SEMICONDUCTOR MEMORY DEVICE

Abstract: In a semiconductor memory device including word lines (WL) and bit lines (BL), a regular circuit area comprising el­ ements regularly arranged in line with the word lines and/or the bit lines is divided into a plurality of blocks (1-1, 1-2). Provided between the divided blocks are irregular or peripheral circuit areas (2). Provided outside of the divided blocks are pads (P₁ to P₁₆).

Description: The present invention relates to a semiconductor memory device. A layout of a semiconductor memory device such as a dynamic or static random access memory (RAM) is divided mainly into a regular circuit area, a peripheral circuit area, and a bonding pad area. Provided in the regular circuit area are repeated circuits regularly in line with word lines and/or bit lines. For example, memory cells are arranged in line with the word lines and the bit lines, row decoders are arranged in line with the word lines, and sense amplifiers and column decoders are arranged in line with the bit lines. Contrary to the above, no word line and no bit line is provided in the peripheral circuit area. That is, irregular pattern circuits are provided in the peripheral circuit area. A layout for such a regular circuit area, an irregular or peripheral circuit area, and a bonding pad area is important when considering the high capacity of a semiconductor device. According to one prior art layout of a semiconductor memory device, two peripheral circuit areas are provided on both sides of a regular circuit area. Further provided outside of the peripheral circuit areas are bonding pad areas. In this case, the peripheral circuit areas have to be connected directly or indirectly to each pad of the bonding pad areas. Therefore, one of the peripheral circuit areas has to be connected substantially to each pad located on the opposite side thereof, and vice versa. In this case, one peripheral circuit is connected directly to a power supply pad and some pads located on the opposite side thereof, and via the other peripheral circuit is connected to the other signal pads located on the opposite side thereof. As a result, the total line width of the signal lines and power supply lines linking the peripheral circuits and the pads and bypassing the regular circuit area becomes large, thereby reducing the area of the regular circuit area, which is disadvantageous to enabling high capacity. In addition, when the above-mentioned device is mounted on a cerdip or plastic package, some of bonding posts of the package may be superimposed on the others, in order to reduce the capacitances of the connections between the bonding pads of the device and the bonding posts of the package. This reduces the entire area of the device, thereby reducing the area of the regular circuit area, which is also disadvantageous to enabling high capacity. Further, there are many types of packages. For example, from a viewpoint of shapes, there are DIP's, leadless packages, flat packages, and the like, and from a viewpoint of materials and sealed states, there are metal sealed packages, cerdip packages, plastic packages, and the like. The configuration of the bonding posts of a package depends upon the type of package. However, in a semiconductor device, each pad has a purpose different from that of the other pads. Therefore, when a semiconductor device is designed for a certain type of package, such a semiconductor device may not be mounted on another type of package, due to the different arrangement of the bonding posts of the package. If such a semiconductor device is forced to be mounted on another type of package, the connections linking the bonding pads and the bonding posts become overlong, thereby reducing the cavity of the package and increasing their capacitances. Also, wire-bonding operations for the above-mentioned connections become difficult, thereby increasing the manufacturing cost. It is therefore desirable to provide a high capacity semiconductor memory device. It is also desirable to provide a semiconductor memory device having a low manufacturing cost. JP-A-52-58327 discloses a semiconductor memory device having features corresponding to those of the preamble of accompanying claim 1. In this device, bonding pads are arranged all around the periphery of the device. There is no attempt to minimise the overall size of the device. An article in New Electronics, Vol. 15, No. 16, August 1982, entitled "Dynamic RAMs" discloses a semiconductor memory device having two separated memory cell arrays arranged along a short side of the device, and arranged between the memory cell arrays are a row decoder, column decoder, etc. An I/O circuit, clock, etc., are provided outside the memory cell arrays adjacent the edge of the short side. According to the present invention, there is provided a semiconductor memory device having the features set out in Claim 1. The present invention can reduce the total line width of the signal and power supply lines linking the peripheral circuit areas and the pads and bypassing the divided regular circuit areas. As a result, the occupied area of the regular circuit area is increased so as to increase the capacity thereof. An embodiment of the present invention provides a plurality of pads, each pad having the same purpose. One of the pads having the same purpose can be selected and connected to one bonding post of a requested package, thereby shortening the connections linking the bonding pads and the bonding posts. As a result, the cavity of the package can be reduced, the capacitances of the connections linked between the bonding pads and the bonding posts can also be reduced, and in addition, a wire-bonding operation for these connections becomes easy, thereby reducing the manufacturing cost. Reference will now be made, by way of example to the accompanying drawings, wherein:- Fig. 1A is a layout diagram of a prior art semiconductor memory device; Fig. 1B is a partial layout diagram of the device of Fig. 1 mounted on a cerdip or plastic package; Fig. 2A is a layout diagram of a semiconductor memory device for explaining the present invention; Fig. 2B is a detailed layout diagram of the device of Fig. 2A; Fig. 2C is a layout diagram of a modification of the device of Fig. 2A; Fig. 3A is a layout diagram of another semiconductor memory device for explaining the present invention; Fig. 3B is a partial layout diagram of the device of Fig. 3A mounted on a cerdip or plastic package; Fig. 3C is a layout diagram of a modification of the device of Fig. 3A; Fig. 4A is a layout diagram of an embodiment of a semiconductor memory device according to the present invention; Fig. 4B is a layout diagram of the device of Fig. 4A mounted on a package of the metal-seal type; Fig. 4C is a layout diagram of the device of Fig. 4A mounted on a cerdip or plastic package; Fig. 4D is a layout diagram of the device of Fig. 4A mounted on a leadless chip carrier; and Figs. 5A, 5B, 5C, and 5D are circuit diagrams of a circuit for the connections for the pads of Fig. 4A. In Fig. 1A, an example of a prior art a 16-pin dynamic RAM is illustrated. Provided on both sides of a regular circuit area 1 are peripheral circuit areas 2-1 and 2-2. The regular circuit area 1 comprises memory cells, row decoders, column decoders, sense amplifiers, and the like arranged in line with word lines and/or bit lines. The peripheral circuit areas 2-1 and 2-2 comprise irregular pattern circuits. In addition, provided outside of the peripheral circuit areas 2-1 and 2-2 are bonding pads P₁ through P₁₆. Here, the pad P₁₆ is for a power supply V SS , the pad P₈ is for a power supply V CC , and the other pads are for control signals and address signals. The device of Fig. 1 is suitable for a dual-inline package (DIP). In Fig. 1, both of the peripheral circuit areas 2-1 and 2-2 have to be connected directly or indirectly to the pads P₁ to P₁₆. That is, the peripheral circuit 2-1 is connected directly to the power supply pad P₈ , and via the peripheral circuit 2-2, is connected to the pads P₅ , P₆ , P₇ , P₉ , P₁₀ , P₁₁ , and P₁₂. In this case, the peripheral circuit 2-2 converts signals from the pads P₅ , P₆ , P₇ , P₉ , P₁₀ , P₁₁ , and P₁₂ , into timing signals, control signals and the like, and transmits them to the peripheral circuit 2-1 via signal lines at areas X and Y. Similarly, the peripheral circuit 2-2 is connected directly to the power supply pad P₁₆ , and via the peripheral circuit 2-1, is connected to the pads P₁ , P₂ , P₃ , P₄ , P₁₃ , P₁₄ , and P₁₅. In this case, the peripheral circuit 2-1 converts signals from the pads P₁ , P₂ , P₃ , P₄ , P₁₃ , P₁₄ , and P₁₅ , into timing signals, control signals and the like, and transmits them to the peripheral circuit 2-2 via signal lines at the areas X and Y. Therefore, the pads P₅ to P₁₂ are substantially connected via the areas X and Y to the peripheral circuit area 2-1, while the pads P₁ to P₄ and P₁₃ to P₁₆ are substantially connected also via the areas X and Y to the peripheral circuit area 2-2. For example, at the areas X and Y, the line width of each power supply line for the pads P₈ and P₁₆ is about 100 µm, so that the resistance thereof is sufficiently low. In addition, the line width of each signal line for the other pads is 6 µm, and the number thereof is 20 to 30. Therefore, the total line width of the lines at the areas X and Y is 100 x 2 + 6 x (20 ∼ 30) = 300 to 400 µm. This total width limits the area of the regular circuit area 1, which is disadvantageous to enabling high capacity. In addition, as illustrated in Fig. 1B, when the device of Fig. 1A is mounted on a cerdip or plastic package 3 having bonding posts 4-1, 4-2, 4-3, 4-4, ..., wires W between the pads P₁ , P₂ , P₃ , and P₄ , and the bonding posts 4-1, 4-2, 4-3, and 4-4 are shortened to reduce their capacitances. In this case, however, the bonding post 4-3 of the third pin is superimposed on the bonding post 4-4 of the fourth pin at a portion Z. This also limits the area of the device of Fig. 1, and, accordingly, is disadvantageous to enabling high capacity. Further, if the device of Fig. 1A is mounted on a leadless chip carrier, some of the connections linked between the bonding pads and the bonding posts become remarkably long, thereby reducing the cavity of the package and increasing their capacitances, and a wire-bonding operation for the connections becomes difficult. In Fig. 2A, which is useful for explaining the present invention, and in Fig. 2B, which is a more detailed layout diagram of Fig. 2A, regular circuit areas 1-1 and 1-2 are provided at the right and left sides of the device, and a peripheral circuit area 2 is provided therebetween. In addition, bonding pads P₁ through P₁₆ are provided outside of the regular circuit areas 1-1 and 1-2. As shown in Fig. 2B, each of the regular circuit areas 1-1 and 1-2 comprises four memory cell arrays 101, 102, 103 and 104 having memory cells at intersections between word lines WL and bit lines BL, two row decoder areas 105 and 106 having one row decoder for every word line, two column decoder areas 107 and 108 having one column decoder for every bit line, and four sense amplifier areas 109, 110, 111, and 112 having one sense amplifier for each bit line pair. Provided commonly for the regular circuit areas 1-1 and 1-2 are lines 5 for address signals, a bit line charging signal, a word line driving signal, a sense amplifier driving signal, a column decoder driving signal, and the like. In Fig. 2A, the distance between the peripheral circuit area 2 and the power supply pads P₈ and P₁₆ is half that of the device shown in Fig. 1A. Therefore, the width of the power supply lines between the peripheral circuit 2 and the power supply pads P₈ and P₁₆ can be halved in view of their resistances, and, in addition, the number of power supply lines passing through the areas X' and Y' can be halved. Therefore, the total width of the lines at the areas X' and Y' is almost one quarter that of the device shown in Fig. 1A in consideration of the other lines. Note that, since the number of lines at the areas X' and Y' on both sides of the regular circuit areas 1-1 and 1-2 are different from each other, the positions of regular circuit areas 1-1 and 1-2 at the Y direction may differ from each other. In Fig. 2C, which is a modification of the device of Fig. 2A, four regular circuit areas 1-1, 1-2, 1-3, and 1-4 are provided, and three peripheral circuit areas 2-1, 2-2, and 2-3 are provided therebetween. In addition, pads P₁ through P₁₆ are provided outside of the regular circuit areas 1-1 and 1-4. In this device of Fig. 2C, the distance between the peripheral circuit such as 2-1 and the power supply pads P₈ is about three-quarters of that shown in Fig. 1A. Therefore, the width of the power supply lines between the peripheral circuits and the power supply pads can be reduced in view of their resistances, as compared with that of Fig. 1A. Therefore, the total width of the lines at areas X'' and Y'' is reduced as compared with that of Fig. 1A. Note that the devices of Figs. 2A and 2C are expected to be mounted on a DIP. In Fig. 3A, which is also useful for explaining the present invention, the pads P₄ , P₅ , P₁₂ , and P₁₃ are provided at the center of the device, i.e., outside of the peripheral circuit area 2, since this device of Fig. 3A is, in this case, expected on a cerdip or plastic package. That is, as shown in Fig. 3B, when the device of Fig. 3A is mounted on a cerdip or plastic package, the bonding post 4-3 of the third pin is not superimposed on the bonding post 4-4 of the fourth pin, so that the margin of the package is increased, thereby increasing the capacity of the device of Fig. 3A. Fig. 3C is a modification of the device of Fig. 3A, and also corresponds to Fig. 2C. That is, as compared with the device of Fig. 2C, the pads P₁₄ and P₃ are arranged outside of the peripheral circuit area 2-1, the pads P₁₃ , P₁₂ , P₄ , and P₅ are arranged outside of the peripheral circuit area 2-2, and the pads P₁₁ and P₆ are arranged outside of the peripheral circuit area 2-3. This type of device shown in Fig. 3C is also expected to be mounted on a cerdip or plastic package. Thus, the total width of lines bypassing the regular circuit areas can be reduced, thereby attaining a large capacity of a device. In Fig. 4A, which illustrates an embodiment of the present invention, pads P'₄ , P'₅ , P'₁₂ , and P'₁₃ are added to the elements of Fig. 2A. Note that the pads P'₄ , P'₅ , P'₁₂ , and P'₁₃ have the same purpose as the pads P₄ , P₅ , P₁₂ , and P₁₃ , respectively. Therefore, one of the pads P₄ and P'₄ , one of the pads P₅ and P'₅ , one of the pads P₁₂ and P'₁₂ , and one of the pads P₁₃ and P'₁₃ are selected and connected by the wire bonding operation to the respective bonding posts of a package. As a result, the device of Fig. 4A can be mounted on various types of packages. Fig. 4B shows the case where the device of Fig. 4A is mounted on a ceramic package of a metal-sealed type. In this case, bonding posts are arranged on both sides of the package (not shown). That is, the posts 4-1, 4-2, 4-3, 4-4, 4-13, 4-14, 4-15, and 4-16 are arranged on the left side of the package, while the pads 4-5, 4-6, 4-7, 4-8, 4-9, 4-10, 4-11, and 4-12 are arranged on the right side of the package. Therefore, in this case, the pads P₁ through P₁₆ of the device are connected by wires W to the bonding pads 4-1 through 4-16, respectively, and the pads P'₄ , P'₅ , P'₁₂ , P'₁₃ have no connections to the bonding posts. Note that the provision of bonding posts on the up and down sides of a metal-sealed type package reduces the cavity thereof. Therefore, such bonding posts are not usually provided. Fig. 4C shows the case where the device of Fig. 4A is mounted on a cerdip or plastic package. In this case, bonding posts are also present on the up and down sides of the package (not shown). That is, it is usually difficult to arrange all the bonding posts on both sides of a cerdip or plastic package. Therefore, the pads P'₄ , P'₅ , P'₁₂ , and P'₁₃ are connected by wires W to the bonding posts 4-4, 4-5, 4-12, and 4-13, respectively, and the pads P₄ , P₅ , P₁₂ , and P₁₃ have no connections to the bonding posts, since the pads P'₄ , P'₅ , P'₁₂ , and P'₁₃ are closer to the bonding posts 4-4, 4-5, 4-12, and 4-13 than the pads P₄ , P₅ , P₁₂ , and P₁₃. Fig. 4D shows the case where the device of Fig. 4A is mounted on a leadless chip carrier. In this case, bonding posts are arranged equidistantly on all sides of the carrier (not shown), and it is not necessary to carry out a wire-bonding operation upon all of the bonding posts. Therefore, although the pads P'₄ , P'₅ , P'₁₂ , and P'₁₃ are connected by wires W to the bonding 4-4, 4-5, 4-12, and 4-13, respectively, the pads P₄ , P₅ , P₁₂ , and P₁₃ have no connections to the posts, and the posts 4-17 through 4-24 have no connections to the pads. Thus, since a plurality of pads having the same purpose are provided on a semiconductor device, one of the pads having the same purpose is selected for the arrangement of the bonding posts of a certain type of package. The above-mentioned pads having the same purpose have to be connected together to each other at an interior circuit of the device. For this, there is prepared a circuit for connecting the pads having the same purpose to each other. Such a circuit for the pads 13 and 13' is illustrated in Fig. 5A, 5B, 5C, or 5D. In Fig. 5A, the pads P₁₃ and P'₁₃ are connected directly to the same conductive layer, such as an aluminium layer, which leads to the interior circuit of the device. In this circuit of Fig. 5A, however, when the pad P₁₃ is used, the capacitance of the pad P'₁₃ serves also as the capacitance of the pad P₁₃ , thereby reducing the propagation speed of a signal thereon. In Fig. 5B, the pads P₁₃ and P'₁₃ are connected to gates G₁ and G₂ connected in parallel within the interior circuit. Therefore, the circuit of Fig. 5B dissolves the disadvantage of the device of Fig. 5A. However, since a non-used pad such as P'₁₃ is in a floating state, the gate G₂ may operate due to noise or the like, thereby inviting an erroneous operation. Note that the gates G₁ and G₂ are of a metal-oxide semiconductor (MOS) transistor type, however, another type of gate such as a bipolar transistor can be used in accordance with the type of device. In Fig. 5C, depletion-type transistors G₃ and G₄ are added to the elements of Fig. 5B. Therefore, a non-used pad such as P'₁₃ is earthed by the transistor G₄ , thereby preventing the pad P'₁₃ from being in a floating state. Thus, the disadvantage of the circuit of Fig. 5B is dissolved. Of course, the conductivity of the depletion-type transistors G₃ and G₄ is designed in consideration of the potential at the used pad such as P₁₃ being at a suitable value. Note that enhancement-type drain-gate connected transistors can be used instead of the depletion-type transistors G₃ and G₄. In Fig. 5D, enhancement-type transistors G'₃ and G'₄ are used as the means for preventing non-used pads from being in a floating state. The transistors G'₃ and G'₄ are selected by a selection circuit by depletion-type transistors G₅ and G₆ , and an enhancement-type transistor G₇. An additional pad V CC * is provided. Note that the transistors G₆ and G₇ constitute an inverter INV. In the circuit of Fig. 5D, when the pad V CC * is opened, i.e., when the pad V CC * has only a connection to the node N₁ , the potential at the node N₁ is at the ground level, so that the transistor G'₃ is cut off. Thus, the pad P₁₃ is in a use state. In addition, the potential at the node N₂ becomes high so as to turn on the transistor G'₄. As a result, the pad P'₁₃ is grounded and accordingly, the pad P'₁₃ is in a no-use state. In the circuit of Fig. 5D, when the pad V CC * is bonded to the pad P₈ which is for the power supply V CC , the potential at the node N₁ becomes high so as to turn on the transistor G'₃. Thus, the pad P₁₃ is in a no-use state. In addition, the potential at the node N₂ becomes low, so as to cut off the transistor G'₄. Thus, the pad P'₁₃ is in a use state. Thus, in the circuit of Fig. 5D, a non-used pad is selected and grounded, thereby preventing the non-used pad from being in a floating state. As explained hereinbefore, the regular circuit areas including memory cells can be increased, thereby enhancing the capacity thereof.

Claims: A semiconductor memory device having a rectangular shape with a long side and a short side and comprising:- a plurality of word lines (WL); a plurality of bit lines (BL); at least two separated regular circuit area means (1-1, 1-2) arranged along the long side of the device and each comprising elements arranged regularly in line with said word lines or said bit lines; irregular circuit area means (2) comprising elements irregularly arranged relative to said word lines and said bit lines; and bonding pad areas arranged on the periphery of said device, comprising first bonding pads (P₁, ..., P₁₆) arranged outside said separated regular circuit area means along the short side of said device; characterised in that:- said irregular circuit area means (2) are arranged between said separated regular circuit area means (1-1, 1-2); and in that connecting means, for operatively connecting said bonding pads to said irregular circuit area means, are arranged in regions (X', X'', Y', Y'') between said regular circuit area means (1-1, 1-2) and the edge of the long side of the device the distance between the regular circuit area means and the edge of the long side of the device being too narrow to accommodate bonding pad areas in between. A device as set forth in claim 1, further comprising second bonding pads (P'₄, P'₅, P'₁₂, P'₁₃) arranged outside said irregular circuit area means along the long side of said device, said second bonding pads (P'₄, P'₅, P'₁₂, P'₁₃) having the same specific purpose as corresponding ones (P₄, P₅, P₁₂, P₁₃) of said first bonding pads. A device as set forth in claim 2, further comprising a plurality of gates connected in parallel (G1, G2), each of said gates having a control terminal which is connected by said connecting means to a respective one of said pads (13, 13') having the same specific purpose. A device as set forth in claim 3, further comprising means (G₃, G₄, G'₃, G'₄), each connected to a respective one of said pads having the same specific purpose, for preventing the potential thereof from being in a floating state. A device as set forth in claim 4, further comprising a means (G₅, G₆, G₇), connected to said preventing means (G'₃, G'₄) for said pads (P₁₃, P'₁₃) having the same specific purpose, for selecting and operating one of said preventing means.

Inventors: NAKANO, TOMIO, SATO, KIMIAKI, TAKEMAE, YOSHIHIRO
Applicants: FUJITSU LIMITED
Application year: 1984
Main classification: G11C5
IPC codes: G11C5, H01L21, G11C11, H01L27