Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Finishing or perfecting composition or product
Reexamination Certificate
2000-01-11
2001-05-29
Michl, Paul R. (Department: 1714)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Finishing or perfecting composition or product
C430S329000, C510S176000
Reexamination Certificate
active
06238849
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the use of cyclic ureas as wetting agents in aqueous photoresist developer and electronics cleaning compositions.
BACKGROUND OF THE INVENTION
The demands of semiconductor manufacture have required the use of high performance surfactants and wetting agents in photoresist developer formulations. As line features shrink to smaller sizes and photoresist substrate materials become more aliphatic in nature (i.e. having lower surface energy), aqueous developer solutions are being formulated with surface tension reducing agents. Another requirement for these developers is that they have a low tendency to foam. This is accentuated by the movement toward larger wafer sizes. Low foam formation is particularly important when using spray-puddle techniques because microbubble entrainment during spreading of the solution over the photoresist surface can lead to defects. Surfactants that have been used in the past to increase wetting of the photoresist typically lead to higher foam formation. For the most part the industry has focused on the effect of surfactant on photoresist performance, such as contrast, critical dimension, and feature sharpness. Although the cleaning ability of underlying substrates is enhanced by typical surfactants, foam formation still remains a problem.
Tetramethylammonium hydroxide (TMAH) is the chemical of choice in aqueous alkaline solutions for developing photoresists according to
Microlithography, Science and Technology
, edited by J. R. Sheats and B. W. Smith, Marcel Dekker, Inc., 1998, pp 551-553. Surfactants are added to the aqueous TMAH solutions to reduce development time and scumming and to improve surface wetting.
U.S. Pat. No. 5,985,968 discloses the use of 1,1-dialkyl ureas to reduce equilibrium and dynamic surface tension in aqueous compositions.
U.S. Pat. No. 5,972,431 discloses the use of certain cyclic ureas to reduce equilibrium and dynamic surface tension in aqueous compositions.
There are few references describing low foam surfactants in photoresist developer compositions. JP 10-319606 discloses that commercially available ethylene oxide (EO)/propylene oxide (PO) block polymers give good wetting and low foam.
JP 03-062034 discloses polyoxyalkylene dimethyl polysiloxanes as good surfactants with low foam in photoresist developer formulations. Polysiloxanes are known to rearrange or decompose under conditions of high pH.
Although there are a few references to the use of ureas in photoresist developer compositions, they are not related to the use as surface active agents.
U.S. Pat. No. 4,997,748 discloses cyclic nitrogen compounds at levels of 0.1 to 10 wt % to decrease scum formation and enhance image sharpness during photoresist development. Among the cyclic nitrogen compounds taught is the cyclic urea 1,3-dimethyl-2-imidazolidinone. Since the nitrogen compounds are not amphipathic, it is not likely that they will lower surface tensions at low concentrations, and their utility appears to be based on properties other than surface tension reduction. 1,3-dimethyl-2-imidazolidinone is well known as a very good solvent and not as a surface-active material.
Maekawa et al, “Dissolution Inhibitory Effect of Urea Additives on a Carboxyl Polymer Through a Supramolecular Structure”, disclose the use of 1,3-disubstituted ureas to modify the dissolution characteristics of photosensitive carboxyl-polymers in TMAH solution. The amounts of the ureas were not specified, but it is clear that their role is to actively bind to the resin and not to lower the surface tension of the developer.
SUMMARY OF THE INVENTION
This invention provides water-based photoresist developing, or electronics cleaning, compositions having reduced equilibrium and dynamic surface tension by incorporation of an effective amount of certain cyclic urea compounds of the structure
where R is a C6 to C12 alkyl group or R″O—(CH
2
)
m
—, R″ is a C4 to C12 alkyl group, m is 2-4 and n is 1 or 2.
By “water-based”, “aqueous” or “aqueous medium” we mean, for purposes of this invention, a solvent or liquid dispersing medium which comprises at least about 90 wt %, preferably at least about 95 wt %, water. Obviously, an all water medium is also included. Also for purposes of the present invention, the terms “photoresist developing” and “electronics cleaning” are interchangeable.
Also provided is a method for developing a photoresist after exposure to radiation by applying to the photoresist surface a water-based developer composition containing an effective amount of a cyclic urea compound of the above structure for reducing the dynamic surface tension of the composition.
There are significant advantages associated with the use of these cyclic urea compounds in water-based photoresist developer, or electronics cleaning, compositions and these advantages include:
an ability to control the foaming characteristics of the water-based compositions; and
an ability to formulate low surface tension aqueous electronics cleaning and processing solutions, including photoresist developer solutions, for the semiconductor manufacturing industry with good wetting and extremely low foam.
The use of these materials in photoresist developer formulations is of particular importance because of their ability to provide all the advantages of surface tension lowering plus outstanding performance in reducing the formation of foam and doing so while maintaining good contrast for photoresist developing applications.
DETAILED DESCRIPTION OF THE INVENTION
This invention relates to the use of compounds of the formula
where R is a C6 to C12 alkyl group or R″O—(CH
2
)
m
—, R″ is a C4 to C12 alkyl group, m is 2-4 and n is 1 or 2 for the reduction of equilibrium and dynamic surface tension and low foaming in water-based photoresist developer formulations. It is desirable that an aqueous solution of the cyclic urea demonstrates a dynamic surface tension of less than 45 dynes/cm at a concentration of ≦5 wt % in water at 23° C. and 1 bubble/second according to the maximum-bubble-pressure method. The maximum-bubble-pressure method of measuring surface tension is described in
Langmuir
1986, 2, 428-432, which is incorporated by reference.
The cyclic ureas suitable for use in the present invention are those taught in U.S. Pat. No. 5,972,431, which patent also teaches how to make these cyclic ureas.
Generally, in the practice of this invention, it is desirable to choose alkyl groups such that the resulting cyclic ureas have a solubility in water of at least 0.001 wt %, preferably from 0.001 to 1 wt %, and most preferably from 0.05 to 0.5 wt %.
The alkyl group R may be a linear, branched, or cyclic C6 to C12 hydrocarbon moiety. In general, lower numbers of alkyl carbon or a higher degree of branching will increase the solubility of the surfactant but decrease the efficiency (i.e. a greater amount will be required to obtain a given reduction in surface tension). Examples of suitable alkyl groups include 1-hexyl, 2-hexyl, 3-hexyl, cyclohexyl, 1-octyl, 2-ethylhexyl, 2-octyl, 3-octyl, isooctyl, cyclooctyl, n-nonyl, 2-nonyl, 3-nonyl, 4-nonyl, isononyl, n-decyl, isodecyl, 2-decyl, 3-decyl, n-dodecyl, cyclododecyl, and the like. Of course, this list is not comprehensive, and the particular alkyl group chosen for a particular use will depend on the performance characteristics required for that application. Derivatives in which the alkyl group is a mixture of isomers are also suitable for the practice of this invention. C7 to C10 hydrocarbon derivatives are preferred and C8 hydrocarbon derivatives are especially preferred.
Compounds in which the higher alkyl group contains ether linkages, i.e., R″O—(CH
2
)
m
—, where R″ is a C4 to C12 alkyl group, m is 2-4 and n is 1 or 2, are also suitable for use in this invention. Examples of suitable C4 to C12 alkyl groups include 1-butyl, 2-butyl, t-butyl, 1-pentyl, 2-pentyl, 3-pentyl, neopentyl, 1-hexyl, 2-hexyl, 3-hexyl, cyclohexyl, 1-octyl, 2-ethylhexyl, 2-octyl, 3-octyl, isooctyl, cyclooctyl, n-nonyl, 2-nonyl, 3-nonyl, 4-n
Lassila Kevin Rodney
Marsella John Anthony
Air Products and Chemicals Inc.
Leach Michael
Michl Paul R.
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