JPH03150353A - Reactive ion plating method - Google Patents

Abstract

PURPOSE:To generate high-density plasma and to easily form a uniform cubic boron nitride (cBN) film on a substrate surface at a high speed by forming parallel magnetic fields between B of an evaporating source and the substrate at the time of forming the cBN film by a reactive ion plating method on the substrate. CONSTITUTION:A crucible 20 contg. the B is placed in a vacuum chamber 1 and the substrate 3 is mounted in the upper direction opposite thereto. The substrate 3 is heated by a heater 31 and a gaseous mixture composed of N and Ar is supplied from a nozzle 4 into the vacuum chamber 1. The B in the crucible 20 is heated and evaporated by the electron beam 21 and a voltage is impressed between a cathode 6 and auxiliary anode 9 provided in the intermediate position of the crucible 20 and the substrate 3 to form the increased density plasma 5 by the parallel magnetic fields generated by magnets 8a, 8b provided behind the two electrodes 6 and 9. The vapor of the B passing in this plasma and the ionized gaseous N rapidly and stably form the uniform film of the high-hardness cBN on the substrate 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a reactive ion plating method, and particularly to a hot cathode discharge type ion plating method using a magnetic field.

[Conventional technology and its technical issues]

Reactive ion plating is one of the methods for forming a thin film of metal nitride, oxide, or carbide on the surface of a workpiece.

Regarding this reactive ion plating method, the following proposals have been made in the past.

■Method of introducing gas above the evaporation source and ionizing the evaporated particles from the evaporation source by arranging an ionizing electrode near the evaporation source and applying a positive voltage to cause arc discharge. (Refer to Publication No. 57553) ■ Arc discharge type ion plating method, ie.

A method of arranging an ionization electrode near an evaporation source, further arranging a thermionic emission filament between the evaporation source and the ionization electrode, and emitting thermoelectrons from this thermionic emission filament (Japanese Utility Model Publication No. 59-4045) (Reference) ■ A method in which a thermionic emission filament is placed near the evaporation source to emit thermionic electrons, and an activation nozzle to which a positive voltage is applied is placed on the opposite side to introduce ionized gas (activation method). (Reactive evaporation method using a nozzle) ■A method in which a thermionic emitting filament and an ionization electrode are placed facing each other near and above the evaporation source, and gas is introduced from a separate position (arc-like plasma ion plating method) However, - In all of these prior art techniques, a plasma generation mechanism is provided near the evaporation source, and evaporation and plasma formation are linked. For this reason, not only is it difficult to arbitrarily control the ion plasma, but the ions may disappear due to recombination between ions and electrons, or the plasma may be confined by the deflection magnetic field of the electron beam, reducing the number of ions that enter the workpiece.

There was a problem that high ion density could not be obtained.

In addition, when discharging only the introduced gas, I
Unless the pressure is about r or higher, plasma cannot be stably formed, and there are problems in that the discharge current only flows at most about IOA, and -plasma becomes localized.

Incidentally, cBN (cubic boron nitride) has recently attracted attention as a thin film. This is because cBN has a hardness second only to diamond, and unlike diamond, it has stable properties that do not react with iron.

Also. This is because it has properties such as good thermal conductivity, good insulation properties, and good chemical stability.

However, like diamond, cBN is a high-temperature, high-pressure phase, and is a material that is difficult to ionize.

For this reason, it has been practically difficult to industrially produce such cBN thin films using the prior art. Countermeasures for this include reducing the distance between the evaporation source and the substrate to prevent a decrease in the number of ions incident on the substrate, moving the thermionic emission filament and ionization electrode away from the evaporation source, and increasing the distance between the electrodes to widen the plasma space. There are ways to expand this.

However, even with this method, since there is no magnetic field, in order to obtain a discharge current of several amperes, the pressure must be increased to lX 10 T.
The vacuum must be as low as orr or higher.

However, when forming a film at a pressure higher than IXIO-Torr, special consideration must be given to the exhaust system and evaporation source.

That is, in the former case, since the oil diffusion pump cannot be operated at such high pressure, a conductance valve must be inserted in the middle to reduce the conductance. The latter is.

When an electron gun is used as an evaporation source under high pressure, abnormal discharge is likely to occur. Gas diffusion slows down the nuclear power plant, and since boron is an insulator, it causes bumping when large amounts of power are applied to increase the evaporation rate.

The present invention was devised to solve the above-mentioned problems, and its purpose is to easily generate high-density plasma in a high vacuum without requiring special consideration for the exhaust system or evaporation source. The object of the present invention is to provide a reactive ion plating method that can form a high-performance thin film represented by cBN easily and at a relatively high speed.

[Means to solve the problem]

In order to achieve the above object, the present invention creates plasma not by a simple hot cathode discharge, but by superimposing a parallel magnetic field on the electric field generated by the hot cathode discharge.

That is, the feature of the present invention is that in a reactive ion plating method, a gas is introduced into a vacuum chamber, and a cathode for thermionic emission is placed in a region between the evaporation source and the substrate or in a region near the substrate. A parallel magnetic field is used between the anode and the anode to which a positive voltage is applied, and the material particles evaporated from the evaporation source are passed through this plasma, while a negative voltage or high frequency is applied to the substrate. The purpose is to extract the ions generated in the plasma and cause them to collide with the workpiece.

The present invention is effective in creating a high-temperature, high-pressure phase compound film represented by cBN, and can also be applied to creating various high-performance thin films such as AfiN, TiN, and Tic.

The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows an example of an apparatus for implementing the present invention and an overview of the ion plating method using the apparatus.

Reference numeral 1 denotes a vacuum chamber, which is provided with an exhaust passage IO at its bottom and is evacuated by a vacuum pump (not shown) to create a high vacuum.

Reference numeral 2 denotes an evaporation source provided below inside the vacuum chamber 1, which includes a crucible 20 containing an evaporation material T such as a metal, and a means for heating and evaporating it, such as an electron gun or a resistance heater 2.
1. The evaporation source is not necessarily single, and may be a multi-source evaporation mechanism using, for example, a plurality of multi-point electron guns or single-point electron guns.

Reference numeral 3 denotes a substrate on which a workpiece is attached, and is arranged above the vacuum chamber 1 so as to face the evaporation source 2 (crucible portion). The distance between the substrate 3 and the evaporation source 2 should generally be 250 to 600 n- in order to stably evaporate boron at a film formation rate of 0.2 to 1.5 nu/see. be. The substrate 3 is connected to a bias power supply 30 in the square section, and a negative DC voltage or high frequency voltage is applied thereto. The substrate 3 is heated by a heater 31 and rotated by a rotating shaft connected to an actuator as necessary.

Reference numeral 4 denotes a gas nozzle, which is arranged at a desired location within the vacuum chamber 1, for example, on the side of the evaporation source 2, and has an introduction pipe 4 extending outside the vacuum chamber 1.
Argon, nitrogen gas,
Hydrogen gas, oxygen, or a mixture of two or more thereof is introduced into the vacuum chamber 1.

5 is a plasma generation mechanism that is a feature of the present invention. The plasma generation mechanism consists of a cathode 6 for emitting thermionic electrons, an anode facing the cathode 6, and a cathode 6 placed horizontally in the same horizontal plane as the cathode 6 and the anode, and in the same direction as the direction of the electric field formed by the cathode 6 and the anode. It consists of a pair of magnets 8a and 8b arranged so as to form a magnetic field, and preferably an auxiliary anode 9 is arranged on the anode side.

The entire plasma generation mechanism 5 is placed in a vacuum chamber 1 between the evaporation source 2 and the substrate, that is, at least between the evaporation source 2 and the substrate.
Installed at a distance of 50 mm or more. Preferably, the vicinity of the substrate 3, specifically, the perpendicular distance from the bottom surface of the substrate 3 in FIG. II n x at a position of 5 to 150 mm. This is to avoid the influence of the deflection magnetic field of the electron beam when an electron gun is used, and to increase the amount of ions incident on the substrate 3 as much as possible when forming a thin film of a high-temperature, high-pressure phase such as cBN. However, since being too close to the substrate 3 is rather undesirable, it should be within the above range. Also. The distance between the cathode 6 and the anode 6 is preferably widened in order to widen the plasma space, and is, for example, 200 m to 500 m.

The cathode 6 is made of a filament made of a hot cathode material such as W, Ta, or W/Th, and emits thermoelectrons when heated by a power supply 60. The anode may be wired to the magnet 8b on the side facing the cathode 6 as shown in Fig. 1, and the magnet itself may be used as an electrode, or an electrode 70 may be separately installed on the front side of the magnet 8b as shown in Fig. 1a. It may be composed of

In either case, a positive DC or AC voltage with respect to the ground potential, for example, a DC voltage of 40 to 70 V, is applied to the anode by the power source 71.

The magnets 8a and 8b face each other directly, and in order to form high-density plasma, the strength of the magnetic field is preferably 20 to 400e at the midpoint between both magnets, with a lower limit of 2000e.
This is because if the magnetic field is weaker than this, the thermoelectrons cannot be sufficiently accelerated, and the upper limit is set to 400a to avoid any influence on the electron gun.

The present invention forms a parallel (horizontal) magnetic field on a line segment connecting the cathode 6 and anode 7, and does not generate a magnetic field in a direction perpendicular to the line segment connecting the cathode 6 and anode 7. In the latter method, although ion bombardment using gas is possible, the magnetic field generator is located on the line connecting the evaporation source and the substrate, which prevents the diffusion of evaporated particles and prevents film formation.

In addition, as a method of parallelizing the magnetic fields of the magnets 8a and 8b more reliably, as shown in FIG.
Iron plate and soft steel plate on the front of 80b.

Magnetic bodies 81a and 81b such as silicon steel plates may be arranged, and this is also included in the present invention.

The auxiliary anode 9 is used for stabilizing the discharge (ignition of plasma), and a voltage approximately five times that of the anode is applied by a power source 90. It is desirable that this auxiliary anode 9 be constructed with a circuit such that the voltage decreases as plasma is formed.

Next, the process of forming a compound thin film using this apparatus will be explained.

First, a workpiece is attached to the substrate 3, and while the workpiece is heated to a required temperature by the heater 31, the inside of the vacuum chamber l is evacuated through the exhaust passage 10 while operating the vacuum pump. After that, the heater 31 is stopped, and the gas nozzle 4 is inserted into the vacuum chamber 1.
After introducing a gas such as argon and performing ion bombardment for a required period of time as a pretreatment, film formation is performed.

In this film-forming step, a gas of a predetermined component is introduced into the vacuum chamber 1 through the gas nozzle 4, a high positive voltage is applied to the auxiliary tube r9, the cathode 6 is energized, and a positive voltage is applied to the anode. This, together with the parallel magnetic fields of the magnets 8a and 8b, forms plasma Pa. In this state, the heating means 21 of the evaporation source 2 is operated to evaporate the evaporation material T.

These evaporated particles rise, pass through the plasma P, and are attached to the workpiece. On the other hand, gas ions generated in the plasma are attracted by the negative voltage applied to the substrate 2 or the self-bias voltage generated by the high frequency, and the workpiece is collided with the top. As a result, a reaction product film is deposited on the workpiece.

In the present invention, the plasma generation mechanism 5 includes a pair of magnets 8a in addition to the cathodes 6 and 7.

8b are placed in the same plane, which results in the
) A parallel magnetic field as shown in (b) is formed. cathode 6
Since the anode and the anode are placed in a parallel magnetic field, the thermionic electron e emitted from the cathode 6 due to the magnetic field and electric field has a velocity component in a direction different from the direction of the magnetic field, as shown in Figure 3 (a) and (b). It is accelerated in the direction of the electric field, that is, toward the anode, while performing cyclotron motion. Vacuum chamber 1
A gas is introduced into the chamber in advance, and ionization occurs when the gas molecules collide with the accelerated electrons as described above.

The gas molecules are ionized and a plasma is formed.

This plasma is densified by a parallel magnetic field as shown in Figure 2 CB> (b), which cancels out the negative space charge near the cathode due to thermionic emission, which increases the saturation current value of the hot cathode (filament). I = A T”exp(-eψ
8T) (However, [I] = Amp/ai, A:
A current flows from the cathode to the anode with a constant that varies depending on the material: T: absolute temperature, e: electron load, Φ: Boltzmann's constant, and φ: work function. Since the heat dissipation current is proportional to the cathode temperature, it is possible to easily flow about 20 A, and the initial velocity of the thermoelectrons at this time is sufficiently small compared to the magnetic and electric fields, so the flow is as shown in Figure 3 (a). As shown in b), it becomes almost a sheet beam shape, and therefore.

A high-density plasma space can be stably formed between the magnets 8a and 8b.

Since the plasma generation mechanism is independent of the evaporation means of the evaporation source 2, etc., plasma can be controlled arbitrarily and easily. Moreover, since the plasma generation region is located at a sufficient distance from the evaporation source 2, there is no problem of recombination between ions and electrons, and even light ions are not affected by the magnetic field of the electron beam. Furthermore, by using a parallel magnetic field, it is possible to form high-density plasma with the introduced gas in a wide space.
Compounds with vapors that are difficult to ionize can be easily formed. Further, in the present invention, since the self-bias voltage does not decrease even if the discharge current increases, the acceleration voltage for attracting ions can be set to 100 V or less. 2b is significantly smaller than the approximately 300 V of the method using an activated nozzle, and is economical.

In addition, when the magnetic field mechanism is used as shown in FIG. 4, the mirror-like formation of the magnetic field is suppressed and a better parallel magnetic field is created, so that the plasma density is averaged.

This improves the uniformity of the film and also increases the compound content.

In addition, when using the auxiliary anode 9 and applying a voltage approximately 5 times that of the anode, the discharge starting pressure is approximately 1xlO''T compared to approximately 2.5x10-tonorr when not used.
Since the temperature can be lowered to 0.05 to 10.0 m, it is possible to form a film in a higher vacuum.

It goes without saying that in the film forming step, a film rich in evaporated components may be formed as an intermediate layer between the workpiece and the compound thin film, as appropriate, in order to improve adhesion to the base material.

Although the film forming conditions depend on the film material, etc., they may generally be appropriately selected from the following conditions.

Pressure Crab 2-8 X 10- Torr Substrate temperature = 250℃ or more Anode voltage: 40-70V Anode current: 2-20A Cathode heating current: 30-50A Bias power supply power: Soow or less Electron gun electric crab 1.7-2. 3KW [Example] A cBN thin film was created according to the present invention.

1. The apparatus shown in FIG. 1 was used. The plasma generation mechanism was installed at a position of 10 mm from the substrate and 400 mm from the evaporation source.

A pair of ferrite magnets were used as the magnets. The spacing between magnets is 2
It was set to 20■. The magnetic field strength at the midpoint between the magnets is 400e.
It is. The anode was placed in front of the magnet. A tungsten wire filament with a diameter of 1 m and a total length of about 15 G was used as the cathode. Purity of evaporation material is 99. Part of boron was used.

■First, attach a silicon wafer to the substrate using a jig, and while heating it to 300°C with a heater, heat the inside of the tank to 1 x 1.
The chamber was evacuated to a pressure of 0'' Torr, then the heater was stopped, and argon ion bombardment was performed for 5 minutes.The bombardment conditions were: pressure crab 5 x 101 Torr;
Substrate high frequency power = 300W, anode voltage/current = 60
v・5A.

(2) After bombardment, a mixed gas of Ar/Nz was introduced to form plasma, and then boron was evaporated with an electron gun. In order to improve the adhesion of the films, the gas flow rate was changed to grow a B film, a B-rich film, and a CBN film. The film forming conditions at this time are shown in Table 1 below.

Table 1 Elapsed time Pressure Ar jl Nz amount R
F direction - (sin) (Torr)
(seem) (sccs+)
(W) 10~4 13X10-old 56 1 0
1200134~J1.30 j5xlO-382~8
111~91350118.30~11 l 5xlO
l 81 l 9 l 3501111~20
15xlo-l 81 1 9 13001 and - anode voltage/current: 60V-14A, electron gun knee 8.5KV, 270mA, cathode heating current: 44A. These parameters were kept constant during film formation. The evaporation rate of boron is 0.5 to 0.6 n@/see, and the temperature inside the tank is 300°C at the beginning of film formation, and although the temperature rose above this during film formation, the process was generally carried out in a low temperature range. did it.

■The results of analyzing the obtained thin film by infrared absorption spectroscopy are shown in Figure 5, and the results of analyzing it by X-ray diffraction are shown in Figure 6.
As shown in FIG. 5, an absorption band can be seen at 1100Qll-1, so it is identified as cBN. Furthermore, as is clear from FIG. 6, a peak corresponding to cBN 111 appears.

The obtained thin film has a hardness of Hv4000 or more.

In addition, since a B-rich film was formed in the middle, adhesion was good, and no peeling occurred even when 30 W of ultrasonic vibration was applied for 5 hours.

②Furthermore, the film was formed by placing a mild steel plate on the front of the magnet case. As a result, the uniformity of the film thickness is improved,
The cBN content (Re) is also the RF puff of the substrate - 350W
This resulted in a significant increase of 72%.

〔Effect of the invention〕

According to the present invention described above, even under conditions where both electrodes of the hot cathode discharge are separated from the evaporation source and a sufficient distance between the electrodes is provided, and in a high vacuum of 1.5 A discharge current flows, forming a high-density plasma, and this high-density plasma can be formed in a wide space.For this reason, it is possible to easily create compounds with substances that are difficult to ionize, for example, to create high-temperature, high-pressure compounds that are difficult to create. The cBN phase can be obtained easily and at a relatively high speed.Also, since high-density plasma can be formed even in high vacuum, special consideration is not required for the exhaust system or evaporation source, and the equipment configuration is relatively simple. It is simple and provides excellent results.

[Brief explanation of the drawing]

Figure 1 is a schematic configuration diagram of the ion plating method of the present invention and the apparatus used for its implementation, Figure 1a is a partial explanatory diagram showing another example of the anode, and Figure 2 (a) is the magnetic field of the plasma generation part. A plan view showing the distribution, FIG. 2(b) is a side view of the same, FIG. 3(a) is a plan view schematically showing the flow of electrons in the plasma generation part, and FIG. 3(b) is a side view of the same. 4 is a plan view showing another embodiment of the plasma generation mechanism, and FIG. 5 is an infrared absorption spectrogram of the thin film obtained by the present invention.
FIG. 6 is also an X-ray diffraction diagram. ■・−・Vacuum chamber, 2・−・Evaporation source, 3−・・Substrate, 4・
- Gas nozzle, 5- Plasma generation mechanism, 6...
Cathode, 7...-Anode, 8a, 8b...-Magnet,
9...Auxiliary anode, W-Work, PR-Plasma Patent applicant Shinko Seiki Co., Ltd. Agent Patent attorney Kuro 1) Hiroshi Yasushi Figure 1. Figure 1a Figure 5 Wave! ! Me1CP540F\>, lz Diffraction angle 2θ (
Cu9 Procedural amendment December 7, 1999 Commissioner of the Patent Office Fumiyoshi Yoshida Examiner of the Patent Office 1, Indication of the case 1999 Patent Application No. 287434 2, Name of the invention Reactive ion plating method 3. Relationship with the case of the person making the amendment Patent applicant Shinko Seiki Co., Ltd. 4, Agent Saturn Building, 1-14-5 Kyobashi, Chuo-ku, Tokyo 104 Tel: 564-5948 Ibanpe 5, Notification of reasons for refusal Date Initiation 1 1.12゜Completion 1 Amendment 1: In the specification of the present application, in the 6th line of page 8, r n m J is corrected to lr m m J. 2. In the specification of the present application, lines 12 to 16 on page 14 are corrected as follows. ``I can. 1 or more

Claims (3)

[Claims] (1) Place an evaporation source of evaporation material and a substrate facing it in a vacuum chamber, and in the presence of a reactive gas, the material particles evaporated from the evaporation source are ionized using hot cathode discharge and react with the workpiece. In the ion plating method that attaches a produced film, a gas is introduced into a vacuum chamber, and a cathode for thermionic emission is opposed to and placed in a region near the substrate or in the middle of the distance between the evaporation source and the substrate. Plasma is formed using a parallel magnetic field between the anodes to which a voltage of A reactive ion plating method characterized by extracting ions and colliding them onto a workpiece. (2) A pair of magnets arranged so that the magnetic field is formed in the same direction as the electric field formed by these electrodes, as a means for forming a parallel magnetic field between the thermionic emission cathode and the anode facing it. The reactive ion plating method according to claim 1, which uses the following. (3) The reactive ion plating method according to claim 1, which includes igniting the plasma by arranging an auxiliary anode to which a positive voltage is applied near the anode.