CN116130516A - Semiconductor device for radio frequency power amplifier - Google Patents

Abstract

The invention provides a semiconductor device for a radio frequency power amplifier, comprising: a substrate layer configured to be formed by GaAs; a sub-collector layer configured on the substrate layer and configured to be formed by n+ -doped GaAs; a collector layer configured on the sub-collector layer and configured to be formed by an n-doped wide bandgap material, wherein a forbidden bandwidth of the wide bandgap material is greater than a forbidden bandwidth of GaAs; a collector metal layer disposed on the collector layer; a base layer configured on the collector layer and configured to be formed by p+ -doped GaAs; a base metal layer disposed on the base layer; an emitter layer configured on the base layer and configured to be formed by n-type doped InGaP; an emitter cap layer configured on the base layer; and an emitter metal layer configured on the emitter cap layer, wherein the collector layer is configured such that a maximum current and voltage swing at the collector layer is within a safe operating region of the semiconductor device, wherein the safe operating region of the semiconductor device is defined as a safe operating region when the semiconductor device is in a forward active region.

Description

Semiconductor Devices for RF Power Amplifiers

technical field

The present invention relates to the field of wireless communication, more specifically, to a semiconductor device of a radio frequency power amplifier used for wireless communication.

Background technique

4G and/or 5G RF power amplifiers (PAs) used in mobile terminals such as mobile phones are usually fabricated using Gallium Arsenide Heterojunction Bipolar Transistor (GaAs HBT) process. In the early GaAs HBT process, the AlGaAs/GaAs heterojunction interface was dominant. With the development of InGaP/GaAs heterojunction technology, InGaP/GaAs heterojunction technology has gradually become the mainstream of GaAs HBT technology.

Contents of the invention

One aspect of the present invention is to propose a semiconductor device for a radio frequency power amplifier, including: a substrate layer configured to be formed by GaAs; a sub-collector layer configured on the substrate layer and configured as Formed by n+-type doped GaAs; the collector layer, which is configured on the sub-collector layer, and is configured to be formed by n-type doped wide bandgap material, wherein the forbidden band of the wide bandgap material The width is larger than the forbidden band width of GaAs; the collector metal layer is configured on the collector layer; the base layer is configured on the collector layer and is configured to be formed by p+ type doped GaAs; the base a pole metal layer configured on the base layer; an emitter layer configured on the base layer and configured to be formed by n-type doped InGaP; an emitter cap layer configured on the on the base layer; and an emitter metal layer configured on the emitter cap layer, wherein the collector layer is configured such that the maximum current and voltage swing at the collector layer is within the safety of the semiconductor device Within the working area, the safe operating area of the semiconductor device is defined as the safe operating area when the semiconductor device is in the forward active area, and its operating current is in the order of milliamps (mA) to amperes (A) working area. The breakdown voltage of the safe operating area is different from the traditional collector-base reverse breakdown voltage (BV _CBO ) or collector-emitter reverse breakdown voltage (BV _CEO ). In general, the safe operating area The breakdown voltage is less than the collector-base reverse breakdown voltage (BV _CBO ) and is close to the collector-emitter reverse breakdown voltage (BV _CEO ).

One aspect of the present invention is to propose a semiconductor device for a radio frequency power amplifier, wherein the wide bandgap material includes In _x Ga _(1-x) P and In _x Ga _(1-x) As _y P _{(1 -y)} , where x and 1-x represent the ratio of In and Ga elements, and y and 1-y represent the ratio of As and P elements.

One aspect of the present invention is to provide a semiconductor device for a radio frequency power amplifier, wherein, when the wide bandgap material is In _x Ga _(1-x) P, the thickness of the collector layer is configured to be less than The first threshold, preferably, the first threshold is 50nm.

One aspect of the present invention is to propose a semiconductor device for a radio frequency power amplifier, wherein, when the wide bandgap material is In _x Ga _(1-x) As _y P _(1-y) , the collector The thickness of the layer is configured to be smaller than a second threshold, preferably, the second threshold is 50 nm.

An aspect of the present invention is to provide a semiconductor device for a radio frequency power amplifier, wherein x is in a first ratio range of 0.45 to 0.55.

An aspect of the present invention is to provide a semiconductor device for a radio frequency power amplifier, wherein y is in the second ratio range of 0.45 to 0.55.

An aspect of the present invention is to propose a semiconductor device for a radio frequency power amplifier, wherein the semiconductor device is configured for a 5G radio frequency power amplifier, and the 5G radio frequency power amplifier has a maximum power of 4.4V-5.5V Operating Voltage.

One aspect of the present invention is to propose a semiconductor device for a radio frequency power amplifier, wherein the semiconductor device is applied in a power stage amplifying unit of the 5G radio frequency power amplifier.

Description of drawings

1 is a cross-sectional view showing a semiconductor device for a radio frequency power amplifier;

Fig. 2 is the schematic diagram showing the energy band structure of the semiconductor device adopting InGaP/GaAs SHBT process;

3 is a schematic diagram illustrating the difference between an open-emitter condition, an open-base condition, and a normal operation condition of a semiconductor device of a radio frequency power amplifier;

4 is a cross-sectional view of a semiconductor device for a radio frequency power amplifier according to an embodiment of the present invention;

5 is a schematic diagram showing an energy band structure of a semiconductor device for a radio frequency power amplifier according to an embodiment of the present invention;

FIG. 6A shows a breakdown diagram of the energy band structure of a single heterojunction semiconductor device for a radio frequency power amplifier;

Fig. 6B shows a breakdown diagram of the energy band structure of a double heterojunction semiconductor device for a radio frequency power amplifier;

Fig. 7 is a comparison diagram showing the safe operating area of the semiconductor device of the radio frequency power amplifier manufactured by GaAs SHBT process and GaAs DHBT process;

8 is a cross-sectional view showing a semiconductor device for a radio frequency power amplifier according to another embodiment of the present invention;

9 is a schematic diagram showing an energy band structure of a semiconductor device for a radio frequency power amplifier according to another embodiment of the present invention; and

FIG. 10 is a circuit block diagram showing a radio frequency power amplifier including a semiconductor device according to an embodiment of the present invention.

Detailed ways

Before proceeding to the detailed description that follows, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document. The terms "couple," "connect," and their derivatives refer to any direct or indirect communication between two or more elements, whether or not those elements are in physical contact with each other. The terms "transmit", "receive" and "communicate" and their derivatives cover both direct and indirect communications. The terms "include" and "comprising" and their derivatives mean including but not limited to. The term "or" is inclusive, meaning and/or. The phrase "associated with" and its derivatives mean to include, comprise, interconnect, contain, comprise, connect or be connected to, couple to or be coupled with, ...communicating, cooperating, interweaving, juxtaposing, approaching, binding or being bound to, having, having attributes, having relation to or being related to, etc. The term "controller" refers to any device, system, or portion thereof that controls at least one operation. Such a controller may be implemented in hardware, or a combination of hardware and software and/or firmware. The functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. The phrase "at least one", when used in conjunction with a list of items, means that various combinations of one or more of the listed items may be used, and that only one of the listed items may be required. For example, "at least one of A, B, and C" includes any one of the following combinations: A, B, C, A and B, A and C, B and C, A and B and C.

Definitions for other certain words and phrases are provided throughout this patent document. Those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases.

In this patent document, the application combination of circuit blocks and the division of sub-circuit blocks are only for illustration, and the application combination of circuit blocks and the division of sub-circuit blocks can be in different ways without departing from the scope of the present disclosure.

1 through 9, discussed below, and the various embodiments used to describe the principles of the disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged system or device.

In the current mainstream 4G mobile phones and other terminals, the 4G RF power amplifiers used are usually manufactured using the InGaP/GaAsHBT process. Among them, the InGaP/GaAs heterojunction means that the emitter adopts an InGaP structure, and the base and collector adopt a GaAs structure. The emitter and base are heterojunctions, and the base and collector are homojunctions. Therefore, the above process is called Gallium Arsenide Single Heterojunction Process (GaAs SHBT). For the 4G communication system, the RF power amplifier uses a working voltage of about 3.4V to meet the linearity and transmit power requirements of the 4G communication system. For the GaAs SHBT process, the corresponding safe operation area (Safe Operation Area, SOA) can satisfy the safe operation of the RF power amplifier at 3.4V. Those skilled in the art should understand that 3.4V refers to the operating voltage when the radio frequency power amplifier transmits maximum power, 3.4V is not a specific value, and it may include 3.0V-3.5V.

In 5G application scenarios, such as 5G mobile phone terminals, 5G module terminals, 5G small base stations or 5G Internet of Vehicles C-V2X, 5G communication systems have higher requirements for indicators such as linearity and transmission power than 4G LTE communication systems. a lot of. When the 5G RF power amplifier has high linearity and high power output, it needs to use a working voltage of about 5V. For example, a 5G mobile phone needs to use a DC-DC voltage conversion circuit with a boost function to increase the voltage of the power supply battery to 5V to provide 5V working power for the RF power amplifier. Using SOA corresponding to the GaAs SHBT process is difficult to meet the requirements of RF power amplifiers to work safely at 5V. It often has linearity or output power that does not meet the standard, and in severe cases, it will cause the RF power amplifier to burn out. Those skilled in the art should understand that 5V refers to the operating voltage when the radio frequency power amplifier transmits maximum power, 5V is not a specific value, and it may include 4.4V-5.5V.

At present, some GaAs SHBT processes have improved the key technical parameters of the breakdown voltage (BVCEO and BVCBO), which can support the design of 5G RF power amplifiers nominally, but linearity deterioration or burn-in still occur in practical applications. .

Therefore, using breakdown voltage (BVCEO and BVCBO) technical indicators to judge whether the requirements of 5G radio frequency power amplifiers are met cannot ensure that 5G radio frequency power amplifiers can work normally, so the present invention provides a method for judging semiconductor devices based on safe operating area (SOA) Whether it meets the technical solution of the working requirements of 5G radio frequency power amplifier.

FIG. 1 is a cross-sectional view showing a semiconductor device used in a radio frequency power amplifier.

Referring to FIG. 1 , from the perspective of the epitaxial layer structure, the semiconductor device includes from top to bottom: an emitter metal layer 101, an emitter capping layer 102, an emitter n-type doped layer (InGaP) 103, a base metal layer 104, Base p+ type doped layer (GaAs) 105 , collector metal layer 106 , collector n type doped layer (GaAs) 107 , sub-collector n+ type doped layer (GaAs) 108 and substrate layer (GaAs) 109 . In Figure 1, the emitter and base are heterojunction structures, while the base and collector are homojunction structures. For the RF power amplifier prepared by GaAs HBT process, its internal transistor is a vertical vertical structure, and the energy band analysis method is generally used for physical performance analysis.

FIG. 2 is a schematic diagram showing an energy band structure of a semiconductor device employing an InGaP/GaAs SHBT process.

Referring to Fig. 2, in the energy band structure of the 4G RF power amplifier prepared by the InGaP GaAs single heterojunction (SHBT) process, because the minority electrons are moving faster, the transistor usually uses the NPN structure, that is, the emitter E (EmitterInGaP ) and the collector C (Collector GaAs) are n-type doped, and the base B (Base GaAs) is p-type doped. The power core unit in the RF power amplifier adopts a common emitter amplification structure, that is, the emitter is connected to a common ground node. The power core unit is in the energy band structure of the forward active region. In the NPN structure in the forward active region, the B-E junction is forward-conducting, and the electrons in the emitter will cross the B-E junction and be injected into the base region from the emitter region, while the B-C junction is reverse biased, and the reverse bias voltage will be determined by the base The region diffuses to the B-C junction space charge region and all the electrons are swept into the collector region.

In the case of an open emitter, the reverse current generated by the reverse bias applied at the B-C junction is mainly composed of the electron current diffused from the base region to the barrier region and the hole current diffused from the collector region to the barrier region. Since the minority carriers in the base region are electrons and the minority carriers in the collector region are holes, the total current is relatively weak, generally at the microampere (uA) level. When the reverse bias voltage increases to a certain value, the electric field in the barrier region is very strong, and the electrons and holes in the barrier region generate greater kinetic energy due to the drift effect of the strong electric field. The high-energy electrons and holes excite the electrons in the full band to generate new electron and hole pairs; the new electron and hole pairs continue to excite other electrons in the full band... The above process leads to multiple collisions Ionization produces a large number of electron and hole pairs, which increases the number of carriers dramatically, and the large reverse current generated by it will lead to the breakdown of the B-C junction barrier region. At this time, the B-C junction reverse bias value is Collector-base reverse breakdown voltage (BVCBO).

In the case of open base, a voltage is applied across the C-E junction. At this time, both ends of the B-C junction are still under reverse bias. In this case, additional consideration needs to be given to injecting a part of the emitter into the base region, and then passing through the base region. The more to the collector barrier region, the contribution of the electron current that finally reaches the collector region. Since the base is in an open state and the B-E junction voltage has not yet been turned on, the current formed by this injection is relatively weak, generally at the microampere (uA) level. In the case of an open emitter, there is no additional electron current injected from the emitter to the base. In the case of an open base, this part of the electronic current will accelerate the formation of a large current in the collector barrier region and accelerate the breakdown of the B-C junction barrier region. At this time, the voltage at both ends of the C-E junction is collector-emitter reverse Breakdown Voltage (BVCEO). Obviously, BVCEO is smaller than BVCBO.

However, when the RF power amplifier is working normally, it is not in the above two situations, but in the forward active region. At this time, the normal working current of the power core unit is in the milliampere (mA) to ampere (A) level, which is far greater than the microampere (uA) level, as shown in FIG. 3 . FIG. 3 is a schematic diagram showing the difference between an emitter open condition, a base open condition, and a normal operation condition of a semiconductor device of a radio frequency power amplifier.

From the perspective of the energy band structure of the forward active region, when the RF power amplifier transmits at high power, the BE junction is forward biased, so that the energy of the ECN at the bottom of the conduction band of the emitter is close to the ECP of the bottom of the conduction band of the base, so that the BE junction is positive In the case of conduction, a large number of electrons will be injected into the base region from the emitter. The huge electron current formed by the emitter injection does not exist in the case of open emitter or open base. When this part of electrons is swept from the base region to the collector barrier region by the accelerating electric field, it will obviously be further accelerated. Breakdown of the BC junction barrier region. Obviously, when the emitter injection current (ICE) is large, for example, at the level of A, the corresponding breakdown voltage (BVCE) will decrease; when the injection current (ICE) becomes small, for example, at the level of mA , the corresponding breakdown voltage (BVCE) will increase; when the injection current (ICE) is as small as uA, for example, the corresponding breakdown voltage (BVCE) will be close to BVCEO, which is similar to the case of open base. In this way, a corresponding relationship between ICE and BVCE is formed, which is called a safe operating area (SOA) here. Within this range, the radio frequency power amplifier is safe, but if it exceeds this range, the performance of the radio frequency power amplifier will be degraded or the pn junction will be broken down and burned. Referring to Figure 3, since the traditional analysis does not take into account the influence of the forward active region on the device operation, it is not objective to use the BV _CEO or BV _CBO of the transistor to evaluate whether the RF power amplifier can work safely. The present invention provides a technical solution for judging whether a semiconductor device meets the operating index of a 5G radio frequency power amplifier based on the safe operating area (SOA) of a transistor, and provides a semiconductor device meeting the operating index of a 5G radio frequency power amplifier. Referring to Fig. 3, when the radio frequency power amplifier is working normally, since the semiconductor device therein is in the forward active region, the normal operating current of the semiconductor device (transistor) of the radio frequency power amplifier is in milliamps (mA) to amperes (A). The order of magnitude is far greater than the microampere (uA) level. Therefore, the safe operating area of semiconductor devices is limited to the working area where the operating current is in the order of milliamps (mA) to amperes (A), and the breakdown voltage of the safe operating area is different from that of the traditional collector-base reverse Breakdown voltage (BVCBO) or collector-emitter reverse breakdown voltage (BVCEO), in general, the breakdown voltage of the safe operating area is less than the collector-base reverse breakdown voltage (BVCBO), and with The collector-emitter reverse breakdown voltage (BVCEO) is close.

When the 4G RF power amplifier works in the forward active region, for example, under the supply voltage of 3.4V, the maximum current and voltage swing at the collector of the semiconductor device in the 4G RF power amplifier are within GaAs SHBT SOA, so , when the GaAs SHBT structure transistor is used, it can still ensure the normal operation of the 4G RF power amplifier. When the 5G RF power amplifier works in the forward active region, at a supply voltage of, for example, 5V, the maximum current and voltage swing at the collector of the semiconductor device in the 5G RF power amplifier has exceeded that provided by the GaAs SHBT process SOA scope. Since the B-C junctions of the GaAsSHBT process are homojunctions, both of which are GaAs structures, the band gap Eg(GaAs) of GaAs=1.43eV. Compared with the InGaP/GaAs heterojunction, the narrow bandgap collector region of this structure is more prone to impact ionization, resulting in a smaller SOA range, making semiconductor devices based on the GaAs SHBT process unable to meet the working needs of 5G RF power amplifiers. If the B-C junction is changed to a heterojunction, and the collector area is changed to a wide bandgap structure, the occurrence of carrier impact ionization in the collector area can be reduced, and the range of SOA can be increased accordingly.

In 5G application scenarios, the linearity or output power of the 5G RF power amplifier prepared by the GaAs SHBT process is insufficient, and the RF power amplifier will also burn out under the 5V working voltage. The invention provides a 5G radio frequency power amplifier prepared by a gallium arsenide double heterojunction (GaAs DHBT) epitaxial process, wherein the collector region of the GaAs DHBT process adopts a wide bandgap structure, so that the power core unit SOA has a larger range. The current and voltage swing ranges of the 5G RF power amplifier prepared by this process are still within the SOA at a working voltage of 5V, so as to avoid or reduce the occurrence of the above-mentioned problems.

4 is a cross-sectional view of a semiconductor device for a radio frequency power amplifier according to an embodiment of the present invention.

Referring to FIG. 4, the semiconductor device includes from top to bottom: an emitter metal layer 401, an emitter capping layer 402, an emitter n-type doped layer (InGaP) 403, a base metal layer 404, and a base p+-type doped layer. (GaAs) 405, collector metal layer 406, collector n-type doped layer (In _x Ga _(1-x) P) 407, sub-collector n+ type doped layer (GaAs) 408 and substrate layer (GaAs) 409 . Among them, the emitter metal layer 401, the base metal layer 404, and the collector metal layer 406 are used to form connections with external circuit wires; the emitter capping layer 402 enables the emitter metal layer 401 to obtain good ohmic contact with the epitaxial layer, And the stress caused by lattice mismatch between the emitter metal layer 401 and the emitter layer 403 is relieved. Compared with the collector GaAs structure, the collector of the semiconductor device according to the embodiment of the present invention adopts a wide bandgap In _x Ga _(1-x) P structure, where x and 1-x represent the ratio of In and Ga elements.

Compared with the GaAs SHBT process, the GaAs DHBT according to the embodiment of the present invention changes the epitaxial layer of the collector from an n-type doped GaAs structure to an n-type doped In _x Ga _(1-x) P, and at the same time, compared For the n-type doped GaAs structure, the thickness of the In _x Ga _(1-x) P epitaxial layer is appropriately reduced, for example, so that the collector layer is configured such that its thickness is smaller than a first threshold, preferably, the first threshold 50nm. The base epitaxial layer is still a GaAs structure, so that the BC junction becomes a heterojunction, forming a GaAs DHBT structure.

FIG. 5 is a schematic diagram showing an energy band structure of a semiconductor device for a radio frequency power amplifier according to an embodiment of the present invention. Referring to Figure 5, since the forbidden band width of In _x Ga _(1-x) P is larger than that of GaAs, it will form a barrier peak in the barrier layer of the collector region, which will prevent electrons from entering the collector from the base region. electric area. By properly controlling the concentration and thickness of In and Ga elements in the n-type doped layer of In _x Ga _(1-x) P, the energy band peak in the barrier region can be effectively reduced, so as not to affect the electrical properties of the GaAs DHBT structure.

When the power-level transistor works in the forward active region, the electrons in the barrier layer of the collector region are accelerated under the large electric field formed by the applied voltage in the collector region. As the applied voltage increases (3.4V to 5V, until a larger transient swing voltage), electrons carrying greater energy will cross the forbidden band to the valence band, and the valence electrons in the full band will be excited to form More carriers generated by impact ionization. However, after the collector region adopts a wide bandgap InGaP structure, electrons need more energy to cross the forbidden band. The semiconductor device formed by using the GaAs DHBT process makes when the applied voltage of the 5G RF power amplifier increases to 5V, the maximum current and voltage swing at the collector are within the GaAs DHBT SOA, thus ensuring the 5G RF power Amplifier is functioning normally.

When growing and preparing GaAs heterojunction epitaxial layers, it is necessary to consider the lattice matching between different materials to reduce the stress and crystal structure defects between the upper and lower layers of the heterojunction. If there is a combination of ternary or quaternary elements, the percentages of group III and group V elements need to be considered to improve the lattice matching between the upper and lower layers of the heterojunction.

The lattice constant of GaAs is 0.565nm, the lattice constant of GaP is 0.545nm, and the lattice constant of InP is 0.586nm.

According to an embodiment of the present invention, a GaAs structure is used in the base, and an In _(x) Ga _(1-x) P structure is used in the collector. Considering the degree of lattice matching, x=0.49, that is, the composition of In is 49%, and the composition of Ga is 51%. It is claimed here that the x value is not a fixed value, and the x component can fluctuate between 0.45 and 0.55 during actual preparation. Among them, when the composition of In is 49%, and the composition of Ga is 51%, the forbidden band width of In _(0.49) Ga _(0.51) P is Eg_InGaP (1.91eV), and the forbidden band width of GaAs is Eg_GaAs (1.43 eV).

When the transistor is operating in the forward active region, the base and collector are reverse biased. As the reverse bias increases, due to the action of the electric field, the electrons in the conduction band and the holes in the valence band in the depletion region will have greater energy. When the energy reaches a certain value, the electrons in the valence band will break away from the original electrons. Hole pairs cross the forbidden band to the conduction band; at the same time, the holes in the conduction band will also leave the original electron-hole pairs and cross the forbidden band to the valence band. In this way, under the action of a strong electric field, the number of carriers increases sharply. In the following, under the same energy and the same spanning distance (Xn), that is, under the same mechanism, the difference between the single heterojunction and the double heterojunction will be discussed.

In the case of a single heterojunction, both the base and the collector are GaAs structures, and when the reverse bias voltage increases to the first breakdown value (Vbc_s), the electrons in the valence band cross the forbidden band to reach the conduction band; at the same time, The holes in the conduction band cross the forbidden band to reach the valence band, and the spanning distance at this time is Xn.

In the case of a double heterojunction, the base is a GaAs structure, and the collector is an In _(x) Ga _(1-x) P structure. When the reverse bias voltage increases to the second breakdown value (Vbc_d), the valence band The electrons in the conduction band cross the forbidden band to the conduction band; at the same time, the holes in the conduction band cross the forbidden band to the valence band, and the crossing distance at this time is still Xn. Since the forbidden band width of In _(x) Ga _(1-x) P is larger than that of GaAs, to keep electrons or holes at the same spanning distance, it is necessary to increase the reverse bias value (Vbc_d), so that the depletion region The forbidden band width is narrowed so that its width distance is equal to Xn. Fig. 6 A shows the breakdown schematic diagram of the energy band structure of the single heterojunction semiconductor device used for radio frequency power amplifier, and Fig. 6 B shows the energy band structure of the double heterojunction semiconductor device used for radio frequency power amplifier The breakdown schematic diagram. Referring to FIG. 6A and FIG. 6B , when the collector in the semiconductor device is replaced with a wide bandgap structure, its reverse bias value Vbc_d is greater than Vbc_s.

The relationship between Xn and the reverse bias voltage Vbc and the forbidden band width Eg is shown in Formula 1 below.

where Xn is the spanning distance, Eg is the bandgap width, N is the doping concentration, q is the charge magnitude, Vbc is the reverse bias voltage, and ε _r ε ₀ is the dielectric constant. According to formula 1, to maintain the same Xn, the value of Eg and Vbc needs to be increased or decreased at the same time.

When the 5G RF power amplifier is working normally, the BC PN junction of the semiconductor device in it works under the reverse bias voltage, and the reverse bias voltage will gradually increase or decrease as the output impedance changes. When the reverse bias voltage gradually increases to Vbc_s or Vbc_d, a large current in the PN junction is formed. At this time, the breakdown of the PN junction is very likely to occur. At this time, since the transistor works normally in the positive active region, the BC PN junction is under a critical reverse bias voltage, and the output current and voltage range at this time is called the safe operating area (SOA) of the transistor, where , the safe operating area of a semiconductor device is limited to the working area where its operating current is in the order of milliamps (mA) to ampere (A), and the breakdown voltage of the safe operating area is different from the traditional collector-base reverse breakdown voltage (BV _CBO ) or collector-emitter reverse breakdown voltage (BV _CEO ), in general, the breakdown voltage of the safe operating area is less than the collector-base reverse breakdown voltage (BV _CBO ), and It is close to the collector-emitter reverse breakdown voltage (BV _CEO ).

FIG. 7 is a comparison diagram showing safe operating areas of semiconductor devices of radio frequency power amplifiers manufactured using a GaAs SHBT process and a GaAs DHBT process.

Referring to Figure 7, when a GaAs double heterojunction (DHBT) process is used to design and prepare a 5G RF power amplifier; at the same time, a 5G RF power amplifier is also designed and manufactured using the same GaAs flow single heterojunction (SHBT) process Next, based on the same design and layout structure, 5G RF power amplifiers of different processes with the same design parameters and layout structure were prepared. Test the safe operating area (SOA) range of the power stage transistors respectively, and the actual ranges of GaAs SHBT SOA and GaAs DHBT SOA are shown in Figure 7.

Referring to Fig. 7, since the collector region of GaAs DHBT adopts the wide bandgap In _x Ga _(1-x) P structure, its Vbc_d value is greater than the Vbc_s value of GaAs SHBT, that is, the range of GaAs DHBT SOA is wider than that of GaAs SHBT SOA Large, so that the 5G RF power amplifier can work safely under 3.4V and 5V voltage.

In addition, compared with the semiconductor transistor formed by the GaAs SHBT process, the semiconductor transistor formed by the GaAs DHBT introduces a thinner InGaP and InGaAsP layer with a wide bandgap structure at the collector, which can further effectively reduce the carrier flow in the collector region. The transit time significantly improves the characteristic frequency of the device. Therefore, it has better high-frequency characteristics, making GaAs DHBT form a semiconductor transistor to better adapt to 5G RF power amplifiers in high frequency (N41, N77, N79 frequency bands )Applications.

Since the semiconductor transistor formed by the GaAs DHBT adopts the InGaP and InGaAsP layers with a wide bandgap structure, it expands the safe operating area of the radio frequency power amplifier. Compared with the semiconductor transistor formed by GaAs SHBT, the doping concentration of the GaAs layer in the sub-collector region of the transistor of the DHBT structure can be appropriately reduced, and the mobility of carriers in the sub-collector region will also be greatly improved and reduced. The transit time of carriers in the sub-collector region. According to an embodiment of the present invention, the doping concentration of the GaAs layer in the sub-collector region may be configured to be lower than the first doping concentration threshold, for example, lower than 1×10e16/cm ³ . According to another embodiment of the present invention, the sub-collector layer may also be configured to include: a lower sub-collector layer with a concentration of 5x10e18/cm ³ , and the lower sub-collector layer is configured as a highly doped region to reduce The contact resistance of the collector region and the GaAs substrate, and it is configured to have a thickness of 500nm; the middle sub-collector layer, its concentration is 1x10e16/cm ³ , and it is configured to have a thickness of 500nm, by putting the middle sub-collector The electrode layer is configured to be doped with a low concentration to reduce the impact ionization of the collector region and increase the mobility of the collector region, thereby improving the high-frequency performance of the semiconductor device; the upper sub-collector layer has a concentration of 5x10e18/cm ³ GaAs layer, and is configured to have a thickness of 5 nm. Those skilled in the art should understand that, in order to increase the electron mobility in the collector region, the GaAs concentration of other layers can also be appropriately reduced so that the minimum doping concentration layer is lower than 1×10e16/cm ³ . According to the above configuration, the characteristic frequency of the semiconductor device is also improved, so that the semiconductor transistor formed by GaAs DHBT can be better adapted to the application of 5G RF power amplifier in high frequency (N41, N77, N79 frequency bands).

FIG. 8 is a cross-sectional view showing a semiconductor device for a radio frequency power amplifier according to another embodiment of the present invention.

Referring to FIG. 8, the semiconductor device includes from top to bottom: an emitter metal layer 701, an emitter capping layer 702, an emitter n-type doped layer (InGaP) 703, a base metal layer 704, and a base p+-type doped layer. (GaAs) 705, collector metal layer 706, collector n-type doped layer (In _x Ga _(1-x) As _y P _(1-y) ) 707, sub-collector n+ type doped layer (GaAs) 708 and substrate layer (GaAs) 709 . In this embodiment, the collector adopts a wide bandgap In _x Ga _(1-x) As _y P _(1-y) structure. By adding As elements in the collector epitaxial layer, an n-type doped InGaAsP group four element combination is formed, where x and 1-x represent the ratio of In and Ga elements, y and 1-y represent As and P elements proportion.

FIG. 9 is a schematic diagram showing an energy band structure of a semiconductor device for a radio frequency power amplifier according to another embodiment of the present invention. Referring to FIG. 9, since the forbidden band width of In _x Ga _(1-x) As _y P _(1-y) is larger than that of GaAs, a potential barrier peak will also be formed in the barrier layer of the collector region. By properly controlling the concentration and thickness of n-type doping in In _x Ga _(1-x) As _y P _(1-y) , for example, the collector layer is configured such that its thickness is smaller than the second threshold, while controlling the individual elements therein The ratio can effectively reduce the energy band peak in the barrier region, so as not to affect the electrical performance of the GaAs DHBT structure. Due to the introduction of As elements, two energy band peaks will be formed in the potential barrier region, but it will not affect the electrical performance of GaAs DHBT. According to an embodiment of the present invention, the In _x Ga _(1-x) As _y P _(1-y) epitaxial layer thickness (collector layer thickness) can be configured to be smaller than the second threshold, preferably, the second threshold is 50nm .

Since the collector region in GaAs DHBT adopts a wide bandgap In _x Ga _(1-x) As _y P _(1-y) structure, the range of GaAs DHBTSOA is larger than that of GaAs SHBT SOA, so this structure can also be Satisfied that the 5G RF power amplifier can work safely under 3.4V and 5V voltage.

Due to the limitation of the lattice constant. When the GaAs structure is used for the base and the In _(x) Ga _(1-x) P structure is used for the collector, x needs to be within the first ratio range to maintain a good lattice matching. Since the ratio of the x component is limited, for example, in the range of 0.45 to 0.55, the adjustment of the forbidden band width of the collector is also limited. If it is necessary to further increase or decrease the bandgap of the collector structure, As elements can be introduced, and by adjusting the ratio of elements, a set of four elements In _x Ga _(1-x) As _y P _(1-y) can be formed electrode. Here, the y component ratio can be set, for example, within a range of 0.45 to 0.55. In this way, by adjusting the values of x and y, the GaAs structure of the base has a lattice constant that matches that of the GaAs structure of the base, and at the same time, the value of the forbidden band width of the collector structure is also adjusted.

FIG. 10 is a circuit block diagram showing a radio frequency power amplifier including a semiconductor device according to an embodiment of the present invention.

Referring to FIG. 10 , the structure is described by taking a radio frequency power amplifier with a two-stage structure as an example. In Figure 9, the 5G RF power amplifier is mainly composed of a driver-stage amplifying unit, a power-stage amplifying unit, a driver-stage bias circuit, a power-stage bias circuit, and input, inter-stage, and output matching networks. The semiconductor device prepared by the GaAs DHBT process can be used in the power stage amplifying unit (output stage amplifying unit) of the 5G RF power amplifier to form an amplifier circuit. Since the SOA range of the semiconductor device formed by the GaAs DHBT process is larger, its It can ensure that the 5G RF power amplifier can work safely under 5V voltage. It should be understood by those skilled in the art that although an example of applying the semiconductor device formed by the GaAs DHBT process to the power level amplifying unit in the 5G radio frequency power amplifier is shown in the present invention, but without departing from the scope of the present invention, It can be applied to other parts of the circuit, for example, it can be applied to the driver stage amplification unit in the 5G RF power amplifier.

Although the power unit of a radio frequency amplifier using a common emitter amplification structure is shown in the above-mentioned example, those skilled in the art should understand that the concept of the present invention can also be applied to power units of other structural types of amplifiers, for example, the present invention The power unit of the RF amplifier can also be a common collector amplifier.

According to an embodiment of the present invention, the semiconductor device is designed according to the safe operating area (SOA) of the transistor to meet the working requirements of the 5G RF power amplifier, so as to avoid breakdown of the transistor of the RF power amplifier in the working state.

At the same time, in order to meet the requirements of 5G RF power amplifier working at 5V voltage, it is necessary to increase the SOA range of the GaAs HBT process so that its SOA can completely cover all working ranges of the voltage and current swing of the 5G RF power amplifier, so as to ensure that the chip works safely without burning out . According to an embodiment of the present invention, by adopting a wide bandgap collector region structure, the forbidden band width of the collector barrier region is increased, and the impact ionization of carriers in the collector barrier region is suppressed. In addition, by appropriately reducing the thickness of the collector barrier region, the acceleration distance of carriers in the electric field is reduced, and the total kinetic energy generated by them is reduced, so that the semiconductor device is within the SOA range.

Although the present disclosure has been described with an exemplary embodiment, various changes and modifications may be suggested to one skilled in the art. The present disclosure is intended to cover such changes and modifications as come within the scope of the appended claims.

Nothing in the present invention should be read as implying that any particular element, step or function is an essential element which must be included in the claim scope. The scope of patented subject matter is defined only by the claims.

Claims (10)

1. A semiconductor device for a radio frequency power amplifier, comprising: a substrate layer configured to be formed by GaAs; a sub-collector layer configured on the substrate layer and configured to be formed by n+ type doped GaAs; a collector layer configured on the sub-collector layer and configured to be formed by an n-type doped wide bandgap material, wherein the bandgap of the wide bandgap material is greater than that of GaAs; a collector metal layer disposed on the collector layer; a base layer configured on the collector layer and configured to be formed by p+ type doped GaAs; a base metal layer configured on the base layer; an emitter layer configured on the base layer and configured to be formed by n-type doped InGaP; an emitter capping layer disposed on the base layer; and an emitter metal layer disposed on the emitter capping layer, Wherein, the collector layer is configured such that the maximum current and voltage swing at the collector layer is within the safe operating area of the semiconductor device, wherein the safe operating area of the semiconductor device is defined as when the semiconductor device is in Safe operating area when facing the active area. 2. The semiconductor device for radio frequency power amplifier according to claim 1, wherein the safe operating area of the semiconductor device is limited to the operating area where its operating current is in the order of milliamps (mA) to amperes (A) . 3. The semiconductor device for a radio frequency power amplifier according to claim 1, wherein said wide bandgap material comprises In _x Ga _(1-x) P and In _x Ga _(1-x) As _y P _{(1- y)} , Here, x and 1-x represent ratios of In and Ga elements, and y and 1-y represent ratios of As and P elements. 4. The semiconductor device for a radio frequency power amplifier according to claim 3, wherein, when the wide bandgap material is In _x Ga _(1-x) P, the thickness of the collector layer is configured to be less than 50nm first threshold. 5. The semiconductor device for radio frequency power amplifier according to claim 3, wherein, when the wide bandgap material is In _x Ga _(1-x) As _y P _(1-y) , the collector layer The thickness is configured to be less than the second threshold of 50 nm. 6. The semiconductor device for a radio frequency power amplifier according to claim 3, wherein x is in a first ratio range of 0.45 to 0.55. 7. The semiconductor device for a radio frequency power amplifier according to claim 3, wherein y is in the second ratio range of 0.45 to 0.55. 8. The semiconductor device for a radio frequency power amplifier according to claim 1, wherein the semiconductor device is configured for a 5G radio frequency power amplifier, and the 5G radio frequency power amplifier has a maximum power operation of 4.4V-5.5V Voltage. 9. The semiconductor device for a radio frequency power amplifier according to claim 8, wherein the semiconductor device is applied in a power stage amplifying unit of the 5G radio frequency power amplifier. 10. The semiconductor device for a radio frequency power amplifier according to claim 1, wherein the sub-collector layer is configured with a doping concentration smaller than the first doping concentration.

Images