Technique of forming over an irregular surface a polysilicon layer with a smooth surface
First Claim
1. A method of forming a structure on an integrated circuit substrate, comprising the steps of:
- depositing a layer of field oxide on said substrate,etching channels in said field oxide layer,depositing a layer of polysilicon across the field oxide and the channels to a thickness wherein a top surface of the polysilicon layer is substantially smooth across the channels,oxidizing the polysilicon layer top surface to a uniform depth thereacross, andstripping away the oxidized polysilicon material, thereby to leave a polysilicon layer with a substantially smooth surface across the channels.
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Accused Products
Abstract
Techniques of forming a flash EEPROM cell array with the size of individual cells being reduced, thereby increasing the number of cells which may be formed on a semiconductor substrate of a given size. Use of dielectric spacers in several steps of the process controls areas being etched or implanted with ions to something smaller than can be obtained by the highest resolution photolithography. Both split-channel and non-split-channel (no select transistor) types of memory cells are included. Example cells employ three polysilicon layers, having separate floating, control and erase gates. A technique of forming the memory cell gates with greater uniformity of conductivity level includes depositing undoped polysilicon and then using ion implantation to introduce the dopant. Field oxide is formed at an early stage in the process by CVD deposition and dry etching. The memory cell array and adjacent peripheral components are formed in a coordinated manner on a single integrated circuit chip.
437 Citations
8 Claims
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1. A method of forming a structure on an integrated circuit substrate, comprising the steps of:
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depositing a layer of field oxide on said substrate, etching channels in said field oxide layer, depositing a layer of polysilicon across the field oxide and the channels to a thickness wherein a top surface of the polysilicon layer is substantially smooth across the channels, oxidizing the polysilicon layer top surface to a uniform depth thereacross, and stripping away the oxidized polysilicon material, thereby to leave a polysilicon layer with a substantially smooth surface across the channels. - View Dependent Claims (2, 3, 4, 5)
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6. A method of forming a structure on an integrated circuit substrate, comprising:
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depositing a layer of dielectric material supported by said substrate, forming channels in the dielectric layer by removing portions thereof according to a pattern, forming a layer of polysilicon material over the dielectric layer and extending into the channels, said polysilicon layer having a thickness T over the dielectric layer such that, if the polysilicon layer was deposited only to said thickness T, the polysilicon layer would have depressions in a top surface thereof over the channels, the polysilicon layer forming step including; depositing said layer of polysilicon to a thickness in excess of T over the dielectric layer until the top surface of the polysilicon no longer contains said depressions, and removing a portion of the polysilicon layer until its thickness over the dielectric layer is equal to T. - View Dependent Claims (7, 8)
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Specification