JPH10172502A - Ion irradiating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an electron in a plasma introduced from a plasma shower device from escaping to a ground potential portion, and efficiently introduce the electron to a substrate. SOLUTION: A reflector cylinder 74 is disposed in the vicinity of an outlet of a plasma shower device 30. A suppresser electrode 80 is disposed at the end upstream of the reflector cylinder 74, and a guiding coil 86 is wound around the vicinity of the end downstream of the reflector cylinder 74. The reflector cylinder 74 is adapted to allow an ion beam 2 to pass therethrough and a plasma 34 to introduce thereinto from the plasma shower device 30, and is made of non-magnetic metal and is made to be a negative potential with respect to a ground potential by a leading power source. The ion beam 2 passes a slot 82 formed at the suppresser electrode 80, which is disposed in such a manner insulative from the reflector cylinder 74 and is made to be a negative potential with respect to the ground potential by a suppresser power source 84. The guiding coil 86 is adapted to generate a magnetic flux 90 along a traveling direction of the ion beam 2 inside the reflector cylinder 74.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of electrically scanning an ion beam by an electric field or a magnetic field, and mechanically scanning a substrate in a direction substantially orthogonal to a scanning direction of the ion beam, so as to scan the ion beam on the substrate. The present invention relates to a so-called hybrid scan type ion irradiation apparatus which performs a process such as ion implantation on a substrate by irradiating a beam, and more specifically to an improvement in means for suppressing charging (charge up) of the substrate.

[0002]

2. Description of the Related Art A hybrid scan type ion irradiation apparatus is disclosed in, for example, Japanese Patent Application Laid-Open No. Hei 4-22900, an example of which is shown in FIG.

This ion irradiation apparatus converts a spot-shaped ion beam 2 extracted from an ion source (not shown) and subjected to mass separation, acceleration and the like as necessary into a scanning power supply 1.
6 are electrostatically driven at a high speed in the X direction (for example, in the horizontal direction; the same applies hereinafter) by the cooperation of the two sets of scanning electrodes 4 and 6 to which the scanning voltages 180 ° out of phase from each other are applied, for example, about several hundred Hz The scanner is configured to perform parallel scanning (parallel scan), and irradiate the substrate (for example, a wafer) 8 held by the holder 10 with a process such as ion implantation.

In this example, the scanning power supplies 16
It outputs scanning voltages + V and −V in the form of triangular waves having a phase difference of 0 °. The scanning signal generator 18 generates a scanning signal S in the form of a triangular wave. High voltage amplifiers 20 and 22 for outputting scanning voltages + V and -V, respectively.

On the other hand, a holder 10 for holding the substrate 8 is attached to an arm 12, and the arm 12 is reciprocated by a reversible motor (for example, a direct drive motor) 14 as shown by an arrow R, so that the holder 10 is ionized. In the scanning area 3 of the beam 2, reciprocating scanning is performed mechanically in a Y direction (for example, a vertical direction; the same applies hereinafter) substantially orthogonal to the X direction. Cooperation with this scanning of the ion beam 2 (hybrid scanning)
Thereby, the entire surface of the substrate 8 is uniformly irradiated with ions.

In the case of the hybrid scan method,
In some cases, the ion beam 2 is scanned by a magnetic field. In some cases, the ion beam 2 is not always scanned in parallel as in this example. The holder 10 may be reciprocated linearly in the Y direction by a linear driving device.

When a substrate is subjected to a process such as ion implantation, the surface of the substrate is positively charged with the irradiation of the ion beam, particularly when the surface is an insulator. There is.

As means for preventing such charging of the substrate, a plasma is supplied in the vicinity of the ion beam, and low-energy electrons in the plasma are drawn into the ion beam by the potential of the ion beam, and are supplied together with the ion beam. A so-called plasma shower system has been proposed in which the substrate is supplied to the substrate and the substrate is prevented from being charged.

An example is shown in FIG. 4 (this figure shows an ion beam 2
This is a diagram viewed from the rear in the traveling direction of the holder 10). The following device is provided in a portion immediately upstream of the holder 10 shown in FIG.

That is, a shower device installation table 66 is provided at a position outside the scanning region 3 of the ion beam 2 in the X direction and not hit by the ion beam 2, and the ion beam scanning region 3 Is generated outside the vicinity of the center 3c of the ion beam scanning region 3 from the direction orthogonal to the ion beam scanning direction X.
And a guide coil 60 for diffusing the plasma 34 from the plasma shower device 30 along the ion beam scanning area 3.

The shower device mounting table 66 is attached to a vacuum container (not shown) for accommodating the holder 10 described above or for keeping the path of the ion beam 2 at a vacuum.
The shower device installation table 66 has a long hole 68 long in the direction along the ion beam scanning region 3 for introducing the plasma 34.
, And in this example, it is made of a non-magnetic metal.

The plasma shower device 30 includes a plasma generation vessel 3 having a small hole 33 on the ion beam scanning area 3 side.
2 in which a gas 38 is introduced. A filament 36 is provided in the plasma generation container 32, and a filament power supply 40 for heating the filament 36 is connected to both ends of the filament 36. An arc power supply 42 is connected between one end of the filament 36 and the plasma generation container 32 so that the negative side of the filament power supply 40 is on the negative side. The plasma generation container 32 is set to the ground potential.

A shower magnet coil 50 serving as a source magnet and a plasma guide is wound around the outside of the plasma generation vessel 32 so as to be electrically insulated therefrom. In the region near the exit, magnetic fluxes along their axial directions are generated. 48 is a bobbin of the coil 50, 46 is an insulator,
Reference numeral 52 denotes a DC power supply for exciting the coil 50. The plasma generation container 32 and the bobbin 48 are made of a non-magnetic metal in this example.

A magnetic flux is generated between the plasma shower device 30 and the shower device mounting table 66 in a direction connecting the plasma shower device 30 and the shower device mounting table 66. A guide coil 60 is provided. 58 is a bobbin of the coil 60, 64 is an insulator, and 62 is a DC power supply for exciting the coil 60. The bobbin 58 is provided with a lid plate 54 having a long hole 56. The cover plate 54 also serves as a plasma extraction electrode, and a negative voltage of, for example, about −10 V to −20 V is applied from the extraction power supply 44. The cover plate 54 and the bobbin 58
Is also made of a non-magnetic metal in this example.

The direction of the magnetic flux generated by the guide coil 60 may be upward or downward in FIG. 4, but when the plasma shower device 30 has the shower device coil 50 as described above, both directions may be used. It is assumed that the directions of the magnetic flux are matched. In this case, the magnetic flux 70 generated by the coils 50 and 60 is connected well without repulsion, and as shown schematically in FIG. 4, the outlet of the plasma 34 of the plasma shower device 30 (ie, the small hole 33). ) From the vicinity to the entire area of the ion beam scanning area 3, the light beam spreads almost symmetrically and at an appropriate angle.

When a predetermined voltage is output from the power supplies 42 and 44, the filament 36 is heated by the power supply 40 and the gas 38 is introduced.
An arc discharge occurs in the tube 2, thereby ionizing the gas 38 to generate a plasma 34. The plasma 34 is guided by the magnetic flux generated by the coil 50 and is guided into the guide coil 60 through the small hole 33. The electrons in the plasma 34 guided into the guide coil 60 in this manner have output voltages of the power sources 40, 42, and 44 of at most 2
Since the voltage is about 0 V or less, the energy is as low as about 20 eV or less at most.

The plasma 34 introduced into the guide coil 60 diffuses right and left along the magnetic flux 70, that is, in the ion beam scanning direction X, and thus diffuses substantially uniformly throughout the ion beam scanning region 3. . As a result, the ion beam 2 diffuses not only near the center 3c of the ion beam scanning area 3 but also anywhere on the ion beam scanning area 3, that is, regardless of the ion beam 2 scanning position. The electrons in the plasma 34 are drawn into the ion beam 2 by the positive potential. The electrons drawn into the ion beam 2 reach the substrate 8 (see FIG. 3) together with the ion beam 2, and neutralize the positive charge accompanying the ion beam irradiation on the substrate surface. In this manner, positive charging of the substrate 8 due to ion beam irradiation can be suppressed. Moreover, since the potential of the substrate surface due to the electrons does not become higher than the energy of the electrons incident thereon on the negative side, the negative charging of the substrate 8 is also suppressed by using the low energy electrons in the plasma 34. be able to. Further, since the guide coil 60 is provided, even when the ion beam 2 is scanned at a high speed as described above, the charging of the substrate 8 due to the ion beam irradiation is suppressed almost uniformly in the entire ion beam scanning region 3. can do.

[0018]

However, in the above-described ion irradiation apparatus, around the ion beam scanning area 3 near the exit of the plasma shower apparatus 30, the above-described shower apparatus installation base 66 and the above-described shower apparatus mounting table 66 are provided. And a part of the electrons in the plasma 34 extracted as described above together with the ion beam 2 and the substrate 8. , But most of the electrons escape to the surrounding earth potential.
For this reason, a sufficient amount of electrons was not supplied to the substrate 8, and the charging of the substrate 8 due to ion beam irradiation could not be sufficiently suppressed. Further, in the above structure, if a sufficient amount of electrons are to be supplied to the substrate 8, the filament 36 constituting the plasma shower device 30 is strongly heated to increase the arc discharge current, thereby reducing the density of the plasma 34 generated there. It must be very high, which will shorten the life of the filament 36. In addition, the peripheral devices are heated by the thermal diffusion accompanying the filament heating or the like, which adversely affects the processing of the substrate 8.

Accordingly, it is a primary object of the present invention to prevent electrons in plasma derived from a plasma shower device from escaping to a ground potential portion and to efficiently guide the electrons to a substrate.

[0020]

An ion irradiation apparatus according to the present invention is provided near an outlet of the plasma shower apparatus, in which plasma from the plasma shower apparatus is introduced, and the ion beam is applied to the inside. A reflector tube made of a non-magnetic metal and having a negative potential with respect to the ground potential, and an upstream portion of the reflector tube which is electrically insulated from the reflector tube. And a suppressor electrode through which the ion beam passes and which is set to a negative potential with respect to the ground potential, and which is wound around the reflector tube, and inside the reflector tube, the ion beam And a guide coil for generating a magnetic flux along the traveling direction.

According to the above configuration, ions in the plasma derived from the plasma shower device are introduced into the reflector cylinder by being pulled to the negative potential since the reflector cylinder has a negative potential. At this time, the electrons in the plasma are also drawn into the reflector cylinder together with the ions by the positive charges of the surrounding ions. In this way, the plasma derived from the plasma shower device is introduced into the reflector cylinder.

Since the ion beam passes through the interior of the reflector cylinder, a part of the electrons in the plasma introduced into the reflector cylinder as described above is drawn into the ion beam by its positive potential, and together with the ion beam, Reach Other electrons try to escape from inside the reflector cylinder because the inside of the reflector cylinder is negative potential.However, since there is a suppressor electrode with a negative potential on the upstream side, it cannot escape to the upstream side and only goes to the downstream side. Can not. A substrate is disposed downstream of the reflector tube, and a gap exists between the substrate and the reflector tube to allow mechanical scanning of the substrate. Since the magnetic flux is formed along the direction of passage of the ion beam by the guide coil wound around, the electrons traveling downstream cannot cross the magnetic flux, and are guided to the substrate by the magnetic flux.

In this way, it is possible to prevent electrons in the plasma derived from the plasma shower device from escaping to the ground potential portion and efficiently guide the electrons to the substrate. As a result, the charge accompanying the ion beam irradiation of the substrate can be efficiently neutralized.

[0024]

FIG. 1 is a cross-sectional view showing an example of the vicinity of a plasma shower device in an ion irradiation apparatus according to the present invention, and corresponds to a BB cross section in FIG. FIG.
FIG. 2 is a cross-sectional view around the reflector cylinder of FIG.
It corresponds to a cross section. Parts that are the same as or correspond to those in the preceding example in FIG. 4 are denoted by the same reference numerals, and differences from the preceding example will be mainly described below. Note that the configuration of the ion irradiation apparatus is the same as that described with reference to FIG. 3, for example, and therefore, reference is made thereto.

In this embodiment, the ion beam scanning region 3 is located near the outlet of the plasma shower device 30 described above, more specifically, below the shower device mounting table 66 (ie, on the ion beam scanning region 3 side). Reflector tube 74 around which the ion beam 2 passes
Are electrically insulated from the shower device installation base 66 by the insulator 72.

In this example, the reflector cylinder 74 has a rectangular tube shape having a rectangular cross section, which has a large width W and a small height H along the ion beam scanning area 3 and is long along the traveling direction of the ion beam 2. You are. The width W of the reflector cylinder 74
Preferably, the height H is set to a minimum dimension that does not allow the ion beam scanning area 3 to hit the ion beam scanning area 3. In this example, the width H is slightly larger than the width and height of the ion beam scanning area 3. It is preferable that the downstream side of the reflector cylinder 74 be close to the holder 10 to reduce the gap 92 between the substrate 8 held by the holder 10 and the downstream end of the reflector cylinder 74.

The upper surface of the reflector cylinder 74 is provided with a long hole 76 such as an ellipse or an ellipse which is long in the direction along the ion beam scanning area 3. The plasma 34 expanded at 60 passes through the elongated hole 76 to the reflector cylinder 7.
4 is introduced.

The reflector cylinder 74 is made of a non-magnetic metal such as stainless steel or aluminum so as to shield a magnetic flux 90 generated by a guide coil 86 described later or not to disturb the magnetic flux 70 described above. In this example, the reflector cylinder 74 is connected to the negative electrode side of the above-described lead-out power supply 44 via a conducting wire 94, thereby being set to a negative potential of about -10V to -20V with respect to the ground potential. However, a DC power supply different from the drawer power supply 44 may be provided to set the reflector cylinder 74 to the negative potential as described above.

An insulator 78 electrically insulates the reflector cylinder 74 from the reflector cylinder 74 so as to cover the upstream end (upstream in the traveling direction of the ion beam 2). 80 are provided. The suppressor electrode 80 has a long hole 82 such as an oval or an ellipse that is long in the direction along the ion beam scanning area 3, and the ion beam 2 passes through the long hole 82. Since the suppressor electrode 80 is provided at the end opposite to the guide coil 86 and is far away from the coil, the suppressor electrode 80 does not necessarily need to be made of a non-magnetic metal. From the viewpoint of preventing the magnetic flux 90 and the magnetic flux 70 described above from being disturbed as much as possible, it is preferable to use a nonmagnetic metal such as stainless steel or aluminum. The suppressor electrode 80 is controlled by a suppressor power supply 84 to a voltage between -10 V and-
A negative potential of about 20 V is applied.

A second guide coil 86 is wound around the vicinity of the downstream end of the reflector cylinder 74. The guide coil 86 is connected to a DC power supply 84 connected thereto.
To generate a magnetic flux 90 in the reflector cylinder 74 along the length direction of the reflector cylinder 74, that is, along the traveling direction of the ion beam 2. However, the direction of the magnetic flux 90 may be opposite to that in the illustrated example.

According to the above configuration, the plasma 34 derived from the plasma shower device 30 is
0, and is spread along the ion beam scanning area 3 so that the reflector cylinder 7
4 and is introduced into the reflector cylinder 74 through the long hole 76. In this case, since the reflector cylinder 74 is at a negative potential, ions in the plasma 34
And is introduced into the reflector cylinder 74.
At the same time, the electrons in the plasma 34 are attracted by the positive charges of the surrounding ions and are introduced into the reflector cylinder 74 together with the ions. Thus, the plasma shower device 3
The plasma 34 derived from 0 is introduced into the reflector cylinder 74.

Since the ion beam 2 passes through the interior of the reflector cylinder 74, a part of the electrons in the plasma 34 introduced into the reflector cylinder 74 as described above is drawn into the ion beam 2 by its positive potential. Ion beam 2
Together with the substrate 8. Other electrons try to escape from the interior of the reflector cylinder 74 because the inside of the reflector cylinder 74 has a negative potential. However, since there is a suppressor electrode 80 with a negative potential on the upstream side, the electrons cannot escape to the upstream side but only to the downstream side. It is not possible. The substrate 8 is disposed on the downstream side of the reflector cylinder 74, and the gap 92 described above exists between the substrate 8 and the reflector cylinder 74.
, The magnetic flux 90 is formed by the guide coil 86 along the ion beam passing direction, so that electrons traveling downstream cannot cross the magnetic flux 90,
The magnetic flux 90 guides the magnetic flux 90 to the substrate 8. Therefore, electrons do not escape from the gap 92 to the ground potential portion.

In this way, the plasma shower device 3
Electrons in the plasma 34 derived from 0 can be prevented from escaping to the ground potential portion, and the electrons can be efficiently guided to the substrate 8 by the magnetic flux 90. As a result, it is possible to efficiently neutralize the charging caused by the irradiation of the substrate 8 with the ion beam. Further, as described in the prior art, there is also a problem that the filament 36 of the plasma shower device 30 is strongly heated, thereby shortening the life of the filament 36 and adversely affecting the substrate processing due to heat diffusion from the filament 36. Absent.

The potentials of the reflector cylinder 74 and the suppressor electrode 80 are set to -10V to -20V as described above.
The reason why it is preferable is that the ions in the plasma 34 introduced into the reflector cylinder 74
Even if secondary electrons are emitted therefrom by colliding with the inner wall of the electrode or the suppressor electrode 80, the energy of the secondary electrons becomes 10 to 20 eV or less. This is because negative charging is not caused.

[0035]

As described above, according to the present invention, since the reflector cylinder, the suppressor electrode and the guide coil as described above are provided, the electrons in the plasma introduced into the reflector cylinder escape to the ground potential portion. To prevent
Since the electrons can be guided to the substrate side by the magnetic flux generated by the guide coil, the electrons can be efficiently guided to the substrate. As a result, the charge accompanying the ion beam irradiation of the substrate can be efficiently neutralized. Also,
There is no problem that the life of the filament constituting the plasma shower device is shortened or the heat diffusion from the filament adversely affects the substrate processing.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example around a plasma shower device in an ion irradiation apparatus according to the present invention, and corresponds to a cross section taken along line BB of FIG.

FIG. 2 is a sectional view around the reflector cylinder of FIG.
AA section of FIG.

FIG. 3 is a perspective view partially showing an example of a hybrid scan type ion irradiation apparatus.

FIG. 4 is a cross-sectional view showing the periphery of a plasma shower device in the ion irradiation apparatus of the prior art.

[Explanation of symbols]

 2 Ion beam 3 Ion beam scanning area 8 Substrate 30 Plasma shower device 34 Plasma 74 Reflector cylinder 80 Suppressor electrode 86 Guide coil 90 Magnetic flux

Claims (1)

[Claims] 1. An ion beam is scanned one-dimensionally, and a holder holding a substrate is mechanically scanned in a direction substantially orthogonal to an ion beam scanning direction to irradiate the substrate on the holder with the ion beam. An ion irradiation apparatus that is provided near the upstream side of the holder and has a plasma shower apparatus that generates plasma and supplies it to the ion beam scanning region.
It is provided in the vicinity of the outlet of the plasma shower device, and has a cylindrical shape through which the plasma from the plasma shower device is introduced, and through which the ion beam passes. A reflector cylinder which is set to a negative potential with respect to the electric potential, and which is provided at an upstream portion of the reflector cylinder so as to be electrically insulated from the reflector cylinder and through which the ion beam passes, and A reflector coil wound around the reflector tube, and a guide coil for generating a magnetic flux along the traveling direction of the ion beam inside the reflector tube. Ion irradiation device.