JPH0821361B2 - Ion implanter and charge neutralizer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ion implantation apparatus and a charge neutralizer used when forming an impurity layer on a semiconductor substrate in a semiconductor manufacturing process.

[Conventional technology]

An ion implantation method is known as a method for forming an impurity layer on a semiconductor substrate. FIG. 3 is a schematic view showing an example of a conventional mechanical scan type device, which is called a high current ion implanter among the ion implanters. The ion implanter 1 is roughly divided into three parts, which are an ion source part 2, a beamline part 3 and an end station part 4, respectively. The ion source unit 2 electrostatically extracts ions from the ion source 5 that generates high-density plasma by arc discharge,
And the extraction electrode system 6 which accelerates. The beam line unit 3 is a magnetic field deflection type mass analyzer 8 that selects only necessary dopant ions from the ion beam 7 emitted from the ion source unit 2, a shaping slit 9 that adjusts the shape of the ion beam 7, and a focus of an analysis magnet. Located and consists of an analysis slit 10 for selecting the required dopant ions. The end station unit 4 includes a Faraday cage 11 for measuring a beam current, a beam catcher 12, a disk 14 on which a semiconductor substrate 13 is placed and which scans the substrate so that the ion beam 7 is uniformly injected into the substrate, and a charge neutralizer. It consists of 15 working electron guns.

Ion implantation is performed as follows using the ion implantation apparatus configured as described above. First, high density plasma is generated using the dopant gas or solid vapor required for the ion source 5. Then, ions are extracted by the extraction electrode system 6 and at the same time, desired acceleration energy is applied. The accelerated ion beam 7 is selected by the mass analyzer 8 as the necessary dopant ions, and the shaping slit 9 and the analysis slit are selected.
At 10 the shape of the ion beam is adjusted and the target is guided.
On the other hand, the substrate 13 is conveyed to the disc 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 is rotated at a predetermined rotation speed as shown in FIG. Such a method is called a mechanical scan method,
Thereby, ion implantation is performed on the entire surfaces of the plurality of substrates 13. The translational movement is performed a plurality of times to improve the 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 product. In the figure, the substrate 13 is, for example, of P conductivity type, a thick field insulating film 20 is formed on the main surface of the substrate 13, and a gate insulating film is formed in a part of the active region between the insulating films 20. Thin insulating film
21 is formed, and the gate electrode 22 is formed on the thin oxide film 21. In this state, the substrate 13 on both sides of the gate electrode 22
It is intended to form an impurity region serving as a source / drain on the top. 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 have N conductivity type.

When performing ion implantation on the insulating film in this way, especially 1 m
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 FIG. 5 is conventionally used. The action of this charge neutralizer accelerates primary electrons emitted from the electron gun 15 with an electric field of about 300 V and irradiates the facing Faraday cage 11 with the electrons, thereby generating secondary electrons 23. Part of this secondary electron 23 is supplied to the substrate 13,
The positive charge accumulated on the gate electrode 22 is neutralized. In this way, dielectric breakdown of the gate insulating film 21 can be prevented.

[Problems to be Solved by the Invention]

In the conventional ion implanter, as described above, the electron gun 15
By irradiation of primary electrons emitted from the Faraday cage 11
The secondary electrons 23 generated from the surface neutralize the positive charges accumulated on the gate electrode 22, but some of the primary electrons reach the substrate 13 by reflection. Therefore, there is a problem that high-speed electrons having an energy of 300 eV charge up the substrate 13 negatively to cause dielectric breakdown due to negative charges, and even if the dielectric breakdown does not occur, the gate insulating film 22 is deteriorated.

The present invention has been made to solve the problems of the conventional ones described above, and optimizes the electron energy of the charge neutralizer, suppresses the charge amount on the substrate 13, and causes the dielectric breakdown of the gate insulating film 22. It is an object to provide an ion implanter and a charge neutralizer capable of optimizing prevention.

[Means for solving the problem]

An ion implantation apparatus according to the present invention includes an ion source, an ion beam optical system including a mass analyzer that selects a desired dopant ion from an ion beam emitted from the ion source, a disk that holds a substrate to be processed, and a vacuum. In an ion implanter consisting of an exhaust system, on the front surface of the substrate to be processed, has an extraction electrode for extracting electrons from the plasma, and a deceleration electrode for decelerating the electrons extracted by the extraction electrode, with an energy of 50 eV or less. A magnetic multipole plasma generator for supplying electrons is arranged.

Further, the charge neutralizer according to the present invention is provided on the front surface of the substrate to be processed, has an extraction electrode for extracting electrons from the plasma, and a deceleration electrode for decelerating the electrons extracted by the extraction electrode. It is provided with a magnetic multi-pole plasma generator that supplies electrons of 50 eV or less and neutralizes the electric charges charged on the substrate to be processed during ion implantation.

[Action]

In the present invention, a magnetic multipole type plasma generator is used as an electron source, and since this magnetic multipole type plasma generator forms a cusp magnetic field without a magnetic field in the plasma, the electron temperature can be increased only by applying an electric field. High density plasma of several eV can be easily extracted. The 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 portion on the semiconductor substrate, and the charge can be neutralized. Therefore, optimal charge neutralization can be performed even when the charge-up amount varies depending on the ion implantation conditions and device conditions.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. First
FIG. 1 is a schematic diagram showing the structure of an ion implanter 30 according to an embodiment of the present invention. Note that the description overlapping with the description of the conventional technique is omitted as appropriate. In the figure, 2 to 10 and 12 to 13 are the same as conventional ones. What is shown in FIG. 1 is different from that shown in FIG. 4 in the following points. That is, the electron source 31 provided with a magnetic multi-pole plasma generator is provided as a charge neutralizer.

FIG. 2 is a diagram showing a schematic configuration of a charge neutralizer 31 which is a main part of the ion implantation apparatus 30. In the figure, 40 is the arc chamber of the plasma generator, which serves as the anode. Reference numeral 41 denotes a cathode, and a permanent magnet (Sm-Co) 42 is arranged on the outer circumference of the arc chamber 40 to form a multicusp magnetic field. A gas cylinder 43 is introduced into the arc chamber 40 through the gas inlet 44. 45 is an extraction electrode, which uses a porous type to extract electrons in a large area. 46 is a deceleration electrode,
It is an electrode that guides the electrons extracted from the arc chamber 40 to the Faraday cage 11. 47 is electron source 31
It is a vacuum pump that differentially exhausts the inside to maintain 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 about 1 × 10 ⁻³ To.
Set to rr. Next, the cathode 41 is directly heated by the current supplied from the filament power source 48 to generate thermionic emission type arc discharge. When the arc current is set to about 3 A at an arc voltage of 50 V, a stable high density plasma with an electron density of about 10 ¹² cm ^-12 can be generated. The electron temperature at this time is 2-3 eV.
Is. After extracting the electrons from the extraction electrode 46 from this plasma, 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 by using the ion implanter 30 including the charge neutralizer configured as described above will be described. First, the ion beam 7 is extracted from the ion source 5, and only the necessary dopant ions are selected by the mass analyzer 8 and the analysis slit 10.

At this time, desired beam energy and beam current are set. On the other hand, the substrate 13 is conveyed to the disc 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 is shown in the figure A.
While rotating at a predetermined rotation speed as described above, translational motion B is performed, and ion implantation is performed on the entire surfaces of the plurality of substrates 13.

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

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

Therefore, it is possible to implant ions without being charged up in the gate electrode 22 even when implanting ions with a beam current of 1 mA or more.

〔The invention's effect〕

As described above, according to the ion implantation apparatus of the present invention, an ion source, an ion beam optical system including a mass analyzer that selects a desired dopant ion from an ion beam emitted from the ion source, and an object to be processed. In an ion implantation apparatus including a disk holding a substrate and a vacuum exhaust system, an extraction electrode for extracting electrons from plasma and a deceleration electrode for decelerating the electrons extracted by the extraction electrode are provided on the front surface of the substrate to be processed. And the energy
Since the magnetic multipole type plasma generator that supplies electrons of 50 eV or less is arranged, it is possible to generate a uniform electron cloud with a large area. Therefore, even if the insulating film is formed on the substrate, charge-up due to ion implantation can be eliminated, and damage due to electrons can be eliminated.

Therefore, there is an effect that an ion implantation apparatus capable of forming a highly reliable semiconductor device can be obtained.

Further, according to the charge neutralizing group according to the present invention, it has an extraction electrode that is disposed on the front surface of the substrate to be processed and that extracts electrons from the plasma, and a deceleration electrode that decelerates the electrons extracted by the extraction electrode. Since it is equipped with a magnetic multi-pole plasma generator that supplies electrons with an energy of 50 eV or less and neutralizes the charges that charge the substrate to be processed during ion implantation, it is possible to create a uniform electron cloud with a large area. Can be generated. Therefore, even if the insulating film is formed on the substrate, there is an effect that a charge neutralizer capable of eliminating charge-up by ions and damage by electrons can be obtained.

[Brief description of drawings]

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 of FIG. 1, and FIG. 3 is a conventional technique of ion implantation. FIG. 4 is a schematic diagram showing the structure of the device, FIG. 4 is a diagram for explaining ion implantation into a semiconductor substrate, and FIG. 5 is an explanatory diagram showing a conventional charge neutralizer. In the figure, 1 is an ion implantation apparatus, 2 is an ion source section, and 3
Is a beam line part, 4 is an end station part, 5 is an ion source, 6 is an extraction electrode system, 7 is an ion beam, 8 is a mass analyzer, 9 is a shaping slit, 10 is an analysis slit, and 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. The same reference numerals in the drawings indicate the same or corresponding parts.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-218142 (JP, A) JP-A-62-103952 (JP, A) Actual development: Sho-59-107473 (JP, U)

Claims (2)

[Claims] 1. An ion source, an ion beam optical system including a mass analyzer for selecting desired dopant ions from an ion beam emitted from the ion source, a disk for holding a substrate to be processed, and a vacuum exhaust system. In the ion implantation apparatus, the front surface of the substrate to be processed has an extraction electrode for extracting electrons from plasma and a deceleration electrode for decelerating the electrons extracted by the extraction electrode, and supplies electrons with an energy of 50 eV or less. An ion implantation apparatus comprising a magnetic multipole plasma generator. 2. An electron supply electrode having an extraction electrode for extracting electrons from plasma and a deceleration electrode for decelerating the electrons extracted by the extraction electrode, the electron being provided on the front surface of the substrate to be processed and having an energy of 50 eV or less. A charge neutralizer comprising a magnetic multi-polarity plasma generator that neutralizes the charges on the substrate to be processed during ion implantation.