JP2006253599A - Plasma processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma processing apparatus by which both adherence of reaction products to an inner wall of a vacuum container and contamination by metal can be suppressed even when alumina ceramics is used for a window sealed with dielectric materials of the vacuum container. <P>SOLUTION: With respect to the plasma processing apparatus, alumina ceramics is used for the window 20 sealed with dielectric materials of the vacuum container 21, plasma is produced in an etching treatment chamber 11 by using inductive coupling antennas 15 and electrostatic capacitive coupling antennas 10 and a workpiece 18 placed on a sample stand 12 is subjected to plasma treatment. Further, quartz cover glass 22 is provided on the underside of the window 20 sealed with dielectric materials. In this way, etching of alumina ceramics as a base material of the window 20 sealed with dielectric materials by plasma is suppressed by the quartz cover glass 22. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a plasma processing apparatus for generating an electric field by supplying high-frequency power to an antenna, generating plasma by the electric field, and performing surface treatment such as etching of a substrate or formation of a thin film by the plasma.

In recent years, in the field of semiconductor device manufacturing, ferromagnetic and antiferromagnetic materials such as NiFe, PtMn and IrMn, noble metal materials such as Pt, Ir, Au, Ta and Ru, or Al ₂ O ₃ , HfO ₂ and Ta ₂ O ₃ High-dielectric materials such as PZT, BST, and SBT are not only used for semiconductor devices typified by conventional DRAM and ASIC, but also for new memory devices such as FRAM and MRAM. Yes.

However, these materials, unlike Si, Al, and SiO ₂ that have been widely used as semiconductor device materials, have a low vapor pressure of reaction products during etching, and are therefore difficult to etch during dry etching. There is a characteristic.

  In addition, in the case of these materials, once the reaction product generated by etching is detached from the wafer, it adheres to the inner wall of the reaction vessel without being evacuated. , Stability over time such as uniformity and processing perpendicularity) was hindered, and the productivity of etching processing was deteriorated.

  Therefore, in such an inductively coupled plasma processing apparatus intended for dry etching of a nonvolatile material, a capacitively coupled antenna is provided between the inductively coupled antenna and the plasma, and the capacitively coupled antenna has a high frequency power. In the past, there has been known an apparatus capable of reducing the adhesion of reaction products to the inner wall of the vacuum container or cleaning the inner wall of the vacuum container (see, for example, Patent Document 1 and Patent Document 2). .

And in these prior arts, as a dielectric sealing window placed between the inductively coupled antenna and the plasma, the capacitively coupled antenna installed immediately above it and the action on the plasma by the inductively coupled antenna are ensured, In order to maintain sufficient mechanical strength, members such as alumina (Al ₂ O ₃ ) ceramics having a high dielectric constant and high mechanical strength are used.
JP-A-10-275694 JP 2000-323298 A

  The above prior art does not give consideration to the influence of the voltage due to the capacitively coupled antenna on the dielectric sealing window, and there is a problem with the occurrence of metal contamination due to the use of alumina ceramics in the dielectric sealing window. was there.

  In a plasma processing apparatus in which plasma is generated by the magnetic field of an inductively coupled antenna, a voltage is applied to the capacitively coupled antenna to reduce adhesion of reaction products to the dielectric sealing window portion of alumina ceramics, or cleaning. In the case of an apparatus that enables this, etching by plasma is also generated in the base material itself of the dielectric sealing window.

  At this time, if metal impurities such as Al (aluminum) and Mg (magnesium) are contained in the base material of the dielectric sealing window portion, these impurities are struck out into the plasma, and the object to be processed is Here, metal contamination is caused. However, in the case of alumina ceramics, it is usual that Al or Mg is contained as an impurity, and therefore metal contamination occurs in the prior art.

  An object of the present invention is to provide a plasma processing apparatus capable of suppressing both adhesion of reaction products and metal contamination to the inner wall of a vacuum vessel even when alumina ceramic is used for a dielectric sealing window portion of the vacuum vessel. It is in.

  The object is to provide a coil-shaped inductively coupled antenna and a plate-shaped capacitively coupled antenna. The magnetic field generated by the inductively coupled antenna and the electric field generated by the capacitively coupled antenna are transferred from the dielectric sealing window to the processing chamber. In a plasma processing apparatus for processing a semiconductor by introducing and generating plasma, a quartz plate is provided on a surface of the dielectric sealing window portion facing the processing chamber, and the mother of the dielectric sealing window portion is provided. Etching by the plasma with respect to the alumina ceramic material is achieved by the quartz plate.

  At this time, the quartz plate had a thickness of a voltage induced on the surface of the dielectric sealing window portion facing the processing chamber by the capacitive coupling antenna. The value may be selected such that the decrease due to is about 80%.

  According to the present invention, it is possible to etch a nonvolatile material without attaching a reaction product to the dielectric sealing window and without causing contamination by the metal contained in the alumina ceramic.

  Hereinafter, an etching processing apparatus according to the present invention will be described in detail with reference to the illustrated embodiments.

  FIG. 1 shows an example of a plasma etching apparatus according to an embodiment of the present invention. In this case, the etching process chamber 11 is partitioned by a vacuum vessel 21 having a dielectric sealing window 20 and a process gas introduction part 13. ing. A sample stage 12 is provided in the etching processing chamber 11, and an object to be processed 18 is placed thereon.

At this time, the dielectric sealing window portion 20 is made of alumina (Al ₂ O ₃ ) ceramics as described above and functions to induce a magnetic field and an electric field in the etching chamber 11. A plate-like capacitively coupled antenna 19 is installed on the upper surface (the outer surface of the etching chamber), and a coil-shaped inductively coupled antenna 15 is installed on the upper portion thereof. Here, the capacitive coupling antenna 19 is formed of a tungsten coating layer produced by a thermal spraying method.

  A high frequency device 16 is connected to the inductive coupling antenna 15 and the capacitive coupling antenna 19 so that, for example, a high frequency power of 13 MHz is supplied to each. For this reason, the high frequency device 16 is provided with a 13 MHz high frequency power source and a matching box.

  In addition, another high-frequency device 17 is connected to the sample stage 12 so that the ion energy incident on the workpiece 18 placed thereon can be controlled.

  Here, a quartz cover glass 22 is provided on the lower surface of the dielectric sealing window 20 (the inner surface of the etching chamber), which is a quartz cover glass 22 as shown in detail in FIG. The bolt 23 is screwed to the lower surface of the dielectric sealing window 20. At this time, the thickness of the alumina ceramic dielectric sealing window 20 is, for example, 15 mm, and the quartz cover glass 22 is, for example, 2 mm in thickness.

  In the plasma processing, high-frequency power is supplied from the high-frequency device 16 to the coiled inductive coupling antenna 15 to generate plasma in the etching chamber 11. At this time, the high-frequency device 16 has a plate-like capacitance. High frequency power is also supplied to the coupling antenna 19, and power of arbitrary strength can be supplied to both the inductive coupling antenna 15 and the capacitive coupling antenna 19.

  As already described, in the case of a non-volatile material such as Pt or Ir, the amount of reaction products adhering to the dielectric sealing window 20 during the etching process increases, causing plasma non-ignition and foreign matter generation. . Therefore, during the etching process, a high frequency voltage is applied to the capacitive coupling antenna 19 so that the reaction product does not adhere to the dielectric sealing window 20.

  This is because, when a voltage is applied to the capacitive coupling antenna 19, a bias is applied to the lower surface of the dielectric sealing window portion 20, and ions in the plasma are attracted to cause sputter etching, thereby causing a reaction product. In this case, in order to efficiently suppress the deposition of the reaction product, the electric field generated by the capacitive coupling antenna 19 is applied to the dielectric sealing window. It is necessary to be efficiently guided from the upper surface to the lower surface of the portion 20.

  For this purpose, the dielectric sealing window portion 20 must be made of a material having a high dielectric constant ε (for example, about ε = 9) and a sufficient strength even if it is thin. Ceramics are suitable, and therefore, in this embodiment, as described above, the thickness can be reduced to about 15 mm.

  By the way, when a voltage is applied to the capacitively coupled antenna 19 in this way, no matter how the applied voltage is appropriately adjusted, the alumina ceramic itself that is the base material of the dielectric sealing window portion 20 is etched. As a result, although suppression of the reaction product is obtained, impurities are deposited from the base material of the dielectric sealing window portion 20 along with this.

  At this time, the alumina ceramic is generally limited to a purity of about 99.5%, and usually contains about 2500 ppm of Mg (magnesium) and Al (aluminum) as impurities. When a voltage is applied to the antenna 19, Mg or Al is knocked out from the alumina ceramic, which is the base material of the dielectric sealing window portion 20, into the plasma, and undesired metals are mixed into the object to be processed. Metal contamination will be caused. It has already been described that this is a problem of the above-described prior art.

Therefore, in this embodiment, the quartz cover glass 22 is provided on the lower surface of the dielectric sealing window portion 20 as shown in the figure. As is well known, the quartz material is composed of SiO ₂ and contains very few impurities, so that there is almost no risk of metal contamination due to the sputtering of the surface.

  Therefore, according to this embodiment, suppression of reaction products due to the use of the capacitively coupled antenna can be obtained without the risk of metal contamination. As a result, plasma suitable for dry etching of nonvolatile materials can be obtained. A processing device can be provided.

  Here, FIG. 3 shows an effective voltage induced on the lower surface of the dielectric sealing window portion 20 with respect to the voltage applied to the capacitive coupling antenna 19, that is, a base material of the dielectric sealing window portion 20. FIG. 6 is a characteristic diagram showing the relationship between voltages that cause ion sputtering in alumina ceramics. First, the characteristics when the dielectric sealing window 20 is made of alumina ceramics with a thickness of 15 mm and there is no quartz cover glass 22 are shown. Is X, and when the quartz cover glass 22 having a thickness of 2 mm is provided, that is, the characteristic in the embodiment of the present invention is indicated as Y. At this time, the thickness of the dielectric sealing window portion is referred to as a reference. The characteristic when it consists only of 30 mm quartz is shown as Z.

  First, when the dielectric sealing window is made of only 15 mm thick alumina ceramics, as shown in characteristic X, if the applied voltage of the capacitively coupled antenna is about 800 V, the dielectric sealing is performed. The effective voltage on the lower surface of the stop window portion is a voltage of 100 to 150 V suitable for suppressing the reaction product, and the plasma treatment can be performed without attaching the reaction product.

  However, in the case of this characteristic X, that is, when the dielectric sealing window portion is composed only of alumina ceramic having a thickness of 15 mm, it goes without saying that the occurrence of the metal contamination described above cannot be avoided.

  Next, in the case of the characteristic Y when the dielectric sealing window portion is a combination of 15 mm thick alumina ceramics with a 2 mm thick quartz cover glass, the applied voltage of the capacitively coupled antenna is about 1000 V. By doing so, it can be seen that the effective voltage on the lower surface of the dielectric sealing window becomes a voltage of 100 to 150 V suitable for suppression of the reaction product, and plasma treatment can be performed without attaching the reaction product.

  That is, in the case of the above embodiment, in order to obtain a voltage of 100 to 150 V suitable for suppressing the reaction product as an effective voltage on the lower surface of the dielectric sealing window, an applied voltage of the capacitive coupling antenna 19 is obtained. It is necessary to increase the voltage to about 1000%, which is about 20% higher than in the case of the characteristic X. However, such a voltage increase is practically easy without any problem, and thus plasma treatment can be performed without attaching a reaction product. .

  Therefore, according to this embodiment, metal contamination can be suppressed only by increasing the applied voltage to the capacitively coupled antenna 19 by about 20%, and the advantages of the inductively coupled plasma processing apparatus can be fully enjoyed. I understand.

  Incidentally, in the above embodiment, the thickness of the quartz cover glass 22 is 2 mm, and the voltage applied to the capacitively coupled antenna 19 at this time is 1000 V, as is apparent from the characteristic Y in FIG. As apparent from the characteristic X in FIG. 3, since the applied voltage in the absence of the quartz cover glass is 800 V, the decrease in the applied voltage due to the provision of the quartz cover glass having a thickness of 2 mm is about 80%. Can do.

  Here, the characteristic Z shown as a reference example will be described. In this case, as shown in the figure, even if the applied voltage of the capacitively coupled antenna is increased to 2000V, the effective voltage on the lower surface is only 30V. In this case, it can be seen that a sufficient reaction product suppressing effect cannot be obtained.

  Here, even in the case of a quartz window, it may seem that the thickness should be made thinner than 30 mm. However, the reason why the thickness is set to be as large as 30 mm is to obtain the mechanical strength necessary to withstand atmospheric pressure. In the case of quartz, the thickness is set to 30 mm, and finally the alumina having a thickness of 15 mm is used. This is because only mechanical strength equivalent to that of ceramics can be obtained.

  As described above, according to the embodiment of the present invention, the dielectric sealing window portion 20 is made of alumina ceramic having high mechanical strength, and the quartz cover glass 22 having an appropriate thickness is provided on the inner surface thereof. The non-volatile material can be etched without attaching a reaction product and without causing contamination by the metal contained in the alumina ceramic.

  In the above embodiment, the case where the present invention is applied to a plasma etching apparatus for manufacturing a semiconductor device has been described. However, the present invention is not limited to the field of manufacturing a semiconductor device. It can also be applied to film formation and surface treatment of various materials, and is particularly suitable for etching of nonvolatile materials and plasma CVD in which a large amount of deposits adhere to the wall surface.

It is sectional drawing which shows one Embodiment of the plasma processing apparatus by this invention. It is detail drawing of the dielectric material sealing window part in one Embodiment of this invention. It is a characteristic view for demonstrating the effect of this invention.

Explanation of symbols

11: Etching chamber 12: Sample stage 13: Process gas introduction part 15: Inductive coupling antenna 16: High-frequency device (for antenna)
17: High-frequency device (for sample stage)
18: Object to be treated 19: Capacitive coupling antenna 20: Dielectric sealing window 21: Vacuum container 22: Quartz cover glass 23: Quartz bolt

Claims (2)

A coil-shaped inductively coupled antenna and a plate-shaped capacitively coupled antenna are provided, and a magnetic field by the inductively coupled antenna and an electric field by the capacitively coupled antenna are introduced into a processing chamber from a dielectric sealing window and plasma In a plasma processing apparatus for processing a semiconductor,
A quartz plate is provided on the surface of the dielectric sealing window that faces the processing chamber,
The plasma processing apparatus is configured such that etching by the plasma on the alumina ceramic which is a base material of the dielectric sealing window portion is suppressed by the quartz plate. The plasma processing apparatus according to claim 1,
The thickness of the quartz plate is reduced by the presence of the quartz plate of the voltage induced on the surface of the dielectric sealing window portion facing the processing chamber by the capacitively coupled antenna. An etching apparatus characterized by being selected to have a value of about 80%.

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