United Microelectronics Corp.

Shing-Ren Shev

Chen-Chiu Hsue

Kuan-Cheng Su

Chen-Hui Chung

A ROM device with an array of cells has conductors formed in a substrate. Insulation is formed, and parallel conductors are formed orthogonally to the line regions, as thin as about 2000 .ANG.. Glass insulation having a thickness of about 3000 .ANG. or less, formed over the conductors is is reflowed. Contacts and a metal layer on the glass insulation are formed. Resist is patterned and used for etching the resist pattern in the metal. Removal of the second resist and device passivation with a layer having a thickness of about 1000 .ANG., precede activation of the impurity ions by annealing the device at less than or equal to about 520.degree. C. in a reducing gas atmosphere. After resist removal, a second resist is formed and exposed with a custom code pattern to form a mask. Ions are implanted into the substrate with a dosage of between about 1 E 14 and 3 E 14 atoms/cm.sup.2 with an energy of less than or equal to 200 keV adjacent to the conductors through the openings in the insulation.

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Tau Yuan, Taiwan

Shing-Ren Shev