KR20050021574A - Ion source and coaxial inductive coupler for ion implantation system - Google Patents

Abstract

An ion source with elongated slits is provided that provides a ribbon ion beam for use in an ion implantation system. This source generates azimuthal multi-cusped magnetic fields to trap the plasma, including a cylindrical magnet disposed within the housing as well as a coaxial inductive coupling antenna for RF excitation of the plasma in the cylindrical source housing. Let's do it. Also disclosed is a liner for internal hydration that provides a thermal barrier between the plasma and the outer housing wall to mitigate or reduce condensation in the plasma confinement chamber.

Description

ION SOURCE AND COAXIAL INDUCTIVE COUPLER FOR ION IMPLANTATION SYSTEM}

This application is a partial consecutive application of patent application 10 / 136,047, entitled "ION SOURCE PROVIDING RIBBON BEAM WITH CONTROLLABLE DENSITY PROFILE", filed May 1, 2002.

The present invention relates generally to ion implantation systems, and more particularly to ion sources for providing ribbon beams in ion implantation systems.

Ion implantation systems or ion implanters are widely used to dope semiconductors with impurities in the manufacture of integrated circuits as well as flat panel displays. In such a system, the ion source ionizes the desired dopant element, which is extracted from the source in the form of an ion beam of desired energy. The ion beam then injects the workpiece into the dopant element towards the surface of the workpiece, such as a semiconductor wafer. As in the manufacture of transistor devices on a wafer, ions in the ion beam penetrate the surface of the wafer to form the desired conductive region. The implantation process is typically performed in a high vacuum processing chamber, which prevents dispersion of the ion beam due to collisions with residual gas molecules, thereby minimizing the risk of contamination of the wafer with particles carried into the air. Although flat panel displays typically do not include a mass spectrometer, a typical ion implanter is an ion source that generates an ion beam, a beamline that includes a mass spectrometer that mass resolving the ion beam, and a semiconductor wafer to be implanted by the ion beam. Or a target chamber comprising another substrate. In a high energy injection system, an accelerator device is provided between the mass spectrometer and the target chamber to accelerate ions to high energy.

Conventional ion sources include a plasma compartment having an inlet hole for injecting the gas to be ionized into the plasma and an outlet hole opening for extracting the plasma to form an ion beam. One example of a gas is phosphine. When phosphine is exposed to an energy source, such as active electrons or radio frequency (RF) energy, phosphine dissociates to form electrostatic phosphorus (P +) ions and hydrogen ions that dope the workpiece. Typically, phosphine is injected into a plasma compartment and then exposed to an energy source, generating phosphorus ions and hydrogen ions. Typically, phosphine is injected into a plasma compartment and then exposed to an energy source to generate both phosphorus ions and hydrogen ions. The plasma contains not only the desired ions for injection into the workpiece but also the undesirable ions that are by-products of the dissociation and ionization process. The phosphorus ions and hydrogen ions are then extracted into the ion beam through the outlet using an extraction device that includes an activated extraction electrode. Examples of other typical dopant elements comprising a source gas include phosphorus (P), arsenic (As) or boron (B).

The dose and energy of implanted ions vary depending on the implantation desired for a given application. Ion dose controls the concentration of implanted ions for a given semiconductor material. Typically, high current injectors are used for high dose implants, while medium current injectors are used for lower dose applications. Ion energy is used to control the junction depth in semiconductor devices, where the energy level of ions in the ion beam determines the depth of implanted ions. Due to the ever-increasing size of semiconductor devices, there is a need for beamline configurations that act to deliver high beam currents at low energy. High beam current provides the required dose level, while low energy makes the implant shallow. In addition, the trend toward ever increasing device complexity on semiconductor wafers necessitates careful control over the uniformity of the injection beam being scanned throughout the workpiece.

The ionization process in the ion source is accomplished by extracting electrons and then colliding with the ionizable material in the ion source chamber. This extraction has already been accomplished using heated cathodes or RF excitation antennas. The cathode is heated to release electrons and then accelerated with sufficient energy for the ionization process, while the RF antenna generates an electric field that accelerates the plasma electrons with sufficient energy to continue the ionization process. The antenna may be located outside of the plasma chamber exposed in the plasma compartment of the ion source or separated by the dielectric window. The antenna is activated by RF alternating current which induces a time varying magnetic field in the plasma compartment. This magnetic field then induces an electric field in the area occupied by generating free electrons in the original source chamber. These free electrons are accelerated by the induced electric field and collide with the ionizable material in the ion source chamber, generating a plasma current in the ion chamber, which is generally in a direction parallel and opposite to the current in the antenna. The ions are then extracted from the plasma chamber by one or more activatable extraction electrodes located near the small outlet, providing an ion beam of small cross section (relative to the size of the workpiece).

In many ion implantation systems, a cylindrical ion beam is provided to a wafer target through mechanical and / or magnetic scanning to implant this target as desired. A batch implanter simultaneously implants several wafers that are rotated through the implant path in a controlled manner. Ion beams are shaped according to ion source extraction apertures and the following shaping devices such as mass spectrometers, resolving holes, quadrupole magnets, and ion accelerators, which result in small cross-sectional ion beams (relative to the size of the injected workpiece). Provided on the target wafer or wafers. The beam and / or target are translated relative to each other to scan the workpiece. However, to reduce the complexity of such an implant system, it is desirable to reduce the scanning mechanism and provide an elongated ribbon-shaped ion beam. In the case of a ribbon beam of sufficient longitudinal length, a single mechanism scan is used to inject the entire wafer without the need for additional mechanical or magnetic raster-type scanning devices. Accordingly, it would be desirable to provide a ribbon beam ion source that provides an elongated ion beam having a uniform longitudinal density profile for use in such an implant system.

1A is a cross sectional end view of a typical ion source with a coaxial inductively excited antenna in accordance with an aspect of the present invention.

FIG. 1B is a cross sectional end view of the ion source of FIG. 1A with a series of extraction electrodes located near the exit. FIG.

Figure 1C is a cross sectional end view of another exemplary ion source with a coaxial inductively excited antenna in accordance with the present invention.

FIG. 2A is a cross-sectional view taken along line 2a-2a of FIG. 1C showing a circumferentially disposed plasma constrained magnet and a coaxial inductive excitation antenna disposed to generate an orientation magnetic field in the chamber in accordance with another aspect of the present invention. Top view of the building.

FIG. 2B is a partial bottom plan view taken along line 2b-2b of FIG. 1C showing additional details of the plasma confinement magnet and azimuth magnetic field in the plasma compartment; FIG.

FIG. 2C is a simplified bottom plan view in cross section showing one implementation of a coaxial excitation antenna capacitively coupled at both ends in accordance with another aspect of the present invention. FIG.

FIG. 2D is a simplified bottom plan view schematically illustrating the electrical circuit of the coaxial excitation antenna of FIG. 2C. FIG.

Fig. 2E is a simplified bottom plan view of a cross section showing another exemplary implementation of a coaxial excitation antenna capacitively coupled at one end.

FIG. 2F is a simplified bottom plan view schematically illustrating the electrical circuit of the coaxial excitation antenna of FIG. 2E. FIG.

3A shows a density profile control device for selectively adjusting a density profile associated with an elongated longitudinal ion beam extracted from an ion source plasma compartment in accordance with another aspect of the present invention, lines 3a-3a of FIG. 1C. Thus seen bottom plan view.

FIG. 3B is an end view of a cross section of the ion source of FIG. 3A, showing an adjustable magnetic field generated by the density profile control device. FIG.

4A and 4B are end views in cross section of the ion source of FIGS. 3A and 3B, showing magnetic field contours in the plasma compartment for two different settings of the density profile control device.

5 is a simplified perspective view of an exemplary ion source showing an elongated ribbon-shaped ion beam extracted in accordance with the present invention.

The present invention relates to an ion source for an ion implantation system in which an elongated or ribbon-shaped ion beam of uniform or controllable density can be implanted into a workpiece such as a semiconductor wafer or flat panel display. The present invention provides an ion source in which a uniform plasma is provided in an elongated plasma compartment, from which the ribbon-shaped ion beam is extracted through an elongated outlet or extraction slit having a relatively large aspect ratio. The stretched ribbon beam is then used to implant the semiconductor wafer in a single mechanical scan, thereby simplifying the implantation system. In one implementation, the present invention is used to provide a ribbon beam up to 400 mm long, to facilitate a single scan injection of a 300 mm semiconductor wafer workpiece.

In order to control the uniformity of the extracted ion beam, the present invention advantageously provides coaxial RF excitation in a generally cylindrical source chamber to uniformly generate ionized plasma therein. Uniform plasma confinement in the plasma chamber is further enhanced by providing circumferentially extending multi-cusped magnets that provide an azimuth magnetic field in the plasma chamber. The elongated outlet or extraction slit is then provided to a plasma chamber for extraction using the elongated activatable extraction electrode to form a ribbon beam. The uniformity of the ions in the plasma chamber facilitates the provision of a uniform ribbon beam to uniformly inject wafer targets with high mold density and small feature size. In addition, a thermal barrier, such as a cylindrical liner, may be provided in the plasma chamber, which raises the plasma temperature to mitigate condensation in the plasma chamber. This facilitates the conversion from one implantation species to another without contaminants due to conventional condensation in conventional RF excited ion (eg, "cold wall") sources.

One aspect of the invention provides an ion source comprising a housing having a cylindrical plasma compartment disposed along a longitudinal axis for generating a plasma, an antenna coaxially disposed in the plasma chamber along this axis, and an RF source for activating the antenna. The housing includes a cylindrical conductive chamber extending longitudinally between the first and second ends, the longitudinally extending outlet capable of extracting the ion beam from the plasma, the extended outlet being for example about It can be any longitudinal length, such as 400 mm and can have a high aspect ratio to provide an elongated ribbon shaped ion beam. The antenna includes first and second terminals, where the first terminal is connected to the RF source and the second terminal is electrically connected to the chamber wall at the second end, where the chamber wall provides a return path for the RF source. A portion of the antenna between the first and second terminals extends longitudinally in the plasma compartment along the axis, releasing energy into the plasma chamber.

Thus, the coaxial antenna facilitates uniform excitation of the plasma to provide a uniform ion source for extracting the ribbon beam. The RF source has two outputs including a first output connected to the first antenna terminal and a second output connected to the first end of the chamber wall. In this way, the RF source, antenna, and chamber wall form a substantially coaxial electrical circuit to provide alternating current to the exposed portions of the antenna to induce an ionizing field in the plasma compartment. The capacitor may be provided between the first RF source output and the antenna first terminal and / or between the second end of the chamber wall and the second antenna terminal.

Another aspect of the invention provides an ion source for providing an ion beam in an ion implantation system, which includes a housing defining a cylindrical plasma compartment disposed along a longitudinal axis. The housing includes a generally cylindrical conductive chamber wall with an elongated outlet extending in the longitudinal direction and an antenna extending partially within the plasma compartment that releases energy therein. A plurality of magnets are provided, which are radially spaced from the axis and longitudinally spaced from each other in the plasma compartment. Adjacent magnet pairs are made of opposing magnets, creating a longitudinal magnetic field near the chamber wall to trap the plasma in the plasma compartment. In one embodiment, the magnet is a permanent magnet that extends circumferentially individually around a portion of the interior of the chamber wall between opposite sides of the outlet.

In order to achieve the above and related objects, aspects and implementation manners of the present invention have been illustrated in detail in the following description and the annexed drawings. These represent some of the various ways in which the principles of the invention may be used. Other aspects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.

The present invention will now be described with reference to the drawings in which like reference numerals refer to like elements. The present invention provides an ion source device that produces an elongated ion beam in an ion implantation system having a controllable density profile and other novel features that improve the uniformity of the ionized plasma within the source. One implementation of various aspects of the invention is shown and described below. However, it will be appreciated that these examples and descriptions of the invention are exemplary in nature and that one or more aspects or novel features of the invention may be practiced with systems other than those illustrated and described herein.

Referring first to FIGS. 1A-1C and 2A, an ion source 2 according to the present invention is shown, which can be used to create an elongated ribbon beam for use in an ion implantation system. This source comprises a housing 4 defining an elongated generally cylindrical plasma compartment 6 disposed along the longitudinal axis 8, in which the plasma is phosphine (PH3), phosphorus (P), arsenic It is generated by ionizing a source material such as (As), boron (B), and the like (not shown). The housing 4 generally extends longitudinally between each of the first and second ends 14 and 16, with an elongated outlet or extraction slit 18 extending longitudinally capable of extracting the ion beam from the plasma. It includes a generally cylindrical conductive chamber wall 10. The opening 18 accesses the extraction device to a plasma defined within the chamber 6 to extract a ribbon-shaped beam of significant length (eg 400 mm) from the plasma in a uniform or controllable manner.

One aspect of the present invention is to coaxially excite the plasma in the chamber 6 to facilitate plasma uniformity in the source 2. To this end, the illustrated ion source 2 uses an antenna 20 comprising first and second terminals 20a and 20b, respectively, which are coaxially located along the longitudinal axis 8. Coaxial or concentric positions of the antenna 20 and the conductive chamber wall 10 facilitate the uniformity of the plasma along the longitudinal length of the source 2. The first terminal 20a is connected to the RF plasma oscillator source 22 at the first end 14 and the second terminal 20b is electrically connected to the chamber wall at the endpoint 21 at the second end 16. Where these terminals 20a and 20b are AC coupled using capacitors 24a and 24b respectively.

The chamber 6 is maintained in vacuum using a bushing 27 between the inner portion of the antenna and the capacitor 24. Antenna 20 has an inductance L and, together with capacitor 24, forms a resonant circuit to generate a plasma in chamber 6 by providing RF excitation to the source gas, one output of RF source 22 being It is connected to the antenna terminal 24a and the other output is connected to the termination point 23 at the first end 14 of the wall 10. Thus, RF source 22, antenna 20, capacitor 24 and conductive chamber wall 10 form a substantially coaxial electrical circuit to provide alternating current in the exposed portion of antenna 20 to provide a plasma compartment 6. Induces an electric field within The combination of antenna 20 and capacitor 24 form a series resonant circuit at the frequency of RF source 22. Thus, the voltage across this circuit is minimized. If the capacitor 24 is of the same value, the voltage at the center of the antenna 20 is also minimized. This is desirable to minimize sputtering of the antenna 20 (or antenna shielding) material.

The central portion of the antenna 20 between the terminals 20a and 20b extends longitudinally along the axis 8 to couple energy into the chamber 6 so that the AC RF current passing through the antenna 20 is reduced to a plasma compartment ( 6) creates a time-varying magnetic field within The magnetic field then induces an electric field in the area occupied (initially) by generating free electrons that are originally accelerated in the chamber 6. The accelerated electrons then collide with the ionizable material, generating more electrons, which are also accelerated by the RF field until the plasma is established. In the steady state, RF induced ionization compensates for plasma loss to the chamber walls as well as other loss mechanisms due to incomplete limitations. The plasma current in the chamber 6 is generally parallel and opposite to the direction of the current in the antenna 20.

As a further variant, the antenna is surrounded by an insulating tube which can form a vacuum partition, instead of the bushing 27. In this case, the antenna and capacitor are kept at atmospheric pressure and insulated from the plasma. This configuration broadens the choice of plasma material (without considering plasma contamination) and minimizes capacitance between the antenna and the plasma. While a typical source 2 includes a cylindrical plasma compartment 6, other elongated generally cylindrical shapes are possible within the scope of the present invention. As used herein, the term generally cylindrical includes such other elongated shapes that configure the coaxial excitation antenna to uniformly excite the plasma for extraction of the elongated ribbon-shaped ion beam.

1A and 1B illustrate one implementation of a source 2 in which a longitudinally extending permanent magnet 40 is positioned within the source to provide multi-cusped plasma confinement fields in the chamber 6. The way is shown. 1C-5 illustrate another implementation of the source 2 that generates an azimuth confining field in the chamber 6 using a permanent magnet 46 extending in the circumferential direction. As will be described in more detail below, such a plasma confining magnetic field is generated near the inner wall of the chamber 6 to trap the plasma in a particular area within the chamber 6. The ions from the plasma are then extracted in the pre-extraction region 56 by one or more activatable extraction electrodes 26a-26e located near the outlet 18 (FIGS. 1B and 1C), generally ribbon- It provides a shaped ion beam, in which electrode 26 is activated using power source 28. The electrode 26 includes an elongated extraction slit 30 that extracts the beam, thereby providing a ribbon-shaped beam with a large aspect ratio. Note that any suitable extraction device may be used in accordance with the present invention, wherein the extraction electrode 26 and the slit 30 through it are not necessarily shown in their original size. In addition, the inductance L of the antenna 20 and the capacitance of the capacitor 24 can be selected to provide resonance conditions at any suitable RF frequency, and any conventional RF source 22 implements various aspects of the present invention. Can be used to

Referring also to Figures 2C-2F, capacitive coupling of antenna 20 and power source 22 can be accomplished in various ways in accordance with the present invention. One configuration is shown briefly in FIG. 2C (eg, similar to FIG. 1C) and schematically in FIG. 2D. This configuration is useful for allowing the center of the antenna 20 to operate in close proximity to RF ground (eg, virtual ground), which improves the uniformity of power coupled to the plasma. Thus, the antenna configuration facilitates uniform beam extraction by supporting a sufficient amount of ionized plasma to be used along the longitudinal length of the plasma chamber 6. In addition, there is no DC path from antenna 20 to ground in FIGS. 2C and 2D, which prevents undesirable depletion of plasma current at source 2. Another possible configuration is shown in Figures 2E and 2F, where a single capacitor 24 is provided at the first end 14, and the second end 16 of the antenna 20 is formed on the wall 10. It is grounded at the two ends 16 (for example by welding). In addition to the configurations illustrated and described herein, other configurations are possible within the scope of the present invention.

Referring again to FIGS. 1C and 2A, a typical ion source 2 provides an inner liner 32 that provides a cylindrical inner surface of the housing 4 and creates a thermal barrier between the conductive wall 10 and the plasma in the compartment 6. ). Excitation of the plasma in the chamber 6 heats the plasma. In the past, the inner wall of the plasma chamber remained quite cold, which allowed the longitudinally extending permanent magnets to operate properly. However, this temperature gradient between the wall and the plasma caused condensation. Then, when the ion sources are switched to receive the implanted species from each other, condensation of the material from the prior source gas remains as a contaminant. According to the present invention, the liner 32 raises the gas temperature inside the chamber 6 (eg, about 600 ° F.) to mitigate this condensation.

In this respect, the conductive chamber wall 10 is made of aluminum, while the liner 32 is preferably made of a material such as tungsten. Since the chamber 6 is operated in vacuo, very poor thermal connections are made between the liner 32 and the wall 10, resulting in almost no thermal conductivity between them. Thus, for example, when used with arsenic source material, arsenic will remain in vapor form and will not condense on liner 32. Other materials may be used for the liner 32. However, because the mass of tungsten is much larger than that of a typical implant material, tungsten is used in the illustrated ion source 2, which in turn is contaminated by subsequent mass spectroscopy, contaminating the beam provided onto the final implant target. I will not let you.

As shown in Figures 1A and 1B, ion source 2 may also include a permanent magnet 40 extending longitudinally spaced circumferentially from each other at 42 ° and about 45 °, which The permanent magnet has alternating N and S pole faces of the same height as the inner surface of the liner 32. The magnet 40a has an N pole facing the interior of the chamber 6 and the magnet 40b has an S pole facing the interior. When positioned accordingly, the longitudinally extending magnet 40 provides the multipoint magnetic field 44 shown in FIG. 1A. The magnetic field 44 is generally concentrated near the inner surface of the liner 32 to confine the ionized plasma away from the liner 52 to concentrate or radially ionize the ionized plasma towards the center of the plasma chamber 6. Limit it. As will be explained in more detail below, the ion source 2 also includes an electromagnet 5 pair to provide each adjustable magnetic field in the pre-extraction region 56 of the chamber 6 from the source 2. Control the density profile of the extracted beam.

Referring now to FIGS. 1C, 2A, and 2B, another aspect of the present invention is a permanent magnet 46 extending radially away from the axis 8 in the chamber 6 and extending longitudinally apart from one another. To provide an azimuth magnetic field confining field 48 near the inner surface of the liner 32, where the magnet 46a has an N pole facing the axis 8 and the magnet 46b has an axis 8. It has an S pole facing. Magnet 46 is configured as shown in Figures 2A and 2B to form opposite pairs of opposing magnets. Adjacent pairs operate to generate an azimuth magnetic field 48 near the liner 32 to trap the plasma in the plasma confinement chamber 6. Alternatively, a single magnet (N or S) row can be used, with a passive return yoke on the opposite side. The magnet 46 provides a relatively low magnetic field strength in the center of the chamber 6 (eg along the axis 8) and provides a higher magnetic field strength in the liner 32. In this way, a strong slope is set from the edge of the liner 32 to the axis 8. This gradient allows the plasma to move freely near the center of the cylindrical chamber 6, while directing the ionized plasma towards the center and limiting it away from the liner 32. The freedom of movement at the center of the chamber 6 is useful for improving the uniformity of the plasma along the longitudinal length of the source 2.

Note that the angular spacing of the magnets 40 extending longitudinally in FIGS. 1A and 1B (eg, about 42 ° and 45 °) is symmetric with respect to the source 2 shown. Small angles between the magnets 40 can be used over most of the perimeter except for the outlet 18. The asymmetry caused by the blocking of the cusp fields 44 at the time of extraction penetrates the large field towards the center of the source 2. Thus, the pitch of the limiting magnet 40 extending in the longitudinal direction is limited. However, the number of closeness of the magnet 46 extending in the circumferential direction of FIGS. 1C-5 is not limited. Thus, by providing any number of such magnets 46 in accordance with the present invention, any desired limiting magnetic field profile can be achieved within the interior of the source 2. Thus, the magnetic field slope can be designed to any desired value near the liner 32 by using the magnet 46. Thus, although shown as having such a magnet 46, any number of such magnets is contemplated within the scope of the present invention, whereby better limiting control can be achieved, especially near the outlet 18. In addition, although shown as extending circumferentially around the entire periphery of the liner 32, other configurations of such a magnet 46 (not shown) are considered to be within the scope of the present invention.

While the typical implementations illustrated and described herein include both a longitudinally extending limiting magnet 40 and a circumferentially extending magnet 46, the azimuth magnetic field 48 is limited by the magnet 40. It may be provided separately from or in combination with the field 44. In this regard, it will be appreciated that the ion source within the scope of the present invention may comprise any combination of magnets 40 and / or 46. In addition, although a typical ion source 2 couples a circumferentially extending magnet 46 in combination with a coaxial excitation antenna 20, other implementations of the invention have one or both of these features or their equivalents. It is considered to be in the range of.

Referring now to Figures 3A, 3B, and 5, another aspect of the present invention provides a control device 60 that selectively adjusts the density profile associated with the elongated longitudinal ion beam extracted from the plasma compartment 6. . Density profile adjustment features of the present invention can be used in connection with any ribbon beam source, but are not limited to those described and described herein. In addition, the profile adjustment feature can be used according to the invention, alone or in combination with the coaxial excitation and / or orientation limitation features illustrated and described above. The control device 60 includes a pre-extraction region 56 which extracts the ribbon beam from the ion source 2 and a plurality of magnet pairs near the excitation exit 18.

The magnet pair includes upper and lower electromagnets 50a and 50b, which have activatable windings that can induce current in a controlled manner to provide an adjustable magnetic field 52 between them. . The magnets 50a and 50b are arranged on both sides of the outlet 18 to provide an adjustable magnetic field 52 in the pre-extraction area 56 inside the chamber 6 near the outlet 18 to extract the ribbon beam. Adjust the density profile. The electromagnet 50 provides a magnetic pole of a first magnet (eg, N in the illustrated example) in which the first magnet 50a faces the second magnet 50b, and the second magnet 50b is a first magnet. It provides a magnetic pole of the second magnetic (S) facing the magnet 50a. In this way, the magnets 50a and 50b of each magnet pair are integrated to provide an adjustable magnetic field 52 in the pre-extraction area 56. While other positions are deemed to be within the scope of the present invention, these magnet pairs 50a and 50b are located on the housing 4 of the source 2, thereby selectively generating a variable or adjustable magnetic field near the extraction electrode 26. To the pre-extraction area.

In a typical source 2, eight such magnet pairs 50 are shown. However, any number of such magnet pairs 50 can be provided in accordance with the present invention. In addition, by using other types of magnets (eg permanent magnets), a number of adjustable magnetic fields can be achieved to control the profile of the ribbon beam. As shown in Figures 3A and 5, each of the magnetic fields 52 associated with each pair of magnets 50 is regulated through a control system 62 that provides a control signal to the DC power supply 64, so that an individual electromagnet 50 Excitation of the coil windings associated with The control system 62 is connected to a power source 64 and individually adjusts the current supplied to the magnet pair to generate a magnetic field generated by the magnet pair in the pre-extraction area 56 according to the desired density profile for the extracted ion beam. Adjust 52. Control of each magnetic field 52 selectively limits the amount of ionized plasma available in the pre-extraction region 56, where increasing the magnetic field 52 associated with a given magnet pair 50 causes Reduce the amount of plasma flowing out of the chamber.

Thus, in the illustrated implementation, the longitudinal length of the source 2 (eg the width of the ribbon beam thereby) is segmented into eight portions or slices respectively associated with the magnet pairs 50a and 50b. The ability to selectively limit the plasma flowing out of the outlet 18 for each slice allows control over the resulting density profile of the beam when extracted from the plasma chamber 6 in the pre-extraction region 56. Using known algorithms, including but not limited to feedback, feed-forward, prediction, or any other type, depending on the desired profile at the source 2 or at the desired profile downstream at the injection target (not shown) Thus control can be performed. This provides, for example, a utility for correcting or compensating for non-uniformity of the source 2 or next (eg downstream) device in the overall injection system. For example, the non-uniformity of the beam in the pre-extraction area 56 may be accommodated, but some or all of the magnet pairs 50a, 50b may pass between the source 2 and the target wafer or panel display (not shown). It can be used to compensate for non-uniformity in mass spectrometry or acceleration stages. In this regard, the control system 62 may further include an ion detector, such as a Faraday cup, located near the pre-extraction region 56 and / or in the workpiece (not shown) being injected.

Thus, an injection system using the source 2 and the density profile control device 60 is provided with an appropriate sensor and feedback device (not shown) to measure the beam profile and provide a corresponding measurement signal when provided on the target workpiece. To the control system 62. The control system 62 then makes appropriate adjustments to excite the electromagnet 50 (e.g., using the power source 64) to correct or compensate for any deviation from the desired profile in the workpiece. Alternatively, the power supply 64 can be adjusted manually and additionally integrated with a single power supply with each output for a separate pair of magnets. In addition, the magnets 50a and 50b of the individual magnet pairs are activated with the same current, such that a single (eg adjustable) power source is used for each magnet pair.

Referring now to FIGS. 4A and 4B, the operation of the profile control device 60 is additionally shown, in which two slices or longitudinal portions of the source 2 are shown in cross-section with different electromagnet adjustment levels. . 4A shows a magnet pair comprising magnets 50a 'and 50b' which are activated to a first level to provide a first level that limits extraction of ions from chamber 6 by extraction electrode 26. As shown in FIG. The magnetic field contour is shown by four regions 71, 72, 73 and 74 with different magnetic field intensities, where a relatively high magnetic field strength is provided to the region 71 near the line 32 and in succession to this region. Low magnetic field strengths are provided in regions 72, 73, and 74. As described above, the magnetic field strength in regions 72-74 is controlled by the electromagnets 50a 'and 50b' as well as the azimuth magnetic field generated by the columnar limiting magnet 46 in the slice shown in Figure 4A. It is the accumulation result of the magnetic field 52. Note that when the magnetic field is the weakest (eg, region 74), the density of the ionized plasma is greatest in chamber 6. Thus, the highest plasma density is in region 74, while the lowest density is in region 71 near liner 32.

The ionized plasma in the chamber 6 is most free to move around in the region 74 when these regions have the lowest magnetic field strength, while there is little or no ionized plasma in the outer region 71. . In FIG. 4A, the electromagnets 50a 'and 50b' are activated at relatively high levels, limiting the flow of ions into the slit 30 of the extraction electrode 26 through the pre-extraction region. Thus, the extracted ion beam slice 80 ′ draws most of the ions from region 73. However, according to the present invention, other slices along the longitudinal length of the ribbon beam 80 may be adjusted differently. Referring now to FIG. 4B, adjacent slices of the source 2 are shown in cross-section, where the electromagnets 50a "and 50b" are activated at lower levels, so that fewer restrictions on ion extraction are pre-extracted. Area 56 is provided. As can be seen in Figure 4B, a slice 80 "of the extracted beam draws ions from the lower magnetic field intensity region 74. The present invention provides a relative level of activity for a plurality of magnet pairs in the profile control device 60. It will be appreciated that any combination of and any number of such magnet pairs may be provided, achieving any desired beam density profile.

Referring to Figure 5, source 2 is shown in a simplified form, where certain details, such as the power supply and control system, are not shown for brevity. This source 2 provides an elongated ribbon shaped beam 80 having a length 82 and a width 84 having a large aspect ratio. The beam is segmented into eight parts or slices due to the eight magnet pairs 50a and 50b of the control device 60 so that the density profile of the beam 80 can be tailored for a particular use. In one implementation, the beam length 82 is about 400 mm, facilitating single-scan injection of a 300 mm wafer target or flat panel display. However, any preferred beam length 82 is possible within the scope of the present invention. In addition, any desired width 84 can be achieved by appropriately size the slit 30 of the outlet and extraction electrode 26 in the source housing 4. In addition, note that the extraction electrode 26 may be implemented in any suitable manner in addition to the five such electrodes 26 and that the illustrated electrode 26 does not necessarily need to be shown in its original size.

While the present invention has been shown and described above in connection with certain aspects and implementations, those skilled in the art will recognize that equivalent changes and modifications may be made based on the present specification and the accompanying drawings. In particular, with respect to the various functions performed by the above-described components (assemblies, devices, circuits, systems, etc.), such components are described, although they are not structurally identical to the described structure for performing the functions of the typical implementation of the present invention. The term (including "means") used to refer to any part that performs a particular function of the described part (ie, functionally equivalent) unless otherwise indicated. In this regard, it will be appreciated that the invention also includes computer-readable media having computer-executable instructions for performing the steps of the various methods of the invention. In addition, while certain features of the invention have been described with reference to only one implementation of the various implementations, such features may be combined with one or more other features of other implementations that are desirable and useful for a given or particular application. have. In addition, the terms "comprise", "comprising", "have", "have", "having", "jinin", and other forms of expression of these terms are used in the description or claims, which term "comprising" Should be considered similar.

Claims (23)

An ion source for providing an ion beam to an ion implantation system, A housing defining an elongated plasma compartment disposed along a longitudinal axis that generates plasma by ionizing a source material, the housing having first and second elongated longitudinally extending outlets for extracting ion beams from the plasma, respectively; A housing comprising a generally cylindrical conductive chamber wall extending longitudinally between the ends; An antenna comprising first and second terminals, the second terminal being electrically connected to the chamber wall at a second end and a portion of the antenna between the first and second terminals along an axis coupling energy to the plasma chamber An antenna extending longitudinally within the plasma compartment; And, An RF source for activating the antenna with a radio frequency signal in the frequency range of 1 to 100 MHz, the RF source being electrically connected to a first output of the chamber wall and a first output electrically connected to a first terminal of the antenna A second output, wherein the RF source, the antenna and the chamber wall form a substantially coaxial circuit to provide alternating current to an exposed portion of the antenna to induce an ionizing field in the plasma compartment. Containing ion source. The method of claim 1, And a first capacitor connected between the first output of the RF source and the first terminal of the antenna. The method of claim 2, And a second capacitor connected between the second end of the chamber and the second terminal of the antenna. The method of claim 1, And a capacitor connected between the second end of the chamber wall and the second terminal of the antenna. The method of claim 1, And an insulator tube surrounding the antenna. The method of claim 3, wherein And further comprising a plurality of magnets radially spaced from an axis in the plasma compartment and longitudinally spaced from one another to form one or more adjacent pairs, each adjacent pair being opposing magnets to confine the plasma within the plasma compartment. An ion source, which generates a longitudinal magnetic field near a wall. The method of claim 6, And wherein each of said plurality of magnets extends circumferentially around a portion inside a chamber wall between opposite sides of said outlet. The method of claim 6, And the plurality of magnets are permanent magnets. The method of claim 1, And further comprising a plurality of magnets radially spaced apart from the axis in the plasma compartment and longitudinally spaced from one another to form one or more adjacent pairs, each adjacent pair being opposing magnetic to confine the plasma within the plasma compartment. And generate an azimuth magnetic field near the chamber wall. The method of claim 1, And a cylindrical liner disposed in the plasma compartment between the chamber wall and the axis where the plasma is generated, the liner providing a thermal barrier between the plasma and the chamber wall to prevent condensation of source material within the plasma compartment. An ion source, characterized in that. The method of claim 10, And the liner comprises tungsten. The method of claim 1, And further comprising a plurality of extraction electrodes located outside the chamber wall near the outlet, wherein the extraction electrodes can be activated to provide an electric field to extract the ion beam elongated from the plasma compartment through the outlet. Ion source. An ion source for providing an ion beam to an ion implantation system, A housing defining a generally cylindrical plasma compartment disposed along a longitudinal axis that generates a plasma by ionizing the source material, the housing having a first longitudinally extending outlet that extracts the ion beam from the plasma, respectively; A housing comprising a generally cylindrical conductive chamber wall extending longitudinally between the two ends; An antenna extending partially in the plasma compartment for discharging energy into the plasma chamber; An RF source for providing an alternating RF to the antenna to form an electrical circuit with the antenna for inducing an ionizing electric field in the plasma compartment; and A plurality of magnets radially spaced from an axis in the plasma compartment and longitudinally spaced from one another to form one or more adjacent pairs, each adjacent pair consisting of opposing magnets, near the chamber wall for confining the plasma within the plasma compartment; An ion source comprising a plurality of magnets to generate a bearing magnetic field in the. The method of claim 13, Each of said plurality of magnets extending circumferentially around a portion of the interior of the chamber wall between opposite sides of said outlet. The method of claim 13, And the plurality of magnets are permanent magnets. The method of claim 13, And the antenna is located along an axis coaxially with the chamber wall. An ion source for providing an ion beam to an ion implantation system, A housing comprising a cylindrical chamber wall and first and second circular end walls attached to first and second ends of the chamber wall, the housing generating a plasma containing ions by ionizing a source material. The cylindrical chamber wall including an elongated outlet capable of extracting an ion beam from the plasma; An antenna comprising first and second terminals, wherein the second terminal is electrically connected to a second end wall and a portion of the antenna is coaxially positioned relative to the chamber wall between the first and second terminals to transfer energy to the plasma. An antenna, emitting into the chamber; And, An RF source for activating the antenna with a radio frequency signal, the RF source comprising a first output electrically connected to a first terminal of the antenna and a second output electrically connected to the end wall; And the antenna, the chamber wall and the first and second end walls form an electrical circuit to provide alternating current to exposed portions of the antenna to induce an ionizing field in the plasma compartment. sauce. The method of claim 17, And a capacitor connected between the first output of the RF source and the first terminal of the antenna. The method of claim 17, And a capacitor connected between the second end wall and the second terminal of the antenna. The method of claim 19, The antenna and the capacitor constitute a resonant circuit at a frequency of the RF source. The method of claim 17, And further comprising a plurality of magnets radially spaced from the antenna in the plasma compartment and longitudinally spaced from one another to form one or more adjacent pairs, each adjacent pair consisting of opposing magnets, the plasma within the plasma compartment And generate a longitudinal magnetic field near the chamber wall to trap. The method of claim 21, Each of said plurality of magnets extending circumferentially around a portion of the interior of said chamber wall between opposite sides of said outlet. The method of claim 17, And a cylindrical liner disposed in the plasma compartment between the chamber wall and the antenna from which the plasma is generated, the liner providing a thermal barrier between the plasma and the chamber wall to condense the source material within the plasma compartment. Preventing an ion source.