Abstract: A method of fabricating a read only memory. After forming bit lines and word lines in a substrate, a coding process is performed. A photoresist layer is formed on the substrate while performing the coding process. The photoresist layer covering a part of a first channel region under the word line is exposed, and then the photoresist layer covering a part of a second channel region under the word lines is exposed. A development step is performed to remove the photoresist layer that has been exposed. Using the remaining photoresist layer as a mask to perform an ion implantation, a coding area is formed in the first channel region and the second channel region. The photoresist layer is removed.

Abstract: A method of fabricating a read only memory. After forming bit lines and word lines in a substrate, a coding process is performed. A photoresist layer is formed on the substrate while performing the coding process. The photoresist layer covering a part of a first channel region under the word line is exposed, and then the photoresist layer covering a part of a second channel region under the word lines is exposed. A development step is performed to remove the photoresist layer that has been exposed. Using the remaining photoresist layer as a mask to perform an ion implantation, a coding area is formed in the first channel region and the second channel region. The photoresist layer is removed.

Abstract: In the manufacturing of VLSI circuits, production of overlay is a critical step. To obtain a higher resolution and alignment accuracy in microlithographic process, overlay errors must be measured so that overlay errors can be reduced to a tolerable level. This invention provides an overlay error model and a sampling strategy. Utilizing the overlay model and sampling strategy, a device for measuring overlay errors is also designed.

Abstract: Conventionally, efforts to improve the yield of chips produced on a wafer focused on defect reduction. Another approach is optimizing wafer exposure patterns. The present invention includes a computer-based procedure and apparatus to expose cells on the surface of a wafer so as to maximize the number of dies produced from a wafer. The invention is useful in the exposure of six and eight inch wafers, as well as larger wafers.