Aluminum film sputtering method and aluminum film

Abstract

This application provides an aluminum film sputtering method and an aluminum film. The aluminum film sputtering method includes a substrate cooling process, which includes the following steps: a first cooling process, in which the temperature of the substrate is cooled to 25 degrees Celsius at a first average cooling rate; and a second cooling process, in which the temperature of the substrate is cooled to a target cooling temperature at a second average cooling rate. The first average cooling rate is higher than the second average cooling rate. This application adds a programmed cooling step to the substrate, dividing the cooling into two stages by controlling the cooling rate and time. Through the two-stage aluminum film sputtering process, the aluminum film growth process is controlled. Only a single target sputtering is required to achieve the dual technical effects of reducing aluminum film roughness and controllable dielectric constant. The technical solution of this application is simple and has good technical effects.

Description

Technical Field

[0001] The invention relates to the field of sputtering coating in semiconductor integrated circuit manufacturing technology, and in particular to an aluminum film sputtering method and an aluminum film. Background Art

[0002] Super-diffraction films play a very important role in improving the lithography resolution in integrated circuit manufacturing, especially metal-dielectric multilayer film structures. In a specific metal-dielectric multilayer film structure, the localized plasmons generated on the surface of the metal film are determined by its surface roughness and composite dielectric constant. If the metal surface roughness is too large, the localized plasmon field on the surface of the metal film will be disordered, which is not conducive to its optical properties as a super-diffraction lens. Therefore, in practical applications, it is expected that the surface roughness of the metal film should be as small as possible; and the sensitivity and quality of the localized plasmons on the surface of the metal film are determined by its composite dielectric constant. If the composite dielectric constant of the metal film is controllable, the optimal range of composite dielectric constants can be selected according to actual needs to combine different technical requirements, thereby meeting the requirements of sensing sensitivity or super-diffraction imaging.

[0003] At present, the research on super-diffraction film layers mainly focuses on silver materials. Chinese patent CN115233159 A discloses a method for preparing a silver film with controllable roughness and dielectric constant, but this scheme requires the simultaneous sputtering of silver target and aluminum nitride target, and the dielectric constant and roughness of the silver film are controlled by adjusting the doping concentration of aluminum nitride. Two target materials need to be prepared in advance, and the process is relatively complicated. Therefore, how to prepare an aluminum film with controllable roughness and dielectric constant is a technical difficulty in this field. Summary of the invention

[0004] In order to at least solve the above technical problems, the present application provides an aluminum film sputtering method and an aluminum film. The present application uses only one target material for sputtering, and by adding a program cooling step for the substrate during the preparation process, through the confinement and film formation of two cooling programs, the technical effect of reducing the roughness of the aluminum film and adjusting the dielectric constant of the aluminum film is achieved.

[0005] In order to achieve the above technical effects, the technical solution adopted in this application is:

[0006] In one aspect, the present application provides a method for sputtering an aluminum film, wherein the aluminum film is obtained by sputtering an aluminum target onto a substrate.

[0007] The aluminum film sputtering method comprises a cooling treatment step for the substrate,

[0008] The cooling process can cool the substrate to 10-22° C., and the cooling time is 5-15 minutes.

[0009] The cooling process comprises the following steps:

[0010] a first cooling process, wherein the substrate is cooled to 25 degrees Celsius at a first average cooling rate, the required time being a first cooling time, and sputtering is performed once;

[0011] A second cooling process, in which the temperature of the substrate is cooled to a target cooling temperature at a second average cooling rate, and the required time is a second cooling time. During the second cooling process, secondary sputtering is performed to obtain a target aluminum film;

[0012] The first average cooling rate is higher than the second average cooling rate;

[0013] The first cooling time is shorter than the second cooling time.

[0014] In a possible implementation, the first average cooling rate is 1-3° C. / min.

[0015] In a possible implementation, the second average cooling rate is 0.5-1° C. / min.

[0016] In a possible implementation, the aluminum film sputtering method provided in the present application further includes the following steps:

[0017] Step S1: pre-treating a substrate to obtain a pre-treated first substrate;

[0018] Step S2: performing a first cooling process on the first substrate to obtain a cooled second substrate;

[0019] Step S3: Under predetermined preparation conditions, argon gas is introduced into the chamber, the sputtering power of the aluminum target is adjusted, a sputtering is performed on the second substrate, and then a second cooling treatment is performed on the second substrate, and a second sputtering is performed at the same time, so that several roughness-sputtering power curves of the aluminum film prepared in a pure argon gas environment can be obtained, and the first condition is determined according to the roughness-sputtering power curves;

[0020] Step S4: under predetermined preparation conditions, the second substrate is replaced, a mixed gas of argon and oxygen in different proportions is introduced into the chamber, and the aluminum target is sputtered once and twice on the second substrate that has undergone the first cooling treatment and the second cooling treatment, to obtain a plurality of dielectric constant-wavelength curves of the aluminum film prepared in a gas environment of a mixture of argon and oxygen in different proportions;

[0021] Step S5: Based on the target dielectric constant of the aluminum film at a specific wavelength, determine the second condition according to the multiple dielectric constant-wavelength curves obtained in step S4;

[0022] Step S6: Based on the first condition and the second condition, a low-roughness aluminum film with a target dielectric constant is prepared under predetermined preparation conditions.

[0023] In a possible implementation, step S1 includes the following steps:

[0024] Drying the substrate to obtain a dried substrate;

[0025] The dried substrate is pre-sputtered to remove surface impurities.

[0026] Preferably, the drying process comprises the following steps: heating the substrate to 100-150° C. under vacuum conditions and keeping the temperature for 20-40 seconds.

[0027] Preferably, the pre-sputtering comprises the following steps: Under the conditions of , argon gas was introduced and 200~400W of RF power was applied for a duration of 4~8s.

[0028] In a possible implementation, the predetermined preparation conditions of step S3 include:

[0029] The cavity is evacuated to form a vacuum cavity; argon gas is introduced into the vacuum cavity, and the vacuum degree of the vacuum cavity is in the range of less than .

[0030] In a possible implementation, step S3 includes: using DC sputtering on an aluminum target to sputter and deposit an aluminum film on a substrate that has been cooled; adjusting the sputtering power of the DC sputtering to deposit and prepare a plurality of aluminum films at different sputtering powers.

[0031] In a possible implementation, the first condition is: the sputtering power of the direct current sputtering of the aluminum target when the roughness of the aluminum film is minimum.

[0032] Preferably, the thickness of the plurality of aluminum films is equal, and the thickness of the aluminum film is 10-100 nm.

[0033] In a possible implementation, step S4 includes evacuating the cavity to form a vacuum cavity; introducing a mixed gas of argon and oxygen into the vacuum cavity, and the vacuum degree of the vacuum cavity is in the range of .

[0034] Preferably, the volume proportion of argon in the mixed gas of argon and oxygen is 20% to 100%.

[0035] In a possible implementation, step S4 includes: using an ellipsometer to collect dielectric constant data of each aluminum film at 193nm~1690nm; fitting the dielectric constant data at different wavelengths to obtain a dielectric constant-wavelength curve of each aluminum film.

[0036] In a possible implementation, the second condition is: the volume of oxygen in a mixed gas of argon and oxygen corresponding to a target dielectric constant of the aluminum film at a specific wavelength.

[0037] In one possible implementation, step S5 includes: determining a first dielectric constant-wavelength curve corresponding to the specific wavelength and the target dielectric constant among multiple dielectric constant-wavelength curves according to the target dielectric constant of the target aluminum film at a specific wavelength, and determining the volume of oxygen in the corresponding argon and oxygen mixed gas according to the first dielectric constant-wavelength curve.

[0038] In a possible implementation, the aluminum film sputtering method can be applied to an 8-inch magnetron sputtering device, and the power of the coating sputtering is 500W to 5000W.

[0039] In a possible implementation, the material of the substrate includes one of Si, SiO2, Ge, SiBARC, ZnO, GaAs, GaN, SiC, and InP.

[0040] In a second aspect, the present application also provides an aluminum film with low roughness and controllable dielectric constant, which is prepared according to the aforementioned method for preparing an aluminum film with low roughness and controllable dielectric constant.

[0041] Technical advantages of this application:

[0042] Compared with the technical solution in the prior art that requires the use of dual target materials (such as silver target materials and nitride target materials) for joint sputtering control, the present application adds a program cooling step for the substrate. By controlling the cooling speed and time, the cooling is divided into two stages. Through the two-stage aluminum film sputtering process, the aluminum film growth process is controlled. Only single target sputtering is required to achieve the dual technical effects of reducing the roughness of the aluminum film and controlling the dielectric constant. The technical solution is simple and the technical effect is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 A cooling step flow chart provided in one embodiment of the present application;

[0044] Figure 2 A flow chart of a method for preparing an aluminum film with low roughness and controllable dielectric constant provided in one embodiment of the present application;

[0045] Figure 3 A schematic diagram of the structure of an apparatus for preparing an aluminum film provided in one embodiment of the present application;

[0046] Figure 4 This is an AFM schematic diagram of the aluminum film prepared in Example 1 of the present application;

[0047] Figure 5These are curves of aluminum films with different roughness obtained at different sputtering powers in Example 1 of the present application;

[0048] Figure 6 This is an AFM schematic diagram of an aluminum film prepared at a specified sputtering power in Example 1 of the present application;

[0049] Figure 7 The curve of the real part of the dielectric constant of the aluminum film prepared in Example 1 of the present application at different incident light wavelengths;

[0050] Figure 8 The curve of the imaginary part of the dielectric constant of the aluminum film obtained in Example 1 of the present application at different incident light wavelengths;

[0051] Fig. 9 This is an AFM schematic diagram of the aluminum film prepared in Example 2 of the present application;

[0052] Fig.10 This is an AFM schematic diagram of the aluminum film prepared in Comparative Example 1 of the present application;

[0053] Fig.11 This is an AFM schematic diagram of the aluminum film prepared in Comparative Example 2 of the present application. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0055] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0056] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0057] In the description of this application, it should be noted that the terms "upper", "lower", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the application is usually placed when in use, which is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0058] In the description of this application, it should also be noted that, unless otherwise clearly specified and limited, the terms "disposed", "connected", "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 a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0059] It should be noted that, in the absence of conflict, different features in the embodiments of the present application may be combined with each other.

[0060] Sputtering is a relatively mature film-making method in the existing technology. Sputtering refers to the use of energetic particles (such as positive ions) to bombard the target material in a vacuum environment, so that atoms or atomic groups on the surface of the target material escape. The escaped atoms form a thin film with the same composition as the target material on the surface of the substrate. This method of preparing thin films is called sputtering. The target material here can be various metal target materials or various metal compound target materials. The specific target material type and substrate type selected depend on the actual working conditions.

[0061] At present, sputtering is mainly used to form metal or alloy films, especially for the production of electrodes for electronic components and infrared reflective films on glass surfaces. Compared with evaporation coating, the target material (film material) does not undergo phase change during sputtering coating, the compound composition is stable, and the alloy is not easy to fractionate, so a wide range of film materials are suitable for preparation. Since the energy of the particles deposited on the substrate by sputtering is 50 times higher than that during evaporation, they have a cleaning and heating effect on the substrate, so the formed film has a strong adhesion. In particular, sputtering coating is easy to control the composition of the film. Through direct sputtering or reactive sputtering, various alloy films, compound films, multilayer films and composite films with large areas of uniformity can be prepared. Sputtering coating is easy to achieve continuous, automated operation and large-scale production.

[0062] For film formation by sputtering, it is expected that the surface roughness of the metal film layer should be as small as possible; and the sensitivity, quality and other parameters of the localized plasmon on the surface of the metal film layer are determined by its composite dielectric constant. If the composite dielectric constant of the metal film is controllable, the composite dielectric constant in the optimal range can be selected according to actual needs to combine different technical needs, thereby meeting the requirements of sensor sensitivity or super-diffraction imaging. Therefore, the researchers hope to develop a film with adjustable roughness and dielectric constant, which is more conducive to practical applications. During the research and development process of this application, it was found that the roughness can be reduced by programmed cooling of the substrate.

[0063] The present application provides an aluminum film sputtering method, wherein the aluminum film is obtained by sputtering an aluminum target material onto a substrate.

[0064] See also Figure 1 The aluminum film sputtering method includes a cooling treatment step for the substrate,

[0065] The cooling process can cool the substrate to 10-22° C., and the cooling time is 5-15 minutes.

[0066] The cooling process comprises the following steps:

[0067] a first cooling process, wherein the substrate is cooled to 25 degrees Celsius at a first average cooling rate, the required time being a first cooling time, and sputtering is performed once;

[0068] A second cooling process, in which the temperature of the substrate is cooled to a target cooling temperature at a second average cooling rate, and the required time is a second cooling time. During the second cooling process, secondary sputtering is performed to obtain a target aluminum film;

[0069] The first average cooling rate is higher than the second average cooling rate;

[0070] The first cooling time is shorter than the second cooling time.

[0071] In the prior art CN115233159A, the growth mode of silver atoms on the substrate to be plated is changed by doping aluminum nitride to achieve the technical effect of reducing the surface roughness of the silver film, but this method requires two target materials to be sputtered together and the doping concentration of aluminum nitride needs to be controlled. Although the prior art CN114855122A also mentions a similar cooling scheme, it is necessary to set a buffer layer with better wettability with the target metal to refine the metal grains and achieve a similar technical effect.

[0072] In the present application, a programmed cooling method is used to process the substrate. The substrate is cooled to 25°C for the first time by a relatively fast cooling rate, and the first sputtering is performed. The first cooling can preliminarily improve the growth mode of the Al film and enhance the wettability between the Al film and the substrate. However, the first cooling process is relatively fast. Due to the existence of interatomic forces, in a relatively short period of time, the interatomic forces are stronger than the forces between atoms and the substrate. Therefore, the Al film tends to generate separate atomic nuclei on the surface of the substrate rather than forming a film. However, at the same time, due to the cooling effect of the substrate, the bonding force between the Al atomic nuclei and the substrate is also relatively strong, and the first layer of the base film formed is also relatively firm.

[0073] The cooling rate of the second cooling is slower. The substrate is cooled again from 25°C and then sputtered. At this time, due to the slow cooling rate, the Al atoms can slowly bond with the substrate surface, the bonding force is stronger, and there is more time for migration and rearrangement, so that the Al atoms can be inserted into the gaps of the Al atomic nuclei during the first cooling, and a dense aluminum film can be formed through the bonding force between Al-Al and the bonding force between Al and substrate; in addition, the atomic nuclei formed in the first cooling step can also play a confining role, limiting the position of the aluminum atoms formed by sputtering in the second cooling step, so that the generated aluminum film can be as smooth as possible, which helps to further reduce the roughness of the aluminum film.

[0074] If the first average cooling rate is lower than the second average cooling rate, and the first cooling time is longer than the second cooling time, Al atoms will tend to form a film directly during the first cooling, and during the subsequent second cooling, Al atoms will directly form small Al atomic nuclei on the surface of the film, and the roughness of the aluminum film will increase.

[0075] Specifically, the aluminum film sputtering of the present application is divided into two stages:

[0076] The first stage: the atomic small nucleus mode stage. Due to the fast cooling speed and short cooling time, the wettability between Al atoms and the substrate is weaker than the interatomic force. The target metal atoms reaching the surface of the substrate tend to bond with each other first and then combine with the substrate. Therefore, the target metal atoms first condense into countless isolated Al atomic small nuclei on the substrate surface, and then form a three-dimensional island, which plays a confining role.

[0077] The second stage: the film formation stage. In this stage, the cooling rate is slow and the cooling time is long. The wettability between Al atoms and the substrate is large and stronger than the interaction between Al atoms. Therefore, with the secondary sputtering, the target metal (i.e., Al metal) continues to deposit on the substrate surface and in the middle of the Al atomic nuclei. The gap between two adjacent islands decreases and is gradually filled with Al metal atoms to form a continuous, complete, and smooth metal Al film.

[0078] Here, there are multiple solutions for cooling the substrate. For example, water cooling, air cooling, liquid nitrogen cooling, contact ice cooling, vacuum cooling, etc. can be used. Water cooling is used in this application. Cooling water is passed under the heater at the bottom of the substrate for continuous cooling. The coating process is carried out after the target temperature is reached.

[0079] In this application, due to the technical principles described above, the first average cooling rate needs to be higher than the above-mentioned second average cooling rate; the first cooling time is lower than the second cooling time. Exemplarily, the first average cooling rate can be 2~5℃ / min, such as 2, 2.5, 3, 3.5, 4, 4.5, 5℃ / min, the second average cooling rate can be 0.5~1.5℃ / min, such as 0.5, 1, 1.5℃ / min, the first cooling time can be 1~3min, such as 1, 2, 3min, and the second cooling time can be 4~12min, such as 4, 5, 6, 7, 8, 9, 10, 11, 12min. If the cooling rate is too fast and the cooling time is too short, the technical effect cannot be achieved; if the cooling rate is too slow and the cooling time is too long, the processing time is extended, and the purpose of improving the technical effect cannot be significantly achieved.

[0080] The first sputtering can be performed at the same time as the first cooling treatment, or it can be performed after the first cooling treatment is completed. Performing it at the same time as the first cooling treatment can effectively save processing time, but due to the high substrate temperature, the wettability between Al atoms and the substrate is poor, and the effect is not good; therefore, generally the first sputtering is performed after the first cooling treatment. The secondary sputtering process needs to be performed at the same time as the second cooling treatment. Sputtering during continuous cooling helps to enhance the wettability and interaction between Al atoms and the substrate, and the coating effect is better.

[0081] Here, the processing time of the coating sputtering is considered based on the aluminum film thickness required for actual working conditions. For example, the time for the first sputtering and the second sputtering can be 1 to 5 minutes.

[0082] In one embodiment of the present application, the first average cooling rate is 1-3°C / min.

[0083] In one embodiment of the present application, the second average cooling rate is 0.5-1°C / min.

[0084] As mentioned above, too fast or too slow cooling speed cannot achieve the best technical effect. When the first average cooling speed is 1~3℃ / min and the second average cooling speed is 0.5~1℃ / min, the experimental effect is best.

[0085] In one embodiment of the present application, a method for sputtering an aluminum film including the above cooling step is also provided, see Figure 2 , comprising the following steps:

[0086] Step S1: pre-treating a substrate to obtain a pre-treated first substrate;

[0087] The pretreatment here serves the purpose of cleaning the substrate and removing impurities on the surface of the substrate. Any technical means that can achieve the purpose of removing impurities can be applied to step S1;

[0088] Step S2: performing a first cooling treatment on the first substrate to obtain a cooled second substrate; this step is to cool the substrate to 25° C.;

[0089] Step S3: Under predetermined preparation conditions, argon gas is introduced into the chamber, the sputtering power of the aluminum target is adjusted, a sputtering is performed on the second substrate, and then a second cooling treatment is performed on the second substrate, and a second sputtering is performed at the same time, so that several roughness-sputtering power curves of the aluminum film prepared in a pure argon gas environment can be obtained, and the first condition is determined according to the roughness-sputtering power curves;

[0090] As described above, the first sputtering can be performed simultaneously with the first cooling, or after the first cooling. In one embodiment of the present application, cooling is performed first and then sputtering is performed. Exemplarily, the first cooling and the first sputtering can also be performed simultaneously; the second cooling treatment and the secondary sputtering need to be performed simultaneously.

[0091] Adjusting the sputtering power of the aluminum target can control the growth rate of the aluminum film, and the growth rate of the aluminum film will mainly affect the surface roughness of the aluminum film. Therefore, by repeating steps S1 to S3, adjusting the sputtering power of the aluminum target can obtain a series of corresponding curves between the roughness of the aluminum film and the sputtering power of the target, and determining the sputtering power of the target according to the set first condition, such as a specified roughness of a certain aluminum film. Here, the sputtering power adjustment range of the aluminum target is 500 to 5000W, and illustratively, 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000W can be selected.

[0092] Step S4: under predetermined preparation conditions, a mixed gas of argon and oxygen in different proportions is introduced into the chamber, and the aluminum target is sputtered once and twice on the second substrate that has undergone the first cooling treatment and the second cooling treatment, to obtain multiple dielectric constant-wavelength curves of the aluminum film prepared in the gas environment of the mixed gas of argon and oxygen in different proportions;

[0093] In step S4, the processing method of the sputtered substrate is the same as above, that is, repeating steps S1 to S2, performing pretreatment and cooling treatment, and the sputtering method is the same as described in step S3, that is, first cooling the substrate and then sputtering; the second cooling treatment and secondary sputtering need to be performed simultaneously.

[0094] In step S4, the dielectric constant-wavelength curve of the aluminum film is regulated by adding different proportions of oxygen, so that the real part and imaginary part of the dielectric constant at a specific wavelength can reach values ​​different from those of the traditional aluminum film. By introducing oxygen into the vacuum cavity, the growth mode of aluminum atoms forming a thin film on the substrate surface is changed, and the purpose of effectively regulating the physical properties such as the composite dielectric constant of the aluminum film can be achieved by adjusting the proportion of oxygen introduced. By adjusting the proportion of oxygen, the dielectric constant of the prepared aluminum film will change. The real part and imaginary part of the dielectric constant of the prepared multiple aluminum film samples at different incident light wavelengths are measured using an ellipsometer, and the data of the real part and imaginary part of the dielectric constant obtained are fitted and plotted to obtain multiple curves of the change of the dielectric constant with the wavelength of the incident light, that is, multiple dielectric constant-wavelength curves.

[0095] It should be noted that the dielectric constant-wavelength curve includes a curve showing a change of the real part of the dielectric constant with the wavelength of the incident light and a curve showing a change of the imaginary part of the dielectric constant with the wavelength of the incident light.

[0096] Exemplarily, the preparation method disclosed in the present invention can also be extended to the scope of regulating other optical properties of aluminum film, such as refractive index, transmittance, etc. In the prior art, similar effects can also be achieved by introducing nitrogen. Since the chemical activity of oxygen is higher than that of nitrogen, the required concentration of oxygen is about 1 / 10 of that of nitrogen to achieve similar effects. The technical solution provided in this application adjusts the volume percentage of oxygen during the preparation process, and does not introduce impurity atoms into the film, thereby achieving adjustable dielectric constant and expanding the application range of aluminum film.

[0097] During application, the volume ratio (concentration value) of oxygen introduced during the film-making process can be selected according to technical requirements so that the real and imaginary parts of the dielectric constant reach the target values.

[0098] In step S4, the sputtering power of the aluminum target is adjusted in the range of 500-5000 W. For example, 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, and 5000 W can be selected.

[0099] Step S5: Based on the target dielectric constant of the aluminum film at a specific wavelength, determine the second condition according to the multiple dielectric constant-wavelength curves obtained in step S4;

[0100] According to the target dielectric constant of the target aluminum film at a specific wavelength, the corresponding dielectric constant-wavelength curve can be determined from the multiple dielectric constant-wavelength curves obtained in step S4, that is, the curve where the point corresponding to the specific wavelength and the target dielectric constant is located. Each dielectric constant-wavelength curve corresponds to a specific ratio of argon and oxygen. The second condition, that is, the ratio of argon and oxygen, can be determined according to the target dielectric constant. It can be the ratio of argon or the ratio of oxygen. The ratio of argon and oxygen can be adjusted by the valve control value of the two gases.

[0101] Step S6: Based on the first condition and the second condition, a low-roughness aluminum film with a target dielectric constant is prepared under predetermined preparation conditions.

[0102] The first condition here is the sputtering power of the aluminum target determined in step S3, and the second condition is the ratio of argon and oxygen determined in step S5. By determining the first condition and the second condition, a low-roughness aluminum film with a target dielectric constant can be prepared.

[0103] In one embodiment provided in the present application, the structure of the device for performing the aluminum film sputtering method is as follows: Figure 3 shown.

[0104] In one embodiment provided in the present application, step S1 includes the following steps:

[0105] Drying the substrate to obtain a dried substrate;

[0106] The dried substrate is pre-sputtered to remove surface impurities.

[0107] The drying step can remove the residual moisture in the substrate; the pre-sputtering can remove impurities on the surface of the substrate. Here, drying includes various methods, such as vacuum oven drying, hot air drying, etc.

[0108] Exemplarily, the drying process includes the following steps: heating the substrate to 100-150° C. under vacuum conditions and keeping the temperature for 20-40 seconds.

[0109] Exemplarily, the pre-sputtering comprises the following steps: Under the conditions of , argon gas is introduced, 200~400W of RF power is applied, and the duration is 4~8s. This pre-sputtering parameter can effectively remove impurities and oxide layers on the surface of the substrate.

[0110] In one embodiment provided in the present application, the predetermined preparation conditions of step S3 include:

[0111] The cavity is evacuated to form a vacuum cavity; argon gas is introduced into the vacuum cavity, and the vacuum degree of the vacuum cavity is in the range of less than Before depositing the aluminum film, the deposition chamber can be evacuated to a high vacuum using molecular pumps, cold pumps, ion pumps, and other equipment, and then argon gas is introduced into the vacuum chamber to reduce the working chamber pressure to below , Argon is mainly used to bombard the target and adjust the chamber pressure.

[0112] In one embodiment provided in the present application, step S3 includes: using radio frequency sputtering on an aluminum target to sputter-deposit an aluminum film onto a second substrate; adjusting the sputtering power of the DC sputtering to deposit and prepare multiple aluminum films at different sputtering powers.

[0113] In one embodiment provided in the present application, the first condition is: the sputtering power of the aluminum target material DC sputtering when the aluminum film roughness is minimum. The first condition mentioned above can be a specific aluminum film roughness. In this implementation, the first condition is the sputtering power when the aluminum film roughness is minimum.

[0114] In one embodiment provided in the present application, the thickness of the plurality of aluminum films is equal, and the thickness of the aluminum films is 10-100 nm. The aluminum films shown here include the plurality of aluminum films prepared by changing the sputtering power in step S3, and the plurality of aluminum films prepared by using different proportions of argon and oxygen in step S4.

[0115] The thickness of the aluminum film should not be too thin, otherwise it may not form a continuous film, and a dotted structure will be formed, and various physical properties will seriously decline; its thickness should not be too thick, otherwise it will be difficult to characterize the dielectric constant and other physical performance parameters of the aluminum film by existing means, and the results will not be of reference value. The thickness of the aluminum film is controlled by controlling the sputtering time, that is, an aluminum film test piece is prepared under certain process parameters and sputtering time, and the thickness of the aluminum film is characterized by a four-probe, and the sputtering time required to prepare an aluminum film of a specific thickness under the process parameters is calculated. Multiple aluminum films prepared under different processes are controlled to have the same thickness to eliminate the influence of thickness variables on the dielectric constant of the aluminum film. The thickness of the aluminum film can also be characterized using SEM and step profilers.

[0116] In one embodiment provided in the present application, step S4 includes evacuating the cavity to form a vacuum cavity; introducing a mixed gas of argon and oxygen into the vacuum cavity, and the vacuum degree of the vacuum cavity is in the range of As described in step S3, before depositing the aluminum film, the deposition chamber can be evacuated to a high vacuum using a molecular pump, a cold pump, an ion pump, and the like, and then argon gas is introduced into the vacuum chamber to reduce the working chamber pressure to below , Argon is mainly used to bombard the target and adjust the chamber pressure.

[0117] In one embodiment provided in the present application, the volume proportion of argon in the mixed gas of argon and oxygen is 20% to 100%. Exemplarily, it can be 20, 30, 40, 50, 60, 70, 80, 90, 100%. By introducing oxygen into the vacuum cavity, the growth mode of aluminum atoms forming a thin film on the surface of the substrate is changed, and the purpose of effectively regulating the physical properties such as the composite dielectric constant of the aluminum film can be achieved by adjusting the proportion of oxygen introduced.

[0118] In one embodiment provided in the present application, step S4 includes: using an ellipsometer to collect dielectric constant data of each aluminum film at 193nm~1690nm, which is the wavelength range of the xenon lamp of the laboratory ellipsometer. The dielectric constant data at different wavelengths are fitted to obtain a dielectric constant-wavelength curve of each aluminum film.

[0119] In one embodiment provided in the present application, the second condition is: the volume of oxygen in a mixed gas of argon and oxygen corresponding to the target dielectric constant of the aluminum film at a specific wavelength. The second condition can be the volume of argon or the volume of oxygen. In the present embodiment, the second condition is the volume of oxygen.

[0120] In one embodiment provided in the present application, step S5 includes: determining a first dielectric constant-wavelength curve corresponding to the specific wavelength and the target dielectric constant among multiple dielectric constant-wavelength curves according to the target dielectric constant of the target aluminum film at a specific wavelength, and determining the volume of oxygen in the corresponding argon and oxygen mixed gas according to the first dielectric constant-wavelength curve.

[0121] In one embodiment provided in the present application, the aluminum film sputtering method can be applied to an 8-inch magnetron sputtering device, and the coating sputtering power is 500W to 5000W. For example, 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, and 5000W can be selected. If applied to a coating device of a smaller or larger size, the power value of the power supply used can be reduced or increased accordingly.

[0122] In one embodiment provided in the present application, the material of the substrate includes one of Si, SiO2, Ge, SiBARC, ZnO, GaAs, GaN, SiC, and InP. The preparation method disclosed in the present invention is widely applicable to the surface material of the substrate, and different substrate materials can be selected according to actual working conditions. There are differences in hardness between different substrates.

[0123] In a second aspect, the present application also provides an aluminum film with low roughness and controllable dielectric constant, which is prepared according to the aforementioned method for preparing an aluminum film with low roughness and controllable dielectric constant.

[0124] The method for preparing an aluminum film with low roughness and controllable dielectric constant provided in this embodiment includes: based on the expected real and imaginary parts of the dielectric constant of the target aluminum film at a specific incident wavelength and the required roughness, selecting a range of process parameters for preparing the aluminum film, including target material sputtering power and oxygen content, and performing step-by-step cooling and sputtering on the basis of programmed cooling of the substrate to prepare an aluminum film with low roughness and controllable dielectric constant.

[0125] The present disclosure is further described below through specific examples. The following examples are only used to illustrate the present disclosure, and the scope of the present disclosure is not limited thereto.

[0126] In the present application, the roughness of the aluminum film is mainly measured by atomic force microscopy. After the sample is obtained, the RMS of the sample surface is measured by atomic force microscopy.

[0127] Example 1

[0128] S1: Place the silicon-based substrate to be coated into the drying (degassing) chamber of the magnetron sputtering equipment, control the substrate and target to rotate at a certain speed, and perform drying and degassing treatment on the silicon-based substrate: heat the silicon-based substrate to 120°C under vacuum conditions, keep the temperature for 30 seconds, and remove the water vapor adsorbed on the surface of the material;

[0129] S2: Under vacuum conditions, the substrate is transferred to a pre-cleaning chamber to pre-clean the surface of the silicon-based substrate: at a vacuum degree of Under the condition of , argon gas was introduced, and 300W of radio frequency power was applied to the silicon substrate for a duration of 6s;

[0130] S3: Cooling water is passed under the bottom of the silicon-based substrate for 3 minutes, and the substrate is cooled to 25°C at a cooling rate of 2°C / min;

[0131] S4: under vacuum conditions, the substrate is transferred to a deposition chamber, argon gas is introduced into the vacuum chamber, and the vacuum degree of the vacuum chamber is controlled within a range of ; Turn on the aluminum target, baffle and power supply, use 500W DC sputtering power for the aluminum target, and sputter-deposit a thin film on the substrate cooled to 25°C; subsequently, continue to cool the bottom of the silicon-based substrate with cooling water for 10 minutes, cool the substrate to 22°C at a cooling rate of 0.5°C / min, continue to use 500W DC sputtering power for the aluminum target, and sputter-deposit a thin film on the substrate to obtain an aluminum film, and control the sputtering time to control the thickness of the aluminum film;

[0132] S5: After a complete sputtering cycle is completed, the sputtering power is changed to 500, 1000, 2000, 3000, and 4000 W, and steps S1 to S4 are repeated to obtain different aluminum films under different sputtering powers. The curves of aluminum films with different roughness obtained under different sputtering powers are plotted, and the sputtering power corresponding to the aluminum film with the lowest roughness is 1000 W.

[0133] S6: Repeat steps S1 to S3, introduce 20% oxygen + 80% argon into the vacuum chamber, and control the vacuum degree of the vacuum chamber to , turn on the aluminum target, the baffle and the power supply, use 400W DC sputtering power for the aluminum target, and sputter-deposit a thin film on the substrate; subsequently, cool the bottom of the silicon-based substrate with cooling water for 10 minutes, cool the substrate to 20°C at a cooling rate of 0.5°C / min, continue to use 1000W DC sputtering power for the aluminum target, and sputter-deposit a thin film on the substrate to obtain an aluminum film, and control the sputtering time to control the thickness of the aluminum film;

[0134] S7: After a complete sputtering, the atmosphere ratio of oxygen and argon is changed to 0% + 100%, 40% + 60%, 30% + 70% to prepare a series of aluminum film samples with the same thickness, and the real and imaginary parts of the dielectric constants under different incident light wavelengths are measured to draw a series of dielectric constant-wavelength curves of aluminum films prepared under different preparation conditions;

[0135] S8: Based on the target dielectric constant of the target aluminum film at an incident wavelength of 365 nm, and according to the multiple dielectric constant-wavelength curves obtained in step S7, determining that the ratio of the oxygen and argon mixed gas to be introduced is 20% + 80%;

[0136] S9: Repeat steps S1 to S3, and introduce 20% + 80% oxygen and argon mixed gas into the vacuum chamber again, and control the vacuum degree of the vacuum chamber to be within the range of , open the aluminum target baffle and power supply, use 1000W DC sputtering power for the aluminum target, and sputter deposit a thin film on the substrate; then pass cooling water under the bottom of the silicon-based substrate for 10 minutes, cool the substrate to 20°C at a cooling rate of 0.5°C / min, and continue to use 1000W DC sputtering power for the aluminum target to obtain the target aluminum film.

[0137] The final target aluminum film AFM image can be found at Figure 4 The thickness of the prepared aluminum film is 50nm (THK=50nm) and the roughness RMS=1.59nm, which meets the actual needs.

[0138] Figure 5As an example, in step S5, when the sputtering power is 500, 1000, 2000, 3000, and 4000 W, the aluminum film curves with different roughness obtained under different sputtering powers are given. It can be obtained that the sputtering power corresponding to the aluminum film with the lowest roughness is 1000 W. The corresponding relationship between the surface roughness of the aluminum film corresponding to each sputtering power is shown in Table 1. Figure 6 As an example, an AFM image of an aluminum film obtained when the sputtering power is 4000 W is given, and the roughness is significantly higher than that of the aluminum film prepared at 1000 W, indicating that the sputtering power has a significant effect on the roughness of the aluminum film.

[0139] Table 1 Aluminum films with different roughness prepared at different sputtering powers

[0140]

[0141] Figure 7 , Figure 8 As an example, a series of aluminum film samples with the same thickness are prepared by changing the atmosphere ratio of oxygen and argon to 0% + 100%, 40% + 60%, 30% + 70%, and 20% + 80% in step S7, and curves of measuring the real and imaginary parts of the dielectric constants under different wavelengths of incident light are obtained.

[0142] In order to meet different technical requirements, a series of aluminum films were prepared through steps S6 to S8 by adjusting the ratio of oxygen and argon, and the dielectric constant-wavelength function of aluminum films prepared with different process parameters was characterized by ellipsometer. Figure 7 is the curve of the real part of the dielectric constant changing with the wavelength of the incident light, Figure 8 This is the curve of the imaginary part of the dielectric constant changing with the wavelength of the incident light.

[0143] It can be seen that when the oxygen ratio changes, both the real and imaginary parts of the dielectric constant change. The ratio of oxygen to argon can be selected according to the target wavelength.

[0144] Example 2

[0145] S1: Place the silicon-based substrate to be coated into the drying (degassing) chamber of the magnetron sputtering equipment, control the substrate and target to rotate at a certain speed, and dry and degas the zinc oxide substrate: heat the zinc oxide substrate to 120°C under vacuum conditions, keep it warm for 30 seconds, and remove the water vapor adsorbed on the surface of the material;

[0146] S2: Under vacuum conditions, the substrate is transferred to a pre-cleaning chamber to pre-clean the surface of the silicon-based substrate: at a vacuum degree of Under the condition of , argon gas was introduced, and 350W of radio frequency power was applied to the zinc oxide substrate for 8s;

[0147] S3: The substrate is transferred to a deposition chamber under vacuum conditions, and cooling water is passed under the bottom of the silicon-based substrate for cooling for 3 minutes, and the substrate is cooled to 25°C at a cooling rate of 2°C / min;

[0148] S4: Introduce argon gas into the vacuum chamber to control the vacuum degree of the vacuum chamber within the range of ,; turn on the aluminum target, baffle and power supply, use 500W DC sputtering power for the aluminum target, and sputter-deposit a thin film on the substrate cooled to 25°C; subsequently, continue to pass cooling water under the bottom of the zinc oxide substrate for 15 minutes, cool the substrate to 17.5°C at a cooling rate of 0.5°C / min, continue to use 500W DC sputtering power for the aluminum target, and sputter-deposit a thin film on the substrate to obtain an aluminum film, and control the sputtering time to control the thickness of the aluminum film;

[0149] S5: After a complete sputtering is completed, the sputtering power is changed to 500, 1000, 2000, 3000, and 4000 W, and steps S1 to S4 are repeated to obtain different aluminum films under different sputtering powers. The aluminum film curves with different roughness obtained under different sputtering powers are plotted, and the sputtering power corresponding to the aluminum film with the lowest roughness is 1000 W.

[0150] S6: Repeat steps S1 to S3, introduce 20% oxygen + 80% argon into the vacuum chamber, and control the vacuum degree of the vacuum chamber to ,; turn on the aluminum target, the baffle and the power supply, use 1000W DC sputtering power for the aluminum target, and sputter-deposit a thin film on the substrate; subsequently, continue to cool the bottom of the zinc oxide substrate with cooling water for 15 minutes, cool the substrate to 17.5°C at a cooling rate of 0.5°C / min, continue to use 1000W DC sputtering power for the aluminum target, and sputter-deposit a thin film on the substrate to obtain an aluminum film, and control the sputtering time to control the thickness of the aluminum film;

[0151] S7: After a complete sputtering, the atmosphere ratio of oxygen and argon is changed to 30% + 70%, 40% + 60%, 50% + 50%, 60% + 40% to prepare a series of aluminum film samples with the same thickness, and the real and imaginary parts of the dielectric constants under different incident light wavelengths are measured to draw a series of dielectric constant-wavelength curves of aluminum films prepared under different preparation conditions;

[0152] S8: Based on the target dielectric constant of the target aluminum film at an incident wavelength of 365 nm, and according to the multiple dielectric constant-wavelength curves obtained in step S7, determining that the ratio of the oxygen and argon mixed gas introduced is 40% + 60%;

[0153] S9: Repeat steps S1 to S3, and introduce 40% + 60% oxygen and argon mixed gas into the vacuum chamber again, and control the vacuum degree of the vacuum chamber to be within the range of , open the aluminum target baffle and power supply, use 1000W DC sputtering power for the aluminum target, and sputter deposit thin film on the substrate; then cool the zinc oxide substrate with cooling water for 15 minutes, cool the substrate to 17.5℃ at a cooling rate of 0.5℃ / min, and continue to use 1000W DC sputtering power for the aluminum target to obtain the target aluminum film. The atomic force microscope image of the final target aluminum film can be found in Fig. 9 The thickness of the aluminum film prepared is 50nm (THK=50nm), RMS=1.04nm, which meets the actual needs. The roughness of the aluminum film prepared at a lower temperature and a higher oxygen ratio is further reduced.

[0154] Comparative Example 1

[0155] Compared with Example 1, the step of cooling the substrate is removed.

[0156] S1: Place the silicon-based substrate to be coated into the deposition chamber of the magnetron sputtering equipment, control the substrate and the target to rotate at a certain speed, and perform drying and degassing treatment on the silicon-based substrate: heat the silicon-based substrate to 120°C under vacuum conditions, keep the temperature for 30 seconds, and remove the water vapor adsorbed on the surface of the material;

[0157] S2: Pre-clean the surface of the silicon-based substrate: at a vacuum degree of Under the condition of , argon gas was introduced, and 300W of radio frequency power was applied to the silicon substrate for a duration of 6s;

[0158] S3: Introduce argon gas into the vacuum chamber to control the vacuum degree of the vacuum chamber within the range of , turn on the aluminum target, baffle and power supply, use 1000W DC sputtering power for the aluminum target, sputter and deposit a thin film on the silicon substrate, and control the sputtering time to control the thickness of the aluminum film;

[0159] S4: After a complete sputtering cycle is completed, the sputtering power is changed to 500, 1000, 2000, 3000, and 4000 W, and steps S1 to S3 are repeated to obtain different aluminum films under different sputtering powers. The curves of aluminum films with different roughness obtained under different sputtering powers are plotted, and the sputtering power corresponding to the aluminum film with the lowest roughness is 1000 W.

[0160] S5: Repeat steps S1 to S2, introduce 20% oxygen + 80% argon into the vacuum chamber, and control the vacuum degree of the vacuum chamber to ,; Turn on the aluminum target, baffle and power supply, use 1000W DC sputtering power for the aluminum target, and control the sputtering time to control the aluminum film thickness;

[0161] S6: After a complete sputtering, the atmosphere ratio of oxygen and argon is changed to 0% + 100%, 40% + 60%, 30% + 70% to prepare a series of aluminum film samples with the same thickness, and the real and imaginary parts of the dielectric constants under different incident light wavelengths are measured to draw a series of dielectric constant-wavelength curves of aluminum films prepared under different preparation conditions;

[0162] S7: Based on the target dielectric constant of the target aluminum film at an incident wavelength of 365 nm, and according to the multiple dielectric constant-wavelength curves obtained in step S7, determining that the ratio of the oxygen and argon mixed gas to be introduced is 20% + 80%;

[0163] S8: 20% + 80% oxygen and argon mixed gas is introduced into the vacuum chamber again, and the vacuum degree of the vacuum chamber is controlled within the range of , open the aluminum target baffle and power supply, use 1000W DC sputtering power on the aluminum target to obtain the target aluminum film.

[0164] The final target aluminum film AFM image can be found at Fig.10 The roughness of the prepared aluminum film is RMS=5.85nm, which is significantly higher than that of the target aluminum film obtained in Example 1. This is because the substrate is not cooled, the interaction force between the Al film and the substrate is strong, the growth is poor, and a smooth film cannot be formed.

[0165] Comparative Example 2

[0166] Compared with Example 1, the substrate is directly cooled to the target temperature without a programmed temperature reduction step.

[0167] S1: Place the silicon-based substrate to be coated into the deposition chamber of the magnetron sputtering equipment, control the substrate and the target to rotate at a certain speed, and perform drying and degassing treatment on the silicon-based substrate: heat the silicon-based substrate to 120°C under vacuum conditions, keep the temperature for 30 seconds, and remove the water vapor adsorbed on the surface of the material;

[0168] S2: Pre-clean the surface of the silicon-based substrate: at a vacuum degree of Under the condition of , argon gas was introduced, and 300W of radio frequency power was applied to the silicon substrate for a duration of 6s;

[0169] S3: Cooling water is passed under the bottom of the silicon-based substrate for 3 minutes, and the substrate is cooled to 20°C at a cooling rate of 2°C / min;

[0170] S4: Introduce argon gas into the vacuum chamber to control the vacuum degree of the vacuum chamber within the range of , turn on the aluminum target, baffle and power supply, use 500W DC sputtering power for the aluminum target, sputter and deposit a thin film on the substrate cooled to 20°C, and control the thickness of the aluminum film by controlling the sputtering time;

[0171] S5: After a complete sputtering cycle is completed, the sputtering power is changed to 500, 1000, 2000, 3000, and 4000 W, and steps S1 to S4 are repeated to obtain different aluminum films under different sputtering powers. The aluminum film curves with different roughness obtained under different sputtering powers are plotted, and the sputtering power corresponding to the aluminum film with the lowest roughness is 1000 W.

[0172] S6: Repeat steps S1 to S3, introduce 20% oxygen + 80% argon into the vacuum chamber, and control the vacuum degree of the vacuum chamber to , turn on the aluminum target, baffle and power supply, use 1000W DC sputtering power for the aluminum target, sputter and deposit a thin film on a substrate at 20°C, and control the thickness of the aluminum film by controlling the sputtering time;

[0173] S7: After a complete sputtering, the atmosphere ratio of oxygen and argon is changed to 0% + 100%, 40% + 60%, 30% + 70% to prepare a series of aluminum film samples with the same thickness, and the real and imaginary parts of the dielectric constants under different incident light wavelengths are measured to draw a series of dielectric constant-wavelength curves of aluminum films prepared under different preparation conditions;

[0174] S8: Based on the target dielectric constant of the target aluminum film at an incident wavelength of 365 nm, and according to the multiple dielectric constant-wavelength curves obtained in step S7, determining that the ratio of the oxygen and argon mixed gas to be introduced is 20% + 80%;

[0175] S9: Repeat steps S1 to S3, and pass 20% + 80% oxygen and argon mixed gas into the vacuum chamber again, and control the vacuum degree of the vacuum chamber to be within the range of , open the aluminum target baffle and power supply, use 1000W DC sputtering power for the aluminum target, and sputter-deposit a thin film on a substrate at 20°C to obtain the target aluminum film. The atomic force microscope image of the final target aluminum film can be found in Fig.11 The roughness of the prepared aluminum film RMS = 2.25nm, which is slightly higher than that of the target aluminum film obtained in Example 1.

[0176] This is because comparative example 2 uses direct cooling instead of programmed cooling, which does not give Al atoms time to slowly bond with the substrate surface and migrate and rearrange, resulting in the formed aluminum film not being smooth enough. Therefore, the technical effect of programmed cooling can also be demonstrated.

[0177] The aluminum film preparation method disclosed in the present application adopts a programmed cooling method. Through the confinement of small Al atomic nuclei and the subsequent slow deposition of Al atoms, the formed Al film is relatively smooth, has low roughness, and has good technical effects. The technology of the present application is based on the relatively mature magnetron sputtering equipment, with low modification and consumables costs and relatively simple operation. By simply adjusting the ratio of the introduced gas, the composite dielectric constant of the aluminum film can be effectively controlled, thereby overcoming the technical difficulties of the aluminum film in practical applications, and effectively reducing the surface roughness of the aluminum film, greatly expanding the scope of application of the aluminum film in optoelectronic devices.

[0178] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present disclosure. It should be understood that the above description is only a specific embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure should be included in the protection scope of the present disclosure.

Claims

1. A method for sputtering an aluminum film, comprising the following steps: Step S1: pre-treating a substrate to obtain a pre-treated first substrate; Step S2: performing a first cooling process on the first substrate to obtain a cooled second substrate; The first cooling treatment cools the temperature of the first substrate to 25° C. at a first average cooling rate, and the required time is a first cooling time, and the first average cooling rate is 1-3° C. / min; Step S3: Under predetermined preparation conditions, argon gas is introduced into the chamber, the sputtering power of the aluminum target is adjusted, sputtering is performed once onto the second substrate, the second substrate is subjected to a second cooling treatment, and a second sputtering is performed simultaneously, so that several roughness-sputtering power curves of multiple aluminum films prepared in a pure argon gas environment can be obtained, and a first condition is determined according to the roughness-sputtering power curves, wherein the first condition is the sputtering power of the aluminum target material by DC sputtering when the roughness of the aluminum film is minimum; The second cooling process cools the temperature of the second substrate to a target cooling temperature at a second average cooling rate, and the required time is a second cooling time, and the second average cooling rate is 0.5-1°C / min; The first average cooling rate is higher than the second average cooling rate; The first cooling time is shorter than the second cooling time; After the first cooling treatment and the second cooling treatment, the substrate can be cooled to 10-22° C., and the cooling time is 5-15 minutes; Step S4: under predetermined preparation conditions, a mixed gas of argon and oxygen in different proportions is introduced into the chamber, and the aluminum target is sputtered once and twice on the second substrate that has undergone the first cooling treatment and the second cooling treatment, to obtain multiple dielectric constant-wavelength curves of the aluminum film prepared in the gas environment of the mixed gas of argon and oxygen in different proportions; Step S5: Based on the target dielectric constant of the aluminum film at a specific wavelength, a second condition is determined according to the multiple dielectric constant-wavelength curves obtained in step S4, wherein the second condition is: the volume of oxygen in the mixed gas of argon and oxygen corresponding to the target dielectric constant of the aluminum film at the specific wavelength; Step S6: Based on the first condition and the second condition, a low-roughness aluminum film with a target dielectric constant is prepared under predetermined preparation conditions.

2. The aluminum film sputtering method according to claim 1, characterized in that: The step S1 comprises the following steps: Drying the substrate to obtain a dried substrate; The dried substrate is pre-sputtered to remove surface impurities.

3. The aluminum film sputtering method according to claim 2, characterized in that: The drying process comprises the following steps: heating the substrate to 100-150° C. under vacuum conditions and keeping the temperature for 20-40 seconds.

4. The aluminum film sputtering method according to claim 2, characterized in that: The pre-sputtering comprises the following steps: Under the conditions of , argon gas was introduced and 200~400W of RF power was applied for a duration of 4~8s.

5. The aluminum film sputtering method according to claim 1, characterized in that: The predetermined preparation conditions of step S3 include: The cavity is evacuated to form a vacuum cavity; argon gas is introduced into the vacuum cavity, and the vacuum degree of the vacuum cavity is in the range of less than .

6. The aluminum film sputtering method according to claim 1, characterized in that: The predetermined preparation conditions of step S4 include: The cavity is evacuated to form a vacuum cavity; a mixed gas of argon and oxygen is introduced into the vacuum cavity. The vacuum degree of the vacuum cavity is in the range of .

7. The aluminum film sputtering method according to claim 1, characterized in that: In the step S4, the volume proportion of argon in the mixed gas of argon and oxygen is 20% to 100%.

8. The aluminum film sputtering method according to claim 1, characterized in that: The aluminum film sputtering method can be applied to an 8-inch magnetron sputtering device, and the power of the coating sputtering is 500W to 5000W.

9. The aluminum film sputtering method according to claim 1, characterized in that: The material of the substrate includes one of Si, SiO2, Ge, SiBARC, ZnO, GaAs, GaN, SiC, and InP.

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