Test structure for detecting etching performance of cut-off layer
By adding a test structure of surrounding the second metal wire around the design pattern, the problem of high cost and time-consuming detection of the cut-off layer etching performance in the prior art is solved, a fast and economical detection effect is achieved, and a safety window for the process is provided.
Patent Information
- Application Number
- CN202421927116.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-09
- Publication Date
- 2025-06-20
- Estimated Expiration
- 2034-08-09
AI Technical Summary
In advanced integrated circuit manufacturing processes at nodes of 10 nm or below, the prior art methods for detecting the etching performance of the etching layer require post-slicing TEM analysis, which is costly and time-consuming, and cannot quickly and economically detect the selection performance of the etching layer.
A test structure for detecting etching performance of a cut-off layer is provided, including at least one test unit consisting of a first metal wire, a second metal wire and a cut-off structure. By adding a second metal wire around the design pattern where a process problem may occur, the etching process selection performance of the cut-off layer is detected, and the process capability window for etching process selectivity of the cut-off structure is judged by measuring the resistance of the second metal wire.
The test structure has low design complexity and high process compatibility. It can quickly and economically detect the etching performance of the cut-off layer. It provides a variety of test units to effectively obtain a safety window for the process, reducing detection costs and time.
Smart Images
Figure CN223006775U_ABST
Abstract
Description
Technical Field
[0001] The utility model belongs to the technical field of semiconductor manufacturing, and particularly relates to a test structure for detecting the etching performance of a cut layer. Background Technique
[0002] In the advanced integrated circuit manufacturing process of 10 nm and below nodes, the use of EUV lithography machines can greatly shorten the process flow; if limited by the use of machines, the back-end process (Back End of Line, BEOL) can still achieve copper interconnect technology through the self-aligned lithography-etching-lithography-etching (SALELE) process.
[0003] In the advanced process of 10 nm and below nodes, the natural isolation between the endpoints of the back-end metal lines can no longer meet the design requirements, so a cut layer is introduced to achieve the isolation between the metal line endpoints in the metal layer. In a high-density metal interconnect layer, the use of a cut layer can achieve the isolation between metal line endpoints, so that the distance between the ends of metal lines is less than the exposure limit size of the exposure process, thereby increasing the density of the metal interconnect layer and improving the integration of integrated circuits.
[0004] The general implementation method is to form a graphic groove of the cut structure of the cut layer by dry etching, and fill the material into the groove to achieve the purpose of cutting the metal line, thereby realizing the isolation between metal line endpoints. Figure 1 It is a schematic diagram of the formation process of the cut structure. First, use a cut mask to determine the position of the graphic groove of the cut structure to be formed, and then perform etching. The filler 1 under the cut mask area will be selectively etched and removed to form a cut structure groove. Then, fill the filler 2 at the cut structure groove, and then perform etching again to etch the filler 1 to form a metal line groove for subsequent metal line filling. Since the filler 2 is not etched at this time, the isolation between metal line endpoints is realized. As Figure 1 shown in A of, when the etching selectivity is good, the cut structure groove only exists inside the sidewall and there is no damage to the sidewall, and the subsequent metal line filling is normal; as Figure 1 shown in B of, if the selectivity of this process is poor, during the formation of the cut structure groove, the material that should have been retained will be removed, causing damage to the sidewall, and then resulting in an increase in the graphic groove of the cut structure, blocking the subsequent metal line filling, and even causing adjacent metal lines to be disconnected, making the circuit fail.
[0005] Currently, the conventional failure test method for this process requires TEM (transmission electron microscope) analysis after slicing and sample preparation, which is costly and time-consuming; therefore, a new type of test structure needs to be provided for such process weak points to improve the detection speed and reduce the cost. Summary of the Invention
[0006] In order to solve all or part of the above-mentioned problems in the prior art, the present invention provides a test structure for detecting the etching performance of a cut layer, so as to detect the selection performance of the etching process of the graphic groove of the cut structure of the cut layer.
[0007] To achieve the above object, the present invention provides a test structure for detecting the etching performance of a cut layer, including at least one test unit; the test unit includes a first metal wire, a second metal wire and a cut structure; the first metal wire and the second metal wire belong to the same metal layer, and the cut structure is used to cut the metal wire of the metal layer; at least one cut structure is arranged on the first metal wire to cut the first metal wire; the second metal wire is arranged around the first metal wire in a surrounding manner, and both ends of the second metal wire are led out as pins. The design complexity of this test structure is low. By adding a second metal wire arranged in a surrounding manner around the design pattern where process problems may occur, the selection performance of the etching process of the cut layer can be detected; at the same time, this test structure does not require the introduction of other process processes and has extremely high process compatibility. Through this test structure, the resistance of the second metal wire can be measured by the two-terminal method, and the process ability window of the etching process selectivity of the cut structure can be judged by the change of the resistance value, and the detection is fast and the cost is low.
[0008] At least a part of the first metal wire is parallel to the second metal wire located around the first metal wire. The parallel arrangement of adjacent metal wires can simplify the design of the test structure and also conform more to the actual production process.
[0009] In the test unit, multiple cut structures arranged on the same first metal wire are parallel to each other. Repeatedly arranging multiple cut structures on the same first metal wire is beneficial to improving the detection sensitivity.
[0010] Multiple first metal wires are arranged in the test unit, and the second metal wire is arranged around the multiple first metal wires in a serpentine surrounding manner, and the distance between the part of the second metal wire parallel to the first metal wire and the adjacent first metal wire is equal. It can be used for simultaneous testing of multiple metal wires, and the serpentine surrounding arrangement can reduce the layout area.
[0011] The test structure includes multiple test units, and at least two test units with the same distance value are included in the multiple test units; the distance value refers to the distance value between the part of the second metal wire parallel to the first metal wire and the adjacent first metal wire in the test unit. Repeatedly arranging the same test unit can improve the accuracy of the test results.
[0012] The test structure includes a plurality of test units, and the plurality of test units include test units with different distance values; the test units with different distance values are sequentially set with a preset distance value step difference; the distance value refers to the distance between the part of the second metal wire parallel to the first metal wire and the adjacent first metal wire in the test unit. By setting a plurality of test units with different distance values and matching an appropriate distance step, the safety window of this process can be effectively obtained.
[0013] The test structure includes a plurality of test units, and the plurality of test units are respectively connected for testing. Each test unit is tested separately, and a single test structure can be used to complete multiple test purposes simultaneously.
[0014] The test structure includes a plurality of test units, and the plurality of test units are connected in series for testing. Connecting a plurality of test units in series can increase the utilization area and improve the detection efficiency.
[0015] The line width of the first metal wire is 5 - 30 nm; the line width of the second metal wire is 5 - 30 nm; the line width of the cutting structure is 5 - 30 nm, and the length is 80 - 1000 nm. By changing the dimensions of the cutting structure, the first metal wire, and the second metal wire to conform to the process node, it can adapt to process settings in different situations and effectively improve the applicable range of this test structure.
[0016] In the test unit, the distance between the part of the second metal wire parallel to the first metal wire and the adjacent first metal wire is 5 - 30 nm. By changing the mutual positional relationship between the first metal wire and the second metal wire to conform to the process node, it can adapt to process settings in different situations and obtain the process window range.
[0017] Compared with the prior art, the main beneficial effects of the present utility model are as follows: 1) The test structure provided by the present utility model has a low design complexity. Only by adding a serpentine metal wire around the design pattern can the selectivity of the etching process of the cutting layer be detected; 2) No other process needs to be introduced, and it has extremely high process compatibility; 3) A variety of test units are provided, and through the combination of different test units, the safety window of the process can be effectively obtained. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] In order to more clearly illustrate the technical solutions in the specific embodiments of the present utility model, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following described drawings are only some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.
[0019] Figure 1Schematic diagram of the formation process of the cutting structure. Figure 1 In [diagram], A is the schematic diagram when the etching selectivity is good. Figure 1 In [diagram], B is the schematic diagram when the etching selectivity is poor.
[0020] Figure 2 Schematic diagram of a design pattern where problems may occur in an etching process.
[0021] Figure 3 Schematic diagram of a test structure provided in the first embodiment of the present invention.
[0022] Figure 4 Schematic diagram of a test structure provided in the second embodiment of the present invention. Detailed implementation manners
[0023] Regarding the foregoing and other technical contents, features, and effects of the present invention, they will be clearly presented in the following detailed description of a preferred embodiment in conjunction with the reference drawings. The directional terms mentioned in the following embodiments, such as: up, down, left, right, front, or back, etc., are only with reference to the directions of the attached drawings. Therefore, the directional terms used are for illustration and not for limiting the present invention.
[0024] The test structure involved in the present invention includes test units. According to different test conditions, the test structure can be composed of one test unit or a combination of multiple test units. The following uses two embodiments in conjunction with the drawings to separately describe the test structure.
[0025] Embodiment 1:
[0026] Figure 2 Schematic diagram of a design pattern where problems may occur in an etching process. Figure 3 Schematic diagram of a test structure provided in the first embodiment of the present invention.
[0027] As Figure 2 shown, it is a schematic diagram of a design pattern of a metal layer. There are several first metal lines in the same metal layer. When a cutting structure of a cutting layer is horizontally arranged on the first metal line, it is possible that the etching process selectivity of the cutting layer (the cutting layer is composed of several cutting structures in the same layer) affects the metal layer pattern design. In the past, in order to detect the failure of this process, it was usually necessary to make a sliced sample and then perform TEM analysis, which is costly and time-consuming. This embodiment provides a test structure. As Figure 3 shown, by adding serpentine metal lines around the design pattern where process problems may occur, the test structure as shown in Figure 3 is formed. In other embodiments, it is not required that the design pattern where problems may occur must be as shown in Figure 2As shown, it can be various other types of design graphics, and a test structure can be formed by adding metal lines around it. The design complexity of this test structure is low.
[0028] As Figure 3 shown, in this embodiment, a test structure for detecting the etching performance of a cutting layer includes a test unit. In this embodiment, the test unit includes two first metal lines, and the two first metal lines are arranged in parallel in the up-down direction. Second metal lines are arranged around the two first metal lines in a surrounding manner. The first metal lines and the second metal lines belong to the same metal layer; the first metal lines are at least partially parallel to the second metal lines located around the first metal lines, that is, the second metal lines on the upper and lower sides of the first metal lines are both parallel to the first metal lines; the distances from the first metal lines to the second metal lines on the upper and lower sides of the first metal lines are the same (in this application, the distance value between the part of the second metal line parallel to the first metal line and the adjacent first metal line in the test unit, that is, the distance value between the part of the second metal line parallel to the first metal line and the two adjacent sides of its adjacent first metal line is called the distance value).
[0029] In this embodiment, 4 cutting structures (the cutting structures are used to cut the metal lines of the metal layer) are arranged in parallel across each first metal line, that is, 4 are arranged in parallel with each other. From Figure 3 it can be seen that when drawing the layout, the length of the cutting structure will exceed the line width of the first metal line and even overlap with the second metal line. This is because it is considered that during actual manufacturing, the length of the cutting structure will be reduced. If the size during layout drawing is just enough to cut the first metal line, it will cause the manufactured cutting structure to be unable to cut the first metal line. Therefore, generally during drawing, the length of the cutting structure will be extended to the second metal line so that it can cut the first metal line. In other embodiments, if the process can achieve precise manufacturing of the cutting structure, its length can be drawn normally or not extended to the second metal line, and this patent does not make specific limitations.
[0030] In other embodiments, the number of cutting structures on the first metal line in each test unit is at least one. When multiple cutting structures are provided, the multiple cutting structures are arranged in parallel on the first metal line with a certain spacing between them.
[0031] In this embodiment, the second metal lines arranged around the two first metal lines are integrated, and test pins Pin1 and test pins Pin2 are also provided at both ends of the test link formed by the second metal lines for taking out tests. Here, a part of both ends of the second metal line can be set as test pins Pin1 and test pins Pin2 for taking out, which can achieve the purpose of simplifying the test structure.
[0032] When there are multiple test units in the test structure, according to different test purposes, multiple test units can be separately connected out for testing, or the second metal lines in multiple test units can be connected in series with each other and then connected out for testing. Of course, some test units can be separately connected out for testing, and some test units can be connected in series and then connected out for testing. Taking the series connection test of two test units as an example, the two test units can be connected in a serpentine series, that is, the second metal lines in the two test units are connected in series by connecting the head and the tail. After the two test units are connected in series, test pins Pin1 and test pin Pin2 are set at both ends of the test link formed by the series connection of the second metal lines for connecting out for testing.
[0033] In this embodiment, the line width range of the cutting structure is 5 - 30 nm, and the length range of the cutting structure is 80 - 1000 nm; the line width range of the first metal line and the second metal line is 5 - 30 nm; the distance from the part of the second metal line parallel to the first metal line to the adjacent first metal line, that is, the distance value is 5 - 30 nm; the length of the overlapping area between both ends of the cutting structure and the second metal line is 0 - 30 nm, that is, the cutting structure can not overlap with the second metal layer. If there is an overlapping area between the two, the overlapping length of each end of the cutting structure and the second metal line in the extending direction of the cutting structure is below 30 nm.
[0034] As Figure 3 shown, testing can be carried out by connecting out through the above test pins Pin1 and test pin Pin2. The resistance of the test structure can be measured by the two - terminal method. By the measurement result, the safety window of the cutting structure for cutting the first metal line to the surrounding metal lines can be judged, that is, the groove etching process selection performance of the cutting structure can be characterized, and the detection is fast and the cost is low. The measured resistance can be compared with the theoretical resistance of the second metal line in the test structure. If the measured resistance value is too large, it indicates that the selection performance of the etching process is poor, and the sidewall is removed during the etching process and the second metal line is at least partially disconnected.
[0035] Embodiment 2:
[0036] As Figure 4 shown is a schematic diagram of a test structure provided by Embodiment 2 of the present utility model.
[0037] As Figure 4 shown, the test structure in this embodiment is composed of 3 test units, and the basic structure of each test unit is similar to that of Embodiment 1. A in Figure 4 can be regarded as the basic control unit, B in Figure 4 , C in Figure 4 , and Figure 4The difference of A in [description] lies in that in the test unit, the distances from the part of the second metal wire parallel to the first metal wire to the adjacent first metal wires are different. From Figure 4 A in [description] to Figure 4 C in [description], the distance values of the second metal wire to the adjacent first metal wires increase in sequence. The increase of the distance values can be set according to a preset distance value step difference, or can be freely set according to the test purpose. When testing this test structure, the resistance values measured by the 3 test units with different distance values and the corresponding relationship between the distance values from the part of the second metal wire parallel to the first metal wire in the test unit to the first metal wire can be used to determine the safety window of the etching process of the cut layer (the safety window refers to the distance that does not affect its adjacent metal wires during etching). When it is not enough to judge through 3 test units with different distance values or when you want to further clarify the safety window of the etching process, more test units with different distance values can be set.
[0038] In other embodiments, there are at least 2 test units, and the specific quantity can be set according to the actual situation. Among the multiple test units, there can be at least two test units with the same distance value.
[0039] When there are multiple test units in the test structure, according to different test purposes, multiple test units can be separately connected out for testing, or at least part of the second metal wires of multiple test units can be connected in series with each other and then connected out for testing.
[0040] In other embodiments, the differences between multiple test units can be various variables, such as the line width of the cut structure, the length of the cut structure, the line widths of the first metal wire and the second metal wire, the distance from the second metal wire to the first metal wire, and the length of the overlapping area between both ends of the cut structure and the second metal wire, etc.
[0041] In other embodiments, the test units forming the test structure can be the test units in one embodiment, or a combination of any multiple test units in multiple embodiments. It is not required that each test unit maintains the same or different number of variables, and can be set according to the specific application scenario to obtain the safety window of this process.
Claims
1. A test structure for detecting the etching performance of a cutting layer, characterized in that: including at least one test unit; The test unit includes a first metal wire, a second metal wire and a cutting structure; the first metal wire and the second metal wire belong to the same metal layer, and the cutting structure is used to cut the metal wire of the metal layer; At least one of the cutting structures is disposed on the first metal wire, and is used to cut off the first metal wire; The second metal wire is disposed around the first metal wire, and two ends of the second metal wire are connected as pins.
2. A test structure for detecting the etching performance of a cutting layer according to claim 1, characterized in that: The first metal line is at least partially parallel to the second metal line located around the first metal line.
3. A test structure for detecting the etching performance of a cutting layer according to claim 1, characterized in that: In the test unit, a plurality of cutting structures arranged on the same first metal line are arranged in parallel.
4. A test structure for detecting the etching performance of a cutting layer according to claim 1, characterized in that: The test unit is provided with a plurality of first metal wires, the second metal wires are arranged around the plurality of first metal wires in a serpentine shape, and the portion of the second metal wire parallel to the first metal wire is equidistant from the adjacent first metal wire.
5. The test structure for detecting the etching performance of the cutting layer according to claim 1, characterized in that: The test structure includes a plurality of test units, wherein the plurality of test units include at least two test units with the same distance value; The distance value refers to a distance value between a portion of the second metal line parallel to the first metal line and an adjacent first metal line in the test unit.
6. A test structure for detecting the etching performance of a cutting layer according to claim 1, characterized in that: The test structure includes a plurality of test units, wherein the plurality of test units include a plurality of test units with different distance values; The plurality of test units with different distance values are sequentially arranged with preset distance value step differences; The distance value refers to a distance value between a portion of the second metal line parallel to the first metal line and an adjacent first metal line in the test unit.
7. A test structure for detecting the etching performance of a cutting layer according to claim 1, characterized in that: The test structure includes a plurality of test units, and the plurality of test units are respectively connected for testing.
8. The test structure for detecting the etching performance of the cutting layer according to claim 1, characterized in that: The test structure includes a plurality of test units, and the plurality of test units are tested in series.
9. The test structure for detecting the etching performance of the cutting layer according to claim 1, characterized in that: The line width of the first metal line is 5-30nm; The line width of the second metal line is 5-30nm; The line width of the cut structure is 5-30 nm, and the length is 80-1000 nm.
10. The test structure for detecting the etching performance of the cutting layer according to claim 1, characterized in that: In the test unit, a distance between a portion of the second metal wire parallel to the first metal wire and an adjacent first metal wire is 5-30 nm.