Patent Publication Number: US-9891521-B2

Title: Method for depositing thin film

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2014-0161825 filed in the Korean Intellectual Property Office on Nov. 19, 2014, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     (a) Field of the Invention 
     The present invention relates to a method of depositing a thin film. 
     (b) Description of the Related Art 
     In a recent semiconductor-depositing process, a method using a silicon dioxide (SiO2) film as a sacrificial layer has been proposed. Particularly, a sacrificial layer made of silicon dioxide (SiO2) is mainly used in a photolithography process of a semiconductor process. 
     However, when a photoresist (PR) used in the photolithography process is deposited on a silicon dioxide (SiO2) film, an oxygen radical, which is a reaction gas, reacts with carbon and hydrogen contained in the photoresist and thus the photoresist is shrunk, such that a critical dimension (CD) of the photoresist may be changed. 
     The above information disclosed in this Background section is only to enhance the understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in an effort to provide a method of depositing a thin film that is capable of preventing a photoresist from shrinking even though a silicon dioxide film is deposited on the photoresist. 
     An exemplary embodiment of the present invention provides a method of depositing a thin film, including: a step of forming a protective layer containing silicon on a substrate; and a step of forming a sacrificial layer on the protective layer, wherein the protective layer and the sacrificial layer may include silicon (Si). 
     The step of forming the protective layer may include: a step of supplying a purge gas during a first time t 1 , a second time t 2 , a third time t 3 , and a fourth time t 4 ; a step of supplying a first precursor during the first time t 1 ; and a step of supplying a first plasma during the third time t 3 . 
     The step of forming the protective layer may include: a step of supplying the purge gas during the first time t 1 , the second time t 2 , the third time t 3 , and the fourth time t 4 ; a step of supplying the first precursor during the first time t 1 , the second time t 2 , the third time t 3 , and the fourth time t 4 ; and a step of supplying the first plasma during the third time t 3 . 
     The step of forming the protective layer may include: a step of supplying the first precursor during the first time t 1 ; a step of supplying the first plasma during the third time t 3 , and a step of stopping supply of the gas during the second time t 2  between the first time t 1  and the third time t 3 . 
     The step of forming the sacrificial layer may include: a step of supplying the purge gas during a fifth time t 5 , a sixth time t 6 , a seventh time t 7 , and an eighth time t 8 ; a step of supplying the second precursor during the fifth time t 5 ; a step of supplying a reaction gas during the fifth time t 5  to the eighth time t 8 ; and a step of supplying a second plasma during the seventh time t 7 . 
     The first precursor and the second precursor may be the same or different. 
     The first precursor and the second precursor may each include at least one of alkoxide-based, amine-based, aminosilane-based, and chloride-based precursors that respectively contain silicon (Si). 
     The first precursor and the second precursor may each include at least one of TSA, (SiH3)3N; DSO, (SiH3)2; DSMA, (SiH3)2NMe; DSEA, (SiH3)2NEt; DSIPA, (SiH3)2N(iPr); DSTBA, (SiH3)2N(tBu); DEAS, SiH3NEt2; DIPAS, SiH3N(iPr)2; DTBAS, SiH3N(tBu)2; BDEAS, SiH2 (NEt2)2; BDMAS, SiH2 (NMe2)2; BTBAS, SiH2(NHtBu)2; BITS, SiH2(NHSiMe3)2; TEOS, Si(OEt)4; SiCl4; HCD, Si2Cl6; DCS, SiH2Cl2; 3DMAS, SiH(N(Me)2)3; BEMAS, Si H2[N(Et)(Me)]2; AHEAD, Si2 (NHEt)6; TEAS, Si(NHEt)4; and Si3H8, and the reaction gas may include at least one of oxygen (O2), ozone (O3), nitrous oxide (N2O), and nitrogen monoxide (NO). 
     The step of forming the protective layer and the step of forming the sacrificial layer may be performed in-situ in a single reactor, or may be separately performed ex-situ in a plurality of separate reactors. 
     According to the embodiments of the present invention, it is possible to prevent a photoresist from shrinking even though a silicon dioxide film is deposited on the photoresist. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a schematic timing chart of a gas-supplying cycle of a method of depositing a thin film according to an exemplary embodiment of the present invention. 
         FIG. 2  illustrates a schematic timing chart of a gas-supplying cycle of a method of depositing a thin film according to another exemplary embodiment of the present invention. 
         FIG. 3  illustrates a schematic timing chart of a gas-supplying cycle of a method of depositing a thin film according to a further exemplary embodiment of the present invention. 
         FIG. 4  illustrates a result graph of an experimental example of the present invention. 
         FIGS. 5A and 5B  each illustrate a result graph of another experimental example of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. 
     In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like reference numerals designate like elements throughout the specification. It will be understood that when an element such as a layer, film, region, or substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. 
     A method of depositing a thin film according to an exemplary embodiment of the present invention will now be described with reference to the accompanying drawings. 
     A method of depositing a thin film according to an exemplary embodiment of the present invention will be described with reference to  FIG. 1 .  FIG. 1  illustrates a schematic timing chart of a gas-supplying cycle of a method of depositing a thin film according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 1 , a method of depositing a thin film according to the present exemplary embodiment includes a first gas-supplying cycle (m cycle) and a second gas-supplying cycle (n cycle). The first gas-supplying cycle (m cycle) is a step of forming a protective layer on a substrate, and the second gas-supplying cycle (n cycle) is a step of forming a sacrificial layer. 
     In the first gas-supplying cycle (m cycle), while a purge gas is supplied during a first time t 1  to a fourth time t 4 , a first precursor is supplied during the first time t 1 , and a first plasma is supplied during a third time t 3 . 
     The first precursor supplied in a reaction space during the first time t 1 , when the first plasma is supplied during the third time t 3 , is coated on the substrate to form a protective layer. 
     After a photoresist is formed on the substrate, when the first gas-supplying cycle (m cycle) is repeated at least one time or more, a first precursor layer is coated on the photoresist such that the protective layer is formed. During the first gas-supplying cycle (m cycle), the first precursor and the first plasma may be alternately and repeatedly supplied. 
     After the protective layer having a determined thickness is coated on the photoresist, the second gas-supplying cycle (n cycle) is repeated. 
     In the second gas-supplying cycle (n cycle), while the purge gas is supplied during a fifth time t 5  to an eighth time t 8 , a second precursor is supplied during the fifth time t 5 , and while a reaction gas is supplied during the fifth time t 5  to an eighth time t 8 , a second plasma is supplied during a seventh time t 7 . 
     The second precursor supplied during the fifth time t 5  is absorbed on the coated protective layer, and the supplied reaction gas is activated by the second plasma supplied during the seventh time t 7 , and reacts with the absorbed second precursor, thereby forming a predetermined thin film. 
     The second gas-supplying cycle (n cycle) is repeated until a thin film with a predetermined thickness is formed, thereby depositing the thin film with the predetermined thickness. 
     The precursor includes silicon (Si). More specifically, the precursor may include at least one of alkoxide-based, amine-based, aminosilane-based, and chloride-based precursors that respectively contain silicon (Si). For example, the precursor may include at least one of TSA, (SiH3)3N; DSO, (SiH3)2; DSMA, (SiH3)2NMe; DSEA, (SiH3)2NEt; DSIPA, (SiH3)2N(iPr); DSTBA, (SiH3)2N(tBu); DEAS, SiH3NEt2; DIPAS, SiH3N(iPr)2; DTBAS, SiH3N(tBu)2; BDEAS, SiH2 (NEt2)2; BDMAS, SiH2 (NMe2)2; BTBAS, SiH2(NHtBu)2; BITS, SiH2(NHSiMe3)2; TEOS, Si(OEt)4; SiCl4; HCD, Si2Cl6; DCS, SiH2Cl2; 3DMAS, SiH(N(Me)2)3; BEMAS, Si H2[N(Et)(Me)]2; AHEAD, Si2 (NHEt)6; TEAS, Si(NHEt)4; and Si3H8, and the reaction gas may include at least one of oxygen (O2), ozone (O3), nitrous oxide (N2O), and nitrogen monoxide (NO). 
     The first precursor supplied during the first gas-supplying cycle (m cycle) and the second precursor supplied during the second gas-supplying cycle (n cycle) may be the same or different. 
     As such, according to the exemplary embodiment of the present invention, the reaction gas supplied during the second gas-supplying cycle (n cycle) does not react with the photoresist, by including the first gas-supplying cycle (m cycle) for coating the protective layer with the predetermined thickness on the photoresist before the second gas-supplying cycle (n cycle) for depositing the thin film such as the sacrificial layer. The photoresist is coated by supplying a source gas without the reaction gas during the first gas-supplying cycle (m cycle) for coating the protective layer. More specifically, after introducing the precursor into a reactor, the source gas is coated on the photoresist by supplying the purge gas, for example, argon plasma (Ar plasma) activating argon (Ar). As such, since the protective layer is formed without inflow of the reaction gas, the carbon and the hydrogen of which the photoresist is made are not damaged to remain intact in the photoresist, thus it is possible to prevent the photoresist from deforming or shrinking. 
     The first gas-supplying cycle (m cycle) for coating the protective layer with the predetermined thickness on the photoresist and the second gas-supplying cycle (n cycle) for depositing the thin film such as the sacrificial layer may be performed in-situ in a single reactor, and alternatively, they may be separately performed ex-situ in a plurality of reactors. When the first gas-supplying cycle (m cycle) for coating the protective layer and the second gas-supplying cycle (n cycle) for depositing the thin film such as the sacrificial layer are performed in-situ in the single reactor, since the formation of the protective layer and the sacrificial layer is performed in the single reactor, before the sacrificial layer is formed, the protective layer may be formed without deterioration of deposition efficiency of the thin film. 
     Next, a method of depositing a thin film according to another exemplary embodiment of the present invention will be described with reference to  FIG. 2 . FIG.  2  illustrates a schematic timing chart of a gas-supplying cycle of a method of depositing a thin film according to another exemplary embodiment of the present invention. 
     Referring to  FIG. 2 , a method of depositing a thin film according to the present exemplary embodiment includes a first gas-supplying cycle (m cycle) and a second gas-supplying cycle (n cycle). The first gas-supplying cycle (m cycle) is a step of coating a protective layer on a substrate, and the second gas-supplying cycle (n cycle) is a step of forming a sacrificial layer. 
     In the first gas-supplying cycle (m cycle), while a purge gas and a first precursor are supplied during a first time t 1  to a fourth time t 4 , a first precursor is supplied during the first time t 1 , and a first plasma is supplied during a third time t 3 . 
     The first precursor supplied in a reaction space during the first time t 1  to the fourth time t 4 , when the first plasma is supplied during the third time t 3 , is coated on the substrate to form a protective layer. 
     After a photoresist is already formed on the substrate, when the first gas-supplying cycle (m cycle) is repeated at least one time or more, a first precursor layer is coated on the photoresist such that the protective layer is formed. In the first gas-supplying cycle (m cycle), while the first precursor is continuously supplied, the first plasma may be intermittently and repeatedly supplied. 
     After the protective layer having a determined thickness is coated on the photoresist, the second gas-supplying cycle (n cycle) is repeated. 
     In the second gas-supplying cycle (n cycle), while the purge gas is supplied during a fifth time t 5  to an eighth time t 8 , a second precursor is supplied during the fifth time t 5 , and while a reaction gas is supplied during the fifth time t 5  to an eighth time t 8 , a second plasma is supplied during a seventh time t 7 . 
     The second precursor supplied during the fifth time t 5  is absorbed on the coated protective layer, and the supplied reaction gas is activated by the second plasma supplied during the seventh time t 7 , and reacts with the absorbed second precursor, thereby forming a predetermined thin film. 
     The second gas-supplying cycle (n cycle) is repeated until a thin film with a predetermined thickness is formed, thereby depositing the thin film with the predetermined thickness. 
     The precursor contains silicon (Si). More specifically, the precursor may include at least one of alkoxide-based, amine-based, aminosilane-based, and chloride-based precursors that respectively contain silicon (Si). For example, the precursor may include at least one of TSA, (SiH3)3N; DSO, (SiH3)2; DSMA, (SiH3)2NMe; DSEA, (SiH3)2NEt; DSIPA, (SiH3)2N(iPr); DSTBA, (SiH3)2N(tBu); DEAS, SiH3NEt2; DIPAS, SiH3N(iPr)2; DTBAS, SiH3N(tBu)2; BDEAS, SiH2 (NEt2)2; BDMAS, SiH2 (NMe2)2; BTBAS, SiH2(NHtBu)2; BITS, SiH2(NHSiMe3)2; TEOS, Si(OEt)4; SiCl4; HCD, Si2Cl6; DCS, SiH2Cl2; 3DMAS, SiH(N(Me)2)3; BEMAS, Si H2[N(Et)(Me)]2; AHEAD, Si2 (NHEt)6; TEAS, Si(NHEt)4; and Si3H8, and the reaction gas may include at least one of oxygen (O2), ozone (O3), nitrous oxide (N2O), and nitrogen monoxide (NO). 
     The first precursor supplied during the first gas-supplying cycle (m cycle) and the second precursor supplied during the second gas-supplying cycle (n cycle) may be the same or different. 
     As such, according to the exemplary embodiment of the present invention, the reaction gas supplied during the second gas-supplying cycle (n cycle) does not react with the photoresist, by including the first gas-supplying cycle (m cycle) for coating the protective layer with the predetermined thickness on the photoresist before the second gas-supplying cycle (n cycle) for depositing the thin film such as the sacrificial layer. The photoresist is coated by supplying a source gas without the reaction gas during the first gas-supplying cycle (m cycle) for coating the protective layer. More specifically, after introducing the precursor into a reactor, the source gas is coated on the photoresist by supplying the purge gas, for example, argon plasma (Ar plasma) activating argon (Ar). As such, since the protective layer is formed without inflow of the reaction gas, the carbon and the hydrogen of which the photoresist is made are not damaged to remain intact in the photoresist, thus it is possible to prevent the photoresist from deforming or shrinking. 
     The first gas-supplying cycle (m cycle) for coating the protective layer with the predetermined thickness on the photoresist and the second gas-supplying cycle (n cycle) for depositing the thin film such as the sacrificial layer may be performed in-situ in a single reactor, and alternatively, they may be separately performed ex-situ in a plurality of reactors. When the first gas-supplying cycle (m cycle) for coating the protective layer and the second gas-supplying cycle (n cycle) for depositing the thin film such as the sacrificial layer are performed in-situ in the single reactor, since the formation of the protective layer and the sacrificial layer is performed in the single reactor, before the sacrificial layer is formed, the protective layer may be formed without deterioration of deposition efficiency of the thin film and productivity. 
     A method of depositing a thin film according to a further exemplary embodiment of the present invention will now be described with reference to  FIG. 3 .  FIG. 3  illustrates a schematic timing chart of a gas-supplying cycle of a method of depositing a thin film according to a further exemplary embodiment of the present invention. 
     Referring to  FIG. 3 , a method of depositing a thin film according to the present exemplary embodiment includes a first gas-supplying cycle (m cycle) and a second gas-supplying cycle (n cycle). The first gas-supplying cycle (m cycle) is a step of coating a protective layer on a substrate, and the second gas-supplying cycle (n cycle) is a step of forming a sacrificial layer. 
     In the first gas-supplying cycle (m cycle), while a first precursor is supplied during a first time t 1 , the gas-supplying cycle is stopped during a second time t 2 , and a purge gas and a first plasma are supplied during a third time t 3 . 
     The first precursor supplied in a reaction space during the first time t 1 , when the first plasma is supplied during the third time t 3 , is coated on the substrate to form a protective layer. 
     After a photoresist is already formed on the substrate, when the first gas-supplying cycle (m cycle) is repeated at least one time or more, a first precursor layer is coated on the photoresist such that the protective layer is formed. During the first gas-supplying cycle (m cycle), the first precursor and the first plasma may be alternately and repeatedly supplied. 
     After the protective layer having a determined thickness is coated on the photoresist, the second gas-supplying cycle (n cycle) is repeated. 
     In the second gas-supplying cycle (n cycle), while the purge gas is supplied during a fifth time t 5  to an eighth time t 8 , a second precursor is supplied during the fifth time t 5 , and while a reaction gas is supplied during the fifth time t 5  to an eighth time t 8 , a second plasma is supplied during a seventh time t 7 . 
     The second precursor supplied during the fifth time t 5  is absorbed on the coated protective layer, and the supplied reaction gas is activated by the second plasma supplied during the seventh time t 7 , and reacts with the absorbed second precursor, thereby forming a predetermined thin film. 
     The second gas-supplying cycle (n cycle) is repeated until a thin film with a predetermined thickness is formed, thereby depositing the thin film with the predetermined thickness. 
     The precursor contains silicon (Si). More specifically, the precursor may include at least one of alkoxide-based, amine-based, aminosilane-based, and chloride-based precursors that respectively contain silicon (Si). For example, the precursor may include at least one of TSA, (SiH3)3N; DSO, (SiH3)2; DSMA, (SiH3)2NMe; DSEA, (SiH3)2NEt; DSIPA, (SiH3)2N(iPr); DSTBA, (SiH3)2N(tBu); DEAS, SiH3NEt2; DIPAS, SiH3N(iPr)2; DTBAS, SiH3N(tBu)2; BDEAS, SiH2 (NEt2)2; BDMAS, SiH2 (NMe2)2; BTBAS, SiH2(NHtBu)2; BITS, SiH2(NHSiMe3)2; TEOS, Si(OEt)4; SiCl4; HCD, Si2Cl6; DCS, SiH2Cl2; 3DMAS, SiH(N(Me)2)3; BEMAS, Si H2[N(Et)(Me)]2; AHEAD, Si2 (NHEt)6; TEAS, Si(NHEt)4; and Si3H8, and the reaction gas may include at least one of oxygen (O2), ozone (O3), nitrous oxide (N2O), and nitrogen monoxide (NO). 
     The first precursor supplied during the first gas-supplying cycle (m cycle) and the second precursor supplied during the second gas-supplying cycle (n cycle) may be the same or different. 
     As such, according to the exemplary embodiment of the present invention, the reaction gas supplied during the second gas-supplying cycle (n cycle) does not react with the photoresist, by including the first gas-supplying cycle (m cycle) for coating the protective layer with the predetermined thickness on the photoresist before the second gas-supplying cycle (n cycle) for depositing the thin film such as the sacrificial layer. The photoresist is coated by supplying a source gas without the reaction gas during the first gas-supplying cycle (m cycle) for coating the protective layer. More specifically, after introducing the precursor into a reactor, the source gas is coated on the photoresist by supplying the purge gas, for example, argon plasma (Ar plasma) activating argon (Ar). As such, since the protective layer is formed without inflow of the reaction gas, the carbon and the hydrogen of which the photoresist is made are not damaged to remain intact in the photoresist, thus it is possible to prevent the photoresist from deforming or shrinking. 
     The first gas-supplying cycle (m cycle) for coating the protective layer with the predetermined thickness on the photoresist and the second gas-supplying cycle (n cycle) for depositing the thin film such as the sacrificial layer may be performed in-situ in a single reactor, and alternatively, they may be separately performed ex-situ in a plurality of reactors. When the first gas-supplying cycle (m cycle) for coating the protective layer and the second gas-supplying cycle (n cycle) for depositing the thin film such as the sacrificial layer are performed in-situ in the single reactor, since the formation of the protective layer and the sacrificial layer is performed in the single reactor, before the sacrificial layer is formed, the protective layer may be formed without deterioration of deposition efficiency of the thin film and productivity. 
     A result of an experimental example of the present invention will be described with reference to  FIG. 4 . In the experimental example, with respect to a case of stacking the protective layer and the sacrificial layer by repeating the second gas-supplying cycle (n cycle) after the first gas-supplying cycle (m cycle) for coating the protective layer on the photoresist according to the method of depositing the thin film according to the exemplary embodiment of the present invention, and a case of forming only the sacrificial layer on the photoresist according to a conventional method of depositing the thin film, shrinkages of the photoresists were respectively measured, and the measured results are shown in  FIG. 4 . 
     Referring to  FIG. 4 , the photoresist was shrunk by about 2 Å when the sacrificial layer was formed after the protective layer was coated on the photoresist according to the method of depositing the thin film of the exemplary embodiment of the present invention, while the photoresist was shrunk by about 50 Å when only the sacrificial layer was formed on the photoresist according to the conventional method of depositing the thin film. As such, according to the method of depositing the thin film according to the exemplary embodiment of the present invention, even though the sacrificial layer containing silicon is stacked on the photoresist, it can be seen that deformation such as shrinkage of the photoresist is less generated by introducing a protective layer before depositing a sacrificial layer. 
     A result of another experimental example of the present invention will be described with reference to  FIGS. 5A and 5B . When the protective layer and the sacrificial layer were stacked by repeating the second gas-supplying cycle (n cycle) after the first gas-supplying cycle (m cycle) for coating the protective layer on the photoresist according to the method of depositing the thin film according to the exemplary embodiment of the present invention, components of the thin film were analyzed by auger electron spectroscopy (AES), and the analyzed results are shown in  FIGS. 5A and 5B . 
     Referring to  FIG. 5A , it can be seen that the silicon (Si) film (layer) was formed during the first gas-supplying cycle (m cycle) for depositing the protective layer, and referring to  FIG. 5B , it can be seen that the silicon dioxide (SiO2) film (or layer) was formed during the second gas-supplying cycle (n cycle) for forming the sacrificial layer. As such, according to the exemplary embodiment of the present invention, it can be seen that the protective layer containing silicon may be formed without the reaction gas by supplying the precursor containing silicon and the purge gas plasma such as argon. 
     As such, according to the exemplary embodiment of the present invention, the protective layer made of silicon is formed on the photoresist, and then the sacrificial layer comprised of the silicon dioxide layer is formed on the protective layer, thereby reducing a negative influence exerted to the photoresist due to the reaction gas supplied when the sacrificial layer is formed. Therefore, it is possible to prevent the photoresist from shrinking even though a sacrificial layer such as the silicon dioxide film is stacked on the photoresist by introducing a protective layer before depositing a sacrificial layer. 
     While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.