JP5257399B2 - Ion source and ion implantation apparatus - Google Patents

Description

  The present invention relates to an electron impact ion source (also referred to as a bucket ion source, a multipole magnetic ion source, or a multicusp ion source) that forms a cusp magnetic field in a plasma generation container, and ion implantation using this ion source. It relates to the device.

  As this type of bucket-type ion source, as shown in Patent Document 1, a plasma generation container having a rectangular parallelepiped shape into which ion source gas is introduced, and disposed outside the side surface of the plasma generation container, Some have a plurality of magnets that form a cusp magnetic field, and a filament that is inserted into the inside through a side wall (rear side wall) that faces an ion extraction port formed on the front side wall of the plasma generation container. In this ion source, the plasma generation container also serves as an anode, and electrons emitted from the filament are discharged in the plasma generation container to ionize the ion source gas to generate plasma. An ion beam is extracted from the plasma by using an extraction electrode system provided in the vicinity of the ion extraction port.

  In the ion source having the above-described configuration, the filament is supported by a support mechanism having a current introduction terminal for supplying current to the filament, and is inserted into the inside from the rear side wall of the plasma generation container. Further, the plurality of magnets are arranged by being attached to a support member provided on the outside of the side wall (including the rear side wall) of the plasma generation container using bolts or the like.

  However, since the filament is inserted and a plurality of magnets are arranged on the rear side wall of the plasma generation container, an insertion region in which the filament is inserted and a plurality of magnets are inserted in order to facilitate replacement of the filament or magnet. It is necessary to configure so that the arrangement area where the magnets are arranged does not overlap. That is, it is necessary to insert the filament while avoiding the region where the plurality of magnets are arranged, and there is a restriction on the attachment position. In addition, it is necessary to arrange | position the support mechanism of a filament avoiding the arrangement | positioning area | region of a magnet. Then, the filament and its support mechanism must be designed according to the arrangement mode of the magnet, and there is a problem that it is difficult to arrange a particularly large filament and support mechanism.

  On the other hand, since the arrangement of magnets is an important parameter that determines the confinement efficiency of electrons and plasma, the degree of freedom in arrangement is small. For example, in order to increase the efficiency of electron confinement by a cusp magnetic field, there is a demand to arrange a plurality of magnets with a predetermined size at equal intervals outside each side wall (excluding the front side wall) of the plasma generation container. There is. However, since the filament and its support mechanism are arranged on the rear side wall, it is difficult to arrange a plurality of magnets with a predetermined dimension at equal intervals, and there is a problem that the above confinement efficiency must be sacrificed to some extent. .

  As described above, in the conventional ion source, since the size of the filament is restricted by the arrangement of the magnet, not only a sufficient amount of electron emission cannot be obtained, but also the arrangement of the magnet is restricted by the filament. Therefore, it has been considered that it is difficult to improve the plasma generation efficiency in the plasma generation container because the electron confinement efficiency is poor due to the inhomogeneity of the cusp magnetic field. Further, in the conventional ion source, it is difficult to make the plasma distribution uniform, and it is also difficult to make the ion density in the ion beam uniform.

JP 2007-115511 A

  Accordingly, the present invention has been made to solve the above problems all at once, and its main object is to improve plasma generation efficiency in an electron impact ion source that forms a cusp magnetic field in a plasma generation container. To do.

  That is, an ion source according to the present invention is a container having a rectangular parallelepiped shape for generating plasma inside by introducing an ion source gas, the plasma generation container having an ion extraction port formed on one side wall, A plurality of magnets that are provided outside along the outer surface of the other side wall other than the side wall where the ion extraction port is formed, and that form a cusp magnetic field inside the plasma generation vessel, and between adjacent side walls of the plasma generation vessel And one or more filaments that are inserted from the corners to be formed and emit electrons to cause discharge in the plasma generation container to ionize the ion source gas to generate plasma. It is characterized by.

  In such a case, by providing a filament inserted from the corner portion, a dead space in which a conventional magnet is not disposed is effectively used, and all the side walls (excluding the side walls on which ion extraction ports are formed are excluded). ), The arrangement of the magnets can be made suitable without being restricted by the filament. Thereby, the effect of confining electrons by the cusp magnetic field can be improved, and the plasma generation efficiency can be improved. In addition, since the cusp magnetic field generated at the corner of the plasma generation container has a relatively small magnetic field strength, not only the electrons emitted from the filament tip but also the tip of the filament can be inserted by inserting the filament from the corner. Electrons emitted from the plasma can be confined and the electrons can be effectively used. As a result, plasma generation efficiency can be improved. Furthermore, if the filament is arranged at the corner where the magnet is not arranged, a relatively large filament support mechanism may be provided as compared with the case where the filament is arranged on the side wall (for example, the rear end wall) where the magnet is arranged. This makes it possible to increase the rigidity of the support mechanism and to cope with large filaments.

  When arranging a plurality of magnets on all the side walls other than the side wall where the ion extraction port is formed, in order to simplify the arrangement configuration and make the cusp magnetic field formed in the plasma generation container uniform. Preferably, the plurality of magnets are supported at substantially equal intervals on a support plate made of a substantially flat ferromagnetic material provided to face the outer surface of each of the other side walls.

  As an example of a specific arrangement mode of the filament, in order to increase the number of electrons emitted into the plasma generation container to improve the plasma generation efficiency and extract more ion beams, the filament However, it is desirable to be provided at a plurality of corners.

  As another example of a specific arrangement mode of the filament, in order to increase the number of electrons emitted into the plasma generation container to improve the plasma generation efficiency and to extract a larger number of ion beams. It is desirable that a plurality of the filaments are provided at one corner along the corner.

  As a specific arrangement mode of the filament, in order to make the plasma distribution in the plasma generation container easy to be uniform and to enable uniform ion beam extraction, the filament has a longitudinal direction of the ion extraction port and an ion extraction direction. It is desirable to be provided in the corner | angular part in a symmetrical position with respect to the plane which consists of

  In order to prevent the filaments from coming into contact with each other in a state where the filaments are arranged in the plasma generation container, and to be able to arrange a large number of filaments, the filaments provided at the corners at the symmetrical positions are: It is desirable that they are provided at different positions in the direction along the corner.

  According to the present invention configured as described above, plasma generation efficiency can be improved in an electron impact ion source that forms a cusp magnetic field (multipolar magnetic field) in a plasma generation container.

It is a mimetic diagram showing the whole ion implanter composition concerning one embodiment of the present invention. It is XY sectional drawing which shows typically the structure of the ion source of the embodiment. It is XZ sectional drawing which shows the structure of the ion source of the embodiment typically. It is the figure seen from the ion extraction direction which shows arrangement | positioning of the filament of the embodiment. It is a figure which shows the cusp magnetic field distribution in XZ plane in a plasma production container. It is a figure which shows the modification of a filament arrangement | positioning. It is a figure which shows the modification of a filament arrangement | positioning. It is a figure which shows the modification of a filament arrangement | positioning.

  Hereinafter, an embodiment of an ion implantation apparatus according to the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the ion implantation apparatus 100 according to the present embodiment causes an ion beam IB extracted from the ion source 2 to be incident on the substrate W held by the holding unit 51 of the substrate driving device 5 and enters the substrate W. It is configured to perform ion implantation. The path (beam line) of the ion beam IB from the ion source 2 to the substrate driving device 5 is surrounded by a vacuum container (not shown), and is kept in a vacuum atmosphere during ion implantation.

  In this embodiment, the ion beam IB extracted from the ion source 2 and made incident on the substrate W has a width in the Y direction, which is the front and back direction of the paper surface of FIG. 1, sufficiently larger than the thickness in the direction perpendicular to it (X direction). It has a large ribbon shape. The width of the ion beam IB when entering the substrate W is slightly larger than the dimension of the substrate W in the same direction.

  In this embodiment, a mass separation magnet 3 and a separation slit 4 constituting mass separation means for mass separation of the ion beam IB extracted from the ion source 2 are provided between the ion source 2 and the holding unit 51. Yes. The mass separation magnet 3 selects and derives desired ions by bending the ion beam IB in the thickness direction. The separation slit 4 is provided on the downstream side of the mass separation magnet 3 and cooperates with the mass separation magnet 3 to select and pass the desired ions.

  In this embodiment, the substrate driving device 5 is configured so that the substrate W held by the holding unit 51 is in a direction along the thickness of the ion beam IB incident on the substrate W (in other words, a direction crossing the width). Mechanically reciprocating. In this embodiment, the substrate driving device 5 itself reciprocates in the X direction along a rail (not shown). By reciprocating the substrate W and the ion beam IB having a ribbon shape, the ion beam IB can be incident on the entire surface of the substrate W to perform ion implantation.

  Therefore, as shown in FIGS. 2 and 3, the ion source 2 of the present embodiment is a container for generating plasma inside by introducing an ion source gas, and plasma in which an ion extraction port 21H is formed. A generation vessel 21 and a plurality of magnets 22 provided outside the plasma generation vessel 21 to form a cusp magnetic field (more precisely, a multi-cusp magnetic field, also referred to as a multipolar magnetic field) inside the plasma generation vessel 21; One or more (a plurality in the present embodiment) filaments 23 constituting ionization means for generating plasma by ionizing the ion source gas by electron impact in the plasma generation container 21 and the vicinity of the ion extraction port 21H of the plasma generation container 21 And an extraction electrode system 24 that accelerates and extracts the ion beam IB from the plasma by the action of an electric field.

  As shown in FIG. 2, the extraction electrode system 24 includes a plasma electrode 241, an extraction electrode 242, a suppression electrode 243, and a ground electrode 244 arranged from the most plasma side to the downstream side. Further, an insulator 245 is provided between the plasma electrode 241 and the plasma generation container 21 as an insulating means for electrically insulating the two from each other. Further, the electrodes 241 to 244 are electrically insulated from each other by an insulator 246, for example.

  The plasma generation container 21 is a rectangular parallelepiped container, and, as shown in FIGS. 3 and 4, ion extraction that extends along the longitudinal direction of the side wall 21a on one side wall (specifically, the front side wall 21a). A mouth 21H is formed. The extraction direction of the ion beam IB is the X direction, the longitudinal direction of the ion extraction port 21H is the Y direction, and the direction orthogonal to the X direction and the Y direction is the Z direction. In FIG. 4, the ion extraction port 21H is formed along the longitudinal direction of the front side wall 21a at the center of the front side wall 21a. The ion extraction port 21H is formed in the longitudinal direction of the front side wall 21a (that is, the Y direction). It does not have to be along.

  As shown in FIGS. 3 and 4, the plurality of magnets 22 are provided outside along the outer surfaces of the side walls 21 b to 21 f other than the side wall (front side wall 21 a) where the ion extraction port 21 </ b> H is formed. A cusp magnetic field is formed in the vicinity of the inner surfaces of the side walls 21b to 21f of the plasma generation vessel 21. Each magnet 22 of the present embodiment is a permanent magnet, but an electromagnet may be used. Specifically, the plurality of magnets 22 are supported by five substantially rectangular flat plate-like support plates 25 provided to face the outer surfaces of the side walls 21b to 21f. In each support plate 25, the plurality of magnets 22 are provided at substantially equal intervals. On the other hand, each support plate 25 provided facing the outer surface of each of the side walls 21b to 21f is easier to manufacture if it is composed of one large plate, but the one plate is further divided into smaller pieces. It doesn't matter. That is, the number of support plates 25 is not limited to five and may be more than this. The material of the support plate 25 is preferably a ferromagnetic body made of iron or the like. With such a configuration, effects such as strengthening the magnetic field distribution inside the plasma generation container 21 and preventing leakage of the magnetic field to the outside of the plasma generation container 21 can be expected. The desired magnetic field distribution can be easily obtained.

  The plurality of magnets 22 provided on each support plate 25 are arranged so that their polarities are different from each other along the ion extraction direction. Further, magnets 22 having the same polarity are arranged in a direction orthogonal to the ion outlet 21H. In addition, the magnet 22 is arrange | positioned along the circumferential direction in the support plate 25 provided facing the back side wall 21b, and it arranges so that polarity may mutually differ toward the center part. The cusp magnetic field formed by the plurality of magnets 22 arranged in this way is as shown in FIG. FIG. 5 shows a case where three rows of magnets 22 are arranged on each support plate 25 when viewed from the Z direction. The magnets 22 having the same polarity may be arranged along the ion extraction direction, and the magnets 22 having different polarities may be arranged in a direction orthogonal to the ion extraction direction. In addition, the arrangement of the magnets 22 can be changed as appropriate.

  The plurality of filaments 23 are provided by being inserted into the inside from corners 21 </ b> K formed between adjacent side walls of the plasma generation container 21. Specifically, the plurality of filaments 23 are provided at the plurality of corners 21K. In this embodiment, as shown in FIG. 3, the filaments 23 are symmetrical with respect to the plane formed by the longitudinal direction of the ion extraction port 21H and the ion extraction direction. It is provided at the corner 21K at the position (corner 21K formed on the long side of the rear side wall 21b). As shown in FIG. 4, a plurality of filaments 23 are provided along each corner 21 </ b> K in each corner 21 </ b> K, and the corners are not in contact with the filaments 23 provided on the corner 21 </ b> K at the symmetrical position. They are provided at different positions in the direction (Y direction) along 21K.

  In each corner portion 21K, the filament 23 is fixed so as to have an inclination angle of about 45 degrees with respect to each adjacent side wall (side wall 21d and side wall 21b, side wall 21c and side wall 21b) forming the corner portion 21K. Further, the filament 23 is interposed between the end sides 25x of the support plate 25 provided to face the side walls 21b to 21d outside the adjacent side walls (side wall 21d and side wall 21b, side wall 21c and side wall 21b). It is fixed to a mounting portion 21K1 formed at the corner portion 21K.

  Each filament 23 is supported by a filament support mechanism 26, and a filament power source for heating the filament 23 is connected to the filament support mechanism 26. And the filament 23 is arrange | positioned in the plasma generation container 21 by fixing the filament support mechanism 26 to the attaching part 21K1 formed in the corner | angular part 21K of the plasma generation container 21. FIG. Further, a DC arc power source is connected between one end of each filament 23 (in this example, positive electrode end) and the plasma generation vessel 21 with the latter as the positive electrode side, and the plasma generation vessel 21 also serves as an anode. ing. An arc discharge is generated between each filament 23 and the plasma generation vessel 21, and the ion source gas is ionized by the impact of electrons generated at that time, thereby generating plasma that is distributed long in the width direction of the ion beam IB. It can be generated in the container 21 with good uniformity. That is, in this example, the ionization means is constituted by the filament 23, the filament power supply, and the arc power supply.

<Effect of this embodiment>
According to the ion implantation apparatus 100 according to the present embodiment configured as described above, the filament 23 is inserted and provided from the corner portion 21K, thereby effectively utilizing the dead space in which the conventional magnet 22 is not disposed, The filaments 23 can be arranged in the plasma generation vessel 21 without hindering the arrangement of the magnets 22 on the side walls (excluding the side wall where the outlet is formed). Thereby, the effect of confining electrons by the cusp magnetic field can be improved, and the plasma generation efficiency can be improved.

  Further, since the cusp magnetic field generated at the corner 21K of the plasma generation container 21 has a relatively small magnetic field strength, not only the electrons emitted from the tip of the filament by inserting the filament 23 from the corner 21K, As a result of being able to confine electrons emitted from other than the tip of the filament 23 and effectively utilizing the electrons, plasma generation efficiency can be improved.

  In addition, if the filament 23 is arranged at the corner 21K where the magnet 22 is not arranged, the filament is relatively large as compared to the case where the filament 22 is arranged at another part (for example, the rear side wall 21b). 23 support mechanisms 26 can be provided, whereby the rigidity of the support mechanism 26 is increased and the large filaments 23 can be accommodated.

<Other modified embodiments>
The present invention is not limited to the above embodiment.

  For example, the corner 21K where the filament 23 is provided is not limited to the above embodiment, and may be provided at the corner 21K formed on the long side of the front side wall 21a where the ion extraction port 21H is formed as shown in FIG. However, as shown in FIG. 7, the filaments 23 may be provided on the corners 21K formed on the long side of the front side wall 21a and the corners 21K formed on the long side of the rear side wall 21b. In addition, as shown in FIG. 8, a filament 23 may be provided at a corner portion 21K formed on at least one side of the side walls 21e and 21f facing each other in the Z direction.

  Further, the ion source of the above-described embodiment emits a substantially ribbon-like ion beam having a ribbon-like shape in which the dimension in the X direction is larger than the dimension in the Y direction. It may be what you do.

  In addition, it goes without saying that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 100 ... Ion implantation apparatus 2 ... Ion source 21 ... Plasma production vessel 21H ... Ion extraction port 21a ... One side wall (front side wall)
21b-21f ... Other side wall 21K ... Corner 22 ... Multiple magnets 23 ... Filament 25 ... Support plate

Claims (7)

A plasma generating container in which an ion source gas is introduced to form a rectangular parallelepiped for generating plasma therein, and an ion extraction port is formed on one side wall;
A plurality of magnets provided outside along the outer surface of the side wall other than the side wall where the ion extraction port is formed, and forming a cusp magnetic field inside the plasma generation container;
Inserted into the inside from the corner formed between the adjacent side walls of the plasma generation container, and emits electrons to cause discharge in the plasma generation container to ionize the ion source gas to generate plasma. An ion source comprising one or more filaments.   2. The ion source according to claim 1, wherein the plurality of magnets are supported at substantially equal intervals on a support plate made of a substantially flat ferromagnetic material provided facing the outer surface of each of the other side walls.   The ion source according to claim 1, wherein the filament is provided at a plurality of corners.   The ion source according to claim 1, wherein a plurality of the filaments are provided at one corner along the corner.   5. The ion source according to claim 1, wherein the filament is provided at a corner portion symmetrical with respect to a plane formed by the longitudinal direction of the ion extraction port and the ion extraction direction.   6. The ion source according to claim 5, wherein the filaments provided at the corners at the symmetrical positions are provided at different positions in the direction along the corners.   An ion implantation apparatus using the ion source according to claim 1.