Epitaxial configuration
By employing a controlled growth process with alternating gas introduction and high-temperature conditions, the method addresses the issue of poor nucleation layer quality in HEMTs, resulting in improved nitride epitaxial layer quality in HEMTs.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- GLOBALWAFERS CO LTD
- Filing Date
- 2026-04-22
- Publication Date
- 2026-07-29
AI Technical Summary
The challenge in High Electron Mobility Transistors (HEMTs) is to achieve a nucleation layer with good epitaxial quality to facilitate smooth two-dimensional growth on substrates with mismatched crystal lattices, which affects the overall quality of the epitaxial layer.
A method involving multiple growth steps with alternating gas introduction and cessation, using an aluminum-containing gas and nitrogen-containing gas, at controlled high temperatures and pressures, to form a nucleation layer with specific thickness and properties, followed by growing a nitride epitaxial layer.
The method results in a nitride epitaxial layer with improved epitaxial quality, as indicated by reduced full width at half maximum (FWHM) of the (002) crystal plane and lower dislocation defect density, enhancing the overall epitaxial structure.
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Figure 2026123130000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to an epitaxial structure, and particularly to an epitaxial structure having good epitaxial quality.
Background Art
[0002] A known High Electron Mobility Transistor (HEMT) is a transistor having a two-dimensional electron gas (2-DEG). The two-dimensional electron gas is close to the hetero-junction surface in two types of materials having different band gaps. Since the high electron mobility transistor uses the two-dimensional electron gas with high electron mobility as the carrier channel of the transistor without using the doping region as the carrier channel of the transistor, it has characteristics such as a high breakdown voltage, a high electron mobility, a low on-resistance, and a low input capacitance, and is widely applied to high-power semiconductor devices.
[0003] In order to alleviate the problem that the crystal lattice of the epitaxial layer and the substrate cannot match, and to promote the smooth two-dimensional growth of the epitaxial layer above the substrate, it is common to install a nucleation layer between the epitaxial layer and the substrate in the high electron mobility transistor as a transition layer located between the two heterogeneous structures. However, the epitaxial quality in the nucleation layer directly affects the appearance of the quality of the epitaxial layer. Therefore, how to provide a nucleation layer having good epitaxial quality becomes a problem that should be solved as soon as possible.
Summary of the Invention
Problems to be Solved by the Invention
[0004] In view of this, an object of the present invention is to provide an epitaxial structure and a manufacturing method thereof that can provide a nucleation layer having good epitaxial quality. [Means for solving the problem]
[0005] To achieve the above objectives, the present invention provides a method for manufacturing an epitaxial structure, comprising: providing a silicon carbide substrate installed in a growth chamber; forming a nucleation layer on the surface of the silicon carbide substrate, wherein the process gas necessary for growing the nucleation layer includes a first gas; the process for growing the nucleation layer includes performing a growth step, the growth step includes performing a first operation followed by a second operation, the first operation includes introducing the first gas into the growth chamber, the second operation includes stopping so as not to introduce the first gas into the growth chamber, and repeating the growth step multiple times to form the nucleation layer; and forming a nitride epitaxial layer on the surface of the nucleation layer.
[0006] Of these, a nucleation layer with a thickness of 2 nm or less can be grown by performing the aforementioned growth step just once.
[0007] Of these, the second operation includes stopping the introduction of the first gas into the growth chamber and then maintaining it for a second time interval of 30 seconds or more and 180 seconds or less.
[0008] Of these, the epitaxial growth rate of the nucleation layer is 1.6 or higher and 3.5 nm / min or lower.
[0009] Of these, the process gas necessary for growing the nucleation layer includes a second gas which is a nitrogen-containing gas, and when growing the nucleation layer, the second gas is introduced into the growth chamber without interruption.
[0010] Of these, the first gas is an aluminum-containing gas.
[0011] When performing the aforementioned growth step, the growth chamber is controlled to maintain a high temperature.
[0012] The aforementioned high temperature is 1150 degrees Celsius or higher and 1250 degrees Celsius or lower.
[0013] Of these, the nucleating layer contains aluminum-containing nitride.
[0014] The epitaxial configuration further provided by the present invention includes a silicon carbide substrate, a nucleating layer, and a nitride epitaxial layer, wherein the nucleating layer is located above the silicon carbide substrate and in direct contact with the silicon carbide substrate, and when the thickness of the nucleating layer is 70 nm or more, the full width at half maximum (FWHM) of the (002) crystal plane in the nitride epitaxial layer is less than 150 arcsec, and the nitride epitaxial layer is located above the nucleating layer and in direct contact with the nucleating layer.
[0015] In particular, if the thickness of the nucleation layer is less than 100 nm and 70 nm or more, the full width at half maximum (FWHM) of the (002) crystal plane in the nucleation layer is less than 150 arcsec.
[0016] Of these, when scanning only a 5um*5um area using an atomic force microscope, the root mean square roughness (RMS) of the surface of the nucleation layer is less than 0.2 nm.
[0017] Of these, the nucleation layer has a dislocation defect density of 10 8 / cm 2 It is less than.
[0018] In particular, if the thickness of the nitride epitaxial layer is less than 2 μm and 1.5 μm or more, the full width at half maximum (FWHM) of the (002) crystal plane in the nitride epitaxial layer is less than 50 arcsec.
[0019] In particular, if the thickness of the nitride epitaxial layer is less than 1.5 μm and 1 μm or more, the full width at half maximum (FWHM) of the (002) crystal plane in the nitride epitaxial layer is 50 arcsec or more and 100 arcsec or less.
[0020] In the case where the thickness of the nitride epitaxial layer is less than 1 μm and 0.7 μm or more, the full width at half maximum (FWHM) of the (002) crystal plane in the nitride epitaxial layer is 100 arcsec or more and less than 150 arcsec.
[0021] Of these, the nucleating layer contains aluminum-containing nitride.
[0022] The epitaxial structure further provided by the present invention includes a silicon carbide substrate, a nucleating layer, and a nitride epitaxial layer, wherein the nucleating layer is located above the silicon carbide substrate and in direct contact with the silicon carbide substrate, and when the thickness of the nucleating layer is less than 70 nm, the full width at half maximum (FWHM) of the (002) crystal plane in the nucleating layer is 200 arcsec or less and 150 arcsec or more, and the nitride epitaxial layer is located above the nucleating layer and in direct contact with the nucleating layer.
[0023] The epitaxial structure further provided by the present invention includes a silicon carbide substrate, a nucleating layer, and a nitride epitaxial layer, wherein the nucleating layer is located above the silicon carbide substrate and in direct contact with the silicon carbide substrate, the nucleating layer has a thickness of 70 nm or more, the nitride epitaxial layer is located above the nucleating layer and in direct contact with the nucleating layer, and when the thickness of the nitride epitaxial layer is less than 0.7 μm and 0.4 μm or more, the full width at half maximum (FWHM) of the (002) crystal plane in the nitride epitaxial layer is 150 arcsec or more and 200 arcsec or less.
[0024] The epitaxial structure further provided by the present invention includes a silicon carbide substrate, a nucleation layer, and a nitride epitaxial layer. The nucleation layer is located above the silicon carbide substrate and is in direct contact with the silicon carbide substrate. The nucleation layer has a thickness of 70 nm or more. The nitride epitaxial layer is located above the nucleation layer and is in direct contact with the nucleation layer. When the thickness of the nitride epitaxial layer is less than 0.4 μm, the full width at half maximum (FWHM) of the (002) crystal plane in the nitride epitaxial layer is 200 arcsec or more and 300 arcsec or less.
Effects of the Invention
[0025] The effect of the present invention is that by forming the nucleation layer to grow by the manufacturing method of the epitaxial structure, a good quality appearance can be obtained in the nitride epitaxial layer located above. When the thickness of the nucleation layer is 70 nm or more, the full width at half maximum (FWHM) of the (002) crystal plane in the nitride epitaxial layer becomes less than 150 arcsec.
Brief Description of the Drawings
[0026] [Figure 1] It is a flowchart showing a method for manufacturing an epitaxial structure according to a preferred embodiment of the present invention. [Figure 2] It is a schematic diagram showing the control of gas when growing the nucleation layer according to the above preferred embodiment. [Figure 3] It is a schematic diagram showing the epitaxial structure according to the above preferred embodiment. [Figure 4] It is a graph showing the thickness and full width at half maximum of the nitride epitaxial layers according to Examples 1 to 3 and Comparative Examples 1 to 3.
Modes for Carrying Out the Invention
[0027] To further clarify the present invention, preferred embodiments will be described in detail below with reference to the drawings. Figure 1 is a flowchart showing a method for manufacturing an epitaxial structure 1 according to a preferred embodiment of the present invention. The method for manufacturing the epitaxial structure 1 includes the following steps.
[0028] Step S02 provides the silicon carbide substrate 10 installed in the growth chamber. The silicon carbide substrate 10 may, for example, be a silicon carbide substrate 10 with an angle of inclination of 4 degrees, and preferably a silicon carbide substrate 10 with an angle of inclination of 0 degrees. Next, it will be described that in this embodiment, the epitaxial process is carried out by metal-organic chemical vapor deposition (MOCVD). The growth chamber is the growth chamber of the metal-organic chemical vapor deposition equipment.
[0029] Step S04 is to form a nucleation layer 20 on the surface of the silicon carbide substrate 10. The process gas necessary for growing the nucleation layer 20 includes a first gas. The process for growing the nucleation layer 20 includes performing growth step A. As shown in Figure 2, growth step A includes performing a first operation A1 followed by a second operation A2. The first operation A1 includes introducing the first gas into the growth chamber. The second operation A2 includes stopping so as not to introduce the first gas into the growth chamber, and repeating growth step A multiple times to form the nucleation layer 20.
[0030] In this embodiment, the nucleating layer 20 contains an aluminum-containing nitride. In this embodiment, the nucleating layer 20 contains aluminum nitride (AlN). In other embodiments, the nucleating layer 20 may further contain aluminum gallium nitride (AlGaN). For example, the nucleating layer 20 may be a superlattice layer formed by swapping aluminum nitride and aluminum gallium nitride.
[0031] Of these, the first gas is an aluminum-containing gas. In this embodiment, the first gas is described using trimethylaluminum (TMA) as an example, while in other embodiments, it may be triethylaluminium (TEAL). Further, the process gas necessary for growing the nucleating layer 20 includes a second gas. The second gas is a nitrogen-containing gas. When growing the nucleating layer 20, the second gas is introduced into the growth chamber without interruption. In this embodiment, the second gas is described using ammonia (NH3) as an example. That is, when forming the nucleating layer 20, ammonia (NH3) is continuously introduced into the growth chamber to prevent the nucleating layer 20 from decomposing, and the operation of introducing trimethylaluminum into the growth chamber and stopping the introduction of trimethylaluminum is repeated and controlled until the nucleating layer 20 with the expected thickness is formed.
[0032] Of these, a nucleation layer 20 with a thickness of 2 nm or less can be grown by performing growth step A just once. Performing growth step A just once means performing the first operation A1 and the second operation A2 just once each. The nucleation layer 20 has an epitaxial growth rate of 1.6 nm / min or more and 3.5 nm / min or less.
[0033] Next, when performing the growth step A, the growth chamber is controlled to maintain a high temperature. The high temperature is 1150 degrees Celsius or higher and 1250 degrees Celsius or lower. The pressure in the growth chamber is controlled to be maintained at 30 tors or higher and 150 tors or lower. The second operation A2 includes stopping the introduction of the first gas into the growth chamber and maintaining this for a time interval T. The time interval T is 30 seconds or higher and 180 seconds or lower. In other words, when the first operation A1 is performed to introduce trimethylaluminum into the growth chamber, epitaxial growth of the nucleation layer 20 is carried out at the high temperature and the above chamber pressure. When the second operation A2 is performed to stop the introduction of trimethylaluminum into the growth chamber, annealing is carried out at the same high temperature and pressure as in the above operation. Compared to conventional epitaxial methods, which involve removing the nucleated layer from the growth chamber after epitaxial fusion is complete and performing annealing only once, the present invention allows for the execution of growth step A multiple times and the completion of both epitaxial fusion and annealing in the same growth chamber. This enables the achievement of epitaxial quality equivalent to that of conventional epitaxial methods, which involve high temperatures and long processing times, using a relatively short annealing time and a relatively low annealing temperature. Consequently, it is possible to achieve the technical effects of shortening the annealing time and lowering the annealing temperature.
[0034] Step S06 involves forming a nitride epitaxial layer 30 on the surface of the nucleation layer 20. In this embodiment, the nitride epitaxial layer 30 contains gallium nitride (GaN).
[0035] Referring to Figure 3, the epitaxial structure 1 manufactured using the manufacturing method of the epitaxial structure 1 includes the silicon carbide substrate 10, the nucleation layer 20, and the nitride epitaxial layer 30. Of these, the epitaxial structure 1 is applied to the high electron mobility transistor, and may have other components, such as a barrier layer 40, further grown above the nitride epitaxial layer 30.
[0036] As shown in Figure 3, the nucleating layer 20 is located above the silicon carbide substrate 10 and is in direct contact with the silicon carbide substrate 10. The nitride epitaxial layer 30 is located above the nucleating layer 20 and is in direct contact with the nucleating layer 20. When the thickness of the nucleating layer 20 is 70 nm or more, the nitride epitaxial layer 30 is measured using an X-ray diffractometer (XRD), and the full width at half maximum (FWHM) of the (002) crystal plane in the nitride epitaxial layer 30 is less than 150 arcsec. As can be seen from this, the epitaxial structure 1 manufactured using the manufacturing method of the epitaxial structure has good epitaxial quality in the nitride epitaxial layer 30.
[0037] Of these, if the thickness of the nucleating layer 20 is less than 100 nm and 70 nm or more, the full width at half maximum (FWHM) of the (002) crystal plane in the nucleating layer 20 is less than 150 arcsec. If the thickness of the nucleating layer 20 is less than 70 nm, the full width at half maximum (FWHM) of the (002) crystal plane in the nucleating layer 20 is 200 arcsec or less and 150 arcsec or more.
[0038] Of these, if the thickness of the nucleating layer 20 is 70 nm or more, and the thickness of the nitride epitaxial layer 30 is less than 2 μm and 1.5 μm or more, then the full width at half maximum (FWHM) of the (002) crystal plane in the nitride epitaxial layer 30 is less than 50 arcsec. If the thickness of the nucleating layer 20 is 70 nm or more, and the thickness of the nitride epitaxial layer 30 is less than 1.5 μm and 1 μm or more, then the full width at half maximum (FWHM) of the (002) crystal plane in the nitride epitaxial layer 30 is 50 arcsec or more and less than 100 arcsec. In the case where the thickness of the nucleating layer 20 is 70 nm or more, and the thickness of the nitride epitaxial layer 30 is less than 1 μm and 0.7 μm or more, the full width at half maximum (FWHM) of the (002) crystal plane in the nitride epitaxial layer 30 is 100 arcsec or more and less than 150 arcsec. In the case where the thickness of the nucleating layer 20 is 70 nm or more, and the thickness of the nitride epitaxial layer 30 is less than 0.7 μm and 0.4 μm or more, the full width at half maximum (FWHM) of the (002) crystal plane in the nitride epitaxial layer 30 is 150 arcsec or more and less than 200 arcsec. In particular, if the thickness of the nucleating layer 20 is 70 nm or more, and the thickness of the nitride epitaxial layer 30 is less than 0.4 μm, then the full width at half maximum (FWHM) of the (002) crystal plane in the nitride epitaxial layer 30 is 200 arcsec or more and 300 arcsec or less.
[0039] Of these, when scanning only a 5um*5um area using an atomic force microscope, the root mean square roughness (RMS) of the surface of the nucleation layer 20 is less than 0.2 nm. The nucleation layer 20 has a dislocation defect density of 10 8 / cm 2 It is less than.
[0040] Comparative Examples 1 to 3 and Examples 1 to 3 will be explained further. Examples 1 to 3 are the results of measuring the nitride epitaxial layer 30 via an X-ray diffractometer (XRD) for epitaxial structures 1 manufactured using the above-described method for manufacturing epitaxial structures. The epitaxial structure 1 includes the silicon carbide substrate 10, the nucleation layer 20, the nitride epitaxial layer 30, and the barrier layer 40 in the order described above. Further explanation is provided that the formation layer 20 can be grown to a thickness of 1 nm by a single execution of the growth step A. When performing the growth step A, the growth chamber is maintained at a high temperature of 1170 degrees Celsius while the pressure inside the chamber is controlled to 75 torr. The epitaxial structures 1 in Examples 1 to 3 all have a nucleation layer 20 with a thickness of 90 nm and a (002) crystal plane full width at half maximum (FWHM) equal to 100 arcsec. The difference between the epitaxial configuration 1 in Examples 1 to 3 and the present example is the thickness of the nitride epitaxial layer 30. In Example 1, the thickness of the nitride epitaxial layer 30 is 1 μm; in Example 2, the thickness of the nitride epitaxial layer 30 is 0.7 μm; and in Example 3, the thickness of the nitride epitaxial layer is 0.4 μm.
[0041] Comparative Examples 1 to 3 show the results of measuring the nitride epitaxial layer via X-ray diffraction (XRD) for epitaxial structures manufactured using a conventional epitaxial method. The epitaxial structures manufactured using the conventional epitaxial method process similarly include, in order, a silicon carbide substrate, a nucleation layer, a nitride epitaxial layer, and a barrier layer. The conventional epitaxial method differs from the method for manufacturing the epitaxial structure according to the present invention in that, in the conventional epitaxial method, when forming the nucleation layer, once the epitaxial formation of the nucleation layer is completed, it is removed from the growth chamber and annealed, and then the nitride epitaxial layer is formed above the nucleation layer. Of these, the epitaxial structures in Comparative Examples 1 to 3 all have a nucleation layer with a thickness of 90 nm and a (002) crystal plane full width at half maximum (FWHM) equal to 300 arcsec. The difference between the epitaxial configurations of Comparative Examples 1 to 3 and those of Comparative Examples 1 to 3 lies in the thickness of the nitride epitaxial layer. In Comparative Example 1, the thickness of the nitride epitaxial layer is 2 μm; in Comparative Example 2, the thickness of the nitride epitaxial layer is 1.5 μm; and in Comparative Example 3, the thickness of the nitride epitaxial layer is 1 μm.
[0042] As shown in Figure 4, in both the comparative example and the example, the thicker the nitride epitaxial layer 30, the better the FWHM of the (002) crystal plane in the nitride epitaxial layer 30, indicating favorable epitaxial quality. Comparing Comparative Example 3 and Example 1, although the nitride epitaxial layers in Comparative Example 3 and Example 1 have the same thickness, the FWHM of the (002) crystal plane in the nitride epitaxial layer of Example 1 is 118 arcsec, while the FWHM of the (002) crystal plane in the nitride epitaxial layer of Comparative Example 3 is 154 arcsec. In other words, the nitride epitaxial layer of Example 1 has relatively better epitaxial quality than that of Comparative Example 3. In addition, for epitaxial structures manufactured using conventional epitaxial methods, it is necessary to grow a relatively thick nitride epitaxial layer to obtain relatively good epitaxial quality. However, it can be inferred that for epitaxial structures manufactured using the epitaxial method according to the present invention, the same epitaxial quality can be obtained by growing a relatively thin nitride epitaxial layer.
[0043] Based on the above, by forming the nucleating layer 20 through the manufacturing method of the epitaxial structure, the nitride epitaxial layer 30 located above can exhibit good quality.
[0044] The above are merely preferred embodiments of the present invention, and it goes without saying that any equivalent substitutions based on the specification and scope of the present invention are included within the scope of the present invention. [Explanation of Symbols]
[0045] 1. Epitaxial configuration 10 Silicon carbide substrate 20 Nucleation layer 30 Nitride epitaxial layer 40 Barrier layer A Growth Step A1 First action A2 Second action T time interval S02, S04, S06 Step
Claims
1. Silicon carbide substrate and A nucleating layer located above the silicon carbide substrate and in direct contact with the silicon carbide substrate, comprising an aluminum-containing nitride, It includes a gallium-containing nitride epitaxial layer located above the nucleation layer and in direct contact with the nucleation layer, An epitaxial structure characterized in that the thickness of the nucleation layer is 70 nm or more, and the full width at half maximum (FWHM) of the (002) crystal plane in the nitride epitaxial layer is less than 150 arcsec.
2. The epitaxial structure according to claim 1, characterized in that the nucleating layer has a thickness of less than 100 nm and 70 nm or more, and the full width at half maximum (FWHM) of the (002) crystal plane in the nucleating layer is less than 150 arcsec.
3. The epitaxial structure according to claim 1, characterized in that when an area of only 5um x 5um is scanned via an atomic force microscope, the root mean square roughness (Root Mean Square roughness, RMS) of the surface of the nucleation layer is less than 0.2 nm.
4. The nucleation layer has a dislocation defect density of 10 8 / cm 2 The epitaxial configuration according to claim 1, characterized in that it is less than [a certain value].
5. The epitaxial structure according to claim 1, characterized in that the thickness of the nucleating layer is 70 nm or more, the thickness of the nitride epitaxial layer is less than 2 μm and 1.5 μm or more, and the full width at half maximum (FWHM) of the (002) crystal plane in the nitride epitaxial layer is less than 50 arcsec.
6. The epitaxial structure according to claim 1, characterized in that the thickness of the nucleating layer is 70 nm or more, the thickness of the nitride epitaxial layer is less than 1.5 μm and 1 μm or more, and the full width at half maximum (FWHM) of the (002) crystal plane in the nitride epitaxial layer is 50 arcsec or more and 100 arcsec or less.
7. The epitaxial structure according to claim 1, characterized in that the thickness of the nucleating layer is 70 nm or more, the thickness of the nitride epitaxial layer is less than 1 μm and 0.7 μm or more, and the full width at half maximum (FWHM) of the (002) crystal plane in the nitride epitaxial layer is 100 arcsec or more and less than 150 arcsec.
8. Silicon carbide substrate and A nucleating layer located above the silicon carbide substrate and in direct contact with the silicon carbide substrate, comprising an aluminum-containing nitride, having a thickness of less than 70 nm, and having a total width at half maximum (FWHM) of the (002) crystal plane in the nucleating layer of 200 arcsec or less and 150 arcsec or more, An epitaxial structure characterized by comprising a gallium-containing nitride epitaxial layer located above the nucleation layer and in direct contact with the nucleation layer.
9. Silicon carbide substrate and A nucleating layer located above the silicon carbide substrate and in direct contact with the silicon carbide substrate, containing an aluminum-containing nitride, and further having a thickness of 70 nm or more, An epitaxial structure characterized by comprising: a gallium-containing nitride epitaxial layer located above the nucleating layer and in direct contact with the nucleating layer, wherein the nitride epitaxial layer has a thickness of less than 0.7 μm and 0.4 μm or more, and the (002) crystal plane in the nitride epitaxial layer has a full width at half maximum (FWHM) of 150 arcsec or more and less than 200 arcsec.
10. Silicon carbide substrate and A nucleating layer located above the silicon carbide substrate and in direct contact with the silicon carbide substrate, comprising an aluminum-containing nitride and having a thickness of 70 nm or more, An epitaxial structure characterized by comprising: a gallium-containing nitride epitaxial layer located above the nucleating layer and in direct contact with the nucleating layer, wherein the nitride epitaxial layer has a thickness of less than 0.4 μm and the (002) crystal plane in the nitride epitaxial layer has a full width at half maximum (FWHM) of 200 arcsec or more and 300 arcsec or less.