Method for regulating surface band bending of beta-gallium oxide by hydrogen plasma

Abstract

The application discloses a method for regulating surface band bending of beta-gallium oxide by hydrogen plasma, wherein the beta-Ga2O3 is cleaved under vacuum to study the band condition of the intrinsic beta-Ga2O3; meanwhile, the H2Plasma treatment and vacuum annealing treatment (RTA) of the method for regulating surface band bending of beta-gallium oxide by hydrogen plasma are both based on ultrahigh vacuum conditions, and the sample surface is maintained at the atomic level in a clean state through a vacuum transfer device, so that the interference of impurities in the treatment and transfer process is effectively avoided; meanwhile, the original band bending can be reduced through the H2 plasma treatment, and then the band bending can be restored to the state before the H2 plasma treatment through rapid annealing treatment, at this time, the oxygen vacancies can be further supplemented through O2 atmosphere annealing to adjust the band bending.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor material surface treatment, and particularly relates to a method for regulating surface band bending of beta-gallium oxide by hydrogen plasma. BACKGROUND

[0002] At present, the surface state of beta-Ga2O3 is just starting, and the adsorption and desorption process of the -OH group on the surface of beta-Ga2O3 is determined by different cleaning conditions and different sample states, and the coverage of the surface -OH group is closely related to the band bending of beta-Ga2O3.

[0003] Beta-Ga2O3 has unintentionally doped n-type conductivity, although the traditional view considers that O vacancies are the source of this conductivity, but the density functional theory (DFT) finds that oxygen vacancies are not shallow donors in Ga2O3, and considers that H may be the cause of n-type conductivity, but no corresponding confirmation has been obtained in experiments, and the existing technology currently lacks exploration of the intrinsic band bending of beta-Ga2O3, so that the internal correlation mechanism of the -OH group and the band bending of beta-Ga2O3 cannot be determined.

[0004] In the traditional experiments and technologies, the surface of beta-Ga2O3 is basically exposed in the atmosphere, and it is difficult to study the natural surface band of beta-Ga2O3 without impurity adsorption, and in the traditional technology, the transfer between the various treatments and characterizations of the surface of beta-Ga2O3 needs to be exposed in the atmosphere, and it is difficult to avoid contamination in the transfer process, and the adsorption of H2O on the surface may be the cause of the band bending of beta-Ga2O3.

[0005] Therefore, the prior art still needs to be improved and developed. SUMMARY

[0006] In view of the above problems in the prior art, the present application aims to provide a method for regulating the surface band bending of beta-gallium oxide by hydrogen plasma, and aims to solve the problem that the degree of surface band bending of beta-Ga2O3 cannot be controlled in the prior art.

[0007] The technical scheme of the present application is as follows:

[0008] A method for regulating the surface band bending of beta-gallium oxide by hydrogen plasma, comprising the following steps:

[0009] The beta-Ga2O3 is placed in a plasma treatment chamber under vacuum conditions, and hydrogen plasma treatment is performed to obtain H atom modified beta-Ga2O3, so as to realize the regulation of the surface band bending of beta-Ga2O3.

[0010] The method for regulating the surface band bending of beta-gallium oxide by hydrogen plasma, wherein the plasma power of the hydrogen plasma treatment is 5-450 W, and the treatment time is 5-60 min.

[0011] The method for regulating the surface band bending of beta-gallium oxide by hydrogen plasma, wherein after the step of obtaining the H atom modified beta-Ga2O3, the method further comprises the step of:

[0012] The H atom modified beta-Ga2O3 is transferred into an annealing furnace by a vacuum transfer device for vacuum annealing treatment, so as to restore the regulated surface band bending of beta-Ga2O3.

[0013] The method for regulating the surface band bending of beta-gallium oxide by hydrogen plasma, wherein the temperature of the vacuum annealing treatment is 400-1100 DEG C, and the time of the vacuum annealing treatment is 1-2 h.

[0014] The method for regulating the surface band bending of beta-gallium oxide by hydrogen plasma, wherein after the vacuum annealing treatment, the method further comprises the step of: performing oxygen annealing treatment on the beta-Ga2O3 in an oxygen atmosphere, supplementing oxygen vacancies, and adjusting the surface band bending of the beta-Ga2O3.

[0015] The method for regulating the surface band bending of beta-gallium oxide by hydrogen plasma, wherein the temperature of the oxygen annealing treatment is 400-1000 DEG C, and the time of the oxygen annealing treatment is 0.5-1.5 h.

[0016] The method for regulating the surface band bending of beta-gallium oxide by hydrogen plasma, wherein before the step of performing hydrogen plasma treatment, the method further comprises the step of:

[0017] The beta-Ga2O3 is placed in an XPS pretreatment chamber, under vacuum conditions, the beta-Ga2O3 is subjected to scratch treatment by a cutter, then is subjected to breaking by a lever in the XPS pretreatment chamber, so as to obtain a vacuum cleavage surface, and then the beta-Ga2O3 is transferred into the XPS chamber by the vacuum transfer device, so as to perform corner XPS test and valence band spectrum test, and determine the surface band bending of the beta-Ga2O3.

[0018] The method for regulating the surface band bending of beta-gallium oxide by hydrogen plasma, wherein the vacuum cleavage surface is a (100) surface.

[0019] The method for regulating the surface band bending of beta-gallium oxide by hydrogen plasma, wherein the beta-Ga2O3 is transferred into an XPS chamber by a vacuum transfer device for corner XPS test and valence band spectrum test after being treated by hydrogen plasma, and the change of the surface band bending of the beta-Ga2O3 before and after being treated by hydrogen plasma is obtained.

[0020] Beneficial effects: The application provides a method for regulating the surface band bending of beta-gallium oxide by hydrogen plasma, which studies the band condition of intrinsic beta-Ga2O3 by cleaving the beta-Ga2O3 in vacuum; meanwhile, the H2 Plasma treatment and vacuum annealing treatment (RTA) of the method for regulating the surface band bending of beta-gallium oxide by hydrogen plasma are both based on ultrahigh vacuum conditions, and the sample surface is maintained at the atomic level by being transferred into various characterization devices by a vacuum transfer device, so that the interference of impurities in the treatment and transfer process is effectively avoided; and the treatment process of H2 Plasma does not damage the surface of beta-Ga2O3, but only modifies the surface H atoms, and the band bending degree of the surface of beta-Ga2O3 can be controlled and regulated by the treatment process to meet the production requirements, which is very beneficial to explore the ohmic contact of beta-Ga2O3 devices. The original band bending can be reduced by H2 plasma treatment, and then the band bending can be restored to the state before H2 plasma treatment by rapid annealing treatment, at which time the oxygen vacancies can be further supplemented by O2 atmosphere annealing to adjust the band bending. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 Figure 1 is a schematic diagram of the cleavage process and XPS test of a beta-Ga2O3 (100) surface;

[0022] Figure 2 Figure 2 is a schematic diagram of the angle relationship between a beta-Ga2O3 (100) surface and a (-201) surface;

[0023] Figure 3 Figure 3 is a surface morphology diagram of a beta-Ga2O3 (100) cleavage surface, Figure 3 Figure 4 is an enlarged diagram of the surface morphology of a beta-Ga2O3 (100) cleavage surface;

[0024] Figure 4 Figure 5 is a schematic diagram of the surface atomic arrangement of a beta-Ga2O3 (100) surface;

[0025] Figure 5 Figure 6 is a diagram of the surface step height data of a beta-Ga2O3 (100) surface;

[0026] Figure 6 Figure 7 is a diagram of the O1s fine spectrum of a beta-Ga2O3 (100) UHV and air cleavage surface,Figure 6 Fig. 6 (b) is the O element peak separation spectrum of the β-Ga2O3(100) UHV cleavage surface, Figure 6 Fig. 6 (c) is the O element peak separation spectrum of the β-Ga2O3(100) Air cleavage surface;

[0027] Figure 7 Fig. 7 (a) is a comparison diagram of the valence band spectrum of the β-Ga2O3(100) UHV and Air cleavage surfaces, Figure 7 Fig. 7 (b) is a schematic diagram of the surface band bending,

[0028] Figure 8 Fig. 8 (a) is a corner XPS test diagram of the β-Ga2O3(-201) surface, Figure 8 Fig. 8 (b) is a diagram of the relationship between the Ga3d binding energy and the probe degree, Figure 8 Fig. 8 (c) is a diagram of the valence band spectrum test and fitting result,

[0029] Figure 9 Fig. 9 (a) is a corner XPS test diagram of the β-Ga2O3(-201) surface after H2 plasma action, Figure 9 Fig. 9 (b) is a diagram of the relationship between the Ga3d binding energy and the probe degree after H2 plasma action, Figure 9 Fig. 9 (c) is a diagram of the valence band spectrum test and fitting result after H2 plasma action, Figure 9 Fig. 9 (d) is a diagram of the change of the valence band spectrum before and after H2 plasma treatment,

[0030] Figure 10 Fig. 10 (a) is a diagram of the O1s peak separation and peak position change of the β-Ga2O3 bare chip, H2 plasma action and annealing temperature of 300℃, 400℃ and 600℃, Figure 10 Fig. 10 (b) is a diagram of the change of the valence band spectrum of the β-Ga2O3 bare chip, H2 plasma action and annealing temperature of 300℃, 400℃ and 600℃, Figure 10 Fig. 10 (c) is a diagram of the change of the valence band spectrum to the Fermi level spacing and the band bending of the β-Ga2O3 bare chip, H2 plasma action and annealing temperature of 300℃, 400℃ and 600℃. DETAILED DESCRIPTION

[0031] The present application provides a method for adjusting the surface band bending of β-gallium oxide by hydrogen plasma. In order to make the purpose, technical scheme and effect of the present application more clear and explicit, the present application will be further described in detail. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0032] In the embodiments and the claims, unless otherwise limited, the articles "a," "an," and "the" are also intended to include plural referents unless the context clearly indicates otherwise. The terms "first," "second," and the like, as used in the description and the claims, can be used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or an ordered sequence. Accordingly, a feature specified as "first" or "second" can implicitly include at least one of the other feature.

[0033] It should further be understood that the word "comprising" used in the specification of the application means that the features, integers, steps, operations, elements, and / or components that follow the word are present, but not excluding the presence or addition of one or more additional features, integers, steps, operations, elements, components, and / or groups thereof. The word "comprising" is used in the sense that "including" or "consisting of" is used in the specification and claims.

[0034] It should be understood by those skilled in the art that unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It should also be understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless specifically so defined in the specification and claims.

[0035] To verify that the upward band bending of the β-Ga2O3 surface is caused by the -OH groups on the surface, the present embodiment verifies it by cleaving β-Ga2O3 in vacuum and in air, and testing it by XPS and linear extrapolation of valence band spectra, specifically including the steps of:

[0036] A β-Ga2O3 single crystal sample is provided, which is subjected to scratch treatment (soft knife slicing, scratch depth 500 μm) in an XPS pretreatment chamber before being placed in the XPS cavity, and the scratch is made along the Figure 1 The vacuum (100) cleavage surface is obtained by using the operating rod in the XPS pretreatment chamber along the dotted line portion of Figure 2 As shown in (100) and (-201) crystal planes, the angle between the (100) surface and the (-201) crystal plane is 53.6°. As shown in Figure 3 The vacuum-cleaved (100) surface of β-Ga2O3 has an atomically flat surface, with a surface roughness RMS of only 0.055 nm, and the (100) surface atomic arrangement is as shown in Figure 4 Figure 5 ​The step height is approximately equal to the height of half a unit cell,

[0037] The test by XPS shows that the intensity of C is reduced in the ultra-high vacuum (UHV) cleavage compared with the air (Air) cleavage; the relative proportion of the surface -OH is reduced in the O1s spectrum, Figure 6 The distance between the valence band top and the Fermi level obtained by the linear extrapolation method of the valence band spectrum ( Figure 7 ) is 4.4 eV (Air cleavage sample) and 4.7 eV (UHV cleavage sample), and the band bending values obtained therefrom are +0.23 eV (Air cleavage) and -0.065 eV (UHV cleavage), respectively.

[0038] This reveals that the upward band bending of the β-Ga2O3 surface is caused by the -OH groups on the surface.

[0039] Based on this, the application provides a method for regulating the surface band bending of β-gallium oxide by hydrogen plasma, comprising the steps of:

[0040] The β-Ga2O3 is placed in a plasma processing chamber under vacuum conditions for hydrogen plasma treatment to obtain H atom modified β-Ga2O3, thereby regulating the surface band bending of the β-Ga2O3.

[0041] In this embodiment, the original band bending of the β-Ga2O3 is reduced by hydrogen plasma treatment, and then the band bending can be restored to the state before the H2 plasma treatment by rapid vacuum annealing treatment, thereby realizing reversible regulation of the surface band bending of the β-Ga2O3. And the H2 plasma treatment and vacuum annealing treatment in the regulation method are both carried out under ultra-high vacuum conditions, transferred to various characterization devices by a vacuum transfer device, maintaining the cleanliness of the sample surface at the atomic level, effectively avoiding the interference of impurities in the process of treatment and transfer, while the treatment process of the H2 plasma has no damage to the surface of the β-Ga2O3, but only a surface H atom modification process, which can controllably regulate the degree of band bending of the surface of the β-Ga2O3 to meet the production requirements.

[0042] Specifically, the free -OH adsorbed on the surface of β-Ga2O3 will cause upward band bending; H and oxygen vacancies will form downward band bending. Taking the β-Ga2O3 (100) surface cleaved in vacuum as an example, the (100) surface has 2% -OH bonds and oxygen vacancies; while the sample not cleaved in vacuum has 10% -OH, which causes upward band bending (+0.23 eV); the -OH concentration of the sample cleaved in vacuum decreases to 2%, and due to the effect of oxygen vacancies being higher than that of -OH, it changes from upward to downward band bending (-0.065 eV), which shows that vacuum cleavage can modulate the degree of band bending; when the β-Ga2O3 is treated by hydrogen plasma, after the neutralization of H and -OH, the remaining H combines with the oxygen in Ga2O3, which is different from the adsorbed -OH ions, and its effect on band bending is opposite to that of the adsorbed free -OH; then when the β-Ga2O3 treated by hydrogen plasma is treated by RTA, H desorbs, takes away a certain amount of oxygen in Ga2O3, and returns to the surface with a certain amount of oxygen vacancies, so that the band bending is restored, realizing the reversible regulation of the surface band bending of β-Ga2O3.

[0043] Again taking the β-Ga2O3 (-201) surface as an example, because the (-201) surface is not a cleaved surface, it cannot be cleaved. The corner XPS test and valence band spectrum test (as shown in Figure 8 ) are performed on the (-201) surface β-Ga2O3 to determine that the surface band bending is +0.74 eV; the initial upward band bending of the β-Ga2O3 (-201) surface is (+1.15 eV), and after H2 plasma treatment, a part of H and -OH neutralize, and the upward band bending is weakened to +0.45 eV (as shown in Figure 9 ); then it is transferred to a rapid annealing furnace by a vacuum transfer device for RTA treatment at different temperatures (the treatment temperatures are 300°C, 400°C and 600°C respectively), and H desorbs, and Figure 10 it can be seen from the above that when the vacuum annealing temperature reaches 400°C or above, the band bending is restored to the initial band bending range (+1.0 eV). Since the remaining -OH concentration is less than the initial value, the amount of restored band bending is slightly less than the initial amount of band bending. This proves that the surface band bending of β-Ga2O3 can be reversibly regulated by H2 plasma treatment and RTA treatment.

[0044] In some embodiments, the vacuum transfer device can be, but is not limited to, a vacuum interconnection pipeline, a vacuum suitcase, and a vacuum sample box.

[0045] In some embodiments, the Plasma power of the hydrogen plasma treatment is 5-450 W, and the treatment time is 5-60 min. Through the hydrogen plasma treatment, the remaining H combines with the oxygen in Ga2O3 after the neutralization of H and -OH, weakening the band bending. Moreover, the hydrogen plasma treatment only modifies the surface in this embodiment, and almost no damage occurs because the atomic radius of H atom is very small.

[0046] In some embodiments, the H2 plasma treatment can be replaced by NH3 plasma treatment, which can also achieve the same effect.

[0047] In some embodiments, after the step of obtaining the H atom modified β-Ga2O3, the method further comprises the step of: transferring the H atom modified β-Ga2O3 to an annealing furnace through a vacuum transfer device for vacuum annealing treatment, so as to restore the surface band bending of the regulated β-Ga2O3.

[0048] In some embodiments, the temperature of the vacuum annealing treatment is 400-1100 °C, and the time of the vacuum annealing treatment is 1-2 h. Through the vacuum annealing treatment, the H2O formed by the neutralization of H and -OH during the H2 plasma treatment can be evaporated, and the H combined with the oxygen in Ga2O3 can be desorbed, taking away some oxygen in Ga2O3 to the surface with a certain oxygen vacancy, so as to restore the band bending and realize the reversible regulation of the surface band bending of β-Ga2O3.

[0049] In some embodiments, after the vacuum annealing treatment, the β-Ga2O3 is subjected to oxygen annealing treatment in an oxygen atmosphere to supplement the oxygen vacancy and adjust the band bending of the β-Ga2O3. Thus, the surface band bending of the β-Ga2O3 can be controllably regulated according to the production requirements.

[0050] In some embodiments, the temperature of the oxygen annealing treatment is 400-1000 °C, and the time of the vacuum annealing treatment is 0.5-1.5 h.

[0051] In some embodiments, before the step of performing the hydrogen plasma treatment, the method further comprises the step of:

[0052] In the XPS pretreatment chamber, the β-Ga2O3 is subjected to scratch treatment by a knife, and then is subjected to breaking treatment by a lever in the XPS pretreatment chamber to obtain a vacuum cleavage surface. Then, the β-Ga2O3 is transferred to the XPS chamber through the vacuum transfer device for corner XPS test and valence band spectrum test to determine the surface band bending of the β-Ga2O3.

[0053] The intrinsic surface energy band of the beta-Ga2O3 is measured by cleaving the (100) surface of the beta-Ga2O3 in a pre-treatment chamber of XPS under an ultra-high vacuum environment, so as to avoid contamination caused by the atmosphere.

[0054] In some embodiments, the tool is a diamond knife or the like capable of making surface scratches.

[0055] In some embodiments, the vacuum cleaved surface is a (100) surface, which is a natural cleaved surface of the beta-Ga2O3.

[0056] In some embodiments, when the vacuum transfer device is a vacuum interconnection pipeline, the XPS pre-treatment chamber, the XPS chamber, the plasma treatment chamber and the annealing furnace are sequentially connected by the vacuum interconnection pipeline; contamination caused by exposure to the atmosphere during the transfer process is avoided, the sample surface is maintained at the atomic level, and the interference of impurities during the treatment and transfer process is effectively avoided.

[0057] In some embodiments, the beta-Ga2O3 is transferred to the XPS chamber by the vacuum transfer device after being treated by the hydrogen plasma, and then corner XPS testing and valence band spectrum testing are performed to obtain the change in the surface energy band bending of the beta-Ga2O3 before and after the hydrogen plasma treatment.

[0058] In summary, the present application provides a method for adjusting the surface energy band bending of beta-gallium oxide by hydrogen plasma, which cleaves the beta-Ga2O3 in a vacuum to study the energy band of the intrinsic beta-Ga2O3; at the same time, the H2 Plasma treatment and the vacuum annealing treatment (RTA) of the method for adjusting the surface energy band bending of beta-gallium oxide by hydrogen plasma are both based on an ultra-high vacuum condition, and the vacuum transfer device is used to transfer the sample to various characterization devices, so as to maintain the cleanliness of the sample surface at the atomic level and effectively avoid the interference of impurities during the treatment and transfer process; and the treatment process of the H2 Plasma does not cause damage to the surface of the beta-Ga2O3, but only modifies the surface H atoms, and the treatment by the method can controllably adjust the degree of the energy band bending of the beta-Ga2O3 surface to meet the production requirements, which is very beneficial to the exploration of ohmic contact of beta-Ga2O3 devices. The original energy band bending can be reduced by the H2 plasma treatment, and then the energy band bending can be restored to the state before the H2 plasma treatment by the rapid annealing treatment, and at this time, the oxygen vacancies can be further supplemented by O2 atmosphere annealing to adjust the energy band bending.

[0059] It should be understood that the application of the present application is not limited to the above examples, and those skilled in the art can make improvements or changes according to the above description, and all these improvements and changes shall belong to the protection scope of the appended claims of the present application.

Claims

1. A method for controlling the bending of the energy bands on the surface of β-gallium oxide using hydrogen plasma, characterized in that, Including the following steps: The β-Ga2O3 was placed in a plasma processing chamber under vacuum conditions and subjected to hydrogen plasma treatment to obtain H-atom modified β-Ga2O3, thereby achieving the control of the surface band bending of β-Ga2O3. The H-atom-modified β-Ga2O3 was transferred to an annealing furnace via a vacuum transfer device for vacuum annealing to restore the regulated surface band bending of β-Ga2O3. After the vacuum annealing treatment, the method further includes the step of: performing oxygen annealing treatment on the β-Ga2O3 in an oxygen atmosphere to replenish oxygen vacancies and adjust the surface band bending of the β-Ga2O3. The plasma power of the hydrogen plasma treatment is 5~450W, and the treatment time is 5~60min; the temperature of the vacuum annealing treatment is 400~1100℃, and the vacuum annealing treatment time is 1~2h; the temperature of the oxygen annealing treatment is 400~1000℃, and the oxygen annealing treatment time is 0.5~1.5h.

2. The method for controlling the bending of the energy bands on the surface of β-gallium oxide using hydrogen plasma according to claim 1, characterized in that, Before the hydrogen plasma treatment step, the method further includes the following step: The β-Ga2O3 was placed in an XPS pretreatment chamber. Under vacuum conditions, the β-Ga2O3 was scratched using a tool. Then, it was broken off using an operating rod in the XPS pretreatment chamber to obtain a vacuum cleavage surface. The surface was then transferred to the XPS chamber via a vacuum transfer device for corner XPS testing and valence band spectroscopy testing to determine the surface band curvature of the β-Ga2O3.

3. The method for controlling the bending of the energy bands on the surface of β-gallium oxide using hydrogen plasma according to claim 2, characterized in that, The vacuum cleavage surface is the (100) surface.

4. The method for controlling the bending of the β-gallium oxide surface bands using hydrogen plasma according to claim 2, characterized in that, After being treated with hydrogen plasma, the β-Ga2O3 was transferred to an XPS chamber via a vacuum transfer device for angular XPS testing and valence band spectroscopy testing, thereby obtaining the changes in surface band bending of the β-Ga2O3 before and after hydrogen plasma treatment.

Images