Aug. 16, 2007  US 2007/0191243 Al  4  remove the residue, however, at 180 sec. (3 min.) removal is  complete (FIG. 4d). Had values above a pH=6 have been  tested, they would have resulted in little or no change in  residue appearance for the identified exposure times.  [0034]  A characteristic beveling of the edge where the  hard mask and side wall meet is observed in the exposure  times of 180 sec. (3 min.) (FIGS.  4b, 4d  and 4/), but does not  appear as pronounced in the 45 second exposure (see FIGS.  4a,  4c, and  4e  ). Since the hard mask is composed of thermal  oxide (see FIG.  2),  it stands to reason that effects may exist  from the ionized fluorine, especially for longer periods (i.e.,  180sec.). In observing 180 sec. (3 min.) at pH 5.1 and 5.5  (FIGS.  4b  and  4d,  respectively), it is seen that a slight outline  forming at the edge indicates that there may be some  recession or attack occurring here. However, at the reduced  exposure time of 45 sec. and pH 5.1 (FIG.  4a),  the edge  appears to be very straight with little or no hard mask etch  (beveling). This beveling or edge attack requires cross› section analysis to determine the exact effects that exist.  [0035]  A closer look at the oxide mask condition upon  exposure to the invention with an approximate pH=5 at  times of 45 sec. and 180 sec. suggests that mask removal is  occurring with time. TEM analysis is used to conclude this  phenomena by cross-section sample preparation. A FEI  Strata Dual-Beam 235 FIB-SEM (focused ion beam-scan› ning electron microscope) was used to prepare TEM  samples. Samples were coated with approximately 300  A  of  chromium (Cr) in a Denton Hi-Res 100 sputter coater, then  coated with a thin layer of epoxy, and an additional 300  A  of Cr to planarize and protect the sample from ion beam  damage and provide a conductive sample surface. TEM  samples were prepared using the AutoTEM software built  into the FIB-SEM. A 1 µm  layer of platinum was deposited  over the area where the sample was made via ion-assisted  deposition using the gas injection system on the FIB-SEM as  part of the AutoTEM routine. The slices were lifted out and  placed on a conductive web and transferred to acquire TEM  images using a JEOL 2010F field emission gun operated at  an accelerating voltage 200 keV. Conventional TEM images  were recorded using a Gatan multi-scan digital camera  (Model MSC794). Results on prepared samples indicates  that a 45 second exposure still maintains a 47 nm (approxi› mately 500  A)  thickness of SiO$_{2}$ ,  whereas at a 180 second  exposure the SiO$_{2 }$ layer appears to be completely gone, as  shown by reference to FIGS.  Sa  and  Sb.  The TEM photos  shown in FIG.  Sa  are cross section analyses for patterned  wafer exposure produced according to the invention with  approximately pH=5 at times of 45 sec. and 180 sec. (3 min.)  as a determination of edge bevel (hard mask attack). The  representations of FIGS.  Sa  and  Sb  indicate that the longer  time exposure of 180 sec. (3 min.) (FIG.  Sb)  results in  thermal oxide (hard mask) removal.  [0036]  Performance of the invention has been demon› strated to be sensitive with pH and performs in the range of  5-5.5, depending upon the process time and potentially, the  tool. The post-etch residue break-up and removal may  involve particulate generation as observed in the SEM  photos in FIGS.  4a-4f  (pH=5.01, granular appearance).  These particles may have a tendency to redeposit and cause  irregularities in the device topography and directly cause  failure in its performance. Small particles attached to a  substrate surface are bound by capillary adhesion energy.  This energy can be reduced by decreasing the energy at the  solid-liquid interface ( contact angle) through surface tension  reduction.  It  is therefore important to ensure that good  wetting (i.e., low surface tension and contact angle) is  maintained throughout removal and rinsing, such that any  particle generation is easily rinsed away. FIG.  6  depicts the  change in surface tension of various surfactant additions to  the invention formulation as it is mixed (rinsed) with DI  water. Shown are surface tension changes upon mixing with  different surfactants versus reference (no surfactant). Mix› ture of a hydrocarbon and fluorocarbon exhibits synergism,  indicated by the best reduction in surface tension over the  range of complete rinsing.  [0037]  Reduction of both surface tension and contact  angle can be achieved by mixing surface active agents.  It  is  known that hydrocarbon surfactants (HC Surf) are effective  at the liquid-solid interface ( contact angle) while fluorocar› bon surfactants (FC Surf) are best used for air-liquid inter› actions (surface tension). These systems were tested neat  (reference) and in mixtures within the invention while  mixing with DI water (rinsing effect). Care was taken for  aqueous systems of high solids to prevent triggering the  phenomena of salting out. The differences between HC Surf  and FC Surf chemistries in a neat form is significant. The HC  Surf offers a moderate plunge in surface tension yet main› tains it over a wide range while the FC Surf exhibits a more  dramatic reduction but is lost with dilution. Tests were  performed by surface tension using a Fisher Scientific  Tensiometer 21 with NBS standards. The best is achieved  with mixtures of both (Surf Mix) to give good reduction over  a prolonged mixing range to near complete rinsing with DI  Water as illustrated by FIG.  6.  [0038]  The invention is desired for use in spray tooling  which are common to wafer fabrication areas. Chemistries  which are successful in such tools must exhibit low foam  character. Foaming capacity was tested on the surfactant  mixture using Draves foam-height measurement techniques.  The method involves a specific volume of analyte, normally  50 milliliters (ml), inserted into a 100 ml size graduated  cylinder with cap. The cylinder is capped and shaken for a  specific period of time, normally 15-30 sec., and immedi› ately set onto a flat surface while observing the numeric  gradations, which are superimposed onto the liquid. The  measurement of foam height over the liquid level, in units of  ml, are recorded within 5-10 sec. from shaking. The foam  height may also be measured at increments of time extend› ing from shaking, normally at 1 min. intervals. Since the  interest in this invention is the level of foam generated in a  spray tool, the foam height is measured within 5-10 sec. of  shaking. Values of foam height for a range of surfactants and  mixtures are reported in Table 1.  TABLE 1  *Note:  Solution concentrations >0.1 exhibit emulsion character.  Concentration Foam Height  Surfactant  (%w/w)  (ml)  Zonyl  fi  FSO-100  0.01-0.05  5-10  Plurofac  fi  SL-92  0.1-0.3  25-30  Pluronic  fi  17B  0.1-0.3  <2*  Zonyl  fi  FSO-100 & Pluronic  fi  17B  0.05-0.1  <5  [0039]  The data in FIG.  6  and in Table 1, it is observed that  a mixture of surfactants Zonylfi FSO-100 and Pluronicfi 