JP3341496B2 - Multi-layer wiring structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer wiring structure used in a semiconductor device, in which an upper wiring and a lower wiring are connected at a plurality of contact portions.

[0002]

2. Description of the Related Art In a multilayer wiring structure used for a semiconductor device, one connection between an upper wiring and a lower wiring is constituted by one contact portion or a plurality of contact portions having the same contact diameter.

[0003]

However, in a structure in which one contact portion is used for connection, disconnection occurs due to poor coverage at a step portion of the contact portion. Further, in a structure in which the contact portions are connected by one contact portion, the contact portion is formed in a square shape. As a result, the current tends to concentrate on the corners of the contact portions, and Joule heat is generated at the corners, and the contact portions are broken. In a structure in which a plurality of contact portions having the same contact diameter are connected to each other, current concentrates on a contact portion corresponding to a shortest current path among current paths flowing through each contact portion, and the portion generates Joule heat. Therefore, the contact part is destroyed. The destruction also affects other contact portions, and the entire contact portion is destroyed, resulting in disconnection.

An object of the present invention is to provide a multilayer wiring structure having connections at a plurality of contact portions in which current is prevented from being concentrated on a specific contact portion and destruction of the contact portion is prevented.

[0005]

SUMMARY OF THE INVENTION The present invention is a multilayer wiring structure made to achieve the above object. That is,
In a multi-layer wiring structure in which one connection between an upper wiring and a lower wiring is connected by a plurality of contact portions, a resistance value of a contact portion, which is a shortest current route among current paths passing through each contact portion, is set to another contact portion. It is smaller than the resistance value. As a structure for reducing the resistance value of the contact portion, the contact resistance of the contact portion is made smaller than the contact resistance of the other contact portions by forming a large cross-sectional area of the contact portion which is the shortest current path. .

[0006]

In the above multilayer wiring structure, one connection between the upper wiring and the lower wiring is formed by a plurality of contact portions, and the resistance value of the contact portion which is the shortest current path among the current paths passing through the contact portions is formed. Is smaller than the resistance values of the other contact portions, the current of the contact portion, which is the shortest current path, easily flows. For this reason, the current density of each contact portion tends to be equalized, and at least each contact portion has a current density equal to or lower than a level that does not cause breakdown. Therefore, even if Joule heat is generated in the contact portion, the contact portion does not reach a state in which the contact portion generates a calorific value. In addition, since the cross-sectional area of the contact portion is made large as a structure for reducing the resistance value of the contact portion that is the shortest current path, the resistance of the contact portion is reduced by the inverse relationship between the resistance and the cross-sectional area of the conductor. Become smaller. Therefore, according to Ohm's law, the current flowing through the contact portion increases at a constant voltage, but the current density decreases as a whole, so that Joule heating decreases.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to the schematic diagram of FIG. In the figure, (1) shows a perspective view in which the interlayer insulating film is omitted, and (2) shows a cross-sectional view.

As shown in FIG. 1, a lower wiring 21 is provided on a substrate 11. An interlayer insulating film 12 is formed on the substrate 11 so as to cover the lower wiring 21. An upper wiring 31 is provided on the upper surface of the interlayer insulating film 12 at a right angle to the lower wiring 21. That is, in a planar layout, the lower layer wiring 21 and the upper layer wiring 31 are arranged substantially in an L shape. The lower wiring 21 is formed, for example, to have a width of 3.0 μm, a length of 7.5 μm, and a thickness of 0.6 μm.
For example, width 2.5 μm, length 7.5 μm, thickness 0.7
μm. Then, a plurality of contact portions 41, 42, 4 for connecting the lower wiring 21 and the upper wiring 31 are formed.
Reference numerals 3 and 44 are provided on the interlayer insulating film 12. The contact portions 41 to 44 are arranged in a state where the distances between the centers are equal.

In the multilayer wiring structure 1, for example, when a current flows from the upper wiring 31 to the lower wiring 21 in the direction indicated by the arrow A, the path A passing through the contact portion 42 is the shortest current path. And a path c passing through the contact portions 41 and 44,
D) The current path becomes longer in the order of path e passing through the contact part 43. Since the current tends to concentrate on the shortest current path, the resistance value of the contact
1, 43, 44. At this time, the resistance values of the contact portions 41 to 44 are set so that the current densities of the contact portions 41 to 44 become substantially equal.
By approaching the state where the current density is equalized, the amount of heat generated per unit volume at each of the contact portions 41 to 44 approaches the state where the current density is equalized. Naturally, the current density of each of the contact portions 41 to 44 is set to a value that does not cause destruction due to Joule heat generated by the current flowing through each of the contact portions 41 to 44.

As a structure for reducing the resistance value of the contact portion 42, the diameter of the contact portion 42 is made larger than those of the other contact portions 41, 43, 44. For example, the lower wiring 21, the upper wiring 31, and the contact portions 41 to 44 are formed of aluminum, and the diameter of the contact portion 42 is set to 0.35 μm.
m, the diameter of the contact portions 41, 44 is 0.30 μm, 0.
When the contact portion 43 was formed to have a diameter of 28 μm and the diameter of the contact portion 43 was set to 0.25 μm, and a voltage was applied so that a potential difference of 1 V was generated between the lower wiring 21 and the upper wiring 31, the results shown in Table 1 were obtained. . Table 1 also shows, as Comparative Example 1, a case where each diameter of the contact portions 41 to 44 is 0.29 μm. Further, whether or not each of the contact portions 41 to 44 at each diameter can be used is indicated by ○ and ×. When it can be used, it is judged as ○, and when it cannot be used, it is judged as ×.

[0011]

[Table 1]

As is clear from Table 1, by increasing the diameter of the contact portion 42 at which the current path becomes the shortest from 0.29 μm to 0.35 μm, the calorific value of the contact portion 42 is not destroyed. Can be reduced to the level. That is, when the diameter of the contact portion 42 is 0.29 μm, the calorific value is 10.38 J /
(Μm ³ · s), so that the calorific value is such that aluminum is melted. Therefore, the contact portion 42 expands and is broken. Therefore, the judgment of the contact portion 42 is “×”. On the other hand, in the contact portion 42 of the present invention, the calorific value remains at 7.058 J / (μm ³ · s). The heat value of the other contact portions 41, 43, 44 is 4.79.
^{6J / (μm 3 · s)} , 2.873J / (μm 3 ·
s), 4.049 J / (μm ³ · s). For this reason, the allowable calorific value [for example, 8.9 J / (μm ³ ·
s)], the contact portions 41 to 44 are not broken. Therefore, the judgment is ○.

Further, as shown in FIG.
The upper wiring 31 is substantially parallel to one of the L-shaped wirings 21 a of the lower wiring 21. A plurality of contact portions 41, 42, 43, 44 for connecting the lower wiring 21 and the upper wiring 31 are formed in the lower and upper wirings 2.
It is provided on an interlayer insulating film (not shown) formed between 1 and 31. In the multilayer wiring structure 2, when a current flows from the upper wiring 31 to the lower wiring 21, the length of the current path flowing through the wiring 21a of the lower wiring 21 extending in the same direction as the current flowing through the upper wiring 31 is as follows. The current paths passing through any of the contact portions 41 to 44 are the same. Therefore,
Attention should be paid to the current flowing in the direction of the lower wiring 21b extending in the direction perpendicular to the upper wiring 31 on the planar layout. As a result, the contact portion 42 at the same position as in the first embodiment may be formed large.

Next, a second embodiment will be described with reference to the schematic configuration diagram of FIG. In the figure, (1) shows a perspective view in which the interlayer insulating film is omitted, and (2) shows a cross-sectional view. The same components as those described in FIG. 1 are denoted by the same reference numerals.

As shown in FIG. 3, a lower wiring 21 is provided on the substrate 11. An interlayer insulating film 12 is formed on the substrate 11 so as to cover the lower wiring 21. On the upper surface of the interlayer insulating film 12, an upper wiring 31 is provided substantially in parallel with the lower wiring 21. That is,
When viewed in a planar layout, the lower wiring 21 and the upper wiring 31
Are arranged so as to substantially overlap with each other. The lower wiring 2
1 has a width of, for example, 3.0 μm, a length of 7.5 μm, and a thickness of 0.6 μm. The upper wiring 31 has a width of, for example, 3.0 μm, a length of 7.5 μm, and a thickness of, for example. 0.7μ
m. Then, the lower wiring 21 and the upper wiring 3
1 and a plurality of contact portions 41, 42, 43,
44 is provided on the interlayer insulating film 12. The contact portions 41 to 44 are arranged in a state where the distances between the centers are equal.

In the multilayer wiring structure 3, for example, when a current flows from the upper wiring 31 to the lower wiring 21 in the direction indicated by the arrow, the path passing through the contact portions 42 and 44 is the shortest current path. Then, the current path becomes longer in the paths ， and 通 る passing through the contact portions 41 and 43. Since the current tends to concentrate on the shortest current path, the contact portions 42,
The resistance value of 44 is made smaller than the resistance values of the other contact portions 41 and 43.

As a structure for reducing the resistance value of the contact portions 42 and 44, the diameter of the contact portions 42 and 44 is increased. For example, the lower wiring 21, the upper wiring 31, and the contact portions 41 to 44 are formed of aluminum, the diameter of the contact portions 42 and 44 is 0.35 μm, and the contact portions 41 and 44 are formed of aluminum.
When the diameter of 43 was formed to 0.25 μm and a voltage was applied so that a potential difference of 1 V was generated between the lower wiring 21 and the upper wiring 31, the results are as shown in Table 2. Table 2 also shows
As Comparative Example 2, each diameter of the contact portions 41 to 44 was set to 0.3.
The case of 0 μm is shown. Further, whether or not each of the contact portions 41 to 44 in each diameter can be used is indicated by ×, and when it can be used, it is judged as ○, and when it cannot be used, it is judged as ×.

[0018]

[Table 2]

As is apparent from Table 2, the diameter of the contact portions 42 and 44 at which the current path becomes the shortest is 0.30 μm.
By increasing from m to 0.35 μm, the heat generation of the contact portions 42 and 44 can be reduced to a level that does not cause destruction. That is, 9.253 when the diameter of the contact portions 42 and 44 is 0.30 μm.
Since the heat value is J / (μm ³ · s), the contact portions 42 and 44 are melted. Therefore, the contact portion 4
2,44 expand and destroy. Therefore, the judgment is ×
become. On the other hand, in the contact portions 42 and 44 of the present invention, the calorific value remains at 6.447 J / (μm ³ · s). The calorific value of the other contact portions 41 and 43 is 2.856 J /
(Μm ³ · s). For this reason, since the amount of generated heat is less than the allowable calorific value [for example, 8.9 J / (μm ³ · s)], each of the contact portions 41 to 44 is not broken. Therefore, the judgment is ○.

Next, a third embodiment will be described with reference to the schematic configuration diagram of FIG. In the figure, (1) shows a perspective view in which the interlayer insulating film is omitted, and (2) shows a cross-sectional view. The same components as those described in FIG. 1 are denoted by the same reference numerals.

As shown in FIG. 4, a lower wiring 21 is provided on a substrate 11. An interlayer insulating film 12 is formed on the substrate 11 so as to cover the lower wiring 21. An upper wiring 31 is provided on the upper surface of the interlayer insulating film 12 at a right angle to the lower wiring 21. That is, in a plan layout, the lower wiring 21 and the upper wiring 31 are arranged in a state of forming an almost inverted T-shape. Further, a plurality of contact portions 41, 42, 43, 44 for connecting the lower wiring 21 and the upper wiring 31 are provided in the interlayer insulating film 12.

In the multilayer wiring structure 4, for example, when a current flows from the upper wiring 31 to the lower wiring 21 in the direction indicated by the arrow, the path through the contact portions 42 and 44 is the shortest current path. The current paths of the paths S and S passing through the contact portions 41 and 43 become longer. Since the current tends to concentrate on the shortest current path, the contact portions 42,
The resistance value of 44 is made smaller than the resistance values of the other contact portions 41 and 43. In the case where the current flows only to one side of the lower wiring 21, it is the same as the case of the first embodiment.

As a structure for reducing the resistance value of the contact portions 42 and 44, the diameter of the contact portions 42 and 44 is increased. For example, the lower wiring 21, the upper wiring 31, and the contact portions 41 to 44 are formed of aluminum, the diameter of the contact portions 42 and 44 is 0.35 μm, and the contact portions 41 and 44 are formed of aluminum.
43 is formed to have a diameter of 0.25 μm.

As described above, by forming the diameters of the contact portions 42 and 44 having the shortest current path to be large, the heat generation of the contact portions 42 and 44 can be reduced to a level that does not cause destruction. .

Also, as shown in FIGS. 5A and 5B, when the lower wiring 21 is formed in a bent state, it is almost the same as in the third embodiment, so that the contact portion 42 is formed. , 44 may be formed to have a larger diameter than the other contact portions 41, 43 so as to reduce the resistance value.

Next, a fourth embodiment will be described with reference to the schematic configuration diagram of FIG. In the figure, (1) shows a perspective view in which the interlayer insulating film is omitted, and (2) shows a cross-sectional view. The same components as those described in FIG. 1 are denoted by the same reference numerals.

As shown in FIG. 6, a lower wiring 21 is provided on a substrate 11. This lower layer wiring 21 is a wiring 2
The wiring 1a and the wiring 21c are formed in a straight line, and the wirings 21b and 21d are formed in a state orthogonal to the straight line, thereby forming a wiring 21 having a + shape. An interlayer insulating film (not shown) is formed on the substrate 11 so as to cover the lower wiring 21. On the upper surface of the interlayer insulating film (not shown), an upper wiring 31 is provided substantially parallel to the wiring 21a of the lower wiring 21. That is, when viewed in a planar layout, the wiring 21a and the upper wiring 31 are arranged so as to substantially overlap each other. Each wiring 21 of the lower wiring 21
A plurality of contact portions 41, 42, 43, and 44 for connecting the intersection 21o of a to 21d and the upper wiring 31 are provided in the interlayer insulating film (not shown).

In the multilayer wiring structure 5, for example, when a current flows from the upper wiring 31 to the lower wiring 21 in the direction of the arrow, the path through the contact portions 42 and 44 becomes the shortest current path. The current paths of the paths T and G passing through the contact portions 41 and 43 become longer. Since the current tends to concentrate on the shortest current path, the contact portions 42,
The resistance value of 44 is made smaller than the resistance values of the other contact portions 41 and 43.

As a structure for reducing the resistance value of the contact portions 42 and 44, the diameter of the contact portions 42 and 44 is increased. For example, the lower wiring 21, the upper wiring 31, and the contact portions 41 to 44 are formed of aluminum, the diameter of the contact portions 42 and 44 is 0.35 μm, and the contact portions 41 and 44 are formed of aluminum.
43 is formed to have a diameter of 0.25 μm.

As described above, by forming the diameters of the contact portions 42 and 44 having the shortest current path to be large, the heat generation of the contact portions 42 and 44 can be reduced to a level that does not cause destruction. .

In the fourth embodiment, the lower wiring 2
The case where the current flows only through the one wiring 21a is the same as the second embodiment, and the case where the current flows only through the wirings 21b and 21d of the lower wiring 21 is the same as the third embodiment.
When current flows only through the wiring 21a and the wiring 21b, and when the wiring 21c and the wiring 21d are not formed, the first embodiment and the second embodiment are combined. The current path passing through 44 is the shortest path. Therefore, the diameter of the contact portion 44 is formed larger than the diameters of the other contact portions. On the other hand, wiring 2
1a also when the current flows only through the wiring 21d and when the wiring 21c and the wiring 21b are not formed.
Since the embodiment and the second embodiment are in a combined state,
This is the shortest path of the current path passing through the contact portion 42. Therefore, the diameter of the contact portion 42 is formed larger than the diameters of the other contact portions. Further, when no current flows through the wiring 21c, and when the wiring 21c is not formed, the above-described second and third embodiments are combined, so that the current passing through the contact portions 42 and 44 is reduced. This is the shortest current path. Therefore, the contact portions 42, 44
Is formed larger than the diameters of the other contact portions.

It should be noted that the numerical values shown in the above embodiments are merely examples, and may vary depending on the wiring shape, wiring size, wiring thickness, contact size, contact depth, and the like. It is not limited to the numerical values shown above.

[0033]

As described above, according to the present invention,
One connection between the upper layer wiring and the lower layer wiring is formed by a plurality of contact portions, and the resistance value of the contact portion that is the shortest current path among the current paths passing through each contact portion is calculated from the resistance values of the other contact portions. Therefore, the current in the contact portion, which is the shortest current path, easily flows. For this reason, the current density of each contact portion is almost equalized,
Each contact portion has a current density at least equal to or lower than a level at which no destruction occurs. Therefore, destruction of the contact portion due to Joule heat is eliminated, and the reliability of the wiring can be improved. Further, as a structure for reducing the resistance value of the contact portion, the cross-sectional area of the contact portion serving as the shortest current path is formed large, so that the current density flowing through the contact portion is reduced. Therefore, Joule heat generation can be suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a first embodiment of the present invention.

FIG. 2 is another wiring configuration diagram of the first embodiment.

FIG. 3 is a schematic configuration diagram of a second embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a third embodiment of the present invention.

FIG. 5 is another wiring configuration diagram of the third embodiment.

FIG. 6 is a schematic configuration diagram of a fourth embodiment of the present invention.

[Explanation of symbols]

 1, 3 to 5 Multilayer wiring structure 21 Lower layer wiring 31 Upper layer wiring 41 to 44 Contact part

Claims (1)

(57) [Claims] A single connection between an upper wiring and a lower wiring is provided.
In a multilayer wiring structure constituted by the number of contact portions, said one of the current path through each contact portion, said by larger than the cross-sectional area of the other of the contact portion the cross-sectional area of the contact portion having the shortest current path A multilayer wiring structure wherein the resistance value of a contact portion is smaller than the resistance values of other contact portions.