JP2774352B2 - Ion beam irradiation equipment - Google Patents

Description

The present invention relates to, for example, surface modification of insulators or semiconductors,
The present invention relates to an ion beam irradiation apparatus used for processing, film formation, and the like, and more specifically, to an ion beam irradiation apparatus having an electron shower apparatus that can control the surface potential of a sample that is wholly or partially electrically insulated. is there.

[Prior Art] Among ion irradiation techniques, for example, a semiconductor ion implantation apparatus has been put to practical use as an impurity doping technique for an integrated circuit. However, when high-current As ⁺ ion implantation is performed on a high-density integrated circuit such as a 4Mbit DRAM with a submicron line width or insulating layer thickness, the insulating layer and insulating layer in the integrated circuit will The enclosed exposed semiconductor layer and conductive layer
Since the potential is increased due to the accumulation of positive charges by the incident ion beam (hereinafter referred to as positive charging), the subsequent ion beam is deflected to cause non-uniform implantation or sometimes electrical breakdown. The integrated circuit becomes inoperable. Therefore, even if a large current type ion implantation apparatus is introduced for the purpose of improving the throughput, the ion current value must be limited to such a degree that the positive charging phenomenon does not significantly occur in the integrated circuit. It is a problem. FIG. 7 shows, for example, a conventional ion beam provided with an electron shower device for neutralizing positive charging by an ion beam disclosed in Japanese Patent Application Laid-Open No. 24347/1987 by the present applicant developed to solve this problem. An irradiation device. In the figure,
(1) is a sample such as a semiconductor having an integrated circuit placed on a sample stage (2), (3) is an accelerated ion beam applied to the sample (1), and (4) is a specific ion. An aperture for passing only seeds, (5) is an electron shower device for supplying electrons for neutralizing the positive charge generated on the surface of the sample (1) to the ion beam (3), and using a first power supply (6) An electron emission source (7), which is composed of a filament that emits electrons when heated, is arranged so that the sample (1) side is widened with respect to the traveling direction of the ion beam (3) (arrow Ii in the drawing). The sample (1) is arranged on the ion beam (3) side of the electron emission source (7).
It has a V-shaped cross section that spreads out to the side, and one side of the electron incidence surface (9a) is parallel to the electron emission source (7), and is connected to the electron emission source (7) by the second power supply (8). A grid-shaped electron extraction electrode (9) to which a positive potential is applied and through which electrons can pass, and the other surface of the electron extraction electrode (9) on the ion beam (3) side of the electron extraction electrode (9). Is arranged in parallel with the electron emission surface (9b), a positive potential is applied to the electron emission source (7) by the third power supply (10), and a lattice-like electron energy control through which electrons can pass. The electrode (11) and the electron emission source (7) are arranged so as to surround the portions other than the ion beam (3) side, and the fourth power supply (12) gives a negative potential to the electron emission source (7), An electron shield electrode for preventing electrons emitted from the electron emission source (7) from diffusing to the outside. Pole (13) and ion beam (3)
In order to prevent the electrons inside the ion beam (3) from moving in the direction opposite to the traveling direction Ii, a negative potential is applied to the sample stage (2) by the fifth power supply (14) to prevent backflow. It comprises a shield electrode (15), and a sixth power supply (16) for applying a negative potential to the sample stage (2) to the electron emission source (7).

FIG. 8 is a diagram for explaining the movement of electrons emitted from the electron emission source (7) in FIG.

Next, the operation will be described with reference to FIG. 7 and FIG. An electron emission source (7) supplied with power from a first power supply (6)
Is heated to a high temperature at which thermionic electrons can be sufficiently emitted and emitted,
The voltage Va is applied to the electron extraction electrode (9) by the second power supply (8).
When electrons are applied, electrons are extracted from the electroluminescent source (7). At this time, if the temperature of the electron emission source (7) is sufficiently high,
The current Ie of the electrons emitted from the electron emission source (7) follows the space charge limiting formula (Ie = KVa ^3/2 ). Here, K is a coefficient that depends on the initial velocity of electrons, the shape of the electrodes, the distance between the electrodes, and the like. The electron incident surface (9a) of the electron emission source (7) and the electron extraction electrode (9) are parallel, and the electron emission surface (9b) of the electron extraction electrode (9) and the electron energy control electrode (11) are ion beams. The angle between the electron incident surface (9a) and the electron emitting surface (9b) is parallel to the traveling direction Ii of (3) and is θ. That is, the direction of the electron extraction by the electron extraction electrode (9) and the direction of the electron deceleration by the electron energy control electrode (11) are different by an angle θ, and the electrons extracted from the electron emission source (7) by the electron extraction electrode (9). Is perpendicularly incident on the electron incident surface (9a) and goes straight to the electron emitting surface (9b). At this time, the electron velocity V ₁ is determined by the voltage Va of the second power supply (8) applied to the electron extraction electrode (9), Here, e is the amount of electrodes of electrons, and m is the mass of electrons.

Next, the electrons are decelerated by the electron energy control electrode (11). The direction of the deceleration is perpendicular to the electron emission surface (9b) and the electron energy control electrode (11), and the electron emission surface (9b) and the electron deceleration formed Vz of the direction parallel to the energy control electrode (11), the value of _{V Z = V 1 sinθ ...... (} 2) is stored in the deceleration.

Meanwhile the energy of the decelerated electrons is determined by the voltage Vc of the third power source (10) which is applied to the electron energy control electrode (11), its speed V ₂ is It is. Accordingly, electrons traveling from the electron energy control electrode (11) toward the ion beam (3) are emitted from the electron energy control electrode (11) at an emission angle α.

This is from the above equations (1), (2) and (3). Becomes Where the right side of equation (4) When the value of is equal to or greater than 1, electrons cannot pass through the electron energy control electrode (11).

In equation (4), for example, when electrons are extracted at Va = 300 V and the energy of the electrons is controlled at Vc = 10 V,
If θ = 10 °, electrons are emitted at α = 18 °. Therefore,
Since the electrons emitted from the electron energy control electrode (11) and supplied to the ion beam (3) have a velocity component Vz in the direction of the sample (1), the electron shower device ( If the electron transfer speed is controlled by providing a potential gradient between 5) and the sample (1), the number of ions and electrons reaching the sample (1) can be made equal, and the surface of the sample (1) becomes It will be electrically neutralized.

In addition, even when secondary electrons are emitted from the sample (1) due to the irradiation of the ion beam (3) and the sample (1) is positively charged, the sample (1) is further supplied with the same amount of electrons as the secondary electron emission amount. The positive charging of 1) can be neutralized.

[Problems to be Solved by the Invention] Since the conventional ion beam irradiation apparatus is configured as described above, the angle between the electron incidence surface and the electron emission surface of the electron extraction electrode of the electron shower device is set to a finite θ. In order to achieve this, it is necessary to process the shape of the electron extraction electrode in a complicated manner, or to assemble the electron emission source, the electron extraction electrode, and the electron energy control electrode with high precision so as to have a predetermined arrangement. .

The present invention has been made in order to solve the above-mentioned problems, and is an ion beam irradiation apparatus provided with an electron shower apparatus that can easily process electrodes and assemble an electron emission source and a power supply and efficiently supply electrons toward a sample. The purpose is to obtain.

[Means for Solving the Problems] An ion beam irradiation apparatus according to the present invention has an ion beam for irradiating a sample, an electron emission source for emitting electrons supplied to the ion beam, and an electron inlet. And an electron extraction electrode for extracting electrons from the electron emission source toward the ion beam through the inlet.
An electron energy control electrode that has an electron extraction port, decelerates the electrons extracted by the electron extraction electrode, and emits the ion beam through the extraction port to the ion beam, wherein the electrons emitted from the electron energy control electrode The thickness of at least one of the two electrodes is changed above and below the inlet or outlet so as to have a component directed toward the sample.

[Operation] In the ion beam irradiation apparatus according to the present invention, the thickness of at least one of the electron extraction electrode and the electron energy control electrode is changed above and below the electron inlet or outlet of the two electrodes, so that electrons are emitted. The crossing equipotential surface is inclined with respect to the traveling direction of the electrons.

Embodiment An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, (7) is an electron emission source arranged so as to have a length in a direction perpendicular to the traveling direction of the ion beam indicated by an arrow Ii in the figure, and (9) is an electron emission port (17). An electron extraction electrode having a large thickness on the lower side and protruding toward the ion beam (3), and the upper and lower sides of the inlet (17) on the electron emission source (7) side are configured to be flush with each other.
An electron energy control electrode (11) has a large thickness above the electron extraction port (18) and protrudes to the opposite side of the ion beam (3). Are arranged on the same plane. The other components are the same as the corresponding portions in FIG.

FIG. 2 is a view for explaining the movement of electrons emitted from the electron emission source (7) in FIG.

Next, the operation will be described with reference to FIG. 1 and FIG. The electron extraction electrode (9) and the electron energy control electrode (1) of the electron shower device (5) shown in FIG.
The deceleration electric field formed during 1) is represented by an equipotential surface (19) as shown in the figure. Electrons extracted from the electron emission source (7) by the electron extraction electrode (9) enter the deceleration electric field perpendicular to the axis of the ion beam (3). The electrons are decelerated in the decelerating electric field in the direction perpendicular to the equipotential surface (19), so that the equipotential surface (19) near the electron inlet (17) and the electron outlet (18) with respect to the ion beam (3) axis If the inclination is θ, it becomes the same as the case of the conventional device of FIG.
The emission angle α of the electron is Becomes Thus, the electrons emitted from the electron energy control electrode (11) and supplied to the ion beam (3) have a velocity component in the direction of the sample (1), and the sixth power supply (1)
According to 6), electrons can be easily moved toward the sample (1) only by giving a slight potential gradient between the electron shower device (5) and the sample (1).

In the first embodiment, the thickness of the electron extraction electrode (9) is large below the electron inlet (17), and the upper and lower sides of the electron inlet (17) are flush on the electron emission source (7) side. The thickness of the electron energy control electrode (11) is large on the upper side of the electron extraction port (18), and the upper and lower sides of the extraction port (18) are on the same plane on the ion beam (3) side. Although the configuration is described, as shown in FIGS. 3 (A) and 3 (B), only one of the electron extraction electrode (9) or the electron energy control electrode (11) is provided with one of the electron inlets (17). The thickness may be large on the lower side or on the upper side of the take-out opening (18), and the same effect as in the first embodiment can be obtained.

In the first and second embodiments, the case where the upper electrode (9c) and the lower electrode (9d) of the electron extraction electrode (9) are on the same plane on the electron emission source (7) side will be described. However, as shown in FIGS. 4 (A), 4 (B) and 4 (C), the lower electrode (9d) protrudes toward the electron emission source (7) on the electron incident surface side of the electron extraction electrode (9). In this case, the same effects as those of the first and second embodiments can be obtained.

In the first to third embodiments, the upper electrode (9c) and the lower electrode (9d) of the electron extraction electrode (9) have a uniform thickness, and the electron energy control electrode (9 11)
The case where the upper electrode (11c) and the lower electrode (11d) are arranged at the same distance from the electron orbit axis of the electron shower device (5) has been described, but as shown in FIG. The thickness of the lower electrode (9d) of the extraction electrode (9) is not uniform, and the upper electrode (11c) and the lower electrode (11d) of the electron energy control electrode (11) are an electron shower device ( The arrangement 5) may not be arranged at the same distance from the electron orbital axis, and the same effects as those of the first to third embodiments can be obtained.

Further, the electrode shape of the electron energy control electrode (11) on the side of the ion beam (3) may be any shape as long as it does not hinder the trajectory of the electrons and the trajectory of the ion beam (3).

FIG. 6 shows a fifth embodiment, in which two electron shower devices (5) are arranged on two opposing surfaces across an ion beam (3), and each electron shower device (5) is provided. The electron emitted from the electron beam intersects on the trajectory of the ion beam (3) and is arranged so as to irradiate an opposite position on the sample (1).
-Α can be small.

Further, in the fifth embodiment, the electron shower device (5) is described as being disposed on two surfaces opposed to each other with the ion beam (3) interposed therebetween. However, the cylinder is axially symmetric with respect to the ion beam (3). An electron shower device (5) having a shape may be used, and the same effect as in the fifth embodiment can be obtained.

[Effects of the Invention] As described above, according to the present invention, an ion beam irradiating apparatus can be used to irradiate a sample with an ion beam, an electron emission source that emits electrons supplied to the ion beam, and an electron intake port. Having an electron extraction electrode for extracting electrons from the electron emission source toward the ion beam through the intake port, and having an electron extraction port and decelerating the electrons extracted by the electron extraction electrode. An electron energy control electrode that emits to the ion beam through the extraction port, so that electrons emitted from the electron energy control electrode have a component directed toward the sample,
Since the thickness of at least one of the two electrodes is changed above and below the inlet or the outlet, processing of the electrodes and assembling of the electron emission source and the electrodes are easy, and electrons are efficiently transferred in the direction of the sample. An ion beam irradiation device provided with an electron shower device that can supply well can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an ion beam irradiation apparatus according to one embodiment of the present invention, FIG. 2 is a view for explaining the movement of electrons in the apparatus of FIG. 1, and FIGS. FIG. 6 is a schematic cross-sectional view showing an electron shower device of an ion beam irradiation apparatus according to another embodiment of the present invention. FIG. 6 is a schematic cross-sectional view showing an ion beam irradiation apparatus according to still another embodiment of the present invention. FIG. 1 is a schematic sectional view showing a conventional ion beam irradiation apparatus, and FIG. 8 is a view for explaining the movement of electrons in the apparatus shown in FIG. In the figure, (1) is a sample, (3) is an ion beam,
(7) is an electron emission source, (9) is an electron extraction electrode, (1)
1) is an electron energy control electrode, (17) is an electron inlet, and (18) is an electron outlet. In the drawings, the same reference numerals indicate the same or corresponding parts.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-54858 (JP, A) JP-A-63-299041 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01J 37/317 H01J 37/04 H01L 21/265

Claims (1)

(57) [Claims] An ion beam for irradiating a sample, an electron emission source for emitting electrons supplied to the ion beam,
An electron extraction electrode that has an electron intake and extracts electrons from the electron emission source toward the ion beam through the intake, and an electron that has an electron extraction port and is extracted by the electron extraction electrode. An ion beam irradiation apparatus including an electron energy control electrode that decelerates and emits the ion beam through the extraction port,
The thickness of at least one of the two electrodes is changed above and below the inlet or outlet so that the electrons emitted from the electron energy control electrode have a component directed toward the sample. Characteristic ion beam irradiation equipment.