Stack package utilizing through vias and re-distribution lines

[0001] The present application claims priority to Korean patent application number 10-2006-0025054 filed on Mar. 17, 2006, which is incorporated by reference in its entirety.

[0002] The present invention relates to a stack package, and more particularly, to a stack package using re-distribution lines and solder balls.

[0003] As the performances of electric and electronic products are improved, techniques for mounting an increased number of packages to a substrate having a limited size have been researched. Generally, in a stack package, one semiconductor chip is mounted to a substrate, which increases the difficulty of attaining a desired capacity.

[0004] As a method of increasing the capacity of a memory chip, that is, for accomplishing high integration, it is generally known in the art that an increased number of cells are formed in a limited space. However, this method requires use of high-precision process techniques involving a fine design rule and results in a substantially longer development time. Accordingly, a stacking technology has been developed as a method for easily realizing high integration, and research for the stacking technology has been active.

[0005] As used in the semiconductor industry, the term “stacking” means to vertically arrange at least two semiconductor chips to increase memory capacity. For example, by stacking two 256M DRAM chips, 512M DRAM can be configured in a single package. In addition, stacking technology provides advantages in mounting density and mounting area utilization efficiency.

[0006] With respect to stacking at least two semiconductor chips, a method in which at least two semiconductor chips are stacked in one package, and a method in which at least two packages are stacked, are known in the art.

[0007] FIG. 1 is a cross-sectional view illustrating the conventional stack package manufactured by the first method. Referring to FIG. 1, three semiconductor chips 110, 120 and 130, of different sizes that possess bonding pads 112, 122 and 132 on the peripheral portions thereof, are stacked on a printed circuit board (hereinafter referred to as “PCB”) 100. The bonding pads 112, 122 and 132 of the respective semiconductor chips 110, 120 and 130 and the circuit patterns 102 of the PCB 100 are connected to each other by metal wires 140. The upper surface of the PCB 100, including the semiconductor chips 110, 120 and 130 and the metal wires 140, is molded by a molding material 150. Solder balls 160, providing electrical connections to external circuits, are attached to the lower surface of the PCB 100.

[0008] However, in the conventional stack package resulting from the construction method described above, since the bonding pads 112, 122 and 132 are formed on the peripheral portions of the semiconductor chips 110, 120 and 130 and connected to the circuit patterns 102 of the PCB 100 by the metal wires 140, same-size semiconductor chips cannot be stacked unless a tape containing a shock-absorbing substance is interposed between two adjoining semiconductor chips. Furthermore, because the electrical connections in a conventional stack package are formed by the metal wires 140, it is difficult to apply the stack package in high-speed products. Moreover, the presence of wire loops in the conventional stack package increases the size of the package.

[0009] The embodiments of the present invention are directed to a stack package which can stack same-size semiconductor chips without using a tape containing a shock-absorbing substance.

[0010] Further, the embodiments of the present invention are directed to a stack package which can be easily applied to high-speed products.

[0011] Moreover, the embodiments of the present invention are directed to a stack package with a decreased overall size.

[0012] In one embodiment, a stack package comprises a PCB formed with circuit patterns and having electrode terminals located on the upper surface thereof and ball lands located on the lower surface thereof; at least two semiconductor chips stacked on the PCB in a face-down manner, each having first re-distribution lines formed on the upper surface thereof and connected to the bonding pads, through silicon vias formed therethrough and connected to the first re-distribution lines, and second re-distribution lines formed on the lower surface thereof and connected to the through silicon vias; first solder balls interposed between the first and second re-distribution lines of the stacked semiconductor chips, which face each other, thereby forming electrical and physical connections therebetween; second solder balls interposed between the first re-distribution lines of the lowermost semiconductor chip of the stacked semiconductor chips and the electrode terminals of the printed circuit board, thereby forming electrical and physical connections therebetween; a molding material for molding the upper surface of the printed circuit board including the stacked semiconductor chips; and third solder balls attached to the ball lands on the lower surface of the printed circuit board, serving as mounting means.

[0013] The first and second re-distribution lines are formed of copper.

[0014] The through silicon vias are formed of copper or nickel/gold.

[0015] Each through silicon via includes an insulation layer formed on the interface between the semiconductor chip and the through silicon via.

[0016] The stack package further comprises solder resists formed on the upper and lower surfaces of each semiconductor chip, which expose only portions of the first and second re-distribution lines.

[0017] The semiconductor chips are the same size, and the first and second re-distribution lines of the semiconductor chips are formed to be of the same size.

[0018] The semiconductor chips are different sizes, and the second re-distribution lines of one semiconductor chip are formed to have lengths for allowing the second re-distribution lines to connect to the corresponding first re-distribution lines of the other semiconductor chip.

[0023] In the present invention, through silicon vias (hereinafter referred to as “TSVs”) and re-distribution lines are formed in respective semiconductor chips to be stacked, and the stack of the aforementioned semiconductor chips is formed by connecting the re-distribution lines to one another.

[0024] In the stack package according to the present invention, the TSVs, re-distribution lines and solder balls form the electrical connections between the semiconductor chips, which provide several advantages. First, this allows the stack package to be applied to high-speed products through minimization of the electrical signal transmittance path. Second, not only semiconductor chips of different sizes but also semiconductor chips of the same size can be easily stacked upon one another without interposing a tape containing a shock-absorbing substance between two adjoining semiconductor chips. Third, the overall size of the stack package can be decreased since it is not necessary to consider wire loops.

[0025] Hereafter, a stack package in accordance with one embodiment of the present invention will be described in detail with reference to FIGS. 2A and 2B. FIG. 2A is a cross-sectional view illustrating a semiconductor chip formed with re-distribution lines and TSVs. FIG. 2B is a cross-sectional view illustrating a stack package in which semiconductor chips formed with re-distribution lines and TSVs are stacked on a printed circuit board (PCB).

[0026] Referring to FIG. 2A, a semiconductor chip 210 has bonding pads 212 located on the peripheral portions of the upper surface thereof. Adjacent to the bonding pads 212, TSVs 214 are defined through the semiconductor chip 210. First re-distribution lines 216 and second re-distribution lines 217 are formed on the upper and lower surfaces of the semiconductor chip 210 such that the first re-distribution lines 216 and the second re-distribution lines 217 are respectively connected to the upper and lower ends of the TSVs 214. The first re-distribution lines 216 are connected to the upper ends of the TSVs 214 as well as the bonding pads 212. Solder resists 218 are formed on the upper and lower surfaces of the semiconductor chip 210 including the first re-distribution lines 216 and the second re-distribution lines 217, such that only portions of the first re-distribution lines 216 and the second re-distribution lines 217 are exposed.

[0027] The bonding pads 212 are formed on the upper surface of the semiconductor chip 210 irrespective of the sizes and positions of the TSVs 214. Each TSV 214 is formed in a manner such that copper or nickel/gold is filled in a via hole defined through the semiconductor chip 210. In particular, the TSV 214 includes an insulation layer (not shown), which is formed on the interface between the semiconductor chip 210 and the TSV 214, for electrical insulation. The first re-distribution lines 216 and the second re-distribution lines 217 are formed of copper.

[0028] Referring to FIG. 2B, a PCB 200 is provided. The PCB 200 is formed with circuit patterns (not shown) and has electrode terminals 202 located on the upper surface thereof and ball lands 204 located on the lower surface thereof. At least two, for example, three semiconductor chips 210, 220 and 230 in FIG. 2B, each having the configuration as described above, are stacked on the PCB 200 in a face-down manner.

[0029] Here, the stacked semiconductor chips 210, 220 and 230 are electrically and physically connected to one another by first solder balls 260a, which are interposed between the first re-distribution lines 226 and 236 and the second re-distribution lines 217 and 227 facing each other. The lowermost semiconductor chip 210 of the stacked semiconductor chips 210, 220 and 230 and the PCB 200 are electrically and physically connected to each other by second solder balls 260b which are interposed between the bonding pads 212 and the electrode terminals 202 facing each other.

[0030] In order to prevent the semiconductor chips 210, 220 and 230 from being damaged by outer circumstances, the upper surface of the PCB 200 including the stacked semiconductor chips 210, 220 and 230 is molded by a molding material 250. Third solder balls 260c, which serve as mounting means to external circuits, are attached to the ball lands 204 on the lower surface of the PCB 200. In FIG. 2B, the reference numerals 224 and 234 designate TSVs which are respectively formed through the semiconductor chips 220 and 230; the reference numerals 222 and 232 designate the bonding pads which are respectively formed on the semiconductor chips 220 and 230; and the reference numeral 237 designates the second re-distribution lines which are formed on the semiconductor chip 230.

[0031] In the stack package according to the present invention, the electrical connections between the semiconductor chips and the electrical connections between the semiconductor chips and the PCB are formed using the TSVs, re-distribution lines, and solder balls rather than metal wires. Therefore, the electrical signal transmittance path can be shortened to the minimum distance according to the present invention, and the stack package can therefore be advantageously applied to high-speed products. Also, in the present invention, because the metal wires are not used, it is not necessary to consider wire loops, and therefore the overall size of the stack package can be decreased.

[0032] In addition, in the present invention, as shown in FIG. 3, solder balls 360 can be attached over the entire surface of the semiconductor chip 310 through rearrangement of bonding pads and TSVs. Therefore, semiconductor chips of not only the same size but also different sizes can be easily stacked without using tapes containing a shock-absorbing substance.

[0033] FIG. 4 is a cross-sectional view illustrating a stack package in accordance with another embodiment of the present invention. Referring to FIG. 1, in the stack package according to an embodiment, semiconductor chips 410, 420 and 430, each having a different size, are stacked upon one another. This is enabled by the fact that the attachment positions of the first solder balls 460a and second solder balls 460b can be optionally adjusted through rearrangement of the bonding pads 412, 422 and 432 and TSVs 414, 424 and 434. That is to say, in the present embodiment, by adjusting the lengths of the first re-distribution lines 416, 426 and 436 and the second re-distribution lines 417, 427 and 437 and adjusting the exposure positions thereof from the solder resists 418, 428 and 438 in the respective semiconductor chips 410, 420 and 430, the attachment positions of the first solder balls 460a and the second solder balls 460b can be optionally adjusted, whereby the semiconductor chips having different sizes can be easily stacked.

[0034] Meanwhile, in the stack package according to one embodiment of the present invention as described above and illustrated in FIG. 2, if the stacked semiconductor chips 210, 220 and 230 are of the same size, the first re-distribution lines 216, 226 and 236 and the second re-distribution lines 217, 227 and 237 of the respective semiconductor chips 210, 220 and 230 are formed to have the same length. In contrast, in the stack package according to another embodiment of the present invention as described above and illustrated in FIG. 4, if the stacked semiconductor chips 410, 420 and 430 are of different sizes, the first re-distribution lines 416, 426 and 436 and the second re-distribution lines 417, 427 and 437 of the respective semiconductor chips 410, 420 and 430 are formed to have different lengths. For example, the second re-distribution lines 417, 427 and 437 of the respective semiconductor chips 410, 420 and 430 are formed to have lengths which allow the second re-distribution lines 417, 427 and 437 to connect to the corresponding first re-distribution lines 426 and 436 of the upwardly located semiconductor chips 420 and 430.

[0035] In the stack package, the upper surface of the PCB 400 including the stacked semiconductor chips 410, 420 and 430 is molded by a molding material. In FIG. 4, the reference numeral 460c designates third solder balls.

[0036] As is apparent from the above description, the stack package according to various embodiments of the present invention provides advantages in that, since electrical connections between the semiconductor chips and between a semiconductor chip and the PCB are formed through TSVs and re-distribution lines without the use of metal wires, the stack package can be easily applied to high-speed products. Also, in the present invention, because wire loops are not adopted, the overall size of the stack package can be decreased.

[0037] Further, because the positions of solder balls can be appropriately adjusted in the present invention, not only semiconductor chips of different sizes but also uniform-size semiconductor chips can be easily stacked without using specific tapes containing a shock-absorbing substance.

[0038] Moreover, because solder balls can be attached over the entire surface of the semiconductor chip in the present invention, the stress induced in the semiconductor chip can be dispersed over a large area, whereby it is possible to provide a stack package having improved reliability.

[0039] Although specific embodiments of the present invention have been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and the spirit of the invention as disclosed in the accompanying claims.