Precision stylus control system

Abstract

The system includes a processor configured to excite a pair of torque coils with a force signal to generate a magnetic force between the pair of torque coils and an internal magnet in a control arm positioned between the two torque coils. The control arm is connected to a probe arm, and the magnetic force rotates the control arm and probe arm around a pivot joint, bringing the probe tip of the probe arm into contact with the surface of the sample. After exciting the sensing subsystem with an excitation signal, the processor receives a detection signal difference from the sensing subsystem that is proportional to the rotational position of the control arm, corresponding to the height of the probe tip relative to the surface of the sample.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the priority of the assigned U.S. Provisional Patent Application No. 63 / 460,988, filed on April 21, 2023, the disclosure of which is incorporated herein by reference.

[0002] This disclosure relates to a stylus shape measurement system for the measurement and testing of surface shapes for research, development, and manufacturing.

Background Art

[0003] With the development of the manufacturing industry, there is an increasing demand for yield management, specifically, for measurement and inspection systems. Although the critical dimensions continue to shrink, the industry needs to shorten the time to achieve high - yield and high - value production. By minimizing the total time from detecting a yield problem to correcting it, the return on investment of manufacturers is maximized.

[0004] As an example of manufacturing challenges, manufacturing semiconductor devices such as logic devices and memory devices typically involves processing a sample such as a semiconductor wafer using a number of manufacturing processes to form various features and multiple levels of semiconductor devices. For example, lithography is a semiconductor manufacturing process that includes transferring a pattern from a reticle to a photoresist disposed on a semiconductor wafer. Further examples of semiconductor manufacturing processes include, but are not limited to, chemical mechanical polishing (CMP), etching, deposition, and ion implantation. The placement of multiple semiconductor devices manufactured on a single semiconductor wafer may be separated into individual semiconductor devices.

[0005] Measurement processes are used at various stages during semiconductor manufacturing to monitor and control the process. Unlike inspection processes, which detect defects on a wafer, measurement processes are used to measure one or more characteristics of a wafer that cannot be determined using existing inspection tools. Measurement processes can be used to measure one or more characteristics of a wafer so that the performance of the process can be determined from those characteristics. For example, a measurement process can measure the dimensions of features formed on a wafer during the process (e.g., line width, thickness, etc.). In addition, if one or more characteristics of a wafer are unacceptable (e.g., outside a predetermined range), the measured values ​​of one or more characteristics of the wafer may be used to modify one or more parameters of the process so that additional wafers produced by the process have acceptable characteristics.

[0006] Several measurement processes utilize a stylus or probe to measure the surface of a sample. For example, a stylus can be positioned in contact with the sample surface and scanned across the sample to measure its shape and the dimensions of its surface features, or it can perform indentation and scratching tests by applying force to the sample surface with the stylus. However, open-loop stylus shape measurement systems lack feedback from a mechanism that detects the stylus position, which can be applied to a mechanism that controls the force and positioning of the stylus. Therefore, measurement sensitivity and force control depend on system calibration, and open-loop systems have low adaptability to different operating modes, different sample measurements, or real-time changes to the measurement environment. In addition, separate system configurations and calibrations are required to perform force and position measurements. These separate configurations and calibrations are interrupted by any subsequent changes to the stylus or environment. For example, open-loop force control systems have the challenge of not responding to temperature-induced drift of the applied force. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] U.S. Patent No. 6314800 [Patent Document 2] U.S. Patent Application Publication No. 2014 / 0331511 [Overview of the project] [Problems that the invention aims to solve]

[0008] Therefore, a closed-loop stylus shape measurement system with integrated force and positioning control is required. [Means for solving the problem]

[0009] One embodiment of the present disclosure provides a system. The system may include a probe arm equipped with a probe tip. The probe tip may be configured to contact the surface of a sample.

[0010] The system may further include a control arm connected to the probe arm. The control arm may contain an internal magnet.

[0011] The system may further include one or more torque coils positioned on either side of the control arm. One or more torque coils may be configured to cause rotation of the control arm around the pivot joint based on their interaction with an internal magnet.

[0012] The system may further include a sensing subsystem. This sensing subsystem may be configured to measure the rotational position of the control arm.

[0013] The system may further include a processor that electronically communicates with one or more torque coils and a sensing subsystem. The processor may be configured to excite at least one of the one or more torque coils with a force signal to generate a magnetic force between the one or more torque coils and an internal magnet, thereby causing a control arm to rotate around a pivot joint, thereby causing a probe arm connected to the control arm to rotate around the pivot joint, and the probe tip to contact the surface of the sample. The processor may further be configured to excite the sensing subsystem with an excitation signal. The processor may further be configured to receive a sensing signal difference from the sensing subsystem that is proportional to the rotational position of the control arm, corresponding to the height of the probe tip relative to the surface of the sample. The sensing signal difference may be a voltage difference or a current difference.

[0014] In some embodiments, the processor may include a servo loop integrator. The servo loop integrator may be configured to control the force signal by applying the rotational position of the control arm, determined from the sensing subsystem, as feedback.

[0015] In some embodiments, the processor may be further configured to determine a force signal adjusted based on feedback from the rotational position or force of a control arm in order to generate a preset force, and to excite at least one of one or more torque coils with the adjusted force signal, thereby bringing the probe tip into contact with the surface of the sample with a preset force.

[0016] In some embodiments, the processor may be further configured to determine a force signal adjusted based on feedback from the rotational position or force of a control arm in order to position the probe tip at a preset height, to excite at least one of one or more torque coils with the adjusted force signal so as to position the probe tip at a preset height relative to the surface of the sample, and to verify that the probe tip is positioned at the preset height based on a sensing signal difference received from the sensing subsystem.

[0017] In some embodiments, the processor may be further configured to generate a modulated force signal and to excite at least one of one or more torque coils with the modulated force signal, thereby causing the height of the probe tip to vibrate relative to the surface of the sample.

[0018] In some embodiments, the sensing subsystem may comprise a primary coil and a pair of secondary coils positioned on either side of the primary coil. The core of the pivot joint may be surrounded by the primary coil and the pair of secondary coils, so that a change in the rotational position of the control arm may move the core within the primary coil and the pair of secondary coils, and the difference in sensing signals measured from the pair of secondary coils may be proportional to the position of the core.

[0019] In some embodiments, the primary coil and the pair of secondary coils may be coaxial, and the core can move linearly within the primary coil and the pair of secondary coils.

[0020] In some embodiments, the primary coil and the pair of secondary coils may be concircular, and the core can move angularly within the primary coil and the pair of secondary coils.

[0021] In some embodiments, the sensing subsystem may include a primary coil and a secondary coil disposed on the opposite side of the primary coil. The core of the control arm may be disposed between the primary coil and the secondary coil, such that a change in the rotational position of the control arm may move the core between the primary coil and the secondary coil, and the detected signal difference measured from the secondary coil may be proportional to the position of the core.

[0022] In some embodiments, the system may further include an external magnet. The external magnet may be configured to attract the internal magnet of the control arm, whereby the control arm can rotate to a retracted position where the probe tip can be separated from the surface of the sample. One or more torque coils may be configured to cause rotation of the control arm against the attraction of the external magnet.

[0023] In some embodiments, the external magnet may be movable between a first position and a second position. In the first position, the external magnet may be proximal to the internal magnet to attract the internal magnet of the control arm, and in the second position, the external magnet may be distal from the internal magnet to allow free rotation of the control arm.

[0024] In some embodiments, the pivot joint may include a torsion bar configured to bias the control arm towards a neutral position. In the neutral position, the probe tip may be separated from the surface of the sample, and one or more torque coils may be configured to rotate the control arm against the bias of the torsion bar.

[0025] In some embodiments, the processor may be further configured to excite one of the one or more torque coils with a force signal to control the direction in which the control arm rotates around the pivot joint based on magnetic force.

[0026] Another embodiment of the present disclosure provides a method. The method may include exciting a pair of torque coils with a force signal to generate a magnetic force between the pair of torque coils and an internal magnet of a control arm disposed therebetween. The control arm may be connected to a probe arm, and the magnetic force can rotate the control arm and the probe arm around a pivot joint to contact a probe tip of the probe arm with the surface of a sample. By exciting one of the pair of torque coils with a force signal, the direction in which the control arm rotates around the pivot joint based on the magnetic force can be controlled.

[0027] The method may further include exciting a sensing subsystem with an excitation signal and measuring a sensed signal difference from the sensing subsystem that is proportional to the rotational position of the control arm, where the sensed signal difference is a voltage difference or a current difference, and determining the height of the probe tip relative to the surface of the sample based on the rotational position of the control arm.

[0028] In some embodiments, the method may further include applying, as feedback within a servo loop, the rotational position of the control arm determined from the sensing subsystem to control the force signal.

[0029] In some embodiments, the method may further include determining an adjusted force signal based on the rotational position of the control arm or feedback from the force to generate a preset force, and exciting the pair of torque coils with the adjusted force signal to thereby contact the probe tip with the surface of the sample with the preset force.

[0030] In some embodiments, the method may further include determining a force signal adjusted based on feedback from the rotational position or force of a control arm in order to position the probe tip at a preset height; exciting a pair of torque coils with the adjusted force signal so as to position the probe tip at a preset height relative to the surface of the sample; and confirming that the probe tip is positioned at the preset height based on the difference in sensing signals from a sensing subsystem.

[0031] In some embodiments, the method may further include generating a modulated force signal and exciting a pair of torque coils with the modulated force signal, thereby causing the height of the probe tip to vibrate relative to the surface of the sample.

[0032] To fully understand the nature and purpose of this disclosure, the following detailed description should be referred to in conjunction with the attached drawings. [Brief explanation of the drawing]

[0033] [Figure 1] This is a diagram of a system according to one embodiment of the present disclosure. [Figure 2] This is a schematic communication diagram of a processor according to one embodiment of the present disclosure. [Figure 3] This is a diagram of a system according to another embodiment of the present disclosure. [Figure 4] This is a diagram of a system according to another embodiment of the present disclosure. [Figure 5A] This is a longitudinal cross-sectional view of a pivot joint of a system according to one embodiment of the present disclosure. [Figure 5B] Figure 5A is a cross-sectional view of the pivot joint. [Figure 6A] This is a longitudinal cross-sectional view of a pivot joint of a system according to another embodiment of the present disclosure. [Figure 6B] Figure 6A is a cross-sectional view of the pivot joint. [Figure 7]This is a flowchart of a method according to one embodiment of the present disclosure. [Figure 8] Figure 7 is a flowchart of the method steps for force commands in the method shown. [Figure 9] Figure 7 is a flowchart of the method steps for the positioning command in the method shown. [Figure 10] Figure 7 is a flowchart of the method steps for the modulation command in the method shown. [Figure 11] This is a block diagram of a control system according to one embodiment of the present disclosure. [Modes for carrying out the invention]

[0034] While the claimed subject matter is described in relation to specific embodiments, other embodiments, including those that do not provide all of the advantages and features described herein, are also within the scope of this disclosure. Various structural, logical, processing step, and electronic modifications may be made without departing from the scope of this disclosure. Therefore, the scope of this disclosure is defined solely by reference to the appended claims.

[0035] One embodiment of the present disclosure provides a system 100, as shown in Figures 1 to 4. System 100 may be a stylus shape measuring system configured to measure the shape of a sample 101. The sample 101 may be planar or substantially planar and may have inclinations or features within the dynamic range of system 100. Such features may include, for example, machined metal parts, polished glass, lenses, mirrors, etc. The sample 101 may be a semiconductor wafer, including silicon, GaAs, GaN, SiN, SiC, ceramic, substrate, display panel, coupon, metal, inorganic, conductive, insulating, unpatterned, patterned, relatively smooth, relatively rough, or having a shaped surface, and including other samples or workpieces encountered in industries including, but not limited to, semiconductors, power devices, MEMS devices, LED devices, the automotive industry, and general process development across many material and device types. System 100 may comprise a probe arm 110 having a probe tip 111 positioned at one end. The probe tip 111 may be made of diamond, sapphire, tungsten, layered, coated, or other material or alloy that can be manufactured into a probe shape and can retain their shape when scanned. The probe tip 111 may be configured to contact the surface of sample 101 to measure a series of individual points within the dynamic range of system 100 (e.g., a point cloud), the height and feature size of steps on the surface of sample 101, or to perform surface shape measurements. The probe tip 111 may have a tapered shape (e.g., conical, pyramidal, spherical, or other steeply walled or shallow shape) that can provide an upward force to the probe tip 111 when contacting features laterally during scanning or point-to-point contact, in order to contact the surface of sample 101 between narrow features and particles or fabricated features. The concentric angle of the probe tip 111 may vary from more than 90° to less than 20°. The radius of the probe tip 111 can range from over 50 microns to less than 40 nm, with smaller radii allowing for the measurement of smaller geometric shapes.Probe tips 111 having a smaller diameter may be more susceptible to damage and wear, and it can benefit from the high-sensitivity closed-loop servo system 100 of this disclosure to reduce the likelihood of wear and damage. For example, system 100 can allow the use of smaller sized probe tips 111, which can improve the stylus resolution that would otherwise not be achievable. Improved resolution allows for the characterization of smaller feature sizes, which can be beneficial for many industries.

[0036] The system 100 may further include a control arm 120. The control arm 120 may be connected to the probe arm 110. For example, the probe arm 110 may be cantilevered from the control arm 120. The control arm 120 may be configured to pivot around a pivot joint 115. Based on the connection between the probe arm 110 and the control arm 120, the rotation of the control arm 120 around the pivot joint 115 can cause a corresponding rotation of the probe arm 110 and the probe tip 111 connected thereto. The control arm 120 may include an internal magnet 125. The internal magnet 125 may be a permanent magnet located within or connected to the control arm 120.

[0037] The system 100 may further comprise a pair of torque coils 130. The pair of torque coils 130 may be positioned on either side of the internal magnet 125 of the control arm 120. For example, the pair of torque coils 130 may include a first torque coil 131 and a second torque coil 132, each positioned on either side of the internal magnet 125 of the control arm 120. The pair of torque coils 130 may be configured to cause rotation of the control arm 120 around the pivot joint 115 based on their interaction with the internal magnet 125, as further described below. Each torque coil in the pair of torque coils 130 may comprise one or more coils. In some embodiments, the pair of torque coils 130 may comprise a single torque coil.

[0038] System 100 may further include a processor 140. The processor 140 may include a microprocessor, microcontroller, FPGA, or other device.

[0039] The processor 140 may be coupled to a component of the system 100 in any suitable manner (for example, via one or more transmission media, which may include wired and / or wireless transmission media) so that the processor 140 can receive outputs. The processor 140 may be configured to perform several functions using its outputs. A test tool may receive instructions or other information from the processor 140. The processor 140 may optionally communicate electronically with another test tool, measurement tool, repair tool, or review tool (not shown) to receive additional information or send instructions.

[0040] The processor 140 may be part of a variety of systems, including personal computer systems, image computers, mainframe computer systems, workstations, network equipment, internet equipment, or other devices. The subsystem or system may also include any suitable processor known in the art, such as a parallel processor. In addition, the subsystem or system may include a platform having high-speed processing and software, either as a standalone tool or a networked tool.

[0041] The processor 140 may be located within the system 100 or another device, or it may be part of the system 100 or another device if it is not located within the system 100 or another device. For example, the processor 140 may be part of a standalone control unit or it may be located within a centralized quality control unit. Multiple processors 140 may be used to define multiple subsystems of the system 100.

[0042] The processor 140 may actually be implemented by any combination of hardware, software, and firmware. Furthermore, its functions as described herein may be performed by a single unit or distributed among different components, each of which may be implemented sequentially by any combination of hardware, software, and firmware. Program code, instructions, configuration data, reference tables, calibration data, and algorithms for the processor 140 to implement various methods and functions may be stored in a readable storage medium such as memory.

[0043] If the system 100 includes two or more subsystems, different processors 140 may be coupled to one another so that images, data, information, instructions, etc., can be transmitted between subsystems. For example, one subsystem may be coupled to an additional subsystem by any suitable transmission medium, which may include any suitable wired and / or wireless transmission medium known in the art. Two or more such subsystems may also be effectively coupled by a shared computer-readable storage medium (not shown).

[0044] The processor 140 may be configured to perform several functions using the outputs of the system 100 or other outputs. For example, the processor 140 may be configured to send outputs to an electronic data storage unit or another storage medium. The processor 140 may be further configured as described herein.

[0045] The processor 140 may be configured according to any of the embodiments described herein. The processor 140 may also be configured to perform other functions or additional steps using the output of system 100 or images or data from other sources.

[0046] The processor 140 may be communicatively coupled to any of the various components or subsystems of System 100 in any manner known in the art. Furthermore, the processor 140 may be configured to receive and / or acquire data or information from other systems (e.g., inspection systems such as review tools, inspection results from remote databases containing design data, etc.) via a transmission medium which may include wired and / or wireless portions. In this way, the transmission medium can function as a data link between the processor 140 and other subsystems of System 100 or systems outside of System 100. Various steps, functions, and / or operations of System 100 and methods disclosed herein are performed by one or more of the following: electronic circuits, logic gates, multiplexers, programmable logic devices, ASICs, FPGAs, analog or digital controls / switches, microcontrollers, or computing systems. Program instructions implementing methods such as those described herein may be transmitted via or stored on a carrier medium. Carrier media may include storage media such as read-only memory, random-access memory, magnetic or optical disks, non-volatile memory, solid-state memory, and magnetic tape. Carrier media may also include transmission media such as wires, cables, PCB traces, or wireless transmission links. For example, the various steps described throughout this disclosure may be performed by a single processor 140 (or computer subsystem), or alternatively, by multiple processors 140 (or multiple computer subsystems). Furthermore, different subsystems of system 100 may include one or more computing systems or logical systems. Therefore, the above description should not be construed as an limitation to this disclosure, but merely as an example.

[0047] As shown in Figure 2, the processor 140 can electronically communicate with the pair of torque coils 130 and other elements of the system 100. The processor 140 may be configured to excite at least one of the pair of torque coils 130 with a force signal 141 to generate a magnetic force between the pair of torque coils 130 and the internal magnet 125. In other words, when the force signal 141 is applied to at least one of the first torque coil 131 and the second torque coil 132, an electromagnetic field may be generated that may repel or attract the internal magnet 125, depending on the magnitude and direction of the magnetic force applied to the internal magnet 125 from the electromagnetic field. The magnetic force can rotate the control arm 120 around the pivot joint 115, thereby rotating the probe arm 110 connected to the control arm 120. Depending on the direction of rotation, the magnetic force can cause the probe tip 111 to contact the surface of the sample 101 and descend, or to lift it from the surface of the sample 101. The processor 140 may be configured to excite at least one of the first coil 131 and the second coil 132 with a force signal 141 to control the direction in which the control arm 120 rotates around the pivot joint 115. In some embodiments, the processor 140 may be configured to excite both the first coil 131 and the second coil 132 with the force signal 141. The processor 140 may include a force signal generator 142 configured to generate the force signal 141. The magnetic force may be modulated by a control input circuit to adjust the downforce applied to the probe tip 111 when it is made to contact the surface of the sample 101 and while it is in contact with the surface of the sample 101. In some embodiments, the first coil 131 and the second coil 132 may be connected in series so that both the first coil 131 and the second coil 132 encounter the same current, and each coil can generate a magnetic field in the same direction to generate a larger resultant force from the pair of torque coils 130.In some embodiments, the system 100 may include only one torque coil (e.g., one of the first coil 131 or the second coil 132), which can reduce the manufacturing cost of the system 100 by reducing the number of parts, and the single torque coil can be used to generate a magnetic force.

[0048] The system 100 may further include a sensing subsystem 150. The sensing subsystem 150 may be configured to measure the rotational position of the control arm 120. For example, the processor 140 may be configured to excite the sensing subsystem 150 with an excitation signal 143, and the sensing subsystem 150 may be configured to measure a sensing signal difference 145 based on the excitation signal 143. The processor 140 may include an excitation signal generator 144 configured to generate the excitation signal 143. The sensing signal difference 145 may correspond to the rotational position of the control arm 120, and more specifically, to the height of the probe tip 111 relative to the sample 101. The sensing signal difference 145 may be a voltage difference or a current difference.

[0049] In some embodiments, the sensing subsystem 150 may comprise a primary coil 151 and a pair of secondary coils 152, as shown in Figures 1 and 3. For example, the sensing subsystem 150 may be a linear displacement sensor or an angular displacement sensor. The pair of secondary coils 152 may be positioned on either side of the primary coil 151. The processor 140 may be configured to excite the primary coil 151 with an excitation signal 143, and the sensing subsystem 150 may be configured to measure a sensing signal difference 145 between the pair of secondary coils 152. The system 100 may further include a core 155 surrounded by the primary coil 151 and the pair of secondary coils 152. The core 155 can be made from a magnetic material with high permeability and low hysteresis, such as NiFe alloy, iron, or an iron alloy, or from another material. The core 155 may be an extension of the probe arm 110, pivot joint 115, or control arm 120. A change in the rotational position of the control arm 120 can move the core 155 within the primary coil 151 and the pair of secondary coils 152. The position of the core 155 relative to the pair of secondary coils 152 may affect the detection signal difference 145 measured by the detection subsystem 150. For example, a detection signal difference 145 of zero may indicate that the core 155 is equidistant between the pair of secondary coils 152, as their relative voltages cancel each other out. However, if the core 155 moves in a direction closer to one of the secondary coils 152, the detection signal difference 145 becomes non-zero, and a positive or negative value of the detection signal difference 145 indicates the rotational direction of the control arm, with the magnitude of the detection signal difference 145 being proportional to the rotational position of the control arm 120 and the displacement of the probe tip 111.

[0050] In some embodiments, the sensing subsystem 150 may be configured as an angular displacement sensor capable of measuring the rotational displacement of the core 155, as shown in Figure 1. For example, the primary coil 151 and the pair of secondary coils 152 may be concircular along an arc 154, and the core 155 can move along the same arc 154 within the primary coil 151 and the pair of secondary coils 152. The position of the core 155 along the arc 154 relative to the pair of secondary coils 152 may be proportional to the rotational position of the control arm 120. Thus, the sensing signal difference 145 measured by the sensing subsystem 150 may correspond to the displacement of the probe tip 111. In one example, both the primary coil 151 and the pair of secondary coils 152 may each have more than 1000 windings within their respective coils, thereby increasing the gain and sensitivity of the sensing subsystem 150.

[0051] In some embodiments, the sensing subsystem 150 may be configured as a linear displacement sensor capable of measuring the linear displacement of the core 155, as shown in Figure 3. For example, the primary coil 151 and the pair of secondary coils 152 may be coaxial along the axis 153, and the core 155 can move linearly along the same axis 153 within the primary coil 151 and the pair of secondary coils 152. The linear position of the core 155 along the axis 153 relative to the pair of secondary coils 152 may be proportional to the rotational position of the control arm 120. Thus, the sensing signal difference 145 measured by the sensing subsystem 150 may correspond to the displacement of the probe tip 111.

[0052] In some embodiments, the sensing subsystem 150 may comprise a primary coil 151 and a secondary coil 156, as shown in Figure 4. The secondary coil 156 may be located on the opposite side of the primary coil 151. The core 155 of the control arm 120 may be located between the primary coil 151 and the secondary coil 156. The processor 140 may be configured to excite the primary coil 151 with an excitation signal 143, and the sensing subsystem 150 may be configured to measure the sensing signal difference 145 from the secondary coil 156. Changes in the rotational position of the control arm 120 can move the core 155 relative to the primary coil 151 and the secondary coil 156. The position of the core 155 relative to the secondary coil 156 may affect the sensing signal difference 145 measured by the sensing subsystem 150. For example, if the core 155 moves in a direction closer to the primary coil 151 or secondary coil 156, the magnitude of the detection signal difference 145 may be proportional to the rotational position of the control arm 120 and the displacement of the probe tip 111.

[0053] In some embodiments, the system 100 may further include additional magnets that can retract the control arm 120 to a reference or stationary position. Such a function of the system 100 may be useful during power-off states. The additional magnets may introduce a biasing force, but the system 100 can compensate for these forces. For example, as shown in Figure 4, the system 100 may further include an external magnet 160. The external magnet 160 may be a permanent magnet configured to attract the internal magnet 125 of the control arm 120, thereby rotating the control arm 120 to a retracted position. In the retracted position, the probe tip 111 may be separated from the surface of the sample 101 to prevent damage to the probe tip 111 when the system 100 is not in use. It should be understood that a pair of torque coils 130 may be configured to cause rotation of the control arm 120 in opposition to the attraction of the external magnet 160. In other words, since the external magnet 160 attracts the internal magnet 125, the magnetic force generated by the pair of torque coils 130 may be greater than the force from the external magnet 160 in order to rotate the control arm 120 in a direction that causes the probe tip 111 to contact the surface of the sample 101.

[0054] In some embodiments, the external magnet 160 may be movable within the housing 165 of the system 100 between a first position and a second position, as shown in Figure 4. In the first position, the external magnet 160 may be proximal to the internal magnet 125 to attract it and rotate the control arm 120 to a retracted position. In the second position, the external magnet 160 may be distal to the internal magnet 125 to not attract it and allow the control arm 120 to rotate freely. With the external magnet 160 in the second position, the magnetic force generated by the pair of torque coils 130 is small, so the control arm 120 can rotate in a direction in which the probe tip 111 contacts the surface of the sample 101. The position of the external magnet 160 may be manually adjustable (e.g., by a screw, slide, or other moving mechanism) and can be set to the first or second position during calibration of the system 100.

[0055] In some embodiments, the pivot joint 115 may comprise a torsion bar 116 (shown in Figures 5-6), a leaf spring, a jewel bearing or scribed bearing, or other types of biasing means for small-angle rotation. The torsion bar 116 may be connected at both ends to the housing 165 with a control arm 120 positioned between them. The torsion bar 116 may be configured to bias the control arm 120 toward a neutral position. In the neutral position, the probe tip 111 may be separated from the surface of the sample 101, thereby allowing the sample 101 to be placed on or removed from the system 100 without damaging the probe tip 111 between processing steps. The angular range of the control arm 120 may depend on the length of the torsion bar 116, the length of the control arm 120, and the manufacturing tolerances of the elements of the system 100 that allow the probe tip 111 to move toward the neutral position and make contact with the surface of the sample 101. It should be understood that a pair of torque coils 130 may be configured to cause rotation of the control arm 120 in opposition to the biasing force on the torsion bar 116. In other words, since the torsion bar 116 is configured to bias the control arm toward the neutral position, the magnetic force generated by the pair of torque coils 130 may be greater than the force from the torsion bar 116 to rotate the control arm 120 toward the direction away from the neutral position so that the probe tip 111 can contact the surface of the sample 101. In some embodiments, the torsion bar 116 may have a circular cross-section, as shown in Figures 5A and 5B. Alternatively, the torsion bar 116 may have a cruciate cross-section, as shown in Figures 6A and 6B. A torsion bar 116 with a cruciate cross-section may have better rigidity on the non-rotating axis compared to a torsion bar 116 with a circular cross-section, which can minimize lateral movement of the control arm 120 and allow for precise positioning. Increasing the length of the torsion bar 116 can also increase rigidity while still allowing sufficient angular degrees of freedom.The height and thickness of the cross-sectional shape can also be adjusted so that the height controls the stiffness, and the thickness prevents buckling and undesirable modal shape responses.

[0056] In some embodiments, the processor 140 may include a servo-loop integrator 146, as shown in Figure 2. The servo-loop integrator 146 may be configured to control the force signal 141 by applying the rotational position of the control arm 120, determined from the sensing subsystem 150, as feedback. For example, the servo-loop integrator 146 may receive a sensing signal difference 145 measured by the sensing subsystem 150 and apply the feedback of the rotational position of the control arm 120 to the force signal generator 142 to adjust the force signal 141. In other words, the servo-loop integrator 146 can provide closed-loop operation of the system 100 for precise positioning and force control of the probe tip 111. The servo-loop integrator 146 may be configured to control the mechanical resonant frequency. The servo-loop integrator 146 may be further configured to control the settling time of the position of the probe tip 111. For example, if the probe tip 111 is rapidly traversing the surface of the sample 101, the servo loop integrator 146 can provide feedback to the system 100 so as not to restrict the up-and-down movement of the control arm 120 at a given frequency, thereby actively damping the mechanical resonance of the control arm 120 and the torsion bar 116.

[0057] In one example, the processor 140 may be configured to determine an adjusted force signal 141 based on feedback from the rotational position or force of the control arm 120 in order to generate a preset force. The feedback may indicate that the control arm 120 is in a position where the probe tip 111 is in contact with the surface of the sample 101, and as a result, further rotation of the control arm 120 will cause the probe tip 111 to exert a force on the surface of the sample 101. Thus, the processor 140 can determine an adjusted force signal 141 that generates a preset force. The processor 140 may be further configured to excite at least one of the pair of torque coils 130 with the adjusted force signal 141, thereby causing the probe tip 111 to contact the surface of the sample 101 with a preset force. The preset force may be adapted based on the material of the sample 101, for example, to bring the sample 101 into contact with the probe tip 111 with an appropriate force for measuring soft and hard materials. The preset force helps minimize wear on the probe tip 111, makes scanning soft samples easier, and also protects the sample 101 during testing.

[0058] In another example, the processor 140 may be configured to determine an adjusted force signal 141 based on feedback from the rotational position or force of the control arm 120 in order to position the probe tip 111 at a preset height. The feedback may indicate that the control arm 120 is positioned at a height different from the preset height, and as a result, further rotation of the control arm 120 will move the probe tip 111 so that it is positioned at the preset height. Thus, the processor 140 can determine an adjusted force signal 141 to position the probe tip 111 at the preset height based on the currently measured position. The processor 140 may be further configured to excite at least one of the pair of torque coils 130 with the adjusted force signal 141, thereby rotating the control arm 120 to position the probe tip 111 at the preset height. The processor 140 may be further configured to verify that the probe tip 111 is positioned at the preset height based on a sensing signal difference 145 received from the sensing subsystem 150. Therefore, the feedback information can enable precise positioning of the probe tip 111 and periodic adjustment of the force signal 141 during measurement. Precise positioning can enable measurement of fragile samples or samples with small features such as height or roughness.

[0059] In some embodiments, the processor 140 may be configured to generate a modulated force signal 147. For example, a force signal generator 142 may be configured to generate a modulated force signal 147. Alternatively, the processor 140 may further include a filter configured to modulate the force signal 141 generated by the force signal generator 142 to generate a modulated force signal 147. The modulated force signal 147 may be applied to the primary coil 151. The modulated force signal 147 may be an vibration signal. The processor 140 may further be configured to excite at least one of a pair of torque coils 130 with the modulated force signal 147, thereby causing the internal magnet 125 to vibrate between the pair of torque coils 130, and causing the probe tip 111 to vibrate against the surface of the sample 101. By vibrating up and down, the probe tip 111 can reduce the likelihood of it getting stuck in the highly viscous sample 101. This can also reduce wear on the probe tip 111 and allow smaller and more fragile samples to be scanned.

[0060] In some embodiments, the processor 140 may be configured to bring the probe tip 111 into contact with the surface of the sample 101 at a single point, then use a pair of torque coils 130 to lift the surface of the sample 101 to a safe height, translate the probe tip 111 to a second position, bring the probe tip 111 into contact with the surface of the sample 101 with a constant force, and continue point contact at several other locations on the surface of the sample 101 to generate a point cloud that can be used to generate an absolute height map. This can reduce wear on the probe tip 111 and improve measurement throughput, especially for large samples 101, and can allow larger and smaller samples 101 to be measured when scanning is not required for measurement, and can allow scanning of fragile or adhesive samples 101 when constant contact scanning is not practical.

[0061] In some embodiments, the processor 140 may be configured to dynamically compensate for the spring constant of the sensing subsystem 150 in real time throughout the full dynamic range of the height sensor. This can also reduce wear on the probe tip 111, allow smaller and more fragile samples 101 to be scanned, and reduce errors in the measured apparent height.

[0062] In some embodiments, the sample 101 may be positioned on a stage 105. The stage 105 may be movable in one or more directions in a plane (i.e., in the x and y directions) or out of a plane (i.e., in the z direction) by one or more actuators. The processor 140 may be configured to position the sample 101 by sending commands 148 to the stage 105 via a transceiver 149 to move one or more actuators. For example, the processor 140 may be configured to send commands 148 to move the stage 105 to scan the probe tip 111 across the surface of the sample 101, and the rotational position of the control arm 120 measured by the sensing subsystem 150 may indicate the shape of the sample 101 in the scanning direction. The processor 140 may be configured to control the speed of movement of the stage 105, where a faster scanning speed can increase throughput and a slower scanning speed can increase measurement accuracy. The processor 140 may further be configured to set a preset force and / or preset height of the probe tip 111 during scanning, as described above.

[0063] In system 100, the rotational position of the control arm 120 can be controlled via force signals 141 applied to a pair of torque coils 130, and the sensing subsystem 150 can determine the rotational position of the control arm 120 and provide feedback for closed-loop control. Thus, system 100 can provide precise positioning and force control in an integrated system.

[0064] Another embodiment of the present disclosure provides Method 200. As shown in Figure 7, Method 200 may include the following steps:

[0065] In step 210, the pair of torque coils are excited by a force signal to generate a magnetic force between the pair of torque coils and the internal magnet of the control arm positioned between them. The control arm may be connected to a probe arm, and the magnetic force can rotate the control arm and probe arm around a pivot joint, allowing the probe tip of the probe arm to come into contact with the surface of the sample.

[0066] In one embodiment, step 210 may include exciting one of a pair of torque coils with a force signal to control the direction in which the control arm rotates around the pivot joint based on magnetic force. For example, one of the torque coils may be excited to rotate the control arm in a controlled direction by attracting or repelling the internal magnet of the control arm. Alternatively, step 210 may include exciting both torque coils with different force signals to control the direction in which the control arm rotates around the pivot joint based on magnetic force. For example, each torque coil may be excited to rotate the control arm in a controlled direction by attracting / repelling the internal magnet of the control arm. Each torque coil may be excited so that the combined magnetic force from both torque coils controls the direction of rotation of the control arm.

[0067] In step 220, the sensing subsystem is energized with an excitation signal. The sensing subsystem may be configured, for example, as an angular displacement sensor, a linear displacement sensor, a two-coil structure, or other sensor configuration, according to any of the embodiments of system 100 described above.

[0068] In step 230, the detection signal difference from the detection subsystem is measured. The detection signal difference may be proportional to the rotational position of the control arm. The detection signal difference may be a voltage difference or a current difference. Specifically, a change in the rotational position of the control arm can move the core of the control arm relative to the primary coil and a pair of secondary coils. By measuring the detection signal difference in the pair of secondary coils, the direction and magnitude of the rotation of the control arm can be determined.

[0069] In step 240, the height of the probe tip relative to the sample surface is determined based on the rotational position of the control arm. For example, based on the rotation of the control arm, the corresponding rotational position of the probe arm can indicate the height of the probe tip. Based on contact with the sample, the height of the probe tip relative to the sample surface and the height of the sample surface features can be determined.

[0070] In step 250, the rotational position of the control arm, determined from the sensing subsystem, is applied as feedback within the servo loop to control the force signal. In other words, the rotational position of the control arm may be used to provide closed-loop operation for precise positioning and force control of the probe tip, as further described below.

[0071] In some embodiments, method 200 may further include a force command 260. The force command 260 can cause the probe tip to apply a controlled force to the surface of a sample, for example, for use in a scraping or indentation test of the sample. Upon receiving the force command 260, method 200 may include the following additional steps shown in Figure 8.

[0072] In step 261, a modified force signal is determined based on feedback from the rotational position or force of the control arm in order to generate a preset force. For example, based on the position information of the control arm, it may be determined when the probe tip contacts the surface of the sample and what additional rotation of the control arm causes the probe tip to apply a preset force to the sample. Thus, the modified force signal may be an adjustment (e.g., increase or decrease) to the force signal applied to at least one of a pair of torque coils that rotate the control arm to generate the preset force.

[0073] In step 262, a pair of torque coils are excited with a controlled force signal, thereby bringing the probe tip into contact with the sample surface with a preset force. The force applied to the sample may be confirmed to be the preset force based on the difference in detection signals from the detection subsystem. The closed-loop feedback of method 200 can enable precise control of the force applied to the sample surface by the probe tip for scratching and indentation tests.

[0074] In some embodiments, method 200 may further include a positioning command 270. The positioning command 270 may be configured to position the probe tip at a preset height relative to the surface of the sample for accurate positioning and measurement. Upon receiving the positioning command 270, method 200 may include the following additional steps shown in Figure 9.

[0075] In step 271, an adjusted force signal is determined based on feedback from the rotational position or force of the control arm in order to position the probe tip at a preset height. For example, based on the position information of the control arm, it may be determined where the current position of the probe tip is and what additional rotation of the control arm will position the probe tip at the preset height. Thus, the adjusted force signal may be an adjustment (e.g., increase or decrease) to the force signal applied to at least one of a pair of torque coils that rotate the control arm to position the probe tip at the preset height.

[0076] In step 272, a pair of torque coils are energized with a controlled force signal, thereby positioning the probe tip at a preset height relative to the surface of the sample.

[0077] In step 273, the probe tip position is confirmed to be at a preset height based on the detection signal difference from the detection subsystem. The closed-loop feedback of method 200 can enable precise control of the probe tip position for accurate positioning and measurement of features on the surface of the sample.

[0078] In some embodiments, method 200 may further include a modulation command 280, which may be configured to vibrate the probe tip relative to the surface of the sample. Upon receiving the modulation command 280, method 200 may include the following additional steps shown in Figure 10.

[0079] In step 281, a modulated force signal is generated. The modulated force signal can invert or interrupt the force signal that is periodically applied to a pair of torque coils. Therefore, the modulated force signal may be a separate signal from the force signal, or it may be generated by passing the force signal through a filter to produce a modulated force signal.

[0080] In step 282, a pair of torque coils are excited with a controlled force signal, thereby vibrating the probe tip relative to the surface of the sample. By vibrating up and down, the probe tip can reduce the possibility of it getting stuck in the highly viscous sample.

[0081] In method 200, the rotational position of the control arm can be controlled via force signals applied to a pair of torque coils, and a sensing subsystem can determine the rotational position of the control arm and provide feedback for closed-loop control. Thus, method 200 can provide precise positioning and force control in an integrated system.

[0082] A block diagram of a control system for a precision stylus is shown in Figure 11. The control system may be a closed-loop system and may be applicable to any embodiment of system 100 and method 200 described herein. The elements of the control system shown in Figure 11 are further described below.

[0083] The control system may include a probe detection chip. The probe detection chip may correspond to the probe chip 111 of the system 100 described above.

[0084] The control system may further include a position sensor excitation signal synthesizer. The position sensor excitation signal synthesizer can generate a pure sine wave to drive the primary coil. The position sensor excitation signal synthesizer may correspond to an excitation signal generator 144 configured to generate the excitation signal 143 of the system 100 described above.

[0085] The control system may further include a primary coil and a secondary coil of the position sensor. The primary coil of the position sensor may be driven by a sinusoidal current drive that induces an alternating magnetic flux in a movable core that moves with the profiler probe tip. The sensor core can move between the secondary coils. The alternating magnetic flux in the core induced by the primary winding is differentially coupled to the secondary winding. The primary coil of the position sensor may correspond to the primary coil 151 of the system 100 described above, and the secondary coil of the position sensor may correspond to the pair of secondary coils 152 of the system 100 described above.

[0086] The control system may further include a position sensor buffer amplifier. The position sensor buffer amplifier can extract a coupled signal from the sensor coil that is proportional to the magnitude of the position and has a phase indicating the sign of the position relative to the center of the sensor movement.

[0087] The control system may further include a forser coil. The forser coil can induce bidirectional force on a magnet attached to the probe shaft, enabling closed-loop damping of the probe tip's movement. The forser coil can induce precise pressure on the probe tip in contact with the test specimen. The forser coil may correspond to the pair of torque coils 130 of the system 100 described above.

[0088] The control system may also include a pull-back magnet. The pull-back magnet may be positioned above the probe shaft magnet, which exerts a slight attractive force on the shaft when the unit is not powered. The pull-back function can protect the test specimen and probe tip in the event of a power loss in the system. The pull-back magnet may correspond to the external magnet 160 of the system 100 described above.

[0089] The control system may further include a position sensor signal demodulator and a low-pass filter. The demodulator can convert the probe tip positioning signal from a sinusoidal waveform to a DC voltage waveform. The demodulator may be coupled with a low-pass filter that can remove residual ripple from the probe positioning signal.

[0090] The control system may further include a servo loop integrator. The servo loop integrator can drive the probe tip to a null position. The control system may further include a servo loop lead / lag filter compensator. Lead / lag filters may be used to compensate for the phase and gain of the probe positioning servo loop. The control system may further include a servo loop forser drive power amplifier. The servo loop power amplifier can drive the forser coil to force the sensor shaft to a desired position. The loop power amplifier may have an input to enable downforce drive current.

[0091] The control system may further include profiler tip positioning commands and a feedback buffer. The command buffer can interface with the host system to activate downforce, modulation, and pull-back functions, and can also provide a path output for current feedback signals. The current feedback signal may be proportional to the force driving the probe downforce. A servo loop modulation signal may allow the probe tip to be driven by a variable signal to enable tapping.

[0092] The control system may further include a probe positioning output buffer. The probe positioning output buffer performs final compensation of the positioning output, performs optional linearity compensation as needed, and can provide multiple gain amplifiers to allow sensitivity to be selected by the user. Higher gain stages may further utilize offset circuits that shift data within the output voltage aperture. The unit gain output may be directly proportional to the probe position. For example, 10 volts may be proportional to a 2 mm range of the probe tip. The gain of a 10-volt positioning output can provide a positioning output 10 times the sensitivity. For example, 10 volts may be proportional to a probe deflection of 200 microns. A nulling circuit can allow the 10-volt output window to be shifted along a virtual 100-volt range. The gain of a 100-volt positioning output can provide a positioning output 100 times the sensitivity. For example, 10 volts is proportional to a probe deflection of 20 microns. A nulling circuit can allow the 10-volt output window to be shifted along a virtual 1000-volt range. The probe positioning signal may be the filtered output of a demodulator that is directly proportional to the position of the probe tip.

[0093] The control system may further include a probe positioning buffer aperture reset. The aperture reset can allow the user to shift the aperture window within a range that can be displayed by the test system.

[0094] A downforce enable signal can connect the downforce signal to the control loop. Downforce loop enablement can control the integral gain of the control loop. In low-gain mode, the integrator may be disabled. A forser drive current sense signal may be fed back into the control loop to allow constant downforce to be regulated. A demodulator reference signal may be synchronized with the excitation signal to allow precise control of the phase of the demodulator process.

[0095] While this disclosure describes one or more specific embodiments, it will be understood that other embodiments of this disclosure can be constructed without departing from the scope of this disclosure. Therefore, this disclosure is considered to be limited only by the appended claims and their reasonable interpretation.

Claims

1. A probe arm equipped with a probe tip, wherein the probe tip is configured to contact the surface of a sample, A control arm connected to the probe arm, wherein the control arm includes an internal magnet, One or more torque coils are positioned on both sides of the internal magnet of the control arm, wherein the one or more torque coils are configured to cause rotation of the control arm around a pivot joint based on their interaction with the internal magnet. One or more torque coils, A detection subsystem configured to measure the rotational position of the control arm, A processor that electronically communicates with one or more torque coils and the detection subsystem, wherein the processor In order to generate a magnetic force between the one or more torque coils and the internal magnet, at least one of the one or more torque coils is excited with a force signal, thereby rotating the control arm around the pivot joint, thereby rotating the probe arm connected to the control arm around the pivot joint, and bringing the probe tip into contact with the surface of the sample. The aforementioned detection subsystem is excited with an excitation signal. Receiving a detection signal difference from the detection subsystem that is proportional to the rotational position of the control arm and corresponds to the height of the probe tip relative to the surface of the sample, wherein the detection signal difference is a voltage difference or a current difference. A processor and A system equipped with these features.

2. The system according to claim 1, wherein the processor includes a servo loop integrator configured to control the force signal by applying the rotational position of the control arm determined from the sensing subsystem as feedback.

3. The aforementioned processor, To generate a preset force, a force signal adjusted based on feedback from the rotational position or force of the control arm is determined. At least one of the one or more torque coils is excited with the adjusted force signal, thereby bringing the probe tip into contact with the surface of the sample with the preset force. The system according to claim 1, further configured as follows.

4. The aforementioned processor, In order to position the probe tip at a preset height, a force signal adjusted based on feedback from the rotational position or force of the control arm is determined. At least one of the one or more torque coils is excited with the adjusted force signal, thereby positioning the probe tip at the preset height relative to the surface of the sample. Based on the detection signal difference received from the detection subsystem, it is confirmed that the probe tip is positioned at the preset height. The system according to claim 1, further configured as follows.

5. The aforementioned processor, Generate a modulated force signal, At least one of the one or more torque coils is excited with the modulated force signal, thereby causing the height of the probe tip to vibrate relative to the surface of the sample. The system according to claim 1, further configured as follows.

6. The detection subsystem, Primary coil and A pair of secondary coils arranged on both sides of the primary coil and Equipped with, The core of the pivot joint is surrounded by the primary coil and the pair of secondary coils, and as a result, the change in the rotational position of the control arm moves the core within the primary coil and the pair of secondary coils, and the difference in the detection signals measured from the pair of secondary coils is proportional to the position of the core. The system according to claim 1.

7. The system according to claim 6, wherein the primary coil and the pair of secondary coils are coaxial, and the core moves linearly within the primary coil and the pair of secondary coils.

8. The system according to claim 6, wherein the primary coil and the pair of secondary coils are concircular, and the core moves angularly within the primary coil and the pair of secondary coils.

9. The detection subsystem, Primary coil and A secondary coil is positioned on the opposite side of the primary coil. Equipped with, The core of the control arm is positioned between the primary coil and the secondary coil, and as a result, a change in the rotational position of the control arm causes the core to move between the primary coil and the secondary coil, and the difference in the detection signal measured from the secondary coil is proportional to the position of the core. The system according to claim 1.

10. The system according to claim 1, further comprising an external magnet configured to attract the internal magnet of the control arm, thereby rotating the control arm to a retracted position where the probe tip is separated from the surface of the sample.

11. The system according to claim 10, wherein one or more torque coils are configured to cause rotation of the control arm in opposition to the attraction of the external magnet.

12. The system according to claim 10, wherein the external magnet is movable between a first position and a second position, in the first position the external magnet is located proximal to the internal magnet to attract the internal magnet of the control arm, and in the second position the external magnet is located distal to the internal magnet to allow free rotation of the control arm.

13. The system according to claim 1, wherein the pivot joint includes a torsion bar configured to bias the control arm toward a neutral position, the probe tip is spaced apart from the surface of the sample, and one or more torque coils are configured to rotate the control arm against the bias of the torsion bar.

14. The aforementioned processor, One of the one or more torque coils is excited by the force signal to control the direction in which the control arm rotates around the pivot joint based on the magnetic force. The system according to claim 1, further configured as follows.

15. The method involves exciting a pair of torque coils with a force signal to generate a magnetic force between the pair of torque coils and an internal magnet of a control arm positioned between the pair of torque coils, wherein the control arm is connected to a probe arm, and the magnetic force causes the control arm and the probe arm to rotate around a pivot joint, causing the probe tip of the probe arm to contact the surface of the sample. Exciting the detection subsystem with an excitation signal, Measuring the difference in detection signals from the detection subsystem that is proportional to the rotational position of the control arm, wherein the difference in detection signals is a voltage difference or a current difference. The height of the probe tip relative to the surface of the sample is determined based on the rotational position of the control arm. Methods that include...

16. To control the force signal, the rotational position of the control arm determined from the sensing subsystem is applied as feedback within the servo loop. The method according to claim 15, further comprising:

17. To generate a preset force, a force signal is determined that is adjusted based on feedback from the rotational position or force of the control arm, The pair of torque coils are excited with the adjusted force signal, thereby causing the probe tip to come into contact with the surface of the sample with the preset force. The method according to claim 15, further comprising:

18. To position the probe tip at a preset height, a force signal adjusted based on feedback from the rotational position or force of the control arm is determined. The pair of torque coils are excited with the adjusted force signal, thereby positioning the probe tip at the preset height relative to the surface of the sample. Based on the difference in the detection signal from the detection subsystem, it is confirmed that the probe tip is positioned at the preset height. The method according to claim 15, further comprising:

19. To generate a modulated force signal, The pair of torque coils are excited with the modulated force signal, thereby causing the height of the probe tip to vibrate relative to the surface of the sample. The method according to claim 15, further comprising:

20. Exciting the pair of torque coils with the force signal is This includes exciting one of the pair of torque coils with the force signal to control the direction in which the control arm rotates around the pivot joint based on the magnetic force, The method according to claim 15.

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