1. Field of the Invention
The present disclosure relates to a semiconductor device, and particularly to a semiconductor device having a chip on chip (CoC) structure.
2. Description of the Related Art
In recent years, as semiconductors have been increasingly miniaturized, a number of transistors constituting an LSI goes on increasing. Furthermore, as a component of the LSI, especially a system becomes complicated and large, memory capacity needed by a system LSI is problematically increased, so that there is a need for a method for highly efficiently mounting the system LSI having a large-scale memory.
Meanwhile, as for a method for connecting the LSI to a package, a wire bonding method and a flip chip method are widely used. When a memory is mounted by the mounting methods, the memory is to be mounted on a system LSI chip, a chip mounting substrate, or a mounting substrate, so that mounting capacity is limited, a large substrate mounting area is needed, and mounting cost is high. To solve these problems, the CoC structure is employed.
A semiconductor device having a general CoC structure is provided such that semiconductor chips each having a plurality of pads on its circuit formation surface are disposed so that their circuit formation surfaces are opposed to each other, and the semiconductor chips are electrically connected to each other through bumps disposed on the pads. When such a CoC structure is employed, the plurality of semiconductor chips can be mounted on the substrate, so that the chips can be efficiently connected in a small area, compared with the normal wire bonding and flip chip methods.
Meanwhile, when the CoC structure is employed, a power supply voltage is supplied to an upper semiconductor chip through a lower semiconductor chip, so that the problem is that voltage drop (IR drop) occurs due to lack of power supply voltage in the upper semiconductor chip. In addition, since the lower semiconductor chip is covered with the upper semiconductor chip, it is difficult to supply the power supply voltage from a part just above a center portion of the lower semiconductor chip, so that voltage drop also occurs in supplying the power supply voltage to the center portion of the lower semiconductor chip. Thus, an operation speed of a transistor of the LSI becomes uneven due to this influence, so that this influence is to be considered, otherwise operation timing of the LSI is affected, and serious problems are caused with LSI operation failure and an yield.
To solve the above problems, PTL 1 discloses a semiconductor device in which the CoC structure is employed, and mounting positions of a plurality of semiconductor chips stacked on the wiring substrate are displaced so that a power supply voltage can be directly supplied from the substrate to the upper mounted chip.
Furthermore, PTL 2 discloses a semiconductor device in which the CoC structure is employed, and a semiconductor logic circuit chip which is smaller than a semiconductor memory chip is stacked on the semiconductor memory chip, in order to miniaturize the semiconductor device.
Furthermore, PTL 3 discloses a semiconductor device in which interposer substrates are provided between a plurality of semiconductor elements. More specifically, a pad is formed on one surface of the interposer substrate, and a pad is formed on the other surface of the interposer substrate so as to be disposed at a plane position matching a plane position of a pad of the semiconductor element positioned on the other surface, and the pad formed on the one surface is connected to the pad formed on the other surface in the interposer substrate.
PTL1: Unexamined Japanese Patent Publication No. 2008-159607
PTL2: Unexamined Japanese Patent Publication No. 2010-141080
PTL3: Unexamined Japanese Patent Publication No. 2010-278334
According to the semiconductor device in PTL 1, since it is assumed that the stacked positions of the chip mounted on the upper side and the chip mounted on the lower side are displaced, the power supply voltage only can be directly supplied from the substrate to the one side of the chip surface facing the substrate, so that it is extremely difficult to stably supply the power supply voltage in a chip surface. In addition, since the chip is displaced, an area of a resin mounting substrate is increased, and cost is increased due to the increase in size of the substrate.
According to the semiconductor device in PTL 2, since it is assumed that the chip mounted on the upper side is smaller than the chip mounted on the lower side, the CoC structure cannot be employed in a case where the lower side chip is small.
According to the semiconductor device in PTL 3, the semiconductor chips vertically stacked through a through-silicon via (TSV) are connected through the interposer substrate, circuits on the upper and lower chips can be efficiently connected, but regarding the prevention in power supply voltage drop in the chip center portion, its effect is limited.
According to the present disclosure, in a semiconductor device including a plurality of semiconductor chips connected as a CoC structure, provided is a configuration capable of stably supplying a power supply voltage to a center portion of the upper and lower chips at the time of CoC mounting.
According to one aspect of the present disclosure, a semiconductor device includes a substrate, a first semiconductor chip placed on the substrate, having a circuit formation surface on an upper surface provided opposite to a surface facing the substrate, and including a TSV electrode and a connection pad electrically connected to the substrate, a second semiconductor chip placed on the upper surface of the first semiconductor chip, and electrically connected to the first semiconductor chip through a bump, a connection member for electrically connecting the connection pad of the first semiconductor chip to the substrate, and a redistribution layer (RDL) formed on the upper surface of the first semiconductor chip, and electrically connected to the TSV electrode.
According to the aspect, power can be supplied from the substrate to the upper surface of the first semiconductor chip, that is, the circuit formation surface through the TSV electrode formed in the first semiconductor chip, and the redistribution layer formed on the upper surface of the first semiconductor chip. Therefore, the power supply voltage can be stably supplied to the chip center portion.
According to the present disclosure, in the semiconductor device having the plurality of semiconductor chips connected with the CoC form, while the cost is kept down, the power supply voltage can be stably supplied to the center portions of the upper and lower chips at the time of the CoC mounting, without regard to the sizes of the upper and lower chips. Therefore, it is possible to prevent timing performance degradation and a functional defect caused by variation in speed of the transistor operation, so that the semiconductor device can be improved in performance and reliability.
A semiconductor device according to this exemplary embodiment will be described with reference to the drawings. A common component is marked with the same reference and its description will occasionally not be given.
As shown in
Wire bonding pads 104A are formed on first semiconductor chip 101 around a mount region of second semiconductor chip 102. Wire 106 electrically connects wire bonding pad 104A to substrate 103 by wire bonding. Furthermore, through-silicon via (TSV) electrode (silicon penetration electrode) 108 is formed in first semiconductor chip 101. At least one TSV electrode 108 is electrically connected to substrate 103. Here, as one example, at a lower surface of first semiconductor chip 101, TSV electrode 108 is connected to substrate electrode 109 of substrate 103 through a conductive resin or conductive film 110. In addition, TSV electrode 108 in first semiconductor chip 101 may be electrically connected to substrate electrode 109 through solder, a bump, or a redistribution layer, instead of the conductive resin or conductive film 110.
One TSV electrode 108 is disposed at a position matching a position of upper bump 105 when planarly viewed, and electrically connected to upper bump 105. Another TSV electrode 108 is not disposed at the position matching the position of upper bump 105 when planarly viewed, and not electrically connected to upper bump 105. In addition, TSV electrode 108 may be electrically connected or not connected to a wiring in first semiconductor chip 101.
Furthermore, redistribution layer 111 is formed on the upper surface of first semiconductor chip 101. TSV electrode 108 is electrically connected to redistribution layer 111 on the upper surface of first semiconductor chip 101 through a chip surface wiring, for example. A power supply wiring or a ground wiring is connected to redistribution layer 111 in first semiconductor chip 101. Mold resin 112 seals first and second semiconductor chips 101 and 102, and wire 106.
As shown in
A plurality of power supply systems can be formed by forming TSV electrode 108 and bump 105 with respect to each of the plurality of power supply systems, and connecting bump 105 to redistribution layer 111 and to an electrode in the chip on first and second semiconductor chips 101 and 102.
Redistribution layer 111 can be formed in the same step as a step of manufacturing bump 105. For example, they are formed by opening a resist in the regions for redistribution layer 111 and bump 105 on first semiconductor chip 101, performing electrolytic plating with Cu and Sn, and removing the resist. A material of redistribution layer 111 and bump 105 may be any material as long as it is a metal material, and a low-resistance metal such as Cu, solder, Ni, Au, Al, or their alloy is more favorably used.
In a case where the power supply and the ground wiring are used in combination, two redistribution layers 111 are drawn to the chip center portion, thereby creating the power supply wirings having two potentials. In this configuration, with redistribution layers 111 drawn to the center portions of first and second semiconductor chips 101 and 102, the power supply voltage can be stably supplied to the chip center portion, so that the power supply voltage can be prevented from dropping in the chip center portion in the CoC structure.
In addition, TSV electrode 108 in first semiconductor chip 101 is connected to substrate electrode 109 through the conductive resin or conductive film 110. When this connection position is set in the center portion of semiconductor chip 101, and a center portion of substrate 103, a power supply wiring path from ball terminal 114 of substrate 103 to an internal element in first semiconductor chip 101 can be shorter, and a resistance can be reduced.
More specifically, a height of redistribution layer 111 is about 3 μm, and this is about three times higher than a diffusion wiring layer (having a height of 1 μm) provided in first and second semiconductor chips 101 and 102. Therefore, wiring resistance of a height component can be reduced to about ⅓. In addition, redistribution layer 111 and bump 105 may be formed of the same metal material as the same layer.
With the above configuration, the power supply voltage can be also stably supplied to a mesh power supply and a vertically-penetrating power supply constituted by wirings in first and second semiconductor chips 101 and 102, through redistribution layer 111 and TSV electrode 108. Furthermore, regarding an influence of a transfer of an L component, since TSV electrode 108 serving as the power supply wiring is thicker than conventional wire 106, the influence on first and second semiconductor chips 101 and 102 can be small. Furthermore, a conductive path extending to substrate 103 through thick TSV electrode 108 can be formed in the center portion of first semiconductor chip 101, so that a heat releasing property can be improved in the CoC stacked type chip.
In addition, in a case where the semiconductor chip is large in size, many terminals (such as half a total number of the terminals) are needed for the wire bonding to supply the power supply voltage, but by partially replacing those terminals with the TSV electrode to share the power supply, a number of the terminals can be reduced, and the chip size can be reduced. That is, a number of the chips obtained per wafer can be increased, and a package size can be miniaturized.
According to a general configuration of a conventional CoC package employing a simple TSV technique, a stacked body constituted by a plurality of chips formed of CoC is directly connected to a mother substrate by flip-chip bonding, or a lower surface of a lower chip is connected after its mounting pitch is increased by redistribution technique. In this configuration, in a case where connection portions having the CoC structure concentrate in a center portion especially, it is necessary to narrow a pitch of the TSVs, and make a redistribution layer fine down on the lower surface of the lower chip.
Meanwhile, according to this exemplary embodiment, the circuit formation surface of the lower chip faces upward, and only the terminal for the power supply voltage (or grounding) is drawn to the substrate through the TSV. With this configuration, a number of the TSVs can be reduced, and the TSVs can be formed at rough pitches, so that the semiconductor device can be manufactured with high yield and at low cost. Furthermore, as for remaining signal lines and power voltage supply lines, they are connected to the wire bonding pads through the wiring in the chip or the redistribution layer.
Furthermore, the power supply voltage terminal extracted through the TSV is formed in such a manner that a pattern having the same potential is connected to the same wiring on the substrate according to a number of its kind, and the plurality of TSVs are connected to the one pattern having the same potential on the substrate.
With the above configuration, a number of the wire bonding pads is reduced, wiring designs on the lower chip and the substrate can be easily designed, and a number of layers and a size of the substrate can be reduced.
As shown in
With this configuration, since expansion portion 121 is formed, the stable chip stacked structure can be realized even when first semiconductor chip 101 is smaller in size than second semiconductor chip 102. Therefore, the power supply voltage can be stably supplied to the chip center portion through redistribution layer 111 serving as the power supply wiring drawn to the chip center portion through TSV electrode 108, so that the power supply voltage can be prevented from dropping in the chip center portion in the CoC structure.
At least one TSV electrode 108 is formed in second semiconductor chip 102. TSV electrode 108 in second semiconductor chip 102 is electrically connected to TSV electrode 108 in first semiconductor chip 101 through connection terminal 104 and bump 105. In addition, redistribution layer 111 is formed on the lower surface of third semiconductor chip 116. Redistribution layer 111 of third semiconductor chip 116 is electrically connected to TSV electrode 108 in second semiconductor chip 102 through connection terminal 104 and bump 105.
As described above, when TSV electrode 108 is also formed in second semiconductor chip 102, the power supply voltage can be stably supplied to the chip center portion through redistribution layer 111 serving as the power supply wiring drawn to the chip center portion of third semiconductor chip 116 through TSV electrode 108, so that the power supply voltage can be prevented from dropping in the chip center portion in the CoC structure.
With this configuration, since expansion portion 122 is formed, a stable chip stacked structure can be realized even when second semiconductor chip 102 is smaller in size than third semiconductor chip 116. Therefore, the power supply voltage can be stably supplied to the chip center portion through redistribution layer 111 serving as the power supply wiring drawn to the chip center portion through TSV electrode 108, so that the power supply voltage can be prevented from dropping in the chip center portion in the CoC structure.
Furthermore, heat releasing plate 117 made of metal is provided so as to cover the chip stacked structure. Heat releasing plate 117 is electrically connected to substrate electrode 109 of substrate 103. In addition, TSV electrode 108 is formed in third semiconductor chip 116, and TSV electrode 108 is electrically connected to heat releasing plate 117 on the upper surface of third semiconductor chip 116 through a conductive resin or conductive film 110.
With this configuration, as for the power supply path between second semiconductor chip 102, and the first and third semiconductor chips 101 and 116 provided on its upper and lower sides, due to the formation of redistribution layer 111, its lateral position can be freely set without regard to the disposed position of bump 105. As a result, a degree of freedom in bonding the upper and lower chip layers can be improved in the chip stacked structure.
Redistribution layer 111 can be optionally formed on any of the upper surfaces and the lower surfaces of semiconductor chips 101, 102, and 116. Furthermore, the position of the power supply path can be changed optionally according to the position of redistribution layer 111. Furthermore, the wiring to configure the power supply path in the lateral direction of the chip may be the wiring in the chip other than redistribution layer 111. When the wiring in the chip is used in combination with redistribution layer 111, an effect of reducing the resistance of the power supply path can be more improved.
Furthermore, the conductive path can be ensured from an upper portion of uppermost third semiconductor chip 116 through substrate electrode 109, and the conductive resin or conductive film 110. Thus, in addition to the power supply voltage supplied from the lower portion of the conventional stacked chip structure, the power supply voltage can be supplied from the upper portion of the stacked chip structure, so that the voltage can be more effectively prevented from dropping due to the lack of the power supply voltage in third semiconductor chip 116.
In addition, heat releasing plate 117 is provided for one power supply system in
In addition, wire bonding pad 104B is formed on second semiconductor chip 102, and wire 106B electrically connects wire bonding pad 104B to substrate 103 by wire bonding. In addition, a wire bonding pad may be provided on third semiconductor chip 116 and connected to the substrate 103 by wire bonding.
When the power supply or the ground wiring is connected to capacitor element 118, the power supply and the grounding can be prevented from fluctuating due to circuit operations of semiconductor chips 101, 102, and 116. As a result, the power supply voltage can be stably supplied to the center portion of the chip, so that the power supply voltage can be prevented from dropping in the center portion of the chip in the CoC structure. Furthermore, when the plurality of wire bonding structures are formed, the power supply can be reinforced in a middle layer of the chip stacked structure. Therefore, the power supply voltage can be stably supplied to the chip center portion, and the power supply voltage can be prevented from dropping in the chip center portion at the time of CoC bonding.
Furthermore, capacitor element 118 is disposed on the uppermost portion of the chip stacked structure in
The above exemplary embodiment and the variations show the configuration in which the two or three semiconductor chips are stacked, but the same effect can be provided in a configuration in which four or more semiconductor chips are stacked. In addition, the circuit formation surface of each semiconductor chip may be the upper surface or the lower surface. Furthermore, the TSV electrode may penetrate from the upper surface to the lower surface of the semiconductor chip, or it may penetrate from the in-chip wiring in the chip to a rear surface of the chip.
Furthermore, each semiconductor chip may have a circuit function other than the memory and the system LSI.
Furthermore, the above exemplary embodiment and variations have described the configuration in which the TSV electrode is formed in the lower chip connected to the substrate, and the power supply voltage is supplied (or grounded) from this TSV electrode to the lower chip and the upper chip, but as another configuration, the wire bonding and the TSV electrode may be formed in the upper chip instead of the lower chip to supply the power supply voltage. More specifically, the power supply voltage is supplied from the substrate to the upper chip through the wire bonding, and then the power supply voltage is supplied to the center portion of the lower chip through the TSV electrode formed in the upper chip. At this time, the wire bonding between the upper chip and the substrate for supplying the power supply voltage is to be provided with a wire thicker than the other signal lines. In addition, the power supply voltage can be stably supplied from the upper chip by use of the redistribution layer formed on the circuit surface of the lower chip.
In the above, the present disclosure has been described in detail based on the exemplary embodiment and its variations, but the present disclosure is not limited to the above exemplary embodiment and the like. Various variations and modifications can be made without departing from the scope of the present disclosure, and the present disclosure includes a case where a plurality of exemplary embodiments are combined, or the components are partially replaced with an alternative one which is not described in the exemplary embodiment.
According to the present disclosure, the power supply can be stably supplied to the center portions of the upper and lower chips at the time of CoC mounting, so that the present disclosure can be applied to various electronic devices using the semiconductor device having the CoC structure.
Number | Date | Country | Kind |
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2013-046487 | Mar 2013 | JP | national |
Number | Date | Country | |
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Parent | PCT/JP2013/006013 | Oct 2013 | US |
Child | 14841768 | US |