The present disclosure relates to semiconductor devices, particularly to a semiconductor device with a structure in which a plurality of semiconductor chips are directly bonded together by bumps.
LSI technology, which is a key technology for multimedia equipment, has been steadily developed in recent years in order to achieve higher-speed data transmission and larger capacity. With this development, a packaging technique for an interface between LSI and electronic equipment has also been developed to achieve higher densities.
A known high-density package is a system-in package (SIP) in which multiple LSI devices are integrated in a single package for a system. Some SIPs employ a package in which multiple semiconductor chips are mounted on a common circuit board (an interposer). Another known package has a chip-on-chip (CoC) structure of a stacked chip type in which multiple semiconductor chips are stacked by using, as a circuit board, not an interposer but another semiconductor chip.
To achieve multiple pins in the SIP described above, flip-chip bonding has been put into practical use in recent years. In the flip-chip bonding, minute bumps (metal projections) are formed on electrode pads on a surface of a semiconductor chip and a surface of a circuit board (or a semiconductor chip), and these surfaces are bonded together and are electrically coupled to each other (face-to-face joint).
In addition, the technique of using a through-silicon via (TSV) is employed as one of packaging techniques for higher densities. The use of the TSV enables electrodes to be also formed on a back surface of a wafer. In view of this, it is also proposed that minute bumps in the shape of electrode pads are formed on the back surface of a semiconductor chip having a TSV and the front surface of another semiconductor chip, and these chips are electrically bonded together (face-to-back bonding).
In such a bonding technique, a semiconductor chip provided with a plurality of bumps are mounted by using a bonder on a circuit board also provided with a plurality of bumps.
In this case, a semiconductor chip and either a circuit board or a semiconductor chip are accurately positioned relative to each other with, for example, image recognition by using a bonder, and then, bumps on the semiconductor chip and bumps on the circuit board are oriented face to face and a pressure is applied to the bumps.
Accordingly, unless the positioning of the semiconductor chip and the circuit board, for example, is not accurately performed, when the bumps are actually oriented face to face and a pressure is applied to the bumps, a displacement between the bumps causes the bumps to slide, and the semiconductor chip to slide accordingly. This sliding of the semiconductor chip causes joint defects (e.g., an increase in resistance, an open defect, and a short-circuit defect in a bump joint). As the pitch of the bumps increases, these defects become more conspicuous because the margin for the displacement among the bumps decreases.
In view of this, in a typical technique for bonding, a projecting stud bump for alignment is formed on a semiconductor chip and a recessed guide hole for alignment is formed in a circuit board on which the chip is to be mounted such that position adjustment is performed by inserting the tip of the stud bump into the guide hole (see, for example, Japanese Unexamined Patent Publication No. H07-50316).
Similarly, in another proposed technique for bonding, a first projecting alignment feature is formed on a first semiconductor chip and a recessed second alignment feature is formed on a second semiconductor chip, and a tip of the first projecting alignment feature is inserted in the second alignment feature so that position adjustment is performed (see, for example, Japanese Unexamined Patent Publication No. 2011-517114).