JPH0864166A - Ion implanting device - Google Patents

Abstract

PURPOSE: To prevent continuous generation of an arc, and resume ion implantation without continuing the generation of the arc by discontinuing voltage supply for a short time immediately after arc discharge was generated to extinguish the arc discharge, then resuming the ion implantation. CONSTITUTION: An ion extracted from an ion source 4 by extraction voltage is accelerated or decelerated with an accelerating electrode 22, and implanted into a wafer W. When arc discharge is generated between an extraction electrode 10 and the ion source 4 during ion implanting operation, the arc discharge is detected with an arc discharge detecting part 40. A timer circuit 60 of a voltage apply discontinuing part 42 is operated responding to the detection, for the extinguished time of the arc discharge, for example about 8ms, output voltage of an inverter is controlled zero, and recovered after 20ms to the normal operation to continue the ion implantation. When frequency of arc detection reaches the specified number within a specified time, a voltage application discontinuing part 44 considers that serious problems are generated and completely stops the operation of an extraction power source 28.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an ion implantation apparatus.

[0002]

2. Description of the Related Art Generally, as an apparatus for introducing impurities in a semiconductor device manufacturing process, an ion implantation apparatus is used because the amount of impurities introduced can be precisely controlled and the number of ions can be grasped for processing. Has been.

In this ion implantation apparatus, a gas such as a halogen compound is brought into a plasma state, an electric field is applied to the gas by an electrode provided on the way to extract ions, and a predetermined magnetic field is applied to the extracted ion beam. Thus, impurity ions are eliminated and only predetermined ions are subjected to mass spectrometry, and the energy of the extracted ions is further increased or decreased to be injected into the object to be processed.

This will be specifically described with reference to FIGS. 4 and 5. FIG. 4 is a sectional view showing a general ion implantation apparatus,
FIG. 5 is a circuit diagram showing a power supply system of the device shown in FIG. As shown in the figure, the ion implantation apparatus 2 has an ion source 4 for converting a supply gas into a plasma, and the ion source 4 is provided with a pipe 8 in a gas box 6 for supplying halogen gas or the like required for the ion source 4. Connected through. An extraction electrode 10 is provided on the exit side to extract positive ions from the ion source 4, and the extracted ion beam B1 is accelerated and passes through a variable slit 12 and then a mass having a strong electromagnetic magnet 14. After passing through the analyzer 16, only predetermined necessary ions are taken out here, and impurity ions are excluded. The extracted ions are further accelerated through the mass slit 18 and then further accelerated or decelerated by the multistage accelerating electrodes 22 arranged in the accelerating tube 20 and attached to the rotatable wafer disk 26 in the disk chamber 24. Is injected into the semiconductor wafer W.
In addition, since the degree of vacuum has a great influence on the performance of the ion implantation apparatus, the portion through which the ion beam B passes is filled with, for example, 10 ⁻⁶ by a turbo molecular pump, a cryopump or the like.
A high vacuum of about Torr is maintained.

As shown in FIG. 5, an extraction power supply circuit 30 having an extraction power supply 28 that is variable so as to output a high voltage DC of about 60 KV at maximum is connected to the ion source 4 to extract the ion beam B1. The other pole is connected to the extraction electrode 10 via the shunt resistor R1 and the terminal 32. Also, the acceleration electrode 22
Between the terminal 32 and the terminal 32, for example, 140KV maximum
An accelerating power source 34, which is variably output so as to output a high voltage, is connected, and ion implantation can be performed at an energy of 200 KV at maximum.

[0006]

By the way, when the ion implantation operation is continuously performed, impurities are attached to the extraction electrode 10 and its vicinity, which causes arc discharge between the extraction electrode 10 and the ion source 4. If it is extremely dirty, it may fall into a short state. Therefore, the conventional power supply circuit is equipped with a protection circuit that forcibly shuts off the power supply circuit when an overcurrent flows through the power supply circuit for a certain period of time regardless of arc discharge or short circuit. Also, maintenance work for removing dirt is being performed. When returning, the operator turns on the power again to continue ion implantation.

However, even though the maintenance work for removing the dirt and the like adhering to the extraction electrode 10 is being carried out, the electrode itself is not stable immediately after the removal operation, or the maintenance time is missed due to the severe dirt. , The detection becomes too sensitive to arc discharge, etc.
There is a problem in that FFs occur frequently, and as a result, the ion implantation itself becomes intermittent, which adversely affects the wafer.

In order to solve this problem, it is conceivable to lengthen the permissible time for overcurrent to reduce the intermittentness of ion implantation, but in this case, arc discharge or short-circuit may continue for a long time. Since it appears, there is a high possibility of causing an abnormal situation in the power supply circuit, which is not preferable.

The present invention focuses on the above problems,
It was created to solve this effectively. It is an object of the present invention to provide an ion implanter in which voltage application is temporarily interrupted for a short time when arc discharge occurs.

[0010]

According to the present invention, in order to solve the above-mentioned problems, various ions extracted by an extraction voltage of an extraction power supply circuit connected to an ion source are passed through a mass analyzer having an electromagnetic magnet. In the ion implantation device that separates predetermined ions by doing so and implants the separated ions into the object to be processed, arc discharge that determines whether or not arc discharge has occurred based on the current supplied to the extraction power supply circuit The detection unit and the voltage application interruption unit for interrupting the voltage supply from the extraction power supply circuit for a predetermined time when the arc discharge detection unit detects an arc discharge are configured.

[0011]

Since the present invention is configured as described above, when the current flowing in the extraction power supply circuit exceeds a predetermined value, the arc discharge detection unit determines that arc discharge has occurred. Upon receiving this determination signal, the voltage application interruption unit controls the extraction power supply circuit to interrupt the voltage application for a predetermined time, for example, several milliseconds after the arc is detected. During this interruption of the voltage application, the arc discharge subsides, and by subsequently applying the extraction voltage again, it becomes possible to restart the ion implantation without continuing the arc.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the ion implantation apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a configuration diagram showing an electric circuit of an ion implantation apparatus according to the present invention, and FIGS. 2 and 3 are waveform diagrams showing current or voltage waveforms of respective portions in FIG.

First, the overall structure of the ion implantation apparatus of the present invention is the same as that shown in FIGS. That is, this ion implanter has an ion source 4 for converting the supply gas into plasma, and a filament 36 for emitting electrons is arranged in the ion source 4. A gas box 6 for supplying a gas required for the ion source 4 is connected to the ion source 4 through a pipe 8. As the supply gas, depending on the type of ions to be injected, AsH
₃ , PH ₃ , BF _3, etc. can be used.

An extraction electrode 10 is provided on the outlet side for extracting positive ions from the ion source 4,
The extracted ion beam B is accelerated, passes through the variable slit 12, and then passes through a mass analyzer 16 having a strong electromagnetic magnet 14, where only predetermined necessary ions are taken out and impurity ions are excluded. . The extracted ions are further accelerated through the mass slit 18 and then further accelerated or decelerated by the multistage accelerating electrodes 22 arranged in the accelerating tube 20 and attached to the rotatable wafer disk 26 in the disk chamber 24. Is injected into the semiconductor wafer W.

Further, since the degree of vacuum has a great influence on the performance of the ion implantation apparatus, the inside of the portion through which the ion beam B passes is maintained at a high vacuum of, for example, about 10 ^-6 Torr by a turbo molecular pump, a cryopump or the like. are doing.

As shown in FIG. 5, in order to extract the ion beam B1, the ion source 4 is connected to an extraction power supply circuit 30 having an extraction power supply 28 that is variable so as to be able to output a high voltage DC of about 60 KV at maximum. The other pole is connected to the extraction electrode 10 via the shunt resistor R1 and the terminal 32. Also, the acceleration electrode 22
Between the terminal 32 and the terminal 32, for example, 140KV maximum
An accelerating power source 34, which is variably output so as to output a high voltage, is connected, and ion implantation can be performed at an energy of 200 KV at maximum.

An electric circuit, which is a feature of the present invention, is connected to the drawer power supply circuit 30. Specifically, as shown in FIG. 1, a voltage detection unit 38 is connected to both ends of the shunt resistor R1 of the extraction power supply circuit 30 to detect the ion extraction current, and this detection value is input to the arc discharge detection unit 40. Has been done. The output of the detection unit 40 is input to the voltage application suspending unit 42 and the voltage application suspending unit 44, which are features of the present invention.

The output of the voltage application suspending section 42 is input to an inverter control section 46 which controls the drive of the drawing power supply 28 composed of, for example, an inverter control power supply, and the output of the voltage application stopping section 44 is on the drawing power supply 28 side. Is input to. The output of the voltage detection unit 38 is the overload current detection unit 4
8 is also connected, and this output is input to the pull-out power supply 28 side.

The arc discharge detecting section 40 is mainly composed of a comparator 50 for comparing the detected current value with the arc reference current value, an SR flip-flop 52 for receiving the output, and an inverter 54 for connecting the output and the reset terminal. When an electric current of, for example, 5 to 7 times the maximum output current under normal conditions is detected, it is recognized that an arc has occurred, and that fact can be output. Therefore, the arc reference current value is set to a value which is 5 to 7 times the maximum output current under normal conditions. The SR flip-flop 52 outputs the arc recognition signal having a sharp waveform output from the comparator 50 by, for example, several μ.
It is a circuit that shapes the pulse-like waveform of seconds.

The voltage application stopping unit 44 is mainly composed of, for example, an inverter 56 and a counter 58, and when the arc discharge is detected a predetermined number of times, for example, 15 times within a predetermined time, for example, 2 minutes, the first The stop signal of is output. Therefore, this counter 58 has
A timer 59 that measures a predetermined time and a reset unit 61 that resets the counter 58 when the arc discharge is not detected a predetermined number of times within the predetermined time are provided.

The voltage application suspending section 42 is provided in the inverter 5
8 and a timer circuit 60 that outputs an interruption signal for a predetermined time, for example, several milliseconds when the arc detection signal is input, and this interruption signal is output as described later. Only during this period, the output voltage of the extraction power source 28 can be made zero.

The overload current detection section 48 compares the detected current value of the voltage detection section 38 with the overload current reference value and a comparator 62 for outputting this output to a predetermined time constant, for example, 1.0.
A resistor 64 and a capacitor 66 that integrate with a time constant of about a second
And the output of this integration circuit 68 is
When the predetermined value determined by the time constant is reached, the pull-out power supply 28
Flip-flop 7 for outputting a second stop signal toward
It is mainly composed of 0 and 0. The overload current reference value is set to, for example, a value 1.1 times the maximum output current value in the normal state, and therefore 1.1 times the maximum output current in the normal state.
When a double current flows for 1.0 second, it is considered abnormal and the supply of the extraction voltage is stopped.

The inverter control unit 46 compares the set voltage supplied from a main control unit (not shown) that controls the entire ion implantation apparatus with the feedback voltage of the extraction voltage, and this comparator 72. Inverter control circuit 74 that outputs a command signal based on the output of 72
It is mainly composed of and. The interruption signal output from the voltage application interruption unit 42 is input to the set voltage input terminal side of the inverter control circuit 74 and the comparator 72.

The extraction power source 28 includes an AC power source 76 and
Diode bridge rectifier circuit 78 and inverter 80
And a booster 82. The high voltage direct current of, for example, a maximum of 60 KV generated here can be applied between the ion source 4 and the extraction electrode 10. The command signal output from the inverter control circuit 74 is input to the inverter 80 to control the output voltage having a value based on the command, and the first and second stop signals are AC signals. The open / close switch 84 of the power supply 76 is input to the drive unit to open / close the switch.

Next, the operation of this embodiment configured as described above will be described with reference to FIG. First, the inverter control unit 46 is operated according to a set voltage from a central control unit (not shown).
Command signal S1 from the inverter control circuit 74 of
Is output, and the inverter 80 of the extraction power supply 28 applies an output voltage having a value corresponding to the command signal S1 from the booster 82 between the ion source 4 and the extraction electrode 10. In this case, the polarity is such that the ion source 4 side is the positive pole and the extraction electrode 10 side is the negative pole.

Here, a predetermined gas, for example, AsH _{3 in} the case of As injection, is introduced into the ion source 4 from the gas box 6, while electrons are emitted from the surface of the filament 36, and the electrons are positive electrodes. As it moves toward the ion source 4, it collides with particles of the dopant gas to form As positive ions.

The beam B1 of As positive ions is extracted by the extraction electrode 10 while being accelerated, and the variable slit 12 is formed.
Is introduced into the mass analyzer 16 through which the strength of the internal magnetic field is adjusted by appropriately controlling the current of the electromagnetic magnet 14, and only the necessary ion species are bent by 90 degrees and pass therethrough. . Unwanted ionic species are trapped on the cooled inner wall or the like by drawing an orbit of an arc larger or smaller than 90 degrees.

The ion species extracted here are the acceleration tube 20.
Is further accelerated or decelerated by the accelerating electrode 22 and is injected into the wafer surface held by the wafer disk 26 with a predetermined energy.

During such normal ion implantation operation, if the extraction electrode 10 is contaminated with dirt and arc discharge occurs between the extraction electrode 10 of the negative pole and the ion source 4 of the positive pole, for example, it is regulated. An arc discharge is detected by the arc discharge detector 40 because a current several times as large as the current temporarily flows. Then, in response to this detection, the timer circuit 60 of the voltage application suspending unit 42 operates, and after the arc detection, the time at which the arc discharge will disappear, for example, 8 m.
For about a second, the output voltage of the inverter is suppressed to zero, and after 200 msec, normal operation is restored and ion implantation is continued.

When the arc detection as described above is detected a predetermined number of times, for example, 12 times within a predetermined period of time, for example, 2 minutes, it is considered as a serious failure. As a result, the operation of the drawing power source 28 is completely stopped.

Further, the overload current detection unit 48 does not deal with arc discharge but protects the power supply circuit when an overcurrent continuously flows. For example, the maximum allowable current due to a failure such as a short circuit. When an overcurrent of 1.1 times or more continues for, for example, about 1.0 second, it is regarded as a serious failure and the operation of the extraction power supply 28 is completely stopped.

The above operation will be described in detail with reference to the waveform charts shown in FIGS. The alphabet of the figure number in FIG. 2 shows the waveform of the same alphabet part in FIG. That is, FIG. 2A is the output voltage of the extraction power source, FIG. 2B is the output current, that is, the input to the comparator 50 of the arc discharge detection unit 40, FIG. 2C is the output of the comparator 50, and FIG. D) is an input signal to the timer circuit 60 (arc detection signal), FIG. 2 (E) is an output signal from the timer circuit 60 (inverter interruption signal), and FIG. 2 (F) is an input signal to the counter 58 (count clock signal). ), FIG. 2 (G) is the count number, FIG. 2 (H) is the count reset timer signal, and FIG.
(I) is a count clear signal, and FIG. 2 (J) is a counter 5
8 output signals (first interruption signal) are shown respectively.

First, the maximum allowable current of 7 is reached by arc discharge.
When an output current of up to 8 times flows and becomes higher than the arc detection level (FIG. 2 (B)), a sharp pulsed analog wave is output from the comparator 50 as an arc recognition signal (FIG. 2).
(C)), which is waveform-shaped by the SR flip-flop 52 and outputs a rectangular wave. This arc detection signal is inverted by the inverter 58 of the voltage application interruption unit 42 and input to the timer circuit 60 (FIG. 2 (D)).

Then, the timer circuit 60 outputs an interruption signal having a pulse width of a predetermined time, for example, 8 msec in which the arc discharge will be extinguished (FIG. 2 (E)). This interruption signal is input to the set voltage input side of the comparator 72 of the inverter control unit 48 and the inverter control circuit 74, pulls the set voltage from the central control unit to zero, and forcibly instructs the output voltage of zero volt. The inverter control circuit 74 is also instructed to set the output voltage to zero volt for 8 msec. In this case, the interruption signal is sent to the comparator 7.
The control may be performed by inputting only to one of the two and the inverter control circuit 74, but the reliability of the operation can be secured by inputting to both elements. In particular, by inputting the interruption signal to the inverter control circuit 74, quicker control becomes possible as compared with the case where it is input only to the comparator 72 side.

Inverter control unit 4 receiving this interruption signal
6 receives the drawing current 28 to the inverter 80 and outputs the command signal S1 so that the output voltage becomes zero for 8 msec. As a result, the supply of the output voltage (FIG. 2A) and the output current (FIG. 2B) is stopped for 8 msec, and the arc discharge that has occurred is stopped. Then, when 8 msec has elapsed, the normal voltage is applied again within 200 msec, and the ion implantation is restarted.

By temporarily suppressing the output voltage for a short time each time an arc discharge or the like occurs, it is possible to prevent the arc discharge from continuously occurring and to completely shut off the output due to the arc discharge. Can be suppressed as much as possible.

Further, the arc detection signal is sent to the voltage application stopping unit 4
4 is also input to the counter 58 (FIG. 2 (F)),
This number is counted every time the arc discharge is detected by the arc discharge detector 40. If the count value is counted less than a set number of times within a predetermined time, for example, 2 minutes (120 seconds) from the detection of the first arc, the count value is cleared (FIG. 2 (G),
2H, the first half of FIG. 2I), when an arc discharge is detected a set number of times, for example, 15 times within a predetermined time, this counter 58 is regarded as a relatively serious failure and the counter 58 is 1 stop signal (Fig. 2 (J)), the AC power source 7
6 is supplied to the drive unit of the open / close switch 84 and is forcedly opened to cut off the output (FIG. 2 (G), FIG. 2 (H),
The latter half of FIG. 2 (I)). The voltage supply is not restarted until the operator closes the open / close switch 84 again.

As described above, when the frequency of arc discharge is high, the output voltage is forcibly cut off because the characteristics of the ion-implanted wafer are deteriorated or it is not preferable for the power supply circuit. The set number of times is, for example, 1 to
The number of times can be arbitrarily set at 15 times, and the count reset period can also be arbitrarily set within a range of, for example, 30 seconds to 120 seconds.

Next, turning to FIG. 3, FIG.
3B shows the input signal of the flip-flop 70 of the overload current detector 48, and FIG. 3C shows the output signal of the flip-flop 70 (second stop). Signal).

The detected value of the output current (FIG. 3 (A)) is also input to the overload current detecting section 48. For example, when the current which is 1.1 times the maximum allowable current is detected, the comparator 62 outputs the current value. A pulsed overcurrent detection signal is output only. In general, the period of arc discharge is on the order of microseconds, and the pulse wave at that time is cut by the integrating circuit 68, so that the supply voltage is not interrupted, but a short circuit or the like occurs in the electrodes. When an overcurrent flows for a relatively long period (time constant defined by the integrating circuit 68, for example, 1.0 second or more), a pulse wave, that is, a second stop signal (FIG. 3C) is output from the flip-flop 70. Latter half) is output, and the drive unit of the open / close switch 84 is operated in the same manner as described above to bring it into the open state, thereby cutting off the output voltage. As a result, the output voltage can be forcibly cut off when an excessive current flows for a long time, for example, one second due to a short circuit or the like without detecting arc discharge, and the power supply circuit and the like can be protected.

As described above, in the present embodiment, when an arc discharge occurs, immediately after that, the supply of the output voltage is temporarily stopped for a time sufficient to extinguish the arc discharge,
After that, since the output voltage is supplied again, the ion implantation operation is not interrupted for a long period of time, and the substantially continuous ion implantation operation can be performed. Therefore, it is possible to prevent the characteristics of the semiconductor wafer from being adversely affected.

When a large number of arc discharges are detected within a predetermined time, the voltage application stopping unit 44 detects this and considers it as a comparatively large obstacle, and may turn off the drawing power source. Therefore, the power supply circuit and other circuits can be protected almost certainly. Further, when an excessive current continuously flows due to a short circuit or the like, the overload current detection unit 4
8 operates, the power supply circuit and the like can be protected by turning off the drawing power supply from the original in the same manner as described above.

The above-mentioned respective circuit configurations are not limited to this, and any configuration may be adopted as long as the same operation as described above is performed. Further, although the semiconductor wafer has been described as an example of the object to be processed, the object is not limited to this and, for example, an LCD substrate or the like can be used.

[0044]

As described above, according to the ion implantation apparatus of the present invention, the following excellent operational effects can be exhibited. When an arc discharge occurs, immediately after that, the output voltage supply is temporarily interrupted for a short time, so that it is possible not only to prevent the arc from being continuously generated but also to perform the ion implantation operation. It will not be interrupted for a long time, and a substantially continuous ion implantation operation can be performed. Therefore, it is possible to significantly prevent the characteristics of the object to be processed from being adversely affected.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an electric circuit of an ion implantation apparatus according to the present invention.

FIG. 2 is a waveform diagram showing a waveform of a current or a voltage of each part in FIG.

FIG. 3 is a waveform diagram showing a waveform of current or voltage of each part in FIG.

FIG. 4 is a cross-sectional view showing a general ion implantation device.

5 is a circuit diagram showing a power supply system of the device shown in FIG.

[Explanation of symbols]

 2 Ion implanter 4 Ion source 10 Extraction electrode 14 Electromagnetic magnet 16 Mass spectrometer 22 Accelerating electrode 28 Extraction power supply 30 Extraction power supply circuit 36 Filter 40 Arc discharge detection unit 42 Voltage application interruption unit 44 Voltage application suspension unit 46 Inverter control unit 48 Overpass Load current detection unit 52 RS flip-flop 60 Timer circuit 74 Inverter control circuit 80 Inverter B1 Ion beam S1 Command signal W Semiconductor wafer (processing target)

Claims (2)

[Claims] 1. A variety of ions extracted by an extraction voltage of an extraction power supply circuit connected to an ion source are passed through a mass analyzer having an electromagnetic magnet to separate predetermined ions, and the separated ions are processed. In an ion implanter for implanting into the body, an arc discharge detection unit that determines whether or not arc discharge has occurred based on the current supplied to the extraction power supply circuit, and when this arc discharge detection unit detects arc discharge. An ion implantation apparatus comprising a voltage application interruption unit for interrupting the voltage supply from the extraction power supply circuit for a predetermined time. 2. The pull-out power supply circuit has an inverter control power supply that operates according to a command signal from the inverter control unit, and the voltage application suspending unit directs the inverter control unit so that the output voltage becomes zero. The ion implantation apparatus according to claim 1, wherein the ion implantation apparatus is configured to output an interruption signal.