JPS6126597A - Method and device for forming thin film - Google Patents

Abstract

PURPOSE:To obtain a thin film having improved physical properties in a high deposition speed, by impressing a magnetic field having a component in the direction along the plate face of a substrate on which a thin film is formed, generating a gas discharge in a zone in the vicinity of the substrate. CONSTITUTION:The vacuum tank 21, the electrode 22, the gas inlet 24, the heater 26, and the magnet 25 to provide a magnetic field having a component in the direction along the plate face of the substrate 23 are set. The substrate 23 is placed on the electrode 22, a gas at a given pressure is introduced from the gas inlet 24, and the substrate is heated by the heater 26, etc. In this state, when negative voltage or high-frequency voltage is impressed to the electrode 22, discharge is started to generate the plasma 27. The plasma 27 exists locally in the vicinity of the substrate surface due to magnetic field, especially in the zone 28 wherein a magnetic field parallel to the plate face of the substrate exists, and does not extend in the whole vacuum tank. By this localization of the plasma, a high electric current value is obtained even by lowering the voltage between the substrate and the plasma, a formation speed of thin film can be extremely enlarged, and a value >=1,000Angstrom /min is easily obtained.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a thin film forming method and a thin film forming apparatus capable of forming a thin film at a high deposition rate. It is used to form a thin film by generating heat, and its field of use is mainly in the manufacture of semiconductor devices.

[Conventional technology]

Vacuum deposition methods and vapor phase growth methods are widely used to form thin films constituting semiconductor devices and the like.

In particular, in the latter vapor phase growth method, the elements that form the source of the thin film can be supplied in a gaseous state. For this reason, there is an advantage that thin films, which are difficult to form using vacuum evaporation methods, can be easily formed.

However, in the normal vapor phase growth method (CVD method), the temperature of the substrate required to form a thin film is extremely high, and as a result,
The reality is that the application area of this method is limited to an extremely narrow range. The problem of high substrate temperature was solved by exciting the plasma while supplying the gas necessary to form the thin film instead of raising the temperature of the substrate. This method is called a plasma vapor deposition method (plasma CVD method) because it uses plasma. deer,
Although thin films can be formed at lower substrate temperatures than conventional CVD methods, various problems remain.

The principle of the plasma CVD method will be described below, taking as an example a silicon nitride film that occupies an extremely important position in semiconductor devices. Figure 1 shows the widely used plasma C
It is a schematic diagram of a VD device. Electrode 12 inside vacuum chamber 11
After placing the substrate 15 on top, the gas inlet 1 provided in the vacuum chamber
4, the gas containing the elements constituting the thin film, in this case S
A mixed gas of iH4 and NH or N2 is heated to several tens of Pa.
A pressure ranging from 100 Pa to several 100 Pa is introduced. moreover,
With the substrate heated by the heater 15 or the like, a negative voltage or high frequency voltage is applied to the electrode 12 to generate plasma 16.

This plasma promotes the decomposition of SiH4, NHB and N, and the ionization and excitation of their molecules and atoms.
A silicon nitride film is formed at a relatively low substrate temperature of 300°C to 500°C.

[Problem that the invention seeks to solve]

However, in the conventional method described above, as shown in FIG. 1, plasma is generated not only near the substrate surface but also throughout the vacuum chamber. This results in several important problems.

One of the problems with the conventional method is that the thin film formation rate is slow and remains in the range of several thousand one to several hundred twenty-seven minutes. The reason for this is that the plasma spreads uniformly in the vacuum chamber9.
This is because the current value flowing into the substrate is small. On the other hand, to increase the formation rate, the value of this current must be increased, which leads to an increase in the voltage between the plasma and the substrate, which - sputter-etches the formed thin film. It's coming. For the reasons mentioned above, conventional methods have had an upper limit on the formation rate as previously mentioned. Furthermore, another problem with the conventional method is that a thin film is also formed on the inner wall of the vacuum chamber.

If the thin film formed on the inner wall of the vacuum chamber peels off during film formation, it will make the plasma unstable and impair the properties of the thin film on the substrate. For this reason, it is difficult to obtain a thin film with excellent properties unless the inner wall of the vacuum chamber is thoroughly cleaned.

In the above-mentioned embodiments, the case where an inorganic gas is used has been described, but when a gas containing an organic gas such as meta-y or ethane is introduced and a discharge is caused, a thin film made of organic material 1 is polymerized and formed. This method is sometimes called a plasma polymerization method to distinguish it from the case of inorganic materials. This plasma polymerization can also be carried out using equipment essentially similar to that shown in FIG. In this case as well, as in the case of inorganic materials, there is a drawback that the thin film formation rate is slow and a thin film is also formed on the inner wall of the vacuum chamber.

As mentioned above, conventional methods have been known to reduce the manufacturing yield and reliability of devices manufactured using thin films due to the high cost of manufacturing them. There were some drawbacks.

[Means for Solving the Problems] In order to eliminate these drawbacks, the present invention applies a magnetic field having a component in a direction overflowing to the surface of the substrate on which a thin film is to be formed, and then , causing a discharge of gas. Examples of the present invention will be shown and explained in detail below.

〔Example〕

An embodiment of the invention is shown in FIG. Similar to the conventional apparatus shown in FIG. Electrode 22° Gas inlet 24. It has a heater 26. However, unlike the conventional one, a magnet 25 is newly installed to provide a magnetic field with a component that overflows the surface of one substrate 25.

After placing the substrate 23 on the electrode 22 in such an apparatus and introducing a predetermined gas at a desired pressure from the gas inlet 24,
The substrate is heated by the heater 26.

Note that the substrate may be heated before the gas is introduced.

In this state, when a negative voltage or a high frequency voltage is applied to the electrode 22, discharge starts and plasma 27 is generated, as in the conventional case. However, due to the magnetic field, this plasma 27 is localized near the substrate surface, particularly in the region 2B where the magnetic field parallel to the plate surface of the substrate exists, and does not spread throughout the vacuum chamber. Due to this localization of the plasma, a high current value can be obtained even if the voltage between the substrate and the plasma is low.
The thin film formation speed is significantly higher than that of the conventional method, and 1
ooo;7tr.

Obtaining the above values is also easy. Furthermore, since the plasma is not distributed throughout the vacuum chamber, formation of a thin film on the inner wall of the vacuum chamber is prevented. As a result, peeling of the thin film from the inner wall of the vacuum chamber can be reduced, and plasma stability and film properties can be improved. In addition, when a magnetic field is applied externally, the gas pressure is
Plasma is generated stably even at lower temperatures than conventional ones. Therefore, it becomes easy to set the conditions for forming the thin film, and at the same time, the amount of gas that is exhausted without contributing to the formation of the thin film can be reduced.

The strength of the magnetic field, which plays an essential role in the present invention, is required to be several tens of Gauss or more. Furthermore, in the embodiment shown in FIG. 2, it is effective to place a pole piece 29 for the purpose of stabilizing the strength of the magnetic field.

Further, it is clear from the above description that the present invention is suitable for forming thin films of an extremely wide range of materials, regardless of whether they are organic or inorganic.

FIG. 3 shows a part of another embodiment of the present invention, which is aimed at making thin film formation more uniform. Substrate 31. Electrode 32. Magnet 33. and a pole piece 34. A thin film can be obtained at a particularly high formation rate in the region 35 where a magnetic field exists in a direction parallel to the surface of the substrate. However, by moving the substrate relative to the direction transverse to the magnetic field, that is, in the direction of arrow 36 in the figure, uniformity on the substrate can be achieved and the present invention can be more effectively implemented.

Incidentally, even if such an exercise is performed, the advantages of the present invention explained using FIG. 2 will not be impaired.

Here, for reference, when we compare the typical conditions in the embodiment of the present invention using the formation of a silicon nitride film similar to the conventional example, we find that the substrate heating temperature is almost the same, about 600 to 500 °C, and the applied negative voltage or The high frequency voltage may be on the same level as in conventional plasma CVD or may be lower, the applied magnetic field strength may be on the order of several tens of Gauss to 1K Gauss, and the gas pressure may be on the order of 10 to 100 lower than in the conventional plasma CVD. Plasma is generated stably even at such a low gas pressure, so when forming a silicon nitride film, it is possible to select a gas pressure from a wider range than before, and the thin film formation conditions The settings become easier. This makes it possible to vary the density, etc. of the silicon nitride film over a wide range.

〔Effect of the invention〕

As explained above, according to the present invention, since a high-quality thin film can be obtained at a high formation rate, devices using the same can be made at low cost, and furthermore, the manufacturing yield and reliability of the device can be improved. I have an invention.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a conventional plasma CVD apparatus, Figure 2
The figure is a sectional view of one embodiment of the apparatus of the present invention, and FIG. 3 is an explanatory diagram of a configuration for implementing the present invention more effectively. 11.21...Vacuum chamber, 12,22.32...
Electrode, 13, 23.31... Substrate, 14.2
4...Gas inlet, 15.26...Heater. 16.27...Plasma, 25.33...Magnet, 28...A region where a magnetic field exists parallel to the plate surface of the substrate (
(regions where plasma is particularly dense), 29.
34...Pole piece, 35...A region where a magnetic field exists in a direction parallel to the plate surface of the substrate, 36...Arrow.

Claims (3)

[Claims] (1) A step of installing a substrate on which a thin film is to be deposited in a vacuum chamber, a step of introducing a gas containing an element constituting the thin film into the vacuum chamber, and before or after the step of introducing the gas. heating the substrate on which the thin film is to be deposited, and generating a discharge of the gas in a region near the substrate in the vacuum chamber while applying a magnetic field having a component in a direction along the plate surface of the substrate; A method for forming a thin film, comprising the step of tightening. (2) a vacuum chamber, a support placed in the vacuum chamber on which a substrate on which a thin film is deposited, a means for introducing a gas containing an element constituting the thin film into the vacuum chamber, and heating the substrate; means for applying a magnetic field having a component in a direction along the plate surface of the substrate, and means for applying a negative voltage or a high frequency voltage to a region near the substrate in the vacuum chamber. . A thin film forming apparatus, characterized in that it is configured to generate a discharge of the gas. (3) a vacuum chamber, a support placed in the vacuum chamber on which a substrate is deposited, a means for introducing a gas containing an element constituting the thin film into the vacuum chamber, and heating the substrate; means for applying a magnetic field having a component in a direction along the plate surface of the substrate, and means for applying a negative voltage or a high frequency voltage to a region near the substrate in the vacuum chamber. Formation of a thin film, characterized in that the method is configured to generate a discharge of the gas, and further includes means for moving the substrate relative to a magnetic field having a component in a direction along the plate surface of the substrate. Device.