JP2824609B2 - Ion implantation method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion implantation method and apparatus for implanting impurities into a semiconductor substrate when manufacturing various semiconductor devices, and more particularly, to ionize impurities such as As, P, and B. The present invention relates to a method and an apparatus for accelerating this into a semiconductor substrate by accelerating at a high voltage.

[0002]

2. Description of the Related Art When manufacturing a semiconductor such as an IC, first, a device wafer (a substrate generally made of silicon crystal) is used.
Then, impurities such as As, P, and B are introduced into the substrate, and a P-type layer or an n-type layer is formed near the surface of the wafer.

When an impurity is introduced into a semiconductor as described above, an impurity concentration distribution is formed in the depth direction of the semiconductor.

Since the impurity concentration distribution is an important factor in determining the device characteristics of a device, it is necessary to control the concentration distribution with high precision in order to realize desired device characteristics.

[0005] In particular, it is important to control this concentration distribution with extremely high precision in manufacturing a fine element constituting a super LSI which has been widely used in recent years.

An ion implantation method is known as a technique for controlling the concentration distribution with extremely high precision, and an ion implantation apparatus is known as an apparatus for performing the ion implantation method.

That is, the ion implantation method is As, P, B
In this method, impurities such as donors or acceptors are introduced into a semiconductor by ionizing impurities such as ions and accelerating the ions at a high voltage and implanting them into a semiconductor substrate. In this ion implantation method, the implantation depth of the impurity can be controlled by controlling the acceleration voltage of the ion beam, and the amount of the impurity can be controlled by controlling the magnitude of the ion current. It is easy to make the impurity concentration in the depth direction a desired distribution. Particularly, since the magnitude of the ion current can be directly measured, the concentration distribution can be controlled with high accuracy by feeding back the measured value.

As described above, the ion implantation method has a great advantage that the concentration distribution of impurities in a semiconductor can be controlled with high accuracy. On the other hand, when ions collide with the semiconductor, the impact of the semiconductor on the semiconductor is reduced. There is also a drawback that secondary electrons are knocked out from the surface of the semiconductor device, whereby the semiconductor surface is positively charged and the semiconductor device may be destroyed.

Therefore, conventionally, in order to prevent the semiconductor surface from being positively charged and prevent the destruction of the semiconductor device, the semiconductor surface is irradiated with ions from the electron shower device at the same time as the irradiation of the ions. Is known to prevent the positively charged particles from being positively charged.

That is, in the ion implantation method to which the electron shower technique is added, the positive charge generated on the semiconductor surface by supplementing the charge amount of the electrons emitted from the semiconductor surface by the irradiation of the ion beam with the electrons from the electron shower device. Of the semiconductor device, thereby preventing electrostatic breakdown due to charging of the semiconductor device.

[0011]

However, when the above-described electron shower technique is applied to the ion implantation method, the following various problems occur.

That is, to cancel the positive charge depending on implantation conditions such as the amount of ion beam current, implanted ion species, implantation angle, implantation acceleration voltage, and ion beam shape, and also on the type of semiconductor substrate on which the ion implantation is performed. Since the optimum amount of electron shower changes, the optimum amount of electron shower must be determined for each of these injection conditions and the type of semiconductor substrate, and the conditions of the electron shower device must be set so as to achieve this amount of electron shower. The arrangement of measurement data and the operation of the apparatus are complicated.

In general, the region irradiated with the electron shower on the semiconductor surface is wider than the region irradiated with the ion beam. Therefore, the region irradiated with only the electron shower is outside the region irradiated with the ion beam. And this region will be negatively charged. In particular, when the amount of the ion beam is large, the amount of the electron shower for preventing the positive charge is correspondingly large, so that the amount of the negative charge in the region irradiated with only the electron shower becomes large, and the semiconductor device is destroyed. There is a risk.

In addition, in order to efficiently generate an electron shower, a gas such as Ar is often introduced into the electron shower device. In such a case, ions such as Ar leaked from the electron shower device cause ions to be generated. The degree of vacuum in the injection device may be deteriorated.

As described above, since the electron shower technique has various problems, an alternative technique capable of relaxing the positive charge on the surface of the semiconductor substrate as described above has been required.

The present invention has been made in view of such circumstances, and alleviates the positive charge on the surface of a semiconductor substrate due to ion beam irradiation without relying on electron irradiation from an electron shower device. It is an object of the present invention to provide an ion implantation method and apparatus capable of preventing electric breakdown.

[0017]

SUMMARY OF THE INVENTION An ion implantation method and apparatus according to the present invention provide secondary electrons emitted from a semiconductor substrate when the semiconductor substrate is irradiated with an ion beam for ion implantation. Are attracted to the substrate surface by a magnetic field generated in the vicinity of the substrate surface to give a negative charge to the substrate.

That is, according to the ion implantation method of the present invention, in the ion implantation method of irradiating a surface of a semiconductor substrate with an ion beam and implanting desired ions into the inside of the semiconductor substrate, the ion beam is injected into the surface of the semiconductor substrate. Simultaneously with the irradiation, secondary electrons emitted from the semiconductor substrate by the irradiation of the ion beam and electrons present in the ion beam are attracted to the surface of the semiconductor substrate. A magnet provided on the electrode for accelerating the ion beam positioned substantially continuously extends from one side end to the other side end of the semiconductor substrate near the surface of the semiconductor substrate substantially in parallel with the surface of the semiconductor substrate. It is characterized by generating a curved line of magnetic force having parallel portions.

Further, the ion implantation apparatus of the present invention is an ion implantation apparatus for irradiating a surface of a semiconductor substrate with an ion beam to implant desired ions into the inside of the semiconductor substrate. A magnet provided on an acceleration electrode of the ion beam, which is located at a predetermined distance from the surface of the semiconductor substrate, in order to attract secondary electrons emitted from the substrate and electrons present in the ion beam to the surface of the semiconductor substrate. Accordingly, magnetic field generation for generating a curved magnetic field line having a substantially parallel portion extending substantially parallel to the surface of the semiconductor substrate continuously from one side end to the other side end of the semiconductor substrate in the vicinity of the surface of the semiconductor substrate It is characterized by having means.

Here, the “simultaneous with irradiation” is not required until the irradiation time of the ion beam and the generation time of the magnetic field completely coincide with each other. Means to generate a magnetic field before it becomes large enough to destroy.

[0021]

According to the above-described ion implantation method and apparatus of the present invention, secondary electrons emitted from a semiconductor substrate by ion beam irradiation and electrons contained in the ion beam are generated by a magnetic field generated near the surface of the substrate. Since the substrate is attracted to the surface of the substrate and a negative charge is applied to the surface of the substrate, the amount of positive charge due to ion beam irradiation can be reduced, and electrostatic breakdown of the semiconductor substrate can be prevented.

Therefore, since the electronic shower device is not always required, various problems which have conventionally occurred when the electronic shower device is used can be solved.

In particular, the amount of charge of the secondary electrons pulled back to the surface of the semiconductor substrate increases with an increase in the amount of charge of the secondary electrons emitted from the substrate.
Since the amount of charge of the electrons present in the ion beam also changes substantially in proportion to the amount of the ion beam current, various electron injection conditions and various types of semiconductor substrates required when using an electron shower device are used. The complicated operation of setting the conditions of the apparatus in response can be eliminated.

In addition, it is possible to prevent electrostatic breakdown of the semiconductor substrate caused by irradiating only the electron shower in the region outside the ion beam irradiation region of the semiconductor substrate to generate negative charge, and to prevent the electron shower device from being damaged. It is possible to prevent the degree of vacuum in the ion implantation apparatus from deteriorating due to leakage of the sealed Ar gas or the like. Further, the ion implantation method and apparatus of the present invention,
In generating the magnetic field, a magnet provided on an acceleration electrode of an ion beam located at a predetermined distance from the surface of the semiconductor substrate, from one side end to the other side end of the substrate in the vicinity of the surface of the semiconductor substrate. Since it is configured to generate curved lines of magnetic force having substantially parallel portions that extend substantially parallel to the surface of the substrate, the following operation is achieved. i) When mounting a plurality of semiconductor substrates on the mounting means,
If the magnet for generating the magnetic field lines is provided on the mounting means, it is necessary to provide a magnet at each mounting position of the semiconductor substrate of the mounting means. Therefore, even when a plurality of semiconductor substrates are mounted on the mounting means, the magnet may be provided only on the ion beam accelerating electrode, that is, only at one location, which simplifies the device configuration. In addition, the cost of the apparatus can be reduced. ii) If the lines of magnetic force are generated as close to the surface of the semiconductor substrate as possible, electrons can be more strongly attracted to the surface of the semiconductor substrate. However, if the magnetic field lines are linear, the magnet must also be disposed very close to the surface of the semiconductor substrate in order to generate the magnetic field lines very close to the surface of the semiconductor substrate. In particular, when the magnet is provided on a member that moves relatively to the semiconductor substrate and is moved relatively to the substrate, the magnet and the surface of the semiconductor substrate are required to avoid interference between the two when moving. It is difficult to dispose the magnet in a position very close to the surface of the semiconductor substrate because it is necessary to secure a predetermined clearance between them. Therefore, it is not possible to obtain a stronger effect of attracting electrons by magnetic field lines. However, when the curved magnetic field lines are used, the curved magnetic field lines extend far, so that even if a magnet is provided at a position distant from the semiconductor substrate surface, the magnetic field lines can be easily generated at a position very close to the semiconductor substrate surface. . However, in the method and the apparatus of the present invention, since the curved magnetic field lines are generated as described above, even if the magnet is provided on the ion beam accelerating electrode remote from the surface of the semiconductor substrate, the linear magnetic field lines are generated. Unlike the case where the magnetic field lines are generated, the lines of magnetic force can be easily generated very close to the surface of the semiconductor substrate, and a stronger effect of attracting electrons by the lines of magnetic force can be obtained. iii) Further, as described above, a curved magnetic field line having a substantially parallel portion extending substantially parallel to the surface of the semiconductor substrate continuously from one side end to the other side end of the semiconductor substrate is generated as described above. As a result, a magnetic field can be formed by substantially parallel lines of magnetic force over the entire surface of the semiconductor substrate, and a stronger effect of attracting electrons by the lines of magnetic force can be obtained at this point.

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic view showing a part of an ion implantation apparatus according to an embodiment of the present invention. That is, this apparatus accelerates impurity ions such as P, As, and B and generates an ion beam 1 (not shown), an electrode unit 2 that re-accelerates the ion beam 1, and an ion beam 1 A wafer mounting paddle 4 for mounting and holding a wafer 3 to be irradiated with ions and performing ion implantation, and a paddle drive for reciprocating the paddle 4 in a direction perpendicular to the ion beam 1 (the direction of arrow A in the figure). (Not shown).

The electrode section 2 is formed in a disk shape centering on the axis of the ion beam 1, and has a rectangular through hole 2 A through which the ion beam 1 passes at the center.

When the wafer 3 is irradiated with the ion beam 1,
Impurity ions constituting the ion beam 1 are bombarded into the wafer 3, and the impurities are formed so as to have a predetermined concentration distribution in the depth direction with a predetermined depth from the surface of the wafer 3 as a maximum concentration point. . As a result, the surface layer of the wafer 3 is formed as a P-type layer or an n-type layer depending on the type of impurities to be introduced.

The ion implantation apparatus of this embodiment employs a batch system in which a large number of wafers 3 are loaded and processed at one time. As shown in FIG. 2, which is a plan view from the irradiation direction of the ion beam 1, A large number of paddles 4 are mounted around the rotating plate 4C. That is, the paddle 4 includes a mounting table 4A on which the wafer 3 is mounted, and the mounting table 4A
The arm 4B is connected to the
A is disposed at substantially equal intervals on the circumference around the rotation axis of the rotating plate 4C.

The rotary plate 4C is driven by the paddle driving unit described above so as to rotate at high speed (for example, 1000 rpm or more) in the direction of arrow B while reciprocating at a low speed (for example, several cm / sec) in the direction of arrow A in the figure. As a result, the mounting table 4A and the wafer 3 rotate at high speed around the rotation axis of the rotating plate 4C while reciprocating.

The irradiation position of the ion beam 1 is fixed, and the plurality of wafers 3 reciprocate and rotate with respect to the ion beam 1 as described above, so that the ion beam 1 is uniformly scanned on each wafer 3. Will be done. The ion current of the ion beam 1 is, for example, 3 to 12 m.
A, and the ion accelerating voltage is, for example, 10 to 120.
kV.

The main feature of the apparatus of the present invention is that a magnetic field generating means for generating a magnetic field for attracting electrons capable of relaxing the positive charge is provided on the surface of the wafer 3 positively charged by ion irradiation. is there. In the apparatus of this embodiment, as shown in FIG. 1, a plurality of permanent magnets 5 are arranged in the electrode section 2 to constitute a magnetic field generating means.

That is, the permanent magnet 5 has a rectangular parallelepiped shape. As shown in FIG. 3, the permanent magnet 5 has magnet insertion holes 6A and 6B formed along a circumference centered on the center axis of the electrode 2. About 5 to 9 pieces are inserted at equal intervals.

The permanent magnet 5 inserted into the magnet insertion hole 6A is arranged so that the outer peripheral side has an S pole and the inner peripheral side has an N pole, and the permanent magnet 5 inserted into the magnet insertion hole 6B has an inner peripheral side. It is arranged so that the S pole and the outer peripheral side become the N pole.

Therefore, as shown in FIG. 4 (a), the lines of magnetic force 7 generated by these permanent magnets 5 are changed from the group of permanent magnets 5A to the group of permanent magnets 5B near the through-hole 2A, and to the group of permanent magnets outside the electrode 2. From the group 5B, it goes to the permanent magnet group 5A.

FIG. 4B shows a vertical cross section (a cross section taken along the line II) of FIG. 4A.

In the apparatus of this embodiment, as shown in FIG. 4 (b), the curved magnetic force lines 7 coming out of the permanent magnet group 5B, making a large turn around the outside of the electrode 2, and returning to the permanent magnet group 5A.
And more specifically, the magnetic field lines 7 are parallel to and near the surface of the wafer 3 described above.
In the vicinity of the surface of the wafer 3, from one side end to the other side end of the wafer 3 (from the lower side end to the upper side end of the wafer 3 in FIG. It is adjusted to have a substantially parallel portion extending substantially in parallel. That is, the direction of the magnetic field is near the surface of the wafer 3 and parallel to the surface. The intensity of the magnetic field in the vicinity of the surface is, for example, 10 gauss or more.

When such a magnetic field is formed near the surface of the wafer 3, electrons existing near the surface of the wafer 3 are attracted to the surface of the wafer 3.

In the ion implantation method, secondary electrons are emitted from the wafer 3 by the irradiation of the ion beam, and this is a main cause, and the surface of the wafer 3 is easily charged positively. As described above, if the secondary electrons 11 emitted by the magnetic field and the electrons 12 floating in the ion beam 1 are attracted to the surface of the wafer 3, the negative charges of these electrons 11, 12 are obtained. Thereby, the positive charge on the surface can be reduced.

Further, the number of the emitted secondary electrons and the number of the electrons which are drawn back to the wafer 3 among the secondary electrons have a positive correlation, and the number of the secondary electrons depends on the magnetization strength of the permanent magnet 5. Since the correlation coefficient is determined, there is no need to change the electron irradiation condition for preventing positive charging according to other ion implantation conditions, the type of material forming the wafer 3, and the like, and the positive charging preventing operation is easy.

The electrons in the ion beam 1 are used to assist the secondary electrons drawn back to the wafer 3 in supplying the negative charges as described above. By controlling the number of electrons in the ion beam 1 attracted to the wafer 3 by controlling the number of electrons, it is possible to substantially cancel the positive charges on the surface of the wafer 3. Since it can be considered that the number of electrons in the ion beam 1 is substantially proportional only to the magnitude of the beam current, it is easy to control the intensity of the above-mentioned magnetization. Become.

It should be noted that the ion implantation method and apparatus of the present invention are not limited to those in the above-described embodiment, and various modifications can be made.

In the above-described embodiment, the magnetic field is always formed. However, a magnetic field for preventing positive charging may be generated in accordance with the timing of ion beam irradiation. In this case, an electromagnet may be used instead of the permanent magnet, and the intensity of magnetization may be controlled by changing the current flowing through the electromagnet.

The position of the magnetic field generating means is as follows.
Instead of the position of the electrode 2 shown in FIG.

In FIG. 3, the direction of the ion beam 1 may be reversed with respect to the electrode 2. In this case, the same effect as in the above embodiment can be obtained.

It is also possible to provide an electron shower device in the ion implanter to irradiate the surface of the wafer with electrons to assist the electrons drawn back to the wafer by the above-described magnetic field generating means.

In the above embodiment, the method of scanning the ion beam by moving the wafer is employed. Instead, the method of scanning the ion beam by moving the ion beam with respect to the wafer is employed. It is also possible.

Further, the number of wafers disposed at one time in the apparatus is not limited to the one in the above embodiment, but may be one or an arbitrary plural number.

[0049]

As described above, according to the ion implantation method and apparatus of the present invention, the secondary electron and the ion beam that are ejected by the ion beam irradiation by the magnetic field generated near the surface of the semiconductor substrate. Since the electrons present therein are attracted to the substrate surface to offset the positive charges that can be generated on the semiconductor substrate surface, the positive charge on the semiconductor substrate surface can be prevented, and the electrostatic breakdown of the semiconductor device can be prevented. .

According to the method and apparatus of the present invention,
Secondary electrons related to secondary electron emission that caused the semiconductor substrate surface to become positively charged are returned to the semiconductor surface;
This negative charge is generated because the electron beam in the ion beam whose amount depends only on the magnitude of the beam current of the ion beam is attracted to the semiconductor surface to provide a negative charge that relaxes the positive charge on the semiconductor surface. In this case, it is not necessary to consider various ion implantation conditions and the type of the semiconductor substrate, and the operation for preventing positive charging becomes extremely easy.

Further, as in the case where an electron shower device is used, the semiconductor substrate may be negatively charged outside the ion beam irradiation area, or may leak in the ion implantation device due to leakage of Ar gas or the like used in the electron shower device. It is possible to prevent the problem that the degree of vacuum is deteriorated.
Furthermore, according to the method and the apparatus of the present invention, when the magnetic field is generated, the magnet for generating the magnetic field lines is provided on the ion beam acceleration electrode. For example, a plurality of semiconductor substrates are mounted on the mounting means. It is only necessary to provide the magnet at one place on the on-beam accelerating electrode even in the case of performing, and it is possible to simplify the device configuration and reduce the device cost,
Also, since the magnetic field lines are formed in the vicinity of the surface of the semiconductor substrate as curved magnetic field lines having substantially parallel portions extending from one side end of the substrate to the other side end substantially in parallel with the surface of the substrate, the curved lines are formed. This makes it possible to easily generate magnetic force lines very close to the surface of the semiconductor substrate even if the magnet arrangement position is far from the surface of the semiconductor substrate, and continuously from one side end of the semiconductor substrate to the other side end. By having a substantially parallel portion extending substantially in parallel with the surface of the substrate, it is possible to generate a magnetic field with substantially parallel lines of magnetic force over the entire surface of the semiconductor substrate, thereby providing a stronger electron attracting effect. Obtainable.

[Brief description of the drawings]

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

FIG. 2 is a schematic view showing the entire wafer mounting paddle of the apparatus shown in FIG. 1;

FIG. 3 is a schematic diagram showing the electrodes of the apparatus shown in FIG. 1 in detail;

FIG. 4 is a schematic diagram showing magnetic field lines generated by a permanent magnet of the device shown in FIG. 1;

FIG. 5 is a schematic diagram for explaining the operation of the device shown in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ion beam 2 Electrode 3 Wafer 4 Paddle 5 Permanent magnet 7 Line of magnetic force 11 Secondary electron 12 Electron in ion beam

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiko Matsunaga 14-3 Shinsen, Narita-shi, Chiba Nogedaira Industrial Park In-house Applied Materials Japan Co., Ltd. (56) References JP-A-3-219545 (JP, A JP-A-64-84559 (JP, A) JP-A-61-206151 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01J 37/317 C23C 14/48 H01L 21 / 268

Claims (2)

(57) [Claims] 1. An ion implantation method for irradiating a surface of a semiconductor substrate with an ion beam and implanting desired ions into the inside of the semiconductor substrate, wherein the ion beam is irradiated on the surface of the semiconductor substrate, Of the ion beam located at a predetermined distance from the surface of the semiconductor substrate to attract the secondary electrons emitted from the semiconductor substrate and the electrons present in the ion beam to the surface of the semiconductor substrate by the irradiation of the ion beam. A curved portion having a substantially parallel portion extending from one side end to the other side end of the semiconductor substrate in the vicinity of the surface of the semiconductor substrate in the vicinity of the surface of the semiconductor substrate so as to extend substantially parallel to the surface of the semiconductor substrate; An ion implantation method characterized by generating lines of magnetic force. 2. An ion implantation apparatus for irradiating a surface of a semiconductor substrate with an ion beam and implanting desired ions into the inside of the semiconductor substrate, comprising: a secondary electron emitted from the semiconductor substrate by the irradiation of the ion beam; In order to attract the electrons present in the ion beam to the surface of the semiconductor substrate, a magnet provided on the electrode for accelerating the ion beam located at a predetermined distance from the surface of the semiconductor substrate provides a magnet near the surface of the semiconductor substrate. A magnetic field generating means for generating a curved line of magnetic force having a substantially parallel portion extending substantially parallel to the surface of the semiconductor substrate continuously from one side end to the other side end of the semiconductor substrate. Ion implanter.