Stacked chip-size package type semiconductor device capable of being decreased in size

[0002] 1. Field of the Invention

[0003] The present invention relates to a semiconductor device, and more particularly, to a stacked chip-size package (CSP) type semiconductor device.

[0004] 2. Description of the Related Art

[0005] Recently, semiconductor packages have been developed to adopt stacked chip-size packages (CSPs) having substantially the same size as that of semiconductor chips.

[0006] A prior art stacked chip-size package type semiconductor device (see: JP-A-2000-307057) is constructed by a plurality of semiconductor chips stacked on a substrate. In this case, an upper one of the semiconductor chips is smaller than an lower one of the semiconductor chips. This will be explained later in detail.

[0007] In the above-described prior art stacked chip-size package type semiconductor device, however, since the largest semiconductor chip is the lowest semiconductor chip, all bonding wires connected between the semiconductor chips and the substrate are outside of the largest semiconductor chip, the substrate is much larger than the largest semiconductor chip, which would increase the stacked chip-size package in size.

[0008] It is an object of the present invention to provide a stacked chip-size package type semiconductor device capable of being decreased in size.

[0009] According to the present invention, in a semiconductor device including a substrate, a first semiconductor chip directly or indirectly on the substrate, and a second semiconductor chip located on the first semiconductor chip, the second semiconductor chip has a larger dimension than that of the first semiconductor chip.

[0010] If the second semiconductor chip is largest, the largest semiconductor chip is not the lowest semiconductor chip. As a result, some of bonding wires are inside of the largest semiconductor chip, so that the size of the substrate can be brought close to that of the largest semiconductor chip.

[0011] The present invention will be more clearly understood from the description set forth below, as compared with the prior art, with reference to the accompanying drawings, wherein:

[0012] FIG. 1 is a cross-sectional view illustrating a prior art stacked chip-size package type semiconductor device;

[0013] FIG. 2 is a cross-sectional view illustrating a first embodiment of the stacked chip-size package type semiconductor device according to the present invention;

[0014] FIGS. 3A, 3B and 3C are cross-sectional views for explaining a method for manufacturing the stacked chip-size package type semiconductor device of FIG. 2;

[0015] FIG. 4 is a partly-cut perspective view of the thermoplastic adhesive layer of FIGS. 3B and 3C;

[0016] FIGS. 5A and 5B are cross-sectional views for explaining the effect of the first embodiment of the present invention as compared with the prior art;

[0017] FIG. 6 is a cross-sectional view illustrating a modification of the stacked chip-size package type semiconductor device of FIG. 2;

[0018] FIG. 7 is a partly-cut, perspective view illustrating a modification of the thermoplastic adhesive layer of FIG. 4;

[0019] FIG. 8 is a cross-sectional view illustrating a second embodiment of the stacked chip-size package type semiconductor device according to the present invention;

[0020] FIGS. 9A and 9B are cross-sectional views for explaining a method for manufacturing the stacked chip-size package type semiconductor device of FIG. 8;

[0021] FIG. 10 is a cross-sectional view illustrating a third embodiment of the stacked chip-size package type semiconductor device according to the present invention; and

[0022] FIGS. 11A and 11B are cross-sectional views for explaining a method for manufacturing the stacked chip-size package type semiconductor device of FIG. 10.

[0023] Before the description of the preferred embodiments, a prior art stacked chip-size package type semiconductor device will be explained with reference to FIG. 1 (see: JP-A-2000-307057).

[0024] In FIG. 1, reference numeral 101 designates a substrate made of glass epoxy or the like. Semiconductor chips 102, 103 and 104 are mounted in this sequence by adhesive sheets (not shown) on a front surface of the substrate 101. Note that, the semiconductor chip 102 is larger than the semiconductor chip 103, and the semiconductor chip 103 is larger than the semiconductor chip 104. Bonding wires 105, 106 and 107 are connected between electrode pads (not shown) of the semiconductor chips 102, 103 and 104 and conductive pads (not shown) of the substrate 101. The semiconductor chips 102, 103 and 104 associated with the bonding wires 105, 106 and 107 are sealed by an epoxy resin layer 108. On the other hand, solder balls 109 are provided on a back surface of the substrate 101, and are connected through internal connections (not shown) within the substrate 101 to the conductive pads thereof.

[0025] In the stacked chip-size package type semiconductor device of FIG. 1, however, the bonding wire 105 is outside of the largest semiconductor chip 102, the bonding wire 106 is outside of the bonding wire 105 and the bonding wire 107 is outside of the bonding wire 106, thus preventing the bonding wires 105, 106 and 107 from being short-circuited. That is, all the bonding wires 105, 106 and 107 are outside of the largest semiconductor chip 102, so that the substrate 101 is much larger than the largest semiconductor chip 102, which would increase the stacked chip-size package in size.

[0026] In FIG. 2, which illustrates a first embodiment of the stacked chip-size package type semiconductor device according to the present invention, reference numeral 1 designates a substrate made of glass epoxy or the like. Semiconductor chips 4, 3 and 2 are mounted in this sequence on a front surface of the substrate 1. Note that, the semiconductor chip 2 is larger than the semiconductor chip 3, and the semiconductor chip 3 is larger than the semiconductor chip 4. In this case, the semiconductor chip 4 is adhered by an adhesive sheet (not shown) to the substrate 1. Also, the semiconductor chip 3 is adhered by a thermoplastic adhesive layer 3ato the semiconductor chip 4, and the semiconductor chip 2 is adhered by a thermoplastic adhesive layer 2ato the semiconductor chip 3. Bonding wires 5, 6 and 7 are connected between electrode pads (not shown) of the semiconductor chips 2, 3 and 4 and conductive pads (not shown) of the substrate 1. The semiconductor chips 2, 3 and 4 associated with the bonding wires 5, 6 and 7 are sealed by an epoxy resin layer 8. On the other hand, solder balls 9 are provided on a back surface of the substrate 1, and are connected through internal connections (not shown) within the substrate 1 to the conductive pads thereof.

[0027] In the stacked chip-size package type semiconductor device of FIG. 2, since only the bonding wire 5 is outside of the largest semiconductor chip 2, i.e., the bonding wires 6 and 7 hardly affect the size of the substrate 1, the size of the substrate 1 is brought close to that of the largest semiconductor chip 2, which would decrease the stacked chip-size package in size.

[0028] The method for manufacturing the stacked chip-size package type semiconductor device of FIG. 2 is explained next with reference to FIGS. 3A, 3B, 3C and 4.

[0029] First, referring to FIG. 3A, a semiconductor chip 4 is mounted by an adhesive sheet (not shown) on a front surface of a substrate 1. Then, bonding wire 7 is connected between electrode pads (not shown) of the semiconductor chip 4 and conductive pads (not shown) of the substrate 1.

[0030] Next, referring to FIG. 3B, a semiconductor chip 3 with a back surface coated by a thermoplastic adhesive layer 3ais prepared. In this case, as illustrated in FIG. 4, the thermoplastic adhesive layer 3ais constructed by an about 100 to 200 μm thick centered pedestal portion 301 for being in contact with the semiconductor chip 4, an about 100 to 400 μm thick peripheral reinforcement portion 302 for preventing the semiconductor chip 3 from being deformed by a wire bonding operation and a thin portion 303 between the centered pedestal portion 301 and the peripheral reinforcement portion 302 for encapsulating the bonding wire 7. Then, the semiconductor chip 3 with the thermoplastic adhesive layer 3ais moved down to the semiconductor chip 4, so that the centered pedestal portion 301 of the thermoplastic adhesive layer 3ais in contact with the semiconductor chip 4. Then, a heat operation is performed upon the thermoplastic adhesive layer 3a, so that the semiconductor chip 3 is mounted on the semiconductor chip 4. Then, bonding wire 6 is connected between electrode pads (not shown) of the semiconductor chip 3 and conductive pads (not shown) of the substrate 1.

[0031] Next, referring to FIG. 3C, a semiconductor chip 2 with a back surface coated by a thermoplastic adhesive layer 2ais prepared. In this case, as illustrated in FIG. 4, the thermoplastic adhesive layer 2ais also constructed by an about 100 to 200 μm thick centered pedestal portion 201 for being in contact with the semiconductor chip 3, an about 100 to 400 μm thick peripheral reinforcement portion 202 for preventing the semiconductor chip 2 from being deformed by a wire bonding operation and a thin portion 203 between the centered pedestal portion 201 and the peripheral reinforcement portion 202 for encapsulating the bonding wire 6. Then, the semiconductor chip 2 with the thermoplastic adhesive layer 2ais moved down to the semiconductor chip 3, so that the centered pedestal portion 201 of the thermoplastic adhesive layer 2ais in contact with the semiconductor chip 3. Then, a heat operation is performed upon the thermoplastic adhesive layer 2a, so that the semiconductor chip 2 is mounted on the semiconductor chip 3. Then, bonding wire 5 is connected between electrode pads (not shown) of the semiconductor chip 2 and conductive pads (not shown) of the substrate 1.

[0032] Finally, the semiconductor chips 2, 3 and 4 associated with the bonding wires 5, 6 and 7 are sealed by an epoxy resin layer 8 (see: FIG. 2), and solder balls 9 (see FIG. 2) are provided on a back surface of the substrate 1, to thereby complete the stacked chip-size package type semiconductor device of FIG. 2.

[0033] In the stacked chip-size package type semiconductor device of FIG. 1, the bonding wires 105, 106 and 107 are outside of the largest semiconductor chip 102 (see: FIG. 5A). On the other hand, in the stacked chip-size package type semiconductor device of FIG. 2, the bonding wire 5 is outside of the largest semiconductor chip 5 while the bonding wires 6 and 7 are inside of the largest semiconductor chip 5 (see: FIG. 5B). Thus, the length of the substrate 1 can be shortened by 2·ΔL as compared with the substrate 101, which would decrease the stacked chip-size package type semiconductor device of FIG. 2 in size. Additionally, the total length of bonding wire made of Au can be decreased, which would decrease the manufacturing cost.

[0034] Further, since the peripheral reinforcement portion 303 (203) of the thermoplastic adhesive layer 2a(3a) has a high rigidity, even when a load is applied by a wire operation to the semiconductor chip 3 or 2, the semiconductor chip 3 or 2 is hardly deformed.

[0035] Although the thin portion 303(203) is provided in the thermoplastic adhesive layer 3a(2a), the thin portion 303(203) can be removed as illustrated in FIGS. 6 and 7 which are modifications of FIGS. 2 and 4, respectively.

[0036] In FIG. 8, which illustrates a second embodiment of the stacked chip-size package type semiconductor device according to the present invention, the semiconductor chips 3, 4 and 2 are mounted in this sequence on a front surface of the substrate 1. In this case, the semiconductor chip 3 is adhered by an adhesive sheet (not shown) to the substrate 1. Also, the semiconductor chip 4 is adhered by an adhesive sheet (not shown) to the semiconductor chip 3, and the semiconductor chip 2 is adhered by a thermoplastic adhesive layer 2ato the semiconductor chip 4.

[0037] Even in the stacked chip-size package type semiconductor device of FIG. 8, since only the bonding wire 5 is outside of the largest semiconductor chip 2, i.e., the bonding wires 6 and 7 hardly affect the size of the substrate 1, the size of the substrate 1 is brought close to that of the largest semiconductor chip 2, which would decrease the stacked chip-size package in size.

[0038] The method for manufacturing the stacked chip-size package type semiconductor device of FIG. 8 is explained next with reference to FIGS. 9A and 9B.

[0039] First, referring to FIG. 9A, semiconductor chips 3 and 4 are mounted by adhesive sheets (not shown) on a front surface of a substrate 1. Then, bonding wires 6 and 7 are connected between electrode pads (not shown) of the semiconductor chips 3 and 4 and conductive pads (not shown) of the substrate 1.

[0040] Next, referring to FIG. 9B, a semiconductor chip 2 with a back surface coated by a thermoplastic adhesive layer 2aas illustrated in FIG. 4 is prepared. Then, the semiconductor chip 2 with the thermoplastic adhesive layer 2ais moved down to the semiconductor chip 4, so that the centered pedestal portion 201 of the thermoplastic adhesive layer 2ais in contact with the semiconductor chip 4. Then, a heat operation is performed upon the thermoplastic adhesive layer 2a, so that the semiconductor chip 2 is mounted on the semiconductor chip 4. Then, bonding wire 5 is connected between electrode pads (not shown) of the semiconductor chip 2 and conductive pads (not shown) of the substrate 1.

[0041] Finally, the semiconductor chips 2, 3 and 4 associated with the bonding wires 5, 6 and 7 are sealed by an epoxy resin layer 8 (see: FIG. 8), and solder balls 9 (see FIG. 8) are provided on a back surface of the substrate 1, to thereby complete the stacked chip-size package type semiconductor device of FIG. 8.

[0042] Even in the above-described second embodiment, although the thin portion 203 is provided in the thermoplastic adhesive layer 2a, the thin portion 203 can be removed.

[0043] In FIG. 10, which illustrates a third embodiment of the stacked chip-size package type semiconductor device according to the present invention, the semiconductor chips 4, 2 and 3 are mounted in this sequence on a front surface of the substrate 1. In this case, the semiconductor chip 4 is adhered by an adhesive sheet (not shown) to the substrate 1. Also, the semiconductor chip 2 is adhered by a thermoplastic adhesive layer 2ato the semiconductor chip 4, and the semiconductor chip 3 is adhered by an adhesive sheet (not shown) to the semiconductor chip 2.

[0044] In the stacked chip-size package type semiconductor device of FIG. 10, since the bonding wires 5 and 6 are outside of the largest semiconductor chip 2, i.e., the bonding wire 7 hardly affects the size of the substrate 1, the size of the substrate 1 is brought close to that of the largest semiconductor chip 2, which would decrease the stacked chip-size package in size.

[0045] The method for manufacturing the stacked chip-size package type semiconductor device of FIG. 10 is explained next with reference to FIGS. 11A and 11B.

[0046] First, referring to FIG. 11A, a semiconductor chip 4 is mounted by an adhesive sheet (not shown) on a front surface of a substrate 1. Then, bonding wire 7 is connected between electrode pads (not shown) of the semiconductor chip 4 and conductive pads (not shown) of the substrate 1.

[0047] Next, referring to FIG. 11B, a semiconductor chip 2 with a back surface coated by a thermoplastic adhesive layer 2aas illustrated in FIG. 4 is prepared. Then, the semiconductor chip 2 with the thermoplastic adhesive layer 2ais moved down to the semiconductor chip 4, so that the centered pedestal portion 201 of the thermoplastic adhesive layer 2ais in contact with the semiconductor chip 4. Then, a heat operation is performed upon the thermoplastic adhesive layer 2a, so that the semiconductor chip 2 is mounted on the semiconductor chip 4. Then, a semiconductor chip 3 is adhered by an adhesive sheet (not shown) to the semiconductor chip 2. Then, bonding wires 5 and 6 are connected between electrode pads (not shown) of the semiconductor chips 2 and 3 and conductive pads (not shown) of the substrate 1.

[0048] Finally, the semiconductor chips 2, 3 and 4 associated with the bonding wires 5, 6 and 7 are sealed by an epoxy resin layer 8 (see: FIG. 10), and solder balls 9 (see FIG. 10) are provided on a back surface of the substrate 1, to thereby complete the stacked chip-size package type semiconductor device of FIG. 10.

[0049] In the above-described third embodiment, although the thin portion 203 is provided in the thermoplastic adhesive layer 2a, the thin portion 203 can be removed.

[0050] In the above-described embodiments, three semiconductor chips are stacked on a substrate, however, the present invention can be applied to a stacked chip-size package where two, four or more semiconductor chips are stacked.

[0051] As explained hereinabove, according to the present invention, since the largest semiconductor chip is not the lowest semiconductor chip, the total number of bonding wires outside of the largest semiconductor chip is decreased, so that the size of a substrate can be brought close to that the largest semiconductor chip, thus decreasing the stacked chip-size package in size.