JPH0731996B2 - Ion implanter - Google Patents

Description

TECHNICAL FIELD The present invention relates to an ion implantation apparatus.

(Prior Art) As is well known, this type of device performs mass analysis of ions extracted from an ion source, passes necessary ions through an analysis slit, then accelerates them with an accelerating tube, and then scans them with a scanning electrode. It is designed to be injected into a target such as a wafer.

FIG. 2 shows a conventional ion implanter of this kind. 1 is an ion source, 2 is an extraction electrode, 3 is an analysis magnet that forms a magnetic field for mass analysis, for example, analysis, 4 is an analysis slit, and 5 is an analysis slit.
Is an accelerating tube, 6 is a focusing lens, 7 is a vertical scanning electrode, 8 is a horizontal scanning electrode, and 9 is a target.

The ions generated by the ion source 1 are extracted by the voltage applied between the ion source 1 and the extraction electrode 2, and are made incident on the analysis magnet 3 from there to undergo mass analysis. After that, necessary ions enter the accelerating tube 5 through the analysis slit 4 and are focused by the focusing lens 6. Subsequently, scanning is performed by the vertical scanning electrode 7 and the horizontal scanning electrode 8 and the target 9 is implanted. At this time, a bias voltage for deflecting the beam at a constant angle θ is applied to the horizontal scanning electrode 8 in addition to the scanning voltage in order to remove the neutral particles contained in the ions.

By the way, according to such a configuration, when the ions analyzed by the analysis magnet 3 enter the acceleration tube 5,
It may collide with the residual gas existing in the accelerating tube 5 to generate various kinds of impurity ions. The ions thus generated receive the energy determined by the place where they are generated from the electric field in the accelerating tube 5 and enter the focusing lens 6, and then both the vertical and horizontal scanning electrodes 7, 8
Scanned by.

The trajectory of the impurity ions is different from the required ions and may be removed from the required ions by the above-mentioned deflection, but in many cases, the impurity ions are incident on the target 9. Further, at that time, since the respective charges of the necessary ions and the unnecessary ions are not distinguished from each other, the implantation amount of the necessary ions becomes non-uniform.

Further, in the conventional ion implanter, there is an intrinsic cause of nonuniform implantation as described below. That is, since the bias voltage for eliminating the neutral particles is biased to the scanning voltage for scanning the necessary ions as described above, the speed at which the ions scan the surface of the target 9 is biased. , So that the ion implantation dose is essentially
It becomes non-uniform in the sample plane.

(Problems to be Solved by the Invention) An object of the present invention is to improve the accuracy of ion implantation by avoiding mixing of impurity ions and by eliminating the need for a bias during deflection.

(Means for Solving Problems) The present invention provides a second analysis unit and an analysis slit behind a focusing lens, whereby necessary ions are
That is, it is characterized in that it is separated from impurity ions or neutral particles, and only the necessary ions are scanned by both vertical and horizontal scanning electrodes and injected into the target.

(Embodiment) An embodiment of the present invention will be described with reference to FIG.

In addition, the same reference numerals as those in FIG. 2 indicate the same or corresponding portions. According to this invention, behind the acceleration tube 5,
More specifically, the second analysis unit 10 is arranged behind the focusing lens 6 and before the vertical scanning electrode 7. This analysis department
A second analysis slit 11 is installed behind 10.

The analysis unit 10 and the analysis slit 11 are for separating and removing the impurity ions and neutral particles described above from the necessary ions. The analysis unit 10 may be configured by an electrostatic deflection plate instead of the analysis magnet.

In the above configuration, of the ions focused by the focusing lens 6 through the accelerating tube 5, the impurity ions and neutral particles contained therein are separated from the necessary ions by the analysis unit 10 and the analysis slit 11. . This separation is the same as the analysis operation by the analysis magnet 3, and a magnetic field or an electric field determined by the separation target ions or the like may be formed in the analysis section 10. Further, the analysis slit 11 has impurity ions, neutral particles have a certain width in energy,
Although there is a variation in the angle of deflection in the analysis unit 10 depending on the energy, this is also for effectively eliminating this variation.

Necessary ions analyzed by the analysis unit 10 and the analysis slit 11 are subsequently scanned by both the vertical and horizontal scanning electrodes 7 and 8 and injected into the target 9. At this time, the traveling direction of the ions is parallel to the scanning electrode, and thus it is not necessary to apply a bias as in the conventional case. Therefore, it suffices to apply only the voltage necessary for scanning to each scan electrode, so that the non-uniform injection due to the application of the bias voltage can be eliminated.

(Effects of the Invention) As described in detail above, according to the present invention, it is possible to prevent the mixing of impurity ions and to eliminate the need for bias deflection, thereby achieving uniform ion implantation.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a sectional view of a conventional example. 1 ... Ion source, 3 ... Mass spectrometric section, 4 ... Analysis slit, 7 ... Vertical scanning electrode, 8 ... Horizontal scanning electrode, 9 ...
Target, 10 ... Second analysis section, 11 ... Second analysis slit,

Claims (1)

[Claims] 1. An ion source, a mass analyzer for analyzing ions from the ion source, an accelerating tube for accelerating the ions analyzed by the mass analyzer, and a focusing lens for focusing the ions from the accelerating tube. And a scanning electrode which scans ions from the focusing lens, in a rear stage of the focusing lens and before the scanning electrode, impurity ions, neutral particles, etc. are separated from necessary ions. An ion implantation apparatus in which an analyzing section and an analyzing slit are provided, and the scanning electrode is installed in parallel with a traveling direction of necessary ions from the analyzing slit.