JP2006114933A - Reactive ion etching device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reactive ion etching device capable of facilitating etching in microfabrication on a width of 0.3 μm or smaller without causing etch stop by using magnetic neutral loop discharge. <P>SOLUTION: The reactive dry etching device is configured in such a way as to employ an NLD etching device, to introduce an etching assist gas from an upper part of a vacuum chamber, to introduce a main etching gas to a substrate side near a magnetic neutral line, and to exhaust the gases from a lower part of a substrate electrode so as to increase an effective exhaust velocity thereof in a low pressure environment. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a reactive ion etching apparatus that uses plasma to etch a material on a semiconductor, an electronic component, or other substrate.

  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. In the vacuum chamber A, an anode B and a cathode, that is, a substrate electrode C are arranged to face each other, a reactive gas is introduced from the anode B, and a high-frequency power source E is connected to the substrate electrode C through a matching circuit D.

  FIG. 4 shows another example of a parallel plate type etching apparatus. In this case, a high frequency power source G is also connected to the electrode B via a matching circuit F, and high frequency powers having different frequencies are applied to the upper and lower electrodes. Is done.

  FIG. 5 shows a conventional example of an ECR etching apparatus, in which μ waves are introduced from the upper part of the vacuum chamber A through the dielectric window B, and high-density plasma is formed by electron cyclotron resonance at 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 is provided in the vacuum chamber A outside the dielectric sidewall A1 of the vacuum chamber A. A high frequency power is applied to the antenna B from the plasma generating high frequency power source C, and an etching gas mainly composed of a halogen-based gas is introduced from the vicinity of the upper top plate A2 through the flow controller, and the gas is introduced into the vacuum chamber A. Then, the plasma is formed at a low pressure, the introduced gas is decomposed, and the generated atoms, molecules, radicals, and ions are actively used, and a high-frequency electric field is applied from the high-frequency power source E to the substrate electrode D in contact with the plasma. It is configured to etch the substrate placed on D.

  FIG. 7 shows a modification of the structure shown in FIG. 6, in which the upper wall of the vacuum chamber A is placed on a flat dielectric F to form a spiral antenna G to form inductively coupled plasma. . The method shown in FIG. 6 is called ICP (Inductively Coupled Plasma), and the method shown in FIG. 6 is called TCP (Transfer Coupled Plasma) for distinction.

  FIG. 8 shows a magnetic neutral line discharge etching apparatus previously proposed by the present inventors in Japanese Patent Laid-Open No. 7-263192. In the previously proposed apparatus, a magnetic neutral line E is formed inside the vacuum chamber A by three magnetic field coils B, C, D placed outside the dielectric cylindrical wall A1 at the top of the vacuum chamber A. A configuration in which a ring-shaped plasma is formed by applying a high-frequency electric field from the antenna high-frequency power source G to the single antenna F disposed inside the intermediate magnetic field coil C along the magnetic neutral line E. Has been. Further, the etching gas is introduced from the vicinity of the upper top plate A2 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 H below the vacuum chamber A from a bias high frequency power source I.

  Even though these are different in discharge system, gas is introduced from the upper flange or its periphery. This is because the introduced gas needs to be sufficiently decomposed in the plasma space while diffusing to the substrate.

As a representative example, the ICP etching shown in FIG. 6 will be described.
Etching gas is introduced from the vicinity of the upper flange, high frequency power is applied to the antenna B installed outside the dielectric cylindrical partition wall A1, 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, a shower plate having a large number of holes is generally provided in the upper flange, through which the gas is introduced into the vacuum chamber. The 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 is uniform, and the substrate is uniformly etched. By the way, the uniformity of plasma density and potential in ICP etching is greatly influenced by the chamber structure and pressure. If the chamber structure is determined, the pressure condition for obtaining uniformity is almost uniquely determined, and the selection range of the condition is extremely narrow.

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

  The device has become denser and the processing width has become finer, and it has become impossible to cope with the same gas introduction and exhaustion methods as in the past. In etching, the substrate material is irradiated with highly reactive radicals and ions and gasified by the reaction with the substrate material to etch the substrate material. However, the etching is not necessarily performed, and shape control is also required. For this purpose, in addition to the etchant, a substance that adheres to the wall surface in the micropore and protects the side wall not exposed to ions must also be generated in the plasma. In the microfabrication with a width of 0.3 μm or less, the relative concentration of the etchant and the protective substance becomes important. If the protective material is too much for the etchant, the micropores having a width of 0.3 μm or less are filled with the protective material, so-called etch stop occurs and cannot be removed. On the other hand, if the protective material is too small, the side wall is scraped off by the etchant, bowing occurs, and the desired shape cannot be obtained.

  In the etching apparatus shown in FIG. 3 and FIG. 4, since the pressure is high, a large amount of adhering substances are generated due to collision between molecules, and fine processing with a width of 0.3 μm or less cannot be performed.

  5 to 8, even when the introduced gas passes through a large plasma space, decomposition proceeds and a large amount of adhesive substances are generated, so that fine processing with a width of 0.3 μm or less is difficult. This is because, since the plasma density is high and the effective exhaust speed under low pressure is low, the residence time of the gas is long, and overdecomposition occurs while reaching the vicinity of the substrate.

  Accordingly, an object of the present invention is to provide a reactive ion etching apparatus that solves the above-described problems and can perform etching without generating an etch stop in fine processing with a width of 0.3 μm or less.

  In order to achieve the above object, in the reactive ion etching apparatus according to the present invention, an etching auxiliary gas is introduced from the upper part of the vacuum chamber using an NLD etching apparatus, and etching is performed on the substrate side in the vicinity of the magnetic neutral line. In order to increase the effective exhaust speed under a low pressure by introducing a gas, the exhaust is performed from the lower part of the substrate electrode.

  That is, according to the present invention, there is provided a magnifying generating means for forming an annular magnetic neutral line that is continuously located in the vacuum chamber and having a magnetic field of zero, and alternating along the magnetic neutral line. It has plasma generation means that has multiple high-frequency coils including a single layer to generate discharge plasma on this magnetic neutral wire by applying an electric field, and introduces a gas mainly composed of halogen gas into the vacuum The plasma is generated at low pressure and the introduced gas is decomposed. The generated atoms, molecules, radicals, and ions are used, and an alternating electric field or high-frequency electric field is applied to the substrate electrode in contact with the plasma and placed on the electrode. In a reactive ion etching apparatus for etching a substrate, an etching auxiliary gas introducing means provided on an electrode facing the substrate electrode and introducing an etching auxiliary gas from the electrode; An etching main gas introduction means that is provided near the magnetic neutral line and introduces an etching main gas from the circumferential direction on the substrate electrode side. When a turbo molecular pump with an exhaust speed of 3000 liters / second is used. The substrate electrode is supported by a support member with a gap through which gas passes between the side and bottom and the vacuum chamber wall so that the effective pumping speed is 1500 liters / second or more in an approximate Ar value, A vacuum exhaust system is connected to the bottom of the vacuum chamber, and gas is discharged from below the substrate electrode.

  The etching auxiliary gas introducing means may preferably comprise a shower plate provided on the counter electrode.

  The etching main gas introduction means may preferably comprise a ring which is arranged above the substrate electrode and on the peripheral extension surface of the substrate electrode and which supplies the etching main gas radially inward.

  Further, a gap through which gas passes is provided between the side and bottom of the substrate electrode and the vacuum chamber wall, and an evacuation 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 etching main gases include CF ₄ , C ₃ F ₈ , C ₄ F _8, and the like. The etching main gas is decomposed when the plasma density is increased or the residence time in the plasma is increased, and a large amount of CF and CF ₂ radicals which are adhesive substances are generated.

  Since the process main gas is introduced near the substrate using a magnetic neutral wire discharge device that can form plasma in a region where the plasma density is not higher than necessary, the ratio of the etchant substance and the adhesive substance that reaches the substrate Can be changed. Further, since the exhaust is performed from below the substrate, the effective exhaust speed is improved by 1.5 to 2 times, and the operating flow range can be expanded. Increasing the flow rate means that the gas residence time will be shortened. By extending the operating flow rate range, the gas residence time can be varied over a wide range, making it easy to control the etchant and adhering substances. become.

  As described above, in the reactive ion etching apparatus according to the present invention, the etching auxiliary gas is introduced from the upper part of the vacuum chamber, the etching main gas is introduced on the substrate side in the vicinity of the magnetic neutral line, and the effective pumping rate under low pressure. In order to increase the size of the substrate, the exhaust gas is exhausted from the bottom of the substrate electrode, so that the amount of etchant and adhesive material incident on the substrate can be controlled, and as a result, dry etching that can handle microfabrication with a width of 0.3 μm or less is possible. It becomes. Therefore, the present invention greatly contributes to the reactive ion etching process used for processing semiconductors and electronic parts.

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 is provided with a cylindrical dielectric side wall 2 at the top thereof, and a magnetic field generation for forming a magnetic neutral line in the vacuum chamber 1 outside the dielectric side wall 2. Three magnetic field coils 3, 4, 5 constituting the means are provided, and a magnetic neutral wire 6 is formed 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, 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 upper part of the vacuum chamber 1 by 3, 4, and 5 to generate discharge plasma in the magnetic neutral line.

  The top plate 9 at the top of the vacuum chamber 1 is hermetically fixed to the top flange of the dielectric side wall 2, and the top plate 9 is provided with a shower plate 10 for introducing an etching auxiliary gas. Not connected to an etching auxiliary gas source.

  An etching main gas introduction ring 11 is disposed in the vicinity of the magnetic neutral line 6 in the vacuum chamber 1, and this ring 11 directs the etching main gas from an etching main gas source (not shown) toward the center of the vacuum chamber 1. A plurality of small holes toward the center of the chamber or a narrow orifice extending over the entire circumference is formed on the circumference. The etching main gas introduction ring 11 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 is supported by the support member 13 with a gap for allowing gas to pass between the side and bottom portions of the substrate electrode 12 and the vacuum chamber wall. That is, the lower portion of the vacuum chamber 1 below the substrate electrode 12 is highly effective. In order to obtain the exhaust speed, the difference between the outer diameter of the substrate electrode 12 and the inner diameter of the lower portion of the vacuum chamber 1 is 40 mm or more in the radial direction. The substrate electrode 12 is connected to a high frequency power source 14 for applying an RF bias.

Further, an exhaust system 15 comprising a turbo molecular pump is connected to the bottom of the vacuum chamber 1 below the substrate electrode 12. When a turbo molecular pump having a pumping speed of 3000 liters / second is used, the effective pumping speed at the substrate electrode portion is 1550 liters / second when the gas is argon and 970 liters / second when the gas is C ₄ F ₈ . Since the conventional pumping speed is 890 liters / second when the gas is argon and 480 liters / second when the gas is C ₄ F ₈ , the effective pumping speed is improved by about 1.7 to 2 times.
Here, the effective exhaust speed is Seff = 1 / ((1 / S) + (1 / C)) = SC / (S + C)
The conductance at that time is expressed by the following equation.
C = k / √M where k is a proportional constant
M: Mass number When the mass is large, the conductance decreases and the effective exhaust speed decreases. In other words, the effective exhaust speed changes as the mass number changes.

FIG. 2 is a diagram showing the mass dependence of the effective exhaust speed. Since Ar has a mass number of 40, the effective exhaust speed is 1500 liters / second. Since C ₄ F ₈ has a mass number of 200, the effective exhaust speed is about 920 liters / second. In addition, what represented gas 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 of FIG. 1, the power of the plasma generating high frequency power supply 8 is 1.5 KW, the power of the substrate bias high frequency power supply 14 is 500 W, the pressure is 5 mTorr, the etching auxiliary gas is 135 sccm, and the etching main gas is C ₄ F ₈ . At 23 sccm, the etching rate of the silicon oxide film was 732 nm / min, and the etching rate of silicon was 52 nm / min. The selection ratio at this time was 14.

On the other hand, when the etching is performed under the same pressure condition by introducing 90 sccm of argon as an auxiliary etching gas and 15 sccm of C ₄ F ₈ as an etching main gas using the conventional exhaust method shown in FIG. The etching rate of the film was 610 nm / min, and the etching rate of silicon was 51 nm / min. The selection ratio at this time is 12. Therefore, by improving the effective exhaust speed and increasing the gas flow rate by 1.5 times, both the etch rate and the selection ratio were 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 introduced gas can be increased by the improvement in the exhaust speed, and the residence time in the plasma has been shortened, so that the excessive decomposition can be suppressed.

  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.

The schematic diagram which shows one Example of this invention. The graph which shows the mass dependence of the effective exhaust speed measured using the apparatus of FIG. The schematic diagram which shows an example of the conventional parallel plate type | mold etching apparatus. The schematic diagram which shows the conventional tripolar etching apparatus. The schematic diagram which shows the conventional ECR etching apparatus. The schematic diagram which shows the conventional inductive coupling type etching apparatus. The schematic diagram which shows the conventional transfer coupling type etching apparatus. The schematic diagram which shows the conventional magnetic neutral wire discharge type 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 6: Magnetic neutral wire 7: High frequency coil 8: High frequency power source 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 (3)

  A magnetic lift generating means for forming an annular magnetic neutral line that is continuously present in the vacuum chamber and having a magnetic field of zero is provided, and an alternating electric field is applied along the magnetic neutral line to generate the magnetic neutral line. It has plasma generating means provided with multiple high frequency coils including a single layer for generating discharge plasma on a wire, and a gas mainly composed of a halogen-based gas is introduced into a vacuum to form a plasma at a low pressure. Reactive ions that break down the introduced gas and use the generated atoms, molecules, radicals, and ions to apply an alternating electric field or high-frequency excitation to the substrate electrode in contact with the plasma to etch the substrate placed on the electrode In the etching apparatus, an etching auxiliary gas introduction means for introducing an etching auxiliary gas from the electrode, which is provided on the electrode facing the substrate electrode, and a magnetic neutral line are provided. Etching main gas introduction means for introducing the etching main gas from the circumferential direction to the substrate electrode side, and the effective pumping speed when using a turbo molecular pump with a pumping speed of 3000 liters / second is 1500 as an approximate Ar value The substrate electrode is supported by a support member with a gap through which gas passes between the side and bottom and the vacuum chamber wall so as to be at least 1 liter / second, and a vacuum exhaust system is provided at the bottom of the vacuum chamber. Are connected to each other, and gas is discharged from below the substrate electrode.   The reactive ion etching apparatus according to claim 1, wherein the etching auxiliary gas introducing means comprises a shower plate provided on the counter electrode. 2. The reactive ion etching according to claim 1, wherein the etching main gas introducing means comprises a ring which is arranged above the peripheral extension surface of the substrate electrode and is adapted to supply the etching main gas radially inward. apparatus.

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