Characterizing integrated circuit devices using a vapor cell sensor

Abstract

In a general aspect, a vapor cell sensor is used to detect electromagnetic signals from integrated circuit devices. In some implementations, a system includes a control system and a probe head. The probe head includes a vapor cell sensor that contains a vapor. The control system is configured to move a stage to position the probe head relative to an integrated circuit device; communicate input optical signals to the probe head; receive, at an optical detector, output optical signals from the probe head, the output optical signals being generated based on interactions between the vapor and the input optical signals in the presence of electromagnetic signals from the integrated circuit device; and process, by operation of a signal processing system, electrical signals produced by the optical detector based on the received output optical signals to determine a condition of the integrated circuit device.

Description

Characterizing Integrated Circuit Devices Using a Vapor Cell SensorCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 608,680, filed December 11, 2023, entitled "Characterizing Integrated Circuit Devices using a Rydberg Microprobe [RMP] system.” The above-referenced priority document is incorporated herein by reference.TECHNICAL FIELD

[0002] The following description relates to using a vapor cell sensor to characterize integrated circuit [IC] devices.BACKGROUND

[0003] Characterization of IC devices has been performed to ensure proper operation and reliability of electronic systems. These characterizations can provide valuable insights into the behavior of IC devices under various operating conditions and help identify potential issues that could lead to system failures.BRIEF DESCRIPTION OF THE DRAWINGS

[0004] FIG. 1 is a schematic diagram showing aspects of an example Rydberg microprobe [RMP] system.

[0005] FIG. 2 is a schematic diagram showing aspects of a probe head of an example RMP system.

[0006] FIGS. 3A-3B are schematic diagrams showing different views of example probe heads of an RMP system.

[0007] FIG. 4 is an image showing a top view of an example vapor cell.

[0008] FIG. 5 is a schematic diagram showing a perspective view of an example vapor cell.

[0009] FIG. 6 is a flow chart showing aspects of an example process for characterizing IC devices.DETAILED DESCRIPTION

[0010] In a general aspect, a system that includes one or more vapor cell sensors can be used to detect electromagnetic radiation emitted from integrated circuit [IC] devices. In some examples, the system can be implemented as a Rydberg microprobe [RMP] system having a probe head that includes a vapor cell sensor. In some cases, the system can be configured to detect out-of-band spurious emissions [which may include, e.g., harmonics, inter-modulations, other non-linear induced emissions, etc.] and other types of signals from IC devices. In some implementations, the systems described here can be used to characterize radio frequency integrated circuits [RFIC], high-speed digital / mixed ICs, advanced packaging [without or without antenna integrated], and other types of IC devices. In certain instances, the systems described here can measure nonlinear, linear, and electromagnetic field compliance [EMC] / electromagnetic interference [EMI] using over- the-air measurement without contacting the device under test [DUT].

[0011] In some implementations, an RMP system includes a probe head and a control system communicably coupled to the probe head. In some instances, the probe head can include a vapor cell sensor which utilizes the quantum states of Rydberg atoms for absolute measurement of millimeter, microwave, and even terahertz electric-fields [e.g., 1 MHz-1 THz] emitted from high-frequency and high-speed electronic devices, circuits, and systems. In some cases, the vapor cell sensor of the probe head includes a capillary with an elongated body bonded to, and in fluidic communication with, a primary vapor cell. The capillary can be used, for example, to provide improved spatial resolution and to allow access to the confined space of an IC when in contact with electrical probes. The vapor cell sensor can be optically connected to the control system [e.g., the laser control system 104 and the signal processing system 106 in FIG. 1] to receive input signals from the control system and to communicate output signals to the control system. In some instances, the vapor cell sensor of the probe head can also provide RF imaging capabilities. The control system may be configured to process the output signals to determine a condition of theelectronic device under test [DUT], for example, for diagnostics, quality control, or other purposes.

[0012] In some implementations, the systems and techniques described here can provide technical advantages and improvements relative to conventional technologies. For example, the probe head of the RMP system can be configured to perform near field characterization of electromagnetic emissions from integrated circuit devices. The probe head can enable broadband testing of electromagnetic radiation with site-specific testing capabilities. The systems and techniques presented here may enable over-the-air [OTA] testing processes that are non-invasive. In some implementations, the probe head of the RMP system is small compared to typical RF wavelengths, and made of dielectric materials. The probe head of the RMP system may be self-calibrated, with accuracy that does not drift over time. In some instances, a single probe head can span > 100 GHz, such that the probe head does not have to be changed to measure harmonics emanating from the DUT. The systems and methods presented here may improve accuracy, repeatability, simplicity, and cost of the characterization of integrated circuit devices. In some cases, the methods and systems presented here can provide accurate and repeatable characterization of integrated circuit devices. In some examples, the methods and systems presented here allow characterization of integrated circuit devices at various phases, for example, after the integrated circuits and devices have been deployed, in a production cycle, during installation, and also in the research and development phase. In some cases, a combination of these and potentially other advantages and improvements may be obtained.

[0013] FIG. 1 is a schematic diagram showing aspects of an example system 100. As shown in FIG. 1, the example system 100 includes a probe head 102 and a control system 110. The control system 110 is communicably coupled to the probe head 102 via a transmission medium 112, e.g., optical fiber s] or other types of waveguides. As shown in FIG. 1, the example control system 110 includes two or more laser sources 116, a laser control system 104, a signal processing system 106, an interface 108, and a memory unit 114; the control system 110 may include other components in some cases. The system 100 may include additional or different features, and the components of the system 100 may operate as described with respect to FIG. 1 or in another manner.

[0014] The example control system 110 shown in FIG. 1 includes a laser control system 104, a signal processing system 106, a user interface 108, a memory unit 114, two or more laser sources 116, and potentially other components. In some implementations, the control system 110 receives, detects, and converts output optical signals from the probe head 102 to analog electrical signals which can be further converted to digital signals for processing. For example, the system 100 may include multiple probe heads, with each probe head coupled to the control system 110 by a respective transmission medium. The system 100 may include two or more probe heads 102 that share the same laser source 116; or they be connected to multiple laser sources 116. As another example, each laser source 116 may be connected to one probe head 102; or at least a subset of the probe heads 102. In some instances, the two or more probe heads 102 and the laser sources 116 may be connected in another manner. As another example, the system 100 may include a mounting system for the probe head 102. For instance, the probe head 102 may be mounted to a transferable mounting stage such that the probe head 102 can be translated relative to a static wafer holder or a probe station where the DUT resides. The system 100 may be configured to perform operations shown in the example process 600, or the system 100 may be configured to operate in another manner.

[0015] In some instances, the example system 100 can be used to perform linear, nonlinear, EMC / EMI characterization of various integrated circuit devices with or without packaging, e.g., radio frequency integrated circuits [RFICs], antenna in package (AiP), antenna-on-package [AoP], high-speed digital integrated circuits [ICs] on wafer, chiplets, system-in-package [SiP ], and multi-chip modules [MCM], and other IC devices, in particular for 5G-NR and other millimeter-wave applications. For example, the example system 100 may be used to characterize functional blocks, such as linear amplifiers; nonlinear functional blocks, such as frequency multipliers and harmonic mixers; and multi-state functional blocks, such as switches and phase shifters. In some cases, the example system 100 can provide accurate, contactless, and self-calibrated measurement with an ultrabroadband carrier bandwidth [e.g., 1 MHz to 300 GHz]. The ultra-broadband nature of the example system 100 can be used for nonlinear characterization or conformance-testing of various IC devices because the same probe head can detect harmonics of the fundamentalsignal emitted from the various IC devices. The system 100 can measure harmonics and inter-modulations for FR2 (>24.25 GHz) transmitters by changing the coupling laser wavelength in order to tune to a different radio frequency wave target frequency. In some implementations, the system 100 does not require an external mixer or RF amplifiers. In some examples, the system 100 can provide the capability to perform characterization of S- parameters within as close to a wavelength of the integrated circuit devices.

[0016] In some implementations, the system 100 can be configured to characterize transmitters in AiP and AoP devices, such as a power amplifier, by detecting transmitter harmonics exceeding acceptable thresholds. For example, the system 100 may enable measurement of antenna gain patterns, amplifier linearity, calibration of the relative phase between antenna patch elements, out-of-band [OOB] and spurious emissions, and other characteristics of transmitters in AiP and AoP devices. In some implementations, OOB emissions are the unwanted emissions immediately outside the channel bandwidth resulting from the modulation process and non-linearity in the transmitter. Spurious emissions occur due to unwanted transmitter effects such as harmonics emission, parasitic emission, intermodulation products, and frequency conversion products.

[0017] In some implementations, the system 100 may be used to characterize high speed digital integrated circuit devices. For example, high-speed switching, located in single functional blocks, as well very high-speed multiconductor buses for interconnections between the functional blocks, such as CPU / GPU to memory like SRAM can be characterized by detecting harmonics caused by the fast-switching edge rates. For example, an edge rate of 6 GHz may generate harmonics well into the millimeter-wave regime, for example, the 5th harmonic can be at 30 GHz. The system 100 may allow characterization of fast edge rates and comparison with the design parameters. Such measurements enable one to achieve the desired performance of high-speed integrated circuits, minimize crosstalk at the near-end and far-end of fast switching multiconductor buses within and outside high-speed ICs, and to perform other useful functions.

[0018] In some implementations, the example system 100 may be also used for the 5G- 6G requirement of EMC which requires a wide range of frequencies for testing unwanted emissions including harmonics, inter-modulations, and spurious emissions. The examplesystem 100 can fundamentally simplify the linear and nonlinear characterization of IC devices with high spectral and spatial resolution.

[0019] In some implementations, the probe head 102 includes a Rydberg atom-based vapor cell sensor containing a vapor in an enclosed volume. During operation of the system 100, the vapor in the vapor cell sensor is used as a medium to interact with electromagnetic radiation emitted from a DUT. In some implementations, the vapor cell sensor of the probe head 102 utilizes the quantum states of Rydberg atoms for absolute measurement of millimeter-wave signals emitted from the DUT. In some instances, the probe head 102 may be implemented as a metrology vapor cell, a glass vapor cell, a microelectromechanical system [MEMS] vapor cell, or another type of engineered vapor cell based on metamaterial or photonic crystal principles. In certain cases, the vapor can be enclosed in a thin electromagnetically transparent housing, such as one made from polylactic acid (PLA) plastic or other dielectric material. The transparent housing can accommodate a holder for the vapor cell and its waveguide.

[0020] In some implementations, the probe head 102 utilizes the quantum states of Rydberg atoms [e.g., Rydberg states] for absolute measurement of electromagnetic radiation emitted from the DUT. The probe head 102 can be omni-directional and selfcalibrated. In some instances, the probe head 102 can be implemented with a wide carrier bandwidth so that the probe head 102 does not need to be changed in order to detect the electromagnetic radiation emitted from the DUT. In some instances, the system 100 can be used to interact with respective electromagnetic radiation and detect out-of-band emissions and spurious emissions from the DUT. In some implementations, output optical signals from the vapor cell sensor 112 are used to determine a condition of the DUT, which in some cases can be used for characterizing of system failures and performance degradation or for other purposes.

[0021] In some implementations, the vapor cell sensor of the probe head 102 is formed at least in part [wholly or partially formed] of a dielectric material that is transparent to the electromagnetic radiation. In some implementations, the vapor cell sensor of the probe head 102 is configured to perform Rydberg atom-based radio frequency sensing. In some examples, the vapor cell sensor of the probe head 102 includes a primary vapor cell whichmay be of the type described, for example, in the one or more of the following publications: "Microwave electrometry with Rydberg atoms in a vapor cell using bright atomic resonances,” by J. A. Sedlacek, et al. (Nature Physics 8, 819-824, 2012); "Rydberg-Atom Sensors in Bichromatic Radio-Frequency Fields” by Noaman et al. (Phys. Rev. Applied 20, 024068, 2023); "The Origins of Rydberg Atom Electrometer Transient Response and its Impact on Radio-Frequency Pulse Sensing” by Bohaichuk et al. (Physical Review Applied 18, 034030, 202); "Rydberg Atom-based Electrometry using a Self-heterodyne Frequency Comb Readout and Preparation Scheme” by Dixon et al. (Physical Review Applied 19, 034078, 2023); "A Three-Photon Rydberg Atom-Based Radio Frequency Sensing Scheme with Narrow Linewidth” by Bohaichuk et al. (arXiv:2304.07409vl [physics.atom-ph], 2023); "Sub -wavelength microwave electric field imaging using Rydberg atoms inside atomic vapor cells” by Fan et al. (arXiv:1403.3596vl [physics.atom-ph], 2014), "Quantum Assisted Electrometry using Bright Atomic Resonances”, arXiv: 1205.4461 [physics.atom- ph], 2012; U.S. Patent No. 11,681,016, U.S. Patent No. 11,137,432. Other types or configurations of the primary vapor cell of the vapor cell sensor in the probe head 102 may be used in some cases. The dielectric material may define a window for the primary vapor cell, through which, the electromagnetic radiation is received. Examples of the dielectric material include silicon, silicate-based glasses, and quartz. The vapor cell sensor may include atoms in a vapor state (e.g., vaporized 87Rb or 133Cs) that alter an optical transmission in response to the electromagnetic radiation. The optical transmission may be influenced by optical transitions of the atoms in the vapor state.

[0022] In some implementations, the vapor cell sensor of the probe head 102 includes a capillary with an elongated body bonded to the primary vapor cell sensor. The elongated body of the capillary defines an interior volume that is in fluidic communication with an interior volume of the primary vapor cell sensor together to hold the vapor in the vapor cell sensor. In some instances, output optical signals generated based on the interaction of the vapor in the vapor cell sensor, especially the vapor in the elongated body of the capillary (e.g., at the tip of the capillary) near the DUT, and the electromagnetic radiation emitted from the DUT are independent of the orientation of the vapor cell sensor relative to the DUT. For example, the vapor cell sensor may be rotated (e.g., spatially reoriented withrespect to the DUT) without impacting the output optical signals generated by the vapor cell sensor. In other words, the vapor cell sensor can be omni-directional such that its operation is invariant under spatial rotations, providing a higher degree of stability. The output optical signals generated by the example probe head 102 are orientationindependent and rotation-invariant due to the physical [e.g., material) properties of the vapor cell sensor. Because the measurements obtained from the vapor cell sensor are orientation-independent and generally insensitive to changes in the spatial orientation of the vapor cell sensor, the measurements are highly repeatable and more robust. Thus, the example probe head 102 can provide more stable measurements, which can be reliably compared and tracked over time and at different locations.

[0023] As shown in FIG. 1, the control system 110 is configured to communicate input optical signals [e.g., laser signals from two or more laser sources) to the probe head 102 and to receive / process the output optical signals from the probe head 102. In some cases, the laser signals generated by the two or more laser sources 116 may be delivered to the probe head 102 in free-space so that the probe beam transmission through the vapor cell can be imaged on a camera or optical detector. In some cases, the system 100 can implement an imaging process that uses single-pixel imaging technologies such as, for example, the technologies described in U.S. Patent No. 10,509,065, U.S. Patent No.10,802,066, and U.S. Patent No. 11,112, 298. Such an arrangement can provide massively parallel data acquisition, which in some cases can speed up measurement times. In some cases, the imaging plane can increase the vertical resolution of the vapor cell sensor, e.g., the transverse spatial resolution, and the depth of field can be engineered into the system. In some instances, the probe head 102 may be implemented as the example probe head 500 shown in FIG. 5 or in another manner.

[0024] In some instances, the capillary of the vapor cell sensor in the probe head 102 may be configured as a hollow core photonic crystal fiber, or hollow core optical fiber attached to the primary vapor cell. In some instances, a hollow core photonic crystal fiber can enable light to propagate through a hollow central core. In some instances, a hollow core photonic crystal fiber may have hollow central core surrounded by a lattice of air holes. The capillary based on a hollow core photonic crystal fiber can guide light usingphotonic bandgap or anti-resonance effect. The capillary can offer reduced losses. The tip of the capillary may have a size [e.g., width or diameter) in a range of less than 100 pm, less than 300 pm, less than 2 mm, or in another range; and can be positioned near the surface of the DUT [e.g., 10-100 pm or another range). The capillary attached to the primary vapor cell allows the system 100 to locally characterize the DUT with a high spatial resolution. In some instances, the probe head 102 may be implemented as any of the example probe heads 210, 300, 330, 400 in FIGS. 2-4, or in another manner.

[0025] In some implementations, the elongated body of the capillary defines a hollow interior and thus a portion of an interior volume of the vapor cell sensor. The elongated body includes two opposite ends. A first end includes a port, when mechanically bonded with the primary vapor cell, allowing a fluidic connection to a cavity of the primary vapor cell and a flow of a vapor between the cavity in the dielectric body of the primary vapor cell and the hollow interior of the capillary through the port. The capillary includes a reflective window on a second opposite end occluding the hollow interior and seal the vapor in the hollow interior. In some instances, the second end of the capillary is placed in proximity to the DUT with a distance in a range of 10-100 pm or another range. In some instances, the capillary may be fluidically connected to the cavity of the dielectric body via a through hole in an optical window.

[0026] The probe head 102 can be made in different shapes and sizes, for example, to tailor the probe head 102 to a particular application or environment. For example, a larger probe head [e.g., the example probe head 500 shown in FIG. 5) can be used for AiP and AoP, while a probe head with a capillary-bonded vapor cell sensor [e.g., the example probe head 200, 300, 330 shown in FIGS. 2-3B) can be used for RFICs. In some cases, the components of the system 100 can be integrated into wafer probe stations with a stage for positioning the DUT relative to the probe head 102 and electrical probes to form electrical contacts.

[0027] In some instances, the probe head 102 may further include waveguides, lasers, detectors, and other optical components integrated together on one or more photonic chips using photonic integrated circuit technology. The integrated optical components may be further integrated with a vapor cell sensor on the probe head 102, in the control system 110, or may be configured in another manner.

[0028] In some aspects of operation, after one or more electrical contacts are formed to the DUT and electrical signals are applied to the DUT through the one or more electrical contacts, measurements can be carried out by positioning the probe head 102 adjacent to the DUT [e.g., close enough to detect electromagnetic signals emitted from the DUT). The DUT can be scanned by shifting the probe head 102 across the surface of the DUT; while measuring the electromagnetic signals emitted from the DUT based on the detected output optical signals. Spatial mapping of the properties of the emitted electromagnetic signals can be created, e.g., frequencies, polarizations, phases, and amplitudes. The electromagnetic signals can be time dependent where a carrier frequency is targeted and time domain signals are acquired and then interrogated, e.g., Fourier transformed, or continuous wave to measure powers. In some instances, the input optical signals [e.g., a coupling laser signal) to the vapor cell sensor can be tuned to change the targeted carrier frequency.

[0029] In some implementations, the probe head 102 is mechanically supported on a piezoelectric scanner, the oscillation of which can be modulated [e.g., frequency of the oscillation, magnitude of the oscillation, or both) so as to modify the motion of the probe head 102 relative to the DUT. In some instances, the modulated oscillation can be used to determine a background signal, for example, from the portion of the vapor that is not interacting with the electromagnetic signal emitted from the DUT [e.g., the vapor in the cavity), and to extract the output optical signals from the tip of the capillary that is in proximity with the DUT where the electromagnetic signal is the strongest. In some instances, other methods can be used for signal extraction and enhancement for example, using lock-in detection methods.

[0030] In some implementations, the two or more laser sources 116 are configured to generate two or more optical signals that include a coupling optical signal and a probe optical signal. In the example shown in FIG. 1, the two or more laser sources 116 are in optical communication with the probe head 102 and as such, the coupling and probe optical signals can interact with the vapor in the vapor cell sensor of the probe head 102. Such interaction may allow the vapor cell sensor to perform Rydberg atom-based radio frequency sensing, e.g., by generating an output optical signal that is based on the coupling and probe optical signals. In some implementations, the output optical signal mayrepresent the response of the vapor of Rydberg atoms in the vapor cell sensor to the electromagnetic signal received from the DUT. For example, the output optical signal from the vapor cell sensor can be generated using electromagnetically induced transparency [EIT] or electromagnetically induced absorption [EIA]. In some instances, a sub-Doppler method is useful for higher spectral resolution in the Autler-Townes regime and higher sensitivity.

[0031] In some instances, the lasers are locked to a stable, narrow bandwidth reference such as a frequency comb signal, interferometer, atomic or molecular absorption line, or another type of reference. To read out the output optical signal from the vapor cell sensor, either of the lasers can be scanned or the probe laser can be used to generate a frequency comb in an optical heterodyne setup. When a frequency comb is used, a real-time spectrum analyzer can be used to detect the output signal. In the case of a frequency comb, it is not necessary to scan either of the laser systems to read out the output signal, although it is possible to use scanning and a frequency comb in combination with each other. The frequency comb read out may be implemented, for example, as described in "Rydberg Atom-based Electrometry using a Self-heterodyne Frequency Comb Readout and Preparation Scheme”, Physical Review Applied 19, 034078, 2023. In some cases, pulsed readout can be performed, for example, as described in U.S. Patent No. 11,681,016 and "The Origins of Rydberg Atom Electrometer Transient Response and its Impact on Radio- Frequency Pulse Sensing”, Physical Review Applied 18, 034030, 2022. In some cases, other methods can be used to acquire the transmitter signals, perhaps in combination with laser frequency changes.

[0032] In some implementations, the laser sources 116 includes a coupling laser and a probe laser. In some instances, the coupling laser can be tuned to different Rydberg states to target different RF frequencies. Spectral signals within a bandwidth [e.g., ~250 MHz or another bandwidth] of the target frequency can be detected by analyzing the optical spectra, for example, as described in the publication "Rydberg-Atom Sensors in Bichromatic Radio-Frequency Fields”, Phys. Rev. Applied 20, 024068, 2023, for a single Rydberg transition and / or detuning the coupling and probe lasers that may be used for Rydberg atom-based sensing. The optical signal necessary for monitoring the lasers andkeeping them stable can be routed via the waveguide 112 through all or part of the system 100. The optical signal can be directed to the vapor cell of the probe head 102 in free-space [e.g., the probe head 102 is implemented as the probe head 500 shown in FIG. 5) or through optical fiber [e.g., when the probe head 102 is implemented as the probe head 210, 300, 330, 400 shown in FIGS. 2-4). Feedback to control the lasers, including feed forwards, can be realized using FPGAs, analog electronics, or another processor-based system that can be controlled through a user interface and through autonomous control layers operating in different types of processors.

[0033] In some implementations, the laser control system 104 is configured to communicate control signals to the two or more laser sources 116 and other optical and electrical components of the system 100, for example, comb generators to generate frequency comb signals, frequency separators to separate frequency components in frequency comb signals from each other by a common frequency spacing, frequency shifters to shift the frequency components by a frequency magnitude, etc.

[0034] In some instances, the signal processing system 106 of the control system 110 includes an optical detector to detect the output optical signals from the vapor cell sensor. The optical detector senses changes in the transmission of the light in the vapor cell sensor caused by the electromagnetic emission from the DUT. The output optical signal can be converted by the optical detector to analog electrical signals which can be further converted to a digital signal that can be processed on a FPGA, GPU, computer processor, or some combination thereof, including specialized hybrid processors. In some instances, the memory unit 114 is configured to store the digital signal as a function of time generated from the optical detector; and the digital signal can be processed by passing through multiple matched filters to identify the periodicity, arrival time, and various other characteristics of the electromagnetic emission from the DUT. In some instances, the matched filtering process may be implemented as described in "The Origins of Rydberg Atom Electrometer Transient Response and its Impact on Radio-Frequency Pulse Sensing” Physical Review Applied 18, 034030, 2022, U.S. Patent No. 11,681,016, or using other techniques.

[0035] In some implementations, the system 100 is also capable of detecting nonlinearity in continuous wave signals in addition to radio frequency pulses generated by the DUT. RF pulses from the DUT can be averaged together over time or acquired in realtime. The signal train can be subjected to Fourier transform analysis in the FPGA or processing unit. Data from the FPGA or processing unit is used to locate and measure incoming signals that vary in time and space, calculate parameters such as peak power, decode transmission information, and calculate derivative information based on the measurements. The data can be made available in whole or in part to users via the user interface 108 of the control system 110. The digital signals can be stored in the memory unit 114 of the control system 110 for future evaluation in whole or in part, including the calculated data.

[0036] In some instances, the control system 110 may include computer-readable code that can be run on a processor. The computer-readable code may be presented on the user interface 108; and it may be modified or updated by the user to modify values of control parameters of the laser control system 104 and values of processing parameters of the signal processing system 106. The user interface 108 may also run diagnostics to monitor the health of the system. In some instances, the control system 110 includes an autonomous system interfacing with the user through the user interface 108, as does the signal processing system. In some instances, the autonomous system may be configured to automatically run in the background to keep the laser frequencies fixed, to control laser power, to potentially control some signal processing, e.g., using matched filters or in another manner, or to perform other functions.

[0037] FIG. 2 is a schematic diagram showing aspects of an example Rydberg Microprobe [RMP] system 200. As shown in FIG. 2, the example RMP system 200 includes electrical probes 202RX, 202TX, a stage 204 and a probe head 210. The probe head 210 is coupled to other components of the RMP system 200 [e.g., the control system 110 of FIG. 1) through an optical fiber 216. In some instances, the probe head 210 may be implemented as the example probe head 102, 300, 330, 400 as shown in FIGS. 1, 3A-3B, 4 or in another manner. In some instances, the probe head 210 of the RMP system 200 can be configured to perform linear, nonlinear, and EMC / EMI characterization of a DUT 206.

[0038] As shown in FIG. 2, the stage 204 is configured to provide high-precision movement in multiple axes, allowing accurate positioning of the probe head 210 over specific locations on the DUT 206. This precision allows accurate characterization of the DUT 206 at high spatial resolution. In some instances, the stage 204 may be configured to provide automated movement enabling automated testing procedures, reducing the need for manual adjustments and improving overall efficiency and repeatability of tests. In some instances, the stage 204 includes a linear movement control unit for linearly shifting the stage 204 in X-Y-Z directions, a rotation control unit for rotating the stage 204 along X-Y-Z axis, micro-positioners for fine adjustment, vacuum line for securing the DUT 206 on the stage 204, a temperature control unit for maintaining a controlled temperature environment, motors / actuators, an optical microscope, and other components.

[0039] In some instances, the DUT 206 is supported on the stage 204. For example, the DUT 206 may include high-frequency and high-speed devices. Circuits and integrated systems are typically tested on-wafer for both research and development as well as production. The DUT 206 may include RFICs, AiP, AoP, high-speed digital ICs on wafer, high-speed digital / mixed ICs, chiplets, SiP, MCM, or other IC devices. RFICs typically operate between 1-100 GHz. For 5G-NR, RFICs operate in both microwave and millimeterwave bands. Linear, nonlinear, and EMC / EMI aspects of the DUT 206 can be of significant importance for compliance with industrial and government regulatory requirements and can be tested using the probe head 210 of the RMP system 200.

[0040] In some instances, the electrical probes 202TX, 202RX each may include a mechanical structure or assembly that holds and positions probing needles or probes which allow formation of one or more electrical contacts with the DUT 206. In some instances, the DUT 206 may only form a single electrical contact with the electrical probe 202RX. In this case, the output of the DUT 206 may be terminated to transmit electrical signals. For example, when characterizing an RFIC device connected to an antenna, a single electrical contact using the electrical probe 202RX for example can be formed with the RIFC device for communicating electrical signals to the RFIC device. The probe head 210 may be positioned for receiving and detecting the RF signals emitted from the antenna. In someinstances, the electrical probes 202TX, 202RX are configured to form two or more electrical contacts with the DUT 206.

[0041] As shown in FIG. 2, the probe head 210 includes a primary vapor cell 212 and a capillary 214 bonded to the primary vapor cell 212 and aligned with the optical fiber 216. The capillary 214 and the primary vapor cell 212 are also in fluidic communication with each other. A first interior volume defined by the primary vapor cell 212 is fluidically joined with a second interior volume defined by the elongated body of the capillary 214. The tip of the capillary 214 is positioned near the DUT 206. The input optical signals received from the optical fiber 216 can travel through the interior volume of the primary vapor cell 212 and the interior volume of the elongated body of the capillary 214 to a reflective window at the tip of the capillary 214, which can reflect the input optical signals back to the optical fiber 216 and further to the control system for analysis. In some instances, positioning of the tip of the capillary 214 can be guided using an integrated camera. The camera can be configured to optically magnify the tip of the capillary 214 and the DUT 206 so as to position the tip of the capillary 214 with a high precision, e.g., in a range of microns or another range. In certain examples, laser positioning can also be implemented through the probe head 210 to position it adjacent to the DUT 206 precisely. In some cases, electrical signals can be communicated to the DUT 206 via the electrical probes 202TX, 202RX, for example, being placed adjacent the DUT [e.g., within 100’s of microns from the DUT). In some instances, when electrical contacts are formed and electrical signals are communicated to the DUT 206, electromagnetic signals to be detected by the probe head 210 can be generated by the DUT 206. When the electrical probes 202TX and 202RX are placed away from the DUT 206, the primary vapor cell 212 of the probe head 210 can be implemented without the capillary 214, for example using the probe head 500 shown in FIG. 5 for conducting measurements using a free-space coupling of the light to and from the vapor cell of the probe head.

[0042] FIGS. 3A and 3B include schematic diagrams showing different views of example probe heads 300, 330. In some instances, the probe heads 300, 330 can be used in an RMP system for characterizing integrated circuit devices. The example probe heads 300, 330 each includes a vapor cell sensor 302, 332, and an optical fiber 310 coupled to the vaporcell sensors 302, 332 through a lens system 312. As shown in FIG. 3A, the vapor cell sensor 302 includes a primary vapor cell 320A and a capillary 320B bonded to the primary vapor cell 320A. As shown in FIG. 3B, the vapor cell sensor 332 includes a primary vapor cell 340A and a capillary 340B bonded to the primary vapor cell 340B. Each capillary 320B, 340B includes an opening on a first end and a reflective surface on a second end. Each capillary 320B, 340B also includes interior surfaces that define a first portion of an interior volume of the vapor cell sensor 302, 332. The interior volume of the vapor cell sensor 302, 332 includes a vapor having Rydberg states that can be used to sense electromagnetic signals emitted from integrated circuit devices. Each of the primary vapor cells 320A, 340A includes interior surfaces that define a second portion of the interior volume of the vapor cell sensor 302, 332 and a port which is positioned relative to the opening of the capillary to join the first and second portions of the interior volume of the vapor cell sensor 302, 332. The example probe heads 300, 330 each may include additional or different features, and the components of the probe heads 300, 330 may operate as described with respect to FIG. 3A-3B or in another manner. In some instances, the probe heads 300, 330 may be used to perform operations in the example process 600 of FIG. 6.

[0043] In some implementations, each of the vapor cell sensors 302, 332 is a selfcalibrated sensor; and its calibration can be maintained over long measurement times. The vapor cell sensor 302, 332 can measure power accurately, for example, at FR2 frequencies. The spatial resolution of the probe heads 300, 330 is set by the overlap of the laser beams used in the Rydberg atom-based sensor. Sub-wavelength imaging can be obtained using the example probe head 300, 330. The example probe heads 300, 330 are an over-the-air [OTA] sensor and do not have to contact the surface of the DUT. The example probe heads 300, 330 are electromagnetically transparent so they can minimally perturb the electromagnetic emission that they probe. The example probe heads 300, 330 have a broad carrier bandwidth [e.g., 1 MHz-1 THz) so they can shift the sensing frequency by changing the coupling laser frequency - no mechanical changes are necessary, so recalibration and repositioning are not required. The overall approach is parallelizable through imaging. Each of the probe heads 300, 330 delivers the baseband signal directly to an opticaldetector whose output analog electrical signal can be directly converted to a digital signal for digital signal processing.

[0044] As shown in FIGS. 3A-3B, the primary vapor cells 320A, 340A each include a dielectric body 306 with an optical window 308A bonded to the dielectric body 306 on a first side. The dielectric body 306 may be a substrate that has opposing planar surfaces. However, other configurations are possible for the dielectric body 306. Moreover, although FIGS. 3A-3B depict the dielectric body 306 as being a rectangular prism with a squareshaped cross-section, other shapes are possible. The optical window 308A may also be a substrate defined by opposing planar surfaces. However, other configurations are possible for the optical window 308A. In general, the optical window 308A includes one surface adapted to mate [or bond] against a surface of the dielectric body 306, thereby allowing a hermetic, vacuum seal to form [e.g., via a contact bond or an anodic bond].

[0045] In some instances, the dielectric body 306 may be formed of a material highly transparent to electric fields [or electromagnetic radiation] measured by the vapor cell sensor 302, 332. The material may be an insulating material having a high resistivity, e.g., p>108 fl-cm or another value, and may also correspond to a single crystal, a polycrystalline ceramic, or an amorphous glass. For example, the dielectric body 306 may be formed of silicon. In another example, the dielectric body 306 may be formed of a glass that includes silicon oxide [e.g., SiCh, SiOx, etc.], such as vitreous silica, a borosilicate glass, or an aluminosilicate glass. In some instances, the material of the dielectric body 306 is an oxide material such as magnesium oxide [e.g., MgO], aluminum oxide [e.g., AI2O3], silicon dioxide [e.g., SiCh], titanium dioxide [e.g., TiCh), zirconium dioxide, [e.g., ZrCh), yttrium oxide [e.g., Y2O3], lanthanum oxide [e.g., La20s], and so forth. The oxide material may be non- stoichiometric [e.g., SiOx], and may also be a combination of one or more binary oxides [e.g., Y:ZrO2, LaAlOs, etc.]. In other instances, the material of the dielectric body 306 is a nonoxide material such as silicon [Si], diamond [C], gallium nitride [GaN], calcium fluoride [CaF2], and so forth. In these instances, an adhesion layer may be disposed on the dielectric body 306 to define the surface of the dielectric body 306. The adhesion layer may be capable of bonding to the non-oxide material of the dielectric body 306 while also being capable of forming a contact bond with the optical window 308A. For example, thedielectric body 306 may be formed of silicon and the example vapor cell sensor 302 may include an adhesion layer that includes silicon oxide [e.g., SiCh, SiOx, etc.) on the dielectric body 306. This adhesion layer may define the surface of the dielectric body 306 and may be capable of forming a contact bond that includes siloxane bonds and anodic bonds.

[0046] As shown in FIGS. 3A-3B, the dielectric body 306 includes a cavity 316 which is configured to hold a vapor [or a source of the vapor) and partially defines a portion of the interior surfaces of the primary vapor cell 320A, 340A. In some instances, the cavity 316 may extend from an opening into the dielectric body 306 and completely through the dielectric body 306. The cavity 316 may have a uniform cross-section along its extension through the dielectric body. However, in some variations, the cross-section of cavity 316 may vary along its extension direction. As shown in FIG. 3A, the vapor cell sensor 302 only includes one optical window 308A on a first surface which partially defines a portion of the interior surfaces of the primary vapor cell sensor 320A. In this case, the port of the primary vapor cell 320A is defined on a surface of the dielectric body 306. The capillary 320B is directly bonded to the dielectric body 306 of the primary vapor cell 320A.

[0047] As shown in FIG. 3B, the vapor cell sensor 332 in FIG. 3B includes a first optical window 308B and a second optical window 334 bonded to a second surface of the dielectric body 306 opposite to the first optical window 308A. In some instances, the first and second optical windows 308A, 334 define respective portions of the interior surfaces of the primary vapor cell 340A. In some implementations, the second optical window 334 of the probe head 330 in FIG. 3B includes a through hole to allow fluidic communication between the cavity of the dielectric body 306 and the hollow interior 324 of the capillary 304. In this case, the port of the primary vapor cell 340A is defined by the through hole on the second optical window 334; and the port of the primary vapor cell 340A passes through the second optical window 334. In other words, when the second optical window 334 is bonded to the dielectric body 306, the through hole 336 aligns with the opening of the cavity 316 of the primary vapor cell 340A; and the through hole 336 becomes the port of the primary vapor cell 340A. In this case, the capillary 340B is bonded to the primary vapor cell 340A through the second optical window 334. In some instances, the second optical window 334 may be implemented as the first optical window 308A.

[0048] In some instances, the vapor in the cavity 316 of the dielectric body 306 may include constituents such as a gas of alkali-metal atoms, a noble gas, a gas of diatomic halogen molecules, or a gas of organic molecules. For example, the vapor may include a gas of alkali-metal atoms [e.g., K, Rb, Cs, etc.], a noble gas [e.g., He, Ne, Ar, Kr, etc.], or both. In another example, the vapor may include a gas of diatomic halogen molecules [e.g., F2, Ch, Bn, etc.], a noble gas, or both. In yet another example, the vapor may include a gas of organic molecules [e.g., acetylene], a noble gas, or both. Other combinations for the vapor are possible, including other constituents.

[0049] In some implementations, the dielectric body 306 includes one or more pockets 314. In some implementations, each pocket 314 is communicably coupled to the cavity 316; and is configured to hold a liquid or solid material, e.g., a vapor source, coating materials, getters, or other materials. For example, the vapor source in a pocket 314 may generate the vapor in response to an energetic stimulus, such as heat, exposure to ultraviolet radiation, and so forth. In some instances, a getter may be barium [barium azide], titanium or other material that can absorb [by reacting with] O2, N2, etc. In some instances, a getter can act like a pump inside the vapor cell sensor for pumping background gases in the vapor cell sensor 302. In some implementations, the vapor source may reside in the cavity 316. In certain examples, the pockets 314 and the cavity 316 may be formed using laser cutting or other techniques in the dielectric body 306. In some instances, interior surfaces of the cavity 316 and the pockets 314 can be coated with materials to prevent atomic depolarization or to suppress the effect of atoms attaching to the interior surface of the cavity 316 or the pockets 314. The dielectric body 306 may be a multi-pocketed silicon or glass frame. In some instances, the size of the frame may be 6 mmx 6 mm in cross-section with a thickness of around 1-2 mm.

[0050] In some instances, the dielectric body 306 may also include a plurality of holes between the cavity 316 and a side of the dielectric body 306. The plurality of holes may define an array of holes. The plurality of holes may reduce a refractive index mismatch between the dielectric body 306 and an ambient environment thereof [e.g., air] when the example vapor cell 302 receives electromagnetic radiation from the DUT. The plurality of holes may also reduce a scattering cross-section of the example vapor cell 302 whenreceiving the electromagnetic radiation as well as increasing a uniformity of the electromagnetic radiation in the cavity 316. In some implementations, the example vapor cell 302, 332 are configured to detect a target radiation, such as an electromagnetic radiation having a frequency ranging from 1 MHz to 1 THz. In such implementations, the plurality of holes can be sized to have a largest dimension no greater than a wavelength of the target radiation, and the target radiation may have a wavelength of in a range of equal to or greater than 0.3 mm.

[0051] In some instances, the plurality of holes may encircle a perimeter of the cavity 316. For example, the plurality of holes may include two or more subsets of holes, each having a different shape. In some implementations, the plurality of holes includes a pattern of holes repeating around a perimeter. For example, if the plurality of holes includes two or more subsets of holes, the two or more subsets of holes may be arranged relative to each other along the perimeter to define a pattern.

[0052] In some instances, the plurality of holes extends completely through the dielectric body 306. In certain instances, a portion [or all] of the holes extends only partially through the dielectric body 306. In some variations, one or more holes may vary in cross-section along an extension into the dielectric body 306. Moreover, the extension into the dielectric body 306 need not be perpendicular to the surface or be straight. In some instances, the extension is angled relative to the surface of the dielectric body 306. In some instances, the extension follows a curved pathway into the dielectric body 306. In some instances, the holes may be implemented as the holes 408 in the example probe head 400 shown in FIG. 4, or in another manner.

[0053] In some instances, the optical window 308A may be formed of a material that is highly transparent to electromagnetic radiation [e.g., laser light] used to probe the vapor sealed within the cavity 316 of the dielectric body 306. For example, the material of the optical window 308A may be transparent to infrared wavelengths of electromagnetic radiation [e.g., 700-1000 nm], visible wavelengths of electromagnetic radiation [e.g., 400- 700 nm], or ultraviolet wavelengths of electromagnetic radiation [e.g., 200-400 nm]. Moreover, the material of the optical window 308A may be an insulating material having a high resistivity, e.g., p>108 fl-cm or another value, and may also correspond to a singlecrystal, a polycrystalline ceramic, or an amorphous glass. For example, the material of the optical window 308A may include silicon oxide [e.g., SiCh, SiOx, etc.), such as found within quartz, vitreous silica, or a borosilicate glass. In another example, the material of the optical window 308A may include aluminum oxide [e.g., AI2O3, AlxOy, etc.), such as found in sapphire or an aluminosilicate glass. In some instances, the material of the optical window 308A is an oxide material such as magnesium oxide [e.g., MgO), aluminum oxide [e.g., AI2O3), silicon dioxide [e.g., SiCh), titanium dioxide [e.g., T1O2), zirconium dioxide, [e.g., ZrCh), yttrium oxide [e.g., Y2O3), lanthanum oxide [e.g., La2Os), and so forth. The oxide material may be non-stoichiometric [e.g., SiOx), and may also be a combination of one or more binary oxides [e.g., Y:ZrO2, LaAlOs, etc.). In other instances, the material of the dielectric body 306 is a non-oxide material such as diamond [C), calcium fluoride [CaF), and so forth. As shown in FIGS. 3A-3B, the optical window 308A covers and seals the cavity 316 and the pockets 314 in the dielectric body 306. In some implementations, the optical window 308A is coated with an anti-reflection coating. When the anti-reflection coating is facing the cavity 316 and the pockets 314, the anti-reflection coating may be inert to cesium reaction; and can also be made to bond to the dielectric body 306. In some instances, the anti-reflection coating may be on the exterior surface of the optical window 308A to accommodate better laser transmission through the vapor cell sensor 302, 332. In some instances, the optical window 308A may be optically opaque in the visible wavelength; and may have a thickness in a range less than 100 pm. In some instances, the optical window 308A may include silicon due to its low gas permeation. The dielectric body 306 and the optical window 308A may be bonded together using an anodic bond, a contact bond, a fired glass-frit bond, or another type of bond.

[0054] In certain examples, the capillary 340B can be less than 100 pm in diameter, 300 pm in diameter, 1 mm in diameter, or may be in another range. The length of the elongated body 304 of the capillary 340B can be in the range of tens of millimeters or multiple centimeters, and may be configured to clear the wafer probes that supply signals to the DUT. The capillary 340B may be machined with both ends polished. The capillary 340B can be bonded to a reflective window 308B on one end in a furnace or in another manner. The reflective window 308B can at least reflect the input optical signals received from theoptical fiber 310 via the primary vapor cell 340A. In some implementations, the reflective window 308B allows both the co-propagating and counter-propagating electromagnetically induced transparency [EIT] or electromagnetically induced absorption [EIA] signals to be observed, enabling the detuning of the laser systems to be determined and compensated.

[0055] As shown in FIGS. 3A-3B, the elongated body 304 of the capillary 320B, 340B includes a wall 322 and a hollow interior 324. In some instances, the hollow interior 324 extends from one end to the opposite end of the elongated body 304. In some instances, the capillary 320B can be directly bonded to the dielectric body 306 of the primary vapor cell 320A as shown in the example probe head 300 in FIG. 3A. In some instances, the capillary 340B can be bonded to the optical window 334 of the primary vapor cell 340A as shown in the example probe head 330 in FIG. 3B. In some implementations, the hollow interior 324 of the elongated body 304 is fluidically coupled to the cavity 316 in the dielectric body 306 of the primary vapor cell 320A, 340A allowing the vapor in the cavity 316 to pass from the cavity 316 through a port 326 on the dielectric body 306 to the hollow interior 324 of the elongated body 304. In some instances, the diameter of cross-section of the hollow interior 324 may be greater than the cross section of the cavity 316 or at least greater than the cross section of the port 326 in the dielectric body 306 or a through hole 336 in the optical window 334.

[0056] In some implementations, the optical fiber 310 is optically coupled to the primary vapor cell 320A, 340A through a lens system 312. The lens system 312 is configured to shape the input optical signals received from the optical fiber 310. The lens system 312 may be a single GRIN lens, a ball lens, or another type of lens; or the lens system 312 may include multiple lenses. In some instances, the lens system 312 may include a polarization control unit, which can be implemented as a waveplate, a polarizer, or other optical components. The optical fiber 310 can be polarization preserving, single mode or multi-mode fiber. In some instances, the lens system 312 can be mechanically attached to the optical window 308A on the first side of the dielectric body 306. In some implementations, the lens system 312 and optical fiber 310 are configured to separate the returning laser signal [probe laser] to direct it to the receiving detector under a directionalcoupling configuration. In some instances, the lens system 312 and the optical fiber 310 may be configured in another manner.

[0057] In some implementations, the vapor cell sensors 302, 332 are communicably coupled to a control system [e.g., the control system 110 in the example system 100 of FIG. 1] through the optical fiber 310. The laser signals generated from the control system can be communicated to the vapor cell sensor 302, 332 through the optical fiber 310. In some cases, other types of waveguides, like photonic integrated circuits, can be used to transport the light to the tip of the capillary 320B, 340B through the cavity 316 of the dielectric body 306. Different light delivery systems, including those designed to image over some areas of the probe head are possible. In these systems, it is possible to engineer the depth of field using an optical imaging system. When the probe heads 300, 330 are designed for a specific point to be detected, e.g., single pixel sensor, the optical imaging system can be engineered for a small depth of focus to control the spatial resolution in the direction normal to the reflective window 308B.

[0058] Once the first and second optical windows 308A, 334 and the elongated body 304 of the capillaries 320B, 340B are constructed, the capillaries 320A, 340B can be bonded to the dielectric body 306 of the primary vapor cell 320A, 320B. In some implementations, the hollow interior 324 of the elongated body 304 is pumped out; and filled with the vapor, getters, coating materials, or other materials. The elongated body 304 is then sealed with the reflective window 308B and the dielectric body 306 is sealed with the first optical window 308A. In some instances, the reflective window 308B may be bonded to the elongated body 304 in atmosphere [ambient pressure] prior to the bonding of the first window 308A to the dielectric body 306 in vacuum. Once capped, the optical fiber 310 and the lens system 312 can be bonded, e.g., glued to the first optical window 308A. In some instances, the optical fiber 310 and the lens system 312 may be configured relative to the vapor cell sensor 302, 332 in another manner. For example, a capillary tube can be used to allow the lens system 312 to be optically coupled to the first optical window 308A without having direct contact with the first optical window 308A. The optical fiber 310 and the lens system 312 alignment can direct the light to the first optical window 308A through the cavity 316 across the hollow interior of the elongated body 304; and capturethe reflected laser signals from the reflective window 308B of the capillary 320B, 340B in order to transport it through the optical fiber 310 to one or more optical detector of the control system.

[0059] In some aspects of operation, light is delivered to the vapor cell sensor 302, 332 from the lens system 312 so that it passes through the first optical window 308A, the cavity 316, the hollow interior 324 of the elongated body 304, and reflects off the reflective window 308B back into the optical fiber 310. In these cases, a lens such as a gradient-index [GRIN] lens collimates the laser light into a beam that has a spot size on the order of 100 microns. The probe laser light reflected back through the vapor cell sensor 302 can be collected on the optical fiber 310 and separated using a fiber optic splitter and polarization optics, e.g., a quarter waveplate and a polarizing beam splitter. In some instances, other optical configurations may be possible. The reflected light can be directed to one or more optical detectors where it is converted to electrical signals that are fed to a signal processing system [e.g., the signal processing system 106 of the system 100 in FIG. 1].

[0060] In some cases, a stage [e.g., the stage 204 in the RMP system 200] for mounting the DUT can be moved to interact with the probe heads 300, 330. In some instances, the probe heads 300, 330 may be implemented as the probe head 210, 400 in FIGS. 2, 4, or in another manner. In some instances, the example probe heads 300, 330 may be attached to a scanner configured to accurately position the tip of the capillary 320B, 340B.

[0061] FIG. 4 is an image showing a top view of an example probe head 400. The example probe head 400 includes a vapor cell sensor 410 which includes an optical window 402, a dielectric body 404, a cavity 406, and patterned holes 408. In some instances, the optical window 402, the dielectric body 404, the cavity 406, and the patterned holes 408 are implemented as the respective components in the vapor cell sensor 302 described in FIGS. 3A-3B. The example probe head 400 may be implemented and operated as the probe head 102, 210, 300, 330 in FIGS. 1, 2, 3A-3B. The patterned holes 408 are voids having sub -wavelength dimensions for a target electromagnetic radiation that is to be measured by the vapor cell sensor 410. Moreover, the structures maintain the mechanical integrity of the vapor cell 410 with regards to a vacuum-tight seal and handling during manufacturing and deployment. The example probe head 400 may be opticallycoupled to a control system through a waveguide such as an optical fiber (not shown). In some implementations, the patterned holes 408 are larger than a wavelength of the target electromagnetic radiation if scattering of the incident radiation and interference are used to either enhance or eliminate the electromagnetic field. In other words, the vapor cell sensor 410 may have a low radio frequency scattering cross-section. The cavity 406 of the vapor cell sensor 410 is also fluidically coupled to a capillary (not shown) on the bottom side the dielectric body 404 opposite to the optical window 402.

[0062] FIG. 5 is a schematic diagram showing a perspective view of an example probe head 500. As shown in FIG. 5, the probe head 500 includes a vapor cell sensor 510 having a dielectric body with a lattice structure 504. The lattice structure 504 of the dielectric body of the vapor cell sensor 510 defines multiple cavities 502. The example lattice structure 504 is configured to support optical windows (not shown) with a thickness for example in a range, e.g., less than < 100 pm. The example lattice structure 504 has the structural integrity to support the necessary vacuum pressure within the cavities 502. In some instances, the thickness of the example vapor cell 510 may be less than 1 mm. As shown in FIG. 5, the lattice structure 504 includes slots 506 cut in the lattice structure 504 between neighboring cavities 502 to allow the vapor to pass through the cavities 502. The cavities 502 of the vapor cell sensor 510 can define multiple sensing regions for the probe head 500. In some instances, the probe head 500 can be positioned relative to the surface of the DUT according to the measurement geometry. For example, when a large area close to the DUT is available, the probe head 500 can be positioned close to the surface of a substrate where the DUT resides to measure near field electromagnetic emission from the DUT. In some instances, the probe head 500 may be optically coupled to a light source over free space.

[0063] In some instances, narrow walls of the lattice structure 504 of the vapor cell sensor 510 can be formed by machining so as to reduce the interaction between the dielectric body of the vapor cell sensor 510 with the electromagnetic fields from the DUT. In some instances, multiple vapor cell sensors 510 may be connected to one another to form arrays since their scattering cross-sections are small relative to their geometric crosssections. The interference of a probe head 500 with one another can be reduced. Thespatial resolution in the vertical direction can be set by the thickness of the probe head 500. The vertical spatial resolution can be increased by decreasing the thickness of the probe head 500 using an approach such as the vapor cell shown in FIG. 5. One or more techniques described in the publication "Sub -wavelength microwave electric field imaging using Rydberg atoms inside atomic vapor cells” arXiv:1403.3596vl [physics. atom-ph], 2014; U.S. Patent No. 10,509,065; or U.S. Patent No. 10,802,066 may be used in some cases. In some instances, laser beams may be focused on the probe head 500 to increase the vertical spatial resolution.

[0064] FIG. 6 is a flow chart showing aspects of an example process 600 for characterizing integrated circuit devices. The example process 600 can be used, for example, to operate the example systems 100, 200 in FIGS. 1-2 or another type of system. The process 600 may be performed, at least in part, by a system that includes a probe head which may be implemented as the probe head 102, 210, 300, 330, 400, 500 shown in FIGS. 1-5. For instance, the example process 600 can be used to perform linear or non-linear characterization of electromagnetic emissions from a DUT residing on a substrate. The example process 600 may include additional or different operations, including operations performed by additional or different components, and the operations may be performed in the order shown or in another order. In some implementations, one or more operations in the example process 600 can be performed by a computer system, for instance, by a digital computer system having one or more digital processors [e.g., data processing apparatus of the control system 110 in FIG. 1] that execute instructions [e.g., instructions stored in the memory unit 114 of the control system 110 in FIG. 1].

[0065] At 602, a DUT is received. In some instances, the DUT may be carried by a substrate. The DUT may be implemented as the DUT 206 and may be positioned on a stage of a RMP system [e.g., the stage 204 of the RMP system 200 in FIG. 2). In some instances, the DUT may include radio frequency integrated circuits [RFICs], antenna in package [AiP], antenna-on-package [AoP], high-speed digital integrated circuits [ICs] on wafer, chiplets, system-in-package [SiP], and multi-chip modules [MCM], and other IC devices, in particular for 5G-NR and other millimeter-wave applications.

[0066] At 604, electrical contacts are formed with the DUT. In some instances, the electrical contacts may be formed by positioning electrical probes on contact pads or terminals associated with the DUT. In some instances, a single electrical contact or multiple electrical contacts may be formed with the DUT.

[0067] At 606, a probe head is positioned adjacent to the DUT. The probe head can be supported and moved by a mounting system across the surface of the DUT. In certain examples, the probe head is fixed and the position of the probe head relative to the DUT can be adjusted by adjusting the position and orientation of the stage supporting the DUT. In some instances, the position of the probe head relative to the surface of the DUT is determined by the geometry of the probe head and the available space [e.g., partially defined by the electrical probes, optical microscope, etc.). In some implementations, the probe head of the RMP system is operated under a reflective mode.

[0068] At 608, electromagnetic radiation from the DUT is detected. After the probe head is positioned relative to the DUT, electrical signals can be applied to the DUT through the electrical contacts. Electromagnetic radiation emitted from the DUT during operation can interact with the vapor in the vapor cell sensor or the vapor in the capillary of the probe head according to the design of the probe head. Input optical signals generated by a control system [e.g., the laser sources 116 of the control system 110 in FIG. 1) can be directed through a transmission media [e.g., optical fiber or free space) to the probe head to interact with the electromagnetic signals and measure the response of the vapor to the received electromagnetic signals. In some instances, the interaction can be detected by receiving output optical signals from the probe head, converting the received output optical signals to electrical signals, and processing the electrical signals. In some instances, the operating frequency of the vapor cell sensor can be tuned to detect harmonics of the central frequency. In certain examples, the coupling laser can be tuned to sense a higher-order harmonic [e.g., second, third or other high-order) emitted from the DUT. In some examples, the bandwidth of the vapor cell is ~100 GHz, which may be accessed without making any changes except for the wavelength of one of the laser fields used to configure the vapor cell sensor. In some implementations, the RMP system is configured to cover a frequency range for RFICs, high-speed-ICs, multi-chip packaging, AiP, and AoP. RFICs, in particular for 5G-NR and other millimeter-wave applications. The solution significantly simplifies the measurements, reducing the time and cost of characterizing integrated circuit devices.

[0069] In some implementations, a vapor cell sensor of the probe head is tuned to a carrier frequency of radio frequency radiation emitted from the DUT. In this case, the RMP system can be configured according to the carrier frequency. In particular, a laser control system and a signal processing system [e.g., the laser control system 104 and the signal processing system 106 of the control system 110 in the system 100 shown in FIG. 1] may be configured by inputting the carrier frequency through a user interface [e.g., the user interface 108]. In some instances, the RMP system may be configured to scan a frequency range around the carrier frequency. For example, for a DUT with a frequency of the electromagnetic signals at 28 GHz, the RMP system can be configured to scan a frequency range from 26 GHz to 30 GHz, e.g., to search for the electromagnetic signals emitted from the DUT. In some instances, the carrier frequency and its harmonics are in a microwave frequency range below 7.125 GHz, a millimeter-wave frequency range above 24.25 GHz, or in another frequency range. For example, a coupling laser in the RMP testing system 100 or one of the coupling lasers when the system 100 includes more than two lasers that can be tuned to a Rydberg state with a resonance frequency overlapping with the frequency of the electromagnetic signals emitted from the DUT. In some instances, the RMP system may be tuned to allow an interaction between the vapor of Rydberg atoms in the vapor cell sensor and the input optical signals in the presence of the radio frequency radiation at the carrier frequency and its harmonics emitted by the DUT.

[0070] In some instances, the vapor cell sensor can be fine-tuned to a frequency range overlapping with the frequency of the electromagnetic signals emitted from the DUT. For example, the frequency range of the electromagnetic signals emitted from the DUT may be known; and the vapor cell sensor can be tuned to a frequency range overlapping with the frequency of the electromagnetic signal in the frequency domain. In some instances, the frequency range of the electromagnetic signals emitted from the DUT may be unknown; and the operating frequency of the vapor cell sensor can be adjusted in order to scan a broader frequency range before focusing on a narrower frequency range that overlaps withthe frequency range of the electromagnetic signals emitted from the DUT for optimum sensitivity.

[0071] In some implementations, output optical signals are generated by the vapor cell sensor based on an interaction between the vapor cell sensor and the input optical signals in the presence of the electromagnetic signals from the DUT. In some implementations, two or more laser sources are configured to generate input optical signals that include at least one coupling optical signal and at least one probe optical signal. The two or more laser sources are in optical communication with the vapor cell sensor of the probe head through a transmission medium [e.g., in free-space or through optical fiber] and as such, the coupling and probe optical signals can interact with the vapor having Rydberg states in the vapor cell sensor. Such interaction may allow the vapor cell sensor to perform Rydberg atom-based radio frequency sensing, and thereby generate the output optical signals based on the coupling and probe optical signals. In some implementations, the output optical signals may represent the response of the vapor having Rydberg states in the vapor cell sensor to the electromagnetic signals emitted from the DUT. In some instances, a vapor having Rydberg states can be a vapor of Rydberg atoms [e.g., Rb, Cs, etc.], Rydberg molecules [e.g., H2, 12, etc.] or possibly both. For example, the output optical signals from the vapor cell sensor can be generated using electromagnetically induced transparency [EIT] or electromagnetically induced absorption [EIA]. In some instances, a sub-Doppler method can be used to obtain higher spectral resolution in the Autler-Townes regime and higher sensitivity. In some instances, the one or more input optical signals are locked to a stable, narrow bandwidth reference such as a frequency comb, interferometer, atomic or molecular absorption line, or another type of reference.

[0072] In some instances, the coupling or probe optical signal can be scanned to obtain the output optical signals. In certain examples, the probe optical signal can be used to generate a frequency comb in an optical heterodyne setup to obtain the first set of output optical signals. In some instances, a frequency comb read out of the output optical signals can be implemented as described in the publication "Rydberg Atom-based Electrometry using a Self-heterodyne Frequency Comb Readout and Preparation Scheme,” Physical Review Applied 19, 034078, 2023, or it may be possible to perform such a readout inanother manner. In some instances, pulsed readout can be used to acquire the transmitter signals, perhaps in combination with laser frequency changes, as described in the publications "Sensing signals that include radio frequency pulses,” U.S. Patent No. 11,681,016, issued June 20, 2023, and "The Origins of Rydberg Atom Electrometer Transient Response and its Impact on Radio-Frequency Pulse Sensing,” Physical Review Applied 18, 034030, 2022; or it may be possible to acquire transmitter signals in another manner. In some instances, the coupling optical signal of the EIT or EIA-like system can be tuned to different Rydberg states to target different RF frequencies. In some instances, spectral signals within a bandwidth of ~250 MHz of the target frequency can be detected by analyzing the optical spectra for a single Rydberg transition and / or detuning the coupling and probe lasers that may be used for Rydberg atom-based sensing as described in the publication "Rydberg-Atom Sensors in Bichromatic Radio-Frequency Fields,” Phys. Rev. Applied 20, 024068, 2023; or it may be possible to detect spectral signals in another manner. The optical signal for monitoring the laser sources and keeping them stable can be routed via the waveguide through all or part of the RMP system. Feedback to control the laser sources, including feed forwards, can be realized using FPGAs, analog electronics, or another processor-based system that can be controlled through a user interface and through autonomous control layers operating in different types of processors. When a frequency comb is used, the signal processing system of the RMP system may include a real-time spectrum analyzer which can be used to detect the output optical signals. In the case of a frequency comb, it is not necessary to scan either of the coupling and probe optical signals to read out the output optical signals, although it is possible to use scanning and a frequency comb in combination with each other.

[0073] In some instances, an average optical spectrum may be obtained. For example, the average optical spectrum may be obtained using a frequency comb, or another technique. In some instances, the results can be fit to identify spurious signals within a specified range [e.g., ~250 MHz) of the carrier frequency using a software without tuning to a different Rydberg state. For example, the spurious signals may include signals that do not have the correct periodicities and those at unwanted frequencies. In some instances, an interferer close to the carrier frequency can lead to perturbed spectra, and a power scan ofthe beam can be used to identify avoided crossing in the data as described in the publication "Rydberg-Atom Sensors in Bichromatic Radio-Frequency Fields,” Phys. Rev. Applied 20, 024068, 2023.

[0074] In some instances, two sets of laser beams can be passed through the vapor cell sensor. One set of laser beams can be configured to detect the electromagnetic signals while the other set of laser beams with the probe beam configured as the frequency comb, is configured to acquire the spectrum. In some instances, when only one set of laser beams is used, a lock signal can be generated from the central comb line.

[0075] At 610, output signals are analyzed. In some instances, output optical signals include the optical signals reflected from the vapor cell sensor, either from the reflective window of the primary vapor cell or the capillary. The output optical signals can be detected, converted and analyzed to characterize the electromagnetic signals emitted from the DUT. For example, the output optical signals can be communicated from the probe head via the optical fibers to an optical detector where the output optical signals are converted to analog electrical signals. In this case, the optical detector can sense changes in the transmission caused by the electromagnetic signals to the vapor cell sensor; and convert the output optical signals to respective analog electrical signals. In some instances, the analog electrical signals are then converted [e.g., using analog-to-digital conversion circuitry, or otherwise] to digital data that can be processed on a FPGA, GPU, computer processor, or some combination thereof, including specialized hybrid processors.

[0076] The signal processing system [e.g., the signal processing system 106 in FIG. 1] acquires the analog electrical signals from the optical detector. The analog electrical signals include the baseband signal ata chosen center frequency. The analog electrical signals can be digitized and stored in a digital format. The digitized signals can be processed, for example, in a massively parallel fashion using field programmable gate arrays [FPGAs] or graphics processing units [GPUs]. After analysis, testing results for the specific spatial location and testing time are saved and compiled.

[0077] In some implementations, the digital data is processed to detect a condition of the DUT. In some instances, the digital data can be used to detect the electromagneticsignals. For example, the electromagnetic signals may be decoded using matched filters. In some instances, the digital data may be used to determine different parameters of the DUT, such as its power. In some instances, the one or more matched filters are applied to the digital data to generate a filtered signal. In some instances, the digital data may be compared to a response template, which represents a known response of the vapor to a target radio frequency pulse, by operation of a signal processing system (e.g., the signal processing system 106 in FIG. 1). These correlation coefficients are the projections of the possible symbols on the incoming signals at the maximum time of correlation, e.g., the matched filter aligned with the pulse carrying the synchronization signals. If unwanted interference signals exist within the signal bandwidth (pulse in the time domain) the projection will not strongly correlate with a single symbol. The information can be used to determine the properties of the electromagnetic signals. In some examples, a convolution function may be applied to the digital data and response template to generate the filtered signal. In some instances, the filtered signal may be further processed, by operation of the signal processing system, to determine properties of the electromagnetic signals experienced by the vapor in the vapor cell sensor over the time period. For example, the filtered signals may be processed; and at least one of the properties of the electromagnetic signals experienced by the vapor in a time period can be identified, including a start time, a duration, an amplitude, a frequency, a polarization, and other properties.

[0078] In some instances, the digital data can be subjected to Fourier transform analysis in the FPGA or processing unit. Data from the FPGA or processing unit can be used to locate and measure incoming signals that vary in time and space, calculate parameters such as peak power, decode transmission information, and calculate derivative information based on the measurements.

[0079] In some implementations, the electromagnetic signals can be identified by detecting an amplitude or phase change in the output optical signals. In some implementations, a phase shift [e.g., a pi phase shift] in the synchronization signal is detected. For example, the phase to amplitude conversion can occur because electromagnetically induced transparency [EIT] and electromagnetically induced absorption [EIA] are both coherent processes that depend on the phase of the drivingfields, one of which is the electromagnetic signals emitted from the DUT. Under EIT or EIA conditions, a phase change of the electromagnetic signals causes a change in the probe laser transition polarization of the atomic vapor. A phase shift induces a change in the probe laser transmission. The transient response, which can induce both additional absorption and transmission, is due to the system equilibrating through optical pumping.

[0080] A phase change of the electromagnetic signals can lead to a change in the interference phenomena that are used to dress the atom so that it is sensitive to the electromagnetic signal, as well as readout the electromagnetic signal. When the phase of the electromagnetic signal changes, the transmission, or analogously the absorption, of the probe laser beam will exhibit large changes. The changes can be of the same size as an amplitude modulated RF field. The magnitude of the signal depends on the strength of the RF field and its phase. The phase change and the amplitude can both be used for encoding signals for applications like communications. The fact that the phase can be detected in this way is very useful because it is an all-optical method for detecting phase. In other words, the detection of phase does not require a local RF oscillator. Additionally, in many variations, there is no need for additional lasers or phase stabilization of the lasers. In some examples, looped excitation schemes can be used to extract the phase all-optically.

[0081] In some implementations, the matched filters may also allow the system to pick out and / or separate the transient response and the steady-state response of the vapor in the vapor cell sensor. In some variations, the steady state response may occur at the backend of an RF pulse while the transient response is found at the leading edge of the RF pulse. The phase information is carried in the transient response of the one or more vapor cell sensors while the amplitude is associated with their steady-state signal. The matched filters can, in certain cases, be run in a massively parallel fashion using field programmable gate arrays [FPGAs] or graphics processing units [GPUs]. For example, two sets of EIT / EIA lasers can pass through a single vapor cell with one set detuned from resonance to add a phase shift of TT / 2. The two channels allow the in-phase [I] and out-of-phase components [Q] of the incoming RF wave to be detected in a single measurement [e.g., arbitrary phase and amplitude of the incoming RF wave].

[0082] Once the electromagnetic signal is identified, properties of the electromagnetic signals can be determined. For example, the periodicity, arrival time, and various other properties of incoming, time dependent electromagnetic signals received by the vapor cell sensor from the DUT can be identified. In some implementations, an amplitude of a single pulse of the electromagnetic signals is measured to determine a power level of the electromagnetic signal. In certain instances, a set of pulses of the electromagnetic signal is detected; and the set of pulses of the electromagnetic signal can be averaged. In some instances, the digital data, the filtered signals, etc. can be stored in the memory unit 114 of the control system 110 for future evaluation in whole or in part, including the calculated data.

[0083] In some instances, the radio frequency detection frequency can be tuned across the channels to characterize the channel power at a fundamental frequency and its harmonics. For example, the vapor cell sensor can be tuned to different frequencies around the carrier frequency, the amplitude values of the RF electric fields at different frequencies can be measured. The fundamental and harmonic emission from the DUT can be measured by changing the wavelength of the coupling laser of the same vapor cell sensor. Both the control signals and communications signals can be analyzed and recorded to characterize the condition of the DUT

[0084] In some instances, the harmonic of the carrier frequency of the electromagnetic signals can be detected by looking at the time-dependent signal at a target frequency. The signal can be synchronized with the fundamental signal by using multiple Rydberg atom sensor channels. Once a harmonic is detected, the signal can be subject to a Fourier transform to interrogate the spectral content in the signal. In some instances, a signal as a function of the coupling laser frequency can also be used. By detecting the signal as a function of coupling laser frequency the detuning of the RF frequency from the Rydberg RF detection frequency can be determined by, for example, measuring the asymmetry of the Autler-Townes peaks. Detuning of the RF frequency from the Rydberg states transition frequency changes the mixture of bright and dark states that form the two Autler-Townes states making one transition stronger than the other. The relative amplitude of the Autler- Townes states can be used to determine detuning from the Rydberg RF transition.

[0085] In some instances, nonlinearity in the electromagnetic signals can be detected in addition to RF pulses received from the DUT. The electromagnetic signals from the DUT can be averaged together over time or acquired in real-time.

[0086] In some implementations, the output optical signals are used to determine a measured value of a power level of the RF pulses at a harmonic of the carrier frequency, e.g., a nonlinear emission power level. In some instances, the measurement of a particular DUT at its harmonics is the same as measuring the fundamental frequency, e.g., by measuring an amplitude of a single pulse or by averaging the amplitude of a set of pulses, except the vapor cell sensor is tuned to the harmonic frequency as described above. The measured value of the nonlinear emission power level with a predetermined threshold value of the nonlinear emission power level to determine the condition of the DUT. In some cases, the predetermined threshold values are regulatory threshold values according to EMC requirements, EMF requirements, or other requirements, specified by government regulatory agencies, for example, by the Federal Communications Commission [FCC] of the United States or by a regulatory body of another jurisdiction. In some cases, the regulatory threshold values include values specified by a standards body or a standards document. For example, the 3GPP specifications for Tx [transmitter) spurious emissions provide a regulatory threshold value, e.g., the maximum level of spurious emissions. In some examples, the maximum level of spurious emissions is -36 dBm in a frequency range of 30 MHz and 1000 MHz; -30 dBm for a frequency range of 1GHz and 12.75 GHz; and -13 dBm for a frequency range of 12.75 GHz and second harmonic of the upper frequency edge of the uplink operating band in GHz. In some instances, the regulatory threshold value of the nonlinear emission or spurious emission power levels may have a different value for different countries or regions according to specific reginal regulations or requirements.

[0087] In some implementations, location information of the vapor cell sensor at a measurement location is obtained by operation of a location detection system of the RMP system. For example, the location information of the vapor cell sensor at the measurement location can be detected by operation of the location detection system [e.g., a camera). In some instances, a condition of the DUT determined using the example process 600 can be associated with the location of the DUT where the measurement is performed. In someinstances, the vapor cell sensor of the RMP system can be moved to a different measurement location; the RMP system with the vapor cell sensor at the new measurement location can interact with the electromagnetic signals emitted by the DUT; and a condition of the DUT at the new measurement location can be detected and associated with the new measurement location.

[0088] In some implementations, measurement results for the specific spatial location and testing time are saved and compiled. The output of the control system from the measurement may include the power at the different measurement points [frequencies, positions, etc.]. Harmonics emission exceeding acceptable thresholds are good indicators of transmitter excessive nonlinearity [such as lower than expected IdB-compression points of the power amplifiers]. In some instances, transmitter power at different frequencies may be obtained.

[0089] After these operations, data may be analyzed for diagnostic purposes. For example, when a spurious emission is detected based on the measurement, the system 100 can alert the technicians so that they can take corrective actions. For example, the technician can inform the fabrication engineers to adjust parameters used in the fabrication process.

[0090] In some instances, the operations 608, 610 are repeated for the higher-order harmonics. For example, the coupling laser frequency can be changed to tune to a different Rydberg state that has an RF resonance near the harmonics. Thus, the fundamental and harmonic emission of the DUT can be seamlessly measured by changing the wavelength of the coupling laser of the Rydberg atom-based sensing system using the same vapor cell. In some instances, operations 608, 610 may be repeated for third, fourth, or other high-order harmonic as needed. In some instances, the operations 606, 608, 610 in the example process 600 may be repeated for different spatial positions by shifting the location of the probe head [e.g., the capillary] relative to the position on the DUT. In some instances, the operations 604, 606, 608, 610 in the example process 600 may be repeated to form new electrical contacts; and to characterize the other devices or the other part of the integrated circuits on the same substrate. In some instances, the operations 602, 604, 606, 608, 610 inthe example process 600 may be repeated for characterizing integrated circuit devices on different substrates.

[0091] Some of the subject matter and operations described in this specification can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware, including the structures disclosed in this specification and their structural equivalents, or in combinations of one or more of them. Some of the subject matter described in this specification can be implemented as one or more computer programs, i.e., one or more modules of computer program instructions, encoded on a computer storage medium for execution by, or to control the operation of, data-processing apparatus. A computer storage medium can be, or can be included in, a computer-readable storage device, a computer-readable storage substrate, a random or serial access memory array or device, or a combination of one or more of them. Moreover, while a computer storage medium is not a propagated signal, a computer storage medium can be a source or destination of computer program instructions encoded in an artificially generated propagated signal. The computer storage medium can also be, or be included in, one or more separate physical components or media.

[0092] Some of the operations described in this specification can be implemented as operations performed by a data processing apparatus on data stored on one or more computer-readable storage devices or received from other sources.

[0093] The term "data-processing apparatus” encompasses all kinds of apparatus, devices, and machines for processing data, including by way of example a programmable processor, a computer, a system on a chip, or multiple ones, or combinations, of the foregoing. The apparatus can include special purpose logic circuitry, e.g., an FPGA [field programmable gate array) or an ASIC [application specific integrated circuit). The apparatus can also include, in addition to hardware, code that creates an execution environment for the computer program in question, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, a crossplatform runtime environment, a virtual machine, or a combination of one or more of them.

[0094] A computer program [also known as a program, software, software application, script, or code] can be written in any form of programming language, including compiled or interpreted languages, declarative or procedural languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, object, or other unit suitable for use in a computing environment. A computer program may, but need not, correspond to a file in a file system. A program can be stored in a portion of a file that holds other programs or data [e.g., one or more scripts stored in a markup language document], in a single file dedicated to the program, or in multiple coordinated files [e.g., files that store one or more modules, sub programs, or portions of code]. A computer program can be deployed to be executed on one computer or on multiple computers that are located at one site or distributed across multiple sites and interconnected by a communication network.

[0095] Some of the processes and logic flows described in this specification can be performed by one or more programmable processors executing one or more computer programs to perform actions by operating on input data and generating output. The processes and logic flows can also be performed by, and apparatus can also be implemented as, special purpose logic circuitry, e.g., an FPGA [field programmable gate array] or an ASIC [application specific integrated circuit].

[0096] In a general aspect, a Rydberg microprobe [RMP] system is used to characterize integrated circuit devices.

[0097] In a first example, a system includes a probe head and a control system communicably coupled to the probe head. The probe head includes a vapor cell sensor containing a vapor. The control system is configured to perform operations including moving a stage to position the probe head relative to an integrated circuit device; communicating input optical signals to the probe head, the input optical signals comprising laser signals; receiving, at an optical detector of the control system, output optical signals from the probe head, the output optical signals being generated based on interactions between the vapor and the input optical signals in the presence of electromagnetic signals from the integrated circuit device; and processing, by operation of a signal processingsystem of the control system, electrical signals produced by the optical detector based on the received output optical signals to determine a condition of the integrated circuit device.

[0098] Implementations of the first example may include one or more of the following features. The control system includes two or more lasers configured to generate the input optical signals. Moving the stage includes at least one of translating or rotating the integrated circuit device relative to the probe head. The system includes electrical probes which are configured to electrically contact the integrated circuit device and cause the integrated circuit device to produce the electromagnetic signals. The vapor cell sensor includes a dielectric body which includes an internal lattice structure within an internal volume of the vapor cell sensor.

[0099] Implementations of the first example may include one or more of the following features. The vapor cell sensor includes a primary vapor cell and a capillary bonded to the primary vapor cell. The capillary includes a hollow core photonic crystal fiber. The primary vapor cell defines a first interior volume, and the capillary defines a second interior volume that is in fluid communication with the first interior volume. The primary vapor cell includes a plurality of pockets fluidically connected to one another, each pocket is configured to hold at least one of a vapor source, a coating material, or getters for pumping background gases. The probe head includes a lens system and one or more optical fibers that define an optical path between the control system and the vapor cell sensor. The optical path is configured to communicate the input optical signals to the vapor cell sensor from the control system, and the optical path is configured to communicate the output optical signals from the vapor cell sensor to the control system. The vapor cell sensor includes a reflective surface, and the output optical signals are based on the input optical signals reflected by the reflected surface. The integrated circuit device includes one of an antenna in package (AiP), an antenna-on-package [AoP], a system-in-package [SiP ], or a multi-chip module [MCM].

[0100] In a second example, a method includes positioning a probe head relative to an integrated circuit device, the probe head including a vapor cell sensor containing a vapor; receiving, at the probe head, input optical signals from a control system; detecting, by operation of an optical detector, output optical signals from the vapor cell sensor, theoutput optical signals generated based on interactions between the vapor, the input optical signals, and electromagnetic signals from the integrated circuit device; and determining, by operation of a signal processing system, a condition of the integrated circuit device by processing electrical signals produced by the optical detector based on the detected output optical signals.

[0101] Implementations of the second example may include one or more of the following features. Positioning the probe head includes at least one of translating or rotating the integrated circuit device relative to the probe head. The method includes electrically contacting electrical probes to the integrated circuit device; and causing the integrated circuit device to produce the electromagnetic signals. The control system includes two or more lasers, and receiving the input optical signals includes causing the two or more lasers to generate the input optical signals. The vapor cell sensor includes a dielectric body comprising an internal lattice structure within an internal volume of the vapor cell sensor.

[0102] Implementations of the second example may include one or more of the following features. The vapor cell sensor includes a primary vapor cell and a capillary bonded to the primary vapor cell. The primary vapor cell defines a first interior volume, and the capillary defines a second interior volume that is in fluid communication with the first interior volume. Receiving the input optical signals includes communicating the input optical signals through the first and second interior volumes; and detecting the output optical signals including communicating the output optical signals to the optical detector through the first and second interior volumes. The method includes communicating a control signal to iteratively move the stage to reposition the probe head relative to the integrated circuit device. The probe head includes a lens system and one or more optical fibers that define an optical path between the control system and the vapor cell sensor, receiving the input optical signals comprises communicating the input optical signals to the vapor cell sensor via the one or more optical fibers and the lens system, and detecting the output optical signals comprises receiving the output optical signals from the vapor cell sensor via the lens system and the one or more optical fibers. The integrated circuit deviceincludes one of the following: an antenna in package [AiP], an antenna-on-package [AoP], a system-in-package [SiP], or a multi-chip module [MCM].

[0103] In a third example, a vapor cell sensor includes a capillary and a primary vapor cell. The capillary includes an elongate body which includes a first end, a second end, interior surfaces, an opening and a reflective surface. The interior surface defines a first portion of an interior volume of the vapor cell sensor, and the interior volume includes a vapor having Rydberg states. The opening resides at the first end of the capillary, and the reflective surface is bonded to the second end of the capillary. The primary vapor cell includes a dielectric body bonded to the first end of capillary. The dielectric body includes interior surfaces and a port. The interior surfaces define a second portion of the interior volume of the vapor cell sensor; and the portis positioned, relative to the opening, to join the first and second portions of the interior volume.

[0104] Implementations of the third example may include one or more of the following features. The port is a first port, the dielectric body includes a second port, and the primary vapor cell comprises an optical window bonded to the dielectric body to form a seal around the second port. The optical window is a first optical window, the dielectric body includes a second optical window, the second optical window is positioned between the first port of the dielectric body and the opening of the capillary, and the second optical window comprises a through hole that is positioned relative to the port and the opening to join the first and second portions of the interior volume. The vapor cell sensor includes an optical fiber attached to the optical window through a lens system, and the optical fiber is configured to deliver input optical signals from the optical window to the reflective surface through the first and second portions of the interior volume of the vapor cell sensor; and an optical detector configured to receive output optical signals, the output optical signals including reflected optical signals from the reflective surface.

[0105] In a fourth example, a method of manufacturing a vapor cell sensor includes obtaining a capillary having an elongated body which includes a first end, a second end, interior surfaces, and an opening. The interior surfaces define a first portion of an interior volume of the vapor cell sensor, and the opening resides at the first end of the capillary. The method includes obtaining a primary vapor cell which includes interior surfaces and aport. The interior surfaces define a second portion of the interior volume of the vapor cell sensor. The method further includes bonding the primary vapor cell to the capillary such that the port is positioned relative to the opening of the capillary to join the first and second portions of the interior volume.

[0106] Implementations of the fourth example may include one or more of the following features. The method includes assembling the primary vapor cell which includes bonding an optical window to a dielectric body. The optical window and the dielectric body define first and second portions of the interior surfaces of the primary vapor cell. The method includes prior to bonding the optical window, forming an anti-reflection coating on a surface of the optical window. The optical window is a first optical window, and assembling the primary vapor cell includes obtaining a second optical window including the port, and bonding the second optical window to the dielectric body. The second optical window defines a portion of the interior surfaces of the primary vapor cell. The method includes after bonding the primary vapor cell to the capillary, filling the interior volume of the vapor cell sensor with a vapor including Rydberg states, and bonding a reflective window to the second end of the capillary to enclose the vapor in the interior volume of the vapor cell sensor.

[0107] While this specification contains many details, these should not be understood as limitations on the scope of what may be claimed, but rather as descriptions of features specific to particular examples. Certain features that are described in this specification or shown in the drawings in the context of separate implementations can also be combined. Conversely, various features that are described or shown in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable sub-combination.

[0108] Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the implementations described above should not be understood as requiring suchseparation in all implementations, and it should be understood that the described program components and systems can generally be integrated together in a single product or packaged into multiple products.

[0109] A number of embodiments have been described. Nevertheless, it will be understood that various modifications can be made. Accordingly, other embodiments are within the scope of the following claims.

Claims

CLAIMSWhat is claimed is:

1. A system comprising: a probe head comprising a vapor cell sensor containing a vapor; and a control system communicably coupled to the probe head, the control system being configured to perform operations comprising: moving a stage to position the probe head relative to an integrated circuit device; communicating input optical signals to the probe head, the input optical signals comprising laser signals; receiving, at an optical detector of the control system, output optical signals from the probe head, the output optical signals being generated based on the input optical signals interacting with the vapor in the presence of electromagnetic signals from the integrated circuit device; and processing, by operation of a signal processing system of the control system, electrical signals produced by the optical detector based on the received output optical signals to determine a condition of the integrated circuit device.

2. The system of claim 1, wherein the control system comprises two or more lasers configured to generate the input optical signals.

3. The system of claim 1, wherein moving the stage comprises at least one of translating or rotating the integrated circuit device relative to the probe head.

4. The system of claim 1, comprising electrical probes configured to electrically contact the integrated circuit device and cause the integrated circuit device to produce the electromagnetic signals.

5. The system of any of claims 1 - 4, wherein the vapor cell sensor comprises a primary vapor cell and a capillary bonded to the primary vapor cell.

6. The system of claim 5, wherein the capillary comprises a hollow core photonic crystal fiber.

7. The system of claim 5, wherein the primary vapor cell defines a first interior volume, and the capillary defines a second interior volume that is in fluid communication with the first interior volume.

8. The system of claim 5, wherein the primary vapor cell comprises a plurality of pockets that are fluidically connected to one another, each pocket configured to hold one of: a vapor source, a coating material, and a getter.

9. The system of any of claims 1 - 4, wherein the probe head comprises a lens system and one or more optical fibers that define an optical path between the control system and the vapor cell sensor.

10. The system of claim 9, wherein the optical path is configured to communicate the input optical signals to the vapor cell sensor from the control system, and the optical path is configured to communicate the output optical signals from the vapor cell sensor to the control system.

11. The system of claim 9, wherein the vapor cell sensor comprises a reflective surface, and the output optical signals are based on the input optical signals reflected by the reflected surface.

12. The system of any of claims 1 - 4, wherein the integrated circuit device comprises one of: an antenna in package (AiP), an antenna-on-package (AoP), a system-in-package (SiP), or a multi-chip module (MCM).

13. The system of any of claims 1 - 4, wherein the vapor cell sensor comprises a dielectric body comprising an internal lattice structure within an internal volume of the vapor cell sensor.

14. A method comprising: positioning a probe head relative to an integrated circuit device, the probe head comprising a vapor cell sensor containing a vapor; receiving, at the probe head, input optical signals from a control system; detecting, by operation of an optical detector, output optical signals from the vapor cell sensor, the output optical signals generated based on the input optical signals interacting with the vapor in the presence of electromagnetic signals from the integrated circuit device; and determining, by operation of a signal processing system, a condition of the integrated circuit device by processing electrical signals produced by the optical detector based on the detected output optical signals.

15. The method of claim 14, wherein positioning the probe head comprises at least one of translating or rotating the integrated circuit device relative to the probe head.

16. The method of claim 14, comprising: electrically contacting electrical probes to the integrated circuit device; and causing the integrated circuit device to produce the electromagnetic signals.

17. The method of claim 14, wherein the control system comprises two or more lasers, and the method comprises generating the input optical signals by operation of the two or more lasers.

18. The method of claim 14, wherein the vapor cell sensor comprises a dielectric body comprising an internal lattice structure within an internal volume of the vapor cell sensor.

19. The method of any of claims 14 - 18, wherein the vapor cell sensor comprises a primary vapor cell and a capillary bonded to the primary vapor cell.

20. The method of claim 14 - 18, wherein the primary vapor cell defines a first interior volume, and the capillary defines a second interior volume that is in fluid communication with the first interior volume, and the method comprises: communicating the input optical signals through the first and second interior volumes; andcommunicating the output optical signals through the first and second interior volumes.

21. The method of any of claims 14 - 18, comprising iteratively moving the stage to reposition the probe head relative to the integrated circuit device.

22. The method of any of claims 14 - 18, wherein the probe head comprises a lens system and one or more optical fibers that define an optical path between the control system and the vapor cell sensor, and the method comprises: communicating the input optical signals to the vapor cell sensor via the one or more optical fibers and the lens system; and communicating the output optical signals from the vapor cell sensor via the lens system and the one or more optical fibers.

23. The method of any of claims 14 - 18, wherein the integrated circuit device comprises one of: an antenna in package (AiP), an antenna-on-package (AoP), a system-in-package (SiP), or a multi-chip module (MCM).

24. A vapor cell sensor, comprising: a capillary comprising an elongate body, the elongate body comprising: a first end; a second end; interior surfaces that define a first portion of an interior volume of the vapor cell sensor, the interior volume comprising a vapor having Rydberg states; an opening at the first end of the capillary; and a reflective surface at the second end of the capillary; and a primary vapor cell bonded to the first end of capillary and comprising: interior surfaces that define a second portion of the interior volume of the vapor cell sensor; anda port that is positioned, relative to the opening, to join the first and second portions of the interior volume.

25. The vapor cell sensor of claim 24, wherein the primary vapor cell comprises: a dielectric body that defines a first portion of the interior surfaces of the primary vapor cell ; and an optical window that defines a second portion of the interior surfaces of the primary vapor cell, wherein the optical window is bonded to the dielectric body.

26. The vapor cell sensor of claim 25, wherein the optical window is a first optical window, the primary vapor cell comprises a second optical window that defines a third portion of the interior surfaces of the primary vapor cell, and the port passes through the second optical window.

27. The vapor cell sensor of claim 25, comprising: an optical fiber attached to the optical window by a lens system and configured to deliver input optical signals to the vapor cell sensor; and an optical detector configured to receive output optical signals from the vapor cell sensor.

28. The vapor cell sensor of claim 25, wherein the primary vapor cell comprises a plurality of pockets that are fluidically connected to one another, each pocket configured to hold one of: a vapor source, a coating material, and a getter.

29. A method of manufacturing a vapor cell sensor comprising: obtaining a capillary having an elongated body, wherein the elongated body comprises: a first end, a second end, interior surfaces that define a first portion of an interior volume of the vapor cell sensor, andan opening at the first end of the capillary, obtaining a primary vapor cell comprising: interior surfaces that define a second portion of the interior volume of the vapor cell sensor, and a port; and bonding the primary vapor cell to the capillary such that the port is positioned relative to the opening of the capillary to join the first and second portions of the interior volume.

30. The method of claim 29, comprising assembling the primary vapor cell, wherein assembling the primary vapor cell comprises bonding an optical window to a dielectric body, wherein the optical window and the dielectric body define first and second portions of the interior surfaces of the primary vapor cell.

31. The method of claim 30, comprising: prior to bonding the optical window, forming an anti-reflection coating on a surface of the optical window.

32. The method of claim 30, wherein the optical window is a first optical window, and assembling the primary vapor cell comprises: obtaining a second optical window comprising the port, and bonding the second optical window to the dielectric body, wherein the second optical window defines a third portion of the interior surfaces of the primary vapor cell.

33. The method of claim 29, comprising: after bonding the primary vapor cell to the capillary, filling the interior volume of the vapor cell sensor with a vapor comprising Rydberg states, and bonding a reflective window to the second end of the capillary to enclose the vapor in the interior volume of the vapor cell sensor.

34. The method of claim 29, wherein the primary vapor cell comprises a plurality of pockets that are fluidically connected to one another, each pocket configured to hold one of: a vapor source,a coating material, and a getter.

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