US 6,147,008 AGranted

Creation of multiple gate oxide with high thickness ratio in flash memory process

AssigneeChartered Semiconductor Manufacturing Ltd.

InventorsSiow Lee Chwa, Ying Jin, Yung-Tao Lin

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Abstract

A new method is provided for the creation of an oxide layer that contains three different thicknesses. A first layer of oxide is grown on the surface of a substrate; a first layer of photoresist is deposited and patterned thereby partially exposing the surface of the underlying first layer of oxide. A nitrogen implant is performed into the surface of the underlying substrate; the photoresist mask of the first layer of photoresist is removed. A second layer of photoresist is deposited and patterned, the first layer of oxide is removed from above and surrounding the implanted regions of the substrate. The second mask of resist is removed. The first layer of oxide is reduced in thickness, its thickness is restored to a first thickness by a blanket growth of a second layer of oxide over the exposed surface of the substrate (where no ion implant has been performed) to a third thickness, over the surface of the substrate where the ion implant has been performed to a second thickness and over the surface of the first layer of oxide thereby restoring this layer of oxide to its original first thickness.

Claims11

Dependent claims

A method of controlling gate oxide thickness in the fabrication of semiconductor devices, comprising the steps of:

providing a semiconductor substrate;
forming a layer of sacrificial oxide on the surface of said semiconductor substrate;
depositing a first layer over the surface of said layer of sacrificial oxide;
patterning and etching said first layer thereby creating an opening in said first layer said opening to extend to the surface of said layer of sacrificial oxide;
performing an ion implant into the surface of said semiconductor substrate whereby said ion implant aligns with said opening in said first layer;
removing said first layer from the surface of said layer of sacrificial oxide;
depositing a second layer over the surface of said layer of sacrificial oxide;
patterning and etching said second layer thereby creating an opening in said second layer said opening to include and expand beyond the area of said sacrificial oxide that overlies said ion implant;
removing said sacrificial oxide from the surface of said semiconductor substrate in accordance with said opening in said second layer thereby creating a patterned layer of sacrificial oxide thereby furthermore exposing the surface of said substrate underneath said opening;
removing said second layer from the surface of said layer of sacrificial oxide thereby exposing the surface of said patterned layer of sacrificial oxide;
reducing the thickness of said patterned layer of sacrificial oxide a measurable amount;
and
blanket growing a second layer of oxide over said patterned layer of sacrificial oxide thereby including said exposed surface of said substrate.

10 more elements

A method of controlling gate oxide thickness in the fabrication of semiconductor devices, comprising the steps of:

providing a silicon semiconductor substrate;
forming a layer of sacrificial oxide on the surface of said semiconductor substrate;
depositing a first layer over the surface of said layer of sacrificial oxide to a thickness of about 10,000 Angstrom or any thickness of said first layer that stops the implanting of particular ions into the surface of the substrate that is covered with said first layer;
patterning said first layer thereby creating an opening in said first layer said opening to extend to the surface of said layer of sacrificial oxide;
performing a nitrogen ion implant into the surface of said semiconductor with a dose of between about 10.sup.12 and 10.sup.16 ions per cm.sup.2 with an energy of between about 10 and 50 KeV into said substrate whereby said ion implant aligns with said opening in said first layer;
removing said first layer from the surface of said layer of sacrificial oxide;
depositing a second layer over the surface of said layer of sacrificial oxide;
patterning said second layer thereby removing said second layer from the surface of said sacrificial oxide over a measurable area said measurable area to include and expand beyond the area of said sacrificial oxide that overlies said ion implant;
removing said sacrificial oxide from the surface of said semiconductor substrate in accordance with said measurable area over which said second layer has been removed thereby creating a patterned layer of sacrificial oxide thereby furthermore exposing the surface of said substrate underneath said measurable area of said sacrificial oxide;
removing said second layer thereby exposing the surface of said patterned layer of sacrificial oxide;
reducing the thickness of said patterned layer of sacrificial oxide by a measurable amount;
and
growing a second layer of oxide to a thickness of about 65 Angstrom over said patterned layer of sacrificial oxide thereby including said exposed surface of said substrate.

10 more elements

Dependencies are inferred from the claim text.