Chemical mechanical polishing system

Abstract

This invention provides a chemical mechanical polishing (CMP) system, comprising: a pre-processor unit storing a wafer; a main body for polishing the wafer; a robotic arm that interacts between the pre-processor unit and the main body to transfer the wafer; a pre-measurement unit for measuring the thickness of the wafer before polishing during wafer transfer; and a post-measurement unit for measuring the thickness of the wafer after polishing during wafer transfer. This invention integrates a wafer thickness measurement module into the CMP system, enabling real-time measurement of the film thickness on the wafer surface before and after polishing during wafer transfer. The polishing process can be adjusted based on historical changes in the surface deposition layer thickness before and after wafer polishing, as well as the initial thickness of the next incoming wafer.

Description

Technical Field

[0001] This invention belongs to the field of wafer manufacturing technology, and more specifically, relates to a chemical mechanical polishing system. Background Technology

[0002] Integrated circuits (ICs) are the core and lifeline of the information technology industry. ICs are generally formed by successively depositing conductive layers, semiconductor layers, or insulating layers on a silicon wafer. This results in a thin film of filler layers deposited on the wafer surface. During the manufacturing process, a planarization operation is performed on the surface film.

[0003] Chemical mechanical polishing (CMP) is a recognized planarization method. This planarization method achieves the planarization of the film layer through the dual action of physical abrasion and chemical reaction. During polishing, a polishing pad is placed on the polishing table, and the wafer is fixed on the carrier head. The polishing slurry, which includes abrasive particles and abrasive paste, is delivered from the polishing slurry tube to the polishing slurry arm and flows to the polishing pad through the polishing slurry arm. The carrier head contacts the wafer and the polishing pad, applies pressure and rotates it, and then polishes the wafer film layer.

[0004] Various optical measurement systems, such as spectral or elliptic polarization measurement systems, can be used to measure thickness before and after polishing, for example, in-line measurement modules or stand-alone measurement devices. In addition, various in-situ monitoring techniques, such as optical or eddy current detection, can be used to detect the polishing endpoint.

[0005] Existing technologies for measuring the thickness of transparent dielectric films and semiconductor thin films on wafer surfaces generally employ measurement equipment externally mounted on one side of the main unit for offline wafer thickness measurement, which reduces the wafer thickness per unit area (WPH) of the production line and is also costly. Summary of the Invention

[0006] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, this invention proposes a chemical mechanical polishing system.

[0007] An embodiment of the present invention provides a chemical mechanical polishing system, comprising:

[0008] The front-end unit stores the wafers inside.

[0009] The main body of the equipment is used for polishing wafers;

[0010] A robotic arm interacts between the front-end unit and the main body of the device to transfer wafers;

[0011] The pre-value measurement unit is used to measure the thickness of the wafer before polishing during wafer transfer.

[0012] The after-value measurement unit is used to measure the thickness of the polished wafer during wafer transfer.

[0013] In some embodiments, the main body of the equipment includes a polishing unit, a cleaning unit, a drying unit, and a transfer unit, and the wafer is sequentially transferred between the pre-processing unit, the polishing unit, the cleaning unit, the drying unit, and the transfer unit.

[0014] In some embodiments, the robotic arm is located between the front unit and the device body, and is used to feed the wafer from the front unit into the polishing unit, and to send the wafer from the transfer unit back to the front unit.

[0015] In some embodiments, the preceding measurement unit is located on the wafer transport path between the wafer exit port of the preceding unit and the main body of the device.

[0016] In some embodiments, the post-value measurement unit is located on the wafer transfer path between the device body and the wafer inlet of the front unit.

[0017] In some embodiments, the pre-value measurement unit and the post-value measurement unit are configured to emit probe light toward the wafer.

[0018] In some embodiments, the robotic arm carries the wafer at a constant speed, and the pre-value measurement unit and the post-value measurement unit emit probe light onto the wafer surface multiple times within a fixed time interval to obtain measurement values ​​at different points on the wafer.

[0019] In some embodiments, the pre-value measurement unit and the post-value measurement unit are located in a plane that is perpendicular to the wafer diameter. As the wafer moves, the probe light is perpendicularly irradiated onto the wafer surface and moves along the wafer diameter direction.

[0020] In some embodiments, the preceding value measurement unit includes a preceding value measurement probe and a preceding value measurement controller connected thereto;

[0021] The aftervalue measurement unit includes an aftervalue measurement probe and an aftervalue measurement controller connected thereto.

[0022] In some embodiments, the preceding value measurement controller and the following value measurement controller are each electrically connected to the host computer independently.

[0023] Compared with the prior art, the beneficial effects of the present invention include:

[0024] This invention integrates a wafer thickness measurement module into a chemical mechanical polishing system, enabling real-time measurement of the film thickness on the wafer surface before and after polishing during wafer transport. The polishing process is adjusted based on the historical relationship between the thickness of the deposited layer on the surface before and after wafer polishing and the initial thickness of the next incoming wafer. Attached Figure Description

[0025] The advantages of the present invention will become clearer and easier to understand through the following detailed description in conjunction with the accompanying drawings, which are merely illustrative and do not limit the scope of protection of the present invention, wherein:

[0026] Figure 1 A schematic diagram of a chemical mechanical polishing system provided in an embodiment of the present invention is shown;

[0027] Figure 2 This is a front view showing the detection process of a pre-value measurement unit provided in an embodiment of the present invention;

[0028] Figure 3 This diagram illustrates the structure of the pre-value measurement unit and the post-value measurement unit provided in an embodiment of the present invention.

[0029] Figure 4 A top view of a wafer inspection process provided in an embodiment of the present invention is shown;

[0030] Figure 5 A schematic diagram of the structure of a polishing unit provided in an embodiment of the present invention is shown;

[0031] Figure 6 A schematic diagram of the structure of a cleaning unit provided in an embodiment of the present invention is shown;

[0032] Figure 7 An optical path diagram of the pre-value measurement probe provided in an embodiment of the present invention is shown;

[0033] Figure 8 A schematic diagram of the structure of a pre-value measurement unit provided in an embodiment of the present invention is shown;

[0034] Figure 9 A schematic diagram of the structure of a measuring module provided in an embodiment of the present invention is shown;

[0035] Figure 10 A flowchart of a polishing parameter control method provided in an embodiment of the present invention is shown. Detailed Implementation

[0036] The technical solutions of the present invention will be described in detail below with reference to specific embodiments and accompanying drawings. The embodiments described herein are specific implementations of the present invention, used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary, and should not be construed as limiting the implementation methods or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can employ other obvious technical solutions based on the content disclosed in the claims and specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein.

[0037] The accompanying drawings in this specification are schematic diagrams to aid in illustrating the concept of the invention, and schematically show the shapes of the various parts and their interrelationships. It should be understood that, in order to clearly demonstrate the structure of the components in the embodiments of the invention, the drawings are not drawn to the same scale, and the same reference numerals are used to indicate the same parts in the drawings. The technical solutions of the invention will be further described below through specific embodiments.

[0038] In this invention, "Chemical Mechanical Polishing (CMP)" is also referred to as "Chemical Mechanical Planarization (CMP)". A wafer (W) is also called a substrate, with the same meaning and practical function.

[0039] In one specific implementation, such as Figure 1 As shown, this embodiment provides a chemical mechanical polishing system, including:

[0040] The front-end unit 100 stores the wafer w internally;

[0041] The main body of the equipment is used for polishing wafers w;

[0042] The robotic arm 200 interacts between the front unit 100 and the main body of the equipment to transfer the wafer w;

[0043] The preceding value measurement unit 700 is used to measure the thickness of the wafer w before polishing during the wafer w transfer process;

[0044] The after-value measurement unit 800 is used to measure the thickness of the polished wafer w during the wafer w transfer process.

[0045] In this embodiment, a pre-value measurement unit 700 and a post-value measurement unit 800 are installed between the front unit 100 (EFEM) and the main body of the equipment. Before chemical mechanical polishing, the robot arm 200 in the EFEM will transfer the wafer w in the wafer box to the temporary storage station of the main body of the equipment. During this transfer process, the pre-value measurement unit 700 completes the film thickness measurement of the wafer w and obtains the thickness of the wafer w before polishing.

[0046] The wafer w is polished, cleaned and dried in the main body of the equipment. After the processing is completed, the robot arm 200 in the EFEM will take the wafer w out from the temporary storage station of the main body of the equipment. During this transfer process, the post-value measurement unit 800 completes the film thickness measurement of the wafer w to obtain the thickness of the polished wafer w.

[0047] Based on information such as the relationship between the wafer thickness before and after polishing, the wafer thickness after polishing, polishing process parameters, and the thickness of the incoming material before polishing, the process parameters for subsequent polishing are adjusted to improve the quality of integrated circuit manufacturing.

[0048] The chemical mechanical polishing system provided in this embodiment integrates the film thickness measurement module of wafer w into the chemical mechanical polishing system. During the transfer of wafer w, the thickness of the film layer on the surface of wafer w before and after polishing can be measured in real time. The polishing process can be adjusted based on the historical relationship of the thickness change of the surface deposited layer of wafer w before and after polishing and the initial thickness of the next wafer w.

[0049] It should be noted that the front unit 100 has two or more front loading sections for holding wafer cassettes, each containing multiple wafers w. The front loading sections are configured adjacent to the housing of the chemical mechanical polishing system and arranged along the width of the housing. The front loading sections may house open-end cassettes, SMIF (Standard Manufacturing Interface) cassettes, or FOUP (Front Opening Unified Pod). SMIF and FOUP are sealed containers that internally house wafer cassettes and are covered by partitions, thereby maintaining relative isolation between their internal and external spaces.

[0050] A moving mechanism is arranged on the front unit 100 along the arrangement of the front loading section, and at least one robot arm 200 is provided on the moving mechanism, which is capable of moving along the arrangement direction of the wafer cassette. The robot arm 200 is configured to move on the moving mechanism and is capable of storing and retrieving wafers w mounted in the wafer cassette of the front loading section. The robot arm 200 removes the unprocessed wafer w from the wafer cassette and returns the processed wafer w to the wafer cassette.

[0051] The interior of the pre-filter unit 100 needs to be kept clean, therefore the pressure inside the pre-filter unit 100 needs to be maintained at a higher level than that of the main body of the equipment. At the same time, a filter unit is installed inside the pre-filter unit 100. This filter unit has a clean air filter such as a HEPA filter, ULPA filter or chemical filter. The filter unit removes contaminated air containing particulates, toxic vapors or toxic gases from the pre-filter unit 100 to maintain the cleanliness of the interior of the pre-filter unit 100.

[0052] Furthermore, the main body of the equipment includes a polishing unit 300, a cleaning unit 400, a drying unit 500, and a transfer unit 600 arranged sequentially along the transport direction of the wafer w. The wafer w is transferred sequentially between the front unit 100, the polishing unit 300, the cleaning unit 400, the drying unit 500, and the transfer unit 600. A robotic arm 200 is located between the front unit 100 and the main body of the equipment, used to feed the wafer w from the front unit 100 into the polishing unit 300, and to send the wafer w back from the transfer unit 600 to the front unit 100.

[0053] The following is a brief description of the structure of the polishing unit 300, the cleaning unit 400, and the drying unit 500:

[0054] The polishing unit 300 is the area for global planarization of the wafer w. The polishing unit 300 has at least one set of polishing equipment. When there are multiple polishing equipment, each polishing equipment can be arranged along the length of the housing.

[0055] Figure 5 The embodiment shown provides a polishing unit 300, the main structure of which may include a polishing disc 310, a bearing head 330, a polishing liquid supply device 340, and a dressing device 350.

[0056] The polishing disc 310 can rotate around its axis, and a polishing pad 320 with an abrasive surface is mounted on its surface. The polishing pad 320 can be a hard pad made of polyurethane foam, a soft pad made of suede, or a sponge, etc. The type of polishing pad 320 is selected according to the material of the object being treated and the state of the contaminants to be removed.

[0057] The carrier head 330 is used to hold the wafer w and press the wafer w onto the surface of the polishing pad 320 on the polishing disk 310. The wafer w is held on the lower surface of the carrier head 330 by vacuum adsorption and rotates around its axis to polish the wafer w under the action of the polishing fluid and the polishing pad 320.

[0058] The polishing slurry supply device 340 is used to supply polishing slurry and finishing fluid (e.g., pure water) to the surface of the polishing pad 320. Specifically, the polishing slurry supply device 340 includes a pure water nozzle for supplying pure water to the polishing surface of the wafer w, and the pure water nozzle is connected to a pure water supply source via a pure water pipe. A control valve is provided on the pure water pipe to open and close the pure water pipe, allowing pure water to be supplied to the polishing surface of the wafer w at any time by opening and closing the control valve. In addition, the polishing slurry supply device 340 also includes a chemical nozzle for supplying polishing slurry to the polishing surface of the wafer w, and the chemical nozzle is connected to a chemical supply source via a chemical pipe. A control valve is provided on the chemical pipe to open and close the chemical pipe, allowing chemical to be supplied to the polishing surface of the wafer w at any time by opening and closing the control valve. During chemical mechanical polishing, the polishing slurry is supplied from the polishing slurry supply device 340 to the polishing surface of the polishing pad 320, and the wafer w, which is to be polished, is pressed against the polishing surface of the polishing pad 320 by the bearing head 330 and polished.

[0059] The dresser 350 is used to dress the grinding surface of the polishing pad 320. The polishing pad 320 can remove impurity particles remaining on the surface of the polishing pad 320, such as grinding particles in the polishing fluid and waste materials falling off the surface of the wafer w. The dresser 350 can also adjust the surface morphology of the polishing pad 320 to meet the polishing process requirements, thereby stabilizing the polishing removal rate of the wafer w and achieving global planarization of the wafer w.

[0060] During chemical mechanical polishing of wafer w, the carrier head 330 rotates while reciprocating radially along the polishing disk 310, gradually removing surface imperfections from the wafer w in contact with the polishing pad 320. Simultaneously, the polishing disk 310 rotates, and the polishing slurry supply device 340 sprays polishing slurry onto the surface of the polishing pad 320. Under the chemical action of the polishing slurry, the relative movement between the carrier head 330 and the polishing disk 310 causes the wafer w to rub against the polishing pad 320, thus achieving polishing.

[0061] A polishing slurry composed of submicron or nano abrasive particles and a chemical solution flows between the wafer w and the polishing pad 320. The polishing slurry is uniformly distributed under the action of the transmission and rotational centrifugal force of the polishing pad 320 to form a liquid film between the wafer w and the polishing pad 320. The chemical components in the liquid react with the wafer w, converting insoluble substances into soluble substances. Then, these chemical reactants are removed from the surface of the wafer w by the micromechanical friction of the abrasive particles and dissolved into the flowing liquid and carried away. The surface material is removed in the alternating process of chemical film formation and mechanical film removal to achieve surface planarization, thereby achieving the purpose of global planarization.

[0062] During polishing, the dresser 350 is used to trim and activate the surface morphology of the polishing pad 320. The dresser 350 can remove impurity particles remaining on the surface of the polishing pad 320, such as abrasive particles in the polishing slurry and waste material detached from the wafer surface. It can also smooth out surface deformation of the polishing pad 320 caused by abrasion, ensuring the consistency of the surface morphology of the polishing pad 320 during polishing, thereby maintaining a stable polishing removal rate.

[0063] After chemical mechanical polishing, wafers need to undergo post-processing such as cleaning and drying. The purpose of this is to avoid contamination of semiconductor devices by trace ions and metal particles, and to ensure the performance and yield of semiconductor devices.

[0064] Cleaning methods can include two-fluid jet cleaning, roller brush cleaning, or megasonic cleaning. Two-fluid jet cleaning involves ejecting tiny droplets (mist) carried by high-speed gas from a two-fluid nozzle towards the wafer w, impacting the wafer w surface. The shock waves generated by the impact of these droplets remove particles from the wafer w surface. Roller brush cleaning can be divided into vertical roller brush cleaning and horizontal roller brush cleaning, depending on the wafer w's placement. Megasonic cleaning applies ultrasonic waves to the cleaning fluid, causing the force generated by the vibrational acceleration of the cleaning fluid molecules to act on the adhering particles, thus removing them.

[0065] The cleaning unit 400 in the chemical mechanical polishing system provided in this embodiment preferably adopts a vertical cleaning device. Figure 6 In the illustrated embodiment, the vertical cleaning apparatus includes: a tank 410 having an internal cavity for cleaning the wafer w; a cleaning assembly 420 including roller brushes located on both sides of the wafer w; a support assembly located below the cleaning assembly 420 and in contact with the edge of the wafer w for supporting and limiting the rotation of the wafer w in a vertical plane; and a spray assembly 450 for spraying cleaning fluid onto the surface of the wafer w.

[0066] Specifically, the cleaning assembly 420 includes two roller brushes, which are respectively disposed on both sides of the wafer w. The two roller brushes rotate in opposite directions to perform rolling brushing on the surface of the wafer w. For example, one roller brush rotates clockwise while the other roller brush rotates counterclockwise. Particularly preferably, the rotation direction of the two roller brushes is opposite to that of the wafer w surface, so that the roller brushes generate an upward frictional force on the wafer w when rotating, thereby maximizing the relative speed between the roller brush and the wafer w in the area where the cleaning fluid falls, thus improving the cleaning effect.

[0067] The roller brush includes a hollow shaft and a sponge covering the outer periphery of the hollow shaft. The roller brush is mounted on a pair of rotatable fixed structures. One end of the fixed structure of the roller brush is provided with a liquid inlet hole, through which liquid (cleaning liquid or rinsing liquid) is supplied to the interior of the hollow shaft of the roller brush. Several liquid outlet holes are evenly distributed on the hollow shaft so that the liquid inside the shaft can pass through the liquid outlet holes to reach the sponge and seep out from the sponge, thereby moisturizing the roller brush and forming a liquid film on the surface of the sponge, preventing the sponge from directly contacting the wafer and causing contaminants on the sponge to stick back and contaminate the wafer.

[0068] The support assembly includes a first drive wheel 430, a second drive wheel 450, and a speed measuring wheel 440. The speed measuring wheel 440 is located at the bottom edge of the wafer w, and the first drive wheel 430 and the second drive wheel 450 are symmetrically arranged on both sides of the speed measuring wheel 440 with the speed measuring wheel 440 as the center.

[0069] During wafer cleaning, the first drive wheel 430 and the second drive wheel 450 rotate under the drive of their respective drive motors. The roller brushes on both sides of wafer w contact the surface of wafer w and rotate around their axes. Under the action of friction, wafer w, vertically positioned in the gap between the two roller brushes, rotates around its axis. The rolling roller brushes contact the rotating wafer w to remove contaminants from its surface. During wafer w's rotation, the speed measuring wheel 440 is passively rotated. A rear-mounted sensor calculates the number of rotations of the speed measuring wheel 440, thereby estimating the rotational speed of wafer w and monitoring its cleaning status.

[0070] The spray assembly 450 includes two spray bars located above the cleaning assembly 420 and parallel to each other. Multiple nozzles are evenly distributed on the spray bars, and the cleaning fluid sprayed by the nozzles at least covers the contact area between the cleaning assembly 420 and the wafer w.

[0071] After cleaning, the wafer w is sent to the drying unit 500 for drying. Selectable drying methods include rotary drying and Marangoni drying. Rotary drying involves the wafer w being horizontally clamped by jaws and rotated at high speed to remove residual cleaning solution from its surface. Marangoni drying involves first creating a thin water film on the outer surface of the wafer w with flowing deionized water, followed by introducing a large amount of isopropanol gas to remove the water film, thus drying the wafer w.

[0072] The significant difference between the chemical mechanical polishing system provided in this embodiment and the prior art is that a pre-measurement unit 700 is provided between the pre-positioning unit 100 and the polishing unit 300 for real-time measurement of the thickness of the wafer w along the movement path of the robot arm 200 from the pre-positioning unit 100 into the polishing unit 300. A post-measurement unit 800 is provided between the transfer unit 600 and the pre-positioning unit 100 for real-time measurement of the thickness of the wafer w along the movement path of the robot arm 200 from the transfer unit 600 into the pre-positioning unit 100.

[0073] The preceding value measurement unit 700 and the following value measurement unit 800 are configured to emit probe light onto the wafer w. The preceding value measurement unit 700 and the following value measurement unit 800 are located in a plane perpendicular to the diameter of the wafer w. As the wafer w moves, the probe light is perpendicularly incident on the surface of the wafer w. The light spot 715 formed by the probe light on the surface of the wafer w moves along the diameter direction of the wafer w (e.g., ...). Figure 4 (As shown).

[0074] At least a portion of the deposited layer on the surface of wafer w allows probe light of a specific wavelength to pass through and interact with the material beneath the deposited layer. The reflected light is formed after being reflected from the material below. Different film thicknesses produce different spectra of reflected light. The changes in the absorption spectrum are collected by a detector or sensor and converted into an electrical signal. This electrical signal can be calculated by a host computer 900 to obtain optical data to determine the thickness or other properties of the film being measured.

[0075] Specifically, such as Figure 2 and Figure 3 As shown, the front value measurement unit 700 includes a front value measurement probe 710 and a front value measurement controller 720 connected thereto, and the back value measurement unit 800 includes a back value measurement probe 810 and a back value measurement controller 820 connected thereto. The front value measurement controller 720 and the back value measurement controller 820 are electrically connected to the host computer 900 independently.

[0076] In this embodiment, the front value measurement probe 710 and the back value measurement probe 810 have the same structure. Taking the front value measurement controller 720 as an example, its structure is briefly described as follows:

[0077] like Figure 7 As shown, the preceding value measurement probe 710 includes a beam splitter 712, a first lens 711, a second lens 714, and a third lens 713.

[0078] A first lens 711 and a beam splitter 712 are sequentially arranged along the light transmission direction in the optical path between the light source 721 and the surface of the wafer w. The first lens 711 is used to expand the probe light. The beam splitter 712 is used to reflect the probe light and transmit the reflected light, so that the probe light emitted by the light source 721 is reflected by the beam splitter 712 and then incident on the surface of the wafer w in a direction perpendicular to the surface of the wafer w. The reflected light formed after reflection on the surface of the wafer w passes through the beam splitter 712 in a direction perpendicular to the surface of the wafer w and is incident on the measurement module 722.

[0079] A second lens 714 is disposed in the optical path between the measurement module 722 and the beam splitter 712. The second lens 714 is used to focus the reflected light onto the measurement module 722.

[0080] A third lens 713 is disposed in the optical path between the beam splitter 712 and the wafer w. The third lens 713 is used to focus the probe light onto the surface of the wafer w. The third lens 713 is coaxial with the probe light reflected by the beam splitter 712, thereby expanding and collimating the light emitted from the light source 721 to form the probe light. The beam splitter 712 and the optical axis of the probe light have a preset angle, thereby reflecting the probe light onto the surface of the wafer w. The preset angle matches the positional relationship between the beam splitter 712 and the surface of the wafer w.

[0081] In this embodiment, the preceding value measurement controller 720 and the following value measurement controller 820 have the same structure and may include a light source 721, a spectrometer, and supporting circuitry, such as a control circuit, power supply, clock circuit, and cache. The light source 721 can be operated to emit white light with a wavelength of 300-1000nm. Xenon lamps, halogen lamps, deuterium lamps, LDLS, etc., can be used as the light source 721. The host computer 900 may include a central processing unit (CPU), memory, and supporting circuitry.

[0082] Specifically, taking the previous value measurement controller 720 as an example, its structure is briefly described as follows:

[0083] like Figure 8 As shown, the pre-value measurement controller 720 includes a light source 721, a measurement module 722, and a calculation module 724. The pre-value measurement probe 710 is connected to the light source 721 and the measurement module 722 via an optical fiber 723. Preferably, a Y-shaped optical fiber is used to connect the pre-value measurement probe 710, the light source 721, and the measurement module 722. The Y-shaped optical fiber includes a main optical fiber and two branch optical fibers extending from one end of the main optical fiber, namely a first branch optical fiber and a second branch optical fiber. The pre-value measurement probe 710 is connected to the main optical fiber, and the first and second branch optical fibers are connected to the light source 721 and the measurement module 722, respectively.

[0084] The probe light generated by the light source 721 can include the near-infrared region within the wavelength range, and preferably generates low-coherence light as the probe light. The light source 721 is optically connected to the first branch optical fiber. The probe light generated by the light source 721 is guided to the surface of the wafer w by the first branch optical fiber and emitted through the pre-value measurement probe 710 to illuminate the surface of the wafer w.

[0085] The measurement module 722 is optically connected to the second branch optical fiber. The probe light is reflected on the surface of the wafer w to generate reflected light. The reflected light enters the second branch optical fiber through the pre-value measurement probe 710 and is transmitted to the measurement module 722 by the second branch optical fiber. The measurement module 722 outputs the wavelength intensity distribution of the reflected light as the detection result to the calculation module 724.

[0086] The calculation module 724 calculates the optical properties of the sample based on the detection results output from the measurement module 722. The calculation module 724 can be implemented using a processor that executes the program, or using hardware devices such as a field-programmable gate array (FPGA), application-specific integrated circuit (ASIC), or system-on-a-chip (SoC).

[0087] The computing module 724 is connected to the host computer 900 via interface 725. The data exchange between interface 725 and the host computer 900 includes the measurement results of optical properties calculated by the computing module 724, and can also exchange data and attribute information used in calculating the reflectance interference spectrum of the film layer on the wafer w surface. Interface 725 can use Ethernet, wireless LAN, USB and other transmission media.

[0088] The host computer 900 calculates the reflection spectrum based on the wavelength intensity distribution contained in the reflected light, performs wavenumber transformation on the reflection spectrum to obtain the wavenumber transformed reflection spectrum, performs fast Fourier transform on the wavenumber transformed reflection spectrum based on the uniformly spaced discrete wavenumber data, determines the wavenumber spectral power based on the discrete wavenumber data after the fast Fourier transform, detects the optical film thickness based on the peak position appearing in the power spectrum, and calculates the film thickness on the surface of wafer w by dividing the measured optical film thickness by the refractive index of the deposited layer on the surface of wafer w.

[0089] The host computer 900 can also calculate the film thickness based on the wavelength dependence of the refractive index of the film layers on the wafer w surface. After calculating the reflection spectrum R(λ), the wavenumber K(λ) = 2πn(λ) / λ is calculated based on the refractive index n(λ) of each wavelength. Subsequently, the wavenumber-transformed reflectance R1≡R / (1-R) ​​is calculated based on the reflectance R of each wavelength. The power spectrum is calculated by performing a Fourier transform on the wavenumber-transformed reflection spectrum R1(K) with respect to the wavenumber K(λ). This wavenumber-transformed reflection spectrum R1(K) represents the relationship between the calculated wavenumber K and the wavenumber-transformed reflectance R1 for each wavelength. Based on the peak positions appearing in the power spectrum, the optical film thickness is detected. This method can accurately calculate the thickness of each layer on the surface of the wafer w containing multiple deposited layers.

[0090] like Figure 9 As shown, the measurement module 722 includes a slit 7221, a light shield 7222, a filter 7223, a collimating lens 7224, a diffraction grating 7225, a focusing lens 7226, and a light receiver 7227 arranged sequentially along the optical path of the reflected light.

[0091] The slit 7221 is used to adjust the diameter of the reflected light spot 715. The light shield 7222 is used to block the reflected light incident on the light receiver 7227. The filter 7223 is used to filter wavelength components outside the measurement wavelength range contained in the reflected light incident on the light receiver 7227, for example, it can filter light in the 400nm-600nm range. In some embodiments, the filter 7223 can also be used to filter reflected light with wavelengths below 400nm to reduce the damage of reflected light in this wavelength range to the dielectric layer of the wafer w.

[0092] The collimating lens 7224 reflects the light incident through the slit 7221 into parallel light and guides the parallel light to the diffraction grating 7225. The diffraction grating 7225 separates the incident light according to wavelength and guides it to the photodetector 7227. Diffracted waves at specific wavelength intervals are reflected by the diffraction grating 7225 in different directions and illuminate different photodetector elements.

[0093] The focusing lens 7226 focuses the reflected light from the diffraction grating 7225 after wavelength separation and images it onto the detection surface of the photodetector 7227. The photodetector 7227 receives the light after wavelength separation by the diffraction grating 7225. The photodetector 7227 has multiple photodetector elements arranged in a neat row, and each photodetector element outputs an electrical signal representing the intensity of each wavelength component in the spectrum after the light is separated by the diffraction grating 7225.

[0094] Before measuring wafer w, this invention can also perform in-situ detection on wafer w. The following description uses in-situ detection during the previous value measurement process as an example:

[0095] During the transfer of wafer w, when wafer w appears directly below the projection surface of the preceding value measurement probe 710, the preceding value measurement probe 710 receives reflected light. The preceding value measurement controller 720 sets the state variable to 1 based on the received reflection spectrum or reflectivity being greater than a certain threshold. The host computer 900 reads the state variable as 1 and commands the controller to transmit and store the film thickness information of wafer w. During this process, the robot arm 200 controls wafer w to move at a uniform speed, and the controller collects film thickness information at fixed time intervals. Therefore, the relationship between the measured thickness and the position of the measurement point on wafer w can be obtained.

[0096] If the current value measurement probe 710 does not receive reflected light, the controller sets the state variable to 0 based on the received reflection spectrum or reflectivity being less than a certain threshold. The host computer 900 reads the state variable as 0 and stops storing the thickness information of wafer w.

[0097] The in-situ detection of the aftervalue measurement process is similar to the above process and will not be described again.

[0098] The above illustrates one possible method for obtaining the location information of the measurement point, namely, discrimination based on the magnitude of the reflectance spectrum or reflectivity. Alternatively, the location information of the measurement point can also be obtained by reading the encoder information of the robotic arm 200. Of course, the above are only a few exemplary methods for obtaining location information, and this embodiment does not exclude the use of other information acquisition schemes.

[0099] Based on the above, the working principle of the chemical mechanical polishing system provided in this embodiment will be briefly described as follows:

[0100] During chemical mechanical polishing, the robot arm 200 in the front-end unit takes the wafer w out of the wafer cassette loading position and transfers it to the polishing unit 300. The pre-value measurement unit 700 is located above the wafer w transfer path and completes the pre-value measurement of the wafer w thickness during the wafer w transfer process, obtaining the relationship data between any position on the diameter of the wafer w and the thickness at this time.

[0101] Wafer w is polished in polishing unit 300. After polishing, robot arm 200 removes wafer w from polishing unit 300 and transfers it to cleaning unit 400 and drying unit 500 for cleaning and drying in sequence, and then transfers it to transfer unit 600. Robot arm 200 removes wafer w from transfer unit 600. Post-value measurement unit 800 is located above the wafer w transfer path and completes post-value measurement of wafer w thickness during wafer w transfer, obtaining the relationship data between any position on the diameter of wafer w and thickness at this time.

[0102] exist Figure 10 The illustrated embodiment provides an exemplary method for controlling polishing parameters, which specifically includes the following steps:

[0103] (1) Before the wafer w is moved into the polishing unit 300, its thickness information before polishing is measured;

[0104] (2) The wafer w is polished in the polishing unit 300 according to the process parameters given by the system;

[0105] (3) During the process of removing the wafer w from the polishing unit 300, measure its thickness information after polishing.

[0106] (4) The process control system calculates the amount of material removed from each zone of wafer w based on the actual deviation between the previous film thickness data and the target value of each zone.

[0107] (5) The process control system calculates the amount of material removed from each zone of wafer w under the set polishing time and polishing pressure based on the back film thickness data of wafer w.

[0108] (6) The process control system establishes a corresponding process control model based on the polishing process information, such as the pressure of each zone, polishing time, service life of polishing pad 320, and removal rate. When the wafer w is moved into the polishing unit 300, the previous thickness information measured by the previous value measurement unit 700 and the expected target value are input into the process control model to obtain the polishing process parameters, so that the wafer w can achieve the expected value according to the set process parameters.

[0109] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A chemical mechanical polishing system, characterized by, include: The front-end unit stores the wafers inside. The main body of the equipment is used for polishing wafers; A robotic arm interacts between the front-end unit and the main body of the equipment to transfer wafers; The pre-value measurement unit above the wafer transport path is used to measure the thickness of the wafer before polishing during wafer transport. The post-value measurement unit above the wafer transport path is used to measure the thickness of the polished wafer during the wafer transport process; the pre-value measurement unit and the post-value measurement unit are respectively configured to emit probe light to the wafer. As the wafer moves, the probe light moves along the diameter direction of the wafer to obtain the relationship data between any position on the wafer diameter and the thickness. The host computer is configured to: calculate the reflection spectrum R(λ) based on the wavelength intensity distribution contained in the reflected light formed by the wafer reflection probe light; calculate the wave number K(λ) = 2πn(λ) / λ based on the refractive index n(λ) of each wavelength; calculate the wave number transformed reflectance R1 = R / (1-R) ​​based on the reflectance R of each wavelength; calculate the power spectrum by performing a Fourier transform on the wave number transformed reflection spectrum R1(K) with respect to the wave number K(λ); and detect the optical film thickness based on the peak position of the power spectrum to calculate the film thickness of each layer on the wafer surface containing multiple deposition layers. The process control system is configured to: calculate the removal amount of each zone of the wafer based on the actual deviation between the previous film thickness data and the target value of each zone; calculate the removal amount of each zone of the wafer under the set polishing time and polishing pressure based on the subsequent film thickness data of the wafer; and input the previous thickness information and the expected target value into the process control model when the wafer is moved into the polishing unit to obtain the polishing process parameters, so that the wafer can achieve the expected value according to the set process parameters. The wavenumber-transformed reflectance spectrum R1(K) represents the relationship between the wavenumber K and the wavenumber-transformed reflectance R1 for each wavelength, calculated separately.

2. The chemical mechanical polishing system of claim 1, wherein, The main body of the equipment includes a polishing unit, a cleaning unit, a drying unit, and a transfer unit. Wafers are transferred sequentially between the pre-processing unit, the polishing unit, the cleaning unit, the drying unit, and the transfer unit.

3. The chemical mechanical polishing system according to claim 2, characterized in that, The robotic arm is located between the front unit and the main body of the equipment, and is used to feed the wafer from the front unit into the polishing unit, and to send the wafer from the transfer unit back to the front unit.

4. The chemical mechanical polishing system according to any one of claims 1 to 3, characterized in that, The preceding value measurement unit is located on the wafer transport path between the wafer exit port of the preceding unit and the main body of the device.

5. The chemical mechanical polishing system according to any one of claims 1 to 3, characterized in that, The post-value measurement unit is located on the wafer transfer path between the main body of the device and the wafer inlet of the front unit.

6. The chemical mechanical polishing system according to claim 1, characterized in that, The robotic arm carries the wafer at a constant speed, and the pre-value measurement unit and the post-value measurement unit emit probe light onto the wafer surface multiple times within a fixed time interval to obtain measurement values ​​at different points on the wafer.

7. The chemical mechanical polishing system according to any one of claims 1 to 3, characterized in that, The preceding value measurement unit and the following value measurement unit are located in a plane that contains the wafer diameter and is perpendicular to the wafer.

8. The chemical mechanical polishing system according to any one of claims 1 to 3, characterized in that, The preceding value measurement unit includes a preceding value measurement probe and a preceding value measurement controller connected thereto; The aftervalue measurement unit includes an aftervalue measurement probe and an aftervalue measurement controller connected thereto.

9. The chemical mechanical polishing system according to claim 8, characterized in that, The preceding value measurement controller and the following value measurement controller are each independently electrically connected to the host computer.

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