CN111816639B - Test structure for monitoring alignment failure of through holes in SRAM storage area - Google Patents
Test structure for monitoring alignment failure of through holes in SRAM storage area Download PDFInfo
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- CN111816639B CN111816639B CN202010693411.9A CN202010693411A CN111816639B CN 111816639 B CN111816639 B CN 111816639B CN 202010693411 A CN202010693411 A CN 202010693411A CN 111816639 B CN111816639 B CN 111816639B
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- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L22/00—Testing or measuring during manufacture or treatment; Reliability measurements, i.e. testing of parts without further processing to modify the parts as such; Structural arrangements therefor
- H01L22/30—Structural arrangements specially adapted for testing or measuring during manufacture or treatment, or specially adapted for reliability measurements
- H01L22/32—Additional lead-in metallisation on a device or substrate, e.g. additional pads or pad portions, lines in the scribe line, sacrificed conductors
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- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/003—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring position, not involving coordinate determination
Abstract
The invention provides a test structure for monitoring the alignment failure of a through hole of an SRAM storage area, which comprises a first test unit and/or a second test unit; the first test unit is used for testing whether the through hole of the SRAM storage area has lateral drift; and the second test unit is used for testing whether the through hole of the SRAM storage area has longitudinal drift. The invention judges whether the through hole has transverse drift through the first test unit, can detect whether the tungsten plug formed in the through hole of the SRAM storage area communicates with the upper metal layer and the lower metal layer, and/or can judge whether the through hole has longitudinal drift through the second test unit, and can detect whether the tungsten plug formed in the through hole of the SRAM storage area communicates with the upper metal layer and the lower metal layer, thereby monitoring whether the through hole of the SRAM storage area has alignment failure.
Description
Technical Field
The invention relates to the field of semiconductor integrated circuit manufacturing, in particular to a test structure for monitoring through hole alignment failure of an SRAM storage area.
Background
A Static Random Access Memory (SRAM) is a Memory with a Static Access function, which can store data stored therein without a refresh circuit, and has advantages of large capacity, faster reading speed than a Dynamic Random Access Memory (DRAM), etc., however, the SRAM requires more than 6T transistors to store one Bit of information, as shown in fig. 1a, the SRAM requires 6T transistors to store one Bit of information, which affects the integration of the SRAM, and the complicated wiring (layout) thereof brings many challenges to the manufacturing process. Especially, the metal layer with high density is patterned, and the defect monitoring means is not effective at the factory, so that the SRAM failure problem is caused.
SRAM failures are often represented by simple read errors, such as 0 to 1, or 1 to 0, but the actual failure analysis process is complicated, such as failure analysis by failure address location and/or SEM slice confirmation of topography.
Disclosure of Invention
The invention aims to provide a test structure for monitoring the alignment failure of a through hole of an SRAM storage area, which can simply and conveniently test and judge whether the alignment of the through hole of the SRAM storage area is failed or not.
In order to solve the above problems, the present invention provides a test structure for monitoring the via alignment failure of an SRAM memory area, which includes a first test unit and/or a second test unit;
the first test unit is used for testing whether the through hole of the SRAM storage area has lateral drift; and
the second testing unit is used for testing whether the through hole of the SRAM storage area has longitudinal drift.
Optionally, the SRAM storage region has a first metal line extending laterally and/or longitudinally through the SRAM storage region;
the first testing unit is used for testing whether a first through hole adjacent to a first metal line longitudinally penetrating through the SRAM storage area has lateral drift; and
the second testing unit is used for testing whether the first through hole adjacent to the first metal line transversely penetrating through the SRAM storage area has longitudinal drift.
Further, the SRAM storage area comprises a plurality of lower metal layers, a first through hole, a tungsten plug formed in the first through hole and an upper metal layer which are sequentially arranged from bottom to top;
the lower metal layer comprises a first metal line, a second metal line and a third metal line, the second metal line is arranged adjacent to the first metal line, and the second metal line is connected with the upper metal layer through the tungsten plug; the third metal line and the second metal line are arranged adjacently, and the third metal line is positioned on one side of the second metal line far away from the first metal line; and the tungsten plugs in the first through holes are communicated with the second metal lines and the upper metal layer, and the first through holes are arranged on a straight line which is approximately parallel to the first metal lines.
Further, the first test unit and the second test unit respectively comprise a lower virtual metal layer, a plurality of first virtual through holes and an upper virtual metal layer which are sequentially arranged from bottom to top, and the first virtual through holes are communicated with the lower virtual metal layer and the upper virtual metal layer;
tungsten plugs are filled in the first virtual through holes, and the upper layer virtual metal layer is connected with the tungsten plugs in the first virtual through holes in series;
the first dummy through hole and the first through hole are formed simultaneously, the shape of the first dummy through hole is the same as that of the first through hole, the lower dummy metal layer and the lower metal layer are formed simultaneously, and the upper dummy metal layer and the upper metal layer are formed simultaneously.
Further, the lower dummy metal layer of the first test unit includes:
the first virtual metal lines are arranged along the longitudinal direction;
the plurality of second virtual metal lines are arranged along the extending direction of the second virtual metal lines, and the arranged plurality of second virtual metal lines form a first connecting structure; and the number of the first and second groups,
and the third virtual metal lines are arranged on one side of the second virtual metal lines far away from the first virtual metal lines.
Further, the lower dummy metal layer of the second test unit includes:
the first virtual metal lines are arranged along the transverse direction;
the second virtual metal lines are arranged along the extending direction of the second virtual metal lines, and the second connection structure is formed by the arranged second virtual metal lines; and (c) a second step of,
and the third virtual metal lines are arranged on one side, far away from the first virtual metal lines, of the second virtual metal lines.
Furthermore, the first connection structure includes a plurality of first portions, the first portions of the first connection structure are disposed in parallel with the first dummy metal lines of the first test unit, and the first dummy vias of the first test unit are formed on the first portions of the first connection structure; and
the second connection structure comprises a plurality of first parts, the first parts of the second connection structure are arranged in parallel with the first virtual metal lines of the second test unit, and the first virtual through holes of the second test unit are formed in the first parts of the second connection structure.
Further, the first connection structure includes a plurality of first portions and a plurality of second portions, the first portions of the first connection structure are disposed in parallel with the first dummy metal lines of the first test unit, the first dummy vias of the first test unit are formed on the first portions of the first connection structure, and the second portions of the first connection structure connect the adjacent first portions, so that the first portions and the second portions of the first connection structure are connected in series; and
the second connection structure comprises a plurality of first parts and a plurality of second parts, the first parts of the second connection structure are arranged in parallel with the first virtual metal lines of the second test unit, the first virtual through holes of the second test unit are formed on the first parts of the second connection structure, and the second parts of the second connection structure are connected with the adjacent first parts, so that the first parts and the second parts of the second connection structure are connected in series.
Furthermore, the first connecting structures are arranged in a serpentine shape, and the second connecting structures are arranged in a serpentine shape.
Furthermore, the shape of the upper layer dummy metal layer of the first test unit is substantially the same as that of the first connection structure, the upper layer dummy metal layer connects the first dummy through holes of the first test unit in series and has two free ends, and the two free ends are respectively used for connecting positive pressure and negative pressure to judge whether the first dummy through holes of the first test unit drift laterally; and
the shape of the upper virtual metal layer of the second test unit is approximately the same as that of the second connection structure, the first virtual through holes of the second test unit are connected in series and provided with two free ends, and the two free ends are respectively used for connecting positive pressure and negative pressure so as to judge whether the first virtual through holes of the second test unit vertically drift.
Compared with the prior art, the invention has the following beneficial effects:
the invention provides a test structure for monitoring the alignment failure of a through hole of an SRAM storage area, which comprises a first test unit and/or a second test unit; the first test unit is used for testing whether the through hole of the SRAM storage area has lateral drift; and the second test unit is used for testing whether the through hole of the SRAM storage area has longitudinal drift. The invention judges whether the through hole has transverse drift through the first test unit, can detect whether the tungsten plug formed in the through hole of the SRAM storage area communicates with the upper metal layer and the lower metal layer, and/or can judge whether the through hole has longitudinal drift through the second test unit, and can detect whether the tungsten plug formed in the through hole of the SRAM storage area communicates with the upper metal layer and the lower metal layer, thereby monitoring whether the through hole of the SRAM storage area has alignment failure.
Furthermore, the first testing unit is used for testing whether the first through hole adjacent to the first metal line longitudinally penetrating through the SRAM storage area has lateral drift; and the second test unit is used for testing whether the first through hole adjacent to the first metal line transversely penetrating through the SRAM storage area has longitudinal drift or not so as to monitor whether the through hole of the SRAM storage area is aligned and failed or not.
Drawings
FIG. 1a is a circuit diagram of a typical six transistor SRAM (6T SRAM) cell;
FIG. 1b is a distribution diagram of SRAM failure occurring in a wafer;
FIG. 2 is a schematic diagram of layout of lower metal layers and vias of an SRAM memory region;
FIG. 3 is a schematic structural diagram of a test structure for monitoring via alignment failure in an SRAM memory area according to an embodiment of the present invention;
FIG. 4 is a schematic structural diagram of a test structure for monitoring via alignment failure in an SRAM memory area according to a third embodiment of the present invention;
description of reference numerals:
a-failed SRAM;
10-a lower metal layer; 11-a first metal line; 12-a second metal line; 13-a third metal line; 20-a through hole; 21-a first via;
100-a first test unit; 110-a first dummy metal line; 120 a-a second dummy metal line; 120-a first connecting structure; 121-a first portion; 122-a second portion; 130-a third dummy metal line; 140-a first virtual via;
200-a second test unit; 210-a first dummy metal line; 220-a second connecting structure; 221-a first portion; 230-a third dummy metal line; 240-first virtual via.
Detailed Description
As shown in fig. 1b, the locations of the failed SRAMs a are distributed more at the edge of the wafer. Through easy failure analysis (EFA, PFA), the inventor finds that tungsten loss occurs in a tungsten plug connecting an upper metal layer and a lower metal layer, and the upper metal layer and the lower metal layer cannot be normally communicated due to the tungsten loss, so that SRAM failure is caused. Analysis shows that the tungsten loss of the tungsten plug is caused by the deviation of the through hole formed with the tungsten plug, and specifically, after the through hole is deviated, the bottom of the through hole exposes the dielectric layer exposed by the lower metal layer but not the surface of the lower metal layer. In the CMP (Chemical Mechanical Polishing) process of the tungsten plug, the environment of the dielectric layer is complex relative to the situation that the bottom of the via exposes the surface of the lower metal layer, which results in tungsten filling failure. In addition, slurry in the CMP process permeates to the exposed surface of the lower metal layer along the via hole, causing corrosion of the lower metal layer. These defects cannot be discovered in time during the manufacturing process and require detailed failure analysis after subsequent CP testing.
Further analysis has found that offset vias are typically found in the lower metal layers near the metal lines that extend through the SRAM memory region, particularly those that extend through the SRAM memory region, and that the vias that laterally or longitudinally cover the surface of the underlying metal layer below them are more susceptible to drift due to their smaller process window.
Based on the above research, the test structure for monitoring the alignment failure of the through hole of the SRAM memory area provided by the present invention can test whether the tungsten plug formed in the through hole near the metal line penetrating through the SRAM memory area has tungsten missing, that is, can detect whether the tungsten plug formed in the through hole near the metal line penetrating through the SRAM memory area communicates with the upper metal layer and the lower metal layer.
A test structure for monitoring SRAM memory area via alignment failure according to the present invention will be described in further detail below. The present invention will now be described in more detail with reference to the accompanying drawings, in which preferred embodiments of the invention are shown, it being understood that one skilled in the art may modify the invention herein described while still achieving the advantageous effects of the invention. Accordingly, the following description should be construed as broadly as possible to those skilled in the art and not as limiting the invention.
In the interest of clarity, not all features of an actual implementation are described. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific details must be set forth in order to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art.
In order to make the objects and features of the present invention more comprehensible, embodiments of the present invention are described in detail below with reference to the accompanying drawings. It is to be noted that the drawings are in a very simplified form and are all used in a non-precise ratio for the purpose of facilitating and distinctly aiding in the description of the embodiments of the invention.
Example one
FIG. 2 is a schematic diagram of layout of lower metal layers and vias of an SRAM memory region. As shown in fig. 2, the SRAM memory area includes SRAM cells arranged in an array, and assuming that the arrangement direction of the rows of the SRAM cells is a horizontal direction, the arrangement direction of the columns of the SRAM cells is a vertical direction.
The SRAM storage area comprises a plurality of lower metal layers 10, through holes 20, tungsten plugs formed in the through holes and upper metal layers (not shown in the figure), wherein the lower metal layers 10, the through holes 20, the tungsten plugs and the upper metal layers are sequentially arranged from bottom to top, and the tungsten plugs are used for communicating the lower metal layers 10 and the upper metal layers. The lower metal layer 10 may be any metal layer other than the top metal layer, and the upper metal layer may be any metal layer other than the first metal layer. In this embodiment, the lower metal layer 10 is, for example, a first metal layer, and the upper metal layer is a second metal layer.
The lower metal layer 10 includes a first metal line 11, a second metal line 12, and a third metal line 13. The first metal line 11 penetrates through the SRAM storage region, and the first metal line 11 may be parallel to a column of an SRAM array of the SRAM storage region, so that the direction of the first metal line 11 is, for example, arranged along a longitudinal direction. The second metal line 12 is adjacent to the first metal line 11, and the second metal line 12 is connected to the upper metal layer through the tungsten plug. The third metal line 13 is, for example, in a square shape, a straight strip shape, an L shape, or other conventional shapes, and is disposed near the second metal line 12, specifically, the third metal line 13 is disposed adjacent to the second metal line 12, and the third metal line 13 is located on a side of the second metal line 12 away from the first metal line 11. The through holes 20 include a plurality of first through holes 21, and tungsten plugs in the first through holes 21 communicate with the second metal lines 12 and the upper metal layer. The first via 21 covers the surface of the second metal line 12 in the lateral direction, so that the drift of the first via 21 is most pronounced when the via 20 drifts. Specifically, because the first via 21 is disposed adjacent to the first metal line 11, when the lower metal layer 10 is formed, the first metal line 11 physically presses the second metal line 12 in a transverse direction, so that when the via 20 is formed thereon, a large alignment deviation exists between the first via 21 and the second metal line 12 in the transverse direction, that is, the first via 21 drifts in the transverse direction, thereby causing the SRAM to fail. Therefore, the size of the first via 21 in the lateral direction is the same as the size of the second metal line 12 in the lateral direction, that is, the size of the first via 21 in the width direction of the second metal line 12 is the same as the width size of the second metal line 12, and the first via 21 is easily shifted in the lateral direction. In the present embodiment, the through holes 20 include a plurality of the first through holes 21, and are disposed on a straight line substantially parallel to the first metal line 11.
Fig. 3 is a schematic structural diagram of a test structure for monitoring SRAM memory area via alignment failure according to this embodiment. Referring to fig. 3 and fig. 2, the present embodiment provides a test structure for monitoring SRAM memory area via alignment failure.
The test structure comprises a first test unit 100, wherein the first test unit 100 is used for testing whether a through hole of an SRAM storage area has lateral drift, and further, the first test unit is used for testing whether a first through hole adjacent to a first metal line longitudinally penetrating through the SRAM storage area has lateral drift. The first test unit 100 sequentially comprises a lower virtual metal layer, a plurality of first virtual through holes 140 and an upper virtual metal layer from bottom to top, the first virtual through holes 140 are communicated with the lower virtual metal layer and the upper virtual metal layer, tungsten plugs are filled in the first virtual through holes 140, and the upper virtual metal layer is connected in series with a plurality of tungsten plugs in the first virtual through holes. The first dummy via 140 is formed at the same time as the first via 21, and the shape of the first dummy via 140 is the same as that of the first via 21, and the cross-sectional dimension of the first dummy via 140 is the same as that of the first via 21. The lower virtual metal layer and the lower metal layer are formed at the same time, and the upper virtual metal layer and the upper metal layer are formed at the same time.
The lower dummy metal layer includes a plurality of first dummy metal lines 110, a plurality of second dummy metal lines 120a, and a plurality of third dummy metal lines 130, the first dummy metal lines 110 are disposed along a longitudinal direction, the shape of the first dummy metal lines 110 is the same as that of the first metal lines 11, the first dummy metal lines 110 and the first metal lines 11 are, for example, both long strips, and the width (the direction perpendicular to the extending direction of the first metal lines 11, i.e., the transverse direction in this embodiment) of the first dummy metal lines 110 is the same as that of the first metal lines 11, and the lengths may be the same or different as required. The second dummy metal lines 120a are, for example, long. The plurality of second dummy metal lines 120a are arranged along an extending direction of the second dummy metal lines 120a, the arranged plurality of second dummy metal lines 120a form a first connection structure 120, the first connection structure 120 includes a plurality of first portions 121, or includes a plurality of first portions 121 and a plurality of second portions 122, the plurality of first portions are arranged in parallel with the first dummy metal lines, and the first dummy vias 140 are formed on the first portions 121 of the first connection structure 120. The second portion 122 connects the adjacent first portions 121 such that the first and second portions 121 and 122 are connected in series. The first connecting structure 120 is, for example, U-shaped, Z-shaped, bow-shaped, rectangular wave-shaped, or the like. The distance between the first portions 121 and the adjacent first dummy metal lines 110 is the same as the distance between the second metal line 12 and the first metal line 11.
The third dummy metal line 130 is disposed on a side of the second dummy metal line 120a away from the first dummy metal line 110, and has a shape identical to that of the third metal line 13, and a size identical to or different from that of the third metal line 13 (for example, the third metal line 13 is scaled up or down). The distance between the third dummy metal line 130 and the second dummy metal line 120a adjacent to the third dummy metal line 130 may be the same as the distance between the third metal line 13 and the second metal line 12, or may be enlarged or reduced according to the scaling of the third dummy metal line 130.
In one embodiment, the first test unit 100 includes one of the first dummy metal lines 110, and the first connection structure 120 includes one or two first portions, one of the first portions 121 is disposed in parallel and adjacent to one side of the first dummy metal line 110; two first portions 121 are disposed in parallel and adjacent to each other on two sides of the first dummy metal line 110. Two of the first portions 121 may be connected in series by one second portion 122, or may be separately provided without the second portions being connected in series. In another embodiment, the first test unit 100 includes at least two first dummy metal lines 110, the first connection structure 120 is disposed in a serpentine shape, and a first portion of the first connection structure is disposed in parallel with the adjacent first dummy metal lines 110. The third dummy metal line 130 is disposed at least at a space between adjacent first portions 121, and a distance between the third dummy metal line 130 and the first portions 121 is the same as a distance between the third metal line 13 and the first metal line 11, so that the first dummy via 140 formed subsequently and the first via 21 have the same formation environment.
The first dummy vias 140 are formed above the first portion 121 of the first connection structure 120, such that a plurality of the first dummy vias 140 are arranged along the extending direction of the first dummy metal line 110, and the length of the first dummy vias 140 in the transverse direction is less than or equal to the length of the second dummy metal line in the width direction (i.e., the transverse direction). Preferably, the length of the first dummy via 140 in the lateral direction is equal to the length of the second dummy metal line 120a in the lateral direction. When the first dummy via 140 is shifted laterally under the extrusion of the first dummy metal line 110, it is obtained that the first via 21 is shifted.
The upper dummy metal layer connects the tungsten plugs in the first dummy via 140 in series, and the upper dummy metal layer is, for example, a metal line similar to the first connection structure 120 in shape and has two free ends, and the two free ends are respectively connected with positive pressure and negative pressure to determine whether the first dummy via 140 has lateral drift, thereby determining whether the first via 21 has lateral drift, and further detecting whether the tungsten plugs formed in the first via 21 near the metal line penetrating through the SRAM memory area communicate the upper metal layer and the lower metal layer.
Example two
The difference from the first embodiment is that the first metal line penetrates through the SRAM storage region, and the first metal line may be parallel to a row of an SRAM array of the SRAM storage region, so that the direction of the first metal line is, for example, arranged in a lateral direction. The first metal line has longitudinal physical extrusion on the second metal line, so that when the through hole is formed, alignment deviation exists between the first through hole and the second metal line in the longitudinal direction, that is, the first through hole drifts in the transverse direction, and the SRAM is prone to failure.
The test structure comprises a second test unit, wherein the whole of the second test unit and the whole of the first test unit form an included angle of 90 degrees, namely the second test unit can be obtained by rotating the first test unit by 90 degrees in a plane formed by the longitudinal direction and the transverse direction from the longitudinal direction to the transverse direction.
The second testing unit is used for testing whether the through hole of the SRAM storage area has longitudinal drift, and further, the second testing unit is used for testing whether the first through hole adjacent to the first metal line transversely penetrating through the SRAM storage area has longitudinal drift. The second testing unit sequentially comprises a lower virtual metal layer, a plurality of first virtual through holes and an upper virtual metal layer from bottom to top, the lower virtual metal layer comprises a plurality of first virtual metal lines, a plurality of second virtual metal lines and a plurality of third virtual metal lines, and the first virtual metal lines are arranged along the transverse direction. The plurality of second virtual metal lines are arranged along the extending direction of the second virtual metal lines, and the plurality of second virtual metal lines after arrangement form a second connecting structure. The first part of the second connecting structure is arranged along the transverse direction and is arranged adjacent to the first virtual metal line in parallel, so that whether the first virtual through hole drifts longitudinally can be judged, and whether a tungsten plug formed in the first through hole near the metal line penetrating through the SRAM storage area communicates with the upper metal layer and the lower metal layer can be detected.
EXAMPLE III
Fig. 4 is a schematic structural diagram of a test structure for monitoring an SRAM memory area via alignment failure according to a third embodiment of the present invention. As shown in fig. 4, the lower metal layer of the SRAM memory area of this embodiment has at least two first metal lines, and the extending direction of at least one of the first metal lines is different from the extending direction of the other first metal lines. In this embodiment, two first metal lines are disposed in the lower metal layer of the SRAM memory region, where one first metal line is parallel to a row of the SRAM array of the SRAM memory region, and the other first metal line is parallel to a column of the SRAM array of the SRAM memory region.
The test structure comprises a first test unit 100 and a second test unit 200, wherein the first test unit 100 comprises a plurality of first virtual metal lines 110 arranged in parallel, the first virtual metal lines 110 of the first test unit 100 are arranged along the longitudinal direction, the first test unit 100 further comprises a first connecting structure 120 arranged in a serpentine shape, a plurality of first parts 121 of the first connecting structure 120 are arranged in parallel and adjacent to the first virtual metal lines 110 of the first test unit, and third virtual metal lines 130 are arranged at intervals between adjacent first parts 121, so that each first part 121 is always adjacent to the first virtual metal lines 110 and the third virtual metal lines 130 and is positioned between the first virtual metal lines 110 and the third virtual metal lines 130. The shape of the third dummy metal line 130 includes any one of an L shape, a long strip shape, and a rectangle, or a combination of two, and the specific shape thereof can be determined according to the distance of the interval between the adjacent first portions and/or the shape of the first portions.
The first dummy via 140 is disposed on the first portion 121, the shape of the upper dummy metal layer of the first test unit 100 is substantially the same as the first connection structure, the first dummy via 140 of the first test unit 100 is connected in series and has two free ends, and the two free ends are respectively connected with positive pressure and negative pressure to determine whether the first dummy via has lateral drift, thereby determining whether the first via has lateral drift, and further detecting whether a tungsten plug formed in the first via near a metal line penetrating through the SRAM memory area communicates the upper metal layer and the lower metal layer.
The second test unit 200 includes a plurality of first dummy metal lines 210 arranged in parallel, the first dummy metal lines 210 are arranged along a transverse direction, the first dummy metal lines 110 and the first dummy metal lines 210 enclose a rectangle, and the adjacent first dummy metal lines 110 and the first dummy metal lines 210 may not be connected.
The second test unit 200 further includes a second connection structure 220 arranged in a serpentine shape, a plurality of first portions 221 of the second connection structure 220 are parallel to and adjacent to the first dummy metal lines 210, and the third dummy metal lines 230 are disposed at intervals between adjacent first portions 221, so that each first portion 221 is always adjacent to the first dummy metal lines 210 and the third dummy metal lines 230 and is located between the first dummy metal lines 210 and the third dummy metal lines 230. The shape of the third dummy metal line 230 includes any one or a combination of L-shape, straight bar shape and rectangle shape, and the specific shape thereof can be determined according to the distance of the interval between the adjacent first portions 221 and/or the shape of the first portions.
The first dummy via 240 of the second test unit is disposed on the first portion 221 of the second test unit, the shape of the upper dummy metal layer of the second test unit 200 is substantially the same as the second connection structure 220, the first dummy via 240 of the second test unit is connected in series and has two free ends, and the two free ends are respectively connected with positive pressure and negative pressure, so as to determine whether the first dummy via has longitudinal drift, and further detect whether the tungsten plug formed in the first via near the metal line penetrating through the SRAM memory area communicates the upper metal layer and the lower metal layer.
Of course, the present embodiment is also applicable to an SRAM memory area having only the first metal line extending in one direction, and in this case, only the first test unit or the second test unit needs to be tested.
In summary, the test structure for monitoring the alignment failure of the through hole in the SRAM memory area according to the present invention includes a first test unit and/or a second test unit; the first test unit is used for testing whether the through hole of the SRAM storage area has lateral drift; and the second test unit is used for testing whether the through hole of the SRAM storage area has longitudinal drift. . The invention judges whether the through hole has transverse drift through the first test unit, can detect whether the tungsten plug formed in the through hole of the SRAM storage area communicates with the upper metal layer and the lower metal layer, and/or can judge whether the through hole has longitudinal drift through the second test unit, and can detect whether the tungsten plug formed in the through hole of the SRAM storage area communicates with the upper metal layer and the lower metal layer, thereby monitoring whether the through hole of the SRAM storage area has alignment failure.
Furthermore, the first testing unit is used for testing whether the first through hole adjacent to the first metal line longitudinally penetrating through the SRAM storage area has lateral drift; and the second test unit is used for testing whether the first through hole adjacent to the first metal line transversely penetrating through the SRAM storage area has longitudinal drift or not so as to monitor whether the through hole of the SRAM storage area has alignment failure or not.
In addition, unless otherwise specified or indicated, the description of the terms "first" and "second" in the specification is only used for distinguishing various components, elements, steps and the like in the specification, and is not used for representing logical relationships or sequential relationships among the various components, elements, steps and the like.
It is to be understood that while the present invention has been described in conjunction with the preferred embodiments thereof, it is not intended to limit the invention to those embodiments. It will be apparent to those skilled in the art that many changes and modifications can be made, or equivalents employed, to the presently disclosed embodiments without departing from the intended scope of the invention. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention are within the scope of the technical solution of the present invention, unless the technical essence of the present invention is not departed from the content of the technical solution of the present invention.
Claims (9)
1. A test structure for monitoring through hole alignment failure of an SRAM storage area is characterized by comprising a first test unit and/or a second test unit, wherein the SRAM storage area comprises a plurality of lower metal layers, a first through hole, a tungsten plug formed in the first through hole and an upper metal layer which are sequentially arranged from bottom to top; the lower metal layer is provided with a first metal line which transversely and/or longitudinally penetrates through the SRAM storage area;
the first testing unit comprises two free ends and is used for testing whether a first through hole adjacent to a first metal line longitudinally penetrating through the SRAM storage area has transverse drift or not by respectively connecting positive pressure and negative pressure to the two free ends; and
the second testing unit comprises two free ends and is used for testing whether the first through hole adjacent to the first metal line transversely penetrating through the SRAM storage area has longitudinal drift or not by respectively connecting positive pressure and negative pressure to the two free ends.
2. The test structure of claim 1, wherein the lower metal layer further comprises a second metal line and a third metal line, the second metal line being disposed adjacent to the first metal line, the second metal line connecting the upper metal layer through the tungsten plug; the third metal line is arranged adjacent to the second metal line, and the third metal line is positioned on one side of the second metal line, which is far away from the first metal line; and the tungsten plug in the first through hole is communicated with the second metal line and the upper metal layer, and the plurality of first through holes are arranged on a straight line parallel to the first metal line.
3. The test structure of claim 2, wherein the first test unit and the second test unit each comprise a lower dummy metal layer, a plurality of first dummy vias, and an upper dummy metal layer sequentially arranged from bottom to top;
the first virtual through hole is communicated with the lower virtual metal layer and the upper virtual metal layer, a tungsten plug is filled in the first virtual through hole, and the upper virtual metal layer is connected with the tungsten plugs in the first virtual through holes in series;
the first dummy through hole and the first through hole are formed simultaneously, the shape of the first dummy through hole is the same as that of the first through hole, the lower dummy metal layer and the lower metal layer are formed simultaneously, and the upper dummy metal layer and the upper metal layer are formed simultaneously.
4. The test structure of claim 3, wherein the lower dummy metal layer of the first test cell comprises:
the first virtual metal lines are arranged along the longitudinal direction;
the plurality of second virtual metal lines are arranged along the extending direction of the second virtual metal lines, and the arranged plurality of second virtual metal lines form a first connecting structure; and the number of the first and second groups,
and the third virtual metal lines are arranged on one side of the second virtual metal lines far away from the first virtual metal lines.
5. The test structure of claim 4, wherein the lower dummy metal layer of the second test cell comprises:
the first virtual metal lines are arranged along the transverse direction;
the plurality of second virtual metal lines are arranged along the extending direction of the second virtual metal lines, and the arranged plurality of second virtual metal lines form a second connecting structure; and the number of the first and second groups,
and the third virtual metal lines are arranged on one side of the second virtual metal lines far away from the first virtual metal lines.
6. The test structure of claim 5,
when the arranged second virtual metal lines form a first connection structure, the first connection structure comprises a plurality of first parts, the first parts of the first connection structure are arranged in parallel with the first virtual metal lines of the first test unit, and the first virtual through holes of the first test unit are formed in the first parts of the first connection structure; and
when the second connection structure is formed by the arranged second virtual metal lines, the second connection structure comprises a plurality of first parts, the first parts of the second connection structure are arranged in parallel with the first virtual metal lines of the second test unit, and the first virtual through holes of the second test unit are formed in the first parts of the second connection structure.
7. The test structure of claim 5,
when the arranged second virtual metal lines form a first connection structure, the first connection structure comprises a plurality of first parts and a plurality of second parts, the first parts of the first connection structure and the first virtual metal lines of the first test unit are arranged in parallel, the first virtual through holes of the first test unit are formed on the first parts of the first connection structure, and the second parts of the first connection structure are connected with the adjacent first parts, so that the first parts and the second parts of the first connection structure are connected in series; and
when the arranged second virtual metal lines form a second connection structure, the second connection structure comprises a plurality of first parts and a plurality of second parts, the first parts of the second connection structure and the first virtual metal lines of the second test unit are arranged in parallel, the first virtual through holes of the second test unit are formed in the first parts of the second connection structure, and the second parts of the second connection structure are connected with the adjacent first parts, so that the first parts and the second parts of the second connection structure are connected in series.
8. The test structure of claim 5, wherein the first connection structure is in a serpentine arrangement and the second connection structure is in a serpentine arrangement.
9. The test structure of claim 5,
the shape of the upper virtual metal layer of the first test unit is the same as that of the first connecting structure, the first virtual through holes of the first test unit are connected in series and provided with two free ends, and the two free ends are respectively used for connecting positive pressure and negative pressure so as to judge whether the first virtual through holes of the first test unit transversely drift or not; and
the shape of the upper virtual metal layer of the second test unit is the same as that of the second connection structure, the first virtual through holes of the second test unit are connected in series and provided with two free ends, and the two free ends are respectively used for connecting positive pressure and negative pressure so as to judge whether the first virtual through holes of the second test unit vertically drift.
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