A method for doping metal atoms in gallium oxide materials

Abstract

The application discloses a method for doping metal atoms in gallium oxide material, which comprises the following steps: step 1, selecting C-sapphire as a substrate material; step 2, preparing a beta-Ga2O3 thin film material on the substrate material by adopting radio frequency magnetron sputtering; step 3, placing the sample after magnetron sputtering into a horizontal tube type high-temperature diffusion furnace to perform post annealing treatment; step 4, detecting the thin film structure and the crystal surface roughness of the sample after annealing by adopting XRD and AFM testing instruments; step 5, doping: preparing a composite structure of 'Ga2O3 / metal / ... / metal / Ga2O3' on the same substrate by alternately adopting radio frequency sputtering Ga2O3 and direct current sputtering metal thin film to perform magnetron sputtering; and step 6, performing annealing treatment on the obtained composite structure sample by adopting a diffusion furnace after the doping is completed; and the technical problem that the existing technology is difficult to improve the p-type Ga2O3 conductive capacity is solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of microelectronic doping technology, and particularly relates to a method for doping metal atoms in gallium oxide material. BACKGROUND

[0002] With the rapid development of the semiconductor industry and integrated circuit technology, ultra-wide bandgap semiconductors are slowly rising. One of the direct bandgap ultra-wide bandgap semiconductor materials, gallium oxide (Ga2O3), has a huge application prospect in the fields of power electronic devices, such as power electronic devices, blind ultraviolet photodetectors, light-emitting diodes, information storage, radio and microwave, gas sensors, transparent conductive electrodes, etc., due to its super-high breakdown field strength and other advantages.

[0003] Pure semiconductors generate carriers for conduction by intrinsic excitation, but the number of carriers generated by intrinsic excitation is small, the conduction ability is extremely weak, and it is easily affected by external factors such as temperature. Doping can improve the conductivity, transparency and luminescence of Ga2O3 and other properties, because doping can change the internal structure of the crystal and its properties (such as adjusting lattice stress, inducing structural phase transition, improving crystal quality, optimizing physical properties, etc.). In order to make the semiconductor have specific properties, doping technology is essential.

[0004] Power electronic devices based on power semiconductors are composed of transistors and diodes, and transistors require p-type and n-type semiconductors. Ga2O3 exhibits weak n-type conductivity due to the presence of oxygen vacancy defects under intrinsic conditions, and a large number of experimental results show that the acceptor impurities doped are deep transition energy levels, that is, the resistivity of the obtained p-type Ga2O3 is particularly large, which also leads to the difficulty in obtaining p-type Ga2O3, greatly limiting the application of Ga2O3 in devices. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a method for doping metal atoms in gallium oxide material, to solve the technical problem that it is difficult to improve the conduction ability of p-type Ga2O3 in the prior art.

[0006] The technical scheme of the present application is:

[0007] A method for doping metal atoms in gallium oxide material, comprising:

[0008] Step 1, selecting C-sapphire (Al2O3) as a substrate material;

[0009] Step 2, preparing a β-Ga2O3 thin film material on the substrate material by radio frequency magnetron sputtering;

[0010] Step 3, the sample after magnetron sputtering is put into a horizontal tube type high temperature diffusion furnace for post annealing treatment;

[0011] Step 4, after annealing, the film structure and the crystal surface roughness of the sample are detected by XRD and AFM testing instruments;

[0012] Step 5, doping: a double-target alternation, i.e. RF sputtering Ga2O3 and DC sputtering metal thin film, is used to alternately sputter on the same substrate to prepare a composite structure of "Ga2O3 / metal / … / metal / Ga2O3" by magnetron sputtering;

[0013] Step 6, after the doping is completed, the diffusion furnace is used to anneal the obtained composite structure sample, and the annealing parameters are the same as those in step 3.2.

[0014] It also includes:

[0015] Step 7, the film material sample is characterized by XRD and AFM, and the properties of the "Ga2O3 / metal / … / metal / Ga2O3" composite structure are detected;

[0016] Step 8, a laser zone melting experiment is designed, and a high-energy laser beam is used to scan the sample;

[0017] Step 9, after laser zone melting, the "Ga2O3 / metal / … / metal / Ga2O3" composite structure is tested for structural properties and electrical properties by using the characterization equipment.

[0018] Step 1, when selecting the substrate material, the substrate is cleaned, and the cleaning method is:

[0019] Step 1.1, first cut the sapphire substrate into 1×1cm 2 square, and put it into a polytetrafluoroethylene cleaning basket for deionized water washing;

[0020] Step 1.2, then sequentially ultrasonic clean the substrate in anhydrous ethanol, acetone, and anhydrous ethanol solution for 15 minutes;

[0021] Step 1.3, then wash with deionized water, and after completion, dry with nitrogen and put into a nitrogen cabinet for standby.

[0022] Step 2, the method for preparing β-Ga2O3 thin film material on the substrate material by RF magnetron sputtering specifically includes:

[0023] Step 2.1, put the cleaned sapphire substrate into the RF magnetron sputtering instrument, fix the oxygen and argon flow ratio, working pressure, sputtering power and deposition time of the magnetron sputtering, and only change the substrate temperature to obtain the optimal substrate temperature;

[0024] Step 2.2, synchronously with step 2.1, the optimal magnetic sputtering process parameters are obtained in sequence; the optimal parameters are: substrate temperature 500 DEG C, oxygen flow rate 2.3 sccm, argon flow rate 46.2 sccm, oxygen to argon ratio 2.3:46.2, working pressure 1.0 Pa, sputtering power 150 W, and deposition time 90 min. The specific method of annealing treatment comprises the following steps:

[0025] Step 3.1, fixing the annealing temperature and annealing time, and only changing the annealing atmosphere, the optimal annealing atmosphere is obtained;

[0026] Step 3.2, synchronously with step 3.1, the optimal annealing process parameters are obtained in sequence; the optimal parameters are: annealing temperature 1000 DEG C, oxygen annealing atmosphere, and annealing time 90 min.

[0027] The specific method of step 5 is as follows: first, sputtering Ga2O3 film on the sapphire substrate, then sputtering metal film on the basis, then sputtering Ga2O3 film, and repeating the above steps alternately, and finally sputtering Ga2O3 film on the surface as the end.

[0028] The time for sputtering metal film is less than the time for sputtering gallium oxide film.

[0029] The method of laser zone melting experiment is as follows: the optical system focuses the laser, the powder nozzle focuses the powder flow, and the two focal points are coincided, the focused laser melts the powder flow and the substrate, and the metallurgical bonding is formed after cooling and solidification, the relative movement of the substrate and the processing head is realized by the movement system, and finally the laser zone melting of the whole substrate surface is realized.

[0030] The energy of the laser, i.e. the power, meets the requirement of melting the beta-Ga2O3 composite structure film, but the sapphire substrate is not melted.

[0031] The beneficial effects of the present application are as follows:

[0032] The process technology of the present application for doping metal atoms in gallium oxide material utilizes the magnetic sputtering method to dope metal atoms into Ga2O3, has the advantages of simple process operation and dense plating effect, is beneficial to realize the experimental process and obtain good doping effect. The present application focuses on doping metal atoms into Ga2O3, is beneficial to the doping of various feasible metal atoms, has a wide application range, provides excellent conditions and new ideas for the p-type doping research of Ga2O3. Most of the metal atoms doped into Ga2O3 belong to p-type doping, the present application is beneficial to realize the p-type doping of Ga2O3, obtain Ga2O3 thin film materials with different conductivities, solve the difficult problem that the p-type conductive ability is difficult to improve at the present stage, obtain Ga2O3 pn junction conductive diodes and transistors, prepare large power electronic devices based on ultra-wide bandgap semiconductor Ga2O3 and other application devices, and expand the overall development of ultra-wide bandgap semiconductors.

[0033] The technical problems that the prior art has difficulty in improving the conductivity of p-type Ga2O3 are solved. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The flowchart is a schematic diagram of the present application;

[0035] Figure 2 The cross-sectional schematic diagram of the composite structure prepared in the specific embodiment of the present application is shown. DETAILED DESCRIPTION

[0036] Step 1, selecting C-sapphire (Al2O3) as a substrate material to prepare a β-Ga2O3 thin film.

[0037] Step 1.1, cleaning the substrate. Unclean substrates have adverse effects on the adhesion of the thin film to the substrate and the continuity of the thin film. In order to ensure that the quality of the thin film material is not affected, the substrate needs to be strictly cleaned. The cleaning process is as follows: first, cut the sapphire substrate into 1×1 cm square size, and put it into a polytetrafluoroethylene cleaning basket for deionized water flushing, so as to remove the large particles attached during the preparation of the substrate and the residual slag during the cutting. Then, sequentially ultrasonic clean the substrate in anhydrous ethanol, acetone and anhydrous ethanol solution for 15 min, so as to effectively remove the organic impurities of the substrate. Finally, flush with deionized water, the purpose is to clean the organic solution used in the previous step, so as to avoid affecting the subsequent experiment. After completion, dry with nitrogen and put into a nitrogen cabinet for standby. 2 Step 1.1, cleaning the substrate. Unclean substrates have adverse effects on the adhesion of the thin film to the substrate and the continuity of the thin film. In order to ensure that the quality of the thin film material is not affected, the substrate needs to be strictly cleaned. The cleaning process is as follows: first, cut the sapphire substrate into 1×1 cm square size, and put it into a polytetrafluoroethylene cleaning basket for deionized water flushing, so as to remove the large particles attached during the preparation of the substrate and the residual slag during the cutting. Then, sequentially ultrasonic clean the substrate in anhydrous ethanol, acetone and anhydrous ethanol solution for 15 min, so as to effectively remove the organic impurities of the substrate. Finally, flush with deionized water, the purpose is to clean the organic solution used in the previous step, so as to avoid affecting the subsequent experiment. After completion, dry with nitrogen and put into a nitrogen cabinet for standby.

[0038] Step 2, preparing high-quality β-Ga2O3 thin film material by radio frequency magnetron sputtering.

[0039] Step 2.1, doping is based on high-quality thin film material, and high-quality β-Ga2O3 thin film material needs to be prepared. Put the cleaned sapphire substrate into the radio frequency magnetron sputtering instrument, fix the oxygen and argon flow ratio, working pressure, sputtering power and deposition time of the magnetron sputtering, only change the substrate temperature, and obtain samples with different substrate temperatures (200℃, 300℃, 400℃, 500℃ and 550℃) respectively;

[0040] Step 2.2, the method of step 2.1, in turn, can obtain samples of different oxygen and argon flow ratios (1.2 sccm:46.2 sccm, 1.8 sccm:46.2 sccm, 2.3 sccm:46.2 sccm, 2.8 sccm:46.2 sccm, 4.6 sccm:46.2 sccm, 9.2 sccm:46.2 sccm and 18.4 sccm:46.2 sccm), samples of different working pressures (0.6 Pa, 1.0 Pa, 1.4 Pa, 1.9 Pa, 2.5 Pa and 3.0 Pa), samples of different sputtering powers (90 W, 110 W, 130 W, 150 W and 170 W) and samples of different deposition times (30 min, 60 min, 90 min and 120 min).

[0041] Step 3, the sample after magnetron sputtering is placed in a horizontal tube type high temperature diffusion furnace for post-annealing treatment.

[0042] Step 3.1, in order to obtain the optimal process parameters of the radio frequency magnetron sputtering in step 2, the sample is annealed by fixing the annealing temperature, annealing time and annealing atmosphere;

[0043] Step 3.2, in order to obtain the optimal process parameters of the annealing, the sample of different annealing atmospheres (oxygen and nitrogen) is obtained by fixing the annealing temperature and annealing time and only changing the annealing atmosphere; Step 3.3, the method of step 3.2, in turn, can obtain samples of different annealing temperatures (600℃, 700℃, 800℃, 900℃, 1000℃ and 1100℃) and samples of different annealing times (60min, 90min, 120min, 150min and 180min).

[0044] Step 4, after annealing, the film structure and the crystal surface roughness of the sample are detected by XRD and AFM testing instruments. Through the comparison and analysis of the XRD graph and the AFM graph, under the conditions of a substrate temperature of 500℃, an oxygen flow of 2.3 sccm, an argon flow of 46.2 sccm (oxygen to argon ratio 2.3:46.2), a working pressure of 1.0 Pa, a sputtering power of 150 W, a deposition time of 90 min, an annealing temperature of 1000℃, an oxygen annealing atmosphere and an annealing time of 90 min, the XRD peak intensity of the sample film is the strongest and the half peak width is the smallest, that is, the crystalline quality of the film is the best; at the same time, the AFM graph shows that under the above parameter conditions, the atomic distribution of the crystal surface is the most flat and dense, the surface roughness is the smallest, and the surface morphology structure of the film is the best.

[0045] Step 5, Doping: The "Ga2O3 / metal / … / metal / Ga2O3" composite structure is prepared by magnetron sputtering on the same substrate using double-target alternation (radio frequency sputtering Ga2O3, direct current sputtering metal film). First, Ga2O3 film is sputtered on the sapphire substrate, then metal film is sputtered on the basis, and then Ga2O3 film is sputtered, and so on. Finally, Ga2O3 film is sputtered on the surface as the end, and the structure is as shown in Figure 1 The number of alternations depends on the thickness of the sputtered gallium oxide monolayer. The thinner the gallium oxide monolayer, the more the number of alternations. The main reason is that if the overall gallium oxide film is too thin, the crystal quality of the gallium oxide film will decrease, and the doping effect of gallium oxide will also decrease, that is, it is more difficult to achieve P-type doping. The process of sputtering metal film is actually a doping process, so the time of sputtering metal film should be less than the time of sputtering gallium oxide film. After sputtering Ga2O3, the baffle on the magnetron sputtering instrument is quickly moved to the side of the Ga2O3 target to play a shielding role, avoiding the deposition of excess gallium oxide on the sapphire substrate. Then the base is rotated and moved to the position directly below the metal target for metal sputtering. After metal sputtering, the baffle is moved to the side of the metal target, and then the base is moved to the position directly below the Ga2O3 target, and so on.

[0046] Step 6, After doping, the obtained composite structure sample is annealed in a diffusion furnace, and the annealing parameters are the optimal parameters obtained in step 4.

[0047] Step 7, The film material sample is characterized by XRD and AFM to detect the properties of the "Ga2O3 / metal / … / metal / Ga2O3" composite structure.

[0048] Step 8, Laser zone melting experiment is designed, and high-energy laser beam is used to scan the sample. Due to the limitation of experimental conditions and the requirement of good physical properties of β-Ga2O3 film on annealing temperature, high-temperature annealing is likely to fail to make metal impurity atoms enter the lattice of gallium oxide. The principle of laser zone melting is as follows: the optical system focuses the laser, the powder nozzle focuses the powder flow, and the two focal points are coincided. The focused laser melts the powder flow and the substrate, and after cooling and solidification, a metallurgical bond is formed. The movement system realizes the relative movement of the substrate and the processing head, and finally realizes the laser zone melting of the whole substrate surface. The energy (power) of the laser should meet the requirements of melting the β-Ga2O3 composite structure film, but not melting the sapphire substrate. After the β-Ga2O3 composite structure film is zone melted and recrystallized, it is ensured that the metal impurity atoms enter the lattice and ionize to form effective doping.

[0049] Step 9, After laser zone melting, the structure and electrical properties of the "Ga2O3 / metal / … / metal / Ga2O3" composite structure are tested by characterization equipment.

Claims

1. A method for doping metal atoms into gallium oxide material, characterized in that: It includes: Step 1: Select C-plane sapphire (Al2O3) as the substrate material; Step 2: β-Ga2O3 thin film material is prepared on the substrate material by radio frequency magnetron sputtering; Step 3: Place the magnetron sputtered sample into a horizontal tube high-temperature diffusion furnace for post-annealing treatment; Specific methods for annealing include: Step 3.1: Fix the annealing temperature and annealing time, and only change the annealing atmosphere to obtain the optimal annealing atmosphere; Step 3.2, the same as step 3.1, yields the optimal annealing process parameters; the optimal parameters are: annealing temperature 1000℃, oxygen annealing atmosphere, and annealing time 90 min. Step 4: After annealing, the thin film structure and crystal surface roughness of the sample are detected using XRD and AFM instruments. Step 5, Doping: A composite structure of "Ga2O3 / metal / ... / metal / Ga2O3" is prepared by alternating dual-target sputtering, i.e., alternating RF sputtering of Ga2O3 and DC sputtering of metal thin films on the same substrate using magnetron sputtering. Step 6: After doping, the obtained composite structure sample is annealed in a diffusion furnace with the same annealing parameters as in step 3.

2. Step 7: Characterize the thin film material sample using XRD and AFM to detect the properties of the "Ga2O3 / metal / ... / metal / Ga2O3" composite structure; Step 8: Design a laser zone melting experiment by scanning the sample with a high-energy laser beam; Step 9: After laser zone melting, the structural and electrical properties of the "Ga2O3 / metal / ... / metal / Ga2O3" composite structure are tested using characterization equipment.

2. The method for doping metal atoms in gallium oxide material according to claim 1, characterized in that: Step 1 involves cleaning the substrate when selecting the substrate material. The cleaning method is as follows: Step 1.1: First, cut the sapphire substrate into 1×1cm pieces. 2 The square shape was placed in a polytetrafluoroethylene cleaning basket and rinsed with deionized water. Step 1.2: Next, ultrasonically clean the substrate in anhydrous ethanol, acetone, and anhydrous ethanol solutions for 15 minutes in sequence. Step 1.3: Rinse with deionized water, then dry with nitrogen and place in a nitrogen cabinet for later use.

3. The method for doping metal atoms in gallium oxide material according to claim 1, characterized in that: Step 2 describes the method for preparing β-Ga2O3 thin films on a substrate material using radio frequency magnetron sputtering, which specifically includes: Step 2.1: Place the cleaned sapphire substrate into an RF magnetron sputtering instrument, fix the oxygen and argon flow ratio, working pressure, sputtering power and deposition time of the magnetron sputtering, and only change the substrate temperature to obtain the optimal substrate temperature; Step 2.2, the same as step 2.1, are used to obtain the optimal magnetron sputtering process parameters. The optimal parameters are: substrate temperature 500℃, oxygen flow rate 2.3 sccm, argon flow rate 46.2 sccm, oxygen-argon ratio 2.3:46.2, working pressure 1.0 Pa, sputtering power 150 W, and deposition time 90 min.

4. The method for doping metal atoms in gallium oxide material according to claim 1, characterized in that: The specific method for doping in step 5 is as follows: first, a Ga2O3 thin film is sputtered on a sapphire substrate, then a metal thin film is sputtered on it, then another Ga2O3 thin film is sputtered, and so on, and finally a Ga2O3 thin film is sputtered on the surface to finish.

5. The method for doping metal atoms in gallium oxide material according to claim 4, characterized in that: The time for sputtering metal thin films must be less than the time for sputtering gallium oxide thin films.

6. The method for doping metal atoms in gallium oxide material according to claim 1, characterized in that: The method of laser zone melting experiment is as follows: the optical system focuses the laser, the powder feeding nozzle focuses the powder flow and makes the two focal points coincide. The focused laser melts the powder flow and the substrate. After cooling and solidification, a metallurgical bond is formed. The motion system realizes the relative movement between the substrate and the processing head, and finally realizes laser zone melting of the entire substrate surface.

7. The method for doping metal atoms in gallium oxide material according to claim 6, characterized in that: The laser energy, i.e., power, is sufficient to melt the β-Ga2O3 composite film, but the sapphire substrate does not melt.

Images