JP5072488B2 - Cleaning method for dry etching equipment - Google Patents

Description

  The present invention relates to a cleaning method for a dry etching apparatus, and more particularly to a cleaning method for removing an etching reaction product attached to an inner wall of a chamber in a plasma etching apparatus.

  Plasma etching apparatuses are widely used in the field of microfabrication, such as manufacturing processes for optical components such as microlenses and manufacturing processes for semiconductor devices. In a plasma etching apparatus, an etching reaction gas is supplied into a chamber, high-frequency power is supplied from an electrode arranged in the chamber or a coil arranged outside the chamber to generate plasma in the chamber, and the plasma etching is performed in the chamber. The placed object to be etched is subjected to an etching process.

  In plasma etching, reactive gas ions generated by plasma act on the surface of an object to be etched, and the surface is processed. At this time, the object to be etched and the etching gas react to generate an etching reaction product. Most of the reaction product is discharged from the chamber together with the exhaust gas, but a part of the reaction product adheres to the inner wall of the chamber.

  Therefore, in the plasma etching apparatus, when the object to be etched is processed once or several times, a cleaning gas such as oxygen is supplied into the chamber instead of the etching gas as a reaction gas, and plasma is generated to generate plasma. A cleaning operation for removing an etching reaction product adhering to the substrate is performed.

As a method for efficiently performing the cleaning operation, a magnetic field generating means is provided on the outer periphery of the chamber, and when the cleaning gas plasma is generated during cleaning, the magnetic field generating means causes the plasma in the chamber to be uniformly distributed in the chamber. There has been proposed a method of removing even etching reaction products adhering to the corners of the inner wall of the chamber by making the plasma density in the chamber uniform by causing fluidization to spread (see Patent Document 1).
JP 2002-252203 A

  In the proposed cleaning method, a magnetic field is applied so that the plasma in the chamber at the time of cleaning becomes uniform in the chamber. However, since the absolute number of active species in the plasma that can be used for cleaning in the chamber does not change, the plasma density decreases if it is uniformly distributed in the chamber. As a result, the plasma processing time for cleaning becomes longer, and the operation rate of the etching apparatus is lowered correspondingly, and the manufacturing cost is increased.

  Therefore, an object of the present invention is to enable the cleaning of the chamber to be completed in a short time.

  During the etching process, an etching reaction product adhering to the inner wall of the chamber may fall and accumulate on the object to be etched, thereby reducing the quality of the etching process. It is known that the deposit is formed by peeling off the etching reaction product attached to the inner wall of the chamber. According to the results of the study by the present inventor, it is found that there is a high probability that the deposit that becomes an obstacle to the etching process is caused by the peeling of the etching reaction product from the etching gas introduction portion in the inner wall of the chamber. It was. This is considered to be because the probability that the reaction product attached to the inner wall of the chamber peels off due to the impact of the etching gas flow.

  Therefore, the present invention is based on this knowledge, and does not equalize the plasma density in the chamber at the time of cleaning as in the proposed cleaning method, but mainly by concentrating the plasma density in the vicinity of the gas introduction part. And the cleaning processing time is shortened.

  That is, according to the present invention, in a dry etching apparatus having a gas introduction part in the upper part of the etching chamber, a cleaning gas is introduced into the etching chamber, and plasma is generated in the etching chamber so that the plasma density is increased in the upper part of the etching chamber. Cleaning method.

  Although the present invention can be applied to various dry etching apparatuses, the applied dry etching apparatus is a magnetic medium in which a plurality of magnetic field coils surrounding the outer peripheral side of the etching chamber are arranged at different heights. In the case of an actinic discharge plasma processing apparatus, the etching chamber is configured so that the plasma density is increased at the upper part in the etching chamber by selectively operating one of those magnetic field coils at the time of cleaning. To generate plasma.

  In the present invention, since the plasma density in the chamber is concentrated in the vicinity of the gas introduction portion during cleaning, it is possible to clean a portion where the etching reaction product attached to the inner wall of the chamber has a high probability of peeling in a short time. Thus, the cleaning processing time can be shortened. As a result, conventionally, depending on the processing conditions, cleaning is performed for each substrate processing, or measures for defective etching processing are taken by extending the cleaning time, so the ratio of the cleaning time to the operating time of the etching apparatus increases. However, according to the present invention, since the cleaning processing time can be shortened, the operating rate of the etching apparatus can be increased and the cost of the etching process can be reduced.

[Example 1]
FIG. 1 schematically shows a magnetic neutron discharge (NLD) plasma processing apparatus as an example of a dry etching apparatus to which the present invention is applied. The chamber 2 has a cylindrical shape, and a substrate electrode 4 on which an object to be etched is placed is provided at the bottom. A gas supply unit 6 for supplying an etching gas or a cleaning gas is disposed in the upper part of the chamber. In the apparatus of this example, the outlet is arranged on the circumference so that the etching gas or the cleaning gas is uniformly supplied into the chamber from the upper peripheral corner in the chamber 2. In order to generate plasma in the chamber 2, electrodes or antennas for supplying high-frequency power are arranged (not shown) around the chamber or outside the chamber. Further, three magnetic field coils 8a, 8b, 8c surrounding the outer peripheral side of the chamber 2 are arranged, the magnetic field coil 8a being the highest upper position, the magnetic field coil 8b being the middle position, and the magnetic field coil 8c being the lowest lower position. It is arranged to be. In order to exhaust the inside of the chamber 20, an exhaust system 28 is provided in the chamber 20.

  When an etching process is performed on an object to be etched placed on the substrate electrode 4, high-frequency power for generating plasma is applied to the electrode or antenna coil, and a bias voltage is applied to the substrate electrode 4. A current is supplied to all of the magnetic field coils 8a to 8c, and currents in opposite directions are supplied to the magnetic field coils 8b and 8c, respectively. By energizing the magnetic field coils 8a to 8c, a magnetic neutral line is formed in the central portion of the chamber 2, and a ring-shaped plasma is formed in the central portion of the chamber 2 along the magnetic neutral line. This contributes to the etching process of the etched product.

  In the cleaning process for removing the etching reaction product adhering to the inner wall in the chamber 2, for example, oxygen is supplied as a cleaning gas into the chamber 2 to generate plasma as in the etching. No bias voltage is applied to the substrate electrode 4. With respect to the magnetic field coils 8a to 8c, conventionally, as shown in FIG. 1A, current is supplied only to the middle magnetic field coil 8b, and no current is supplied to the upper and lower magnetic field coils 8a and 8c. As a result, the density of the cleaning plasma 12 increases at the center of the chamber 2.

  In contrast, the cleaning method of the embodiment is different from the conventional method in energizing the magnetic field coils 8a to 8c. Other conditions are the same. As shown in FIG. 1B, in the magnetic field coils 8a to 8c, a current is supplied only to the uppermost magnetic field coil 8a, and no current is supplied to the middle and lower magnetic field coils 8b and 8c. As a result, the density of the cleaning plasma 14 is increased in the upper part of the chamber 2. The plasma 14 mainly cleans the vicinity of the gas supply unit 6 disposed in the upper part of the chamber 2.

In this embodiment, the results of cleaning when an NLD etching apparatus is used to produce a microlens array on a glass substrate will be described below.
The dry etching conditions for the glass substrate are: CF ₄ as a reaction gas is supplied to the chamber at a flow rate of 50 sccm, the degree of vacuum is 1 mTorr, high-frequency power (antenna power) for generating plasma is 1000 W, and the substrate electrode 4 is applied. The bias power is 500 W. A current of 30 A is supplied to the magnetic field coil 8 a, a current of 50 A is supplied to the magnetic field coil 8 b, and a current of 30 A is supplied to the magnetic field coil 8 c, and the energization direction to the magnetic field coils 8 a and 8 c is opposite to that of the magnetic field coil 8 b. The glass substrate is etched by processing for 7 minutes under the conditions. Cleaning is performed for 2 minutes every 7 minutes of etching.

The cleaning conditions are as follows.
(Conventional conditions)
This is a conventional cleaning condition. Oxygen is supplied as a reaction gas at a flow rate of 100 sccm, the degree of vacuum is 2 mTorr, the antenna power is 1000 W, and the bias power is 0. Regarding the energization of the magnetic field coils 8a to 8c, the magnetic field coil 8a is 0, the magnetic field coil 8b is 50A, and the magnetic field coil 8c is 0.

(Example conditions)
The conditions of the reaction gas, the degree of vacuum, the antenna power, and the bias power are the same as those of the conventional conditions. Regarding the energization of the magnetic field coils 8a to 8c, the magnetic field coil 8a is 30A, and the magnetic field coils 8b and 8c are 0. That is, the conventional conditions and the conditions of the examples are the same except for the energization conditions for the magnetic field coils 8a to 8c.

  As for the cleaning method applied to this dry etching apparatus, the effects of the conventional method and the effects of the embodiment shown above are shown in comparison with FIG. The horizontal axis of FIG. 2 represents the number of etching processes as an input batch. According to this result, the defect occurrence rate of etching processing increases as the number of etching processes increases when cleaning is performed under the conventional conditions, whereas the number of etching processes increases when cleaning is performed under the conditions of the example. However, it can be seen that the defect rate has not increased. This is because the cleaning in the vicinity of the gas introduction portion is not sufficiently performed in the cleaning under the conventional conditions, whereas in the method of the embodiment, the vicinity of the gas introduction portion where the reaction product adhering to the inner wall of the chamber is separated is well cleaned. As a result, the defect rate does not increase even when the number of times of the etching process is advanced.

( Reference example )
FIG. 3 shows a reference example in which the present invention is applied to a parallel plate type CCP (Capacitor Coupled Plasma) etching apparatus. A substrate electrode 22 for placing an object to be etched and applying a bias voltage is disposed in the lower part of the chamber 20, and a gas inlet 24 is provided in the upper part of the chamber 20, and a gas connected to the gas inlet 24. An introduction part 26 is provided in the upper part of the chamber 20. The gas introduction part 26 has a plate shape having a large number of openings. The gas introduction unit 26 is configured to supply the reaction gas or the cleaning gas uniformly from above in the chamber 20. In order to exhaust the inside of the chamber 20, an exhaust system 28 is provided in the chamber 20.

  A high frequency power source 30 for supplying antenna power for generating plasma is connected from an upper electrode (not shown) disposed in the upper portion of the chamber 20, and a high frequency power source 32 for supplying bias power is connected to the substrate electrode 22. It is connected.

  In this parallel plate etching apparatus, when dry etching is performed, an etching gas is supplied as a reaction gas from the gas inlet 26 into the chamber 20, and high frequency power is supplied from the power sources 30 and 32 to the upper electrode and the substrate electrode 32, respectively. Then, a plasma is formed by the etching gas. The plasma is drawn to the substrate electrode 22 side by a bias voltage applied to the substrate electrode 22, and an object to be etched placed on the substrate electrode 22 is processed.

  At the time of cleaning, in the conventional method, as shown in FIG. 3A, cleaning is performed in a state where high-frequency power is supplied to the upper electrode and the substrate electrode 22 as in the etching process. Therefore, the plasma 34 by the cleaning gas in the chamber 20 is generated at the same position as that during the etching process.

On the other hand, in the method of the reference example , as shown in FIG. 3B, the supply of bias power to the substrate electrode 22 is cut off during cleaning. As a result, the plasma 36 due to the cleaning gas in the chamber 20 at the time of cleaning is generated in the vicinity of the upper electrode, and the etching reaction product adhering in the vicinity of the gas introducing portion 26 can be efficiently removed.

It is a schematic sectional drawing which shows the cleaning method applied to a NLD dry etching apparatus, (A) is the conventional method, (B) is the method of one Example. It is a graph which compares the effect of the cleaning method applied to the NLD dry etching apparatus with the method of the conventional method and the method of one Example. It is a schematic sectional drawing which shows the cleaning method applied to a CCP parallel plate type dry etching apparatus, (A) is a conventional method, (B) is a method of a reference example .

Explanation of symbols

2,20 Chamber 4,22 Substrate electrode 6,26 Gas supply part 8a, 8b, 8c Magnetic field coil 12, 14, 34, 36 Plasma 30, 32 High frequency power supply

Claims (1)

In a cleaning method of a magnetic neutral discharge plasma processing apparatus having a gas introduction part at an upper part in an etching chamber, and a plurality of magnetic field coils surrounding the outer peripheral side of the etching chamber being arranged at different heights ,
A cleaning gas is introduced into the etching chamber, and a plasma disposed in the upper part of the etching chamber is selectively activated by introducing a cleaning gas into the etching chamber so that the plasma density is increased in the upper part of the etching chamber. A cleaning method comprising only a cleaning step to be generated.

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