JPH11111708A - Method for plasma film treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the contamination of a substrate with particles, when a film treated on the substrate with plasma. SOLUTION: An SiOF film is formed on a substrate composed of a wafer W in a vacuum vessel 2 by introducing a microwave having a frequency of about 2.45 GHz to the vessel 2, and at the same time, generating plasma from a film forming gas by causing electronic cyclotron resonance by forming magnetic field of about 875 Gauss in the vessel 2. The temperature of the inside wall surface of the vessel 2 is controlled to a temperature of, for example, 80 deg.C which is higher than the temperature T0 which is reached when the plasma is generated during the course of a series of process cycles of carrying the wafer W in the vessel 2, forming the film on the wafer W, and carrying the wafer W out of the vessel 2 by forming flow passages 31 through the entire wall body of the vessel 2 and making temperature-controlled Garudane (CR) to flow through the passages 31. Therefore, the peeling off of the SiOF film formed on the surface of the wafer W from the wafer W due to thermal deformation can be suppressed, and accordingly, the contamination of the wafer W with particles is suppressed, because the internal surface of the vessel 2 is maintained at a fixed temperature independent of the generation and dissipation of the plasma.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a plasma film forming method for forming an insulating film on a substrate by plasma, for example.

[0002]

2. Description of the Related Art One of the methods for performing a film forming process on a semiconductor wafer is a process using plasma. This processing is performed by introducing a processing gas into a vacuum vessel provided with a wafer mounting table and supplying, for example, electromagnetic energy to the processing gas to form a plasma. As a method of supplying electromagnetic energy, a method using electron cyclotron resonance (ECR), which is an interaction between a microwave and a magnetic field, and an ICP (Inductive Coupled) are used.
There is known a method of applying an electric field and a magnetic field to a processing gas from a coil wound around a dome-shaped container, which is called “Plasma”.

An example of a conventional plasma processing apparatus for performing an ECR plasma process will be described with reference to FIG. 6 taking a film forming process as an example.
At the same time as supplying the microwave of 5 GHz through the waveguide 11, the magnetic field strength at the position indicated by the dotted line in FIG.
A magnetic field is applied by the electromagnetic coil 12 so as to be Gaussian, and a plasma generating gas, for example, an Ar gas and an O ₂ gas is turned into a high density plasma by the interaction (resonance) between the microwave and the magnetic field, and a film is formed by the plasma. The reactive gas introduced into the chamber 1B, for example, a SiF ₄ gas or a SiH ₄ gas is activated to form active species, and the surface of the semiconductor wafer W (hereinafter referred to as “wafer W”) on the mounting table 13 is subjected to sputter etching. The deposition is performed simultaneously.

In such a plasma processing apparatus,
For example, when a film forming process of an insulating film such as a SiOF film or a SiO ₂ film is performed, these films also adhere to the inner wall surface of the film forming chamber 1B. When the thickness becomes too large, the adhered film is peeled off, causing particles. Therefore, for example, every time 12 wafers W are formed, an F-based cleaning gas such as CF ₄ gas or NF ₃ gas is introduced into the vacuum vessel, the gas is activated by plasma, and the activated species is deposited. It is removed by reacting with the film.

[0005]

When plasma is generated in the vacuum vessel, the temperature of the inner wall of the vacuum vessel rises due to the heat of the plasma. For example, the above-described SiOF film is formed using SiF ₄ gas. In the process, the temperature is raised to around 80 ° C. On the other hand, when the plasma disappears, the temperature of the inner wall surface decreases, so that the temperature of the inner wall surface greatly changes in a series of cycles in which a wafer is carried into a vacuum vessel, formed into a film, and carried out. For this reason, a thin film such as a SiOF film adhered to the inner wall surface tends to be thermally deformed and peeled off from the inner wall surface. In particular, the insulating film such as a SiOF film or a SiO ₂ film has a low adhesion, and this tendency is large, which causes a particle contamination of the wafer.

The present invention has been made under such circumstances, and an object of the present invention is to provide a method capable of suppressing particle contamination of a substrate when performing a film forming process on the substrate by plasma. is there.

[0007]

According to the present invention, a substrate is loaded into a vacuum vessel, a processing gas is turned into plasma, and a film is formed on the substrate by the plasma. After performing a series of process cycles for carrying out of the container a predetermined number of times, a method of removing a thin film adhered to the inside of the vacuum container with a cleaning gas, wherein the temperature of the inner wall surface of the vacuum container during the process cycle is measured by plasma. Is maintained at a substantially constant temperature that is equal to or higher than the temperature T0 of the inner wall surface that is reached when the airflow occurs. Here, the temperature of the inner wall of the vacuum vessel is
Instead of maintaining a substantially constant temperature equal to or higher than the temperature T0, a constant temperature equal to or lower than the temperature T0 and in the vicinity thereof may be maintained.

[0008]

FIG. 1 is a sectional view showing an embodiment of a plasma film forming apparatus for carrying out the method of the present invention. In FIG. 1, reference numeral 2 denotes a vacuum vessel formed of, for example, aluminum or the like. . The vacuum vessel 2 includes a plasma chamber 21 located above and generating plasma, and a film forming chamber 22 connected below and connected to the plasma chamber 21. The vacuum container 2
Is grounded to zero potential.

An upper end of the vacuum vessel 2 is opened, and a transmission window 23 made of a member that transmits a high frequency (microwave), for example, aluminum nitride (AlN) is hermetically provided in this portion. The transmission window 23 is provided on the support ring 2.
The outer peripheral edge is airtightly supported by the transmission window 2.
The vacuum state in the vacuum vessel 2 is maintained by the support ring 3 and the support ring 24.

For example, a flow path 31 for adjusting the temperature for allowing the thermostatic agent to flow is formed inside the vacuum vessel 2, for example, on the entire wall. Further, for example, a temperature detecting unit 32 composed of, for example, a platinum resistance temperature detector for detecting the temperature of the inner wall is provided on the inner wall of the film forming chamber 22, and the temperature is adjusted based on the detected value of the temperature detecting unit 32. The thermostatic agent, for example, Galden, whose temperature has been adjusted by the section 33, flows through the flow channel 31.

On the outside of the transmission window 23, for example, a combination of a rectangular waveguide, a cylindrical waveguide, and a conical waveguide for supplying microwaves of, eg, 2.45 GHz into the plasma chamber 21 is provided. A configured waveguide 25 is provided. The exit side end of the waveguide 25 is connected to the upper surface of the transmission window 23, and the entrance side end is connected to a high frequency power supply 26 for plasma generation. Waves can be guided through the waveguide 25 and introduced into the plasma chamber 21 through the transmission window 23.

A gas nozzle 4 for supplying a plasma gas, for example, is provided on an upper side of a side wall defining the plasma chamber 21.
1 are arranged evenly along the circumferential direction,
A plasma gas source (not shown) is connected to the gas nozzle 41, and Ar gas or O
Plasma gas such as _two gases can be supplied evenly and evenly. Although only two gas nozzles 41 are shown in the figure to avoid complication of the drawing, more gas nozzles 41 are actually provided.

On the other hand, the upper part of the film forming chamber 22, ie, the plasma chamber 21
A ring-shaped film-forming gas supply unit 4
2 are provided. A gas supply port 42a is formed on the inner peripheral surface of the film forming gas supply unit 42, and a film forming gas such as SiF ₄ gas supplied to the film forming gas supply unit 42 from a film forming gas source (not shown). Are ejected from the gas supply port 42a.

A ring-shaped main electromagnetic coil 51 is arranged on the outer periphery of the side wall that partitions the plasma chamber 21 so as to approach and surround the plasma chamber 21. On the side, a ring-shaped auxiliary electromagnetic coil 52 is arranged, so that a magnetic field B, for example, 875 gauss from the plasma chamber 21 to the film formation chamber 22 can be formed from the top to the bottom.

In the film forming chamber 22, a mounting table 6 for mounting a wafer W is provided so as to be able to move up and down between a processing position and a transfer position of the wafer W. The mounting table 6 is provided with a dielectric plate 62 having a built-in heater and electrodes on a main body 61 made of, for example, aluminum, and the surface is configured as an electrostatic chuck. A DC power supply (not shown) for an electrostatic chuck is connected to the electrode,
The high-frequency power supply unit 63 is connected so as to apply a bias voltage for drawing ions into the wafer W.

Next, a series of process cycles performed by the above-described plasma film forming apparatus will be described using a case where an interlayer insulating film made of, for example, an SiOF film is formed on a wafer W as a substrate. First, a gate valve (not shown) provided on the side wall of the vacuum vessel 2 is opened to open a transfer arm (not shown).
A wafer W of, eg, an 8-inch size having, for example, an aluminum wiring formed on its surface is loaded from a load lock chamber (not shown) and placed on the mounting table 6.

Subsequently, after closing the gate valve to seal the inside, the mounting table 6 is raised to the processing position, the internal atmosphere is exhausted by an exhaust pipe (not shown), and the interior is evacuated to a predetermined degree of vacuum. A plasma gas such as an Ar gas and an O ₂ gas are introduced at a predetermined flow rate, and a film forming gas such as a SiF ₄ gas is introduced from the film forming gas supply unit at a predetermined flow rate. Then, the interior of the vacuum vessel 2 is maintained at a predetermined process pressure, a 13.56 MHz bias voltage is applied to the mounting table 6 by the high frequency power supply unit 63, and the surface temperature of the mounting table 6 is set to, for example, 200 ° C.

In the plasma chamber 21, a high frequency power supply 26
A high frequency (microwave) M of 2.45 GHz reaches the ceiling of the vacuum vessel 2 and is introduced into the plasma chamber 21 through the transmission window 23. On the other hand, a magnetic field B is formed in the vacuum vessel 2 by the main electromagnetic coil 51 and the auxiliary electromagnetic coil 52, and at the point where the intensity of the magnetic field B becomes 875 gauss,
Electron cyclotron resonance is generated by the interaction between the magnetic field and the microwave, and the resonance converts the plasma gas into plasma and increases the density. The use of a plasma gas stabilizes the plasma.

The generated plasma flows from the plasma chamber 21 toward the film forming chamber 22 as a plasma flow, and the SiF ₄ gas supplied here is activated (plasmaized) by the plasma flow to form active species. (Plasma) is formed. On the other hand, the plasma ions are drawn into the wafer W by the bias voltage, and the pattern (recess) on the surface of the wafer W is formed.
While shaving off the corners of the SiOF film deposited on the surface by the sputter etching action of plasma ions,
An SiOF film is formed and embedded in the recess.

Subsequently, the processed wafer W having the SiOF film formed thereon is transferred from the vacuum vessel 2 to
After being carried out to the lock chamber, the next wafer W to be processed is carried in from the load lock chamber, mounted on the mounting table 6 (replacement of the wafer W), and the film formation of the wafer W is performed again.
In this way, the process cycle of the film forming process is performed, for example, 12 times (the film forming process is performed on the 12 wafers W), and
End a series of process cycles.

Next, the SiOF film deposited in the vacuum vessel 2 is cleaned by a series of process cycles.
In this cleaning, cleaning gas such as NF ₃ gas and N ₂ gas, for example, is introduced into the plasma chamber 21 from the gas nozzle 41 at a predetermined flow rate. Then, the inside of the vacuum vessel 2 is maintained at a predetermined process pressure, and an electron cyclotron resonance is generated by the interaction between the microwave and the magnetic field as in the case of the film forming process, and an active species of a cleaning gas is formed by the resonance. This active species reacts with the SiOF film adhering to the inside of the vacuum vessel 2 to convert the SiOF film into, for example, SiF _4.
Decompose and remove.

Next, the temperature control of the inner wall surface of the vacuum vessel 2 performed in the process cycle of the film forming process will be described with reference to FIG. After the cleaning is completed, the temperature-controlled Galden is passed through the flow path 31 to raise the temperature of the inner wall surface of the vacuum vessel 2 to a temperature equal to or higher than the inner wall temperature T0 reached when plasma is generated, for example. In the process of forming the SiOF film, the temperature is controlled to a temperature T1 of 80 ° C. or higher. Then, wafer W
Is carried into the vacuum vessel 2 to perform a film forming process, and a series of process cycles are performed. During this process cycle,
Temperature control is performed so that the temperature of the inner wall surface of the vacuum vessel 2 is maintained at substantially the temperature T1.

At this time, no temperature control is performed in the cleaning, but the temperature of the inner wall surface during the cleaning is lower than that during the film forming process. For example, in the cleaning of the SiOF film, the temperature is lower than the temperature T0. The temperature is, for example, about 70 ° C.
This is because the temperature in the vacuum vessel 2 depends on the bias power, but the bias power is not applied at the time of cleaning, so that the temperature of the wall surface at the time of cleaning becomes lower than at the time of film formation.

In FIG. 2, the cleaning time is shorter than the process cycle, and the operation of loading and unloading the wafer W is not performed. For convenience of illustration, the temperature of the inner wall surface during cleaning is substantially constant. Although the temperature of the inner wall surface at the start of the process cycle and at the start of cleaning is described to change rapidly, it actually changes gradually.

By performing the temperature control in this manner, during the process cycle, the temperature of the inner wall surface is constantly controlled to a substantially constant temperature T1 which is equal to or higher than the temperature T0 reached when plasma is generated. Generation of particles due to the peeling of the film is suppressed, and particle contamination of the wafer W is prevented.

Here, an experimental example actually conducted by the present inventors to confirm the relationship between the temperature control of the inner wall surface and the number of particles will be described. Using the plasma film forming apparatus shown in FIG. 1 described above, each of Ar gas and O ₂ gas s 300s
Introducing SiF ₄ gas into the film forming chamber 22 at a flow rate of 120 sccm while introducing the SiF ₄ gas into the film forming chamber 22 at a flow rate of ccm and 160 sccm, and setting the high frequency power to 2700 W, the bias power to 2700 W, and the pressure in the vacuum chamber 2 to 0 .4P
As a, the temperature of the inner wall surface of the vacuum vessel 2 was changed, and a SiOF film was formed on an 8-inch wafer W by the same process cycle as in the above-described embodiment. -The number of ticicles was checked.

At this time, the number of particles was measured by Surfscan 6420 manufactured by Tencol. The results are shown in FIG. 3. Here, “no control of the horizontal axis” means that the temperature of the inner wall surface is 25 ° C. when the temperature control of the inner wall surface is not performed.
Is shown.

As a result, when the temperature of the inner wall surface is controlled, the number of particles is smaller than when the temperature is not controlled. It was confirmed that the number of ticules was considerably reduced.

The reason why the number of particles decreases when the temperature of the inner wall surface is controlled to a temperature of 80 ° C. or higher is presumed to be due to the following reasons. First, in the SiOF film formation process, it has been confirmed that the temperature of the inner wall surface when plasma is generated is about 80 ° C., but the temperature of the inner wall surface is set to a substantially constant temperature of 80 ° C. or higher. If controlled, the temperature of the inner wall surface during the process cycle will be substantially constant regardless of the generation and disappearance of plasma. Therefore, thermal deformation of the SiOF film adhered to the inner wall surface is prevented, and it is considered that the SiOF film is prevented from cracking due to the thermal deformation and peeling off of the SiOF film due to the crack.

Second, when the inner wall surface is heated to 80 ° C. or higher, Si
Since the adhesion of the OF film to the inner wall surface is enhanced, and the SiOF film adheres more firmly to the inner wall surface and is less likely to be peeled off from the inner wall surface, the particles during the process cycle are also considered from this viewpoint. Is considered to be prevented.

When the present inventors actually conducted an experiment to confirm the temperature dependence of the adhesion strength of the SiOF film, the results shown in FIG. 4 were obtained. In this experiment, the Ar gas and the O ₂ gas were introduced into the plasma chamber 21 at flow rates of 300 sccm and 160 sccm, respectively, and the SiF ₄ gas was supplied for 120 s using the plasma film forming apparatus shown in FIG.
The high-frequency power is introduced into the film forming chamber 22 at a flow rate of 2 cm.
700 W, the bias power was 2700 W, the pressure in the vacuum vessel 2 was 0.4 Pa, the temperature of the inner wall surface of the vacuum vessel 2 was changed, a SiOF film was formed on an aluminum plate, and the adhesion strength of the SiOF film was measured in Sebastian. Was measured by the method. According to this result, the higher the temperature of the inner wall surface during film formation,
It was confirmed that the adhesion strength of the SiOF film was large, especially when the temperature of the inner wall surface was 80 ° C. or more, the adhesion strength was 6 kps.
It was recognized that it became i or more.

As described above, in the present embodiment, it is desirable to perform a series of process cycles of the film forming process at a temperature equal to or higher than the temperature T0, for example, at a substantially constant temperature of 80 ° C. or higher in the case of a SiOF film. In the case where an O-ring is used for the vacuum vessel 2, for example, the upper limit of the temperature is 200 ° C. or less, preferably 15 ° C. in consideration of the resistance of the O-ring.
It is desirable to set the temperature to 0 ° C. or lower.

As described above, in the present embodiment, the temperature control is also performed at the time of cleaning, and for example, the cleaning of the SiOF film is performed.
In the ning, the temperature of the inner wall surface may be controlled to a temperature of 80 ° C. or higher. In this case, the cleaning is a chemical reaction, and the reaction speed increases as the temperature increases. Therefore, the cleaning time is shortened, and as a result, the throughput of the entire film forming process is improved.
When the present inventors conducted an experiment to confirm the temperature dependency of the cleaning of the SiOF film, the result shown in FIG. 5 was obtained, and the cleaning time required the temperature of the inner wall surface to increase. It became clear that it became shorter.

In this experiment, Ar gas, O ₂ gas and SiF ₄ gas were respectively introduced at a predetermined flow rate using the plasma film forming apparatus shown in FIG.
W, the bias power was 2700 W, the pressure in the vacuum vessel 2 was 0.4 Pa, and the SiOF
After the film was formed, NF ₃ gas and N ₂ gas were introduced as cleaning gases at flow rates of 1000 sccm and 500 sccm, respectively, with a high frequency power of 1200 W, a bias power of 0 W, and a pressure in the vacuum vessel 2 of 400 Pa. Cleaning was performed while controlling the temperature of the inner wall surface of the vacuum vessel 2, and the cleaning time was measured.

Here, the end point of the cleaning is determined by measuring the luminescence intensity of the active species of O generated by the decomposition of the SiOF film, and the luminescence intensity gradually decreases as the cleaning proceeds. Since the value becomes zero at the end of the cleaning, the time until the emission intensity of the O active species becomes zero is defined as the cleaning time.

As described above, during the process cycle of the film forming process and the cleaning, the inner wall surface of the vacuum vessel 2 is kept at the same temperature, for example, the temperature T0 or more which is reached when plasma for the film forming process is generated. If you control to
Since the temperature of the inner wall surface does not decrease during cleaning, the process cycle can be started immediately after the completion of the cleaning without waiting for the temperature to stabilize. Throughput can be improved.

Further, in the present embodiment, the temperature of the inner wall surface of the vacuum vessel 2 is not limited to the temperature above the temperature T0, and may be a temperature below the temperature T0 as long as the temperature is in the vicinity of this temperature.
If the temperature is close to the temperature T0, even if the temperature is equal to or lower than the temperature T0, the rate of temperature change of the inner wall surface due to generation and disappearance of plasma is small, and it is considered that thermal deformation of the SiOF film is unlikely to occur. .

As described above, in the present invention, instead of allowing Galden to flow through the flow path 31 to control the temperature of the inner wall surface, a heating means is buried in the inner wall surface of the vacuum vessel 2 to thereby control the temperature. It may be. Further, the method of the present invention
In addition to the iOF film forming process, the present invention can be applied to a SiO ₂ film, a CF film, an organic insulating film forming process, and the like. For example, in the case of a SiO ₂ film forming process, the temperature T0 is about 70 ° C. Therefore, it is desirable to carry out the process cycle at a substantially constant temperature of 70 ° C. or higher.

[0039]

According to the plasma processing apparatus of the present invention, when performing a film forming process on a substrate by plasma,
Particle contamination of the substrate can be suppressed.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a plasma film forming apparatus for carrying out a method of the present invention.

FIG. 2 is an explanatory diagram showing a process cycle of a film forming process of the method of the present invention.

FIG. 3 is a characteristic diagram showing a relationship between the temperature of the inner wall surface and the number of generated particles.

FIG. 4 is a characteristic diagram showing the temperature dependence of the SiOF film.

FIG. 5 is a characteristic diagram showing temperature dependency of a cleaning time.

FIG. 6 is a sectional view showing a conventional plasma processing apparatus.

[Explanation of symbols]

 2 Vacuum Vessel 21 Plasma Chamber 22 Film Formation Chamber 25 Waveguide 26 High-Frequency Power Supply 31 Flow Path 32 Temperature Detector 33 Adjuster 51 Main Electromagnetic Coil 6 Mounting Table W Semiconductor Wafer

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Masahide Saito 5-3-6 Akasaka, Minato-ku, Tokyo Inside Tokyo Electron Limited

Claims (2)

[Claims] 1. A series of process cycles in which a substrate is carried into a vacuum vessel, a process gas is turned into plasma, the film is formed on the substrate by the plasma, and then the substrate is carried out of the vacuum vessel. After performing a number of times, in a method of removing a thin film adhered in the vacuum vessel with a cleaning gas, the temperature of the inner wall surface of the vacuum vessel during the process cycle is increased when plasma is generated. A plasma film forming method, wherein the temperature is maintained at a substantially constant temperature equal to or higher than the wall temperature T0. 2. The method according to claim 1, wherein the temperature of the inner wall surface of the vacuum vessel is maintained at a constant temperature equal to or lower than the temperature T0, instead of being maintained at a substantially constant temperature equal to or higher than the temperature T0. Plasma film formation processing method.