JPH0195452A - Ion source device - Google Patents

Abstract

PURPOSE:To obtain an ion source device of a high ion beam utilization rate by constituting ion guide-out electrodes with a multiplicity of bar-like electrodes running parallel to each other, thereby reducing rate of collision diffusion to charge conversion of an ion beam. CONSTITUTION:Ion guide-out electrodes are constituted with a multiplicity of bar-like electrodes running parallel to each other. Making the direction of the gaps between the bar-like electrodes 5 same with that of the longitudinal direction of a slit, neutral molecules discharged out of an opening 1 may pass through these gaps easily to the back side of the bar-like electrodes 5. This increases the conductance of the neutral molecule flow remarkably, reduces pressures around said opening, remarkably decreases the rate of collision diffusion to charge conversion of an ion beam, and improves ion beam utilization rate. Further, while electric field concentrates on the surface of the bar-like electrodes 5 of the ion guide-out electrodes, the electric field is broardened in the vicinity of the opening of a semi-closed vessel, producing little difference in the ion guide-out effect, with a similar electric field distribution to that of the case in which a plate-like ion guide-out electrode is used.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an ion beam device that extracts ions from plasma and utilizes the extracted ions, such as an ion implanter used in semiconductor manufacturing processes. Regarding the ion source device in.

[Conventional technology]

FIG. 5 shows a perspective view of a conventional ion source device, a semi-closed container 2 provided with an opening l to form a semi-closed space.
A gas or metal vapor is introduced through the gas inlet 3 and turned into plasma by suitable means such as those used to generate a low-pressure arc. Furthermore, a plate-shaped ion extraction electrode 50 is arranged to face the opening l, and between the two, a voltage of about 10 kV to about 1
An ion beam 4 is extracted from the plasma by applying a DC high voltage of 0 kV. This ion beam is used for introducing impurities into semiconductor wafers, modifying metal surfaces, and the like. Note that the ion source device is housed in a vacuum container, and this vacuum container is evacuated using an oil diffusion pump or the like.

[Problem that the invention seeks to solve]

Problems with the ion source device configured as described above are as follows. That is, when gas is supplied from the gas inlet 3, several tens of percent of the gas is released from the opening 1 as neutral molecules. The released gas creates a pressure around the opening that is determined by the degree of ease of flow around the opening. As an ion source device, the pressure is 1 in the plasma part.
0-"Torr, preferably as low as possible outside the housing, the former for stable plasma formation, the latter for collision scattering of the ion beam onto neutral molecules and charge conversion: A" (high speed) 10A (low speed) - A (high speed) + A (low speed)
This is to prevent this. Here, A'' (high speed) is a high-speed ion accelerated by the electrostatic field between the ion extraction W pole and the semi-closed container, A (low speed) is a low-speed neutral molecule simply released from the opening, and A ( A" (high velocity) is a fast neutral molecule that loses its charge and loses its function as an ion when a fast ion collides with a slow neutral molecule, and A" (low velocity) is a fast neutral molecule that becomes charged due to a collision with a fast ion. It is a slow-moving ion.

When such collisional scattering and charge conversion of the ion beam occur, the efficiency of using ions as a device decreases. The conversion is as high as several percent, and the ion utilization efficiency decreases accordingly.

The ease of gas flow, or conductance, around the opening, which affects the magnitude of collision scattering and charge conversion, can be more easily determined by modeling the configuration of the ion source device as shown in Figure 7. I can understand. Here, the upper part of the straight line indicated by the reference numeral 11 means a semi-enclosed space in which plasma is generated, and the lower part means a vacuum container, that is, a housing 12 that accommodates the semi-enclosed container 2 (FIG. 5) forming the semi-enclosed space. , indicates a space connected to an evacuation system (not shown), and do is the width of an opening formed in a slit shape, and a plate-shaped ion extraction electrode 13 is disposed opposite to this.

Neutral molecules released from a semi-closed space where the pressure is kept at P through an opening with a width do are blocked by the ion extraction electrode 13 and cannot freely diffuse, and the conductance of the flow is Although it varies depending on the dimensions do, M and L, it is roughly only one-third of the case where it can be freely diffused as shown in Part 6, that is, a plate-shaped ion extraction electrode as a structure. Since there are 13,
The pressure at each part increases, and as a result, the aforementioned collision scattering and charge conversion occur, which reduces the efficiency of ion beam utilization and has an adverse effect. Incidentally, scattering is also unfavorable in terms of the design of the particle optical system.

An object of the present invention is to provide an ion source device that reduces the rate of collision scattering and charge conversion of ion beams and has high ion beam utilization efficiency.

[Means for solving problems]

In order to achieve the above object, the present invention provides a semi-closed container that is provided with an opening to form a semi-closed space and in which a target gas is turned into plasma; In an ion source device comprising an ion extraction electrode 5 disposed in a semi-closed container to form an electrostatic field between the ion extraction electrode 5 and a semi-closed container to extract ions in the plasma from the opening, a plurality of ion extraction electrodes running parallel to each other extend through the ion extraction electrode. It shall be constructed using rod-shaped electrodes.

[Effect]

In this way, when the ion extraction electrode is constructed using a plurality of rod-shaped electrodes running parallel to each other, and the opening of a semi-closed container is formed in the shape of a slit, the direction of the gap between the i-shaped electrodes can be changed. By aligning the slit with the longitudinal direction of the slit, the neutral molecules released from the opening can easily crawl through this gap and pass behind the rod-shaped electrode, so the conductance of the flow of neutral molecules is significantly increased. As the opening becomes larger, the pressure around the opening decreases, and the ratio of collision scattering and charge conversion of the ion beam by neutral molecules is significantly reduced, improving the efficiency of using the ion beam. Moreover, the electrostatic field formed between the ion extraction electrode and the semi-closed container configured in this way is concentrated on the rod-shaped electrode surface of the ion extraction electrode, but spreads near the opening of the semi-closed container. The electric field distribution is the same as when a plate-shaped ion extraction electrode is used, and there is almost no difference in the ion extraction effect.

〔Example〕

FIG. 1 shows the configuration of an ion source device according to a first embodiment of the present invention. The ion extraction electrode is formed by arranging the rod-shaped electrodes 5 and integrating the rod-shaped electrodes 5 using the fixing fittings 6. Normally, the interval between the semi-closed container and the ion extraction electrode is several to ten. Therefore, if the diameter of the rod-shaped electrode is selected to be several U, the electric field of the opposing portion will be higher near the rod-shaped electrode than in the case of a plate-shaped electrode, but it will not change much near the opening. Similar ion extraction is possible.

FIG. 2 shows a modification of the embodiment shown in FIG.

In FIG. 1, the rod-shaped electrode is integrated using a fixture 6, and this fixture 6 is fixed to a vacuum container or housing that houses the ion source device, but in the modified example shown in FIG. The end portions of the rod-shaped electrodes are each bent into an L-shape to form a fixing portion, and the fixing portions are directly fixed to the housing, thereby simplifying the ion extraction electrode structure.

FIG. 3 shows the configuration of an ion source device according to a second embodiment of the present invention. This embodiment shows an example of arrangement of rod-shaped electrodes when the electric field on the ion extraction electrode side is also intended to be brought close to the plate-shaped electrode. In addition, rod-shaped electrodes 7 as shield electrodes are arranged on both sides of the pair of rod-shaped electrodes shown in FIG. In this case, it is possible to further reduce the diameter of the central pair of rod-shaped electrodes, and the smaller the electrode dimensions, the lower the probability of collision of neutral molecules with the electrodes, and the greater the conductance. Therefore, since the pressure is reduced, the ratio of collision scattering and charge conversion is reduced, making it possible to provide an ion source device with high ion beam utilization efficiency.

FIG. 4 shows the configuration of an ion source device according to a third embodiment of the present invention. According to this configuration, the ion extraction electrode is formed by rolling the end of a rectangular metal plate into a rod shape to form an electrode portion 15a. The flat part following the electrode part is a flow rectifying part 15b.
The electrodes 15 are arranged in pairs to face the opening 1, and the effect on the flow of neutral molecules and the formation of an electrostatic field around the opening are the same as those described in the first embodiment.
This is the same as the rod-shaped electrode in the second embodiment. Therefore, here, the electrode 15 constituted by the electrode portion 15a and the rectifying portion 15b is also referred to as a rod-shaped electrode, although it is not geometrically rod-shaped.

〔Effect of the invention〕

As described above, according to the present invention, there is provided a semi-enclosed container having an opening to form a semi-enclosed space in which a target gas is turned into plasma, and a container facing the opening of the semi-enclosed container. An ion source device comprising: an ion extraction electrode arranged to form an electrostatic field with a semi-closed container to extract ions in the plasma from the opening, a plurality of rod-shaped electrodes running parallel to each other on the ion extraction electrode; The plasma chamber (semi-closed container) of the ion extraction electrode is configured using
By reducing the dimension facing the opening, the conductance around the opening increases for the flow of neutral molecules released from the opening, and the gas generated by the neutral molecules released into the space between the plasma chamber and the ion extraction electrode increases. The pressure is reduced, and an ion beam device in which the rate of collisional scattering and charge conversion by neutral molecules of the ion beam is small, and therefore the ion beam is used efficiently, can be provided.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the configuration of an ion source device according to a first embodiment of the present invention, and FIG. 2 is a perspective view showing the configuration of an ion source device according to a modification of the first embodiment shown in FIG. , FIG. 3 is a perspective view showing the configuration of an ion source device according to a second embodiment of the present invention, FIG. 4 is a diagram showing the configuration principle of an ion source device according to a third embodiment of the present invention, and FIG. 5 is a conventional diagram. FIG. 6 is a perspective view showing the configuration of an ion source device according to an example; FIG. 6 is a model diagram illustrating the conductance with respect to the flow of neutral molecules released from the opening of the semi-closed container when there is no ion extraction electrode; FIG. 7 FIG. 2 is a model diagram illustrating the conductance with respect to the flow of neutral molecules released from the opening of the semi-closed container when the ion extraction electrode is a plate-shaped electrode. 18 opening, 2: semi-closed container, 4: ion beam, 5,
7, 8, 15: rod-shaped electrode, 50: ion extraction electrode. ,). Iwao Yamaguchi, 7th figure 1
Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] 1) An electrostatic field is created between a semi-enclosed container with an opening to form a semi-enclosed space in which the target gas is turned into plasma, and a semi-enclosed container placed opposite the opening of the semi-enclosed container. An ion source device comprising: an ion extraction electrode that forms an ion extraction electrode and extracts ions in plasma from the opening, wherein the ion extraction electrode is configured using a plurality of rod-shaped electrodes running parallel to each other. source device.