JPH11241190A - Reactive ion etching device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate plasma with good uniformity and to improve the etching uniformity by connecting a high frequency power line and a ground line in which the capacitors are symmetrically arranged to a high frequency coil which applies a high frequency electric field along an annular magnetic neutral line formed in a vacuum chamber. SOLUTION: Electromagnetic coils 3 to 5 are arranged outside a dialectic side wall of a vacuum chamber 1 to generate a magnetic field and to form an annular magnetic neutral line in the chamber. Further, a high frequency electric field is applied along the neutral line by an antenna coil 7 in which one end is connected to a high frequency power supply 9 and the other end is grounded. An etching gas essentially comprisinga halogen gas is introduced through a shown plate 17 disposed on a counter electrode 16 to form a low pressure plasma ring on the magnetic neutral line. The gas is decomposed buy the plasma to generate atoms, molecules, radicals, ions or the like to each a substrate 15 disposed on a substrate electrode 12 connected to a bias high frequency power supply 14. Further, a capacitor 8 to supply the power and a capacitor 10 for grounding are symmetrically connected to the antenna coil 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a reactive ion etching apparatus for etching a substance on a semiconductor, an electronic component, or another substrate using plasma.

[0002]

2. Description of the Related Art FIG. 4 of the accompanying drawings shows an inductively coupled discharge etching apparatus according to the prior art. An antenna B comprising a coil for generating discharge plasma in a vacuum chamber A is connected to a dielectric side wall A1 of the vacuum chamber A. A high frequency power is applied from a high frequency power supply C for plasma generation to the high frequency antenna B, and an etching gas mainly composed of a halogen-based gas is introduced from around the upper top plate A2 through a flow rate controller, and the gas is removed. Introduced into the vacuum chamber A,
It forms plasma at low pressure and decomposes the introduced gas,
The generated atoms, molecules, radicals, and ions are positively used, and a high-frequency electric field is applied from a high-frequency power source E to a substrate electrode D that is in contact with plasma to etch a substrate mounted on the substrate electrode D. ing.

FIG. 5 shows a magnetic neutral beam discharge etching apparatus proposed by the present inventors in Japanese Patent Application Laid-Open No. 7-263192. The previously proposed device is a three-dimensional device mounted outside the dielectric cylindrical wall A1 at the top of the vacuum chamber A.
A magnetic neutral line E is formed inside the vacuum chamber A by the two magnetic field coils B, C, and D. A high-frequency antenna coil F is arranged inside the intermediate magnetic field coil C along the magnetic neutral line E. High-frequency power is applied to the high-frequency antenna coil F from a high-frequency power source for antenna G via a capacitor in a matching box, and the other end of the antenna coil is grounded. As a result, a ring-shaped plasma is formed. The etching gas is introduced from around the upper top plate A2 through the flow controller, and the pressure is controlled by the aperture ratio of the contactance valve. A high frequency power source I for bias is applied to a substrate electrode H below the vacuum chamber A.
, High frequency power is applied.

In FIG. 6, the present inventors have previously proposed a flat permanent magnet type magnetic neutral beam etching apparatus as a permanent magnet type etching apparatus in Japanese Patent Application No. 7-217965. In the device proposed earlier, a magnetic neutral wire is formed inside the vacuum chamber A by two donut-shaped permanent magnets C and D mounted on a dielectric B provided on an upper top plate of the vacuum chamber A. A high-frequency antenna E is arranged 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 in which a magnetic field coil for forming a magnetic neutral line and a permanent magnet are removed from the configuration shown in FIGS.

A magnetic neutral beam 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 having no magnetic field, electrons in the plasma gather there, and the electrons are accelerated by a circumferential electric field emitted from the antenna F to induce a ring electron current. The direction of this ring-shaped 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, which is in a floating state due to the blocking capacitor, has a negative self-bias potential, and positive ions in the plasma are attracted to etch the substance on the substrate. In the magnetic neutral wire discharge, a high-density plasma is formed in a portion of the magnetic neutral wire 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]

In the conventional method as described above, when power is introduced to an antenna larger than 300φ, the antenna becomes longer and the inductance becomes larger, so that the electric field generated in the antenna becomes non-uniform. The non-uniformity of the electric field leads to non-uniformity of the plasma, resulting in non-uniformity of the etching. Therefore, it is very difficult to obtain high etching uniformity in an inductively coupled discharge device having a dielectric partition larger than 3OOφ.

When a 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 wall larger than 300φ. Serial multiplexed antennas are not used because of their increased 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, consequently, the substrate etching uniformity become a problem. Experiments so far have revealed that the etching rate decreases near the power introduction portion of the antenna.

To avoid this, Japanese Patent Application No. 9-123905 has proposed using a parallel dual antenna. When a parallel dual antenna is used, the improvement in density and the non-uniformity in plasma generation are alleviated, and etching uniformity of ± 5% or less can be easily obtained. However, as the area of the wafer is increased and the integration of the device is advanced, the accuracy required for the processing apparatus is also high, and the accuracy is required to be ± 1%.
It has become necessary to achieve etching uniformity. To achieve this, it is necessary to further improve the uniformity of the plasma. Therefore, an object of the present invention is to provide a reactive ion etching apparatus capable of improving the uniformity of plasma formed and improving the etching uniformity.

[0009]

According to the present invention, there is provided, in accordance with the present invention, a magnetic field for forming an annular magnetic neutral line which is a position of zero magnetic field continuously present in a vacuum chamber. A plasma generating device having a generating means and a high-frequency coil for applying a high-frequency electric field along the magnetic neutral line to generate a discharge plasma in the magnetic neutral line is provided. A main gas is introduced into a vacuum, plasma is formed at a low pressure and the introduced gas is plasma-decomposed, and the generated atoms, molecules, radicals, and ions are actively used. In a reactive ion etching apparatus that applies a high-frequency electric field to etch a substrate placed on an electrode, a capacitor is arranged at the grounding portion of the high-frequency coil, Of and symmetrically arranged with respect to the power inlet and outlet portion, configured so that the time average 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. With this configuration, the uniformity of the formed plasma is improved, and the etching uniformity can be improved.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to an embodiment of the present invention, a plurality of magnetic field coils forming an annular magnetic neutral line in a vacuum chamber are provided outside the vacuum chamber, and a high frequency bias is applied to a lower portion of the vacuum chamber. A substrate electrode is provided, a part of the wall of the vacuum chamber is made of a dielectric material, a high-frequency antenna coil for generating plasma is arranged outside the substrate, and a capacitor is provided in a high-frequency power introduction part and a ground part of the high-frequency antenna coil. A reactive ion etching apparatus configured to introduce high frequency power is provided.

When power is supplied to the high-frequency antenna coil through a matching circuit, the high-frequency antenna coil is generally connected via a capacitor, and the other end is directly grounded. In this way, the discharge is performed by providing the condenser only in the power introduction section. Thereby, etching uniformity of about ± 5% can be obtained. However, when the etching uniformity was examined in detail, it was found that dense plasma was formed near the introduction portion or near the ground portion. This seems to be due to the non-uniformity of the antenna coil potential. This non-uniformity is considered to be due to the method of introducing power to the antenna coil. For this reason, it has been found that the uniformity of etching is further improved by introducing a capacitor also on the ground portion side. This can be understood as follows.

The antenna coil sandwiched between the capacitors can be replaced with an equivalent circuit of -CLCC-.
When a capacitor is not provided on the ground side, it becomes -CL-, and the introduction part and the ground part are not symmetric. Therefore,
When condensers are symmetrically placed in the introduction section and the ground section,
Assuming that a dense plasma is formed near the introduction portion when a forward high-frequency current flows through the antenna, a dense plasma is formed near the ground portion when a reverse high-frequency current flows. When a condenser is provided only on the introduction side,
Even if a dense plasma is formed near the introduction portion by the forward current, the dense plasma is not formed near the ground portion because there is no capacitor on the ground portion side when the reverse current flows. As a result, it can be understood that by arranging the condenser in both the introduction part and the ground part, the density of the plasma generated by the antenna coil is eliminated, and a time-average uniform plasma is formed. This effect is the same in ICP (inductively coupled plasma) without applying a magnetic field.
The effect is small compared to D plasma. As a result, compared to the conventional case where a condenser is provided only on the introduction section side,
The uniformity of the plasma density as a time average was improved, and the etching uniformity of about ± 5 to 7% in the past was improved to about ± 2 to 3%.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. FIG. 1 shows an embodiment of the etching apparatus according to the present invention. In FIG. 1, reference numeral 1 denotes a vacuum chamber having a cylindrical side wall 2 made of quartz, for example, and three coils 3 constituting a magnetic field generating means on the outside thereof.
4 and 5 are provided along the axis on substantially the same circumference. As shown in the drawing, the same constant current in the same direction is applied to the upper and lower two electromagnetic coils 3 and 5, and the opposite current is applied to the intermediate coil 4. As a result, a position where a continuous magnetic field is zero is formed inside the cylindrical side wall 2 near the level of the intermediate coil 4, and a ring-shaped magnetic neutral line 6 is formed. The size of the ring-shaped magnetic neutral wire 6 can be appropriately set by changing the ratio of the current flowing through the upper and lower two coils 3 and 5 to the current flowing through the intermediate coil 4. Of the magnetic neutral wire 6 in the vertical direction is determined by the ratio of the current flowing through the coil 3 and the coil 5. For example, if the current flowing in the upper coil 3 is larger than the current flowing in the lower coil 5, the position where the magnetic neutral wire 6 is formed is lowered toward the coil 5, and conversely, the position where the magnetic neutral wire 6 is formed is the coil 3 Go up to the side. As the current flowing through the intermediate coil 4 increases, the diameter of the ring of the magnetic neutral wire 6 decreases, and at the same time, the gradient of the magnetic field at the position where the magnetic field is zero gradually decreases.

Between the intermediate coil 4 and the cylindrical side wall 2, there is provided a high-frequency electric field generating antenna 7 serving as an electric field generating means, and connected to a plasma generating high-frequency power source 9 via an RF introducing capacitor 8. . The antenna 7 is grounded via a grounding capacitor 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 supply 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 face the substrate electrode 12, and the counter electrode 16 has a shower plate for introducing an etching assist gas as shown in the figure. The shower plate 17 is connected to an etching assist 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 material such as SiO ₂ , Si, C, or SiC which does not adversely affect the etching. The vacuum chamber 1 is evacuated from an exhaust port 1a by a vacuum exhaust system (not shown). Although not shown, the vacuum chamber 1 is provided with a gas introduction unit for introducing a main etching gas.

The operation and operation of the illustrated apparatus configured as described above will be described. Using the apparatus shown in 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, and argon is used as an auxiliary gas.
90 sccm (85%), 10 sccm of C ₄ F ₈ as etching main gas
(15%) was introduced and etching was performed under a pressure of 3 mTorr. As a result, an etching rate of 3600 Å / min was obtained, and it was found that a very uniform etching distribution of ± 2.8% was obtained. FIG. 2A shows the result at that time. For comparison, when the condenser was provided only at the introduction portion of the antenna, the obtained etching rate was 3500 angstroms / minute and the etching distribution was ± 6.6% as shown in FIG. The slight increase in the etch rate in the case of the present invention is presumably due to the fact that a capacitor was introduced into the ground portion of the antenna, so that power was efficiently applied even in the opposite phase.

FIG. 3 shows the results of experiments at ICP.
(A) shows the etching uniformity when a conventional power application method is used, and (b) shows the etching uniformity obtained by connecting a capacitor also to the ground side. In the case of ICP, there is almost no effect since the ring electron current does not flow in the plasma.

In the illustrated embodiment, an example in which the present invention is applied to a cylindrical NLD etching apparatus has been described. However, it is needless to say that the same effect can be obtained by applying it to a flat plate NLD etching apparatus. It is also clear that it can be expected when applied to a magnetic neutral discharge plasma CVD apparatus.

[0018]

As described above, according to the present invention, the capacitor is arranged at the grounding portion of the high-frequency coil, and is arranged symmetrically with respect to the power introduction / exit portion to the high-frequency coil.
Since the time average value of power introduction in the high-frequency coil is configured to be the same near the introduction part and near the grounding part,
High-frequency power can be uniformly applied, plasma with higher uniformity can be formed, and highly uniform etching can be performed in fine processing using a large-area substrate. Therefore, the present invention greatly contributes to the reactive ion etching process used for processing semiconductors and electronic components.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of one embodiment of an etching apparatus according to the present invention.

FIGS. 2A and 2B are graphs showing calculation examples of an etching rate and an etching distribution, wherein FIG. 2A shows a case of the present invention and FIG. 2B shows a case of a conventional method.

FIG. 3 is a graph showing a calculation example of an etching rate and an etching distribution in the inductively coupled plasma method;
(A) shows the case of the conventional system, and (b) shows the case where a capacitor is also provided on the ground side as in the present invention.

FIG. 4 is a schematic sectional view of a conventional inductively coupled discharge etching apparatus.

FIG. 5 is a schematic sectional view of a conventional magnetic neutral beam discharge etching apparatus.

FIG. 6 is a schematic cross-sectional view of a conventional etching apparatus using a flat plate type magnetic neutral discharge.

[Explanation of symbols]

 1: vacuum chamber 2: cylindrical side wall 3, 4, 5: coil forming magnetic field generating means 6: plasma ring formed in circular magnetic neutral wire 7: high frequency electric field generating antenna forming electric field generating means 8: introduction 9: High frequency power supply for plasma generation 10: Grounding capacitor 11: Insulator 12: Substrate electrode 14: High frequency power supply for bias 15: Substrate to be processed 16: Counter electrode 17: Shower plate for introducing auxiliary etching gas

Claims (1)

[Claims] 1. 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 is provided, and a high-frequency electric field is applied along the magnetic neutral line. It has a plasma generator equipped with a high-frequency coil for generating discharge plasma on this magnetic neutral line, and introduces a gas mainly composed of halogen-based gas into vacuum, and forms and introduces plasma at low pressure. Reactivity of plasma decomposition of gas and active use of generated atoms, molecules, radicals, and ions, and applying an alternating electric field or a high-frequency electric field to the substrate electrode in contact with the plasma to etch the substrate mounted on the electrode In the ion etching system, a plurality of magnetic field coils forming a circular magnetic neutral line inside the vacuum chamber are set outside the vacuum chamber, and a high-frequency bias is applied to the lower part of the vacuum chamber. A substrate electrode to be applied is provided, a part of the wall of the vacuum chamber is made of a dielectric material, and a high-frequency antenna coil for generating plasma is arranged outside the vacuum chamber. A reactive ion etching apparatus characterized by being provided so as to introduce high frequency power.