JPH049865B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an ion implantation device used for manufacturing semiconductor devices, and more specifically, the present invention relates to an ion implantation device that is used for manufacturing semiconductor devices, and more specifically, the present invention relates to an ion implantation device that is capable of implanting impurity amounts into a semiconductor substrate etc. more precisely than conventional ion implantation devices. The present invention relates to an improved ion implantation device that can be controlled.

[Technical background of the invention] Ion implantation technology is widely used as a technology for introducing impurities into semiconductors in the manufacture of semiconductor devices, and in the current semiconductor device manufacturing process, so-called medium current ion implantation equipment is the most widespread. .

FIG. 2 is a schematic diagram showing the structure of a medium current ion implantation device that is currently most commonly used. In the figure, 1 is an ion source that generates source plasma, 2 is an extraction electrode for extracting an ion beam from the ion source, 3 is a mass analyzer that selects only the necessary ion beam from the extracted ion beams, and 4 7 is an acceleration tube for accelerating a selected ion beam; 5 is an electrostatic focusing lens for focusing the accelerated ion beam; 6 is a vertical scanning plate for vertically scanning the focused ion beam;
8 is a horizontal scanning plate for scanning the ion beam in the horizontal direction; 8 is a horizontal scanning plate for scanning the ion beam in the horizontal direction; A deflection plate 9 is used to make the neutralized particles (molecules or atoms) in the ion beam go straight and separate them, and 9 is a shielding plate with which the neutralized particles separated from the ion beam collide.
The shielding plate 9 is made of a material such as graphite or Al, which does not produce particles that have a negative impact on the system due to the collision of neutralized particles than the material of the beam tube 11. It is electrically grounded through the main body of the ion implantation apparatus by pasting it on the beam tube 11 or the like. Further, the entire system is maintained at high vacuum by a cryopump and an oil diffusion pump (not shown). Note that since each of these device elements is already well known, detailed explanation thereof will be omitted.

[Problems in the Background Art] When implanting impurity ions into a semiconductor wafer or the like using a known medium current ion implantation device as described above, conventionally, the amount of charge of ions in the sample chamber 12 in which the sample S is placed is measured. However, this method of controlling the amount of implanted impurities has a problem in that it is not possible to accurately control the amount of implanted impurities. That is, in the ion implantation apparatus as described above, although the neutralized particles generated in the path from the acceleration tube 4 to the deflection plate 8 are separated, the neutralized particles generated in the path from the deflection plate 8 to the sample S are separated. This is because particles are injected into the sample S together with ions, so even if the amount of charge of the ions in the sample chamber 12 is measured, the measured value will not match the actual amount of impurities implanted.

Incidentally, it is not uncommon for 10% of the ions to become neutralized on the path from the deflection plate 8 to the sample S, depending on factors such as variations in the degree of vacuum within the system. In addition, none of the conventional ion implanters is equipped with a means for measuring the amount of neutralized particles, whether up to the deflection plate or after the deflection plate.

Therefore, since the known ion implantation apparatus described above cannot control the implantation amount accurately, it has been impossible to achieve high precision in the formation of various layers and films in the manufacture of semiconductor devices.

[Object of the Invention] An object of the present invention is to provide an improved ion implantation device that solves the problems in the known ion implantation devices and is capable of performing ion implantation with higher precision than conventional devices. It is.

[Summary of the Invention] The ion implantation device improved by this invention is characterized by electrically measuring the amount of secondary electrons generated corresponding to the neutralized particles generated in the path from the mass spectrometer to the deflection plate. By doing so, it is possible to estimate the amount of neutralized particles generated on the next path from the deflection plate to the sample. Theoretically, the amount of ion beam current I that becomes neutralized particles from the mass spectrometer 3 to the deflection plate 8 is expressed by the following equation.

I=I ₀ − ₀ e−l/L I ₀ : Initial beam current l : Distance from mass spectrometer to deflection plate L : Mean free path given by degree of vacuum and atomic radius However, actually neutralization The amount of ion beam current that produces particles is considerably different from the theoretical amount I due to differences in ion implantation equipment and operating conditions employed.

In the configuration of the ion implanter of the present invention, the shield plate 9 is insulated from the ion implanter main body and separately grounded, and secondary electron emission at the shield plate 9 (this is caused by neutralized particles colliding with the shield plate 9). A device (or circuit) for measuring current due to the phenomenon in which secondary electrons are generated from the surface of the shielding plate 9 is connected to the grounding circuit of the shielding plate 9. The ion beam current amount I _t that actually becomes a neutral particle is converted.

Therefore, the correction term α for the ion implanter and its operating conditions is calculated from I _t =α·I, and then the beam current amount I that actually produces neutral particles in the path from the deflection plate 9 to the sample S is determined. _s
is estimated by the following equation corrected by the correction term α.

I _s = α (It − I _{t e} −l _s /L _s ) I _t : Initial beam current amount at the deflection plate l _s : Distance from the deflection plate to the sample L _s : From the degree of vacuum and atomic radius In the ion implantation apparatus of the present invention, the amount of neutral atoms and neutral molecules that are neutralized and injected into the sample, causing a miscount of the injection amount, can be estimated. It becomes possible to correct the amount of impurity implanted into the sample.

[Embodiments of the Invention] FIG. 1 is a schematic diagram for explaining the outline of the main structure of an ion implantation device of the present invention and the operation of the device, and in the same figure, the same reference numerals as in FIG. 2 are used. The parts are the same as those of a conventional ion implanter.

The ion implantation apparatus of the present invention shown in FIG. 1 is characterized in that a secondary electron generation amount measuring device 10 is connected to the grounding circuit 9a of the shielding plate 9.

The shielding plate 9 generally has a configuration in which a metal plate is installed, and therefore, when molecules, atoms, or electron particles collide with this, secondary electron emission occurs, and as a result, the ground circuit 9 is connected to the ground. A weak current i is generated. In the present invention, a current measuring device (secondary electron generation amount measuring device 1) using this secondary electron emission is used.
0) was connected to the ground circuit 9a of the shielding plate 9, and the measuring device 10 was electrically connected to the control device of the ion implantation device. Therefore, the amount of neutralized particles generated on the path up to the deflection plate can be electrically measured, and as a result, the amount of neutralized particles generated after the deflection plate and injected into the sample S can be precisely measured. Not only can it be estimated, but also the amount of impurity implanted can be accurately controlled by stopping or correcting ion implantation using the control device of the ion implantation apparatus.

In FIG. 1, arrows N indicate the flow of neutralized particles, and arrows J indicate the flow of ions injected into the sample S. Further, e ⁻ represents secondary electrons generated in the shielding plate 9.

[Effects of the Invention] As is clear from the above explanation, according to the present invention, an improved ion implantation device that can perform ion implantation more accurately than conventional ion implantation devices can be obtained. As a result, elements can be formed with higher precision in manufacturing semiconductor devices.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram schematically showing the main parts of the invention in the device of the present invention and the flow of particles such as ions in the device of the present invention, and FIG. 2 is a schematic diagram of a conventional medium current ion implantation device. . DESCRIPTION OF SYMBOLS 1... Ion source, 2... Extraction electrode, 3... Mass spectrometer, 4... Acceleration coil, 5... Electrostatic focusing lens, 6... Vertical scanning plate, 7... Horizontal scanning plate, 8
... Deflection plate, 9 ... Shielding plate, 9a ... Ground circuit,
10...Secondary electron generation amount measuring device, 11...Beam tube, 12...Sample chamber.

Claims (1)

[Claims of Claims] 1. An extraction electrode that extracts ions generated in the ion source, a mass spectrometry system that selects necessary ions from among the extracted ions, an acceleration system that accelerates the selected ions, and a focusing system that focuses the accelerated ions. system,
A scanning system that controls the focused ion beam to scan the sample surface; a deflection system that separates neutralized particles from within the ion beam and deflects the ion beam toward the sample surface; In an ion implanter equipped with a shielding plate that collides with neutralized particles and a sample chamber in which the deflected ion beam is injected into the sample, the shielding plate is insulated from the ion implanter main body and grounded separately. In addition, a secondary electron generation measuring device for measuring the amount of secondary electrons generated from the shielding plate when the neutralized particles collide with the shielding plate is provided in the grounding circuit of the shielding plate. Ion implantation equipment.