US5874345A
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Method for planarizing TEOS SiO2 filled shallow isolation trenches
Assignee: International Business Machines Corp
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Filing: 1996-11-18
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Granted: 1999-02-23
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Expires: 2016-11-18
Abstract
Abstract According to the present invention, there is disclosed a method for planarizing TEOS SiO 2 filled shallow isolation trenches according to a planarization main step which is comprised of three processing steps. The starting structure (10) consists of a silicon substrate (11) coated by a patterned Si 3 N 4 layer (12) which delineates shallow trenches (20A, 20B) with a conformal layer (22) of TEOS SiO 2 formed thereon. A planarizing medium, typically two superimposed photoresist layers (24.25) is formed onto the resulting structure to provide a substantially planar surface. At this stage of the fabrication, the structure is standard. Now, this planar surface is translated by a non selective two-steps plasma etching in the TEOS SiO 2 layer (22). Next, should some photoresist material remain onto the structure it would be removed. Finally, a highly selective TEOS SiO 2 /Si 3 N 4 RIE etching step is performed which stops on the Si 3 N 4 layer. The preferred chemistry is C 4 F 8 /Ar or C 4 F 8 /CO/Ar mixture. There is no longer the notion of process window because both the "silicon polish" and "Si 3 N 4 pad residuals" type of defects are eliminated. The present method offers significant advantages in terms of final test yield improvement, cost reduction and reproducibility.
Inventors
- 👤 Philippe Coronel
- 👤 Frederic Lebrun
- 👤 Renzo MacCagnan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 12:09
CPC Classifications
H; H10; H10W; H10W10/00; H10W10/01; H10W10/011; H10W10/014; H10W10/0143; H10W10/0145; H10W10/10; H10W10/17; Y; Y10; Y10S; Y10S148/00; Y10S148/05
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
156 words
An improved method for planarizing TEOS SiO 2 filled shallow isolation trenches formed in a semiconductor structure (10) consisting of a silicon substrate (11) coated by a patterned Si 3 N 4 layer (12) which delineates shallow trenches (20A, 20B) formed therein with a conformal layer (22) of TEOS SiO 2 formed thereon filling the trenches; said method comprising the steps of: a) forming a planarizing medium (24.25) onto the structure to produce a substantially planar surface; b) translating said substantially planar surface into the TEOS SiO 2 layer by dry etching with low or no selectivity (about 1/1) but high uniformity (less than about 3%); and, c) dry etching the structure with a highly selective TEOS SiO 2 /Si 3 N 4 chemistry that etches TEOS SiO 2 at least eight times faster than Si 3 N 4 and stopping etching when the top surface of said Si 3 N 4 patterned layer is reached.
Claim 2
Dependent Claim
156 words
An improved method for planarizing TEOS SiO 2 filled shallow isolation trenches formed in a semiconductor structure (10) consisting of a silicon substrate (11) coated by a patterned Si 3 N 4 layer (12) which delineates shallow trenches (20A, 20B) formed therein with a conformal layer (22) of TEOS SiO 2 formed thereon filling the trenches; said method comprising the steps of: a) forming a planarizing medium (24.25) onto the structure to produce a substantially planar surface; b) translating said substantially planar surface into the TEOS SiO 2 layer by dry etching with low or no selectivity (about 1/1) but high uniformity (less than about 3%); and, c) dry etching the structure with a highly selective TEOS SiO 2 /Si 3 N 4 chemistry that etches TEOS SiO 2 at least eight times faster than Si 3 N 4 and stopping etching when the top surface of said Si 3 N 4 patterned layer is reached.
Claim 3
Dependent Claim
19 words
The method of claim 1 wherein said highly selective chemistry consists of a C 4 F 8 /Ar mixture.
Claim 4
Dependent Claim
84 words
The method of claim 2 wherein the dry etching of step c) is conducted in a reaction chamber of a plasma etcher tool with the following operating conditions: Ar . . . : 150 sccm C 4 F 8 . . . : 5 sccm Pressure . . . : 40 Pa (150 mTorr) Mag field . . . : 50 Gauss RF Power . . . : 800 W Sel.Si 3 N 4 /TEOS : 9/1 (blanket) Uniformity . . . : <4%.
Claim 5
Dependent Claim
19 words
The method of claim 1 wherein said highly selective chemistry consists of a C 4 F 8 /CO/Ar mixture.
Claim 6
Dependent Claim
92 words
The method of claim 4 wherein said dry etching step of step c) is conducted in a reaction chamber of a plasma etcher tool with the following operating conditions: Ar . . . : 150 sccm CO . . . : 60 sccm C 4 F 8 . . . : 5 sccm Pressure . . . : 40 Pa (150 mTorr) Mag field . . . : 50 Gauss RF Power . . . : 800 W Sel.Si 3 N 4 /TEOS : 15/1 (blanket) Uniformity . . . : <4%.
Claim 7
Dependent Claim
16 words
The method of claim 5 wherein step c) includes an overetch to produce the desired wrap-around.
Claim 8
Dependent Claim
60 words
The method of claim 1 wherein said step a) of forming a planarizing medium comprises the sub-steps of: a1) depositing a first layer (24) of a photoresist material with a thickness slightly greater than the thickness of the TEOS SiO 2 layer; and, a2) depositing a second photoresist layer (25) over said first layer to produce said substantially planar surface.
Claim 9
Dependent Claim
18 words
The method of claim 7 wherein the same photoresist material is used for the first and second layers.
Claim 10
Dependent Claim
34 words
The method of claim 8 wherein said step b) of translating is performed in a single step by dry etching in a plasma etcher tool in a single chamber thereof and no chemistry change.
Claim 11
Dependent Claim
12 words
The method of claim 9 wherein said chemistry essentially consists of CHF3/NF3.
Claim 12
Dependent Claim
42 words
The method of claim 8 wherein said step b) of translating is performed in two steps (steps 1 and 2) by dry etching in a plasma etcher tool with the same chemistry but different etch parameters and in the same chamber thereof.
Claim 13
Dependent Claim
12 words
The method of claim 11 wherein said chemistry essentially consists of CHF3/NF3.
Claim 14
Dependent Claim
162 words
The method of claim 12 wherein the operating conditions for steps 1 and 2 are given below: Step 1 CHF3 . . . : 70 sccm NF3 . . . : 60 sccm Pressure . . . : 24 Pa (180 mTorr) Mag. field . . . : 0 Gauss RF Power . . . : 560 W Select. AT2/TEOS: 1.5/1 (blanket) Uniformity . . . : <2% Step 2 CHF3 . . . : 95 sccm NF3 . . . : 35 sccm Pressure . . . : 40 Pa (300 mTorr) Mag field . . . : 8 Gauss RF Power . . . : 700 W CHF 3 . . . : 95 sccm NF 3 . . . : 35 sccm Pressure . . . : 40 Pa (300 mTorr) Mag field . . . : 8 Gauss RF Power . . . : 700 W Select. AT1/TEOS: 0.95 to 1.05/1 (blanket) Uniformity . . . : <1%.
Claim 15
Dependent Claim
20 words
The method of claim 8 further comprising the step of: d) removing the remaining patterned Si 3 N 4 layer.
Claim 16
Dependent Claim
16 words
The method of claim 8 wherein the TEOS SiO 2 layer is annealed prior step a).
Claim 17
Dependent Claim
21 words
The method of claim 11 wherein said patterned Si 3 N 4 layer top surface is detected by an interferometric technique.
References Cited (Backward Citations)
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