JP3265987B2 - Ion irradiation equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion irradiation apparatus, such as an ion implantation apparatus, for irradiating a substrate with an ion beam in a vacuum to perform a treatment such as ion implantation, and more specifically, to an ion irradiation apparatus. The present invention relates to an improvement in means for suppressing charging (charge-up) of a substrate.

[0002]

2. Description of the Related Art An example of this type of ion irradiation apparatus is disclosed in, for example, JP-A-7-78587, which is shown in FIG.

This ion irradiation apparatus basically irradiates a substrate (for example, a wafer) 6 held in a holder 4 housed in a vacuum vessel (not shown) with an ion beam 2 to perform ion implantation or the like. It is configured to perform processing.
The holder 4 has a case of a wafer disk for batch processing and a case of a platen for single-wafer processing. The holder shown in the figure is an example of the former case. Translated from front to back.

On the path of the ion beam 2, a cylindrical Faraday cup 8 for receiving secondary electrons emitted when the ion beam 2 hits the holder 4 and the like and preventing the electron from escaping to the ground is provided. On the upstream side of the holder 4, and further in this example, a catch plate 10 for receiving the ion beam 2 when the holder 4 is translated outside is provided downstream of the holder 4, respectively. The holder 4 and the catch plate 10 are electrically connected in parallel to each other and connected to the beam current measuring device 12.

[0005] The ion beam 2 is applied to the substrate 6 on the holder 4 through the inside of the Faraday cup 8, whereby the substrate 6 is subjected to a process such as ion implantation. At this time, in order to prevent the surface of the substrate 6 from being positively charged and causing problems such as electric discharge due to the irradiation of the ion beam 2, particularly when the surface is an insulator, Take steps.

That is, a first plasma generation vessel 14 is provided outside the Faraday cup 8, and has a small hole 16 in a portion on the Faraday cup 8 side, and has an inside for ionizing, for example, xenon gas or the like. Gas 18 is introduced. In the first plasma generation container 14, a filament 20 is provided.
And a DC filament power supply 22 for the heating is connected to both ends. 51 to 57 are insulators.

In the vicinity of the exit side of the small hole 16 of the first plasma generation vessel 14, a second hole 27 having small holes 27 and 28
A plasma generation container 26 is provided.

In the vicinity of the exit side of the small hole 28 on the Faraday cup 8 side of the second plasma generation vessel 26, the small hole 2
An extraction electrode 32 having a small hole 34 is provided at a position opposing the electrode 8. An end of the extraction electrode 32 on the Faraday cup side is inserted into the Faraday cup 8 through a hole 9 provided in a part of a wall surface of the Faraday cup 8. Both 32 and 8 are set to the same potential.

A coil 38 which is excited by a DC power supply 38 is wound around the outer periphery of a portion extending from the first plasma generation container 14 to the extraction electrode 32, whereby the extraction electrode is drawn out of the first plasma generation container 14. The magnetic flux B is generated along the axial direction in the region extending to the inside 32.

[0010] A cylindrical reflector electrode 46 is provided near the wall surface in the Faraday cup 8. Both 46,
A direct-current reflector power supply 48 is connected between the terminals 8 with the former 46 serving as the negative electrode side.

A DC arc power supply 42 is connected between the second plasma generation vessel 26 and the positive electrode of the filament power supply 22 with the former being on the negative side. A resistor 40 of, for example, about 150Ω is connected between the second plasma generation container 26 and the first plasma generation container 14. A DC extraction power supply 44 is connected between the second plasma generation container 26 and the extraction electrode 32 with the former being the positive electrode side. The output voltages V _{1 to} V _{4 of the} respective power supplies 22, 42, 44 and 48
Typical examples of, V ₁ is 8V, V ₂ is 15V, V ₃ are 5V and V ₄ are 20V.

The thermoelectrons generated from the filament 20 are
The voltage V ₂ applied via the resistor 40 draws the gas to the wall surface side of the first plasma generation container 14, and collides with the gas 18 on the way to ionize it, thereby generating the plasma 24. At this time, the magnetic flux B contributes to generation and maintenance of the plasma 24.

When the plasma 24 is generated, a current flows through the resistor 40 and a potential difference ΔV of, for example, about ten
Occurs. The electrons in the plasma 24 are drawn into the second plasma generation container 26 by the acceleration electric field due to the potential difference ΔV and guided by the magnetic flux B.

A gas 18 flows into the second plasma generation container 26 from the first plasma generation container 14 side, and the electrons extracted therefrom collide with the gas to ionize it, where it is re-emitted. A plasma 30 is created. The ions in the plasma 30 are converted to the voltage (extraction voltage) V
_It is drawn into the Faraday cup 8 by the accelerating electric field by ₃ and guided by the magnetic flux B. At this time,
As the ions move (ie, are pulled by the electric field of the ions), the extraction voltage V
Electrons having an energy higher than ₃ are decelerated by the same voltage V ₃ and guided by the magnetic flux B, and are extracted into the Faraday cup 8 together with the ions. That is, the plasma 30 generated in the second plasma generation container 26 is introduced into the Faraday cup 8. The energy of the electrons in the plasma 30 introduced into the Faraday cup 8 in this manner is a low energy of about 10 eV or less.

The ions in the plasma 30 introduced into the Faraday cup 8 are collected by a reflector electrode 46 having a negative potential, and the electrons in the plasma 30 are pushed back to the center by the reflector electrode 46 and pass therethrough. Is drawn into the ion beam 2 by the electric field.

When the substrate 6 is charged, a potential gradient is generated in the axial direction of the ion beam due to the charge. The electrons drawn into the ion beam 2 are attracted to the substrate 6 by the potential gradient, and the ions on the surface of the substrate are ionized. Neutralizes positive charge associated with beam irradiation. If the positive charges are neutralized, the attraction of electrons into the substrate 6 automatically stops. In this manner, the electrons are supplied to the substrate 6 without any excess or shortage, so that the positive charging of the substrate 6 due to the ion beam irradiation can be effectively suppressed. Moreover, 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.
By utilizing the low-energy electrons in the plasma 30 as described above, negative charging of the substrate 6 can also be suppressed.

[0017]

Considering the structure of the electrons existing in the reflector electrode 46 of the above-mentioned ion irradiation apparatus, in addition to the electrons in the plasma 30 introduced as described above, the electrons emitted from the filament 20 are also considered. Thermal electrons and secondary electrons emitted from the reflector electrode 46 when the ions in the plasma 30 collide with the reflector electrode 46, and these electrons become a problem.

This will be described with reference to the potential distribution diagram of FIG. The potential difference between the negative end of the filament 20 and the Faraday cup 8 is (V ₁ + V ₂ −V ₃ ). As described above, when V ₁ is 8 V, V ₂ is 15 V, and V ₃ is 5 V, the potential difference is 18 V become. Therefore, the energy of the above thermoelectrons is 18 eV at maximum with respect to the Faraday cup 8.
become. The potential difference between the reflector electrode 46 and the Faraday cup 8 is V _4, which is
In the case of V, the energy of the secondary electrons becomes 20 eV at maximum with respect to the Faraday cup 8.

Although the amount of these electrons is smaller than that of the above-mentioned electrons, the amount of the plasma 30 drawn into the Faraday cup 8 increases as the amount of the plasma 30 increases. When a relatively high-energy electron such as and is introduced into the Faraday cup 8, it reaches the substrate 6, and the substrate 6 can be charged negatively to a voltage corresponding to the energy of the electron. So substrate 6
This causes a relatively large negative charge.

Furthermore, in recent years, the device formed on the surface of the substrate 6 has been miniaturized, so that the problem of the negative charging has become more serious.

Accordingly, the present invention reduces the energy of the thermoelectrons emitted from the filament to the Faraday cup and the energy of the secondary electrons emitted from the reflector electrode to the Faraday cup to reduce the negative charge of the substrate. The main purpose is to control.

[0022]

According to the present invention, there is provided an ion irradiation apparatus comprising: a hole provided in a part of a wall surface of the Faraday cup; a hole provided near the outside of the hole; A plasma generating container having a small hole on the cup side, a filament provided in the plasma generating container, and a wall near the inside of the Faraday cup which is electrically insulated therefrom and corresponds to the hole of the Faraday cup A cylindrical reflector electrode having a hole at a position to be communicated, a communication tube communicating between the hole portion of the reflector electrode and the periphery of the small hole of the plasma generation container, and from the inside of the plasma generation container to the inside of the communication tube. In the region, magnetic flux generating means for generating a magnetic flux along their axial direction, a DC filament power supply connected to both ends of the filament, A DC arc power supply connected between the negative electrode of the filament power supply and the plasma generation vessel with the former being the negative electrode side, and a DC arc power supply connected between the negative electrode of the filament power supply and the Faraday cup with the former being the negative electrode side. DC energy setting power supply, further connected the reflector electrode to the positive electrode of the filament power supply,
Further, the output voltage of the energy setting power supply is set to 10 V or less.

According to the above configuration, the plasma is generated in the plasma generating container, and the plasma is guided through the small holes and the communication cylinder of the plasma generating container and guided by the magnetic flux generated by the magnetic flux generating means. Can be introduced. The action of neutralizing the positive charge on the substrate surface by the electrons in the plasma thus introduced is the same as in the case of the conventional example.

Further, the potential difference between the negative end of the filament and the Faraday cup is defined by the output voltage of the energy setting power supply, and does not depend on the output voltage of the filament power supply or the output voltage of the arc power supply. Specifically, it becomes 10 V or less. Therefore, the energy of the thermoelectrons emitted from the filament to the Faraday cup is suppressed to 10 eV or less.

The potential difference between the reflector electrode and the Faraday cup is a value obtained by subtracting the output voltage of the energy setting power supply from the output voltage of the filament power supply, and is usually ± several volts or less. Therefore, when ions in the plasma introduced into the Faraday cup 8 collide with the reflector electrode, the energy of secondary electrons emitted therefrom is several e.
V or less.

Therefore, even if thermions from the filament or secondary electrons from the reflector electrode reach the substrate, the substrate cannot be charged negatively with a voltage higher than the voltage corresponding to the energy of the electrons. In addition, the negative charge of the substrate can be suppressed small.

[0027]

FIG. 1 is a sectional view showing an example of an ion irradiation apparatus according to the present invention. Parts that are the same as or correspond to those in the conventional example of FIG. 3 are denoted by the same reference numerals, and differences from the conventional example will be mainly described below.

In this embodiment, a plasma generating container 14a corresponding to the first plasma generating container 14 of the conventional example is provided near the outside of the hole 9 of the Faraday cup 8 described above. That is, the plasma generation container 14a has the small holes 16 in the part on the Faraday cup 8 side, and the gas 18 is introduced into the inside. A filament 20 is provided inside, and a filament power supply 22 is connected to both ends. The magnitude of the output voltage V _{1 is} the same as that of the conventional example and is, for example, 8V. The diameter of the small hole 16 is, for example, about 2 mmφ.

An arc power source 42 is connected between the negative electrode of the filament power source 22 and the plasma generation vessel 14a, with the former being the negative electrode side, unlike the conventional example. The magnitude of the output voltage V _{2 is} the same as that of the conventional example.
It is. With the above configuration, the plasma 24 can be generated in the plasma generation container 14a in the same manner as in the conventional example.

The aforementioned reflector electrode 46 has a diameter of, for example, 30 at a position corresponding to the hole 9 of the Faraday cup 8.
It has a hole 47 of about mmφ. In this example, the portion of the hole 47 and the periphery of the small hole 16 of the plasma generation container 14a are communicated by a communication tube 60 made of metal. More specifically, in this example, the distal end portion including the small hole 16 of the plasma generation container 14a is inserted into the communication tube 60, and both are electrically insulated by the insulator 52 and vacuum sealed. . In this example, the communication cylinder 60 and the reflector electrode 46 are electrically connected. A portion where the communication tube 60 passes through the hole 9 of the Faraday cup 8 is electrically insulated by an insulator 58.

A DC power supply 3 is provided on the outer periphery of the communication cylinder 60.
The coil 36 excited by the coil 8 is wound insulated from the communication tube 60, and these constitute a magnetic flux generating means, and are arranged in a region from the inside of the plasma generation vessel 14 a to the inside of the communication tube 60. A magnetic flux B is generated along the axial direction. That is, the coil 36 also serves as a magnet for generating the plasma 24 and a magnet for guiding the plasma 24. Note that the direction of the magnetic flux B may be opposite to that shown in the figure.

The reflector electrode 46 is connected to the positive electrode of the filament power supply 22 via the communication tube 60 and is set at the same potential as the positive electrode. However, the communication tube 60 may be made of an insulator, and the reflector electrode 46 may be directly connected to the positive electrode of the filament power supply 22.

A DC energy setting power source 62 is connected between the negative electrode of the filament power source 22 and the Faraday cup 8 with the former being the negative electrode side. The output voltage V ₅ are below 10V.

According to the above configuration, the plasma generation vessel 14
a of the plasma generation container 14a and the communication tube 60.
And into the Faraday cup 8, guided by the magnetic flux B by the coil 36. In this way, the electron energy in the plasma 24 to be introduced into the Faraday cup 8 is defined by the output voltage V ₅ of the energy setting power supply 62. That is, the output voltage V ₅ are the following 10V as described above,
Low energy of 10 eV or less. This plasma 24
The action of neutralizing the positive charge on the substrate surface by the low-energy electrons inside is the same as in the conventional example.

In this embodiment, the energy of thermoelectrons emitted from the filament 20 and the reflector electrode 4
The energy of secondary electrons emitted from 6 will be described with reference to the potential distribution diagram of FIG. In FIG. 2, the voltage V ₁ ,
The V ₂ and V _5, are illustrated in each 8V, 15V and 5V.

The potential difference between the negative end of the filament 20 and the Faraday cup 8 is defined by the output voltage V ₅ of the energy setting power supply 62 and depends on the output voltage V ₁ of the filament power supply 22 and the output voltage V ₂ of the arc power supply 42. Disappears. Specifically, it becomes 10 V or less. Therefore, the energy of the thermoelectrons emitted from the filament 20 to the Faraday cup 8 is suppressed to 10 eV or less.

The potential difference between the reflector electrode 46 and the Faraday cup 8 is a value (V ₁ -V ₅ ) obtained by subtracting the output voltage V ₅ of the energy setting power supply 62 from the output voltage V ₁ of the filament power supply 22. Is less than ± several volts. For example, in the case of the example of FIG. 2, the potential of the reflector electrode 46 is higher by several volts (specifically, 3 V), but depending on the magnitudes of both the voltages V ₁ and V ₅ , this may be reversed. is there. In any case, Faraday Cup 8
When ions in the plasma 24 introduced into the inside collide with the reflector electrode 46, the energy of secondary electrons emitted therefrom is suppressed to several eV or less.

Therefore, even if such thermoelectrons from the filament 20 or secondary electrons from the reflector electrode 46 reach the substrate 6, the substrate 6 is negatively charged to a voltage higher than the voltage corresponding to the energy of the electrons. Therefore, negative charging of the substrate 6 can be suppressed to a small level.

Since the reflector electrode 46 is at a negative potential of (V ₂ -V ₁ ) with respect to the plasma generating vessel 14a, the negative potential causes the ions in the plasma 24 introduced into the Faraday cup 8 to be recovered. In addition, the action of pushing back the electrons in the plasma 24 can be performed.

The holder 4 and the catch plate 1
Instead of setting the potential of 0 to the same potential as the Faraday cup 8 as in the above example, the output voltage V ₆ is about 1 to 2 V by setting the holder 4 to the negative side between them as shown by the broken line in FIG. And a bias power supply 64 of the
May be set to a potential lower than the Faraday cup 8. By doing so, it is possible to restrict electrons having an energy smaller than the energy corresponding to the output voltage V ₆ from reaching the substrate 6.

The coil 36 and the DC power supply 38
Instead of this, a plurality of or single permanent magnets may be provided outside the communication cylinder 60 to generate the magnetic flux B as described above, thereby forming a magnetic flux generating means.

[0042]

As described above, according to the present invention, the potential difference between the negative end of the filament and the Faraday cup is defined by the output voltage of the energy setting power supply and depends on the output voltage of the filament power supply and the output voltage of the arc power supply. No longer. Specifically, it becomes 10 V or less. Therefore, the energy of the thermoelectrons emitted from the filament to the Faraday cup is suppressed to 10 eV or less.

The potential difference between the reflector electrode and the Faraday cup is a value obtained by subtracting the output voltage of the energy setting power source from the output voltage of the filament power source, and is usually ± several volts or less. Therefore, when ions in the plasma introduced into the Faraday cup collide with the reflector electrode, the energy of secondary electrons emitted therefrom is several eV.
It can be suppressed below.

Therefore, even if the thermoelectrons from such a filament or the secondary electrons from the reflector electrode reach the substrate, the substrate cannot be charged more negatively than the voltage corresponding to the energy of the electrons. In addition, negative charging of the substrate can be suppressed to a small level. As a result, it is possible to sufficiently cope with miniaturization of devices formed on the substrate surface.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of an ion irradiation apparatus according to the present invention.

FIG. 2 is a diagram showing an example of a potential distribution at points a to d and g in the apparatus of FIG.

FIG. 3 is a cross-sectional view illustrating an example of a conventional ion irradiation apparatus.

4 is a diagram showing an example of a potential distribution at points a to f in the device of FIG.

[Explanation of symbols]

 2 Ion beam 4 Holder 6 Substrate 8 Faraday cup 14a Plasma generation container 20 Filament 22 Filament power supply 24 Plasma 36 Coil (magnetic flux generating means) 42 Arc power supply 46 Reflector electrode 60 Communication cylinder 62 Energy setting power supply

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01J 37/317 C23C 14/48 H01J 37/20 H01L 21/265

Claims (1)

(57) [Claims] 1. A holder for holding a substrate, and a cylindrical Faraday cup provided upstream of the holder for preventing secondary electrons from escaping to the ground. An ion beam is passed through the Faraday cup. In an ion irradiation apparatus that irradiates a substrate on a holder to perform processing on the substrate,
A hole provided in a part of the wall surface of the Faraday cup,
A plasma generation container provided near the outside of the hole and into which gas is introduced and having a small hole on the Faraday cup side, a filament provided in the plasma generation container, and a wall near the inside of the Faraday cup. Then, a cylindrical reflector electrode which is provided electrically insulated and has a hole at a position corresponding to the hole of the Faraday cup, and a portion of the hole of the reflector electrode and around a small hole of the plasma generation container are arranged. A communication tube to be communicated, a magnetic flux generating means for generating a magnetic flux along the axial direction in a region from the inside of the plasma generation container to the inside of the communication tube, and a DC filament power source connected to both ends of the filament. A DC arc power supply connected between the negative electrode of the filament power supply and the plasma generation vessel with the former being the negative electrode side; A direct current energy setting power supply connected between the negative electrode of the filament power supply and the Faraday cup with the former being the negative electrode side, further connecting the reflector electrode to the positive electrode of the filament power supply, and An ion irradiation apparatus characterized in that the output voltage is set to 10 V or less.