Method for preventing crystallization of ZrO2 dielectric layer of MIM capacitor

Abstract

The invention discloses a method for preventing crystallization of a ZrO2 dielectric layer of an MIM capacitor, the dielectric layer of the MIM capacitor is an AL2O3 / ZrO2 / Al2O3 laminated film, and deposition of the laminated film is completed in a reaction chamber; after the first layer of Al2O3 of the laminated film is formed, normal-temperature O3 is introduced to treat the surface of the wafer; the introduced O3 has higher reaction activity, and after normal-temperature gas enters the reaction chamber, the high-temperature wafer can be cooled, so that the ZrO2 layer has a slow nucleation rate at the initial nucleation stage, and a stable covalent bond structure is formed. Meanwhile, O3 can fully react with unreacted TMA, so that surface defects are reduced. After the O3 treatment step is finished, ZrCl4 is continuously used for carrying out ZrO2 nucleation.

Description

Technical Field

[0001] This invention relates to the field of semiconductor devices, and in particular to a method for preventing the crystallization of the ZrO2 dielectric layer in MIM capacitors. Background Technology

[0002] With the increasing density requirements of MIM capacitors (i.e., capacitors consisting of upper and lower metal plates and an intermediate insulating dielectric layer between them inside the chip), high-k value stacked AL2O3 / ZrO2 has been introduced as the intermediate dielectric layer of MIM, where the k-value of ZrO2 can reach 25. To achieve the AL2O3 / ZrO2 / Al2O3 stacked structure, the MIM dielectric layer is deposited directly in a single reaction chamber. Existing processes mainly involve the reaction of TMA (trimethylaluminum) with water vapor to generate a layer... A layer of alumina with a thickness of [thickness] is then deposited through the reaction of ZrCl4 and water vapor. A thick layer of ZrO2 is then reacted with TMA (trimethylaluminum) and water vapor to form a final layer. Thick aluminum oxide.

[0003] Currently, ZrO2 can use α-Zr (liquid) or ZrCl4 (solid) as precursors. However, due to limitations in equipment and solid gas cylinders, only ZrCl4 can meet the requirements for one-step molding of the laminated structure, and it needs to maintain the same operating temperature as Al2O3. The operating temperature of Al2O3 is 270℃, while that of ZrCl4 is 180–250℃. Furthermore, because there are unreacted TMA (trimethylaluminum) contact sites on the surface of Al2O3 in a single reaction chamber, these sites affect the formation of chemical bonds in ZrO2, introducing defects that can lead to crystallization or phase transitions, resulting in MIM capacitor failure. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for preventing the crystallization of the ZrO2 dielectric layer in MIM capacitors.

[0005] To address the aforementioned problems, this invention provides a method for preventing the crystallization of the ZrO2 dielectric layer in a MIM capacitor. The dielectric layer of the MIM capacitor is an Al2O3 / ZrO2 / Al2O3 stacked film, and the deposition of the stacked film is completed inside a reaction chamber. After the formation of the first Al2O3 layer of the stacked film, room-temperature O3 is introduced to treat the wafer surface for more than 30 seconds, thereby cooling down and converting all unreacted TMA sites on the surface into Al2O3, thus inhibiting the crystallization of the intermediate ZrO2 layer.

[0006] Furthermore, the O3 has higher reactivity. After entering the reaction chamber at room temperature, it cools the wafer, resulting in slower nucleation of ZrO2 in the early stage, forming a stable covalent bond structure. At the same time, O3 reacts fully with unreacted TMA, reducing surface defects.

[0007] The method for preventing ZrO2 dielectric layer crystallization in MIM capacitors according to the present invention mainly includes the following steps:

[0008] S1, firstly, a titanium nitride layer is formed on the wafer surface;

[0009] S2, the first Al2O3 layer deposition process is carried out; TMA is introduced to react with water vapor to generate the Al2O3 layer;

[0010] S3 involves an O3 treatment process, in which room-temperature O3 is introduced into the reaction chamber to cool the wafer while reacting with the remaining TMA; after completion, the reaction chamber is emptied, leaving no gaseous residue.

[0011] S4, ZrCl4 and water vapor are introduced into the reaction chamber again to complete the deposition of the ZrO2 layer;

[0012] S5, TMA is introduced to react with water vapor to generate an Al2O3 layer, thus completing the fabrication of the AL2O3 / ZrO2 / Al2O3 stacked membrane.

[0013] Furthermore, in S1, the thickness of the titanium nitride layer is...

[0014] Furthermore, in step S2, TMA and water vapor are deposited using a cross-flow ALD deposition method, with TMA and water vapor being introduced sequentially to complete the deposition of the Al2O3 layer; the thickness of the generated Al2O3 layer is...

[0015] Furthermore, in step S3, room temperature O3 is introduced to treat the wafer surface for 30 seconds. While cooling the wafer, the O3 fully reacts with the remaining TMA that was not completely reacted in the previous step, thereby reducing surface defects.

[0016] Furthermore, in S4, the deposition thickness of the ZrO2 layer is...

[0017] Furthermore, in S5, the thickness of the Al2O3 layer formed by the second deposition is...

[0018] The method for preventing ZrO2 dielectric layer crystallization in MIM capacitors described in this invention involves treating the wafer surface with room-temperature O3 for 30 seconds after the first Al2O3 layer is deposited, during the formation of the Al2O3 / ZrO2 / Al2O3 multilayer film. Because unreacted TMA adsorption sites remain on the wafer surface after the reaction of TMA and H2O, ZrCl4 tends to focus at defects during the subsequent ZrO2 layer fabrication. Combined with the high reaction temperature of the previous process step, this easily leads to ZrO2 crystallization at the interface. The introduced O3 has higher reactivity; the room-temperature gas entering the reaction chamber cools the high-temperature wafer, resulting in a slower nucleation rate in the initial stage of ZrO2 layer nucleation, leading to a stable covalent bond structure. Simultaneously, O3 can fully react with unreacted TMA, reducing surface defects. After the O3 treatment step, ZrCl4 is used for ZrO2 nucleation. Attached Figure Description

[0019] Figure 1 This is a flowchart of the method for preventing ZrO2 dielectric layer crystallization in MIM capacitors according to the present invention. Detailed Implementation

[0020] The following detailed description, in conjunction with the accompanying drawings, provides specific embodiments of the present invention and clearly and completely describes the technical solutions of the present invention. However, the present invention is not limited to the following embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The advantages and features of the present invention will become clearer from the following description and claims. It should be noted that the accompanying drawings are all in a very simplified form and use non-precise ratios, and are only used for the purpose of conveniently and clearly illustrating the embodiments of the present invention. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] This invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, for clarity, the dimensions and relative dimensions of layers and regions may be exaggerated, and the same reference numerals denote the same elements throughout. In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0022] As described in the background section, because the Al₂O₃ surface has incompletely reacted TMA contact sites in a reaction chamber, these sites can affect the formation of subsequent ZrO₂ chemical bonds, introducing defects that can lead to crystallization or phase transitions, resulting in MIM dielectric layer failure. To address this problem, this invention proposes a method to prevent ZrO₂ crystallization in Al₂O₃ / ZrO₂ / Al₂O₃ laminated films. The main technical principle is that after the initial Al₂O₃ formation, room-temperature O₃ is introduced for >30s to cool the wafer and convert all unreacted TMA sites on the wafer surface into Al₂O₃, thereby inhibiting the surface growth rate of ZrO₂, preventing the breakdown of ZrO₂ chemical bonds, and thus inhibiting ZrO₂ crystallization.

[0023] Specifically, in forming the AL2O3 / ZrO2 / Al2O3 stacked film, after the first AL2O3 deposition, the wafer surface is treated with room-temperature O3 for at least 30 seconds. Because unreacted TMA adsorption sites remain on the surface after the reaction of TMA and H2O, the ZrCl4 feed gas focuses at defects during ZrO2 film formation. Combined with the relatively high reaction temperature of 270℃, this leads to ZrO2 crystallization at the interface. O3, with its higher reactivity, cools the high-temperature wafer upon entering the reaction chamber at room temperature, resulting in slower nucleation of the ZrO2 film in the initial stage, forming a stable covalent bond structure. Simultaneously, O3 can fully react with unreacted TMA, reducing surface defects. After O3 treatment, ZrCl4 is used for ZrO2 nucleation.

[0024] In one embodiment, the method for preventing ZrO2 dielectric layer crystallization in MIM capacitors according to the present invention mainly includes the following steps:

[0025] S1. First, a titanium nitride layer is formed on the wafer surface; this titanium nitride layer can serve as the lower electrode layer of the MIM capacitor. The titanium nitride layer can be formed using processes such as sputtering, and the resulting film thickness is...

[0026] S2, the first Al2O3 layer deposition process is performed; TMA and water vapor (H2O) are introduced and reacted at 207°C to form an Al2O3 layer. TMA and water vapor are deposited using a cross-flow ALD deposition method, with TMA and water vapor introduced sequentially to complete the Al2O3 layer deposition; the thickness of the generated Al2O3 layer is [missing information].

[0027] S3 involves an O3 treatment process, in which room-temperature O3 is introduced into the reaction chamber to cool the wafer while reacting with the remaining TMA from the previous step, reducing surface defects. The room-temperature O3 treatment lasts for at least 30 seconds.

[0028] After completion, all gas in the reaction chamber is emptied, leaving no gaseous residue.

[0029] S4, ZrCl4 and water vapor are introduced into the reaction chamber again to complete the deposition of the ZrO2 layer, forming a film with a thickness of [missing information].

[0030] S5, TMA is introduced to react with water vapor to generate a thickness of [missing information]. The Al2O3 layer was added to complete the fabrication of the AL2O3 / ZrO2 / Al2O3 stacked film.

[0031] After the first Al₂O₃ layer is deposited, the wafer surface is treated with room-temperature O₃ for 30 seconds. Because unreacted TMA adsorption sites remain on the wafer surface after the reaction of TMA and H₂O, ZrCl₄ tends to focus at defects during the subsequent ZrO₂ layer fabrication. Combined with the high reaction temperature of the previous process step, this easily leads to ZrO₂ crystallization at the interface. The introduced O₃, with its higher reactivity, cools the high-temperature wafer upon entering the reaction chamber, resulting in a slower nucleation rate in the initial stage of ZrO₂ layer formation, leading to a stable covalent bond structure. Simultaneously, O₃ can fully react with unreacted TMA, reducing surface defects.

[0032] The method of this invention was used to fabricate the dielectric layer of a multilayer MIM capacitor. The experimental results showed that the TiN+Al2O3+ZrO2+Al2O3+TiN structure had a smooth film surface and no ZrO2 film crystallization.

[0033] The above are merely preferred embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preventing crystallization of the ZrO2 dielectric layer in a MIM capacitor, characterized in that: The dielectric layer of the MIM capacitor is an Al2O3 / ZrO2 / Al2O3 multilayer film, and the deposition of the multilayer film is completed inside a reaction chamber. After the formation of the first Al2O3 layer of the multilayer film, room temperature O3 is introduced to cool the wafer surface and convert all the unreacted TMA sites on the wafer surface during the fabrication of Al2O3 into Al2O3, thereby inhibiting the crystallization of ZrO2 during the fabrication of the intermediate ZrO2 dielectric layer.

2. The method for preventing ZrO2 dielectric layer crystallization in MIM capacitors as described in claim 1, characterized in that: The O3 has higher reactivity. After entering the reaction chamber at room temperature, it cools the wafer for at least 30 seconds. After processing, ZrO2 is deposited, which achieves slower nucleation in the early stage of ZrO2 nucleation and forms a stable covalent bond structure. At the same time, O3 reacts fully with unreacted TMA to reduce surface defects.

3. The method for preventing ZrO2 dielectric layer crystallization in MIM capacitors as described in claim 1, characterized in that: The main steps are: S1, firstly, a titanium nitride layer is formed on the wafer surface; S2, the first Al2O3 layer deposition process is carried out; TMA is introduced to react with water vapor to generate the Al2O3 layer; S3 involves an O3 treatment process, in which room-temperature O3 is introduced into the reaction chamber to cool the wafer while reacting with the remaining TMA; after completion, the reaction chamber is emptied, leaving no gaseous residue. S4, ZrCl4 and water vapor are introduced into the reaction chamber again to complete the deposition of the ZrO2 layer; S5, TMA is introduced to react with water vapor to generate an Al2O3 layer, thus completing the fabrication of the Al2O3 / ZrO2 / Al2O3 stacked membrane.

4. The method for preventing ZrO2 dielectric layer crystallization in MIM capacitors as described in claim 3, characterized in that: In S1, the thickness of the titanium nitride layer is 5. The method for preventing ZrO2 dielectric layer crystallization in MIM capacitors as described in claim 3, characterized in that: In step S2, TMA and water vapor are deposited using a cross-flow ALD deposition method. TMA and water vapor are introduced sequentially, and the internal temperature of the reaction chamber is 270°C, completing the deposition of the Al2O3 layer. The thickness of the generated Al2O3 layer is...

6. The method for preventing ZrO2 dielectric layer crystallization in MIM capacitors as described in claim 1, characterized in that: In step S3, room temperature O3 is introduced to treat the wafer surface for 30 seconds. While cooling the wafer, the O3 fully reacts with the remaining TMA that was not completely reacted in the previous step, reducing surface defects.

7. The method for preventing ZrO2 dielectric layer crystallization in MIM capacitors as described in claim 1, characterized in that: In S4, the deposition thickness of the ZrO2 layer is...

8. The method for preventing ZrO2 dielectric layer crystallization in MIM capacitors as described in claim 1, characterized in that: In step S5, the thickness of the Al2O3 layer formed by the second deposition is...

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