Ⅲ-N semiconductor structure and method of manufacturing the same

Abstract

A III-N semiconductor structure and a method for manufacturing the same are disclosed, wherein a superlattice structure layer formed of AlGaN and InAlN materials is used as a buffer layer, and a III-N material is grown on the superlattice structure layer. The disclosed III-N semiconductor structure comprises: a substrate including a silicon material; a seed layer formed on the substrate including an aluminum nitride (AlN) material; a superlattice structure layer formed on the seed layer in which a plurality of superlattice units are stacked in sequence; and a cap layer formed on the superlattice structure layer including a gallium nitride (GaN) material, wherein the superlattice units include a first layer composed of an AlxGa1-xN material having 0≤x≤1 and a second layer composed of an InyAl1-yN material having 0<y≤0.4.

Description

Technology Field

[0001] The present disclosure relates to a III-N semiconductor structure formed by using a superlattice structure layer as a buffer layer and growing a III-N material on the superlattice structure layer, and a method for manufacturing the same. Background Technology

[0002] III-N materials such as gallium nitride (GaN) are materials required for the manufacture of advanced semiconductor devices, and GaN and its compounds are promising as wide-band-gap semiconductor materials suitable for optoelectronic device fields such as blue light and ultraviolet light-emitting devices and lasers, as well as electronic device fields such as high-frequency / high-power devices such as RF transistors and power transistors.

[0003] Silicon (Si) substrates are economical and promising as base substrates for growing III-N materials such as gallium nitride (GaN) and for growing gallium nitride layers. Silicon substrates are not only inexpensive and have the advantages of excellent electrical and thermal conductivity, but they can also be used in larger sizes. However, the difference in lattice constants and coefficients of thermal expansion between gallium nitride and silicon can be a serious problem and can hinder the successful growth of epitaxial layers.

[0004] To solve this, strain can be controlled between the lower layer (silicon substrate or aluminum nitride seed layer) and the upper layer (gallium nitride layer) by forming a superlattice structure layer composed of Al, Ga, and N on a silicon substrate on which an aluminum nitride (AlN) seed layer is formed. The strain can be controlled by forming an average lattice constant by mutually adjusting the Al and Ga compositions and thickness ratios of each layer constituting the superlattice structure layer, which is a buffer layer. The average lattice constant of the buffer layer can be determined by considering the lattice constant of the lower layer and the lattice constant of the upper layer so that bending or cracking of the semiconductor structure is controlled when the growth of all epitaxial layers is finished.

[0005] However, when setting the average lattice constant of a superlattice structure buffer layer composed of Al, Ga, and N by considering the difference in lattice constants between the lower and upper layers, the continuity of the lattice constant may be considered, and if the upper layer is gallium nitride, the average lattice constant will inevitably approach the lattice constant of gallium nitride. For the average lattice constant to approach the lattice constant of gallium nitride, the Al composition in the AlGaN layer of the superlattice unit of the AlGaN / AlN buffer layer composed of Al, Ga, and N must be lowered or the thickness of the AlGaN layer must be increased, which inevitably leads to a smaller average band gap and consequently lower insulation properties. The problem to be solved

[0006] The present invention provides a III-N semiconductor structure capable of controlling strain occurring when epitaxially growing a III-N material on a heterogeneous substrate while maintaining a high bandgap, and a method for manufacturing the same. means of solving the problem

[0007] A III-N semiconductor structure according to one embodiment of the present invention comprises: a substrate comprising a silicon material; a seed layer formed on the substrate comprising an aluminum nitride (AlN) material; a superlattice structure layer formed on the seed layer wherein a plurality of superlattice units are stacked in sequence; and a cap layer formed on the superlattice structure layer comprising a gallium nitride (GaN) material, wherein the superlattice units are Al such that 0 ≤ x ≤ 1 x Ga 1-x A first layer composed of N material and In such that 0 < y ≤ 0.4 y Al 1-y It includes a second layer composed of N material.

[0008] The thickness of the above superlattice unit may be 30 nm or less.

[0009] The average lattice constant of the superlattice structure layer may have a value between the lattice constant of the seed layer and the lattice constant of the cap layer.

[0010] In the plurality of superlattice units stacked sequentially on the seed layer, the lattice constant of the superlattice unit may have a larger value as it moves further away from the seed layer.

[0011] The bandgap energy of the above superlattice structure layer can have a value greater than the bandgap energy of the above cap layer.

[0012] The above superlattice structure layer may include 50 or more superlattice units.

[0013] In the above superlattice unit, the ratio of the thickness of the second layer to the first layer may be 1:10 to 10:1.

[0014] The seed layer, the superlattice structure layer, and the cap layer can be grown by molecular beam epitaxy (MBE) or metal organic chemical vapor deposition (MOCVD).

[0015] A method for manufacturing a III-N semiconductor structure according to an embodiment of the present invention comprises the steps of: providing a substrate comprising a silicon material; forming a seed layer comprising an aluminum nitride (AlN) material on the substrate; forming a superlattice structure layer in which a plurality of superlattice units are sequentially stacked on the seed layer; and growing a gallium nitride (GaN) material on the superlattice structure layer to form a cap layer, wherein the superlattice units are Al nitrides such that 0 ≤ x ≤ 1 x Ga 1-x A first layer composed of N material and In such that 0 < y ≤ 0.4 y Al 1-y It includes a second layer composed of N material.

[0016] In the step of forming the superlattice structure layer, the thickness of the superlattice unit can be 30 nm or less.

[0017] In the step of forming the superlattice structure layer, the average lattice constant of the superlattice structure layer can be adjusted to have a value between the lattice constant of the seed layer and the lattice constant of the cap layer.

[0018] In the step of forming the superlattice structure layer, the lattice constant of the superlattice unit can be adjusted to have a larger value as it moves further away from the seed layer.

[0019] In the step of forming the superlattice structure layer, the bandgap energy of the superlattice structure layer can be adjusted to have a value greater than the bandgap energy of the cap layer.

[0020] In the step of forming the superlattice structure layer, the superlattice structure layer may have at least 50 superlattice units stacked thereon.

[0021] In the step of forming the superlattice structure layer, the ratio of the thickness of the second layer to the first layer can be adjusted to be 1:10 to 10:1.

[0022] The seed layer, the superlattice structure layer, and the cap layer can be grown by molecular beam epitaxy (MBE) or metal organic chemical vapor deposition (MOCVD). Effects of the invention

[0023] According to the disclosed III-N semiconductor structure and method for manufacturing the same, when forming a semiconductor structure by epitaxially growing a III-N material on a silicon substrate, by using a superlattice structure layer including AlGaN material and InAlN material as a buffer layer, the occurrence of bending or cracking can be prevented when the growth of the epitaxial structure is finished.

[0024] In addition, by using a superlattice structure layer containing AlGaN and InAlN materials as a buffer layer, the band gap can be maintained at a high value, and accordingly, the insulation properties of the III-N semiconductor structure can be improved. Brief explanation of the drawing

[0025] FIG. 1 is a cross-sectional view of a III-N semiconductor structure according to one embodiment. FIG. 2 is a cross-sectional view of a superlattice structure layer of a III-N semiconductor structure according to one embodiment. FIG. 3 is a cross-sectional view of a superlattice structure layer of a III-N semiconductor structure according to another embodiment. Figure 4 is a graph showing the correlation between the lattice constant and the band gap of a III-N semiconductor material. Specific details for implementing the invention

[0026] Embodiments of the present invention are described below with reference to the attached drawings so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein. Furthermore, in order to clearly explain the present invention in the drawings, parts unrelated to the explanation have been omitted, and similar parts throughout the specification are denoted by similar reference numerals.

[0027] Throughout the specification, when a part is described as being "connected" to another part, this includes not only cases where they are "directly connected," but also cases where they are "electrically connected" with other components interposed between them. Furthermore, when a part is described as "including" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0028] FIG. 1 is a cross-sectional view of a III-N semiconductor structure (100) according to one embodiment.

[0029] Referring to FIG. 1, a III-N semiconductor structure (100) includes a substrate (110), a seed layer (120) provided on the substrate (110), a superlattice structure layer (130) provided on the seed layer (120), and a cap layer (140) provided on the superlattice structure layer (130).

[0030] The substrate (110) generally has the crystal orientation of (111), but it is also possible to have other crystal orientations. The substrate (110) may be a silicon carbide substrate, a silicon substrate, or an SOI (Silicon on Insulator) substrate, and the SOI substrate may have a thickness between about 450 and 2,000 μm.

[0031] A seed layer (120) is provided on a substrate (110). The seed layer (120) is intended to grow a superlattice structure layer (130) used as a buffer layer and can provide a crystal lattice structure that serves as a seed for the superlattice structure layer (130). The seed layer (120) may include a III-N-based material such as aluminum nitride (AlN).

[0032] A superlattice structure layer (130) is provided on a seed layer (120). To compensate for thermal tensile stress that occurs while cooling the wafer after growing a III-N semiconductor structure, the superlattice structure layer (130) can provide compressive stress. A superlattice structure layer (130) formed by stacking a plurality of superlattice units (135) shown in FIG. 2 can be effective in providing compressive stress within the growth plane and filtering dislocations.

[0033] FIG. 2 is a cross-sectional view of a superlattice structure layer (130) of a III-N semiconductor structure (100) according to one embodiment. Referring to FIG. 2, the superlattice structure layer (130) has layers of materials (first layer (131) and second layer (132)) having alternating different lattice constants, and a pair of first layers (131) and second layers (132) form a superlattice unit (135). The alternating plurality of first layers (131) and second layers (132) of the superlattice structure layer (130) can cause compressive stress and tensile stress to alternate.

[0034] The first layer (131) and the second layer (132) each have a lattice constant. One of the lattice constants is larger than the other. For example, the first layer (131) may have a larger lattice constant than the second layer (132), or the second layer (132) may have a larger lattice constant than the first layer (131).

[0035] Referring to FIG. 4, which illustrates the correlation between the lattice constant and the band gap of a III-N semiconductor material, the lattice constant of the seed layer (120) containing aluminum nitride (AlN) material has a smaller value than the lattice constant of the cap layer (140) containing gallium nitride (GaN) material. Additionally, the average lattice constant of the superlattice structure layer (130) formed by a plurality of superlattice units (135) may have a value between the lattice constant of the seed layer (120) and the lattice constant of the cap layer (140).

[0036] Compressive stress is formed when the average lattice constant of the superlattice structure layer (130) is greater than the lattice constant of the seed layer (120), which is the lower layer, and smaller than the lattice constant of the cap layer (140), which is the upper layer. Then, when a cap layer (140) having a lattice constant greater than that of the superlattice structure layer (130) is grown on the superlattice structure layer (130), the compressive stress continues to increase. The compressive stress can offset the tensile stress caused by the difference in thermal expansion coefficients when the growth of the cap layer (140) is finished and the temperature is lowered to room temperature. Through this, bending or cracking of the III-N semiconductor structure (100) can be controlled.

[0037] The first layer (131) of the superlattice unit (135) is Al x Ga 1-x It may include N (0≤x≤1) material, and the second layer (132) is In y Al 1-y It may include N (0 < y ≤ 0.4) material. Al constituting the first layer (131) x Ga 1-x Composition of N (0≤x≤1) material and In constituting the second layer (132) y Al 1-y By appropriately adjusting the composition of the material N (0 < y ≤ 0.4) and the thickness of the first layer (131) and the second layer (132), the average lattice constant of the superlattice structure layer (130) can be adjusted to have a value between the lattice constant of the seed layer (120) and the lattice constant of the cap layer (140).

[0038] The bandgap energy of the superlattice structure layer (130) can have a greater value than the bandgap energy of the cap layer (140) containing gallium nitride (GaN) material, thereby ensuring the insulation characteristics of the III-N semiconductor structure (100).

[0039] In particular, referring to FIG. 4, the bandgap energy of the superlattice structure layer (130) composed of AlGaN material and InAlN material can have a higher bandgap energy than that of the superlattice structure layer composed only of Al, Ga, and N.

[0040] Specifically, in a composition (P1, P2) in which a first layer (131) containing an AlGaN material and a second layer (132) containing an InAlN material have a value between the lattice constant of the AlN material (seed layer) and the lattice constant of the GaN material (cap layer), the average lattice constant of the superlattice structure layer (130) formed by the alternating first layer (131) and second layer (132) has the same value as the lattice constant of the compositions P1 and P2. Additionally, the bandgap energy of the superlattice structure layer (130) has a bandgap energy between the P1 point and the P2 point.

[0041] Meanwhile, a superlattice structure layer composed only of Al, Ga, and N has a band gap energy at point P2, and this band gap energy is smaller than the band gap energy of a superlattice structure layer (130) composed of AlGaN material and InAlN material.

[0042] When setting the average lattice constant of the superlattice structure layer (130) by considering the difference in lattice constants between the lower layer, the seed layer (120), and the upper layer, the cap layer (140), the continuity of the lattice constant must be considered. Therefore, if the upper layer, the cap layer (140), contains gallium nitride (GaN) material, the average lattice constant of the superlattice structure layer (130) must inevitably approach the lattice constant of gallium nitride. In FIG. 4, for the average lattice constant of the superlattice structure layer to approach the lattice constant of gallium nitride, the bandgap energy of the superlattice structure layer must inevitably decrease, and consequently, the insulation properties are reduced. However, according to one embodiment of the present invention, the superlattice structure layer (130) composed of AlGaN material and InAlN material has a higher bandgap energy than the superlattice structure layer composed only of Al, Ga, and N, so the insulation properties of the III-N semiconductor structure can be secured.

[0043] The superlattice structure layer (130) may include 50 to 400 superlattice units (135). The thickness of the superlattice units (135) may be 3 nm to 30 nm, and the first layer (131) and the second layer (132) of the superlattice units (135) may have the same thickness. According to another embodiment, the thickness of the first layer (131) and the thickness of the second layer (132) may be different from each other.

[0044] In the superlattice unit (135), the thick layer may be at least twice as thick, at least three times as thick, or at least four times as thick as the other layer. The ratio between the thicknesses of the first layer (131) and the second layer (132) may be, for example, any combination between 1:10 and 10:1.

[0045] Referring again to FIG. 1, the cap layer (140) is provided on the superlattice structure layer (130) and includes a III-N-based material. As described above, the cap layer (140) may include a gallium nitride material, may have a lattice constant greater than that of the superlattice structure layer (130), and may have a bandgap energy smaller than that of the superlattice structure layer (130).

[0046] Layers of the III-N semiconductor structure (100) can be grown by molecular beam epitaxy (MBE) or metal organic chemical vapor deposition (MOCVD).

[0047] FIG. 3 is a cross-sectional view of a superlattice structure layer (230) of a III-N semiconductor structure according to another embodiment. The superlattice structure layer (230) is formed on the seed layer (120) of FIG. 1 and replaces the aforementioned superlattice structure layer (130), and other than the configuration described below, it is identical to the superlattice structure layer (130).

[0048] Referring to FIG. 3, the average lattice constant of the superlattice structure layer (230) can be adjusted to have a value greater than that of the lattice constant of the seed layer (120) and the lattice constant of the cap layer (140). Additionally, the superlattice structure layer (230) includes a plurality of superlattice units (235, 235', 235"), and the lattice constant of the superlattice unit stacked far from the seed layer (120) can be configured to have a value greater than that of the superlattice unit stacked close to the seed layer (120). For example, the lattice constant of the superlattice unit (235') has a value greater than that of the superlattice unit (235), and the lattice constant of the superlattice unit (235") has a value greater than that of the superlattice unit (235').

[0049] The superlattice units (235, 235', 235") each include a first layer (231, 231', 231") and a second layer (232, 232', 232"), and the first layer (231, 231', 231") is Al x Ga 1-x It may include a material N (0≤x≤1), and the second layer (232, 232', 232") is In y Al 1-y It may include a material N (0 < y ≤ 0.4). The lattice constant of the superlattice unit (235, 235', 235") can be adjusted so that the superlattice unit further from the seed layer (120) has a higher lattice constant value, that is, a value close to the lattice constant value of the cap layer (140) containing gallium nitride (GaN) material, by appropriately adjusting the composition of the material of the first layer (231, 231', 231") and the second layer (232, 232', 232") and the thickness of the first layer (231, 231', 231") and the second layer (232, 232', 232").

[0050] Additionally, in the superlattice structure layer (230), the lattice constant of the superlattice unit can be adjusted to increase stepwise according to a specific period as it moves further away from the seed layer (120). For example, whenever 50 superlattice units are stacked on the seed layer (120), the lattice constant of the next 50 superlattice units stacked can be adjusted to increase compared to the lattice constant of the previously stacked 50 superlattice units.

[0051] Accordingly, the average lattice constant of the superlattice structure layer (230) formed according to the present embodiment has a value between the lattice constant of the seed layer (120) and the lattice constant of the cap layer (140), and at the same time, can have a higher lattice constant as it goes from the seed layer (120) toward the cap layer (140).

[0052] Through the above structure, the range of change in the lattice constant can be reduced as it goes toward the seed layer (120), the superlattice structure layer (230), and the cap layer (140), and the continuity of the lattice constant between layers can be increased. Therefore, when the growth of the epitaxially grown III-N semiconductor structure is finished, the occurrence of bending or cracking can be further prevented.

[0053] Although III-N semiconductor structures and methods for manufacturing the same have been described above with reference to embodiments illustrated in the drawings, this is merely illustrative, and those skilled in the art will understand that various modifications and equivalent alternative embodiments are possible therefrom. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the invention is defined by the claims, not by the foregoing description, and all variations within the equivalent scope should be interpreted as being included in the invention. Explanation of the symbols

[0054] 100 … III-N semiconductor structure 110 … substrate 120 … Seed layer 130, 230 … superlattice structure layer 131, 231, 231', 231" … 1st floor 132, 232, 232', 232" … 2nd floor 135, 235, 235', 235" … superlattice unit 140 … cap layer

Claims

Claim 1 A III-N semiconductor structure comprises: a substrate including a silicon material; a seed layer formed on the substrate including an aluminum nitride (AlN) material; a superlattice structure layer formed on the seed layer in which a plurality of superlattice units are stacked in sequence; and a cap layer formed on the superlattice structure layer including a gallium nitride (GaN) material, wherein the superlattice units are Al such that 0 ≤ x ≤ 1 x Ga 1-x A first layer composed of N material and In such that 0 < y ≤ 0.4 y Al 1-y A III-N semiconductor structure comprising a second layer composed of N material, wherein the thick layer of the superlattice unit is 2, 3, or 4 times thicker than the other layer. Claim 2 A III-N semiconductor structure according to claim 1, wherein the thickness of the superlattice unit is 30 nm or less. Claim 3 A III-N semiconductor structure according to claim 1, wherein the average lattice constant of the superlattice structure layer has a value between the lattice constant of the seed layer and the lattice constant of the cap layer. Claim 4 A III-N semiconductor structure according to claim 3, wherein, in the plurality of superlattice units sequentially stacked on the seed layer, the lattice constant of the superlattice unit has a larger value as it moves away from the seed layer. Claim 5 A III-N semiconductor structure according to claim 1, wherein the bandgap energy of the superlattice structure layer has a value greater than the bandgap energy of the cap layer. Claim 6 A III-N semiconductor structure according to claim 1, wherein the superlattice structure layer comprises 50 to 400 superlattice units. Claim 7 A III-N semiconductor structure according to claim 1, wherein the seed layer, the superlattice structure layer, and the cap layer are grown by molecular beam epitaxy (MBE) or metal organic chemical vapor deposition (MOCVD). Claim 8 A method for manufacturing a III-N semiconductor structure comprises the steps of: providing a substrate containing a silicon material; forming a seed layer containing an aluminum nitride (AlN) material on the substrate; forming a superlattice structure layer in which a plurality of superlattice units are sequentially stacked on the seed layer; and growing a gallium nitride (GaN) material on the superlattice structure layer to form a cap layer, wherein the superlattice units are Al nitrides such that 0 ≤ x ≤ 1 x Ga 1-x A first layer composed of N material and In such that 0 < y ≤ 0.4 y Al 1-y A method for manufacturing a III-N semiconductor structure comprising a second layer composed of N material, wherein, in the step of forming the superlattice structure layer, the thick layer of the superlattice unit is adjusted to be 2, 3, or 4 times thicker than the other layer. Claim 9 A method for manufacturing a III-N semiconductor structure according to claim 8, wherein, in the step of forming the superlattice structure layer, the thickness of the superlattice unit is 30 nm or less. Claim 10 A method for manufacturing a III-N semiconductor structure according to claim 8, wherein, in the step of forming the superlattice structure layer, the average lattice constant of the superlattice structure layer is adjusted to have a value between the lattice constant of the seed layer and the lattice constant of the cap layer. Claim 11 A method for manufacturing a III-N semiconductor structure according to claim 10, wherein, in the step of forming the superlattice structure layer, the lattice constant of the superlattice unit is adjusted to have a larger value as it moves further away from the seed layer. Claim 12 A method for manufacturing a III-N semiconductor structure according to claim 8, wherein, in the step of forming the superlattice structure layer, the bandgap energy of the superlattice structure layer is adjusted to have a value greater than the bandgap energy of the cap layer. Claim 13 A method for manufacturing a III-N semiconductor structure according to claim 8, wherein, in the step of forming the superlattice structure layer, the superlattice structure layer comprises at least 50 superlattice units stacked thereon. Claim 14 A method for manufacturing a III-N semiconductor structure according to claim 8, wherein the seed layer, the superlattice structure layer, and the cap layer are grown by molecular beam epitaxy (MBE) or metal organic chemical vapor deposition (MOCVD).

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