JPH01167941A - Control method for ion beam implantation - Google Patents

Abstract

PURPOSE:To enable ion beams to be controlled at a high speed at the source thereof by controlling the ON-OFF of the implantation of the ion beams on the basis of the ON-OFF of an arc power source. CONSTITUTION:In order to control the implantation of ion beams, first of all, at a time t1, a filament power source VF is turned on to preliminarily heat the ion beams. Next, at a time t2, in order to implant only desired ion beams into a workpiece, a spectrometric magnet exciting power source VSM is excited up to a specific value, and as well, an acceleration power source Vacc and an extraction power source VEX are turned on so as to be risen to the specific value. At a time t3, an arc power source Va is turned on so that raw gas staying inside an arc chamber is turned into plasma, while the ion beams are extracted from the chamber under a high voltage by the effect of the extraction power source VEX. At a time t4, if any abnormality, for example, abnormal discharge, is generated, the arc power source Va is turned off so as to dissipate the plasma, thereby turning off the ion beams. At a time t5, after the recovery of the the temporary abnormality, the arc power source Va is turned on so as to generate the plasma, and thereat, the ion beams can be instantly turned on.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to an ion beam implantation control method for controlling on/off of ion implantation using an ion beam, which is used in the manufacture of semiconductor devices.

[Prior art]

FIG. 3 shows an example of the configuration of an ion implantation apparatus related to this type of conventional ion beam implantation control method.

The ion beam 9 emitted from the ion source 1 supplied with raw material gas is accelerated at high speed in the acceleration tube 3 to which a high voltage is applied, and after passing through the vacuum vessel 8, the beam is deflected. , beam shutters, and are implanted through the slit 6 into a workpiece 72 mounted on a mounting device 71 of an end station, which is an ion implantation section. The bending radius R of the ion beam bent by the mass spectrometer 4 is expressed as follows. Here, B is the magnetic flux density 2 of the mass spectrometer 4
m is the mass of the ion, ■ is the accelerating voltage, q is the number of charges on the ion, and e is the elementary charge, that is, 1.602×10 C. Therefore, in order to implant a desired ion beam into the workpiece 72 with a desired energy, it is necessary that the accelerating voltage V and the magnetic flux density B be accurately applied.

@4 Figure 4 shows the ion source 1 and the smagnet 13 of the acceleration tube l, and the arc ij source (Va
) 14, 74 lame 7) power source (vr) 15° source magnet power source (VsM) 16. On the other hand, the acceleration tube 31 has an extraction electrode 31. which extracts and focuses the ion beam 9. Lens electrode 32° Ground electrode 3
3 and the drawer TIR (VEX) that is the power source for each
34, L/:ys power supply (V/)35. It is composed of an acceleration power source (Vacc) 36.

Here, the operation of the ion source 1 used in the above conventional example and the present invention described later will be briefly described. Arc chamber 11
When a raw material gas for ion implantation is introduced into the arc chamber 11 through a gas introduction pipe 21, and the filament 12 disposed inside the arc chamber 11 is heated with electricity, thermoelectrons are generated. These electrons are applied to the filament 12 by the arc power source 1.
4 toward the arc chamber 11, which is positively charged. Here, when a magnetic field is applied in the arc chamber 11 from the source magnet 13# in a direction perpendicular to the traveling direction of the electrons, the electrons are moved into the arc chamber 11 by this magnetic field.
As it moves toward 1, it receives the Lorentz force and moves in a spiral. For this reason, the distance the electrons travel from the filament 12 to the arc chamber 11 becomes longer, and the probability of collision with gas molecules increases.The electrons collide with the gas molecules sufficiently, and as a result, ions and electrons form inside the arc chamber 11. It becomes a filled plasma state. In order to extract positive ions from this plasma, an extraction electrode 31 to which a high voltage such as a negative potential with respect to the arc chamber is applied is disposed in the acceleration tube 1.

Therefore, positive ions in the plasma are extracted from the arc chamber 11 as an ion beam 9 by the electric field caused by this negative voltage.

Now, in the ion implantation apparatus of the configuration example shown in FIG. 3, the ion beam 9 is Ion beam implantation control is required to turn it on and off. Conventionally, for this control, a beam shutter, which is a mechanical passage opening/closing mechanism that allows the ion beam 9 to pass through and block it, is installed in front of the end station (FIG. 3) to turn on and off the ion beam implantation. A method of controlling off was used.

FIG. 5 shows an example of the configuration of a cylindrical beam shutter. By aligning the hole 51 penetrating the cylinder with the traveling direction of the ion beam 9, the ion beam 9 passes through the beam shutters and the implantation is turned on, and by rotating the cylinder, the direction of the hole 51 is set perpendicular to the ion beam 9. By doing so, the ion beam 9 is blocked by the beam shutters and the implantation is turned off.

FIG. 6 shows an example of a conventional ion beam on/off sequence. In Figure 6, VAM is the analysis magnet excitation power supply +, and l is the ion beam at the ion source exit.

In2 is the ion beam just before the workpiece. Ion implantation on/off control using beam shutter interaction is the sixth step.
This is done as in the example sequence shown in the figure.

[Problem that the invention seeks to solve]

The problems with this type of conventional ion beam implantation control method are as follows. That is, in the control using the beam shutter described above, since the ion beam continuously generated from the ion source is mechanically blocked, there is a problem that heat generation due to the energy of the ion beam increases. Furthermore, since the beam shutter is opened and closed mechanically, it takes a long time to open and close it, and there is a problem that even if there is a need to turn off the ion beam instantaneously, such as when an abnormality occurs in the ion beam, it cannot be done in time. Furthermore, since the beam shutter is inserted into the path of the ion beam, the beam path becomes correspondingly longer, resulting in problems such as a reduction in the efficiency with which the ion beam reaches the workpiece.

Instead of this mechanical beam shutter, the following methods can be considered as a control method for turning on and off ion beam implantation. That is, (1) Turn on and off the source magnet power supply VIIM.

@Turn the filament power supply VF on and off.

Supply and stop supply of 0 raw material gas.

■Turn the drawer power supply VEX on and off.

■Turn on and off the acceleration power supply VaCC.

Turn on and off the θ analysis magnet excitation power supply VAM.

This is a method such as However, although point (2) is possible, instantaneous application of high voltage is not preferable to the power supply. (2), (2), and 0 are unsuitable because the response is slow, similar to the mechanical beam shutter. In addition, (2) and (2) are also unsuitable because there is a possibility that an undesired impurity ion beam may be implanted into the workpiece due to a change in the energy of the ion beam during the on-off transition and a change in the redundant precipitation ability.

An object of the present invention is to eliminate the above-mentioned conventional problems and to implant an ion beam into a workpiece with a short response time without the need for a mechanical beam shutter.

The purpose of the present invention is to provide a fast shut-off control method for ion beams, especially in winter.

[Means for solving problems]

In order to solve the above problems, according to the present invention, a raw material gas consisting of nine desired atoms is introduced into an arc chamber of an ion source equipped with an arc power source, a plasma is generated in the arc chamber, and the plasma is accelerated. extracting, focusing, and accelerating ions from the plasma as an ion beam by a tube;
In a method of separating and extracting the ion beam using a mass spectrometer and controlling injection of the extracted ion beam into a workpiece, turning on and off the injection of the ion beam,
Control is performed by turning on and off the arc power source.

[Effect]

As mentioned above, by turning on and off the arc power supply with a quick response and good reproducibility, can the ion source be used? By electrically controlling the generation and extinction of plasma at high speed, it becomes possible to control the on/off of ion beam implantation with a short response time.

[lol example]

FIG. 1 shows an example of the configuration of an ion implantation apparatus related to an ion beam implantation control method according to an embodiment of the present invention. The same members as in FIG. 3 are given the same reference numerals, and their explanations will be omitted. As is clear from the figure, the difference from the apparatus of FIG. 3, which uses a conventional ion beam implantation control method, is that it does not include a beam shutter.

FIG. 2 shows an example of an ion beam on/off sequence according to an embodiment of the present invention. Explaining the ion beam implantation control method of the present invention based on FIG. 2Q First, at time tl, the filament power supply vr of the ion source is turned on in preparation for plasma generation to preheat the filament. Next, in preparation for implanting only the desired ion beam into the workpiece ζ, the analysis magnet excitation power source VA
When M is excited to a specified value, the accelerating power source Vacc 2 and the arcing source VEX are turned on and raised to the specified value. After the above conditions are established, when the arc power source Va is turned on at time t3, the raw material gas in the arc chamber becomes plasma in an extremely short period of several m3 to several IQms as the arc power source Va rises, and the The voltage draws the ion beam out of the arc chamber. At this time, the acceleration power supply Vacc i6, which determines the energy of the ion beam, and the analysis magnet excitation power supply VA
Since N is already in a stable state, only the desired ion beam is implanted into the workpiece even during the ion beam startup transient phenomenon.

If some kind of short-term abnormality such as abnormal discharge occurs at time t4 and it becomes necessary to shut off the ion beam instantly, the arc power supply ■ If a is immediately turned off, the plasma also disappears immediately and the ion beam is turned off. At this time, the analysis magnet excitation power source VAM, acceleration power source vacc, etc. continue to operate in a stable state unless there is any abnormality in themselves, so that an ion beam of undesired impurities is not implanted into the workpiece. In addition, if a temporary abnormality occurs in the acceleration power supply VaCC, etc., there is a possibility that an ion beam containing undesired impurities will be implanted into the workpiece due to the energy change of the ion beam, but the arc power supply Va is turned off. By doing so, it is possible to turn off the ion beam at high speed, so the impact can be minimized. When the temporary abnormality is recovered at time ts, it is possible to generate plasma by turning on the 1-arc power source Va and to immediately turn on the ion beam.

〔Effect of the invention〕

As described above, according to the present invention, as a method for controlling the on/off of ion beam implantation, a method is adopted in which plasma is generated and extinguished by turning on and off the arc power of the ion source. It becomes possible to perform high-speed control at the source. This also eliminates the need for a mechanical beam shutter, which shortens the beam path and reduces ion beam divergence and neutralization, making it possible to increase the efficiency with which the ion beam reaches the workpiece. . Furthermore, the generation of heat due to collision of the ion beam with the beam shutter can also be prevented.

In particular, by controlling the ion beam with an arc power source,
The response is fast and the ion beam can be turned off in a short time even in the event of a temporary abnormality in the system, and even though the ion beam is turned on and off at the source itself, the energy and analysis characteristics of the ion beam are maintained even when restarting. can be obtained with good reproducibility.

[Brief explanation of the drawing]

Figure wc1 is a diagram showing an example of the configuration of an ion implantation apparatus related to an ion beam implantation control method according to an embodiment of the present invention.
FIG. 3 is a diagram showing an example of an ion beam on/off sequence according to an embodiment of the present invention; FIG. 3 is a diagram showing an example of the configuration of an ion implantation apparatus related to a conventional ion beam implantation control method
Figure 4 shows the ion source and accelerator tube! Figure showing 8 examples, f!
FIG. 5 is a diagram showing an example of the configuration of a conventional beam shutter, and FIG. 6 is a diagram showing an example of a conventional ion beam on/off sequence. 1: Ion source, 14: Arc power supply, Accelerator tube, Tan: Beam shutter. 2nd mouth

Claims (1)

[Claims] (1) A raw material gas consisting of desired atoms and molecules is introduced into an arc chamber of an ion source equipped with an arc power source, a plasma is generated in the arc chamber, and ions are extracted from the plasma as an ion beam by an acceleration tube. In the method of focusing, accelerating, separating and extracting the ion beam using a mass spectrometer, and controlling the injection of the extracted ion beam into a workpiece, the injection of the ion beam is turned on and off by the arc. An ion beam implantation control method characterized by controlling by turning on and off a power supply.