Ion beam profile analysis using optical tomography

Abstract

An ion beam characterization system has one or more sensors positioned relative to an ion beam. The one or more sensors image a portion of the ion beam within a predetermined range of angles and positions of the one or more sensors relative to the portion of the ion beam and define imaging data associated with the portion of the ion beam. A controller is configured to define a two-dimensional profile of the portion of the ion beam based at least in part on the imaging data. The two-dimensional profile is based at least in part on the predetermined range of angles and positions of the one or more sensors relative to the ion beam and light associated with the ion beam. A sensor receives light associated with the ion beam and provides a signal to the controller based on the received light.

Description

[0001] Cross-reference of related applications This application claims the benefit of U.S. Provisional Application No. 63 / 581,283, filed September 8, 2023, entitled “Optical Beam Tomography,” the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates generally to ion implantation systems, and more specifically to systems and methods for characterizing and controlling ion beams. Background Technology

[0003] In semiconductor device manufacturing, ion implantation is used to dope semiconductors with impurities. Ion implantation systems are typically used to dope workpieces (such as semiconductor wafers) with ions from an ion beam to produce n-type or p-type material doping, or to form passivation layers during integrated circuit manufacturing. This beam treatment is typically used to selectively implant impurities containing specified dopant materials into wafers at predetermined energy levels and controlled concentrations to produce semiconductor materials during integrated circuit manufacturing. When used to dope semiconductor wafers, ion implantation systems implant selected ion species into the workpiece to produce the desired intrinsic material. For example, implanting ions from source materials such as antimony, arsenic, or phosphorus results in "n-type" intrinsic material wafers, while "p-type" intrinsic material wafers are typically generated from ions from source materials such as boron, gallium, or indium.

[0004] A typical ion implanter includes an ion source, an ion extraction unit, a mass analysis unit, a beam delivery unit, and a wafer processing unit. The ion source generates ions of the desired atomic or molecular dopant species. These ions are extracted from the ion source by an extraction system (typically a set of electrodes) that excites and directs the ion stream from the source, forming an ion beam. In the mass analysis unit, the desired ions are separated from the ion beam, typically by mass dispersion or separation of the extracted ion beam using magnetic dipoles. The beam delivery unit is typically a vacuum system containing a series of focusing devices that transports the ion beam to the wafer processing unit while maintaining the desired characteristics of the ion beam. Finally, the semiconductor wafer is moved into or out of the wafer processing unit via a wafer handling system (which may include one or more robotic arms) to place the wafer to be processed in front of the ion beam and remove the processed wafer from the ion implanter. Summary of the Invention

[0005] Therefore, this disclosure provides systems and apparatus for characterizing and controlling ion beams in ion implantation systems. Accordingly, a simplified overview of this disclosure is given below to provide a basic understanding of some aspects of the invention. This overview is not a broad summary of the invention. It is neither intended to identify key or essential elements of the invention nor to depict its scope. Its purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that follows.

[0006] According to one exemplary aspect of this disclosure, an ion beam characterization system is provided, wherein the ion beam characterization system includes one or more sensors positioned relative to an ion beam, wherein the one or more sensors are configured to image a portion of the ion beam. For example, the one or more sensors are configured to image that portion of the ion beam within a predetermined range of angles and positions of the one or more sensors relative to that portion of the ion beam, thereby defining imaging data associated with that portion of the ion beam.

[0007] The ion beam characterization system further includes a controller configured to define a two-dimensional profile of that portion of the ion beam. For example, the controller is configured to define the two-dimensional profile of that portion of the ion beam at least in part based on imaging data. For example, the controller is further configured to calculate the two-dimensional profile of that portion of the ion beam at least in part based on the position and / or angle of the one or more sensors relative to the ion beam and the light associated with the ion beam.

[0008] For example, one or more sensors are configured to receive light associated with the ion beam and provide signals to a controller based on the light received by the one or more sensors. For example, an ion beam characterization system may include a motion-changing device associated with one or more sensors, wherein the motion-changing device is configured to selectively control the light received by the one or more sensors.

[0009] In one example, the motion transformation device is operatively coupled to one or more sensors and configured to selectively move one or more sensors relative to the ion beam in one or more directions. For example, the motion transformation device may include a translation device configured to selectively translate and / or rotate one or more sensors relative to the ion beam.

[0010] For example, an ion beam characterization system may further include an aperture device selectively positioned between one or more sensors and an ion beam, wherein the aperture device includes one or more apertures configured to control the amount of light received by the one or more sensors.

[0011] In one example, the motion transformation device is configured to selectively move the aperture device relative to the ion beam in one or more directions, and wherein the controller is further configured to calculate a two-dimensional profile of that portion of the ion beam based at least in part on the position of one or more apertures relative to the ion beam.

[0012] In another example, the motion device includes a translation device configured to selectively translate and / or rotate the aperture device relative to the ion beam. For example, one or more apertures may consist of multiple apertures positioned relative to the ion beam at corresponding multiple angles.

[0013] In yet another example, the ion beam characterization system further includes a gas source configured to supply gas to a region associated with that portion of the ion beam. The gas may be supplied at a predetermined flow rate. For example, the ion beam is configured to form a plasma with the gas, wherein light associated with the ion beam is associated with light emitted from the plasma.

[0014] For example, the controller of the ion beam characterization system and one or more sensors substantially define the tomographic imaging system. For instance, a two-dimensional profile may be defined by a pixel matrix. In one example, the pixel matrix is ​​associated with that portion of the ion beam.

[0015] To achieve the foregoing and related objectives, this disclosure includes the features fully described below and particularly pointed out in the claims. The following description and drawings illustrate certain illustrative embodiments of the invention in detail. However, these embodiments only indicate a few of the various ways in which the principles of the invention can be employed. Other objects, advantages, and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings. Attached Figure Description

[0016] Figure 1 A schematic diagram of an ion beam characterization system based on several exemplary aspects of this disclosure.

[0017] Figure 2 This is a schematic diagram of an ion beam characterization system with multiple sensors according to several exemplary aspects of this disclosure.

[0018] Figure 3 This is a block diagram of a vacuum system having an ion beam characterization system according to several exemplary aspects of this disclosure. Detailed Implementation

[0019] This disclosure generally relates to a system, apparatus, and method for characterizing and controlling the ion density of an ion beam in an ion implantation system. Specifically, this disclosure provides a non-invasive measurement system and method for measuring the two-dimensional beam current density of an ion beam via multiple measurements using one or more collimating sensors. Therefore, the system and method provide for the determination and calculation of the two-dimensional intensity of the ion beam.

[0020] Therefore, the invention will now be described with reference to the accompanying drawings, wherein like reference numerals may be used throughout to refer to like elements. It should be understood that these descriptions are merely illustrative and should not be construed as limiting. In the following description, numerous specific details are set forth for purposes of explanation in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without these specific details. Furthermore, the scope of the invention is not intended to be limited to the embodiments or examples described below with reference to the accompanying drawings, but is intended to be limited only to the appended claims and their equivalents.

[0021] It should be noted that the accompanying drawings are provided to illustrate some aspects of embodiments of this disclosure, and therefore the drawings are to be considered illustrative only. In particular, the elements shown in the drawings are not necessarily drawn to scale, and the placement of various elements in the drawings is chosen to provide a clear understanding of the respective embodiments and should not be construed as a representation of the actual relative positions of various components in an embodiment according to the invention. Furthermore, features of the various embodiments and examples described herein can be combined with each other unless otherwise specifically stated.

[0022] It should also be understood that any direct connection or coupling between functional blocks, devices, components, elements, or other physical or functional units shown in the figures or described herein may also be achieved through indirect connections or couplings. Furthermore, it should be understood that functional blocks or units shown in the figures may be implemented as separate features or circuits in one embodiment, and may alternatively be implemented wholly or partially in a common feature or circuit in another embodiment. For example, several functional modules may be implemented as software running on a general-purpose processor (such as a signal processor). It should also be understood that, unless otherwise stated, any connection described herein as a wired connection may also be implemented as a wireless connection.

[0023] This disclosure provides a non-invasive measurement of the two-dimensional beam current density of an ion beam by using a collimating sensor to perform multiple measurements, thereby enabling the calculation of the two-dimensional intensity of the ion beam.

[0024] For example, this disclosure envisions measuring the width of an ion beam by means of a camera mounted above or otherwise positioned above the ion beam. For example, the camera could be directly aligned with the ion beam via a window or via a mirror positioned at a predetermined angle (e.g., 45 degrees) relative to the camera and the ion beam. For example, the camera could be arranged and configured to collect light emitted through the depth of the ion beam.

[0025] This disclosure recognizes that the optical emission intensity of an ion beam may not precisely correspond to the ion density of the ion beam, but it can provide a means of characterizing the width of the ion beam. For example, optical emission intensity can be used as a feedback mechanism for ion beam tuning. Optical emission imaging of the ion beam is considered an attractive metrological method compared to inserting a profilometer into the beamline because optical emission imaging does not affect or interfere with the ion beam.

[0026] It should be understood that imaging from above the ion beam using a camera can have limitations. For example, the intensity recorded at the (x, z) position (where the z-axis is oriented along the ion beam's direction of travel, and the x-axis is horizontal or perpendicular to the ion beam's direction of travel) is an integrated signal of all emission volumes along the y-axis at a given (x, z) position; therefore, variations in the ion beam's vertical intensity along the y-axis may not be captured. This disclosure recognizes that characterizing ion density variations along the y-axis to identify so-called "hot spots" and "hollow regions" in the ion beam, and controlling or otherwise manipulating beamline parameters to control or eliminate such variations in real-time or near real-time, would be advantageous.

[0027] In one example of this disclosure, one or more collimating sensors are provided, thereby selectively changing the position and angle relative to the ion beam to generate a dataset from which intensity variations on the y-axis can be determined, modeled, or constructed. Unlike some methods used in computer-assisted tomography (CAT) scanning systems for medical and fault analysis imaging that utilize illumination sources, this disclosure envisions a configuration and analysis scheme in which a signal is generated rather than absorbed in the region of interest, thus eliminating the need for an illumination source.

[0028] Based on one example, one principle of this disclosure is... Figure 1 As shown, the ion beam characterization system 100 includes one or more sensors 105 (e.g., collimating sensors, also known as detectors) that are positioned relative to the ion beam 110 at a predetermined (e.g., fixed) position L and angle. θ Positioning. For example, the region of interest 115 of the ion beam 110 is divided into multiple pixels 120 (e.g., illustrated as an 8×10 pixel array, however various configurations and pixel numbers are also considered), thereby determining the predetermined position L and angle of the sensor 105. θThe region of interest is known. A motion device 125 (e.g., a stepping system) can be configured to translate and / or rotate the sensor 105 to acquire n angles at corresponding n profilometer positions 130 along the profilometer path 135. θ n Thus, multiple pixels 120 can be mapped, as well as the distances traversed by each pixel of the generated light to reach one or more sensors 105 for each of the corresponding multiple pixels.

[0029] The total distance between the center of ray 140 of the nth starting pixel 120 and the kth position L of sensor 105 R n It is given by the following formula: (1), For example, the summation in equation (1) is understood to be over the multiple pixels 120 traversed by ray 140, thereby r k The distance between the last pixel 120 and the sensor 105 includes the thickness of the window 145 through which the ray 140 passes. Although not shown, an offset can be further considered in equation (1), whereby the offset can be a result of refraction through the window 145. For example, this offset can account for the angle at which the ray 140 from the ion beam 110 passes through the window 145, as well as the characteristics of the window (e.g., the thickness and refractive index of the window). For example, a coating (not shown) on the window 145 can cause signal loss, which depends on the location where the ray 140 from the ion beam 110 enters the window.

[0030] Therefore, the total amount of light collected by sensor 105 at any profilometer position 130 is determined by the sum of the contributions from all pixels 120 along the projection path 150 of ray 140 from the origin pixel 155 to sensor 105 (minus any light scattered between the pixel and the sensor and / or any loss at window 145). For example, the contribution from each pixel 120 attenuates with the square of its distance from sensor 105. For example, the total intensity decreases by a coefficient proportional to the square of the distance between pixel 120 and sensor 105. Furthermore, the scattering of light can be further explained by a term depending on the ion density within each pixel between the starting pixel 155 and sensor 105.

[0031] Thus, the light collected at the sensor position and / or angle can be defined as: (2), WindowLoss represents the percentage of light loss caused by window 145.

[0032] Whatever other improvements may be included, such as various inverse square terms attributable to the decrease in light reaching a scattering pixel with the square of the distance between that pixel and the starting pixel, and understanding that a portion of the light scattered at the intermediate pixel will still reach sensor 105, a set of equations can be provided for multiple positions L and angles on the sensor. θ The measurement is performed below. For example, the set of equations may include one or more of the following: a set of intensities that are numerically equal to the number of pixels 120 being measured, a set of loss terms that are numerically equal to the number of pixels measured in the x-direction, and known coefficients derived from the geometric problem.

[0033] In one example, multiple measurements are performed, generating multiple equations for overdetermined solving of the problem. This allows for optimal estimation calculations and may include considerations of noise levels in the measurements, timing of the measurements (e.g., how recently the measurements were performed), or other factors. The calculations used to generate the optimal set of intensity and loss terms may depend on the number of pixels 120 measured, thereby optimizing or minimizing computational requirements based on multiple sizes (in pixels) of the region of interest 115.

[0034] According to another example of this disclosure, multiple sensors 105 may be provided to advantageously improve data acquisition speed. For example, such as Figure 2 As shown, an ion beam characterization system 160 is provided, which includes a sensor array 165, the sensor array including a plurality of sensors 170A to 170G. Each of the plurality of sensors 170A to 170G can be similar to Figure 1 The sensor 105 is configured as shown. It should be noted that although the sensor array 165 may include any number of sensors 105, it is not limited to the number of sensors described or illustrated herein.

[0035] This disclosure further recognizes that it is conceivable Figure 1 and Figure 2 Various configurations of the ion beam characterization systems 100 and 160 are used to improve the speed and / or accuracy of characterization of the region of interest 115 of the ion beam 110. For example, Figure 1 and Figure 2 The sensors 105 and 170A-170G (e.g., including associated collimators) can be configured as a slotted structure 175 along the z-axis to optimize the signal-to-noise ratio. Furthermore, various configurations can optimize the acquisition speed, thereby allowing the measured output to be the emission average along a predetermined sampling length.

[0036] In other examples, this disclosure envisions multiple sensors 170A-170G mounted on a single head (not shown), whereby the single head is configured to translate and / or rotate simultaneously or synchronously along the travel paths of the multiple sensors via a motion-changing device 125. For example, the multiple sensors 170A-170G may be fixed in an array, whereby the array is configured to translate or scan in the y-direction (by...). Figure 2 (As indicated by arrow 180). In another example, multiple sensors 170A-170G may be configured as a fixed array and positioned close to a rotating disk device (not shown). For example, the rotating disk device may include a disk having multiple slots configured to pass through it, whereby the slots are defined at various angles. The disk may be further positioned adjacent to the multiple sensors 170A-170G, and the rotating device is configured to operate along a sensing path associated with the multiple sensors (e.g., ...). Figure 1 The projection path 150) is a rotating disk. Thus, the movement of the rotating device is limited to the rotation of the disk relative to the multiple sensors 170A to 170G.

[0037] This disclosure also contemplates other variations falling within the scope of this disclosure, such as calculations associated with a relatively small number of pixels 120, and increasing the number of pixels when signal 185 is provided to controller 190 (e.g., a computer processor), thereby providing a better estimate of the signal-to-noise ratio, etc. In another example, in order to understand Figure 1 and Figure 2 The ion beam characterization systems 100 and 160 can be used to assess the effects of various variations, and can acquire a dataset of a predetermined size to calculate an initial intensity estimate, thereby refreshing the data in a first-in, first-out manner. In this way, the oldest data in the dataset is replaced by the latest data, and the estimated intensity is recalculated when additional data becomes available.

[0038] This disclosure recognizes that, Figure 1 The ion beam characterization system 100 and / or Figure 2 The ion beam characterization system 160 can be advantageously integrated into a semiconductor processing system, such as an ion implantation system. Thus, according to one aspect of this disclosure, Figure 3An exemplary semiconductor processing system 200 in which various aspects of the present invention can be implemented is shown. The semiconductor processing system 200 in this example includes an ion implantation system 202; however, various other types of semiconductor processing systems or vacuum systems, such as plasma processing systems or other processing systems, are also contemplated. For example, the ion implantation system 202 includes a terminal 204, a beam assembly 206, and a terminal station 208. Generally, an ion source 210 in the terminal 204 is coupled to a power source 212 to ionize a dopant gas into multiple ions and form an ion beam 214. In this example, the ion beam 214 is guided through a beam guide 216 and exits an aperture 218 toward the terminal station 208. In the terminal station 208, the ion beam 214 bombards a workpiece 220 (e.g., a semiconductor such as a silicon wafer, display panel, etc.), which is selectively clamped or mounted to an electrostatic chuck 222 (ESC). Once embedded in the lattice of the workpiece 220, the implanted ions alter the physical and / or chemical properties of the workpiece. Therefore, ion implantation is used in various applications in semiconductor device manufacturing, metal finishing, and materials science research.

[0039] For example, the ion implantation system 202 may further include an ion beam characterization system 224, for example... Figure 1 Ion beam characterization system 100 or Figure 2 The ion beam characterization system 160 in the example. Figure 3 The controller 226 can be configured to selectively control the semiconductor processing system 200, including the ion beam characterization system 224.

[0040] This disclosure envisions an ion beam characterization system 224 comprising a tomographic imaging system that uses multiple measurements along multiple different projection directions through the sample to construct a two-dimensional image of the object under consideration (e.g., ion beam 214). Thus, the real-time, non-invasive two-dimensional profile of ion beam 214 can be advantageously used for tuning the ion implantation system 202. For example, signals generated within the object (e.g., light from the plasma generated by ions in ion beam 214) can be measured to determine various characteristics of the ion beam.

[0041] In one example, this disclosure employs an algebraic method to characterize a portion of the full ion beam. It should be noted that although an algebraic method is described herein, this disclosure also understands that various other techniques for characterizing ion beams fall within the scope of this disclosure.

[0042] In this example, a portion of the ion beam 214 is defined as the characterization region 228 (e.g., Figures 1 to 2The region of interest (110) is defined as follows: the region of interest is divided into a predetermined number of m units or pixels. As described above, multiple contour analysis locations are provided, and for each contour analysis location, a contribution (e.g., a measurement vector) from each unit is calculated to define the weight associated with each unit. Each measurement vector can be further projected onto an m-dimensional hyperplane, thereby iterating the measurement and calculation process to define a solution.

[0043] This disclosure recognizes, for example, from Figure 2 The signal 185 received by the multiple sensors 170A-170G may not be proportional to the ion density. Instead, the signal 185 can be compared with the signal received by the ion beam 110. Figure 3 The light produced is associated with the action of a gas (e.g., nitrogen) provided by gas source 230. Therefore, this disclosure contemplates one or more flow rates (e.g., 10 sccm or less) and / or types of gases flowing from gas source 230 into characterization region 228, for example, with… Figure 3 The terminal station 208 of the ion implantation system 202 is associated.

[0044] Alternatively, this disclosure envisions the presence of trace background gases in most vacuum systems (e.g., ion implantation system 202), such background gases being sufficient for the characterization described herein. For example, this disclosure further envisions no gas flow to characterization region 228. It should be noted that, in this example, characterization region 228 is... Figure 3 The terminal station 208 is associated with it; however, this disclosure envisions that the characterization region may be located at any location in the ion implantation system 202 where it is desired to characterize the ion beam 214.

[0045] While the invention has been shown and described with respect to one or more specific embodiments, it should be noted that the above embodiments are merely examples of some embodiments of implementing the invention, and the application of the invention is not limited to these embodiments. In particular, with respect to the different functions performed by the components (assemblies, devices, circuits, etc.) described above, unless otherwise specified, the terminology used to describe these components (including references to "device") is intended to correspond to any component that performs the specified function of the described component (i.e., functionally equivalent), even if structurally not equivalent to the disclosed structure that performs the function described in the exemplary embodiments of the invention herein. Furthermore, while a particular feature of the invention may be disclosed only with respect to one of several embodiments, such a feature may be combined with one or more other features of other embodiments when it may be desirable and advantageous for any given or particular application. Therefore, the invention is not limited to the above-described embodiments, but is intended to be limited only by the appended claims and their equivalents.

Claims

1. An ion beam characterization system, comprising: One or more sensors positioned relative to an ion beam, wherein the one or more sensors are configured to image the portion of the ion beam within a predetermined range of angles and positions of the one or more sensors relative to a portion of the ion beam, thereby defining imaging data associated with the portion of the ion beam; as well as A controller configured to define a two-dimensional profile of said portion of the ion beam, at least in part, based on said imaging data.

2. The ion beam characterization system according to claim 1, wherein, The controller is configured to calculate, at least in part, a two-dimensional profile of the portion of the ion beam based on a predetermined range of angles and positions of the one or more sensors relative to the ion beam and the light associated with the ion beam.

3. The ion beam characterization system according to claim 2, wherein, The one or more sensors are configured to receive light associated with the ion beam and to provide signals to the controller based on the light received by the one or more sensors.

4. The ion beam characterization system of claim 3, further comprising a motion-changing device associated with the one or more sensors, wherein the motion-changing device is configured to selectively control the light received by the one or more sensors.

5. The ion beam characterization system according to claim 4, wherein, The motion-changing device is operatively coupled to the one or more sensors and configured to selectively move the one or more sensors relative to the ion beam in one or more directions.

6. The ion beam characterization system according to claim 5, wherein, The motion transformation device includes a translation device configured to selectively translate one or more sensors relative to the ion beam.

7. The ion beam characterization system according to claim 5, wherein, The motion-changing device includes a rotating device configured to selectively rotate the one or more sensors relative to the ion beam.

8. The ion beam characterization system of claim 4, further comprising an aperture device selectively positioned between the one or more sensors and the ion beam, wherein, The aperture device includes one or more apertures configured to control the amount of light received by the one or more sensors.

9. The ion beam characterization system according to claim 8, wherein, The motion-changing device is configured to selectively move the aperture device relative to the ion beam in one or more directions, and wherein the controller is further configured to calculate a two-dimensional profile of the portion of the ion beam based at least in part on the position of the one or more apertures relative to the ion beam.

10. The ion beam characterization system according to claim 9, wherein, The motion-changing device includes a translation device configured to selectively translate the aperture device relative to the ion beam.

11. The ion beam characterization system according to claim 8, wherein, The motion-changing device includes a rotating device configured to selectively rotate the aperture device relative to the ion beam.

12. The ion beam characterization system according to claim 8, wherein, The one or more apertures consist of a plurality of apertures positioned at corresponding multiple angles relative to the ion beam.

13. The ion beam characterization system of claim 2, further comprising a gas source configured to supply gas to a region associated with said portion of the ion beam.

14. The ion beam characterization system according to claim 13, wherein, The ion beam is configured to form a plasma with the gas, wherein the light associated with the ion beam is associated with light emitted from the plasma.

15. The ion beam characterization system according to claim 2, wherein, The controller and the one or more sensors substantially define the tomographic imaging system.

16. The ion beam characterization system according to claim 1, wherein, The two-dimensional contour is defined by a pixel matrix.

17. The ion beam characterization system according to claim 16, wherein, The pixel matrix is ​​associated with the portion of the ion beam.

18. An ion beam characterization system, comprising: Multiple sensors, positioned relative to an ion beam and configured to receive light associated with a portion of the ion beam, wherein the multiple sensors are configured to define imaging data based on the light received by the multiple sensors within a predetermined range of angles and positions of the multiple sensors relative to the portion of the ion beam; and A controller is configured to receive the imaging data and, at least in part, define a two-dimensional profile of the portion of the ion beam based on the imaging data.

19. The ion beam characterization system of claim 18, further comprising a motion-changing device associated with the plurality of sensors, wherein, The motion-changing device is configured to selectively control the light received by the plurality of sensors.

20. The ion beam characterization system of claim 19, further comprising an aperture device selectively positioned between the plurality of sensors and the ion beam, wherein, The aperture device includes one or more apertures configured to control the amount of light received by the plurality of sensors, wherein the transformation motion device is configured to selectively move the aperture device relative to the ion beam in one or more directions, and wherein the controller is further configured to calculate a two-dimensional profile of the portion of the ion beam based at least in part on the position of the one or more apertures relative to the ion beam.

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