Amorphous carbon film and deposition method thereof

Abstract

To provide an amorphous carbon film that has relatively low compression stress while having high selection ratio, and to provide a vapor deposition method for the same.SOLUTION: A vapor deposition method for an amorphous carbon film includes steps of: (a) loading a substrate W into a chamber 2; and (b) depositing an amorphous carbon film doped with oxygen and nitrogen on a substrate W with vapor deposition by discharging a precursor including carbon, a precursor including oxygen, and a precursor including nitrogen.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a deposition technique for an amorphous carbon film, which is mainly used as a hard mask in a semiconductor manufacturing process, and more particularly to an amorphous carbon film having a high selectivity and a relatively low compressive stress, and a deposition method thereof. [Background technology]

[0002] In recent years, NAND device structures that are being applied in semiconductor manufacturing processes include horizontal NAND structures and vertical NAND structures. Due to the demand for finer patterns, much research has been conducted on vertical NAND (VNAND) structures.

[0003] Achieving a vertical NAND structure requires a hard mask process that requires high selectivity. To meet this requirement, amorphous carbon films (ACLs) have been used as a typical hard mask. An amorphous carbon film is deposited as a hard mask on a multi-layer insulating film, consisting of tens to hundreds of layers of silicon oxide and silicon nitride stacked vertically, using a plasma-enhanced chemical vapor deposition (PECVD) process. Then, an etching process is used to form elongated holes that penetrate vertically through the multi-layer insulating film.

[0004] Considering the high number of multi-layer insulating films in vertical NAND devices, the amorphous carbon film needs to have a high selectivity in order to function properly as a hard mask.

[0005] Various methods have been proposed for increasing the selectivity of amorphous carbon films. For example, Korean Patent Publication No. 10-2017-0093003 (published on August 14, 2017) discloses a method for depositing an amorphous carbon film having a multilayer structure in which boron-doped carbon films and non-boron-doped carbon films are alternately stacked by repeating the steps of depositing a carbon film not doped with a dopant using a hydrocarbon precursor and depositing a carbon film doped with a dopant using a hydrocarbon precursor and a boron precursor.

[0006] On the other hand, as the selectivity of the amorphous carbon film increases, the compressive stress also tends to increase, but if the compressive stress increases too much, problems may occur in wafer chucking, resulting in a decrease in device yield. Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention provides a method for depositing an amorphous carbon film having a relatively low compressive stress while having a high selectivity by controlling the PECVD process.

[0008] Another problem to be solved by the present invention is to provide an amorphous carbon film that has a high selectivity and yet a relatively low compressive stress. [Means for solving the problem]

[0009] In order to solve the above problems, according to one embodiment of the present invention, a method for depositing an amorphous carbon film includes: (a) loading a substrate into a chamber; and (b) discharging a carbon-containing precursor, an oxygen-containing precursor, and a nitrogen-containing precursor to deposit an oxygen- and nitrogen-doped amorphous carbon film on the substrate.

[0010] The carbon-containing precursor may be a gaseous carbon compound.

[0011] The oxygen-containing precursor may be oxygen gas, and the oxygen gas may be supplied into the chamber at a flow rate of 80 to 500 sccm.

[0012] The nitrogen-containing precursor may include nitrogen gas, and the nitrogen gas may be supplied into the chamber at a flow rate of 100 to 1000 sccm.

[0013] The step (b) can be performed under the 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.

[0014] The carbon-containing precursor may be supplied together with Ar or He.

[0015] To solve the above problems, an amorphous carbon film according to one embodiment of the present invention has a carbon matrix doped with oxygen and nitrogen, and is characterized by having a compressive stress of 200 MPa or less and a modulus of 40 MPa or more.

[0016] The amorphous carbon film can exhibit a Vickers hardness of 5.0 GPa or more. [Effects of the Invention]

[0017] 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 carbon-containing precursor, an oxygen-containing precursor, and a nitrogen-containing precursor.

[0018] The amorphous carbon film doped with oxygen and nitrogen according to the present invention has a high selectivity and low compressive stress, thereby suppressing wafer fixation defects that can occur due to excessively high compressive stress.

[0019] In addition, the oxygen- and nitrogen-doped amorphous carbon film according to the present invention may have a high modulus while having low compressive stress, and may be used as a hard mask for manufacturing a vertical NAND device, for example, without increasing the thickness of the amorphous carbon film.

[0020] The effects of the present invention are not limited to those mentioned above, and other effects not mentioned above will be clearly understood by those skilled in the art from the detailed description below. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a diagram illustrating a method for depositing an amorphous carbon film according to the present invention; [Figure 2] 1 is a diagram schematically illustrating an example of a PECVD apparatus used in the method for depositing an amorphous carbon film according to the present invention. [Figure 3] FIG. 1 is a graph showing the stress and hardness of amorphous carbon films deposited according to the examples and comparative examples. [Figure 4] FIG. 1 is a graph showing the stress and modulus of amorphous carbon films deposited according to the examples and comparative examples. [Figure 5] FIG. 1 is a diagram showing the hardness and modulus of amorphous carbon films deposited according to the examples and comparative examples. DETAILED DESCRIPTION OF THE INVENTION

[0022] The advantages and features of the present invention, as well as methods for achieving them, will become more apparent from the following detailed description of the embodiments in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and may be embodied in various different forms. However, these embodiments are provided to complete the disclosure of the present invention and fully convey the scope of the invention to those skilled in the art. The present invention is defined only by the scope of the claims.

[0023] References to an element or layer being "on top of" or "below" another element or layer include not only directly on top of or directly below the other element or layer, but also when there are other layers or elements between them. Furthermore, when an element is described as being "coupled," "bonded," or "connected" to another element, it should be understood that the elements may be directly coupled or connected to each other, but also that there may be other elements "intervening" between each element, or each element may be "coupled," "coupled," or "connected" through other elements.

[0024] The terms used in this specification are for the purpose of describing embodiments and are therefore not intended to limit the present invention. In this specification, the singular form includes the plural form unless the context clearly dictates otherwise. As used in this specification, the terms "comprise" and / or "include" do not exclude the presence or addition of one or more other elements, elements, steps and / or operations.

[0025] Hereinafter, an amorphous carbon film and a method for depositing the same according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0026] 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 etching selectivity and high rigidity, making them suitable for use as hard masks in semiconductor manufacturing processes, especially processes that require deep vertical etching.

[0027] However, as the thickness of the material to be etched increases, such as in the multilayer insulating film of a vertical NAND device, the thickness of the amorphous carbon film must also increase to function as a hard mask until the end of etching. Increasing the thickness of the amorphous carbon film can lead to problems such as reduced productivity and reduced critical dimension (CD) characteristics. Therefore, an amorphous carbon film with high selectivity and high modulus is required, which can be achieved by an amorphous carbon film with compressive stress. However, if the compressive stress is too high, problems such as poor wafer fixation can occur. Therefore, an amorphous carbon film with high selectivity and relatively low compressive stress is required. After extensive research, the inventors of the present invention discovered that when depositing an amorphous carbon film using a plasma-enhanced chemical vapor deposition (PECVD) process, doping with oxygen (O2) and nitrogen (N2) allows the deposition of an amorphous carbon film with high selectivity and relatively low compressive stress.

[0028] This is because dissociated species of oxygen and nitrogen generated by the plasma process can react with hydrogen dissociated from hydrocarbons, such as C3H6, reducing the hydrogen content, which can increase the proportion of carbon films formed with sp3 structure rather than sp2 structure.

[0029] As a result, even if the compressive stress is similar, the sp3 structure is increased, which allows the deposition of an amorphous carbon film that is relatively harder and has excellent selectivity. Similarly, even if the selectivity is similar, the deposition of an amorphous carbon film that has low compressive stress can be achieved.

[0030] FIG. 1 is a schematic diagram showing a method for depositing an amorphous carbon film according to the present invention.

[0031] Referring to FIG. 1, the method for depositing an amorphous carbon film includes a substrate loading step (S110) and an Oxygen-doped and Nitrogen-doped Amorphous Carbon Layer (ONACL) deposition step (S120).

[0032] The method for depositing the amorphous carbon film shown in FIG. 1 can use, for example, a PECVD apparatus shown in FIG.

[0033] Referring to FIG. 2, the illustrated PECVD apparatus 1 comprises a gas supply line (S), a chamber 2, a showerhead 3, a susceptor 4, an RF power supply 5, and a first electrode 6.

[0034] The gas supply line (S) serves to supply reactive gases, inert gases, etc., from outside the chamber 2 to the inside of 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. In another example, each gas supply line may be connected to the chamber 2.

[0035] For example, when the carbon-containing precursor is a hydrocarbon gas and the oxygen-containing precursor is oxygen gas, they are more likely to react with each other, and therefore it is preferable that they are supplied separately to the chamber and then contact each other in the chamber 2. It is more preferable that the hydrocarbon gas and the oxygen gas contact each other between the showerhead 3 and the susceptor 4.

[0036] The gases supplied to the interior of the chamber via one or more gas supply lines can be a carbon-containing precursor, an oxygen-containing precursor, a nitrogen-containing precursor, an inert gas, etc. The carbon-containing precursor can be supplied independently to the interior of the chamber without a carrier gas, or can be supplied together with an inert gas as a carrier gas. Similarly, the oxygen-containing precursor or the nitrogen-containing precursor can be supplied independently to the interior of the chamber, or can be supplied together with an inert gas.

[0037] On the other hand, when the precursor containing carbon is in a liquid state, it may be vaporized through a vaporizer and supplied into the chamber.

[0038] The inert gas may be supplied into the chamber together with the other precursors, or may be supplied into the chamber via a separate gas supply line.

[0039] The shower head 3 is provided at the upper side of the interior of the chamber 2 and sprays gases introduced through the gas supply line (S) into the interior of the chamber.

[0040] A susceptor 4 is provided at the bottom inside the chamber 2, on which a substrate (W) such as a wafer is loaded (supported). The susceptor 4 may be provided with a temperature control means for heating / cooling the substrate. The susceptor 4 may also function as a ground electrode, as in the example shown in FIG. 1. A separate ground line 8 may be provided to further improve grounding. Although not shown, the susceptor 4 itself may be connected to a high frequency power source or a DC power source to form a second electrode (bias electrode).

[0041] The first electrode 6 is electrically connected to the RF power supply 5 and is used as an electrode for plasma discharge within the chamber 2. In the example shown 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. Thus, RF power generated by the RF power supply 5 is applied to the inside of the process chamber 2 through the first electrode 6 and the showerhead 3. The RF filter 7 serves to remove signal interference generated around the process chamber 2.

[0042] The method for depositing an amorphous carbon film according to the present invention can use the PECVD apparatus exemplified in FIG. 2 as well as various other known PECVD apparatuses.

[0043] 1, in the substrate loading step (S110), a substrate (W) is loaded onto a susceptor 4 in the chamber, and then the inside of the process chamber 2 is evacuated using an external vacuum system (not shown).

[0044] In the ONICALC deposition step (S120), a carbon-containing precursor, an oxygen-containing precursor, and a nitrogen-containing precursor are discharged to deposit an oxygen- and nitrogen-doped amorphous carbon film on the substrate. That is, while starting to supply the carbon-containing precursor, the inert gas, the oxygen-containing precursor, and the nitrogen-containing precursor, RF power of about 1000 to 3000 W is applied from the RF power source 5 to discharge the carbon compound gas between the showerhead 3 and the susceptor 4, thereby depositing an amorphous carbon film on the substrate.

[0045] The carbon-containing precursor, the oxygen-containing precursor, and the nitrogen-containing precursor may be discharged inside chamber 2 of the PECVD apparatus shown in Figure 2. In another example, at least some of the carbon-containing precursor, the oxygen-containing precursor, and the nitrogen-containing precursor may be discharged in a remote plasma system (RPS) outside the chamber and then supplied to the chamber.

[0046] The carbon-containing precursor may be a liquid carbon compound such as methanol (CHOH) or a gaseous carbon compound such as a gaseous hydrocarbon such as acetylene (C2H2) or propylene (C3H6). Liquid carbon compounds require a separate vaporizer, while gaseous carbon compounds may be more advantageous for depositing amorphous carbon films with high selectivity. In the present invention, selectivity refers to the selectivity relative to SiO2 unless otherwise specified. Therefore, it is more preferable to use a gaseous carbon compound as the carbon-containing precursor.

[0047] The supply rate of the carbon-containing precursor may be set differently depending on the thickness of the amorphous carbon film to be deposited, the temperature of the process chamber, etc., and may be, for example, at a flow rate of 500 to 1500 sccm.

[0048] The carbon-containing precursor may be supplied into the chamber together with an inert gas such as helium gas (He) or argon gas (Ar). The inert gases may be supplied into the process chamber at a flow rate of about 4000 sccm or less. For example, argon gas may be supplied into the chamber at a flow rate of 2000 to 4000 sccm, and helium gas may be supplied into the chamber at a flow rate of 200 to 1000 sccm, but this is not limiting.

[0049] On the other hand, when an amorphous carbon film with high selectivity is deposited using only a gaseous carbon compound, the compressive stress may be excessively increased. To solve this problem, the present invention deposits an oxygen- and nitrogen-doped amorphous carbon film using a carbon-containing precursor, an oxygen-containing precursor, and a nitrogen-containing precursor.

[0050] The oxygen-containing precursor may be a gas containing oxygen such as oxygen gas (O2) or ozone gas (O3), of which oxygen gas is more preferred.The nitrogen-containing precursor may be a gas containing nitrogen such as nitrogen gas (N2) or ammonia gas (NH3), of which nitrogen gas is more preferred.

[0051] Alternatively, precursors containing both oxygen and nitrogen, such as nitrogen oxides such as NO, NO, and NO, may also be used. However, when nitrogen oxides are used, the deposition rate of the amorphous carbon film may be excessively low compared to when oxygen gas and nitrogen gas are used separately.

[0052] The oxygen-containing precursor may be supplied into the chamber at a flow rate of 80 to 500 sccm. The nitrogen-containing precursor may 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 too low, it may be difficult to simultaneously achieve the desired high selectivity and low compressive stress due to insufficient oxygen and / or nitrogen doping. Conversely, if the flow rate of the oxygen-containing precursor or the nitrogen-containing precursor is too high, no further effect is obtained and properties such as the modulus of the amorphous carbon film may be reduced.

[0053] The OACL deposition step (S120) can be performed under typical conditions for depositing an amorphous carbon film. For example, the OACL 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 present invention, an amorphous carbon film is deposited using a typical PECVD process, but an oxygen-containing precursor and a nitrogen-containing precursor are supplied to the chamber together with a carbon-containing precursor.

[0054] 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 carbon-containing precursor, an oxygen-containing precursor, and a nitrogen-containing precursor.

[0055] The amorphous carbon film according to the present invention has a carbon matrix doped with oxygen and nitrogen. Because the amorphous carbon film according to the present invention is doped with oxygen and nitrogen, it 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, but in most cases 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, but unusually has a relatively low compressive stress of 200 MPa or less. This can be seen in Figure 4.

[0056] As a result, the oxygen- and nitrogen-doped amorphous carbon film according to the present invention can have a high modulus while having low compressive stress, and can be used, for example, as a hard mask for manufacturing a vertical NAND device without increasing the thickness of the amorphous carbon film.

[0057] Furthermore, the amorphous carbon film according to the present invention can exhibit a Vickers hardness of 5.0 GPa or more. Similarly, the amorphous carbon film according to the present invention exhibits a high hardness of 5.0 GPa or more and has a relatively low compressive stress of 200 MPa or less. This can be seen from FIG. 3.

[0058] Example The structure and operation of the present invention will be described in more detail below with reference to preferred embodiments of the present invention, which are presented as preferred examples of the present invention and are not to be construed as limiting the present invention in any way.

[0059] The contents not described here will not be explained here because they can be easily inferred by those skilled in the art.

[0060] Under the conditions shown in Table 1, the amorphous carbon films according to Examples 1 to 14 were deposited, and under the conditions shown in Table 2, the amorphous carbon films according to Comparative Examples 1 to 8 were deposited.

[0061] [Table 1]

[0062] [Table 2]

[0063] FIG. 3 shows the stress and hardness of an amorphous carbon film (ONACL) deposited according to an example and an amorphous carbon film (ACL) deposited according to a comparative example. FIG. 4 shows the stress and modulus of the amorphous carbon films deposited according to the example and the comparative example. FIG. 5 shows the hardness and modulus of the amorphous carbon films deposited according to the example and the comparative example. In FIGS. 3 to 5, the amorphous carbon film deposited according to the example is represented as ONACL, and the amorphous carbon film deposited according to the comparative example is represented as ACL.

[0064] 3, it can be seen that the amorphous carbon films deposited according to the Examples and the Comparative Examples exhibit Vickers hardnesses of approximately 5.0 GPa or more, with the exception of exceptional cases. In particular, the amorphous carbon films deposited according to the Examples have a Vickers hardness similar to that of the amorphous carbon films deposited according to the Comparative Examples, but the amorphous carbon films deposited according to the Examples have a relatively small compressive stress compared to the amorphous carbon films deposited according to the Comparative Examples, which have a relatively large compressive stress.

[0065] 4, it can be seen that the amorphous carbon films deposited according to the Examples and the Comparative Examples exhibit moduli of approximately 40 MPa or more, with the exception of exceptional cases. In particular, the amorphous carbon films deposited according to the Examples have moduli similar to those of the Comparative Examples, but the amorphous carbon films deposited according to the Comparative Examples have relatively large compressive stresses, while the amorphous carbon films deposited according to the Examples have relatively small compressive stresses.

[0066] Meanwhile, referring to FIG. 5, in the case of the amorphous carbon film deposited according to the example and the amorphous carbon film deposited according to the comparative example, as the hardness increases, the modulus also tends to increase.

[0067] Table 3 shows the properties 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.

[0068] [Table 3]

[0069] The selectivity in Table 3 is the selectivity to SiO2, and the selectivity of the amorphous carbon film according to Comparative Example 9 is set to 100%, and the relative selectivity of the other amorphous carbon films is shown.

[0070] Referring to Table 3, the amorphous carbon film according to Comparative Example 10, which had a very slow deposition rate without the supply of O2 and N2, exhibited a higher selectivity than the amorphous carbon film according to Comparative Example 9, but also exhibited a significantly increased compressive stress.

[0071] In contrast, the amorphous carbon films prepared in Examples 15 and 16, in which O and N were supplied together with C3H6, exhibited a high selectivity similar to that of the amorphous carbon film prepared in Comparative Example 10, but had a relatively low compressive stress and a faster deposition rate than that of Comparative Example 10.

[0072] Furthermore, the amorphous carbon films of Examples 15 and 16 exhibited a relatively high absorption coefficient compared to Comparative Example 9. The higher the absorption coefficient, the closer the amorphous carbon film became to black in color, indicating an increase in film density.

[0073] Therefore, based on the results in Table 3, it can be said that using a gaseous hydrocarbon together with an oxygen-containing precursor and a nitrogen-containing precursor is more advantageous for depositing an amorphous carbon film with high selectivity and low compressive strength.

[0074] Although the present invention has been described above with reference to the preferred embodiments, various modifications and variations within the skill of those skilled in the art may be made. These modifications and variations are considered to be within the scope of the present invention as long as they do not deviate from the scope of the present invention. Therefore, the scope of the present invention should be determined by the scope of the claims set forth below. [Explanation of symbols]

[0075] 1 PECVD equipment 2 chambers 3. Shower head 4 susceptor 5 RF power supply 6 1st electrode 7 RF Filter 8 Ground Line

Claims

1. (a) loading a substrate into a chamber; (b) discharging a carbon-containing precursor, an oxygen-containing precursor, and a nitrogen-containing precursor to deposit an oxygen- and nitrogen-doped amorphous carbon film on the substrate; Including, the oxygen-containing precursor is delivered into the chamber at a flow rate of 80 to 500 sccm; The nitrogen-containing precursor is supplied into the chamber at a flow rate of 100 to 1000 sccm. A method for depositing amorphous carbon films.

2. The carbon-containing precursor is a gaseous carbon compound. The method for depositing an amorphous carbon film according to claim 1.

3. The oxygen-containing precursor is oxygen gas. The method for depositing an amorphous carbon film according to claim 1.

4. The nitrogen-containing precursor is nitrogen gas. The method for depositing an amorphous carbon film according to claim 1.

5. The step (b) is performed under the 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. The method for depositing an amorphous carbon film according to claim 1.

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