A mom test structure and test chip for monitoring back end of line health
By employing a chain structure design with symmetrical metal wires and through holes in the MOM test structure, the problem of not being able to simultaneously measure metal resistance and capacitance in existing technologies is solved, achieving the effect of accurately assessing the health status of downstream processes on the same structure.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- GUANGLIWEI (BEIJING) TECHNOLOGY CO LTD
- Filing Date
- 2025-08-11
- Publication Date
- 2026-06-16
AI Technical Summary
In existing technologies, MOM capacitor structures cannot simultaneously measure metal resistance and capacitance, leading to data fitting bias or distortion, and making it impossible to accurately assess the health status of downstream processes.
Design a MOM test structure to simultaneously monitor metal resistance and capacitance on the same structure. By using symmetrical metal wires and through holes to form a chain structure, the simultaneous testing of resistance and capacitance can be achieved.
By improving area utilization, ensuring consistent metal structure and via density, reducing the impact of process differences, achieving accurate resistance and capacitance testing, and accurately assessing the health status of downstream processes.
Smart Images
Figure CN224368288U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of integrated circuit design and manufacturing, and in particular relates to a MOM test structure and test chip for monitoring the health of back-end processes. Background Technology
[0002] Current analog integrated circuits utilize various types of integrated capacitors, such as MOS (Metal-Oxide-Semiconductor), pn junctions, MIM (Metal-Insulator-Metal), MOM (Metal-Oxide-Metal), and others. Among these, MOM capacitors are one of the most widely used capacitors due to their excellent characteristics: 1) high capacitance density; 2) low parasitic capacitance; 3) symmetrical planar structure; 4) excellent RF characteristics; 5) good matching characteristics; 6) compatibility with back-end processes, requiring no additional masks or process steps, resulting in low cost. In actual chip manufacturing, MOM capacitors utilize the capacitive coupling effect between the board formed by standard metallized wiring and optional vias, ensuring good compatibility with existing processes. Therefore, they can also be used to monitor the health of back-end processes, such as overlay accuracy.
[0003] Currently, the MOM (Metal-on-Mold) structure used by various Testkey (electrical test structure) design companies and Fab (Fabrication Plant, semiconductor wafer fab) is a comb-and-teeth structure, which can only measure capacitance and cannot measure the resistance of the metal wires or vias used. See Figure 1 for details; among them, Figure 1A To measure the capacitance between single layers in a MOM structure (test pins are comb11 and comb12), Figure 1BThe MOM structure is used to measure the capacitance between upper and lower layers (test pins are comb11 and comb12, or comb21 and comb22). If further analysis of the downstream process is required, an additional KLV (Kelvin) structure needs to be designed to test the resistor value for correlation analysis, thereby determining whether the health problem in the downstream process is due to linewidth, overlay, or height offset. However, designing the resistance and capacitance test structures separately has several drawbacks: 1) It requires additional area to place the test keys; 2) The density of the metal structure or vias in the resistance test structure cannot be matched with that in the capacitance test structure. Typically, the density of the metal structure or vias in the resistance test structure is lower than that in the capacitance test structure. This density difference will affect the etching and chemical physical polishing processes, causing the data obtained from the resistance test structure to be further affected by the actual process, ultimately leading to data fitting deviations or even distortions; 3) Due to differences in placement or local environment, different test keys may still experience data fitting deviations or even distortions even when using the same metal layer or via layer.
[0004] Therefore, a solution is needed that can test resistance and capacitance on the same structure, while enabling rapid and accurate monitoring of metal resistance and in-layer capacitance, so as to accurately assess the health status of the current product's downstream processes. Utility Model Content
[0005] To address all or part of the problems in the prior art, this invention provides a test structure, test circuit, and test chip capable of simultaneously monitoring the performance of downstream metal processing, such as metal resistors and MOM capacitors.
[0006] Firstly, this embodiment provides a MOM test structure for monitoring the health of downstream processes, including at least two adjacent metal layers and at least one via layer for connecting the two adjacent metal layers;
[0007] The metal layer is provided with a plurality of first metal wires and a plurality of second metal wires, and the first metal wires and the second metal wires are arranged alternately in the metal layer.
[0008] The through-hole layer is provided with a plurality of first through holes and a plurality of second through holes, and the first through holes and the second through holes are arranged alternately in the through-hole layer;
[0009] Multiple first metal wires in at least two adjacent metal layers are connected by multiple first through holes in at least one of the through-hole layers to form a first chain structure; at least one first pin is provided at each end of the first chain structure.
[0010] Multiple second metal wires in at least two adjacent metal layers are connected by multiple second through holes in at least one of the through-hole layers to form a second chain structure; each end of the second chain structure is provided with at least one second pin.
[0011] In some embodiments, two first pins are provided at each end of the first chain structure;
[0012] The second chain structure has two second pins at each end.
[0013] In some embodiments, the four first pins at both ends of the first chain structure are used to test the resistance value of the first chain structure.
[0014] In some embodiments, the four second pins at both ends of the second chain structure are used to test the resistance value of the second chain structure.
[0015] In some embodiments, the first pin and the second pin are used to test the capacitance value between the first chain structure and the second chain structure.
[0016] In some embodiments, the first chain structure and the second chain structure satisfy at least one of the following symmetry rules:
[0017] 1) The metal lines belonging to the first chain structure and the second chain structure in the metal layer are symmetrical; the symmetry includes central symmetry and midline symmetry;
[0018] 2) The vias belonging to the first chain structure and the second chain structure in the via layer are symmetrical; the symmetry includes central symmetry and midline symmetry;
[0019] 3) The number, line width, and bus length of the metal lines belonging to the first chain structure and the second chain structure in the metal layer are the same;
[0020] 4) The number, diameter, and total area of the through holes belonging to the first chain structure and the second chain structure in the through hole layer are the same.
[0021] In some embodiments, at least two first pins at both ends of the first chain structure and at least two second pins at both ends of the second chain structure are used to test process mismatch.
[0022] In some embodiments, the MOM test structure for monitoring the health of downstream processes includes two adjacent metal layers: a lower metal layer and an upper metal layer, and a via layer for connecting the two adjacent metal layers;
[0023] Multiple first metal wires in the lower metal layer and the upper metal layer are connected by multiple first through holes in the through hole layer to form a first chain structure;
[0024] Multiple second metal wires in the lower and upper metal layers are connected by multiple second through holes in the through-hole layer to form a second chain structure.
[0025] In some embodiments, the MOM test structure for monitoring the health of downstream processes includes three adjacent metal layers: a lower metal layer, a middle metal layer, and an upper metal layer, and two via layers for connecting the two adjacent metal layers: a lower via layer and an upper via layer.
[0026] Multiple first metal wires in the lower metal layer and the middle metal layer are connected by multiple first through holes in the lower through hole layer, and multiple first metal wires in the middle metal layer and the upper metal layer are connected by multiple first through holes in the upper through hole layer, forming a first chain structure.
[0027] Multiple second metal wires in the lower and middle metal layers are connected by multiple second through holes in the lower through hole layer, and multiple second metal wires in the middle and upper metal layers are connected by multiple second through holes in the upper through hole layer, forming a second chain structure.
[0028] Secondly, this embodiment provides a test chip, including the MOM test structure for monitoring the health of the back-end process as described in the first aspect above.
[0029] The aforementioned MOM test structure for monitoring the health of downstream processes allows for the design of both resistance and capacitance test structures on the same structure. This not only effectively improves area utilization but also ensures complete consistency in the density of metal structures or vias across both the resistance and capacitance test structures. This avoids the impact of differences in actual manufacturing processes and enables accurate assessment of the health status of the current product's downstream processes. Furthermore, a test chip is disclosed that possesses the performance and beneficial effects of the aforementioned MOM test structure for monitoring the health of downstream processes. Attached Figure Description
[0030] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0031] Figure 1AThis is a schematic diagram of a MOM structure for measuring capacitance between single layers in the prior art;
[0032] Figure 1B This is a schematic diagram of a MOM structure for measuring the capacitance between upper and lower layers in the prior art;
[0033] Figure 2A This is a top view of the upper metal layer of a MOM test structure used for monitoring the health of downstream processes in one embodiment;
[0034] Figure 2B This is a top view of the lower metal layer of a MOM test structure used for monitoring the health of downstream processes in one embodiment;
[0035] Figure 3A This is a top view of the upper metal layer of a MOM test structure used for monitoring the health of downstream processes in another embodiment;
[0036] Figure 3B This is a top view of the middle metal layer of a MOM test structure used for monitoring the health of downstream processes in another embodiment;
[0037] Figure 3C This is a top view of the lower metal layer of a MOM test structure used for monitoring the health of downstream processes in another embodiment;
[0038] Figure 3D This is a left view of a MOM test structure used for monitoring downstream process health in another embodiment;
[0039] Figure 4 This is a schematic diagram of the resistance-capacitance correlation curve of the MOM structure under ideal conditions.
[0040] Figure 5 This is a scatter plot of the resistance-capacitance correlation of test results for MOM structures in the prior art.
[0041] Figure 6 This is a scatter plot of the resistance-capacitance correlation curve of the test results of the MOM test structure used to monitor the health of downstream processes in one embodiment. Detailed Implementation
[0042] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.
[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.
[0044] It should also be understood that the terms "comprising / including" or "having," etc., specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, in this specification, the term "and / or" includes any and all combinations of the associated listed items.
[0045] Currently, design companies like Testkey and major wafer fabs typically design resistance and capacitance test structures separately. This is because the density of metal structures or vias in the resistance and capacitance test structures cannot be matched. Generally, the density of metal structures or vias in the resistance test structure is lower than that in the capacitance test structure. This density difference will further affect the etching and chemical physical polishing processes, causing the data obtained from the resistance test structure and the capacitance test structure to be further affected by the actual process, ultimately leading to deviations or even distortions in the data fitting of the test results.
[0046] To achieve simultaneous monitoring of resistance and capacitance on the same structure, please refer to... Figures 2A-2B and Figures 3A-3D This embodiment provides a MOM test structure for monitoring the health of downstream processes, including at least two adjacent metal layers and at least one via layer for connecting the two adjacent metal layers.
[0047] Multiple first metal wires and multiple second metal wires are respectively disposed in the metal layer, and the first metal wires and the second metal wires are arranged alternately in the metal layer.
[0048] The through-hole layer is provided with a plurality of first through holes and a plurality of second through holes, and the first through holes and the second through holes are arranged alternately in the through-hole layer;
[0049] Multiple first metal wires in at least two adjacent metal layers are connected by multiple first through holes in at least one through-hole layer to form a first chain structure; at least one first pin is provided at each end of the first chain structure.
[0050] Multiple second metal wires in at least two adjacent metal layers are connected by multiple second through holes in at least one of the through-hole layers to form a second chain structure; each end of the second chain structure is provided with at least one second pin.
[0051] The aforementioned MOM test structure for monitoring the health of downstream processes allows for the design of both resistance and capacitance test structures on the same structure. This not only effectively improves area utilization but also ensures that the density of metal structures or vias is completely consistent across the resistance and capacitance test structures. This avoids the impact of differences in actual manufacturing processes and effectively guarantees a strong correlation between the test results (resistance Rs and capacitance Cap). As a result, the health status of the current product's downstream processes can be accurately assessed based on this correlation.
[0052] It should be noted that, in this embodiment, the number of first pins at both ends of the first chain structure and the number of second pins at both ends of the second chain structure can be two, that is, one first pin is provided at each end of the first chain structure and one second pin is provided at each end of the second chain structure, so that the resistance value of the first chain structure or the second chain structure can be measured using the two-end method respectively; or they can be four, that is, two first pins are provided at each end of the first chain structure and two second pins are provided at each end of the second chain structure, so that the resistance value of the first chain structure or the second chain structure can be measured using the four-end method respectively. The number of pins can be set according to the specific needs of the application scenario, and this application does not impose any specific limitations.
[0053] In this embodiment, the first chain structure has two first pins at each end, and the second chain structure has two second pins at each end. The four first pins at both ends of the first chain structure are used to test the resistance value of the first chain structure; the four second pins at both ends of the second chain structure are used to test the resistance value of the second chain structure.
[0054] Specifically, the resistance value of the first chain structure (i.e., the resistance value of the first chain structure between the first pins pinV1 and pinV2) can be measured using a four-terminal KLV test through the four first pins (pinV1, pinV2, pinI1, pinI2) at both ends; the resistance value of the second chain structure (i.e., the resistance value of the second chain structure between the second pins pinV1 and pinV2) can be measured using a four-terminal KLV test through the four second pins (pinV1, pinV2, pinI1, pinI2) at both ends. The principle of the four-terminal KLV is as follows: pinI1 is usually supplied with 1V (or 0.6V). Two voltages V1 and V2 are measured at pinV1 and pinV2 respectively, and two currents I1 and I2 are measured at pinI1 and pinI2 respectively. Under normal circumstances, I1 = I2 (the difference is not greater than 1uA), and the resistance value Rs is calculated as (V1-V2) / I2.
[0055] In this embodiment, the first pin and the second pin are used to test the capacitance value between the first chain structure and the second chain structure. That is, one first pin is selected in the first chain structure and one second pin is selected in the second chain structure, which can be used to test the capacitance value between the first chain structure and the second chain structure.
[0056] Specifically, a high voltage is applied to the first pin and a low voltage is applied to the second pin. The first and second chain structures will charge and discharge due to the voltage difference. By integrating the current from the repeated charging and discharging at the first pin, the capacitance value between the first and second chain structures can be calculated.
[0057] In this embodiment, the first chain structure and the second chain structure satisfy at least one of the following symmetry rules:
[0058] 1) The metal lines belonging to the first chain structure and the second chain structure in the metal layer are symmetrical; the symmetry includes central symmetry and midline symmetry;
[0059] 2) The through-holes in the through-hole layer that belong to the first chain structure and the second chain structure are symmetrical; the symmetry includes central symmetry and midline symmetry;
[0060] 3) The number, line width, and bus length of metal lines belonging to the first chain structure and the second chain structure in the metal layer are the same;
[0061] 4) The number, diameter, and total area of the through holes belonging to the first chain structure and the second chain structure in the through hole layer are the same.
[0062] Specifically, such as Figure 2A As shown, the metal lines belonging to the first chain structure and the second chain structure in the Upper metal layer are arranged symmetrically at the center, and the number, line width, and bus length of the metal lines belonging to the first chain structure and the second chain structure are the same; for example... Figure 2B As shown, the metal lines belonging to the first chain structure and the second chain structure in the lower metal layer are arranged symmetrically at the center, and the number, line width, and bus length of the metal lines belonging to the first chain structure and the second chain structure are the same; for example... Figure 2A and 2B As shown, the vias belonging to the first chain structure and the second chain structure in the via layer Via are arranged symmetrically at the center, and the number, diameter, and total area of the vias belonging to the first chain structure and the second chain structure are as follows (i.e., as shown in the figure). Figure 2A and 2BIn this diagram, the total area of the vias in the first chain structure refers to the total area of the vias indicated by comb1, and the total area of the vias in the second chain structure refers to the total area of the vias indicated by comb2. These are all identical. This structural design ensures that the MOM test structure used for monitoring the health of downstream processes in this embodiment possesses strong symmetry.
[0063] In this embodiment, at least two first pins at both ends of the first chain structure and at least two second pins at both ends of the second chain structure are used to test process mismatch. Because the MOM test structure for monitoring the health of downstream processes in this embodiment has strong symmetry, the resistance values measured by the first chain structure and the second chain structure can be used to analyze process mismatch; for example, if the measured resistance values of the first chain structure and the second chain structure differ greatly, it may indicate that the height / linewidth process is uneven.
[0064] In some of these embodiments, such as Figures 2A-2B As shown, the MOM test structure for monitoring the health of downstream processes includes two adjacent metal layers: a lower metal layer and an upper metal layer, and a via layer for connecting the two adjacent metal layers.
[0065] Multiple first metal wires (Comb1) in the lower metal layer and the upper metal layer are connected by multiple first through holes (Comb1) in the through hole layer to form a first chain structure (Comb1);
[0066] Multiple second metal wires (Comb2) in the lower and upper metal layers are connected by multiple second through holes (Comb2) in the through hole layer to form a second chain structure (Comb2).
[0067] It should be noted that in this embodiment, Upper metal and Lower metal refer to adjacent metal layers, that is, Lower metal is the lower metal layer and Upper metal is the upper metal layer. However, this application does not specifically limit which metal layer Upper metal and Lower metal are.
[0068] In some of these embodiments, such as Figures 3A-3DAs shown, the MOM test structure for monitoring the health of downstream processes includes three adjacent metal layers: a lower metal layer, a middle metal layer, and an upper metal layer, as well as two via layers for connecting the two adjacent metal layers: a lower via layer (Via1) and an upper via layer (Via2).
[0069] Multiple first metal wires (Comb1) in the lower metal layer and the middle metal layer are connected by multiple first through holes (Comb1) in the lower through hole layer, and multiple first metal wires (Comb1) in the middle metal layer and the upper metal layer are connected by multiple first through holes (Comb1) in the upper through hole layer, forming a first chain structure (Comb1).
[0070] Multiple second metal wires (Comb2) in the lower and middle metal layers are connected by multiple second through holes (Comb2) in the lower through hole layer, and multiple second metal wires (Comb2) in the middle and upper metal layers are connected by multiple second through holes (Comb2) in the upper through hole layer, forming a second chain structure (Comb2).
[0071] It should be noted that in this embodiment, Upper metal and Middle metal, Middle metal and Lower metal respectively represent adjacent metal layers, that is, Lower metal is the lower metal layer, Middle metal is the middle metal layer, and Upper metal is the upper metal layer. However, this application does not specifically limit which metal layer Upper metal, Middle metal, and Lower metal are.
[0072] This embodiment of the MOM (Motion of Management) test structure for monitoring downstream process health also has significant advantages in the analysis of test result data. For example... Figure 4 The figure shows a schematic diagram of the resistance-capacitance correlation curve obtained by fitting the resistance Rs and capacitance Cap of the test results of the MOM structure under ideal conditions. However, as shown in the figure... Figure 1A , Figure 1B To perform correlation fitting between resistance Rs and capacitance Cap using the conventional capacitance test structure shown, a different resistance test structure is used. After measuring resistance Rs and capacitance Cap, correlation fitting is performed, resulting in the following... Figure 5 The diagram shows a scatter plot illustrating the resistance-capacitance correlation; from Figure 5 It can be seen that the distance Figure 4The ideal state varies greatly, resulting in poor fitting performance and difficulty in capturing outliers. However, using methods such as... Figures 2A-2B The MOM test structure shown is used to monitor the health of downstream processes. It can simultaneously measure resistance Rs and capacitance Cap, and then perform correlation fitting to obtain the following results: Figure 6 The scatter plot of the resistance-capacitance correlation shown below; clearly compared to Figure 5 Closer Figure 4 In the ideal state, the fitting effect is significantly improved, and it can accurately capture... Figure 6 Outliers marked with dashed boxes are problematic dies and will be used for subsequent process health assessments.
[0073] In one embodiment, a test chip is also provided, comprising: the MOM test structure for monitoring the health of downstream processes described above. The solution provided by this test chip includes the implementation schemes described in the MOM test structure for monitoring the health of downstream processes, and will not be repeated here.
[0074] In the description of this specification, the references to terms such as "some embodiments," "other embodiments," "ideal embodiments," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example that are included in at least one embodiment or example of this application. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.
[0075] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0076] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.
Claims
1. A MOM (Multi-Operator) test structure for monitoring downstream process health, characterized in that, It includes at least two adjacent metal layers, and at least one through-hole layer for connecting the two adjacent metal layers; The metal layer is provided with a plurality of first metal wires and a plurality of second metal wires, and the first metal wires and the second metal wires are arranged alternately in the metal layer. The through-hole layer is provided with a plurality of first through holes and a plurality of second through holes, and the first through holes and the second through holes are arranged alternately in the through-hole layer; Multiple first metal wires in at least two adjacent metal layers are connected by multiple first through holes in at least one of the through-hole layers to form a first chain structure; at least one first pin is provided at each end of the first chain structure. Multiple second metal wires in at least two adjacent metal layers are connected by multiple second through holes in at least one of the through-hole layers to form a second chain structure; each end of the second chain structure is provided with at least one second pin.
2. The MOM test structure for monitoring downstream process health according to claim 1, characterized in that, The first chain structure has two first pins at each end; The second chain structure has two second pins at each end.
3. The MOM test structure for monitoring downstream process health according to claim 2, characterized in that, The four first pins at both ends of the first chain structure are used to test the resistance value of the first chain structure.
4. The MOM test structure for monitoring downstream process health according to claim 2, characterized in that, The four second pins at both ends of the second chain structure are used to test the resistance value of the second chain structure.
5. The MOM test structure for monitoring downstream process health according to claim 1, characterized in that, The first pin and the second pin are used to test the capacitance value between the first chain structure and the second chain structure.
6. The MOM test structure for monitoring downstream process health according to claim 1, characterized in that, The first chain structure and the second chain structure satisfy at least one of the following symmetry rules: 1) The metal lines belonging to the first chain structure and the second chain structure in the metal layer are symmetrical; the symmetry includes central symmetry and midline symmetry; 2) The vias belonging to the first chain structure and the second chain structure in the via layer are symmetrical; the symmetry includes central symmetry and midline symmetry; 3) The number, line width, and bus length of the metal lines belonging to the first chain structure and the second chain structure in the metal layer are the same; 4) The number, diameter, and total area of the through holes belonging to the first chain structure and the second chain structure in the through hole layer are the same.
7. The MOM test structure for monitoring downstream process health according to claim 6, characterized in that, At least two first pins at both ends of the first chain structure and at least two second pins at both ends of the second chain structure are used to test process mismatch.
8. The MOM test structure for monitoring downstream process health according to claim 1, characterized in that, It includes two adjacent metal layers: a lower metal layer and an upper metal layer, and a via layer for connecting the two adjacent metal layers; Multiple first metal wires in the lower metal layer and the upper metal layer are connected by multiple first through holes in the through hole layer to form a first chain structure; Multiple second metal wires in the lower and upper metal layers are connected by multiple second through holes in the through-hole layer to form a second chain structure.
9. The MOM test structure for monitoring downstream process health according to claim 1, characterized in that, It includes three adjacent metal layers: a lower metal layer, a middle metal layer, and an upper metal layer, as well as two via layers for connecting the two adjacent metal layers: a lower via layer and an upper via layer. Multiple first metal wires in the lower metal layer and the middle metal layer are connected by multiple first through holes in the lower through hole layer, and multiple first metal wires in the middle metal layer and the upper metal layer are connected by multiple first through holes in the upper through hole layer, forming a first chain structure. Multiple second metal wires in the lower and middle metal layers are connected by multiple second through holes in the lower through hole layer, and multiple second metal wires in the middle and upper metal layers are connected by multiple second through holes in the upper through hole layer, forming a second chain structure.
10. A test chip, characterized in that, Includes the MOM test structure for monitoring downstream process health as described in any one of claims 1 to 9.