JPH11120954A - Ion implanting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and precisely measure the ion close without being influenced by the inflow of an electron current or a neutrally particled ion beam by measuring the number of scattered particles Rutherford scattered backward by a matter to be irradiated. SOLUTION: An ion beam 2 consisting of a high-speed particle group having a high energy of 500 keV or more is Rutherford scattered backward in the collision with a matter 4 to be irradiated. The Rutherford scattered ion particle is captured at a prescribed backward angle by a RBS detector 7 formed of, for example, a multichannel analyzer. A slit 13 limits the scattering three- dimensional angle of the scattered particle incident on the RBS detector 7. A wave height analyzer 8 is connected to the RBS detector 7, and the energy spectrum is measured thereby and inputted to a control means 9. On the basis of the particle number measured by the wave height analyzer 8, the ion dose is determined. Namely, the irradiation is stopped by use of a slit 10 when it reaches a prescribed ion dose by the control means 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion implantation apparatus, and more particularly to an ion implantation apparatus capable of accurately measuring an irradiation amount of an ion beam applied to a semiconductor wafer or the like.

[0002]

2. Description of the Related Art For example, in a technique for forming an impurity layer of B, As, P, etc. on a semiconductor wafer, the semiconductor wafer is irradiated with an ion beam formed by ionizing impurity particles and electrically accelerating the impurity particles. There is an ion implanter for implanting particles. In this ion implantation apparatus, when forming an impurity layer as described above, how many impurity particles are irradiated per unit area (dose amount) is important in determining physical properties of an object to be irradiated. Usually, a current measuring device called a Faraday cup is used for measuring the irradiation amount. An ion implantation apparatus having a Faraday cup in a measurement system is disclosed in, for example, Japanese Patent Application Laid-Open No. 63-128543. Here, FIG. 2 is a diagram showing a schematic configuration of the ion implantation apparatus described in the above-mentioned reference. As shown in FIG. 2, in the ion implantation apparatus described in the above-mentioned reference document, a flag Faraday 23 for measuring a beam current at the time of beam setup is installed in a beam line section 22 for introducing an ion beam into a semiconductor wafer 21. At the subsequent stage of the flag Faraday 23, a disk Faraday 24 for measuring an ion beam current at the time of ion implantation is provided.
In this ion implantation apparatus, a plurality of semiconductor wafers 21
Are provided on the rotating disk 25 in an annular shape, and the ion beam is incident on the disk Faraday 24 through a slit 26 provided on the rotating disk 25. Also,
An ammeter 27 is connected to the flag Faraday 23 and the disk Faraday 24, and the number of irradiated particles is determined by the amount of current of the inflowing ion beam.

When a non-conductive material such as a semiconductor wafer or an insulator is continuously irradiated with an ion beam, an object to be irradiated is charged, that is, charged up. In order to avoid the influence of the charge-up, in such an ion implantation apparatus, a means for emitting electrons called an electron shower 28 is provided near the rotating disk 25.
That is, the semiconductor wafer 21 charged by the ion beam 21
These charges are neutralized by the electron charges from the electron shower 28. However, when the electrons from the electron shower 28 enter the disk Faraday 24 or the like, the current amount of the ion beam changes, and it becomes difficult to accurately measure the ion irradiation amount. For this reason, in the above ion implantation apparatus, the electron shower 28 is provided in a region where the ion beam does not pass. Another example of an ion implantation apparatus using a Faraday cup is a technique described in Japanese Patent Application Laid-Open No. 61-16456. In the ion implantation apparatus according to this document, the number of particles neutralized before reaching the irradiation object is estimated based on the degree of vacuum at that time, and the measurement of the ion irradiation amount is made more accurate. The need to estimate the number of neutralized particles arises from the use of the Faraday cup. In the measurement using the Faraday cup, the ion irradiation amount is determined based on the number of charges of the ions and the measured current amount. In other words, measurement cannot be performed unless the particles are charged particles. Therefore, it is necessary for the Faraday cup to perform some kind of correction on particles that are neutralized and have a large kinetic energy and are injected into the irradiation target.

[0004]

When a Faraday cup is used to measure the amount of ion irradiation as described above, accurate measurement can be performed because the ion beam is neutralized or electrons flow from an electron shower. Basically, it is difficult to perform the operation, and there is a problem that the configuration becomes complicated to eliminate the influence. In order to solve such a conventional technique, the present invention improves an ion implantation apparatus and measures the number of scattered particles back-scattered by Rutherford, so that the ion irradiation amount can be easily and accurately measured. It is intended to provide an injection device.

[0005]

In order to achieve the above object, the present invention provides an ion implantation apparatus for irradiating an object with an ion beam and implanting ion particles into the object. The ion implantation apparatus is characterized in that the number of scattered particles backscattered by Rutherford is measured to measure the amount of ion irradiation on the object to be irradiated. In the above ion implanter,
Since the ion irradiation amount is measured based on the ion particles back-scattered by Rutherford by the irradiation object, simple and accurate measurement can be performed without being affected by the inflow of electron current or neutralization of the ion beam as in the past. It can be carried out. In the above ion implantation apparatus, for example, if a scattering solid angle limiting means for limiting the scattering solid angle of the scattering particles to be measured is provided,
Measurement leakage (pile-up) of scattered particles can be prevented, and the measurement accuracy can be further improved. further,
If the ion irradiation amount is determined based on the number of scattered particles having a specific energy among the measured scattered particles, scattered particles with unnecessary scattering conditions can be removed from the measurement, and the measurement accuracy can be further improved. . Further, if the ion implantation apparatus is provided with control means for changing the parameters of the ion beam based on the measured ion irradiation amount, for example, the ion irradiation amount becomes a predetermined amount based on the measured ion irradiation amount. It is possible to automatically perform the control of stopping the irradiation of the ion beam when it reaches, or changing the irradiation amount of the ion beam to another value. still,
The energy of the ion beam used in the ion implantation apparatus is preferably 500 keV or more. Further, for example, a slit is used as the scattering solid angle limiting means. Further, the object to be irradiated is, for example, a semiconductor wafer.

[0006]

Embodiments of the present invention will be described below with reference to the accompanying drawings to provide an understanding of the present invention.
The following embodiment is a specific example of the present invention and does not limit the technical scope of the present invention. FIG. 1 is a diagram showing a schematic configuration of an ion implantation apparatus according to one embodiment of the present invention. As shown in FIG. 1, an ion implantation apparatus according to an embodiment of the present invention is an ion source 1 for ionizing and accelerating impurity particles such as B, As, and P, and is extracted from the ion source 1. A mass analyzer 3 for removing unnecessary ion particles contained in the ion beam 2, a rotating disk 5 for disposing an irradiation object 4 such as a semiconductor wafer, and a charge disk for preventing the rotating disk 5 from being charged up. An electron shower 6, an RBS detector 7 for detecting ion particles backscattered by Rutherford from the irradiation object 4, a pulse height analyzer 8 for analyzing an energy spectrum of the scattered particles, and an ion beam based on an output from the pulse height analyzer 8. Control means 9 for determining the dose and changing the parameters of the ion beam.

Hereinafter, details of the ion implantation apparatus will be described. First, in the ion source 1, for example, B, A
Impurity particles such as s and P are ionized in a vacuum and are extracted and accelerated with an appropriate acceleration voltage. The acceleration voltage at this time is set to, for example, 500 kV or more. The beam line of the ion beam 2 extracted from the ion source 1 is provided with a mass analyzer 3 composed of, for example, a pair of sector magnets. The path of the ion beam 2 is changed with a radius of rotation corresponding to the magnetic flux applied in the mass analyzer 3. Although the ion beam 2 contains unnecessary ions such as congener ions having different charge numbers, the ions are separated and removed from the beam line by the function of the mass analyzer 3. The ion beam 2 having passed through the mass analyzer 3 is applied to a semiconductor wafer, which is an object 4 to be irradiated, through a slit 10. The slit 10 is for adjusting the irradiation amount of the ion beam 2, and the passage area of the ion beam 2 is controlled by the control unit 9. The irradiation object 4 to be irradiated with the ion beam 2 is disposed on the rotating disk 5 in an annular shape. The rotating disk 5 is provided with several to dozens of objects 4 to be irradiated, and can be rotated at a predetermined speed by driving means 11 such as a motor. An electron shower 6 is provided near the rotating disk 5. The current monitor 12
It is connected between the rotating disk 5 and the electron shower 6, and adjusts the amount of electrons emitted from the electron shower 6 so that the current becomes zero, thereby preventing the rotating disk 5 from being charged up.

Incidentally, the ion beam 2 is 500 keV
It is a high-speed particle group having the above energy, and the Rutherford backscattering is dominant in the scattering that occurs at the time of collision with the irradiation object 4. In order to capture the Rutherford backscattered ion particles, an RBS detector 7 composed of, for example, a multi-channel analyzer is installed at a predetermined back angle. The particles subjected to Rutherford scattering by the irradiation object 4 pass through the slit 13 and are detected as particles by the RBS detector 7. Note that the slit 13 is for limiting the solid angle of scattering of the scattering particles incident on the RBS detector 7, and reduces a measurement error due to leakage measurement (pile-up) of the particles. A wave height analyzer 8 is connected to the RBS detector 7, and an energy spectrum is measured. This energy spectrum is measured by a counter and D / A
It is input to the control means 9 via the converter. And
The ion irradiation amount is determined based on the number of scattered particles measured by the wave height analyzer 8. The following equation shows the relationship between the number of scattered particles determined by Rutherford backscattering and the amount of ion irradiation.

(Equation 1) According to the above equation, the control means 9 monitors the ion irradiation amount in real time. Then, when a predetermined ion irradiation amount is reached, the control means 9 performs control such as immediately stopping irradiation to the irradiation target 4 using the slit 5 or the like. As described above, in the above-described ion implantation apparatus, the amount of ion irradiation is measured based on the number of scattered particles that have been backscattered by Rutherford by the irradiation object. Accurate measurement can be performed.

[0009]

In the above embodiment, the ion irradiation dose is determined without particularly limiting the energy band of the scattered particles incident on the RBS detector 7, but only the scattered particles having a specific energy are counted from the energy spectrum. The ion irradiation amount may be determined as follows. In this case, it is possible to specify the atom at which the ion particles collided or the depth at which the scattering occurs in the irradiation object 4, so that more accurate measurement can be performed. Also, R
The scattered particles incident on the BS detector 7 may include not only those scattered by the object 4 but also those scattered by the rotating disk 5. The material of the disk 5 may be changed. Such an ion implantation apparatus is also an example of the ion implantation apparatus according to the present invention.

[0010]

As described above, the present invention relates to an ion implantation apparatus for irradiating an object with an ion beam and injecting ion particles into the object. An ion implantation apparatus is characterized in that the number of ions is measured to measure the amount of ion irradiation on the object to be irradiated. In the above-described ion implantation apparatus, the ion irradiation amount is measured based on the ion particles back-scattered by Rutherford by the irradiation object. Simple and accurate measurements can be made. For example, if the ion implantation apparatus is provided with a scattering solid angle limiting means for limiting the scattering solid angle of the scattering particles to be measured, it is possible to prevent measurement leakage (pile-up) of the scattering particles and further improve the measurement accuracy. Can be done. Further, if the ion irradiation amount is determined based on the number of the scattering particles having the specific energy among the measured scattering particles, the scattering particles with unnecessary scattering conditions are removed from the measurement to further improve the measurement accuracy. Can be. Further, if the ion implantation apparatus is provided with control means for changing the parameters of the ion beam based on the measured ion irradiation amount, for example, the ion irradiation amount becomes a predetermined amount based on the measured ion irradiation amount. It is possible to automatically perform the control of stopping the irradiation of the ion beam when it reaches, or changing the irradiation amount of the ion beam to another value. The energy of the ion beam used in the ion implantation apparatus is preferably 50
It is 0 keV or more. Further, for example, a slit is used as the scattering solid angle limiting means. Further, the object to be irradiated is, for example, a semiconductor wafer.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing an example of a conventional ion implantation apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Ion source 2 ... Ion beam 3 ... Mass analyzer 4 ... Irradiation object 5 ... Rotating disk 6 ... Electron shower 7 ... RBS detector 8 ... Crest height analyzer 9 ... Control means 13 ... Slit

Claims (7)

[Claims] In an ion implantation apparatus for irradiating an object with an ion beam and implanting ion particles into the object, the number of scattered particles that have been Rutherford backscattered by the object is measured. An ion implantation apparatus characterized by measuring an amount of ion irradiation on an object to be irradiated. 2. The ion implantation apparatus according to claim 1, further comprising scattering solid angle limiting means for limiting the scattering solid angle of the scattering particles to be measured. 3. The ion implantation apparatus according to claim 1, wherein the ion irradiation amount is determined based on the number of scattering particles having a specific energy among the measured scattering particles. 4. The ion implantation apparatus according to claim 1, further comprising control means for changing a parameter of the ion beam based on the measured ion irradiation amount. 5. The ion implantation apparatus according to claim 1, wherein said ion beam has an energy of 500 keV or more. 6. The ion implantation apparatus according to claim 1, wherein said scattering solid angle limiting means is a slit. 7. The ion implantation apparatus according to claim 1, wherein the object to be irradiated is a semiconductor wafer.