Electrical test structure for measuring overlay precision of metal layer and through hole

Abstract

The utility model provides an electrical property test structure for measuring overlay precision of a metal layer and a through hole. The electrical property test structure comprises a first test structure and a second test structure, each of the first test structure and the second test structure comprises a first metal layer, a second metal layer, a through hole and a test bonding pad; the second metal layer / first metal layer in the first test structure / second test structure is comb-shaped and comprises a plurality of second metal comb teeth / first metal comb teeth; a plurality of through holes are formed in the second metal comb teeth / the first metal comb teeth at intervals; the first metal layer / the second metal layer at least comprises a plurality of first metal strips / second metal strips which are arranged at intervals, and the through holes are formed between the adjacent first metal strips / second metal strips; and the distance between at least two through holes at different positions in the second metal comb teeth and the first metal strip / second metal strip close to the first metal strip / second metal strip is set according to a preset rule. According to the scheme, the problem of how to accurately and comprehensively measure alignment deviation of the through hole, the upper-layer metal wire and the lower-layer metal wire is solved.

Description

Technical Field

[0001] The utility model relates to a semiconductor device, in particular to an electrical test structure for measuring the overlay accuracy of a metal layer and a via hole. Background Art

[0002] In order to meet the requirements of the overall electrical performance of an integrated circuit, in the specific manufacturing process of a chip, circuit patterns of different structures are often stacked layer by layer. Among them, the stacking in the front-end manufacturing process of the integrated circuit is mainly the gate and the contact hole, and the stacking in the back-end is mainly the via hole and the metal wire.

[0003] Since the via hole and the metal wire are multi-layer repeated structures in the back-end, in order to ensure the accuracy and repeatability of the integrated circuit manufacturing process, it is necessary to accurately measure the alignment deviation between the via hole and the metal wire, thereby improving the yield of the product.

[0004] In the prior art, one way is to measure the alignment deviation value between the via hole and the metal wire by an optical method. However, for the optical method, due to its own limitation of the wavelength resolution, when the device size is continuously reduced, this method cannot accurately measure the alignment deviation between the via hole and the metal wire.

[0005] In addition, the current test structure designed by electrical testing confirms the accuracy and repeatability of the manufacturing process by detecting the alignment deviation between the lower metal wire and the via hole. However, this test structure cannot capture the alignment offset between the via hole and the upper metal wire, and thus cannot achieve precise control of the via hole and the upper and lower metal wires, and is limited in practical applications.

[0006] Therefore, how to accurately and comprehensively test the alignment deviation between the via hole and the metal wire has become a technical problem that those skilled in the art urgently need to solve. Summary of the Utility Model

[0007] The utility model provides an electrical test structure for measuring the overlay accuracy of a metal layer and a via hole to solve the problem of how to accurately and comprehensively measure the alignment deviation between the via hole, the upper metal wire and the lower metal wire.

[0008] According to the first aspect of the utility model, there is provided an electrical test structure for measuring the overlay accuracy of a metal layer and a via hole, including:

[0009] A first test structure and a second test structure;

[0010] Both the first test structure and the second test structure include a first metal layer, a second metal layer, a via hole and a test pad; the via hole is located between the first metal layer and the second metal layer, and the second metal layer is located above the first metal layer; the test pad is respectively connected to the first metal layer and the second metal layer above the second metal layer; wherein,

[0011] In the first test structure, the second metal layer has a comb shape and includes a plurality of second metal comb teeth; a plurality of the through holes are arranged at intervals on the second metal comb teeth; the first metal layer includes at least a plurality of first metal strips arranged at intervals, and the through holes are arranged between adjacent first metal strips; the distances between the through holes and the adjacent first metal strips at at least two different positions are set according to a preset rule.

[0012] In the second test structure, the first metal layer has a comb shape and includes a plurality of first metal comb teeth; a plurality of the through holes are arranged at intervals on the first metal comb teeth; the second metal layer includes at least a plurality of second metal strips arranged at intervals, and the through holes are arranged between adjacent second metal strips; the distances between the through holes and the adjacent second metal strips at at least two different positions are set according to a preset rule.

[0013] Optionally, the preset rule is that the distance between the through hole at the nth position and the adjacent first / second metal strip is equal and is n*A; the distance between the through hole at the mth position and the adjacent first / second metal strip is equal and is m*A; both n and m are natural numbers.

[0014] Optionally, it further includes a third test structure and a fourth test structure. The third test structure is the structure obtained by rotating the first test structure by 90 degrees, and is used to measure the offset of the through hole from the first metal layer in the direction perpendicular to the direction measured by the first test structure.

[0015] The fourth test structure is the structure obtained by rotating the second test structure by 90 degrees, and is used to measure the offset of the through hole from the second metal layer in the direction perpendicular to the direction measured by the second test structure.

[0016] Optionally, each of the plurality of first metal strips arranged at intervals is connected out through its own independent test pad.

[0017] Optionally, the distances between two adjacent through holes and their respective adjacent first metal strips are n*A and (n + 1)*A respectively.

[0018] Optionally, the plurality of first metal strips arranged at intervals are divided into a plurality of first metal units; the first metal strips in the first metal unit are arranged at equal intervals, and the adjacent left and right first metal strips of the plurality of through holes in the first metal unit are connected by metal and are connected out through a first left test pad and a first right test pad in a unified manner. The first metal unit has a cross-comb shape; the second metal layer corresponds to the plurality of first metal units and is divided into a plurality of second metal units in a comb shape, and the plurality of second metal units are connected by metal and are connected out through a second test pad in a unified manner.

[0019] Optionally, the distances between the vias in two adjacent first metal units and their respective adjacent first metal strips are n*A and (n + 1)*A, respectively.

[0020] Compared with the prior art, the present utility model has the following beneficial effects:

[0021] The technical solution provided by the present utility model can not only obtain the offset of the via in the X direction relative to the first metal layer by using the first test structure, but also obtain the overall offset of the via and the second metal layer relative to the second metal layer in the X direction by using the second test structure; thus, the offset of the second metal layer relative to the first metal layer in the X direction can be obtained through the above two offsets. Compared with the prior art solution that is only limited to measuring the offset of the via, the technical solution provided by the present utility model can measure the offsets of the upper and lower metal layers and the via simultaneously, solve the problem that the offset of the second metal layer (upper metal layer) cannot be measured simultaneously when measuring the offset of the via and the first metal layer, make up for the deficiency of the prior art that only focuses on the deviation of the via from the first metal layer and ignores the deviation calculation of the second metal layer, and improve the accuracy of deviation measurement.

[0022] In a further technical solution, the offset of the via relative to the first metal layer in the Y direction can be obtained by using the third test structure, and the overall offset of the via and the second metal layer relative to the first metal layer in the Y direction can be obtained by using the fourth test structure. Thus, the offset of the second metal layer relative to the first metal layer in the Y direction can be obtained through the above two offsets. Therefore, through the first test structure, the second test structure, the third test structure, and the fourth test structure provided by the technical solution of the present utility model, the offsets of the via relative to the first metal layer in the X and Y directions, and the offsets of the second metal layer relative to the first metal layer in the X and Y directions can be obtained; realizing the simultaneous measurement of the offsets of the upper and lower metal layers and the via in the X and Y directions, thereby obtaining more comprehensive and accurate offsets in each direction, and greatly improving the accuracy of offset measurement. Description of the Drawings

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present utility model. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0024] Figure 1 It is a schematic structural diagram of the second metal layer corresponding to several first metal units after several first metal strips arranged at intervals in the first test structure;

[0025] Figure 2 are the schematic structural diagram (a) and cross-sectional view (b) of the first test structure;

[0026] Figures 3(A) and 3(B) are the top view (a) and cross-sectional view (b) of the offset of the through hole in the X direction relative to the first metal layer when the through hole is offset to the left and to the right respectively in the embodiment of the present utility model;

[0027] Figure 4 is the schematic structural diagram corresponding to the second metal layer and the several first metal units after several first metal strips arranged at intervals in the third test structure are divided into several first metal units;

[0028] Figure 5 are the schematic structural diagram (a) and cross-sectional view (b) of the third test structure;

[0029] Figures 6(A) and 6(B) are the top view (a) and cross-sectional view (b) of the offset of the through hole in the Y direction relative to the first metal layer when the through hole is offset downward and upward respectively;

[0030] Figure 7 is the schematic structural diagram corresponding to the first metal layer and the several second metal units after several second metal strips arranged at intervals in the second test structure are divided into several second metal units;

[0031] Figure 8 are the schematic structural diagram (a) and cross-sectional view (b) of the second test structure;

[0032] Figures 9(A) and 9(B) are the top view (a) and cross-sectional view (b) of the total deviation of the through hole in the X direction and the second metal layer relative to the first metal layer when the through hole and the second metal layer are offset to the left and to the right as a whole;

[0033] Figure 10 is the schematic structural diagram corresponding to the first metal layer and the several second metal units after several second metal strips arranged at intervals in the fourth test structure are divided into several second metal units;

[0034] Figure 11 are the schematic structural diagram (a) and cross-sectional view (b) of the fourth test structure;

[0035] Figures 12(A) and 12(B) are the top view (a) and cross-sectional view (b) of the total deviation of the through hole in the Y direction and the second metal layer relative to the first metal layer when the through hole and the second metal layer are offset downward and upward as a whole. Detailed implementation manners

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are only a part rather than all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0037] The terms "first", "second", "third", "fourth", etc. (if any) in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and do not necessarily need to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order different from those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0038] In view of the fact that the prior art cannot accurately and comprehensively test the alignment deviation between the through holes and the metal lines, the present application proposes an electrical test structure for measuring the overlay accuracy of the metal layer and the through holes. The electrical test structure for measuring the overlay accuracy of the metal layer and the through holes includes:

[0039] A first test structure and a second test structure;

[0040] Both the first test structure and the second test structure include a first metal layer, a second metal layer, a through hole and a test pad; the through hole is located between the first metal layer and the second metal layer, and the second metal layer is located above the first metal layer; the test pads are respectively connected to the first metal layer and the second metal layer above the second metal layer; wherein,

[0041] In the first test structure, the second metal layer is in a comb shape and includes a plurality of second metal teeth; a plurality of the through holes are arranged at intervals on the second metal teeth; the first metal layer includes at least a plurality of first metal strips arranged at intervals, and the through holes are arranged between adjacent first metal strips; the distances between the through holes at at least two different positions and the adjacent first metal strips are set according to a preset rule;

[0042] In the second test structure, the first metal layer has a comb shape and includes a plurality of first metal comb teeth; a plurality of the through holes are arranged at intervals on the first metal comb teeth; the second metal layer at least includes a plurality of second metal strips arranged at intervals, and the through holes are arranged between adjacent second metal strips; the distances between the through holes and the adjacent second metal strips at at least two different positions are set according to a preset rule.

[0043] The electrical test structure for measuring the overlay accuracy of the metal layer and the through hole proposed by the present utility model can measure the offset of the through hole relative to the first metal layer in the X direction through the first test structure. Through the second test structure, the total offset of the through hole and the second metal layer relative to the first metal layer in the X direction can be measured. And through the first test structure and the second test structure, the offset of the second metal layer relative to the first metal layer in the X direction can be accurately calculated. This electrical test structure can simultaneously measure the offsets of the upper and lower metal layers and the through holes, thus solving the problem of incomplete offset measurement caused by the inability to measure the offset of the second metal layer in the prior art and avoiding the problem of inaccurate offset evaluation. Compared with the prior art, the offset measured by the present utility model is more comprehensive, and the evaluation of the offset based on this is more accurate.

[0044] Furthermore, the electrical test structure for measuring the overlay accuracy of the metal layer and the through hole provided by the present utility model further includes a third test structure and a fourth test structure. The third test structure is the structure obtained by rotating the first test structure by 90 degrees and is used to measure the offset of the through hole relative to the first metal layer in the direction perpendicular to the direction measured by the first test structure;

[0045] The fourth test structure is the structure obtained by rotating the second test structure by 90 degrees and is used to measure the offset of the through hole relative to the second metal layer in the direction perpendicular to the direction measured by the second test structure.

[0046] The third test structure is used to detect the offset of the through hole relative to the first metal layer in the Y direction. The fourth test structure is used to detect the overall offset of the through hole and the second metal layer relative to the first metal layer in the Y direction. Thus, the offset of the through hole relative to the first metal layer in the Y direction can be obtained by using the third test structure, and the overall offset of the through hole and the second metal layer relative to the first metal layer in the Y direction can be obtained by using the fourth test structure. Thus, the offset of the second metal layer relative to the first metal layer in the Y direction can be obtained through the aforementioned two offsets.

[0047] The technical solution of the present utility model will be described in detail below with specific embodiments. These specific embodiments below can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments.

[0048] Please refer to Figure 1 to FIG. 3, Figure 7to Figure 9, wherein, Figure 2 is a schematic structural diagram and a cross-sectional view of a first test structure of an electrical test structure for measuring the overlay accuracy of a metal layer and a via hole according to an embodiment of the present invention; Figure 1 is a schematic structural diagram of the second metal layer corresponding to several first metal units after several first metal strips arranged at intervals in the first test structure are divided into several first metal units; FIGS. 3(A) and 3(B) are a top view (a) and a cross-sectional view (b) of the offset of the via hole in the X direction relative to the first metal layer in the case of the via hole shifting to the left and the via hole shifting to the right respectively in the embodiment of the present invention; Figure 8 is a schematic diagram and a cross-sectional view of a second test structure therein, Figure 7 is a schematic structural diagram of the first metal layer corresponding to several second metal units after several second metal strips arranged at intervals in the second test structure are divided into several second metal units; FIGS. 9(A) and 9(B) are a top view (a) and a cross-sectional view (b) of the total deviation of the via hole and the second metal layer relative to the first metal layer in the X direction in the case of the overall left shift and right shift of the via hole and the second metal layer.

[0049] The electrical test structure for measuring the overlay accuracy of a metal layer and a via hole provided by the embodiment of the present invention includes a first test structure 10 and a second test structure 20. As Figure 2 shown, the first test structure can be understood that the second layer of metal is a comb structure, that is, the comb structure is on the upper layer of metal. As Figure 8 shown, the second test structure can be understood that the first layer of metal is a comb structure, that is, the comb structure is on the lower layer of metal. The first test structure and the second test structure will be specifically introduced below.

[0050] Among them, for the first test structure 10, please refer to Figures 1 - 3(A) and FIG. 3(B).

[0051] As Figure 2 shown, the first test structure includes a first metal layer, a second metal layer, a via hole 100 and test pads; the via hole 100 is located between the first metal layer and the second metal layer, and the second metal layer is located above the first metal layer; the test pads are respectively connected to the first metal layer and the second metal layer above the second metal layer. Specifically, the second test pad PAD-X is connected to the second metal layer; the first left test pad 104 (i.e., PAD-nL) and the first right test pad 105 (i.e., PAD-nR) are connected to the first metal layer.

[0052] Among them, in the first test structure, the second metal layer is in a comb shape and includes a plurality of second metal comb teeth; a plurality of the through holes 100 are arranged at intervals on the second metal comb teeth; the first metal layer includes at least a plurality of first metal strips arranged at intervals, for example, as Figure 2 shown, the adjacent first metal strips are respectively denoted as the left first metal strip 101 and the right first metal strip 102; the through hole 100 is arranged between the adjacent first metal strips; the distances between the through holes 100 at at least two different positions and the adjacent first metal strips are set according to a preset rule.

[0053] Among them, for the second test structure 20, please refer to Figures 7 - 9(A) and FIG. 9(B).

[0054] As Figure 8 shown, the second test structure includes a first metal layer, a second metal layer, through holes 200, and test pads; the through holes 200 are located between the first metal layer and the second metal layer, and the second metal layer is located above the first metal layer; the test pads are respectively connected to the first metal layer and the second metal layer above the second metal layer. Specifically, the second test pad 108 (i.e., PAD-X # ) is connected to the first metal layer; the first left test pad 204 (i.e., PAD-nL # ) and the first right test pad 205 (i.e., PAD-nR # ) are connected to the second metal layer.

[0055] Among them, in the second test structure, the first metal layer is in a comb shape and includes a plurality of first metal comb teeth; a plurality of the through holes 200 are arranged at intervals on the first metal comb teeth; the second metal layer includes at least a plurality of second metal strips arranged at intervals. For example, the adjacent second metal strips are respectively denoted as the left second metal strip 201 and the right second metal strip 202; the through hole 200 is arranged between the adjacent second metal strips; the distances between the through holes 200 at at least two different positions and the adjacent second metal strips are set according to a preset rule.

[0056] Among them, the preset rule is, for example, that the distance between the through hole at the nth position and the adjacent first / second metal strip is equal and is n*A; the distance between the through hole at the mth position and the adjacent first / second metal strip is equal and is m*A; both n and m are natural numbers. For example, it can be understood that: in the Figure 2 shown first test structure, the distances between the through holes at the nth position and the first metal strips are the same and are n*A; and in the Figure 8 shown second test structure, the distances between the through holes at the mth position and the second metal strips are the same and are m*A. Of course, it can also be understood that in the Figure 2In the first test structure shown, the distance between the through holes at the m-th position and the first metal strip is the same, and is m*A; and Figure 8 in the second test structure shown, the distance between the through holes at the n-th position and the second metal strip is the same, and is n*A.

[0057] As an example, Figure 2 as shown, in the first test structure, several first metal strips arranged at intervals are each connected out through independent test pads. Specifically, the left first metal strip 101 adjacent to each column of through holes 100 is led out through the first left test pad 104 (i.e., PAD-nL), and the right first metal strip 102 is led out through the first right test pad 105 (i.e., PAD-nR).

[0058] Similarly, Figure 8 as shown, in the second test structure, several second metal strips arranged at intervals are each connected out through independent test pads. Specifically, the left second metal strip 201 adjacent to each column of through holes 200 is led out through the first left test pad 204 (i.e., PAD-nL # ) and the right second metal strip 20 is led out through the first right test pad 205 (i.e., PAD-nR # ).

[0059] Furthermore, Figure 2 in the first test structure shown, the distances between the two adjacent through holes and their respective adjacent first metal strips are n*A and (n + 1)*A respectively; similarly, Figure 8 in the second test structure shown, the distances between the two adjacent through holes and their respective adjacent second metal strips are n*A and (n + 1)*A respectively. Since the through holes are set at different distances from the first metal strip / second metal strip, if current is measured between the corresponding two test pads, the offset can be judged according to the corresponding distance, which is simple and convenient.

[0060] Please combine on the basis of Figure 2 with Figure 1 , Figure 1As shown, a series of test units can be set in the first test structure in the embodiment of the present utility model. Specifically, several first metal strips arranged at intervals in the first test structure are divided into several first metal units, thereby forming a series of test units. A plurality of first metal strips in each first metal unit are arranged at equal intervals, and adjacent left first metal strips 101 of several columns of through-holes 100 in each first metal unit are respectively connected in a unified manner through metal connection to corresponding first left test pads 104; for convenience of description, a plurality of first left test pads 104 are respectively denoted as PAD-1L, PAD-2L, PAD-3L, … PAD-(N-1)L, PAD-NL; adjacent right first metal strips 102 of several columns of through-holes 100 in the first metal unit are respectively connected to corresponding first right test pads 105; for convenience of description, a plurality of first right test pads are respectively denoted as PAD-1R, PAD-2R, PAD-3R, … PAD-(N-1)R, PAD-NR; the first metal unit is in a cross-comb shape. The second metal layer corresponds to the several first metal units and is divided into several second metal units in a comb shape, and the several second metal units are connected in a unified manner through metal connection and led out through a second test pad 106 (i.e., PAD-X); by connecting several second metal units together on the same test pad, the area can be saved and the electrical test can be conveniently carried out.

[0061] Similarly, please combine on the basis of Figure 8 and Figure 7 , as Figure 7 shown, a series of test units can be set in the second test structure in the embodiment of the present utility model. Specifically, several second metal strips arranged at intervals in the second test structure are divided into several second metal units, thereby forming a series of test units. A plurality of second metal strips in each second metal unit are arranged at equal intervals, and adjacent left second metal strips 201 of several columns of through-holes 200 in the second metal unit are respectively connected in a unified manner through metal connection to corresponding first left test pads 204; for convenience of description, a plurality of first left test pads 204 are respectively denoted as PAD-1L # , PAD-2L # , PAD-3L # , … PAD-(N-1)L # , PAD-NL # ; adjacent right second metal strips 202 of several columns of through-holes 200 in the second metal unit are respectively connected to corresponding first right test pads 205; for convenience of description, a plurality of first right test pads are respectively denoted as PAD-1R # , PAD-2R # , PAD-3R # , … PAD-(N-1)R # , PAD-NR# ; The second metal unit is in a cross comb shape. The first metal layer corresponds to the several second metal units and is divided into several first metal units 203 in a comb shape. The several first metal units 203 are connected through metal and are jointly led out through the second test pad 108 (i.e., PAD-X # ). By connecting several first metal units 203 to the same test pad, the area can be saved and the electrical test can be conveniently carried out.

[0062] As an alternative implementation, as Figure 1 shown, in each test unit of the first test structure, the through hole is placed in the middle between the adjacent left first metal strip 101 and right first metal strip 102; and the distances from the through hole to the adjacent left first metal strip 101 and right first metal strip 102 are equal; among them, the distances from the through holes in several test units to their respective adjacent left first metal strips 101 are respectively Among them, is the minimum measurement scale value, which can be defined according to the accuracy requirements, such as 0.5nm, 1nm, 2nm, etc.; the minimum measurement scale value of the designed structure alignment deviation measurement can be defined according to the requirements, and different accuracies are adapted according to different process nodes to meet the requirements of each node. Among them, N is the total number of units set according to the requirements.

[0063] Furthermore, the distances from the through holes in two adjacent first metal units to their respective adjacent left first metal strip 101 and right first metal strip 102 are n*A and (n + 1)*A respectively. Since the through holes are set at different distances from the first metal strip, if there is current measured between the corresponding two test pads, the offset amount can be judged according to the corresponding distances, which is simple and convenient.

[0064] Similarly, as an alternative implementation, as Figure 7 shown, in each test unit of the second test structure, the through hole is placed in the middle between the adjacent left second metal strip 201 and right second metal strip 202, and the distances from the through hole to the adjacent left second metal strip 201 and right second metal strip 202 are equal; among them, the distances of several test units are respectively Among them, is the minimum measurement scale value, which can be defined according to the accuracy requirements, such as 0.5nm, 1nm, 2nm, etc.; N is the total number of units set according to the requirements.

[0065] Furthermore, the distances from the through holes in two adjacent second metal units to their respective adjacent left second metal strip 201 and right second metal strip 202 are n*A and (n + 1)*A respectively. Since the through holes are set at different distances from the second metal strip, if there is current measured between the corresponding two test pads, the offset amount can be judged according to the corresponding distances, which is simple and convenient.

[0066] Regarding the test principle of the first test structure, please refer to FIGS. 3(A) and 3(B). Among them, FIG. 3(A) is a top view (a) and a cross-sectional view (b) in which the through hole is offset to the left, and the through hole in the X direction is offset relative to the first metal layer; FIG. 3(B) is a top view (a) and a cross-sectional view (b) in which the through hole is offset to the right, and the through hole in the X direction is offset relative to the first metal layer.

[0067] Based on Figure 1 this, please refer to FIG. 3(A). When the through hole 100 is offset to the left by n (where n = 1, 2, 3... N - 1, N), in the actual process manufacturing, the through hole 100, the left first metal strip 101, and the second metal unit 103 will be short-circuited in the test unit with a corresponding pitch of n. The distance between the through hole 100 and the right first metal strip 102 is 2n. During electrical testing, a current will be detected between the second test pad PAD-X and the first left test pad 104 (i.e., PAD-nL).

[0068] Based on Figure 1 this, please refer to FIG. 3(B). When the through hole 100 is offset to the right by n (where n = 1, 2, 3... N - 1, N), in the actual process manufacturing, the through hole 100, the right first metal strip 102, and the second metal unit 103 will be short-circuited in the test unit with a corresponding pitch of n. The distance between the through hole 100 and the left first metal strip 101 is 2n. During electrical testing, a current will be detected between the second test pad PAD-X and the first right test pad 105 (i.e., PAD-nR).

[0069] It can be seen that the measurement result can be simply and quickly judged by whether a current can be detected in each test unit. Compared with the prior art, the solution of the present utility model has the advantages of higher efficiency and more accurate precision.

[0070] In addition, as a preferred embodiment, a logic operation device and a display device for offset calculation can be additionally provided. The logic operation device can obtain the offset based on the detected current and output it to the display device, and the display device can display the corresponding offset. In this embodiment, the offset of the through hole relative to the first metal layer in the X direction can be displayed.

[0071] Regarding the test principle of the second test structure, please refer to FIGS. 9(A) and 9(B). Among them, FIG. 9(A) is a top view (a) and a cross-sectional view (b) of the total left offset of the through hole and the second metal layer, and the total deviation of the through hole and the second metal layer in the X direction relative to the first metal layer; FIG. 9(B) is a top view (a) and a cross-sectional view (b) of the total right offset of the through hole and the second metal layer, and the total deviation of the through hole and the second metal layer in the X direction relative to the first metal layer.

[0072] Based on Figure 7 , please refer to FIG. 9(A). When the through hole 200 and the second metal layer are generally shifted to the left by n (where n = 1, 2, 3... N-1, N), in the actual process manufacturing, the test unit with a corresponding spacing of n will have a short circuit of the through hole 200, the left second metal strip 201, and the first metal unit 203. The spacing between the through hole 200 and the right second metal strip 202 is 2n. During the electrical test, a current will be detected between the second test pad 108 (i.e., PAD-X # ) and the first left test pad 204 (i.e., PAD-nL # ).

[0073] Based on Figure 7 , please refer to FIG. 9(B). When the through hole 200 and the second metal layer are generally shifted to the right by n (where n = 1, 2, 3... N-1, N), in the actual process manufacturing, the test unit with a corresponding spacing of n will have a short circuit of the through hole 200, the right second metal strip 202, and the first metal unit 203. The spacing between the through hole 200 and the left second metal strip 201 is 2n. During the electrical test, a current will be detected between the second test pad 108 (i.e., PAD-X # ) and the first right test pad 205 (i.e., PAD-nR # ).

[0074] It can be seen that in this embodiment, the overall offset amount of the through hole 200 and the second metal layer relative to the first metal layer in the X direction can be displayed, thus making up for the deficiency of the prior art that only focuses on the deviation of the through hole from the lower metal layer (the first metal layer) while ignoring the deviation of the upper metal layer (the second metal layer) relative to the lower metal layer (the first metal layer).

[0075] As a further preferred embodiment, the electrical test structure for measuring the overlay accuracy of the metal layer and the through hole provided by the present invention further includes a third test structure and a fourth test structure on the basis of including the aforementioned first test structure and second test structure; wherein, the third test structure is the structure after rotating the first test structure by 90 degrees, and is used to measure the offset amount of the through hole from the first metal layer in a direction perpendicular to the direction measured by the first test structure. The fourth test structure is the structure after rotating the second test structure by 90 degrees, and is used to measure the offset amount of the through hole from the second metal layer in a direction perpendicular to the direction measured by the second test structure.

[0076] The third test structure and the fourth test structure will be described in detail below.

[0077] Regarding the third test structure, please refer to Figures 4 - 6(A) and 6(B), wherein, Figure 5 is the schematic diagram (a) and cross-sectional view (b) of the third test structure; Figure 4It is a schematic structural diagram of the second metal layer corresponding to several first metal units obtained by dividing several first metal strips arranged at intervals in the third test structure; FIGS. 6(A) and 6(B) are a top view (a) and a cross-sectional view (b) of the offset of the through hole in the Y direction relative to the first metal layer in the case of downward offset and upward offset of the through hole.

[0078] As Figure 4 and Figure 5 shown, the third test structure 30 is Figure 1 the structure obtained by rotating the first test structure 10 shown in FIG. 1 by 90 degrees. Among them, each test unit in the third test structure 30 is obtained by rotating the corresponding test unit in the first test structure 10 by 90 degrees; the third test structure 30 is used to test the offset amount of the through hole relative to the first metal layer in the direction perpendicular to the direction measured by the first test structure 10. Similarly, the second metal units 103 in each test unit are connected together through metal connection to the second test pad 107 (i.e., PAD-Y). In this embodiment, the offset amount of the through hole relative to the first metal layer in the Y direction can be detected by the third test structure. The third test structure is only rotated by 90 degrees relative to the first test structure, resulting in a change in direction, from the X direction (horizontal direction or left-right direction) to the Y direction (vertical direction or up-down direction); in addition, other aspects of the third test structure are similar to those of the first test structure and will not be elaborated here.

[0079] Regarding the test principle of the third test structure, please refer to FIGS. 6(A) and 6(B), where FIG. 6(A) is a top view (a) and a cross-sectional view (b) of the offset of the through hole in the Y direction relative to the first metal layer when the through hole is downwardly offset; FIG. 6(B) is a top view (a) and a cross-sectional view (b) of the offset of the through hole in the Y direction relative to the first metal layer when the through hole is downwardly offset.

[0080] On Figure 4 this basis, please refer to FIG. 6(A). When the through hole 100 is downwardly offset by nA (where n = 1, 2, 3... N-1, N), in the actual process manufacturing, the through hole 100, the upper first metal strip 102, and the second metal unit 103 will be short-circuited in the test unit with a corresponding spacing of nA, and the spacing between the through hole 100 and the lower first metal strip 101 will be 2nA. During electrical testing, a current will be detected between the second test pad 107 (i.e., PAD-Y) and the first left test pad 104 (i.e., PAD-nB).

[0081] On Figure 4Based on this, please refer to FIG. 6(B). When the through hole 100 is upwardly offset by nA (where n = 1, 2, 3... N - 1, N), in the actual process manufacturing, the test unit with a corresponding pitch of nA will have a short circuit between the through hole 100, the first lower metal strip 101, and the second metal unit 103. The distance between the through hole 100 and the first upper metal strip 102 is 2nA. During electrical testing, a current will be detected between the second test pad 107 (i.e., PAD - Y) and the first right test pad 105 (i.e., PAD - nT).

[0082] Similarly, as a preferred embodiment, a logic operation device and a display device for offset calculation can be additionally provided. The logic operation device can obtain the offset based on the detected current and output it to the display device. Through the display device, the offset of the through hole 100 relative to the first metal layer in the Y direction can be displayed.

[0083] Regarding the fourth test structure, please refer to FIGS. 10 - 12(A) and 12(B); wherein, Figure 11 FIG. 12(A) is a schematic structural diagram (a) and a cross-sectional view (b) of the fourth test structure; Figure 10 FIG. 12(B) is a schematic structural diagram of the first metal layer and the corresponding structure of the several second metal units formed by dividing several second metal strips arranged at intervals in the fourth test structure; FIGS. 12(A) and 12(B) are a top view (a) and a cross-sectional view (b) of the total deviation of the through hole in the Y direction relative to the first metal layer when the through hole and the second metal layer are generally downwardly and upwardly offset.

[0084] As shown in Figure 10 and Figure 11 FIG. 12(A) and FIG. 12(B), the fourth test structure 40 is Figure 7 the structure obtained by rotating the second test structure 20 shown in FIG. 12(A) by 90 degrees. Each test unit in the fourth test structure 40 is obtained by rotating the corresponding test unit in the second test structure 20 by 90 degrees; the fourth test structure 40 is used to test the overall offset of the through hole and the second metal layer relative to the first metal layer in a direction perpendicular to the direction measured by the second test structure. Similarly, the first metal unit 203 in each test unit is integrally connected to the second test pad 109 (i.e., PAD - Y # ) through metal connection. In this embodiment, the overall offset of the through hole and the second metal layer relative to the first metal layer in the Y direction can be detected through the fourth test structure. The fourth test structure is only rotated by 90 degrees compared to the second test structure, thus causing a change in direction, from the X direction (horizontal direction or left - right direction) to the Y direction (vertical direction or up - down direction); other aspects of the fourth test structure are similar to those of the second test structure and will not be elaborated here.

[0085] Regarding the test principle of the fourth test structure, please refer to FIGS. 12(A) and 12(B). FIGS. 12(A) and 12(B) are a top view (a) and a cross-sectional view (b) of the total deviation of the through hole and the second metal layer in the Y direction relative to the first metal layer in the case of overall downward and upward offsets of the through hole and the second metal layer.

[0086] Based on Figure 10 , please refer to FIG. 12(A). When the through hole 200 and the second metal layer are overall downward offset by nA (where n = 1, 2, 3... N - 1, N), in the actual process manufacturing, the test unit with a corresponding pitch of nA will have a short circuit of the through hole 200, the second metal strip 201 below, and the first metal unit 203. The distance between the through hole 200 and the second metal strip 202 above is 2nA. During electrical testing, a current will be detected between the second test pad 109 (i.e., PAD - Y # ) and the first left test pad 204 (i.e., PAD - nB # ).

[0087] Based on Figure 10 , please refer to FIG. 12(B). When the through hole 200 and the second metal layer are overall upward offset by nA (where n = 1, 2, 3... N - 1, N), in the actual process manufacturing, the test unit with a corresponding pitch of nA will have a short circuit of the through hole 200, the second metal strip 202 above, and the first metal unit 203. The distance between the through hole 200 and the second metal layer 201 below is 2nA. During electrical testing, a current will be detected between the second test pad 109 (i.e., PAD - Y # ) and the first right test pad 205 (i.e., PAD - nT # ).

[0088] Thus, in this embodiment, through the fourth test structure, it is possible to measure the overall offset of the through hole 200 and the second metal layer relative to the first metal layer in the Y direction.

[0089] It can be seen from this that the technical solution provided by the embodiment of the present utility model can obtain the offset of the through hole relative to the first metal layer in the X direction by using the first test structure, and obtain the overall offset of the through hole and the second metal layer relative to the first metal layer in the X direction by using the second test structure. Thus, the offset of the second metal layer relative to the first metal layer in the X direction can be obtained through the above two offsets. For example: when the first test structure detects that the offset of the through hole relative to the first metal layer in the X direction is A, and the second test structure detects that the overall offset of the through hole and the second metal layer relative to the first metal layer in the X direction is 0, through simple calculation, it can be obtained that the offset of the second metal layer relative to the first metal layer in the X direction is -A, that is, the second metal layer and the through hole are respectively offset by A to the right and A to the left relative to the first metal layer.

[0090] In a further technical solution of the present utility model, the offset of the through hole relative to the first metal layer in the Y direction can be obtained by using the third test structure, and the overall offset of the through hole and the second metal layer relative to the first metal layer in the Y direction can be obtained by using the fourth test structure. Thus, the offset of the second metal layer relative to the first metal layer in the Y direction can be obtained through the above two offsets. The calculation process is similar to that of the first test structure and the second test structure described above, and will not be repeated.

[0091] Moreover, the electrical test structure provided by the present utility model for measuring the overlay accuracy of the metal layer and the through hole can not only meet the measurement of the vertical layer deviation of the through hole, but also meet the measurement requirements of the vertical layer deviation of the contact hole and the top through hole.

[0092] The technical solution provided by the present utility model can not only obtain the offset of the through hole relative to the first metal layer in the X direction by using the first test structure, but also obtain the overall offset of the through hole and the second metal layer relative to the second metal layer in the X direction by using the second test structure; thus, the offset of the second metal layer relative to the first metal layer in the X direction can be obtained through the above two offsets. Compared with the prior art solution that is only limited to measuring the offset of the through hole, the technical solution provided by the present utility model can simultaneously measure the offsets of the upper and lower metal layers and the through hole, solves the problem that the offset of the second metal layer (upper metal layer) cannot be measured simultaneously when measuring the offset of the through hole and the first metal layer, makes up for the deficiency of the prior art that only focuses on the deviation of the through hole from the first metal layer and ignores the deviation calculation of the second metal layer, and improves the accuracy of deviation measurement.

[0093] In a further technical solution, the offset of the vias in the Y direction relative to the first metal layer can be obtained by using the third test structure, and the overall offset of the vias and the second metal layer in the Y direction relative to the first metal layer can be obtained by the fourth test structure. Thus, the offset of the second metal layer relative to the first metal layer in the Y direction can be obtained from the above two offsets. Therefore, through the first test structure, the second test structure, the third test structure, and the fourth test structure provided in the technical solution of the present invention, the offset of the vias relative to the first metal layer in the X and Y directions, and the offset of the second metal layer relative to the first metal layer in the X / Y directions can be obtained; the offset of the upper and lower metal layers and the vias in the X and Y directions is measured simultaneously, so that more comprehensive and accurate offsets in each direction are obtained, and the accuracy of offset measurement is greatly improved.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrical test structure for measuring the overlay accuracy of a metal layer and a via, characterized in that Including: A first test structure and a second test structure; Both the first test structure and the second test structure include a first metal layer, a second metal layer, vias, and test pads; the vias are located between the first metal layer and the second metal layer, and the second metal layer is located above the first metal layer; the test pads are respectively connected to the first metal layer and the second metal layer above the second metal layer; wherein, In the first test structure, the second metal layer is in a comb shape and includes a plurality of second metal comb teeth; a plurality of the vias are arranged at intervals on the second metal comb teeth; the first metal layer at least includes a plurality of first metal strips arranged at intervals, and the vias are arranged between adjacent first metal strips; the distances between the vias at at least two different positions and the adjacent first metal strips are set according to a preset rule; In the second test structure, the first metal layer is in a comb shape and includes a plurality of first metal comb teeth; a plurality of the vias are arranged at intervals on the first metal comb teeth; the second metal layer at least includes a plurality of second metal strips arranged at intervals, and the vias are arranged between adjacent second metal strips; the distances between the vias at at least two different positions and the adjacent second metal strips are set according to a preset rule.

2. The electrical test structure for measuring the overlay accuracy of the metal layer and the via hole as described in claim 1, wherein, The preset rule is that the distance between the via at the nth position and the adjacent first / second metal strip is equal and is n*A; the distance between the via at the mth position and the adjacent first / second metal strip is equal and is m*A; both n and m are natural numbers.

3. The electrical test structure for measuring the overlay accuracy of a metal layer and a via hole as described in claim 2, wherein It further includes a third test structure and a fourth test structure, The third test structure is the structure after the first test structure is rotated by 90 degrees, and is used to measure the offset of the via from the first metal layer in the direction perpendicular to the direction measured by the first test structure; The fourth test structure is the structure after the second test structure is rotated by 90 degrees, and is used to measure the offset of the via from the second metal layer in the direction perpendicular to the direction measured by the second test structure.

4. The electrical test structure for measuring the overlay accuracy of the metal layer and the via hole as described in claim 2, wherein Each of the plurality of first metal strips arranged at intervals is connected out through its own independent test pad.

5. The electrical test structure for measuring the overlay accuracy of the metal layer and the via hole as described in claim 4, characterized in that, The distances between the two adjacent vias and their respective adjacent first metal strips are n*A and (n + 1)*A respectively.

6. The electrical test structure for measuring the overlay accuracy of the metal layer and the via as described in claim 2, wherein, The plurality of first metal strips arranged at intervals are divided into a plurality of first metal units; the first metal strips in the first metal unit are arranged at equal intervals, and the adjacent left and right first metal strips of the plurality of columns of vias in the first metal unit are connected through metal and are uniformly connected out through a first left test pad and a first right test pad, and the first metal unit is in a cross comb shape; the second metal layer corresponds to the plurality of first metal units and is divided into a plurality of second metal units in a comb shape, and the plurality of second metal units are connected through metal and are uniformly connected out through a second test pad.

7. The electrical test structure for measuring the overlay accuracy of the metal layer and the via hole as described in claim 6, characterized in that, The distances between the vias in two adjacent first metal units and their respective adjacent first metal strips are n*A and (n + 1)*A respectively.

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