An integrated module based on MZI and a chemical mechanical polishing endpoint detection system

Abstract

The application provides an integrated module based on MZI, comprising: a light source providing coherent light; a lens assembly; an MZI photon chip, which splits the coherent light provided by the light source into a signal light beam and a reference light beam, makes the signal light beam irradiate to a measured object via the lens assembly, and makes the signal light beam reflected by the measured object return to the MZI photon chip via the lens assembly, combines the signal light beam with the reference light beam to form an interference light beam and outputs; and a photodetector, which receives the interference light beam output from the MZI photon chip, detects the light intensity change of the interference light beam and converts it into an electric signal.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor manufacturing technology, and relates to polishing endpoint monitoring technology, particularly to an integrated module based on MZI and a chemical mechanical polishing endpoint detection system. Background Technology

[0002] With Moore's Law approaching saturation in microelectronic chip integration, the photonic path offers a new engine and new computing and network architecture, bringing new opportunities for high-throughput data transmission and computing. Photonic chip technology fully leverages mature CMOS infrastructure and experience, breaking through the limitations of existing optoelectronic technologies in terms of cost, power consumption, and integration density, making it one of the key chip technologies in the post-Moore's Law era. High-performance silicon-based photonic chips based on optoelectronic heterogeneous integration technology, by integrating silicon with other functional materials (such as germanium, thin-film lithium niobate, silicon nitride, and silicon oxide thin films), will enable multifunctional and high-efficiency optoelectronic devices. These devices will have broad application potential in fields such as communication, sensing, and quantum computing.

[0003] In multilayer thin-film material stacking, Chemical Mechanical Polishing (CMP) is a technique considered the only current technology capable of achieving global wafer surface planarization in integrated circuit manufacturing. It achieves atomic-level ultra-high flatness, directly impacting the final chip quality and yield. In multilayer thin-film material stacking, CMP effectively flattens the surface, ensuring the precision and uniformity of subsequent photolithography and deposition processes. Real-time monitoring not only precisely controls the removal amount, preventing material loss from over-planarization or surface unevenness from under-planarization, but also improves process efficiency. Timely termination of the thin-film CMP process reduces unnecessary time and resource consumption, increasing production efficiency. Furthermore, real-time monitoring ensures consistent planarization across batches of chips, guaranteeing device consistency and improving product yield and consistency.

[0004] Chemical Mechanical Polishing (CMP) is hailed as the only technology currently available capable of achieving global planarization of wafer surfaces in integrated circuit manufacturing, reaching atomic-level ultra-high flatness. Its effectiveness directly impacts the final chip quality and yield. One of the most crucial requirements of CMP is determining when to stop the polishing process, known as End Point Detection (EPD). This determines when the CMP process should cease, i.e., when the desired flatness and thickness have been achieved. Generally, process control methods primarily rely on non-real-time ellipsometer measurements of the film thickness to calculate a specific amount of polishing and then convert this into polishing time based on the machine's polishing rate. Its advantage lies in relatively low equipment requirements. However, for multi-layered film structures like Shallow Trench Isolation (STI), front-end film data acquisition is complex and affected by rate variations, necessitating increased measurement frequency to enhance process control capabilities. Therefore, its application has certain limitations. Furthermore, for photonic chips, film thickness directly affects photon mode distribution and optical coupling efficiency, making high-precision control of film thickness a critical factor. Summary of the Invention

[0005] The technical problem that the invention aims to solve

[0006] Some CMP equipment features an end-point inspection system equipped with an air-conditioning temperature control system, a laser interferometer, and a micrometer. After the workpiece is processed, it is placed in the air-conditioning temperature control system to eliminate surface stress. Then, a Techo laser interferometer and a micrometer are used to measure the actual material removal rate of the workpiece after processing. However, the accuracy of a micrometer is generally 0.01 mm or 0.001 mm (1 μm), which is not suitable for end-point monitoring of thin films at the hundred-nanometer level in CMP.

[0007] There are also acoustic monitoring systems that use changes in sound wave signals to detect the polishing endpoint; friction monitoring systems that measure changes in friction during polishing to determine the degree of removal, used to capture material interfaces and compensate for changes in consumable and feed wafer thickness; electrochemical monitoring systems that monitor changes in current or voltage to determine the degree of material removal; and optical monitoring systems that use reflectance spectroscopy or interferometry to monitor surface changes in real time. However, acoustic monitoring systems are greatly affected by noise and have complex signal processing; friction monitoring systems are easily affected by the polishing pad and liquid properties; and electrochemical monitoring systems can only effectively monitor the removal of the metal layer.

[0008] Currently, some high-end CMP equipment both domestically and internationally incorporates white-light interferometry systems. The working principle of white-light interferometry utilizes the multi-wavelength spectrum of a broadband light source (such as white light). Different wavelengths of white light produce their own interference fringes, and the periods of these fringes differ depending on the wavelength. Therefore, the final interference pattern is the superposition of interference fringes from all wavelengths. To interpret the white-light interferometry data, Fourier transforms or other calculations are required across the entire spectrum to extract interference information at different wavelengths. For sub-nanometer precision, the complex spectral demodulation process increases computational cost and measurement errors. Furthermore, this method may be affected in multilayer thin-film structures in the following ways:

[0009] (1) Complex interference fringes caused by multilayer thin film structures (multiple layers of multilayer films). In multilayer thin film structures, the interfaces between different layers will generate multiple reflections and transmissions, resulting in superposition of interference fringes. The thickness and refractive index of each layer will affect the interference fringes, making the interference signal complex and difficult to resolve. More complex algorithms and models are needed to separate the interference contribution of each layer, significantly increasing the difficulty of signal processing. For multilayer materials with relatively similar optical properties, such as silicon oxide and silicon nitride (the refractive index of silicon oxide is 1.35-1.5, and the refractive index of silicon nitride is about 2.0), this optical endpoint detection method becomes very unstable in some cases.

[0010] (2) Spectral analysis is sensitive to materials and thickness. White light interferometry relies on multi-wavelength spectral analysis, and the analysis results are limited by the refractive index dispersion of the material (i.e., the refractive index varies with wavelength) and the range of film thickness. If the refractive index dispersion of the multilayer film is strong or the film thickness exceeds the range of single-layer analysis (e.g., integer multiples of wavelength), the thickness analysis will be inaccurate. Therefore, in complex multilayer film structures, the analyzed spectral fringes may become blurred or non-unique. The thickness contrast of multilayer films also limits the ability to accurately analyze the thickness variations of thin layers, especially during dynamic removal processes, when some layers in a multilayer film are thinner (e.g., nanometer-scale) while others are thicker. The interference signal from the thicker layers may mask the contribution of the thinner layers. Therefore, it is difficult to accurately analyze the thickness variations of thin layers, especially during dynamic removal processes.

[0011] To address the aforementioned issues, this invention proposes an integrated module based on an MZI (Mach-Zehnder interferometer) and a chemical mechanical polishing endpoint detection system. Addressing the need for sub-nanometer-level endpoint monitoring accuracy during the chemical mechanical polishing of thin films such as silicon oxide and silicon nitride, this invention utilizes an MZI integrated module employing a photonic chip with a single-wavelength narrowband light source (e.g., laser). Measurement can be achieved by analyzing the phase change at a specific wavelength, eliminating the need for complex calculations involving multi-wavelength spectral fringes. Furthermore, in multilayer thin film structures, single-wavelength optical interference is only affected by optical path differences in relevant regions, effectively avoiding the complexity caused by multi-wavelength superposition in white light interference. This significantly improves monitoring efficiency and accuracy, resulting in higher resolution.

[0012] Technical solutions to solve technical problems

[0013] According to one aspect of the present invention, an MZI-based integrated module is provided, comprising: a light source providing coherent light; a lens assembly; an MZI photonic chip that splits the coherent light provided by the light source into a signal beam and a reference beam, such that the signal beam illuminates an object under test via the lens assembly, and the signal beam reflected by the object under test returns to the MZI photonic chip via the lens assembly and merges with the reference beam to form an interference beam for output; and a photodetector that receives the interference beam output from the MZI photonic chip, detects changes in the light intensity of the interference beam, and converts them into an electrical signal.

[0014] Further, the MZI photonic chip includes: a beam splitter that receives coherent light from the light source and splits the coherent light into a signal beam and a reference beam for output; a first interferometer arm that propagates the signal beam output from the beam splitter; a second interferometer arm that propagates the reference beam output from the beam splitter; and a fiber optic circulator integrated into the first interferometer arm, which is a multi-port non-reciprocal optical device having a first port, a second port, and a third port, which directs the signal beam from the beam splitter through the lens assembly along a first specific path to illuminate the object under test, so that the object under test... The reflected signal beam returns to the fiber optic circulator via the lens assembly along a second specific path and is output from the third port, wherein the first specific path is the path from the first port to the lens assembly via the second port, and the second specific path is a path isolated from the first specific path from the lens assembly to the third port via the second port; a first coupler directs the reflected signal beam out from the third port of the fiber optic circulator; and a combiner recombines the signal beam directed out from the first coupler and the reference beam to generate the interference beam.

[0015] Furthermore, the first interferometer arm and the second interferometer arm are formed as waveguides, the path from the second port to the lens assembly in the first specific path and the path from the lens assembly to the second port in the second specific path are formed as optical fibers, the path from the third port to the first coupler is formed as the optical fiber, and the MZI photonic chip also has a microelectromechanical system (MEMS) deformable mirror, which is integrated into the second interferometer arm, and the phase of the reference beam split from the beam splitter is dynamically adjusted by the MEMS deformable mirror.

[0016] Furthermore, the lens assembly comprises a microlens for amplifying the characteristics of the light beam and a collimating lens for ensuring that the light beam illuminates the object under test in a parallel state. The signal beam output from the MZI photonic chip is sequentially irradiated onto the object under test via the microlens and the collimating lens. The signal beam reflected by the object under test is sequentially returned to the MZI photonic chip via the collimating lens and the microlens. By adjusting and focusing the signal beam output from the MZI photonic chip or the signal beam reflected by the object under test, the surface characteristics of the object under test are measured.

[0017] Furthermore, it also includes a second coupler that directs the electrical signal from the photodetector to an analog or digital signal via an analog-to-digital converter, and performs analysis based on digital filtering or Fourier transform.

[0018] Furthermore, the paths from the light source to the MZI photonic chip, from the MZI photonic chip to the photodetector, and from the photodetector to the second coupler are formed as waveguides, and the path from the second coupler to the phase analysis module is formed as an optical fiber. The light source, the MZI photonic chip, and the photodetector are integrated into a photonic integrated chip or a silicon-based optoelectronic chip.

[0019] Furthermore, the light source is a laser, providing coherent light as a monochromatic beam or a dual laser source.

[0020] According to another aspect of the present invention, a chemical mechanical polishing endpoint detection system is provided, comprising a polishing head for supporting a test object, a polishing disc and a polishing pad configured opposite to the polishing head for polishing the surface of the test object, a transparent window corresponding to the test object being formed on the polishing head or the polishing pad, and at least one MZI-based integrated module as described above being disposed within the transparent window, wherein the signal beam of the MZI-based integrated module passes through the transparent window and irradiates the surface film of the test object, and during the chemical mechanical polishing process, the interference beam generated by the change in the thickness of the surface film of the test object being formed is monitored in real time by the MZI-based integrated module, and the real-time thickness change of the surface film is calculated to determine the progress of the surface film removal.

[0021] Furthermore, the transparent window is a quartz window or a sapphire window.

[0022] Furthermore, the object being tested is a transparent or translucent dielectric thin film material.

[0023] Invention Effects

[0024] According to the present invention, an integrated module based on a Mach-Zehnder interferometer (MZI) and a chemical mechanical polishing endpoint detection system are provided. Addressing the requirement for sub-nanometer-level endpoint monitoring accuracy during the chemical mechanical polishing process of thin films such as silicon oxide and silicon nitride, the integrated module utilizes a photonic chip employing a single-wavelength narrowband light source (e.g., laser) to perform measurements by analyzing phase changes at a specific wavelength, eliminating the need for complex calculations involving multi-wavelength spectral fringes. Furthermore, in multilayer thin film structures, single-wavelength optical interference is only affected by optical path differences in relevant regions, effectively avoiding the complexity caused by multi-wavelength superposition in white light interference. This significantly improves monitoring efficiency and accuracy, resulting in higher resolution. Attached Figure Description

[0025] This disclosure can be better understood by describing exemplary embodiments of the present disclosure in conjunction with the accompanying drawings, in which:

[0026] Labeling Explanation: 10 Chemical Mechanical Polishing System, 11 Polishing Fluid Supply System, 12 Polishing Head, 121 Upper Housing, 122 Pressure Airbag, 123 Holding Ring, 124 Retaining Ring Pressure Airbag, 125 Air Film, 126 Air Film Base Plate, 127 Air Float, 13 Polishing Disc, 14 Polishing Pad, 15 Dresser, 16 Wafer, 100 Chemical Mechanical Polishing Endpoint Detection System, 20 MZI-based Integrated Module, 21 MZI Photonic Chip, 211 Beam Splitter, 212 Beam Combiner, 213 Signal Beam Interferometer Arm; 214 Reference Beam Interferometer Arm, L sig Geometric length of the signal beam interferometer arm, L ref Reference beam interferometer arm geometry, 215 fiber optic circulator, 216 first coupler, 217 MEMS deformable mirror, 218 second coupler, 22 laser, 23 photodetector, 24 lens assembly, 241 microlens, 242 collimating lens, 25 phase analysis module, h wafer thickness.

[0027] Figure 1 This is a general schematic diagram representing a chemical mechanical polishing system.

[0028] Figure 2 This is a block diagram of the MZI-based integrated module according to Embodiment 1 of the present invention and a block diagram of the chemical mechanical polishing endpoint detection system using the MZI-based integrated module.

[0029] Figure 3 This is a schematic diagram illustrating the structure of a photonic integrated chip in the MZI-based integrated module according to Embodiment 1 of the present invention.

[0030] Figure 4This is a schematic diagram showing the structure of the chemical mechanical polishing endpoint detection system according to Embodiment 2 of the present invention, in which an MZI-based integrated module is integrated into the polishing head.

[0031] Figure 5 This is a schematic diagram showing the structure of the chemical mechanical polishing endpoint detection system according to Embodiment 2 of the present invention, in which an MZI-based integrated module is integrated into the polishing pad. Detailed Implementation

[0032] Embodiments of this disclosure will now be described in more detail with reference to the accompanying drawings. While some embodiments of this disclosure are shown in the drawings, it should be understood that this disclosure can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of this disclosure. It should be understood that the accompanying drawings and embodiments of this disclosure are for illustrative purposes only and are not intended to limit the scope of protection of this disclosure.

[0033] In the description of this disclosure, it should be noted that, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," etc., indicating orientation or positional relationship are only for the convenience of describing this disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. "Vertical" is not vertical in the strict sense, but within the allowable tolerance range. "Parallel" is not parallel in the strict sense, but within the allowable tolerance range.

[0034] The directional terms used in the following description refer to the directions shown in the figures and are not intended to limit the specific structure of this disclosure. It should also be noted that, unless otherwise explicitly specified and limited, the terms "assembly," "connected," "linked," "relative," "interlocking," and "connected" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this disclosure based on the specific circumstances.

[0035] In this document, the term "implementation" means that a particular feature, structure, or characteristic described in connection with an implementation may be included in at least one implementation of this disclosure. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same implementation, nor is it a separate or alternative implementation mutually exclusive with other implementations. It will be explicitly and implicitly understood by those skilled in the art that the implementations described herein can be combined with other implementations.

[0036] Chemical mechanical polishing (CMP)

[0037] Figure 1 This is a general structural diagram of the chemical mechanical polishing system 10 (hereinafter referred to as CMP system 10). For example... Figure 1 As shown, a CMP system 10 generally includes a polishing head 12, a polishing disk 13, a polishing pad 14, a polishing slurry supply system 11 and supply system, a pressure control system, and a speed control system. In the CMP system 10, a wafer 16 is used as the test object and is held by a rotating polishing head 12, which presses it onto a rotating polishing pad 14 with a certain pressure. The polishing slurry flows between the surface of the wafer 16 and the polishing pad 14. Under the synergistic effect of chemical etching and mechanical polishing, the surface of the wafer 16 achieves efficient removal of excess material and global nanoscale planarization.

[0038] Mach-Zehnder interferometer structural diagram

[0039] The Mach-Zehnder interferometer (MZI) is a classic optical interferometer that uses the principle of light interference to measure physical quantities such as phase difference, optical path difference, and refractive index change. It is primarily an optical device consisting of two beam splitters and two optical paths (upper and lower arms). The beam splitters divide the input coherent light into two parts, which enter the upper and lower arms respectively. Due to the difference in optical path length or refractive index between the two arms, a phase difference is generated as the light propagates within them. The two beams are then recombined by the second beam splitter, resulting in interference. By analyzing the change in the intensity of the output light signal based on the interference result, the phase change information of the input light signal can be obtained, allowing for the measurement of various physical quantities that cause optical path difference.

[0040] Implementation Method 1

[0041] Embodiment 1 of the present invention is an integrated module based on conventional MZI, which differs from conventional MZI in terms of integration, sensitivity, real-time performance, environmental adaptability and application scenarios, and can efficiently and accurately detect, for example, changes in the surface thickness of the object being measured.

[0042] Figure 2This is a block diagram illustrating the MZI-based integrated module 20 (hereinafter sometimes referred to as the MZI integrated module or integrated module) according to Embodiment 1 of the present invention. The MZI integrated module 20 mainly includes a laser 22, a lens assembly 24, an MZI photonic chip 21, and a photodetector 23.

[0043] Laser 22

[0044] Laser 22 serves as a light source and can be used to provide coherent light of a single wavelength.

[0045] In addition, laser 22 can also serve as a dual laser source to provide coherent light of dual wavelengths. For example, dual-wavelength differential detection can be achieved by using dual laser sources of 1310nm / 1550nm, which can suppress common-mode noise such as refractive index fluctuations and improve the ability to resist environmental interference.

[0046] Lens assembly 24

[0047] The lens assembly 24 consists of a microlens 241 for amplifying the beam and a collimating lens 242 for ensuring that the beam is irradiated onto the wafer 16 in a parallel state.

[0048] The signal beam output from the MZI photonic chip 21 can be sequentially irradiated onto the wafer 16 via the microscope lens 241 and the collimating lens 242.

[0049] Furthermore, the signal beam reflected by wafer 16, i.e. the reflected beam, is sequentially returned to the MZI photonic chip described below by collimating lens 242 and microlens 241.

[0050] By adjusting and focusing the signal beam output from the MZI photonic chip 21 or the signal beam reflected by the wafer 16, the surface features of the wafer 16 can be measured. In other words, the collimating lens 242 and the microlens 241 work together on the wafer 16 to adjust and focus the beam, thereby achieving precise measurement of the surface features of the wafer 16. The collimating lens 242 ensures that the diverging signal beam is collimated into a parallel beam that illuminates the wafer 16, while the microlens further magnifies these features for more detailed observation and analysis.

[0051] MZI photonic chip 21

[0052] The MZI photonic chip 21 splits the coherent light provided by the laser 22 into a signal beam and a reference beam. The signal beam is directed onto the wafer 16 via a lens assembly 24. The signal beam reflected by the wafer 16 returns to the MZI photonic chip 21 via the lens assembly 24 and merges with the reference beam to form an interference beam for output. The MZI photonic chip 21 mainly includes:

[0053] Beam splitter 211 receives coherent light from laser 22 and splits it into a signal beam and a reference beam for output. The main function of the beam splitter is to split the incident beam into two paths. However, if it is necessary to distribute the input optical signal (also called the beam) into different waveguides according to a certain ratio to achieve beam splitting and coupling, a directional coupler is required. A directional coupler is a type of beam splitter. By precisely designing the structural parameters of the directional coupler, such as the width, spacing, and length of the waveguides, the beam splitting ratio and coupling efficiency can be controlled to meet the operating requirements of MZI.

[0054] Signal beam interferometer arm 213, which is equivalent to the first interferometer arm, is used to propagate the signal beam output from beam splitter 211 to beam combiner 212 (described later). Let the geometric length of signal beam interferometer arm 213 be L. sig Furthermore, the signal beam interferometer arm 213 is formed as a waveguide.

[0055] A reference beam interferometer arm 214, which is equivalent to a second interferometer arm, is used to propagate the reference beam output from the beam splitter 211 to the beam combiner 212 (described later). Let the geometric length of the reference beam interferometer arm 214 be L. ref Sometimes the above L sig and L ref Called length L sig Length L ref Length L sig and length L ref Different lengths or different media can be used, thus introducing a phase difference. In addition, the reference beam interferometer arm 214 is formed as a waveguide.

[0056] The fiber optic circulator 215, integrated into the signal beam interferometer arm 213, is a multi-port non-reciprocal optical device with a first port 1, a second port 2, and a third port 3. It directs the signal beam from the beam splitter 211 along a first specific path via the lens assembly 24 to the object under test (DUT). The signal beam, reflecting off the DUT and carrying information about the DUT, returns via the lens assembly 24 to the fiber optic circulator 215 along a second specific path and is output from the third port 3. The first specific path is the path from the first port 1 through the second port 2 to the lens assembly 24, and the second specific path is isolated from the first specific path, extending from the lens assembly through the second port 2 to the third port 3. By using the fiber optic circulator 215, it is ensured that the beam propagates only along specific paths, achieving unidirectional beam transmission and isolation. Furthermore, the paths from the second port 2 to the lens assembly 24 in the first specific path and from the lens assembly 24 to the second port 2 in the second specific path are formed as optical fibers, and the path from the third port 3 to the grating coupler 216 is also formed as an optical fiber.

[0057] The first coupler 216 directs the signal beam reflected from the object under test from the third port 3 of the fiber optic circulator 215 to the combiner 212, which will be described later. The first coupler 216 is a grating coupler.

[0058] A beam combiner 212 recombines the signal beam directionally output from the first coupler 216 and the aforementioned reference beam to generate an interference beam.

[0059] MEMS deformable mirror 217, which is equivalent to a microelectromechanical system deformable mirror, is integrated into the reference beam interferometer arm 214. The phase of the reference beam split from the beam splitter 211 is dynamically adjusted by the MEMS deformable mirror 217.

[0060] Photodetector 23

[0061] The photodetector 23 receives the interference beam (sometimes referred to below as interference fringes or interference signals) output from the MZI photonic chip 21, detects the changes in the light intensity of the interference beam, and converts them into electrical signals.

[0062] In addition, the MZI integrated module 20 may also include a second coupler 218 and a phase analysis module 25.

[0063] Second coupler 218

[0064] The second coupler 218 directs the electrical signal from the photodetector 23 to a specific direction.

[0065] Phase Analysis Module 25

[0066] The phase analysis module 25 converts the electrical signal directionally output from the second coupler 218 into an analog or digital signal via an analog-to-digital converter, and then performs analog-to-digital conversion using digital signal processing techniques such as digital filtering and Fourier transform before analysis. Specifically, the phase analysis module 25 receives the electrical signal output from the photodetector 23, converts it into a digital signal via its built-in analog-to-digital converter, and then analyzes it on the image screen, ultimately outputting a digital signal, such as the numerical value of the film thickness on the surface of the measured object. The path from the second coupler 218 to the phase analysis module 25 is formed by an optical fiber.

[0067] waveguide

[0068] Integrating MZI on a photonic chip requires the fabrication of optical waveguides to guide the propagation of light.

[0069] Waveguides are formed within the MZI integrated module, allowing various light beams to propagate. For example, coherent light emitted from laser 22 propagates through the waveguide to beam splitter 211, and interference beams output from combiner 212 propagate through the waveguide to photodetector 23. The path from photodetector 23 to second coupler 218 is also formed as a waveguide. Furthermore, as described above, signal beam interference arm 213 and reference beam interference arm 214 are configured as waveguides for beam propagation. The high-quality waveguide structure within the photonic integrated chip reduces optical losses, improves the contrast of the interference signal, and enhances detection accuracy. Figure 3 This is a schematic diagram illustrating the structure of the MZI integrated module according to Embodiment 1 of the present invention. Figure 3 As shown, the laser 22, the MZI photonic chip 21, and the photodetector 23 can be integrated into a single photonic integrated chip or a silicon-based optoelectronic chip.

[0070] In addition, as an iteration of laser 22, it can also be fabricated by bonding III-V substrates to silicon wafers using techniques such as low-temperature plasma bonding, and coupling light into silicon waveguides via evanescent wave coupling; or III-V materials can be directly epitaxially grown on silicon substrates.

[0071] The basic working principle of the MZI integrated module is explained below. The basic working principle of the MZI integrated module is based on the interference phenomenon generated by the optical path difference between the two beams in the interferometer arm. The phase difference between the two interferometer arms in the MZI integrated module is as follows:

[0072]

[0073] in,

[0074] n sig L sig The refractive index and geometric length of the signal beam interferometer arm

[0075] n ref L ref The refractive index and geometric length of the reference beam interferometer arm

[0076] Phase difference between the two interferometer arms

[0077] λ: wavelength of the light source

[0078] During CMP, the change in film thickness Δh alters the optical path length of the signal beam interferometer arm. Assume the film refractive index is n. film Furthermore, since only the change in film thickness affects the optical path length of the signal beam interferometer arm, the phase difference... The relationship with the change in film thickness Δh is as follows:

[0079]

[0080] Therefore, changes in film thickness and refractive index ultimately translate into changes in the optical path difference between the two interference arms. By quantifying the film thickness change through phase difference variation, the CMP process can be monitored. For typical oxide films (e.g., silicon oxide, n≈1.46) and ultraviolet / near-infrared light sources (e.g., λ=1550nm), A thickness change of 0.1 nm can produce approximately 5.9 × 10⁻⁶ ppm. -4 The phase difference in rads far exceeds the limits of traditional electrical detection.

[0081] A transparent thin film allows light to propagate and be reflected within it; therefore, as the film thickness h changes, the phase of the interference fringes changes. It is highly sensitive, and the progress of thin film removal is then determined by real-time monitoring of the interference signal.

[0082] As described above, the present invention utilizes coherent light generated by the light source in the MZI integrated module, and splits the coherent light into a reference beam and a signal beam by a beam splitter 211. The signal beam illuminates the surface of the object under test. When the surface of the object under test undergoes minute changes at the sub-nanometer level, the optical path of the signal beam also changes accordingly. The reference beam and the signal beam carrying information on the thickness change of the surface of the object under test interfere at the beam combiner 212 to form interference fringes. After the photodetector 23 captures the interference fringes, the real-time thickness change of the surface of the object under test can be accurately calculated by analyzing the phase of the fringes.

[0083] The MZI integrated module can not only detect the surface of the object under test, such as the thickness of a thin film, but also detect multi-layer structures by means of phase changes caused by differences in the optical paths of different layers. It can also detect surface roughness and defects because defects on the surface or inside the material can cause local changes in the optical path, and anomalies in the interference pattern can reveal the location and nature of the defects.

[0084] Implementation Method 2

[0085] Embodiment 2 of the present invention is an example of integrating the above-mentioned MZI integration module into a CMP. Figure 2 A block diagram of a chemical mechanical polishing endpoint detection system using an MZI integrated module is also shown.

[0086] As an example, the MZI integration module 20 can be integrated into the polishing head 12. Figure 4 This is a schematic diagram showing the structure of the chemical mechanical polishing endpoint detection system 100 according to Embodiment 2 of the present invention, in which the MZI integrated module 20 is integrated into the polishing head 12.

[0087] like Figure 2 , 4As shown, the polishing head 12 includes an upper housing 121, a pressure air bladder 122, a retaining ring 123, a retaining ring pressure air bladder 124, an air film 125, and an air film base plate 126. The air film base plate 126 is arranged adjacent to the wafer 16, which is the object to be tested, in the vertical direction of the polishing head. The air film base plate 126 and the wafer 16 are supported by the retaining ring 123. When viewed on paper, the air film base plate 126 and the wafer 16 are supported on both sides by the retaining ring 123. The polishing pad 14 is arranged vertically opposite to the air film base plate 126 of the polishing head 12, and the polishing pad 14 polishes the surface film of the wafer 16.

[0088] A transparent window corresponding to the wafer 16 is provided on the air film base plate 126 of the polishing head 12. At least one MZI integrated module 20 as described in Embodiment 1 is provided on the inner side of the transparent window on the air film base plate 126. The signal beam of the MZI integrated module 20 passes through the transparent window and illuminates the surface of the wafer 16.

[0089] The transparent window is, for example, a quartz window or a sapphire window. The wafer 16 is, for example, made of a transparent or semi-transparent dielectric thin film material. The signal beam of the MZI integrated module 20 is the signal beam from the two beams split by the beam splitter 211 from the beam emitted by the laser 22. This signal beam, following a specific optical path from the first port 1 to the second port 2 of the fiber optic circulator 215, illuminates the wafer 16 via the lens assembly 24 and the aforementioned transparent window, and passes through the thin film area on the surface of the wafer 16. Simultaneously, the signal beam reflected by the wafer 16, carrying information such as the film thickness variation of the wafer 16, returns to the fiber optic circulator 215 via the aforementioned transparent window and the lens assembly 24, following a specific optical path from the second port 2 to the third port 3 of the fiber optic circulator 215, and is output from the third port 3 of the fiber optic circulator 215. Then, the reflected signal beam carrying information such as the film thickness change of wafer 16 is directed to the combiner 212 by the first coupler 216, and re-merged with the reference beam in the combiner 212. Since the film thickness changes slightly at the sub-nanometer level due to polishing during the thin film CMP process, the optical path of the reflected beam in the signal beam interference arm also changes, which directly leads to the movement of the interference fringes.

[0090] Based on this, during the chemical mechanical polishing process, the interference signal generated by the thickness change of the test object is monitored in real time by the MZI integrated module, and the real-time thickness change of the film is calculated to determine the progress of film removal.

[0091] As another embodiment, the MZI integration module 20 can also be integrated into the polishing pad 14. Figure 5This is a schematic diagram illustrating the structure of the chemical mechanical polishing endpoint detection system according to Embodiment 2 of the present invention, in which the MZI integrated module is integrated into the polishing pad 14. Since the polishing head 12, wafer 16, and polishing pad are configured identically in the chemical mechanical polishing endpoint detection system, therefore... Figure 5 The illustrations of polishing head 12 and wafer 16 are omitted.

[0092] like Figure 5 In this embodiment, the MZI integrated module 20 can be disposed in the polishing pad 14. A transparent window is formed on the surface of the polishing pad 14 adjacent to the wafer 16. That is, a transparent window corresponding to the wafer 16 is formed on the polishing pad 14, and at least one MZI integrated module 20 as described in Embodiment 1 is disposed on the inner side of the transparent window of the polishing pad 14. The signal beam of the MZI integrated module 20 passes through the transparent window and illuminates the surface of the wafer 16.

[0093] Similar to the embodiment described above, the transparent window is, for example, a quartz window or a sapphire window. The wafer 16 is, for example, made of a transparent or semi-transparent dielectric thin film material. The signal beam of the MZI integrated module 20 is the signal beam from the two beams split by the beam splitter 211 from the beam emitted by the laser 22. This signal beam, following a specific optical path from the first port 1 to the second port 2 of the fiber optic circulator 215, illuminates the wafer 16 via the lens assembly 24 and the aforementioned transparent window, and passes through the thin film area on the surface of the wafer 16. Simultaneously, the signal beam reflected by the wafer 16, carrying information such as the film thickness variation of the wafer 16, i.e., the reflected beam, returns to the fiber optic circulator 215 via the aforementioned transparent window and the lens assembly 24, following a specific optical path from the second port 2 to the third port 3 of the fiber optic circulator 215, and is output from the third port 3 of the fiber optic circulator 215. Then, the signal beam carrying information such as the film thickness change of wafer 16 is directed to the combiner 212 through the first coupler 216, and re-merged with the reference beam in the combiner 212. Since the film thickness changes slightly at the sub-nanometer level due to polishing during the thin film CMP process, the optical path of the reflected beam in the signal beam interference arm also changes, which directly leads to the movement of the interference fringes.

[0094] Based on this, during the chemical mechanical polishing process, the interference beam generated by the thickness change of the test object is monitored in real time by the MZI integrated module 20, and the real-time thickness change of the thin film is calculated to determine the progress of thin film removal.

[0095] As described above, the following effect can be achieved.

[0096] For thin film materials, especially (semi)transparent dielectric thin film materials, CMP can not only obtain a very smooth surface, but also realize real-time monitoring of the (sub)nanometer-level removal thickness of the thin film material planarization, preventing material loss caused by over-planarization or surface unevenness caused by under-planarization, and also improving processing efficiency and benefits.

[0097] In addition, the MZI integrated module is small in size, making it easy to integrate with CMP equipment. It occupies little space, simplifies the complexity of the system, and makes it easier to achieve real-time and accurate inspection and control of the CMP process.

[0098] It is highly sensitive to small changes in phase or optical path difference, enabling the detection of nanoscale thin film thickness changes and achieving precise monitoring of material removal during CMP.

[0099] Due to the high speed of optical transmission, MZI can provide rapid detection results, enabling real-time monitoring and feedback of the CMP process, and facilitating timely adjustment of process parameters.

[0100] Because there are no macroscopic mechanical moving parts, integrated photonic chips are more stable and have stronger resistance to vibration and environmental interference. Therefore, integrated photonic chips are not sensitive to interference from environmental vibration, temperature changes and other factors, and are more stable and reliable in measurement results than traditional free-space optical systems.

[0101] As a chip-level device, the MZI module can be easily integrated with electronic control systems and data processing units, which is beneficial for realizing the automation and intelligence of CMP equipment.

[0102] Furthermore, the application of MZI and its integrated photonic chips and silicon-based optoelectronic chips in CMP endpoint monitoring is a real-time, high-precision detection method. MZI-based integrated modules are suitable for all CMP equipment.

[0103] The detection method of the chemical mechanical polishing endpoint detection system is briefly described below. A signal beam based on the MZI integrated module 20 is passed through the aforementioned transparent window and irradiates the surface of the wafer 16. During the chemical mechanical polishing process, the interference signal generated in real time due to the thickness change of the thin film on the surface of the wafer 16 is monitored by the MZI integrated module 20, and the real-time thickness change of the thin film is calculated to determine the progress of thin film removal.

[0104] It should be understood that the above description is illustrative rather than restrictive.

[0105] For example, the modular and flexible combination and upgrade scheme of the components of the system based on the present invention includes methods for signal analysis and data processing.

[0106] Alternatively, for example, MZI-based Michelson interferometers and Fabry-Perot interferometers can also be used for monitoring CMP processes. In principle, the functionality of these two interferometers can be attempted to be realized through the design and improvement of the MZI. For instance, by adjusting the length and refractive index of the two arms of the MZI, or by introducing specific optical elements, the change in the optical path difference between the two arms in a Michelson interferometer can be simulated, thereby producing similar interference fringes. Alternatively, a resonant cavity structure similar to that of a Fabry-Perot interferometer can be constructed using the two arms of the MZI, and multi-beam interference can be generated by controlling the reflectivity and optical path within the cavity.

[0107] For example, the above-described embodiments (and / or aspects thereof) can be used in combination with each other. Furthermore, many modifications can be made to adapt particular conditions or materials to the teachings of the various embodiments of the invention without departing from the scope of the invention. While the dimensions and types of materials described herein are used to define parameters of the various embodiments of the invention, the embodiments are not intended to be limiting but are exemplary. Many other embodiments will become apparent to those skilled in the art upon reading the above description. Therefore, the scope of the various embodiments of the invention should be determined by reference to the appended claims and the full scope of their equivalents.

Claims

1. An integrated module based on MZI, characterized in that, include: A light source that provides coherent light; Lens assembly; The MZI photonic chip splits the coherent light provided by the light source into a signal beam and a reference beam. The signal beam is then directed onto the object under test via the lens assembly. The signal beam reflected by the object under test returns to the MZI photonic chip via the lens assembly and merges with the reference beam to form an interference beam for output. A photodetector receives the interference beam output from the MZI photonic chip, detects changes in the light intensity of the interference beam, and converts them into electrical signals.

2. The MZI-based integrated module as described in claim 1, characterized in that, The MZI photonic chip has the following characteristics: A beam splitter receives the coherent light from the light source and splits the coherent light into the signal beam and the reference beam for output. A first interferometer arm that propagates the signal beam output from the beam splitter; A second interferometer arm that propagates the reference beam output from the beam splitter; An optical fiber circulator, integrated into the first interferometer arm, is a multi-port non-reciprocal optical device having a first port, a second port, and a third port. It directs a signal beam from the beam splitter onto the object under test via a first specific path through the lens assembly. The signal beam reflected by the object under test returns to the optical fiber circulator via the lens assembly via a second specific path and is output from the third port. The first specific path is the path from the first port through the second port to the lens assembly, and the second specific path is a path isolated from the first specific path from the lens assembly through the second port to the third port. A first coupler that directs the reflected signal beam out from the third port of the fiber optic circulator; and A beam combiner that recombines the signal beam and the reference beam oriented from the first coupler to generate the interference beam.

3. The MZI-based integrated module as described in claim 2, characterized in that, The first interferometer arm and the second interferometer arm form a waveguide. The path from the second port to the lens assembly in the first specific path and the path from the lens assembly to the second port in the second specific path are formed as optical fibers. The path from the third port to the first coupler is formed as the optical fiber. The MZI photonic chip also features a microelectromechanical system (MEMS) deformable mirror, which is integrated into the second interferometer arm. The phase of the reference beam split from the beam splitter is dynamically adjusted by the deformable mirror of the microelectromechanical system.

4. The MZI-based integrated module as described in claim 1, characterized in that, The lens assembly consists of a microlens for amplifying the characteristics of the light beam and a collimating lens for ensuring that the light beam is incident on the object under test in a parallel state. The signal beam output from the MZI photonic chip is sequentially transmitted through the microscope lens and the collimating lens to illuminate the object under test. The signal beam reflected by the object under test passes sequentially through the collimating lens and the microscope lens before returning to the MZI photonic chip. The surface features of the object under test are measured by adjusting and focusing the signal beam output from the MZI photonic chip or the signal beam reflected by the object under test.

5. The MZI-based integrated module as described in claim 1, characterized in that, Also includes: A second coupler that directs the electrical signal from the photodetector to a specific direction. as well as The phase analysis module converts the electrical signal directionally output from the second coupler into an analog or digital signal using an analog-to-digital converter, and performs analysis based on digital filtering or Fourier transform.

6. The MZI-based integrated module as described in claim 5, characterized in that, The paths propagating from the light source to the MZI photonic chip, from the MZI photonic chip to the photodetector, and from the photodetector to the second coupler are formed as waveguides. The path propagating from the second coupler to the phase analysis module is formed as an optical fiber. The light source, the MZI photonic chip, and the photodetector are integrated into a single photonic integrated chip or a silicon-based optoelectronic chip.

7. The MZI-based integrated module as described in any one of claims 1 to 6, characterized in that, The light source is a laser, providing coherent light as a monochromatic beam or a dual laser source.

8. A chemical mechanical polishing endpoint detection system, comprising a polishing head for supporting a test object, a polishing disc and a polishing pad disposed opposite to the polishing head for polishing the surface of the test object, characterized in that... A transparent window corresponding to the object under test is formed on the polishing head or the polishing pad. At least one MZI-based integrated module as described in any one of claims 1 to 7 is disposed within the transparent window. The signal beam of the MZI-based integrated module passes through the transparent window and illuminates the surface film of the object under test. During the chemical mechanical polishing process, the interference beam generated by the change in the thickness of the surface film of the test object is monitored in real time by the MZI-based integrated module, and the real-time thickness change of the surface film is calculated to determine the progress of the surface film removal.

9. The chemical mechanical polishing endpoint detection system as described in claim 8, characterized in that, The transparent window is a quartz window or a sapphire window.

10. The chemical mechanical polishing endpoint detection system as described in claim 8, characterized in that, The test object is a transparent or semi-transparent dielectric thin film material.

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