Light delivery using optical fiber into vacuum chamber

Abstract

To provide a laser-enhanced voltage contrast system using optical fibers.SOLUTION: A system includes a vacuum chamber with a stage that secures a wafer. Light is directed into an optical fiber from a laser source outside the vacuum chamber. The optical fiber transmits all wavelengths of light from the laser source through the walls of the vacuum chamber and into the vacuum chamber.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE This disclosure relates to optical fiber delivery systems. [Background technology]

[0002] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Patent Application No. 62 / 806,208, filed February 15, 2019, the disclosure of which is incorporated herein by reference.

[0003] Advances in the semiconductor manufacturing industry are placing increasing expectations on yield management, particularly for metrology and inspection systems. Not only are critical dimensions continuing to shrink, but the industry is also under pressure to achieve high yields and high-value production in shorter times. Reducing the total time between detecting a yield problem and correcting it is critical to the return on investment for semiconductor manufacturers.

[0004] In the fabrication of 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 layers of the semiconductor devices. For example, lithography is a semiconductor manufacturing process that transfers a pattern from a reticle onto a photoresist array 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. Multiple semiconductor devices may be fabricated in an array on a single semiconductor wafer, which may then be separated into individual semiconductor devices.

[0005] Inspection processes are used at various steps during semiconductor manufacturing, whereby detecting wafer-side defects can help increase the yield and, therefore, profitability of the manufacturing process. Inspection has always been an important part of the manufacture of semiconductor devices, such as integrated circuits. However, as semiconductor device dimensions decrease, even smaller defects can cause device malfunctions, making inspection more important than ever for the successful manufacture of acceptable semiconductor devices. For example, as semiconductor device dimensions decrease, the detection of smaller-sized defects becomes necessary because even relatively small defects can cause unwanted anomalies in those semiconductor devices.

[0006] However, as design rules shrink, semiconductor manufacturing processes may operate closer to the performance limits of those processes. Additionally, because of the shrinking design rules, even smaller defects may affect the device's electrical parameters, driving more sensitive inspection. As design rules shrink, the population of potential yield-related defects detected by inspection grows dramatically, as does the population of nuisance defects detected by inspection. Thus, more defects may be detected on those wafers, making process corrections difficult and expensive to resolve. By identifying which of those defects actually affect the device's electrical parameters and yield, process control methods may focus on those defects while largely ignoring others. Furthermore, with smaller design rules, process-induced faults may be more likely to be systematic. That is, process-induced faults tend to occur in a given design pattern that is often repeated many times within the design. Eliminating spatially systematic electrical related defects can impact yield.

[0007] Laser-enhanced voltage contrast (LEVC) has been used in conjunction with scanning electron microscopes (SEMs). For example, two different voltage contrast effects can be conveniently switched under illumination. This allows for the detection of defects that would otherwise go undetected at the high speeds required for SEM inspection. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] U.S. Patent No. 6,507,388 [Patent Document 2] U.S. Patent Application Publication No. 2003 / 0007539 Summary of the Invention [Problem to be solved by the invention]

[0009] Previously, optical windows were installed at the air-vacuum junction. Separate free-space laser beams with fixed wavelengths were applied individually, one after the other. Switching between the wavelengths required laser swapping and subsequent optical realignment. Polarization could not be changed. The wavelengths used were not coupled, making switching between wavelengths time-consuming. The use of optical windows required a straight line from the light source to the area of ​​interest.

[0010] The feedthroughs connecting the optical fiber to the vacuum chamber have also been problematic. Previously, several O-rings were used to form a seal, exerting a radial force on the optical fiber, creating a vacuum barrier. However, compressive forces (e.g., axial or radial) on the optical fiber can cause transmission losses, particularly in the visible red wavelengths.

[0011] Polymers have been used around optical fibers to replace O-rings, but they have not been able to provide a sufficient hermetic seal because the polymers have a higher leak rate than is needed for many manufacturing applications, including semiconductor testing.

[0012] Therefore, an improved system is needed. [Means for solving the problem]

[0013] In a first embodiment, an apparatus is provided that includes a vacuum chamber, a stage disposed within the vacuum chamber and configured to hold a wafer, a laser light source disposed outside the vacuum chamber, an optical fiber that transmits all wavelengths of light generated by the laser light source through a wall of the vacuum chamber into the vacuum chamber, and a bleaching and polarization unit.

[0014] The apparatus may include an electron beam source that directs an electron beam at the stage.

[0015] The wavelength of the light transmitted by the optical fiber may be 200 nm to 2000 nm.

[0016] The laser light source may include a plurality of lasers and a plurality of dichroic mirrors.

[0017] The laser light source may further include a plurality of lasers, a polarization dependent beam splitter, and a plurality of half-wave plates.

[0018] The optical fiber may be a multimode fiber or a single mode fiber.

[0019] The apparatus may further include a waveplate disposed within the vacuum chamber to receive light from the optical fiber, the waveplate being a half waveplate or a quarter waveplate.

[0020] The bleaching and polarizing unit may include a turning mirror disposed within the vacuum chamber, the turning mirror configured to receive light from the optical fiber and direct the light from the optical fiber toward the stage, and at least one bleaching lens configured to collimate the light received from the optical fiber and / or form an image of the light on the wafer.

[0021] The decolorizing and polarizing unit may comprise a curved mirror, for example a spherical mirror or a parabolic mirror.

[0022] The light from the laser light source may have a plurality of wavelengths.

[0023] The device may further include a flange surrounding the optical fiber. The flange may be disposed within a wall of the vacuum chamber. In one example, the flange may include an outer member disposed around the optical fiber and a polymer layer disposed between the optical fiber and the outer member. The polymer layer may be radially compressed to form a hermetic seal. The hermetic seal between the optical fiber and the outer member may further include a metal-to-metal seal.

[0024] Alternatively, the flange may be an elastomeric seal that can be radially compressed to form a hermetic seal.

[0025] A second embodiment provides a method for directing light from a laser light source into a vacuum chamber via an optical fiber. The optical fiber transmits all wavelengths of light generated by the laser light source through a wall of the vacuum chamber into the vacuum chamber. The light is directed to a bleaching and polarization unit within the vacuum chamber. The light is directed to a wafer held on a stage disposed within the vacuum chamber.

[0026] The method can further include directing an electron beam within the vacuum chamber toward the wafer.

[0027] The wavelength of the light can be set to 200 nm to 2000 nm.

[0028] The decolorizing and polarizing unit may include a turning mirror or a curved mirror.

[0029] For a more complete understanding of the nature and purpose of the present disclosure, reference should be made to the accompanying drawings in conjunction with the detailed description below. [Brief explanation of the drawings]

[0030] [Figure 1] FIG. 1 illustrates one embodiment of a system according to the present disclosure. [Figure 2] FIG. 2 illustrates one embodiment of wafer illumination using the system of FIG. 1. [Figure 3] FIG. 2 illustrates an embodiment of a laser light source for the system of FIG. 1. [Figure 4] 2 is an exploded cross-sectional view of one embodiment of an in-flange seal that can be used in the system of FIG. 1. [Figure 5] 2 is an exploded cross-sectional view of another embodiment of an in-flange seal that can be used in the system of FIG. 1. FIG. [Figure 6] 1 is a flowchart of one embodiment of a method according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0031] Although certain embodiments describe the claimed subject matter, other embodiments exist 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 this disclosure. Accordingly, the scope of this disclosure is determined solely by reference to the appended claims.

[0032] Voltage contrast effects in electron beam images can be varied on certain wafer features (e.g., integrated circuits) by exposing the electron beam image area to light during imaging. The electron beam can be, for example, part of a scanning electron microscope (SEM). In one example, an open tungsten contact can be detected while an n+ contact in a p-doped region is under laser illumination. Such laser-enhanced voltage contrast (LEVC) can be generated in an electron beam tool at, for example, a 57° angle of incidence. While 57° is used as an example, orthogonal and other oblique angles can also be used. Using wavelengths in the blue-red visible spectrum allows for different penetration depths into the wafer where the effect can occur.

[0033] In the disclosed embodiments, an optical fiber guides multiple wavelengths in the visible spectrum from blue (400 nm) to red (685 nm). The optical fiber can also guide other wavelengths, such as ultraviolet (e.g., 10 nm or 200 nm) or infrared (e.g., 700 nm) down to 2000 nm. The light source or sources can be located outside the vacuum column. The optical fiber transmits the light into the vacuum column. Using achromatic optics, the desired area of ​​interest on the wafer can be uniformly illuminated across the broad wavelength range. Additionally, the polarization orientation of the laser light can be adapted to enhance the LEVC effect.

[0034] The multi-wavelength system according to the embodiments of the present disclosure can be used for LEVC applications on electron beam inspection or review tools, such as those used in semiconductor and other industries. The system can use fiber optics and laser combiner modules. The system can use free-space lasers and dichroic filters. The delivery optics can provide approximately the same spot size regardless of wavelength.

[0035] The delivery optics can also provide polarization control of the incident light and modulation capabilities that allow the illumination to be turned on and off on a frame-by-frame, line-by-line, or pixel-by-pixel basis. By turning the laser on and off, the feature can be linked to the electron beam so that the light beam and electron beam work in a coordinated manner. The contrast and / or wavelength can be adjusted at various points on the wafer.

[0036] FIG. 1 illustrates one embodiment of a system 100. The system 100 uses multi-wavelength fiber delivery for LEVC, allowing light to be transmitted at multiple wavelengths across a broad visible spectrum using a single optical fiber 106. The system 100 is scalable; the number of wavelengths traveling through the optical fiber 106 can be increased, for example, through the use of a laser 110 and a dichroic mirror 111. The laser output power can be electronically controlled using the laser current. Attenuators are not required; thus, no active components are required within the system 100, reducing maintenance. Because the wavelengths are coupled into a single optical fiber 106, the lasers for each wavelength can be electronically activated.

[0037] The use of a flexible optical fiber 106 to deliver laser light inside the vacuum chamber 101 provides additional options for positioning components within the system 100. For example, the optical fiber 106 can be positioned next to the acceleration coil near the wafer 104, which would not be possible without a fiber-guided solution. The illumination angle can be approximately 57° or other angles, which can enhance penetration into the wafer.

[0038] This system has a vacuum chamber 101 surrounded by a wall 102. Inside the vacuum chamber 101, there is a stage 103, which is configured to be able to firmly hold a wafer 104. In other words, the stage 103 and the wafer 104 can be located within a vacuum pressure region. -9 Less than 10 Torr -10 Less than Torr is sufficient.

[0039] A laser light source 105 is located outside the vacuum chamber 101. That is, the laser light source 105 may be located, for example, in an area of ​​atmospheric pressure or near atmospheric pressure. The light from the laser light source 105 may be multi-wavelength. The laser light source 105 may include one or more lasers 110 and one or more dichroic mirrors 111.

[0040] The optical fiber 106 can transmit all wavelengths of light generated by the laser source 105 into the vacuum chamber 101. That is, the optical fiber 106 transmits light from atmospheric pressure to vacuum and can be 1 meter or longer. An example of the optical fiber 106 is an optical glass fiber. The optical fiber 106 can be a multimode fiber or a single-mode fiber.

[0041] The optical fiber 106 can be continuous, running from the laser source 105 through the wall 102 of the vacuum chamber 101 to an output coupler 112 within the vacuum chamber 101. The output coupler 112 is a bare fiber end sealed within a flange, which mechanically couples the fiber end to other mechanical components. This means that no coupling loss occurs during the air-to-vacuum transition. The optical fiber 106 is sealed within a flange 113.

[0042] The system 100 may also include coupling, imaging, and / or illumination optics that illuminate the wafer 104 with light from the optical fiber 106 .

[0043] As an example, a polarization-maintaining single-mode optical fiber 106 is used. The polarization of the light emitted from this optical fiber 106 is fixed, and the LEVC effect can be enhanced by changing the direction using a wave plate (e.g., a half-wave plate or a quarter-wave plate). It is also possible to measure the effect of polarization on the LEVC effect of various tungsten plugs on a wafer, for example. Furthermore, since the direction of polarization is determined by the core shape of the optical fiber 106, the linear polarization can also be rotated by rotating the fiber connector at the output end of the optical fiber 106.

[0044] The wavelength of the light transmitted by the optical fiber 106 can be, for example, 400 nm to 680 nm, or 400 nm to 700 nm. Other wavelengths are possible; these ranges are merely examples. The wavelengths can also be less than 400 nm or greater than 2000 nm.

[0045] The system 100 also includes a bleaching and polarizing unit 107, which may be located within the vacuum chamber 101 and is located in the path of the light emitted from the optical fiber 106. The bleaching and polarizing unit 107 may collimate the light received from the optical fiber and / or form an image of the light on the wafer 104.

[0046] The system 100 includes an electron beam source 108 that directs an electron beam 109 toward the stage 103. The electron beam source 108 is depicted within the vacuum chamber 101, but can also be located outside the vacuum chamber 101. The electron beam 109 is conveyed through the vacuum chamber 101 toward, for example, a wafer 104.

[0047] In the embodiment of FIG. 1, laser light sources 105 with three different wavelengths λ1, λ2, and λ3 are combined by a dichroic mirror 111 and a strong reflector 114, and then the three different wavelengths are coupled into an optical fiber 106. The optical fiber 106 is continuous and sealed within a flange 113 at the vacuum-to-air transition. The output end of the fiber 106 has an achromatic lens that collimates the light from the optical fiber 106. Polarization control in the polarization unit 107 within the vacuum chamber 101 can be performed using a half-wave plate or a quarter-wave plate. The broadband laser beam is directed onto the wafer 104 by a turning mirror 115. The turning mirror 115 can receive the light from the optical fiber 106 and direct it toward the stage 103 or the wafer 104 on the stage 103.

[0048] The broadband laser beam emitted within the vacuum chamber 101 can be decolorized by a decolorizing system or a curved mirror. A lens system can also be used instead of the curved mirror.

[0049] The system 100 can use a working distance of approximately 50 mm from its optics to the surface of the wafer 104, although other distances are possible, which can improve spot stability on the surface of the wafer 104. This reduced working distance can reduce the angular tolerance of the mirror angle stability and the optical beam pointing stability by, for example, a factor of six.

[0050] Figure 2 illustrates one embodiment of wafer illumination using the system 100 of Figure 1. The wafer 104 is illuminated using a turning mirror 115, which can be, for example, a spherical or parabolic mirror similar to that depicted in Figure 2. The connector of the optical fiber 106 can be rotated relative to the output coupler 112 to adjust its polarization. The magnification of the fiber core on the wafer 104 can be adjusted to illuminate the wafer 104 with a desired spot size.

[0051] The wafer 104 can be illuminated using the "dirty focus concept." The image formed by the optical fiber 106 is formed slightly before the wafer 104. That is, as shown in FIGS. 1 and 2, the light is slightly diffused as it reaches the wafer 104. This allows the spot size at the wafer 104 to be larger than the diffraction-limited spot size at the focal region. This larger spot size can be adapted to the field of view appropriate for the electron beam 109. This spot size adaptation can also be achieved by adjusting the positional relationship between the output end of the optical fiber 106 and the focusing lens or mirror.

[0052] Figure 3 shows one embodiment of a laser source 105 for the system 100 of Figure 1. The laser power guided in the optical fiber 106 can be increased by combining two polarization states into one optical fiber 106. Laser beams can be combined to produce higher powers by adding the different polarization states together using a polarization-dependent beam splitter. Figure 3 shows the lens L, polarization-dependent beam splitter PBS, half-wave plate λ / 2, and individual lasers, along with their corresponding polarization states: s-polarized, p-polarized, or x-polarized, with the x-polarized light at a 45° angle between s- and p-polarized.

[0053] 3 embodiment, all laser wavelengths are coupled into a single optical fiber 106, allowing for fast and simple electronic switching between them. This increases the throughput of the system, as the area can be interrogated with multiple wavelengths to optimize the LEVC contrast for different defect types. This is achieved by tuning the light intensity at the different wavelengths, as their relative penetration depths vary by a factor of 10.

[0054] Figure 4 is an exploded cross-sectional view of one embodiment of a seal within flange 113 that can be used with system 100 of Figure 1. Figure 5 is an exploded cross-sectional view of another embodiment of a seal within flange 113 that can be used with system 100 of Figure 1. As can be seen in Figure 1, a seal can be provided within flange 113 around optical fiber 106. The seal and flange 113 can be located within the wall of vacuum chamber 101.

[0055] In Figure 4, the optical fiber 106 passes through a flange 200. This flange 200 is an example of the flange 113 in Figure 1. The flange 200 has a strain relief unit 201 and a spacer 202. The spacer 202 is configured to fit inside the strain relief unit 201. The spacer 202 may be made of aluminum or other materials.

[0056] The spacer 202 can also be configured to fit inside a seal fitting 203, such as a Swagelok® or other type of seal fitting. The seal fitting 203 can be adapter welded. A seal 204 can be inserted into the end of the seal fitting 203 opposite the spacer 202. A cover 205 and a sleeve 206 can also be provided. The sleeve 206 can be stainless steel. A stainless steel tube 207 can surround the optical fiber 106. The seal fitting 203 can be positioned within the wall 102.

[0057] The seal 204 has an outer member 208, which defines an inlet 211. The inlet 211 can be opened and closed, for example, using a nipple. A seal joint seal 210, for example, made of metal, is disposed on the outer member 208. The seal joint seal 210 can provide a metal-to-metal seal with the seal joint 203. A polymer layer 209 is disposed between the outer member 208 and the optical fiber 106. The polymer layer 209 can be inserted into the seal 204 through the inlet 211.

[0058] The outer member 208 may be made of Viton® or other vacuum compatible material with low outgassing. The outer member 208 may also be made of aluminum or other metals or alloys. The polymer layer 209 may be an epoxy. The epoxy may be vacuum compatible with low outgassing.

[0059] A metal-to-metal seal can be used to form the hermetic seal between seal joint 203 and seal 204. For example, the seal joint can be replaced with a metal-to-metal fusion welded joint to reduce outgassing.

[0060] The optical fiber 106 may have a manifold cover inside its seal 204 .

[0061] The flange 200 can be inserted into the wall of the vacuum chamber 101 without fiber coupling, thereby achieving a transmission rate of over 90% for wavelengths ranging from ultraviolet to infrared, although other wavelengths may also be used. A polarization extinction ratio of 1:30 or greater can be achieved. These transmission rates and polarization extinction ratios are achieved because little or no stress is applied to the optical fiber 106.

[0062] Tests using the embodiment of Figure 4 showed greater than 90% transmission of red, green and blue light. Polarization extinction ratios were greater than 30.

[0063] In Figure 5, optical fiber 106 passes through flange 300, which is an example of flange 113 in Figure 1. Flange 300 has an elastomeric seal 304 that can be inserted into the end of seal joint 203 opposite spacer 202. Elastomer seal 304 can be made of Viton® or other vacuum compatible material with low outgassing. Elastomer seal 304 can also be made of silicone.

[0064] The optical fiber 106 may have a manifold cover inside its elastomer seal 304 .

[0065] In one example, the elastomeric seal 304 can be compressed to form a hermetic seal with the seal joint 203. Controlling and minimizing axial and radial stresses on the optical fiber 106 can result in transmission losses of less than 5% and polarization extinction ratios of greater than 1:30.

[0066] The embodiment of FIG. 5 achieves a transmission rate of over 90% for wavelengths ranging from ultraviolet to infrared, and a transmission rate of 2×10 -10 Helium leak rates of less than atm·cc / s can be achieved. Other wavelengths are also acceptable. The embodiment of Figure 5 provides an ultra-high vacuum compatible, low-loss, polarization-maintaining single-mode fiber vacuum feedthrough.

[0067] A hermetic seal for the optical fiber 106 can be achieved with a two-component polymer sealant between the optical fiber 106 and the interior of a small-bore, thick-walled tube, or with a precision-molded elastomeric seal 304. The tube surrounds the optical fiber 106, providing a hermetic metal-to-metal seal. The elastomeric seal 304 is compressed a predetermined amount to provide the hermetic seal.

[0068] An ultra-high vacuum version can be constructed by replacing the quick flange with a crushed copper gasket flange.

[0069] The strain relief unit 201 is typically located on the vacuum side of the wall that holds the flange 200 or flange 300. The cover 205 and sleeve 206 are typically located on the atmosphere side of the wall that holds the flange 200 or flange 300.

[0070] The seal joint 203 allows the seal 204 or the elastomeric seal 304 to be squeezed evenly. The seal 204 and the elastomeric seal 304 squeeze the optical fiber 106 when inserted into the collar of the seal joint 203. Most or all of the pressure acting on the optical fiber 106 is along the radial direction of the optical fiber 106. Because the axial pressure acting on the optical fiber 106 is reduced or eliminated, there is less room for the optical fiber 106 to twist. The optical fiber 106 can generally withstand radial compression.

[0071] The optical fiber 106 may be bare within the seal 204 or elastomeric seal 304, i.e., the coating or jacket surrounding the optical fiber 106 may be removed, thereby reducing leakage through the seal 204 or elastomeric seal 304. Adhesive may be added where the bare optical fiber 106 meets a metal member, further reducing leakage.

[0072] 4 and 5 provide approximately 15% better transmission of red, green, and blue wavelengths than conventional seal designs, which apply axial force to the optical fiber 106.

[0073] FIG. 6 is a flowchart of one embodiment of a method 400 that can be implemented in the system 100 of FIG. 1. In 401, light from a laser light source is directed into a vacuum chamber via an optical fiber. The optical fiber transmits all wavelengths of light generated by the laser light source into the vacuum chamber. The laser light source may be located outside the vacuum chamber. The wavelength of the light may be between 200 nm and 2000 nm, for example, between 400 nm and 680 nm.

[0074] At 402, the light is directed to a bleaching and polarizing unit within the vacuum chamber, which may include a turning or curved mirror.

[0075] In 403, the light is directed onto a wafer held on a stage disposed within the vacuum chamber.

[0076] The method 400 can further include directing an electron beam within the vacuum chamber toward the wafer, and the electron beam and light can be directed toward the wafer in a synchronous manner.

[0077] Although the present disclosure has been described with reference to one or more specific embodiments, it will be understood that other embodiments of the present disclosure may be made without departing from the spirit and scope of the present disclosure, and that the present disclosure is to be limited only by the appended claims and their reasonable interpretation.

Claims

1. a vacuum chamber; a stage disposed within the vacuum chamber and configured to hold a wafer; a laser light source including a plurality of lasers, the laser light source being disposed outside the vacuum chamber; an optical fiber that simultaneously transmits all of the wavelengths of light generated by the laser light source through a wall of the vacuum chamber into the vacuum chamber; a bleaching and polarization unit disposed in the vacuum chamber, which receives light from the optical fiber, rotates the light, and adjusts its polarization; a scanning electron microscope having an electron beam source for directing an electron beam at the wafer to inspect the wafer for defects; a flange surrounding the optical fiber, the flange comprising: A distortion reduction unit, A spacer; A seal joint; Stickers and one end of the spacer is configured to fit inside the strain relief unit and the other end is configured to fit inside the seal joint; the seal is inserted into an end of the seal joint opposite the spacer, and the seal joint is disposed within a wall of the vacuum chamber; The laser light source Polarization-dependent beam splitter for combining laser beams with different polarization states Equipped with An apparatus for laser-enhanced voltage contrast inspection of an area of ​​a wafer under inspection using multiple wavelengths by electronically switching between said multiple wavelengths.

2. 2. The apparatus of claim 1, wherein the wavelength of light transmitted by the optical fiber is between 200 nm and 2000 nm.

3. 10. The apparatus of claim 1, wherein the laser light source further comprises a plurality of dichroic mirrors.

4. 10. The apparatus of claim 1, wherein the laser light source further comprises a plurality of half-wave plates.

5. 10. The apparatus of claim 1, wherein the optical fiber is a multimode fiber.

6. 10. The apparatus of claim 1, wherein the optical fiber is a single mode fiber.

7. 10. The apparatus of claim 1, further comprising a waveplate disposed within the vacuum chamber to receive the light from the optical fiber.

8. 8. The apparatus of claim 7, wherein the wave plate is a half wave plate or a quarter wave plate.

9. 2. The device according to claim 1, wherein the bleaching and polarizing unit comprises: a turning mirror disposed within the vacuum chamber to receive the light from the optical fiber, the turning mirror configured to direct the light from the optical fiber to the stage; at least one achromatic lens disposed within the vacuum chamber, the achromatic lens configured to collimate and / or image light received from the optical fiber onto the wafer; A device having:

10. 2. The apparatus according to claim 1, wherein the decolorizing and polarizing unit comprises a curved mirror, the curved mirror being a spherical mirror or a parabolic mirror.

11. 2. The apparatus of claim 1, wherein the seal of the flange comprises: an outer member disposed around the optical fiber; a polymer layer disposed between the optical fiber and the outer member, the polymer layer being radially compressed to form a hermetic seal; A device having:

12. 12. The apparatus of claim 11, wherein the hermetic seal between the optical fiber and the outer member further comprises a metal-to-metal seal.

13. 10. The apparatus of claim 1, wherein the seal on the flange is an elastomeric seal, the elastomeric seal being radially compressed to form a hermetic seal.

14. directing light from a plurality of lasers in a laser source into a vacuum chamber via optical fibers, such that the optical fibers simultaneously transmit all of the plurality of wavelengths of light produced by the laser source through a wall of the vacuum chamber and into the vacuum chamber; directing light from the optical fiber to a bleaching and polarizing unit within the vacuum chamber; directing the light at a wafer held on a stage disposed within the vacuum chamber; a flange surrounding the optical fiber, A distortion reduction unit, A spacer; A seal joint; Stickers and one end of the spacer is configured to fit inside the strain relief unit and the other end is configured to fit inside the seal joint; the seal is inserted into an end of the seal joint opposite the spacer, and the seal joint is disposed within a wall of the vacuum chamber; The laser light source Polarization-dependent beam splitter for combining laser beams with different polarization states Equipped with A method for inspecting a wafer for defects using a combination of laser-enhanced voltage contrast and a scanning electron microscope with multiple wavelengths to inspect an area of ​​the wafer by electronically switching between the multiple wavelengths.

15. 15. The method of claim 14, further comprising directing an electron beam within the vacuum chamber toward the wafer.

16. 15. The method of claim 14, wherein the wavelength of the light is between 200 nm and 2000 nm.

17. The method according to claim 14, wherein the decolorizing and polarizing unit comprises a turning mirror or a curved mirror.

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