.

Accordingly, the diamond thin film layer grown in the vertical direction as a diamond thin film layer according to the present invention is similar to a thin film of a discontinuous polycrystalline type in which the surface portion of the thin film is in the form of hydrogen (H ₂ ) and methane (CH ₄ ) is the ratio of methane (CH ₄₎ should be high relative to the one of the mixed gas. The present invention with reference to experimental results suggest that controlling the ratio of a mixed gas of hydrogen (H ₂₎ and methane (CH ₄₎ methane (CH ₄₎ as a 3~5vol%. If the ratio of methane (CH ₄ ) is lower than 3 vol%, continuous thin film is formed and the wedge bond with the cubic boron nitride (cBN) film is not formed. If the ratio of methane (CH ₄ ) is higher than 5 vol% Is accelerated to increase the lattice constant difference between the cubic boron nitride (cBN) thin film and the cubic boron nitride (cBN) thin film. However, when the deposition temperature of the diamond is as low as 900 ° C or less, it is possible to realize the structure of <diamond thin film layer grown in the vertical direction> even at a low methane concentration of 1% or less.

On the other hand, the compressive residual stress of the cubic boron nitride (cBN) thin film grown in the vertical direction grows in the vertical direction when the vertically grown diamond thin film layer and the cubic boron nitride (cBN) And serves as a factor for enhancing the mechanical bonding force with the diamond thin film layer of the plate-like structure. That is, although a conventional cubic boron nitride (cBN) thin film is easily peeled off from a substrate (or a thin film) having a large residual compressive stress, the compression residual stress of the cubic boron nitride (cBN) And acts as a factor for improving the peeling property.

The present invention provides a technique for controlling the supply timing of hydrogen (H ₂ ) during the deposition of a cubic boron nitride (cBN) thin film to further improve the peeling property of the cubic boron nitride (cBN) thin film.

(CBN) thin film on a diamond thin film was described in US Pat. No. 7,445,513. However, in the case of a cubic boron nitride (cBN) thin film formed on a diamond thin film, the possibility of inhibiting the formation of boron nitride (tBN) The formation of buried boron nitride (tBN) is inevitable during thin film growth. Furthermore, the deterioration of the interfacial properties between the cubic boron nitride (cBN) thin film and the diamond thin film during the hydrogen supply can be attributed to the fact that during growth of the buried boron nitride (tBN) formed in the initial stage of the cubic boron nitride (cBN) (TBN) and diamond film due to the reaction of the thin film. Thus, in the present invention, by supplying hydrogen after completion of the growth of the annealed boron nitride (tBN), the interfacial characteristics between the buried boron nitride (tBN) and the diamond thin film are prevented from being lowered and the boron nitride It is possible to obtain an effect of minimizing the residual stress. The annealed boron nitride (tBN) is structurally hexagonal and distinguished from cubic boron nitride (cBN) having a cubic structure, and the growth of boron nitride (tBN) having a hexagonal structure is completed It is technically feasible to selectively supply hydrogen at the point in time.

Considering that a cubic boron nitride (cBN) thin film is deposited in an empty space of a vertically grown diamond thin film layer, a cubic boron nitride (cBN) thin film having a predetermined thickness is deposited on the diamond thin film layer Hydrogen (H ₂ ) may be supplied at the time point.

The cubic boron nitride (cBN) thin film can be a sputtering process or an ion beam deposition process. The reaction gas is a mixed gas of argon (Ar), nitrogen (N ₂ ), hydrogen (H ₂ ) and boron nitride by growing the time of completion and the mixed gas is supplied to the argon (Ar) and nitrogen (N _2), after the growth completion of the nancheung boron nitride (tBN) is a mixture of argon (Ar), nitrogen (N _2), hydrogen (H ₂₎ Gas is supplied. Of course, hydrogen (H ₂ ) may not be contained in the reaction gas until the growth of the cubic boron nitride (cBN) thin film having a certain thickness after the completion of growth of the boron nitride (tBN), which is caused by the deposition of the diamond thin film layer and the cubic boron nitride cBN).

Hereinafter, the laminated body of the diamond thin film and the cBN thin film according to the present invention and the method for producing the same will be described in detail with reference to the embodiments, and the characteristics of the cBN thin film manufactured will be described below.

<Example 1: Surface texture change of diamond thin film according to CH ₄ ratio>

Diamond thin films were grown by HFCVD (hot filament chemical vapor deposition) method. The deposition pressure was maintained at 15 torr, the temperature of the silicon (Si) substrate was maintained at about 950 ° C, and the filament temperature was maintained at about 2300 ° C. The reaction gas was a mixed gas of methane (CH ₄₎ is 1~3% vol containing hydrogen (H ₂₎ and methane (CH ₄₎ the flow rate was 500sccm.

A SEM photograph showing the surface morphology of the diamond film according to Fig. 2a to 2c are methane (CH ₄₎ a mixing ratio, when the 2a is methane (CH ₄₎ comprises 1vol%, Figure 2b is methane (CH ₄₎ is If included 2vol%, Figure 2c shows the case of methane (CH ₄₎ comprises 3vol%. Referring to FIGS. 2A to 2C, it can be seen that a continuous diamond thin film having crystallinity is grown when 1 vol% of methane (CH ₄ ) is included, and when the amount of methane (CH ₄ ) is 2 vol% But a nanocrystalline diamond thin film having a very small crystal size is formed. On the other hand, when 3 vol% of methane (CH ₄ ) is contained, plate-shaped diamond particles are formed and grown in the vertical direction on the substrate, which corresponds to the above-described 'diamond- do.

&Lt; Example 2: Bonding property with cBN thin film according to the shape of diamond thin film layer >

We investigated the bonding properties of cBN thin films depending on the crystal structure of the diamond thin film layer. Three specimens were prepared for comparison. The first specimen was a cBN thin film deposited on a silicon substrate and the second specimen was deposited on a diamond thin film layer (corresponding to FIG. 2B) grown using a mixed gas containing 2 vol% of methane (CH ₄ ) of Example 1 cBN thin film was deposited on the diamond thin film layer (FIG. 2C), and the third specimen was the cBN thin film deposited on the diamond thin film layer (corresponding to FIG. 2C) grown using the mixed gas containing 3 vol% of methane (CH ₄ )

The cBN thin films were deposited using an asymmetric magnetron sputtering system. A hexagonal BN target with a diameter of about 5 cm was used and connected to a 400 W, 13.56 MHz high frequency power source. The silicon (Si) substrate was placed on a molybdenum (Mo) support with a diameter of about 10 cm. In order to apply a negative bias to the substrate, a high frequency power of 200 Kmz was connected to the substrate support, and a power of -40 V was applied. The reaction chamber was evacuated to a pressure of 10 ^-6 mtorr or less, and an Ar-N ₂ mixed gas containing 10 vol% of nitrogen was supplied into the chamber and maintained at a pressure of 2 mtorr. The silicon substrate was cleaned using a common organic solvent, and then mounted in a chamber. The deposition was carried out for 3 hours, and the thickness of the deposited thin film was about 1 um. Hydrogen was added to reduce the residual stress of cBN thin films during deposition. Six minutes after the start of the deposition, 7 sccm of hydrogen was added to the mixed gas. At this time, the flow rate of the Ar-N ₂ mixed gas was 20 sccm.

When the cBN thin film is exposed to the atmosphere, peeling occurs after a certain period of time. In the case of the first specimen, exfoliation occurred only in the water exposed in the atmosphere, and the second specimen was exfoliated in 4 weeks. On the other hand, no peeling was observed even after several months in the case of the third period.

Meanwhile, the flow rate of H ₂ was increased from 0 to 11 sccm while the flow rate of the total reaction gas was fixed at 20 sccm. FIG. 3 shows the residual stresses of the cBN thin films according to the amount of hydrogen added, and it can be confirmed that the residual stress decreases as the amount of hydrogen added increases. However, the deposited cBN thin film appeared to be peeled off immediately upon exposure to the atmosphere. Despite the remarkable decrease in residual stress due to hydrogenation, the sharp peeling of the cBN thin film indicates that the interface layer between the diamond thin film and the cBN thin film is very weak and hydrogenation is the reason. Therefore, a solution to this problem is required.

Thus, the cBN thin film was synthesized by controlling the supply timing of hydrogen. Specifically, hydrogen was further supplied at the point of 2 minutes, 4 minutes, and 6 minutes after the deposition, and only Ar-N ₂ mixed gas was supplied to the reaction gas before hydrogen was supplied. As the hydrogen supply time was delayed, the peeling of the cBN thin film was remarkably decreased. When the hydrogen supply time was 2 minutes and 4 minutes, the peeling was started at 2 days and 5 days, respectively, and at 6 minutes, no peeling was observed even after 1 week. Growth rate and electron microscopic analysis of cBN thin films revealed that the tBN thin film was grown to around 6 minutes from the time of deposition, and then the cBN thin film was grown. It is possible to improve the interfacial characteristics between the grown thin film and the nanocrystalline diamond thin film and to improve the residual stress characteristics of the grown cBN thin film.

Claims (5)

Forming a diamond thin film layer having a vertically grown plate-like structure by using a hot filament chemical vapor deposition (HFCVD) method; And
And depositing a cubic boron nitride (cBN) thin film on the diamond thin film layer,
The cubic boron nitride (cBN) thin film is deposited in the void space of the vertically grown diamond thin film layer, and the vertically grown diamond thin film layer and the cubic boron nitride (cBN) The wedge forms a wedge,
The HFCVD method uses a mixed gas of hydrogen (H ₂ ) and methane (CH ₄ ), the ratio of methane (CH ₄ ) is 3 to 5 vol%
Wherein the diamond thin film layer grown in the vertical direction is a discontinuous thin film on the surface of the thin film.
delete delete The method of claim 1, wherein a tBN (turbostratic BN) thin film is formed on the diamond thin film layer before the cubic boron nitride (cBN) thin film is formed, and the cubic boron nitride (cBN) thin film and the tBN (turbostratic BN) , Or an ion beam deposition process,
A mixed gas of argon (Ar) and nitrogen (N ₂ ) is supplied as a reactive gas until the tBN thin film is formed. After the completion of the growth of the tBN thin film, argon (Ar), nitrogen (N ₂ ) Wherein a mixed gas of hydrogen (H ₂ ) is supplied to the reaction gas.
A cubic boron nitride (cBN) thin film is stacked on a diamond thin film layer having a vertically grown plate shape,
(CBN) thin film is filled in the void space of the vertically grown diamond thin film layer, and the vertically grown diamond thin film layer and the cubic boron nitride (cBN) thin film are stacked The wedge forms a wedge,
Wherein the diamond thin film layer having a planar structure grown in the vertical direction is a discontinuous thin film on the surface of the thin film.

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