Image sensing array with charge isolation

• US 4,912,537 A
• Filed: 06/24/1988
• Issued: 03/27/1990
• Est. Priority Date: 06/24/1988
• Status: Expired due to Term

• Current Assignee: Senshin Capital LLC (Intellectual Ventures LLC)
• Original Assignee: Polaroid Corporation (PLR IP Holdings LLC)
• Inventors: Boyd, Stuart D. J.
• Primary Examiner(s): James, Andrew J.
• Assistant Examiner(s): Jackson, Jr., Jerome
• Application Number:
  US07/211,468
• Time in Patent Office: 641 Days
• Field of Search: 357/59, 357/23.7, 357/30, 357/32, 357/24 LR, 250/578, 358/213.12, 358/213.19
• US Class Current: 257/229
• CPC Class Codes: H01L 27/14643 Photodiode arrays; MOS imagers

Abstract

A semiconductor image sensing array for an electronic still image camera comprising a plurality of light sensing elements may be electronically shuttered by a gate control electrode in each light sensing element which operates simultaneously to inhibit the further transfer of signal charges to the substrate while isolating the signal charges transferred to the substrate during the previous scene light integration.

Claims

1. A solid state light sensing element comprising:

a semiconductor substrate of a first select conductivity type having a first select region of ion implantation, and a second select region of a second select conductivity type opposite to said first select conductivity type spaced apart from said first region and cooperatively associated with said substrate in a manner defining a diode;

means for receiving light and converting the photons of the received light to signal charges; and

semiconductor gating means operatively associated with said substrate and said converting means for controlling the flow of signal charges from said converting means to said diode, said grating means comprising a gate control electrode extending over said first ion implanted region of said substrate such that upon energization of said gate electrode to a first select potential, said gating means operates to conduct signal charges from said converting means to said diode and said gate control electrode operates to establish a first potential well region in said first ion implanted region underlying said gate control electrode and extending to said second region, said first potential well being deepest in the region immediately underlying said gate control electrode so as to cause charges from said diode to enter said deepest portion of said first potential well region, and such that upon energization of said gate control electrode to a second select potential below said first potential wherein said gating means operates to discontinue the conduction of signal charges from said converting means to said diode and said gate control electrode operates to establish a second potential well region in said first ion implanted region of less depth than said first potential well region so as to isolate the signal charges held therein.

2. The light sensing element of claim 1 wherein said semiconductor gating means comprises a field effect transistor.

3. The light sensing element of claim 2 wherein said field effect transistor comprises a first layer of an oxide of silicon overlying a portion of said substrate, a second layer of polysilicon overlying said first layer and sufficiently doped to define said gate control electrode, a third layer of an oxide of silicon overlying said gate control electrode layer, a fourth layer of polysilicon overlying said third layer and said gate control electrode layer and connecting to said second region of said diode, said fourth layer of polysilicon, being suitably doped and/or ion implanted to define source, drain and channel regions for said field effect transistor.

4. The light sensing element of claim 3 wherein:

said second region is diffused into said substrate, said substrate is doped to be a P type conductivity, said second region is doped to be an N type conductivity and the boundary between said substrate and said second region defines a PN junction.

5. The light sensing element of claim 3 wherein said converting means comprises a photodiode.

6. The light sensing element of claim 5 wherein said photodiode comprises a metallized cathode electrode layer in electrical connection with respect to the source electrode of said field effect transistor, an amorphous silicon layer overlying said cathode electrode and a transparent anode electrode overlying said amorphous silicon layer.

7. A solid state image sensing array comprising:

a semiconductor substrate of a first select conductivity type;

a plurality of light sensing elements disposed about said substrate in rows and columns each of said light sensing elements comprising a first select region of ion implantation in said substrate;

a second select region of a second select conductivity type opposite to said first select conductivity type spaced apart from said first region and cooperatively associated with said substrate in a manner defining a diode;

means for receiving light and converting the photons of the received light to signal charges;

semiconductor gating means operatively associated with said substrate and said converting means for controlling the flow of signal charges from said converting means to said first diode, said gating means comprising a gate control electrode extending over said first ion implanted region of said substrate such that upon energization of said gate control electrode to a first select potential, said gating means operates to conduct signal charges from said converting means to said diode and said gate control electrode operates to establish a first potential well region in said first ion implanted region underlying said gate control electrode and extending to said second region, said first potential well being deepest in the region immediately underlying said gate control electrode so as to cause charges from said diode to enter said deepest portion of said first potential well region, and such that upon energization of said gate control electrode to a second select potential below said first select potential, said gating means operates to discontinue the conduction of charges from said converting means to said diode and said gate control electrode operates to establish a second potential well region in said first ion implanted region of less depth than said first potential well region so as to isolate the charges held therein;

a plurality of conductive column strips each connecting to a select number of said gate control electrodes, and each being selectively energizable to energize said connecting gate control electrodes;

a plurality of conductive row electrodes each located in spaced apart relation relative to a different one of said gate control electrodes; and

a plurality of conductive row straps each connecting to a select number of said row electrodes, and each being selectively energizable to energize said connecting row electrodes.

8. The image sensing array of claim 7 wherein each of said semiconductor gating means for each light sensing element comprises a field effect transistor.

9. The image sensing array of claim 8 wherein said field effect transistor of each light sensing element comprises a first layer of an oxide of silicon overlying a portion of said substrate, a second layer of polysilicon overlying said first layer and sufficiently doped to define said gate control electrodes, a third layer of an oxide of silicon overlying said gate control electrode layer, a fourth layer of polysilicon overlying said third layer and said gate control electrode layer and connecting to said second region of said diode, said fourth layer of polysilicon being suitably doped and/or ion implanted to define source, drain and channel regions for said field effect transistor.

10. The image sensing array of claim 9 wherein said second region of each light sensing element is diffused into said substrate, said substrate is doped to be a P type conductivity, said second region is doped to be an N type conductivity and the boundary between said substrate and said second region defines a PN junction.

11. The image sensing array of claim 9 wherein said converting means for each of said light sensing elements comprises a photodiode.

12. The image sensing array of claim 11 wherein each of said photodiodes comprises a metallized cathode electrode layer in electrical connection with respect to the source electrode of said field effect transistor, an amorphous silicon layer overlying said cathode electrode and a transparent anode electrode overlying said amorphous silicon layer.