JP3365226B2 - Ion implanter - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion implantation apparatus provided with an acceleration / deceleration device in which a plurality of high-frequency type acceleration / deceleration cavities are arranged in series. The present invention relates to means for expanding the energy variable range of the acceleration / deceleration device. 2. Description of the Related Art A high-frequency linear accelerator comprising a plurality of high-frequency accelerating / decelerating cavities arranged in series as an ion accelerating means in one of ion implanters having a high energy of ion acceleration energy on the order of MeV. There is an ion implantation apparatus using a type of acceleration / deceleration device, and a conventional example thereof is shown in FIGS. 5 and 6, respectively. This ion implantation apparatus accelerates or decelerates bunch-like (collective) ions 2 extracted from an ion source (not shown) and subjected to mass separation and pre-acceleration as required by an acceleration / deceleration device 4. After that, mass separation is performed as necessary, and the resultant is incident on a target (for example, a semiconductor substrate) 6 to perform ion implantation on the target 6. It should be noted that the entire path of the ions 2 is set in a vacuum atmosphere. If the pre-acceleration means is, for example, a high-frequency accelerator such as an Alvaret type, a Widley type or an RFQ type, the bunch-like ions 2 can be obtained as they are. If the pre-acceleration means is a direct current type accelerator such as a tandem type of electrostatic accelerating tube, the DC
The bunch-shaped ions 2 can be obtained by bunching the beam with a buncher. The acceleration / deceleration device 4 includes a plurality of two-gap type (in the case of FIG. 5) or
It has a gap-type (in the case of the example of FIG. 6) acceleration / deceleration cavity 10 and a plurality of high-frequency power supplies 20 for independently supplying high-frequency power to each acceleration / deceleration cavity 10. The respective acceleration / deceleration cavities 10 are connected by a drift tube 30. Instead of the drift tube 30, a Q lens that prevents divergence of the beam may be provided. Each of the acceleration / deceleration cavities 10 has two ground electrodes 14 disposed at the entrance and exit of the cavity 12, and one (in the case of FIG. 5) or two (FIG. 6) disposed therebetween.
5) and two (in the case of FIG. 5) or three (in the case of FIG. 6) gaps 18 are formed between these electrodes. I have. Each acceleration / deceleration cavity 10 is, for example, a quarter-wave resonance cavity, and uses π-mode resonance. The π mode, the gap distance L _n to be described later, refers to a mode that is set to a distance corresponding to 1/2 of the high-frequency power of the phase. The distance L between the gaps of the respective acceleration / deceleration cavities 10
_n (n indicates the order from the front, and n = 1, 2, 3,...
・) Is larger in the latter stage, that is, L ₁ <L ₂ <L ₃
<L ₄ ... The reason will be described later. The supply of high-frequency power from each high-frequency power supply 20 to each corresponding acceleration / deceleration cavity 10 is performed by, for example, a coupling coil 22 or by capacitive coupling. Since the high-frequency power supply 20 is provided independently for each of the acceleration / deceleration cavities 10, the phase and power of the high-frequency power supplied to each of the acceleration / deceleration cavities 10
Can be controlled independently of each other. The operation principle of the two-gap type acceleration / deceleration cavity 10 will be described with reference to FIG. 7, and the operation principle of the three-gap type acceleration / deceleration cavity 10 will be described with reference to FIG. As described above, the high-frequency power source 20 is not directly connected to the acceleration / deceleration electrode 16. Referring first to FIG. 7, this acceleration / deceleration cavity 10
Resonates, a potential V (t) expressed by the equation 1 is generated at the acceleration / deceleration electrode 16. V ₀ is the voltage amplitude, ω is the angular velocity, t
Is time. E in the figure shows an example of the electric field at that time. [0011] Equation 1] _{V (t) = V 0 cos} (ωt) [0012] Now, assuming that the speed of the ions 2 at acceleration cavity 10. little changes, corresponding to the gap distance L _n Considering the case where a monovalent ion 2 of velocity is incident,
The ion 2 has V ₀ cos φ × F at the first gap 18.
(Φ is the phase of the high-frequency power when the ions 2 pass through the center of the gap 18, and F is a coefficient relating to the time of passing through the gap 18). Further, when passing through the second gap 18, the phase of the high-frequency power advances by π (because of the π mode resonance), so that the ions 2 receive the same energy again, and as a result, 2 V is applied to one acceleration / deceleration cavity 10.
It is accelerated with energy of ₀ cos φ × F. In the case of the three-gap type, referring to FIG.
At the time of the π mode resonance, a potential having a phase difference of 180 degrees between the two acceleration / deceleration electrodes 16, that is, V (t) and −V (t) shown in Expression 1 are generated. In that case, the central gap 18
Is twice as large as the electric field of the other gaps 18, so that the ions 2 are V ₀ cosφ × F and 2V ₀ cosφ at the first, second and third gaps 18, respectively.
× F and V ₀ cosφ × F energy,
As a result, the acceleration / deceleration cavity 10 is accelerated by the energy of 4V ₀ cos φ × F. An advantage of such a deceleration cavity 10 is that it is possible to accelerate or decelerate even-ion having a velocity that is not fully compatible with the gap distance L _n. In other words, by adjusting the phase φ of the supplied high frequency power, an acceleration or deceleration electric field of a certain magnitude can always be given to the ions 2 in the gap 18. Further, by changing the RF power supply, it is possible to control the voltage amplitude V _0, has a relatively wide energy variability. In this case, the two-gap type or three-gap type acceleration / deceleration cavity 10 is used because the acceleration / deceleration efficiency T (Transmit Time F) with respect to the velocity of the incident ion 2 is used.
This is because the change in actor is relatively small. An example is shown in FIG. In this figure, the incident velocity v of the ion 2 is
Is shown by a ratio of ion velocity β (= v / c) for the speed of light c, acceleration efficiency T, when the optimum value beta ₀ to incoming velocity of ions 2 corresponds exactly to the gap distance L _n It becomes maximum and decreases gradually when the incident velocity is higher, but decreases rapidly when the incident velocity is low. [0016] and the distance L _n between the gap, the relationship between the optimum value beta _0, when the π mode resonance, represented by the number 2. λ is the resonance wavelength. L _n = β ₀ λ / 2 The conventional acceleration / deceleration device 4 using such an acceleration / deceleration cavity 10 is normally set in an acceleration mode for accelerating the ions 2. maximum gap distance L _n of each stage as the energy is obtained has been determined in this acceleration mode. Thus, the gap distance L _n, as described above, are large enough acceleration cavities 10 of the subsequent stage. However, if the acceleration / deceleration device 4 attempts to decelerate the ions 2 incident thereon, it can only be decelerated at most in the first stage acceleration / deceleration cavity 10. This is because, in the second-stage acceleration / deceleration cavity 10, the gap distance L ₂ is originally optimized for acceleration, so considering the velocity of the ions 2 decelerated in the first step, the gap distance L _{2 is} considered. Is too large, in other words, the ion velocity ratio β is smaller than the optimum value β ₀ ,
This is because the acceleration / deceleration efficiency T sharply decreases as shown in FIG. Qualitatively, considering the two-gap type acceleration / deceleration cavity 10, even when decelerating in the first gap 18, the high-frequency power becomes the phase on the acceleration side when the ions 2 pass in the second gap 18. Acceleration at the leverage can happen. From the third stage onward, the acceleration / deceleration efficiency T is further reduced. Therefore, in the acceleration / deceleration device 4 as described above,
The energy range that can be decelerated is much narrower than the energy range that can be accelerated, and there is a problem that the entire energy variable range is narrower. Accordingly, the present invention has a main object of expanding the entire energy variable range by expanding the energy range in which the above-described acceleration / deceleration device can decelerate. According to the ion implantation apparatus of the present invention, the gap between the first stage acceleration / deceleration cavity and the gap is located immediately after the first stage acceleration / deceleration cavity of the acceleration / deceleration device. One or more two-gap or three-gap type acceleration / deceleration cavities with a small distance are inserted in series at a later stage with a smaller distance between the gaps, and high-frequency power is supplied to the inserted acceleration / deceleration cavities. It is characterized in that one or more high-frequency power supplies that are supplied independently of each other are provided. According to the above configuration, the distance between the gaps of the acceleration / deceleration cavity inserted immediately after the first stage of the acceleration / deceleration device is smaller than that of the acceleration / deceleration cavity of the first stage. Even when the ions are decelerated in the first-stage acceleration / deceleration cavity, the ions from the first stage can be efficiently decelerated by the acceleration / deceleration cavity inserted immediately after the first stage. Therefore, the energy range in which deceleration can be performed is widened. In the acceleration mode, even when ions are accelerated in the first-stage acceleration / deceleration cavity, in the 2-gap type or 3-gap type acceleration / deceleration cavity, the ion velocity is lower than the optimum value as described above. Since the acceleration / deceleration efficiency decreases less on the high-speed side than on the low-speed side, ions can be accelerated relatively efficiently by the acceleration / deceleration cavity inserted immediately after the first stage. Therefore, the energy range that can be accelerated is wide. As a result, the entire energy variable range of the acceleration / deceleration device can be expanded. FIG. 1 and FIG. 2 show an embodiment using a two-gap type acceleration / deceleration cavity, and FIGS. 3 and 4 show an embodiment using a three-gap type acceleration / deceleration cavity. Shown respectively.
5 and 6 are denoted by the same reference numerals, and differences from the conventional example will be mainly described below. 7 to 9 are also applied to the following embodiments. The ion implantation apparatus shown in FIG. 1 includes an acceleration / deceleration device 4a corresponding to the conventional acceleration / deceleration device 4 shown in FIG.
₁ is set to correspond exactly to the velocity of the ions 2 incident on it, ie, L ₁ = β ₀ λ / 2.
β ₀ and λ are as described above. This is the same in the embodiments of FIGS. Immediately after the first-stage acceleration / deceleration cavity 10, that is, at the second stage in this example, a two-gap type acceleration / deceleration cavity having a smaller gap distance than the first-stage acceleration / deceleration cavity 10 is used. One deceleration cavity 10 is inserted. The distance between the gaps in the third and subsequent stages of the acceleration / deceleration cavity 10 is larger than the distance between the gaps in the first stage and larger in the later stages. Equation 3 collectively shows the relationship between the gap distances L _n (n is the same as described above, and the same applies to the following) at each stage in this embodiment. L ₁ > L ₂ , L ₁ <L ₃ <L ₄ ... The distance L between the gaps of the acceleration / deceleration cavities 10 in each stage
_n is, specifically, the ion 2 to be most efficiently accelerated or decelerated.
, The energy range to be accelerated / decelerated, and the voltage amplitude V ₀ when the maximum power is applied,
May be set in a range that satisfies the relationship shown in FIG. A high-frequency power supply 20 for independently supplying high-frequency power to each of the acceleration / deceleration cavities 10 is connected to each of the acceleration / deceleration cavities 10.
The coupling means between each high-frequency power supply 20 and each acceleration / deceleration cavity 10 is as follows:
As described above. The second-stage acceleration / deceleration cavity 10 in the acceleration / deceleration device 4a has a smaller gap distance than the first-stage acceleration / deceleration cavity 10, so the first-stage acceleration / deceleration cavity 10 It is easier to adapt to the slower ions 2. Therefore, when using the acceleration / deceleration device 4a in the deceleration mode,
First, the ions 2 are decelerated by the first-stage acceleration / deceleration cavity 10. In this case, the ions 2 from the first stage are further efficiently decelerated by the second-stage acceleration / deceleration cavity 10. Can be. Therefore, in the acceleration / deceleration device 4a, the energy range in which deceleration can be performed is wider than that in the conventional example shown in FIG. In the deceleration mode, the acceleration / deceleration cavities 10 of the third and subsequent stages particularly have a larger inter-gap distance than the decelerated ions 2 as they approach the later stages. It is usually difficult to slow down. Therefore, in that case, the third and subsequent stages of the acceleration / deceleration cavity 10
In particular, the operation of the acceleration / deceleration cavity 10 may be stopped without supplying high-frequency power to the acceleration / deceleration cavity 10 on the subsequent stage. In this case, the ions 2 pass through the acceleration / deceleration cavity 10 without any change. When the acceleration / deceleration device 4a is used in the acceleration mode, the ions 2 are first accelerated by the first-stage acceleration / deceleration cavity 10. In this case, the second-stage acceleration / deceleration cavity is used. For 10, the velocity of the ions 2 is higher than the optimal velocity for the inter-gap distance L ₂ of the second-stage acceleration / deceleration cavity 10 (that is, the above β ₀ in terms of the ion velocity ratio). In the two-gap type or three-gap type acceleration / deceleration cavity 10, as described above with reference to FIG.
Since towards the higher speed side than the rate the optimum value beta ₀ ion 2 is less reduction in the acceleration and deceleration efficiency T than the low speed side, that is, toward the high speed side is larger allowable range of the acceleration and deceleration efficiency T, the second The ions 2 can be accelerated relatively efficiently also by the acceleration / deceleration cavity 10 of the stage. That is, the second-stage acceleration / deceleration cavity 10 can be sufficiently used not only for deceleration but also for acceleration of the ions 2. Of course, in the accelerating and decelerating cavities 10 of the third and subsequent stages, as shown in Equation 3, the distance between the gaps of the accelerating and decelerating cavities 10 of the first stage is larger and the distance between the gaps of the latter is larger. Because it is bigger, Ion 2
Can be accelerated efficiently. Therefore, in the acceleration / deceleration device 4a, the energy range in which acceleration can be performed is wide. If it is desired to further increase the energy range that can be decelerated, immediately after the second-stage acceleration / deceleration cavity 10, one or more acceleration / deceleration cavities 10 having a smaller gap distance are inserted in series. May be. In the third stage, the acceleration / deceleration cavity 1 in which the gap distance L ₃ is smaller than that in the second stage
FIG. 2 shows an embodiment in which 0 is further inserted. The relationship between the gap distances L _n at each stage in this embodiment is shown in Equation 4. ## EQU4 ## L ₁ > L ₂ > L ₃ , L ₁ <L ₄ <L ₅ ... In the case of the embodiment shown in FIG. too small eyes of acceleration cavities 10 the gap distance L ₃ of, but can not be successfully set the RF power of the phase so as to correspond to the acceleration or deceleration cavity 10 may occur, in which case, acceleration In the mode, high-frequency power does not need to be supplied to the third-stage acceleration / deceleration cavity 10, and further acceleration may be performed in the fourth and subsequent stages. In the embodiment shown in FIGS. 3 and 4, each of the acceleration / deceleration cavities 10 is of a three-gap type.
2 is the same as that of the embodiment of FIG. 2, and the description thereof will be referred to, and the duplicate description will be omitted here. The number of stages of the accelerating and decelerating cavities 10 constituting the accelerating and decelerating device 4a is not limited to the one described in the above example, but may be any number of stages, and specifically, it is necessary. What is necessary is just to determine according to an energy range etc. As described above, according to the present invention, the acceleration / deceleration cavity having a small gap distance inserted immediately after the acceleration / deceleration cavity of the first stage of the acceleration / deceleration device further enhances the first stage. Ions from the acceleration / deceleration cavity can be efficiently decelerated, and the energy range in which the ions can be decelerated is widened. Moreover,
In a two-gap type or three-gap type acceleration / deceleration cavity, the acceleration / deceleration efficiency on the high-speed side is lower than the low-speed side on the ion velocity than the optimum value. The deceleration cavity can also accelerate ions relatively efficiently. Therefore, the energy range that can be accelerated is wide. As a result, the entire energy variable range of the acceleration / deceleration device can be expanded. In addition, since various ions can be accelerated to a wide range of energy and implanted into the target, the applicable range of the ion implantation apparatus is expanded.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view partially showing an example of an ion implantation apparatus according to the present invention including an acceleration / deceleration device using a two-gap type acceleration / deceleration cavity. FIG. 2 is a view partially showing another example of an ion implantation apparatus according to the present invention including an acceleration / deceleration device using a two-gap type acceleration / deceleration cavity. FIG. 3 is a diagram partially showing an example of an ion implantation apparatus according to the present invention including an acceleration / deceleration device using a three-gap type acceleration / deceleration cavity. FIG. 4 is a diagram partially showing another example of an ion implantation apparatus according to the present invention including an acceleration / deceleration device using a three-gap type acceleration / deceleration cavity. FIG. 5 is a view partially showing an example of a conventional ion implantation apparatus including an acceleration / deceleration device using a two-gap type acceleration / deceleration cavity. FIG. 6 is a view partially showing an example of a conventional ion implantation apparatus including an acceleration / deceleration device using a three-gap type acceleration / deceleration cavity. FIG. 7 is a view showing the operation principle of a two-gap type acceleration / deceleration cavity. FIG. 8 is a diagram showing the operation principle of a three-gap type acceleration / deceleration cavity. FIG. 9 is a diagram showing an example of a change in acceleration / deceleration efficiency of an acceleration / deceleration cavity with respect to the velocity of incident ions. [Description of Signs] 2 Ions 4a Acceleration / deceleration device 6 Target 10 Acceleration / deceleration cavity 18 Gap 20 High frequency power supply L _n Distance between gaps

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-10-125274 (JP, A) JP-A-9-237700 (JP, A) JP-A-9-260100 (JP, A) JP-A-62- 295400 (JP, A) JP-A-61-264650 (JP, A) JP-A-60-121655 (JP, A) JP-A-62-272446 (JP, A) JP-A-64-21073 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01J 37/317 H01L 21/265 603

Claims (1)

(1) A plurality of two-gap or three-gap type acceleration / deceleration cavities which are arranged in series with each other and have a larger distance between gaps in later stages, and respective acceleration / deceleration cavities. An acceleration / deceleration device including a plurality of high-frequency power supplies for independently supplying high-frequency power to the cavity is provided, and the bunch-shaped ions are accelerated or decelerated by the acceleration / deceleration device to be incident on a target. In the ion implantation apparatus configured to perform ion implantation on a target, immediately after the first-stage acceleration / deceleration cavity of the acceleration / deceleration device, at least one of the two or more 2 whose gap distance is smaller than that of the first-stage acceleration / deceleration cavity. Gap-type or three-gap-type acceleration / deceleration cavities, the later ones having a smaller gap distance are inserted in series with each other, and high-frequency power is applied to each inserted acceleration / deceleration cavity. An ion implantation apparatus comprising one or more high-frequency power supplies independently supplied.