http://www.freepatentsonline.com/495...

BACKGROUND OF THE INVENTION

The present invention relates to a semiconductor memory and, more particularly, to a technique which may be effectively applied, for example, to dynamic type RAMs (Random Access Memories) or the like which are designed so that it is possible to achieve expansion of type on the basis of a common semiconductor substrate (base chip).

There is one type of dynamic RAM which enables selection of various kinds of operating mode, for example, static column mode, page mode, etc., and also selection of units in which storage data is input and output, that is, bit patterns, according to customer's needs. This type of dynamic RAM is arranged such that operating modes and bit patterns are simultaneously changed simply by changing a part of a photomask applied to a common semiconductor substrate or by selectively effecting bonding between predetermined pads, by way of example.

SUMMARY OF THE INVENTION

The inventors of the present application have revealed that, as the memory capacity and operating speed of dynamic RAMs increase and the operating modes thereof are diversified, the following problems have been experienced with the above-described conventional method wherein the operating modes and bit patterns are changed simply by changing a part of a photomask applied to a common semiconductor substrate or by selectively effecting bonding between predetermined pads.

Namely, in the case where operating modes and bit patterns are .changed simply by changing a part of photomask applied to a common semiconductor substrate, it is necessary to prepare a large number of different kinds of photomask so that desired expansion of type is enabled, and this leads to an increase in the development manhour and also complicates the management of masks. Further, since change of photomasks is usually carried out in the middle of a manufacturing process, it is difficult to cope with an urgent change of type. On the other hand, in the case where operating modes and bit patterns are changed simply by selectively effecting bonding between predetermined pads, the above-described problems are eliminated, but the number of required bonding pads increases and the chip area also increases instead. Since it is necessary in order to change bit patterns to alter the input/output path of storage data, gates or the like must be added to the input/output path so that the altered input/output path can work as desired. This prevents optimization of the signal path in the dynamic RAM and limits the reduction in the access time.

Dynamic RAMs are described, for example, in "Nikkei Electronics", June 3, 1985, Nikkei McGraw-Hill, pp. 209 to 231.

It is an object of the present invention to provide a semiconductor memory such as a dynamic type RAM or the like which is designed so that it is possible to effect efficient expansion of type without lowering the operating characteristics.

The above and other objects and novel features of the present invention will become apparent from the following description of the preferred embodiments thereof taken in conjunction with the accompanying drawings.

The following is a brief summary of a principal one of the inventions disclosed in the present application.

According to the invention, an operating mode of a dynamic type RAM or the like is set by selectively carrying out bonding between predetermined pads on a common semiconductor substrate (base chip) and a bit pattern of the RAM is set by selectively changing a part of a photomask applied to the common semiconductor substrate.

By virtue of the above-described means, it is possible to change over operating modes from one to another by selectively carrying out bonding between predetermined pads without the need to change photomasks and it is also possible to change over bit patterns from one to another by changing a part of a photomask without lowering signal transmission characteristics of the circuit. Accordingly, expansion of type of a dynamic type RAM or the like can be efficiently realized without wastefully increasing the number of bonding pads or photomasks and without lowering operating characteristics such as access time.

Be well