JP2014096297A - Plasma processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma processing apparatus with a simple configuration capable of removing deposits over the whole surface of an inner wall surface of a vacuum chamber without generating abnormal discharge in the vacuum chamber.SOLUTION: A plasma processing apparatus comprises: a vacuum chamber; plasma generation means for generating a plasma in the vacuum chamber; an electrode arranged along one outer wall of the vacuum chamber; and a power supply applying a voltage to the electrode 6 so that ions in the plasma are introduced into an inner wall surface of the vacuum chamber in a state that the plasma is generated in the vacuum chamber. The electrode 6 comprises: a base 61; a plurality of main branch parts 62 extending from the base in a radial direction point-symmetrically with respect to the base; and sub branch parts 63 dividing each space sectioned by the main branch parts adjacent to each other into a plurality of spaces, and protrusively provided to the main branch part. When the voltage is applied to the electrode from the power supply, ions are introduced over the whole surface of the inner wall surface of the vacuum chamber opposed to the electrode.

Description

  The present invention relates to a plasma processing apparatus, and more particularly, to a vacuum chamber, plasma generating means for generating plasma in the vacuum chamber, an electrode disposed along one outer wall of the vacuum chamber, and plasma in the vacuum chamber. And a power source for applying a voltage to an electrode so that ions in the plasma are drawn into an inner wall surface of a vacuum chamber in a generated state.

  Conventionally, such a plasma processing apparatus is known, for example, from Patent Document 1. In this device, planar electrodes are disposed along one outer wall of the vacuum chamber. This electrode has a disk-shaped base and a plurality of branches extending in the radial direction from the base, and the tip of each branch is divided into two branches. When a voltage is applied to such an electrode, ions in the plasma are drawn into the inner wall surface of the vacuum chamber, and deposits on the inner wall surface are removed by sputter etching by the drawn ions.

  By the way, in order to remove deposits over the entire inner wall surface of the vacuum chamber facing the electrode, it is necessary to draw ions over the entire inner wall surface. In the thing of the said patent document 1, the moving means comprised with the motor is further provided, and the electrode is attached to the rotating shaft of this moving means. Then, the electrode is rotated at a constant speed by the operation of the moving means, and the branch portion of the electrode is scanned over the entire outer wall of the vacuum chamber.

  However, if the moving means as described above is provided, there is a problem that the apparatus configuration becomes complicated and the cost is increased. Moreover, it has been confirmed by the present inventors that abnormal discharge occurs in the vacuum chamber when the electrode is rotated by the moving means.

JP-A-10-152784

  In view of the above, the present invention provides a plasma processing apparatus having a simple configuration capable of removing deposits over the entire inner wall surface of a vacuum chamber without causing abnormal discharge in the vacuum chamber. Let that be the issue.

  In order to solve the above problems, the present invention provides a vacuum chamber, plasma generating means for generating plasma in the vacuum chamber, an electrode disposed along one outer wall of the vacuum chamber, and plasma in the vacuum chamber. In a plasma processing apparatus comprising a power source for applying a voltage to an electrode so that ions in the plasma are drawn into the inner wall surface of the vacuum chamber in a generated state, the electrode has a base portion and the base portion as a starting point. A plurality of main branches extending radially from the base so as to be symmetrical, and a follower protruding from the main branch that divides the space defined by the adjacent main branches into a plurality of parts. And when the voltage is applied to the electrode from the power source, ions are drawn over the entire inner wall surface of the vacuum chamber facing the electrode.

  According to the present invention, since the space defined by the adjacent main branches is subdivided by the follower, when a voltage is applied to the main branch and follower of the electrode, the main branch and follower are applied to the main branch and follower. Ions can be drawn over the entire inner wall surface of the opposing vacuum chamber, and deposits can be removed over the entire inner wall surface. In this case, since there is no need to provide a moving means unlike the conventional example, the apparatus configuration can be simplified, and abnormal discharge can be prevented from occurring in the vacuum chamber.

  In the plasma processing apparatus of the present invention, in which the electrode has a circular outline in plan view, the main branch portion is provided at a base portion at intervals of 45 ° or 60 ° in the circumferential direction, and the follower branch portion It is preferable to be provided on one side at equal intervals in the radial direction and in parallel with the other main branches. According to this, the space defined by the main branch portions adjacent to each other can be equally divided by the slave branch portions. In this case, it is preferable that the interval between adjacent follower portions is equal to or greater than the width of the follower portion in plan view. In the present invention, “equivalent” does not mean exact coincidence, but means substantially equal. If the distance between the follower portions is shorter than the width, the induction electric field is shielded and inductive coupling discharge does not occur. For example, the width of the follower portion is preferably set in a range of 3 to 10 mm, and the interval between the follower portions is preferably set in a range of 3 to 25 mm. When the width of the follower portion is longer than 10 mm, or when the interval between the follower portions is longer than 25 mm, the ions are not drawn over the entire inner wall surface, and there are places where deposits remain on the inner wall surface. .

  In the present invention, in the case of further comprising end point detection means for irradiating the substrate surface through the outer wall, receiving reflected light from the substrate surface, and detecting an end point of processing based on the received reflected light, It is preferable that a through-hole that allows transmission of light for end point detection is formed in the base. In this case, since the deposit on the inner wall surface of the vacuum chamber facing the through hole can be removed, the scattering and absorption of the light for endpoint detection by the deposit can be suppressed, so that the endpoint detection can be performed with high accuracy.

  In this invention, it is preferable that the said through-hole is provided with the projection part which protrudes toward a radial inside at predetermined intervals in the circumferential direction. According to this, even if the diameter of the through hole is large (for example, φ5 mm or more), the deposits on the inner wall surface of the vacuum chamber facing the through hole can be removed.

  In the present invention, it is preferable that a quartz plate having a through hole is provided between the inner wall surface and the substrate, and a sapphire plate is installed in the through hole so that light for end point detection passes. The sapphire plate has higher resistance to ion irradiation (less surface roughness) than the quartz plate. Since such a sapphire plate is configured to allow light to pass, it is possible to further suppress scattering and absorption of light for endpoint detection due to surface roughness as compared to the case where light passes through a quartz plate. And since these quartz plates and sapphire plates may be replaced when the amount of deposits reaches a predetermined amount, the maintainability can be improved compared to the case where deposits adhere to the inner wall surface.

The schematic diagram which shows the structure of the plasma processing apparatus of 1st Embodiment of this invention. The top view of the electrode shown in FIG. The schematic diagram which shows the structure of the plasma processing apparatus of 2nd Embodiment of this invention. The top view of the electrode shown in FIG. The photograph which shows the experimental result of this invention.

  Hereinafter, the plasma processing apparatus according to the first embodiment of the present invention will be described with reference to the drawings, taking a dry etching apparatus as an example. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.

  Referring to FIG. 1, M1 is an ICP (inductively coupled plasma) type etching apparatus, and the etching apparatus M1 includes a bottomed cylindrical vacuum chamber 1. The upper opening of the vacuum chamber 1 is closed with a top plate 11 formed of a dielectric material such as quartz. The top plate 11 constitutes one outer wall of the vacuum chamber 1, and the lower surface 11 a constitutes the inner wall surface of the vacuum chamber 1. A flange 1a is provided in the upper portion of the side wall of the vacuum chamber 1, and a concave groove 1b is formed on the upper surface of the flange. A gap between the flange 1a and the top plate 11 is sealed by an O-ring 12 fitted in the concave groove 1b. Yes.

  A substrate stage 2 is provided at the bottom of the vacuum chamber 1 so that the substrate S to be processed can be positioned and held by a known electrostatic chuck (not shown) with its processing surface facing upward. The substrate stage 2 is connected to an output from the high frequency power supply E1 so that a bias potential can be applied to the substrate S. In addition, a heater or a refrigerant flow path may be incorporated in the substrate stage 2 so that the substrate S can be heated or cooled to a predetermined temperature.

  An exhaust pipe 3 leading to vacuum exhaust means such as a vacuum pump (not shown) is connected to the bottom of the vacuum chamber 1 so that the inside of the vacuum chamber 1 can be evacuated. Further, a gas pipe 4 communicating with a gas source is connected to the side wall of the vacuum chamber 1 via a flow rate control means (mass flow controller) (not shown) so that an etching gas can be introduced into the vacuum chamber 1 at a predetermined flow rate. ing.

  A loop antenna coil 5 having a plurality of stages (two stages in the present embodiment) is provided outside the top plate 11, and an output from the high frequency power source E2 is connected to the antenna coil 5 to generate plasma. High frequency power can be input. The antenna coil 5 and the high-frequency power source E2 constitute “plasma generating means” of the present invention.

  An electrode 6 is disposed along the top plate 11 between the top plate 11 and the antenna coil 5. The output from the high-frequency power source E2 is connected to the electrode 6 via a variable capacitor (for example, 10 pF to 100 pF) 7. When a voltage is applied to the electrode 6 in a state where plasma is generated in the vacuum chamber 1, Ions are drawn over the entire lower surface 11 a of the top plate 11 facing the electrode 6.

  Referring to FIG. 2, the electrode 6 includes a base portion 61, and a plurality of (six in this embodiment) main branch portions 62 extending radially from the base portion 61 so as to be symmetric with respect to the base portion 61. , And a sub-branch portion 63 protruding from the main branch portion 62 that divides the space defined by the adjacent main branch portions 62 into a plurality of portions. In the present embodiment, the electrode 6 has a circular outline in plan view, the main branches 62 are provided on the base 61 at intervals of 60 ° in the circumferential direction, and the follower 63 is arranged on one side of the main branch 62. It is provided at equal intervals in the direction and in parallel with the adjacent main branches 62. In this case, the interval d between the adjacent branch parts 63 is preferably equal to or greater than the width w of the branch part 63 in plan view. Here, the cross-sectional shape of the follower portion 63 is not particularly limited, and the follower portion 63 can be formed in, for example, a rectangular shape or a circular shape, and the width w is a flat surface of the follower portion 63. The maximum width when viewed visually. Further, the follower portion 63 is not limited to the one having a constant width from the connection end to the one end with the one side of the main branch portion 62, and the width may be changed. When the width of the follower 63 changes, the width w is the maximum value of the changing width. If the distance d between the follower portions 63 is shorter than the width w, the induction electric field is shielded and inductive coupling discharge does not occur. The width w of the follower 63 is preferably set in the range of 3 to 10 mm, and the distance d is preferably set in the range of 3 to 25 mm. For example, when the width w is set to 4 mm, the interval d is set in the range of 4 to 25 mm. When the width w is longer than 10 mm or when the distance d is longer than 25 mm, ions are not drawn over the entire surface of the top plate lower surface 10a, and there are places where deposits remain on the top plate lower surface 10a. Hereinafter, an etching method using the etching apparatus M1 will be described.

  First, the substrate S is transported and placed on the substrate stage 2 using a transport robot (not shown) in a state where the vacuum exhaust means is operated and the vacuum chamber 1 is evacuated to a desired degree of vacuum. Ar gas is introduced into the vacuum chamber 1 from the gas pipe 4 at a flow rate of 20 to 100 sccm. Next, plasma is generated in the vacuum chamber 1 by applying, for example, 500 W to 2000 W of high frequency power of 13.56 MHz from the high frequency power source E <b> 2 to the antenna coil 5. At the same time, by applying, for example, 100 W to 1000 W of high frequency power of 12.5 MHz to the substrate S, ions are drawn into the substrate and etching is performed. At this time, by applying a voltage of 1000 V to 5000 V to the electrode 6, ions are drawn over the entire inner surface 11 a of the top plate 11, and deposits are removed over the entire inner surface 11 a.

  According to the first embodiment described above, since the space defined by the adjacent main branch portions 62 is subdivided by the follower portion 63, when voltage is applied to the main branch portion 62 and the follower portion 63 of the electrode 6. The ions can be drawn over the entire lower surface 11a of the top plate 11 facing the main branch 62 and the follower 63, and the deposits can be removed over the entire lower surface 11a. In this case, since it is not necessary to provide a moving means unlike the conventional example, the apparatus configuration can be simplified, and abnormal discharge in the vacuum chamber 1 can be prevented.

  Next, the plasma processing apparatus according to the second embodiment of the present invention will be described with reference to FIG. 3 using the etching apparatus M2 as an example. The etching apparatus M2 includes, for example, an interference type film thickness measuring unit as the end point detecting unit 8. As the interference-type film thickness measuring means 8, a well-known device composed of a laser light source, a light receiving unit, an optical system, etc. (not shown) can be used, and therefore detailed description thereof is omitted here.

  A step 1c that is recessed in the radial direction is formed in the upper opening of the vacuum chamber 1, and the quartz plate 13 is placed between the top plate 11 and the substrate S by dropping the quartz plate 13 into the step 1c. The quartz plate 13 has a through hole 13a in the vicinity of the center thereof, and a sapphire plate 14 is installed in the through hole 13a so that light for end point detection can pass therethrough.

  In other words, the laser light emitted from the laser light source of the film thickness measuring means 8 is applied to the surface of the substrate S through the top plate 11 and the sapphire plate 14. The laser light is reflected on the surface of the substrate S. At this time, interference occurs due to the optical path length difference corresponding to the film thickness of the thin film. The reflected light thus interfered is received by the light receiving unit, and the interference intensity of the received reflected light is obtained. The end point of etching can be detected by monitoring the interference intensity by a control means described later.

  Referring to FIG. 4, a base 64 of electrode 60 is provided with a through hole that allows transmission of light for end point detection. Here, if the diameter of the through-hole exceeds φ3 mm, when a voltage is applied to the electrode 60, the portion of ions that are attracted partially facing the base portion 64 of the top plate lower surface 11 a is reduced, so that deposits remain in the portion. Malfunctions can occur. Therefore, by providing a projection 64a projecting radially inward in the circumferential direction at a predetermined interval (for example, 60 °) in the through hole of the base 64, a portion facing the base 64 of the top plate lower surface 11a is provided. Ions can be drawn.

  The etching apparatus M2 includes a control unit C including a computer, a sequencer, a driver, and the like, and the operations of the above-described components, the end point detection unit 8, and the like are controlled in an integrated manner.

  According to the second embodiment described above, the base 64 of the electrode 60 is provided with a through hole that allows transmission of light for end point detection, and the top plate 11 and the sapphire plate 14 that are opposed to the through hole are attached to the base plate 64. Since the removal is performed, the scattering and absorption of the light for detecting the end point due to the adhering matter can be suppressed, so that the end point can be detected with high accuracy. The sapphire plate 14 is more resistant to ion irradiation than the quartz plate 13 (less surface roughness), and is advantageous in that it can suppress light scattering and absorption due to surface roughness.

  In addition, since the quartz plate 13 and the sapphire plate 14 are disposed between the top plate 11 and the substrate S, the deposits on the top plate 11 can be greatly reduced. Since the quartz plate 13 and the sapphire plate 14 may be exchanged when the deposit reaches a predetermined amount, the maintainability can be improved compared to the case where the deposit adheres to the top plate 11.

  In order to confirm the effect of the above embodiment, the following experiment was performed. In this experiment, the substrate to be processed was a silicon substrate having an Au film formed on the surface, and the Au film was etched using the etching apparatus M1. Here, the width w of the follower 63 of the electrode 6 is 4 mm, the interval d is 22 mm, and the etching conditions are: Ar gas flow rate: 50 sccm, process pressure: 0.5 Pa, high frequency power (bias): 12 .5 MHz, 500 W, high frequency power (antenna): 13.56 MHz, 500 W. After the etching, the state of the lower surface 11a of the top plate 11 was confirmed. As a result, as shown in FIG. 5, it was confirmed that deposits were removed over the entire lower surface 11a, and ions could be drawn over the entire lower surface 11a.

  The present invention is not limited to the above embodiment. For example, in the above embodiment, the etching apparatus has been described as an example. However, the plasma processing apparatus is not limited to this, and the present invention can be applied to, for example, a sputtering apparatus. In this case, the end point may be detected by monitoring the film thickness of the thin film formed on the substrate surface by the film thickness measuring means 8. In the etching apparatuses M1 and M2, a permanent magnet can be arranged between the electrode 6 and the antenna coil 5.

  In the above embodiment, the case where six main branch portions 62 are provided in the base 61 at intervals of 60 ° has been described as an example. The same effect can be obtained in this case.

  In the second embodiment, the quartz plate 13 and the sapphire plate 14 are provided between the top plate 11 and the substrate S, but these need not be provided. In this case, it is preferable that the top plate 11 is made of quartz, a through hole is formed in the vicinity of the center, and a sapphire plate is provided so that light for end point detection passes. According to this, compared with the case where light passes through the top plate 11, scattering and absorption of light for end point detection can be further suppressed.

DESCRIPTION OF SYMBOLS M ... Etching apparatus (plasma processing apparatus), 1 ... Vacuum chamber, 6 ... Electrode, 8 ... Film thickness measurement means (end point detection means), 11 ... Top plate (one outer wall), 11a ... Lower surface (inner wall surface), 13 ... quartz plate, 14 ... sapphire plate, 61, 64 ... base, 62 ... main branch, 63 ... follower, 64a ... projection.

Claims (6)

A vacuum chamber, plasma generating means for generating plasma in the vacuum chamber, electrodes arranged along one outer wall of the vacuum chamber, and ions in the plasma are vacuumed in a state where the plasma is generated in the vacuum chamber. In a plasma processing apparatus comprising a power source for applying a voltage to an electrode so as to be drawn into the inner wall surface of the chamber,
The electrode divides a space defined by a base, a plurality of main branches extending in the radial direction from the base so as to be point-symmetric with respect to the base, and a main branch adjacent to each other. And a branch portion projecting from the main branch portion, and when a voltage is applied to the electrode from the power supply, ions are drawn over the entire inner wall surface of the vacuum chamber facing the electrode. A plasma processing apparatus. The plasma processing apparatus according to claim 1, wherein the electrode has a circular outline in plan view.
The main branches are provided at the base at intervals of 45 ° or 60 ° in the circumferential direction, and the follower is provided at one side of the main branch at equal intervals in the radial direction and in parallel with the other main branches. A plasma processing apparatus.   The plasma processing apparatus according to claim 2, wherein an interval between adjacent follower portions is equal to or greater than a width in plan view of the follower portions. In the plasma processing apparatus of any one of Claims 1-3,
Irradiating the substrate surface with light through the outer wall, receiving reflected light from the substrate surface, and further comprising an end point detecting means for detecting an end point of processing based on the received reflected light,
A plasma processing apparatus, wherein a through-hole that allows transmission of light for detecting an end point is formed in a base portion of the electrode. The plasma processing apparatus according to claim 4, wherein
The said through-hole is provided with the projection part which protrudes toward a radial inside at predetermined intervals in the circumferential direction, The plasma processing apparatus characterized by the above-mentioned. The plasma processing apparatus according to claim 4 or 5,
A plasma processing apparatus, wherein a quartz plate having a through hole is provided between the inner wall surface and the substrate, and a sapphire plate is installed in the through hole so that light for end point detection passes.