Semiconductor device and manufacturing method thereof

Abstract

To provide a semiconductor device capable of selectively forming a nitride film and the manufacturing method thereof.SOLUTION: According to one embodiment, a method for manufacturing a semiconductor device includes forming a first film containing oxygen. The method also includes forming a second film containing nitrogen. In addition, the method etches surfaces of the first film and the second film using a material containing halogen. Furthermore, the method includes forming a third film containing nitrogen on the surfaces of the first film and the second film. The third film is formed by alternately performing first processing for forming a part of the third film and second processing for etching a part of the third film using the material containing halogen.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] FIELD Embodiments of the present invention relate to a semiconductor device and a manufacturing method thereof. [Background technology]

[0002] When forming a second nitride film on the surface of an oxide film and a first nitride film, there are cases where it is desired to selectively form the second nitride film on the surface of the first nitride film. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent Application Publication No. US2021 / 0305043 Summary of the Invention [Problem to be solved by the invention]

[0004] A semiconductor device capable of selectively forming a nitride film and a method for manufacturing the same are provided. [Means for solving the problem]

[0005] According to one embodiment, a method for manufacturing a semiconductor device includes forming a first film containing oxygen. The method further includes forming a second film containing nitrogen. The method further includes etching surfaces of the first film and the second film using a substance containing a halogen. The method further includes forming a third film containing nitrogen on the surfaces of the first film and the second film. The third film is formed by alternately performing a first process for forming a portion of the third film and a second process for etching a portion of the third film using a substance containing a halogen. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is a cross-sectional view (1 / 2) illustrating a method for manufacturing the semiconductor device according to the first embodiment. [Figure 2]1 is a cross-sectional view (2 / 2) illustrating the method for manufacturing the semiconductor device according to the first embodiment. [Figure 3] 4 is a graph for explaining the method for manufacturing the semiconductor device according to the first embodiment. [Figure 4] 3A to 3C are enlarged cross-sectional views for explaining the method for manufacturing the semiconductor device according to the first embodiment. [Figure 5] 4 is a cross-sectional view (1 / 2) illustrating a method for manufacturing the semiconductor device according to the first embodiment. [Figure 6] 4 is a cross-sectional view (2 / 2) illustrating the method for manufacturing the semiconductor device according to the first embodiment. [Figure 7] 4 is a graph for explaining the method for manufacturing the semiconductor device according to the first embodiment. [Figure 8] 2A and 2B are graphs and cross-sectional views illustrating a method for manufacturing the semiconductor device according to the first embodiment. [Figure 9] FIG. 10 is a cross-sectional view showing the structure of a semiconductor device according to a second embodiment. [Figure 10] 10 is a cross-sectional view (1 / 4) showing a method for manufacturing a semiconductor device according to a second embodiment. [Figure 11] 10 is a cross-sectional view (2 / 4) illustrating a method for manufacturing a semiconductor device according to a second embodiment. [Figure 12] 10 is a cross-sectional view (3 / 4) illustrating a method for manufacturing a semiconductor device according to a second embodiment. [Figure 13] 10 is a cross-sectional view (4 / 4) illustrating the method for manufacturing the semiconductor device according to the second embodiment. [Figure 14] 10 is a cross-sectional view (1 / 2) illustrating details of the method for manufacturing the semiconductor device according to the second embodiment. FIG. [Figure 15] 10 is a cross-sectional view (2 / 2) illustrating details of the method for manufacturing the semiconductor device according to the second embodiment. FIG. [Figure 16] 10A and 10B are graphs and cross-sectional views illustrating a method for manufacturing a semiconductor device according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. In Figures 1 to 16, the same components are denoted by the same reference numerals, and duplicated descriptions will be omitted.

[0008] (First embodiment) 1 and 2 are cross-sectional views for explaining the method for manufacturing the semiconductor device of the first embodiment.

[0009] First, an oxide film 2 and a nitride film 3 are formed on a substrate 1 (FIG. 1(a)). The substrate 1 is, for example, a semiconductor substrate such as a Si (silicon) substrate. FIG. 1(a) shows an X direction and a Y direction that are parallel to the surface of the substrate 1 and perpendicular to each other, and a Z direction that is perpendicular to the surface of the substrate 1. The X direction, the Y direction, and the Z direction intersect with each other. In this specification, the +Z direction is treated as the upward direction, and the -Z direction is treated as the downward direction. Note that the -Z direction may or may not coincide with the direction of gravity.

[0010] The oxide film 2 is, for example, an SiO2 film (silicon oxide film). The oxide film 2 may further contain atoms other than Si and O. The composition ratio of Si to O in the oxide film 2 is not limited to 1:2 and may be other ratios. The oxide film 2 is formed on the substrate 1 by, for example, CVD (Chemical Vapor Deposition). The oxide film 2 is an example of a first film.

[0011] The nitride film 3 is, for example, a SiN film (silicon nitride film). The nitride film 3 may further contain atoms other than Si and N. The composition ratio of Si to N in the nitride film 3 is not limited to 1:1 and may be other ratios. The nitrogen concentration in the nitride film 3 is higher than the nitrogen concentration in the oxide film 2. The nitride film 3 is formed on the substrate 1 by, for example, CVD. The nitride film 3 is an example of the second film.

[0012] The oxide film 2 and the nitride film 3 may be formed directly on the substrate 1, or may be formed on the substrate 1 via another film. The oxide film 2 may be formed before or after the formation of the nitride film 3. Although the oxide film 2 and the nitride film 3 are adjacent to each other in the X direction in FIG. 1(a), they may also be adjacent to each other in other directions (for example, the Z direction).

[0013] Thereafter, a native oxide film 4 is formed on the surface of the nitride film 3 (FIG. 1(b)). The native oxide film 4 is, for example, an SiO2 film. In FIG. 1(b), a part of the nitride film 3 is transformed into the native oxide film 4 by natural oxidation. The native oxide film 4 is formed, for example, by carrying the substrate 1 from the inside to the outside of a chamber of a semiconductor manufacturing device (for example, a CVD device).

[0014] Next, the native oxide film 4 is removed by wet etching (FIG. 1(c)). This wet etching is performed using, for example, a dHF (dilute hydrofluoric acid) aqueous solution. This dHF aqueous solution is an example of a substance containing a halogen. The step of FIG. 1(c) may also be performed by dry etching using a substance containing a halogen.

[0015] In the step of FIG. 1(c), the surfaces of the oxide film 2 and the nitride film 3 are also etched, and parts of the oxide film 2 and the nitride film 3 are also removed (FIG. 2(a)). Furthermore, F atoms derived from the dHF aqueous solution are added to the surfaces of the oxide film 2 and the nitride film 3. At this time, the concentration of F atoms on the surface of the nitride film 3 becomes higher than the concentration of F atoms on the surface of the oxide film 2. Details of this phenomenon will be described later. The surfaces of the oxide film 2 and the nitride film 3 may further be treated with IPA (isopropyl alcohol).

[0016] Next, a nitride film 5 is formed on the entire surface of the substrate 1 (FIG. 2(b)). As a result, a nitride film 5 is formed on the surface of the nitride film 3 (FIG. 2(b)), and further, a nitride film 5 is formed on the surface of the oxide film 2 (FIG. 2(c)). FIGS. 2(b) and 2(c) show the film thickness W1 of the nitride film 5 formed on the nitride film 3, the film thickness W2 of the nitride film 5 formed on the oxide film 2, and the difference ΔW between the film thicknesses W1 and W2 (ΔW=W1-W2). This difference ΔW is also called the incubation difference.

[0017] The nitride film 5 is, for example, a SiN film. The nitride film 5 may further contain atoms other than Si and N. The composition ratio of Si to N in the nitride film 5 is not limited to 1:1 and may be other ratios. The nitride film 5 is formed on the oxide film 2 and the nitride film 3 by, for example, CVD. This CVD is, for example, ALD (Atomic Layer Deposition). The nitride film 5 of this embodiment is formed using, for example, SiH2Cl2 (dichlorosilane) gas as a Si source gas and NH3 (ammonia) gas as an N source gas. The nitride film 5 and nitride film 6 described later are examples of the third film.

[0018] In this embodiment, the F atoms added to the surfaces of the oxide film 2 and the nitride film 3 promote the formation of the nitride film 5. As described above, the concentration of F atoms on the surface of the nitride film 3 is higher than the concentration of F atoms on the surface of the oxide film 2. Therefore, the nitride film 5 starts to form from the surface of the nitride film 3 (FIG. 2(b)), and then starts to form from the surface of the oxide film 2 (FIG. 2(c)). As a result, the film thickness W1 of the nitride film 5 on the nitride film 3 becomes thicker than the film thickness W2 of the nitride film 5 on the oxide film 2 (FIG. 2(c)). Details of this phenomenon will be described later.

[0019] FIG. 3 is a graph for explaining the method for manufacturing the semiconductor device according to the first embodiment.

[0020] The horizontal axis of FIG. 3 represents the elapsed time in the steps of FIGS. 2(b) and 2(c). The vertical axis of FIG. 3 represents the film thicknesses W1 and W2 of the nitride film 5 in the steps of FIGS. 2(b) and 2(c). In this embodiment, the film thicknesses W1 and W2 increase at the same rate, as shown in FIG. 3. However, in this embodiment, the nitride film 5 begins to form from the surface of the nitride film 3 (FIG. 2(b)), and then begins to form from the surface of the oxide film 2 (FIG. 2(c)). Therefore, in FIG. 3, the line representing the film thickness W2 is located below the line representing the film thickness W1. Because the film thicknesses W1 and W2 increase at the same rate, the difference ΔW between the film thicknesses W1 and W2 remains constant regardless of time.

[0021] FIG. 4 is an enlarged cross-sectional view for explaining the method for manufacturing the semiconductor device of the first embodiment.

[0022] FIG. 4 shows F atoms added to the oxide film 2 and the nitride film 3. When wet etching is performed in the step of FIG. 1(c), F atoms derived from the dHF aqueous solution are added to the surfaces and interiors of the oxide film 2 and the nitride film 3. The F atoms added to the surfaces of the oxide film 2 and the nitride film 3 become reactive groups when the nitride film 5 is formed. Since F atoms are more easily added to the nitride film 3 than to the oxide film 2, the concentration of F atoms on the surface of the nitride film 3 is higher than the concentration of F atoms on the surface of the oxide film 2, as shown in FIG. 4.

[0023] 4 further shows SiH2Cl2 molecules. In this embodiment, the SiH2Cl2 molecules react with F atoms on the surfaces of the oxide film 2 and nitride film 3 in the steps of FIG. 2(b) and FIG. 2(c), thereby forming nitride film 5. At this time, it is thought that H atoms in the SiH2Cl2 molecules cause F atoms to desorb from the surfaces of the oxide film 2 and nitride film 3.

[0024] FIG. 4 further shows SiH2Cl2 molecules "M1" heading toward the surface of nitride film 3 and SiH2Cl2 molecules "M2" heading toward the surface of nitride film 3. In this embodiment, the concentration of F atoms on the surface of nitride film 3 is higher than the concentration of F atoms on the surface of oxide film 2. Therefore, SiH2Cl2 molecules "M1" easily approach F atoms on the surface of nitride film 3, but SiH2Cl2 molecules "M2" have difficulty approaching F atoms on the surface of oxide film 2. As a result, it is thought that nitride film 5 starts to form from the surface of nitride film 3 (FIG. 2(b)), and then starts to form from the surface of oxide film 2 (FIG. 2(c)).

[0025] When nitride film 5 begins to form on the surface of oxide film 2, the surfaces of nitride film 3 and oxide film 2 are also covered with nitride film 5. Therefore, it is considered that the ease with which nitride film 5 forms on oxide film 2 is the same as the ease with which nitride film 5 forms on nitride film 3. As a result, it is considered that film thicknesses W1 and W2 increase at the same rate (FIG. 3).

[0026] It should be noted that as the pressure when forming nitride film 5 decreases, the difference ΔW between film thickness W1 and film thickness W2 increases. This is thought to be because as the pressure decreases, SiH2Cl2 molecules are less likely to collide with the surfaces of oxide film 2 and nitride film 3, which promotes the formation of nitride film 5 more on the surface of nitride film 3 than on the surface of oxide film 2. It is desirable that this pressure be, for example, 50 Pa or less. This pressure is, for example, the pressure inside the chamber of a semiconductor manufacturing apparatus (e.g., an ALD apparatus) in which substrate 1 is housed when nitride film 5 is formed.

[0027] 2(b) and 2(c), the nitride film 5 is formed not only on the surface of the nitride film 3 but also on the surface of the oxide film 2. Therefore, if it is desired to selectively form the nitride film 5 on the surface of the nitride film 3, it is necessary to terminate the formation of the nitride film 5 before the nitride film 5 is formed on the surface of the oxide film 2. However, if the formation of the nitride film 5 is terminated in this manner, it becomes difficult to form a thick nitride film 5.

[0028] Therefore, it is desirable to form the nitride film 5 (and nitride film 6) of this embodiment by the method shown in Figures 5 and 6. Specifically, the nitride film 5 (and nitride film 6) is formed by the steps of Figures 5(a) to 6(c) instead of the steps of Figures 2(b) and 2(c).

[0029] 5 and 6 are cross-sectional views showing the method for manufacturing the semiconductor device of the first embodiment.

[0030] First, after the steps of FIGS. 1(a) to 2(a) are performed, a nitride film 5 is formed on the entire surface of the substrate 1 (FIG. 5(a)). As a result, a nitride film 5 is formed on the surface of the nitride film 3, and further, a nitride film 5 also begins to form on the surface of the oxide film 2. The nitride film 5 shown in FIG. 5(a) includes a portion 5a formed on the nitride film 3 and a portion 5b formed on the oxide film 2. The step of FIG. 5(a) ends when the portion 5b begins to form. Hereinafter, the step of FIG. 5(a) will also be referred to as the "forming process." This forming process is an example of the first process.

[0031] As described above, the nitride film 5 is, for example, a SiN film. The nitride film 5 may further contain atoms other than Si and N. The composition ratio of Si to N in the nitride film 5 is not limited to 1:1 and may be other ratios. The nitride film 5 is formed on the oxide film 2 and the nitride film 3 by, for example, CVD. This CVD is, for example, ALD. The nitride film 5 of this embodiment is formed using, for example, SiH2Cl2 gas as a Si source gas and NH3 gas as an N source gas. The nitride film 5 and the nitride film 6 described later are examples of the third film.

[0032] Next, a portion of the nitride film 5 is removed by wet etching (FIG. 5(b)). This wet etching is performed using, for example, a dHF aqueous solution. This dHF aqueous solution is an example of a substance containing a halogen. The step of FIG. 5(b) may also be performed by dry etching using a substance containing a halogen. Hereinafter, the step of FIG. 5(b) will also be referred to as the "etching process." This etching process is an example of the second process.

[0033] In the step of FIG. 5(b), the portion 5b of the nitride film 5 is removed, and the portion 5a of the nitride film 5 is also partially removed (FIG. 5(c)). As a result, the surfaces of the oxide film 2 and the portion 5a are also etched, and the oxide film 2 and the portion 5a are also partially removed. Furthermore, F atoms derived from the dHF aqueous solution are added to the surfaces of the oxide film 2 and the portion 5a. At this time, the concentration of F atoms on the surface of the portion 5a becomes higher than the concentration of F atoms on the surface of the oxide film 2 for the reasons described above.

[0034] According to this embodiment, by performing the above-described forming and etching processes, it is possible to selectively form a nitride film 5 (portion 5a) on the surface of the nitride film 3. However, the thickness of the nitride film 5 formed by the above-described forming and etching processes is approximately the same as the thickness of the nitride film 5 formed in the steps of FIGS. 2(b) and 2(c). Therefore, in this embodiment, the above-described forming and etching processes are alternately repeated. This makes it possible to selectively form a thick nitride film on the surface of the nitride film 3. In other words, it is possible to increase the difference in thickness between the nitride film formed on the surface of the nitride film 3 and the nitride film formed on the surface of the oxide film 2. The thickness of the nitride film 5 shown in FIG. 5(c) is, for example, less than 4 nm.

[0035] Next, a nitride film 6 is formed on the entire surface of the substrate 1 (FIG. 6(a)). As a result, the nitride film 6 is formed on the surface of the nitride film 5, and further, the nitride film 6 also begins to form on the surface of the oxide film 2. The nitride film 6 shown in FIG. 6(a) includes a portion 6a formed on the nitride film 5 and a portion 6b formed on the oxide film 2. The process of FIG. 6(a) ends when the portion 6b begins to form. The process of FIG. 5(a) is the "first formation process," while the process of FIG. 6(a) is the "second formation process."

[0036] Details of the nitride film 6 are similar to those of the nitride film 5. The nitride film 6 is, for example, a SiN film. The nitride film 6 may further contain atoms other than Si and N. The composition ratio of Si to N in the nitride film 6 is not limited to 1:1 and may be other ratios. The nitride film 6 is formed on the oxide film 2 and the nitride film 5 by, for example, CVD. This CVD is, for example, ALD. The nitride film 6 of this embodiment is formed using, for example, SiH2Cl2 gas as a Si source gas and NH3 gas as an N source gas. The nitride film 6 and the aforementioned nitride film 5 are examples of the third film.

[0037] Next, a portion of the nitride film 5 is removed by wet etching (FIG. 6(b)). This wet etching is performed using, for example, a dHF aqueous solution. This dHF aqueous solution is an example of a substance containing a halogen. The process of FIG. 6(b) may also be performed by dry etching using a substance containing a halogen. The process of FIG. 5(b) is the "first etching process," while the process of FIG. 6(b) is the "second etching process."

[0038] In the step of FIG. 6(b), the portion 6b of the nitride film 6 is removed, and the portion 6a of the nitride film 6 is also partially removed (FIG. 6(c)). As a result, the surfaces of the oxide film 2 and the portion 6a are also etched, and parts of the oxide film 2 and the portion 6a are also removed. Furthermore, F atoms derived from the dHF aqueous solution are added to the surfaces of the oxide film 2 and the portion 6a. At this time, the concentration of F atoms on the surface of the portion 6a becomes higher than the concentration of F atoms on the surface of the oxide film 2 for the reasons described above.

[0039] According to this embodiment, by alternately repeating the above-described formation process and etching process, it is possible to selectively form thick nitride films 5, 6 (portions 5a, 6a) on the surface of nitride film 3. In this embodiment, two formation processes and two etching processes are alternately performed, but three or more formation processes and three or more etching processes may be alternately performed. This makes it possible to selectively form an even thicker nitride film on the surface of nitride film 3. The total thickness of nitride films 5, 6 shown in FIG. 6(c) is, for example, 4 nm or more.

[0040] Thereafter, various devices, wiring layers, plugs, pads, interlayer insulating films, etc. are formed on the substrate 1. In this manner, the semiconductor device of this embodiment is manufactured.

[0041] FIG. 7 is a graph for explaining the method for manufacturing the semiconductor device according to the first embodiment.

[0042] The horizontal axis of FIG. 7 represents the elapsed time in the steps of FIGS. 5(a) to 6(c). The first cycle represents the first formation process and the first etching process (FIGS. 5(a) to 5(c)). The second cycle represents the second formation process and the second etching process (FIGS. 6(a) to 6(c)). The third cycle represents the third formation process and the third etching process. The vertical axis of FIG. 7 represents the film thicknesses W1 and W2 in the steps of FIGS. 5(a) to 6(c). Film thickness W1 represents the film thickness of the nitride film on nitride film 3 (portions 5a and 6a of nitride films 5 and 6). Film thickness W2 represents the film thickness of the nitride film on oxide film 2 (portions 5b and 6b of nitride films 5 and 6).

[0043] At the end of the first cycle, the film thickness W2 increases slightly from zero. This represents the film thickness of portion 5b shown in FIG. 5(a). Because portion 5b is removed by the first etching process, the film thickness W2 in the first cycle subsequently returns to zero. The difference between the film thickness W1 and the film thickness W2 in the first cycle is the aforementioned ΔW at the end of the first formation process.

[0044] At the end of the second cycle, the film thickness W2 also increases slightly from zero. This represents the film thickness of portion 6b shown in FIG. 6(a). Because portion 6b is removed by the second etching process, the film thickness W2 in the second cycle subsequently returns to zero. The difference between film thickness W1 and film thickness W2 in the second cycle becomes ΔW', which is larger than the above-mentioned ΔW, at the end of the second formation process. This corresponds to the total film thickness of portions 5a and 6a being larger than the film thickness of portion 5a.

[0045] At the end of the third cycle, the film thickness W2 also increases slightly from zero. The details of the third cycle and subsequent cycles are the same as those of the second cycle. Therefore, the film thickness W2 in the third cycle subsequently returns to zero. The difference between the film thickness W1 and the film thickness W2 in the third cycle becomes ΔW″, which is larger than the above-mentioned ΔW′, at the end of the third formation process.

[0046] FIG. 8 is a graph and cross-sectional views for explaining the method for manufacturing the semiconductor device of the first embodiment.

[0047] The cross-sectional view of Fig. 8 shows the same cross-section as the cross-section shown in Fig. 6(c). The graph of Fig. 8 shows the F concentration distribution along the Z direction in the nitride films 3, 5, and 6. The Z direction corresponds to the film thickness direction of the nitride films 3, 5, and 6. The Z direction in this embodiment is an example of the first direction.

[0048] As described above, the steps of FIG. 1(c), FIG. 5(b), and FIG. 6(b) are performed using a dHF aqueous solution. In these steps, F atoms derived from the dHF aqueous solution are added to the surfaces and interiors of the nitride films 3, 5, and 6, respectively. As a result, the F concentration distribution along the Z direction in the nitride films 3, 5, and 6 has multiple concentration peaks, as shown in FIG. 8. These concentration peaks are formed near the surfaces of the nitride film 3, the nitride film 5, and the nitride film 6, respectively. When the above-described formation process and etching process are repeated N times (N is an integer equal to or greater than 2), N+1 such concentration peaks will appear.

[0049] Next, the above-mentioned forming process and etching process will be described in further detail with reference to Figures 5(a) to 6(c). Note that the following description of the etching process is also applicable to the etching in the step of Figure 1(c).

[0050] In the formation process, a Si source gas other than SiH2Cl2 gas may be used, and an N source gas other than NH3 gas may be used. The Si source gas may contain, for example, an inorganic compound gas such as SiH4 gas, SiH3Cl gas, or SiHCl3 gas (Si represents silicon, H represents hydrogen, and Cl represents chlorine). The N source gas may contain, for example, a nitriding agent gas such as N2H4 (N represents nitrogen, and H represents hydrogen). The Si source gas is an example of a first gas, and the N source gas is an example of a second gas. The formation process of this embodiment is preferably performed at 50 Pa or less. This makes it possible to promote the formation of nitride films 5 and 6.

[0051] In the etching process, an etching solution other than the dHF aqueous solution may be used, and an etching gas may be used instead of the etching solution. The etching process of this embodiment may be wet etching or dry etching, as long as the addition of a halogen as described above is possible. The etching solution or etching gas may contain a halogen other than F (fluorine), such as Cl (chlorine), Br (bromine), or I (iodine). The etching solution or etching gas may contain, for example, F2, HF, NF3, SiF4, or ClF (F represents fluorine, H represents hydrogen, N represents nitrogen, Si represents silicon, and Cl represents chlorine). According to this embodiment, adding a halogen to the surface of the nitride film 3 or the like makes it possible to selectively form a nitride film 5 on the surface of the nitride film 3. This also applies to adding a halogen to the surfaces of the nitride films 5 and 6.

[0052] When the etching process is performed using an etching gas, the forming process and etching process of this embodiment are performed by alternately repeating a step of supplying a Si source gas and an N source gas to the substrate 1 and a step of supplying an etching gas to the substrate 1. This makes it possible to alternately repeat the forming process and the etching process. In this case, it is desirable to perform a purging process of the chamber containing the substrate 1 between the forming process and the etching process.

[0053] As described above, in this embodiment, when a nitride film including nitride films 5 and 6 is formed on the surfaces of oxide film 2 and nitride film 3, this nitride film (5, 6) is formed by alternately performing a forming process for forming a portion of this nitride film (5, 6) and an etching process for etching a portion of this nitride film (5, 6) using a substance containing halogen. Therefore, according to this embodiment, it is possible to selectively form this nitride film (5, 6). Specifically, it is possible to selectively form this nitride film (5, 6) on the surface of nitride film 3, out of the surfaces of oxide film 2 and nitride film 3.

[0054] (Second embodiment) 9 is a cross-sectional view showing the structure of a semiconductor device according to a second embodiment. The semiconductor device according to this embodiment includes, for example, a three-dimensional semiconductor memory. The semiconductor device according to this embodiment and a manufacturing method thereof correspond to an example of the semiconductor device according to the first embodiment and a manufacturing method thereof.

[0055] The semiconductor device of this embodiment includes a substrate 11, a plurality of insulating films 12, a plurality of electrode layers 13, a plurality of block insulating films 14, a charge storage film 15, a tunnel insulating film 16, a channel semiconductor layer 17, a core insulating film 18, and a plurality of insulating films 19. Each electrode layer 13 includes a barrier metal layer 13a and an electrode material layer 13b. The charge storage film 15 includes a plurality of outer peripheral films 15a and an inner peripheral film 15b. Each insulating film 12 is an example of a first film. The inner peripheral film 15b is an example of a second film and a first portion. Each outer peripheral film 15a is an example of a third film and a second portion.

[0056] The substrate 11 is, for example, a semiconductor substrate such as a Si substrate. Fig. 9 shows an X direction and a Y direction which are parallel to the surface of the substrate 11 and perpendicular to each other, and a Z direction which is perpendicular to the surface of the substrate 11. The substrate 11 of this embodiment corresponds to the substrate 1 of the first embodiment.

[0057] The above-mentioned multiple insulating films 12 and multiple electrode layers 13 are alternately stacked on the substrate 11 to form a laminated film P. The laminated film P further includes a block insulating film 14 and a peripheral film 15a provided in this order on the side surface of each electrode layer 13.

[0058] Each insulating film 12 is, for example, an SiO 2 film. Each insulating film 12 may further contain atoms other than Si and O. Each insulating film 12 of this embodiment corresponds to the oxide film 2 of the first embodiment.

[0059] Each electrode layer 13 includes a barrier metal layer 13a and an electrode material layer 13b formed in this order between adjacent insulating films 12. The barrier metal layer 13a is, for example, a TiN (titanium nitride) layer. The electrode material layer 13b is, for example, a W (tungsten) layer. Each electrode layer 13 functions, for example, as a word line of a three-dimensional semiconductor memory.

[0060] Each block insulating film 14 is provided on a side surface of the electrode layer 13 in the stacked film P. Therefore, in the stacked film P, a plurality of insulating films 12 and a plurality of block insulating films 14 are alternately stacked along the Z direction. Each block insulating film 14 is, for example, a SiO2 film. Each block insulating film 14 may include a metal insulating film instead of or in addition to the SiO2 film.

[0061] Each outer peripheral film 15a of the charge storage film 15 is provided on a side surface of the block insulating film 14 in the stacked film P. Therefore, in the stacked film P, a plurality of insulating films 12 and a plurality of outer peripheral films 15a are alternately stacked along the Z direction. These outer peripheral films 15a are formed on the side surfaces of the inner peripheral films 15b of the charge storage film 15 and are in contact with the inner peripheral films 15b. Each outer peripheral film 15a is, for example, a SiN film. Each outer peripheral film 15a may further contain atoms other than Si and N. Each outer peripheral film 15a in this embodiment corresponds to the nitride films 5 and 6 in the first embodiment.

[0062] Each insulating film 19 is formed on a side surface of the insulating film 12. In FIG. 9, a plurality of peripheral films 15a and a plurality of insulating films 19 are alternately stacked along the Z direction. The insulating films 19 are used as an etching stopper when a replacement step, which will be described later, is performed. Each insulating film 19 is, for example, a SiO2 film.

[0063] The inner peripheral film 15b of the charge storage film 15, the tunnel insulating film 16, the channel semiconductor layer 17, and the core insulating film 18 are formed in this order in the stacked film P, and form a columnar portion C having a columnar shape extending in the Z direction. Each block insulating film 14, each outer peripheral film 15a of the charge storage film 15, and the insulating film 19 have an annular shape surrounding the columnar portion C.

[0064] The inner periphery film 15b of the charge storage film 15 is provided on the side surfaces of the outer periphery films 15a and the insulating films 19. The inner periphery film 15b, together with the outer periphery films 15a, form the charge storage film 15. The charge storage film 15 is capable of storing signal charges for a three-dimensional semiconductor memory. The inner periphery film 15b is, for example, a SiN film. The inner periphery film 15b may further contain atoms other than Si and N. The inner periphery film 15b of this embodiment corresponds to the nitride film 3 of the first embodiment.

[0065] The tunnel insulating film 16 is formed on the side surface of the inner circumferential film 15b of the charge storage film 15. The tunnel insulating film 16 is, for example, an SiO2 film.

[0066] The channel semiconductor layer 17 is formed on the side surface of the tunnel insulating film 16. The channel semiconductor layer 17 is, for example, a polysilicon layer.

[0067] The core insulating film 18 is formed on the side surface of the channel semiconductor layer 17. The core insulating film 18 is, for example, an SiO2 film.

[0068] 10 to 13 are cross-sectional views showing a method for manufacturing the semiconductor device of the second embodiment.

[0069] First, a plurality of insulating films 12 and a plurality of sacrificial films 21 are alternately formed on a substrate 11 (FIG. 10(a)). As a result, a stacked film P including these insulating films 12 and sacrificial films 21 is formed on the substrate 11. These insulating films 12 and sacrificial films 21 are formed by CVD such as ALD, for example. Each sacrificial film 21 is, for example, a SiN film. Each sacrificial film 21 is an example of a fourth film.

[0070] Next, a memory hole H1 is formed in the stacked film P by lithography and RIE (Reactive Ion Etching) (FIG. 10(b)). The memory hole H1 has, for example, a circular shape in a plan view. The memory hole H1 is an example of a hole.

[0071] Next, the insulating film 19, the inner periphery film 15b, the tunnel insulating film 16, the channel semiconductor layer 17, and the core insulating film 18 are formed in this order in the memory hole H1 (FIG. 11(a)). As a result, the insulating film 19 is formed on the side surface of the stacked film P in the memory hole H1, and a columnar portion C including the inner periphery film 15b, the tunnel insulating film 16, the channel semiconductor layer 17, and the core insulating film 18 is formed on the side surface of the insulating film 19 in the memory hole H1. The insulating film 19, the inner periphery film 15b, the tunnel insulating film 16, the channel semiconductor layer 17, and the core insulating film 18 are formed by CVD such as ALD, for example.

[0072] Next, slits (not shown) are formed in the laminated film P, and each sacrificial film 21 is removed by wet etching through the slits (FIG. 11(b)). As a result, multiple recesses H2 are formed in the laminated film P. In this wet etching, the insulating film 19 is used as an etching stopper. Therefore, the side surfaces of the insulating film 19 are exposed on the side surfaces of these recesses H2.

[0073] Next, the insulating film 19 exposed in the recesses H2 is etched by wet etching from these recesses H2 (FIG. 12(a)). As a result, the insulating film 19 near each recess H2 is removed, and the side surface of the inner circumferential film 15b is exposed in each recess H2. Furthermore, the insulating film 19 is divided into multiple parts, similar to the multiple insulating films 19 shown in FIG. 9. This wet etching is performed using, for example, a dHF aqueous solution. This dHF aqueous solution is an example of a substance containing halogen. The step of etching the insulating film 19 in FIG. 12(a) is performed similarly to the step of removing the native oxide film 4 in FIG. 1(b).

[0074] 12(a), the surfaces of the insulating film 12 and the inner circumferential film 15b exposed in the recess H2 are also etched, and parts of the insulating film 12 and the inner circumferential film 15b are also removed. Furthermore, F atoms derived from the dHF aqueous solution are added to the surfaces of the insulating film 12 and the inner circumferential film 15b. At this time, for the reasons described above, the concentration of F atoms on the surface of the inner circumferential film 15b (SiN film) becomes higher than the concentration of F atoms on the surface of the insulating film 12 (SiO2 film).

[0075] Next, an outer peripheral film 15a is formed on the side surface of the inner peripheral film 15b exposed in each recess H2 (FIG. 12(b)). As a result, a charge storage film 15 including the inner peripheral film 15b and a plurality of outer peripheral films 15a is formed on the substrate 11. According to this embodiment, for the same reason as the nitride films 5 and 6 in the first embodiment, it is possible to selectively form these outer peripheral films 15a on the surface (side surface) of the inner peripheral film 15b. In FIG. 12(b), these outer peripheral films 15a are selectively formed on the surface of the inner peripheral film 15b out of the surfaces of the insulating film 12 and the inner peripheral film 15b. Further details of the process of FIG. 12(b) will be described later.

[0076] Next, the side surface of each outer periphery film 15a is oxidized from each recess H2 (FIG. 13(a)). As a result, a block insulating film 14 is formed on the side surface of each outer periphery film 15a. In FIG. 13(a), a plurality of outer periphery films 15a and a plurality of block insulating films 14 are formed in this order on the side surface of the inner periphery film 15b.

[0077] Next, a barrier metal layer 13a and an electrode material layer 13b are formed in this order in each recess H2 (FIG. 13(b)). As a result, an electrode layer 13 is formed in each recess H2. In FIG. 13(b), a plurality of outer peripheral films 15a, a plurality of block insulating films 14, and a plurality of electrode layers 13 are formed in this order on the side surfaces of the inner peripheral film 15b. In this way, the plurality of sacrificial films 21 are replaced with a plurality of electrode layers 13, etc. (replacement process).

[0078] Thereafter, various devices, wiring layers, plugs, pads, interlayer insulating films, etc. are formed on the substrate 11. In this manner, the semiconductor device of this embodiment is manufactured.

[0079] 14 and 15 are cross-sectional views showing details of the method for manufacturing the semiconductor device of the second embodiment. Figures 14(a) to 15(b) show details of the step of Figure 12(b). The process of forming the peripheral film 15a in Figures 14(a) to 15(b) corresponds to the process of forming the nitride films 5 and 6 in Figures 5(a) to 6(c).

[0080] First, a nitride film 31 for the outer periphery film 15a is formed over the entire surface of the substrate 11 (FIG. 14(a)). As a result, the nitride film 31 is formed on the surface of the inner periphery film 15b, and further, the nitride film 31 also begins to form on the surface of the insulating film 12. The nitride film 31 shown in FIG. 14(a) includes a portion 31a formed on the surface of the inner periphery film 15b and a portion 31b formed on the surface of the insulating film 12. The process of FIG. 14(a) ends when the portion 31b begins to form. Hereinafter, the process of FIG. 14(a) will also be referred to as the "forming process." This forming process is an example of the first process.

[0081] The nitride film 31 is, for example, a SiN film. The nitride film 31 may further contain atoms other than Si and N. The nitride film 31 is formed, for example, by CVD such as ALD. The nitride film 31 of this embodiment is formed, for example, using SiH2Cl2 gas as a Si source gas and NH3 gas as an N source gas. The nitride film 31 and a nitride film 32 described later are examples of the third film and the second portion.

[0082] Next, a portion of the nitride film 31 is removed by wet etching (FIG. 14(b)). This wet etching is performed using, for example, a dHF aqueous solution. This dHF aqueous solution is an example of a substance containing halogen. Hereinafter, the step of FIG. 14(b) will also be referred to as the "etching process." This etching process is an example of the second process.

[0083] 14(b), the portion 31b of the nitride film 31 is removed, and the portion 31a of the nitride film 31 is also partially removed. As a result, the surfaces of the insulating film 12 and the portion 31a are also etched, and the insulating film 12 and the portion 31a are also partially removed. Furthermore, F atoms derived from the dHF aqueous solution are added to the surfaces of the insulating film 12 and the portion 31a. At this time, the concentration of F atoms on the surface of the portion 31a becomes higher than the concentration of F atoms on the surface of the insulating film 12 for the reasons described above.

[0084] According to this embodiment, the above-described formation and etching processes enable selective formation of nitride film 31 (portion 31a) on the surface of inner circumferential film 15b. However, the thickness of nitride film 31 formed by the above-described formation and etching processes is approximately the same as the thickness of nitride film 5 formed in the steps of FIGS. 2(b) and 2(c). Therefore, in this embodiment, the above-described formation and etching processes are alternately repeated. This enables selective formation of a thick nitride film on the surface of inner circumferential film 15b. The thickness of nitride film 31 shown in FIG. 14(c) is, for example, less than 4 nm.

[0085] Next, a nitride film 32 for the peripheral film 15a is formed over the entire surface of the substrate 1 (FIG. 15(a)). As a result, a nitride film 32 is formed on the surface of the nitride film 31, and further, a nitride film 32 begins to form on the surface of the insulating film 12. The nitride film 32 shown in FIG. 15(a) includes a portion 32a formed on the surface of the nitride film 31 and a portion 32b formed on the surface of the insulating film 12. The process of FIG. 15(a) ends when the portion 32b begins to form. The process of FIG. 14(a) is the "first formation process," while the process of FIG. 15(a) is the "second formation process."

[0086] Details of the nitride film 32 are similar to those of the nitride film 31. The nitride film 32 is, for example, a SiN film. The nitride film 32 may further contain atoms other than Si and N. The nitride film 32 is formed, for example, by CVD such as ALD. The nitride film 32 of this embodiment is formed, for example, using SiH2Cl2 gas as a Si source gas and NH3 gas as an N source gas. The nitride film 32 and the aforementioned nitride film 31 are examples of the third film and the second portion.

[0087] Next, a portion of the nitride film 32 is removed by wet etching (FIG. 15(b)). This wet etching is performed using, for example, a dHF aqueous solution. This dHF aqueous solution is an example of a substance containing a halogen. The process in FIG. 14(b) is the "first etching process," while the process in FIG. 15(b) is the "second etching process."

[0088] 15(b), the portion 32b of the nitride film 32 is removed, and the portion 32a of the nitride film 32 is also partially removed. As a result, the surfaces of the insulating film 12 and the portion 32a are also etched, and the oxide film 2 and the portion 6a are also partially removed. Furthermore, F atoms derived from the dHF aqueous solution are added to the surfaces of the insulating film 12 and the portion 32a. At this time, the concentration of F atoms on the surface of the portion 32a becomes higher than the concentration of F atoms on the surface of the insulating film 12 for the reasons described above.

[0089] According to this embodiment, by alternately repeating the above-described formation process and etching process, it is possible to selectively form thick nitride films 31, 32 (portions 31a, 32a) on the surface of the inner circumferential film 15b. In this embodiment, two formation processes and two etching processes are alternately performed, but three or more formation processes and three or more etching processes may be alternately performed. This makes it possible to selectively form an even thicker nitride film on the surface of the inner circumferential film 15b. The total thickness of the nitride films 31, 32 shown in FIG. 15(b), i.e., the thickness of the outer circumferential film 15a, is, for example, 4 nm or more.

[0090] The details of the formation process and etching process of the first embodiment are also applicable to the formation process and etching process of this embodiment. Furthermore, the details of the etching process of the first embodiment are also applicable to the etching process of the present embodiment in the step of Fig. 12(a) in the same way as the etching process of the first embodiment in Fig. 1(c).

[0091] FIG. 16 is a graph and cross-sectional views for explaining the method for manufacturing the semiconductor device of the first embodiment.

[0092] The cross-sectional view of FIG. 16 shows the same cross-section as the cross-sections shown in FIG. 9 and FIG. 13(b). The graph of FIG. 16 shows the F concentration distribution along the X direction in the charge storage film 15. The X direction shown in FIG. 16 corresponds to the film thickness direction of the charge storage film 15, that is, the radial direction of the columnar portion C. The X direction shown in FIG. 16 is an example of a first direction. On the other hand, the Z direction shown in FIG. 16 corresponds to the stacking direction of the stacked film P.

[0093] As described above, the steps of FIG. 12(a), FIG. 14(b), and FIG. 15(b) are performed using a dHF solution. In these steps, F atoms derived from the dHF solution are added to the surfaces and interiors of the inner circumferential film 15b, the nitride film 31, and the nitride film 32, respectively. As a result, the F concentration distribution along the X direction in the inner circumferential film 15b, the nitride film 31, and the nitride film 32 has multiple concentration peaks, as shown in FIG. 16. These concentration peaks are formed near the surface of the inner circumferential film 15b, the nitride film 31, and the nitride film 32, respectively. When the above-described formation process and etching process are repeated M times (M is an integer equal to or greater than 2), M+1 such concentration peaks will appear.

[0094] As described above, according to this embodiment, it is possible to selectively form the outer circumferential film 15a, similarly to the nitride films 5 and 6 of the first embodiment. Specifically, it is possible to selectively form the outer circumferential film 15a on the surface of the inner circumferential film 15b out of the surfaces of the insulating film 12 and the inner circumferential film 15b.

[0095] Although several embodiments have been described above, these embodiments are presented only as examples and are not intended to limit the scope of the invention. The novel apparatus and method described herein may be embodied in various other forms. Furthermore, various omissions, substitutions, and modifications may be made to the forms of the apparatus and method described herein without departing from the spirit of the invention. The appended claims and their equivalents are intended to cover such forms and modifications that fall within the scope and spirit of the invention. [Explanation of symbols]

[0096] 1: substrate, 2: oxide film, 3: nitride film, 4: native oxide film, 5: Nitride film, 5a: part, 5b: part, 6: nitride film, 6a: part, 6b: part, 11: substrate, 12: insulating film, 13: electrode layer, 13a: barrier metal layer, 13b: electrode material layer, 14: block insulating film, 15: charge storage film, 15a: outer peripheral film, 15b: inner peripheral film, 16: tunnel insulating film, 17: channel semiconductor layer, 18: core insulating film, 19: insulating film, 21: sacrificial film, 31: Nitride film, 31a: part, 31b: part, 32: nitride film, 32a: part, 32b: part

Claims

1. forming a first film which is a silicon oxide film; forming a second film which is a silicon nitride film; Etching the surfaces of the first film and the second film using a substance containing a halogen; forming a third film, which is a silicon nitride film, on surfaces of the first film and the second film; This includes: the third film is formed by alternately performing a first process for forming a part of the third film and a second process for etching a part of the third film using a substance containing a halogen; the third film is formed so that a halogen concentration distribution along a first direction in the third film has a plurality of concentration peaks; A method for manufacturing a semiconductor device.

2. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the third film is selectively formed on the surface of the second film out of the surfaces of the first film and the second film by alternately performing the first treatment and the second treatment.

3. 3. The method for manufacturing a semiconductor device according to claim 1, wherein the first film contains silicon and oxygen, and the second film and the third film contain silicon and nitrogen.

4. 4. The method for manufacturing a semiconductor device according to claim 1, wherein the first treatment is performed using a first gas containing silicon and a second gas containing nitrogen.

5. The method for manufacturing a semiconductor device according to claim 4 , wherein the first gas contains an inorganic compound.

6. The first gas is SiH ４ , SiH ３ Cl, SiH ２ Cl ２ , or SiHCl ３ 6. The method for manufacturing a semiconductor device according to claim 4, wherein Si represents silicon, H represents hydrogen, and Cl represents chlorine.

7. The method for manufacturing a semiconductor device according to claim 4 , wherein the second gas contains a nitriding agent.

8. The second gas is NH ３ or N ２ H ４ 8. The method for manufacturing a semiconductor device according to claim 4, further comprising the steps of: (N represents nitrogen, and H represents hydrogen).

9. The method for manufacturing a semiconductor device according to claim 1 , wherein the first treatment is performed at a pressure of 50 Pa or less.

10. The method for manufacturing a semiconductor device according to claim 1 , wherein the second treatment is performed so as to add halogen to the third film.

11. The method for manufacturing a semiconductor device according to claim 1 , wherein the second treatment is performed using a liquid containing a halogen.

12. 12. The method for manufacturing a semiconductor device according to claim 1, wherein the second treatment is performed using a substance containing F (fluorine), Cl (chlorine), Br (bromine), or I (iodine).

13. The second process is F ２ , HF, NF ３ , SiF ４ 13. The method for manufacturing a semiconductor device according to claim 1, wherein the method is carried out using a fluorine-containing film or ClF (where F represents fluorine, H represents hydrogen, N represents nitrogen, Si represents silicon, and Cl represents chlorine).

14. The method for manufacturing a semiconductor device according to claim 1 , wherein the first direction is a thickness direction of the third film.

15. forming a laminated film including a plurality of insulating films each being a silicon oxide film and a plurality of fourth films alternately; forming a hole in the laminated film; forming a first portion, which is a silicon nitride film included in a charge storage film, and a semiconductor layer in the hole; removing the fourth films to form recesses in the film stack; etching the insulating films and the surface of the first portion from the recesses using a substance containing a halogen; forming a plurality of second portions, each of which is a silicon nitride film, included in the charge storage film and a plurality of electrode layers in the plurality of recesses; This includes: A method for manufacturing a semiconductor device, wherein the second portion is formed by alternately performing a first process that forms a portion of the second portion and a second process that etches a portion of the second portion using a substance containing a halogen.

16. 16. The method for manufacturing a semiconductor device according to claim 15, wherein the second portion is selectively formed on the surface of the first portion out of the insulating film and the surface of the first portion by alternately performing the first treatment and the second treatment.

17. a laminated film including a plurality of insulating films, each of which is a silicon oxide film, and a plurality of electrode layers, alternating with each other; a first portion that is a silicon nitride film included in a charge storage film provided in the stacked film; a semiconductor layer provided in the stacked film with respect to the plurality of insulating films and the plurality of electrode layers via the first portion; a plurality of second portions, each of which is a silicon nitride film, included in the charge storage film and provided between the electrode layer and the first portion and alternately provided with the plurality of insulating films; A semiconductor device, wherein a halogen concentration distribution along the first direction in at least any of the second portions has a plurality of concentration peaks.

18. 18. The semiconductor device according to claim 17, wherein the first direction is a film thickness direction of at least one of the second portions.

19. 19. The semiconductor device according to claim 17, wherein the first direction is a direction intersecting a stacking direction of the stacked film.

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