Tricholine phosphate surface treating agent

The use of tricholine phosphate, tris [(2-hydroxyethyl) trimethylammonium] phosphate as a surface treating agent employed during the manufacture of printed wire boards, semiconductors and the like, particularly as a stripper for photoresists and as a cleaner for silicon wafers, furnace tubes and the like.

FIELD OF THE INVENTION 
This invention relates to a surface treating agent used during the 
manufacture of printed wire boards, semiconductors and the like. It is 
particularly useful as a stripper for photoresists. It is also useful for 
cleaning silicon wafers, furnace tubes and the like. In particular it 
relates to the use of tricholine phosphate, 
tris[(2-hydroxyethyl)trimethylammonium]phosphate in these roles. 
BACKGROUND TO THE INVENTION 
It has been known to prepare printed circuits, chemically-machined parts, 
etched articles and the like by first applying a thin layer of a 
photosensitive resist to the surface of a substrate. There are two types 
of resists available: negative-working and positive-working. A 
negative-working resist is initially soluble in its developer but, after 
exposure to light of the proper wave length, becomes hardened and 
insoluble. Positive-acting resists are initially insoluble but become 
soluble upon being exposed. Polymeric images are then formed by exposing 
the layer, imagewise, to actinic radiation. Exposed or unexposed areas of 
the layer, as the case may be, are removed to form a resist image of 
polymeric material. The areas left unprotected by the resist image are 
permanently modified by being etched or having material deposited thereon. 
Finally, the remaining resist is stripped from the part. 
U.S. Pat. No. 3,887,450 (Giliano et al.) describes using alkaline aqueous 
solutions as developers for negative-working photoresists. Among a large 
group of suggested bases, tetrasubstituted ammonium hydroxide and basic 
soluble salts thereof are disclosed. Strong alkalies or proprietary 
stripping formulas are taught for stripping. 
U.S. Pat. No. 4,379,830 (Deutsch et al.) describes an improved alkaline 
developer for positive-working photoresists employing bases made from, 
among a list of anions, phosphates, and among a list of cations, 
quaternary ammonium ions, together with at least one neutral salt. 
U.S. Pat. No. 4,530,895 (Simon et al.) describes an alkaline developer for 
positive-working photoresists employing quaternary ammonium bases and 
salts thereof. 
U.S. Pat. Nos. 4,294,911 and 4,464,461 (Guild) describe the use of an 
aqueous solution of quaternary alkanol ammonium hydroxide as a developing 
agent for positive-working photoresists and positive-working lithographic 
printing plates. They teach that these quaternary ammonium compounds 
decompose without stabilizers. 
U.S. Pat. Nos. 4,239,661 and 4,339,340 (Muraoka et al.) describe the use of 
an aqueous solution of trialkyl(hydroxyalkyl) ammonium hydroxide, 
preferably choline base, as a cleaning agent for semiconductor wafers, as 
an etchant for metal layers used as wiring, and as a developer and 
stripper for positive working photoresist films. 
Choline, also known as choline base, (2-hydroxyethyl)trimethylammonium 
hydroxide, is a well-known organic base suitable for stripping photoresist 
and for a variety of other uses. Aqueous and lower-alcohol solutions of 
choline base are useful in electronic applications such as photoresist 
developing and stripping, anisotropic etching, and cleaning. 
Aqueous solutions typically are about 0.01 to 40 weight percent (wt.%) 
choline base. They are generally prepared and shipped as concentrates 
having at least 10 wt.% choline base. The concentrates are typically 
diluted to concentrations of about 1 to 5 wt.% choline base for use. 
Solutions of choline base in lower alcohols such as methanol, in 
concentrations as high as 50 wt.% choline, have been suggested for use as 
replacements for (alcoholic) solutions of common alkalis, catalysts, 
curing agents, hydrolytic agents, neutralizing agents and solubilizing 
agents, as well as for pH control. 
It has been hypothesized that when choline base contacts polymeric 
photoresists it partially decomposes into trimethylamine (TMA) and 
ethylene glycol and its oxidized decomposition products, creating adequate 
action to make it an effective stripping agent. Unfortunately, this 
results in extremely repugnant fishy odors, probably due to the TMA being 
released. 
While some decomposition may be desired when the choline base contacts the 
polymeric photoresist, choline base's tendency to decompose, particularly 
during shipment and storage, has the unwanted consequences of darkening 
and changing its performance as a developing and stripping agent. To 
prevent or retard such decomposition with its consequences, inexpensive 
stabilizers that do not interfere with the intended use have been sought. 
U.S. Pat. No. 4,686,002 teaches one such system for solutions of choline 
base in water and/or lower alcohols. Formaldehyde and paraformaldehyde are 
taught as improved stabilizers over the prior art stabilizers of sulfites 
and semicarbazides used in aqueous choline base and of the 
ethylenediamine, typically used in methanolic choline base. 
But, stabilizers add to the cost of operation, only reduce the rate of 
decomposition and may be the source of unwanted ions that can have a 
deleterious effect on the electronic product being treated with the 
choline base. Tight limits for particular ions and residues that may be 
present are specified by the electronics industry. For example, in printed 
wire board manufacture, no residue following the normal post-bake period 
is allowed because even traces of impurities such as alkali metals would 
interfere in the operation of the electronic circuits. 
It would be desirable to have a developer/stripper as effective as choline 
base, but which is stable without the addition of stabilizers that add 
cost, are only partially effective and impart undesirable ions or leave 
residues on the electronics workpiece and which doesn't have an extremely 
repugnant fishy odor. 
SUMMARY OF THE INVENTION 
In tricholine phosphate, tris[(2-hydroxyethyl)trimethylammonium]phosphate, 
a stripper/developer approaching the ideal has been found. It is fast 
acting; removes film in desirable particle sizes; does not readily 
decompose, particularly during storage and shipping, emitting odors and 
losing activity; is non-toxic, non-flammable and safe to handle; does not 
swell polymerized photoresist; leaves no residue or a residue that can 
easily be removed with an aqueous system; will not etch metals used in 
printed circuits; is relatively inexpensive; and is highly selective in 
its action. 
The tricholine phosphate (TCP) is a completely ionized salt in an aqueous 
solution having a pH of about 12 at all practical concentrations. It can 
be used as a direct replacement for choline base as a stripper/developer 
and in other applications. Unlike choline base, TCP does not have the 
strong fishy odor and, as a fully ionized salt in an aqueous solution, is 
stable without the addition of stabilizers. 
DETAILED DESCRIPTION OF THE INVENTION 
This invention comprises the use of aqueous solutions of tricholine 
phosphate (TCP) as a surface treating agent for removing (developing and 
stripping) both positive-working and negative-working photoresists from 
substrates and for cleaning surfaces, particularly those encountered in 
the manufacture of printed wire boards and semiconductor intermediate 
products. 
TCP is a fully ionized salt in water, having a pH of 11 to 13. The pH can 
be adjusted for the particular end use. Preferably, it should be about 12 
within the range of end use concentrations. 
TCP can be produced by reacting trimethylamine (TMA) with aqueous 
phosphoric acid at about 20.degree.-60.degree. C. and an autogenous 
pressure of about 10-50 pounds per square inch gauge (psig) to form 
trimethylamine phosphate salt. The temperature may be higher or lower 
depending on the pressure rating of the vessel in which the reaction is 
carried out and the time of reaction. Higher temperature will result in 
higher pressures and shorter reaction times. The trimethylamine phosphate 
salt in solution that is formed is then reacted in situ with ethylene 
oxide at about the same temperature and pressure as in the 
TMS-phosphoric-acid reaction to typically make up to about 50 wt.% TCP 
salt in water solution. 
TCP can also be prepared by producing choline base in situ by reacting 
ethylene oxide and TMA in an aqueous solution and then reacting the 
choline base in situ with about 1/3 moles of phosphoric acid per mole of 
choline base. The temperatures and pressures for the production of choline 
base are about the same as in the 
TMA-phosphoric-acid-followed-by-ethylene-oxide method. The neutralization 
of the strong base with the weak phosphoric acid to form the alkaline salt 
can be carried out at ambient conditions. 
TCP is preferably stored and shipped in a concentrated form, typically at 
least 15 to 30 wt.% TCP, to avoid the cost of shipping and storing excess 
wafer. The concentrate is diluted for use, as desired, to a sufficient 
concentration for accomplishing its particular intended surface treating 
purpose by adding other compounds typically used for that surface treating 
purpose. 
Surfaces that can be treated include the interior of a quartz furnace tube, 
the surface of a wafer as sliced from an input, a wafer in which an 
impurity has been diffused, an oxide film produced on the wafer, a 
photoresist mounted on the surface of the wafer, and a metal layer 
deposited on the surface of the wafer, a printed wire board, a metal layer 
on the surface of the printed wire board, and a photoresist mounted on the 
surface of the printed wire board or metal layer thereon. 
It may be used in removing any photoresist film of the type known to the 
semiconductor, printed wire board, and photolithographic industries that 
can be developed or stripped in alkali. These photoresists are of two main 
types: negative-working and positive-working. 
It can be used as a direct replacement for choline base in these 
stripping/developing applications as well as in other applications for 
choline base, employing essentially the same treating conditions that 
would be used in the case of choline base. That is to say: the 
concentration of TCP as the principle alkaline component in the surface 
treating solution may be in about the same concentration range as choline 
base. By principle alkaline component, it is meant that the TCP will be 
the most highly alkaline component that provides the properties that 
enable faster action. The TCP should be compatible with the other 
components of the treating solution such as solvents, surfactants, buffers 
and metal complexing agents. These other components may be the same 
compounds present in the same concentration range as in the case of 
choline base. The temperature and time of operation should be about the 
same as in the case of choline base. Thus, from the details presented 
herein and in the references disclosed in the "Background of the 
Invention" and incorporated herein by reference, a person of ordinary 
skill in the art should be able to use the TCP aqueous solution of this 
invention in these applications. 
As a developing agent for negative-working photoresists used primarily in 
printed wire board and printing applications, the TCP has limited utility 
due to the short time in which it strips polymerized resist. If it is to 
be used in this application, its concentration would have to be extremely 
low or its pH would have to be adjusted to less than 11 to reduce its 
stripping ability. 
As a developing agent for positive-working photoresists used primarily in 
semiconductor applications, TCP should be as effective as choline base in 
the concentrations normally used for choline base. These concentrations 
are stated to be about 0.01 to 20 wt.%, more preferably 0.01 to 5 wt.%, 
especially 1 to 3 wt.%. The treating solution will contain, in addition to 
TCP and water, materials specific to and known to those skilled in the art 
for the particular photoresist. Treatment will preferably be by spraying 
or immersion and the temperature of the treating solution will depend upon 
the speed of the line, the photoresist used, the treating formulation and 
other factors. Temperatures of up to about 100.degree. C., preferably 
70.degree. to 90.degree. C. can be used. The pH of the solution will 
depend on the resists and conditions employed. 
As a stripping agent, the concentration of TCP in the surface treating 
solution should again be about the same as in the case of choline base. 
The effective concentration will depend, upon line speed, temperature, the 
resist used and the other components and characteristics of the stripping 
mixture. Generally, the treating solution should contain as its principle 
alkaline component about 0.1 to 30 wt.% TCP. In printed wire boards, it is 
preferably as high as or higher than in semiconductor applications. In 
printed wire boards, it would be preferable greater than 1 and more 
preferably between 2 and 11 wt.%. In semiconductors, it would be 
preferably 1 to 3 wt.%, most generally about 2 wt.%. The treating solution 
preferably will contain, in addition to TCP and water, materials specific 
to and known to those skilled in the art for the particular photoresist. 
Temperatures of up to about 100.degree. C., preferably 70.degree. to 
90.degree. C. can be used. The pH of the solution again will depend on the 
resists and conditions employed, but typically, for currently known 
resists, will preferably be about 11 to 13 and more preferably about 12. 
Treatment will preferably be by spraying or immersion. Agitation as in an 
ultrasonic cleaner is preferable. 
Where used as a surface cleaner of organic and inorganic contaminants on an 
intermediate product obtained in manufacturing a semiconductor device, the 
piece being washed by the TCP aqueous solution of the invention has only 
to be immersed 5 to 20 minutes in the solution kept at 
70.degree.-90.degree. C. and, more preferably, is subjected to ultrasonic 
cleaning. The solution used in this case contains 0.1 to 30 wt.%, more 
preferably 0.2 to 10 wt.%, especially 0.5 to 5 wt.% of TCP. 
When used for treating semiconductor intermediate products, the TCP aqueous 
solution is preferably substantially free of metal ions, that is, the 
alkali metal ion concentration is preferably less than 1 ppm, and more 
preferably as low as 0.01 ppm. The halide ion concentration is preferably 
then lower than 1 ppm, and more preferably lower than 0.01 ppm. 
For non-semiconductor uses, the higher concentrations of both alkali metal 
and halide ions are permissible. For example, up to 10,000 ppm alkali 
metal ions may be present without interfering with the intended use. 
The TCP aqueous solution of this invention is effective with both negative- 
and positive-working photoresists. As such, it will find its greatest use 
with negative-working photoresists in the printed wire board area where 
high speed exposing equipment is used and the photoresists are at least a 
half millimeter and generally 1 to 3 millimeters thick. It will find its 
greatest use with positive-working photoresists in the semiconductor area 
where the speed of exposure is sufficient because of the extremely thin 
coatings (micrometers thick) and because of their good resolving power and 
clear-cut image outlining. 
For illustration of TCP's utility as a stripping/developing agent, the 
remainder of the discussion will focus on positive-working resists and 
particularly on quinone diazide compounds which comprise the majority of 
positive-working photoresists. The examples will focus on the 
negative-working resists, in particular, the dry-film variety such as 
Riston.RTM. and Laminar.RTM. that are laminated onto the substrate. 
The quinone diazides are extensively described in the patent literature as 
used in positive-working photoresists. The monomeric quinone diazide can 
be incorporated in an alkali-soluble resinous binder or reacted with an 
alkali-soluble resinous material so that it can be used satisfactorily as 
a resist material or can withstand the wear on printing plates. 
Photosensitive polymeric compounds are formed from the condensation 
reaction of a quinone diazide such as 
1,2-naphthoquinone-2-diazide-5-sulfonyl chloride with a 
phenol-formaldehyde resin. 
The phenol-formaldehyde resins, such as novolac or resole resins, are 
described in Chapter XV of "Synthetic Resins in Coatings," H. P. Preuss, 
Noyes Development Corporation (1965), Pearl River, N.Y. Novolac resins are 
prepared by the condensation of phenols and aldehydes under acidic 
conditions whereas resole resins are prepared under basic conditions. More 
generally, they are produced by the reaction of a phenolic compound having 
two or three reactive aromatic ring hydrogen positions with an aldehyde or 
aldehyde-liberating compound capable of undergoing phenol-aldehyde 
condensation. The most suitable phenolic resins are those which are 
insoluble in water and trichloroethylene but readily soluble in 
conventional organic solvents such as methyl ethyl ketone, acetone, 
methanol, and ethanol. Phenolic resins having a particularly desirable 
combination of properties are those which have an average molecular weight 
in the range between about 350 and 40,000 and preferably in the range 
between about 350 and 2000, and preferred phenolic resins are 
cresol-formaldehyde and phenolformaldehyde. 
Photosensitive compositions can be prepared as a solution of the 
photosensitive polymeric compound alone or mixed with film-forming 
non-photosensitive materials. The weight ratio of photosensitive polymer 
to non-light sensitive polymer can be in the range of about 1:1 to about 
99:1. As the amount of quinone diazide used in a photosensitive 
composition is increased, the described amount of non-photosensitive 
polymer decreases. 
The non-photosensitive polymers are typically addition homopolymers or 
interpolymers formed by the addition polymerization of one or more 
ethylenically unsaturated compounds, generally having a molecular weight 
in the range of 2000-50,000. They include polymers of vinyl amines, 
halides, esters, and the like, styrenes, acrylates, butadiene, 
chloroprene, etc. Other non-photosensitive polymers suitable for use in 
the present invention are film-forming condensation resins. 
It will be recognized that additional components can be included in the 
coating compositions described herein. For example, dyes and/or pigments 
can be included to obtain colored images and resins, stabilizers and 
surface active agents can be utilized to improve properties such as film 
formation, coating properties, adhesion of the coatings to the supports 
employed, mechanical strength, and chemical resistance. 
Photosensitive polymers in a liquid system can be placed onto a support or 
substrate in accordance with the usual practices such as by spraying, 
dipping or whirl-coating, and then drying the coating. If desired, a 
postbake of 10 to 30 minutes at 80.degree.-100.degree. C. is performed to 
remove residual solvent. Alternatively, they may be made into a preformed 
film of photoresist which may be laminated onto the substrate. 
Concentrations of photosensitive polymer in the coating solutions are 
dependent upon the nature of the polymer, the supports and the coating 
methods employed. Particularly useful coatings are obtained when the 
coating solutions contain from about 0.05% to about 25% by weight of 
photosensitive polymer. 
The support can also carry a filter or antihalation layer composed of a 
dyed polymer layer which absorbs the exposing radiation after it passes 
through the photosensitive layer and eliminates unwanted reflection from 
the support. A yellow dye in a polymeric binder, such as one of the 
polymers referred to above as suitable subcoatings, is an especially 
effective antihalation layer when ultraviolet radiation is employed as the 
exposing radiation. 
The optimum coating thickness of a photosensitive layer will depend upon 
such factors as the use to which the coating will be put, the particular 
photosensitive polymer employed, and the nature of other components which 
may be present in the coating. Typically, the thickness for a 
semiconductor is in the micrometer range, whereas the thickness for 
printed wire board is a half millimeter, generally 1 to 3 millimeters. 
The coating is then exposed imagewise (through a pattern) by conventional 
methods to a source of acitinic radiation which is preferably a source 
which is rich in ultraviolet light. Suitable sources include carbon arc 
lamps, mercury vapor lamps, fluorescent lamps, tungsten filament lamps, 
lasers, and the like. 
The exposed elements can then be developed by spraying, flushing, soaking, 
swabbing, or otherwise treating the photosensitive layers with sufficient 
quantities of TCP aqueous surface treating solution of an adequate TCP 
concentration at a sufficient temperature for a sufficient time to remove 
the exposed areas of the coating while leaving the unexposed areas 
unaffected. The quantities, concentrations and temperature will vary as 
discussed earlier for semiconductor applications using positive-working 
photoresists. 
The development time can vary widely depending on such factors as the 
strength of the solution, the particular photosensitive composition 
utilized, and the thickness of the photosensitive layer. The time can 
range from a few seconds to several minutes, most typically from about 30 
seconds to about 120 seconds. 
The developed image is rinsed with distilled water, dried and, optionally, 
post-baked for 15 to 30 minutes at 80.degree.-120.degree. C. 
The exposed areas of the substrate can then be modified, for example, 
etched by an appropriate etching solution. 
The unexposed areas can then be stripped by spraying, flushing, soaking, 
swabbing, or otherwise treating the photosensitive layers with sufficient 
quantities of TCP aqueous surface treating solution of an adequate TCP 
concentration at a sufficient temperature for a sufficient time to remove 
the unexposed areas of the coating while not effecting the modified 
substrate. Agitation such as by an ultrasonic bath preferably is used. The 
quantities, concentrations and temperature will vary as discussed earlier. 
The concentration of TCP in the aqueous solution used in stripping may be 
0.1 to 30 wt.%. That is, it may be the same as that used in developing if 
time of treating is longer but, generally, is at higher concentrations, 
for example, from about 1 to about 3 wt.% for semiconductors and from 1 to 
11 wt.% or higher for printed wire boards. 
The stripping time can vary widely depending on such factors as the 
concentration of TCP and other components in the solution, the particular 
photosensitive composition utilized, and the thickness of the 
photosensitive layer. The time can range from a few seconds to several 
minutes, most typically from about 30 seconds to about 120 seconds.

The invention is further illustrated, without limitation, by the following 
examples employing negative-working photoresists. 
EXAMPLES 
Example 1 is the method used to produce the tricholine phosphate (TCP) that 
was tested in the examples that are documented in Tables I through VI that 
follow. The TCP used was 27 weight percent (wt.%) TCP in water. The 
choline base, available from Syntex Agribusiness, Inc., was 45 wt.% 
choline base in methanol. 
Examples 2 to 7 were screening tests made to evaluate the effectiveness of 
adding TCP to a typical blank solution used to remove photoresists versus 
the blank solution alone and the blank solution with choline base added. 
Example 1 
Distilled water (260 ml.) and 30 grams (gm.) 85 wt. phosphoric acid (30 
gm.) were added to a 500 ml. Parr reactor in a shaker. Trimethylamine (53 
gm.) was added rapidly with the temperature rising to about 40.degree. C. 
and the pressure to about 16 psig. The pressure was then bled off and 
ethylene oxide (42 gm.) was slowly but steadily added from a cylinder. 
Pressure was periodically bled back to 0 psig. After addition of the 
ethylene oxide, the Parr reactor was shaken for an additional 20 minutes 
while cooling to complete the reaction. This procedure was repeated two 
times. Water (200 ml.) was added on one of the runs and the product from 
each of the runs was combined. The combined material was distilled in 
vacuo (distillation pot temperature was 68.degree. C.) to remove any 
excess ethylene oxide and unreacted trimethylamine. Activated carbon was 
added, mixed and filtered out removing any polymers that may have been 
formed. 
The above procedure was essentially repeated two more times and the product 
from each was combined with the above. The resulting product was analyzed 
using standard wet chemical methods for choline and phosphoric acid and 
was found to have 3.15 moles of choline per mole of phosphoric acid. The 
calculated amount of phosphoric acid to bring the ratio to 3 to 1 was 
added. The material was mixed for one and one half hours under vacuum with 
a slow nitrogen bleed and then reassayed. The ratio was found to be 3.04 
moles of choline per mole of phosphoric acid. The concentration of the 
resulting tricholine phosphate solution was 27 wt.% TCP. A sample of the 
solution was diluted to a concentration of 5.4 wt.% TCP and the pH was 
measured and found to be 11.9. 
EXAMPLES 2 TO 7 
Blank solutions A, B and C containing no TCP or choline are solutions 
typical of those used to remove dry film photoresists. Blank C, however, 
does not normally remove dry film without the addition of an alkaline 
activator and therefore was not tested alone for stripping performance. 
The dry films used in these examples are typical of those used in the 
printed wire board industry. Riston.RTM. 218 is a negative-working, 
semi-aqueous-processable, photopolymer dry film resist and 3615 is a 
negative-working, aqueous-processable, photopolymer dry film resist 
available from E. I. du Pont de Nemours and Company. Laminar.RTM. TA is a 
negative-working, aqueous-processable, photopolymer dry film resist and 
Laminar.RTM. AX is a negative-working, semi-aqueous-processable, 
photopolymer dry film resist available from Morton Thiokol, Inc. 
Since methanolic choline base is known to decompose slowly even if 
stabilized, laboratory stock choline base that had been stored for an 
extended period of time was compared to fresh methanolic choline base as 
received from the manufacturer just prior to the test in which it was 
used. 
In each example, the dry film resist for each test was applied in the same 
thickness to a printed circuit substrate and similarly exposed to actinic 
radiation. It was then immersed in a bath maintained at 125.+-.5.degree. 
F. The time at which the film first began to lift (first time listed in 
the table), the time at which it was completely removed (last time listed) 
and the size of the removed particles were determined and are recorded in 
th tables. 
The odors emanating from the baths were also observed. No objectionable 
fishy odor was generated by any bath containing the TCP, whereas such an 
odor was generated in those containing choline base. 
Example 2 
Table I compares the effectiveness of 100 milliliters (ml) of Blank A which 
consisted of 8 ml of 2-aminoethanol, 10 ml of 2-butoxyethanol and 82 ml of 
water, with Blank A modified by the addition of 1 and 2 ml of laboratory 
stock choline base in methanol (Stock Choline), by the addition of 1 and 2 
ml of contemporaneously received choline base in methanol (Fresh Choline) 
and by 1 and 2 ml of tricholine phosphate in water (TCP). Percentages in 
the table are volume/volume percentages. 
In the high amine, high glycol ether bath (Blank B), the addition of 1-2% 
(v/v) of 27 wt.% aqueous TCP was comparable to or only slightly less 
effective than with the addition of 1-2% (v/v) of 45 wt.% fresh methanolic 
choline base. While some difference in effectiveness on storage is 
apparent in the case of the methanolic choline base, TCP performance 
should not change on storage as the choline base, since the TCP is stable 
as a salt. 
TABLE I 
______________________________________ 
Tricholine Phosphate and Choline Base in High 
Amine, High Glycol Ether Solution 
Du Pont Dynachem 
Riston .RTM. 218 
Laminar .RTM. AX 
Stripping Particle Stripping 
Particle 
Solution Time (min) 
Size (in) 
Time (min) 
Size (in) 
______________________________________ 
Blank A* 3-3.25 1/8-1/4 1.25-1.5 
1/16-1/8 
Blank A + 
2.25-2.5 1/8-1/4 1.0-1.25 
1/16 
1% Stock 
Chloine 
Blank A + 
2.0-2.25 1/8-1/4 0.75-1.0 
1/16 
2% Stock 
Choline 
Blank A + 
2.0-2.25 1/8-1/4 1.0-1.25 
1/16 
1% Fresh 
Choline 
Blank A + 
1.75-2.0 1/8-1/4 0.75-1.0 
1/16 
2% Fresh 
Choline 
Blank A + 
2.25-2.5 1/8-1/4 1.0-1.5 
1/16 
1% TCP 
Blank A + 
2.25-2.5 1/8-1/4 1.0-1.25 
1/16 
2% TCP 
______________________________________ 
*Blank A: 
2-aminoethanol 8 ml 
2-butoxyethanol 10 ml 
water 82 ml 
Example 3 
Table II compares the effectiveness of 100 milliliters (ml) of Blank B 
which consisted of 4 ml of 2-aminoethanol, 2 ml of 2-butoxyethanol and 94 
ml of water, with Blank B modified by the addition of 1 and 2 ml of 
laboratory stock choline base in methanol (Stock Choline), by the addition 
of 1 and 2 ml of contemporaneously received choline base in methanol 
(Fresh Choline) and by 1 and 2 ml of tricholine phosphate in water (TCP). 
Percentages in the table are volume/volume percentages. 
In the moderate amine, low glycol ether bath (Blank B), the addition of 
1-2% (v/v) of 27 wt.% aqueous TCP was comparable to the addition of 1-2% 
(v/v) of 45 wt.% fresh methanolic choline base. The TCP modified Blank 
performed better than the blank only at 2%. 
TABLE II 
______________________________________ 
Tricholine Phosphate and Choline Base in Moderate 
Amine, Low Glycol Ether Solution 
Du Pont Dynachem 
Riston .RTM. 3615 
Laminar .RTM. TA 
Stripping Particle Stripping Particle 
Solution Time (min) 
Size (in) 
Time (min) 
Size (in) 
______________________________________ 
Blank B* 1-1.25 1/8-1/4 1.5-1.75 1/8-1/4 
Blank B + 
0.75-1.0 1/8 1.33-1.66 1/16-1/8 
1% Stock 
Choline 
Blank B + 
0.75-1.0 1/8 1.25-1.5 1/16-1/8 
2% Stock 
Choline 
Blank B + 
1.0-1.25 1/8 1.5-2.0 1/16 
1% Fresh 
Choline 
Blank B + 
0.75-1.0 1/8 1.33-1.66 1/16 
2% Fresh 
Choline 
Blank B + 
1.0-1.25 1/8 1.5-2.0 1/16-1/8 
1% TCP 
Blank B + 
0.75-1.0 1/8 1.33-1.75 1/16-1/8 
2% TCP 
______________________________________ 
*Blank B: 
2-aminoethanol 4 ml 
2-butoxyethanol 2 ml 
water 94 ml 
Example 4 
Table III compares the effectiveness of 100 milliliters (ml) of Blank C 
which consisted of 10 ml of 2-butoxyethanol and 90 ml of water, with Blank 
C modified by the addition of 1 and 2 ml of contemporaneously received 
choline base in methanol (Fresh Choline) and by 1 and 2 ml of tricholine 
phosphate in water (TCP). Percentages in the table are volume/volume 
percentages. 
In the high glycol ether bath (Blank C), the addition of 1-2% (v/v) of 27 
wt.% aqueous TCP was better in the case of Riston.RTM. 218 and comparable 
or slightly inferior in the case of Laminar to the addition of 1-2% (v/v) 
of 45 wt.% fresh methanolic choline base. 
TABLE III 
______________________________________ 
Tricholine Phosphate and Choline Base in 
High Glycol Ether Solution 
Dynachem 
Du Pont Riston .RTM. 218 
Laminar .RTM. AX 
Stripping Particle Stripping 
Particle 
Solution Time (min) 
Size (in) Time (min) 
Size (in) 
______________________________________ 
Blank C* Not Tested Not Tested 
Blank C + 
6.0-7.5 1/16 1.5-2.5 1/16 
1% Fresh 
Choline 
Blank C + 
6.0-7.5 1/16 1.5-2.5 1/16 
2% Fresh 
Choline 
Blank C + 
5.75-7.25 1/16 1.75-2.25 
1/16 
1% TCP 
Blank C + 
5.5-6.5 1/16 1.75-2.25 
1/16 
2% TCP 
______________________________________ 
*Blank C: 
2-butoxyethanol 10 ml 
water 90 ml 
Example 5-7 
Since the choline base solution contained 45 wt.% of the active ingredient 
and the TCP only contained 27 wt.% of the active ingredient, higher volume 
percentages of TCP solution were added than the normal 1-2% to each of the 
blanks. The Riston.RTM. and Laminar.RTM. resists were tested in the 
solutions. Additions of TCP were continued in each case until the 
reduction in stripping time and particle size leveled off. As can be seen 
from the following tables, TCP performance is at least comparable, if not 
better, than that of choline base on a weight-of-active-ingredient basis. 
Example 5 tests TCP in high amine, high glycol ether solution (Blank A). 
Results are shown in Table IV. 
Example 6 tests TCP in moderate amine, low glycolether solution (Blank B). 
Results are shown in Table V. 
Example 7 tests TCP in high glycol ether solution (Blank C). Results are 
shown in Table VI. 
TABLE IV 
______________________________________ 
Tricholine Phosphate in High 
Amine, High Glycol Ether Solution 
Du Pont Riston .RTM. 218 
Stripping Particle 
Solution Time (min) 
Size (in) 
______________________________________ 
Blank A* 2.25-3.0 1/8-3/8 
Blank A + 1.5-2.5 1/8-1/2 
2% TCP 
Blank A + 1.5-2.0 1/8-1/4 
4% TCP 
Blank A + 1.25-2.0 1/8-1/4 
6% TCP 
______________________________________ 
*Blank A: 
2-aminoethanol 8 ml 
2-butoxyethanol 10 ml 
water 82 ml 
TABLE V 
______________________________________ 
Tricholine Phosphate in Moderate 
Amine, Low Glycol Ether Solution 
Du Pont Dynachem 
Riston .RTM. 3615 Laminar .RTM. TA 
Stripping Particle Stripping 
Particle 
Solution 
Time (min) Size (in) 
Time (min) 
Size (in) 
______________________________________ 
Blank B* 
0.75-1.5 1/8-1/4 1.5-1.75 
1/8-1/16 
Blank B + 
0.75-1.0 1/16-1/8 0.75-1.25 
1/32-1/16 
2% TCP 
Blank B + 
0.75-1.0 1/16 0.75-1.0 
1/32 
4% TCP 
Blank B + 
0.75-1.25 1/16 0.75-1.25 
1/64-1/32 
6% TCP 
______________________________________ 
*Blank B: 
2-aminoethanol 4 ml 
2-butoxyethanol 2 ml 
water 94 ml 
TABLE VI 
__________________________________________________________________________ 
Tricholine Phosphate in 
High Glycol Ether Solution 
Du Pont Du Pont Dynachem 
Riston .RTM. 218 
Riston .RTM. 3615 
Laminar .RTM. TA 
Stripping 
Particle 
Stripping 
Particle 
Stripping 
Particle 
Solution 
Time (min) 
Size (in) 
Time (min) 
Size (in) 
Time (min) 
Size (in) 
__________________________________________________________________________ 
Blank C* 
Not Tested Not Tested 
Not Tested 
Blank C + 
4.25-5.75 
1/8-1/4 
1.0-1.25 
1/8-1/4 
1.5-1.75 
1/8-1/4 
2% TCP 
Blank C + 
3.0-4.25 
1/8 1.0-1.25 
1/8-1/4 
1.25-1.5 
1/8-1/4 
4% TCP 
Blank C + 
2.5-4.0 
1/16 1.0-1.25 
1/8-1/4 
1.0-1.25 
1/8 
6% TCP 
Blank C + 
2.5-4.5 
1/16 0.75-1.0 
1/16-1/8 
1.0-1.25 
1/8 
8% TCP 
Blank C + 
2.5-4.0 
1/32 0.75-1.25 
1/16-1/8 
1.0-1.25 
1/8 
10% TCP 
__________________________________________________________________________ 
*Blank C: 
2-butoxyethanol 10 ml 
water 90 ml