JPH0815063B2 - Ion beam irradiation apparatus and ion beam irradiation method - Google Patents

Description

DETAILED DESCRIPTION [Overview] Ion beam selection means for selectively passing an ion beam irradiated from an ion source and separated by its mass, and ion beam selection means for rapidly diverging the ion beam. An ion beam irradiation device equipped with a lens for collimating the ion beam and a parallelism measuring means for measuring the parallelism of the ion beam, and an ion beam irradiated by an ion source and separated by its mass is selected as the ion beam. The ion beam that is selectively diverged by means of the ion beam selection means and is rapidly diverged by the ion beam selection means is collimated by using a lens, and the parallelism measuring means for measuring the parallelism of the ion beam is used. Measures and determines the degree of convergence of this lens based on the detection output of the parallelism measuring means that measures the parallelism of this ion beam BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion beam irradiation apparatus and an ion beam irradiation method, and more particularly to an improvement for injecting a large current ion beam into a wide area at a small irradiation angle. Is.

Ion beam irradiation devices are widely used for implanting impurities into semiconductor substrates, but in recent years, increased current has been promoted in order to increase throughput in high dose regions,
A device with a beam current of 10 mA or more is also in practical use.

In order to efficiently transport these beams of 10 mA or more, it is necessary to make the beam line through which the beam passes as short as possible, and a device to shorten the distance from the ion beam selection means to the wafer has been developed. It is about 80 cm.

On the other hand, it is necessary to increase the irradiation area in order to prevent problems such as destruction of the insulating film due to discharge due to sewage-up and temperature rise due to conversion of kinetic energy of ion beam for semiconductor wafer target of high current beam. The vertical or horizontal dimension is 4 cm or more.

Under the circumstances as described above, there is a demand for an ion beam irradiation apparatus and an ion beam irradiation method capable of injecting a large current ion beam into a large area at a small irradiation angle.

[Conventional technology]

In a conventional ion beam irradiation apparatus, an ion beam emitted from an ion beam source (not shown) is separated by a mass analyzer (not shown) by utilizing a mass difference, and the converged ion beam 12 is ion beam selection means, for example, a second ion beam selection means. It is designed to be introduced into the analysis hole 1 shown in the figure.

As shown in FIG. 2, the divergent beam 12a that has diverged after passing through the mass analysis hole 1 diverges while reaching the wafer 5 from the mass analysis hole 1 and is irradiated on the wafer 5.

The acceleration voltage of the ion beam source has recently increased to 200K
A large amount of V has come to be used, but in such a case various obstacles will occur if the irradiation area is small, so in order to irradiate a large amount of ion beam, It was necessary to irradiate a large area so as to reduce the beam current of.

For that purpose, the distance between the mass analysis hole 1 and the wafer 5 is increased to sufficiently diverge the divergent beam 12a that has passed through the mass analysis hole 1. However, this is disadvantageous in terms of beam transport efficiency as described above. Is. Therefore, when it is attempted to sufficiently diverge the divergent beam 12a in a short distance, the irradiation angle θ becomes larger as the divergent beam 12a diverges than in the vertical irradiation.

[Problems to be solved by the invention]

The problem with the conventional ion beam irradiation apparatus described above is that the acceleration voltage of the ion beam source increases,
When a wafer is irradiated with a large current beam, problems such as dielectric breakdown due to charge-up and temperature rise will occur.To prevent this, increase the irradiated area and reduce the beam current per unit area. It is necessary to sufficiently diverge the ion beam for this purpose, but if the distance between the mass analysis hole and the wafer is made long in order to diverge the ion beam, the beam transport efficiency will decrease. This means that the ion beam must be sufficiently diverged in a short distance, and the irradiation angle is inevitably larger than that in vertical irradiation.

For example, if you spread it to 6 cm within 20 cm, the beam divergence angle is 1
It becomes 7 °. This means that when viewed from the target side, the beam incident angle becomes the central value ± 8.5 °,
This has adverse effects such as a decrease in the shadowing effect and an increase in the amount of the ion beam under the mask.

All of these impede device miniaturization and high integration.

The present invention has an object to provide an ion beam irradiation apparatus and an ion beam irradiation method in which the irradiation angle does not increase even if the irradiation area is increased in the above situation.

[Means for solving problems]

The ion beam irradiation apparatus of the present invention includes an ion beam selection means for selectively passing an ion beam irradiated by an ion source and separated by its mass, and the ions diverged rapidly by the ion beam selection means. The ion beam irradiation method of the present invention is configured so as to include a lens for collimating a beam and a parallelism measuring means for measuring the parallelism of the ion beam. The ion beam selectively passing through the ion beam selecting means, parallelizing the ion beam selected by the ion beam selecting means and rapidly diverging using a lens, and Measurement process using parallelism measuring means for measuring parallelism, and parallelism measurement for measuring parallelism of this ion beam Based on the detection output of the stage, determines the convergence degree of the lens is configured to include a step of adjusting.

[Action]

That is, in the present invention, the ion beam diverging after passing through the ion beam selecting means can be made parallel by a lens provided between the ion beam selecting means and the target disk on which the wafer is mounted. It becomes possible to vertically irradiate a large current beam onto a region on the wafer surface having an area larger than the area of the holes of the selecting means, and the ion beam parallelism measuring means is provided, and the ions measured by the parallelism measuring means are provided. Since the convergence of this lens is adjusted by the detection output of the beam, it becomes possible to irradiate a parallel ion beam with a small irradiation angle.

〔Example〕

 An embodiment of the present invention will be described below with reference to FIG.

As shown in FIG. 1 (a), in the present embodiment, the ion beam emitted from the ion beam source (not shown) is separated by a mass analyzer (not shown) by utilizing the mass difference, and converges more rapidly than before. The ion beam 2 thus generated is subjected to ion beam selection means, for example, the mass analysis hole 1 shown in the figure.
It is supposed to be introduced in.

The divergent beam 2a diverged after passing through the mass analysis hole 1 is composed of three electrodes, and the focal length is controlled by the voltage applied to the central electrode. When passing through the electrostatic lens 3 whose distance is equal to the distance, a parallel ion beam 2 of ± 1 ° is formed, which is irradiated onto the wafer 5 mounted on the target disk 4.

The target disk 4 reciprocates in a direction perpendicular to the irradiation direction of the ion beam 2 while rotating about its central axis, so that the wafer 5 on the target disk 4 is uniformly irradiated with the ion beam 2. Has become.

In the ion beam irradiation apparatus having such a configuration,
The ion beam 2 is rapidly diverged to a large area after passing through the mass analysis hole 1 to become a divergent beam 2a, so that the beam current per unit area can be reduced, but since it is diverged rapidly, When irradiating the wafer 5 as it is,
The irradiation angle remarkably increases, the shadowing effect decreases, and the amount of the ion beam 2 penetrating under the mask increases, which hinders the miniaturization and high integration of devices formed on the wafer 5.

Therefore, an electrostatic lens 3 is arranged between the mass analysis hole 1 and the wafer 5 so that the divergent beam 2a can be converted into a parallel ion beam 2 and can be irradiated onto the wafer 5.

In this case, between the electrostatic lens 3 and the wafer 5, as shown in FIG. 1 (b), the measuring electrodes 7 are provided at the ends of the cylinders of substantially parallel ground potential at both ends of the irradiation region of the ion beam 2. The current value of the ion beam 2 flowing into the electrode 7 is measured by an ammeter 8 and the electrostatic lens power source 6 is controlled so that the current value is maximized to measure the parallelism for correcting the convergence state of the ion beam 2. The parallelism of the ion beam 2 by ± 1
Stabilized to °.

As the lens, a magnetostatic lens, a plasma lens, or the like can be used in addition to the electrostatic lens 3 described above.

In this way, the ion beam 2 is separated and rapidly converged by a mass analyzer (not shown), and the ion beam 2 is rapidly diverged by the mass analysis hole 1 into a divergent beam 2a,
The electrostatic lens 3 makes the divergent beam 2a a parallel ion beam 2, and the parallelism measuring means can stabilize the parallelism of the ion beam 2 to ± 1 °.

〔The invention's effect〕

As described above, according to the present invention, the ion beam is separated and rapidly converged by the mass analyzer, the ion beam is rapidly diverged by the weight analysis hole, and the distance between the mass analysis hole and the wafer is shortened, which is extremely simple. By providing a lens and an ion beam parallelism measuring means of various configurations, it becomes possible to convert an ion beam into a parallel ion beam of ± 1 ° and irradiate a large area on the wafer surface, thereby reducing the shadowing effect. It has the advantage of being able to prevent an increase in the amount of ion beam penetrating under the mask and the like, and is extremely industrially useful because it can be expected to have a significant economic and quality improving effect.

[Brief description of drawings]

FIG. 1 is a view showing an embodiment according to the present invention, FIG. 2 is a side sectional view showing a conventional ion beam irradiation apparatus,
Is. In the figure, 1 is a mass analysis hole, 2 is an ion beam, 2a is a divergent beam,
3 is an electrostatic lens, 4 is a target disk, 5 is a wafer, 6 is an electrostatic lens power source, 7 is a measuring electrode, and 8 is an ammeter.

Claims (2)

[Claims] 1. An ion beam selection means for selectively passing an ion beam irradiated by an ion source and separated by its mass, and the ion beam selected by the ion beam selection means and rapidly diverged. And a parallelism measuring means for measuring the parallelism of the ion beam. 2. A step of selectively passing an ion beam, which is irradiated by an ion source and separated by its mass, by using an ion beam selecting means, and the ions which are selected by the ion beam selecting means and are rapidly diverged. A step of collimating the beam using a lens, a step of measuring the parallelism of the ion beam using a parallelism measuring means, and a detection output of the parallelism measuring means of measuring the parallelism of the ion beam. Based on the above, a step of determining and adjusting the degree of convergence of the lens is provided.