Mixed aldehyde novolak resins and high contrast high thermal stability positive photoresists prepared therefrom

Abstract

Novolak resins are provided which are the condensation product of (a) a phenol, phenol derivative, or mixtures thereof, and (b) a mixture of formaldehyde or a formaldehyde precursor and an aromatic aldehyde. When the aromatic aldehyde is a monohydroxy aromatic aldehyde, the novolak resin is especially useful in positive photoresist formulations in combination with a photosensitizer such as a naphthoquinone sensitizer.

Description

חוק הפטנטים׳ תשכ״ז-1967PATENT LAW, 5727- 1967Application for PatentFor Office Use57202 / 89I (Name and address of applicant, and in case of body corporate-place of incorporationNorton Thiokoi, Inc., a Delaware Corporation, of 110 North Wacker Drive, Chicago, Illinois 60606-1560, U.S.A.Owner, by virtue ofSunlt Suresh D1x1tof an invention the title of which Is assIgrwntbytheinwntoM...............1) Richard Michael Lazarus 2) Randall William Kautz 3)(Hebrew) מרפים מסוג נובולק המבוססים על תערובת אלדתירים ופומורזיסס בעלי קונטרסט גבות ויציבות מרמים גבוהה מתוכנו ממרפים אלת.MIXED ALDEHYDE NOVOLAK RESINS AND HIGH CONTRAST HIGH THERMAL              (En°li,h>STABILITY POSITIVE PHOTORESISTS PREPARED THEREFROMhereby apply for a patent to be granted to me in respect thereof.                              0200 כזאת 3* יגתן לי עליה• בקשת חלוקה — Application of Division • בקשת פטנט מוסף - Application for Patent Addition • דרישה דין קדימה Priority Claim מבקשת פטנט from' Application No............................. מם׳ dated               מיום • לבקשה / לפסנס to Patent ZAppl. No............ מם׳ dated..........................מיום מססר / סימן Number / Mark תאריך Date מדינת האגוד Convention Country 07 / 175,473 07 / 297,828 07 / 227,404 31.3.1988 22.4.1988 2.8.1888 U.S .A. U.S.A. U.S.A. בזה / עוד יוגש OwCvv              *sFiv P.O.A : general / iJwWfwAPwflrcWtfWKjTM’IWKMwer-filed in case............................................הוגש בענין המען למסירת מסמכים כישראל as.    «. . > - ,Address for Service in Israel Cohen Zedek & Rapaport P.O. Box 33116........................................ T«T “Avfv.......................................... ............. ....... .שנת.....3... בחודש.rd..........היום of the year              of                ThisFor Office UseSignature of Applicant»ריך הפרםום:-^-ב221_1״^__«€«4 Pobhartioaזאריד מוזי™----------_ fcafeg twThis from, impressed with the Seal of the Patent Office and indicating the number and date of filing, certifies the filing of the plication the particular, of which are set our above.Delete whatever is inapplicable מחק את המיותר • .....MIXED ALDEHYDE NOVOLAK RESINS AND HIGH CONTRAST HIGH THERMALSTABILITY POSITIVE PHOTORESISTS PREPARED THEREFROMMIXED ALDEHYDE NOVOLAK RESINSAND HIGH CONTRAST HIGH THERMALSTABILITY POSITIVE PHOTORESISTS PREPARED THEREFROMABSTRACT OF THE DISCLOSURENovolak resins are provided which are the condensation product of (a) a phenol, phenol derivative, or mixtures thereof, and (b) a mixture of formaldehyde or a formaldehyde precursor and an aromatic aldehyde. When the aromatic aldehyde is a monohydroxy aromatic aldehyde, the novolak resin is especially useful in positive photoresist formulations.MIXED ALDEHYDE NOVOLAK RESINS AND HIGH CONTRAST HIGH THERMAL STABILITY POSITIVE PHOTORESISTS PREPARED THEREFROM BACKGROUND OF THE INVENTION1.   Field of the InventionThe present invention relates generally to novolak resins, and, in particular, to novolak resins which are prepared using a mixture of aldehydes.The present invention also relates generally to radiation-sensitive positive photoresist compositions and particularly to such compositions containing a novolak resin prepared from a mixture of aldehydes.2.   Description of the Prior ArtPositive photoresist formulations such as are described in, for example, U.S. Patents Nos. 3,666,473; 4,115,128; 4,173,470; 4,377,631; 4,536,465; and 4,529,682 (each of whic is hereby incorporated by reference herein), include alkali-soluble phenol-formaldehyde or cresol-formaldehyde resins together with light-sensitive materials, usually a substituted naphthoquinone diazide compound. The resins and sensitizers are dissolved in an organic solvent or mixture of solvents and are applied in a thin film or coating to a substrate suitable for the particular application desired.The novolak resin component of these photoresist formulations is soluble in alkaline aqueous solution, but th naphthoquinone sensitizer acts as a dissolution rate inhibit with respect to the resin. Upon exposure of selected areas the coated substrate to actinic radiation, however, the sensitizer undergoes a radiation-induced structural transformation which decreases its efficiency as a dissoluti rate inhibitor for the novolak and, subsequently, the expose areas of the coating are rendered more soluble than the unexposed areas. This difference in solubility rates causes the exposed areas of the photoresist coating to be dissolved when the substrate is immersed in alkaline developing solution while the unexposed areas are largely unaffected, thus producing a positive relief pattern of photoresist on the substrate.Positive photoresists, especially those used to prepare microelectronic silicon wafers and chips, are often subjected to temperatures during the manufacture of the finished article which are high enough to have a deleterious effect on the photoresist. Thus, positive photoresists having improved thermal stability have long been sought. However, it is also very important that the photoresist be capable of providing high optical resolution so that precise patterns can be applied to the substrate. While positive photoresists having high resolution and contrast characteristics, such as DYNALITH EPR-5000 resist sold by the Dynachem Division of Morton Thiokol, Inc., are known, and positive photoresists having good thermal stability, such as DYNALITH OFPR-800 resist also sold by the Dynachem Division of Morton Thiokol, Inc., are also known, the art has yet to develop a positive photoresist which combines these thermal stability and high resolution and high contrast characteristics. In fact, formulation of a positive photoresist to enhance one of these characteristics normally adversely affects the other characteristic, i.e. photoresists with good thermal stability do not provide high resolution and high contrast and vice versa.It has now been quite surprisingly found that positive photoresists having both a high degree of thermal stability and high resolution can be made when the novolak resin employed is prepared from a mixture of aldehydes comprising formaldehyde (or a formaldehyde precursor) and a monohydroxy aromatic aldehyde.SUMMARY OF THE INVENTIONIn accordance with the present invention, there is provided a new, improved class of novolak resins which are the condensation product of (a) a phenol, phenol derivative or mixture thereof, and (b) an aldehyde, wherein the improvement comprises using as the aldehyde a mixture of formaldehyde (or formaldehyde precursor) and an aromatic aldehyde.There is also provided in accordance with the present invention an improved positive photoresist comprising a novolak resin and photosensitizer wherein the improvement comprises employing as the novolak resin the condensation product of (a) a phenol, phenol derivative or mixture thereof, and (b) a mixture of aldehydes comprising formaldehyde (or a formaldehyde precursor) and a monohydroxy aromatic aldehyde.Further provided in accordance with the present invention is a positive photoresist composition comprising:A.   a novolak resin comprising the condensation product of (a) a phenol, phenol derivative or mixture thereof, and (b) a mixture of aldehydes comprising formaldehyde (or a formaldehyde precursor) and a monohydroxy aromatic aldehyde; andB.   a photosensitizer.The present invention also provides a method of forming a resist pattern on a substrate comprising:I. coating said substrate with a layer of a positive photoresist composition;II. exposing said layer patternwise to actinic radiation; andIII. removing the exposed portion of said layer with an aqueous alkaline developer for the exposed resist composition to uncover the areas of the substrate beneath the exposed portions;said positive photoresist comprising, prior to exposure:A. a novolak resin comprising the condensation product of (a) a phenol, phenol derivative or mixture thereof, and (b) a mixture of aldehydes comprising formaldehyde (or a formaldehyde precursor) and a monohydroxy aromatic aldehyde; andB. a photosensitizer.In accordance with the present invention, there is also provided a substrate coated with a thermally stable and highly resolved, exposed resist pattern, said resist pattern being formed from a positive photoresist composition which, prior to exposure to actinic radiation, comprises:A.   a novolak resin comprising the condensation product of (a) a phenol, phenol derivative or mixture thereof, and (b) a mixture of aldehyde comprising formaldehyde (or a formaldehyde precursor) and a monohydroxy aromatic aldehyde; andB.   a photosensitizer.DETAILED DESCRIPTION OF PREFERRED EMBODIMENTSThe novolak resins of the present invention are prepared from (1) phenol or a phenol derivative, and (2) a mixture of aldehydes which contains formaldehyde (or a formaldehyde precursor) and an aromatic aldehyde. The .phenol and phenol derivatives useful in preparing these novolak resins include, but are not limited to, phenol, m-cresol, p-cresol, o-cresol, and mixtures thereof. Other examples of phenol derivatives may be found in H. Hiraoka, "Functionally Substituted Novolak Resins: Lithographic Applications, Radiation Chemistry, and Photooxidation", Materials For Microlithography, ACS Symposium Series No. 266 (1984) which is hereby incorporated by reference herein. They may also contain other substituents on the aromatic ring including, for example, alkyl or halogen moieties.The mixed aldehydes useful in preparing the novolak resins of the present invention contain formaldehyde or a formaldehyde precursor. As used herein, "formaldehyde precursor" refers to compounds, such as 1,3,5-S-trioxane and paraformaldehyde which, under the reaction conditions employed to prepare the novolak resin will produce formaldehyde. As used herein, the term "formaldehyde" is understood to include both formaldehyde per se and formaldehyde precursors. The second component of the aldehyde mixture is any aromatic aldehyde which will form a novolak resin with phenol or a phenol derivative. In general, however, these aromatic aldehydes include, but are not limited to, compounds having the general formula:CHOwhere R is halogen (e.g. chlorine), alkyl (e.g. C^-C^ alkyl). Examples of preferred aromatic aldehydes include benzaldehyde, 2-chlorobenzaldehyde, and monohydroxy aromatic aldehydes such as 2-hydroxybenzaldehyde, 3-hydroxybenzaldehyde, and 4-hydroxybenzaldehyde. Mixtures of aromatic aldehydes may also be used. The monohydroxybenzaldehydes are particularly preferred since they produce novolak resin which may be used to make high resolution, high thermal stability positive photoresists .The relative amounts of the phenol or phenol derivative and mixed aldehydes used to prepare to novolak resins of the present invention may vary considerably. In general, these relative amounts are chosen to produce novolak resins having high melting points (Tg), high degree of substitution at the bridging carbons and relatively low molecular weights (compared to novolak resins prepared from formaldehyde only). Typically, the following amounts of reactants are employed to produce the novolak resins of this invention.Moles total aldehyde Moles total phenol or phenol derivativex 100 = about 60% to about 95%Moles aromatic aldehyde Moles total aldehydex 100 = about 15% to about 95%In a preferred embodiment, the phenol component is a mixture of phenol derivatives; namely, a mixture of m-cresol and p-cresol. When such a mixture is employed, it typically contains the following relative amounts of m- and p-cresol;Moles m-cresol Moles total cresolx 100 = about 30% to about 75%Given the above reactants and their relative amounts, one of ordinary skill in the art would be capable of preparing the novolak resins of the present invention without undue experimentation. Basically, all of the ingredients are placed in a suitable reaction vessel and a nonreactive solvent addecf. An acid catalyst, such as p-toluenesulfonic acid, is added in a mole ratio of moles catalyst / moles total cresol of about 0.01 to about 0.04. The reaction mixture is then raised to reflux temperature and reflux maintained until no more by-product water is produced, indicating that the reaction is complete.The novolak resins of the present invention are especially useful in positive photoresist formulations. These formulations typically contain a novolak resin, a sensitizer (or "photoactive component"), solvent and various additives such as colorants, striation aids, and the like. In commercial positive photoresists, the novolak resin is most commonly a cresol-formaldehyde novolak and the photoactive component is a diazo quinone compound. Examples of diazo quinone compounds include 2,3,4-trihydroxybenzophenone-l, 2-napthoquinonediazide-5-sulfonic acid mono-, di-, andIt is not uncommon for commercially available cresols to contain minor amounts of o-cresol. Therefore, "Moles total cresol" refers to moles of m-, p-, and o-cresol (if any) and not just m- and p-cresol. It is preferred, however, that the o-cresol content be less than about 1% of the total cresol. triesters and 2,3,4-trihydroxybenzophenone-1,2-naphthoquinone -2-diazo-4-sulfonic acid mono-, di-, and triesters. Examples of these and other diazo sensitizers may be found in U.S. Patent No. 4,499,171 issued February 12, 1985 to Hosaka et al., which is hereby incorporated by reference herein. Examples of solvents include, but are not limited to, propylene glycol monomethyl ether acetate (PMA), ethyl cellosolve acetate, ethyl 3-ethoxy propionate, diglyme, butyrolactone, xylene, and butyl acetate.The critical components of the positive resist formulation, namely, the novolak resin of the present invention and the photoactive component, can be employed over a wide range of relative amounts. In general, it is necessary only that sufficient photoactive component be employed to produce a resist which is photoimagable and that the amount of novolak resin be bindingly effective. In terms of relative amounts, the positive photoresists of this invention may contain from about 2 parts by weight (pbw) novolak resin per pbw photoactive component to about 6 pbw novolak resin per pbw photoactive component. Preferably, a ratio of about 4 pbw novolak resin per pbw photoactive component is employed.The amount of solvent in the resist may likewise vary considerably. Generally, all that is required is that sufficient solvent be employed to produce a desired coating thickness under the given coating conditions, e.g. spin speed and pre-bake temperature. Typically, however, enough solvent is added to the positive photoresist formulation to produce a photoresist having about 25-30% solids.The positive resists of this invention may also contain various additives such as colorants, striation aids, and the like. Also, the novolak resin component of the resist may be comprised entirely of the novolak resins of the present invention, or may contain up to about 35 weight percent (based on the total weight of the resin component of the resist) of a conventional novolak resin, such as a cresol / formaldehyde novolak resin prepared using a mixture of 65-70% m-cresol and 30-35% p-cresol.Positive resists formulated with the novolak resins of the present invention which are prepared from the preferred monohydroxybenzaldehydes have relatively high thermal stability. For example, resists which employ the formaldehyde / monohydroxybenzaldehyde mixture are stable for at least about 30 minutes in a conventional oven at temperatures of about 200-220°C whereas the aforementioned DYNALITH(S) EPR-5000 resist is stable only to about 140°C and DYNALITHOFPR-800 resist is stable only to about 180°C when baked for about 30 minutes in a conventional oven.The following examples illustrate the present invention:EXAMPLE 1This example illustrates a typical procedure for making the novolak resins of the present invention.The following reagents were used in the amounts indicated:REAGENT AMOUNT m-cresol 125.9 g p-cresol 103.0 g o-hydroxybenzaldehyde (98%) 123.6 g trioxane 30.1 g Isopropyl acetate 313.5 g p-toluenesulfonic acid ‘H20 catalyst 4.0 g All of the ingredients, except the catalyst, were combined in a suitable reaction vessel. The catalyst was then added and the resulting reaction mixture was heated at reflux temperature. Reflux was continued until no more by-product water was produced, which indicated completion of the reaction. The resulting novolak resin was then recovered.EXAMPLES 2-30Novolak resins in accordance with this invention were prepared in a manner similar to that of Example 1 using the reagents indicated in Table I below.No. Cresol A Cresol B Aid. 1 Ald.t2 Cat. 1Rc 2Rf 3Ra 4Rh 5Rw °C_______Hr.m-cresol p-cresol Formaid 4HB° pTSA 0.349 0.645 0.188 0.025 1.55 95-120 27 m-cresol p-cresol Formaid 4HB pTSA 0.350 0.640 0.500 0.025 0.95 95-120 24 m-cresol p-cresol Formaid 4HB pTSA 0.350 0.700 0.500 0.040 1.04 95-120 15 m-cresol p-cresol Formaid 4HB pTSA 0.450 0.700 0.500 0.040 1.04 95-120 16 m-cresol p-cresol Formaid 4HB pTSA 0.450 0.760 0.500 0.040 1.04 95-120 16 m-cresol p-cresol Formaid 4HB pTSA 0.550 0.700 .0.490 0.040 1.04 95-120 16 m-cresol p-cresol Formaid 4HB pTSA 0.550 0.760 0.486 0.040 1.13 95-120 15 m-cresol p-cresol Formaid 4HB pTSA 0.550 0.810 0.500 0.040 1.20 95-120 15 m-cresol p-cresol Formaid 4HB pTSA 0.647 0.705 0.497 0.032 1.04 95-120 16 m-cresol p-cresol Formaid 4HB pTSA 0.650 0.760 0.500 0.040 1.13 95-120 15 m-cresol p-cresol Formaid 2HB8 pTSA 0.350 0.666 0.508 0.025 0.960 95-120 17 Rc            = moles m-cresol / total moles cresolRf            = total moles aldehyde / total moles cresol3Ra            = moles Aldehyde 2 / total moles aldehydeZ,Rh            =  moles catalyst / total moles cresol^Rw            =  moles water / total moles cresol84HB           =  4-hydroxybenzaldehyde2pTSA          =  p-toluenesulfonic acidg2HB           = 2-hydroxybenzaldehydeBenz          = benzaldehydeCresol A Cresol B Aid. 1 Aid. t2 Cat. 1Rc zRf Ra ^Rh Rw °C Hr. m-cresol p-cresol Formaid 2HB pTSA 0.350 0.747 0.500 0.040 1.180 95-120 15 m-cresol p-cresol Formaid 2HB pTSA 0.449 0.698 0.500 0.040 1.040 95-120 16 m-cresol p-cresol Formaid 2HB pTSA 0.450 0.764 0.500 0.040 1.130 95-120 14 m-cresol p-cresol Formaid 2HB pTSA 0.550 0.708 0.549 0.040 1.040 95-120 15 m-cresol p-cresol Formaid 2HB pTSA 0.550 0.767 0.491 0.040 1.130 95-120 15 m-cresol p-cresol 9 Triox 2HB pTSA 0.550 0.756 0.503 0.020 0.248 85-95 15 m-cresol p-cresol Triox 2HB pTSA 0.550 0.784 0.498 0.015 0.020 110-115 11 m-cresol p-cresol Triox 2HB pTSA 0.550 0.788 0.502 0.020 0.264 100-105 10 0.812 0.502 20 28 m-cresol p-cresol Triox 2HB pTSA 0.550 0.856 0.502 0.010 0.533 100-105 28 m-cresol p-cresol Triox 2HB pTSA 0.550 0.950 0.500 0.010 0.535 100-105 24 ¼0           = moles m-cresol / total moles cresolRf            = total moles aldehyde / total moles cresolRa            = moles aldehyde 2 / total moles aldehydeRh            = moles catalyst / total moles cresolRw 64HB 7pTSA 82HB 9 Benz = moles water / total moles cresol = 4-hydroxybenzaldehyde = p-toluenesulfonic acid = 2-hydroxybenzaldehyde = benzaldehyde No.Cresol A Cresol B Aid. 1 Aid.. 2 Cat. 1Rc 2Rf 3Ra 4Rh 5Rw °C Hr. m-cresol p-cresol Triox 2HB pTSA 0.551 0.379 1.000 0.010 0.010 110-135 10 0.766 0.506 20 m-cresol p-cresol Triox 2HB pTSA 0.550 0.427 1.000 0.010 0.535 100-105 14 0.854 0.502 28 m-cresol p-cresol Triox 2HB pTSA 0.547 0.423 1.000 0.010 0.010 100-135 11 0.846 0.499 22 m-cresol p-cresol Triox 2HB pTSA 0.548 0.944 0.495 0.010 0.010 115-120 18 m-cresol p-cresol Triox 2HB pTSA 0.550 0.900 0.250 0.010 0.010 115-120 19 m-cresol p-cresol Triox 2HB pTSA 0.550 0.900 0.500 0.010 0.010 115-120 19 m-cresol p-cresol Triox 2HB pTSA 0.550 0.900 0.750 0.010 0.010 --- 19 m-cresol p-cresol Formaid 9 Benz pTSA 0.55   0.9    0.75 0.01 0.01 -- 1Rc = moles m-cresol / total moles cresol 2Rf = total moles aldehyde / total moles cresol 3Ra = moles aldehyde 2 / total moles aldehyde 4Rh = moles catalyst / total moles cresol 5Rw = moles water / total moles cresol 64HB = 4-hydroxybenzaldehyde 7pTSA = p-toluenesulfonic acid 82HB = 2-hydroxybenzaldehyde 9 Benz = benzaldehyde COMPARATIVE EXAMPLES A - JFor comparative purposes, novolak resins prepared from a single aldehyde were made using a procedure similar to that of Example 1 and the reagents shown in Table A.ICresol A Cresol B Aid. 1 Aid. 2 Cat. Rc Rf Ra Rh Rw °C Hr. m-cresol p-cresol - Benzald pTSA 0.354 0.631 1.000 0.036 0.04 100-120 4 m-cresol p-cresol ־ 2ClBenzalda pTSA 0.354 0.640 1.000 0.039 0.04 95-110 4 m-cresol p-cresol ־ 4HB pTSA 0.354 0.640 1.000 0.040 0.04 100-130 4 m-cresol p-cresol - 4HB pTSA 0.354 0.640 1.000 0.040 0.04 100-130 4 m-cresol p-cresol ־ 4HB pTSA 0.350 0.810 1.000 0.039 0.04 100-105 2 m-cresol p-cresol - 4HB pTSA 0.749 0.637 1.000 0.039 0.04 95-105 13 m-cresol p-cresol ־ 4HB pTSA 0.750 0.805 1.000 0.039 0.04 100-105 2 m-cresol p-cresol - 2HB pTSA 0.354 0.639 1.000 0.040 0.04 100-120 7 m-cresol p-cresol - 2HB pTSA 0.350 0.750 1.000 0.040 0.04 100-105 8 m-cresol p-cresol - Piperonal pTSA 0.350 0.375 1.000 0.040 0.04 100-120 16 a2ClBenzald = 2-chlorobenzaldehydeEXAMPLES 31 -  54 ANDCOMPARATIVE EXAMPLES K - TThe novolak resins prepared in the foregoing examples were used to formulate positive photoresists. The photoresist 5 was prepared by simply blending the ingredients shown in Table II below in the amounts indicated.No. Novolak 1 from Ex. No. / Amnt. Novolak 2^ / Amnt. Amnt. PACc Amnt. PMA Other 1 2 / 13.89 7.48 5.33 73.00 0.28 2 3 / 13.89 7.48 5.33 73.00 0.28 3 4 / 14.05 7.55 5.39 72.72 0.28 4 5 / 14.05 7.57 5.40 72.69 0.28 5 7 / 14.09 7.58 5.41 72.62 0.28 6 8 / 13.89 7.48 5.33 73.00 0.28 7 9 / 14.02 7.55 5.39 72.72 0.28 10 / 14.05 7.55 5.39 72.72 0.28 11 / 14.05 7.55 5.39 72.72 0.28 12 / 14.04 7.55 5.39 72.72 0.28 1 13 / 14.04 7.55 5.39 72.72 0.28 14 / 13.89 ' 7.48 5.34 72.99 0.28 15 / 13.89 7.48 5.34 73.00 0.27 16 / 13.48 7.19 6.17 72.87 0.27 17 / 16.80 8.96 7.69 66.26 0.29 22 / 11.92 6.35 5.45 76.65 0.26 23 / 14.04 7.54 5.39 72.74 0.28 All amounts are weight percent based on total weight.Novolak 2 is a low molecular weight cresol / formaldehyde novolak. PAC = photoactive component.No. Novolak 1 from Ex. No . / Amnt. Novolak 2 / Amnt. Amnt. PACc Amnt. PMA Other 8 24 / 12.48 6.66 5.71 74.88 0.26 9 25 / 14.04 7.54 5.39 72.73 0.28 0 26 / 14.04 7.54 5.39 72.73 0.28 1 27 / 14.04 7.55 5.39 72.75 0.28 2 28 / 14.04 7.55 5.39 72.74 0.28 3 29 / 14.04 7.55 5.39 72.75 0.28 4 30 / 21.69 11.67 8.33 57.6 0.74 A / 14.00 7.53 5.38 72.83 0.28 B / 13.87 7.47 5.34 73.04 0.28 C / 13.87 7.47 5.33 73.05 0.28 D / 13.87 7.47 5.33 73.03 0.28 E / 14.01 7.54 5.39 72.78 0.28 F / 13.87 7.47 5.34 73.04 0.28 G / 14.01 7.54 5.39 72.77 0.28 H / 13.99 7.54 5.39 72.80 0.28 1 / 14.03 7.56 5.39 72.73 0.28 J / 14.03 7.56 5.39 72.73 0.28 The following examples illustrate the performance of the positive photoresist formulations of Examples 31-54 and Comparative Examples K-T.EXAMPLES 55 - 78 AND COMPARATIVE EXAMPLES U ־ DPEach, in turn, of the resist compositions of Examples 31-54 and Comparative Examples K-T was spin coated on a track coater manufactured by Silicon Valley Group, California, onto thermally-grown silicon / silicon dioxide coated wafers of 4 inch diameter and 5000 Angstrom oxide thickness. A uniform coating of 1.0 pm of resist film was obtained at a spinning velocity of 3,500 revolutions per minute. The coated wafers were then soft baked either in an air circulating oven at 120°C for 30 minutes or on a track with hot plate at 110°C for 60 seconds. The resist film thickness was then measured with a Nanospec AFT thickness measuring tool.The coated wafers were exposed with an Ultratech ultrastep 1000 (1:1) projection stepper fitted with a lens of N.A. 0.325 to provide ultraviolet exposure radiation in the range of 390 nm-450 nm. A Micromask mask with line and space widths of varying sizes, including some as small as 0.75 pm; was used to provide a selective exposure pattern. Exposure times were varied in order to determine the photospeed of the resist, i.e., the minimum amount of exposure energy (intensity x time) in millijoules / cm which will solubilize the exposed areas of the resist so that the resist in the exposed areas will be completely removed / cleared during development.The exposed resist coated wafers produced as described above were placed in Teflon wafer boats and either immersed in a one-galIon Teflon container containing DYNALITH NMD-3 developer, which is an aqueous alkaline solution stabilized at about 19°C± 1°C, or processed on track developing equipment manufactured by Silicon Valley Group, California. The wafers were allowed to remain immersed in the developer solution for 60 seconds. Upon removal from the developer, the wafers were rinsed in deionized water and dried by a burst of nitrogen gas or by placing them in a spin dryer. Following development, the wafers were examined with an optical microscope at a "1000X” magnification.Post-baking of the developed wafers was done in an air circulating oven at about 150°C, 280°C, or 200°C for 30 minutes to increase the adhesion and chemical resistance of the undissolved portions of the coatings. Post-bake flow of the images were examined by an optical microscope at "1000X" magnification.The results of these performance tests are shown in Table III below:No. Resist from Photospeed Developer Dev. Time %FL^ Residue6 Bridges^ Side Wall^ Ek. No.mJ / cm( Seconds )31 >100 0.1N DE-3h 60 0.47 0 2.00 *1 ontrol*) (85) (0.2N DE-3) (240) (0.34) (0) (1.50) - 32 75 0.1N DE-3 60 1.28 0 0.75 0 Control) (85) (0.2N DE-3) (240) (0.34) (0) (1.50) - 33 56 9.2N DE-3 60 0.00 0 0.75 - ontrol) (68) (0.2N DE-3) (240) (0) (0) (1.25) - 34 80 0.1N DE-3 60 - 0 1.00 0 30 0.2N DE-3 30 18.04 0 1.00 - Control) (65) (0.3N DE-3) (60) (0.48) (0) (1-50) - 35 105 0.2N DE-3 30 1.07 0 0.75 1־ ontrol) (65) (0.3N DE-3) (60) (0.48) (0) (1.50) ־ 36 95 0.1N DE-3 60 1.67 0 0.75 *1 ontrol) (85) (0.2N DE-3) (240) (0.34) (0) (1-50) - d ef gh%FL = percent film loss in unexposed areasResidue is measured on a 0-10 scale, 0 being no residue; 10 being full coverage of 1 micron lines and spacesBridges = largest geometry bridged (microns)Side wall parameter qualifies as more (+1), same as (0), orless (-1) vertical compared to the controlDE-3 = DYNALITH developer sold by the Dynachem Division of Morton Thiokol, Inc.                          _All control tests were performed with DYNALITH EPR-5000 positive photoresist sold by the Dynachem Division of Morton Thiokol, Inc.E No. Resist from Photospeed Developer Dev. Time %FL Residue Bridges Side Wall _____________Ex. No._______mJ / cm____________ (Seconds)       ________________________________37 ontrol) 70 (80) 0.1N DE-3 (0.2N DE-3) 60 (240) 3.34 (0) 0 (0) 0.75 (1.50) 38 45 0.2N DE-3 60 4.33 0 0.75 ontrol) (68) (0.2N DE-3) (240) (0) (0) (1.25) 39 30 0.1N DE-3 60 18.01 0 0.75 ontrol) (80) (0.2N DE-3) (240) (0) (0) (1.50) 40 40 0.2N DE-3 30 3.81 0 1.00 ontrol) (155) (0.2N DE-3) (60) (0) (0) (1.5) 41 70 (0.2N DE-3) 30 2.6 0 0.80 Control) (65) (0.3N DE-3) (60) (0.48) (0) (1.5) 42 38 0.2N DE-3 30 9.72 0 1.00 ontrol) (139) (0.2N DE-3) (30) (0) (0) (1.5) 43 38 0.2N DE-3 30 5.81 0 1.00 ontrol) (139) (0.2N DE-3) (30) (0) (0) (1.5) 44 55 0.2N DE-3 30 4.65 0 0.80 ontrol) (155) (0.2N DE-3) (60) (0) (0) (1.5) 45 60 0.2N DE-3 30 3.84 0 0.80 ontrol) (155) (0.2N DE-3) (60) (0) (0) (1.5) 46 35 0.2N DE-3 30 5.80 0 1.00 -1 ontrol) (145) (0.2N DE-3) (60) (0.21) (0) (1.5) (0) No. Resist Ex. from No. Photospjed mJ / cmz Developer Ul 47 >300 0.2N DE-3 ntrol) (155) (0.2N DE-3) 48 45 0.2N DE-3 ontrol) (145) (0.2N DE-3) 49 >270 0.2N DE-3 Control) (155) (0.2N DE-3) 50 185 0.2N DE-3 Control (155) (0.2N DE-3) 51 245 0.2N DE-3 52 165 0.2N DE-3 53 70 0.2N DE-3 Control) (155) (0.2N DE-3) 54 300 1.0N DE-3 trol) (125) (0.2N DE-3) K >600 2.70 NMD3J L >600 2.70 NMD3 J 2.70 NMD3 = 2.70^ tetramethylammonium hydroxide in waterDev. Time (Seconds ) %FL Residue Bridges Side Wall 60 1.00 10 unmeas. (60) (0) (0) (1.5) ־ 30 0 0 1.00 -1 (60) (0.21) (0) (1.5) (0) 60 1.50 10 unmeas. - (60) (0) (0) (1.5) - 60 0 0 >0.8 0 (60) (0) (0) (1.5) (0) 60 0.35 0 1.00 60 0.52 0 0.80 60 0.23 0 <0.80 (60) (0.07) (0) (1.50) 60 2.13 1.0 2.0 (60) (0) (0) (1.5) 480 0.00 - - 480 0.00 - - No. Resist from Ex. No. Photospjed mJ 1 cm I Developer Dev. Time ( Seconds ) %FL Residue Bridges Side Wall M 100 0.62 TMAHk 180 4.78 *1 110 Dev. A 30 2.01 9 0.75 + 1 40 0.2N DE-3 60 11.12 8 0.75 - N 100 0.62TMAH 180 6.66 10 0.75 + 1 110 Dev. A 30 4.01 9 0.75 +1 40 0.2N DE-3 60 10.68 8 0.75 0 Control) (55) (2.40 TMAH) (180) (1.00) (0) (1.50) - Control) (85) (0.2N DE-3) (240) (0.60) (0) (1.50) 0 40 0.1N DE-3 60 14.54 5 1.75 ontrol) (107) (0.2N DE-3) (120) (0) (0) (1.50) P 75 0.6N DE-3 60 3.54 0 0.75 -1 ntrol) (>110) (0.6N DE-3) (60) (0) (0) (1.25) AA       Q 73 0. IN DE-3 60 10.29 3 0.75 ontrol (107) (0.2N DE-3) (120) (0) (0) (1.50) R 50 0.2N DE-3 60 10.49 0 0.75 ontrol) (107) (0.2N DE-3) (120) (0) (0) (1.25) S 78 0.2N DE-3 60 1.17 0 0.75 trol) (68) (0.2N DE-3) (240) (0) (0) (1.25) DD       T 50 0.2N DE-3 60 6.35 0 1.00 Co trol) (69) (0.2N DE-3) (240) - (0) (1.50) Jr0.62 ן TMAH = 0.62% tetramethylammonium hydroxide in water Dev. A = High contrast developer

Claims

WE CLAIM:

1. In a novolak resin which is the condensation product of (a) a phenol, phenol derivative, or mixtures thereof, and (b) an aldehyde, the improvement comprising using as the aldehyde a mixture of formaldehyde or formaldehyde precursor and an aromatic aldehyde.

2. The novolak resin of Claim 1 wherein the phenol component is a mixture of m- and p-cresol.

3. The novolak resin of Claim 1aldehyde components are present in the moles total aldehyde moles total phenol or phenol derivativemoles aromatic aldehyde moles total aldehyde.

4. The novolak resin p-cresol are present in the moles m-cresol moles total cresol.wherein the phenol and following amounts:x 100 = about 60% to about 95¾.x 100 = about 15% to about 95%of Claim 2 wherein the m- and following amounts:x 100 = about 30% to about 75%5. In a positive photoresist comprising a novolak resin and photosensitizer the improvement comprising employing as the novolak resin the condensation product of (a) a phenol, phenol derivative, or mixture thereof, and (b) a mixture of aldehydes comprising formaldehyde or a formaldehyde precursor and a monohydroxy aromatic aldehyde.

6. The positive photoresist of Claim 5 wherein the phenol component of the novolak resin is a mixture of m- andp-cresol.

7. The positive photoresist of Claim 5 wherein the aldehyde component of the novolak resin is a mixture of formaldehyde and a monohydroxy aromatic aldehyde selected from2-hydroxybenzaldehyde, 3-hydroxybenzaldehyde, and 4-hydroxybenzaldehyde.8.pheno1 and present in molesThe positive photoresist of aldehyde components of the 1 the following amounts: total aldehydeClaim 5 novolakwherein the resin aremoles total phenol or phenol derivativex 100about60% to about 95%moles monohydroxy aromatic aldehyde moles total aldehyde.x 100about15% to about 95%9. The positive photoresist ofClaim6 wherein the m-and p-cresol are present in the following amounts:moles m-cresolmoles total cresol.x 100 = about 30% to about 75%10.  A positive photoresist composition comprising:A.   a novolak resin comprising the condensation product of (a) a phenol, phenol derivative, or mixture thereof, and (b) a mixture of aldehydes comprising formaldehyde or formaldehyde precursor and a monohydroxy aromatic aldehyde; andB.   a photosensitizer.

11. The positive photoresist of Claim 10 wherein the phenol component of the novolak resin is a mixture of m- and p-cresol.

12. The positive photoresist of Claim 10 wherein the aldehyde component of the novolak resin is a mixture of formaldehyde and monohydroxy aromatic aldehyde selected from 2־hydroxybenzaldehyde, 3-hydroxybenzaldehyde, and 4-hydroxybenzaldehyde.

13. The positive photoresist of phenol and aldehyde components of the present in the following amounts: moles total aldehyde moles total phenol or phenol derivativeClaim 10 wherein the novolak resin arex 100about60% to about 95%moles monohydroxy aromatic aldehyde moles total aldehyde.x 100about15% to about 95%14. The positive photoresist ofClaim11 wherein the m-and p-cresol are present in the following amounts:moles m-cresol moles total cresol.x 100 = about30% to about 75%15.  The positive photoresist of Claim 10 wherein the photosensitizer is a naphthoquinone diazide sensitizer.

16. The positive photoresist of Claim 15 wherein the naphthoquinone diazide sensitizer is selected from the group consisting of esters of 1,2-naphthoquinone-2-diazo-4-sulfonic acid and esters of 1,2-naphthoquinone-2-diazo-5-sulfonic acid17.  The positive photoresist of Claim 16 wherein the naphthoquinone diazide sensitizer is selected from the group consisting of2.3.4- trihydroxybenzophenone-1,2-naphthoquinone-2-diazo-4-sulfonic acid monoester; 2,3,4-trihydroxybenzophenone-1,2-naphthoqui1^>ne-2-diazo-4-sulfonic acid diester;2.3.4- trihyroxybenzophenone-1,2-naphthoquinone-2-diazo-4-sulfonic acid triester and mixtures thereof.

18. The positive photoresist of Claim 16 wherein the naphthoquinone diazide sensitizer is selected from the group consisting of2.3.4- trihydroxybenzophenone-1,2-naphthoquinone-2-diazo-5-sulfonic acid monoester; 2,3,4-trihydroxybenzophenone-1,2-naphthoquinone-2-diazo-5-sulfonic acid diester; 2,3,4-trihydroxybenzophenone-1,2-naphthoquinone-2-diazo-5- sulfonic acid triester and mixtures thereof.

19. A method of forming a resist pattern on a substrate comprising:I. coating said substrate with a layer of a positive photoresist composition;II. exposing said layer patternwise to actinic radiation; andIII. removing the exposed portion of said layer with an aqueous alkaline developer for the exposed resist composition to uncover the areas of the substrate beneath the exposed portions; said positive photoresist comprising, prior to exposure:A.   a novolak resin comprising the condensation product of (a) a phenol, phenol derivative, or mixture thereof, and (b) a mixture of aldehydes comprising formaldehyde or a formaldehyde precursor and a monohydroxy aromatic aldehyde; andB.   a photosensitizer.

20. The method of Claim 19 wherein the phenol component of the novolak resin is a mixture of m- and p-cresol.

21. The method of Claim 19 wherein the aldehyde component of the novolak resin is a mixture of formaldehyde and a monohydroxy aromatic aldehyde selected from2-hydroxybenzaldehyde, 3-hydroxybenzaldehyde, and 4-hydroxybenzaldehyde.

22. The method of Claim 19 wherein the phenol and aldehyde components of the novolak resin are present in the following amounts:moles total aldehyde moles total phenol or phenol derivativex 100 = about 60% to about 95%moles monohydroxy aromatic aldehydemoles total aldehyde.x 100 = about 15% to about 95%23. The method of Claim 20 wherein the m- and p-cresolare present in the following amounts:moles m-cresolmoles total cresol.x 100 = about 30% to about 75%24.  A substrate coated with a thermally stable and highly resolved, exposed resist pattern, said resist pattern being formed from a positive photoresist composition which, prior to exposure to actinic radiation, comprises:A.   a novolak resin comprising the condensation product of (a) a phenol, phenol derivative, or mixture thereof; and (b) a mixture of aldehydes comprising formaldehyde or a formaldehyde precursor and a monohydroxy aromatic aldehyde; andB.   a photosensitizer.

25. The substrate of Claim 24 wherein the phenol component of the novolak resin is a mixture of m- and p-cresol.

26. The positive photoresist of Claim 24 wherein the aldehyde component of the novolak resin is a mixture of formaldehyde and a monohydroxy aromatic aldehyde selected from 2-hydroxybenzaldehyde, 3-hydroxybenzaldehyde, and4-hydroxybenzaldehyde.

27. The substrate of Claim 24 wherein the phenol and aldehyde components of the novolak resin are present in the following amounts:moles total aldehyde moles total phenol or phenol derivativex 100 = about 60% to about 95%moles monohydroxy aromatic aldehyde moles total aldehyde.x 100 = about 15% to about 95%28. The substrateof Claim 25 wherein them-andp-cresol are present in moles m-cresol moles total cresolthe following amounts:x 100about30%toabout 75%29. The substrateof Claim 24whereinthephotosensitizer is a naphthoquinonediazidesensitizer.

30. The substrate of Claim 29 wherein the naphthoquinone diazide sensitizer is selected from the group consisting of esters of l,2-naphthoquinone-2-diazo-4-sulfonic acid and esters of 1,2-naphthoquinone-2-diazo-5-sulfonic acid.        *31. The substrate of Claim 30 wherein the naphthoquinone diazide sensitizer is selected from the groupconsisting of2,3,4-trihydroxybenzophenone-1,2-naphthoquinone-2־diazo4־-sulfonic acid monoester; 2,3,4-trihydroxybenzophenone-l,2-naphthoquinone-2-diazo4־-sulfonic acid diester;2,3,4- trihy^roxybenzophenone-1,2-naphthoquinone-2-diazo-4-sulfonic acid triester and mixturesthereof.

32. The substrate of Claim 30 wherein the naphthoquinone diazide sensitizer is selected from the group consisting of2,3,4-trihydroxybenzophenone-1,2-naphthoquinone-2-diazo-5-sulfonic acid monoester; 2,3,4-trihydroxybenzophenone-l,2-naphthoquinone-2-diazo-5-sulfonic acid diester; 2,3,4-trihydroxybenzophenone-1,2-naphthoquinone-2-diazo-5- su1fonic acid triester and mixtures thereof.

33. Novolak resins being the condensation product defined in claim 1, substantially as hereinbefore described and with reference to any of the examples.

34. Positive photoresists based on novolaks defined in claim 1 or claimed in claim 33, substantially as hereinbefore described and with reference to any of the examples.ATTORNEYS FOR APPLICANT