Test structure and test method for mom capacitors
By designing a MOM capacitor test structure and utilizing a combination of a common reference ground and an independent test voltage, the change in metal layer current is monitored, solving the problem in existing technologies that cannot accurately determine the failure location of MOM capacitors, and realizing rapid and accurate failure analysis and reliability assessment.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HUAHONG INTEGRATED CIRCUIT (CHENGDU) CO LTD
- Filing Date
- 2026-03-30
- Publication Date
- 2026-06-23
Smart Images
Figure CN122270118A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor technology, and in particular to a test structure and test method for MOM capacitors. Background Technology
[0002] MOM (Metal-Oxide-Metal) capacitors are a common capacitor structure widely used in modern chip design, such as filters, power management circuits, radio frequency (RF) circuits, analog circuits, and digital circuit designs in integrated circuits. MOM capacitors are generally interdigitated capacitors formed by metal interconnects. To save area, multiple metal layers can be stacked. Since no additional processes are required, the capacitor fabrication can be completed using only metal layers, enabling high capacitance density and making it the mainstream capacitor structure application.
[0003] To assess the reliability of MOM capacitors, time-dependent dielectric breakdown (TDDB) testing is typically performed. This involves monitoring the breakdown time of the Low-k dielectric between metal layers under a constant electric field to predict the lifespan of the MOM capacitor. As those skilled in the art will understand, Low-k dielectrics are used to reduce capacitance between metal interconnects, thereby lowering signal delay and power consumption. Compared to traditional SiO2, they are more susceptible to process defects (porosity, impurities, etc.), leading to an increased risk of TDDB breakdown. TDDB predicts the lifespan of the Low-k dielectric by monitoring the Low-k breakdown time between metal-to-metal layers under a constant electric field.
[0004] When determining the failure location in the TDDB test of MOM capacitor structure, the failure of MOM capacitor first occurs at the location with the worst reliability of the contained metal layers. Subsequent failure analysis is required to locate the specific failed metal layer and the failure location, which is time-consuming and labor-intensive. Furthermore, the existing technology does not provide an accurate and clear method for testing MOM capacitors to determine the specific metal layer and failure location of MOM capacitor failure. Summary of the Invention
[0005] The purpose of this invention is to provide a test structure and test method for MOM capacitors, so as to solve the problem that the existing test methods for MOM capacitors cannot accurately and clearly determine the specific metal layer and failure location of MOM capacitor failure.
[0006] To address the aforementioned technical problems, based on one aspect of the present invention, a test structure for a MOM capacitor is provided. The MOM capacitor comprises stacked multiple metal layers. The test structure includes low-potential pads, multiple high-potential pads, and multiple current monitoring terminals. The low-potential application terminals of each metal layer of the MOM capacitor are commonly connected to the low-potential pads. The high-potential application terminals of different metal layers are respectively connected to different high-potential pads. The low-potential pads provide a reference ground, and the high-potential pads are used to apply a test voltage. The multiple current monitoring terminals correspond one-to-one with each of the multiple metal layers, and are used to monitor the current changes of the corresponding metal layer.
[0007] Optionally, the metal layer includes a first metal comb-shaped component and a second metal comb-shaped component;
[0008] The first metal comb-shaped component includes a first comb base and a plurality of first fingers. The first comb base extends along a first direction, and the first fingers extend from the first comb base along a second direction. The plurality of first fingers are arranged at intervals along the first direction. The first comb base is connected to the low-potential pad.
[0009] The second metal comb-shaped component includes a second comb base and a plurality of second fingers. The second comb base extends along a first direction, and the second fingers extend from the second comb base along a second direction. The plurality of second fingers are arranged sequentially at intervals along the first direction. The second comb base is connected to the corresponding high-potential pad.
[0010] The first finger and the second finger are arranged alternately and at intervals along the first direction, which is perpendicular to the second direction.
[0011] Optionally, the first and second fingers of each metal layer are spaced apart from each other by a dielectric material.
[0012] Optionally, the first fingers between different metal layers are connected through a first metal through-hole, and the second fingers between different metal layers are connected through a second metal through-hole.
[0013] Optionally, the test voltage values connected to the multiple high-potential pads may be the same or different.
[0014] Optionally, the current monitoring terminal determines whether the metal layer has failed and locates the failure position based on the jump factor of the current in the metal layer.
[0015] Optionally, if the current fed back from the current monitoring terminals of the three sequentially adjacent metal layers all change, and the current jump factor of the middle metal layer is larger, then it is determined that the middle metal layer of the three sequentially adjacent metal layers has failed, and the failure location is determined.
[0016] Optionally, if the current jump factor of the middle metal layer is larger and the current jump factor reaches a preset multiple, then it is determined that the middle metal layer of the three adjacent metal layers has failed, and the failure location is determined.
[0017] According to another aspect of the present invention, the present invention also provides a method for testing MOM capacitors, comprising:
[0018] The low-potential application terminals of each metal layer of the MOM capacitor are connected to the same reference ground, and the high-potential application terminals of each metal layer are connected to the test voltages of different voltage sources.
[0019] Monitor the current changes of each metal layer, and determine the failed metal layer based on the current changes of each metal layer, as well as locate the failure location in the failed metal layer.
[0020] Optionally, if the current of each of the three adjacent metal layers changes, and the current jump factor of the middle metal layer is greater, then it is determined that the middle metal layer of the three adjacent metal layers has failed, and the failure location is determined.
[0021] The test structure of the MOM capacitor as shown above connects the low-potential application terminal of each metal layer of the MOM capacitor to a common reference ground through a low-potential pad, and the high-potential application terminal of each metal layer is connected to an independent test voltage through an independent high-potential pad. The current change of the metal layer is monitored through the corresponding current monitoring terminal of each metal layer. Thus, during the test, the failure metal layer and the location of the failure can be quickly and accurately analyzed and located through the current change, without the need for additional failure analysis. It can also evaluate the reliability of the dielectric between the metal layers and the overall reliability of the MOM capacitor.
[0022] It should be noted that since the test method and the test structure are based on the same inventive concept and have the same or corresponding specific technical features, the test method and the test structure have the same technical effect, and will not be repeated here. Attached Figure Description
[0023] Those skilled in the art will understand that the accompanying drawings are provided to better understand the invention and do not constitute any limitation on the scope of the invention. Wherein:
[0024] Figure 1 This is a structural diagram of a MOM capacitor;
[0025] Figure 2 This is a test diagram of MOM capacitors in existing technology;
[0026] Figure 3 This is a schematic diagram of the test structure of a MOM capacitor according to an embodiment of the present invention;
[0027] Figure 4 This is a plan view of the test structure of a MOM capacitor according to an embodiment of the present invention;
[0028] Figure 5 This is a longitudinal cross-sectional view of a MOM capacitor according to an embodiment of the present invention;
[0029] Figure 6 This is a current variation diagram of the metal layer according to an embodiment of the present invention. Detailed Implementation
[0030] To make the objectives, advantages, and features of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale, and are only used to facilitate and clarify the explanation of the embodiments of this invention. Furthermore, the structures shown in the drawings are often part of the actual structures. In particular, different figures may emphasize different aspects and may sometimes use different scales.
[0031] As used in this invention, the singular forms “a,” “an,” and “the” include plural objects; the term “or” is generally used to mean “and / or”; the term “a number” is generally used to mean “at least one”; and the term “at least two” is generally used to mean “two or more”. Furthermore, the terms “first,” “second,” and “third” are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as “first,” “second,” or “third” may explicitly or implicitly include one or at least two of that feature. “One end” and “the other end,” as well as “proximal end” and “distal end,” generally refer to two corresponding parts, including not only endpoints. The terms “installed,” “connected,” and “joined” should be interpreted broadly, for example, as a fixed connection, a detachable connection, or an integral part; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediate medium; or a connection within two elements or an interaction between two elements. Furthermore, as used in this invention, the phrase "one element is disposed on another element" generally only indicates that there is a connection, coupling, cooperation, or transmission relationship between the two elements, and the connection, coupling, cooperation, or transmission between the two elements can be direct or indirect through an intermediate element. It should not be construed as indicating or implying a spatial positional relationship between the two elements, i.e., one element can be located arbitrarily inside, outside, above, below, or to one side of the other element, unless otherwise explicitly stated. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.
[0032] Figure 1 This is a structural diagram of a MOM capacitor. Figure 2 This is a test diagram of a MOM capacitor in existing technology. (See attached image.) Figure 1 and Figure 2 MOM capacitors consist of multiple stacked metal layers, each with a low-potential application terminal (Combs B) and a high-potential application terminal (Combs A). In existing technology, when performing reliability testing on MOM capacitors, the low-potential application terminals (Combs B) of each metal layer are connected to a common low-potential pad (PAD1), and the high-potential application terminals (Combs A) of each layer are connected to a common high-potential pad (PAD2). The low-potential pad (PAD1) provides a reference ground (GND), and the high-potential pad is connected to the test voltage (V). Thus, the TDDB reliability test of MOM capacitors primarily assesses the dielectric reliability between the metal layers by applying a constant test voltage and characterizes interlayer dielectric failure by detecting changes in current. Generally, a sudden change in current exceeding 10 times is considered a dielectric breakdown. This characterization method cannot accurately pinpoint the failure location of the MOM layer and requires secondary analysis and confirmation by subsequent personnel.
[0033] Based on this, the present invention proposes a test structure for MOM capacitors, see reference. Figure 3 and Figure 4 The test structure includes a low-potential pad PAD1, multiple high-potential pads PAD2~PADn, and multiple current monitoring terminals (not shown). The low-potential application terminals (Combs B) of each metal layer of the MOM capacitor are collectively connected to the low-potential pad PAD1. The high-potential application terminals (Combs A) of different metal layers are respectively connected to different high-potential pads. For example, the (X-1)th metal layer is connected to the high-potential pad PAD5, the Xth metal layer is connected to the high-potential pad PAD4, the X+1th metal layer is connected to the high-potential pad PAD3, and the X+2th metal layer is connected to the high-potential pad PAD2. See also... Figure 4 The Xth metal layer is M X This indicates that, correspondingly, the (X+1)th metal layer uses M... X+1 This indicates that the other metal layers can be derived accordingly, and will not be elaborated further here. The low-potential pad PAD1 provides a reference ground, while the high-potential pads PAD2~PADn are used to connect the test voltage. Multiple current monitoring terminals correspond one-to-one with multiple metal layers, and are used to monitor the current changes of the corresponding metal layer. The test voltage values connected to the multiple high-potential pads PAD2~PADn may be the same or different. Thus, this invention differs from the conventional MOM capacitor test structure. This invention proposes connecting the low-potential application terminal Combs B of each metal layer of the MOM capacitor to a common reference ground via the low-potential pad PAD1, and connecting the high-potential application terminal Combs A of each metal layer to an independent test voltage via an independent high-potential pad. This allows for analysis of the current changes corresponding to each metal layer during TDDB reliability assessment, enabling both inter-metal dielectric reliability assessment and real-time monitoring of failure locations, thus providing an overall evaluation of the MOM capacitor's reliability.
[0034] Further, see Figure 2 and Figure 4 Regarding the structure of the metal layer of the MOM capacitor, the metal layer includes a first metal comb-shaped component and a second metal comb-shaped component. The first metal comb-shaped component includes a first comb base 11 and a plurality of first fingers 12. The first comb base 11 is along a first direction ( Figure 4 Extending laterally, the first finger 12 extends from the first comb base 11 along the second direction (in the middle). Figure 4The first comb component extends vertically, with multiple first fingers 12 arranged sequentially at intervals along the first direction. A low-potential application terminal (Combs B) is disposed on the first comb substrate 11, which is connected to the low-potential pad PAD1. The second metal comb component includes a second comb substrate 21 and multiple second fingers 22. The second comb substrate 21 extends along the first direction, and the second fingers 22 extend from the second comb substrate 21 along a second direction. Multiple second fingers 22 are arranged sequentially at intervals along the first direction. A high-potential application terminal (Combs A) is disposed on the second comb substrate 21, which is connected to the corresponding high-potential pad. The multiple first fingers 12 and multiple second fingers 22 are arranged alternately and at intervals along the first direction, which is perpendicular to the second direction. The first fingers 12 and second fingers 22 of each metal layer are spaced apart by a dielectric material. The first fingers 11 between different metal layers are connected through a first metal via, and the second fingers 22 between different metal layers are connected through a second metal via. The metal through-holes are filled with tungsten plugs and other metals.
[0035] Furthermore, the current monitoring terminal determines whether the metal layer has failed and locates the failure point based on the current jump factor of the metal layer. For example, if the current jump factor of the metal layer reaches a preset multiple of 10, the metal layer is considered to have failed.
[0036] For example, if the current fed back from the current monitoring terminals of the three adjacent metal layers all change, and the current jump factor of the middle metal layer is larger, then it is determined that the middle metal layer of the three adjacent metal layers has failed, and the failure location is determined based on the current change.
[0037] For example, see Figure 5 and Figure 6 , Figure 6 The vertical axis represents "Sensing Current," characterizing the current change value. When comprehensively evaluating the reliability of the MOM capacitor, the current is analyzed through the corresponding current monitoring terminal. X-1 Current variation in the metal layer of the layer, M X Current variation in the metal layer and M X-1 The change in current in the metal layer of the layer, if M X If the current jump factor of the metal layer is the largest and reaches the preset multiple, then M is considered to be... X The metal layer of the layer fails, and the location of the failure is determined. For example, M X Current change ΔI in the metal layer of the layer Mx The maximum, considered M X The metal layer of the layer fails, in Figure 5 In the text, "Burn out" represents M.X The failure of the metal layer depends on the specific location of the failure.
[0038] This invention also provides a method for testing MOM capacitors, the method comprising:
[0039] The low-potential application terminals of each metal layer of the MOM capacitor are connected to the same reference ground, and the high-potential application terminals of each metal layer are connected to the test voltages of different voltage sources.
[0040] Monitor the current changes of each metal layer, and determine the failed metal layer based on the current changes of each metal layer, as well as locate the failure location in the failed metal layer.
[0041] Furthermore, if the current of each of the three adjacent metal layers changes, and the current jump factor of the middle metal layer is greater, then it is determined that the middle metal layer of the three adjacent metal layers has failed, and the failure location is determined.
[0042] It should be noted that those skilled in the art can understand the test method described above based on the aforementioned test structure for MOM capacitors, and will not be elaborated further here.
[0043] The above description is only a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the present invention.
Claims
1. A test structure for a MOM capacitor, the MOM capacitor comprising stacked multilayer metal layers, characterized in that, The test structure includes a low-potential pad, multiple high-potential pads, and multiple current monitoring terminals. The low-potential application terminals of each metal layer of the MOM capacitor are connected to the low-potential pads, and the high-potential application terminals of different metal layers are connected to different high-potential pads. The low-potential pads provide a reference ground, and the high-potential pads are used to connect the test voltage. The multiple current monitoring terminals correspond one-to-one with the multiple metal layers, and the current monitoring terminals are used to monitor the current changes of the corresponding metal layers.
2. The test structure for the MOM capacitor according to claim 1, characterized in that, The metal layer includes a first metal comb-shaped component and a second metal comb-shaped component; The first metal comb-shaped component includes a first comb base and a plurality of first fingers. The first comb base extends along a first direction, and the first fingers extend from the first comb base along a second direction. The plurality of first fingers are arranged at intervals along the first direction. The first comb base is connected to the low-potential pad. The second metal comb-shaped component includes a second comb base and a plurality of second fingers. The second comb base extends along a first direction, and the second fingers extend from the second comb base along a second direction. The plurality of second fingers are arranged sequentially at intervals along the first direction. The second comb base is connected to the corresponding high-potential pad. The first finger and the second finger are arranged alternately and at intervals along the first direction, which is perpendicular to the second direction.
3. The test structure for the MOM capacitor according to claim 2, characterized in that, The first and second fingers of each metal layer are spaced apart from each other by a dielectric material.
4. The test structure for the MOM capacitor according to claim 2, characterized in that, The first fingers between the different metal layers are connected through a first metal through-hole, and the second fingers between the different metal layers are connected through a second metal through-hole.
5. The test structure for the MOM capacitor according to claim 1, characterized in that, The test voltage values connected to the multiple high-potential pads may be the same or different.
6. The test structure for the MOM capacitor according to claim 1, characterized in that, The current monitoring terminal determines whether the metal layer has failed and locates the failure point based on the current jump factor of the metal layer.
7. The test structure for the MOM capacitor according to claim 6, characterized in that, If the current fed back from the current monitoring terminals of the three adjacent metal layers all change, and the current jump factor of the middle metal layer is larger, then it is determined that the middle metal layer of the three adjacent metal layers has failed, and the failure location is determined.
8. The test structure for the MOM capacitor according to claim 7, characterized in that, If the current jump factor of the middle metal layer is larger and the current jump factor reaches a preset multiple, then it is determined that the middle metal layer of the three adjacent metal layers has failed, and the failure location is determined.
9. A test method for a MOM capacitor, wherein the MOM capacitor comprises stacked multilayer metal layers, characterized in that, The testing method includes: The low-potential application terminals of each metal layer of the MOM capacitor are connected to the same reference ground, and the high-potential application terminals of each metal layer are connected to the test voltages of different voltage sources. Monitor the current changes of each metal layer, and determine the failed metal layer based on the current changes of each metal layer, as well as locate the failure location in the failed metal layer.
10. The test method for MOM capacitors according to claim 9, characterized in that, If the current of each of the three adjacent metal layers changes, and the current jump factor of the middle metal layer is greater, then it is determined that the middle metal layer of the three adjacent metal layers has failed, and the failure location is determined.