JPH025347A - Ion implantation - Google Patents

Abstract

PURPOSE:To improve uniformity by collimating an ion beam with two electrostatic deflection systems and holding an irradiated surface at a required angle. CONSTITUTION:An ion beam which has passed through a primary electrostatic deflection system 24 is collimated with a ground mask 27 and enters a secondary electrostatic deflection system 31. Voltages based on oppositely biased triangular wave scanning signals and approximately synchronous with those of scanning plates 22, 23 respectively of the same directions with those of vertical and horizontal deflection plates 29, 30 are applied to the vertical and horizontal deflection plates 29, 30 to make the ion beam parallel to be an ion beam 21b which passes through a beam adjustment mechanism 32 and a ground mask 33, and is irradiated to a semiconductor wafer 35 on a platen 34. The platen 34 is capable of fixing its inclination to set a required tilting angle to the wafer 35 for preventing channeling. The wafer is further rotated by a rotary mechanism 36 about a rotary axis perpendicular to and passing approximate center of the irradiated surface. Uniformity is considerably improved in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an ion implantation method that facilitates the prevention of channeling.

(Prior Art) In general, ion implantation technology is widely used as a technology for doping an object to be processed, such as a silicon or gallium arsenide substrate, with impurities.

As an ion implanter used for such ion implantation,
For example, in a medium current type ion implanter, as shown in FIG. 4, an ion beam 4 output from an ion beam generator 3 consisting of an ion generator 1, a mass analysis magnet 2, etc. is accelerated by an accelerator 5, After being shaped into a predetermined beam by the quadrupole electrostatic lens 6, it is scanned in the x-y direction by the action of the electric fields of the vertical scanning plate 7 and the horizontal scanning plate 8, collimated by the ground mask 9, and sent to the platen 10.
It is configured to irradiate an object to be processed, such as a semiconductor wafer 11, placed above. In addition, the semiconductor wafer 11
is a desired angle, for example 7@, for the purpose of preventing channeling, etc.
The tilt angle is set to a certain degree.

(Problem to be Solved by the Invention) In the case of forming a shallow junction, for example, implantation is performed with low energy by lowering the accelerating voltage in the accelerator 5. In particular, the channeling phenomenon is a problem. For this reason, it is necessary to set a large tilt angle, but in the case of the conventional fan scanning irradiation type ion implanter mentioned above, it is not possible to set a sufficient tilt angle for the following reasons. There has been a problem in that it is difficult to narrow the distribution of implanted ions and set the center of the distribution to a desired depth.

That is, in the conventional fan-shaped scanning irradiation described above, the beam incidence angle differs depending on the part of the object to be processed, for example, the beam incidence angle differs between the central part and the peripheral part of the semiconductor wafer to which the ion beam is irradiated. Therefore, various problems occur depending on the position of the object to be processed at which the beam incidence angle required to prevent channeling is set.

For example, if the setting position is at the upper part of the slope of the workpiece, the beam incidence angle will be closer to a right angle at the lower part of the slope, making it insufficient to prevent channeling at the lower part of the slope. Further, if the setting position is near the center of the object to be processed, the beam incidence angle becomes too small at the upper part of the slope, resulting in non-uniform ion implantation such as the formation of blind portions due to pattern grooves in the semiconductor wafer, etc.

Furthermore, in ion implantation using fan-shaped scanning irradiation, there is a fundamental problem that, as described above, the beam incidence angle varies depending on the part of the object to be processed, making it difficult to perform uniform ion implantation.

The present invention has been made to address the problems of the prior art, and even when the ion implantation depth is set to be shallow, channeling can be uniformly suppressed over the entire workpiece, thereby improving uniformity in ion implantation work. The purpose of the present invention is to provide an ion implantation method with significantly improved performance.

[Structure of the Invention] (Means for Solving the Problems) That is, the present invention provides an ion implantation method in which ions are implanted into the workpiece by scanning an ion beam onto the workpiece. The ion beam is deflected horizontally and vertically by a first electrostatic deflection system, and then the ion beam from the first electrostatic deflection system is converted into a parallel beam by a second electrostatic deflection system, and the parallel beam is converted into a parallel beam. The ion beam is scanned and irradiated onto the workpiece, which is held so that the irradiation surface is at a desired angle with respect to the parallel beam, and the ion beam implantation angle at each position on the irradiation surface of the workpiece is determined. The feature is that ion implantation is performed at a nearly constant setting.

(Function) In the ion implantation method of the present invention, the ion beam electrostatically scanned in the vertical and horizontal directions by the first electrostatic deflection system is scanned in parallel by the second electrostatic deflection system. It is possible to easily obtain a parallel beam. Then, this collimated ion beam is scanned and irradiated onto the workpiece held at a desired angle of inclination.
It becomes possible to make the beam incidence angle at each position of the object to be processed substantially constant. As a result, when creating a shallow bond, even if the tilt angle of the workpiece is set to a large value, the beam incidence angle at each position on the workpiece remains almost constant, making it easy to channel the entire workpiece. Prevention is easily possible. Furthermore, the occurrence of blinds and non-uniform ion implantation due to differences in beam incidence angles are also prevented.

(Example) Hereinafter, an example in which the ion implantation method of the present invention is applied to a medium current type ion implanter will be described with reference to the drawings. Note that FIG. 1(a) is a plan view of one embodiment, and FIG. 1(b) is a plan view of one embodiment.
) shows its side view.

An ion beam 21 outputted from an ion source (not shown) and shaped into a desired beam shape by an analysis magnet, an accelerator tube, an electrostatic lens, etc. (not shown) is scanned in the vertical direction (hereinafter referred to as the y direction). plate 22 and the horizontal direction (hereinafter referred to as
(referred to as the X direction) enters a primary electrostatic deflection system 24 constituted by a scanning plate 23.

For example, as shown in FIGS. 2 and 3, the y-direction scanning plate 22 and the X-direction scanning plate 23 have a frequency IL7. ! For example, a voltage based on a scanning signal of a triangular wave of frequency 101911 z (Fig. 3 (a)) is applied to the X-direction scanning plate 23 of a triangular wave of 9 Hz (Fig. 2 (a)), and at this time, a voltage is applied between each electrode. Due to the change in the electric field, the incident ion beam 21 is deflected in a predetermined direction, and scanning irradiation of the beam is performed.

Further, in the X-direction scanning plate 23, the applied voltage is controlled so that the ion beam 21 is bent at an offset angle θ, for example 7°, with respect to the beam traveling axis, and neutral ions mixed in the ion beam 21 are Miscellaneous ions such as ions are sorted at this beam bending part and fly in a direction different from the desired ions, for example, in a straight direction 25, and collide with a shield 26 made of carbon, for example, to prevent them from entering the direction of the object to be processed. be done.

In this way, the ion beam that has passed through the primary electrostatic deflection system 24 is collimated by the first ground mask 27, passes through the secondary electron suppression electrode 28, and then passes through the X-direction deflection plate 29 and the X-direction deflection plate 30. The beam enters a secondary electrostatic deflection system 31 consisting of:

For example, as shown in FIG. 2(b), the X-direction deflection plate 29 is applied with a voltage based on a triangular wave scanning signal that is almost synchronized with the Y-direction scanning plate 22 and has a reverse bias, so that the incident ions are The beam 21 is slightly repelled toward the center between the electrodes of the X-direction deflection plate 29, and is turned into a parallel beam with respect to the Y-direction.

The ion beam 21 a that has been converted into a parallel beam in the y direction by the X direction deflection plate 29 then enters the X direction deflection plate 30 . As shown in FIG. 3(b), the X-direction deflection plate 30 is also applied with a voltage based on a triangular wave scanning signal that is almost synchronized with the X-direction scanning plate 23 and has a reverse bias. Parallel beams are also created in the X direction using the same principle as the deflection plate 29.

In this way, the ion beam that has passed through the secondary electrostatic deflection system 31 becomes an ion beam 21b parallel to the x-y direction, and the beam adjustment mechanism 32 and the second
The light passes through the ground mask 33 and is scanned and irradiated onto an object to be processed, such as a semiconductor wafer 35, placed on a platen 34.

Further, the platen 34 can be tilted and fixed to the semiconductor wafer 35 so that a desired tilt angle, for example, a large tilt angle of 10' or more can be set for the purpose of preventing channeling.

Further, the platen 34 is connected to a rotation mechanism 36, and ions are implanted into the semiconductor wafer 35, which is the object to be processed, while being rotated around a rotation axis that passes through approximately the center of the wafer 35 and is perpendicular to the surface to be irradiated. It is configured as follows.

In addition, a ground electrode 3 is arranged on the ion beam irradiation axis so as to sandwich each deflection plate 29, 30 of the secondary electrostatic deflection system.
7.38.39 are for preventing the electric field from sagging at the ends of each deflection plate 29.30.

Ion implantation in an ion implantation apparatus having such a configuration involves scanning ions in parallel by the first and second electrostatic deflection systems into a workpiece that is held at an angle that sufficiently prevents channeling. Ion implantation is performed by scanning and irradiating the beam with a substantially constant beam incidence angle at each position on the irradiated surface.

In this way, in the ion implantation apparatus of this embodiment,
Since a deflection electrode is provided that independently parallelizes the X-direction component and the Y-direction component of the ion beam scanned in the X3/direction, it is possible to easily obtain an accurate parallel beam, and this parallel By scanning and irradiating a beam-formed ion beam, uniform ion implantation processing into a semiconductor wafer can be performed.

By scanning and irradiating this collimated ion beam onto the workpiece held at an angle, it is possible to make the beam incidence angle at each position on the irradiation surface of the workpiece almost constant. . Therefore, even if the tilt angle is set large during ion implantation at low energy, for example, channeling can be uniformly prevented over the entire object to be processed. Furthermore, by performing ion implantation while rotating the object to be processed, the occurrence of blind portions at the bottom and sides of the pattern grooves due to the tilt angle being set can be effectively prevented.

In addition, by performing ion implantation while rotating the workpiece, uniform ion implantation can be performed even if the voltage applied to the electrostatic deflection system fluctuates or noise occurs, and the amount of ions implanted into the semiconductor wafer can be uniformly implanted. improvement can be achieved.

[Effects of the Invention] As explained above, according to the ion implantation method of the present invention, channeling can be uniformly prevented over the entire object to be processed, and ions can be reliably implanted to a desired depth. Not only is this possible, but it can also greatly contribute to improving uniformity in ion implantation processing operations.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention.
a) is a plan view of this embodiment, FIG. 1(b) is a side view thereof, and FIGS. 2 and 3 are diagrams showing waveforms of scanning signals for beam deflection used in one embodiment of the present invention. FIG. 4 is a diagram showing the configuration of a conventional ion implantation device. 21...Ion beam, 22...Y direction scanning plate, 23...X direction scanning plate, 24...
...Primary electrostatic deflection system, 29...Y direction deflection plate, 30...X direction deflection plate, 31...
Secondary electrostatic deflection system, 34... platen, 35.
... Semiconductor wafer, 36 ... Rotating mechanism. Applicant Chiru ψParian Co., Ltd. Agent Patent Attorney Sasa Suyama −

Claims (1)

[Claims] In an ion implantation method in which ions are implanted into a workpiece by scanning an ion beam onto the workpiece, the ion beam ejected from an ion source is horizontally and The ion beam from the first electrostatic deflection system is deflected in the vertical direction, and then the ion beam from the first electrostatic deflection system is converted into a parallel beam by a second electrostatic deflection system, and this parallel beam is directed toward the irradiated surface with respect to the parallel beam. Scanning and irradiating the workpiece held so that the angle is at a desired angle,
An ion implantation method characterized in that ion implantation is performed by setting an ion beam implantation angle at each position of the irradiated surface of the workpiece to be substantially constant.