CLEAVABLE ADDITIVES FOR USE IN A METHOD OF MAKING A SEMICONDUCTOR SUBSTRATE

Abstract

The use of an organic compound as cleavable additive, preferably as cleavable surfactant, in the modification and/or treatment of at least one surface of a semiconductor substrate is described. Moreover, it is described a method of making a semiconductor substrate, comprising contacting at least one surface thereof with an organic compound, or with a composition comprising it, to treat or modify said surface, cleaving said organic compound into a set of fragments and removing said set of fragments from the contacted surface. More in particular, a method of cleaning or rinsing a semiconductor substrate or an intermediate semiconductor substrate is described. In addition, a compound is described which is suitable for the uses and methods pointed out above and which preferably is a cleavable surfactant.

Claims

1-6. (canceled)

7. A method of making a semiconductor substrate, the method comprising: making or providing a semiconductor substrate, having at least one surface, contacting said at least one surface with an organic compound of the following formula (I):
A-L-B  (I), or a salt thereof, wherein A is a straight-chain or branched aliphatic hydrocarbon group having a total number of 4 to 20 carbon atoms, which is substituted by 1 to 4 ether groups, or is unsubstituted, B is a straight-chain or branched aliphatic hydrocarbon group having a total number of 1 to 6 carbon atoms, which is substituted by one or two ionic groups independently selected from the group consisting of anionic groups and cationic groups and L is a urethane group, so that said at least one surface is modified or treated, and subsequently cleaving said organic compound or the salt thereof on said at least one surface into a set of fragments.

8. The method of claim 7, wherein said contacting is conducted so as to achieve at least one effect selected from the group consisting of modifying by pore-sealing of low-k dielectric materials, repairing films of low-k dielectric materials, changing a zeta-potential of said at least one surface of the intermediate semiconductor substrate, changing a contact angle on said at least one surface of the intermediate semiconductor substrate, changing adsorption or adhesion properties of said at least one surface of the intermediate semiconductor substrate in relation to the compound of formula I and/or inhibiting corrosion; and treating by cleaning and/or rinsing; and/or said cleaving comprises thermally cleaving said compound of formula I or the salt thereof on said at least one surface into a set of fragments, and/or said removing said set of fragments from said at least one surface comprises evaporating fragments.

9. The method of claim 7, wherein the compound of formula I or the salt thereof has a molecular weight not exceeding 1500 g/mol.

10. A method of cleaning and/or rinsing a semiconductor substrate, the method comprising the following steps: making or providing a semiconductor substrate having at least one surface and having one or more materials on at least one of said at least one surface, contacting said one or more materials with an organic compound of the following formula I:
A-L-B  (I), or a salt thereof, wherein A is a straight-chain or branched aliphatic hydrocarbon group having a total number of 4 to 20 carbon atoms, which is substituted by 1 to 4 ether groups, or is unsubstituted, B is a straight-chain or branched aliphatic hydrocarbon group having a total number of 1 to 6 carbon atoms, which is substituted by one or two ionic groups independently selected from the group consisting of anionic groups and cationic groups, and L is a urethane group, removing an amount of said compound of formula I or the salt thereof from said at least one surface, together with one or more of said one or more materials, to obtain a cleaned or rinsed semiconductor substrate having a residual amount of said compound of formula I or the salt thereof attached to at least one of said at least one surface, cleaving a fraction or total of said residual amount into a set of fragments by heating to a cleaving temperature at a cleaving pressure, each fragment having a boiling point below said cleaving temperature, at the cleaving pressure applied, and removing said set of fragments from said at least one surface by evaporation.

11. The method of claim 10, wherein the removing of said set of fragments comprises evaporating said fragments at said cleaving temperature or at a temperature below said cleaving temperature and/or at said cleaving pressure or at a pressure below said cleaving pressure.

12. The method of claim 10, wherein, in said compound of formula I or the salt thereof, A is a monovalent group 10-CH.sub.2—, where R.sup.1 is a straight-chain or branched aliphatic hydrocarbon group having a total number of 4 to 20 carbon atoms; and B is a monovalent ionic group of the following formula II ##STR00017## where R.sup.2 is a straight-chain or branched aliphatic hydrocarbon group having a total number of 1 to 6 carbon atoms and Y.sup.+ is a singly charged ammonium cation which is unsubstituted or substituted by 1 to 3 C.sub.1-C.sub.4-alkyl groups.

13. A compound of the following formula Ib, wherein ##STR00018## R.sup.1 is a straight-chain or branched aliphatic hydrocarbon group having a total number of 4 to 20 carbon atoms, R.sup.2 is a straight-chain or branched aliphatic hydrocarbon group having a total number of 1 to 6 carbon atoms, and Y.sup.+ is a singly charged ammonium cation which is unsubstituted or substituted by 1 to 3 C.sub.1-C.sub.4-alkyl groups.

14. The compound of claim 13, wherein R.sup.1 is a straight-chain or branched aliphatic hydrocarbon group having a total number of 7 to 14 carbon atoms, R.sup.2 is a straight-chain or branched aliphatic hydrocarbon group having a total number of 1 to 2 carbon atoms, and Y.sup.+ is ammonium.

15. (canceled)

Description

EXAMPLES

[0416] The following examples are meant to further explain and illustrate the invention without limiting its scope.

Example 1: Synthesis of Compounds of Formula Ib

General Procedure

a) Synthesis of Alkyl Isocyanates

[0417] Where a required isocyanate was not purchased (or was not commercially available), it was synthesized from the corresponding primary amine by treatment with diphosgene (CAS RN 503-38-8) according to the following general procedure (see reaction scheme 1, RS-1, below), as generally known in the art:

##STR00009##

[0418] R.sup.1 and R.sup.2 in reaction schemes 1 and 2 (RS-1, RS-2) have the meanings or preferred meanings as given above for the compound of formula Ib.

[0419] In a 1000 ml 4-necked round-bottom flask equipped with stirrer, thermometer and reflux condenser, the respective primary alkyl amine (1.0 molar equivalent) was dissolved in chloro benzene (2 g chloro benzene per 1 g alkyl amine) and stirred at room temperature for 20 min. After cooling to 0° C., diphosgene (1.0 molar equivalent) was added dropwise. The resulting mixture was stirred for 3 h at 0° C. and subsequently for 20 h at 20° C. Then the mixture was gently heated to 125° C. and stirred at this temperature for 8 h. The solvent was removed in a rotary evaporator at 80° C. and 10-20 hPa within 2 hours. The desired structure was confirmed by .sup.1H-NMR in each case. Where needed, the resulting isocyanate was purified by distillation.

b) Synthesis of Alkyl Urethane Alkylene Carboxylic Acid Methyl Esters

[0420] ##STR00010##

[0421] In a 500 ml 4-necked round-bottom flask equipped with stirrer, thermometer and reflux condenser, the respective alkyl isocyanate (for preparation see procedural step a) above; 1.0 molar equivalent) was dissolved in dichloro methane (7.2 g dichloro methane per 1 g alkyl isocyanate) and stirred at room temperature for 20 min. After cooling to 0° C., trimethylamine (0.1 molar equivalent) and N,N-dimethylaminopyridine (0.01 molar equivalent) was added. Then, glycolic acid methyl ester (1.0 molar equivalent) was added dropwise within 1 h at 0° C. The resulting mixture was allowed to warm to 20° C. and stirred for 20 h at this temperature. Then, the mixture was gently heated to 50° C. and stirred at this temperature for 20 h. The mixture was allowed to cool to 20° C. and a further amount of dichloro methane (6 g dichloro methane per 1 g alkyl isocyanate) was added. The organic phase was extracted with 1 M aqueous hydrochloric acid (half the volume of the dichloro methane volume). The organic layer was separated and dried over MgSO.sub.4. The dried organic solvent was removed in a rotary evaporator at 40° C. and a pressure of 10-20 hPa within 4 hours. The desired structure was confirmed by .sup.1H-NMR in each case.

c) Synthesis of Alkyl Urethane Alkylene Carboxylic Acids

[0422] In a 500 ml 4-necked round-bottom flask equipped with stirrer, thermometer and reflux condenser, the alkyl urethane alkylene carboxylic acid methyl ester (for preparation see procedural step b) above, 1.0 molar equivalent) was mixed with water (6.2 g water per 1 g alkyl urethane alkylene carboxylic acid methyl ester) and sodium hydroxide solution (1.0 molar equivalent, 50% w/w NaOH in water) at room temperature. The mixture was stirred for 20 h at 20° C. and afterwards for 24 h at 50° C. Then, the mixture was allowed to cool to 20° C. and tert-butyl methyl ether (0.67 g tert-butyl methyl ether per 1 g water) was added, and the mixture was stirred for another 2 h at 20° C. The mixture was then gently warmed to 50° C. until the cloudy phases turned clear. The mixture was completely transferred into a separation funnel and phases were separated at 40° C. After separation, the aqueous phase was cooled to 5° C. and treated with concentrated hydrochloric acid (1.0 molar equivalent). The water was removed in a rotary evaporator at 80° C. and 10 hPa within 4 hours to yield the alkyl urethane alkylene carboxylic acids. The desired structure was confirmed by .sup.1H-NMR in each case.

d) Synthesis of Alkyl Urethane Alkylene Carboxylate Ammonium Salts

[0423] In a 1000 ml 1-necked round-bottom flask the alkyl urethane alkylene carboxylic acid (for preparation see procedural step c) above; 1.0 molar equivalent) was mixed with ethanol (15.6.2 g ethanol per 1 g alkyl urethane alkylene carboxylic acid) and a solution of ammonia s in ethanol (10 molar equivalents NH.sub.3 of a 4% w/w solution of NH.sub.3 in ethanol) at room temperature. The flask was fitted to a rotary evaporator and rotated for 30 min at 25° C. and 2 h at 60° C. The ethanol was gently removed at 60° C. and reduced pressure (30 to 200 hPa) within 4 hours. The crude ammonium salt was mixed with tert-butyl methyl ether (3 g tert-butyl methyl ether per 1 g crude ammonium salt) at 60° C. in an ultrasonic bath and then cooled to 20° C. The purified ammonium salt was filtered off and traces of tert-butyl methyl ether were removed by applying gently reduced pressure. The desired structure was confirmed by .sup.1H-NMR in each case.

[0424] The following compounds of formula Ib were obtained according to the general procedure in the total yields as provided here below (% yield in relation to starting material used in procedural step a) or b), as given below):

[0425] Compound of formula III: 59% in relation to material used in procedural step b).

[0426] .sup.1H-NMR of the compound of formula III in MeOD (tetramethylsilane, “TMS”, as reference standard): δ=0.8-1.0 ppm (m, 6H, 2×CH.sub.3 of alkyl moiety), 1.1-1.6 ppm (m, 9H, CH and CH.sub.2 of alkyl moiety), 3.0-3.1 ppm (d, 2H, CH.sub.2 close to N of urethane group), 3.3 ppm (MeOH), 4.35-4.5 ppm (s, 2H, CH.sub.2 between carboxylate and urethane group), NH.sub.4 and NH: broad signals

[0427] Compound of formula IV: 37% in relation to material used in procedural step a).

[0428] .sup.1H-NMR of compound of formula IV in MeOD (TMS): δ=0.8-1.0 ppm (m, 6H, 2×CH.sub.3 of alkyl moiety), 1.1-1.6 ppm (m, 13H, CH and CH.sub.2 of alkyl moiety), 3.0-3.1 ppm (d, 2H, CH.sub.2 close to N of urethane group), 3.3 ppm (MeOH), 4.35-4.5 ppm (s, 2H, CH.sub.2 between carboxylate and urethane group), NH.sub.4 and NH: broad signals

[0429] Compound of formula V: 43% in relation to material used in procedural step a).

[0430] .sup.1H-NMR of compound of formula V in MeOD (TMS): δ=0.8-1.6 ppm (m, 25H, CH.sub.2 and CH.sub.3 of alkyl moiety), 3.0-3.1 ppm (d, 2H, CH.sub.2 close to N of urethane group), 3.3 ppm (MeOH), 4.35-4.5 ppm (s, 2H, CH.sub.2 between carboxylate and urethane group), NH.sub.4 and NH: broad signals

[0431] Compound of formula VI: 18% in relation to material used in procedural step b).

[0432] .sup.1H-NMR of compound of formula VI in MeOD (tetramethylsilane as reference standard): δ=0.8-1.0 ppm (t, 3H, CH.sub.3 of alkyl moiety), 1.1-1.6 ppm (m, 20H, 10×CH.sub.2 of alkyl moiety), 3.0-3.1 ppm (d, 2H, CH.sub.2 close to N of urethane group), 3.3 ppm (MeOH), 4.35-4.5 ppm (s, 2H, CH.sub.2 between carboxylate and urethane group), NH.sub.4 and NH: broad signals.

[0433] Compound of formula VII: 51% in relation to material used in procedural step a).

Example 2: Synthesis of Comparative Compounds of Formulae X and XI

a) Amidation

[0434] ##STR00011##

[0435] In a 250 ml 4-necked round-bottom flask equipped with stirrer, thermometer and reflux condenser, maleic acid anhydride (19.61 g, 0.20 mol, 1.0 molar equivalent) was dissolved in acetic acid (100 ml) and stirred at 25° C. Afterwards, 2-ethylhexylamine (25.85 g, 0.20 mol, 1.0 molar equivalent) was added dropwise over 2 h. Then, the resulting mixture was stirred and heated at 80° C. for 6 h and subsequently for 92 h at 25° C. The solvent was removed in a rotary evaporator at 80° C. and 10-20 hPa within 2 hours. 1H-NMR of the crude product showed single formation of the desired amide ((2Z)-4-[(2-ethylhexyl)amino]-4-oxo-2-butenoic acid, CAS RN 6975-33-3).

b) Chlorination and Cyclisation

[0436] ##STR00012##

[0437] In a 1000 ml 4-necked round-bottom flask equipped with stirrer, thermometer and reflux condenser, crude product from step a) (35.38 g, 0.156 mol, 1.0 molar equivalent) was dissolved in dichloromethane (500 ml) stirred at 10° C. N,N-dimethytformamide (0.19 g) was added. Afterwards, oxalyl chloride (21.93 g, 0.173 mol, 1.1 molar equivalent) was added dropwise over 45 min. Then, the resulting mixture was stirred and heated at 25° C. for 16 h and subsequently for 92 h at 25° C. The solvent was removed in a rotary evaporator at 80° C. and 10-20 hPa within 2 hours. .sup.1H-NMR of the crude mixture showed single formation of the desired chlorinated imide (“3-chloro-1-(2-ethyhexyl)pyrrolidine-2,5-dione”).

c) Elimination

[0438] ##STR00013##

[0439] In a 1000 ml 4-necked round-bottom flask equipped with stirrer, thermometer and reflux condenser, crude product from step b) (37.5 g, 0.153 mol, 1.0 molar equivalent) was dissolved in dichloromethane (500 ml) stirred at 25° C. Afterwards, triethyl amine (23.16 g, 0.229 mol, 1.5 molar equivalent) was added at 25° C. dropwise over 15 min. Then, the resulting mixture was stirred at 25° C. for 24 h. The organic phase was extracted with aqueous solution of hydrochloric acid (2×500 ml of 1 N HCl in water). The organic phase was dried over magnesium sulfate, which was filtered off. The solvent was removed in a rotary evaporator at 50° C. and 10-20 hPa within 2 hours. .sup.1H-NMR of the crude mixture showed single formation of the desired maleic acid imide (1-(-ethylhexyl)-1H-pyrrole-2,5-dione; CAS RN 48149-71-9).

d) Diels-Alder Reaction

[0440] ##STR00014##

[0441] In a 250 ml 4-necked round-bottom flask equipped with stirrer, thermometer and reflux condenser, crude product from step c) (19.6 g, 0.094 mol, 1.0 molar equivalent) was mixed with 2-furane carboxylic acid (10.50 g, 0.094 mol, 1.0 molar equivalent) at 60° C. Then, the resulting mixture was stirred at 70° C. for 25.5 h. Afterwards, tert-butyl methyl ether (150 ml) was added at 25° C. and mixture was stirred for 1 h. Then, n-pentane (150 ml) was added and mixture was stirred for 1 h at 25° C. Small amounts of a precipitate are formed and filtered off. The solvent was removed in a rotary evaporator at 50° C. and 10-20 hPa within 2 hours. 18.3 g of product was isolated. .sup.1H-NMR of the crude product confirmed formation of the Diels-Alder-adducts (mixture of 2 compounds, see reaction scheme above).

e) Neutralisation

[0442] In a 1000 ml 4-necked round-bottom flask equipped with stirrer, thermometer and reflux condenser, crude product from step d) (6 g) was dissolved in ethanol (20 ml) and stirred at 20° C. Then, 40 ml of NH.sub.4OH in water (25 wt.-% in water) was added at 25° C. over 30 min. Then, the resulting mixture was diluted with methanol (500 g) and charcoal (10 g) was added. Charcoal was filtered off and the solvent was gently removed at 25° C. and at a pressure of <10 hPa. 6 g of a crude product was isolated. .sup.1H-NMR of the crude mixture showed formation of the desired ammonia salts of the Diels-Alder adducts of formulae X and XI. The product was dissolved in water to obtain an aqueous solution with 15 wt.-% active content.

[0443] For the glass tube test (see example 3, below), the mixture of compounds of formulae X and XI was dried by removing the solvents (water and methanol) and the resulting solid was used in the test.

Example 3: Glass Tube Test

[0444] The following compounds were tested in example 3 (“test compounds”):

[0445] Compound of formula V according to the invention.

[0446] Mixture of compound of formula X (a Diels-Alder adduct):

##STR00015##

and compound of formula XI (a Diels-Alder adduct):

##STR00016##

(not according to the invention) for comparison (for synthesis see example 2, above).

[0447] The total weight (mass) of an empty cylindrical quartz glass tube (length: 3 cm, diameter: 20 cm; not containing any test compound) was measured at room temperature. Then, the test compounds (1.35 g) were loaded into the quartz glass tube in each case and the total weight (mass) of the quartz glass tube filled with the test compounds was measured at room temperature. The quartz glass tube filled with a respective test compound was then evacuated to a pressure of 1 mbar (1 hPa) and heated to a temperature of 200° C. for 30 min. After cooling to room temperature, the total weight (mass) of the quartz glass tube (including the remainders/residuals from the test compounds or their fragments) was measured again.

[0448] The difference in weight (mass) of the quartz glass tube found after loading the test compound (mass of quartz glass tube plus test compound) and the weight (mass) of the quartz glass tube found after heating and evacuation (i.e. cleaving and removing of the test compound; mass of quartz glass tube plus remainders/residuals from the test compound or its fragments) was calculated and the results are shown in table 1 below in each case (i) as mass remaining of the test compounds after heating and evacuation and (ii) as mass percent remaining of the test compounds after heating and evacuation in relation to the total mass of test compound previously loaded to the quartz glass tube (differential measurement of masses).

TABLE-US-00001 TABLE 1 Test results from glass tube decomposition test Compound Result Compound of formula V 1 mg residual found after heating and (according to the invention) evacuation (0.074 wt.-%) Mixture of compound of formula 400 mg residual found after heating X and compound of formula XI and evacuation (29.6 wt.-%) (comparison, not according to the invention)

Example 4: Watermark Test

[0449] The following compounds (surfactants) were tested in example 4 (“test compounds”):

[0450] Compound of formula VII (according to the invention); Linear dodecyl benzene sulfonate and Lutensol T08 (both not according to the invention) for comparison.

[0451] Four drops of a 0.5 g/L clear solution of the test compounds in water were dropped on the surface of a SiO.sub.2 plate. The solution was allowed to dry and was then heated to 200° C. for 30 min.

[0452] After cooling to room temperature, it was found by visual inspection and photography that the residues of linear dodecyl benzene sulfonate (not according to the invention) and the residues of Lutensol T08 (not according to the invention) could not be evaporated without visible remainder from the surface of the SiO.sub.2 plate but that a ring of surfactant agglomerate remained on the plate's surface after heating.

[0453] In contrast, it was found by visual inspection that the compound of formula VII (according to the invention) could be evaporated without visible remainder from the surface of the SiO.sub.2 plate under the test conditions and that the plate's surface appeared free from visible residues after heating.

Example 5: Contact Angle Test

[0454] The compounds (“cleavable surfactants” of formula Ib according to the invention) shown in table 2 below were tested in example 5 (“test compounds”).

[0455] Contact angles between a drop of pure water and the planar solid surface of a silicon wafer were measured according to the sessile drop method with the device OCA 200 from DataPhysics and Data Physics standard software, according to standard test method ASTM D7490-13.

[0456] About 10 μl of water were dropped from a syringe from a distance of about 0.5 cm onto the wafer's surface. As soon as the water droplet hit the surface, up to 200 pictures per second were taken by a high speed video camera. The contour of each droplet was analyzed and the contact angle, which is (as usual) the angle between the solid sample surface and the tangent of the droplet's shape at the edge of the droplet, was determined. The contact angel was recorded as function of time up to 100 seconds and provided as contact angle as measured after 10 s in table 2 below.

[0457] A silicon wafer was cleaned in aqueous HF (1% w/w in water) solution and rinsed with water followed by heating the wafer at 200° C. for 1 h. The resulting contact angle of water on the wafers surface was found to be about 120° in all cases (see table 2: “pre-treatment value”).

[0458] A test solution (0.5 g/L of the respective test compound in water, see table 2 below) and pure water (control) were adjusted to a pH value of 6.2, applied to the wafer's surface and the wafer's surface dried at room temperature in each case. The contact angle of water was then determined on the wafer's surface after this pre-treatment with the test solution and water. It was found that the contact angles of water determined at the positions on the wafers surface where the test solution had been applied (and dried) showed reduced values (see table 2: “treatment value”) when compared with the contact angle values of water determined at the positions where the pure water had been applied.

[0459] The silicon wafer was then heated to 200° C. for 30 min and cooled to room temperature again to remove the test compounds from its surface. The contact angle of water was then again determined at the positions as explained above (see table 2: “post-treatment value”). It was found that after the heat treatment, the contact angles of water determined at the positions on the wafer's surface where the test solution had been applied, nearly reached the pre-treatment values again. The results from the contact angle test are summarized in table 2 below:

TABLE-US-00002 TABLE 2 Results from contact angle test Contact Contact angle of Contact angle of water [°] - angle of water - [°] pre- water [°] - post- Test Compound or treatment treatment treatment Control value value value Water 112 109 113 Compound of formula III 123 73 122 Compound of formula IV 117 77 119 Compound of formula V 119 29 108 Compound of formula VII 117 36 105

[0460] The results from example 5 show that the test compounds according to the invention (“cleavable surfactants”) could be contacted with the surface of a silicon wafer for the purpose of treating or modifying, in particular cleaning or rinsing, the contacted surface and—after being cleaved by the trigger of heat (heating to a temperature of 200° C.)—could be removed or completely removed again by evaporation.