Amorphous carbon film and method of depositing the same

Abstract

A method for depositing an amorphous carbon film having a high selectivity ratio and relatively low compressive stress is disclosed. A method for depositing an amorphous carbon film according to one embodiment of the present invention comprises: (a) loading a substrate into a chamber; and (b) discharging a precursor containing carbon, a precursor containing oxygen, and a precursor containing nitrogen to deposit an oxygen and nitrogen-doped amorphous carbon film on the substrate.

Description

Technology Field

[0001] The present invention relates to a technology for depositing amorphous carbon films, which are primarily used as hard masks in semiconductor manufacturing processes. More specifically, the present invention relates to an amorphous carbon film having a high selectivity ratio and relatively low compressive stress, and a method for depositing the same. Background Technology

[0003] Horizontal and vertical NAND structures are currently being applied in semiconductor manufacturing processes. As finer patterns are required, significant research is currently being conducted on vertical NAND (VNAND) structures.

[0004] To achieve a vertical NAND structure, a hard mask process requiring high selectivity is required. To satisfy these requirements, an amorphous carbon film (ACL) has been used as a representative hard mask. An amorphous carbon film is deposited as a hard mask on a multilayer insulating film in which silicon oxide and silicon nitride films are alternately stacked in tens to hundreds of layers in the vertical direction using a Plasma Enhanced Chemical Vapor Deposition (PECVD) process, and then a narrow, long hole is formed that penetrates the multilayer insulating film vertically through an etching process.

[0006] Considering the high number of layers in multilayer insulating films in vertical NAND devices, the selectivity of the amorphous carbon film must be high for it to properly function as a hard mask.

[0007] Several methods have been proposed to increase the selectivity of amorphous carbon films. For example, Patent Document 1 discloses a method for depositing a multilayer structure of amorphous carbon films in which boron-doped carbon films and boron-non-doped carbon films are alternately stacked by repeating the steps of depositing a carbon film without dopants using a hydrocarbon precursor and depositing a carbon film with dopants using a hydrocarbon precursor and a boron precursor.

[0009] Meanwhile, as the selectivity of the amorphous carbon film increases, compressive stress also tends to increase. However, if compressive stress increases excessively, problems may arise during wafer chucking, which can result in a decrease in device yield. Prior art literature

[0011] Published Patent Application No. 10-2017-0093003 (Published Aug. 14, 2017) The problem to be solved

[0012] The problem that the present invention aims to solve is to provide a method for depositing an amorphous carbon film having high selectivity and relatively low compressive stress through PECVD process control.

[0013] In addition, the problem that the present invention aims to solve is to provide an amorphous carbon film having a high selectivity while having relatively low compressive stress. means of solving the problem

[0015] A method for depositing an amorphous carbon film according to an embodiment of the present invention for solving the above problem comprises: (a) a step of loading a substrate into a chamber; and (b) a step of depositing an amorphous carbon film doped with oxygen and nitrogen on the substrate by discharging a precursor containing carbon, a precursor containing oxygen, and a precursor containing nitrogen.

[0016] The above-mentioned carbon-containing precursor may include a carbon compound in a gaseous state.

[0017] The oxygen-containing precursor may include oxygen gas. The oxygen gas may be supplied into the chamber at a flow rate of 80 to 500 sccm.

[0018] The above-mentioned nitrogen-containing precursor may contain nitrogen gas. The above-mentioned nitrogen gas may be supplied into the chamber at a flow rate of 100 to 1000 sccm.

[0019] The above step (b) can be performed under conditions of process pressure 3 to 8 Torr, plasma power 1000 to 3000 W, and substrate temperature 400 to 650°C.

[0020] The above carbon-containing precursor can be supplied together with Ar or He.

[0022] According to one embodiment of the present invention for solving the above problem, an amorphous carbon film is doped with oxygen and nitrogen in a carbon matrix and is characterized by having a compressive stress of 200 MPa or less and a modulus of 40 MPa or more.

[0023] The above amorphous carbon film can exhibit a Vickers hardness of 5.0 GPa or higher. Effects of the invention

[0025] According to the method for depositing an amorphous carbon film according to the present invention, an amorphous carbon film doped with oxygen and nitrogen can be deposited by using a precursor containing oxygen and a precursor containing nitrogen together with a precursor containing carbon.

[0026] The oxygen and nitrogen-doped amorphous carbon film according to the present invention was able to have a high selectivity ratio while having low compressive stress. Therefore, the oxygen and nitrogen-doped amorphous carbon film can suppress wafer fixation defects that may occur due to excessively high compressive stress.

[0027] In addition, the oxygen and nitrogen-doped amorphous carbon film according to the present invention can have low compressive stress and also high modulus, so it can be used as a hard mask for, for example, manufacturing a vertical NAND device without increasing the thickness of the amorphous carbon film.

[0028] The effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the detailed description below. Brief explanation of the drawing

[0030] Figure 1 schematically illustrates an amorphous carbon film deposition method according to the present invention. FIG. 2 schematically illustrates an example of a PECVD apparatus that can be used in the amorphous carbon film deposition method according to the present invention. Figure 3 shows the stress and hardness of amorphous carbon films deposited according to the examples and comparative examples. Figure 4 shows the stress and modulus of amorphous carbon films deposited according to the examples and comparative examples. Figure 5 shows the hardness and modulus of amorphous carbon films deposited according to the examples and comparative examples. Specific details for implementing the invention

[0031] The advantages and features of the present invention and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims.

[0032] When an element or layer is described as being "above" or "below" another element or layer, it includes not only being directly above or below the other element or layer, but also cases where another layer or element is interposed in the middle. Additionally, when it is stated that an element is "connected," "combined," or "joined" to another element, it should be understood that while the elements may be directly connected or joined to each other, other elements may be "interposed" between each element, or that each element may be "connected," "combined," or "joined" through other elements.

[0033] The terms used herein are for describing the embodiments and are therefore not intended to limit the invention. In this specification, the singular form includes the plural form unless specifically stated otherwise in the text. As used in this specification, "comprising" and / or "comprising" does not exclude the presence or addition of one or more other elements, elements, steps, and / or actions to the mentioned elements, components, steps, and / or actions.

[0034] The amorphous carbon film and the deposition method according to a preferred embodiment of the present invention will be described in detail below with reference to the attached drawings.

[0036] Generally, an amorphous carbon film refers to a film in which carbon is arranged in an amorphous state, unlike graphite in which carbon is regularly arranged. Amorphous carbon films have high etch selectivity and high rigidity, making them suitable for use as hard masks in semiconductor manufacturing processes, particularly in processes requiring deep vertical etching.

[0037] However, when the thickness of the material to be etched increases, such as the multilayer insulating film of a vertical NAND device, the thickness of the amorphous carbon film must also be increased to perform the role of a hard mask until the etching is finished. An increase in the thickness of the amorphous carbon film can lead to problems such as reduced productivity and deterioration of CD (Critical Dimension) characteristics. Therefore, an amorphous carbon film having a high modulus along with a high selectivity is required, which can be achieved by an amorphous carbon film having compressive stress. However, if the compressive stress is too high, problems such as wafer fixation failure may occur. Therefore, an amorphous carbon film having a relatively low compressive stress while having a high selectivity is required. As a result of long research, the inventors of the present invention discovered that when oxygen (O2) and nitrogen (N2) are doped together during the deposition of an amorphous carbon film using a Plasma Enhanced Chemical Vapor Deposition (PECVD) process, an amorphous carbon film having a relatively low compressive stress while having a high selectivity can be deposited.

[0038] This is attributed to the fact that oxygen and nitrogen dissociation species generated through the plasma process react with hydrogen dissociated from hydrocarbons, such as C3H6, thereby reducing the hydrogen content and, consequently, increasing the formation ratio of carbon films with sp3 structures compared to sp2 structures.

[0039] As a result, even with similar compressive stress, a relatively harder amorphous carbon film with excellent selectivity can be deposited due to the effect of increased sp3 structure. Similarly, even with similar selectivity, an amorphous carbon film with low compressive stress can be deposited.

[0041] Figure 1 schematically illustrates an amorphous carbon film deposition method according to the present invention.

[0042] Referring to FIG. 1, the illustrated amorphous carbon film deposition method includes a substrate loading step (S110) and an ONACL deposition step (S120).

[0043] The amorphous carbon film deposition method shown in Fig. 1 can utilize, for example, the PECVD apparatus shown in Fig. 2.

[0044] Referring to FIG. 2, the illustrated PECVD device is equipped with a gas supply line (S), a chamber (2), a shower head (3), a susceptor (4), an RF power source (5), and a first electrode (6).

[0045] The gas supply line (S) serves to supply reaction gas, inert gas, etc., from outside the chamber (2) into the chamber (2). In FIG. 2, only one gas supply line (S) connected to the chamber (2) is shown. In this case, multiple gas supply lines may be connected to one gas supply line connected to the chamber (2). As another example, each gas supply line may be connected to the chamber (2).

[0046] For example, if the carbon-containing precursor is a hydrocarbon gas and the oxygen-containing precursor is an oxygen gas, since the likelihood of reaction is somewhat high, it is preferable for them to be supplied to the chamber separately and then come into contact with each other within the chamber (2). It is more preferable for the hydrocarbon gas and the oxygen gas to come into contact between the showerhead (3) and the susceptor (4).

[0047] The gas supplied into the chamber through one or more gas supply lines may be a carbon-containing precursor, an oxygen-containing precursor, a nitrogen-containing precursor, and an inert gas. The carbon-containing precursor may be supplied independently into the chamber without a carrier gas, or supplied into the chamber together with an inert gas as a carrier gas. Similarly, the oxygen-containing precursor or the nitrogen-containing precursor may also be supplied independently into the chamber or supplied into the chamber together with an inert gas.

[0048] Meanwhile, if the carbon-containing precursor is in a liquid state, it can be vaporized through a vaporizer and supplied into the chamber.

[0049] The inert gas can be supplied into the chamber along with other precursors, or supplied into the chamber through a separate gas supply line.

[0050] The shower head (3) is provided on the upper side inside the chamber (2) and sprays gas injected through the gas supply line (S) into the chamber.

[0051] A susceptor (4) is provided on the lower side inside the chamber (2) to which a substrate (W), such as a wafer, is loaded (supported). The susceptor (4) may be equipped with a temperature control means for heating / cooling the substrate. Additionally, the susceptor (4) may function as a ground electrode, as shown in the example in FIG. 1. A separate ground line (8) may be provided to further improve ground performance. Although not shown, the susceptor (4) itself may be configured as a second electrode (bias electrode) by connecting a high-frequency power source or a DC power source.

[0052] The first electrode (6) is electrically connected to the RF power source (5) and used as an electrode for plasma discharge within the chamber (2). In the example illustrated in FIG. 1, the showerhead (3) is electrically connected (3a) to the first electrode (6) so that the first electrode (6) and the showerhead (3) function together as a single electrode. Accordingly, RF power generated from the RF power source (5) is applied into the process chamber (2) through the first electrode (6) and the showerhead (3). The RF filter (7) serves to remove signal interference occurring around the process chamber (2).

[0053] The method for depositing an amorphous carbon film according to the present invention may use various known PECVD devices in addition to the PECVD device exemplified in FIG. 2.

[0055] Returning to Fig. 1, in the substrate loading step (S110), a substrate (W) is loaded onto a susceptor (4) inside the chamber. Afterwards, the inside of the process chamber (2) is vacuumed using an external vacuum system (not shown).

[0056] In the ONACL deposition step (S120), an oxygen- and nitrogen-doped amorphous carbon film is deposited on a substrate by discharging a precursor containing carbon, a precursor containing oxygen, and a precursor containing nitrogen. That is, while starting the supply of a carbon-containing precursor and an inert gas, and a precursor containing oxygen and a precursor containing nitrogen, an RF power of about 1000 to 3000 W is applied from an RF power source (5) to discharge a carbon compound gas between a showerhead (3) and a susceptor (4) to deposit an amorphous carbon film on a substrate.

[0057] A precursor containing carbon, a precursor containing oxygen, and a precursor containing nitrogen can be discharged inside the chamber (2) of the PECVD device shown in FIG. 2. As another example, at least some of the precursors containing carbon, oxygen, and nitrogen can be discharged from a remote plasma system (RPS) outside the chamber and supplied into the chamber.

[0058] Carbon-containing precursors may be liquid carbon compounds such as methanol (CH3OH) or gaseous carbon compounds such as gaseous hydrocarbons like acetylene (C2H2) or propene (C3H6). Among these, liquid carbon compounds necessarily require a separate vaporizer, whereas gaseous carbon compounds may be more advantageous for depositing amorphous carbon films with high selectivity. In the present invention, selectivity refers to selectivity with respect to SiO2 unless otherwise noted. Therefore, it is more preferable to use gaseous carbon compounds as carbon-containing precursors.

[0059] The supply amount of the carbon-containing precursor can be set differently depending on the thickness of the amorphous carbon film to be deposited, the process chamber temperature, etc., and can be supplied at a flow rate of, for example, 500 to 1500 sccm.

[0060] In addition, a carbon-containing precursor can be supplied into the chamber along with an inert gas such as helium gas (He) or argon gas (Ar). The inert gas can be supplied into the process chamber at a flow rate of approximately 4000 sccm or less. For example, argon gas can be supplied into the chamber at a flow rate of 2000 to 4000 sccm and helium gas at a flow rate of 200 to 1000 sccm, but is not limited thereto.

[0061] Meanwhile, when depositing an amorphous carbon film with high selectivity using only gaseous carbon compounds, compressive stress may increase excessively. In order to solve this problem, the present invention deposited an oxygen and nitrogen-doped amorphous carbon film by using a precursor containing oxygen and a precursor containing nitrogen together with a precursor containing carbon.

[0062] The oxygen-containing precursor can be a gas containing oxygen, such as oxygen gas (O2) or ozone gas (O3), and among these, it is more preferable to use oxygen gas. The nitrogen-containing precursor can be a gas containing nitrogen, such as nitrogen gas (N2) or ammonia gas (NH3), and among these, it is more preferable to use nitrogen gas.

[0063] Meanwhile, precursors containing both oxygen and nitrogen, such as nitrogen oxides like NO, NO2, and N2O, may also be considered. However, when using nitrogen oxides, the deposition rate of the amorphous carbon film may become excessively low compared to when oxygen and nitrogen gases are used individually.

[0064] Oxygen-containing precursors can be supplied into the chamber at a flow rate of 80 to 500 sccm. Nitrogen-containing precursors can be supplied into the chamber at a flow rate of 100 to 1000 sccm. If the flow rate of the oxygen-containing precursor or the nitrogen-containing precursor is excessively low, it may be difficult to simultaneously achieve the target high selectivity and low compressive stress due to insufficient doping of oxygen and / or nitrogen. Conversely, if the flow rate of the oxygen-containing precursor or the nitrogen-containing precursor is excessively high, it may degrade properties such as the modulus of the amorphous carbon film without further effect.

[0066] The ONACL deposition step (S120) can be performed under normal amorphous carbon film deposition conditions. For example, the ONACL deposition step (S120) can be performed under conditions of a process pressure of 3 to 8 Torr, a plasma power of 1000 to 3000 W, and a substrate temperature of 400 to 650°C. That is, in the case of the present invention, an amorphous carbon film is deposited by a normal PECVD process, wherein a precursor containing oxygen and a precursor containing nitrogen are supplied together with a precursor containing carbon in the chamber.

[0068] According to the method for depositing an amorphous carbon film according to the present invention as described above, an amorphous carbon film doped with oxygen and nitrogen can be deposited by using a precursor containing oxygen and a precursor containing nitrogen together with a precursor containing carbon.

[0069] The amorphous carbon film according to the present invention is doped with oxygen and nitrogen in a carbon matrix. Through the doping of oxygen and nitrogen, the amorphous carbon film according to the present invention can have a compressive stress of 200 MPa or less and a modulus of 40 MPa or more. Amorphous carbon films deposited by a high-temperature PECVD process using gaseous hydrocarbons can also have a modulus of 40 MPa or more, in which case most have a high compressive stress of 200 MPa or more. In contrast, the amorphous carbon film according to the present invention has a modulus of 40 MPa or more while uniquely having a relatively low compressive stress of 200 MPa or less. This can also be confirmed through Fig. 4.

[0070] Accordingly, the oxygen and nitrogen-doped amorphous carbon film according to the present invention can have low compressive stress and also high modulus, so it can be used as a hard mask for, for example, manufacturing a vertical NAND device without increasing the thickness of the amorphous carbon film.

[0071] In addition, the amorphous carbon film according to the present invention can exhibit a Vickers hardness of 5.0 GPa or higher. Likewise, the amorphous carbon film according to the present invention exhibits a high hardness of 5.0 GPa or higher while having a relatively low compressive stress of 200 MPa or lower. This can also be confirmed through FIG. 3.

[0073] Examples

[0074] Hereinafter, the structure and operation of the present invention will be explained in more detail through preferred embodiments of the present invention. However, these are presented as preferred examples of the present invention and should not be interpreted in any way as limiting the present invention.

[0075] Details not listed here can be sufficiently technically inferred by a person skilled in this field, so their explanation will be omitted.

[0077] Amorphous carbon films according to Examples 1 to 14 were deposited under the conditions listed in Table 1, and amorphous carbon films according to Comparative Examples 1 to 8 were deposited under the conditions listed in Table 2.

[0078] [Table 1]

[0079]

[0080] [Table 2]

[0081]

[0082] FIG. 3 shows the stress and hardness of amorphous carbon films deposited according to the examples and comparative examples. FIG. 4 shows the stress and modulus of amorphous carbon films deposited according to the examples and comparative examples. FIG. 5 shows the hardness and modulus of amorphous carbon films deposited according to the examples and comparative examples. In FIG. 3 to 5, the amorphous carbon films deposited according to the examples are labeled ONACL, and the amorphous carbon films deposited according to the comparative examples are labeled ACL.

[0083] Referring to FIG. 3, it can be seen that the amorphous carbon films deposited according to the embodiment and the amorphous carbon films deposited according to the comparative example generally exhibit a Vickers hardness of 5.0 GPa or higher, except for exceptional cases. In particular, the amorphous carbon films deposited according to the embodiment have a Vickers hardness similar to that of the amorphous carbon films deposited according to the comparative example, but it can be seen that while the amorphous carbon films deposited according to the comparative example have a relatively large compressive stress, the amorphous carbon films deposited according to the embodiment have a relatively small compressive stress.

[0084] Referring to FIG. 4, it can be seen that the amorphous carbon films deposited according to the embodiment and the amorphous carbon films deposited according to the comparative example generally exhibit a modulus of 40 MPa or higher, except for exceptional cases. In particular, the amorphous carbon films deposited according to the embodiment have a modulus similar to that of the amorphous carbon films deposited according to the comparative example, but it can be seen that while the amorphous carbon films deposited according to the comparative example have a relatively large compressive stress, the amorphous carbon films deposited according to the embodiment have a relatively small compressive stress.

[0085] Meanwhile, referring to FIG. 5, in the case of the amorphous carbon films deposited according to the embodiment and the amorphous carbon films deposited according to the comparative example, it can be seen that as hardness increases, the modulus also tends to increase.

[0087] Table 3 shows the characteristics of the amorphous carbon films prepared according to Comparative Examples 9 and 10 and Examples 15 and 16. In Comparative Examples 9 and 10 and Examples 15 and 16, the same process conditions were applied except for the conditions shown in Table 3.

[0088] [Table 3]

[0089]

[0090] In Table 3, the selectivity is the selectivity for SiO2, with the selectivity of the amorphous carbon film according to Comparative Example 9 set to 100% and the relative selectivity of the remaining amorphous carbon films.

[0091] Referring to Table 3, in the case of the amorphous carbon film according to Comparative Example 10, which has a very slow deposition rate without O2 and N2 supply, it showed a higher selectivity ratio compared to the amorphous carbon film according to Comparative Example 9, but it can be seen that the compressive stress also increased significantly.

[0092] In contrast, in the case of the amorphous carbon film according to Examples 15 and 16, in which O2 and N2 were supplied together with C3H6, although it exhibits a high selectivity similar to that of the amorphous carbon film according to Comparative Example 10, it can be seen that the compressive stress is relatively low and the deposition rate is also faster than that of Comparative Example 10.

[0093] In addition, the amorphous carbon films according to Examples 15 and 16 exhibited a relatively higher absorption coefficient compared to Comparative Example 9. A higher absorption coefficient indicates that the amorphous carbon film is closer to black and that the density of the film has increased.

[0094] Therefore, based on the results in Table 3, using oxygen-containing precursors and nitrogen-containing precursors along with gaseous hydrocarbons can be seen as more advantageous for depositing amorphous carbon films with high selectivity and low compressive strength.

[0096] Although the present invention has been described above with reference to embodiments, various changes and modifications may be made by those skilled in the art. Such changes and modifications are considered to be within the scope of the present invention as long as they do not depart from the scope of the present invention. Accordingly, the scope of rights of the present invention should be determined by the claims set forth below. Explanation of the symbols

[0098] 1: PECVD device 2: Chamber 3: Shower head 4: Susceptor 5: RF Power 6: First electrode 7: RF filter 8: Ground line

Claims

Claim 1 A method for depositing an amorphous carbon film comprising: (a) a step of loading a substrate into a chamber; and (b) a step of depositing an oxygen and nitrogen-doped amorphous carbon film on the substrate by discharging a precursor containing carbon, a precursor containing oxygen, and a precursor containing nitrogen, wherein the precursor containing oxygen is supplied into the chamber at a flow rate of 80 to 500 sccm and the precursor containing nitrogen is supplied into the chamber at a flow rate of 100 to 1000 sccm. Claim 2 A method for depositing an amorphous carbon film according to claim 1, wherein the carbon-containing precursor comprises a carbon compound in a gaseous state. Claim 3 A method for depositing an amorphous carbon film according to claim 1, wherein the oxygen-containing precursor comprises oxygen gas. Claim 4 A method for depositing an amorphous carbon film according to claim 1, characterized in that the nitrogen-containing precursor is nitrogen gas. Claim 5 A method for depositing an amorphous carbon film according to claim 1, wherein step (b) is performed under conditions of a process pressure of 3 to 8 Torr, a plasma power of 1000 to 3000 W, and a substrate temperature of 400 to 650°C. Claim 6 delete Claim 7 delete Claim 8 delete Claim 9 delete

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