JPH06100399A - Production of boron phoshide nitride - Google Patents

Abstract

PURPOSE:To obtain BPxN1-x film used for coating film, etc., having high hardness and high environmental resistance by specifying substrate temperature using high-frequency plasma CVD method under reduced pressure in synthesizing boron nitride phosphide from gas mixture containing N, P and B atoms as essential components and a hydrogen-containing gas. CONSTITUTION:A washed substrate 1 is installed on a substrate holder 2 connected to a high frequency electric source 3 and an electrode opposite to the holder is ground. The substrate holder 2 is heated by a heater 5 and then the substrate 1 is heated to 850-1400 deg.C by a heater 5 and the raw material gases are allowed to flow into a reaction chamber 6 to keep the interior of the reaction chamber 6 to prescribed pressure and high frequency bias is applied onto the substrate 1 to form high frequency plasma 7 on the substrate. Thereby, raw material gasses are allowed to react with each other to readily synthesis BPxN1-x on the substrate. Furthermore, at least part of the hydrogen gas is preferably substituted with a halogen gas and/or a dilute gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a boron nitride phosphide thin film used for a high hardness coating, a high environmental resistance coating and the like.

[0002]

2. Description of the Related Art As a high hardness coating and a high environmental resistance coating,
Boron nitride (BN) is already well known. Mainly four crystalline phases have been reported for solids consisting only of boron and nitrogen. Hexagonal (h-BN), cubic (c
-BN), wurtzite hexagonal (w-BN), and rhombohedral (r-BN). Among these, c-BN is expected to be applied to high hardness coatings and functional devices. c-
BN has a zinc blende type crystal structure, is the second hardest in all crystals after diamond, and has excellent heat resistance, environmental resistance, and heat conduction characteristics. It is also known that by doping Be or Si therein, each exhibits n- and p-type conduction. There are two methods for synthesizing c-BN, a high-pressure synthesizing method and a vapor-phase synthesizing method. The former is high in cost, and the product contains a large amount of impurities, and only fine crystals of several mm or less can be obtained. On the other hand, in the latter case, it is difficult to obtain a single-phase thin film, and only fine crystals of 100 nm or less can be obtained.
The synthesis of BN is difficult.

Phosphorus (P) is contained in the same group V element as nitrogen, and boron phosphide (BP) consisting of boron and phosphorus is a cubic zinc blende type crystal and also has a high hardness. In addition, when B or P in them is slightly excessive, n and p are respectively increased.
Shows type conduction. Si single crystal or SiC by vapor phase synthesis method
A single crystal is obtained by epitaxially growing on the single crystal. However, it is not as hard as c-BN and is inferior in chemical durability to c-BN.

Further, almost no reports have so far been made on solids consisting of only three components of boron, phosphorus and nitrogen, and the following two documents are the only ones. In Japanese Patent Laid-Open No. 63-65081, B (P, P, is added to the interface to enhance the adhesion of a cubic boron nitride (c-BN) film.
N) It has been proposed to synthesize crystals, PCl ₃ and PH ₃ as phosphorus sources, and BCl ₃ and BH as boron sources.
₃ , using NH ₃ , N ₂ or the like as a nitrogen source,
It is described that (N, P) was synthesized by a low pressure plasma CVD method at 300 ° C. to 800 ° C. and 5 to 20 Torr.
The obtained cubic boron nitride film was c-B by X-ray diffractometry.
N structure confirmed, Micro Vickers hardness 4000k
Although it is described as g / mm ² or more, no confirmation has been made for the B (N, P) film provided on the interface. S.Motojima, H.Hotta, K.Goto; Mater.Lett. 8 (19
89) 457, the synthesis of an amorphous BNP ternary translucent solid is described, and PC is used as a raw material.
using l ₃ , BCl ₃ , NH ₃ , H ₂ and Ar, heat C
Amorphous B-N-at a temperature of 500 to 700 ° C. according to the VD method.
A P-ternary translucent solid is obtained. The above synthesis methods (1) and (2) can yield only an amorphous film or a film having extremely poor crystallinity.

[0005]

Although cubic boron nitride has excellent properties, it is extremely difficult to synthesize it as described above. In particular, even a single crystal of μm size has not been obtained by the vapor phase synthesis method. Further, although cubic boron phosphide is relatively easy to synthesize a single crystal, the obtained one has a relatively low electron mobility and a hardness inferior to that of c-BN. On the other hand, there have been almost no reports on solids consisting of only boron, phosphorus and nitrogen as described above. Since the conventionally synthesized B-N-P ternary substance is synthesized at 800 ° C. or lower, it can only be a polycrystal having an amorphous or extremely poor crystallinity. The present invention has been made in view of the above circumstances, and is a substance that can be synthesized more easily than c-BN and has properties superior to BP, that is, boron nitride phosphide BP _X N _1-X. The present invention is intended to provide a manufacturing method of.

[0006]

Means for Solving the Problems As a means for solving the above problems, the present invention synthesizes boron nitride phosphide on a substrate from a gas containing at least one kind of nitrogen atom, phosphorus atom and boron atom and a gas containing hydrogen. In this method, the high frequency plasma CVD method is used under reduced pressure, and the substrate heating temperature is set to 8
A method for producing boron nitride phosphide, characterized in that the temperature is 50 ° C to 1400 ° C. In the present invention, substituting at least a part of the hydrogen-containing gas with a halogen gas and / or a rare gas can be mentioned as a particularly preferred embodiment.

[0007]

The present invention will be described below with reference to the drawings. In FIG. 1, the cleaned substrate 1 is placed on a substrate holder 2. A high frequency power source 3 is connected to the substrate holder 2, and an electrode 4 installed on the counter electrode is grounded.
Further, the substrate holder 2 can be heated by using the heater 5. First, in the reaction chamber 6 of the above apparatus, 10 ⁻⁶ To
After vacuuming to rr or less, the heater 1 heats the substrate 1 to a predetermined temperature, that is, 850 to 1400 ° C. After reaching a predetermined temperature, a raw material gas is caused to flow to have a predetermined pressure, and a high frequency bias is applied to form a high frequency plasma on the substrate 1, whereby the raw material gas is reacted and BP _X N _{1-X is transferred} to the substrate 1. Combine on top.

It is known that boron nitride has a zinc blende type cubic system composed of sp ³ hybrid orbitals, but its synthesis is extremely difficult. On the other hand, it is known that boron phosphide is easily synthesized by the thermal CVD method and grows epitaxially on a Si single crystal substrate. The same group V nitrogen is sp ² or s
While p-orbitals are easy to take, in general, electrons that are involved in phosphorus bonds are easy to take, as well as p orbitals, sp ³ , sp
² d, sp ² d ² and the like. The sp ² hybrid orbit is relatively difficult to take. For this reason, BP is a sphalerite type whose stable phase in the standard state is composed of sp ³ hybrid orbitals.
As of May 1992, no crystal form other than zinc blende type has been found as a crystal in which B and P have a composition ratio of 1: 1. As described above, the crystal composed of ternary elements of boron, nitrogen and phosphorus has an advantage that the zinc blende type cubic crystal form is easier to synthesize than boron nitride because it contains phosphorus.

The boron phosphide nitride BP according to the present invention
The range of x in which _X N _1-X can take a cubic system is 0.1 <x
<1. If B is 1 with respect to the target composition (BP _X N _1-X ), N is 3 (1-
x)>N> (1-x), P needs to be P> 10x. It is necessary to increase the ratio of N / B and P / N as the film forming temperature becomes various. A particularly preferable range of B, P and N in the obtained film is 1>x> 0.
It is 6.

The source gases used in the present invention include the following. As a phosphorus (P) source, P hydrides such as PH ₃ and PH ₅ , P halides such as PF
₃ , PCl ₃ , PBr ₃ , PI _{3 and the} like, and organic phosphorus compounds such as P (CH ₃ ) ₃ and P (C ₂ H ₅ ) ₃ can be mentioned.
As a source of boron (B), a hydride of B such as B ₂
H ₆ , B ₄ H _10, etc. B halides such as PF ₃ ,
BCl ₃ , BBr ₃ , BI _{3 and the} like, and organic boron compounds such as B (CH ₃ ) ₃ and B (C ₂ H ₅ ) ₃ can be mentioned.
As a nitrogen (N) source, a hydride of N, for example, NH ₃ , N
₂ H ₄ , N ₃ H, etc. N halides such as NF,
Examples include organic nitrogen compounds such as NCl _{3 and the} like, such as phenolamine.

In the present invention, in addition to the above raw material gases,
Add hydrogen-containing gas to. Of B atom by hydrogen containing gas
The dilution concentration is preferably 1.0% or less. 1.0
%, The deposition rate of boron atoms becomes too high,
Since it is easy to form a boron-boron bond,
I can't get a good one. As the hydrogen-containing gas,
H ₂, H₂O, HF, etc., CH_FourSuch as organic gas
It can also be used. In addition, at least the hydrogen-containing gas
For example, F₂, Cl₂, Br₂Halogen gas such as /
Or, for example, He, Ne, Ar, Kr, Xe, etc.
It is particularly preferable to replace with gas. The above gas is boron
-BP, such as boron or phosphorus-phosphorus_XN_1-XSynthesize
In addition to suppressing the formation of unfavorable bonds,
It is thought that any allotrope has an effect of removing by etching
To be However, part of it may be halogen gas and / or rare gas.
The hydrogen-containing gas that is replaced by gas is nitrogen, phosphorus, or boron.
Does not include hydrides.

In the present invention, the substrate has a temperature of 850 ° C. to 1
Heat in the range of 400 ° C. It does not crystallize below 850 ° C. If it exceeds 1400 ° C, there are few substrates that can withstand this temperature. It is also inconvenient because phosphorus and nitrogen are easily released and cubic crystals are not formed. As the heating means for the substrate, various heating means known in this technical field such as a heater, a halogen lamp, and infrared irradiation shown as 5 in FIG. 1 can be used.

The pressure during synthesis depends on the heating method, but is preferably in the range of 0.01 Torr to 150 Torr. If it is less than 0.01 Torr, the flow rate of the gas that can be supplied becomes extremely small, and the film formation rate becomes extremely small, which is not practical. Further, it becomes difficult to maintain the discharge by the high frequency plasma, and the gas flow in the reaction tube becomes long, so that only a film having poor crystallinity can be obtained. In addition, the depressurization condition varies depending on the frequency used and the like.
In the case of Hz high frequency plasma, 0.5 to 5 Torr,
5-1 in case of microwave plasma of 2.45 MHz
A preferable range is about 00 Torr.

The film thickness of the boron nitride phosphide obtained according to the present invention can be controlled by changing the film formation time.

[0015]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. [Examples 1 to 14 and Comparative Examples 1 and 2] The results shown in Table 1, Table 2, and Table 3 below were obtained by using the apparatus shown in FIG. 1 and using plasma with a high frequency of 13.56 MHz for 1 hour. Shown in. Regarding the obtained film, the thin film X-ray diffraction method (XR
The crystal phase is identified by D), and the chemical analysis method (ESCA) is used.
The amount of elements contained in the film was investigated by. For the evaluation of crystallinity, the full width at half maximum of 111 reflection obtained by XRD (the half width becomes smaller when the crystallinity is good) was used. The film thickness obtained in each of Examples 1 to 14 is 5 to 7 μm. For comparison, the case where the substrate temperature is set to 700 ° C. under the same conditions as in the example is referred to as comparative example 1, and the substrate is simply set to 1000 ° C.
Comparative Example 2 shows the case where the high-frequency plasma was not formed by heating to 1. The meanings of the abbreviations in Tables 1 to 3 are as follows. c: cubic phase (cubic system) a: amorphous (amorphous, amorphous)

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

[Table 3]

As shown in Tables 1 to 3, Examples 1 to 14
Since the XRD half widths are all 0.5 ° or less and the crystallinity is very good, it is clear that the cubic single-phase boron nitride phosphide is obtained by the present invention. Further, it is understood that the high-frequency plasma CVD method under reduced pressure and the substrate heating temperature range of the present invention are effective.

[0020]

INDUSTRIAL APPLICABILITY The present invention can produce a cubic single-phase boron nitride phosphide which is promising as a high hardness coating and a high environmental resistance coating.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating an example of the method for producing boron nitride phosphide according to the present invention.

[Explanation of sign]

 1 substrate 2 substrate holder 3 high frequency power supply 4 electrode 5 heating heater 6 reaction chamber

Claims (2)

[Claims] 1. A method of synthesizing boron nitride phosphide on a substrate from a gas containing at least one kind of nitrogen atom, phosphorus atom, and boron atom and a gas containing hydrogen, using a high-frequency plasma CVD method under reduced pressure, and Substrate heating temperature is 85
The method for producing boron nitride phosphide is characterized in that the temperature is 0 ° C to 1400 ° C. 2. The method for producing boron nitride phosphide according to claim 1, wherein at least a part of the hydrogen-containing gas is replaced with a halogen gas and / or a rare gas.