JP2644958B2 - Ion source device and ion implantation device provided with the ion source device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-energy ion implanter for accelerating an ion beam to a high energy of MeV class using a high-frequency accelerator and implanting the accelerated ions into a sample substrate, and a source suitable for the ion source. The present invention relates to an ion source device that generates an ion beam having a low emittance.

[0002]

2. Description of the Related Art The structure of a high-current ion source device used in a conventional high-energy ion implantation apparatus will be described with reference to FIG.

In FIG. 4, a plasma source 4 is placed in a mirror magnetic field generated by an air-core coil 3. In addition, 2.4
A microwave and a discharge gas of 5 GHz are introduced to generate high-density plasma. Next, the ion beam 2 is extracted from the plasma using the extraction electrode 6 of the acceleration-deceleration system.

As such an ion source device, for example, as disclosed in Japanese Patent Application Laid-Open No. 63-114032, ion extraction is performed by using an extraction electrode from a high-density plasma generated by microwave discharge in a mirror magnetic field. Microwave ion source devices that extract the beam were used.

[0005] The conventional microwave ion source device has a feature that a large current beam can be stably extracted for a long time because plasma of high temperature and high density can be generated. However, it is very difficult to control the emittance indicating the quality of the ion beam extracted from the ion source device, as in other types of ion source devices. When trying to adjust the emittance, the plasma state changes greatly, so that the emittance could not be reduced while maintaining high current beam extraction performance.

[0006]

However, the quality of the emittance affects the transmittance of the ion beam current reaching the implantation chamber at the last stage of the ion beam implantation apparatus. In particular, it is known that in a high-frequency accelerator, unless a high-quality low emittance beam is introduced, the beam transmittance in the accelerator is greatly reduced.

That is, in the ion implantation apparatus, there is a problem that even if a large current beam is extracted from the ion source apparatus, if the emittance of the ion source apparatus is large, the beam reaching the implantation chamber is drastically reduced.

Further, since the emittance varies depending on the properties of the plasma of the ion source device, it is necessary to change the parameters (for example, ion temperature, electron temperature, etc.) of the plasma of the ion source device in order to adjust the emittance. However, in the prior art, when they are changed, the extraction characteristics of the ion beam also change at the same time, and as a result, there is a problem that the beam current greatly changes. That is, in the conventional ion source device, there is a problem that the emittance and the current extraction performance cannot be independently controlled.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ion source for a high-energy ion implanter in which the emittance of the beam can be independently controlled without impairing the beam current.
It is to provide a low emittance ion source.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a microwave ion source apparatus which can generate a high-density plasma suitable for extracting a large current beam. This can be achieved by an ion beam implanter having an independently provided ion source device.

That is, in the ion source device, a plasma generated by another plasma source is introduced into a mirror magnetic field generated by excitation of two air-core coils, and further, a mirror magnetic field is changed to change the plasma state. A means for changing the intensity ratio is provided. Thereby, the emittance of the ion beam extracted by the extraction electrode can be controlled.

[0012]

In describing the operation of the present invention, first, the definition of emittance and the behavior of plasma particles due to the mirror magnetic field will be described.

FIG. 2 is a diagram illustrating the emittance of an ion beam. As shown in FIG. 2A, a slit 1 having a small hole is placed in the ion beam 2, and the spread angle θ of the ion beam 2a coming out of the small hole is measured. FIG. 2- (B) shows the result of measuring the angle θ while changing the position r of the small hole. At this time, the area of the figure drawn in FIG. 2- (B) is the emittance. When the beam is controlled by a lens or the like, the shape of the emittance changes, but the area does not change.

In the ion implantation apparatus, the transmittance of the ion beam from the ion source apparatus to the beam irradiation chamber changes depending on the magnitude of the emittance. In particular, in order to obtain a large current beam, it is necessary to increase the beam current extracted from the ion source device and reduce the emittance.

As can be seen from the definition, the emittance is determined by the magnitude of the ion velocity in a direction perpendicular to the traveling direction of the ion beam. The magnitude of the ion velocity changes depending on the ion temperature in the plasma of the plasma chamber from which the ions are extracted. The temperature of ions in the plasma is determined by the plasma generation method.

On the other hand, when the plasma generation conditions are changed,
Since various plasma parameters (electron temperature, plasma density, etc.) change simultaneously and complicatedly, it is difficult to control only the ion temperature alone while keeping the plasma density constant.

Next, it is possible to excite two air core coils.
Regarding the behavior of charged particles in the so-called mirror magnetic field,
The following are known.

First, FIG. 3A shows a mirror magnetic field shape. When charged particles such as plasma are put in a magnetic field created by the two air-core coils 3a and 3b, most of the particles reciprocate between the two coils. This is because the magnetic field at the coil acts as if it were a mirror and reflects charged particles. However, some particles escape in the axial direction without being reflected.

FIG. 3B shows the distribution of particles having a velocity component Vx in the magnetic field direction and a component Vy in a direction perpendicular to the magnetic field direction velocity among particles in the mirror magnetic field. If the plasma is isotropic, the particles will be uniformly distributed within the circle.

V of each particle reciprocating in the mirror magnetic field
The change of x and Vy becomes a circular shape as shown in FIG. 3B, but at the position of the center of the coil, FIG.
Particles having the velocity component indicated by the hatched portion escape in the axial direction without being reflected in the mirror magnetic field. After the particles in the shaded area have escaped, the particles in the other velocity spaces sequentially enter the shaded area due to mutual collision, so that the particles escape one after another in the axial direction. Here, the angle θ indicating the shaded area changes depending on the intensity ratio Bo / Bm of the mirror magnetic field,
θ = sin ⁻¹ √ (Bo / Bm). here,
Bo is the magnetic flux density at the center of the mirror magnetic field, and Bm is the magnetic flux density at the mirror point.

That is, Vy of a particle exiting the mirror magnetic field has a smaller value than when the particle is in the mirror magnetic field. The emittance of the ion beam extracted from the plasma has a small value when the Vy component is small.

Accordingly, if the particles that escape from the mirror magnetic field are extracted as an ion beam, an ion source device with a small emittance can be obtained. In particular, if a mechanism for changing the mirror magnetic field ratio is provided, the angle θ changes, so that the emittance of particles that escape from the mirror magnetic field can be adjusted.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, several embodiments relating to an ion source apparatus to which the present invention is applied will be described. Next, an embodiment relating to an ion implantation apparatus provided with these ion source devices will be described.

FIG. 1 is a view for explaining a first embodiment of the ion source device according to the present invention. The embodiment shown in FIG. 1 includes a plasma source unit 102 and an adjusting unit 101 connected to the same axis to adjust the emittance.

The plasma source unit 102 includes an air-core coil 3a having a power supply device (not shown) for generating a mirror magnetic field.
3b, a plasma source 4 for generating plasma, an insulator 5 that transmits microwaves and shields the microwave introduction part and the plasma source part 102, and an adjustment unit 1 using the magnetic field.
And a yoke 9 made of a magnetic material such as iron to minimize the effect on the yoke.

The adjusting unit 101 introduces plasma generated by the plasma source 4 and air-core coils 7a and 7b having a power supply device (not shown) for generating a mirror magnetic field independently of the mirror magnetic field. It comprises a plasma chamber 10, an ion beam extraction electrode 6 for extracting the ion beam 2 therefrom, and yokes 8a, 8b, 8c made of a magnetic material such as iron. Here, 8b is a movable yoke for changing the mirror magnetic field intensity ratio. The lines of magnetic force generated by the excitation of the coils 7a and 7b mainly pass through the yokes 8a, 8b and 8c, and therefore do not affect the magnetic field distribution and strength of the plasma source 4.

The microwaves are introduced into the plasma source 4 through the insulator 5 from the left side in FIG. 1, and the gas introduced from the lower side in FIG. 1 is turned into plasma by microwave discharge. Of the generated plasma particles, coils 3a, 3a
Particles having a velocity distribution determined by the mirror magnetic field intensity ratio due to b escape this magnetic field and move to the plasma chamber 10 placed in the mirror magnetic field generated by the coils 7a and 7b.

Further, in the plasma chamber 10, plasma particles having a velocity distribution determined by the mirror magnetic field intensity ratio formed by the coils 7 a and 7 b escape from the mirror magnetic field and go to the extraction surface of the extraction electrode 6. The mirror magnetic field intensity ratio of the plasma chamber 10 can be easily changed by mechanically moving the yoke 8b in and out in the axial direction (see the arrow in FIG. 1). Therefore, the velocity distribution in the Y direction of the plasma escaping from the mirror magnetic field can be controlled, and the emittance of the extracted ions can be adjusted. At this time, the plasma source section 102 is not affected at all. That is, various plasma parameters are not changed.

In this embodiment, the ion beam emittance of various ion species was measured. As a result, at an extraction ion beam current of several mA to several tens mA,
It was shown that changing the mirror magnetic field intensity ratio of the plasma chamber 10 changed the beam emittance value in the range of several times to several tens times. Here, the extraction voltage of the ion source device is several k.
Experiments were performed at V-50 kV.

With respect to this voltage / current range, the measured value of the normalized emittance obtained by normalizing the emittance value with the ion beam velocity was about 0.1 πcm · mrad in the related art. However, in this embodiment, 0.01πcm · mrad
It can be seen that it can be made much smaller than the conventional example.

Next, a second embodiment relating to the ion source device will be described. In the first embodiment, only a mirror magnetic field having a simple shape is applied to the plasma source 4 for generating plasma. Instead, a multipole magnetic field disclosed in JP-A-63-114032 is superposed. Even when a multi-charged ion generating plasma source is used, the emittance can be controlled.

FIG. 5 is a diagram for explaining a second embodiment relating to the ion source device. The adjusting unit 101 is the same as that of FIG.

In FIG. 5, in addition to the mirror magnetic field, the permanent magnet 1
3a and 13b are arranged in a multipolar manner around the plasma source 4,
Plasma temperature and plasma density are further increased. Also in this case, the adjustment unit 101 is moved from the mirror magnetic field end of the plasma source 4.
Since high-temperature, high-density plasma is introduced into the substrate, it is possible to increase the current of the extraction beam 2 having a low emittance.

In particular, in the first embodiment, monovalent ions can be efficiently generated by the plasma source 4, whereas in the present embodiment, multivalent ions of two or more valences can be efficiently generated. A high current multiply charged ion beam can be obtained.

Next, a third embodiment will be described. In the first and second embodiments, the yoke attached to the coil is moved mechanically to change the mirror magnetic field intensity ratio.

However, in the third embodiment (FIG. 7) described here, a method of electrically changing this is adopted. That is, the auxiliary coil 11 was placed between the air core coils 7a and 7b, and the mirror ratio was changed by changing the exciting current flowing through the auxiliary coil 11 by the power supply device 18. Also in this example, the emittance of the extraction beam 2 could be easily controlled.

Next, a fourth embodiment relating to the ion source device will be described. In the first, second and third embodiments, FIG.
As shown in (1), the plasma source unit 102 and the adjustment unit 101 each have a pair of coils, and independently generate a mirror magnetic field. However, the plasma source unit 102 and the adjusting unit 10
A similar mirror magnetic field can be generated with three coils by omitting any of the coils near the connection point of 1.

In the fourth embodiment, as shown in FIG. 8, the coil 7a forming the mirror magnetic field of the plasma chamber 10 in FIG. 1 is removed, and the coil 3b is shared. That is, the coils 3a and 3b and the coils 3b and 7b form a mirror magnetic field.

The ranges of the emittance controllability with respect to the beam current measured in the present embodiment are the same as those of the first, second and third embodiments.
In the conventional ion source device, the emittance fluctuates greatly when the beam current or the ion source device voltage changes by several tens% or more. Also, the emittance of this example could be controlled to the order of 0.01 πcm · mrad.

In the fourth embodiment, the coil 7a shown in FIG.
However, the same result can be obtained even if the coil 3b is omitted.

Further, in the first, second, third and fourth embodiments, one plasma source is connected to the plasma chamber 10 placed in the mirror magnetic field for adjusting the emittance. However, as in the fifth embodiment shown in FIG. 9, if another plurality of plasma source units 102 (two in this example are added) are added to the center of the adjustment unit 101 from above and below, the plasma density increases. Therefore, the current of the extracted ion beam 2 can be increased. In this case, it is obvious from the operation of the invention that an ion beam having a low emittance and a larger current can be easily extracted.

Next, an embodiment of a MeV energy ion implantation device having the ion source device shown in the above embodiment will be described.

FIG. 6 is a diagram illustrating an example of the embodiment. In this embodiment, an ion source device including any one of the plasma source unit 102 and the adjustment unit 101 described in the above embodiment, a mass separator 15 that changes an ion trajectory by a magnetic field, and a beam by a magnetic field or an electric field. It comprises a converging lens 16, an RFQ accelerator 14 for accelerating ions to MeV energy, and a beam irradiation chamber 17 for projecting the ions into an object (not shown) such as a semiconductor substrate. Here, as the accelerator 14, for example, an RFQ (high-frequency quadrupole) accelerator disclosed in Japanese Patent Application No. 58-226860 can be used.

The ions generated from the ion source devices 101/102 are selected by a mass separator 15, and only the selected ions are converged by a lens 16 and accelerated to a predetermined energy by an accelerator 14, thereby irradiating a beam. The object to be irradiated held in the chamber 17 is irradiated.

The RFQ accelerator 14 has such a property that the beam transmittance in the accelerator is largely influenced by the emittance of the incident beam. Therefore, in order to obtain a high-current MeV beam of the mA class, it is particularly necessary that a beam having a low emittance be incident on the accelerator 14.

In the case of the conventional ion source device shown in FIG.
The operating conditions for lowering the emittance of the ion source device and the operating conditions for extracting a large current beam are different. Therefore, in the ion implantation apparatus of the present embodiment, when a conventional ion source apparatus is used, the transmittance of the accelerator changes depending on the required beam energy and the incident beam current value, and in a wide range of operating conditions of the RFQ accelerator,
I could not accelerate efficiently.

Next, when the ion source device is replaced with the ion source device of the present invention, a high beam transmittance of 90% or more over a wide operating frequency range of the RFQ accelerator, that is, a wide acceleration energy range, is obtained by using B (boron), Obtained for P (phosphorus) and As (arsenic) ion beams. This is because the incident ion beam emittance could be controlled to a small value (in the order of 0.01 πcm · mrad) according to various ion species and acceleration conditions.

[0048]

According to the present invention, the emittance of the extracted ion beam can be adjusted independently of the operation parameters of the ion source device for the ion source device for the high energy ion implantation device. As a result, not only an ion source device having a low emittance can be provided, but also by applying the present invention to an ion implantation device, the implantation current can be increased, and a large current MeV class beam ion implantation device of mA or more in a wide acceleration energy range. Can be provided.

[0049]

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment showing the principle of an ion source device based on the present invention.

FIGS. 2A and 2B are explanatory diagrams illustrating the definition of ion beam emittance. FIGS.

FIGS. 3A and 3B are illustrations of a definition of a mirror magnetic field and distribution of charged particles in the mirror magnetic field in a velocity space.

FIG. 4 is a configuration diagram of a conventional microwave ion source device.

FIG. 5 is a configuration diagram of a second embodiment of the ion source device according to the present invention.

FIG. 6 is a block diagram of an embodiment of an ion implantation apparatus according to the present invention.

FIG. 7 is a configuration diagram of a third embodiment of the ion source device according to the present invention.

FIG. 8 is a configuration diagram of a fourth embodiment of the ion source device according to the present invention.

FIG. 9 is a configuration diagram of a fifth embodiment of the ion source device according to the present invention.

[Explanation of symbols]

1 ... Beam shielding slit 2 ... Ion beam 3
a, 3b: air-core coil, 4: microwave plasma source,
5: insulator, 6: ion beam extraction electrode, 7a, 7
b: air-core coil, 8a, 8c, 8d: magnetic material yoke, 8b: movable yoke, 9: magnetic material yoke, 10
... Plasma chamber, 11 ... Auxiliary coil, 12 ... Lines of magnetic force,
13a, 13b: permanent magnet, 14: RFQ accelerator, 1
5: Mass separator, 16: Lens, 17: Beam irradiation chamber, 18: Power supply device, 101: Adjustment unit, 102: Plasma source unit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical indication H01L 21/265 H01L 21/265 D (72) Inventor Kuniyuki Sakudo Omikamachi, Hitachi, Ibaraki, Japan No. 1-1, Hitachi, Ltd. Hitachi Research Laboratory (56) References JP-A-4-132145 (JP, A) JP-A-4-338639 (JP, A) JP-A-2-114433 (JP, A)

Claims (8)

(57) [Claims] 1. An ion source device having a plasma generating source for generating ions, wherein the ion source is disposed adjacent to the plasma generating source and on a side from which ions are extracted, introduces generated ions, and adjusts emittance of an extracted ion beam. has an adjustment unit for the adjustment unit, placed away at least two coils on the same axis, is excited as generated magnetic force lines are the same direction, and introduced from the plasma source ion Means for forming a first mirror magnetic field for confining the first mirror magnetic field, and changing at least one of the magnetic field intensity and the magnetic field line distribution of the formed first mirror magnetic field to change the mirror magnetic field intensity ratio of the first mirror magnetic field And an ion source device. 2. The method of claim 1, separately from the first mirror field, means for generating a second mirror field comprising at least two coils, further comprising a microwave introducing portion, the plasma An ion source device, wherein the generation source is placed in the second mirror magnetic field and generates charged particles by discharge by the microwave introduced from the microwave introduction unit. 3. The apparatus according to claim 1, wherein the means for changing the mirror magnetic field intensity ratio of the first mirror magnetic field comprises at least two mirrors forming the first mirror magnetic field.
It has one or more yokes made of a magnetic material disposed between two coils among the above coils, and changes a state occupied by the one or more yokes in the inter-coil region . The ion source device , wherein the mirror magnetic field intensity ratio is changed. 4. The apparatus according to claim 1, wherein said means for changing a mirror magnetic field intensity ratio of said first mirror magnetic field includes at least two magnetic field elements forming said first mirror magnetic field.
Comprising a coil and a power supply device for supplying power to the coil disposed between the two coils of more coils, the
By changing the current flowing through the coil by the power supply device ,
The ion source apparatus, characterized in that for changing the mirror field intensity ratio. 5. A claim 2, ions, characterized by further comprising means for generating a multi-pole magnetic field to be superimposed on the second mirror magnetic field is placed with the plasma source Source equipment. 6. The apparatus according to claim 2 , wherein said second mirror magnetic field and said first mirror magnetic field are different from each other.
Adjacent to the end of each coil group among the two sets of coil groups generated
One of the two coils located together is omitted and the other is
An ion source device characterized by generating both mirror magnetic fields by sharing the same . 7. The claim 1, further comprising another plurality of plasma generating source is a plasma generation source, charged particles generated above each plasma source
Are introduced into the adjustment unit , respectively. 8. An ion implantation apparatus having an ion source device for generating specific ions, an ion accelerator for accelerating ions extracted from the ion source device, and a implantation chamber for irradiating the accelerated ion beam. the ion source device comprises a plasma generating source for generating ions, introducing generated ions, and an adjustment unit for adjusting the emittance of the emitted ion beam, wherein the adjusting unit includes at least two coaxially installed off the coils, is excited as generated magnetic force lines are the same direction, means for forming a first mirror field for confining charged particles introduced from the plasma generation source, before
Means for changing at least one of the magnetic field intensity and the magnetic field line distribution of the first mirror magnetic field thus formed to change the mirror magnetic field intensity ratio of the first mirror magnetic field.