Patent Number: 055436153
Section: summary

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a beam charge exchanging apparatus for converting a fast charged particle beam such as an ion beam into a neutral particle beam, the apparatus being employed in the manufacture of semiconductors or the like. 2. Prior Art Conventionally, an apparatus shown in FIG. 7, which is known as a gas cell, has been widely used as a charge exchanging apparatus. The gas cell includes a gas container 6, which is placed in a vacuum container and includes holes 16 through which a charged particle beam is passed. The charged particle beam 1 which is passed through the gas container 6 collides with a gas 3, which is introduced in the gas container through a gas introducing pipe (not shown), whereby charges are exchanged between the charged particle beam and the gas. There is another conventional apparatus called a metallic vapor cell which employs an alkaline metallic vapor such as Li as a gas for the cell. In this apparatus, the charged particle beam 1 is passed through the vapor so as to cause the charged particle to collide with the metallic vapor, whereby charges are exchanged therebetween. In the conventional gas cell, however, since gas 3 is introduced into the gas container 6 located in the vacuum container, the holes 16 of the gas container 6 should be made small to prevent the vacuum from deteriorating due to the diffusion of gas from the gas cell. For this reason, it has been impossible to obtain many gas particles or charged particles in the gas cell. The metallic vapor cell has a similar drawback in that the quantity of beams introduced in the container is limited if the vacuum level is to be maintained has another drawback in that the container body is damaged by the chemically active alkaline metal. According to the charge neutralizing method based on a molecular beam as disclosed in Japanese Patent Laid-Open Appln. No. 5-129096 which has recently been published, the charge exchanging efficiency is low because the number of molecules is limited and, therefore, it is difficult to accomplish a charge exchange for a large quantity of beams. Furthermore, using the aforesaid method to change a large quantity of ion beams into neutral beams requires a large apparatus. Hence, it has been difficult to obtain high-energy neutral particle beams effectively, and the highest possible energy value which could be obtained using this method is limited to a few KeV. Furthermore, in the conventional charge exchanging apparatus, there was no means for immediately measuring the quantity of neutral particles after charge exchange. SUMMARY OF THE INVENTION Therefore, this invention has been made to solve the above problems, and it is an object of the present invention to provide an apparatus which is capable of exchanging the charges of a large quantity of high-energy beams with another media with high efficiency. It is an another object of the present invention to provide an apparatus which is capable of exchanging the charges of a large quantity of high-energy beams with another media with high efficiency and of measuring the quantity of obtained neutral particles. In order to accomplish the first object, the present invention provides a beam charge exchanging apparatus including a gas fluid container disposed in a vacuum and having holes for passing allowing a particle beam to pass through the container; a source of gas; and means for introducing the gas/fluid into the container at a high speed so that the fast particle beam will collide with the high speed gas/fluid in the container and a charge exchange will occur therebetween that converts the particle beam into a neutral particle beam. In order to accomplish the second object, the apparatus further includes means for detecting the quantity of neutral particles resulting from the exchange of charges by detecting the quantity of ionized fluid generated as an electric current. According to the present invention as described above, a charged particle beam is passed through a high speed gas/fluid having directivity in the container so as to convert the charged particle beam into a neutral particle beam. Therefore, the problem in which the high speed gas/fluid diffuses out of the container through the holes can be prevented. Hence, it is possible to make the holes of the container larger to increase the area of contact between the gas/fluid and the charged particle beam within the container, whereby a highly efficient charge exchange can be achieved, leading to the production of higher energy beams. As the charged particle beam is passed through the high speed gas/fluid, the high speed gas/fluid obtains surplus charges resulting from the charge exchange. Accordingly, the high speed gas/fluid is charged, i.e. is ionized. The ionized gas/fluid can be collected on an ion capturing electrode and the quantity of ions in the gas/fluid can be measured by measuring the current flowing through the electrode. Thus, the quantity of the neutral particles in the neutral beam can be measured. The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which preferred embodiments of the present invention are described by way of illustrative examples.