A monoclinic hafnium dioxide film with adjustable orientation and preparation method thereof

Abstract

The present invention discloses a monoclinic hafnium dioxide film with adjustable orientation and a preparation method thereof, belonging to the technical field of thin film materials. It is prepared by adopting a dual-temperature zone hot wall horizontal chemical vapor deposition device, placing a precursor in the first temperature zone of the deposition device, and placing a single crystal silicon substrate in the second temperature zone of the deposition device; vacuuming and heating, the first temperature zone target temperature is 190-210°C, the second temperature zone target temperature is 500-1100°C, and the two are controlled to reach the target temperature at the same time; when the target temperature is about to be reached, a reaction gas is introduced to a target pressure of 100-2000Pa, and the precursor vapor in the first temperature zone is transported to the surface of the silicon substrate in the second temperature zone with a reaction gas for reaction, the flow rate of the reaction gas is 10-500sccm, and the reaction ends to obtain a monoclinic hafnium dioxide film. This method can stably regulate the orientation of the monoclinic hafnium dioxide film, and the prepared film structure is continuous and uniform, and the thickness is controllable.

Description

Technical Field

[0001] The present invention belongs to the field of thin film material preparation, and in particular relates to a monoclinic hafnium dioxide thin film with adjustable orientation and a preparation method thereof. Background Art

[0002] In recent years, hafnium dioxide has been widely studied as a substitute for silicon dioxide in the gate oxide insulating layer of complementary metal oxide semiconductor devices. Hafnium dioxide has a high dielectric constant (22-25), a high breakdown field strength (3.9-6.7 MV / cm), and good thermal insulation (3-10 W·m -1 ·K -1 ), as well as advantages such as high melting point (3173K) and high hardness (28GPa), are expected to realize composite functional media with dielectric, heat resistance and wear resistance to replace traditional layered media structures and become the ideal material for the dielectric layer of the new generation of highly integrated chips.

[0003] Hafnium dioxide has a stable monoclinic crystal structure at room temperature and pressure, and thin films of hafnium dioxide with different orientations exhibit distinct physical properties. Thin films with a (111) orientation have a high dielectric constant (24-25), making them suitable for electrical insulation as high-k layers in silicon-based semiconductors. Thin films with a (100) orientation exhibit excellent thermal insulation properties and can be used as thermal barrier coatings for aerospace applications. Therefore, the preparation of thin films of hafnium dioxide with different orientations for use in various applications is an urgent challenge.

[0004] Among the many possible deposition technologies, the current methods for preparing hafnium dioxide mainly include atomic layer deposition and pulsed laser deposition. Atomic layer deposition requires the use of chemical adsorption to cause a single atomic film to react layer by layer on the substrate. After several cycles, a homogeneous thin film with highly consistent composition can be obtained. However, the deposition rate is too low, and after the adsorption amount exceeds dozens of layers, the introduction of impurities such as carbon, hydrogen, and nitrogen from the precursor and activator becomes increasingly obvious, causing film contamination. The most important thing is that the film after atomic layer deposition is amorphous and requires an annealing process for crystallization. The annealed film is randomly oriented, and its physical properties are one order of magnitude lower than those of a single-oriented film. The connectivity and compatibility between the thin film dielectric layer and the substrate of the pulsed laser deposited film are poor, resulting in a significant reduction in thermal shock resistance and wear resistance. In addition, the deposition rate is generally low, and the preparation uniformity and controllability are poor, making it difficult to apply to standardized production.

[0005] Therefore, there is an urgent need to find a method for preparing a hafnium dioxide thin film with a controllable deposition rate, good uniformity and high purity and a specific orientation. Summary of the Invention

[0006] The main purpose of the present invention is to address the deficiencies in the prior art and provide a monoclinic hafnium dioxide film with adjustable orientation and a preparation method thereof. The method can stably regulate the orientation of the monoclinic hafnium dioxide film, and the resulting film structure is continuous and uniform, and the thickness is controllable, providing a simple and efficient means for regulating the orientation of the monoclinic hafnium dioxide film.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] A method for preparing a monoclinic hafnium dioxide thin film with adjustable orientation is provided, comprising the following steps:

[0009] 1) Using a dual-temperature zone hot-wall horizontal chemical vapor deposition apparatus, placing the precursor in the first temperature zone of the deposition apparatus and placing the single crystal silicon substrate in the second temperature zone of the deposition apparatus;

[0010] 2) Evacuate to below 10 Pa and start heating; the target temperature of the first temperature zone is 190-210°C, and the target temperature of the second temperature zone is 500-1100°C, and the first temperature zone and the second temperature zone are controlled to reach the target temperature at the same time; 50-70 seconds before reaching the target temperature, introduce reaction gas to a target pressure of 100-2000 Pa, and transport the precursor vapor in the first temperature zone to the surface of the silicon substrate in the second temperature zone with the reaction gas for reaction. The flow rate of the reaction gas is 10-500 seem. Upon completion of the reaction, a monoclinic hafnium dioxide film with adjustable orientation is obtained.

[0011] According to the above scheme, in step 1), the precursor is hafnium acetylacetonate powder.

[0012] According to the above scheme, in step 1), the single crystal silicon substrate is a (100) oriented silicon single crystal substrate, which is single-sided polished.

[0013] According to the above scheme, in step 1), the single crystal silicon substrate is ultrasonically cleaned using isopropyl alcohol, ethanol, and ultrapure water. Preferably, each ultrasonic cleaning is performed for 8-12 minutes. Isopropyl alcohol can effectively dissolve grease and other organic matter, accelerating the cleaning process. Ethanol can dissolve isopropyl alcohol and remove residual isopropyl alcohol from the substrate. Ultrapure water can wash away the ethanol. Ultrasonic cleaning makes the cleaning more thorough, ensuring a clean environment for the growth of the hafnium dioxide film on the substrate.

[0014] According to the above scheme, in step 1), the dual-temperature zone hot wall horizontal chemical vapor deposition device adopts nickel-chromium alloy dual resistance wire heating, and the heating power of the two temperature zones is 2.5-3kW.

[0015] According to the above scheme, in step 1), the precursor is placed on an alumina ceramic boat in the first temperature zone of the deposition device, and the substrate is placed on an alumina ceramic boat in the second temperature zone of the deposition device.

[0016] Preferably, the porcelain boats in the two temperature zones are placed in parallel with a distance of 14-16 cm, and the precursor and the substrate are kept at the same horizontal plane.

[0017] According to the above scheme, in step 2), the heating rate of the first temperature zone is 3-8°C / min, and the heating rate of the second temperature zone is 15-20°C / min.

[0018] According to the above scheme, in step 2), the reaction gas is O2. O2 serves as both a reaction gas and a dilution gas, which can not only increase the reaction rate, but also save energy and reduce consumption, and simplify the device.

[0019] According to the above scheme, when the target temperature of the first temperature zone is 203-210°C, the target temperature of the second temperature zone is 500-800°C, the target pressure is 600-2000Pa, and the reaction gas flow rate is 300-500sccm, a film with a (111) orientation structure is obtained.

[0020] According to the above scheme, the target temperature of the first temperature zone is 190-196°C, the target temperature of the second temperature zone is 900-1100°C, the target pressure is 100-400Pa, and the reaction gas flow rate is 10-150sccm to obtain a (100) oriented structure film.

[0021] According to the above scheme, in step 2), the reaction time is 5-10 min.

[0022] According to the above scheme, in step 3), the thickness of the monoclinic hafnium dioxide film obtained is 200-300 nm.

[0023] According to the above scheme, in step 3), the monoclinic hafnium dioxide thin film obtained has a (100) orientation structure, a (111) orientation structure, or a mixed orientation structure of (100) and (111).

[0024] Provided is a monoclinic hafnium dioxide film with controllable orientation prepared by the preparation method.

[0025] According to the above solution, the monoclinic hafnium dioxide film has a (100) orientation structure, a (111) orientation structure, or a mixed orientation structure of (100) and (111).

[0026] The present invention provides a method for regulating the orientation of a monoclinic hafnium dioxide film. The method adopts a dual-temperature zone chemical vapor deposition device structure, regulates the temperature of the first temperature zone to change the volatilization rate of the precursor, and regulates the temperature of the second temperature zone to change the decomposition rate of the precursor. The method utilizes the different surface energies of the (111) and (100) crystal planes of monoclinic hafnium dioxide to set different process conditions to obtain hafnium dioxide with different orientations. The method adopts a low-temperature and high-pressure method to prepare a (111) oriented hafnium dioxide film. Low temperature is more conducive to the growth of the (111) plane. However, at low temperature, the precursor decomposes slowly and the growth rate is low. Therefore, the temperature of the first temperature zone is increased, the volatilization rate of the precursor is increased, and the pressure and the reaction gas flow rate are increased to increase the precursor concentration as much as possible to ensure uniform growth of the film layer. The method adopts a high-temperature and low-pressure method to prepare a (100) oriented hafnium dioxide film. High temperature is more conducive to the growth of the (100) plane. However, at high temperature, the precursor decomposes quickly, which easily causes the film layer to accumulate at the same position on the substrate, resulting in uneven film layer. Therefore, the temperature of the first temperature zone is lowered, the volatilization rate of the precursor is reduced, and the pressure and reaction gas flow rate are reduced to reduce the precursor concentration as much as possible, and finally the controllable growth of the oriented structure of the hafnium dioxide film is achieved.

[0027] The beneficial effects of the present invention are as follows:

[0028] 1. The present invention provides a method for regulating the orientation of monoclinic hafnium dioxide thin films. By utilizing the different surface energies of the (111) and (100) crystal planes of monoclinic hafnium dioxide, a dual-temperature zone chemical vapor deposition device structure is adopted. The temperatures of the precursor and the substrate are controlled in two independent temperature zones respectively. Combined with the control of the reaction gas flow rate and pressure, (111) and (100) oriented hafnium dioxide thin films are accurately prepared respectively. The method has simple process, easy operation, controllable deposition rate, low cost, good repeatability, and the thickness and composition of the obtained film are uniform. Hafnium dioxide thin films with different orientations can be prepared as needed, laying a foundation for the standardized preparation of two oriented films, and has important application prospects.

[0029] 2. The present invention adopts a single solid precursor and utilizes the decomposition products of the precursor to prepare the film. The by-products are all gaseous and will not cause pollution to the film layer, and the film layer has high purity. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 These are the XRD patterns of the hafnium dioxide films obtained in Examples 1, 2, and 3 of the present invention; wherein (a) is the XRD pattern of the (111) oriented monoclinic hafnium dioxide film obtained in Example 1, and (b) and (c) are the XRD patterns of the (100) oriented monoclinic hafnium dioxide films obtained in Examples 2 and 3.

[0031] Figure 2These are the surface and cross-sectional SEM images of the hafnium dioxide films obtained in Examples 1, 2, and 3 of the present invention; wherein (a) and (d) are the surface and cross-sectional SEM images of the (111)-oriented hafnium dioxide film obtained in Example 1, respectively; (b) and (e) are the surface and cross-sectional SEM images of the (100)-oriented hafnium dioxide film obtained in Example 2, respectively; (c) and (f) are the surface and cross-sectional SEM images of the (100)-oriented hafnium dioxide film obtained in Example 3, respectively.

[0032] Figure 3 These are the XPS spectra of the hafnium dioxide thin films obtained in Examples 1, 2, and 3 of the present invention; wherein (a) and (d) are the XPS spectra of hafnium and oxygen elements in the (111) oriented monoclinic hafnium dioxide thin film obtained in Example 1, (b) and (e) are the XPS spectra of hafnium and oxygen elements in the (100) oriented monoclinic hafnium dioxide thin film obtained in Example 2, and (c) and (f) are the XPS spectra of hafnium and oxygen elements in the (100) oriented hafnium dioxide thin film obtained in Example 3, respectively.

[0033] Figure 4 Schematic diagram of the reaction device in an embodiment of the present invention. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0035] Example 1

[0036] A method for regulating the orientation of a monoclinic hafnium dioxide film is provided, comprising the following steps:

[0037] 1) Cutting area is 1×1cm 2 The (100) single crystal silicon wafer was ultrasonically cleaned for 10 min using isopropyl alcohol (purity of 99.5 wt%), ethanol (concentration of 99.5 wt%) and ultrapure water in sequence;

[0038] 2) Using a dual-zone hot-wall horizontal chemical vapor deposition apparatus, 0.2g of hafnium acetylacetonate powder was weighed using a balance and spread evenly onto an alumina boat in the first zone of the deposition apparatus. The cleaned single crystal silicon wafer obtained in step 1) was placed onto an alumina boat in the second zone. The boat was then placed back into the deposition apparatus, ensuring the two boats were parallel and 14cm apart. The target pressure was set to 600Pa, the target temperature in the first zone to 205°C, and the target temperature in the second zone to 800°C.

[0039] 3) Close the flange at the cavity outlet, turn on the vacuum pump and evacuate to 7Pa; set the two-temperature zone heating program, the first temperature zone is heated to 205℃ at a rate of 5.13℃ / min, and the second temperature zone is heated to 800℃ at a rate of 20℃ / min, and the two temperature zones reach the target temperature at the same time. 1 minute before reaching the target temperature, turn on the automatic gas flow controller, adjust the knob to introduce 300sccmO2, and adjust the baffle valve to make the cavity pressure reach 600Pa. After reaching the target temperature, the program automatically starts timing, maintains the target temperature for 5 minutes, and then stops heating;

[0040] 4) Turn off the fully automatic gas flow controller, adjust the baffle valve to pump the chamber pressure to 7 Pa again, and cool the deposition device naturally at room temperature to obtain the (111) oriented monoclinic hafnium dioxide.

[0041] Example 2

[0042] A method for regulating the orientation of a monoclinic hafnium dioxide film is provided, comprising the following steps:

[0043] 1) Cutting area is 1×1cm 2 The (100) single crystal silicon wafer was ultrasonically cleaned for 10 min using isopropyl alcohol (purity of 99.5 wt%), ethanol (concentration of 99.5 wt%) and ultrapure water in sequence;

[0044] 2) Using a dual-zone hot-wall horizontal chemical vapor deposition apparatus, 0.2g of hafnium acetylacetonate powder was weighed using a balance and spread evenly onto an alumina boat in the first zone of the deposition apparatus. The cleaned single crystal silicon wafer obtained in step 1) was placed onto an alumina boat in the second zone. The boat was then placed back into the deposition apparatus, ensuring the two boats were parallel and 14cm apart. The target pressure was set to 200Pa, the target temperature in the first zone to 195°C, and the target temperature in the second zone to 1100°C.

[0045] 3) Close the flange at the cavity outlet, turn on the vacuum pump and evacuate to 7Pa; set the two-temperature zone heating program, the first temperature zone is heated to 195℃ at a rate of 3.55℃ / min, and the second temperature zone is heated to 1100℃ at a rate of 20℃ / min, and the two temperature zones reach the target temperature at the same time. 1 minute before reaching the target temperature, turn on the automatic gas flow controller, adjust the knob to pass 100sccmO2, and adjust the baffle valve to make the cavity pressure reach 200Pa. After reaching the target temperature, the program automatically starts timing, maintains the target temperature for 5 minutes, and then stops heating;

[0046] 4) Turn off the fully automatic gas flow controller, adjust the baffle valve to pump the chamber pressure to 7 Pa again, and cool the deposition device naturally at room temperature to obtain the (100) oriented monoclinic hafnium dioxide.

[0047] Example 3

[0048] A method for regulating the orientation of a monoclinic hafnium dioxide film is provided, comprising the following steps:

[0049] 1) Cutting area is 1×1cm 2 The (100) single crystal silicon wafer was ultrasonically cleaned for 10 min using isopropyl alcohol (purity of 99.5 wt%), ethanol (concentration of 99.5 wt%) and ultrapure water in sequence;

[0050] 2) Using a dual-zone hot-wall horizontal chemical vapor deposition apparatus, 0.2g of hafnium acetylacetonate powder was weighed using a balance and spread evenly onto an alumina boat in the first zone of the deposition apparatus. The cleaned single crystal silicon wafer obtained in step 1) was placed onto an alumina boat in the second zone. The boat was then placed back into the deposition apparatus, ensuring the two boats were parallel and 14cm apart. The target pressure was set to 400Pa, the target temperature in the first zone to 192°C, and the target temperature in the second zone to 1000°C.

[0051] 3) Close the flange at the cavity outlet, turn on the vacuum pump and evacuate to 7Pa; set the two-temperature zone heating program, the first temperature zone is heated to 192℃ at a rate of 3.84℃ / min, and the second temperature zone is heated to 1000℃ at a rate of 20℃ / min, and the two temperature zones reach the target temperature at the same time. 65s before reaching the target temperature, turn on the automatic gas flow controller, adjust the knob to introduce 150sccmO2, and adjust the baffle valve to make the cavity pressure reach 400Pa. After reaching the target temperature, the program automatically starts timing, maintains the target temperature for 5 minutes, and then stops heating;

[0052] 4) Turn off the fully automatic gas flow controller, adjust the baffle valve to pump the chamber pressure to 7 Pa again, and cool the deposition device naturally at room temperature to obtain the (100) oriented monoclinic hafnium dioxide.

[0053] Figure 1 The XRD patterns of the hafnium dioxide films obtained in Examples 1, 2, and 3 of the present invention are shown. Figure 1 It shows that the film grains at 800℃ are (111) preferred orientation, with a half-peak width of 0.39° and good crystallinity; Figure 2 It shows that the film grains at 1100℃ are (100) oriented, with a half-peak width of 0.22°, indicating good crystallinity; Figure 3 It shows that the film grains are (100) oriented at 1000℃, the half-peak width is 0.13°, and the crystallinity is good.

[0054] Figure 2 The surface and cross-sectional SEM images of the hafnium dioxide films obtained in Examples 1, 2, and 3 of the present invention are shown. Figure 2 (a) shows that the film surface is cauliflower-shaped with a small number of holes on the surface. Figure 2 (d) shows that the cross section of the film is smooth and the thickness is 200 nm; Figure 2 (b) shows that the film surface is granular, with a grain size of 10-20nm and a dense surface. Figure 2 (e) shows that the cross section of the membrane is feather-like and has a thickness of 250 nm; Figure 2 (c) shows that the film surface is sugar cube-shaped, with a grain size of 30-45nm and a dense surface. Figure 2 (e) shows that the cross section of the film is granular and has a thickness of 250 nm.

[0055] Figure 3 The XPS spectra of the hafnium dioxide thin films obtained in Examples 1, 2, and 3 of the present invention are shown. Figure 3 (a) is the 4f orbital of Hf element. The 4f7 / 2 and 4f5 / 2 split peaks appear in the figure, and the binding energy is located at 16-18eV, indicating that the Hf element in the product is tetravalent. Figure 3 (d) is the 1s orbital of the O element. Three split peaks of O-Hf, OH, and OC appear in the figure, indicating that the film layer is hafnium dioxide with a small amount of hydroxyl and carbon. Figure 3 (b) is the 4f orbital of the Hf element. The 4f7 / 2 and 4f5 / 2 split peaks appear in the figure, and the binding energy is located at 18-20eV, indicating that the Hf element in the product is tetravalent. Figure 3 (e) is the 1s orbital of the O element. Two split peaks, O-Hf and OC, appear in the figure, indicating that the film layer is hafnium dioxide with a small amount of carbon. Figure 3 (c) is the 4f orbital of the Hf element. The 4f7 / 2 and 4f5 / 2 split peaks appear in the figure, and the binding energy is located at 17-19eV, indicating that the Hf element in the product is tetravalent. Figure 3 (f) is the 1s orbital of the O element. Two split peaks, O-Hf and OC, appear in the figure, indicating that the film layer is hafnium dioxide with a small amount of carbon.

[0056] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all such improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A method for preparing a monoclinic hafnium dioxide thin film with adjustable orientation, characterized in that: The following steps are involved: 1) Using a dual-temperature zone hot-wall horizontal chemical vapor deposition apparatus, placing the precursor in the first temperature zone of the deposition apparatus and placing the single crystal silicon substrate in the second temperature zone of the deposition apparatus; 2) Evacuate to below 10 Pa and start heating. The target temperature of the first temperature zone is 190-210°C, and the target temperature of the second temperature zone is 500-1100°C. Control the first and second temperature zones to reach the target temperatures at the same time. 50-70 seconds before reaching the target temperature, the reaction gas is introduced to a target pressure of 100-2000 Pa, and the precursor vapor in the first temperature zone is transported to the surface of the silicon substrate in the second temperature zone by the reaction gas for reaction. The flow rate of the reaction gas is 10-500 sccm. When the reaction is completed, a monoclinic hafnium dioxide film with controllable orientation is obtained; wherein: When the target temperature of the first temperature zone is 203-210 ℃, the target temperature of the second temperature zone is 500-800 ℃, the target pressure is 600-2000 Pa, and the reaction gas flow rate is 300-500 sccm, a film with a (111) orientation structure is obtained; when the target temperature of the first temperature zone is 190-196 ℃, the target temperature of the second temperature zone is 900-1100 ℃, the target pressure is 100-400 Pa, and the reaction gas flow rate is 10-150 sccm, a film with a (100) orientation structure is obtained.

2. The preparation method according to claim 1, characterized in that In the step 1), the precursor is hafnium acetylacetonate powder.

3. The preparation method according to claim 1, characterized in that In the step 1), the single crystal silicon substrate is a (100) oriented silicon single crystal substrate, which is single-sided polished.

4. The preparation method according to claim 1, characterized in that In the step 2), the heating rate of the first temperature zone is 3-8°C / min, and the heating rate of the second temperature zone is 15-20°C / min.

5. The preparation method according to claim 1, characterized in that In step 1), the precursor is placed on an alumina porcelain boat in the first temperature zone of the deposition apparatus, and the substrate is placed on an alumina porcelain boat in the second temperature zone of the deposition apparatus; the porcelain boats in the two temperature zones are placed parallel to each other with a distance of 14-16 cm, and the precursor and the substrate are kept on the same horizontal plane.

6. The preparation method according to claim 1, characterized in that In the step 2), the reaction gas is O2.

7. The preparation method according to claim 1, characterized in that In the step 2), the reaction time is 5-10 min.

8. The preparation method according to claim 1, characterized in that In the step 2), the obtained monoclinic hafnium dioxide film has a (100) orientation structure, a (111) orientation structure, or a mixed orientation structure of (100) and (111).

9. A monoclinic hafnium dioxide thin film with controllable orientation prepared by the preparation method according to any one of claims 1 to 8.

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