JPH1167725A - Plasma etching device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the applied a pulse bias uniform within the surface of the material to be etched and to make the distribution of the characteristics of the etching of material in the plane uniform by providing the structure, wherein the interval between the material and a grounding electrode is changed. SOLUTION: A dry etching device has a magnetron 8 for generating plasma 4 and a magnetic field coil 5. Furthermore, a power supply 3 for applying a frequency of 20 MHz or higher as a bias and a pulse voltage to a sample stage 6 is provided. A wafer 1 to etch is provided on the sample stage 6. At a position facing the water 1, a grounding electrode 11 at the ground potential is provided. The grounding electrode 11 has the curved shape. At the central part, the distance to the material to be etched is small, and the distance is large at the surrounding part. Thus, the nonuniformity of the bias application caused by the effect of the magnetic field and structure of the processing chamber can be largely decreased. The etching speed on the surface of the large-diameter wafer and the uniformity of the etched shape can be enhanced.

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 more particularly to a plasma etching apparatus capable of performing high-precision fine processing and suitable for manufacturing a semiconductor device having a high integration density.

[0002]

2. Description of the Related Art In conventional plasma etching, as described in, for example, Japanese Patent Application Laid-Open No. 8-13977, a pulse voltage is applied as a bias applied to a sample to control the shape, and in particular, a local side called notching is formed. There was a method to prevent etching. This method uses a pulse bias instead of the RF bias that has been used in the past. This method accelerates electrons, which was difficult in the past, and accelerates the incidence of electrons on the bottom of the fine pattern to charge up. Problem can be prevented.

In the conventional plasma etching, an optimum frequency of a high frequency voltage has been selected as a bias applied to a sample. Normally 400KHz
To 13.56 MHz, but higher RF biases may be used in some cases.

[0004]

As described above, with a high-frequency RF bias or a pulse bias including a high-frequency component as a frequency component of a voltage waveform, whether an effective bias is applied to the center and the periphery of the object to be etched. But the difference was the problem. This tendency was particularly remarkable in an apparatus using a magnetic field for plasma generation as shown in FIG. This is because an electric field is applied in a direction crossing the magnetic field generated in the vertical direction of the processing chamber, so that the movement of electrons is restricted by the magnetic field and an electric resistance component is generated in the horizontal direction. In other words, the closer to the side of the processing chamber, the smaller the resistance component is at the periphery of the object to be etched, and conversely, the greater the resistance component is at the center of the object to be etched. As a result, it has been found that the pulse bias is more likely to be applied to the object to be etched toward the periphery of the object to be etched, and is less likely to be applied to the center of the object to be etched. As described above, if the in-plane non-uniformity of the object to be etched exists in the manner of applying the bias voltage, there is a problem that the non-uniformity of the etching characteristics such as the etch rate is caused.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problem of a conventional dry etching apparatus for applying a pulse bias, to make the pulse bias uniform in the surface of the object to be etched, and to improve the etching characteristics of the object to be etched. It is an object of the present invention to provide a dry etching apparatus capable of making the in-plane distribution uniform.

Another object of the present invention is to provide a dry etching apparatus for applying a high-frequency bias of 20 MHz or more, to make the bias applied uniformly in the surface of the object to be etched, and to provide an in-plane distribution of the etching characteristics of the object to be etched. And to provide a dry etching apparatus capable of making the etching uniform.

[0007]

As a first method for achieving the above object, as shown in FIG. 2, an electrode connected to a ground potential is provided at a position facing an object to be etched, and In order to make the distribution of the electric field uniform, the distance between the object to be etched and the ground electrode is changed. Since such a ground electrode is located at a position facing the object to be etched, the bias electric field can be aligned to some extent in the vertical direction. This improves the uniformity of the bias. further,
Since the distance between the ground electrode and the object to be etched is narrow at the center and widely changed at the periphery as shown in FIG. It is less likely to be applied at the periphery. By this effect, the conventional bias non-uniformity which occurs in the case of FIG. 1 can be uniformed with high precision.

As a second method for achieving the above object, a ground electrode having a structure as shown in FIG. 4 can be used. According to this method, the area of the ground electrode is changed between the central part and the peripheral part instead of changing the electrode interval as shown in FIG. 2, that is, the central electrode area is increased and the peripheral electrode area is reduced. .

As a third method for achieving the above object, there is a method of reducing the intensity of a magnetic field used for assisting plasma generation as shown in FIG. In the conventional electron cyclotron resonance plasma etching apparatus shown in FIG. 1, a microwave of 2.45 GHz and a magnetic field of 875 Gauss are used for plasma excitation, but in the apparatus of FIG. Can be used to excite plasma. When the magnetic field intensity is set to 1/5 or less of the conventional value, the lateral resistance to the bias electric field as described above is reduced, and the uniformity of the bias can be improved.

[0010]

According to the present invention, by providing a ground electrode at a position facing an object to be etched, the uniformity of bias application can be greatly improved. Further, the uniformity can be further improved by optimizing the shape of the ground electrode. Also, in the electron cyclotron resonance type plasma etching apparatus, the uniformity of the bias can be improved by reducing the magnetic field intensity.

(Embodiment 1) FIG. 2 shows an example of a dry etching apparatus according to the present invention. As shown in FIG. 2, the dry etching apparatus of the present embodiment includes a magnetron 8 for generating a plasma 4 and a magnetic field coil 5, and further applies a pulse voltage as a bias to a sample stage 6. It has a power supply 3. The wafer 1 to be subjected to the etching process is set on the sample stage 6. A pulse voltage is applied to the sample stage 6 to accelerate ions in the plasma 4. A counter ground electrode 11 having a ground potential was provided at a position facing the wafer. The antenna 12 and the ground electrode are insulated, and the microwave generated by the magnetron 8 is supplied from the coaxial line 10 to the antenna.

The ground electrode 11 has a curved shape as shown in FIG. 2, and the distance from the object to be etched is short at the center.
Far away in the periphery. The interval at this time is 10 cm at the center,
The outermost space was 15 cm. In FIG. 2,
Reference numeral 2 denotes a processing chamber, and 7 denotes an exhaust pump.

Using this dry etching apparatus, the polysilicon film formed on the SiO ₂ film covering the silicon wafer was etched with chlorine gas. Etching conditions are microwave discharge power of 2.45 GHz 800
W, gas pressure 1 Pa, gas flow rate 100 sccm, pulse voltage 800 KHz, positive pulse width 100 ns, positive pulse height +1
00V was applied.

As a result, there is almost no side etching called notching occurring at the interface between polysilicon and SiO _2, and as shown in FIG. 3, the uniformity of the etching rate of polysilicon in the wafer surface is also large. (Curve (b)). At this time, the uniformity of the etching rate within the wafer surface was within ± 3%. Here, the curve (a) is a result of the uniformity by the conventional apparatus shown in FIG. Also, the uniformity of the etched shape on the wafer surface is high, and the difference in the width of the processed shape between the central portion and the peripheral portion of the wafer is 0.
05 microns or less.

(Embodiment 2) Using the same etching apparatus as in Embodiment 1, as shown in FIG. 4, a structure was adopted in which the area of the ground electrode was changed between the central part and the peripheral part. At this time, the diameter of the whole electrode was 20 cm, the diameter of the wafer was also 20 cm, the diameter of the center of the ground electrode was 10 cm, and the width of the ground electrode at the periphery was 1 cm.
With this counter electrode structure, high etching rate uniformity almost similar to the result of the curve (b) shown in FIG. 3 was obtained. Also, as a bias power source, 40M instead of the pulse voltage
Hz high frequency voltage was applied. In this case, similarly, the uniformity of the etching rate was within ± 3%.

(Embodiment 3) In this embodiment, the etching apparatus shown in FIG. 5 was used. The structure of the counter ground electrode was a flat plate type structure as shown in FIG. At the same time, the electromagnetic wave frequency for plasma excitation was set to 500 MHz, and the magnetic field intensity for electron cyclotron resonance was set to 178 gauss. In this case, the magnetic field intensity is about 1/5 of the magnetic field intensity of the apparatus shown in FIG. As described above, the influence of the non-uniformity of the bias is reduced by reducing the magnetic field strength, and the etching rate can be reduced by the simple flat plate structure without using the counter ground electrode having the structure shown in FIGS. Was improved to almost the same level as the curve (b) in FIG.

[0017]

As is apparent from the above, according to the present invention, when a pulse bias or other high frequency of 20 MHz or more is used as a bias, the influence of the magnetic field and the unevenness of the bias due to the processing chamber structure are not uniform. Performance can be greatly reduced, and in etching large-diameter wafers,
The uniformity of the etching rate and the etching shape in the wafer surface can be extremely increased.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a plasma etching apparatus showing an example of bias application by a conventional apparatus.

FIG. 2 is a longitudinal sectional view of a plasma etching apparatus showing a first embodiment of the present invention.

FIG. 3 is a measurement diagram of a relationship between an etching rate and a wafer position showing the effect of the first embodiment of the present invention.

4A and 4B are a longitudinal sectional view and a plan view of an electrode plate for applying a ground potential according to a second embodiment of the present invention.

FIG. 5 is a longitudinal sectional view of a plasma etching apparatus showing a third embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Wafer, 2 ... Processing room, 3 ... Pulse power supply, 4 ... Plasma, 5 ... Magnetic field coil, 6 ... Sample stand, 7 ... Exhaust pump, 8
... magnetron, 9 ... waveguide, 10 ... coaxial line, 11 ...
Opposing ground electrode, 12 ... antenna, 13 ... electromagnetic wave generator,
14 ... electric field, 15 ... magnetic field.

Claims (5)

[Claims] A vacuum processing chamber for etching an object to be etched by using a plasma of a processing gas; a unit for exhausting the vacuum processing chamber; a unit for generating a plasma of the processing gas; Disposed on the sample stage for placing the object to be etched thereon, and a means for applying any one of a predetermined high frequency voltage or a pulse voltage of 20 MHz or more to the object to be etched or the sample stage as a bias voltage, A plasma etching apparatus comprising at least a ground potential electrode provided at a position facing an object to be etched. 2. The plasma etching apparatus according to claim 1, wherein the distance between the ground potential electrode and the object to be etched is narrow at the center of the ground electrode and wide at the periphery. 3. The plasma etching apparatus according to claim 1, wherein said ground potential electrode is separated into a central portion and a peripheral portion, and an area of the central portion is larger than an area of the peripheral portion. 4. A vacuum processing chamber for etching an object to be etched using plasma of a processing gas, a unit for exhausting the vacuum processing chamber, a unit for generating a plasma of the processing gas, and a vacuum processing chamber. A sample stage for placing the object to be etched thereon, and a means for applying any one of a predetermined high frequency voltage or a pulse voltage of 20 MHz or more to the object to be etched or the sample stage as a bias voltage, An electromagnetic coil used as an auxiliary means for plasma generation, and at least a ground potential electrode provided at a position facing the object to be etched, wherein the maximum value of the magnetic field strength of the electromagnetic coil is 300 Gauss or less. Characteristic plasma etching equipment. 5. The plasma etching apparatus according to claim 1, wherein said plasma etching apparatus is an electron cyclotron resonance plasma etching apparatus.