| 摘要 |
PURPOSE: A method for fabricating a mask ROM is provided to reduce turn around time according to custom data by implanting a code ion after forming a metal pattern. CONSTITUTION: Pluralities of buried bit lines(33) are formed at regular intervals in a semiconductor substrate(30), and pluralities of word lines(35) are formed at regular intervals perpendicularly to the buried bit lines(33). An oxide layer(36) is then deposited over the word lines(35), and a BPSG layer(37) is deposited on the oxide layer(36). The BPSG layer(37) is then reflowed by heat treatment, and contact holes are formed therein to electrically connect the buried bit lines(33). Thereafter, a metal pattern(38) is formed in and over the contact holes to be in contact with the bit lines(33). Then, a ROM code mask is patterned over the metal pattern(38) by a photoresist layer, and the oxide layer(36) and the BPSG layer(37) are selectively etched through the ROM code mask to expose the word lines(35). Next, a code ion such as boron is implanted, and a passivation layer(40) is formed on the entire surface.
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