JPH0578171B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a dry etching apparatus used in forming patterns for semiconductor integrated circuits and the like.

[Prior art]

In recent years, with the miniaturization of semiconductor integrated circuits, large-scale integrated circuits with minimum pattern dimensions of 1 μm or less are also being prototyped.
It has been developed and is beginning to be mass produced. This fine pattern cannot be processed by conventional wet etching, and anisotropic etching using dry etching has become an indispensable technique for processing these integrated circuits. There are several types of dry etching equipment. One of them is
A sample is placed on a high-frequency application electrode in a reaction vessel equipped with parallel plate electrodes, and the sample is etched using high-frequency plasma of a reactive gas containing halides such as fluorine and chlorine such as CF ₄ and CCl ₄ . This is a reactive ion etching device. This reactive ion etching equipment can process aluminum, silicon oxide films,
It is possible to perform anisotropic etching of polysilicon films, etc. while maintaining a high etching speed ratio relative to the photoresist and underlying material.
Dry etching has become mainstream in recent VLSI manufacturing processes.

However, even with this reactive ion etching equipment, if you try to perform microfabrication on a mass production scale,
It has become clear that various problems arise. For example, when etching a silicon oxide film with a mixed gas of CHF ₃ and O ₂ , the etching speed is very high.
Since the etching rate is as low as 500 Å/min, when etching a silicon oxide film of 5000 Å, an etching time of approximately 12 to 15 minutes including additional etching is required.
If the high frequency power is increased in an attempt to increase the etching rate, the plasma potential will rise and the rate of spatter on the reaction vessel wall will increase, and the substrate surface may become contaminated with heavy metals etc. that are the constituent materials of the reaction vessel. High-energy ion bombardment can adversely affect device characteristics.

Furthermore, in the case of aluminum etching and polysilicon etching, the etching rate is as low as 1000 Å/min at a practical level.
For this reason, when this dry etching apparatus is used as a mass production apparatus, a so-called batch type processing apparatus that processes about 6 to 10 sheets at the same time is superior in terms of cost performance. However, as the diameter of wafers has recently become larger, such as 125 mm or 150 mm, if these are to be processed using the batch type processing apparatus, the area of the electrodes must be increased. For this reason, the device has to become larger. Moreover, the uniformity of etching rate within the wafer surface tends to deteriorate. As described above, it is extremely difficult to microfabricate large-diameter wafers using ordinary batch-type processing equipment.

On the other hand, as a single wafer processing apparatus that processes each wafer one by one, a parallel plate type high-speed etching apparatus that achieves an etching speed of about 1 μm/min has been proposed. However, when etching is performed at high speed using this apparatus, there is a drawback that the etching processing characteristics are poor, and in particular, the device is seriously damaged by ion bombardment, and satisfactory characteristics are not necessarily obtained in microfabrication.

In response to these problems, a high-speed magnetron etching method has recently been proposed that uses a magnetic field to perform high-speed etching in a pressure region that is one to two orders of magnitude lower than the previous method ( For example, see Japanese Patent Application Laid-Open No. 57-98678). However, in this type of apparatus, the plasma tends to concentrate only in the area where the electric field and the magnetic field are exactly perpendicular to each other, so the uniformity of the etching rate distribution within the wafer surface is poor. For this reason, JP-A-58-
As disclosed in Japanese Patent No. 53832, it is necessary to drive the magnet and move it frequently to change the magnetic field and to equalize the etching rate distribution within the wafer. Not only does the mechanism require a large amount of expense, but it also has the disadvantage that etching cannot be performed at high speed.

[Purpose of the invention]

An object of the present invention is to eliminate the drawbacks of the conventional high-speed magnetron etching apparatus described above, to easily improve the poor uniformity of the etching rate within the surface of the sample, and to be able to etch the sample at high speed. The purpose of the present invention is to provide a dry etching device that can perform dry etching.

[Structure of the Invention] According to the present invention, a first electrode provided in a reaction vessel and including a columnar electrode and a flange-shaped electrode electrically connected to both ends of the columnar electrode; a second electrode that surrounds at least the columnar electrode at intervals; and a second electrode that is provided outside the reaction vessel and that applies a magnetic field parallel to the axis of the columnar electrode of the first electrode. and a magnetic field generating device generated in the space between the second electrodes, the first
A negative voltage relative to the second electrode is continuously or intermittently applied to the electrode by a power source, and the substrate on the surface of the columnar electrode of the first electrode is caused to be exposed to plasma of an active gas introduced into the reaction vessel. A dry etching device characterized by etching is obtained.

[Example] Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a dry etching apparatus according to one embodiment of the present invention. In FIG. 1, 101 is a prismatic electrode. A sample 102 is supported on each columnar surface of this prismatic electrode 101. 103 and 104
is a metal end plate connected to the prismatic electrode 101 so as to be kept at the same potential as the prismatic electrode 101.
The prismatic electrode 101 and end plates 103 and 104, which serve as flanges at both ends, constitute a cathode. Both end plates 103 and 104 each have an insulator 1
05 and 106, shields 107 and 1
08 to prevent unnecessary discharge from occurring on the back surfaces of the end plates 103 and 104, etc. A cathode composed of the columnar electrode 101 and both end plates 103 and 104 is connected to a high frequency power source 109. In addition, a conductive reaction vessel 11 constituting the anode
0 is grounded. The reaction vessel 110 is connected to a vacuum pump (not shown) via an exhaust conduit 111 and an exhaust valve 112. Reactive gas is introduced into reaction vessel 110 through gas controller 113 . 114 and 115 are columnar electrodes 1
01, and a vacuum vessel 1 facing the columnar electrode 101.
This is an electromagnetic coil for generating a magnetic field B approximately parallel to the axis of the columnar electrode 101 in the space between the columnar electrode 101 and the side plate.

Now, in order to operate the apparatus of this embodiment as described above, first, the reaction vessel 110 is connected to the exhaust conduit 111.
After evacuating to a vacuum of about 10 ^-3 to 10 ^-5 Torr, the gas is passed through the gas controller 113 and CF ₄ or
Introduce a halogenated active gas such as BCl ₃ and maintain the degree of vacuum at 10 to 10 ^-3 Torr. In this state, RF power supply 10
9, when high frequency power is applied between the cathode composed of the columnar electrode 101 and the end plates 103 and 104 and the reaction vessel (ie, anode) 110, plasma is generated around the columnar electrode 101. The potential gradient, that is, the lines of electric force generated in the ion sheath between the columnar electrode 101 and the plasma,
4 and 115, the electrons rotate around the columnar electrode 101 while performing a cycloidal or trochoidal spiral motion. At this time, the electron is 117
As shown in and 118, when the columnar electrode 101 is diffused toward the end, there are flanges, that is, end plates 103 and 104 at both ends of the columnar electrode 101 which are negatively biased like the columnar electrode 101. As shown in the figure, the electrons are repelled by the end plates 103 and 104 and returned to the center of the columnar electrode 101. Since this state is repeated, a region with extremely high plasma density is generated near the columnar electrode 101. When such high-density plasma is generated, the impedance of the plasma decreases, so that a large ion current can be passed through the cathode at a low voltage. Therefore, the etching speed of the sample 102 supported on the columnar surface of the columnar electrode 101 can be dramatically improved compared to the conventional etching method. In addition, the incident energy of ions incident on the sample 102 can be measured in comparison with a conventional reactive ion etching apparatus. Furthermore, since the plasma can be concentrated around the columnar electrode 101 by the flange portions, that is, the end plates 103 and 104, it is possible to improve the uniformity of the etching rate within the surface of the sample 102, and to prevent ion incidence. Etching can be performed with less damage caused by impurity contamination.

FIG. 2 is a sectional view taken along line A-A' in FIG. In the figure,
The columnar electrode 101 is a square prism, and the end plate 103 is a square. The other end plate 104 is also square. The sample 102 is supported by each of the four columnar surfaces of the columnar electrode 101. Further, a portion of the columnar electrode 101 other than the sample 102 is covered with a cover plate 201 made of quartz, Teflon, or the like. Further, the mutually opposing surfaces of the end plates 103 and 104 are also covered with a similar cover plate. The interior of the columnar electrode 101 is water-cooled by flowing water through a water-cooling pipe 202 .

In FIG. 2, the configuration is such that four samples 102 can be etched at the same time, but if the shape of the columnar electrode 101 is a flat prismatic column, two samples 102 can be etched at the same time. Furthermore, if the columnar electrode 101 is made of a polygonal column such as a triangular column, hexagonal column, or octagonal column, it is possible to etch several other electrodes at the same time. That is, the columnar electrode 101 is an N-prismatic column (however, N
may be an integer greater than or equal to 3). Furthermore, if a large number of samples are supported on one columnar surface of the columnar electrode 101, a larger number of samples can be etched at the same time. Further, the shape of the end plates 103 and 104 may be similar to the cross-sectional outline of the columnar electrode 101, or may be circular or elliptical.

FIG. 3 is a diagram showing the structure of a cathode in an embodiment in which the present invention is applied to an etching apparatus for single-sheet processing. In this embodiment, the columnar electrode 101 is a flat prismatic structure whose inside can be cooled with water, and the sample 102 is held on one surface of the columnar electrode 101. Further, in this example, the end plates 103 and 104 have a rectangular shape. The columnar electrode 101 is a water-cooled pipe 2
Water cooling is performed by flowing water through channels 03 and 204. When a magnetic field is applied in the direction shown by arrow B by the electromagnetic coils 114 and 115 (see FIG. 1) and an RF voltage is applied to the columnar electrode 101, the columnar electrode 101 is negatively biased and electrons are transferred to the columnar electrode 101. Rotate around. At this time, the end plate 103
and 104 prevent electrons from scattering from the vicinity of the columnar electrode 101, so that high-density plasma is uniformly generated around the columnar electrode 101, and high-speed etching can be realized without uneven etching rate. In this method, the sample 102 can be easily taken in and out of the reaction container by an automatic device, and therefore it can be applied to an automatic device in which sample transportation is automated. Of course, it is more effective to cover the columnar electrode surface on which the sample 102 is not placed, the mutually opposing surfaces of the end plates 103 and 104, etc. with the aforementioned cover plate to prevent contamination with impurities and improve the etching rate.

Incidentally, in the embodiment of the present invention described above, the electromagnetic coils 114 and 115 are used as the magnetic field generating means, but it goes without saying that permanent magnets may also be used.
Further, as the power source 109, a DC power source may be used.

The active gas introduced into the reaction vessel 101 is a gas containing a halide such as fluorine or chlorine, or a gas containing a halide and an inert gas.
A gas containing at least one of oxygen, hydrogen, nitrogen, etc. is highly effective.

In addition, the material of the cover plate 201 is as follows:
Organic polymers, organic polymers containing fluorine,
An appropriate material is selected and used from among substances such as quartz, carbon, and silicon.

〔Effect of the invention〕

As explained above, the dry etching apparatus of the present invention can easily and uniformly generate high-density plasma on the sample surface by providing the flange portion, etc. Etching can be easily achieved without causing significant damage to the sample.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention. FIG. 2 is a sectional view taken along line A-A' in FIG. FIG. 3 is a diagram showing the structure of a cathode in an embodiment in which the present invention is applied to a single wafer processing apparatus. 101... Column electrode, 102... Sample, 10
3,104...End plate (flange part), 105,1
06...Insulator, 107,108...Shield,
109...High frequency power supply, 110...Reaction container, 1
11...Exhaust pipe, 112...Exhaust valve, 11
3... Gas controller, 114, 115... Coil, 201... Cover plate, 202, 20
3,204...Water cooling pipe.

Claims (1)

[Scope of Claims] 1. A first electrode provided in a reaction vessel and including a columnar electrode and a flange-shaped electrode electrically connected to both ends of the columnar electrode; a second electrode surrounding the columnar electrode at intervals; and a second electrode provided outside the reaction vessel to apply a magnetic field parallel to the axis of the columnar electrode of the first electrode to the first and second electrodes. a magnetic field generating device that generates a magnetic field in a space between the electrodes, and a negative voltage relative to the second electrode is continuously or intermittently applied to the first electrode by a power supply, and the columnar shape of the first electrode is A dry etching apparatus characterized in that a substrate on the surface of an electrode is etched by plasma of an active gas introduced into the reaction vessel. 2. The dry etching apparatus according to claim 1, wherein the power source supplies high frequency or DC voltage. 3 The columnar electrode of the first electrode is an N-prismatic column (however,
3. The dry etching apparatus according to claim 1, wherein N is an integer of 3 or more.