Verification of X-ray diffraction angles in ion implantation equipment

Abstract

An ion implanter that facilitates channeling an ion beam into a crystalline structure of a workpiece is disclosed. The ion implanter includes an ion source that generates an ion beam, a platen that supports a workpiece having a crystalline structure, an X-ray source that generates an X-ray beam, where at least a portion of the X-ray beam impinges on the workpiece to generate diffracted X-rays, an X-ray detector positioned to receive the diffracted X-rays, and a controller in communication with the X-ray source, the platen, and the X-ray detector. The controller includes instructions that enable the ion implanter to perform a rocking curve test after the workpiece is placed on the platen and calculate an orientation of the platen for the ion implantation process based on results of the rocking curve test to facilitate channeling the ion beam into the crystalline structure of the workpiece.

Description

[Technical Field]

[0001] This application claims priority to U.S. Patent Application No. 18 / 091,041, filed December 29, 2022, the disclosure of which is incorporated by reference in its entirety.

[0002] SUMMARY OF THE INVENTION Embodiments of the present disclosure relate to an ion implanter that uses X-ray diffraction (XRD) to perform angle adjustment before implantation. [Background technology]

[0003] Silicon has long been the primary material used in semiconductor workpieces, which are used to create transistors, memory elements, amplifiers, and other devices.

[0004] Recently, an increasing number of semiconductor devices are being fabricated using alternative workpieces with various crystal structures. Some of these alternative workpieces include silicon carbide (SiC), gallium nitride (GaN), and gallium arsenide (GaAs).

[0005] In some scenarios, it is desirable to perform the ion implantation process in such a way that the ions are directed into channels in the crystal structure, which requires precise alignment of the ion beam with the crystal lattice. For silicon workpieces, the orientation of the workpiece is well known; however, other workpieces may differ. For example, silicon carbide has a much more complex crystal structure than silicon. In fact, silicon carbide can form a variety of different polytypes with different crystal structures.

[0006] Additionally, the specifications attached to SiC workpieces can be difficult to understand, which can complicate workpiece orientation identification. Due to crystal growth conditions, the c-axis of 4H SiC crystals typically deviates 4° + / - 1° from the normal to the workpiece surface, and the direction of this tilt is not always apparent. The magnitude and direction of the tilt can also vary from workpiece to workpiece and from point to point on the workpiece. This can result in varying process results as the ion beam moves in and out of channeling conditions.

[0007] Therefore, it would be beneficial to have an ion implanter and method for implanting ions into a workpiece that can determine and monitor the crystallographic orientation of the workpiece prior to the ion implantation process to facilitate channeling of the ion beam into the workpiece. Summary of the Invention

[0008] According to one embodiment, an ion implanter is disclosed. The ion implanter includes an ion source that generates an ion beam, a platen that supports a workpiece having a crystalline structure, an X-ray source that generates an X-ray beam, where at least a portion of the X-ray beam impinges on the workpiece to generate diffracted X-rays, an X-ray detector positioned to receive the diffracted X-rays, and a controller in communication with the X-ray source, the platen, and the X-ray detector. The controller includes a memory device containing instructions that, when executed by the controller, enable the ion implanter to perform a rocking curve test after the workpiece is placed on the platen and calculate an orientation of the platen for the ion implantation process based on the results of the rocking curve test to facilitate channeling of the ion beam into the crystalline structure of the workpiece. In certain embodiments, the memory device further includes instructions that, when executed by the controller, enable the ion implanter to perform the ion implantation process while the workpiece is placed on the platen in the calculated orientation. In some embodiments, the rocking curve test is performed while the platen is placed in a loading position, with the clamping surface of the platen being horizontal in the loading position. In some embodiments, the rocking curve test is performed at multiple locations on the workpiece. In a specific embodiment, the workpiece is rotated about an axis that passes through the center of the platen and is perpendicular to the clamping surface of the platen so that the X-ray beam impinges on the workpiece at a new location. In a specific embodiment, the ion beam has a width in the X-direction and a height in the Y-direction, and the platen is translated in the Y-direction so that the X-ray beam impinges on the workpiece at a new location.In some embodiments, the platen is adapted to tilt about an X-axis and a Y-axis, the X-axis passing through the center of the platen and parallel to the width of the ion beam, and the Y-axis passing through the center of the platen and parallel to the height of the ion beam; a rocking curve test is performed while the platen is tilted about the X-axis to determine an X-tilt angle with a maximum intensity; a rocking curve test is performed while the platen is tilted about the Y-axis to determine a Y-tilt angle with a maximum intensity; and the controller calculates an orientation to be used for the ion implantation process based on the X-tilt angle and Y-tilt angle determined during the rocking curve test. In certain embodiments, the X-ray detector is a two-dimensional sensor array; estimated X-tilt angle and estimated Y-tilt angle are determined without tilting the workpiece; and the rocking curve test is performed by tilting about the estimated X-tilt angle and estimated Y-tilt angle. In some embodiments, the ion implanter includes a collimator positioned to receive an X-ray beam from the X-ray source and collimate the X-ray beam to deliver a portion of the X-ray beam to the workpiece. In some embodiments, the platen, X-ray source, and X-ray detector are disposed within a process chamber configured to receive the ion beam. In certain embodiments, the X-ray source and X-ray detector are disposed at the top of the process chamber. In some embodiments, the platen is disposed within the process chamber configured to receive the ion beam, and at least one of the X-ray source and X-ray detector is disposed outside the process chamber, and a window is disposed within the process chamber to allow X-rays to pass between the process chamber and the environment outside the process chamber. In some embodiments, the X-ray source and X-ray detector are movable to adjust the angle at which the X-ray beam strikes the workpiece.

[0009] According to another embodiment, an ion implanter is disclosed. an auxiliary chamber disposed proximate to the process chamber, the auxiliary chamber including an X-ray source for generating an X-ray beam, wherein at least a portion of the X-ray beam impinges on the workpiece to generate diffracted X-rays, and an X-ray detector disposed to receive the diffracted X-rays; a workpiece handling robot for transferring the workpiece from the auxiliary chamber to the process chamber; and a controller in communication with the X-ray source, the auxiliary platen, the X-ray detector, the platen, and the workpiece handling robot, the controller comprising a memory device containing instructions, when executed by the controller, that enable the ion implanter to: perform a rocking curve test after the workpiece is disposed on the auxiliary platen; calculate an orientation of the workpiece for the ion implantation process based on results of the rocking curve test to facilitate channeling of the ion beam into the crystalline structure of the workpiece; and transfer the workpiece to the platen in the process chamber using the workpiece handling robot. In some embodiments, the ion implanter includes a second X-ray source and a second X-ray detector, and the memory device further includes instructions that, when executed by the controller, enable the ion implanter to perform a second rocking curve test in the process chamber using the second X-ray source and the second X-ray detector after the workpiece has been transferred to the process chamber. In certain embodiments, the second X-ray source and the second X-ray detector are disposed in the process chamber. In certain embodiments, the platen includes a heater, and the memory device further includes instructions that, when executed by the controller, enable the ion implanter to heat the platen after the workpiece has been transferred to the process chamber and to perform a second rocking curve test in the process chamber using the second X-ray source and the second X-ray detector after the workpiece has reached a desired temperature.In certain embodiments, the second X-ray source and the second X-ray detector are disposed within the process chamber. In some embodiments, the X-ray detector comprises a two-dimensional sensor array, and estimated X and Y tilt angles are determined during the rocking curve test, and a second rocking curve test is performed within the process chamber by tilting the platen about the estimated X and Y tilt angles. In some embodiments, the memory device further includes instructions that, when executed by the controller, enable the ion implanter to perform an ion implantation process while the workpiece is positioned on the platen in the calculated orientation.

[0010] For a better understanding of the present disclosure, reference is made to the accompanying drawings, which are incorporated herein by reference. [Brief explanation of the drawings]

[0011] [Figure 1] 1 illustrates an ion implanter according to one embodiment. [Figure 2A] 1 illustrates one configuration of an X-ray source and X-ray detector within a process chamber. [Figure 2B] 1 illustrates an alternative configuration of an X-ray source and an X-ray detector within a process chamber. [Figure 2C] 1 illustrates a third configuration of an X-ray source and an X-ray detector within a process chamber. [Figure 2D] 1 shows the configuration of an X-ray source and an X-ray detector outside the process chamber. [Figure 3] 1 shows the rotation and tilt of the workpiece on the platen. [Figure 4] 1 illustrates an X-ray source and collimator according to one embodiment. [Figure 5] 2 illustrates one sequence that may be used to process a workpiece using the ion implanter of FIG. 1. [Figure 6] 2 illustrates one embodiment of a rocking curve test that may be performed using the ion implanter of FIG. 1. [Figure 7] 1 illustrates an ion implanter according to another embodiment. [Figure 8] 8 illustrates one sequence that may be used to process a workpiece using the ion implanter of FIG. 7. DETAILED DESCRIPTION OF THE INVENTION

[0012] As mentioned above, it can be beneficial in some cases to perform a channeling implant. The term "channeling implant" refers to an implant performed such that ions are implanted along channels in the crystalline structure of a workpiece, such as a SiC wafer. However, it can be difficult to properly orient the workpiece so that the incident ion beam is aligned with the channels. The accuracy of this alignment depends on several parameters, but in particular the energy of the ions, and effective channeling is achieved using a maximum angular deviation that decreases with increasing energy. The critical angle for channeling is given by: TIFF2026506435000002.tif15170where ψ is the critical angle and U(r crit ) is the potential energy of the channel walls determined by the crystal lattice, and E is the kinetic energy of the ions. The angular tolerance of the channel can be a few degrees at a few keV, but can be as small as 0.05° for high-energy implants of a few MeV.

[0013] FIG. 1 shows a first embodiment of an ion implanter 1 in which angle adjustment and verification can be performed using XRD before performing an implant.

[0014] In some embodiments, the ion implanter 1 may be a high-energy or medium-current beamline ion implanter capable of producing implant energies of 1 MeV or greater. In other embodiments, the implant energies produced by the ion implanter 1 may be less than 1 MeV. The ion implanter 1 includes an ion source 200 that is used to produce an extracted ion beam 201. In one embodiment, the ion source 200 may be a Bernas ion source or an indirectly heated cathode (IHC) ion source. Of course, other types of ion sources may also be used. A source gas is supplied to the ion source 200, which is then activated to produce ions. Extraction optics (not shown) are then used to extract these ions from the ion source 200 and form the extracted ion beam 201.

[0015] The extracted ion beam 201 may be directed to a mass analyzer 205 that passes only certain ion species. Ions exiting the mass analyzer 205 are directed to an accelerator component 210. The accelerator component 210 serves to accelerate ions entering the component from low to high energy. The accelerator component 210 can have a variety of configurations.

[0016] In one embodiment, the accelerator component 210 may be an acceleration column with multiple biased electrodes that help accelerate the ion beam. As the ions pass through the column, the electrodes can be biased more negatively, accelerating the positive ions.

[0017] In another embodiment, the accelerator component 210 may be a tandem accelerator, in which negative ions are admitted to a first accelerator column and accelerated to a first energy, after which electrons are removed to create positive ions, which are then accelerated to a final higher energy by a second accelerator column.

[0018] In another embodiment, the accelerator component 210 may be a linear accelerator (LINAC). In this embodiment, a separate buncher may receive the ion beam from the ion source 200 and generate a focused pulsed ion beam. A series of resonators or accelerators may be activated by respective RF signals to accelerate the incoming pulsed beam to a desired high energy level.

[0019] In all of these embodiments, after exiting the accelerator component 210, the spot-shaped ion beam 211 may enter a scanner 215. The scanner 215 widens the spot-shaped ion beam 211 into multiple diverging ion beamlets. In other words, the scanner 215 creates diverging ion trajectory paths. The scanner 215 may be electrostatic or magnetic. The ion beam widens with the use of the scanner 215. The direction in which the scanner 215 moves the beam is sometimes referred to as the X-direction. It should be noted that the ion beam exiting the scanner 215 is much wider than it is tall.

[0020] The angle corrector 220 is designed to deflect ions in the scanned ion beam to generate an ion beam 230 having a parallel ion trajectory and to focus the scanned ion beam. Specifically, the angle corrector 220 is used to change diverging ion trajectory paths into substantially parallel paths for the ion beam 230. In some embodiments, the angle corrector 220 may comprise magnetic pole pieces spaced apart to define a gap and a magnet coil coupled to a power source. The scanned ion beam passes through the gap between the magnetic pole pieces and is deflected in response to the magnetic field within the gap. In other embodiments, the angle corrector 220 may be an electrostatic lens, sometimes referred to as a collimating lens.

[0021] Of course, the ion implanter may include other components such as quadrupole lenses, additional electrodes for accelerating or decelerating the beam, and other elements.

[0022] An ion beam 230 enters the process chamber 100. In Figure 1, a top view of the ion implanter 1 is shown with the height of the ion beam 230 perpendicular to the plane of the page. For ease of explanation, a Cartesian coordinate system can be defined, with the Z direction defined by the path of the ion beam 230. The ion beam 230 has a height in the Y direction and a width in the X direction, as shown in Figure 1.

[0023] As shown in FIG. 1, an ion beam 230 enters a process chamber 100 in which a workpiece to be implanted is located. The workpiece 10 is positioned on a clamping surface 169 of a platen 160. The platen 160 may be capable of movement in multiple directions and rotation. In FIG. 1, the platen 160 is in the operating or implant position, with the clamping surface 169 of the platen 160 approximately perpendicular to the ion beam 230. This is the orientation of the platen 160 during ion implantation. In this embodiment, an X-ray source 110 and an X-ray detector 130 are positioned on either side of the platen 160 in the X-direction, or width direction.

[0024] FIG. 2A shows a perspective view of process chamber 100, with an X-ray source 110 and an X-ray detector 130 disposed within process chamber 100, positioned on either side of platen 160 in the X direction.

[0025] However, other embodiments are possible. Figure 2B shows a perspective view of process chamber 100 according to another embodiment. In this embodiment, X-ray source 110 and X-ray detector 130 are disposed within process chamber 100 and are positioned on either side of platen 160 in the Y or height direction.

[0026] The workpiece 10 can be moved in one or more dimensions by the platen 160. For example, the platen 160 can move in the Y direction (corresponding to the height of the ion beam 230) so that the entire workpiece 10 is exposed to the ion beam 230 after the platen 160 moves through the ion beam 230. The platen 160 can also tilt and rotate about multiple axes.

[0027] FIG. 3 illustrates a platen 160 and its various rotational orientations. FIG. 3 shows a perspective view of the rotatable platen 160, also referred to as a rotat. The platen 160 can have three axes. There can be a twist axis 161 that is perpendicular to the clamping surface 169 of the platen 160 and passes through the center of the platen 160. Rotation around this twist axis 161 is referred to as the twist angle 162. There is an X-axis 163 that passes through the center of the platen, is parallel to the clamping surface 169 of the platen 160, and is perpendicular to the twist axis 161. The X-axis 163 is parallel to the width dimension of the ion beam 230. The tilt around the X-axis 163 is referred to as the X-tilt angle 164. There is also a Y-axis 165 that also passes through the center of the platen 160, is parallel to the clamping surface 169 of the platen 160, and is perpendicular to the twist axis 161 and the X-axis 163. The tilt around the Y-axis 165 is referred to as the Y-tilt angle 166.

[0028] Also located within the process chamber 100 are an X-ray source 110 and an X-ray detector 130. Also shown in FIG. 4, a collimator 115 may be used to receive the X-ray beam from the X-ray source 110 and collimate the X-rays to form an emitted X-ray beam 120. In some embodiments, the X-ray source 110 may be a filtered Cu target X-ray source, as known in the art, or other suitable X-ray source. The collimator 115 may be used to generate a closely parallel beam that can be directed toward a specific region of the workpiece 10. In some embodiments, the collimator 115 comprises one or more slits. In other embodiments, the collimator 115 comprises one or more crystals, such as germanium or silicon crystals. In one embodiment shown in FIG. 4, the X-ray beam from the X-ray source 110 enters a germanium crystal 118 from one face and reflects off two internal surfaces along the (220) direction before exiting the crystal as emitted X-ray beam 120. This is sometimes called a Ge(220)-2 reflective collimator or monochromator. In another embodiment, two crystals are arranged so that when the X-rays exit the first germanium crystal, they enter the second germanium crystal, are reflected again by two internal surfaces along the (220) direction, and then exit as the emitted X-ray beam 120. This is sometimes called a Ge(220)-4 reflective collimator or monochromator. In another embodiment, the crystals may be arranged so that the X-ray beam from the X-ray source 110 enters one face and is reflected by two internal surfaces along the (440) direction. The X-rays then exit the first germanium crystal and enter the second germanium crystal, where they are again reflected by two internal surfaces along the (440) direction, and then exit as the emitted X-ray beam 120. This is sometimes called a Ge(440)-4 reflective collimator or monochromator. Of course, other collimators may be used. The crystals allow only the X-ray beam with the desired trajectory to pass through the crystal and reach the workpiece 10. In each of these embodiments, the x-ray source 110 generates an x-ray beam, at least a portion of which ultimately impinges on the workpiece 10 as an emitted x-ray beam 120 .

[0029] The X-ray detector 130 can be used to measure the diffracted X-rays 125 from the workpiece and plot the detected amount of diffracted X-rays 125, also called intensity, as a function of the X and Y tilt angles, as shown in graph 135 of FIG. 1. X-ray detectors 130 are well known and will not be described in further detail here. In some embodiments, the X-ray source 110, workpiece 10, and X-ray detector 130 are positioned to achieve a Bragg scattering angle given by the Bragg equation: λ=2dsinθ where λ is the wavelength of the X-rays (0.1541 nm for Cu Kα X-rays) and d is the spacing between crystal planes. For 4H SiC with a (0001) orientation, the selection rule gives c / 4 = 0.251 nm for the spacing of the (0004) planes, and θ = arcsin(λ / 2d) = 17.8°.

[0030] For X-ray beams of different wavelengths or workpieces of different materials, the X-ray source 110 and the X-ray detector 130 can be positioned at different angles. Note that both the X-ray source 110 and the X-ray detector 130 are positioned at the same angle relative to the workpiece 10.

[0031] In another embodiment, the X-ray source and X-ray detector are mounted on an articulating arm to allow for different diffraction angles for different crystal lattice spacings.

[0032] In another embodiment, the X-ray detector 130 may be a one-dimensional or two-dimensional sensor array that can be used to enable detection of a range of X-ray diffraction angles. In these embodiments, the X-ray detector 130 comprises multiple sensors, each adapted to detect X-rays. This one-dimensional or two-dimensional X-ray detector may also be referred to as an extended X-ray detector. In this way, the extended X-ray detector can provide information about multiple angles simultaneously, rather than receiving information about only a single angle.

[0033] A controller 280 is used to control the ion implanter 1. The controller 280 includes a processing unit 281 and an associated memory device 282. The memory device 282 includes instructions 283 that, when executed by the processing unit 281, enable the system to perform the functions described herein. The controller 280 can control the twist angle 162, X tilt angle 164, and Y tilt angle 166 of the platen 160. The controller 280 is also in communication with components of the ion implanter 1, including the X-ray source 110 and the X-ray detector 130. The memory device 282 can be any non-transitory storage medium, including non-volatile memory such as flash ROM, electrically erasable ROM, or other suitable device. In other embodiments, the memory device 282 can be volatile memory such as RAM or DRAM. In certain embodiments, the controller 280 can be a general-purpose computer, an embedded processor, or a specially designed microcontroller. The actual implementation of the controller 280 is not limited by this disclosure.

[0034] Having described one configuration of the ion implanter 1, the operation of the system will now be described.

[0035] One mode of operation is illustrated in FIG. 5. As shown in box 500 of FIG. 5, the workpiece 10 is placed on the clamping surface 169 of the platen 160 within the process chamber 100. The platen 160 is placed in an operating position. The controller 280 can then perform a rocking curve test using the X-ray source 110, the X-ray detector 130, and the platen 160, as shown in box 510. As is well known, rocking curve tests are used in conjunction with XRD to identify the orientation of the workpiece's crystalline structure. Specifically, in a rocking curve test, the angle of the workpiece is varied as an X-ray beam impinges on the workpiece. The X-rays are diffracted and received by the X-ray detector. The angle of the workpiece at which the intensity of the diffracted X-rays is greatest is the direction of maximum channeling. The rocking curve test can be performed in one direction or two directions, for example, by tilting the workpiece about the X-axis 163 and / or by tilting the workpiece about the Y-axis 165.

[0036] The controller 280 then stores the X and Y tilt angles that resulted in the peak intensity, as shown in box 520. Based on this information, the controller 280 can determine the crystallographic orientation of the workpiece 10, as shown in box 530, and therefore the proper orientation of the workpiece 10 during subsequent implants. For example, SiC has several different polytypes, such as 2H, 4H, 6H, 15R, and 3C. Each polytype can utilize a different set of optimal tilt angles. By performing a rocking curve test, the controller 280 can identify the polytype and also the exact orientation of the workpiece. Once the X and Y tilt angles are calculated, these calculated angles can be used during the ion implantation process, as shown in box 540.

[0037] 2A, where the ion beam 230 is precisely in the Z direction and the X-ray source 110 and X-ray detector 130 are angled symmetrically relative to the Z direction, optimal channeling occurs at the workpiece angle at which the X-ray diffraction intensity is maximized. Several circumstances may modify this simple algorithm. For example, if precision measurements of the ion beam 230 show that it is slightly angled relative to the Z axis, or if the X-ray source 110 or X-ray detector 130 are displaced from their ideal positions due to mechanical tolerances, the implant angle must be shifted from the angle of maximum diffraction intensity to account for these shifts.

[0038] By determining the X- and Y-tilt angles that maximize the intensity of the X-ray emission, the controller 280 can identify the appropriate orientation of the platen 160 to use for the implant process to facilitate channeling. Specifically, in some embodiments, it may be desirable to perform the implant when the workpiece is oriented on the platen 160 for a channeled implant. This allows the implant ions to be implanted deeper (for a given energy) with less damage to the workpiece. In some embodiments, the X- and Y-tilt angles are selected to maximize channeling.

[0039] FIG. 6 illustrates one sequence that can be used to perform a rocking curve test. First, the X-ray source 110 and the X-ray detector 130 are enabled, as shown in box 600. Next, the controller 280 varies the X-tilt angle 164 of the platen 160 while the emitted X-ray beam 120 is directed at the workpiece 10, as shown in box 610. The range of X-tilt angles used during the rocking curve test can vary. For example, in some embodiments, the workpiece can be tilted ±5°. In other embodiments, the angle range can be smaller, such as ±1° or ±2°. In still other embodiments, the angle range can be greater than 5°. As shown in box 620, the X-ray detector 130 is used to record the intensity of the diffracted X-rays 125, and the controller 280 stores these recorded intensities as a function of the X-tilt angle. The result of this process can be a graph 135, as shown in FIG. 1, or a table of values. Next, the controller 280 varies the Y-tilt angle 166 of the platen 160 while the emitted X-ray beam 120 is directed at the workpiece 10, as shown in box 630. In some embodiments, the X-tilt angle is set to the X-tilt angle that exhibits the greatest intensity. Again, the range of Y-tilt angles used during the rocking curve test can be varied, as previously described. As shown in box 640, the X-ray detector 130 is used to record the intensity of the diffracted X-rays 125, and the controller 280 stores these recorded intensities as a function of Y-tilt angle. The result of this process may be a second graph 135, as shown in FIG. 1, or one or more tables, each containing tilt angles and corresponding intensity values. Once this is complete, the controller 280 can disable the X-ray source 110 and the X-ray detector 130. Note that in some embodiments, the rocking curve test is performed for only one tilt angle. For example, in some embodiments, boxes 610-620 or boxes 630-640 may be omitted.

[0040] In yet other embodiments, if an extended X-ray detector is used, the variation in the X and Y tilt angles can be smaller. For example, if a two-dimensional X-ray detector is used, the controller 280 can determine the X and Y tilt angles that produced the highest intensity without rotating the workpiece. In another embodiment in which an extended X-ray detector is used, the initial output from the extended X-ray detector is used to set estimated X and Y tilt angles, and then a rocking curve test is performed to tilt the platen around these estimated angles. For example, an initial scan may indicate that the highest intensity is detected at tilt angles X1 and Y1. Then, a rocking curve test can be performed using, for example, an X tilt angle of X1±1° and a Y tilt angle of Y1±1°.

[0041] In some embodiments, it may be beneficial to perform rocking curve tests at multiple locations on the workpiece. This can be accomplished in several ways. In one embodiment, the platen 160 can be moved in the Y direction so that the emitted X-ray beam 120 strikes different locations on the workpiece. In another embodiment, the platen 160 can be rotated about the torsion axis 161 so that the emitted X-ray beam 120 strikes different locations on the workpiece. In another embodiment, the platen 160 can be moved in the Y direction and rotated about the torsion axis 161. In each of these embodiments, the sequence shown in FIG. 6 can be repeated as the workpiece 10 is moved or rotated. In some embodiments, the results of multiple rocking curve tests can be averaged to determine appropriate X and Y tilt angles for the implantation process. In other embodiments, the X and Y tilt angles can vary as a function of the position of the platen 160 in the Y direction. For example, if the X and / or Y tilt angles vary along the Y direction, the tilt of the platen 160 can be changed as the ion beam 230 scans the workpiece 10. If the X-tilt angle and / or Y-tilt angle varies along the X-axis, the angle corrector 220 can be adjusted to account for the change in Y-tilt to produce a convergent or divergent ion beam, and the rotation of the scan plate can be adjusted to introduce a twist into the trajectory to account for the change in X-tilt.

[0042] In some embodiments, the platen 160 may also heat the workpiece 10 to a high temperature, for example, above 350° C. In some embodiments, the high temperature may be 500° C. or higher. In these embodiments, the rocking curve test may not begin until the workpiece 10 reaches the desired temperature.

[0043] In other embodiments, the rocking curve test may be performed before the workpiece is heated and then again after it is heated. Thus, changes in the rocking curve test results may be the result of thermal warping or distortion of the workpiece, which can be compensated for by additional clamping force (electrostatic or mechanical). Alternatively, the orientation of the platen 160 can be adjusted to achieve an optimal compromise for the workpiece shape at the implant temperature.

[0044] While FIGS. 1 and 2A-2B show rocking curve tests being performed while the platen 160 is in the operating position, other embodiments are possible. FIG. 2C shows a perspective view of the process chamber 100. In this embodiment, the platen 160 is positioned in the loading position, with the clamping surface of the platen 160 horizontal. In this embodiment, the X-ray source 110 and X-ray detector 130 are located inside the process chamber 100 near the top of the process chamber 100. The area near the top of the process chamber 100 may have fewer contaminants than other areas. In this embodiment, the X-tilt angle is set to 90° to place the platen 160 in the loading position. The X-tilt angle is then varied around this tilt angle. In other words, in the embodiment of FIGS. 1 and 2A-2B, the X-tilt angle is varied around 0°, whereas in the embodiment of FIG. 2C, the X-tilt angle is varied around 90°.

[0045] In yet another embodiment, at least one of the X-ray source 110 or the X-ray detector 130 can be located outside the process chamber 100, as shown in FIG. 2D . For example, a window can be located in the wall of the process chamber 100 to allow X-rays to pass through the window. In one embodiment, both the X-ray source 110 and the X-ray detector 130 are located outside the process chamber 100. In this embodiment, X-rays from the X-ray source 110 pass through a first window into the process chamber 100, where they impinge on the workpiece 10. The diffracted X-rays pass through a second window to the X-ray detector 130. In some embodiments, the window can be a thin polymer film, a diamond-like carbon window, or a beryllium window. The X-ray source 110 and / or the X-ray detector 130 can be located as shown in FIG. 2D or above the top surface of the process chamber 100.

[0046] In certain embodiments, the rocking curve test may be performed in a chamber different from the process chamber, one such embodiment being shown in Figure 7. Although not shown, the ion implanter 1 may include an ion source 200, a mass analyzer 205, accelerator components 210, a scanner 215, and an angle corrector 220.

[0047] In this embodiment, the x-ray source 110 and the x-ray detector 130 are located within an auxiliary chamber 300. An auxiliary platen 310 is also located within the auxiliary chamber 300. This auxiliary platen 310 may be similar to the platen 160 described above in that it may rotate about one or more axes.

[0048] In this manner, rocking curve testing can be performed within the auxiliary chamber 300, potentially improving throughput since the process chamber 100 is not used for rocking curve testing. Thus, in this embodiment, the rocking curve testing is performed within the auxiliary chamber 300, and the workpiece handling robot 320 is used to move the workpiece to the process chamber 100. The rocking curve testing can be performed with the clamping surface of the auxiliary platen 310 vertical, as shown in FIG. 7. In other embodiments, the rocking curve testing can be performed with the clamping surface of the auxiliary platen 310 horizontal, similar to the embodiment shown in FIG. 2C. A sequence illustrating the operations associated with this embodiment is shown in FIG. 8.

[0049] As shown in box 800, a workpiece is placed on the clamping surface of the auxiliary platen 310 in the auxiliary chamber 300. The workpiece is identified. Next, in box 810, the controller 280 performs a rocking curve test, as described in FIG. 6 . The controller 280 stores the X and Y tilt angles at which the detected intensity peaked, as shown in box 820. These tilt angles can then be used to calculate an orientation to be used during a subsequent ion implantation process, as shown in box 830. The controller 280 then stores the workpiece ID and the orientation associated with the workpiece, as shown in box 840. The controller 280 then moves the workpiece to the process chamber 100 using the workpiece handling robot 320 while maintaining the workpiece orientation, as shown in box 850. Once the workpiece is in the process chamber 100, the controller 280 identifies the workpiece and uses the calculated orientation (i.e., the X and Y tilt angles) associated with the workpiece for the ion implantation process, as shown in box 860. This approach minimizes the time that the workpieces reside within the process chamber 100, increasing throughput.

[0050] In some embodiments, the controller may store the X and Y tilt angles from box 830 and not calculate the orientation to be used for the implant process until some later time.

[0051] In yet another embodiment, the X-ray source 110 and the X-ray detector 130 may be duplicated, with the X-ray source 110 located in the auxiliary chamber 300 and the process chamber 100. Similarly, the X-ray detector 130 may be located in the auxiliary chamber 300 and the process chamber 100. In this embodiment, a rocking curve test may be performed in the auxiliary chamber 300. The workpiece may be heated after being moved to the process chamber 100. The temperature change may affect the orientation during the ion implantation process. Therefore, after heating, a second rocking curve test may be repeated. However, because a preliminary rocking curve test has already been performed in the auxiliary chamber 300, the range of angles used in the second rocking curve test may be narrowed, allowing the test to be completed more quickly.

[0052] In one embodiment, an extended X-ray detector can be placed in auxiliary chamber 300 to determine estimated X and Y tilt angles without tilting the workpiece. These estimated X and Y tilt angles are used as the center of a rocking curve test performed in process chamber 100.

[0053] While the above disclosure refers to a SiC workpiece, it is understood that the system is not limited to silicon carbide. In one embodiment, if the shape of the workpiece is known, the X-ray source 110 and X-ray detector 130 can be moved to the appropriate angles to satisfy the Bragg equation. Movement of these components can be performed manually or controlled by controller 280.

[0054] In another embodiment, the system can be used with workpieces of various shapes. In this embodiment, the collimator 115 shown in FIG. 4 may not be used, allowing for a much wider range of angles for the emitted X-ray beam 120. In this embodiment, the X-ray source 110 can produce a wide spectrum of energies or wavelengths such that the Bragg equation is satisfied for a wide range of crystal lattice spacings and scattering angles. This can be achieved by using a tungsten target and electron energies high enough to produce bremsstrahlung radiation rather than characteristic X-ray energies.

[0055] In this way, the Bragg equation is satisfied over a wider range of angles, allowing one configuration of X-ray source 110 and X-ray detector 130 to be used to accommodate a variety of crystal types.

[0056] In another embodiment, the X-ray source 110 can utilize a wide range of angles to determine the type of crystalline structure possessed by the workpiece. Once the crystalline structure is determined, the X-ray source 110 and the X-ray detector 130 can be moved to an angle appropriate for that crystalline structure. For example, the X-ray source 110 and the X-ray detector 130 may be movable so that they can be moved to set the appropriate angle. In this case, the X-ray source 110 may also incorporate a collimator 115 that narrows the range of angles available for the emitted X-ray beam 120. In this manner, the controller 280 performs a coarse rocking curve test to determine the crystalline structure, and then a fine rocking curve test to identify the channeling direction.

[0057] The embodiments described above in this application can have many advantages. The use of an XRD in the process chamber allows for precise control of the angle of incidence of the ion beam 230, which maximizes the degree of channeling of the workpiece. Channeling allows for deeper implants at a given energy. In some tests, performing a channeled implant can result in a peak ion concentration 0.5 μm deeper than a non-channeled implant. In other tests, performing a channeled implant can result in a more box-shaped ion concentration. Additionally, channeling can reduce the amount of damage caused by the implant. In certain embodiments, the amount of damage is reduced sufficiently that the workpiece is not heated prior to implantation, reducing the time spent in the process chamber. Additionally, the use of an XRD can reduce the likelihood of workpiece misorientation, potentially improving yield.

[0058] The scope of the present disclosure is not limited by the specific embodiments described herein. Indeed, various other embodiments and modifications of the present disclosure, in addition to those described herein, will be apparent to those skilled in the art from the foregoing description and the accompanying drawings. Accordingly, such other embodiments and modifications are intended to be included within the scope of the present disclosure. Moreover, while the present disclosure has been described herein in the context of particular implementations in particular environments for particular purposes, those skilled in the art will recognize that its utility is not limited in this respect, and that the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Accordingly, the claims set forth below should be construed in light of the full scope and spirit of the present disclosure as described herein.

Claims

1. 1. An ion implantation apparatus comprising: an ion source for generating an ion beam; a platen for supporting a workpiece having a crystalline structure; an X-ray source for generating an X-ray beam, at least a portion of the X-ray beam impinging on the workpiece to generate diffracted X-rays; an X-ray detector positioned to receive the diffracted X-rays; a controller in communication with the x-ray source, the platen, and the x-ray detector; the controller comprising a memory device containing instructions that, when executed by the controller, cause the ion implanter to: performing a rocking curve test after the workpiece is placed on the platen; calculating an orientation of the platen for an ion implantation process based on results of the rocking curve test to facilitate channeling of the ion beam into the crystalline structure of the workpiece; and This ion implanter makes it possible.

2. 10. The ion implanter of claim 1, wherein the memory device further comprises instructions that, when executed by the controller, enable the ion implanter to perform an ion implantation process while the workpiece is positioned on the platen in the pre-calculated orientation.

3. 2. The ion implanter of claim 1, wherein the rocking curve test is performed while the platen is disposed in a loading position, and a clamping surface of the platen is horizontal in the loading position.

4. 10. The ion implanter of claim 1, wherein the rocking curve test is performed at multiple locations on the workpiece.

5. 5. The ion implanter of claim 4, wherein the workpiece is rotated about an axis passing through a center of the platen and perpendicular to a clamping surface of the platen so that the x-ray beam impinges on the workpiece at a new location.

6. 5. The ion implanter of claim 4, wherein the ion beam has a width in an X-direction and a height in a Y-direction, and the platen is translated in the Y-direction so that the X-ray beam impinges on the workpiece at a new location.

7. 2. The ion implanter of claim 1, wherein the platen is adapted to tilt about an X-axis and a Y-axis, the X-axis passing through a center of the platen and parallel to a width of the ion beam, and the Y-axis passing through the center of the platen and parallel to a height of the ion beam; the rocking curve test is performed while the platen is tilted about the X-axis to determine an X-tilt angle having a maximum intensity of the diffracted X-rays, and the rocking curve test is performed while the platen is tilted about the Y-axis to determine a Y-tilt angle having a maximum intensity of the diffracted X-rays; and the controller calculates an orientation to be used for the ion implantation process based on the X-tilt angle and the Y-tilt angle determined during the rocking curve test.

8. 8. The ion implanter of claim 7, wherein the X-ray detector is a two-dimensional sensor array such that estimated X and Y tilt angles are determined without tilting the workpiece, and the rocking curve test is performed by tilting about the estimated X and Y tilt angles.

9. 10. The ion implanter of claim 1, further comprising a collimator positioned to receive the X-ray beam from the X-ray source and collimate the X-ray beam to deliver the portion of the X-ray beam to the workpiece.

10. 10. The ion implanter of claim 1, wherein the platen, the X-ray source, and the X-ray detector are disposed within a process chamber configured to receive the ion beam.

11. 11. The ion implanter of claim 10, wherein the X-ray source and the X-ray detector are located above the process chamber.

12. 2. The ion implanter of claim 1, wherein the platen is disposed within a process chamber configured to receive the ion beam, and wherein at least one of the X-ray source and the X-ray detector is disposed outside the process chamber, and wherein a window is disposed within the process chamber to allow X-rays to pass between the process chamber and an environment outside the process chamber.

13. 2. The ion implanter of claim 1, wherein said X-ray source and said X-ray detector are movable to adjust the angle at which said X-ray beam strikes said workpiece.

14. 1. An ion implantation apparatus comprising: an ion source for generating an ion beam; a process chamber, the ion beam entering the process chamber and a platen disposed within the process chamber; an auxiliary chamber separate from the process chamber, an auxiliary platen adapted to support a workpiece having a crystalline structure; an X-ray source for generating an X-ray beam, at least a portion of the X-ray beam impinging on the workpiece to generate diffracted X-rays; an X-ray detector positioned to receive the diffracted X-rays; an auxiliary chamber including a controller in communication with the x-ray source, the auxiliary platen, the x-ray detector, and the platen; the controller comprising a memory device containing instructions that, when executed by the controller, cause the ion implanter to: performing a rocking curve test after the workpiece is placed on the auxiliary platen; calculating an orientation of the workpiece for an ion implantation process based on results of the rocking curve test to facilitate channeling of the ion beam into the crystalline structure of the workpiece; orienting the platen within the process chamber using the pre-calculated orientation after the workpiece is placed on the platen; This ion implanter makes it possible.

15. the ion implanter further comprising a second X-ray source and a second X-ray detector; The memory device, when executed by the controller, causes the ion implanter to: performing a second rocking curve test in the process chamber using the second X-ray source and the second X-ray detector after the workpiece is transferred to the process chamber; 15. The ion implanter of claim 14, further comprising instructions to enable:

16. 16. The ion implanter of claim 15, wherein the second X-ray source and the second X-ray detector are located within the process chamber.

17. the platen includes a heater; The memory device, when executed by the controller, causes the ion implanter to: heating the platen after the workpiece is transferred to the process chamber; performing the second rocking curve test in the process chamber using the second X-ray source and the second X-ray detector after the workpiece reaches a desired temperature; 16. The ion implanter of claim 15, further comprising instructions to enable:

18. 18. The ion implanter of claim 17, wherein the second X-ray source and the second X-ray detector are located within the process chamber.

19. 15. The ion implanter of claim 14, wherein the X-ray detector comprises a two-dimensional sensor array such that estimated X and Y tilt angles are determined during the rocking curve test, and a second rocking curve test is performed in the process chamber by tilting the platen about the estimated X and Y tilt angles.

20. 15. The ion implanter of claim 14, wherein the memory device further comprises instructions that, when executed by the controller, enable the ion implanter to perform an ion implantation process while the workpiece is positioned on the platen in the pre-calculated orientation.

21. 15. The ion implanter of claim 14, wherein the rocking curve test is performed at multiple locations on the workpiece.

22. 22. The ion implanter of claim 21, wherein the workpiece is rotated about an axis passing through a center of the auxiliary platen and perpendicular to a clamping surface of the auxiliary platen so that the x-ray beam impinges on the workpiece at a new location.

23. 23. The ion implanter of claim 22, wherein the ion beam has a width in an X-direction and a height in a Y-direction, and the assist platen is translated in the Y-direction so that the X-ray beam impinges on the workpiece at a new location.

24. 15. The ion implanter of claim 14, wherein the auxiliary platen is adapted to tilt about an X-axis and a Y-axis, the X-axis passing through a center of the auxiliary platen and parallel to a width of the ion beam, and the Y-axis passing through the center of the auxiliary platen and parallel to a height of the ion beam, the rocking curve test being performed while the auxiliary platen is tilted about the X-axis to determine an X-tilt angle having a maximum intensity of the diffracted X-rays, and the rocking curve test being performed while the auxiliary platen is tilted about the Y-axis to determine a Y-tilt angle having a maximum intensity of the diffracted X-rays, and the controller calculates an orientation to be used for the ion implantation process based on the X-tilt angle and the Y-tilt angle determined during the rocking curve test.

25. 25. The ion implanter of claim 24, wherein the X-ray detector is a two-dimensional sensor array such that estimated X and Y tilt angles are determined without tilting the workpiece, and the rocking curve test is performed by tilting about the estimated X and Y tilt angles.

26. 15. The ion implanter of claim 14, further comprising a collimator positioned to receive the X-ray beam from the X-ray source and collimate the X-ray beam to deliver the portion of the X-ray beam to the workpiece.

27. The controller, when executed by the controller, causes the ion implanter to: determining the identity of the workpiece being subjected to the rocking curve test; storing the ID of the workpiece and the orientation associated with the workpiece for future use; 15. The ion implanter of claim 14, further comprising instructions to enable:

28. The controller, when executed by the controller, causes the ion implanter to: again detecting the ID of the workpiece before placing the workpiece on the platen; selecting the pre-calculated orientation based on the ID of the platen; 28. The ion implanter of claim 27, further comprising instructions to enable:

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