Solid State Scientific Corporation

Sprague Electric Company

Mark A Halfacre

David S Pan

Alexander H Owens

Wing K Huie

Brian K Rosier

Kanak C Sarma

A memory device, based upon a field effect transistor having a floating gate is constructed for use in a silicon integrated circuit array of similar memory devices. The memory device includes only two polysilicon layers, a portion of each polysilicon layer being connected to each other through a via hole in an intervening silicon dioxide layer to form the floating gate.

Memory device with interconnected polysilicon layers and method for

A CMOS EPROM is made wherein the typical EPROM device is an N-channel IGFET having a control gate self-aligned with an underlying floating gate. In this process the EPROM floating gate and the gates of both the P-channel and N-channel peripheral circuit transistors are formed from a first deposited polysilicon layer. The EPROM control gate is formed from a second deposited polysilicon layer. This CMOS EPROM process employs a surprisingly few photoresist steps and is compatible with a high temperature oxidation step for making a very high quality intergate polysilicon oxide in the EPROM devices.

Method for making a self-aligned CMOS EPROM wherein the EPROM floating

A process for making an integrated cirucit EPROM having an array of EPROM devices and CMOS peripheral circuits, including blanket depositions of a first and a second polysilicon layers on a silicon substrate and removing portions of those polysilicon layers. The EPROM floating gate is made from the first polysilicon layer, and the EPROM control gate as well as the P-channel and N-channel gates of the peripheral transistors are all made from the second polysilicon layer. Independently adjustable thresholds for each of the three device types are made possible by forming an N-well at the substrate region at which the P-channel device is to be built, blanket implanting all three channels prior to selectively forming the first polysilicon layer over the EPROM region, and then selectively doping the channels of the N- and P-channel devices only.

Method of making a CMOS EPROM with independently selectable thresholds

A CMOS EPROM or the like is made wherein the basic memory device or EPROM device is an N-channel IGFET (insulated gate field effect transistor) having a control gate self-aligned with an underlying floating gate. The sources and drains of the EPROM devices as well as the sources and drains of peripheral N-channel transistors, are made by implanting with arsenic and with phosphorous. When heated, the faster diffusing phosphorous outruns, and extends from the bulk of, the arsenic so that these sources and drains extend slightly under the adjacent gate. This extension of the drain in the memory device enables a faster programming capability. A similar but oppositely directed lateral extension of all these sources and drains reduces the leakage to the substrate and reduces the chances of shorts to the substrate due to slightly misaligned metal to source and drain contacts.

Method for double doping sources and drains in an EPROM

CMOS transistors are fabricated in a P substrate using N- well regions. These wells are positioned to prevent aluminum spiking in the N channel devices. After P guard rings are formed for both P and N channel devices, additional masking and implantation are performed to produce N guard rings in the P channel devices. Before the transistors are formed, an implantation of P type impurities is performed causing the P channel devices, when they are formed, to have a PMOS buried channel.

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Horsham, PA, United States of America

Mark A Halfacre