Static information storage and retrieval – Addressing – Particular decoder or driver circuit
Reexamination Certificate
2000-02-28
2001-07-03
Elms, Richard (Department: 2824)
Static information storage and retrieval
Addressing
Particular decoder or driver circuit
C365S201000
Reexamination Certificate
active
06256257
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to semiconductor memory devices and to driving a plurality of wordlines during burn-in of a device with a row decoder having limited driving ability.
2. Description of the Related Art
Advances in semiconductor technology have increased the capabilities of semiconductor devices and made the devices smaller. In particular, the demand for semiconductor memory devices having large capacity has rapidly increased with the development of computers. In response to that demand, semiconductor memory devices have become smaller while still providing large storage capacity. Accordingly, memory cells in the semiconductor memory devices must be small, and the row decoders for selecting the memory cells are correspondingly small. Such row decoders commonly include NMOS transistors for decoding received row addresses. These NMOS transistors must be small to make the row decoders compact. Accordingly, the driving abilities of the row decoders are small.
To improve the reliability of the semiconductor memory devices, a wafer containing a plurality of semiconductor memory devices often undergoes a burn-in test process. The wafer burn-in test process applies burn-in stress to the wafer and functionally tests the semiconductor memory devices on the wafer. In particular, the burn-in test sequentially or simultaneously activates wordlines in the semiconductor memory devices while applying the burn-in stress to the wafer. Simultaneously activating multiple wordlines during the burn-in test may require a driving ability that is greater than the driving ability of the row decoder, particularly when the row decoder is small. As a result, the row decoder used for normal memory accesses cannot drive a plurality of wordlines during the wafer burn-in, which results in an incomplete wafer burn-in test. Accordingly, the semiconductor memory devices that pass the burn-in test may be unreliable.
SUMMARY OF THE INVENTION
In accordance with an aspect of the present invention, a semiconductor memory device includes a burn-in controller that allows the device to sufficiently drive a plurality of wordlines for a wafer burn-in test even when a row decoder is otherwise inadequate for driving multiple wordlines.
One embodiment of the invention is a semiconductor memory device including a predecoder, a row decoding block, a wordline driving block, and a burn-in controller. The predecoder receives an external row address and predecodes the row address to generate a plurality of predecoding signals. The row decoding block, which is connected to the burn-in controller and the wordline driving block, generates a plurality of wordline enable signals that control the wordline driving block when the burn-in controller sets the semiconductor memory device in a wafer burn-in mode.
In accordance with another aspect of the invention, the row decoding block includes a plurality of main row decoders. Each main row decoder includes a main row decoding unit connected to the burn-in controller. The main row decoding unit receives upper predecoding signals from among the plurality of predecoding signals and decodes the upper predecoding signals when a master clock signal is enabled. The main row decoding unit connects to at least four wordline enable signal generators, which connect to the wordline driving block. The wordline enable signal generators receive a precharging signal and lower predecoding signals from among the plurality of predecoding signals and generate the wordline enable signals. The wordline enable signal generators deactivate the wordline enable signals when the precharging signal is asserted, and assert the wordline enable signals in response to the lower predecoding signals and the output of the burn-in controller.
According to the present invention, the semiconductor memory device can sufficiently activate the plurality of wordlines during the wafer burn-in although the driving ability of the row decoder is small.
REFERENCES:
patent: 5471429 (1995-11-01), Lee et al.
patent: 5590079 (1996-12-01), Lee et al.
patent: 5638331 (1997-06-01), Cha et al.
patent: 5680362 (1997-10-01), Parris et al.
patent: 5986917 (1999-11-01), Lee
patent: 6084808 (2000-07-01), Lim et al.
Lee Sun-min
Park Youn-sik
Elms Richard
Heid David W.
Phung Anh
Samsung Electronics Co,. Ltd.
Skjerven Morrill & MacPherson LLP
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