JPH0452612B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to an improvement in a method for dry cleaning a film forming apparatus.

(b) Background of technology In the manufacturing process of semiconductor devices, thin films such as polycrystalline silicon (Si), silicon dioxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), or phosphosilicate glass (PSG) are deposited on substrates. It is often done to form These thin films are often formed by a chemical vapor deposition method (hereinafter abbreviated as CVD method), but sputtering methods are also used.

As the scale of integration of semiconductor integrated circuit devices increases, it becomes increasingly necessary to improve their reliability, and it is becoming increasingly important to improve thin film characteristics and reduce defects in the thin film forming process.

(c) Prior art and problems As is well known, thin film formation by CVD method, sputtering method, etc. is performed in a sealed device.
The thin film forming substance is widely deposited not only on the target substrate but also on various parts of the manufacturing apparatus, such as the electrodes supporting the substrate and the inner walls of the apparatus. The film deposited on each part of the device becomes a source of contamination, for example by peeling off and falling, and must therefore be removed frequently.

It is troublesome to disassemble and clean such a device in order to remove the film that has adhered to the inside of the device, and a dry cleaning method that performs dry etching by forming plasma inside the device that reaches the inner walls, etc. is preferred.

FIG. 1 is a schematic diagram showing an example of dry cleaning of a plasma CVD apparatus. In the figure, 1 is a substrate device, 2 is an upper electrode, 3 is a cleaning electrode, 4 is a chamber wall, 5 is a gas introduction pipe, and 6 is an exhaust pipe. Thin film formation using this device is performed on the substrate electrode 1.
This is usually done by applying high frequency power between the electrode 2 and the upper electrode 2 to turn the raw material gas into plasma. At this time, as described above, the thin film-forming substance is deposited on the substrate electrode 1 as well as on the inner surface of the chamber wall 4.

When this adherent material is silicon-based as mentioned above, in conventional dry cleaning, the etchant is, for example, a mixed gas of carbon tetrafluoride (CF ₄ ):oxygen (O ₂ )=80:20, or A mixed gas of about 80:20 of sulfur fluoride (SF ₆ ) and oxygen (O ₂ ) is used. That is, the pressure at which these etchant gases are introduced into the damper through the gas introduction pipe 5 is set to, for example, about 1 [torr], and between the substrate electrode 1 and the upper electrode 2, or between the substrate electrode 1 and the cleaning electrode 3, for example. Plasma is generated by applying high frequency power of about 0.3 [W/cm ² ], and the film deposited inside the device is etched away. In this etching, the cleaning electrode 3 has the effect of spreading the plasma widely within the apparatus and etching the inner wall surface of the chamber.

However, when using the conventional etchant gas, there is a problem that the etching rate is low and the dry etching process takes a long time.

That is, for example, when the deposited film is Si ₃ N ₄ , in the example of CF ₄ +O ₂ described above, the etching rate of both the electrode part and the inner wall of the chamber is about 100 [nm/min], and the etching rate of SF ₆ +O 2 is about 100 [nm/min]. In example ₂ , the dissociation rate is low and the spread of the plasma is less than that of CF ₄ + O ₂ , so the velocity is about 600 [nm/min] at the electrode, but 100 [nm/min] at the inner wall of the chamber.
The speed remains at about [min].

As mentioned earlier, the need for dry cleaning of plasma CVD equipment, low pressure CVD equipment, sputtering equipment, etc. is increasing in order to ensure and improve the reliability of semiconductor devices, and it is becoming more and more effective to clean these equipment in a shorter time than before. There is a need for a method that can be implemented in a consistent manner.

(d) Purpose of the Invention The object of the present invention is to provide a dry cleaning method that removes at a high etching rate a film containing silicon deposited inside a film forming apparatus by methods such as plasma CVD, low pressure CVD, and sputtering. shall be.

(e) Structure of the Invention The object of the present invention is to generate plasma using a mixed gas containing carbon tetrafluoride, sulfur hexafluoride, and oxygen in a film forming apparatus having a plasma generation electrode. This is accomplished by a dry cleaning method that removes the silicon-containing film deposited inside the device by etching.

(f) Examples of the invention The present invention will be specifically explained below using examples.

The film forming apparatus to which the present invention is applied is, for example, a plasma CVD apparatus as shown in FIG. 1, or a sputtering apparatus as schematically shown in FIG. Of course, it is necessary to have a means for forming the

In the sputtering apparatus shown in FIG.
1 is a substrate electrode, 12 is a target, 13 is a cleaning electrode, 14 is a chamber wall, 15 is a gas introduction pipe, 16 is an exhaust pipe, 17 is a cathode, 18 is an anode, and 19 is a shielding plate. is placed in front of the target to protect it during cleaning.

In the present invention, a mixed gas of CF ₄ , SF ₆ , and O ₂ is used as an etchant gas for cleaning, and the flow rate ratio is approximately 20 to 60 [%] for each of CF ₄ and SF ₆ , and 20 [%] for O _2. ] degree. Generally, when the flow rate ratio of CF ₄ is increased, the plasma spreads well, and when the flow rate ratio of SF ₆ is increased, the plasma tends to gather between the electrodes. Depending on factors such as distribution, CF ₄ and
Select the optimal value of flow ratio with SF ₆ . As is already known, O ₂ has the effect of inhibiting the formation of non-volatile polymers.

For example, the flow rate ratio of the mixed gas according to the present invention is
CF ₄ :SF ₆ :O ₂ =40:40:20, the pressure inside the device is about 1 [torr], and the substrate electrode 1 or 1
1 and the cleaning electrode 3 or 13, for example.
If a high frequency power of about 0.3 [W/cm ² ] is applied to generate plasma, for example, the deposited film becomes Si ₃
When using N ₄ , an etching rate of about 500 [nm/min] can be obtained for both the electrode section and the chamber inner wall section. That is, as mentioned earlier
It is possible to realize high-speed etching on the entire inside of the device, which is close to the etching speed obtained only on the electrode portion in the conventional example using SF ₆ +O ₂ .

The mixed gas according to the present invention includes, in addition to silicon nitride (Si ₃ N ₄ ), polycrystalline silicon (Si), silicon dioxide (SiO ₂ ), silicon carbon monoxide (SiO), silicon oxynitride (SixOyNz), and silicate glass. Similar effects can be obtained with silicone-based deposits such as .

Furthermore, the structure and electrode arrangement of the film forming apparatus are not limited to the structures exemplified above, and the present invention can be applied to apparatuses having similar structures.

(g) Effects of the Invention As explained above, according to the present invention, dry cleaning for removing silicon-containing films deposited on the inside of film forming equipment, which is often used in the manufacturing process of semiconductor devices, etc., can be efficiently carried out. This makes it possible to achieve the effect of promoting improvements in the reliability and characteristics of semiconductor devices and the like.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are schematic diagrams showing an example of a film forming apparatus to which the present invention can be applied. In the figure, 1 and 11 are substrate electrodes, 2 is an upper electrode, 3 and 13 are cleaning electrodes, 4 and 14 are chamber walls, 5 and 15 are gas introduction pipes,
6 and 16 are exhaust pipes, 12 is a target, 17 is a cathode, 18 is an anode, and 19 is a shielding plate.

Claims (1)

[Claims] 1. Plasma is generated using a mixed gas containing carbon tetrafluoride, sulfur hexafluoride, and oxygen in a film forming apparatus having a plasma generation electrode, and a film containing silicon deposited inside the apparatus is etched. A dry cleaning method characterized by removing.