Method for reducing leakage current of aluminum oxide film

Abstract

The invention provides a method for reducing the leakage current of an aluminum oxide film, and the method specifically comprises the steps: carrying out the first reaction of trimethylaluminum and alcohol on the surface of a wafer, so as to obtain a first aluminum oxide film, and carrying out the second reaction of trimethylaluminum and water on the surface of the first aluminum oxide film, so as to obtain a second aluminum oxide film. According to the method, alcohol and water are combined as reactants, so that the film leakage current of the prepared aluminum oxide film can be reduced. According to the method disclosed by the invention, alcohol and water are combined as reactants, so that the compactness of the prepared aluminum oxide film can be improved, and the water vapor transmission rate is further reduced.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductors, and particularly relates to a method for reducing the leakage current of an alumina thin film. Background Art

[0002] In the prior art, the semiconductor alumina thin film deposition process is usually prepared by the reaction of trimethylaluminum and water. However, water has relatively strong oxidizing properties and is likely to cause the oxidation of the underlying metal to form an interfacial oxide layer. Alcohols, as co-reactants, can avoid the oxidation of the underlying metal and are considered as substitutes for water. However, the alumina thin films formed by using alcohols as reactants generally have high carbon impurities, poor film compactness, and high leakage current. Therefore, there is an urgent need in the art to provide a method for preparing an alumina thin film that is not easily oxidized and has a low leakage current. Summary of the Invention

[0003] The object of the present invention is to provide a method for reducing the leakage current of an alumina thin film.

[0004] In a first aspect of the present invention, a method for preparing an alumina film is provided. The method includes first subjecting trimethylaluminum and an alcohol to a first reaction on the surface of a wafer to obtain a first alumina film, and then subjecting trimethylaluminum and water to a second reaction on the surface of the first alumina film to obtain a second alumina film.

[0005] In one or more embodiments, in the first reaction, trimethylaluminum is introduced first, and then the alcohol is introduced.

[0006] In one or more embodiments, in the second reaction, trimethylaluminum is introduced first, and then water is introduced.

[0007] In one or more embodiments, the first reaction is carried out under the purge of a purge gas.

[0008] In one or more embodiments, the second reaction is carried out under the purge of a purge gas.

[0009] In one or more embodiments, the reaction temperature of the first reaction is 300 - 500 °C.

[0010] In one or more embodiments, the reaction temperature of the second reaction is 180 - 300 °C.

[0011] In one or more embodiments, the reaction pressure of the first reaction is 1 - 3 torr.

[0012] In one or more embodiments, the reaction pressure of the second reaction is 1 - 3 torr.

[0013] In one or more embodiments, the alcohol is selected from one or more of methanol, ethanol, isopropanol, and tert-butanol.

[0014] In one or more embodiments, the purge gas includes a first purge gas and a second purge gas, and the first purge gas and the second purge gas are each independently selected from one or both of argon and nitrogen.

[0015] In one or more embodiments, in the first reaction, the flow rate of the first purge gas is 3000 - 6000 sccm, and the flow rate of the second purge gas is 1000 - 3000 sccm; alternatively, in the first reaction, the flow rate of the second purge gas is 3000 - 6000 sccm, and the flow rate of the first purge gas is 1000 - 3000 sccm.

[0016] In one or more embodiments, in the first reaction, the flow rate of the carrier gas including trimethylaluminum is 500 - 1500 sccm.

[0017] In one or more embodiments, in the first reaction, the introduction time of the carrier including trimethylaluminum is 0.1 - 0.5 s.

[0018] In one or more embodiments, in the first reaction, the flow rate of the carrier gas including the alcohol is 1000 - 2000 sccm.

[0019] In one or more embodiments, in the first reaction, the introduction time of the carrier gas including the alcohol is 0.3 - 1 s.

[0020] In one or more embodiments, in the second reaction, the flow rate of the first purge gas is 3000 - 6000 sccm, and the flow rate of the second purge gas is 1000 - 3000 sccm; alternatively, in the second reaction, the flow rate of the second purge gas is 3000 - 6000 sccm, and the flow rate of the first purge gas is 1000 - 3000 sccm.

[0021] In one or more embodiments, in the second reaction, the flow rate of the carrier gas including trimethylaluminum is 400 - 800 sccm.

[0022] In one or more embodiments, in the second reaction, the introduction time of the carrier gas including trimethylaluminum is 0.1 - 0.2 s.

[0023] In one or more embodiments, in the second reaction, the flow rate of the carrier gas including water is 300 - 500 sccm.

[0024] In one or more embodiments, in the second reaction, the introduction time of the carrier gas including water is 0.2 - 0.5 s.

[0025] In one or more embodiments, the first reaction includes one or more first process cycles, and each first process cycle includes: introducing trimethylaluminum onto the wafer surface first and then introducing alcohol onto the wafer surface under the purge of the purge gas.

[0026] In one or more embodiments, the second reaction includes one or more second process cycles, and each second process cycle includes: introducing trimethylaluminum onto the wafer surface first and then introducing water onto the wafer surface under the purge of the purge gas.

[0027] In one or more embodiments, each first process cycle lasts for 1.5 - 5 s.

[0028] In one or more embodiments, the first reaction includes 10 - 100 first process cycles.

[0029] In one or more embodiments, each second process cycle lasts for 0.7 - 5 s.

[0030] In one or more embodiments, the second reaction includes 10 - 100 second process cycles.

[0031] In one or more embodiments, in the first reaction, after the last first process cycle is completed, the purge gas continues to purge for 5 - 60 s.

[0032] In one or more embodiments, in the second reaction, after the last second process cycle is completed, the purge gas continues to purge for 5 - 60 s.

[0033] In one or more embodiments, after the first reaction ends, the wafer is cooled.

[0034] In the second aspect of the present invention, there is provided an alumina film prepared by using the method described in the first aspect of the present invention.

[0035] In one or more embodiments, the leakage current of the alumina film is 1×10 -9 -10×10 -9 A / cm 2 。

[0036] In the third aspect of the present invention, there is provided a semiconductor device including the alumina film described in the second aspect of the present invention.

[0037] In the fourth aspect of the present invention, there is provided a method for improving the denseness of an alumina film and / or reducing the leakage current of an alumina film, and the method includes the steps of first reacting trimethylaluminum with alcohol to obtain alumina and then reacting trimethylaluminum with water to obtain alumina.

[0038] The present invention has the following beneficial effects:

[0039] (1) The method of the present invention combines alcohol and water as reactants, which can reduce the thin film leakage current of the prepared alumina film.

[0040] (2) The method of the present invention combines alcohol and water as reactants, which can improve the densification of the prepared alumina film, thereby reducing the water vapor transmission rate (WVTR).

[0041] (3) The method of the present invention combines alcohol and water as reactants, and can prepare an alumina film with improved film quality and reduce the thermal budget of the machine.

[0042] (4) The method of the present invention first uses alcohol and trimethylaluminum as reactants to pre-generate an alumina thin film to avoid oxidation of the metal substrate. On this basis, using water and trimethylaluminum as reactants to continue to stack and generate an alumina film can reduce the carbon impurity content of the film, reduce the thin film leakage current, and improve the densification of the film. The film prepared by the method of the present invention is beneficial for protecting the underlying metal as a barrier layer and can also prevent water vapor penetration in OLED encapsulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is a device diagram for implementing the method of the present invention in one or more embodiments of the present invention.

[0044] Figure 2 is a process parameter diagram of the method of the present invention.

[0045] Figure 3 is a flowchart of the method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0046] To enable those skilled in the art to understand the features and effects of the present invention, the following provides a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein shall have the ordinary meaning understood by those skilled in the art for the present invention. In case of conflict, the definition in this specification shall prevail.

[0047] The theories or mechanisms described and disclosed herein, whether correct or incorrect, shall not limit the scope of the present invention in any way, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0048] In this article, "comprising", "including", "containing" and similar terms cover the meanings of "consisting essentially of" and "consisting of". For example, when it is disclosed herein that "A comprises B and C", it should be considered that "A consists essentially of B and C" and "A consists of B and C" have been disclosed herein.

[0049] In this document, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, the description of a numerical range or percentage range should be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values (including integers and fractions) within the range.

[0050] In this document, unless otherwise specified, the percentage refers to the mass percentage, and the ratio refers to the mass ratio.

[0051] In this document, when describing embodiments or examples, it should be understood that it is not intended to limit the present invention to these embodiments or examples. On the contrary, all alternatives, improvements, and equivalents of the methods and materials described in the present invention can be covered within the scope defined by the claims.

[0052] In this document, for the sake of concise description, all possible combinations of all technical features in each embodiment or example are not described. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered to be within the scope described in this specification.

[0053] The present invention uses alcohol and water as reactants respectively to prepare an alumina film. The prepared alumina film can not only ensure that the underlying metal is not oxidized but also has a low leakage current.

[0054] The present invention provides a method for preparing an alumina film. The method includes the steps of first reacting trimethylaluminum with alcohol to obtain alumina and then reacting trimethylaluminum with water to obtain alumina. Preferably, the method includes first reacting trimethylaluminum with alcohol on the surface of a wafer to obtain a first alumina film, and then reacting trimethylaluminum with water on the surface of the first alumina film to obtain a second alumina film.

[0055] In some embodiments, in the first reaction, trimethylaluminum is introduced first, and then alcohol is introduced. Preferably, the first reaction includes one or more first process cycles. The first process cycle includes: under the purge of the purge gas, trimethylaluminum is first introduced on the surface of the wafer, and then alcohol is introduced on the surface of the wafer.

[0056] In some embodiments, in the second reaction, trimethylaluminum is introduced first, and then water is introduced. Preferably, the second reaction includes one or more second process cycles. The second process cycle includes: under the purge of the purge gas, trimethylaluminum is first introduced on the surface of the wafer, and then water is introduced on the surface of the wafer.

[0057] In some embodiments, the first reaction is carried out under a purge gas sweep. In some embodiments, the second reaction is carried out under a purge gas sweep. In some embodiments, the purge gas includes a first purge gas and a second purge gas, and the first purge gas and the second purge gas are each independently selected from one or both of argon and nitrogen. In some embodiments, in the first reaction, the flow rate of the first purge gas is 3000 - 6000 sccm, such as 3000 sccm, 4000 sccm, 5000 sccm, 6000 sccm, and the flow rate of the second purge gas is 1000 - 3000 sccm, such as 1000 sccm, 2000 sccm, 3000 sccm; alternatively, in the first reaction, the flow rate of the second purge gas is 3000 - 6000 sccm, such as 3000 sccm, 4000 sccm, 5000 sccm, 6000 sccm, and the flow rate of the first purge gas is 1000 - 3000 sccm, such as 1000 sccm, 2000 sccm, 3000 sccm. In some embodiments, in the second reaction, the flow rate of the first purge gas is 3000 - 6000 sccm, such as 3000 sccm, 4000 sccm, 5000 sccm, 6000 sccm, and the flow rate of the second purge gas is 1000 - 3000 sccm, such as 1000 sccm, 2000 sccm, 3000 sccm; alternatively, in the second reaction, the flow rate of the second purge gas is 3000 - 6000 sccm, such as 3000 sccm, 4000 sccm, 5000 sccm, 6000 sccm, and the flow rate of the first purge gas is 1000 - 3000 sccm, such as 1000 sccm, 2000 sccm, 3000 sccm.

[0058] In some embodiments, the reaction temperature of the first reaction is 300 - 500 °C, such as 350 °C, 400 °C, 450 °C, 500 °C, and is preferably 300 - 350 °C, 350 - 500 °C, 350 - 400 °C. Compared with the reaction of trimethylaluminum with water, the reaction of trimethylaluminum with alcohol needs to be carried out at a relatively higher temperature.

[0059] In some embodiments, the reaction temperature of the second reaction is 180 - 300 °C, such as 200 °C, 220 °C, 250 °C, 280 °C, 300 °C, and is preferably 180 - 200 °C, 200 - 300 °C, 200 - 250 °C.

[0060] In some embodiments, the reaction pressure of the first reaction is 1 - 3 torr, such as 1 torr, 2 torr, 3 torr, and is preferably 1 - 2 torr, 2 - 3 torr.

[0061] In some embodiments, the reaction pressure of the second reaction is 1 - 3 torr, such as 1.5 torr, 2 torr, 3 torr, preferably 1.5 - 2 torr, 1 - 1.5 torr.

[0062] In some embodiments, the alcohol is selected from one or more of methanol, ethanol, isopropanol, and tert-butanol; preferably tert-butanol.

[0063] In some embodiments, in the first reaction, the flow rate of the carrier gas including trimethylaluminum is 500 - 1500 sccm, such as 500 sccm, 800 sccm, 1000 sccm, 1200 sccm, 1500 sccm, preferably 500 - 1000 sccm, 1000 - 1500 sccm.

[0064] In some embodiments, in the first reaction, the introduction time of the carrier including trimethylaluminum is 0.1 - 0.5 s, such as 0.1 s, 0.2 s, 0.3 s, 0.4 s, 0.5 s, preferably 0.1 - 0.3 s, 0.3 - 0.5 s.

[0065] In some embodiments, in the first reaction, the flow rate of the carrier gas including the alcohol is 1000 - 2000 sccm, such as 1300 sccm, 1500 sccm, 1800 sccm, 2000 sccm, preferably 1000 - 1500 sccm, 1500 - 2000 sccm.

[0066] In some embodiments, in the first reaction, the introduction time of the carrier gas including the alcohol is 0.3 - 1 s, such as 0.4 s, 0.5 s, 0.6 s, 0.7 s, 0.8 s, 0.9 s, preferably 0.3 - 0.6 s, 0.6 - 1 s, 0.6 - 0.9 s.

[0067] In some embodiments, in the second reaction, the flow rate of the carrier gas including trimethylaluminum is 400 - 800 sccm, such as 400 sccm, 500 sccm, 600 sccm, 700 sccm, 800 sccm, preferably 500 - 800 sccm, 600 - 800 sccm, 700 - 800 sccm.

[0068] In some embodiments, in the second reaction, the introduction time of the carrier gas including trimethylaluminum is 0.1 - 0.2 s, such as 0.1 s.

[0069] In some embodiments, in the second reaction, the flow rate of the carrier gas including water is 300 - 500 sccm, such as 300 sccm, 350 sccm, 400 sccm, 450 sccm, 500 sccm, preferably 400 - 500 sccm, 450 - 500 sccm.

[0070] In some embodiments, in the second reaction, the introduction time of the carrier gas including water is 0.2 - 0.5 s, such as 0.2 s, 0.3 s, 0.4 s, 0.5 s, preferably 0.2 - 0.4 s, 0.2 - 0.3 s.

[0071] In some embodiments, the first primary process cycle is carried out for 1.5 - 5 s, such as 1.5 s, 2 s, 2.5 s, 3 s, 3.5 s, 4 s, 5 s, preferably 1.5 - 3 s, 3 - 5 s, 2 - 3 s.

[0072] In some embodiments, the first reaction includes 10 - 100 first process cycles, such as 20 times, 30 times, 40 times, 50 times, 60 times, 70 times, 80 times, preferably 10 - 40 times, 40 - 80 times, 40 - 60 times. The appropriate number of cycles can be selected according to the thickness of the first alumina film to be prepared. The thickness of the first alumina film can be For example For example

[0073] In some embodiments, the first secondary process cycle is carried out for 0.7 - 5 s, such as 0.7 s, 1 s, 1.5 s, 2 s, 2.5 s, 3 s, 3.5 s, 4 s, 5 s, preferably 0.7 - 2.5 s, 2.5 - 5 s, 1 - 3 s.

[0074] In some embodiments, the second process cycle includes 10 - 100 second process cycles, such as 20 times, 30 times, 40 times, 50 times, 60 times, 70 times, 80 times, preferably 10 - 40 times, 40 - 80 times, 40 - 60 times. The appropriate number of cycles can be selected according to the thickness of the second alumina film to be prepared. The thickness of the second alumina film can be For example For example

[0075] In some embodiments, in the first reaction, after the last first process cycle is completed, the purge gas is continuously purged for 5 - 60 s, such as 5 s, 10 s, 15 s, 20 s, 25 s, 30 s, 40 s, 50 s, 60 s, preferably 5 - 10 s, 10 - 50 s, 10 - 30 s, 10 - 20 s.

[0076] In some embodiments, in the second reaction, after the last second process cycle is completed, the purge gas is continuously purged for 5 - 60 s, such as 5 s, 10 s, 15 s, 20 s, 25 s, 30 s, 40 s, 50 s, 60 s, preferably 5 - 10 s, 10 - 50 s, 10 - 30 s, 10 - 20 s.

[0077] In some embodiments, after the first reaction is completed, the wafer is cooled.

[0078] In some embodiments, the method comprises the following steps:

[0079] S1 - Ensure the stability of the chamber environment to ensure the normal progress of the process;

[0080] S2 - Reach the process conditions in advance and preheat the wafer;

[0081] S3 - Introduce trimethylaluminum to adsorb it on the wafer and blow away the surface by - products;

[0082] S4 - Introduce alcohol to react to form an aluminum oxide film and blow away the surface by - products;

[0083] S5 - After the process is completed, purge the chamber again to prevent the residue of by - products and restore the chamber to its initial state;

[0084] S6 - Cool the wafer to make preparations in advance for entering the low - temperature chamber;

[0085] S7 - Reach the process conditions in advance and preheat the wafer;

[0086] S8 - Introduce trimethylaluminum to adsorb it on the wafer and blow away the surface by - products;

[0087] S9 - Introduce water to react to form an aluminum oxide film and blow away the surface by - products;

[0088] S10 - After the process is completed, purge the chamber again to prevent the residue of by - products and restore the chamber to its initial state;

[0089] S11 - After the process is completed, transfer back the wafer.

[0090] As Figure 1 shown, the wafer is transferred from the quartz cassette into the right - hand high - temperature chamber for the reaction of alcohol reactant and trimethylaluminum to form an aluminum oxide film with a certain thickness. After the reaction is completed, the wafer is taken out and cooled for several seconds, and then transferred into the left - hand low - temperature chamber for the reaction of water reactant and trimethylaluminum. After the reaction is completed, the wafer is transferred back to the quartz cassette and the process ends.

[0091] In some embodiments, a wafer including a metal substrate is first transferred to a chamber where alcohol is used as a reactant. The temperature of this chamber is relatively high to ensure that the heating plate rises to the process position, the pressure inside the chamber reaches the process pressure, the side of the metal substrate is preheated, and a purge gas is circulated. In the process cycle, trimethylaluminum injection and purge, as well as alcohol injection and purge steps, are carried out separately. After the cycle ends, the purge gas is turned off, the heating plate is reset, and pressure control is stopped. An alumina film is formed on the surface of the metal substrate of the wafer.

[0092] In some embodiments, the wafer is taken out from the high-temperature chamber and cooled for a period of time, and then the wafer is transferred to a chamber where water is used as a reactant. Since the temperature of this chamber is relatively low, it is necessary to ensure that the surface temperature of the wafer decreases. Ensure that the heating plate rises to the process position, the pressure inside the chamber reaches the process pressure, the side of the preformed alumina film is preheated, and a purge gas is circulated. In the process cycle, trimethylaluminum injection and purge, as well as water injection and purge steps, are carried out separately. After the cycle ends, the purge gas is turned off, the heating plate is reset, and pressure control is stopped. The wafer is transferred back to the crystal cassette, and the process ends.

[0093] The present invention also provides an alumina film prepared by using the method of the present invention. In some embodiments, the leakage current of the alumina film is 1×10 -9 -10×10 -9 A / cm 2 , for example, 1×10 -9 A / cm 2 , 2×10 -9 A / cm 2 , 3×10 -9 A / cm 2 , 4×10 -9 A / cm 2 , 5×10 -9 A / cm 2 , 6×10 -9 A / cm 2 , 7×10 -9 A / cm 2 , 8×10 -9 A / cm 2 , 9×10 -9 A / cm 2 , preferably 1×10 -9 -8×10 - 9 A / cm 2 or 8×10 -9 -10×10 -9 A / cm 2 .

[0094] The present invention also provides a semiconductor device including the alumina film of the present invention. Preferably, the semiconductor device is a wafer. In some embodiments, the wafer includes a silicon layer, a metal substrate layer disposed on one side of the silicon layer, and an alumina film disposed on the side of the metal substrate layer away from the silicon layer.

[0095] The present invention also provides a method for improving the denseness of an alumina film and / or reducing the leakage current of an alumina film. The method includes the steps of first reacting trimethylaluminum with an alcohol to obtain alumina, and then reacting trimethylaluminum with water to obtain alumina. Preferably, the method includes first performing a first reaction of trimethylaluminum with an alcohol on the surface of a wafer to obtain a first alumina film, and then performing a second reaction of trimethylaluminum with water on the surface of the first alumina film to obtain a second alumina film. The first reaction and the second reaction are as described in any of the embodiments herein.

[0096] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. The experimental methods without specific conditions noted in the following embodiments are generally carried out under conventional conditions or according to the conditions recommended by the manufacturers. Unless otherwise specified, percentages and parts are calculated by weight.

[0097] In this article, both the first purge gas and the second purge gas are nitrogen.

[0098] In this article, the alcohol is tert-butanol.

[0099] In this article, a wafer with a copper substrate is used, and the preparation method is as follows:

[0100] 1. Wafer pretreatment

[0101] Cleaning: Use organic solvents (such as acetone and ethanol) to remove organic impurities on the surface of the uncoated wafer, and then rinse it thoroughly with deionized water. Then use a chemical cleaning solution (such as a sulfuric acid-hydrogen peroxide mixture) to remove metal impurities and natural oxide layers on the wafer surface, and finally rinse it thoroughly with deionized water to ensure that the wafer surface is clean and free of contamination.

[0102] Roughening: Immerse the cleaned wafer in a specific roughening solution to form a microscopic rough structure on the wafer surface to increase the adhesion between copper and the wafer surface. After roughening, rinse it with deionized water and perform a drying treatment.

[0103] 2. Depositing a seed layer

[0104] Sputtering coating: Deposit a thin copper seed layer on the wafer surface through the sputtering process of physical vapor deposition (PVD). Place the wafer in a sputtering coating device, evacuate to a certain pressure (such as 10 -6 -10 -4Pa), and then introduce an inert gas such as argon. Under the action of high voltage, argon ions bombard the copper target, causing copper atoms to sputter onto the surface of the wafer to form a uniform seed layer, with a thickness generally between dozens of nanometers and hundreds of nanometers.

[0105] 3. Copper electroplating

[0106] Prepare the electroplating solution: Configure an electroplating solution containing copper sulfate, sulfuric acid, chloride ions, and additives (such as brighteners, leveling agents, etc.). Among them, copper sulfate provides the source of copper ions, sulfuric acid is used to adjust the acidity of the electroplating solution, chloride ions help improve the electroplating effect, and additives are used to improve the quality and performance of the coating.

[0107] Install the wafer: Place the wafer coated with the seed layer into the electroplating tank as the cathode, and at the same time place a copper anode. Ensure that the distance between the wafer and the anode is uniform, generally maintained at about 5 - 10 cm.

[0108] Electroplating process: Connect the power supply and apply a certain current density and voltage for electroplating. During the electroplating process, control parameters such as the temperature and stirring speed of the electroplating solution to ensure the uniform reduction and deposition of copper ions on the surface of the wafer. The electroplating time depends on the required thickness of the copper layer.

[0109] 4. Post-treatment

[0110] Cleaning: After electroplating is completed, take out the wafer from the electroplating tank and immediately rinse it with deionized water to remove the residual electroplating solution on the surface.

[0111] Drying: Use methods such as blowing dry with nitrogen or drying on a hot plate to dry the wafer to prevent impurities such as water stains from remaining on the surface of the wafer.

[0112] 5. Process parameters

[0113] Composition of the electroplating solution: The concentration of copper sulfate is generally between 150 - 250 g / L, the concentration of sulfuric acid is between 50 - 200 g / L, and the concentration of chloride ions is between 50 - 150 ppm. The content of additives is adjusted according to specific product requirements and the electroplating solution formula. Usually, the content of the brightener is between 0.1 - 1 g / L, and the content of the leveling agent is between 0.01 - 0.1 g / L.

[0114] Current density: Generally between 1 - 10 A / dm 2 For the electroplating of some high-precision wafers, the current density may be controlled between 2 - 5 A / dm 2 .

[0115] Voltage: Usually between 1 - 5 V, and the specific voltage value is related to factors such as the current density and the resistance of the electroplating solution.

[0116] Temperature: The temperature of the electroplating solution is generally controlled at 20 - 40 °C. A higher temperature helps to increase the electroplating speed, but an excessively high temperature may lead to a decline in the coating quality.

[0117] Stirring speed: The stirring speed is generally 100 - 500 r / min. Appropriate stirring can evenly distribute the ions in the electroplating solution and improve the uniformity of the coating.

[0118] Example 1

[0119] S1 - Raise the reaction chamber to 350 °C, evacuate to a low pressure, and check for leaks. If the leak check is normal.

[0120] S2 - Transfer the wafer with a copper substrate into the chamber. Move the heating plate to the process position by about 15 mm. Pre - flow the first purge gas at about 5000 sccm and the second purge gas at about 2000 sccm. Control the chamber pressure to the process pressure of 2 torr in advance to reach the process conditions and pre - heat the wafer.

[0121] S3 - Introduce a carrier gas containing trimethylaluminum at about 1000 sccm for a duration of about 0.3 s. Purge the wafer surface to allow trimethylaluminum to adsorb onto the wafer and blow away the surface by - products.

[0122] S4 - Introduce a carrier gas containing alcohol at about 1500 sccm for a duration of about 0.6 s. React the alcohol to form an aluminum oxide film and blow away the surface by - products.

[0123] S5 - After 40 process cycles, stop introducing trimethylaluminum and alcohol. Continue to purge the chamber with the first and second purge gases for about 10 s, then stop all gas flows. Reset the heating plate, return the chamber pressure to the low pressure, transfer the wafer out, and the process ends. Purge the chamber again to prevent the residue of by - products and restore the chamber to its initial state.

[0124] S6 - Cool the wafer in the waiting area for 60 s to pre - prepare for entering the low - temperature chamber.

[0125] S7 - Transfer the wafer into a chamber at about 200 °C again. Move the heating plate to the process position by about 10 mm. Pre - flow the first purge gas at about 4000 sccm and the second purge gas at about 1500 sccm. Control the chamber pressure to the process pressure of 1.5 torr in advance to reach the process conditions and pre - heat the wafer.

[0126] S8 - Introduce a carrier gas containing trimethylaluminum at about 800 sccm for a duration of about 0.1 s. Purge the wafer surface to allow trimethylaluminum to adsorb onto the wafer and blow away the surface by - products.

[0127] S9 - Introduce a carrier gas containing water at about 500 sccm for a duration of about 0.2 s. React the water to form an aluminum oxide film and blow away the surface by - products.

[0128] After 60 process cycles, stop introducing trimethylaluminum and water. Continue purging the chamber with the first purging gas and the second purging gas for about 10 s, then stop all gas flows. Reset the heating plate, and the chamber pressure returns to the low pressure. Transfer out the wafer, and the process ends. Purge the chamber again to prevent the residue of by-products and restore the chamber to its initial state.

[0129] S11 - The process ends, and transfer back the wafer.

[0130] The alumina film prepared by this method has good film compactness, relatively low leakage current, and the metal under the film layer is not easily oxidized.

[0131] Comparative Example 1

[0132] Transfer the wafer with a copper substrate into a chamber at a temperature of 350 °C. Move the heating plate to the process position by about 15 mm. The first purging gas preflows at about 5000 sccm, and the second purging gas preflows at about 2000 sccm. Control the chamber pressure to the process pressure of 2 torr. Introduce the carrier gas including trimethylaluminum at about 1000 sccm for a duration of about 0.3 s to purge the wafer surface. The first purging gas and the second purging gas purge the wafer surface for about 1 s. Introduce the carrier gas including alcohol at about 1500 sccm for a duration of about 0.6 s. The first purging gas and the second purging gas purge the wafer surface for about 1.5 s. After multiple process cycles, stop introducing trimethylaluminum and alcohol. Continue purging the chamber with the first purging gas and the second purging gas for about 10 s, then stop all gas flows. Reset the heating plate, and the chamber pressure returns to the low pressure. Transfer the wafer out of the chamber. After cooling for 60 s, transfer it back to the FOUP, and an alumina film with a film thickness is formed on the wafer surface. Test the leakage current of the wafer prepared in the high-temperature chamber and the oxidability of the metal under the film layer.

[0133] The film layer prepared by this method has poor film compactness and high leakage current in the test, but due to the low oxidability of alcohol, the metal under the film layer is not easily oxidized.

[0134] Comparative Example 2

[0135] Transfer the wafer with a copper substrate into a chamber at a temperature of 200 °C. Move the heating plate to the process position by about 10 mm. The pre-flow of the first purge gas is about 4000 sccm, and the pre-flow of the second purge gas is about 1500 sccm. Control the chamber pressure to the process pressure of 1.5 torr. Introduce a carrier gas including trimethylaluminum at about 800 sccm for about 0.1 s to purge the wafer surface. The first purge gas and the second purge gas purge the wafer surface for about 0.8 s. Introduce a carrier gas including water at about 500 sccm for about 0.2 s. The first purge gas and the second purge gas purge the wafer surface for about 1 s. After multiple process cycles, stop introducing trimethylaluminum and water. The first purge gas and the second purge gas continue to purge the chamber for about 10 s and then stop all gas flows. Reset the heating plate, return the chamber pressure to the base pressure, transfer the wafer out of the chamber. After waiting for 30 s to cool, transfer it back to the FOUP, and an aluminum oxide film with a film thickness of is formed on the wafer surface. Test the leakage current of the wafer fabricated in the low-temperature chamber and the oxidability of the metal under the film layer.

[0136] The film layer fabricated by this method is tested to be relatively dense with low leakage current, but the metal under the film layer is oxidized.

[0137] Test Example 1

[0138] (I) General Test Method for Leakage Current (DC Test Method)

[0139] 1. Applicable Scenarios

[0140] The aluminum oxide thin film is used as an insulating layer.

[0141] 2. Test Structure

[0142] MIS Structure (Metal - Al2O3 - Si): Used to evaluate the semiconductor interface quality.

[0143] 3. Key Parameters

[0144] Voltage Range: Usually 0 V to the breakdown voltage (the breakdown field strength of Al2O3 is about 10 7 V / cm, which needs to be adjusted according to the thickness). The breakdown field strength of Al2O3 with a thickness of about 7*10 6 V / cm, The breakdown field strength of Al2O3 with a thickness of about 6*10 6 V / cm.

[0145] Current Measurement Range: 1 fA to 100 mA.

[0146] 4. Analysis of Typical Results

[0147] Type of I - V Curve:

[0148] (1) Low voltage region: Tunneling current (Fowler-Nordheim tunneling or direct tunneling, depending on the thickness).

[0149] (2) High voltage region: Trap-assisted tunneling or thermionic emission.

[0150] (3) Breakdown characteristics: Distinguish between intrinsic breakdown (uniform field strength) and defect breakdown (local hot spots).

[0151] (II) Test the leakage current of the film prepared in Comparative Example 1

[0152] 1. Initial settings

[0153] Voltage sweep mode: Linear Sweep.

[0154] Starting voltage: 0 V.

[0155] Ending voltage: 5 V (estimated according to the breakdown field strength, corresponding breakdown voltage is about 4 - 8 V).

[0156] Scanning rate: 10 mV / s (slow scan to reduce electrical stress damage).

[0157] Current range:

[0158] (1) Non-breakdown region: 100 pA - 1 μA (auto range).

[0159] (2) Breakdown protection: Set the current upper limit to 1 mA (to avoid instrument overload).

[0160] 2. Execute the test

[0161] Pre-test: Apply 0 V bias voltage and record the baseline noise (ideal value < 1 pA).

[0162] Forward bias voltage scan: Gradually increase from 0 V to 5 V and record the I-V curve.

[0163] Key data points:

[0164] (1) When the current exceeds 1 μA, mark it as "soft breakdown".

[0165] (2) When the current suddenly increases to 1 mA (triggering protection), record the "hard breakdown voltage" (such as 4.5 V).

[0166] Reverse bias voltage scan (optional): Decrease from 0 V to -5 V and observe whether there is a rectification effect.

[0167] 3. Data processing

[0168] Calculate the current density: Example: Measured current 10 nA, electrode area 7.85×10 -6cm 2 →

[0169] Current density = 10×10 -9 A / 7.85×10 -6 cm 2 ≈1.27×10 -3 A / cm 2 (i.e., 1.27 mA / cm 2 ).

[0170] Plot the I-V curve: Horizontal axis: Voltage (V); Vertical axis: Logarithmic coordinate current (Log(I)).

[0171] Typical curve characteristics:

[0172] (1) Low voltage region (<2V): The current shows exponential growth (dominated by tunneling effect).

[0173] (2) Medium voltage region (2 - 4V): The current shows linear growth (space charge limited current).

[0174] (3) High voltage region (>4V): The current rises sharply (breakdown occurs).

[0175] (III) Test the leakage current of the film prepared in Comparative Example 2

[0176] Repeat the test method of Test Example 2, with the differences being:

[0177] Termination voltage: Increased to 8V (breakdown voltage is about 6 - 12V).

[0178] Current range: Non-breakdown region: 10 pA - 1 μA (due to increased thickness, the leakage current is lower).

[0179] Expected result: Breakdown voltage is about 6 - 7V, and the current density before breakdown ≤ 1×10 -6 A / cm 2 (@1 MV / cm).

[0180] (IV) Test the leakage current of the film prepared in Example 1

[0181] Use a method similar to the above (I), (II), and (III) to test the leakage current of the film prepared in Example 1

[0182] The leakage currents of the films prepared in Example and Comparative Examples 1 - 2 are shown in Table 1

[0183] Test Example 2, Wafer Oxidation Test

[0184] 1. Test method

[0185] In semiconductor processes, aluminum oxide (Al2O3) films are often used as passivation layers or dielectric layers to protect the underlying metals (such as aluminum, copper, etc.) from oxidation or corrosion. The principle of X-ray photoelectron spectroscopy (XPS) is to excite the surface electrons of the sample with X-rays and analyze the electron binding energy to determine the chemical state of the element (such as metallic state, oxidized state). By combining argon ion etching to strip the Al2O3 film layer by layer, the oxidation state of the underlying metal (such as Cu → Cu2O / CuO) can be detected. The elemental distribution from the surface layer to a depth of about 10 nm can be detected, which is suitable for thin Al2O3 films (such as nanoscale films prepared by atomic layer deposition).

[0186] 2. Test Standards

[0187] Calculate the atomic ratio of O to metal (M) (O / M) through the XPS peak area. For pure metal: O / M ≈ 0. For complete oxidation: O / M ≈ 1 (copper substrate). For partial oxidation: O / M is between 0 and the complete oxidation value. If the O / M at the interface is significantly higher than the value of the metal bulk, it indicates that the metal is easily oxidized. If the O / M at the interface is closer to the value of the metal bulk, it indicates that the metal is not easily oxidized.

[0188] Table 1

[0189]

Claims

1. A method for preparing an alumina film, characterized in that, The method includes first causing trimethylaluminum to react with an alcohol on the surface of a wafer to produce a first aluminum oxide film, and then causing trimethylaluminum to react with water on the surface of the first aluminum oxide film to produce a second aluminum oxide film.

2. The method according to claim 1, wherein: In the first reaction, trimethylaluminum is introduced first, and then the alcohol is introduced; In the second reaction, trimethylaluminum is introduced first, and then water is introduced; The first reaction is carried out under purging with a purge gas; The second reaction is carried out under purging with a purge gas.

3. The method according to claim 2, wherein The method has one or more of the following characteristics: The reaction temperature of the first reaction is 300 - 500 °C; The reaction temperature of the second reaction is 180 - 300 °C; The reaction pressure of the first reaction is 1 - 3 torr; The reaction pressure of the second reaction is 1 - 3 torr; The alcohol is selected from one or more of methanol, ethanol, isopropanol, and tert-butanol; The purge gas includes a first purge gas and a second purge gas, and the first purge gas and the second purge gas are each independently selected from one or two of argon and nitrogen.

4. The method according to claim 3, wherein The method has one or more of the following characteristics: In the first reaction, the flow rate of the first purge gas is 3000 - 6000 sccm, and the flow rate of the second purge gas is 1000 - 3000 sccm; or, in the first reaction, the flow rate of the second purge gas is 3000 - 6000 sccm, and the flow rate of the first purge gas is 1000 - 3000 sccm; In the first reaction, the flow rate of the carrier gas containing trimethylaluminum is 500 - 1500 sccm; In the first reaction, the introduction time of the carrier containing trimethylaluminum is 0.1 - 0.5 s; In the first reaction, the flow rate of the carrier gas containing the alcohol is 1000 - 2000 sccm; In the first reaction, the introduction time of the carrier gas containing the alcohol is 0.3 - 1 s; In the second reaction, the flow rate of the first purge gas is 3000 - 6000 sccm, and the flow rate of the second purge gas is 1000 - 3000 sccm; or, in the second reaction, the flow rate of the second purge gas is 3000 - 6000 sccm, and the flow rate of the first purge gas is 1000 - 3000 sccm; In the second reaction, the flow rate of the carrier gas containing trimethylaluminum is 400 - 800 sccm; In the second reaction, the introduction time of the carrier gas containing trimethylaluminum is 0.1 - 0.2 s; In the second reaction, the flow rate of the carrier gas containing water is 300 - 500 sccm; In the second reaction, the introduction time of the carrier gas containing water is 0.2 - 0.5 s.

5. The method according to claim 4, wherein: The first reaction includes one or more first process cycles, and the first process cycle includes: under purging with the purge gas, first introducing trimethylaluminum on the surface of the wafer, and then introducing the alcohol on the surface of the wafer; and / or, The second reaction includes one or more second process cycles, and each second process cycle includes: introducing trimethylaluminum onto the wafer surface first under the purge of the purge gas, and then introducing water onto the wafer surface.

6. The method according to claim 5, wherein The method has one or more of the following features: Each first process cycle lasts for 1.5 - 5 s; The first reaction includes 10 - 100 first process cycles; Each second process cycle lasts for 0.7 - 5 s; The second reaction includes 10 - 100 second process cycles; In the first reaction, after the last first process cycle is completed, the purge gas continues to purge for 5 - 60 s; In the second reaction, after the last second process cycle is completed, the purge gas continues to purge for 5 - 60 s; After the first reaction ends, cool the wafer.

7. An alumina film prepared by the method according to any one of claims 1 - 6.

8. The alumina film according to claim 7, characterized in that, The leakage current of the aluminum oxide film is 1*10 -9 -10*10 - 9 A / cm 2 .

9. A semiconductor device including the alumina film according to claim 7 or 8.

10. A method for improving the density of an alumina film and / or reducing the leakage current of an alumina film, characterized in that, The method includes the steps of first reacting trimethylaluminum with an alcohol to obtain alumina, and then reacting trimethylaluminum with water to obtain alumina; preferably, the method includes first performing a first reaction of trimethylaluminum with an alcohol on the wafer surface to obtain a first alumina film, and then performing a second reaction of trimethylaluminum with water on the surface of the first alumina film to obtain a second alumina film, wherein the first reaction and the second reaction are as described in any one of claims 1 - 6.

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