Process for forming an electrically programmable read-only memory cell
First Claim
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1. A process for forming an electrically programmable read-only memory cell comprising the steps of:
- forming a first layer over a semiconductor substrate;
forming an opening through the first layer;
forming a spacer adjacent to the opening in the first layer;
forming a floating gate overlying the substrate, wherein the floating gate has a T-shape and is formed after the step of forming the spacer;
removing the first layer and spacer after the step of forming the floating gate;
forming an intergate dielectric layer lying adjacent to the floating gate, wherein the intergate dielectric layer has a uniform thickness adjacent to the floating gate; and
forming a control gate lying adjacent to the intergate dielectric layer, wherein a portion of the control gate underlies a portion of the floating gate.
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Abstract
EPROM cells include T-shaped floating gates (61, 171) and control gates that surround virtually all of the floating gates (61, 171) except for the portion of the floating gates (61, 171) that lie on a gate dielectric layer (51, 151). The EPROM cells may include customized well regions (22, 122) to allow flash erasing or individual cell erasing for electrically erasable EPROMs. Many different configurations of the memory cells are possible. The configurations of the source regions, drain regions, and well regions (22, 122) may be determined by how a user of the memory cells wants to program or erase the memory cells.
39 Citations
22 Claims
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1. A process for forming an electrically programmable read-only memory cell comprising the steps of:
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forming a first layer over a semiconductor substrate; forming an opening through the first layer; forming a spacer adjacent to the opening in the first layer; forming a floating gate overlying the substrate, wherein the floating gate has a T-shape and is formed after the step of forming the spacer; removing the first layer and spacer after the step of forming the floating gate;
forming an intergate dielectric layer lying adjacent to the floating gate, wherein the intergate dielectric layer has a uniform thickness adjacent to the floating gate; andforming a control gate lying adjacent to the intergate dielectric layer, wherein a portion of the control gate underlies a portion of the floating gate. - View Dependent Claims (2, 3, 4, 10)
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5. A process for forming a semiconductor device including a first plurality of electrically programmable read-only memory cells comprising the steps of:
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forming a first well region having a first conductivity type within a semiconductor substrate having a second conductivity type that is opposite the first conductivity type; forming a second well region having the second conductivity type within the first well region; forming floating gates, wherein; a first plurality of floating gates are formed over the substrate; a second plurality of floating gates are formed over the first well region; and a third plurality of floating gates are formed over the second well region; forming an intergate dielectric layer lying adjacent the floating gates; and forming word lines lying adjacent to the intergate dielectric layer. - View Dependent Claims (6, 7, 8, 9)
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11. A process for forming an electrically programmable read-only memory cell comprising the steps of:
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forming a gate dielectric layer over a semiconductor substrate; forming a floating gate over the gate dielectric layer, wherein the step of forming the floating gate comprises steps of; forming a first silicon layer over the gate dielectric layer; patterning the first silicon layer to form a first silicon member; forming spacers adjacent to the first silicon member; forming a first layer over the substrate, wherein the spacers and the first layer include different materials; polishing the first silicon member to form a trunk portion of the floating gate, wherein the trunk portion has a trunk width; forming a second silicon member over the trunk portion to form the floating gate, wherein; the second silicon member is a cross-bar portion of the floating gate; and the cross-bar portion has a cross-bar width that is wider than the trunk width; forming an intergate dielectric layer lying adjacent to the floating gate, wherein the intergate dielectric layer has a uniform thickness adjacent to the floating gate; and forming a control gate lying adjacent to the intergate dielectric layer, wherein a portion of the control gate underlies a portion of the floating gate. - View Dependent Claims (12, 13, 14)
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15. A process for forming an electrically programmable read-only memory cell comprising the steps of:
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forming a gate dielectric layer over a semiconductor substrate; forming a floating gate on the gate dielectric layer, wherein the floating gate has a T-shape with a wide portion and a narrow portion that lies on the gate dielectric layer; forming an intergate dielectric layer lying adjacent to the floating gate, wherein the intergate dielectric layer has a uniform thickness adjacent to the floating gate; and forming a control gate lying adjacent to the intergate dielectric layer, wherein a portion of the control gate underlies a portion of the floating gate. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22)
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Specification