Patent Application
20240186405
The present application relates to a high-electron-mobility transistor structure as well as a fabricating method and use thereof, belonging to the technical field of semiconductor devices.
New-generation wide bandgap semiconductor material gallium nitride (GaN) simultaneously has the advantages of high breakdown voltage (3.1 MV/cm), high-electron-mobility (about 1500 cm2/V·s) and the like. A GaN-based heterostructure (such as AlGaN/GaN, AlInGaN/GaN and AlN/GaN) can form high-density two-dimensional electron gas (2DEG) without deliberate doping due to the presence of polarization effect, and therefore it becomes an ideal selection of a new-generation electronic device, namely transverse high-electron-mobility transistor (HEMT). GaN HEMT has the significant advantages of high current density, high voltage tolerance, high frequency and the like, and therefore as a radiofrequency power amplifier (PA), it has been successfully applied to 5G core infrastructures such as a base station, and is gradually replacing the traditional silicon-based lateral double-diffused metal-oxide-semiconductor (LDMOS) device and continuously plays an important role in the whole 5G communication technology.
In the field of consumer electronics having a wider market prospect, the silicon-based GaN HEMT has attractions in the application of low-cost radio frequency (RF)/millimeter wave (MM Wave) as well. Compared with the traditional gallium arsenide (GaAs) heterojunction bipolar transistor (HBT), GaN HEMT exhibits stronger power output ability and more excellent heat dissipation performance, so it can stand out its inherent advantages in 5G communication services with higher power requirements, and is expected to be applied to transmitting terminal PA in RF front-end modules of mobile phones. However, currently, there is no GaN RFHEMT that is really applied to mobile terminals for the reasons that the conventional GaN HEMT has inherent defects in the aspect of device structures: along a channel direction, there are gate-source access regions and gate-drain access regions of the device, thus introducing a large proportion of series resistance Rac so that voltages effectively applied to both sides of the channel are greatly reduced, the saturation behavior of the output current of the device is physically fundamentally restricted, thereby resulting in the occurrence of pinch saturation ahead of speed saturation so as not to reduce the Vknee (Knee Voltage), as shown in
In order to solve the above problems, it is a feasible solution to shorten a source-drain spacing as far as possible under the condition of allowing a semiconductor process technology. By using the solution, a source-drain high electric field can be built in a case of small source-drain voltage, so that speed saturation occurs ahead of pinch saturation, thereby effectively reducing the knee voltage. At present, researchers adopt a side wall technology to fabricate GaN HEMT having a source-drain spacing of 130 nm; also, researchers adopt the conventional photolithographic process and electron beam exposure technology to fabricate short channel GaN HEMT (<500 nm). However, neither of the devices fabricated by using the above solution avoids gate-source access regions and gate-drain access regions, so the linearity degradation of the device when outputting high current is relatively serious.
In another aspect, it is extremely difficult to fabricate enhanced GaN HEMT applied to RF (and millimeter wave) by using the conventional solution, and therefore the enhanced working mode of PA is necessary for the RF frontend of the mobile intelligent terminal in order to simplify the system and reduce the area of the chip. At present, for only Intel in the world, a barrier layer slow etching technology is utilized to fabricate enhanced GaN RFHEMT. However, this technology puts forward extremely high requirements on etching accuracy and controllability, which is difficult to achieve. Besides, researchers propose a p-NiO gate electrode technology to develop enhanced GaN RFHEMT, however, p-NiO difficultly grows to a certain extent, and has poor thermal stability.
The main objective of the present application is to provide a near full-gate controlled high-electron-mobility transistor structure of T-type gate, which uses a composite layer composed of a heavily doped ohmic contact layer and a high resistance layer as a support layer and realizes spatial isolation from the heavily doped ohmic contact layer by utilizing air, as well as a fabricating method and use thereof, in order to overcome the defects in the prior art.
To achieve the above-mentioned objective of the present application, the present application adopts the following technical solution:
One aspect of the present application provides a high-electron-mobility transistor structure, comprising:
One aspect of the present application provides another high-electron-mobility transistor structure, comprising an epitaxial structure as well as a source electrode, a drain electrode and a gate electrode which are matched with the epitaxial structure, wherein the epitaxial structure comprises a heterojunction in which a carrier channel is formed, the carrier channel is distributed in a region covered by the orthographic projection of the gate electrode on the epitaxial structure; wherein, the epitaxial structure further comprises a heavily doped region and a high resistance region, the heavily doped region is arranged on the heterojunction and forms ohmic contact with the carrier channel, the source electrode, the drain electrode and the heavily doped region form ohmic contact, the high resistance region is arranged on the heavily doped region, and the source electrode is isolated from the gate electrode by the high resistance region and the drain electrode is isolated from the gate electrode by the high resistance region.
Another aspect of the present application provides a fabricating method of a high-electron-mobility transistor structure, comprising:
Another aspect of the present application further provides a fabricating method of a high-electron-mobility transistor structure, comprising:
Another aspect of the present application further provides use of the high-electron-mobility transistor structure in fabricating power amplifiers, radio frequency devices, communication devices or electronic devices.
Another aspect of the present application further provides a power amplifier, comprising the high-electron-mobility transistor structure.
Compared with the prior art, the present application has the advantages:
To more clearly illustrating the technical solution in the embodiments of the present application or in the prior art, the accompanying drawings required to be used in the embodiments or in the prior art will be simply discussed below, obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by persons of ordinary skill in the art without creative efforts.
In view of the defects in the prior art, the applicant of this case puts forward the technical solution of the present application through long-term researches and lots of practices. The present application provides a high-electron-mobility transistor structure. The composite layer of the heavily doped layer and the high resistance layer is grown by secondary epitaxy. On the one hand, the heavily doped region formed by the heavily doped layer can effectively reduce the source-drain ohmic contact resistance, and on the other hand, gate-source and gate-drain high resistance materials can effectively reduce the parasitic capacitance and suppress the leakage of the gate electrode, thereby ensuring the reliability of the device while improving the frequency characteristics of the device.
One aspect of the embodiments of the present application provides a high-electron-mobility transistor structure, which, for example, can be a GaN electronic device structure, comprising:
That is, the orthographic projection of the gate foot of the gate electrode on the first semiconductor layer basically coincides with the orthographic projection of the second semiconductor layer on the first semiconductor layer. Preferably, the orthographic projection of the gate foot coincides with the orthographic projection of the second semiconductor layer on the first semiconductor layer.
In some embodiments, the gate electrode comprises a first part and a second part which are successively distributed in a direction away from the second semiconductor layer, wherein the first part is the gate foot and the radial size of the first part is smaller than or equal to that of the second part. Especially, the gate electrode consists of the first part and the second part, the radial size of the first part is smaller than that of the second part. Where, the first part and the second part can be integrally formed.
In some specific embodiments, the gate electrode is a T-type gate, but is not limited thereto. For example, the gate electrode can also be a T-type gate, a trapezoid-type gate electrode, etc.
In some embodiments, the second semiconductor layer is relatively thin and the gate electrode is isolated from the second semiconductor layer by the dielectric layer, thereby forming an enhanced device. Of course, the second semiconductor layer is relatively thick and the dielectric layer cannot be arranged between the gate electrode and the second semiconductor layer, thereby forming a depletion-mode device.
In some embodiments, an insertion layer is also arranged between the first semiconductor layer and the second semiconductor layer.
In some embodiments, a cap layer is also distributed between the dielectric layer and the second semiconductor layer.
In some embodiments, the epitaxial structure also comprises an ohmic contact layer, the ohmic contact layer is in contact with the carrier channel, the source electrode and the drain electrode are both arranged on the ohmic contact layer and form ohmic contact with the ohmic contact layer.
Further, the ohmic contact layer is arranged on the first semiconductor layer and is in contact with the carrier channel.
In some embodiments, the ohmic contact layer and the carrier channel form ohmic contact.
In some embodiments, a groove is distributed between a source electrode region and a drain electrode region on the ohmic contact layer, the bottom of the at least gate foot and the second semiconductor layer are both arranged in the groove. Further, the gate foot of the gate electrode can be entirely arranged in the groove.
Further, an included angle of 60-90° is formed between the side wall of the groove and the surface of the first semiconductor layer, especially preferably an included of 90°. That is, the side wall of the groove is almost vertical to the surface of the first semiconductor layer. Further, the gate cap of the gate electrode covers the groove.
In some embodiments, the gate electrode is electrically isolated from the ohmic contact layer by the dielectric layer, the dielectric layer arranged between the gate electrode and the ohmic contact layer can be defined as a dielectric side wall; or, the gate electrode is isolated from the heavily doped ohmic contact layer by air.
More preferably, the epitaxial structure can adopt a thin barrier structure. Of course, in same cases, the epitaxial structure can also adopt a thick barrier structure.
More preferably, the radial size of the gate foot of the gate electrode can be set as 10 nm-500 nm.
In some embodiments, the epitaxial structure can further comprise a P-type layer arranged on the second semiconductor layer, etc., and the gate electrode is arranged on the P-type layer, so as to form a P-type gate enhanced device.
In some embodiments, the ohmic contact layer is also provided with a sacrificial layer, and the at least local regions of the source electrode, the drain electrode and the gate electrode are exposed out of the sacrificial layer. The material of the sacrificial layer includes but is not limited to PI glue, BCB glue (Benzo-Cyclobutene), SOG (Spin-on-glass) or other low-k dielectric materials, and can be removed by technological means, so as to realize spatial separation with the heavily doped ohmic contact layer by utilizing air.
Further, the material of the epitaxial structure includes but is not limited to III-V group compounds. For example, the above-mentioned first semiconductor layer can be understood as a channel layer, and the material of the first semiconductor layer can include GaN, etc. The above-mentioned second semiconductor layer can be understood as a barrier layer, and the material of the second semiconductor layer can include AlGaN, AlN, AlInN or AlInGaN, etc, especially heavily doped n-type GaN. The material of the above-mentioned insertion layer can include AlN, etc.
In some embodiments, the material of the dielectric layer includes Al2O3, SiO2, HfO2, AlON, silicon nitride and the like, or combinations thereof, such as Al2O3/AlN, Al2O3/HfO2 and other composite gate electrode media, but is not limited thereto.
In some embodiments, the GaN electronic device structure includes an N-polar HEMT device structure or an HEMT device structure with a back barrier structure, but is not limited thereto.
In some embodiments, the high-electron-mobility transistor structure also includes a substrate where the epitaxial structure is formed. The material of the substrate includes but is not limited to silicon, sapphire, silicon carbide, gallium nitride, aluminum nitride, etc. In addition, the epitaxial structure can also include a nucleating layer, a buffer layer and the like which are grown on the substrate in turn, which is familiar in the art and will not be described in detail here.
In the above embodiments of the present application, a GaN electronic device structure with short channel, full gate electrode control, series resistance and no near access regions is formed by directly constructing a gate electrode (such as a T-type gate electrode) between the source electrode and the drain electrode, which can effectively reduce the knee voltage of the device and improve the linearity of the device. Moreover, the GaN electronic device structure is completely suitable for depletion-mode and enhancement-mode HEMT devices. In particular, when a thin barrier-based heterojunction epitaxial structure is adopted, the enhanced device can be realized without a groove gate etching process. Meanwhile, the device has large transconductance, which is conducive to significantly improving the PA power gain of the device.
Some embodiments of the present application further provide a fabricating method of a high-electron-mobility transistor structure, comprising:
In some embodiments, the fabricating method specifically comprises:
In some embodiments, the fabricating method further comprises: growing an ohmic contact layer on a region of the surface of the first semiconductor layer that is not covered by the second semiconductor layer, and allowing the surface of the ohmic contact layer to be higher than that of the surface of the second semiconductor layer, so as to form a groove in the ohmic contact layer, then removing the mask and fabricating the gate electrode, and at least allowing the bottom of the gate foot to be distributed in the groove.
In some embodiments, the fabricating method further comprises: after the ohmic contact layer is grown, removing the mask and then forming a continuous dielectric layer on the ohmic contact layer and the second semiconductor layer, then fabricating the gate electrode on the dielectric layer, and forming a window on the dielectric layer, and fabricating the source electrode and the drain electrode in the window.
Where, a process of fabricating the gate electrode can be carried out before or after a process of fabricating the source electrode and the drain electrode.
In some embodiments, the fabricating method further comprises: after the ohmic contact layer is grown, fabricating the source electrode and the drain electrode on the ohmic contact layer, then forming a continuous sacrificial layer on the ohmic contact layer, and embedding the source electrode and the drain electrode into the sacrificial layer, and at least allowing the surface of the mask to be exposed out of the sacrificial layer, then removing the mask layer, and fabricating the gate electrode on the second semiconductor layer;
After the fabrication of the source electrode, drain electrode and gate electrode is completed, the sacrificial layer can be removed, so as to realize spatial isolation from the heavily doped ohmic contact layer by utilizing air, or the sacrificial layer can be retained and used as a support layer for the gate electrode and the like.
In some embodiments, the fabricating method specifically comprises: arranging the mask on the gate electrode region of the second semiconductor layer, and at least forming the dielectric layer on the side wall of the mask, then successively etching the second semiconductor layer and growing the ohmic contact layer on the first semiconductor layer.
In some embodiments, the fabricating method further comprises: performing an operation of active region isolation on the epitaxial structure, wherein such the operation can be implemented according to well-known modes in the art.
In some embodiments, the gate electrode includes a gate foot and a gate cap which are sequentially distributed in a direction away from the second semiconductor layer, wherein the radial size of the gate foot is smaller than or equal to that of the gate cap. Preferably, the gate electrode includes a T-type gate, but is not limited thereto.
In the above embodiments of the present application, the mask can be formed by a photoresist or a dielectric film, and can be graphically processed by exposure, developing and other methods that are familiar in the art, and can also be removed by wet etching and other modes that are familiar in the art.
In the above embodiments of the present application, each structural layer in the epitaxial structure can be grown by metal organic vapor deposition (MOCVD), atomic layer deposition (ALD), plasma enhanced chemical vapor deposition (PECVD) and other physical and/or chemical vapor deposition methods that are familiar in the art.
In the above embodiments of the present application, the dielectric layer can be fabricated by ALD or other physical and chemical vapor deposition methods.
In the above embodiments of the present application, the source electrode, the drain electrode and the gate electrode can be formed by sputtering, evaporation and other methods that are known in the art and a metal stripping technology.
In preferred embodiments of the present application, the above-mentioned GaN electronic device structure is fabricated by using thin barrier heterostructure-based GaN HEMT epitaxial structure and by virtue of secondary epitaxial growth ohm technology, which can be defined as a near-full gate controlled short channel device. This GaN electronic device structure can simultaneously realize a low knee voltage and an enhanced operation mode, thus meeting the RF front-end PA application scenarios. Compared with the existing GaN RFHEMT, this GaN electronic device structure has no gate-source access regions and gate-drain access regions, and the entire short channel is effectively regulated by the gate electrode, thereby eliminating the nonlinear effect induced by RGS resistance degradation on the basis of achieving speed saturation. In particular, in the aspect of implementing the enhanced working mode, since the epitaxial structure of this GaN electronic device structure uses a thin barrier and does not require dry etching and other processes, thus avoiding the etching damage of the existing groove gate enhanced HEMT device during the fabricating so as to greatly improve the fabricating reliability and stability of the device; in the aspect of suppressing the parasitic effect, the high-frequency parasitic effect can be greatly suppressed due to the T-type gate structure that realizes spatial isolation from the heavily doped ohmic contact layer by utilizing air. Meanwhile, the thin barrier means a large gate capacitance, which is helpful to greatly improve the transconductance of this GaN electronic device structure, thus ultimately improving the power gain of PA.
Some embodiments of the present application also provide the use of the GaN electronic device structure in fabricating power amplifiers, radio frequency devices, communication devices or electronic devices. Further, the power amplifier can be a RF wave band power amplifier, or a millimeter wave band power amplifier, a terahertz wave band power amplifier, etc., and is not limited thereto. The electronic devices can be mobile phones, tablet computers or other smart devices, and are not limited thereto.
Another aspect of the present application also provides a high-electron-mobility transistor structure, including an epitaxial structure, and a source electrode, a drain electrode and a gate electrode which are matched with the epitaxial structure. The epitaxial structure includes a heterojunction where a carrier channel is formed, and the carrier channel is distributed in a region covered by the orthographic projection of the gate electrode on the epitaxial structure; wherein, the epitaxial structure also includes a heavily doped region and a high resistance region. The heavily doped region is arranged on the heterojunction and forms ohmic contact with the carrier channel. Both the source electrode and the drain electrode form ohmic contact with the heavily doped region. The high resistance region is arranged on the heavily doped region, and the source electrode is isolated from the gate electrode by the high resistance region, and the drain electrode is isolated from the gate electrode by the high resistance region.
It should be noted that the heavily doped region and high resistance region can be considered as the highly doped ohmic contact layer.
In some embodiments, the upper surface of the heavily doped region is higher than the surface of the carrier channel.
Where, the material of the heavily doped region can be GaN, or a combination of any one or more of InGaN, AlInGaN or AlGaN, and is not limited thereto. The material of the high resistance region can be GaN, or a combination of any one or more s of SiN, AlN, InGaN, AlInGaN or AlGaN, but is not limited thereto.
In some embodiments, the heterojunction is mainly composed of a first semiconductor layer and a second semiconductor layer arranged on the first semiconductor layer. The heavily doped region includes a first heavily doped region matched with the source electrode and a second heavily doped region matched with the drain electrode. The first heavily doped region and the second heavily doped region are respectively located at both sides of the second semiconductor layer, and the high resistance region includes a first high resistance region matched with the source electrode and a second high resistance region matched with the drain electrode. The at least local regions of the source electrode and the drain electrode pass through the first high resistance region and the second high resistance region and then form ohmic contact with the first heavily doped region and the second heavily doped region. The first heavily doped region and the first high resistance region jointly constitute the source electrode contact region of the high-electron-mobility transistor structure, and the second heavily doped region and the second high resistance region jointly constitute the drain electrode contact region of the high-electron-mobility transistor structure.
Where, the first semiconductor layer is the first semiconductor layer of the high-electron-mobility transistor structure, the thickness of the first semiconductor layer is 5-200 nm, and the material of the first semiconductor layer can be a GaN material; the second semiconductor layer is the second semiconductor layer of the high-electron-mobility transistor structure. The thickness of the second semiconductor layer is 1-100 nm, and the material of the second semiconductor layer can be a combination of any one or more of AlGaN-based, AlN-based, AlInN-based and AlInGaN-based materials, but is not limited thereto.
In some embodiments, the carrier channel can be a two-dimensional electron gas channel, and the heavily doped region is of n type; or, the carrier channel is a two-dimensional hole gas channel, and the heavily doped region is of p type.
In some embodiments, the material of the epitaxial structure can be a Ga polar surface or an N polar surface. A device structure with the two-dimensional electron gas channel, which is fabricated on the Ga polar surface, is consistent with a device structure with a two-dimensional hole gas channel, which is fabricated on the N-polar surface. The device structure with the two-dimensional hole gas channel, which is fabricated on the Ga polar surface is consistent with device structure with the two-dimensional electron gas channel, which is fabricated on the N-polar surface.
In some embodiments, the first semiconductor layer includes a first region and a second region, a bulge portion is formed on the first region, the second semiconductor layer is arranged on the bulge portion, the first heavily doped region and the second heavily doped region are arranged on the second region and distributed at both sides of the bulge portion.
In some embodiments, the epitaxial structure further includes a cap layer arranged on the second semiconductor layer. The thickness of the cap layer is 0-100 nm. The material of the cap layer can be a GaN material and SiN, but are not limited thereto.
In some embodiments, the epitaxial structure further includes an insertion layer distributed between the first semiconductor layer and the second semiconductor layer. The thickness of the insertion layer is 0-10 nm, and the material of the insertion layer can be an AlN material, but is not limited thereto.
In some embodiments, the epitaxial structure further includes a buffer layer distributed between the substrate and the first semiconductor layer.
In some embodiments, the buffer layer can be selectively doped.
In some embodiments, the epitaxial structure further includes a back barrier layer distributed between the buffer layer and the first semiconductor layer. The material of the back barrier layer can be AlN and AlGaN, but is not limited thereto.
In some embodiments, the gate electrode can be a T-type gate, which includes a gate cap and a gate foot which are arranged in an axial direction, wherein the gate cap is arranged on the high resistance region and supported by the high resistance region, the gate foot is arranged in the epitaxial structure, the size of the gate cap in a source-drain channel direction is larger than that of the gate foot in the source-drain channel direction, and the carrier channel is distributed right below the gate foot, and the size of the gate foot in the source-drain channel direction is smaller than or equal to the length of the two-dimensional electron gas channel.
In some preferred embodiments, a side wall dielectric layer is also arranged between the side wall of the gate foot and the high resistance region, and the material of the side wall dielectric layer can be SiN. The method for forming the side wall dielectric layer can be a low pressure chemical vapor deposition (LPCVD) method, but is not limited thereto.
In some embodiments, a dielectric layer is also arranged between the gate electrode and the heterojunction. The material of the dielectric layer can be one or more of SiO2, HfO2, Al2O3, AlN, AlON and SiN. The method for forming the dielectric layer can be the ALD method, and is not limited thereto.
In some embodiments, the dielectric layer also extends to cover the surface of the epitaxial structure, and the source electrode and the drain electrode are matched with the epitaxial structure through the corresponding window formed on the dielectric layer.
In some embodiments, the dielectric layer is also used for obstructing the gate electrode and the high resistance region, or the gate electrode is directly isolated from the high resistance region by air.
In some embodiments, the high resistance region can be epitaxially formed on the heavily doped region in a secondary epitaxy mode, or be formed by local transformation of the heavily doped region. For example, the heavily doped region material can be transformed into high resistance material through thermal diffusion, ion injection, plasma treatment and other methods, or by any other ways that can form the high resistance material layer.
In the above embodiments, an interface between the heavily doped region and the high resistance region can be controlled by mutation doping or gradual doping as long as it is ensured that the surface of the heavily doped region is higher than the surface of the carrier channel.
In some embodiments, the high-electron-mobility transistor structure also includes an isolation region which is formed in the epitaxial structure and used for isolating the active region of the high-electron-mobility transistor structure. The isolation region is distributed at both sides of the epitaxial structure, which at least extends from the surface of the epitaxial structure below the first semiconductor layer in the axial direction.
In some embodiments, the isolation region can be formed by an N ion injection technology, with an injection energy being 100-400 keV and an N ion injection dose being 1012-1017/cm2, and the injection depth is below the first semiconductor layer. The isolation region can adopt the etching method to etch the epitaxial layer of the active region below the first semiconductor layer.
Another aspect of the present application also provides a fabricating method of a high-electron-mobility transistor structure, including:
Further, the fabricating method specifically comprises:
In some embodiments, the materials of the source electrode and the drain electrode can be Ti/Al/Ni/Au, or other metal systems that can form ohmic contact with n-type or p-type heavily doped regions; the material of the gate electrode can be Ni/Au, or a material system which can form Schottky contact with the second semiconductor layer, such as Ni/Pt/Au, Ni/Pt and P—GaN.
In some embodiments, the fabricating method specifically further includes: forming a dielectric layer between the gate electrode and the heterojunction.
In some embodiments, the fabricating method specifically further includes: forming a side wall dielectric layer between the gate foot of the gate electrode and the high resistance region.
It should be noted that under the condition that the growth shape of the ohmic contact region composed of the high resistance region and the heavily doped region can be regulated, the dielectric layer or the side wall dielectric layer cannot be formed as well.
In some embodiments, the fabricating method specifically further includes: forming a buffer layer between the substrate and the first semiconductor layer.
In some embodiments, the material of the substrate can be selected from any one of silicon, sapphire, silicon carbide, gallium nitride and aluminum nitride, and is not limited thereto.
In some more specific embodiments, the fabricating method can include the following steps:
In other more specific embodiments, in Step 6), the cured electronic photoresist is used as the mask, the heavily doped layer is epitaxially grown in the source electrode contact region and the drain electrode contact region which are subjected to etching to form the heavily doped region, the thickness and doping concentration of the heavily doped region ensure that the heavily doped region forms good ohmic contact with the carrier channel, and then the semiconductor material at the specified depth from the surface of the heavily doped layer to the inside of the heavily doped layer is transformed into the high resistance material, thus forming the high resistance region and the heavily doped region in the heavily doped layer, and the specified depth is higher than the surface of the carrier channel.
Another aspect of the present application further provides a power amplifier, including the high-electron-mobility transistor structure.
In some embodiments, the power amplifier includes radio frequency wave band power amplifier, a millimeter wave band power amplifier or a terahertz wave band power amplifier, etc.
Next, the technical solution of the present application will be described clearly and completely in combination with the attached drawings and specific embodiments. Obviously, the described embodiments are parts of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, other embodiments obtained by persons of ordinary skill in the art without creative efforts are all included within the scope of protection in the present application. And, unless otherwise specified, the fabricating processes involved in the following embodiments of the present application are all the existing processes in the field, and the process parameters are not specifically defined here.
Referring to
In this embodiment, a groove is formed in this n-type layer. The insertion layer 50, the barrier layer 60 and the cap layer 70 are all distributed in the groove. Where, the gate electrode 104 is a T-type gate, and the gate foot of the gate electrode is also arranged in the groove. The gate cap is arranged on the n-type layer. The source electrode 102 and the drain electrode 103 are formed on the n-type layer and form ohmic contact with the n-type layer.
This epitaxial structure can also have an active region isolation structure formed by ion injection and other methods. Meanwhile, a continuous dielectric layer 101 can be formed between the n-type layer and the cap layer 70 and the gate electrode 104, thus forming an enhanced device.
In this embodiment, this epitaxial structure preferably adopts a thin barrier design. Through such the design, on the one hand, short channel devices can be fabricated, and the entire channel is almost effectively controlled by the gate electrode (that is, the gate length LG≤source-drain spacing LDS). Because there are no gate-source access regions and gate-drain access regions, the linearity degeneration problem of the device caused by RGS high-field non-linear behavior can be effectively suppressed while significantly reducing the difficulty of obtaining the low knee voltage of the device; on the other hand, since the thin barrier epitaxial structure is adopted and the gate electrode can perform electron concentration regulation on the entire channel, the enhanced device can be fabricated without the help of a complex technology. Meanwhile, the thin barrier means the large gate capacitance, which is conducive to improving the transconductance of the device so as to ultimately improve the PA power gain.
Referring to
Further, the epitaxial structure further includes a heavily doped region and a high resistance region. The heavily doped region includes a first heavily doped region 801 which is matched with the source electrode 102 and a second heavily doped region 802 which is matched with the drain electrode 103. The first heavily doped region 801 and the second heavily doped region 802 are arranged on the second region of the GaN second semiconductor layer 30 and form good ohmic contact with the two-dimensional electron gas channel 40, the high resistance region includes a first high resistance region 901 which is matched with the source electrode 102 and a second high resistance region 902 which is matched with the drain electrode 103. The local regions of the source electrode 102 and the drain electrode 103 pass through the first high resistance region 901 and the second high resistance region 902 and then respectively form ohmic contact with the first heavily doped region 801 and the second heavily doped region 802, and the source electrode 102 is isolated from the gate electrode 104 by the first high resistance region 901, the drain electrode 103 is isolated from the gate electrode 104 by the second high resistance region 902, and the surfaces of the first heavily doped region 801 and the second heavily doped region 802 are higher than the surface of the two-dimensional electron gas channel 40.
Where, the first heavily doped region 801 and the second heavily doped region 802 are n-type heavily doped GaN materials, and the first high resistance region 901 and the second high resistance region 902 are high resistance GaN materials.
Specifically, the gate electrode 104 is a T-type gate, which includes a gate cap and a gate foot which are arranged in the axial direction, wherein the two ends of the gate cap are respectively arranged on the first high resistance region 901 and the second high resistance region 902 and supported by the first high resistance region 901 and the second high resistance region 902, and the gate foot is arranged in the epitaxial structure, the diameter of the gate cap is greater than that of the gate foot, and the two-dimensional electronic gas channel 40 is distributed right below the gate foot, and the diameter of the gate foot is greater than or equal to the length of the two-dimensional electron gas channel 40, so as to achieve a near-full gate controlled high-electron-mobility transistor structure.
Specifically, SiN side wall dielectric layers 100 are also arranged between the gate foot of the gate electrode 104 and the first high resistance region 901 and between the gate foot of the gate electrode 104 and the second high resistance region 902, and a Al2O3 dielectric layer 101 is also arranged between the gate electrode 104 and the surface of the epitaxial structure.
Next, referring to
Next, the technical solution of the present application will be further described in detail in combination with embodiments and accompanying drawings. These embodiments are implemented on the premise of the technical solution of the present application, and the detailed embodiments and specific operation processes are given, however, the protection scope of the present application is not limited to the following examples.
A GaN HEMT structure (hereinafter called a device for short) provided in this example is basically the same as a GaN electronic device structure as shown in
S1, epitaxial structures of a device based on a thin second semiconductor layer heterojunction were epitaxially grown through metal organic chemical vapor deposition (MOCVD), as shown in
S2, the size, namely, the gate electrode length IG, of the gate foot of the T-type gate electrode (called “T-type gate” for short) of the device was defined by using hydrogen silsesquioxane (HSQ) electronic photoresist or other photoresists, as shown in
S3, the HSQ electronic photoresist was cured by using an annealing process, wherein the adopted annealing temperature was about 400° C., as shown in
S4, a source-drain ohmic contact region was etched. The gate electrode of the source-drain ohmic contact region was etched by adopting an inductive coupled plasma (ICP) etching technology and using the cured HSQ electronic photoresist as a mask, wherein the etching rate was controlled to 1-20 nm/min, as shown in
S5, the secondary epitaxy was performed on the ohmic contact layer. n-type heavily doped n++ GaN was subjected to epitaxial growth by adopting metal-organic vapor deposition (MOCVD) and using the cured HSQ electronic photoresist as the mask to form an ohmic contact layer, wherein the doping concentration and thickness ensured that the ohmic contact layer electrically formed good ohmic contact with the channel, as shown in
S6, the HSQ electronic photoresist was removed. The HSQ electronic photoresist was removed by using a BOE solution (or HF solution), as shown in
S7, an active region was isolated. Isolation was performed by using an N ion injection technology, wherein the ion injection energy was 150-400 KeV ion injection, the ion injection dose was 1012-1014/cm2, and the injection depth exceeded a buffer layer by about 50-250 nm, as shown in
S8, a gate electrode dielectric was deposited. A dielectric layer (called “gate dielectric” for short) was deposited by using an atom layer deposition (ALD) technology, wherein an Al2O3 dielectric layer has a thickness of 1-5 nm, as shown in
S9, a T-type gate electrode (called “T-type gate” for short) was fabricated. A Ni/AuT-type gate with a thickness of 50 nm/250 nm was fabricated by using secondary epitaxial ohmic contact layer as a T-type gate support layer and adopting a photoetching process and electronic beam evaporation technology, as shown in
S10, a source electrode and a drain electrode were fabricated. Via a source and drain ohmic contact windowing process, the source electrode and the drain electrode were fabricated by using an electron beam evaporation technology and formed ohmic contact with the ohmic contact layer. One of the source electrode and the drain electrode can be a Ti/Au ohmic contact electrode with a thickness of 50 nm/250 nm, as shown in
A GaN HEMT structure (hereinafter called a device for short) provided in this example is basically the same as a GaN electronic device structure as shown in
S1-S3, S1-S3 are similar to steps S1-S3 in the fabricating method of the device in example 1, the gate foot of the T-type gate was defined by using the HSQ electronic photoresist and then annealed and cured, as shown in
S4, a dielectric layer was deposited. The dielectric layer was deposited by using an ALD technology. For example, a silicon nitride dielectric layer with a thickness of 1-5 nm can be deposited, as shown in
S5, a dielectric side wall was formed. A silicon nitride dielectric layer was etched by reactive ion etch (RIE) so as to form the dielectric side wall, as shown in
S6, a source-drain ohmic contact region was etched. The gate electrode of the source-drain ohmic contact region was etched by adopting an ICP etching technology and using the cured HSQ electronic photoresist as the mask, wherein the etching rate was controlled to 1-20 nm/min, as shown in
S7, the secondary epitaxy of the ohmic contact layer was performed. n-type heavily doped n++ GaN was subjected to epitaxial growth by adopting MOCVD and using the cured HSQ electronic photoresist as the mask to form an ohmic contact layer, wherein the doping concentration and thickness ensured that the ohmic contact layer formed good ohmic contact with the channel, as shown in
S8, an active region was isolated. Isolation was performed by using an N ion injection technology, wherein the ion injection energy was 150-400 KeV ion injection, the ion injection dose was 1012-1014/cm2, and the injection depth exceeded a buffer layer by about 50-250 nm, as shown in
S9, a source electrode and a drain electrode were fabricated. The source electrode and the drain electrode were fabricated by using an electron beam evaporation technology and formed ohmic contact with the ohmic contact layer. The source electrode and the drain electrode can be a Ti/Au ohm electrode with a thickness of 50 nm/250 nm, as shown in
S10, a sacrificial layer was spin-coated. The sacrificial layer was spin-coated with polyimide (PI). The spin-coating thickness ensured that the surface of the wafer was covered with patterns (that is, at least higher than the heights of the HSQ electronic photoresist, and the source electrode and the drain electrode, as shown in
S11, chemical mechanical polishing (CMP). The sacrificial layer was subjected to CMP treatment to expose the cured HSQ electronic photoresist, as shown in
S12, the HSQ electronic photoresist was removed. The HSQ electronic photoresist was removed with BOE solution (or HF solution), as shown in
S13, a T-type gate was fabricated. A Ni/Au T-type gate with a thickness of 50 nm/250 nm was fabricated by using the sacrificial layer as the support layer and adopting a photoetching process and electron beam evaporation technology, as shown in
S14, the sacrificial layer was removed. The sacrificial layer was removed by using an organic solvent or plasma Ashing, so as to realize the T-gate structure that was subjected to spatial isolation from the heavily doped ohmic contact layer by utilizing air, as shown in
The device provided in this example is a depletion-mode device, but a dielectric layer is arranged between the gate electrode and the cap layer so that the device becomes an enhanced device.
A fabricating method of a high-electron-mobility transistor structure as shown in
Step 1), successively epitaxially growing a GaN buffer layer 20 with a thickness of 1500 nm, a GaN first semiconductor layer 30 with a thickness of 150 nm, an AlN insertion layer 50 with a thickness of 1 nm, an AlGaN second semiconductor layer 60 with a thickness of 5 nm and a GaN cap layer 70 with a thickness of 2 nm on a sapphire substrate 10, wherein a two-dimensional electron gas channel 40 was formed below the surface of the GaN first semiconductor layer 30 close to the surface of the AlN insertion layer 50, as shown in
Step 2), defining the size, namely, the gate electrode length LG≈50-500 nm, of the gate foot of the T-type gate on the epitaxial structure by using HSQ electronic photoresist 106, as shown in
Step 3), the HSQ electronic photoresist 106 was cured by an annealing process, wherein the annealing temperature was about 400° C., as shown in
Step 4), a SiN sidewall dielectric layer with a thickness of 5 nm was deposited on the device surface formed in step 3) by using a low pressure chemical vapor deposition (LPCVD), as shown in
Step 5), a source electrode contact region and a drain electrode contact region were etched by using the cured HSQ electronic photoresist 106 as the mask and using ICP, and the GaN cap layers 70, the AlGaN second semiconductor layers 60, the AlN insertion layers 50 and the partially thickness of GaN first semiconductor layers 30 in the source electrode contact region and the drain electrode contact region were removed, so that the region of the GaN first semiconductor layer 30 corresponding to the gate electrode 104 was formed into a bulge portion, the AlN insertion layers 50, the AlGaN second semiconductor layers 60 and the GaN cap layers 70 of the rest part were distributed on the bulge portion, as shown in
Step 6), an n-type heavily doped GaN material layers were epitaxially grown in the source electrode contact region and the drain electrode contact region which were subjected to etching by continuing to use the cured HSQ electronic photoresist 106 as the mask and adopting the MOCVD technology to form a first heavily doped region 801 and a second doped region 802, the thicknesses and doping concentrations of the first heavily doped region 801 and the second doped region 802 (i.e., the surfaces of the heavily doped region 801 and the second doped region 802 were higher than the surface of a two-dimensional electron gas channel 40) ensured that the first doped region and the second doped region formed good ohmic contact with the two-dimensional electron gas channel 40, then high resistance GaN material layers were epitaxially grown on the first heavily doped region 801 and the second doped region 802 to form a first high resistance region 901 and a second high resistance region 902, as shown in
Step 7), the HSQ electronic photoresist 106 was removed by using BOE solution or HF solution, as shown in
Step 8), the isolation region 105 of the active region was formed at both sides of the epitaxial structure by using an N ion injection technology, wherein the N ion injection energy was 100-400 keV, the N ion injection dose was 1012-1015/cm2, and the injection depth exceeded the GaN buffer layer 20 by about 50-250 nm, as shown in
Step 9), a Al2O3 dielectric layer 101 with a thickness of 1 nm was deposited on the surface of the device formed in step 8) by using ALD, as shown in
Step 10), the gate electrode 104 was fabricated by using the first high resistance region 901 and the second high resistance region 902 as the support layers of the gate cap of the gate electrode 104, wherein the gate electrode 104 was made of Ni/Au, and had a thickness of 50 nm/250 nm, as shown in
Step 11), windows were formed on the Al2O3 dielectric layer 101, the first high resistance region 901 and the second high resistance region 902, and the source electrodes 102 and the drain electrodes 103 were fabricated in the windows by using use the electron beam evaporation technology, wherein the source electrode and the drain electrode were made of Ti/Au and had a thickness of 50 nm/250 nm, and the fabrication of the high-electron-mobility transistor structure was completed, as shown in
It is noted that the process steps in this example can be adjusted according to practical situations, as long as the final device can be implemented, which is well-known to those skilled in the art, and cannot be described in detail.
A fabricating method of a high-electron-mobility transistor structure as shown in
Step 6), an n-type heavily doped GaN material layer was epitaxially grown in the source electrode contact region and the drain electrode contact region which were subjected to etching by using the cured HSQ electron photoresist 106 as the mask to form the first heavily doped region 801 and the second heavily doped region 802, the thicknesses and doping concentrations of the first heavily doped region 801 and the second doped region 802 ensured that the first heavily doped region and the second doped region formed good ohmic contact with the two-dimensional electron gas channel 40, as shown in
In the above examples of the present application, the self-alignment process and secondary epitaxy technology are adopted, and the heavily doped layer and high resistance layer composite is used as the support layer, and the T-type gate is directly built between the source electrode and the drain electrode, thereby realizing a high-electron-mobility transistor structure with short channel, near-full gate control, no access region series resistance and low parasitic effect, and improving the frequency characteristics and output efficiency of the device while effectively reducing the knee voltage of the device and improving the linearity of the device. Meanwhile, the high-electron-mobility transistor structure provided by the present application adopts the thin barrier-based heterojunction epitaxial structure, so as to fabricate the enhanced device fabrication without the groove gate etching process. Furthermore, the thin barrier-based material structure makes the device have large transconductance, which is conducive to improving the gain of the RF power amplifier.
Moreover, the high-electron-mobility transistor structure provided in the examples of the present application is also applicable to GaN HEMT devices with a back barrier structure or other back structures, as well as GaN HEMT devices with various polarity planes, including a Ga surface, an N surface, etc.
In addition, the applicant of this case also conducted experiments with other raw materials, process operation and process conditions described in this specification with reference to the aforementioned embodiments, and obtained relatively ideal results.
It should be understood that the technical solution of the present application is not limited to the limitations of the above specific implementation cases. Without departing from the scope of protection of the purpose and claims of the present application, technical deformations made according to the technical solution of the present application are all included within the scope of protection of the present application.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202111528051.8 | Dec 2021 | CN | national |
| 202210490618.5 | May 2022 | CN | national |
This application is the national phase entry of International Application No. PCT/CN2022/124581, filed on Oct. 11, 2022, which is based upon and claims priority to Chinese Patent Application No. 202111528051.8, filed on Dec. 13, 2021; and Chinese Patent Application No. 202210490618.5, filed on May 10, 2022, the entire contents of which are incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2022/124581 | 10/11/2022 | WO |
