JPS627852A - Formation of thin film - Google Patents

Abstract

PURPOSE:To increase the deposition rate of a film and to improve productivity in the stage of forming the thin film by a sputtering method by specifying the surface shape of a target material. CONSTITUTION:An Si substrate as a substrate 17 to be treated is installed on a lower electrode 13 and the inside of a vacuum vessel 11 is evacuated to a prescribed degree of vacuum in the stage of forming, for example, a silicon oxide film by a sputtering device. For example, gaseous Ar is introduced into the vessel from an introducing port 18 and the inside of the vessel 11 is maintained under a prescribed gaseous pressure. A high-frequency power source 15 is then turned on to impress the prescribed high-frequency voltage between upper and lower electrodes 12 and 13 to generate an electric discharge so that the target material 16 is sputtered by Ar ions and the silicon oxide film is deposited on the substrate 17. The surface shape of the material 16 is thereby made into a recessed shape. Then the released atoms are directed toward the substrate 17 to be formed with the film thereon and the deposition rate is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for forming a thin film, and particularly to improvement of a target material in a sputtering method.

[Technical Background of the Invention and Problems Therewith] Sputtering is a widely used method for forming a thin film on a substrate such as a semiconductor wafer. In general sputtering method, 10-1 to 10
', a discharge is generated in a vacuum of about [Torr], and cations are accelerated by the cathode falling voltage and collided with the cathode, and at this time, due to sputtering of the cations, atoms are emitted from the target material placed on the cathode part. A thin film is formed by depositing on a substrate.

However, this method has the problem that the film deposition rate is slow and it takes a long time to obtain a film of a desired thickness. In this method, incoming positive ions impart part of their kinetic energy to the constituent atoms of the target as a result of elastic scattering with the constituent atoms in the process of penetrating into the target. When the kinetic energy is sufficient to overcome the potential barrier formed by the constituent atoms surrounding the constituent atoms, the atom is knocked-on from the lattice point;
Furthermore, by successively colliding with nearby constituent atoms, a so-called collision cascade (knock-on cascade) is created.
ade) occurs. When this collision cascade reaches the target surface, if the kinetic energy of the atoms near the surface of the target is sufficient to exceed the surface binding energy, the atoms will be ejected from the target surface into the vacuum.

Therefore, it is assumed that most of the sputtered atoms are ejected from the first and second layers on the target surface, and the surface atoms are sequentially scraped off by sputtering.

Therefore, the film deposition rate can be increased to some extent by increasing the number of released atoms, that is, by changing sputtering conditions such as power output and pressure. However, even if the sputtering conditions are improved in this way, the deposition rate of an insulating film such as a silicon oxide film is only 100 [A/
min,], and it takes a long time to form a thick film, and the slow deposition rate remains a serious problem in sputtering.

By the way, it has been common practice to use a target material with a flat surface shape, but when the surface shape is flat, as mentioned above, the atoms near the surface of the target are emitted. Therefore, the ejected atoms are affected by the surface shape and spread over a wide range. It is thought that this reduces the rate of atoms reaching the substrate, slowing down the film deposition rate.

[Object of the Invention] The present invention has been made in view of the above-mentioned circumstances, and basically aims at increasing the film deposition rate without improving the sputtering apparatus and improving productivity.

[Summary of the Invention] Therefore, the present invention focuses on converging atoms emitted from a target material by sputtering and increasing the rate of reaching the substrate. By making the shape concave, the emitted atoms are directed toward the substrate on which the film is to be formed, increasing the deposition rate.

That is, by processing the peripheral part of the target material to be thicker than the central part, atoms flying out of the target material are focused, the rate of atoms reaching the substrate is increased, and the film deposition rate is increased.

[Effects of the Invention] According to the present invention, since the surface of the target material is made concave, the ejected atoms are focused and the rate of reaching the substrate is increased, and the deposition rate of the thin film is increased, resulting in a significant increase in productivity. improve.

Furthermore, there is no need to make any improvements to the sputtering apparatus itself, and the sputtering apparatus can be implemented simply by changing the shape of the target material, so it is easy to manufacture and has great practical advantages.

[Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing a schematic configuration of a sputtering apparatus used in the method of the embodiment of the present invention.

This sputtering apparatus is composed of a vacuum chamber 11 (sputter chamber), and a flat upper electrode (cathode) 12 and a lower electrode 13 (anode) which are arranged facing each other in the vacuum chamber.

A high frequency power source 1 is connected to the upper electrode 12 via a matching pin 14.
High frequency power is supplied from 5. Further, on the lower surface of the upper electrode 12, a target material 16 made of quartz glass (SiOz) is placed, for example, in the case of forming a silicon oxide film.
is installed.

As shown in the cross-sectional view of FIG. 2 (FIGS. 1 and 2 are not to scale), this target material 16 has a main surface that is part of a spherical surface and has an arcuate cross-section. The thickness is t1=10 [#] at the center and t2”3 at the periphery.
It is in the shape of a disc with a diameter R of 20 cm.

Further, the lower electrode 13 is normally grounded, and a substrate 17 to be processed, such as a semiconductor wafer, is placed thereon.

Furthermore, a gas inlet 18 for introducing gas and a gas outlet 19 for discharging gas are provided on both sides of the vacuum container 11 to face each other.

In addition, in FIG. 1, 20.21 represents both electrodes 12.13, respectively.
This is an insulating material for electrically insulating the vacuum container 11 and the vacuum container 11.

Next, a method for forming a silicon oxide film using the above sputtering apparatus will be described.

First, a silicon substrate as a substrate to be processed 17 is placed on the lower electrode 13, and the inside of the vacuum chamber 11 is heated to 1×10-6 [Tor].
After evacuation to a degree of vacuum of approximately
The gas pressure inside the vacuum container 11 is maintained at 10 mtorrl.

Next, the high frequency power supply 15 is turned on and, for example, 1 [KW
] is applied to generate a discharge between the upper electrode 12 and the lower electrode 13, the target material 16 is sputtered with argon ions, and a silicon oxide film is deposited on the silicon substrate 17. At this time, the distance between the target material 16 and the silicon substrate 17 is 7.5 [Cl1l].

When a silicon oxide film was formed on a silicon substrate in this manner, the deposition rate was 320 [A/min].

When a target material with a flat surface is used as in the past, the deposition rate under the same conditions is 100 [A/
min, 1 F atta.

That is, according to the method of the embodiment of the present invention, a deposition rate three times or more can be obtained compared to the conventional method.

Although the shape of the main surface of the target material is a part of a spherical surface in the example and has an arcuate cross section, it is not necessarily limited to this, and may be a surface having multiple tapers. It may be a composite surface, as long as it has a shape where the peripheral part is thicker than the central part, that is, the surface is concave so that the emitted atoms are focused.

Further, it goes without saying that the material of the target material is not limited to quartz glass, and may be appropriately selected as necessary.

Furthermore, the configuration of the device is not limited to the embodiments, and the present invention includes a magnetron sputtering device in which a magnet is placed on an upper electrode supporting a target material to cause drift movement of electrons in an electromagnetic field space, and a target material to be processed. Appropriate bias voltage is also applied to the lower electrode on which the substrate is placed so that some of the ions flow into the vicinity of the surface of the substrate to be processed.During the deposition process, the surface of the substrate to be processed is bombarded by the ions and the deposited film is The present invention is also effective with other devices such as a bias sputtering device that purifies the deposited film by ejecting the gas adsorbed on the surface.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a schematic configuration of a sputtering apparatus used in the method of an embodiment of the present invention, and FIG. 2 is a sectional view showing the shape of a target material used in the method. 11... Vacuum container, 12... Upper electrode, 13...
Lower electrode, 14... matching box, 15... high frequency power supply,
16...Target material, 17...Substrate to be processed, 1
8... Gas inlet, 19... Gas outlet, 20.2
1...Insulating material. Figure 1 Figure 2

Claims (1)

[Claims] In a thin film forming method in which a target material is sputtered with ions generated by electric discharge to deposit a thin film on a substrate to be processed, the target material is 1. A method for forming a thin film, characterized in that a thin film formed with a concave surface is used.