Metering integrated with vacuum processing

Abstract

A system includes a vacuum chamber having a wafer chuck therein and a side window inclined relative to the wafer chuck. A wafer stage is positioned below the wafer chuck, the wafer stage being configured to rotate the wafer chuck and to move the wafer chuck vertically. Comprising an illumination correction lens is configured to receive the light and direct the light through an illumination vacuum window in the side window to form a light spot on the wafer. Comprising a collection correction lens is configured to receive light from the light spot through a collection vacuum window in the side window and direct the light to the detector. The transfer module is configured to move the illumination optics and the collection optics parallel to the illumination vacuum window and the collection vacuum window, respectively. The illumination correction lens and the collection correction lens are configured to reduce chromatic aberration.

Description

Cross-references to metrology-related patents and applications integrated with vacuum processing

[0001] This application claims priority and benefit to U.S. non-provisional patent application No. 18 / 478,946, filed on September 29, 2023, which is incorporated herein by reference in its entirety. Technical Field

[0002] This disclosure relates generally to semiconductor processing, and more specifically to wafer characterization and a system configured to perform wafer metrology. Background Technology

[0003] In the fabrication of semiconductor devices (especially at the microscale), various manufacturing processes are performed, such as film deposition, etch mask creation, patterning, material etching and removal, and doping. These processes are repeated to form the desired semiconductor device elements on a substrate, and are typically performed in a vacuum environment. Summary of the Invention

[0004] This disclosure relates to a method for wafer characterization and a system configured to characterize a wafer.

[0005] According to a first aspect of this disclosure, a system is provided. The system includes a vacuum chamber having a wafer chuck within the vacuum chamber and a side window tilted relative to the wafer chuck. The wafer chuck is configured to receive a wafer. The system also includes a wafer stage positioned below and mechanically coupled to the wafer chuck. The wafer stage is configured to rotate the wafer chuck and move it in a vertical direction substantially perpendicular to the wafer chuck. The system further includes illumination optics configured to receive light from a light source and guide the light through an illumination vacuum window in the side window to form a light spot on the wafer. The illumination optics include an illumination correction lens. The system further includes a collection optics configured to receive light from the light spot through a collection vacuum window in the side window and guide the light to a detector. The collection optics include a collection correction lens. The system further includes a transfer module configured to move the illumination optics and the collection optics parallel to the illumination vacuum window and the collection vacuum window, respectively. The illumination correction lens and the collection correction lens are configured to reduce optical aberrations.

[0006] In some embodiments, the wafer stage is located outside the vacuum chamber.

[0007] In some embodiments, the system further includes a journal bearing that mechanically connects the wafer stage to the wafer chuck and, in the case of a vacuum seal, extends through the bottom portion of the vacuum chamber.

[0008] In some embodiments, the wafer stage is located inside a vacuum chamber.

[0009] In some embodiments, the wafer stage is configured to rotate the wafer chuck and move the wafer chuck in the vertical direction, without moving the wafer in the horizontal direction parallel to the wafer chuck.

[0010] In some embodiments, the irradiation optics and the collection optics are mounted on a transfer module configured to move the irradiation optics and the collection optics simultaneously.

[0011] In some embodiments, the light source and detector are mounted on a transfer module configured to move the light source, detector, illumination optics and collection optics simultaneously.

[0012] In some embodiments, the light source and detector are separate from the transfer module and are configured to remain stationary when the transfer module moves the irradiating optics and the collecting optics.

[0013] In some embodiments, the optics are illuminated and collected outside the vacuum chamber.

[0014] In some embodiments, the illumination correction lens and the collection correction lens are spaced apart from the vacuum chamber.

[0015] In some embodiments, the illumination optics further include a polarizer and an optical objective selected from a group consisting of a single aspherical mirror and a pair of off-axis spherical mirrors.

[0016] In some embodiments, the transfer module is configured to move the light spot at least between the edge of the wafer and the center of the wafer.

[0017] In some embodiments, the system further includes a controller configured to adjust the relative position of the light spot on the wafer by rotating the wafer via a wafer stage, moving the light spot via a transfer module, or a combination of both.

[0018] In some embodiments, the transfer module includes a stage on which illumination optics and collection optics are mounted, and the stage is configured to move in a longitudinal direction parallel to the side window.

[0019] In some embodiments, the side window is substantially perpendicular to the optical path of light and is substantially transparent to light.

[0020] In some embodiments, the detector may be a spectrometer.

[0021] In some embodiments, the detector, illumination optics, and collection optics are configured as an ellipsometer.

[0022] In some embodiments, the ellipsometer is configured as a spectroscopic ellipsometer with a rotating polarizer.

[0023] In some embodiments, the system further includes a processing chamber connected to a vacuum chamber and configured to perform surface treatment on the wafer in a vacuum.

[0024] According to a second aspect of this disclosure, a method for wafer characterization is provided. The method includes guiding light through an illumination optics and an illumination vacuum window of a vacuum chamber to form a light spot on a wafer placed on a wafer chuck in a vacuum chamber. The illumination optics include an illumination correction lens. The illumination vacuum window is tilted relative to the wafer chuck. The method further includes detecting light from the light spot passing through a collection optics and a collection vacuum window of the vacuum chamber. The collection optics include a collection correction lens. The collection vacuum window is tilted relative to the wafer chuck. The method further includes adjusting the relative position of the light spot on the wafer by rotating the wafer via a wafer stage, moving the light spot via a transfer module, or a combination of both. The illumination correction lens and the collection correction lens are configured to reduce optical aberrations, including chromatic aberration and monochromatic aberrations such as astigmatism, coma, distortion, field curvature, spherical aberration, etc. The wafer stage is positioned below and mechanically coupled to the wafer chuck and is configured to rotate the wafer chuck. The transfer module is configured to move the irradiation optics and the collection optics parallel to the irradiation vacuum window and the collection vacuum window, respectively.

[0025] In some embodiments, the wafer stage, illumination optics, and collection optics are located outside the vacuum chamber.

[0026] In some embodiments, the wafer stage and wafer chuck are mechanically connected via journal bearings that, when equipped with vacuum seals, extend through the bottom portion of the vacuum chamber.

[0027] It should be noted that the Summary of this Invention does not specify every embodiment and / or additional novel aspect of the invention disclosed or claimed herein. Rather, the Summary provides only a preliminary discussion of different embodiments and corresponding points of novelty. For additional details and / or possible perspectives on the invention and embodiments, the reader is directed to the Detailed Description of this Disclosure and the corresponding drawings, which are discussed further below. Attached Figure Description

[0028] A better understanding of the various aspects of this disclosure will be achieved by reading the following detailed description in conjunction with the accompanying drawings. It should be noted that, in accordance with standard industry practice, the various features are not drawn to scale. In fact, for clarity of discussion, the dimensions of the various features may be increased or decreased.

[0029] Figures 1A and 1B show perspective views of a system according to some embodiments of this disclosure.

[0030] Figure 2 illustrates a schematic optical path of a system according to some embodiments of this disclosure.

[0031] Figure 3 shows a perspective view of a system according to some embodiments of this disclosure.

[0032] Figure 4 shows a flowchart of a method for characterizing a wafer according to some embodiments of this disclosure. Detailed Implementation

[0033] The following disclosure provides numerous different embodiments or examples for implementing various features of the provided subject matter. Specific examples of components and arrangements are described below to simplify this disclosure. Of course, these are merely examples and are not intended to be limiting. For example, forming a first feature on or on a second feature in the following description may include embodiments where the first and second features are in direct contact, and may also include embodiments where additional features may be formed between the first and second features, such that the first and second features are not in direct contact. Furthermore, reference numerals and / or letters may be repeated in various examples in this disclosure. Such repetition is for simplicity and clarity and does not in itself define the relationship between the various embodiments and / or configurations discussed. Further, for ease of description, spatial relative terms such as “top,” “bottom,” “below,” “under,” “lower,” “above,” “upper,” etc., may be used herein to describe the relationship between one element or feature as shown in the figures and another element or feature. In addition to the orientations depicted in the figures, spatial relative terms are intended to encompass different orientations of the device during use or operation. The device may be oriented in other ways (rotated 90 degrees or in other orientations), and therefore the spatial relative descriptors used herein may also be interpreted accordingly.

[0034] For clarity, the order of discussion of the different steps described herein has been presented. In general, these steps can be performed in any suitable order. Additionally, although each of the different features, techniques, configurations, etc., herein may be discussed in different places within this disclosure, it is intended that each of the concepts can be performed independently of or in combination with each other. Therefore, the invention can be embodied and viewed in many different ways.

[0035] In the accompanying drawings, similar reference numerals refer to the same or corresponding parts in all these views. Additionally, as used herein, unless otherwise stated, the words "a / an" etc. generally carry the meaning of "one or more".

[0036] In addition, the terms “approximately,” “about,” “about,” and similar terms generally refer to a range of identified values ​​that include a margin of 20%, 10%, or preferably 5%, as well as any values ​​in between.

[0037] There is an unmet need for a highly sensitive metrology solution in a vacuum environment for measuring thin films and patterned structures on semiconductor wafers during or after deposition, etching, and other semiconductor processes. For example, when depositing multiple films, it may be necessary to perform metrology measurements between deposition processes without disrupting the vacuum. Alternatively, during the deposition or etching of a single layer film, it may be desirable to monitor or verify film thickness or semiconductor structure parameters to precisely control the process endpoint. However, removing the wafer from the vacuum environment can lead to rapid oxidation or contamination of the unprotected film in air and is also time-consuming. Furthermore, switching back and forth between different environments can alter the wafer temperature.

[0038] At the same time, new semiconductor nodes present new challenges for metrology. As film thicknesses shrink to the nanometer or even angstrom level, the requirements for metrological sensitivity become increasingly stringent. For example, it may be necessary to measure nanometer-thick films with sub-angstrom sensitivity. These requirements necessitate certain capabilities (if achievable) that were previously limited to stand-alone metrological tools, such as large angle of incidence (AOI) optical spectroscopic ellipsometers or similar configurations, capable of measuring the polarization characteristics of samples.

[0039] The techniques described in this article include optical devices with large incident angles (e.g., AOI > 60 degrees) capable of wide-band (e.g., 200–800 nm) elliptically polarized measurements of thin films and semiconductor structures in a vacuum. This could be particularly useful, for example, for controlling deposition processes where sub-angstrom-level sensitivity is required to measure 10 nm thick TiN, SiN, or SiO2 films on Si substrates.

[0040] According to some aspects of this disclosure, the metrology subsystem of the processing tool may include a vacuum chamber having a chuck for holding the wafer on a rotating stage. Optical sensors may include a broadband irradiator and irradiation and collection optics, allowing light to be sent into the vacuum chamber and onto a wafer sample, then specular reflections from the wafer sample are collected and analyzed using a spectral sensor, such as a spectrometer. The vacuum chamber may have a window that is substantially transparent to incident and reflected light within a desired wavelength range. The window is mounted substantially perpendicular to the respective paths of the irradiation and collection beams. In some embodiments, a compact broadband irradiation source, irradiation optics, collection optics, and spectral detector are configured in a single compact assembly. This assembly may be mounted on a linear stage that allows the entire optics assembly to be transferred parallel to the window over a range slightly larger than the wafer radius, and allows the optics to sample wafer positions from center to edge. Combined with the rotating stage for the chuck and wafer, the linear stage for the optics provides the ability to measure any and all desired locations on the wafer.

[0041] Figures 1A and 1B show perspective views of a system 100 according to some embodiments of the present disclosure, and Figure 2 shows a schematic optical path 200 of the system 100 according to some embodiments of the present disclosure.

[0042] As shown, system 100 includes a vacuum chamber 110 in which a wafer chuck 111 is disposed and side windows 113 (e.g., 113A and 113B) are inclined relative to the wafer chuck 111. System 100 also includes a wafer stage 120 positioned below and mechanically coupled to the wafer chuck 111. Wafer stage 120 is configured to rotate and / or move the wafer chuck 111 in the Z direction as needed. System 100 further includes an optical subsystem having, for example, an illumination optics 130 and a collection optics 140. Illumination optics 130 is configured to receive light from a light source 103 and guide the light through an illumination vacuum window 113A in the side window 113 to form a light spot 107 on the wafer 101. The collecting optics 140 is configured to receive light from the light spot 107 through the collecting vacuum window 113B in the side window 113 and guide the light to the detector 105. The system 100 further includes a transfer module 150 configured to move the illumination optics 130 and the collecting optics 140 parallel to the illumination vacuum window 113A and the collecting vacuum window 113B, respectively.

[0043] In some embodiments, a wafer chuck 111 in the vacuum chamber 110 may be configured to receive a wafer 101. The wafer chuck 111 may include an electrostatic adsorption and edge-holding chuck capable of holding the semiconductor wafer in a vacuum, for example, during chuck rotation. The vacuum chamber 110 may include a mechanical housing having one or more (e.g., two) openings, allowing the wafer 101 to be loaded and unloaded from one or more (e.g., both) sides of the vacuum chamber 110. For example, the wafer 101 may be loaded from one side of the vacuum chamber 110, measured, and then removed from the opposite side of the vacuum chamber. Therefore, additional functionality can be performed by a wafer transfer station.

[0044] Although not shown, it should be understood that the vacuum chamber 110 may include a wafer lifting mechanism configured to: lift the wafer 101 from the wafer chuck 111, for example by using a lifting pin or edge clamping mechanism, so that a wafer manipulator / fork can move into the vacuum chamber 110 and place the wafer 101 on the wafer lifting mechanism, to further place the wafer 101 on the wafer chuck 111; or remove the wafer 101 from the wafer lifting mechanism and remove it from the vacuum chamber 110.

[0045] The side windows 113 of the vacuum chamber 110 may include optically transparent windows configured to allow illumination light from the optical subsystem to enter the vacuum chamber 110 and to allow reflected or scattered light to exit the vacuum chamber 110 for further detection and analysis. Identical, similar, or additional optically transparent windows (e.g., 115) may be used for wafer-guided cameras and sensors (e.g., 108). For example, the X-stage 108 may be configured to allow light to pass through the top window 115 of the vacuum chamber 110 at approximately 1... The wafer position of the wafer 101 inside the vacuum chamber 110 is measured with an accuracy of m or less. Such optical windows (e.g., 113 and 115) can be designed to correct for chromatic aberration and other optical aberrations and allow for simultaneous measurements over a wide wavelength range.

[0046] Because the side windows 113 of the vacuum chamber 110 are inclined relative to the wafer chuck 111, the vacuum chamber 110 can have a trapezoidal cross-section in the XZ plane. Each of the side windows can independently form an acute angle with the wafer chuck 111 (e.g., 1°, 5°, 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80°, 85°, 89°, or any value between these values). The acute angle is preferably in the range of 30° to 60°, preferably 35° to 55°, preferably 40° to 50°, and preferably about 45°.

[0047] In some embodiments, the wafer stage 120 may be configured to rotate and / or move the wafer 101 in the Z direction as needed. The wafer stage 120 may include a Z-stage 121 and a T-stage 123. The Z-stage 121 may be mechanically connected to the T-stage 123. The Z-stage 121 is configured to move the wafer 101 in the Z direction. The T-stage 123 is configured to rotate the wafer 101 via a rotary connector 127 and may include a rotational mechanism capable of rotating the wafer 101 at a 20° angle. A high-precision rotary stage for positioning wafer 101 is used with an accuracy of rad or less. A rotary connector 127 can be connected to the electrostatic chuck wires. That is, the rotary connector 127 can connect to and supply power to the (rotating) wafer chuck 111, while the other end of the rotary connector 127 is fixed.

[0048] Additionally, system 100 may include a journal bearing 125 that mechanically connects wafer stage 120 to wafer chuck 111 and, with the aid of a vacuum seal or other sub-assembly, extends through the bottom portion 117 of vacuum chamber 110. This vacuum seal or other sub-assembly allows the rotating stage, outside the vacuum environment, to be rigidly connected to the wafer chuck 111, inside the vacuum environment and outside the vacuum environment, without disrupting the vacuum, even during stage and chuck rotation. Therefore, vacuum chamber 110 can be maintained at a vacuum pressure when the Z stage 121 moves wafer 101 in the Z direction and / or when the T stage 123 rotates wafer 101.

[0049] In the example of Figure 1B, the wafer stage 120 is outside the vacuum chamber 110 and connected to the wafer chuck 111 via a journal bearing 125. In another example (not shown for simplicity), the wafer stage 120 can be mounted inside the vacuum chamber 110, eliminating the need for the journal bearing 125. That is, the vacuum chamber 110 can be enlarged to include components in region 129 other than the journal bearing 125 (e.g., the Z-stage 121, T-stage 123, and rotary connector 127). Accordingly, the bottom portion 117 of the vacuum chamber 110 is not penetrated but is instead positioned below the Z-stage 121, T-stage 123, and rotary connector 127.

[0050] In some embodiments, the optical subsystem may include a light source 103 configured to emit light (indicated by dashed lines in Figures 1A and 1B; and by dashed and solid lines in Figure 2) and a detector 105 configured to detect reflected and / or scattered light. As previously mentioned, illumination optics 130 is configured to receive light from the light source 103 and guide the light to a light spot 107 on the wafer 101 through illumination vacuum window 113A, while collection optics 140 is configured to receive light from the light spot 107 through collection vacuum window 113B and guide the light to detector 105. Additionally, the optical subsystem is configured such that the side window 113 is substantially perpendicular to the optical path of the light and substantially transparent to light.

[0051] Light source 103 may include a single, multi-wavelength, or broadband illumination source. In a preferred embodiment, light source 103 may provide sufficient radiation in a wavelength range from approximately 200 nm to approximately 800 nm, including the entire visible spectrum in addition to some ultraviolet and infrared radiation. In a non-limiting embodiment, light source 103 may be a compact laser-driven light source (LDLS) directly coupled to illumination optics 130. Alternatively, illumination light may be transmitted via one or more optical fibers.

[0052] Illumination optics 130 may include illumination polarization optics 131. In a preferred embodiment, a Rochon prism linear polarizer (e.g., 131) may be mounted inside the shaft of a high-precision motor, such that all illumination light passes through the Rochon prism linear polarizer and is split into two orthogonal polarizations. One of these two orthogonal polarizations is blocked, while the other is transmitted, thereby producing linearly polarized illumination light that rotates over time. Alternatively, a polarizer and compensator configuration may be used to produce circular polarization, and the polarization of the illumination light may be controlled and changed over time in other ways. Illumination optics 130 may optionally include a reflector 132, as illustrated in the example of FIG1B.

[0053] The illumination optics 130 may further include a long-working-distance illumination optics 133, which operates substantially through a vacuum window (e.g., 113A) to illuminate a sample on a wafer 101 inside the vacuum chamber 110 and produce a sample on the wafer 101 with a size of 5 to 100. Within the range of m (e.g., 5) m, 10 m, 20 m, 30 m, 40 m, 50 m, 60 m, 70 m, 80 m, 90 m, 100 A small spot of light (e.g., 107) of m and any value therein. The long working distance illumination optics 133 can be substantially reflective and include an optical objective consisting of a pair of off-axis spherical mirrors or a single aspherical mirror.

[0054] The illumination optics 130 may further include an illumination correction lens 135 disposed between an optical objective (e.g., 133) and a vacuum window (e.g., 113A). The illumination correction lens 135 is configured to reduce chromatic aberration, compensate for distortions (e.g., caused by the illumination vacuum window 113A), reduce the size of the light spot 107, and make the illumination optics 130 more compact than it would be without the illumination correction lens 135.

[0055] Additionally, the illumination vacuum window 113A itself can perform chromaticity correction or other optical aberration correction, thereby reducing the wavelength dependence of the optical illumination point (e.g., 107) and enabling the use of a substantially wide-band light source (e.g., 200 nm to 800 nm or greater), while reducing the overall system size to meet system footprint requirements. Alternatively, the illumination optics 130 can be configured such that its entire illumination path can perform chromaticity correction to support the use of a substantially wide-band light source (e.g., 200 nm to 800 nm or greater). Furthermore, the collection vacuum window 113B can be configured to have similar characteristics to the illumination vacuum window 113A.

[0056] Referring again to Figures 1A, 1B, and 2, the collecting optics 140 may include a collecting correction lens 145 positioned between the collecting vacuum window 113B and the collecting objective (e.g., 143). The collecting correction lens 145 is configured to reduce chromatic aberration, compensate for distortions (e.g., caused by the collecting vacuum window 113B), reduce the size of the light spot 107, and make the collecting optics 140 more compact than it would be without the collecting correction lens 145.

[0057] The collecting optics 140 may also include a long-working-distance collecting optics 143 that operates substantially through a vacuum window (e.g., 113B) to collect light reflected and / or scattered by the sample (e.g., wafer 101) and project the light into a spectroscopic detector (e.g., 105). The collecting optical path of the collecting optics 140 may be substantially reflective and includes an optical objective (e.g., 143) consisting of a pair of off-axis spherical mirrors or a single aspherical mirror. It should be noted that when a pair of off-axis spherical mirrors is included, the illuminating objective (e.g., 133) and the collecting objective (e.g., 143) may be oriented substantially 90 degrees relative to each other (as observed along the optical path, e.g., the principal ray) for polarization correction purposes.

[0058] The collecting optics 140 may further include a collecting polarization optics 141, which may be similar to the illuminating polarization optics 131. Thus, as described above, and for the sake of brevity, these descriptions will be omitted herein. In a preferred embodiment, the polarization configuration is fixed, and the illuminating polarization varies over time. Alternatively, the illuminating polarization is fixed, while the collecting polarization varies over time.

[0059] In some embodiments, detector 105 is a directly coupled spectrometer capable of analyzing multiple wavelengths in the range of approximately 200 nm to 800 nm. The spectrometer acquisition operation will also be synchronized with changes in the polarization configuration of system 100 (e.g., a rotating polarizer on the illumination side). Alternatively, detector 105 may be configured to analyze a single wavelength.

[0060] It should be noted that the optical module, or more precisely, the detector 105, may include one or more measurement channels (or multiple detectors), including any combination of the following: an oblique incidence ellipsometry, a near-normal incidence (e.g., incident angle < 20°) polarized or non-polarized reflectometer, a channel of a pattern recognition imaging camera for wafer navigation and surface defect detection, a channel for non-specular reflection measurements, etc. The aforementioned measurement channels may have co-located or closely spaced measurement illumination points.

[0061] In some embodiments, system 100 includes an autofocus sensing subsystem that may substantially share a main optical path originating from light source 103, reaching wafer 101, and then passing through a collection objective (e.g., 143) and reaching a beam splitter 149, where a portion of the collected light can be directed to a (dedicated) autofocus sensor 106. Alternatively, the autofocus sensing subsystem may utilize a completely independent illuminator and optical path. This autofocus sensing subsystem may operate in conjunction with a Z-stage subsystem (e.g., 121) that allows wafer 101 to move up and down relative to the optical subsystem within a vacuum, while the Z-stage 121 itself may be positioned outside the vacuum environment and uses journal bearings 125 and vacuum seals to move a wafer chuck 111 carrying wafer 101 within the vacuum environment. The Z-stage 121 may be mechanically connected to a T-stage 123, both located outside the vacuum environment, with the T-stage 123 positioned on top of the Z-stage 121. The T-stage 123 can be mechanically connected to the journal bearing 125 and the wafer chuck 111 inside the vacuum environment.

[0062] As previously mentioned, the transfer module 150 is configured to move the illumination optics 130 and the collection optics 140 parallel to the illumination vacuum window 113A and the collection vacuum window 113B, respectively. In this document, the transfer module 150 may include a common stage with a movement transfer function, on which the complete optical module is mounted. That is, the optical subsystem including the light source 103, detector 105, illumination optics 130, and collection optics 140 can be mounted on the transfer module 150, such that the transfer module 150 is configured to move the light source 103, detector 105, illumination optics 130, and collection optics 140 simultaneously or individually. It should be noted that only a portion of the common stage is shown herein for clarity of other components. Additionally, the illumination correction lens 135, the collection correction lens 145, and the transfer stage 150 may be spaced apart from the vacuum chamber 110. For example, the illumination optics 130 and collection optics 140 and / or the transfer module 150 may be mounted on a frame 109 without contacting the vacuum chamber 110. Off-axis lenses (e.g., 133 and 143), illumination correction lens 135, and collection correction lens 145 can be rigidly attached to their respective objective housings and together form a respective objective assembly, which can be suspended on one or more rails of the frame 109.

[0063] In some embodiments, the travel range of the transfer module 150 may be substantially similar to or slightly larger than the wafer radius, such that, in conjunction with the wafer rotational motion on the rotating stage (e.g., 123), the integrated metrology module (e.g., 100) can measure any location on the wafer 101. In other words, the transfer module 150 can be configured to move the light spot 107 at least between the edge and center of the wafer 101, for example, back and forth along a straight path along the longitudinal direction (e.g., the Y direction) of the side window 113. Simultaneously, the wafer stage 120 can rotate the wafer 101 about its center. Therefore, the light irradiation point or light spot 107 can reach all locations on the wafer 101.

[0064] In some embodiments, system 100 may optionally include controller 160. Other components of system 100 may be connected to and controlled by controller 160, which may optionally be connected to corresponding memory storage units and user interfaces (both not shown). Various characterization operations may be performed via the user interface and stored in the memory units. Accordingly, wafer 101 may be characterized using various elliptic polarization techniques and models.

[0065] In a non-limiting example, controller 160 is coupled to wafer stage 120 and transfer module 150. Therefore, controller 160 is configured to adjust the relative position of spot 107 on wafer 101 by rotating wafer 101 via wafer stage 120, moving spot 107 via transfer module 150, or a combination of both. Controller 160 may be further coupled to autofocus sensor 106 to perform an autofocus process.

[0066] It will be appreciated that the controller 160 can be coupled to various components of the system 100 to receive inputs from and provide outputs to these components. For example, the controller 160 can be configured to receive data from the detector 105. The controller 160 can also be configured to adjust knobs and control settings for the light source 103, detector 105, wafer stage 120, illumination optics 130, collection optics 140, and / or transfer module 150. Of course, these adjustments can also be made manually.

[0067] Controller 160 can be implemented in a variety of ways. In one example, controller 160 is a computer. In another example, controller 160 includes one or more programmable integrated circuits programmed to provide the functions described herein. For example, one or more processors (e.g., microprocessors, microcontrollers, central processing units, etc.), programmable logic devices (e.g., complex programmable logic devices (CPLDs), field-programmable gate arrays (FPGAs), etc.), and / or other programmable integrated circuits can be programmed using software or other programming instructions to implement the functions of prohibited plasma process schemes. It should be further noted that the software or other programming instructions can be stored in one or more non-transitory computer-readable media (e.g., memory storage devices, flash memory, DRAM memory, reprogrammable storage devices, hard disk drives, floppy disks, DVDs, CD-ROMs, etc.), and the software or other programming instructions, when executed by the programmable integrated circuit, cause the programmable integrated circuit to perform the processes, functions, and / or capabilities described herein. Other variations can also be implemented.

[0068] Referring again to Figures 1A, 1B, and 2, it should be understood that not all of the components described above are necessary for system 100. Depending on specific needs, system 100 may include some or all of the aforementioned components. For example, system 100 may include vacuum chamber 110, wafer stage 120, illumination optics 130, collection optics 140, and transfer module 150, but not light source 103 and / or detector 105. The user can then add light source 103, detector 105, and / or controller 160 after building or purchasing system 100.

[0069] Figure 3 shows a perspective view of a system 300 according to some embodiments of the present disclosure. As shown, the system 300 includes a vacuum chamber 110 having a side window 113. The system 300 may also include a wafer chuck (e.g., 111) and a wafer stage (e.g., 120), which are not shown herein for simplicity.

[0070] System 300 may further include an optical subsystem having, for example, an illumination optics 230 and a collection optics 240. The illumination optics 230 is configured to receive light from the light source 103 and guide the light through an illumination vacuum window 113A in a side window 113 to form a light spot 107 on the wafer 101. The collection optics 240 is configured to receive light from the light spot 107 through a collection vacuum window (e.g., 113B; not shown) in the side window 113 and guide the light to a detector 105.

[0071] Specifically, the illumination optics 230 may include a reflector 231 and an optical component 233 corresponding to the long-working-distance illumination optics 133. Similarly, the collection optics 240 may include a reflector 241 and an optical component 243 corresponding to the long-working-distance collection optics 143. Although not shown, it should be understood that the system 300 may include correction lenses corresponding to the illumination correction lens 135 and the collection correction lens 145.

[0072] System 300 may further include a transfer module 250 configured to move the illumination optics 230 and the collection optics 240 parallel to the illumination vacuum window 113A and the collection vacuum window, respectively. It should be noted that the light source 103 and / or detector 105 are separate from the transfer module 250 and may be fixedly attached to a frame (e.g., rack 109 in Figures 1A and 1B) or stage. In contrast, the illumination optics 230 and the collection optics 240 may be mounted on a stage of the transfer module 250, which is configured to move parallel to the longitudinal direction (e.g., the Y direction) of the side window 113.

[0073] System 300 may further include a controller 160 coupled to a wafer stage (e.g., 120; not shown) and a transfer module 250. Thus, controller 160 is configured to adjust the relative position of the light spot 107 on wafer 101 by rotating wafer 101 via wafer stage (e.g., 120), moving light spot 107 via transfer module 250, or a combination of both.

[0074] In some embodiments, system 300 may further include at least one processing chamber 170 connected to vacuum chamber 110 and configured to perform surface treatment on wafer 101 in a vacuum. Accordingly, vacuum chamber 110 includes one or more openings 119 (e.g., gates, inlets, outlets, etc.) for transferring wafer 101 between vacuum chamber 110 and at least one processing chamber 170 under vacuum conditions (i.e., without disrupting the vacuum during transfer). At least one processing chamber 170 may perform surface treatments including, but not limited to, film deposition, etching, photolithographic patterning, doping, cleaning, heating, etc. Although not shown in Figures 1A and 1B for simplicity, it should be understood that system 100 may also include at least one processing chamber 170 connected to vacuum chamber 110 and configured to perform surface treatment on wafer 101 in a vacuum.

[0075] In a non-limiting example, at least one processing chamber 170 includes a plasma processing chamber. At least one processing chamber 170 can be a capacitively coupled plasma processing chamber, an inductively coupled plasma processing chamber, a microwave plasma processing chamber, or a radial line slot antenna (RLSA). TM This includes microwave plasma processing chambers, electron cyclotron resonance (ECR) plasma processing chambers, or other types of processing systems or combinations thereof. Therefore, those skilled in the art will recognize that the techniques described herein can be used with any of a wide variety of plasma processing systems. Plasma chambers can be used for a wide variety of operations, including but not limited to etching, deposition, cleaning, plasma polymerization, plasma-enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), atomic layer etching (ALE), etc. The structure of plasma chambers is well known to those skilled in the art. It will be recognized that different and / or additional plasma processing systems can be implemented while still utilizing the techniques described herein.

[0076] Figure 4 illustrates a flowchart of a method 400 for characterizing a wafer according to some embodiments of this disclosure. In step S410, light is guided through an illumination optics and an illumination vacuum window of a vacuum chamber to form a light spot on a wafer placed on a wafer chuck in a vacuum chamber. The illumination optics include an illumination correction lens. The illumination vacuum window is tilted relative to the wafer chuck. In step S420, light from the light spot passing through a collection optics and a collection vacuum window of the vacuum chamber is detected. The collection optics include a collection correction lens. The collection vacuum window is tilted relative to the wafer chuck. In step S430, the relative position of the light spot on the wafer is adjusted by rotating the wafer via a wafer stage, moving the light spot via a transfer module, or a combination of both. The illumination correction lens and the collection correction lens are configured to reduce chromatic aberration. The wafer stage is positioned below and mechanically coupled to the wafer chuck and is configured to rotate the wafer chuck. The transfer module is configured to move the illumination optics and the collection optics parallel to the illumination vacuum window and the collection vacuum window, respectively.

[0077] The technique presented in this paper offers several advantages over conventional systems and methods. First, it enables the integration of long-working-distance optics with a vacuum chamber and the provision of corrective lenses on both the illumination and collection sides, thereby allowing for reductions in coma and chromatic aberration and providing the ability to perform polarization measurements. This allows for the utilization of small light spots (e.g., substantially less than 40 nm). m, preferably less than 30 m, preferably less than 20 m, preferably less than 10 m) Achieving sub-angstrom level sensitivity on thin films. Second, the wafer manipulation platform (e.g., wafer chuck 111 and wafer stage 120) described herein includes a stage that allows the wafer to rotate and move along the Z-axis, while complete optical device modules (e.g., 103, 105, 130, and 140) can be mounted on a linear stage (e.g., transfer module 150) to provide the ability to measure any location on the wafer. Third, the optical components of the system (e.g., 100, 300, etc.) and transfer module 150 can be flexibly integrated to meet various design requirements. For example, complete optical device modules (e.g., 103, 105, 130, and 140) can be mounted on transfer module 150. Alternatively, the optical components of system 300 can have fixed illumination and / or detection modules, with only the illumination and collection portions of the optical link placed on a moving stage (see, for example, Figure 3). In this case, the illumination and detection modules (e.g., 130 and 140) will be free-space coupled to the moving portions of the optical link in the collimation space.

[0078] Alternatively, systems 100, 300, etc., can be built as new systems to reduce vacuum space, thereby reducing the load on the vacuum pump and shortening the evacuation time to achieve a vacuum. Alternatively, systems 100, 300, etc., can be built into existing semiconductor tools or equipment. For example, existing semiconductor tools may include a vacuum chamber 110, but the space of this chamber is limited, insufficient to allow wafer 101 to move horizontally (e.g., in the X and Y directions). The transfer module 150 and wafer stage 120 (and optionally, journal bearing 125) can solve this problem, enabling measurement of all positions of wafer 101 without horizontal movement of wafer 101.

[0079] In the foregoing description, specific details, such as the particular geometry of the machining system and the description of the various components and processes used therein, have been set forth. However, it should be understood that the techniques described herein can be practiced in other embodiments departing from these specific details, and such details are for illustrative purposes rather than limiting. The embodiments disclosed herein have been described with reference to the accompanying drawings. Similarly, specific figures, materials, and configurations have been set forth for illustrative purposes to provide a thorough understanding. However, embodiments can be practiced without such specific details. Components having substantially the same functional construction are indicated by similar reference numerals, and therefore any redundant descriptions may be omitted.

[0080] Various techniques have been described as multiple discontinuous operations to aid in understanding the various embodiments. The order of description should not be construed as implying that these operations must be performed in sequence. In fact, these operations do not need to be performed in the presented order. The described operations may be performed in an order different from the order of the described embodiments. In additional embodiments, various additional operations may be performed and / or the described operations may be omitted.

[0081] As used herein, "substrate" or "wafer" generally refers to the object being processed according to the invention. A substrate may include any material portion or structure of a device (particularly a semiconductor or other electronic device) and may be, for example, a base substrate structure (such as a semiconductor wafer, a photomask), or a layer on or overlying a base substrate structure (such as a thin film). Therefore, a substrate is not limited to any particular base structure, underlying layer, or overlying layer, whether patterned or unpatterned, but is contemplated to include any such layer or base structure, and any combination of layers and / or base structures. This description may refer to specific types of substrates, but this is for illustrative purposes only.

[0082] The substrate can be any suitable substrate, such as a silicon (Si) substrate, a germanium (Ge) substrate, a silicon-germanium (SiGe) substrate, and / or a silicon-on-insulator (SOI) substrate. The substrate can include semiconductor materials, such as group IV semiconductors, group III-V compound semiconductors, or group II-VI oxide semiconductors. Group IV semiconductors can include Si, Ge, or SiGe. The substrate can be a bulk wafer or an epitaxial layer.

[0083] Those skilled in the art will also understand that many changes can be made to the operation of the techniques explained above while still achieving the same objectives of the invention. The scope of this disclosure is intended to cover such changes. Therefore, the above description of embodiments of the invention is not intended to be limiting. Rather, any limitations on embodiments of the invention are set forth in the appended claims.

Claims

1. A system comprising: A vacuum chamber, comprising a wafer chuck within the vacuum chamber and side windows tilted relative to the wafer chuck, the wafer chuck being configured to receive a wafer; a wafer stage, positioned below and mechanically coupled to the wafer chuck, the wafer stage being configured to rotate the wafer chuck and move the wafer chuck in a vertical direction substantially perpendicular to the wafer chuck; an illumination optics configured to receive light from a light source and guide the light through illumination vacuum windows in the side windows to form a light spot on the wafer, the illumination optics including an illumination correction lens; a collection optics configured to receive light from the light spot through collection vacuum windows in the side windows and guide the light to a detector, the collection optics including a collection correction lens; and a transfer module configured to move the illumination optics and the collection optics parallel to the illumination vacuum windows and the collection vacuum windows, respectively, wherein the illumination correction lens and the collection correction lens are configured to reduce optical aberrations.

2. The system as claimed in claim 1, wherein, The wafer stage is located outside the vacuum chamber.

3. The system of claim 2, further comprising a journal bearing that mechanically connects the wafer stage to the wafer chuck and, with a vacuum seal, extends through the bottom portion of the vacuum chamber.

4. The system as claimed in claim 1, wherein, The wafer stage is located inside the vacuum chamber.

5. The system as claimed in claim 1, wherein, The wafer stage is configured to rotate the wafer chuck and move the wafer chuck in the vertical direction, without moving the wafer in the horizontal direction parallel to the wafer chuck.

6. The system of claim 1, wherein, The irradiation optics and the collection optics are mounted on the transfer module, which is configured to move the irradiation optics and the collection optics simultaneously.

7. The system of claim 6, wherein, The light source and the detector are mounted on the transfer module, which is configured to move the light source, the detector, the illumination optics and the collection optics simultaneously.

8. The system of claim 6, wherein, The light source and the detector are separate from the transfer module and are configured to remain stationary when the transfer module moves the irradiation optics and the collection optics.

9. The system as claimed in claim 1, wherein, The irradiation optics and the collection optics are located outside the vacuum chamber.

10. The system of claim 9, wherein, The illumination correction lens and the collection correction lens are spaced apart from the vacuum chamber.

11. The system of claim 10, wherein, The illumination optics further include a polarizer and an optical objective selected from a group consisting of a single aspherical mirror and a pair of off-axis spherical mirrors.

12. The system of claim 1, wherein, The transfer module is configured to move the light spot at least between the edge of the wafer and the center of the wafer.

13. The system of claim 12, further comprising a controller configured to adjust the relative position of the light spot on the wafer by rotating the wafer via the wafer stage, moving the light spot via the transfer module, or a combination of both.

14. The system of claim 12, wherein: The transfer module includes a stage on which the illumination optics and the collection optics are mounted, and the stage is configured to move in a longitudinal direction parallel to the side windows.

15. The system of claim 1, wherein, These side windows are substantially perpendicular to the optical path of the light and are substantially transparent to the light.

16. The system of claim 1, wherein, The detector is a spectrometer.

17. The system of claim 1, wherein, The detector, the illumination optics, and the collection optics are configured as an ellipsometer.

18. The system of claim 17, wherein, The ellipsometer is configured as a spectroscopic ellipsometer with a rotating polarizer.

19. The system of claim 1, further comprising a processing chamber connected to the vacuum chamber and configured to perform surface treatment on the wafer in a vacuum.

20. A method for wafer characterization, the method comprising: Light is guided to form a light spot on a wafer placed on a wafer chuck in the vacuum chamber by means of an illumination optics and an illumination vacuum window of the vacuum chamber, the illumination optics including an illumination correction lens, and the illumination vacuum window tilted relative to the wafer chuck; light from the light spot passing through a collection optics and a collection vacuum window of the vacuum chamber is detected, the collection optics including a collection correction lens, and the collection vacuum window tilted relative to the wafer chuck; and the relative position of the light spot on the wafer is adjusted by rotating the wafer via a wafer stage, moving the light spot via a transfer module, or a combination of both, wherein the illumination correction lens and the collection correction lens are configured to reduce chromatic aberration, the wafer stage is positioned below and mechanically coupled to the wafer chuck and configured to rotate the wafer chuck, and the transfer module is configured to move the illumination optics and the collection optics parallel to the illumination vacuum window and the collection vacuum window, respectively.

21. The method of claim 20, wherein, The wafer stage, the illumination optics, and the collection optics are located outside the vacuum chamber.

22. The method of claim 21, wherein, The wafer stage and the wafer chuck are mechanically connected via a journal bearing that extends through the bottom portion of the vacuum chamber with a vacuum seal.

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