Process for forming contact openings through oxide layers

Claim 2

In the fabrication of an integrated circuit, where a substrate is covered with a thermally grown oxide layer and where a substantially thicker deposited oxide layer containing phosphorus is formed over the grown oxide layer, a process for forming an opening and tapered contact through the oxide layers to expose a region in the substrate comprising the steps of: forming a photoresist layer over said deposited oxide layer with an opening through said photoresist layer over said region; etching through said phosphorus containing deposited oxide layer with a wet etchant such that a tapered opening is formed through said deposited oxide layer extending to said grown oxide layer; removing said photoresist layer; and, forming an ohmic contact in said tapered opening through said oxide layers; whereby a tapered contact is formed through said oxide layers.

Claim 3

The process defined by claim 1 wherein said wet etchant comprises hydrofluoric acid and ammonium fluoride solution.

Claim 4

The process defined by claim 2 wherein said plasma etchant is an anisotrophic plasma etchant comprising C 2 F 6 and CHF 3 .

Claim 5

In the fabrication of metal-oxide-semiconductor integrated circuits, where a substrate is covered with a thermally grown oxide layer and where a deposited oxide layer substantially thicker than said grown oxide layer which contains approximately 8% or more phosphorus is formed over the said grown oxide layer, a process for forming an opening and contact member through the oxide layers to contact a doped region in said substrate, comprising the steps of: forming a photoresist layer over said deposited oxide layer with an opening through said photoresist layer over said doped region; etching through said phosphorus containing deposited oxide layer with a wet etchant such that a tapered opening is formed through said deposited oxide layer extending to said grown oxide layer; etching through said grown oxide layer with an anisotropic plasma etchant in alignment with said opening through said photoresist layer, until said substrate is exposed at said doped region; removing said photoresist layer, and, forming a contact member in said tapered opening through said oxide layers in contact with said doped region, whereby a tapered contact member is formed through said oxide layers.

Claim 6

In the fabrication of metal-oxide-semiconductor integrated circuits, where a substrate is covered with a thermally grown oxide layer and where a deposited oxide layer substantially thicker than said grown oxide layer which contains approximately 8% or more phosphorus is formed over the said grown oxide layer, a process for forming an opening and contact member through the oxide layers to contact a doped region in said substrate, comprising the steps of: forming a photoresist layer over said deposited oxide layer with an opening through said photoresist layer over said doped region; etching through said phosphorus containing deposited oxide layer with a wet etchant such that a tapered opening is formed through said deposited oxide layer extending to said grown oxide layer; etching through said grown oxide layer with an anisotropic plasma etchant in alignment with said opening through said photoresist layer, until said substrate is exposed at said doped region; removing said photoresist layer, and, forming a contact member in said tapered opening through said oxide layers in contact with said doped region, whereby a tapered contact member is formed through said oxide layers.

Claim 7

The process defined by claim 4 wherein said wet etchant comprises hydrofluoric acid and ammonium fluoride solution.

Claim 8

The process defined by claim 5 wherein said plasma etchant comprises C 2 F 6 and CHF 3 .

Claim 9

In the fabrication of metal-oxide-semiconductor integrated circuits, where a substrate is covered with a thermally grown oxide layer and where a substantially thicker deposited oxide layer containing phosphorus is formed above said grown oxide layer, a process for making contact to a doped region in said substrate comprising the steps of: forming a photoresist layer over said deposited oxide layer with an opening over said doped region; etching through said phosphorus containing deposited oxide layer with a wet etchant such that a tapered opening is formed through said deposited oxide layer extending to said grown oxide layer; etching through said grown oxide layer with a plasma etchant in alignment with said opening through said photoresist layer, until said substrate is exposed at said doped region; removing said photoresist layer; and, forming a metal alloy contact member in said opening through said oxide layers in contact with said doped region in said substrate; whereby a tapered contact member is formed without high temperature steps.

Claim 10

In the fabrication of metal-oxide-semiconductor integrated circuits, where a substrate is covered with a thermally grown oxide layer and where a substantially thicker deposited oxide layer containing phosphorus is formed above said grown oxide layer, a process for making contact to a doped region in said substrate comprising the steps of: forming a photoresist layer over said deposited oxide layer with an opening over said doped region; etching through said phosphorus containing deposited oxide layer with a wet etchant such that a tapered opening is formed through said deposited oxide layer extending to said grown oxide layer; etching through said grown oxide layer with a plasma etchant in alignment with said opening through said photoresist layer, until said substrate is exposed at said doped region; removing said photoresist layer; and, forming a metal alloy contact member in said opening through said oxide layers in contact with said doped region in said substrate; whereby a tapered contact member is formed without high temperature steps.

Claim 11

The process defined by claim 7 wherein said contact member comprises an aluminum silicon alloy.

Claim 12

In the fabrication of metal-oxide-semiconductor integrated circuits, where a substrate is covered with a thermally grown oxide layer and where a substantially thicker deposited oxide layer low in phosphorus is formed over said grown oxide layer, a process for forming a contact through said oxide layers to contact a region in said substrate comprising the steps of: forming a silicon nitride layer over said thermally grown oxide layer prior to the formation of said deposited oxide layer; forming a photoresist layer over said deposited oxide layer with an opening through said photoresist layer above said region; etching through said deposited oxide layer using a wet etchant, said etching continuing until said silicon nitride layer is reached which layer acts as an etchant stop for said wet etchant; etching through said silicon nitride layer and thermal oxide layer with an anisotropic plasma etchant thereby exposing said substrate; and, forming a contact member through said oxide layers and said silicon nitride layer; whereby a contact member is formed which is tapered.

Claim 13

In the fabrication of metal-oxide-semiconductor integrated circuits, where a substrate is covered with a thermally grown oxide layer and where a substantially thicker deposited oxide layer low in phosphorus is formed over said grown oxide layer, a process for forming a contact through said oxide layers to contact a region in said substrate comprising the steps of: forming a silicon nitride layer over said thermally grown oxide layer prior to the formation of said deposited oxide layer; forming a photoresist layer over said deposited oxide layer with an opening through said photoresist layer above said region; etching through said deposited oxide layer using a wet etchant, said etching continuing until said silicon nitride layer is reached which layer acts as an etchant stop for said wet etchant; etching through said silicon nitride layer and thermal oxide layer with an anisotropic plasma etchant thereby exposing said substrate; and, forming a contact member through said oxide layers and said silicon nitride layer; whereby a contact member is formed which is tapered.

Claim 14

The process defined by claim 9 wherein said deposited oxide layer contains approximately 4% or less of phosphorus.