DE2334007A1 - DISPENSING SOLUTION AND ITS USE - Google Patents

Description

Serial No. 270125 Addendum to patent application P 2Ο49945.Ο

Many inorganic materials are currently used in the electronics and electrical industries and in the electrical industry Research, which can be collectively referred to as electrical engineering «used as support materials, insulators, conductors and semiconductors · During the installation of these materials it is often required to coat them during processing · The polymeric organic matter must then be removed · There is therefore a need for an outlet limit that will reduce the organic matter from a wide variety inorganic materials are removed in the electronic and electrical industry without attacking or destroying these inorganic materials.For example, ceramic

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materials widely used in electrical and electronic Industry as insulators »cores, circuit documents and Waffles used

Generally, these ceramics included insulating ceramics generally consisting essentially of metal oxides, complexes of metal oxides, and mixtures thereof including metal oxide and metal oxide complexes such as silicon dioxide, titanium dioxide, kaolinite, magnesium oxide, barium titanate, lead titanate zirconate, aluminum oxide, and magnetic ceramics such as metal complexes or metal oxide soft magnetic beads of the general formula MOFe ₂ 0_, in which M is a divalent metal ion, such as copper, nickel, cobalt, bison, zinc, magnesium or manganese, and hard magnetic

Ferrites such as barium ferrite (BaO.6Fe ₂ O) and magnetopium exist
bit (PbO.6Fe ₂ O "y. Known ceramic materials consist of such metal oxides and metal oxide complexes. For example, porcelain consists of sintered KaoHnite

₃ .2SiO ₂ * 2H ₂ O), and glass is made of silicon dioxide ₂ ), and a, mixture of oxides is used to make steatite (3 MgO.4SiO ₂ , H ₂ O), e ± a ceramic material with a high dielectric constant, Manufacture · Ceramic materials with particularly high dielectric constants are also produced from metal oxides or metal oxide complexes or mixtures thereof · For example, barium titanate (BaTiO, -) is used to produce a

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Ceramic material with a dielectric constant of about 2000 used · Nitrides of silicon and germanium can be used as a substrate for printed circuits and many chemically unbound conductive and semiconducting surfaces are used in electrical engineering and consist of elements such as aluminum, titanium, zirconium, chromium, molybdenum, tungsten, nickel, palladium, platinum, Copper, silver, gold, silicon, carbon, germanium, tin, lead, zinc and cadmium.

The required stripping solution must therefore be effective in terms of removal of organic coatings from this wide variety of different inorganic materials without attacking the inorganic materials

In electrical engineering, removal became more organic Layers or films of this wide variety of materials without corrosive effects, therefore, as one Considered a big problem · For example, in recent years, there is an urgent need in manufacturing emerged from semiconductors for electronic purposes · It is a common one to manufacture semiconductors Method for certain work, the desired circuit diagram on a silicon or gerraanium part or a silicon dioxide layer or some other layer on top of it in many processing stages · This Circuit diagrams are commonly used in the part or the

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Layer by selective etching using a Etching resistor etched into the desired circuit diagram · This is usually done in such a way that an the semiconductor with a polymeric photoresistor (either with positive or negative acting types, which by a stencil with visible or ultraviolet light, or Radiation from another energy source, such as electron beams, are irradiated). The rays exposed part of the photoresistive film in the case of positive resistors or the part of the photoresist andsfilmes not exposed to light in the case of negative acting resistances is dissolved and removed by a developer solvent. The remaining photoresist film is usually dried and baked, leaving behind the desired circuit diagram made of a polymeric material.

that material that resists etching, i.e. that of the

Chemicals for the desired etching or other treatment of the semiconductor surfaces that are not of the polymer resistor material are protected, is not attacked. For the etching it is necessary remove the remaining polymeric material that resisted the etching

A group of solutions suitable for removing organic polymeric scale from the above materials have now been found. The solutions are suitable for the stripping described above without attacking or destroying the numerous inorganic materials involved

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Such a self-deposition method is used in the electrical and electronic industry. The stripping solutions of the invention do not cause etching, peeling, or other visible degradation of these inorganic materials, even after five or ten coating cycles and removal of the etch-resisting material, and adversely affect them not the electrical resistance or conductivity of the materials. The solutions according to the invention comprise sulfuric acid, sufficient nitric acid (0.3 $ to 80 " HJSO") to increase the solubility of chromium trioxide (CrO ₃ ) substantially asu, 0.2, preferably 0.3 to the saturation concentration of the Solution at 30 ° C on CrO ₃ . Preferably, no more weight 5t incorporated roaming solution than 2 chromic acid solution in db Off, and the stripping is very effective, and the Korroaon to a minimum depressed when the concentration is below 0.9%. The stripping effect will

drastically reduced when the concentration of chromic acid

falls below ^ 2 ^. The sulfuric acid and nitric acid together make up at least 75% of the solution and the amount of water present can vary from about 2% to about 20%, preferably from about 2 to about 16 % . Even more effective stripping is obtained when the water concentration is less than 6 % by weight of the solution. Much larger proportions of water lead to a significantly lower stripping effect.

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The surface grazing capacity of the solutions according to the invention increases when the CrO content rises and the preferred solutions are those which contain the highest proportions of CrO which are still permissible without causing attack by the inorganic substance Solutions according to the invention, which contain less than 2 # of the CrO ", one obtains an effective stripping at room temperature (10 to kO C) of coatings which could only be stripped effectively with known stripping agents at temperatures of 90 to 100 C or above.

CrO “can be added to the systems concerned in any convenient form. A convenient form is commercially available in the crystalline state as the anhydride of chromic acid. CrO "can also conveniently be added to the systems in the form of salts. Examples are the chromate salts such as Na ₂ CrO ^ .10H ₂ O, H ₂ CrO. and (NH ^ CrO ^ as well as the dichromate salts _{, such as Na 2} Cr ₂ O _{7 .2H 2} O, KJCt and

The CrO ^ solubility peaks at equivalent sulfuric acid concentrations of about $ 85. Although the presently preferred compositions have a CrO ^ content less than the maximum solubility, the equivalent sulfuric acid concentration is preferably at least 75% or the equivalent sulfuric acid concentration or the anhydrous

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Sulfuric acid concentration, as it is called here, means

The nitric acid concentration also turned out to be critical.Insufficient nitric acid reduces the stripping efficiency, while excessive nitric acid increases corrosion beyond acceptable limits · General the nitric acid concentration should be kept below about 15% by weight in order to avoid corrosive effects Avoid, and preferably it should be kept to about $ 5 or less · Using effective streak solutions very little corrosive effect is obtained if the Nitric acid concentration is maintained below 1 #, although at least 0.3 wt .- ^ nitric acid is required are to obtain an effective off-wiping effect. It is important to keep corrosive effects to a minimum be reduced, since generally less than 25 Angstrom units the surface thickness can be removed during stripping without adverse effects to exercise the surface

The compositions according to the invention can be smaller Contain quantities of other ingredients as long as they do not interfere with the intended use «fluorine, chlorine, alkali metals or Brdalkali metals, borates, phosphates or other materials that the silicon articles or the

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Can attack silicon dioxide film »must not be present in active concentrations» Depending on the application and the specific CrO “concentration in the stripping solutions according to the invention, alkali metals or other cations, which are introduced in the form of salts, can be tolerated if they are not are in an active concentration · The concentration at which a particular cation or cations are active can easily be determined by routine experimentation · For a particular application, for reasons of economy and convenience, it may be desirable to use a sodium salt of chromic acid up to Tolerance limit to use · The remainder of CrO ", which may be required, could then be added in the form of the acid anhydride or a salt in which the cation is not objectionable, such as the ammonium salt. For some purposes it is preferred to have the solutions essentially completely free of cations such as Na ⁺ , K ⁺ and NH ^ ⁺ , in which case the CrO- is added in other than salt form. With the practically complete keeping free of cations it is intended to have only trace amounts of cation impurities which are introduced with the H-SO4 and HNO “, such as, for example, on the order of 10 ppm and less.

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The weight percent CRO_, as mentioned herein, refer to the CRO_ residue and not the connection that is the source of Ohromationen · Thus has a part dichromate ait 2 chromium atoms higher CrO "-Äquivalenz as part of a Chromatsalzes with only a chromium atom ·

In the manufacture of semiconductors from silicon dioxide-coated silicon articles, films of metallic aluminum or other metals are often combined with the silicon dioxide films under such circumstances that adhesive strips which are innocuous to aluminum or the other metal must be used. For this purpose, reference is made, for example, to the USA patent specification 3 426 kZZ · With regard to the corrosive effect on aluminum, the stripping solutions according to the invention have proven to be as good as or better than known stripping solutions used for such a purpose, if they are used at suitable stripping temperatures.

No special process is required to prepare the solutions of the present invention · Water and then sulfuric acid can be added to the nitric acid with stirring and cooling, and then the CrO- can be added with further stirring and cooling · Part of the water or all of the water can be present as part of one or both of the acids used, or a nitric acid containing more than the desired amount of wafer can be used,

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then oleum instead of part of the sulfuric acid or is used in place of all of the sulfuric acid.

The solutions can be used in the usual way to remove coatings} deposits etc. can be used object to be cleaned by immersion, with the help of a flowing stream, or be washed in the solution with stirring, or by applying a spray jet judges the subject. The solutions have the important advantage that they are not only available at normal room temperatures are effective, but that they are also effective at elevated temperatures and at such temperatures with increased cleaning speed can be used. Thus, their use at temperatures of 100 ° C or so results in extremely rapid removal from Ätzgrund, such as Xodak-Metallätzgrund, which usually referred to as "EWER" and is a product of Eastman Kodak Company is *

The following examples serve to further illustrate the invention. Example 1 explains the production of the Solutions.

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709 parts of 70.5 h of nitric acid were placed in a glass round-bottomed flask with a cooling bath, mixer, thermoset and drying tube. Then 792 parts of distilled water and 849 parts of 95.56% sulfuric acid were added successively and gradually with stirring and cooling. The temperature was kept between 20 and 30 ° C. After the addition of sulfuric acid had ended with the formation of the solvent, the temperature was lowered to 0 to 5 ° C., since at this temperature CrO, is more soluble therein. _{68.5 parts of CrO 5} (as crystals of chromic anhydride) were then added to 1,000 parts of the solvent. admitted. Parts here mean weight parts. .. .. ·

To the solutions according to the invention with regard to their use in the manufacture of semiconductors, the following

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test carried out. Silicon flakes coated with a silicon dioxide film (8,000 Angstroms thick, vapor-grown films) commercially by methods commonly used in the semiconductor industry were used as test samples. A base solution commercially available for this purpose was uniformly applied to the film using known centrifugal casting techniques. The composition used is a xylene solution of a prepolymer of the polyisoprene type and a sensitizer or developer for promoting hardening and unibodying. The composition is available from East-MKt Kodak Company under the trade designation "KMER". The prepolymer is capable of being cured by rays of light at or near the visible to oil-violet limit, ie at wavelengths of about 315 to $ 80 m * \ i and particularly near the middle of this range. It is converted into a protective coating that is insoluble in xylene. The overlying platelets were heated to a temperature of about 100 ° C. for about 30 minutes in order to evaporate the solvent away. They were then masked with an opaque stencil to cover portions of the coating and then exposed to light rays from a 600 watt We3tinghouse-Larape "Oxy Movie Flood" from a distance of about 22 cm for about 1/2 minute to cure the coating and make it insoluble close. The plaques were then dipped and washed in KMER solvent (xylene) to remove the uncured portions of the coating. The flakes were then baked at 160 ° C (or 200 ° C where indicated) for 30 minutes to further cure the polymer. Every tile

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now had a silicon dioxide film on one surface, which was partially exposed and partially protected by a hardened organic polymer.

In order to test the stiffening effects of the various stripping solutions, a plate was immersed in the stripping solution to be tested at 27 to 28 ° C, unless otherwise stated.

for

- And - the time given in the following table. The flat file was then washed by immersion in Ha33er and then placed in a stream of distilled water. The waved "platelets were examined visually and microscopically (at 20-fold" kerVerößermig) to determine the extent of removal of the polymer and the constitution of the silicon dioxide layer ". ·

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Equivalents
H ₀ SO ,,, % Tabel ENT % Solvent CrO, - Minutes for
the training
fencing (2) . 85.5 Consentration as j
5.0 j
6.35 0.5 to 1.0 At-
st> iel 94.1 H SO 38.7 13.8 3.1 1, δ- 1 73.5 81.2 40.0 3.6 0.93 1.5 to 4.0 2 (1) 73.5 57.7 40.0 15.9 0.5 1.5 to 4.0 3 79.5 44.1 40.0 15.9. 3.33 1.0+; 1.5- 4th 94.3 44.1 10.8 12.3 2.04 1.5- 5 ^: 85.5 * J7.7 1.0 5.2 6.42 1.5+; 4.0- 6 (1) 85.5 84.0 1.0 14.4 6.42 0.08 (3) 7th 85.5 84.6 1.0 14.4 0.5 1.5 to 4.0 8th 94.5 84.6 1.0 14.4 2.22 1.5+; 4.0- % 71 * 5 84.6 72.0 5.4. 2.83 1.5- IG 97.5 93.6 10.0 8.0 4.32 0.5 il 97.5 20.0 1.0 2.25 0.46 1.5- 12th 85.5. 87.75 0.5 2.5 5.61 1.5- 13th 94.5 -.ν -.-. 96.5 40.0 14.4 9.25 1.5- 14th 85.1 3.3 15th 56.7

16 79.5 71.5 10.0 18.5 1.86 4.0 to 10

(1) The coating was then baked at 200 ° C. for 30 minutes.

(2) The minus sign in this column indicates a complete removal in less than the specified time. Da3 plus sign means that in the given time everything was removed except for a trace.

(3) Test at the ordinary stripping temperature of 90 bx3 100 ° C.

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A silicon dioxide platelets, which was coated with vapor-deposited titanium was further coated with a polymeric Photowideretandsüberzug (etching base) as in Examples 1-16 · The coating was then treated with a solution of 90 <jL HgSQjL, 0, k 56 HNO ₃ and 0, 5 1 » CrO ₃ and the remainder water, all percentages being based on the weight of the total solution, stripped out · The percentage of H ₂ SOj is the equivalent weight excluding. Vasser. The total polymeric coating was in 30 "to about ° 0 sec. Then removed, the wafer was kept further for about 100 min. At 25 ⁰ C in the solution to the titanium coating with an original thickness of 183 to remove · The corrosion rate bezüglidi the The surface was determined to be less than 1.8 X.1 titanium per minute

The procedure of Example 17 was repeated except that the wafer was coated with 1000% silicon nitride. The polymeric photoresistive coating was stripped off in about 30 to 90 seconds and after the wafer was exposed to the solution for 100 minutes it was less than 250 A of the silicon nitride layer removed. The rate of corrosion of the silicon nitride surface by the stripping solution was thus determined to be less than about 2.5% per minute.

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ORIGINAL INSPECTED

A strip of tantalum was exposed to the stripping solution used in Example 18. After exposing separate samples to the solution for 90 hours at 69 ° C, 119 hours at 46 ° C, and 119 hours at 24 ° C, the rate of corrosion was calculated and found a value less than 0.02 % per minute in each case.

The procedure of Example 19 was repeated except that the stripping solution contained 1% nitric acid and the metal strip used was an aluminum strip. The rate of corrosion used to determine the strip Was exposed to the solution for 45 hours at 25 ° C calculated with less than 0.02 Å per minute.

The procedure of Example 20 was repeated except that the stripping solution was 10 wt. Chromic acid, 80 $ sulfuric acid and the remainder contained water The rate of corrosion on the aluminum after 45 hours at 25 ° C was calculated to be about 0.4 A * per minute «

Example 22

As in Example 1, a germanium flake was coated with a polymeric photoresist coating. The platelet was then exposed to a stripping solution containing 0.3

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Wt .- $ chromic acid, 0 _t 4 wt .- # HNO-, 90 # equivalent _{weighted H 2} SOl and the remainder contained water · The polymeric coating was removed from the solution after exposure to the solution for about 2 minutes · It was no corrosion of the germanium surface found after these two steps

A stripping solution containing 0.5 # CrO-, 0.6 ^ Nitric acid, 90 equivalent percent en HpSOj, and water was with all percentages based on the weight of the total solution · One drop of the solution was added to a surface is given to each of the following materials: porcelain, glass, steatite, barium titanate, barium ferrite, chromium, Molybdenum, tungsten, nickel, copper, silver, gold, silicon, tin, lead and cadmium. After the respective surface had been exposed to the drop for two minutes, none of the materials showed any corrosion, and the etching of the Surface for all of these materials was less than 25 pounds of thickness *

Copper lining s "orden with thin films of machine oil, acrylonitrile-butadiene-styrene polymer, coated styrene polymer, paraffin wax, polyurethane and polypropylene · The strips were then immersed in a Ausstreif18sung containing 0» 5% CrO ", 0.6 ή" nitric acid, 90 Equivalent percent H ^ Ok

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u contained water all films were removed after 2 minutes

Prior to the present invention, compositions "containing nitric acid, chromic acid and sulfuric acid" were described for other purposes such as cleaning chemical processing equipment, but these compositions differ fundamentally from those of the present invention in that they contain higher concentrations of nitric acid than those that are corrosive increase effects, and since they generally comprise a substantial component that increases the activity of the composition · Such compositions are described in the US Patent 2 172 I71, 2,497,905, 2 90k 4I4, 3,060,071 and 3,523,825 · the Compositions according to these patents are generally unsuitable for the purposes of the present invention because they have neither the slipping efficiency nor the low corrosivity of the present solutions. The US Patent 3,523,825

the

describes a composition which is similar to the present invention, but there is no indication that the The composition described therein could have low corrosive effects on materials used in electrical Used in industry

All quantitative proportions expressed in numbers are given in the description on a weight basis, based on the sliding solution, unless otherwise stated,

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Of course, can vorgenoanaen within the spirit modifications · examples, it is clear to those skilled in the art that various additives may be added to the stripping solutions according to the invention ₉ without the fundamental properties of the stripping solutions are changed · Examples are Verdikkungsmittelj such as colloidal silica ·

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Claims (1)

23340Q7 Claims Stripping solution comprising sulfuric acid, chromic acid, nitric acid and water, according to the patent ··. ·. ·. (Patent application P 20 k9 9 ^ 5.0), characterized in that it contains about 0.2 to 2 wt .- ^ chromic acid, about 0.3 to 15 wt .- $ nitric acid, about 2 to 20 wt .- # water and as The remainder of anhydrous sulfuric acid contains 2 «From strip solution according to claim 1, characterized in that it contains no more than 0.9% by weight of chromic acid and not contains more than about 5% by weight of nitric acid 3 · From streif18 solution according to claim 1 and 2, characterized in that it is about 0.3 to less than about 0.9 wt .- ^ Chromic acid, about 0.3 to 5 wt .- ^ nitric acid, about 2 to Contains 16% by weight of water and the remainder anhydrous sulfuric acid. k · stripping solution according to claim 1 and 2, characterized in that it comprises about 0.2 to 0.9 parts by weight of chromic acid 56, from about 0.3 to 5 wt .-% nitric acid, about 2 to 16 wt -. $> Water and the remainder contains anhydrous sulfuric acid 5 x stripping k according to claim, characterized in that it contains less than 1 wt .- ^ nitric acid and less than 6 wt · - contains £ Waeer. 309884/1133 - 21 - 6. Use of a strip solution in claims 1 to 5 for the treatment of materials used in electrical engineering with etching of their surface in a thickness of veniger 25 A for 2 minutes at room temperature 7 · Use according to claim 6 for treating ceramic Materials made from metal oxides »metal oxide complexes or Mixtures thereof 8 «Use according to claim 7 for the treatment of silicon dioxide, titanium dioxide, kaolinite, magnesium oxide, barium titanate, lead titanate zirconate, aluminum oxide, barium ferrite, magnetopium bit or soft magnetic perrites of the general formula MOFe ₂ O-, in which M is a divalent metal ion from the group consisting of copper, nickel, Cobalt, iron, zinc, magnesium or manganese means 9 · Use according to claim 6 for removing organic Deposits of silicon nitride or germanium nitride surfaces 10. Use according to claim 6 for removing organic deposits from surfaces made of elemental aluminum, Titanium, zirconium, chromium, molybdenum, tungsten, nickel, palladium, platinum, copper, silver, gold, silicon, carbon, Germanium, tin, lead, zinc or cadmium, especially from aluminum, titanium, silicon or germanium 309884/1133