JP6296529B2 - Ion implanter - Google Patents

Description

  The present invention relates to an ion implantation apparatus used in a so-called minimal fab production system.

Currently, as a manufacturing system for semiconductor devices, etc., it is basically based on the production of one device on a 0.5 inch size (half inch size, to be precise, 12.5 mm diameter) wafer. It is possible to respond appropriately to small-volume production and multi-product production by making it easy to relocate these unit processing devices to a flow shop, job shop, etc. A minimal fab production system has been proposed by the present applicant. (Patent Document 1)
The current semiconductor manufacturing system is 300 to 500 billion yen to start up the latest semiconductor factory (mega fab production system) with the larger and higher cost of the equipment itself as the wafer diameter increases (from 12 inches) It is said that huge investment funds are required. In addition, a system using a large-diameter wafer is efficient for mass production. However, if the device is operated for high-mix low-volume production, the number of pieces required by the user is limited due to problems such as availability. The manufacturing cost will be very high.
On the other hand, in this minimal fab production system, wafers with a very small diameter of about 0.5 inches are processed, and it is expected that a very small capital investment of about 1/1000 compared with the current semiconductor manufacturing system is required. In addition, it is expected to be a production system suitable for high-mix low-volume production due to low operating costs.

In this minimal fab production system, a unit processing device whose outer shape is standardized is used.
This unit processing apparatus is responsible for one of the individual processes in the processing process of the semiconductor manufacturing apparatus (in Patent Document 1, this is defined as “single process”). Yes, it is a resist coating device, a wafer exposure device, a developing device, and an ion implantation device. These unit processing devices are arranged in a semiconductor manufacturing recipe order (processing flow order). Wafers, which are workpieces, are sequentially conveyed between the unit processing apparatuses arranged in order, and the corresponding processing is sequentially performed in each unit processing apparatus.

Therefore, this unit processing device can be arranged freely according to the recipe every time the recipe is changed, and is also set in advance on the work floor when the arrangement is changed. It is portable and standardized so that it can be transported by people so that it can be connected to regularly arranged juxtaposed supply systems, drainage systems, and power supply systems.
The size of this unit processing unit is 0.30m width x 0.45m depth x 1.44m height, and it is not only small in size, but even if 60 units are arranged according to the semiconductor manufacturing recipe, its occupied floor The area is small compared to existing 12-inch semiconductor manufacturing equipment.

Another feature of the minimal fab production system is that the wafer, which is a workpiece, is transported between unit processing apparatuses by a unique hermetic transfer system that is cut off from the outside air. Therefore, it is sufficient that only a predetermined processing space in each unit processing apparatus is a necessary processing atmosphere that is blocked from outside air, for example, a clean room space or a vacuum state space. There is no need to place it in a clean room. This is fundamentally different from the existing semiconductor manufacturing system in which the semiconductor processing apparatus itself is arranged in a huge clean room.
Therefore, in this minimal fab production system, it is not necessary to arrange the apparatus in the clean room, so that the worker can work in a normal working environment without being forced to work in the clean room. It also saves energy as there is no need to create a huge clean room space.
As described above, the minimal fab production system is attracting attention as an innovative next-generation production system, not a production system in which a conventional apparatus is simply reduced in size.

In the current semiconductor manufacturing system, an ion implantation apparatus is an indispensable apparatus.
However, since the existing ion implantation apparatus uses a high voltage or a strong magnetic field for generation and control of the ion beam, the apparatus is inevitable to be large regardless of the wafer size.
In fact, even a relatively small device for research and development has a size of several meters or more, and a device for a large-diameter wafer incorporated in a production line is larger. Even a typical medium-current ion implantation apparatus occupies a floor area of 3 m × 7 m or more with a main body alone, and the price is about 1 billion yen, and more auxiliary facilities are required. Thus, existing ion implanters are too large and expensive to be incorporated into a minimal fab production system.

An example of such an existing ion implantation apparatus is shown in FIG.
First, the source gas from the gas supply system 2 is ionized by the ion source 3. The ion source 3 is biased at a positive potential with respect to the extraction electrode 4, and the ionized ions are extracted as a beam by an acceleration voltage of 10 to 100 kV applied between the ion source 3 and the extraction electrode 4 (previous stage). Accelerator) and the mass separator 8.
The mass separator 8 is for separating ion species having a specific mass, and among the ion beams including a plurality of ion species emitted from the ion source 3, a specific ion to be implanted into the wafer (target 12). Select only ionic species. The ion beam selected here is accelerated (or decelerated) by the post accelerator 9 so as to have a predetermined implantation energy. In this latter stage acceleration, the beam line from the ion source 3 to the mass separator 8 and its incidental facilities are arranged on the high voltage gantry 1 and the entire high voltage gantry 1 is connected to the ground potential by the accelerating power source 5 for the latter stage acceleration. By biasing it to a positive high voltage.
The implantation energy differs depending on the depth of ion implantation required in the wafer (target 12). For example, in a general CMOS process, a high energy ion beam of up to about 200 keV is required. In order to cope with such high-voltage acceleration, the high-voltage mount 1 is insulated so as to ensure a withstand voltage of 200 kV or higher. Further, power is supplied to the ion source 3, the mass separator 8, and the like through an insulating transformer 6 having an insulation resistance of 200 kV or more between input and output.

The ion beam thus accelerated is deflected in the XY direction by the XY deflector 10 that applies an electric field or a magnetic field in order to scan the entire surface of the wafer (target 12).
Such an existing ion implantation apparatus is a large apparatus having a total length of 7 m or more as shown in FIG.

JP 2012-54414 A

The factors that cause the existing ion implantation apparatus to be so large (factors having a long beam length) are summarized as follows.
(1) A space for high voltage insulation is required.
In the existing apparatus configuration, many main components including the mass separator 8 from the ion source 3 to the acceleration tube 9 have a high voltage of 100 kV or more. For this reason, a space and a distance are required to insulate the high-voltage gantry 1 on which these are installed, and in the atmosphere, it is necessary to provide a space of 30 cm or more between the outer wall of the ground potential device.

(2) A large insulation transformer 6 is required.
In order to supply necessary power to the ion source 3, the mass separator 8 and the like on the high voltage gantry 1, an insulating transformer 6 having a high withstand voltage is required. This is usually a large size of 1 m or more, and the larger the higher the withstand voltage and the higher power, the larger the size. Further, in order to control the ion source 3, the ion source gas supply system 2, the mass separator 8 and the like placed in the high voltage section, it is necessary to use a control system such as an optical fiber or a control rod, and the apparatus is complicated. Become.

(3) The mass separator 8 is large.
In the existing large-scale apparatus, a large current ion beam of about mA is used to cope with a large-diameter wafer. In this case, the pre-stage acceleration energy is at least 10 keV or more and a beam in a low energy region of several keV or less. There is no transportation. This is because low-energy high-current ions have high ion density, and the beam tends to diverge due to charge repulsion between adjacent ions (this is called the space charge effect). This is because the ion beam diverges and disappears immediately. For this reason, beam transport with high energy of 30 keV or higher is usually performed, and all components such as mass separators are becoming enormous.
Mass separation is performed by deflection by a magnetic field, but usually an electromagnet of 1 m or more is used. The reason why the electromagnet becomes large in this way is that the ion extraction and transport energy is as high as 30 keV or more as described above, and therefore the radius of curvature of the ion beam in the magnetic field cannot be reduced. Another reason for the large size of the mass separator 8 is that an apparatus for implanting various ion species requires a high mass resolution (Δm / q <1) to prevent contamination.

(4) Increase in size of the ion source 3.
As the diameter of the wafer increases, a large current ion beam is required, so that the ion source 3 is also enlarged.

(5) A long beam path is required for XY scanning.
In order to inject ions uniformly over the entire surface of the wafer, XY scanning of the ion beam is performed after acceleration. Since ions have high energy after subsequent acceleration, they are difficult to bend in an electric or magnetic field. Therefore, in order to scan the beam over the entire large-diameter wafer, it is necessary to take a long beam path to the wafer.

(6) Large wafer transfer mechanism.
Since the diameter of the wafer has increased, wafer introduction, transfer robots, and the like have increased in size according to the wafer size.
Among the above factors, (4) to (6) are expected to be miniaturized when the wafer size is reduced, but other dimensions are determined by physical laws such as the radius of curvature of ion deflection and high voltage insulation resistance. Therefore, it is irrelevant to the wafer size.

  As explained above, the size of the unit processing equipment standardized in the minimal fab production system is 0.30m wide x 0.45m deep x 1.44m high, which is the mass separator used in existing ion implanters. Or smaller than the size of the space for insulation. That is, with the existing ion implantation method, it is impossible to realize the size of the unit processing apparatus incorporated in the minimal fab production system.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide an extremely small ion implantation apparatus that can be incorporated into such a minimal fab production system.

In order to achieve the above object, the present invention provides:
A wafer stage on which a half-inch wafer is placed, an ion generator that generates ions from one kind of ion source gas , a pre-stage accelerator that extracts ions from the ion generator, and an ion beam extracted by the pre-stage accelerator a mass separator for mass separation, the XY deflector for scanning the ion beam selected by the mass separator in the XY direction, and the post-accelerator for accelerating a scanned ion beam to the wafer by the XY deflector, its A beamline vacuum vessel for storing them, and performing the mass separation by controlling a magnetic field using a permanent magnet and an electric field orthogonal to the magnetic field,
The ion beam control from the ion generator to the XY deflector is performed in a low energy region of 5 keV or less, and the ion beam control by the post-accelerator is applied to the wafer with the beamline vacuum vessel at the ground potential. The ion implantation apparatus is characterized in that it is performed at a negative high voltage.
Here, the “unit processing apparatus” is defined as one responsible for one of individual processes (that is, one process in the recipe) in the process of the semiconductor manufacturing apparatus, as in the above-described conventional example.

According to the present invention configured as described above, since the ion beam control from the ion generator to the mass separator is performed in a low energy region, an electric field / magnetic field orthogonal (ExB) type Wien filter using a permanent magnet is used. The mass separator can be downsized.
Further, since the control is performed in the low energy region, it is easy to bend by an electric field or a magnetic field, so that the beam scan with the XY deflector can be performed with a shorter beam path.
In addition, since the voltage to be applied is about several kV, the insulation of the components inside the beamline vacuum vessel is only about a few millimeters, so the components arranged inside the beamline vacuum vessel can be downsized.
Furthermore, since the beam transport energy is low, the voltage required for beam control such as a focusing lens and XY deflection can be reduced, and the control power supply for that purpose can be reduced.

Further, by setting the ion generator side to the ground potential and setting only the target wafer stage to a high voltage, the spatial distance required for high voltage insulation can be extremely shortened.
In addition, since all atmospheric components such as ion generators, beam line components, and injection chambers can be set to ground potential, they can be installed in close proximity to the unit processing unit case, and the inside of the narrow case is limited. Even installation is possible. In addition, a large insulation transformer, optical communication equipment, and the like are not required, and the entire apparatus can be reduced in size and cost.

Further, the present invention performs extraction from the ion generator and beam convergence, mass separation, beam transport and control until XY deflection in a low energy region of 5 keV or less, more desirably 2 keV or less, and finally a target wafer Since the implantation energy and the implantation depth are controlled by performing the post-stage acceleration with the voltage applied to, there is no need to decelerate the ions in the post-stage acceleration stage, and therefore there is no concern about energy contamination.
In addition, the beam line length from the ion generator to the wafer is as short as possible, desirably 0.5 m or less, and the beam current is as small as ~ μA, so that the space charge effect of the beam is negligible and almost no loss. In this state, the ion beam can be transported to the wafer. In the present invention, the unit processing apparatus has a single function limited to the use of one kind of ion source gas per unit. Furthermore, in the apparatus for the mass production line of the minimal fab production system, a single-function ion implantation apparatus optimized for each implantation condition (ion species, implantation energy) is used. As a result, the apparatus can be further reduced in size and can be manufactured at a low cost, so that an ion implantation apparatus suitable for a minimal fab production system can be obtained.

  With this configuration, the ion implantation apparatus according to the present invention can significantly shorten the length of the beam line from the ion generator to the wafer as compared with the conventional apparatus, and each component can be attached to the apparatus housing. Since the control system can be miniaturized, the control system can be easily incorporated into the unit processing apparatus in the minimal fab production system.

  According to the present invention, since the beam line length from the ion generator to the target wafer in the ion implantation apparatus can be extremely shortened compared to the conventional apparatus, an ion implantation apparatus suitable for a minimal fab production system is provided. Can be provided.

Explanatory drawing of the existing ion implantation apparatus. Explanatory drawing of the ion implantation apparatus which concerns on the embodiment of this invention. The form example by the side of the back | latter stage accelerator which concerns on the embodiment of this invention. The another example of the back | latter stage accelerator side which concerns on the embodiment of this invention. Explanatory drawing of the unit processing apparatus incorporating the ion implantation apparatus which concerns on the embodiment of this invention. The argon ion beam mass separation spectrum distribution map by the ExB type mass separator which concerns on the example of embodiment of this invention. 1 is an external perspective view of an ion implantation apparatus according to an embodiment of the present invention. Illustration of required ion implantation conditions

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 5 is an explanatory view of a unit processing apparatus M for a minimal fab production system in which an ion implantation apparatus S according to an embodiment of the present invention is incorporated (a view seen through from the side of the apparatus). FIG. 7 is a perspective view thereof.
This unit processing device M has the same outer shape as the above-described minimal fab production system, and has a width (x) 0.30 m × depth (y) 0.45 m × height (z) 1.44 m. An injection device S is arranged.
The unit processing device M has a main body portion Ma for storing the beam line and the like of the ion implantation device S, and a control storage portion Mb for storing the vacuum pump 37, the control device 38, and the like. The front portion of the unit processing apparatus M is a front chamber Mc for transporting the wafer into the unit processing apparatus main body Ma. The front chamber Mc is configured to be common to all the unit processing apparatuses M.

<Wafer transfer system>
Wafers (targets) 33 to be processed by the ion implantation apparatus S are stored one by one in a wafer storage shuttle (not shown) and transferred to the unit processing apparatus M. The shuttle is configured so that a single wafer having a diameter of 0.5 inch (half inch size, precisely 12.5 mm in diameter) is stored in a state of being shielded from the outside air.

A docking port 42 that connects the front chamber Mc and the shuttle is provided in the upper portion of the front chamber Mc. A wafer transfer space 39 connected to the docking port 42 is provided inside the front chamber Mc, and the wafer transfer space 39 is configured to be in a high vacuum state by a high vacuum pump 36 ′. Yes. An airtight gate valve 43 is provided between the wafer transfer space 39 and the processing chamber 44 of the ion implantation apparatus S. Further, in the wafer transfer space 39, the wafer 33 in the shuttle on the docking port 42 is taken out in a state of being shut off from the outside air, and the taken out wafer 33 is passed through the gate valve 43 opened to the wafer stage 34. A vacuum transfer mechanism (not shown) for transferring is provided.
Further, a display type operation panel 41 is provided above the front chamber Mc.

As described above, this minimal fab production system includes a closed-type transport mechanism (Particle-Lock Airtight Docking: which consists of a shuttle, a vacuum transport mechanism in the front chamber Mc, etc., which completely blocks fine particles and gas molecules from the outside world in principle. PLAD system).
The wafer 33 as a target is carried by the PLAD system from another unit processing apparatus onto the wafer stage 34 in the processing chamber 44 of the ion implantation apparatus S via a shuttle. The wafer 33 ion-implanted on the wafer stage 34 is carried out (returned) into the shuttle on the docking port 42 by the PLAD system.

<Gas supply system>
The source gas for ion implantation (ion source gas) is supplied from a small gas cylinder 21 installed in the apparatus through a gas flow rate adjusting valve 22. A safe delivery source (SDS) of BF3, PH3, AsH3 is used as a source gas for the implantation of boron, phosphorus, and arsenic required for semiconductor fabrication.
What is important here is that in the unit processing apparatus M for the minimal fab production system, one ion source gas is used for each unit processing apparatus M. In other words, the conventional apparatus does not have a configuration in which a plurality of ion source gases are switched and used. A boron ion implantation apparatus, a phosphorus ion implantation apparatus, or an arsenic ion implantation apparatus is configured as a separate unit processing apparatus M.
When it is necessary to implant a plurality of ion species, one unit processing device M dedicated to each ion species is prepared and used in order. Since the unit processing apparatuses for the minimal fab production system are all small and low in price, even if a plurality of apparatuses are introduced in this way, they are smaller and less expensive than the conventional apparatus.

In the present invention, the reason why such a unit processing apparatus M is configured for each ion source gas is as follows.
(1) Since the conventional ion implantation apparatus is expensive, a gas supply system that switches and uses a plurality of ion source gases so that one apparatus can cope with implantation of various ion species. It has been incorporated.
However, since such a gas supply system requires a large space, it cannot be introduced into a minimal fab production system.
(2) When a plurality of ion source gases are switched and used, a use history remains inside the ion generator (the ions are implanted and accumulated in the components inside the ion generator). There arises a problem that ions of the gas species that have been used up to now come out. In order to eliminate this contamination, a mass separator having a high resolution for separating the contamination is required on the downstream side. In particular, semiconductor process ion implantation uses BF3 gas for boron implantation and PH3 gas for phosphorus implantation. BF + ions (m / q = 30) obtained when BF3 gas is used and P + ions obtained when PH3 gas is used (m / q = 31) has only 1 difference in mass number, and it is necessary to have the ability to separate them.
However, such a high-resolution mass separator must use a large electromagnet on the metric scale, which is very large.

FIG. 8 shows the ion implantation conditions required for each semiconductor (each part) by the relationship between the ion implantation amount (ion / cm 2) and the implantation energy (keV). Under this ion implantation condition, if the gate length is shortened, the required implantation energy shifts to the left side (the side where the implantation energy is low). However, at present, according to the semiconductor manufacturing design rule that is normally performed, as shown by the line G in FIG. 8, the required minimum implantation energy is about 5 keV in any case.
Therefore, in the present invention, beam control and beam transport from ion source to mass separation to XY deflection are performed at the minimum implantation energy of 5 keV or less (preferably 2 keV or less), and the necessary energy beyond this is obtained by post-acceleration. I decided to do it. Therefore, unlike the conventional apparatus, it is not necessary to decelerate the ion beam at the subsequent acceleration stage.
By controlling the ion beam with low energy in this way, energy contamination which is a problem in the conventional apparatus does not occur (details will be described later). In addition, the beam line upstream of the post-acceleration stage is transported at a much lower beam energy than before, so the mass separator and other control devices that make up the beam line can be made extremely small. Thus, the beam line length can be shortened.

A supplementary explanation of this problem of energy contamination will be given.
In the conventional ion implantation apparatus, since the beam line length is as long as about 10 m, the ion beam cannot be transported by the influence of divergence due to space charge at a low energy of about several keV. In order to avoid this, it must be transported with a high energy of several tens keV or more, and in this case, when performing a low energy implantation of about several keV, it must be decelerated immediately before the wafer. However, when ions with energy of several tens of keV or more collide with residual gas molecules, etc., they capture electrons and become neutral atoms, so such neutral atoms cannot be controlled and are not decelerated as they are. Is injected into the wafer. This is called energy contamination.
In order to avoid this, it is necessary to take measures such as evacuating the transport beam line with a large high-vacuum device and inserting a deflector or the like in the beam line to reduce residual gas molecules as much as possible or to remove energy contamination components. However, since the device is further increased in size and cost, it cannot be used in a device for a minimal fab production system.
In the present invention, since the beam transport energy during transport (5 keV or less, preferably 2 keV or less) is less than the implantation energy, even if neutralized ions are formed, the energy does not exceed the implantation energy. Can be eliminated. In the first place, since the beam line length is short, the probability of neutralization is very small.

<Beam line configuration and unit processing unit upper part>
In this embodiment, as shown in FIG. 5, between the ion generator 23 and the wafer stage 34, an ion extraction electrode (pre-accelerator) 40, a neutral particle remover are sequentially arranged along the ion beam line. 24, a differential exhaust slit 25, a focusing lens 26, a first XY deflection electrode 27, an ExB type mass separator 28, a mass separation slit 29, a second XY deflection electrode 30, a post-acceleration electrode 31 and a secondary electron suppression electrode 32 are arranged. To do.
Here, as shown in FIG. 2, the ion beam transport energy is set to 5 keV or less (preferably 2 keV or less) on the upstream side of the post-acceleration pre-acceleration electrode 31. This is extremely lower than the conventional front stage accelerator 4 (10 to 100 keV) shown in FIG. Thus, by reducing the ion beam transport energy incident on the mass separator, the ExB type mass separator 28 can be adopted as the mass separator.
Further, by arranging all these ion beam line configurations inside the beam line vacuum vessel 50, the entire ion beam line is accommodated in the beam line vacuum vessel 50. The beam line vacuum vessel 50 is set to the ground potential except for a current introduction terminal for introducing a control voltage or the like to an electrode or the like disposed inside the vessel.

A space having an outer shape larger than that of the upper portion is provided in the lower portion of the beamline vacuum vessel 50, and this space is used as a processing chamber 44. A wafer stage 34 is disposed in the center in the horizontal direction of the processing chamber 44. The processing chamber 44 is spatially connected to the wafer transfer space 39 in the front chamber Mc via the gate valve 43.
In the main body Ma of the unit processing apparatus M, a beam line vacuum vessel 50, a post-acceleration high-voltage power source 35 for applying a negative high voltage to the wafer stage 34, and a high vacuum pump 36 for the processing chamber 44 are arranged. Has been.
The main body Ma is an atmospheric space. Therefore, the outside of the beamline vacuum vessel 50 that accommodates the entire beamline is in contact with the atmosphere and is grounded as described above.

<Exhaust system and lower unit processing unit>
For the vacuum evacuation in the ion beam line including the processing chamber 44, a small turbo molecular pump with an exhaust speed of 80 L / s and a diaphragm pump with an exhaust speed of 50 L / min are used on the back pressure side. Since the total volume of the inside of the beamline vacuum vessel 50 is as very small as about 1 L, even such a small exhaust system can obtain a vacuum degree of about 10 ⁻⁶ Pa without any gas load.

In addition, since the wafer transfer system (PLAD) is connected to the ion beam line from the atmosphere side as described above, the wafer transfer space 39 receives the wafer from the atmosphere side to the vacuum. A high vacuum pump 36 'for introduction is connected. The main exhaust uses an ultra-small turbo molecular pump with a pumping speed of 10 L / s. However, the volume of the vacuum container in the wafer transfer space 39 is very small, so a vacuum of about 10 ⁻³ Pa in a short time. Degree is obtained.

  In the control storage unit Mb of the unit processing apparatus M, an auxiliary pump 37 for assisting the high vacuum pumps 36 and 36 ′, a control circuit unit 38 for controlling the entire unit processing apparatus M, and a floor are arranged in advance. A connection system (not shown) for connecting to a supply system, a drainage system, a power supply system, and the like is provided.

<Operation of each component>
The operation of each component constituting the ion beam line will be described in the order of arrangement.
The ion generator 23 is an electron impact type, and ions are formed by accelerating the thermal electrons from the filament heated by energization and applying them to the ion source gas.
The ions thus formed are extracted by an extraction electrode (pre-accelerator) 40 so that the beam transport energy is 5 keV or less (preferably 2 keV or less).
The neutral particle remover 24 removes neutral particles from the extracted ion beam by electrostatic deflection.
The converging lens 26 is used for converging the ion beam extracted from the ion generator 23 to a predetermined width because the trajectory is widened as it is.
Here, a differential exhaust slit 25 is provided between the ion generator 23 and the focusing lens 26 in order to minimize the flow of the ion source gas into the ion beam line.

The first XY deflection electrode 27 is provided for fine adjustment and correction of the ion beam trajectory.
The ExB-type mass separator 28 selects the target ion species from the ion beam input from the incident port based on the mass of the ion species, and passes only the ion beam composed of the selected ion species through the exit slit.
The second XY deflection electrode 30 is applied with a periodically changing voltage waveform, and the ion beam consisting of the selected ion species is periodically swung in the XY direction so that the ion beam reaches the entire surface of the wafer 33. Control. At this time, the voltage waveform applied to the second XY deflection electrode 30 is adjusted so that the ion implantation density is uniform at any position on the wafer 33.

A secondary electron suppression electrode 32 having a cup-type structure is provided in front of the wafer stage 34 (upstream side), and a bias potential of −90 V is applied to the wafer stage potential.
The wafer stage 34 is applied with a post-acceleration voltage of -30 KV at maximum by a post-acceleration high-voltage power supply 35. As a result, the ion beam is incident on the wafer stage 34 to which a negative high voltage potential is applied.
In this embodiment, the maximum voltage output of the post-acceleration power supply 35 used is set to -30 kV. However, by using a higher voltage power supply as necessary, the injection energy up to about 200 keV as shown in FIG. (Ion beam transport energy) can be obtained.

As described above, the ion beam A is finally accelerated by the negative high voltage applied to the wafer stage 34 and is injected into the wafer 33 with the required implantation energy.
When the ion beam A is incident on the wafer 33, secondary electrons B are emitted from the surface of the wafer 33. Here, as shown in FIG. 3, if there is nothing between the wafer stage 34 and the ground potential electrode 31, the secondary electrons B have a negative charge opposite to the ions, so that the ground potential opposite to the ions is present. It is accelerated toward the 31st side. The acceleration energy of the secondary electrons is the same as the subsequent acceleration energy of the ions. When secondary electrons are accelerated to an energy of several keV or more and hit a metal material such as an electrode, X-rays p harmful to the human body are generated, which may come out of the apparatus.

In order to prevent this, as shown in FIG. 4, an intermediate electrode (secondary electron suppression electrode) for suppressing secondary electrons B generated in front of the wafer 33 between the wafer stage 34 and the post-acceleration electrode 31 is provided. 32 is provided. A bias voltage q having a negative polarity with respect to the voltage of the wafer stage 34 is applied to the secondary electron suppressing electrode 32 by a post-acceleration high voltage power supply 35. Thereby, an electric field for returning the secondary electrons B in the direction of the wafer 33 is formed.
Since the emission energy of the secondary electrons B generated when the ions hit the solid surface is 30 eV or less at the maximum, the bias voltage q is such that the bias voltage q pushes back the secondary electrons, specifically, −30 V or more. By doing so, most of the secondary electrons B are returned to the wafer 33 side. In the present embodiment, as described above, the bias voltage q is set to -90V.
This secondary electron suppression is necessary not only to prevent leakage of X-rays p but also to accurately measure the ion beam current injected into the wafer 33.

The ion implantation amount can be obtained from the integrated value of the ion beam current. In the method of the present invention, since the wafer stage 34 has a high voltage potential, it is not possible to connect an ammeter directly to the wafer stage 34 as in the conventional apparatus. Can not.
Therefore, in this embodiment, as shown in FIGS. 3 and 4, an ammeter 60 is connected between the ground potential and the high voltage power supply 35 and the current flowing from the wafer 33 through the high voltage power supply 35 is measured. Then, the amount of ion implantation is obtained by integrating these.

  The secondary electron suppression electrode 32 functions as a flat plate or a disk, but the cup structure covering the entire wafer stage 34 as shown in FIG. It is more desirable because it is also effective.

As shown in FIGS. 2 and 8, the ion beam transport energy from the ion generator 23 to the second XY deflection electrode 30 is desirably 5 keV or less, and about 1 keV unless a significant decrease in beam transport efficiency occurs. It is desirable to lower the value to a lower value because a higher mass separation performance can be obtained.
In this way, the ion beam transport energy is set to 5 keV or less (preferably 2 keV or less) compared with the existing ion implantation apparatus which is usually at least 10 keV or more and usually 30 keV or more. Obviously low energy.
Performing the beam transport energy from the ion generator to XY deflection for mass separation and beam scanning in the low energy region of 5 keV or less has the following advantages.
(1) The mass separator can be reduced in size.
Since the ion beam is more easily bent in the magnetic field as the energy is lower, the mass separator can be miniaturized. Further, under the same mass separation conditions, the mass resolution is improved as the ion passage energy is lowered.
(2) The beam line can be shortened.
Since it becomes easy to bend by an electric field and a magnetic field, XY deflection for beam scanning can be performed with a shorter beam path, and the beam line can be shortened.
(3) The components inside the beam line can be reduced in size.
Insulation of the components inside the beamline vacuum vessel 50 is only about several mm if the applied voltage is about several kV, which is advantageous for downsizing the components inside the beamline.
(4) The control circuit can be downsized.
If the beam transport energy is low, the voltage required for beam control such as a focusing lens and XY deflection also becomes low, and the control power source may be small. Since the unit processing apparatus in the minimal fab production system has a very small casing, there is a space for installing only a small control power supply. Therefore, it is advantageous to be able to use a small power supply as much as possible.
(5) The influence of divergence and energy contamination due to the space charge effect can be eliminated.
Since a large current wafer apparatus uses a large current beam (-mA), a large amount of outgas is generated from the resist during irradiation, and energy contamination is likely to occur. In addition, when attempting to control the beam transport energy amount in the post-acceleration stage, there is a case where it is necessary to decelerate, in which case energy contamination is likely to occur. Further, when the beam length is increased, not only the influence of energy contamination but also the beam divergence due to the space charge effect is likely to occur.
On the other hand, in this embodiment, the beam length can be shortened and the beam current is as small as .mu.A, so that the influence of divergence and energy contamination due to the space charge effect can be eliminated. Further, since acceleration is performed to a desired ion beam transport energy in the subsequent acceleration stage (since it is not necessary to decelerate), energy contamination caused by deceleration can be eliminated.
(6) Commercially available inexpensive off-the-shelf products can be used.
If it is 5 kV or less, a power supply, a connector, etc. exist as consumer goods, and since these can be utilized, it is inexpensive.

Thus, if the beam transport energy from the ion generator 23 to the ExB type mass separator 28 is 5 keV or less, the ExB type mass separator 28 can ensure sufficient ion resolution even if the beam transport distance is short. The ExB type mass separator 28 itself can be reduced in size.
As the beam line length is shortened, the decrease in transport efficiency due to the influence of beam divergence and the like is reduced.

In the present embodiment, the mass separator 28 is configured as an ExB type mass separator.
In this ExB type mass separator 28, a magnetic field of about 3000 gauss orthogonal to the ion beam axis is applied by a magnetic circuit using a neodymium magnet. Electrodes for applying electric fields orthogonal to the static magnetic field are provided, and mass separation is performed by controlling the voltage applied to the electrodes.
Further, when a neodymium magnet or a samarium cobalt magnet is used for the ExB type mass separator 28 in this way, a strong magnetic field of 2000 gauss or more can be easily obtained even with a small magnet of about several centimeters square. It can be downsized to about 10cm.
A mass separation slit 29 is provided on the exit side of the ExB mass separator 28. By passing only ion species traveling straight, an ion beam of only a specific ion species required is obtained.

Thus, by using the ExB type Wien filter using a permanent magnet for the mass separator 28, both the mass separator body and the control power source can be miniaturized.
The magnetic field deflection method using an electromagnet used in a conventional apparatus has a high mass resolution and good controllability, so that it is an optimal choice when the apparatus size is not limited. However, due to the fact that the electromagnet body becomes very large, depending on the design, water cooling is required for heat removal, and the constant current control power supply necessary for electromagnet coil control becomes very large, etc. Not suitable for conversion. Moreover, even if the passing beam energy is low, it is difficult to make the unit processing apparatus M a size that can be adopted.
On the other hand, with the ExB type mass separator 28, mass separation is possible by controlling the orthogonal electric field strength under a constant magnetic field, so that a permanent magnet can be used for magnetic field generation. Can be downsized. Also, the constant voltage control power source used for electric field control is overwhelmingly smaller than the electromagnet control power source, and is therefore suitable for an ion implantation apparatus disposed in the unit processing apparatus M.

In the present embodiment, a separate unit processing apparatus M is configured for each required ion species or each ion source gas.
Even though the ExB-type mass separator 28 can shorten the beam line, the ExB-type mass separator 28 is inferior in mass resolution as compared with the conventional type. For example, it is difficult to separate BF + and P + having a mass number different by one. However, if only one kind of gas is used, it has sufficient performance for separation of ion species generated by ionization (in the case of BF3 gas, B ++, B +, F +, BF +, BF2 +, etc.). Therefore, the ion implantation apparatus for the minimal fab production system is limited to only one kind of gas to be installed in one apparatus and eliminates contamination by using no other ion source gas. .
Thereby, even if it is very small, the ion implantation apparatus which has sufficient mass separation performance can be obtained.

With the above configuration, the ion beam path from the ion beam outlet of the ion generator 23 to the wafer 33 can be shortened to about 30 cm.
Therefore, as shown in FIG. 5, all necessary components such as the beam line vacuum vessel 50, the ion source gas cylinder 21, the high vacuum pumps 36 and 36 ', the control circuit 38, etc. are the housing of the unit processing apparatus M. It can be stored inside.

A beam performance test result of the ion implantation apparatus S configured as described above is shown below.
In the test, argon gas was used as the ion source gas. The beam transport energy from the ion generator 23 to the post-acceleration pre-acceleration electrode 31 was set to 1 keV.
The obtained ion beam current was a maximum of 1 μA for Ar monovalent ions after mass separation. With this ion beam current, the time required to implant 1E14 ions per square centimeter over the entire half-inch size minimal wafer was about 10 seconds.

FIG. 6 shows a mass separation spectrum of an argon ion beam using the ExB type mass separator 28 in the present embodiment. It can be seen that the monovalent and divalent ions of argon are separated and detected.
The upper part of FIG. 6 shows the detection positions of ion species that appear when BF3 gas and PH3 gas are used in the present invention. From the peak width (= mass resolution) obtained in the argon gas test, it can be seen that there is an ability to separate all ionic species even when using BF3 in which many ionic species appear.
When the power consumption of the device was measured using an electric power meter, the maximum was 400W at startup and 330W or less during steady operation. This is extremely energy saving as 1/100 or less of the existing ion implantation apparatus.

Such extremely energy saving is as follows.
In this embodiment, no electromagnet is used for beam control including mass separation. An electromagnet is a device that consumes a large amount of power with or without a beam. By eliminating this, significant energy savings are possible. In this embodiment, all beam control including mass separation is performed by electric field control. The power consumption of the constant voltage power source used for the electric field control is about 1 W per power source, and even when a plurality of units are used, the beam control can be performed with very little power.
Furthermore, in this embodiment, since the volume of the vacuum vessel including the processing chamber from the ion generator is as small as about 1 L, the vacuum pump to be used is a small pump whose exhaust speed is 1/100 or less of the conventional apparatus. One is enough. A vacuum pump is a device that requires a large amount of power to use a motor. By reducing the size, the power consumption of the apparatus is greatly reduced.

In addition, this embodiment also has an advantage that ultra-low energy ion implantation with an implantation energy of several keV can be performed with extremely high efficiency as compared with the conventional apparatus. This is due to the following reason.
In the ion implanter S in the minimal fab production system, the required ion current is 1/1/2 that of the existing 12 inch (about 300 mm) diameter wafer device because the wafer area is as small as a half inch size (12.5 mm diameter). 1000, that is, about several μA is sufficient, and the ion density is extremely low. Furthermore, the beam line length from the ion generator 23 to the wafer 33 needs to be very short due to the limitation of the external size of the unit processing apparatus M. On the other hand, since the beam transport distance is extremely short, the divergence effect of the ion beam is Even if the ion beam has an ion beam transport energy of a very low ion beam energy of about 1 to 2 keV, the ion beam can be transported to the wafer 33 with almost no loss.
In recent years, ultra-shallow implantation in the several keV region has become important in advanced LSI processes with miniaturization, but the problem is that beam utilization efficiency (transport efficiency) becomes extremely poor in existing ion implantation systems. ing. On the other hand, in the apparatus configuration of the present invention, it is possible to perform such ultra shallow implantation without reducing the efficiency as described above, and it is not necessary to decelerate ions. No worries.

  In this embodiment, the ion generator 32 side is set to the ground potential, and only the wafer stage on which the target 33 is placed is set to a high voltage. This produces the following advantages and effects.

The spatial distance required for high voltage insulation can be greatly reduced, and the device size can be greatly reduced.
Compared to the atmosphere, the insulation resistance in a high vacuum is high, and the resistance is 100 kV or more even at a spatial distance of about 1 cm. Therefore, the space distance necessary for insulation between the wafer stage 34 to which a high voltage is applied and the beamline vacuum vessel 50 serving as the ground potential is sufficiently safe even if it is about several centimeters even at a high voltage of about 200 kV. . Since the wafer stage 34 for a half-inch size (diameter 12.5 mm) minimal wafer can be reduced to about 5 cm or less, even if the wafer stage 34 is placed in a small beamline vacuum vessel 50 having an inner diameter of about 10 cm, the wafer Sufficient insulation can be ensured between the stage 34 and the beamline vacuum vessel 50.

  In the present embodiment, all components on the atmosphere side such as the ion generator 23 and the beam line vacuum vessel 50 shown in FIG. 2 are set to the ground potential. Along with this, it is possible to install them almost closely to the apparatus housing. As a result, even within a minimal housing with a minimal device width of 30 cm, it can be installed without problems. In addition, since the high voltage portion is not exposed to the outside, it is safe for the operator.

Furthermore, in this embodiment, a conventional large-sized insulating transformer, optical communication equipment, and the like are not required, and the apparatus can be reduced in size and cost.
In the conventional apparatus configuration shown in FIG. 1, an ion source 3 placed in a high voltage section, a large insulation transformer 6 for supplying power to the mass separator 8 and the like, and the ground potential side for controlling them. An optical communication device (not shown) is required. On the other hand, in the present embodiment, there is no device for controlling the high voltage section as shown in FIG. 2, so these devices are unnecessary. Therefore, there is no need for a space for installing these devices, and the apparatus can be downsized. It is also effective for cost reduction.

As another embodiment, the unit processing apparatus M in the minimal fab production system can be configured by optimizing the implantation conditions (ion species and implantation energy) for each ion implantation process to have a single function.
The ion implantation energy region used in the semiconductor manufacturing process ranges widely from several keV to over 100 keV. An apparatus that can cover all of them complicates the apparatus configuration and increases the apparatus price. On the other hand, in the mass production line in the minimal fab production system, only one process is performed by one device including other devices. Therefore, once it is incorporated into the mass production line, it can be used only under substantially the same ion implantation conditions. Therefore, it is possible to provide a single-function unit processing apparatus that is optimized only for the ion implantation conditions and that eliminates other extra equipment and functions.
By doing so, it is possible to reduce the price of the ion implantation apparatus itself. Since a large number of ion implantation apparatuses will be introduced in the mass production line, the single function with limited functions is very effective in reducing the investment amount of the production line in the minimal fab production system.

Thus, the ion implantation apparatus of the present invention can be an optimum ion implantation apparatus for use in a unit processing apparatus having a standardized outer shape used in a minimal fab production system using a half-inch wafer. .
However, the present invention is not limited to use in a minimal fab production system, and can be easily introduced as an extremely small, energy-saving, and inexpensive ion implantation apparatus, for example, in research and development at universities and small-scale experiments at companies.

  In the present invention, the type of ion generator to be used is not limited, but it is desirable that the ion generator be as small as possible, power saving, high efficiency, low cost, and excellent in stability and durability. Ion generation is preferably performed continuously rather than pulsed in time. This is because, when ions are generated in a pulse shape, the ion density increases, and beam divergence may occur due to repulsion of charges. Therefore, the ion generator 23 that can obtain a continuous ion beam that is constant in time is desirable.

21 Source gas 23 Ion generator 24 Neutral particle remover 25 Differential exhaust slit 26 Condensing lens 27 First XY deflection electrode 28 ExB type mass separator 29 Mass separation slit 30 Second XY deflection electrode 31 Post-acceleration electrode 32 Secondary electrons Suppression electrode 33 Target (wafer)
34 Wafer stage 35 High-speed power supply 36, 36 'for subsequent stage acceleration Vacuum pump 39 Wafer transfer space 40 Extraction electrode (front stage accelerator)
42 Docking Port 43 Gate Valve 44 Processing Chamber 50 Beamline Vacuum Container A Ion Beam M Unit Processing Device Ma Main Body Mb Control Storage Unit Mc Front Chamber S Ion Implantation Device

Claims (5)

A wafer stage on which a half-inch wafer is placed ;
An ion generator for generating ions from one kind of ion source gas ;
A pre-accelerator for extracting ions from the ion generator;
A mass separator for mass-separating the ion beam extracted by the former accelerator;
An XY deflector that scans an ion beam selected by the mass separator in an XY direction;
A post-accelerator for accelerating a scanned ion beam to the wafer by the XY deflector,
Its has a beam line vacuum container for storing the these,
The mass separation is performed by controlling a magnetic field using a permanent magnet and an electric field orthogonal to the magnetic field,
While performing ion beam control from the ion generator to the XY deflector in a low energy region of 5 keV or less,
An ion implantation apparatus characterized in that the ion beam control by the post accelerator is performed with a negative high voltage applied to the wafer while the beam line vacuum vessel is at a ground potential. The ion implantation apparatus according to claim 1, wherein a secondary electron suppression electrode that applies a potential of −30 V or more to the wafer is disposed in front of the wafer. A wafer stage on which a half-inch wafer is placed ;
An ion generator for generating ions from one kind of ion source gas ;
A pre-accelerator for extracting ions from the ion generator;
A mass separator for mass-separating the ion beam extracted by the former accelerator;
An XY deflector that scans an ion beam selected by the mass separator in an XY direction;
A post-accelerator for accelerating a scanned ion beam to c E c by the XY deflector,
Its has a beam line vacuum container for storing the these,
The mass separation is performed by controlling a magnetic field using a permanent magnet and an electric field orthogonal to the magnetic field,
Ion beam control from the ion generator to the XY deflector is performed below an implantation energy region corresponding to a gate length of a semiconductor manufactured by implanting ions into the wafer,
The ion beam control by the post-stage accelerator is a control for accelerating to an implantation energy necessary for ion implantation by applying a negative high voltage to the wafer with the beam line vacuum vessel as a ground potential and controlling the high voltage. An ion implantation apparatus characterized by: A main body in which the ion implantation apparatus according to any one of claims 1 to 3 is accommodated;
To have a, a front chamber for conveying the wafer to the body portion
Unit process and wherein a call. The unit processing apparatus according to claim 4 , wherein
The unit processing apparatus is characterized in that the ion implantation apparatus has an implantation condition adapted to a predetermined ion implantation process.