Flash memory cell with self-aligned gates and fabrication process
First Claim
Patent Images
1. In a memory cell:
- a substrate having an active area, an oxide layer formed on the substrate above the active area, a relatively thin floating gate having a side wall with a rounded curvature positioned above the oxide layer, a control gate which is substantially thicker than the floating gate positioned above and in vertical alignment with the floating gate, a dielectric film between the floating gate and the control gate, a select gate positioned to one side of the control gate and facing the side wall of the floating gate with the rounded curvature, a tunnel oxide between the select gate and the floating gate, and a tunneling path for the migration of electrons during erase operations extending from the side wall of the floating gate with the rounded curvature through the tunnel oxide to the select gate.
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Abstract
Nonvolatile memory cell and process in which a control gate or a thick dielectric film is used as a mask in the formation of a floating gate and also as a step in the formation and alignment of a select gate. The floating gate is relatively thin and has a side wall with a rounded curvature which, in some embodiments, serves as a tunneling window for electrons migrating to the select gate during erase operations. In other embodiments, the gate oxide beneath the floating gate is relatively thin, and the electrons tunnel through the gate oxide to the source region in the substrate below.
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Citations
7 Claims
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1. In a memory cell:
- a substrate having an active area, an oxide layer formed on the substrate above the active area, a relatively thin floating gate having a side wall with a rounded curvature positioned above the oxide layer, a control gate which is substantially thicker than the floating gate positioned above and in vertical alignment with the floating gate, a dielectric film between the floating gate and the control gate, a select gate positioned to one side of the control gate and facing the side wall of the floating gate with the rounded curvature, a tunnel oxide between the select gate and the floating gate, and a tunneling path for the migration of electrons during erase operations extending from the side wall of the floating gate with the rounded curvature through the tunnel oxide to the select gate.
- View Dependent Claims (2)
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3. In a memory cell:
- a substrate having an active area, an oxide layer formed on the substrate above the active area, a relatively thin floating gate having a side wall with a rounded curvature positioned above the oxide layer, a dielectric film which is substantially thicker than the floating gate positioned above and in vertical alignment with the floating gate, a select gate positioned to one side of the control gate and facing the side wall of the floating gate with the rounded curvature, a tunnel oxide between the select gate and the floating gate, and a tunneling path for the migration of electrons during erase operations extending from the side wall of the floating gate with the rounded curvature through the tunnel oxide to the select gate.
- View Dependent Claims (4, 5)
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6. In a memory cell:
- a substrate having an active area, a relatively thin gate oxide layer formed on the substrate above the active area, a relatively thin floating gate having a side wall with a rounded curvature positioned above the oxide layer, a control gate which is substantially thicker than the floating gate positioned above and in vertical alignment with the floating gate, a dielectric film between the floating gate and the control gate, a select gate positioned to one side of the control gate and facing the side wall of the floating gate with the rounded curvature, a relatively thick oxide layer between the select gate and the floating gate, a source region formed in the substrate with a portion of the source region overlapping beneath the floating gate, and a tunneling path for the migration of electrons during erase operations extending from the floating gate through the gate oxide layer to the overlapping portion of the source region.
- View Dependent Claims (7)
Specification