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US 5,665,621 AGranted
Read-only-memory process with self-aligned coding
AssigneeUnited Microelectronics Corp.
InventorGary Hong
Life of this patent
Estimating the term…
Abstract
A process of fabricating a read-only-memory using a self-aligned technique for coding. By forming cap layers on word lines and forming stoppers between the stacked word lines/cap layers, sufficient tolerance for coding mask misalignment can be provided to ensure the alignment of coding even when misalignment happens. Therefore the problem of partially turned-off adjacent memory cells is eliminated.
Claims21
A process of fabricating a non-volatile memory on a semiconductor substrate, comprising the following steps of:
- (a) forming buried bit lines in the semiconductor substrate and forming word lines on the semiconductor substrate;
- (b) forming cap layers over the word lines to form stacked word lines/cap layers;
- (c) forming stoppers between the stacked word lines/cap layers with a resulting thickness of the stoppers from the semiconductor substrate being larger than a thickness of the word lines relative to the semiconductor substrate,
- (1) depositing a photoresist on the semiconductor substrate between and over the stacked word lines/cap layers,
- (2) etching back the photoresist to form exposed top surfaces of the cap layers with photoresist therebetween, the photoresist having a resulting thickness relative to the semiconductor substrate larger than the thickness of the word lines relative to the semiconductor substrate;
- (d) forming a coding mask and defining planned coding windows;
- (e) removing the cap layers which are exposed through the coding windows;
- and,
- (f) implanting ions into the semiconductor substrate through the word lines which are exposed through the coding windows, the stoppers being used to prevent penetration of the ions.
6 more elements
A process of fabricating a non-volatile memory on a semiconductor substrate, comprising the following steps of:
- (a) forming buried bit lines in the semiconductor substrate and forming word lines on the semiconductor substrate;
- (b) forming cap layers over the word lines to form stacked word lines/cap layers;
- (c) forming stoppers between the stacked word lines/cap layers by,
- (1) depositing a photoresist on the semiconductor substrate between and over the stacked word lines/cap layers,
- (2) etching back the photoresist to form exposed top surfaces of the cap layers with photoresist therebetween;
- (d) removing the cap layers;
- (e) forming a coding mask and defining planned coding windows;
- and,
- (f) implanting ions into the semiconductor substrate through the word lines which are exposed through the coding windows, wherein the stoppers are used to prevent penetration of the ions.
6 more elements
Dependencies are inferred from the claim text.