JP2569812B2 - High energy ion implanter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apparatus for implanting ions into a semiconductor substrate, a metal material, or the like.

<Prior Art> In general, a conventional ion implantation apparatus accelerates ions from an ion source by a DC voltage power supply, and sweeps the accelerated ions using an electromagnetic field or mechanical means. And the like.

<Problems to be Solved by the Invention> By the way, in recent years, as the ion implantation technology becomes an important technology of the doping process in the production process of the semiconductor integrated circuit, it is desired to perform ion implantation of higher energy and higher current than before. There is a growing demand.

In order to meet such a demand, an acceleration system using a high-frequency accelerator capable of accelerating a higher-energy, higher-current ion beam is being developed instead of the conventional DC high-voltage power supply.

Among radio frequency accelerators, in particular, radio frequency quadrupole accelerators (RFQs)
Accelerators) have the characteristic of accelerating while converging the beam, so that it is possible to accelerate without diverging a high-current ion beam. It is considered the best accelerator to do.

However, in a high-frequency accelerator, generally, unless the resonance frequency is continuously variable, the acceleration energy is not continuously variable, and the RFQ accelerator is also considered to be the same (for example, Nuclear Instrument and Methods in Physics Rese).
arch B37 / 38 (1989), K. TOKIGUCHI et al., “Ion Beam
Acceleration Us-ing Variable Frequency RFQ). On the other hand, ion implanters often require continuous variability of acceleration energy. Therefore, in order to use an RFQ accelerator for such applications, it is considered to vary the resonance frequency of the RFQ accelerator. Literature).

However, in this attempt, the structure of the RFQ accelerator with a variable resonance frequency is complex and at the research stage, and in addition, the RFQ accelerator of the variable frequency type has a higher resonance Q value than the RFQ accelerator of the fixed frequency type. The level is reduced from the level of about 10 ^{4 to the} level of about 10 ^3, and as a result, a large amount of high-frequency power (about 100 Kw) may be consumed.

The present invention has been made in view of such a point, and drives a target such as a semiconductor substrate without changing the resonance frequency of the RFQ accelerator, that is, without using a complicated resonance frequency variable type RFQ accelerator. It is an object of the present invention to provide a high-energy ion implanter capable of continuously changing ion energy in a wide range.

<Means for Solving the Problems> A configuration for achieving the above object will be described with reference to FIG. 1 corresponding to the embodiment. The high energy ion implantation apparatus according to the present invention includes an ion source 1, An RFQ accelerator (high-frequency quadrupole accelerator) 3 for introducing an ion beam from the ion source 1 and a high-frequency voltage to be applied to the RFQ accelerator 3 are applied to the RFQ accelerator 3 while maintaining a constant resonance frequency. A voltage setting means (RF) capable of setting any one of a plurality of voltage values such that the acceleration energy can change stepwise
RF amplifier (Q amplifier) 7, a high-frequency accelerator (for example, a single drift tube linac) 4 for introducing ions after acceleration by the RFQ accelerator 3, and a high-frequency voltage supplied to the high-frequency accelerator 4 and a phase thereof are changed. It is characterized by having means (SDTL RF amplifier 9 and phase shifter 10) for continuously accelerating and decelerating ions introduced into the high-frequency accelerator 4 within a predetermined energy range.

<Operation> The ion beam B from the ion source 1 is first accelerated by the RFQ accelerator 3, and the RFQ accelerator 3 changes its resonance frequency by changing the applied high-frequency voltage as described later. It is possible to change the acceleration energy stepwise without any change.

The ion beam B accelerated to a desired energy level by the RFQ accelerator 3 is continuously accelerated and decelerated within a certain energy range by the next-stage high-frequency accelerator 4 at each selected step level. Can be continuously varied from low energy to high energy.

Here, the RFQ accelerator has four electrodes 61a to 61d (vanes) having waveforms formed along the axial direction of the cylinder formed in the cylindrical tank 60 in the cylindrical tank 60, as schematically shown in a perspective view in FIG. ) Is applied to a cavity resonator having the same resonance frequency to resonate the cavity resonator, and a cavity having a predetermined speed is placed in a space surrounded by the tips of the electrodes 61a to 61d. In this case, the charged particles are accelerated by introducing the charged particles, and it is generally considered that the acceleration energy does not change unless the resonance frequency is changed as described above.

That is, in the high-frequency accelerator, the incident speed (energy) of the particles, the arrangement position of the electrodes (the cycle of the vane waveform in the RFQ accelerator) and the applied high-frequency voltage value are factors having a close relationship with each other. Even if it is changed, the acceleration energy is not changed and remains constant as long as other factors are constant. Rather, if the high-frequency voltage value is greatly reduced, the charged particles cannot be accelerated at all. It is generally described that the reason for this is that when the high-frequency voltage is reduced, the speed of the charged particles is reduced in the acceleration electric field, and the acceleration conditions are not satisfied in relation to the period of the electrode waveform.

In response to such a general theory, the present inventors have applied a high-frequency voltage applied to the electrode of the RFQ accelerator to the introduction speed of charged particles, the frequency of the applied high-frequency voltage (resonance frequency),
And a method of changing the acceleration energy without changing the resonance frequency by shifting by a predetermined amount below the voltage value satisfying the acceleration condition based on the period of the waveform formed on the electrode, and has already proposed and Yes (Japanese Patent Application
63-176540).

According to this acceleration energy control method, ions accelerated to a certain speed are introduced into the RFQ accelerator, and only the high-frequency voltage is shifted downward by a predetermined amount from the original design voltage value, so that the acceleration energy is stepped. Which has been confirmed by experiment.

The present invention takes advantage of this point, by selectively accelerating the energy of the ions from the ion source in a stepwise manner without changing the resonance frequency of the ions by an RFQ accelerator, and applying a predetermined energy such as a single-drift tube linac in the next stage. By continuously guiding the acceleration energy within the energy range to a high-frequency accelerator whose acceleration energy is variable, it is possible to continuously change the acceleration energy over a wide energy range as a whole.

<Embodiment> FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

The ions generated from the ion source 1 are accelerated to a predetermined initial energy by the DC voltage supplied to the ion source 1. The resulting ion beam B first
After being subjected to mass analysis by the former magnet 2 to become a beam of only target ions, the beam is incident on the RFQ accelerator 3 having a fixed frequency.

The RFQ accelerator 3 has the same structure as the conventional one shown in FIG. 6, but employs the above-described method of controlling the acceleration energy by shifting the applied high-frequency voltage. the magnitude of the high frequency power P ₁ supplied from the resonance frequency can be changed at an acceleration energy of stepwise remain fixed.

Ion beam B accelerated by this RFQ accelerator 3
Then enter the single drift tube linac 4, where it is further accelerated or decelerated.

This single drift tube linac 4 is the second
Has the structure shown in cross-section in FIG, by changing the charged high frequency power P ₂ and its phase as described later, it is possible to continuously change the acceleration (deceleration) energy.

Then, the ion beam B having passed through the single drift tube linac 4 is subjected to mass analysis again by the subsequent magnet 5, and then guided to the wafer W to which rotation and translation are given in the end station 6.

Now, the RFQ accelerator 3, the high frequency power P ₁ from RFQ accelerator amplifier 7 is introduced, the RFQ accelerator amplifier 7 inputs the constant frequency (resonance frequency) signal from the oscillator 8, the input obtaining a high-frequency power P ₁ amplifies the signal. Then, the voltage amplitude of the high frequency power P ₁ is, RFQ
It can be arbitrarily changed by operating a voltage setting device attached to the accelerator amplifier 7. Note that RF is actually
The voltage applied to the Q accelerator 3 is detected by a voltage detector, and the detection signal is compared with a voltage set value. Based on the result, the RFQ is set so that the high-frequency power P ₁ maintains the set amplitude value. The amplification degree of the accelerator amplifier 7 is automatically adjusted.

In RFQ accelerator 3, thus to the magnitude of the high frequency power P ₁ to be inputted to the, the acceleration energy FIG. 3 (a) ~
One of an acceleration energy of E ₀ to E ₂ shown in (c) can be selected stepwise.

On the other hand, single drift tube linac 4
The high frequency power P ₂ is supplied from the single drift tube linac amplifier 9, and the phase of the high frequency is shifted by Δφ with respect to the high frequency signal from the oscillator 8 by the phase shifter 10.

Here, the single drift tube linac generally has a high frequency phase φ _in when an ion beam is incident.
And the voltage V generated in the drift tube, energized change in V · cos [phi _in the ion beam, as it provides the energy change of V · cos [phi _out when emitted similarly, the sum V · a (cosφ _in + cosφ _out) It will make a change.

Now, in the single drift tube linac 4 in the embodiment of FIG. 1, φ _in is controlled by Δφ by the phase shifter 10, and V is also supplied by the single drift tube linac amplifier 9 independently of φ _in. Since it is controlled by the power P ₂ , V · cos φ _in is an amount that can be continuously changed. In addition, φ because _out is uniquely determined if it is determined that V · cosφ _in, eventually V · (cosφ _in + cos
φ _out ) is an amount that can be continuously changed. Therefore, the single drift tube linac 4 can continuously accelerate and decelerate the ion beam B.

This single continuous acceleration and deceleration range due to drift tube linac 4 δE (= | V · ( cosφ in + cosφ out)
|).

Then, assuming that the step width of each of the energy levels E _{0 to} E ₂ selectable by the RFQ accelerator 3 is ΔE ₁ and ΔE _{2 as} shown in FIG. 3, continuous addition at each incident energy of the single drift tube linac 4 is performed. As shown in FIG. 4, the deceleration ranges δE ₀ , δE ₁ and δE ₂ are set to ΔE ₁
And approximately equal to ΔE ₂ , so as to slightly overlap each other, it is possible to realize a wide range of continuous energy variability as shown in FIG.

In the method in which the acceleration energy is changed stepwise by changing the applied high-frequency voltage, a plurality of energy peaks of emitted ions may appear. Therefore, in order to guide only ions of the target energy to the single drift tube linac 4, the positions of the single drift tube linac 4 and the rear magnet 5 may be interchanged in the embodiment of FIG. However,
Even in the arrangement of FIG. 1, mass analysis is performed after the single drift tube linac 4, so that only ions of a desired energy are eventually led to the wafer W,
This position may be either.

In the embodiment shown in FIG. 1, the phase of the high frequency supplied to the single drift tube linac 4 is controlled by the phase shifter 10. However, the same effect can be obtained by changing the position of the single drift tube linac 4 with respect to the RFQ accelerator 3. Obtainable.

Furthermore, it is a matter of course that a high-frequency accelerator having a continuously variable energy other than the single drift tube linac can be used as the accelerator in the subsequent stage of the RFQ accelerator.

<Effects of the Invention> As described above, according to the present invention, the frequency of the RFQ accelerator is not changed without using a resonance frequency variable RFQ accelerator which is not yet practically used because of its complexity and high cost. First, the ion beam was first accelerated to one of a plurality of different acceleration energies in a stepwise manner using an RFQ accelerator that applied such a control method, using a method of changing the acceleration energy in a stepwise manner. After that, the next-stage high-frequency accelerator accelerates continuously within a predetermined energy range, so that a high-energy ion implanter with a wide range of continuous energy variability as a whole can be realized, which brings about an innovative advance in the semiconductor manufacturing process. Is expected.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, FIG. 2 is a cross-sectional view showing the structure of the single drift tube linac 4, and FIG. 3 is an explanatory diagram of a stepwise change in acceleration energy by the RFQ accelerator 3. FIG. 4 is an explanatory diagram of a continuous acceleration / deceleration range of energy by the single drift tube linac 4, FIG. 5 is an explanatory diagram of a continuous variable range of energy, and FIG. 6 is a partial sectional view showing the structure of the RFQ accelerator. It is. DESCRIPTION OF SYMBOLS 1 ... Ion source 2 ... Front stage magnet 3 ... RFQ accelerator 4 ... Single drift tube linac 5 ... Rear stage magnet 6 ... End station 7 ... RF amplifier for RFQ accelerator 8 ... Oscillator 9 ... Single drift tube Linac amplifier 10: Phase shifter B: Ion beam W: Wafer

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-121655 (JP, A) JP-A-2-27699 (JP, A) IEEE Catalog. NO. 87 CH2387-9 "(1987) IEEE PARTIPLE ACCELATOR CONTROL CONFERENCE Accelerator Evaluating and Technology" March 16-19, 1987. Washout on, D.W. C Volume1 of 3 pages 267-269

Claims (1)

(57) [Claims] An ion source, a high-frequency quadrupole accelerator for introducing an ion beam from the ion source, and a high-frequency voltage to be applied to the high-frequency quadrupole accelerator. Voltage setting means capable of setting the acceleration energy to any one of a plurality of voltage values such that the acceleration energy can be changed stepwise while maintaining the frequency, and a high-frequency accelerator for introducing ions after acceleration by the high-frequency quadrupole accelerator, A high-energy ion implanter comprising means for continuously changing acceleration and deceleration of ions introduced into the high-frequency accelerator in a predetermined energy range by changing a high-frequency voltage supplied to the high-frequency accelerator and a phase thereof.