JP2591079Y2 - Current measuring device for charged particle beam - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charged particle beam current measuring device for measuring the beam current of a charged particle beam, which is used for a charged particle beam device such as an ion implantation device. The present invention relates to a cooling structure of a Faraday cup that can be cooled.

[0002]

2. Description of the Related Art An ion implantation apparatus ionizes impurities to be diffused, selectively extracts the impurity ions by mass spectrometry using a magnetic field, accelerates the ions as necessary, and irradiates the ion irradiation target with ions. This is for implanting impurities into the irradiation object. This ion implantation apparatus is an important apparatus for manufacturing integrated circuits at present because it can implant impurities that determine device characteristics in an arbitrary amount and depth with good controllability in a semiconductor process.

In the above ion implantation apparatus, the beam current of an ion beam is measured during the implantation process in order to uniformly implant ions into an ion irradiation target such as a semiconductor wafer and to control the amount of implantation to a specified value. It is necessary to count the ion implantation amount (dose amount).

For example, while a spot-shaped ion beam is electrostatically or electromagnetically scanned in the X direction (for example, horizontal direction), the beam irradiation object side is scanned in the Y direction (for example, vertical direction) orthogonal to the X direction (scanning direction). In a so-called hybrid scan type medium-current ion implanter that is mechanically driven in (1), a Faraday cup (so-called dose Farade) is installed at an end in a beam scanning area, and the current amount of the ion beam incident on the Faraday cup Is measured by a beam current measurement unit including a current / voltage conversion circuit, an amplification circuit, an analog / digital conversion circuit, an integration circuit, and the like.

Since the ion beam having a relatively high energy is directly applied to the Faraday cup, an increase in the temperature of the Faraday cup is inevitable. However, in the current medium-current ion implantation apparatus, since the energy of the ion beam is not so large, a large problem hardly occurs due to the temperature rise of the Faraday cup.
For this reason, cooling of the Faraday cup has not been considered so far.

Normally, carbon is used as the material of the Faraday cup, so it is difficult to form a coolant passage in the Faraday cup and to flow the cooling water. Cooling water cannot be flowed directly into the Faraday cup because it must be electrically insulated from the ground potential side. For this reason, the conventional cooling of the Faraday cup is performed by natural cooling, or even if the cooling is performed by forced cooling, the refrigerant is placed inside a metal mounting member made of stainless steel or the like for mounting the Faraday cup to the ion implantation apparatus main body. All that is required is to form a passage and allow the cooling water to flow through the water medium passage.

[0007]

[Problem to be solved by the invention] By the way, today,
In order to realize further miniaturization and mass production of devices, a medium-current ion implanter capable of performing an implantation process by increasing the beam amount compared with the current ion implanter is desired. In the apparatus, the energy given from the beam increases with the increase in the beam amount of the ion beam, so the temperature of the Faraday cup receiving the irradiation of the ion beam becomes higher than before, and the following, which has not existed in the past, such as the following: Problems arise.

[0008] That is, when the Faraday cup rises above a certain temperature, thermoelectrons jump out from the surface.
In this case, since the thermoelectrons jumping out of the Faraday cup are also measured as the beam current, an accurate beam current amount cannot be measured.

[0009] Further, the components constituting the Faraday cup expand due to a rise in temperature, and cracks occur in the components,
Alternatively, component damage such as melting of the component occurs.

A Faraday cup for measuring the amount of current of an ion beam is used in a high vacuum, and is therefore provided in a vacuum chamber sealed with a vacuum by an O-ring. The temperature of the periphery of the Faraday cup also rises considerably due to the rise in temperature, but when the flange of the vacuum chamber that seals the vacuum is heated, the O-ring attached to the vacuum chamber deforms or melts. However, vacuum sealing becomes impossible.

The present invention has been made in view of the above, and an object of the present invention is to provide a charged particle beam current measuring device capable of efficiently cooling a Faraday cup and solving the above-mentioned problems. It is in.

[0012]

SUMMARY OF THE INVENTION A charged particle beam current measuring device according to the present invention is provided in a vacuum, electrically insulated from other members by insulating means, and has a cup-like shape having a charged particle beam entrance. In order to solve the above-mentioned problem, the following means have been taken.

That is, the charged particle beam current measuring device is provided so as to cover the outer surface of the Faraday cup, and has a black cooling cover whose inner surface facing the outer surface of the Faraday cup is black. The outer surface of the Faraday cup is black, and a coolant passage for flowing a coolant is formed inside the cooling cover.

[0014]

Since the Faraday cup is provided in a vacuum, cooling of the Faraday cup by convective heat transfer cannot be expected. In addition, since the Faraday cup must be insulated from other parts, it is not possible to flow cooling water directly into the Faraday cup, and to increase the insulation, the contact area between the Faraday cup and the insulating means is large. Since the heat of the Faraday cup cannot be transferred to other members by heat conduction via the insulating means having low thermal conductivity, the cooling of the Faraday cup by heat conduction cannot be expected. In addition, all objects emit radiant energy, but the amount of emitted radiant energy increases rapidly with temperature, so that radiant heat transfer (radiative heat transfer) becomes dominant at high temperatures. From the above, it is considered that when the temperature of the Faraday cup increases due to the energy of the beam incident on the Faraday cup, the heat of the Faraday cup moves to the surrounding members by radiation.

According to the above configuration, since the outer surface of the Faraday cup is covered with the cooling cover, heat of the Faraday cup moves to the cooling cover by radiation. The outer surface of the Faraday cup and the inner surface facing the outer surface of the Faraday cup in the cooling cover,
Since both are treated in black, heat transfer by radiation between the Faraday cup and the cooling cover is high. For this reason, the heat of the Faraday cup, whose temperature has increased due to the energy of the beam, efficiently moves to the cooling cover.

A coolant passage is formed inside the cooling cover, and when a coolant such as cooling water flows through the coolant passage, heat transferred from the Faraday cup to the cooling cover is transmitted to the coolant and is transferred to the outside together with the coolant. Is discharged to

As described above, since the heat of the Faraday cup efficiently moves to the cooling cover and is discharged to the outside by the refrigerant, the cooling efficiency of the Faraday cup can be improved.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

As shown in FIG. 1, the charged particle beam current measuring apparatus according to the present embodiment includes a box-shaped cup-shaped carbon Faraday cup 1 having a beam entrance 1a through which a beam is incident. A cooling cover 2 that covers the entire outer surface of the Faraday cup 1 except for the beam entrance 1a of the decup 1; A beam passage hole 2a for passing a beam is provided in a portion of the cooling cover 2 corresponding to the beam entrance 1a of the Faraday cup 1.
Are drilled.

A coolant passage 2b is provided inside the cooling cover 2.
Is formed, and a coolant such as cooling water passes through the coolant passage 2b to cool the cooling cover 2.
The cooling cover 2 is formed of a material having a high thermal conductivity and a workability sufficient to form the refrigerant passage 2b therein, for example, a metal such as aluminum or stainless steel.

The Faraday cup 1 and the cooling cover 2 are separated by an insulating washer 3, an insulating washer 4, and a mounting bolt 5 so that the distance between the outer surface of the Faraday cup 1 and the inner surface of the cooling cover 2 can be any position. It is fixed so as to have a substantially constant distance. The insulating washer 3 as insulating means is interposed between the Faraday cup 1 and the cooling cover 2 so as to insulate the two from each other.

The Faraday cup 1 is connected to a beam current measuring unit (not shown) for measuring a current amount of a charged particle beam such as an ion beam incident on the Faraday cup 1.
It is connected by a current detection lead wire (not shown).
The beam current measurement unit includes a current / voltage conversion circuit that converts a beam current flowing into the Faraday cup 1 into a voltage, an amplification circuit that amplifies a signal converted into a voltage, and an analog / digital conversion of an output of the amplification circuit at high speed. Analog /
It is composed of a digital conversion circuit, an integration circuit for integrating the output of the analog / digital conversion circuit every predetermined time, and the like.

The cooling cover 2 is fixed to a main body of a device (for example, an ion implantation device) using the current measuring device by a fixing means such as a bolt (not shown). The device main body in which the current measuring device is used is usually at the ground potential, and the cooling cover 2 has the same potential as the device main body.

A portion 2c (a portion indicated by a two-dot chain line in the figure) of the inner surface of the cooling cover 2 facing the outer surface of the Faraday cup 1 is subjected to a surface treatment in black. As a specific example of the surface treatment, the cooling cover 2
When aluminum is used, black alumite processing is used, and when stainless steel is used, black non-charged nickel plating processing is used.

The cooling cover 2 has only to be black at least at a portion 2c of the inner surface thereof facing the outer surface of the Faraday cup 1, but of course, the entire surface of the cooling cover 2 is black. May be processed.

In the above configuration, as shown in FIG. 2, a current measuring device for a charged particle beam is used to apply a spot-shaped ion beam 10 to two sets of parallel plate electrodes (first scanning electrodes 11).
a and 11b and the second scanning electrodes 12a and 12b) perform parallel scanning (parallel scanning) in the X direction (for example, the horizontal direction), and move the holding member 14 holding the wafer 13 in the Y direction (orthogonal to the X direction). (For example, vertical direction)
An example in which the present invention is applied to a medium-current ion implanter of a hybrid scan type that is mechanically driven is described below.

A substantially triangular scan voltage having a phase difference of 180 degrees from the scan power source 6 is applied to the first scan electrodes 11a and 11b from the scan power source 6, and the second scan electrodes 12a and 12b are also applied to the second scan electrodes 12a and 12b. A scanning voltage having a substantially triangular waveform having a phase difference of 180 degrees from the scanning power supply 6 is applied. The same scan voltage is applied to the first scan electrode 11a and the second scan electrode 12b, and the same scan voltage is applied to the first scan electrode 11b and the second scan electrode 12a. As a result, the spot-like ion beam 10 passing substantially at the center between the first scan electrodes 11a and 11b becomes a fan-shaped scan beam due to the electric field formed between the first scan electrodes 11a and 11b. 2 scanning electrodes 12a
A parallel beam is formed by the electric field formed between the electrodes 12b.

A mask 15 having a slit-like opening 15a is arranged behind the second scanning electrodes 12a and 12b. The opening 15a of the mask 15 is arranged in the beam scanning area, and only the ion beam 10 that has passed through the opening 15a is irradiated on the wafer 13 held by the holding member 14 behind the opening. .

The opening 15 in the mask 15
On the side of a, the ion beam 10 is
An opening 15b through which the light is incident is formed, and a dose farad 16 is provided behind the opening 15b. The dose Faraday 16 is used to count an implantation amount (dose amount) and to confirm an overscan of the ion beam 10.

A multipoint back Faraday 17 having a structure in which a plurality of Faraday cups are densely arranged in the beam scanning direction is provided behind the injection position (behind the holding member 14). When moving out of the irradiation area (that is, at the time of mechanical overscan), the ion beam 10 that has passed through the opening 15 a of the mask 15 is incident on the multipoint back Faraday 17.
The back Faraday 17 is used when obtaining a dose correction coefficient for correcting a measurement error of a dose amount caused by an error between a beam current measurement value by the dose Faraday 16 and a current of a beam actually irradiated on the wafer 13. For the purpose of making the beam scanning speed substantially constant, a multi-point front Faraday (not shown) having a structure in which a plurality of Faraday cups are densely arranged in the beam scanning direction in a position in front of the injection position is provided for the purpose of making the beam scanning speed substantially constant. It is also used to determine the beam incident angle.

Several Faraday cups are provided in the ion implantation apparatus according to their functions. Among them, the ion beam 10 is always incident during the implantation process, and the temperature rise is particularly large. The Faraday having the configuration shown in FIG. 1 is applied to the above-described dose Faraday 16 and multipoint back Faraday 17. That is, the ion beam 10 enters the Faraday cup when the ion beam 10 is overscanned on the dose Faraday 16 and when the holding member 14 of the wafer 13 is overscanned on the multipoint back Faraday 17. Since a temperature rise is unavoidable, it is very effective to apply the Faraday having the configuration shown in FIG.

In FIG. 1, when the temperature of the Faraday cup 1 rises due to the energy of the beam incident on the Faraday cup 1, the Faraday cup 1 is radiated (radiated).
Is transferred to the cooling cover 2. In radiant heat transfer,
The heat transfer (heat transfer) is determined by the spacing between the structures, the facing area, and their blackness. In the present embodiment, the distance between the Faraday cup 1 and the cooling cover 2 is so small that the insulation between the two can be maintained, and the Faraday cup except for the beam entrance 1a of the Faraday cup 1 is provided. The outer surface of the cooling cover 2 is entirely covered with a cooling cover 2, and the Faraday cup 1 is made of a carbon having a blackness of 1.0 and faces the outer surface of the Faraday cup 1 on the inner surface of the cooling cover 2. Since the surface 2c has been subjected to the surface treatment in black, the heat transfer by radiation is very high.

The heat transferred from the Faraday cup 1 to the cooling cover 2 by the radiant heat transfer as described above is conducted to the cooling water flowing through the refrigerant passage 2b in the cooling cover 2, and is discharged to the outside together with the cooling water. You.

The Faraday cup 1 is provided between the Faraday cup 1 and the cooling cover 2 so as to prevent a current of the incident beam from flowing toward the cooling cover 2 at the ground potential. The washer 3 is interposed. In order to ensure high insulation, the contact area between the Faraday cup 1 and the insulating washer 3 is small, and the heat of the Faraday cup 1 is transferred to the cooling cover 2 by heat conduction via the insulating washer 3 having low thermal conductivity. Only a few move. Further, since the inside of the beam passage is in a vacuum, it is not expected that the heat of the Faraday cup 1 moves to the other due to convective heat transfer. Therefore, most of the heat transfer of the Faraday cup 1 is caused by radiant heat transfer, and as described above, the outer surface of the Faraday cup 1 is entirely covered with the cooling cover 2 and the inner surface of the Faraday cup 1 is thus covered. Of the Faraday cup 1 can be surface-treated in black to improve heat transfer by radiation, thereby improving the cooling efficiency of the Faraday cup 1. In particular, all objects emit radiant energy. However, since the amount of radiant energy increases rapidly with temperature, heat transfer by radiation becomes dominant at high temperatures. The application of the present invention is very effective for a Faraday cup having a high temperature, such as the point back Faraday 17.

As described above, the charged particle beam current measuring apparatus of this embodiment is provided in a vacuum while being insulated from other members by the insulating washer 3 as an insulating means, and has an outer surface black. , A cup-shaped Faraday cup 1 having a beam entrance 1 a, and a cooling cover 2 provided to cover the outer surface of the Faraday cup 1 and having a black inner surface facing the outer surface of the Faraday cup 1. The cooling cover 2 has a configuration in which a coolant passage 2b for flowing cooling water as a coolant is formed inside the cooling cover 2.

As a result, the heat transfer due to radiation between the Faraday cup 1 and the cooling cover 2 is greatly improved. For this reason, the heat of the Faraday cup 1, whose temperature has increased due to the energy of the beam, efficiently moves to the cooling cover 2 and is discharged to the outside by the cooling water flowing through the refrigerant passage 2 b in the cooling cover 2. 1 can improve the cooling efficiency.

For example, in cooling only by natural heat radiation, if an ion beam of relatively high energy is incident into the Faraday cup for about 15 minutes, the Faraday cup becomes 400
If the temperature rises above [K] and the irradiation of the ion beam is continued thereafter, the Faraday cup is further heated, and the metal in the peripheral portion thereof is melted, and thermoelectrons jump out of the Faraday cup 1. On the other hand, according to the configuration of the present embodiment, the temperature rise of the Faraday cup 1 can be suppressed to about 350 [K] even if the ion beam is incident on the Faraday cup 1 under the same conditions as described above. With such a temperature rise, there is no melting or damage of the metal in the periphery of the Faraday cup 1, and generation of thermoelectrons from the Faraday cup 1 can be suppressed. Therefore, the use of the charged particle beam current measuring device of the present embodiment enables accurate measurement of the beam current.

The Faraday cup 1 and the cooling cover 2
The material of the Faraday cup is not limited to the above, and even if any material is used, at least the outer surface of the Faraday cup 1 and the inner surface of the cooling cover 2 facing the outer surface of the Faraday cup 1 are black. (As much blackness as possible
(The closer to 1.0, the better).

In the above embodiment, an example is shown in which the present invention is applied to an ion implantation apparatus. However, the present invention can be applied to other charged particle beam apparatuses which need to measure a beam current. The embodiments described above are intended to clarify the technical contents of the present invention, and should not be construed as being limited to such specific examples in a narrow sense. Various changes can be made within the scope of the claims.

[0040]

As described above, the charged particle beam current measuring device of the present invention is provided so as to cover the outer surface portion of the Faraday cup, and the inner surface portion facing the outer surface portion of the Faraday cup is provided. The Faraday cup has a black cooling cover, the outer surface of the Faraday cup is black, and a cooling medium passage for flowing a cooling medium is formed inside the cooling cover.

Therefore, the heat transfer by the radiation between the Faraday cup and the cooling cover is greatly improved, and the heat of the Faraday cup whose temperature has increased due to the energy of the beam is efficiently generated by the refrigerant flowing through the refrigerant passage in the cooling cover. Since the air is well discharged to the outside, the cooling efficiency of the Faraday cup can be improved. Therefore, it is possible to suppress the generation of thermoelectrons from the Faraday cup, to achieve accurate beam current measurement, and to reduce the adverse effect of heat on members surrounding the Faraday cup.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an embodiment of the present invention and showing a configuration of a Faraday cup and a cooling cover of a charged particle beam current measuring device.

FIG. 2 is a schematic diagram showing an application example of the charged particle beam current measuring device of the present invention to an ion implantation device, and is a schematic configuration diagram showing a main part of the ion implantation device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Faraday cup 1a Beam entrance 2 Cooling cover 2b Refrigerant passage 3 Insulating washer (insulating means)

Claims (1)

(57) [Scope of request for utility model registration] 1. A charged particle beam current measuring device comprising a cup-shaped Faraday cup provided in a vacuum and electrically insulated from other members by insulating means, and having a charged particle beam entrance. The Faraday cup has an outer surface part black, and is provided so as to cover the outer surface part of the Faraday cup, and an inner surface part facing the outer surface part of the Faraday cup includes a black cooling cover, A current measuring device for a charged particle beam, wherein a coolant passage for flowing a coolant is formed inside the cooling cover.