JPH0242724A - Treating method - Google Patents

Abstract

PURPOSE:To enable cleaning treatment to be carried out in a short time by introducing a cleaning gas into a treating container and convert the gas into plasma in the electric and magnetic field environment within the treating container. CONSTITUTION:A cleaning gas is introduced into a gas introduction chamber 11a by decompressing the interior of a vacuum container 11 to a predetermined pressure. Then, an annular magnetic coil 15 is electrified to form a magnetic field A in the vacuum container 11, and further, high frequency power is supplied to a high frequency electrode 17 to form an electric field B in the vacuum container 11. The kinetic energy of electrons provided by the cycloid motion thereof is used as the energy to convert the cleaning gas (NF3) into plasma, and the interior of the vacuum container 11 is cleaned by the collision and the chemical reaction of this plasma. Thus, high energy plasma is formed and the interior of the treating container, etc., can be cleaned perfectly in a short time.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a processing method.

(Prior art) As a method of forming a thin film on a substrate such as a semiconductor wafer,
Conventionally, CVD (chemical vapor d)
eposit4on) is often used. This CV
D is performed using, for example, a cold wall type CVD apparatus. A cold wall CVD apparatus heats a substrate via a susceptor in order to suppress reactions in a gas phase. Figure 4 shows cold wall type CV.
An example of D device is shown. This device is.

It is inserted into the processing container 1 through a stepped cylindrical processing container 1 and an opening provided at the bottom of the processing container 1,
It includes a cylindrical high frequency electrode 5 connected to a high frequency power source 6. A flange is provided on the lower circumference of the cylindrical high-frequency electrode 5, and this flange is fixed to the bottom surface of the processing container 1 via a ring-shaped insulating member 8.

The upper small cylindrical part of the stepped cylindrical processing container 1 is the gas introduction chamber 1
a, and the lower large cylindrical portion is the processing chamber 1b. A gas introduction pipe 4 for introducing source gas is provided on the upper surface of the gas introduction chamber 1a. In addition, on the side of the processing chamber 1b,
A gas exhaust pipe 9 is provided for exhausting raw material gas. Further, inside the processing chamber 1b, a susceptor 3 for placing and heating a substrate 2, which is an object to be processed, is arranged.

Formation of a thin film using the cold wall type CVD apparatus shown in FIG. 4 is carried out as follows. First, the pressure inside the processing container 1 is reduced to a predetermined pressure. Next, a raw material gas for forming a thin film is introduced from the gas introduction pipe 4 into the processing chamber Ib through the gas introduction chamber 1a. After introducing the raw material gas into the processing chamber Ib, a thin film is formed by normal thermal CVD. After forming the thin film, the gas is discharged from the gas discharge pipe 9.

In the cold wall CVD apparatus described above, a zero cleaning process using plasma is usually performed on the surface of the object to be processed, such as a semiconductor wafer, as a pretreatment. This is to remove a natural oxide film or the like formed on the surface of the substrate. The natural oxide film formed on the surface of the wafer acts as an electrically insulating film, so 4M, 16M
It is desirable to remove them as the integration becomes higher. Similarly, it is desirable to remove undesirable impurities deposited on the inner walls of the reaction vessel and the surface of the susceptor. This is because when forming a thin film on the wafer surface, these impurities may peel off and adhere to the wafer.

The cleaning process described above can be used to remove impurities deposited not only on the wafer surface but also on areas other than the wafer. This cleaning process is generally performed as follows. - First, a chemically stable leaning gas is introduced into the processing container 1 instead of the raw material gas.

Thereafter, a high frequency current is supplied to the high frequency electrode 5 to turn the gas introduced into the processing container 1 into a plasma state. Then,
The object to be cleaned is cleaned by etching it with this plasma. Such a leaning technique is disclosed in, for example, Japanese Patent Laid-Open No. 142839/1983.

(Problems to be Solved by the Invention) By the way, the above-mentioned CVD apparatus generally takes up a large space on the wafer. This improves the flow of raw material gas by taking up a large space above the wafer.
This is also to increase the ratio between the amount of raw material gas supplied into the processing container and the amount of raw material gas consumed within the processing container. Thereby, uniform film thickness and film quality can be ensured. Therefore, CVD apparatuses typically operate by applying a high-frequency electric field between a high-frequency electrode and the inner wall of a processing chamber, which corresponds to a ground electrode. As a result, the distance between the electrodes becomes longer and the strength of the electric field generated between the high-frequency electrode and the processing container becomes weaker, making it difficult to obtain high-energy plasma necessary for etching. As a result, the wafer surface, susceptor surface, etc. cannot be completely cleaned. Furthermore, since the energy of the generated plasma is low, there is a problem in that the time required for cleaning becomes longer and the time required for one entire operation becomes longer.

The present invention has been made in view of the above-mentioned problems, and provides a processing method that completely cleans the inside of the processing container and the object to be processed before processing, thereby allowing for good processing. be.

[Structure of the invention]

(Means for Solving the Problems) The present invention includes a step of introducing a cleaning gas into a processing container, and cleaning the inside of the processing container by converting the cleaning gas into plasma in an electric field and magnetic field atmosphere inside the processing container. The present invention provides a processing method characterized by comprising a step of performing the following steps.

Furthermore, the present invention provides a processing method characterized in that the inside of the processing container is cleaned in advance every time an object to be processed is carried into the processing container.

(Operation and Effect) That is, the present invention includes a step of introducing a cleaning gas into a processing container, and a step of converting the cleaning gas into plasma in an electric field and magnetic field atmosphere in the processing container to clean the inside of the processing container. By having this, high-energy plasma is generated, making it possible to completely clean the inside of the processing container and the like in a short time.

Furthermore, each time an object to be processed is brought into the processing container, the inside of the processing container is cleaned in advance to completely remove impurities that would interfere with the processing from inside the processing container, and then the object to be processed is processed. be able to.

(Example) Next, embodiments of the invention will be described with reference to the drawings.

FIG. 1 is a diagram schematically showing a cross section of an apparatus that can be used in the method of the present invention. As shown in FIG. 1, the vacuum container 11, which is a stepped cylindrical processing container, has an upper small cylindrical portion and a lower large cylindrical portion. This upper small cylindrical portion is a gas introduction chamber 11a, and the lower large cylindrical portion is a processing chamber 11b.

A gas introduction pipe 14 for introducing gas is provided on the upper surface of the gas introduction chamber 11a. A cleaning gas is introduced from this gas introduction pipe 14 when a cleaning process is to be performed, and a source gas is introduced when a thin film is to be formed. Further, on the side surface of the lower large cylindrical portion 11b, a plurality of gas exhaust pipes 20 for discharging gas are provided on the same circumference.

The gas after each process is exhausted through this gas exhaust pipe 20. Further, inside the processing chamber 11b, a susceptor 13 for placing and heating an object to be processed, such as a semiconductor wafer 12, is provided.

On the outer surface of the gas introduction chamber 11a, approximately parallel to the susceptor 13 disposed inside the vacuum container 11,
An annular magnetic coil 15 is provided. This annular magnetic coil 15 forms a magnetic field within the vacuum vessel 11 .

An opening 11c is formed in the lower surface of the vacuum container 11. A cylindrical high-frequency electrode 17 is inserted into the vacuum container 11 into the opening 11c. A flange is provided on the lower circumference of the cylindrical high-frequency electrode 17, and this flange is fixed to the bottom surface of the vacuum vessel 11 via a ring-shaped insulating member 18.

A high frequency power source 16 is connected to this high frequency electrode 17 . A susceptor 13 is placed on the upper surface of the high frequency electrode 17. Moreover, inside the high frequency electrode 17.

A heating mechanism for heating the susceptor 13, for example a heating heater 19, is housed.

A method of forming a thin film according to the invention using such an apparatus will be described below.

First, the inside of the vacuum container 11 is reduced to a predetermined pressure, for example, 10"-' Torr, by an exhaust device (not shown). Thereafter, a cleaning gas, for example, NF is applied.

is introduced into the gas introduction chamber 11a from the gas introduction pipe 14.

Next, a current is applied to the annular magnetic coil 15 to
A magnetic field A is formed within. Furthermore, high frequency power is supplied to the high frequency electrode 17 to form an electric field B within the vacuum container 11 . The frequency of the high frequency power supplied to the high frequency electrode 17 is, for example, 13.56 MHz. The magnetic lines of force of the magnetic field A and the electric lines of force of the electric field B intersect at right angles in a certain region. In a region where the lines of magnetic force of the magnetic field A and the lines of electric force of the electric field B are orthogonal to each other, the interaction causes the electrons of the gas existing in that region to undergo cycloidal motion. The kinetic energy of the electrons generated by this cycloidal motion becomes energy for converting the cleaning gas (NF3) into plasma. In this way, a high energy plasma region is formed. The generated high-energy plasma accelerates along the lines of magnetic force of the magnetic field A and collides with the inner wall of the vacuum vessel 11, the susceptor 13, and the like. The interior of the vacuum container 11 is cleaned by this plasma collision and chemical reaction.

When cleaning the surface of the wafer, after cleaning the inside of the vacuum container 11 using the above procedure,
First, the gas used for cleaning is discharged through the gas discharge pipe 20. Next, the susceptor 1 inside the vacuum container 11
The substrate 12 is placed on the substrate 3. Thereafter, the cleaning gas is introduced into the vacuum container 11 from the gas introduction pipe 14 again. After introducing the gas, cleaning is performed in the same manner as above.

After finishing the cleaning, the gas used for cleaning is discharged from the gas exhaust pipe 20.

Next, a raw material gas corresponding to the thin film to be formed is introduced into the vacuum container 11 from the gas introduction pipe 14.

Thereafter, a normal film forming process is performed. For example, thermal CVD is performed by heating the substrate 12 placed on the susceptor 13 using a heater 19 housed inside the high-frequency electrode 17 . Further, the film can also be formed by plasma CVD.

According to such a method, the inside of the vacuum container 11 can be completely cleaned in a short time, so that a good thin film can be efficiently formed on the surface of the substrate. The reason why the inside of the vacuum container 11 can be completely cleaned in a short time is because the energy of the plasma formed in the above method is high. This high-energy plasma is formed by the interaction between the magnetic field A and the electric field B formed within the vacuum vessel 11. Therefore, the distance between the high frequency electrode 17 and the vacuum vessel 11, which is a ground electrode, which is an important element in conventional cleaning using plasma, does not pose a big problem in the method of the present invention.

Other apparatus can also be used in the thin film forming method of this invention. FIG. 2 shows a cross-sectional view of one such device. While the device shown in FIG. 1 is equipped with a cylindrical high-frequency electrode 17 at the bottom of the vacuum container 11,
In the device shown in FIG. 2, a flat high-frequency electrode 21 is provided at the center of the annular magnetic coil 15. A high frequency power source 16 is connected to this high frequency electrode 21 . By arranging the flat electrodes in this manner, it is possible to form a stronger electric field. Therefore, the apparatus shown in FIG. 2 can generate higher energy plasma. Further, by arranging the movable ground electrode 41 above the susceptor 13 as shown in FIG. 2, the electric field formed by the high frequency electrode 21 can be further strengthened. This movable ground electrode 41 becomes unnecessary when forming a film by CVD or the like. Therefore, when forming a film, it is necessary to remove it from above the susceptor 13.

FIG. 3 is a cross-sectional view of yet another apparatus that can be used in the thin film forming method of the present invention. While the device shown in FIG. 1 is equipped with a high-frequency electrode 17 for forming an electric field and a toroidal magnetic coil 15 for forming a magnetic field, this device has an electron cyclotron resonance (E
CR) A plasma generation mechanism is provided. A concrete explanation is as follows. In FIG. 3, one end of a microwave waveguide 31 is connected to the upper surface of the gas introduction chamber 11a. The other end of this microwave waveguide 31 is connected to a microwave generation mechanism 32. The microwave output from the microwave generation mechanism 32 is transmitted through the microwave waveguide 31 and guided into the vacuum container 11 .

Next, an embodiment of the method of the present invention using the apparatus shown in FIG. 3 will be described.

First, the inside of the vacuum container 11 is reduced to a predetermined pressure, for example, 10-' Torr, using an exhaust device (not shown). Thereafter, a cleaning gas such as NF3 is introduced from the gas introduction pipe 14 into the gas introduction chamber 11a.

Next, from the microwave generation mechanism 32, for example, 2.45G
Outputs Hz microwave. The output microwave is introduced into the vacuum container 11 through the waveguide 31.

Next, while introducing microwaves into the vacuum container 11, a current is applied to the annular magnetic coil 15 to form a magnetic field inside the vacuum container 11. At this time, when the frequency of the microwave and the strength of the magnetic field satisfy certain conditions, the electrons of the gas existing in the vacuum container 11 cause cyclotron resonance. For example, this condition is satisfied when the microwave frequency is 2.45 GHz and the magnetic field strength is 875 Gauss, and the gas electrons cause cyclotron resonance. Electrons that cause cyclotron resonance acquire large kinetic energy and generate high-energy plasma. The inside of the vacuum container 11 is cleaned using this high-energy plasma.

When cleaning the surface of the substrate/board, after cleaning the inside of the vacuum container 11 using the above procedure,
First, the gas used for cleaning is discharged through the gas discharge pipe 20. Next, the susceptor 1 inside the vacuum container 11
The wafer 12 is placed on the wafer 3. Thereafter, the cleaning gas is introduced into the vacuum container 11 from the gas introduction pipe 14 again. After introducing the gas, cleaning is performed in the same manner as above.

After finishing the cleaning, the gas used for cleaning is discharged from the gas exhaust pipe 20.

Next, a raw material gas corresponding to the thin film to be formed is introduced into the vacuum vessel 11 from the gas introduction pipe 14.

Thereafter, a normal film forming process is performed.

By providing the ECR plasma generating means in this manner, the high frequency electrode 17 in the apparatus shown in FIG. 1 becomes unnecessary. Therefore, the degree of freedom in designing the vicinity of the susceptor 13 increases. For example, as shown in FIG.
A vacuum chamber 34 closed with quartz glass 33 or the like may be provided on the back surface of the vacuum container 11, and a light heat source 35 such as a halogen lamp or an infrared lamp may be provided outside the vacuum container 11. In this case, the heat emitted from the light heat source 35 is transferred to the quartz glass 3.
3 to heat the susceptor 13.

In the thin film forming method of the present invention, a chemically stable inert gas or etching gas can be used as the cleaning gas. Inert gases are usually
Ar (argon gas) is used. In addition, as the etching gas, SF6.
NFl, CF4, etc. can be used, and NF is particularly preferred.

In the cleaning step of the thin film forming method of the present invention, an electric field is formed in the reaction container and a magnetic field is generated,
This interaction generates high-energy plasma.

The electric field within the processing container can be formed by, for example, providing two electrodes within the processing container. These electrodes may be two plate electrodes,
The processing container itself can also be used as an electrode. The power supplied to the electrodes when forming the electric field is 50 to IKw.
It is preferable that -Also, instead of using electrodes to form an electric field.

Microwaves can also be used. In this case, microwaves are generated outside the processing container and introduced into the processing container.

In the processing container, the magnetic field is such that at least some of the lines of force (lines of magnetic force) of the magnetic field are lines of force (lines of electric force) of the electric field.
It is formed perpendicular to the This magnetic field can be formed by, for example, a permanent magnet, an electromagnet, or the like. The strength of the magnetic field created is typically 30-300 Gauss. When microwaves with a frequency of 2.45 GHz are used as the electric field, it is most desirable that the magnetic field strength is 875 Gauss.

In such a system in which a magnetic field is formed together with an electric field, in a region where the magnetic and electric lines of force intersect at right angles, cycloidal motion of the electrons of gas molecules existing in that region occurs. This electron kinetic energy is converted into energy to convert the gas into plasma. This generates high-energy plasma.

This cleaning step can clean the inside of the processing container, such as the inner wall of the processing container and the susceptor. especially,
Thoroughly cleaning the susceptor that supports the object to be processed is important for forming better thin films.

In this cleaning process, it is desirable to heat the object to be cleaned in advance to a high temperature state. The higher the temperature, the better, but 500
The temperature is preferably 800°C or higher, preferably 800°C or higher.

After finishing the cleaning, the gas used for cleaning is discharged from the processing container, and then a raw material gas for forming a thin film is introduced into the processing container. Various gases can be used as the source gas depending on the type of thin film to be formed. For example, when forming an SL film on an object to be processed,
SiH4,5i (QCH)4, etc. can be used.

The thin film can be formed on the surface of the object to be processed using a method similar to a commonly used film forming method.

In the thin film forming method of the present invention, it is possible not only to clean the inside of the processing container such as the inner wall of the processing container and the susceptor, but also to clean the surface of the object to be processed. In this case, in the cleaning step, after cleaning the inside of the processing container, the object to be processed, such as a semiconductor wafer, is carried into the processing container, and the surface of the object to be processed is soft etched in the same way as cleaning the inside of the processing container. Let's do it.

In the above embodiments, the treatment after cleaning was explained as CVD, but the present invention is not limited to this, and similar effects can be obtained by etching, ashing, sputtering, and other treatments.

As described above, according to this embodiment, the cleaning gas inside the processing container is cleaned by introducing the cleaning gas into the processing container and converting the cleaning gas into plasma in the electric field and magnetic field atmosphere inside the processing container. By providing this step, the inside of the processing container, the surface of the object to be processed, etc. can be completely cleaned in a short time.

In addition, each time an object to be processed is brought into the processing container, the inside of the processing container is cleaned in advance to completely remove impurities that would interfere with processing from inside the processing container, and then the object to be processed is processed. This makes it possible to improve yield.

[Brief explanation of the drawing]

FIG. 1 shows a CVD process for explaining one embodiment of the method of the present invention.
2 and 3 are explanatory diagrams of other embodiments of the method of the present invention, and FIG. 4 is a conventional cold wall type CVD
It is a block diagram of a device. 11... Vacuum container 12... Wafer 13.
...Susceptor 14...Gas introduction pipe 15...
・Magnetic coil 16...High frequency power supply 17...
High frequency electrode 19... Coil 21... High frequency electrode 31... Microwave waveguide 32... Microwave generation mechanism

Claims (2)

[Claims] (1) It is characterized by comprising a step of introducing a cleaning gas into the processing container, and a step of converting the cleaning gas into plasma in an electric field and magnetic field atmosphere in the processing container to clean the inside of the processing container. processing method. (2) A processing method characterized in that the inside of the processing container is cleaned in advance every time an object to be processed is carried into the processing container.