JPH0625859A - Cvd film forming device and plasma cleaning method - Google Patents

Abstract

PURPOSE:To hold the quality of the next CVD film at a high grade without lowering a cleaning speed by mounting a specific protective jig to an electrode imposed with the substrate at the time of subjecting the excess CVD film sticking to the electrode in the CVD film forming device to plasma cleaning. CONSTITUTION:The substrate 107 consisting of a semiconductor, etc., is mounted to a lower electrode 103 in a vacuum chamber 104 and is disposed to face an upper electrode 102; thereafter, a gaseous mixture composed of SiH4 and N2O is introduced from a gas introducing port 105 of the upper electrode 102 and a high-frequency voltage is impressed to the two electrodes 102, 103 by a high-frequency power source 101, by which an SiO2 CVD film is formed on the substrate 107. The excess SiO2 film is stuck on the upper electrode 102 and the inside surface of the vessel 104 as well and, therefore, the lower electrode 103 of the small deposition of the excess SiO2 is coated with a protective jig 108, such as Si substrate, after the substrate 107 is taken out of the vacuum chamber 104; thereafter the etching gas mixed with a fluoride gas such as CF4 and O2 is introduced into the vessel 104 and the high-frequency voltage is impressed between the two electrodes 102 and 103. The excess SiO2 film is thus removed and cleaned by plasma cleaning.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CVD film forming apparatus and a plasma cleaning method.

[0002]

2. Description of the Related Art In a conventional method for cleaning a CVD film forming apparatus, taking a method for producing a silicon oxide film by a plasma CVD method as an example, electrodes 202 and 203 whose surfaces are insulated are arranged in parallel as shown in FIG. Then, the silicon substrate 207 on which the CVD film is to be deposited is conveyed into the vacuum container 204 kept at a constant temperature, the interior of the container is evacuated, and then monosilane and nitrous oxide are flown. After the flow rate and the pressure of the gas reach a predetermined value, a high frequency (RF) is applied to the electrode, and the silicon oxide film is vapor-grown for a certain period of time.
Stop F). After the gas in the container is exhausted by vacuuming, the substrate 207 is carried out.

After the substrate is carried out, a mixed gas of fluorine-based etching gas such as NF ₃ and CF ₄ and O ₂ or N ₂ O is flown and RF is applied to form an extra gas formed in the vacuum container. A so-called plasma cleaning for etching away a different silicon oxide film was performed.

[0004]

If a large amount of extra CVD film remains in the reaction vessel, it is likely to peel off and adhere to the semiconductor substrate. The extra CVD film attached to the semiconductor substrate causes a decrease in yield of the semiconductor device and a reliability problem. Therefore, it is necessary to keep the inside of the reaction container clean, and the plasma cleaning time is lengthened. There is a need. 1 at a time in one reaction vessel
In a so-called single-wafer CVD film forming apparatus for growing a single CVD film, plasma cleaning is required every time one semiconductor substrate is formed.

However, an extra CV is formed around the electrodes.
Although the D film is deposited, the surplus CVD film is not deposited because the surface of the lower electrode is covered with the semiconductor substrate. According to the conventional technique, when the inside of the reaction vessel is plasma-cleaned, the etching of the electrode surface ends early and is over-etched. Excessive etching of the electrodes
The life of the electrode itself is shortened, the production of the plasma CVD film becomes unstable, and at the same time, the quality of the electrode is deteriorated, causing a reliability problem.

In order to reduce the damage due to overetching of the electrodes, it is necessary to reduce the RF output.
At the same time, the etching rate also decreases. In the single-wafer CVD film forming apparatus, the solution by reducing the RF output cannot be adopted because the decrease in the etching rate affects the mass productivity.

However, the present invention is intended to solve such a problem, and an object of the present invention is to perform proper etching without lowering the etching rate during plasma cleaning of a CVD film forming apparatus.
A VD film forming apparatus and a plasma cleaning method are provided, and by extension, a CVD film having stable quality is provided with high productivity.

[0008]

A CVD film forming apparatus according to the present invention is characterized in that 1) a jig for protecting electrodes during plasma cleaning is provided in a preliminary exhaust chamber, and a mechanism for protecting electrodes during cleaning is provided. To do.

2) The above-mentioned jig for protecting electrodes is a silicon substrate.

3) The above-mentioned jig for protecting electrodes is made of aluminum or an aluminum alloy.

In the plasma cleaning method according to the present invention, the CVD film forming apparatus is used to: a) apply a high frequency (RF) to remove the CVD film on the electrode surface; and b) cover the electrode with a jig. The process is characterized by comprising the following steps: c) removing excess CVD film in the reaction chamber.

[0012]

Embodiments of the present invention will now be described in detail with reference to the schematic sectional view of FIG. 1 and the timing chart of FIG. 2 by taking the formation and cleaning of a 600 nm silicon oxide film as an example. Note that FIG. 1A is a sectional view in which the vacuum container is vertically divided, and FIG. 1B is a sectional view seen from above.

First, the semiconductor substrate (wafer) 107 contained in the cassette 110 is set outside the CVD film forming apparatus. During the cleaning (C
Jig 10 to protect the electrode against VD film etching)
8 are installed. In addition, a standby place 111 in which a plurality of semiconductor substrates can be installed is prepared in the preliminary exhaust chamber.
The semiconductor substrate 107 on which semiconductor elements such as transistors and resistors and aluminum wiring are formed is used as the cassette 11
It is transported from 0 to the preliminary exhaust chamber 109. Preliminary exhaust chamber 10
9 is evacuated to the same pressure as the vacuum container 104. The inside of the vacuum container 104 is maintained at about 400 ° C., and the insulated upper electrode 102 and lower electrode 103 are arranged in parallel. The electrode and the semiconductor substrate 107 are moved to a predetermined position, and a frequency of 13.5 is applied to the electrodes 12 and 13 under the conditions of monosilane gas of about 100 SCCM, nitrous oxide gas of about 1500 SCCM and pressure of about 5 Torr.
Applying a high frequency (RF) of 500W at 6MHz for 50 seconds, about 60
A 0 nm silicon oxide film is formed.

After the substrate on which the silicon oxide film has been formed is unloaded, an electrode protection jig 108 made of a silicon substrate installed in the preliminary exhaust chamber is transported to the vacuum container 104 to cover the lower electrode 103. After this, CF ₄ 100SCCM, O
₂ Introduce 200SCCM into the vacuum vessel and control the pressure to 2 Torr. After the gas flow rate and pressure reach the set values, the upper electrode 10
2 and lower electrode 103, frequency 13.56MHz, output 700
A radio frequency (RF) of W is applied for 50 seconds. The silicon oxide film in the reaction vessel is decomposed and removed by the reaction with the etching gas turned into plasma. After the etching is completed, the electrode protection jig is taken out of the vacuum container and returned to the standby position in the preliminary exhaust chamber. This deposition and cleaning process is repeated for the number of semiconductor substrates installed in the preliminary exhaust chamber.

After the deposition of the last semiconductor substrate placed in the preliminary exhaust chamber 109 is completed, the electrode protection jig 108
When the cleaning is started by putting it in the vacuum container, the preliminary exhaust chamber 109 is filled with nitrogen, and the semiconductor substrate 107 on which the silicon oxide film is formed is returned to the cassette 110.
After the preliminary evacuation chamber 109 is evacuated, the electrode protection jig is carried out of the vacuum container and returned to the standby position in the preliminary evacuation chamber.

In an apparatus that does not have a mechanism for holding a semiconductor substrate in the preliminary exhaust chamber, as shown in FIG. 3, during cleaning of the vacuum container 104, the preliminary exhaust chamber 109 is filled with nitrogen to fill the silicon oxide. The film-formed semiconductor substrate 107 is returned to the cassette. When a plurality of semiconductor substrates are continuously processed, the next semiconductor substrate is transferred into the preliminary exhaust chamber. After the preliminary exhaust chamber 109 is evacuated, the electrode protection jig 108 is returned from the reaction chamber plasma-cleaned by the etching gas to the standby position in the preliminary exhaust chamber. Then, the process of carrying the semiconductor substrate into the reaction chamber and performing deposition is repeated.

Lower electrode 103 during plasma cleaning
Is not excessively etched because it is covered with the electrode protection jig 108, and the excess silicon oxide film deposited on the outer periphery of the vacuum container and the surface of the upper electrode 102 is efficiently decomposed and removed. Therefore, the etching time does not increase.

Further, the electrode protection jig 108 is installed in the preliminary exhaust chamber, and the inside of the vacuum container is cleaned while the semiconductor substrate is transferred between the cassette and the reaction chamber.
It also becomes possible to prevent a decrease in mass productivity.

Regarding the jig for protecting the electrode, here,
Although a silicon substrate is used as an example, the reaction temperature is 40
If the temperature is about 0 ° C., a material such as aluminum or its alloy that is less likely to be deteriorated by an etching gas can be applied without any particular problem. The silicon substrate can also be applied to tungsten CVD which requires a reaction temperature of 500 ° C. or higher. This jig can be repeatedly used until the generation of foreign matter increases due to deterioration, which is advantageous in terms of mass productivity.

The shape of the jig is preferably the same as or smaller than that of the semiconductor substrate.

Although a monosilane-nitrous oxide-based silicon oxide film has been described here, a TEOS-oxygen-based silicon oxide film, a monosilane-ammonia-based silicon nitride film, and a WF ₆ / H ₂ -based film are used. Similar results were obtained for cleaning a CVD film such as a tungsten film. Further, there is no problem with the silicon oxide film doped with impurities such as P (adjacent) and B (boron), and C
The present invention can be applied regardless of whether or not RF is applied when the VD film is formed. Particularly, it is effective for a single-wafer CVD film forming apparatus that alternately performs deposition and plasma cleaning, but it is also applicable to the case where a plurality of electrodes are provided in the same reaction container and a large number of semiconductor substrates are processed at the same time. is there.

As for the etching gas, in addition to CF ₄ / O ₂ , C ₂ F ₆ / O ₂ , NF ₃ / O ₂ and NF ₃ corresponding to the CVD film are used.
A gas such as / N ₂ O is also applicable. In particular, with NF ₃ / O ₂ and NF ₃ / N ₂ O based etching gas, the deterioration of the silicon substrate is small, the quality can be maintained for a long time, and the mass productivity is improved. Also, C ₂
In the conventional F ₆ / O ₂ system etching, deterioration of the lower electrode was remarkable and it was necessary to replace it once every 5,000 sheets.
It is possible to use 000 sheets continuously, which contributes to stable quality and improved productivity.

[0023]

As described above, according to the present invention, it becomes possible to supply a stable CVD film for a long period of time without lowering the mass productivity by protecting the electrodes during plasma cleaning, and at the same time The reliability can be improved. Further, the longevity of the electrodes improves mass productivity.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a CVD film forming apparatus according to an embodiment of the present invention.

FIG. 2 is a timing chart showing a method of manufacturing a semiconductor device according to an embodiment of the invention.

FIG. 3 is a timing chart showing a method for manufacturing a semiconductor device according to an embodiment of the present invention.

FIG. 4 is a schematic sectional view of a conventional CVD film forming apparatus.

[Explanation of symbols]

 101, 201 ... RF oscillator 102, 202 ... Upper electrode 103, 203 ... Lower electrode 104, 204 ... Vacuum container 105, 205 ... Gas inlet 106, 206 ... Gas outlet 107, 207 ... Semiconductor substrate 108 ... Electrode protection jig 109 ... Preliminary exhaust chamber 110 ... Cassette 111 ... Standby place for semiconductor substrate

Claims (4)

[Claims] 1. A CVD method for removing an excess CVD film (chemical vapor deposition film) in a reaction chamber by introducing a cleaning gas into the reaction chamber and applying a high frequency (RF).
In the film forming apparatus, a jig for protecting the electrode during plasma cleaning is provided in the preliminary exhaust chamber, and the CVD film forming apparatus has a mechanism for protecting the electrode during plasma cleaning. 2. A CVD film forming apparatus, wherein the electrode protecting jig according to claim 1 is a silicon substrate. 3. A CVD film forming apparatus, wherein the jig for protecting the electrode according to claim 1 is an aluminum or aluminum alloy substrate. 4. Using the CVD film forming apparatus according to claim 1, a) applying a high frequency (RF) to remove the CVD film on the electrode surface, and b) covering the electrode with a jig. A plasma cleaning method comprising the steps of: (c) removing excess CVD film in the reaction chamber.