JPS62272446A - Ion implanting apparatus - Google Patents

Abstract

PURPOSE:To make a plurality of RF oscillators needless without high voltage needed, by installing a means of generating ion beams comparatively low in energy and an ion acceleration stage where the ion beams are accelerated and ejected. CONSTITUTION:Ion beams i1, whose energy is comparatively as low as the energy regulated by voltage impressed on a drawn-out electrode 13, are ejected from an ion beam generation means 10. These ejection ion beams i1 are made incident to an ion acceleration stage 20 and accelerated there. In the acceleration stage 20, a high-frequency signal from at least one high-frequency signal generator 21 is impressed on a lagging wave circuit 22 and the lagging wave circuit 22 is composed so that excessive speed of the incident ion beams i1 passing and being accelerated there is identical to a phase speed of the high-frequency signal. Therefore, the incident ion beams i1 are consecutively accelerated in order, and ion beams i2 accelerated at high speeds are ejected from the ejection port. Only ions i3 having desirable energy, out of the acceleration ions i2, are then ejected through an energy filter 30.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Summary] Low-energy ions generated using a relatively low-voltage power source are controlled by a method in which the phase velocity of a high-frequency signal changes from the ion entrance to the exit exit. This is an ion implantation device that accelerates ions through an ion acceleration stage having a slow wave circuit adjusted to achieve high speed along the ion implantation.

[Industrial application field]

The present invention relates to an accelerated ion injection device, and more particularly to an accelerating device for an ion implantation device for doping semiconductor wafers with impurity ions.

[Prior art and problems to be solved by the invention]

Ion implanters are used to dope semiconductor wafers with impurities. FIG. 4 shows a configuration diagram of a conventional ion implantation apparatus and a conceptual diagram of doping impurity ions into a semiconductor wafer. In the ion implantation device, a first power supply, typically at a maximum voltage of 175 to 160 KV, is connected between an external casing 4 and an internal casing 41 which are grounded. Inside the internal housing 41, a second power source 45, typically a voltage of 25 to 40 KV, is applied between the ion source 43 and the extraction electrode 44, and this voltage causes the ion source 43 to eject an ion beam. . The ejected ion beam is introduced into the mass analysis magnet 46, and when a magnetic flux density B exists in the illustrated direction, the light mass ions i11 and the heavy mass ions ih collide with the inner wall of the analysis magnet 46 and are absorbed. , ions of desired mass are ejected. (The ions ejected from the mass analysis magnet 46 are further selected by a slit 47, accelerated by an accelerator 42, and introduced into the irradiation housing 5.On the low potential side of the power source 45, the mass analysis magnet 46, The slit 47 and the entrance side of the accelerator 42 have the same potential as the internal housing 41. Therefore, the voltage of the power source 48 is higher than the ground.The accelerator 42 performs electric field acceleration using this potential difference.Inside of the irradiation housing 5 is a vacuum and the target mechanism is placed inside it.

A sectional view of the target mechanism of FIG. 4 is shown in FIG. The target mechanism 3 includes an aluminum support shaft 32
The target disc 31 made of aluminum is attached to the target disc 31. The wafer 2 to be ion-irradiated is mounted on the surface of the target disk 31 . The target mechanism 3 is placed in a vacuum atmosphere within the irradiation housing 5 in the position shown in FIG. 5, and is rotated about the rotation axis O-0'.

As a result, the wafer 2 placed on the periphery of the surface of the target disk 31 is sequentially irradiated with the ion beam ION, and ions are implanted into the wafer.

Note that the target mechanism 3 is arranged in the vertical direction v within the irradiation housing s.
-v', so that ion implantation can be performed on the entire surface of the wafer 2.

As semiconductor devices become more highly integrated and more complex, ions are required to be implanted into wafers at deeper depths. It is said that the energy of the accelerated ions is approximately proportional to the energy of the ions.The energy of the accelerated ions is proportional to the sum of the voltage applied to the accelerator 42 and the voltage of the ion extraction power supply 45.In the above example, the The sum of the voltage applied to the ion extraction power source 45 and the voltage of the ion extraction power source 45 was a maximum of 200 KV.Therefore, when ion implantation is required to be 10 times as deep as the ion implantation by the ion implantation device described above, the power source 48 has a voltage of approximately 2 MV. A power source with a certain voltage is required.

However, first of all, using a voltage as high as 2 MV for the power supply 48 itself is quite technically and economically difficult. Next, when an extremely high voltage of 2 MV is used, a problem arises in that it is extremely difficult to insulate the device. Moreover, the length of the accelerator becomes considerably long, and the overall size of the ion implantation apparatus becomes very large.

As a solution to the above-mentioned problem regarding the high voltage to be applied to the accelerator, a tandem accelerator 5A shown in FIG.
Ion implantation devices using ion implantation devices are known. The ion implantation apparatus shown in FIG. 6 includes a negative ion generation source 9, an accelerator 5A for accelerating negative ions i, 1 ejected from the negative ion generation source, and a device for removing impurities from among the accelerated ions i, 1. The mass spectrometry magnet 9B has a mass spectrometry magnet 9B of
Ions that have passed through B are implanted into the wafer mounted on the target mechanism 3. The accelerator 5A includes electrodes 51 and 53 provided in tandem and a power source 5 connected to the electrode 51.
It is composed of 2. On the other hand, the electrode 53 is grounded. The entire accelerator 5A is in a vacuum, but the degree of vacuum is slightly lowered in the C3 section near the electrode 51 (.As a result,
Negative ions 11' are accelerated by the electrode 51, and due to the reduced degree of vacuum, interact with residual gas, and positive ions generated by losing electrons are accelerated by the electrode 53 and ejected. Since the accelerated ions include ions of various valences, unnecessary ones are removed by the mass spectrometry magnet 9B.

In the above ion implantation apparatus, the accelerator 5A accelerates in two steps, positive and negative, by the electrodes 51 and 53 provided in tandem, so that the power source 52 connected to the electrode 51 is connected to the power source 48 in FIG. The advantage is that it only costs half. However, although there are such advantages, according to the above-mentioned example, a voltage as high as IMV is still applied, and the problem of insulation still remains. Furthermore, it is necessary to generate negative ions as an ion source, and there is a problem in that a special negative ion generation source 9A is required.

Another example of a conventional ion implantation device is shown in FIG.

The ion implantation apparatus shown in FIG. 7 is composed of an ion generating means 10 and an accelerator 5B having the same structure as the internal housing 41 shown in FIG. 4. The accelerator 5B has electrodes 61 to 69 installed in the axial direction, high frequency (RF) oscillators 71 to 75 connected to every other electrode, and electrodes 62, 64, 66, to which no high frequency oscillator is connected. 68
is grounded to the earth together with the ground line of the beam irradiation mechanism 3. Ions 11 ejected from the ion generating means 10
'' is input between the first electrode 61 and the RF oscillator 71 reaches the electrode 61, and almost at the same time the RF electric field is reversed, then it is accelerated by the grounded electrode 62, and then alternately The ion implanter is accelerated by an electric field.Since such an ion implanter does not require an ultra-high voltage, the above-mentioned insulation problem in the ion implanter is solved.However, a large number of RF oscillators must be used, and
A problem encountered is that adjusting these phases and gains is complex and cumbersome.

[Means to solve the problem]

The present invention solves the problems related to the above-mentioned ion implantation apparatus, and a block diagram of the principle of the ion implantation apparatus of the present invention that solves the above problems is shown in FIG.

That is, in the invention, means 10 for generating an ion beam i having a relatively low energy comparable to the energy defined by the voltage applied to the extraction electrode;
An ion acceleration stage 20 that receives an ion beam 11 from the ion beam generating means, accelerates the incident ion beam, and ejects it, and includes a high frequency signal generator 21 and a slow wave circuit 22, and the slow wave circuit An ion implantation device is provided, comprising: an ion implantation device configured such that the phase velocity of a high frequency signal from the high frequency signal generator applied to the ion beam increases in a predetermined relationship from the input side to the exit side. be done.

Further, in the present invention, more preferably, an energy filter 30 is further provided after the ion acceleration stage to allow only ions i of a predetermined energy to pass among the accelerated ions 12.

[For production]

The ion beam generating means 10 emits an ion beam with a relatively low energy equivalent to the energy defined by the voltage applied to the extraction electrode.

The ejected ion beam is introduced into the ion acceleration stage 20 and accelerated. In the ion acceleration stage 20, a high frequency signal from at least one high frequency signal generator 21 is applied to a slow wave circuit 22. The incident ion beam is sequentially and continuously accelerated.

More preferably, only desired ions i3 of the accelerated ions 12 ejected from the ion acceleration stage 20 are extracted via the energy filter 30.

〔Example〕

An embodiment of the invention will be described with reference to FIG.

The ion implantation apparatus shown in FIG. 2 has the same components as those shown in FIG. The ion beam generating means 10 is comprised of an ion extraction electrode 14, a mass manalyzer 15, and a slit 16. The voltage of the extraction power supply 13 is
1 is grounded to the ground, typically 25 to 30
It is KV. Here, the housing 11 is grounded to the earth, and the fourth
Although a high voltage is not applied as shown in the figure, this is not essential, and another acceleration means (corresponding to FIG. 42) may be provided between the acceleration stage 20 and the acceleration stage 20.

The ion implantation apparatus includes an acceleration stage 20 after the ion beam generation means 10, and the acceleration means includes a high frequency signal generator 21 that generates a high frequency signal, typically several MH.
, and a slow wave circuit 22. slow wave circuit 2
2 includes a metal cylinder 221, metal cylinders 231 to 235 installed in the cylinder, and cylinders 231 to 235 supported and fixed to the cylinder.
It is composed of a helical coil 222 disposed in the inner space of 235 and a terminating resistor 223 connected to the helical coil. The high frequency signal generator 21 is connected to one end of the helical coil 222, and a high frequency signal is applied to the helical coil. The terminating resistor 223 is provided to prevent reflection. Here, along the axial direction of the acceleration stage, the helical coil 222 has a unit length d near the ion injection port, a number of turns per turn N, and a unit length near the ion injection port 6%, provided that c
t, = dS, number of turns per turn N.

It is larger than . Therefore, the high frequency signal travels per unit length near the entrance for a time of 1. is larger than the time t it takes for the fuel to travel per unit length in the vicinity of the injection port. Naturally, the inductance L1 per unit length near the entrance port is larger than the inductance per unit length near the exit port. On the other hand, regarding the cylinders 231 to 235, along the axial direction of the acceleration stage, the length of the inner cylinder 231 near the entrance port is shorter than the length of the inner cylinder 235 near the exit port. Therefore, inner cylinder 2
The capacitance CI of 31 is smaller than the capacitance C3 of the inner cylinder 235, and the inductance and capacitance between the entrance and exit ports are set to be continuous between the above-mentioned values, respectively. The above-described slow wave circuit 22 is configured such that a resonant circuit of inductance and capacitance is formed in response to the high frequency signal of the high frequency signal generator 21 everywhere along the axial direction.

Preferably, the ion implanter includes an energy filter 3 comprising an electrode 31 and a slit 32 after the acceleration stage 20.
0 is set.

The above-described ion beam generating means lO, ion acceleration stage 20, and energy filter 30 are placed in a vacuum atmosphere.

The operation of the ion implanter shown in FIG. 2 will be described.

As described above with reference to FIG. 4, ions i of a desired mass are ejected from the ion generating means IO. The energy of this ion il corresponds to the voltage applied to the extraction electrode 13. This ion 1. is introduced into the entrance of the ion acceleration stage 20, more specifically the slow wave circuit 22. The incident ions i are transmitted to the high frequency generator 21 through a resonant circuit consisting of the capacitance of the inner cylinders 231 to 235 and the helical coil 222.
A high frequency signal is applied to accelerate the process. Here, the helical coil 222 is wound roughly from the entrance to the exit, and is wound so that the phase velocity of the high frequency signal along the axial direction of the acceleration stage 20 increases sequentially. The incident ions 11 are accelerated and gradually become faster, and the acceleration speed of the ions is set to be equal to the phase velocity.

Therefore, the incident ion 1. are sequentially and continuously accelerated by the slow wave circuit 22, and the ions 12 accelerated at high speed are ejected from the ejection port.

The ejected accelerated ions 12 are introduced into the energy filter 30, and an electric field is applied between the electrodes 31 to bend the traveling direction according to the energy, so that the ions i with the desired energy are
3 is injected through the slit 32. The ejected ions are implanted into a semiconductor wafer.

In the embodiments described above, the ion generating means 1o has a relatively low voltage applied to the extraction electrode 14, in this example, 2
Since only a voltage of about 5 to 30 KV is applied,
No insulation problems arise. Further, as shown in FIG. 4, a high voltage for acceleration is not required, and no insulation treatment is required for this purpose. Further, the acceleration stage 20 has a large number of RF
No generator is required, basically only one RF generator is required. Therefore, the cost of the equipment is low and there is no need for complex phase adjustment between multiple RF generators.

In the embodiment of FIG. 2, phase adjustment may be required. The phase can be adjusted by changing the diameters of the cylinders 231 to 235 as shown by arrow A in the figure to change the capacitance.

FIG. 3 shows another embodiment of the slow wave circuit of the present invention.

The slow wave circuit shown in FIG. 2 uses a helical coil, while the slow wave circuit shown in FIG. 3 uses a filtering three-type slow wave circuit 25. The configuration other than the slow wave circuit 25 is the same as that shown in FIG. 2, so a description thereof will be omitted. The filtering three-type slow wave circuit 25 has comb tooth shaped circuits 251 to 259 provided inside a cylinder 250, and the high frequency signal from the high frequency generator 21 is applied to the comb teeth through the cylinder 250, and Incident ions il are accelerated by a longitudinal electric field mode or a transverse electric field mode between both circuits of the comb or between output circuits of opposing combs. As in the case of FIG. 2, the axial spacing of the comb teeth of the comb tooth shaped circuits 251 to 259 is set so as to match the advancing speed of the incident ions whose phase velocity has been accelerated.

As a result, the incident ions are sequentially and continuously accelerated by the phase velocity, and the accelerated ions i! is ejected from the injection port.

Although the above embodiments have been described in connection with an ion implantation device, the present invention is not limited to an ion implantation device, but can be applied to a device using an ion acceleration stage based on the concept illustrated in FIG. 2 or 3. .

〔effect〕

As described above, according to the present invention, an acceleration stage that does not require high voltage or a large number of high frequency generators, is relatively small, and is capable of accelerating low energy ions into considerably high energy ions. An apparatus having the following is provided.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the principle of the present invention, Fig. 2 is a block diagram of an ion implanter according to an embodiment of the present invention, and Fig. 3 is a diagram of a slow wave circuit applied to an ion implanter according to another embodiment of the present invention. A cross-sectional view, Figure 4 is a configuration diagram of a conventional ion implanter, and Figure 5 is a diagram of a conventional ion implanter.
The figure shows a cross-sectional view of the target mechanism, and FIGS. 6 and 7 are configuration diagrams of other conventional ion implantation apparatuses. (Explanation of symbols) 10... Ion beam generating means, 11... Housing, 12... Ion source, 13
. . . Extraction power source, 14 . . . Extraction electrode, 15.
...Mass analyzer, 16...Slit, 20...
Ion acceleration stage, 21... RF oscillator, 22... Slow wave circuit, 221... Cylinder, 222... Spiral coil 223... Termination resistor, 231-235
...Inner cylinder, 25...Filtered wave type slow wave circuit, 30...
・Energy filter, 31... Electrode, 32... Slit. Block diagram of the principle of the present invention Fig. 1 10...Ion beam generating means 30...Energy filter Fig. 3 A sectional view of a slow wave circuit according to another embodiment of the present invention Fig. 4 Configuration diagram of a conventional ion implantation apparatus Figure 4 Cross-sectional view of the targt mechanism $5 Figure

Claims (1)

[Claims] 1. Means for generating an ion beam with relatively low energy equivalent to the energy specified by the voltage applied to the extraction electrode; and a means for receiving the ion beam from the ion beam generating means; An ion acceleration stage for accelerating and ejecting an incident ion beam, comprising a high frequency signal generator and a slow wave circuit, the phase of the high frequency signal from the high frequency signal generator applied to the incident ion beam by the slow wave circuit. An ion implanter comprising: an ion implanter configured such that the velocity increases in a predetermined relationship from the input side to the exit side. 2. The ion implantation apparatus according to claim 1, wherein the slow wave circuit is a spiral slow wave circuit. 3. The ion implantation apparatus according to claim 1, wherein the slow wave circuit is a filter type slow wave circuit. 4. The ion implantation apparatus according to claim 2 or 3, wherein the slow wave circuit is provided with means for adjusting at least one of the high frequency electric field strength and the phase velocity of the high frequency signal. 5. Claim 1, further comprising an energy filter provided after the ion acceleration stage to allow only ions of a predetermined energy to pass among the accelerated ions.
The ion implantation device according to any one of items 1 to 4.