JP3399608B2 - Ion implanter - 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 implantation apparatus, and more particularly, to a structure of an electron emitting portion used for preventing static charge of a target object during ion implantation.

[0002]

2. Description of the Related Art As is well known, at the time of manufacturing a semiconductor wafer, for example, an ion implantation apparatus may be used to implant impurities into a semiconductor wafer (hereinafter simply referred to as a wafer) to be processed.

In this ion implantation process, wafers accommodated in a cassette are arranged on a circular processing table by a handling device in a processing chamber kept in a vacuum atmosphere, and the processing table is rotated and slid. The wafer is scanned by and the ion beam is uniformly irradiated.

As a structure of such an ion beam irradiation apparatus, for example, there is a structure shown in FIG.

That is, this ion beam irradiation apparatus is
The extraction electrode 2, the mass spectrometer 3, and the extraction direction of the gas emitted from the ion source 1 (direction indicated by an arrow in the drawing),
The slit 4 and the acceleration tube 5 are provided. Then, in the ion beam irradiation apparatus having such a configuration, the ion source 1
The gas or vapor injected from the plasma is turned into plasma, and only the positive ions in this plasma are extracted by the extraction electrode 2 with a certain energy, and then mass analysis is performed by the mass analyzer 3 to separate the desired ions. Further, the slit 4 separates the film. In addition, the separated ion beam is accelerated to the final energy through the accelerating tube 5, and then is irradiated to the wafer W arranged on the processing table 7 driven by the motor 6, and the surface of the wafer W is irradiated. Impurity is injected into.

Further, in the figure, reference numeral 8 indicates a Faraday cup, which confine secondary electrons generated when ions are injected into the wafer surface so as not to flow out to accurately measure the amount of ion injection. It is for.

By the way, when the ion beam is injected into the wafer, positive charges of ions are accumulated in the insulating film exposed on the surface of the wafer, and when the charge amount exceeds the dielectric breakdown charge amount, the insulating film is destroyed. Defective wafers are obtained. Further, even if the dielectric breakdown does not occur, there is an adverse effect of attaching particulates.

Therefore, a plasma generator is provided near the wafer at a position facing the ion beam, and the electrons in the plasma generated by the plasma generator are attracted to the wafer surface by the potential gradient between the plasma generator and the wafer. The surface of the wafer may be electrically neutralized.

As a mechanism for the above neutralization, for example, in FIG. 3, there is a structure provided with a plasma generating portion 9 connected to a Faraday cup 8 located near the wafer. The plasma generating unit 9 has a plasma generating chamber composed of a wall made of, for example, carbon or molybdenum, and a thermoelectron emitting filament 9A arranged in the chamber, and is introduced into the plasma generating chamber. Plasma is generated by colliding the thermoelectrons from the filament 9A with a reaction gas such as argon gas. An opening is provided on the side of the Faraday cup 8 in the plasma generation chamber, and this opening utilizes the fact that when the wafer is charged, a potential gradient is generated between the wafer surface and the plasma generation chamber. It is designed to emit electrons from the generation chamber. Further, the electrons emitted from the opening are attracted to the surface of the wafer by the above potential gradient and neutralize the charged positive charges.

The filament 9A provided in the plasma generating section 9 is supported by, for example, the structure shown in FIG.

That is, the filament 9A is supported by the filament clamp 9A1 made of a conductive member. The filament clamp 9A1 is inserted through an insulating member 9A2 attached to the wall of the plasma generation unit 9, and has a taper portion at one end in the insertion direction, that is, the side on which the filament 9A is supported, and another insertion direction. Threaded portions projecting from the insulating member 9A2 are formed at the ends. A clamp holder 9A3 fixed to the insulating member 9A2 and fitted into the tapered portion is provided at a position facing the tapered portion of the filament clamp 9A1, and a filament terminal is provided at a screw portion of the filament clamp 9A1. 9A4 is screwed in.

In such a structure, the insulating member 9
Insert the filament clamp 9A1 from below A2,
The filament terminal 9A 4 is temporarily fixed to the threaded portion of the filament clamp 9A1. Then filament 9
A is inserted into the slit formed in the taper portion of the filament clamp 9A1, and the filament terminal 9A4 is inserted.
The filament clamp 9A 1 is moved upward by screwing in, and the width of the slit is reduced by reducing the diameter of the taper portion, whereby the filament 9A can be clamped and held.

[0013] Thus, the feed line to the full I Lament 9A is configured via the slit formed in the tapered portion of the filament clamp 9A 1 and filament terminal 9A4 and filament clamps 9A 1 being screwed It will be.

[0014]

However, the structure of the filament shown in FIG. 4 has a problem that the contact resistance in the power feeding path to the filament is not stable.

[0015] That is, the filament 9A is constituted the feed line via the filament clamp 9A 1 and filament terminal 9A4, filament clamps 9
Since the both ends of A 1 in the axial direction are only pseudo-unified, the contact resistance at that portion is not stable.

[0016] More specifically, only the filament 9A is merely held by the filament clamp 9A 1, also, the filament clamp 9A 1 and filament terminal 9A4 merely been screwed. Therefore, it cannot be said that the contact state at the sandwiching portion and the screw coupling portion is uniform. For example, when the clamping pressure on the filament 9A is not sufficiently obtained due to the moving stroke of the filament clamp 9A 1 screwed together, the contact with the inner surface of the taper portion becomes unstable. Also in the threaded coupling portion of the filament clamp 9A 1 and filament terminal 9A4, contact of the threads with each other can not be said all the same in the thread engagement region, sometimes the contact state in the screw connection area is not uniform. For this reason, if the contact state is not uniform, the contact resistance also varies, and if only partial contact is obtained, the contact part may be welded due to discharge or abnormal heating at the contact position. There is.

On the other hand, when such welding occurs, the replacement of the consumable filament 9A is also adversely affected.
That is, the parts to be replaced in the above structure are
Although filament 9A only is sandwiched I Lament clamp 9A 1 is equivalent to, the welding occurs at the junction with the feed path, it is impossible to separate the components each other at that portion. Therefore, not only the filament 9A but also the filament clamp 9 to which it is coupled
Since it is impossible even taken out of the filament terminals 9A4 coupled by A 1 and the threaded portion, the result, it is necessary to replace the assembly itself, including the insulation member 9A2.

For this reason, it becomes necessary to replace even the parts that do not need to be replaced, which increases the parts procurement cost.

On the other hand, if the contact state is non-uniform as described above, the heat generation state of the filament 9A also becomes non-uniform. Therefore, when the amount of heat generated by the filament 9A is unstable, the amount of thermoelectrons emitted is also unstable, and it may not be possible to neutralize the positive charges accumulated on the wafer. The cause of the change in the amount of emitted thermoelectrons is not only the amount of heat generated, but also the amount of plasma generated. This plasma production amount is also affected by the collision stroke length of the thermoelectrons and the reaction gas. For this reason, if the filaments are arranged in an inappropriate position, a desired amount of generated plasma cannot be obtained, and in some cases, sufficient electrons cannot be emitted to neutralize the charges accumulated on the object to be processed. .

Therefore, in view of the problem of the electrode support structure in the above-mentioned conventional ion implanter, the object of the present invention is to minimize the number of parts when exchanging and to cause contact failure. It is an object of the present invention to provide an ion implantation apparatus having an electrode support structure capable of stabilizing the amount of heat generated in the filament by eliminating the above, and reliably suppressing the accumulation of positive charges generated by ion irradiation.

[0021]

In order to achieve this object, the invention according to claim 1 is an ion implantation apparatus for implanting impurities into an object to be processed under a reduced pressure atmosphere, wherein the object to be ion-implanted is processed. The thermoelectron emission unit is disposed in the vicinity and includes a plasma generation unit into which a plasma generation gas is introduced, and a thermoelectron emission unit including a filament that is disposed in the plasma generation unit and emits thermoelectrons. The filament clamp is fixed to the casing of the plasma generating unit, and the filament clamp is composed of a pair of rods, the end of which is integrated in advance with one end in the axial direction and has an electrode connecting portion at the other end in the axial direction. comprising an insulating member having an insertion portion of the clamp, and an insulating holding member insertion has been described above filaments clamped to the insulating member is fixed to the insulating member, the upper Filament clamp, the absolute
The electrode connecting portion protruding from the edge member and the pair of locks.
And a step portion formed in the middle of the
Is in surface contact with the above step, and one surface of the step is used as a reference.
It forms a spacer that positions the filament.
It is characterized in that that.

[0022]

The invention according to claim 2, in claim 1 Te Hey <br/>, and the filament clamp and the filament, is characterized in that it is integrated in a state of surface contact by caulking.

The invention according to claim 3 is the invention according to claim 1 or 2.
Oite, the filament is characterized by being smaller in diameter than the pair of rods.

[0025]

According to the present invention, the filament clamp is provided with a pair of rods in which the end of the filament is integrated in advance with one end in the axial direction and the electrode connecting portion is provided at the other end in the axial direction. For this reason, since there is no portion for connecting the parts to each other in the range from the electrode connecting portion to the filament, it is possible to eliminate the contact failure that occurs when the connecting portion is provided. Moreover, since the filament having the coupling portion and the filament clamp are brought into surface contact with each other by integral processing by caulking, the contact state at this portion is also uniform. Therefore, it is possible to eliminate a portion that causes discharge or abnormal heating due to poor contact in the range from the electrode connection portion to the filament, and thus it is possible to suppress an increase in replacement parts due to welding. In particular, the replacement parts can be limited to only the filament and the filament clamp which are integrated in advance.

Further, according to the present invention, a holding member as a spacer for fixing the filament clamp inserted into the insulating member to the insulating member and for positioning the filament is provided. Moreover, the holding member can be fitted to the stepped portion formed on the filament clamp. For this reason, the filament clamp is not only fixed to the insulating member by being fitted to the holding member, but also the filament can be positioned with reference to the one surface of the step portion when fitted to the insulating member.

Further, in the present invention, the filament and the filament clamp, which are integrated in a surface contact state by caulking, have a smaller diameter than the filament clamp. Therefore, the heat generation amount of the filament in the power supply path reaching the filament can be increased as compared with other portions. Therefore, it is possible to stabilize the amount of heat generated in the filament without causing abnormal heating in the area reaching the filament and since there is no portion where the contact resistance changes in the area reaching the filament.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the embodiments shown in the drawings.

FIG. 1 shows the structure of a thermoelectron emission unit in a plasma generation unit used in the ion implantation apparatus according to the present invention.

That is, the thermoelectron emission unit 10 includes the insulating member 12 attached to the housing of the plasma generating unit corresponding to the plasma generating unit 9 shown in FIG. 3 and the filament clamp 14 inserted into the insulating member 12. I have it.

The filament clamp 14 is an insulating member 1.
It is composed of a pair of rods made of tungsten and inserted into the support hole 12A made in 2. The one end in the insertion direction is downward from the lower surface of the insulating member 12, and the other end in the insertion direction is from the upper surface of the insulating member 12. It projects upwards respectively.
And, at one axial end of the filament clamp 14,
An end portion of a U-shaped filament 16 (hereinafter referred to as a filament) is integrated in advance, and an electrode connecting portion 14A to which an electrode (not shown) from a power feeding portion is attached is formed at the other end in the insertion direction. ing. In the present embodiment, the outer diameter dimension of the electrode connecting portion 14A in the filament clamp 14 is set to be smaller than the portion inserted in the insulating member 12, and for example, the portion inserted in the insulating member 12 is 4 mm. However, the electrode connection part is 3 mm
Is set to. This is the filament clamp 14
This is for preventing the electrode connection portion 14A from interfering with the hole edge of the insulating member 12 when the electrode connecting portion 14A is extracted from the insulating member 12.

Further, a hole (not shown) having a depth of about 10 mm is formed in the center of one end of the filament clamp 14 in which the filament 16 is integrated, in the insertion direction. The filament 16 can be inserted.

On the other hand, the filament 16 is made of a tungsten wire having a diameter smaller than that of the filament clamp 14, and the end portion of the filament 16 is formed by the filament clamp 14.
By being caulked after being inserted into the hole, the inner surface of the hole is integrated with the inner surface of the hole.

By the way, the filament clamp 14
There is a possibility that the product may fall in the direction of gravity if it is simply inserted into the insulating member 12. Therefore, in this embodiment, a structure for fixing the filament clamp 14 to the insulating member 12 is provided.

That is, the portion of the filament clamp 14 projecting upward from the insulating member 12 has a stepped portion 14B having a diameter smaller than that of the portion inserted into the insulating member 12.
Are formed. The stepped portion 14B has a structure shown in FIG.
As shown in FIG. 5, the elongated hole 18A formed in the holding member 18 placed on the upper surface of the insulating member 12 can be fitted. The holding member 18 is formed with a long hole 18B for inserting the fastening member 20 in addition to the long hole 18A, and the fastening member 20 inserted into the long hole 18B is a screw formed on the insulating member 12. By being tightened in the hole, the filament clamp 14 is fixed on the insulating member 12 with one surface of the stepped portion 14B placed thereon.

Further, the holding member 18 is configured as a spacer for positioning the filament 16 with one surface of the stepped portion 14B of the filament clamp 14 placed as a reference. In other words, the position of the curved tip portion of the filament 16 inserted into one end of the filament clamp 14 in the insertion direction is defined by the depth of the hole formed in the filament clamp 14.
Therefore, since the amount of protrusion of the filament 16 is constant, the distance from the one surface of the step 18B to the curved tip of the filament 16 can be maintained in a constant state.

Since this embodiment has the above-mentioned structure,
When assembling the electrode portion 10, first, the filament clamp 14 is inserted into the hole of the insulating member 12. Prior to insertion of the filament clamp 14, the filament 16 is inserted into the other axial end of the filament clamp 14, and the inserted portion is caulked to integrate the filament 16 into the filament clamp 14. By doing so, it is possible to reduce the number of processes in the assembly stage. After inserting the filament clamp 14 into the insulating member 12, the elongated hole 18A of the holding member 18 is inserted.
After being fitted to the step portion 14B of the filament clamp 14, the holding member 18 is fixed to the upper surface of the insulating member 12 by using 20 as a fastening member.

The thermoelectron emission portion 10 thus assembled is mechanically provided in a region from the electrode portion 14A located at one axial end of the filament clamp 14 to the integral portion with the filament 16 located at the other axial end. There is no intervening connecting part, and there is no part that causes poor contact in that region. Therefore, since there is no portion where the contact resistance changes in the power feeding path from the electrode portion 14A to the filament 16,
The amount of power supplied to the filament 16 can always be made constant. Therefore, the calorific value of the filament 16 can be always maintained constant, and the thermoelectrons necessary for neutralization can be generated in a constant state. Moreover, since there is no portion where the contact resistance changes, discharge and abnormal heating that occur when such a portion is present are prevented, so that welding does not occur in the power supply path.

On the other hand, when power is supplied to the filament 16, the difference in outer diameter between the filament clamp 14 and the filament 16 is set. In this case, the outer diameter of the filament 16 is set smaller. Therefore, the amount of heat generated in the filament 16 can be made larger than that in other portions, so that the filament 16 can generate concentrated heat. Therefore, the amount of power supplied to the filament 16 is constant, and the amount of thermoelectrons generated in the filament 16 can be constant.

When replacing the filament 9A, the fastening member 20 is loosened to remove the elongated hole 18A of the holding member 18 from the stepped portion 14B of the filament clamp 14, and the filament clamp 14 is pulled out from the hole of the insulating member 12.
In this case, since the outer diameter of the electrode portion 14A of the filament clamp 14 is smaller than the outer diameter of the main body of the filament clamp 14, the filament clamp 14 can be easily pulled out downward in FIG. Moreover, since there is no mechanical connection between the insulating member 12 and the filament clamp 14, neither of the two will weld. Therefore, as a replacement part, the filament clamp 14 and the filament clamp 14 are integrated. Filament 16
Only the number of replacement parts can be reduced compared to the conventional structure.

The present invention is not limited to the above embodiments, but various modifications can be made within the scope of the gist of the present invention. For example, the filament clamp need only have a rod shape, and its cross-sectional shape is not specified, and it may have a polygonal cross-sectional shape.

[0042]

As described above, according to the present invention, a structure is provided between one end in the axial direction of the filament clamp where the connecting portion to which the electrode from the power feeding portion is connected is located and the other end in the axial direction where the filament is coupled. Since the connecting portion is not present in the power feeding path, the mechanical connecting structure such as fitting and fastening can be eliminated. For this reason, it is possible to prevent welding due to electric discharge or abnormal heating at the connecting portion which occurs when the mechanical connecting structure is provided. Therefore, the occurrence of a welded portion in the power supply path can be prevented, and the number of parts required for replacement can be reduced. In particular, when replacing, only the filament and the filament clamp that are integrated by crimping in advance are sufficient. .

Further, the filament clamp is attached to the insulating member by a holding member fitted to a step portion formed on a part of the rod. Therefore, the filament is
It is possible to position the filament clamp on the basis of the one surface of the stepped portion of the filament clamp with which the holding member is fitted. Therefore, the thermoelectron emission position can be set to the optimum position according to the plasma generation condition.

Further, according to the present invention, since the filament integrated with the filament clamp by caulking has a diameter smaller than that of the filament clamp and generates a large amount of heat, a portion other than the filament is abnormally heated. It is possible to prevent a situation in which the state is reached. Moreover, since there is no place where the contact resistance changes in the range up to the filament, it is possible to stabilize the amount of heat generated by the filament. Therefore, it is possible to stably release the thermoelectrons necessary for neutralizing the charge by ion irradiation.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a structure of an electrode unit in a plasma generating unit used in an ion implantation apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view of an electrode unit shown in FIG.

FIG. 3 is a schematic diagram for explaining a conventional structure of an ion implantation device.

4 is a cross-sectional view showing an example of an electrode structure of a plasma generating unit for charge neutralization used in the ion implantation apparatus shown in FIG.

[Explanation of symbols]

9 Plasma generation unit equivalent to plasma generation unit 10 Thermionic emission part 12 Insulation member 14 filament clamp 14A electrode part 14B step 16 filament 18 Positioning member

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-190134 (JP, A) JP-A-5-251061 (JP, A) Actual opening 1-164657 (JP, U) Actual opening 1- 103248 (JP, U) Actual development Sho 59-74659 (JP, U) Actual development Sho 60-112068 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01J 37/317 C23C 14 / 48 H01J 27/20 H01J 37/08 H01L 21/265

Claims (3)

(57) [Claims] 1. An ion implantation apparatus for implanting impurities into an object to be processed under a reduced pressure atmosphere, the plasma generating unit being disposed in the vicinity of the object to be ion-implanted and into which a plasma-generating gas is introduced. A thermoelectron emission part disposed in the plasma generation part and provided with a filament for emitting thermoelectrons, wherein the thermoelectron emission part has an end portion of the filament previously integrated with one end in the axial direction, A filament clamp including a pair of rods having an electrode connecting portion at an end, an insulating member fixed to the housing of the plasma generation unit and having an insertion portion of the filament clamp, and the filament inserted in the insulating member. An insulating holding member for fixing the clamp to the insulating member, the filament clamp protruding from the insulating member.
Formed between the electrode connection part and the pair of rods.
And the holding member is in surface contact with the stepped portion, and one surface of the stepped portion is provided.
Spacer for positioning filament based on
Ion implantation apparatus characterized by constituting the. Wherein Oite in claim 1, and the filament clamp and the filament, ion implantation apparatus, characterized in that it is integrated in a state of surface contact by caulking. 3. Oite to claim 1 or 2, the filaments ion implantation apparatus characterized by being smaller in diameter than the pair of rods.