United Microelectronics Corp.

Han-Shen Lo

Te-Sun Wu

Hsin-Li Chen

Kun-Luh Chen

Heng Sheng Huang

Wood Wu

Stephen S Fu

A read only memory cell array and method of operation thereof comprises an array of memory transistor cells, a plurality of word lines, a plurality of bit lines, a plurality of select bit lines, a plurality of bank select lines for enabling reading of a selected bank in the array connected to bank select transistors in the bank, a select even line adapted for enabling reading of even cells in a selected bank connected to select even cell transistors in the bank, and a select odd line adapted for enabling reading of odd cells in a selected bank connected to select odd cell transistors in the array.

High density ROM with select lines

A ROM IC includes an extra bit line. The extra bit line outputs a first binary logic signal when a word line in a no-use area is attempted to be read and a second binary logic signal when a word line in a use area is attempted to be read. The output of the extra bit line overrides the normal output of the ROM when a word line in a no-use area is attempted to be read, so that the output of a read operation in the no-use area is always a predetermined binary value. This predetermined binary output value occurs in spite of the fact that because of a defect the actual logic value of a storage location in the word line to be read in the no-use area is other than a desired value. When a word line in the use area is read, the output of the extra bit line does not override the actual binary value stored in the word line. Using the extra bit line and associated override circuitry, a ROM IC with a few defects in a no-use area may still be used in an application. It should be noted that the addition of the extra bit line in the ROM does not significantly increase the amount of chip 'real estate' occupied by the ROM.

Bypass scheme for ROM IC

A cost-effective and manufacturable method for producing ROM integrated circuits with closely-spaced self-aligned conductive lines, on the order of 0.3 micrometers apart, is described. Parallel, conductive semiconductor device structures are formed in a semiconductor substrate. An insulating layer is formed over the semiconductor substrate. A first conductive polysilicon layer is formed over the insulating layer. The first conductive polysilicon layer is patterned to form first polysilicon conductor lines which are parallel to each other, and orthogonal to the parallel, conductive semiconductor device structures. A first silicon oxide layer is formed on and between the first polysilicon conductor lines. The first silicon oxide layer is anisotropically etched to produce sidewall structures on the first polysilicon conductor lines. A second silicon oxide layer is formed on and between the first polysilicon conductor lines. A second conductive polysilicon layer is formed over the first polysilicon conductor lines and in openings between the first polysilicon conductor lines. The second conductive polysilicon layer is etched back to form second polysilicon conductor lines, parallel to, between and self-aligned with the first polysilicon conductor lines, and separated from the first polysilicon conductor lines by width of the sidewall structures.

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Chu-pei, Taiwan

Han-Shen Lo