JP2019169327A - Ion source, ion beam irradiation apparatus - Google Patents

Abstract

To provide an ion source capable of changing a ratio of ions in an ion beam extracted with an inexpensive and simple configuration.SOLUTION: An ion source 1 includes: a plasma generation vessel 2; an opening H formed in the plasma generation vessel 2; a lid 5 in which a beam extraction hole 4 for extracting an ion beam through the opening H is formed; and an elastic body S that urges the lid 5 toward the plasma generation vessel 2 side. A spacer 8 is sandwiched between the lid 5 and the plasma generation vessel 2.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ion source capable of changing a ratio of ions contained in an ion beam and an ion beam irradiation apparatus including the ion source.

  As an ion source capable of changing the ratio of ions contained in an ion beam extracted from the ion source, an ion source described in Patent Document 1 is known.

The ion source of Patent Document 1 has a mechanism for changing the cathode position according to the type of ionized gas for manufacturing P-type and N-type semiconductor elements. With this mechanism, the ratio of the ions contained in the ion beam is changed by changing the distance between the cathode position and the ion emission surface of the plasma generation container.
Specifically, when the ionized gas is PH ₃ , the cathode position is ion-injected in order to increase the ratio of PH _x ⁺ (x is an integer of 1 to 3) having a relatively heavy mass in the generated plasma. Move closer to the surface. On the other hand, the ionized gas is in the case of BF3 is away from the ion exit surface of the cathode position than that of PH ₃ to increase the relatively light mass B ⁺ ratio of.

  However, since the operation for changing the cathode position requires a large-scale mechanism, there is a concern that the cost of the ion source becomes high. In addition, since the cathode that has become brittle due to a change with time is moved, there is a concern that the cathode may be broken by an impact accompanying the movement of the cathode.

JP2006-164894A

  The present invention has been made to solve the above problems, and an object of the present invention is to provide an ion source capable of changing the ratio of ions in an ion beam extracted with an inexpensive and simple configuration.

The ion source is
A plasma generation vessel;
An opening formed in the plasma generation vessel;
A lid formed with a beam extraction hole for extracting an ion beam through the opening;
An elastic body that urges the lid toward the plasma generation container,
A spacer is sandwiched between the lid and the plasma generation container.

If it is an ion source of the said structure, it will become possible to extract ion with comparatively light mass efficiently by the spacer pinched | interposed between the cover body and the plasma production | generation container. On the other hand, in order to efficiently extract relatively heavy ions, the spacer may be removed.
In addition, since it is only necessary to sandwich the spacer, a complicated mechanism for moving the cathode as in the prior art is not required. As a result, the price of the ion source is low and the configuration is simple. Further, since the cathode is not moved, the cathode is not broken as the cathode moves.

  Depending on the arrangement of the ion source, the spacer may be displaced or the lid may be displaced. In order to position each part, it is desirable that the plasma generation container and the lid are positioned by positioning pins, and the positioning pins pass through the spacers.

To adjust the distribution of the ion beam extracted from the ion source,
The lid includes a first lid and a second lid that are divided in the ion beam extraction direction,
One lid has a single beam extraction hole,
The other lid has a plurality of beam extraction holes,
It is desirable that the single beam extraction hole includes the plurality of beam extraction holes as viewed from the ion beam extraction direction.

With the above configuration, since one lid has a plurality of beam extraction holes, the distribution of the ion beam extracted from the ion source can be set to a desired distribution by setting the distribution of the beam extraction holes to a desired distribution. It becomes possible to set to.
In addition, since the beam extraction hole of one lid is large enough to include the plurality of beam extraction holes formed in the other lid, a plurality of beam extraction holes are formed in each lid. Compared to the case, the positioning of both is simple.

Furthermore, to improve the extraction efficiency of the ion beam from the ion source,
The plurality of beam extraction holes are preferably formed in the first lid.

  If it is the said structure, it can prevent that the ion beam pulled out through the beam extraction hole formed in the 1st cover body collides with a 2nd cover body, and lose | disappears.

For spacer mounting position,
The spacer is preferably sandwiched between the first lid and the plasma container.

As ion beam irradiation devices such as ion implantation devices and ion beam etching devices,
The above-described ion source is used.

With a spacer sandwiched between the lid and the plasma generation container, it is possible to efficiently extract ions having a relatively light mass. On the other hand, in order to efficiently extract relatively heavy ions, the spacer may be removed.
In addition, since it is only necessary to sandwich the spacer, a complicated mechanism for moving the cathode as in the prior art is not required. As a result, the price of the ion source is low and the configuration is simple. Further, since the cathode is not moved, the cathode is not broken as the cathode moves.

Sectional drawing of the ion source which concerns on 1st embodiment Sectional drawing of the ion source which concerns on 2nd embodiment Explanatory drawing of the ion beam extraction hole formed in each cover body in the ion source of FIG. Explanatory drawing about split type lid

  FIG. 1 is a sectional view of an ion source according to the first embodiment. The Z direction shown in the figure is the extraction direction of the ion beam extracted from the ion source 1, and the Y direction is the longitudinal direction of the plasma generation container 2 having a substantially rectangular parallelepiped shape. The X direction is a direction orthogonal to the Z direction and the Y direction. The definition of each direction is the same in FIGS.

A gas port G for introducing an ionized gas such as BF ₃ or PH ₃ is provided on one surface of the plasma generation container 2. Further, a cathode C is attached to another surface of the plasma generation container 2. The cathode C is a filament that emits electrons for ionizing the gas introduced into the container and generating plasma in the container, or an indirectly heated cathode made of a combination of a plate-like cathode and a filament.
Furthermore, an opening H that connects the inside of the container and the outside of the container is formed at the end of the plasma generation container 2 (end on the Z direction side).

  The ion source 1 is an electron impact type ion source and includes an electromagnet (not shown) that generates a magnetic field along the longitudinal direction (Y direction) inside the container, outside the plasma generation container 2.

On the downstream side (Z direction side) of the opening H, a plurality of electrodes for extracting an ion beam with a predetermined energy through the opening H are arranged.
The electrode is composed of a lid 5 arranged closest to the plasma generation container 2 and an extraction electrode system 6 arranged downstream thereof. In each electrode, a beam extraction hole 4 is formed at a position corresponding to the opening H of the plasma generation container 2.

Protrusions P are provided on the side wall of the plasma generation container 2 so as to face the lid 5 in the Z direction. A coil spring S is suspended between the projection P and the lid 5, and the lid 5 is urged toward the plasma generation container 2 by the coil spring S.
A plurality of the coil springs S may be arranged according to the shape of the plasma generation container 2. In the present embodiment, a plurality of coil springs S are provided in the Y direction with the plasma generation container 2 sandwiched in the X direction.

  The spacer 8 is, for example, an annular member, and is sandwiched between the plasma generation container 2 and the lid 5. A fastening member such as a bolt is not used between the plasma generation container 2, the spacer 8, and the lid 5. For this reason, the seizure of the fastening member at a high temperature can be prevented.

In order to prevent the displacement of the spacer 8 and the lid 5 that may occur when the ion source 1 is transported or attached, the plasma generation container 2 and the lid 5 are positioned by the positioning pins 7. It is desirable. For example, a configuration in which the positioning pin 7 penetrates the spacer 8 is used.
The illustrated positioning pin 7 is configured to be attached to the end face of the plasma generation vessel 2, but may be attached to the lid 5 side. In that case, the recess 9 for housing the positioning pin 7 formed on the lid 5 side is formed on the end surface of the plasma generation vessel 2.

In the case where a plurality of positioning pins 7 are provided on the end face of the plasma generation container 2, it is desirable to arrange them at diagonal positions across the opening H. When a plurality of positioning pins 7 are provided, the positioning pins 7 may be attached to the lid 5 side in a certain place, and the positioning pins 7 may be attached to the plasma generation container 2 side in another place.
Note that the number of positioning pins 7 may be one if the positional deviation of each part due to the rotation of the member around the positioning pins 7 is slight.

  In the configuration of the ion source 1 shown in FIG. 1, a dense plasma is generated in the vicinity of the cathode C. Ions contained in the plasma travel while spirally moving in the magnetic field generated in the container. At this time, the turning radius increases as the mass of the ion increases.

  As shown in the present embodiment, the distance between the lid 5 and the cathode C is increased by providing the spacer 8. If this distance becomes longer, the allowable ion turning radius between the lid 5 and the cathode C becomes larger, but the other place (for example, between the cathode C and the inner wall surface of the plasma generation vessel 2 in the X direction). ) Does not change, ions having a relatively large mass that spirally move with a large turning radius collide with the inner wall surface of the plasma generation vessel 2 and disappear.

As a result, the proportion of ions with a relatively high mass contained in the ion beam extracted from the plasma generation container 2 is reduced, so that ions with a relatively low mass can be efficiently extracted.
On the other hand, when it is desired to efficiently extract ions having a relatively heavy mass, it is only necessary to remove the sandwiched spacer 8.
By using this configuration, a mechanism for moving the cathode as in the prior art becomes unnecessary, so that the apparatus price is low and the configuration is simple. Further, the cathode is not broken by moving the cathode.

FIG. 2 is a cross-sectional view of an ion source according to the second embodiment. The difference from FIG. 1 is that the lid 5 is composed of a first lid 51 and a second lid 52 that are divided in the ion beam extraction direction.
Each lid 51, 52 has a beam extraction hole 4, but one lid has a single beam extraction hole, and the other lid has a plurality of beam extraction holes. Is formed.

If the specific example of the beam extraction hole 4 is given, it will become the structure shown in FIG. FIG. 3 shows the lids 51 and 52 as viewed from the Z direction side. For example, two beam extraction holes 41 are formed in the first lid 51. These beam extraction holes 41 are included in a single beam extraction hole 4 formed in the second lid 52, as depicted by a broken line on the right side of FIG.
A single beam extraction hole similar to the beam extraction hole 4 of the second lid 52 is also formed in each electrode constituting the extraction electrode system 6 disposed on the Z direction side of the second lid 52. Has been.

As shown in FIG. 3, if one beam has a plurality of beam extraction holes and the other cover has such a size that the beam extraction holes include these beam extraction holes, By setting the plurality of beam extraction holes formed in the lid to a predetermined distribution, the distribution of the ion beam extracted from the ion source 1 can be set to a predetermined one.
In addition, since the beam extraction hole of the other lid is large enough to include a plurality of beam extraction holes formed in one lid, when forming a plurality of beam extraction holes in each lid Compared to the above, there are advantages such as simple alignment of both.

  In consideration of ion beam extraction efficiency, the plurality of beam extraction holes are preferably formed in the first lid 51. When a plurality of beam extraction holes 4 are formed in the second lid 52 on the side far from the plasma, and a single beam extraction hole 4 is formed in the first lid 51 on the side near the plasma, the first A part of the ion beam that has passed through the beam extraction hole 4 of the lid 51 collides with the second lid 52 and disappears.

In order to avoid the disappearance of the ion beam, it is preferable to form a plurality of beam extraction holes in the first lid 51 when forming a plurality of beam extraction holes in any one of the lids. In FIG. 3, since it is assumed that a ribbon beam long in the Y direction is extracted from the ion source, the beam extraction holes 41 of the first lid 51 are arranged side by side in the Y direction. The arrangement of the holes may be appropriately changed according to the shape of the ion beam drawn from the ion source 1.
Further, the number of divisions of the lid in the Z direction is not limited to two, and the lid may be divided into two or more.

  In the above-described embodiment, the plasma generation container having an approximately rectangular parallelepiped shape has been described as an example, but various shapes such as a cylinder and a cube may be adopted as the shape of the container. Moreover, although the beam extraction hole 4 has been described as a hole long in the Y direction, it may be a hole long in the X direction. Furthermore, the shape when viewed from the Z direction may be a circular shape or a square shape.

Although an integral structure is assumed as the spacer 8, for example, it may be composed of two or more members having the same thickness (dimension in the Z direction).
Alternatively, a plurality of spacers having different thicknesses may be prepared so that the distance between the cathode C and the lid 5 can be set stepwise.

  The ion source of the present invention may be used in an ion implantation apparatus or ion beam etching apparatus known as an ion beam irradiation apparatus. For example, when used in an ion implantation apparatus, when manufacturing P-type and N-type semiconductor elements, one spacer is prepared, and the presence or absence of the spacer is made to correspond to the cathode position when manufacturing each semiconductor element. It is possible to keep it.

  Although the structure which connects the projection part P of the plasma production container 2 and the cover body 5 with the coil spring S was employ | adopted, the ion source of this invention is not necessarily restricted to this structure. For example, a configuration may be adopted in which a leaf spring is attached to the inner wall of the flange in which the ion source 1 is disposed, and the end surface on the Z direction side of the lid 5 is urged toward the plasma generation container with the leaf spring.

  The cathode C only needs to emit electrons, and an electron gun that emits electrons of a predetermined energy may be used in the plasma generation container. Further, the cathode C may be arranged either inside or outside the plasma generation container.

Although the 1st and 2nd cover bodies 51 and 52 may be comprised by one member shown in FIG. 3, you may comprise each cover body by the some member. FIG. 4 shows an example in which the lid 5 is composed of a plurality of members. A plurality of members (5A to 5D) shown in FIG. 4 (A) are prepared and combined as shown in FIGS. 4 (B) and 4 (C), so that lids having various beam extraction holes can be obtained. It may be configured.
In addition, the lid body having the illustrated divided structure has an advantage in that, for example, when the lid body is partially worn by sputtering by plasma or ion beam, only the corresponding part is replaced.

  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.

1. Ion source 2. 2. Plasma generation container Opening 4. 4. Beam extraction hole Lid 51. First lid 52. Second lid body 6. Extraction electrode system 7. Positioning pin8. Spacer 9. Recess C. Cathode G. Gas port P.I. Projection S. Elastic body

Claims (6)

A plasma generation vessel;
An opening formed in the plasma generation vessel;
A lid formed with a beam extraction hole for extracting an ion beam through the opening;
An elastic body that urges the lid toward the plasma generation container,
An ion source having a spacer sandwiched between the lid and the plasma generation container. The plasma generation container and the lid are fixed with positioning pins,
The ion source according to claim 1, wherein the positioning pin passes through the spacer. The lid includes a first lid and a second lid that are divided in the ion beam extraction direction,
One lid has a single beam extraction hole,
The other lid has a plurality of beam extraction holes,
The ion source according to claim 1, wherein the single beam extraction hole includes the plurality of beam extraction holes as viewed from the extraction direction of the ion beam.   The ion source according to claim 3, wherein the plurality of beam extraction holes are formed in the first lid.   The ion source according to claim 3 or 4, wherein the spacer is sandwiched between the first lid and the plasma container.   An ion beam irradiation apparatus comprising the ion source according to claim 1.