JPS6396265A - Method and device for forming thin insulating film - Google Patents

Abstract

PURPOSE:To uniformly form an insulating film having high purity and excellent adhesiveness, by installing a thermoelectron releasing source between a substrate and evaporating source in a vacuum vessel in which a specific pressure is maintained and adequately controlling the high-frequency electric power and negative voltage to be impressed to the substrate. CONSTITUTION:An atmospheric gas is introduced from a gas introducing pipe 9 into the vacuum vessel 1 and the inside of the vessel is evacuated through a gas discharge port 13 and is kept under 10<-2>Torr. The high-frequency voltage is then impressed by an RF power source 11 to the substrate 3 heated adequately by a heater 4 to discharge electricity so that the metal vapor from a metal evaporating source 2 and the gas are ionized. A bias voltage is further impressed to the substrate 3 to concentrate said ions onto the surface and to form the insulating film. The thermoelectron releasing source 7 and the electrode 5 impressed with a positive potential are disposed between the substrate 3 and evaporating source 2 of the above-mentioned device to accelerate the above- mentioned ionization. The high-frequency electric power to be thrown to the substrate 3 is controlled to >=1W/cm<2> and the negative voltage by the high-frequency self bias to <=1kV, by which the good discharge state is maintained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method and a forming apparatus for forming an insulating thin film on a substrate, and more specifically, to a method and a forming apparatus for forming an insulating thin film on a substrate, and in particular, to form a highly pure insulating thin film uniformly and with good adhesion. The present invention relates to a forming method and a forming apparatus.

[Prior art] Cubic boron nitride (Cubic Boron N1tri)
Insulating materials represented by CBN (hereinafter referred to as CBN) are useful as heat sinks and passivation films for ICs due to their excellent electrical insulation and thermal conductivity.
In addition, because it is extremely hard and has excellent wear resistance and heat resistance, it is also useful as a coating material for the base material surface of metal and ceramic machine tools, especially for cutting tool steel base materials for difficult-to-cut materials and high-speed cutting. It is attracting attention as a surface coating material for tool steel base materials.

As a method for coating the above-mentioned insulating substance, that is, a method for forming an insulating thin film, for example, a thermal CVD method is used.

Examples include plasma CVD method, RF sputtering method, and ion blating method. Among these methods, the ion blating method is a bombardment method that uses the kinetic energy of ions, so it can efficiently obtain a film with excellent adhesion to the substrate even though it operates at a lower temperature than other methods. This method is highly praised for its practical use.

By the way, the problem when forming an insulating thin film on a substrate using the ion blating method is that, unlike when forming a conductive thin film, the insulating material that has begun to accumulate on the substrate is bombarded by positive ions. One example of this is a phenomenon in which the substrate becomes positively charged and no more collisions of positive ions occur even if a negative voltage is applied to the substrate (charge-up phenomenon). Therefore, in order to prevent this, high frequency (RF) is applied to the board.
) In addition to applying a voltage to prevent charging, ion blating is performed by utilizing the phenomenon that electrons, which have a smaller mass than positive ions, gather near the substrate.

However, in film formation using conventional RF bias ion blating, if a discharge is to be maintained under a gas pressure of 10-2 Torr or less, the negative voltage due to self-bias will exceed IKV.
There is a drawback that the voltage is as high as the above, and therefore the sputtering effect takes priority and it becomes difficult to form a film. Furthermore, since the amount of ion bombardment is low, the ion current value of the substrate is low, making it difficult to form a hard insulating film.

Therefore, in the currently proposed practical RF bias ion blating method and device, a positive potential is applied to the nozzle for introducing a gas such as a reactive gas (nozzle bias method).
The resulting discharge is used to increase the amount of ions produced, thereby improving film formability and hardening the produced film. FIGS. 3 and 4 are schematic explanatory diagrams showing the ion blating apparatus proposed by the authors, and it has been reported that they succeeded in forming a highly insulating CBN film.

Ionization methods in ion brating include, for example, DC glow discharge method (Mattox method), RF excitation method, multi-cathode method, holocathode (CD) discharge method, DC arc discharge method (probe method), multi-cathode and bias method. There are various methods such as a combination of probes, and the examples shown in Figures 3 and 4 both use the activation nozzle method.In other words, the above two methods are methods for activating a reactive gas (for example, N2). In each case, a DC positive potential is applied to the N2 gas introduction nozzle, and in the example shown in Figure 3, thermionic electrons emitted from the HCD gun are used when B in the crucible is melted by HCD, and in the example shown in Figure 4. When B is melted with an electron beam, thermoelectrons emitted from separately attached emitters are used to generate N2 gas discharge at the tip of each gas introduction nozzle and activate N2.

[Problems to be Solved by the Invention] However, in the above-mentioned nozzle bias method, since a discharge current on the order of several amperes flows through the small-area gas introduction nozzle, the nozzle metal melts and eventually evaporates and gets mixed into the film. This may cause a decrease in the purity of the insulating film. Further, in the nozzle bias method, since a discharge occurs between a nozzle at a positive potential and a chamber at an earth potential, the discharge state is localized, and uniform film formation is difficult when the substrate area is large. Furthermore, since the discharge area of the nozzle is small, the entire discharge surface is covered by the adhesion of evaporative insulators, making it difficult to sustain discharge.

The present invention aims to provide a method and apparatus for forming an insulating thin film that can uniformly form an insulating film of high purity and excellent adhesion on a large-area substrate.

[Means for Solving the Problem] The method of the present invention achieves the above object by applying high-frequency power to the substrate while maintaining the inside of the vacuum chamber at 10-” Torr or less to insulate the surface of the substrate. In forming the thin film, a thermionic emission source and an electrode to which a positive potential is applied are installed between the substrate and the evaporation source, and the high frequency power input to the substrate is set to I W / C 1 m2 or more and by high frequency self-bias. The main point is to control the negative voltage to below IKV, and the device of the present invention places a substrate and an evaporation source in a vacuum chamber and applies a high frequency voltage to the substrate to form an insulating thin film on the surface of the substrate. This is an insulating thin film forming apparatus, and its gist lies in that a thermionic emission source and an electrode to which a positive potential is applied are installed between the substrate and the evaporation source.

[Function] In the present invention, when forming an insulating thin film on the surface of a substrate, an atmospheric gas (reactive gas, inert gas, mixed gas thereof, etc.) of 10 '' Torr or less is introduced into the vacuum chamber, or the atmosphere is (adjust to 10-2 Torr or less while introducing gas or after introducing it), place a metal evaporation source (electron beam evaporation source, resistance heating evaporation source, HCD evaporation source, etc.), and apply RF power to the substrate. The resulting discharge region ionizes the gas and metal vapor. At this time, the high frequency power input to the board is I W /
cm" or more, and the negative voltage due to high-frequency self-bias is controlled to be less than IKV. However, simply controlling the voltage and power to the above values does not allow a stable discharge state to be formed, and it is difficult to form a satisfactory thin film. Therefore, in the present invention, an electrode to which a positive potential is applied is installed between the substrate and the metal evaporation source, and a thermionic emission source is installed opposite to the 7M electrode, thereby generating an arc discharge. let me,
Assists in the ionization of gases and metal vapors. As a result, a good discharge state can be obtained under conditions that satisfy the above-mentioned RF self-bias voltage and RF power.

That is, in the present invention, unlike the conventional nozzle bias method in which a positive potential is applied to the gas introduction nozzle, a positive potential is applied to an independent electrode, so the emitted thermoelectrons are uniformly received over a wide area and are transferred to the substrate. However, a uniform discharge state can be formed. Further, the discharge current can be increased in response to an increase in the area of the substrate. Furthermore, since the RF self-bias voltage is applied to the substrate, it is possible to avoid the charge-up phenomenon on the surface of the insulating film formed on the substrate, and the acceleration energy of ions (ion bombardment) can be effectively used. It is possible to obtain an insulating film with excellent sealability with materials. Furthermore, since the input RF power is set at 1 W/cm2 or more, weakly bonded products are sputter-etched, and film formation of high-pressure, high-temperature stable phases such as CBN and diamond can be realized due to the thermal spike effect. Furthermore, since the present invention employs RF discharge, the ambient gas pressure can be lowered than in the past, and a highly pure film can be formed.

In addition to the above effects, the present invention suppresses the negative voltage due to the RF self-bias to a small voltage below IKv as described above, so that the film formation rate can be higher than the sputtering rate, and high-speed film formation can be achieved.

[Example 1] Fig. 1 is a cross-sectional explanatory view showing an ion blating apparatus of the present invention for carrying out the method of the present invention, in which 1 is a vacuum vessel, 2 is a metal evaporation source, 3 is a substrate, 5 is an electrode, 7 indicates thermionic emission sources, respectively.

The vacuum container 1 is provided with an atmospheric gas introduction pipe 9 and an exhaust port 13 connected to a vacuum pump (not shown), and inside thereof, a substrate 3 and a metal evaporation source 2 are arranged vertically facing each other. , and a thermionic emission source 7 and an electrode 5 are provided at an intermediate height position between the substrate 3 and the metal evaporation source 2 so as to face each other in the left-right direction.

Although the substrate 3 is shown as a flat plate in the figure, the tool corresponds to this when, for example, an insulating film is to be formed on the surface of a tool. 11 and a self-bias control circuit 12 are connected in parallel, and a heater 4 is installed near the back side of the substrate 3 to heat the substrate 3 to a predetermined temperature.

The thermionic emission source 7 is a thermionic supply source for forming a discharge state between the electrode 5 and is connected to an AC power source 8, and the surface of the electrode 5 facing the thermionic emission source is formed of an MO plate. However, it is a plate-shaped body with a water-cooled structure inside, and a DC power source 6 is connected to this, and a positive potential is applied thereto. Metal evaporation source 2
B, which is a metal for evaporation, is stored in the crucible 2a, and an electron beam gun 15 is also provided, and metal vapor is generated by irradiation with an electron beam. A shutter 14 is provided below the electrode 5 and above the metal evaporation source 2 so as to be openable and closable to control the evaporation of the metal.

When forming a CBN film on the substrate 3 using the ion blating apparatus of the present invention having such a configuration, the interior of the vacuum vessel 1 with the shutter 14 open is 9 x 10''.
After exhausting to below Torr, N from the gas introduction nozzle 9
Introducing 2/Ar mixed gas to 5×10-3 Tor
An atmosphere of r is formed, and an electron beam is irradiated onto B in the Ruppo 2a to evaporate the B. Then, the AC power supply 8 is turned on to cause the thermionic emission source 7 to emit thermoelectrons, and the DC power supply 6 is turned on and a positive voltage of 40 to 50V is applied to the electrode 5, thereby adjusting the current value flowing through the electrode 5 to 9A. arc discharge starts. Also, using the heater 4, the substrate 3 is
℃, high frequency power of 2 W/cm 2 was applied to the substrate 3 to form a film. The substrate self-bias voltage is -800
v.

When the BH film formed on the substrate was subjected to an infrared absorption spectrum, the chart shown in FIG. 5 was obtained. In FIG. 5, an absorption spectrum (residual line) indicating CBN was observed in the wavelength range of about 105105O. In addition, the produced film was subjected to electron beam diffraction, and the results were analyzed, and as shown in Table 1, A37M25-1033
A match was confirmed. Furthermore, the film composition was analyzed by Auger spectroscopy, and as shown in FIG. 6, it was confirmed that the film was a highly pure BH film containing no impurities other than trace amounts of C and O.

Table 1 BH interstitial positivity compared to ASTM values) Diffraction line intensity W...Weak VS...Very strong VW...Very weak Figure 2 is a cross section showing another embodiment of the present invention In this explanatory diagram, the configuration of the device is approximately the same as the example in Figure 1, but the gas introduction nozzle 9
The structure is slightly different in that it is formed integrally with the thermionic emission source 7. That is, in this example, reactive gas such as N2 is directly injected into the thermionic emission region, so plasma formation by arc discharge is promoted, plasma density can be increased, and better film formation performance and quality can be achieved. Obtainable.

Furthermore, as shown in Fig. 1.2, in the present invention, the orientation angle θ of the electrode 5 surface that receives thermionic electrons with respect to the substrate has an influence on making the arc discharge uniform with respect to the substrate. By adjusting θ to an appropriate angle of 0° to 45°, the plasma state can be applied uniformly to the substrate.

In addition, in the above embodiment, the metal raw material B was evaporated by electron beam irradiation, but various heating and evaporation methods can be used in addition to the electron beam, such as HCD discharge and high frequency heating. When using HCD discharge, thermionic electrons are emitted from the HCD electrode, so it can also be used as a thermionic emission source, and the thermionic emission source shown in FIG. 1.2 is not required.

In addition to CBH, examples of insulating materials that can be formed into a film in the present invention include TiO2゜A1□03. Examples include SiC hard carbon (diamond, 1-C).

[Effects of the Invention] Since the present invention is configured as described above, uniform and stable arc discharge can be achieved, and a film can be formed uniformly and at high speed on a large area substrate. Furthermore, an insulating film of high purity and high adhesion to the substrate can be obtained.

[Brief explanation of the drawing]

1 and 2 are cross-sectional explanatory diagrams showing embodiments of the present invention, and 3.
, 4 is a schematic diagram explaining the conventional method, FIG. 5 is a chart showing the infrared spectrum of the CBH film obtained in the example, and FIG. 6 is a graph showing the results of Auger spectroscopy of the same CBN film. 1... Vacuum container 2... Metal evaporation source 3...
- Substrate 4... Heater 5... Electrode 6... DC power source 7... Thermionic emission source 8... AC power source 9... Gas introduction pipe 1
1...RF' source 13...Gas exhaust port 14
...Shutter 15...Electron beam gun

Claims (3)

[Claims] (1) When applying high frequency power to the substrate to form an insulating thin film on the substrate surface while maintaining the inside of the vacuum chamber at 10^-^2 Torr or less, the thermionic emission source and the electrode to which a positive potential was applied are An insulating thin film is installed between a substrate and an evaporation source, and is characterized in that the high frequency power input to the substrate is controlled to 1 W/cm^2 or more, and the negative voltage due to high frequency self-bias is controlled to 1 KV or less. Formation method. (2) An insulating thin film forming apparatus in which a substrate and an evaporation source are placed in a vacuum chamber and a high frequency voltage is applied to the substrate to form an insulating thin film on the substrate surface, in which thermionic electrons are placed between the substrate and the evaporation source. An insulating thin film forming apparatus characterized in that an emission source and an electrode to which a positive potential is applied are installed. (3) The insulating thin film forming apparatus according to claim 2, wherein the electrode surface of the electrode to which a positive potential is applied is inclined with respect to the substrate.