[0001]CROSS-REFERENCE TO RELATED APPLICATION
This application claims the priority benefit of Japanese Patent Application No. 2000-296328, filed Sep. 28, 2000, the entire disclosure of which is incorporated herein by reference.
[0002]BACKGROUND OF THE INVENTION
1. Field of the invention
This invention relates to a semiconductor device, and more particularly, to a multi-chip package type semiconductor device in which more than one IC chip can be packaged.
2. Description of the related art
In the related art, there are several types of multi-chip packages in which more than one IC chip can be packaged. One typical multi-chip package is a stack type multi-chip package that packages at least two IC chips in a stacked manner.
In the stack type multi-chip package, the semiconductor device includes an insulating substrate, a first semiconductor chip formed on the insulating substrate and a second semiconductor chip, which is formed on the first semiconductor chip. Each of the semiconductor chips includes terminal pads, and the insulating substrate includes internal terminals. In the stack type multi-chip package, the terminal pads of the first semiconductor chip are connected to the internal terminals by a first conductive wire, and the, terminal pads of the second semiconductor chip are connected to the internal terminals by a second conductive wire. The insulating substrate, a first semiconductor chip and a second semiconductor chip are encapsulated by a sealing material, such as resin.
According to the stack type multi-chip package structure, since the second semiconductor chip is mounted on the first semiconductor chip, the distance between one of the terminal pads on the second semiconductor chip and one of the internal terminals, which is closest to the second semiconductor chip, is longer than that between one of the terminal pads on the first semiconductor chip and one of the internal terminals, which is closest to the first semiconductor chip. Therefore, the second conductive wire that connects the terminal pad of the second semiconductor chip to the internal terminal should be longer than the first conductive wire that connects the terminal pad of the first semiconductor chip to the internal terminal.
When the semiconductor device including conductive wires having the different lengths is encapsulated by the sealing material, the second conductive wire that is longer than the first conductive wire is pushed by injection pressure from the sealing material. As a result, the second conductive wire may contact an adjacent conductive wire so that circuits of the second semiconductor chip may short.
[0003]SUMMARY OF THE INVENTION
It is therefore an object of the invention to resolve the above-described problem in a multi-chip package type semiconductor device.
The object is achieved by a multi-chip package type semiconductor device including an insulating substrate having first and second conductive patterns thereon, a first semiconductor chip having a first internal circuit on the insulating substrate, the first semiconductor chip having a first terminal pad connecting to the first internal circuit and a conductive relay pad isolated from the first terminal pad, and the conductive relay pad including a first area and a second area, a second semiconductor chip on the first semiconductor chip, the second semiconductor chip being smaller than the first semiconductor chip, and having a second internal circuit and having a second terminal pad connecting to the second internal circuit, a first bonding wire connecting the first terminal pad to the first conductive pattern, a second bonding wire connecting the second conductive pattern to the conductive relay pad in the first area, and a third bonding wire connecting the conductive relay pad in the second area to the second terminal pad wherein the lengths of the first, second and third bonding wire are approximately the same.
The above and further objects and novel features of the invention will more fully appear from the following detailed description, appended claims and accompanying drawings.
[0004]BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view of a multi-chip package type semiconductor device according to a first embodiment of the invention;
FIG. 2A is an enlarged perspective view of a corner of the multi-chip package type semiconductor device of FIG. 1 ;
FIG. 2B is an enlarged perspective view of a corner of the multi-chip package type semiconductor device according to a first alternative embodiment of the first embodiment of the invention;
FIG. 2C is an enlarged perspective view of a corner of the multi-chip package type semiconductor device according to a second alternative embodiment of the first embodiment of the invention;
FIG. 3 is an enlarged perspective view of a corner of a multi-chip package type semiconductor device according to the second embodiment of the invention;
FIG. 4 is a sectional view of a multi-chippackage type semiconductor device according to a third embodiment of the invention;
FIG. 5 is an enlarged perspective view of a corner of the multi-chip package type semiconductor device of FIG. 4 ; and
FIG. 6 is an enlarged perspective view of a corner of a multi-chip package type semiconductor device according to the fourth embodiment of the invention.
[0005]DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0006]First Preferred Embodiment
Referring to FIG. 1 , a multi-chip package type semiconductor device includes an insulating substrate 1 , a first semiconductor chip 3 and a second semiconductor chip 5 . The first semiconductor chip 3 is fixed on the insulating substrate 1 by adhesive material 2 . The second semiconductor chip 5 is smaller than the first semiconductor chip 3 , and is fixed on the center of the first semiconductor chip 3 by adhesive material 4 . First and second conductive patterns 6 a , 6 b acting as internal terminals are formed on the top surface of the insulating substrate 1 , on which the first semiconductor chip 3 is mounted. a third conductive patterns 7 for connecting the semiconductor device 1 to an unillustrated external device electrically via a bump electrode 10 are formed on the back surface of the insulating substrate 1 . The first conductive pattern 6 a is formed in order to receive signals from the first semiconductor chip 3 , and the second conductive pattern 6 b is formed in order to receive signals from the second semiconductor chip 5 . Each of the first and second conductive patterns 6 a , 6 b is electrically connected to one of the third conductive patterns 7 via a through-hole, which is formed in the insulating substrate 1 .
Referring to FIG. 1 and FIG. 2A , the first semiconductor chip 3 includes a first terminal pad 11 a and a relay pad 11 b having a first area X and a second area Y on its top surface. The relay pad 11 b is larger than the terminal pad 11 a . The terminal pad 11 a is connected to a first internal circuit 3 a formed in the semiconductor chip 3 , and the relay pad 11 b is electrically isolated from the first internal circuit 3 a and the first terminal pad 11 a formed on the semiconductor chip 3 . The second semiconductor chip 5 includes a second terminal pad 13 , which is connected to a second internal circuit 5 a formed on the semiconductor chip 5 . As described above, since the second semiconductor chip 5 is smaller than the first semiconductor chip 3 and the second semiconductor chip 5 is mounted on the center of the first semiconductor chip 3 , the first terminal pad 11 a and the relay pad 11 b can be formed on the periphery of the first semiconductor chip 3 .
The top surface of the semiconductor chip 3 , except for the first terminal pad 11 a and the relay pad 11 b , is covered by a passivation layer such as a silicon nitride layer, and therefore, the first terminal pad 11 a and the relay pad 11 b are exposed. The top surface of the semiconductor chip 5 , except for the second terminal pad 13 , is also covered by a passivation layer such as a silicon nitride layer, and therefore, the second terminal pad 13 is exposed.
Referring to FIG. 2A , a first metal bump 15 is formed on the relay pad 11 b in the first area of the first semiconductor chip 3 , and a second metal bump 16 is formed on each second terminal pad 13 of the second semiconductor chip 5 . The first and second metal bumps 15 , 16 can be formed according to the wire bonding technology.
The first conductive pattern 6 a on the insulating substrate 1 is connected to the first terminal pad 11 a by a first bonding wire 17 according to the following method. First, one end of the first bonding wire 17 is connected to the first terminal pad 11 a by the well-known ball bonding method, as the first bond, which means a beginning connection. Then, the other end of the first bonding wire 17 is thermally pressed onto the first conductive pattern 6 a , as the second bond, which means an ending connection.
The second conductive pattern 6 b is connected to the second terminal pad 13 by a second bonding wire 18 a and a third bonding wire 18 b according the following method. First, one end of the second bonding wire 18 a is connected to the second conductive pattern 6 b by the ball bonding method, as the first bond. Then, the other end of the second bonding wire 18 a is connected to the first metal bump 15 , as the second bond. Second, one end of the third bonding wire 18 b is connected to the relay pad in the second area Y by the ball bonding method, as the first bond. Then, the other end of the third bonding wire 18 b is connected to the second metal bump 16 , as the second bond. In this embodiment, although the connection between the second conductive pattern 6 b and the first semiconductor chip 3 is made prior to the connection between the second terminal pad 13 on the second semiconductor chip 5 and the relay pad 11 b on the first semiconductor chip 3 , the connection between the second terminal pad 13 on the second semiconductor chip 5 and the relay pad 11 b on the first semiconductor chip 3 may be made first. Since the distance between the second terminal pad 13 and the relay pad 11 b equals the distance between the relay pad 11 b and the second conductive pattern 6 b , which equals the distance between the first terminal pad 11 a and the first conductive pattern 6 b , the lengths of the first, second and third bonding wires 17 , 18 a , 18 b can be approximately the same.
In the first embodiment, the relay pad 11 b is formed in a rectangular shape, and its longer side is parallel to the side of the first semiconductor chip 3 . However, it is possible to form the rectangularly-shaped relay pad 11 b whose shorter side is parallel to the side of the first semiconductor chip 3 as shown in FIG. 2 B. In this case, the second bonding wire 18 a connects the second conductive pattern 6 b to a first area X of the rectangularly-shaped relay pad 11 b , which is relatively close to the side of the first semiconductor chip 3 , and the third bonding wire 18 b connects the second terminal pad 13 to a second area Y of the rectangularly-shaped relay pad 11 b , which is relatively far to the side of the first semiconductor chip 3 . Although the location where the second semiconductor chip 5 is mounted is restricted, it is possible to form each of the first and second wires 17 and 18 a so as not to be formed perpendicular to the side of the semiconductor chips 3 , in order to avoid the contact between the first and second wires 17 and 18 a effectively.
Further, the relay pad 11 b can be formed large enough to space the first metal bump 15 from the one end of the third bonding wire 18 b on the large relay pad 11 b if the space allows, as shown in FIG. 2 C. In this case, the flexibility in forming the second and third wires 18 a , 18 b is improved.
According to the first embodiment of the invention, the second terminal pad 13 of the second semiconductor chip 5 is not directly connected to the second conductive pattern 6 b of the insulating substrate 1 , and the second terminal pad 13 is connected to the second conductive pattern 6 b via the relay pad 11 b by using the second and third bonding wires 18 a , 18 b , each of which has approximately the same length as the first bonding wire 17 . Therefore, it is not necessary to use a long bonding wire to connect the second terminal pad 13 to the second conductive pattern 6 b in the first embodiment. As a result, it is possible to avoid unnecessary contact of the bonding wires, which are next to each other when the semiconductor device 100 is encapsulated by the sealing material.
Further, the relay pad 11 b is formed larger than the first terminal pad 11 a so that the first metal bump 15 is formed on the relay pad 11 b in the first area X and the first bond of the third bonding wire can be made on the same relay pad 11 b in the second area Y Therefore, since the second and third bonding wires 18 a 18 b can be connected in the different area in the relay pad 11 b , stress of the wire bonding on the relay pad 11 can be reduced.
Moreover, since the first bond of the third bonding wire 18 b is made on the relay pad 11 b of the first semiconductor chip 3 , and the second bond of the third bonding wire 18 b is made on the second terminal pad 13 of the second semiconductor chip 5 , the third bonding wire 18 b having a low height wiring loop can be formed. Therefore, since the sealing material 19 can be thin, the thin package semiconductor device can be realized.
As described above, the entire surface of the relay pad 11 is exposed from the passivation layer. However, when the relay pad 11 b is formed large enough to space the first metal bump 15 from the one end of the third bombing wire 18 on the large relay pad 11 b , as shown in FIG. 2C , the passivation layer can be formed on the relay pad between the first metal bump 15 and the one end of the third bombing wire 18 b.
[0007]Second Preferred Embodiment
The difference between the first and second embodiments is in the method the wire bonding to connect the first terminal pad 11 a of the first semiconductor chip 3 or the second terminal pad 13 of the second semiconductor chip 5 to the first and second conductive patterns 6 a , 6 b.
Referring to FIG. 3 , a first metal bump 21 is formed on the relay pad 11 b in the second area Y and no metal bump is formed on the second terminal pad 13 of the second semiconductor chip 5 and on the relay pad in the first area X of the first semiconductor chip 3 . The connection between the first semiconductor chip 3 and the first conductive pattern 6 a is made in the same way as described in the first embodiment. The connection between the second semiconductor chip 5 and the second conductive pattern 6 b is made by the following method. The second conductive pattern 6 b is connected to the second terminal pad 13 by a second bonding wire 23 a and a third bonding wire 23 b . First, one end of the second bonding wire 23 a is connected to the relay pad 11 b in the first area X by the ball bonding method, as the first bond. Then, the other end of the second bonding wire 23 a is connected to the second conductive pattern 6 b , as the second bond. Second, one end of the third bonding wire 23 b is connected to the second terminal pad 13 of the second semiconductor chip 5 by the ball bonding method, as the first bond. Then, the other end of the third bonding wire 23 b is connected to the metal bump 21 formed on the relay pad 11 b in the second area Y as the second bond.
According to the second embodiment, since the first bond of the third wire 23 b is made at the second terminal pad 13 by the ball bonding method, it is not necessary to form any metal bumps on the second terminal pad 13 . Therefore, in addition to the benefits of the first embodiment, it is possible to delete the process of forming the metal bumps on the second terminal pad 13 .
[0008]Third Preferred Embodiment
A semiconductor device 200 of the third embodiment is explained below with reference to FIGS. 4 and 5 . The same reference numbers in FIGS. 1-3 designate the same or similar components in FIGS. 4 and 5 .
Referring to FIGS. 4 and 5 , a first semiconductor chip 3 includes a first terminal pad 31 a and a relay pad 31 b , as in the first and second embodiments. However, the size of the first terminal pad 31 a almost equals that of the relay pad 31 b in the third embodiment. The first terminal pad 31 a is connected to a first internal circuit 3 a of the first semiconductor chip 3 and the relay pad 31 b is isolated electrically from the first terminal pad 31 a and the first internal circuit 3 a of the first semiconductor chip 3 . A first metal bump 32 is formed on the relay pad 31 b , and the surface of the first terminal pad 31 a is exposed.
A second semiconductor chip 5 , which is fixed on the first semiconductor chip 3 , includes a second terminal pad 34 , which connects to a second internal circuit 5 a . A second metal bump 35 is formed on the second terminal pad 34 .
The first semiconductor chip 3 is connected to a first conductive pattern 6 a formed on an insulating substrate 1 by a first bonding wire 33 . The method of connecting the first semiconductor chip 3 to the first conductive pattern 6 a is the same as that described in the first embodiment. That is, the first bond of the first bonding wire 33 by the ball bonding method is made at the first terminal pad 31 b , and the second bond of the first bonding is made at the first conductive pattern 6 a.
The second semiconductor chip 5 is connected to a second conductive pattern 6 b formed on the insulating substrate 1 by second and third bonding wires 36 a , 36 b in the following method. First, one end of the second bonding wire 36 a is connected to the second conductive pattern 6 b by the ball bonding method, as the first bond. Then, the other end of the second bonding wire 36 a is connected to the first metal bump 32 on the relay pad 31 b , as the second bond. Second, one end of the third bonding wire 36 b is connected to the first metal bump 32 on which the other end of the second bonding wire 36 a is connected, by the ball bonding method, as the first bond. Then, the other end of the third bonding wire 36 b is connected to the second metal bump 35 , as the second bond.
According to the third embodiment , in addition to the benefits of the first embodiment, the following benefit can be expected. Since the first bond of the third bonding wire 36 b is made on the second bond of the second bonding wire 36 a , it is not necessary to form the large relay pad, such as the relay pad 11 b shown in FIGS. 2A through 2C and 3 . Therefore, space between the relay pad 31 b and the first terminal pad 31 a can be secured enough.
[0009]Fourth Preferred Embodiment
The difference between the third and fourth embodiment is a method of the wire bonding to connect a first terminal pad 41 a of the first semiconductor chip 3 or a second terminal pad 44 of the second semiconductor chip 5 to the first and second conductive patterns 6 a , 6 b . So, the same reference numbers in FIG. 4 designate the same or similar components in the fourth embodiment shown in FIG. 6 .
Referring to FIG. 6 , a first metal bump 42 is formed on the relay pad 41 b and no metal bump is formed on the first and second terminal pads 41 b , 44 on the first and second semiconductor chips 3 , 5 . The connection between the first semiconductor chip 3 and the first conductive pattern 6 a is made using a first bonding wire 43 in the same way as described in the third embodiment. The connection between the second semiconductor chip 5 and the second conductive pattern 6 b is made by the following method. The second conductive pattern 6 b is connected to the second terminal pad 44 by a second bonding wire 46 a and a third bonding wire 46 b . First, one end of the third bonding wire 46 b is connected to the second terminal pad 44 by the ball bonding method, as the first bond. Then, the other end of the third bonding wire 46 b is connected to the first metal bump 42 , as the second bond. Second, one end of the second bonding wire 46 a is connected to the second conductive pattern 6 b by the ball bonding method, as the first bond. Then, the other end of the second bonding wire 36 a is connected to the first metal bump 42 on the relay pad 41 b , as the second bond. In this embodiment, although the connection between the second terminal pad 44 on the second semiconductor chip 5 and the relay pad 41 b on the first semiconductor chip is made prior to the connection between the second conductive pattern 6 b and the first semiconductor chip 3 , the connection between the second conductive pattern 6 b and the first semiconductor chip 3 may be made first. In either way, the second bonds of both of the second and third bonding wire 46 a , 46 b are made on the first metal bump 42 .
According to the fourth embodiment, since the second bonds of both of the second and third bonding wire 46 a , 46 b are made on the first metal bump 42 , it is not necessary to form any metal bumps on the second terminal pad 44 . Therefore, in addition to the benefits of the third embodiment, it is possible to delete the process of forming the metal bumps on the second terminal pad 13 .
Various other modifications of the illustrated embodiments, as well as other embodiments of the invention, will be apparent to those skilled in the art on reference to this description. For example, in all embodiments, the semiconductor chip 3 is fixed on the insulating substrate 1 . However, the invention can be applied to the multi-chip package type semiconductor devices formed on the lead frame. In this case, a inner lead is used instead of conductive pattern 6 a , 6 b , and the first semiconductor is fixed on a die pad of the lead frame. Therefore, the appended claims are intended to cover any such modifications or embodiments as fall within the true scope of the invention.
