US6337255B1
Expired / Lapsed
US
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Method for forming a trench structure in a silicon substrate
Assignee: Infineon Technologies AG
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Filing: 2000-03-24
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Granted: 2002-01-08
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Expires: 2020-03-24
Abstract
Abstract A method for forming a trench structure in a silicon substrate, which trench structure serves for electrically insulating a first region of the substrate from a second substrate region. The method proceeds from a growth of a thermal oxide layer on the substrate surface and an application and patterning of a mask layer over the thermal oxide layer. A trench of predetermined depth is subsequently etched into the silicon substrate through the patterned mask layer. The trench is filled by a deposition of a conformal covering oxide layer on the substrate with an essentially uniform thickness that is sufficient for completely filling the trench. Afterwards, a polysilicon layer is deposited on the covering oxide layer and a chemical mechanical planarization method is carried out with high selectivity S between the polysilicon material and the oxide material in order to obtain a flat surface. In a further method step, the layer is additionally removed by an essentially nonselective, joint etching of the polysilicon material and of the oxide material while maintaining a planar surface produced in the preceding planarization step. The etching operation is carried out at least until all the polysilicon material has been removed in a region of the trench.
Inventors
- 👤 Stephan Bradl
- 👤 Olaf Heitzsch
- 👤 Michael Schmidt
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 22:59
CPC Classifications
H; H10; H10W; H10W10/00; H10W10/01; H10W10/011; H10W10/014; H10W10/10; H10W10/17; H10P; H10P50/00; H10P50/20; H10P50/26; H10P50/264; H10P50/266; H10P50/267; H10P50/268; H10P50/28; H10P50/282; H10P50/283; H10P52/00; H10P52/40; H10P52/403; H10W10/0143; H10W10/0145; Y; Y10; Y10S; Y10S438/00; Y10S438/969
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
232 words
A method for forming a trench structure in a silicon substrate, the trench structure electrically insulating a first region of the silicon substrate from a second region of the silicon substrate, the method which comprises: growing a thermal oxide layer on a surface of the silicon substrate; applying and patterning a mask layer over the thermal oxide layer resulting in a patterned mask layer; etching a trench using the patterned mask layer down to a predetermined depth into the silicon substrate; depositing a substantially conformal covering oxide layer with a substantially uniform thickness that is sufficient for completely filling the trench; depositing a polysilicon layer on the conformal covering oxide layer, a thickness of the polysilicon layer corresponding at least the predetermined depth of the trench; chemical mechanical polishing of the polysilicon layer as far as a level of a surface of the conformal covering oxide layer with high selectivity between a polysilicon material of the polysilicon layer and an oxide material of the conformal covering oxide layer; and substantially nonselective, joint etching of the polysilicon material of the polysilicon layer and of the oxide material of the covering oxide layer while maintaining a planar surface produced in accordance with the chemical mechanical polishing step, the substantially nonselective etching step being carried out at least until all the polysilicon material of the polysilicon layer being removed in a region of the trench.
Claim 2
Independent Claim
232 words
A method for forming a trench structure in a silicon substrate, the trench structure electrically insulating a first region of the silicon substrate from a second region of the silicon substrate, the method which comprises: growing a thermal oxide layer on a surface of the silicon substrate; applying and patterning a mask layer over the thermal oxide layer resulting in a patterned mask layer; etching a trench using the patterned mask layer down to a predetermined depth into the silicon substrate; depositing a substantially conformal covering oxide layer with a substantially uniform thickness that is sufficient for completely filling the trench; depositing a polysilicon layer on the conformal covering oxide layer, a thickness of the polysilicon layer corresponding at least the predetermined depth of the trench; chemical mechanical polishing of the polysilicon layer as far as a level of a surface of the conformal covering oxide layer with high selectivity between a polysilicon material of the polysilicon layer and an oxide material of the conformal covering oxide layer; and substantially nonselective, joint etching of the polysilicon material of the polysilicon layer and of the oxide material of the covering oxide layer while maintaining a planar surface produced in accordance with the chemical mechanical polishing step, the substantially nonselective etching step being carried out at least until all the polysilicon material of the polysilicon layer being removed in a region of the trench.
Claim 3
Dependent Claim
26 words
The method according to claim 1 , which comprises performing the substantially nonselective, joint etching step as a plasma etching step including reactive ion etching (RIE).
Claim 4
Dependent Claim
27 words
The method according to claim 1 , which comprises using NF 3 /N 2 /CHF 3 gases as etching gases in the substantially nonselective, joint etching step.
Claim 5
Dependent Claim
65 words
The method according to claim 1 , which comprises depositing the thickness of the conformal covering oxide layer to be larger than a trench depth and the substantially nonselective, joint etching step is continued after the removal of all the polysilicon material of the polysilicon layer until a remaining part of the conformal covering oxide layer has a predetermined thickness above an unetched substrate surface.
Claim 6
Dependent Claim
23 words
The method according to claim 1 , which comprises applying a silicon nitride layer to the thermal oxide layer after the growing step.
Claim 7
Dependent Claim
35 words
The method according to claim 1 , which comprises performing the substantially nonselective, joint etching step to have a selectivity between the oxide and the polysilicon material in a range of from 0.95 to 1.05.
Claim 8
Dependent Claim
28 words
The method according to claim 1 , which comprises carrying out a selective wet etching step in order to remove the oxide material after the nonselective, etching step.
Claim 9
Dependent Claim
40 words
The method according to claim 7 , which comprises controlling the selective wet etching step such that a predetermined distance can be set between a surface of the oxide material in the trench and the surface of the silicon substrate.
Claim 10
Dependent Claim
37 words
The method according to claim 1 , which comprises epitaxially growing a thin oxide support conformally on the silicon substrate between the step of etching the trench and the step of depositing the conformal covering oxide layer.
Claim 11
Dependent Claim
21 words
The method according claim 1 , which comprises depositing the conformal covering oxide layer by a TEOS vapor phase deposition step.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2005-01-07 | 2005-07-09 | 2006-01-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2009-01-07 | 2009-07-09 | 2010-01-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2013-01-07 | 2013-07-09 | 2014-01-08 | $7700.00 | Window Closed / Lapsed |