Method of forming improved interface and thin film using high density radicals

Abstract

To provide a method for reducing the interface defect density of a silicon substrate and an oxide film formed on the silicon substrate.SOLUTION: A method of forming an oxide film using a deposition apparatus includes depositing an insulating film on a silicon substrate, and forming SiO2 between the silicon substrate and the insulating film by annealing using OH radicals on the insulating film using the deposition apparatus.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for improving interface and thin film properties using high density radicals. [Background technology]

[0002] With the development of technology, semiconductors, which are the foundation of core technologies of the Fourth Industrial Revolution such as artificial intelligence, big data, 5G, and self-driving cars, are requiring multi-layer structures and complex circuit patterns to improve the speed of non-memory (System LSI) devices and increase the capacity of memory (DRAM, 3D_VNAND).

[0003] As a result, semiconductor patterning technology with a line width of 5nm or less has been secured through the introduction of EUV (Extreme Ultraviolet) and other technologies. However, there are still issues that need to be resolved, such as unevenness in thin film thickness, poor deposition of high aspect ratio contact holes, and poor step coverage, which are emerging as limitations of existing thin film deposition technology.

[0004] Furthermore, during the manufacture of semiconductor devices, the interface between the underlying film and the deposited film has a high defect density, which deteriorates electrical characteristics and reduces the yield of the device.

[0005] Furthermore, impurities are generated inside the film during the deposition process, and in order to remove these impurities, a subsequent heat treatment process must be introduced to densify the film.

[0006] FIG. 1 is an exemplary diagram showing a conventional process for improving interface and thin film properties.

[0007] First, in the first embodiment, as shown in FIG. 1(a), SiO2 or high-k is deposited on a substrate (100) by techniques such as CVD or ALD. However, such conventional techniques result in a high density of interface defects at the interface between the substrate (100) and the deposition surface. In such cases, only physical bonding exists between the substrate (100) and the insulating film, resulting in a significant number of defects between the substrate (100) and the insulating film. In other words, the substrate (100) and the insulating film are not strongly bonded.

[0008] In the second embodiment, which solves the problems of the first embodiment, as shown in Figure 1(b), a thin layer of SiO2 is first oxidized on the substrate, and then SiO2 or high-k is deposited using techniques such as CVD or ALD. In this case, the initial SiO2 deposition is done through oxidation, resulting in a low interface defect density on the substrate (100). This increases the bonding strength between the substrate (100) and the insulating film, but the second embodiment also has the limitation of still having physical defects between the SiO2 and the insulating film. Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention is intended to solve the problems of the prior art described above, and one embodiment of the present invention aims to penetrate a reactive gas to the interface during a subsequent heat treatment using high-density radicals in order to solve the problems of surface reactions of a film due to low reaction energy and defects due to non-uniform diffusion when applying a PDA (Post Deposition Anneal) technique.

[0010] Another goal is to form a film with low defect density and high density by inducing penetration and substitution reactions using high-density radicals to remove impurities within the film and form homogeneous chemical bonding with the interface. [Means for solving the problem]

[0011] As a technical means for achieving the above technical object, a method for forming an oxide film using a deposition apparatus can include the steps of: (a) depositing an insulating film on a silicon substrate; and (b) forming SiO2 between the silicon substrate and the insulating film by annealing the insulating film with OH radicals using the deposition apparatus.

[0012] In addition, the step (a) can deposit the insulating film based on either a CVD or ALD technique.

[0013] The insulating film can be made of either silicon oxide or high-k.

[0014] In addition, in the step (c), OH radicals penetrate into the insulating film and react with silicon contained in the silicon substrate, thereby forming a thin film of SiO2.

[0015] In addition, in step (c), the thickness of the SiO2 layer between the silicon substrate and the insulating film can be adjusted by adjusting the annealing temperature and time.

[0016] In addition, the process of injecting OH radicals in step (b) can be carried out at a process temperature between 480 and 730 degrees.

[0017] Furthermore, steps (a) to (c) can be included in the process of forming a gate oxide film in the process of forming a semiconductor element. [Effects of the Invention]

[0018] The present invention is intended to solve the problems of the prior art described above. According to one embodiment of the present invention, when applying a PDA (Post Deposition Anneal) technique, in order to solve the problems of surface reactions of a film due to low reaction energy and defects due to uneven diffusion, a reactive gas can be penetrated to the interface during a subsequent heat treatment by using high-density radicals.

[0019] In addition, by using high-density radicals to induce penetration and substitution reactions, impurities within the film are removed and homogeneous chemical bonding is performed with the interface, resulting in the formation of a highly dense film with low defect density. [Brief explanation of the drawings]

[0020] [Figure 1] 1A and 1B are exemplary diagrams showing a conventional process for improving interface and thin film properties; [Figure 2] 1 is an operational flowchart of a deposition process using high-density radicals to improve interface and thin film properties according to an embodiment of the present invention. [Figure 3] 1A and 1B are diagrams illustrating a deposition process in which high-density radicals are used to improve interface and thin film properties according to an embodiment of the present invention. [Figure 4a] 1 is an exemplary diagram showing the thickness of a deposition surface when annealing is performed using high-density radicals and other gases according to an embodiment of the present invention; [Figure 4b] FIG. 4 is an exemplary diagram showing the thickness of a deposition surface as a function of annealing time according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, with reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily understand the present invention. However, the present invention may be embodied in several different forms and is not limited to the embodiments described herein. In order to clearly explain the present invention in the drawings, parts that are not relevant to the description will be omitted, and like parts will be designated by like reference numerals throughout the specification.

[0022] Throughout the specification, when a part is "connected" to another part, this includes not only "directly connected" but also "electrically connected" with another element therebetween. Furthermore, when a part is said to "include" a certain component, this does not mean that it excludes other components, but that it can further include other components, unless otherwise specified.

[0023] The following examples are provided to aid in understanding the present invention and are not intended to limit the scope of the present invention. Therefore, inventions within the same scope that perform the same functions as the present invention also fall within the scope of the present invention.

[0024] As defined in the following specification of the present invention, thin film or deposition can refer to a process in semiconductor manufacturing in which a thin oxide or metal coating is formed on a wafer (substrate) surface by alternating molecular adsorption and substitution. Therefore, each process described in the following specification can be performed using a radical unit or deposition device, and thin film deposition can be achieved through techniques such as atomic layer deposition (ALD) or chemical vapor deposition (CVD).

[0025] FIG. 2 is an operational flowchart of a deposition process that utilizes high-density radicals to improve interface and thin film properties according to one embodiment of the present invention.

[0026] At this time, the following steps S110 to S130 may be included in the process of forming a gate oxide film among the processes of forming a semiconductor device.

[0027] Referring to FIG. 2, the deposition apparatus can deposit an insulating film 110 on a silicon substrate 100 (S110).

[0028] In step (S110), as shown in (a) and (b) of FIG. 3, an insulating film (110) is deposited on a silicon substrate (100). The deposition of the insulating film (110) can be performed based on either a CVD or ALD technique.

[0029] In addition, the insulating film 110 formed in step S110 may be composed of either a silicon oxide film or a high-k film.

[0030] Next, a deposition apparatus is used to form an SiO2 thin film (120) between the silicon substrate (100) and the insulating film (110) by annealing the insulating film (110) with OH radicals (S120).

[0031] In steps S120 to S130, as shown in (c) and (d) of Figure 3, OH radicals are injected onto the insulating film 110 to perform OH radical annealing. At this time, the OH radicals penetrate into the insulating film 110 and react with silicon contained in the silicon substrate 100, thereby forming a thin SiO2 film 120 at the interface, as shown in (d) of Figure 3.

[0032] This is because OH radicals penetrate the insulating film (110) and oxidize the area between the insulating film (110) and the silicon substrate (100), resulting in the formation of SiOx (meaning SiO or SiO2) at the interface between the insulating film (110) and the silicon substrate (100).

[0033] At this time, the first interface (121) where the SiO2 thin film (120) and the insulating film (110) come into contact, and the second interface (122) where the silicon substrate (110) and the SiO2 thin film (120) come into contact both have low interfacial bonding density (chemical bonding), which reduces impurities in the film and results in high bonding strength.

[0034] The conventional annealing process aims to improve the interface characteristics on the top surface of the insulating film (110), and has traditionally used various gases such as N2, H2, and O2 during the annealing process. However, this conventional process has a limitation in that gases such as N2 do not penetrate deep into the insulating film (110).

[0035] However, the purpose of the annealing process performed in step S130 is to allow OH radicals to penetrate deeply into the insulating film 110. Therefore, the OH radicals that penetrate the insulating film 110 according to the process proposed in the present invention can form an oxide film 130 between the silicon substrate 100 and the insulating film 110, thereby forming a strong bond between the silicon substrate 100 and the insulating film 110. That is, the OH radicals reduce impurities in the insulating film 110, densifying the insulating film 110 and forming SiO2 with a strong bond between the substrate 100 and the insulating film 110.

[0036] In addition, the SiO2 layer formed through steps S110 to S130 is different from the conventional technology in that it is not formed sequentially, but is formed in reverse order after forming the insulating film (110).

[0037] In addition, the thin film formed first on the substrate is generally preferably a high-k material (e.g., Al2O3, but including various other high-k materials), but in some cases can be made of SiO2. In this case, in the process proposed by the present invention, the SiO2 thin film (120) must be deposited by CVD (Chemical Vapor Deposition) or ALD (Atomic Layer Deposition), and the SiO2 thin film (120) formed through thermal oxidation is not included in the technology proposed by the present invention. This is because the interface layer formed at the interface through the technology proposed by the present invention reacts with the silicon substrate (100) to form SiO2.

[0038] FIG. 4a is a diagram for comparing the thickness of the insulating film formed when annealing is performed using a conventional gas in the process of the present invention using High-k.

[0039] Figure 4a (a) shows an example of a cross section when only a high-k insulating film is deposited. At this time, it can be seen that the high-k Al2O3 (210) is formed to a predetermined thickness, and a thin SiO2 layer (220) is formed between the substrate and the high-k film.

[0040] 4a(b) shows an optimum example formed by applying the technology of the present invention, that is, an example in which a thin film is formed using Al2O3 as a high-k component and OH radicals.

[0041] In the cross section formed by performing steps S110 to S120, a SiO2 layer (220) having a predetermined thickness may be formed under the high-k film. The graph below the cross-sectional photograph of the thin film shows the concentration of each component as a function of the depth of the thin film, with the y-axis representing intensity and the x-axis representing the depth of the thin film. Unlike the other graphs, in the case of Figure 4a (b), it can be seen that the N concentration is always uniform as the depth changes. It can also be seen that the SiO2 layer (220) formed through the process proposed in the present invention is the thickest.

[0042] Figure 4a (c) shows an example of a cross section of the deposition surface when high-k is deposited and then annealed in O2 gas, and Figure 4a (d) shows an example of a cross section of the deposition surface when high-k is deposited and then annealed in N2 gas.

[0043] In this case, in both Figures 4a (c) and (d), annealing was performed at a high temperature of 920°C, and it can be seen that the thickness of the high-k (Al2O3 layer 210) is thinner than in Figures 4a (a) and (b). In other words, the conventional process shown in Figures 4a (c) and (d) has the problem that after the process, the high-k (Al2O3 layer 210) becomes thinner than its initial deposition thickness. Therefore, the process proposed in the present invention does not thin the high-k (Al2O3 layer 210) formed, and the SiO2 layer 220 is deposited to a predetermined thickness, reducing the interface defect density, confirming its technological superiority.

[0044] Meanwhile, the process proposed in the present invention can adjust the thickness of the SiO2 thin film (120) between the silicon substrate (100) and the insulating film (110) by adjusting the annealing temperature and time, and the process of injecting OH radicals can be carried out at a process temperature between 480 and 730°C.

[0045] For example, (a) to (d) of FIG. 4b are illustrative diagrams showing the thicknesses of the deposition surface produced by annealing with OH radicals for 5 minutes, 30 minutes, 45 minutes, and 60 minutes, respectively.

[0046] After 5 minutes of annealing, Figure 4b (a) shows that the high-k Al2O3 layer (210) and SiO2 layer (220) have thicknesses of 109.7A and 40.5A, respectively. Figure 4b (b) shows that the Al2O3 layer (210) and SiO2 layer (220) have thicknesses of 106.9A and 79.1A, respectively. Figure 4b (c) and (d) show that the Al2O3 layer (210) and SiO2 layer (220) have thicknesses of 93.5A, 119.0A, 96.8A, and 205.8A, respectively. Therefore, as the annealing time increases, the SiO2 layer (220) thickens while minimizing the change in thickness of the Al2O3 layer (210). Users can select the annealing time that best suits their desired SiO2 layer (220) thickness.

[0047] The above description of the present invention is for illustrative purposes only, and those skilled in the art will understand that the present invention can be easily modified into other specific forms without changing the technical spirit or essential characteristics of the present invention. Therefore, the above-described embodiments should be understood to be illustrative in all respects and not limiting. For example, each component described as a single unit can be implemented in a distributed manner, and similarly, each component described as a distributed unit can be implemented in a combined manner.

[0048] The scope of the present invention is indicated by the claims that follow rather than by the above detailed description, and all modifications and variations that fall within the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

Claims

1. A method for forming an oxide film using a deposition apparatus, comprising: (a) depositing an insulating film on a silicon substrate; (b) Post-deposition annealing is performed on the insulating film using high-density OH radicals to induce a substitution reaction between the silicon substrate and the insulating film, thereby forming SiO ２ and forming Including, The step (b) comprises: The OH radicals penetrate into the insulating film and react with silicon contained in the silicon substrate to form the SiO thin film, adjusting the annealing temperature and the annealing time to adjust the thickness of the SiO2; As the annealing time increases, the thickness of the insulating film is minimized and the SiO ２ The goal is to thicken the A method for forming an oxide film using a vapor deposition device.

2. The step (a) comprises: The insulating film is deposited based on either CVD or ALD techniques. A method for forming an oxide film by using the deposition apparatus according to claim 1.

3. the insulating film is made of either a silicon oxide film or a high-k film; A method for forming an oxide film by using the deposition apparatus according to claim 1.

4. The step (b) of injecting the OH radicals is carried out at a process temperature of 480 to 730 degrees. A method for forming an oxide film by using the deposition apparatus according to claim 1.

5. The steps (a) and (b) are included in a process of forming a gate oxide film in a process of forming a semiconductor device. A method for forming an oxide film by using the deposition apparatus according to claim 1.

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