HEMT device ohmic contact manufacturing method and HEMT device
Patent Information
- Application Number
- JP2023011292
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-02-01
- Filing Date
- 2023-01-27
- Publication Date
- 2026-01-21
AI Technical Summary
The fabrication process of ohmic contacts in HEMT devices, particularly those without gold, faces issues such as high surface roughness and insufficiently low contact and access resistances, leading to potential malfunctions and mechanical instability due to high annealing temperatures and metal contamination.
The use of a carbon-rich interface portion, such as titanium carbide or tantalum carbide, in combination with a stack of metal layers, allows for the formation of ohmic contacts at lower temperatures (400-500°C) with reduced surface roughness and lower contact resistance.
This approach results in HEMT devices with optimal electrical performance and reduced likelihood of malfunction, maintaining mechanical stability while avoiding the need for dedicated equipment and isolated fabrication areas.
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Abstract
Description
Technical Field
[0001] The present invention relates to a method for manufacturing an ohmic contact of a high electron mobility transistor (HEMT) and a HEMT device.
Background Art
[0002] HEMT devices are known, in which case the conductive channel is based on the formation of a two-dimensional electron gas (2DEG) with high mobility at the interface between a heterojunction, i.e., semiconductor materials having different band gaps. For example, HEMT devices based on a heterojunction between an aluminum gallium nitride (AlGaN) layer and a gallium nitride (GaN) layer are known.
[0003] HEMT devices based on an AlGaN / GaN heterojunction or heterostructure provide several advantages that make them particularly suitable for different application examples and widely used. For example, the high breakdown threshold of HEMT devices is used for high-performance power switches, the high mobility of electrons in the conductive channel enables the provision of high-frequency amplifiers, and furthermore, the high concentration of electrons in the 2DEG enables obtaining a low on-state resistance (R ON ).
[0004] Furthermore, HEMT devices for radio frequency (RF) application examples typically have better RF performance than similar silicon LDMOS devices.
[0005] Known HEMT devices are formed in a semiconductor body including a substrate and a heterostructure, and have a source region and a drain region that make an ohmic contact with the heterostructure.
[0006] Generally, the source region and the drain region are composed of a metallization including gold that enables achieving low contact and access resistance.
[0007] However, the manufacturing process for gold-containing ohmic contacts requires annealing at temperatures even higher than 800°C. Our research has shown that such high temperatures can cause mechanical stability problems and electrical malfunctions in HEMT equipment.
[0008] Furthermore, forming ohmic contacts with gold is not easily achievable in a CMOS line due to the metal contamination caused by the gold, requiring dedicated equipment and a separate manufacturing area.
[0009] According to an alternative approach, the ohmic contact is formed from a laminate of metal layers consisting of a titanium layer in contact with the heterostructure surface and an aluminum layer extending over the titanium layer, without the presence of gold.
[0010] This alternative approach allows the annealing temperature to be reduced to 600°C.
[0011] However, the inventors have found that this temperature reduction is insufficient in certain applications. More specifically, the inventors have found that the ohmic contacts of known gold-free HEMT devices have high surface roughness, for example, a root mean square (RMS) value of 100 nm measured by an atomic force microscope (AFM), which can cause malfunctions and breakdowns of the HEMT device.
[0012] Furthermore, the contact and access resistance of the ohmic contact is not sufficiently low in certain applications. [Overview of the Initiative] [Problems that the invention aims to solve]
[0013] The object of the present invention is to eliminate the drawbacks of the prior art described above. [Means for solving the problem]
[0014] According to the present invention, as defined in the claims, a HEMT device and a method for manufacturing the same are provided.
[0015] To better understand the present invention, the embodiments thereof will be described below by way of purely non-limiting examples with reference to the accompanying drawings.
Brief Description of the Drawings
[0016] [Figure 1] Cross-sectional view of a HEMT device according to an embodiment of the present invention. [Figure 2] Partial cross-sectional view of the HEMT device of FIG. 1. [Figure 3] Partial cross-sectional view of the HEMT device of FIG. 2 at a certain stage of successive manufacturing processes. [Figure 4] Partial cross-sectional view of the HEMT device of FIG. 2 at a certain stage of successive manufacturing processes. [Figure 5] Partial cross-sectional view of the HEMT device of FIG. 2 at a certain stage of successive manufacturing processes. [Figure 6] Partial cross-sectional view of the HEMT device of FIG. 2 at a certain stage of successive manufacturing processes. [Figure 7] Partial cross-sectional view of the HEMT device of FIG. 2 at a certain stage of successive manufacturing processes. [Figure 8] Cross-sectional view of a HEMT device according to different embodiments of the present invention. [Figure 9] Partial cross-sectional view of the HEMT device of FIG. 8. [Figure 10] Partial cross-sectional view of the HEMT device of FIG. 9 at a certain stage of successive manufacturing processes. [Figure 11] Partial cross-sectional view of the HEMT device of FIG. 9 at a certain stage of successive manufacturing processes. [Figure 12] Partial cross-sectional view of the HEMT device of FIG. 9 at a certain stage of successive manufacturing processes. [Figure 13] Partial cross-sectional view of the HEMT device of FIG. 9 at a certain stage of successive manufacturing processes. [Figure 14]Partial cross-sectional view of the HEMT device of FIG. 9 at a certain stage of successive manufacturing processes. [Figure 15] Partial cross-sectional view of the HEMT device of FIG. 9 at a certain stage of successive manufacturing processes. [Figure 16] Partial cross-sectional view of the HEMT device of FIG. 9 at a certain stage of successive manufacturing processes. [Figure 17] Partial cross-sectional view of the HEMT device of FIG. 9 at a certain stage of successive manufacturing processes.
Embodiments for Carrying Out the Invention
[0017] FIG. 1 shows a HEMT device 1 in a Cartesian coordinate system XYZ composed of a first axis X, a second axis Y, and a third axis Z.
[0018] The HEMT device 1 is normally on. However, alternatively, the HEMT device 1 can also be normally off.
[0019] The HEMT device 1 is formed in a body 5 that has a first surface 5A and a second surface 5B and includes a substrate 6 and a heterostructure 8 extending on the substrate 6.
[0020] For example, a semiconductor substrate 6 such as silicon or silicon carbide, or other substances such as sapphire (Al 23 extends between the second surface 5B of the body 5 and each surface 6A.
[0021] The heterostructure 8 includes a compound semiconductor material of elements in Group III-V, and extends on the surface 6a of the substrate 6 to form the first surface 5A of the body 5.
[0022] The heterostructure 8 extends on the substrate 6 and has a surface 10A, which is an alloy containing gallium nitride such as gallium nitride (GaN) or InGaN, in this case a channel layer 10 of a first semiconductor material such as intrinsic gallium nitride (GaN), and extends between the surface 10A of the channel layer 10 and the first surface 5A of the body 5, which is for example Al x a 1-x AlInGaN, In x a 1-x , Al x n 1-x l, a compound based on a ternary or quaternary alloy of gallium nitride such as AlScN, which in this case is formed by a barrier layer 11 of a second semiconductor material such as intrinsic aluminum gallium nitride (AlGaN).
[0023] The channel layer 10 has a thickness along the third axis Z of, for example, between approximately 1 μm and 5 μm, and the barrier layer 11 has a thickness along the third axis Z of, for example, between approximately 5 nm and 30 nm.
[0024] The heterostructure 8 houses the active region 20, shown by the dotted line in Figure 1, which, in use, houses the conductive channel of the HEMT apparatus 1. The conductive channel is based on the formation of a layer of two-dimensional gas (2DEG) due to the difference in the band gap between the channel layer 10 and the barrier layer 11, and is formed by high-mobility charge carriers, such as electrons.
[0025] The HEMT device 1 includes a source region 15 and a drain region 16 that extend in direct electrical contact with the heterostructure 8, and a gate region 18 that extends parallel to the first axis X between the source region 15 and the drain region 16, also in direct electrical contact with the heterostructure 8.
[0026] The HEMT device 1 further includes an insulating or passivation layer 22 of a dielectric material, such as silicon nitride or silicon oxide, extending over the first surface 5A of the body 5.
[0027] In this embodiment, the insulating layer 22 covers the source region 15 and the drain region 16.
[0028] The gate region 18 can be formed by a single conductive layer or, for example, by a laminate of multiple conductive layers or a laminate of multiple conductive and insulating layers, and is suitable for forming a Schottky contact with the heterostructure 8, and in this case with the barrier layer 11.
[0029] The gate region 18 forms the gate electrode G of the HEMT device 1.
[0030] The gate region 18 is separated laterally along the first axis X from the source region 15 and the drain region 16 by the respective portions of the insulating layer 22.
[0031] In detail, the gate region 18 extends through the insulating layer 22 along the third axis Z of the insulating layer 22 for its entire thickness, up to the first surface 5A of the body 5.
[0032] However, according to other embodiments not shown herein, the gate region 18 may have a portion that extends to a certain depth within the heterostructure 8.
[0033] The source region 15 and the drain region 16 are in ohmic contact with the heterostructure 8.
[0034] In practice, the source region 15 and the drain region 16 form the source electrode S and drain electrode D of the HEMT device 1, respectively.
[0035] In this embodiment, the source region 15 and the drain region 16 are identical. Therefore, for the sake of explanation, only the source region 15 will be described below. However, it should be noted that the description of the source region 15 also applies to the drain region 16 unless otherwise specifically noted.
[0036] However, it will be apparent to those skilled in the art that, for example, depending on the specific application, the source region 15 and the drain region 16 may differ from each other by being formed from different materials or having different shapes and dimensions.
[0037] The source region 15, shown in detail in Figure 2, has an upper surface 28 and is formed by an interface portion 25 that extends in direct contact with the heterostructure 8 and a central body portion 26 that extends on the interface portion 25.
[0038] The interface portion 25 is made of a carbon-containing compound, such as a compound containing titanium and carbon or a compound containing carbon and tantalum.
[0039] In detail, the interface portion 25 can be made of a metal carbide such as titanium carbide (TiC) or tantalum carbide (TaC).
[0040] The interface portion 25 extends on the first surface 5A of the semiconductor body 5 in direct electrical contact with the barrier layer 11 and has a thickness along the third axis Z between, for example, 1 nm and 10 nm, and in particular between 1 nm and 5 nm.
[0041] The interface portion 25 forms an ohmic contact between the source region 15 and the heterostructure 8.
[0042] In this embodiment, the central body portion 26 is formed by a laminate of multiple metal layers, which includes a first central layer 26A of a material selected from titanium or tantalum that extends over the interface portion 25, a second central layer 26B of a metal such as aluminum that extends over the first central layer 26A, and a third central layer 26C of a metal such as titanium, tantalum, tungsten, or titanium nitride that extends over the second central layer 26B and forms the upper surface 28.
[0043] The second central layer 26B has a thickness along the third axis Z between, for example, 10 nm and 300 nm, and functions as a filling body for the source region 15.
[0044] The third central layer 26C acts as an encasing or protective layer for the source region 15.
[0045] However, the central body portion 26 can be formed by a different number of layers, depending on the specific application. For example, the third central layer 26C can be omitted.
[0046] Additionally or alternatively, the first central layer 26A may be omitted, as described below with respect to the manufacturing process of the source region 15.
[0047] In fact, according to one embodiment, the second central layer 26B can extend directly onto the interface portion 25.
[0048] According to a different embodiment, the central body portion 26 can be formed solely by the second filling layer 26B.
[0049] The inventors have verified that the interface portion 25 of the carbon-rich source region 15 forms an ohmic contact with the heterostructure 8, which has an even lower contact resistance than that which would be obtained if the interface portion 25 were carbon-free.
[0050] As described below regarding the manufacturing process of the source region 25, such ohmic contacts can be formed by low-temperature annealing, for example, below 550°C, particularly at temperatures between 400°C and 500°C.
[0051] Furthermore, the inventors have verified that the upper surface 28 of the source region 15 has an even lower surface roughness than that of the ohmic contacts of known HEMT devices, for example, less than 100 nm.
[0052] As a result, the HEMT device 1 has optimal electrical performance and the probability of malfunction or damage occurring is low.
[0053] Hereafter, with reference to Figures 3 to 7, the manufacturing process of the HEMT apparatus 1, particularly the manufacturing process leading to the formation of the source region 15, will be described.
[0054] As will be apparent to those skilled in the art, the manufacturing process for forming the source region 15, as described with reference to Figures 3 to 7, is also applicable to the formation of the drain region 16. For example, the drain region 16 can be formed simultaneously with the source region 15.
[0055] Furthermore, Figures 3 to 7 do not illustrate the steps (in context, earlier and / or later steps) for forming the gate region 18, electrical contact metallization, the overall electrical connection, and all other elements that are known and not shown herein but are useful or necessary for the operation of the HEMT apparatus 1.
[0056] Figure 3 shows a cross-section of the work body 50 having a first surface 50A and a second surface 50B. Elements of the work body 50 that are common to all those described with reference to Figures 1 and 2 are indicated by the same reference numbers, and further detailed descriptions are omitted.
[0057] In the working body 50, a heterostructure 8 encompassing the substrate 6, the channel layer 10, and the barrier layer 11 has already been formed. The heterostructure 8, in particular the barrier layer 11, forms the first surface 50A of the working body 50.
[0058] Next, referring to Figure 4, a mask 60 having a window 62 is formed on the first surface 50A of the work body 50.
[0059] The mask 60 can be formed by known lithography and etching processes, for example, the mask 60 can be formed by a positive, negative, or two-layer type photoresist.
[0060] The window 62 extends along the third axis Z through the thickness of the mask 60, and it is desirable to leave a portion of the first surface 50A of the work body 50 exposed, thereby forming the source region 15.
[0061] Referring to Figure 5, for example, a carbon working interface layer 65 is formed on the working body 50 via vapor deposition, sputtering, chemical vapor deposition (CVD), etc.
[0062] The working interface layer 65 has a thickness along the third axis Z, for example, between 1 nm and 10 nm.
[0063] In particular, the working interface layer 65 can have a thickness along the third axis Z between 1 nm and 5 nm, depending on the intended thickness of the interface portion 25.
[0064] The work interface layer 65 includes a reaction portion 66 that extends inside the window 62, i.e., over the exposed portion of the first surface 50A of the work body 50, and a spurious portion 67 that extends above the mask 60.
[0065] Next, referring to Figure 6, a metal work layer 70 is formed on the work interface layer 65, for example, by vapor deposition, sputtering, chemical vapor deposition (CVD), etc.
[0066] The metal working laminate 70 includes a reaction layer 70A selected between titanium and tantalum that extends directly over the working interface layer 65.
[0067] The reaction layer 70A has a thickness along the third axis, for example, between 2 nm and 10 nm.
[0068] In this embodiment, the metal work laminate 70 also includes a filling layer 70B made of, for example, aluminum, which extends over the reaction layer 70A, and a protective layer 70C made of, for example, titanium, tantalum, or tungsten, which extends over the filling layer 70B.
[0069] The packed layer 70B has a thickness between, for example, 10 nm and 300 nm.
[0070] The metal work layer 70 is formed both inside the window 62, i.e., on the reaction portion 66 of the work interface layer 65, and on the mask 60.
[0071] The portion of the metal work laminate 70 that is attached to the mask 60 rests on the spurious portion 67 of the work interface layer 65, forming a spurious attachment as shown overall by reference numeral 72 in Figure 6.
[0072] Next, the mask 60 is removed by a lift-off process of a known type. Along with the mask 60, the spurious adhering portion 72 is also removed.
[0073] Next, referring to Figure 7, the work body 50 is exposed to the annealing process as schematically shown by arrow 80 in Figure 7.
[0074] This annealing can be carried out in a protected environment (e.g., in a nitrogen or argon atmosphere) at temperatures between 400°C and 600°C, particularly below 550°C.
[0075] The annealing can be rapid thermal annealing (RTA) or any other type of annealing known to be present.
[0076] During the annealing period, the reaction portion 66 of the carbon working interface layer 65 reacts with the titanium or tantalum reaction layer 70A to form the interface portion 25 of the source region 15 shown in Figures 1 and 2.
[0077] Depending on the thickness of the reaction portion 66, the thickness of the reaction layer 70A, and the duration of the annealing, the reaction layer 70A may only partially react with the reaction portion 66, and the remaining portion of the reaction layer 70A may form the first central layer 26A shown in Figure 2.
[0078] However, the reaction layer 70A can react completely with the reaction portion 66 of the working interface layer 65, in which case the second central layer 26B (corresponding to the packed layer 70B) extends directly onto the interface portion 25 in the HEMT apparatus 1 shown in Figures 1 and 2.
[0079] For example, the HEMT apparatus 1 is formed after further manufacturing processes of a known type, such as the formation of the gate region 18, the dicing of the work body 50, and the formation of electrical connections.
[0080] The presence of the working interface layer 65 enables the formation of ohmic contact with the heterostructure 8 at already low temperatures, for example, 550°C or even lower.
[0081] The inventors have verified that annealing at such low temperatures makes it possible to obtain a low roughness on the upper surface 28 of the source region 15. For example, the inventors have verified that the roughness of the upper surface 28 of the source region 15 may have a root mean square (RMS) value of approximately 10 nm, as measured by an atomic force microscope (AFM).
[0082] Furthermore, the annealing that generates the reaction between the reaction portion 66 and the reaction layer 70A results in the resulting interface portion 25 being an epitaxial layer with respect to the crystalline layer and heterostructure 8, which can be observed by TEM (transmission electron microscope) and XRD (X-ray diffraction) analysis.
[0083] Figure 8 shows a different embodiment of the HEMT apparatus of the present invention, indicated here by reference numeral 100. The HEMT apparatus 100 has a substantially similar structure to the HEMT apparatus 1 in Figure 1, and therefore, the same reference numerals are used for common elements, and further explanation is omitted.
[0084] The HEMT apparatus 100 has a first surface 5A and a second surface 5B and is formed within a body 5 that encloses the substrate 6 and the heterostructure 8. The heterostructure 8 also encloses the channel layer 10 and the barrier layer 11 and houses the active region 20.
[0085] The HEMT device 100 further includes a source region indicated here as 115 and a drain region indicated here as 116, and the gate region 18 extends along the first axis X between the source region 115 and the drain region 116.
[0086] The gate region 18 extends along the third axis Z, penetrating the thickness of the insulating layer 22, until it reaches the first surface 5A of the body 5.
[0087] In this embodiment, the source region 115 and the drain region 116 are recessed and extend from the first surface 5A of the body 5 into the interior of the heterostructure 8, making ohmic contact with the heterostructure 8 and, in particular, with the conductive channels housed within the active region 20.
[0088] Furthermore, in this embodiment, the source region 115 and the drain region 116 form the source electrode S and drain electrode D of the HEMT device 100, respectively. Moreover, the source region 115 and the drain electrode 116 are equivalent to each other, and therefore, for the sake of explanation, only the source electrode 115 will be referred to from now on. However, what is described for the source region 115 also applies to the drain region 116 unless otherwise specified.
[0089] However, as will be apparent to those skilled in the art, the source region 115 and the drain region 116 can be different from each other, for example, they can be made of different materials or have different shapes and dimensions depending on the specific application.
[0090] As shown in detail in Figure 9, the source region 115 extends through the barrier layer 11 and terminates in the barrier layer 11.
[0091] In one embodiment not shown herein, the source region 115 can extend through the thickness of the barrier layer 11 until it reaches the surface 10A of the channel layer 10.
[0092] In further embodiments not shown herein, the source region 115 can penetrate the thickness of the barrier layer 11 along the third axis Z and extend partially through the thickness of the channel layer 10 along the third axis. That is, the source region 115 can terminate within the channel layer 10.
[0093] The source region 115 is also formed by an interface portion 125 that extends in direct contact with the heterostructure 8 and a central body portion 126 that extends over the interface portion 125 and forms the upper surface 128 of the source region 115.
[0094] The interface portion 125 also consists of a carbon-containing compound, such as a titanium and carbon compound or a carbon and tantalum compound.
[0095] In detail, the interface portion 125 may be made of a metal carbide, such as titanium carbide (TiC) or tantalum carbide (TaC).
[0096] The central body portion 126 is also formed by a first central layer 126A made of titanium or tantalum, a second central layer 126B made of a metal such as aluminum, and a third central layer 126C made of a metal such as titanium, tantalum, tungsten, or titanium nitride.
[0097] Further details regarding the interface portion 25 and central body portion 26 of HEMT device 1 apply to the interface portion 125 and central body portion 126 of HEMT device 100, respectively. Therefore, further detailed explanations of the interface portion 125 and central body portion 126 are omitted here.
[0098] Hereafter, with reference to Figure 10-17, the manufacturing process of the HEMT apparatus 100, particularly the manufacturing process leading to the formation of the source region 115, will be described.
[0099] As will be apparent to those skilled in the art, the manufacturing process for forming the source region 115, as described with reference to Figure 10-17, also applies to the formation of the drain region 116. For example, the drain region 116 can be formed simultaneously with the source region 115.
[0100] Furthermore, Figure 10-17 does not illustrate the steps (in context, earlier and / or later steps) for forming the gate region 18, the electrical contact metallization, the overall electrical connections, and other known but not shown elements that are useful or necessary for the operation of the HEMT device 100.
[0101] Figure 10 shows a cross-section of the work body 150 having a first surface 150A and a second surface 150B. Elements of the work body 150 that are common with those described with reference to Figures 8 and 9 are given the same reference numerals, and further detailed descriptions of them are omitted.
[0102] In the working body 150, a heterostructure 8 encompassing the substrate 6, the channel layer 10, and the barrier layer 11 has already been formed. In this case, the heterostructure 8, and in particular the barrier layer 11, forms the first surface 150A of the working body 150.
[0103] Furthermore, a sacrificial layer laminate 153 is formed on the first surface 150A, which is intended to form a mask for the formation of the source region 115, and encompasses the first sacrificial layer 154 and the second sacrificial layer 155.
[0104] The first sacrificial layer 154 consists of a non-photosensitive material, for example, a solution of a non-photosensitive organic polymer, and has a thickness along a third axis Z, which is selected as a function of the thickness of the metal to be deposited. The first sacrificial layer 154 extends over the first surface 150A of the work body 150.
[0105] The second sacrificial layer 155 is made of a photosensitive material, such as a photoresist, and extends over the first sacrificial layer 154.
[0106] The first and second sacrificial layers 154 and 155 can be attached via spin coating technology.
[0107] Next, referring to Figure 11, a second sacrificial layer 155 is patterned through known lithography and development processes to selectively remove a portion of the second sacrificial layer 155 and form a window 157 in the area of the work body 150 where the source area 115 is to be formed.
[0108] Since the first sacrificial layer 154 is not photosensitive, the lithography process of the second sacrificial layer 155 has no effect on the first sacrificial layer 154. At the end of the development of the second sacrificial layer 155, the first sacrificial layer 154 is partially exposed at the window 157. During this process, isotropic etching of the first sacrificial layer 154 also occurs, uniformly removing the area of the first sacrificial layer 154 exposed by the window 157. Since the etching is of the isotropic type, a portion of the first sacrificial layer below the second sacrificial layer 155 is also removed. In practice, an under-etch or undercut phenomenon is observed, and therefore, an undercut region 159 is formed on the side of the window 157 along the first axis X, extending below the second sacrificial layer 155.
[0109] The removal of the first sacrificial layer 154 proceeds until it reaches the first surface 150A of the work body 150.
[0110] Next, referring to Figure 12, for example, a recess 162 is formed in the heterostructure 8 at the window 157 by etching.
[0111] In this embodiment, the recess 162 extends from the first surface 150A of the barrier layer 11 and terminates within the barrier layer 11.
[0112] Subsequently, referring to Figure 13, a carbon working interface layer 165 is formed on the working body 150 using the sacrificial layer laminate 153 as a mask, for example, by vapor deposition, sputtering, or chemical vapor deposition (CVD). The working interface layer 165 includes a reaction portion 166 that is in direct contact with the barrier layer 11 and extends into the recess 162, and a spurious portion 167 that extends onto the second sacrificial layer 155.
[0113] The working interface portion 165 has a thickness between, for example, 1 nm and 10 nm.
[0114] In particular, the working interface layer 165 can have a thickness along the third axis Z between 1 nm and 5 nm, depending on the intended thickness of the resulting interface portion 125.
[0115] In this embodiment, the reaction portion 166 of the work interface layer 165 also partially extends onto the first surface 150A of the work body 150 on the side of the recess 162. In practice, the reaction portion 166 is a conformal and continuous portion with respect to the wall of the barrier layer 11 that forms the recess 162.
[0116] Next, referring to Figure 14, a known type of lift-off process is performed, during which the first and second sacrificial layers 154 and 155 are removed. At the same time, the spurious portion 167 of the working interface layer 165 is also removed.
[0117] Next, referring to Figure 15, the metal work layer 170 is formed on the work body 105 via a blanket-type adhesion process. In practice, the metal work layer 170 is formed both on the first surface 150A of the work body 150 and on the reaction portion 166 of the work interface layer 165.
[0118] The metal work laminate 170 includes a titanium or tantalum reaction layer 170A that extends over the reaction portion 166 of the work interface layer 165.
[0119] The reaction layer 170A has a thickness between, for example, 2 nm and 10 nm.
[0120] In this embodiment, the metal work laminate 170 also includes a filling layer 170B, for example, made of aluminum, extending over the reaction layer 170A, and a protective layer 170C, for example, made of titanium, tantalum, tungsten, etc., extending over the filling layer 170B.
[0121] The packed layer 170B has a thickness between, for example, 10 nm and 300 nm.
[0122] Referring to Figure 16, a selective etching process is used to selectively remove portions of the metal workpiece 170 that extend outside the region intended to form the source region 115.
[0123] In practice, only the body portion extending over the reaction portion 166 of the work interface layer 165 remains within the laminated metal layers 170.
[0124] Subsequently, referring to Figure 17, the work body 150 is exposed for annealing, which is the same as described with reference to Figure 7, and therefore a detailed explanation is omitted here.
[0125] Following this annealing, the reaction portion 166 of the working interface layer 165 reacts with the reaction layer 170A to form the interface portion 125 of the source region 115 shown in Figures 8 and 9.
[0126] For example, the HEMT apparatus 100 is formed through further manufacturing processes of known types, such as the formation of the gate region 18, the dicing of the work body 150, and the formation of the electrical connections.
[0127] The use of the sacrificial layer laminate 153, particularly the presence of the undercut region 159, makes it possible to improve the reliability of the lift-off process and, therefore, the reliability of the manufacturing process of the HEMT apparatus 100.
[0128] Finally, it goes without saying that various modifications and variations can be made to the HEMT apparatus 1, 100 and related manufacturing methods described and illustrated herein without departing from the technical scope of the present invention.
[0129] For example, the channel layer 10 and the barrier layer 11 can each be formed by superimposing multiple layers on each other, depending on the specific application, such as one or more layers of appropriately doped or intrinsic type GaN, or GaN-based alloys.
[0130] Referring to HEMT apparatus 1, the source region 15, drain region 16, and gate region 18 can extend along the second axis Y in known manner in different shapes and forms depending on the specific application, and therefore a description of such manners is omitted. For example, in a plan view not shown here, the source region 15, drain region 16, and gate region 18 can have the shape of an elongated strip along the second axis Y, or they can have a circular shape or any other shape, whether regular or irregular.
[0131] For example, the source region 15, the drain region 16, and the gate region 18 can each form a part of the respective region having an even more complex shape, and can be electrically connected to other parts via specific electrical connections.
[0132] Similar considerations apply to the shape and form of the source region 115, drain region 116, and gate region 18 of the HEMT device 100.
[0133] It is possible to combine the above-described embodiments to form further solutions.
Claims
1. From a working body (50; 150) containing a semiconductor heterostructure (8) A method for manufacturing a HEMT device (1; 100) comprising forming a conductive region (15, 16; 115, 116) having an interface portion (25) in ohmic contact with the semiconductor heterostructure, the forming of the conductive region comprising: forming a first reaction region (66; 166) on the semiconductor heterostructure, the first reaction region (66; 166) comprising carbon; forming a metal laminate (70; 170) in contact with and extending from said first reaction region and including a second reaction region (70A; 170A); and annealing the work body so that the first reaction region (66; 166) reacts with the second reaction region (70A; 170A) to form an interface portion (25; 125) of the conductive region, the interface portion comprising a compound containing carbon; A method that encompasses the above.
2. 2. The method of claim 1, wherein the second reaction region (70A; 170A) comprises titanium or tantalum.
3. 3. A method according to claim 1 or 2, wherein the first reaction region (66:166) has a thickness between 1 nm and 10 nm, in particular between 1 nm and 5 nm.
4. 2. The method of claim 1, wherein annealing the work body is performed at a temperature between 400 and 550°C, in particular between 400 and 500°C.
5. 10. The method of claim 1, wherein forming a conductive region further comprises forming a recess (162) in the semiconductor heterostructure (8), and wherein the first reaction region (166) is formed in the recess.
6. the semiconductor heterostructure (8) having a surface (50A; 150A) and forming a first reaction region (66:166), forming a mask (60; 153) on the surface of the semiconductor heterostructure; depositing an interface layer (65; 165) comprising carbon on said surface (150A) of said semiconductor heterostructure (8); and performing a lift-off process of the mask (60:153); 10. The method of claim 1, comprising:
7. forming a metal laminate (70; 170) depositing a second reaction region (70A; 170A) on said first reaction region (66; 166); and depositing a filler region (70B; 170B) on said second reaction region; 10. The method of claim 1, comprising:
8. 8. The method of claim 7, wherein the fill region comprises aluminum.
9. In the HEMT device (1;100), a semiconductor heterostructure (8); Conductive regions (15, 16; 115, 116) in ohmic contact with the semiconductor heterostructure; wherein the conductive region includes an interface portion (25; 125) comprising carbon and extending in direct contact with the semiconductor heterostructure.
10. 10. A HEMT device according to claim 9, wherein the interface portions (25; 125) of the conductive regions (15, 16; 115, 116) consist of metal carbide.
11. 11. A HEMT device according to claim 9 or 10, wherein the interface portion (25; 125) of the conductive region (15, 16; 115, 116) is a compound comprising carbon and titanium or a compound comprising carbon and tantalum.
12. 10. The HEMT device of claim 9, wherein the conductive region further comprises a central body portion (26; 126) including at least one metal layer (26A, 26B, 26C; 126A, 126B, 126C) extending over the interface portion.
13. 13. The HEMT device according to claim 12, wherein said at least one metal layer is an aluminum layer (26B; 126B).
14. 10. The HEMT device of claim 9, wherein the conductive region (15, 16; 115, 116) has an upper surface (28; 128) with a roughness, the roughness having a root-mean-square value lower than 100 nm.
15. 10. The HEMT device of claim 9, wherein the conductive regions (115, 116) are recessed and extend partially inside the semiconductor heterostructure.