KR20010067192A - Plasma cvd apparatus and method for cleaning a chamber of the plasma cvd apparatus - Google Patents

Abstract

PURPOSE: To highly retain the working ratio and throughput of a semiconductor fabricating equipment and also to prevent the reduction of the yield of a semiconductor system, in chamber cleaning for a plasma CVD system having a fixed high-frequency matching circuit, at the time of cleaning depositions on the inner wall of the system, by fixing the opening degree of a CVD chamber pressure control valve, then monitoring the change in the reflecting electric power of high-frequency electric power to detect the end point of the cleaning and executing the cleaning for a suitable time. CONSTITUTION: In a plasma CVD system having a fixed high-frequency matching circuit, at the time of cleaning depositions on the inner wall of a chamber, the opening degree of a CVD chamber pressure control valve is fixed, and then, the reflecting electric power of high-frequency electric power is monitored, by which the end point of the cleaning is detected.

Description

Chamber cleaning method of plasma CD apparatus and plasma CD apparatus {PLASMA CVD APPARATUS AND METHOD FOR CLEANING A CHAMBER OF THE PLASMA CVD APPARATUS}

The present invention relates to a chamber cleaning method of a plasma CVD apparatus and a plasma CVD apparatus implementing the method.

Conventionally, in the manufacture of various semiconductor devices, plasma CVD apparatuses are widely used in various film forming processes such as conductive layers and insulating layers.

In the plasma CVD apparatus, a substrate such as a semiconductor is disposed on a susceptor in a CVD chamber, and the pressure is controlled by a pressure regulating valve such as a throttle valve provided on an exhaust line of the CVD chamber that is connected to the susceptor so as to face the high frequency electrode to the vacuum pump. While maintaining the constant, gas is introduced, and plasma is discharged between the high frequency electrode and the substrate to form a film on the substrate.

In the plasma CVD apparatus, the film forming operation is repeatedly performed to deposit the reaction product on the inner wall of the CVD chamber or the like. As the deposits on the inner wall of the CVD chamber increase, the impedance in the CVD chamber changes to prevent the generation of stable plasma, and the film thickness distribution, film quality, etc. of the deposited film deteriorate. In addition, when the deposit on the inner wall of the CVD chamber increases, the deposit peels off and causes foreign matters.

For this reason, the plasma CVD apparatus needs to perform cleaning in a CVD chamber every fixed film formation time. Dry etching (plasma cleaning) using plasma is widely used for cleaning in the CVD chamber.

In general, the cleaning in the chamber is carried out with a long margin so as not to leave a residual film in the chamber. However, if the margin is taken too large, the cleaning time becomes longer, resulting in a decrease in the throughput of the equipment, and the over etching damages the members in the chamber. As a result, the deterioration of the chamber constituents is accelerated, and the maintenance cycle is shortened, thereby reducing the operation rate of the equipment.

Excessive etching may also cause foreign matters due to deterioration of the above-described chamber components or precipitation of products by cleaning gas, which may lower the yield of semiconductor products.

On the other hand, if the cleaning time is too short, the film formed in the chamber remains, and if the processing is continued, the thin film gradually deposits, and if this becomes thick to some extent, the film is peeled off and becomes foreign matter and adheres to the wafer, thereby lowering the yield of the semiconductor product. Therefore, the cleaning time needs to be managed appropriately.

Here, the high frequency power control system generally used in the plasma CVD apparatus will be briefly referred to using the drawings. 5 is an example of a block diagram of a plasma CVD chamber and a high frequency power control system. The high frequency oscillator 21 supplies the high frequency power (forward power) designated by the voltage signal 25 from the control circuit 24 to the CVD chamber 23 via the matcher 22. The high frequency oscillator 21 has a function of monitoring the forward power and the reflected power of the oscillating high frequency to output as a voltage signal 26.

In the plasma CVD apparatus having the fixed high frequency matching circuit, the impedance of the matching unit 22 is kept constant by the voltage signal 27 from the control circuit 24. Moreover, the plasma CVD apparatus which has a fixed high frequency matching circuit may have a matching machine which does not have a function which changes an impedance.

During film formation or plasma cleaning, the impedance of the CVD chamber 23 changes due to a change in the amount of deposit deposited on the inner wall of the CVD chamber. When the impedance of the matching unit 22 is fixed, the reflected power changes with the change in the impedance of the CVD chamber 23.

The high frequency power supplied from the high frequency oscillator 21 to the CVD chamber 23 is the difference between the forward power and the reflected power. For this reason, when the forward power output from the high frequency oscillator 21 is constant, the change of the reflected power becomes the change of the high frequency power supplied to the CVD chamber 23, which makes the processing performed in the CVD chamber 23 unstable. .

In the high frequency power control of the CVD apparatus having the fixed matching circuit, in order to prevent the processing performed in the CVD chamber 23 from becoming unstable due to the change in the reflected power, while the processing is being performed in the CVD chamber 23, the high frequency oscillator is removed from the high frequency oscillator. The forward power and the reflected power are monitored to control the forward power so that the difference between the forward power and the reflected power becomes constant.

As described above, in the plasma CVD apparatus having the fixed high frequency matching circuit, the monitor of the reflected power is a function provided as a standard.

Next, a mechanism for keeping the chamber pressure during cleaning in a general plasma CVD apparatus constant will be described briefly. In the conventional plasma CVD apparatus, the number of pulse signals of voltage is appropriately adjusted for a dedicated valve for adjusting the conductance of the exhaust pipe, called an APC (Auto Pressure Controller) valve, based on the chamber pressure during cleaning based on the pressure gauge attached to the chamber. By supplying while changing, it is adjusting so that it may become a fixed value at all times. One of the main components constituting the APC valve is the throttle valve, and the chamber pressure is controlled by changing the conductance of the pipe by changing the angle of the throttle valve inside the APC valve.

By the way, as an end point detection method of plasma cleaning, as described, for example in Unexamined-Japanese-Patent No. 9-82645, there exists a method of detecting from the change of the light emission intensity of a light emitting material. When detecting the end point of the plasma cleaning from the change in the emission intensity, it is common for the plasma CVD apparatus to attach an observation window for observing plasma emission on the sidewall surface of the CVD chamber, and to install a light receiver outside the chamber adjacent to the window.

In the plasma CVD apparatus having a fixed high frequency matching circuit, for example, as described in Japanese Patent Laid-Open No. 8-236412, cleaning is performed by detecting whether or not the high frequency reflected power during plasma cleaning reaches a stable level. There is a method for detecting the end point.

However, in the method for detecting the end point of cleaning from the change in the emission intensity of the light emitting material, the reaction product is also deposited on the inner wall surface of the observation window during the film formation, so that the change in the emission intensity of the plasma cannot be stably detected for a long time. Further, the installation of a light receiving system for measuring the light emission intensity of the light emitting material leads to the complexity and cost of the device.

Further, in the plasma CVD apparatus having the fixed high frequency matching circuit, in the method of detecting the end point of cleaning by detecting whether the high frequency reflected power has reached a stable level, the amount of change in the reflected power during cleaning is small or CVD It is difficult to determine the cleaning end point due to a phenomenon such as the change in the reflected power even after the deposit of the chamber inner wall is removed.

It is an object of the present invention to solve the above problems and to provide a cleaning method of a plasma CVD apparatus which can accurately detect the end point at low cost.

1 is a schematic configuration diagram of a parallel plate type plasma CVD apparatus which is an example of a plasma CVD apparatus to which a plasma cleaning method according to the present invention is applied.

2 is a graph showing the relationship between plasma cleaning time and CVD chamber pressure.

Fig. 3 is a graph showing the relationship between plasma cleaning time after 1000 nm deposition of silicon oxide film, reflected power, and F radical emission intensity;

Fig. 4 is a graph showing the relationship between plasma cleaning time after 2000 nm deposition of silicon oxide film, reflected power, and F radical emission intensity.

Fig. 5 is a block diagram showing an example of a plasma CVD chamber and a high frequency power control system.

<Explanation of symbols for the main parts of the drawings>

1: CVD chamber

2: substrate

3: susceptor

4: heating means

5: high frequency electrode

6: high frequency oscillator

7: high frequency matcher

8: gas supply system

9: exhaust system

10: throttle valve (pressure control valve)

11: pressure gauge

The chamber cleaning method of the plasma CVD apparatus according to the present invention is a plasma CVD apparatus having a fixed high frequency matching circuit, when the deposit on the inner wall of the apparatus is cleaned using plasma, the opening degree of the CVD chamber pressure control valve is fixed, and then the high frequency. By monitoring the reflected power of the electric power, the end point of cleaning is detected by the variation of the reflected power.

In addition, the plasma CVD apparatus of the present invention has a means for automatically performing a series of cleaning treatments such as stopping of the gas and high frequency used for cleaning after the time calculated by the set calculation method from the detection time of the end point. .

First, the principle and operation | movement of the chamber cleaning method of the plasma CVD apparatus by this invention are demonstrated.

When the film is formed in the plasma CVD apparatus, the reaction product adheres to the CVD chamber and the impedance in the CVD chamber changes. When plasma cleaning is performed from this state, the product in the CVD chamber is removed, and the impedance gradually returns to the value before film formation.

When plasma cleaning is performed with the opening of the CVD chamber pressure control valve fixed, the pressure of the CVD chamber increases with cleaning initiation and application of high frequency, and decreases as product removal in the CVD chamber proceeds. Become a politician

The change in the CVD chamber pressure accompanying the progress of cleaning amplifies the amount of impedance change in the CVD chamber accompanying the progress of plasma cleaning as compared with the case where the CVD chamber pressure during the cleaning is constantly controlled. This impedance change is captured by high frequency reflected power, and the end point of plasma cleaning is detected.

The function of monitoring the reflected power and the function of fixing the opening of the throttle valve are functions provided as standard in a plasma CVD apparatus having a fixed high frequency matching circuit.

In the present invention, in the above-described chamber pressure control method, the pulse signal of the voltage is stopped so as to stop the opening degree of the APC valve at a predetermined value at a set value at which the inside of the chamber becomes a proper pressure without performing feedback from the pressure gauge during the cleaning process. It is possible to easily fix the opening of the throttle valve by stopping the valve. Therefore, the present invention detects the correct end point without adding a special function for detecting the end point of the plasma cleaning to the plasma CVD apparatus.

EMBODIMENT OF THE INVENTION Hereinafter, specific embodiment of this invention is described, referring drawings.

Figure 1 shows a parallel plate plasma CVD apparatus. In the plasma CVD apparatus, the susceptor 3 which arrange | positions the board | substrate 2 used as a film-forming object is arrange | positioned in the CVD chamber 1 which maintains a vacuum state. The susceptor 3 is provided with heating means 4 for maintaining the substrate at a constant temperature.

On the upper part of the susceptor 3, opposite high frequency electrodes 5 are arranged. A high frequency oscillator 6 for supplying high frequency power is connected to the high frequency electrode 5 via a matcher 7 having a fixed high frequency matching circuit. In addition, the high frequency electrode 5 is provided with a gas supply system 8 for supplying a gas necessary for film formation and plasma cleaning.

An exhaust system 9 such as a vacuum pump for exhausting the gas in the CVD chamber is connected to the CVD chamber via a throttle valve 10 (pressure control valve) for maintaining a constant pressure in the CVD chamber. In the CVD chamber, a pressure gauge 11 for monitoring the CVD chamber pressure is provided.

Next, a method of detecting the end point of chamber cleaning when the parallel plate type plasma CVD apparatus of FIG. 1 is used will be described.

FIG. 2 shows a state in which the CVD chamber pressure is changed in the case where plasma cleaning is performed by introducing a cleaning gas into the chamber after forming a silicon oxide film at 1000 nm and 20OO nm in the CVD chamber of FIG. Shows.

The CVD chamber pressure was monitored by the pressure gauge 11 shown in FIG. 1 to confirm that the CVD chamber pressure was changed during the plasma cleaning.

In Fig. 2, when the thick solid line curve is formed by forming the silicon oxide film at 1000 nm, the thin solid line curve shows the state of change in the CVD chamber pressure when the silicon oxide film is formed by 2000 nm.

After the deposition of the silicon oxide film in the CVD chamber, the pressure in the CVD chamber was set to a condition of C ₂ F ₆ flow rate 900 sccm, NF ₃ flow rate 135 sccm, 0 ₂ flow rate 1250 sccm, susceptor temperature 400 ° C., throttle valve opening 60%. As shown in Fig. 2, it is maintained at 4 Torr.

In this state, the high frequency electric power 4000W was supplied (time t1 in FIG. 2), and cleaning was started.

After the start of cleaning, the CVD chamber pressure decreases with time as shown in FIG. Thereafter, the CVD chamber pressure was about 40 seconds after the start of cleaning (time t2 in FIG. 2) for cleaning after 1000 nm deposition of silicon oxide film, and about 70 seconds after the start of cleaning for cleaning after 2000 nm deposition of silicon oxide film (time of FIG. 2). In t3), each becomes a constant value. In this way, by performing plasma cleaning with the opening of the pressure control valve fixed, the CVD chamber pressure during cleaning changes with the progress of cleaning.

Fig. 3 shows the change in the reflected power and the change in the emission intensity of the F radical in the plasma cleaning after forming the silicon oxide film at 1000 nm. 4 shows the change in the reflected power and the change in the emission intensity of the SiF radicals in the plasma cleaning after forming the silicon oxide film at 2000 nm.

Since the monitor of the reflected power is a function which is provided in a standard in the plasma CVD apparatus which has a fixed high frequency matching circuit, it was used.

The time change of the emission intensity of F radical was monitored from the emission observation window installed in the CVD chamber. After the plasma cleaning starts, the increase in the emission intensity of the F radical stops and is stabilized to a constant value is the end point of the cleaning.

As shown in Figs. 3 and 4, the reflected power takes a minimum after an extremely short increase at the start of the plasma cleaning (time t1 in Figs. 3 and 4), and then increases with the passage of time. After that, the reflected power was about 40 seconds after the start of cleaning (time t2 in Fig. 3) for cleaning after 100 Onm deposition of silicon oxide film, and about 70 seconds after the start of cleaning for cleaning after 2000 nm deposition of silicon oxide film (time t3 in Fig. 4). ) Are constant values.

The emission intensity of the F radical increases with the passage of time after the plasma cleaning starts. Thereafter, the emission intensity of F radical is about 35 seconds after the start of cleaning in cleaning after 1000 nm deposition of silicon oxide film (time T2 in Fig. 3), and about 60 seconds after the start of cleaning in cleaning after 2000 nm deposition of silicon oxide film (Fig. 4). Are constant at each time T3).

Therefore, in the cleaning after the silicon oxide film 100 nm deposition, the time until the increase in the reflected power during cleaning stops (about 40 seconds) is about 13 of the time until the increase in the emission intensity of the F radical stops (about 35 seconds). % Increase is expected.

In the cleaning after 2000 nm deposition of silicon oxide film, the time until the increase of the reflected power during cleaning stops (about 70 seconds) is about the time until the increase of the F radical emission intensity stops (about 60 seconds). It is expected to increase by 17%.

Thus, in this embodiment, it was verified by the light emission intensity of the light emitting material conventionally used that the end point of the plasma cleaning can be detected from the change of the reflected power.

Therefore, if the supply of high frequency power is stopped, that is, the stop of cleaning is set to the time until the increase in the reflected power during cleaning stops, this is an increase of about 13 to 17% of the time until the increase in the emission intensity of F radical stops. On average, it is about 15% increase in time. In this way, the inside of the chamber can be kept in a good state, and the adhesion of the fine particles to the semiconductor substrate can be kept low while maintaining the throughput and the operation rate.

From the above results, in the plasma cleaning of the plasma CVD apparatus having the fixed high frequency matching circuit, it is possible to accurately detect the end point of the plasma cleaning by fixing the opening of the pressure control valve and then monitoring the change in the reflected power.

By detecting the end point of cleaning in this way, it is possible to stop the supply of the gas used for the cleaning and the supply of the high frequency power at an appropriate timing.

In addition, as described above, according to the present embodiment, a plasma CVD apparatus capable of detecting the end point of CVD chamber cleaning and automatically terminating the cleaning process at an appropriate timing can be obtained.

That is, according to this embodiment, in the plasma CVD apparatus which has a fixed high frequency matching circuit, the reflection power of a high frequency electric power is changed during the cleaning of the chamber inner wall adhesion | attachment which uses the plasma by fixing the opening degree of a CVD chamber pressure control valve. And means for monitoring the end point of cleaning. Furthermore, a means for automatically terminating the cleaning process including stopping of the gas and high frequency used for cleaning may be provided after the time calculated by the set calculation method from the detection time of the end point by a microcomputer or the like. .

In addition, this invention is not limited to embodiment mentioned above.

That is, in this invention, it is not limited to the example of the to-be-processed object mentioned above, For example, it can apply to the plasma cleaning after depositing various thin films, such as a silicon nitride film and a carbon fluoride film.

In addition, the present invention is not limited to the above-described cleaning gas supply example, and can be applied to plasma cleaning using various etching gases such as NF ₃ alone or a mixture of C ₃ F ₈ and 0 ₂ .

As described above, according to the present invention, when performing plasma cleaning in a plasma CVD apparatus having a fixed high frequency matching circuit, by monitoring a change in reflected power, the end point of the plasma cleaning can be avoided without incurring complicated apparatus and high cost. Can be detected accurately.

Claims (3)

In a plasma CVD apparatus having a fixed high frequency matching circuit, the opening of the CVD chamber pressure control valve is fixed to clean the deposits on the inner wall of the chamber using plasma, and the change of the reflected power of the high frequency power is monitored to thereby determine the end point of the cleaning. Detecting the chamber of the plasma CVD apparatus. The chamber cleaning method of a plasma CVD apparatus according to claim 1, wherein the end point of the cleaning is detected to stop the supply of high frequency power. In the plasma CVD apparatus having a fixed high frequency matching circuit, the end point of cleaning is detected by monitoring the change of the reflected power of high frequency power during the cleaning of the chamber inner wall deposits performed by using a plasma while fixing the opening of the CVD chamber pressure control valve. Means for automatically performing a termination process of the cleaning process including stopping of the gas and high frequency used for cleaning after a time calculated by the set calculation method from the detection time of the end point; Device.