JPH10330970A - Reactive ion etching device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate fine working without generating etch stop by introducing an etching auxiliary gas from an upper part near a magnetic neutron ray at a substrate side and discharging from a substrate electrode lower part at a specified flow rate or more. SOLUTION: A shower plate 10, which is fixed, as sealed, to an upper flange of a cylindrical dielectric body side wall 2 is arranged to a ceiling plate 9 of a vacuum chamber 1 upper part and facing a substrate electrode 12, further, this shower plate is connected to an etching auxiliary gas source. A ring 11 formed with plural small holes, etc., is arranged near a magnetic neutron ray 6 in the vacuum chamber 1, therefrom an etching principal gas is supplied toward a vacuum chamber 1 center to a substrate electrode 12 side. The substrate electrode 12 is supported with arranging a clearance for gas passing between a side part/bottom part of the substrate electrode 12 and the vacuum chamber 1 wall in order to obtain a large effective discharge flow rate, in a discharge system 15, the effective discharge flow rate is set to >=1500 l/sec in a term of Ar, discharging from the substrate electrode 12 lower part.

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 Various types of etching apparatuses are known in the prior art, and the most widely used etching apparatus is a parallel plate type as shown in FIG. 3 of the accompanying drawings. . Vacuum chamber A
An anode B and a cathode, that is, a substrate electrode C, are arranged to face each other, a reaction gas is introduced from the anode B, and a high-frequency power source E is connected to the substrate electrode C via a matching circuit D. FIG. 4 shows another example of a parallel plate type etching apparatus. In this case, a high frequency power supply G is connected to the electrode B via a matching circuit F, and high frequency powers having different frequencies are applied to upper and lower electrodes. Is done.

FIG. 5 shows a conventional example of an ECR etching apparatus, in which a microwave is introduced from the upper part of a vacuum chamber A through a dielectric window B, and a high-density plasma is formed by electron cyclotron resonance in a magnetic field of 875 Gauss. .

FIG. 6 shows an inductively coupled discharge etching apparatus in which an antenna B composed of a single coil for generating discharge plasma in a vacuum chamber A is provided outside a dielectric side wall A1 of the vacuum chamber A. A high-frequency power is applied to the high-frequency antenna B from a high-frequency power source C for plasma generation, 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 from the vacuum chamber A. To form a plasma at a low pressure, decompose the introduced gas, actively use the generated atoms, molecules, radicals, and ions, and apply a high-frequency electric field from a high-frequency power source E to a substrate electrode D in contact with the plasma. The substrate mounted on the substrate electrode D is etched. FIG. 7 shows a modification of the embodiment shown in FIG.
A spiral antenna G is mounted thereon, and is configured to form inductively coupled plasma. ICP using the method of Fig. 6
(Inductively Coupled Plasma), and the method in FIG.
It is distinguished by calling it CP (Transfer Coupled Plasma).

FIG. 8 shows that the inventors of the present invention have previously described Japanese Patent Application Laid-Open
1 shows a magnetic neutral discharge etching apparatus proposed in Japanese Patent No. 263192. The device proposed earlier is a vacuum chamber A
A magnetic neutral line E is formed inside the vacuum chamber A by the three magnetic field coils B, C, and D mounted on the outside of the dielectric cylindrical wall A1 on the upper side of the magnetic neutral line E. A ring-shaped plasma is formed by applying a high-frequency electric field from a high-frequency power source for antenna G to a single antenna F disposed inside the magnetic field coil C of the first embodiment. 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. High frequency power is applied from a high frequency power source I for bias to a substrate electrode H below the vacuum chamber A.

The gas is introduced from the upper flange or its periphery even though the discharge method is different. This is because it was considered that the introduced gas needed to be sufficiently decomposed in the plasma space while diffusing to the substrate.

As a representative example, the ICP shown in FIG.
The etching will be described. The etching gas is introduced from the vicinity of the upper flange, and high-frequency power is applied to the antenna B installed outside the dielectric cylindrical partition wall A1, whereby plasma is formed and the introduced gas is decomposed. At this time, since the distribution of the plasma and the introduced gas is required to be uniform on the substrate, generally, a shower plate having a large number of holes is provided on an upper flange, through which the gas is introduced into the vacuum chamber. You. If the gas flow is uniform and the plasma density and potential are uniform, the density distribution of etchants (radicals and ions) generated in the plasma becomes uniform, and the substrate is etched uniformly. By the way, I
The plasma density and the uniformity of potential in CP etching are greatly affected by the chamber structure and pressure. Once the chamber structure is determined, the pressure conditions for obtaining uniformity are almost uniquely determined, and the range of conditions to be selected is extremely narrow.

On the other hand, in the magnetic neutral beam discharge (NLD) etching apparatus shown in FIG. 8, the position of the magnetic neutral beam can be freely changed, and the plasma density and potential are controlled in a low-pressure gas region where ICP does not occur. Therefore, conditions with good etching uniformity can be easily set.

[0009]

As the density of devices has become higher and the processing width has become finer, it has become impossible to cope with the conventional gas introduction and exhaust methods. In etching, a highly reactive radical and ions are irradiated on the substrate to gasify and etch the substrate material by reaction with the substrate material.
It is not only necessary to simply cut, but shape control is also required.
For this purpose, in addition to the etchant, a substance which adheres to the wall surface inside the micropore and functions to protect the side wall not exposed to ions must be generated in the plasma. In microfabrication with a width of 0.3 μm or less, the relative concentration between the etchant and the protective substance becomes important. If the amount of the protective substance becomes too large with respect to the etchant, the fine holes having a width of 0.3 μm or less are filled with the protective substance, so that a so-called etch stop occurs, and the fine holes cannot be removed. On the other hand, if the amount of the protective material is too small, the side wall is shaved by the etchant, causing bowing, and a desired shape cannot be obtained.

In the etching apparatus shown in FIGS. 3 and 4, since the pressure is high, a large amount of adhered substances are generated due to collision between molecules, and fine processing with a width of 0.3 μm or less cannot be performed. Even in the method shown in FIGS. 5 to 8, the decomposition proceeds while the introduced gas passes through the large plasma space, and a large amount of adhered substances are generated. Therefore, it is difficult to perform fine processing with a width of 0.3 μm or less.
This is because, since the plasma density is high and the effective pumping speed under low pressure is low, the residence time of the gas is long, and over-decomposition occurs while reaching the vicinity of the substrate.

Accordingly, an object of the present invention is to provide a reactive ion etching apparatus capable of solving the above-mentioned problem and performing etching without generating an etch stop in fine processing with a width of 0.3 μm or less.

[0012]

In order to achieve the above object, in a dry etching apparatus according to the present invention,
Using an NLD etching device, an etching assist gas is introduced from the upper part of the vacuum chamber, an etching main gas is introduced to the substrate side near the magnetic neutral line, and the effective pumping speed under low pressure is increased. It is configured to exhaust.

[0013]

According to an embodiment of the present invention, there is provided a magnetic levitation generating means for forming an annular magnetic neutral line which is a position of zero magnetic field continuously present in a vacuum chamber, A plasma generating means comprising a single high frequency coil including a single coil for generating a discharge plasma in the magnetic neutral line by applying an alternating electric field along the magnetic neutral line; A main gas is introduced into a vacuum, plasma is formed at low pressure and the introduced gas is decomposed, and the generated atoms, molecules, radicals, and ions are used positively. An alternating electric field or high frequency is applied to the substrate electrode in contact with the plasma. In a reactive ion etching apparatus for etching a substrate placed on an electrode by applying an electric potential, the reactive ion etching apparatus is provided on an electrode facing a substrate electrode, and an etching auxiliary gas is introduced from this electrode. An etching auxiliary gas introducing means and an etching main gas introducing means provided in the vicinity of the magnetic neutral line and introducing the etching main gas from the circumferential direction to the substrate electrode side, and the effective pumping speed is calculated as an approximate Ar value of 1500. The gas is discharged from below the substrate electrode at a rate of 1 liter / sec or more. Preferably, the etching assist gas introducing means may be constituted by a shower plate provided on the counter electrode. The means for introducing the main etching gas may preferably comprise a ring arranged above the substrate electrode and on the peripheral extension of the substrate electrode and adapted to supply the main etching gas radially inward. Further, a gap is provided between the side and bottom of the substrate electrode and the wall of the vacuum chamber to allow gas to pass therethrough, and a vacuum exhaust system is connected to the bottom of the vacuum chamber.

For example, in the case of oxide film etching, substances used as an etching auxiliary gas include argon, hydrogen, carbon monoxide and the like, and CF ₄ , C ₃ F ₈ , C ₄ F _{8 and the} like as main etching gases. There is. The etching main gas is decomposed when the plasma density increases or the residence time in the plasma increases, and CF and C, which are adherent substances,
F ₂ radicals are generated more. Since the process main gas is introduced near the substrate using a magnetic neutral beam discharge device that can form plasma in a region where the plasma density is not unnecessarily high, the ratio of the etchant substance to the adherent substance that reaches the substrate Can be changed. Furthermore, since the gas is evacuated from below the substrate, the effective evacuating speed is improved 1.5 to 2 times, and the operating flow rate range can be widened. An increase in the flow rate means a shorter residence time of the gas, and a wider operating flow range allows the residence time of the gas to be varied over a wider range, making it easier to control the etchant and adherent substances. become.

[0015]

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 reactive ion etching apparatus of the present invention. In the illustrated etching apparatus, reference numeral 1 denotes a vacuum chamber, which is provided with a cylindrical dielectric side wall 2 at an upper portion thereof, and a magnetic field generation for forming a magnetic neutral line in the vacuum chamber 1 is provided outside the dielectric side wall 2. Three magnetic field coils 3, 4, 5 constituting the means are provided and form a magnetic neutral line 6 in the upper part of the vacuum chamber 1. Between the intermediate magnetic field coil 4 and the outside of the dielectric side wall 2, there is a single high frequency coil 7 for generating multiple plasmas.
The high-frequency coil 7 is connected to a high-frequency power source 8 and applies an alternating electric field along a magnetic neutral line 6 formed on the upper part of the vacuum chamber 1 by three magnetic field coils 3, 4, and 5, thereby Discharge plasma is generated in the neutral wire. A top plate 9 on the upper part of the vacuum chamber 1 is hermetically fixed to an upper flange of the dielectric side wall 2 and a shower plate for introducing an etching auxiliary gas is provided on the top plate 9.
A shower plate 10 is provided, and the shower plate 10 is connected to an etching assist gas source (not shown).

In the vicinity of the magnetic neutral wire 6 in the vacuum chamber 1, a ring 11 for introducing a main etching gas is disposed. A plurality of small holes or circumferentially narrow orifices are formed on the circumference to feed toward the center. The ring 11 for introducing the main etching gas is positioned above the substrate electrode 12 and substantially on the peripheral extension surface of the substrate electrode 12, as shown in the figure. The substrate electrode 12
It is supported by a support member 13 with a gap through which gas passes between the side and bottom thereof and the vacuum chamber wall. That is, the lower part of the vacuum chamber 1 below the substrate electrode 12 has a large effective pumping speed. The difference between the outer diameter of the substrate electrode 12 and the inner diameter of the lower part of the vacuum chamber 1 is 40 in the radial direction.
mm or more. The substrate electrode 12 is connected to a high-frequency power supply 14 for applying an RF bias. Further substrate electrodes
An exhaust system 15 composed of a turbo-molecular pump is connected to the bottom of the vacuum chamber 1 below the vacuum chamber 12. The effective pumping speed at the substrate electrode when using a turbo molecular pump having a pumping speed of 3000 l / s is 1550 when the gas is argon.
l / s, and 970 l / s when the gas is C ₄ F ₈ . The conventional pumping speed is 890 l / s when the gas is argon and the gas is C ₄ F ₈
In this case, the pumping speed is 480 l / s, so that the effective pumping speed is improved about 1.7 to 2 times. As a result, when the mass is large, the conductance decreases and the effective pumping speed decreases. That is, when the mass number changes, the effective pumping speed changes.

FIG. 2 is a diagram showing the mass dependence of the effective pumping speed. Since Ar has a mass number of 40, the effective pumping speed is 1500
l / s. Since C ₄ F ₈ has a mass number of 200, the effective pumping speed is about 920 l / s. The gas represented by the mass number of Ar is an Ar conversion value.

The 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 8 was 1.5 KW, the power of the substrate bias high-frequency power supply 14 was 500 W, the pressure was 5 mTorr, argon was 135 sccm as an auxiliary etching gas, and C ₄ F ₈ was used as an etching main gas.
Is 23 sccm, the etching rate of the silicon oxide film is 732 nm / min, and the etching rate of silicon is 52 nm.
/ Min. The selectivity at this time was 14. on the other hand,
For comparison, using the conventional evacuation method shown in FIG. 8, when etching was performed under the same pressure conditions by introducing 90 sccm of argon as an etching auxiliary gas and 15 sccm of C ₄ F ₈ as an etching main gas, the silicon oxide film was etched. The etching rate is 610 nm / min, and the etching rate of silicon is 51 nm.
/ Min. The selection ratio at this time is 12. Therefore,
By increasing the effective pumping speed and increasing the gas flow rate by 1.5 times, both the etching speed and the selectivity have been improved by 1.2 times. Furthermore, when the controllability of the pattern shape was confirmed with a fine pattern, it was found that a pattern having a diameter of 0.3 μm could be etched almost vertically, and the shape control became easy. This is probably because the flow rate of the gas to be introduced can be increased by the improvement in the pumping speed, and the residence time in the plasma is shortened, so that the over-decomposition can be suppressed.

In the illustrated embodiment, an example in which the present invention is applied to an NLD etching apparatus has been described. However, it is needless to say that the same effect can be expected when applied to an NLD plasma CVD apparatus.

[0020]

As described above, in the reactive ion etching apparatus according to the present invention, an etching auxiliary gas is introduced from the upper portion of the vacuum chamber, and an etching main gas is introduced into the substrate near the magnetic neutral line. In order to increase the effective pumping speed under low pressure, it is configured to exhaust from the lower part of the substrate electrode, so that the amount of the etchant and the adhering substance incident on the substrate can be controlled, resulting in fine processing of 0.3 μm width or less. It is possible to perform dry etching that can be used. Therefore, the present invention greatly contributes to the reactive ion etching process used for processing semiconductors and electronic parts.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing one embodiment of the present invention.

FIG. 2 is a graph showing the mass dependence of the effective pumping speed actually measured using the apparatus of FIG.

FIG. 3 is a schematic diagram showing an example of a conventional parallel plate type etching apparatus.

FIG. 4 is a schematic diagram showing a conventional three-electrode etching apparatus.

FIG. 5 is a schematic diagram showing a conventional ECR etching apparatus.

FIG. 6 is a schematic diagram showing a conventional inductively coupled etching apparatus.

FIG. 7 is a schematic diagram showing a conventional transfer-coupling type etching apparatus.

FIG. 8 is a schematic diagram showing a conventional magnetic neutral discharge type etching apparatus.

[Explanation of symbols]

 1: vacuum chamber 2: cylindrical dielectric side wall 3: magnetic field coil 4: magnetic field coil 6: magnetic neutral wire 7: high frequency coil 8: high frequency power supply for plasma generation 9: top plate 10: shower plate 11 : Ring 12: Substrate electrode 13: Support member 14: High frequency power supply 15: Exhaust system

Claims (4)

[Claims] 1. A magnetic head for generating an annular magnetic neutral line, which is a position of zero magnetic field continuously present in a vacuum chamber, is provided, and an alternating electric field is applied along the magnetic neutral line. It has a plasma generating means provided with a multiple high frequency coil including a single layer for generating a discharge plasma on the magnetic neutral line, and introduces a gas mainly composed of a halogen-based gas into a vacuum, A plasma is formed at the same time as the introduced gas is decomposed and the generated atoms, molecules, radicals, and ions are positively used, and an alternating electric field or a high-frequency electric field is applied to the substrate electrode in contact with the plasma to be placed on the electrode. A reactive ion etching apparatus for etching an etched substrate, an etching auxiliary gas introducing means provided on an electrode facing the substrate electrode, for introducing an etching auxiliary gas from the electrode, An etching main gas introducing means for introducing an etching main gas from the circumferential direction to the substrate electrode side, provided near the neutral line, and having an effective pumping speed of at least 1500 liters / sec. A reactive ion etching apparatus configured to discharge gas from below. 2. An etching auxiliary gas introducing means comprising a shower plate provided on a counter electrode.
6. The reactive ion etching apparatus according to 5. 3. The etching main gas introducing means comprises a ring disposed above the substrate electrode and on the peripheral extension surface of the substrate electrode, and adapted to supply the etching main gas inward in the radial direction. The reactive ion etching apparatus according to claim 1. 4. The reactive ion etching according to claim 1, wherein a gap is provided between the side and bottom of the substrate electrode and the vacuum chamber wall, and a vacuum exhaust system is connected to the bottom of the vacuum chamber. apparatus.