JPH0432568A - Ion treating device - Google Patents

Abstract

PURPOSE:To subject a work to an ion treatment while surely neutralizing the charges of the work by neutralizing the positive charges generated in the work with the electrons from an electron source consisting of the electron source consisting of an indirectly-heated cathode having a thermal filaments and a heater. CONSTITUTION:A semiconductor wafer 4 held on the inner side face of a disk 3 is irradiated with an ion beam 1 consisting of positive ions. An electron supplying mechanism 5 is provided in the prescribed position of the above-mentioned ion beam introducing pipe 2. The indirectly-heated cathode 8 therein is constituted of a heater 8a, an insulating member 8b on the outer side thereof and further a thermal filament 8c as a thermion generating body covering the outer side thereof. Further, an electron drawing out electrode 10 and an electric field limiting electrode 11 are disposed between the cathode and the ion beam introducing pipe 2. While the electrons (e) generated by this indirectly-heated cathode 8 are controlled, the electrons are fed into the ion beam introducing pipe 2 and are supplied to the semiconductor wafer 4. The energy of the electrons are accurately and uniformly controlled in this way and the work is subjected to the ion treatment while the charges of the work are surely neutralized.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to an ion processing device.

(Prior Art) Ion processing apparatuses, such as ion implantation apparatuses, have been widely used in recent years as apparatuses for introducing impurities into objects to be processed. Since this ion implantation apparatus can control the implantation amount, implantation depth, etc. with high precision, it is becoming an indispensable apparatus especially when introducing impurities into semiconductor wafers.

Generally, in ion implantation technology, positively charged ions are accelerated by an electric field and irradiated onto a semiconductor wafer.
In ion implantation equipment with high current (about several amperes), when accelerated positive ions collide with the semiconductor wafer, electrons are knocked out of the semiconductor wafer and positive charges accumulate on the surface of the insulator. , the surface of the semiconductor sea urchin is easily charged positively. For this reason, there is a possibility that an insulator portion (insulating film) formed on a semiconductor wafer may be damaged by electrostatic discharge due to accumulated positive charges, especially in today's highly integrated semiconductor wafer. Therefore, in the ion implantation apparatus, it is necessary to prevent the semiconductor wafer from being charged with electricity due to ion implantation.

For this reason, conventional methods have been used, for example, to collide high-energy primary electrons with the inner wall surface of an ion beam introduction tube to generate low-energy (for example, several electron volts) secondary electrons, and then supply these secondary electrons to semiconductor wafers. An ion implantation apparatus is used which is equipped with an electron supply device that neutralizes positive charges accumulated in a semiconductor wafer.

In such ion implantation equipment, high-energy primary electrons reflected from the inner wall of the ion beam introduction tube are supplied to the semiconductor wafer, and as a result, an excessive number of electrons are supplied onto the semiconductor wafer, and negative charges accumulate on the semiconductor wafer. However, the insulating film may be destroyed.

Note that due to ion beam irradiation, the resist adhered to the surface of the semiconductor wafer may be scattered and the inner wall of the ion beam introduction tube may be contaminated by this resist. This risk is especially increased when contaminated with chlorine, because negative charges are accumulated there and negative electrons are more likely to be reflected.

Furthermore, in recent years, as semiconductor devices have become more highly integrated, insulating films formed on semiconductor wafers have also tended to be thinner, resulting in lower resistance to electrostatic breakdown. For this reason, the above-described electrostatic breakdown of the insulating film is becoming a particularly serious problem.

In addition, in order to solve such problems, for example,
No. 2-298357 and other publications propose an apparatus for generating thermoelectrons from a filament, extracting the thermoelectrons with an electron extracting electrode, and supplying the thermoelectrons to a semiconductor wafer to neutralize the positive charge on the semiconductor wafer.

In such an apparatus, it is easier to control the energy of electrons supplied to the semiconductor wafer than in the above-described apparatus that generates secondary electrons from primary electrons. Therefore, it is possible to prevent the semiconductor wafer from being excessively supplied with high-energy electrons, becoming negatively charged, and destroying the insulating film due to accumulation of negative charges.

(Problem to be solved by the invention) However, even in the above-mentioned ion processing apparatus, it is possible to control the energy of electrons supplied to the semiconductor wafer accurately and uniformly, and to reliably reduce the charge on the semiconductor wafer. Naturally, it is required to carry out the ion treatment while neutralizing.

The present invention has been made in response to such conventional circumstances, and it is possible to precisely and uniformly control the energy of electrons supplied to the object to be processed, while reliably neutralizing the electric charge of the object to be processed. The present invention aims to provide an ion processing apparatus capable of performing ion processing.

[Structure of the Invention] (Means for Solving the Problems) That is, the present invention provides means for irradiating an object to be treated with an ion beam, and electrons generated by this means to neutralize positive charges on the object to be treated. The ion processing apparatus is characterized in that the electron source of the electron supply means is constituted by an indirectly heated cathode equipped with a hot filament and a heater.

The present invention also provides a means for irradiating an ion beam onto a workpiece, and an electron supply means for supplying electrons generated by an electron source to the workpiece to neutralize positive charges on the workpiece. The ion processing apparatus is characterized in that the electron source is constituted by a plurality of filaments that are divided in the longitudinal direction and connected in parallel to a power source.

(Function) In the ion processing apparatus according to claim 1 of the present invention having the above configuration, the electron source of the electron supply means for neutralizing the positive charge generated in the object to be processed is provided with a hot filament and a heating heater. It consists of a thermal cathode.

Further, in the ion processing apparatus according to claim 2 of the present invention, the electron source is constituted by a plurality of filaments that are divided in the longitudinal direction and connected in parallel to a power source.

Therefore, it is possible to suppress the potential gradient generated in the longitudinal direction of the electron source due to the electrical resistance, and it is possible to equalize the energy of electrons emitted from each part of the electron source. Therefore, the energy of electrons supplied to the object to be processed can be uniformly controlled with high precision, and ion processing can be performed while reliably neutralizing the electric charge of the object to be processed.

Therefore, for example, it is possible to prevent the insulating film formed on the surface of the semiconductor sea urchin l\ from being damaged by electrostatic discharge due to the accumulation of positive or negative charges, and to perform a good ion treatment.

(Example) Hereinafter, an example in which the present invention is applied to an ion implantation device will be described with reference to the drawings.

As shown in Figure 1, an ion beam 1 consisting of positive ions
A disc 3 shaped like a disc is provided at the end of the ion beam introduction tube 2 for guiding the ion beam. A plurality of (for example, more than ten) semiconductor wafers 4 are held on the inner surface of the disk 3, and the configuration is such that each semiconductor wafer 4 is irradiated with the ion beam 1 while the disk 3 is rotated as shown by the arrow in the figure. has been done.

As is well known, an ion source, an ion extraction electrode, a mass spectrometry magnet, an acceleration tube, a deflection electrode (all not shown), etc. are provided on the side of the ion beam introduction tube 2 from which the ion beam 1 comes. A desired ion beam 1 is formed by these devices.

Further, an electron supply mechanism 5 is provided at a predetermined portion of the ion beam introduction tube 2 near the disk 3, for example, at the top.

That is, as shown in FIG. 2, an electron supply mechanism 5 made of a conductive material such as aluminum is installed on the outside of the upper part of the ion beam introduction tube 2 via an insulating member 6 made of ceramic or the like. A housing 7 is provided.

Also, inside the housing 7 is an indirectly heated cathode 8 as an electron source formed in the shape of a rod, for example, a round rod, and the electrons e emitted from the indirectly heated cathode 8 are reflected in the direction of the ion beam introduction tube 2. A concave reflective plate 9 is provided.

The indirectly heated cathode 8 includes a round rod-shaped heater 8a provided on the shaft core, an insulating member 8b made of a material such as ceramics, and provided in an annular shape so as to cover the outside of the heater 8a, and this insulating member It is composed of a thermoelectron generator, such as a hot filament 8C, which is provided so as to cover the outside of 8b. Then, by energizing the heater 8a, the hot filament 8C is heated and the hot electrons e are emitted from the hot filament 8c. A plurality of such cathodes 8 may be arranged in parallel as required, or may be formed into a planar cathode.

Furthermore, the insulating member 6 provided between the ion beam introduction tube 2 and the ion beam introduction tube 2 is provided with electron extraction electrodes 1 and 1 in order from the housing 7 side.
0 and the electric field limiting electrode 11 are held.

The electron extraction electrode 10 is for extracting electrons e from the indirectly heated cathode 8 into the ion beam introduction tube 2, and as shown in FIG. , and a mesh 10b made of a conductive member fixed to the frame 10a, and is configured so that electrons can pass through the openings of the mesh 10b.

Further, the electric field limiting electrode 11 is for limiting the electric field formed in the ion beam introduction tube 2 by the electron extraction electrode 10, and is configured in a mesh shape like the electron extraction electrode 10 described above. A pulsed electronic cutoff voltage may be appropriately applied to any of the electrodes 10, 11 to control the amount of electrons.

In the ion implantation apparatus of this embodiment having the above configuration, the ion beam introduction tube 2 and the housing 7 are kept at the same potential (for example, OV). Then, the semiconductor wafer 4 is irradiated with the ion beam 1. At the same time, the power supply 12 supplies electricity to the heater 8a of the indirectly heated cathode 8 to heat the hot filament 8c, and the power supply 13 applies a predetermined voltage to the hot filament 8c, for example -5.
(2) A predetermined voltage is applied to the reflector 9 by the power supply 14, for example, -30V.
, by applying a predetermined voltage, e.g., +50V, to the electron extraction electrode 10 by the power supply 15 and a predetermined voltage, e.g., +50V, to the electric field limiting electrode 11 by the power supply 16, electrons e are sent into the ion beam introduction tube 2 from the hot filament 8C, Supply electrons e to the semiconductor sea urchin/%4.

At this time, the electrons e emitted from the hot filament 8C of the indirectly heated cathode 8 and supplied to the semiconductor urchin/X4 have energy corresponding to the potential difference between the semiconductor wafer 4 and the hot filament 8C. That is, in the above applied voltage example,
Semiconductor sea urchin t14 (OV) and hot filament 8c (
-5V) is 5■, so the electron e is 5eV
It has the energy of

Here, the hot filament 8 of the indirectly heated cathode 8 has less electrical resistance than a directly heated filament. Therefore, the potential gradient in the longitudinal direction of the hot filament 8C is small, and the potential difference at both ends is close to zero, so
The energy of the electrons e emitted from each part of the hot filament 8C is almost uniform.

That is, by setting the potential difference between the semiconductor wafer 4 and the filament 8 to a desired value, only electrons having a desired uniform energy can be supplied to the semiconductor wafer 4.

Therefore, electrons with high energy such as primary electrons are not supplied to the semiconductor wafer 4, and electrons are excessively supplied to the semiconductor wafer 4, causing the insulating film formed on the surface of the semiconductor wafer 4 to become negative. Electrostatic damage due to charge accumulation can be prevented.

Further, as shown in the well-known Langmuir formula, the amount of electrons extracted from the hot filament 8C is proportional to the 3/2 power of the voltage V between the hot filament 8C and the electron extraction electrode 10, and the amount of electrons extracted from the hot filament 8C is and the electron extraction electrode 10 is inversely proportional to the square of the distance d.

Therefore, in the ion implantation apparatus of this embodiment, even if the potential difference between the semiconductor wafer 4 and the hot filament 8C is set to be small (or set to the same potential) as described above, the power source 15 is used to connect the electron extraction electrode 10. By setting the applied voltage to a certain level (for example, +500V), a large amount of electrons can be extracted from the hot filament 8C.

Therefore, it is possible to supply an amount of electrons e that can sufficiently neutralize the positive charges generated on the semiconductor wafer 4 by the irradiation with the ion beam 1, and the insulating film formed on the surface of the semiconductor wafer 4 becomes positively charged. It is possible to prevent electrostatic damage caused by accumulation of .

As described above, the electric field limiting electrode 11 is used to limit the electric field formed inside the ion beam introduction tube 2 by the electron extraction electrode 10 and to separate the inside of the ion beam introduction tube 2 from the inside of the electron supply mechanism 5. belongs to. That is, the electric field limiting electrode 11 is set to a lower potential than the electron extraction electrode 10, and suppresses the electric field formed within the ion beam introduction tube 2. However, if the set potential of the electric field limiting electrode 11 becomes lower than the set potential of the filament 8, it becomes impossible to extract the electrons e, and therefore, as described above, it is set to about +50V, for example.

However, this electric field limiting electrode 11 can also be omitted.

FIG. 4 shows the main part configuration of an ion implantation apparatus according to another embodiment, and the same parts as in the above-mentioned embodiment are given the same reference numerals.

In the ion implantation apparatus of this embodiment, the electron source includes a plurality of filaments, for example four filaments 20a, 20b, which are divided in the longitudinal direction and connected in parallel to a power source 12 for heating the filaments.
It is composed of 20c and 20d. The filaments 20a, 20b, 20c, and 20d are each made of a spiral wire made of a material such as tungsten.

In this embodiment with the above configuration, for example, the undivided 1
Compared to the case where one filament is used, the voltage of the power supply 12 for filament heating can be reduced to 1/4 (1/n if the number of divisions is n), and the electric resistance generated in the longitudinal direction of the electron source The potential gradient can be reduced to 1/4 (1/n if the number of divisions is n) compared to when one filament is used.

Therefore, filaments 20a, 20b, 20c, 2
The energy of the electrons e emitted from each part of 0d can be made uniform, and the same effect as in the above embodiment can be obtained.

In the above embodiment, an example was explained in which the electron source was constituted by filaments 20a, 20b, 20c, and 20d divided into four parts in the longitudinal direction, but the present invention is not limited to this embodiment. The number of divisions may be 2 or more. In this case, increasing the number of divisions will make the electron energy more uniform, but this will complicate the structure and increase manufacturing costs, so the number of divisions is
For example, it is necessary to select the number appropriately, such as about 2 to 6.

In the above embodiment, the electron source is a filament 2 made of a spiral wire made of a material such as tungsten.
0a, 20b, 20c, and 20d, but they can also be constructed using, for example, rod-shaped members with low electrical resistance.

In the above embodiment, an example in which the present invention is applied to an ion implantation device has been described, but any device that positively charges the device by irradiating an ion beam may be used. For example, it may be applied to ion repair such as mask repair and wafer repair.

[Effects of the Invention] As explained above, according to the ion processing apparatus of the present invention, the energy of electrons supplied to the object to be processed can be uniformly controlled with high accuracy, and the electric charge of the object to be processed can be reliably controlled. Ion treatment can be performed while neutralizing.

Therefore, for example, it is possible to prevent an insulating film formed on the surface of a semiconductor wafer from being damaged by electrostatic discharge due to the accumulation of positive or negative charges, and to perform a good ion implantation process.

[Brief explanation of drawings]

1 and 2 are diagrams showing the configuration of main parts of an ion implantation device according to an embodiment of the present invention, FIG. 3 is a diagram showing the configuration of an electron extraction electrode of the ion implantation device of FIG. 1, and FIG. FIG. 2 is a diagram showing a main part configuration of an ion implantation apparatus according to another embodiment. 1...Ion beam, 2...Ion beam introduction tube, 3...Disc, 4...
Semiconductor wafer, 5...Electron supply mechanism, 6...
...Insulating member, 7...Housing, 8...
Indirectly heated cathode, 8a... Heater, 8b...
...Insulating member, 8C...Hot filament, 9
... Reflection plate, 10 ... Electron extraction electrode, 11 ... Electric field limiting electrode, 12 to 16 ...
...Power supply, 20a, 20b, 20c, 20d...
···filament.

Claims (2)

[Claims] (1) In an ion processing apparatus comprising means for irradiating an ion beam onto a workpiece, and an electron supply means for neutralizing positive charges on the workpiece generated by the means, the electrons of the electron supply means An ion processing device characterized in that the source is constituted by an indirectly heated cathode equipped with a hot filament and a heater. (2) Ions comprising means for irradiating an ion beam onto a workpiece, and electron supply means for supplying electrons generated by an electron source to the workpiece to neutralize positive charges on the workpiece. An ion processing apparatus, characterized in that the electron source is constituted by a plurality of filaments that are divided in the longitudinal direction and connected in parallel to a power source.