Multi-spot optical system and method of use

Abstract

The invention relates to a multi-spot optical system and a method of use. The present disclosure provides an optical system, a semiconductor processing system, and a method for processing a semiconductor wafer. In one example, the optical system includes: (1) a light source configured to provide source light to a source plane to form a plurality of first sub-beams; (2) an optical element configured to modify each of the plurality of first sub-beams according to a predetermined pattern to form a plurality of interrogation spots on a wafer, wherein the optical element is further configured to modify each of the plurality of first sub-beams after reflection from the wafer to form a plurality of second sub-beams on an image plane; and (3) a spectrometer configured to receive collected light from the plurality of second sub-beams.

Description

[0001] Cross-reference to related applications

[0002] This application claims the benefit of U.S. Provisional Application Serial No. 63 / 647,513, filed by John Corless on May 14, 2024, and U.S. Provisional Application Serial No. 63 / 567,314, also filed by John Corless on March 19, 2024, which are commonly assigned with the present application and are incorporated herein by reference in their entirety. Technical Field

[0003] The present disclosure relates generally to spectroscopy systems and methods of use, and more particularly to improvements in systems for monitoring optical signals from multiple points within semiconductor processing equipment during semiconductor processing. Background Art

[0004] Optical monitoring of semiconductor processes is a well-established method for controlling processes such as etching, deposition, chemical mechanical polishing, and implantation. Optical emission spectroscopy (OES) and interferometric endpoint (IEP) are two basic types of operating modes for data collection. In OES applications, light emitted from a process, typically a plasma, is collected and analyzed to identify and track changes in atomic and molecular species that indicate the state or progress of the monitored process. In IEP applications, light is typically supplied and directed onto a workpiece from an external source, such as a flash lamp. After reflection from the workpiece, the sourced light carries information in the form of the reflectivity of the workpiece, which indicates the state of the workpiece. Extraction and modeling of the reflectivity of the workpiece allows for understanding film thickness and feature size / depth / width, as well as other properties. Summary of the Invention

[0005] In one aspect, an optical system is disclosed. In one example, the optical system includes: (1) a light source configured to provide source light to a source plane to form a plurality of first sub-beams; (2) an optical element configured to modify each of the plurality of first sub-beams according to a predetermined pattern to form a plurality of interrogation light spots on a wafer, wherein the optical element is further configured to modify each of the plurality of first sub-beams after reflection from the wafer to form a plurality of second sub-beams on an image plane; and (3) a spectrometer configured to receive collected light from the plurality of second sub-beams.

[0006] In another aspect, the present disclosure provides a semiconductor processing system. In one example, the processing system includes: (1) a processing chamber; (2) a light source configured to provide source light to a plurality of first optical fibers; (3) a spectrometer configured to receive collected light from a plurality of second optical fibers; and (4) an interrogation zone including a plurality of interrogation light spots on a wafer within the processing chamber, wherein each of the plurality of interrogation light spots is defined by a paired arrangement of the plurality of first and second optical fibers.

[0007] In yet another aspect, a method for processing a semiconductor wafer is disclosed. In one example, the method includes: (1) illuminating a wafer within a semiconductor processing chamber with light provided by a light source via a plurality of first optical fibers; (2) collecting the light reflected from the wafer via a plurality of second optical fibers; (3) processing the collected light using a multi-input spectrometer; and (4) providing one or more control trends based on the processing for controlling the processing of the wafer. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Reference is now made to the following description taken in conjunction with the accompanying drawings, in which:

[0009] Figure 1 is a block diagram of a system for monitoring and / or controlling the state of a plasma or non-plasma process within a semiconductor process tool using an OES and / or IEP;

[0010] Figure 2 is a simplified diagram of the beamforming portion of a typical refraction system for an IEP;

[0011] Figure 3 is a simplified diagram of a multiplexed beamforming portion of a refraction system for an IEP according to the present disclosure;

[0012] Figures 4A to 4C is an expression association according to the present disclosure Figure 3 a set of performance data graphs for a design of a system of the type described;

[0013] Figures 5A to 5D is a 3D diagram of an alternative multiplexed beamforming portion of a refractive system for an IEP according to the present disclosure;

[0014] Figure 6A and 6B According to the present disclosure Figures 5A to 5D Another diagram of an alternative multiplexing beamforming portion of a refractive system;

[0015] Figure 7 describes an example of a multi-mode optical circulator that may be used with the multi-point optical system disclosed herein;

[0016] Figure 8An example illustrating the target beam layout on a wafer;

[0017] Figure 9 illustrates example configurations of optical fibers for separating incoming and outgoing beamlets using fiber pairing and defocusing in accordance with the principles of the present disclosure;

[0018] Figure 10A and 10B illustrate Figure 9 Specific performance data of fiber arrangements and examples of their variation with defocus in different wavelength ranges;

[0019] Figure 11 a block diagram illustrating various optical, electrical, and computational components of a spectrometer and certain related systems in accordance with the principles of the present disclosure;

[0020] Figure 12 Describes computing devices that can be used for the processes disclosed herein (e.g., identifying signals in spectral data and processing the signals); and

[0021] Figure 13 A flow chart illustrating a method 1300 for processing a semiconductor wafer according to the principles of the present disclosure. DETAILED DESCRIPTION

[0022] In the following description, reference is made to the accompanying drawings which form a part thereof, and specific embodiments in which the present invention may be implemented are shown in the accompanying drawings by way of illustration. These embodiments are described in sufficient detail to enable those skilled in the art to practice the present invention, and it should be understood that other embodiments may be utilized. It should also be understood that structural changes, process changes, and system changes may be made without departing from the spirit and scope of the present invention. Therefore, the following description should not be considered as limiting. For clarity of explanation, similar features shown in the accompanying drawings are indicated by similar reference numerals, and similar features shown in alternative embodiments as shown in the accompanying drawings are indicated by similar reference numerals. Other features of the present invention will be apparent from the accompanying drawings and the following detailed description. It should be noted that for the purpose of clarity of explanation, some elements in the drawings may not be drawn to scale.

[0023] The continuous evolution of semiconductor processing towards faster processes, smaller feature sizes, more complex structures, larger wafers, and more sophisticated process chemistries places significant demands on process monitoring technologies. For example, higher data rates are required to accurately monitor the much faster etch rates on very thin layers, where variations measured in angstroms (a few atomic layers) are critical, such as for fin field-effect transistor (FINFET) and three-dimensional NAND (3D NAND) structures. In many cases, wider optical bandwidths and greater signal-to-noise ratios are required for both OES and IEP methodologies to aid in detecting small changes in either or both reflectivity and optical emission.

[0024] Large wafer sizes with small overall component feature sizes and stringent requirements for uniformity within and across wafers place numerous constraints on semiconductor processing equipment design. These constraints can limit the introduction of features that support optical monitoring access. For example, typical wafer interrogation typically uses the signal integration from a single, relatively large spot to characterize the representative state of the wafer process. As the complexity and diversity of structures, films, film stacks, and structural geometries on a wafer continue to increase, using a single, large spot to characterize the representative state of the wafer becomes insufficient.

[0025] Particularly relating to monitoring and evaluating the status of semiconductor processes within process tools, Figure 1 A block diagram illustrating a processing system 100 that utilizes an OES and / or IEP to monitor and / or control the state of a plasma or non-plasma process within a semiconductor process tool 110. The semiconductor process tool 110 (or simply process tool 110) will typically consist of Figure 1 A workpiece, represented by a wafer 120 in FIG. 1 , and possibly a process plasma 130, are enclosed in a typically partially evacuated volume of a processing chamber 135, which may contain various process gases. The process tool 110 may include one or more optical interfaces 140 to allow observation of the processing chamber 135 at different locations and orientations. The interfaces 140 may include various types of optical components, such as, but not limited to, optical filters, lenses, windows, apertures, mirrors, beam splitters, optical fibers, and the like.

[0026] For IEP applications, light source 150 may be connected to interface 140 directly or via fiber optic cable assembly 153. As shown in this configuration, interface 140 is oriented orthogonal to the surface of wafer 120 and is typically centered relative to the surface. Light from light source 150 may enter the interior volume of processing chamber 135 in the form of a collimated beam 155. Light beam 155 may be received again by interface 140 after reflecting from wafer 120. In common applications, interface 140 may be an optical collimator. After being received by interface 140, the light may be transmitted via fiber optic cable assembly 157 to spectrometer 160 for detection and conversion to a digital signal. The light may include sourced and detected light, and may include, for example, a wavelength range from deep ultraviolet (DUV) to near infrared (NIR). The wavelength of interest may be selected from any sub-range of the wavelength range.

[0027] After spectrometer 160 detects the received optical signal and converts it into an analog electrical signal, the analog electrical signal is typically amplified and digitized within a subsystem of spectrometer 160 and passed to signal processor 170. Signal processor 170, which may be, for example, an industrial PC, PLC, or other system, employs one or more algorithms to generate output 180, such as an analog or digital control value representing, for example, the intensity of a specific wavelength or the ratio of two wavelength bands. Signal processor 170 may alternatively be integrated with spectrometer 160 rather than a separate device. Signal processor 170 may employ an OES algorithm that analyzes the emission intensity signal at a predetermined wavelength(s) and determines trend parameters that correlate with the state of the process and can be used to assess such state, such as endpoint detection, etch depth, etc. For IEP applications, signal processor 170 may employ an algorithm that analyzes a broad bandwidth portion of the spectrum to determine film thickness. See, for example, U.S. Patent 7,049,156, "System and Method for In-situ Monitor and Control of Film Thickness and Trench Depth," which is incorporated herein by reference. The output 180 may be transmitted to the process tool 110 via the communication link 185 for use in monitoring and / or modifying the production process occurring within the chamber 135 of the process tool 110.

[0028] Figure 1 The components shown and described are simplified for convenience and are well known. In addition to common functions, the spectrometer 160 or signal processor 170 may also be configured to identify steady-state and transient optical and non-optical signals and process these signals according to the methods and / or features disclosed herein. Thus, the spectrometer 160 or signal processor 170 may include algorithms, processing capabilities and / or logic for identifying and processing optical signals and time trends extracted therefrom. In addition, the spectrometer 160 or signal processor 170 may also be configured to process multiple signal points collected (multiple collected signal points) according to the devices, systems and methods disclosed herein. For example, Figures 5A to 5D 6A to 6B provide examples of collecting specific spatial information from multiple collection signal points or reflected sub-beams. Figures 5A to 5DAs an example, the reflected sub-beams 581-587 (also referred to as multiple collection signal points) can be provided to the spectrometer 160 via the fiber optic cable assembly 157, which in this example would have seven individual optical fibers (one for each sub-beam). The optical signal from each of the individual sub-beams 581-587 can provide a unique input to the spectrometer 160 and can be processed in a variety of ways. For example, each of the sub-beams 581-587 can be processed individually (or independently), in combination with at least one or more of the sub-beams 581-587, or all of the sub-beams 581-587 can be processed together.

[0029] The number of collected beamlets may correspond to the number of individual optical inputs to the spectrometer 160. However, the number of beamlets is not limited by the number of optical inputs. For example, the collected beamlets may be multiplexed and provided to the optical inputs. Thus, the number of collected beamlets may be greater than the number of optical inputs to the spectrometer 160 (i.e., the number of collected beamlets may be greater than the number of inputs N). The number of collected beamlets may also be less than the number of optical inputs N (i.e., the number of collected beamlets may be less than the number of inputs N). The collected beamlets may be from either the IEP or OES operating mode. For example, the number of collected beamlets may be between 2 and 10 beamlets.

[0030] Additional processing may also be performed on the processed beamlets. For example, the signal processor 170 may perform additional processing based on the combined information from the individually processed beamlets, such as averaging the output values ​​from the processed beamlets 581 to 587. Various trends or different types of data may be extracted from processing the output values ​​of the processed beamlets 581 to 587. The obtained information may be provided to the processing tool 110, for example, to control the process. Trend lines may also be determined and control signals generated based on processing one or more of the beamlets. For example, seven independent trend lines may be determined based on the seven beamlets 581 to 587 and sent as seven parallel control signals.

[0031] The algorithms, processing capabilities, and / or logic may be in the form of hardware, software, firmware, or any combination thereof. The algorithms, processing capabilities, and / or logic may be within a single computing device or may be distributed across multiple devices, such as the spectrometer 160 and the signal processor 170. Although this system and other systems described herein are based on refraction systems, it should be understood that systems based on reflection and / or combined refraction / reflection systems are possible and may be created and adapted according to the principles and examples described and disclosed herein.

[0032] Figure 2A simplified diagram of a beamforming subsystem 200 of a typical refraction system for an IEP is shown. The subsystem 200 generally includes a source and receive fiber optic cable subassembly 210 (an example of fiber optic cable assembly 153), which may be formed from two or more individual optical fibers arranged to provide light to subsequent components and receive light from previous components of the beamforming subsystem 200. An enlarged inset of the fiber optic cable subassembly 210 shows a random arrangement of 19 optical fibers, for example, arranged in a close-packed or hexagonally packed configuration. In this example, 8 optical fibers (colored black) may be considered source fibers and 11 optical fibers (colored white) may be considered receive fibers. The source fibers direct light toward a lens 220, which refracts the light and thereby forms a beam 230 (which may correspond to a source fiber) that is directed toward a wafer 240. Figure 1 After reflecting from the wafer 240, the light passes through the lens 220 and is collected by the receiving optical fiber.

[0033] Lens 220, which may form the basis of interface 140, may typically have a diameter ranging from 0.5" to 1.0", with a focal length appropriate to the numerical aperture (NA) and other properties of the system. Instead of the single lens shown, lens 220 may be replaced by using a doublet, triplet, or other compound lens set, or may be replaced by an equivalent reflective element. For a collimating system, the spot size of the light beam produced by lens 220 on wafer 240 is typically similar to the diameter of the clear aperture of lens 220. For a focusing system, the spot size of the light beam on wafer 240 may be similar to the diameter of the fiber bundle of the fiber optic cable subassembly 210, such as indicated by the magnified illustration, or modified according to the design magnification of the optical system.

[0034] Typically, subsystem 200 provides a measurement of the spot size, which is an average of the optical response of the entire region. This large region can contain a wide variety of structures and / or film stacks, each of which provides very different signals that, when incoherently summed in this subsystem, are obscured and unusable for characterization and process control. This integrated signal can be divided into sub-portions by perforating the light beam and / or by individually collecting and processing the signal from each of the individual receiving fibers. However, these methods generally do not provide specific spatial information from wafer 240 because the combined action of the optical fibers of fiber optic cable subassembly 210 and lens 220 mixes the signal both spatially and angularly.

[0035] like Figure 3 Specific spatial information can be displayed via Figure 2The multiplexing and possible miniaturization of subsystem 200 is provided. Subsystem 300 includes multiple sets of discrete lenses and fiber optic cables to provide multiple sets of individual spatial information. Fiber optic cable subassemblies 310 to 313 can each be composed of a limited number of optical fibers, such as a single pair of source and receiving optical fibers shown in enlargement of subassembly 310. The optical fibers can have various commonly available core diameters, such as 50, 100, 200, 400, and 600 microns. The limited number of optical fibers facilitates miniaturization. Lenses 320 to 323 of subsystem 300 (which can correspond to Figure 1 The interfaces 140 of the wafer 340 can be physically discrete and form a so-called "beamlet" system (as shown), or can be physically connected and form a so-called "lenslet" system. Lenses 320-323 can be single lenses or more complex lens groups. Each fiber optic cable and lens pair (e.g., 310 and 320) cooperates to form a beam (e.g., 330). Other pairs form beams 331-333. All beams can be reflected from spatially distinct regions of the wafer 340 and provide information therefrom. Beams 330-333 can correspond to Figure 1 The source and receiving optical fibers may be radially symmetric with respect to the axis of the optical system. For example, the source and receiving optical fiber pairs of subassembly 310 may be radially symmetric with respect to the axis of lens 320.

[0036] Although subsystem 300 shows four combinations of optical fibers, lenses, and beams in a 1D linear pattern, any number of combinations can be placed in a 2D pattern, such as a square array, a hexagonal array, a circular pattern, and so on. The size of the individual beam spots on wafer 340 and the boundary regions of the collection of lenslets or beamlet combinations can be designed to suit specific or general applications. For example, the diameter of the individual beam spots can range from less than 1 mm to greater than 5 mm, and the entire subsystem can be confined to a 25 mm diameter region on wafer 340. The selection of individual beam sizes and boundary regions can be determined based on feature size, pattern density, and other properties of wafer 340. Alternatively or additionally, the selection of individual beam sizes and boundary regions can be determined based on process parameters (e.g., non-uniformity requirements) or tool requirements (e.g., available physical access).

[0037] The design and optimization of each combination depends on design parameters such as the fiber core size and the number of source and receive fibers, the focal length of the lenses, the NA of the overall combination, and the requirement for uniformity of the optical spot size across wavelengths. Especially for systems based on single-lens designs, focal length and wavelength sensitivity can lead to significant variations in coupling efficiency and optical spot size. Furthermore, the miniaturization of these systems and the tolerance variations of lenses, fibers, and mechanical components increase the challenges of aligning the fibers to the lenses and to each other on mechanical fixtures for practical implementation of the systems into processing tools. Figures 4A to 4C It indicates association Figure 3 A set of performance data graphs for a design of a system of the type described.

[0038] Figure 4A is a plot of beam spot size versus wavelength, showing a strong variation in diameter in the UV region for wavelengths less than about 0.4 microns. Figure 4B is a plot of signal coupling efficiency versus wavelength, demonstrating the wavelength dependence as the system varies the spot size and the degree of focusing or collimation of the light at the wafer surface depending on the nominal fiber-to-lens distance for a given focal length lens. Figure 4C This is a plot of signal coupling efficiency versus wavelength for varying fiber-to-lens defocus distances, highlighting the system's sensitivity to at least one mechanical tolerance. The efficiency is expressed as the IMAE efficiency, which corresponds to the number of IMAE operations used by the optical design software ZEMAX to perform the analysis.

[0039] Figures 5A to 5D is a 3D diagram of an alternative multiplexed beam shaping portion of a refractive system 500 for an IEP. A single interface, such as interface 140, is shown, but more beams can be used with a wafer 550 having more optical interfaces. Figure 5A Source plane 510 is shown providing light to form sub-beams 521-527 (e.g., multiple source signal points, or simply multiple source points). The sub-beams are directed toward beam splitter 530, which then directs the light to lens 540 and then onto wafer 550, forming interrogation light spots 561-567 (e.g., multiple interrogation signal points, or simply multiple interrogation points). After reflecting from wafer 550, the sub-beams pass again through lens 540 and then through beam splitter 530 to image plane 570, where each reflected sub-beam 581-587 (e.g., multiple collection signal points, or simply multiple collection points) can be independently collected by a corresponding optical fiber (not shown). The correspondence between different signal points (e.g., multiple source, interrogation, and collection points) can be one-to-one. The number of sub-beams can be, for example, between 2 and 10.

[0040] The working f# and magnification of system 500 can be determined based on the desired working distance and magnification. For example, based on a lens 540 having a nominal focal length of 5F and other lenses in the system having a nominal focal length of F (e.g., Figure 6B 5. A system using lenses 537 and 539 (e.g., lenses 537 and 539) provides a magnification of 5x. In the depicted example, lens 540 may have a focal length of 200 mm and a diameter of 20 mm. This lens selection results in a system working distance (the distance from lens 540 to wafer 550) of approximately 200 mm. When a 200 μm core fiber is used with this system, the nominal diameters of the source and signal beamlets will each be 200 μm, and the nominal diameter of the interrogation spot size will be 1000 μm.

[0041] Figure 5BA magnified region surrounding source plane 510 and beamlets 521-527 is shown. In this example, seven beamlets are presented, but more or fewer beamlets may be defined and used. Source plane 510 may be a common source plane, such as a light pipe from a source point with a diameter large enough to enclose all desired beamlets. For example, for an interrogation spot size of ~1 mm in diameter and a system operating at 5x magnification, the diameter of the light pipe may be approximately 3 mm or larger, resulting in an interrogation region (including all individual interrogation spots) of approximately 15 mm. The light pipe may typically be formed from fused silica for broad spectral (200-800 nm) performance, or may be formed from other suitable materials. Illumination for the light pipe may be provided by a light source such as a pulsed xenon flash lamp.

[0042] Using a light pipe to define the source planes and common source of the sub-beams offers advantages over using individual optical fibers for each sub-beam. For example, a light pipe provides a common, uniform source plane, while individual optical fibers may have to be focused independently. Furthermore, a light pipe provides a large-area source field, eliminating the need to laterally align individual source fibers to individual signal fibers. Furthermore, while uniform illumination from the light pipe illuminates a larger interrogation zone, using a light pipe that provides uniform illumination allows for the removal of individual source fibers, allowing individual receiving fibers to receive any subset of the light reflected within that zone. Consequently, the system can be considered self-aligning, requiring less complex alignment and construction of the signal receiving fiber assembly. Self-alignment can include the freedom allowed for alignment of individual source fibers with the light pipe or light source and / or the freedom allowed for alignment of the signal fibers relative to the larger illuminated interrogation zone provided by the light pipe. For example, a source light pipe can create a uniform illumination plane that continuously samples the wafer across its image area as it passes through the optical system. Reflected light is then passed back through the optical system and re-imaged onto plane 570. Individual optical fibers are positioned in the receiving plane to receive the returned light. Each receiving fiber collects a subset of the entire beam, originating from a specific location on the light pipe, traveling to and detecting a specific location on the wafer, and then reflecting back into the fiber. This is self-aligning because the receiving fiber can be moved and still collects valid light from the wafer, but only in a translated position on the wafer and originating from a slightly different location on the light pipe. Light pipes also provide improved illumination intensity uniformity for each sub-beam compared to individual fiber sources.

[0043] Figure 5C A magnified interrogation region 555 is shown about the intersection of incident beamlets 561-567 with wafer 550. As described above, the beamlets may provide interrogation spot diameters of approximately 1 mm to 5 mm and be enclosed within an overall diameter of approximately 15 mm to 50 mm. Figure 5DA magnified region around signal plane 570 and signal beamlets 581-587 is shown. Each signal beamlet can be approximately 1 mm apart and arranged in a hexagonal pattern. The pattern can be defined based on the configuration of the supporting fiber optic cable assembly (not shown). The pattern can also be influenced by the features to be inspected on wafer 550. Engineering preferences, wafer design, and OEM requirements are other examples of the basis for pattern selection.

[0044] In conjunction with the source light guide, the supporting fiber optic assembly can be changed or reconfigured to provide new wafer sampling modes without having to change the source of the beamlets. Thus, the light source can remain unchanged, while the configuration of the collection beamlets can be adapted. Such mode changes can include different spatial mappings, different interrogation spot sizes (via fiber core size variations), different numbers of collection beamlets, and so on. Additionally, the source and signal functions of the system can be reversed by illuminating the system via the signal fiber and collecting light at the source plane. This functionality can be used to add an adjustable mechanism to the fiber layout to allow fine-tuning of the measurement position (e.g., reversing the light to provide a probe beam to illuminate the wafer 500 for setup purposes).

[0045] Figures 6A to 6B yes Figures 5A to 5D FIG. 5 is another diagram of an alternative multiplexing beam shaping portion of a refraction system 500 . Figure 6A A cross-sectional view of the system 500 is shown to allow for indication of the beam stop 535 and Figure 6B 5. The beam stop 535 is located at the focal plane of the system 500 and controls the bi-telecentric performance of the system 500. The bi-telecentric system performance is valuable in the system 500 so that all beamlets of each type: source beamlets 521-527, interrogation beamlets 561-567, and signal beamlets 581-587, are formed on a common surface and are orthogonally incident on the interrogation and signal surfaces. This avoids individual longitudinal adjustments of each beamlet at one or more of the source plane, the wafer surface, or the signal plane.

[0046] Figure 6B exhibit Figure 6A, to illustrate various additional features of system 500. After leaving the source plane, the sub-beams 521 to 527 pass through lens 537 and may be collimated by the lens. Lens 537 may be a single lens, a double lens, or other more complex lens group. After lens 537, the sub-beams approach beam splitter 530 and are reflected by beam splitter 530. Beam splitter 530 may be, for example, a broad spectrum polka-dot beam splitter, a cube beam splitter, or other known beam splitter types with or without coatings. For the described design, the diameter of beam splitter 530 may be approximately 25 mm. After reflection from beam splitter 530, the sub-beams are directed through beam stop 535, which may have a diameter of, for example, from 10 mm to 20 mm and may depend on the system magnification, working distance, and interrogation beam spot size. The focal length of beam stop 535 is placed away from lens 537 so that the system is telecentric in object space. Lens 540 ( Figure 6A ) places its focal length away from the beam stop 535 so that the sub-beam is telecentric at the wafer plane and is therefore incident orthogonally to the wafer plane. After reflecting from the wafer 550 (more specifically, the interrogation zone 555 of the wafer 550) and passing through the beam splitter 530, the sub-beam enters the lens 539 and can be focused by the lens 539. The lens 539 can be equivalent to the lens 537 in material composition and properties, for example, being a fused silica single lens or an air-spaced double lens with a focal length of 40 mm and a diameter of ~12 mm. The lens 539 places its focal length away from the beam stop 535 so that the beam is telecentric in the signal plane to aid in efficient coupling to the signal fiber. Note that two lenses 537 and 539 are shown, but depending on the focal length and NA requirements, a single lens can be used with the beam splitter 530 placed in the converging region of this single lens group to provide separation of the outgoing and incoming sub-beams. The lenses 540 and Figure 6B The components can correspond to Figure 1 interface 140.

[0047] association Figures 5A to 5D and Figures 6A to 6BThe described and illustrated bi-telecentric system can be modified into a simpler system by removing certain components and adjusting others. These variations in bi-telecentricity result in certain performance trade-offs and limitations, but can also offer certain advantages in terms of reducing system complexity, cost, and size. Specifically, a simplified system based on system 500 can remove lenses 537 and 539, and can also remove or reposition aperture 535. The focal length and position of lens 540 relative to beamsplitter 530 and wafer 550 can also be adjusted. The position of lens 540 defines the system aperture. Typically, beamsplitter 530 is retained to separate the source and signal sub-beams due to the bi-conjugate nature of imaging in this double-pass optical system. As with system 500, in this simplified system, a light guide can be used for the source to simplify alignment with the signal fiber and facilitate configuration of potential signal fiber variations, thereby supporting interrogation of spot size and / or position. By simplifying the system, multiple source points need not be used to collect multiple signal points. Advantageously, this eliminates or at least reduces the need to align multiple points for sourcing with multiple points for collection. Thus, using the simplified system, a single, larger beam can be created on wafer 550 compared to system 500, but when using the same configuration of collection beamlets, the same effective detection pattern can be used on wafer 550 as in system 500. Furthermore, as with system 500, the light source of the simplified system can be considered self-aligning and can remain constant while the configuration of the collection beamlets is changed. Thus, the simplified system can also have an adaptive interrogation spot pattern.

[0048] Compared to a dual telecentric system design, the simplified system provides a narrower and more limited field of view, which can result in interrogating beamlets (e.g. Figure 5C 567) do not all intersect the wafer surface orthogonally. Specifically, a central coaxial beamlet (e.g., beamlet 564) may intersect wafer 550 orthogonally, but peripheral beamlets (e.g., 561-563 and 565-567) may not intersect the wafer orthogonally. A narrower field of view may also manifest as intensity variation from beamlet to beamlet, with the highest intensity beamlets on-axis and lower intensity beamlets at the periphery. Variations in field of view and intensity limits can be accommodated to desired system performance by making design changes to at least the lens radius, working distance, source / signal / interrogation spot size, fiber diameter, and overall interrogation spot diameter.

[0049] One aspect to consider in multi-point systems is separating the source and signal sub-beams, taking into account that the imaging design naturally returns light to the same location. For example, in system 500, the source plane 510 and the signal plane 570 are conjugate and would overlap if not spatially separated using beam splitter 530. One option for multi-point optical systems that helps address the beam separation challenge is to use a multi-mode optical circulator.

[0050] Figure 7An example of a multi-mode optical circulator 700 that can be used with the multi-point optical systems disclosed herein, such as system 500, is described. For example, multiple multi-mode optical circulators 700 can be used in place of beam splitter 530, simplifying system integration and alignment of other components (e.g., beam stop 535, lens 537, and lens 539). Using circulator 700, components such as lenses 537 and 539 can be removed from the system and unused in certain system configurations. Multi-mode optical circulator 700 is a three-port device configured so that light travels in only one direction, and light entering any port exits the next port. Thus, light entering port 1 from a light source can be provided to the wafer via port 2, and light entering port 2 from the wafer can be provided to a spectrometer via port 3. Using FIG. 5 as an example, sub-beam 524 entering port 1 is provided as sub-beam 564 via port 2 to wafer 550, serving as an interrogation point, and reflected sub-beam 564 is then provided via port 2 to a spectrometer via port 3. Specifically, through the functionality of circulator 700, direct optical signal communication between port 1 (light source) and port 3 (optical signal) is avoided because any optical signal provided in this manner does not contain the desired information from the chip and is therefore considered an error or background signal. The individual ports of circulator 700 can be formed by multiple individual multimode optical fibers, and a single optical fiber can be connected to each port. Therefore, multimode optical circulator 700 can achieve the use of a single optical fiber on port 2 for both interrogating and collecting sub-beams. As with sub-beams 524, 564, and 584, multimode optical circulator 700 can be used for each of the corresponding multipoint sub-beam groups of system 500. For example, with respect to Figures 5A to 5D , seven circulators 700 can be used in place of beam splitter 530 and lenses 537 and 539. Each port 1 optical fiber can be coupled to a light source individually or using a unified optical connection (e.g., via source plane 510). The optical fibers of port 2 can be combined into a single optical terminal (e.g., an SMA terminal) and spatially arranged in a desired pattern to provide multiple interrogation spots in interrogation zone 555. Each of the optical fibers of port 3 can provide a unique channel to a multi-channel spectrometer (e.g., spectrometer 160) via fiber optic cable assembly 157. Additionally, an optical circulator (e.g., multimode optical circulator 700) can be used to configure source and receive fibers in pairs, for example, for beamlets 524 and 584. Multimode optical circulator 700 can be used with systems with, for example, 400 to 800 nm bandwidth or with wider bandwidth systems (e.g., 200 to 800 nm). To improve robustness, a BX jacket can be used with the optical fibers connected to multimode optical circulator 700. Optical subsystems employing circulators may include appropriately placed aperture stops to operate the optical system in a telecentric manner to improve source and signal level uniformity across multiple interrogation spots within the interrogation zone.

[0051] Figure 8An example of a target beam layout 800 on a wafer, such as wafer 550, is illustrated. The example target beam layout 800 includes four sub-beams 810, 820, 830, 840 provided to wafer 550. Each of the sub-beams 810, 820, 830, 840 may correspond to a Figure 1 1 and optical interface 140. In other words, the target beam layout 800 may represent a layout of four optical interfaces 140 and beams 155. Each of the individual beams on the wafer 550 is shown as a 1 mm circle, + / - 2 mm from the origin in the X and Y directions. The rectangular beam layout 800 may be used to replace Figures 5A to 5D As an example, beamlet 810 is shown within interrogation zone 555 of wafer 550 and will be described below. Figure 9 The discussion of FIG. 1 is used to illustrate another optical fiber and optical configuration that combines features of one or more previously discussed configurations.

[0052] Figure 9 An example paired fiber configuration 900 is illustrated for separating incoming and outgoing beamlets using defined fiber patterning (spatial mapping) and defocusing in accordance with the principles of the present disclosure. Figure 3 Similar to what is shown in , optical fibers can be used in pairs, but also similar to Figure 2 , the fiber pairs can be integrated into a common bundle of multiple fiber pairs. The fiber configuration 900 can be used with, for example Figure 2 The single lens of the lens 220 is used together and avoids the need for multiple lenses (such as Figure 3 320 to 323 or the beam splitter 530 of FIG5 ). Figure 2 As noted in the discussion of , the use of a single lens and randomized fiber pattern results in a lack of specific spatial information, however, by patterning the fibers in pairs and using defocusing of the optical system, specific spatial information can be at least partially received. In fiber layout 900, each fiber pair is labeled with a common letter, i.e., A / A is the first pair, B / B is the second pair, etc. Due to symmetry, identification of a specific receiving fiber or source fiber is not required, and they are generally interchangeable, but should be coordinated with an appropriately selected light source or spectrometer as needed. Each receiving and source fiber pair is radially displaced from the axis of symmetry of the optical system, which can be achieved by using lenses (e.g., Figure 2 The receiving and source fiber pair A / A may correspond to Figure 8 810, and additional fiber pairs (e.g., B / B, C / C, and D / D) correspond to sub-beams 820, 830, and 840. Fiber configuration 900 can be integrated into a single or multiple lens subsystem design including subsystems 200 and 300.

[0053] While fiber configuration 900 indicates specific fiber pairs and a specific arrangement and number of pairs, it should be understood that more or fewer pairs may be used, and that numerous other pairwise combinations may be defined and used. Additionally, as with the unlabeled center fiber, specific individual fibers within a fiber pair may not be used and are simply provided to provide the desired geometry. Furthermore, while fiber pairs are used herein as examples, it should be understood that more complex groupings are possible. For example, a three-lens pair A / D / I may be combined and used to define a larger interrogation spot. Figure 10A and 10B An example illustrating how defocus as a subsystem optimization parameter affects signal efficiency (IMAE parameter of Zemax modeling software) for a paired design used with a singlet lens. Figure 10A A defocus of 0.22 mm in the wavelength range of 400 to 800 nm was exhibited, resulting in an average value of approximately 0.08. Figure 10B It exhibits a defocus of -3.4 mm in the 240 to 340 nm wavelength range, with improved efficiency in a narrow range and a corresponding decrease in efficiency at other wavelengths.

[0054] Figure 11 is a block diagram of an optical system 1100 including a spectrometer 1110 and certain related systems according to one embodiment of the present disclosure. The spectrometer 1110 may incorporate the systems, features, and methods disclosed herein to facilitate measuring, characterizing, analyzing, and processing optical signals from semiconductor processes and may be used with Figure 1 Spectrometer 1110 may receive optical signals from external optical device 1130, for example, via fiber optic cable assembly 157 or 159, and may send the data to external system 1120, for example, after integration and conversion. Figure 1 The output 180 of the optical spectrum analyzer 1110 may also be used to control the spectrometer 1110 by, for example, selecting an operating mode or controlling the integration timing as defined herein. The spectrometer 1110 may include an optical interface 1140, such as a subminiature assembly (SMA) or ferrule connector (FC) fiber optic connector or other optomechanical interface. Further optical components 1145, such as slits, lenses, filters, and gratings, may be used to form, direct, and chromatically separate the received optical signals and direct them to the sensor 1150 for integration and conversion. The low-level functions of the sensor 1150 may be controlled by elements such as an FPGA 1160 and a processor 1170. After optical-to-electrical conversion, the analog signal may be directed to an A / D converter 1180 and converted from an electrical analog signal to an electrical digital signal, which may then be stored in a memory 1190 for immediate or later use and transmission, for example to an external system 1120 (see Figure 1 Although some interfaces and relationships are indicated by arrows, Figure 11Not all interactions and control relationships are indicated in FIG. For example, multiple sub-beams can be collected as disclosed herein for processing by, for example, appropriate adaptation of optical interface 1140 to include multiple individual input capabilities for each signal sub-beam. Thus, spectrometer 1100 can be configured (i.e., designed, constructed, or programmed with the logic and / or features necessary to perform one or more tasks) for processing multiple sub-beams. Spectrometer 1110 also includes a power supply 1195, which can be a conventional AC or DC power supply typically included in spectrometers.

[0055] Figure 12 A computing device 1200 is described that can be used for the processes disclosed herein, such as identifying and processing signals in spectral data. Computing device 1200 may be a spectrometer or a portion of a spectrometer, such as spectrometers 160 or 1110 disclosed herein. Computing device 1200 may include at least one interface 1232, memory 1234, and a processor 1236. Interface 1232 includes the necessary hardware, software, or a combination thereof for receiving, for example, raw spectral data and transmitting, for example, processed spectral data. A portion of interface 1232 may also include the necessary hardware, software, or a combination thereof for communicating analog or digital electrical signals. Interface 1232 may be a conventional interface that communicates via various communication systems, connections, buses, and the like according to a protocol, such as a standard protocol or a proprietary protocol (for example, interface 1232 may support I2C, USB, RS232, SPI, or MODBUS). Memory 1234 is configured to store various software and digital data aspects related to computing device 1200. In addition, the memory 1234 is configured to store a series of operating instructions corresponding to one or more algorithms that guide the operation of the processor 1236, which, when activated, processes, for example, a plurality of sub-beams collected as disclosed herein. The memory 1234 can be a non-transitory computer-readable medium (e.g., flash memory and / or other media).

[0056] The processor 1236 is configured to direct the operation of the computing device 1200. Thus, the processor 1236 includes the necessary logic for communicating with the interface 1232 and the memory 1234 and performing the functions described herein to identify and process a plurality of collected beamlets.

[0057] Figure 13 A flow chart illustrating a method 1300 for processing a semiconductor wafer according to the principles of the present disclosure is provided. The method 1300 may be implemented using, for example, a method described herein (e.g., in Figure 1 The method 1300 begins with step 1305.

[0058] In step 1310, a semiconductor wafer is held within a semiconductor processing chamber. The semiconductor processing chamber may be a typical chamber used to process semiconductor wafers, and the wafer may be held according to industry practices.

[0059] In step 1320, the wafer is illuminated with light provided by a light source via a plurality of first optical fibers. The first optical fibers can be, for example, source fibers disclosed herein. The light source can be, for example, a xenon flash lamp. A light guide can be used with the light source.

[0060] The wafer can be illuminated at various interrogation points. The interrogation points on the wafer can be arranged according to a predetermined pattern. The pattern can be, for example, a linear pattern, a circular pattern, a hexagonal pattern, or a rectangular pattern. Other two-dimensional patterns can also be used. The pattern can be defined based on the configuration of the supporting fiber optic cable assembly and can also be influenced by, for example, the features to be inspected or monitored on the wafer, engineering preferences, wafer design, or OEM requirements. The pattern can be selected based on a combination of these considerations. As described herein, the pattern can be adaptive.

[0061] In step 1330, light reflected from the wafer is collected via a plurality of second optical fibers. The second optical fibers may be receiving optical fibers and may be part of a fiber optic cable assembly connected to a spectrometer. For example, the plurality of second optical fibers may be optical fibers of fiber optic cable assembly 157.

[0062] The number of the plurality of second optical fibers may correspond to the number of individual optical inputs of the spectrometer, but is not determined by the number of individual optical inputs. For example, the number of the plurality of second optical fibers may be the same, greater, or less than the number of individual optical inputs of the multi-input spectrometer.

[0063] In step 1340, the collected light is processed. The collected light may be processed by a multi-input spectrometer for detection and conversion into a digital signal. The collected light from each of the plurality of second optical fibers may be provided to a unique input of the multi-input spectrometer for processing. For example, the light (or sub-beams) on each of the plurality of second optical fibers may be processed individually (or independently), in combination with at least one other (or less than all combinations), or all may be processed together.

[0064] The processing performed by the multi-input spectrometer can be based on combining information from the individually processed beamlets, such as averaging the output values. Various trends or different types of data can be extracted from processing the output values ​​of the processed beamlets. For example, a trend line can be determined for each of the beamlets.

[0065] In step 1350, one or more control trends are provided to the processing chamber for controlling the processing of the wafer in the processing chamber according to the process. In step 1360, the wafer can then be processed using the received control trends. Method 1300 continues to step 1370 and ends.

[0066] The optical measurement systems and subsystems described herein may be subjected to the above-described and other changes without departing from the scope thereof. For example, although certain examples are described in relation to semiconductor wafer processing equipment, it will be understood that the optical measurement systems described herein may be applicable to other types of processing equipment, such as roll-to-roll film processing, solar cell manufacturing, or any application in which high-precision optical measurements may be required. In addition, although certain embodiments discussed herein describe the use of common optical analysis devices, such as imaging spectrometers, it will be understood that multiple optical analysis devices with known relative sensitivities may be utilized. In addition, although the term "wafer" has been used herein when describing aspects of the invention, it will be understood that other types of workpieces may be used, such as quartz plates, phase shift masks, LED substrates, and other non-semiconductor processing related substrates and workpieces, including solid, gaseous, and liquid workpieces.

[0067] The embodiments described herein were chosen and described in order to best explain the principles of the invention and its practical application, and to enable others skilled in the art to understand the various embodiments of the invention and various modifications as are suitable for a particular intended use. The specific embodiments described herein are in no way intended to limit the scope of the invention, as the invention can be practiced in a variety of variations and environments without departing from the scope and intent of the invention. Therefore, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features described herein.

[0068] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or combinations thereof.

[0069] As will be appreciated by those skilled in the art, portions disclosed herein may be embodied as methods, systems, or computer program products. Thus, the disclosed portions may take the form of entirely hardware embodiments, entirely software embodiments (including firmware, resident software, microcode, etc.), or embodiments combining software and hardware aspects, all collectively referred to herein as "circuits" or "modules." Each of the example independent technical solutions of the present disclosure may include, in combination, one or more of the following elements.

[0070] Element 1: wherein the optical system further comprises a light pipe proximate to the source plane. Element 2: wherein the predetermined pattern of interrogation light spots is adaptable. Element 3: wherein the plurality of first sub-beams comprises between 2 and 10 sub-beams. Element 4: wherein each of the plurality of second sub-beams is independently collected and processed. Element 5: wherein the optical element comprises at least one of a lens, a beam splitter, a beam stop, and an optical circulator. Element 6: wherein the pattern of interrogation light spots is one of a linear pattern, a circular pattern, a hexagonal pattern, or a rectangular pattern. Element 7: wherein the light source provides source light to the source plane via fiber optics, and each of the plurality of first sub-beams is defined by a separate optical fiber. Element 8: wherein the spectrometer is configured to receive collected light from the image plane via fiber optics, and each of the plurality of second sub-beams is defined by a separate optical fiber. Element 9: wherein the individual optical fibers defining the plurality of first sub-beams and the individual optical fibers defining the plurality of second sub-beams are paired radially symmetric with respect to an axis of the optical system. Element 10: wherein the paired arrangement of the plurality of first and second optical fibers is configured as a plurality of optical circulators. Element 11: It further includes a light pipe proximate to the light source and the plurality of first optical fibers. Element 12: The plurality of interrogation light spots includes between 2 and 10 interrogation light spots. Element 13: The spectrometer individually processes the collected light from the plurality of second optical fibers. Element 14: The pattern of interrogation light spots is one of a linear pattern, a circular pattern, a hexagonal pattern, or a rectangular pattern. Element 15: It further includes defining the plurality of interrogation light spots on the semiconductor wafer according to a predetermined pattern. Element 16: The predetermined pattern is selected based on features to be monitored on the semiconductor wafer. Element 17: Processing the collected light to provide one or more control trends for controlling processing of the wafer includes combining collected light from a plurality of the plurality of second optical fibers.

Claims

1. An optical system comprising: a light source configured to provide source light to a source plane to form a plurality of first sub-beams; an optical element configured to modify each of the plurality of first beamlets according to a predetermined pattern to form a plurality of interrogation spots on a wafer, the optical element further configured to modify each of the plurality of first beamlets after reflection from the wafer to form a plurality of second beamlets on an image plane; and A spectrometer is configured to receive the collected light from the plurality of second sub-beams.

2. The optical system of claim 1, wherein the optical system further comprises a light pipe proximate to the source plane.

3. The optical system of claim 2, wherein the predetermined pattern of interrogation spots is adaptable. The optical system of claim 1 , wherein the plurality of first beamlets comprises between 2 and 10 beamlets. The optical system of claim 1 , wherein each of the plurality of second sub-beams is collected and processed independently.

6. The optical system of claim 1, wherein the optical element comprises at least one of a lens, a beam splitter, a beam stop, and an optical circulator.

7. The optical system of claim 1, wherein the pattern of the interrogating light spots is one of a linear pattern, a circular pattern, a hexagonal pattern, or a rectangular pattern.

8. The optical system of claim 1, wherein the light source provides the source light to the source plane in an optical fiber manner, and each of the plurality of first sub-beams is defined by a respective optical fiber.

9. The optical system of claim 8, wherein the spectrometer is configured to receive the collected light from the image plane fiber-optically, and each of the plurality of second beamlets is defined by a respective optical fiber.

10. The optical system of claim 9, wherein the individual optical fibers defining the plurality of first sub-beams and the individual optical fibers defining the plurality of second sub-beams are radially symmetric in pairs relative to an axis of the optical system.

11. A semiconductor processing system comprising: a processing chamber; a light source configured to provide source light to the plurality of first optical fibers; a spectrometer configured to receive the collected light from the plurality of second optical fibers; and An interrogation zone includes a plurality of interrogation light spots on a wafer within the processing chamber, wherein each of the plurality of interrogation light spots is defined by a paired arrangement of the plurality of first and second optical fibers.

12. The semiconductor processing system of claim 11, wherein the paired arrangement of the plurality of first and second optical fibers is configured as a plurality of optical circulators.

13. The semiconductor processing system of claim 11, further comprising a light pipe proximate to the light source and the plurality of first optical fibers.

14. The semiconductor processing system of claim 11, wherein the plurality of interrogation spots comprises between 2 and 10 interrogation spots.

15. The semiconductor processing system of claim 11, wherein the spectrometer individually processes the collected light from the plurality of second optical fibers.

16. The semiconductor processing system of claim 11, wherein the pattern of the interrogation spots is one of a linear pattern, a circular pattern, a hexagonal pattern, or a rectangular pattern.

17. A method for processing a semiconductor wafer, comprising: illuminating a wafer within a semiconductor processing chamber with light provided by a light source via a plurality of first optical fibers; collecting the light reflected from the wafer via a plurality of second optical fibers; processing the collected light using a multi-input spectrometer; and One or more control trends are provided based on the processing for controlling the processing of the wafer.

18. The method for processing a semiconductor wafer according to claim 17, further comprising defining a plurality of interrogation spots on the semiconductor wafer according to a predetermined pattern.

19. The method for processing a semiconductor wafer according to claim 18, wherein the predetermined pattern is selected according to features to be monitored on the semiconductor wafer.

20. The method for processing a semiconductor wafer of claim 17, wherein said processing said collected light to provide one or more control trends for controlling said processing of said wafer comprises combining collected light from a plurality of said plurality of second optical fibers.

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