TW201920323A - Process for controlling the orientation of the nanodomains of a block copolymer - Google Patents

Abstract

The invention relates to a process for controlling the orientation of the nanodomains of a block copolymer (BCP), the lower interface of which is in contact with the surface, neutralized beforehand, of a substrate, the said block copolymer being capable of nanostructuring itself to give nanodomains with a predetermined period (L0), over a minimum thickness (t) at least equal to half of the said period (L0), the said process being characterized in that it consists in depositing the said block copolymer (BCP) on the said substrate, so that its total thickness (T+t) is at least two times greater and preferably at least three times greater than the said minimum thickness (t).

Description

Method for controlling nano-domain orientation of block copolymer

The invention relates to the field of controlling the nanodomain orientation of a block copolymer, which is produced during the nanostructuring of the block copolymer. The orientation depends in particular on the surface energy at each interface of the block copolymer.

More specifically, the present invention relates to a method for controlling the nano-domain orientation of a block copolymer whose upper interface is in contact with a gaseous compound or a mixture of gaseous compounds. In addition, the present invention relates to a method for producing a nanolithography resist from a block copolymer, which method comprises the stages of a method of controlling the block orientation of the block copolymer.

The development of nanotechnology has made it possible to miniaturize products, especially in the fields of microelectronics and microelectromechanical systems (MEMS). At present, traditional lithographic techniques are no longer able to meet these continuing demands for miniaturization, as they cannot produce structures smaller than 60 nm in size.

Therefore, it is necessary to adjust the lithography technology and create an etching resist, which makes it possible to create increasingly smaller patterns with high resolution. With block copolymers, the arrangement of the constituent blocks of the copolymer can be constructed by phase separation between the blocks to form a nano-domain with a size of less than 50 nm. Due to this nanostructured ability, the use of block copolymers in the field of electronics or optoelectronics is now well known.

However, block copolymers intended to form nanolithography resists must exhibit a nanodomain oriented vertically to the surface of the substrate so that one of the blocks of the block copolymer can then be selectively removed and created with residual Blocked porous membrane. The pattern thus created in the porous membrane can then be transferred to the underlying substrate by etching.

The surface energy (expressed as γ _x ) of a given material is defined as the excess energy on the surface of that material compared to the material within its body. When the material is in liquid form, its surface energy corresponds to its surface tension.

Each block of the block copolymer ... J i exhibits a surface energy (denoted γ _i ... γ _j), which is specific to the block, and depending on the chemical composition of the block, that is, Depends on the chemical nature of the monomers or comonomers made up of the blocks. Likewise, each constituent material of the substrate exhibits its own surface energy value.

In addition, when the block copolymer interacts with a given material "x" (which may be a gas, liquid, solid surface, or another polymer phase), each block i ... j of the block copolymer exhibits Show the interaction parameters of the Flory-Huggins type expressed as χ _ix , for example, the interface energy expressed as “γ _ix ”, where γ _ix = γ _i- (γ _x cos θ _ix ), Where θ _ix is the contact angle between materials i and x. Therefore, the interaction parameter between the two blocks i and j of the block copolymer is expressed as χ _ij .

Jia et al. Have shown in the Journal of Macromolecular Science , B, 2011, 50, 1042 that there is a relationship between the surface energy γ _i connected to a given material _i and the Hildebrand solubility parameter δ _i . In fact, the Flory-Herkins interaction parameters between two given materials i and x are indirectly related to the surface energy γ _i and γ _x specific to that material. Therefore, the physical phenomena of interactions occurring at the interface of materials are described by surface energy or interaction parameters.

In order to obtain a structured nanodomain structure of the block copolymer that is perfectly perpendicular to the underlying substrate, it seems necessary to precisely control the interaction of the block copolymer and the different interfaces with which it physically contacts. Generally, a block copolymer is in contact with two interfaces: in the following description, it is called the "lower" interface (in contact with the underlying substrate) and it is called the "upper" interface (in contact with another compound or mixture of compounds). Generally, at the self-organizing temperature in the nanometer domain, the compound or mixture of compounds at the upper interface is composed of ambient air or a controlled composition of the atmosphere.

When the surface energy of each interface is not controlled, there is usually a specific orientation of the pattern of the block copolymer, and more particularly an orientation parallel to the substrate, regardless of the type of the block copolymer. This parallel orientation is mainly due to the fact that at the self-organizing temperature of the block copolymer, the compound at the substrate and / or the upper interface exhibits a better affinity for one of the constituent blocks of the block copolymer. In other words, the block i of the block copolymer interacts with the Flory-Herkins type of the underlying substrate (expressed as χ _{i- substrate} ) and / or the block i of the block copolymer and Flory-Herkins-type interaction parameters (expressed as χ _{i- air} ) of compounds on the upper interface (for example, air) are much smaller than zero or greater than zero, and the interfacial energy γ _{i- substrate} and / or γ _{i -The air is} not equal to each other.

Therefore, the required structuring, that is to say, the area that is perpendicular to the surface of the substrate (the pattern of which can be, for example, cylindrical, layered, spiral, or spherical) requires more than controlling the lower interface (that is, with the lower layer) The surface energy at the interface of the substrate also needs to control the surface energy at the upper interface.

In the case of using a block copolymer as a nano-structured resist applied to microelectronics (lithography, memory points, waveguides, etc.), the purpose is to guide by generating a predetermined pattern on the underlying substrate in advance Orientation of different blocks of a given block copolymer.

There are two main techniques that make it possible to control and guide the orientation of the blocks of the block copolymer on the substrate: graphoepitaxy and chemical epitaxy. Cartographic epitaxy uses topological constraints to force block copolymers to self-organize in a predetermined space comparable to the periodicity of block copolymers. To this end, drawing epitaxy involves forming a main pattern on the surface of the substrate called a guide. These guides, which have any chemical affinity for the blocks of the block copolymer, define the area in which a layer of block copolymer is deposited. The guide makes it possible to control the organization of the blocks of the block copolymer to form a higher-resolution secondary pattern in these regions. Generally, the guide is formed by a photolithography method.

In addition, the surface of the substrate between the guides can be neutralized so that the surface in contact with the subsequently deposited block copolymer does not exhibit a better affinity for one of the blocks. To this end, Mansky et al., Science, Vol. 275, pages 1458-1460 (7 March 1997) showed, for example, statistical poly (methyl methacrylate-co-styrene) functionalized by hydroxyl functional groups at the end of the chain. ) (PMMA-r-PS) copolymer can well graft the copolymer on the surface of a silicon substrate exhibiting a layer of natural oxide (Si / natural SiO ₂ ), and can obtain an embedded structure for nanometer structure. Block copolymers have non-preferential surface energy. The key point of this method is to obtain a graft layer so that it can act as a barrier to a specific surface energy of the substrate. The interfacial energy of this barrier with a given block of a block copolymer is equivalent for each block i ... j of the block copolymer, and is calculated by grafting the proportion of comonomers present in the copolymer To adjust. Therefore, the grafting of this statistical copolymer makes it possible to suppress the better affinity of one of the blocks of the block copolymer to the surface of the substrate, thereby preventing a better orientation of the nano-domain parallel to the surface of the substrate. The grafting reaction can be obtained by any known method (thermal, photochemical, oxidation / reduction, etc.).

Chemical epitaxy uses a comparison of the chemical affinity between the pre-drawn pattern on the substrate itself and the different blocks of the block copolymer. Therefore, a pattern showing a high affinity for only one block of the block copolymer is drawn on the surface of the underlying substrate in advance, so that the blocks of the block copolymer can be vertically oriented, and the remaining surface faces the block copolymer. The blocks did not exhibit a specific affinity. For this reason, on the one hand, a layer containing a neutral region (e.g., composed of a grafted statistical copolymer) does not exhibit a specific affinity for the blocks of the block copolymer to be deposited, and on the other hand, the A block copolymer (for example, consisting of a homopolymer grafted to one of the blocks of the block copolymer to be deposited and used as the anchoring point for this block of the block copolymer) has Areas of affinity are deposited on the surface of the substrate. The homopolymer as the anchor point can be made to have a width slightly larger than that of the block with better affinity, and in this case, the "pseudo-uniform (pseudo- equitable) "distribution. Such a layer is called "pseudo-neutral" because it may make the blocks of the block copolymer uniform or "pseudo-uniform" distribution on the substrate surface, with the result that the layer does not exhibit (in its overall nature) and Preferred affinity for one of the blocks of the block copolymer. Therefore, for this block copolymer, such a chemical epitaxial layer on the surface of the substrate is considered to be neutral.

Although the techniques just described make it possible to effectively direct the self-assembly of block copolymers in one or more specific directions, they are not sufficient to obtain a block orientation perfectly perpendicular to the substrate surface. This is because, in order to obtain this orientation perpendicular to the substrate surface across the minimum thickness, it must be able to produce a "neutral" substrate / block copolymer and block copolymer / ambient atmospheric interface, that is, block The blocks of the copolymer do not exhibit a dominant affinity for each of the different interfaces relative to each other.

In particular, when one of the blocks of a block copolymer exhibits a better affinity for a compound at an interface, the nanodomain has a tendency to be oriented parallel to the interface itself. The diagram in Figure 1 illustrates the situation where the surface energy at the upper interface between the block copolymer labeled BCP and ambient air is uncontrolled in the example, and the lower interface between the lower substrate and the block copolymer is shown in the figure. The area indicated by black in 1 (including homopolymer of one of the blocks of the block copolymer to be deposited) and the area indicated by hatching in FIG. 1 (including statistical copolymers where the block to the block copolymer is neutral) ) Shows a chemical epitaxial pattern to guide the orientation of the blocks. The chemical epitaxial surface does not exhibit a better affinity with one of the blocks of the block copolymer in its overall properties, that is, the Flory-Herkins parameters χ _{i- substrate} and χ _{j- substrate} The blocks i ... j of the block copolymer are equal. The surface of the substrate thus chemically epitaxial is then considered neutral to the block copolymer. In this case, the layer of one of the blocks i or j of the block copolymer exhibits the strongest affinity with air during the annealing process (stage labeled 1 in FIG. 1) that may make the copolymer structure (in the figure In the example of 1, it is the No. 2 block), which is self-organized at the top of the block copolymer film, that is, at the interface with air, and is oriented parallel to the interface itself. It is then impossible to obtain a nano-domain that is perfectly perpendicular to the substrate surface throughout a minimum thickness "t" that is at least equal to the period L _{0 of the} copolymer.

In order to obtain the structure of the nano-domain of the block copolymer that is perfectly perpendicular to the upper and lower interfaces, the interfacial tension between the material at the interface and the blocks of the block copolymer must be equal.

When the surface energy at the interface of the copolymer is poorly controlled, due to the imperfect perpendicularity of the nanodomain of the block copolymer during self-assembly (actually even a structure that is completely parallel to the interface) The obvious flaws of this will become obvious.

Although the neutrality of the lower interface between the block copolymer and the underlying substrate is currently well controlled, the upper interface between the block copolymer and the gaseous compound or a mixture of gaseous compounds (e.g., such as the atmosphere) is significantly less affected. control.

However, there are various methods described below to overcome this, and the surface energy at the lower interface between the block copolymer and the underlying substrate is controlled in the following three methods.

The first solution may include annealing the block copolymer in the presence of a gas mixture, so that neutral conditions with respect to each block of the block copolymer may be satisfied. However, the composition of this gas mixture seems very complicated.

The second solution consists in using block copolymers when the compound mixture at the upper interface is composed of ambient air, the constituent blocks of which exhibit the same (or very similar) surface energy to each other at the self-organizing temperature. In this case, the vertical structure of the nano-domain of the block copolymer is obtained on the one hand by the block copolymer / neutralization substrate interface, and on the other hand, by the block i of the block copolymer BCP ... j Naturally obtained with an affinity comparable to the composition at the upper interface (in this case the air in the example). Then this case is χ _{i- substrate} ~ ... ~ χ _{j- substrate} (preferably = 0) and _{γi- air} ~ ... ~ γj _{- air} . However, there are only a limited number of block copolymers with this unique feature. This is for example the case of the block copolymer PS-b-PMMA. However, the Flory-Hergins interaction parameter of the copolymer PS-b-PMMA is low, that is, 0.039 at the self-organizing temperature of the copolymer of 150 ° C, which limits the minimum nano-domain produced size.

In addition, the surface energy of a given material depends on the temperature. In fact, if the self-organizing temperature is increased, for example, when a block copolymer with a high weight or a high period is required, a large amount of energy is required to obtain the correct structure. For each block pair of the block copolymer at the upper interface The compounds can still be regarded as equivalent in terms of affinity, and the difference in surface energy of the blocks may become too great. In this case, an increase in self-organizing temperature may cause defects related to non-vertical assembly due to the difference in surface energy between the blocks of the block copolymer at the self-organizing temperature.

The envisaged final solution is described by Bates et al. In a publication entitled "Polarity-switching top coats enable orientation of sub-10nm block copolymer domains", Science, 2012, Vol. 338, pp 775–779, and In the document US 2013280497, it consists of controlling poly (trimethylsilylstyrene-b-lactide) or poly (trimethylsilylstyrene-b-lactide) by introducing an upper layer (also referred to as a "top coat") deposited on the surface of the block copolymer. Surface energy of the (styrene-b-trimethylsilylstyrene-b-styrene) type at the interface above a nanostructured block copolymer. In this document, a polar topcoat is deposited on a nanostructured block copolymer film by spin coating. The topcoat is soluble in acidic or alkaline aqueous solutions, which allows it to be applied to the top surface of water-insoluble block copolymers. In the examples, the top coating is soluble in an aqueous ammonium hydroxide solution. The topcoat system is an alternating or alternating copolymer whose composition comprises maleic anhydride. In solution, the opening of the maleic anhydride ring causes the top coat to lose ammonia. During the self-organization of the block copolymer at the annealing temperature, the ring of maleic anhydride of the top coat recloses, the top coat undergoes a transition to a less polar state and becomes neutral relative to the block copolymer , So that the nano-domain and the lower and upper interfaces are oriented vertically. The topcoat is then removed by washing in an acidic or alkaline solution.

Likewise, document US 2014238954A describes the same principle as document US 2013280497, but it is applied to block copolymers containing blocks of the silsesquioxane type.

As shown in Figure 2, this solution makes it possible to replace the upper interface between the block copolymer BCP to be organized and a gaseous compound or a mixture of gaseous compounds (such as air) with a block copolymer-topcoat interface. In the phase marked 2, a block copolymer is deposited on a surface of a pre-neutralized substrate by generating a chemical epitaxial pattern. The thickness "t" of the block copolymer BCP is deposited throughout the period L ₀ of the copolymer. Then, in stage 3, a top coat is deposited. Annealing is then performed in stage 4 to structure the block copolymer BCP nano. Finally, once the block copolymer is organized, the topcoat is removed in stage 5 in order to maintain nanostructured blocks having a nanodomain perfectly perpendicular to the substrate surface and throughout the entire thickness "t" Copolymer film. In this case, the material of the top coat exhibits equal affinity for each block i ... j of the block copolymer BCP at the considered assembly temperature (χ _i-TC = ... = χ _j-TC (Better = ~ 0)).

The comparison of Figures 1 and 2 illustrates the use of tops when block copolymers (one of which (the second block) exhibits better affinity for the ambient atmosphere (Figure 1)) are guided by chemical epitaxy. Advantages of coatings (Figure 2). It is clear that during stage 4 of nanostructured by annealing, the topcoat layer orients the nanodomains of the block copolymer perpendicular to the substrate surface throughout the entire thickness "t" of the block copolymer BCP film. "T" is at least the film thickness period of a block copolymer ( "L _0") in an amount, in order to then be able to transfer the pattern to the substrate. If a top coat is not used (as shown in Figure 1), the block copolymer film is not completely uniform in its thickness "t", that is, the perpendicularity of the nano-domain at the minimum thickness "t" is not reached, Because block 2 has a better affinity for the ambient atmosphere.

However, the use of topcoats and their design and their integration into the overall scheme of assembling block copolymers present several fundamental problems that are difficult to solve. The first difficulty is the deposition of the top coating itself. Therefore, during the deposition process, if the block copolymer previously deposited on the substrate is not to be dissolved again, the constituent material of the top coat must be dissolved in a solvent in which the block copolymer itself is insoluble. The topcoat must also be easily removable, for example by rinsing in a suitable solvent, preferably itself compatible with the standards of electronic equipment. In addition, the top coat must exhibit equal interfacial tension to the different blocks of the nanostructured block copolymer during the heat treatment. Given all these difficulties, chemical synthesis of the top coating material can be a challenge in itself. There may also be potential problems with the thermal stability of the topcoat and the density of the topcoat material, which should preferably be lower than the block copolymer. Therefore, even though there are few solutions for topcoat systems to produce block copolymers of a given chemistry, in all cases, in order to obtain patterns that are beneficial for the targeted nanolithography application, guided block copolymerization was found The process of block orientation and nano-structuring of the material is therefore complicated, which impairs the simplicity of the block copolymer for these applications.

Nonetheless, the use of a topcoat seems to be a priori requirement for the nanodomain of the block copolymer to be oriented perpendicular to the substrate. When the block copolymer in question is guided by techniques such as mapping epitaxy or chemical epitaxy This is even more the case with time lapses, otherwise the effort to create a pattern on the substrate to guide the block copolymer will be meaningless.

The different methods described above for controlling the surface energy at the interface above the block copolymer deposited on the substrate whose surface is neutralized in advance are still too cumbersome and difficult to implement as a whole, and cannot significantly reduce copolymerization with the block Defect rate related to the imperfect perpendicularity of the pattern of the object. In addition, the solutions envisaged seemed too complex to be compatible with industrial applications.

Coexisting with these different technical problems, the manufacture of block copolymer BCP films with acceptable defect content (due to poor verticality or grain boundaries, etc.) for applications in the electronics field is another type of problem in controlling the film and substrate. "Wetting" and / or adhesion properties of the wood. This is because TP Russell et al. In the paper Macromolecules, 2017, 50 (12), 4597-4609; M. Geoghegan et al. , Prog. Polym. Sci., 2003, 28, 261-302; PG de Gennes, Rev. Many studies have been reported in Mod. Phys., 1985, 57, 827-863, which have shown, for example, the quality (homogeneity, continuity) of any material (such as polymer) films deposited on a given substrate Depends on different parameters inside the material / substrate system under consideration. These parameters include, inter alia, the surface energy and interfacial tension of each component of the system, temperature, film thickness, or the nature of these components (solid, liquid, molecular composition, etc.). Generally, it is therefore widely accepted that substrates that exhibit low surface energy are difficult to "wet" / adhere. Therefore, polymer films on this type of substrate will tend to have very uneven thicknesses when the polymer remains free to change after deposition (e.g., heat above the glass transition temperature of the polymer) This is especially true during heating. Similarly, the thinner the polymer film deposited, that is, at least one time the molecular radius of the molecular chain of the polymer under consideration, it will tend to be unstable or metastable. This is especially true when the energy is different from the surface energy of the polymer and when the system can be changed freely. Finally, the instability of a polymer film deposited on a substrate generally increases as the "annealing temperature / annealing time" pair increases.

Same as block copolymer BCP / substrate interface, when using a "top coat" type layer, the same type of dewetting phenomena appear at the upper interface, especially when this upper layer is in liquid form . This is because capillary wave amplification of the topcoat film and its interaction with the underlying film of the block copolymer BCP due to hydrodynamic phenomena (see, for example, Langmuir, 1993, 9 by F. Brochart-Wyart et al.) 3682-3690), this type of stack has a particularly unstable tendency and leads to the introduction of severe defects in the form of discontinuous block copolymer BCP films, making them unsuitable for use in, for example, electronic devices.

In fact, for the purposes of electronic applications, or for another area of continuous block copolymer BCP films that require a minimum surface area across the substrate (the block copolymer is deposited along a minimum thickness "t"), these different points In the face of a dedicated block copolymer BCP system, when block copolymer BCP films are deposited on a functionalized substrate, in order to reduce possible assembly defects, it becomes dangerous to combine high temperature annealing. Therefore, for all blocks, The interface energy of the blocks is in equilibrium with the interface energy of the solid surface (in other words, each block of the BCP "sees" that the surface energy of the substrate is different from itself). For example, dewetting phenomena such as block copolymers of PS-b-PMMA have been reported (RA Farrell et al., ACS Nano, 2011, 5, 1073-1085), and the PS and PMMA blocks show relatively high surface energy. In fact, films based on these block copolymers should be more stable in dewetting than films based on block copolymers whose blocks exhibit lower surface energy.

Therefore, in the case of using a block copolymer such as a film BCP (for example, as a lithography resist), it is necessary not only to be able to control the affinity of the upper interface in order to ensure the perpendicularity of the pattern with respect to the substrate, but also to ensure the The film of the block copolymer BCP does cover all surfaces of the substrate under consideration without surface dewetting, and it is also necessary to ensure that when using this top layer of the topcoat type, the deposited block copolymer BCP film and The top coatings do not dewet at all.

[technical problem]

It is therefore an object of the present invention to overcome at least one disadvantage of the prior art. The purpose of the present invention is in particular to provide a simple alternative solution that can be industrially performed to control the orientation of the nano-domain of any block copolymer such that the nano-domain is oriented perpendicular to the substrate and the upper interface itself over the minimum thickness "t", the minimum thickness "t" L ₀ at least equal to half period of the block copolymer, which is carried out without the use of a particular type neutral layer of the top coat.

Another object of the present invention is to stabilize the block copolymer film deposited on a pre-neutralized substrate (with regard to possible wetting phenomenon of the substrate).

[Invention Brief]

For this reason, the subject of the present invention is a method for controlling the orientation of the nano-domain of a block copolymer. The lower interface of the block copolymer is in contact with the surface of a substrate that is neutralized in advance. Structured to provide a nano-domain with a predetermined period throughout a minimum thickness that is at least equal to half of the period, the method is characterized in that it includes depositing the block copolymer on the substrate such that The thickness is at least two times greater than the minimum thickness, and preferably at least three times greater than the minimum thickness.

Therefore, the excess thickness (whose deposition is greater than the minimum thickness) can make up for a better affinity of one of the blocks of the block copolymer to the components of the upper interface (eg, air). In addition, this considerable excess thickness also makes it possible to stabilize the possible dewetting of the deposited block copolymer BCP film against neutralized substrates. Therefore, the extra thickness makes it possible to allow, for example, higher annealing temperature / assembly time pairs, or to slow down the kinetics of dewetting or eliminate them completely.

Other optional characteristics according to the method of controlling the nano-domain orientation of the block copolymer:
-Select the minimum thickness in a way that is equal to an integer or semi-integral multiple of the period (L ₀ ) (to structure the block copolymer throughout the minimum thickness itself); the multiple is less than or equal to 15 and preferably less than Or equal to 10;
-The stage after the block copolymer deposition includes self-organizing the block copolymer so that it is structured over at least the minimum thickness nanometer;
-The self-organization of the block copolymer may be performed by any suitable technique or combination of appropriate techniques known to those skilled in the art, and the preferred technique is heat treatment;
-Contacting the upper interface of the block copolymer with a compound or mixture of compounds of a defined molecular composition in gaseous form at the tissue temperature of the block copolymer;
-The compound or mixture of compounds exhibits a specific affinity for at least one block of the block copolymer;
-The compound or mixture of compounds at the upper interface is neutral for each block of the block copolymer BCP;
-The substrate contains or does not contain a pattern, which is pre-drawn by a lithography stage of any nature or a series of lithography stages prior to the deposition phase of the block copolymer film. The epitaxial technique, or a combination of these two techniques, directs the structure of the block copolymer to obtain a neutralized surface.

Another object of the present invention is a method for manufacturing a nanolithography resist starting from a block copolymer. The lower interface of the block copolymer is in contact with the surface of the underlying substrate beforehand. The method includes controlling as described above. A stage of the method for orienting the nano-domain of a block copolymer, and is characterized in that after the nano-structuring of the block copolymer, the excess thickness of the block copolymer is removed to leave the A nanostructured block copolymer film that is perpendicular to the substrate, and then at least one block of the block copolymer film is removed to form a porous film that can be used as a nanolithography resist.

Other optional features based on the manufacturing method of the resist:
-The removal stage of excess thickness is performed by chemical mechanical polishing, solvent, ion impact or plasma type treatment or by any combination of these treatments sequentially or simultaneously;
-Removal of excess thickness is performed by plasma dry etching;
-The removal stage of one or more blocks of the block copolymer film is performed by dry etching;
-The stages of removing excess thickness and removing one or more blocks of the block copolymer film are performed continuously in the same etching machine by plasma etching;
-The block copolymer can be fully or partially subjected to a crosslinking / curing stage before the stage of removing the excess thickness;
-The cross-linking / curing stage is by exposing the block copolymer to light radiation of a defined wavelength selected from ultraviolet radiation, ultraviolet / visible radiation or infrared radiation, and / or electronic radiation, and / or chemical treatment, And / or atomic or ion impact.

Finally, the subject matter of the present invention is a nanolithographic resist obtained according to the method described above.

[Detailed invention]

The term "polymer" is known to mean (statistical, gradient, block or alternating) copolymers or homopolymers.

The term "monomer" is used in relation to molecules that can be polymerized.

The term "polymerization" is used in relation to a method of converting a monomer or a mixture of monomers into a polymer.

The term "copolymer" is known to refer to a polymer that combines several different monomer units together.

The term "statistic copolymer" is known to mean a copolymer in which the distribution of monomer units along a chain follows a statistical law, such as Bernoulli (zero-order Markov) or a first-order or Second-order Markov type. When repeating units are randomly distributed along the chain, the polymer is formed by the Bernoulli method and is called a random copolymer. The term "random copolymer" is often used even when the statistical methods prevalent during copolymer synthesis are unclear.

The term "gradient copolymer" is known to mean a copolymer in which the distribution of monomer units gradually changes along the chain.

The term "alternating copolymer" is known to mean a copolymer comprising at least two monomeric entities that are alternately distributed along the chain.

The term "block copolymer" is known to mean a polymer comprising one or more uninterrupted sequences of each individual polymer entity, the polymer sequences being chemically different from one another and via chemistry (covalent, ionic, hydrogen or (Position) bonds to each other. These polymer sequences are also called polymer blocks. These blocks exhibit phase separation parameters (Flory-Herkins interaction parameters) such that if the degree of polymerization of each block is greater than a critical value, they are immiscible with each other and separate into nanodomains.

It is known that the above term "miscibility" refers to the ability of two or more compounds to be completely mixed to form a homogeneous or "pseudo-homogeneous" phase, that is, there are no obvious short-range or long-range crystals or Quasicrystal symmetrical phase. When the sum of the glass transition temperature (Tg) of the mixture is exactly smaller than the sum of the Tg values of the isolated compounds, the miscibility of the mixture can be determined.

In the description, reference is made to both "self-assembly" and "self-organization" or "nanostructured" to describe the known phenomenon of phase separation of block copolymers, also called the annealing temperature at the assembly temperature.

It is known that the term "period of a block copolymer" (denoted as L ₀ ) means the minimum distance between two adjacent domains having the same chemical composition separated by domains having different chemical compositions.

It is known that the minimum thickness "t" indicates the thickness of the block copolymer film used as a nanolithography resist, and below this thickness, it is no longer possible to transfer the pattern of the block copolymer film to the underlying substrate. Generally, for a block copolymer with a high phase separation parameter χ, this minimum thickness "t" is at least equal to half the period L ₀ of the block copolymer.

The term "porous membrane" means a block copolymer film in which one or more nano-domains have been removed (leaving pores), the shape of the pores corresponds to the shape of the removed nano-domains, and it can be spherical, Cylindrical, layered or spiral.

A "neutral" or "pseudoneutral" surface is known to mean a surface that does not exhibit a better affinity for one of the blocks of the block copolymer in its overall properties. As a result, the blocks of the block copolymer can be made equitable or "pseudo-equitable" on the surface.

The neutralization of the substrate surface makes it possible to obtain such a "neutral" or "pseudo-neutral" surface.

When the surface energy of a reference material and the block copolymer of a given block copolymer, or more specifically the interfacial tension, are compared at a given temperature, and more specifically at a temperature at which the block copolymer can self-organize Compare below.

The term "lower interface" of a nanostructured block copolymer is known to mean the interface that is in contact with the underlying substrate on which the block copolymer is deposited. It should be noted that this lower interface is neutralized throughout the subsequent description, that is, its overall properties do not show a better affinity for one of the blocks of the block copolymer.

The term "upper interface" or "upper surface" of block copolymers known to be nanostructured refers to contact with a compound or mixture of compounds of defined molecules that are gaseous at the self-organizing temperature of the nanodomain. interface. In the examples described later in this specification, the mixture of the compounds is composed of ambient air, but the present invention is by no means limited to this case. Therefore, the gaseous compound at the upper interface can also be a controlled atmosphere.

Regarding the nano-structured block copolymer film (referred to as BCP in the subsequent description), it contains "n" blocks, where n is any integer greater than or equal to two. The block copolymer BCP is more specifically defined by the following formula:

Where A, B, C, D, ..., Z are pure or pure entities representing blocks or statistics or random or gradient or alternating copolymers (that is, each block is a group of The monomers of the same chemical nature are polymerized together, or a group of comonomers are copolymerized together) block "i" ... "j".

Therefore, the blocks "i" ... "j" of the block copolymer BCP to be nanostructured can be written in the following form: i = a _i -co-b _i -co -...- co- z _i , where all or part of i ≠ ... ≠ j.

In each block of the block copolymer BCP i ... j, as the monomer units of the entities of a _i ... z _i is the volume fraction may be between 1-99%.

The volume fraction of each block i ... j may be between 5% and 95% of the block copolymer BCP.

Volume fraction is defined as the volume of the entity relative to the volume of the block, or the volume of the block relative to the volume of the block copolymer.

The volume fraction of each block of the copolymer or each block of the block copolymer was measured in the manner described below. In a copolymer in which at least one entity or one block (if related to a block copolymer) contains several comonomers, the mole fraction of each monomer in the entire copolymer can be measured by proton NMR, and then by The molar mass of each monomer unit was used to work back the mass fraction. In order to obtain the mass fraction of each entity of each block or block of the copolymer, it is sufficient to increase the mass fraction of the constituent comonomer of the entity or block. The volume fraction of each entity or block can then be determined from the mass fraction of each entity or block and from the density of the polymer forming the entity or block. However, it is often not possible to obtain the density of a polymer whose monomers are copolymerized. In this case, the volume fraction of the entity or block is determined from its mass fraction and from the density of the compound that accounts for the majority of the weight in the entity or block.

The block copolymer BCP may have a molecular weight of 1,000 to 500,000 g.mol ^-1 .

Block copolymers BCP can exhibit any type of structure: linear, star-branched (three-armed or multi-armed), grafted, dendritic, or comb-shaped.

Regarding the method for controlling the nano-domain orientation of the block copolymer BCP, it is itself deposited on the underlying substrate (the surface of the substrate has been previously neutralized). The principle of the present invention is to use the block copolymer BCP A better affinity for the gaseous material (air) at the upper interface is combined with the high thickness of the block copolymer BCP, so as to effectively screen out this better affinity from the lower part of the block copolymer film and stabilize the embedding Possible dewetting of the segmented copolymer film to the substrate in order to orient the nanodomains of the block copolymer in the desired direction during the nanostructured phase of the block copolymer BCP over a minimum thickness (t) .

The underlying substrate may be a solid of inorganic, organic or metallic nature. In a specific example, it can be made of silicon. Its surface is pre-neutralized. To this end, the substrate includes or does not include a pattern, which is pre-drawn by a lithography stage of any nature or a series of lithography stages before the deposition phase of the block copolymer BCP film, the pattern is intended to The technique of epitaxy or patterning epitaxy, or a combination of these two techniques, guides the organization of the block copolymer BCP to obtain a neutralized surface.

The block copolymer is capable of structuring its own nanometers into a nanometer domain with a period (L ₀ ) throughout a minimum thickness (t), which is at least equal to half of the period (L ₀ ).

In order to neutralize the upper interface, the block copolymer is advantageously deposited on the substrate with a total thickness (T + t), the total thickness (T + t) representing the sum of the minimum thickness (t) and the excess thickness (T), It is at least twice larger than this minimum thickness (t).

More preferably, this total thickness (T + t) is at least three times greater than the minimum thickness (t).

The minimum thickness (t) represents the thickness through which the block copolymer must be nanostructured in order to be able to subsequently etch the pattern in the underlying substrate by means of the nanostructured block copolymer. Segment copolymers are used as nanolithographic resists. For copolymers with high phase separation parameters, this minimum thickness (t) is at least equal to half the nanostructured period (L ₀ ) of the block copolymer.

Figure 3 illustrates stage 6 of depositing a block copolymer BCP on a pre-neutralized substrate surface by chemical epitaxy. The block copolymer BCP is advantageously deposited throughout the total thickness (T + t). Then, the excess thickness “T” of the block copolymer BCP makes it possible to screen and protect the minimum thickness “t” of the block copolymer BCP from one of the blocks of the block copolymer (in FIG. 3 The better affinity effect of block 2 in the example). Therefore, the air in contact with the upper surface of the block copolymer BCP will not affect the deep-layer copolymer, especially the minimum thickness "t" throughout. Therefore, the method of controlling the nano-domain orientation of the block copolymer according to the present invention is universal and applicable to any block copolymer chemical system.

Selecting a minimum total thickness (T + t) of a block copolymer BCP, such that: (T + t) ≥ 2t , preferably (T + t) ≥ 3t, where "t" is equal to at least half of the L _0.

In addition, the present invention is not limited to obtaining the minimum thickness "t" of a half of the period L ₀ . This is because the minimum thickness can be advantageously selected such that it is equal to an integer multiple or a half integer multiple of the period (L ₀ ), which multiple is less than or equal to 15, and preferably less than or equal to 10. Therefore, if it is desired to spread the nanoscale domain of the block copolymer perpendicular to the lower interface and the upper interface with a minimum thickness "t" equal to 2L ₀ , it is recommended that the total thickness (T + t) be at least 4L ₀ to 6L ₀ (= 2t to 3t) block copolymer. Similarly, if it is desired that the structure, for example, span the nano-domain of block copolymers with a minimum thickness "t" equal to 3L ₀ perpendicular to the lower and upper interfaces, it is recommended that the total thickness (T + t) be at least 6L ₀ to 9L ₀ (= 2t to 3t) block copolymer.

Block copolymers can be deposited according to techniques known to those skilled in the art, such as, for example, spin coating, doctor blade, knife system, or slot die system technology. To this end, the block copolymer BCP is previously mixed in a solvent.

The stage subsequent to the deposition of the block copolymer BCP consists in self-organizing the block copolymer BCP, structuring it over at least the minimum thickness "t" itself. To this end, the self-organization of the block copolymer can be performed by any suitable technique or a combination of appropriate techniques known to those skilled in the art. Preferably, it is performed by subjecting a stack comprising a substrate (whose surface has been previously neutralized) and a block copolymer to a heat treatment. The block copolymer is then self-structured under the action of heat treatment, and the obtained nano-domains are oriented perpendicular to the surface of the substrate itself over at least the minimum thickness "t".

Regarding the method for manufacturing nanolithography resist, when the block copolymer BCP is nanostructured and its pattern is oriented perpendicular to the substrate surface over at least the minimum thickness "t", it is recommended to remove the excess thickness "T "(Stage 7 of Fig. 3) to obtain a nanostructured block copolymer BCP film. The film is intended to act as a resist in subsequent nanolithographic processes to transfer its pattern to the underlying substrate.

To this end, the excess thickness "T" of the block copolymer can be removed by chemical mechanical polishing (CMP), solvent, ion impact, or plasma processing, or by any combination of these processing sequentially or simultaneously.

Preferably, the removal of the excess thickness "T" of the block copolymer is performed, for example, by dry etching (such as plasma etching), wherein the chemical nature of the gas used is selected so that it does not affect the block copolymer. A given block of BCP exhibits specific selectivity. Therefore, etching is performed at the same rate for all blocks of the block copolymer BCP. Therefore, the etching of the excess thickness "T" is performed until the previously selected minimum thickness "t" of the block copolymer BCP remains on the substrate.

In one example, the block copolymer is, for example, deposited over a total thickness (T + t) of at least greater than 50 nm, and the excess thickness "T" is removed to retain a minimum thickness "t" of less than 45 nm, preferably less than 40 nm. For example, this may be a block copolymer with a period L ₀ equal to 20 nm, and for example, it is desirable that the minimum thickness “t” is equal to L ₀ or up to 2 L ₀ .

Before removing the excess thickness T, the block copolymer may be fully or partially subjected to a crosslinking / curing stage.

The cross-linking / curing stage may be performed by exposing the block copolymer BCP to a defined wavelength of optical radiation selected from ultraviolet radiation, ultraviolet / visible radiation or infrared radiation, and / or electronic radiation, and / or chemical treatment, and / Or atomic or ion impact.

After removing this excess thickness T, a nano-structured block copolymer BCP film with a thickness "t" is then obtained, the nano-domain of which is oriented perpendicular to the surface of the underlying substrate, as shown in Fig. 3. Then, after removing at least one of its blocks to leave a porous film, this block copolymer film can be used as a resist, so that its pattern can be transferred to the underlying substrate by the nanolithography method.

The removal of one or more blocks of the block copolymer film can be performed by any known method, such as wet etching (using a solvent capable of dissolving the block to be removed while retaining other blocks) or dry etching .

When wet etching is selected, all or part of the block copolymer film may be stimulated before removing one or more blocks of the remaining block copolymer film. This stimulus can be generated, for example, by exposure to UV-visible radiation, electron beams, or liquids having, for example, acid / base or oxidation / reduction properties. This stimulation can then induce chemical modification on all or part of the block copolymer BCP by cleaving the polymer chain, forming an ionic entity, and the like. This modification then helps to dissolve one or more blocks of the copolymer to be removed in a solvent or solvent mixture, where the other blocks of the copolymer BCP are insoluble before or after exposure to the stimulus .

In one example, if the block copolymer to be used as a resist is a PS-b-PMMA block copolymer, then the PMMA polymer can be cleaved by exposing the block copolymer film to the stimulation of UV radiation Chain, while bringing about cross-linking of PS polymer chains. In this case, the PMMA pattern of the block copolymer can be removed by dissolving in a solvent or solvent mixture selected wisely by those skilled in the art.

For example, another method of removing one or more blocks of a block copolymer film consists in using dry etching, such as plasma etching. This plasma etching is preferred because it can be performed in the same machine as the stage of removing the excess thickness "T"; only the chemical properties of the constituent gases of the plasma must be changed in order to selectively remove Remove blocks and keep other blocks.

Similarly, another advantage of this plasma etching is that the excess thickness "T" is removed, the blocks of the block copolymer film are removed, and then the pattern of the block copolymer film is transferred into the underlying substrate, which can be performed on the same etching machine. In progress. In this case, depending on the material to be removed, only the chemical nature of the plasma gas needs to be changed or not required.

In order to simplify the description, the atmosphere is only described as a constituent compound of the upper interface. However, many gaseous compounds or mixtures of compounds exist at the tissue temperature of the block copolymer capable of constituting such an interface.

Other salient features and advantages of the present invention will become apparent by reading the description given by way of illustrative and non-limiting example with reference to the accompanying drawing, which shows:

‧ Figure 1 has described a cross-sectional view of a block copolymer when the surface energy of the upper interface is uncontrolled. The block copolymer is deposited on a substrate whose surface is before the annealing stage required for its self-assembly and It is then neutralized by generating a chemical epitaxial pattern,

‧ Figure 2 has described the cross-sectional view of the block copolymer when the block copolymer is covered with a specific upper layer and surface neutralized before the annealing stage. The block copolymer is deposited on the substrate and its surface is Its self-assembly is neutralized before and after the annealing stage by generating chemical epitaxial patterns,

‧ Fig. 3 is a cross-sectional view of a block copolymer at different stages including the method for controlling the nano-domain orientation of a block copolymer according to the present invention, which allows the block copolymer to be structured in its own nanometer, so that Its nano-domain is oriented perpendicular to the surface of the substrate over the minimum thickness "t".

Claims (13)

A method for controlling the surface energy of the upper interface of a block copolymer (BCP). The lower interface of the block copolymer is in contact with the surface of a pre-neutralized substrate. The block copolymer can be nanostructured by itself to Providing a nano-domain with a predetermined period (L ₀ ) throughout the minimum thickness (t), the minimum thickness (t) being at least equal to half of the period (L ₀ ), the method is characterized in that it includes the block copolymer (BCP) is deposited on the substrate such that its total thickness (T + t) is at least two times greater than the minimum thickness (t), and preferably at least three times greater. The minimum thickness is selected to be equal to the period (L ₀ ) is an integer multiple or a half integer multiple, the multiple is greater than or equal to 0.5 and less than or equal to 15, and more preferably less than or equal to 10. A method as claimed in claim 1, wherein the stage subsequent to depositing the block copolymer (BCP) comprises performing self-organization of the block copolymer (BCP) to structure the nanostructures over at least the minimum thickness (t). A method as claimed in claim 1 or 2, wherein the upper interface of the block copolymer is in contact with a compound or mixture of compounds of a defined molecular composition which is a gaseous form at the temperature of the block copolymer structure. The method of claim 3, wherein the compound or a mixture of compounds exhibits a specific affinity for at least one block of the block copolymer (BCP). The method of claim 3, wherein the compound or a mixture of compounds at the upper interface is neutral to each block of the block copolymer (BCP). The method of claim 1 or 2, wherein the substrate includes or does not include a pattern, and the pattern is pre-drawn by a lithography stage or a series of lithography stages before the deposition stage of the block copolymer (BCP) film The pattern is intended to guide the organization of the block copolymer (BCP) by a technique called chemical epitaxy or graphoepitaxy or a combination of these two techniques to achieve neutralization surface. A method for making nanolithography resist from a block copolymer (BCP), the lower interface of the block copolymer being in contact with the surface of a pre-neutralized lower substrate, the method comprising as in claims 1 to 6 A stage of a method for controlling the nanodomain orientation of a block copolymer (BCP), characterized in that after the nanostructure of the block copolymer (BCP) is structured, the excess of the block copolymer is removed Thickness (T) to leave a nanostructured block copolymer film perpendicular to the substrate throughout the minimum thickness (t), and then remove at least one block of the block copolymer film to A porous film capable of being used as a nanolithography resist is formed. The method of claim 7, wherein the excess thickness is performed by chemical mechanical polishing (CMP), solvent, ion impact, or plasma type processing, or by any combination of these processing sequentially or simultaneously (T ) 'S removal phase. The method of claim 7 or 8, wherein the removal of the excess thickness (T) is performed by plasma dry etching. The method of claim 7 or 8, wherein the removal stage of one or more blocks of the block copolymer film is performed by dry etching. The method of claim 7 or 8, wherein the stages of removing the excess thickness (T) and removing one or more blocks of the block copolymer film are continuously performed in the same etching machine by plasma etching . The method as claimed in claim 7 or 8, wherein the block copolymer (BCP) can be completely or partially subjected to a crosslinking / curing stage before the stage of removing the excess thickness (T). The method of claim 12, wherein the crosslinking / curing stage is by exposing the block copolymer (BCP) to light radiation of a defined wavelength selected from ultraviolet radiation, ultraviolet / visible radiation, or infrared radiation, and / Or by electronic radiation, and / or chemical treatment, and / or atomic or ion impact.