Test structure convenient for TEM sample preparation

Abstract

The invention provides a test structure convenient for TEM sample preparation, and the test structure comprises a front-layer metal layer which comprises a first front-layer disconnected metal wire, a second front-layer disconnected metal wire and a front-layer target metal wire which extend along a first direction, the first front-layer disconnected metal wire and the second front-layer disconnected metal wire are located on the two sides of the front-layer target metal wire; the rear-layer metal layer is formed above the front-layer metal layer and comprises a first rear-layer disconnected metal wire, a second rear-layer disconnected metal wire and a rear-layer target metal wire which extend along a second direction; the first rear-layer disconnected metal wire and the second rear-layer disconnected metal wire are located on the two sides of the rear-layer target metal wire, and the rear-layer target metal wire is connected with the front-layer target metal wire through an ISO through hole. According to the invention, the problem of inaccurate positioning of the target through hole during existing TEM sample preparation is solved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing technology, and particularly to a test structure facilitating TEM sample preparation. Background Art

[0002] During the research and development of advanced semiconductor processes, various Test Key structures are designed to detect problems existing in the processes. For example, a test structure for monitoring the Iso via process, which is characterized by having multiple dense metal lines (Dense metal line) with the same size, but one of the metals and the upper metal are led out through a single via (as Figure 1 shown) for monitoring the Iso via process. If electrical resistance appears in the electrical test, TEM is required to observe the morphology of the single via to confirm the failure mechanism and improve the process conditions. Currently, TEM samples are all prepared by FIB. For the sample preparation of this test structure, the most important step is to locate the target through-hole. If the location is inaccurate, the TEM sample preparation will fail.

[0003] In the process of TEM sample preparation for this test structure, due to the consistent metal structures before and after, it is very difficult to determine the position of the target through-hole. The conventional positioning method can only first confirm the target position through high-voltage observation by SEM (scanning electron microscope), and then combine with FIB (focused ion beam technology) marking to assist in target positioning. However, this positioning method is prone to positioning errors, and high-voltage observation will cause deformation of the low dielectric constant inter-metal dielectric layer (low k IMD), thereby destroying the morphology of the target through-hole (as Figure 2 shown). Summary of the Invention

[0004] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a test structure facilitating TEM sample preparation, which is used to solve the problem of inaccurate positioning of the target through-hole during existing TEM sample preparation.

[0005] To achieve the above object and other related objects, the present invention provides a test structure facilitating TEM sample preparation, and the test structure includes:

[0006] A front metal layer, the front metal layer includes a first front-disconnected metal line, a second front-disconnected metal line and a front target metal line extending along a first direction, and the first front-disconnected metal line and the second front-disconnected metal line are spaced on both sides of the front target metal line;

[0007] A back metal layer is formed above the front metal layer. The back metal layer includes a first back-disconnected metal line, a second back-disconnected metal line, and a back target metal line extending in a second direction. The first back-disconnected metal line and the second back-disconnected metal line are spaced on both sides of the back target metal line, and the back target metal line is connected to the front target metal line through an ISO via hole.

[0008] Wherein, the first front-disconnected metal line and the second front-disconnected metal line are disconnected at a position below the back target metal line, and the first back-disconnected metal line and the second back-disconnected metal line are disconnected at a position above the front target metal line.

[0009] Optionally, the length of the disconnection of the first front-disconnected metal line and the length of the disconnection of the second front-disconnected metal line are both less than the distance between the first back-disconnected metal line and the second back-disconnected metal line.

[0010] Optionally, the length of the disconnection of the first back-disconnected metal line and the length of the disconnection of the second back-disconnected metal line are both less than the distance between the first front-disconnected metal line and the second front-disconnected metal line.

[0011] Optionally, the first front-disconnected metal line and the second front-disconnected metal line are both disposed adjacent to the front target metal line.

[0012] Optionally, the first front-disconnected metal line and the second front-disconnected metal line are not connected to the back metal layer.

[0013] Optionally, the first back-disconnected metal line and the second back-disconnected metal line are both disposed adjacent to the back target metal line.

[0014] Optionally, the first back-disconnected metal line and the second back-disconnected metal line are not connected to the front metal layer.

[0015] Optionally, the front metal layer further includes a plurality of pseudo-front metal lines, and the pseudo-front metal lines are spaced on a side of the first front-disconnected metal line and the second front-disconnected metal line away from the front target metal line, and the pseudo-front metal lines are not connected to the back metal layer.

[0016] Optionally, the back metal layer further includes a plurality of pseudo-back metal lines, and the pseudo-back metal lines are spaced on a side of the first back-disconnected metal line and the second back-disconnected metal line away from the back target metal line, and the pseudo-back metal lines are not connected to the front metal layer.

[0017] Optionally, the front metal layer is formed above the active region of the device, and the front target metal line is connected to the active region of the device through a contact hole.

[0018] Optionally, the metal filled in the ISO via includes copper, copper alloy or tungsten.

[0019] As described above, the test structure for facilitating TEM sample preparation of the present invention realizes precise positioning of the ISO via by adding breaks (i.e., Metal cut) on both sides in different directions of the ISO via connecting the front metal layer and the rear metal layer. Description of the Drawings

[0020] Figure 1 Shown as a schematic diagram of an existing test structure.

[0021] Figure 2 Shown as Figure 1 SEM image of IMD damage defects of the test structure.

[0022] Figure 3 Shown as a schematic diagram of the test structure of the present invention.

[0023] Figure 4 Shown as a schematic cross-sectional structure diagram of the present invention cut along the first direction X.

[0024] Figure 5 Shown as a schematic cross-sectional structure diagram of the present invention cut along the second direction Y.

[0025] Description of the Reference Numerals in the Drawings

[0026] 11: First front-layer disconnected metal line; 12: Second front-layer disconnected metal line; 13: Front target metal line; 14: Pseudo front metal line; 21: First rear-layer disconnected metal line; 22: Second rear-layer disconnected metal line; 23: Rear target metal line; 24: Pseudo rear metal line; 30: ISO via; 40: Active region of the device; 50: Interconnect metal layer Detailed Embodiments

[0027] The following specifically illustrates the embodiments of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0028] Please refer to Figures 1 to 5It should be noted that the illustrations provided in this embodiment only schematically illustrate the basic concept of the present invention. Although only the components related to the present invention are shown in the illustrations, rather than being drawn according to the number, shape, and size of the components in actual implementation, the form, number, and ratio of each component in actual implementation can be arbitrarily changed, and the layout form of its components may also be more complex.

[0029] As Figure 3 shown, this embodiment provides a test structure convenient for TEM sample preparation, and the test structure includes:

[0030] The front metal layer M x-1 wherein the front metal layer M x-1 includes a first front-disconnected metal wire 11, a second front-disconnected metal wire 12, and a front target metal wire 13 extending along the first direction X, and the first front-disconnected metal wire 11 and the second front-disconnected metal wire 12 are spaced on both sides of the front target metal wire 13;

[0031] The rear metal layer M x wherein the rear metal layer M x is formed above the front metal layer M x-1 and includes a first rear-disconnected metal wire 21, a second rear-disconnected metal wire 22, and a rear target metal wire 23 extending along the second direction Y, and the first rear-disconnected metal wire 21 and the second rear-disconnected metal wire 22 are spaced on both sides of the rear target metal wire 23, and the rear target metal wire 23 is connected to the front target metal wire 13 through an ISO via 30;

[0032] Among them, the first front-disconnected metal wire 11 and the second front-disconnected metal wire 12 are disconnected at positions below the rear target metal wire 23, and the first rear-disconnected metal wire 21 and the second rear-disconnected metal wire 22 are disconnected at positions above the front target metal wire 13.

[0033] In this embodiment, the first direction is the X direction, the second direction is the Y direction, and the first direction is perpendicular to the second direction.

[0034] Specifically, the front metal layer M x-1 is formed above the device active region 40, and the front target metal wire 13 is connected to the device active region 40 through a contact hole.

[0035] In this embodiment, multiple interconnection metal layers 50 are formed above the device active region 40, and the multiple interconnection metal layers 50 are connected through contact holes, and the bottommost interconnection metal layer 50 is connected to the device active region 40 through a contact hole. At this time, the front metal layer M x-1Formed on the surface of the uppermost interconnect metal layer 50.

[0036] Specifically, the pre-layer metal layer M x-1 Further includes a plurality of pseudo-pre-layer metal lines 14, and the pseudo-pre-layer metal lines 14 are spaced apart on a side of the first pre-layer disconnection metal line 11 and the second pre-layer disconnection metal line 12 away from the pre-layer target metal line 13, and the pseudo-pre-layer metal lines 14 and the post-layer metal layer M x Are not connected.

[0037] Specifically, the length of the disconnection of the first pre-layer disconnection metal line 11 and the length of the disconnection of the second pre-layer disconnection metal line 12 are both less than the distance between the first post-layer disconnection metal line 21 and the second post-layer disconnection metal line 22.

[0038] Specifically, the first pre-layer disconnection metal line 11 and the second pre-layer disconnection metal line 12 are both disposed adjacent to the pre-layer target metal line 13.

[0039] Specifically, the first pre-layer disconnection metal line 11 and the second pre-layer disconnection metal line 12 and the post-layer metal layer M x Are not connected therebetween.

[0040] Specifically, the post-layer metal layer M x Further includes a plurality of pseudo-post-layer metal lines 24, and the pseudo-post-layer metal lines 24 are spaced apart on a side of the first post-layer disconnection metal line 21 and the second post-layer disconnection metal line 22 away from the post-layer target metal line 23, and the pseudo-post-layer metal lines 24 and the pre-layer metal layer M x-1 Are not connected.

[0041] Specifically, the length of the disconnection of the first post-layer disconnection metal line 21 and the length of the disconnection of the second post-layer disconnection metal line 22 are both less than the distance between the first pre-layer disconnection metal line 11 and the second pre-layer disconnection metal line 12.

[0042] Specifically, the first post-layer disconnection metal line 21 and the second post-layer disconnection metal line 22 are both disposed adjacent to the post-layer target metal line 23.

[0043] Specifically, the first post-layer disconnection metal line 21 and the second post-layer disconnection metal line 22 and the pre-layer metal layer M x-1 Are not connected therebetween.

[0044] Specifically, the metal filled in the ISO via 30 includes copper, copper alloy or tungsten.

[0045] As Figure 4 Shown, during the sample preparation process, along the first direction X for the pre-layer metal layer M x-1Perform cutting. Before cutting to the ISO via 30, first cut the disconnection points of the first front-layer disconnection metal wire 11 and the second front-layer disconnection metal wire 12 at the front and back. At this time, from the structure, it can be seen that the metal wire adjacent to the first front-layer disconnection metal wire 11 or the second front-layer disconnection metal wire 12 is the front-layer target metal wire 13, which is also the metal wire where the ISO via 30 is located. After that, use FIB to cut off the disconnection points of the first front-layer disconnection metal wire 11 or the second front-layer disconnection metal wire 12.

[0046] As Figure 5 shown, during the sample preparation process, cut the back-layer metal layer M x along the second direction Y. Before cutting to the ISO via 30, the disconnection points (metal cut) of the first back-layer disconnection metal wire 21 and the second back-layer disconnection metal wire 22 will also be cut. At this time, from the structure, it can be seen that the metal wire adjacent to the first back-layer disconnection metal wire 21 or the second back-layer disconnection metal wire 22 is the back-layer target metal wire 23, which is also the metal wire where the ISO via 30 is located. After that, use FIB to cut off the disconnection points (metal cut) of the first back-layer disconnection metal wire 21 or the second back-layer disconnection metal wire 22.

[0047] In summary, for the test structure facilitating TEM sample preparation of the present invention, by adding disconnection points (i.e., Metal cut) on both sides in different directions of the ISO via connecting the front-layer metal layer and the back-layer metal layer, the precise positioning of the ISO via is achieved. Therefore, the present invention effectively overcomes various disadvantages in the prior art and has high industrial utilization value.

[0048] The above embodiments are only illustrative of the principles and effects of the present invention, and are not used to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A test structure facilitating TEM sample preparation, characterized in that, The test structure includes: A front metal layer, which includes a first front-disconnected metal line, a second front-disconnected metal line, and a front target metal line extending in a first direction. The first front-disconnected metal line and the second front-disconnected metal line are spaced on both sides of the front target metal line. A back metal layer formed above the front metal layer, which includes a first back-disconnected metal line, a second back-disconnected metal line, and a back target metal line extending in a second direction. The first back-disconnected metal line and the second back-disconnected metal line are spaced on both sides of the back target metal line. The back target metal line is connected to the front target metal line through an ISO via hole. Wherein, the first front-disconnected metal line and the second front-disconnected metal line are disconnected at positions below the back target metal line, and the first back-disconnected metal line and the second back-disconnected metal line are disconnected at positions above the front target metal line.

2. The test structure facilitating TEM sample preparation according to claim 1, wherein The lengths of the disconnection of the first front-disconnected metal line and the second front-disconnected metal line are both less than the distance between the first back-disconnected metal line and the second back-disconnected metal line.

3. The test structure facilitating TEM sample preparation according to claim 1, wherein The lengths of the disconnection of the first back-disconnected metal line and the second back-disconnected metal line are both less than the distance between the first front-disconnected metal line and the second front-disconnected metal line.

4. The test structure facilitating TEM sample preparation according to claim 1, wherein Both the first front-disconnected metal line and the second front-disconnected metal line are disposed adjacent to the front target metal line.

5. The test structure facilitating TEM sample preparation according to claim 1, wherein There is no connection between the first front-disconnected metal line and the second front-disconnected metal line and the back metal layer.

6. The test structure facilitating TEM sample preparation according to claim 1, wherein Both the first back-disconnected metal line and the second back-disconnected metal line are disposed adjacent to the back target metal line.

7. The test structure facilitating TEM sample preparation according to claim 1, characterized in that, There is no connection between the first back-disconnected metal line and the second back-disconnected metal line and the front metal layer.

8. The test structure facilitating TEM sample preparation according to claim 1, characterized in that, The front metal layer further includes a plurality of pseudo-front metal lines, and the pseudo-front metal lines are spaced on a side of the first front-disconnected metal line and the second front-disconnected metal line away from the front target metal line, and there is no connection between the pseudo-front metal lines and the back metal layer.

9. The test structure facilitating TEM sample preparation according to claim 1, wherein The back metal layer further includes a plurality of pseudo-back metal lines, and the pseudo-back metal lines are spaced on a side of the first back-disconnected metal line and the second back-disconnected metal line away from the back target metal line, and there is no connection between the pseudo-back metal lines and the front metal layer.

10. The test structure for facilitating TEM sample preparation according to claim 1, characterized in that, The front metal layer is formed above the active region of the device, and the front target metal line is connected to the active region of the device through a contact hole.

11. The test structure facilitating TEM sample preparation according to claim 1, wherein The metal filled in the ISO via hole includes copper, copper alloy or tungsten.

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