Method of making a charge-coupled device imager

Abstract

The present invention relates to a method of forming a frame transfer CCD imager having in a substrate of single crystalline silicon of one conductivity type a plurality of parallel channels of the opposite conductivity type extending along a surface of the substrate, channel stop regions between the channels, blooming drains within the channel stop regions and potential barrier region beneath each blooming drain. The method includes forming on the surface of the substrate a first masking layer of silicon oxide and a second masking layer of a photoresist over the first masking layer. Aligned openings are formed in the first and second masking layers with the openings in the first masking layer having sides which taper back under the second masking layer. Ions of a desired conductivity modifier are implanted into the substrate through the aligned openings to form the blooming drains. The second masking layer is removed and ions of a conductivity modifier are implanted through the openings in the first masking layer and through the thin portions of the tapered sides of the openings to form a region around each of the blooming drains. A portion of this region beneath the blooming drains forms the potential barrier regions and the portions at each side of the blooming drains defines the channel stop regions. The first masking layer is then removed and ions of a conductivity modifier are implanted into the entire surface of the substrate to form the channels and the channel stop regions.