A heterojunction bipolar transistor and its MOCVD epitaxial growth method

Abstract

This invention belongs to the technical field of heterojunction bipolar transistors (HBTs), specifically relating to a HBT and its MOCVD epitaxial growth method. The HBT provided by this invention includes a transition layer disposed between the base region and the emitter layer. The MOCVD epitaxial growth method includes growing the transition layer on the surface of the base region using a linearly variable-temperature staged pulsed metal-organic chemical vapor deposition (MOCVD) method. During the total growth time of the linearly variable-temperature staged pulsed MOCVD method, PH3 is continuously introduced, and trimethylindium, trimethylgallium, and silane are introduced in single-cycle staged pulses. From the initial time T1 to the initial time TN, the reaction chamber temperature linearly increases from the base region growth temperature to the emitter layer growth temperature. The HBT obtained by the method provided by this invention has high gain, low sheet resistance, and high reliability.

Description

Technical Field

[0001] This invention belongs to the field of heterojunction bipolar transistor technology, specifically relating to a heterojunction bipolar transistor and its MOCVD epitaxial growth method. Background Technology

[0002] Heterojunction bipolar transistors (HBTs) are novel transistors built upon traditional bipolar junction transistors (BJTs) by using materials with a wider bandgap for the emitter region and a narrower bandgap for the base region. HBTs made with group III-V semiconductors (such as GaAs) offer advantages such as high power, excellent linearity, high cutoff frequency, and low power loss due to their heterogeneous bandgap structure. They are commonly used in mobile phones, WiFi terminals, and their base stations, including radio frequency (RF) power amplifiers. The rapid improvement in the performance of GaAs-based HBTs is attributed to the use of wide-bandgap emitters for high base doping, and advancements in bandgap engineering and epitaxial growth techniques. For example, using InGaAs / InGaP, GaAsSb / InGaP, and GaAsPBi / InGaP materials for the base and emitter regions, respectively, reduces the electron transport time of the HBT, thereby improving its high-frequency performance, such as high current-gain cutoff frequency (ft) and maximum oscillation frequency (fmax).

[0003] However, the base layer and emitter layer of an HBT have different growth temperature requirements. After the base region is grown, it is necessary to wait for the growth temperature to transition from a low temperature to a high temperature. During this time, the carrier concentration in the base layer may diffuse, which can significantly affect the subsequent growth of the emitter layer. Therefore, in the epitaxial growth of GaInP / InGaAs HBTs, how to grow InGaAs and GaInP materials that meet the design requirements while considering the temperature transition between the base and emitter regions of the GaInP / InGaAs HBT transistor is a key challenge in fabricating high-performance HBT epitaxial wafers. Summary of the Invention

[0004] The purpose of this invention is to provide a heterojunction bipolar transistor and its MOCVD epitaxial growth method. The heterojunction bipolar transistor obtained by the method provided by this invention has high gain and good reliability.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides an MOCVD epitaxial growth method for a heterojunction bipolar transistor, wherein the heterojunction bipolar transistor includes a substrate, and a buffer layer, a collector region ohmic contact layer, a collector region etch stop layer, a collector region, a base region, an emitter layer, a sub-emitter layer, and an emitter region ohmic contact layer are sequentially disposed on the surface of the substrate.

[0007] The heterojunction bipolar transistor further includes: a transition layer disposed between the base region and the emitter layer;

[0008] The MOCVD epitaxial growth method includes the following steps;

[0009] (1) A buffer layer, a collector region ohmic contact layer, a collector region etch stop layer, a collector region and a base region are sequentially grown on the surface of the substrate;

[0010] (2) A transition layer is grown on the surface of the base region by linear temperature-varying stage pulsed metalorganic chemical vapor deposition. The total growth time of the linear temperature-varying stage pulsed metalorganic chemical vapor deposition is divided into T1 + t1 + T2 + t2 + T3 + t3 +... + TN-1 + tN-1 + TN, where T1 < T2 < T3 <... < TN, and N is a positive integer greater than or equal to 3; PH3 is continuously introduced during the total growth time of the linear temperature-varying stage pulsed metalorganic chemical vapor deposition, trimethylindium, trimethylgallium and silane are introduced during T1, T2, T3,..., TN-1 and TN, and trimethylindium, trimethylgallium and silane are not introduced during t1, t2, t3,..., and tN-1; the temperature of the reaction chamber linearly increases from the base region growth temperature to the emitter layer growth temperature from the initial moment of T1 to the initial moment of TN;

[0011] (3) An emitter layer, a sub-emitter layer and an emitter region ohmic contact layer are sequentially grown on the surface of the transition layer to obtain a heterojunction bipolar transistor.

[0012] Preferably, in step (2), the flow rate of PH3 is set to 400 sccm, the source flow rate of trimethylindium is set to 200 sccm, and the source flow rate of silane is set to 30 sccm; trimethylgallium is introduced into the reaction chamber through a double dilution pipeline, and the flow rate of TMGa introduced into the reaction chamber is 2.4 sccm.

[0013] Preferably, in step (2), the temperature of the reaction chamber at the initial moment of T1 is 570 °C, and the temperature of the reaction chamber at the initial moment of TN is 640 °C.

[0014] Preferably, the time of T1 is set to 2 s, the time of T2 is set to 3 s, the time of T3 is set to 4 s,..., and the time of TN is set to N + 1 s.

[0015] Preferably, the times of t1, t2, t3, t4, t5,..., and tN-1 are all set to 1 s.

[0016] Preferably, in step (2), the total growth time of the linear temperature-varying stage pulsed metalorganic chemical vapor deposition is 132 s; the thickness of the transition layer is 3.6 nm.

[0017] Preferably, the transition layer is made of N-type doped GaInP; the doping element of the N-type doped GaInP is Si, and the doping concentration is 4E17 cm⁻¹. -3 .

[0018] Preferably, the temperature of the buffer layer, the ohmic contact layer of the current collector region, the corrosion stop layer of the current collector region, and the reaction chamber during the growth of the current collector region is 680°C.

[0019] The reaction chamber temperature during the growth of the substrate region is 570℃;

[0020] The reaction chamber temperature is 640°C during the growth of the emitter layer, sub-emitter layer, and ohmic contact layer in the emitter region.

[0021] Preferably, the buffer layer is made of GaAs, with Si as the doping element and a doping concentration of 1E18cm⁻¹. -3 The thickness of the buffer layer is 100 nm;

[0022] The ohmic contact layer of the current collector region is made of GaAs, with Si as the doping element and a doping concentration of 5E18cm⁻¹. -3 The thickness of the ohmic contact layer in the current collector region is 500 nm;

[0023] The corrosion stop layer in the current collector region is made of GaInP, with Si as the doping element and a doping concentration of 5E18cm⁻¹. -3 The thickness of the corrosion stop layer in the current collecting region is 80 nm;

[0024] The current collector region is made of GaAs, with Si as the dopant element and a doping concentration of 0.5–5E17 cm⁻¹. -3 The thickness of the current collector region is 1100 nm;

[0025] The base region is made of In 0.06 GaAs, doped with C, with a doping concentration of 4E19m -3 The thickness of the base region is 50 nm;

[0026] The emitter layer is made of GaInP, and the doping element is Si with a doping concentration of 4E17m. -3 The thickness of the emission layer is 30 nm;

[0027] The sub-emitter layer is made of GaAs, with Si as the doping element and a doping concentration of 5E18m. -3 The thickness of the sub-emitting layer is 140 nm;

[0028] The material of the ohmic contact layer in the launch area is In 0.5 GaAs, doped with Te, with a doping concentration of 2E19m -3, the thickness of the emitter region ohmic contact layer is 110 nm.

[0029] The present invention provides a heterojunction bipolar transistor obtained by the MOCVD epitaxial growth method of the above technical solution. The heterojunction bipolar transistor includes a substrate, a buffer layer, a collector region ohmic contact layer, a collector region etch stop layer, a collector region, a base region, an emitter layer, a sub-emitter layer, and an emitter region ohmic contact layer sequentially disposed on the surface of the substrate;

[0030] The heterojunction bipolar transistor further includes: a transition layer disposed between the base region and the emitter layer.

[0031] The present invention provides a MOCVD epitaxial growth method for a heterojunction bipolar transistor. A transition layer is grown on the surface of the base region by a linear temperature change stepwise pulsed metal organic chemical vapor deposition method. The total growth time of the linear temperature change stepwise pulsed metal organic chemical vapor deposition method is divided into T1 + t1 + T2 + t2 + T3 + t3 +... + TN-1 + tN-1 + TN, where T1 < T2 < T3 <... < TN, and N is a positive integer greater than or equal to 3; PH3 is continuously introduced during the total growth time of the linear temperature change stepwise pulsed metal organic chemical vapor deposition method, trimethylindium, trimethylgallium, and silane are introduced during T1, T2, T3,..., TN-1, and TN, and trimethylindium, trimethylgallium, and silane are not introduced during t1, t2, t3,..., and tN-1; the temperature of the reaction chamber linearly increases from the base region growth temperature to the emitter layer growth temperature during the time from the initial moment of T1 to the initial moment of TN.

[0032] The HBT obtained by the MOCVD epitaxial growth method provided by the present invention has the following technical effects:

[0033] (1) The HBT epitaxial wafer has a high current gain.

[0034] In the growth of heterojunction (GaInP / InGaAs) bipolar transistors, the inherent bandgap difference between the emitter layer (N-GaInP) and the base layer (P-InGaAs) results in a potential barrier peak at the GaInP / InGaAs heterojunction, hindering electron diffusion from the emitter region to the base region and leading to low emission efficiency. This invention addresses this by employing a linearly variable-temperature staged pulse deposition method to grow a transition layer (GaInP) of the same material as the emitter layer. The bandgap variation of the GaInP transition layer is controlled primarily by linearly increasing the growth temperature and adjusting the GaSource ingress time. This reduces the bandgap difference between the resulting low-Ga-content GaInP transition layer and the base InGaAs layer, effectively lowering the potential barrier peak at the GaInP / InGaAs heterojunction. Simultaneously, electrons in the emitter layer (also called the emitter region) tunnel more easily into the base region, further improving emission efficiency. Furthermore, the discontinuity of the stepped bandgap in the GaInP transition layer hinders reverse hole injection into the base region, significantly improving the electron injection efficiency and current gain of the HBT.

[0035] This invention employs a variable-temperature pulsed stepwise growth method for GaInP epitaxial layers. Under low-temperature conditions, a very thin nucleation layer is first formed using short pulses and stabilized (trimethylindium, trimethylgallium, and silane are introduced within time T1 to form the nucleation layer for the transition layer, allowing sufficient time for the nucleation layer atoms to migrate to their lowest energy point within time t1), reducing stacking faults and vacancies. Then, based on the nucleation layer, a single-cycle staged pulsed gas flow is used for growth and deposition. As the temperature increases and the Ga source introduction time lengthens, the GaInP transition layer changes from disordered to ordered, and the thickness and bandgap width of the transition layer increase layer by layer, eventually growing into a lattice-matched GaInP emitter layer, effectively improving the crystal quality of the emitter layer and increasing the emission efficiency. At the same time, the transition layer does not change the In composition and doping of the base region, further improving the current gain of the HBT epitaxial wafer.

[0036] (2) HBT epitaxial wafers have low sheet resistance and high reliability.

[0037] This invention utilizes the temperature transition time from the base region to the emitter region and employs a variable-temperature pulse growth method to avoid doping diffusion caused by the base region waiting for temperature changes, thereby maintaining a uniformly high doping in the base region, resulting in lower sheet resistance and uniformity. At the same time, the method provided by this invention has low epitaxial cost, short growth time for GaInP transition layer (only 132 seconds), and improves the growth quality of both the emitter and base regions, with short growth time and low manufacturing cost.

[0038] In this invention, after the transition layer is grown, the temperature is stabilized at the growth temperature of the emitter layer (640°C). The lattice-matched GaInP emitter layer that is then grown will not be affected by temperature changes. This method effectively reduces interface defects between the base region and the emitter region caused by waiting for temperature changes, thereby improving the reliability of the HBT epitaxial wafer.

[0039] Furthermore, in this invention, in step (2), the flow rate of PH3 is set to 400 sccm. In the pulsed growth method of step (2) of this invention, the high partial pressure ratio of PH3 (400 sccm) is maintained, which is beneficial to accelerate the migration rate of surface atoms during the growth process and enable the atoms to reach the stable state of the lowest energy point more quickly. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the HBT epitaxial structure in this invention;

[0041] Figure 1 In the middle: 10 is the substrate, 20 is the buffer layer, 30 is the ohmic contact layer of the collector region, 40 is the etch stop layer of the collector region, 50 is the collector region, 60 is the base region, 70 is the emitter layer, 80 is the sub-emitter layer, 90 is the ohmic contact layer of the emitter region, and 71 is the transition layer.

[0042] Figure 2 The relationship between temperature, gas pulse introduction method, Ga composition and growth time in the MOCVD reaction chamber;

[0043] Figure 3 This is a comparison of the bandgap of the HBT of this invention with that of a conventional HBT;

[0044] Figure 4 This is a comparison of the results of the present invention with those of conventional methods;

[0045] Figure 5 The sheet resistance test results of the HBTs grown in the embodiments of the present invention are shown. Detailed Implementation

[0046] This invention provides an MOCVD epitaxial growth method for a heterojunction bipolar transistor, wherein the heterojunction bipolar transistor includes a substrate, and a buffer layer, a collector region ohmic contact layer, a collector region etch stop layer, a collector region, a base region, an emitter layer, a sub-emitter layer, and an emitter region ohmic contact layer are sequentially disposed on the surface of the substrate.

[0047] The heterojunction bipolar transistor further includes a transition layer disposed between the base region and the emitter layer;

[0048] The MOCVD epitaxial growth method includes the following steps;

[0049] (1) A buffer layer, a collector region ohmic contact layer, a collector region etch stop layer, a collector region, and a base region are sequentially grown on the surface of the substrate.

[0050] (2) A transition layer is grown on the surface of the base region by linear temperature change staged pulse metal organic chemical vapor deposition. The total growth time of the linear temperature change staged pulse metal organic chemical vapor deposition is divided into T1 + t1 + T2 + t2 + T3 + t3 + …… + TN-1 + tN-1 + TN, where T1 < T2 < T3 < …… < TN, and N is a positive integer ≥ 3. PH3 is continuously introduced during the total growth time of the linear temperature change staged pulse metal organic chemical vapor deposition. Trimethylindium, trimethylgallium, and silane are introduced during T1, T2, T3, …… TN-1, and TN. Trimethylindium, trimethylgallium, and silane are not introduced during t1, t2, t3, ……, and tN-1. The temperature of the reaction chamber linearly increases from the base region growth temperature to the emitter layer growth temperature from the initial moment of T1 to the initial moment of TN.

[0051] (3) An emitter layer, a sub-emitter layer, and an emitter region ohmic contact layer are sequentially grown on the surface of the transition layer to obtain a heterojunction bipolar transistor.

[0052] In the present invention, unless otherwise specified, all preparation raw materials / components are commercially available products well-known to those skilled in the art.

[0053] The present invention provides a MOCVD epitaxial growth method for a heterojunction bipolar transistor. In the present invention, the heterojunction bipolar transistor is a GaInP / InGaAs heterojunction bipolar transistor. The structure of the heterojunction bipolar transistor is as Figure 1 shown. The following combines Figure 1 to describe the structure of the heterojunction bipolar transistor provided by the present invention in detail.

[0054] The heterojunction bipolar transistor provided by the present invention includes a substrate 10. The material of the substrate 10 is preferably SI-GaAs. The conductivity of the substrate 10 is preferably 4×10 8 Ω·cm. The thickness of the substrate 10 is preferably 675 μm.

[0055] The heterojunction bipolar transistor provided by the present invention includes a buffer layer 20 disposed on the surface of the substrate 10. In the present invention, the material of the buffer layer 20 is preferably GaAs, the doping element is preferably Si, and the doping concentration is preferably 1E18cm -3 , and the thickness of the buffer layer 20 is preferably 100 nm.

[0056] The heterojunction bipolar transistor provided by the present invention includes a collector region ohmic contact layer 30 disposed on the surface of the buffer layer 20. In the present invention, the material of the collector region ohmic contact layer 30 is preferably GaAs, the doping element is preferably Si, and the doping concentration is preferably 5E18cm⁻¹. -3 The thickness of the ohmic contact layer in the current collector region is preferably 500 nm.

[0057] The heterojunction bipolar transistor provided by the present invention includes a collector region etch stop layer 40 disposed on the surface of the collector region ohmic contact layer 30. In the present invention, the material of the collector region etch stop layer 40 is preferably GaInP, the doping element is preferably Si, and the doping concentration is preferably 5E18cm⁻¹. -3 The thickness of the corrosion stop layer in the current collecting region is preferably 80 nm.

[0058] The heterojunction bipolar transistor provided by this invention includes a collector region 50 disposed on the surface of a collector region etched stop layer 40. In this invention, the material of the collector region 50 is preferably GaAs, the doping element is preferably Si, and the doping concentration is preferably 0.5–5E17cm⁻¹. -3 The thickness of the current collector region is preferably 1100 nm.

[0059] The heterojunction bipolar transistor provided by the present invention includes a base region 60 disposed on the surface of a collector region 50. In the present invention, the material of the base region 60 is preferably In. 0.06 GaAs, preferably doped with C, and preferably with a doping concentration of 4E19m. -3 The thickness of the base region is preferably 50 nm.

[0060] The heterojunction bipolar transistor provided by the present invention includes a transition layer 71 disposed on the surface of the base region 60. In the present invention, the material of the transition layer 71 is preferably N-type doped GaInP; the doping element of the N-type doped GaInP is preferably Si, and the doping concentration is preferably 4E17 cm⁻¹. -3 The thickness of the transition layer 71 is preferably 3.6 nm.

[0061] The heterojunction bipolar transistor provided by the present invention includes an emitter layer 70 disposed on the surface of the transition layer 71. In the present invention, the material of the emitter layer 70 is preferably GaInP, the doping element is preferably Si, and the doping concentration is preferably 4E17m. -3 The thickness of the emission layer 70 is preferably 30 nm.

[0062] The heterojunction bipolar transistor provided by the present invention includes a sub-emitter layer 80 disposed on the surface of the emitter layer 70. In the present invention, the material of the sub-emitter layer 80 is preferably GaAs, the doping element is preferably Si, and the doping concentration is preferably 5E18m.-3 The thickness of the sub-emitting layer is preferably 140 nm.

[0063] The heterojunction bipolar transistor provided by the present invention includes an emitter ohmic contact layer 90 disposed on the surface of the sub-emitter layer 80. In the present invention, the material of the emitter ohmic contact layer 90 is preferably In. 0.5 GaAs, preferably doped with Te, with a preferred doping concentration of 2E19m. -3 The thickness of the ohmic contact layer in the emission region is preferably 110 nm.

[0064] The MOCVD epitaxial growth method provided by this invention includes the following steps:

[0065] In this invention, a buffer layer, a collector region ohmic contact layer, a collector region etch stop layer, a collector region, and a base region are sequentially grown on the surface of a substrate. In this invention, the buffer layer, collector region ohmic contact layer, collector region etch stop layer, collector region, and base region are grown using metal-organic chemical vapor deposition (MOCVD). In a specific embodiment of this invention, the substrate 10 is preferably placed in an MOCVD system (Aixtron) to sequentially grow the buffer layer 20, collector region ohmic contact layer 30, collector region etch stop layer 40, collector region 50, and base region 60. The preferred reaction chamber temperature during the growth of the buffer layer 20, the ohmic contact layer 30, the corrosion stop layer 40, and the collector region 50 is 680°C. The preferred reaction chamber temperature during the growth of the base region 60 is 570°C. The preferred reaction chamber pressure is 100 mbar. In this invention, H2 is used as the carrier gas, and trimethylindium (TMIn), trimethylgallium (TMGa), carbon tetrachloride (CCl4), silane (SiH4), trimethylarsine (TMAs), arsine (AsH3), and phosphine (PH3) are used as the reaction source gases. Trimethylgallium (TMGa) is continuously introduced, and silane (SiH4) is used as the buffer layer, the ohmic contact layer, the corrosion stop layer, and the doping gas for the collector region. Carbon tetrachloride is used as the doping gas for the collector region. Carbon (CCl4) is used as the dopant gas for the base region. The preferred source flow rate for TMGa is 100 sccm. AsH3 is introduced to grow the N-GaAs buffer layer and the N-GaAs collector region ohmic contact layer. Then, AsH3 is switched to PH3, and trimethylgallium (TMGa) and trimethylindium (TMIn) are introduced to grow the GaInP collector region etching stop layer. The preferred source flow rate for TMGa is 15 sccm, and for TMIn it is 600 sccm. Then, PH3 is switched to AsH3 to grow the GaAs collector region, and the preferred source flow rate for TMGa is 100 sccm. The reaction chamber temperature is rapidly cooled from 680℃ to 570℃, and then trimethylgallium (TMGa) and trimethylindium (TMIn) are introduced to grow the InGaAs base region. The preferred source flow rate for TMGa is 15 sccm, and for TMIn it is 600 sccm.

[0066] After obtaining the base region, in the present invention, PH3, trimethylindium, and trimethylgallium are used as reaction source gases on the surface of the base region, and silane is used as a doping source gas. The transition layer is grown by linear temperature-changing stepwise pulse metalorganic chemical vapor deposition. The total growth time of the linear temperature-changing stepwise pulse metalorganic chemical vapor deposition is divided into T1 + t1 + T2 + t2 + T3 + t3 + …… + TN-1 + tN-1 + TN, where T1 < T2 < T3 < …… < TN, and N is a positive integer greater than or equal to 3. During the total growth time of the linear temperature-changing stepwise pulse metalorganic chemical vapor deposition, PH3 is continuously introduced. Trimethylindium, trimethylgallium, and silane are introduced at times T1, T2, T3, …… TN-1, and TN. Trimethylindium, trimethylgallium, and silane are not introduced during times t1, t2, t3, ……, and tN-1. The temperature of the reaction chamber linearly increases from the base region growth temperature to the emitter layer growth temperature from the initial moment of T1 to the initial moment of TN.

[0067] In the present invention, the transition layer 71 is grown by linear temperature-changing stepwise pulse metalorganic chemical vapor deposition. In a specific embodiment of the present invention, the transition layer 71 is grown in a MOCVD system (Aixtron). After the growth of the base region is completed, the present invention switches AsH3 to PH3. The flow rate of PH3 is preferably set to 400 sccm. Under the protection of 400 sccm of PH3 gas, trimethylindium (TMIn), trimethylgallium (TMGa), and silane (SiH4) are then introduced into the MOCVD reaction chamber in a pulsed manner to grow the GaInP transition layer. Among them, the Source flow rate of TMIn is preferably set to 200 sccm, the Source flow rate of SiH4 is preferably set to 30 sccm, and TMGa is preferably introduced into the reaction chamber through a double dilution pipeline, and its Source / Dilute / inject flow rates are 20 sccm / 200 sccm / 27 sccm respectively. The gas concentration introduced into the reaction chamber through the double dilution pipeline can be calculated by the following formula 1:

[0068]

[0069] In formula 1, S is the actual gas flow rate introduced into the reaction chamber, F Source 、F Dilute 、F Inject respectively represent the flow rates of Source, Dilute, and Injetct. Therefore, the flow rate of TMGa introduced into the reaction chamber is 2.4 sccm. The growth rate of the GaInP epitaxial layer is linearly related to the flow rates of In and Ga. The growth rate of the GaInP transition layer can be calculated to be 0.03 nm / s.

[0070] In a specific embodiment of the present invention, time T1 is preferably set to 2s, time T2 is preferably set to 3s, time T3 is preferably set to 4s, ..., and time TN is preferably set to N+1s. Time t1, t2, t3, t4, t5, ... and tN-1 are all preferably set to 1s. The initial reaction chamber temperature at time T1 is preferably 570℃, and the initial reaction chamber temperature at time TN is preferably 640℃. In the present invention, the total growth time of the pulsed metal-organic chemical vapor deposition method is 132s, of which the actual total growth time (T1+T2+T3+...+TN-1+TN) is 119s, and the total interval time (t1+t2+t3+...+tN-1) is 13s; the thickness of the transition layer is 120s × 0.03nm / s = 3.6nm. The total growth time of the pulsed metal-organic chemical vapor deposition method is calculated from the starting time of T1 to the ending time of TN.

[0071] In a specific embodiment of the present invention Figure 1 The relationship between temperature, gas pulse introduction method, GaInP composition change and growth time in the MOCVD reaction chamber during the transition layer growth process is presented. At a reaction chamber temperature of 570℃, a pulse is applied for 2 seconds within a time period of T1 = 1 second, during which TMGa, TMIn, and SiH4 are introduced to grow a GaInP nucleation layer, while the reaction chamber temperature increases linearly. The pulse is then turned off for 1 second, allowing sufficient time for the nucleation layer atoms to migrate to their lowest energy point. A pulse is applied for 3 seconds within a time period of T2 = 4 seconds, during which TMGa, TMIn, and SiH4 are introduced again to grow an epitaxial layer of a certain thickness. The duration of each pulse deposition and growth increases by 1 second, while the pulse off time remains constant. A stable epitaxial layer is formed when the pulse is turned off. During the intermittent phase, the pulse time reaches TN and lasts for N+1 seconds, during which TMGa, TMIn, and SiH4 are introduced again to grow an epitaxial layer of a certain thickness, while the reaction chamber temperature reaches 640℃, where N ≥ 3 and is an integer. In this pulsed growth method, maintaining a high partial pressure ratio of PH3 (400 sccm) is beneficial for accelerating the migration rate of surface atoms during growth, allowing atoms to reach their stable state at the lowest energy point more quickly.

[0072] After obtaining the transition layer, the present invention sequentially grows an emitter layer, a sub-emitter layer, and an emitter ohmic contact layer on the surface of the transition layer to obtain a heterojunction bipolar transistor. In this invention, the growth of the emitter layer 70, the sub-emitter layer 80, and the emitter ohmic contact layer 90 is preferably performed in an MOCVD system (Aixtron). The preferred reaction chamber temperature during the growth of the emitter layer 70, the sub-emitter layer 80, and the emitter ohmic contact layer 90 is 640°C, the reaction chamber pressure is 100 mbar, H2 is used as the carrier gas, and one or more of trimethylindium (TMIn), trimethylgallium (TMGa), silane (SiH4), trimethylarsine (TMAs), arsine (AsH3), and phosphine (PH3) are used as the reaction source gas. The emitter layer 70, the sub-emitter layer 80, and the emitter ohmic contact layer 90 are grown sequentially, wherein the doping reaction source for the emitter ohmic contact layer 90 is Te metal. The present invention does not have specific requirements for the specific growth method of the emitter layer 70, the sub-emitter layer 80, and the emitter ohmic contact layer 90.

[0073] In a specific embodiment of the present invention, during the growth of the emitter layer 70: the flow rate of PH3 is set to 800 sccm, the source flow rate of TMIn is preferably set to 400 sccm, the source flow rate of SiH4 is preferably set to 30 sccm, and TMGa is preferably introduced into the reaction chamber through a dual dilution pipeline with source / dilute / inject flow rates of 50 sccm / 150 sccm / 50 sccm, respectively. The gas concentration introduced into the reaction chamber through the dual dilution pipeline can be calculated using the following formula 1:

[0074]

[0075] In Formula 1, S is the actual gas flow rate introduced into the reaction chamber, and F... Source F Dilute F Inject These represent the flow rates of Source, Dilute, and Injection, respectively. Therefore, the flow rate of TMGa introduced into the reaction chamber is 12 sccm; the growth rate of the GaInP epitaxial layer is linearly related to the flow rates of In and Ga, and the calculated growth rate of GaInP is 0.15 nm / s. The growth time of the GaInP emitter region is 200 seconds, and the growth thickness of the GaInP emitter region is 30 nm.

[0076] This invention provides a heterojunction bipolar transistor obtained by the MOCVD epitaxial growth method described above. The heterojunction bipolar transistor includes a substrate, and a buffer layer, a collector region ohmic contact layer, a collector region etch stop layer, a collector region, a base region, an emitter layer, a sub-emitter layer, and an emitter region ohmic contact layer are sequentially disposed on the surface of the substrate.

[0077] The heterojunction bipolar transistor further includes a transition layer disposed between the base region and the emitter layer.

[0078] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0079] Example 1

[0080] The schematic diagram of the HBT epitaxial structure provided in this embodiment of the invention is shown below. Figure 1 As shown in Table 1, this embodiment provides information on the materials, thicknesses, doping elements, doping concentrations, and corresponding functions of each layer of the HBT epitaxial structure. A junction bipolar transistor epitaxial wafer was fabricated according to the structure shown in Table 1.

[0081] Table 1. Information on the HBT epitaxial structure provided in Example 1

[0082] Serial Number Epitaxial materials thickness wavelength dopant Doping Remark 90 <![CDATA[In 0.5 GaAs]]> 110nm Te <![CDATA[2E19cm -3 ]]> Launch area ohmic contact layer 80 GaAs 140nm / Si <![CDATA[5E18cm -3 ]]> Sub-launching layer 70 GaInP 30nm Si <![CDATA[4E17cm -3 ]]> emission layer 71 GaInP 3.6nm Si <![CDATA[4E17cm -3 ]]> transition layer 60 <![CDATA[In 0.06 GaAs]]> 50nm / C <![CDATA[4E19cm -3 ]]> base area 50 GaAs 1100nm / Si <![CDATA[0.5-5E17cm -3 ]]> Collection area 40 GaInP 80nm Si <![CDATA[5E18cm -3 ]]> Corrosion stop layer in the collector area 30 GaAs 500nm / Si <![CDATA[5E18cm -3 ]]> Ohmic contact layer of collector region 20 GaAs 100nm / Si <![CDATA[1E18cm -3 ]]> Buffer layer 10 SI-GaAs 675um / / substrate

[0083] In this embodiment, the resistivity is 4×10⁻⁶. 8 GaAs with a density of Ω·cm was used as the growth substrate and grown in an Aixtron MOCVD system. The reaction chamber pressure was 100 mbar, the growth temperature was 680 °C, and H2 was used as the carrier gas. Trimethylindium (TMIn), trimethylgallium (TMGa), carbon tetrachloride (CCl4), silane (SiH4), trimethylarsine (TMAs), arsine (AsH3), and phosphine (PH3) were used as the source gases. TMGa was continuously introduced, with silane (SiH4) used as a buffer layer, an ohmic contact layer for the collector region, an etching stop layer for the collector region, and a dopant gas for the collector region. Carbon tetrachloride (CCl4) was used as the dopant gas for the base region. The TMGa source flow... The flow rate was set to 100 sccm. AsH3 was introduced to grow an N-GaAs buffer layer and an N-GaAs collector region ohmic contact layer. Then, AsH3 was switched to PH3, and trimethylgallium (TMGa) and trimethylindium (TMIn) were introduced to grow a GaInP collector region etching stop layer. The source flow rate of TMGa was set to 15 sccm, and the source flow rate of TMIn was set to 600 sccm. Then, PH3 was switched to AsH3 to grow the GaAs collector region, and the source flow rate of TMGa was set to 100 sccm. The reaction chamber was rapidly cooled to 570℃, and then trimethylgallium (TMGa) and trimethylindium (TMIn) were introduced to grow the InGaAs base region. The source flow rate of TMGa was set to 15 sccm, and the source flow rate of TMIn was set to 600 sccm.

[0084] Then, AsH3 was switched to PH3. Under the protection of PH3 gas at 400 sccm, trimethylindium (TMIn), trimethylgallium (TMGa), and silane (SiH4) were pulsed into the MOCVD reaction chamber to grow a GaInP transition layer. The source flow rate of TMIn was set to 200 sccm, the source flow rate of SiH4 was set to 30 sccm, and TMGa was introduced into the reaction chamber through a dual dilution pipeline with source / dilute / inject flow rates of 20 sccm / 200 sccm / 27 sccm, respectively. The gas concentration introduced into the reaction chamber through the dual dilution pipeline can be calculated using the following formula 1:

[0085]

[0086] In Formula 1, S is the actual gas flow rate introduced into the reaction chamber, and F... Source F Dilute F Inject These represent the flow rates of Source, Dilute, and Injection, respectively. Therefore, the flow rate of TMGa introduced into the reaction chamber is 2.4 sccm; the growth rate of the GaInP epitaxial layer is linearly related to the flow rates of In and Ga, and the growth rate of the GaInP transition layer can be calculated to be 0.03 nm / s. The total growth time is 132 seconds, and the thickness of the GaInP transition layer region is 3.6 nm.

[0087] Figure 2 The relationship between temperature, gas pulse introduction method, GaInP composition change and growth time in the MOCVD reaction chamber is presented. At a reaction chamber temperature of 570℃, a pulse is applied for 2 seconds within a time period of T1 = 1 second, during which TMGa, TMIn, and SiH4 are introduced to grow a GaInP nucleation layer, while the reaction chamber temperature increases linearly. The pulse is then turned off for 1 second, allowing sufficient time for the nucleation layer atoms to migrate to their lowest energy point. A pulse is applied for 3 seconds within a time period of T2 = 4 seconds, during which TMGa, TMIn, and SiH4 are introduced again to grow an epitaxial layer of a certain thickness. The duration of each pulse deposition and growth increases by 1 second, while the pulse off time remains constant. A stable epitaxial layer is formed when the pulse is turned off. During the intermittent phase, the pulse time reaches TN and lasts for N+1 seconds, during which TMGa, TMIn, and SiH4 are introduced again to grow an epitaxial layer of a certain thickness, while the reaction chamber temperature reaches 640℃, where N ≥ 3 and is an integer. In this pulsed growth method, maintaining a high partial pressure ratio of PH3 (400 sccm) is beneficial for accelerating the migration rate of surface atoms during growth, allowing atoms to reach their stable state at the lowest energy point more quickly.

[0088] Figure 3This paper compares the bandgap of the HBT of this invention with that of a conventional HBT. In conventional HBTs, the GaInP and InGaAs materials have a fixed bandgap difference, resulting in a potential barrier peak in the GaInP / InGaAs heterojunction. In contrast, this invention employs a linearly temperature-controlled pulse deposition of a GaInP transition layer with a gradually varying bandgap. The bandgap step change is controlled primarily by adjusting the growth temperature of the GaInP transition layer and the Ga source. The reduced bandgap difference between the low-Ga-content GaInP transition layer and the base InGaAs layer effectively reduces the potential barrier peak at the GaInP / InGaAs heterojunction, lowering the turn-on voltage Von and improving device performance. Simultaneously, electrons in the emitter region tunnel more easily into the base region, further improving emission efficiency. However, the discontinuity of the stepped bandgap in the GaInP transition layer hinders reverse hole injection into the base region. After growing a high-Ga-content GaInP transition layer, a lattice-matched, high-quality emitter GaInP epitaxial layer is then grown. The transition layer does not affect the composition and doping of the base and emitter regions, thus achieving a high-quality, high-gain HBT. Compared to this invention, the conventional HBT process uses the same equipment and substrate. The growth processes for the buffer layer, collector ohmic contact layer, collector region etch barrier layer, collector region, and base region on the substrate surface are the same as in Example 1. The difference lies in the following: after the base region is grown, TMGa, TMIn, and CCl4 are immediately shut off, and then the temperature is raised to prepare for the growth of the emitter region. By raising the set temperature from 570°C to 640°C rapidly for approximately 120 seconds, the TMAs valve is immediately shut off, the PH3 valve is opened, and the PH3 source flow rate is 800 sccm. Then, source gases such as TMGa, TMIn, and SiH4 are introduced to grow the GaInP emitter epitaxial layer (same as in Example 1). Then, the GaAs sub-emitter layer (also called the sub-emitter region) and the InGaAs emitter ohmic contact layer are grown, thus forming a complete HBT epitaxial structure produced by the conventional HBT process.

[0089] This invention first introduces short pulses into TMGa, TMIn, and SiH4 to form a very thin nucleation layer and stabilize it, reducing stacking faults and vacancies. Then, based on the nucleation layer, a single-cycle pulsed gas flow is used to linearly increase the reaction chamber temperature from 570℃ to 640℃, and the Ga source is adjusted to grow GaInP epitaxial transition layers with varying band gaps of different thicknesses. The total thickness is 3.6 nm, and the total time is 132 seconds. Subsequently, a doping concentration of 4E17 cm⁻¹ is grown. -3 A GaInP emitter layer is formed, followed by the growth of a GaAs sub-emitter layer and an InGaAs emitter region ohmic contact layer, thus forming a complete HBT epitaxial structure.

[0090] This invention effectively optimizes the temperature transition process between the base and emitter regions and grows a GaInP transition layer with a tunable stepped bandgap. This significantly reduces the barrier spike at the GaInP / InGaAs heterojunction, improving emitter efficiency and current gain without affecting the quality of the base epitaxial layer. Using this invention, the gain beta of the HBT increases significantly, such as... Figure 4 As shown. Simultaneously, the GaInP transition layer matches the GaInP lattice, improving the quality of the emitter region epitaxial layer and avoiding doping diffusion in the base region while waiting for temperature changes. This ensures the base region maintains uniform high doping, resulting in lower sheet resistance and uniformity. Using this invention, the average sheet resistance of the HBT epitaxial wafer is 7.51 ohm / sq, and Std is 0.45%. Figure 5 As shown.

[0091] As can be seen from the above embodiments, the present invention uses a linear temperature-controlled staged pulsed metal-organic chemical vapor deposition (MOCVD) method to grow a transition layer on the surface of the base region. During the total growth time of the linear temperature-controlled staged pulsed MOCVD method, PH3 is continuously introduced, and trimethylindium, trimethylgallium, and silane are introduced in single-cycle staged pulses. From the initial time T1 to the initial time TN, the reaction chamber temperature increases linearly from the base region growth temperature to the emitter layer growth temperature. The heterojunction bipolar transistor obtained by the method provided by the present invention has high gain, low sheet resistance, and good reliability.

[0092] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for MOCVD epitaxial growth of a heterojunction bipolar transistor, characterized by, The heterojunction bipolar transistor comprises a substrate, a buffer layer, a collector region ohmic contact layer, a collector region etching stop layer, a collector region, a base region, an emitter layer, a sub-emitter layer and an emitter region ohmic contact layer arranged on the surface of the substrate in sequence; The heterojunction bipolar transistor further comprises a transition layer arranged between the base region and the emitter layer. The MOCVD epitaxial growth method comprises the following steps; (1) growing a buffer layer, a collector region ohmic contact layer, a collector region etching stop layer, a collector region and a base region on the surface of the substrate in sequence; (2) growing a transition layer on the surface of the base region by using a linear temperature variation stage type pulse metal organic chemical vapor deposition method, wherein the total growth time of the linear temperature variation stage type pulse metal organic chemical vapor deposition method is divided into T1+t1+T2+t2+T3+t3+…+TN-1+tN-1+TN, T1 (3) growing an emitter layer, a sub-emitter layer and an emitter region ohmic contact layer on the surface of the transition layer in sequence to obtain a heterojunction bipolar transistor.

2. The MOCVD epitaxial growth method according to claim 1, wherein In step (2), the PH3 flow rate is set to 400 sccm, the Source flow rate of trimethylindium is set to 200 sccm, and the Source flow rate of silane is set to 30 sccm; trimethylgallium is introduced into the reaction chamber through a double-dilution pipeline, and the TMGa flow rate introduced into the reaction chamber is 2.4 sccm.

3. The MOCVD epitaxial growth method according to claim 1, wherein In step (2), the reaction chamber temperature at the initial moment of T1 is 570℃, and the reaction chamber temperature at the initial moment of TN is 640℃.

4. The MOCVD epitaxial growth method according to claim 1, wherein T1 time is set to 2s, T2 time is set to 3s, T3 time is set to 4s, …, and TN time is set to N+1s.

5. The MOCVD epitaxial growth method according to claim 1, wherein t1, t2, t3, t4, t5, …, and tN-1 time are all set to 1s.

6. The MOCVD epitaxial growth method according to any one of claims 1 to 5, characterized by, In step (2), the total growth time of the linear temperature variation stage type pulse metal organic chemical vapor deposition method is 132s; and the thickness of the transition layer is 3.6nm.

7. The MOCVD epitaxial growth method according to claim 1, wherein The material of the transition layer is N-doped GaInP; the doping element of the N-doped GaInP is Si, and the doping concentration is 4E17 cm -3 .

8. The MOCVD epitaxial growth method according to claim 1, wherein, The reaction chamber temperature is 680℃ during the growth of the buffer layer, the collector region ohmic contact layer, the collector region etching stop layer and the collector region; The reaction chamber temperature is 570℃ during the growth of the base region; The reaction chamber temperature is 640℃ during the growth of the emitter layer, the sub-emitter layer and the emitter region ohmic contact layer.

9. The MOCVD epitaxial growth method according to claim 1 or 8, wherein The material of the buffer layer is GaAs, the doping element is Si, the doping concentration is 1E18 cm -3 The thickness of the buffer layer is 100 nm. The material of the collecting area ohmic contact layer is GaAs, the doping element is Si, and the doping concentration is 5E18cm -3 The thickness of the collecting area ohmic contact layer is 500nm. The material of the collector region etching stop layer is GaInP, the doping element is Si, and the doping concentration is 5E18cm -3 The thickness of the collector region etching stop layer is 80nm. The material of the collector region is GaAs, the doping element is Si, the doping concentration is 0.5-5E17 cm -3 The thickness of the collector region is 1100 nm. The material of the base region is In 0.06 GaAs, the doping element is C, and the doping concentration is 4E19m -3 The thickness of the base region is 50nm; The material of the emitting layer is GaInP, the doping element is Si, and the doping concentration is 4E17m -3 The thickness of the emitting layer is 30nm. The material of the auxiliary emission layer is GaAs, the doping element is Si, the doping concentration is 5E18m -3 The thickness of the auxiliary emission layer is 140nm; The material of the ohmic contact layer of the emitting region is In 0.5 GaAs, the doping element is Te, and the doping concentration is 2E19m -3 The thickness of the ohmic contact layer of the emitting region is 110 nm.

10. The heterojunction bipolar transistor obtained by the MOCVD epitaxial growth method according to any one of claims 1 to 9, characterized by, The heterojunction bipolar transistor comprises a substrate, a buffer layer, a collector region ohmic contact layer, a collector region etching stop layer, a collector region, a base region, an emitter layer, a sub-emitter layer and an emitter region ohmic contact layer arranged on the surface of the substrate in sequence; The heterojunction bipolar transistor further comprises a transition layer arranged between the base region and the emitter layer.

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