Combining focused ion beam milling and scanning electron microscope imaging

Abstract

A combined focused ion beam / scanning electron beam system includes an electron source that generates an electron beam and an ion source that generates an ion beam. An electron beam column directs the electron beam at an orthogonal angle to a top surface of a stage. An ion beam column directs the ion beam to the stage. The ion beam is at an angle to the electron beam. A detector receives the electron beam reflected from a wafer on the stage.

Description

[Technical field]

[0001] The present disclosure relates to semiconductor wafer processing. [Background technology]

[0002] As the semiconductor manufacturing industry evolves, the demands on yield management, especially for metrology and inspection systems, continue to grow. As critical dimensions continue to shrink, the industry still needs to reduce the time to achieve high yields and high value production. Reducing the total time from detecting a yield problem to correcting it maximizes the return on investment for semiconductor manufacturers.

[0003] In fabricating semiconductor devices, such as logic and memory devices, semiconductor wafers are typically processed using a number of manufacturing processes to form the various features and multiple tiers of the semiconductor devices. For example, in a semiconductor manufacturing process known as lithography, a pattern is transferred from a reticle onto a photoresist disposed on the semiconductor wafer. Further examples of semiconductor manufacturing processes include, but are not limited to, chemical mechanical polishing (CMP), etching, deposition, and ion implantation. A plurality of semiconductor devices may be fabricated in an array on a semiconductor wafer and then separated into individual semiconductor devices.

[0004] Figure 1 shows three examples of vertical semiconductor devices, including 3D NAND devices. 3D NAND devices and other 3D architectures face defect inspection challenges due to their geometry. Electron beams can have difficulty imaging defects deep in trenches. In (a), embedded defects including voids, spouts, bridges, and particles are present. In (b), a well-etched channel is shown on the left, while the channel on the right is tilted. In (c), a well-etched channel is shown on the left, while a channel that was not etched through is shown in the center, and a channel with residue is shown on the right. These defects are difficult to detect with standard inspection equipment.

[0005] Traditionally, thin specimens are prepared for transmission electron microscopy (TEM) using focused ion beam (FIB) and scanning electron microscope (SEM). A portion of the specimen, such as a 3D NAND device or other 3D architecture, is removed by scanning the FIB spot over the specimen surface. The milling process can be monitored in real time by collecting secondary electron signals on an on-board detector, but the image quality is usually not high due to poor ion beam resolution and signal collection efficiency. Therefore, SEM is required to determine the milling end point since it can provide better imaging capability. After the lamella is prepared, a micromanipulator transfers it to a TEM holder for further TEM imaging and analysis.

[0006] Traditionally, SEM imaging is usually turned off when FIB sputtering is performed because the magnetic field from the SEM column objective lens deflects the ion beam by several hundred micrometers. The process of turning on and off the SEM column objective lens is relatively long due to the hysteresis and settling of the magnetic material. To shorten the process time by keeping the SEM column objective lens turned on, the ion beam deflection can be compensated by a deflector in the FIB column to align the ion beam with the electron beam at the specimen. However, this deflection compensation still introduces some off-axis aberrations, causing the ion beam spot to increase in size and deform in shape. In addition, ion beam scanning to sputter materials is also a slow process because the scanning bandwidth can be limited by the scanning voltage, which depends on the desired field of view (FOV). Furthermore, the equipped SEM is only used to provide high-resolution images, and lacks the ability to review and inspect semiconductor defects. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] US Patent Application Publication No. 2009 / 0230299 [Patent Document 2] Japanese Patent Application Publication No. 04-274341 Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, improved systems and techniques are needed. [Means for solving the problem]

[0009] In a first embodiment, a system is provided. The system includes a stage configured to hold a wafer, an electron source generating an electron beam, a scanning electron beam column coupled to the electron source, a detector configured to receive the electron beam reflected from a wafer on the stage, an ion source generating an ion beam, and an ion beam column coupled to the ion source. The scanning electron beam column directs an electron beam at the stage. The electron beam is directed at an orthogonal angle to a top surface of the stage. The ion beam column directs an ion beam at the stage. The ion beam column directs the ion beam at an angle to the electron beam.

[0010] The scanning electron beam column may include a gun lens, an aperture, a condensing lens, at least two deflectors, and an objective lens. In one example, the objective lens is disposed on the path of the electron beam between the stage and the electron source. At least two deflectors are disposed on the path of the electron beam between the objective lens and the electron source. A condensing lens is disposed on the path of the electron beam between the at least two deflectors and the electron source. An aperture is disposed on the path of the electron beam between the condensing lens and the electron source. A gun lens is disposed on the path of the electron beam between the aperture and the electron source.

[0011] The ion beam column may include a condensing lens, a deflector, an aperture, a beam bender, and an objective lens. In one example, the objective lens is disposed in the path of the ion beam between the stage and the ion source. The beam bender is disposed in the path of the ion beam between the objective lens and the ion source. The aperture is disposed in the path of the ion beam between the beam bender and the ion source. The deflector is disposed in the path of the ion beam between the aperture and the ion source. The condensing lens is disposed in the path of the ion beam between the deflector and the ion source.

[0012] The ion beam column may be configured to bend the ion beam within the ion beam column.

[0013] The ion beam column may be electrostatic.

[0014] The system may further include a xenon source in fluid communication with the ion source.

[0015] The ion beam column may provide a Gaussian beam mode and / or a projection beam mode.

[0016] The angle can be between 50° and 60°. For example, the angle can be 60°.

[0017] The system may further include a second ion source generating a second ion beam and a second ion beam column coupled to the second ion source. The second ion beam column may direct the second ion beam at the stage. The second ion beam column may direct the second ion beam at an azimuth angle of 90 degrees relative to the ion beam.

[0018] The system may further include a processor configured to control blanking of the ion beam and the electron beam.

[0019] In a second embodiment, a method is provided in which an ion beam is directed at a wafer on a stage to mill the wafer with the ion beam. The ion beam is directed through an ion beam column. The ion beam is blanked so that the ion beam does not reach the wafer. During the blanking, an electron beam is directed at the wafer. The electron beam is directed through an electron beam column. The ion beam column directs the ion beam at an angle to the electron beam. The electron beam is directed at an orthogonal angle to a top surface of the wafer. The depth to which the ion beam mills the wafer can be determined using the electron beam and a processor.

[0020] The ion beam may contain xenon ions.

[0021] The ion beam may also be bent within the ion beam column.

[0022] The angle can be set to 50° to 60°. For example, the angle can be set to 60°.

[0023] The method may further include imaging the wafer by detecting a signal of the electron beam reflected from the wafer and performing defect inspection of the wafer using a processor.

[0024] The method can further include directing a second ion beam at the wafer on the stage, the second ion beam being directed at an azimuth angle of 90 degrees relative to the ion beam.

[0025] For a more complete understanding of the nature and objects of the present disclosure, reference should be made to the following detailed description taken in conjunction with the accompanying drawings, in which: [Brief description of the drawings]

[0026] [Figure 1] A diagram depicting three examples of 3D NAND devices and their defects. [Diagram 2] 1 is a schematic diagram of a FIB optical system according to the present disclosure. [Diagram 3] 1 is a schematic diagram of an SEM optical system according to the present disclosure. [Figure 4] FIG. 1 is a graph comparing relative sputtering rates and angles of incidence when using xenon for various materials used in semiconductor devices. [Diagram 5] FIG. 1 is a block diagram of a blanking synchronization system. [Figure 6] FIG. 1 illustrates one embodiment of ion beam-electron beam synchronization. [Figure 7] FIG. 1 illustrates one embodiment of a Gaussian beam mode. [Figure 8] FIG. 8 illustrates the beam profile produced by the Gaussian beam mode of FIG. 7. [Figure 9] FIG. 1 illustrates one embodiment of a projection beam mode. [Figure 10] FIG. 10 illustrates the beam profile produced by the projection beam mode of FIG. 9. [Figure 11] FIG. 1 is an example beam profile diagram showing the dispersion along the bending direction caused by a beam bender due to energy spread in the ion beam. [Figure 12] FIG. 1 illustrates a delay and view mode of operation. [Figure 13] FIG. 1 illustrates a slice and image mode of operation. [Figure 14] FIG. 1 illustrates an embodiment of a system having a second ion beam. [Figure 15] 1 is a flow chart of a method according to the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Although the claimed subject matter is described in terms of certain embodiments, other embodiments are within the scope of this disclosure, including embodiments that do not provide all of the benefits and features described herein. Various structural, logical, process step, and electronic changes may be made without departing from the scope of the disclosure. Thus, the scope of the disclosure is defined solely by reference to the appended claims.

[0028] The disclosed embodiments combine a FIB for high speed milling and a SEM for high speed imaging. The system can be used to delayer materials and then review and / or inspect defects in semiconductor wafers. These defects can include those embedded deep within or at the bottom of high aspect ratio (HAR) trenches or holes. The system has a high throughput that makes it competitive with other FIB tools for preparing TEM specimens and performing failure analysis on semiconductor devices.

[0029] Large beam currents can be used with FIBs. Because FIBs are used for sputtering, resolution is less of a concern than for beams used for imaging. The ion beam cannot be deflected by the objective lens in the SEM optics. The magnetic field that an SEM objective lens exhibits will be free of static magnetic fields between the objective lens and the wafer. A weak deflection field can be produced for heavy ion beams by the magnetic field, but this can be compensated for by using an upper deflector in the ion column.

[0030] A beam bender can be used to bend the ion beam from a tilt angle to a final incidence angle, and can also act as a blanker.

[0031] The FIB can be switched between a Gaussian beam and a projection beam by changing the strength of the objective lens in the column. The projection beam mode is best used during operation to its advantage.

[0032] FIG. 2 is a schematic diagram of the FIB optics in system 100, and FIG. 3 is a schematic diagram of the SEM optics. System 100 has a vertical SEM column and a tilted FIB column. This dual beam tool can operate as a semiconductor defect review and / or inspection tool. Compared to preparation of TEM lamellae for deep defects, the disclosed embodiments can improve throughput by more than 100 times.

[0033] The system 100 includes a stage 102 configured to hold a wafer 101. An ion beam 104 is generated in an ion source 103, which may be a combination plasma source and accelerator. An ion beam column 105 is coupled to the ion source 103. The ion beam column 105 is configured to direct the ion beam 104 at the stage 102. As shown in FIG. 2, the ion beam 104 is directed at the stage 102 at an angle to an electron beam axis (detailed in FIG. 3), which may be orthogonal to the stage 102 or the top surface of the wafer 101. The orientation of the ion beam 104 is neither parallel nor perpendicular to the electron beam axis.

[0034] The tilted ion beam column 105 may have an optical architecture similar to that of an electron beam. The ion beam column 105 includes a condensing lens 106, a first deflector 107, an aperture 108, a beam bender 109, a second deflector 110, and an objective lens 111. The ion beam column 105 is coupled to the ion source 103 and may have fewer deflectors than the corresponding electron beam column. The ion beam column 105 may instead include a beam bender 109 and one or more deflectors upstream of the objective lens 111. The ion beam 104 may originate from the ion source 103 and pass through the condensing lens 106 and the first deflector 107 before reaching the aperture 108. Downstream of the aperture 108, the ion beam 104 passes through a beam bender 109, a deflector 110 and an objective lens 111 before reaching the wafer 101. As shown in Fig. 2, the ion beam column 105, e.g. electrostatic, can be used to bend the ion beam 104. That is, the condensing lens 106, the first deflector 107, the beam bender 109, the second deflector 110 and / or the objective lens 111 can be electrostatic.

[0035] The ion beam source 103 may emit an ion species, such as xenon. Xenon is heavy and inert. The ion beam source 103 may be connected to a source 112, such as one containing xenon or other species, such as argon or gallium. The ions are emitted from the ion source 103 in the form of an ion beam 104. The ion beam current in the system 100 is typically greater than 100 nA to improve throughput. For example, the ion beam current may be between 100 nA and 1 μA. The ion beam energy may be between 10 keV and 20 keV. The resolution of the ion beam 104 may be less important than the throughput in some applications.

[0036] The condensing lens 106 is disposed between the first deflector 107 and the ion source 103 on the path of the ion beam 104. The condensing lens 106 can focus the ion beam 104. An example of the condensing lens 106 is an Einzel lens.

[0037] The first deflector 107 is disposed on the path of the ion beam 104 between the aperture 108 and the ion source 103. The first deflector 107 deflects or otherwise adjusts the path of the ion beam 104. The aperture 108 is disposed on the path of the ion beam 104 between the beam bender 109 and the ion source 103. The aperture 108 is operatively coupled to the first deflector 107.

[0038] The beam bender 109 is disposed between the objective lens 111 and the ion source 103 on the path of the ion beam 104. The beam bender 109 according to one example bends the axis of the ion beam 104 from 45° with respect to an angle perpendicular to the surface of the stage 102 or the wafer 101 to 60° with respect to an angle perpendicular to the surface of the stage 102 or the wafer 101.

[0039] The beam bender 109 can also be a blanker. This blanker function prevents the ion beam 104 from colliding with the wafer 102. In one example, during blanking, the ion beam can be directed to a Faraday cup to monitor ion beam stability.

[0040] The angle of the ion beam 104 can be between 50° and 60° relative to the normal to the surface of the stage 102 or wafer 101, although other angles are possible. Simulations have shown that an ion beam 104 incidence angle of approximately 60° results in minimal variation in xenon ion sputtering rates for six materials common in the semiconductor industry. The effect of incidence angle is shown in FIG. 4. Different ion species may have different optimum incidence angles than xenon.

[0041] In one example, the angle of the ion beam column 105 is fixed. In such a design, the angle of the ion beam is changed by adjusting the electrostatic components of the ion beam column. However, the axis of the ion beam column 105 itself is not altered and the components within the ion beam column 105 do not move. In this ion beam column 105, instead of translating the components within the ion beam column 105 relative to each other or to the components outside the ion beam column 105, the ion beam is deflected to adjust the angle of incidence.

[0042] 2, a second deflector 110 is disposed between the objective lens 111 and the beam bender 109 on the path of the ion beam 104. The second deflector 110 enables scanning with the beam.

[0043] The objective lens 111 is disposed between the stage 102 and the ion source 103 on the path of the ion beam 104. The objective lens 111 can provide the ion beam 104 with resolution.

[0044] A scanning electron beam column 120 is depicted in Figure 3. The ion beam axis of the ion beam 104 in Figure 2 is depicted in Figure 3. The electron beam column 120 is coupled to an electron source 121 that generates an electron beam 122. The electron source 121 may be a Schottky electron source, a cold field emission electron source, a thermal field emission electron source, a thermionic emission electron source, or other electron emitting device. The electron beam column 120 directs the electron beam 122 at the wafer 101 on the stage 102. The electron beam 122 and the ion beam 104 may be directed to the same point on the wafer 101.

[0045] An example scanning electron beam column 120 includes a gun lens 123, a first deflector 124, an aperture 125, a condensing lens 126, a detector 127, a second deflector 128 (which may include one, two or more sets of deflectors), and an objective lens 129. The detector 127 is configured to receive the electron beam reflected from the wafer 101 on the stage 102 and collect the resulting signal. The electron beam 122 may originate from an electron source 121 and pass through the gun lens 123 and the first deflector 124 before reaching the aperture 125. Downstream of the aperture 125, the electron beam 122 passes through the condensing lens 126, the detector 127, the second deflector 128, and the objective lens 129. Some or all of the electron beam 122 is reflected from the surface of the wafer 101 and passes through an objective lens 129 and a second deflector 128 before reaching a detector 127. A signal from the detector 127 can be used to determine the milling depth and for defect inspection.

[0046] The objective lens 129 is disposed between the stage 102 and the electron source 121 on the path of the electron beam 122. The objective lens 129 can impart resolution to the electron beam 122, thereby affecting collection efficiency.

[0047] The second deflector 128 (which can be at least two deflectors) is disposed on the path of the electron beam 122 between the objective lens 129 and the electron source 121. The second deflector 128 can be used to scan the FOV with the electron beam 122.

[0048] The condensing lens 126 is disposed on the path of the electron beam 122, between the second deflector 128 and the electron source 121. The condensing lens 126 can focus the electron beam 122.

[0049] The detector 127 is disposed between the second deflector 128 and the condenser lens 126 on the path of the electron beam 122. The detector 127 can be configured based on a specific application. For review applications, the detector 127 can be designed to enhance topographic information of defects. The detector 127 can be or include one or more Energy Dispersive X-ray Spectroscopy (EDX) detectors for defect review purposes. For inspection applications, the detector 127 can be designed to separate the physical space of electrons to detect special defects such as shallow buried defects, HAR defects, voltage contrast (VC) defects, or physical defects.

[0050] The aperture 125 is disposed on the path of the electron beam 122, between the condenser lens 126 and the electron source 121. The aperture 125 can be monitored.

[0051] The gun lens 123 is disposed on the path of the electron beam 122 between the aperture 125 and the electron source 121 .

[0052] The first deflector 124 is disposed in the path of the electron beam 122 between the gun lens 123 and the aperture 125. The first deflector 124 can align the electron beam 122 or blank the electron beam 122. The electron beam 122 can be blanked against an aperture (e.g., aperture 125), although other blanking options are possible.

[0053] During operation, the system 100 may operate both the SEM and FIB columns. The ion source 103, ion beam column 105, electron source 121, and electron beam column 120 may be operated. First, the wafer 101 may be imaged using the electron beam column 120. In one example, the ion beam may be blanked during the imaging. In another example, the ion source 103 and ion beam column 105 may be activated after the imaging. The stage 102 may be moved to a desired position using an actuator. The electron beam column 120 may then blank the electron beam 122 to allow the ion beam 104 in the ion beam column 105 to be directed at the wafer 101 to begin milling the wafer 101. Once the designated area of ​​the wafer 101 has been milled to the desired depth, the ion beam 104 may be blanked again (e.g., using the beam bender 109) to prevent the ion beam 104 from impinging on the wafer 101. Then, the electron beam 122 is directed to the wafer 101 to image the milled area. According to one example, the electron beam 122 is not blanked and is allowed to impinge on the wafer 101. The synchronization of the ion beam milling and the electron beam imaging is shown in Figures 5 and 6. In Figures 5 and 6, t1 is the sputtering period (i.e. milling), t2 is the imaging period, and t3 is the interval between t1 and t2. Switching between imaging and milling modes can be performed by changing the strength of the objective lens in the electron beam column.

[0054] A processor (e.g., an interface PC and / or an image scanning processor) can be used to control the blanking of the ion beam and / or the electron beam. The processor can determine t1, t2, and t3 for operation. The processor can also be used to determine any milling depth and relate it to t1. The processor is coupled to the components in the system 100. The processor typically includes a programmable processor programmed in software and / or firmware to perform the functions described herein, as well as digital and / or analog interfaces suitable for connection to other elements of the system 100. Alternatively or additionally, the processor may include hardwired and / or programmable hardware logic circuits to perform at least some of the functions of the processor. Although the processor is shown as a single functional block in FIG. 5 for simplicity, in practice the processor may include a number of interconnected control units and interfaces suitable for receiving and outputting the signals depicted in the figures and described in the text. Program codes or instructions for a processor to implement the methods and functions disclosed herein may be stored in a readable storage medium, such as a memory in an interface PC or other memory.

[0055] Typically, there are two modes of focused ion beams: Gaussian beam mode and projection beam mode. These modes are shown in Figures 7 to 10. In the Gaussian beam mode in Figure 7, the object plane of the objective lens is the image plane of the condenser lens. In the projection beam mode in Figure 9, the object plane of the objective lens is the aperture plane. To mill a specified area, scanning can be used in the Gaussian beam mode. Scanning can be avoided in the projection beam mode. Since imaging during the ion beam milling process is not necessary, scanning can be avoided by using the projection beam mode. The projection mode has high throughput and is insensitive to lens aberrations. However, the Gaussian mode may be preferred for some applications.

[0056] Tilting the ion beam by approximately 60° as depicted in Figure 2 can affect the elongation effect of the ion beam spot on the wafer. The beam width can be doubled along the incidence plane while the vertical width can remain the same. Therefore, if a square projected ion beam spot on the wafer is desired, an oval aperture opening can be used as shown in Figure 11.

[0057] The beam bender 109 can act as a blanker, bending the ion beam 104 from 45° at the top of the ion beam column 105 to 60° at the bottom of the ion beam column 105 in one example. The 60° tilt at the top of the ion beam column 105 may mechanically interfere with the main chamber housing. However, the beam bender can introduce dispersion on the beam spot due to the energy spread of the ion beam. As shown in FIG. 11, this dispersion on the ion beam spot does not degrade the uniformity in the central area.

[0058] Multiple ion beams can be used as shown in FIG. 14. In an embodiment, the system has one electron beam column along with two ion beam columns. The second ion beam column has an azimuth angle of 90 degrees with respect to the first ion beam column. The incidence angle of the second ion beam can be the same as that of the first ion beam, i.e., 60 degrees with respect to the wafer normal (i.e., the electron beam axis). Two staggered ion beam columns can provide two different sputtering directions, which can help achieve better planarity of the milled area. The second ion beam column can have a different ion species and a smaller beam current for fine milling. The second ion beam column can be similar to that depicted in FIG. 2.

[0059] FIG. 15 is a flow chart of method 200. In 201, an ion beam is directed at a wafer on a stage, and the ion beam mills the wafer. The ion beam can be xenon ions or other species. The ion beam is directed through an ion beam column. For example, the ion beam can be directed through ion beam column 105 of system 100. As shown in FIG. 2, the ion beam can be bent within the ion beam column.

[0060] At 102, the ion beam is blanked so that it does not reach the wafer. Then, at 103, an electron beam is directed at the wafer during the blanking. The electron beam is directed through an electron beam column, such as electron beam column 120 in system 100. The ion beam column directs the ion beam at an angle to the electron beam. The angle can be between 50° and 60°, e.g., 60°. The electron beam can be directed at a perpendicular angle to the top surface of the wafer on the stage.

[0061] At 104, a processor is used to determine the depth to which the wafer has been milled by the ion beam and that obtained using the electron beam, which may also be used to image the wafer for defect inspection.

[0062] According to one example, a second ion beam can be directed at the wafer on the stage. The second ion beam can be directed at a 90° azimuth angle with respect to the ion beam.

[0063] Various operation modes can be employed. Two operation modes are shown in Figures 12 and 13. In Figure 12, a delay and view mode is depicted. In (a), SEM imaging is performed prior to milling. In (b), the area of ​​interest is milled to a desired depth (e.g. hundreds of nanometers to tens of micrometers). In (c), SEM imaging is performed to review or inspect defects. By ending the milling above the defects, damage to those defects can be avoided.

[0064] The slice-and-image mode is depicted in Figure 13. The area of ​​interest is sputtered to a small depth (e.g., a few nanometers to a few tens of nanometers) and an SEM image is captured. This sputtering and imaging process can be repeated multiple times until the desired depth is reached. By post-processing the series of SEM images, a 3D volume of the specimen can be reconstructed.

[0065] SEM imaging can be performed prior to milling, but alternatively, a separate optical inspection tool can be used to sample the wafer and possibly find hot spots.

[0066] Method 200 may use system 100 or other embodiments disclosed herein, resulting in high throughput. Fast milling may be achieved, for example, by using heavy ion species, high beam current, projected beam mode, and / or large angles of incidence. Fast SEM imaging may be performed using fast detection chains and electronics. The objective lens of the SEM column is kept on when switching from imaging to milling, since the ion beam deflection caused by its magnetic field is within acceptable limits. Even if a single deflector is used to compensate for the ion beam deflection, the resulting aberrations that change the uniformity of the projected ion beam spot are still typically acceptable.

[0067] The SEM allows for the review and / or inspection of semiconductor defects in advanced or next generation semiconductor devices. For example, the system allows for the detection of extreme HAR defects (e.g., HAR>100:1) that are not detectable by currently available technology. For extreme HAR defects, the system allows for the use of a FIB to gradually mill away the depth of the trench or hole (i.e., reduce the HAR from 100:1 to less than 50:1). The defect can then be detected by the SEM column.

[0068] Although the present disclosure has been described in connection with one or more specific embodiments, it will be understood that other embodiments of the present disclosure may be made without departing from the scope of the present disclosure, that is, the present disclosure is to be considered limited only by the appended claims and the reasonable interpretation thereof.

Claims

1. 1. A system comprising: a stage configured to hold a wafer; an electron source for generating an electron beam; a scanning electron beam column coupled to the electron source for directing the electron beam toward the stage, the scanning electron beam column directing the electron beam at an orthogonal angle to a top surface of the stage; a detector configured to receive the electron beam reflected from the wafer on the stage; an ion source for generating an ion beam; an ion beam column coupled to the ion source to direct the ion beam toward the stage, the ion beam column directing the ion beam at an angle relative to the electron beam; A system comprising:

2. 2. The system of claim 1, wherein the scanning electron beam column comprises a gun lens, an aperture, a condensing lens, at least two deflectors, and an objective lens.

3. 3. The system of claim 2, wherein the objective lens is disposed on a path of the electron beam between the stage and the electron source, the at least two deflectors are disposed on the path of the electron beam between the objective lens and the electron source, the condenser lens is disposed on the path of the electron beam between the at least two deflectors and the electron source, the aperture is disposed on the path of the electron beam between the condenser lens and the electron source, and the gun lens is disposed on the path of the electron beam between the aperture and the electron source.

4. 10. The system of claim 1, wherein the ion beam column comprises a condensing lens, a deflector, an aperture, a beam bender, and an objective lens.

5. 5. The system of claim 4, wherein the objective lens is disposed on a path of the ion beam between the stage and the ion source, the beam bender is disposed on the path of the ion beam between the objective lens and the ion source, the aperture is disposed on the path of the ion beam between the beam bender and the ion source, the deflector is disposed on the path of the ion beam between the aperture and the ion source, and the condenser lens is disposed on the path of the ion beam between the deflector and the ion source.

6. 10. The system of claim 1, wherein the ion beam column is configured to bend the ion beam within the ion beam column.

7. 10. The system of claim 1, wherein the ion beam column is electrostatic.

8. 10. The system of claim 1, further comprising a xenon source in fluid communication with the ion source.

9. 10. The system of claim 1, wherein the ion beam column provides a Gaussian beam mode and a projection beam mode.

10. 2. The system of claim 1, wherein the angle is between 50° and 60°.

11. 11. The system of claim 10, wherein the angle is 60 degrees.

12. 2. The system of claim 1, further comprising: a second ion source generating a second ion beam; a second ion beam column coupled to the second ion source for directing the second ion beam toward the stage, the second ion beam column directing the second ion beam at an azimuth angle of 90° relative to the ion beam; A system comprising:

13. 10. The system of claim 1, further comprising a processor configured to control blanking of the ion beam and the electron beam.

14. 1. A method comprising: directing an ion beam at a wafer on a stage to mill the wafer with the ion beam, wherein the ion beam is directed through an ion beam column; blanking the ion beam so that the ion beam does not reach the wafer; directing an electron beam at the wafer during the blanking, wherein the electron beam is directed through an electron beam column, the ion beam column directs the ion beam at an angle to the electron beam, and the electron beam is directed at an orthogonal angle to a top surface of the wafer; and determining, using the electron beam and using a processor, the depth to which the wafer will be milled by the ion beam; method.

15. 15. The method of claim 14, wherein the ion beam comprises xenon ions.

16. 15. The method of claim 14, wherein the ion beam is bent within the ion beam column.

17. The method of claim 14, wherein the angle is between 50° and 60°.

18. 18. The method of claim 17, wherein the angle is 60 degrees.

19. 15. The method of claim 14, further comprising imaging the wafer by detecting a signal of the electron beam reflected from the wafer, and performing defect inspection of the wafer using a processor.

20. 15. The method of claim 14, further comprising directing a second ion beam at the wafer on the stage, the second ion beam being directed at a 90° azimuth angle relative to the ion beam.

Images