JP3605490B2 - Reactive ion etching equipment - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a reactive ion etching apparatus for etching semiconductors, electronic components, and other substances on a substrate using plasma.
[0002]
[Prior art]
The inventors of the present application have previously proposed a flat permanent magnet type magnetic neutral beam etching apparatus as shown in FIG. 3 as a permanent magnet type etching apparatus in Japanese Patent Application No. 7-217965. In the device proposed earlier, a magnetic neutral line is formed inside the vacuum chamber A by two permanent magnets C and D mounted on the dielectric B on the upper part of the vacuum chamber A, and the magnetic neutral line is formed along the magnetic neutral line. A single antenna E having a circular cross section (diameter of about 10 mm) is arranged between the two permanent magnets C and D, a gas is introduced, and a high-frequency electric field is applied to the antenna to form a ring-shaped plasma. Is configured. It was also proposed to use a flat antenna having a width of about 10 mm in place of the antenna having a circular cross section. In this case, if the width and the diameter were almost the same, the characteristics of the plasma formed were almost the same. A high frequency power for bias is applied to the lower substrate electrode F.
[0003]
The operation of the magnetic neutral beam discharge etching apparatus shown in FIG. 3 configured as described above will be described.
The etching gas is introduced from a gas inlet G provided near the upper flange of the vacuum chamber A, and a high frequency power is applied to an antenna E installed on the dielectric disk B to form a plasma, whereby the introduced gas is decomposed. You. A high frequency power for bias is applied to the lower substrate electrode F. The substrate electrode F, which is in a floating state by the blocking capacitor H, has a negative self-bias potential, and positive ions in the plasma are attracted to etch the substance on the substrate. This method, plasma easily with charged particle density of ^1O 11 ^{cm -3} is formed.
[0004]
[Problems to be solved by the invention]
However, it has been found that when the above-mentioned proposed apparatus is applied to etching of a resist pattern having a fine structure using a halogen-based gas, there is a disadvantage that etching of fine holes cannot be sufficiently performed. . To find out why, the amounts of ions and radicals were measured with a mass spectrometer. The results are shown in FIGS.
FIG. 4 shows the pressure dependence of the ion and radical signal strengths when using a narrow flat plate antenna (width 15 mm), and FIG. 5 shows the ion and radical signals when using a wide flat plate antenna (width 60 mm). This shows the pressure dependence of strength. The gas type and the mixing ratio are Ar (90%) and C ₄ F ₈ (10%). When a flat antenna having a small width is used, both CF ⁺ ions and CF radicals are measured with a large signal intensity, and decrease with an increase in pressure. On the other hand, when a wide antenna is used, the signal strength of CF ⁺ ions is small at low pressure and increases with pressure. Conversely, CF radicals decrease significantly with pressure at low pressures. Further, it was also found that C ⁺ and C atoms, which were not observed at a large signal intensity when a narrow antenna was used, were observed.
[0005]
From the results of the above mass spectrometry, the reason that etching of fine holes cannot be performed sufficiently when a narrow antenna is used is that a large amount of CF ⁺ ions is used to etch a resist because an efficient discharge plasma is formed. It is thought to be. In other words, it is considered that the etching product of the organic resist due to CF ⁺ ions enters the inside of the hole and causes an etch stop.
In etching, the substrate is irradiated with highly reactive radicals and ions to react with the substrate material to gasify and etch the substrate material.However, it is not merely a matter of shaving, and shape control becomes more important with miniaturization. Is coming. For this purpose, in addition to the etchant, a substance that adheres to the wall surface and functions to protect the side wall that is not exposed to ions must be generated in the plasma.
In fine processing with a width of 0.3 μm or less, the relative concentration of the etchant and the protective substance and the relative amount reaching the inside of the hole are important. If the protective substance becomes too much for the etchant, the O.D. The fine pores having a width of 3 μm or less are filled with the protective substance, so-called etch stop occurs, and cannot be cut. Conversely, if the amount of the protective material is too small, the side wall is shaved by the etchant, bowing occurs, and a desired shape cannot be obtained.
When the width of the antenna is increased, a high-energy electron component accelerated by the antenna potential increases, and a substance having a higher ionization energy is easily ionized. The ionization energy of CF radical is about 9.2 eV, the ionization energy of Ar is 15.8 eV, and the ionization energy of C atom is 11.3 eV. Therefore, in a plasma having a low electron temperature, CF radicals are easily ionized, but Ar and C are hardly ionized.
[0006]
Then, the present invention solves the above problem and solves the problem of O.D. It is an object of the present invention to provide a reactive dry etching apparatus applicable to fine processing with a width of 3 μm or less.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a reactive ion etching apparatus according to the present invention comprises 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, Plasma generating means including a single coil antenna for generating an alternating electric field or a high-frequency electric field along the magnetic neutral line to generate discharge plasma in the magnetic neutral line, A gas containing a gas is introduced into a vacuum chamber to form plasma, and an alternating voltage or a high-frequency voltage is applied to a substrate electrode on which a substrate to be processed is installed to etch the substrate. The magnetic field generating means is cylindrical and has a small diameter disk-shaped or donut-shaped first wall disposed above the dielectric. A permanent magnet and an annular second permanent magnet having an inner diameter larger than the first permanent magnet, forming a magnetic neutral line at a position in the vacuum chamber corresponding to between the first permanent magnet and the second permanent magnet, The antenna is formed to have a width in a range of 40 mm to 80 mm , and generates a plasma in which at least one of Ar ^{+ and} C ⁺ is increased along a magnetic neutral line.
[0008]
In the reactive ion etching apparatus of the present invention, by using a wide antenna, a component of electrostatic coupling as well as an inductive coupling component increases as a component contributing to discharge. That is, the plasma is formed and maintained by the azimuthally induced electric field radiated from the antenna and the high-frequency potential generated on the antenna surface. Ar and C atoms having high ionization energy are ionized by this discharge component.
Therefore, it is considered that even if the adhesive substance generated by the reaction between CF ⁺ and the resist enters the holes, sputter by a large amount of Ar ⁺ also occurs in the holes, so that no etch stop occurs. Actually, when a hole having a diameter of 0.2 μm was etched at 30 OmTorr, no etch stop occurred and a vertical processed shape was obtained. This effect was confirmed in the range of 40 mm to 80 mm as the width of the antenna.
[0009]
【Example】
An embodiment of the present invention will be described below with reference to FIGS.
FIG. 1 shows an embodiment of an etching apparatus according to the present invention. In the illustrated apparatus, reference numeral 1 denotes a cylindrical vacuum chamber forming a process chamber having an exhaust port 1a, and the upper surface thereof is covered with a flat dielectric partition 2. A disk-shaped or donut-shaped permanent magnet 3 and a donut-shaped plate-shaped permanent magnet 4 having an inner diameter larger than that of the permanent magnet 3 and having the same polarity as the permanent magnet 3 are formed on the outer surface of the flat dielectric partition 2. The two permanent magnets 3 and 4 are mounted concentrically and constitute a magnetic field generating means for forming a magnetic neutral line in the vacuum chamber 1. Between the disk-shaped or donut-shaped permanent magnet 3 and the donut-shaped plate-shaped permanent magnet 4, a wide single-plasma-generating high-frequency coil 5 having a width of about 40 to 80 mm constituting an electric field generating means is arranged. The high-frequency coil 5 is connected to a high-frequency power source 6 for plasma generation, and applies an alternating electric field along the magnetic neutral line formed in the vacuum chamber 1 by the permanent magnets 3 and 4 to generate a discharge plasma in the magnetic neutral line. I am trying to do it.
Further, a substrate electrode 7 is provided via an insulator member 8 at a position parallel to and away from the surface of the magnetic neutral line formed in the vacuum chamber 1. Connected to power supply 9. Reference numeral 10 denotes a gas inlet.
[0010]
In the illustrated apparatus configured as described above, the power of the 13.56 MHz plasma generating high frequency power supply 6 was set to 1.0 kW, the 100 kHz substrate bias high frequency power supply 9 was set to Vdc-200 V, and the vacuum chamber 1 was set. When the internal pressure was 30 mTorr, argon was 360 sccm, and C ₄ S ₈ was 40 sccm, the etching rate of the silicon oxide film was about 5OO nm / min, and a vertical etching shape was obtained.
[0011]
From this, as described above, when a wide antenna is used, a large amount of Ar ⁺ and C ⁺ ions are generated, so that the adhering substance generated by the reaction between CF ⁺ and the resist enters the holes. Also, it is considered that sputter due to a large amount of Ar ⁺ also occurred in the hole, and no etch stop occurred.
[0012]
Further, in order to examine the effect of the wide antenna, the same measurement as in FIGS. 4 and 5 was performed without a magnetic field (inductively coupled plasma: ICP). The result is shown in FIG. It can be seen that the characteristics shown in FIG. 2 are clearly different from those in FIGS. From this, it can be seen that when the wide antenna is used, even if the pressure is high, the plasma has the characteristics of the magnetic neutral discharge plasma and also has the electrostatic coupling plasma component.
[0013]
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 a similar effect can be expected when applied to an NLD plasma CVD apparatus.
[0014]
【The invention's effect】
As described above, according to the present invention, since a wide antenna is used as a single high-frequency coil for generating discharge plasma, the induction electric field in the azimuthal direction radiated from the antenna is Plasma is formed and maintained by the generated high-frequency potential, and Ar and C atoms having high ionization energy are ionized by this discharge component. As a result, the adhering substance incident on the fine holes can be removed by sputtering, and dry etching capable of coping with fine processing with a width of 0.3 μm or less has become possible. Therefore, the present invention greatly contributes to a reactive ion etching process used for processing semiconductors and electronic components.
[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 pressure dependence of ion and radical signal intensities in the apparatus shown in FIG.
FIG. 3 is a schematic diagram showing a conventional plate permanent magnet type magnetic neutral beam etching apparatus.
FIG. 4 is a graph showing pressure dependence of ion and radical signal intensities in a conventional device using a narrow flat plate antenna.
FIG. 5 is a graph showing the pressure dependence of ion and radical signal intensities in an experiment using a wide flat plate antenna.
[Explanation of symbols]
1: a cylindrical vacuum chamber 2: a plate-shaped dielectric partition wall 3: a disk-shaped or donut-shaped permanent magnet 4: a donut-shaped plate-shaped permanent magnet 5: a wide single high-frequency plasma generating coil 6 forming an electric field generating means: High frequency power source 7 for plasma generation: substrate electrode 8: insulator member 9: high frequency power source 10: gas inlet

Claims (1)

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 applying an alternating electric field or a high-frequency electric field along the formed magnetic neutral line, A plasma generating means including a single coil antenna for generating a discharge plasma in the magnetic neutral line, and introducing a gas including an argon and a fluorocarbon-based gas into the vacuum chamber to form a plasma; A reactive ion etching apparatus that applies an alternating voltage or a high-frequency voltage to a substrate electrode on which a substrate to be processed is installed and etches the substrate.
The vacuum chamber is cylindrical and the upper wall thereof is formed of a disk-shaped dielectric;
The magnetic field generating means includes a small disk-shaped or donut-shaped first permanent magnet disposed above the dielectric and an annular second permanent magnet having an inner diameter larger than the first permanent magnet, Forming a magnetic neutral line at a position in the vacuum chamber corresponding to between the first permanent magnet and the second permanent magnet,
The reactive ion , wherein the antenna is formed to have a width in a range of 40 mm to 80 mm , and generates a plasma in which at least one of Ar ^{+ and} C ⁺ is increased along the magnetic neutral line. Etching equipment.

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