Process for forming in a silicon oxide layer a portion with vertical side walls

Claim 2

A process of forming over a substrate a silicon oxide layer having a pattern of openings with substantially vertical side walls comprising the steps of: forming a layer of silicon oxide over a surface of the substrate; forming a mask over the silicon oxide layer leaving exposed the pattern desired in the silicon oxide layer; partially removing by a wet etchant the silicon oxide exposed in the pattern, leaving sloped regions in the silicon oxide layer where it underlies the edges of the mask; irradiating the substrate with high energy particles to damage selectively the silicon oxide layer; and removing by a wet etchant the remainder of the exposed silicon oxide to form in the silicon oxide layer the desired pattern of openings with substantially vertical side walls.

Claim 3

The process of claim 1 in which the partial removal step removes about two thirds of the thickness of the exposed silicon oxide layer.

Claim 4

The process of claim 2 in which the partial removal step involves etching in buffered hydrofluoric acid.

Claim 5

The process of claim 1 in which silicon ions are the high energy particles used to irradiate the substrate.

Claim 6

The process of claim 2 in which the substrate is monocrystalline silicon.

Claim 7

The process of claim 5 in which silicon ions are the high energy particles used to irradiate the silicon substrate.

Claim 8

The process of forming a patterned insulated layer buried in a silicon crystal substrate comprising the steps of: forming a layer of silicon oxide over a surface of the substrate; forming a mask over the silicon oxide layer leaving exposed the pattern desired in the silicon oxide layer; partially removing by a wet etchant the silicon oxide exposed in the pattern, leaving sloped regions in the silicon oxide layer where it underlies the edges of the mask; irradiating the substrate with high energy particles to damage selectively the silicon oxide layer; removing by a wet etchant the remainder of the exposed silicon oxide to form in the silicon oxide layer the desired pattern of openings with substantially vertical side walls; implanting ions through the patterned silicon oxide layer for forming a buried ion-rich layer in the silicon substrate; and heating the substrate for converting the ion-rich layer into a buried insulating layer.

Claim 9

The process of forming a patterned insulated layer buried in a silicon crystal substrate comprising the steps of: forming a layer of silicon oxide over a surface of the substrate; forming a mask over the silicon oxide layer leaving exposed the pattern desired in the silicon oxide layer; partially removing by a wet etchant the silicon oxide exposed in the pattern, leaving sloped regions in the silicon oxide layer where it underlies the edges of the mask; irradiating the substrate with high energy particles to damage selectively the silicon oxide layer; removing by a wet etchant the remainder of the exposed silicon oxide to form in the silicon oxide layer the desired pattern of openings with substantially vertical side walls; implanting ions through the patterned silicon oxide layer for forming a buried ion-rich layer in the silicon substrate; and heating the substrate for converting the ion-rich layer into a buried insulating layer.

Claim 10

The process of claim 7 in which the silicon substrate is flooded with electrons during the ion implantation step.

Claim 11

The process of claim 8 in which the ions implanted are oxygen ions and the buried insulating layer formed is an oxide layer.

Claim 12

The process of claim 8 in which the ions implanted are nitrogen ions and the buried insulating layer is a nitride layer.

Claim 13

The process of forming a patterned silicon oxide layer in a silicon crystal substrate comprising the steps of: forming a layer of silicon oxide over a surface of the substrate; forming a mask over the silicon oxide layer, leaving exposed a pattern in the silicon oxide layer; partially removing by a wet etchant the silicon oxide exposed in the pattern, leaving sloped regions in the silicon oxide layer where it underlies the edges of the mask; irradiating the substrate with high energy silicon ions to damage the silicon oxide layer; removing by a wet etchant the remainder of the exposed silicon oxide to form in the silicon oxide layer the desired pattern of openings with substantially vertical walls; implanting oxygen ions through the patterned silicon oxide layer for forming an oxygen-rich layer several tenths of a micron thick and about a tenth of a micron from the surface in the silicon substrate, while flooding the substrate with electrons; and heating the substrate for converting the oxygen-rich layer into a buried silicon-oxide layer.

Claim 14

The process of forming a patterned silicon oxide layer in a silicon crystal substrate comprising the steps of: forming a layer of silicon oxide over a surface of the substrate; forming a mask over the silicon oxide layer, leaving exposed a pattern in the silicon oxide layer; partially removing by a wet etchant the silicon oxide exposed in the pattern, leaving sloped regions in the silicon oxide layer where it underlies the edges of the mask; irradiating the substrate with high energy silicon ions to damage the silicon oxide layer; removing by a wet etchant the remainder of the exposed silicon oxide to form in the silicon oxide layer the desired pattern of openings with substantially vertical walls; implanting oxygen ions through the patterned silicon oxide layer for forming an oxygen-rich layer several tenths of a micron thick and about a tenth of a micron from the surface in the silicon substrate, while flooding the substrate with electrons; and heating the substrate for converting the oxygen-rich layer into a buried silicon-oxide layer.