JP3360673B2 - Ion source - 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 source for use in, for example, an ion implanter for manufacturing semiconductor devices, and more particularly to an ion source using an organometallic vapor as a raw material. The present invention relates to means for suppressing clogging of a nozzle provided at a location where steam is introduced into a plasma generation container.

[0002]

2. Description of the Related Art FIG. 4 shows an example of a conventional ion source.
This ion source is called a Bernas type ion source, and a similar one is described in Japanese Patent Application Laid-Open No. 9-35648.

The ion source includes a metal (for example, stainless steel) plasma generation container 2 also serving as an anode, a filament 8 provided on one side of the plasma generation container 2, and a filament 8 provided on the other side of the plasma generation container 2. The apparatus includes a reflection electrode 10 provided therein and an ion extraction slit 4 provided on a wall surface of the plasma generation container 2. Near the outlet of the ion extraction slit 4, an extraction electrode 14 for extracting an ion beam 16 from the plasma 12 generated in the plasma generation container 2 is provided. Plasma generation container 2
Inside, a magnetic field 18 is applied from the outside.

[0004] The plasma generation vessel 2 includes an insulating spacer 32.
Are supported from a metal (for example, stainless steel) flange 28 by a plurality of metal (for example, stainless steel) columns 30. The flange 28 is also a vacuum partition, and the outside (the lower side in FIG. 4) is in the atmosphere, and the inside (the upper side in FIG. 4) is evacuated. Insulation spacer 32
Is made of, for example, ceramics such as alumina, and in this example, has both electrical insulation and thermal insulation.

[0005] The plasma generation vessel 2 has a steam inlet 6 on the wall thereof, and the steam inlet 6 has a nozzle 20.
The steam supply pipe 22 made of metal (for example, stainless steel) is connected to the nozzle 20. The steam supply pipe 22 passes through the flange 28 and is fixed to the flange 28. From an organometallic vapor generation source (not shown) provided in the atmosphere, a vapor supply pipe 22 and a nozzle 2
The organic metal vapor 24 is introduced as a raw material for plasma generation into the plasma generation container 2 through the chamber 0 and the vapor inlet 6.

Referring to FIG. 5, the nozzle 20 is made of an integral body of a heat insulating material (for example, ceramics such as alumina) having a lower thermal conductivity than metal. In this example, the nozzle 20 has both heat insulation and electric insulation. .

The organometallic vapor 24 is obtained by vaporizing (gasifying), for example, trimethylindium [In (CH ₃ ) ₃ ], triethylindium [In (C ₂ H ₅ ) ₃ ] or the like.

In such an ion source, the filament 8 is energized and heated while the inside and outside of the plasma generation vessel 2 are evacuated and the organometallic vapor 24 is introduced into the plasma production vessel 2 at an appropriate flow rate. An arc discharge voltage is applied between the plasma generation vessel 2 and the plasma generation vessel 2 to generate an arc discharge therebetween, whereby the organometallic vapor 24 is ionized and the plasma 12 is generated. Then, an ion beam 16 containing ions of the metal constituting the organometallic vapor 24 can be extracted from the plasma 12. For example, when the organometallic vapor 24 is trimethylindium or triethylindium as described above, the ion beam 16 containing indium ions can be extracted.

The reflection electrode 10 repels the electrons emitted from the filament 8 and acts to increase the ionization efficiency of the organometallic vapor 24, and thus the generation efficiency of the plasma 12.

[0010]

The plasma generating vessel 2 is arranged in a vacuum, and the insulating spacer 3
When the ion beam 16 is extracted by introducing the organometallic vapor 24, the filament 8 is energized and heated, or plasma is generated by arc discharge. It gets hot due to the power input for it. For example, it becomes about several hundred degrees Celsius. Also,
It is better to keep the plasma generation vessel 2 at a high temperature.
This is preferred for reasons such as increasing the production efficiency of 2.

On the other hand, the steam supply pipe 22 is connected to a flange 28, which is kept at about room temperature in order to connect the ion source to other equipment. It may be cooled by water cooling or the like as necessary. Therefore, the temperature of the steam supply pipe 22 is governed by the temperature of the flange 28 due to the heat conduction with the flange 28, and is much lower than the temperature of the plasma generation vessel 2. For example, it is about room temperature.

A nozzle 20 made of the above-mentioned heat insulating material is provided for the purpose of, for example, thermally insulating the high-temperature plasma generation vessel 2 from the low-temperature steam supply pipe 22.

Conventionally, however, the nozzle 20 has a more specific structure in which the vicinity of the tip is formed of a metal (for example, indium) deposited from an organic metal vapor 24 as shown by a two-dot chain line in FIG. However, there is a problem that it is easily clogged by the C.34. Until now, phosphorus (P) and arsenic (As)
When introducing a gas containing, the clogging of the nozzle 20 did not cause much problem, but when the organometallic vapor 24 as described above was introduced, the clogging became very easy.

The cause is considered as follows. That is, the organic metal vapor 2 introduced into the plasma generation vessel 2
4 is converted into plasma in the plasma generation vessel 2 or is thermally decomposed near the wall surface of the plasma generation vessel 2, whereby a pure metal having a boiling point much higher than that of the organometallic state is deposited. For example, trimethylindium can be handled in a gas state at about 90 ° C., but the boiling point of indium is as high as 2080 ° C.

The tip of the nozzle 20 is connected to the vapor inlet 6 and the plasma
(See FIG. 4), so that the extremely high boiling point metal deposited as described above reaches near the tip of the nozzle 20. In the vicinity of the tip of the nozzle 20, the nozzle 2 from the wall of the plasma generation vessel 2 to the steam supply pipe 22
Since a large amount of heat escapes (heat conduction) through 0 and a large decrease in temperature (see a conventional example in FIG. 2B described later), the metal is easily precipitated and the deposited metal is less likely to re-evaporate. This metal becomes the deposit 34 and clogs the vicinity of the tip of the nozzle 20. On the other hand, since phosphorus and arsenic have much lower boiling points or sublimation points than the above metals, clogging of the nozzle 20 did not cause much problem.

When the nozzle 20 is clogged, the supply amount of the organometallic vapor 24 into the plasma generation vessel 2 decreases, so that the density of the plasma 12 decreases and the beam amount of the ion beam 16 decreases. Drawer becomes difficult.

In order to prevent this, the ion source must be disassembled and the nozzle 20 needs to be cleaned frequently, which requires a lot of trouble and lowers the operating efficiency of the ion source.

Therefore, the present invention has a main object of suppressing the nozzle clogging as described above.

[0019]

According to one aspect of the present invention, there is provided an ion source in which the nozzle has a lower thermal conductivity than metal.
A connection made of heat insulating material that is thinner than before and after
With two or more nozzle parts connected in series
It is characterized in that it is configured.

According to the above configuration, the connection portion is located before and after the connection portion.
Heat insulation part which is thinner and has higher thermal resistance than before and after
The connection, that is, the heat insulating portion, suppresses the escape of heat from the wall of the plasma generation vessel to the steam supply pipe, so that the temperature of the nozzle near the vapor inlet of the plasma generation vessel is kept high. You will be drooped. As a result, deposition of metal from the organometallic vapor near the tip of the nozzle is reduced, and re-evaporation of the deposited metal is also increased. Therefore, the amount of deposition of the metal is reduced, and clogging of the nozzle can be suppressed.

[0021]

FIG. 1 is an enlarged sectional view showing an example of the vicinity of a nozzle of an ion source according to the present invention. Since the entire configuration of the ion source is the same as, for example, FIG. 4, the drawing and the above description will be referred to, and redundant description will be omitted here.

The ion source according to the present invention includes a nozzle 40 having the following structure in place of the nozzle 20 of the conventional ion source. Connected to the steam inlet 6. That is, the nozzle 40 connects the steam inlet 6 of the plasma generation container 2 and the tip of the steam supply pipe 22.

In this example, the nozzle 40 is composed of two nozzle parts 42 and 44 connected in series to each other at a connection portion 45 that is narrower than the front and rear. More specifically,
A narrower connection 45 at the front of the rear nozzle component 44 is inserted into the rear of the front nozzle component 42. The thinned connection 4 at the front of the front nozzle part 42
3 is inserted into the steam inlet 6 of the plasma generation vessel 2, and a steam supply pipe 22 is provided in the rear part of the rear nozzle component 44.
Is inserted. A space 46 is provided around the connection portion 45 in this example.

The nozzle parts 42 and 44 are both made of a heat insulating material having a lower thermal conductivity than metal.
This heat insulating material is, for example, alumina (Al ₂ O ₃ ), but ceramics such as 3Al ₂ O ₃ .2SiO ₂ , zirconia, and sialon can also be used.

In this example, although the nozzle parts 42 and 44 also have electrical insulation between the plasma generation vessel 2 and the steam supply pipe 22, this electrical insulation is performed by using another insulating material. May be.

It is preferable that the thickness of the connecting portion 45 is reduced as far as the strength allows. By doing so, the heat insulating effect can be further enhanced.

The diameters of the holes in the nozzle parts 42 and 44, and even the holes in the steam supply pipe 22, are preferably substantially equal to each other, as in this example. By doing so, the flow of the organometallic vapor 24 in the nozzle 40 can be made smooth, and the deposition of metal can be further reduced.

Since the connecting portion 45 is thinner than its front and rear portions, the heat resistance is larger than that of its front and rear portions.
With this connecting portion 45, a heat insulating portion having a higher thermal resistance than before and after is formed between a portion connected to the steam inlet 6 and a portion connected to the steam supply pipe 22. The connecting portion 45, that is, the heat insulating portion is preferably located at a position where the metal generated in the plasma 12 in the plasma generating container 2 does not substantially diffuse. If it does so, the said connection part 4
5 (heat insulating portion) can be prevented from depositing a metal.

The connection portion 45, that is, the heat insulating portion, suppresses the escape (heat conduction) of heat from the wall surface of the plasma generation container 2 to the steam supply pipe 22, so that it is close to the vapor inlet 6 of the plasma generation container 2. Part of the nozzle 40 is maintained at a high temperature. As a result, deposition of metal from the organometallic vapor 24 near the tip of the nozzle 40 is reduced, and re-evaporation of the deposited metal is also increased. Can be.

Moreover, like the nozzle 40, the connecting portion 4
5 is not integrated with the rear part of the nozzle part 42,
If the structure is inserted into the rear part of the nozzle part 42, the thermal resistance generated at the inserted part can also be effectively used for heat insulation, so that the heat insulating effect at the connection part 45 is further improved.

Further, as in the nozzle 40, the connecting portion 45
If a space 46 is provided around the front nozzle part 4
2 can prevent contact between the rear end face and the front end face of the thicker part of the rear nozzle component 44, and can completely cut off heat conduction at portions other than the connection portion 45, so that the heat insulating effect at the connection portion 45 can be further improved. Further improve.

FIG. 2A shows the vicinity of the nozzle 40 again.
A schematic temperature distribution in the vicinity is shown as an example in FIG. 2B. The temperature drop from the inner wall surface of the plasma generation vessel 2 to the connection part 45 is small, and the temperature drops sharply at the connection part 45,
Eventually, the temperature of the steam supply pipe 22 (for example, about room temperature) is reached. That is, the vicinity of the tip of the nozzle 40 close to the wall surface of the plasma generation vessel 2 is more specifically the front nozzle part 42.
Is maintained in a high temperature region close to the temperature of the inner wall surface of the plasma generation container 2. Thereby, as described above, the organometallic vapor 24 near the tip of the nozzle 40
Clogging can be suppressed by reducing the amount of deposition of metal precipitated from the steel.

For comparison, a temperature distribution when the conventional nozzle 20 shown in FIG. 5 is used is shown by a two-dot chain line in FIG. 2B as a conventional example. The overall length, material, etc. of the nozzles are the same for both nozzles 40 and 20. In the conventional example, since the heat insulating portion is not provided in the nozzle 20, the heat transfer (heat release) from the wall surface of the plasma generation container 2 to the steam supply pipe 22 is large, and the temperature is relatively low up to the vicinity of the tip of the nozzle 20. Is imminent. Also, by the escape of heat,
The temperature of the inner wall surface of the plasma generation vessel 2 is also lower than in the case of the above embodiment. For this reason, in the conventional example, the vicinity of the tip of the nozzle 20 was easily clogged.

FIG. 3 shows a measurement result of a change in weight of the nozzle. In the drawing, the conventional example is the case of the nozzle 20 shown in FIG. 5, and the embodiment is the case of the nozzle 40 shown in FIG.
Also in this case, the overall length, material, and the like of both nozzles 20 and 40 are set to the same condition.

The nozzle weight increases with the elapse of the operation time. This weight increase corresponds to the amount of the deposit 34 described above. It can be seen that the example has a smaller amount of adhesion and is less likely to clog the nozzle.

From FIG. 3, it may seem at first glance that there is not much difference in the weight increase of the nozzle. Greatly inhibits. For example, in the conventional nozzle 20 shown in FIG. 5, the operation time is about 15 hours, and the beam amount of the ion beam 16 is 2 initially.
Experiments show that the nozzle 40 of the embodiment shown in FIG. 1 hardly reduces the beam amount of the ion beam 16 even when the operating time is about 33 hours, which is about twice that of the nozzle 40 shown in FIG. Has been verified.

That is, in the conventional nozzle 20, as shown in FIG. 5, the metal (deposit 34) concentrates and adheres to a specific portion near the tip, so that it is very easy to clog. 2, the temperature of the front nozzle part 42 as a whole is high as shown in FIG. 2, and the metal (deposit) is dispersed almost entirely on the inner surface of the nozzle part 42 so as to be substantially uniform with substantially the same thickness. Even though the amount of adhesion does not seem to be much different from that of the conventional example, the nozzle 4
0 is much harder to clog.

As described above, when the nozzle 40 as described above is used, the operable time of the ion source can be extended at least twice or more as compared with the case where the conventional nozzle 20 is used. As a result, the trouble of disassembling and cleaning the ion source is reduced, and the operation efficiency of the ion source is improved.

Further, when the nozzle 40 is used, when the input power (specifically, arc discharge current) to the plasma 12 in the plasma generation container 2 is compared under the same condition, the nozzle 40 is more effective than when the conventional nozzle 20 is used. Also, it has been confirmed by experiments that the beam amount of the ion beam 16 can be increased. This is because, as shown in FIG. 2B, according to the nozzle 40, the temperature of the inner wall surface of the plasma generation container 2 also increases, and thereby, it is separated from the organometallic vapor 24 and adheres to the inner wall surface of the plasma generation container 2. This is considered to be because the re-evaporation effect of the adhered metal increases and the amount of metal ions in the plasma 12 increases.

The nozzle 40 has a nozzle part 4
This is an example of a two-stage structure in which two and 44 are connected in series, but with the same idea, three or more nozzle parts are connected in series (for example, inserted one after another as described above).
A structure having more than one step may be used. By doing so, two or more stages of heat insulating portions having higher thermal resistance than before and after are formed.
The heat insulating effect and the effect of suppressing clogging of the nozzle are further improved.

The present invention is not limited to the above-mentioned Bernas-type ion source, but may be any other type of ion source, for example, Kauffman type, Freeman type, PIG.
The present invention can be widely applied to ion sources such as a type, a bucket type (multipole magnetic field type), and an ECR type.

[0042]

Since the present invention is configured as described above, it has the following effects.

[0043]

According to the first aspect of the present invention, the connecting part connecting the nozzle parts forms a heat insulating part having a larger thermal resistance than the front and rear parts.
The escape of heat from the wall of the container to the steam supply pipe is reduced.
Of the part near the vapor inlet of the plasma generation vessel
The nozzle will be kept hot. As a result, the nozzle
Metal deposition from the organometallic vapor near the tip of
In addition, the re-evaporation of the deposited metal increases,
Reduces the amount of deposits and suppresses nozzle clogging.
You. As a result, the trouble of disassembling and cleaning the ion source is reduced, and
The operation efficiency of the ion source is also improved.

According to the second aspect of the present invention, the thermal resistance generated at the insertion portion can also be effectively used for heat insulation, and further, by providing a space around the connection portion, heat conduction at portions other than the connection portion can be achieved. Can be completely cut off,
The heat insulating effect at the connection portion is further improved, and the effect of suppressing clogging of the nozzle is further improved.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view showing an example of the vicinity of a nozzle of an ion source according to the present invention.

FIG. 2 is a diagram showing a schematic temperature distribution near a nozzle of FIG. 1;

FIG. 3 is a diagram illustrating an example of a measurement result of a change in weight of a nozzle.

FIG. 4 is a diagram showing an example of a conventional ion source.

FIG. 5 is an enlarged sectional view near a nozzle in FIG. 4;

[Explanation of symbols]

 Reference Signs List 2 Plasma generation container 6 Steam inlet 22 Steam supply pipe 24 Organometallic vapor 40 Nozzle 42, 44 Nozzle part 45 Connection part (heat insulation part)

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01J 27/02 H01J 37/08 H01J 37/317

Claims (2)

(57) [Claims] 1. A plasma generating container having a vapor inlet for converting an organic metal vapor introduced from the vapor inlet into a plasma, and a plasma generating container connected to the vapor introducing port of the plasma generating container and having a temperature higher than that of the metal. An ion comprising a nozzle made of a heat insulating material having a low conductivity, and a vapor supply pipe connected to the nozzle and supplying the organometallic vapor to the nozzle and introducing the organometallic vapor through the nozzle into the plasma generation vessel. In the source, the nozzle is made of a heat insulating material having a lower thermal conductivity than metal, and is formed of two or more nozzle parts each connected in series at a connection portion smaller than the front and rear. An ion source characterized by the following. 2. A method slender connection portions than the other at the front of the rear of the nozzle part, with inserted into the rear portion of the front of the nozzle component of claim 1, characterized in that a space is provided around the connection portion ions source.