JPH04367226A - Apparatus and method for plasma etching - Google Patents

Abstract

PURPOSE:To provide an apparatus and a method, for a plasma etching operation. wherein it is possible to prevent a semiconductor element during an etching process from being contaminated with a material for an electrode and with a material for an inner wall on a reaction chamber. CONSTITUTION:Electrodes 4, 5 are installed by keeping their interval sufficiently small in such a way that a plasma discharge region 12 can be confined in the space between the electrodes 4, 5; specimens 6, 7 to be etched are mounted individually on the electrodes 4, 5; high-frequency electric power is applied alternately to the individual electrodes 4, 5. Thereby, an etching operation is executed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma etching apparatus and a plasma etching method used for etching a sample to be processed with plasma in the manufacturing process of semiconductor devices and the like.

0002

[Prior Art] Plasma etching equipment used for dry etching processing for etching various thin films such as semiconductor devices, ashing processing for removing resist films, etc. performs dry etching using reactive components in gas plasma. , has been widely used in LSI manufacturing processes in recent years. As a conventional plasma etching apparatus, there is a parallel plate type plasma etching apparatus that uses a technique of generating plasma by applying a high frequency voltage of about 10 KHz to 30 KHz to one of parallel plate electrodes in a vacuum. This type of device is disclosed, for example, in Japanese Patent Application Laid-Open No. 56-87670.

FIG. 2 is a schematic diagram showing an example of a conventional parallel plate type plasma etching apparatus. In this figure, 21 is a reaction chamber, 22 is an upper electrode, 23 is a lower electrode, 2
4 is a matching circuit, 25 is a high frequency power supply, 26 is a vacuum evacuation device, 27 is an etching gas supply device, 28 is a gas plasma, and 29 is a sample to be etched. In the above plasma etching apparatus, in the grounded reaction chamber 21,
The upper electrode 22 and the lower electrode 23 face each other in parallel. The lower electrode 23 is grounded, and the upper electrode 22 is connected to a high frequency power source 25 via a matching circuit 24. The reaction chamber 21 is evacuated to a high vacuum by an evacuation device 26, and etching gas is introduced from an etching gas supply device 27. In this state, when high frequency power is applied to the upper electrode 22, a discharge occurs between the electrodes 22 and 23, and gas plasma 28 is generated. The chemically active species in this plasma etch the sample to be etched 29 placed on the lower electrode 23 .

In addition to this example, there are other methods for electrically connecting the electrodes, such as applying high frequency power to the lower electrode and grounding the upper electrode, and applying high frequency power to each of the upper and lower electrodes. As described above, the conventional parallel plate plasma etching apparatus generates plasma by applying high frequency power to the etching gas introduced between the parallel plate electrodes, and accelerates the generated plasma to form a plasma between the parallel plate electrodes. A sample to be etched placed on one side was to be etched. In the above-described dry etching apparatus, the electrode used to convert fluorocarbon or carbon chloride-based etching gas into plasma by discharge is made of, for example, stainless steel, SiC, graphite, or the like.

[0005]

[Problems to be Solved by the Invention] However, in conventional plasma etching equipment, the counter electrode (the electrode facing the electrode on which the sample to be etched is mounted) is exposed to plasma, and the entire reaction chamber is Plasma spreads. Conventionally, no consideration has been given to the effects of this plasma on the counter electrode and the reaction chamber wall, and when the counter electrode and the reaction chamber wall are exposed to plasma, reactions with chemically active species, ion bombardment, etc. This causes a problem in that impurities fly into the plasma and adhere to the sample to be etched, degrading device characteristics. That is, ions in the plasma accelerated by the electric field collide with the counter electrode to knock out electrode material particles, or chemically active species in the plasma react with the counter electrode to create impurities. Further, the chemically active species in the diffused plasma react with the inner wall of the reaction chamber and etch it, thereby creating impurities. These impurities fly and adhere to the sample to be etched. For example, when the surface of a stainless steel electrode is hit (sputtered) with ions or molecules, the sputtered heavy metals such as Fe and Ni contaminate the sample to be etched, while the carbon particles ejected by sputtering of a graphite electrode contaminate the sample to be etched. It falls and adheres to the sample, causing pattern defects, resulting in deterioration of device characteristics and reduction in device yield.

[0006]Also, methods have been proposed in which the electrodes or the reaction chamber walls are made of materials that do not significantly affect the device characteristics, or the electrodes are coated to prevent deterioration of the device characteristics due to contamination with impurities. In this case, new problems such as severe deterioration of the electrode constituent material and the need to frequently replace the electrode have arisen.

The present invention provides a plasma etching apparatus and a plasma etching method that can prevent electrode materials and reaction chamber wall materials from contaminating semiconductor elements during the etching process, as well as prevent consumption of electrodes and reaction chamber materials. The purpose is to provide.

[0008]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a reaction chamber into which an etching gas is introduced, a vacuum evacuation device for evacuating the inside of the reaction chamber, and a vacuum evacuation device installed opposite to each other in the reaction chamber. a pair of electrodes, and a power applying means for applying high frequency power to the etching gas introduced between the pair of electrodes, generating gas plasma between the pair of electrodes by applying the high frequency power, In a plasma etching apparatus configured to etch the surface of a sample to be processed held by at least one of the pair of electrodes, the pair of electrodes are arranged at an interval such that a plasma discharge region is substantially confined between the electrodes, The power applying means is configured to apply high frequency power to one of the pair of electrodes and to be able to switch the application of the high frequency power to the other of the pair of electrodes. In the plasma etching method of the present invention, a sample to be processed is placed on each of a pair of electrodes installed facing each other in a reaction chamber, and after the reaction chamber is evacuated, an etching gas is introduced, and the etching gas is introduced into the reaction chamber. By alternately applying high-frequency power to each electrode, a gas plasma discharge region substantially confined between the electrodes is formed, and the sample to be processed is etched.

[0009]

According to the present invention, etching gas is turned into plasma between the electrodes, and a plasma discharge region is formed. Since the distance between the pair of electrodes is formed sufficiently narrow,
This gas plasma discharge region is substantially confined between the pair of electrodes and does not spread to other regions such as the inner wall of the reaction chamber. The sample to be processed placed on each of the facing electrodes is etched by applying high frequency power alternately to each electrode. Furthermore, since the etched portions of the samples placed on both electrodes are gasified, contamination between the samples to be processed does not occur.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic diagram showing an embodiment of a plasma etching apparatus according to the present invention. In this figure, 1
2 is a reaction chamber, 2 is a vacuum evacuation device for evacuating the inside of reaction chamber 1, and 3
is an etching gas supply device that supplies etching gas into the reaction chamber 1; 4 and 5 are a pair of electrodes with the same shape; 6 and 7 are samples to be etched placed on electrodes 4 and 5, respectively; 8 is a high frequency power supply, 9 is a high frequency power switch, 10 and 11 are electrodes 4 and 5, respectively.
A matching circuit 12 is a plasma discharge region formed between electrodes 4 and 5.

As shown in FIG. 1, in this plasma etching apparatus, high frequency power is applied from a high frequency power source 8 to the electrodes 4 and 5 via a high frequency power switch 9 and matching circuits 10 and 11. . Further, the distance between the electrodes 4 and 5 is kept sufficiently small so that the generated plasma discharge region is substantially confined in the space between them, and the sample to be etched is placed on each of the electrodes 4 and 5. Note that the sample to be etched placed on the upper electrode 5 is held by an electrostatic chuck in consideration of impurities flying away due to ion bombardment. Also,
The size of the sample to be etched placed on the electrodes 4 and 5 is:
It is smaller than electrodes 4 and 5.

When generating plasma in the apparatus configured as described above, first, the evacuation device 2 is operated, and the reaction chamber 1 is
is evacuated to high vacuum. Next, etching gas supply device 3
An etching gas is introduced into the reaction chamber 1 at a predetermined pressure or a predetermined flow rate. Here, when high frequency power is applied to the electrodes 4 or 5, a discharge occurs between the electrodes 4 and 5, and a plasma discharge region 12 is formed. At this time,
When the diameter of the electrodes 4 and 5 was set to 150 mm, the distance between the two electrodes was set to 5 mm or less, and the pressure was set to 100 pa and the RF power was set to 500 W, the plasma was concentrated between the two electrodes without spreading throughout the reaction chamber. That is, the plasma discharge region 12 is substantially confined in the space between the electrodes 4 and 5. As a result, the plasma discharge area does not spread to other areas such as the inner wall of the reaction chamber 1, so the influence of the plasma on the inner wall of the reaction chamber 1 can be reduced.
It is possible to prevent the sample to be etched from being contaminated by the inner wall material of the reaction chamber 1, and also to prevent the inner wall of the reaction chamber 1 from deteriorating. Incidentally, the interval for concentrating the plasma between the electrodes 4 and 5 changes depending on the pressure and RF power.

Plasma etching is performed by switching the high frequency power using the high frequency power switch 9 and matching circuits 10 and 11 and applying the high frequency power to the respective electrodes 4 and 5. That is, when etching a sample to be etched placed on the electrode 4, the electrode 5 is controlled to be a grounded electrode or a floating electrode, and the electrode 4 is controlled to be a high frequency application electrode, and plasma is generated between the electrodes 4 and 5. to proceed with etching. When etching the sample to be etched on the electrode 5, the etching progresses by controlling the electrode 5 to be a high frequency application electrode and the electrode 4 to be a ground electrode or a floating electrode. At this time, the etching rate of the sample to be etched can be made uniform by applying high frequency power to the electrodes 4 and 5 alternately, for example, by switching periodically at sufficiently short intervals with respect to the total etching time. can. In the above embodiment, a cathode-coupled type etching apparatus was described in which high-frequency power is applied to the electrode on which the sample to be etched is placed, but an anodic-coupled type etching apparatus in which high-frequency power is applied to a counter electrode may also be used.

[0014] In addition to the above-mentioned method, the high-frequency power can be switched by a method of switching the high-frequency power between the early stage and the late stage of etching. The method will be explained below. First, a dummy sample is placed on the upper electrode 5, a first sample to be etched is placed on the lower electrode 4, and an etching gas is supplied into the reaction chamber 1 and maintained at a constant pressure. In this state, high frequency power is applied to the electrode 4 to start etching. Next, when the etching of the first sample to be etched has progressed halfway, the etching is temporarily stopped and the electrode 5 is etched.
The upper dummy sample is carried out of the reaction chamber 1, and a second sample to be etched is placed on the electrode 5. Subsequently, high frequency power is applied to the electrode 5 to ground or float the electrode 4, and the second sample to be etched is etched. After that, high frequency power is applied to the electrode 4 again, and the first
Continue etching the sample to be etched. When etching of the sample to be etched on the electrode 4 is completed, the first sample to be etched is carried out, a third sample to be etched is placed on the electrode 4, and etching is continued in the same manner. Even if such a method is adopted, it is possible to uniformize the etching of each sample to be etched placed on the electrodes 4 and 5.

Although the present invention has been specifically explained above based on examples, it goes without saying that the present invention is not limited to the above-mentioned examples and can be modified in various ways without departing from the gist thereof. do not have. For example, in the example, the sample to be etched on the upper electrode was held by an electrostatic chuck, but other means such as a clamp may be used. Furthermore, although the sample to be etched placed on the electrode was chosen to be smaller than the electrodes 4 and 5 as shown in FIG. 1, it may be the same size as the electrodes 4 and 5.

[0016]

Effects of the Invention As described above in detail, according to the plasma etching apparatus and plasma etching method of the present invention, materials other than the sample to be etched, such as electrode materials and reaction chamber wall materials, are etched and deteriorated. In addition, it is possible to prevent the sample to be etched from being contaminated by these impurities. Furthermore, since the counter electrode in the present invention is not directly exposed to plasma and does not use materials that deteriorate rapidly, the life of the electrode material is long.
This has the effect of allowing the equipment to be used more efficiently.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a plasma etching apparatus of the present invention.

FIG. 2 is a schematic configuration diagram showing an example of a conventional plasma etching apparatus.

[Explanation of symbols]

1 Reaction chamber 2 Vacuum exhaust equipment 3 Etching gas supply device 4 Electrode 5 Electrode 6 Etching sample 7 Etching sample 8 High frequency power supply 9 High frequency power switch 10 Matching circuit 11 Matching circuit 12 Plasma discharge area

Claims (2)

[Claims] Claim 1: A reaction chamber into which an etching gas is introduced, a vacuum evacuation device for evacuating the inside of the reaction chamber, a pair of electrodes installed opposite to each other in the reaction chamber, and an etching gas introduced between the pair of electrodes. a power applying means for applying high frequency power to the etching gas, the application of the high frequency power generates gas plasma between the pair of electrodes, and the surface of the sample to be processed held by at least one of the pair of electrodes. In the plasma etching apparatus, the pair of electrodes are arranged at a distance such that a plasma discharge region is substantially confined between the electrodes,
The power applying means is characterized in that it is configured to apply high frequency power to one of the pair of electrodes and to switch the application of the high frequency power to the other of the pair of electrodes. Plasma etching processing equipment. 2. A sample to be processed is placed on each of a pair of electrodes installed facing each other in a reaction chamber, and after the reaction chamber is evacuated, an etching gas is introduced, and the etching gas is alternately applied to each of the pair of electrodes. A plasma etching method characterized in that a gas plasma discharge region substantially confined between the electrodes is formed by applying high frequency power to etching the sample to be processed.