JPH03134947A - Ion implantation device - Google Patents

Abstract

PURPOSE:To have optimum neutralization of electric charges even in the case with different charge-up amounts by using an electron source which is a multiple magnet pole type plasma generator capable of supplying low energy stably to the front face of a target base board. CONSTITUTION:As an electric charge neutralizer is installed an electron source 31 which is equipped with a multiple magnet pole type plasma generator. Ion beam 7 is drawn out of an ion source, and only necessary dopant ions are selected by a mass spectrometer 8 and an analyzing slit 10. At this time, the beam energy and beam current is set to respective desired values. On the other hand, a base board 13 is transported to a disc 14 and located in place. Then the disc 14 is rotted in the arrow A direction and at the same time put in parallel motion shown by the arrow B. The electric charge neutralizer is set in such a condition that electrons are fed into a Faraday cage prior to ion implantation to the base board 13 and that electrons having an energy below 30eV are supplied to the front face of the base board 13. This enables neutralization by the electron cloud at the front face of base board even though the ion implantation charges positively the gate electrode on the base board.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ion implantation device used for forming an impurity layer on a semiconductor substrate in a semiconductor manufacturing process.

[Conventional technology]

Ion implantation is a method for forming an impurity layer on a semiconductor substrate. FIG. 3 is a schematic diagram showing an example of a conventional mechanical scan type ion implanter, which is called a high current ion implanter among ion implanters. This ion implanter 1 is roughly divided into three parts, each with an ion source part 2.
, a beam line section 3, and an end station section 4.

The ion source section 2 includes an ion source 5 that generates high-density plasma by arc discharge, and an extraction electrode system 6 that electrostatically extracts and accelerates ions.

The beam line section 3 includes a magnetic field deflection type mass analyzer 8 that selects only necessary dopant ions from the ion beam 7 emitted from the ion source section 2, a shaping slit 9 that adjusts the shape of the ion beam 7, and a focal point of an analysis magnet. It consists of an analysis slit 10 for selecting the desired dopant ions.

The end station section 4 includes a Faraday cage 11 for measuring beam current, a beam catch 12, and a semiconductor substrate 1.
It consists of a disk 14 on which an ion beam 7 is placed and scanned so that the ion beam 7 is uniformly implanted into the substrate, and an electron gun 15 which functions as a charge neutralizer.

Ion implantation is performed in the following manner using the ion implantation apparatus configured as described above. First, a high-density plasma is generated using a dopant gas or solid vapor necessary for the ion source 5. Next, the extraction electrode system 6 extracts the ions and at the same time applies desired acceleration energy. The accelerated ions adjust the shape of the ion beam and guide it to the target. On the other hand, the substrate 13 is transported to the disk 14 and placed at a predetermined position. At this time, a plurality of substrates 13 are usually placed.

Next, the disk 14 in the initial position rotates at a predetermined number of rotations as shown in the figure, and a translational movement B is performed. Such a method is called a mechanical scan method, and ions are implanted into the entire surfaces of the plurality of substrates 13 using this method. Note that the translational movement is performed multiple times to improve injection uniformity.

By the way, when this ion implantation is performed, a pattern is usually already formed on the substrate 13. FIG. 4 shows an example of the patterned material. The figure shows the board 13
is of the P conductivity type, for example, and a thick field insulating film 20 is formed on the main surface of this substrate 13, and a thin insulating film 21 that becomes a gate insulating film is formed in a part of the active region in the region sandwiched between these insulating films 20. is formed, and a gate electrode 22 is formed on this thin oxide film 21. In this state, gate electrode 2
This is intended to form impurity regions that will become sources and drains on the substrate 13 on both sides of the substrate 20.

In this case, the ion beam 7 is, for example, an ion beam of phosphorus, arsenic, or the like in order to form the source/drain to be of N conductivity type.

When performing ion implantation onto an insulating film in this way, especially
When ion implantation is performed with a beam current of A or more, there is a high possibility that dielectric breakdown of the gate insulating film 21 will occur. In order to prevent this dielectric breakdown, a charge neutralizer as shown in Figure 5 has conventionally been used. The action of this charge neutralizer is to accelerate the primary electrons emitted from the electron gun 15 with an electric field of about 300V and irradiate them onto the Faraday cage 11 facing the faraday cage 11, thereby generating secondary electrons 23. A part of the secondary electrons 23 is supplied to the substrate processing 3 and neutralizes the positive charges accumulated on the gate electrode 22. In this way, dielectric breakdown of the gate insulating film 21 can be prevented.

[Problem to be solved by the invention]

In the conventional ion implanter, as described above, the electron gun 15
Faraday cage 1 by irradiation with primary electrons emitted from
Although the positive charges accumulated on the gate electrode 22 are neutralized by the secondary electrons 23 generated from one surface, some of the negative electrons also reach the substrate 13 by reflection. For this reason 30
There is a problem in that high-speed electrons with an energy of 0 eV charge up the substrate 13 negatively, causing dielectric breakdown due to the negative charge, and deteriorating the gate insulating film 22 even if dielectric breakdown does not occur.

The present invention has been made to solve the problems of the conventional ones as described above, and it optimizes the electron energy of the charge neutralizer, suppresses the amount of charge on the substrate 13, and reduces the amount of charge on the gate insulating film 2.
It is an object of the present invention to provide an ion implantation device capable of optimizing prevention of dielectric breakdown (2).

[Means to solve the problem]

The ion implantation apparatus according to the present invention is configured to use a magnetic multipolar plasma generator as a charge neutralizer, extract electrons from the plasma generator, and generate an electron cloud on the front surface of a semiconductor substrate serving as a target. It is.

[Effect]

In the present invention, a magnetic multipole plasma generator is used as an electron source, and since this magnetic multipolar plasma generator forms a cusp magnetic field with no magnetic field in the plasma, the electron temperature can be changed simply by applying an electric field. High-density plasma of several eV can be easily extracted. These low-energy electrons are supplied to the front surface of the target semiconductor substrate to generate an electron cloud. Therefore, electrons are supplied only to the positively charged portions of the semiconductor substrate, and the charges can be neutralized. Therefore, optimal charge neutralization can be performed even when the charge-up amount varies depending on ion implantation conditions and device conditions.

〔Example〕

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

FIG. 1 shows an ion implantation device 3 according to an embodiment of the present invention.
FIG. 2 is a schematic diagram showing the configuration of 0. Note that the description of parts that overlap with the description of the conventional technology is omitted as appropriate. In the figure, 2 to 10 and 12 to 13 are the same as the conventional one. The difference between what is shown in FIG. 1 and what is shown in FIG. 4 is as follows. That is, an electron source 31 equipped with a magnetic multipolar plasma generator as a charge neutralizer.
The point is that the .

FIG. 2 is a diagram showing a schematic configuration of a charge neutralizer 31, which is a main part of this ion implantation device 30. In the figure, 40
is the arc chamber of the plasma generator and serves as the anode. 41 is a cathode, and a permanent magnet (Sm-Co) 42 is arranged around the outer periphery of the arc chamber 40 to form a multi-cusp magnetic field. 43 is a gas cylinder, gas inlet 4
4 into the arc chamber 40. 45 is an extraction electrode, and a porous type was used to extract electrons over a large area. 46 is a deceleration electrode, which is an electrode that guides electrons extracted from the arc chamber 40 to the Faraday cage 11. 47 is a vacuum pump that differentially pumps the inside of the electron source 31 and maintains a high vacuum inside the Faraday cage 11.

The electron source 31 configured as described above operates as follows. First, a rare gas such as Ar, Kr, or Xe is introduced into the arc chamber 40 and the pressure is set to approximately 1×10″3 TOrr.

Next, the cathode 41 is directly heated by a current supplied from the filament power source 48, and a thermionic emission type arc discharge is generated. When the arc voltage is 50V and the arc current is about 3A, a stable high-density plasma with an electron density of about lO"c+ff12 can be generated. Also, the electron temperature at this time is 2 to 3 eV. From this plasma, the extraction electrode 46
After extracting more electrons, the deceleration electrode 46 decelerates the electrons accelerated by the extraction electrode. During this time, the inside of the electron source 31 is constantly evacuated by the vacuum pump 47.

Next, a method for implanting ions into the substrate 13 using the ion implantation bag 230 equipped with the charge neutralizer configured as described above will be described. First, the ion beam 7 is extracted from the ion source 5, and only necessary dopant ions are selected by the mass spectrometer 8 and the analysis slit 10.

At this time, set the desired beam energy and beam current. On the other hand, the substrate 13 is transported to the disk 14,
It is placed in a predetermined position. At this time, a plurality of substrates 13 are usually placed. Next, the disk 14 at the initial position rotates at a predetermined rotational speed as shown in the figure A, and a translational movement B is performed, so that ions are implanted into the entire surface of the plurality of substrates 13.

By the way, the charge neutralizer supplies electrons into the Faraday cage 11 from an electron source before ion implantation into the substrate 13.

As a result, even if the gate electrode 22 on the substrate 13 is positively charged by ion implantation, it is neutralized by the electron cloud formed on the front surface of the substrate 13.

Therefore, even when ion implantation is performed with a beam current of 1 mA or more, it is possible to implant ions without charging up the gate electrode 22.

〔Effect of the invention〕

As described above, according to the ion implantation apparatus according to the present invention, since the electron source is a magnetic multipole plasma generator that can stably supply low energy to the front surface of the target substrate, a uniform electron cloud can be generated over a large area. can be generated. Therefore, even if an insulating film is formed on the substrate, charge-up due to ion implantation can be eliminated, and damage caused by electrons can also be eliminated.

Therefore, there is an effect that a semiconductor device with high reliability can be formed.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the configuration of an ion implantation apparatus according to an embodiment of the present invention, FIG. 2 is an explanatory diagram showing the structure of the charge neutralizer shown in FIG. 1, and FIG. 3 is a conventional ion implantation method. FIG. 4 is a schematic diagram showing the configuration of the device, FIG. 4 is a diagram explaining ion implantation into a semiconductor substrate, and FIG. 5 is an explanatory diagram showing a charge neutralizer of late prior art. In the figure, 1 is an ion implanter, 2 is an ion source, and 3 is an ion implanter.
is a beam line section, 4 is an end station section, 5 is an ion source, 6 is an extraction electrode system, 7 is an ion beam, 8 is a mass spectrometer, 9 is a shaping slit, 10 is an analysis slit,
11 is a Faraday cage, 13 is a substrate, 14 is a disk, 15 is an electron gun, 20 is a field insulating film, 21 is a gate insulating film, 22 is a gate electrode, 23 is a secondary electron, 31 is an electron source, 40 is an arc chamber 41 is a cathode, 42 is a permanent magnet, 43 is a gas cylinder, 44 is a gas inlet, 45 is an extraction electrode, 46 is a deceleration electrode, and 47 is a vacuum pump. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) An ion beam system consisting of an ion source, an ion beam optical system including a mass analyzer that selects desired dopant ions from the ion beam emitted from the ion source, a disk that holds the substrate to be processed, and a vacuum evacuation system. An ion implantation apparatus characterized in that a magnetic multipolar plasma generator for supplying electrons with an energy of 50 eV or less is disposed in front of the substrate to be processed.