JP4236873B2 - Magnetron plasma processing equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetron plasma processing apparatus that performs magnetron plasma processing on a substrate to be processed such as a semiconductor wafer.
[0002]
[Prior art]
In recent years, a magnetron plasma etching apparatus has been put to practical use that generates high-density plasma in a relatively low-pressure atmosphere and performs fine processing etching. In this apparatus, a magnetic field leaked from a permanent magnet is applied so that a magnetic flux penetrates a semiconductor wafer (hereinafter simply referred to as a wafer) substantially horizontally, and a high-frequency electric field orthogonal thereto is applied. Etching is performed with extremely high efficiency using the drift motion of electrons generated in the process.
[0003]
In addition, it is the magnetic field perpendicular to the electric field that contributes to the electron drift motion, that is, the magnetic field horizontal to the wafer. Therefore, a more uniform and uniform horizontal magnetic field is formed on the wafer to achieve high uniformity. In order to form plasma, a dipole ring magnet is used as such a permanent magnet. In this dipole ring magnet, a plurality of anisotropic segment columnar magnets are arranged in a ring shape outside the chamber, and the direction of magnetization of the plurality of anisotropic segment columnar magnets is gradually shifted to be uniform as a whole. A horizontal magnetic field is formed.
[0004]
By the way, not only in such a magnetron plasma etching apparatus but also in a plasma processing apparatus, in order to prevent plasma from reaching the lower part of the chamber and causing abnormal discharge, a support table and a chamber wall for supporting a wafer are provided. An annular baffle plate is provided at a lower position between the wafers to block the plasma.
[0005]
[Problems to be solved by the invention]
However, in the case of a magnetron plasma processing apparatus typified by the above-described magnetron plasma etching apparatus, the magnet is designed so that a horizontal magnetic field is formed on the upper surface of the wafer, so that it is provided below the wafer support position. Magnetic lines of force pass through the baffle plate obliquely with respect to the baffle plate, and electrons that spiral in the direction of the magnetic field easily pass through the holes in the baffle plate, so that the baffle plate can sufficiently block the plasma. Without this, plasma leakage or abnormal discharge below the baffle plate occurs.
[0006]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a magnetron plasma processing apparatus in which plasma leakage and abnormal discharge are unlikely to occur below a baffle plate in a chamber.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a chamber in which a substrate to be processed is inserted and held in an airtight manner, an upper electrode and a lower electrode provided opposite to each other in the chamber, and the upper electrode and the lower electrode. An electric field forming means for forming an electric field between the electrodes, a processing gas supply means for supplying a processing gas into the chamber, and a processing space between the upper electrode and the lower electrode, perpendicular to the electric field direction and in one direction A magnetron plasma processing apparatus for performing a magnetron plasma process on the substrate while the substrate to be processed is supported on the lower electrode, the inner wall of the chamber and the lower electrode A baffle plate for blocking plasma provided so as to cover a space between the baffle and the baffle plate in a vertical section thereof. , Magnetron plasma, characterized in that said inclined at an inclination angle substantially the same angle in the vertical direction of the magnetic field, the vertical component of the magnetic field relative to the baffle plate is configured to not substantially exist at the present position A processing device is provided.
[0008]
In a magnetron plasma processing apparatus, since a magnet is usually designed so that a horizontal magnetic field is formed on the upper surface of the substrate to be processed, there is a baffle plate that is installed below the support position of the substrate to be processed. In position, the magnetic field is formed so as to be inclined in a direction rising from the center of the chamber toward the chamber wall. Therefore, the baffle plate is configured to be inclined at substantially the same angle as the vertical inclination angle of the magnetic field at the position where the baffle plate is located, and the baffle plate is aligned with the direction of the magnetic field. As a result, the vertical component of the magnetic field substantially does not exist, and electrons that spirally move along the direction of the magnetic field are less likely to pass through the holes formed in the baffle plate, thereby enhancing the plasma blocking effect. Therefore, it is possible to make it difficult for plasma leakage and abnormal discharge to occur.
[0009]
In the magnetron plasma processing apparatus of the present invention, the chamber may have a substantially cylindrical shape, the lower electrode may have a substantially cylindrical shape, and the baffle plate may have a substantially conical shape. The baffle plate may form a circular, elliptical, or slit-shaped hole. Furthermore, the magnetic field forming means may include a dipole ring magnet in which a plurality of anisotropic segment magnets are arranged in a ring shape around the chamber.
[0010]
In the present specification, the “vertical direction” refers to the direction of gravity.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view showing a magnetron RIE plasma etching apparatus according to an embodiment of the present invention. This etching apparatus is airtight, has a stepped cylindrical shape including a small-diameter upper portion 1a and a large-diameter lower portion 1b, and has a chamber (processing vessel) 1 made of, for example, aluminum. The chamber 1 is grounded.
[0012]
In the chamber 1, there is provided a support table 2 that horizontally supports a wafer W as an object to be processed and functions as a lower electrode. The support table 2 includes, for example, a core member 2a made of aluminum, an insulating member 3 that covers the side and bottom of the core member 2a, and a support base 4 that is made of a conductor that supports the core member 2a and the insulating member 3. is doing.
[0013]
An electrostatic chuck 6 for electrostatically attracting and holding the wafer W is provided on the upper surface of the support table 2. The electrostatic chuck 6 is made of an insulator, and an electrode 6a is provided therein. A DC power supply 16 is connected to the electrode 6a. When a voltage is applied from the DC power supply 16, the wafer W is attracted by electrostatic force, for example, Coulomb force.
[0014]
A focus ring 5 is provided on the outer periphery of the electrostatic chuck 6 on the support table 2 so that the surface is flush with the surface of the wafer W attracted to the electrostatic chuck 6.
[0015]
A refrigerant chamber 17 is provided inside the core member 2a of the support table 2, and the refrigerant is introduced into the refrigerant chamber 17 through the refrigerant introduction pipe 17a, discharged from the refrigerant discharge pipe 17b, and circulated. The cold heat is transferred to the wafer W via the support table 2, whereby the processing surface of the wafer W is controlled to a desired temperature. Further, even if the chamber 1 is evacuated by the exhaust system 12 and kept in a vacuum, a cooling gas such as He gas is introduced into the gas so that the wafer W can be effectively cooled by the refrigerant circulated in the refrigerant chamber 17. It is introduced by the mechanism 18 between the surface of the electrostatic chuck 6 and the back surface of the wafer W through the gas supply line 19.
[0016]
The support table 2 can be moved up and down by a ball screw mechanism including a ball screw 7, and a drive portion below the support base 4 is covered with a bellows 8 made of stainless steel (SUS). A bellows cover 9 is provided outside the bellows 8.
[0017]
A conical baffle plate 10 is provided below the wafer W between the support table 2 and the inner wall of the chamber 1. The baffle plate 10 is attached to the attachment member 24 and the chamber 1 on the outer periphery of the support table 2, and is grounded through the chamber 1. The baffle plate 10 will be described in detail later.
[0018]
An exhaust port 11 is formed on the side wall of the lower portion 1 b of the chamber 1, and an exhaust system 12 is connected to the exhaust port 11. The inside of the chamber 1 can be depressurized to a predetermined degree of vacuum by operating a vacuum pump of the exhaust system 12. On the other hand, a gate valve 13 for opening and closing the loading / unloading port of the semiconductor wafer W is provided on the upper side wall of the lower portion 1 b of the chamber 1.
[0019]
A high frequency power supply 15 for plasma formation is connected to the support table 2 through a matching unit 14, and a high frequency power having a predetermined frequency of 13.56 MHz or higher (for example, 13.56 MHz, 40 MHz) from the high frequency power supply 15. Is supplied to the support table 2. On the other hand, a shower head 20 that functions as an upper electrode is provided in parallel with each other so as to face the support table 2, and the shower head 20 is grounded. Therefore, the support table 2 functioning as the lower electrode and the shower head 20 functioning as the upper electrode constitute a pair of parallel plate electrodes.
[0020]
The shower head 20 is provided in the top wall portion of the chamber 1, and a number of gas discharge holes 22 are formed in the lower surface thereof, and a gas introduction portion 20 a is formed in the upper portion thereof, and a space 21 is formed therein. Has been. A gas supply pipe 23a is connected to the gas introduction part 20a, and a processing gas supply system 23 for supplying a processing gas for etching is connected to the other end of the gas supply pipe 23a. As the processing gas supplied from the processing gas supply system 23, a gas usually used in this field, such as a halogen-based gas, Ar gas, or O ₂ gas, can be used.
[0021]
Then, a predetermined processing gas from the processing gas supply system 23 reaches the space 21 of the shower head 20 through the gas supply pipe 23 a and the gas introduction part 20 a and is discharged into the chamber 1 from the gas discharge hole 22.
[0022]
On the other hand, a dipole ring magnet 30 is disposed concentrically around the upper portion 1 a of the chamber 1. As shown in the horizontal sectional view of FIG. 2, the dipole ring magnet 30 is configured by attaching a plurality of anisotropic segment columnar magnets 31 to a ring-shaped magnetic casing 32. In this example, 16 anisotropic segment columnar magnets 31 having a cylindrical shape are arranged in a ring shape. In FIG. 2, the arrows shown in the anisotropic segment columnar magnet 31 indicate the direction of magnetization. As shown in this figure, the magnetization directions of the plurality of anisotropic segment columnar magnets 31 are gradually shifted. As a result, a uniform horizontal magnetic field B directed in one direction as a whole is formed on the wafer W.
[0023]
Therefore, in the space between the support table 2 and the shower head 20, a vertical electric field E is formed by the high frequency power supply 15 and the dipole ring magnet 30 is placed on the wafer W as schematically shown in FIG. A horizontal magnetic field B is formed on the surface, and a magnetron discharge is generated by the orthogonal electromagnetic field thus formed. As a result, plasma of an etching gas in a high energy state is formed, and a predetermined film on the wafer W is etched.
[0024]
Next, the baffle plate 10 will be described in detail. 4 is a perspective view showing a part of the baffle plate 10 cut away, FIG. 5 is a plan view showing a part of the baffle plate 10, and FIG. 6 is an enlarged cross-sectional view showing the mounting state of the baffle plate 10. is there. The baffle plate 10 is formed by thermally spraying a metal, for example, aluminum, ceramics, for example, alumina, and enhances resistance to plasma. The baffle plate 10 has a conical body 10a having a circular hole into which a support table is inserted at the center and a large number of circular gas passage holes 10b on the surface thereof, and a mounting portion 1c of the chamber 1. The outer mounting portion 10c is inserted into and attached to the cutout portion 1d (see FIG. 6), and the inner mounting portion 10d is attached to the mounting member 24 around the support table 2.
[0025]
The outer attachment portion 10 c has a bolt insertion hole 10 e, and the outer attachment portion 10 c and the chamber attachment portion 1 c are attached by a plurality of bolts 25 inserted from the upper part of the chamber 1. On the other hand, the inner attachment portion 10d has a bolt insertion hole 10f, and the inner attachment portion 10d and the attachment member 24 are attached by bolts 26.
[0026]
Since the main body 10a has a conical shape as described above, the buffer plate 10 is configured to be inclined upward at an angle θ from the center side toward the end side in the vertical cross section. In this case, as shown in FIG. 7A, the angle θ is substantially the same as the magnetic field inclination angle (the inclination angle of the magnetic field lines passing through the baffle plate 10) at the position where the baffle plate 10 is present. It is preferable to form.
[0027]
The diameter and aspect ratio of the gas passage hole 10b are determined so that the plasma does not pass through as much as possible and sufficient exhaust conductance can be secured. For example, the diameter is set to 1.7 mm, and the height (that is, the thickness of the baffle plate 10) is set to 3 mm. The shape of the gas passage hole 10b is not limited to a circle but may be an ellipse or a slit. As shown in FIG. 6, the insulating member 3 is divided into three members 3a, 3b, and 3c.
[0028]
Next, the operation of the magnetron RIE plasma etching apparatus configured as described above will be described.
[0029]
First, the gate valve 13 is opened and the wafer W having such a structure is loaded into the chamber 1 and placed on the support table 2. Then, the support table 2 is raised to the position shown in the figure, and the vacuum of the exhaust system 12 is set. The chamber 1 is evacuated through the exhaust port 11 by a pump.
[0030]
Then, a predetermined processing gas for etching is introduced into the chamber 1 from the processing gas supply system 23, and the pressure in the chamber is maintained at, for example, about 1.33 to 13.3 Pa. A predetermined high frequency power of 56 MHz or more is supplied. At this time, the wafer W is attracted and held on the electrostatic chuck 6 by, for example, Coulomb force when a predetermined voltage is applied to the electrode 6a of the electrostatic chuck 6 from the DC power supply 16, and the shower head which is the upper electrode. A high frequency electric field is formed between 20 and the support table 2 which is a lower electrode. Since the horizontal magnetic field B is formed on the upper surface of the wafer W by the dipole ring magnet 30, an orthogonal electromagnetic field is formed in the processing space between the electrodes on which the wafer W exists, and magnetron discharge is caused by the drift of electrons generated thereby. Is generated. Then, a predetermined film of the wafer W is etched by the plasma of the etching gas formed by the magnetron discharge.
[0031]
In this case, the horizontal magnetic field directed in one direction has a horizontal magnetic flux direction on the upper surface of the wafer W as shown in FIGS. 7A and 7B when viewed in a vertical section. As the distance from the wafer W increases in the vertical direction, the vertical component increases.
[0032]
In such a situation, in the case of the baffle plate 10 ′ arranged horizontally as in the prior art, as shown in FIG. 7B, the magnetic field lines pass obliquely with respect to the baffle plate, and the baffle plate 10 Since there are relatively many vertical components of the magnetic field at the existing position, electrons that spirally move along the magnetic field are likely to pass through the holes of the baffle plate 10 ', so that the baffle plate 10' sufficiently blocks the plasma. However, plasma leakage and abnormal discharge occur below the baffle plate 10 '.
[0033]
On the other hand, in the present embodiment, the main body 10a of the baffle plate 10 is formed in a conical shape, and the baffle plate 10 is configured to incline upward from the center side toward the end side in the vertical section thereof. As shown in FIG. 7 (a), the baffle plate 10 is arranged along the direction of the magnetic field lines, that is, the direction of the magnetic field, and electrons that spirally move along the magnetic flux are formed on the baffle plate during the etching process. It becomes difficult to pass through the holes, and the plasma blocking effect can be enhanced. Therefore, it is possible to make it difficult for plasma leakage and abnormal discharge to occur.
[0034]
In this case, the inclination angle θ of the baffle plate 10 is inclined at substantially the same angle as the vertical inclination angle of the magnetic field lines passing therethrough, that is, the vertical inclination angle of the magnetic field at the position where the baffle plate 10 is present. Is preferred. Thereby, the perpendicular component of the magnetic field with respect to the baffle plate 10 is substantially absent, and the plasma blocking effect can be further enhanced.
[0035]
Next, the result of obtaining the optimum arrangement of the baffle plates by simulation of the direction of the magnetic field will be described. Here, for a 300 mm wafer apparatus, the magnetic flux density at the wafer center was set to 12000 μT (120 Gauss). The result is shown in FIG. FIG. 8A shows a case where the vertical position of the wafer upper surface is Z = 0 and the baffle plate is horizontally arranged so that the thickness center is Z = −50 (mm). In this case, It can be seen that the magnetic field at the position where the baffle plate is present has a relatively large vertical component and a small plasma shielding effect. On the other hand, as shown in FIG. 8 (b), it is confirmed that if the central portion of the baffle plate is lowered and inclined, and θ is 23.85 °, it is substantially the same as the inclination angle of the magnetic field. It was done.
[0036]
Based on this result, a conical baffle plate having such an inclination angle was actually created, and when this was incorporated into the apparatus and a magnetron plasma test was conducted, almost no plasma leak occurred, and the baffle plate was below the baffle plate. It was confirmed that abnormal discharge hardly occurred.
[0037]
In addition, this invention is not limited to the said embodiment, A various deformation | transformation is possible. For example, although the dipole ring magnet is used in the above embodiment, the dipole ring magnet may not necessarily be used as the magnetic field forming unit as long as a magnetic field is formed across the chamber.
[0038]
In the above embodiment, the chamber is formed in a cylindrical shape, the support table is formed in a columnar shape, and the baffle plate is formed in a conical shape. However, the present invention is not limited to this. And various shapes can be taken according to the shape of the support table.
[0039]
Furthermore, in the said embodiment, although the example which applied this invention to the magnetron plasma etching apparatus was shown, it can apply not only to this but another plasma processing. That is, a magnetron plasma CVD apparatus can be obtained by changing the processing gas from an etching gas to a known CVD gas, or a magnetron plasma sputtering can be performed by placing a target in the chamber so as to face the object to be processed. It can also be a device. Furthermore, although the case where a semiconductor wafer is used as the substrate to be processed has been described, the present invention is not limited to this, and other substrates such as a liquid crystal display (LCD) substrate may be used.
[0040]
【The invention's effect】
As described above, according to the present invention, the baffle plate is configured to incline upward from the center side toward the end side in the vertical cross section thereof, so that the baffle plate is aligned with the direction of the magnetic field. This makes it difficult for electrons that spirally move along the magnetic field to pass through the holes formed in the baffle plate, thereby enhancing the plasma blocking effect. Therefore, it is possible to make it difficult for plasma leakage and abnormal discharge to occur.
[0041]
In addition, by setting the tilt angle of the baffle plate to be substantially the same as the tilt angle in the vertical direction of the magnetic field at the position where the baffle plate exists, the vertical component of the magnetic field with respect to the baffle plate is substantially absent, and the plasma blocking effect Can be further increased.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a magnetron RIE plasma etching apparatus according to an embodiment of the present invention.
2 is a horizontal cross-sectional view schematically showing a dipole ring magnet arranged around the chamber of the apparatus of FIG. 1. FIG.
FIG. 3 is a schematic diagram for explaining an electric field and a magnetic field formed in the chamber.
4 is a perspective view showing a part of the baffle plate of the apparatus of FIG.
FIG. 5 is a plan view showing a part of a baffle plate of the apparatus of FIG. 1;
6 is an enlarged cross-sectional view showing a baffle plate attached state of the apparatus of FIG.
FIG. 7 is a schematic diagram showing the arrangement of baffle plates and the direction of magnetic flux used in the embodiment of the present invention, and the schematic diagram showing the arrangement of conventional baffle plates and the direction of magnetic flux.
FIG. 8 is a diagram showing a simulation result of the direction of a magnetic field, a conventional baffle plate arrangement, and an optimum baffle plate arrangement in the present embodiment.
[Explanation of symbols]
1; Chamber 2; Support table (lower electrode)
3; Insulating member 5; Focus ring 6; Electrostatic chuck 10; Baffle plate 12; Exhaust system 15; High-frequency power source 17; Refrigerant chamber 18;
23; processing gas supply system 30; dipole ring magnet W; semiconductor wafer

Claims (4)

A chamber in which the substrate to be processed is loaded and kept airtight;
An upper electrode and a lower electrode provided opposite to each other in the chamber;
An electric field forming means for forming an electric field between the upper electrode and the lower electrode;
A processing gas supply means for supplying a processing gas into the chamber;
The processing space between the upper electrode and the lower electrode is provided with magnetic field forming means for forming a magnetic field orthogonal to the electric field direction and directed in one direction, and the substrate is processed in a state where the substrate to be processed is supported by the lower electrode A magnetron plasma processing apparatus for performing magnetron plasma processing on
A baffle plate for blocking plasma provided to cover a space between the inner wall of the chamber and the lower electrode;
Said baffle plate is in its vertical cross section, inclined at an inclination angle substantially the same angle in the vertical direction of the magnetic field at the present position, the vertical component of the magnetic field relative to the baffle plate is configured to not substantially exist and magnetron plasma processing apparatus, characterized in that are.   2. The magnetron plasma processing apparatus according to claim 1, wherein the chamber has a substantially cylindrical shape, the lower electrode has a substantially cylindrical shape, and the baffle plate has a substantially conical shape.   The magnetron plasma processing apparatus according to claim 1, wherein the baffle plate is formed with a circular, elliptical, or slit-shaped hole.   The said magnetic field formation means has a dipole ring magnet formed by arrange | positioning several anisotropic segment magnets in the ring shape around the said chamber, The Claim 1 characterized by the above-mentioned. Magnetron plasma processing equipment.

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