Gallium oxide film based on single mask and growth method thereof

Abstract

The invention discloses a gallium oxide thin film based on a single mask and a growth method thereof, relates to a semiconductor thin film technology, and provides the scheme aiming at the problem that a high-quality single-domain gallium oxide thin film is lacked in the prior art. Arranging a buffer layer on the substrate, and laterally growing epsilon-phase gallium oxide crystals on the buffer layer and healing the epsilon-phase gallium oxide crystals; and isolating the mixed domain part by using the barrier layer, and carrying out secondary growth on the exposed single domain part to obtain the high-quality single domain gallium oxide thin film. The method has the advantages that the problem of rotation domain can be solved while high-quality epsilon-phase gallium oxide heteroepitaxy is maintained. And after the film finally grows, the upper part of the film is a high-purity single domain crystal. The substrate does not need to be prevented from being damaged deliberately, and the working difficulty is greatly reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor thin films, and particularly relates to a single-masked gallium oxide thin film and a growth method thereof. BACKGROUND

[0002] As an emerging ultra-wide bandgap semiconductor material, gallium oxide material is a strong candidate material in the fields of high-power devices, high-temperature and high-voltage devices. Among them, ε-Ga2O3 can theoretically produce a high concentration of two-dimensional electron gas, and is expected to replace AlGaN / GaN heterojunction, so it has attracted widespread attention from scholars.

[0003] However, since the ε phase gallium oxide is a metastable phase, there is a lack of means to grow single crystals, so high-quality ε-Ga2O3 single crystals cannot be obtained by homoepitaxy, and can only be grown by heteroepitaxy. Commonly used heteroepitaxial materials include Si(111), sapphire (Al2O3) substrates. However, since the ε phase gallium oxide belongs to the orthorhombic structure and has two-fold symmetry, while the silicon (111) substrate has three-fold symmetry, the symmetry between the material itself and the substrate does not match, resulting in the formation of three-fold rotation domains of ε phase gallium oxide during growth. The b-type domain and the c-type domain are rotated by +120° and -120°, respectively, relative to the a-type domain. Research papers (Japanese Journal of Applied Physics, 59(11), 115501, 2020) have also confirmed the existence of 120° rotation domains.

[0004] The existence of the rotation domain problem seriously hinders the preparation of high-quality ε phase gallium oxide single crystal thin films with a single domain structure. Moreover, there is a large lattice mismatch between ε-Ga2O3 and Si(111) substrate (~ 24.2%), and a layer of amorphous oxide layer is easily formed on the surface of the Si substrate, which makes it impossible to directly realize heteroepitaxy of ε-Ga2O3 on the Si substrate. In order to solve the above problems, the anisotropy of ε phase gallium oxide can be used to induce the appearance of local single domain structure, and then combined with lateral epitaxy technology, ε phase gallium oxide single crystal thin film with complete non-rotation domain can be realized.

[0005] Traditional lateral epitaxy needs to prepare two layers of patterned masks, and often needs to be etched when making the patterned mask, and the aluminum nitride buffer layer for growth will be damaged during etching, thus affecting the subsequent heteroepitaxial growth, thereby affecting the crystal quality of heteroepitaxy. Some people in the prior art have proposed a method (CN 116666196A Non-rotating domain of kappa-Ga2O3 film and preparation method of kappa-(AlxGa1-x)2O3 / kappa-Ga2O3 heterojunction), which directly grows on the substrate. The sample can only achieve a small part of filtering of the rotating domain, and a high-quality single-domain crystal has not been obtained. On the other hand, it needs to be pointed out that more and more scholars in research work regard epsilon phase and kappa phase as different names of gallium oxide. SUMMARY

[0006] The present application aims to provide a single-masked gallium oxide film and a growth method thereof to solve the problems existing in the prior art.

[0007] The single-masked gallium oxide film in the present application is provided with a plurality of buffer layers on a substrate; the width of the buffer layer is w1, and the spacing between adjacent buffer layers is d1; mixed domain epsilon phase gallium oxide is grown on the buffer layer; the single-side epitaxial distance of the mixed domain epsilon phase gallium oxide on the corresponding buffer layer is L; a barrier layer for growing the corresponding mixed domain epsilon phase gallium oxide is arranged above each mixed domain epsilon phase gallium oxide; the width of the barrier layer is w2, and the spacing between adjacent barrier layers is d2; single-domain epsilon phase gallium oxide is grown on the outside of the mixed domain epsilon phase gallium oxide and above the barrier layer;

[0008] Each dimension satisfies the following relationship:

[0009] w1+d1=w2+d2;

[0010] w2>w1+2*L;

[0011] w1≤d1;

[0012] 50μm≥d1≥3μm.

[0013] The substrate is one of silicon (111) or silicon (100).

[0014] The arrangement direction of the buffer layer is parallel to the silicon <112 _ > or silicon <11 _ 0 crystal direction.

[0015] The buffer layer is AlN.

[0016] The barrier layer is silicon dioxide.

[0017] The thickness of the barrier layer is greater than 10nm.

[0018] The gallium oxide thin film growth method based on a single mask in the application comprises the following steps:

[0019] S1. A patterned buffer layer is arranged on a substrate;

[0020] S2. A gallium oxide crystal is grown on the buffer layer by using a lateral epitaxy technique, and the gallium oxide crystal grown on each buffer layer is healed in a lateral interval;

[0021] S3. A patterned barrier layer is arranged on the healed gallium oxide crystal; the barrier layer is adapted to the underlying buffer layer in shape and vertical position; and the width w2 of the barrier layer is greater than w1+2*L;

[0022] S4. The gallium oxide crystal is continuously grown, and finally a gallium oxide thin film with a single domain in the upper part is obtained.

[0023] The patterned etching treatment of the buffer layer reaches a depth below the substrate surface.

[0024] The gallium source used for growing the gallium oxide crystal is one of trimethyl gallium, triethyl gallium and gallium chloride; and the oxygen source is one or a mixture of multiple of oxygen, laughing gas and water.

[0025] The temperature used for growing the gallium oxide crystal is between 500-800℃.

[0026] The gallium oxide thin film based on a single mask and the growth method thereof in the application have the following technical advantages:

[0027] (1) The problem of rotation domain is solved while maintaining high-quality ε-phase gallium oxide heteroepitaxy. The upper part of the thin film after final growth is ensured to be a single-domain crystal with high purity.

[0028] (3) The technical defect that the etching of the substrate and / or the buffer layer is damaged, thereby affecting the crystalline quality of heteroepitaxy, is avoided in the prior art. In the application, the substrate is not intentionally damaged, which greatly reduces the work difficulty. Even to improve the specified position of crystal growth, the substrate surface is intentionally etched sufficiently to avoid interference with the growth position when growing on the patterned buffer layer. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a structural schematic diagram of the gallium oxide thin film in the application.

[0030] Figure 2 is Figure 1 a sectional view in A-A direction of

[0031] Figure 3 is a flowchart of the growth method in the application Figure 1 .

[0032] Figure 4 is a flowchart of the growth method described in the present application Figure 2 .

[0033] Figure 5 is a flowchart of the growth method described in the present application Figure 3 .

[0034] Figure 6 is a flowchart of the growth method described in the present application Figure 4 .

[0035] Figure 7 is a sectional view of the state shown in Figure 6 .

[0036] Figure 8 is a partial enlarged view of Figure 7 .

[0037] Figure 9 is a cross-sectional SEM characterization result graph of the state shown in Figure 5 , wherein the SEM scanning direction is the same as the y-axis direction in Figure 1 .

[0038] Figure 10 is a planar SEM characterization result graph of a gallium oxide film described in the present application, wherein the SEM scanning direction is opposite to the z-axis direction in Figure 1 .

[0039] Figure 11 is a planar SEM characterization result graph of a gallium oxide film of a comparative example, wherein the SEM scanning direction is the same as Figure 10 .

[0040] Reference signs: 100 - substrate, 200 - buffer layer, 301 - mixed domain ε-phase gallium oxide, 302 - single domain ε-phase gallium oxide, 400 - barrier layer. DETAILED DESCRIPTION

[0041] As shown in Figure 1 , Figure 2 , a gallium oxide film structure based on a single mask described in the present application is as follows: a plurality of buffer layers 200 are arranged on a substrate 100. The width of the buffer layer 200 is w1, and the spacing between adjacent buffer layers 200 is d1. Mixed domain ε-phase gallium oxide 301 is grown on the buffer layer 200. The mixed domain ε-phase gallium oxide 301 is unilaterally epitaxial on the corresponding buffer layer 200 with a distance of L. A barrier layer 400 corresponding to each mixed domain ε-phase gallium oxide 301 is arranged above each mixed domain ε-phase gallium oxide 301 to prevent the growth of the mixed domain ε-phase gallium oxide 301. The width of the barrier layer 400 is w2, and the spacing between adjacent barrier layers 400 is d2. Single domain ε-phase gallium oxide 302 is grown on the outside of the mixed domain ε-phase gallium oxide 301 and above the barrier layer 400.

[0042] Each dimension satisfies the following relationship:

[0043] w1+d1=w2+d2;w2>w1+2*L;w1≤d1;50μm≥d1≥3μm.

[0044] In one embodiment, the substrate 100 is one of silicon (111) or silicon (100). The buffer layer 200 is arranged in a direction parallel to the silicon <112 _ >or silicon <11 _ 0crystal orientation.

[0045] The buffer layer 200 is AlN. The barrier layer 400 is silicon dioxide. The thickness of the barrier layer 400 is greater than 10 nm, which ensures that the subsequent gallium oxide crystal growth will not be disturbed by the underlying mixed-domain ε-phase gallium oxide 301.

[0046] The gallium oxide thin film growth method based on a single mask in the present application comprises the following steps:

[0047] S1. A patterned buffer layer 200 is provided on the substrate 100, as shown in FIG. 1. In the technical solution disclosed in the present patent, those skilled in the art can easily think of setting the patterned buffer layer 200 as a number of strip-shaped structures extending inwards, or concentric circular structures spaced apart from each other, or matrix structures distributed in an array, and so on. Figure 3

[0048] S2. Gallium oxide crystals are grown on the buffer layer 200 using lateral epitaxy technology, obtaining a structure as shown in FIG. 2. At this time, the crystals are mixed-domain ε-phase gallium oxide 301. Then the gallium oxide crystals are continuously grown, and the gallium oxide crystals grown on each buffer layer 200 are healed in the lateral interval, as shown in FIG. 3. At this time, the crystals between the phase mixed-domain ε-phase gallium oxide 301 are single-domain ε-phase gallium oxide 302. Figure 4 Figure 5 The gallium source used for the growth of the gallium oxide crystals is one of trimethyl gallium, triethyl gallium, and gallium chloride. The oxygen source used is one or a mixture of more than one of oxygen, laughing gas, and water. The temperature used for the growth of the gallium oxide crystals is between 500°C and 800°C.

[0049] After many experiments, it is found that the size of the buffer layer 200 has a direct relationship with the purification of the rotation domain and the healing of the crystals. Some data with representative significance are extracted and shown in the following table.

[0050] Sample w1 (pm) d1 (pm) w1 + d1 (pm) Patterning conditions Experimental results 1 5 25 30 w1 < d1 ; 50 μm ≥ d1 ≥ 3 μm Monodomain 2 15 15 30 w1 = d1 ; 50 pm > d1 > 3 pm Monodomain 3 1 3 4 w1 < d1 ; d1 = 3 μm Monodomain 4 30 50 80 w1 < d1 ; d1 = 50 μm Monodomain 5 25 5 30 w1 > d1 ; 50 pm > d1 > 3 pm Mixed domain 6 2 2.5 4.5 w1 < d1 ; d1 < 3 μm Mixed domain 7 5 60 65 w1 < d1 ; d1 > 50 μm Not healable 8 65 60 125 w1 > d1 ; d1 > 50 pm Not healable

[0051] ​​The experimental result "single domain" in the table means that after the mixed domain ε-phase gallium oxide 301 is grown on the buffer layer 200, the single domain ε-phase gallium oxide 302 can continue to be grown outside the mixed domain ε-phase gallium oxide 301 and can be healed, which is the target result of the patent. The experimental result "mixed domain" means that the gallium oxide crystal grown on the buffer layer 200 only contains mixed domain crystals after healing and does not contain single domain crystals. The experimental result "unable to heal" means that the gallium oxide crystal grown on the buffer layer 200 cannot be healed, and the sample preparation fails.

[0052] After detecting all the samples prepared successfully, it is found that as long as the single domain crystal can be grown, the single side distance of the mixed domain crystal epitaxially grown out of the buffer layer 200 is generally 1-1.5 μm, which is independent of the thickness of the buffer layer 200 and the growth thickness of the gallium oxide. Therefore, when the width w2 of the subsequent barrier layer 400 is selected, only the maximum value L is taken, that is, the value of w2 is slightly greater than w1+2*L, which can ensure that the mixed domain ε-phase gallium oxide 301 is completely covered, and the process operation is facilitated. Corresponding to sample 6 in the above table, the total width of the mixed domain grown laterally at both ends is close to or equal to 3 μm, and when d1 is not set enough, the lateral growth width is too small, thereby affecting the growth of the single domain, and the final result is the mixed domain. When d1 is greater than 50 μm, such as samples 7 and 8, the distance is too large, which affects the lateral epitaxial process, so that the sample is difficult to heal.

[0053] From the above table, it can be seen that as long as the relationship of w1≤d1; 50 μm≥d1≥3 μm is met, the single domain ε-phase gallium oxide 302 can be grown from the side surface of the mixed domain ε-phase gallium oxide 301 and successfully healed. The lateral epitaxial growth result after healing is observed by a scanning electron microscope, and the characterization result is shown in Figure 9 , which shows that the surface of the first lateral epitaxy can be completely healed. Since the thickness of the buffer layer 200 is generally in the scale of tens to hundreds of nanometers, the buffer layer 200 in Figure 9 cannot be distinguished by the naked eye.

[0054] S3. A patterned barrier layer 400 is arranged on the healed gallium oxide crystal. The shape and vertical position of the barrier layer 400 are adapted to the buffer layer 200 below. And the width w2 of the barrier layer 400 is greater than w1+2*L, as shown in Figure 6 , Figure 7 and Figure 8 .

[0055] S4. Continue to grow the gallium oxide crystal, and finally obtain the gallium oxide thin film with the upper part being single domain, as shown in Figure 1 and Figure 2 . The surface of the finally prepared sample is observed by a scanning electron microscope, and the characterization result is shown in Figure 10As shown, it is shown that the surface of the epsilon phase gallium oxide single crystal thin film prepared by lateral epitaxy is flat, the grown epsilon phase gallium oxide filters the influence of the rotation domain, and the surface morphology presents a growth mode of step flow.

[0056] In the present application, the principle of realizing rotation domain filtering by twice lateral epitaxial growth is as follows: the epsilon phase gallium oxide belongs to an orthogonal structure, and due to the mismatch of its rotation symmetry and the substrate, the epsilon phase gallium oxide is prone to appear triple rotation domains. By performing the first lateral epitaxy on the patterned buffer layer 200, the epsilon phase gallium oxide is subjected to epitaxial growth under the influence of the rotation domain. The mixed rotation domain is allowed to appear only in a controllable range slightly larger than the width of the buffer layer 200, and the remaining part is a type a domain area. Based on the healing after the first lateral epitaxy, the positions of the epsilon phase gallium oxide mixed domain area and the type a domain area are determined according to the patterned structure. Then, the patterned barrier layer 400 is prepared as a growth mask to effectively filter the epsilon phase gallium oxide rotation domain, and the window area of the mask only leaves the growth surface of the crystal domain, and then the second lateral epitaxial growth is performed, that is, the epitaxial growth is performed based on the single crystal domain area and the single mask, so that a silicon-based epsilon phase gallium oxide single crystal thin film without rotation domain is obtained.

[0057] Further, in order to improve the quality of the single crystal domain, the patterned etching treatment depth of the buffer layer 200 reaches the surface of the substrate 100 in step S1. The AlN in the blank area needs to be completely removed, and the AlN pattern area is completely retained. Then, the growth of the first lateral epitaxial layer of the epsilon phase gallium oxide is performed, so that the epsilon phase gallium oxide can be grown on the etched AlN surface, which can avoid the orientation disorder of the epsilon phase gallium oxide epitaxial growth, and the epsilon phase gallium oxide grown on the AlN pattern area can grow normally. As a comparison, the etching depth is set to not reach the inside of the substrate when the buffer layer 200 is patterned. Then, the first layer of epsilon phase gallium oxide is subjected to lateral epitaxial growth. As shown in Figure 11 As shown, the SEM observation of the surface of the finally prepared sample shows that when the etching depth is not accurately controlled, the buffer layer patterning is poor, and the lateral epitaxial growth causes the crystal structure of the epsilon phase gallium oxide to be damaged, which seriously affects the preparation of the epsilon phase gallium oxide single crystal.

[0058] For those skilled in the art, other various corresponding changes and modifications can be made according to the above described technical solutions and concepts, and all of these changes and modifications should belong to the protection scope of the claims of the present application.

Claims

1. A single-mask-based gallium oxide thin film, characterized by, A plurality of buffer layers (200) are arranged on a substrate (100); the width of the buffer layer (200) is w1, and the interval between adjacent buffer layers (200) is d1; a mixed-domain ε-phase gallium oxide (301) is grown on the buffer layer (200); the single-side epitaxial distance of the mixed-domain ε-phase gallium oxide (301) on the corresponding buffer layer (200) is L; a barrier layer (400) corresponding to the growth of the mixed-domain ε-phase gallium oxide (301) is arranged above each mixed-domain ε-phase gallium oxide (301); the width of the barrier layer (400) is w2, and the interval between adjacent barrier layers (400) is d2; a single-domain ε-phase gallium oxide (302) is grown on the outside of the mixed-domain ε-phase gallium oxide (301) and above the barrier layer (400); The dimensions satisfy the following relationships: w1+d1=w2+d2; w2>w1+2*L; w1≤d1; 50μm≥d1≥3μm.

2. The single-mask based gallium oxide thin film of claim 1, wherein, The substrate (100) is one of silicon (111) or silicon (100).

3. The single mask based gallium oxide thin film of claim 2, wherein, The buffer layer (200) is arranged in a direction parallel to the silicon <112 _ > or silicon <11 _ 0 crystal orientation.

4. The single-mask based gallium oxide film of claim 1, wherein, The buffer layer (200) is AlN.

5. The single mask based gallium oxide thin film of claim 1, wherein, The barrier layer (400) is silicon dioxide.

6. The single-mask based gallium oxide film of claim 5, wherein, The thickness of the barrier layer (400) is greater than 10nm.

7. A growth method for growing the gallium oxide thin film according to any one of claims 1 to 6, characterized by, The method comprises the following steps: S1. A patterned buffer layer (200) is arranged on a substrate (100); S2. A gallium oxide crystal is grown on the buffer layer (200) by using a lateral epitaxial technology, and the gallium oxide crystal grown on each buffer layer (200) is healed in the lateral interval; S3. A patterned barrier layer (400) is arranged on the healed gallium oxide crystal; the shape and vertical position of the barrier layer (400) are matched with the underlying buffer layer (200); and the width w2 of the barrier layer (400) is greater than w1+2*L; S4. The gallium oxide crystal is continuously grown, and a gallium oxide thin film with a single domain on the upper part is finally obtained.

8. The growth method of claim 7, wherein, In the step S1, the patterned buffer layer (200) is etched to a depth below the surface of the substrate (100).

9. The growth method of claim 7, wherein, The gallium source used for growing the gallium oxide crystal is one of trimethyl gallium, triethyl gallium, and gallium chloride; and the oxygen source is one or a mixture of more than one of oxygen, laughing gas, and water.

10. The growth method of claim 7, wherein, The temperature used for growing the gallium oxide crystal is between 500℃ and 800℃.

Images