JP4243615B2 - Reactive ion etching system - Google Patents

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.

  As an etching apparatus which has been most frequently used in the prior art, there is a parallel plate type as shown in FIG. 2 of the accompanying drawings. This etching apparatus is provided with an insulator B in a vacuum chamber A as shown in the figure. The substrate electrode C is disposed, the upper electrode D is provided on the upper part of the vacuum chamber A so as to face the substrate electrode C, and the substrate electrode C is connected to the high frequency bias power source E so that the high frequency bias voltage is applied. The ions generated by the discharge are used for the reaction.

  FIG. 3 shows a conventional three-electrode coupling type etching apparatus. In this case, the upper electrode D is attached to the vacuum chamber A through an insulator F and connected to a high-frequency power source G. When oxide film etching is performed with this apparatus, high-frequency power having different frequencies is applied to the substrate electrode C and the upper electrode D.

  FIG. 4 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 K is formed inside the vacuum chamber A by three magnetic field coils H, I, J mounted 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 a high-frequency power source M for an antenna to a single antenna L disposed inside the intermediate magnetic field coil I along the magnetic neutral line K. Has been. The etching gas is introduced from a shower plate provided near the upper top plate A2 through the flow controller, and the pressure is controlled by the opening ratio of the conductance valve. High frequency power is applied to the substrate electrode C below the vacuum chamber A from a bias high frequency power source E. The etching gas is introduced from the vicinity of the upper flange of the vacuum chamber A, and the high frequency power is applied to the single antenna L disposed between the outside of the dielectric cylindrical wall A1 and the intermediate magnetic field coil I, thereby generating plasma. As a result, the introduced gas is decomposed. High frequency power for bias is applied from a high frequency power source E for bias to the substrate electrode C under the vacuum chamber A. The substrate electrode C, which is in a floating state by the blocking capacitor, has a negative self-bias potential, and positive ions in the plasma are attracted to etch the material on the substrate.

The operation of the etching apparatus of the prior art as exemplified above will be described with respect to the parallel plate type etching shown in FIG. 2 as an example.
The etching gas is introduced from the vicinity of the upper flange, and high frequency power is applied to the substrate electrode C to form plasma, whereby 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. . 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 etched uniformly. By the way, the uniformity of plasma density and potential in a parallel plate etching apparatus is greatly influenced by the vacuum chamber structure and pressure. If the vacuum 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 shown in FIG. 4, the position of the magnetic neutral line can be freely changed and the plasma density and potential can be controlled in a low gas pressure region. Conditions with good uniformity can be set easily.

  In the parallel plate type etching apparatus and the three-electrode type etching apparatus that have been used in the past, the operating pressure is high and the conditions for achieving uniformity are extremely high depending on the device structure. Since it is narrow, it has become impossible to cope with an etching process requiring a large diameter and fine processing. For this reason, a magnetic neutral wire discharge etching apparatus has been proposed that can obtain a high-density plasma at a low pressure and can control the uniformity (see, for example, JP-A-7-263192).

  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 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 as shown in FIGS. 2 and 3, since the pressure is high, a large amount of adhering substances are generated due to collision between molecules, and it is difficult to perform microfabrication with a width of 0.3 μm or less. The magnetic neutral wire discharge method shown in FIG. 4 generates a high-density plasma at a low pressure, and thus exhibits excellent etching characteristics. However, since the dielectric wall surface is used, the maintenance of the apparatus and the cost are low. Less than the former.

  Therefore, an object of the present invention is to provide a reactive ion etching apparatus capable of solving the above-described problems and performing fine processing with a width of 0.3 μm or less.

  In order to achieve the above object, a magnetic neutral line generating cylindrical coil is installed outside the vacuum chamber without changing the structure of a conventional cathode coupled etching apparatus or a three-electrode etching apparatus. Magnetic neutral lines are formed on the substrate to improve the plasma density and to form an etching plasma that can control the uniformity at a low pressure.

According to one embodiment of the present invention, a reactive ion etching apparatus that introduces a gas mainly composed of a halogen-based gas into a vacuum and generates plasma in a vacuum chamber to etch an object to be processed. ,
3 arranged on the outer periphery of the vacuum chamber so as to generate an annular magnetic field zero magnetic field continuously present in the vacuum chamber having a cylindrical portion and spaced apart from the substrate. Magnetic field generating means having two cylindrical coils ;
Wherein disposed in a vacuum chamber, said magnetic field generating means by a high frequency electric field is added the radio frequency electric field to generate discharge plasma in a space containing the magnetic neutral line generated in the magnetic neutral line produced in the vacuum chamber Means,
The high-frequency electric field generating means has a pair of electrodes arranged by inserting the magnetic neutral wire up and down,
Among the pair of electrodes, a bias high-frequency power source is connected to a substrate electrode on which the object to be processed is placed, and a discharge high-frequency power source is connected to an upper electrode installed facing the substrate electrode ,
The substrate electrode and the upper electrode are joined to the vacuum chamber via an insulator member,
The current of at least an intermediate coil among the three cylindrical coils is variable .

In the apparatus of the present invention, the high frequency supplied by the bias high frequency power supply and the high frequency supplied by the discharge high frequency power supply may be different. Further, the currents of the three cylindrical coils can be varied, and the diameter of the magnetic neutral wire can be changed.

  With the above-described configuration, according to the present invention, it is possible to form an etching plasma that can control the uniformity at a low pressure while improving the plasma density. It has become possible to provide a dry etching apparatus that can be used. Therefore, the present invention greatly contributes to the reactive ion etching process used for processing semiconductors and electronic parts.

An embodiment of the present invention will be described below with reference to FIG. 1 of the accompanying drawings.
FIG. 1 shows an embodiment of an etching apparatus according to the present invention configured as a three-electrode type. In this embodiment, a substrate electrode 13 is provided through an insulator member 12 inside a cylindrical vacuum chamber 11 forming a process chamber having an exhaust port 11a. The substrate electrode 13 is an RF bias. Is connected to a high-frequency power source 14 for applying.

  The counter electrode 15 is joined to the upper flange 11b of the vacuum chamber 11 via an insulator member 16, and is connected to a discharge high-frequency power source 17.

  A shower plate 18 for introducing an etching gas is provided inside the counter electrode 15 so as to oppose the substrate electrode 13. Further, three cylindrical coils 19, 20, 21 constituting a magnetic field generating means for forming a magnetic neutral line in the vacuum chamber 11 are provided on the outer peripheral portion of the vacuum chamber 11. A magnetic neutral wire 22 is formed in the vacuum chamber 11 by the coil.

Using the apparatus having the structure shown in FIG. 1, the power of the plasma generating high frequency power supply 17 is 1.5 kW (13.56 MHz), the power of the substrate bias high frequency power supply 14 is 500 W (800 kHz), the pressure is 10 mTorr, and argon is used as an auxiliary gas. When 170 sccm and C ₄ F ₈ as the main etching gas were 30 sccm, the etching rate of the silicon oxide film was 550 nm / min, and the etching rate of silicon was 46 nm / min. The selection ratio at this time was 12.

  For comparison, when the conventional three-electrode etching apparatus shown in FIG. 3 is used, the etching rate of the silicon oxide film obtained under the same conditions is 350 nm / min, and the etching rate of silicon is 48 nm / min. there were. The selection ratio at this time is about 7.

  Therefore, it is considered that the formation of the magnetic neutral line according to the present invention results in the plasma being confined in the magnetic neutral line portion, the plasma density is increased, and an efficient plasma is formed, and the etching rate and selectivity are improved. It is done. Further, when the diameter of the magnetic neutral wire 22 was changed by changing the current of the intermediate cylindrical coil 20, it was found that the uniformity can be controlled in the range of ± 15% to ± 3%.

For example, when CF ₄ , C ₃ F ₈ , C ₄ F ₈ or the like is used as an etching gas and an oxide film is etched by the conventional method shown in FIGS. 2 and 3, the decomposition proceeds because the etching gas has a low plasma density. First, the etching rate is low and a large amount of CF ₂ radicals that are easily polymerized are generated. In addition, when the plasma density is high or the residence time in the plasma is long as in the ECR etching apparatus, decomposition proceeds and a large amount of C and CF radicals that are adherent substances are generated although the etching rate is high.

  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 etchant material and adhesive material that reaches the substrate can be formed within an appropriate range, so that the etching shape can be easily formed. Can be controlled.

  It is also possible to control the etching uniformity by increasing or decreasing the diameter of the magnetic neutral wire.

  In the illustrated embodiment, an example in which the present invention is applied to an etching apparatus has been described, but a similar effect can be expected when a plasma CVD apparatus is used.

The schematic diagram which shows one Example of this invention. The schematic diagram which shows the conventional parallel plate type | mold etching apparatus. The schematic diagram which shows the conventional 3 electrode type | mold etching apparatus. The schematic diagram which shows the conventional magnetic neutral wire discharge type etching apparatus.

Explanation of symbols

11: Cylindrical vacuum chamber 12: Insulator member 13: Substrate electrode 14: High frequency power source for bias 15: Counter electrode 16: Insulator member 17: High frequency power source for discharge 18: Shower plate 19: Cylindrical coil 20: Cylindrical shape Coil 21: Cylindrical coil 22: Magnetic neutral wire

Claims (3)

A reactive ion etching apparatus that introduces a gas mainly containing a halogen-based gas into a vacuum and generates plasma in a vacuum chamber to etch an object to be processed.
3 arranged on the outer periphery of the vacuum chamber so as to generate an annular magnetic field zero magnetic field continuously present in the vacuum chamber having a cylindrical portion and spaced apart from the substrate. Magnetic field generating means having two cylindrical coils ;
Wherein disposed in a vacuum chamber, said magnetic field generating means by a high frequency electric field is added the radio frequency electric field to generate discharge plasma in a space containing the magnetic neutral line generated in the magnetic neutral line produced in the vacuum chamber Means,
The high-frequency electric field generating means has a pair of electrodes arranged by inserting the magnetic neutral wire up and down,
Among the pair of electrodes, a bias high-frequency power source is connected to a substrate electrode on which the object to be processed is placed, and a discharge high-frequency power source is connected to an upper electrode installed facing the substrate electrode ,
The substrate electrode and the upper electrode are joined to the vacuum chamber via an insulator member,
The reactive ion etching apparatus , wherein a current of at least an intermediate coil among the three cylindrical coils is variable .   2. The reactive ion etching apparatus according to claim 1, wherein a high-frequency frequency supplied from the high-frequency power source for bias is different from a high-frequency frequency supplied from the high-frequency power source for discharging. The reactive ion etching apparatus according to claim 1, wherein currents of the three cylindrical coils are variable, and a diameter of the magnetic neutral wire can be changed.

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