3D imaging by liquid immersion

Abstract

A method of 3D imaging includes immersing an objective lens of a microscope at least partially in a liquid film formed on a wafer. The objective lens is spaced apart from the wafer. The microscope includes a light source configured to emit light of one or more wavelengths. A first image of a region within the wafer is captured using the one or more wavelengths. The wafer is moved toward or away from the objective lens while the objective lens is kept at least partially immersed in the liquid film and spaced apart from the wafer. A second image of the region is captured using the one or more wavelengths.

Description

250284W0013D IMAGING BY LIQUID IMMERSIONCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Nonprovisional Application No.19 / 010,779, filed on January 6, 2025, the application of which is hereby incorporated herein by reference in its entirety.INCORPORATION BY REFERENCE

[0002] Aspects of the present disclosure are related to Applicant’s co-pending application titled “3D IMAGING BY LIQUID IMMERSION WITH TILT AND / OR ROTATION” with Attorney DocketNo. 250285 WO01, which is incorporated herein by reference in its entirety.FIELD OF THE INVENTION

[0003] This disclosure relates generally to semiconductor processing and more specifically to wafer characterization and a system configured to perform wafer characterization.BACKGROUND

[0004] In the manufacture of a semiconductor device (especially on the microscopic scale), various fabrication processes are executed such as film -forming depositions, etch mask creation, patterning, material etching and removal, and doping treatments. These processes are performed repeatedly to form desired semiconductor device elements on a substrate. Various techniques have been developed to characterize the semiconductor device elements formed on the substrate to monitor the manufacturing process as well as to evaluate the manufactured product.SUMMARY

[0005] The present disclosure relates to a method of 3D imaging and an imaging system.

[0006] According to aspect (1) of the disclosure, a method of 3D imaging is provided. The method includes immersing an objective lens of a microscope at least partially in a liquid film formed on a wafer. The objective lens is spaced apart from the wafer. The microscope includes a light source configured to emit light of one or more wavelengths. A first image of a region within the wafer is captured using the one or more wavelengths. The wafer is moved toward or away from the objective lens while the objective lens is kept at least partially immersed in the250284W001liquid film and spaced apart from the wafer. A second image of the region is captured using the one or more wavelengths.

[0007] Aspect (2) includes the method of aspect (1), wherein the wafer is moved toward or away from the objective lens using magnetically controlled movement.

[0008] Aspect (3) includes the method of aspect (2), wherein the wafer is placed on a wafer carrier including a first magnet. The wafer carrier is placed on a wafer chuck including a second magnet. At least one of the first magnet or the second magnet includes an electromagnet. The movingthe wafer includes adjusting an electrical currentthatpasses through the electromagnet.

[0009] Aspect (4) includes the method of aspect (3), wherein the first magnet includes a permanent magnet, and the wafer chuck is an electrostatic chuck or reverse electrostatic chuck.

[0010] Aspect (5) includes the method of aspect (1), wherein the wafer is moved toward or away from the objective lens by adjusting a gas pressure.

[0011] Aspect (6) includes the method of aspect (5), wherein the wafer is placed on a wafer carrier including a gas cavity, and the moving the wafer includes adjusting the gas pressure between the wafer and the wafer carrier via the gas cavity.

[0012] Aspect(7) includes the method of aspect(6), wherein the wafer chuck is an air chuck.

[0013] Aspect (8) includes the method of aspect (1), further including formingthe liquid film by immersing the wafer in a liquid contained within a housing.

[0014] Aspect (9) includes the method of aspect ( 1 ), further including f orming the liquid film by continuously dispensing a liquid onto the wafer to keep the objective lens at least partially immersed in the liquid film.

[0015] Aspect (10) includes the method of aspect (1), wherein the liquid film completely covers the wafer.

[0016] Aspect (11 ) includes the method of aspect (1 ), wherein the liquid film partially covers the wafer.

[0017] Aspect (12) includes the method of aspect (1), wherein the one or more wavelengths consists of a single wavelength.

[0018] Aspect (13) includes the method of aspect (1), wherein the one or more wavelengths includes a plurality of discrete wavelengths.

[0019] Aspect (14) includes the method of aspect (1), wherein the one or more wavelengths includes a range of continuous wavelengths.

[0020] Aspect (15) includes the method of aspect (1), wherein the liquid film includes water, oil or both.250284W001

[0021] Aspect (16) includes the method of aspect (1 ), wherein the liquid film includes a layer of water.

[0022] Aspect (17) includes the method of aspect (1), further including moving the microscope by a robotic arm in the vertical direction, in a horizontal direction perpendicular to the vertical direction, or both.

[0023] Aspect (18) includes the method of aspect (1), wherein the wafer includes a dielectric material and a structure embedded in the dielectric material. The light of one or more wavelengths is configured to penetrate the dielectric material and reach the structure.

[0024] According to aspect (19) of the disclosure, an imaging system is provided. The imaging system includes a housing, a wafer carrier positioned in the housing and configured to receive a wafer, and a microscope including a light source configured to emit light of one or more wavelengths, optics configured to direct the light to the wafer, and a detector. The wafer carrier is configured to move the wafer toward or away from the objective lens using magnetically controlled movement or by adjusting a gas pressure between the wafer and the wafer carrier. The optics include an objective lens at least partially immersed in a liquid film formed on the wafer. The detector is configured to image the wafer at a plurality of vertical positions.

[0025] Aspect (20) includes the method of aspect (19), wherein the wafer carrier includes a gas cavity and is configured to move the wafer toward or away from the objective lens by adjusting the gas pressure via the gas cavity.

[0026] Aspect (21) includes the method of aspect (20), wherein the wafer carrier is an air chuck.

[0027] Aspect (22) includes the method of aspect (19), further including a wafer chuck placed below the wafer carrier. The wafer carrier includes a first magnet. The wafer chuck includes a second magnet. At least one of the first magnet or the second magnet includes an electromagnet. The wafer carrier is configured to move the wafer toward or away from the objective lens by adjusting an electrical current that passes through the electromagnet.

[0028] Aspect (23) includes the method of aspect (22), wherein the first magnet is a permanent magnet. The second magnet includes the electromagnet. The wafer chuck is an electrostatic chuck or reverse electrostatic chuck.

[0029] Aspect (24) includes the method of aspect (19), further including a robotic arm configured to move the microscope.250284W001

[0030] Aspect (25) includes the method of aspect (19), further including a liquid dispenser configured to continuously dispense a liquid at the wafer to maintain the liquid film on the wafer.

[0031] Aspect (26) includes the method of aspect (25), wherein the liquid includes water, and the liquid dispenser is configured to continuously dispense the liquid at the wafer to keep the objective lens at least partially immersed in the liquid film.

[0032] Aspect (27) includes the method of aspect (26), further including a container configured to collect the liquid leavingthe wafer and provide the liquid for the liquid dispenser.

[0033] Aspect (28) includes the method of aspect (19), wherein the housing is configured to contain a liquid such that the liquid film is formed on the wafer, and the liquid is stationary.

[0034] According to aspect (29) of the disclosure, an imaging system is provided. The imaging system includes a housing, a wafer carrier, a microscope, a liquid supply mechanism and a controller. The wafer carrier is positioned in the housing and configured to receive a wafer. The microscope includes a light source configured to emit light of one or more wavelengths, optics configured to direct the light to the wafer, and a detector configured to image the wafer. The optics includes an objective lens configured for at least partial immersion in a liquid film formed on the wafer. The liquid supply mechanism is configured to maintain the liquid film between the wafer and the objective lens. The wafer carrier is configured to move the wafer toward the objective lens and away from the objective lens using magnetically controlled movement. The detector is configured to capture a series of images for a given location on the wafer at a series of distances between the wafer and the objective lens as the wafer carrier moves the wafer toward or away from the objective lens. The controller is configured to receive the series of images and create a three -dimensional rendering of the wafer at the given point location for defect identification.

[0035] Note that this summary section does not specify every embodiment and / or incrementally novel aspect of the present disclosure or claimed invention. Instead, this summary only provides a preliminary discussion of different embodiments and corresponding points of novelty. For additional details and / or possible perspectives of the invention and embodiments, the reader is directed to the Detailed Description section and corresponding figures of the present disclosure as further discussed below.BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the250284W001standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be increased or reduced for clarity of discussion.

[0037] Figure 1 A shows a vertical cross-sectional view of an imaging system in accordance with some embodiments of the present disclosure.

[0038] Figure IB shows a vertical cross-sectional view of an imaging system in accordance with some embodiments of the present disclosure.

[0039] Figure 1 C shows a vertical cross-sectional view of an imaging system in accordance with some embodiments of the present disclosure.

[0040] Figure 2 shows a flow chart of an imaging process, in accordance with some embodiments of the present disclosure.

[0041] Figures 3A and 3B show vertical cross-sectional views of an imaging system at various intermediate steps of imaging, in accordance with some embodiments of the present disclosure.

[0042] Figure 4 A shows a vertical cross-sectional view of an imaging system in accordance with some embodiments of the present disclosure.

[0043] Figure 4B shows a vertical cross-sectional view of an imaging system in accordance with some embodiments of the present disclosure.

[0044] Figure 4C shows a vertical cross-sectional view of an imaging system in accordance with some embodiments of the present disclosure.

[0045] Figure 5 shows a flow chart of an imaging process, in accordance with some embodiments of the present disclosure.

[0046] Figures 6A and 6B show vertical cross-sectional views of an imaging system at various intermediate steps of imaging, in accordance with some embodiments of the present disclosure.

[0047] Figure 7 shows a flow chart of an imaging process, in accordance with some embodiments of the present disclosure.DETAILED DESCRIPTION

[0048] The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples andare notintendedto be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also250284W001include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and / or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and / or configurations discussed. Further, spatially relative terms, such as “top,” “bottom,” “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature’s relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

[0049] The order of discussion of the different steps as described herein has been presented for clarity’s sake. In general, these steps can be performed in any suitable order. Additionally, although each of the different features, techniques, configurations, etc. herein may be discussed in different places of this disclosure, it is intended that each of the concepts can be executed independently of each other or in combination with each other. Accordingly, the present invention can be embodied and viewed in many different ways.

[0050] In the drawings, like reference numerals designate identical or corresponding parts throughout the several views. Additionally, as used herein, the words “a”, “an” and the like generally carry a meaning of “one or more”, unless stated otherwise.

[0051] Furthermore, the terms, “approximately”, “approximate”, “about” and similar terms generally refer to ranges that include the identified value within a margin of 20%, 10%, or preferably 5%, and any values therebetween.

[0052] A numerical range represented by "to" includes numerical values at both ends, unless specified otherwise.

[0053] Three-dimensional (3D) integration, i.e. the vertical stacking of multiple devices, aims to overcome scaling limitations experienced in planar devices by increasing transistor density in volume rather than area. For example, device stacking has been successfully demonstrated and implemented by the flash memory industry with the adoption of 3D NAND. Nevertheless, 3D characterization of semiconductor structures has been elusive.

[0054] The present disclosure provides a method and a system for defect analysis in circuit elements by employing an enhanced resolution 3D defect imaging system. Techniques herein use a liquid film at the wafer surface, a mechanical or magnetic chuck for elevation250284W001adjustments, and at least one wavelength for defect classification. The method involves scanning while elevating the wafer using a magnetic field at various heights and moving the chuck in minute increments (e.g. one-nanometer increments) to create a holographic 3D defect image. A differential pressure mechanism (e.g. based on fluid or obtained by gate or vacuum) enhances the microscope's resolution, and the 3D defect can be inserted into an artificial intelligence (Al) engine for further analysis. This efficientandnon -destructive testingapproach allows for comprehensive 3D analysis of circuit elements, with applications in transistors, memory cells, and other circuit elements, with significant improvements in 3D defect classification and analysis.

[0055] According to aspects of the present disclosure, a liquid film can be placed on a wafer surface to form an immersion layer which can be one or more layers to enhance the resolution of a microscope. The liquid film between the optics and the wafer is useful in at least two aspects: (1) to reduce the DOF; and (2) to keep the wafer cool to avoid heating and degrading the device properties. Due to the liquid film, DOF (depth of focus) of the microscope can be smaller than feature size. DOF need to be smaller than the size of the defect in order to obtain the 3D image; otherwise only a 2D image is available. Additionally, process control cooling can maintain the substrate at a low temperature, thus allowing for all electromagnetic spectrum wavelengths.

[0056] The wafer chuck can be elevatedto different heights to augment 3D layeringby using magnets or controlling a gas pressure. A multiple wavelength tool can be used to classify defects, utilizing visible and / or non-visible spectra or a single wavelength. An augmented chuck design is configured to tilt the wafer while performing scans whereas conventional techniques do not exist to identify or classify defect types and to drill down with a 3D probe. The wafer chuck may be moveable at ± 1 nm increments in all directions (e.g. in the X, Y and / or Z directions) to make a holographic 3D defect image e.g. by capturing an image at each location.

[0057] Therefore, techniques herein allow to look at 3D analysis of the entirety of a transistor, a memory cell or any circuit element. Techniques herein enable a non-destructive 3D test for defect classification. The 3D defect can be inserted into an Al engine for further analysis. Techniques herein also enable a drill-down metrology, a drill -down-and-tomography combination, drill-down analysis features, drill-down Al integration and optimization, a hyperspectral imaging system, etc. Techniques herein can further be utilized to enhance the defect analysis of an existing tool by providing a method of using a 3D microscope for defect250284W001analysis hyper spectrum based on fluorescent signal analysis for defects to improve classification.

[0058] The present disclosure provides a system and a method for defect analysis in a wafer. The system includes a wafer chuck designed to hold the wafer, a liquid film at the wafer / imaging optical interface, and a set of magnets for 3D layering. A hyperspectral imaging device generates images in multiple wavelengths (e.g. continuous spectral bands with fine wavelength resolution) to classify defects. This approach allows for a non -destructive 3D test for defect classification, enablingthe 3D analysis of entire transistors, memory cells, or any circuit elements. Techniques herein provide an efficient and effective solution for defect analysis and offer significant advantages in the field of semiconductor manufacturing.

[0059] Figure 1A shows a vertical cross-sectional view of an imaging system (hereinafter referred to as a system 100 A) in accordance with some embodiments of the present disclosure. The system 100 A includes a housing 140 A and a wafer carrier 110 positioned in the housing 140A and configured to receive a wafer 101. A wafer chuck 120 is placed below the wafer carrier 110. The wafer carrier 110 and the wafer chuck 120 are configured to move the wafer 101 toward or away from an objective lens 136 of a microscope 130 using magnetically controlled movement, for example in a vertical direction (e.g. the Z direction) parallel to a gravity direction by magnetic forces, for 3D layering. It should be understood that the vertical direction or the Z direction may not be perfectly parallel to the gravity direction and may be at an angle with the gravity direction. The angle is not particularly limited and can for example be 0°-30° e.g. 0°, 1°, 2°, 3°, 5°, 10°, 20°, 30° or any values therebetween.

[0060] As illustrated, the wafer carrier 110 can include one or more first magnets 111 e.g. first magnets Il la, 111b, 111c, 111 d and 11 le as shown. The wafer chuck 120 can include one or more second magnets 121 e.g. second magnets 121a, 121b, 121c, 121 d and 121e as shown. At least one of the one or more first magnets 111 or the one or more second magnets 121 is an electromagnet, whose magnetic field can be adjusted by adjusting an electrical current, which passes through the electromagnet, in order to move the wafer 101 up or down in the Z direction, which will be further explained in detail in Figures 3 A-3B.

[0061] When the one or more first magnets 111 and / or the one or more second magnets 121 include a plurality of electromagnets, the plurality of electromagnets can be controlled together (e.g. electrically connected to a common electrical source to receive a same electrical current). Alternatively or additionally, the plurality of electromagnets may include separate electromagnetic units (e.g. 121 a-121 e) that are independent of each other, and the separate electromagnetic units are configured to receive separate electrical currents.250284W001

[0062] In some embodiments, the first magnets 1 Ila- 1 lie are permanent magnets while the second magnets 121a-121e are electromagnets. For instance, the wafer chuck 120 can be an electrostatic chuck or reverse electrostatic chuck. In some embodiments, the first magnets 11 la-11 le are electromagnets while the second magnets 12 la- 12 le are permanent magnets. In some embodiments, the first magnets 11 la-11 le and the second magnets 12 la-121 e are all electromagnets. In some embodiments, the first magnets 11 la-11 le include both at least one permanent magnet and at least one electromagnet. In some embodiments, the second magnets 121a-121e include both at least one permanent magnet and at least one electromagnet.

[0063] The system 100 A can also include a liquid dispenser 105 that is configured to continuously or non-stop dispense a liquid (e.g. 103’ in Figure IB) at the wafer 101 to form a liquid film 103 on the wafer 101 during operation. The liquid dispenser 105 can bein the form of a nozzle, a syringe, a sprayer, a pipe or the like. By controlling the dispensing rate (e.g. the volume of the liquid per unit time), a thickness of the liquid may be steadily formed over a fraction or preferably the entirety of the wafer 101 to form the liquid film 103 that may or may not be uniform in the XY plane. A position of the liquid dispenser 105 is not particularly limited, and any number of liquid dispensers can be used. For instance, two or more liquid dispensers (e.g. 105) can be positioned around a periphery of the optics 135.

[0064] An excessive amount (not shown) of the liquid leavingthe wafer 101 can be collected in the housing 140 A. For instance, the housing 140 A can include a valve 143 and a container 141 for storing the excessive amount of the liquid, which may be directed back to the liquid dispenser 105 and dispensed at the wafer 101 for recycling purposes.

[0065] The chemical composition of the liquid (e.g. 103’ in Figure IB) is not particularly limited and can include, but is not limited to, water and oil such as a synthetic immersion oil, a cedarwood oil, a silicone oil, glycerol or the like. The liquid film 103 can include one or more layers depending on the specific applications. Preferably, the liquid film 103 is a single layer of water. Alternatively, the liquid can be an aqueous solution as long as the solute(s) therein does not react with the wafer 101 or dope the wafer 101.

[0066] Thesystem 100Afurtherincludesthemicroscopel30thatincludesalightsource 131 configured to emit light of one or more wavelengths, optics 135 configured to direct the light to the wafer 101, and a detector 133 configured to image the wafer 101 at a plurality of vertical positions e.g. at different heights or Z positions. Particularly, the optics 135 can include the objective lens 136 that is at least partially immersed in the liquid film 103. The detector 133 can be configured to capture a series of images for a given location on the wafer 101 at a series of distances between the wafer 101 and the objective lens 136 as the wafer carrier 110 moves250284W001the wafer 101 toward or away from the objective lens 136. The optics 135 can be in the form of an optical tower or optical tower stand. A robotic arm 107 can be configured to move the microscope 130 in the X, Y and / or Z directions.

[0067] The one or more wavelengths are not particularly limited and may include the entire electromagnetic spectrum including gamma rays, X-rays, ultraviolet light, visible light, infrared light, microwaves and radio waves. Preferably, the one or more wavelengths include ultraviolet light, visible light and / or infrared light. Preferably, the one or more wavelengths include visible light and / or infrared light. Preferably, the one or more wavelengths include infrared light. Additionally, the one or more wavelengths can include a range of continuous wavelengths (e.g. a continuous spectral band), a plurality of discrete wavelengths or a single wavelength during operation.

[0068] While shown to have a thickness, the region 102 can have a negligible thickness compared to a thickness of the wafer 101. For instance, the region 102 can represent a (virtual) image plane of the microscope 130. The region 102 can have any X and Y positions within the wafer 101 without particular limitations. In some embodiments, the region 102 is offset from a center of the wafer 101. In some embodiments, the center of the wafer 101 is located in the region 102. In other words, the region 102 may or may notbe offset from the center of the wafer 101.

[0069] The region 102 can have any Z position within the wafer 101 without particular limitations. In some embodiments, the wafer 101 includes dielectric material(s) at or near a top surface 101’ of the wafer 101, and the one or more wavelengths include at least an infrared wavelength that can penetrate the dielectric material(s). As a result, a relatively large depth (e.g. the entirety of the depth) of the wafer 101 can be imaged. In some embodiments, the wafer 101 includes metal material(s) at or near the top surface 101’, and the one or more wavelengths may not penetrate the metal material(s). Accordingly, a relatively small depth of the wafer 101 can be imaged. Preferably, the region 102 is closer to the top surface 101’ of the wafer 101 than a bottom surface 101” of the wafer 101. For instance, the region 102 may be below the top surface 101’ of the wafer 101 by 0-1000 nm e.g. 0 nm, 1 nm, 5 nm, 10 nm, 20 nm, 50 nm, 100 nm, 200 nm, 500 nm, 1000 nm or any values therebetween. In the case of 0 nm, the region 102 is at the top surface 101’ of the wafer 101.

[0070] The wafer 101 can include any materials (e.g. metals, dielectrics, semiconductors, etc.) formed on a substrate. These materials can form any circuit elements including, but not limited to, a transistor, a resistor, a capacitor, a memory cell, a peripheral circuit, an analog circuit, a digital circuit, a radio frequency circuit and / or any other circuit element. The250284W001microscope 130 can be used to image any part of the wafer 101, includingthe aforementioned circuit elements or defects during manufacturing. The present disclosure will be focused on defect analysis for illustrative purposes. Accordingly, the system 100 A may also be referred to as a 3D defect imaging system.

[0071] “ Substrate” as used herein generically refers to an object being processed in accordance with the invention. The substrate may include any material portion or structure of a device, particularly a semiconductor or other electronics device, and may, for example, be a base substrate structure, such as a semiconductor wafer, reticle, or a layer on or overlying a base substrate structure such as a thin film. Thus, substrate is not limited to any particular base structure, underlying layer or overlying layer, patterned or un -patterned, but rather, is contemplated to include any such layer or base structure, and any combination of layers and / or base structures. The description may reference particular types of substrates, but this is for illustrative purposes only. The substrate can be any suitable substrate, such as a silicon (Si) substrate, a germanium (Ge) substrate, a silicon -germanium (SiGe) substrate, and / or a silicon-on-insulator (SOI) sub strate. The sub strate may include a semiconductor material, for example, a Group IV semiconductor, a Group III-V compound semiconductor, or a Group II-VI oxide semiconductor. The Group IV semiconductor may include Si, Ge, or SiGe. The substrate may be a bulk wafer or an epitaxial layer.

[0072] A distance DI between a bottom of the objective lens 136 and a top of the liquid film 103 is not particularly limited and can be 0.001 mm - 2 mm e.g. 0.001 mm, 0.01 mm, 0.02 mm, 0.03 mm, 0.05 mm, 0.07 mm, 0.1 mm, 0.2 mm, 0.3 mm, 0.5 mm, 0.7 mm, 1 mm, 2 mm or any values therebetween. A thickness T of the liquid film 103 is not particularly limited and can be 0.001 mm - 50 mm e.g. 0.001 mm, 0.01 mm, 0.1 mm, 0.5 mm, 1 mm, 2 mm, 5 mm, 10 mm, 20 mm, 50 mm, or any values therebetween. T is equal to or larger than DI and is preferably larger than D 1. Both T and DI can be adjusted based on the type and / or size of a defect to be analyzed.

[0073] The system 100A can optionally include a controller 150. The controller 150 may optionally be connected to a memory storage unit and a user interface (all not shown). Various operations can be executed via the user interface. Various data and parameter settings can be stored in the memory storage unit.

[0074] The controller 150 may be coupled to one or more components of the system 100A to receive inputs from and provide outputs to the one or more components. For example, the controller 150 can be configured to receive image data from the detector 133 and show the image data on the user interface. The controller 150 can control the detector 133 to capture250284W001images of the wafer 101 during a continuous scan while the wafer 101 and / or the microscope 130 are moving e.g. in the X, Y and / or Z directions. For example, the controller 150 can be configured to send commands to the detector 133 for the detector 133 to capture a series of images for a given location on the wafer 101 at a series of distances between the wafer 101 and the objective lens 136 as the wafer carrier 110 moves the wafer 101 toward or away from the objective lens 136. The controller 150 can further be configured to receive the series of images from the detector 133 and create a three-dimensional rendering of the wafer 101 at the given point location for defect identification. The controller 150 can also be coupled to the robotic arm 107 to receive positional information of the microscope 130 from the robotic arm 107 and provide commands to move the robotic arm 107 in order to move the microscope 130. The controller 150 can further be coupled to the wafer carrier 110 and / or the wafer chuck 120 to control an electrical current(s) that passes through the aforementioned electromagnet(s) to move the wafer 101 up or down. The controller 150 can further be coupled to the liquid dispenser 105 and / or the container 141 to regulate liquid dispensing and / or recycling Additionally, the controller 150 can be configured to adjust knobs and control settings for the one or more components of the system 100A as mentioned above. Of course such adjustments can be manually made as well.

[0075] The controller 150 can be implemented in a wide variety of manners. In one example, the controller 150 is a computer. In another example, the controller 150 includes one or more programmable integrated circuits that are programmed to provide the functionality described herein. For example, one or more processors (e.g. microprocessor, microcontroller, central processing unit, etc.), programmable logic devices (e.g. complex programmable logic device (CPLD)), field programmable gate array (FPGA), etc.), and / or other programmable integrated circuits can be programmed with software or other programming instructions to implement the functionality of a proscribedplasma process recipe. Itisfurthernotedthatthe software or other programming instructions can be stored in one or more non -transitory computer-readable mediums (e.g. memory storage devices, FLASH memory, DRAM memory, reprogrammable storage devices, hard drives, floppy disks, DVDs, CD-ROMs, etc.), and the software or other programming instructions when executed by the programmable integrated circuits cause the programmable integrated circuits to perform the processes, functions, and / or capabilities described herein. Other variations could also be implemented.

[0076] In some embodiments, the system 100 A represents a magnetic chuck option with defect selection in the X, Y and Z directions using a magnetic field without tilt or rotation. An optical tower (e.g. 135) can include at least one lens (e.g. 136) and a light source (e.g. 131)250284W001such as lasers capable of emitting the entire electromagnetic spectrum frequencies. The optical tower can be fixed while the wafer 101 is allowed to scan in the X, Y and Z as well as theta (angular) directions. Alternatively, the microscope 130 can scan in the XY plane while the wafer 101 does not move in theXY plane. Of course, the microscope 130 and the wafer 101 can both scan in the XY plane together.

[0077] Any type of magnetic field generation can be used. For instance, the magnetic field can b e modulated to increase or decrease magnetic regions in different states using a split chuck magnetic design. The optical tower can penetrate into the liquid film 103 above the wafer 101 at different heights to create a 3D image. The magnetic field is changed to obtain different / height locations while scanning in the XY plane.

[0078] In some embodiments, the system 100A can operate in a continuous scan and image capturing mode. For instance, the microscope 130 can be used to capture a series of images, while the wafer 101 is movedin ± 1 nm increments in the X, Y and / or Z directions, in order to create a 3D defect image. The series of images can be input into the controller 150 which will then analyze and process the series of images. For example, the controller may include an artificial intelligence (Al) engine or algorithm to create the 3D defect image, which can be used as a non-destructive test for defect classification.

[0079] Figure IB shows a vertical cross-sectional view of an imaging system (hereinafter referred to as a system 100B) in accordance with some embodiments of the present disclosure. The embodimentof the system 100B is similar to the embodiment of the system 100A. Note that similar or identical components are labeled with similar or identical numerals in the present disclosure unless specified otherwise. Descriptions that have been provided once before will be omitted for simplicity purposes.

[0080] As illustrated, the system 100B includes a housing 140B. The liquid dispenser 105 can be used to fill the housing 140B with a liquid 103’ to form the liquid film 103 that is uniform in the XY plane. It should be understood that boundaries are shown between the liquid 103 ’ and the liquid film 103 merely for illustrative purposes. As the liquid film 103 is part of the liquid 103’, such boundaries do not exist in actuality. Alternatively or additionally, the liquid 103’ can be filled into the housing MOB manually.

[0081] Figure 1C shows a vertical cross-sectional view of an imaging system (hereinafter referred to as a system 100C) in accordance with some embodiments of the present disclosure. The embodiment of the system 100C is similar to the embodiment of the system 100A. Herein, a fraction (or a localized area, or a pattern) of the wafer 101 is covered with a liquid film 104. Accordingly, a housing (e.g. 140Aor MOB) and / or the liquid dispenser 105250284W001may or may notbe necessary. The liquid film 104 can be replaced or replenished during an imagine process to maintain optical resolution. The liquid film 104 can include water or oil as discussed above. Preferably, the liquid film 104 includes a liquid that has a high surface tension such as water. Accordingly, the liquid film 104 can be in the form of a droplet or droplets merged together.

[0082] Figure 2 shows a flow chart of an imaging process 200, in accordance with some embodiments of the present disclosure. At step S210, an objective lens of a microscope is immersed atleast partially in a liquid film formed on a wafer. The objective lens is spaced apart from the wafer. The microscope includes a light source configured to emit light of one or more wavelengths. At step S220, a first image of a region within the wafer is captured using the one or more wavelengths. At step S230, the wafer is moved toward or away from the objective lens using magnetically controlled movement while the objective lens is kept at least partially immersed in the liquid film and spaced apart from the wafer. At step S240, a second image of the region is captured using the one or more wavelengths.

[0083] Figures 3A and 3B show vertical cross-sectional views of an imaging system (herein after referred to as a system 300) at various intermediate steps of imaging, in accordance with some embodiments of the present disclosure. The system 300 can be the system 100A, 100B, 100C or the like. When the system 300 is the system 100A or 100B, some components (e.g. 107, 150, 140A / 140B, 131 and 133) are omitted for simplicity purposes. Additionally, it should be understood that the imaging processes described in Figures 3 A-3B using the liquid film 103 for illustration purposes are also applicable to the system 100C wherein the liquid film 104 is used.

[0084] In Figure 3A, the wafer carrier 110 and the wafer chuck 120 are in contact with each other. The wafer carrier 110 and the wafer chuck 120 may have magnetic attraction or no magnetic force between each other. Themicroscope 130 can capture a firstimage of theregion 102 of the wafer 101. As discussed earlier, the region 102 may be below the top surface 101’ of the wafer 101 by 0-1000 nm, and the present disclosure will be focused on defect analysis for illustrative purposes so the system 300 may also be referred to as a 3D defect imaging system.

[0085] In Figure 3B, the wafer chuck 120 and the microscope 130 are stationary while the wafer carrier 110 is elevated in the Z direction using magnetically controlled movement or by magnetic forces. As a result, the region 102 imaged by the microscope 130 (or the image plane of the microscope 130) is relatively “moved” down, and the microscope 130 can capture a second image of the wafer 101 at a different position. The magnetically controlled movement250284W001can be tuned so that the wafer 101 can move at ± 1 nm increments in the Z direction for the microscope 130 to image. As explained earlier, at least one of the one or more first magnets 111 or the one or more second magnets 121 is an electromagnet, whose magnetic field can be adjusted by adjusting an electrical current, which passes through the electromagnet, in order to move the wafer 101 up ordown in the Z direction. Additionally, the wafer 101 may be further moved up or down by adjusting the magnetically controlled movement, and the microscope 130 can capture additional images of the wafer 101 at various Z positions as well as X and Y positions.

[0086] Figure 4A shows a vertical cross-sectional view of an imaging system (hereinafter referred to as a system 400 A) in accordance with some embodiments of the present disclosure. The embodiment of the system 400 A is similar to the embodiment of the system 100 A. Herein, the system 400 A includes a wafer carrier 115. The wafer carrier 115 can include gas cavities 119 and is configured to hold the wafer 101 onthe wafer carrier 115 by creating vacuum via the gas cavities 119. The wafer carrier 115 can also be configured to elevate the wafer 101 in the Z direction by creating a positive gas pressure via the gas cavities 119 to repel the wafer 101 from the wafer carrier 115, which will be further explained in detail in Figures 6A and 6B. During operation, the wafer 101 can be held on the wafer carrier 115 by the gas cavities 119 and / or components 117 such as pins, clamps and / or the like for example as shown in Figure 4C. It should be understood that the wafer carrier 110 can also include the components 117 such as pins, clamps and / or the like to hold the wafer 101.

[0087] Additionally, the controller 150 may be coupled to the wafer carrier 115 to receive inputs from and provide outputs to the wafer carrier 115. Particularly, the controller 150 can control a gas pressure between the wafer 101 and the wafer carrier 115 via the gas cavities 119 of the wafer carrier 115.

[0088] In some embodiments, the system 400A represents a mechanical chuck option enabled by vacuum attraction and repulsion, withouttilt or rotation. An optical tower (e.g. 135) can include at least one lens (e.g. 136) and a light source (e.g. 131) such as lasers capable of emitting the entire electromagnetic spectrum frequencies. The optical tower can be fixed while the wafer 101 is allowed to scan in the X, Y and Z as well as theta (angular) directions. Alternatively, the microscope 130 can scan in the XY plane while the wafer 101 does not move in the XY plane. Of course, the microscope 130 and the wafer 101 can both scan in the XY plane together. No magnetic chuck is required for this option. This option uses vacuum attraction (e.g. vacuum in the gas cavities 119) to attach the wafer 101 to the wafer carrier 115250284W001as well as vacuum repulsion (e.g. a positive gas pressure in the gas cavities 119) to elevate the wafer 101 from the wafer carrier 115 to various Z- heights.

[0089] Figure 4B shows a vertical cross-sectional view of an imaging system (hereinafter referred to as a system 400B) in accordance with some embodiments of the present disclosure. The embodiment of the system 400B is similar to the embodiment of the system 400A and the embodiment of the system 100C. Herein, a fraction of the wafer 101 is covered with a liquid film 104.

[0090] Figure 5 shows a flow chart of an imaging process 500, in accordance with some embodiments of the present disclosure. At step S510, an objective lens of a microscope is immersed atleast partially in a liquid film formed on a wafer. The objective lens is spaced apart from the wafer. The microscope includes a light source configured to emit light of one or more wavelengths. At step S20, a first image of a region within the wafer is captured using the one or more wavelengths. At step S530, the wafer is moved toward or away from the objective lens by adjusting a gas pressure while the objective lens is kept at least partially immersed in the liquid film and spaced apart from the wafer. At step S540, a second image of the region is captured using the one or more wavelengths.

[0091] Figures 6A and 6B show vertical cross-sectional views of an imaging system (hereinafter referred to as a system 600) at various intermediate steps of imaging, in accordance with some embodiments of the present disclosure. The system 600 can be the system 400A, 400B or the like. When the system 600 is the system 400A, some components (e.g. 107, 150, 140A / 140B, 131 and 133) are omitted for simplicity purposes. Additionally, it should be understood that the imaging processes described in Figures 6 A and 6B using the liquid film 103 for illustration purposes are also applicable to the system 400B wherein the liquid film 104 is used.

[0092] In Figure 6A, the wafer carrier 115 and the wafer 101 are in contact with each other. The gas cavities 119 can be used to create vacuum between the wafer carrier 115 and the wafer 101 or be off to create no vacuum. The microscope 130 can capture a first image of the region 102 of the wafer 101. As discussed earlier, the region 102 may be below the top surface 101’ of the wafer 101 by 0-1000 nm, and the present disclosure will be focused on defect analysis for illustrative purposes so the system 600 may also be referred to as a 3D defect imaging system.

[0093] In Figure 6B, the microscope 130 is stationary while the wafer 101 is elevated from the wafer carrier 115 by adjustingagas pressure between the wafer 101 and the wafer carrier 115 via the gas cavities 119. In otherwords, gas canbe discharged from the gas cavities 119250284W001to repel the wafer 101 from the wafer carrier 115. As a result, the region 102 imaged by the microscope 130 (or the image plane of the microscope 130) is relatively “moved” down, and the microscope 130 can capture a second image of the wafer 101 at a different position. Additionally, the wafer 101 may be further moved up or down by adjusting the gas pressure between the wafer 101 and the wafer carrier 115 via the gas cavities 119, and the microscope 130 can capture additional images of the wafer 101 at various Z positions as well as X and Y positions.

[0094] Figure 7 shows a flow chart of an imaging process 700, in accordance with some embodiments of the present disclosure. At step S710, an objective lens of a microscope is immersed atleast partially in a liquid film formed on a wafer. The objective lens is spaced apart from the wafer. The microscope includes a light source configured to emit light of one or more wavelengths. At step S720, a first image of a region within the wafer is captured using the one or more wavelengths. At step S730, the wafer is moved toward or away from the objective lens while the objective lens is kept at least partially immersed in the liquid film and spaced apart from the wafer. At step S740, a second image of the region is captured using the one or more wavelengths.

[0095] In the preceding description, specific details have been set forth, such as a particular geometry of a processing system and descriptions of various components and processesused therein. It should be understood, however, that techniques herein may be practiced in other embodiments that depart from these specific details, and that such details are for purposes of explanation and not limitation. Embodiments disclosed herein have been described with reference to the accompanying drawings. Similarly, for purposes of explanation, specific numbers, materials, and configurations have been set forth in order to provide a thorough understanding. Nevertheless, embodiments may be practiced without such specific details. Components having substantially the same functional constructions are denoted by like reference characters, and thus any redundant descriptions may be omitted.

[0096] Various techniques have been described as multiple discrete operations to assist in understanding the various embodiments. The order of description should not be constmed as to imply that these operations are necessarily order dependent. Indeed, these operations need not be performed in the order of presentation. Operations described may be performed in a different order than the described embodiment. Various additional operations may be performed and / or described operations may be omitted in additional embodiments.

[0097] Those skilled in the art will also understand that there can be many variations made to the operations of the techniques explained above while still achievingthe same objectives250284W001of the invention. Such variations are intended to be covered by the scope of this disclosure. As such, the foregoing descriptions of embodiments of the invention are not intended to be limiting. Rather, any limitations to embodiments of the invention are presented in the following claims.

Claims

1. 250284W001WHAT IS CLAIMED IS:

1. A method of 3D imaging, the method comprising:immersing an objective lens of a microscope at least partially in a liquid film formed on a wafer, the objective lens spaced apart from the wafer, the microscope comprising a light source configured to emit light of one or more wavelengths;capturing a first image of a region within the wafer using the one or more wavelengths;moving the wafer toward or away from the objective lens while keeping the objective lens at least partially immersed in the liquid film and spaced apart from the wafer; andcapturing a second image of the region using the one or more wavelengths.

2. The method of claim 1 , wherein:the wafer is moved toward or away from the objective lens using magnetically controlled movement.

3. The method of claim 2, wherein:the wafer is placed on a wafer carrier comprising a first magnet, the wafer carrier is placed on a wafer chuck comprising a second magnet, at least one of the first magnet or the second magnet comprises an electromagnet, andthe moving the wafer comprises adjusting an electrical current that passes through the electromagnet.

4. The method of claim 3 , wherein:the first magnet comprises a permanent magnet, andthe wafer chuck is an electrostatic chuck or reverse electrostatic chuck.

5. The method of claim 1 , wherein:the wafer is moved toward or away from the objective lens by adjusting a gas pressure.

6. The method of claim 5, wherein:the wafer is placed on a wafer carrier comprising a gas cavity, and250284W001the moving the wafer comprises adjusting the gas pressure between the wafer and the wafer carrier via the gas cavity.

7. The method of claim 6, wherein:the wafer chuck is an air chuck.

8. The method of claim 1 , further comprising:forming the liquid film by immersing the wafer in a liquid contained within a housing.

9. The method of claim 1 , further comprising:forming the liquid film by continuously dispensing a liquid onto the wafer to keep the objective lens at least partially immersed in the liquid film .

10. The method of claim 1 , wherein:the liquid film comprises a layer of water.

11. The method of claim 1 , wherein the wafer comprises:a dielectric material; anda structure embedded in the dielectric material,wherein the light of one or more wavelengths is configured to penetrate the dielectric material and reach the structure.

12. An imaging system, comprising:a housing;a wafer carrier positioned in the housing and configured to receive a wafer; and a microscope comprising a light source configured to emit light of one or more wavelengths, optics configured to direct the light to the wafer, and a detector, wherein the wafer carrier is configured to move the wafer toward or away from the objective lens using magnetically controlled movement or by adjusting a gas pressure between the wafer and the wafer carrier,wherein the optics comprise an objective lens at least partially immersed in a liquid film formed on the wafer, andthe detectoris configured to image the wafer at a plurality of vertical positions.250284W00113. The imaging system of claim 12, wherein:the wafer carrier comprises a gas cavity and is configured to move the wafer toward or away from the objective lens by adjusting the gas pressure viathe gas cavity.

14. The imaging system of claim 13, wherein:the wafer carrier is an air chuck.

15. The imaging system of claim 12, further comprising a wafer chuck placed below the wafer carrier, wherein:the wafer carrier comprises a first magnet,the wafer chuck comprises a second magnet,at least one of the first magnet or the second magnet comprises an electromagnet, andthe wafer carrier is configured to move the wafer toward or away from the objective lens by adjusting an electrical current that passes through the electromagnet.

16. The imaging system of claim 15, wherein:the first magnet is a permanent magnet,the second magnet comprises the electromagnet, andthe wafer chuck is an electrostatic chuck or reverse electrostatic chuck.

17. The imaging system of claim 12, further comprising:a robotic arm configured to move the microscope .

18. The imaging system of claim 12, further comprising:a liquid dispenser configured to continuously dispense a liquid at the wafer to maintain the liquid film on the wafer.

19. The imaging system of claim 12, wherein:the housing is configured to contain a liquid such that the liquid film is formed on the wafer, andthe liquid is stationary.250284W00120. An imaging system, comprising:a housing;a wafer carrier positioned in the housing and configured to receive a wafer; a microscope comprising a light source configured to emit light of one or more wavelengths, optics configured to direct the light to the wafer, and a detector configured to image the wafer, the optics comprising an objective lens configured for at least partial immersion in a liquid film formed on the wafer;a liquid supply mechanism configured to maintain the liquid film between the wafer and the objective lens, anda controller, whereinthe wafer carrieris configured to move the wafer toward the objective lens and away from the objective lens using magnetically controlled movement, the detector is configured to capture a series of images for a given location on the wafer at a series of distances between the wafer and the objective lens as the wafer carrier moves the wafer toward or away from the objective lens, andthe controller is configured to receive the series of images and create a three-dimensional rendering of the wafer at the given point location for defect identification.the detector is configured to capture a series of images for a given location on the wafer at a series of distances between the wafer and the objective lens as the wafer carrier moves the wafertoward or away from the objective lens, andthe controller is configured to receive the series of images and create a three -dimensional rendering of the wafer at the given point location for defect identification.

Images