JPH051588B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an ion implantation apparatus, and in particular, to an apparatus for implanting ions into a semiconductor substrate, which improves the operating efficiency and enables efficient ion implantation. It relates to an ion implantation device.

[Prior Art] As an ion implantation device that accelerates impurity ions generated in an ion source using a high electric field and implants them into a semiconductor substrate, there is an ion implantation device that has a hot cathode type ion source, for example, a Freeman type ion source. This is widely used as an ion implantation device for semiconductor manufacturing equipment because it generates ions in a stable state and is easy to maintain. In such an apparatus, it is necessary to periodically clean the ion source and replace parts such as the ion source chamber (ion source head).

FIG. 3a shows an example of such a conventional Freeman-type ion implantation device, in which the third
FIG. b is an explanatory diagram of the ion source.

1 is an ion source, in which positive ions are extracted from the ion source 1 with constant energy and sent to an electrode 2.
and subjected to mass analysis by a mass spectrometer 3. Then, the desired ions completely separated by the slit 4 are accelerated to the final energy by the acceleration tube 5.

Next, the ion beam is focused by a quadrupole lens 6 to have a convergence point on the substrate surface 12, controlled by scanning electrodes 7 and 8 so that the implantation amount is uniformly distributed on the substrate, and controlled by a deflection electrode 9. It is bent and passes through the mask 10 and Faraday cup 11 to reach the substrate 12.

Here, as shown in FIG. 3b, the ions are ionized in the ion source chamber 22, which has been evacuated to a degree of vacuum of about 1×10 ^-1 torr.
The ion beam is extracted as an ion beam in a direction perpendicular to the rod-shaped filament 21 placed there.

In addition, 20 is an ion source housing,
23, 23 are electromagnets, 24 is a ground electrode, 25 is a slit, 26 is a gas inlet, and 27 is an ion beam.

By the way, as such an ion source is used, the rod-shaped filament 21 naturally wears out and breaks. If the filament of the ion source breaks, the ion source chamber itself is heated considerably, so it must be kept in a vacuum and allowed to cool naturally.

Further, the ion source housing 20 and the ion source chamber 22 may be ion-burned and contaminated. When such a state occurs, it is necessary to stop the ion implantation operation and perform an operation such as replacing the ion source chamber 22 or cleaning the ion source housing 20 itself.

[Problem to be solved] The natural cooling takes at least several hours, and if this time is short, the ion source chamber itself is exposed to the atmosphere, which oxidizes the material, such as molybdenum, and ions There is a problem in that the life of the source chamber itself is shortened.

In addition, when replacing the ion source chamber, the ion implanter must be stopped for at least several hours to perform vacuum extraction and dry firing of the ion source chamber itself to release gas. , work efficiency is very poor.

Furthermore, in cases such as when a high voltage discharge occurs due to dirt on the ion source housing itself, the housing itself must be removed from the main body, disassembled, and cleaned. After disassembly and cleaning, the ion source housing must be reassembled. , the ion source chamber must be attached to the ion implanter and evacuated, but this process takes longer than the above-mentioned case of dry firing the ion source chamber itself.

Having to interrupt the ion implantation work to replace or disassemble the ion implantation work is equivalent to the equipment being taken down by the user, and this also means that the MTBF (average This is also the reason why the time (failure interval) does not increase.

Therefore, the time during which the device is not operating from the filament exchange to the ion implantation operation,
The time when the equipment is not in operation, from cleaning work to ion implantation operation, is a large amount of lost time in today's world where the demand for semiconductor equipment is increasing, and performing the above work reduces the equipment operating rate. Doing so is a big problem.

By the way, it is no exaggeration to say that the performance of an ion implanter depends on the resolution of an analysis system based on a mass spectrometer. A high resolution is required of a mass spectrometer in ion implantation, and in particular, high resolution is required in order to manufacture semiconductor devices with high density and high integration these days. For this purpose, various adjustment mechanisms are provided to adjust the magnetic field of the mass spectrometer and its focus, and also adjust the extraction voltage.

Therefore, in order to solve the aforementioned problem of lower availability, it is possible to install two ion sources and switch to the other when one is unavailable, but it is possible to Even after starting up, it takes time to adjust each part before it can be used, resulting in a large amount of time lost before it can actually be used.

[Purpose of the Invention] The present invention has been made in view of the problems of the prior art, and can solve these problems and improve the operating rate of an ion implanter. The purpose of the present invention is to provide an ion implantation device.

[Means for Solving the Problems] By the way, there are two possible causes for the short lifespan of current ion source chambers.

There is a problem with the lifespan of the filament itself.
In other words, the filament becomes thin and breaks.

Even if the filament does not break, the ion source housing itself becomes dirty and generates many high electric field discharges, making it virtually unusable.

Regarding the cause of this, it can be said that even if the life of the filament increases in the future, this is a phenomenon that will always occur over time.

Therefore, the present invention focuses on extending the actual time for the ion implantation operation while accepting these two causes. That is,
By installing two ion sources and switching between them, when one is unavailable, the other can be activated to shorten the interruption time of ion implantation work. For other ion sources that are sometimes unusable at the same time, the time is used to naturally cool down the ion source chamber, or the time is used to remove the ion source housing.

In this way, the operation preparation work for the unusable ion source is carried out at the same time as the ion implantation work for the currently operating ion source, and during this time, the unusable ion source side is brought to atmospheric conditions, and then the operation is started. To enable immediate backup of ion implantation work when one of them becomes unusable.

Backup of this immediate ion implantation work,
In order to solve the above-mentioned problems, the present invention selectively receives ion beams from first and second ion sources at symmetrical positions and switches the polarity of the current that generates the magnetic field for mass analysis. Accordingly, a mass analyzer is provided which performs mass analysis on the ion beam received at the symmetrical position and sends it to the acceleration tube from the same mouth, and the first and second ion sources are connected to the mass analyzer. One that is arranged in symmetrical positions, one of the first and second ion sources is selectively operated, and while the selected one ion source is in operation, the other is subjected to operation preparation processing. This configuration employs a configuration in which the current polarity of the mass spectrometer is switched along with selection of operation of either the first or second ion source.

[Function] By placing the mass spectrometer and the first and second ion sources in symmetrical positions, basic adjustments can be made by simply switching the mass spectrometer's current polarity, eliminating the need for basic adjustments. become. Therefore, if the backup side is evacuated and kept physically operational, immediate backup is possible.

Furthermore, with this configuration, even if the filament of one ion source breaks, ions can be generated from the other ion source and the ion implantation operation can be continued, and the ion source chamber of one ion source itself can be used. This allows sufficient time for natural cooling while maintaining the vacuum, allowing for sufficient natural cooling. Therefore, not only can Chiyamba's own lifespan be extended, but also during this time,
There is no need to interrupt ion implantation.

Also, even if one unusable ion source is being evacuated after replacing the filament and gas is being vented by dry firing the ion source chamber and the ion source itself, ions cannot be implanted from the other ion source during this time. Therefore, the efficiency of ion implantation work can be improved.

Furthermore, in cases where high voltage occurs due to dirt on the ion source housing itself, the housing itself must be removed from the main body, disassembled and cleaned, and after disassembly and cleaning, the ion source housing must be reassembled and the ion implanter Although the ion source is attached and evacuated, even if one ion source is being disassembled and cleaned, ion implantation can be continued from the other ion source.

Therefore, the time during which the device is not operating from the filament exchange to the ion implantation operation,
The time during which the device is not in operation from the cleaning operation to the ion implantation operation becomes almost a short period of time related to the transition of these operations, and the operating rate of the ion implantation layer is greatly improved.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram mainly showing the ion source portion of the ion implantation apparatus of the present invention, and FIG. 2 is an explanatory diagram of its power supply circuit. Components that are the same as those in FIGS. 3a and 3b are designated by the same reference numerals.

In FIG. 1, reference numeral 30 denotes an ion implantation device, which is equipped with first and second ion sources 31 and 32.
1 and 32 are laid out at symmetrical positions with respect to the mass spectrometer 39, respectively. Each of these ion sources 31 and 32 is controlled by a power supply circuit 40 shown in FIG. 2 to selectively bring one of them into operation and the other to prepare for operation.

In FIG. 1, numeral 33 is a power supply unit in which this power supply circuit 40 is built-in, and the ion source power supply 41
and a dry firing power supply 42 and its switching circuit section 4
It consists of 3. Reference numeral 34 in FIG. 1 is a gas box, which has valves corresponding to the first ion source 31 and the second ion source 32 inside.
Alternatively, gas is supplied to one or both of the second ion sources 32 from a built-in cylinder.

Further, 35a is a first ion source 32 diffusion pump provided corresponding to the first ion source 31, and 35b is a second ion source 32 diffusion pump provided corresponding to the second ion source 32. It is an ion source diffusion pump.

The first ion source diffusion pump 35a is a first ion source diffusion pump 35a.
The mass spectrometer 39 behind the openable and closable first blocking section 37a provided in the ion beam introduction tube 36a of
It communicates with the side.

On the other hand, the second ion source diffusion pump 35b
communicates with the mass spectrometer 39 side behind the openable and closable second blocking section 37b provided in the second ion beam introduction tube 36b. Here is the blocking part 37
a and 37b are provided to separate one ion source in operation and the other ion source in preparation for operation so that they do not influence each other.

Now, the first ion source 31 generates an ion beam 38a, and the second ion source 32 generates an ion beam 38a.
A second ion beam 38b is generated, these are:
The variable slit 4 passes through the same mass spectrometer 39.
It is converged in the direction of and reaches the acceleration tube 5.

Here, the mass analyzer 39 is a double-headed type whose curved structure is expanded symmetrically in order to receive ion beams from both directions, and when the first ion source 31 is used and the second ion source 32 is used. The polarity of the current is switched depending on the time. As a result, one mass spectrometer 39 can be used, and the entire device can be miniaturized.

At the ion beam exit of this mass spectrometer 39,
In order to converge the emitted ion beam, a magnetic pole (or variable angle shim) or the like is provided as an angle-adjustable adjustment section for magnetic focus. By setting these magnetic poles to the first and second positions, the ion beam from the first ion source 31 and the ion beam from the second ion source 32 are respectively focused on the opening position of the variable slit 4. be able to.

The magnetic pole is driven by a stepping motor or the like so that the angle can be adjusted within a specific range between the first set position and the second set position.

By providing the mass spectrometer 39 with such a structure, one mass spectrometer can measure the variable slit 4.
The convergence of the ion beam on the side can be easily adjusted.

Now, the switching circuit 43 in FIG. 2 consists of two switching switches 43a,
43b, and a changeover switch 4
3a is a switch that switches and connects the ion source power source 41 to either the first or second ion source 31 or 32; In addition, the changeover switch 43b is connected to the dry firing power supply 4.
This is a switch that switches and connects the ion source 2 to the other ion source of the first and second ion sources 31 and 32 to which the ion source power source 41 is not connected, and operates in conjunction with the changeover switch 43a.

In addition, 44 is a power supply switch for the ion source power supply 41, and 45 is a power supply switch for the dry firing power supply 42, and it is sufficient to prepare a low-precision power supply as the dry firing power supply 42. It is something.

Next, to explain the ion implantation method of the ion implantation apparatus having the above configuration, firstly, when the filament of one ion source, for example, the first ion source 31, is broken, the cooling of the ion source chamber and the I will do it. At this time,
The first blocking section 37a is operated to close the first ion beam introduction tube 36a, and the second blocking section 37b is opened.

Next, the switching circuit 43 of the power supply section 33 shown in FIG. The ion source 32 side is operated to intermittent the ion implantation operation. Note that this switching may be performed with the ion source power supply switch 44 turned on, or may be performed after it is once turned off.

By the way, in this case, the ion beam 38 in ion implantation from this second ion source 32
Even if b enters the first ion source 31,
Since the first blocking section 37a is closed, the first blocking section 37a is closed.
The ion source 31 has no influence. The first ion source 31 can then independently enter a state of natural cooling.

When the ion source chamber of the first ion source 31 has cooled down sufficiently, the ion source chamber 22 is replaced. By doing this,
It is possible to prevent the ion source chamber 22 and the ion source housing 20 from oxidizing, thereby improving their service life.

Here, the first and second blocking parts 37a and 37b are configured by, for example, a shutter and an air valve,
In addition to blocking the ion beam, the ion source side and mass analyzer 3
By partitioning the room from the 9 side and making it an independent chamber in terms of pressure, the ion source chamber can be replaced without interrupting the ion implantation work. Furthermore, if the structure is simply a shutter that blocks the ion beam, the ion implantation operation would be temporarily stopped at this point, but the cooling operation and the ion implantation operation can proceed at the same time.

Note that the shutters of the blocking parts 37a and 37b are provided with a protective film on at least the surface on the mass spectrometer 39 side where ions collide, and this protective film may be provided by coating, for example, graphite or the like. I can do it.

Now, when the replacement of the ion source chamber of the first ion source 31 is completed, dry firing operation of the replaced ion source chamber is started. this is,
This is done by turning on the dry firing start switch 45 shown in FIG.

Even during this dry firing, the ion implantation operation of the second ion source 32 is continued intermittently. Then, when the dry firing is completed, the first ion source 32 enters a standby state, either as it is or after being evacuated, and ends its operation preparation process.

Note that the time required to replace the ion source chamber is only a few minutes, so it is negligible with respect to the overall operating time. Furthermore, if the blocking section is simply a shutter that blocks the ion beam, the ion implantation operation will be temporarily stopped. This will be done after the draw.

In this way, the ion implantation operation is continued by the second ion source 32, and when the filament of the second ion source 32 eventually breaks, the ion source chamber of the second ion source 32 is opened. It will be cooled down.

At this time, the second blocking section 37b is operated to close the second ion beam introduction tube 36b and to open the first blocking section 37b.
Next, the switching circuit 4 of the power supply section 33 shown in FIG.
3, switch to the selective connection side of the first ion source 31, supply power from the ion source power supply 41 to the first ion source 32, operate the first ion source 31 side, and perform ion implantation. Intermittent work.

Then, in the same manner as described above, the first ion source 31 is placed in an operating state, and the second ion source 32 is subjected to operation preparation processing.

By the way, when the ion source housing itself becomes dirty, the ion source itself must be taken out from the main body, the ion source housing removed, and disassembled for cleaning. In this case as well, the same applies to the case of exchanging the ion source chamber, but air valves are provided in the first and second shutoff parts 37a and 37b, and the ion source side and the mass spectrometer 39 side are connected. If the two chambers are partitioned into separate rooms in terms of pressure, there is an advantage that this disassembly work can be done independently of the ion implantation work by the other ion source in operation.

Moreover, if the interrupting parts 37a and 37b are simply comprised of shutters, the ion implantation operation from the other operating ion source is interrupted only when the ion source itself is removed. After disassembling and cleaning and assembling, the ion implantation work is again interrupted and reinstalled. This makes it possible to improve the operating rate of ion implantation work compared to the conventional method.

In this way, one of the first and second ion sources that is ready for operation is operated, and while this one ion source is in operation, the operation preparation process is performed for the other ion source. That is, while maintenance work is being performed on one ion source, ion implantation work can be continued using the other ion source, and in particular, replacement work such as the ion source chamber can be performed only after it has been sufficiently cooled. .

By the way, the power supply for dry firing is economical because it allows the use of a power supply that is not highly accurate, and while the other ion source is operating, one ion source can be started up to a ready-to-use state. I can do it. Therefore, in effect almost 100
It is possible to secure an operating rate close to %.

As explained above, in this embodiment, two ion source systems are provided so that the ion source chamber can be fired even during ion implantation work, but it is possible to use more than one ion source. , is not limited to two, and its arrangement is:
As seen in the embodiment, it is not necessary to provide them symmetrically at opposing positions.

In addition, in the example, two ion source systems are provided, each is provided with an independent vacuum evacuation system, and an independent dry firing power supply is provided, and the power supply system and gas box are commonly used. There are various things that can be shared, including vaporizer systems, ion source electromagnet power systems, and more. However, it goes without saying that various power supply systems such as gas boxes may be provided independently.

Further, in the embodiment, a blocking portion is provided on the ion beam introduction tube side to block the ion beam from the ion source, but the location does not matter as long as it can block the ion beam. Particularly in the case of a structure in which a plurality of ion sources are not arranged in opposing positions, such a blocking part is not necessarily necessary.

[Effects of the Invention] As can be understood from the above explanation, the ion implantation method of the present invention is an ion implantation method in an ion implantation apparatus having a first and second ion source. One of the second ion sources that is ready for operation is operated, and while this one ion source is operating, the operation preparation process is performed for the other ion source. Even if the filament of one ion source breaks, ions can be generated from the other ion source and the ion implantation operation can be continued, and the ion source chamber of one ion source can be kept in a vacuum and allowed to cool down slowly and naturally. can be secured.

As a result, sufficient natural cooling can be achieved, the life of the chamber itself can be extended, and there is no need to interrupt ion implantation during this period.

In addition, even if one ion source that is unusable is being evacuated after replacing the filament and the ion source chamber and ion source itself are being degassed by dry firing, ions can be injected from the other ion source during this time. The efficiency of ion implantation work can be improved.

Furthermore, in cases where high voltage discharge occurs due to dirt on the ion source housing itself, the chamber itself must be removed from the main body, disassembled and cleaned, and after disassembly and cleaning, the ion source housing must be reassembled and the ion implanter Although one ion source is attached to the other to perform vacuuming, even if one ion source is being disassembled and cleaned, ion implantation can be continued from the other ion source.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram centered on the ion source portion of the ion implantation device of the present invention, FIG. 2 is an explanatory diagram of its power supply circuit, and FIG. 3a is a diagram of the conventional Freeman type ion implantation device. An explanatory diagram showing an example,
FIG. 3b is an explanatory diagram of the ion source. 30... Ion implanter, 31... First ion source, 32... Second ion source, 33...
...power supply unit, 34...gas box, 35a...first ion source diffusion pump, 35b...second ion source diffusion pump, 36a...first ion beam introduction tube, 36b...second ion beam Introductory tube, 37a...first cutoff section, 37b...first cutoff section, 39...mass spectrometer, 40...power supply circuit, 41...power supply for ion source, 42...power supply for dry firing , 43...Switching circuit section.

Claims (1)

[Scope of Claims] 1. A first ion source and a second ion source, wherein an ion beam of atoms extracted from either of the ion sources is subjected to mass analysis and then accelerated in an acceleration tube;
In an ion implanter that implants accelerated ion atoms into a workpiece, ion beams from the first and second ion sources are selectively received at symmetrical positions, and the polarity of the current that generates the magnetic field for mass spectrometry is switched. The first and second ion sources are connected to the mass analyzer, and the first and second ion sources are connected to the mass analyzer. and one of the first and second ion sources is selectively operated, and while the selected one ion source is in operation, the other is provided for operation preparation processing. An ion implantation apparatus characterized in that the current polarity of the mass spectrometer is switched with selection of operation of either one of the first and second ion sources. 2. Mass spectrometry, in which first and second extraction electrodes are provided corresponding to the first and second ion sources, and ion beams extracted from the first and second ion sources are introduced into a mass spectrometer. The first and second ion beam introduction tubes are provided symmetrically with respect to the device, and the ion sources in operation are provided corresponding to the conduits of the first and second ion beam introduction tubes, respectively, and operation preparation processing is performed. The ion source includes first and second cutoff parts that separate the ion source so as not to affect each other, and a power supply for the ion source.
Either the cutoff section or the second cutoff section is set to an open state, the other is set to a cutoff state, and the ion source power supply is connected to the ion source on the side corresponding to the open state, thereby generating an ion beam. 2. The ion implantation apparatus according to claim 1, wherein the ion implantation apparatus is operated in a state where the ion source is in the cut-off state, and an operation preparation process is performed on the ion source corresponding to the cut-off state.