The present invention relates to a semiconductor package, and particularly, relates to a configuration of a semiconductor package having stacked semiconductor chips.
In a semiconductor device, particularly, in a DRAM (Dynamic Random Access Memory), a package having stacked semiconductor chips (bare chips), what is called a DDP (Dual Die Package), is used to enlarge memory size.
A bare chip of the DRAM generally has a center pad configuration having plural boding pads laid out in the center area of a chip surface. Therefore, boding using a long wire is necessary for electrical connection with a package substrate and the bare chip
However, when a first-layer semiconductor chip is connected to a package substrate and then a second-layer semiconductor chip is stacked on the first-layer semiconductor chip using plural bonding wires, the following problems occur due to a variation in the height of a long wire. That is, at the time of mounting the second-layer semiconductor chip on the plural bonding wires, it becomes difficult to horizontally mount the second-layer semiconductor chip in good balance. Therefore, large load is applied to a part of the semiconductor chip, and the surface of the first-layer semiconductor chip is brought into contact with the bonding wires.
When the second-layer semiconductor chip is mounted with an inclination, the pressure is concentrated to a part of the second-layer semiconductor chip at the time of bonding the second-layer semiconductor chip. Therefore, this causes a risk that first-layer bonding wires are pressed down and are brought into contact with the first-layer semiconductor chip.
To solve this problem, there has been proposed a technique of laying out a line-state supporting structure along a surface facing the first-layer semiconductor chip, or laying out a separated mound-shaped supporting structure on a corner of the first-layer semiconductor chip, and supporting the second-layer semiconductor chip with this supporting structure (Japanese Patent Application Laid-open No. 2004-312008).
However, according to the method disclosed in Japanese Patent Application Laid-open No. 2004-312008, the supporting structure is laid out in a line state along the surface facing the first-layer semiconductor chip, or is laid out in a separated mound shape on the corner of the first-layer semiconductor chip, as described above. Therefore, an electrode pad (a bonding pad) cannot be formed at the position where the supporting structure is laid out.
Among semiconductor chips of a center-pad configuration, electrode pads for power supply or for grounding are often laid out around the semiconductor chip. Therefore, according to the technique disclosed in the patent document, the supporting structure becomes a hindrance of the layout of the electrode pad, and the degree of freedom of the layout of the electrode pads decreases.
The method disclosed in the patent document also requires materials and processes to form the supporting structure. Therefore it results in cost increase. Incidentally, semiconductor packages using bonding wires are also described in, for example, Japanese Patent Application Laid-open No. 2003-163314, Japanese Patent Application Laid-open No. 2002-43357 and U.S. Pat. No. 6,472,758.
The present invention has been achieved in view of the light of the above problems, and an object of the present invention is to provide a semiconductor package having stacked semiconductor chips capable of preventing bonding failures without decreasing the degree of freedom of the layout of the electrode pads and without increasing a special manufacturing process.
The semiconductor package according to the present invention includes: a package substrate on the surface of which a plurality of connection terminals are provided; a first semiconductor chip on the surface of which a plurality of bonding pads are provided; a plurality of bonding wires that connect between the plurality of connection terminals and the plurality of bonding pads, respectively; a first resin formed to fill a gap between the plurality of bonding wires and the surface of the first semiconductor chip; and a second semiconductor chip provided on the plurality of bonding wires via a film-shaped second resin, wherein at least three of the plurality of bonding wires have substantially the same height and are higher than other bonding wires.
As explained above, according to the present invention, at least three bonding wires are formed at substantially the same height and also higher than other bonding wires on the first semiconductor chip. Therefore, the at least three bonding wires can support the second semiconductor chip. Consequently, at the time of mounting the second semiconductor chip, the bonding wires on the first semiconductor chip can be prevented from being in contact with the upper surface of the first semiconductor chip.
Therefore, the supporting structure as described in Japanese Patent Application Laid-open No. 2004-312008 becomes unnecessary. In addition, the bonding pads (electrode pads) can be freely laid out not only in the center area of the first semiconductor chip but also in the peripheral area.
The above and other objects, features and advantages of this invention will become more apparent by reference to the following detailed description of the invention taken in conjunction with the accompanying drawings, wherein:
Preferred embodiments of the present invention will be explained below in detail with reference to the accompanying drawings.
As shown in
The first-layer semiconductor chip 100 is mounted on the package substrate 10. Plural boding pads (center pads) 101 are laid out in two rows in the center area of the surface of the semiconductor chip 100.
With plural bonding wires 102h and 102l, the bonding pads arranged at the right side of the center pads 101 are connected to the connection terminals 11 provided at the right side of the package substrate 10, respectively. Also, the bonding pads arranged at the left side of the center pads 101 are connected to the connection terminals 11 provided at the left side of the package substrate 10, respectively.
Among the plural bonding wires, four bonding wires 102h close to the corners of the semiconductor chip 100 are formed higher than the other bonding wires 102l. Instead of dummy wires, wires actually electrically used can be used for the bonding wires 102h. Therefore, dummy bonding pads or dummy connection terminals are not necessary, and the surfaces of the semiconductor chip 100 and the package substrate 10 can be used effectively.
The top plan view of
As shown in
As shown in
As described above, in the present embodiment, the four bonding wires 102h located at the corners are formed to have larger heights than other bonding wires among the plural bonding wires. A second-layer semiconductor chip is stacked on these bonding wires. A process from the lamination of the second-layer semiconductor chip till the completion of the semiconductor package by finally molding the whole is explained below with reference to
First, as shown in
In other words, as shown in
As shown in
As shown in
Next, the bonding pads (the center pads) 201 provided on the surface of the semiconductor chip 200 and the connection terminals 11 on the package substrate 10 are connected by bonding wires 202, respectively. At this time, the semiconductor chip 200 is supported horizontally by the bonding wires 102h on the semiconductor chip 100. Therefore, even when bonding is performed on the semiconductor chip 200, concentration of the pressure to a part of the semiconductor chip 200 at the time of bonding can be prevented. Consequently, the risk that the bonding wires on the semiconductor chip 100 are pressed to be in contact with the semiconductor chip 100 can be prevented.
In the present embodiment, a further semiconductor layer is not stacked on the semiconductor chip 200. Therefore, none of the plural bonding wires 202 formed on the semiconductor chip 200 do not need to have a large height.
Last, as shown in
As described above, according to the present embodiment, out of the plural bonding wires to be formed on the lower-layer semiconductor chip 100, the four bonding wires 102h laid out at the corners of the semiconductor chip 100 are formed higher than the other bonding wires 102l. The four bonding wires 102h are set to have substantially equal heights. Accordingly, the four bonding wires 102h have substantially the same large heights. Therefore, the upper-layer semiconductor chip 200 formed on the four bonding wires 102h are supported by these bonding wires 102h. Consequently, even when a variation occurs in the heights of the bonding wires 201l, the semiconductor chip 200 can be supported horizontally by the bonding wires 102h regardless of the variation in the heights of the bonding wires 102l. As a result, a contact between the bonding wires on the semiconductor chip 100 and the upper surface of the semiconductor chip 100 can be prevented.
Further, a supporting structure that supports the upper-layer semiconductor chip as required by the conventional technique does not need to be formed. Therefore, an additional manufacturing process is not necessary.
In the present embodiment, while the four boding wires 102h formed at the corners of the semiconductor chip 100 have large heights, the number of the boding wires 102h does not need to be four and can be at least three, when the upper-layer semiconductor chip 200 can be supported approximately horizontally. The high bonding wires are not necessarily required to be formed at the corners of the semiconductor chip 100, and can be formed at other suitable positions. However, when the bonding wires formed at the corners of the semiconductor chip 100 have large heights, the upper-layer semiconductor chip 200 can be supported more stably.
As shown in
When the supporting structure that supports the upper-layer semiconductor chip is formed on the periphery of the lower-layer semiconductor chip like in the above-described conventional technique, the supporting structure becomes a hindrance, and pads cannot be provided on the periphery. However, according to the present embodiment, bonding pads can be freely provided on the surface of the semiconductor chip 100.
Particularly, the electrode pads for power supply or for grounding are often laid out in the peripheral areas as well as in the center area of the semiconductor chip 100. Therefore, when the peripheral pads 101f are used like in the present modification, detour wiring of the power supply line and the ground line inside the semiconductor chip 100 can be avoided.
In the present embodiment, the bonding wires 102h at the corners of the semiconductor chip 100 can be also set high like in the above embodiment. Alternately, the bonding wires 102h can be formed at the same heights (L) as those of the bonding wires 102l, and at least three of the bonding wires 102f can be formed higher (the height: H).
Alternatively, at least three suitable bonding wires among the whole bonding wires 102h, 102l, and 102f can be selected and set to be higher than the other bonding wires. When it is easier to form the short bonding wires to be higher than long bonding wires because of the performance of a bonding device, for example, bonding wires to be set high can be selected from among the short bonding wires 102f. On the other hand, when it is easier to form the long bonding wires to be higher than short bonding wires, bonding wires to be set high can be selected from among the long bonding wires 102h and 102l.
While a preferred embodiment of the present invention has been described hereinbefore, the present invention is not limited to the aforementioned embodiment and various modifications can be made without departing from the spirit of the present invention. It goes without saying that such modifications are included in the scope of the present invention.
For example, the bonding wires to be formed high are not necessarily the ones that actually electrically connect between the semiconductor chip and the package substrate, and dummy wires can be used. The use of dummy wires is effective when the stress applied to the bonding wires 102h is large. When the stress applied to the bonding wires 102h is large, the bonding wires 102h to be formed high have a risk of being broken. However, when the dummy wires are used, damage given to the dummy wires has little influence to the actual operation, and reliability of the product can be increased.
In the present embodiment, while two semiconductor chips are stacked on the package substrate, three or more semiconductor chips can be also stacked. When three or more semiconductor chips are stacked, at least three bonding wires of each of other semiconductor chips than the top-layer semiconductor chip are formed high.
Number | Date | Country | Kind |
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2007-034625 | Feb 2007 | JP | national |