JPS63230875A - Ion-beam irradiation device - Google Patents

Abstract

PURPOSE:To stably neutralize the electric charge of the ion on the surface of a sample irrespective of the current density and shape of the ion beam by providing a means for pulling out an electron toward an ion beam and a means for controlling the energy of the electron to the neutralizer of the title ion-beam irradiation device. CONSTITUTION:When an ion beam 10 is projected on the surface of the sample 7, an electron is emitted from the electron source 1 of the neutralizer 11 to neutralize the ion beam 10. A first diffusion preventive means 4 for preventing the diffusion of the electron emitted from the electron source 1 to the outside, a second diffusion preventive means 6 for preventing the diffusion of the electron taken into the ion beam orbit in the direction opposite to the flow of the ion beam 10, a means 20 for pulling out the electron emitted from the electron source 1 toward the ion beam orbit, and a means 22 for controlling the energy of the pulled-out electron are provided to the neutralizer 11. As a result, the probability of capturing electrons by the ion beam 10 is maximized irrespective of the current density, etc., of the ion.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is applicable to, for example, surface modification of insulators or semiconductors,
This invention relates to an ion beam irradiation device used for processing, film formation, etc. Specifically, the present invention relates to an ion beam irradiation device having a neutralizer capable of controlling the surface potential of a sample whose whole or part is electrically insulated.

[Conventional technology]

Among ion irradiation techniques, for example, semiconductor ion implanters have been put to practical use as a technique for doping impurities into integrated circuits.

However, when high-current As ion implantation is performed on a high-density integrated circuit, such as a tMbit DRAM, which has submicron line width and insulation layer thickness,
The exposed semiconductor layer and conductive layer surrounded by the insulating layer and the insulating layer in the integrated circuit become high potential due to the accumulation of positive charge (hereinafter referred to as positive charging) due to the incident ion beam, which causes subsequent ion beam deflection. If uneven injection occurs due to
Sometimes electrical breakdown occurs, rendering the integrated circuit inoperable.

Therefore, even if a high-current ion implanter is introduced for the purpose of improving throughput, the ion current must be limited to a value that does not significantly cause positive charging in integrated circuits, which is a major practical problem. It becomes.

To solve this problem, there is a method of coating the surface of the integrated circuit with a conductive material and then performing ion implantation. For details of this method, see, for example, Japanese Unexamined Patent Publication No. 57-75
As discussed in JP-A No. 468, JP-A-58-75468, JP-A-60-188757, etc., the process of coating a conductive material and its removal is added before and after the implantation process, so it is difficult to integrate. The entire circuit manufacturing process becomes complicated, leading to lower yield and throughput.

Therefore, as a method to prevent positive charging on the surface of an integrated circuit, a method of neutralizing the ion beam by supplying electrons into the ion beam or onto the surface of the integrated circuit (hereinafter referred to as a sample) is attracting attention in practice. There is.

As a conventional example of neutralizing an ion beam using electrons,
There is a method of preventing positive charging by directly injecting electrons into the sample (for example, Japanese Patent Application Laid-Open No. 59-204281).
Since the surface of the sample that is not irradiated with the ion beam is also irradiated with the electron flow, there is a problem that negative charging occurs due to the electrons in that area, resulting in dielectric breakdown of the sample.

Also, "Method and Apparatus for Enhanced Neutralization of Positively Charged Ion Beams" by David Earp Robertson et al.
(Japanese Patent Laid-open No. 57-87056), primary electrons are accelerated and applied to a dummy target, and the 2
This method uses secondary electrons to neutralize the ion beam. This method is effective in that it uses secondary electrons with low energy of about 1 oeV in the energy distribution of secondary electrons emitted from the dummy target. Practical problems remain, such as the amount of secondary electrons emitted varies widely depending on the influence of electrons on the sample and the surface condition of the dummy target.

Furthermore, as a method of neutralizing an ion beam proposed by the present applicant, an apparatus for neutralizing an ion beam (hereinafter referred to as
There is a neutralizer (called a neutralizer).

In the figure, (1) is an electron emission source that emits electrons, for example a filament, which is heated by a first power source (2),
A stain position is applied to the second power source (3). (4) is a first diffusion prevention means for preventing electrons generated from the filament (1), such as thermoelectrons, from diffusing to the outside; for example, an electronic shield electrode is used to prevent the electrons generated from the filament (1) from diffusing to the outside; A potential is applied. (6) is drawn out into the ion beam orbit,
A second diffusion prevention means that prevents electrons taken into the ion beam from diffusing in a direction opposite to the traveling direction of the ion beam. It will be done.

(7) is a sample, (9) is a sample stage, and αG is an ion beam.

αη is a neutralizer that neutralizes the charge of ions on the surface of the sample (7).

FIG. 4 is a schematic diagram of an ion beam implantation device, which is an example of a conventional ion beam irradiation device.

In the figure, (2) is an ion source that generates a large current ion beam, (to) is an ion extraction electrode, and a negative maintained at a potential. ) is maintained at ground potential by a deceleration electrode. M is an acceleration extraction power source, αη is a mass separator, and (to) is an aperture that allows only mass-separated specific ion species to pass through.

Figure 5 is a graph of neutralization characteristics using the neutralizer shown in Figure 8, showing the charged state on the surface of a sample whose entire surface is an insulator as a function of changes in ion beam current. Ar
The ion current (mA) is shown, and the vertical axis shows the potential (KV) due to charging of the ion beam.

Next, the operation will be explained. The ion beam αO incident on the neutralizer (b) draws electrons emitted from the filament (1) installed very close into the ion beam current until the potential difference between the two becomes zero, and the neutralizer The ion beam αG near αυ is neutralized. Neutralization in this case does not mean that individual ions in the ion beam αO combine with electrons to become completely neutral particles, but rather that the ion density and electron density in the ion beam αO are equal. While ions act as a beam and electrons act as electrons, the electrons are trapped in the positive electric field formed by the ion beam itself! ! (hereinafter referred to as the plasma state).

A second power supply (3) is applied to the neutralizer αυ whose interior is in a plasma state.
When a negative potential is applied to the sample (7), a potential gradient is generated between the sample (7) and the electrons in the plasma move toward the sample (7). Now, since the ion density and electron density in the ion beam αG are equal, the second power source (3) adjusts the electron movement speed so that the electron movement speed to the sample (7) and the ion beam incidence speed are the same. If controlled, the numbers of ions and electrons reaching the sample (7) are equal and will be neutralized on the surface of the sample (7). To express this phenomenon simply in a mathematical formula, let Ee be the electron movement energy required for neutralization, the electron mass m, the electron movement speed Me, the ion incident energy Ei1, the ion mass M, and the ion incident speed Vi. Ee=-mVe
, Ei=-! -MVi'', and Ee=MEi holds from the Ve=Vio condition. In other words, even if the incident ion species changes, the above equation holds, so neutralization is possible.

In addition, the positive charging of the sample (7) caused by the emission of secondary electrons from the sample (7) during ion irradiation also increases the transfer energy of the electrons, causing the same amount of electrons to be emitted. This problem is eliminated by supplying it from the neutralizer aη, and the neutralization of the surface of the sample (7) is maintained.

Further, when a potential fluctuation occurs in the sample (7) due to positive charging, the electron transfer energy also changes according to the potential fluctuation, and the amount of electrons is always automatically adjusted.

In addition, the electronic shield electrode (4) is a filament (1)
Since a negative potential is applied to the sample (7), electrons are prevented from diffusing to the outside, and electrons are efficiently supplied to the ion beam αG, and electrons are prevented from directly entering the sample (7). The shield electrode (6) has the role of preventing electrons in the ion beam trajectory from moving toward the ions 5 (2) and efficiently supplying electrons within the ion beam αG toward the sample (7).

As shown in FIG. 4, a large current ion implantation apparatus (3) is mainly composed of an ion source (2), a mass separator αη for selecting necessary ions, and an implantation chamber.
2) is generally a plasma type that can generate a large current ion beam aO.

Therefore, for example, when the current value of the ion beam aO is changed, the emission surface of the ion beam αG of the ion source (2) changes, and the trajectory of the ion beam (II1) changes.As a result, the neutralizer aυ is installed. The density distribution and beam shape of the nearby ion beam αG change.Therefore, as shown in the graph of FIG. 6, the potential due to the charging of the sample surface changes with respect to the current value of the ion beam QO.

[Problem that the invention seeks to solve]

Conventional ion beam irradiation equipment is configured as described above, so that (I) negative charging occurs due to primary electrons or reflected electrons, (II) the amount of secondary electron emission changes,
There were problems such as changes in the charged state of the sample surface. Furthermore, regarding the neutralizer that can eliminate (+1, (II)), there is a problem in that the charged state of the sample surface changes with changes in the density distribution and beam shape of the ion beam.

This invention was made to solve the above-mentioned problems, and it can constantly neutralize the sample surface even if the density distribution, shape, and current amount of the ion beam changes, and also reduces negative charging caused by electrons. The purpose of this study is to obtain an ion beam irradiation device that can be used.

[Means for solving problems]

The ion beam irradiation apparatus according to the present invention includes an electron emission source that generates electrons, an electron extraction means for extracting the electrons generated from the electron emission source toward the ion beam trajectory, and an electron energy source that controls the energy of the extracted electrons. a control means, a first diffusion prevention means for preventing the electrons generated by the electron emission source from diffusing to the outside, and a first diffusion prevention means for preventing the electrons generated in the electron emission source from diffusing to the outside; It is equipped with a neutralizer having a second diffusion prevention means for preventing diffusion.

[Effect]

The neutralizer in this invention extracts a certain amount of shims from an electron emission source by an electron extraction means, and controls the energy of the electrons by an electron energy control means so that the probability of electron capture by the ion beam is maximized. ), turns the ion beam into a plasma state.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, a gradient is provided between the filament (1) and the ion beam trajectory, and the electrons from the filament (1) are
An electronic withdrawal means for withdrawing from the power source (2),
The electron extraction electrode (2) is provided between the electron extraction electrode slope and the ion beam trajectory, and is an electronic energy control means for controlling the energy of the extracted electrons at the 61st source. The negative of the fifth current (2), the negative of the sixth power source (to), and one end of the filament (1) are connected so that they have the same potential as shown in the figure. , the electron extraction electrode (1) and the electron energy control [pole] have a grid-like shape, for example, and are made of a high melting point material such as molybdenum so that the electrons extracted from the filament (1) can pass therethrough.

Next, the operation will be explained. Filament (1) #1
1st until the temperature reaches a high enough temperature to emit enough 8 electrons. [source(
2) Heat. When the filament (1) is set as negative and the electron extraction voltage Wi is set as positive, for example, when a voltage of Va is applied from the fifth power supply Q1), if the filament (1) is in a high temperature state that sufficiently clears the space charge region,
The space charge equation according to Polsson is established, and the electron current density Je is given by Je=KIVa'. However, K1
is a coefficient that depends on the initial velocity wave of electrons, the distance between electrodes, the shape of electrodes, etc. From the above equation, the electron current density Je is increased or decreased according to the 8/2 power of the extraction voltage.

Next, minus the filament (1) at the 6th *[(to),
A voltage of Vc is applied to the electronic energy control electrode, with the voltage Vc being positive. In this case, if Vc = Va, the electron extraction voltage Wi(1) and the electronic energy control voltage a
i) are at the same potential 6, and the electron flow extracted at a voltage of Va passes through the electron energy control electrode (2) while retaining the same energy. Furthermore, if Vc = 0, the electron flow accelerated at the electron extraction electrode (1) is rapidly decelerated as it approaches the electron energy control electrode (2), and as a result, the electron flow accelerates near the electron energy control electrode (2). stop. Therefore, for example, when applying Vc=10V,
An electron stream with toeV energy moves from the electron energy control chamber's pole (2) in the direction of the ion beam trajectory.

The ion beam αG extracted from the ion source (2) passes through the mass separator α force and enters the neutralizer aυ. Neutralizer 0
In 1), even if ion beams QO with different ion density distributions, beam cross-sectional shapes, and beam diameters are incident, electrons of the ion beam αO are captured in the neutralization region 7 of the neutralizer αυ by controlling the electron energy. Good electron energy and amount of electrons commensurate with the cross-sectional area can be taken into the volume of the ion beam Q(I), forming a plasma state with the same amount of ion density and electron density.

The subsequent operations are the same as those described in the prior art and serve the purpose of the present invention. Figure 2 shows the same Ar ion current (mA
), the results show the potential (KV) due to charging of the ion beam. As is clear from the figure, the potential due to charging is low and constant regardless of the amount of ion current. Therefore, even if the ion beam density distribution, beam shape, and current amount change, the sample surface can always be stably neutralized.

In the above embodiment, the neutralizer αυ was installed at the aperture position that allows only the mass-separated specific ion species to pass through, but neutralization is possible regardless of the shape of the ion beam 00. Ion beam QO is a neutralizer (b)
Anywhere between the mass separator a force and the sample can be used as long as it can penetrate inside.

In addition, the energy of electrons can be controlled to form a plasma state with the ion beam 00 in accordance with the energy of the ion beam αO, so it can be used not only for ion beam implantation but also for processing semiconductors and insulators such as film formation. It can be applied to various processes and can be attached to these devices as desired. Furthermore, the same effects as in the above embodiment can be achieved with respect to the process and equipment for forming, for example, a 5-inch composite film on metal.

Further, the shape of the electrodes (e) and @ is not limited to a grid shape, but may be any shape that allows electrons to pass therethrough.

Furthermore, the way in which potential is applied to each part is not limited to the above embodiment.

〔Effect of the invention〕

As described above, according to the present invention, there is provided an electron emission source that generates electrons, an electron extraction means for extracting the electrons generated from the electron emission source toward the ion beam trajectory, and an electron energy source that controls the energy of the extracted electrons. a control means, a first diffusion prevention means for preventing the electrons generated by the electron emission source from diffusing to the outside, and a first diffusion prevention means for preventing the electrons generated by the electron emission source from diffusing to the outside; The second step is to prevent the spread of
Equipped with a neutralizer with diffusion prevention means, it is possible to control the electron energy and maximize the probability of electron capture by the ion beam, regardless of changes in the ion current density, etc. It has the effect of neutralizing the charge of ions on the sample surface regardless of current density, shape, etc.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional configuration diagram showing a neutralizer related to an ion beam irradiation apparatus according to an embodiment of the present invention, FIG. 2 is a graph showing neutralization characteristics according to an embodiment of the present invention, and FIG. FIG. 4 is a cross-sectional configuration diagram showing a neutralizer related to a conventional ion beam irradiation device, FIG. 4 is a schematic configuration diagram showing a conventional ion beam irradiation device, and FIG. 5 is a graph showing neutralization characteristics related to the conventional device. . (1)...Electron emission source, (4)...First diffusion prevention means, (6)...Second diffusion prevention means, αυ...Neutralizer, Zeng...Electron extraction means, (2)...Electronic energy control means. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (3)

[Claims] (1) In an ion beam irradiation device that irradiates an ion beam onto a sample surface, an electron emission source that generates electrons, an electron extraction means that extracts the electrons generated from the electron emission source toward the ion beam trajectory, and an electronic energy control means for controlling energy; a first means for preventing electrons generated in the electron emission source from diffusing to the outside;
A neutralizer having a diffusion prevention means and a second diffusion prevention means for preventing electrons drawn into the ion beam trajectory and taken into the ion beam from diffusing in a direction opposite to the traveling direction of the ion beam. Ion beam irradiation equipment. (2) The ion beam irradiation apparatus according to claim 1, wherein the electron extraction means is an electron extraction electrode disposed between the electron emission source and the ion beam trajectory and through which electrons can pass. . (3) Claim 1 or 2, characterized in that the electron energy control means is an electron energy control electrode disposed between the electron extraction means and the ion beam trajectory and through which electrons can pass. The ion beam irradiation device described.