Forming method of MIM capacitor
By forming a buffer layer on the lower electrode layer in the MIM capacitor production process and introducing TMA gas into the ALD process for pre-treatment, the problems of slow deposition rate and poor film formation in the ALD process are solved, and more efficient deposition and more uniform film formation are achieved.
Patent Information
- Application Number
- CN202510382005.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-28
- Publication Date
- 2025-06-24
AI Technical Summary
In the prior art, when the alumina film is deposited as a dielectric layer of MIM capacitors through the ALD process, the deposition rate is slow and the film formation uniformity is poor.
A buffer layer is formed on the lower electrode layer, and TMA gas is introduced into the ALD machine for pre-treatment, which improves the adsorption site and adsorption amount of TMA, thereby improving the deposition speed and film formation uniformity of the ALD process.
Through the formation of the buffer layer, the induction period time of the ALD process is reduced, the deposition rate and film formation uniformity are improved, and the overall uniformity of the film layer is significantly improved.
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Figure CN120201732A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of semiconductor devices and integrated circuits, and particularly to a method for forming a metal-insulator-metal (MIM) capacitor. Background Art
[0002] Capacitive elements are often used as electronic passive devices in integrated circuits such as radio frequency and monolithic microwave. Common capacitive elements include metal-oxide-semiconductor (MOS) capacitors, PN junction capacitors, and metal-insulator-metal (MIM) capacitors. Among them, MIM capacitors are widely used in semiconductor integrated circuit manufacturing because they are easy to integrate into metal interconnect structures.
[0003] Atomic layer deposition (ALD) is a growth process for forming high-quality atomic-scale thin films. In semiconductor manufacturing processes, it is often used to prepare high dielectric constant (high-k, where the dielectric constant k is usually greater than 10) dielectric layers such as aluminum oxide (Al2O3) and hafnium oxide (HfO2). Among them, aluminum oxide is a commonly used high-k dielectric and can be used as the dielectric layer in MIM capacitors.
[0004] However, forming an aluminum oxide layer using the ALD process has the defect of slow deposition rate. Especially when the aluminum oxide layer is used as the dielectric layer of the MIM capacitor, a thickness of more than 100 angstroms is usually required, which reduces production efficiency. At the same time, the deposition rate of the ALD process is easily affected by the previous layer of dielectric, reaction mode, density of active reaction sites on the dielectric surface, and reaction temperature, etc., and is easily affected by preparation conditions. In addition, during the process of growing the aluminum oxide layer by the ALD process, the substrate will affect the adsorption of trimethyl-aluminum (TMA), thereby affecting the in-plane uniformity. Summary of the Invention
[0005] The present application provides a method for forming a MIM capacitor, which can solve the problems of slow deposition rate and poor film formation uniformity caused by depositing an aluminum oxide thin film as the dielectric layer of the MIM capacitor in related technologies. The method includes:
[0006] Forming a buffer layer on the lower electrode layer, where the lower electrode layer is formed on the wafer;
[0007] Placing the wafer in the reaction chamber of an ALD machine and introducing TMA gas for pretreatment;
[0008] Perform at least one growth cycle to form an aluminum oxide thin film above the lower electrode layer, and sequentially introduce water vapor and TMA gas during each growth cycle;
[0009] Form an upper electrode layer on the aluminum oxide thin film.
[0010] In some embodiments, the lower electrode layer includes a titanium nitride layer and a tantalum nitride layer.
[0011] In some embodiments, the buffer layer includes titanium and tantalum.
[0012] In some embodiments, forming a buffer layer on the lower electrode layer includes:
[0013] Place the wafer in the reaction chamber of a PVD tool, and deposit a titanium nitride layer and a tantalum nitride layer on the wafer through PVD process to form the lower electrode layer;
[0014] Stop introducing nitrogen gas into the reaction chamber of the PVD tool, and deposit titanium and tantalum on the lower electrode layer to form the buffer layer.
[0015] In some embodiments, the time for preprocessing by introducing TMA gas is greater than 5 seconds.
[0016] In some embodiments, the temperature of the water vapor introduced during each growth cycle is maintained at 180 °C to 250 °C.
[0017] The technical solution of this application has at least the following advantages:
[0018] By forming a buffer layer after forming the lower electrode layer in the manufacturing process of the MIM capacitor, TMA in the subsequent ALD process is more likely to be adsorbed on the film surface, and the carbonyl group in TMA is more likely to undergo chemisorption with the metal elements in the buffer layer, so there are more adsorption sites and adsorption amounts than hydroxyl groups, thereby reducing the induction period time, improving the deposition rate of the ALD process, and the surface nucleation is more uniform, and the overall uniformity of the formed thin film layer is also significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.
[0020] Figure 1 It is a flowchart of a method for forming a MIM capacitor provided by an exemplary embodiment of the present application;
[0021] Figures 2 to 5 It is a schematic diagram showing the formation process of a MIM capacitor provided by an exemplary embodiment of the present application. Detailed implementation manners
[0022] The technical solutions in the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some but not all of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the protection scope of the present application.
[0023] In the description of the present application, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present application. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and should not be construed as indicating or implying relative importance.
[0024] In the description of the present application, it should be noted that unless otherwise clearly defined and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can also be the communication inside two elements. It can be a wireless connection or a wired connection. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations.
[0025] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.
[0026] Refer to Figure 1 , which shows a flowchart of a method for forming a MIM capacitor provided by an exemplary embodiment of the present application. As Figure 1 shown, the method includes:
[0027] Step S1, forming a buffer layer on the lower electrode layer, and the lower electrode layer is formed on the wafer.
[0028] Refer to Figure 2 , which shows a cross-sectional schematic diagram after the buffer layer is formed. Exemplarily, as Figure 2As shown, a lower electrode layer 221 is formed on the wafer 210, and a buffer layer 2211 is formed on the lower electrode layer 221. Among them, the lower electrode layer 221 includes a titanium nitride (TiN) layer and a tantalum nitride (TaN) layer, and the buffer layer 2211 includes titanium (Ti) and tantalum (Ta). Among them, the thickness of the electrode layer 221 is 500 angstroms to 1000 angstroms, and the thickness of the buffer layer 2211 is 10 angstroms to 30 angstroms.
[0029] Exemplarily, step S1 includes but is not limited to: placing the wafer in the reaction chamber of a physical vapor deposition (PVD) machine tool, and depositing a titanium nitride layer and a tantalum nitride layer on the wafer through the PVD process to form a lower electrode layer; stopping the supply of nitrogen gas (N2) to the reaction chamber of the PVD machine tool, and depositing titanium and tantalum on the lower electrode layer to form a buffer layer. After the lower electrode layer is deposited, only by continuing to place the wafer in the reaction chamber of the PVD machine tool and stopping the supply of nitrogen gas to the reaction chamber of the PVD machine tool, a buffer layer can be formed on the surface of the lower electrode layer. The metal elements (titanium and tantalum) in the buffer layer are used to increase the adsorption sites and adsorption amount of TMA in the ALD process, thereby increasing the deposition rate of the ALD process.
[0030] Step S2, place the wafer in the reaction chamber of an ALD machine tool and introduce TMA gas for pretreatment.
[0031] Reference Figure 3 , which shows a schematic diagram of introducing TMA gas for pretreatment. Exemplarily, as Figure 3 shown, place the wafer 210 in the reaction chamber of the ALD machine tool and introduce TMA gas for pretreatment (the pretreatment time is greater than 5 seconds (s)). Compared with water vapor (H2O), the carbonyl group in TMA will form a chemisorption with the titanium element and tantalum element in the buffer layer 2111, so there are more adsorption sites and adsorption amount than hydroxyl groups, reducing the induction period time in the deposition process.
[0032] Step S3, perform at least one growth cycle to form an aluminum oxide film above the lower electrode layer, and sequentially introduce water vapor and TMA gas during each growth cycle.
[0033] Reference Figure 4 , which shows a cross-sectional schematic diagram of forming an aluminum oxide film. Exemplarily, as Figure 4 shown, perform at least one growth cycle to form an aluminum oxide film 222 above the lower electrode layer 221. This aluminum oxide film 222 serves as the dielectric layer of the MIM capacitor, and water vapor and TMA gas are sequentially introduced during each growth cycle. Among them, the temperature of the introduced water vapor is maintained at 180 degrees Celsius (°C) to 250 degrees Celsius.
[0034] Step S4, form an upper electrode layer on the alumina thin film.
[0035] Reference Figure 5 , which shows a schematic cross-sectional view after forming the upper electrode layer. Exemplarily, as Figure 5 shown, after forming the alumina thin film 222 by the ALD process, a metal layer can be deposited on the alumina thin film 222 as the upper electrode layer 223 of the MIM capacitor.
[0036] In summary, in the embodiments of the present application, by forming a buffer layer after forming the lower electrode layer in the manufacturing process of the MIM capacitor, TMA in the subsequent ALD process is more likely to be adsorbed on the thin film surface, and the carbonyl group in TMA is more likely to undergo chemisorption with the metal elements in the buffer layer, so there are more adsorption sites and adsorption amounts than hydroxyl groups, thereby reducing the induction period time, improving the deposition rate of the ALD process, and the surface nucleation is more uniform, and the overall uniformity of the formed thin film layer is also significantly improved.
[0037] Obviously, the above embodiments are only examples for clear illustration and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present application.
Claims
1. A method for forming a MIM capacitor, characterized in that: include: forming a buffer layer on a lower electrode layer, wherein the lower electrode layer is formed on a wafer; The wafer is placed in a reaction chamber of an ALD machine and TMA gas is introduced for pretreatment; Performing at least one growth cycle to form an aluminum oxide film on the lower electrode layer, and sequentially introducing water vapor and TMA gas during each growth cycle; An upper electrode layer is formed on the aluminum oxide film.
2. The method according to claim 1, characterized in that: The lower electrode layer includes a titanium nitride layer and a tantalum nitride layer.
3. The method according to claim 2, characterized in that The buffer layer includes titanium and tantalum.
4. The method according to claim 3, characterized in that: The step of forming a buffer layer on the lower electrode layer comprises: Placing the wafer in a reaction chamber of a PVD machine, and depositing a titanium nitride layer and a tantalum nitride layer on the wafer by a PVD process to form the lower electrode layer; The nitrogen gas is stopped from entering the reaction chamber of the PVD machine, and titanium and tantalum are deposited on the lower electrode layer to form the buffer layer.
5. The method according to any one of claims 1 to 4, characterized in that: The time for introducing TMA gas for pretreatment is greater than 5 seconds.
6. The method according to claim 5, characterized in that The temperature of the water vapor introduced during each growth cycle was maintained at 180°C to 250°C.