JP3884854B2 - Reactive ion etching system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a reactive ion etching apparatus that uses plasma to etch a material on a semiconductor, an electronic component, or other substrate.
[0002]
[Prior art]
FIG. 4 of the accompanying drawings shows an inductively coupled discharge etching apparatus according to the prior art, in which an antenna B made of a coil for generating discharge plasma is provided in the vacuum chamber A outside the dielectric side wall A1. A high frequency power is applied to the high frequency antenna B from a high frequency power source C for plasma generation, and an etching gas mainly composed of a halogen-based gas is introduced from the vicinity of the upper top plate A2 through the flow controller, and the gas is introduced into the vacuum chamber A. Introduces and forms plasma at a low pressure, decomposes the introduced gas, and positively uses the generated atoms, molecules, radicals and ions, and applies a high-frequency electric field from a high-frequency power source E to the substrate electrode D in contact with the plasma. The substrate placed on the electrode D is configured to be etched.
[0003]
FIG. 5 shows a magnetic neutral wire discharge etching apparatus previously proposed by the present inventors in Japanese Patent Laid-Open No. 7-263192. In the previously proposed apparatus, a magnetic neutral line E is formed inside the vacuum chamber A by three magnetic field coils B, C, D placed outside the dielectric cylindrical wall A1 at the top of the vacuum chamber A. A high-frequency antenna coil F is disposed inside the intermediate magnetic field coil C along the magnetic neutral line E, and high-frequency power is supplied to the high-frequency antenna coil F from the antenna high-frequency power source G via a capacitor in the matching box. The other end of the antenna coil is grounded. Thereby, a ring-shaped plasma is formed. Further, the etching gas is introduced from the vicinity of the upper top plate A2 through the flow controller, and the pressure is controlled by the opening ratio of the contact valve. A high frequency power is applied to the substrate electrode H below the vacuum chamber A from a bias high frequency power source I.
[0004]
In FIG. 6, the inventors previously proposed a flat permanent magnet type magnetic neutral wire etching apparatus as a permanent magnet type etching apparatus in Japanese Patent Application No. 7-217965. In the previously proposed apparatus, a magnetic neutral line is formed inside the vacuum chamber A by the two donut-shaped permanent magnets C and D placed on the dielectric B provided on the upper top plate of the vacuum chamber A. A high-frequency antenna E is disposed between the two permanent magnets C and D along the magnetic neutral line, a gas is introduced, and a high-frequency electric field is applied to the high-frequency antenna E to form a ring-shaped plasma. It is configured. In this case, the partition wall of the cylindrical vacuum chamber A is made of metal.
There is also known an inductively coupled discharge type etching apparatus configured by removing the magnetic field coil and the permanent magnet for forming the magnetic neutral line in the configuration shown in FIGS.
[0005]
The magnetic neutral wire discharge etching apparatus shown in FIG. 5 will be described. The etching gas is introduced from the vicinity of the upper flange, and high frequency power is applied to the antenna F installed outside the dielectric cylindrical wall A1 to form plasma, and the introduced gas is decomposed. Since the magnetic neutral line is a loop of zero magnetic field, electrons in the plasma gather there, and the electrons are accelerated by the circumferential electric field emitted from the antenna F to induce a circular electron current. The direction of the annular electron current changes every half cycle of the high-frequency current. A high frequency power for bias is applied to the lower substrate electrode H. The substrate electrode H in a floating state by the blocking capacitor has a negative self-bias potential, and positive ions in the plasma are attracted to etch the material on the substrate.
In the magnetic neutral line discharge, a high-density plasma is formed in the portion of the magnetic neutral line formed on the ring in a vacuum, so that an induction electric field formed along the ring is effectively used. By this method, a plasma having a charged particle density of 10 ¹¹ cm ^{−3 is} easily formed.
[0006]
[Problems to be solved by the invention]
In the conventional method as described above, when power is introduced into an antenna larger than 300φ, the antenna is long and the inductance is increased, so that the electric field generated in the antenna is nonuniform. Electric field non-uniformity leads to plasma non-uniformity, resulting in etch non-uniformity. For this reason, it is very difficult to obtain high etching uniformity in an inductively coupled discharge device having a dielectric partition larger than 3OOφ.
[0007]
When high frequency power of 13.56 MHz is applied to the antenna, a single or parallel multiplex antenna is used in an inductively coupled discharge device having a dielectric partition larger than 3OOφ. Serial multiplex antennas are not used because of their large impedance. In particular, when a single antenna is used, the impedance becomes large, and the plasma uniformity at the power introduction output portion to the antenna, and thus the substrate etching uniformity becomes a problem. In previous experiments, it has been found that the etching rate is reduced in the vicinity of the power introduction portion of the antenna.
[0008]
In order to avoid this, it was proposed in Japanese Patent Application No. 9-123905 to use a parallel dual antenna. When a parallel dual antenna is used, the density improvement and the non-uniformity in plasma generation are alleviated, and an etching uniformity of ± 5% or less can be easily obtained.
However, as the area of wafers and the integration of devices have increased, the accuracy required for processing apparatuses has increased, and it has become necessary to achieve ± 1% etching uniformity. To achieve this, the plasma uniformity needs to be further improved.
Accordingly, an object of the present invention is to provide a reactive ion etching apparatus capable of improving the uniformity of plasma to be formed and improving the etching uniformity.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, there is provided a magnetic field generating means for forming an annular magnetic neutral line which is a position of zero magnetic field continuously present in a vacuum chamber, and A plasma generator with a high-frequency coil for generating a discharge plasma in this magnetic neutral wire by applying a high-frequency electric field along the sexual line and introducing a gas mainly composed of a halogen-based gas into the vacuum The plasma is generated at low pressure and the introduced gas is decomposed into plasma, and the generated atoms, molecules, radicals, and ions are actively used, and an alternating electric field or a high-frequency electric field is applied to the substrate electrode in contact with the plasma on the electrode. In a reactive ion etching apparatus that etches the substrate mounted, a capacitor is placed in the grounding part of the high-frequency coil and symmetrical with respect to the power introduction / extraction part to the high-frequency coil. Arranged to be configured to time average value of the power transfer in the high-frequency coil is the same in the vicinity of the ground portion and the vicinity of the inlet portion.
By configuring in this way, the uniformity of the formed plasma is improved and the etching uniformity can be improved.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
According to the embodiment of the present invention, a plurality of field coils to form a circular magnetic neutral line in the vacuum chamber located outside the side of the cylindrical side wall of the vacuum chamber, applying a high frequency bias to the bottom of the vacuum chamber A substrate electrode is provided, the cylindrical side wall in the vacuum chamber is made of a dielectric, a high frequency antenna coil for generating plasma is arranged between the magnetic field coils and the cylindrical side wall, and high frequency power is introduced to the high frequency antenna coil. A reactive ion etching apparatus configured to introduce a high-frequency power by providing a capacitor in the section and the ground section is provided.
[0011]
When power is supplied to the high frequency antenna coil through the matching circuit, the high frequency antenna coil is generally connected via a capacitor and the other end is directly grounded. In this way, discharging is performed by providing a capacitor only in the power introduction section. Thereby, an etching uniformity of around ± 5% can be obtained. However, when the etching uniformity was examined in detail, it was found that a dense plasma was formed near the introduction part or the grounding part. This seems to be because the antenna coil potential is non-uniform. This non-uniformity is considered to be due to the power introduction method to the antenna coil. For this reason, it has been found that the etching uniformity is further improved by introducing a capacitor to the grounding portion side. This can be understood as follows.
[0012]
The antenna coil sandwiched between capacitors can be replaced with an equivalent circuit of -CLC-. When no capacitor is provided on the ground side, it becomes -CL-, and the introduction part and the ground part are not symmetrical. Therefore, when capacitors are symmetrically arranged in the introduction part and the grounding part, if a high-frequency current in the forward direction flows through the antenna and a dense plasma is formed in the vicinity of the introduction part, grounding occurs when a high-frequency current in the reverse direction flows. Deep plasma is formed near the portion. When a capacitor is provided only on the introduction part side, even if a strong plasma is formed near the introduction part due to a forward current, there is no capacitor on the ground part side when a reverse current flows, No deep plasma is formed. As a result, it is understood that the density of the plasma generated by the antenna coil is eliminated by arranging the capacitors in both the introduction part and the grounding part, and uniform plasma is formed on a time average basis.
This effect is the same in ICP (inductively coupled plasma) without applying a magnetic field, but the effect is small as compared with NLD plasma in which an induced annular current flows in a magnetic neutral line. As a result, compared with the conventional case where the capacitor is provided only on the introduction portion side, the uniformity of the plasma density as a time average is improved, and the etching uniformity of about ± 5 to 7% is about ± 2 to 3%. Improved.
[0013]
【Example】
An embodiment of the present invention will be described below with reference to FIG. 1 of the accompanying drawings.
FIG. 1 shows an embodiment of an etching apparatus according to the present invention. In FIG. 1, reference numeral 1 denotes a vacuum chamber, which is provided with a cylindrical side wall 2 made of, for example, quartz, and three coils 3, 4, 5 constituting magnetic field generating means are arranged on substantially the same circumference on the outside thereof. It is provided along. As shown in the figure, the same constant current in the same direction is supplied to the upper and lower electromagnetic coils 3 and 5, and the current in the opposite direction is supplied to the intermediate coil 4. Thereby, the position of the magnetic field zero continuous inside the cylindrical side wall 2 is formed near the level of the intermediate coil 4, and an annular magnetic neutral line 6 is formed. The size of the ring-shaped magnetic neutral wire 6 can be set as appropriate by changing the ratio of the current flowing through the upper and lower coils 3, 5 and the current flowing through the intermediate coil 4. The position of the magnetic neutral wire 6 in the vertical direction is determined by the ratio of currents flowing through the coils 3 and 5. For example, when the current flowing through the upper coil 3 is made larger than the current flowing through the lower coil 5, the position where the magnetic neutral wire 6 can be lowered to the coil 5 side, and conversely, the position where the magnetic neutral wire 6 can be formed is the coil 3. Go up to the side. As the current flowing through the intermediate coil 4 is increased, the diameter of the ring of the magnetic neutral wire 6 becomes smaller and the gradient of the magnetic field at the zero magnetic field position becomes gentler.
[0014]
Between the intermediate coil 4 and the cylindrical side wall 2, a high frequency electric field generating antenna 7 constituting an electric field generating means is provided, and is connected to a plasma generating high frequency power source 9 through an RF introduction part capacitor 8. The antenna 7 is grounded via a grounding condenser 10.
A substrate electrode 12 is provided in the vacuum chamber 1 via an insulator 11, and the substrate electrode 12 is connected to a bias high-frequency power source 14 via a capacitor 13. A substrate 15 to be processed is mounted on the substrate electrode 12 by an electrostatic chuck made of an insulator.
A counter electrode 16 made of a conductive material is provided at the upper end of the cylindrical side wall 2 of the vacuum chamber 1 so as to be opposed to the substrate electrode 12, and this counter electrode 16 is a shower plate for introducing an etching auxiliary gas as shown. The shower plate 17 communicates with an etching auxiliary gas source (not shown) through a gas passage (not shown) provided in the counter electrode 16. The inner surface of the counter electrode 16, particularly the portion exposed to the plasma, that is, the shower plate 17, is made of or covered with a substance such as SiO ₂ , Si, C, or SiC that does not adversely affect the etching. The vacuum chamber 1 is evacuated from an exhaust port 1a by a vacuum exhaust system (not shown). Further, although not shown, the vacuum chamber 1 is provided with a gas introduction part for introducing an etching main gas.
[0015]
The operation and operation of the illustrated apparatus configured as described above will be described.
Using the apparatus of FIG. 1, the power of the plasma generating high frequency power supply 9 is 1.5 KW, the power of the substrate bias high frequency power supply 14 (2 MHz) is 600 W, argon is 90 sccm (85%) as an auxiliary gas, and C _{4 is} an etching main gas. When F ₈ was introduced at 10 sccm (15%) and etching was performed at a pressure of 3 mTorr, an etching rate of 3600 angstrom / min was obtained, and it was found that the etching distribution was very highly uniform as ± 2.8%. It was. FIG. 2 (a) shows the result at that time. For comparison, when there was a capacitor only at the antenna introduction part, the etching rate obtained as shown in (b) was 3500 angstroms / minute, and the etching distribution was ± 6.6%. The reason why the etching rate slightly increased in the case of the present invention seems to be that power was efficiently applied even in the reverse phase because a capacitor was also introduced into the ground portion of the antenna.
[0016]
FIG. 3 shows the experimental results in ICP. (A) is the etching uniformity when the conventional power application method is used, and (b) is the etching uniformity obtained by connecting a capacitor to the ground portion side. In the case of ICP, since an annular electron current does not flow in plasma, there is almost no effect.
[0017]
In the illustrated embodiment, an example in which the present invention is applied to a cylindrical NLD etching apparatus has been described, but it goes without saying that the same effect can be achieved by applying it to a flat plate type NLD etching apparatus. In addition, it can be expected even when applied to a magnetic neutral discharge plasma CVD apparatus.
[0018]
【The invention's effect】
As described above, according to the present invention, the capacitor is disposed in the grounding portion of the high frequency coil, and is disposed symmetrically with respect to the power introduction / extraction portion to the high frequency coil, so that the time average value of power introduction in the high frequency coil is Is configured to be the same in the vicinity of the introduction portion and the ground portion, so that high-frequency power can be applied uniformly, plasma with higher uniformity can be formed, and a large-area substrate can be used. Highly uniform etching can be performed in the fine processing. Therefore, the present invention greatly contributes to the reactive ion etching process used in semiconductor and electronic component processing.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of an embodiment of an etching apparatus according to the present invention.
FIGS. 2A and 2B are graphs showing calculation examples of etching rate and etching distribution. FIG. 2A shows the case of the present invention, and FIG. 2B shows the case of the conventional method.
FIGS. 3A and 3B are graphs showing examples of calculation of etching rate and etching distribution in the inductively coupled plasma method, where FIG. 3A shows a conventional method, and FIG. 3B shows a case where a capacitor is provided on the ground side as in the present invention. It is.
FIG. 4 is a schematic sectional view of a conventional inductively coupled discharge etching apparatus.
FIG. 5 is a schematic cross-sectional view of a conventional magnetic neutral wire discharge etching apparatus.
FIG. 6 is a schematic cross-sectional view of a conventional etching apparatus using flat plate type magnetic neutral wire discharge.
[Explanation of symbols]
1: Vacuum chamber 2: Cylindrical side walls 3, 4, 5: Coil forming magnetic field generating means 6: Plasma ring formed on annular magnetic neutral wire 7: High frequency electric field generating antenna 8 forming electric field generating means: Introduction Capacitor 9: High frequency power supply for plasma generation
10: Grounding condenser
11: Insulator
12: Substrate electrode
14: Bias high frequency power supply
15: Substrate to be processed
16: Counter electrode
17: Shower plate for introducing etching auxiliary gas

Claims (1)

Provided is a magnetic field generating means for forming an annular magnetic neutral line that is continuously present in the vacuum chamber and having a magnetic field of zero, and a high-frequency electric field is applied along the magnetic neutral line to generate the magnetic neutral line. Has a plasma generator provided with a high-frequency coil for generating discharge plasma. A gas mainly composed of a halogen-based gas is introduced into a vacuum to form a plasma at a low pressure and to decompose the introduced gas into a plasma. In the reactive ion etching apparatus that positively utilizes the generated atoms, molecules, radicals, and ions, applies an alternating electric field or a high frequency electric field to the substrate electrode in contact with the plasma, and etches the substrate placed on the electrode. a plurality of field coils to form a circular magnetic neutral line in the vacuum chamber located outside the side of the cylindrical side wall of the vacuum chamber, the bottom of the vacuum chamber Provided substrate electrodes for applying a high frequency bias, the cylindrical side wall of the vacuum chamber composed of a dielectric, disposed a high-frequency antenna coil for generating plasma between the plurality of magnetic field coils and the cylindrical side wall, the high frequency antenna A reactive ion etching apparatus characterized in that a high frequency power is introduced by providing a capacitor at a high frequency power introduction part and a grounding part of a coil.

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