PROCESS FOR REDUCING DEFECTS IN AN ORDERED FILM OF BLOCK COPOLYMERS

Abstract

Provided is a process for reducing the number of defects of an ordered film of a diblock copolymer on a surface. The process includes curing, on a surface, a composition including a diblock copolymer at a structuring temperature between the Tg of the diblock copolymer and the decomposition temperature of the diblock copolymer to form an ordered film of the diblock copolymer on the substrate. The composition has a product Xeffective*N of between 10.5 and 40 at the structuring temperature, where Xeffective is the Flory-Huggins parameter of the diblock copolymer and N is the total degree of polymerization of the blocks of the diblock copolymer.

Claims

1-9: (canceled)

10. A process for reducing the number of defects of an ordered film of a diblock copolymer on a surface, comprising: curing, on a surface, a composition comprising at least one diblock copolymer at a structuring temperature between the highest Tg of the at least one diblock copolymer and the decomposition temperature of the at least one diblock copolymer to form an ordered film comprising the at least one diblock copolymer on the substrate, wherein the diblock copolymer has a structure A-b-(B-co-C), wherein A represents a block consisting of monomer A, B-co-C represents a block consisting of monomer B and monomer C, and monomer C may optionally be the same as monomer A; and the composition has a product Xeffective*N of between 10.5 and 40 at the structuring temperature, wherein Xeffective is the Flory-Huggins parameter of the at least one diblock copolymer, and N is the total degree of polymerization of the blocks of the at least one diblock copolymer.

11. The process of claim 10, further comprising, prior to the curing: depositing a mixture comprising the at least one diblock copolymer and a solvent on the substrate.

12. The process of claim 11, further comprising, subsequent to the depositing and prior to the curing: evaporating the solvent.

13. The process of claim 10, wherein monomer A and monomer C are styrene, and monomer B is methyl methacrylate.

14. The process of claim 10, wherein the at least one diblock copolymer is synthesized anionically.

15. The process of claim 10, wherein the at least one diblock copolymer is prepared by controlled radical polymerization.

16. The process of claim 15, wherein the at least one diblock copolymer is prepared by nitroxide-mediated radical polymerization.

17. The process of claim 16, wherein the at least one diblock copolymer is prepared by N-tert-butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide-mediated radical polymerization.

18. The process of claim 10, wherein the ordered film has an orientation that is perpendicular to the surface.

19. The process of claim 10, wherein the ordered film has hexagonal cylindrical form.

20. The process of claim 10, wherein the ordered film has lamellar type form.

21. The process of claim 10, wherein the substrate is silicon, germanium, platinum, tungsten, gold, titanium nitride, graphene, or a Bottom Anti-Reflective Coating (BARC).

22. The process of claim 10, wherein the composition has a product Xeffective*N of between 15 and 30 at the structuring temperature.

23. The process of claim 10, wherein the composition has a product Xeffective*N of between 17 and 25 at the structuring temperature.

24. The process of claim 10, wherein the at least one diblock copolymer has a molecular weight of 100 to 500,000 g/mol, as measured by size exclusion chromatography.

25. The process of claim 10, wherein the structuring temperature is less than 400 C.

26. The process of claim 10, wherein the structuring temperature is less than 300 C.

27. The process of claim 10, wherein the structuring temperature is less than 270 C.

28. An ordered film produced by the process of claim 10.

29. A mask obtained from the ordered film of claim 28.

Description

EXAMPLE n 1

[0051] All the block copolymers were synthezied according to WO2015/011035.

[0052] Determination of X and X.sub.eff for block copolymers (BCPs) involved in the study:

PS-b-PMMA BCPs:

[0053] The X parameter for PS-b-PMMA system was measured experimentally in Y. Zhao & al., Macromolecules, 2008, 41 (24), pp 9948-9951, its value is given by the equation (1):

X.sub.SM=0.0282+(4.46/T), (1)

where T is the self-assembly process temperature.
thus at 225 C. for instance, X.sub.SM0.03715.

PS-b-P(MMA-co-S) BCPs:

[0054] From G. ten Brinke & al., Macromolecules, 1983, 16, 1827-1832., for a diblock copolymer where only one of the block is constituted of two different comonomers, written as A-b-(B-co-C), the Flory-Huggins parameter of this system, written as X.sub.eff, can be determined by the formula (2):

X.sub.eff=b.sup.2X.sub.BC+b(X.sub.ABX.sub.ACX.sub.BC)+X.sub.AC (2)

where:
a, b, c, are the volumic fraction corresponding to each monomer in the block copolymer (for instance, b is the volumic fraction of B monomer)
X.sub.AB, X.sub.AC, X.sub.BC, are the respective Flory-Huggins interaction parameter between each relative monomers in the block copolymer (i.e. X.sub.AB represent the interaction between the monomers A and B)

[0055] In the particular case where monomer C is the same than the one denoted A in the BCP formula, then (2) is simplified in: (3) X.sub.eff=b.sup.2X.sub.AB.

[0056] Since the relation (4) b=(1c) is true, then equation (3) turns also to:

X.sub.eff=(1c).sup.2X.sub.AB (5)

[0057] Thus in this particular case the X.sub.eff parameter is a function of only the volumic fraction of the added co-monomer C in the modified block, in the notation A-b-(B-co-C) as compared to the simplest A-b-B one, and the initial x parameter between monomers A and B.

[0058] By analogy to the system of interest noted PS-b-P(MMA-co-S), the relation (5) becomes:

X.sub.eff=(1s).sup.2X.sub.SM (6)

[0059] Where s is the volumic fraction of styrene monomer introduced in the initial PMMA block, and X.sub.SM is the classical Flory-Huggins interaction parameter between styrene and methylmethacrylate blocks.

[0060] By progressively varying the styrenic fraction in the MMA block, and combining the relations (1) and (6), the X.sub.eff parameter is known for each value of the self-assembly temperature. The following table (Table 1) gathers these as-calculated values of X.sub.eff for each point of interest in the styrene fraction versus self-assembly temperature matrix.

TABLE-US-00001 TABLE 1 Value of X.sub.eff for the BCP PS-b-P(MMA-co-S) system, calculated for specific values of styrene volumic fraction and self-assembly temperature. Self-assembly temperature ( C.) 215 220 225 230 235 240 250 Volumic 0 0.03734 0.03725 0.03716 0.03707 0.03698 0.03689 0.03673 fraction 0.1 0.03024 0.03017 0.03010 0.03002 0.02995 0.02988 0.02975 of 0.15 0.02698 0.02691 0.02685 0.02678 0.02672 0.02666 0.02654 styrene 0.2 0.02390 0.02384 0.02378 0.02372 0.02367 0.02361 0.02351 in the 0.25 0.02100 0.02095 0.02090 0.02085 0.02080 0.02075 0.02066 (MMA-co- 0.3 0.01830 0.01825 0.01821 0.01816 0.01812 0.01808 0.01800 S) block 0.35 0.01578 0.01574 0.01570 0.01566 0.01562 0.01559 0.01552 0.4 0.01344 0.01341 0.01338 0.01334 0.01331 0.01328 0.01322 0.5 0.00933 0.00931 0.00929 0.00927 0.00924 0.00922 0.00918 0.6 0.00597 0.00596 0.00594 0.00593 0.00592 0.00590 0.00588 0.7 0.00336 0.00335 0.00334 0.00334 0.00333 0.00332 0.00331 0.8 0.00149 0.00149 0.00149 0.00148 0.00148 0.00148 0.00147 0.9 0.00037 0.00037 0.00037 0.00037 0.00037 0.00037 0.00037 1 0 0 0 0 0 0 0

[0061] From the Table 1, the variation of the X.sub.eff parameter as function of the styrene volumic fraction and for a specific temperature (225 C.) can be plotted on a graph as shown in FIG. 2, for a better understanding and representation.

[0062] FIG. 2 shows values of X.sub.eff for a PS-b-P(MMA-co-S) system extracted from Table 1 for a particular temperature (225 C.) across the whole possible range of styrene volumic fraction.

EXAMPLE n 2

[0063] Extraction and calculus of X*N or X.sub.eff*N values for synthesized BCPs in the context of the invention:

TABLE-US-00002 TABLE 2 Molecular characteristics of BCPs used in the examples (.sup.(a)determined from SEM experiment; .sup.(b)determined by SEC using standard PS; .sup.(c)determined by .sup.1H NMR; .sup.(d)determined from Mp; .sup.(e)extracted from Table 1). BCP % S in BCP reference Period Mp (MMA- X or X.sub.eff/ X.sub.eff * N architecture n.sup.o (nm).sup.(a) (kg/mol).sup.(b) % PS.sup.(c) % PMMA.sup.(c) co-S).sup.(c) N.sup.(d) temperature.sup.(e) value PS-b-PMMA A 52 136 66 34 1325 0.03672 48.6 (250 C.) PS-b-PMMA B 44 92.2 68.5 31.5 898 0.03698 33.2 (235 C.) PS-b-P(MMA- C 52 87.2 78.5 21.5 25 845 0.02095 17.7 co-S) (220 C.) PS-b-P(MMA- D 44 47.9 78.9 21.1 15 464 0.02691 12.5 co-S) (220 C.)

[0064] For more clarity, BCPs C and D are synthesized within the invention, whereas BCPs A and B are references BCPs presenting respectively the same dimensions (see column period) than C and D but synthesized out of the scope of the invention (standard PS-b-PMMA BCPs taken for the direct comparison with modified ones).

[0065] This example illustrate how the invention can be used to tailor an initial X*N product of given BCPs (i.e. the ones of references BCPs A and B) toward a range of more appropriated values selected as regard to the associated dimension (period) of the system.

EXAMPLE n 3

Realization of Typical BCP Thin Film

[0066] Underlayer powder of appropriate composition and constitution is dissolved in a good solvent, for instance propylene glycol monomethylether acetate (PGMEA), in order to get a 2% by mass solution. The solution is then coated to dryness on a cleaned substrate (i.e. silicon) with an appropriate technique (spin coating, blade coating . . . known in the state of the art) in order to get a film thickness of around 50 nm to 70 nm. The substrate is then baked under an appropriate couple of temperature and time (i.e. 200 C. during 75 seconds, or 220 C. during 10 minutes) in order to ensure the chemical grafting of the underlayer material onto the substrate; the non-grafted material is then washed away from the substrate by a rinse-step in a good solvent, and the functionalized the substrate is blown-dried under a nitrogen (or another inert gaz) stream. In the next step, the BCP solution (typically 1% or 2% by mass in PGMEA) is coated on the as-prepared substrate by spin coating (or any other technique known in the state of the art) in order to get a dry film of desired thickness (typically few tens of nanometer). The BCP film is then baked under an appropriate set of temperature and time conditions (for instance 220 C. during 5 minutes, or any of the other temperatures reported in the Table 2, or by using any other technique or combination of techniques known in the state of the art) in order to promote the self-assembly of the BCP. Optionally, the as-prepared substrate can be immersed in glacial acetic acid during few minutes, then rinsed with deionized water, and then submitted to a mild oxygen plasma during few seconds, in order to enhance the contrast of the nanometric features for SEM characterizations.

[0067] One can notice that in the following experiments and examples, the underlayer material is selected so as to be neutral for the studied block copolymer (i.e. so that it is able to balance the interfacial interaction between the substrate and the different blocks of the BCP material, to get a non-preferential substrate as regard to the different blocks chemistries) in order to get a perpendicular orientation of the BCP features.

[0068] In the following examples, the BCP films are characterized through SEM-imaging experiments with a CD-SEM (Critical Dimensions Scanning Electron Microscope) tool H-9300 from Hitachi. Pictures are taken at constant magnification (appropriated for the dedicated experiment: for instance defectivity experiments are performed at magn. *100 000 to get enough statistics, whereas critical dimensions (CD) ones are performed at magn. *200 000 or magn. *300 000 to get a better precision in the dimensions) in order to allow a careful comparison of the different BCP materials.

EXAMPLE n 4

[0069] The FIG. 3 and FIG. 4 gather the raw CD-SEM results obtained for the comparison of different BCPs systems of interest, under various self-assembly conditions.

[0070] The FIG. 3 is dedicated to the comparison of the PS-b-PMMA and PS-b-P(MMA-co-S) systems of 52 nm period. The film thickness are targeted to be either the same (i.e. 70 nm) and different for the two systems, and the self-assembly temperature is chosen to be best known one for each BCP (i.e. the couple bake temperature/bake time is chosen so as to get the maximum of perpendicular cylinders for each BCP system).

[0071] The FIG. 3 is an example of raw CDSEM pictures obtained for BCP systems of 52 nm period, for various film thicknesses and the best self-assembly process temperature for each BCP (250 C. for PS-b-PMMA, 220 C. for PS-b-P(MMA-co-S), respectively).

[0072] The FIG. 4 is dedicated to the comparison of the PS-b-PMMA and PS-b-P(MMA-co-S) systems of 44 nm period. The comparison is performed for the same film thicknesses (i.e. 35 and 70 nm) or different ones, and for the same self-assembly process (self-assembly bake temperature 220 C. during 5 minutes) for a direct comparison of the two systems.

[0073] FIG. 4 is an example of raw CDSEM pictures obtained for BCP systems of 44 nm period, for various film thicknesses and a self-assembly temperature of 220 C.

[0074] The various SEM images acquired for each BCPs under the various experimental conditions were treated with appropriate softwares already well described in the existing literature (see for instance X. Chevalier &al., Proc. SPIE 9049, Alternative Lithographic Technologies VI, 90490T (Mar. 27, 2014); doi:10.1117/12.2046329), in order to extract their corresponding coordinance defect-level of interest in the frame of the present invention. The extraction process for each picture is depicted in the FIG. 5 a reminder: FIG. 5 is an example of a SEM picture treatment to extract its defectivity level: the raw SEM image (left) is first binarized (middle) and then treated so as to detect each cylinder and its direct environment. Cylinders presenting more or less than six neighbors are counted as a defect, whereas those having exactly 6 neighbors are counted as good ones.

[0075] The CD-SEM pictures treatment results are gathered in the Table 3 below, with the corresponding associated experimental processing parameter. Each defect-level value is determined through the treatment of 10 different picture for the associated conditions, randomly chosen on the sample:

TABLE-US-00003 TABLE 3 Experimental parameters followed for the self-assembly of each BCP depicted in the FIG. 3 and FIG. 4, and their respective defectivity measurement associated (each value of defect percentage is a mean obtained from the treatment of 10 different CDSEM pictures). Self- assembly Film Defect BCP Period temperature thickness level BCP type reference (nm) ( C.) (nm) (%) PS-b-PMMA A 52 250 25 38.5 35 28.2 70 >80 PS-b-P(MMA- C 52 220 50 16.5 co-S) 70 11.8 100 21.5 PS-b-PMMA B 44 220 35 30.0 40 40.2 45 56.7 70 >70 PS-b-P(MMA- D 44 220 35 12.1 co-S) 70 8.6 100 10.8

[0076] The various results gathered in the Table 3, FIG. 4 and FIG. 5, allow the careful comparison of the different BCPs systems in the frame of the invention:

The FIG. 6 compares defectivity results obtained for the systems having 52 nm period; the film thicknesses taken at 70 nm for the two systems clearly indicate that the self-assembly quality is much better thanks to a lower defect level in the case of the system PS-b-P(MMA-co-S), relevant for the invention, as compared to the PS-b-PMMA one. This is valid even if the self-assembly conditions (i.e. bake temperature) are not strictly the same.
FIG. 6 is a graphical representation of the defectivity measurements corresponding to BCPs A and C of 52 nm period reported in the Table 3. It illustrates the better quality for the self-assembly of PS-b-P(MMA-co-S) system as compared to the one of PS-b-PMMA, even for very thick films.
The FIG. 7 compares the defectivity results obtained for BCPs having a 44 nm period; in this case, the two different systems can be directly compared through the same film thicknesses (35 and 70nm) and self-assembly conditions (bake temperature at 220 C. during 5 minutes) experimentally used. In this case again, the measurement indicates a much better self-assembly quality for the PS-b-P(MMA-co-S) system relevant for the invention through a lower defectivity value as compared to the PS-b-PMMA system.
FIG. 7 is a graphical representation of the defectivity measurements corresponding to BCPs B and D of 44nm period reported in the Table 3, for the same self-assembly parameters (self-assembly bake at 220 C. during 5 minutes). It illustrates the better quality for the self-assembly of PS-b-P(MMA-co-S) system as compared to the one of PS-b-PMMA, for the same film thicknesses of thicker films.

[0077] Even if the conditions are not identical ones, the FIGS. 6 and 7 both indicate lower defectivity values the systems in the frame of the invention, independently of the film thickness used (i.e. all the defectivity values are lower for the PS-b-P(MMA-co-S) system than for the PS-b-PMMA one, whatever the film thickness is).

[0078] When the FIG. 6 and FIG. 7 are combined with the X*N or X.sub.eff*N value for the corresponding BCP reported in the Table 2, it clearly highlights the meaningfulness of the control the X*N value for electronic applications, through the architecture and modification of the BCP under the frame of the present invention, i.e. a form A-b-(B-co-C) or A-b-(B-co-A) (like in the PS-b-P(MMA-co-S) example) for the BCP instead of the classical A-b-B one. In other words, the control of X*N or X.sub.eff*N value through the architecture modification (like in the PS-b-P(MMA-co-S)) allows to get better defectivity values than those reported for the non-modified systems.