Source: {"pile_set_name": "USPTO Backgrounds"}

In the fabrication of semiconductor devices such as integrated circuits, memory cells, and the like, a series of manufacturing operations are performed to define features within a chip on a semiconductor wafer (“wafer” hereafter). The chip on the wafer includes integrated circuit devices in the form of multi-level structures defined on a silicon substrate. At a substrate level of the chip, transistor devices with diffusion regions are formed. In subsequent levels of the chip, interconnect metallization lines are patterned and electrically connected to the transistor devices to define a desired integrated circuit device. Also, patterned conductive layers are insulated from other conductive layers by dielectric materials.
The series of manufacturing operations for defining features within the chip on the wafer can include an etching process in which particular portions of a material layer are etched away from the surface of the wafer, such that remaining portions of the material layer form structures to be used in the integrated circuit device. In the etching process, variations in the size and location of areas to be etched away from the surface of the wafer can cause differences in the rate at which material is etched away from one area relative to another area. The variations in the size and location of areas to be etched away from the surface of the wafer is referred to as microloading variation. Therefore, microloading variation across the wafer can cause differences in etch rate across the wafer.
The etching process should continue until each area is etched to completion. Therefore, if a given area is etched to completion faster than other areas, due to differences in etch rate across the wafer caused by microloading variation, the given area will be subjected to a localized overetch period. During the localized overetch period, etching by-products from the etching environment may settle within the given area causing a variation in dimension of the given area, which may correspond to an adverse change in critical dimension of a structure to be defined on the wafer in relation to the given area. Therefore, microloading variation in a given layout to be utilized in an etching process on a wafer may adversely effect dimensional characteristics of correspondingly fabricated structures on the wafer.