Browse Prior Art Database

Buried Channel CCD Double Implant

IP.com Disclosure Number: IPCOM000052167D
Original Publication Date: 1981-May-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Bar-Gadda, O: AUTHOR

Abstract

Fig. 1 shows a cross-section of a buried channel charge-coupled device (CCD) structure having P/+/ channel stop 10 in P-silicon substrate 12. The stop 10 is under recessed silicon dioxide regions 14. The CCD device includes N-channel 15, gate silicon dioxide layer 16 and gate electrode of doped polycrystalline silicon 17.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 98% of the total text.

Page 1 of 2

Buried Channel CCD Double Implant

Fig. 1 shows a cross-section of a buried channel charge-coupled device (CCD) structure having P/+/ channel stop 10 in P-silicon substrate 12. The stop 10 is under recessed silicon dioxide regions 14. The CCD device includes N- channel 15, gate silicon dioxide layer 16 and gate electrode of doped polycrystalline silicon 17.

The narrow width effect arises when the effective channel width W(eff) becomes smaller than approximately twice the depletion layer depth. This results in a drop in channel voltage and a decrease in the effective signal charge capacity. This effect may be reduced by increasing the substrate doping which reduces the depletion layer depth. Assuming the substrate resistivity has been fixed, an additional boron (p-type) implant of moderate dosage and high energy, to be followed by a possible drive-in step, can be used to increase the substrate doping. The final profile is shown in Fig. 2, where N is the number of atoms, X the depth, and Xj the junction depth. This boron implant should be introduced directly before or after the normal phosphorus-buried channel implant and at the same mask level.

The major advantages of this structure include (1) the doubling of charge capacity for the same barrier height, but with reduced overdrive due to the increased channel dosage and reduced depletion layer depth, and (2) reduced leakage due to the reduction in the depletion layer depth.

1

Page 2 of 2

2

[This page contains 3 pic...