Method for making patterns on the surface of a substrate using block copolymers

Abstract

A method for making patterns on the surface of a substrate by graphoepitaxy, includes depositing a layer of resin on the surface of the substrate; making patterns in the resin on the surface of a substrate; curing the patterns in the resin by producing a layer of amorphous carbon on the surface of the patterns in the resin; depositing a layer of statistical copolymer after curing the patterns in the resin; grafting the layer of statistical copolymer onto the patterns in the resin by annealing; and depositing a layer of a block copolymer into the spaces defined by the patterns in the resin after curing the patterns and the grafting of the layer of statistical copolymer.

Claims

1. Method for making patterns on the surface of a substrate by graphoepitaxy comprising: depositing a layer of resin on the surface of the substrate; making patterns in the resin on the surface of the substrate; producing a layer of amorphous carbon on the surface of the patterns in the resin; depositing a layer of random copolymer after producing the layer of amorphous carbon on the surface of the patterns in the resin; grafting the layer of random copolymer onto the patterns in the resin, between the patterns in the resin and onto sides of the patterns in the resin, by annealing; depositing a layer of block copolymer into spaces defined by the patterns in the resin after the grafting.

2. Method according to claim 1, wherein the patterns in the resin are cured by treating the patterns in the resin by a gaseous plasma.

3. Method according to claim 2, wherein the gaseous plasma is a HBr plasma.

4. Method according to claim 1, wherein the patterns in the resin are cured by bombarding the patterns in the resin with ions.

5. Method according to claim 4, wherein the ions are helium or argon ions.

6. Method according to claim 1, wherein the patterns in the resin are formed by optical lithography of the layer of resin.

7. Method according to claim 1, further comprising depositing an antireflective layer on the surface of the substrate.

8. Method according to claim 1 further comprising, following the depositing of the layer of block copolymer, reorganising the layer of block copolymer by annealing.

9. Method according to claim 8, further comprising, following the reorganising, eliminating one of the phases of the layer of reorganised block copolymer.

10. Method according to claim 1 wherein the random copolymer is composed of the same monomers as those which compose the block copolymer.

11. Method according to claim 1 wherein the block copolymer is a lamellar block copolymer.

12. Method according to claim 1, wherein the block copolymer is a cylindrical block copolymer.

13. Method according to claim 1, wherein the layer of random copolymer is grafted onto a top of the patterns in the resin.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) Other characteristics and advantages of the invention will become clearer on reading the detailed description that follows, with reference to the appended figures, which illustrate:

(2) FIGS. 1 to 10, a method according to a first embodiment of carrying out the invention.

(3) For greater clarity, identical or similar elements are marked by identical reference signs in all of the figures.

DETAILED DESCRIPTION OF AT LEAST ONE EMBODIMENT

(4) A method for making a pattern on the surface of a substrate 1 by graphoepitaxy according to an embodiment of realising the invention will now be described with reference to the figures.

(5) The method firstly comprises a step 101 of depositing an antireflective layer 2 on the surface of the substrate 1. This antireflective layer 2 is preferably deposited by spin coating. This antireflective layer 2 is for example a BARC (Bottom Anti-Reflective Coating) layer, a DARC (Dielectric Anti-Reflective Coating) layer, a SiARC (Silicon layer containing an Anti-Reflective Coating) layer, or a stack of the latter layers. After the deposition, the layer is annealed in order to cross link it.

(6) The method comprises a step 102 of depositing a layer of resin 3 on the surface of the antireflective layer 2. This layer of resin 3 is also deposited by spin coating.

(7) The method then comprises a step 103 of lithography of the layer of resin 3 so as to make patterns in the resin 4.

(8) The method then comprises a step 104 of curing the patterns in the resin 4 by producing a layer of amorphous carbon 5 on the surface of the patterns in the resin 4.

(9) According to a first embodiment, this step 104 of curing the patterns in the resin 4 by producing a layer of amorphous carbon 5 on the surface of the patterns in the resin may be carried out by placing the patterns in the resin 4 in a plasma etching. This plasma is preferably a HBr (hydrobromic acid) plasma. This step of etching patterns in the resin by HBr plasma is preferably carried out under a pressure comprised between 1-100 mT and a temperature comprised between 40 C. and 100 C. The flow rate of HBr gas bombarded on the patterns in the resin is preferably comprised between 50 and 500 sccm (1 sccm=1 cm.sup.3/min). The etching device used preferably has a power comprised between 100 and 1500 W. The plasma is formed for a duration typically comprised between 30 and 100 seconds, for example 60 seconds. Those skilled in the art will know how to adapt these conditions to obtain a layer of graphite of sufficient thickness typically comprised between 1 and 5 nanometres.

(10) According to a second embodiment, this step 104 of curing the patterns in the resin 4 by producing a layer of amorphous carbon 5 on the surface of the patterns in the resin may be carried out by bombarding helium or argon ions onto the patterns in the resin 4. In this case, the patterns in the resin 4 are subjected to ion implantation treatments using ionic species such as He or Ar, with an energy between 1 and 5 eV, and for vacuums of the order of 5 e-7 to 5 e-6 torr. The implanted dose will be adapted by those skilled in the art, using available simulation software (for example SRIM software), to obtain an implantation profile enabling a layer of graphite of the required thickness to be obtained on the surface.

(11) In both cases, this step of curing the patterns in the resin by producing a layer of amorphous carbon on the surface of the patterns in the resin 4 enables the patterns in the resin 4 to resist both the solvents used for the deposition by spin coating and to annealings going up to 350 C. Furthermore, during this step, amorphous carbon is produced on the surface of the patterns in the resin, but also at the surface of the antireflective layer 2, and more generally on the surface of any layer made of organic material, which makes it possible to solidify these layers, but also to favour the subsequent grafting of a layer of random copolymer, as will be seen hereafter.

(12) The method then comprises a step of grafting 105 a layer of random copolymer 6.

(13) In the present case, this layer of random copolymer 6 is a layer of PS-r-PMMA which comprises 70% by volume of PS, or polystyrene, and 30% of PMMA, polymethylmethacrylate.

(14) This layer of random copolymer 6 is firstly spread by spin coating by diluting the random copolymer in a suitable solvent, toluene for example. More precisely, preferably 1.5% by weight of PS-r-PMMA is mixed in toluene.

(15) The layer of random copolymer 6 is then thermally grafted by annealing, in the present case at 180 C. for 48 hours under inert atmosphere.

(16) The sample is then rinsed in toluene.

(17) A monolayer of random copolymer 6 is thereby grafted onto the hardened resin, without the step of grafting of this monolayer having damaged the patterns in the resin.

(18) Furthermore, the grafting of the layer of random copolymer is favoured by the presence of the layer of amorphous carbon.

(19) Thus, in the present case, the monolayer of random copolymer 6 is grafted not only onto the sides 7 of the patterns in the resin 4, but also onto the antireflective layer 2, between two successive patterns in the resin 4 and onto the patterns in the resin 4.

(20) This layer of random copolymer 6 makes it possible to neutralise the surfaces on which it is deposited so as to favour the perpendicular arrangement of the domains that will be produced thereafter.

(21) The method then comprises a step 106 of depositing a block copolymer 9 into the spaces defined by the patterns in the resin 4 as well as on the patterns in the resin 4. The block copolymer 9 is preferably composed of the same monomers as the random copolymer that has been deposited previously.

(22) In the present case, the block copolymer 9 used is a lamellar PS-b-PMMA block copolymer containing respectively 50% by volume of polystyrene PS and 50% by volume of polymethylmethacrylate or PMMA.

(23) This block copolymer 9 is spread out by spin coating, using for example a 1.5% solution by weight of block copolymer diluted in toluene. The block copolymer is heated to 240 C. for 10 minutes. The block copolymer then reorganises itself, particularly as a function of the ratio between the polystyrene monomer and the polymethylmethacrylate monomer. Thus, strips of polystyrene and strips of polymethylmethacrylate are obtained. It will be noted that the block copolymer reorganises itself as much in the spaces between the patterns of resin 4 as on the patterns of resin 4.

(24) The method then comprises a step 107 of eliminating one of the phases of the layer of reorganised block copolymer 10, here the polymethylmethacrylate phase. To do so, the layer of reorganised block copolymer 10 is immersed in 99% concentrated acetic acid for 10 minutes.

(25) Polystyrene patterns are thereby obtained, represented in FIG. 9, of very high resolution since the resolution of the patterns obtained is of the same order of magnitude as the length of the chains of monomers of the block copolymer used. The patterns thereby obtained are then used to etch the substrate through openings left between the patterns; at the level of openings situated above the patterns in the resin, these openings emerge into the resin and the substrate is thus not etched at this level (i.e. above the patterns in the resin). The reorganised block copolymer and the resin are then eliminated to only conserve the etched substrate at the level of the spaces between the plots of resin.

(26) Furthermore, the orientation of these patterns depends on the layer of random copolymer 30 and on the place where this layer has been deposited. Thus, in FIG. 9, patterns that extend transversally between two patterns of resin have been obtained, because the layer of random copolymer had also been deposited on the sides of the patterns in the resin.

(27) Instead of obtaining strips thanks to the block copolymer, as represented in FIG. 9, other patterns could be obtained. Thus, if during the step 106 of depositing a block copolymer, a cylindrical PS-b-PMMA block copolymer containing respectively 70% by volume of polystyrene PS and 30% by volume of polymethylmethacrylate or PMMA is used instead of lamellar copolymer, one obtains following step 107 cylinders perpendicular to the substrate, as represented in FIG. 10. In this case, a regular arrangement of cylinders is obtained over the whole surface of the substrate. Once the etching of the substrate through the spaces between the cylinders has been carried out, a regular arrangement of holes is obtained in the substrate. It should be noted here that the absence of random copolymer over the whole surface (particularly on the patterns in the resin or on the sides) would lead to a break in the regular arrangement at the level of the sides of the patterns in the resin so that, after etching, a regular arrangement would be obtained in the zones between each resin pattern but not from one zone to another: the presence of random copolymer over the whole surface made possible thanks to the prior production of a layer of amorphous carbon is thus advantageous to obtain a regular arrangement of patterns transferred by etching into the substrate.

(28) Naturally, the invention is not limited to the embodiments described with reference to the figures and variants could be envisaged without going beyond the scope of the invention. Thus, the invention is not limited to the block copolymers given by way of example, or to the cited random copolymers.