JP4138946B2 - Ion implanter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In the present invention, the ionized and mass-separated chemical element mainly in the manufacturing process of a semiconductor integrated circuit is 1% or less as the distribution of the injection amount on the substrate surface while keeping the incident angle to the substrate constant. The present invention relates to an ion implantation apparatus for implanting a large-diameter substrate with energy of several keV to several hundred keV while maintaining uniformity.
[0002]
[Prior art]
Conventionally, for example, an apparatus having the configuration shown in FIG. 7 is known as a medium current ion implantation apparatus. In this apparatus, an ion source a to which an independent potential is applied and a first sector electromagnet b for mass separation are arranged, and a mass separation slit is provided in front of the first sector electromagnet b along a first optical axis c. d, a cylindrical acceleration tube e, a first electrostatic deflector f made of a multipolar electrode, a second electrostatic deflector g also made of a multipolar electrode, and a fixed substrate h in front thereof. It has an arranged configuration.
[0003]
In this ion implantation apparatus, ions extracted from the ion source a with an energy of, for example, 30 keV are sorted into only ions having a predetermined mass by passing through the first sector electromagnet b and the mass separation slit d, and then the first It flies along the optical axis c, and is accelerated or decelerated from the kettle e to a predetermined energy of several keV to several hundred keV. Ions that have reached a predetermined energy are deflected by the first electrostatic deflector f in a plane including the first optical axis c, and are substantially opposite to the first electrostatic deflector f by the second electrostatic deflector g. And is incident on a fixed substrate h. By performing two-dimensional scanning by changing the deflection angle and the deflection surface of the first electrostatic deflector f and the second electrostatic deflector g, the uniformity of the angle injected into the substrate h is maintained. Ions can be implanted well.
[0004]
In general, in an ion implantation apparatus, a part of ions in flight becomes electrically neutral due to collision with a residual gas or the like, and there is a possibility that electromagnetic control cannot be performed. For the purpose of removing such neutral particles, the second electrostatic deflector g and the substrate h are installed with reference to the second optical axis i shifted by, for example, about 7 degrees with respect to the first optical axis c. .
[0005]
Further, as another example of the conventional medium current ion implantation apparatus, there is also known one in which the configuration ahead of the acceleration tube is the configuration shown in FIG. In the figure, ions separated by mass and having a predetermined energy that have passed through an accelerating tube (not shown) are scanned in a fixed plane by a scanning electromagnet j. A second sector electromagnet k is provided in front of the scanning electromagnet j so that the deflection surface thereof coincides with the scanning surface of the scanning electromagnet j, and the substrate h is mechanically moved in a direction perpendicular to the scanning surface. It is installed on the platen l to be driven. The sector electromagnet generally performs a convex lens action on the ion beam. However, by making the focal point on the entrance side of the second sector electromagnet k coincide with the deflection center of the scanning electromagnet j, the ion irradiated to the substrate h The incident angle is constant regardless of the scanning angle at the scanning electromagnet j. By using both the scanning of the ion beam by the scanning electromagnet j and the mechanical scanning of the platen l, ions can be implanted with good uniformity while keeping the angle implanted into the substrate h constant.
[0006]
As another example of the conventional medium current ion implantation apparatus, a structure shown in FIG. 9 is known. In this apparatus, an electrostatic deflector m composed of a pair of electrodes is provided in front of the mass separation slit d, and the converging electromagnet n having a strong convex lens action on the ion beam is provided in front of the electrostatic deflector m. A rectangular acceleration tube o whose longitudinal direction coincides with the scanning surface of the electrostatic deflector m is provided in front of it. The substrate h is placed on a platen l that is mechanically driven in a direction perpendicular to the scanning plane of the electrostatic deflector m. By making the entrance-side focal point of the converging electromagnet n coincide with the deflection center of the electrostatic deflector m, the angle of the beam incident on the rectangular acceleration tube o becomes constant regardless of the scanning angle. In general, an acceleration tube has a lens effect on an ion beam, but a rectangular acceleration tube has a small lens effect in the longitudinal direction. Therefore, by making the longitudinal direction of the rectangular acceleration tube o coincide with the deflection surface of the electrostatic deflector m, the incident angle of ions irradiated on the substrate h is constant regardless of the scanning angle of the electrostatic deflector m. It becomes. By using both the scanning of the ion beam by the electrostatic deflector m and the mechanical scanning of the platen l, ions can be implanted with good uniformity while keeping the angle of implantation to the substrate h constant.
[0007]
[Problems to be solved by the invention]
The degree of integration of semiconductor integrated circuits increases year by year as the speed of devices increases, and at the same time, the size of substrates used for manufacturing increases from 150 mm to 200 and 300 mm in diameter.
[0008]
In the case of an ion implantation apparatus used in the manufacture of semiconductor integrated circuits, so-called energy contamination in which ions in flight are injected by energy different from a predetermined energy due to charge conversion caused by collision with residual gas, etc. Distribution anomalies in which chemical elements are implanted in a spatially biased manner are a major problem that deteriorates productivity. As the degree of integration of semiconductor devices increases, there is an increasing demand for reducing energy contamination and distribution anomalies.
[0009]
Furthermore, the main purpose is to increase the size of the substrate, and there is a demand for shortening the processing time per substrate despite the increase in the substrate size. In the case of an ion implantation apparatus, it is necessary to increase the current of the ion beam as the substrate size increases. However, the amount of heat input to the substrate increases and degassing tends to increase. Contamination and distribution anomalies are becoming increasingly serious problems.
[0010]
On the other hand, since the ion implantation apparatus is relatively large among semiconductor manufacturing apparatuses, it is not desirable from the layout of a mass production factory that the apparatus be large. As the substrate size increases, the end station must inevitably become large, and this demand cannot be met unless the area in which the ion beam flies is made as small as possible.
[0011]
In the conventional ion implantation apparatus shown in FIG. 7, charge conversion of ions passing through the second electrostatic deflector g leads to an abnormal distribution on the substrate h. On the other hand, since the inner diameter of the second electrostatic deflector g is substantially equal to or larger than the size of the substrate h, the degassing from the substrate is easily diffused immediately into the second electrostatic deflector g. There is a tendency for pressure to increase. Therefore, there is a disadvantage that outgassing increases from the substrate as the beam current increases, and distribution anomalies are likely to occur.
[0012]
Further, in the conventional ion implantation apparatus shown in FIG. 8, in order for ions to be implanted into the substrate h at a constant angle regardless of the scanning angle of the scanning electromagnet j, the scanning electromagnet j is the second sector electromagnet k. It must be in the entrance-side focus. The energy of ions passing through the second sector electromagnet k is equal to the implantation energy. Assuming that phosphorus (P), which is a typical implanted ion, is implanted at 300 keV, an example of the specifications required for the second sector electromagnet k is as follows: the magnetic flux density is 0.3 stellar and the deflection angle is 45 degrees. The orbit radius is 1 meter, and the distance from the entrance of the electromagnet to the entrance side focal point is 1 meter. As a result, the required distance from the scanning electromagnet j to the substrate h is 3 meters.
[0013]
Further, an ion implantation apparatus having the configuration shown in FIG. 9 is also known, and in this apparatus, the energy of ions passing through the focusing electromagnet n is equal to the energy when extracted from the ion source, and is generally relatively about 30 keV. Low. Therefore, the converging electromagnet n is relatively small, and the problem that the distance from the scanning electromagnet j to the second sector electromagnet k becomes longer as in the conventional apparatus of FIG. 8 does not occur. However, in the apparatus of FIG. 9, degassing from the substrate h is relatively easy to diffuse into the rectangular acceleration tube o, so that ions accelerated or decelerated in the rectangular acceleration tube o are charged by collision with the gas. Conversion is performed, and energy is contaminated easily by being injected into the substrate with energy different from the predetermined energy.
[0014]
An object of the present invention is to provide an ion implantation apparatus that solves the above-described problems and does not increase in size even when the substrate size is increased, and that causes less energy contamination and distribution abnormality.
[0015]
[Means for Solving the Problems]
In the present invention, mass-separated ions are accelerated or decelerated to a predetermined energy, and the ion beam is electrostatically scanned in the scanning plane including the reference axis of the beam, and ion implantation is performed along a straight line perpendicular to the scanning plane. In an ion implantation apparatus combined with mechanical scanning for moving a substrate to be moved, a first sector electromagnet for performing mass separation and a mass separation slit are provided in the path of the ion beam, and the front of the mass separation slit is provided. An electrostatic deflector for scanning the beam and an accelerating tube having a plurality of arc-shaped electrodes are sequentially provided, and a deflecting surface in front of the accelerating tube is aligned with the deflecting surface of the electrostatic deflector. 2 sector electromagnets, and the center of curvature of the arc-shaped electrode of the accelerating tube and the entrance-side focal point of the second sector electromagnet are respectively aligned with the deflection center of the electrostatic deflector, I will achieve the purpose of It was. It is also possible to provide a scanning electromagnet instead of the electrostatic deflector, and a third deflecting surface coincides with the scanning surface between the mass separation slit and the electrostatic deflector or the scanning electromagnet. It is preferable to provide a sector electromagnet. Instead of the electrostatic deflector, a third sector electromagnet whose deflection surface coincides with the scanning plane is provided, and a portion of the vacuum chamber through which the ion beam passes is provided with the third sector electromagnet. The ion beam may be scanned within the scanning plane by making them independent and further modulating the potential of ions passing through the third sector electromagnet. Further, the deflection surface of the third sector electromagnet is made to coincide with the deflection surface of the first sector electromagnet for mass separation, and the direction of the magnetic field at the third sector electromagnet is changed to the first sector electromagnet. By reversing the direction of the magnetic field in the electromagnet, it is preferable that the reference axis of the beam at this portion be S-shaped or Z-shaped.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes an ion source that emits ions in a beam shape, and only specific ions from the ion beam are placed in front of the ion source 1. A first sector electromagnet 2 for mass separation and a mass separation slit 3 are provided, and an electrostatic deflection comprising a pair of electrodes 4a and 4b for scanning an ion beam in a fixed plane in front of the slit 3 A vessel 4 is provided. They are placed inside the high voltage terminal 5 which is at a potential that is electrically independent of the ground level. In front of the electrostatic deflector 4, there is provided an acceleration tube 6 made of an arcuate electrode whose center of curvature coincides with the deflection center 4c of the electrostatic deflector 4. In front of the electrostatic deflector 4, the focal point on the entrance side is provided. A second sector electromagnet 7 is provided at a position corresponding to the deflection center 4c, and can be mechanically driven along a straight line perpendicular to the scanning plane of the electrostatic deflector 4, that is, a straight line perpendicular to the paper surface, in front of it. A platen 9 was provided, and a substrate 8 to be ion-implanted was fixed to the platen 9. Instead of the electrostatic deflector 4, a scanning electromagnet (not shown) may be used.
[0017]
As shown in FIG. 2, the accelerating tube 6 is composed of three arc-shaped electrodes 6a, 6b, 6c made of a part of a concentric cylinder, and the first electrode 6a is a high voltage terminal. 5 and the final electrode 6c is electrically at the ground level. The potential of the intermediate electrode 6b is arbitrary, and in the figure, the number of the intermediate electrodes 6b is one, but may be two or more if necessary. However, for all the electrodes, it is necessary that the center of curvature of the deflection surface 4d of the electrostatic deflector 4 serving as a scanner coincides with the deflection center 4c of the deflector 4.
[0018]
In this example, the electric field generated by the arc-shaped electrodes 6a, 6b, 6c formed of a part of the concentric cylinder has a component in the circumferential direction of the concentric circle (that is, the direction of the angle) regardless of the potential formed there. Absent. Therefore, the charged particles scanned in the scanning plane 4d by the electrostatic deflector 4 continue linear motion without changing the trajectory in the scanning plane 4d regardless of acceleration or deceleration in the acceleration tube 6. Further, since the entrance-side focal point of the second sector electromagnet 7 coincides with the deflection center 4 c of the deflector 4, ions that pass through the second sector electromagnet 7 and are incident on the substrate 8 are reflected by the deflector 4. Regardless of the scanning angle and acceleration or deceleration in the accelerating tube 6, the angle is constant with respect to the substrate 8. Simultaneously with the scanning of this bi chromatography beam, by the platen 9 is mechanically scanning the substrate 8 along a straight line perpendicular to the scanning plane 4d, while maintaining its angle to the substrate 8 fixed, uniformity good ion Injection into the substrate 8 is possible.
[0019]
Generally, the distribution abnormality is caused by degassing that occurs when the substrate 8 is irradiated with an ion beam. One object of the present invention is to eliminate this distribution abnormality, and the influence on this will be described as follows. When the size of the substrate 8 is 300 mm in diameter, the beam scanning width needs to be about 40 cm. In this case, the opening area of the second electrostatic deflector g in the conventional apparatus shown in FIG. 7 is about 1170 cm ² or more. In the example of FIG. 10 cm or less is sufficient, the opening area is about 400 cm ^2, which is about 1/3 of the conventional example. Therefore, the extent to which the ion beam collides with the residual gas inside the second fan-shaped electromagnet 7 to cause charge conversion and shifts from a predetermined trajectory to cause distribution anomalies compared to the case of the conventional second electrostatic deflector g. Less than a few.
[0020]
Another object of the present invention is to eliminate energy contamination caused by charge conversion that occurs during acceleration or deceleration. The effects of energy contamination will be described as follows. Generally, the orbit radius R of the charged particles inside the sector electromagnet is given by R = (2Mφ / e) ^1/2 / B. Here, M is the mass of the charged particles, φ is the electrostatic potential, e is the charge, and B is the magnetic flux density of the sector electromagnet. When charge conversion occurs during acceleration or deceleration, the charge e of the charged particles and the electrostatic potential φ change greatly. Accordingly, the trajectories of these particles in the second sector electromagnet 7 are greatly different from the predetermined ones, and most of them are predicted not to reach the substrate 8. Further, since the second sector electromagnet 7 exists between the substrate 8 and the acceleration tube 6, the degree to which the outgas generated from the substrate 8 diffuses to the inside of the acceleration tube 6 is overwhelming compared with the conventional example of FIG. 9. Becomes smaller. Therefore, according to the present invention, the energy contamination is overwhelmingly less than the conventional one.
[0021]
Further, in the apparatus of the present invention, since the acceleration tube 6 is incorporated between the electrostatic deflector 4 and the second sector electromagnet 7, the acceleration tube is connected between the electrostatic deflector and the ion source as in the conventional device. Or it is not necessary to put between a focusing electromagnet and a board | substrate, and the distance between these is utilized effectively. Further, in the apparatus of FIG. 8, the ion beam accelerated to the energy injected into the substrate is scanned, and it is necessary to deflect a high energy ion beam of about 300 keV at most about several degrees. In the apparatus of the present invention, since the ion beam energy is deflected in a relatively small state of about 30 keV, the size of the electrostatic deflector 4 is less than half the size of the second scanning electromagnet j of the apparatus of FIG. Good. In general, the length of the accelerating tube is about 0.5 to 1.0 m, and the length of a deflector for deflecting an ion beam of about 300 keV is also required to be about 0.5 m. In the case of the present invention, the length of the beam system of the apparatus can be realized to be at least about 1 m shorter than that of FIG.
[0022]
The apparatus shown in FIG. 3 is another embodiment of the present invention, in which a configuration in which a third sector electromagnet 10 is provided between the mass separation slit 3 and the electrostatic deflector 4 is shown in FIG. It is different from the one. The ion optical meaning of the third sector electromagnet 10 will be described in principle with reference to FIGS. 4A and 4B. In the ion implantation apparatus, as described above, it is necessary to scan the beam on the substrate while keeping the incident angle to the substrate constant. At the same time, it is desirable that the size of the beam spot on the substrate is sufficiently smaller than the size of the substrate so that the ions are irradiated onto the substrate with good uniformity. In order to satisfy these two requirements, it is required that the mass separation slit, the deflection center of the deflector that scans the beam, the second sector electromagnet as the convex lens, and the substrate have a relationship as shown in FIG. That is, it is necessary that the image A ′ by the convex lens C of the mass separation slit A is formed on the substrate D, and the deflection center B coincides with the entrance-side focal point E of the convex lens C. As is apparent from the principle diagram 4a, the above-described condition cannot be realized unless the mass separation slit A and the deflection center B are separated by a certain distance. On the other hand, as shown in FIG. 4b, by inserting the second convex lens F between the mass separation slit A and the deflection center B, this distance can be greatly shortened. Further, by adopting a third sector electromagnet 10 as shown in FIG. 3 as a lens for the ion beam, not only can the distance between the mass separation slit 3 and the deflector 4 be shortened, but also a high voltage as shown in FIG. The reference axis of the beam inside the terminal 5 is U-shaped, and the overall length of the apparatus can be greatly shortened.
[0023]
The apparatus shown in FIG. 5 is still another embodiment of the present invention, in which the vacuum chamber portion surrounded by the third fan-shaped electromagnet 10 is electrically independent, and the electrostatic deflector 4. 3 is different from that of FIG. In this example, in the vacuum chamber through which the ion beam passes, the chamber portion 13 provided with the third sector electromagnet 10 is electrically isolated by the insulator 12 and the insulator 14. By modulating the potential of the chamber portion 13 with respect to the high voltage terminal 5, the deflection angle of the third sector electromagnet 10 can be changed, thereby scanning the beam. In this embodiment, since the deflector 4 provided in front of the sector electromagnet 10 in the embodiment of FIG. 3 can be omitted, the overall length of the apparatus can be further reduced as compared with the example of FIG.
[0024]
FIG. 6 shows still another embodiment of the present invention, in which the beam deflection direction of the first sector electromagnet 2 is reversed from that of the third sector electromagnet 10. In the ion implantation apparatus, it is the ion source 1 that requires maintenance most frequently. In the example of FIG. 3, the ion source 1 needs to be attached and detached from the space between the high voltage terminal 5 and an end station (not shown). However, in the embodiment of FIG. 6, the ion source 1 can be attached and detached from the outside of the apparatus. Therefore, in this case, the apparatus can be configured by protruding only the ion source without increasing the size of the apparatus, and maintenance is facilitated.
[0025]
【The invention's effect】
As described above, according to the present invention, the first fan-shaped electromagnet, the mass separation slit, the electrostatic deflector are provided in the ion beam path of the ion implantation apparatus that combines the electrostatic scanning of the ion beam and the mechanical scanning of the substrate. A plurality of arcuate acceleration tubes, a second sector electromagnet whose deflection surface coincides with the deflection surface of the electrostatic deflector, the center of curvature of the arcuate electrode of the acceleration tube, and the second The focal point on the entrance side of the fan-shaped electromagnet is aligned with the deflection center of the electrostatic deflector, so that even if the substrate size is large, ion implantation can be performed with little ion distribution anomaly and energy contamination, making the device compact. In addition, there is an effect that an ion implantation apparatus that can be easily maintained can be obtained.
[Brief description of the drawings]
1 is a partially cut plan view showing an embodiment of the present invention. FIG. 2 is a schematic perspective view of the acceleration tube of FIG. 1. FIG. 3 is a partially cut plane showing another embodiment of the present invention. FIG. 4 is an explanatory view of an optical principle in the example of FIG. 3. FIG. 5 is a partially cut plan view showing still another embodiment of the present invention. FIG. 7 is an explanatory view of a conventional medium current ion implantation apparatus. FIG. 8 is an explanatory view of another conventional medium current ion implantation apparatus. Explanatory drawing of current ion implantation system [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Ion source, 2 1st sector electromagnet, 3 Mass separation slit, 4 Electrostatic deflector, 5 High voltage terminal, 6 Accelerating tube, 7 2nd sector electromagnet, 8 Substrate, 9 Platen, 10 3rd sector electromagnet ,

Claims (5)

The ions separated by mass are accelerated or decelerated to a predetermined energy, electrostatic scanning of the ion beam within the scanning plane including the reference axis of the beam, and a substrate on which ions are implanted along a straight line perpendicular to the scanning plane. In an ion implantation apparatus combined with a moving mechanical scan, a first sector electromagnet and a mass separation slit are provided in the path of the ion beam, and the beam is scanned in front of the mass separation slit. And a second sector electromagnet having a deflecting surface in front of the accelerating tube and the deflecting surface of the electrostatic deflector. The ion implantation is characterized in that the center of curvature of the arc-shaped electrode of the accelerating tube and the focal point on the entrance side of the second fan-shaped electromagnet coincide with the deflection center of the electrostatic deflector, respectively. apparatus. Ion implantation apparatus according to claim 1, characterized in that a scanning electromagnet instead of the upper Symbol electrostatic deflector. 3. A third sector electromagnet having a deflection surface coinciding with the scanning surface is provided between the mass separation slit and the electrostatic deflector or the scanning electromagnet. The ion implantation apparatus as described. The third sector electromagnet deflecting surface in place of the upper Symbol electrostatic deflector coincides with the scan surface is provided, a portion where sector electromagnet third among the vacuum chamber for passage of the ion beam are provided 2. The ion implantation apparatus according to claim 1, wherein the ion beam is scanned in the scanning plane by being electrically independent and further modulating the potential of ions passing through the third sector electromagnet. The deflection surface of the third sector electromagnet is made to coincide with the deflection surface of the first sector electromagnet for mass separation, and the direction of the magnetic field in the third sector electromagnet is the same as that of the first sector electromagnet. 5. The ion implantation apparatus according to claim 3, wherein the reference axis of the beam at this portion is made S-shaped or Z-shaped by reversing the direction of the magnetic field.

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