Microlithographic calibration scheme

Claim 2

In a microlithographic system for optically projecting circuit patterns on semiconductor wafers in which alignment between successive exposures is provided by means of a microscope mounted to one side of the optical projection column, there being a metered stage for transporting a wafer between the microscope and the optical projection column, the method of correcting the the baseline vector between the projection column and the microscope, which method comprises: placing, on said stage, a wafer with a light sensitive coating; transporting said wafer to said column using an appropriate baseline vector for controlling movement of said stage; exposing said wafer from a reticle which includes pattern reference markings to produce a visible latent image; without removing said wafer from said stage, transporting said wafer to said microscope; by observing, with said microscope, the latent image on said film, measuring the actual stage movement required to align the latent image of said fiducial markings on said wafer with the microscope; and correcting said baseline vector based on said actual measurement.

Claim 3

In a microlithographic system for optically projecting circuit patterns from projection reticles onto semiconductor wafers in which alignment between successive exposures is provided by means of a microscope mounted to one side of the optical projection column, there being a metered stage for transporting a wafer between the microscope and the optical projection column, the method of correcting alignment between a projection reticle and a wafer, which method comprises: placing, on said stage, a wafer with a light sensitive coating; transporting said wafer to said column using an appropriate baseline vector for controlling movement of said stage; exposing said wafer from a reticle which includes a plurality of pattern reference markings to produce a visible latent image; without removing said wafer from said stage, transporting said wafer to said microscope; by observing, with said microscope, the latent image on said film, measuring the actual stage movement required to align each of the latent image reference markings on said wafer with the microscope; and calculating, from said several measurements, the relative positioning corrections necessary for correcting alignment.

Claim 4

In a microlithographic system for optically projecting circuit patterns from projection reticles onto semiconductor wafers in which alignment between successive exposures is provided by means of a microscope mounted to one side of the optical projection column, there being a metered stage for transporting a wafer between the microscope and the optical projection column, the method of correcting alignment between a projection reticle and a wafer, which method comprises: placing, on said stage, a wafer with a light sensitive coating; transporting said wafer to said column using an appropriate baseline vector for controlling movement of said stage; exposing said wafer from a reticle which includes a plurality of pattern reference markings to produce a visible latent image; without removing said wafer from said stage, transporting said wafer to said microscope; by observing, with said microscope, the latent image on said film, measuring the actual stage movement required to align each of the latent image reference markings on said wafer with the microscope; and calculating, from said several measurements, the relative positioning corrections necessary for correcting alignment.