JP4002317B2 - Plasma sputtering equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plasma sputtering apparatus, and more particularly to an inductively coupled plasma (ICP) type sputtering apparatus.
[0002]
[Prior art]
In the plasma sputtering process, there is a demand for higher density of plasma. The ICP method has been studied as one of such high-density plasma technologies. As shown in FIG. 5, the ICP type sputtering apparatus is provided with a coil 4 in a vacuum chamber 2 of a general direct current bipolar or high frequency bipolar sputtering apparatus, and high frequency power is applied to the coil 4. One that generates density plasma is conceivable.
[0003]
[Problems to be solved by the invention]
In the above-described type of ICP sputtering apparatus, the plasma density tends to be higher in the vicinity of the coil due to the action of the induction electric field generated by the high frequency applied to the coil 4. On the other hand, in the sputtering process, it is required to make the plasma density uniform. Further, in order to reliably fill a high aspect ratio hole or the like, there is a means of ionizing the sputtered atoms to make the sputtered atoms anisotropic. In that case, in particular, ionization in the region above the center of the substrate 6 to be processed. It is necessary to increase the rate. Under such circumstances, it is considered preferable to arrange the coil 4 in the vicinity of the substrate 6 to be processed by making the inner diameter of the coil 4 as small as possible.
[0004]
However, when the inner diameter of the coil 4 is reduced, since the conventional coil 4 is made of copper, adhesion of a metal film to the coil 4 or generation of dust due to resputtering becomes a problem. This problem can be solved by providing an appropriate shield inside the coil 4, but the inner diameter of the coil 4 increases due to the presence of the shield.
[0005]
An object of the present invention is to provide a novel ICP-type plasma sputtering apparatus that can solve the above problems.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a plasma sputtering apparatus that generates inductively coupled plasma in a vacuum chamber, and is a substantially cylindrical one-turn type disposed in the vacuum chamber to generate the inductively coupled plasma. A coil and a high-frequency power source for applying high-frequency power to the coil are provided.
[0007]
When the present invention is applied to a bipolar sputtering apparatus, the coil is disposed between the substrate support means and the target. However, since the coil is substantially cylindrical, it can be used as a shield. The inner diameter can be made sufficiently small.
[0008]
In addition, the coil is made of the same conductive material as the film-forming material, or at least the inner peripheral surface of the coil is covered with the same material as the film-forming material, thereby adhering spatter atoms and generating dust by resputtering. Etc. can be suppressed.
[0009]
When the film forming material is used for the coil as described above, the coil itself can be used as a target by applying a negative potential to the coil. Since plasma is generated near the inner peripheral surface of the coil and tends to be maintained at that position, the ionization rate of sputtered atoms from the coil is improved. Since the substrate support means becomes an anode, the ionized sputter atoms are incident on the substrate on the support means with anisotropy.
[0010]
In order to confine the plasma in the vicinity of the inner peripheral surface of the coil, it is preferable to arrange a plurality of magnets on the outside of the coil to be a magnetron type. In order to make erosion uniform, these magnets may be driven to rotate about the central axis of the coil.
[0011]
Further, when the induction electric field generated by the substantially cylindrical one-turn coil is weak, a spiral coil may be disposed as an auxiliary coil so as to surround the substantially cylindrical coil and connected in series.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 schematically shows a first embodiment of an ICP sputtering apparatus according to the present invention. The illustrated sputtering apparatus is for forming a titanium (Ti) film, and is made of a stainless steel chamber main body 12 constituting a vacuum chamber 10 and a Ti-made electrode disposed at an upper opening portion via an insulating ring 14. And a target 16. A pedestal 18 serving as a substrate supporting means is disposed coaxially with the target 16 inside the chamber body 12. The pedestal 18 is configured to support the semiconductor wafer 20 as a substrate to be processed on the upper surface thereof. The pedestal 18 is made of a conductive material, and is preferably made of Ti that is highly compatible with the Ti sputtering process. The pedestal 18 moves up and down between a process position where the sputtering process is performed by the lift mechanism 22 (position indicated by a solid line in FIG. 1) and a non-process position below it (position indicated by a two-dot chain line in FIG. 1). It is possible to move.
[0013]
An ICP unit 24 for generating plasma used for the sputtering process is disposed in the vacuum chamber 10 of this sputtering apparatus. As clearly shown in FIG. 2, the ICP unit 24 includes a substantially cylindrical coil 26 and a helical coil 28 disposed so as to surround the coil 26.
[0014]
The coil 26 is made of the same conductive material as that of the target 16, that is, Ti, and is substantially cylindrical in appearance. However, the coil 26 functions as a one-turn coil by a slit 30 inserted along the axial direction. Yes. The coil 26 is disposed coaxially with the common axis of the target 16 and the pedestal 18 and has an inner diameter as small as possible. The coil 26 extends from the vicinity of the target 16 to the vicinity of the pedestal 18 at the process position, and is also configured to function as a shield for protecting the chamber body 12 and the like from the sputtered atoms. In FIG. 1, reference numeral 32 indicates a shield for protecting the lower portion that cannot be protected by the coil 26. On the other hand, the outer coil 28 is formed by spirally winding a good conductor, for example, a copper tube, an appropriate number of times, and is connected in series to the substantially cylindrical coil 26, the high-frequency power source 34 and the matching circuit 36. Yes.
[0015]
Further, a negative terminal of a DC power source 38 is connected to the target 16, and a high frequency power source 40 is connected to the pedestal 18 via a matching circuit 42. Further, an Ar gas supply source as a process gas supply means and a vacuum pump for reducing the pressure in the vacuum chamber 10 are connected to the chamber body 12.
[0016]
In the sputtering apparatus having such a configuration, when forming a Ti film on the surface of the semiconductor wafer 20, first, the vacuum pump is operated to depressurize the vacuum chamber 10 to a predetermined degree of vacuum, and then a predetermined amount is supplied from an Ar gas supply source. Ar gas is introduced into the vacuum chamber 10 at a flow rate. Next, the semiconductor wafer 20 is placed on the upper surface of the pedestal 18, and the pedestal 18 is raised and placed at the process position.
[0017]
Thereafter, when the high-frequency power source 34 is turned on and high-frequency power of a predetermined frequency (for example, 2.0 MHz) is applied to the coils 26 and 28, an induction electric field generated by a high-frequency induction magnetic field is formed in the region surrounded by the coils 26 and 28. Occurs. The induced electric field accelerates the electrons existing in the region, thereby generating high-density plasma of Ar gas.
[0018]
When the high frequency power supply 40 is turned on and high frequency power of a predetermined frequency (for example, 1.8 MHz) is applied between the target 16 and the pedestal 18, and the DC power supply 38 is turned on to apply a negative bias to the target 16, plasma is generated. The positive Ar ions inside bombard the target 16 which is negatively charged. When Ar ions collide with the target 16, sputter atoms, that is, Ti particles are ejected from the target 16.
[0019]
The Ti particles are ionized while passing through the high-density plasma generated by the ICP unit 24 and are deposited with anisotropy on the semiconductor wafer 20 placed on the pedestal 18 which is the anode. Is done. Although this operation is the same as that of the conventional configuration, as described above, since the substantially cylindrical coil 26 that defines the plasma generation region also serves as a shield, the inner diameter of the coil 26 is reduced by an amount that does not require the shield. be able to. As a result, it is possible to increase the density of the plasma in the upper region of the central portion of the semiconductor wafer 20 and increase the ionization rate of the Ti particles in the central portion, which was insufficient in the prior art. This increases the anisotropy of the Ti particles to the semiconductor wafer 20 and improves the bottom coverage.
[0020]
Note that the sputtering apparatus of the illustrated embodiment is a planar magnetron type, and a plurality of magnets 44 are disposed above the target 16. The magnetic field formed by these magnets 44 causes electrons to perform trochoidal motion along the surface (lower surface) of the target 16 and confine plasma in the vicinity of the target 16. This also improves the ionization rate of Ti particles in the center.
[0021]
During this sputtering process, Ti particles adhere to the inner peripheral surface of the coil 26. Since the coil 26 is made of the same material as the target 16, the adherence of Ti particles is good. Further, even if resputtering occurs on the coil 26, the resputtered atoms do not become contaminant particles but are deposited on the semiconductor wafer 20 as a film forming material.
[0022]
FIG. 3 schematically shows a second embodiment of the ICP sputtering apparatus according to the present invention. In this embodiment, the Ti substantially cylindrical coil 26 in the ICP unit 24 is also used as a target. For this purpose, in addition to the high frequency power supply 34, a negative terminal of a DC power supply 46 is connected to the coil 26 so as to give a negative potential.
[0023]
A shield 48 is provided at the upper opening of the chamber body 12. The shield 48 is made of Ti or a conductive plate covered with Ti, and is connected to either the ground or the negative terminal of the DC power supply 52 by the changeover switch 50.
[0024]
Further, a plurality of magnets 54 are arranged at equal intervals along the circumferential direction outside the ICP unit 24. These magnets 54 are for confining the plasma generated by the ICP unit 24 in the vicinity of the inner peripheral surface of the coil 26 with a magnetic field. In the illustrated embodiment, the magnet 54 is fixed to the inner wall surface of the chamber body 12, but may be disposed outside the chamber body 12 or may be rotationally driven in the circumferential direction. Other configurations are the same as those in FIG. 1, and the same or corresponding parts are denoted by the same reference numerals, and detailed description thereof is omitted.
[0025]
When the Ti film is formed in such a configuration, the vacuum chamber 10 is depressurized to a predetermined degree of vacuum and Ar gas is introduced into the vacuum chamber 10 as in the first embodiment described above. The pedestal 18 on which the wafer 20 is placed is placed at the process position. Then, the high frequency power supply 34 is turned on and high frequency power is applied to the coils 26 and 28 to generate high density plasma inside the coil 26. The generated high-density plasma tends to gather near the inner peripheral surface of the coil 26 as a characteristic of the ICP method, but the confinement property near the coil is further improved by the action of the magnetic field formed by the surrounding magnet 54. The
[0026]
When the high frequency power supply 34 is turned on and the DC power supply 46 is turned on and a negative potential is applied to the coil 26, Ar ions in the plasma existing in the vicinity of the inner peripheral surface of the coil 26 strike the inner peripheral surface of the coil 26 and Ti particles Sputter. As described above, since the plasma is confined with high density in the vicinity of the coil 26, the sputtering rate becomes extremely high. Moreover, since almost all of the Ti particles sputtered from the coil 26 pass through the high-density plasma near the coil, they are ionized at a very high rate. At this time, if the pressure in the vacuum chamber 10 is increased moderately (several tens of mTorr to 100 mTorr), ionization is further promoted, and Ti particles are scattered in the central portion of the vacuum chamber 10, which is preferable. It is.
[0027]
On the other hand, when the high frequency power supply 40 is turned on and high frequency power is applied between the shield 48 and the pedestal 18, the ionized Ti particles are deposited with anisotropy on the semiconductor wafer 20 on the pedestal 18 that is the anode. When the changeover switch 50 is switched to apply a negative potential to the shield 48, a spatter phenomenon occurs on the lower surface of the shield 48, and Ti particles are released also from the lower surface of the shield 48. Thereby, the distribution of Ti particles in the upper region of the semiconductor wafer 20 can be controlled.
[0028]
As mentioned above, although preferred embodiment of this invention was described in detail, it cannot be overemphasized that this invention is not limited to the said embodiment. For example, in the above embodiment, a high frequency is applied between the pedestal 18 and the target 16 or the shield 48, but a DC voltage may be applied.
[0029]
In the above embodiment, the coil 26 is made of a solid Ti material. However, a conductive substantially cylindrical coil member may be coated with Ti. Of course, the present invention can be applied even when the film forming material is other than Ti.
[0030]
Further, the outer spiral coil 28 is auxiliary, and the number of turns can be set as appropriate, and the coil 28 can be omitted.
[0031]
Furthermore, the slit 30 of the coil 26 can be formed in various shapes in consideration of securing a shielding function, preventing abnormal discharge, countermeasures against short-circuiting due to redeposition, and the like. For example, as shown in FIG. 4, when the slit 30 is formed obliquely with respect to the tangential direction, it is possible to suppress a reduction in the shielding effect at the slit portion.
[0032]
【The invention's effect】
As described above, according to the present invention, since the coil of the ICP unit has a substantially cylindrical shape, it can also be used as a shield. Therefore, when the ICP unit of the present invention is provided in the vacuum chamber, the inner diameter of the coil can be considerably reduced, and the plasma density can be increased even at the inner central portion of the coil. Thereby, when this invention is applied to the conventional bipolar sputtering apparatus, the ionization rate of the sputtered atoms from the center of the target can be improved.
[0033]
In addition, when a substantially cylindrical coil is made of a film forming material or coated with a film forming material, the coil can be used as a target. Since the plasma generated by the ICP method gathers in the vicinity of the coil, when the coil is used as a target, almost all the atoms sputtered from the coil pass through the high-density plasma, and the ionization rate becomes extremely high. .
[0034]
Since the ionized sputtered atoms are incident on the substrate on the supporting means serving as the anode with anisotropy, when the ionization rate is improved according to the present invention, the effect of improving the bottom coverage increases. This is an effective technique corresponding to the progress of high integration and miniaturization of semiconductor devices.
[0035]
Further, when the substantially cylindrical coil is made of a film forming material or coated with the film forming material, there is an effect that problems such as adhesion of sputtered atoms to the coil and generation of dust due to resputtering do not occur.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a first embodiment of a plasma sputtering apparatus to which the present invention is applied.
FIG. 2 is a perspective view schematically showing the configuration of an ICP unit used in the sputtering apparatus of FIG.
FIG. 3 is a schematic view showing a second embodiment of a plasma sputtering apparatus to which the present invention is applied.
FIG. 4 is a partial plan view showing an example of a slit shape of a substantially cylindrical coil.
FIG. 5 is a schematic view showing a conventional ICP type plasma sputtering apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Vacuum chamber, 12 ... Chamber main body, 14 ... Insulating ring, 16 ... Target, 18 ... Pedestal (support means), 20 ... Semiconductor wafer, 22 ... Lift mechanism, 24 ... ICP unit, 26 ... Substantially cylindrical coil, DESCRIPTION OF SYMBOLS 28 ... Spiral coil, 30 ... Slit, 34 ... High frequency power supply, 38 ... DC power supply, 40 ... High frequency power supply, 46 ... DC power supply (bias means), 48 ... Shield, 54 ... Magnet.

Claims (9)

A vacuum chamber, a target, a support means, a substantially cylindrical coil, and a high-frequency power source;
  The target, the support means, and the substantially cylindrical coil are disposed in the vacuum chamber;
  The support means supports a substrate to be processed,
  The target is made of a film forming material, and is disposed to face the support means.
  The substantially cylindrical coil is a one-turn coil having a substantially cylindrical body and having one slit along the axial direction, and the target and the support means are between the target and the support means. Is arranged coaxially with the common axis, and extends from the vicinity of the target to the vicinity of the support means,
  The high frequency power source is connected to the substantially cylindrical coil,
  The substantially cylindrical coil generates inductively coupled plasma by high frequency power applied from the high frequency power source.
Plasma sputtering equipment. The generally cylindrical coil is formed of the film forming the same conductive material as, plasma sputtering apparatus according to claim 1. The plasma sputtering apparatus according to claim 1, wherein at least an inner peripheral surface of the substantially cylindrical coil is coated with the same material as the film forming material. The plasma sputtering apparatus according to claim 2, further comprising a bias unit that applies a negative potential to the substantially cylindrical coil. A vacuum chamber, a shield, a support means, a substantially cylindrical coil, a high frequency power source, and a DC power source
  The shield, the support means, and the generally cylindrical coil are disposed within the vacuum chamber;
  The support means supports a substrate to be processed,
  The shield is made of a conductive material, and is disposed to face the support means.
  The substantially cylindrical coil is a one-turn coil having a substantially cylindrical body and having one slit along the axial direction, and the shield and the support means are provided between the shield and the support means. Is disposed coaxially with the common axis, extends from the vicinity of the shield to the vicinity of the support means, and is made of or coated with a film forming material,
  The high frequency power source is connected to the substantially cylindrical coil,
  The DC power source is connected to the cylindrical coil and applies a negative potential to the cylindrical coil;
  The substantially cylindrical coil generates inductively coupled plasma by high frequency power applied from the high frequency power source.
Plasma sputtering equipment. A plurality of magnets disposed on the outside of the generally cylindrical coil to confine the plasma in the vicinity of the inner peripheral surface of the generally cylindrical coil, plasma sputtering apparatus according to claim 4 or 5. The plasma sputtering apparatus according to claim 6, wherein the magnet is driven to rotate about a central axis of the substantially cylindrical coil. The slit of the substantially cylindrical coil is formed obliquely with respect to the tangential direction in a cross section orthogonal to the central axis of the substantially cylindrical coil. The plasma sputtering apparatus described. Are arranged so as to surround the substantially cylindrical coil, said generally comprises a helical coil connected in series with the high frequency power source and a cylindrical coil, according to any one of claims 1 to 8 Plasma sputtering equipment.

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