JPS61227357A - Ion implantation equipment - Google Patents

Abstract

PURPOSE:To prevent a flow of the secondary ions and to measure the primary ions accurately, by using a magnet as a suppressor and pushing back the secondary ions from a semiconductor wafer to the Faraday cup by its magnetic field. CONSTITUTION:The primary ions consisting of positive ions, generated from an ion source, and, accelerated and selected through an accelerating system and a mass analyzing system, are led into a Faraday cup 2, and implanted into a semiconductor wafer 4 installed on a platen 3. The amount of the implanted primary ions are measured by a current integration device 7 indirectly. At the entrance of the Faraday cup 2 is furnished a mask 10 to control the incident angle of the primary ions at a specific value, and improves the measuring accuracy of the counter 7. Moreover, a suppressor 11 is furnished to form a magnetic field to push back the secondary ions to the semiconductor wafer 4 by applying a current from a power source 10 to the magnet 11, the flow of the secondary ions being prevented by the electric field.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to an ion implantation apparatus for implanting ions into a semiconductor wafer to add impurity atoms to the wafer.

(Technical Background of the Invention and Problems thereof) In an LSI manufacturing process, an ion implantation device is used to add impurity atoms to a semiconductor wafer made of a silicon substrate.

FIG. 2 is a sectional view of a conventional example of this ion implantation apparatus.

Primary ions 1 ionized by high-frequency discharge in an ion source (not shown) are given energy by an acceleration system, and only desired positive ions are selected by a mass spectrometry system and introduced into a Faraday cup 2 . A platen 3 is provided at the end of the Faraday cup 2 so as to be perpendicular to the direction in which the primary ions are introduced. A semiconductor chip 4 is attached to the front surface of the platen 3, and the primary ions 1 are implanted into the wafer 4. It looks like this. Further, in the front part of the semiconductor wafer 4, a guide tube 5 is inserted into the Faraday cup 2 through an insulating material 6 such as an insulator, and a current integrator (curre
nt Int8GrOter) 7 is provided.

This current integrator 7 receives the energy of negative ions implanted into the semiconductor wafer 4, converts the secondary ions generated from within the wafer into current, and measures the amount of implanted primary ions. It is measured indirectly. Therefore, in order to perform accurate measurements, it is necessary to prevent secondary ions from flowing out from within the Faraday cup 2, and a suppressor 8 supported by an insulating material 9 such as an insulator is provided in the artificial part of the Faraday cup 2. There is.

This suppressor 8 conventionally consists of an electrode to which a negative charge of about -500V is applied, and electrically interrupts the artificial part of the Faraday cup 2 to prevent the outflow of secondary ions.

However, in this conventional ion implanter,
Since a negative charge is applied to the suppressor 8, contaminants are likely to adhere to the insulating material 9, such as an insulator, that supports the suppressor 8, and due to this contamination, negative electrons are released from the ground, allowing the current integrator 7 to accurately measure primary ions. The problem was that it became impossible to do so.

(Objective of the Invention) The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an ion implantation apparatus that enables accurate measurement of the amount of negative ion implantation.

(Summary of the Invention) In order to achieve the above object, an ion implantation apparatus according to the present invention uses a magnet as a suppressor, and uses the magnetic field to push primary ions from a semiconductor wafer back into a Faraday cup.

(Embodiment of the Invention) FIG. 1 shows a sectional view of an embodiment of an ion implantation apparatus according to the present invention.

Primary ions 1 generated from ions m<not shown), accelerated through an acceleration system and a mass spectrometry system (not shown), and consisting of selected positive ions are introduced into the Faraday cup 2, and are introduced into the Faraday cup 2 at the end of the Faraday cup 2. The semiconductor wafer 4 is mounted on a platen 3 at the same time. The amount of primary ions implanted is indirectly measured by a current integrator 7.

In other words, the flow integral 17 measures the amount of primary ions by measuring the secondary ions generated from the semiconductor wafer 8 due to the implantation of primary ions. is used as an electrode, and the current value is measured.

Roughly, there is a mask 10 at the entrance of the Faraday cup 2.
is provided to limit the incident angle of the -order ions to a constant value and improve the measurement accuracy of the counter 7. In such an ion implantation apparatus, a suppressor 11 is provided at the entrance of the Faraday cup 2 in order to prevent secondary ions from flowing out of the Faraday cup 2 from the semiconductor wafer 4 during primary ion implantation.
is composed of a magnet that is in contact with the outer wall of the entrance portion of the Faraday cup 2. In this embodiment, the magnet 11 is an electromagnet, and a power supply 12 causes a current to flow through the magnet 11 to generate a magnetic field at the entrance of the Faraday cup 2. In this case, the magnet is arranged to generate a magnetic field that pushes the secondary ions back toward the semiconductor wafer 4 based on Fleming's left-hand rule, and this magnetic field can prevent the secondary ions from flowing out. It is possible. The appropriate magnetic field generated by the magnet b% is 500 Gauss or more. Since outflow of secondary ions can be prevented and there is no inflow of negative charges unlike in the conventional case, the amount of primary ions can be measured extremely accurately by the current integrator 7. Note that in the present invention, the magnet may be a permanent magnet instead of an electromagnet.

〔Effect of the invention〕

As described above, according to the present invention, since the suppressor is configured with a magnet that generates a magnetic field in the direction of pushing back secondary ions into the Faraday cup, it is possible to prevent the outflow of secondary ions and to ensure accurate measurement of -order ions. Become. In addition, since secondary ions are pushed back by a magnetic field and no electric field is used, attached equipment is not contaminated by ions and can be used for a long period of time in good condition.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the ion implantation apparatus of the present invention, and FIG. 2 is a sectional view of a conventional ion implantation apparatus. 1... -order ion, 2... Faraday cup, 3...
...Platen, 4...Semiconductor wafer, 5...Guide tube, 6...Guide, 7...Current integrator, 8...
Suppressor, 9... Insulating material, 10... Mask, 11
...Suppressor. Applicant's agent Kiyoshi Inomata Figure 1 Figure '$2 Figure

Claims (1)

[Scope of Claims] 1. A Faraday cup in which a semiconductor wafer is housed and into which primary ions generated from an ion source are introduced; and secondary ions generated from the semiconductor wafer into the Faraday cup by implantation of the primary ions. An ion implantation apparatus comprising: a measuring means for measuring the amount of primary ions implanted by measuring the amount of primary ions implanted; and a suppressor provided at an inlet of the Faraday cup to prevent secondary ions from flowing out of the Faraday cup. An ion implantation device characterized in that the suppressor is a magnet that generates a magnetic field in a direction that pushes secondary ions back into the Faraday cup. 2. The ion implantation apparatus according to claim 1, wherein the suppressor is an electromagnet. 3. The ion implantation apparatus according to claim 1, wherein the suppressor is a permanent magnet.