Semiconductor wafer bearing alignment mark for use in aligning the wafer with exposure equipment, alignment system for producing alignment signals from the alignment mark, and method of determining the aligned state of a wafer from the alignment mark

Abstract

A semiconductor wafer has an alignment mark for use in aligning the wafer with exposure equipment during the manufacturing of a semiconductor device. The wafer is made by forming a chemical mechanical polishing target layer over an alignment mark layer, chemically-mechanically polishing the target layer to planarize the same, and prior to forming the chemical mechanical polishing target layer over the alignment mark layer, forming a dense pattern of lands or trenches in the alignment layer of dimensions and an inter-spacing preselected to inhibit a dishing phenomenon from occurring in the target layer as the result of its being chemically-mechanically polished. The lands or trenches may be disposed in at least a 2×2 array of rows and columns. An alignment system for use with this wafer irradiates the mark with light, and includes an image sensor which produces both a Y-axis alignment waveform signal from light reflecting from the column(s) of lands or trenches and an X-axis alignment waveform signal from light reflecting from the row(s) of lands or trenches. Alternatively, the lands or trenches may be disposed along at least two lines arranged in the shape of a chevron. In this case, the alignment system scans an illuminated cross-shaped pattern of a reticle across the alignment mark. A photo-detection unit collects the reflected light and determines the relative amounts of light coming from the wafer surface, from one of the lines of lands or trenches of the alignment mark, and from the other such line of lands or trenches.