JPS62208534A - Ion implanter - Google Patents

Abstract

PURPOSE:To complete prescribed implantation without operating an ion implanter at the time of suspension of implantation, by controlling the output power of a magnetron power supply when the implantation is suspended due to the abnormal discharge of an ion source. CONSTITUTION:An overcurrent is detected by a resistor R3, the output from which is compared with a reference value by a comparator 10. A relay RL2 is energized through a transistor Q1 in a stage next to the comparator 10, so that an error signal 20 is sent out to a CPU control section 19. At the same time, a relay RL3 is energized to de-energize the coil of an electromagnetic switch 2 by the contact signal gammal3 to cut off an AC output to a rectifier 3 to cut off a high-voltage output. Since the relay RL3 is self-maintained by the contact signal gammal3, the relay needs to be put out of the self-maintained state when the high-voltage output is applied again. A signal 23 for resetting from the CPU control section 19 is set at the ground potential to automatically put the relay RL3 out of the self-maintained state.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention particularly relates to an ion implantation apparatus for doping impurities into semiconductors and the like.

[Conventional technology]

Regarding the microwave ion source, see Japanese Patent Application Laid-Open No. 51-1192.
87, so I will only briefly explain it.

A microwave ion source requires a microwave electric field and a magnetic field for ionization, and the sample gas introduced therein is turned into plasma and the generated ions are accelerated with high voltage to extract the ion beam. It is. The microwave electric field is generated by a magnetron, and the magnetic field is generated by an electric current flowing through a coil. As a prior art, a schematic configuration of an ion implantation device will be explained with reference to FIG.

In FIG. 1, a microwave ion source 1 includes a magnetron 2 whose output power is controlled by the output of a magnetron power supply 6, a coil 3 whose generated magnetic field is controlled by the output of a magnetic field power supply 7, a sample gas 4, etc. The gas is ionized by the output of the acceleration power source 8 (for example, 120 KV)
The ion beam 18 extracted by the application of the ion beam 18 is selected by the separating section 9 to have only a desired mass number, and is implanted into the wafer 11 mounted on the circumference of the disk 10 in the implantation chamber.

The wafer on the disk is rotated by a rotation motor 12 so that a predetermined implantation amount is uniformly implanted, and (because the beam size is smaller than the wafer diameter) a scan motor 13 is used.
is being scanned. In the above, the mass separation coil is connected to the magnetic field power supply 14, the rotation drive power supply 15 for one disk rotation, and the scan drive power supply g16 for scanning, and are controlled by signals from the computer control section 19. Further, the gas flow rate is connected to a flow rate regulator 5, and the ion beam current is connected to a computer control unit 19 via a current detector 17. In FIG. 1, the ion source, the portion through which the ion beam passes, and the implantation chamber are evacuated, but these are omitted because they are not relevant to the present invention.

[Problem that the invention seeks to solve]

In FIG. 1, while the ion beam is being extracted from the ion source and implantation is being performed, the beam extraction may become impossible due to abnormal discharge of the ion source. The causes of this abnormal discharge in the ion source include dirt inside the ion source due to ionization, discharge due to charge-up in high voltage parts (inside and outside of the ion source), and the phenomenon is extremely severe. In the case of continuous discharge, in the case of sporadic discharge, and in between, depending on the degree of contamination of the ion source, differences depending on the ion species, and the magnitude of the accelerating voltage.

It takes on various aspects. These abnormal discharges can cause minor malfunctions in the control system, and major accidents can include deterioration of parts within the accelerator power supply.

Damage or damage to structural components within the ion source. In addition, the present invention has problems such as the uniformity of the implanted wafer being impaired due to instability of the ion beam.
It is not a solution to the inherent abnormal discharge of the ion source, but rather an automation to reduce as much as possible the downtime of the equipment caused by the discharge.

As mentioned above, abnormal discharge in the ion source varies depending on the accelerating voltage, ion species, size of the ion beam, elapsed time, etc., so it is difficult to keep the cleaning period constant, and generally, based on experience, Currently, a certain engineer determines the cleaning cycle based on statistical judgment. Therefore, every time an overcurrent error occurs (20 in Figure 1), adjust the magnetron power and coil current so that the plasma in the ion source becomes stable, apply the accelerating voltage again, extract the beam, and restart the implantation. It was necessary to start it (manually) and perform additional driving.

[Means for solving problems]

In Fig. 1, the ion beam current returns to the accelerating power source through three paths.For example, in the case of As ions, if the current returning to the accelerating power source is 30 mA, the ion beam current is mass separated and returned to the wafer in the implantation chamber. The arriving ion beam is approximately 1
/3 of 10 mA, and the remaining 20 mA collides with the vacuum vessel (earth potential) while the ion beam passes and is absorbed. By detecting the current returning to this accelerating power supply, and when it exceeds a certain level, it is determined as an overcurrent error, the power is cut off, and a signal is sent to the CPU control unit to interrupt the driving. Minimizing damage to the ion source is a conventional practice. However, since the error must be cleared manually in order to extract the ion beam again, operability was poor. Therefore, we adopted an automatic reset function for automation.

The next measure adopted is to control the output power of the magnetron power supply. That is, the magnetron power initially used for implantation is automatically switched to a lower setting value that does not cause the plasma to disappear, the plasma state is maintained, the ion source is stabilized, and then the ion source is stabilized for a certain period of time. rear,
The initial set value is restored and the accelerating voltage is applied again to obtain the ion beam before the error occurred.

In the embodiment of the present invention, the magnetron power was controlled as described above, but the same function can be obtained by controlling the magnetic field current in the same way, but in experiments, better results were obtained by controlling the magnetron power.

If a discharge error occurs many times even after automatic recovery, the cleaning cycle of the ion source is incorrect or some abnormality has occurred.In that case, stop plasma ignition and restart the ion source. Inspection, maintenance and cleaning work is required.

In order to determine this, a limit is placed on the number of errors that occur within a certain period of time.

[Effect]

In ion implantation equipment that uses a microwave ion source, if implantation is interrupted due to abnormal discharge of the ion source, by controlling the output power of the magnetron power supply, the plasma state can be maintained while the ion source is stabilized. , it is configured to automatically return to the state before the interruption of driving and perform re-driving.

A predetermined implantation can be completed without operating the ion implantation device when implantation is interrupted. Therefore, unmanned operation and improved operating rates are possible.

〔Example〕

Regarding the embodiment of the present invention, first, the hardware part is shown in Fig. 2.
This will be explained with reference to FIG.

FIG. 2 mainly shows a schematic diagram of the accelerating power source 8 shown in FIG. 1 and the exchange of signals with the computer control section 19. Therefore, the signal lines 2° to 23 are the same as in FIG. First, the internal configuration of the acceleration power source 8 will be briefly explained.

In the figure, AC input passes through an electromagnetic circuit breaker 1 and enters an electromagnetic switch 2. This output is turned ON by an external control signal.
10FF will be given. The output is once A by rectifier 3.
C into DC and input the DC to the inverter 4. The transistor in the inverter 4 is pulse width modulated by the modulator 5 and inputs a rectangular wave of 0N10FF to the transformer 6 . The transformer 6 is a high voltage isolation transformer, and the pulse boosted to a high voltage is returned to direct current by the rectifier 7. This is a high voltage (for example, 120 KV) and is output as is. Negative feedback is applied to stabilize this output. First, the output voltage Eo is divided by the resistors Rz and Rz, and the divided voltage (10 of Eo) is
1/10,000) is the reference value (=output setting value) with error amplifier 8.
A closed loop is constructed by inputting the signal to the modulator 5. The reference value is obtained by obtaining the output setting signal 22 (frequency signal) from the CPU control section 19 as an analog voltage by the V/F converter 9. On the other hand, overcurrent detection is performed by resistor R8, and its output is compared with the overcurrent reference value (0, C, LEVEL) by comparator 10. If overcurrent occurs, the primary stage The transistor Q1 excites the relay RL2 and outputs the error signal 20 to the CPU control unit 19, and at the same time
s is excited, and the electromagnetic switch 2 is activated by the contact signal γQ8.
The high voltage output is cut off by de-energizing the coil and cutting off the AC output to the rectifier 3. Relay Rt, x is γQ
Since it is self-held by Qz, it is necessary to release it in order to apply a high voltage again. Conventionally, there is a reset switch Sl in the power supply, which is used to set Qz to 0.
The excitation of FFL relay RL is released and its contact γQ4 is opened to release the self-holding of relay RL s. On the other hand, the coil of the electromagnetic switch 2 is controlled by the 0N10FF signal 21 as well as the transistor Q8 and the contact γ21 of the relay RL1. In the present invention, a reset signal 23 from the CPU control unit 19 is added as a means for automatic recovery. That's what I did. By setting this signal to ground potential, the self-holding state of relay Rba can be released.

FIG. 3 is a diagram showing the relationship between the magnetron power supply 6 and the computer control section 19 in FIG. 1, and is an embodiment in which the magnetron power is switched in two stages. In FIG. 3, the internal structure of the magnetron power supply 6 will first be briefly described. The AC input voltage passes through the electromagnetic circuit breaker 1 and is transferred to the transformer 2.
is input to the electromagnetic switch 5. The output of the transformer 2 is converted into DC by a rectifier 3 and becomes a filament power source for a remagnetron 4. On the other hand, the electromagnetic switch 5 is externally controlled 0N10FF (this ON10FF signal is obtained from the contact signal γQ1 of the transistor Ql and relay RL 1, which are controlled by the control signal 25 from the CPU control unit 19), and The alternating current is inputted to the rectifier 6, and the alternating current becomes direct current and is applied to the inverter 7 (without transistors). This transistor in the inverter is turned ON10FF by the pulse of the modulator 8, and causes a pulse current to flow into the primary side of the transformer 9. The secondary of transformer 9 is boosted (approximately -3.6V) and rectifier 1
At 0, it is returned to direct current again. Its output is connected to one of the filaments of the magnetron, oscillates at a high frequency (2.45 GHz) within the magnetron, and returns from the cathode to the rectifier 10 via a current sensing resistor Rz. The detected voltage of the resistor Rz is compared with the output setting signal by the error amplifier 11 and is negatively fed back to the modulator 8. The output setting signal is sent to the CPU control unit 1.
The set value Vrez in 9 is converted into a frequency by V/F converter 15, which is
2, it becomes an analog voltage and is input to the error amplifier 11.

In the CPU control unit 19, the setting values Vrezz and Vreffi2 for setting the magnetron power can be switched by a switching signal 16 of the switch 13.

The amplifier 14 operates as a switch and V/F buffer amplifier.

An embodiment of the automatic return method will be described with reference to FIGS. 4 and 5. FIG. 4 is a timing chart of automatic return processing, and FIG. 5 is its flowchart.

In Figure 4, overcurrent occurs due to discharge, and at the same time the output of the acceleration power source is cut off, the overcurrent error signal is transmitted to CP.
Sent to the U control unit. (20 in Figure 2) The CPU control section first performs a remote reset of the acceleration power supply (23 in Figure 2).
), then set the magnetron power output setting to a lower value (
Vretz) and outputs (24 in Figure 3) After a certain delay, the ON signal (
21) in FIG. 2 is sent from the CPU control, an accelerating voltage is applied, and the ion beam is extracted again. The beam current is controlled by the CPU at 17 in FIG. 1, but the implantation operation starts after the above-mentioned discharge recovery process is completed and the ion beam reaches the disk wafer again. The driving operation is temporarily interrupted due to an overcurrent error, and the scan drive is also stopped.
Hold that position. After the stable beam is drawn out by the automatic return process, the scanning drive is restarted and the driving operation is automatically continued.

A schematic flowchart of the automatic return process shown in FIG. 5 will be described below. When the first automatic return process is completed, the number of automatic returns is set to one and a timer is started. Thereafter, each time the automatic return process is performed, the number of automatic returns is counted up, and when the time set in the timer is reached, the number of automatic returns is set to O. Additionally, if the number of automatic resets preset in the counter is exceeded while the timer is running, an error message will be displayed without performing automatic reset processing.
In this case, the driving is interrupted. With this function, if overcurrent errors occur frequently, it is possible to notify the operator that it is necessary to reset various conditions such as magnetron power, coil current, gas flow rate, etc., or to clean the ion source.

In the above, it goes without saying that the number of times of automatic return set in the counter can be arbitrarily set by the CPU controller, and that the setting time of the timer can also be arbitrarily set by the CPU controller.

〔Effect of the invention〕

The present invention, as described above, eliminates the need for each operator to perform a restart operation each time implantation is interrupted due to abnormal discharge of the ion source. Therefore, there is an effect of realizing automation and realizing unmanned operation. Since the ion implantation device is used in a manufacturing process that thoroughly reduces waste, unmanned operation has the effect of eliminating the waste generated by humans and also has the effect of reducing labor costs.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the control relationship of the ion implantation apparatus of the present invention.6 Fig. 2 shows an embodiment of the present invention. FIG. FIG. 3 shows an embodiment of the present invention, and is a diagram illustrating the internal configuration of the magnetron power source and the transmission and reception of signals with the CPU control section. Figure 4 shows
This shows an embodiment of the present invention, and is a timing chart showing automatic return of the driving operation. FIG. 5 shows an embodiment of the present invention, and is a drawing showing the operation program flowchart of FIG. 4.

Claims (1)

[Claims] 1. In an ion implantation device using a microwave ion source, the generation of the ion beam is interrupted due to an abnormal discharge of the ion source during implantation of the ion beam into a sample, and the implantation is interrupted. In this case, the method includes means for reducing the plasma density, means for increasing the plasma density again after a certain period of time, and means for extracting the ion beam again and performing additional implantation into the sample, and automatically performs re-implantation. Ion implantation device with functions. 2. The ion implantation apparatus according to claim 1, which has means for counting the number of abnormal discharges within a certain period of time, and has a function of stopping plasma generation when the counted value is larger than a reference value. An ion implantation device with