A method for improving Ni / NiO ohmic contact based on supercritical fluid technology

Abstract

The application discloses a Ni / NiO ohmic contact improvement method based on supercritical fluid technology, which comprises the following steps: depositing a NiO layer on a substrate material, then depositing a metal nickel electrode on the surface of the NiO layer, carrying out annealing treatment on the substrate material, obtaining an ohmic contact, and finally carrying out supercritical reaction on the substrate material, so as to realize the ohmic contact improvement of the substrate material. The method solves the problems of large Ni / NiO ohmic contact resistivity and poor ohmic contact characteristics caused by the existing thermal annealing technology.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of microelectronic devices, and particularly relates to a Ni / NiO ohmic contact improvement method based on supercritical fluid technology. BACKGROUND

[0002] Inorganic nickel oxide (NiO) is a direct wide-bandgap p-type semiconductor with a bandgap of 3.6-4.0 eV, and its crystal structure is simple cubic NaCl structure, belonging to the cubic crystal system Fm-3m space group. In the process of preparing NiO, nickel vacancies will be generated under the condition of oxygen-rich processing, and the Ni 3+ excess positive charge, so that NiO has the conductive characteristics of a p-type semiconductor. Due to its own existence of a large number of intrinsic acceptor defects, it presents p-type conductive characteristics, and becomes a research hotspot in the field of semiconductor devices. Compared with traditional semiconductor materials, NiO has many excellent characteristics, such as large bandgap, good visible light transmittance, high stability, and low manufacturing cost, and has great application potential in many fields such as light-emitting diodes, lasers, photodetectors, and transparent conductive electrodes.

[0003] As early as the early twentieth century, there were reports on the preparation of NiO nanomaterials. In the 1980s and 1990s, NiO materials have been widely studied. Common methods for preparing NiO materials include chemical vapor deposition, magnetron sputtering, sol-gel, and atomic layer deposition.

[0004] In recent years, NiO-based heterojunction diodes have become a research hotspot in the field of semiconductor devices. For example, a prepared NiO / β-Ga2O3 power diode has a breakdown voltage of 1.2 kV; a 25-200℃ temperature-sensitive NiO / GaN heterojunction PN diode; and a NiO / SiC heterojunction diode with a high breakdown voltage of 1.5 kV. In the process of preparing NiO-based heterojunction diodes, the NiO thin film and the metal electrode on the surface usually need to be subjected to heat annealing treatment to form ohmic contact. However, the high temperature in the annealing process will reduce the oxygen content in the NiO thin film and increase the film resistivity, which is not conducive to the improvement of the ohmic contact characteristics.

[0005] Secondly, for NiO-based heterojunction diode, the ohmic contact formed between NiO material and metal electrode has an important influence on the electrical characteristics of the device. The current conventional treatment is to use thermal annealing, that is, the wafer is heated from ambient temperature to target temperature and maintained for a period of time, and then the wafer is heat treated. O2 annealing is carried out at different temperatures of 200-500 DEG C. The number of point defects in the NiO decreases with the release of oxygen atoms after annealing, so that the carrier concentration decreases, the mobility increases, and the resistivity of the NiO film also increases obviously with the increase of the annealing temperature. The desorption of O atoms in the NiO film also occurs under N2 atmosphere, which increases the resistivity of the NiO film. Therefore, it is necessary to solve the problem of increased resistivity after thermal annealing in the process of forming ohmic contact. SUMMARY

[0006] The technical problem to be solved by the present application is to provide a Ni / NiO ohmic contact improvement method based on supercritical fluid technology to solve the problems of high Ni / NiO ohmic contact resistivity and poor ohmic contact characteristics caused by the existing thermal annealing technology.

[0007] The application adopts the following technical solutions:

[0008] A Ni / NiO ohmic contact improvement method based on supercritical fluid technology, which comprises the following steps: depositing a NiO layer on a substrate material, then depositing a metal nickel electrode on the surface of the NiO layer, then annealing the substrate material to obtain ohmic contact, and finally performing supercritical reaction on the substrate material to improve the ohmic contact of the substrate material.

[0009] Specifically, the NiO layer is deposited on the substrate material by using a radio frequency magnetron sputtering method.

[0010] Further, the diameter of the NiO target material used in the radio frequency magnetron sputtering method is 2.54-10.16 cm, the purity of the NiO target material is 99.99%, and oxygen-free copper is used as the back target material.

[0011] Further, before the radio frequency magnetron sputtering method is used, the sputtering power is controlled to be 60-80 W, the sputtering atmosphere is a mixed gas of oxygen and argon, the oxygen accounts for 20-30% of the volume of the mixed gas, and the NiO target material is pre-sputtered for 5-10 min.

[0012] Specifically, the metal nickel electrode is deposited on the surface of the NiO layer by using an electron beam deposition method, and the working pressure is controlled to be 2*10 -6 -3*10 -6 Torr.

[0013] Specifically, the annealing temperature of the thermal annealing treatment is 300-500 DEG C, and the annealing time is 15-30 min.

[0014] Specifically, the thermal annealing is performed in an O2 atmosphere, and the oxygen flow rate is 400-500sccm.

[0015] Specifically, the supercritical treatment is as follows:

[0016] The substrate material forming ohmic contact is sealed and treated, then the reaction gas is filled, the pressure is controlled to be 15-25MPa, the substrate material is heated to 100-200℃, and the process is ended after being kept for 1-2h.

[0017] Specifically, the reaction gas is one or more of oxygen, carbon dioxide and laughing gas.

[0018] Specifically, before depositing the NiO layer on the substrate material, the substrate material is cleaned and pretreated by using a silicon dioxide etching solution or dilute hydrochloric acid to remove the natural oxide layer on the surface of the substrate material.

[0019] Compared with the prior art, the present application has at least the following beneficial effects:

[0020] The Ni / NiO ohmic contact improvement method based on the supercritical fluid technology of the present application performs supercritical fluid treatment on the NiO material, the strong permeability of the gas in the supercritical state increases the oxygen content in the NiO, the crystallinity is better, and the resistivity is reduced, so that the purpose of improving the Ni / NiO ohmic contact characteristics is achieved, and the supercritical treatment process is simple to operate and low in cost, and does not make the device manufacturing process too complex.

[0021] Further, the NiO thin film is prepared by using the radio frequency magnetron sputtering method, under the action of the acceleration electric field, the ions bombard the target material, and the atoms or molecules on the surface of the target material are sputtered to deposit on the substrate to form the thin film, the adhesion between the prepared thin film and the substrate is strong, and the thin film has good uniformity and compactness.

[0022] Further, in order to match the common magnetron sputtering instrument, the NiO target material selects a two-inch or four-inch diameter target material; the NiO material is welded together with the copper back target to prevent deformation, and the copper has good electrical conductivity and thermal conductivity; the NiO target material selects a 99.99% high-purity target material to improve the purity of the prepared NiO thin film.

[0023] Further, the target material is pre-sputtered for 5-10min before formal sputtering to remove the pollutants on the surface of the target material and avoid polluting the deposited NiO thin film.

[0024] Further, the electron beam deposition method is used, the working pressure is 2x10 -6 ~ 3x10 -6 Torr, the metal electrode is prepared in a high vacuum state, the deposition rate is fast and the purity is high.

[0025] Further, the thermal annealing treatment is carried out in the range of 300-500 DEG C, and the temperature is too low to form the ohmic contact, and the temperature is too high to make the ohmic contact characteristics worse. The oxygen flow is selected in the range of 400-500 sccm, and too high or too low is not conducive to the improvement of the ohmic contact characteristics.

[0026] Further, the thermal annealing is carried out in the oxygen atmosphere, and compared with the thermal annealing in the nitrogen atmosphere, the oxygen element can be reduced, and the ohmic contact characteristics can be avoided in the thermal annealing process.

[0027] Further, the pressure in the supercritical treatment process is 15-25 MPa, and the treatment temperature is 100-200 DEG C, so that the gas in the reaction kettle can be kept in the supercritical state, and the treatment process is ended after 1-2 h.

[0028] Further, the supercritical treatment can select any one of oxygen, carbon dioxide or laughing gas, and the resistivity of the NiO material can be reduced in the supercritical state, so that the ohmic contact characteristics can be improved.

[0029] Further, the substrate material needs to be cleaned before the magnetron sputtering, the cleanliness of the substrate is improved, and the influence of the pollutants on the quality of the deposited film is reduced, and the natural oxide layer on the surface of the substrate material is removed by using the silicon dioxide etching liquid or dilute hydrochloric acid.

[0030] In summary, the supercritical fluid technology is used for improving the Ni / NiO ohmic contact, compared with the phenomenon that the oxygen atoms in the NiO film are too much and the contact resistivity is increased caused by the ordinary thermal annealing process, any one of the supercritical O2, CO2 or N2O in the application increases the number of oxygen atoms in the NiO film in the supercritical treatment process, and the specific contact resistance of the ohmic contact can be reduced, so that the quality of the ohmic contact is improved.

[0031] The technical scheme of the application is further described in detail below by means of the drawings and examples. DESCRIPTION OF DRAWINGS

[0032] Figure 1 It is the comparison chart of the Ni / NiO ohmic contact characteristics before and after the supercritical improvement;

[0033] Figure 2 It is the structure schematic view of the supercritical experimental device.

[0034] Among them: 1. The reaction kettle; 2. The heating furnace; 3. The safety explosion-proof valve; 4. The temperature measuring thermocouple; 5. The gas inlet valve; 6. The gas outlet valve. DETAILED DESCRIPTION

[0035] The technical solutions of the present application will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0036] In the present application, all the embodiments and preferred embodiments mentioned in the present application can be combined to form new technical solutions, if not otherwise specified.

[0037] In the present application, all the technical features and preferred features mentioned in the present application can be combined to form new technical solutions, if not otherwise specified.

[0038] In the present application, percentage (%) or part refers to the percentage by weight or weight part of the composition, if not otherwise specified.

[0039] In the present application, each component or its preferred component involved can be combined to form new technical solutions, if not otherwise specified.

[0040] In the present application, unless otherwise specified, the numerical range "a~b" represents a shorthand notation for any real number combination between a and b, wherein a and b are both real numbers. For example, the numerical range "6~22" represents that all the real numbers between "6~22" have been listed herein, and "6~22" is only a shorthand notation for these numerical combinations.

[0041] The lower limit and upper limit of the range disclosed in the present application can be one or more lower limits and one or more upper limits, respectively.

[0042] In the present application, the term "and / or" used herein means any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.

[0043] In the present application, unless otherwise specified, each reaction or operation step can be carried out sequentially or according to the sequence. Preferably, the reaction method herein is carried out sequentially.

[0044] Unless otherwise specified, the professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. In addition, any method or material similar or equivalent to the described content can also be applied in the present application.

[0045] Supercritical fluid refers to fluid in the region above the critical point of temperature and pressure. At different temperatures and pressures, matter appears in different states such as liquid, gas, solid, etc. The point at which the three phases coexist in equilibrium is called the triple point, and the point at which the liquid and gas phases coexist in equilibrium is called the critical point. When the temperature and pressure of a substance simultaneously exceed its critical point, the state of the substance is called supercritical state. The substance in supercritical state can simultaneously have high penetrability of gas and solubility of liquid. The application provides a Ni / NiO ohmic contact improvement method based on supercritical fluid technology. Based on supercritical fluid technology, the gas is filled into the reaction kettle through the booster pump, and the reaction kettle is heated at the same time, so that the reaction chamber is kept at a certain temperature and pressure for a period of time to process the device surface.

[0046] The application is a Ni / NiO ohmic contact improvement method based on supercritical fluid technology, comprising the following steps:

[0047] S1, cleaning the substrate material, and removing the natural oxide layer on the surface of the substrate material by using silicon dioxide etching liquid or dilute hydrochloric acid;

[0048] S2, depositing a NiO layer on the substrate material pretreated in step S1 by using a radio frequency magnetron sputtering method;

[0049] The radio frequency magnetron sputtering uses a NiO target material, the diameter of the NiO target material is 2.54-10.16 cm, the purity of the NiO target material is 99.99%, and oxygen-free copper is used as the back target material.

[0050] The radio frequency magnetron sputtering method needs to be pre-sputtered for 5-10 min before formal sputtering, the whole sputtering process is at room temperature, the sputtering power is 60-80 W, and the sputtering atmosphere is a mixed gas of oxygen and argon, wherein the proportion of oxygen is 20%-30%.

[0051] S3, depositing a metal nickel electrode on the surface of the deposited NiO layer obtained in step S2;

[0052] A nickel metal target is used to prepare a nickel electrode by using an electron beam deposition method, the working pressure is 2x10 -6 -3x10 - 6 Torr.

[0053] S4, performing a thermal annealing treatment on the substrate material on which the metal nickel electrode is deposited in step S3 to obtain an ohmic contact;

[0054] The thermal annealing process is performed in an O2 atmosphere, the annealing temperature is 300-500 DEG C, the oxygen flow rate is 400-500 sccm, and the annealing time is 15-30 min.

[0055] S5, placing the substrate material with ohmic contact formed in step S4 into a supercritical experimental device, filling the supercritical experimental device with a supercritical fluid, filling the supercritical experimental device with a reaction gas, and improving the ohmic contact quality of the substrate material by supercritical treatment.

[0056] The reaction gas is one or more of oxygen (O2), carbon dioxide (CO2), and nitrous oxide (N2O).

[0057] Referring to Figure 2 The supercritical experimental device includes a reaction kettle 1, a heating furnace 2 arranged outside the reaction kettle 1, an air inlet valve 5, an air outlet valve 6, a safety explosion-proof valve 3, and a temperature measuring thermocouple 4 connected to the reaction kettle 1.

[0058] The specific steps of the supercritical treatment are as follows:

[0059] S501, cleaning the reaction kettle 1 with deionized water;

[0060] S502, placing the substrate material with ohmic contact formed in step S4 on a quartz table, then placing the quartz table in the reaction kettle 1 cleaned in step S501, and then sealing the reaction kettle 1;

[0061] S503, opening the air inlet valve 5, filling the reaction kettle 1 sealed in step S502 with a reaction gas through an air inlet pipeline, and increasing the pressure in the reaction kettle 1 to 15-25 MPa;

[0062] S504, monitoring the temperature in the reaction kettle 1 in real time through the temperature measuring thermocouple 4, heating the reaction kettle 1 after the pressure increasing treatment in step S503 to 100-200℃ to enter a supercritical state;

[0063] S505, maintaining the supercritical state in step S504 for 1-2 hours;

[0064] S506, after the reaction in step S505 is completed, opening the air outlet valve 6, cooling the reaction kettle 1 to room temperature and reducing the pressure to atmospheric pressure, opening the reaction kettle 1, taking out the substrate material, and ending the supercritical treatment.

[0065] Referring to Figure 1 Compared with the sample without supercritical treatment, the specific contact resistance p of the Ni / NiO ohmic contact of the sample treated by supercritical oxygen, supercritical carbon dioxide, or supercritical nitrous oxide is sc There is a significant decrease, indicating that the ohmic contact characteristics have been significantly improved and optimized.

[0066] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will be combined with the drawings in the embodiments of the present application to make a clear and complete description of the technical solutions in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0067] Embodiment 1

[0068] S1, cleaning the substrate material, and removing the natural oxide layer on the surface of the substrate material by using a silicon dioxide etching solution or dilute hydrochloric acid, etc.

[0069] S2, pre-sputtering the target material for 5 min, the whole sputtering process is at room temperature, the sputtering power is 60 W, and the sputtering atmosphere is a mixed gas of oxygen and argon, wherein the proportion of oxygen is 20%; then depositing a NiO layer on the substrate material treated in step S1 by using a radio frequency magnetron sputtering method;

[0070] The diameter of the NiO target material is 2.54 cm, and the purity of the target material is 99.99%;

[0071] S3, using a nickel metal target material, controlling the working pressure to be 2x10 -6 Torr, and depositing a metal nickel electrode on the surface of the NiO layer obtained in step S2 by using an electron beam deposition method;

[0072] S4, performing heat annealing treatment on the material in which the metal nickel electrode is deposited in step S3 for 15 min under an O2 atmosphere, controlling the oxygen flow to be 400 sccm, and controlling the annealing temperature to be 300 DEG C, to obtain an ohmic contact;

[0073] S5, placing the material in which the ohmic contact is formed in step S4 into a supercritical experimental device, filling oxygen (O2) into the supercritical experimental device, and improving the quality of the ohmic contact of Ni / NiO by supercritical treatment.

[0074] The specific steps of the supercritical treatment are as follows:

[0075] The reaction kettle is cleaned with deionized water; the substrate material forming ohmic contact is placed on a quartz table, and then the quartz table is placed in the cleaned reaction kettle, and then the reaction kettle is sealed; the inlet valve is opened, and the reaction gas is filled into the sealed reaction kettle through the gas inlet pipeline, so that the pressure in the reaction kettle increases to 15 MPa; the temperature in the reaction kettle is monitored in real time by the temperature measuring thermocouple, and the pressurized reaction kettle 1 is heated to 100℃, and the supercritical state is maintained for 1h; after the reaction is completed, the outlet valve is opened, the reaction kettle is cooled to room temperature, and the pressure is reduced to atmospheric pressure, the reaction kettle 1 is opened, and the substrate material is taken out, and the supercritical treatment is completed.

[0076] After step S5 is completed, the specific resistance of the Ni / NiO ohmic contact is ρ sc from 2.85 / Ω·cm 2 to 0.37 / Ω·cm 2 , and the ohmic contact characteristics are improved.

[0077] Example 2

[0078] S1, the substrate material is cleaned, and the natural oxide layer on the surface of the substrate material is removed by using a silicon dioxide etching solution or dilute hydrochloric acid;

[0079] S2, the target material is pre-sputtered for 6min, the whole sputtering process is at room temperature, the sputtering power is 60W, and the sputtering atmosphere is a mixture of oxygen and argon gas, wherein the oxygen accounts for 22%; then a NiO layer is deposited on the substrate material treated in step S1 by using a radio frequency magnetron sputtering method;

[0080] The diameter of the NiO target material is 5.08cm, and the purity of the target material is 99.99%;

[0081] S3, a nickel metal target material is used, the working pressure is controlled to be 2×10 -6 Torr, and a metal nickel electrode is deposited on the surface of the NiO layer obtained in step S2 by using an electron beam deposition method;

[0082] S4, the material deposited with the metal nickel electrode in step S3 is subjected to heat annealing treatment for 20min under an O2 atmosphere and at an annealing temperature of 350℃, so as to obtain ohmic contact;

[0083] S5, the material forming ohmic contact in step S4 is placed in a supercritical experimental device, oxygen (O2) is filled into the supercritical experimental device, and the quality of the Ni / NiO ohmic contact is improved by supercritical treatment.

[0084] The specific steps of supercritical treatment are as follows:

[0085] The reaction kettle is cleaned with deionized water; the substrate material forming ohmic contact is placed on a quartz table, and then the quartz table is placed in the cleaned reaction kettle, and then the reaction kettle is sealed; the inlet valve is opened, and the reaction gas is filled into the sealed reaction kettle through the gas inlet pipeline, so that the pressure in the reaction kettle increases to 25 MPa; the temperature in the reaction kettle is monitored in real time by the temperature measuring thermocouple, and the pressurized reaction kettle 1 is heated to 120 DEG C and kept in a supercritical state for 1 h; after the reaction is completed, the outlet valve is opened, the reaction kettle is cooled to room temperature, and the pressure is reduced to atmospheric pressure, the reaction kettle 1 is opened, and the substrate material is taken out, and the supercritical treatment is completed.

[0086] After step S5 is completed, the specific resistance of the Ni / NiO ohmic contact is ρ sc from 2.85 / Ω·cm 2 to 0.52 / Ω·cm 2 , and the ohmic contact characteristics are improved.

[0087] Example 3

[0088] S1, the substrate material is cleaned, and the natural oxide layer on the surface of the substrate material is removed by using a silicon dioxide etching solution or dilute hydrochloric acid;

[0089] S2, the target material is pre-sputtered for 7 min, the whole sputtering process is at room temperature, the sputtering power is 70 W, and the sputtering atmosphere is a mixture of oxygen and argon gas, wherein the oxygen accounts for 24%; then a NiO layer is deposited on the substrate material treated in step S1 by using a radio frequency magnetron sputtering method;

[0090] The diameter of the NiO target material is 2.54 cm, and the purity of the target material is 99.99%;

[0091] S3, a nickel metal target material is used, the working pressure is controlled to be 2*10 -6 Torr, and a metal nickel electrode is deposited on the surface of the NiO layer obtained in step S2 by using an electron beam deposition method;

[0092] S4, the material deposited with the metal nickel electrode in step S3 is subjected to heat annealing treatment for 22 min under an O2 atmosphere, with the oxygen flow being controlled to be 440 sccm and the annealing temperature being controlled to be 350 DEG C, to obtain an ohmic contact;

[0093] S5, the material forming the ohmic contact in step S4 is placed in a supercritical experimental device, carbon dioxide (CO2) is filled into the supercritical experimental device, and the quality of the Ni / NiO ohmic contact is improved by supercritical treatment.

[0094] The specific steps of the supercritical treatment are as follows:

[0095] The reaction kettle is cleaned with deionized water; the substrate material forming ohmic contact is placed on a quartz table, and then the quartz table is placed in the cleaned reaction kettle, and then the reaction kettle is sealed; the inlet valve is opened, and the reaction gas is filled into the sealed reaction kettle through the gas inlet pipeline, so that the pressure in the reaction kettle increases to 15 MPa; the temperature in the reaction kettle is monitored in real time by the temperature measuring thermocouple, and the pressurized reaction kettle 1 is heated to 140℃, and the supercritical state is maintained for 1.5h; after the reaction is completed, the outlet valve is opened, the reaction kettle is cooled to room temperature, and the pressure is reduced to atmospheric pressure, the reaction kettle 1 is opened, and the substrate material is taken out, and the supercritical treatment is completed.

[0096] After step S5 is completed, the specific resistance of the Ni / NiO ohmic contact is ρ sc from 2.85 / Ω·cm 2 to 0.96 / Ω·cm 2 , and the ohmic contact characteristics are improved.

[0097] Example 4

[0098] S1, the substrate material is cleaned, and the natural oxide layer on the surface of the substrate material is removed by using a silicon dioxide etching solution or dilute hydrochloric acid;

[0099] S2, the target material is pre-sputtered for 8min, the whole sputtering process is at room temperature, the sputtering power is 70W, and the sputtering atmosphere is a mixture of oxygen and argon gas, wherein the oxygen accounts for 26%; then a NiO layer is deposited on the substrate material treated in step S1 by using a radio frequency magnetron sputtering method;

[0100] The diameter of the NiO target material is 5.08cm, and the purity of the target material is 99.99%;

[0101] S3, a nickel metal target material is used, the working pressure is controlled to be 3×10 -6 Torr, and a metal nickel electrode is deposited on the surface of the NiO layer obtained in step S2 by using an electron beam deposition method;

[0102] S4, the material deposited with the metal nickel electrode in step S3 is subjected to heat annealing treatment for 25min under an O2 atmosphere and at an annealing temperature of 400℃, so as to obtain ohmic contact;

[0103] S5, the material forming ohmic contact in step S4 is placed in a supercritical experimental device, carbon dioxide (CO2) is filled into the supercritical experimental device, and the quality of the Ni / NiO ohmic contact is improved by supercritical treatment.

[0104] The specific steps of the supercritical treatment are as follows:

[0105] The reaction kettle is cleaned with deionized water; the substrate material forming ohmic contact is placed on a quartz table, and then the quartz table is placed in the cleaned reaction kettle, and then the reaction kettle is sealed; the inlet valve is opened, and the reaction gas is filled into the sealed reaction kettle through the gas inlet pipeline, so that the pressure in the reaction kettle increases to 25 MPa; the temperature in the reaction kettle is monitored in real time by the temperature measuring thermocouple, and the pressurized reaction kettle 1 is heated to 160 ℃, and the supercritical state is maintained for 1.5 h; after the reaction is completed, the outlet valve is opened, the reaction kettle is cooled to room temperature, and the pressure is reduced to atmospheric pressure, the reaction kettle 1 is opened, and the substrate material is taken out, and the supercritical treatment is completed.

[0106] After step S5 is completed, the specific resistance of the Ni / NiO ohmic contact is ρ sc from 2.85 / Ω·cm 2 to 0.43 / Ω·cm 2 , and the ohmic contact characteristics are improved.

[0107] Example 5

[0108] S1, the substrate material is cleaned, and the natural oxide layer on the surface of the substrate material is removed by using a silicon dioxide etching solution or dilute hydrochloric acid;

[0109] S2, the target material is pre-sputtered for 9 min, the whole sputtering process is at room temperature, the sputtering power is 80 W, and the sputtering atmosphere is a mixture of oxygen and argon gas, wherein the oxygen accounts for 28%; then a NiO layer is deposited on the substrate material treated in step S1 by using a radio frequency magnetron sputtering method;

[0110] The diameter of the NiO target material is 7.62 cm, and the purity of the target material is 99.99%;

[0111] S3, a nickel metal target material is used, the working pressure is controlled to be 3×10 -6 Torr, and a metal nickel electrode is deposited on the surface of the NiO layer obtained in step S2 by using an electron beam deposition method;

[0112] S4, the material on which the metal nickel electrode is deposited in step S3 is subjected to heat annealing treatment for 28 min under an O2 atmosphere, with the oxygen flow being controlled to be 480 sccm and the annealing temperature being controlled to be 450 ℃, to obtain ohmic contact;

[0113] S5, the material forming ohmic contact in step S4 is placed in a supercritical experimental device, and nitrous oxide (N2O) is filled into the supercritical experimental device, so as to improve the quality of the Ni / NiO ohmic contact by supercritical treatment.

[0114] The specific steps of the supercritical treatment are as follows:

[0115] The reaction kettle is cleaned with deionized water; the substrate material forming ohmic contact is placed on a quartz table, and then the quartz table is placed in the cleaned reaction kettle, and then the reaction kettle is sealed; the inlet valve is opened, and the reaction gas is filled into the sealed reaction kettle through the gas inlet pipeline, so that the pressure in the reaction kettle increases to 15 MPa; the temperature in the reaction kettle is monitored in real time by the temperature measuring thermocouple, and the pressurized reaction kettle 1 is heated to 180 ℃ and kept in a supercritical state for 2 h; after the reaction is completed, the outlet valve is opened, the reaction kettle is cooled to room temperature, and the pressure is reduced to atmospheric pressure, the reaction kettle 1 is opened, and the substrate material is taken out, and the supercritical treatment is completed.

[0116] After step S5 is completed, the specific resistance of the Ni / NiO ohmic contact is ρ sc from 2.85 / Ω·cm 2 to 0.39 / Ω·cm 2 , and the ohmic contact characteristics are improved.

[0117] Example 6

[0118] S1, the substrate material is cleaned, and the natural oxide layer on the surface of the substrate material is removed by using a silicon dioxide etching solution or dilute hydrochloric acid;

[0119] S2, the target material is pre-sputtered for 10 min, the whole sputtering process is at room temperature, the sputtering power is 80 W, and the sputtering atmosphere is a mixture of oxygen and argon gas, wherein the oxygen accounts for 30%; then a NiO layer is deposited on the substrate material treated in step S1 by using a radio frequency magnetron sputtering method;

[0120] The diameter of the NiO target material is 10.16 cm, and the purity of the target material is 99.99%;

[0121] S3, a nickel metal target material is used, the working pressure is controlled to be 3×10 -6 Torr, and a metal nickel electrode is deposited on the surface of the NiO layer obtained in step S2 by using an electron beam deposition method;

[0122] S4, the material on which the metal nickel electrode is deposited in step S3 is subjected to heat annealing treatment for 30 min under an O2 atmosphere, with the oxygen flow being controlled to be 500 sccm and the annealing temperature being controlled to be 500 ℃, to obtain ohmic contact;

[0123] S5, the material forming ohmic contact in step S4 is placed in a supercritical experimental device, and nitrous oxide (N2O) is filled into the supercritical experimental device, so as to improve the quality of the Ni / NiO ohmic contact by supercritical treatment.

[0124] The specific steps of the supercritical treatment are as follows:

[0125] The reaction kettle is cleaned with deionized water; the substrate material forming ohmic contact is placed on a quartz table, and then the quartz table is placed in the cleaned reaction kettle, and then the reaction kettle is sealed; the inlet valve is opened, and the reaction gas is filled into the sealed reaction kettle through the inlet pipeline, so that the pressure in the reaction kettle is increased to 25MPa; the temperature in the reaction kettle is monitored in real time by a temperature measuring thermocouple, and the pressurized reaction kettle 1 is heated to 200 DEG C and kept in a supercritical state for 2h; after the reaction is completed, the outlet valve is opened, the reaction kettle is cooled to room temperature, and the pressure is reduced to atmospheric pressure, the reaction kettle 1 is opened, the substrate material is taken out, and the supercritical treatment is completed.

[0126] After step S5 is completed, the specific contact resistance p of the Ni / NiO ohmic contact sc from 2.85 / Ω·cm 2 to 0.66 / Ω·cm 2 , and the ohmic contact characteristics are improved.

[0127] In summary, the Ni / NiO ohmic contact improvement method based on the supercritical fluid technology can reduce the specific contact resistance of the ohmic contact and improve the quality of the ohmic contact, compared with the problem of poor ohmic contact characteristics caused by the ordinary thermal annealing process.

[0128] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for improving Ni / NiO ohmic contact based on supercritical fluid technology, characterized in that, A NiO layer is deposited on a substrate material, followed by the deposition of a nickel electrode on the surface of the NiO layer. The substrate material is then annealed to obtain an ohmic contact. Finally, a supercritical reaction is performed on the substrate material to improve the ohmic contact. The supercritical treatment specifically involves: The substrate material forming the ohmic contact is sealed, and then a reaction gas is introduced, with the pressure controlled at 15~25MPa. The substrate material is heated to 100~200℃ and held for 1~2 hours before the process ends. The reaction gas is one or more of oxygen, carbon dioxide, and nitrous oxide.

2. The method for improving Ni / NiO ohmic contact based on supercritical fluid technology according to claim 1, characterized in that, A NiO layer was deposited on a substrate material using radio frequency magnetron sputtering.

3. The method for improving Ni / NiO ohmic contact based on supercritical fluid technology according to claim 2, characterized in that, The NiO target used in the radio frequency magnetron sputtering method has a diameter of 2.54~10.16cm, a purity of 99.99%, and uses oxygen-free copper as the back target material.

4. The method for improving Ni / NiO ohmic contact based on supercritical fluid technology according to claim 2, characterized in that, Before using radio frequency magnetron sputtering, the sputtering power is controlled at 60~80W, the sputtering atmosphere is a mixture of oxygen and argon, with oxygen accounting for 20%~30% of the volume of the mixture, and the NiO target is pre-sputtered for 5~10 minutes.

5. The method for improving Ni / NiO ohmic contact based on supercritical fluid technology according to claim 1, characterized in that, Using electron beam deposition, the working pressure is controlled to be Torr deposits a metallic nickel electrode on the surface of a NiO layer.

6. The method for improving Ni / NiO ohmic contact based on supercritical fluid technology according to claim 1, characterized in that, The annealing temperature for hot annealing is 300~500℃, and the annealing time is 15~30min.

7. The method for improving Ni / NiO ohmic contact based on supercritical fluid technology according to claim 1 or 6, characterized in that, The heat annealing process was carried out in an O2 atmosphere with an oxygen flow rate of 400-500 sccm.

8. The method for improving Ni / NiO ohmic contact based on supercritical fluid technology according to claim 1, characterized in that, Before depositing a NiO layer on the substrate material, the substrate material is first cleaned and then pretreated with silicon dioxide etching solution or dilute hydrochloric acid to remove the natural oxide layer on the surface of the substrate material.

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