Integration method for sidewall split gate flash transistor
First Claim
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1. A method of fabricating an electrically programmable read only memory device which is a control/word gate and a floating gate on the side wall of the control/word gate comprising:
- providing a stack of layers on a silicon substrate, which layers include a gate silicon oxide layer, a conductive polysilicon gate layer, a silicon oxide layer and a silicon nitride layer;
etching said silicon nitride layer to the dimension of said control/word gate;
forming a block out mask over said silicon nitride layer of the dimension of said control/word gate to allow only the side uncovered to which said floating gate is to be formed;
vertically etching said stack of layers to said gate silicon oxide layer to form a vertical sidewall while using said silicon nitride layer on said side uncovered as the mask;
removing said block out mask;
forming an insulator layer on said vertical sidewall;
forming a disposable sidewall spacer layer on said vertical sidewall over said insulator layer, wherein the width of said spacer layer is a channel for said device;
ion implanting a N type dopant into said substrate to form a device region therein;
removing said disposable sidewall spacer layer; and
forming a floating gate sidewall spacer on said vertical sidewall and over said channel.
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Abstract
A fabrication method for an electrically programmable read only memory device, which consists of a control/word gate and a floating gate on the side wall of the control gate. The unique material selection and blocking mask sequences allow simple and safe fabrication within the delicate scaled CMOS process environment, of a side wall floating gate with an ultra short channel under the floating gate, which involves double side wall spacer formation i.e., a disposable side wall spacer and the final polysilicon spacer gate.
56 Citations
20 Claims
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1. A method of fabricating an electrically programmable read only memory device which is a control/word gate and a floating gate on the side wall of the control/word gate comprising:
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providing a stack of layers on a silicon substrate, which layers include a gate silicon oxide layer, a conductive polysilicon gate layer, a silicon oxide layer and a silicon nitride layer; etching said silicon nitride layer to the dimension of said control/word gate; forming a block out mask over said silicon nitride layer of the dimension of said control/word gate to allow only the side uncovered to which said floating gate is to be formed; vertically etching said stack of layers to said gate silicon oxide layer to form a vertical sidewall while using said silicon nitride layer on said side uncovered as the mask; removing said block out mask;
forming an insulator layer on said vertical sidewall;forming a disposable sidewall spacer layer on said vertical sidewall over said insulator layer, wherein the width of said spacer layer is a channel for said device; ion implanting a N type dopant into said substrate to form a device region therein; removing said disposable sidewall spacer layer; and forming a floating gate sidewall spacer on said vertical sidewall and over said channel. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of fabricating an electrically programmable read only memory device which is a control/word gate and a floating gate on the side wall of the control/word gate while also fabricating logic gates associated therewith in a same silicon substrate comprising:
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providing a stack of layers on a silicon substrate, which layers include a gate silicon oxide layer, a conductive polysilicon gate layer, a silicon oxide layer and a silicon nitride layer; etching said silicon nitride layer to the dimension of said control/word gate in a memory cell area and to the dimension of the logic gate in non-memory areas; forming a block out mask over said silicon nitride layer of the dimension of said control/word gate to allow only the side uncovered to which said floating gate is to be formed; vertically etching said stack of layers to said gate silicon oxide layer to form a vertical sidewall while using said silicon nitride layer on said side uncovered as the mask; removing said block out mask; forming a insulator layer on said vertical sidewall; forming a disposable sidewall spacer layer on said vertical sidewall and over said insulator layer, wherein the width of said spacer layer is a channel for said device; ion implanting a N type dopant into said substrate to form a device region therein; removing said disposable sidewall spacer layer; forming a floating gate sidewall spacer on said vertical sidewall and over said insulator layer, and over the channel; forming a block out mask over said silicon nitride layer to cover and protect said control/word gate and said floating gate and to allow all other areas to be uncovered; removing the exposed said silicon oxide layer; vertically etching said polysilicon layer to said gate silicon oxide layer to form a vertical sidewall on the opposite side of said floating gate in the memory cell area and to form the logic device gates in logic areas while using said silicon nitride layer on said side uncovered as the mask; removing said block out mask; and forming lightly doped drain devices by ion implantation and using a sidewall spacer technique into logic areas at said logic gates. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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16. A method of fabricating an electrically programmable read only memory device which is a control/word gate, a floating gate on the sidewall of the control/word gate, and an ultra short, non-planar channel comprising:
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providing a stack of layers on a silicon substrate, which layers include a gate silicon oxide layer, a conductive polysilicon gate layer, a silicon oxide layer and a silicon nitride layer; etching said silicon nitride layer to the dimension of said control/word gate; forming a block out mask over said silicon nitride layer of the dimension of said control/word gate to allow only the side uncovered to which said floating gate is to be formed; vertically etching said stack of layers to said gate silicon oxide layer to form a vertical sidewall while using said silicon nitride layer on said side uncovered as the mask; removing said block out mask;
forming a insulator layer on said vertical sidewall;forming a disposable sidewall spacer layer on said vertical sidewall over said insulator layer, wherein the width of said spacer layer is a channel for said device; vertically etching into said substrate to form a step within said substrate; ion implanting a N type dopant into said step within said substrate to form a device region therein within having said non-planar channel; removing said disposable sidewall spacer layer; and forming a floating gate sidewall spacer on said vertical sidewall and over said channel. - View Dependent Claims (17, 18, 19, 20)
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Specification