compositions containing certain organic solvents and a fluorine source are capable of removing photoresist and etching residue.
|
1. A composition suitable for removing photoresist and etching residue which comprises:
a) at least about 50% by weight of a solvent which is tetrahydrofurfuryl alcohol;
b) about 0.005 to about 0.8 by weight of a source of fluorine.
c) up to about 49.9% by weight of water; and
d) up to about 20% by weight of a corrosion inhibitor.
10. A method for removing photoresist or etching residue or both from a substrate wherein comprises contacting said substract with a composition comprising:
a) at least about 50% by weight of a solvent which is tetrahydrofurfuryl alcohol;
b) about 0.005 to about 0.8 by weight of a source of fluorine
c) up to about 49.9% by weight of water; and
d) up to about 20% by weight of a corrosion inhibitor.
0. 35. A composition for removing residues comprising at least one residue selected from photoresist residues, etch residues, and mixtures thereof, the composition comprising:
at least about 50% by weight of an organic solvent comprising:
an alkylene glycol ether; and
at least one solvent selected from propylene glycol and glycerol;
about 0.005 to about 0.8% by weight of a source of fluorine;
up to about 49.9% by weight of water; and
up to about 20% by weight of a corrosion inhibitor.
0. 22. A composition for removing residues comprising at least one residue selected from photoresist residues, etch residues, and mixtures thereof, the composition comprising:
at least about 50% by weight of an organic solvent comprising:
an alkylene glycol ether; and
at least one solvent selected from propylene glycol, ethylene glycol, glycerol, polyvinyl alcohol, ethyl lactate, and N-N-dimethylacetamide;
a source of fluorine;
up to about 49.9% by weight of water; and
optionally up to about 20% by weight of a corrosion inhibitor.
0. 41. A method for removing residues comprising at least one residue selected from photoresist residues, etch residues, and mixtures thereof from a substrate, the method comprising:
contacting the substrate with a composition comprising:
at least about 50% by weight of an organic solvent comprising:
an alkylene glycol ether; and
at least one solvent selected from propylene glycol, ethyl glycol, glycerol, polyvinyl alcohol, ethyl lactate, and N-N-dimethylacetamide;
a source of fluorine;
up to about 49.9% by weight of water; and
optionally up to about 20% by weight of a corrosion inhibitor.
2. The composition of
R1N(R3)R2 wherein R1, R2 and R3 each individually represent H or an alkyl group.
3. The composition of
6. The composition of
said source of fluorine is about 0.05 to about 0.5% by weight, and said water is about 25 to about 35% by weight.
7. The composition of
8. The composition of
11. The method of
R1N(R3)R2F wherein R1, R2 and R3 each individually represent H or an alkyl group.
12. The method of
14. The method of
15. The method of
16. The method of
17. The method of
19. The method of
20. The method of
21. The method of
0. 23. The composition of
R1N(R3)R2 wherein R1, R2 and Ra each individually represent H or an alkyl group.
0. 24. The composition of
0. 25. The composition of
R1N(R3)R2 wherein R1, R2 and R3 each individually represent H or an alkyl group.
0. 26. The composition of
0. 27. The composition of
0. 28. The composition of
0. 29. The composition of
0. 30. The composition of
0. 31. The composition of
0. 32. The composition of
0. 33. The composition of
0. 34. The composition of
0. 36. The composition of
0. 37. The composition of
0. 38. The composition of
0. 39. The composition of
0. 40. The composition of
0. 42. The method of
R1N(R3)R2 wherein R1, R2 and R3 each individually represent H or an alkyl group.
0. 43. The method of
0. 44. The method of
R1N(R3)R2 wherein R1, R2 and R3 each individually represent H or an alkyl group.
0. 45. The method of
0. 46. The method of
0. 47. The method of
0. 48. The method of
0. 49. The method of
0. 50. The method of
0. 51. The method of
0. 52. The method of
0. 53. The composition of
|
|||||||||||||||||||||||||||||||||||||||||||
The present invention is concerned with selectively removing etching residues from a microstructure of an object. The present invention selectively removes residues without attacking metal and or silicon dioxide films exposed to the composition used for removing the residues. In addition, the present invention is concerned with certain cleaning compositions that are suitable for removing etching residues.
Numerous steps are involved in the fabrication of microelectronic structures. Within the manufacturing scheme of fabricating integrated circuits selective etching of semiconductor surfaces is sometimes required. Historically, a number of vastly different types of etching processes, to selectively remove material, have been successfully utilized to varying degrees. Moreover, the selective etching of different layers, within the microelectronic structure, is considered a critical and crucial step in the integrated circuit fabrication process.
Increasingly, reactive ion etching (RIE), is the process of choice for pattern transfer during via, metal line and trench formation. For instance, complex semi-conductor devices such as advanced DRAMS and microprocessors, which require multiple layers of back end of line interconnect wiring, utilize RIE to produce vias, metal lines and trench structures. Vias are used, through the interlayer dielectric, to provide contact between one level of silicon, suicide or metal wiring and the next level of wiring. Metal lines are conductive structures used as device interconnects. Trench structures are used in the formation of metal line structures. Vias, metal lines and trench structures typically expose metals and alloys such as Al, AlCu, Cu, Ti, TiN, Ta, TaN, W, TiW, silicon or a suicide such as a suicide of tungsten, titanium or cobalt. The RIE process typically leaves a residue (of a complex mixture) that may include re-sputtered oxide material as well as possibly organic materials from photoresist and antireflective coating materials used to lithographically define the vias, metal lines and or trench structures.
It would therefore be desirable to provide a selective cleaning material and process capable of removing remaining photoresist as well as the residues caused by selective etching using plasmas in general and RIE specifically. Moreover, it would be desirable to provide a selective cleaning material and process, capable of removing the photoresist and etching residue, that exhibits high selectivity for the residue as compared to metal, silicon, silicide and/or interlevel dielectric materials such as deposited oxides that might also be exposed to the cleaning composition. It would be especially desirable to provide a composition that is compatible with and can be used with such sensitive low-k films as HSQ, MSQ, FOx, black diamond (can you identify these chemically) and TEOS (tetraethylsilicate).
Along these lines, fluoride-containing stripers are usually too aggressive toward sensitive films with low dielectric constant such as HSQ and porous MSQ films.
For example, eventhough formamide is a good protic solvent, it was found that formulations with formamide had decreased compatibility with FOx® films. See Parker, Advances in Organic Chemistry, 5, 1 (1965)
The present invention provides compositions capable of selectively removing photoresist and etching residue from a substrate without attacking metal that might also be exposed to the composition. In addition, the present invention provides compositions that exhibit minimal silicon oxide and in general dielectric lower etch rates.
It has been found according to the present invention that by employing certain selected organic solvents in the formulation of strippers, fluoride containing strippers can be formulated to be compatible with low dielectric constant materials. In this invention, efforts have been made to formulate fluoride-containing strippers that will be less aggressive towards sensitive films with low dielectric constant by selecting certain polar protic solvents. In these formulations, the polar protic solvents have been selected to be the major solvents. As a result of choosing solvents that lead to less fluoride ion aggressiveness in this invention, formulations in the invention are very compatible with FOx®, porous JSR, and the like.
Compositions of the present invention exhibit good compatibility with sensitive low-k films, such as FOx® and porous low-k dielectrics, while at the same time maintaining good cleaning ability.
More particularly, the present invention relates to a composition suitable for removing photoresist and etching residue that comprises:
a) at least about 50% by weight of a solvent selected from the group consisting of tetrafurfuryl alcohol, diacetone alcohol, 1,4-cyclohexanedi-methanol, and alkylene glycol ethers;
b) about 0.005 to about 0.8 by weight of a source of fluorine.
c) up to about 49.9% by weight of water; and
d) up to about 20% by weight of a corrosion inhibitor.
The present invention also relates to a method for removing photoresist and/or etching residue from a substrate that comprises contacting the substrate with the above-disclosed composition.
Other objections and advantages of the present invention will become readily apparent to those skilled in this art from the following detailed description, wherein it is shown and described only the preferred embodiments of the invention, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, without departing from the invention. Accordingly, the description is to be regarded as illustrative in nature and not as restrictive.
The present invention is concerned with selectively removing photoresist and/or etching residues and especially residues cased by reactive ion etching. Moreover, the photoresist and/or etching residues are present in an article that also includes metal, silicon, silicate and/or interlevel dielectric material such as deposited silicon oxides and derivitized silicon oxides such as HSQ, MSQ, FOX, TEOS and Spin-On Glass, wherein both the photoresist and/or residues and the metal, silicon, silicide and/or interlevel dielectric materials will come in contact with the cleaning composition. The present invention provides for selectively removing the photoresist and/or post etch residues without significantly attacking the metal, silicon, silicon dioxide and interlevel dielectric materials. The metal is typically copper, copper alloy, titanium, titanium nitride, tantalum, tantalum nitride, tungsten, titanium/tungsten, aluminum and/or aluminum alloys. The present invention is especially advantageous for structures containing sensitive low k-films. The residues removed according to the present invention are preferably those created by reactive ion etching.
The compositions of the present invention comprise at least about 50% by weight, preferably about 50 to about 80%, and most preferably about 50 to about 70% by weight of at least one organic solvent selected from the group consisting of tetrafurfuryl alcohol, diacetone alcohol, 1,4-cyclohexanedimethanol, and alkylene glycol ethers. The preferred solvents are tetrafurfuryl alcohol and diacetone alcohol. Suitable alkylene glycol ethers include di(ethylene glycol) butyl ether, and propylene glycol methyl ether.
Compositions of the present invention also include a fluoride ion source typically in an amount of about 0.005 to about 0.8% by weight, preferably about 0.05 to about 0.5% by weight.
Typical compounds providing a fluoride ion source according to the present invention are hydrofluoric acid, ammonium fluoride, quaternary ammonium fluorides such as tetramethylammonium fluoride and tetrabutylammonium fluoride, fluoroborates, fluoroboric acid, tetrabutylammonium tetrafluoroborate, and aluminum hexafluoride. Also, a fluoride salt of an aliphatic primary, secondary or tertiary amine can be used. Such have the following formula:
R1N(R3)R2F
wherein R1, R2 and R3 each individually represent H or an alkyl group,
Typically, the total number of carbon atoms in the R1, R2 and R3 groups is 12 carbon atoms or less. The preferred fluoride compounds are ammonium fluoride and tetramethylammonium fluoride.
The composition of the present invention can also contain up to about 49.9% by weight of water, and preferably about 25-35% by weight of water. Preferably the water is deionized water.
Moreover, the compositions of the present invention can also optionally contain up to about 20% by weight, more typically about 0.2 to about 19% by weight of a corrosion inhibiter, especially when the compositions are to come in contact with metals such as copper. Examples of corrosion inhibitors include, but are not limited to catechol, gallic acid, benzotriazole, resorcinol, other phenols, acids or triazoles, and preferably hydroxylamines or acid salts thereof.
Preferred hydroxylamines are diethylhydroxylamine and the lactic acid salts thereof. Ordinarily, hydroxylamines are not considered as being compatible with copper because of their ability to etch. However, in the composition of the present invention they surprisingly inhibit copper corrosion.
The compositions of the present invention typically have a pH of about 2 to about 6.5, and preferably about 4.5 to about 6.5
The compositions of the present invention are compatible with low-k films such as HSQ (FOx), MSQ, SiLK, etc. The formulations are also effective in stripping photoresists and plasma etch residues such as organic residues, organometallic residues, inorganic residues, metallic oxides, or photoresist complexes at low temperatures with very low corrosion of aluminum, copper, titanium or containing substrates.
During the manufacturing process, a photoresist layer is coated on the substrate. Using photolithographic process, a pattern is defined on the photoresist layer. The patterned photoresist layer is thus subjected to plasma etch by which the pattern is transferred to the substrate. Etch residues are generated in the etch stage. Some of the substrates used in this invention are ashed while some are not ashed. When the substrates are ashed the main residues to be cleaned are etchant residues. If the substrates are not ashed, then the main residues to be cleaned or stripped are both etch residues and photoresists.
The following non-limiting examples are presented to further illustrate the present invention.
Examples A-Z shown below are illustrative examples of suitable compositions of the present invention.
Example A
Example B
* Example C
DAA
59.25
DAA
39.25
BEE
59.25
Dl Water
40.45
Dl Water
35.45
Dl Water
40.45
Amm. Fluoride
0.3
Amm. Fluoride
0.3
Amm. Fluoride
0.3
BEE
25
Example D
Example E
Example F
DAA
64.25
DAA
54.25
DAA
54.25
Dl Water
35.45
Dl Water
35.45
Dl Water
35.45
Amm. Fluoride
0.3
Amm. Fluoride
0.3
Amm. Fluoride
0.3
EL
10
DMAc
10
Example G
Example H
Example I
BEE
54.25
BEE
49.25
BEE
39.25
Dl Water
45.45
Dl Water
45.45
Dl Water
55.45
Amm. Fluoride
0.3
Amm. Fluoride
0.3
Amm. Fluoride
0.3
Resorcinol
5
Resorcinol
5
Example J
Example K
Example L
DAA
44.25
glycerol
54.25
glycerol
74.25
Dl Water
35.45
Dl Water
35.45
Dl Water
25.45
Amm. Fluoride
0.3
Amm. Fluoride
0.3
Amm. Fluoride
0.3
EL
20
DMAc
10
Example M
Example N
Example O
THFA
54.25
THFA
44.25
THFA
64.35
Dl Water
45.45
Dl Water
35.5
Dl Water
35
Amm. Fluoride
0.3
Amm. Fluoride
0.3
Amm. Fluoride
0.65
DAA
20
Example P
Example Q
Example R
THFA
59
THFA
54
THFA
54
Dl Water
35.6
Dl Water
35.6
Dl Water
35.6
Amm.
0.4
Amm.
0.4
Amm.
0.4
Bifluoride
Bifluoride
Bifluoride
PG
5
PG
10
EG
10
Example S
Example T
Example U
THFA
59.35
THFA
54.35
THFA
60
Dl Water
35
Dl Water
35
Dl Water
21.2
Amm. Fluoride
0.65
Amm. Fluoride
0.65
Amm. Fluoride
0.8
PVA
5
PVA
10
Glycerol
18
Example V
Example X
Example Y
THFA
60
THFA
55
THFA
65
Dl Water
25.6
Dl Water
25.6
Dl Water
20.6
Amm. Fluoride
0.4
Amm. Fluoride
0.4
Amm. Fluoride
0.4
Glycerol
14
Glycerol
19
Glycerol
14
Example Z
Example Z1
Example Z2
THFA
65
CHDM
54.25
PGME
54.25
Dl Water
19.72
Dl Water
45.45
Dl Water
45.45
Amm. Fluoride
0.48
Amm. Fluoride
0.3
Amm. Fluoride
0.3
Glycerol
10.8
Resorcinol
4
DAA Diacetone alcohol
BEE 2-(2-Butoxyethoxy)ethanol
EL Ethyl lactate
THFA Tetrahydrofurfuryl alcohol
PG Propylene glycol
EG Ethylene glycol
PVA Polyvinyl alcohol
DMAc N,N-dimethylacetamide
CHDM 1,4-cyclohexanedimethanol
PGME Propyleneglycol methyl ether
The above compositions are effective in cleaning and stripping of etch residues and photoresists from aluminum and copper lines and vias. The compositions also showed effectiveness in removing etch residues and photoresists from some low and ultra low dielectric constant materials. They are compatible with the low and ultra low dielectric constant materials.
In the following Examples A1-A6, a positive photoresist is spin-coated on to a substrate. The positive photoresist comprises of diazonaphthoquinone and novolak resin. The photoresist coated is baked at 90° C. for 90 seconds. A pattern is defined on the photoresist by exposure, through a patterned mask, to i-line (365 nm) rays followed by development. The pattern is then transferred via plasma etch to the low-k substrate. The compositions shown in Examples A1-A6 are used to remove remaining photoresist and etching.
Example A1
Example A2
Example A3
PGME
63
PGME
68
THFA
65
Dl Water
22.6
Dl Water
22.6
Dl Water
15.72
Amm. Fluoride
0.8
Amm. Fluoride
0.8
Amm. Fluoride
0.48
PG
10
PG
5
Glycerol
15.8
DEHA
1.8
DEHA
1.8
amm. Citrate
3
lactic acid
1.8
lactic acid
1.8
Example A4
Example A5
Example A6
PGME
35.5
PGME
30.5
t-PGME
30.5
PGPE
20
PGPE
15
PGPE
15
Dl Water
25.9
Dl Water
25.9
Dl Water
25.9
Amm. Fluoride
0.6
Amm. Fluoride
0.6
Amm. Fluoride
0.6
PG
14
PG
14
PG
14
DEHA
2
DEHA
14
DEHA
14
lactic
2
A more detailed discussion of selected examples described above is presented below:
The composition of example A consists of 59.25 weight % of diacetone alcohol, 0.3 weight % of ammonium fluoride, and 40.45 weight % of deionized water. Example A is a cleaning and stripping composition for removing etch residue and photoresists for low-k substrates as well as metal substrates.
The composition of example C consists of 59.25 weight % of 2-(2-butoxyexthoxy)ethanol, 0.3 weight % of ammonium fluoride, and 40.45 weight % of deionized water. Example C is a cleaning and stripping composition for removing etch residues and photoresists from low-k and metal lines as well as vias.
The composition of example H consists of 49.25 weight % of 2-(2-butoxyethoxy)ethanol, 0.3 weight % of ammonium fluoride, 45.45 weight % of deionized water and 5 weight % of resorcinol. The composition is designed for etch residue and photoresist removal on aluminum copper substrates.
The composition of example V consists of 60 weight % of tetrahydrofurfuryl alcohol, 0.4 weight % of ammonium fluoride, 25.6 weight % of deionized water and 14 weight % of glycerol. This composition is also effective is cleaning and stripping of etch residues and photoresists from low-k and metal lines and vias.
The composition of example A1 consists of 63 weight % of propylene glycol methyl ether, 22.6 weight % deionized water, 0.8 weight % of ammonium fluoride, 10 weight % of propylene glycol, 1.8 weight % of diethylhydroxylamine and 1.8 weight % lactic acid. Example H is a cleaning and stripping composition for removing etch residues and photoresists from low-k and metal lines as well as vias.
The composition of example A3 consists of 65 weight % of tetrahydrofurfuryl alcohol, 15.72 weight % deionized water, 0.48 weight % of ammonium fluoride, 15.8 weight % of glycerol and 3 weight % of ammonium citrate. Example A3 a cleaning and stripping composition for removing etch residues and photoresists from low-k and metal lines as well as vias.
The composition of example A4 consists of 35.5 weight % of propylene glycol methyl ether, 20 weight % propylene glycol propyl ether, 25.9 weight % deionized water, 0.6 weight % of ammonium fluoride, 14 weight % of propylene glycol, 2 weight % of diethylhydroxylamine and 2 weight % lactic acid. Example A4 is a cleaning and stripping composition for removing etch residues and photoresists from low-k and metal lines as well as vias.
The composition of example A5 consists of 30.5 weight % of propylene glycol methyl ether, 15 weight % of propylene glycol propyl ether, 25.9 weight % deionized water, 0.6 weight % of ammonium fluoride, 14 weight % of propylene glycol and 14 weight % of diethylhydroxylamine. Example A5 is a cleaning and stripping composition for removing etch residues and photoresists from low-k and metal lines as well as vias.
The composition of example A6 consists of 30.5 weight % of tri(propylene glycol) methyl ether, 15 weight % of propylene glycol propyl ether, 25.9 weight % deionized water, 0.6 weight % of ammonium fluoride, 14 weight % of propylene glycol and 14 weight % of diethylhydroxylamine. Example A6 is a cleaning and stripping composition for removing etch residues and photoresists from low-k and metal lines as well as vias.
All of the examples from the Table are very effective in stripping and cleaning photoresists, etch and ashed residues. The process temperature should not be greater than 40° C. and each of the examples can be used in bath cleaning process, spray tools and single wafer tools.
The foregoing description of the invention illustrates and describes the present invention. Additionally, the disclosure shows and describes only the preferred embodiments of the invention but, as mentioned above, it is to be understood that the invention is capable of use in various other combinations, modifications, and environments and is capable of changes or modifications within the scope of the invention concept as expressed herein, commensurate with the above teachings and/or the skill or knowledge of the relevant art. The embodiments described hereinabove are further intended to explain best modes known of practicing the invention and to enable others skilled in the art to utilize the invention in such, or other, embodiments and with the various modifications required by the particular applications or uses of the invention. Accordingly, the description is not intended to limit the invention to the form disclosed herein. Also, it is intended that the appended claims be construed to include alternative embodiments.
| Patent | Priority | Assignee | Title |
| 8900802, | Feb 23 2013 | JSR Corporation | Positive tone organic solvent developed chemically amplified resist |
| 9028620, | Mar 05 2010 | UTICA LEASECO, LLC ASSIGNEE | Substrate clean solution for copper contamination removal |
| Patent | Priority | Assignee | Title |
| 4617251, | Apr 11 1985 | OCG MICROELECTRONIC MATERIALS, INC | Stripping composition and method of using the same |
| 5106525, | Apr 12 1991 | Arco Chemical Technology, Inc | Paint stripper compositions containing gamma-butyrolactone |
| 5139607, | Apr 23 1991 | VERSUM MATERIALS US, LLC | Alkaline stripping compositions |
| 5279771, | Nov 05 1990 | EKC TECHNOLOGY, INC | Stripping compositions comprising hydroxylamine and alkanolamine |
| 5417877, | Jan 25 1991 | Air Products and Chemicals, Inc | Organic stripping composition |
| 5472830, | Apr 18 1994 | OLIN MICROELECTRONIC CHEMICALS, INC | Non-corrosion photoresist stripping composition |
| 5507978, | May 08 1995 | OLIN MICROELECTRONIC CHEMICALS, INC | Novolak containing photoresist stripper composition |
| 5529887, | Mar 31 1993 | Rohm and Haas Chemicals LLC | Water soluble fluoride-containing solution for removing cured photoresist and solder resist mask |
| 5554312, | Jan 13 1995 | VERSUM MATERIALS US, LLC | Photoresist stripping composition |
| 5753601, | Jan 25 1991 | Air Products and Chemicals, Inc | Organic stripping composition |
| 5792274, | Nov 13 1995 | Tokyo Ohka Kogyo Co., Ltd. | Remover solution composition for resist and method for removing resist using the same |
| 5905063, | Nov 13 1995 | Tokyo Ohka Kogyo Co., Ltd. | Remover solution composition for resist and method for removing resist using the same |
| 5972862, | Aug 09 1996 | Mitsubishi Gas Chemical | Cleaning liquid for semiconductor devices |
| 6261745, | Jun 05 1998 | Tokyo Ohka Kogyo Co., Ltd. | Post-ashing treating liquid compositions and a process for treatment therewith |
| 6372410, | Sep 28 1999 | Mitsubishi Gas Chemical Company, Inc. | Resist stripping composition |
| 6554912, | Mar 27 2000 | Shipley Company, L.L.C. | Polymer remover |
| 6677286, | Jul 10 2002 | VERSUM MATERIALS US, LLC | Compositions for removing etching residue and use thereof |
| 6869921, | Aug 03 2001 | KANTO CHEMICAL CO , INC | Stripping composition |
| 20010001785, | |||
| 20020146647, | |||
| 20030022800, | |||
| 20030114014, | |||
| 20030130147, | |||
| 20030181342, | |||
| JP1995271058, | |||
| JP2001005200, | |||
| JP2001100436, | |||
| JP2001232647, | |||
| JP20012366627, | |||
| JP2001523356, | |||
| JP2002278092, | |||
| WO204233, |
| Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
| Jan 22 2009 | Air Products and Chemicals, Inc. | (assignment on the face of the patent) | / | |||
| Feb 13 2009 | EGBE, MATTHEW | Air Products and Chemicals, Inc | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 022256 | /0127 | |
| Sep 30 2016 | VERSUM MATERIALS US, LLC | CITIBANK, N A , AS COLLATERAL AGENT | PATENT SECURITY AGREEMENT | 040503 | /0442 | |
| Feb 14 2017 | Air Products and Chemicals, Inc | VERSUM MATERIALS US, LLC | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 041772 | /0733 | |
| Oct 07 2019 | CITIBANK, N A , AS AGENT | VERSUM MATERIALS US, LLC | RELEASE BY SECURED PARTY SEE DOCUMENT FOR DETAILS | 050647 | /0001 |
| Date | Maintenance Fee Events |
| Apr 30 2014 | M1552: Payment of Maintenance Fee, 8th Year, Large Entity. |
| Jul 12 2018 | M1553: Payment of Maintenance Fee, 12th Year, Large Entity. |
| Date | Maintenance Schedule |
| Feb 08 2014 | 4 years fee payment window open |
| Aug 08 2014 | 6 months grace period start (w surcharge) |
| Feb 08 2015 | patent expiry (for year 4) |
| Feb 08 2017 | 2 years to revive unintentionally abandoned end. (for year 4) |
| Feb 08 2018 | 8 years fee payment window open |
| Aug 08 2018 | 6 months grace period start (w surcharge) |
| Feb 08 2019 | patent expiry (for year 8) |
| Feb 08 2021 | 2 years to revive unintentionally abandoned end. (for year 8) |
| Feb 08 2022 | 12 years fee payment window open |
| Aug 08 2022 | 6 months grace period start (w surcharge) |
| Feb 08 2023 | patent expiry (for year 12) |
| Feb 08 2025 | 2 years to revive unintentionally abandoned end. (for year 12) |