JP2018163771A - Plasma processing apparatus - Google Patents

Abstract

A plasma processing apparatus that does not require an actuator for rotating a ring magnet is disclosed. A plasma processing apparatus (10) includes a lower electrode (3) on which a work (90) is placed, an upper electrode (4) arranged above the lower electrode (3), and a space located between the lower electrode (3) and the upper electrode (4). A cylindrical magnet 6 that surrounds the cylindrical magnet 6, and a block that is a virtual cone having a bottom surface in a region surrounded by the cylinder magnet 6 and that is arranged at the apex of the cone protruding outside the cylindrical magnet. It has a magnet 7. The magnetic pole on the inner peripheral surface of the tubular magnet 6 and the magnetic pole on the end surface of the block magnet 7 on the tubular magnet 6 side are opposite magnetic poles. [Selection diagram] Figure 1

Description

  The technology disclosed in this specification relates to a plasma processing apparatus for plasma processing a workpiece.

  A plasma processing apparatus exposes a workpiece (for example, a semiconductor substrate) set in a chamber to plasma, thereby surface-treating the workpiece. The plasma processing apparatus includes a plasma etching apparatus that etches the surface of a workpiece, a plasma CVD apparatus that grows a thin film on the surface of the workpiece by CVD (chemical vapor deposition), and the like.

  Before describing the plasma processing apparatus, the plasma drift motion will be described. In general, the plasma in the space where the electric field E and the magnetic field B exist receives a force in the outer product direction of the electric field E and the magnetic field B (hereinafter referred to as “E × B direction”). In general, the movement by the force in the E × B direction is called “drift movement”.

  For example, the plasma processing apparatus of Patent Document 1 rotates plasma by drift motion. The plasma processing apparatus of the document includes a lower electrode on which a work is placed and an upper electrode disposed on the lower electrode. By applying a voltage between the lower electrode and the upper electrode, an electric field E is generated between the lower electrode and the upper electrode. The plasma processing apparatus further includes a dipole ring magnet that surrounds the space between the lower electrode and the upper electrode. The dipole ring magnet is made by arranging a plurality of segment magnets in an annular shape. A magnetic field B perpendicular to the central axis of the dipole ring magnet (and thus parallel to the upper surface of the lower electrode and the lower surface of the upper electrode) is generated in the space inside the dipole ring magnet by the plurality of segment magnets. The plasma existing between the lower electrode and the upper electrode receives a force in an E × B direction (in a plane parallel to the upper surface of the lower electrode and the lower surface of the upper electrode) orthogonal to both the electric field E and the magnetic field B.

  The plasma processing apparatus further includes an actuator for rotating the dipole ring magnet around its central axis. As the dipole ring magnet rotates, the E × B direction also rotates around the central axis of the dipole ring magnet. Thereby, the plasma swirls around the central axis of the dipole ring magnet, stays in the space between the lower electrode and the upper electrode, and the density of the plasma existing between the lower electrode and the upper electrode is increased.

JP 2010-238819 A

  The technique of Patent Document 1 requires an actuator for rotating a dipole ring magnet in order to rotate plasma. The present specification discloses a plasma processing apparatus that does not require an actuator for rotating a magnet.

A plasma processing apparatus disclosed in this specification includes a lower electrode on which a workpiece is placed, an upper electrode disposed on the upper part of the lower electrode, and a cylindrical magnet that surrounds a space located between the lower electrode and the upper electrode. And a block magnet. When attention is paid to the cylindrical magnet, the cylindrical magnet is a conical body that defines the bottom surface, and a conical body whose apex projects outside the cylindrical magnet can be virtually drawn. The block magnet is arranged at the apex position. The magnetic pole on the inner peripheral surface of the cylindrical magnet and the magnetic pole on the cylindrical magnet side end surface of the block magnet are opposite magnetic poles. That is, if the former is N pole, the latter is S pole, and if the former is S pole, the latter is N pole.
The cylindrical magnet may have a cylindrical shape, an elliptical cylindrical shape, or a polygonal cylindrical shape such as a quadrangle. The virtual cone may be a straight cone or an oblique cone. Moreover, the block magnet may be arrange | positioned at the upper part of the cylindrical magnet, and may be arrange | positioned at the lower part of the cylindrical magnet.

  According to this configuration, a magnetic field connecting the cylindrical magnet and the block magnet is mainly obtained inside the cone, and a magnetic field B extending along the side surface of the virtual cone is generated. This magnetic field B intersects with the electric field E generated between the lower electrode and the upper electrode. For example, in the case of a cylindrical shape of a cylindrical magnet, in the plane orthogonal to the electric field E, the E × B direction coincides with the tangential direction over the entire circumference of a circle centering on the central axis of the cylindrical magnet. Thereby, the plasma swirls around the central axis of the cylindrical magnet in a plane orthogonal to the electric field E. Also, when the cylindrical magnet has a rectangular cylindrical shape, the E × B direction makes a round around the central axis of the cylindrical magnet. Thereby, the plasma rotates around the central axis of the cylindrical magnet along a plane orthogonal to the electric field E. That is, the actuator for rotating a cylindrical magnet can be made unnecessary by devising arrangement | positioning of a cylindrical magnet and a block magnet. Details and further improvements of the technology disclosed in this specification will be described in the following “DETAILED DESCRIPTION”.

It is sectional drawing of the plasma processing apparatus of an Example. It is a perspective view of a cylindrical magnet and a block magnet. It is a top view of a cylindrical magnet.

  FIG. 1 shows a plasma processing apparatus 10 of the embodiment. The plasma processing apparatus 10 performs plasma processing on the workpiece 90. The plasma processing apparatus 10 may be a plasma etching apparatus or a plasma CVD apparatus.

  The plasma processing apparatus 10 includes a support base 2. A lower electrode 3 is disposed on the upper surface of the support base 2. The lower electrode 3 has a substantially disk shape. The lower electrode 3 is supported by the support base 2 so that its central axis extends in the vertical direction. A wiring 30 for applying a voltage is connected to the lower electrode 3. The upper surface of the lower electrode 3 is flat. The upper surface of the lower electrode 3 is a stage on which the workpiece 90 is placed.

A plurality of pillars 46 extend upward from the upper surface of the support base 2. The upper plate 44 is fixed to the upper end of each pillar 46. A plurality of pillars 42 extend downward from the lower surface of the upper plate 44. An electrode holding portion 40 is fixed to the lower end of each pillar 42. The upper electrode 4 is fixed to the lower surface of the electrode holding part 40. That is, the upper electrode 4 is supported on the support base 2 via the pillar 46, the upper plate 44, the pillar 42, and the electrode holding portion 40. The upper electrode 4 is located above the lower electrode 3.
The potential of the upper electrode 4 is the potential of the support base 2, that is, the ground potential. The upper electrode 4 has a substantially disk shape. The upper electrode 4 is supported such that its central axis extends in the vertical direction. The upper electrode 4 is supported so that the central axis of the lower electrode 3 coincides.

  The lower electrode 3 and the upper electrode 4 are accommodated in the chamber 5. The outer wall 50 of the chamber 5 includes an upper wall 50a and a cylindrical side wall 50b. A through hole 50c is provided in the upper wall 50a. As will be described later, when the chamber 5 moves downward, the through hole 50 c is blocked by the electrode holding portion 40 from the inside of the outer wall 50. The pillar 42 extending upward from the electrode holding part 40 passes through the through hole 50c. The upper surface of the upper wall 50 a is connected to the lower end of the movable pillar 54 via the connection member 52. The movable pillar 54 is a columnar part that extends vertically. The upper end of the movable pillar 54 is connected to the actuator 56. The actuator 56 is fixed to the upper plate 44. The movable pillar 54 can be moved up and down by operating the actuator 56. As the movable pillar 54 moves up and down, the outer wall 50 moves up and down. By moving the outer wall 50 upward, a gap is formed between the outer wall 50 and the upper surface of the support 2, and the workpiece 90 can be placed on the lower electrode 3 through the gap. Further, by moving the outer wall 50 downward, the through hole 50 c is blocked by the electrode holding portion 40, and the lower opening of the outer wall 50 is blocked by the upper surface of the support base 2. That is, the chamber 5 includes the outer wall 50, the electrode holding unit 40, and the support base 2.

  A gas (for example, an etching gas, a raw material gas for CVD, etc.) is supplied into the chamber 5 from a gas supply port 4 a provided in the center of the upper electrode 4. The gas supplied into the chamber 5 is turned into plasma when a high frequency voltage is applied to the lower electrode 3 via the wiring 30. The workpiece 90 is subjected to a surface treatment by the plasma gas reacting with the workpiece 90. For example, when the gas is an etching gas, the plasma etching gas reacts with the workpiece 90 and the surface of the workpiece 90 is shaved. When the gas is a CVD source gas, the plasma source gas reacts on the surface of the workpiece 90 and a film grows on the surface of the workpiece 90.

  The plasma processing apparatus 10 further includes a cylindrical magnet 6 and a columnar block magnet 7. A cylindrical magnet 6 is arranged so as to surround the outer wall 50. FIG. 2 is a perspective view of the cylindrical magnet 6. The cylindrical magnet 6 has a substantially cylindrical shape and a horizontal cross section is circular. The cylindrical magnet 6 includes a cylindrical magnet holding part 60 and a plurality of segment magnets 62 arranged at equal intervals over the entire inner peripheral surface of the magnet holding part 60. In FIG. 2, one of the plurality of segment magnets 62 is given a reference numeral, and the reference numerals of the other segment magnets are omitted. In each segment magnet 62, the N pole faces the inside of the magnet holding unit 60, and the S pole faces the outside of the magnet holding unit 60. That is, in the cylindrical magnet 6, the entire inner peripheral surface is an N pole.

  Returning to FIG. 1, the description will be continued. The cylindrical magnet 6 is supported on the support base 2 by pillars 64. The cylindrical magnet 6 is supported so that its central axis extends in the vertical direction. The cylindrical magnet 6 is supported so that the central axis coincides with the lower electrode 3 and the upper electrode 4. The vertical width of the cylindrical magnet 6 is smaller than the distance between the lower electrode 3 and the upper electrode 4. The cylindrical magnet 6 is disposed at a height between the lower electrode 3 and the upper electrode 4 in the vertical direction so as to be offset toward the lower electrode 3 side. That is, the cylindrical magnet 6 surrounds a part of the space between the lower electrode 3 and the upper electrode 4.

  The block magnet 7 is disposed above the cylindrical magnet 6. FIG. 2 is a perspective view of the block magnet 7. In FIG. 2, the simplified lower electrode 3, upper electrode 4, and electrode holding portion 40 are drawn by a two-dot chain line. The block magnet 7 is supported on the upper surface of the electrode holding unit 40. The block magnet 7 is supported so that the central axis CL extends in the vertical direction. The block magnet 7 is supported so that the lower electrode 3, the upper electrode 4, and the cylindrical magnet 6 coincide with the central axis CL.

  The diameter of the block magnet 7 is smaller than the diameter of the inner peripheral surface of the cylindrical magnet 6. As shown in FIG. 2, the block magnet 7 is disposed at the apex of a virtual cone IC whose bottom surface is a region surrounded by the edge of the inner peripheral surface of the cylindrical magnet 6 on the block magnet 7 side. The cone IC protrudes from the upper part of the cylindrical magnet 6. The cone IC is a so-called straight cone. The end surface of the block magnet 7 on the cylindrical magnet 6 side is an S pole opposite to the N pole that is the magnetic pole on the inner peripheral surface of the cylindrical magnet 6. Thereby, the magnetic field B along the side surface of the cone IC is generated mainly inside the cone IC so as to connect the cylindrical magnet 6 and the block magnet 7. In other words, the magnetic field B is generated so as to be concentrated from the entire inner peripheral surface of the cylindrical magnet 6 to the lower end surface of the block magnet 7.

  Further, when a high frequency voltage is applied to the lower electrode 3, an electric field E is generated between the lower electrode 3 and the upper electrode 4. The electric field E is parallel to the central axis CL. The electric field E intersects the magnetic field B along the side of the cone IC. The plasma existing in the space between the lower electrode 3 and the upper electrode 4 receives a force in the outer product direction of the electric field E and the magnetic field B (hereinafter referred to as “E × B direction”). This force causes the plasma to drift in the E × B direction.

  The plasma drift motion will be described with reference to FIG. FIG. 3 is a top view of the cylindrical magnet 6 and is a view for explaining the drift motion of plasma existing on the plane III in FIG. The electric field E is generated in a direction from the back surface to the front surface of the paper. On the other hand, the magnetic field B is generated from the edge of the inner peripheral surface of the cylindrical magnet 6 toward a point where the central axis CL of the cylindrical magnet 6 passes in a plan view. The E × B direction coincides with the tangential direction of the circle over the entire circumference of the circle centered on the point through which the central axis CL passes. Plasma existing on a circle centered on a point through which the central axis CL passes is subjected to a force in a tangential direction over the entire circumference of the circle and swivels along the circle. As a result, the plasma remains in the space between the lower electrode 3 and the upper electrode 4, and high-density plasma can be obtained.

  The effect of the present embodiment will be described. The conventional plasma processing apparatus does not include the block magnet 7 but includes a dipole ring magnet that generates a horizontal magnetic field B and an actuator that rotates the dipole ring magnet about its axis. The plasma receives a force in the direction of E × B orthogonal to both the electric field E and the magnetic field B in a plane parallel to the magnetic field B. When the dipole ring magnet rotates, the plasma receives a force in the direction of E × B (that is, a tangent method of the circle) over the entire circumference of the rotation, and rotates along the circle. That is, in the conventional plasma processing apparatus, an actuator that rotates the dipole ring magnet is necessary to rotate the plasma. On the other hand, the plasma processing apparatus 10 of the present embodiment realizes the plasma swirl by devising the arrangement of the cylindrical magnet 6 and the block magnet 7. With the technique of this embodiment, an actuator for rotating the magnet can be dispensed with.

  Hereinafter, points to be noted regarding the technology shown in the embodiments will be described. The block magnet 7 may be disposed below the lower electrode 3. In this case, the cylindrical magnet 6 may be arranged so as to be offset toward the upper electrode 4, and the block magnet 7 may be arranged at the apex of the virtual cone IC that projects to the lower part of the cylindrical magnet 6. Further, the block magnet 7 may be disposed between the lower electrode 3 and the upper electrode 4.

  Further, the central axis of the block magnet 7 may not coincide with the central axis of the cylindrical magnet 6. That is, the block magnet 7 may be disposed at the apex of a virtual oblique cone whose bottom surface is a region surrounded by the edge of the inner peripheral surface of the cylindrical magnet 6 on the block magnet 7 side.

  Moreover, the horizontal cross section of the cylindrical magnet 6 may be elliptical or polygonal, such as a quadrangle. For example, when the cross section of the cylindrical magnet 6 is a quadrangle, the E × B direction goes around the central axis of the cylindrical magnet 6 on a plane orthogonal to the electric field E. The plasma swirls around the central axis.

  The inner peripheral surface of the cylindrical magnet 6 may be an S pole, and the end surface of the block magnet 7 on the cylindrical magnet 6 side may be an N pole.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

2: Support base 3: Lower electrode 4: Upper electrode 4a: Gas supply port 5: Chamber 6: Cylindrical magnet 7: Block magnet 10: Plasma processing apparatus 30: Wiring 40: Electrode holding part 42: Pillar 44: Upper plate 46 : Pillar 50: Outer wall 50a: Upper wall 50b: Side wall 50c: Through hole 52: Connection member 54: Movable pillar 56: Actuator 60: Magnet holding part 62: Segment magnet 90: Workpiece

Claims (1)

An apparatus for plasma processing of workpieces,
A lower electrode on which the workpiece is placed;
An upper electrode disposed on top of the lower electrode;
A cylindrical magnet surrounding a space located between the lower electrode and the upper electrode;
A virtual conical body having a bottom surface in a region surrounded by the cylindrical magnet, comprising a block magnet disposed at the apex of the conical body protruding outside the cylindrical magnet;
The plasma processing apparatus, wherein the magnetic pole on the inner peripheral surface of the cylindrical magnet and the magnetic pole on the cylindrical magnet side end surface of the block magnet are opposite magnetic poles.

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