JPH04282547A - Ion implanting device - Google Patents

Abstract

PURPOSE:To monitor an amount of energy contamination problematical at the time of implanting a polyvalent ion by an in-process. CONSTITUTION:This device has a scanning electrode 12 for scanning an ion beam 4, scanning power supply 16 for supplying scanning voltage to this electrode 12, beam current measuring device 22 for measuring a beam current I by receiving the scanned ion beam 14 and an arithmetic control unit 26. The arithmetic control unit 26 has a function of obtaining an energy spectrum of the ion beam 4 based on the scanning voltage V given from the scanning power supply 16 and the beam current I measured by the beam current measuring device 22, function of detecting a peak of this spectrum to obtain respective heights, function of fixing a peak of an objective ion and a function of comparing the height of the peak of an ion except the objective ion with a reference value to output an alarm signal S in the case of providing the ion exceeding this reference value.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an ion implanter that implants ions into a target by irradiating the target with an ion beam. The present invention relates to means for monitoring in-process (i.e., during actual injection processing).

0002

2. Description of the Related Art FIG. 4 is a schematic plan view showing an example of a conventional ion implantation apparatus.

The ion beam 4 extracted from the ion source 2 is subjected to mass analysis by a mass spectrometer 6, accelerated by an acceleration tube 8, and vertically scanned by a set of scanning electrodes 10 for vertical scanning. The ions are scanned in the horizontal direction by a set of scanning electrodes 12 for horizontal scanning and are incident on a target (for example, a wafer) 14, so that ion implantation is performed over the entire surface of the target. The center of the ion beam 4 is bent (offset) by a predetermined angle in the horizontal direction by the scanning electrode 12 in this example so that the neutral particles contained therein do not enter the target 14 .

0004

[Problems to be Solved by the Invention] However, in the above ion implantation apparatus, when multiply charged ions (mainly doubly charged ions) are implanted into the target 14, energy contamination (that is, mixing of ions with different energies) occurs. becomes a problem.

To explain this in detail, when extracting ions of element A (for example, boron, arsenic, etc.) from the ion source 2, as shown in FIG. At the same time, a monovalent molecular ion A2+ with an energy of 25 KeV is extracted. The latter ions dissociate at a certain rate before entering the mass spectrometer 6 and separate into two singly charged ions A+ each having an energy of 12.5 KeV.

[0006] The energy of the ion is E, and its charge number is q.
Then, if the masses are the same, the mass spectrometer 6 of the ion
Since the radius of curvature at is proportional to the square root of (E/q2), the above 50KeV doubly charged ion A2+ and 12.5K
Since the eV singly charged ions A+ curve in the same orbit, they cannot be separated by the mass spectrometer 6.

[0007] The above-mentioned doubly charged ions A2 emitted from the mass spectrometer 6
A part of + becomes monovalent ions A+ due to charge transfer, and if the accelerating voltage in the accelerating tube 8 is set to 175 KV, for example, the accelerating tube 8 will release the target doubly charged ions A2+ of 400 KeV (this is the energy Target is 200KeV
(corresponding to the monovalent ion A+), 225KeV
The monovalent ion A+ of 187.5 KeV and the monovalent ion A+ of 187.5 KeV come out as different energy ions.

As shown in FIG. 6, an ion beam 4 containing ions with different energies as described above is passed through a scanning electrode 12.
to target ions (for example, the above 400KeV
A2+) is incident on the entire surface of the target 14, ions with higher energy (for example, the above 225 KeV A2+) are deflected only a little, and conversely, lower energy ions (for example, the above 187.5 KeV A2+) are deflected only a little.
+) are deflected to a large extent, energy contamination occurs where these overlap the target ion scanning region.

As a result, in the target 14, as shown in FIG. 7, for example, due to the implantation amount distribution due to different energy ions (low energy ions in the case of this figure), the combined implantation amount distribution differs depending on the target ions. This results in a deviation from the implantation amount distribution, resulting in defective implantation.

SUMMARY OF THE INVENTION Accordingly, the main object of the present invention is to provide an ion implantation apparatus that allows in-process monitoring of the amount of energy contamination, which is a problem during multivalent ion implantation.

[0011]

[Means for Solving the Problems] In order to achieve the above object, an ion implantation apparatus of the present invention includes a scanning electrode for scanning an ion beam, a scanning power source for supplying a scanning voltage to the scanning electrode, and a scanning electrode for scanning an ion beam. A beam current measuring device receives the scanned ion beam and measures the beam current, and an energy spectrum of the ion beam is determined based on the beam current measured by the beam current measuring device and the scanning voltage given from the scanning power supply. function, a function to detect the peaks of this energy spectrum and find the height of each peak, a function to identify the peak of the target ion, and a function to compare the height of the peak of ions other than the target ion with a reference value. The present invention is characterized by comprising an arithmetic and control unit having a function of outputting an alarm signal when there is a problem exceeding the above range.

0012

[Operation] When an ion beam is scanned by a scanning electrode, the ions included in the ion beam bend in different ways depending on their energy, so the scanning voltage is set to one axis (
The energy spectrum of the ion beam can be determined by setting the beam current measured by a beam current measuring device to the other axis (for example, the vertical axis). The arithmetic and control unit obtains this energy spectrum, and outputs an alarm signal if there is any peak height (corresponding to the amount of the ions) other than the target ion that exceeds a reference value. Thereby, the amount of energy contamination can be monitored in-process, and as a result, it is possible to prevent defective injection from occurring.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing the main parts of an ion implantation apparatus according to an embodiment of the present invention. The same reference numerals are given to the same or corresponding parts as in the conventional example shown in FIG. 4, and the differences from the conventional example will be mainly explained below.

In this embodiment, the aforementioned scanning electrode 12 for horizontal scanning is used as the scanning electrode for measuring energy contamination. Note that when measuring energy contamination, there is no need to use the scanning electrode 10 for vertical scanning described above.
It's better to let it rest.

In this embodiment, a slit plate 18 having a slit-like or small-hole-like opening 18a is provided on the upstream side of the scanning electrode 12, thereby forming the ion beam 4 into a narrow shape to increase resolution. I have to. This slit plate 18 is driven back and forth by a drive device 20, and is placed in the path of the ion beam 4 as shown in the figure when measuring energy contamination under the control of an arithmetic and control device 26, which will be described later. time is removed from the path of the ion beam 4. However, this movable slit plate 18 is not essential, and even without it, it is possible to measure the energy spectrum, although the resolution is poor.

A scanning voltage is supplied to the scanning electrode 12 from a scanning power source 16 having a scanning voltage generator 16a that generates a triangular scanning voltage V and a high voltage amplifier 16b that amplifies it to a high voltage. The beam 4 is scanned horizontally in this example.

Further, on the upstream side where the target 14 described above is placed, there is a beam current measuring device (for example, a Faraday cup) 22 having a small diameter and which can be inserted into and removed from the path of the ion beam 4 by a mechanism not shown in this embodiment.
The ion beam 4 scanned by the scanning electrode 12 enters the beam current measuring device 22, and its beam current I is measured. In this embodiment, the measured beam current I is appropriately converted by the converter 24 and inputted to the Y-axis input terminal 26b of the arithmetic and control unit 26, and the aforementioned scanning voltage is generated at the X-axis input terminal 26a. The scanning voltage V output from the device 16a is input.

The arithmetic and control unit 26 has the following functions (1) to (4).

■ The scanning voltage V when the ion beam 4 is scanned by the scanning electrode 12 is taken as the X axis (horizontal axis), and the beam current I measured by the beam current measuring device 22 at that time is
The energy spectrum of the ion beam 4 is determined by setting the Y axis (vertical axis) to . As a result, an energy spectrum as shown in FIG. 2, for example, is obtained. This figure is an example of the ion beam 4 containing ions of three types of energies as previously explained in FIG. 5. Such an energy spectrum is obtained because when the ion beam 4 is scanned by the scanning electrode 12, the ions included in the ion beam 4 bend in different ways depending on their energy. This is because ions with high energy enter the beam current measuring device 22 when the scanning voltage V is large.

(2) Detect the peaks of the energy spectrum obtained above and determine the height of each peak. In the case of the example shown in FIG. 2, peaks P1 to P3 are detected and their respective heights I1 to I3 are determined. This height indicates the amount of each ion.

[0021] From the number of charges and energy of the target ion, it is possible to determine at what scanning voltage V the ion beam 4 is incident on the beam current measuring device 22, so that the target ion can be identified. In the case of the example shown in FIG. 2, peak P2 is the target ion and is identified.

[0022] The height of the peak of ions other than the target ion is compared with a preset reference value, and if any of the peak heights exceeds the reference value, an alarm signal S is output. In the case of the example shown in FIG. 2, if any of I1 and I3 exceeds the reference value, an alarm signal S is output.

[0023] Therefore, according to the above configuration, in-process processing can be performed in-process without having to perform extremely troublesome steps such as injecting a sample into the target 4 and measuring the injection amount distribution in the depth direction. In other words, it is possible to easily monitor the amount of energy contamination during the actual implantation process (more specifically, just before implantation), and as a result, it is possible to prevent defective implantation from occurring. . In this case, for example, ion implantation may be stopped artificially based on the above-mentioned alarm signal S, or this alarm signal S may be sent to a higher-level control device to automatically apply an interlock. .

The present invention is applicable not only to an ion implantation apparatus that scans the ion beam 4 in two orthogonal directions (XY scan) as in the above example, but also to an ion implantation apparatus that electrically scans the ion beam in one direction. Of course, the present invention can also be applied to a so-called hybrid scan type ion implantation apparatus that mechanically scans the target in a direction perpendicular to the target.

For example, FIG. 3 shows an example of a hybrid scan type ion implantation apparatus, in which the ion beam 4 is horizontally scanned in parallel (parallel scan) by two sets of front and rear scan electrodes 28 and 32, and the target is 14 is mechanically scanned in the vertical direction by a drive device 36, and ion implantation is performed over the entire surface of the target 14 by the cooperation of both scans. A deflection electrode 30 that bends (offsets) the ion beam 4 in the vertical direction by a certain angle is provided between the scanning electrodes 28 and 32. For example, this deflection electrode 30 can be used instead of the scanning electrode 12 in FIG. If the configuration is otherwise the same as in FIG. 1, the amount of energy contamination can be easily monitored in-process in the same manner as above.

However, if such a deflection electrode 30 is not provided, a scanning electrode for measuring energy contamination may be provided. Further, unlike the example shown in FIG. 3, a hybrid scan type ion implantation apparatus that does not convert the ion beam 4 into parallel beams may be used.

[0027]

[Effects of the Invention] As described above, according to the present invention, the amount of energy contamination, which is a problem during multivalent ion implantation, can be easily monitored in-process, and as a result, defective implantation can be prevented from occurring. can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing main parts of an ion implantation apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of the energy spectrum of an ion beam.

FIG. 3 is a diagram partially showing an example of a hybrid scan type ion implantation device.

FIG. 4 is a schematic plan view showing an example of a conventional ion implantation device.

FIG. 5 is a schematic diagram showing the causes of generation of different energy ions.

FIG. 6 is a diagram illustrating a situation in which energy contamination occurs in a target.

FIG. 7 is a diagram showing an example of the implantation amount distribution in the depth direction in the target when energy contamination occurs.

[Explanation of symbols]

4 Ion beam 12 Scanning electrode 14 Target 16 Scanning power supply 22 Beam current measuring device 26 Arithmetic control unit

Claims (1)

[Claims] 1. An apparatus for implanting ions into a target by irradiating the target with an ion beam, the apparatus comprising: a scanning electrode for scanning the ion beam; a scanning power source for supplying a scanning voltage to the scanning electrode; and the scanning electrode. a beam current measuring device that receives the ion beam scanned by the device and measures its beam current; and an energy spectrum of the ion beam is determined based on the beam current measured by the beam current measuring device and the scanning voltage given from the scanning power source. A function to detect the peaks of this energy spectrum and determine the height of each peak, a function to identify the peak of the target ion, and a function to compare the heights of the peaks of ions other than the target ion with the reference value. 1. An ion implantation apparatus comprising: an arithmetic and control device having a function of outputting an alarm signal when there is an amount exceeding the above value.