PHOTORESIST STRIPPING COMPOSITION AND METHOD

Abstract: An organic photoresist stripping composition especi­ ally for use with silicon wafers having an insulating layer and metallization on the wafers contains an organic sulfonic acid and 1,2 dihydroxybenzene. The composition also preferably includes a polar or nonpolar organic solvent. This composition will remove both positive and negative photoresist from wafers without attack on either aluminium metallization or silicon dioxide insulation layers when used to contact the photoresist on the wafers.

Description: PHOTORESIST STRIPPING COMPOSITION AND METHOD This invention relates to a novel phenol-free photoresist stripping composition and method, particularly useful in the fabrication of integrated circuits. More particularly, it relates to such a stripping composition and method which is useful for both positive and negative photoresist, and which is free of compounds that have presented safety and environmental problems in prior art photoresist stripping compositions and methods. In the manufacture of integrated circuits, various compositions have been used for stripping organic photoresist polymers from silicon dioxide and other insulator surfaces, as well as metallized silicon dioxide or other insulator surfaces. The photoresist stripper compositions currently in most general use, including 712D photoresist stripper available from EKC Technology, Inc., J-100 photoresist stripper, available from Indust-Ri-Chem, and A-20, A-30 and A-40 photoresist stripper, available from Allied Chemical Corporation, are mixtures of certain organic sulfonic acids, phenol and chlorinated hydrocarbon solvents. A further description of the Allied Chemical compositions is contained in U.S. Patent 4,165,295, which discloses the addition of fluoride ion to a stripping composition to help prevent attack on aluminium. A problem associated with the fluoride ion is that it will attack silicon dioxide. As a result of safety and environmental problems associated with chlorinated hydrocarbon solvents and phenol, it is desired to provide suitable replacements for these components of the compositions. Various photoresist stripper compositions have been offered to the semiconductor industry which do not contain phenol, but they have not proved as suitable in practice as the above compositions. Some of these substitute compositions are also acid-free, but those compositions are effective only on positive photoresist An effective replacement for the generally used above photoresist stripper compositions should meet the following criteria: The composition should be phenol and chlorinated hydrocarbon solvent-free, it should be water rinsable, non-corrosive to silicon, silicon dioxide, aluminium, aluminium silicon alloys, aluminium copper alloys, nickel chromium alloys and gold under normal operating conditions Thus, while the art of photoresist stripper compositions and methods is a well developed one, a need still remains for a suitable replacement stripper composition and method for the compositions and methods currently in general use in the semiconductor industry. We have now developed a photoresist stripping composition which is free of phenol and chlorinated hydrocarbon solvents, and compatible with the metals and insulating layers commonly employed in integrated circuits. This composition does not attack aluminium or silicon dioxide and gives stripping results at least comparable to those obtained using commercially available photoresist stripping compositions containing phenol or a chlorinated hydrocarbon solvent and is suitable for use with both positive and negative photoresists. According to the present invention there is provided a composition for the removal of an organic photoresist from a substrate, which comprises an organic sulfonic acid and 1,2 dihydroxybenzene in sufficient amounts to remove the photoresist from the substrate. The organic sulfonic acid should preferably be present in an amount of from 20 to 90 weight percent of the composition. The 1,2 dihydroxybenzene should preferably be present in an amount from 0.1 to 20 weight percent of the composition. The composition may additionally include an organic solvent, polar or non-polar, typically in an amount of from 1 to 60 weight percent of the composition. The method for stripping photoresist from a substrate of this invention comprises contacting the photoresist with the above composition at a temperature in the range of from 200 to 1500C. The composition is allowed to contact the photoresist for a period of time of from 15 seconds to two hours or more, depending on the photoresist employed and the curing conditions used with the photoresist. While we do not wish to be bound by any particular theory of operation, it is believed that the 1,2 dihydroxybenzene utilized in the composition and method of this invention acts both as a corrosion inhibitor for aluminium, iron and other metals, and as a retardant for the formation of polymeric residue deposits on the metal surfaces during high temperature processing used in stripping photoresist from integrated circuits. With the use of the 1,2 dihydroxybenzene, the composition and method of this invention need not employ phenol or a chlorinated hydrocarbon solvent. Suitable examples of organic sulfonic acids that may be used in the composition and method of this invention include aryl sulfonic acids and alkylaryl sulfonic acids, such as toluene sulfonic acid, xylene sulfonic acid and dodecylbenzene sulfonic acid. Other examples of suitable organic sulfonic acids are given in U.S. Patent 4,165,295. The preferred range for the amount of the organic sulfonic acid present in the composition is from 20 to 60 weight precent, with about 35 weight percent being especially preferred. The preferred range for the amount of 1,2 dihydroxybenzene in the composition is from 3 to 15 weight percent of the composition, with about 5 weight percent of 1,2 dihydroxybenzene being especially preferred. Suitable nonpolar, organic solvents for use in the composition and method of this invention include aromatic hydrocarbons containing from 6 to 14 carbon atoms, such as benzene; aliphatic hydrocarbons containing one to 30 carbon atoms, such as n-pentane, n-octane and dodecane; monoalkyl-substituted aromatic hydrocarbons, such as toluene, ethyl benzene, cumene, octylbenzene, decylbenzene and dodecylbenzene; dialkyl substituted hydrocarbons containing 8 to 20 carbon atoms, such as the ortho, meta and para isomers of xylene and diethylbenzene; trialkylsubstituted aromatic hydrocarbons containing 9 to 20 carbon atoms, such as the 1,2,3-; 1,2,4- and 1,3,5-isomers of trimethyl and triethylbenzene; suitable polar organic solvents include aliphatic ketons containing 3 to 10 carbon atoms, such as acetone, methylethylketone and methylisobutylketone; monoalkyl ethers of ethylene glycol containing three to 10 carbon atoms, such as ethoxyethanol and butoxyethanol; carboxylic acids containing one to four carbon atoms, such as acetic and maleic acid; formamide; N,N-dialkylalkanonylamides containing 3 to 10 carbon atoms, such as dimethylforimamide and dimethylacetamide; N-alkyl lactams containing six to 12 carbon atoms, such as N met1iy#'pyrrolidone; and cyclic aliphatic sulfones containing 4 to 6 carbon atoms, such as tetramethylenesulfone. The preferred nonpolar, organic solvents are xylene, toluene, isopropylnapthalene and decalin. The preferred polar solvents are dimethyl formamide, N-methyl pyrollidone and sulfolane. If present, the solvent desirably comprises from one to 60 weight percent of the composition. The composition of this invention is suitable for use with all of the commonly employed positive and negative photoresists used in the semiconductor industry, including Kodak 747 and 752 negative photoresist; blunt Chemical Waycoat Photoresist, both their positive HPR photoresist and their negative HNR 999 photoresist; Merck Chemical Selectilux photoresist; MacDermid negative photoresist, Shipley AZ series positive photoresist; KTI positive and negative photoresist; and Dyna-Chem Thiokol OMR and OPR photoresist. The following non-limiting Examples illustrate the invention. EXAMPLE I A composition consisting of 300 grams xylene, 150 grams of a sulfonic acid commercially available under the designation LAS 99 from Pilot Chemical, and identified as dodecylbenzene sulfonic acid, and 50 grams of 1,2 dihydroxybenzene, obtained from Crown Zellerbach Corporation, San Francisco, California, is prepared, giving a mixture of 60 weight percent of the xylene, 30 weight percent of the sulfonic acid, and 10 weight percent of the 1,2 dihydroxybenzene. The 1,2 dihydroxybenzene is dissolved in the xylene and acid mixture by heating to 700C. The resulting solution is a dark amber color with precipitation of a certain amount of crystalline material after two hours. Silicon semi conductor wagers metallized with aluminium have a test pattern formed using a commercially available novolak positive photoresist, obtained from KTI Chemical, Santa Clara, California, with exposure, development and curing in accordance with the photoresist manufacturer's instructions. The above solution is used to strip the exposed, developed and cured pattern of the photoresist on their surfaces for fifteen seconds at IOOOCI The photoresist is stripped clean, and the stripping composition is rinsable from the silicon wafters with no visual residue. The composition is then used to strip KT1 Chemical commercially available isoprene negative photoresist, exposed, developed and cured in accordance with the instructions of the manufacturer, from similar aluminium metallized silicon wafers, by immersing the wafers in the composition for fifteen seconds at 1000C. The solution strips the photoresist clean, is water rinsable on the silicon wafers, and leaves no visual residue. EXAMPLE 2 The procedure of Example 1 is repeated, except that the sulfonic acid content is increased to 35 weight percent and the 1,2,dihydroxybenzene content is decreased to 5 weight percent, by utilizing 120 g of the xylene, 7 g of the sulfonic acid and 10 g of the 1,2 dihydroxybenzene. The 1,2 dihydroxybenzene is dissolved in the xylene and sulfonic acid blend at 60 C. Novolak positive photoresist, obtained from KT1 Chemical and Shipley, is exposed, developed and cured in accordance with the instructions of its supplier in a test pattern on aluminized silicon wafers, is stripped by immersing the wafers in the above solution for one minute at 1000C. The photoresist is stripped clean, the stripper is water rinsable from the wafers and no residue is observed. This stripping composition is utilized to remove isoprene negative photoresist, obtained from KTI Chemical and Kodak, exposed, developed and cured in accordance with instructions of its supplier in patterns on aluminized silicon wafers. The wafers are immersed in the stripping composition for one minute at 1000C stripping the negative photoresist clean from the wafers. The stripping composition is water rinsable and no visible residue on the wafers is observed. EXAMPLE 3 The procedure of Example 2 is repeated, except that the composition contains 50 weight percent ethylenecarbonate and 25 weight percent dimethylformamide as the organic solvent, 20 weight percent of the sulfonic acid, and 5 weight percent of the 1,2 dihydroxybenzene. Equivalent results to those obtained in Example 2 are produced. EXAMPLE 4 A life test of the composition utilized in Example 2 is carried out by utilizing KTI Chemical isoprene negative photoresist, applied, exposed, developed and cured in accordance with the instructions of its supplier. The stripping solution is maintained at temperatures 0 between 90 and 120 C for an interim of from zero to seven and one-half hours, with immersion of the silicon wafers in the solution for times of 15, 30 and 60 seconds. Results are shown in the following table: BATH 0 TEMPERATURE, C Interval/strip Time 0 Hr. 15 sec. Resist Resist Clean 30 sec. Resist Clean Clean 60 sec. Some Resist Clean Clean 2 Mr. 15 sec. Some rinse Some rinse Clean spots spots 30 sec. Clean Clean Streak from dirt 60 sec. Clean Clean Clean 4 Hr. 15 sec. Spots Some spots Clean on edges 30 sec. Clean Residue on Clean edge 60 sec. Clean Residue on Residue on edge edge 6 Hr. 15 sec. Clean Very clean Clean 30 sec. Edge spots Edge spots Clean 60 sec. Edge spots Very clean Clean 7-1/2 Hr. 15 sec. Residues Residues Residues 30 sec. Spots on Spots on Spots on edge edge edge 60 sec. Spots on Spots on Spots on edge edge edge These results show that the resist composition is suitable for use under production conditions encountered in the manufacture of integrated circuits, with some deterioration in performance after the composition is maintained at an elevated temperature for several hours. Substitution of other solvents and organic sulfonic acids as described above in the procedure of the above Examples, gives similar advantageous results. It should now be apparent to those skilled in the art that a novel photoresist stripping composition and method capable of achieving the stated objects of this invention has been provided. At least equivalent results are obtained with the composition and method of this invention as compared with results achieved utilizing the sulfonic acid, phenol and chlorinated hydrocarbon solvent photoresist stripping composition in general use in the manufacture of integrated circuits. No attack on aluminium metallurgy or silicon dioxide insulators on silicon wafers is observed with the present invention.

Claims: CLAIMS: 1. A composition for the removal of an organic photoresist from a substrate, which comprises an organic sulfonic acid and 1,2 dihydroxybenzene in sufficient amounts to remove the photoresist from the substrate. 2. A composition as claimed in claim 1 which additionally includes therein a nonpolar, or polar organic solvent. 3. A composition as claimed in claim 2 wherein the nonpolar, organic solvent is an aromatic or alkylaromatic solvent containing from 6 to 20 carbon atoms. 4. A composition as claimed in claim 1 wherein the organic sulfonic acid is present in an amount of from 20 to 90 weight percent, the 1,2 dihydroxybenzene is present in an amount of from 0.1 to 20 weight percent and a nonpolar organic solvent is present in an amount of from 0 to 60 weight percent. 5. A composition as claimed in claim 4 comprising from 30 to 60 weight percent of the organic sulfonic acid and from 3 to 15 weight percent of the 1,2 dihydroxybenzene. 6. A composition as claimed in claim 5 comprising about 35 weight percent of the organic sulfonic acid, about 5 weight percent of the 1,2 dihydroxybenzene, and about 60 weight percent of the nonpolar organic solvent. 7. A composition as claimed in claim 6 wherein the nonpolar organic solvent is xylene. 8. A method of stripping photoresist from a substrate, which comprises contacting the photoresist with a composition as claimed in any one of the preceding claims at a temperature in the range of from 200 to 1500cm 9. A method as claimed in claim 8 wherein the substrate is a metallized inorganic substrate. 10. A method as claimed in claim 9 wherein the substrate is a silicon wafer having a silicon dioxide insulation layer metallized with aluminium.

Inventors: LEE, WAI MUN
Applicants: EKC TECHNOLOGY, INC.
Application year: 1983
Main classification: G03F7
IPC codes: C11D7, G03F7, C11D3