Image the area including the top surface and the hole

Abstract

A method, computer program product, and system for imaging an area including an upper surface and a hole. The method may include: when a charged particle imager is in a first configuration, acquiring a first image of a first type of electrons in the area by the charged particle imager; when the charged particle imager is in a second configuration different from the first configuration, acquiring a second image of the first type of electrons in the area and a first image of the second type of electrons in the area by the charged particle imager; and generating a mixed image of the area based on (i) the first image of the first type of electrons of the upper surface, (ii) the inter-image offset, and (iii) the first image of the second type of electrons at the bottom of the hole.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Application No. 16 / 007,580, filed June 13, 2018, the contents of which are hereby incorporated by reference in their entirety. Technical Field

[0003] The present disclosure relates to methods, computer program products, and systems for imaging an area including an upper surface and an aperture. Background Art

[0004] Integrated circuits are manufactured using highly complex manufacturing processes that can be evaluated during and even after the manufacturing process is complete.

[0005] Evaluation of an integrated circuit may include inspecting the integrated circuit, verifying the integrated circuit, and additionally or alternatively measuring structural elements of the integrated circuit. Deep, narrow holes are difficult to inspect because electrons striking the bottom of the hole and electrons striking the sidewalls of the hole do not leave the hole.

[0006] There is an increasing need to provide an efficient method for inspecting areas including upper surfaces and holes. Summary of the Invention

[0007] A method for imaging an area including an upper surface and a hole can be provided. The method can include: (a) acquiring a first image of a first type of electron in the area by a charged particle imager when the charged particle imager is in a first configuration. The first image of the first type of electron in the area can include a first image of the first type of electron in the upper surface. (b) acquiring a second image of the first type of electron in the area and a first image of the second type of electron in the area by the charged particle imager when the charged particle imager is in a second configuration different from the first configuration. The first image of the second type of electron in the area can include a first image of the second type of electron at the bottom of the hole. (c) calculating an inter-image offset based on a comparison between the first image of the first type of electron in the area and the second image of the first type of electron in the area. (d) generating a mixed image of the area based on (i) the first image of the first type of electron in the upper surface, (ii) the inter-image offset, and (iii) the first image of the second type of electron at the bottom of the hole.

[0008] A computer program product may be provided that stores instructions that, once executed by a computerized system, cause the computerized system to perform the following steps: (a) acquiring, by the charged particle imager, a first image of a first type of electron in the region when the charged particle imager is in a first configuration. The first image of the first type of electron in the region may include a first image of the first type of electron in the upper surface. (b) acquiring, by the charged particle imager, a second image of the first type of electron in the region and a first image of the second type of electron in the region when the charged particle imager is in a second configuration different from the first configuration. The first image of the second type of electron in the region may include a first image of the second type of electron at the bottom of the hole. (c) calculating an inter-image offset based on a comparison between the first image of the first type of electron in the region and the second image of the first type of electron in the region. (d) generating a mixed image of the region based on (i) the first image of the first type of electron in the upper surface, (ii) the inter-image offset, and (iii) the first image of the second type of electron at the bottom of the hole.

[0009] A system for imaging an area including an upper surface and an aperture can be provided, the system comprising a charged particle imager and a processor. The charged particle imager can be arranged and constructed to (a) acquire a first image of a first type of electron in the area when the charged particle imager is in a first configuration; wherein the first image of the first type of electron in the area can include a first image of the first type of electron in the upper surface; and (b) acquire a second image of the first type of electron in the area and a first image of the second type of electron in the area when the charged particle imager is in a second configuration different from the first configuration; wherein the first image of the second type of electron in the area can include a first image of the second type of electron at the bottom of the aperture. The processor can be arranged and constructed to (a) calculate an inter-image offset based on a comparison between the first image of the first type of electron in the area and the second image of the first type of electron in the area; and (b) generate a mixed image of the area based on (i) the first image of the first type of electron in the upper surface, (ii) the inter-image offset, and (iii) the first image of the second type of electron at the bottom of the aperture.

[0010] In some embodiments, a method is provided, the method comprising: setting a focal plane of a charged particle imager to an upper surface of a substrate and acquiring a first secondary electron image of the region, the first secondary electron image of the region comprising a secondary electron image of the upper surface; setting a focal plane of the charged particle imager to a bottom of a hole and acquiring a second secondary electron image of the region and a backscattered electron image of the region, the backscattered electron image of the region comprising a backscattered electron image of the bottom of the hole; calculating an inter-image offset based on a comparison between the first secondary electron image and the second secondary electron image; and generating a hybrid image of the region based on (i) the first secondary electron image of the upper surface, (ii) the inter-image offset, and (iii) the backscattered electron image of the bottom of the hole. In some cases, the hole is a trench formed in the substrate, the trench comprising sidewalls extending within the hole from the upper surface of the substrate to the bottom of the hole, and wherein the second secondary electron image comprises a defocused secondary electron image of the upper surface, and the backscattered electron image further comprises a backscattered electron image of the upper surface and a backscattered electron image of the sidewalls of the hole. And in some embodiments, it relates to a computer program product storing instructions executable by a computerized system to cause the computerized system to perform the above method, while other embodiments relate to a system including a charged particle imager and a processor, the system being configured to image a region and perform the above method. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. However, the invention, both as to its organization and method steps, together with its substrates, features, and advantages, may be best understood by reference to the following detailed description when read in conjunction with the accompanying drawings, in which:

[0012] Figure 1 is an example of an object and charged particle imager;

[0013] Figure 2 is an example of an object and charged particle imager;

[0014] Figure 3 is an example of a region and a variety of images;

[0015] Figure 4 is an example of a region and various images; and

[0016] Figure 5 is an example of a method.

[0017] It should be understood that for simplicity and clarity of illustration, the elements shown in the figures are not necessarily drawn to scale. For example, the dimensions of some elements may be exaggerated relative to other elements for clarity. In addition, where deemed appropriate, reference numerals may be repeated in the various figures to indicate corresponding or similar elements. DETAILED DESCRIPTION

[0018] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other cases, well-known methods, processes, and components have not been described in detail in order to avoid obscuring the present invention.

[0019] Any reference to a method in this specification should apply mutatis mutandis to a system capable of performing the method and a computer program product storing instructions for performing the method.

[0020] Any reference in this specification to a system shall apply mutatis mutandis to a method performable by the system and a computer program product storing instructions for performing the method.

[0021] Any reference in this specification to a computer program product should apply mutatis mutandis to methods performed when instructions stored in the computer program product are executed and to systems arranged and constructed to perform the instructions stored in the computer program product. The computer program product is non-transitory and may include a non-transitory medium for storing the instructions. Non-limiting examples of computer program products are memory chips, integrated circuits, magnetic disks, magnetic memory cells, and memristor memory cells.

[0022] Assigning the same reference number to multiple components may indicate that the components are similar to each other.

[0023] A method for generating a hybrid image of a region including an upper surface and a hole can be provided. The hole is nanometer-sized and has a high aspect ratio. The aspect ratio is the ratio between the depth of the hole and the width of the hole. The high aspect ratio can exceed ten. The nanometer-sized hole means that the width of the hole can be about a few (e.g., between 1 and 9) nanometers or tens of nanometers.

[0024] The following examples involve an object, which may be a semiconductor wafer or any other object having nanometer-sized, high-aspect-ratio holes.

[0025] The blended image may include (a) pixels derived from an image of the upper surface of the region and (b) pixels derived from another image of the bottom of the hole. Pixels near the boundary between the upper surface and the bottom of the hole may be modified to prevent sharp changes between pixels of the blended image. A smoothing function may be applied to selected pixels near the boundary. Any smoothing function may be applied.

[0026] Pixels close to (or adjacent to) the border may be located within a predetermined number of pixels from the border, for example, at a distance from the bottom of the hole that is at most less than a predetermined fraction (eg, between 1% and 15%) of the width.

[0027] The one or more images of the region may be taken by the charged particle imager when in the first configuration.The one or more images of the region may be taken by the charged particle imager when in the second configuration.

[0028] The one or more images captured in each of the first and second configurations may include different types of electron images—eg, backscattered electron images and / or secondary electron images, and / or other types of charged particle images.

[0029] The second configuration differs from the first configuration in at least one charged particle imager parameter. The at least one charged particle imager parameter may be a focus condition, a landing energy condition, a charge condition, an intensity condition, and the like.

[0030] For simplicity of explanation, it is assumed that the second configuration differs from the first configuration in the position of the focal plane of the charged particle imager. For example, when in the first configuration, the focal plane of the charged particle imager corresponds to (substantially falls on) the upper surface. When in the second configuration, the focal plane of the charged particle imager corresponds to (substantially falls on) the bottom of the aperture.

[0031] The phrase "substantially falling on" may include falling exactly on or may deviate by an insignificant amount, such as may deviate by up to a predetermined amount (e.g., up to 2-30 nanometers), or up to a predetermined percentage of the depth of the pore (e.g., up to 5-30% of the depth of the pore).

[0032] For simplicity of description, it is assumed that the one or more images acquired when the charged particle imager is in the first configuration include a first secondary electron image of the region. For simplicity of description, it is further assumed that the one or more images acquired when the charged particle imager is in the second configuration include a second secondary electron image of the region and a first backscattered electron image of the region.

[0033] Compare the first secondary electron image of the area and the second secondary electron image of the area to find the inter-image offset. The hybrid image can be generated by (i) taking pixels of the first secondary electron image to represent the upper surface and (ii) taking pixels of the first backscattered electron image to represent the bottom of the hole. It should be noted that steps (i) and (ii) may include (or may be preceded by) compensation for the inter-image offset. The compensation may include shifting one or more images.

[0034] Figure 1 and Figure 2 An object 100 and a charged particle imager 10 are shown. The charged particle imager 10 includes a stage 30, a processor 50, a memory unit 60, a controller 70, and electron optics. The electron optics include a beam source 12, a condenser lens 14, a first deflector 16, a backscattered electron sensor 18, a second deflector 20, a secondary electron detector 22, and an objective lens 24.

[0035] The stage 30 is arranged to support the object 100 and to move the object. The controller 70 can control the operation of the charged particle imager 10. The processor 50 can generate an image based on the detection signals sent from the backscattered electron sensor 18 and / or the secondary electron detector 22. The processor 50 can be arranged and constructed (e.g., by being programmed) to perform any step of any method described in the specification. The phrases "configured to" and "arranged and constructed to" are used interchangeably. It should be noted that the processor 50 can be located in a remote computer or any other computerized system different from the charged particle imager 10.

[0036] The beam source 12 generates a primary electron beam 40 . Figure 1 The primary electron beam 40 is shown to be deflected twice by the first deflector 16 and the second deflector 20 when passing through the objective lens 24 and impinging on the object 100. The primary electron beam 40 may take any other path. For example, the primary electron beam 40 may be deflected once or more than twice, and the primary electron beam 40 may propagate in any other manner.

[0037] The secondary electron detector 22 has four sections 91 , 92 , 93 and 94 for receiving secondary electrons. The secondary electron detector 22 also serves as a central aperture 23 through which backscattered electrons can pass and reach the backscattered electron sensor 18 .

[0038] Figure 2Secondary electrons 31 are shown impinging on secondary electron detector 22, and backscattered electrons 32 are shown passing through the central aperture and impinging on backscattered electron sensor 18. Backscattered electrons 32 are deflected by second deflector 20 toward backscattered electron sensor 18. In-lens detectors are detectors located within the column of the charged particle imager. Out-of-lens detectors are detectors located outside the column of the charged particle imager.

[0039] Figure 2 The secondary electron detector 22 and the backscattered electrons 32 are shown as in-lens detectors. This is only an example. It should be noted that the electron optics of the charged particle imager 10 can be used with Figure 1 and Figure 2 The electron optics may be different. For example - the secondary electron detector may be any off-lens secondary electron detector, the secondary electron detector may be any in-lens secondary electron detector, the secondary electron detector may include fewer than four segments, the secondary electron detector may have more than four segments, the backscattered electron detector may be any off-lens backscattered electron detector, the backscattered electron detector may be any in-lens backscattered electron detector, the type of detector may be different from the secondary electron detector and the backscattered electron detector, there may be any number of deflectors, the primary electron beam may be perpendicular to the object or not, and the like.

[0040] Figure 3 An example is:

[0041] a. Cross-sectional view of region 101 including upper surface 111 and hole 110. Hole 110 includes bottom 114, sloped sidewalls 113, and upper surface 112. a.

[0042] b. Top view of the area.

[0043] c. A first secondary electron image 120 of the area (acquired when the focal plane corresponds to the upper surface), the first secondary electron image 120 comprising a first secondary electron image 121 of the upper surface and a first secondary electron image 124 of the hole. The first secondary electron image of the hole typically does not include any information because secondary electrons from the hole do not reach the electron optics.

[0044] d. A second secondary electron image 130 of the area (acquired when the focal plane corresponds to the bottom of the aperture), which includes a second secondary electron image 131 of the upper surface and a second secondary electron image 134 of the aperture. The second secondary electron image of the aperture typically does not include any information because the secondary electrons from the aperture do not reach the electron optics. Second secondary electron image 130 is defocused.

[0045] e. A first backscattered electron image 140 of the region (acquired when the focal plane corresponds to the bottom of the hole), the first backscattered electron image 140 including a first backscattered electron image 141 of the upper surface and a first backscattered electron image of the hole. The first backscattered electron image 140 of the region also includes a first backscattered electron image 143 of the sidewalls of the hole and a first backscattered electron image 144 of the bottom of the hole. The first backscattered electron image 144 of the bottom of the hole includes information about the bottom of the hole.

[0046] f. Inter-image offset 129.

[0047] g. A mixed image 150 comprising pixels 151 of the upper surface and pixels 154 of the bottom of the hole.

[0048] Figure 3 The hole is a circular hole - and the inter-image offset 129 can be calculated by trying to find the offset that provides the best correlation between the first secondary electron image of the area and the second secondary electron image of the area. It should be noted that a smoothing operation can be applied to selected pixels near the boundary between the upper surface and the bottom of the hole.

[0049] Figure 4 An example is:

[0050] a. Top view of region 103 includes upper surface 104 and two vertical grooves 211 and 212 , as well as upper surface 104 .

[0051] b. Grayscale distribution 221 of pixels of the second secondary electron image of the area, where the pixels are intercepted along the imaginary line 213.

[0052] c. Gray level distribution 222 of pixels of the first backscattered electron image of the area, the pixels being taken along imaginary line 213 .

[0053] At least one of distributions 221 and 222 is compensated for inter-image offset. The inter-image offset is indicated as 230. Distributions 221 and 222 intersect each other at right intersection 224 and left intersection 223. The area between right intersection 224 and left intersection 223 is referred to as intermediate area 228.

[0054] The mixed image may be generated by selecting pixels from distribution 221 to the right of middle region 228, selecting pixels from distribution 222 at middle region 228, and selecting pixels from distribution 221 to the left of middle region 228. Selected pixels near right intersection 224 and left intersection 223 may undergo a smoothing operation.

[0055] Figure 4The distribution of pixels is shown taken along a single imaginary line 213. Different distributions may be employed along multiple imaginary lines (multiple strips), and a blended image may be generated using the above process when applied to multiple distributions acquired over multiple strips.

[0056] Figure 5 An example of a method 300 is shown. The method 300 may include a series of steps 310, 320, 330, and 340. Step 310 may include acquiring, by the charged particle imager when the charged particle imager is in a first configuration, a first image of a first type of electron in the region. The first image of the first type of electron in the region may include a first image of the first type of electron on the upper surface.

[0057] Step 320 may include acquiring, with the charged particle imager when the charged particle imager is in a second configuration, a second image of the first species of electrons in the region and a first image of the second species of electrons in the region. The second configuration is different from the first configuration. The first image of the second species of electrons in the region may include a first image of the second species of electrons at a bottom of the aperture.

[0058] Step 330 may include calculating an inter-image offset based on a comparison between a first image of the first type of electrons for the region and a second image of the first type of electrons for the region. Step 330 may include comparing the first image of the first type of electrons for the region and the second image of the first type of electrons for the region to find the inter-image offset.

[0059] Step 340 may include generating a mixed image of the region based on (i) a first image of the first type of electrons of the upper surface, (ii) an inter-image offset, and (iii) a first image of the second type of electrons of the bottom of the hole. The first image of the first type of electrons of the region may be a first secondary electron image of the region. The first image of the first type of electrons of the upper surface may be a first secondary electron image of the upper surface. The second image of the first type of electrons of the region may be a second secondary electron image of the region. The first image of the second type of electrons of the region may be a first backscattered electron image of the region. The first image of the second type of electrons of the bottom of the hole may be a first backscattered electron image of the bottom of the hole. The second configuration may differ from the first configuration in the position of the focal plane of the charged particle imager.

[0060] When the charged particle imager is in the first configuration, the focal plane of the charged particle imager may correspond to the upper surface. When the charged particle imager is in the second configuration, the focal plane of the charged particle imager may correspond to the bottom of the hole. The hole may be a groove.

[0061] Step 330 may include searching for latitudinal displacements between pixels of the aperture at a first secondary electron image of the region and latitudinal displacements between corresponding pixels of the aperture at a second secondary electron image of the region. The aperture may be a circular contact. Step 330 may include correlating pixels of the circular contact at the first secondary electron image of the region and pixels of the circular contact at the second secondary electron image of the region.

[0062] Step 340 may include:

[0063] a. Compensating for the inter-image offset to provide an inter-image compensated first backscattered electron image of the bottom of the hole.

[0064] b. Find the intersection between (i) the gray level of a pixel of the first secondary image of the upper surface and (ii) the gray level of a pixel of the inter-image compensated first backscattered electron image of the bottom of the hole.

[0065] c. For the hybrid image, selecting at least a majority of the pixels of the inter-image compensated first backscattered electron image of the bottom of the hole in the intermediate region defined between the intersection points.

[0066] d. For the mixed image, select at least a majority of the pixels of the first secondary electron image of the upper surface outside the intermediate region.

[0067] The method may comprise applying a smoothing function to pixels near the intersection point.At least a majority of the pixels may comprise all pixels, greater than 50% of the pixels, or any percentage of the pixels between 51% and 99%.

[0068] The hole may be a groove, and step 340 may include:

[0069] a. Compensating for inter-image offset to provide inter-image compensated first and second images of the upper surface.

[0070] b. Find the intersections between (i) the gray levels of the pixels of the inter-image compensated first secondary image of the upper surface and (ii) the gray levels of the pixels of the first backscattered electron image of the bottom of the hole.

[0071] c. For the mixed image, selecting at least a majority of the pixels of the first backscattered electron image in the intermediate region defined between the intersection points.

[0072] d. For the mixed image, select at least a majority of the pixels of the inter-image compensated first and second electron images of the upper surface outside the middle region.

[0073] The method may comprise applying a smoothing function to pixels close to the intersection point. It should be noted that a method may be provided, the method comprising:

[0074] a. When the charged particle imager is in a first configuration, acquiring a first image of multiple types of electrons of the region by the charged particle imager;

[0075] b. acquiring a second image of multiple types of electrons in the region by the charged particle imager when the charged particle imager is in the second configuration;

[0076] c. Use the first and second images of some type of electron of the area to perform registration (find the intra-image offset).

[0077] d. Using the first and second images of the other type of electrons of the area to generate a hybrid image - while taking into account the intra-image offset.

[0078] Step (c) may include (or may be preceded by) selecting a certain type of electron. This selection may be based on one or more parameters of the image, such as image smoothness of different types of images. Smoother images may provide more accurate registration. Other parameters may include signal-to-noise ratio and the like.

[0079] In the foregoing specification, the invention has been described with reference to specific examples of embodiments of the invention. It will, however, be evident that various modifications and changes may be made therein without departing from the broader spirit and scope of the invention as set out in the appended claims.

[0080] Furthermore, the terms "front," "back," "top," "bottom," "above," "below," and the like, if any, in the specification and claims are used for descriptive purposes and not necessarily to describe permanent relative positions. It is understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of performing steps in other orientations than those illustrated or otherwise described herein, for example.

[0081] The connection discussed herein can be any type of connection suitable for transmitting signals from or to a corresponding node, unit or device, for example, via an intermediate device. Therefore, unless implied or otherwise stated, a connection can be, for example, a direct connection or an indirect connection. Connections can be illustrated or described with reference to a single connection, multiple connections, unidirectional connections or bidirectional connections. However, different embodiments can change the specific implementation of the connection. For example, a separate unidirectional connection can be used instead of a bidirectional connection, or vice versa. Moreover, multiple connections can be replaced with a single connection that transmits multiple signals serially or in a time-multiplexed manner. Similarly, a single connection that carries multiple signals can be separated into various different connections that carry subsets of these signals. Therefore, there are many options for transmitting signals.

[0082] Although specific conductivity types or potential polarities have been described in the examples, it should be understood that the conductivity types and potential polarities can be reversed. Those skilled in the art will recognize that the boundaries between logic blocks are merely illustrative, and that alternative implementations may merge logic blocks or circuit elements, or impose alternative decompositions of functionality on various logic blocks or circuit elements. Therefore, it should be understood that the architectures described herein are merely exemplary, and that many other architectures that achieve the same functionality may be implemented.

[0083] Any arrangement of components to achieve the same functionality is effectively "associated" so as to achieve the desired functionality. Thus, any two components herein combined to achieve a particular functionality can be considered to be "associated" with each other so that the desired functionality is achieved, regardless of architectures or intermediary components. Likewise, any two components so associated can also be considered to be "operably connected" or "operably coupled" to each other so as to achieve the desired functionality.

[0084] Furthermore, those skilled in the art will recognize that the boundaries between the above steps are merely illustrative. Multiple steps may be combined into a single step, individual steps may be distributed among additional steps, and steps may be performed with at least partial overlap in time. Furthermore, alternative embodiments may include multiple instances of a particular step, and the order of the steps may be altered in various other embodiments.

[0085] Furthermore, for example, in one embodiment, the illustrated examples may be implemented as circuits located on a single integrated circuit or within the same device. Alternatively, the examples may be implemented as any number of separate integrated circuits or separate devices interconnected with each other in a suitable manner.

[0086] However, other modifications, variations, and alternatives are also possible. Therefore, the description and drawings should be regarded as illustrative rather than restrictive. In the claims, any reference signs between parentheses should not be construed as limiting the claim. The word "comprising" does not exclude the presence of other elements or steps listed in the claim. Furthermore, the terms "a" or "an" as used herein are defined as one or more than one. Furthermore, the use of introductory phrases such as "at least one" and "one or more" in the claims should not be construed as implying that the introduction of another claim element by the indefinite article "a" or "an" limits any particular claim containing such introduced claim element to an invention containing only one such element, even when the same claim includes the introductory phrases "one or more" or "at least one" and an indefinite article such as "a" or "an". The same applies when using definite articles. Unless otherwise stated, terms such as "first" and "second" are used to arbitrarily distinguish between the elements described by such terms. Therefore, these terms are not necessarily intended to indicate a temporal or other prioritization of such elements. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used to advantage.

[0087] While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will occur to those skilled in the art. It is therefore to be understood that the appended claims are intended to cover all such modifications and changes that fall within the true spirit of the invention.

Claims

1. A method for imaging an area including an upper surface and a hole, the method comprising: When the charged particle imager is in a first configuration, a first image of a first type of electrons in the region is acquired by the charged particle imager; wherein the first image of the first type of electrons in the region includes a first image of the first type of electrons in the upper surface; When the charged particle imager is in a second configuration different from the first configuration, acquiring by the charged particle imager a second image of the first type of electrons in the region and a first image of the second type of electrons in the region; wherein the first image of the second type of electrons in the region includes the first image of the second type of electrons at the bottom of the hole; calculating an inter-image offset based on a comparison between the first image of the first type of electrons of the region and the second image of the first type of electrons of the region; and A mixed image of the region is generated based on (i) the first image of the first type of electrons of the upper surface, (ii) the inter-image offset, and (iii) the first image of the second type of electrons of the bottom of the hole.

2. The method according to claim 1, wherein the first image of the first type of electrons in the region is the first secondary electron image of the region; wherein the first image of the first type of electrons of the upper surface is the first secondary electron image of the upper surface; wherein the second image of the first type of electrons in the region is the second secondary electron image of the region; wherein the first image of the second type of electrons in the region is the first backscattered electron image of the region; and wherein the first image of the second type of electrons of the bottom of the hole is the first backscattered electron image of the bottom of the hole.

3. The method of claim 2, wherein the second configuration differs from the first configuration in the position of a focal plane of the charged particle imager.

4. A method according to claim 2, wherein when the charged particle imager is in the first configuration, the focal plane of the charged particle imager corresponds to the upper surface; and wherein when the charged particle imager is in the second configuration, the focal plane of the charged particle imager corresponds to the bottom of the hole.

5. A method according to claim 4, wherein the hole is a groove; and wherein the calculation of the inter-image offset includes searching for the latitudinal displacement between each pixel of the hole at the first secondary electron image of the area and the latitudinal displacement between the corresponding pixels of the hole at the second secondary electron image of the area.

6. The method of claim 4, wherein the holes are circular contacts; and wherein, The calculation of the inter-image offset includes correlating pixels of the circular contact at the first secondary electron image of the area with pixels of the circular contact at the second secondary electron image of the area.

7. The method of claim 4, wherein generating the mixed image of the region comprises: a) compensating for the inter-image offset to provide an inter-image compensated first backscattered electron image of the bottom of the hole; b) finding the intersection between (i) the gray level of a pixel of the first secondary electron image of the upper surface and (ii) the gray level of a pixel of the inter-image compensated first backscattered electron image of the bottom of the hole; c) for the mixed image, selecting more than 50% of the pixels of the inter-image compensated first backscattered electron image of the bottom of the hole in an intermediate area defined between the intersection points; and d) For the mixed image, more than 50% of the pixels of the first secondary electron image of the upper surface are selected outside the middle area.

8. The method of claim 4, wherein the aperture is a trench, and wherein generating the hybrid image of the region comprises: a) compensating the inter-image offset to provide an inter-image compensated first secondary electron image of the upper surface; b) finding the intersection between (i) the gray level of a pixel of the inter-image compensated first secondary electron image of the upper surface and (ii) the gray level of a pixel of the first backscattered electron image of the bottom of the hole; c) for the mixed image, selecting more than 50% of the pixels of the first backscattered electron image in an intermediate area defined between the intersection points; and d) For the mixed image, more than 50% of the pixels of the inter-image compensated first secondary electron image of the upper surface are selected outside the middle area.

9. The method of claim 7 or 8, further comprising applying a smoothing function to selected pixels close to the intersection point.

10. A method of imaging an area on a substrate, the substrate comprising an upper surface and a hole formed in the substrate, the hole extending from the upper surface of the substrate to a bottom of the hole, the method comprising: Setting a focal plane of a charged particle imager to the upper surface of the substrate, and acquiring a first secondary electron image of the region, wherein the first secondary electron image of the region includes a secondary electron image of the upper surface; setting the focal plane of the charged particle imager to the bottom of the hole, and acquiring a second secondary electron image of the region and a backscattered electron image of the region, the backscattered electron image of the region including a backscattered electron image of the bottom of the hole; calculating an inter-image offset based on a comparison between the first secondary electron image and the second secondary electron image; and A hybrid image of the region is generated based on (i) the first secondary electron image of the upper surface, (ii) the inter-image offset, and (iii) a backscattered electron image of the bottom of the hole.

11. A method for imaging an area on a substrate according to claim 10, wherein the hole is a groove formed in the substrate, the groove includes a side wall extending from the upper surface of the substrate to the bottom of the hole within the hole, and wherein the second secondary electron image includes a defocused secondary electron image of the upper surface, and the backscattered electron image further includes a backscattered electron image of the upper surface and a backscattered electron image of the side wall of the hole.

12. A computer program product storing instructions which, when executed by a computerized system, cause the computerized system to perform the following steps: When the charged particle imager is in a first configuration, acquiring a first image of a first type of electrons of a region by the charged particle imager; wherein the first image of the first type of electrons of the region comprises a first image of the first type of electrons of an upper surface of the region; When the charged particle imager is in a second configuration different from the first configuration, a second image of the first type of electrons of the region and a first image of the second type of electrons of the region are acquired by the charged particle imager; wherein the first image of the second type of electrons of the region includes the first image of the second type of electrons of the bottom of the holes of the region; calculating an inter-image offset based on a comparison between the first image of the first type of electrons of the region and the second image of the first type of electrons of the region; and A mixed image of the region is generated based on (i) the first image of the first type of electrons of the upper surface, (ii) the inter-image offset, and (iii) the first image of the second type of electrons of the bottom of the hole.

13. A computer program product according to claim 12, wherein the first image of the first type of electrons in the area is a first secondary electron image of the area; wherein the first image of the first type of electrons of the upper surface is a first secondary electron image of the upper surface; wherein the second image of the first type of electrons in the area is a second secondary electron image of the area; wherein the first image of the second type of electrons in the area is a first backscattered electron image of the area; and wherein the first image of the second type of electrons of the bottom of the hole is the first backscattered electron image of the bottom of the hole.

14. A computer program product according to claim 13, wherein when the charged particle imager is in the first configuration, the focal plane of the charged particle imager corresponds to the upper surface; and wherein when the charged particle imager is in the second configuration, the focal plane of the charged particle imager corresponds to the bottom of the hole.

15. The computer program product of claim 13, wherein the calculation of the inter-image offset comprises: The latitudinal displacement between pixels of the grooves at the first secondary electron image of the area and the latitudinal displacement between corresponding pixels of the grooves at the second secondary electron image of the area are searched.

16. A computer program product according to claim 14, wherein the calculation of the inter-image offset includes correlating pixels of the circular contact at the first secondary electron image with pixels of the circular contact at the second secondary electron image.

17. The computer program product of claim 14, wherein generating the blended image of the region comprises: a) compensating for the inter-image offset to provide an inter-image compensated first backscattered electron image of the bottom of the hole; b) finding the intersection between (i) the gray level of a pixel of the first secondary electron image of the upper surface and (ii) the gray level of a pixel of the inter-image compensated first backscattered electron image of the bottom of the hole; c) for the mixed image, selecting more than 50% of the pixels of the inter-image compensated first backscattered electron image of the bottom of the hole in an intermediate area defined between the intersection points; and d) For the mixed image, more than 50% of the pixels of the first secondary electron image of the upper surface are selected outside the middle area.

18. The computer program product of claim 13, wherein the aperture is a trench, and wherein generating the hybrid image of the region comprises: a) compensating the inter-image offset to provide an inter-image compensated first secondary electron image of the upper surface; b) finding the intersection between (i) the gray level of a pixel of the inter-image compensated first secondary electron image of the upper surface and (ii) the gray level of a pixel of the first backscattered electron image of the bottom of the hole; c) for the mixed image, selecting more than 50% of the pixels of the first backscattered electron image in an intermediate area defined between the intersection points; and d) For the mixed image, more than 50% of the pixels of the inter-image compensated first secondary electron image of the upper surface are selected outside the middle area.

19. The computer program product of claim 17 or 18, wherein the instructions, when executed by the computerized system, further cause the computerized system to apply a smoothing function to selected pixels proximate to the intersection.

20. A system for imaging an area including an upper surface and a hole, the system comprising: charged particle imagers and processors; wherein the charged particle imager is arranged and constructed to (a) acquire a first image of a first type of electrons in the region when the charged particle imager is in a first configuration; wherein the first image of the first type of electrons in the region includes a first image of the first type of electrons at the upper surface; and (b) acquire a second image of the first type of electrons in the region and a first image of a second type of electrons in the region when the charged particle imager is in a second configuration different from the first configuration; wherein the first image of the second type of electrons in the region includes a first image of the second type of electrons at the bottom of the hole; wherein the processor is arranged and configured to (a) calculate an inter-image offset based on a comparison between the first image of the first type of electrons of the region and the second image of the first type of electrons of the region; and (b) generating a mixed image of the region based on (i) the first image of the first type of electrons at the upper surface, (ii) the inter-image offset, and (iii) the first image of the second type of electrons at the bottom of the hole.

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