JPH08165584A - Plasma treatment - Google Patents

Abstract

PURPOSE: To provide a plasma treatment excellent in reproducibility of the treatment result. CONSTITUTION: A plasma treating device provided with plural electrodes 3 and 4 to be supplied with a high-frequency power is used in this plasma treatment. A substrate 2 to be worked is placed on the lower electrode 3, and an inert gas for a specified plasma treatment is introduced into a vacuum vessel 1 by a gas feed line not shown in the figure to keep the vessel at a specified vacuum with an evacuating system not shown in the figure. A high-frequency power is supplied to the electrodes 3 and 4, and the gas to be introduced into the vessel 1 is changed from the inert gas to a specified reacting gas after the plasma produced in the vessel 1 is stabilized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing method in a thin film processing technique such as dry etching and plasma CVD.

[0002]

2. Description of the Related Art In recent years, along with the miniaturization of semiconductor elements, in dry etching technology, a high aspect ratio (machining hole, depth / diameter) is processed, and plasma C is used.
High aspect ratio (embedded, depth /
In order to embed (diameter), plasma processing is performed in a higher vacuum.

This is because in dry etching, when a high vacuum is generated in a high vacuum to generate high density plasma, the probability that ions will collide with neutral gas molecules in the ion sheath formed on the surface of the substrate to be processed is small. Since the directionality of ion movement is uniform toward the substrate to be processed, and the ionization degree is high, the ratio of the ion flux reaching the substrate to the incident particle flux of neutral radicals becomes large, and the etching This is because the anisotropy is enhanced and processing with a high aspect ratio becomes possible.

In plasma CVD, when a high vacuum is generated to generate high-density plasma, deposition of a flat portion is faster than that of a slanted portion due to a sputtering effect of ions, and a fine pattern embedding / planarizing action is obtained. This is because embedding with a high aspect ratio becomes possible.

A conventional plasma processing method will be described below.
A first conventional example performed using a plasma processing apparatus, which is a general parallel plate type and has one charging electrode, will be described with reference to FIG.

In FIG. 3, the gas is exhausted by a vacuum system (not shown) and a predetermined gas is supplied from a gas supply system (not shown).
A lower electrode 3 on which a substrate 2 is placed and an upper electrode 4 are arranged in a vacuum container 1 which is maintained at a predetermined degree of vacuum.
High-frequency power is applied between the electrodes 3 and 4 by the lower-electrode high-frequency power source 5 to generate plasma in the vacuum container.

The lower electrode matching circuit 6 is a circuit for matching the load impedance with the characteristic impedance of the connection cable 7.

In the first conventional example, since the plasma processing apparatus having one charging electrode is used, if the degree of vacuum is increased,
There is a problem that the probability of collision between electrons and ions is reduced, it becomes difficult to generate high density plasma at a high vacuum degree, and a desired processing speed cannot be obtained.

Further, in the first conventional example, when the high frequency power is forcibly increased to increase the plasma density, the ion energy becomes too large, the etching selection ratio is lowered, and the substrate is damaged. There is.

In order to solve these problems by the conventional plasma processing method, a general parallel plate type plasma processing apparatus having a plurality of charging electrodes may be used.
The second and third conventional examples in this case will be described with reference to FIGS. 1 and 2.

In FIG. 1 showing a plurality of plasma processing apparatuses in which the charging electrodes used in the second conventional example are different from FIG. 3, a high frequency power for the upper electrode is applied to the upper electrode 4 in order to apply high frequency power. That is, the power source 8 and the upper electrode matching circuit 9 for matching the load impedance with the characteristic impedance of the connection cable 10 are added.

According to the apparatus shown in FIG. 1 used in the second conventional example, the plasma density can be controlled by the high frequency power applied to the upper electrode 4, and the ion energy can be controlled by the high frequency power applied to the lower electrode 3. By controlling each of them independently, it is possible to process the plasma with a considerably high density.

In FIG. 2 showing the plasma processing apparatus used in the third conventional example, what is different from FIG. 3 is that a multi-vortex discharge coil 11 is provided on the upper part. The multi-vortex discharge coil 11 includes a discharge coil high-frequency power source 12 and a discharge coil matching circuit 1 for matching the load impedance with the characteristic impedance of the connection cable 13.
4 is attached.

The apparatus shown in FIG. 2 used in the third conventional example is
This is a high-frequency induction type plasma processing apparatus, and in this type, a high frequency used is as shown in FIG. 3 and a coil having a high frequency used is several MHz is wound around the outer circumference of the vacuum container. There are some (not shown). In these high frequency induction type plasma processing apparatuses, a high frequency magnetic field is generated in the vacuum container 1 by a coil,
This high-frequency magnetic field generates an induction magnetic field in the vacuum container to accelerate electrons to generate plasma. If the coil current is increased, high-density plasma can be generated even in high vacuum.

In the second and third conventional examples using the apparatus shown in FIGS. 1 and 2, a predetermined reaction gas is introduced from a gas supply system (not shown) while the inside of the vacuum container 1 is evacuated by a vacuum system (not shown). When high frequency power is applied to the upper electrode 4 of FIG. 1 or high frequency power is applied to the multi-vortex discharge coil 11 of FIG. 2 while maintaining the inside of the vacuum container 1 at a predetermined degree of vacuum, the vacuum container 1 Plasma is generated in the substrate 2, high-frequency power is applied to the lower electrode 3 on which the substrate 2 is placed, and the ion energy reaching the substrate 2 is controlled to etch and deposit the substrate 2. Plasma treatment such as surface modification can be performed. Then, as described above, since high-density plasma can be generated, a sufficient processing speed can be obtained.

[0016]

However, the above second,
In the third conventional example, it often takes about 2 to 10 seconds from the input of high-frequency power to the stabilization of discharge, and the time is not constant. In normal plasma processing,
Since the time for processing the substrate is about 30 seconds to 2 minutes,
When the time until the above-mentioned discharge is stabilized is subtracted, the time for actual regular discharge is shortened by about 2 to 30% with respect to the set time. For this reason, for example, in the case of etching, there is a problem that the film thickness to be etched varies in the range of about 2 to 30%, and reproducibility of plasma processing cannot be obtained.

It is presumed that this is because the input high frequency powers interfere with each other, which is a phenomenon not seen in the method of applying high frequency power to only one electrode shown in FIG. 3 used in the first conventional example. Is.

This problem is not a problem that can be solved by counting the plasma processing time and managing the time immediately after the discharge is stabilized. This is because by the time the discharge stabilizes, a phenomenon that occurs in a state where the discharge is not stable already occurs, and this affects the plasma treatment result.

This specific example will be described by taking plasma processing etching of a silicon oxide film as an example.

Etching of the silicon oxide film is usually performed by C
The gas containing F and F is converted into plasma, but in the second conventional example using the apparatus of FIG. 1, the discharge of the high frequency power applied to the lower electrode 3 on which the substrate 2 is placed is not stable and the upper electrode 4 During a state in which only the high-frequency voltage applied to is stably discharged, a phenomenon that CF-based polymer is deposited on the substrate 2 occurs. Since this polymer has the property of being difficult to be etched, if there is variation in the time from the application of high-frequency power to the stabilization of discharge, the film thickness of the deposited polymer will vary, and as a result, the etching time after stabilization of discharge will be the same. However, there is a problem that the thickness of the silicon oxide film to be etched varies considerably.

The third conventional example using the apparatus of FIG. 2 also has the same problem as described above.

Not limited to etching of silicon oxide film,
In a thin film processing technique such as plasma CVD, in a second conventional example using the apparatus of FIG. 1 and a third conventional example using the apparatus of FIG. 2, that is, the substrate 2 is placed in the vacuum container 1. In the plasma processing method in which the high frequency power is supplied to the electrodes and coils other than the lower electrode 3, the discharge of the high frequency power applied to the lower electrode 3 on which the substrate 2 is mounted is not stable, and the electrodes other than the lower electrode 3 and The period in which only the high frequency voltage applied to the coil is stably discharged and the period in which the high frequency voltage applied to all electrodes and coils are stably discharged are generated on the substrate 2. Since the phenomenon is often very different, if there is variation in the time from the input of high-frequency power to the stabilization of discharge, the reproducibility of the process is often not obtained even if the time after stabilization of discharge is the same. There is.

An object of the present invention is to solve the above problems and to provide a plasma processing method which is excellent in reproducibility of plasma processing results in a thin film processing technique.

[0024]

In order to solve the above-mentioned problems, the plasma processing method of the first invention of the present application is a plasma processing method using a plasma processing apparatus having a plurality of electrodes to which high-frequency power is supplied. First, after introducing an inert gas for a predetermined plasma treatment into a vacuum container, maintaining a predetermined vacuum degree, supplying high-frequency power to the plurality of electrodes, and after plasma generated in the vacuum container becomes stable. The gas introduced into the vacuum container is switched from the inert gas to a predetermined reaction gas.

In order to solve the above problems, the plasma processing method according to the second aspect of the present invention is a plasma processing method using a plasma processing apparatus provided with an electrode to which high-frequency power is supplied and a discharge coil. Inert gas for plasma treatment is introduced into the vacuum vessel, maintained at a predetermined degree of vacuum, high frequency power is supplied to the electrode and the discharge coil, and after plasma generated in the vacuum vessel is stabilized, The gas introduced into the vacuum container is switched from the inert gas to a predetermined reaction gas.

In order to solve the above-mentioned problems, the plasma processing methods of the first and second inventions of the present application, when the ratio of the reflected power to the input power of the high frequency power decreases and reaches a predetermined ratio, an inert gas is used. Therefore, it is preferable to switch to a predetermined reaction gas, and the predetermined ratio is preferably 1%.

In order to solve the above-mentioned problems, the plasma processing methods of the first and second inventions of the present application have the effect that, even if the inert gas is ionized in the predetermined plasma processing, the deposition and etching by the ions are performed. Gases containing helium, argon or nitrogen, which do not occur, are preferred.

[0028]

In the plasma processing method of the present invention, first, an inert gas for a predetermined plasma processing is introduced into a vacuum container,
Maintaining a predetermined degree of vacuum, supplying high-frequency power to the plurality of electrodes, after the plasma generated in the vacuum container is stabilized, a gas to be introduced into the vacuum container from the inert gas, a predetermined By switching to reactive gas, unnecessary and harmful deposition and etching can be prevented until the discharge stabilizes.The inert gas is replaced with the reactive gas, and the discharge starts from the time when the required deposition or etching begins. Since the processing time can be managed by the time until the stop, it is possible to improve the reproducibility of the plasma processing result.

Further, until the discharge is stabilized, even if high-frequency power is supplied, the portion that is not discharged is reflected, and the ratio of the reflected power to the input power of the high-frequency power is large.
When the discharge is stable, the ratio of the reflected power to the input power becomes small. Therefore, the stabilization of the discharge can be determined by the percentage of the reflected power to the input power. The reflected power is usually measured using a reflected power meter attached to the high frequency power supply.

Depending on the type and conditions of the plasma processing, the reproducibility of the plasma processing will be better when the ratio of the reflected power to the input power is switched at different times. Accordingly, the predetermined ratio may be determined so that both reproducibility and work efficiency are compatible. And 1% is one of the criteria for achieving both reproducibility and efficiency.

If a gas containing helium, argon or nitrogen, which does not cause deposition or etching by ions even when ionized in a predetermined plasma treatment, is used as the inert gas, the result of the plasma treatment can be improved. The reproducibility can be improved.

[0032]

EXAMPLE A first example of the plasma processing method of the present invention will be described with reference to FIG.

In FIG. 1, the gas is exhausted by a vacuum system (not shown) and a predetermined gas is supplied from a gas supply system (not shown).
A lower electrode 3 on which a substrate 2 is placed and an upper electrode 4 are arranged in a vacuum container 1 which is maintained at a predetermined degree of vacuum.
The lower electrode 3 is supplied with high frequency power from the lower electrode high frequency power supply 5 through the lower electrode matching circuit 6. The lower electrode matching circuit 6 is a circuit for matching the load impedance with the characteristic impedance of the connection cable 7. The high frequency power from the high frequency power supply 8 for the upper electrode is supplied to the upper electrode 4 through the upper electrode matching circuit 9. The upper electrode matching circuit 9 is a circuit for matching the load impedance with the characteristic impedance of the connection cable 10.

In the present embodiment, first, in the plasma processing to be performed, the inside of the vacuum container 1 is maintained in a predetermined degree of vacuum of an inert gas that does not deposit even if ionized and does not cause an etching action. Introduced into, to apply a high-frequency power to a plurality of electrodes, to stabilize the discharge, then the inert gas is stably discharged, the reaction gas, that is, in the plasma treatment to be performed, ionized, An operation of depositing by a plasma CVD process and replacing with a gas having an etching action in an etching process is performed. by this,
Until the discharge is stabilized, unnecessary and harmful deposition and etching are prevented, and the processing time is managed from the time when the inert gas is replaced with the reactive gas until the discharge is stopped, and the plasma processing results are reproduced. You can improve your sex.

Further, the ratio of the reflected power to the input power of the high frequency power is large until the discharge is stable, and the ratio of the reflected power to the input power is small if the discharge is stable. The stabilization of the discharge is judged by%. The reflected power is usually measured using a reflected power meter attached to the high frequency power supply. And, the smaller the% of the reflected power is, the more stable the discharge is.
The more you switch with, the better the reproducibility of plasma processing, but
Since the working time is reduced, it is only necessary to set the percentage that makes reproducibility and working efficiency compatible.

In this embodiment, the reflected power is 1% of the input power.
Although the time point is defined as a standard for achieving both reproducibility and work efficiency, it is of course not limited to 1% and may be set according to the actual situation.

The present embodiment will be specifically described below with reference to FIG. 1 by taking the etching of the silicon oxide film as an example.

In the parallel plate type plasma processing apparatus shown in FIG. 1, argon gas was used as the inert gas and the flow rate was 30.
SCCM (standard state gas flow rate per minute), pressure 50
Used in mTorr, the high frequency power source 8 for the upper electrode and the high frequency power source 5 for the lower electrode both have a frequency of 13.56 MHz, and the input power is 1000 W and 300 W, respectively, to discharge.
Generate plasma.

In this embodiment, the reflected power on the upper electrode 4 side was 1% or less of the applied power of 1000 W, that is, 10 W or less, always within 1 second after the power was applied.
On the lower electrode 3 side, until the reflected power becomes 1% or less,
It took 2 seconds in the early case and 5 seconds in the late case.

Immediately after the ratio of the high frequency power supplied to the reflected power to the input power at both upper and lower electrodes became 1% or less, the inert gas argon gas was switched to the reaction gas CHF ₃ gas. The silicon oxide film was etched, and the time of the etching treatment was controlled by the time from the time when the gas was switched from the argon gas to the CHF ₃ gas until the discharge was stopped. CHF ₃ gas flow rate is 30 SC
It was CM. It should be noted that the variation in the degree of vacuum when switching the gas may be limited to about ± 20%.

As a result of processing 100 substrates, the average etching rate was 3050 Å / min, and the variation between the substrates was ± 2.2%, and good results were obtained.

For comparison, the process of generating plasma with an argon gas which is an inert gas was omitted, and 100 substrates were similarly etched. As a result, the average etching rate was 2930 Å / min. The variation was ± 6.5%.

In this case, the etching treatment time was controlled by the time from when the discharge was stabilized until the discharge was stopped.

From the above, it can be confirmed that the present embodiment is excellent in reproducibility of the plasma processing result.

Next, a second embodiment of the plasma processing method of the present invention will be described with reference to FIG.

In FIG. 2, the gas is exhausted by a vacuum system (not shown) and a predetermined gas is supplied from a gas supply system (not shown).
A lower electrode 3 on which a substrate 2 is placed and a multiple vortex discharge coil 11 are arranged in a vacuum container 1 which is maintained at a predetermined degree of vacuum. The lower electrode 3 has a high frequency power source 5 for the lower electrode.
The high frequency power from is supplied via the lower electrode matching circuit 6. The lower electrode matching circuit 6 is a circuit for matching the load impedance with the characteristic impedance of the connection cable 7. The multi-vortex discharge coil 11 is supplied with high frequency power from a high frequency power supply 12 for discharge coil through a matching circuit 13 for discharge coil. The discharge coil matching circuit 13 is a circuit for matching the load impedance with the characteristic impedance of the connection cable 14.

The judgment of the discharge stabilization by the inert gas, the reaction gas, and the reflected power is the same as that of the first embodiment, and the explanation thereof will be omitted.

The present embodiment will be specifically described below with reference to FIG. 2 by taking the etching of the silicon oxide film as an example.

In the high frequency induction type plasma processing apparatus shown in FIG. 2, an argon gas was used as an inert gas at a flow rate of 30 SCCM (a standard state gas flow rate for 1 minute) and a pressure of 10 mTorr. 1
2 and the frequency of the high frequency power source 5 for the lower electrode are both 13.56
MHz, input power 1000W, 300W respectively,
Discharge and generate plasma.

In this embodiment, the reflected power on the side of the multi-vortex discharge coil 11 is 1% or less of the input power of 1000 W, that is,
It was always less than 10 W within 1 second after the power was turned on, but on the lower electrode 3 side, it took 3 seconds at an early time and 10 seconds at a slow time until the reflected power became 1% or less. Needed

In the multi-vortex discharge coil 11 and the lower electrode 3, immediately after the ratio of the high frequency power supplied to the reflected power to the input power is 1% or less, the inert gas argon gas is added to the reaction gas CHF. _The silicon oxide film was etched by switching to the ₃ gas, and the time of the etching process was controlled from the time when the gas was switched from the argon gas to the CHF ₃ gas until the discharge was stopped. The flow rate of CHF ₃ gas was 30 SCCM. It should be noted that the variation in the degree of vacuum when switching the gas may be limited to about ± 20%.

As a result of processing 100 substrates, the average etching rate was 5200 Å / min, and the variation between the substrates was ± 1.8%, and good results were obtained.

For comparison, the process of plasma generation by an inert gas of argon gas was omitted, and 100 substrates were similarly etched. As a result, the average etching rate was 4950 Å / min. The variation was ± 5.1%.

In this case, the etching time was controlled by the time from when the discharge was stabilized until the discharge was stopped.

From the above, it can be confirmed that the present embodiment is excellent in the reproducibility of the plasma processing result.

[0056]

According to the plasma processing method of the present invention, by stabilizing the discharge with an inert gas and then switching to a predetermined reaction gas, unstable, unnecessary and harmful deposition or deposition is possible until the discharge is stabilized. Reproducibility of plasma processing results is controlled by preventing etching from occurring, replacing the inert gas with a reactive gas, and managing the processing time from the time when the required deposition or etching begins to the time the discharge stops. There is an effect that it can be improved.

Further, by determining the stabilization of the discharge by% of the reflected power with respect to the input power of the high frequency power, and setting the timing of switching from the inert gas to the reactive gas, the control of the plasma processing is facilitated and reproduced. There is an effect that both productivity and work efficiency can be achieved at the same time.

If a gas containing helium, argon or nitrogen, which does not cause deposition or etching by ions even when ionized in a predetermined plasma treatment, is used as the inert gas, the result of the plasma treatment can be improved. This has the effect of improving reproducibility.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a parallel plate type plasma processing apparatus having a plurality of electrodes to which high frequency power is applied.

FIG. 2 is a perspective view showing an example of a high frequency induction type plasma processing apparatus to which a plurality of high frequency powers are applied.

FIG. 3 is a perspective view showing an example of a parallel plate type plasma processing apparatus having one electrode to which high frequency power is applied.

[Explanation of symbols]

 1 Vacuum Container 2 Substrate 3 Lower Electrode 4 Upper Electrode 5 Lower Electrode High Frequency Power Supply 6 Lower Electrode Matching Circuit 7 Connection Cable 8 Upper Electrode High Frequency Power Supply 9 Upper Electrode Matching Circuit 10 Connection Cable 11 Multi-vortex Discharge Coil 12 Discharge Coil High frequency power supply 13 Matching circuit for discharge coil 14 Connection cable

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01L 21/3065

Claims (5)

[Claims] 1. A plasma processing method using a plasma processing apparatus provided with a plurality of electrodes to which high-frequency power is supplied. First, an inert gas for a predetermined plasma processing is introduced into a vacuum container to obtain a predetermined vacuum degree. And the high frequency power is supplied to the plurality of electrodes, and after the plasma generated in the vacuum container is stabilized, the gas introduced into the vacuum container is switched from the inert gas to a predetermined reaction gas. A plasma processing method characterized by the above. 2. A plasma processing method using a plasma processing apparatus provided with an electrode to which high-frequency power is supplied and a discharge coil, wherein first, an inert gas for a predetermined plasma processing is introduced into a vacuum container and a predetermined gas is supplied. Maintain a vacuum,
High-frequency power is supplied to the electrodes and the discharge coil, and after the plasma generated in the vacuum container is stabilized, the gas introduced into the vacuum container is switched from the inert gas to a predetermined reaction gas. A characteristic plasma processing method. 3. The plasma processing method according to claim 1, wherein when the ratio of the reflected power to the input power of the high frequency power decreases and reaches a predetermined ratio, the inert gas is changed to a predetermined reaction gas. Plasma processing method to switch to. 4. The plasma processing method according to claim 3, wherein the predetermined ratio is 1%. 5. The plasma processing method according to claim 1, 2, 3, or 4, wherein the inert gas does not cause an action such as ion deposition or etching even if ionized in a predetermined plasma processing. A method of plasma treatment which is a gas containing helium, argon or nitrogen.