Gallium oxide film based on double masks and growth method thereof

Abstract

The invention discloses a gallium oxide thin film based on double masks 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. Utilizing a first mask on the substrate to select a growth region on the patterned buffer layer, and laterally growing epsilon-phase gallium oxide crystals on the growth region and then healing; and isolating the mixed domain part by using a second mask, and carrying out secondary growth on the exposed single domain part to obtain the high-quality single domain gallium oxide 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 first barrier layer is directly laid to shield the growth region, so that the preparation difficulty of the buffer layer can be simplified, and the problem that single-domain growth is finally influenced by disordered growth regions caused by unsatisfactory patterning of the buffer layer is avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor thin films, in particular to a gallium oxide thin film based on double masks and a growth method thereof. BACKGROUND

[0002] As a new material of the fourth generation of ultra-wide band gap semiconductors, gallium oxide has attracted extensive attention in the semiconductor industry due to its band gap width of up to ~4.5-4.9eV. Compared with the third generation of semiconductors, silicon carbide and gallium nitride, gallium oxide has a wider band gap, which means that gallium oxide has a broader application prospect in high pressure, high temperature, high power and radiation. The epsilon phase of gallium oxide is the second stable phase of gallium oxide material, which is different from the most stable beta phase of gallium oxide. The epsilon phase of gallium oxide has a spontaneous polarization effect. Theoretical calculation results show that the epsilon phase of gallium oxide can produce a high concentration of two-dimensional electron gas, which is expected to be higher than AlGaN / GaN heterojunction, and is a very potential material.

[0003] Since the epsilon phase of gallium oxide is a metastable phase, there is no means to grow single crystals, so the epsilon phase of gallium oxide can only be grown by heteroepitaxy. However, gallium oxide materials have a common problem of low thermal conductivity. As the first generation of semiconductors, silicon is the most widely used material in integrated circuits, which has good thermal conductivity. At the same time, the silicon substrate process is mature and the price is cheap, which can be widely used in the field of integrated circuits. The heteroepitaxy of the epsilon phase of gallium oxide on the silicon substrate not only solves the problem of thermal conductivity of gallium oxide materials itself to some extent, but also opens up a new field for the application of the epsilon phase of gallium oxide in the field of integrated circuits.

[0004] However, since the crystal of the epsilon phase of gallium oxide is an orthogonal structure with double symmetry, and the silicon (111) substrate has triple symmetry, the symmetry between the material itself and the substrate does not match, which will cause the epsilon phase of gallium oxide to produce three 120° rotation domains during heteroepitaxy. Research papers (Japanese Journal of Applied Physics, 57, 115601, 2018) have also confirmed the existence of 120° rotation domains. The existence of rotation domain problem makes the epsilon phase of gallium oxide always in a mixed domain state during growth, which seriously hinders the preparation of high-quality epsilon phase of gallium oxide single crystal thin film with single domain structure. Some people in the prior art have proposed a method (CN 116666196 A Non-rotation domain of kappa-Ga2O3 thin 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 the filtering of the rotation domain, and high-quality single crystal has not been obtained. On the other hand, it needs to be pointed out that more and more scholars in research work regard the epsilon phase and kappa phase as different names of a phase of gallium oxide. SUMMARY

[0005] The application aims to provide a double-mask-based gallium oxide film and a growth method thereof to solve the problems of the prior art.

[0006] The double-mask-based gallium oxide film comprises a buffer layer arranged on a substrate, a patterned first barrier layer arranged on the buffer layer, a mixed-domain epsilon-phase gallium oxide arranged on a window area of the first barrier layer, a second barrier layer arranged on an upper end surface of the mixed-domain epsilon-phase gallium oxide, and single-domain epsilon-phase gallium oxides grown on the outside of the mixed-domain epsilon-phase gallium oxide, above the first barrier layer, and above the second barrier layer.

[0007] The first barrier layer has a width of d1, and the window area has a width of w1.

[0008] The second barrier layer has a width of w2, and the interval between adjacent second barrier layers has a length of d2.

[0009] The mixed-domain epsilon-phase gallium oxide extends to the first barrier layer by a distance of L.

[0010] The dimensions satisfy the following relationships:

[0011] w1+d1=w2+d2;

[0012] w2>w1+2*L;

[0013] w1≤d1;

[0014] 50μm≥d1≥3μm.

[0015] The substrate is one of silicon (111) or silicon (100).

[0016] The buffer layer is arranged in parallel to the silicon <112 _ > or silicon <11 _ 0 crystal direction.

[0017] The buffer layer is AlN with a thickness of 1-100 nm.

[0018] The first barrier layer and / or the second barrier layer is silicon dioxide, metal, or silicon nitride.

[0019] The thickness of the second barrier layer is greater than 10 nm.

[0020] The growth method of the double-mask-based gallium oxide film comprises the following steps:

[0021] S1. Preparing a buffer layer on a substrate;

[0022] S2. Preparing a patterned first barrier layer on the buffer layer, wherein the first barrier layer exposes the buffer layer through window areas.

[0023] S3. growing gallium oxide crystal on the exposed buffer layer by using lateral epitaxy technology, and healing the grown gallium oxide crystal in the lateral zone; the corresponding gallium oxide crystal above the window region is a mixed domain crystal, and the mixed domain crystal extends laterally to the upper end face of the first barrier layer by a distance L; the gallium oxide crystal between adjacent mixed domain crystals is a single domain crystal;

[0024] S4. preparing a patterned second barrier layer above the mixed domain crystal; the second barrier layer completely covers the corresponding mixed domain crystal below;

[0025] S5. continuing to grow the gallium oxide crystal, and finally obtaining a gallium oxide thin film with the upper part being a single domain.

[0026] 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.

[0027] The temperature used for growing the gallium oxide crystal is between 500 DEG C and 800 DEG C.

[0028] The gallium oxide thin film and the growth method thereof have the advantages that the problem of rotation domain is solved while maintaining high-quality heteroepitaxy of epsilon phase gallium oxide, and the upper part of the thin film is a high-purity single domain crystal after the thin film is finally grown. The first barrier layer is directly laid to shield the growth area, which can simplify the preparation difficulty of the buffer layer and avoid the problem that the single domain growth is affected due to the disorder of the growth area caused by the non-ideal patterning of the buffer layer. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a structure diagram of the gallium oxide thin film.

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

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

[0032] Figure 4 is a flowchart of the growth method Figure 2 .

[0033] Figure 5 is a flowchart of the growth method Figure 3 .

[0034] Figure 6 is a flowchart of the growth method Figure 4 .

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

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

[0037] Figure 9 is a planar SEM characterization result diagram of a gallium oxide film described in the application.

[0038] Figure 10 is a TEM characterization result diagram of a gallium oxide film described in the application.

[0039] Figure 11 is a TEM characterization result diagram of a sample of the comparative example.

[0040] The figure reference: 100-substrate, 200-buffer layer, 301-mixed domain epsilon phase gallium oxide, 302-single domain epsilon phase gallium oxide, 401-first barrier layer, 402-second barrier layer. DETAILED DESCRIPTION

[0041] In order to realize the growth of high-quality epsilon phase gallium oxide single crystal thin film, the anisotropy of epsilon phase gallium oxide can be used to induce the appearance of local single domain structure, and then combined with lateral epitaxy technology, epsilon phase gallium oxide with complete single domain structure can be realized. Figure 1 、 Figure 2 As shown in the application, a gallium oxide film based on double mask is laid on the substrate 100 with a buffer layer 200, and the buffer layer 200 is laid with a patterned first barrier layer 401. The mixed domain epsilon phase gallium oxide 301 is provided on the window area of the first barrier layer 401. The second barrier layer 402 is laid on the upper end surface of the mixed domain epsilon phase gallium oxide 301. The single domain epsilon phase gallium oxide 302 is grown on the outside of the mixed domain epsilon phase gallium oxide 301, above the first barrier layer 401 and above the second barrier layer 402.

[0042] The width of the first barrier layer 401 is d1, and the window width is w1.

[0043] The width of the second barrier layer 402 is w2, and the interval between adjacent second barrier layers 402 is d2.

[0044] The distance of the lateral epitaxy of the mixed domain epsilon phase gallium oxide 301 to the first barrier layer 401 is L.

[0045] Each dimension satisfies the following relationship:

[0046] w1+d1=w2+d2.

[0047] w2>w1+2*L.

[0048] w1≤d1.

[0049] 50μm≥d1≥3μm.

[0050] 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 _ 0 crystal orientation.

[0051] The buffer layer 200 is AlN with a thickness of 1-100 nm. The first barrier layer 401 and / or the second barrier layer 402 is silicon dioxide or metal or silicon nitride. The second barrier layer 402 has a thickness greater than 10 nm, which ensures that the subsequent gallium oxide crystal growth will not be disturbed by the underlying mixed-domain crystal.

[0052] The gallium oxide thin film growth method based on double masks in the present application comprises the following steps:

[0053] S1. Preparing a buffer layer 200 on a substrate 100.

[0054] S2. Preparing a patterned first barrier layer 401 on the buffer layer 200, which uses an air window region to expose the buffer layer 200 at intervals, as shown in Figure 3 .

[0055] S3. Growing a gallium oxide crystal on the exposed buffer layer 200 using lateral epitaxy. The first gallium oxide crystal is grown above the air window region of the first barrier layer 401, as shown in Figure 4 . At this time, the crystal is a mixed-domain crystal, and the mixed-domain crystal extends laterally to the upper surface of the first barrier layer 401 by a distance L.

[0056] Continuing lateral epitaxy and healing the grown gallium oxide crystal in the lateral interval, as shown in Figure 5 . The gallium oxide crystal between adjacent mixed-domain crystals is a single-domain crystal.

[0057] The gallium source used for growing the gallium oxide crystal is one of trimethyl gallium, triethyl gallium, or gallium chloride. The oxygen source used is one or a mixture of more than one of oxygen, laughing gas, or water. The temperature used for growing the gallium oxide crystal is between 500°C and 800°C.

[0058] After many experiments, it was found that the size of the first barrier layer 401 has a direct relationship with the purification of the rotation domain and the healing of the crystal. Some data with representative significance are extracted and shown in the table below.

[0059]

[0060]

[0061] 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 be continuously 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 and does not contain single domain crystals even after healing. 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.

[0062] After detecting all the successfully prepared samples, it is found that as long as the single domain crystal can be grown, the one-side distance of the mixed domain crystal epitaxially grown on the first barrier layer 401 is generally 1-1.5 μm, which is independent of the thickness and material of the first barrier layer 401 and independent of the growth thickness of the gallium oxide. Therefore, when the width w2 of the subsequent second barrier layer 402 is selected, only the maximum value of L is needed, that is, w2 is slightly larger 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. 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 grown from the side of the mixed domain ε-phase gallium oxide 301 can be successfully healed.

[0063] S4. A patterned second barrier layer 402 is prepared above the mixed domain crystal. The second barrier layer 402 completely covers the corresponding mixed domain crystal below, as shown in Figure 6 、 Figure 7 、 Figure 8 .

[0064] S5. The gallium oxide crystal is continuously grown, and finally a gallium oxide thin film with the structure that the upper part is a single domain crystal, as shown in Figure 1 、 Figure 2 is obtained.

[0065] In the present application, the principle of spin domain filtering is realized by twice lateral epitaxial growth: the epsilon phase gallium oxide belongs to the orthorhombic structure, and due to the mismatch of its spin symmetry and the substrate, the epsilon phase gallium oxide is prone to appear triple spin domains. The first blocking layer 401 is patterned as a first mask to accurately select the buffer layer 200 region for the first epitaxial growth, so that the epsilon phase gallium oxide is epitaxially grown under the influence of spin domains. The mixed spin domains only appear in a controllable range slightly larger than the window region of the first blocking layer 401, and the remaining part is a type a domain region. After the first lateral epitaxial healing, the positions of the epsilon phase gallium oxide mixed domain region and the type a domain region are determined according to the patterned structure. The second blocking layer 402 is patterned as a second mask to effectively filter the epsilon phase gallium oxide spin domains. The window region of the second mask only leaves the growth surface of a single crystal domain, and then the second lateral epitaxial growth is carried out. The single crystal domain region and the double masks are used for epitaxial growth, so that a silicon-based epsilon phase gallium oxide single crystal thin film without spin domains is obtained.

[0066] The surface of the prepared sample is observed by a surface scanning electron microscope, and the result is shown in Figure 9 The surface of the sample prepared by two-step patterned mask is smooth, and the crystallinity is high. The sample is tested by a high-resolution transmission electron microscope, and the characterization result is shown in Figure 10 The grown epsilon phase gallium oxide single crystal lattice is arranged in order, and the selected area diffraction bright spot is a single domain epsilon phase gallium oxide diffraction spot. At this time, the silicon-based epsilon phase gallium oxide crystal quality is high by twice lateral epitaxial growth, the surface presents a step flow growth mode, and the in-plane 120° spin defect is eliminated.

[0067] The comparative example is different from the embodiment in that the second blocking layer 402 is not provided, and the gallium oxide crystal after healing is directly continued to grow. The prepared sample is tested by a cross-section high-resolution transmission electron microscope, and the structure is shown in Figure 11 The in-plane spin still exists in the grown thin film, the selected area diffraction bright spot is dark, and the secondary diffraction peak appears, proving that the sample at this time is still a multi-domain sample.

[0068] For those skilled in the art, other various corresponding changes and deformations can be made according to the above described technical solutions and concepts, and all these changes and deformations should belong to the protection scope of the claims of the present application.

Claims

1. A gallium oxide thin film based on a double mask, characterized in that, A buffer layer (200) is deposited on a substrate (100), and a patterned first barrier layer (401) is deposited on the buffer layer (200); mixed-domain ε-phase gallium oxide (301) is provided in the window area of ​​the first barrier layer (401); a second barrier layer (402) is deposited on the upper surface of the mixed-domain ε-phase gallium oxide (301); single-domain ε-phase gallium oxide (302) is grown on the outside of the mixed-domain ε-phase gallium oxide (301), above the first barrier layer (401), and above the second barrier layer (402); The width of the first barrier layer (401) is d1, and the width of the open window is w1; The width of the second barrier layer (402) is w2, and the interval between adjacent second barrier layers (402) is d2; The distance from the side of the mixed-domain ε-phase gallium oxide (301) to the first barrier layer (401) is L; Each dimension satisfies the following relationship: w1+d1=w2+d2; w2>w1+2*L; w1≤d1; 50μm≥d1≥3μm.

2. The gallium oxide thin film based on a double mask according to claim 1, characterized in that, The substrate (100) is either silicon (111) or silicon (100).

3. The gallium oxide thin film based on a double mask according to claim 2, characterized in that, The buffer layer (200) is arranged parallel to the silicon <112. _ >or silicon<11 _ 0> Crystal orientation.

4. The gallium oxide thin film based on a double mask according to claim 1, characterized in that, The buffer layer (200) is AlN with a thickness of 1-100 nm.

5. The gallium oxide thin film based on a double mask according to claim 1, characterized in that, The first barrier layer (401) and / or the second barrier layer (402) are silicon dioxide, metal, or silicon nitride.

6. The gallium oxide thin film based on a double mask according to claim 1, characterized in that, The thickness of the second barrier layer (402) is greater than 10 nm.

7. A method for growing a gallium oxide thin film as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1. A buffer layer (200) is prepared on a substrate (100); S2. A patterned first barrier layer (401) is prepared on the buffer layer (200), the first barrier layer (401) exposing the buffer layer (200) at intervals using window areas; S3. Gallium oxide crystals are grown on the exposed buffer layer (200) using lateral epitaxy, and the grown gallium oxide crystals are healed in the lateral region; the gallium oxide crystals corresponding to the empty window region are mixed domain crystals, and the mixed domain crystals extend laterally by a distance L to the upper end face of the first barrier layer (401); the gallium oxide crystals between adjacent mixed domain crystals are single domain crystals; S4. A patterned second barrier layer (402) is prepared above the mixed-domain crystal; the second barrier layer (402) completely covers the corresponding mixed-domain crystal below; S5. Continue growing gallium oxide crystals to finally obtain a gallium oxide thin film with single domains on the top.

8. The growth method according to claim 7, characterized in that, The gallium source used for gallium oxide crystal growth is one of trimethylgallium, triethylgallium, and gallium chloride; the oxygen source used is one or more of oxygen, nitrous oxide, and water.

9. The growth method according to claim 7, characterized in that, The temperature used for growing the gallium oxide crystal is between 500℃ and 800℃.

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