JPH0554842A - Method for detecting deviation of beam track - Google Patents

Abstract

PURPOSE:To accurately determine whether or not the track of an ion beam deviates by measuring the difference in the beam current of the ion beam the track of which is fluctuated within the extent to which the beam passes through a slit hole and which has passed through the slit hole. CONSTITUTION:Ions from an ion source 1 are allowed to pass through a takeout electrode 2 and incident on a mass spectrograph 4. Because ripple voltages are superimposed on the electrode 2, the ions progress on a track corresponding to a mass, with fluctuations in the track which correspond to the amount of fluctuation of moving speed caused by the ripple voltages. The ion beam 3 progressing on a specific track and in the direction of a Farady 7 via an ion analysis slit 5 generates a beam current at the Faraday 7 and the beam current is detected by an ammeter 8. The track of the ion beam is thus fluctuated within the extent to which the beam passes through the slit and the difference in the beam current of the ions passing through the slit is measured to accurately determine whether or not the track deviates.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beam orbit deviation detection method for detecting ion beam orbit deviations, and more specifically, to determine the presence or absence of orbit deviations by detecting ripples superimposed on a beam current. The present invention relates to a method for detecting beam trajectory deviation.

[0002]

2. Description of the Related Art Since an ion implantation apparatus can implant required impurity ions into an object to be ion-irradiated at an arbitrary amount and at an arbitrary depth with good controllability, for example, implantation of impurities into a semiconductor or research and development of new materials Is often used for.

The ion beam is usually extracted from the ion source by the extraction electrode at a predetermined speed. However, the ion beam from the ion source is a mixture of a plurality of ion species. In order to implant with good controllability, it is necessary to separate the ion beam into specific ions. Therefore, each ion extracted from the ion source has its orbit separated into mass units of each ion by a mass analyzer having a predetermined magnetic flux density, and only ions flowing in a specific orbit by an analysis slit are subjected to ion irradiation. By passing in the direction, specific ions are irradiated to the ion irradiation target.

By the way, the trajectory of the ion beam in the mass analyzer is determined by the factors consisting of the magnetic flux density of the mass analyzer and the velocity and mass of the ions. Even if one factor changes, the trajectory shifts. Will occur.
When an orbital deviation occurs, the analysis slit allows only ions having a specific orbit to pass therethrough, so that the irradiation amount of ions to the ion irradiation target is changed, resulting in ion implantation. Will reduce the controllability of.

Therefore, conventionally, the above-mentioned orbital deviation is judged from the change in the beam current because the beam current detected by the Faraday arranged near the ion irradiation object corresponds to the ion irradiation amount. This is confirmed by the beam trajectory deviation detection method.

[0006]

However, the ion irradiation dose that determines the beam current is determined not only by the deviation of the trajectory of the ion beam but also by other factors such as the extraction amount of ions from the ion source. Therefore, in the above-described conventional beam trajectory deviation detection method that determines that all changes in the beam current are trajectory deviations, it is inaccurate to determine whether or not the trajectory deviation occurs.

Therefore, it is an object of the present invention to provide a beam orbit deviation detecting method which can accurately determine the presence or absence of an orbit deviation by using a phenomenon caused only by the orbit deviation for determination.

[0008]

In order to solve the above-mentioned problems, the beam trajectory deviation detection method of the present invention provides an ion implantation apparatus in which the total amount of the ion beam traveling on a specific trajectory passes through the slit hole of the analysis slit. Has been adopted. This beam trajectory deviation detection method is characterized by varying the trajectory of the ion beam within the range of passing through the slit hole and determining the presence or absence of the trajectory deviation from the difference in the beam current of the ion beam passing through the slit hole. I am trying.

[0009]

According to the above structure, even if the trajectory of the ion beam fluctuates, the entire amount of the ion beam passes through the slit hole of the analysis slit. Therefore, the fluctuation of the beam current detected by the fluctuation of the trajectory is The only cause is that a part of the ion beam is blocked by the analysis slit due to the trajectory shift. In this beam orbital deviation detection method, since there is a one-to-one correspondence between the fluctuation of the beam current and the orbital deviation, it is possible to accurately determine the presence or absence of the orbital deviation from the difference between the beam currents.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following will describe one embodiment of the present invention with reference to FIGS.

The beam trajectory deviation detecting method according to the present embodiment is adopted in an ion implanter as shown in FIG. This ion implantation apparatus has an ion source 1 for generating ions such as boron ions (B ⁺ ) and arsenic ions (As ⁺ ), and the ion source 1 has an opening for releasing the generated ions to the outside. 1a is formed.

An extraction electrode 2 to which a negative extraction voltage is applied is disposed in front of the opening 1a of the ion source 1, and the extraction electrode 2 is positive in the ion source 1 due to the negative voltage. The charged ions are extracted from the opening 1a to the outside. Further, a ripple voltage of, for example, about 20 kHz is superimposed on the extraction voltage applied to the extraction electrode 2, and the ions extracted due to the potential difference from the extraction electrode 2 have a speed with a fluctuation of the ripple voltage. It is designed to move.

A mass spectrometer 4 having a predetermined magnetic flux density therein is arranged in the traveling direction of the ions extracted by the extraction electrode 2. This mass analyzer 4 is designed to bend the traveling direction of the ions into orbits corresponding to the mass, and the ions in each orbit are generated in the orbits corresponding to the fluctuations in the moving speed caused by the ripple voltage of the extraction voltage. It is designed to proceed with fluctuations.

Ions whose traveling direction is bent by the mass analyzer 4 travel along the trajectories corresponding to the mass as the ion beam 3, and the analysis slit 5 is arranged in the traveling direction of the ion beam 3. It is set up. As shown in FIG. 1, the analysis slit 5 has slit holes 5a.
Is formed, and the slit hole 5a is arranged so as to coincide with the passage path of the ion beam 3 traveling on a specific orbit. The slit hole 5a needs to be formed in such a size that the entire amount of the ion beam 3 accompanied by the fluctuation of the orbit of the ripple voltage passes. Alternatively, the ripple voltage needs to be set within a range in which the entire amount of the ion beam 3 passes through the slit hole 5a of the analysis slit 5.

From the above-mentioned analysis slit 5 to the ion beam 3
An acceleration tube 6 for accelerating the ion beam 3 and an electrostatic lens (not shown) are arranged in the traveling direction of the ion beam 3. Faraday 7 is installed. An ammeter 8 is connected to the Faraday 7, and the ammeter 8 detects the beam current generated in the Faraday 7 by the ion beam 3 and can measure the current value.

As shown in FIG. 4, the ammeter 8 has the following structure.
Beam orbit deviation determining means 9 is connected. The beam orbit shift discriminating means 9 includes an A / D converter 10 and a memory 1.
1 and a CPU (Central Processing Unit) 12, the A / D converter 10 converts the beam current into a digital value and outputs it to the data bus of the memory 11.

The memory 11 is adapted to store the beam current value inputted from the A / D converter 10, and the storing procedure is such that the memory address is sequentially incremented from address 0 at a predetermined time such as 1 μS. The beam current value currently input is stored in the memory area corresponding to each memory address as beam current data. This memory 11 has a data bus and an address bus of CP.
Connected to U12, the CPU 12 accesses the memory address of the memory 11 via the address bus and executes the above-mentioned storage procedure.

The CPU 12 is also adapted to acquire the beam current data of each memory address stored in the memory 11 via the data bus. And CPU
Reference numeral 12 calculates the difference between the beam current data of the preceding and following memory addresses, and determines whether the difference at the stage when the beam current data rises to the maximum value is other than 0 to determine whether or not there is a trajectory deviation. It is supposed to do.

With the above-mentioned structure, the operation of the ion implantation apparatus and the method for detecting beam trajectory deviation will be described.

When the ion source 1 creates positively charged ions, the ions are attracted toward the extraction electrode 2 to which a negative voltage is applied, and extracted from the opening 1a toward the mass analyzer 4. At this time, a ripple voltage of, for example, about 20 kHz is superimposed on the extraction electrode 2, and the ions extracted due to the potential difference from the extraction electrode 2 are stored in the mass spectrometer 4 at a speed having a fluctuation of the ripple voltage. Will be moved.

The ions moving in the mass analyzer 4 travel on the orbits corresponding to the masses, and the ions on the orbits of the orbits corresponding to the fluctuations in the moving speed caused by the ripple voltage of the extraction voltage. It will progress with fluctuations. Then, among the ions that have passed through the mass spectrometer 4, only those ions that have traveled on a specific orbit will travel as the ion beam 3 in the Faraday 7 direction via the analysis slit 5.

Ion beam 3 reaching Faraday 7
Causes a beam current, which is detected by the ammeter 8 and is input to the A / D converter 10 of the beam orbit shift determining means 9 as shown in FIG. become. The beam current input to the A / D converter 10 is converted to a digital beam current value and then output to the data bus of the memory 11.
Then, the beam current value is stored in the memory 11 as beam current data in the memory area corresponding to each memory address by sequentially incrementing the memory address from address 0 at a predetermined time such as 1 μS.

When the storage of the beam current data of the memory 11 is completed, the difference between the beam current data of the preceding and following memory addresses is calculated, and the CPU 12
Whether or not there is a trajectory deviation is determined by determining whether or not the difference at the stage when the beam current data rises and reaches the maximum value is other than zero.

That is, first, as shown in FIG. 1, when the ion beam 3 is passing through the slit hole 5a of the analysis slit 5, even if the trajectory of the ion beam 3 is changed by the ripple voltage. However, the total amount of the ion beam 3 reaches the Faraday 7. Therefore, as shown in FIG. 5, all the differences at the stage when the beam current data rises and reaches the maximum value show 0 value.
In No. 2, it is determined that there is no trajectory deviation.

Next, as shown in FIG.
When the ion beam 3 is in contact with and passes through the analysis slit 5, the ion beam 3 excluding the portion blocked by the analysis slit 5 reaches the Faraday 7. On this occasion,
Since the trajectory of the ion beam 3 varies by the ripple voltage, the area blocked by the analysis slit 5 varies between the range indicated by the solid line and the range indicated by the dotted line.

Therefore, the ion beam 3 to the Faraday 7
The irradiation dose of the
1 stores the beam current data corresponding to this irradiation amount. As a result, the difference at the stage when the beam current data rises and reaches the maximum value indicates a value other than 0, as shown in FIG. 6, so the CPU 12 determines that there is a trajectory deviation.

As described above, the beam trajectory deviation detection method of the present embodiment determines whether or not there is a trajectory deviation based on the fluctuation of the trajectory of the ripple voltage superimposed on the extraction voltage of the extraction electrode 2. However, the fluctuation of the beam current detected by the fluctuation of the trajectory is caused only by a part of the ion beam 3 being blocked by the analysis slit 5 due to the deviation of the trajectory. Therefore, in the beam trajectory deviation detection method of the present embodiment, since the fluctuation of the beam current and the trajectory deviation are in a one-to-one correspondence, it is possible to accurately determine the presence or absence of the trajectory deviation.

[0028]

As described above, the beam trajectory deviation detection method of the present invention is adopted in an ion implantation apparatus in which the total amount of an ion beam propagating in a specific trajectory passes through the slit hole of the analysis slit. The configuration is such that the trajectory of the ion beam is changed within the range of passing through the slit hole, and the presence or absence of the trajectory deviation is determined from the difference in beam current of the ion beam passing through the slit hole.

As a result, even if the orbit fluctuates, the entire amount of the ion beam passes through the slit hole of the analysis slit, so that the fluctuation of the beam current detected by the fluctuation of the orbit is caused by the deviation of the orbit. This is because only a part of the above is blocked by the analysis slit, and as a result, it is possible to accurately determine the presence or absence of a trajectory deviation from the difference in beam current.

[Brief description of drawings]

FIG. 1 illustrates the present invention and is an explanatory diagram showing a state in which a total amount of an ion beam passes through a slit hole of an analysis slit.

FIG. 2 is an explanatory diagram showing a state in which a part of an ion beam is blocked by an analysis slit.

FIG. 3 is a schematic configuration diagram of an ion implantation device.

FIG. 4 is a block diagram of a beam trajectory deviation determination means.

FIG. 5 is an explanatory diagram showing a difference in beam current data.

FIG. 6 is an explanatory diagram showing a difference in beam current data.

[Explanation of symbols]

 1 Ion Source 2 Extraction Electrode 3 Ion Beam 4 Mass Spectrometer 5 Analysis Slit 5a Slit Hole 6 Accelerator Tube 7 Faraday 8 Ammeter 9 Beam Orbit Shift Judgment Means 10 A / D Converter 11 Memory 12 CPU

Claims (1)

[Claims] 1. A beam trajectory deviation detection method for an ion implanter in which the entire amount of an ion beam traveling on a specific trajectory passes through a slit hole of an analysis slit, and the trajectory of the ion beam is varied within a range of passing through the slit hole. A method of detecting a beam orbital deviation, which comprises determining the presence or absence of an orbital deviation from the difference between the beam currents of the ion beams passing through the slit holes.