JPH0693352B2 - Ion implanter - Google Patents

Description

The present invention relates to an ion implanter, and more particularly to an electrode system of the ion implanter suitable for extracting a large current ion beam in a wide range from low energy to high energy. Regarding

[Conventional technology]

Along with the diversification of semiconductor devices, it has been required that the implantation energy of an ion implantation device used for implanting impurity ions into semiconductor elements can be varied in a wide range from 10 kV to 200 kV in terms of voltage. Therefore, an ion implantation apparatus has been considered in which the ion beam is extracted from the ion source at a voltage of about 40 kV, and the implantation energy is adjusted by accelerating or decelerating again immediately before implanting the semiconductor element. An ion implanter that adopts such an energy adjustment method is called a post-acceleration / deceleration type ion implanter, which is described in "Ion Implantation Technique", Springer Berlag, 1982, p. (“Ion Implan
tation Tecknick, "Springer-Verlag (1982), P4).

FIG. 5 is a diagram showing a conventional post-stage acceleration / deceleration type ion implantation device. The ion beam 5 is extracted from the source plasma generated by the ion source 1 by the electric field created by the extraction electrode system 2. An unnecessary component is removed from this ion beam through the mass separation magnet 3 and the mass separation slit 9, and the post-stage acceleration / deceleration electrode system 4 including the electrode 41 to which a high voltage is applied and the ground electrode 42 is formed.
After adjusting the energy with, the ion beam is implanted into the semiconductor element 62 on the rotating disk 61 in the implantation chamber 6.

Further, in the post-stage acceleration / deceleration type ion implanter shown in FIG. 5, there is a conventional example in which the mass separation slit 9 is moved to the downstream side of the post-stage acceleration / deceleration electrode system 4 as shown in FIG.

[Problems to be solved by the invention]

FIG. 7 shows that in the ion implanter shown in FIG. 5, the ion beam 5 consisting of, for example, three components is passed through the mass separation magnet 3 and the mass separation slit 9 to remove the ion beam components 5b and 5c and to extract only the 5a component. It is a figure which shows the principle of mass separation. Ion beam components 5a, 5b, 5c of the mass number and the mass separation magnet 3 under turning radius, _{respectively, M a, M b, M} c, R a, R b,
If R _c , then the following equation holds.

By the way, for example, if M _a = 10 and M _b = 11, then R _b = 1.05R _a , whereas if M _a = 100 and M _b = 101, then R _b = 1.005R _a . As described above, as the mass number of ions increases, it becomes difficult to separate the masses of ion beams having different mass numbers by one. Further, each ion beam has an intensity distribution like 51a, 51b, 51c. Therefore, it is necessary to adjust the slit width of the mass separation slit 9 depending on the balance between the purity of the ion beam passing through the mass separation slit 9 and the beam current amount.

However, in the conventional post-stage acceleration / deceleration type ion implanter shown in FIG. 5, since the mass separation slit 9 is provided on the high voltage side of the post-stage acceleration / deceleration electrode system 4, a mechanism for adjusting the slit width is provided. Mounting and controlling this is technically difficult and costly.

On the other hand, in the conventional example in which the mass separation slit 9 is moved to the downstream side of the post-stage acceleration / deceleration electrode system 4 as shown in FIG. 6, the slit width adjusting mechanism can be easily attached, but there are the following problems. .

FIG. 8 is a diagram showing the beam focus characteristics of the apparatus shown in FIG. FIG. 8 (a) shows the case where the post-stage acceleration / deceleration is not performed, and the 60 keV ion beam 5 is applied to the mass separation slit 9
The position is the thinnest. FIG. 8 (b) shows the case where the second-stage acceleration is 100 kV, and FIG. 8 (c) shows the case where the second-stage deceleration is −40 kV. In the following, in order to facilitate understanding, the ion beam is used as a light beam to proceed with the discussion. When an electric field is generated by providing a potential difference between parallel plate electrodes 41 and 42 having beam passage holes of the same width, a virtual convex lens 10 and a concave lens 11 are formed as a pair as shown in the figure. Thicker than concave lens 11. Therefore, in both cases (b) and (c), the focus point of the ion beam 5 moves to the left (the upstream side of the ion beam), and the width of the ion beam 5 increases at the position of the mass separation slit 9. Therefore, there arises a problem that the performance of mass separation (mass resolution) is reduced.

In view of the above problems, an object of the present invention is to improve the performance of mass separation in a post-stage acceleration / deceleration type ion implanter in which a mass separation slit is installed on the downstream side (ground side) of the post-stage acceleration / deceleration electrode system. is there.

[Means for solving problems]

The present invention relates to a post-acceleration / deceleration type ion implanter in which a mass separation slit is provided on the downstream side of a post-acceleration / deceleration electrode system, in which the post-stage acceleration / deceleration electrode system is opposed to the upstream first electrode and the mass separation slit. And a grounded downstream second electrode and an intermediate electrode provided between the first and second electrodes and having an ion beam passage hole larger than the ion beam passage holes of the first and second electrodes. It is characterized by that.

[Action]

According to the configuration of the present invention, the virtual convex lens and the concave lens formed by the potential difference between the electrodes of the post-acceleration / deceleration electrode system can be made equal in thickness, and the ion beam can be focused to the thinnest at the position of the mass separation slit. Can be made.

〔Example〕

A first embodiment of the present invention will be described with reference to FIG. The ion beam 5 is extracted from the source plasma generated by the ion source 1 by the electric field created by the extraction electrode system 2, and this ion beam is passed through the mass separation magnet 3 and the mass separation slit 9.
Remove unnecessary components. A post-stage acceleration / deceleration electrode system 4 is provided between the mass separation magnet 3 and the mass separation slit 9, and an ion beam whose energy has been adjusted by this is passed through the slit 9 and is implanted into the semiconductor element 62. A high voltage power supply 8 applies a voltage to the extraction electrode system 2 and the post-stage acceleration / deceleration electrode system 4. Since the mass separation slit 9 is installed on the ground side of the post-acceleration / deceleration electrode system 4, it is easy to provide the slit width adjusting mechanism 91 to control the slit width of the slit 9.

FIG. 2 is a diagram showing the arrangement of the post-stage acceleration / deceleration electrode system 4 and the mass separation slits, and FIG. 3 is an enlarged view showing the details thereof. As shown in FIG. 3, the electrodes 41, 42, 43 constituting the post-acceleration / deceleration electrode system 4 are connected to the respective electrode supports 21, 22, 23.
, And a voltage is applied by the high voltage power supply 8 (the electrode 42 is grounded). The size of the ion beam passage hole of the intermediate electrode 43 is made larger than that of the electrodes 41, 42 on both sides. The electrode supports 21, 22, 23 are electrically insulated by the insulator 20. The material of the electrodes 41, 42, 43 is stainless steel, but the mass separation slit 9 generates heat due to collision of the ion beam, so a graphite material resistant to heat is used. The mass separation slit 9 is attached to the slit support 92, and is vertically moved by the slit width adjusting mechanism 91 to adjust the slit width.

FIG. 4 is a diagram showing a beam focus characteristic when a voltage is applied to the electrodes of the post-acceleration / deceleration electrode system 4 to accelerate / decelerate the ion beam. FIG. 4 (a) shows the case where the post-stage acceleration / deceleration is not performed, and the ion beam 5 of 60 keV is thinnest at the position of the mass separation slit 9. Fig. 4 (b) shows the case of post-acceleration of 100kV, and the intermediate electrode 4
Ions are accelerated between the intermediate electrode 43 and the ground electrode 42 by setting the voltage of 3 equal to the voltage of the acceleration electrode 41.
Since the beam passage hole of the intermediate electrode 43 is sufficiently larger than the beam passage hole of the ground electrode 42, the equipotential line 12 seeps out to the acceleration / deceleration electrode 41 side, and the convex lens 10 formed between the acceleration / deceleration electrode 41 and the intermediate electrode 43 is Become thin. Therefore, the convex lens 10 and the concave lens
The thicknesses of 11 are almost equal, and the ion beam 5 is focused most thinly in the vicinity of the position of the mass separation slit 9. on the other hand,
FIG. 4 (c) shows a case of deceleration at the subsequent stage of −40 kV. By setting the voltage of the intermediate electrode 43 equal to the voltage of the earth electrode 42, the ions are decelerated between the acceleration / deceleration electrode 41 and the intermediate electrode 43. . Also in the case of (c), as in the case of (b), the thicknesses of the convex lens 10 and the concave lens 11 are substantially equal to each other, and the ion beam 5 is focused most thinly in the vicinity of the position of the mass separation slit 9. As is clear from the above, the mass separation performance of the ion beam can be kept good regardless of the presence / absence of acceleration / deceleration in the subsequent stage.

Next, a second embodiment of the present invention will be described with reference to FIG.
Between the acceleration / deceleration electrode 41 and the ground electrode 42, there are provided two intermediate electrodes 43 and 44 having beam passage holes larger than the beam passage holes of any of these electrodes.
The second stage acceleration / deceleration electrode system 4 is composed of 2,43,44. Depending on the magnitude of the voltage that accelerates and decelerates the ion beam 5, the intermediate electrode 4
It is possible to switch the voltage of 3,44 and change the section in which ions are accelerated and decelerated. Therefore, even when the acceleration / deceleration voltage becomes large, the ion beam 5 can be focused most thinly in the vicinity of the mass separation slit 9. Further, in the present embodiment, as the mass separation slit 9, a rotary slit 9 whose slit width is variable by rotation is used, but instead of this, the slit as shown in the first embodiment may be used.

FIG. 10 is a diagram showing a third embodiment of the present invention. The peripheral portions of the beam passage holes of the acceleration / deceleration electrode 41 and the ground electrode 42 are made thicker toward the intermediate electrode 43. Here, 60ke
The case of accelerating the V ion beam 5 by 100 kV in the latter stage will be described as an example. The voltages of the acceleration / deceleration electrode 41, the intermediate electrode 43, and the ground electrode 42 are 100 kV, 100 kV, and 0 V, respectively. The electric field due to the potential difference between the intermediate electrode 43 and the ground electrode 42 oozes out between the acceleration / deceleration electrode 41 and the intermediate electrode 43 to form the thin convex lens 10.
On the other hand, the convex lens 10 is provided near the beam passage hole of the ground electrode 42.
A slightly thicker concave lens 11 is formed. This allows
The ion beam 5 is most thinly focused in the vicinity of the mass separation slit 9, and the divergence angle is small, and the narrowly focused range is long.

Finally, a fourth embodiment of the present invention will be described with reference to FIG. The mass separation slit 9 is equipped with a slit position adjusting mechanism 94 capable of adjusting the position of the ion beam 5 in the traveling direction in addition to adjusting the slit width. The high-voltage power supply 8 applies a voltage to the acceleration / deceleration electrode 41 and the intermediate electrode 43, and this voltage data 93 a is sent to the ion trajectory simulator 93. The ion trajectory simulator 93 calculates the trajectory of the ion beam based on these data, and the ion beam 5
Guess the position where is most thinly focused. The slit position adjusting mechanism 94 adjusts the slit position by using the position data 93b as a control signal. By controlling the slit position in this manner, the performance of mass separation does not deteriorate even if the focus position of the beam moves a little due to the subsequent acceleration / deceleration.

〔The invention's effect〕

In the latter-stage acceleration / deceleration type ion implanter of the present invention, the mass separation slit is installed on the downstream side of the latter-stage acceleration / deceleration electrode system, that is, the ground side, so that a mechanism for adjusting the width and position of the mass separation slit can be easily attached. become. Also,
Even when the post-stage acceleration / deceleration is performed, the thinnest focusing position of the ion beam does not largely deviate from the mass separation slit, and the mass separation performance does not deteriorate. Therefore, even if the mass resolution changes depending on the mass number of the extracted ions, a large amount of pure component beams can be extracted,
The mass separation slit installed at the above position can be configured so that the slit width and position can be adjusted from the outside by the slit adjustment mechanism even while the ion implanter is operating, so the operation of the ion implanter is stopped. Since the work of replacing the mass separation slit each time and the like can be eliminated, it is possible to improve the operation rate of the ion implantation device.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an ion implantation apparatus according to an embodiment of the present invention, and FIGS. 2 and 3 are schematic diagrams of the arrangement of a post-stage acceleration / deceleration electrode system and a mass separation slit in FIG. 1, respectively. A detailed view thereof, FIGS. 4 (a), (b), and (c) are explanatory views of its action, FIG. 5 is an overall configuration diagram of a conventional post-stage acceleration / deceleration type ion implantation apparatus, and FIG. Arrangement plan of the latter stage acceleration / deceleration electrode system and the mass separation slit in the conventional example,
The figure is an illustration of the principle of mass separation, Fig. 8 (a), (b),
(C) is a diagram for explaining the operation of the conventional example of FIG. 6, and FIGS. 9, 10, and 11 are diagrams showing other embodiments of the present invention. 1 ... Ion source, 2 ... Ion extraction electrode system 3 ... Mass separation magnet, 4 ... Post-acceleration / deceleration electrode system 5 ... Ion beam, 6 ... Ion implantation chamber 7 ... High-voltage shield, 8 ... High-voltage power supply 9 …… Mass separation slit, 10 …… Virtual convex lens 11 …… Virtual concave lens, 12 …… Equipotential line 20 …… Geisha, 21,22,23 …… Electrode support 41 …… Acceleration / deceleration electrode, 42 …… Ground electrode 43,44 …… Intermediate electrode, 61 …… Rotating disk 62 …… Semiconductor element, 91 …… Slit width adjustment mechanism 92 …… Slit support 93 …… Ion trajectory simulator 93a …… Voltage data, 93b …… Position data 94 …… Slit position adjustment mechanism

Claims (2)

[Claims] 1. An electrode system at a front stage for extracting an ion beam from an ion source, a mass separation magnet for mass-separating the ion beam extracted from the electrode system, and an ion beam mass-separated by the mass separation magnet. In an ion implanter comprising a mass separation slit for passing only a desired component to obtain a pure ion beam, and a latter stage acceleration / deceleration electrode system installed between the mass separation magnet and the mass separation slit. The post-acceleration / deceleration electrode system includes a first electrode facing the mass separation magnet, a grounded second electrode facing the mass separation slit, and ions larger than the ion beam passage holes of the first and second electrodes. The first with a beam passage hole
And an intermediate electrode provided between the second electrode and the second electrode. 2. An ion beam is accelerated by setting the first electrode and the middle intermediate electrode in the latter stage acceleration / deceleration electrode system to the same potential,
The ion implantation device according to claim 1, wherein the second electrode and the intermediate electrode are set to the same potential to decelerate the ion beam.