JP2018170213A - Plasma processing equipment - Google Patents

Abstract

In a plasma processing apparatus, an effective region in which a magnetic field intensity is uniformly adjusted is expanded. A lower electrode on which a workpiece is placed, an upper electrode disposed on the lower electrode, an annular magnet enclosing a space located between the lower electrode and the upper electrode, , An actuator 68 for rotating the annular magnet 6 around its central axis is provided. The annular magnet 6 is configured by arranging a plurality of segment magnets in an annular shape around the central axis. When viewed from the central axis direction, the arrangement range of the segment magnet group 62a in which the magnetization direction faces outward and the arrangement range 62b of the segment magnet group in which the magnetization direction faces inward face each other across the central axis. Yes. When viewed from a direction orthogonal to the central axis, one arrangement range is located on the lower electrode side, and the other arrangement range is located on the upper electrode side. [Selection] Figure 1

Description

  The present specification discloses 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 a CVD (chemical vapor deposition) method, and the like.

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

  For example, the plasma processing apparatus of Patent Document 1 rotates plasma by drift motion. The plasma processing apparatus of Patent Literature 1 includes a lower electrode on which a workpiece 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 surrounding a space located 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. Due to the plurality of segment magnets arranged in an annular shape, a magnetic field H along the plane 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. Occur. The plasma existing between the lower electrode and the upper electrode receives a force in an E × H 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 H.

  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 force in the E × H 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.

  The plasma processing apparatus of Patent Document 1 includes one dipole ring magnet. On the other hand, the plasma processing apparatus of Patent Document 2 includes upper and lower two-stage dipole ring magnets.

Japanese Patent Laid-Open No. 10-144661 JP 2010-238819 A

  A region (hereinafter referred to as “effective region”) in which the magnetic field strength H (or magnetic flux density B) spreads substantially uniformly is formed inside the dipole ring magnet. In the plasma processing apparatus, there is a demand for increasing the proportion of the effective area in the space inside the dipole ring magnet. The dipole ring magnet of Patent Document 1 expands an effective region in a horizontal plane (in a plane parallel to the upper surface of the lower electrode and the lower surface of the upper electrode) by arranging a plurality of segment magnets in an elliptical shape. Moreover, in patent document 2, the expansion of the effective area | region in an up-down direction is expanded by arrange | positioning a dipole ring magnet to two steps up and down.

In order to widen the effective area, it is necessary to adjust various parameters, and there is a limit in the known method. In particular, when the diameters of the chamber and the dipole ring magnet are reduced in order to process a small-diameter workpiece, the known method significantly reduces the effective area.
The present specification discloses a technique for enlarging the effective area, and in particular, a technique capable of ensuring a necessary effective area even when the diameter of the dipole ring magnet is reduced.

A plasma processing apparatus disclosed in the present specification includes a lower electrode on which a workpiece is placed, an upper electrode disposed on the upper part of the lower electrode, and an annular magnet that surrounds a space located between the lower electrode and the upper electrode. And an actuator for rotating the annular magnet around the central axis of the annular magnet. The annular magnet is configured by arranging a plurality of segment magnets in an annular shape around a central axis. When the annular magnet is viewed from the central axis direction, the arrangement range of the segment magnet group in which the magnetization direction faces outward and the arrangement range of the segment magnet group in which the magnetization direction faces inward sandwich the central axis. Facing each other. Further, when viewed from a direction orthogonal to the central axis, one of the pair of arrangement positions described above is located on the lower electrode side, and the other is located on the upper electrode side.
The annular magnet may be circular or elliptical. One arrangement range and the other arrangement range may be symmetric or asymmetric with respect to a plane passing through the central axis. Further, each of the one arrangement range and the other arrangement range may extend over an arc range having a central angle of 180 degrees, or may remain in an arc range narrower than that.

  According to said structure, the magnetic field H which connects the segment magnet group arrange | positioned in one arrangement | positioning range and the segment magnet group arrange | positioned in the other arrangement | positioning range is obtained, and the magnetic field H extended diagonally along an up-down direction Will occur. According to this configuration, the effective area in the vertical direction can be expanded and expanded without increasing the vertical width of each segment magnet. The proportion of the effective area in the space inside the annular magnet can be increased. Details and further improvements of the technology disclosed herein are described in the “Examples” below.

It is sectional drawing of the plasma processing apparatus of Example 1. FIG. It is a top view of a lower stage magnet. It is a top view of an upper stage magnet. It is a top view of an annular magnet. It is an expanded sectional view of the circumference of an annular magnet. 6 is a plan view of an annular magnet of Example 2. FIG.

  FIG. 1 shows a plasma processing apparatus 10 according to the first 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. An 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. When the chamber 5 moves downward as will be described later, 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 an annular magnet 6 and an actuator 68 that rotates the annular magnet 6 around its central axis. The annular magnet 6 is disposed so as to surround the outer wall 50. The annular magnet 6 includes a lower magnet 6a and an upper magnet 6b. FIG. 2 shows the lower magnet 6a as viewed from above. The lower magnet 6a includes an annular magnet holding part 60a and a segment magnet group 62a arranged at equal intervals in an arcuate arrangement range R1 in the inner peripheral surface of the magnet holding part 60a. The horizontal cross section of the magnet holding part 60a is a perfect circle. In FIG. 2, one of the segment magnet groups 62 a is assigned a reference numeral, and the other segment magnets are omitted. The arrangement range R1 is included in a semicircular surface on one side (left side of the drawing) of two surfaces obtained by dividing the inner peripheral surface of the magnet holding portion 60a by a plane passing through the central axis. The magnetization direction of each segment magnet 62a faces the inside of the magnet holding part 60a. In the drawing, the magnetization direction of each segment magnet 62a is indicated by an arrow written in each segment magnet 62a. In this embodiment, the magnetization direction is a direction from the N pole to the S pole. And about each of the segment magnet groups 62a, the straight line along the magnetization direction of each segment magnet 62a passes the central axis CL of the magnet holding | maintenance part 60a.

  FIG. 3 shows the upper magnet 6b in a top view. The upper magnet 6b includes an annular magnet holding portion 60b and a segment magnet group 62b arranged at equal intervals in an arcuate arrangement range R2 in the inner peripheral surface of the magnet holding portion 60b. The horizontal cross section of the magnet holding part 60b is a perfect circle having the same diameter as the magnet holding part 60a of the lower magnet 6a. The segment magnet group 62b is arranged at the same interval as the segment magnet group 62a of the lower magnet 6a. The arrangement range R2 is included in a semicircular surface on the other side (right side of the drawing) of two surfaces obtained by dividing the inner peripheral surface of the magnet holding portion 60b by a plane passing through the central axis CL. The other side R2 is opposite to the one side including the arrangement range R1 of the lower magnet 6a. The magnetization direction of each segment magnet 62b faces the outside of the magnet holding portion 60b. And about each of the segment magnet groups 62b, the straight line along the magnetization direction of each segment magnet 62b passes the central axis CL of the magnet holding | maintenance part 60b.

  The upper magnet 6b is arranged on the upper stage of the lower magnet 6a so that the central axes coincide. FIG. 4 shows the lower magnet 6a and the upper magnet 6b as viewed from above (that is, viewed from the central axis direction). As shown in FIG. 4, the arrangement range R1 of the lower magnet 6a and the arrangement range R2 of the upper magnet 6b face each other across the central axis CL. In the present embodiment, when viewed from the central axis direction, the arrangement range R1 and the arrangement range R2 are symmetric with respect to a straight line passing through the central axis CL. Thereby, the magnetic field H which connects the segment magnet group 62a of the lower magnet 6a and the segment magnet group 62b of the upper magnet 6b inside the lower magnet 6a and the inner side of the upper magnet 6b (that is, inside the annular magnet 6) is obtained. The interval between the arrangement range R1 and the arrangement range R2 is the same as the interval between adjacent segment magnets in the segment magnet group 62a (or 62b). That is, when viewed from the central axis direction, the segment magnet groups 62 a and 62 b are arranged on the inner peripheral surface of the annular magnet 6 at equal intervals.

  Returning to FIG. 1, the description will be continued. The lower magnet 6a and the upper magnet 6b are connected by a rod-like connecting member 64. The upper end of the connecting member 64 is fixed to a circular rotating plate 66. The central axis of the rotating plate 66 coincides with the central axis of the annular magnet 6. The rotating plate 66 is connected to the actuator 68. The actuator 68 is fixed to the upper surface of the support base 2. The actuator 68 rotates the rotating plate 66 around its central axis. Thereby, the annular magnet 6 rotates around its central axis. That is, the annular magnet 6 is rotatably supported by the support base 2 via the connecting member 64, the rotating plate 66 and the actuator 68. The annular magnet 6 is supported so that its central axis extends in the vertical direction. The annular 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 annular magnet 6 (that is, the distance between the lower surface of the lower magnet 6 a and the upper surface of the upper magnet 6 b) is smaller than the distance between the lower electrode 3 and the upper electrode 4. The annular magnet 6 is disposed within a height range between the lower electrode 3 and the upper electrode 4 in the vertical direction. That is, the annular magnet 6 surrounds a part of the space between the lower electrode 3 and the upper electrode 4.

  An electric field E and a magnetic field H generated in the space between the lower electrode 3 and the upper electrode 4 will be described. FIG. 5 is an enlarged cross-sectional view around the lower electrode 3 and the upper electrode 4. In FIG. 5, illustration of the outer wall 50 is omitted. By applying a high frequency voltage 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. On the other hand, the magnetic field H connecting the segment magnet group 62a of the lower magnet 6a and the segment magnet group 62b of the upper magnet 6b is generated obliquely along the vertical direction due to the difference in height between the lower magnet 6a and the upper magnet 6b. The electric field E intersects with the magnetic field H generated obliquely along the vertical direction. 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 H (hereinafter referred to as “E × H direction”). This force causes the plasma to drift in the E × H direction.

  The plasma drift motion will be described with reference to FIG. 4 showing the annular magnet 6 as viewed from above. The electric field E is generated in a direction from the back surface to the front surface of the paper. On the other hand, for example, the magnetic field H passing through the central axis CL is generated in a direction from the left side to the right side of the drawing. The E × H direction coincides with the direction from the lower side to the upper side of the drawing. When the annular magnet 6 is rotated around the central axis CL by the actuator 68, the E × H direction is also rotated around the central axis CL. Thereby, the plasma turns around the central axis CL. Due to the swirling of the plasma, the plasma stays in the space between the lower electrode 3 and the upper electrode 4, and a high-density plasma can be obtained.

  The effect of the present embodiment will be described. The magnetic field strength (that is, the magnetic flux density) of the magnetic field H is not uniform in the entire space inside the annular magnet 6. A region where the magnetic field strength spreads almost uniformly inside the annular magnet 6 is a part of the entire space. Hereinafter, a space having a substantially uniform magnetic field strength is referred to as an “effective region”. If the range of the effective region in the vertical direction (the direction parallel to the central axis CL) is widened, the proportion of the effective region in the entire space inside the annular magnet 6 can be increased. For example, by increasing the proportion of the effective area, it is possible to deal with workpieces having various thicknesses and sizes. For example, a comparative example is assumed in which the segment magnet group 62b of the upper magnet 6b is at the same height as the segment magnet group 62a of the lower magnet 6a. In this comparative example, the lower magnet 6a is a so-called dipole ring magnet. In this comparative example, since the magnetic field H is generated along the horizontal direction, the width of the effective area in the vertical direction is a width W2 that is narrower than the vertical width H1 of the lower magnet 6a. On the other hand, in this embodiment, the magnetic field H extends obliquely between the lower magnet 6a and the upper magnet 6b, so that the vertical range of the effective region S is equal to the vertical width H1 of the lower magnet 6a. The width W1 can be larger than that. That is, in this embodiment, the range of the effective area S in the vertical direction can be made wider than that of the comparative example. In particular, even when the chamber and the annular magnet are reduced in size in order to process a small-diameter workpiece, the effective area can be widened, and the required effective area can be secured even if the size is reduced.

  In order to widen the vertical range of the effective region, for example, in the comparative example described above, a comparative example in which the vertical widths of the segment magnet groups 62a and 62b are further increased is assumed. In this comparative example, each segment magnet is enlarged, and the actuator 68 is enlarged. On the other hand, in this embodiment, the same number of segment magnets as the segment magnets of this comparative example, which is smaller than the segment magnets of the comparative example, can widen the vertical range of the effective area. it can. For this reason, it is not necessary to increase the size of the actuator 68.

  In order to widen the range of the effective area in the vertical direction, for example, a comparative example in which both the lower magnet 6a and the upper magnet 6b are dipole ring magnets is also assumed. In this comparative example, a horizontal magnetic field is generated inside each of the lower magnet 6a and the upper magnet 6b, and when observed from the bottom to the top, the magnetic field strength inside the lower magnet 6a, the lower magnet 6a, and the upper magnet The magnetic field strength in the gap 6b and the magnetic field strength inside the upper magnet 6b change in order. For this reason, the uniformity of the magnetic field strength in the vertical direction can be impaired. On the other hand, in this embodiment, the magnetic field H obliquely passes through the gap between the lower magnet 6a and the upper magnet 6b, so the magnetic field strength inside the lower magnet 6a and the magnetic field in the gap between the lower magnet 6a and the upper magnet 6b. The strength and the magnetic field strength inside the upper magnet 6b can be made the same. The uniformity of the magnetic field strength in the vertical direction is not impaired.

  With reference to FIG. 6, the plasma processing apparatus of Example 2 is demonstrated. The plasma processing apparatus of the present embodiment is the same as the plasma processing apparatus 10 of the first embodiment except that the magnetizing directions of the segment magnet groups 162a and 162b of the annular magnet 106 are different. Below, the annular magnet 106 of Example 2 is demonstrated.

  The arrangement range R3 of the segment magnet group 162a of the lower magnet is the same as the arrangement range R1 of the first embodiment. The magnetization direction of each segment magnet 162 a faces the inside of the annular magnet 106. The magnetization direction of the segment magnet located at the center of the arrangement range R3 is parallel to a straight line passing through the segment magnet and the central axis CL. The magnetization direction of the segment magnet at the end of the arrangement range R3 is not parallel to the straight line passing through the segment magnet and the central axis CL. The magnetization direction of each segment magnet 162a gradually approaches a direction parallel to a straight line passing through each segment magnet 162a and the central axis CL as it approaches the center of the arrangement range R3 from the end of the arrangement range R3. On the other hand, the magnetization direction of each segment magnet 162 b faces the outside of the annular magnet 106. The arrangement range R4 of the segment magnet group 162b of the upper magnet is the same as the arrangement range R2 of the first embodiment. Similarly to each segment magnet 162a, the magnetization direction of each segment magnet 162b is a straight line that gradually passes through each segment magnet 162b and the central axis CL as it approaches the center of the arrangement range R4 from the end of the arrangement range R4. It approaches in the direction parallel to. Also in the present embodiment, similarly to the first embodiment, a magnetic field H extending obliquely along the vertical direction connecting the segment magnet group 162a of the lower magnet and the segment magnet group 162b of the upper magnet is obtained.

Hereinafter, points to be noted regarding the technology shown in the embodiments will be described. The arrangement range of the lower magnet and the arrangement range of the upper magnet do not have to be symmetric with respect to a straight line passing through the central axis when viewed from the central axis direction. For example, the lower magnet arrangement range may be an arcuate range having an angle close to 45 degrees, and the upper magnet arrangement range may be an arcuate range having an angle close to 315 degrees.
Moreover, the space | interval of the arrangement range of a lower stage magnet and the arrangement range of an upper stage magnet may be wider than the space | interval of two adjacent segment magnets in the segment magnet group of a lower stage magnet. For example, when the same number of segment magnets as in the embodiment are arranged, both the lower magnet arrangement range and the upper magnet arrangement range may be an arcuate range having an angle of 90 degrees.
Further, both the lower magnet arrangement range and the upper magnet arrangement range may be included in a partial range of the inner peripheral surface of the annular magnet 6, for example, an arcuate range having 180 degrees.

  The segment magnet group 62a of the lower magnet 6a may face the outside of the lower magnet 6a, and the segment magnet group 62b of the upper magnet 6b may face the inside of the upper magnet 6b.

  Moreover, the horizontal cross section of the magnet holding | maintenance parts 60a and 60b may not be a perfect circle, and may be elliptical. That is, the annular magnet 6 may have an annular shape or an elliptical shape.

  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: annular magnet 6a: lower magnet 6b: upper magnet 10: plasma processing apparatus 30: wiring 40: electrode holder 42: pillar 44: Upper plate 46: pillar 50: outer wall 50a: upper wall 50b: side wall 50c: through hole 52: connecting member 54: movable pillar 56: actuator 60a, 60b: magnet holding portion 62a, 62a: segment magnet 64: connecting member 66: rotation Plate 68: Actuator 90: Work piece 106: Ring magnet 162a, 162b: Segment magnet group B: Magnetic field CL: Center axis E: Electric field R1-R4: Arrangement range S: Effective area

Claims (1)

An apparatus for plasma processing of workpieces,
A lower electrode for placing the workpiece;
An upper electrode disposed on top of the lower electrode;
An annular magnet surrounding a space located between the lower electrode and the upper electrode;
An actuator for rotating the annular magnet around its central axis;
The annular magnet is formed by annularly arranging a plurality of segment magnets around the central axis, and when viewed from the direction of the central axis, an arrangement of segment magnet groups in which the magnetization direction is directed outward. The range and the arrangement range of the segment magnet group whose magnetization direction faces inward are opposed to each other across the central axis, and when viewed from the direction orthogonal to the central axis, One is located on the lower electrode side and the other is located on the upper electrode side.

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