JP2010161007A - Method and device for cleaning ion implantation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for cleaning an ion implantation device, capable of further widely cleaning the inside surface of a mass analyzer. <P>SOLUTION: The method for cleaning an ion implantation device including a drawing electrode for drawing ion beam and a mass analyzer for deflecting the track of the ion beam by a magnetic field includes a step of irradiating the inside surface of the mass analyzer with the ion beam. In the step of irradiating with the ion beam, a drawing voltage to be applied to the drawing electrode is fluctuated, and the intensity of the magnetic field is also fluctuated. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a cleaning method and a cleaning apparatus for an ion implantation apparatus, and more particularly to a technique for cleaning an inner surface of a mass analyzer provided in the ion implantation apparatus using an ion beam.

An ion implantation apparatus including an ion source having an extraction electrode for extracting an ion beam and a mass analyzer having a mass analysis magnet for generating a deflection magnetic field has already been known.
Using this ion implantation apparatus, when ions produced primarily in an ion source are implanted into the surface of a material such as a wafer, only ions having a desired mass are selected and implanted using a mass analyzer. In some cases, unintended ions may be implanted into the material surface. This is a problem when mass-producing products with uniform performance.

The main cause of this problem is that when ions are selected by the mass analyzer, unintended ions (ie, impurity ions) collide with the inner surface of the mass analyzer, resulting in impurity ions. The by-product is deposited on the inner surface. As deposition of by-products proceeds on the inner surface of the mass spectrometer, impurity ions collide with the by-products during ion sorting. As the by-products are decomposed by this collision, new ions containing the constituent elements of the by-products are easily generated secondarily. When the newly generated ions reach the surface of a material such as a wafer, surface contamination or doping due to impurity ions occurs.
In order to avoid such a problem, in the prior art, by changing only the strength of the deflection magnetic field, the inner surface of the mass analyzer is intentionally irradiated with an ion beam to remove by-products from the inner surface. Things have been done. As such a cleaning method, for example, a technique described in Patent Document 1 is known.

Japanese Patent Laid-Open No. 9-36059

However, in the prior art, there is a limit to the area that can be cleaned on the inner surface of the mass analyzer, and a wider area on the inner surface cannot be cleaned.
Accordingly, some aspects of the present invention have been made in view of such problems, and provide a cleaning method and a cleaning apparatus for an ion implantation apparatus that can clean the inner surface of a mass analyzer more widely. The purpose is to do.

  In order to achieve the above object, an ion implantation apparatus cleaning method according to an aspect of the present invention includes an extraction electrode that extracts an ion beam, and a mass analyzer that deflects the trajectory of the ion beam using a magnetic field. An apparatus cleaning method comprising the step of irradiating the inner surface of the mass analyzer with the ion beam, wherein in the step of irradiating the ion beam, the extraction voltage applied to the extraction electrode is varied, and the magnetic field It is characterized by varying the intensity of the.

According to such a cleaning method, the extraction voltage and the intensity of the deflection magnetic field can be varied independently as parameters. The number of combinations derived from the two parameters varies, and the ion beam can be irradiated to a wider area on the inner surface of the mass analyzer compared to the prior art. Thus, a wider area of the inner surface can be cleaned. Thereby, for example, surface contamination of a material such as a wafer or unintended ion doping can be suppressed.
In the cleaning method, the extraction voltage may be periodically changed in the step of irradiating the ion beam.
According to such a cleaning method, since the irradiation of the ion beam onto the inner surface of the mass analyzer can be repeatedly performed, the by-product can be more effectively removed.

Furthermore, in the cleaning method described above, in the step of irradiating the ion beam, the intensity of the magnetic field may be periodically changed.
According to such a cleaning method, irradiation of the ion beam onto the inner surface of the mass analyzer can be repeatedly performed, so that by-products can be more effectively removed.
Furthermore, in the cleaning method, in the step of irradiating the ion beam, the intensity of the magnetic field is periodically changed, and the fluctuation period of the magnetic field intensity is different from the fluctuation period of the extraction voltage. Also good.

According to such a cleaning method, since the fluctuation periods of the two parameters described above are different, the number of parameter combinations derived therefrom is increased. Therefore, the irradiation region of the cleaning ions on the inner surface of the mass analyzer can be enlarged, so that by-products can be effectively removed.
Further, in the above cleaning method, the ion beam may be rare gas ions.
According to such a cleaning method, since a rare gas that is less expensive than a highly reactive gas used in the prior art can be used as cleaning ions, cleaning can be performed at a low running cost. Therefore, since the frequency of performing cleaning or the number of repetitions can be increased at a constant cost, a by-product can be more effectively removed.

In the cleaning method, the ion beam irradiation step includes a first irradiation step and a second irradiation step performed after the first irradiation step, and the ion beam irradiated in the first irradiation step. Is a rare gas ion, and the ion beam irradiated in the second irradiation step may be a dopant ion.
According to such a cleaning method, after the by-product is removed from the inner surface of the mass analyzer using a cleaning gas, the inner surface can be post-cleaned with dopant ions. Thereby, when a dopant ion collides with an inner surface, the ion produced | generated secondary will have the same component element as a dopant. Therefore, when the dopant is implanted into a material such as a wafer, surface contamination of the material or unintentional ion doping can be effectively suppressed.

An ion implantation apparatus according to another aspect of the present invention is an ion implantation apparatus comprising: an extraction electrode that extracts an ion beam; and a mass analyzer that deflects a trajectory of the ion beam by a magnetic field. In the cleaning, a control unit is provided for changing the extraction voltage applied to the extraction electrode and changing the intensity of the magnetic field.
According to such an ion implantation apparatus, the extraction voltage and the intensity of the deflection magnetic field can be varied independently as parameters. As a result, the number of combinations derived from the two parameters varies, and the ion beam can be irradiated to a wider area on the inner surface of the mass analyzer as compared with the prior art. Thus, a wider area of the inner surface can be cleaned. Thereby, it is possible to suppress surface contamination of the above-described material, unintended ion doping, and the like.

The figure which showed the structure of the ion implantation apparatus 100 based on one Embodiment of this invention. 5 is a flowchart showing a cleaning process of the ion implantation apparatus 100. The figure which showed the relationship between extraction voltage and time based on one Embodiment of this invention. The figure which showed the relationship between deflection magnetic field intensity and time based on one Embodiment of this invention. The figure which showed the structure of ion implantation apparatus 100 'which has a control part based on one Embodiment of this invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a conceptual diagram showing a configuration example of an ion implantation apparatus 100 according to an embodiment of the present invention. As shown in FIG. 1, an ion implantation apparatus 100 to be cleaned includes an ion source 1 and a mass analyzer 2, and the ion source 1 includes an ion generation unit 11 having a thermoelectron generating filament 111 and an extraction electrode 12. The mass analyzer 2 includes a mass analysis magnet 21 and a mass analysis tube 22. Further, the mass analysis magnet 21 is supported in the mass analysis magnet housing (not shown) and is installed around the mass analysis tube 22. Here, the mass spectrometry magnet 21 refers to a magnet that generates a deflection magnetic field by passing a current through a magnetic coil (not shown), for example. The mass spectrometer tube 22 is a tube made of, for example, a non-magnetic material and having a substantially fan-shaped appearance, and refers to a tube in which cleaning ions can move inside the tube. Further, the “inner surface of the mass analyzer” means the inner surface of the mass analyzer tube 22 included in the mass analyzer 2, more specifically, the cleaning ion moving path in the mass analyzer tube 22 included in the mass analyzer 2. Refers to the surface. Note that the inside of the ion implantation apparatus 100 is maintained at a desired degree of vacuum.

Next, the in-situ cleaning process procedure according to the embodiment will be described with reference to the flowchart shown in FIG. The “in-situ cleaning” described here refers to cleaning performed on a portion where a by-product is deposited in the usage environment of the mass analyzer 2.
2A to 2D are process diagrams showing each process in the cleaning method according to the present invention. In this specification, the mass analyzer 2 included in the ion implantation apparatus 100 shown in FIG. 1 is cleaned in situ along the steps A to D in FIG. 2 using the cleaning ions 3 generated by the ion source 1. Is assumed. As shown in FIG. 2, the cleaning method includes a gas introduction step (A), an ionization step (B), an ion extraction step (C), and an ion collision step (D).

  In step A of FIG. 2, a gas (that is, a cleaning gas) that is a raw material of the cleaning ions 3 is continuously introduced into the ion generation unit 11 at a desired flow rate. Here, a rare gas is suitable as the cleaning gas to be used. In the prior art, highly reactive gases such as oxygen, hydrogen, and fluorine have been used as cleaning gases. However, in the present invention, it is preferable to use a rare gas that is less expensive than a highly reactive gas as the cleaning gas. As a result, cleaning can be performed at a low running cost, and the frequency of performing cleaning or the number of repetitions can be increased within a certain cost. In the present invention, even an element heavier than a constituent element of a by-product can be used as a cleaning gas by introducing it into the ion generator 11 as a gas.

Next, in the B process of FIG. 2, the thermal electrons generated from the thermoelectron generating filament 111 are collided with the cleaning gas introduced into the ion generating unit 11 in the A process of FIG. Thereby, the introduced cleaning gas is ionized.
2, by applying a desired voltage to the extraction electrode 12, the cleaning ions 3 generated in the step B of FIG. 2 are extracted from the ion generation unit 11 to form the ion beam 4. The formed ion beam 4 is incident on the mass analyzer 2. When the extraction voltage applied to the extraction electrode 12 is periodically changed at the time of incidence, the incident energy of the ion beam 4 to the mass analyzer 2 is also periodically changed. Here, as the periodic variation, as shown in FIG. 3, the extraction voltage may be a sine wave voltage or a triangular wave voltage. Further, with regard to the extraction voltage and the fluctuation period, for example, the minimum value of the applied voltage may be about 30 kilovolts, the maximum value may be about 100 kilovolts, and the fluctuation period may be about 1 second.

  In principle, the degree of deflection of the trajectory of the ion beam 4 in the mass analyzer 2 depends on the intensity of the deflection magnetic field generated by the mass analysis magnet 21 and the ion source 1 when the mass and charge of the cleaning ion 3 are constant. And the extraction voltage (that is, the incident energy to the mass analyzer 2) are uniquely determined. The “orbit deflection degree” described here refers to the degree to which the orbit of the cleaning ions 3 is bent by a magnetic field. When the mass and charge of the cleaning ions 3 are constant and the strength of the deflection magnetic field is constant, the degree of deflection of the trajectory of the ion beam 4 depends on the value of the incident energy. Therefore, by periodically varying the extraction voltage, the ion beam 4 of the cleaning ions 3 can be repeatedly collided with the inner surface of the mass analyzer 2, so that effective cleaning can be performed.

  Next, in step D of FIG. 2, the trajectory of the ion beam 4 of the cleaning ions 3 is deflected by the deflection magnetic field generated by the mass analysis magnet 21, and the ion beam 4 is collided with the inner surface of the mass analyzer 2. In this step, first, the amount of current passed through a magnetic coil (not shown) provided in the mass analysis magnet 21 is periodically changed, and the intensity of the deflection magnetic field generated by the mass analysis magnet 21 is periodically changed. . The fluctuation period of the magnetic field strength is preferably different from the fluctuation period of the extraction voltage. Here, “the fluctuation period is different” means that the fluctuation period of the magnetic field intensity is longer than one time of the fluctuation period of the extraction voltage. In one embodiment of the present invention, for example, it is preferable to make the fluctuation period of the magnetic field intensity longer than 10 times the fluctuation period of the extraction voltage. More preferably, the fluctuation period of the magnetic field strength is made longer than 10 seconds and longer than 10 times the fluctuation period of the extraction voltage. That is, when the fluctuation period of the extraction voltage is 1 second, the fluctuation period of the magnetic field strength may be longer than 10 seconds, and when the fluctuation period of the extraction voltage is 10 seconds, the magnetic field intensity The fluctuation period may be longer than 100 seconds. Note that by making the fluctuation period of the magnetic field intensity longer than 10 seconds, the influence of the residual magnetization that appears when the magnetic field intensity is changed is reduced, and more effective cleaning can be performed.

  Regarding the fluctuation of the magnetic field strength, for example, as shown in FIGS. 4A and 4B, it may be a simple increase or a simple decrease. Moreover, you may increase / decrease sinusoidally. In principle, when the mass and charge of the cleaning ion 3 are constant and the incident energy is constant, the degree of deflection of the trajectory of the ion beam 4 depends on the strength of the deflection magnetic field. Therefore, the ion beam 4 of the cleaning ions 3 can repeatedly collide with the inner surface of the mass analyzer 2 by periodically changing the magnetic field strength.

  Next, the ion beam 4 extracted in the step C in FIG. 2 is passed through the deflection magnetic field. By making the fluctuation period of the deflection magnetic field intensity different from the fluctuation period of the extraction voltage, the number of combinations derived from the set values of the deflection magnetic field intensity and the extraction voltage is increased as compared with the case of the prior art, and the mass analysis tube 22 is obtained. The degree of deflection of the trajectory of the ion beam 4 in the inside also varies. Specifically, when the deflection magnetic field strength is large and the extraction voltage is small, the degree of deflection of the trajectory of the ion beam 4 is large, and therefore, in the vicinity of the entrance 41 of the mass analyzer 2 as shown in FIG. The ion beam 4 collides. In contrast, when the strength of the deflection magnetic field is small and the extraction voltage is large, the degree of deflection of the trajectory of the ion beam 4 is small, so that the ion beam 4 collides with the vicinity 42 of the exit port of the mass analyzer 2. That is, by changing both the deflection magnetic field strength and the extraction voltage, the ion beam 4 can repeatedly collide with the region to be cleaned on the inner surface of the mass analyzer 2. With respect to the timing of starting the fluctuation of the deflection magnetic field strength and the extraction voltage, the two may be changed simultaneously, or the extraction voltage may be changed after the deflection magnetic field intensity is changed. Further, the deflection magnetic field intensity may be changed after the extraction voltage is changed. By repeating the repeated collision of the ion beam 4, the by-product adhering to the cleaning region can be more effectively removed. Therefore, problems such as surface contamination and doping of the material installed in the above-described ion implantation apparatus 100 are solved, and a product with uniform performance can be produced in large quantities.

(Application 1)
In the above embodiment, by incorporating the control unit 31 shown in FIG. 5, it is possible to automatically vary the above-described extraction voltage and deflection magnetic field strength. The control unit 31 incorporates a program for sequence control of each process of the cleaning method according to the embodiment of the present invention. Accordingly, for example, by automatically setting the extraction voltage and deflection magnetic field strength fluctuation period, the maximum and minimum values of the extraction voltage, the amount of current flowing through the magnetic coil included in the mass analysis magnet 21, etc., cleaning is performed automatically. Can be implemented. Therefore, it is possible to reduce the manual work load during maintenance.

(Application example 2)
In the above embodiment, the inner surface of the mass analyzer 2 cleaned in situ using the cleaning gas 3 can be coated with dopant ions (ie, post-cleaning). When performing post cleaning, the same procedure as in the above embodiment is performed. The “dopant” described here refers to an element that is intentionally implanted into a material such as a wafer installed in the ion implantation apparatus 100, and the dopant ion refers to an ion of the element.

  When mass screening is performed using the mass analyzer 2 in the product processing after cleaning, if a dopant ion collides with the inner surface of the mass analyzer 2 that has been post-cleaned in advance, ions composed of the same element as the dopant are secondary. To generate. The “secondary generation” described in this specification is different from the primary ion generation in the ion source 1, and the cleaning ions 3 or dopant ions collide with the inner surface of the mass analyzer 2. This refers to the generation of ions by decomposition of by-products deposited on the inner surface. Even if ions composed of the same element as the dopant arrive and adhere to the surface of the material installed in the ion implantation apparatus 100, the problems such as surface contamination and doping are unlikely to occur. Therefore, the above problem can be solved, and a product with uniform performance can be produced in a large quantity, and the possibility of contamination of impurities in the wafer or the like can be further reduced.

  DESCRIPTION OF SYMBOLS 1 Ion source, 2 Mass analyzer, 3 Cleaning gas, 4 Ion beam, 11 Ion production part, 12 Extraction electrode, 21 Mass analysis magnet, 22 Mass analysis tube, 31 Control part, 41 Cleaning gas when deflection degree is large 42, part where cleaning gas collides when the degree of deflection is small, 100, 100 ′ ion implantation device, 111 filament for generating thermoelectrons

Claims (7)

An extraction electrode for extracting an ion beam;
A mass analyzer that deflects the trajectory of the ion beam by a magnetic field, and a cleaning method for an ion implantation apparatus comprising:
Irradiating the inner surface of the mass analyzer with the ion beam;
In the ion beam irradiation step, the extraction voltage applied to the extraction electrode is changed and the intensity of the magnetic field is changed.   The method of cleaning an ion implantation apparatus according to claim 1, wherein in the step of irradiating the ion beam, the extraction voltage is periodically changed.   3. The cleaning method for an ion implantation apparatus according to claim 1, wherein in the step of irradiating the ion beam, the intensity of the magnetic field is periodically changed.   3. The ion according to claim 2, wherein in the step of irradiating the ion beam, the intensity of the magnetic field is periodically changed, and the fluctuation period of the magnetic field intensity is different from the fluctuation period of the extraction voltage. Cleaning method for injection device.   The ion implantation apparatus cleaning method according to claim 1, wherein the ion beam is a rare gas ion. The step of irradiating the ion beam includes a first irradiation step and a second irradiation step performed after the first irradiation step,
The ion beam irradiated in the first irradiation step is a rare gas ion, and the ion beam irradiated in the second irradiation step is a dopant ion. A method for cleaning an ion implantation apparatus according to one item. An extraction electrode for extracting an ion beam;
A mass analyzer that deflects the orbit of the ion beam by a magnetic field, and an ion implantation apparatus comprising:
An ion implantation apparatus comprising: a controller that varies an extraction voltage applied to the extraction electrode and varies an intensity of the magnetic field when cleaning the ion implantation apparatus.

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