INTEGRATED GAS BOX AND ION SOURCE

An integrated gas box is disclosed. The integrated gas box is an enclosure, wherein one wall of the enclosure includes an aperture. A bushing is affixed to the exterior of this wall. The distal end of the bushing has a flange that is affixed to a wall of the vacuum chamber. The ion source is introduced into the bushing through an access door in the enclosure and slides into the aperture. The base flange of the ion source is sufficiently large such that it cannot pass through the aperture and forms a seal between the bushing and the interior of the integrated gas box. The integrated gas box includes the gas canisters and associated valves which are used to supply feed gas and diluent gasses to the ion source. The integrated gas box also houses the power supplies used to bias the components within the ion source.

FIELD

Embodiments of the present disclosure relate to an integrated gas box, and more particularly a system that includes the gas canisters, power supplies and the ion source in one enclosure.

BACKGROUND

Ion implantation is a common technique to introduce impurities into a workpiece to affect the conductivity of portions of that workpiece. For example, ions that contain elements in Group III, such as boron, aluminum and gallium, may be used to create P-type regions in a silicon workpiece. Ions that contain elements in Group V, such as phosphorus and arsenic, may be used to create N-type regions in the silicon workpiece. Of course, other species may also be used.

In some ion implantation systems, ions are generated in an ion source and are extracted through an extraction aperture. In some embodiments, one or more electrodes, which are electrically biased, are located outside the ion source, proximate the extraction aperture. The voltage applied to one of these electrodes serves to attract ions from within the ion source such that the ions exit the ion source through the extraction aperture.

The ion source may be biased at a high voltage, such as tens or hundreds of kilovolts. Additionally, the power supplies that are used to bias the components within the ion source are referenced to this voltage. Traditionally, the gas canisters which are used to provide gas to the ion source, as well as the power supplies associated with the ion source, are disposed in a separate enclosure, referred to as a gas box, which is biased at the same voltage as the ion source. An umbilical cable is used to deliver the gasses, voltages and currents from the gas box to the ion source, which is separate from the gas box.

As the voltages associated with the ion source increase, so does the possibility of arcing between two components. During an arcing event, the high frequency electromagnetic field induces currents in the umbilical cable, which flow to the components in the gas box. This may cause glitches, or may permanently damage the electronic components in the gas box. This type of failure may render the ion implantation system unusable for an extended period of time while the components in the gas box are replaced.

Therefore, it would be beneficial if there were a system that reduced the likelihood of such a failure, so that the availability of the ion implantation system was not affected.

SUMMARY

An integrated gas box is disclosed. The integrated gas box is an enclosure, wherein one wall of the enclosure includes an aperture. A bushing is affixed to the exterior of this wall. The distal end of the bushing has a flange that is affixed to a wall of the vacuum chamber. The ion source is introduced into the bushing through an access door in the enclosure and slides into the aperture. The base flange of the ion source is sufficiently large such that it cannot pass through the aperture and forms a seal between the bushing and the interior of the integrated gas box. The integrated gas box includes the gas canisters and associated valves which are used to supply feed gas and diluent gasses to the ion source. The integrated gas box also houses the power supplies used to bias the components within the ion source.

According to one embodiment, an ion implantation system is disclosed. The ion implantation system comprises a vacuum chamber that houses: extraction optics; a mass analyzer; a mass resolving device; and a workpiece holder; and an integrated gas box located in atmospheric conditions, the integrated gas box comprising an enclosure comprising a plurality of walls, wherein a wall of the plurality of walls includes an aperture, the enclosure containing one or more gas canisters and one or more power supplies; and a bushing affixed to the wall of the enclosure having the aperture, wherein an ion source is disposed within the bushing and a distal end of the bushing comprises a flange affixed to a wall of the vacuum chamber. In some embodiments, the ion source is insertable into the bushing via an interior of the enclosure. In some embodiments, the ion source creates a seal between the bushing and an interior of the enclosure, such that the ion source is at vacuum conditions. In some embodiments, the enclosure is biased at an enclosure voltage. In some embodiments, the enclosure comprises a first compartment; a second compartment to allow access to the bushing; and a third compartment. In certain embodiments, the one or more gas canisters and associated valves are disposed in the first compartment. In certain embodiments, the one or more power supplies are disposed in the third compartment. In certain embodiments, the second compartment also contains a rack to hold one or more of the one or more power supplies. In some embodiments, the ion source comprises an indirectly heated cathode ion source, having an arc chamber that contains an indirectly heated cathode, a filament disposed behind the indirectly heated cathode, and the one or more power supplies comprise a filament power supply to provide current to the filament, a cathode bias power supply to bias the indirectly heated cathode relative to the filament, and an arc power supply to bias the indirectly heated cathode relative to the arc chamber.

According to another embodiment, an integrated gas box for use with an ion implantation system is disclosed. The integrated gas box comprises an enclosure, having a plurality of walls, wherein the enclosure houses: one or more gas canisters and associated valves to provide gas to an ion source; and one or more power supplies to supply a respective voltage to a plurality of biased components; and wherein an aperture is disposed in a wall of the plurality of walls, and a bushing affixed to the wall having the aperture, such that an interior of the bushing is accessible through an interior of the enclosure, wherein the ion source is configured to be disposed in the bushing. In some embodiments, the enclosure is biased at an enclosure voltage, and wherein a ground reference of the one or more power supplies is the enclosure voltage. In some embodiments, the ion source comprises indirectly heated cathode ion source, having an arc chamber and an indirectly heated cathode. In certain embodiments, the arc chamber comprises a filament disposed behind the indirectly heated cathode, and the one or more power supplies comprise a filament power supply to provide current to the filament, a cathode bias power supply to bias the indirectly heated cathode relative to the filament, and an arc power supply to bias the indirectly heated cathode relative to the arc chamber. In some embodiments, the enclosure comprises a first compartment; a second compartment to allow access to the bushing; and a third compartment. In certain embodiments, the one or more gas canisters and associated valves are disposed in the first compartment. In certain embodiments, the one or more power supplies are disposed in the third compartment. In certain embodiments, the second compartment also contains a rack to hold one or more of the one or more power supplies. In certain embodiments, the third compartment is disposed above the second compartment and the first compartment is disposed below the second compartment.

DETAILED DESCRIPTION

FIG.1shows an ion implantation system that may be used for implanting ions into a workpiece using an ion beam according to one embodiment.

The ion implantation system includes an ion source100comprising a plurality of chamber walls defining an ion source chamber. In certain embodiments, the ion source100may be an IHC ion source. In this embodiment, a cathode is disposed within the ion source chamber. A filament is disposed behind the cathode and energized so as to emit electrons. These electrons are attracted to the cathode, which in turn emits electrons into the ion source chamber. This cathode may be referred to as an indirectly heated cathode (IHC), since the cathode is heated indirectly by the electrons emitted from the filament.

In another embodiment, the ion source100may be an RF ion source. In this embodiment, an RF antenna may be disposed against a dielectric window. This dielectric window may comprise part or all of one of the chamber walls. The RF antenna may comprise an electrically conductive material, such as copper. An RF power supply is in electrical communication with the RF antenna. The RF power supply may supply an RF voltage to the RF antenna. The power supplied by the RF power supply may be between 0.1 and 10 kW and may be any suitable frequency, such as between 1 and 100 MHZ. Further, the power supplied by the RF power supply may be pulsed.

Other embodiments are also possible. For example, the plasma may be generated in a different manner, such as by a Bernas ion source, a capacitively coupled plasma (CCP) source, microwave or ECR (electron-cyclotron-resonance) ion source. The manner in which the plasma is generated is not limited by this disclosure.

One chamber wall, referred to as the extraction plate, includes an extraction aperture. The extraction aperture may be an opening through which the ions1generated in the ion source chamber are extracted and directed toward a workpiece10. The extraction aperture may be any suitable shape. In certain embodiments, the extraction aperture may be oval or rectangular shaped.

Disposed outside and proximate the extraction aperture of the ion source100are extraction optics110. In certain embodiments, the extraction optics110comprise one or more electrodes. In certain embodiments, the extraction optics110comprises a suppression electrode111, which is negatively biased relative to the plasma so as to attract ions through the extraction aperture. The suppression electrode111may be electrically biased using a suppression power supply290(seeFIG.2). The suppression electrode111may be biased so as to be more negative than the extraction plate of the ion source100. In certain embodiments, the suppression electrode111is negatively biased by the suppression power supply290, such as at a voltage of between −3 kV and −15 kV.

In some embodiments, the extraction optics110includes a second electrode112. The second electrode112may be disposed proximate the suppression electrode111. The second electrode112may be electrically connected to a second electrode power supply295(seeFIG.2). In other embodiments, the second electrode112may be electrically grounded so that the second electrode power supply295is not used.

In other embodiments, the extraction optics110may comprise in excess of two electrodes, such as three electrodes or four electrodes. In these embodiments, the electrodes may be functionally and structurally similar to those described above, but may be biased at different voltages.

Each electrode in the extraction optics110may be a single electrically conductive component with an aperture disposed therein. Alternatively, each electrode may be comprised of two electrically conductive components that are spaced apart so as to create the aperture between the two components. The electrodes may be a metal, such as tungsten, molybdenum or titanium. One or more of the electrodes may be electrically connected to ground. In certain embodiments, one or more of the electrodes may be biased using an electrode power supply. The electrode power supply may be used to bias one or more of the electrodes relative to the ion source so as to attract ions through the extraction aperture. The extraction aperture and the apertures in the extraction optics110are aligned such that the ions1pass through apertures.

The electrodes in the extraction optics110may be separated, both physically and electrically, through the use of one or more insulators115. Further, in some embodiments, insulators are also used to separate the ion source100from the suppression electrode111.

Located downstream from the extraction optics110is a mass analyzer120. The mass analyzer120uses magnetic fields to guide the path of the extracted ions1. The magnetic fields affect the flight path of ions according to their mass and charge. A mass resolving device130that has a resolving aperture131is disposed at the output, or distal end, of the mass analyzer120. By proper selection of the magnetic fields, only those ions1that have a selected mass and charge will be directed through the resolving aperture131. Other ions will strike the mass resolving device130or a wall of the mass analyzer120and will not travel any further in the system.

A collimator140may be disposed downstream from the mass resolving device130. The collimator140accepts the extracted ions1that pass through the resolving aperture131and creates a ribbon ion beam formed of a plurality of parallel or nearly parallel beamlets. In other embodiments, the ion beam may be a spot beam. In this embodiment, an electrostatic scanner is used to move the spot beam in the first direction, as defined below.

Located downstream from the collimator140may be an acceleration/deceleration stage150. The acceleration/deceleration stage150may be an electrostatic filter. The electrostatic filter is a beam-line lens component configured to independently control deflection, deceleration, and focus of the ion beam. Located downstream from the acceleration/deceleration stage150is the workpiece holder160.

In some embodiments, one or more lenses may be disposed along the beam line. A lens may be disposed before the mass analyzer120, after the mass analyzer120, before the collimator140or another suitable location.

The workpiece10, which may be, for example, a silicon wafer, a silicon carbide wafer, or a gallium nitride wafer, is disposed on the workpiece holder160.

In certain embodiments, the forward direction of the ion beam is referred to as the Z-direction, the direction perpendicular to this direction and horizontal may be referred to as the first direction or the X-direction, while the direction perpendicular to the Z-direction and vertical may be referred to as the second direction or Y-direction.

In some embodiments, the workpiece holder160is capable of moving in a direction that is perpendicular to the direction of the ion beam. Thus, in operation, the workpiece holder160moves in the second direction from a first position, which may be above the ion beam to a second position, which may be below the ion beam. The workpiece holder160then moves from the second position back to the first position. The ion beam is wider than the workpiece10in the first direction, ensuring that the entirety of the workpiece10is exposed to the ion beam.

FIG.2shows an expanded view of the components related to the ion source100. The ion source100includes an arc chamber200, comprising two opposite ends, and walls201connecting to these ends. The walls201of the arc chamber200may be constructed of an electrically conductive material and may be in electrical communication with one another. In some embodiments, a liner may be disposed proximate one or more of the walls201. A cathode210is disposed in the arc chamber200at a first end206of the arc chamber200. A filament260is disposed behind the cathode210. The filament260is in communication with a filament power supply265. The filament power supply265is configured to pass a current through the filament260, such that the filament260emits thermionic electrons. Cathode bias power supply215biases filament260negatively relative to the cathode210, so these thermionic electrons are accelerated from the filament260toward the cathode210and heat the cathode210when they strike the back surface of cathode210. The cathode bias power supply215may bias the filament260so that it has a voltage that is between, for example, 200V to 1500V more negative than the voltage of the cathode210. The cathode210then emits thermionic electrons on its front surface into arc chamber200.

Thus, the filament power supply265supplies a current to the filament260. The cathode bias power supply215biases the filament260so that it is more negative than the cathode210, so that electrons are attracted toward the cathode210from the filament260. In certain embodiments, the cathode210may be biased relative to the arc chamber200, such as by arc power supply213. In other embodiments, the cathode210may be electrically connected to the arc chamber200, so as to be at the same voltage as the walls201of the arc chamber200. In these embodiments, arc power supply213may not be employed and the cathode210may be electrically connected to the walls201of the arc chamber200.

On the second end207, which is opposite the first end206, a repeller220may be disposed. The repeller220may be biased relative to the arc chamber200by means of a repeller bias power supply223. In other embodiments, the repeller220may be electrically connected to the arc chamber200, so as to be at the same voltage as the walls201of the arc chamber200. In these embodiments, repeller bias power supply223may not be employed and the repeller220may be electrically connected to the walls201of the arc chamber200. In another embodiment, the repeller220may be biased by means of the arc power supply213. In still other embodiments, a repeller220is not employed.

The cathode210and the repeller220are each made of an electrically conductive material, such as a metal or graphite.

In certain embodiments, a magnetic field is generated in the arc chamber200. This magnetic field is intended to confine the electrons along one direction. The magnetic field typically runs parallel to the walls201from the first end206to the second end207. For example, electrons may be confined in a column that is parallel to the direction from the cathode210to the repeller220(i.e. the y direction). Thus, electrons do not experience any electromagnetic force to move in the y direction. However, movement of the electrons in other directions may experience an electromagnetic force.

Disposed on one side of the arc chamber200, referred to as the extraction plate203, may be an extraction aperture204. InFIG.2, the extraction aperture204is disposed on a side that is parallel to the X-Y plane (perpendicular to the page). A gas inlet280may be disposed on one wall of the arc chamber200.

Further, the ion source100may be in communication with at least one gas canister. The gas canister270may contain a dopant gas, a halogen gas, an inert gas, or a diluent gas. In some embodiments, there are more than one gas canister270.

A valve271may be utilized to control the flow of the gas from each of the gas canister270to the ion source100.

As described above, the suppression electrode111is disposed proximate to the extraction aperture204, outside of the ion source100. In certain embodiments, insulators115are used to be physically electrically isolate the suppression electrode111from the extraction plate203. Additional insulators115may be used to physically connect and electrically isolate the second electrode112from the suppression electrode111.

To reduce the possibility of electromagnetic fields causing damage to the ion implantation system, many of the components shown inFIG.2are housed in a single enclosure.

FIGS.3A-3Bshows a diagram showing the general structure of the enclosure300, also referred to as an integrated gas box, as it is incorporated into the ion implantation system.FIG.3Ashows the enclosure without the ion source100installed.FIG.3Bshows the enclosure300with the ion source installed.FIGS.4and5show two specific embodiments of the integrated gas box.

In the embodiments shown inFIGS.3A-3B, the enclosure300is isolated from the ground using enclosure insulators310. The enclosure300may be constructed from a conductive material. Further, the enclosure300may be biased to an enclosure voltage, which is different from earth ground, using an external enclosure power supply301. The enclosure voltage may be more than 100 kV in some embodiments.

The enclosure300may be separated into three compartments, a first compartment320, a second compartment330and a third compartment340. Each of which is described in more detail below. In different embodiments, the dimensions and the functionality contained within the compartments may vary. In certain embodiments, the first compartment320may be below the second compartment330and the third compartment340may be above the second compartment330.

The second compartment330includes a bushing331that extends outward from and is affixed to the exterior of one of the walls of the enclosure300. The bushing331may be constructed from any insulating material with a high dielectric constant. For example, a specially formulated epoxy may be used to form the bushing331. The wall of the enclosure300to which the bushing is affixed includes an aperture335so that the second compartment330allows access to the interior of the bushing331. Thus, the interior of the bushing331may be accessed via the interior of the enclosure300. The distal end of the bushing331includes a flange332. The flange332is used to seal the bushing331to the vacuum chamber390. The flange332covers an opening in a wall of the vacuum chamber390, such that the interior of the bushing331is at vacuum conditions. The interior of the bushing331is hollow. As noted above, the interior of the bushing331may be accessed through the second compartment330because of the aperture335in the wall of the enclosure300.

As seen inFIG.3B, disposed in the interior of the bushing331is the ion source100. Specifically, the arc chamber200, the cathode210, the repeller220and the filament260are disposed in the bushing331. Other components, such as the gas canisters270, valves271and power supplies are located in the enclosure300.

The ion source100is oriented such that the extraction plate203is the wall of the arc chamber200that is located nearest the flange332. In this way, ions are extracted through the extraction aperture204and travel through the flange332into the vacuum chamber390. The extraction optics110, which includes the suppression electrode111and the second electrode112, are disposed within the vacuum chamber390. The mass analyzer120, the mass resolving device130, the collimator140, the acceleration/deceleration stage150and the workpiece holder160(seeFIG.1) are all located within the vacuum chamber390. Thus, the flange332is used to seal the bushing331to the vacuum chamber390such that the interior of the arc chamber200is also maintained at near vacuum conditions.

In some embodiments, the ion source100is removably inserted into the bushing331and forms a seal with the wall of the enclosure300. For example, the ion source100may include a base flange299located on its bottom wall, which is the wall that is opposite the extraction plate203. The ion source100is slid into the bushing331through the aperture335(seeFIG.3A). The aperture335is dimensioned such that the base flange299cannot pass through the aperture335in the enclosure300. Thus, the base flange299seals the ion source100to the enclosure300. This base flange299also forms the boundary between the vacuum conditions in the vacuum chamber390and atmospheric conditions where the enclosure300is located. In other words, the enclosure300is disposed in an atmospheric environment, and only the ion source100, which is disposed within the bushing331, is at vacuum.

FIG.4shows one embodiment of this integrated gas box. In this embodiment, as described above, the enclosure400is isolated from the ground using enclosure insulators410. The enclosure400may be constructed from a conductive material. Further, the enclosure400may be biased to an enclosure voltage, which is different from earth ground, using an external enclosure power supply401. The enclosure voltage may be more than 100 kV in some embodiments.

As noted above, the enclosure400may be separated into three compartments, a first compartment420, a second compartment430and a third compartment440.

The second compartment430may be configured as described with respect toFIG.3. The second compartment430is attached to the bushing331, where the ion source100is located. The distal end of the bushing331includes a flange332. As described above, an aperture in a wall of the enclosure400allows access to the interior of the bushing331.

In certain embodiments, the first compartment420is used to house the gas canisters270and the associated valves271. In certain embodiments, the enclosure400may have a depth such that gas canisters270may be laid on their side within the first compartment420. In other words, the depth of the enclosure400is greater than the height of a gas canister270. In some embodiments, the depth may be at least 30 inches. In addition, the width of the enclosure400may be such that three gas canisters270may be laid next to each other. In some embodiments, the width may be at least 20 inches. The height of the first compartment420may be such that at least two canisters270, both laid on their sides, may be stacked on top of each other. Thus, in this embodiment, a total of six canisters270may be disposed in the first compartment420, wherein all of the canisters270are on their side and there are three canisters270resting on three other canisters. In some embodiments, the valves271may all be disposed above the gas canisters270. The input to each valve271is in communication with a respective gas canister270. The outputs of the valves271may be joined together and enter the gas inlet280of the arc chamber200.

The third compartment440may be used to house the power supplies associated with the ion source100. For example, in certain embodiments, the filament power supply265, the arc power supply213and the cathode bias power supply215may be disposed in the third compartment440. These power supplies may be referenced the voltage applied to the enclosure400. In other words, the ground reference of these power supplies may be the enclosure voltage supplied by external enclosure power supply401. Although not shown, there may be additional power supplies that are disposed in the third compartment440and are similarly grounded. For example, the ion source100may utilize other power supplies, which may be located in the third compartment440. In some embodiments, the third compartment440may be configured as a conventional 19 inch rack. Note that if the width of the enclosure is 20 inches or more, as described above, a standard 19 inch rack may be included in the third compartment440. Thus, in these embodiments, the power supplies are each one or more rack units (RU) in height. In some embodiments, the height of the third compartment440may support up to 12 rack units (RU). Of course, other dimensions are also possible.

As noted above, the ion source100is disposed within the bushing331. The second compartment330may include an access door or other mechanism to allow access to the interior of the enclosure and to the ion source100, such as for purposes of preventative maintenance.

In certain embodiments, the first compartment420may be the lower compartment and the third compartment440may be the upper compartment. Further, the second compartment430may be disposed between the first compartment420and the third compartment440and may be a middle compartment. Thus, in this embodiment, the power supplies are all disposed above the second compartment430and all of the gas canisters270are disposed beneath the second compartment430. The second compartment430is not populated. Rather, it is used to simply allow access to the ion source100. Each compartment may include one or more access doors, to allow access to the interior of the respective compartment.

FIG.5shows another embodiment of an integrated gas box. In this embodiment, the depth of the enclosure500is increased. As described above, the enclosure500is isolated through the use of enclosure insulators510. The enclosure500may be constructed of a conductive material and biased to an enclosure voltage, which is different from earth ground, using an enclosure power supply501. The enclosure voltage may be more than 100 kV in some embodiments. In this embodiment, the depth of the enclosure500is such that it is greater than twice the height of a gas canister270. The width of the enclosure500is as described above with respect toFIG.4. Thus, in this configuration, there may be as many as 12 gas canisters270located in the first compartment520, assuming that two gas canisters may be laid on each other in the vertical direction. As described above, the valves271associated with each gas canister270may be located above the gas canisters270in the first compartment520.

Further, the third compartment540may support standard 19 inch rack mounted power supplies, as described above. However, the number of rack units in the third compartment540may be reduced, as compared to the embodiment inFIG.4. For example, the third compartment540may only support 6 or fewer rack units.

The second compartment530in this embodiment differs than that described inFIG.4. In this embodiment, the second compartment530is partitioned in the depth direction to form a first portion535and a second portion536. Similar to the embodiment ofFIG.4, the first portion535is used to allow access to the ion source100, located in the bushing331. Thus, the bushing331is accessed via an aperture in the first portion535of the second compartment530.

The second portion536may be configured as a traditional 19 inch rack, and may support 6 rack units or more. In this way, one or more of the power supplies may be disposed in the second portion536, while other power supplies are disposed in the third compartment540. In another embodiment, the height of the second compartment530may be such that the third compartment540may be eliminated. As described above, the power supplies contained within the enclosure500may use the enclosure voltage applied by the enclosure power supply501as the ground reference.

The embodiments described above in the present application may have many advantages. As the voltage applied to the ion source increases, the likelihood of an arcing event also increases. These arcing events create electromagnetic fields that can induce a current on signal lines. If the induced current is significant enough, it may permanently damage the components in communication with those signal lines, causing extended periods of down time. By incorporating the power supplies and gas canisters into the same enclosure that houses the ion source, the risk of this induced current is reduced. This may help improve the availability of the ion implantation system.