JP2605692B2 - Ion beam equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in the following order.

A. Industrial application fields B. Summary of the invention C. Prior art [FIGS. 4 and 5] D. Problems to be solved by the invention E. Means for solving problems F. Action G. Implementation Examples [FIGS. 1 to 3] H. Effects of the Invention (A. Industrial Application Field) The present invention relates to an ion beam apparatus, particularly to a gas ion source type ion beam apparatus.

(B. Summary of the Invention) In an ion beam apparatus, the present invention provides a method for increasing the gas pressure of an ion source gas on the tip side of an emitter without increasing the supply amount of the ion source gas, and causing discharge around the emitter. In order to prevent this, a gas ion source supply member made of an insulating material surrounding the emitter inside the thermal shield, and a gas ion source supply member provided on the distal end side of the gas ion source supply member, through which an ion beam is passed, and furthermore than the emitter distal end At least a lid having an opening located on the extension direction side of the emitter and closer to the emitter than the opening of the extraction electrode, wherein the area of the opening of the lid is inside the base side of the gas ion source supply member. It is smaller than the cross-sectional area and smaller than the area of the opening of the extraction electrode. By on source feed member can increase the gas pressure in the ion source gas near the emitter tip by differential pumping, not always necessary to increase the supply amount of the ion source gas to increase its gas pressure. Since the differential evacuation is performed not by the extraction electrode but by the gas ion source supply member having an insulating property, it is not necessary to arrange the extraction electrode in close proximity to the emitter. Since it is possible to block between the electrodes, it is possible to prevent discharge from occurring around the emitter.

(C. Prior Art) [Fig. 4 and Fig. 5] Ion beam equipment is used for exposure, indispensable for the manufacture of ICs and LSIs, implantation of impurity elements into the surface of semiconductor substrates, and processing of semiconductor substrates by ion etching Many are used. FIG. 4 shows an ion gun portion of the ion beam apparatus. In the same figure, a is a refrigerator, b is an insulating sapphire formed on the tip surface of the refrigerator a, c is a needle-shaped emitter protruding from the center of the tip surface of the insulating sapphire b, and d is a cylindrical shape. Is provided so as to shield the peripheral surface of the distal end portion of the refrigerator a and the lower side thereof from the outside. e is a pipe for supplying helium He gas as an ion source gas into the thermal shield d, f is a donut-shaped extraction electrode attached to the lower end of the thermal shield d, and an opening g formed at the center thereof. Is positioned slightly below the tip of the emitter c, and between the emitter c and the extraction electrode f is several KV to several tens KV.
High voltage is applied. Such an ion gun is provided in a vacuum bell jar.

The ion beam generation principle of this ion beam apparatus will be briefly described. Helium He gas supplied from outside into the thermal shield d through the pipe e is an emitter c.
When the air is exhausted from the opening g of the extraction electrode f to the outside of the thermal shield d through the vicinity of the leading end of the lead electrode f, the ion is atomized by a high electric field generated by the high voltage to become an ion beam. Such a gas ion source type ion beam device,
It is necessary that the gas pressure of the helium He gas at the tip side of the emitter c be obtained with sufficient luminance without unnecessarily increasing the supply amount of the helium He gas. This is because the helium He gas supplied into the thermal shield d is at room temperature, while the emitter c is cooled to 10 ° K or less by the refrigerator a. As the amount increases, the temperature of the emitter c naturally increases, and as a result, the brightness of the ion beam decreases.

On the other hand, if the gas pressure of the helium He gas on the tip side of the emitter c is low, the brightness of the ion beam also becomes low. In particular, the ratio of the gas actually ionized to the supplied gas is extremely low, for example, 0.1% or less,
In order to increase the luminance, it is important to increase the gas pressure on the tip side of the emitter c.

This means that it is necessary to meet the so-called trade-off requirement of increasing the gas pressure at the tip of the emitter c without increasing the supply amount of the helium He gas. It has been attempted to respond by performing differential evacuation by making the opening g smaller in diameter by approaching the emitter c.

Japanese Patent Application Laid-Open No. 58-4252 also introduces the provision of a gas introduction mechanism surrounding the emitter in order to further increase the gas pressure of the ion source gas on the tip side of the emitter. On the other hand, gas ion source type ion beam devices basically use a technology to increase the gas pressure at the tip of the emitter by performing differential evacuation using an extraction electrode with an opening. It is only added to increase the pressure slightly.

(D. Problems to be Solved by the Invention) By the way, the above-described conventional differential pumping is based on the extraction electrode f.
Opening g is made small, and the extraction electrode f is connected to the emitter c.
However, there is a problem that discharge easily occurs between the extraction electrode f at the ground level and the emitter to which a positive potential of several K to several tens KV is applied. Was.

However, according to the technique using the gas introduction mechanism introduced in the above-mentioned Japanese Patent Application Laid-Open No. 58-4252, the gas pressure can be slightly increased by providing the gas introduction mechanism. The extraction electrode can be separated from the emitter as much as the pressure can be increased. Therefore, it can be said that discharge can be made slightly less likely to occur. However, even in the ion beam apparatus disclosed in the above-mentioned publication, since the differential evacuation is basically performed by the extraction electrode, the distance that the extraction electrode can be separated from the emitter is very small, and the problem that discharge easily occurs is fundamental. Could not be avoided.

The present invention has been made to solve such a problem, and has an emitter, a thermal shield surrounding the emitter, and a tip of the thermal shield further extending from the tip of the emitter in the extension direction of the emitter. At least an extraction electrode provided at a position corresponding to the emitter and having an opening at a position corresponding to the emitter, and forming a high electric field at the tip of the emitter by applying a high voltage between the emitter and the extraction electrode. Increasing the supply amount of the ion source gas in the ion beam apparatus in which the gas ion source is ionized to generate the ion beam from the tip of the emitter and emit the ion beam to the outside through the opening of the extraction electrode. The gas pressure of the ion source gas on the tip side of the emitter is increased, and no discharge occurs around the emitter It is an object of the present invention to be in.

(E. Means for Solving the Problems) The ion beam apparatus of the present invention includes a gas ion source supply member made of an insulating material surrounding an emitter inside a thermal shield, and a gas ion source supply member provided at a tip end side of the gas ion source supply member. And at least a lid having an opening through which the ion beam passes and which is located further in the direction of extension of the emitter than the tip of the emitter and closer to the emitter than the opening of the extraction electrode. The area is smaller than the internal cross-sectional area on the base side of the gas ion source supply member and smaller than the area of the opening of the extraction electrode.

(F. Function) According to the ion beam apparatus of the present invention, since the opening whose area is smaller than the internal cross-sectional area on the base side of the gas ion source supply member is made to face the tip of the emitter, the differential operation is performed by the gas ion source supply member. Evacuation can be performed, eliminating the need to use the extraction electrode for differential evacuation. Therefore, even if the extraction electrode is sufficiently separated from the emitter, the gas pressure of the ion source gas at the tip of the emitter can be sufficiently increased, so that an ion beam with sufficient luminance can be obtained without fear of discharge. Will be possible.

Further, since the gap between the tip of the emitter and the extraction electrode can be blocked by the lid of the gaseous ion source supply member having an insulating property, discharge between the emitter and the extraction electrode can be more effectively prevented.

(G. Embodiment) [FIGS. 1 to 3] Hereinafter, an ion beam apparatus of the present invention will be described in detail with reference to illustrated embodiments.

FIG. 1 is a sectional view showing one embodiment of the ion beam apparatus of the present invention. In the figure, 1 is a refrigerator, 2 is an insulating sapphire formed on the tip surface of the refrigerator 2, 3 is an emitter mounting portion formed on the tip surface of the insulating sapphire 2, and a gas introduction hole 4 is formed. ing. The gas introduction hole 4 extends substantially horizontally from the peripheral surface of the emitter mounting portion 3 to the center thereof, extends vertically downward from the center portion, and opens at the center of the tip end surface. Are attached without obstructing the gas flow through the opening.

A gas introduction pipe 6 is connected to a portion of the gas introduction hole 4 opened on the peripheral surface of the emitter mounting portion 3. 7 is a thermal shield, 8 is a lead electrode formed at the lower end of the thermal shield 7, and 9 is an opening of the lead electrode 8.

Reference numeral 10 denotes a nozzle formed at the tip end surface of the emitter mounting portion 3 so as to surround the emitter 5. A lid 11 is formed at the tip, an opening 12 is formed at the center of the lid 11, and the opening 12 is formed. It is located slightly below the tip of the emitter 5.

The helium He gas supplied through the gas introduction pipe 6 passes through the gas introduction hole 4 formed in the emitter mounting part 3 and further passes through the portion between the nozzle 10 and the emitter 5 and the lid
The air is differentially evacuated from the opening 12 of the eleventh electrode and is exhausted out of the thermal shield 8 through the opening 9 of the extraction electrode 8.

According to the ion beam apparatus shown in FIG. 1, a nozzle 10 is provided, and a lid 11 having a small opening 12 is provided at the tip of the nozzle 10, whereby the area of the opening 12 is significantly larger than the cross-sectional area inside the nozzle 10. By making the size smaller, it is possible to realize very effective differential exhaust of the helium He gas. Therefore, the opening of the nozzle 10 facing the tip of the emitter 5 without significantly increasing the supply amount of the helium He gas.
The gas pressure of helium He gas around 12 can be increased. Accordingly, an ion beam with extremely high brightness can be obtained.

Since the differential evacuation is performed not by the extraction electrode 8 but by the nozzle 10, the extraction electrode 8 does not need to be individually approached to the emitter 5 and can be sufficiently separated so as not to cause a discharge. . Therefore, it is possible to reliably prevent discharge.

The diameter of the emitter 5 is 0.125 mm, the inner diameter of the nozzle 10 (made of alumina or the like) is 0.2 mm, and the diameter of the opening 12 of the lid 11 is 0.1 mm. Was reduced to less than one tenth of the gas pressure in the bell jar. Specifically, the helium partial pressure at the tip of the emitter 5 could be set to 2 × 10 ⁻⁵ Torr. This gas pressure is about 10 times the helium partial pressure 2 × 10 ⁻⁶ Torr 20 cm below the tip of the emitter 5. still,
The position 20 cm below the tip of the emitter 5 means the position where the semiconductor wafer to be irradiated is placed at the time of exposure or the like (that is, the position of the emitter 5
10 cm below the tip).

As mentioned above, the fact that the gas pressure could be increased by a factor of 10 with the same gas supply amount means that the gas supply amount could be reduced by a factor of 10 with the same gas pressure. It is.

FIG. 2 shows the lid 11 when the same gas pressure is to be maintained.
This figure shows the relationship between the diameter of the opening 12 and the gas flow rate, and it is clear from this figure that the gas flow rate can be reduced by reducing the diameter.

In order to prevent the insulator from being charged up, it is necessary to prevent the beam from irradiating the lid 11, so that the diameter of the opening 12 is not made too small just to reduce the gas flow rate. Can not. Again, it is necessary to increase the expected angle from the emitter tip to some extent.

FIG. 3 shows a modification of the ion beam apparatus of the present invention, in which the diameter of the nozzle 10a is significantly larger than the diameter of the opening 12a of the lid 11a. Thus, various variations can be considered in the present invention.

(H. Effects of the Invention) As described above, the ion beam device of the present invention includes a gas ion source supply member made of an insulating material surrounding an emitter inside a thermal shield, and a tip of the gas ion source supply member. And a lid having an opening that is provided on the side and that is located further in the direction of extension of the emitter than the tip of the emitter through the ion beam and closer to the emitter than the opening of the extraction electrode. Is smaller than the internal cross-sectional area on the base side of the gas ion source supply member and smaller than the area of the opening of the extraction electrode.

Therefore, according to the ion beam apparatus of the present invention, since the opening whose area is smaller than the internal cross-sectional area on the base side of the gas ion source supply member faces the tip of the emitter, differential exhaust is performed by the gas ion source supply member. This eliminates the need to use the extraction electrode for differential evacuation. Therefore, even if the extraction electrode is sufficiently separated from the emitter, the gas pressure of the ion source gas at the tip of the emitter can be sufficiently increased without increasing the gas supply amount. It is possible to obtain an ion beam with high brightness.

Further, since the gap between the tip of the emitter and the extraction electrode can be blocked by the lid of the gaseous ion source supply member having an insulating property, discharge between the emitter and the extraction electrode can be more effectively prevented.

[Brief description of the drawings]

1 and 2 are views for explaining one embodiment of the ion beam apparatus of the present invention. FIG. 1 is a cross-sectional view, and FIG. 2 is a drawing in which the gas pressure between the aperture diameter and the gas flow rate is kept constant. FIG. 3 is a cross-sectional view showing a modification of the ion beam apparatus of the present invention, FIG. 4 is a cross-sectional view showing a conventional example of the ion beam apparatus, and FIG. FIG. 4 is a relationship diagram illustrating a relationship between temperatures. DESCRIPTION OF SYMBOLS 5 ... Emitter, 7 ... Thermal shield, 8 ... Extraction electrode, 10, 10a ... Gas ion source supply member, 11 ...
Lid, 12, 12a ... Opening.

Claims (1)

(57) [Claims] 1. An emitter, a thermal shield surrounding the emitter, and a tip of the thermal shield provided at a position further extending than the tip of the emitter in a direction in which the emitter extends, at a position corresponding to the emitter. At least an extraction electrode having an opening; applying a high voltage between the emitter and the extraction electrode to form a high electric field at the tip of the emitter, thereby ionizing the gaseous ion source to form ions from the tip of the emitter; An ion beam device configured to generate a beam and emit the beam to the outside from the opening of the extraction electrode; a gas ion source supply member made of an insulating material surrounding an emitter inside the thermal shield; It is provided on the tip side of the member and passes the ion beam further than the tip of the emitter. At least a lid having an opening located on the extension direction side of the emitter and closer to the emitter than the opening of the extraction electrode, wherein the area of the opening of the lid is an internal cutoff on the base side of the gas ion source supply member. An ion beam device characterized by being smaller than the area and the area of the opening of the extraction electrode.