JPH0864167A - Ion treatment device - Google Patents

Abstract

PURPOSE: To provide an ion treatment device having an electron shower system capable of uniformly reducing the charged amount on a wafer over the whole surf.ace of the wafer. CONSTITUTION: A wafer W is held on a disc 14 freely rotating within a disc chamber 12, and when the wafer W reached in an ion implantation position by the rotation of the disc, ion beams are irradiated to the wafer to conduct ion treatment. An electron shower system installed in an ion treatment device has a plurality of electron shower guns 20 arranged in the vicinity of the inside of a reflector ring 22 set so that an electron beam stream is passed through, a measuring means 42 for measuring the charged amount distribution on the wafer in the position where the disc is further rotated from an ion implantation position, and a control means 44 for controlling the radiated amount of thermoelectrons irradiated from each electron shower gun based on the charged amount distribution measured with the measuring means 42.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion processing apparatus such as an ion implantation apparatus, and more particularly to an ion processing apparatus capable of uniformly reducing the charge amount of a wafer during ion implantation over the entire surface of the wafer. Is.

[0002]

2. Description of the Related Art In a semiconductor device manufacturing process, a variety of ion treatment apparatuses such as an ion implantation apparatus, an ion beam etching apparatus, an ion plating apparatus, etc. for irradiating a wafer with an ion beam to perform a required treatment or processing. in use. The ion processing apparatus will be described below by taking an example of a high current type mechanical scan type ion implantation apparatus. FIG. 5 is a schematic cross-sectional view showing a configuration of an implanting part of a conventional ion implanting device. This apparatus is provided with a vacuum container (hereinafter referred to as a disk chamber) 12 for introducing the ion beam I.
And a disc 14 which is disposed in the disc chamber 12 and is freely rotatable. A large number of wafer stands 16 are provided on the disk 14 with the same radius from the center of rotation of the disk, and the wafer W is arranged thereon. The ion beam I is introduced into the disc chamber 12 from the introduction port 18 while adjusting its traveling direction, and is irradiated onto the wafer W on the disc 14 which has reached the ion implantation position. The wafer W on the disk 14 is ion-implanted every time when the wafer W reaches the ion-implantation position according to the rotation of the disk 14 rotating at a rotation speed of about 1000 rpm.

By the way, when a wafer is ion-treated by using a high-current type ion implanter, since the beam current is large, the implanted positive ions are densely deposited on the wafer surface, so that the wafer surface is It becomes charged and a potential difference occurs. As a result, discharges often occur at the wafer surface, causing partial electrical breakdown and damaging the wafer. Therefore, the product yield of wafers is reduced.

In order to suppress the discharge phenomenon on the wafer,
It is considered that the potential difference due to charging on the wafer should be limited to preferably about 0V. Therefore, a large current type ion implantation apparatus is usually provided with an electronic shower system in order to reduce the amount of charge on the wafer. The electronic shower system, as shown in FIG.
An electron shower gun 20 that emits thermoelectrons in a direction substantially orthogonal to the ion beam flow I, and a reflector ring 22 that receives thermoelectrons emitted from the electron shower gun 20 and generates secondary electrons by the impact thereof. Have. The thermoelectrons emitted from the electron shower gun 20 and the secondary electrons generated from the reflector ring 22 are generated by the reflector ring 2
The positive ions in the ion beam flowing through 2 are neutralized, and at the same time, they collide with the surface of the wafer W to neutralize the positive charges charged by the ions implanted on the wafer surface to reduce the amount of charge.

In the conventional electronic shower system, one electronic shower gun 20 is provided near the inner surface of the reflector ring 22, and is composed of one filament and a filament power source 24 for heating the filament. There is. The filament has a length of 4 such as tungsten metal.
It is a thin wire with a diameter of 1 cm to 2 mm and a diameter of 1 to 2 mm, and is heated by the filament power supply 24 to emit thermoelectrons. A voltage of minus several hundred volts is applied to the reflector ring 22 and receives thermoelectrons to generate secondary electrons. In FIG. 5, reference numeral 26 is a mask that regulates the flow of the ion beam flow I, and 28 is a vacuum suction port that suctions the inside of the disk chamber 12 and holds it at a predetermined pressure.

[0006]

By the way, although the diameter of the wafer is being increased in order to improve the productivity of the semiconductor device, when the conventional ion processing apparatus is used to perform the ion implantation on the large diameter wafer. , It is difficult to uniformly ion-implant the wafer surface. Therefore, even when the electronic shower system is operated, the distribution of the charge amount on the wafer becomes non-uniform, and the charge amount becomes large at the peripheral portion of the wafer, and conversely, it is attempted to reduce the charge amount at the peripheral portion of the wafer. The phenomenon that the wafer portion close to the filament is negatively charged occurs. As a result, there is a problem that the electric potential locally rises within the wafer surface and a discharge phenomenon occurs.

Therefore, by providing a beam current density monitor,
Recently, a method of making the amount of charge on the wafer uniform by this has been attempted. The beam current density monitor is
As conceptually shown in FIG. 6, a perforated plate having a large number of small holes is arranged between the ion beam flow and the wafer, and an ammeter is provided in each ion beam flow path on the wafer side of the small holes. ,
The amount of ion beams flowing through each ion beam channel is measured. If you draw a graph of measured values corresponding to the position of small holes,
This is a distribution diagram of the beam current density. This is a method in which the ion implantation device is adjusted so that the beam current density is constant based on the distribution diagram of the beam current density, and the ion implantation is performed in the state where the beam current density is most uniform. However, this method can improve the non-uniformity of the charge amount on the wafer surface, but in addition to the problem that it takes time to adjust the beam current density, it also cannot cope with the change in the beam current density over time. Have.

As described above, in the conventional electronic shower system, the electronic shower system is not provided with the control means for adjusting the radiation amount of the electron shower according to the distribution of the charge amount on the wafer surface. However, the charge amount on the wafer could not be reduced uniformly.

Therefore, an object of the present invention is to provide an ion treatment having an electron shower system capable of uniformly reducing the amount of charge on the wafer over the entire surface of the wafer and coping with changes in the beam current density over time. It is to provide a device.

[0010]

In order to achieve the above object, an ion processing apparatus according to the present invention holds a wafer on the surface of a disk that freely rotates in a vacuum container, and the wafer rotates as the disk rotates. Is an apparatus that irradiates the wafer with an ion beam to perform ion processing when the ion implantation position arrives at the ion implantation position, and further receives one electron shower gun and secondary electrons by receiving thermoelectrons emitted from the electron shower gun. An ion processing system equipped with an electron shower system having a reflector ring to generate, and installed so as to penetrate the ion beam flow in an ion processing apparatus that reduces the amount of charge on the wafer by electron shower of thermoelectrons and secondary electrons. A plurality of electron shower guns are placed near the inside of the reflector ring, and in addition, the wafer is moved at a position where the disk is further rotated from the ion implantation position. And a control unit that adjusts the radiation amount of thermoelectrons emitted from each electron shower gun based on the charge amount distribution on the wafer measured by the measuring unit. Is characterized by.

In the present invention, the structure of the reflector ring and each electron shower gun is the same as the conventional one.
The measuring means for measuring the charge amount distribution on the wafer is composed of a sensor network including a plurality of known charge amount sensors arranged on the wafer in a substantially uniform distribution. The control device is
The control device includes a known mechanism, creates a charge amount distribution from measured values input from each charge amount sensor, and controls the output of each electron shower gun based on the obtained charge amount distribution. By preliminarily operating the electron shower gun and the charge amount sensor to establish the correlation between the charge amount distribution and the output of the electron shower gun, the control device is based on the charge amount distribution according to the established correlation. The output of each electronic shower gun can be controlled. From the viewpoint of control response, the control method is preferably a feedback control method.

Since the amount of thermoelectrons emitted from the electron shower gun can be adjusted by increasing or decreasing the voltage applied to the filament or the current flowing through the filament, in the present invention, the amount of charge obtained by the means for measuring the amount of charge distribution is determined. The controller adjusts the voltage or current applied to the filament of each electron shower gun based on the distribution. The adjustment can be performed, for example, by providing a variable resistor in the filament power supply circuit and operating the variable resistor. The present invention relates to an ion implantation device, an ion beam etching device,
It can be applied to an ion processing apparatus such as an ion plating apparatus that needs to reduce the charge amount on the wafer.

[0013]

If the measuring means is provided at the ion implantation position and the distribution of the charge amount on the wafer is measured while the wafer is being ion-implanted, the measuring means will hinder the ion irradiation. Is difficult to measure physically.
Therefore, in the present invention, a measuring unit is provided at a measuring position where the disk is slightly rotated from the ion implantation position, and the charge amount distribution is measured there. Since the disk rotates at a high speed at a rotation speed in the range of 900 rpm to 1300 rpm, the time required from the ion implantation position to the charge amount measurement position is a very short time of several msec. Therefore, the charge amount on the wafer is maintained during the rotation from the ion implantation position to the measurement position, and the charge amount at the time of ion implantation is maintained. Therefore, the distribution of the charge amount measured at the measurement position is This is because it can be regarded as the distribution of the charge amount at the time. In the present invention, the charge amount on the wafer is measured in real time, and the output of each electron shower gun is controlled based on the measured charge amount distribution. Can handle.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the accompanying drawings. FIG. 1 is a schematic view showing a configuration of a main part of an embodiment of an ion treatment apparatus according to the present invention, and FIG. 2 is a conceptual layout view of filaments of an electron shower gun as seen perpendicularly to a cylindrical center line of a reflector ring. 3, FIG. 3 is a plan view of the disk showing the ion implantation position and the charge amount measurement position of the disk, and FIG. 4 is a view showing the flow of control signals. Of the parts shown in FIGS. 1 to 4, the same parts as those in FIG. 5 are designated by the same reference numerals, and the description thereof will be omitted. In addition to the configuration described with reference to FIG. 5, the ion processing apparatus 40 of the present embodiment has five electron shower guns 20A to 20E (simply three in FIG. 1) as an electronic shower system as shown in FIG. (Only shown)
And a charge amount distribution measuring device (hereinafter simply referred to as a measuring device) 42 for measuring the charge amount distribution on the wafer at the measurement position.
1, a controller 44, and a filament power supply adjusting unit (hereinafter simply referred to as adjusting unit) 46A to E (hereinafter simply referred to as adjusting unit) provided in each filament power supply circuit of the electronic shower guns 20A to 20E.
Then, only three are shown).

The electron shower guns 20A to 20E have the same structure as the conventional electron shower guns, and the filaments of the electron shower guns 20A to 20E are arranged near the inside of the reflector ring 22 in the arrangement shown in FIG. Has been done. The arrangement of the filaments shown in FIG. 2 is an example, and the arrangement is not limited to this, and may be, for example, a circumferential arrangement along the inner peripheral surface of the reflector ring 22. The adjusting units 46A to E adjust the filament power sources 24A to E of the electron shower guns 20A to 20E, respectively, to adjust the voltage or current applied to the filaments to adjust the amount of thermoelectrons emitted from the filaments. Is. As the adjustment unit 46, for example, a variable resistor can be used.

The measuring device 42 is composed of five charge amount sensors 48 arranged so as to have a uniform distribution on the wafer surface.
In the sensor network including A to E (see FIG. 4), a known sensor, for example, a charge amount sensor manufactured by Tokyo Cathode Co., Ltd. can be used as the charge amount sensor. As shown in FIG. 3, assuming that the disk 14 is rotating clockwise (in the direction shown in the drawing), the measurement position P2 of the charge amount distribution on the wafer is predetermined from the ion implantation position P1 in the clockwise direction. It is a position rotated by an angle α. The angle α can be arbitrarily set in consideration of the attachment of the charge amount sensor.

As shown in FIG. 4, the control unit 44 creates a charge amount distribution on the wafer from the measured charge amount values respectively input from the charge amount sensors 48A to 48E, and based on the obtained charge amount distributions. A signal is output to the adjusting units 46A to 46E to adjust the filament power sources 24A to 24E of the electron shower guns 20A to 20E to adjust the amount of thermoelectrons emitted from the filaments of the electron shower guns 20A to 20E. Controller 44
In order to reduce the amount of charge on the wafer uniformly over the entire surface of the wafer by using the electron shower gun 20A to
By operating E and the charge amount sensors 48A to 48E, the correlation between the charge amount distribution on the wafer and the output of each electron shower gun is established in advance and is input to the control device 44. During operation of the ion implanter 40, the output of the electron shower gun is controlled based on the charge amount distribution measured according to the established correlation.

As described above, in this embodiment, feedback control is performed to adjust the output of each electron shower gun based on the measured charge amount distribution on the wafer, so that the charge amount on the wafer is desired. Value can be uniformly and surely reduced over the entire surface of the wafer, and the temporal change in beam current density can be immediately dealt with.

[0019]

According to the present invention, a plurality of electron shower guns are arranged in the vicinity of the inside of the reflector ring in an ion processing apparatus in which the amount of charge on the wafer is reduced by the electron shower of thermoelectrons and secondary electrons. Then, by controlling each of the measuring means for measuring the charge amount distribution on the wafer and the electron shower gun at a position where the disk is further rotated from the ion implantation position, the emission amount of thermoelectrons emitted from each electron shower gun is controlled. And control means for adjusting. In the present invention, the charge amount on the wafer is adjusted to a desired value by adjusting the radiation amount of the thermoelectrons emitted from each electron shower gun based on the charge amount distribution on the wafer measured by the measuring means by the control device. It can be uniformly and surely reduced over the entire surface of the wafer. Further, it is possible to immediately deal with a change in beam current density with time. If the ion treatment apparatus according to the present invention is used,
Even for a large-diameter wafer, the entire surface of the wafer can be uniformly subjected to the ion treatment, thereby improving the product yield.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a main part of an embodiment of an ion treatment apparatus according to the present invention.

FIG. 2 is a conceptual layout diagram of filaments of the electron shower gun as viewed orthogonally to the center line of the reflector ring in the cylinder direction.

FIG. 3 is a plan view of a disk showing an ion implantation position and a charge amount measurement position.

FIG. 4 is a diagram showing a flow of control signals.

FIG. 5 is a schematic diagram showing a configuration of an implantation unit of a conventional ion implantation apparatus.

FIG. 6 is a conceptual diagram showing the operating principle of a beam current density monitor.

[Explanation of symbols]

 10 Conventional Ion Implanter 12 Disk Chamber 14 Disk 16 Wafer Stage 18 Inlet 20 Electron Shower Gun 22 Reflector Ring 24 Filament Power Supply 26 Mask for Regulating the Flow of Ion Beam Flow 28 Vacuum Suction Port 40 Ion Processing Apparatus According to the Present Invention Example 42 Charge amount distribution measuring device 44 Control device 46 Filament power supply adjusting unit 48 Charge amount sensor

Claims (1)

[Claims] 1. An apparatus for holding a wafer on the surface of a disk that freely rotates in a vacuum container, and irradiating the wafer that has reached an ion implantation position with the rotation of the disk with an ion beam to perform ion processing. And an electron shower system having one electron shower gun and a reflector ring that receives thermoelectrons emitted from the electron shower gun to generate secondary electrons, and an electron shower of thermoelectrons and secondary electrons In an ion processing system that reduces the amount of electrostatic charge on the wafer by arranging multiple electron shower guns near the inside of the reflector ring installed so that the ion beam flow penetrates, in addition, the disk is ion-implanted. Measuring means for measuring the charge amount distribution on the wafer at a position further rotated from the position, and the charge amount on the wafer measured by the measuring means. An ion processing apparatus comprising: a control unit that adjusts the amount of thermoelectrons emitted from each electron shower gun based on the cloth.