Electronic circuit with embedded memory

Abstract

Circuitry includes first and second circuits spaced apart by an interconnect region. The interconnect region includes a first interconnect and the second circuit includes a stack of semiconductor layers. The first interconnect extends between the first and second circuits to provide communication therebetween. The second circuit operates as a memory circuit.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application is a divisional of application Ser. No. 11 / 092,521, entitled “ELECTRONIC CIRCUIT WITH EMBEDDED MEMORY”, filed on Mar. 29, 2005, which claims priority to U.S. Pat. No. 7,052,941 filed on Jun. 21, 2004, the contents of both of which are incorporated herein by reference.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates generally to semiconductor circuitry and, more particularly, to circuitry which includes memory devices. [0004] 2. Description of the Related Art [0005] Advances in semiconductor manufacturing technology have provided computer chips with integrated circuits that include many millions of active and passive electronic devices, along with the interconnects to provide the desired circuit connections. As is well-known, most integrated circuits include laterally oriented active and passive electronic devices that are carried on a single major surface of a substrate. ...

AI Technical Summary

Problems solved by technology

However, these laterally oriented devices consume significant amounts of chip area.

As a result, the processor circuit is idle for many cycle times while it accesses the main memory.

Hence, cache memory uses a small amount of fast and expensive memory to allow the processor circuit faster access to information normally stored by a large amount of slower, less-expensive memory.

However, there are several problems with doing this.

One problem with doing this is cost.

As mentioned above, the SRAM cells included in cache memory are larger and expensive, so increasing the size of the cache memory would significantly increase the cost of the computer chip.

DRAM cells are less expensive and smaller, but to embed them with the main computer chip will still significantly increase the cost.

One reason the cost increases for both embedded SRAM and DRAM cells is because the number of masks needed to fabricate the main computer chip increases.

This is because the masks used to fabricate the processor and control circuitry are not compatible with the masks used to fabricate SRAM and DRAM memory cells.

Another reason the cost increases is because, as discussed below, the yield in manufacturing computer chips decreases as the size of the computer chip increases.

Another problem is that in today's computer systems, the size of the main memory is much larger than the size of the cache memory.

Thus, to increase the size of the cache memory by increasing the number of SRAM cells included therein would significantly increase the size of the computer chip and decrease its yield.

This presents several problems.

As mentioned above, one problem is that the yield of computer chips in a manufacturing run decreases as their size increases.

A wafer, however, has defects distributed throughout it surface which can negatively impact the operation of the computer chips.

Further, if the computer chip is smaller in size, then more of them can be fabricated from a single wafer, which also decreases costs.

Hence, smaller computer chips increase the yield and decrease the costs.

Another problem is that it is typically desirable to increase the number of devices included in the processor and control circuitry so that the processor can operate faster and perform more complicated operations.

In one way, the computer chip can include devices which are smaller, but this requires advances in lithography and increasingly expensive manufacturing equipment.

The total area of the computer chip can be increased, but as discussed above, this decreases the yield and increases the cost.

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