JPH10270421A - Reactive ion etching apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the dry etching adaptable to fine machining below specified width by providing a wide antenna as a single-winding high frequency coil for generating a discharge plasma to remove an easy-to-deposit material incident on fine holes. SOLUTION: A cylindrical vacuum chamber 1 has a top wall made from a disk-like dielectric 2. A magnetic field generating means is composed of a small-diameter disk-like or doughnut-like permanent magnet 3 disposed on the top of the dielectric 2 and annular permanent magnet 4 having a larger inner diameter than the magnet 3. A wide antenna is disposed on the top of a magnetic neutral line located between the two magnets 3, 4 as a single-winding high frequency coil 5 for generating a discharge plasma, thereby ionizing Ar or C atoms having a high ionizing energy by the discharge component. Thus a reactive dry etching apparatus adaptable to microfabrication below 0.3 μm width can be realized.

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 semiconductors, electronic parts, and other substances on a substrate by using plasma.

[0002]

2. Description of the Related Art The inventors of the present invention 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 placed 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. And two permanent magnets C,
A single antenna E having a circular cross section (diameter of about 10 mm) is arranged between D, and a gas is introduced and a high-frequency electric field is applied to this antenna to form a ring-shaped plasma. 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.

The operation of the magnetic neutral beam discharge etching apparatus shown in FIG. 3 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. By this method, a plasma having a charged particle density of 10 ¹¹ cm ^{-3 is} easily formed.

[0004]

However, when the above-mentioned proposed apparatus is applied to etching of a resist pattern having a fine structure using a halogen-based gas, it is not possible to sufficiently etch fine holes. It turned out to be inconvenient. 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 intensities when using a narrow flat plate antenna (width 15 mm), and FIG. 5 shows a wide flat plate antenna (width 60 mm).
(mm) shows the pressure dependence of the ion and radical signal intensities. Gas type and mixing ratio are Ar (90%), 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 increasing pressure. on the other hand,
When a wide antenna is used, the signal intensity of CF ⁺ ions is small at low pressure and increases with pressure. vice versa,
CF radicals decrease largely with pressure at low pressures. Furthermore, it was 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 above mass spectrometry results, the reason that etching of fine holes cannot be sufficiently performed when a narrow antenna is used is that the amount of CF ⁺ ions is large because an efficient discharge plasma is formed. This is probably because the resist is etched. That is, it is considered that the etching product of the organic resist by 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 gasify and etch the substrate material by reacting with 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 which adheres to the wall surface and protects the side wall 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 amount of the protective material becomes too large relative to the etchant, the pores having a width of 0.3 μm or less are filled with the protective material, so-called etch stop occurs, and the material 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.
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. CF
Radical ionization energy is about 9.2 eV, Ar ionization energy is 15.8 eV, and C atom ionization energy 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.

Therefore, the present invention solves the above-mentioned problem and solves the above-mentioned problem.
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]

In order to achieve the above object, in a reactive dry etching apparatus according to the present invention, a wide antenna is used as a single high-frequency coil for generating discharge plasma.

[0008]

Therefore, 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, A plasma generator comprising a single high-frequency coil for generating a discharge plasma in this magnetic neutral line by applying an alternating electric field along the line, and applying a gas mainly composed of halogen-based gas in a vacuum To form a plasma at low pressure and decompose the introduced gas, actively utilize the generated atoms, molecules, radicals, and ions, and apply an alternating electric field or a high-frequency electric field to the substrate electrode in contact with the plasma, In a reactive ion etching apparatus that etches a substrate placed on a substrate, the upper wall of a cylindrical vacuum chamber is composed of a disk-shaped dielectric, and a magnetic field generating means is disposed above the dielectric. A disk-shaped or donut-shaped permanent magnet with a small diameter and a ring-shaped permanent magnet with a larger inside diameter to form a magnetic neutral line at a position between the two permanent magnets. A wide antenna is arranged as a single high-frequency coil for generating discharge plasma above the line. By using a wide antenna, a component of electrostatic coupling as well as an inductive coupling component as a component contributing to discharge increases. That is, the plasma is formed and maintained by the induction electric field in the azimuthal direction 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 hole, sputter by a large amount of Ar ⁺ also occurs in the hole, so that no etch stop occurs. Actually, a hole of 0.2 μm diameter is
When etched at mTorr, 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]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 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 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. 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.

In the illustrated apparatus configured as described above, 1
The power of the plasma generating high-frequency power supply 6 of 3.56 MHz is 1.0 kW,
High frequency power supply 9 for 100kHz substrate bias is Vdc-200V
And set the pressure in the vacuum chamber 1 to 30mT
When orr and argon were set to 360 sccm and C ₄ S ₈ to 40 sccm, the etching rate of the silicon oxide film was about 500 nm / min.
A vertical etch profile was obtained.

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 has a large size in the holes. It is considered that spattering due to a large amount of Ar ⁺ occurred even in the holes even after the etching, and no etch stop occurred.

Further, in order to investigate the effect of a wide antenna, in the absence of a magnetic field (inductively coupled plasma: ICP),
The same measurements as in FIGS. 4 and 5 were performed. The result is shown in FIG. It can be seen that the characteristics shown in FIG. 2 are clearly different from those of FIGS. From this, it can be seen that when the wide antenna is used, the plasma has the electrostatically coupled plasma component while maintaining the characteristics of the magnetic neutral discharge plasma even when the pressure is high.

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.

[0014]

As described above, according to the present invention, since a wide antenna is used as a single high-frequency coil for generating discharge plasma, induction in the azimuthal direction radiated from the antenna is performed. Plasma is formed and maintained by the electric field and the high-frequency potential generated on the antenna surface, 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 responding to fine processing with a width of 0.3 μm or less has become possible. 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 diagram showing one embodiment of the present invention.

FIG. 2 is a graph showing pressure dependency 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 coil for plasma generation forming an electric field generating means 6: High frequency power supply for plasma generation 7: Substrate electrode 8: Insulator member 9: High frequency power supply 10: Gas inlet

Claims (2)

[Claims] 1. A magnetic field generating means for forming an annular magnetic neutral line at 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 generator with a single high-frequency coil for generating discharge plasma on this magnetic neutral line, and introduces a gas mainly composed of halogen-based gas into vacuum to form plasma at low pressure. At the same time, 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 etch the substrate mounted on the electrode. In a reactive ion etching apparatus,
The upper wall of a cylindrical vacuum chamber is made of a disk-shaped dielectric, and the magnetic field generating means is disposed above the dielectric, and is a small disk-shaped or donut-shaped permanent magnet and an annular permanent magnet having a larger inner diameter than the permanent magnet. To form a magnetic neutral line at a position between two permanent magnets, and a wide antenna as a single high-frequency coil for generating discharge plasma above the magnetic neutral line. A reactive ion etching apparatus, comprising: 2. The reactive ion etching apparatus according to claim 1, wherein the single high-frequency coil for generating discharge plasma has a width in a range of 40 mm to 80 mm.