Manufacturing method of semiconductor device

Abstract

The manufacturing method of the semiconductor device of the present invention has a step forming solder balls on the circuit face of a mother chip, a step making flip chip bonding of the daughter chip after the step forming solder balls on the circuit face of the mother chip, and a step making flip chip bonding of the mother chip on a circuit board using the solder balls.

Claims

1. A manufacturing method of a semiconductor device, comprising the steps of: preparing a mother chip and a daughter chip, the mother chip including, first and second electrodes, and a passivation film formed on a substrate and having openings exposing upper surfaces of the first and second electrodes; forming metal layers on the upper surfaces of the first and second electrodes, respectively; each metal layer includes barrier metal formed on the upper surface of the corresponding electrode and on the passivation film, and a metal post formed on the barrier metal; forming solder balls on the metal posts of the metal layers formed on the first electrodes so that the solder balls are located above the first electrodes; making flip chip bonding of a daughter chip on a circuit face of the mother chip to electrically connect the daughter chip to the metal posts of the metal layers formed on the second electrodes after the step of forming solder balls; and making flip chip bonding of the mother chip on a circuit board by using the solder balls. 2. The manufacturing method of a semiconductor device according to claim 1 , wherein the step of forming solder balls is carried out to a plurality of mother chips formed on one wafer; said method further comprising a step of: separating the plurality of mother chips into individual mother chips by dicing after the step of making flip chip bonding of the daughter chip. 3. The manufacturing method of a semiconductor device according to claim 1 , wherein the step forming solder balls comprises the steps of: forming on the passivation film a resist which has openings to the metal layers formed on the first electrodes; filling up the openings of the resist with solder paste; and forming the solder balls by heating the mother chip and melting the solder paste after removing the resist. 4. The manufacturing method of a semiconductor device according to claim 1 , wherein the step forming solder balls comprises the steps of: piling up on the mother chip a metal mask having openings so that the metal layers formed on the first electrodes fit in the openings of the metal mask; filling up the openings of the metal mask with solder paste; and forming the solder balls by heating the mother chip and melting the solder paste after removing the metal mask. 5. The manufacturing method of a semiconductor device according to claim 1 , wherein the step of forming metal layers includes the steps of: forming barrier metal on the passivation film; forming patterned resist on the barrier metal; forming the metal posts in openings of the patterned resist formed over the first and second pads; removing the patterned resist; and removing a part of the barrier metal using the metal posts as a mask. 6. The manufacturing method of a semiconductor device according to claim 1 , wherein an upper surface of the passivation film is made higher relatively to the upper surfaces of the first and second electrodes, and the whole of the upper surface of each metal post is made higher relatively to the upper surface of the passivation film. 7. A manufacturing method of a semiconductor device comprising the steps of: forming solder balls on a circuit face of a mother chip; making flip chip bonding of a daughter chip on the circuit face of the mother chip after the step of forming solder balls; and making flip chip bonding of the mother chip on a circuit board using the solder balls, wherein the flip chip bonding of the daughter chip is made while a temperature of the mother chips is made lower than a melting point of the solder balls. 8. The manufacturing method of a semiconductor device according to claim 7 , wherein in the step of making flip chip bonding of the daughter chip, the daughter chip is heated when a metal post formed on the mother chip and a metal post formed on the daughter chip are made to bond by thermo-compression via a joining member. 9. The manufacturing method of a semiconductor device according to claim 7 , wherein in the step of making flip chip bonding of the daughter chip, supersonic vibration is applied to the daughter chip when a metal post formed on the mother chip and a metal post formed on the daughter chip are made to bond by thermo-compression. 10. The manufacturing method of a semiconductor device according to claim 7 , wherein the daughter chip includes a jointing member of solder, and in the step of making flip chip bonding of the daughter chip, the daughter chip is heated at a temperature higher than a melting point of the joint member.
BACKGROUND OF THE INVENTION The present application claims priority from Japanese patent application No. 2004-369230 filed on Dec. 21, 2004, the content of which is hereby incorporated by reference into this application. FIELD OF THE INVENTION The present invention relates to a manufacturing method of a semiconductor device which makes flip chip bonding of a daughter chip at a mother chip, and makes flip chip bonding of a mother chip on a circuit board further, and particularly relates to a manufacturing method of a semiconductor device which can efficiently form solder balls to be used in order to make flip chip bonding of the mother chip on the circuit board. BACKGROUND ART In recent years, the semiconductor device which has the COC (chip on chip) structure having made flip chip bonding of a daughter chip at a mother chip, and which made flip chip bonding of the mother chip further at the circuit board is proposed (for example, refer to Japanese Unexamined Patent Publication No. 2004-146728). Conventionally, when manufacturing this semiconductor device, after making flip chip bonding of the daughter chip on the circuit face of a mother chip, solder balls were formed on the circuit face of a mother chip, and flip chip bonding of the mother chip was made on the circuit board using these solder balls. There are many solder balls to connect a circuit board with a mother chip, and for example, it is 1000 or more pieces. Therefore, in order to form solder balls efficiently, it is necessary to use the solder ball formation method of single wafer processing collectively enforced to a plurality of mother chips formed on the wafer. As a solder ball formation method of such single wafer processing, there are a method of applying the resist to the circuit face of a mother chip, and making opening of the resist filling up with solder paste, and a method of laying a metal mask on top of the circuit face of a mother chip, and filling up opening of the metal mask with solder paste. However, when forming solder balls in the manufacturing process of a conventional COC type semiconductor device, a daughter chip is connected and the surface of a mother chip is not flat. Therefore, since the resist could not be applied uniformly, and it was also difficult to process a thin metal mask according to the surface irregularity, the solder ball formation method of the above-mentioned single wafer processing was not able to be used. SUMMARY OF THE INVENTION The present inventions are made to solve the above problems, and the purpose is to obtain a manufacturing method of a semiconductor device which can efficiently form solder balls used in order to make flip chip bonding of a mother chip on a circuit board. A manufacturing method of a semiconductor device of the present invention comprises the steps of: forming solder balls on a circuit face of a mother chip; making flip chip bonding of a daughter chip on the circuit face of the mother chip after the step forming solder balls; and making flip chip bonding of the mother chip on a circuit board using the solder balls. The other features of the present invention are made clear to below. Since the present invention forms solder balls in the phase with little irregularity before making flip chip bonding of the daughter chip on the circuit face of a mother chip, the solder ball formation method of single wafer processing can be used for it. For this reason, the solder balls used in order to make flip chip bonding of the mother chip on the circuit board can be formed efficiently. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flowchart in which the manufacturing method of the semiconductor device concerning Embodiment 1 of the present invention is shown; FIGS. 2A-2F are sectional views showing the step which forms solder balls on the circuit face of a mother chip; FIGS. 3A-3E are sectional views showing the step which forms a daughter chip; FIGS. 4A and 4B are sectional views showing the step which makes flip chip bonding of the daughter chip on the circuit face of a mother chip, and the step which makes flip chip bonding of the mother chip at a circuit board; FIG. 5 is a sectional view showing the semiconductor device concerning Embodiment 2 of the present invention; FIG. 6 is a sectional view showing the semiconductor device concerning Embodiment 3 of the present invention; FIG. 7 is a sectional view showing the semiconductor device concerning Embodiment 4 of the present invention; FIG. 8 is a sectional view showing the semiconductor device concerning Embodiment 5 of the present invention; and FIG. 9 is a sectional view showing the semiconductor device concerning Embodiment 6 of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a flowchart in which the manufacturing method of the semiconductor device concerning Embodiment 1 of the present invention is shown. The manufacturing method of the semiconductor device concerning Embodiment 1 is explained referring to this flowchart and FIGS. 2A-4B . First, the manufacturing process of mother chip 10 and the forming step of solders ball are explained. As shown in FIG. 2A , Al electrode 12 is formed on substrate 11 (circuit face), and the other region is covered with passivation film 13 . And a test is performed by applying a probe to this Al electrode 12 (step S 1 ). This test is conducted to a plurality of mother chips 10 formed on the wafer, respectively, and the wafer map in which the pass or failure of each mother chip 10 on a wafer is shown is created. Next, as shown in FIG. 2B , barrier metal 14 including a multilayer, such as Cu, Ni, Cr, and W, is formed in the whole surface with spatter technology or plating technology. And as shown in FIG. 2C , resist 15 having opening to the region to which Al electrode 12 exists is formed, opening of resist 15 is filled up with Cu etc. with plating technology, and metal post 16 is formed. Then, as shown in FIG. 2D , resist 15 is removed and anisotropic etching of the barrier metal 14 is performed by using metal post 16 as a mask (step S 2 ). The thickness of metal post 16 is about 15 μm, and the pitch of metal post 16 each other is 20-100 μm. Next, as shown in FIG. 2E , resist 17 which has opening to the region forming a solder ball (after-mentioned) is formed, and opening of resist 17 is filled up with solder paste 18 with plating technology (step S 3 ). If very thin gold plating is given to the surface of metal post 16 , since wettability with solder paste 18 is securable, it is desirable. Next, after removing resist 17 , by melting (reflowing) solder paste 18 heating mother chip 10 , solder balls 19 are formed (step S 4 ). Then, cleaning (step S 5 ) and a visual inspection (step S 6 ) are conducted. Solder balls are formed on the circuit face of mother chip 10 by the above steps. Next, the manufacturing process of daughter chip 20 is explained. As shown in FIG. 3A , Al electrode 22 is formed on substrate 21 (circuit face), and the other region is covered with passivation film 23 . And a test is performed by applying a probe to this Al electrode 22 (step S 7 ). This test is conducted to a plurality of daughter chips 20 formed on the wafer, respectively, and the wafer map in which the pass or failure of each daughter chip 20 on a wafer is shown is created. Next, as shown in FIG. 3B , barrier metal 24 including a multilayer, such as Cu, Ni, Cr, and W, is formed in the whole surface with spatter technology or plating technology. And as shown in FIG. 3C , resist 25 having opening to the region to which Al electrode 22 exists is formed, opening of resist 25 is filled up with Cu etc. with plating technology, metal post 26 is formed, and joining member 27 of solder etc. is formed on it. Then, as shown in FIG. 3D , resist 25 is removed and anisotropic etching of the barrier metal 24 is performed by using metal post 26 and joining member 27 as a mask (step S 8 ). The thickness of metal post 26 is about 15 μm, and the pitch of metal post 26 each other is 20-100 μm. Next, as shown in FIG. 3E , a plurality of daughter chips 20 formed on the wafer are individually separated by dicing (step S 9 ). Daughter chip 20 is formed by the above steps. As daughter chip 20 , passive devices, such as a chip capacitor, and active devices, such as a memory, can be used. Next, the step making flip chip bonding of the daughter chip on the circuit face of the mother chip, and the step making flip chip bonding of the mother chip at the circuit board are explained. First, flip chip bonding of the daughter chip 20 which passed by the probe test of step S 7 is made on the circuit face of mother chip 10 which passed the test by the probe test of step S 1 , and the visual inspection of step S 6 (step S 10 ). Concretely, first, as shown in FIG. 4A , mother chip 10 is put on stage 31 , daughter chip 20 is held by handle part 32 , and a mutual circuit face is opposed. And heating daughter chip 20 with the heater formed in handle part 32 to higher temperature than the melting point (183° C.) of solder, for example, 300° C., metal post 16 formed on mother chip 10 and metal post 26 formed on daughter chip 20 are made to bond by thermo-compression via joining member 27 . Since joining member 27 inserted in metal posts 16 and 26 including material which is not melted changes a lot and melts by this, the surface oxide film of joining member 27 is destroyed, and good joining is acquired by fluxless. However, in the case of this thermo compression bonding, the heater formed in stage 31 is adjusted so that temperature of mother chip 10 may be made lower than the melting point of solder ball 19 , for example, 100° C.-150° C., not to make solder ball 19 remelt. Thereby, the oxidation of the surface of solder balls 19 by remelting and the link of solder ball 19 each other can be prevented. Although flip chip bonding of the daughter chip 20 is made maintaining at high temperature rather than the melting point of solder, mother chip 10 has good heat conduction, heat spreads, and since stage 31 in which mother chip 10 is installed has large heat capacity, the rise of temperature is suppressed. Next, a plurality of mother chips 10 formed on the wafer are individually separated by dicing (step S 11 ). And as shown in FIG. 4B , flip chip bonding of mother chip 10 is made on circuit board 33 via solder balls 19 (step S 12 ). As circuit board 33 , a multilayer organic substrate, a silicon interposer, a chip, etc. can be used. Then, under-filling is performed by pouring in resin 34 between mother chip 10 and circuit board 33 (step S 13 ). Outer balls 35 are formed in the underside of circuit board 33 for external connection. By the above steps, the semiconductor device with which flip chip bonding of the daughter chip 20 was made on the circuit face of mother chip 10 , and flip chip bonding of this mother chip 10 was made at the circuit board is manufactured. In this semiconductor device, spacing of solder ball 19 each other is about 200 μm, spacing of metal post 16 (or metal post 26 ) each other is 20-100 μm, the thickness of daughter chip 20 is 50-300 μm, the diameter of a solder ball is 100 μm, and spacing of outer ball 35 each other is 0.6-1.8 mm. As explained above, since solder balls are formed in the phase with little irregularity before making flip chip bonding of the daughter chip 20 on the circuit face of mother chip 10 , the solder ball formation method of single wafer processing can be used. For this reason, the solder balls used in order to make flip chip bonding of the mother chip 10 on a circuit board can be formed efficiently. Sn can be used as joining member 27 , using Cu as metal posts 16 and 26 . In this case, joining member 27 becomes CuSn alloy by thermo compression bonding. Or SnAg (melting point 212° C.) may be used as joining member 27 , using Ni as metal post 26 , using Cu as metal post 16 . By performing Au plating to the metal post surface to which a joining member is connected, it is good to secure wettability. Metal posts 16 and 26 can also be connected by carrying out surface cleaning treatment like plasma treatment. In this case, it is not necessary to destroy a surface oxide film according to deformation of joining member 27 on which the big pressure was put, and they are joinable even if the amount of joining member 27 is reduced. And the leakage of joining member 27 to the side face of metal posts 16 and 26 can be decreased, and the height of metal posts 16 and 26 can be made thin. Thereby, since spacing of mother chip 10 and daughter chip 20 can be narrowed, the stress by the thermal expansion of the resin between chips can be reduced. Embodiment 2 The manufacturing method of the semiconductor device concerning Embodiment 2 differs in the step which deposits solder paste on the circuit face of mother chip 10 from the FIG. 2E of Embodiment 1. Other steps are the same as that of Embodiment 1. That is, as for Embodiment 2, as shown in FIG. 5 , metal mask 36 is laid on top of the circuit face of mother chip 10 so that the region which forms a solder ball, and opening may fit in, and it is filled up by printing solder paste 18 to the opening of metal mask 36 . Then, metal mask 36 is removed, and like FIG. 2F , by melting solder paste heating mother chip 10 , solder balls are formed. Thus, in the step which forms solder balls on the circuit face of mother chip 10 , even if it uses metal mask 36 instead of using resist 17 like Embodiment 1, the same effect as Embodiment 1 can be acquired. Embodiment 3 The manufacturing method of the semiconductor device concerning Embodiment 3 differs in the step which makes flip chip bonding of the daughter chip 20 on the circuit face of mother chip 10 from the FIG. 4A of Embodiment 1. Other steps are the same as that of Embodiment 1. That is, in Embodiment 3, as shown in FIG. 6 , metal posts 16 and 26 include Ni, and Au films 37 and 38 are formed on the surface of both, respectively. Or metal posts 16 and 26 may include Au. In the condition of maintaining mother chip 10 and daughter chip 20 at 150° C., supersonic vibration is applied to daughter chip 20 , and the metal post formed on mother chip 10 and the metal post formed on daughter chip 20 are made to bond by thermo-compression with supersonic vibration. Thus, since thermo compression bonding is possible at temperature lower than Embodiment 1 by applying supersonic vibration, oxidation of the surface of solder balls 19 by remelting and the link of solder ball 19 each other can be prevented. Embodiment 4 FIG. 7 is a sectional view showing the semiconductor device concerning Embodiment 4 of the present invention. As for this semiconductor device, depressed portion 39 is formed in the region corresponding to daughter chip 20 on the top face of circuit board 33 . Other structure is the same as that of Embodiment 1. Thereby, even when daughter chip 20 is thick, flip chip bonding of mother chip 10 and circuit board 33 can be made good. Embodiment 5 FIG. 8 is a sectional view showing the semiconductor device concerning Embodiment 5 of the present invention. As for this semiconductor device, rewiring layer 40 is formed on the circuit face of mother chip 10 of the present invention, and its top is covered with passivation film 41 . However, it is made not to form rewiring layer 40 and passivation film 41 in the region which connects daughter chip 20 . Thereby, since the height of metal posts 16 and 26 is securable, when under-filling, it becomes easy to pour in resin 34 between chips. Embodiment 6 FIG. 9 is a sectional view showing the semiconductor device concerning Embodiment 6 of the present invention. As for this semiconductor device, chip capacitor 42 other than daughter chip 20 is mounted on the circuit face of mother chip 10 . Other structure is the same as that of Embodiment 1. Thus, also when a passive device, such as a chip capacitor, and an active device are loaded together on mother chip 10 , the present invention can be applied, and the same effect can be acquired. Flip chip bonding of the two or more daughter chips 20 may be made at mother chip 10 . In this case, a flash memory and DRAM can be used as daughter chips 20 , for example. As things mentioned above, the present inventions accomplished by the present inventors were concretely explained based on above embodiments, but the present inventions are not limited by above embodiments, but variations and modifications may be made, of course, in various ways in the limit that does not deviate from the gist. Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described. The entire disclosure of a Japanese Patent Application No. 2004-369230, filed on Dec. 21, 2004 including specification, claims, drawings and summary, on which the Convention priority of the present application is based, are incorporated herein by reference in its entirety.

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