This instant specification generally relates to ensuring quality control of materials manufactured in substrate processing systems. More specifically, the instant specification relates to optical inspection of sample uniformity during various stages of manufacturing. This application claims the benefit of priority from U.S. Provisional Application No. 63/392,406 filed on Jul. 26, 2022, which is incorporated herein by reference in its entirety.
Manufacturing of modern materials often involves various deposition techniques, such as chemical vapor deposition (CVD) or physical vapor deposition (PVD) techniques, in which atoms of one or more selected types are deposited on a substrate (wafer) held in low or high vacuum environments that are provided by vacuum deposition chambers. Materials manufactured in this manner may include monocrystals, semiconductor films, fine coatings, and numerous other substances used in practical applications, such as electronic device manufacturing. Many of these applications rely on the purity of the materials grown in substrate processing systems. The need to maintain isolation of the inter-chamber environment and to minimize its exposure to ambient atmosphere and contaminants therein gives rise to various robotic techniques of sample manipulation and inspection. Improving precision, reliability, and efficiency of such robotic techniques presents a number of technological challenges whose successful resolution facilitates continuing progress of electronic device manufacturing. This is especially applicable given that the demands to the quality of chamber manufacturing products are constantly increasing.
In one implementation, disclosed is a method that includes directing a first focused beam to a first location of a sample, detecting a first interference pattern (IP) associated with a first light departing from the first location and generated upon interaction of the first focused beam with the sample, directing a first focused beam to a second location of the sample, and detecting a second IP associated with a second light departing from the second location and generated upon interaction of the first focused beam with the sample. The method further include determining, based on the first IP and the second IP, a magnitude of a difference between a first thickness of the sample at the first location and a second thickness of the sample at the second location, and a sign of the difference between the first thickness of the sample at the first location and the second thickness of the sample at the second location.
In another implementation, disclosed is a system that includes an illumination system to generate a first focused beam, direct the first focused beam to a first location of a sample; and direct the first focused beam to a second location of the sample. The system further includes a detection system to detect a first interference pattern (IP) associated with a first light departing from the first location and generated upon interaction of the first focused beam with the sample, and detect a second IP associated with a second light departing from the second location and generated upon interaction of the first focused beam with the sample. The system further includes a processing device to determine, based on the first IP and the second IP, a magnitude of a difference between a first thickness of the sample at the first location and a second thickness of the sample at the second location, and a sign of the difference between the first thickness of the sample at the first location and the second thickness of the sample at the second location.
In another implementation, disclosed is a semiconductor manufacturing system that includes a semiconductor manufacturing system that includes one or more processing chambers to process a sample and a sample thickness metrology system. The sample thickness metrology system includes an illumination system to generate a first focused beam, direct the first focused beam to a first location of a sample, and direct the first focused beam to a second location of the sample. The sample thickness metrology system further includes a detection system to detect a first interference pattern (IP) associated with a first light departing from the first location and generated upon interaction of the first focused beam with the sample, and detect a second IP associated with a second light departing from the second location and generated upon interaction of the first focused beam with the sample. The sample thickness metrology system further includes a processing device to determine, based on the first IP and the second IP, a magnitude of a difference between a first thickness of the sample at the first location and a second thickness of the sample at the second location, and a sign of the difference between the first thickness of the sample at the first location and the second thickness of the sample at the second location.
Processing operations performed in sample manufacturing systems include material deposition, etching, patterning, chemical or mechanical polishing, and/or various other operations. Most such operations affect thickness of samples as one or more materials can be added (e.g., by deposition) to a sample or removed (e.g., by etching or polishing) from a sample. Thickness can be changed globally (e.g., via uniform sample polishing, film deposition, etc.) or locally (e.g., via patterning, local deposition and/or etching, etc.). Maintaining proper thickness uniformity or ensuring that patterning comports to a specification of a given processing operation is important for efficient and high-quality sample manufacturing. Uncontrolled thickness variations, even as small as several microns, can negatively affect material properties, surface quality, cleanliness (presence of defects and impurities), chemical composition, and/or other physical or chemical characteristics of samples. Similarly, accurate knowledge of the uniformity of the manufacturing yield can be important for an accurate set up of different stages of processing.
Accordingly, ensuring that a thickness profile h(X,Y) of a sample (e.g., wafer with or without patterning and/or one or more films deposited thereon) surface may be represented by a dependence of a height (width, depth) is important as part of process metrology and sample quality control. For example, having an accurate information about thickness variations of samples enables process engineers and/or various algorithms of robotic processing to correct processing errors and sample's imperfections while the sample is still inside the processing system and before a manufacturing process is complete, which can significantly improve sample quality, reduce roughness, and/or the like.
Aspects and embodiments of the present disclosure address these and other challenges of the existing techniques of sample quality control by providing for systems and techniques that implement interference-based thickness measurements. In some embodiments, a semi-transparent or transparent sample (depending on a wavelength of light) can be measured by detecting and tracking changes in an interference pattern that is formed on an array of optical detectors by beams reflected from a top surface and a bottom surface of a sample.
where θ is a refraction angle of beam propagation inside the sample (relative to the normal direction), n is the refractive index of a material of sample 102 at the wavelength of light of beams 104, 106, and 108 (with the extra phase shift n caused by reflection of reflected beam 106 from the top surface of sample 102). Correspondingly, sample 102 operates as a Fabry-Perot interferometer with reflected beams 106 and 108 interfering constructively (high reflectance/low transmittance) when phase Φ1 is an integer number of 2π and interfering destructively when phase Φ1 is a half-integer number of 2π (low reflectance/high transmittance).
Thickness h of (non-uniform) sample 102 can depend on in-plane coordinates X, Y (e.g., Cartesian coordinates, polar coordinates, and/or any other suitable coordinates), h=h(X,Y). If the incident beam is collimated, the light reflected from non-uniform sample 102 displays a sequence of bright and dark interference fringes as the incident beam scans across the surface of sample 102. In particular, according to Eq. (1), two consecutive bright or dark fringes are observed in the reflections from points where thickness h changes by Δh=λ/(2n). This periodic change of the interference patterns formed by a collimated beam, however, does not disambiguate increases in thickness h from decreases in thickness h and, while representative of local variations of the thickness, provides no direct information on the sign of the variations. Furthermore, very smooth variations of thickness do not result in a formation of interference patterns and instead lead to single-valued interferograms whose overall intensity is modulated as the incident beam scans across the surface of sample 102.
As disclosed herein, using a focused beam 104, depicted in
The variations of the total reflected light intensity caused by a combination of reflected beams 106 and 108 can be detected by a detection system that includes a detector array 110, e.g., a digital camera or some other multi-pixel imaging device. Utilizing narrow beams, e.g., as illustrated schematically in
where k=2π/λ is the central wavevector of the beam andR(z) is the local radius of curvature of its wavefront, e.g.,
and E is the amplitude of reflected beam 106 (on its axis at the narrowest point z=0). The extra phase k{right arrow over (r)}2/R(z) is associated with the curved wavefront of the beam.
Similarly, the electric field of the bottom-reflected beam 108 is
where the wavefront is parallel-shifted by {right arrow over (d)}=(d, 0,0) to a distance d that is caused by the beam propagation inside sample 102. (Reflected beam 108 also incurs phase @1 given by Eq. (1), as described above.) Distance d is determined by the angle of incidence θ0 of incident beam 104, e.g., d=2h tan θ cos θ0, where θ and θ0 are related by Snell's law, sin θ0=n sin θ. If imaging plane 112 of detector array 110 is perpendicular to the axes of reflected beams 106 and 108, the distance d also represents the distance between a center O of reflected beam 106 and a center O′ of reflected beam 108, as illustrated by the top-left inset in
The intensity of reflected light, I=|E1+E2|2=I1+I2+IINT, measured by detector array 110, includes the sum of two intensities I1=|E1|2 and I2=|E2|2 and an interference pattern occurring between reflected beam 106 and reflected beam 108, e.g.,
where Φ2({right arrow over (r)}) is a non-uniform (position-dependent) contribution to the total phase
arising from the wavefront curvature. The position-dependent amplitude of the interference pattern is
and varies with the radius-vector {right arrow over (r)} within the imaging plane 112.
For a sample 102 with a uniform (position-independent) profile h(X,Y), interference pattern IINT({right arrow over (r)}), measured by detector array 110, likewise remains constant as focused beam 104 is scanned across the sample. In samples with non-uniform thickness profiles h(X,Y), as thickness h changes with X and/or Y, the uniform phase Φ1 is modified (e.g., as described above) and shifts the interference pattern IINT({right arrow over (r)}) along the x-axis of the detector array 110 (the x-axis, as drawn in
Correspondingly, the direction in which the interference pattern IINT({right arrow over (r)}) shifts can unambiguously identify whether the sample thickness is increasing (Δh>0) along the direction of scanning or decreasing (Δh<0) and the amount of the shift, relative to the detector array 110, can indicate a magnitude of the change Δh.
Although, for the sake of specificity, the techniques of interferometry-based thickness metrology monitoring are often described as being performed using interference patterns in the reflected light, the same or similar techniques can be used with using interference patterns in a light transmitted through a sample. For example, as shown in the bottom-right inset in
The same, or similar, techniques can be used in samples that include one or more layers of material, e.g., a wafer and one or more films deposited thereon. In some embodiments, a change of phase Φ1 associated with the propagation of light though such a layered stack can be computed (or simulated) for specific types and thicknesses of materials of the stack or pre-measured and stored as part of calibration data for each of the stacks for which thickness metrology can be performed. In some instances, the total thickness of the films added to the wafer can be small compared to the total thickness of the wafer. In such instances, a contribution to phase Φ1 of the films can be ignored or modeled with a thickness-dependent value that is determined using computations, simulations, and/or calibration measurements.
Sample 102 can be illuminated using an illumination system that includes a light source 304 that generates an incident beam 114. In some embodiments, as shown in
In some embodiments, a system of mirrors 310 can be used to direct incident beam 114 along a desired path within processing chamber 301. In some embodiments, the illumination system can include expander optics, collimating optics, and/or other optical elements. The illumination system can further include one or more polarizers, configured to polarize incident beam 114 to a specific target polarization, e.g. s-polarization or p-polarization. The illumination subsystem can be capable of controlling intensity of incident beam 114, e.g., by controlling the cross section of incident beam 114 and/or by controlling the intensity of light produced by light source 304.
Incident beam 114 can be focused, using focusing optics 116, into focused beam 104 that is directed onto sample 102. Focusing optics 116 can include one or more lenses and/or one or more curved mirrors.
Light reflected from sample 102 can include multiple beams generated upon a corresponding number of reflections of focused beam 104 by two surfaces of sample 102. Reflected beams can be collected using a detection system that includes a detector array 110. Two reflected beams are illustrated in
In some embodiments, the collection system can further include one or more optical elements (not shown in
In some embodiments, CMOS image sensors used in detector array 110 can be high-speed and low-noise sensors. For example, CMOS image sensors can have speed at or above 1 Gigapixel per second and noise at 10e or less, e.g., in the range of 2e-5e or even less, in some embodiments.
In some embodiments, the thickness metrology system 300 can perform thickness measurements for multiple locations on sample 102. In some embodiments, sample 102 can be supported by a movable stage 318 (e.g., robot blade) that can impart translational and/or rotational motion to sample 102 to reposition the illuminated—by the focused beam 104—spot relative to sample 102. In some embodiments, instead of (or in addition to) repositioning of sample 102, the incident beam 114 (and focused beam 104) can be repositioned. For example, an angle of propagation of incident beam 114 can be controlled by changing orientation of mirror 310-C and a parallel translation of incident beam 114 can be achieved by moving a support platform 320 of mirror 310-C, e.g., in the horizontal direction.
The thickness metrology system 300 can detect interference patterns formed by reflected beams 106 and 108, e.g., as disclosed above in conjunction with
More specifically, two consecutive angles of refraction θ1R and θ2R, for which two adjacent bright (or dark) fringes are observed, result in the phase difference ΔΦ1=2π. (In the description of
Identification of angles θ1R and θ2R can be performed by varying the angle of incidence of focused beam 104. In some embodiments, determination of the absolute thickness using Eq. (8) can be performed with a collimated beam, in some embodiments.
expresses local height of the sample as a function of focal length F of focusing optics 116, wavelength of light λ, and the measured horizontal shift of the incident beam ΔL that causes an interference pattern (observed by detector array 110 in
In some embodiments, instead of measuring the angle difference θ2−θ1 corresponding to a 2π-shift between two bright or two dark interference fringes (e.g., as disclosed above), a difference θ2−θ1 corresponding to a n-shift, e.g., a phase shift between a bright fringe or a dark fringe, can be measured and used for determining the absolute thickness h of the sample.
In some embodiments, instead of using the thickness metrology setup 370 of
In one embodiment, robot blade 410 of robot 408 supports sample 416 when the latter is transferred into one of processing chambers 406. Robot blade 410 can be attached to an extendable arm of robot 408 having a length that is sufficient to reach to different chambers. Sample 412 (and/or sample 416) can be a semiconductor wafer, dielectric wafer, and/or any other object that is transparent (or partially transparent) and that can be placed or transported into one of processing chambers 406, loading station 402, transfer chamber 404, ports connecting transfer chamber 404 to loading station 402 or the processing chambers 406, and/or the like.
Robot blade 410 can deliver (and retrieve) samples to (and from) processing chamber(s) 406 through a slit valve port (not shown) while a lid to processing chamber(s) 406 remains closed. Processing chamber(s) 406 can contain processing gasses, plasma, and various particles used in deposition processes. In some embodiments, a magnetic field can exist inside processing chamber(s) 406. The inside of processing chamber(s) 406 can be held at temperatures and/or pressures that are different from the temperature and/or pressure outside processing chamber(s) 406. Although sample 412 is shown as being supported and moved by robot blade 410 of robot 408, in some embodiments, sample 412 can be transported using a dedicated motion stage or any other suitable movable stage, an existing substrate transfer mechanism, an existing motion mechanism in a process chamber (such as a polishing head or another wafer deployed in a CMP process).
Manufacturing machine 400 can deploy one or more thickness metrology (h-metrology) systems 450 operating as disclosed in conjunction with
A computing device 418 can set up and control execution of at least some processing operations of manufacturing system 400, such as opening loading station 402, receiving samples in loading station 402, moving the received samples from loading station 402 to transfer chamber 404, equalizing pressures/temperatures between transfer chamber 404 and loading station 402 and/or processing chamber(s) 406, transferring the samples into and/or from processing chamber(s) 406, selecting and carrying out processing operations on the samples in processing chamber(s) 406, transferring processing samples back to loading station 402, and/or performing any other suitable operations. Computing device 418 can include an h-metrology control module 420 that controls operations of h-metrology system and a robot blade control module 425 that controls operations of robot blade 410. In one embodiment, h-metrology control module 420 can receive interference patterns detected by individual units of h-metrology control module 420 and determine thickness of pertinent samples.
In some embodiments, h-metrology control module 420 can deploy a Fast Fourier Transform (FFT) analyzer 422 that processes pixelated intensity I(x,y) of the reflected light and identifies position-dependent portion IINT(x,y) of this intensity representative of an interference pattern described in conjunction with
In some embodiments, operations of h-metrology system 450 can be supported by an electronics module 430. Electronics module 430 can include a microcontroller and a memory buffer coupled to the microcontroller. In some embodiments, electronics module 430 can perform at least some processing of the light reflections data, including but not limited to performing FFT computations and identifying profiles of the sample(s). The memory buffer can be used to collect and store data, e.g., a partially or fully processed light reflection data. In some embodiments, the data can be transmitted using a wireless communication circuit. In other embodiments, the data can be transmitted using a wired connection between electronics module 430 and computing device 418. In some embodiments, the data can first be stored (buffered) in the memory buffer prior to being transmitted to computing device 418. In other embodiments, the data can be streamed to computing device 418 as the data is being collected, without being stored in the memory buffer. In some embodiments, the wireless or wired connection can be continuous. In other embodiments, the wireless or wired connection can be established periodically or upon completion of the inspection or some other triggering event, e.g., when a certain minimum degree of sample non-uniformity is detected. Electronics module 430 can further include a power element and a power-up circuit. In some embodiments, the power element can be (or include) a battery. In some embodiments, the power element can be a capacitor. The power element can be rechargeable from a power station. The microcontroller can be coupled to one or more units of h-metrology system 450. In some embodiments, electronics module 430 can also control at least some operations of robot 408. In some embodiments, electronics module 430 can include an accelerometer to facilitate accurate extension and angular rotation of the robot blade 410 and/or rotation of samples 412 and 416 around samples' axes.
Electronics module 430 can further include a wireless communication circuit, e.g., a radio circuitry for receiving wireless instructions from the computing device 418 and for transmitting light reflection data to computing device 418. For example, the radio circuitry can include an RF front end module and an antenna (e.g., a UHF antenna), which can be an internal ceramic antenna, in one embodiment. The batteries may be of a high temperature-tolerant type such as lithium-ion batteries that can be exposed to a chamber temperature of 450 degrees Celsius for a short time period such as one to eight minutes.
The wireless connection facilitated by the RF front end and antenna can support a communication link between the microcontroller and computing device 418, in some embodiments. In some embodiments, the microcontroller integrated with the robot 408 can have a minimal computational functionality sufficient to communicate information to the computing device 418, where most of the processing of information can occur. In other embodiments, the microcontroller can carry out a significant portion of computations, while the computing device 418 can provide computational support for specific, processing-intensive tasks. Data received by the computing device 418 can include data obtained from the inside of the transfer chamber 404, the processing chambers 406, data collected by h-metrology system 450, data temporarily or permanently stored in the memory buffer, and so on. The data stored in the memory buffer and/or transmitted to or from the computing device 418 may be in a raw or processed format.
Some components of electronics module 430 can be located on or at the stationary part of the robot 408. For example, the microcontroller, the memory buffer, and the RF front end may be so located. Other components of electronics module 430 can be located on or at the robot blade 410 of the robot 408 and/or individual units of h-metrology system 450.
At block 510, performed for a plurality of locations of a sample (e.g., sample 102), method 500 can include directing a first focused beam to a respective location of the plurality of locations of the sample (e.g., focused beam 104 in
At block 520, method 500 can continue with detecting, for each of the plurality of locations of the sample, an interference pattern (IP) associated with a light departing from the respective location, e.g., a first (second, etc.) IP associated with a first (second, etc.) light departing from the first location. The light departing from the sample can be generated upon interaction of the first focused beam with the sample. In some embodiments, the first light departing from the first location can include a first reflected beam caused by reflection of the first focused beam from a first surface of the sample at the first location (e.g., reflected beam 106 in
Similarly, the second light departing from the second location can include a third reflected beam caused by reflection of the first focused beam from the first surface of the sample at the second location, and a fourth reflected beam caused by reflection of the first focused beam from the second surface of the sample at the second location.
In some embodiments, the first light departing from the first location can include a first transmitted beam caused by refraction of the first focused beam at the first location (e.g., first transmitted beam 120), and can further include a second transmitted beam caused by combined refraction-reflection of the first focused beam at the first location (e.g., second transmitted beam 122). In such embodiments, the first (second) IP can be, at least partially, caused by curved wavefronts of the first transmitted beam and the second transmitted beam.
The plurality of detected IPs can include a first IP associated with a first light departing from a first location (e.g., X1, Y1) of the plurality of locations. The plurality of detected IPs can further include a second IP associated with a second light departing from a second location (e.g., X2, Y2) of the plurality of locations (e.g., as illustrated in
At block 530, method 500 can continue with determining, based on the first IP and the second IP, a magnitude and a sign of a difference h(X,Y)−h(X′,Y′) between a first thickness of the sample at the first location and a second thickness of the sample at the second location. In some embodiments, as illustrated in the callout block 532, determining the magnitude and the sign of the difference h(X,Y)−h(X′,Y′) can include identifying a displacement (along one or more spatial axes of a detector array, e.g., x-axis) of the second IP relative to the first IP (e.g., as illustrated in
At block 540, method 500 may continue with configuring, responsive to the determined magnitude and sign of the difference h(X,Y)−h(X′,Y′), one or more processing operations of the manufacturing system. For example, configuring the processing operation(s) can include performing some remedial processing of the sample, e.g., performing additional polishing of the sample, etching and/or deposition. In some instances, adjustments can be applied to subsequent samples processed by the manufacturing system. For example, such adjustments can include modifying chemical composition, pressure, temperature, etc., of an environment of some portion of the manufacturing system, such as a processing chamber, a transfer chamber, a loading chamber, and/or the like.
It should be understood that the above description is intended to be illustrative, and not restrictive. Many other embodiment examples will be apparent to those of skill in the art upon reading and understanding the above description. Although the present disclosure describes specific examples, it will be recognized that the systems and methods of the present disclosure are not limited to the examples described herein, but may be practiced with modifications within the scope of the appended claims. Accordingly, the specification and drawings are to be regarded in an illustrative sense rather than a restrictive sense. The scope of the present disclosure should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.
The embodiments of methods, hardware, software, firmware or code set forth above may be implemented via instructions or code stored on a machine-accessible, machine readable, computer accessible, or computer readable medium which are executable by a processing element. “Memory” includes any mechanism that provides (i.e., stores and/or transmits) information in a form readable by a machine, such as a computer or electronic system. For example, “memory” includes random-access memory (RAM), such as static RAM (SRAM) or dynamic RAM (DRAM); ROM; magnetic or optical storage medium; flash memory devices; electrical storage devices; optical storage devices; acoustical storage devices, and any type of tangible machine-readable medium suitable for storing or transmitting electronic instructions or information in a form readable by a machine (e.g., a computer).
Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
In the foregoing specification, a detailed description has been given with reference to specific exemplary embodiments. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the disclosure as set forth in the appended claims. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense. Furthermore, the foregoing use of embodiment, embodiment, and/or other exemplary language does not necessarily refer to the same embodiment or the same example, but may refer to different and distinct embodiments, as well as potentially the same embodiment.
The words “example” or “exemplary” are used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as “example” or “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects or designs. Rather, use of the words “example” or “exemplary” is intended to present concepts in a concrete fashion. As used in this application, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or.” That is, unless specified otherwise, or clear from context, “X includes A or B” is intended to mean any of the natural inclusive permutations. That is, if X includes A; X includes B; or X includes both A and B, then “X includes A or B” is satisfied under any of the foregoing instances. In addition, the articles “a” and “an” as used in this application and the appended claims should generally be construed to mean “one or more” unless specified otherwise or clear from context to be directed to a singular form. Moreover, use of the term “an embodiment” or “one embodiment” or “an embodiment” or “one embodiment” throughout is not intended to mean the same embodiment or embodiment unless described as such. Also, the terms “first,” “second,” “third,” “fourth,” etc. as used herein are meant as labels to distinguish among different elements and may not necessarily have an ordinal meaning according to their numerical designation.
This application claims the benefit of priority from U.S. Provisional Application No. 63/512,441, “DETECTION OF SAMPLE THICKNESS AND SAMPLE THICKNESS VARIATIONS WITH FOCUSED BEAM INTERFERENCE,” filed on Jul. 7, 2023, which is incorporated herein by reference in its entirety.
Number | Date | Country | |
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63512441 | Jul 2023 | US |