JP3367229B2 - Ion processing 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 treatment apparatus, such as an ion implantation apparatus, for irradiating a substrate with an ion beam in a vacuum and performing a treatment such as ion implantation on the substrate.
More specifically, it relates to improvement of means for suppressing the charging (charge-up) of the substrate.

[0002]

BACKGROUND ART The same applicant previously proposed an ion processing apparatus capable of effectively suppressing charging of a substrate due to ion beam irradiation by utilizing low energy electrons in plasma. (Japanese Patent Application No. 5-249)
805).

This will be described with reference to FIG. 4. In this ion processing apparatus, basically, a substrate (for example, a wafer) 6 held by a holder 4 housed in a vacuum container (not shown) is subjected to ion implantation. It is configured to irradiate the beam 2 and to perform processing such as ion implantation on the beam 2.

The holder 4 may be a wafer disk for batch processing or a platen for single wafer processing.
The one shown is an example of the former case, and the arrow A in the vacuum container
It is rotated in the direction and translated in the front and back directions of the paper.

A Faraday system is provided on the path of the ion beam 2 to receive secondary electrons emitted when the ion beam 2 hits the holder 4 and the like, and prevent the escape of the secondary electrons to the ground. A Faraday cup 8 is provided upstream of the holder 4, and in this example, a catch plate 10 that receives the ion beam 2 when the holder 4 is translated outward is provided downstream of the holder 4. Further, the holder 4 and the catch plate 10 are electrically connected in parallel to each other, and are also connected in parallel to the Faraday cup 8 via the current detector 18, and these are connected to the beam current measuring device 7, whereby the ion is detected. The beam current of the beam 2 can be accurately measured.

The ion beam 2 is applied to the substrate 6 on the holder 4 through the Faraday cup 8 so that the substrate 6 is subjected to a process such as ion implantation.

At this time, in order to prevent problems such as discharge from occurring due to positive charging when the surface of the substrate 6, particularly the surface is an insulator, due to the irradiation of the ion beam 2.
A plasma introduction hole 9 is provided in a part of the wall surface of the Faraday cup 8, and a plasma generator 11 is provided outside the plasma introduction hole 9.

The plasma generator 11 has a plasma generator 12 into which a gas for ionization such as xenon gas is introduced and ionizes it by arc discharge or the like to generate plasma 14, and a plasma generator 12 of the plasma generator 12. It is provided with a small hole 13 provided at the outlet part and communicating with the plasma introduction hole 9 of the Faraday cup 8, and a connecting cylinder 15 for connecting the small hole 13 and the plasma introduction hole 9 to each other. The plasma 14 thus introduced is introduced into the Faraday cup 8 through the small hole 13, the connecting cylinder 15 and the plasma introducing hole 9.

The small hole 13 is extremely small, for example, about 1 to 2 mmφ, and it is necessary to provide such a small hole.
Therefore, the conductance of the gas is reduced to prevent the gas introduced into the plasma generation unit 12 of the plasma generation device 11 from flowing into the Faraday cup 8 and reducing the degree of vacuum in the Faraday cup 8 as much as possible. .

A reflector electrode 16 is provided in the peripheral portion of the Faraday cup 8 so as to cover the periphery of the portion where the plasma introduction hole 9 is provided except for the portion of the plasma introduction hole 9. The reflector electrode 16 has a tubular shape (for example, a square tubular shape) corresponding to the Faraday cup 8. The ion beam 2 does not strike the reflector electrode 16.

Between the reflector electrode 16 and the Faraday cup 8, a direct-current reflector power supply 1 for applying a negative voltage to the reflector electrode 16 with respect to the Faraday cup 8.
7 is connected. Plasma 1 generated by ionizing gas in the plasma generator 12 of the plasma generator 11.
The electron energy in 4 is as low as the ionization energy of gas, and more specifically, as low as 10-20 eV or less. Therefore, the reflector power supply 17
The output voltage (i.e. the reflector voltage V _R) is a voltage sufficient to push back the electrons in the plasma 14 to be introduced into the Faraday cup 8, for example, about -30 V.

Ions in the plasma 14 introduced into the Faraday cup 8 are attracted and caught by the reflector electrode 16 having a negative potential. On the other hand, the electrons in the plasma 14 are transmitted to the Faraday cup 8 by the reflector electrode 16.
Of the ion beam 2 passing through the Faraday cup 8 by the electric field.

When the substrate 6 is charged, a potential gradient is generated in the axial direction of the ion beam 2, so that the electrons drawn into the ion beam 2 are attracted to the substrate 6 by the potential gradient and the substrate surface Neutralizes the positive charge that accompanies the ion beam irradiation. When the positive charge is neutralized, the attraction of electrons to the substrate 6 automatically stops. In this way, the electrons are supplied to the substrate 6 without excess or deficiency, so that the positive charging of the substrate 6 due to the ion beam irradiation can be effectively suppressed.

Moreover, since the potential of the surface of the substrate due to the electrons does not become higher than the energy of the electrons incident thereto, the potential of the substrate 6 is negatively charged by utilizing the low energy electrons in the plasma 14. Can also be suppressed.

If it is attempted to supply only the electrons into the Faraday cup 8, it becomes difficult to supply a sufficient amount of electrons due to the space charge limitation, and the space charge limitation becomes stricter as the electron energy is smaller. In this ion treatment device, low energy electrons are extracted together with the ions in a plasma state and introduced into the Faraday cup 8. Therefore, the space charge limitation of the electrons can be relaxed by the ions, and thus the ions can be relaxed. It is possible to supply the Faraday cup 8 with a sufficient amount of low-energy electrons to prevent the substrate 6 from being charged due to the beam irradiation. Further, in this ion treatment device, the low-energy electrons introduced into the Faraday cup 8 are
Since the electric field of the ion beam 2 guides it to the substrate 6 side together with the ion beam 2, the amount of electrons supplied to the substrate 6 naturally decreases when the ion beam is interrupted. Therefore, the substrate when the ion beam 2 is interrupted Negative charging of 6 can be automatically prevented.

[0016]

In the above-described ion processing apparatus, since the small holes 13 of the plasma generator 11 are extremely small as described above, they are formed on the surface of the substrate 6 and scatter with the ion beam irradiation. Vapor generated from the resist or a filament for plasma generation (see, for example, the filament 34 shown in FIG. 3) included in the plasma generation unit 12 of the plasma generation device 11 flows into the vicinity of the small hole 13 and there. The small holes 13 may be clogged up in the Faraday cup 8 and the amount of the plasma 14 introduced into the Faraday cup 8 is reduced, so that the electrons supplied from the plasma 14 to the substrate 6 are reduced. The amount is also reduced, and it becomes impossible to effectively prevent the charging of the substrate 6 due to the ion beam irradiation. As it is, electrostatic breakdown occurs on the surface of the substrate 6. Since there is to fear, I do not go to the translation to be standing.

Therefore, in order to detect whether or not sufficient electrons are supplied to the substrate 6 during the ion beam irradiation, a current detector 18 is provided between the holder 4 and the catch plate 10 and the beam current measuring device 7. A target current I _T flowing through the target current I _T is detected and is detected by the comparison circuit 19.
Compared with a reference value R ₁ set in advance, the target current I
A measure is taken to output the interlock signal S ₁ from the comparison circuit 19 when _T is larger than the reference value R ₁ . When this interlock signal S ₁ is output, for example, the ion beam irradiation on the substrate 6 is immediately stopped by some means.

During the ion beam irradiation, a proper amount of electrons are generated on the substrate 6.
Is supplied to the holder 4 and the catch plate 10, the amount of positive charge due to the ion beam 2 and the amount of negative charge due to electrons are substantially equal to each other, and the target current I _T is substantially 0 or somewhat negative. When the small holes 13 become clogged and the plasma 14 and eventually the electrons from the small holes 13 become insufficient, the target current I _T becomes significantly positive.
Therefore, if the reference value R ₁ is set to be slightly more positive than 0, the target current I _T becomes larger than the reference value R ₁ when the small hole 13 is clogged and the supply amount of the plasma 14 decreases. Therefore, it can be detected by the comparison circuit 19.

However, during the irradiation of the ion beam, secondary electrons are emitted from the substrate 6, the holder 4 and the catch plate 10 due to the irradiation of the ion beam, but the holder 4 is rotated and translated to hit the ion beam 2. Even if the beam current of the ion beam 2 is constant, the amount of emitted secondary electrons fluctuates greatly, and therefore the target current I _T also fluctuates, because the material and location of the target change.
_{If 1} is set strictly, false detection will occur. If the reference value R ₁ is set loosely to prevent this, it is difficult to quickly detect the insufficient supply amount of the plasma 14 due to clogging of the small holes 13 or the like.

The beam current density of the ion beam 2 with which the substrate 6 is irradiated can be variously changed depending on the processing conditions. Depending on the size of the beam current density of the ion beam 2, the amount of the emitted secondary electrons and the plasma 14 can be changed. Since the amount of electrons drawn from the ion beam 2 into the ion beam 2 fluctuates, the target current I _T fluctuates. Therefore, the set value of the reference value R ₁ must be changed according to the beam current density of the ion beam 2. , Very troublesome. If the reference value R ₁ is set to be very loose in order to omit it, it is difficult to quickly detect the insufficient supply amount of the plasma 14 due to clogging of the small holes 13.

Therefore, the present invention is to further improve such a point and to accurately and promptly detect a short supply state of plasma due to clogging of small holes in the plasma generator with one reference value. The main object of the present invention is to provide an ion processing apparatus capable of performing the above.

[0022]

In order to achieve the above object , one of the ion treatment apparatuses according to the present invention is a current detector for detecting a reflector current flowing in the forward direction from the reflector electrode to a reflector power supply, The present invention is characterized by including a comparator circuit that compares the reflector current detected by the current detector with a preset reference value and outputs an interlock signal when the reflector current is smaller than the reference value.

Further, a beam shutter for inserting and removing the ion beam in and out of the ion beam path in the Faraday cup, and a beam shutter for inserting and removing the ion beam in and out of the ion beam path in the Faraday cup are output from the comparison circuit. A shutter drive device may be further provided for blocking the beam by inserting the beam shutter into the ion beam path in response to the interlock signal.

[0024]

A negative voltage is applied to the Faraday cup by the reflector power supply to the reflector electrode. Therefore, when plasma is introduced into the Faraday cup from the plasma generator, the ions in the plasma are negatively charged. Is attracted to and caught by the reflector electrode of the reflector electrode, thereby causing a reflector current to flow in a forward direction from the reflector electrode to the reflector power supply.

When the amount of plasma supplied to the Faraday cup decreases due to clogging of small holes in the plasma generator, the number of ions trapped by the reflector electrode also decreases, and the reflector current decreases accordingly. .

Therefore, by detecting this reflector current with a current detector and comparing it with a preset reference value by a comparison circuit, the plasma supply amount is insufficient due to clogging of small holes in the plasma generator. Can be detected.

Moreover, since a negative voltage is applied to the reflector electrode with respect to the Faraday cup, the secondary electrons emitted from the holder or the like during irradiation of the ion beam are pushed back by this negative voltage, and the reflector electrode. Does not enter. Therefore, the reflector current is not affected by such secondary electrons.

Further, since the reflector electrode is provided in the peripheral portion of the Faraday cup and does not hit the ion beam, the reflector current is hardly affected by the beam current of the ion beam.

Therefore, by determining such a reflector current, only one reference value is required, and it is not necessary to set the reference value loosely. Therefore, the insufficient supply amount of plasma can be accurately and promptly determined. Can be detected.

[0030]

1 is a schematic view showing an ion treatment apparatus according to an embodiment of the present invention. The same or corresponding portions as those of the preceding example of FIG. 4 are denoted by the same reference numerals, and the differences from the preceding example will be mainly described below.

In this embodiment, instead of providing the current detector 18 and the comparison circuit 19 as described above, the reflector current I flowing from the reflector electrode 16 to the reflector power source 17 in the forward direction (the arrow direction in FIG. 1) thereof. a current detector 20 for detecting the _R, by comparing the reference value R ₂ set in advance and reflector current I _R detected by the current detector 20, the inter when the reflector current I _R is smaller than the reference value R ₂ A comparison circuit 21 that outputs the lock signal S ₂ is provided.

Further, in this embodiment, although not essential, the beam shutter 2 which is put in and taken out from the path of the ion beam 2 in the Faraday cup 8 to interrupt the ion beam.
2 and the beam shutter 22 are moved in and out of the path of the ion beam 2 in the Faraday cup 8 as shown by arrow C, and the beam shutter 22 responds to the interlock signal S ₂ output from the comparison circuit 21. And a shutter drive device 23 for blocking the ion beam 2 by inserting 22 into the ion beam path.

The current detector 20 is, for example, a resistor,
A voltage signal proportional to the reflector current I _R flowing therethrough can be output from both ends thereof.

The comparison circuit 21 includes, for example, a comparator or a differential amplifier. Further, an amplifier or the like for amplifying the input / output signal may be provided if necessary.

The shutter drive device 23 is composed of, for example, a reciprocating linear drive source such as a hydraulic / pneumatic cylinder, or a reciprocating rotary drive source such as a motor and a conversion mechanism for converting its rotation into a linear motion.

In this ion processing apparatus, since a negative voltage (that is, the reflector voltage V _R ) is applied to the Faraday cup 8 by the reflector power supply 17 to the reflector electrode 16, the Faraday cup from the plasma generator 11 is applied. When the plasma 14 is introduced into the plasma electrode 8, the ions in the plasma 14 are attracted and captured by the reflector electrode 16 having a negative voltage, so that the ions are forwarded from the reflector electrode 16 to the reflector power source 17 (see FIG. 1). The reflector current I _R flows in the (arrow direction).

When the amount of the plasma 14 supplied to the Faraday cup 8 decreases due to the clogging of the small holes 13 in the plasma generator 11 for the above-mentioned reason, the plasma is also captured by the reflector electrode 16 accordingly. Since the number of ions to be reduced also decreases, the reflector current I _R decreases.

Therefore, the reflector current I _R is detected by the current detector 20 and is compared with the preset reference value R ₂ by the comparison circuit 21 to obtain the reflector current I R.
_The interlock signal S ₂ is output from the comparison circuit 21 when R is smaller than the reference value R ₂ .
It is possible to detect an insufficient supply amount of the plasma 14 due to clogging of the small holes 13 in the plasma generator 11,
As a result, it is possible to detect in advance that charge-up will occur on the substrate 6.

Moreover, since a negative voltage is applied to the Faraday cup 8 from the reflector power supply 17 to the reflector electrode 16, the secondary electrons emitted from the holder 4, the catch plate 10, etc. during the ion beam irradiation are: It is pushed back by this negative voltage and does not enter the reflector electrode 16. Therefore, the reflector current I _R is not affected by such secondary electrons. In this case, the magnitude of the reflector voltage V _R needs to be a voltage sufficient to push back such secondary electrons, but the energy of the secondary electrons is also low energy, which is usually about 10 to 20 eV or less. Therefore, the reflector voltage V _R may be, for example, about −30 V as described above.

Further, since the reflector electrode 16 is provided in the peripheral portion of the Faraday cup 8 and the ion beam 2 does not hit it, the reflector current I _R is
It is hardly affected by the beam current of the ion beam. This can be understood from the fact that the reflector current I _R has a difference of 0.1 mA or less with and without the ion beam as shown in FIG. The beam current with the ion beam in FIG. 2 is 10 mA.

As described above, since the reflector current I _R is hardly affected by anything other than the amount of the plasma 14 supplied into the Faraday cup 8, the reference value is determined by determining such a reflector current I _R. R ₂ may be one, and the reference value R ₂ need not be set loosely and can be set strictly, so that the insufficient supply amount of the plasma 14 from the plasma generator 11 can be detected accurately and promptly. be able to.

For example, referring to FIG. 2, when the reflector voltage V _R is -30 V and the reflector current I _R when the ion beam 2 is not irradiated is I _R1 , the reference value R ₂ is It may be set to be equal to or slightly smaller than _R1 . By doing so, it may be before irradiation of ion beam 2 (without ion beam) or during irradiation (with ion beam), or Regardless of the magnitude of the beam current, it is possible to accurately and promptly detect the insufficient supply amount of the plasma 14 from the plasma generator 11 with one reference value R ₂ .

If the beam shutter 22 and the shutter driving device 23 are provided as in this embodiment, the beam shutter 22 is closed immediately after the interlock signal S ₂ is output from the comparison circuit 21, and the substrate 6 is closed. Since the ion beam 2 irradiated on the substrate 6 can be blocked, when the plasma 14 from the plasma generator 11 falls into a state of insufficient supply, charge-up becomes large on the surface of the substrate 6 and electrostatic breakdown or the like occurs. It can be prevented from happening.

Next, a preferred example of a more specific structure of the plasma generator 11 described above will be described with reference to FIG.

The plasma generator 11 includes the plasma generator 12, the small hole 13 and the connecting cylinder 15 as described above. The plasma generator 12 includes the first plasma generating container 26 and the second plasma generating container 48. , Extraction electrode 5
6, a coil 68 and various power supplies for them.

The first plasma generation container 26 has a small hole 28 in the Faraday cup 8 side, and a gas 32 for ionization such as xenon gas is internally provided via a gas introduction pipe 30. be introduced. A U-shaped filament 34 in this example is provided in the first plasma generation container 26.
The vicinity of the small hole 28 is rounded along the filament 34. A filament power supply 38 for heating the filament 34 is connected to both ends of the filament 34. 36 is an insulator.

In the vicinity of the outlet side of the small hole 28 of the first plasma generating container 26, there are second holes 50 and 52 in the front and rear.
A plasma generation container 48 is provided. Both small holes 50,
52 are aligned with each other, and the small hole 50 faces the small hole 28 of the first plasma generation container 26. This second
The plasma generation container 48 and the first plasma generation container 26 are insulated by a ring-shaped insulator 46.

In the vicinity of the exit side of the small hole 52 on the Faraday cup 8 side of the second plasma generating container 48, the small hole 5 is formed.
The extraction electrode 56 having the above-described small hole 13 is provided at a position opposed to 2. A ring-shaped insulator 55 is provided between the extraction electrode 56 and the second plasma generation container 48.
Is provided.

The extraction electrode 56 and the Faraday cup 8
The metal connecting tube 15 is provided between the plasma introducing hole 9 and the plasma introducing hole 9 without interposing an insulating material. Therefore, the connecting cylinder 15 and the extraction electrode 56 are
Are at the same potential as the Faraday cup 8. In addition,
The connection cylinder 15 and the extraction electrode 56 may be separate bodies as in this example, or may be integrated.

A metal support cylinder 62 is provided in a portion extending from the tip of the first plasma generating container 26 to the outside of the connecting cylinder 15 with ring-shaped insulators 64 and 66 interposed therebetween. Has been. In this example, the support cylinder 62 and the second plasma generation container 48 are connected to each other so that they have the same potential, but this is connected to the second plasma generation container 48 to a plasma generation power source 74 and the like described later. This is to make it easier. The support tube 62 and the second
The plasma generation container 48 is shown as a single body in FIG. 1, but is actually a separate body.

A magnetic field power source 70 is provided outside the support cylinder 62.
Is wound around the first plasma generating chamber 26, so that the magnetic flux B along the axis of the first plasma generating chamber 26 extends from the vicinity of the small hole 28 to the inside of the connecting cylinder 15.
Generate. That is, in this example, the coil 68 and the magnetic field power source 70 form a magnetic flux generating means.
Note that the direction of the magnetic flux B may be toward the first plasma generation container 26 side, which is opposite to that shown in the drawing, and in short, it may be along the axis of the connecting cylinder 15 or the like.

Inside the Faraday cup 8, the reflector electrode 16 that covers the periphery of the portion where the plasma introduction hole 9 is provided except the portion of the plasma introduction hole 9 is provided via an insulator 80. . More specifically, the reflector electrode 16 has a tubular shape (for example, a square tubular shape) corresponding to the Faraday cup 8 and has a hole 79 in a portion corresponding to the plasma introduction hole 9, and this portion is provided with this hole. In the example, a ring-shaped protrusion 84 connected to the Faraday cup 8
Are provided so as not to contact the reflector electrode 16.

In this example, between the second plasma generating container 48 and the filament 34, a direct current plasma is generated with the second plasma generating container 48 side being the positive side via the support cylinder 62 as described above. The power source 74 is connected.
The output voltage of the plasma generating power supply 74 (that is, the plasma generating voltage V _A ) is variable in the range of 0 to 35 V in this example.

Between the second plasma generating container 48 and the first plasma generating container 26, in other words, the plasma generating power source 7
A limiting resistor 72 is connected between the positive side of No. 4 and the first plasma generation container 26. The value of this limiting resistor 72 is
For example, it is about 150Ω.

Further, a direct current drawing power source 76 is connected between the Faraday cup 8 and the filament 34, with the former on the positive side. The output voltage of the extraction power supply 76 (that is, the extraction voltage V _E ) is adjusted and fixed within the range of 5 to 20 V in this example.

In the plasma generator 11, the gas 32 for plasma generation is provided in the first plasma generation container 26.
Is introduced between the first plasma generation container 26 and the Faraday cup 8.
Small hole 2 of plasma generation container 48 and extraction electrode 56
8, 50, 52 and 13 (all have a diameter of, for example, 1 to
2 mmφ), and the conductance to the gas is sufficiently reduced in these small holes 28, 50, 52 and 13, so that the Faraday cup 8 by introducing the gas 32 into the first plasma generation container 26 is connected. The degree of vacuum inside is small.

In the plasma generator 11, the second plasma generation container 48 and the first plasma generation container 26 are connected via the limiting resistor 72, and the plasma 40 is turned on in the first plasma generation container 26. Until the second
The plasma generation container 48 and the first plasma generation container 26 have the same potential, and the plasma generation voltage V _A is applied as it is from the plasma generation power source 74 between the first plasma generation container 26 and the filament 34. Therefore, the thermoelectrons emitted from the filament 34 are attracted to the first plasma generation container 26 side by the plasma generation voltage V _A and collide with the gas 32 introduced into the first plasma generation container 26 on the way. It is ionized, so that the plasma 40 is generated in the first plasma generation container 26. At this time, since the magnetic flux of the coil 68 is generated along the axial direction even in the vicinity of the small hole 28 as described above, this magnetic flux contributes to the generation and maintenance of the plasma 40.

As described above, the first plasma generation container 2
When the plasma 40 is generated in the plasma generator 6,
Through the first plasma generation container 26 and the filament 34
Since a current flows between them, a voltage drop occurs in the limiting resistor 72, and a potential difference ΔV of, for example, about a dozen V is generated between the second plasma generation container 48 and the first plasma generation container 26.
As a result, the voltage applied to the first plasma generation container 26 decreases, so that the plasma 40 generated in the first plasma generation container 26 becomes relatively thin.

Since the potential difference ΔV is generated between the second plasma generation container 48 and the first plasma generation container 26,
Due to the acceleration electric field generated thereby, the first plasma generation container 2
The electrons 42 in the plasma 40 in 6 are extracted into the second plasma generation container 48. The energy of the electrons 42 is from the acceleration energy (this is V _A or V _A plus the voltage of the filament power source 38, for example, about 20 to 25 eV) from the ionization energy (for example, 20 to 25 eV) of energy emitted from the filament 34. It is a low energy of about 30 eV obtained by adding energy (that is, about 10 eV) corresponding to the above-mentioned potential difference ΔV to tens of eV obtained by subtracting about 10 eV), but as described above, the magnetic flux B of the coil 68 is
Are generated from the vicinity of the small hole 28 to the inside of the connecting cylinder 15 along the axial direction thereof, so that the electrons 42 are guided by the magnetic flux B and efficiently along the magnetic flux B in the second plasma generation container 48. Be withdrawn.

The gas 32 has flowed into the second plasma generation container 48 from the first plasma generation container 26 side, and the electrons 4 extracted into the second plasma generation container 48.
2 collides with this gas and ionizes it, so that the plasma 14 is generated again in the second plasma generation container 48. The ionization energy of the gas 32 is about 10 eV, so 3
It can be sufficiently ionized by the electrons 42 having an energy of about 0 eV. Moreover, in the second plasma generation container 48, the electrons 42 make multiple collisions with gas molecules in the process of swirling around the magnetic flux B, so that the ionization efficiency of the gas 32 is high, and therefore, in the second plasma generation container 48. , A plasma 1 having a higher density than the plasma 40 in the first plasma generation container 26 (for example, 3 to 4 times higher density)
4 is generated.

That is, the following effects can be obtained by using the two plasma generating vessels 26 and 48 like the plasma generator 11. That is, in order to supply a sufficient amount of electrons into the Faraday cup 8, the plasma density must be high. In that case, if the dense plasma 40 is created in the first plasma generation container 26 without supplying the second plasma generation container 48 and the concentrated plasma 40 is to be supplied into the Faraday cup 8, in order to do so, the electrons emitted from the filament 34 are generated. It is necessary to increase the amount and the amount of gas 32 for plasma generation.
However, in this case, the filament 34 is consumed quickly, and a large amount of gas 32 leaks into the Faraday cup 8, so that the degree of vacuum in the Faraday cup 8 also deteriorates.

On the other hand, this plasma generator 11
Then, the plasma 40 generated in the first plasma generation container 26 may be thin, and the electrons 42 in the plasma 40 may be thin.
To generate the strong plasma 14 in the second plasma generation container 48, and draw it out to draw the Faraday cup 8
I am trying to supply it inside. As a result, the amount of electrons emitted from the filament 34 can be reduced, so that the consumption of the filament 34 can be delayed and the life thereof can be extended. Moreover, the first plasma generation container 2
Since the amount of the gas 32 supplied into 6 can be reduced and the gas 32 leaking from the first plasma generation container 26 into the second plasma generation container 48 is converted into plasma again there, the small holes 28, Since the conductance to the gas is sufficiently reduced at 50, 52, and 13, the amount of the gas leaking into the Faraday cup 8 is very small, and therefore, the vacuum degree decrease (that is, the gas pressure increase) in the Faraday cup 8 is very small. Can be suppressed. As a result, it is possible to prevent the ion beam 2 and gas molecules from colliding with each other to generate neutral particles and to prevent problems such as injection amount error.

As described above, the second plasma generation container 4
Ions in the plasma 14 generated in the plasma generator 8 are generated in the potential difference (V) between the second plasma generation container 48 and the extraction electrode 56.
_A- V _E ) and the magnetic flux B generated by the coil 68 in cooperation with the accelerating electric field, and the magnetic flux B in the coupling cylinder 15 guides the plasma into the plasma introduction hole. Introduced through 9. At this time, the electrons in the plasma 14 in the second plasma generation container 48 are pulled by the electric field of the ions extracted as described above, and are extracted in the same manner as the ions together with the ions and introduced into the Faraday cup 8. It Faraday cup 8 pulled out in this way
The ions and electrons introduced into the interior are mixed with each other and are in a plasma state.

That is, the plasma 14 generated in the second plasma generating container 48 is drawn out into the connecting cylinder 15, and this is guided by the magnetic flux B and introduced into the Faraday cup 8.

Plasma 1 in the second plasma generation container 48
Since the energy of the electron 42 used to make 4 is about 30 eV as described above, the energy of the electron in the plasma 14 is about 20 eV or less obtained by subtracting the energy 10eV required for the ionization of the gas 32 from this 30 eV. It is distributed in. Among the electrons having such an energy distribution, electrons having an energy of about 10 eV to 20 eV enter the connecting cylinder 15 through the extraction electrode 56, together with the ions, the electric field of the ions and the magnetic flux B by the coil 68.
With the guide of, it is extracted as plasma. At this time, the electrons are decelerated by the potential difference between the second plasma generation chamber 48 and the extraction electrode 56 (V _A -V _E),
When this potential difference is, for example, 10 V, the energy of the electrons extracted together with the ions in the connecting cylinder 15 is mainly distributed to about 10 eV or less.

For the above reason, the energy of the electrons extracted with the ions in the connecting cylinder 15 is 10 eV.
Low energy of about 20 eV or less at most. Such low-energy electrons are very convenient for antistatic charging of the substrate. This is because the problem of charging the substrate is
Since the degree of integration of elements formed on the surface of the substrate increases, the energy of the electrons used for charge suppression is preferably as low as possible in consideration of the negative charging by the electrons, and generally 20 eV or less. Because it is necessary to suppress it.

Plasma 1 drawn out as described above
The low-energy electrons in 4 easily diverge as they are, and easily hit the wall surface of the connecting cylinder 15 and disappear. Therefore, in the plasma generator 11, as described above, the coil 68 is used to generate the magnetic flux B along the axial direction in the region from the vicinity of the small hole 28 of the first plasma generation container 26 to the inside of the connecting cylinder 15. As a result, the low-energy electrons in the plasma 14 are efficiently guided to the Faraday cup 8 along the magnetic flux B while being guided by the magnetic flux B while rotating around the magnetic flux B. It is efficiently introduced into the inside through the plasma introduction hole 9. That is, the existence of the magnetic flux B suppresses the electrons from hitting the wall surface of the connecting cylinder 15 and disappearing, so that the electrons in the plasma 14 are efficiently guided into the Faraday cup 8 even if the energy thereof is low.

As described above, the coil 68 and the magnetic field power source 70 for the coil 68 generate the plasmas 40 and 54 in the first plasma generating container 26 and the second plasma generating container 48.
Means for efficiently and stably generating heat and the connecting cylinder 15
It also serves as a means for efficiently transporting the low-energy electrons inside the Faraday cup 8.

As described above, the ions in the plasma 14 introduced into the Faraday cup 8 as described above are attracted and caught by the reflector electrode 16 having a negative potential. On the other hand, the electrons in the plasma 14 are pushed back to the central portion of the Faraday cup 8 by the reflector electrode 16 and are drawn into the ion beam 2 passing through the Faraday cup 8 by the electric field thereof, which in turn causes the substrate 6 Neutralize the positive charge.

Further, in this example, a ring 86 made of a ferromagnetic material such as soft iron is provided so as to surround the vicinity of the plasma introduction hole 9 of the Faraday cup 8. If such a ring 86 is provided, the coil 68
Since the magnetic force lines coming out of the ring 86 are drawn into the ring 86 and pass through the ring 86, the magnetic flux B from the outlet of the connecting cylinder 15 to the vicinity of the plasma introduction hole 9 is suppressed from spreading and is applied to the axis of the connecting cylinder 15. Approaching parallel. That is, the magnetic flux B can be made parallel to its axis over a long distance.
As a result, the low-energy electrons in the plasma 14 extracted in the connecting cylinder 15 as described above are
Since it can be more reliably prevented from hitting the Faraday cup 8 at the wall near the exit of the plasma or the portion of the plasma introduction hole 9 and disappearing, it is possible to easily enhance the transport efficiency of low energy electrons into the Faraday cup 8. it can.

The drawing power source 76 may be connected between the Faraday cup 8 and the second plasma generating container 48 with the former side being the negative side, instead of being connected as shown in FIG.
In that case, the output voltage (drawing voltage) V _E of the drawing power source 76 becomes the voltage between the second plasma generation container 48 and the drawing electrode 56 as it is.

The coil 68 and the magnetic field power source 70 are also provided.
Instead of the above, a plurality of permanent magnets may be provided outside the support cylinder 62 to generate the magnetic flux B as described above, and thereby the magnetic flux generating means may be configured.

[0073]

Since the present invention is configured as described above, it has the following effects. According to the invention of claim 1
For example, if the small holes in the plasma generator are clogged,
When the amount of plasma supplied to the on-beam path decreases,
Reflector with a negative voltage applied to the potential part of the holder
Ion trapped in the electrode is reduced and reflector current is reduced
Therefore, the comparator circuit compares this reflector current with the reference value.
By comparison, the small holes in the plasma generator are clogged.
It is possible to detect the insufficient supply of plasma due to
it can. Moreover, this reflector current is
The influence of secondary electrons emitted from the holder etc. due to irradiation is
Not affected by the influence of the beam current of the ion beam
Since it receives almost no
Therefore, the reference value can be one, and
Since it is not necessary to set the reference value loosely, the plasma
It is possible to detect the supply shortage condition accurately and promptly.
It

According to the second aspect of the present invention, if the amount of plasma supplied into the Faraday cup decreases due to clogging of small holes in the plasma generator, the reflector current decreases. By comparing with the reference value in the circuit, it is possible to detect the insufficient supply amount of plasma due to clogging of small holes in the plasma generator. Moreover, this reflector current is not affected by the secondary electrons emitted from the holder or the like due to the ion beam irradiation, and is hardly affected by the magnitude of the beam current of the ion beam. Therefore, the reference value may be one, and it is not necessary to set the reference value loosely. Therefore, the insufficient supply amount of plasma can be detected accurately and promptly.

According to the invention of claim 3 , as soon as the interlock signal is output from the comparison circuit, the beam shutter can be closed to block the ion beam applied to the substrate. It is possible to prevent the occurrence of electrostatic breakdown and the like due to large charge-up on the surface of the substrate when the amount of plasma is insufficient.

According to the fourth aspect of the present invention, plasma is generated in the second plasma generation container, and ions and low-energy electrons are extracted from the plasma into the connecting cylinder in a plasma state in which both are mixed, and this is generated by a magnetic field. Since it can be introduced into the Faraday cup while guiding, low energy electrons can be efficiently introduced into the Faraday cup. Moreover, the plasma is supplied to the first plasma generation container and the second plasma generation chamber.
Since the plasma is generated in two stages, that is, in the first plasma generation container, a strong plasma can be generated in the second plasma generation container even if the plasma in the first plasma generation container is thin. The amount of electrons emitted from the inner filament can be reduced, and the life of the filament can be extended. In addition, the amount of gas supplied into the first plasma generation container can be reduced, and the gas leaked into the second plasma generation container is converted into plasma again there. Since the conductance with respect to the gas is sufficiently reduced in each small hole of the plasma generation container and the extraction electrode, it is possible to suppress the decrease in the degree of vacuum in the Faraday cup due to the introduction of the gas into the first plasma generation container to a very small level. As a result, it is possible to prevent the collision of the ion beam and the gas molecules to generate neutral particles and to prevent a defect such as an injection amount error.

The invention of claim 5 also has the same effect as that of the invention of claim 4 , since only the way of connecting the drawing power source is changed.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an ion processing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a reflector voltage-reflector current characteristic with and without an ion beam.

FIG. 3 is a cross-sectional view showing a detailed example around the plasma generator in FIG.

FIG. 4 is a schematic view showing an example of an ion treatment apparatus which is the background of the present invention.

[Explanation of symbols]

2 ion beam 4 holder 6 substrate 8 Faraday cup 9 Plasma introduction hole 11 Plasma generator 12 Plasma generator 13 small holes 14 plasma 16 reflector electrode 17 Reflector power supply 20 Current detector 21 Comparison circuit 22 beam shutter 23 Shutter drive device

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01J 37/317 H01L 21/265

Claims (5)

(57) [Claims] 1. A holder for holding a substrate, comprising:
Beam to the substrate on the holder to process the substrate.
Device provided on the upstream side of the holder.
To introduce plasma into the path of the ion beam
Plasma is generated by ionizing the gas with the plasma introduction hole of
A small hole leading to the plasma introduction hole
Through the small hole and the plasma introduction hole.
Plasma that introduces plasma into the path of the ion beam
And the ion generator so that the ion beam does not hit.
Of the portion where the plasma introduction hole is provided.
A reflector that covers the surroundings except for the plasma introduction hole.
Electrode and the reflector electrode to the potential part of the holder.
Equipped with a direct current reflector power supply that applies a negative voltage to
In the ion treatment device,
Check the reflector current flowing in the forward direction of the reflector power supply.
Output current detector and the reflector detected by this current detector.
Reflector current by comparing it with a preset reference value.
The interlock signal when the
And an ion comparison circuit for outputting.
Processing equipment. 2. A holder for holding a substrate, a Faraday cup having the same potential as that of the holder and provided on the upstream side of the holder to prevent escape of secondary electrons to the ground, and this Faraday cup. And a plasma introduction hole provided in a part of the wall surface of the Faraday cup for generating plasma by ionizing gas. The small hole and the plasma introduction hole communicate with the plasma introduction hole of the Faraday cup. Through a plasma generator that introduces plasma into the Faraday cup through the Faraday cup, and a plasma introduction hole inside the Faraday cup that is insulated from the periphery of the Faraday cup so that it does not hit the ion beam. A reflector electrode that covers the periphery of the part excluding the plasma introduction hole part, and a Faraday cup on this reflector electrode. A direct current reflector power supply for applying a negative voltage to the substrate, and an ion processing apparatus for processing the substrate by irradiating the substrate on the holder with an ion beam through the Faraday cup, in the forward direction from the reflector electrode to the reflector power supply. Comparing circuit that compares the current detector that detects the reflector current flowing through the sensor with the reflector current detected by this current detector and a preset reference value, and outputs an interlock signal when the reflector current is smaller than the reference value. An ion processing apparatus comprising: A beam shutter 3. is out in the path of the ion beam intermittently an ion beam, there is for loading and unloading the beam shutter in the path of the ion beam, an interlock signal output from the comparator circuit 3. The ion processing apparatus according to claim 1, further comprising: a shutter driving device that inserts a beam shutter into the path of the ion beam to block the beam in response to the above. 4. The first plasma generation container, wherein the plasma generator is provided outside the plasma introduction hole of the Faraday cup, has gas introduced therein, and has a small hole on the Faraday cup side; Filament provided in the first plasma generation container, a second plasma generation container provided in the vicinity of the exit side of the small hole of the first plasma generation container and having small holes in the front and rear, and a Faraday of the second plasma generation container A lead electrode provided near the outlet of the small hole on the cup side and having a small hole and having the same potential as the Faraday cup, and a connection for connecting the lead electrode and the plasma introduction hole of the Faraday cup. In the region between the cylinder and the small hole of the first plasma generation container to the inside of the connecting cylinder,
A magnetic flux generating means for generating magnetic flux along those axes, a filament power source for heating the filament, and a direct current plasma generating power source connected between the second plasma generating container and the filament with the former on the positive side. , claim 2 comprising a limiting resistor connected between the second plasma generation chamber and the first plasma generating chamber, the DC and extraction power source for the former is connected to the positive side between the Faraday cup and filament Or the ion treatment apparatus according to the item 3 . 5. The drawing power source is connected between the Faraday cup and the second plasma generating container with the former side being the negative side, instead of being connected between the Faraday cup and the filament with the former side being the positive side. Item 4. The ion treatment device according to item 4 .