US 5,328,866 A · Low temperature oxide layer over field implant mask

Abstract

A thin base oxide is disposed over both an active area and also over a field area of a substrate. A thin silicon-nitride layer is then formed over the base oxide in the active area to protect the underlying substrate from oxygen and/or water vapor during a subsequent field oxidation step. This thin nitride layer is, however, insufficiently thick to serve as a field implant mask in a subsequent field implant step. An additional low temperature oxide (LTO) layer is therefore provided over the nitride layer in the active area. The field implant step is then performed using the base oxide, the thin nitride, and the overlying LTO as a field implant mask. The boundaries of the overlying LTO define a field implant boundary. After the field implant step but before the field oxidation step, the LTO layer is removed from the top of the thin nitride layer. As a result, only the base oxide and the thin nitride layer is disposed over the active area during field oxidation. Therefore, in comparison to previous methods using thicker nitride layers, the present invention employs a thin nitride layer during the field oxidation step, thereby reducing the amount of stress induced in the nitride layer and thereby minimizing problems associated with thick nitride layers such as the introduction of lattice defects into the underlying silicon substrate. The thin nitride process of the present invention may, for example, be incorporated into a BiCDMOS process.

Claims15

Dependent claims

A method, comprising the steps of:

forming a nitride layer over a first oxide layer, said first oxide layer being disposed over a surface of a semiconductor material;
forming a second oxide layer over said nitride layer, said second oxide layer being disposed over a first region of said semiconductor material, said second oxide layer not being disposed over a second region of said semiconductor material;
using said second oxide layer as at least part of an implant mask such that dopant ions are implanted into said second region of said semiconductor material through said first oxide layer and such that substantially no dopant ions are implanted into said first region of said semiconductor material;
removing said second oxide layer such that said nitride layer is disposed over said first region of said semiconductor material but not over said second region of said semiconductor material;
and
thermally growing a thick oxide in said second region of said semiconductor material after said removing step.

3 more elements

A method of fabricating a field oxide region for an integrated circuit, comprising the steps of:

forming a stress-relief oxide layer on a surface of a semiconductor body;
forming a nitride layer over said stress-relief oxide layer;
forming an implant block oxide layer over said nitride layer, said block oxide layer being disposed over a first region of said semiconductor body and not being disposed over a second region of said semiconductor body;
implanting dopant ions of a first type into said second region of said semiconductor material through said stress-relief oxide layer;
forming a photoresist implant mask over a first part of said second region of said semiconductor material, said photoresist implant mask not being disposed over a second part of said second region of said semiconductor material;
implanting dopant ions of a second type into said second part of said second region of said semiconductor material;
removing said photoresist implant mask;
removing said implant block oxide layer;
after removing said implant block oxide layer, thermally growing a thick oxide in said second region of said semiconductor material when at least a part of said first oxide layer is disposed over said second region of said semiconductor body;
and
removing said nitride layer.

8 more elements

A method, comprising the steps of:

thermally growing a first oxide layer on an upper surface of a first region and a second region of a semiconductor body;
forming a nitride layer over said first oxide layer over said first and second regions of said semiconductor body;
depositing a second oxide layer over said nitride layer over said first and second regions of said semiconductor body;
removing said second oxide layer over said second region of said semiconductor body but not removing said second oxide layer over said first region of said semiconductor body;
implanting dopant ions into said second region of said semiconductor body through said first oxide layer over said second region of said semiconductor body using said second oxide layer over said first region of said semiconductor body as at least part of an implant mask such that substantially no ions are implanted into said first region of said semiconductor body, a lateral extent of said second oxide layer defining a boundary of said implant mask;
removing said second oxide layer over said first region of said semiconductor body;
thermally growing a field oxide layer over said second region of said semiconductor body when at least a part of said first oxide layer is disposed over said second region of said semiconductor body, said nitride layer being disposed over said first region of said semiconductor body but not over said second region of said semiconductor body;
and
removing said nitride layer over said first region of said semiconductor body.

6 more elements

Dependencies are inferred from the claim text.

Low temperature oxide layer over field implant mask

Life of this patent

Low temperature oxide layer over field implant mask

Life of this patent

Abstract

Claims15