JP2005060845A - Magnetic field generator for magnetron plasma - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic field generator for magnetron plasma capable of easily realizing satisfactory plasma treatment by suitably setting the intensity of multipole magnetic fields in accordance with treatment such as etching in a multipole magnet (magnetic field generator) using permanent magnets. <P>SOLUTION: In the magnetic field generator for magnetron plasma, a plurality of magnet segments consisting of permanent magnets are arranged so as to be a ring shape, and multipole magnetic fields are formed around the substrate to be treated in a treatment chamber. The magnetic field generator comprises magnetic substance pieces fitted with segment magnets and magnetic substance pieces fitted with no segment magnets, and the multipole magnetic field intensity is controlled by moving at least the magnetic substance pieces fitted with the segment magnets to the radial direction of the magnetic field generator. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a magnetic field generator for magnetron plasma, and more particularly to a magnetic field generator for use in a magnetron plasma processing apparatus that performs plasma processing such as etching on a substrate to be processed such as a semiconductor wafer.

  Conventionally, in the field of semiconductor device manufacturing, plasma is generated in a processing chamber, and this plasma is applied to a substrate to be processed such as a semiconductor wafer disposed in the processing chamber to perform predetermined processing such as etching and film formation. Plasma processing apparatuses to perform are known.

  In such a plasma processing apparatus, in order to perform a favorable process, it is necessary to maintain the plasma state in a favorable state suitable for the plasma process. For this reason, there are many conventional magnetron plasma processing apparatuses equipped with a magnetic field generator for generating a magnetic field for controlling plasma.

As such a magnetic field generator, as shown in FIG. 7, a multipole type magnetic field generator that forms a multipole magnetic field around a substrate to be processed such as a semiconductor wafer disposed horizontally with a surface to be processed facing upward. The device is known. In this apparatus, a plurality of permanent magnets 2 are arranged in a ring shape so that the magnetic poles are alternately changed outside the processing chamber, and a magnetic field is not formed above the semiconductor wafer 4 (or in a weak magnetic field state). A multipole magnetic field is formed around the edge of the wafer 4 to confine the plasma and perform plasma processing on the substrate to be processed. For multipole magnets (magnetic field generators), there are few examples of using electromagnets that consume power, and it is common to use permanent magnets. When permanent magnets are used, the proposal to control the multipole magnetic field itself Never existed before. Further, even when a permanent magnet is used, the magnetic field strength cannot be appropriately adjusted because a ring-shaped magnetic piece is used as shown in FIG. 8 (for example, FIG. 8 of Patent Document 1). ).
JP-A-7-142450

  However, according to research by the present inventors, it has been found that in plasma processing, for example, plasma etching, the etching rate on the surface of the substrate to be processed depends on the strength of the multipole magnetic field. The strength of the multipole magnetic field can be easily adjusted if the magnetic field generator is composed of an electromagnet. However, as described above, the use of an electromagnet causes a problem of increased power consumption. There has never been a proposal to control the multipole magnetic field itself even with an apparatus using the.

  The present invention is for a magnetron plasma that can easily realize a good plasma process by setting an appropriate multipole magnetic field intensity according to a process such as etching in a multipole magnet (magnetic field generator) using a permanent magnet. A magnetic field generator is provided.

  An embodiment according to the present invention is a magnetron plasma magnetic field generator in which a plurality of magnet segments made of permanent magnets are arranged in a ring shape to form a multipole magnetic field around a substrate to be processed in a processing chamber, The magnetic field generator uses a plurality of divided magnetic body pieces, and moves the magnetic body piece to which the magnet segment of the plurality of magnetic body pieces is attached in the radial direction of the magnetic field generator to adjust the multipole magnetic field. It is characterized by performing. Furthermore, the cross-sectional shape of the magnetic piece perpendicular to the central axis of the magnetic field generator is trapezoidal or fan-shaped, and adjacent magnetic pieces are in contact with each other.

  According to the present invention, when plasma processing such as etching is performed with a magnetic field generator using a permanent magnet, the strength of the multipole magnetic field can be appropriately set, so that it is possible to easily perform good plasma processing. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a top view of a multipole magnet (magnetic field generator) 10 according to an embodiment. Further, FIG. 1 shows a vertical wall 12a of a vacuum chamber 12 disposed inside the multipole magnet 10 and A semiconductor wafer 14 placed in the chamber is schematically shown. FIG. 2 shows an outline of a cross section taken along the line AB in FIG. In FIG. 1, for the sake of simplifying the drawing, the illustration of the gantry (magnetic piece support) 13 shown in FIG. 2 is omitted.

  Inside the multipole magnet 10, as described above, there is the vacuum chamber 12, and inside the vacuum chamber 12, a plasma processing apparatus for performing plasma processing on the semiconductor wafer 14 is provided. Since this plasma processing apparatus itself is well known and the present invention is not limited to a specific plasma processing apparatus, FIG. 2 simply shows the upper electrode plate 16 and the lower electrode plate 18 in addition to the semiconductor wafer 14. Therefore, detailed description of the entire plasma processing apparatus will be omitted. As is well known, a high frequency voltage is applied to the upper and lower electrode plates 16 and 18 to change the direction of the electric field between the two electrode plates, and high-density plasma is generated by the interaction between the electric field and the magnetic field. An arrow 19 indicates the direction of the electric field at a certain moment generated between the upper and lower electrodes 16 and 18.

  As shown in FIG. 1, the multipole magnet 10 includes a plurality of magnetic pieces 20 arranged in a ring shape adjacent to each other, and the magnetic pieces 20 are permanent magnets every other piece. A segment magnet 22 is attached (adhered). Although not necessarily clear from FIGS. 1 and 2, the magnetic piece 20 arranged in a ring shape is a plurality of mounts 13 made of a non-magnetic material (arranged in a ring shape like the magnetic piece 20). Is supported by.

  In the multipole magnet 10 shown in FIG. 1, the magnetic piece 20 is divided into 32 pieces and 16 segment magnets 22 are provided. However, the present invention is not limited to such a number. It is sufficient that the magnetic material pieces are divided into two, preferably 8 to 64 pieces, and the segment magnets have the same number as or less than the number of magnetic pieces. The shape of the cross section of the segment magnet 22 perpendicular to the central axis (perpendicular to the paper surface) of the multipole magnet 10 is arbitrary, and may be, for example, a circle, a square, a rectangle, a trapezoid, or a roof tile. In the first embodiment shown in FIG. 1, the sectional shape of the segment magnet 22 is a rectangle. The arrow drawn on the segment magnet 22 indicates the direction of magnetization of the segment magnet.

  As shown in FIG. 1, when the segment magnets 22 are arranged so that their magnetic poles are alternately N and S, a magnetic field (line of magnetic force) in the direction indicated by the arrow 24 is generated in the vicinity of the wall 12a in the vacuum chamber. . The magnetic field strength is, for example, 0.005 to 0.2 T (200 to 2000 G), preferably 0.03 to 0.045 T (300 to 450 G). In this case, a multipole magnetic field is formed so that the central portion of the semiconductor wafer 14 is substantially in a no magnetic field state (or a state where the magnetic field is weakened).

  For example, as shown in FIGS. 1 and 2, the circle inscribed in the segment magnet 22 is D = φ450 mm, the width W of the segment magnet is 40 mm, the thickness TM is 7 mm, the height L is 120 mm, and the magnetic piece 20 When the thickness TY = 9 mm and the height L = 120 mm, a magnetic field of 0.03 T (300 G) is formed in the vicinity of the inner wall of the vacuum chamber 12, thereby exhibiting a function of confining plasma. The segment magnet 22 is a rare earth magnet having a remanent magnetization density of 1.3 T, the magnetic piece 20 is made of low carbon steel S15C, and the mount 13 is made of aluminum.

  The segment magnet 22 is not particularly limited, and for example, a rare earth magnet, a ferrite magnet, an alnico magnet, or the like can be used. The magnetic piece 20 uses pure iron, carbon steel, iron-cobalt steel, stainless steel or the like having ferromagnetic properties, and the base material is aluminum, stainless steel, brass or resin having nonmagnetic properties. Etc. can be used.

  As described above, it is desirable that there is substantially no magnetic field (zero T) at the center of the semiconductor wafer 14. However, in practice, a magnetic field that affects the etching process is not formed in the arrangement portion of the semiconductor wafer 14, and any value that does not substantially affect the wafer process may be used. In the state shown in FIG. 1, for example, a magnetic field having a magnetic flux density of 420 μT (4.2 G) or less exists in the periphery of the wafer.

  Further, as described above, the multipole magnet 10 includes a plurality of magnetic body pieces 20 arranged in a ring shape adjacent to each other, and in each of these magnetic body pieces 20, segment magnets 22 that are permanent magnets are provided. Is attached (adhered). However, the present embodiment is not limited to such an arrangement, and various modifications can be considered.

  For example, as shown in FIG. 3, when the magnetic piece 20 to which the segment magnet 22 is not bonded (not attached) is removed from the multipole magnet 10, the magnetic field strength in the vicinity of the inner wall of the vacuum chamber 12 is changed. Can do. In the modification shown in FIG. 3, the magnetic pieces 20 arranged in a ring shape are similarly supported by a gantry 13 provided in a ring shape, but the gantry 13 is not shown. According to the inventor's experiment, when the multipole magnet 10 is configured as shown in FIG. 3 and the same segment magnet and magnetic material piece as described in FIG. 1 are used, the inner wall of the vacuum chamber 12 (FIG. 1) is used. The magnetic field in the vicinity could be reduced to 0.023T (230G).

  Further, by changing the arrangement position of the “magnetic body piece 20 and the segment magnet 22 bonded to the magnetic body piece” constituting the multipole magnet 10 shown in FIG. The magnetic field strength can be changed. For example, as shown in FIG. 4, two “integrated magnetic pieces 20 and segment magnets 22” and two “magnetic pieces 20 without segment magnets” are alternately arranged, It is also possible to form an 8-pole multipole magnetic field. Thus, when the number of poles is reduced, the magnetic lines of force extend into the vacuum chamber 12 (see FIG. 1), and the magnetic field in the vicinity of the inner wall of the vacuum chamber 12 and the outer periphery of the semiconductor wafer can be increased. Further, although not shown, if four “integrated magnetic pieces 20 and segment magnets 22” and four “magnetic pieces 20 without segment magnets” are alternately arranged, four poles are provided. It is also possible to form a multipole magnetic field. Thus, an appropriate magnetic field can be formed in the vicinity of the inner wall of the vacuum chamber 12 according to the etching process.

  Further, in the multipole magnet 10 described with reference to FIGS. 1, 3, and 4, the magnetic pole piece 20 to which the segment magnet 22 is attached is arranged outside along the radial direction extending from the central axis of the multipole magnet (magnetic field generator) 10. Alternatively, if it is moved inward, the magnetic field strength in the vicinity of the inner wall of the vacuum chamber 12 can be changed. FIG. 5A shows a case where the position of the magnetic piece 20 attached to the gantry 13 is the same as that of FIGS. 1, 3, and 4 (that is, the state before the magnetic piece 20 is moved). (B) shows the state which moved the magnetic body piece 20 attached to the mount frame 13 to radial direction and the outer side.

  According to an experiment by the present inventor, when all of the “magnetic piece 20 with the segment magnet 22 bonded” constituting the multipole magnet 10 shown in FIG. The magnetic field near the inner wall could be reduced to 0.01T (100G). Furthermore, when only the magnetic piece 20 to which the segment magnet 22 is not bonded is moved 20 mm in the radial direction and out of the multipole magnet 10 of FIG. 1 to create a gap between the adjacent magnetic pieces 20. The magnetic field strength near the inner wall of the vacuum chamber 12 can be reduced. In this case, there is an effect similar to removing the magnetic piece 20 to which the segment magnet 22 is not bonded.

  Contrary to the case described above, it is also possible to adjust the magnetic field strength near the inner wall of the vacuum chamber 12 by moving the magnetic piece 20 attached to the gantry 13 in the radial direction and inward.

  As described above, in the present embodiment, the magnetic piece 20 can be removed without preparing a new segment magnet in addition to the segment magnet initially installed to change the strength of the multipole magnetic field. The arrangement of the magnetic piece 20 to which the segment magnet 22 is fixed is changed, the magnetic piece 20 to which the segment magnet 22 is fixed is moved in the radial direction, or the magnetic piece 20 to which the segment magnet 22 is not attached. It is possible to adjust the strength of the multipole magnetic field around the semiconductor wafer 14 provided in the vacuum chamber 12 by moving the sensor in the radial direction.

  The cross-sectional shape of the magnetic piece 20 described above (the cross-sectional shape in a plane perpendicular to the central axis of the multipole magnet which is a magnetic field generator) is trapezoidal or fan-shaped as shown in FIGS. 6 (a) and 6 (b). It is preferable to reduce the loss of magnetic flux on the contact surface as much as possible by making the adjacent magnetic piece 20 into surface contact. That is, when the magnetic piece 20 is supported by the gantry 13 (FIGS. 1 and 4), it is preferable that no gap is formed between the adjacent magnetic pieces 20. For example, as in the comparative example shown in FIG. 6C, when the cross-sectional shape of the magnetic piece is rectangular, a gap is formed between adjacent magnetic pieces 20, and the number of magnetic fluxes decreases due to magnetic saturation. There arises a disadvantage that the number of magnetic fluxes formed in the vacuum chamber 12 is reduced. As described above, if the magnetic flux loss at the contact surface is reduced as much as possible by making the adjacent magnetic body pieces 20 in surface contact, the loss of magnetic flux at the contact surface can be reduced, resulting in the same amount of segments. Even if a magnet is used, the strength of the multipole magnetic field can be increased, so there is an advantage that an expensive magnet can be used effectively.

  In the above embodiment, the case where the present invention is applied to an apparatus for etching a semiconductor wafer has been described. However, the present invention is not limited to such an application example. The substrate may be processed, and can be applied to plasma processing other than etching, for example, a film forming processing apparatus such as CVD.

The figure which shows the outline of embodiment of the multipole magnet (magnetic field generator) which concerns on this invention The figure which shows the cross section in the cutting line AB of FIG. The figure which shows the outline of the modification of embodiment shown in FIG. The figure which shows the outline of the other modification of embodiment shown in FIG. The figure explaining the further another modification of embodiment shown in FIG. Sectional drawing of the pole piece used as Embodiment and the pole piece used for embodiment which concerns on this invention as a comparative example. The figure for demonstrating the conventional multipole magnet (magnetic field generator). The figure for demonstrating the conventional multipole magnet (magnetic field generator).

Explanation of symbols

10: Multipole magnet (magnetic field generator)
12: Vacuum chamber 14: Semiconductor wafer (substrate to be processed)
20: Magnetic piece 22: Segment magnet

Claims (2)

  A magnetic field generator for magnetron plasma in which a plurality of magnet segments made of permanent magnets are arranged in a ring shape and a multipole magnetic field is formed around a substrate to be processed in a processing chamber. Magnetron plasma characterized by performing multipole magnetic field adjustment by moving a magnetic piece to which a magnetic segment of the plurality of magnetic pieces is attached in the radial direction of the magnetic field generator. Magnetic field generator.   2. The magnetron plasma magnetic field according to claim 1, wherein a cross section of the magnetic piece perpendicular to the central axis of the magnetic field generator has a trapezoidal shape or a sector shape, and adjacent magnetic pieces are in contact with each other. Generator.