JP2011017088A - Plasma treatment apparatus for applying sputtering film deposition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capacitive coupling type plasma treatment apparatus for sputtering film deposition, wherein an ion flux with a uniform high concentration is formed on the surface of a substrate, without causing re-deposition to a target.SOLUTION: The plasma treatment apparatus is equipped with: an upper electrode 1 provided with a capacitive coupling type mechanism; a target member 2 which is fitted to the upper electrode and made from a nonmagnetic substance; a plurality of magnets 6 which are arranged on the upper surface of the target member, and between the two of them, have equal distance and also have alternately changing magnetic pole polarities; a lower electrode 3 arranged in parallel with the upper electrode; a wafer 17 mounted on the lower electrode; and a high frequency power source 16 which is operated at a frequency in the range of 10 to 300 MHz and connected to the upper electrode via a matching circuit 15.

Description

  The present invention relates to a plasma processing apparatus for sputter deposition applications, and in particular, plasma at a high frequency (HF or VHF) electrode useful for sputtering processing of metals or dielectric materials during the manufacturing process of integrated circuits in the semiconductor industry. The present invention relates to a plasma assisted sputtering apparatus having an improved plasma source capable of independently controlling ion density and ion energy.

  Large area high density plasma sources with high radial uniformity are highly required to process large area substrates without causing charge induced damage to devices assembled on the surface of the substrate. In particular, it is important to develop a new plasma source for sputter processing of metals and dielectric materials with high deposition film uniformity. The difficulty of obtaining the above characteristics in a conventional plasma source is illustrated using two conventional configurations, as shown in FIGS. 6-9, which are typically 200 mm wafer or flat panel plasma. Applied in processing equipment.

  FIG. 6 shows a simplified conventional magnetron type plasma source for use in sputter deposition applications in the semiconductor industry. The reaction vessel 101 includes an upper electrode 102 made of a nonmagnetic metal, a cylindrical side wall 103, and a lower electrode 104. The upper electrode 102 forms a ceiling plate of the reaction vessel 101, and the lower electrode 104 is provided on the bottom plate 105 of the reaction vessel 101. The upper electrode 102 and the lower electrode 104 are parallel to each other over at least a part of the reaction vessel 101. The side wall 103 and the bottom plate 105 are made of a metal such as stainless steel, for example. The side wall 103 and the bottom plate 105 are grounded. The upper part of the side wall 103 extends upward to create a chamber outside the reaction vessel. The side wall 103 has a dielectric ring 106. A target plate 107 made of a material that needs to be sputtered is fixed to the lower surface of the upper electrode 102. In general, the target plate 107 has a slightly smaller dimension than the upper electrode 102. The combined structure of the upper electrode 102 and the target plate 107 is placed on the dielectric ring 106 to electrically insulate from the rest of the reaction vessel 101. Two magnets 108A and 108B having a circular shape and a ring shape are arranged on the upper surface of the upper electrode 102 in a concentric positional relationship as shown in FIGS. The two magnets 108A and 108B are fixed to the upper electrode 102, and a plate 121 used as a magnetic path is disposed on the two magnets 108A and 108B. The central magnet 108A has a cylindrical shape and does not have any cavities as shown in FIG. The outer magnet 108B has a ring shape. The height and width of each of the magnets 108A and 108B is not critical and is selected according to other dimensions of the reaction vessel 101. The magnets 108 </ b> A and 108 </ b> B are disposed on the upper electrode 102 so as to have opposite polarities toward the inside of the reaction vessel 101. The array of magnets 108A and 108B generates a curvilinear magnetic field 109 between these two magnets.

  The upper electrode 102 is connected via a matching circuit 111 to a high frequency power supply 110 that operates at a frequency in the range of 0.1 MHz to 300 MHz. The frequency of the high frequency power supply 110 is normally 13.56 MHz. When the high frequency power supply supplies power to the upper electrode 102, plasma is generated by a capacitively coupled mechanism. Once the plasma is created, the electrons in the plasma are confined in a curvilinear magnetic field, which results in an increase in plasma density in that region.

  The substrate 112 is disposed on the lower electrode 104, and the lower electrode is electrically insulated from the bottom plate 105 through an insulating material 113. The lower electrode 104 may or may not be supplied with high frequency power from a high frequency power source. If the high frequency power is supplied to the lower electrode 104 by the high frequency power source 114 via the matching circuit 115, the frequency of the high frequency power source is usually in the range of 0.1 MHz to 30 MHz as shown in FIG. When a high frequency current is applied to the lower electrode 104, it is negatively biased, thus causing ion collisions on the surface of the substrate 112. Although ion bombardment causes etching on the film deposited on the substrate 112, the self-bias voltage of the lower electrode 104 is controlled so that the film deposition rate exceeds the film etching rate on the substrate 112.

  The other conventional magnetron type sputtering source shown in FIG. 8 is a slight improvement over the aforementioned plasma source given in FIG. Here, the central magnet 108A is disposed in an off-axis mode in order to form an asymmetric magnetic field 109 below the upper electrode 102. A plan view of this magnet arrangement is shown in FIG. This magnet configuration is rotated about the central axis of the upper electrode 102 (shown as a dotted line 116 in the figure). The magnet array formed by the magnets 108A and 108B shown in FIGS. 8 and 9 rotates asymmetrically.

  Further, examples of conventional plasma processing apparatuses using magnets include those shown in Patent Documents 1 to 4.

JP 2000-156374 A JP 59-133370 A Japanese Patent Laid-Open No. 10-021591 Japanese Patent Laid-Open No. 03-240953

  The parallel plate plasma reactor shown in FIG. 6 has several advantages: large area plasma between parallel electrodes, easy ignition of plasma, and controllability of plasma ion energy at the bottom electrode surface. . If the magnet arrangement given in FIG. 6 is used, a donut-shaped bent magnetic field is generated below the upper electrode 102. Once the plasma is ignited, a higher density plasma in the shape of a donut is formed under the upper electrode 102 by the action of confinement by an electron magnetic field. Since this higher density plasma is mainly confined in the region between the magnetic poles of the magnets 108A and 108B, there is a low plasma density in the vicinity of the magnetic poles of the magnet.

  Furthermore, the strength of the magnetic field increases toward the magnetic pole. This causes mirror reflection of electrons, and the mirror reflection causes a low electron density at the magnetic poles of the magnets 108A and 108B. When the electron density is low, the ion density is also low because the ions are also trapped in the plasma by the electrostatic field generated by the electrons.

  As mentioned above, for two reasons, the ion flow at the pole is smaller, resulting in a lower sputtering rate. However, since high-density plasma exists in a donut shape between the magnetic poles of the magnets 108A and 108B, the surface of the target plate 107 corresponding to the region between the two magnets is strongly sputtered. Some of these sputtered atoms are reflected in the original direction due to scattering by gas molecules and are deposited again on the target plate 107. Since the sputter rate is relatively small at locations on the target plate surface corresponding to the magnetic poles, the deposition of sputtered atoms at these locations is dominant. However, the re-deposited film has a low density and sticks loosely on the target plate 107, thus it easily leaves as particles. Furthermore, the target utilization efficiency is greatly reduced due to etching only in the donut-shaped region.

  To avoid redeposition of sputtered material on the target plate 107, the magnets 108A, 108B are asymmetrically positioned and rotated about the central axis 116 of the upper electrode, as shown in FIG. Even if there is redeposition of sputtered material at the location corresponding to the magnetic pole, the redeposited film is immediately sputtered back into the plasma due to the rotation of the magnet. Thus, the source of particles in the plasma is removed.

  However, the plasma generated with the configuration given in FIG. 8 is non-uniform in the radial direction. This causes a non-uniform ion flow on the surface of the substrate 112. This causes local charge buildup created on the substrate surface, especially if the substrate 112 is negatively biased by applying high frequency power to the lower electrode 104, which is Will eventually result in electrical breakdown of sub-micron devices.

  The object of the present invention is to provide a higher ion concentration and higher ion flux uniformity at the surface of the wafer or substrate and no redeposition due to sputtered material return to the target member, It is an object of the present invention to provide a magnetically enhanced capacitively coupled plasma processing apparatus for sputter deposition applications.

  The configuration of the present invention maintains a magnetically enhanced capacitively coupled plasma below the target member. Magnets are provided under the target member to generate a large number of cluster point cusp fields (magnetic fields), so there is a higher magnetic field strength in the vicinity of the target member, which is higher plasma. Resulting in density. The wafer is in an environment without a magnetic field because the magnetic field rapidly weakens toward the lower electrode on which the wafer is placed. This makes it easy to apply high frequency power to the lower electrode for the purpose of applying a negative bias voltage to the wafer. In addition, the rotation of the magnet array prevents the sputtered atoms from redepositing on the target and makes the erosion shape of the target almost uniform.

  The plasma processing apparatus according to the present invention can generate high-density plasma on the lower side of the target member by generating a number of point cusp magnetic fields by using a plurality of magnets having a predetermined arrangement. By controlling the high frequency power applied to each of the upper electrode and the lower electrode, independent control of the plasma density (or ion flux) and the ion energy colliding with the wafer surface can be easily performed. The present invention is magnetically enhanced for sputter deposition applications by having a higher ion concentration at the substrate surface, higher ion flux uniformity, and no re-deposition of sputtered material back to the target member. A capacitively coupled plasma processing apparatus can be provided.

It is sectional drawing of 1st Embodiment which shows a capacitive coupling type electrode, a target member, and a magnet arrangement. The magnet arrangement | sequence used in 1st Embodiment is shown. It is a longitudinal cross-sectional view of 2nd Embodiment. It is a longitudinal cross-sectional view of 4th Embodiment. It is a side view of the sheet | seat and magnet in 4th Embodiment. It is the schematic which shows the 1st conventional plasma source used for plasma processing. FIG. 7 is a top view of the upper electrode shown in FIG. 6. It is the schematic which shows the 2nd conventional plasma source used for the plasma processing. FIG. 9 is a top view of the upper electrode shown in FIG. 8.

  Hereinafter, preferred embodiments will be described with reference to the accompanying drawings. Details of the present invention will be made clear through the description of the embodiments.

FIG. 2 shows a diagram of a plasma source used for the plasma processing apparatus of the embodiment. FIG. 1 shows a cross-sectional view of the plasma processing apparatus, and FIG. 2 shows a magnet arrangement.

  In the above plasma processing apparatus, the reaction vessel 50 includes an upper electrode 1, a target member 2, a lower electrode 3, a cylindrical side wall 21, a ceiling plate (top plate) 22 a, a bottom plate (bottom plate) 22 b, and a wafer holder 23. ing. The target member 2 is provided on the surface of the upper electrode 1. The plurality of magnets 6 are provided in the cavity 13 between the upper electrode 1 and the target member 2 above the upper surface of the target member 2. Further, the reaction vessel 50 has a gas introduction part 4 and a vacuum exhaust part 5. The evacuation unit 5 is connected to a vacuum pump (not shown).

  The upper electrode 1 is made of a metal such as Al (aluminum), for example, and is disposed on a ring 14a made of a dielectric material such as ceramic. The upper electrode 1 has a circular shape. The dimensions of the upper electrode 11 are not critical and depend on the size of the substrate to be processed. The cylindrical side wall 21, the ceiling plate 22a, and the bottom plate 22b are made of metal and are electrically grounded.

  The target member 2 is made of a metal such as copper, needs to be sputtered, and is deposited on the surface of the wafer 17. The wafer 17 is mounted on the lower electrode 3 provided on the wafer holder 23. The target member 2 is strongly fixed to the upper electrode 1 by, for example, bolts or diffusion bonding. The shapes of the upper electrode 1 and the target member 2 are designed such that a cavity 13 exists between the upper electrode 1 and the target member 2. The diameters of the upper electrode and the target member are not critical and are selected depending on the diameter of the wafer 17. For example, if the wafer diameter is 200 mm, the target diameter is in the range of 200 mm to 350 mm. Similarly, the thickness of the target member 2 below the magnet 6 is not an important matter, and is usually about 15 mm.

  The arrangement of the magnets 6 in the cavity 13 between the upper electrode 1 and the target member 2 is shown in FIG. A plurality of magnets 6 are fixed to a circular sheet 7. The magnets 6 are arranged at an equal distance from each other and have alternating polarities. The spacing between any two adjacent magnets 6 is not critical and can vary in the range of 10 mm to 50 mm. The dimensions of each magnet are the same. The cross-sectional shape of the magnet 6 is a square shape or a circular shape. If the cross-sectional shape is a circular shape, its diameter can vary from 5 mm to 40 mm. If the cross-sectional shape is a square shape, equivalent dimensions are employed. The height of the magnet 6 is not an important matter and can be in the range of 5 mm to 30 mm. Furthermore, the strength of the magnetic field 24 of the magnet 6 is likewise not important. Usually, the strength of the magnet 6 is selected so as to generate a magnetic field having a strength of about 100 to 600 gauss on the lower surface of the target member 2.

  When the magnet 6 is arranged on the target member 2 as described above, the magnetic field lines 24 coming out of any magnetic pole will immediately bend toward the magnetic pole having the closest opposite polarity. This magnet arrangement therefore creates a number of point cusp fields. Since the magnets 6 are arranged so as to approach each other, the magnetic field lines 24 bend at a short distance from the magnet 6. Therefore, this magnet arrangement creates a strong magnetic field 24 in the vicinity of the inner region of the target member 2 and decays very rapidly toward the lower electrode 3. Therefore, by maintaining an appropriate distance between the target member 2 and the lower electrode 3, an environment that is not constrained by a magnetic field on the surface of the lower electrode 3 can be obtained.

  One magnetic pole of each magnet 6 is attached to a sheet 7, which is preferably made of metal. The other magnetic pole of each magnet 6 faces the inside of the plasma processing reaction vessel 50. The sheet 7 to which the magnet 6 is attached is in the cavity 13 between the upper electrode 1 and the target member 2, and is fixed with a support portion for the bearing 8. The sheet 7 can be rotated around one central axis of the upper electrode. Further, a small gap, preferably about 1 mm, is provided between the lower surface of the magnet 6 and the upper surface of the target member. In order to rotate the sheet 7 provided with a plurality of magnets 6, the upper surface of the sheet 7 is connected to a motor 9 via appropriate gear devices 10a and 10b. The gear devices 10a and 10b on the upper surface of the seat 7 are connected by a rod 11 made of an insulating material. This is important for removing high-frequency current flowing through the motor 9 and the magnet 6. The rod 11 made of an insulating material is passed through a small hole 12 formed in the upper electrode 1. The diameter of the small hole 12 formed in the upper electrode 1 is made as small as possible, and this is to prevent high-frequency current from flowing into the cavity between the upper electrode 1 and the target member 2. The magnet array including the sheet 7 is rotated at a predetermined frequency, usually about 5 to 10 Hz. The motor 9 is preferably arranged outside the side wall 21 of the reaction vessel 50 and is operated by a DC or AC current. As described above, the magnet array can be rotated, but other different techniques can be used to rotate the magnet array, such as certain types that can eliminate the use of small holes 12. Magnetic coupling can be used.

  The composite structure composed of the upper electrode 1, the target member 2, and the magnet array is electrically insulated from other parts of the reaction vessel 50 by arranging the dielectric rings 14A and 14B. The upper electrode 1 is connected to a high frequency power supply 16 through a matching circuit 15. The frequency of the high frequency power supply 16 is not an important matter and can be in the range of 10 MHz to 300 MHz.

  The lower electrode 3 is connected to the high frequency power source 18 through the matching circuit 19. The lower electrode 3 is supplied with high frequency power from a high frequency power source 18. The frequency of the high frequency power supply 18 is not an important matter and can be changed in the range of 0.1 MHz to 300 MHz. The high frequency power supply 18 can be omitted. If no high frequency power is applied to the lower electrode 3, the electrical state of the lower electrode 3 is floating or grounded. The exact electrical state of the lower electrode 3 is determined by the processing technique of each wafer.

  As shown in FIG. 1, there is a gas introduction device for the plasma processing reaction vessel 50. A circular tube 20 having a plurality of gas inlets 4 is fixed to the inner surface of the side wall 21. However, different techniques for introducing process gas into the reaction vessel 50 can be employed.

  When high frequency power is applied from the high frequency power supply 16 to the upper electrode 1, a high frequency current flows to the lower surface of the target member 2, and plasma is generated by a capacitive coupling mechanism. Due to the magnetic field 24 in the vicinity of the target member 2, electrons in the plasma perform cyclotron rotation and are confined by being brought close to the target member 2. This results in an increase in plasma density. Since the magnet 6 is provided to create a plurality of bent magnetic fields 24 through the lower surface of the target member 2, a high density plasma is generated in each set of bent magnetic field lines 24. Depending on the number of magnets 6 provided, the number of local high-density plasma sites varies. By adjusting a number of magnets 6 that are close to each other, the total number of high-density plasma generation sites can be increased. Therefore, the average plasma density below the target member 2 can be greatly increased compared to those of the conventional plasma source described in the prior art section.

  With the generation of the plasma, the target member is negatively biased because the surface area of the target member 2 is smaller than the area of the grounded surface with which the plasma is in contact. Due to this negative self-bias voltage, ions in the plasma are accelerated toward the target member 2 to gain energy and collide with the target 2. This sputters the target member 2 and the sputtered material goes to plasma. Some of the sputtered atoms from the target member 2 pass through the plasma and deposit on the surface of the wafer 17. Another part of the sputtered atoms is deposited again on the target member 2, which is due to scattering in the gas state. The remaining sputtered atoms are deposited on the cylindrical sidewall 21 exposed to the plasma and other surfaces.

  Once the plasma is generated under the target member 2, electrons and ions in the vicinity of the target member 2 are driven by E × B. Here, E and B are a DC electric field and a magnetic field on the target surface, respectively. However, this E × B drift of the plasma is locally present in a smaller region defined by the spacing of the magnets 6. This is because the magnet 6 is provided so as to eliminate the E × B drift between adjacent magnets. Therefore, this magnet arrangement produces a plasma that is almost uniform in the radial direction by a diffusion process at several cm below the target member 2. Furthermore, there is no redeposition site on the target member 2 due to the rotation of the magnet 6. This also causes almost uniform erosion of the target member 2, which results in increased target utilization efficiency.

  As explained above, there is no magnetic field at the surface of the lower electrode. Therefore, the high frequency power supplied from the high frequency power supply 18 is applied to the lower electrode 3 without disturbing the plasma uniformity on the wafer surface. If a magnetic field is present at the surface of the wafer, the plasma moves toward the other side of the reaction vessel 50 due to E × B drift, where E and B are the DC electric field and magnetic field strengths at the wafer surface, respectively. It is. By applying an appropriate high frequency power to the lower electrode, its self-bias voltage is changed, thereby changing the energy of the ions impinging on the surface of the wafer.

The plasma processing apparatus according to the first embodiment can generate high-density plasma below the target member as compared with those of the conventional plasma source. It can facilitate sputter deposition of a metal film on the wafer with a uniform deposition rate and a uniform erosion rate of the target member. Furthermore, it facilitates independent control of the plasma density (or ion flux) and the energy of ions impinging on the wafer surface by controlling the high frequency power applied to each of the upper electrode 1 and the lower electrode 2. Can do.
Next, a second embodiment of the present invention will be described with reference to FIG. This embodiment is an extension of the first embodiment. The upper electrode 1 in the second embodiment is supplied with a DC bias voltage from a DC power supply 25 in addition to the high-frequency power from the high-frequency power supply 16. This DC power is supplied via a high-frequency cut-off filter 26, and this cut-off filter protects the DC power supply 25 from a high-frequency current from the high-frequency power supply 16. Except for this added structure, all other configurations are the same as those described in the first embodiment. The other components shown in FIG. 3 that are substantially the same as those described in the first embodiment are each given the same reference number.

  In the second embodiment, application of a negative DC voltage greater than the self-bias voltage created by the plasma results in an increase in the sputtering rate of the target member 2. This results in an increase in the deposition rate on the surface of the wafer 17.

  A third embodiment will be described with reference to FIG. The third embodiment is likewise an extension of the first embodiment. The upper electrode 1 in this embodiment is supplied with other high-frequency current from the second high-frequency power source 27 through the matching circuit 28. With the application of the second high-frequency current to the upper electrode 1, two high-frequency filters 29 and 30 are added to the electric circuit. The high frequency filter 29 cuts off the high frequency current coming from the high frequency power supply 16, and the high frequency filter 30 cuts off the high frequency current coming from the high frequency power supply 27. Except for this modification, all other components are the same as those described in the first embodiment.

  The frequency of the second high-frequency power supply 27 is lower than that of the basic high-frequency power supply 16, and is preferably in the range of 0.1 MHz to 30 MHz. Application of a lower high frequency alternating current from the second high frequency power supply 27 results in an increase in the self-bias voltage on the target member. This causes a higher sputter rate of the target member 2, thereby resulting in a higher deposition rate on the wafer surface.

  A fourth embodiment will be described with reference to FIG. This embodiment is also an extension of the above embodiment. That is, the hardware configuration of the fourth embodiment is the same as that of each embodiment except for the arrangement of magnets. Since only the magnet arrangement has been changed, only the magnet arrangement is shown in FIG. FIG. 5 shows a side view of the plurality of magnets and the sheet 7.

  Except for the height of each magnet 6, other dimensions of the magnet, the strength of the magnet, and the interval between the magnets are the same as those described in the first embodiment. The height of the magnet 6 is changed in the radial direction. For example, the height of the magnet 6 becomes shorter toward the center of the sheet 7 or toward the target member 2 as shown in FIG. As another method, the height of the magnet 6 can be changed. For example, the height of the magnet may be shortened toward the outer edge of the sheet 7. The standard for the change in magnet height is as follows.

  When a magnetic field 24 is present as described in the first embodiment, the plasma density increases and the plasma becomes confined within the region of the magnetic field 24. The increase in plasma density and the strength of confinement vary depending on the strength of the magnetic field. Therefore, by changing the height of the magnet, the strength of the magnetic field below the target member 2 is changed, thereby changing the plasma density and plasma confinement. That is, the height of the magnet can be treated as a parameter for controlling the plasma density parameter in the vicinity of the target member. Depending on the type of wafer process, the power applied, and the pressure applied, it is possible to vary the plasma density radial profile (profile) in the vicinity of the target member 2 to obtain a uniform film formation on the wafer surface. is important. In these situations, the height of the magnet can be varied appropriately as described above to obtain a uniform film on the wafer.

  Similarly, by selecting magnets having different strengths of the magnetic field, the strength of the magnetic field 24 can be varied on the underside of the target member 2 by arranging them in a diametrical contrasting pattern.

1 Upper electrode 2 Target plate 3 Lower electrode 6 Magnet 17 Wafer 21 Cylindrical side wall 21b Bottom plate 23 Wafer holder 50 Reaction vessel

Claims (5)

A reaction vessel comprising a gas introduction part and a vacuum exhaust part;
An upper electrode provided in the reaction vessel and capable of attaching a target member;
A plurality of magnets provided above the target member, arranged vertically and horizontally so as to have alternately different polarities and equal distances between the two, and for forming a magnetic field below the target member;
A lower electrode provided in a position opposite to the upper electrode in the reaction vessel, on which a wafer to be processed is mounted;
A plasma processing apparatus for sputter deposition application, comprising: a high-frequency power source connected to the upper electrode via a matching unit and operating at a frequency in a range of 10 MHz to 300 MHz.   The plasma processing apparatus for sputter deposition application according to claim 1, wherein the plurality of magnets are rotated around a central axis of the upper electrode by a rotation mechanism.   The rotating mechanism is made of a motor, a first gear device connected to the motor, a second gear device provided on a seat having the magnet, and an insulator connecting the first and second gear devices. The plasma processing apparatus for sputter deposition application according to claim 2, further comprising a rod.   The plasma processing apparatus for sputter deposition application according to any one of claims 1 to 3, wherein the upper electrode is connected to a DC power source via a high-frequency cut-off filter.   5. The plasma processing apparatus for sputter deposition application according to claim 1, wherein the upper electrode is connected to a second high-frequency power source through a matching portion.

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