Texas Instruments Corporation

Robert C Frye

Al F Tasch, Jr

Horng-Sen Fu

Charles Robert Hewes

Alan Harry Katz

Robert W Brodersen

Processes for manufacturing two-phase charge coupled devices (CCDs) having marginally overlapping phase electrodes and utilizing a single insulating material. Offset self-alignment techniques are used to achieve accurate location of ion implanted potential well or potential barrier regions to achieve the required asymmetry of potential wells (or threshold voltages) in each gate region of the CCD with small bit or charge storage element sizes leading to structures having a high packing density. Fabrication of surface and buried channel structures is described.

CCD structures with surface potential asymmetry beneath the phase

Insulated gate field effect transistor charge regenerator amplifiers respectively cross-couple the output regions of a pair of two-phase CCD structures with the input regions of those structures. Each amplifier senses the level of binary data charge packets from the output region of one of the shift register structures and in response thereto applies a regenerated and inverted binary data charge packet to the input region of the other shift register structure. One of the amplifiers includes logic gating for inputting and outputting data into and from the shift register structure. A charge regenerator for a two-phase CCD structure comprising first and second shift registers. The charge regenerator comprises a source follower amplifier including a driver transistor, a load transistor and a positive feedback transistor connected between the gate and source of the driver transistor. The gate of the driver transistor is precharged to a predetermined level prior to sensing of the output region charge level and the regenerator inserts into the input region a charge packet corresponding to the data level sensed at the output region, without inversion.

Two-phase CCD regenerator - I/O circuits

Semiconductor memory cells include gate conductor-insulator-semiconductor regions having storage and transfer portions in which the threshold voltage and surface potential-gate conductor voltage characteristics differ as between the storage and transfer portions. This may be achieved by employing relatively thick and relatively thin insulator areas at the storage and transfer portions, or vice versa, with a surface charge accumulation layer at the semiconductor region insulator interface. In a different form of cell structure, the insulator is a uniform thickness layer overlying the storage and transfer portions one of which includes a doped semiconductor region of the same conductivity type as, but higher dopant concentration than, the remainder of the semiconductor region. The difference in threshold voltage and surface potential characteristics is such that in response to first and second defined gate voltage levels, the potential well profile at the storage and transfer portions is changed in a manner permitting write in and read out of logic signal level related charge packets into and from the storage portion. Semiconductor memories include a matrix array of such cell structures, the gate conductor of a line of cells in the matrix forming part of a store/word conductor common to that line and a sense portion of each cell may form part of a common sense line for a line of cells extending perpendicularly to the store/word conductors. The memory cells may be fabricated by a process utilizing photolithographic alignment offset and self-aligning techniques in conjunction with diffusion and ion implantation techniques.

Charge coupled device random access memory

A continuous gate electrode overlies the channel of the CCD and is connected to a uniphase clock pulse source for operation of the CCD. Pairs of gate conductor-insulator-semiconductor regions are defined along the channel. In each pair of regions the surface potential-gate voltage characteristic of one region intersects that of the other region, such that in the OFF condition of a clock pulse the potential well at one region of each pair is deeper than that of the other region; in the ON condition of a clock pulse, this situation is reversed. In this manner, charge packets are propagated along the channel and unidirectionality is achieved by locally implanted potential wells or potential barriers in each of the aforesaid regions. The shift in surface potential gate voltage of one of the regions in each pair of regions, to produce the required intersection, is achieved by an implanted charge accumulation layer at the insulator-semiconductor interface at those regions which, in one embodiment, are defined at locally thickened areas of the insulating layer, so that the threshold voltage is greater than an intermediate regions at which the insulator layer is thinner. In a preferred embodiment, using a uniform thickness insulating layer, the threshold voltage difference is achieved by use of local, heavily doped semiconductor regions spaced along the channel with charge accumulation layers formed at the interface between those regions and the insulating layer. Fabrication techniques employing ion implantation are described for both embodiments.

Uniphase charge coupled devices

Silicon gate CCD structure

Process for manufacturing two-phase charge coupled devices (CCDs) having marginally overlapping phase electrodes and utilizing a single insulating material. Offset self-alignment techniques are used to achieve accurate location of ion implanted potential well or potential barrier regions to achieve the required asymmetry of potential wells (or threshold voltages) in each gate region of the CCD with small bit or charge storage element sizes leading to structures having a high packing density. Fabrication of surface and buried channel structures is described.

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Plano, TX, United States of America

Robert C Frye