JP3940464B2 - Reactive ion etching apparatus and method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a reactive ion etching apparatus and method for etching a material on a semiconductor, an electronic component, or other substrate using plasma.
[0002]
[Prior art]
The present inventors previously proposed a magnetic neutral wire discharge etching apparatus in Japanese Patent Application Laid-Open No. 7-263192. As shown in FIG. 2, the previously proposed apparatus is magnetically neutral inside the vacuum chamber A by three magnetic field coils C, D and E mounted outside the dielectric cylindrical wall B at the top of the vacuum chamber A. A line F is formed, and a ring-shaped plasma is formed by applying a high-frequency electric field from the antenna high-frequency power source H to the single antenna G disposed inside the intermediate magnetic field coil D along the magnetic neutral line F. Is formed. The etching gas is introduced from the vicinity of the upper top plate I 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 J below the vacuum chamber A from a high frequency power source K for bias.
[0003]
The magnetic neutral wire discharge etching apparatus shown in FIG. 2 having such a configuration will be described.
Etching gas is introduced from the vicinity of the upper flange of the vacuum chamber A, and plasma is formed by applying high-frequency power to a single antenna G disposed between the outside of the dielectric cylindrical wall B and the intermediate magnetic field coil D. Then, the introduced gas is decomposed. High frequency power for bias is applied from a high frequency power supply K for bias to the substrate electrode J below the vacuum chamber A. The substrate electrode J that is in a floating state by the blocking capacitor L has a negative self-bias potential, and positive ions in the plasma are attracted to etch the material on the substrate.
[0004]
In the magnetic neutral line discharge, in order to form a high density plasma in the portion of the magnetic neutral line F formed in a ring shape in vacuum, an induction electric field formed along the ring-shaped magnetic neutral line F is effective. It is something to use.
By this method, a plasma having a charged particle density of 10 ¹¹ cm ^{−3 is} easily formed.
[0005]
However, it has been found that when applied to etching of a resist pattern having a fine structure using a halogen-based gas, there is an inconvenience that fine holes cannot be etched sufficiently.
[0006]
[Problems to be solved by the invention]
In etching, the substrate material is irradiated with highly reactive radicals and ions, and the substrate material is gasified and etched by reaction with the substrate material. It has become to. For this purpose, in addition to the etchant, a substance that adheres to the wall surface inside the micropore and protects the side wall not exposed to ions must also be generated in the plasma.
In microfabrication with a width of 0.3 μm or less, the relative concentration of the etchant and the protective material and the relative amount reaching the inside of the hole are important. If the protective material is too much for the etchant, the micropores with a width of 0.3 μm or less will be filled with the protective material, and so-called etch stop will occur, and will not be removed. On the other hand, if the amount of the protective material is too small, the side wall is scraped by the etchant, bowing occurs, and the desired shape cannot be obtained.
In a conventionally used magnetic neutral line discharge etching apparatus, high frequency power is applied to an antenna for forming plasma and an electrically floating electrode for generating a bias voltage. When plasma is formed by introducing a halogen-based gas, gas molecules are decomposed into plasma, and an etchant or a substance that is easily polymerized is generated. When a material that easily polymerizes reaches the substrate electrode, it acts as a protective material, but when it reaches the wall surface of the discharge chamber, it adheres to the wall surface and causes dust.
For this reason, in ICP and NLD having a large discharge chamber, measures are taken to reduce the adhesion as much as possible by heating the wall surface of the vacuum chamber to ˜200 ° C. However, even if the wall of the vacuum chamber is heated, the adherent substance cannot be completely eliminated.
In addition, charge up in the micro holes can be considered as one of the mechanisms that cause the etch stop. Since the substrate bias is negative, ions and radicals fly into the hole and etching proceeds by ion assist. If the hole becomes fine, electron flow becomes insufficient due to the sheath electric field, and charge correction in the hole cannot be performed, and the charge is positively charged. As a result, it is considered that positive ions are prevented from flowing in and etching does not proceed sufficiently.
[0007]
Accordingly, the present invention provides a reactive ion etching apparatus and method using magnetic neutral wire discharge that can solve the above-described problems and can perform etching without causing an etch stop in microfabrication of a width of 0.3 μm or less. It is an object.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the reactive ion etching apparatus using magnetic neutral wire discharge according to the present invention is configured to apply high-frequency power using the top plate of the vacuum chamber as a floating electrode. .
[0009]
DETAILED DESCRIPTION OF THE INVENTION
According to the present invention, a magnetic field generating means for forming an annular magnetic neutral line that is continuously located in the vacuum chamber and is a position of zero magnetic lift is provided, and an alternating electric field is generated along the magnetic neutral line. In addition, this magnetic neutral wire has a plasma generating device provided with multiple high-frequency coils including a single layer for generating discharge plasma, and a gas mainly containing a halogen-based gas is introduced into a vacuum, The substrate placed on the electrode is formed by forming plasma at a low pressure and decomposing the introduced gas, applying an alternating electric field or a high frequency electric field to the substrate electrode in contact with the plasma using the generated atoms, molecules, radicals and ions. In reactive ion etching equipment for etching,
Part of the vacuum chamber is composed of a cylindrical dielectric, and magnetic field generating means for forming an annular magnetic neutral line is composed of a plurality of magnetic field coils arranged outside the dielectric, and is formed in the vacuum chamber. A high-frequency coil for generating plasma is disposed between the dielectric wall of the vacuum chamber and the magnetic field coil in the same plane as the annular magnetic neutral wire, and the high-frequency coil is formed below the vacuum chamber portion made of dielectric. A substrate electrode to which a bias is applied is provided, and another electrode that allows a high-frequency bias to be applied during etching of the substrate is provided on the upper portion of the vacuum chamber formed of a dielectric material opposed to the substrate electrode. made of silicon material or a carbon material or a top plate using these compounds or composites as the top of the inner wall material of the vacuum chamber portion composed of a dielectric, said during etching of the substrate The top plate in the plasma by applying a high frequency bias is sputtered to the electrodes, and characterized by being configured to generate a SiFx or CF x radicals.
Further, reactive ion etching method for etching a substrate by generating by that plasma in the present invention,
An annular magnetic neutral line that is continuously present in the vacuum chamber and where the magnetic lift is zero is formed. A gas mainly composed of a halogen-based gas is introduced into the vacuum chamber, and alternating current is generated along the magnetic neutral line. Adding a lift to generate a discharge plasma in the magnetic neutral line;
Etching the substrate placed on the electrode by applying an alternating electric field or a high-frequency electric field to the substrate electrode on which the substrate is installed; and
Applying a high frequency bias to the top plate of the vacuum chamber facing the substrate electrode while etching the substrate;
Including
As a top plate inner wall material, a cage material, a carbon material, a compound or a composite thereof is used .
[0010]
Since the upper top plate of the vacuum chamber is used as a floating electrode and high frequency power is applied to generate a negative bias on the upper top plate, the upper top plate is always struck by positive ions. As a result, film adhesion to the top plate is suppressed and dust generation from the top plate is suppressed as compared with the case of the conventional top plate having a ground potential.
Furthermore, not only can the generation of dust be suppressed, but also a secondary effect of generating an etchant can be expected by sputtering a polymerized film that adheres to the inner surface of the top plate.
[0011]
When a cage material, carbon material, or a compound or mixture thereof is used as the inner wall material of the top plate, adsorption of fluorine radicals and SiFx. An effect as a generation source of CFx radicals can also be expected. Because fluorine radicals has strong reactivity with silicon, in the case of the process of the Si0 ₂ / Si in which the oxide film and etched, but selectivity fluorine radicals for polytene underlying Si film is poor, as the upper ceiling plate inner wall member If a soot material, a carbon material, or a compound or mixture thereof is used, an effect that fluorine radicals adhere to the sputtered surface and the selectivity to the underlying Si film can be expected.
[0012]
In addition, when high frequency power is applied to the upper top plate, secondary electrons from the upper top plate surface and electrons accelerated by sheath heating jump to the substrate surface and correct the positive charge-up generated in the fine holes. I can expect.
When etching a fine hole with a diameter of O.3μm using a wafer with a silicon oxide film, the etch stop did not occur even under the condition that the etch stop occurred when the conventional ground potential top plate was used. This is probably because the generation of the etchant, the secondary electrons from the upper top surface, and the electrons accelerated by the sheath heating jumped to the substrate surface and corrected the positive charge-up generated in the fine holes.
[0013]
【Example】
Hereinafter, an embodiment of the present invention will be described with reference to FIG. 1 of the accompanying drawings.
FIG. 1 shows an embodiment of a reactive ion etching apparatus of the present invention. In the illustrated etching apparatus, reference numeral 1 denotes a vacuum chamber, which includes an upper plasma generation unit 1a and a substrate electrode unit 1b, and an exhaust port 1c is provided in the substrate electrode unit. The plasma generation unit 1a includes a cylindrical dielectric side wall 2, and three magnetic fields constituting magnetic field generation means for forming a magnetic neutral line in the vacuum chamber-1 outside the dielectric side wall 2. Coils 3, 4, and 5 are provided, and a magnetic neutral wire 6 is formed in the plasma generator 1 a at the top of the vacuum chamber 1.
Between the intermediate magnetic field coil 4 and the outside of the dielectric side wall 2, a multiple high frequency coil 7 for generating plasma including a single layer is arranged, and this high frequency coil 7 is connected to a high frequency power source 8 and three magnetic field coils. An alternating electric field is applied along the magnetic neutral line 6 formed in the plasma generating part 1a at the upper part of the vacuum chamber 1 by means of 3, 4, and 5 so as to generate discharge plasma in the magnetic neutral line.
The top plate 9 of the plasma generator 1a at the top of the vacuum chamber 1 is hermetically fixed to the top flange of the dielectric side wall 2 via an insulator 10, and the top plate 9 is made of a carbon material as an inner wall material. And it is connected to the high frequency bias power source 11 so that a weak high frequency bias is applied, so that the top plate 9 functions as a floating electrode.
Further, a substrate electrode 12 is provided in the lower substrate electrode portion 1b through an insulator member 13 in parallel with the surface formed by the magnetic neutral line formed in the plasma generating portion 1a of the vacuum chamber-1. The substrate electrode 12 is connected to a high frequency power source 14 for applying an RF bias.
Further, a gas introduction port 15 for introducing an etching gas into the vacuum chamber 1 is provided in the plasma generation unit 1a at the upper part of the vacuum chamber-1, and this gas introduction port 15 is not shown, but is a gas supply passage. And an etching gas supply source through a gas flow rate control device for controlling the flow rate of the etching gas.
[0014]
In the experiment with the illustrated apparatus configured as described above, the power of the plasma generating high frequency power supply 8 (13.56 MHz) is 2.OkW, the power of the substrate bias high frequency power supply 14 (800 kHz) is 500 W, and the high frequency power supply 11 is applied to the top plate 9. power (12.5MHz) 200W, Ar90sccm (90 %), C 4 F 8 introduced 10sccm (10%), was etched under a pressure of 3 mTorr, approximately 0.3μm diameter silicon oxide film without etch stop Vertical etching was possible.
In etching under the same conditions in the conventional apparatus configuration, an etch stop occurs at a depth of about 0.5 μm, although there is some difference depending on the pattern width.
Substances attached to the wall include CF, CF ₂ , CF ₃ , C ₂ F ₂ , C ₂ F ₄ , C ₂ F ₅ , C ₃ F ₅ , C ₃ F ₆ , etc., and further decomposed C There are compounds such as ₂ F _X , C ₃ F _X , and C ₄ F _X (x = 1 to 2). These compounds adhere to the wall surface to form a polymerized film. When there is no ion bombardment, the polymer film formed by these compounds becomes a thick film and eventually peels off to become dust. However, when there is an ion bombardment, the formation of the polymer film hardly occurs or even if it occurs, it is sputtered and becomes radicals such as CF, CF ₂ , CF _{3 and the} like, and jumps out into the gas phase to become an etchant.
Due to the effect of this etchant generation and electron acceleration on the top plate, it is considered that the submicron hole pattern could be etched without the etch stop even under the condition where the etch stop occurred in the conventional apparatus configuration. It is not clear which of these two has the main effect because the two effects cannot be separated.
[0015]
In the above example, 200 W is used as the high-frequency power applied to the top plate 9, but this power must be appropriately selected depending on the values of the plasma-generating high-frequency power and the substrate bias high-frequency power. Although a frequency of 12.5 MHz is used, the same effect can be expected at 2 MHz or 27.12 MHz if the frequency is higher than that of the substrate electrode 12.
Further, in the illustrated embodiment, a carbon material is used as the inner wall material of the top plate 9, but instead, it is configured using a straw material or a compound or composite thereof or a compound or composite of a straw material and a carbon material. You can also.
[0016]
In the illustrated embodiment, the example applied to the NLD etching apparatus has been described, but it is needless to say that the same effect can be expected when applied to the NLD plasma CVD apparatus.
[0017]
【The invention's effect】
As described above, the etching apparatus according to the present invention is configured to apply high-frequency power using the top plate in the upper part of the vacuum chamber as a floating electrode. In microfabrication with a width of 3 μm or less, submicron hole pattern etching can be performed without etch stop by introducing high frequency power to the top plate above the discharge chamber and etching in an appropriate power region. Therefore, it 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 schematic diagram showing a conventional magnetic neutral wire etching apparatus.
[Explanation of symbols]
1: Vacuum chamber 2: Cylindrical dielectric side wall 3: Magnetic field coil 4: Magnetic field coil 5: Magnetic field coil 7: High frequency coil 8: High frequency power source 9 for plasma generation 9: Top plate
10: Insulator
11: High frequency bias power supply
12: Substrate electrode
13: Insulator material
14: High frequency power supply
15: Gas inlet

Claims (2)

A magnetic field generating means is provided for forming an annular magnetic neutral line that is continuously located in the vacuum chamber and is located at zero magnetic lift, and an alternating electric field is applied along the magnetic neutral line to provide the magnetic neutral line. A plasma generator having multiple high-frequency coils including a single layer for generating discharge plasma on a wire is provided. A gas mainly composed of a halogen-based gas is introduced into a vacuum to form plasma at a low pressure. Reactive ion etching that decomposes the introduced gas and uses the generated atoms, molecules, radicals, and ions to apply an alternating electric field or a high-frequency electric field to the substrate electrode in contact with the plasma to etch the substrate placed on the electrode In the device
Part of the vacuum chamber is composed of a cylindrical dielectric, and magnetic field generating means for forming an annular magnetic neutral line is composed of a plurality of magnetic field coils arranged outside the dielectric, and is formed in the vacuum chamber. A high-frequency coil for generating plasma is disposed between the dielectric wall of the vacuum chamber and the magnetic field coil in the same plane as the annular magnetic neutral wire, and the high-frequency coil is formed below the vacuum chamber portion made of dielectric. A substrate electrode to which a bias is applied is provided, and another electrode that allows a high-frequency bias to be applied during etching of the substrate is provided on the upper portion of the vacuum chamber formed of a dielectric material opposed to the substrate electrode. made of silicon material or a carbon material or a top plate using these compounds or composites as the top of the inner wall material of the vacuum chamber portion composed of a dielectric, said during etching of the substrate Said at the plasma by applying a high frequency bias to the electrode top plate is sputtered, reactive ion etching apparatus characterized by being configured to generate a SiFx or CF x radicals. An etching method for etching a substrate by generating plasma,
An annular magnetic neutral line, which is a position of zero magnetic lift that exists continuously in the vacuum chamber, is formed, a gas mainly containing a halogen-based gas is introduced into the vacuum chamber, and along the magnetic neutral line Applying alternating current to generate discharge plasma in the magnetic neutral wire;
Etching the substrate placed on the electrode by applying an alternating electric field or a high frequency electric field to the substrate electrode on which the substrate is installed;
Applying a high frequency bias to the top plate of the vacuum chamber facing the substrate electrode while etching the substrate;
Including
As the inner wall material of the top plate, a straw material, a carbon material, a compound or a composite thereof is used.
The reactive ion etching method characterized by the above-mentioned .

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