초록 ▼

An auto-focusing alignment and measurement system for use in precisely positioning a semiconductor substrate with respect to an integrated circuit mask is herein disclosed. This system includes a moveable convergent lens operable with another pair of convergent lenses for alternately focusing images

An auto-focusing alignment and measurement system for use in precisely positioning a semiconductor substrate with respect to an integrated circuit mask is herein disclosed. This system includes a moveable convergent lens operable with another pair of convergent lenses for alternately focusing images of the mask and the substrate onto a photodiode array. The photodiode array serves as a focus detector and, together with associated signal processing circuitry, provides a feedback signal for controlling displacement of the moveable lens to equal the separation between the mask and the substrate with an accuracy better than the depth of field of the optics. An illumination source and viewing optics provide a magnified view of images of both the mask and the substrate superimposed and in focus, thereby facilitating alignment of the substrate with respect to the mask prior to photolithographic printing. This apparatus may also be employed to measure the degree of surface flatness and parallelism between the mask and the substrate and the dimensions of surface features.

대표청구항 ▼

Apparatus for focusing on first and second spaced-apart object planes, said apparatus comprising: first imaging means, movably disposed along an optical axis, for providing a first focal plane disposed toward the first and second object planes; second imaging means, disposed along the optical axis o

Apparatus for focusing on first and second spaced-apart object planes, said apparatus comprising: first imaging means, movably disposed along an optical axis, for providing a first focal plane disposed toward the first and second object planes; second imaging means, disposed along the optical axis on the opposite side of the first imaging means from the first and second object planes, for providing a second focal plane disposed away from the first and second object planes; illumination means for illuminating the first and second object planes; an array of photodiodes disposed along the optical axis at the second focal plane, each photodiode being operable for producing an electrical signal proportional to the intensity of light incident thereon; processing means, coupled to the array of photodiodes, for analyzing the signals therefrom to indicate the focus of images of the first and second object planes at the second focal plane; and control means, coupled to the precessing means, for oscillating the first imaging means along the optical axis to repetitively alternately position the first focal plane in coincidence with the first and second object planes and permit viewing of images of the first and second object planes in focus simultaneously.