MONOLITHIC SEMICONDUCTOR APPARATUS ADAPTED FOR SEQUENTIAL CHARGE TRANSFER

• US 3,660,697 A
• Filed: 02/16/1970
• Issued: 05/02/1972
• Est. Priority Date: 02/16/1970
• Status: Expired due to Term

• Current Assignee: Carl Neil Berglund, Harry Joseph Boll
• Original Assignee: Carl Neil Berglund, Harry Joseph Boll
• Inventors: Boll, Harry Joseph, Berglund, Carl Neil
• Primary Examiner(s): Craig, Jerry D.
• Application Number:
  US05/011,447
• Time in Patent Office: 806 Days
• Field of Search: 317/235,21.1,22.2 307/205,238,251,279,304,221C 328/37
• US Class Current: 327/565
• CPC Class Codes: G11C 19/282 with charge storage in a depletion layer, i.e. charge coupled devices [CCD]
• CPC Class Codes: H01L 27/1055 comprising charge coupled devices of the so-called bucket brigade type
• CPC Class Codes: H01L 29/76808 Input structures
• CPC Class Codes: H01L 29/76841 Two-Phase CCD

Abstract

The invention is a form of monolithic semiconductor apparatus adapted for the storage and manipulation of electronic signals representing information. Basically, the apparatus includes a plurality of spaced localized zones of one type semiconductivity adjacent the surface of a semiconductive bulk portion of the other type conductivity. A plurality of localized electrodes, registered in one-to-one correspondence with the localized zones, are disposed over a dielectric layer covering the semiconductive portions. Each of the electrodes is delimited in lateral extent so as to extend over substantially all of the space between a pair of closest zones and over a substantial portion of only one of that pair of zones so that the capacitance between the electrode and the zone over which it extends is substantially greater than the capacitance between that electrode and the other zone of that pair of zones. Signals in the form of varying deficiencies of majority carriers are stored temporarily in the localized zones and are gated sequentially from one zone to the zone next adjacent upon application of two-phase clock pulses to alternate electrodes. Constant background pulses upon which signals are superimposed are circulated to reduce distortion.

Claims

1. In semiconductor apparatus of the type adapted for storage and sequential transfer of packets of mobile charge carriers representing signal information along the surface of a semiconductive body between an input and an output and comprising:

a semiconductive wafer including a bulk portion of a first type semiconductivity and a plurality of spaced, localized zones of opposite type semiconductivity disposed adjacent and forming a path along the surface of the wafer;

a dielectric layer disposed over said surface and over said localized zones;

a plurality of localized conductive electrodes disposed over the dielectric layer and registered with said localized zones such that each of said conductive electrodes extends over the space between a pair of said zones and over a portion of one zone of the pair of zones;

means for applying a pair of clock voltages alternately to successive ones of said electrodes, said pair of voltages being sufficient to produce in the localized zones a steady state deficiency of majority carriers in the absence of a signal applied to the input of the apparatus, and said pair of voltages additionally being such that their successive application to the electrodes is sufficient to cause the advance of a packet of mobile charge from one zone to the next zone along the path at each alternation of the voltages; and

means for applying a signal to the input of said apparatus for selectively causing in synchronization with the clock voltages a variation in the number of majority carriers from the steady state deficiency level, said variation for representing signal information;

the improvement comprising;

means for superimposing upon the majority carriers representing signal information in the localized zones a fixed, predetermined quantity of background majority carriers, the quantity of the background majority carriers being sufficient that when superimposed upon the number of majority carriers representing information there always results a number of majority carriers greater than the steady state deficiency level, so that at each alternation of the clock voltages there is always transferred from a zone containing carriers representing signal information a net quantity of majority carriers to the succeeding zone along the path.

2. Apparatus as recited in claim 1 further comprising a first conduction path and a second conduction path, every second electrode being coupled to said first conduction path and the remaining electrodes being coupled to the second conduction path;

and wherein the pair of clock voltages are applied to the first and second conduction paths.

3. Apparatus as recited in claim 2 wherein the input means comprises:

another zone of the second type semiconductivity spaced from one of said plurality of zones and disposed in such a manner that the electrode which overlaps said last-mentioned one zone also overlies the space between said another zone and said last-mentioned one zone;

a conductive electrode forming a low resistance electrical connection to said another zone;

a voltage source; and

a resistor connected between said last-mentioned conductive electrode and the voltage source, the resistor and the magnitude of the voltage supplied by the voltage source being adjusted in relation to each other such that the voltage applied to said another zone is sufficient to cause injection therefrom of a sufficient amount of background charge as recited in claim 1.

4. Apparatus as recited in claim 2 wherein the input means comprises:

a first zone of the second type semiconductivity spaced from one of said plurality of zones and disposed in such a manner that the electrode which overlaps said last-mentioned one zone also overlies the space between said first zone and said last-mentioned one zone;

a second zone of the second type semiconductivity spaced from the first zone;

a dielectric overlying the first zone, the second zone, and the space therebetween;

a conductive electrode overlying a portion of the last-mentioned dielectric and being delimited in lateral extent so as to extend over substantially all of the space between the first and second zones and over a substantial portion of the first zone; and

voltage source means coupled to said last-mentioned electrode for applying thereto voltages sufficient to cause predetermined quantities of background charge of the type recited in claim 1 to be drawn from the second zone into the first zone.

5. In a method of operating semiconductor apparatus of the type adapted for storage and sequential transfer of mobile charge carriers representing signal information and localized in instantaneous storage sites along the surface of a semiconductive body between an input portion and an output portion and which comprises:

a storage medium;

a dielectric layer disposed over a surface of the storage medium;

a plurality of localized conductive electrodes disposed over the dielectric layer and forming a path between the input portion and the output portion; and

wherein the method of operation comprises;

applying a pair of clock voltages alternately to successive ones of the electrodes, the pair of voltages being sufficient to cause the advance of a packet of mobile charge carriers from each instantaneous storage site to the next instantaneous storage site along the path at each alternation of the voltages;

applying signals to the input of the apparatus sufficient to cause in synchronization with the clock voltages variations in the number of mobile charge carriers in the input portion, said variations representing signal information;

the improvement comprising;

circulating through the apparatus a fixed, predetermined quantity of mobile background charge carriers superimposed upon the aforementioned mobile charge carriers representing signal information, the quantity of the background charge carriers being sufficient that at each alternation of the clock voltages there is always transferred from each instantaneous storage site a net quantity of mobile charge carriers to the next instantaneous storage site along the path.

6. A method as recited in claim 5 wherein:

the input signals are digital signals applied such that a packet of mobile charge carriers represents a one and the absence of a packet of mobile charge carriers represents a zero; and

the ones and zeros are superimposed upon the background mobile charge carriers.

7. A method as recited in claim 6 wherein the quantity of the background charge is sufficient to reduce signal degradation due to incomplete charge transfer and due to surface state trapping and is insufficient in relation to the magnitude of the applied clock voltages when combined with the mobile charge carriers representing signal information to be greater than the maximum amount of charge which can be completely transferred for that magnitude of clock voltages.

8. A method as recited in claim 5 wherein the input signals and the background charge are applied by irradiating the apparatus sufficiently to cause photogeneration of the mobile charge carriers.