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    MANUFACTURE OF FOUR STATE MASK ROM
    1.
    发明专利
    MANUFACTURE OF FOUR STATE MASK ROM 失效

    公开(公告)号：JPH11176953A

    公开(公告)日：1999-07-02

    申请号：JP2299898

    申请日：1998-02-04

    Applicant: UNITED MICROELECTRONICS CORP

    Inventor： CHUNG CHENG-HUI ,  SHENG YI-CHUNG

    IPC: H01L27/112 ,  H01L21/8246

    Abstract: PROBLEM TO BE SOLVED: To form ROM having four threshold voltages and to store multi-bit data in a single memory unit by manufacturing a double layer structure memory transistor sharing the same gate oxide layer through the use of the manufacture technology of a thin film transistor. SOLUTION: A first photo resist layer 37 is formed so that it covers a semiconductor substrate 300, and a first coding step is executed. Then, second area/ third areas of a channel area 320 are doped. A thin film transistor oxide layer 39 is formed on the substrate 300 and a second polycrystalline silicon layer 41 which is doped in P-type is formed on the substrate 300. A second polycrystalline silicon layer 41 is doped by N-type dopant by using a photo mask 43. A second photo resist layer 44 is formed on the thin film transistor and a second coding step is executed. Thus, four state mask ROM is manufactured by such two coding steps.

    Tetra-state mask read only memory
    4.
    发明专利
    Tetra-state mask read only memory 未知

    公开(公告)号：NL1008061C2

    公开(公告)日：1999-07-20

    申请号：NL1008061

    申请日：1998-01-19

    Applicant: UNITED MICROELECTRONICS CORP

    Inventor： CHUNG CHENG-HUI ,  SHENG YI-CHUNG

    IPC: H01L21/8246 ,  H01L27/112

    Abstract: The ROM is fabricated by providing a semiconductor substrate having a gate oxide layer, a first polysilicon layer, a plurality of source/drain regions, and a plurality of channel regions. By using a first photoresist to dope the channel regions, a first coding step is performed to obtain a transistor having 2 different threshold voltages. A thin film transistor oxide layer is formed over the substrate, patterned and etched to expose the source/drain regions. A second polysilicon layer is formed on the thin film transistor oxide, and a mask used to dope a part of it to form a plurality of doped regions. Using a second photoresist layer as a mask, a part of the second polysilicon layer corresponding to the channel regions is doped and a second coding step performed.

    Method of forming a tetra-state mask read only memory
    8.
    发明专利
    Method of forming a tetra-state mask read only memory 未知

    公开(公告)号：GB2333396A

    公开(公告)日：1999-07-21

    申请号：GB9800789

    申请日：1998-01-14

    Applicant: UNITED MICROELECTRONICS CORP

    Inventor： CHUNG CHENG-HUI ,  SHENG YI-CHUNG

    IPC: H01L21/8246 ,  H01L27/112

    Abstract: Using a first photoresist pattern 37 the channel regions 320 in the substrate are doped by ion implantation thereby performing a first coding step to provide a transistor having two different threshold values. A polysilicon layer 41 is doped by ion implantation using a second photoresist pattern 44 as a mask to perform a second coding step, thereby providing an inverse transistor with two different threshold values. In this manner double layered memory transistors sharing the same gate oxide 39 are used to form a ROM with four threshold values.

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