Fabrication of trench DMOS device having thick bottom shielding oxide
First Claim
1. A method for fabricating a semiconductor device comprising:
- a) forming a trench in the semiconductor layer;
b) forming an oxide-nitride-oxide (ONO) structure on a sidewall and at a bottom of the trench, wherein the ONO structure includes a nitride layer between first and second oxide layers, wherein forming the ONO structure includes forming a first oxide layer on the sidewall and at the bottom of the trench and on top of the semiconductor layer;
forming a nitride layer on top of the first oxide layer; and
forming a second oxide layer on top of the nitride layer; and
c) forming one or more conductive structures in a portion of the trench not occupied by the ONO structure, wherein the one or more conductive structures include a shield gate structure having an insulating material sandwiched between a first conductive structure and a second conductive structure, wherein forming the second oxide layer includes;
filling the trench with the second oxide layer;
etching back the second oxide layer to leave a portion of the second oxide at the bottom of the trench;
forming a spacer layer with the predetermined thickness T1 on the second oxide layer and on the sidewalls of the remaining portions of the trench;
anisotropically etching the spacer layer to form one or more spacers on the sidewall;
anisotropically etching the second oxide layer to a non-zero thickness T2 at the bottom of the trench; and
removing the one or more spacers.
1 Assignment
0 Petitions
Accused Products
Abstract
Semiconductor device fabrication method and devices are disclosed. A device may be fabricated by forming in a semiconductor layer; filling the trench with an insulating material; removing selected portions of the insulating material leaving a portion of the insulating material in a bottom portion of the trench; forming one or more spacers on one or more sidewalls of a remaining portion of the trench; anisotropically etching the insulating material in the bottom portion of the trench using the spacers as a mask to form a trench in the insulator; removing the spacers; and filling the trench in the insulator with a conductive material. Alternatively, an oxide-nitride-oxide (ONO) structure may be formed on a sidewall and at a bottom of the trench and one or more conductive structures may be formed in a portion of the trench not occupied by the ONO structure.
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Citations
14 Claims
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1. A method for fabricating a semiconductor device comprising:
a) forming a trench in the semiconductor layer;
b) forming an oxide-nitride-oxide (ONO) structure on a sidewall and at a bottom of the trench, wherein the ONO structure includes a nitride layer between first and second oxide layers, wherein forming the ONO structure includes forming a first oxide layer on the sidewall and at the bottom of the trench and on top of the semiconductor layer;
forming a nitride layer on top of the first oxide layer; and
forming a second oxide layer on top of the nitride layer; and
c) forming one or more conductive structures in a portion of the trench not occupied by the ONO structure, wherein the one or more conductive structures include a shield gate structure having an insulating material sandwiched between a first conductive structure and a second conductive structure, wherein forming the second oxide layer includes;
filling the trench with the second oxide layer;
etching back the second oxide layer to leave a portion of the second oxide at the bottom of the trench;
forming a spacer layer with the predetermined thickness T1 on the second oxide layer and on the sidewalls of the remaining portions of the trench;
anisotropically etching the spacer layer to form one or more spacers on the sidewall;
anisotropically etching the second oxide layer to a non-zero thickness T2 at the bottom of the trench; and
removing the one or more spacers.- View Dependent Claims (2, 3, 4, 5)
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6. A method for fabricating a semiconductor device comprising:
a) forming a first trench of width A in a semiconductor layer;
b) filling the first trench with an insulating material;
c) removing selected portions of the insulating material leaving a remaining portion of the insulating material on a bottom surface and sidewalls of the first trench;
d) forming one or more spacers with a predetermined thickness T1 on one or more sidewalls of a remaining portion of the first trench;
e) anisotropically etching the remaining portion of the insulating material using the one or more spacers as a mask to form a second trench in the insulating material having a predetermined thickness T2 at a bottom thereof and a width A′
determined by the thickness T1 of the spacers, wherein A′
is less than A, wherein some of the insulating material remains on the bottom surface and sidewalls of the first trench after said anisotropically etching the remaining portion of the insulating material;
f) removing the spacers leaving the remaining portion of the first trench in the semiconductor layer with a width A″
that is greater than A′
; and
g) filling at least the second trench in the insulating material with a conductive material.- View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14)
Specification