• 专利附录
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  • 优先权
    • 专利摘要:
    The invention relates to a method for etching an assembled block copolymer layer comprising first and second polymer phases, the etching process comprising exposing the block copolymer layer assembled to a plasma so as to etch the first polymer phase and simultaneously depositing a carbon layer on the second polymer phase, the etching process being characterized in that the plasma is formed from a gas mixture comprising a depolymerizing gas (Z) and an etching gas selected from hydrocarbons (CxHy).
    公开号:FR3041120A1
    申请号:FR1558483
    申请日:2015-09-11
    公开日:2017-03-17
    发明作者:Nicolas Posseme；Aurelien Sarrazin
    申请人:Commissariat a lEnergie Atomique CEA；Commissariat a lEnergie Atomique et aux Energies Alternatives CEA；
    IPC主号:
    专利说明:

    METHOD FOR SELECTIVELY ENGRAVING BLOCK COPOLYMER TECHNICAL FIELD
    The present invention relates to directed self-assembly techniques of block copolymers ("Directed Self-Assembly", DSA) for generating patterns of very high resolution and density. The invention more particularly relates to an etching process for removing a first phase of a block copolymer selectively with respect to a second phase of the block copolymer.
    STATE OF THE ART
    The resolution limit of optical lithography leads to the exploration of new techniques for making patterns whose critical dimension (CD) is less than 22 nm. Directed self-assembly of block copolymers is considered one of the most promising emerging lithographic techniques because of its simplicity and low cost of implementation.
    Block copolymers are polymers in which two repeating units, a monomer A and a monomer B, form chains linked together by a covalent bond. When the chains are given sufficient mobility, for example by heating these block copolymers, the monomer A chains and the B monomer chains tend to separate into polymer phases or blocks and reorganize under specific conformations. , which depend in particular on the ratio between the monomer A and the monomer B. Depending on this ratio, one can have spheres of A in a matrix of B, or else rolls of A in a matrix of B, or else lamellae of A and strips of B interspersed. The size of the domains of the block A (respectively of the block B) is directly proportional to the length of the chains of the monomer A (respectively of the monomer B). Block copolymers therefore have the property of forming polymer units which can be controlled by the ratio of monomers A and B.
    The known techniques for self-assembly of block copolymers (DSA) can be grouped into two categories, grapho-epitaxy and chemo-epitaxy.
    Grapho-epitaxy consists of forming primary patterns called guides on the surface of a substrate, these patterns delimiting zones within which a layer of block copolymer is deposited. The guide patterns control the organization of the copolymer blocks to form higher resolution secondary patterns within these areas. The guide patterns are conventionally formed by photolithography in a resin layer.
    In chemo-epitaxial DSA techniques, the substrate undergoes a chemical modification of its surface so as to create zones that preferentially attract a single block of the copolymer, or neutral zones preferentially attracting none of the two blocks of the copolymer. Thus, the block copolymer is not randomly organized, but according to the chemical contrast of the substrate. The chemical modification of the substrate may in particular be obtained by grafting a neutralization layer called "brush" ("brush layer" in English), for example formed of a random copolymer.
    DSA techniques make it possible to produce different types of patterns in an integrated circuit substrate. After deposition and assembly of the block copolymer on the substrate, the secondary units are developed by removing one of the two blocks of the copolymer, for example block A, selectively with respect to the other, thus forming patterns in the remaining layer of copolymer (block B). If the domains of the block A are cylinders, the patterns obtained after withdrawal are cylindrical holes. On the other hand, if the domains of block A are lamellae, we obtain patterns in the form of a straight trench. Then, these patterns are transferred by etching to the surface of the substrate, either directly in a dielectric layer, or beforehand in a hard mask covering the dielectric layer.
    The PMMA-b-PS block copolymer, consisting of polymethyl methacrylate (PMMA) and polystyrene (PS), is the most studied in the literature. Indeed, the syntheses of this block copolymer and the corresponding random copolymer (PMMA-r-PS) are easy to achieve and perfectly controlled. The removal of the PMMA phase can be achieved by wet etching, optionally coupled with ultraviolet exposure, or by dry etching using a plasma.
    Wet etching of PMMA, for example in an acetic acid bath, is a highly selective shrinkage technique with respect to polystyrene. The selectivity, that is, the ratio of the PMMA etch rate to the etch rate of polystyrene, is high (greater than 20: 1). However, with this technique, etching residues are redeposited on the etched copolymer layer, blocking part of the patterns obtained in the polystyrene layer which prevents their transfer. In addition, in the case of lamella-shaped areas, wet etching can cause collapse of the polystyrene structures due to large capillary forces.
    Plasma dry etching does not suffer from these drawbacks and is of great economic interest because the pattern transfer step following the PMMA removal step is also plasma etching. Therefore, the same equipment can be used successively for these two steps. Plasmas usually used to etch the PMMA phase are generated from a mixture of argon and oxygen (Ar / 02) or a mixture of oxygen and fluorocarbon gas (eg 02 / CHF3). However, PMMA etching with these plasmas is carried out with a selectivity with respect to polystyrene much lower than that of wet etching (respectively 4.2 and 3.5).
    Thus, other plasmas have been developed in order to increase the selectivity of the (dry) etching of PMMA. For example, in the article ["Highly selective etch gas chemistry design for specified DSAL dry development process", M. Omura et al., Advanced Etch Technology for Nanopatterning III, Proc. SPIE Vol. 9054, 905409, 2014], the authors show that a carbon monoxide (CO) plasma makes it possible to etch PMMA with almost infinite selectivity. Indeed, the PMMA is etched by the CO plasma without the polystyrene being impacted, because a carbonaceous deposit is formed simultaneously on the polystyrene.
    Fig. 1 is a graph showing the etch depth in a PMMA layer and in a polystyrene (PS) layer during CO plasma etching. It illustrates the diode difference between the two layers: etching regime in the case of the PMMA layer (positive etch depth) and deposition regime in the case of the PS layer (negative etch depth).
    When this gas is used alone, a saturation phenomenon occurs at about 30 s of etching, causing a stop of PMMA etching. Indeed, the deposition regime gradually takes over the etching regime and PMMA etching is stopped at an etching depth of about 15 nm by the formation of a carbon layer on the partially etched layer of PMMA. It is therefore not possible to etch more than 15 nm thick PMMA with this single gas.
    To overcome this saturation problem, the carbon monoxide is mixed with hydrogen (H2) in a concentration of less than or equal to 7% and the plasma is generated at a polarization power of about 80 W. It can be seen in FIG. This gas mixture has an etching selectivity much lower than that of carbon monoxide alone, since the addition of hydrogen inhibits the deposition of the carbonaceous layer on the polystyrene. Polystyrene is then etched at the same time as PMMA. This results in an enlargement of the patterns formed in the polystyrene layer (relative to the initial dimensions of the PMMA domains) and difficulties in transferring these patterns into the substrate. Indeed, the polystyrene layer used as a mask during this transfer may not be sufficiently thick.
    SUMMARY OF THE INVENTION
    The object of the present invention is to provide a process for the dry etching of a block copolymer which has a high etch selectivity between the phases or blocks of the copolymer and knows no limit in terms of engraving depth.
    According to the invention, there is a tendency toward this objective by providing a method of etching an assembled block copolymer layer comprising first and second polymer phases, the etching process comprising exposing the assembled block copolymer layer to a plasma so as to etch the first polymer phase and simultaneously deposit a carbon layer on the second polymer phase, the plasma being formed from a gas mixture comprising a depolymerizing gas and an etching gas selected from hydrocarbons .
    Hydrocarbons are organic compounds consisting exclusively of carbon (C) and hydrogen (H) atoms. Their formula is of the form CxHy, where x and y are natural non-zero integers. Like carbon monoxide (CO), a gaseous hydrocarbon can, when mixed with a depolymerizing gas, give rise to a plasma that can both etch the first phase of a block copolymer and cover a carbon deposit (rather than etching) the second phase of the copolymer. Thus, the etching method according to the invention is as selective as the method of the prior art, in which the plasma is formed using only carbon monoxide. However, unlike CO plasma etching, hydrocarbon etching exhibits no saturation phenomena. The etching of the first phase of the block copolymer continues as long as the copolymer layer is exposed to the plasma. In other words, the etching process according to the invention is not limited in terms of the thickness of the block copolymer layer.
    Preferably, the etching process has a ratio of the etching gas flow rate to the depolymerizing gas flow rate of between 0.9 and 1.4.
    The process according to the invention may also have one or more of the following characteristics, considered individually or in any technically possible combination: the etching gas is methane; the etching gas is ethane; the assembled block copolymer layer is exposed to the plasma until the first polymer phase is fully etched; the first polymer phase is organic and has an oxygen atom concentration greater than 20%; the second polymer phase has an oxygen atom concentration of less than 10%; and
    the depolymerizing gas is chosen from among H2, N2, O2, Xe, Ar and He. BRIEF DESCRIPTION OF THE FIGURES Other features and advantages of the invention will emerge clearly from the description given below, by way of indication and not at all. FIG. 1, previously described, represents the etching depth in a PMMA layer and in a polystyrene (PS) layer during carbon monoxide plasma etching. ; FIG. 2 represents an example of a layer of an assembled block copolymer before carrying out the etching process according to the invention; FIG. 3 represents the etch depth in a PMMA layer and in a polystyrene (PS) layer as a function of the time of exposure to a hydrocarbon plasma / depolymerizing gas; and FIGS. 4A and 4B show the evolution of the copolymer layer of FIG. 2 during the etching process according to the invention.
    For the sake of clarity, identical or similar elements are identified by identical reference signs throughout the figures.
    DETAILED DESCRIPTION OF AT LEAST ONE EMBODIMENT
    FIG. 2 shows an assembled block copolymer layer 20 before it is etched by the etching process according to the invention. The copolymer layer 20 comprises first and second polymer phases, denoted respectively 20A and 20B, which are organized into domains. The copolymer of the layer 20 is, for example, the PS-b-PMMA di-block copolymer, that is to say a copolymer consisting of polymethyl methacrylate (PMMA) and polystyrene (PS). Polymer phase 20A here corresponds to PMMA and polymer phase 20B to polystyrene.
    One way to obtain this layer of block copolymer 20 is to deposit the PS-b-PMMA block copolymer on a substrate 21 covered with a neutralization layer 22. The neutralization layer 22 allows the separation of the phases 20A-20B during the step of assembling the block copolymer, in other words the organization of the domains of the copolymer. It is for example formed of a random copolymer layer PS-r-PMMA. Preferably, the PMMA domains (phase 20A) are oriented perpendicular to the substrate 21 and extend over the entire thickness of the copolymer layer 20. According to the ratio between PMMA and polystyrene in the PS-b-PMMA copolymer, the PMMA domains can be in the form of cylinders (this is called a cylindrical block copolymer) or lamellae (lamellar block copolymer).
    The method of plasma etching described below aims to etch the phase of the copolymer containing the most oxygen atoms (the phase of PMMA 20A in the example above) selectively with respect to the other phase (the polystyrene phase 20B), irrespective of the thickness of the copolymer layer 20. For this purpose, the copolymer layer 20 is exposed to a plasma generated from a mixture comprising at least one gaseous hydrocarbon CxHy and a depolymerizing gas hereinafter referred to as "Z".
    In a similar manner to FIG. 1, FIG. 3 represents, as a function of the etching time, the etching depths reached in a PMMA layer and in a polystyrene (PS) layer by virtue of this type of plasma. Like the CO plasma (Fig. 1), the CxHy / Z plasma has a different behavior depending on the material of the layer. The CxHy / Z plasma acts in etching mode on the PMMA layer (represented by a positive etch depth) and in the deposition regime on the PS layer (represented by a negative etch depth).
    Plasma CxHy / Z thus makes it possible to achieve a high selectivity between PMMA and polystyrene insofar as polystyrene is not etched unlike PMMA. Note also in Figure 3 that the etching depth of the plasma CxHy / Z in the PMMA layer does not saturate. On the contrary, it keeps increasing as the engraving progresses. This means that the plasma etching CxHy / Z is not limited in terms of the thickness of the PMMA layer, unlike the CO plasma.
    FIGS. 4A and 4B show the evolution of the copolymer layer 20 when it is exposed to the CxHy / Z plasma, according to the etching method according to the invention. The PMMA phase 20A of the copolymer layer 20 is progressively etched, while a carbon layer 23 is formed above the polystyrene phase 20B (Fig.4A). Since the CxHy / Z plasma is not subjected to any saturation phenomenon, the PMMA phase 20A can be etched entirely irrespective of its thickness, while continuing to apply the plasma to the copolymer layer 20 (FIG. 4B). For a copolymer layer 20 of thickness between 20 nm and 50 nm, the time necessary to fully etch the PMMA phase 20A varies between 20 s and 60 s. The thickness h of the carbonaceous layer 23 increases during the etching of the PMMA, according to the teaching of FIG. 3. At the end of the etching, the thickness h may be between 1 nm and 3 nm.
    The total removal of the PMMA phase, shown in FIG. 4B, forms patterns 24 in a layer 20 now composed solely of polystyrene phase 20B. These patterns 24, in the form of cylindrical holes or straight trenches, open onto the neutralization layer 22 covering the substrate 21.
    The method for etching the copolymer layer 20 is advantageously carried out in a single step in a plasma reactor, either a Capacitively Coupled Plasma (CCP) reactor or an inductively coupled reactor (ICP). , for "Inductively Coupled Plasmas"). The gaseous hydrocarbon is preferably an alkane, such as methane (CH4) or ethane (C2H6), i.e. a saturated hydrocarbon. The ions of this hydrocarbon destroy the PMMA polymer chains by consuming the oxygen they contain. They are also at the origin of the formation of the carbonaceous layer 23 on polystyrene, the latter being insensitive to etching because it does not contain oxygen. The ions of the depolymerizing gas prevent surface chemical modification of PMMA by limiting the degree of polymerization of the hydrocarbon with this material. In other words, they prevent the formation of a polymer on the surface of PMMA. Thus, the carbonaceous layer 23 does not cover the PMMA phase 20A. The depolymerizing gas is for example selected from H2, N2, O2, Xe, Ar and He.
    The hydrocarbon gas CxHy and the depolymerizing gas Z have flow rates into the plasma reactor in a CxHy / Z ratio preferably between 0.9 and 1.4. This ratio of flows is all the greater as the number (x) of carbon atoms in the hydrocarbon (CxHy) is important. It is for example between 0.9 and 1.2 in the case of methane (CH4). The hydrocarbon flow rate and the rate of depolymerizing gas entering the reactor chamber are preferably between 10 sccm and 500 sccm (abbreviation of "Standard Cubic Centimeter per Minute" in English, ie the number of cm 3 of gas flowing per minute under standard conditions of pressure and temperature, ie at a temperature of 0 ° C and a pressure of 1013.25 hPa).
    The other parameters of the CxHy / Z plasma etching are advantageously the following: a power (RF) emitted by the reactor source of between 50 W and 500 W; - a power (DC or RF) polarization of the substrate between 50 W and 500 W; a pressure in the reactor chamber of between 2.67 Pa (20 morr) and 16.00 Pa (120 mTorr). By way of example, the plasma is generated in a CCP reactor by mixing methane (CH4) and dinitrogen (N2), with flow rates of 25 sccm and 25 sccm respectively, and applying a source power of 300 W and a bias power of 60 W at a pressure of 4.00 Pa (30 mTorr). This plasma removes in 40 seconds a PMMA thickness of about 30 nm and deposit in the same time a carbon layer of 3 nm thick on polystyrene.
    The etch selectivity of PMMA with respect to polystyrene by the CxHy / Z plasma is particularly high since the polystyrene phase 20B is covered with the carbonaceous layer 23, instead of being etched. Various tests have been conducted and show that the PMMA phase of a 50 nm thick PS-δ-PMMA copolymer layer can be fully etched by not consuming polystyrene. The PMMA / PS selectivity of the etching process is greater than or equal to 50. Consequently, it is possible to keep constant the critical dimension CD of the patterns 24 during removal of the PMMA (FIG. 4B). Critical dimension means the smallest dimension of the patterns 24 obtained by the development of the block copolymer.
    Despite the differences in plasma conditions between Figures 1 and 3, the two chemistries of PMMA removal selectively at PS can be compared. In FIG. 3, no saturation phenomenon is detected for the CxHy / Z chemistry at 30 s, unlike the CO chemistry shown in FIG. 1. This non-saturation of the PMMA etching is accompanied by a slight carbon deposit on the polystyrene. This deposit greatly facilitates the transfer step of the patterns 24 in the substrate 21, which follows the step of removing the PMMA phase 20A (after opening of the neutralization layer 22). Indeed, the polystyrene phase 20B which serves as an etching mask during this transfer is reinforced by the presence of the carbonaceous layer 23. The etching mask being thicker, the constraints on the choice of the plasma to achieve the transfer patterns 24 can be released.
    Although it has been described by taking the PS-δ-PMMA copolymer as an example, the etching process according to the invention is applicable to all block copolymers comprising a first phase of organic polymer (20A) rich in oxygen, that is, having an oxygen atom concentration of greater than 20%, and a second oxygen-poor (organic or inorganic) polymer phase, ie having an oxygen atom concentration of less than 10%. This is particularly the case for diblock copolymers PS-b-PLA, PDMS-b-PMMA, PDMS-b-PLA, PDMSB-b-PLA, etc. The block copolymer can be either of the cylindrical type or of the lamellar type.
    Finally, the layer of organized block copolymer can obviously be obtained in a manner different from that described above in relation to FIG. 2, in particular by grapho-epitaxy, by chemo-epitaxy using a neutralization layer other than a random copolymer (for example a self-assembled monolayer, SAM), or by a hybrid technique combining grapho-epitaxy and chemo-epitaxy.
    权利要求:
    Claims (7)
    [1" id="c-fr-0001]
    A method of etching an assembled block copolymer layer (20) comprising first and second polymer phases (20A-20B), the etching process comprising exposing the assembled block copolymer layer (20) to a plasma so as to etch the first polymer phase (20A) and simultaneously deposit a carbon layer (23) on the second polymer phase (20B), the etching process being characterized in that the plasma is formed from a gas mixture comprising a depolymerizing gas (Z) and an etching gas selected from hydrocarbons (CxHy).
    [2" id="c-fr-0002]
    2. Method according to claim 1, having a ratio of the flow of etching gas (CxHy) on the depolymerizing gas flow (Z) between 0.9 and 1.4.
    [3" id="c-fr-0003]
    3. Method according to one of claims 1 and 2, wherein the etching gas (CxHy) is methane.
    [4" id="c-fr-0004]
    4. Method according to one of claims 1 and 2, wherein the etching gas (CxHy) is ethane.
    [5" id="c-fr-0005]
    The method of any one of claims 1 to 4, wherein the layer (20) of assembled block copolymer is plasma exposed to fully etch the first polymer phase (20A).
    [6" id="c-fr-0006]
    The process according to any one of claims 1 to 5, wherein the first polymer phase is organic (20A) has an oxygen atom concentration greater than 20%, and wherein the second polymer phase (20B). has an oxygen atom concentration of less than 10%.
    [7" id="c-fr-0007]
    7. Process according to any one of claims 1 to 6, wherein the depolymerizing gas is selected from H2, N2, O2, Xe, Ar and He.
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    同族专利:
    公开号 | 公开日
    EP3347769A1|2018-07-18|
    FR3041120B1|2017-09-29|
    KR20180050743A|2018-05-15|
    EP3347769B1|2019-08-07|
    WO2017042313A1|2017-03-16|
    US20180286697A1|2018-10-04|
    JP2018529233A|2018-10-04|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    EP2733533A2|2012-11-14|2014-05-21|Imec|Etching method using block-copolymers|FR3085389A1|2018-09-03|2020-03-06|Commissariat A L'energie Atomique Et Aux Energies Alternatives|METHOD FOR ETCHING A BLOCK COPOLYMER COMPRISING A SELECTIVE DEPOSITION STEP|US9666447B2|2014-10-28|2017-05-30|Tokyo Electron Limited|Method for selectivity enhancement during dry plasma etching|FR3066498A1|2017-05-22|2018-11-23|Arkema France|METHOD FOR ASSEMBLING BLOCK COPOLYMERS BY MONITORING THE SURFACE ENERGY OF A MATERIAL BY PLASMA REDUCING TREATMENT|
    US10157773B1|2017-11-28|2018-12-18|Taiwan Semiconductor Manufacturing Co., Ltd.|Semiconductor structure having layer with re-entrant profile and method of forming the same|
    FR3085381B1|2018-09-03|2020-10-02|Commissariat Energie Atomique|DIRECTED SELF-ASSEMBLY PROCESS OF A BLOCK COPOLYMER MIXTURE|
    法律状态:
    2016-08-22| PLFP| Fee payment|Year of fee payment: 2 |
    2017-03-17| PLSC| Search report ready|Effective date: 20170317 |
    2017-08-22| PLFP| Fee payment|Year of fee payment: 3 |
    2018-09-28| PLFP| Fee payment|Year of fee payment: 4 |
    2020-10-16| ST| Notification of lapse|Effective date: 20200906 |
    优先权:
    申请号 | 申请日 | 专利标题
    FR1558483A|FR3041120B1|2015-09-11|2015-09-11|METHOD FOR SELECTIVELY ENGRAVING A BLOCK COPOLYMER|FR1558483A| FR3041120B1|2015-09-11|2015-09-11|METHOD FOR SELECTIVELY ENGRAVING A BLOCK COPOLYMER|
    US15/759,123| US20180286697A1|2015-09-11|2016-09-09|Method for selective etching of a block copolymer|
    EP16763794.1A| EP3347769B1|2015-09-11|2016-09-09|Method for selective etching of a block copolymer|
    PCT/EP2016/071268| WO2017042313A1|2015-09-11|2016-09-09|Method for selective etching of a block copolymer|
    KR1020187010216A| KR20180050743A|2015-09-11|2016-09-09|Selective etching method of block copolymer|
    JP2018513002A| JP2018529233A|2015-09-11|2016-09-09|Selective etching method of block copolymer|
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