JPS6130040A - Thin film forming apparatus - Google Patents

Abstract

PURPOSE:To deposite high quality thin films on a substrate placed within a chamber by providing the main and auxiliary plasma chambers connected to each other within a reactor, generating and maintaining the stable plasma within the main chamber, guiding such plasma to the auxiliary chamber and stably maintaining weak plasma. CONSTITUTION:A substrate 7 is heated 6 up to a specified temperature, a substrate holder 3 is grounded or set 23 to a specified potential 24, and a reaction gas is supplied 18 after adjustment of flow rate through a valve 11 and a needle valve 32. The reaction chamber 1 is kept at the specified degree of vacuum with the pumps 26, 28. A high frequency voltage is applied to an electrode 19 from a power supply 5, the main plasma 8 is stably maintained by forming the main follow cathode discharge within the main chamber 80 at the pressure of 5X 10<-1>Torr with a discharge trigger 31. Thereby dispersion can be prevented with the grounded grid 22 and it is effectively extracted to the auxiliary chamber 81. The plasma in the chamber 81 is lowered but since high density plasma is successively supplied from the chamber 80, discharge is maintained stably. According to this apparatus, a high quality Si3N4 thin film can be formed, for example, on the Si substrate 7.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a thin film forming apparatus that utilizes discharge plasma and is used in the manufacture of semiconductor devices such as LSIs.

(Prior art and its problems) FIG. 5 shows a conventionally commonly used plasma CVD apparatus. Reference numeral 1 denotes a reaction vessel that can be kept airtight as required, and a high-frequency power source 5 passes a high-frequency wave from a high-frequency power source 5 to a high-frequency applying electrode 2 installed in the reaction vessel 1 through an insulator 4 for airtight sealing. A voltage is applied. On the other hand, the substrate holder 3 also serves as a ground electrode, and the heater 6
The substrate 7 can be heated to a predetermined temperature.

Reference numeral 9 indicates the direction of introduction of a predetermined gas, and the predetermined gas is introduced into the reaction vessel 1 through a valve 11 .

On the other hand, [2 is the direction of exhaust, from reaction vessel 1 to valve 1
Gas is exhausted through 3.

In this type of conventional plasma CVD apparatus, the pressure range in which the plasma 8 can be stably obtained is 0.5 to aT.

Since the pressure is limited to around rr, the operating pressure is exclusively within this range.

In the case of this device, the discharge itself is 0. Although it is possible to maintain temperatures close to ITorr, in the pressure region lower than 0.5 Torr, the state of the plasma changes significantly due to slight changes in discharge conditions (for example, deviations in high frequency matching, changes in gas flow rate, pressure, etc.) It is not possible to obtain stable plasma, and it becomes impossible to create a high-quality film. For example, the plasma CV manufactured by Nikkei ANELVA
D device PBD-301, 401 type has an operating pressure of 0.5
~l Torr.

Now, the electronic temperature T. In order to increase the pressure p, it is effective to lower the pressure p. However, as mentioned above, the conventional apparatus shown in FIG. 5 has the disadvantage that the plasma 8 becomes unstable when the operating pressure is lower than 0.5 Torr, and this instability makes it difficult to deposit a high-quality thin film. It is difficult to do so.

It is known that films of good quality can be obtained in weak plasma, that is, weak discharge plasma.

For example, strong discharges such as hollow cathode discharge and magnetron discharge operate sufficiently stably at low pressures of 0.5 Torr or less, but these discharges have high plasma density and high luminance of synchrotron radiation. However, if the substrate is placed in these discharge plasmas, the resulting film will be severely damaged by charged particles and/or synchrotron radiation.
It is not possible to obtain a good quality thin film. In addition, in the case of discharge plasma of hollow cathode discharge, the sputtering action is strong and sputtered electrode material etc. may be mixed into the produced film, resulting in the inconvenience. Therefore, if a weak discharge plasma such as that obtained with conventional equipment can be stably maintained at a sufficiently low pressure of 0.5 Torr or less, it is expected that extremely high quality thin films can be deposited in that weak plasma. Ru.

(Objective of the invention) The present invention realizes this ideal, increases the electron temperature, makes gas excitation, dissociation, ionization, etc. effective and active, and also sufficiently stabilizes the excitation, dissociation, ionization, etc. of gas, and makes it possible to achieve high quality in weak discharge plasma. It is an object of the present invention to provide a thin film forming apparatus capable of forming thin films.

(Structure of the Invention) The present invention provides two connected plasma chambers, a main and a sub-chamber, in a reaction vessel, generates and maintains a strong and stable main plasma in the main plasma chamber, and transfers the plasma to the sub-plasma chamber. The above objective is achieved by deriving the method to stably maintain the weak plasma in the secondary plasma chamber and depositing a predetermined thin film on the substrate placed in the secondary plasma chamber.

(Example) Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 1 shows an embodiment of the present invention, in which members corresponding to those in FIG. A high frequency voltage is applied to 19. 21 is a shield plate for the electrode 19. The main plasma chamber 80 is designed so that the plasma 8 is maintained stably and does not spread.
A grid 22 is provided to shield the main plasma chamber 80 and evenly draw out the secondary plasma 8° from the primary plasma chamber 80 to the secondary plasma chamber 81. In this embodiment, a mesh maintained at a ground potential is used as the four-dimensional lid 22.

The plasma in the secondary plasma chamber 81 has a low density and weak light (so-called weak plasma), but since the high-density plasma in the main plasma chamber 80 is continuously drawn out and replenished, the discharge does not occur. Sufficient stability is maintained even at pressures below 0.5 Torr.

As mentioned above, the grid 22 exclusively contains the main plasma 8.
Its mission is to confine the plasma 8" and extract and confine the plasma 8".Therefore, the grid 22 can be formed not only by the mesh shown in this embodiment, but also by a combination of round bars or by drilling holes in a flat plate. Various shapes are possible, such as the shape of
This makes it possible to increase stability. Also, grid 22
Similarly, it is desirable that the potential applied to the grid be controlled according to its shape, and sometimes a floating potential grid is effective.

A predetermined gas is supplied from the direction 9 through the valve 11 into the reaction vessel 1 through a large number of small holes provided inside the ring-shaped blow-off pipe 18, and the reaction vessel 1 is filled with the gas. Note that the flow rate of this predetermined gas introduced can be finely adjusted using the needle valve 32. The substrate holder 3 is attached to the reaction vessel 1 with an insulator 17, and is kept at a floating potential or, if necessary, set to a ground potential using a switch 23.
Alternatively, the output voltage of the power supply 24 is applied thereto.

Reference numeral 26 denotes a vacuum pump for rough evacuation, which allows rough evacuation of the inside of the reaction vessel 1 through a rough evacuation valve 25. 27 is a main valve, and 28 is a high vacuum pump.

As this high vacuum pump 28, a pump such as a diffusion pump, a turbomolecular pump, or a cryopump is used.

31 is a discharge trigger, and the commercial AC voltage ACI00■ is connected to the plug 34. f on transformer 29 through switch 33
The high voltage obtained by the neon transformer 29 is introduced into the reaction vessel 1 through the insulator 15, and serves as a discharge trigger for the main discharge.

According to the apparatus having the configuration shown in FIG.
), NH3 (partial pressure 6,0XIO-3) (therefore, total pressure 8゜0xlO-3Torr), and if a high frequency power of 13.56 MHz 200W is selected as the high frequency power source 5, even at a low pressure of 5xlO-1Torr. A stable discharge was obtained, and a silicon nitride thin film of extremely excellent quality could be obtained on the Si substrate 7.

This silicon nitride film and the conventional plasma CVD method shown in FIG.
A silicon nitride film (SiH.

10 SCCM, N 1 (320 SCCM, N
The infrared absorption spectrum of 280 SC (:M, substrate 300°C) is also shown in FIG. (1) is the infrared absorption spectrum of the film prepared with the apparatus shown in Figure 1, and (2)
is an infrared absorption spectrum of a film produced using the conventional plasma CVD apparatus shown in FIG. Note that both films had the same refractive index of 2°00.

In a silicon nitride film, it is known that the presence of 5i-H bonds and N-H bonds causes deterioration in film quality, but the film (1) prepared in this example has a comparison of absorption intensity of 1180 am-'. It is estimated that the content of N--H bonds is considerably reduced. This improvement in film quality is thought to be due to the lower operating pressure, which caused the electron temperature to rise and the decomposition of NH3 to progress.

Furthermore, in the apparatus shown in FIG. 1, excellent experimental results have been confirmed that when the introduced gas is only SiH4, an a-3i:H film with a very low H content can be obtained. Another embodiment of the invention is shown in FIG. Components corresponding to those in FIG. 1 are given the same reference numerals. Reference numeral 35 denotes a high frequency application electrode made of a magnet, and the magnetron discharge generated in this part has a remarkable effect of maintaining the discharge under high vacuum. The pressure range in which stable discharge is maintained varies depending on the potential shape of the grid 22 described above as well as the strength of the magnet, but for example, even if a fairly rough open grid 22 is used, the magnet surface is It has been confirmed that in the case of Gaussian magnetic flux density, stable discharge can be obtained up to pressures around 5xlO-3 Torr.

The quality of the deposited film obtained with the apparatus shown in FIG. 3 shows the same tendency as in the example using the hollow cathode type high-frequency application electrode shown in FIG. A good film was obtained.

Further, an embodiment of the present invention is shown in FIG. Figure 1.

Components corresponding to those in FIG. 3 are given the same reference numerals. This embodiment is an improved version of the embodiment shown in FIG.
It has a structure in which the directly introduced gas is directly introduced into the main discharge part inside the hollow cathode type high frequency application electrode 19 through the needle valve 32. This will make it even more effective.

Furthermore, an improved version of the device shown in FIG. 4, in which the high-frequency applying electrode 35 made of a magnet shown in FIG. 3 was used in the electrode portion, also showed excellent effects.

In addition to the embodiments shown in Figs. 1, 3, and 4, the shape and structure of the discharge electrode, the shape of the grid, and the mode of excitation were changed to create a structure that is stable in a pressure region of 0.5 Torr or less. Generate the main plasma, and from this generation part,
The apparatus for directing the secondary plasma and depositing the film on the substrate with the secondary plasma can be configured in a variety of ways. The present invention is not limited to each structure of the above embodiments.

(Effects of the Invention) As explained above, the present invention produces extremely high quality thin films in a thin film manufacturing process. The present invention greatly contributes to semiconductor manufacturing equipment and other film forming equipment, and can be said to be an industrially useful invention.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the apparatus according to the invention. Figure 2 shows the infrared absorption spectrum of a film created using a conventional plasma CVD device and the high vacuum plasma CVD method of the present invention.
FIG. 3 is a diagram showing an infrared absorption spectrum of a film produced by apparatus D. FIGS. 3 and 4 are diagrams showing other embodiments of the present invention. FIG. 5 is a diagram showing a conventional plasma CVD apparatus. 1 reaction vessel, 3 substrate holder, 5 high frequency power supply, 6 - heater, 7 ° substrate, 8 main plasma, 8 ° secondary plasma, 22 grid, 80 main plasma chamber, 81 secondary plasma chamber. Patent applicant: Nichiden Anelva Co., Ltd. FIG. 2

Claims (6)

[Claims] (1) In a thin film production device that introduces a specified gas into a reaction vessel and creates a thin film using the plasma of the gas generated by electric discharge, the main plasma chamber has a stable pressure of 5 x 10^-^1 Torr or less. It is characterized by generating and maintaining a main plasma discharge, guiding the plasma to a secondary plasma chamber to maintain this secondary plasma discharge, and depositing a predetermined thin film on a substrate placed in the secondary plasma chamber. Thin film creation device. (2) The main plasma discharge is a hollow cathode discharge and/or a magnetron discharge. A thin film forming apparatus according to claim 1. (3) The thin film forming apparatus according to claim 1 or 2, characterized in that at least a portion of the predetermined gas is introduced directly into the main plasma chamber. (4) Claims 1, 2, or 3, characterized in that a grid is used as a wall that partitions the main plasma chamber and/or the secondary plasma chamber within the reaction vessel.
The thin film forming apparatus described in . (5) The thin film forming apparatus according to claim 4, wherein the potential of the grid is controlled to a predetermined value. (6) The thin film forming apparatus according to claim 4, wherein the potential of the grid is a floating potential.