System and method for reducing measurement errors in interferometric measurement-based metrology

Abstract

The system includes a laser source and a dual interferometer subsystem. The channel of the dual interferometer subsystem includes a first splitter element coupled to a first output beam from the laser source and configured to split the first output beam into a first transmission beam and a first reflection beam; a first power sensor configured to measure the power of the first transmission beam; and a first detector configured to receive a first interference signal from the dual interferometer subsystem and record a first interferogram frame. The system includes a controller coupled to the first power sensor and the first detector of the first channel of the dual interferometer subsystem, the controller being configured to receive a first interferogram frame, receive a first laser power measurement from the first power sensor, and normalize the intensity of the first interferogram frame based on the first laser power measurement to produce a first normalized interferogram frame.

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims the benefits of U.S. Provisional Patent Application No. 63 / 457,814, filed on 7 April 2023 under 119(e) of the U.S. Patent Act, in which the inventors Chen Yuchi and Lai Yicheng, which is incorporated herein by reference in its entirety.

[0002] This disclosure relates to the measurement of substrate shape and thickness variations using a dual interferometer, and more particularly to the measurement and compensation of power fluctuations in interference measurement-based metrology system variations. [Background technology]

[0003] Interferometry is a useful technique for measuring one or more spatial properties of a sample, such as a semiconductor wafer or any other semiconductor or non-semiconductor substrate, based on information associated with the illumination reflected from the test surface of the sample. As semiconductor manufacturing continuously requires higher levels of accuracy and precision, improved interferometry techniques are needed to meet the demands of the latest manufacturing technologies.

[0004] The measurement of variations in the shape and thickness of wafers or thin films is frequently required. Currently, variations in the shape and thickness of bare wafers are measured through methods including dual interferometry. Dual interferometry systems are susceptible to fluctuations in the power of the interferometer's laser, which can lead to increased variability and errors during measurement, thereby significantly limiting the effectiveness of the dual interferometry system. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] U.S. Patent Application Publication No. 2018 / 0226304 [Patent Document 2] U.S. Patent Application Publication No. 2004 / 0105098 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Therefore, it is desirable to provide a system and method that overcomes the shortcomings of the methods discussed above. [Means for solving the problem]

[0007] Systems according to one or more embodiments of the present disclosure are disclosed. In one embodiment, the system includes a laser source. In another embodiment, the system includes a dual interferometer subsystem including a first channel and a second channel. In another embodiment, the first channel of the dual interferometer subsystem includes a first splitter element optically coupled to a first output beam from the laser source and configured to split the first output beam into a first transmission beam and a first reflection beam; a first power sensor configured to measure the power of the first transmission beam; a first detector configured to receive a first interference signal from the dual interferometer subsystem and record a first interferogram frame; and a controller communicatively coupled to the first power sensor and the first detector of the first channel of the dual interferometer subsystem. In another embodiment, the controller includes one or more processors, each configured to execute a set of program instructions stored in memory, the set of program instructions configured to cause the processors to receive a first interferogram frame from a first detector, receive a first laser power measurement from a first power sensor, and normalize the intensity of the first interferogram frame based on the first laser power measurement to produce a first normalized interferogram frame.

[0008] Another system according to one or more embodiments of the present disclosure is disclosed. In one embodiment, the system includes a dual interferometer subsystem configured to measure thickness variations across a substrate. In another embodiment, the system includes a dual interferometer system, a first power sensor, and a controller communicatively coupled to a first detector, the controller including one or more processors, the one or more processors configured to execute a set of program instructions stored in memory. In another embodiment, the set of program instructions is configured to cause one or more processors to receive a first interferogram frame, receive a first laser power measurement, and normalize the intensity of the first interferogram frame based on the first laser power measurement to produce a first normalized interferogram frame.

[0009] Methods for measuring substrate thickness according to one or more embodiments of the present disclosure are disclosed. In one embodiment, the method includes receiving a first interferogram frame from a first detector of a first channel of a dual interferometer wafer geometry system. In another embodiment, the method includes receiving a first laser power measurement from a first power sensor of a first channel of a dual interferometer wafer geometry system. In yet another embodiment, the method includes normalizing the intensity of the first interferogram frame based on the first laser power measurement to produce a first normalized interferogram frame.

[0010] Many of the advantages of this disclosure can be better understood by those skilled in the art by referring to the accompanying drawings. [Brief explanation of the drawing]

[0011] [Figure 1] This is a conceptual diagram of a system for measuring thickness variations of a substrate or film across an entire substrate, according to one or more embodiments of the present disclosure. [Figure 2A] This is a simplified schematic diagram of a dual interferometer subsystem according to one or more embodiments of the present disclosure. [Figure 2B] An enlarged conceptual diagram of one polarization beam splitter and an individual power sensor according to one or more embodiments of the present disclosure. [Figure 2C] A conceptual diagram of a double Fizeau cavity according to one or more embodiments of the present disclosure. [Figure 3] A process flow diagram depicting a method for measuring substrate thickness variations according to one or more embodiments of the present disclosure.

Mode for Carrying Out the Invention

[0012] Here, a detailed discussion will be made with respect to the disclosed subject matter shown in the accompanying drawings.

[0013] Figures 1 through 3 show a system and method for measuring power variations and compensating for measured power variations in a dual interferometric measurement system according to one or more embodiments of the present disclosure. Embodiments of the present disclosure are directed to the use of a power sensor optically coupled to one or more channels of a dual interferometric measurement system and configured to measure the power of an energy source (e.g., a laser source) associated with the dual interferometric measurement system. Embodiments of the present disclosure are further directed to using power measurements from the power sensor in a normalization method in which interferogram frames are normalized based on variations in the power measurements. The system and method reduce measurement errors induced by laser power variations in an interferometric-based wafer geometry metrology system.

[0014] Embodiments of the present disclosure are particularly advantageous because they can be implemented while making improvements in accuracy and having minimal modification to the optical systems and software of existing platforms.

[0015] Figure 1 shows a conceptual diagram of a system 100 for measuring substrate or film thickness variations across a substrate according to one or more embodiments of the present disclosure.

[0016] In an embodiment, the system 100 includes a dual interferometer subsystem 102 (or dual interferometer tool) comprising a first channel 103a and a second channel 103b, one or more power sensors 104a-b, and a controller 106. In an embodiment, the dual interferometer subsystem 102 is configured to measure flatness over the entire substrate 101. The substrate 101 may include any substrate known in the art, including, but not limited to, a semiconductor wafer (e.g., a silicon wafer). The substrate may be coated with one or more films, and may also include one or more prior layers, as will be further discussed in detail herein.

[0017] In one embodiment, the controller 106 includes one or more processors 108 and a memory 110. For example, the memory 110 may hold program instructions configured to cause one or more processors 108 to execute one or more process steps described throughout this disclosure.

[0018] In an embodiment, one or more processors 108 of the controller 106 are communicatively coupled to a dual interferometer subsystem 102 and a power sensor 104. In this regard, one or more processors 108 are configured to receive measurement results from the dual interferometer subsystem 102 and the power sensor 104. In an embodiment, one or more processors are configured to determine the thickness variation of the substrate 101 as a function of position across the substrate 101, based on one or more flatness measurements received from the dual interferometer subsystem and one or more power measurements received from the power sensor 104. It should be noted that the system 100 may be used to measure the thickness variation of the substrate and / or the thickness variation of a thin film deposited on a substrate with or without a preceding layer, which may be further described in detail herein.

[0019] The power sensor 104 may include any power or optical sensor known in the art that can measure the power of a light source such as a laser, although it is not limited to a laser. For example, the power sensor 104 may include a photodetector. The photodetector includes, but is not limited to, metal-semiconductor-metal (MSM) photodetectors, photodiodes, avalanche photodiodes, phototransistors, charge-coupled devices, complementary metal-oxide-semiconductor (CMOS) image sensors, and photomultiplier tubes.

[0020] The dual interferometer subsystem 102 may include any dual interferometer tool known in the art that can measure flatness over the entire substrate 101. For example, the dual interferometer subsystem 102 may include, but is not limited to, a dual-wavelength dual Fizeau interferometer (DWDFI). The dual interferometer subsystem 102 system may be configured to measure any number of spatial characteristics of the substrate 101, such as shape variations, thickness variations, and / or other spatial parameter variations of the sample. In embodiments, the dual interferometer subsystem 102 system may be adapted to perform patterned wafer geometry (PWG) measurements on the sample, thereby extending the dynamic range of the sample gradient (e.g., wafer gradient) measured by the dual interferometer subsystem 102 by binding together different regions of the sample (e.g., wafer) measurement results.

[0021] A description of a dual-wavelength dual-interferometer is found in U.S. Patent No. 6,847,458, published on January 25, 2005, which is incorporated herein by reference in its entirety. A description of a dual-wavelength dual-interferometer is found in U.S. Patent No. 8,068,234, published on November 29, 2011, which is incorporated herein by reference in its entirety. A description of a dual-wavelength dual-interferometer is found in U.S. Patent Application Publication No. 2014 / 0293291, published on October 2, 2014, which is incorporated herein by reference in its entirety. A description of a dual-wavelength dual-interferometer used to measure the shape and thickness of high-gradient samples is found in U.S. Patent No. 7,847,954, published on December 7, 2010, which is incorporated herein by reference in its entirety. It is understood herein that this disclosure may be extended to any phase-shift interferometry system configured to utilize a wavelength-tunable illumination source for phase shift. Accordingly, the following description of the dual interferometer subsystem 102 is not intended to limit this disclosure in any way.

[0022] Figure 2A shows a simplified schematic diagram of a dual interferometer subsystem 102 according to one or more embodiments of the present disclosure.

[0023] In an embodiment, the dual interferometer subsystem 102 includes an illumination source or illuminator 201 configured to provide light along a first channel 103a and a second channel 103b. In an embodiment, the optical first and second channels 103a and 103b of the dual interferometer subsystem 102 include optical fibers 228 and 229 configured to transmit light from an illumination source (e.g., illuminator 201) to interferometer inputs 252 and 253. In an embodiment, the interferometer inputs 252 and 253 include one or more optical elements connected in series with one or more optical fibers 228 and 229. In an embodiment, the interferometer inputs 252 and 253 may include optical fibers 228 and 229. The interferometer inputs 252 and 253 can direct at least a portion of the light from the illuminator 201 to the dual interferometer subsystem 102.

[0024] In an embodiment, the dual interferometer subsystem 102 includes one or more polarizing beam splitters 212, 213 configured to receive light from interferometer inputs 252, 253. In an embodiment, the beam splitters 212, 213 direct a portion of the light to quarter-wavelength plates 254, 255. The light passing through the polarizing beam splitters 212, 213 and through the quarter-wavelength plates 254 and 255 may be circularly polarized. The circularly polarized light may then be received by lenses 214, 215 configured to collimate the light into a beam having a diameter greater than the diameter of the substrate 101. One or more lenses 214, 215 can further direct the collimated beam to reference planes 216, 217 (e.g., parallel reference planes). The substrate 101 may be positioned at the center of a gap 219 defined by the reference planes 216, 217. In this embodiment, the collimated beam can be transmitted through the reference planar surfaces 216 and 217 to reach the substrate 101.

[0025] In this embodiment, each first portion of the transmitted beam is directed toward one or more surfaces 220, 221 of the substrate 101. Furthermore, each second portion of the transmitted beam is directed toward a reference plane of one or more transmission reference planes 216, 217 that are positioned opposite each other.

[0026] In embodiments, the dual interferometer subsystem 102 includes detectors 222, 223 (e.g., a first detector and a second detector). Detectors 222, 223 may include, but are not limited to, one or more CCD detectors, one or more TDI-CCD detectors, one or more CMOS detectors, cameras, or any other photodetectors known in the art. In embodiments, detectors 222, 223 may be configured to detect and / or record portions of illumination reflected from one or more surfaces 220, 221 of the substrate 101 (e.g., a first interference signal and a second interference signal). In embodiments, detectors 222, 223 are configured to detect portions of light reflected from corresponding reference planes of reference planar planes 216, 217.

[0027] In one embodiment, the dual interferometer subsystem 102 includes one or more power sensors 104a-b. One or more power sensors 104 are configured to measure the power of the output beam from the illuminator 201. One or more power sensors 104a-b can measure the power of the output beam from one or more locations within the dual interferometer subsystem 102. For example, one or more power sensors 104a-b may be configured to measure light transmitted through one or more polarizing beam splitters 212, 213. One or more power sensors 104a-b may be mechanically coupled to one or more polarizing beam splitters 212, 213, bonded to one or more polarizing beam splitters 212, 213, or positioned at a specific distance away from the surface of one or more polarizing beam splitters 212, 213, while configured to receive the transmitted light.

[0028] In an embodiment, the system 100 includes one or more controllers 226 communicatively coupled to detectors 222, 223. In an embodiment, one or more controllers 226 acquire information associated with the light detected from detectors 222, 223. In an embodiment, controller 126 can execute a measurement algorithm from program instructions stored in memory to determine one or more spatial properties of the substrate 101 based on measurements from the substrate 101. Measurement algorithms for determining the spatial properties of a sample using a phase-shift interference measurement system are known in the art. It should be noted that any measurement process known in the art can be carried out using the system 100 and one or more controllers 226. Furthermore, the one or more controllers 226 depicted in Figure 2A can be embodied in the controller 106 shown in Figure 1, and vice versa.

[0029] Figure 2B shows an enlarged conceptual diagram of a single polarizing beam splitter 212 and a separate power sensor 104a according to one or more embodiments of the present disclosure. As shown in Figure 2B, the power sensor 104a is oriented with respect to the polarizing beam splitter 212 so that when the first output beam 260 is split into a first transmitted beam 262, a first reflected beam 264, and a first transmitted beam 266, the first transmitted beam 266 aligns with the power sensor 104a so that the power of the first transmitted beam 266 can be measured. The dual interferometer subsystem 102 may further include one or more plano-convex lenses (PCS) 268 which can be further used to collimate or focus the first transmitted beam 266 toward the power sensor 104a. The measurements from the power sensor 104a are then transmitted to one or more controllers 106, 226. For example, the voltage measurement (V) from the power sensor PS The signal can be received by controller 226 via the "analog in" port or pin. Controller 226 receives the laser tuning ramp signal (V) from the piezoelectric stack transducer (PZT). PZT Ramp ) and frame rate trigger voltage (V Trigger) can receive other signals including, but not limited to, the pulse signal.

[0030] In an embodiment, power sensors 104a - b are operable within one or more ranges or settings of one or more parameters (e.g., gain (measured in volts / ampere or V / A), bandwidth, and noise (measured in volts)). For example, power sensors 104a - b can operate with a gain in the range of 1×10 3 V / A to 1×10 7 V / A, with a gain in the range of 1×10 4 V / A to 1×10 6 V / A, or with a gain in the range of 3×10 4 V / A to 3×10 5 V / A. For example, power sensors 104a - b can operate with a gain of approximately 0.75×10 5 V / A. In another example, power sensors 104a - b can operate with a bandwidth in the range of 1 kHz to 10 MHz, 10 kHz to 1 MHz, or 100 kHz to 500 MHz. For example, power sensors 104a - b can operate with a bandwidth of approximately 225 kHz. In another example, power sensors 104a - b can operate with a noise value in the range of 10 μV to 10 mV, 100 μV to 3 mV, or 300 μV to 1 mV. For example, power sensors 104a - b can operate with a noise of approximately 799 μV.

[0031] Figure 2C shows a conceptual diagram of a double Fizeau void 219 according to one or more embodiments of the present disclosure. As shown in Figure 2C, the double Fizeau void 219 may be configured to hold the substrate 101 in a substantially vertical position. For example, the double Fizeau void 219 may include a set of point contact devices (not shown) configured to receive and hold the wafer in a substantially free and substantially upright position. By utilizing two reference planes 216 and 217 that act as reference planes for the interferometer, the double Fizeau interferometer can analyze the spatial relationship between various parameters associated with the substrate and the reference planes 216 and 217 of the substrate.

[0032] The dual interferometer subsystem 102 can simultaneously measure the thickness variation of both the front surface 220 and the back surface 221 of the substrate 101. The shape values ​​at each of the measured points on the front and / or back surfaces can then be calculated using the measured height variation at those points. The wafer shape s(x,y) as a function of the XY position on the wafer surface can be expressed as a function of the gap distance between the surface of the substrate 101 and the corresponding reference planes 216,217.

[0033] In this case, d A (x,y) represents the gap distance between the first reference flat surface 217 of the gap 219 and the first side surface 220 (for example, the front side) of the substrate, d B (x,y) represents the gap distance between the second reference flat surface 216 and the second side surface 221 of the wafer (for example, the back side). In this case, the gap distance d A The (x,y) variation is the thickness t of the first side surface of the substrate. A (x,y) variation and surface r of the reference plane A It is related to the difference with the variation of (x,y). Similarly, the void distance d B The (x,y) variation is due to the thickness t of the second side surface 221 of the substrate. B (x,y) variation and surface r of the reference plane B It can be related to the difference with the variation of (x,y).

[0034] By utilizing these relationships, a two-dimensional XY map of the shape can be constructed by calculating the shape at multiple locations on the substrate. Dual Fizeau interferometry, suitable for measuring the front and back topography of a substrate (e.g., a semiconductor wafer), is described in detail in Klaus Freischlad et al., "Interferometry for Wafer Dimensional Metrology," Proc. SPIE 6672, 1 (2007), which is incorporated herein by reference in its entirety. Furthermore, two-plane interferometry is generally described in U.S. Patent No. 6,847,458, issued on January 25, 2005, and U.S. Patent No. 8,068,234, issued on November 29, 2011, both of which are incorporated herein by reference in their entirety.

[0035] In an embodiment, the dual interferometer subsystem 102 is used to measure the shape and / or thickness variations of the substrate 101. The dual interferometer subsystem 102 is susceptible to errors due to power fluctuations of the first output beam 260 caused by wavelength changes during phase shift. A method for using power measurements from one or more power sensors 104a-b to compensate for power fluctuations is provided below.

[0036] In this embodiment, a model of a phase-shifted interference fringe pattern that takes into account the instability of the laser power can be represented as follows: I(i,j)=I0(i){1+V(j)cos[φ(j)+δ(i)]} Equation 1 However, I0 is a background intensity that may have frame-over-frame variations (taken, for example, by detectors 222, 223), V corresponds to the pixel contrast, i (e.g., subscript i) corresponds to the frame index, and j (e.g., subscript j) corresponds to the pixel index.

number

[0037] In this embodiment, power fluctuations detected in the interferogram frame can be normalized to generate a normalized interferogram frame. For example, laser power fluctuations can be compensated within the interferogram frame by electrically normalizing the intensity of the interferogram frame as follows.

number

number

number

number

[0038] In an embodiment, one or more processors 108 of the controller 106 of system 100 can determine the thickness variation of the substrate 101 as a function of position across the substrate 101 based on one or more flatness measurements from the dual interferometer subsystem 102 and power measurements from power sensors 104a-b. For example, power measurements may be used to electrically normalize the intensity of the interferogram used in determining the thickness variation of the substrate. In an embodiment, one or more processors 108 receive one or more flatness measurements f(x,y) of the substrate 101 as a function of XY position across the substrate 101 from the dual interferometer subsystem 102 and one or more power measurements P of the output beam (e.g., the first transmitted beam 266) from power sensors 104a-b. In an embodiment, one or more processors 108 determine the average thickness of the substrate 101 based on one or more power measurements. In one embodiment, one or more processors 108 determine the thickness variation t(x,y) of the substrate 101 as a function of position across the substrate 101, based on one or more flatness measurements and the average thickness of the substrate 101.

[0039] In an embodiment, the system 100 includes a user interface device communicatively coupled to one or more processors 108 of the controller 106. The user interface device may be utilized by the controller 106 to accept information, selections, and / or instructions from the user. For example, a display may be used to display data or prompts (not shown) to the user. Furthermore, the user can input information, selections, and / or instructions into the memory 110 of the controller 106 via the user interface device.

[0040] The preceding description focuses on a power sensor 104 connected to one or more processors 108, but such a configuration is not a limitation on the scope of the embodiments of this disclosure. In an alternative embodiment, the power information previously discussed herein may be entered into the memory 110 of the controller 106 by a user via a user interface. In this regard, the various thickness variation calculations previously described herein can be performed using the power information entered into the memory 110 via the user interface.

[0041] In an embodiment, once a thickness variation with respect to the substrate 101 is determined, one or more processors 108 can transmit one or more control / adjustment instructions to one or more process tools. For example, in response to a determination that the thickness variation with respect to the substrate 101 and / or film 301 deviates from a desirable thickness variation, one or more processors 108 can adjust one or more parameters of process tools along the semiconductor manufacturing equipment to mitigate the observed imperfection associated with the substrate and / or the final semiconductor device. In this regard, one or more processors 108 can provide feedback information to upstream process tools to adjust process conditions for subsequent substrates following the first substrate along the semiconductor manufacturing line. Furthermore, one or more processors 108 can provide feedforward information to downstream process tools to adjust process conditions for the substrate in question as the substrate progresses along the semiconductor manufacturing line.

[0042] In an embodiment, once the intensity of the first channel 103a and / or the second channel 103b has been determined / monitored, or the intensity of the interferogram frame has been normalized, one or more processors 108 may transmit one or more control / adjustment instructions to one or more components of the system 100 (e.g., an illuminator 201) or to one or more process tools. For example, in response to a determination that the laser power fluctuation has increased, one or more processors 108 may adjust one or more parameters of the illuminator 201 (e.g., output intensity or wavelength). In this regard, one or more processors 108 may provide feedback information to the illuminator 201 to adjust the process conditions for subsequent substrates.

[0043] One or more processors 108 of the controller 106 may include any one or more processing elements known in the art. In this sense, one or more processors 108 may include any microprocessor-type device configured to execute software algorithms and / or instructions. In embodiments, one or more processors 108 may consist of a desktop computer, a mainframe computer system, a workstation, an image computer, a parallel processor, or other computer systems (e.g., networked computers) configured to run programs configured to operate system 100 as described throughout this disclosure. It should be understood that the steps described throughout this disclosure may be performed by a single computer system, or alternatively, by multiple computer systems. Generally, the term “processor” may be broadly defined to include any device having one or more processing elements that execute program instructions from a non-temporary memory medium 110. Furthermore, different subsystems of system 100 (e.g., the dual interferometer subsystem / tool ​​102, the size sensor 104, or the user interface) may include processor elements or logic elements suitable for performing at least a portion of the steps described throughout this disclosure.

[0044] The memory medium 110 may include any memory medium known in the art that is suitable for storing program instructions executable by one or more associated processors 108. For example, the memory medium 110 may include, but is not limited to, read-only memory, random-access memory, magnetic or optical memory devices (e.g., disks), magnetic tape, and solid-state drives. In embodiments, the memory medium 110 is configured to store one or more results from the dual interferometer subsystem 102 and / or the size sensor 104, as well as / or the outputs of various data processing steps described herein. It should be further noted that the memory medium 110 may be housed within a common controller housing that includes one or more processors 108. In alternative embodiments, the memory medium 110 may be located far away from the physical locations of the processors and controller 106. For example, one or more processors 108 of the controller 106 may have access to remote memory (e.g., a server) accessible via a network (e.g., the Internet and an intranet).

[0045] Although Figure 1 depicts the controller 106 as being implemented separately from the dual interferometer subsystem 102 and the magnitude sensor 104, it should be further noted that such a configuration of system 100 is provided for illustrative purposes only and is not a limitation on the scope of this disclosure. For example, the controller 106 may be implemented as the controller for the dual interferometer subsystem 102 and / or the magnitude sensor 104.

[0046] The user interface device may include any user interface known in the art. For example, the user interface may include, but is not limited to, a keyboard, keypad, touchscreen, lever, knob, scroll wheel, trackball, switch, dial, sliding bar, scroll bar, slide, handle, touchpad, paddle, steering wheel, joystick, or bezel input device.

[0047] Figure 3 shows a process flow diagram illustrating a method 300 for measuring substrate thickness variation according to one or more embodiments of the present disclosure. One or more steps of method 300 may be performed by one or more processors 108 of controllers 106, 226 (for example, one or more processors 108 are configured to execute a set of program instructions for one or more steps of method 300 stored in memory 110). In an embodiment, method 300 includes step 302 of receiving a first interferogram frame from a first detector 222 of a first channel 103a of a dual interferometer wafer geometry system 100. In an embodiment, method 300 includes step 304 of receiving a first laser power measurement from a first power sensor 104a of a first channel 103a of a dual interferometer wafer geometry system 100. In an embodiment, method 300 includes step 306 of normalizing the intensity of the first interferogram frame based on the first laser power measurement in order to produce a first normalized interferogram frame. Normalizing the intensity of the first interferogram frame may include, at least in part, a normalization algorithm described herein, such as the algorithm comprising Equation 2. In an embodiment, the method includes a step 308 in which the geometry of the substrate 101 is determined based on the normalized interferogram frame.

[0048] Method 300 may further include the steps of receiving a second interferogram frame from a second detector 227, receiving a second laser power measurement from a second power sensor 104b, and normalizing the intensity of the second interferogram frame based on the second laser power measurement to produce a second normalized interferogram frame. Method 300 may then include the step of determining the geometry (e.g., shape and / or thickness) of the substrate 101 based on the first normalized interferogram frame and the second normalized interferogram frame. In a dual interferometer wafer geometry system 100 using only one power sensor 104a, the determined geometry of the substrate 101 may be based on the first normalized interferogram frame. For example, the geometry of the substrate 101 may be determined based on a first normalized interferogram frame from a first detector 222 and a second unnormalized interferogram frame from a second detector 223.

[0049] While implementations of Method 300 are discussed herein, it is further intended that various steps of Method 300 may be included, excluded, rearranged, and / or implemented in many ways without departing from the essence of the disclosure. Accordingly, the aforementioned embodiments and implementations of Method 300 are included only as examples and are not intended to limit the disclosure in any way.

[0050] All of the methods described herein may include storing the results of one or more steps of the method embodiment in a memory medium. The results may include any of the results described herein and may be stored in any format known in the art. The memory medium may include any memory medium described herein or any other suitable memory medium known in the art. After the results are stored, they may be accessed in the memory medium, used by any of the method or system embodiments described herein, formatted for display to a user, and used by another software module, method, or system, etc. Furthermore, the results may be stored "permanently," "semi-permanently," "temporarily," or for a period of time. For example, the memory medium may be random-access memory (RAM), and the results may not necessarily remain in the memory medium indefinitely.

[0051] It is further intended that each of the embodiments of the above methods may include any other step(s) of any other method(s) described herein. Furthermore, each of the embodiments of the above methods may be carried out by any of the systems described herein.

[0052] Those skilled in the art will understand that it is common in the art to describe devices and / or processes in the form specified herein and then, using engineering practice, integrate such described devices and / or processes into a data processing system. That is, at least a portion of the devices and / or processes described herein can be integrated into a data processing system through a reasonable amount of experimentation. Those skilled in the art will understand that a typical data processing system generally includes one or more of the following: a system unit housing, a video display device, memory such as volatile and non-volatile memory, a processor such as a microprocessor and a digital signal processor, a computer computing entity such as an operating system, a driver, a graphical user interface, and an application program, one or more interaction devices such as a touchpad or a screen, and / or a control system including a feedback loop and a control motor (e.g., feedback for sensing position and / or velocity, a control motor for moving and / or adjusting components and / or quantities). A typical data processing system may be implemented using any suitable commercially available components, such as those commonly found in data computing / communication and / or network computing / communication systems.

[0053] The subject matter described herein may sometimes refer to different components that are included in or connected to other different components. It should be understood that such described architectures are merely illustrative, and that in fact many other architectures can be implemented to achieve the same function. In a conceptual sense, any constructs of components for achieving the same function are effectively “associated” in such a way that the desired function is achieved. Thus, any two components combined herein to achieve a particular function can be considered “associated” with each other, regardless of architecture or intermediate components, in such a way that the desired function is achieved. Similarly, any two components thus associated can also be considered “operably connected” or “operably coupled” with each other to achieve the desired function, and any two components that can be associated in such a way can also be considered “operably coupled” with each other to achieve the desired function. Specific examples of operably connectable components include, but are not limited to, components that are physically matable and / or physically interact, as well as components that are wirelessly interactable and / or wirelessly interact, and / or logically interactable.

[0054] In general, as will be understood by those skilled in the art, terms used herein, particularly in the appended claims (e.g., the body of the appended claims), are generally intended as “open” terms (for example, the term “including” should be interpreted as “including but not limited,” the term “having” should be interpreted as “having at least,” and the term “includes” should be interpreted as “including but not limited,” etc.). Where a particular number is intended in the description of an introduced claim, such intent will be explicitly stated in the claims, and where such statement is absent, it will be understood by those skilled in the art that no such intent exists. For example, for the sake of understanding, the following appended claims may include the use of the introductory phrases “at least one” and “one or more” to introduce the description of the claim. However, the use of such phrases should not be interpreted as the introduction of a claim description with the indefinite article “one:a” or “one:an” being limited to any particular claim containing such introduced description for an invention containing only one such description, and the same applies to the use of the definite article used to introduce a claim description, even when the same claim contains the prefatory phrase “one or more” or “at least one” and an indefinite article such as “one:a” or “one:an” (for example, “one:a” and / or “one:an” should be interpreted as meaning “at least one” or “one or more”). Furthermore, even if a particular number of introduced claim descriptions are explicitly stated, a person skilled in the art will understand that such descriptions should typically be interpreted as meaning at least the number described (for example, the rare description “two descriptions” without other modifiers typically means at least two descriptions, or two or more descriptions).Furthermore, in instances where a similar convention is used, such a configuration is generally intended to mean that a person skilled in the art would understand the convention (for example, that "a system having at least one of A, B, and C" will include, but not limited to, systems having only A, only B, only C, both A and B, both A and C, both B and C, and / or systems having both A, B, and C). It will be further understood by those skilled in the art that any disjunctive word and / or phrase that virtually presents two or more alternative terms should be understood as intended to include one of the terms, either one or both of the terms, even in the specification, claims, or drawings. For example, the phrase "A or B" will be understood to include "A" or "B" or "A and B".

[0055] While specific aspects of the subject matter described herein have been shown and described, modifications and alterations may be made based on the teachings herein without departing from the subject matter described herein and its broader aspects, and it will be apparent to those skilled in the art that the appended claims encompass all such modifications and alterations within their scope, as if they were in the true spirit and scope of the subject matter described herein. Furthermore, it should be understood that the present invention is defined by the appended claims.

Claims

1. Laser source and A dual interferometer subsystem comprising a first channel and a second channel, wherein the first channel of the dual interferometer subsystem is A first splitter element is optically coupled to a first output beam from a laser source and configured to split the first output beam into a first transmission beam and a first reflection beam. A first power sensor configured to measure the power of the first transmitted beam, A first detector configured to receive a first interference signal from the dual interferometer subsystem and record a first interferogram frame. A dual interferometer subsystem having, A controller communicatively coupled to the first power sensor and the first detector of the first channel of the dual interferometer subsystem, wherein the controller includes one or more processors, the one or more processors being configured to execute a set of program instructions stored in memory, and the set of program instructions is configured to execute the one or more processors Receiving the first interferogram frame from the first detector, Receiving a first laser power measurement value from the first power sensor, and To produce a first normalized interferogram frame, the intensity of the first interferogram frame is normalized based on the first laser power measurement. A controller configured to perform the following actions A system characterized by comprising the following features.

2. The system according to claim 1, characterized in that the first laser power measurement value includes the average of a plurality of power measurement values.

3. The system according to claim 1, characterized in that normalizing the intensity of the first interferogram frame includes calculating the product of the average power of all interferogram frames and the intensity of the first interferogram frame.

4. The system according to claim 1, wherein the second channel of the dual interferometer subsystem is A second splitter element coupled to the second output beam of a second laser source and configured to split the second output beam into a second transmission beam and a second reflection beam, A second power sensor configured to measure the power of the second transmitted beam, A second detector configured to receive a second interference signal from the dual interferometer subsystem and record a second interferogram frame, A system characterized by comprising the following features.

5. The system according to claim 1, wherein one or more processors The geometry of the substrate is determined based on the first normalized interferogram frame and at least one of the second interferogram frame or the second normalized interferogram frame. A system characterized by being further configured in such a way.

6. The system according to claim 5, wherein the substrate is Semiconductor wafers A system characterized by including

7. The system according to claim 1, wherein the dual interferometer subsystem is Dual-wavelength dual-Fizeau interferometer (DWDFI) subsystem A system characterized by comprising the following features.

8. The system according to claim 1, wherein the first power sensor comprises a photodetector.

9. The system according to claim 1, wherein the first detector comprises a camera.

10. A dual interferometer subsystem configured to measure thickness variations across the entire substrate, A controller communicatively coupled to the dual interferometer subsystem, the first power sensor, and the first detector, wherein the controller includes one or more processors, and the one or more processors are configured to execute a set of program instructions stored in memory, and the set of program instructions is configured to execute the one or more processors Receiving the first interferogram frame, Receiving the first laser power measurement, and, To produce a first normalized interferogram frame, the intensity of the first interferogram frame is normalized based on the first laser power measurement. A controller configured to perform the following actions A system characterized by comprising the following features.

11. The system according to claim 10, characterized in that normalizing the intensity of the first interferogram frame includes calculating the product of the average power of all interferogram frames and the intensity of the first interferogram frame.

12. The system according to claim 10, wherein the controller is further communicably coupled to a second power sensor and a second detector, and the set of program instructions is transmitted to one or more processors. Receiving the second interferogram frame, Receiving a second laser power measurement, and, To produce a second normalized interferogram frame, the intensity of the second interferogram frame is normalized based on the second laser power measurement. A system characterized by being further configured to perform the following action.

13. The system according to claim 10, wherein one or more processors The geometry of the substrate is determined based on the first normalized interferogram frame and at least one of the second interferogram frame or the second normalized interferogram frame. A system characterized by being further configured in such a way.

14. The system according to claim 10, wherein the dual interferometer subsystem is Dual-wavelength dual-Fizeau interferometer (DWDFI) subsystem A system characterized by comprising the following features.

15. A system according to claim 10, further comprising the first power sensor, wherein the first power sensor comprises a photodetector.

16. A system according to claim 10, further comprising the first detector, wherein the first detector comprises a camera.

17. The system according to claim 10, wherein the substrate is Semiconductor wafers A system characterized by including

18. A method for measuring the thickness of a substrate, The steps include receiving a first interferogram frame from a first detector of a first channel of a dual interferometer wafer geometry system, The steps include receiving a first laser power measurement value from the first power sensor of the first channel of the dual interferometer wafer geometry system, To produce a first normalized interferogram frame, the steps include: normalizing the intensity of the first interferogram frame based on the first laser power measurement; A method characterized by including the following.

19. A method according to claim 18, characterized in that the first laser power measurement value includes the average of a plurality of power measurement values.

20. The method according to claim 18, The steps include receiving a second interferogram frame from a second detector, The steps include receiving a second laser power measurement from a second power sensor, To produce a second normalized interferogram frame, the steps include: normalizing the intensity of the second interferogram frame based on the second laser power measurement; A method characterized by further comprising:

21. A method according to claim 18, characterized in that the step of normalizing the intensity of the first interferogram frame includes the step of calculating the product of the average power of all interferogram frames and the intensity of the first interferogram frame.

22. The method according to claim 20, the step of determining the geometry of a substrate based on the first normalized interferogram frame and the second normalized interferogram frame. A method characterized by further comprising:

23. The method according to claim 18, Steps to determine the geometry of the substrate based on the first normalized interferogram frame and the second interferogram frame or at least one of the second normalized interferogram frame. A method characterized by further comprising:

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