Method for Manufacturing Pillar or Hole Structures in a Layer of a Semiconductor Device, and Associated Semiconductor Structure

Abstract

The present disclosure relates to a method for manufacturing pillar or hole structures in a layer of semiconductor device, and associated semiconductor structure. At least one embodiment relates to a method for manufacturing pillar structures in a layer of a semiconductor device. The pillar structures are arranged at positions forming a hexagonal matrix configuration. The method includes embedding alignment pillar structures in a backfill brush polymer layer. The method also includes providing a BCP layer on a substantially planar surface defined by an upper surface of the alignment pillar structures and the backfill brush polymer layer. Further, the method includes inducing polymer microphase separation of the BCP polymer layer into pillar structures of a first component of the BCP polymer layer embedded in a second component of the BCP polymer layer.

Claims

1. A method for manufacturing pillar structures in a layer of a semiconductor device, wherein the pillar structures are arranged at positions forming a hexagonal matrix configuration, and wherein the method comprises: embedding alignment pillar structures in a backfill brush polymer layer, wherein the backfill brush polymer layer has a thickness that is about equal to a height of the alignment pillar structures, and wherein the alignment pillar structures are at positions corresponding to a subset of the positions forming the hexagonal matrix configuration; providing a BCP layer on a substantially planar surface defined by an upper surface of the alignment pillar structures and the backfill brush polymer layer; and inducing polymer microphase separation of the BCP polymer layer into pillar structures of a first component of the BCP polymer layer embedded in a second component of the BCP polymer layer, wherein the pillar structures of the first component are arranged at positions forming the hexagonal matrix configuration, such that a pillar structure of a first component of the BCP polymer layer is formed on each of the alignment pillar structures.

2. The method according to claim 1, wherein the alignment pillar structures are cross-linked polymer layer pillar structures, and wherein embedding the alignment pillar structures in the backfill brush polymer layer comprises: providing a cross-linked polymer layer on a substrate layer; providing a patterned photoresist layer on the cross-linked polymer layer, wherein the patterned photoresist layer comprises a pattern of photoresist pillars, and wherein a position of the photoresist pillars corresponds to a subset of the positions forming the hexagonal matrix configuration; applying a plasma etch for trimming the photoresist pillars; transferring the pattern of photoresist pillars into the cross-linked polymer layer, resulting in cross-linked polymer layer pillars with reduced diameter at the subset of the positions forming the hexagonal matrix configuration; removing the patterned photoresist layer; providing a second backfill brush polymer layer in between the cross-linked polymer layer pillars, wherein the second backfill brush polymer layer has a thickness that is about equal to a height of the cross-linked polymer layer pillars.

3. The method according to claim 2, wherein providing the second backfill brush polymer layer in between the cross-linked polymer layer pillars, comprises: providing an additional backfill brush polymer layer on and in between the cross-linked polymer layer pillars; grafting the additional backfill brush polymer layer by providing a suitable temperature step, such that at least a lower portion of the additional backfill brush polymer layer is chemically bonded to the substrate layer; and removing an un-bonded portion of the additional backfill brush polymer layer, wherein a thickness of the cross-linked polymer layer and the lower portion of the additional backfill brush polymer layer is predetermined.

4. The method according to claim 3, wherein the thickness of the cross-linked polymer layer is smaller than 10 nm.

5. The method according to claim 1, wherein the alignment pillar structures are provided in a 2D arrangement.

6. The method according to claim 1, wherein a pitch between neighboring alignment pillar structures is about constant and is an integer multiple of a natural periodicity (L.sub.0) of the BCP polymer layer.

7. The method according to claim 6, wherein the alignment pillar structures are arranged according to a secondary hexagonal matrix configuration.

8. The method according to claim 6, wherein the alignment pillar structures are arranged according to a secondary rectangular matrix configuration.

9. The method according to claim 2, wherein providing the patterned photoresist layer on the cross-linked polymer layer is performed by an ArF immersion (ArFi) lithography at 193 nm.

10. The method according claim 2, wherein the cross-linked polymer layer comprises a same material as the first component of the BCP polymer layer.

11. The method according to claim 1, wherein the BCP polymer layer comprises PS-b-PMMA, and wherein the method further comprises selectively removing the PMMA or PS component after the induced polymer microphase separation.

12. The method according to claim 11, further comprising patterning an underlying substrate layer by using a pattern of a remaining component as a mask.

13. The method according to claim 12, further comprising performing sequential infiltration synthesis to transform either the first component or the second component into metallic material to enhance etch selectivity and invert a tone of the pattern of the remaining component as a mask.

14. A method for patterning a first contact layer in a memory device manufacturing process or in a vertical channel transistor manufacturing process, wherein the method is for manufacturing pillar structures in a layer of a semiconductor device, wherein the pillar structures are arranged at positions forming a hexagonal matrix configuration, and wherein the method comprises: embedding alignment pillar structures in a backfill brush polymer layer, wherein the backfill brush polymer layer has a thickness that is about equal to a height of the alignment pillar structures, and wherein the alignment pillar structures are at positions corresponding to a subset of the positions forming the hexagonal matrix configuration; providing a BCP layer on a substantially planar surface defined by an upper surface of the alignment pillar structures and the backfill brush polymer layer; and inducing polymer microphase separation of the BCP polymer layer into pillar structures of a first component of the BCP polymer layer embedded in a second component of the BCP polymer layer, wherein the pillar structures of the first component are arranged at positions forming the hexagonal matrix configuration, such that a pillar structure of a first component of the BCP polymer layer is formed on each of the alignment pillar structures.

15. A semiconductor structure comprising a surface, wherein the surface comprises a predetermined area and an additional area adjacent to the predetermined area, the semiconductor structure comprising: in the predetermined area: alignment pillar structures embedded in a backfill brush polymer layer, wherein the backfill brush polymer layer has a thickness that is about equal to a height of the alignment pillar structures, and wherein the alignment pillar structures are at positions corresponding to a subset of positions forming the hexagonal matrix configuration; and a microphase-separated BCP layer on top of a surface defined by the backfill brush polymer layer and the alignment pillar structures, wherein the microphase-separated BCP layer comprises a first component embedded in a second component, and wherein the first component forms a regular hexagonal matrix configuration; and in the additional area: the microphase-separated BCP layer comprising the first component embedded in the second component, wherein the first component forms a second regular hexagonal matrix configuration, and wherein the positions of the second regular hexagonal matrix configuration of the first component in the additional area do not correspond to positions of a regular extension of the regular hexagonal matrix configuration of the first component in the predetermined area.

16. The method according to claim 14, wherein the alignment pillar structures are cross-linked polymer layer pillar structures, and wherein embedding the alignment pillar structures in the backfill brush polymer layer comprises: providing a cross-linked polymer layer on a substrate layer; providing a patterned photoresist layer on the cross-linked polymer layer, wherein the patterned photoresist layer comprises a pattern of photoresist pillars, and wherein a position of the photoresist pillars corresponds to a subset of the positions forming the hexagonal matrix configuration; applying a plasma etch for trimming the photoresist pillars; transferring the pattern of photoresist pillars into the cross-linked polymer layer, resulting in cross-linked polymer layer pillars with reduced diameter at the subset of the positions forming the hexagonal matrix configuration; removing the patterned photoresist layer; providing a second backfill brush polymer layer in between the cross-linked polymer layer pillars, wherein the second backfill brush polymer layer has a thickness that is about equal to a height of the cross-linked polymer layer pillars.

17. The method according to claim 16, wherein providing the second backfill brush polymer layer in between the cross-linked polymer layer pillars, comprises: providing an additional backfill brush polymer layer on and in between the cross-linked polymer layer pillars; grafting the additional backfill brush polymer layer by providing a suitable temperature step, such that at least a lower portion of the additional backfill brush polymer layer is chemically bonded to the substrate layer; and removing an un-bonded portion of the additional backfill brush polymer layer, wherein a thickness of the cross-linked polymer layer and the lower portion of the additional backfill brush polymer layer is predetermined.

18. The method according to claim 17, wherein the thickness of the cross-linked polymer layer is smaller than 10 nm.

19. The method according to claim 14, wherein the alignment pillar structures are provided in a 2D arrangement.

20. The method according to claim 14, wherein a pitch between neighboring alignment pillar structures is about constant and is an integer multiple of a natural periodicity (L.sub.0) of the BCP polymer layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0068] The disclosure will be further elucidated by means of the following description and the appended figures.

[0069] FIGS. 1(a) to (g) illustrate a process flow according to a preferred embodiment of the present disclosure.

[0070] FIGS. 2(a) to (f) illustrate a process flow according to an alternative embodiment of the present disclosure.

[0071] FIG. 3 shows images representing experimental results according to preferred embodiments of the present disclosure.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0072] The present disclosure will be described with respect to particular embodiments and with reference to certain drawings but the disclosure is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. The dimensions and the relative dimensions do not necessarily correspond to actual reductions to practice of the disclosure.

[0073] Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. The terms are interchangeable under appropriate circumstances and the embodiments of the disclosure can operate in other sequences than described or illustrated herein.

[0074] Furthermore, the various embodiments, although referred to as “preferred” are to be construed as example manners in which the disclosure may be implemented rather than as limiting the scope of the disclosure.

[0075] FIGS. 1(a) to (g) illustrate a process flow according to a preferred embodiment of the present disclosure.

[0076] A substrate or substrate layer 1 is provided (for instance comprising a silicon substrate wafer on which a layer to be patterned is provided, such as for instance a silicon oxide, silicon nitride, titanium nitride, etc layer), which can for instance be a layer stack on an underlying semiconductor wafer (FIG. 1(a)). A cross-linked polymer layer 2 (also called mat layer) is coated on top of the substrate 1. On top of the cross-linked polymer layer 2 a photoresist layer (PR) 3 is coated (FIG. 1(b)). The photoresist layer is patterned with state of the art techniques, selectively with respect to the cross-linked polymer layer 2, to thereby define PR pillars 3′ (FIG. 1(c)). The PR pillars 3′ can have for instance a pitch in between 80 and 150 nm, and a diameter within the range of 35-70 nm. Preferably, all PR pillars 3′ have the similar or the same dimensions, e.g. the same height and diameter. Preferably, the patterning of the photoresist layer is performed by means of ArF immersion (ArFi) lithography at 193 nm. A plasma etch step is applied to trim the photoresist pillars 3′ and to transfer their pattern into said cross-linked polymer layer 2 (FIG. 1(d)), resulting in cross-linked polymer layer pillars 2′, preferably all having similar or the same dimensions, e.g. the same height and diameter, referred to as alignment pillars 2′, with reduced size, e.g. reduced diameter (for instance a pitch in between 80 and 150 nm, and a diameter within the range of 10-50 nm). The alignment pillars are preferably evenly distributed over at least a portion of, or over the whole substrate main surface. For instance, there may be a constant pitch between pillars. Alternatively, a first pitch may be constant in a first direction (e.g. horizontal direction) and a second pitch may be constant along a different, non-parallel, direction (e.g. vertical direction), the first and second pitches being different. They are preferably located at a subset of positions corresponding to the eventual hexagonal matrix configuration required. The main surface of the substrate 1 is modified for brush grafting. For instance, the substrate can be oxidised by the trim etch step, which can facilitate the brush grafting step. The remaining portion of the PR layer 3″ is now removed (FIG. 1(e)).

[0077] The alignment pillar structures 2′ are now being laterally embedded in a backfill brush polymer layer 4 (FIG. 1(f)), for instance comprising a hydroxyl terminated random copolymer comprised of the same monomers as used for the BCP material. A predetermined backfill brush polymer layer is provided on and in between the cross-linked polymer layer pillars 2′, embedding the cross-linked polymer layer pillars 2′ completely. The backfill brush polymer layer is then grafted by providing a suitable temperature step, such that at least a lower portion of the backfill brush polymer layer is chemically bonded (preferably covalently bonded) to the substrate layer. A rinsing process is then applied which removes the portion of the backfill brush polymer layer, leaving only the bonded portion (grafted portion). Hereby, the thickness of the cross-linked polymer layer 2′ and the grafted portion of the backfill brush polymer layer 4 is predetermined, such that they are the same or about the same height.

[0078] A BCP layer 5 is now coated on the substantially planar surface defined by the upper surface of the alignment pillar structures 2′ and the backfill brush polymer layer 4 (FIG. 1(f)). Polymer microphase separation of said BCP polymer layer 5 is induced, such that pillar structures of a first component (5b) of the BCP polymer layer are created, and a complementary structure of a second component (5a) of the BCP polymer layer which is embedding the pillar structures of a first component (5b) laterally. The pillar structures of the first component (5b) are arranged at positions forming the required hexagonal matrix configuration. Hereby, on each alignment pillar structure (2′) a pillar structure of a first component (5b) of the BCP polymer layer is formed, being aligned therewith and preferably having the same diameter as the alignment pillar structure (2′). A frequency multiplication factor of the pre-pattern defined by the alignment pillar structures of 2, 3 or more can be achieved. For instance, the set of alignment pillars forming the pre-pattern may form a rectangular grid, or any other sub-grid of a hexagonal grid, or a hexagonal grid. For instance, the set of alignment pillars may form a hexagonal grid with a pitch which is larger than the natural period of the BCP.

[0079] For instance, in the above process flow, the trim etch transfers the pillar pattern from photoresist 3″ to a cross-linked PMMA (X-PMMA) under-layer (cross-linked polymer layer 2, pillars 2″). The backfill brush layer 4 can be for instance an end-grafting random copolymer of PS-PMMA with a high PS fraction (e.g. within the range of 75 to 95% PS content).

[0080] When replacing instead X-PMMA with cross-linked PS (X-PS) and adjust the backfill brush composition such that the PMMA fraction is higher (for instance within the range of 50 to 75% PS content), this flow can also be used to assemble PS cylinder forming PS-b-PMMA formulations. A step after DSA is preferably the removal of one of the blocks in the BCP. For PS-b-PMMA this block is PMMA as PMMA etches faster than PS in most plasma chemistries and can also be removed with exposure to DUV light which causes chain scission in PMMA and the residue can be rinsed away with organic solvents while PS remains in the film. This means that, if PMMA cylinder forming BCP systems are used, one ends up with holes in a PS film after PMMA removal. On the other hand if one uses PS cylinder forming BCPs, one ends up with pillars of PS after PMMA removal.

[0081] FIG. 2(a) to (f) illustrate a process flow according to an alternative embodiment of the present disclosure, wherein the photoresist layer 3 itself is used for defining alignment pillar structures 3″. This process flow is further similar to the flow described in relation with FIG. 1(a) to (g).

[0082] A substrate or substrate layer 1 is provided (for instance comprising a silicon substrate wafer on which a layer to be patterned is provided, such as for instance a silicon oxide, silicon nitride, titanium nitride, etc layer), which can for instance be a layer stack on an underlying semiconductor wafer (FIG. 2(a)). A photoresist layer (PR) 3 is coated/deposited on top of the substrate 1 (FIG. 2(b)). The photoresist layer 3 is patterned with state of the art techniques, selectively with respect to the substrate, to thereby define PR pillars 3′ (FIG. 2(c)), which are preferably all of similar or the same dimensions, e.g. of the same height and diameter. Preferably, the patterning of the photoresist layer is performed by means of ArF immersion (ArFi) lithography at 193 nm. The PR pillars 3′ can have for instance a pitch in between 80 and 150 nm, and a diameter within the range of 35-70 nm. A plasma etch step is applied to trim the photoresist pillars 3′, resulting in photoresist pillars 3″, referred to as alignment pillars, with reduced size, e.g. reduced diameter and/or height (FIG. 2(d)) (for instance a pitch in between 80 and 150 nm, and a diameter within the range of 10-50 nm). The alignment pillars 3″ are preferably evenly distributed over at least a portion of, or over the whole substrate main surface. The alignment pillars 3″ are all preferably of similar or the same dimensions, e.g. of the same height and diameter. They are preferably located at a subset of positions corresponding to the eventual hexagonal matrix configuration required. For instance, there may be a constant pitch between pillars. Alternatively, a first pitch may be constant in a first direction (e.g. horizontal direction) and a second pitch may be constant along a different, non-parallel, direction (e.g. vertical direction), the first and second pitches being different. The main surface of the substrate 1 is modified for brush grafting.

[0083] The alignment pillar structures 3″ are now being laterally embedded in a backfill brush polymer layer 4 (FIG. 2(e)). A predetermined backfill brush polymer layer is provided on and in between the photoresist pillars 3″, embedding them completely. The backfill brush polymer layer is then grafted by providing a suitable temperature step, such that at least a lower portion of the backfill brush polymer layer is chemically bonded to the substrate layer. A rinsing process is then applied which removes the unbonded (non-bonded) portion of the backfill brush polymer layer, leaving only the bonded portion (grafted portion). Hereby, the thickness of the photoresist pillars 3″ and the grafted portion of the backfill brush polymer layer 4 is predetermined, such that they are the same or about the same height.

[0084] A BCP layer 5 is now coated on the substantially planar surface defined by the upper surface of the alignment pillar structures 2′ and the backfill brush polymer layer 4 (FIG. 2(e)). Polymer micro phase separation of said BCP polymer layer 5 is induced, such that pillar structures of a first component (5b) of the BCP polymer layer are created, and a complementary structure of a second component (5a) of the BCP polymer layer which is embedding the pillar structures of a first component (5b) laterally. The pillar structures of the first component (5b) are arranged at positions forming the required hexagonal matrix configuration. Hereby, on each alignment pillar structure (3″) a pillar structure of a first component (5b) of the BCP polymer layer is formed, being aligned therewith and preferably being of similar or identical diameter as the alignment structure (3″). A frequency multiplication factor of the pre-pattern defined by the alignment pillar structures of 2, 3 or more can be achieved. For instance, the set of alignment pillars forming the pre-pattern may form a rectangular grid, or any other sub-grid of a hexagonal grid, or a hexagonal grid. For instance, the set of alignment pillars may form a hexagonal grid with a pitch which is larger than the natural period of the BCP.

[0085] FIG. 3 shows images representing experimental results according to preferred embodiments of the present disclosure, in which a cross-linked polymer layer is present, according to the flow described in relation with FIG. 1. A cross-linked (x-linked) layer 2 was spin-coated on a substrate 1 and baked at 250° C. for about 2 minutes in a N2 atmosphere. A PR layer 3 was spin-coated on x-linked layer and baked at 100° C. for about 1 minute. ArFi lithography was used to define the PR alignment pillars 3′, using double exposure. An oxygen containing plasma etch chemistry was used in order to trim the PR pillars 3″ and pattern the x-linked layer 2′. A rinse step was applied with a DMSO+TMAH photoresist stripper. Then, a brush polymer layer was spin-coated, baked at 220° C. for 3 minutes, in an N2 atmospere, followed by a rinse step with PGMEA. Then, a BCP layer/film was spin-coated on the surface defined by the remaining brush polymer layer and x-linked alignment structures 2′. The BCP film was baked at 250° C. for 5 minutes, in a N2 atmosphere.

[0086] Preferably, the surface energies of the remaining brush polymer layer and x-linked alignment structures are very similar. In preferred embodiments, a top coat layer can be provided on the surface defined by the remaining brush polymer layer and x-linked alignment structures, which is adapted for modifying the surface energies of one or both of the remaining brush polymer layer and x-linked alignment structures, to further optimise the process, e.g. to make their surface energies more similar. The use of these top coats (top coated layers) is known to the skilled person, as for instance in E. Huang and T. P. Russell, “Using Surface Active Random Copolymers To Control the Domain Orientation in Diblock Copolymer Thin Films”, Macromolecules, 1998, 31 (22), pp 7641-7650; and for instance in Christopher M. Bates et al, “Polarity-Switching Top Coats Enable Orientation of Sub-10-nm Block Copolymer Domains”, Science 9 Nov. 2012: Vol. 338 no. 6108 pp. 775-779.

[0087] It can be noted that the processing can be identical for embodiments according to a flow described in relation with FIG. 2, wherein the double exposure in FIG. 2 (c) is for patterning a (for instance rectangular) array of alignment pillars.

[0088] The images are CD SEM images at 180 k× magnification. Images are provided for three process flows: series I, II, and III. Three different stages in each of these process flows have been depicted. The left images (A) show the photoresist pillar structures after lithography. The central images (B) define the alignment pillar pre-pattern after trimming (after trim etch). The right images (C) show the BCP layer/film BCP film after DSA with PMMA domains removed using Deep UV (DUV) exposure and IPA rinse. The BCP material used here was PS-b-PMMA.

[0089] In flow (I) a 90 nm pitch hexagonal array is provided at lithography level. A 45 nm pitch BCP was used with the cylindrical domain etched after DSA, resulting in a frequency multiplication factor of four.

[0090] In flow (II) a 90 (first direction, e.g. horizontal direction)/78 (second direction, e.g. vertical direction) nm pitch orthogonal array (rectangular array) at lithography level is performed. A 45 nm pitch BCP was used with the cylindrical domain etched after DSA, resulting in a frequency multiplication factor of four.

[0091] In flow (III) a 90 nm pitch hexagonal array is provided at lithography level. A 30 nm pitch BCP was applied with the cylindrical domain etched after DSA, resulting in a frequency multiplication factor of nine.

[0092] It will be appreciated by the skilled person that embodiment according to aspects of the present disclosure can be used for patterning arrays spanning 45 nm to sub-30 nm pitch with ArFi lithography, which meet ITRS roadmap requirements for contact holes until at least 2025. It enables a relatively simple and cheap patterning process for this critical contact layer. It can further be noted that, when assisted by EUVL instead of ArFi, the process can be extended to sub-20 nm pitch thus exceeding the roadmap's predictions for the foreseeable future.

[0093] Further, this process flow can also be used to assemble cylinder forming BCPs different from PS-b-PMMA. The cross-linked mat material and backfill brush composition are preferably predetermined/selected accordingly.

[0094] Another advantage of embodiment according to aspects of the disclosure is that array or cell edges can be defined in the pre-pattern step. Unlike most chemo-epitaxy process flows a separate cut/block mask is not necessary. In the mask design, the area outside the cell edge can be a “dark field” or not exposed to the photolithography scanner's illumination. After photo-resist development, a photo-resist layer can still be present in the area outside the desired cell (e.g. using positive tone development for patterning the pillars). This photo-resist layer can then shield the under-lying cross-linked film from the trim etch. Subsequently, no brush grafts in this region outside the desired cell as the cross-linked under-layer is present to shield the substrate. The BCP molecules that assemble on this area outside the cell will be oriented parallel to the substrate and will not be transferred to the target layer in the pattern transfer process.

[0095] The foregoing description details certain embodiments of the disclosure. It will be appreciated, however, that no matter how detailed the foregoing appears in text, the disclosure may be practiced in many ways.

[0096] While the above detailed description has shown, described, and pointed out novel features of the invention as applied to various embodiments, it will be understood that various omissions, substitutions, and changes in the form and details of the device or process illustrated may be made by those skilled in the technology without departing from the invention.