JP4518328B2 - Filament control device, filament control method, and thermoelectron processing device - Google Patents

Description

  The present invention relates to a filament control device capable of stably controlling the amount of thermoelectrons emitted from a filament, a filament control method using the same, and the thermoelectrons emitted from the filament by using the filament control device. The present invention relates to a thermal electron utilization processing apparatus such as an ion implantation processing apparatus or an electron beam processing processing apparatus that performs thermal electron utilization processing.

  2. Description of the Related Art Conventionally, processing using thermoelectrons emitted from a filament has been widely performed, such as ion implantation processing for manufacturing semiconductor devices and electron beam processing. For example, an ion implantation process is known in which ion implantation is performed on a semiconductor material or the like in a state in which the space charge of the ion beam is neutralized by thermoelectrons to suppress divergence of the ion beam.

  As an example of a conventional ion implantation processing apparatus that performs such ion implantation processing, for example, Patent Document 1 discloses an ion on which a space charge neutralization device is mounted in order to neutralize the space charge of an ion beam by thermal electrons. An injection processing apparatus is disclosed.

FIG. 11 is a schematic diagram showing a schematic configuration example of a conventional space charge neutralization device described in Patent Document 1, and this space charge neutralization device is mounted on an ion implantation processing apparatus.
In FIG. 11, a conventional space charge neutralization apparatus 100 includes a magnetic pole 101, an electron gun 102, a heating power supply 103, and an emission power supply 104. In the conventional ion implantation processing apparatus, mass separation (not shown) is performed. Arranged in the machine. As is well known, a mass separator separates a plurality of ion species having different masses contained in an ion beam while bending the ion beam by the action of a magnetic field.

  The magnetic pole 101 forms a magnetic field B perpendicular to the paper surface in a mass separator (not shown). Due to the action of the magnetic field B, the trajectory of the ion beam 105 introduced into the mass separator from the beam introduction port 101a is curved as shown in the figure.

  The electron gun 102 is attached to the magnetic pole 101 and has a filament 102a and an electron extraction electrode 102b.

The heating power source 103 is a power source connected to the filament 102a in order to heat the filament 102a.
The emission power source 104 is connected between the filament 102a and the electron extraction electrode 102b in order to apply a predetermined voltage.

  With this configuration, in this conventional space charge neutralization apparatus 100, the filament 102a is heated by the heating power source 103, and thermoelectrons are emitted. The thermoelectrons emitted from the filament 102 a are further extracted outside the electron gun 102 by the electron extraction electrode 102 b that is set to a positive potential by the emission power source 104.

  In this way, the trajectory of the electrons extracted from the electron extraction electrode 102 b of the electron gun 102 is curved like the trajectory O in the figure by the action of the magnetic field B, and the trajectory O of this electron intersects the ion beam 105. By doing so, the space charge of the ion beam 105 is neutralized. As a result, divergence of the ion beam due to repulsion between positive ions in the ion beam 105 is suppressed, and a desired non-diverged ion beam can be output.

  By the way, since electrons extracted by the electron extraction electrode 102b have a specific directionality (initial velocity vector in a specific direction), there is a possibility that the curved orbit due to the action of the magnetic field B is only a specific orbit. Therefore, there is a concern that electrons can only exist in a specific part in the mass separator and neutralization of the space charge of the ion beam becomes insufficient.

As a countermeasure against this problem, in Patent Document 1, the voltage applied from the emission power supply 104 to the electron extraction electrode 102b is changed with time. Thereby, the initial velocity of the electrons extracted from the electron extraction electrode 102b is changed temporally, the electron trajectory O is changed temporally, and the electrons are distributed over a wide range in the mass separator.
JP-A-7-161320

  In the conventional space charge neutralization apparatus 100, the thermoelectrons emitted from the filament 102a are extracted to the outside of the electron gun 102 by the electron extraction electrode 102b, and in addition to this, the initial velocity of the electrons is changed with time. Thus, electrons are distributed over a wide range in the mass separator.

  However, when realizing the action of distributing electrons over a wide range in the mass separator, it is not essential to use the electron extraction electrode 102b or to apply a voltage that changes with time. It is also conceivable to use the thermoelectrons as they are.

  The reason is that the thermoelectrons emitted from the filament 102a do not have a specific direction and are directed in a random direction, so that various trajectories can be drawn by the action of the magnetic field B. In this way, it is possible to neutralize the space charge of the ion beam while simplifying the configuration of the conventional space charge neutralization device 100.

  However, when the electron extraction electrode 102b is not provided as described above, the following new problem arises. That is, when the electron extraction electrode 102b is provided, the amount of electrons supplied to the ion beam can be controlled only by adjusting the voltage applied to the electron extraction electrode 102b. In the case where no is provided, it is necessary to accurately control the amount of thermoelectrons emitted from the filament 102a.

  On the other hand, the filament 102a has randomness due to exposure to an ion beam in addition to disturbances that change in a drift manner, such as deterioration over time depending on the energization time (thinning) and temperature rise over time. Disturbances (sudden temperature rise, adhesion and peeling of coatings, etc.) are also acting. Under the influence of these disturbances, it has been difficult to stably control the amount of emitted thermoelectrons with high accuracy.

  The present invention solves the above-mentioned conventional problems, and a filament control device capable of stably controlling the amount of thermoelectrons emitted from a filament with high accuracy, a filament control method using the same, and the filament control device The thermoelectrons emitted from the filament are used to perform ion implantation processing by neutralizing the space charge of the ion beam with thermoelectrons, or to perform electron beam processing using thermoelectrons as an electron beam source. An object of the present invention is to provide a thermoelectron utilization processing apparatus such as an ion implantation processing apparatus or an electron beam processing apparatus that performs the thermoelectron utilization processing to be used.

The filament control device of the present invention is a filament control device for controlling the power consumed by the filament so as to coincide with a predetermined power target value, and measures the resistance value of the filament at a predetermined time interval. A resistance average value calculating means for calculating an average value for a plurality of the resistance values measured during the first period by the resistance measuring means; the average value calculated by the resistance average value calculating means; and Current target value calculation means for calculating the target value of the current to be supplied to the filament from the power target value, and the current target value calculated by the current target value calculation means during the second period as such, with a current control means for controlling the current flowing through the filament, and a timing control means for controlling the timing of said first period and said second period, said first period and the second period The target value of the current is determined by the current control means in the second period starting immediately after the completion of the first period for which the target value of the current has been obtained. The above-mentioned purpose is achieved by this.

The filament control device of the present invention is a filament control device for controlling the power consumed by the filament so as to coincide with a predetermined power target value, and measures the resistance value of the filament at a predetermined time interval. A resistance average value calculating means for calculating an average value for a plurality of the resistance values measured during the first period by the resistance measuring means; the average value calculated by the resistance average value calculating means; and Voltage target value calculation means for calculating the target value of the voltage to be applied to the filament from the power target value, and the voltage target value calculated by the voltage target value calculation means during the second period as such, includes a voltage control means for controlling a voltage applied to the filament, and a timing control means for controlling the timing of said first period and said second period, said first period and the second The voltage control means is configured to repeat the voltage control means in the second period starting immediately after the completion of the first period when the target value of the voltage is obtained. In this way, the above object is achieved.

  Preferably, the current control means in the filament control device of the present invention is a constant current power source.

  Preferably, the voltage control means in the filament control device of the present invention is a constant voltage power source.

  Further preferably, the resistance measuring means in the filament control device of the present invention comprises a current detecting means and a voltage detecting means for measuring a current and a voltage flowing through the filament, and a voltage value measured by the voltage detecting means. Resistance value calculating means for calculating the resistance value by dividing by the current value measured by the means.

Further, preferably, the timing control means in the filament control apparatus of the present invention, the second period is the timing control so as to overlap with at least part of the following first period.

Further, preferably, the timing control means in the filaments controller of the present invention, in the each period, the second period is the timing control in such a manner that after the first period.

  Further preferably, the first period in the filament control device of the present invention is set to 0.001% or more and 0.1% or less of the lifetime of the filament.

Further preferably, the timing control means of the present invention is provided between the resistance measurement means and the resistance average value calculation means, and a signal is sent from the resistance measurement means to the resistance average value calculation means in the first period. First switch means controlled to be capable of outputting;
Provided between the resistance average value calculating means and the current target value calculating means or the voltage target value calculating means, and after the end of the first period (for example, after the end of the first period to the start of the next first period) And a second switch means that is controlled so that a signal can be output from the resistance average value calculating means to the current target value calculating means or the voltage target value calculating means during the period.

  Further preferably, the timing control means of the present invention is provided between the current target value calculation means and the current control means or between the voltage target value calculation means and the voltage control means, and the second It further has a sample and hold circuit controlled to update the target value of the current or the target value of the voltage at the start of each period.

  The thermoelectron utilization processing apparatus of the present invention is a thermoelectron utilization processing apparatus that is equipped with the filament control apparatus of the present invention and performs thermoelectron utilization processing using thermoelectrons emitted from the filament, During the second period, the thermoelectron utilization processing is executed in a state where the current value or voltage value of the filament is controlled by the current control means or the voltage control means, thereby achieving the above object. .

Preferably, in the thermal electron utilization processing apparatus of the present invention, the filament is a neutralizing filament for neutralizing the space charge distribution of the ion beam, and the space of the ion beam is generated by the thermoelectrons emitted from the filament. An ion implantation process is performed while neutralizing the charge distribution.
Further preferably, in the thermal electron utilization processing apparatus of the present invention, the filament is an electron beam source filament for generating an electron beam, and the electron beam processing is performed by the thermoelectrons emitted from the filament.

The filament control method of the present invention is a filament control method for controlling the electric power consumed by the filament so as to coincide with a predetermined power target value, and measuring the resistance value of the filament at a predetermined time interval. A resistance average value calculating step of calculating an average value for the plurality of resistance values measured during the first period in the resistance measuring step, the average value calculated in the resistance average value calculating step, and the A current target value calculation step for calculating a target value of the current to be supplied to the filament from the power target value, and a target value of the current calculated in the current target value calculation step during the second period as described above, have a current control step of controlling the current flowing through the filament, each period consisting of the first period and the second period is intended to be repeated, the eyes of the current Values, in the second period in which the target value of the current is started immediately after completion of the first period obtained, which is used by said current control step, the objects can be achieved.

The filament control method of the present invention is a filament control method for controlling the electric power consumed by the filament so as to coincide with a predetermined power target value, and measuring the resistance value of the filament at a predetermined time interval. A resistance average value calculating step of calculating an average value for the plurality of resistance values measured during the first period in the resistance measuring step, the average value calculated in the resistance average value calculating step, and the A voltage target value calculation step for calculating the target value of the voltage to be applied to the filament from the power target value, and the target value of the voltage calculated in the voltage target value calculation step during the second period as described above, have a voltage control step of controlling the voltage applied to the filament, each period consisting of the first period and the second period is intended to be repeated for the voltage Shirubechi, in the second period in which the target value of the voltage is started immediately after completion of the first period obtained, which is used by the voltage control step, the above-mentioned object can be achieved by the .

Still preferably, in a filament control method of the present invention, the second period is the timing control so as to overlap with at least part of the following first period.
Also, preferably, the filament control system of the present invention, in the each period, the second period is the timing control in such a manner that after the first period.

  The operation of the present invention will be described below with the above configuration.

  In the present invention, the resistance value of the filament is measured a plurality of times at predetermined time intervals in order to control the power consumed by the filament capable of emitting thermoelectrons so as to coincide with a predetermined power target value. Then, the current target value to be supplied to the filament is calculated from the resistance average value during the first period and the filament power target value. During the second period, the current flowing through the filament is controlled so as to coincide with the current target value.

  Alternatively, in order to control the power consumed by the filament capable of emitting thermoelectrons so as to coincide with a predetermined power target value, the resistance value of the filament is measured a plurality of times at predetermined time intervals, and the first period A voltage target value to be applied to the filament is calculated from the average resistance value and the power target value of the filament. During the second period, the voltage applied to the filament is controlled so as to coincide with the voltage target value.

In this way, by setting the current target value or voltage target value for the second period following the resistance measurement result of the immediately preceding first period, the power consumption consumed by the filament in the second period is set to a predetermined power. It is possible to match the target value.
Here, the resistance average value used when setting the current target value and voltage target value in the second period is an average of a plurality of resistance values measured at predetermined time intervals during the first period. The resistance average value excludes the influence of random disturbances such as sudden temperature rise and adhesion or peeling of the coating, and the filament degradation over time (thinning) and temperature rise over time depend on the energization time. It accurately represents the influence of disturbances that change in a drifting manner. By setting the current target value and voltage target value based on this resistance average value, the influence of disturbances that change in a drift, such as filament deterioration over time (thinning) and temperature rise over time, is assured. The power consumption that is suppressed and consumed by the filament can be matched with a predetermined power target value.
Moreover, since the current target value or the voltage target value is only adjusted at the start of the second period, not the real-time power control, there is no possibility that the control system becomes unstable.

  As described above, according to the filament control device of the present invention and the filament control method using the same, the power target value is converted into the current target value based on the filament resistance average value in the immediately preceding first period, and this current target is converted. The filament current in the subsequent second period is controlled by the value.

  Alternatively, based on the resistance average value of the filament in the immediately preceding first period, the power target value is converted into a voltage target value, and the filament voltage in the subsequent second period is controlled by this voltage target value.

  This ensures that the effects of disturbances that change in a drift, such as filament degradation over time (thinning of the filament) and temperature rise over time, are reliably suppressed, and power consumption matches the specified power target value. Can be made. Furthermore, since the real-time power control is not performed and the current target value or the voltage target value is only adjusted at the start of the second period, there is no possibility that the control system becomes unstable.

  In this way, while maintaining the stability of the control system, it is possible to control the power consumption to a predetermined value by reliably suppressing the influence of drifting disturbances, so the amount of thermoelectrons emitted from the filament is increased. Accurate and stable control is possible.

  Furthermore, according to the thermoelectron utilization processing apparatus of the present invention, the amount of thermoelectrons emitted from the filament can be controlled with high accuracy and stability by mounting the filament control apparatus of the present invention. Thermal electron utilization processing such as injection processing (space charge neutralization processing) and electron beam processing can be performed with high reproducibility and high reliability.

  Embodiments 1 and 2 of the filament control device and the filament control method of the present invention, and thermoelectron utilization processing (for example, space charge neutralization) in which the filament control device is mounted and thermoelectrons emitted from the filament are used. Before describing Embodiment 3 of the thermoelectron utilization processing apparatus for performing (processing), first, the technical idea of the present invention will be described.

  An object of the present invention is to stably control the amount of thermoelectrons emitted from a filament with high accuracy. In order to achieve this object, the power consumed by the filament may be controlled to coincide with a predetermined power target value. This is because the amount of thermionic electrons emitted from the filament is determined by the temperature of the filament, that is, the power consumed by the filament.

  Therefore, simply, it should be possible to control the amount of emitted thermal electrons by performing power control that feeds back power consumed by the filament in real time. This will be described with reference to FIG.

FIG. 1 is a block diagram showing a configuration example of a filament control device for explaining the technical idea of the present invention.
In FIG. 1, the filament control device 30 includes a current detector 31a, a voltage detector 31b, a power calculator 31c, a comparator 32a, a gain unit 32b, a driver 32c, and a power supply 34. The current and voltage flowing in the filament 5 are measured by the current detector 31a and the voltage detector 31b, and the power consumption is calculated by the power calculator 31c. The calculated power consumption is compared with a predetermined power target value by the comparator 32a, and current or voltage is supplied to the filament 5 through the gain unit 32b, the driver 32c, and the power source 34 so that they match. It has become so.

  However, with the configuration of the filament control device 30, it is difficult to maintain the stability of the control system and suppress the influence of main disturbances acting on the filament 5.

  As an example, consider the operation of the filament controller 30 when the filament 5 is a neutralizing filament 5 that neutralizes the space charge of the ion beam.

  Depending on the energization time, a disturbance T1 that changes in a drifting (DC-like) manner, such as deterioration over time (thinning) and temperature rise over time, acts on the filament 5 for this purpose. Further, in addition to this disturbance T1, random disturbance T2 such as a sudden temperature rise due to collision of the ion beam and adhesion or peeling of the coating due to the filament 5 being exposed to the ion beam is also present. Works. The filament 5 is repeatedly turned on / off appropriately according to the on / off state of the ion beam output, and the response time immediately after turning on, that is, at the start of control, is required to be as short as possible.

  Under this circumstance, if the filament control device 30 shown in FIG. 1 tries to suppress the disturbance T2 having randomness (that is, a wide frequency band), it is necessary to increase the gain of the gain unit 32b in a wide frequency band. However, when the gain is increased in such a wide frequency band, the phase margin of the control system decreases, and the control system may become unstable and oscillate.

  On the other hand, if the gain is reduced with emphasis on ensuring the stability of the control system, not only the suppression characteristic for the disturbance T2 but also the suppression characteristic for the drift disturbance T1 becomes insufficient. Although it is conceivable to increase only the gain in the low frequency range and improve the suppression characteristic against the drifting disturbance T1, this increases the response time at the start of control and turns the filament on / off. It cannot be applied to repeated uses.

  Therefore, in the power control system that feeds back the power consumed by the filament in real time, such as the filament control device 30 shown in FIG. 1, while maintaining the stability of the control system, the influence of the drifting disturbance T1 is suppressed. It is difficult to reliably suppress.

  On the other hand, when considering a process in which ion implantation for several minutes per substrate is repeatedly performed on a plurality of substrates, such as an ion implantation process in a semiconductor device manufacturing process, the drift disturbance T1 is suppressed. Is particularly important, and the influence of the disturbance T2 is not a big problem.

  This is because the drifting disturbance T1 gradually changes the ion implantation state for each substrate, and thus the characteristics of the device greatly vary when viewed between a plurality of substrates.

  On the other hand, the random disturbance T2 is changed every moment during the ion implantation of one substrate, but can be almost ignored when averaged during this time. This is because the average value of random noise is “0” statistically.

  From the above viewpoint, in the present invention, the influence of the random disturbance T2 is ignored, and the power consumption of the filament 5 is controlled so as to surely suppress the influence of the drifting disturbance T1, and is emitted from the filament 5. The amount of thermoelectrons is controlled with high accuracy and stability. Even when the filament is repeatedly turned on and off, the response time at the start of control is shortened.

Next, specific embodiments 1 and 2 of the filament control device of the present invention and the filament control method using the same, and the ion of the present invention in which the filament control device is mounted on the space charge neutralization device of the mass separator A specific example of the injection processing apparatus (Third Embodiment of Thermoelectron Utilization Processing Apparatus) will be sequentially described with reference to the drawings.
(Embodiment 1)
FIG. 2 is a block diagram illustrating a configuration example of the filament control device according to the first embodiment of the present invention.

  In FIG. 2, the filament control device 10 according to the first embodiment includes a resistance measuring unit 1 that measures the resistance value of the filament 5 at a predetermined time interval, and an average value of a plurality of resistance values measured during the first period A. A resistance average value calculator 2 as a resistance average value calculation means for calculating, and a current target value calculation as a current target value calculation means for calculating a target value of current supplied to the filament 5 based on the average value and the power target value. The constant current power source 4 as current control means for controlling the filament supply current based on the current target value during the second period C, and the start timing and end timing of the first period and the second period. A timing control circuit 6 for outputting a timing control signal (timing pulse) and a first switch as a first switch means controlled by the timing control circuit 6 7, and a second switch 8 and the sample hold circuit 9 as a second switching means. The timing control circuit 6, the first switch 7, the second switch 8, and the sample hold circuit 9 constitute timing control means for controlling each timing in the first period and the second period.

  The resistance measuring means 1 includes a current detector 1a as a current detecting means for measuring the current value I (ti) flowing through the filament 5, and a voltage detector 1b as a voltage detecting means for measuring the voltage value V (ti) of the filament 5. And a resistance calculator 1c as resistance value calculating means for calculating the resistance value R (ti) of the filament 5 based on the measured voltage value and current value. The resistance value R (ti of the filament 5 ) At predetermined time intervals. The resistance calculator 1c acquires the current value I (ti) measured by the current detector 1a and the voltage value V (ti) measured by the voltage detector 1b, and the acquired voltage value V (ti). Is divided by the current value I (ti) to calculate the resistance value R (ti) of the filament 5.

The resistance average value calculator 2 calculates the average value (resistance) of a plurality of resistance values R (ti) (i = 1 to n) measured during the first period A described later by the resistance measuring means 1. Average value) Rave is calculated. The resistance average value Rave calculated by the resistance average value calculator 2 is
Rave = ΣR (ti) / n (i = 1 to n; n is a natural number) (1)
It is expressed as

The current target value calculator 3 calculates the current to be supplied to the filament 5 in the second period C, which will be described later, from the resistance average value Rave calculated by the resistance average value calculator 2 and the power target value Wref of the filament 5. A target value Iref is calculated. The current target value Iref calculated by the current target value calculator 3 is
Iref = (Wref / Rave) ^0.5 (2)
It is expressed as

  The constant current power source 4 is a known constant current power source, and a current target value Iref is given as a set value during a second period C described later, and controls the current I flowing through the filament 5.

  The timing control circuit 6 outputs each timing pulse TP1 representing the start timing and end timing of the first period A and a timing pulse TP2 representing the start timing of the second period C, respectively. As shown in FIG. 4 to be described later, the timing pulse TP1 is a pulse that becomes High level during the first period A, and the start timing (rising edge of TP1) and the ending timing (falling edge of TP1) of the first period A. Represents. The timing pulse TP2 represents the start timing of the second period C (rising edge of TP2).

  The first switch 7 outputs a signal indicating the resistance value R (ti) output from the resistance measuring unit 1 to the resistance average value calculator 2 in the first period A in which the timing pulse TP1 is at the high level.

  The second switch 8 is the resistance average output from the resistance average value calculator 2 during the period in which the timing pulse TP1 is at the low level (period B from the end of the first period A to the start of the next first period A). A signal indicating the value Rave is output to the current target value calculator 3.

  The sample hold circuit 9 outputs a signal indicating the current target value Iref output from the current target value calculator 3 to the constant current power supply 4 at every rising timing of the timing pulse TP2 (start timing of the second period C).

  The operation of the filament control device 10 and the filament control method by the filament control device 10 will be described below with reference to FIGS.

  FIG. 3 is a diagram for explaining an operation flow (filament control method) of the filament control device 10 of FIG. FIG. 4 shows the resistance value R (ti) output from the resistance measuring means 1 in FIG. 2, the resistance average value Rave output from the resistance average value calculator 2 via the second switch 8, and the current target value calculator. 3 is a timing chart schematically showing each time change together with timing pulses TP1 and TP2 for the current target value Iref output from 3 through the sample hold circuit 9. FIG. FIG. 5 is a timing chart showing the power consumption W of the filament 5 of FIG. 2 in comparison with the target value Wref.

  In “Start” in FIG. 3, as shown in FIG. 4, the timing pulse TP1 output from the timing control circuit 6 becomes High level, and the first first period A-1 is started. In the first first period A-1, the initial value Iref (0) of the current target value Iref is given as a set value to the constant current power supply 4, and the filament 5 is controlled by the constant current power supply 4. The

  Next, in the resistance measurement step of step S1 of FIG. 3, as shown in FIG. 4, the filament 5 is detected by the resistance measuring means 1 in a state where the current I of the filament 5 is controlled based on the current target value Iref (0). The resistance value R (ti) is measured at predetermined time intervals. During this time, a random disturbance T2 such as a sudden rise in temperature and adhesion or peeling of the coating acts on the filament 5, and the resistance value R (ti) is shown by a white circle plot in FIG. , Randomly varying. The resistance value R (ti) measured by the resistance measuring means 1 during the first period A-1 (period in which the timing pulse TP1 is at the high level (one voltage level)) is the resistance average value via the first switch 7. It is sent to the calculator 2.

  Furthermore, in the resistance average value calculation step of step S2, as shown in FIG. 4, when the timing pulse TP1 becomes the low level (the other voltage level) and the first period A-1 ends (period B-1), the resistance Acquisition of the resistance value R (ti) by the average value calculator 2 is completed. For a plurality of resistance values R (ti) (i = 1 to n) acquired during the first period A-1, their average value (resistance average value) Rave ( 1) is calculated. Since the influence of the random disturbance T2 acting during the first period A-1 is excluded by the averaging process of the plurality of resistance values R (ti), the calculated resistance average value Rave (1 ) Is a resistance value that accurately reflects the average deterioration state and temperature state of the filament 5 in the first period A-1, as indicated by a black circle plot in FIG. The resistance average value Rave (1) is sent to the current target value calculator 3 via the second switch 8 during the period (period B-1) in which the timing pulse TP1 is at the low level (the other voltage level).

  Furthermore, in the current target value calculation step of step S3, the current target value Iref (1) to be supplied to the filament 5 is calculated by the current target value calculator 3 from the resistance average value Rave (1) and the power target value Wref. Calculation is performed based on the above equation (2). Thereby, based on the resistance average value Rave (1) immediately before (first period A-1) corresponding to the deterioration state and temperature state of the filament 5 over time, the power target value Wref is set to the current target value Iref (1 ). The current target value Iref (1) is sent to the sample hold circuit 9.

  Further, in the current control step of step S4, as shown in FIG. 4, when the timing pulse TP2 output from the timing control circuit 6 becomes high level, the second period C-1 is started in synchronization with the rising timing. The A current target value Iref (1) is sent from the sample hold circuit 9 to the constant current power source 4. The constant current power source 4 uses the current target value Iref (1) indicated by a solid line in FIG. 4 as a set value during the second period C-1 (until the start of the next second period C-2). The current I flowing through the filament 5 is controlled.

  During the current control step of step S4 (second period C-1), the resistance measurement step process of step S4-1 (first period A-2) is performed. In this resistance measurement step, as shown in FIG. 4, the timing pulse TP1 is also at a high level in synchronization with the rising timing of the timing pulse TP2. Thereby, the second first period A-2 is started simultaneously with the start of the second period C-1. Thereafter, operations similar to those in steps S1 to S4 are repeated.

  As described above, the first period A-1, the second period C-1 (first period A-2), the second period C-2 (first period A-3), and so on. While Ck and the next first period A- (k + 1) overlap, the period composed of the first period Ak and the second period Ck is repeated. Thereby, the current of the filament 5 in the next second period C- (k + 1) is controlled based on the resistance average value Rave (k + 1) in the second period Ck (first period A- (k + 1)). .

  The average resistance value Rave (k) indicates the average resistance value in the k-th first period Ak. The current target value Iref (k) indicates a current target value calculated based on the resistance average value Rave (k).

  According to the filament control device 10 and the filament control method using the same according to the first embodiment, as described above, based on the average value Rave (k) of the filament resistance immediately before (first period Ak), the power The target value Wref is converted into a current target value Iref (k), and the current I of the filament 5 in the second period Ck following this (first period Ak) is controlled by the current target value Iref (k). is doing.

  Here, in the resistance average value Rave (k), the influence of the random disturbance T2 is excluded by the averaging process. Therefore, this resistance average value Rave (k) is a resistance value that accurately reflects the average deterioration state and temperature state of the filament 5 in the first period Ak. Therefore, the resistance average value Rave (k) (k = 1, 2,...) Obtained for each repetition of the first period A is time-dependent depending on the energization time as shown by the black circle plot in FIG. It accurately represents a drifting resistance change (disturbance T1) such as excessive deterioration (line thinning) and temperature rise with time.

  In the first embodiment, the current target value Iref (k) (k = 1, 2,...) Is changed according to the change with time of the resistance average value Rave (k) (drift-like resistance change (disturbance T1)). The current I of the filament 5 is controlled by changing as indicated by the solid line in FIG.

  As a result, the influence of the drift disturbance T1 (resistance change with time) can be reliably suppressed, and the power consumption W can be matched with the power target value Wref as shown in FIG.

In addition, in the first embodiment, power control by real-time feedback as shown in FIG. 1 is not performed, and a current target value to be given as a set value to the constant current power source 4 is adjusted every time the second period C starts. Therefore, there is no possibility that the control system becomes unstable.
Further, since the response time at the start of control (at the start of the second period C) is determined by the response time of the constant current power supply 4, as described above, the influence of the drift disturbance T1 (resistance change with time) is affected. The power of the filament can be controlled with a sufficiently short response time while being surely suppressed, and the present invention is sufficiently applicable even when the on / off of the filament is repeated.

  Therefore, according to the first embodiment, the power consumption of the filament can be controlled to a predetermined value by reliably suppressing the influence of the drifting disturbance T1 while maintaining the stability of the control system. Thus, since the filament power can be controlled stably and with high accuracy, the amount of thermoelectrons emitted from the filament can be controlled with high accuracy and stability.

In the first embodiment, since the resistance average value Rave in the first period A is used for the calculation of the current target value in the subsequent second period C, there is a concern about the temporal resistance change during this period. If the first period A is appropriately set to a short time, a large resistance change does not occur and no particular problem occurs. For example, the first period A may be set to 0.001% or more and 0.1% or less of the filament life time. For example, when the filament life time is 500 hours, the first period A may be in the range of 18 seconds to 30 minutes, for example, on the order of minutes.
(Modification of Embodiment 1)
In the first embodiment, the timing pulse TP1 is also set to the high level in synchronization with the rising timing of the timing pulse TP2 so that the second period C-k and the next first period A- (k + 1) overlap. .

  However, the timing of the first period A and the second period C is not necessarily limited to the above timing, and it is sufficient that the second period Ck follows the first period Ak.

  For example, the first period A and the second period C-1 → the second period C-1 → the first period A-2 → the second period C-2 → the first period A-3 →. C and C may be repeated alternately. In this case, as shown in the operation flow of FIG. 6, the filament control device 10 may be operated such that the current measurement step of step S4 is followed by the resistance measurement step of step S1.

  As described above, in the first embodiment, the period including the first period A and the second period C is repeated, and the timing is controlled so that the second period C overlaps at least a part of the next first period A. However, as in the present modification of the first embodiment, the first period A and the second period C are repeated without overlap, and the timing control is performed so that the second period C comes after the first period A. Good.

In order to reduce the time loss, it is preferable to overlap the second period Ck with at least a part of the next first period A- (k + 1). More preferably, as in the first embodiment, it is better that the second period C-k completely includes the next first period A- (k + 1).
(Embodiment 2)
In the first embodiment, the power target value Wref is converted into the current target value Iref (k) based on the resistance average value Rave (k), and the current target value Iref (k) is used in the second period Ck. Although the current I of the filament 5 is controlled, in the second embodiment, the power target value Wref is converted into the voltage target value Vref (k), and the second period C−k is determined by the voltage target value Vref (k). A case of controlling the voltage V of the filament 5 in FIG. Also in this case, the same effects of the present invention as in the case of the first embodiment can be obtained.

  FIG. 7 is a block diagram illustrating a configuration example of the filament control device 20 according to the second embodiment of the present invention.

  In FIG. 7, the filament control device 20 of the second embodiment has a voltage target value calculator 23 as a voltage target value calculator instead of the current target value calculator 3 of the filament controller 10, and further includes a constant current. Instead of the power supply 4, a constant voltage power supply 24 as voltage control means is provided. The other configuration is the same as that of the configuration example of the filament control device 10 of the first embodiment, and the description thereof is omitted here.

In the second embodiment, the voltage target value calculator 23 calculates the target value Vref of the voltage to be applied to the filament 5 from the resistance average value Rave calculated by the resistance average value calculator 2 and the power target value Wref. To do. The voltage target value Vref calculated by the voltage target value calculator 23 is
Vref = (Wref × Rave) ^0.5 (3)
It is expressed as

  The constant voltage power supply 24 is supplied with the voltage target value Vref as a set value in the second period C, and controls the voltage V of the filament 5.

  8 shows a voltage target value Vref output from the voltage target value calculator 23 of FIG. 7 via the sample hold circuit 9, a resistance value R (ti) output from the resistance measuring means 1, and a resistance average value calculator. 2 is a timing chart schematically showing respective time changes of the resistance average value Rave output from 2 through the second switch 8 together with timing pulses TP1 and TP2. FIG.

  According to the filament control device 20 of the second embodiment, the power target value Wref is converted into the voltage target value Vref (k) based on the average value Rave (k) of the filament resistance immediately before (first period Ak). The filament voltage V in the second period Ck following this (first period Ak) is controlled by the voltage target value Vref (k).

  Here, in the resistance average value Rave (k), as in the case of the first embodiment, the influence of the random disturbance T2 is excluded by the averaging process. Therefore, this resistance average value Rave (k) is a resistance value that accurately reflects the average deterioration state and temperature state of the filament 5 in the first period Ak. Therefore, the resistance average value Rave (k) (k = 1, 2,...) Obtained for each repetition of the first period A is time-dependent depending on the energization time as shown by the black circle plot in FIG. It accurately represents a drifting resistance change (disturbance T1) such as excessive deterioration (line thinning) and temperature rise with time.

  In the second embodiment, the voltage target value Vref (k) (k = 1, 2,...) Is changed according to the change with time of the resistance average value Rave (k) (drift-like resistance change (disturbance T1)). The voltage V of the filament 5 is controlled by changing as shown by the solid line in FIG.

As a result, the influence of the drifting disturbance T1 (resistance change with time) can be reliably suppressed, and the power consumption W can be matched with the power target value Wref.
Moreover, in the second embodiment, the power control based on the real-time feedback as shown in FIG. 1 is not performed, and the voltage target value given as the set value to the constant voltage power supply 24 is adjusted every time the second period C is started. Therefore, there is no possibility that the control system becomes unstable.
Further, since the response time at the start of control (at the start of the second period C) is determined by the response time of the constant voltage power supply 24, as described above, the influence of the drift disturbance T1 (resistance change with time) is affected. The power of the filament can be controlled with a sufficiently short response time while being surely suppressed, and the present invention is sufficiently applicable even when the on / off of the filament is repeated.

Therefore, according to the second embodiment, as in the case of the first embodiment, the influence of the drifting disturbance T1 is reliably suppressed while maintaining the stability of the control system, and the power consumption of the filament is predetermined. The value can be controlled. In this way, the power to the filament 5 can be controlled stably and with high accuracy. For this reason, the amount of thermoelectrons emitted from the filament 5 can be controlled with high accuracy and stability.
(Embodiment 3)
According to the filament control device 10 of the first embodiment, the influence of the drifting disturbance T1 is reliably suppressed while maintaining the stability of the control system, and the power consumption of the filament 5 is controlled to a predetermined value. Can do. Since such a filament control device 10 can control the amount of thermoelectrons emitted from the filament 5 with high accuracy and stability, it is applied to various processes using thermoelectrons (thermal electron utilization process). be able to.

  In the third embodiment, as an example, the filament control device 10 of the first embodiment is used, and the space charge of the ion beam is neutralized by the thermal electrons emitted from the filament 5 whose power is controlled by the filament control device 10. An ion implantation processing apparatus that performs ion implantation processing will be described.

  FIG. 9 is a schematic diagram illustrating a schematic configuration example of the ion implantation processing apparatus according to the third embodiment.

  In FIG. 9, an ion implantation processing apparatus 50 according to the third embodiment includes an ion source 51, a mass separator 52, a neutralizing filament 5, and the filament control apparatus 10 according to the first embodiment.

The ion source 51 generates a plurality of types of ions by discharge or the like, and outputs a first ion beam Ia composed of the plurality of types of ions. The ion source 51 generates, for example, a plasma based on a source gas (for example, B ₂ H ₆ diluted with H ₂ ) between the anode 51a and the cathode 51b, and ions (B ₂ H _x ⁺ , B ₁ H _x ⁺ , H _x ^+, etc.) are extracted as the first ion beam Ia by the extraction electrode 51 c provided at the outlet of the ion source 51. Preferably, an ion source filament 51d is provided between the anode 51a and the cathode 51b, and electrons for efficiently generating plasma are supplied.

  The mass separator 52, while curving the first ion beam Ia output from the ion source 51 as indicated by the trajectory Ib in the figure by the magnetic field action, includes a plurality of different masses included in the first ion beam Ia. Separate ionic species from each other. The mass separator 52 is provided with a coil (not shown) alone or as a magnetic circuit including a yoke so that the magnetic field B acts in a direction perpendicular to the paper surface. In addition, an opening 52a is provided at the exit of the mass separator 52 so that only ions having a specific mass bent with a specific orbit radius (or a specific range of orbit radius) can pass through the action of the magnetic field B. Is provided. The ion beam that has passed through the opening 52a is appropriately accelerated as necessary, and is output as the second ion beam Ic. By this second ion beam Ic, an ion implantation process is performed on an object to be processed (for example, a semiconductor substrate).

  The neutralizing filament 5 is attached to the mass separator 52, and the neutralizing filament 5 has a power consumption of a predetermined power target value by the filament control device 10 of the first embodiment. Controlled to match. The neutralizing filament 5 is inserted, for example, from a certain side surface of the mass separator 52 toward the inside, and the number thereof is one or more appropriate numbers.

  In the ion implantation processing apparatus 50 of Embodiment 3, the current I flowing through the neutralizing filament 5 is controlled by the constant current power source 4 of the filament control apparatus 10 shown in FIG. In the second period C, in the state where the current control in step S4 of FIG. 3 is performed), an ion implantation process is performed on the object to be processed (for example, a semiconductor substrate). That is, as shown in the operation flow of FIG. 10, the ion implantation process (step S4-2) is performed every time the second period C is repeated. In FIG. 10, since the operation flow other than the ion implantation process (step S4-2) is the same as that in the first embodiment shown in FIG. 3, the description thereof is omitted here.

  Therefore, according to the ion implantation processing apparatus 50 of the third embodiment, the filament control apparatus 10 of the first embodiment is mounted on the mass separator 52 of the ion implantation processing apparatus 50, so that the stable and high The power consumption of the neutralizing filament 5 can be accurately controlled. Therefore, the ion implantation process can be performed in a state where the amount of thermoelectrons emitted from the neutralizing filament 5 is stably controlled with high accuracy. In addition, the thermoelectrons are not extracted by the electron extraction electrode, but are emitted from the neutralizing filament 5, and therefore do not have a specific direction and are directed in a random direction. For this reason, various trajectories can be drawn by the action of the magnetic field B, and electrons can be distributed over a wide range in the mass separator 52.

  In the third embodiment, since the thermoelectrons controlled to a predetermined amount and distributed over a wide range can be applied to the ion beam Ib, space charge can be neutralized stably and efficiently. it can. As a result, the divergence of the ion beam due to the repulsion between the positive ions in the ion beam Ib can be effectively suppressed, and the desired non-diverged ion beam can be output. By performing ion implantation using such an ion beam, it is possible to manufacture a highly reliable device with good reproducibility without varying the characteristics of the semiconductor device.

  In the third embodiment, the case where the thermoelectrons emitted from the neutralizing filament 5 are used for the purpose of suppressing the divergence of the ion beam has been described. It can also be used for the purpose of preventing charging of a processed product (for example, a semiconductor substrate). In the case of this use, the neutralizing filament 5 and the filament control device 10 do not necessarily have to be mounted on the mass separator 52, and are applied to an ion implantation processing apparatus in which the mass separator 52 is not provided. Is also possible. For example, the neutralizing filament 5 may be provided immediately above the object to be processed (for example, a semiconductor substrate).

  In the third embodiment, the case where the filament control device 10 according to the first embodiment is mounted on the ion implantation processing apparatus 50 for performing the ion implantation processing on the semiconductor substrate has been described. It is also possible to mount the filament control device 10 of the first embodiment as an electron beam source in an electron beam processing apparatus for performing the processing, and in this case as well, the same as in the first and third embodiments. An effect can be obtained. The thermoelectron utilization processing apparatus that performs thermoelectron utilization processing using the thermoelectrons emitted from the filament, such as the ion implantation processing apparatus and the electron beam processing apparatus, includes the filament control apparatus 10 of the first embodiment. In addition, the filament control device 20 of the second embodiment can be mounted. In this case, the same effect as in the second and third embodiments can be obtained.

  As mentioned above, although this invention has been illustrated using preferable Embodiment 1-3 of this invention, this invention should not be limited and limited to this Embodiment 1-3. It is understood that the scope of the present invention should be construed only by the claims. It is understood that those skilled in the art can implement an equivalent range based on the description of the present invention and the common general technical knowledge from the description of specific preferred embodiments 1 to 3 of the present invention. Patents, patent applications, and documents cited herein should be incorporated by reference in their entirety, as if the contents themselves were specifically described herein. Understood.

  The present invention relates to a filament control device, a filament control method, and a filament control device that can stably and accurately control the amount of thermoelectrons emitted from a filament, and the filament control device is mounted on a space charge neutralization device of a mass separator. In the field of a thermal electron utilization processing apparatus such as an ion implantation processing apparatus or an electron beam processing apparatus for performing a thermal electron utilization process utilizing the thermoelectrons emitted from the filament, the resistance average of the filament in the immediately preceding first period Based on the value, the power target value is converted into a current target value, and the filament current in the subsequent second period is controlled by this current target value, or based on the resistance average value of the filament in the immediately preceding first period The electric power target value is converted into a voltage target value, and the filament in the subsequent second period is converted by the voltage target value. By controlling the pressure, it is possible to reliably suppress the influence of disturbances that change in a drifting manner, such as deterioration over time (thinning of the filament) and temperature rise over time, which depend on the energization time. It can be matched with the target value. Furthermore, since the real-time power control is not performed and the current target value or the voltage target value is only adjusted at the start of the second period, there is no possibility that the control system becomes unstable.

  In this way, while maintaining the stability of the control system, it is possible to control the power consumption to a predetermined value by reliably suppressing the influence of drifting disturbances, so the amount of thermoelectrons emitted from the filament is increased. Accurate and stable control is possible. Therefore, thermal electron utilization processing such as ion implantation processing (space charge neutralization processing) and electron beam processing processing can be performed with high reproducibility and high reliability.

It is a block diagram which shows the structural example of the filament control apparatus for demonstrating the technical idea of this invention. It is a block diagram which shows the structural example of the filament control apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the operation | movement flow of the filament control apparatus of FIG. It is a timing diagram for demonstrating the operation | movement flow of the filament control apparatus of FIG. It is a timing diagram which shows the time change of the power consumption W controlled by the filament control apparatus of FIG. It is a figure which shows the operation | movement flow of the filament control apparatus which concerns on the modification of Embodiment 1 of this invention. It is a block diagram which shows the structural example of the filament control apparatus which concerns on Embodiment 2 of this invention. It is a timing diagram for demonstrating the operation | movement flow of the filament control apparatus of FIG. It is a schematic diagram which shows the schematic structural example of the ion implantation processing apparatus which concerns on Embodiment 3 of this invention. It is a figure which shows the operation | movement flow of the ion implantation processing apparatus of FIG. It is a schematic diagram which shows the structural example of the conventional space charge neutralization apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Resistance measuring means 1a Current detector 1b Voltage detector 1c Resistance calculator 2 Resistance average value calculator 3 Current target value calculator 4 Constant current power supply 5 Filament 6 Timing control circuit 7 First switch 8 Second switch 9 Sample hold circuit (SH)
10, 20, 30 Filament control device 23 Voltage target value calculator 24 Constant voltage power supply 31a Current detector 31b Voltage detector 31c Power calculator 32a Comparator 32b Gain unit 32c Driver 34 Power supply 50 Ion implantation processing device 51 Ion source 52 Mass Separator

Claims (17)

A filament control device that controls the power consumed by the filament to match a predetermined power target value,
Resistance measuring means for measuring the resistance value of the filament at predetermined time intervals;
Resistance average value calculating means for calculating an average value for the plurality of resistance values measured during the first period by the resistance measuring means;
Current target value calculation means for calculating a target value of current to be supplied to the filament from the average value calculated by the resistance average value calculation means and the power target value;
Current control means for controlling the current value flowing through the filament so as to coincide with the target value of the current calculated by the current target value calculation means during the second period;
Timing control means for controlling the timing of the first period and the second period ,
Each period consisting of the first period and the second period is repeated,
The target value of the current is a filament control device used by the current control means in the second period started immediately after completion of the first period when the target value of the current is obtained . A filament control device that controls the power consumed by the filament to match a predetermined power target value,
Resistance measuring means for measuring the resistance value of the filament at predetermined time intervals;
Resistance average value calculating means for calculating an average value for the plurality of resistance values measured during the first period by the resistance measuring means;
Voltage target value calculation means for calculating a target value of a voltage to be applied to the filament from the average value calculated by the resistance average value calculation means and the power target value;
Voltage control means for controlling the voltage applied to the filament so as to coincide with the target value of the voltage calculated by the voltage target value calculation means during the second period;
Timing control means for controlling the timing of the first period and the second period ,
Each period consisting of the first period and the second period is repeated,
The filament control device used by the voltage control means in the second period started immediately after the completion of the first period when the target value of the voltage is obtained .   The filament control device according to claim 1, wherein the current control means is a constant current power source.   The filament control device according to claim 2, wherein the voltage control means is a constant voltage power source.   The resistance measurement means includes a current detection means and a voltage detection means for measuring a current and a voltage flowing through the filament, and a voltage value measured by the voltage detection means is divided by a current value measured by the current detection means. The filament control device according to claim 1, further comprising a resistance value calculation unit that calculates the resistance value. It said timing control means, as the second period overlaps with at least a part of the following the first period, filament control apparatus according to claim 1 or 2 for controlling the timing. Said timing control means, said in each period, said such that the second period comes after the first period, filament control apparatus according to claim 1 or 2 for controlling the timing.   The filament control device according to any one of claims 1, 2, 6, and 7, wherein the first period is set to 0.001% or more and 0.1% or less of a lifetime of the filament. The timing control means is provided between the resistance measurement means and the resistance average value calculation means, and is controlled so that a signal can be output from the resistance measurement means to the resistance average value calculation means in the first period. 1 switch means;
Provided between the resistance average value calculation means and the current target value calculation means or the voltage target value calculation means, and after the end of the first period, from the resistance average value calculation means to the current target value calculation means or the The filament control device according to any one of claims 1, 2, and 6 to 8, further comprising second switch means that is controlled so that a signal can be output to the voltage target value calculation means.   The timing control means is provided between the current target value calculation means and the current control means or between the voltage target value calculation means and the voltage control means, and at each start of the second period, The filament control device according to any one of claims 1, 2, and 6 to 9, further comprising a sample and hold circuit controlled to update a target value of current or a target value of voltage. A filament control device according to any one of claims 1 to 10, which is a thermoelectron utilization processing device that performs thermoelectron utilization processing using thermoelectrons emitted from the filament,
The thermoelectron utilization processing apparatus in which the thermoelectron utilization processing is executed in a state where the current value or voltage value of the filament is controlled by the current control means or the voltage control means during the second period.   12. The filament is a neutralizing filament for neutralizing the space charge distribution of the ion beam, and ion implantation is performed by neutralizing the space charge distribution of the ion beam with thermal electrons emitted from the filament. The thermal-electron utilization processing apparatus as described in.   The thermoelectron utilization processing apparatus according to claim 11, wherein the filament is an electron beam source filament for generating an electron beam, and an electron beam processing is performed by thermoelectrons emitted from the filament. A filament control method for controlling power consumed by a filament so as to coincide with a predetermined power target value,
A resistance measuring step of measuring the resistance value of the filament at predetermined time intervals;
A resistance average value calculating step for calculating an average value for the plurality of resistance values measured during the first period in the resistance measuring step;
A current target value calculating step for calculating a target value of a current to be supplied to the filament from the average value calculated in the resistance average value calculating step and the power target value;
During the second period, so as to coincide with the target value of the computed electric current in said current target value calculation step, have a current control step of controlling the current flowing through the filament,
Each period consisting of the first period and the second period is repeated,
The filament control method used by the current control step in the second period started immediately after the completion of the first period when the target value of the current is obtained . A filament control method for controlling power consumed by a filament so as to coincide with a predetermined power target value,
A resistance measuring step of measuring the resistance value of the filament at predetermined time intervals;
A resistance average value calculating step for calculating an average value for the plurality of resistance values measured during the first period in the resistance measuring step;
A voltage target value calculation step for calculating a target value of a voltage to be applied to the filament from the average value calculated in the resistance average value calculation step and the power target value;
During the second period, so as to coincide with the target value of the voltage calculated by the said voltage target value calculation step, have a voltage control step of controlling the voltage applied to the filament,
Each period consisting of the first period and the second period is repeated,
The filament control method used by the voltage control step in the second period starting immediately after the completion of the first period when the target value of the voltage is obtained . Filament control method according to claim 14 or 15 wherein the second period is the timing control so as to overlap with at least part of the following first period. In each period, filament control method according to claim 14 or 15 wherein the second period is the timing control in such a manner that after the first period.

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