Systems and methods for beam angle adjustment in ion implanters

An ion implantation system employs a mass analyzer for both mass analysis and angle correction. An ion source generates an ion beam along a beam path. A mass analyzer is located downstream of the ion source that performs mass analysis and angle correction on the ion beam. A resolving aperture within an aperture assembly is located downstream of the mass analyzer component and along the beam path. The resolving aperture has a size and shape according to a selected mass resolution and a beam envelope of the ion beam. An angle measurement system is located downstream of the resolving aperture and obtains an angle of incidence value of the ion beam. A control system derives a magnetic field adjustment for the mass analyzer according to the angle of incidence value of the ion beam from the angle measurement system.

FIELD OF THE INVENTION

The present invention relates generally to ion implantation systems, and more specifically to systems and methods for performing beam angle adjustments of ion beams in ion implantation systems.

BACKGROUND OF THE INVENTION

In the manufacture of semiconductor devices, ion implantation is used to dope semiconductors with impurities or dopants. Ion beam implanters are used to treat silicon wafers with an ion beam, in order to produce n or p type extrinsic material doping or to form passivation layers during fabrication of an integrated circuit. When used for doping semiconductors, the ion beam implanter injects a selected extrinsic ion species to produce the desired semiconducting material. Implanting ions generated from source materials such as antimony, arsenic or phosphorus results in “n type” extrinsic material wafers, whereas if “p type” extrinsic material wafers are desired, ions generated with source materials such as boron, or indium may be implanted.

Typical ion beam implanters include an ion source for generating positively charged ions from ionizable source materials. The generated ions are formed into a beam and directed along a predetermined beam path to an implantation station. The ion beam implanter may include beam forming and shaping structures extending between the ion source and the implantation station. The beam forming and shaping structures maintain the ion beam and bound an elongated interior cavity or passageway through which the beam passes en route to the implantation station. When operating an implanter, this passageway can be evacuated to reduce the probability of ions being deflected from the predetermined beam path as a result of collisions with gas molecules.

Trajectories of charged particles of given kinetic energy in a magnetic field will differ for different masses (or charge-to-mass ratios) of these particles. Therefore, the part of an extracted ion beam which reaches a desired area of a semiconductor wafer or other target after passing through a constant magnetic field can be made pure since ions of undesirable molecular weight will be deflected to positions away from the beam and implantation of other than desired materials can be avoided. The process of selectively separating ions of desired and undesired charge-to-mass ratios is known as mass analysis. Mass analyzers typically employ a mass analysis magnet creating a dipole magnetic field to deflect various ions in an ion beam via magnetic deflection in an arcuate passageway which will effectively separate ions of different charge-to-mass ratios.

For some ion implantation systems, the physical size of the beam is smaller than a target workpiece, so the beam is scanned in one or more directions in order to adequately cover a surface of the target workpiece. Generally, an electrostatic or magnetic based scanner scans the ion beam in a fast direction and a mechanical device moves the target workpiece in a slow scan direction in order to provide sufficient cover.

Thereafter the ion beam is directed toward a target end station, which holds a target workpiece. Ions within the ion beam implant into the target workpiece, which is ion implantation. One important characteristic of ion implantation is that there exists a uniform angular distribution of ion flux across the surface of the target workpiece, such as a semiconductor wafer. The angular content of the ion beam defines implant properties through crystal channeling effects or shadowing effects under vertical structures, such as photoresist masks or CMOS transistor gates. A non-uniform angular distribution or angular content of the ion beam can lead to uncontrolled and/or undesired implant properties.

Beam diagnostic equipment can be employed to measure the angle content of ion beams. The measurement data can then be employed to adjust angle characteristics of the ion beam. However, conventional approaches can increase complexity of the ion implantation system and undesirably increase the length of path along which the ion beam travels.

SUMMARY OF THE INVENTION

The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention, and is neither intended to identify key or critical elements of the invention nor to delineate the scope of the invention. Rather, the purpose of the summary is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later.

Aspects of the present invention facilitate ion implantation by performing angle adjustments without additional components being added to ion implantation systems. The aspects employ a mass analyzer to perform selected angle adjustments during ion implantation instead of employing separate and/or additional components.

In accordance with one aspect of the invention, an ion implantation system employs a mass analyzer for both mass analysis and angle correction. An ion source generates an ion beam along a beam path. A mass analyzer is located downstream of the ion source that performs mass analysis and angle correction on the ion beam. A resolving aperture within an aperture assembly is located downstream of the mass analyzer component and along the beam path. The resolving aperture has a size and shape according to a selected mass resolution and a beam envelope of the ion beam. An angle measurement system is located downstream of the resolving aperture and obtains an angle of incidence value of the ion beam. A control system derives a magnetic field adjustment for the mass analyzer according to the angle of incidence value of the ion beam from the angle measurement system. Other systems and methods are disclosed.

The following description and annexed drawings set forth in detail certain illustrative aspects and implementations of the invention. These are indicative of but a few of the various ways in which the principles of the invention may be employed.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described with reference to the drawings wherein like reference numerals are used to refer to like elements throughout, and wherein the illustrated structures are not necessarily drawn to scale.

Aspects of the present invention facilitate ion implantation employing a mass analyzer to perform angle correction/adjustment in addition to mass analysis. As a result, angle corrections of the implant angle can be performed without additional components along the beam line.

FIG. 1illustrates an example ion implantation system110in accordance with an aspect of the present invention. The system110is presented for illustrative purposes and it is appreciated that aspects of the invention are not limited to the described ion implantation system and that other suitable ion implantation systems of varied configurations can also be employed.

The system110has a terminal112, a beamline assembly114, and an end station116. The terminal112includes an ion source120powered by a high voltage power supply122that produces and directs an ion beam124to the beamline assembly114. The ion source120generates charged ions that are extracted and formed into the ion beam124, which is directed along a beam path in the beamline assembly114to the end station116.

To generate the ions, a gas of a dopant material (not shown) to be ionized is located within a generation chamber121of the ion source120. The dopant gas can, for example, be fed into the chamber121from a gas source (not shown). In addition to power supply122, it will be appreciated that any number of suitable mechanisms (none of which are shown) can be used to excite free electrons within the ion generation chamber121, such as RF or microwave excitation sources, electron beam injection sources, electromagnetic sources and/or a cathode which creates an arc discharge within the chamber, for example. The excited electrons collide with the dopant gas molecules and ions are generated thereby. Typically, positive ions are generated although the disclosure herein is applicable to systems wherein negative ions are generated as well.

The ions are controllably extracted through a slit118in the chamber121by an ion extraction assembly123, in this example. The ion extraction assembly123comprises a plurality of extraction and/or suppression electrodes125. The extraction assembly123can include, for example, a separate extraction power supply (not shown) to bias the extraction and/or suppression electrodes125to accelerate the ions from the generation chamber121. It can be appreciated that since the ion beam124comprises like charged particles, the beam may have a tendency to blow up or expand radially outwardly as the like charged particles repel one another. It can also be appreciated that beam blow up can be exacerbated in low energy, high current (high perveance) beams where many like charged particles (e.g., high current) are moving in the same direction relatively slowly (e.g., low energy) such that there is an abundance of repulsive forces among the particles, but little particle momentum to keep the particles moving in the direction of the beam path. Accordingly, the extraction assembly123is generally configured so that the beam is extracted at a high energy so that the beam does not blow up (e.g., so that the particles have sufficient momentum to overcome repulsive forces that can lead to beam blow up). Moreover, the beam124, in this example, is generally transferred at a relatively high energy throughout the system and is reduced just before the workpiece130to promote beam containment.

The beamline assembly114has a beamguide132, a mass analyzer126, a scanning system135, and a parallelizer139. The mass analyzer126performs mass analysis and angle correction/adjustment on the ion beam124. The mass analyzer126, in this example, is formed at about a ninety degree angle and comprises one or more magnets (not shown) that serve to establish a (dipole) magnetic field therein. As the beam124enters the mass analyzer126, it is correspondingly bent by the magnetic field such that ions of an inappropriate charge-to-mass ratio are rejected. More particularly, ions having too great or too small a charge-to-mass ratio are deflected into side walls127of the mass analyzer126. In this manner, the mass analyzer126merely allows those ions in the beam124which have the desired charge-to-mass ratio to pass there-through and exit through a resolving aperture134of an aperture assembly133.

The mass analyzer126can perform angle corrections on the ion beam124by controlling or adjusting an amplitude of the magnetic dipole field. This adjustment of the magnetic field causes selected ions having the desired/selected charge-to-mass ratio to travel along a different or altered path. As a result, the resolving aperture134can be adjusted according to the altered path. In one example, the aperture assembly133is movable about an x direction so as to accommodate altered paths through the aperture134. In another example, the aperture134is shaped so as to accommodate a selected range of altered paths. The mass analyzer126and the resolving aperture134allow variations in the magnetic field and resulting altered path while maintaining suitable mass resolution for the system110. More detailed examples of suitable mass analyzer and resolving aperture systems are provided below.

It will be appreciated that ion beam collisions with other particles in the system110can degrade beam integrity. Accordingly, one or more pumps (not shown) may be included to evacuate, at least, the beamguide132and mass analyzer126.

The scanning system135in the illustrated example includes a magnetic scanning element136and a focusing and/or steering element138. Respective power supplies149,150are operatively coupled to the scanning element136and the focusing and steering element138, and more particularly to respective electromagnet pieces136a,136band electrodes138a,138blocated therein. The focusing and steering element138receives the mass analyzed ion beam124having a relatively narrow profile (e.g., a “pencil” beam in the illustrated system110). A voltage applied by the power supply150to the plates138aand138boperates to focus and steer the beam to the scan vertex151of the scanning element136. A voltage waveform applied by the power supply149(which theoretically could be the same supply as150) to the electromagnets136aand136bthen scans the beam124back and forth, in this example. It will be appreciated that the scan vertex151can be defined as the point in the optical path from which each beamlet or scanned part of the beam appears to originate after having been scanned by the scanning element136.

The scanned beam124is then passed through the parallelizer/corrector139, which comprises two dipole magnets139a,139bin the illustrated example. The dipoles are substantially trapezoidal and are oriented to mirror one another to cause the beam124to bend into a substantially s shape. Stated another way, the dipoles have equal angles and radii and opposite directions of curvature.

The parallelizer139causes the scanned beam124to alter its path such that the beam124travels parallel to a beam axis regardless of the scan angle. As a result, the implantation angle is relatively uniform across the workpiece130.

One or more deceleration stages157are located downstream of the parallelization component139in this example. Up to this point in the system110, the beam124is generally transported at a relatively high energy level to mitigate the propensity for beam blow up, which can be particularly high where beam density is elevated such as at scan vertex151, for example. The deceleration stage157comprises one or more electrodes157a,157boperable to decelerate the beam124. The electrodes157are typically apertures thru which the beam travels, may be drawn as straight lines inFIG. 1.

Nevertheless, it will be appreciated that while two electrodes125aand125b,136aand136b,138aand138band157aand157bare respectively illustrated in the exemplary ion extraction assembly123, scanning element136, focusing and steering element138and deceleration stage157, that these elements123,136,138and157may comprise any suitable number of electrodes arranged and biased to accelerate and/or decelerate ions, as well as to focus, bend, deflect, converge, diverge, scan, parallelize and/or decontaminate the ion beam124such as provided in U.S. Pat. No. 6,777,696 to Rathmell et al. the entirety of which is hereby incorporated herein by reference. Additionally, the focusing and steering element138may comprise electrostatic deflection plates (e.g., one or more pairs thereof), as well as an Einzel lens, quadrupoles and/or other focusing elements to focus the ion beam.

The end station116then receives the ion beam124which is directed toward a workpiece130. It is appreciated that different types of end stations116may be employed in the implanter110. For example, a “batch” type end station can simultaneously support multiple workpieces130on a rotating support structure, wherein the workpieces130are rotated through the path of the ion beam until all the workpieces130are completely implanted. A “serial” type end station, on the other hand, supports a single workpiece130along the beam path for implantation, wherein multiple workpieces130are implanted one at a time in serial fashion, with each workpiece130being completely implanted before implantation of the next workpiece130begins. In hybrid systems the workpiece130may be mechanically translated in a first (Y or slow scan) direction while the beam is scanned in a second (X or fast scan) direction to impart the beam124over the entire workpiece130.

The end station116in the illustrated example is a “serial” type end station that supports the single workpiece130along the beam path for implantation. A dosimetry system152is included in the end station116near the workpiece location for calibration measurements prior to implantation operations. During calibration, the beam124passes through dosimetry system152. The dosimetry system152includes one or more profilers156that may continuously traverse a profiler path158, thereby measuring the profile of the scanned beams.

The profiler156, in this example, may comprise a current density sensor, such as a Faraday cup, for example, that measures the current density of the scanned beam, where current density is a function of the angle of implantation (e.g., the relative orientation between the beam and the mechanical surface of the workpiece and/or the relative orientation between the beam and the crystalline lattice structure of the workpiece). The current density sensor moves in a generally orthogonal fashion relative to the scanned beam and thus typically traverses the width of the ribbon beam. The dosimetry system, in one example, measures both beam density distribution and angular distribution.

A control system154is present that can control, communicate with and/or adjust the ion source120, the mass analyzer127, the aperture assembly133, the magnetic scanner136, the parallelizer139, and the dosimetry system152. The control system154may comprise a computer, microprocessor, etc., and may be operable to take measurement values of beam characteristics and adjust parameters accordingly. The control system154can be coupled to the terminal112from which the beam of ions is generated, as well as the mass analyzer126of the beamline assembly114, the scanning element136(e.g., via power supply149), the focusing and steering element138(e.g., via power supply150), the parallelizer139and the deceleration stage157. Accordingly, any of these elements can be adjusted by the control system154to facilitate desired ion. For example, the energy level of the beam can be adapted to adjust junction depths by adjusting the bias applied to electrodes in the ion extraction assembly123and the deceleration stage157, for example.

The strength and orientation of magnetic field(s) generated in the mass analyzer126can be adjusted, such as by regulating the amount of electrical current running through field windings therein to alter the charge to mass ratio of the beam, for example. The angle of implantation can be controlled by adjusting the strength or amplitude of the magnetic field(s) generated in the mass analyzer126in coordination with the aperture assembly133. The control system154can adjust the magnetic field(s) of the mass analyzer126and position of the resolving aperture134according to measurement data from, in this example, the profiler156. The control system154can verify the adjustments via additional measurement data and perform additional adjustments via the mass analyzer126and the resolving aperture134if necessary.

FIG. 2is a diagram illustrating an ion implantation system200employing a mass analyzer for mass analysis and angle correction in accordance with an aspect of the present invention. The system200is provided as an example and it is appreciated that other variations and configurations can be employed for alternate aspects of the invention.

The system200includes an ion source202that generates an ion beam204, a mass analyzer206, a resolving assembly210, an actuator214, a control system216, and an angle measurement system218. The ion source202can be an arc based source, RF based source, electron gun based source, and the like and generates the ion beam204along a beam path having a selected dopant or species of ions for implanting. The ion source202provides the ion beam204with an initial energy and current.

The mass analyzer206is located downstream of the ion source202and performs mass analysis and angle correction on the ion beam204. The mass analyzer206generates a magnetic field that causes particles/ions having a selected charge-to-mass ratio to travel along a desired path. The magnetic field can also be adjusted to accommodate for angle corrections to alter the desired path to yield the angle corrections or adjustments.

Although not shown, a quadrupole lens or other focusing mechanism can be positioned downstream of the mass analyzer206to compensate or mitigate the impact of beam blow up upon the ion beam204.

The resolving assembly210is positioned downstream of the mass analyzer206. The resolving assembly210includes a resolving aperture212through which the ion beam204passes through. The aperture212permits the selected dopants/species to pass through while preventing other particle from passing through. Additionally, the resolving assembly210can be moved along an axis transverse to the path of the ion beam204. This permits the resolving aperture212to be moved in response to changes in the desired path of the ion beam through the mass analyzer206. The actuator214mechanically moves the resolving assembly210such that the resolving aperture212coincides with a path of the ion beam corresponding to angle adjustments performed by the mass analyzer206. In other aspects of the invention, the actuator214can also select other resolving assemblies to accommodate other resolutions and/or other sized beams.

Generally, the resolving aperture212is sized to accommodate the beam envelope of the ion beam204. However, in alternate aspects, the resolving aperture212can be sized to accommodate the beam envelopes across a range of possible beam paths.

The control system216is responsible for controlling and initiating angle adjustments during ion implantation as well as controlling mass analysis. The control system216is coupled to the mass analyzer206and the actuator214and controls both components. Another component, the angle measurement system218, measures angle of incidence values of the ion beam and determines needed adjustment angles. The angle measurement system218can employ Faraday cups or some other suitable measurement device to obtain the measured angle of incidence values. Additionally, the angle measurement system218can derive or measure an average angle of incidence value for the ion beam204. The angle measurement system218then provides adjustment angles or correction values to the control system216based on the measured or derived angle of incidence values and a desired or selected angle of incidence value.

Initially, the control system216sets the magnetic field of the mass analyzer206at a nominal or base angle value, such as zero, and a selected charge-to-mass ratio. Additionally, the control system216sets the initial position of the resoling aperture212to coincide with a nominal path associated with the base angle value. During implantation, a non-zero adjustment angle can be received from the angle measurement system218. Based on the adjustment angle, the control system216adjusts the magnetic field of the mass analyzer such that the selected species having the selected charge-to-mass ratio travels along an altered patch corresponding to the adjustment angle. Additionally, the control system216also adjusts the positioning of the resolving aperture212via the actuator214according to the altered path. Thereafter, the angle measurement system218can provide additional adjustment angles for further adjustment of the implant angle.

FIGS. 3A to 3Care views of a portion of an ion implantation provided to illustrate altered beam paths and angle adjustments in accordance with an aspect of the present invention. The views are provided for illustrative purposes and as examples in order to facilitate understanding of the present invention.

FIG. 3Ais a view301of a portion of an ion implantation system in accordance with an aspect of the present invention wherein an ion beam travels along a base or nominal path320.

A mass analyzer306is located downstream of an ion source (not shown) and performs mass analysis and angle correction on an ion beam. The mass analyzer306generates a magnetic field that causes particles/ions having a selected charge-to-mass ratio to travel along a desired path. The magnetic field can also be adjusted to accommodate for angle corrections to alter the desired path to yield the angle corrections or adjustments. In this figure, the ion beam travels along a base or nominal path320associated with the selected charge-to-mass ratio and a nominal or zero angle adjustment. A focusing mechanism (not shown) can be employed downstream of the mass analyzer306to compensate or mitigate the impact of beam blow up on the ion beam304.

The resolving assembly310is positioned downstream of the lens308. The resolving assembly310includes a resolving aperture312through which the ion beam304passes through. The aperture312permits the selected dopants/species to pass through while preventing other particle from passing through. Additionally, the resolving assembly310can be moved along an axis transverse to the path of the ion beam.

For the nominal path320, the resolving assembly310is placed at a nominal position so that the ion beam can pass through the resolving aperture312while blocking other particles from passing through.

FIG. 3Bis a view302of a portion of the ion implantation system in accordance with an aspect of the present invention wherein an ion beam travels along an altered path322.

The mass analyzer306generates a varied field from that shown and described inFIG. 3Ain order to alter the path of the ion beam. In one example, the mass analyzer306increases the magnitude of the magnetic field generated. As a result, the ion beam travels along the altered path322instead of the nominal path320. The altered path322corresponds to a first angle adjustment or offset. The altered path322passes through the lens308and toward the resolving assembly310.

In this view302, the resolving assembly310is moved in a positive direction such that the resolving aperture312permits passage of the ion beam there through along the altered path322.

Similarly,FIG. 3Cis another view303of a portion of the ion implantation system in accordance with an aspect of the present invention wherein an ion beam travels along an altered path324.

Again, the mass analyzer306generates a varied field from that shown and describedFIG. 3AandFIG. 3Bin order to alter the path of the ion beam. In one example, the mass analyzer306decreases the magnitude of the magnetic field generated. As a result, the ion beam travels along the altered path324instead of the nominal path320. The altered path324corresponds to a second angle adjustment or offset. The altered path324passes through the lens308and toward the resolving assembly310. The resolving assembly310is positioned in a negative direction, in this example, such that the resolving aperture312permits passage of the ion beam there through along the altered path324while blocking non selected species and unwanted particles.

As stated above, the resolving aperture assembly comprises a resolving aperture through which an ion beam travels. The shape and size of the resolving aperture is generally dependent upon the mass resolution and a size and shape of a desired ion beam, also referred to as the beam envelope. A larger resolving aperture yields lower beam resolution in that more unwanted particles and ions can pass through such an aperture. Similarly, a smaller resolving aperture yields greater beam resolution in that less unwanted particles and ions can pass through such an aperture. However, the higher resolution can also prevent more of the selected or desired species from passing through the resolving aperture, thereby causing undesired beam current loss. Thus, resolving apertures are typically sized according to a desired mass resolution and beam envelope.

Additionally, the resolving aperture of the present invention can also be designed to accommodate varied beam paths corresponding to a range of possible angle adjustments. The aboveFIGS. 3A to 3Cdepict some examples of some possible varied paths. The resolving aperture can be appropriately sized to accommodate such varied beam paths.

FIG. 4is a side view of a resolving aperture assembly400in accordance with an aspect of the present invention. The view is provided as an example and is not intended to limit the invention. The assembly400, in this example, can accommodate removable plates that allow changing the resolving aperture employed. Additionally, the assembly400, in this example, can operate with varied shaped beams and/or varied mass resolutions. Thus different sized beams can be employed within such systems and different plates can be employed to accommodate the varied beam envelopes. Additionally, different plates can be employed to accommodate for varied resolutions and ranges of angle adjustments.

InFIG. 4, the assembly400comprises an arm402that holds a resolving plate404. The resolving plate404includes a plurality of resolving apertures406,408,410that selected sizes and shapes, which can correspond to selected beam envelopes, selected resolutions, and/or ranges of angle adjustments.

The first aperture406has a selected size and shape that correspond to a beam envelope, selected resolution, and/or range of angle adjustments. In this example, the x direction of the first aperture is relatively small. Thus, for example, the first aperture406could accommodate a relatively thin ribbon or scanned ion beam.

The second aperture408has a second selected size and a second shape that correspond to a second beam envelope, a second selected resolution, and/or a second range of angle adjustments. As an example, the second aperture408could accommodate a medium thickness ribbon or scanned ion beam.

The third aperture410has a third selected size and a third shape that correspond to a third beam envelope, a third selected resolution, and/or a third range of angle adjustments. As an example, the third aperture could accommodate a relatively thick ribbon or scanned ion beam.

It is noted that the y direction for the apertures406,408,410is depicted as similar for illustrative purposes, however aspects of the invention can also include variations in the y direction. Additionally, aspects of the invention can include more or less apertures on a single plate.

During operation, the assembly400is positioned such that one of the apertures is positioned along a path of an ion beam to remove contaminants or unselected material from the ion beam. The selected aperture corresponds to a selected beam envelope and/or selected mass resolution. It is appreciated that materials or portions of the beam may pass through one of the non selected apertures, but those portions are not generally propagated to a target workpiece.

FIG. 5is a flow diagram of a method500of adjusting the angle of implantation in accordance with an aspect of the present invention. The method500can facilitate uniform angular distribution of ion flux across the surface of a workpiece during ion implantation by correcting or adjusting the angle of implant. It is appreciated that the above figures and descriptions can also be referenced for the method500.

The method500begins at block502wherein parameters of an ion source are selected according to a desired specie, energy, current, and the like. The ion source can be an arc based or non arc based ion source, such as an RF or electron gun base ion source. The specie or species can be selected by selecting one or more source materials for the ion source. The current can be selected by modulating power values and/or electrodes.

Parameters of a mass analyzer are selected at block504according to a charge-to-mass ratio corresponding to the selected species and a base or nominal angle. The parameters, such as current applied to coil windings, are set to yield a magnetic field that causes the selected specie to travel along a nominal or base path corresponding to the nominal angle and pass through the mass analyzer.

An initial positioning of a resolving aperture is also selected at block506. The initial positioning corresponds to the base path and permits passage there through according to a selected mass resolution.

An ion beam is generated as ion implantation is initiated at block508. An average angle of incidence for the ion beam is obtained at block510. The average angle of incidence can be measured in one example. In another example, multiple beam angle measurements are obtained and an average value is derived there from. It is noted that other beam measurements and angle values can also be employed. For example, calculations of the average angle through an optical train of an ion implanter can be employed taking into account the effects of acceleration and/or deceleration whenever applicable.

An angle adjustment is derived from a selected angle of implant and the average angle obtained at block512. For example, if the selected angle is equal to the average angle, the angle adjustment is zero. A magnetic field correction and aperture position correction are determined and applied at block514according to the angle adjustment. The magnetic field correction adjusts the path of the ion beam to correct the angle of the ion beam. The aperture position correction moves the resolving aperture so that the selected species can pass there through.

It is noted that the angle adjustment and/or magnetic field correction can be limited so as to prevent over adjustment. Also, errors in the angle adjustment can be reduced by employing iterative correction algorithms. In such instances, suitable angle correction can take a number of passes.

A corrected average angle of implant is obtained at block516after applying the field and position corrections. The corrected average angle of implant is obtained as in block510. If the second average angle is not sufficiently close to the selected angle of implant or within an acceptable tolerance, as determined at block518, the method returns to block510and continues iteratively until the average angle of the ion beam is within the acceptable tolerance of the selected angle.

It is appreciated that the method500is described in the above order in order to facilitate an understanding of the present invention. It is noted that the method500can be performed with other suitable orderings in accordance with the present invention. Additionally, some blocks can be omitted and other additional functions performed in other aspects of the invention.