Heterojunction bipolar transistor and MOCVD epitaxial growth method thereof

Abstract

The invention belongs to the technical field of heterojunction bipolar transistors, and particularly relates to a heterojunction bipolar transistor and an MOCVD epitaxial growth method thereof. The heterojunction bipolar transistor provided by the invention comprises a transition layer arranged between a base region and an emission layer, and the MOCVD epitaxial growth method comprises the step of growing the transition layer on the surface of the base region by adopting a linear variable-temperature staged pulse metal organic chemical vapor deposition method, pH3 is continuously introduced within the total growth time of the linear variable-temperature staged pulse metal organic chemical vapor deposition method, and trimethyl indium, trimethyl gallium and silane are introduced in a single-cycle staged pulse manner; and the temperature of the reaction chamber is linearly increased from the base region growth temperature to the emission layer growth temperature within the time from the T1 initial moment to the TN initial moment. The heterojunction bipolar transistor obtained by the method provided by the invention is large in gain, low in sheet resistance and good in reliability.

Description

Technical Field

[0001] The invention belongs to the technical field of heterojunction bipolar transistors, and in particular relates to a heterojunction bipolar transistor and an MOCVD epitaxial growth method thereof. Background Art

[0002] Heterojunction Bipolar Transistor (HBT) is a new type of transistor based on the traditional bipolar junction transistor (BJT), which uses materials with wider bandgap to make the emitter region and narrower bandgap materials to make the base region. Among them, HBT made of III-V semiconductor materials (such as GaAs) has the advantages of high power, good linearity, high cutoff frequency and low power loss due to the introduction of heterostructure with discontinuous energy bands. It is usually used in mobile phones, WiFi terminals and their base stations, such as radio frequency (RF) power amplifiers. At present, the rapid improvement of GaAs-based HBT performance is due to the use of wide bandgap emitters to achieve high base doping, as well as the development of bandgap engineering technology and epitaxial growth. For example, the base region and emitter region use InGaAs / InGaP, GaAsSb / InGaP and GaAsPBi / InGaP materials respectively, which can reduce the conduction electron transfer time of HBT, thereby improving the high-frequency performance of HBT, such as high current gain cutoff frequency (ft) and maximum oscillation frequency (fmax).

[0003] However, the HBT base layer and emitter layer have different requirements for growth temperature. After the base layer is grown, it is necessary to wait for the growth temperature to transition from low temperature to high temperature. The carrier concentration of the base layer may diffuse, which has a great impact on the subsequent growth of the emitter layer. Therefore, in the process of GaInP / InGaAs HBT epitaxial growth, how to grow InGaAs and GaInP materials that meet the design requirements according to the temperature transition between the base and emitter regions of the GaInP / InGaAs HBT transistor is a difficult point in the preparation of high-performance HBT epitaxial wafers. Summary of the invention

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

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a MOCVD epitaxial growth method of a heterojunction bipolar transistor, wherein the heterojunction bipolar transistor comprises a substrate, a buffer layer, a collector region ohmic contact layer, a collector region corrosion cutoff layer, a collector region, a base region, an emitter layer, a sub-emitter layer and an emitter region ohmic contact layer sequentially arranged 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 pulse metalorganic chemical vapor deposition. The total growth time of the linear temperature-varying stage 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; PH3 is continuously introduced during the total growth time of the linear temperature-varying stage pulse metalorganic 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;

[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 pulse metalorganic chemical vapor deposition is 132 s; the thickness of the transition layer is 3.6 nm.

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

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

[0019] The temperature of the reaction chamber during the growth of the base region is 570°C;

[0020] The temperature of the reaction chamber is 640° C. when the emission layer, the sub-emission layer and the emission region ohmic contact layer are grown.

[0021] Preferably, the material of the buffer layer is GaAs, the doping element is Si, and the doping concentration is 1E18cm -3 , the thickness of the buffer layer is 100 nm;

[0022] The material of the collector region ohmic contact layer is GaAs, and the doping element is Si, with a doping concentration of 5E18cm -3 , the thickness of the collector region ohmic contact layer is 500nm;

[0023] The collector region etching cutoff layer is made of GaInP, doped with Si at a concentration of 5E18cm -3 , the thickness of the collector area corrosion cut-off layer is 80nm;

[0024] The collector region is made of GaAs, doped with Si, and has a doping concentration of 0.5 to 5E17 cm -3 , the thickness of the collector region is 1100nm;

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

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

[0027] The material of the secondary emission layer is GaAs, the doping element is Si, and the doping concentration is 5E18m -3 , the thickness of the sub-emitting layer is 140nm;

[0028] The material of the emitter region ohmic contact layer is In 0.5 GaAs, doped with Te, doping concentration 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 described in 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-varying stepwise pulsed metalorganic chemical vapor deposition method. The total growth time of the linear temperature-varying stepwise pulsed metalorganic 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-varying stepwise pulsed metalorganic chemical vapor deposition method. 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.

[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] When the present invention grows a heterojunction (GaInP / InGaAs) bipolar transistor, there is an inherent band gap difference between the two materials of the emitter layer (N-GaInP) and the base region (P-InGaAs), which will cause a potential barrier peak to exist at the GaInP / InGaAs heterojunction, making it difficult for the electrons in the emitter region to diffuse into the base region, resulting in a problem of low emission efficiency. The present invention adopts a linear variable temperature stage pulse deposition method to grow a transition layer (GaInP) with the same material as the emitter layer, and mainly regulates the linear growth of the growth temperature of the GaInP transition layer and the introduction time of GaSource to control the band gap change of the GaInP transition layer. The obtained low Ga component GaInP transition layer has a reduced band gap difference with the base region InGaAs layer, thereby effectively reducing the potential barrier peak at the GaInP / InGaAs heterojunction. At the same time, the electrons in the emitter layer (also called the emitter region) are more likely to tunnel into the base region, further improving the emission efficiency; due to the discontinuity of the step band gap of the GaInP transition layer, the reverse injection of holes in the base region is blocked, so the electron injection efficiency and current gain of the HBT are greatly improved.

[0035] The present invention adopts a method for growing a GaInP epitaxial layer in a variable temperature pulse step-by-step manner. Under low temperature conditions, a very thin nucleation layer is first formed by a short pulse and is made to form a stable state (trimethyl indium, trimethyl gallium and silane are introduced within a time T1 to grow a nucleation layer of a transition layer, and within a time t1, the atoms in the nucleation layer are allowed to have enough time to migrate to their lowest energy point), thereby reducing stacking faults and vacancies. Then, on the basis of the nucleation layer, a single-cycle staged pulse gas flow growth deposition is adopted. With the increase of temperature and the increase of the time for the introduction of Ga Source, the GaInP transition layer changes from disorder to order, and the thickness of the transition layer increases layer by layer, and the band gap width also increases layer by layer, and finally grows to a lattice-matched GaInP emission layer, thereby effectively improving the crystal quality of the emission layer and the emission efficiency. Meanwhile, the transition layer does not change the In component and doping of the base region, thereby further improving the current gain of the HBT epitaxial wafer.

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

[0037] The present invention utilizes the transition time of the temperature from the base region to the emitter region and adopts a variable temperature pulse growth method to avoid doping diffusion caused by the base region waiting for temperature change, so that the base region maintains uniform high doping, thereby having lower square resistance and uniformity; at the same time, the method provided by the present invention has low epitaxial cost, short time consumption for growing the GaInP transition layer (only 132 seconds), and improves the growth quality of the emitter region and the base region, with short growth time and low manufacturing cost.

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

[0039] Furthermore, in the present invention, in step (2), the PH3 flow rate is set to 400 sccm. In the pulsed growth method of step (2) of the present invention, a high partial pressure ratio (400 sccm) of PH3 is always maintained, which is beneficial to accelerate the mobility of surface atoms during the growth process and enable the atoms to reach a stable state with the lowest energy point more quickly. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0043] Figure 3 The band gap of the HBT of the present invention is compared with the band gap of the traditional HBT;

[0044] Figure 4 The results of the present invention are compared with the traditional results;

[0045] Figure 5 The figure shows the square resistance test result of the HBT grown according to the embodiment of the present invention. DETAILED DESCRIPTION

[0046] The present invention provides a MOCVD epitaxial growth method of a heterojunction bipolar transistor, wherein the heterojunction bipolar transistor comprises a substrate, a buffer layer, a collector region ohmic contact layer, a collector region corrosion cutoff layer, a collector region, a base region, an emitter layer, a sub-emitter layer and an emitter region ohmic contact layer sequentially arranged on the surface of the substrate;

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

[0048] The MOCVD epitaxial growth method comprises 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-varying stepwise pulsed metalorganic chemical vapor deposition. The total growth time of the linear temperature-varying stepwise 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 stepwise pulsed metalorganic chemical vapor deposition. Trimethylindium, trimethylgallium, and silane are introduced during the times of T1, T2, T3, …… TN-1, and TN, and trimethylindium, trimethylgallium, and silane are not introduced during the times of 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 detail the structure of the heterojunction bipolar transistor provided by the present invention.

[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, 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 comprises 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 -3 The thickness of the collector region ohmic contact layer is preferably 500 nm.

[0057] The heterojunction bipolar transistor provided by the present invention comprises a collector region corrosion 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 corrosion stop layer 40 is preferably GaInP, the doping element is preferably Si, and the doping concentration is preferably 5E18cm -3 The thickness of the collector area corrosion stop layer is preferably 80 nm.

[0058] The heterojunction bipolar transistor provided by the present invention comprises a collector region 50 disposed on the surface of a collector region etching stop layer 40. In the present 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 to 5E17 cm -3 , the thickness of the collector region is preferably 1100nm.

[0059] The heterojunction bipolar transistor provided by the present invention comprises 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, the doping element is preferably C, and the doping concentration is preferably 4E19m -3 , the thickness of the base region is preferably 50nm.

[0060] The heterojunction bipolar transistor provided by the present invention comprises 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 -3 The thickness of the transition layer 71 is preferably 3.6 nm.

[0061] The heterojunction bipolar transistor provided by the present invention comprises an emission layer 70 disposed on the surface of the transition layer 71. In the present invention, the material of the emission 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 comprises a sub-emitting layer 80 disposed on the surface of the emitting layer 70. In the present invention, the material of the sub-emitting layer 80 is preferably GaAs, the doping element is preferably Si, and the doping concentration is preferably 5E18m-3 , the thickness of the sub-emission layer is preferably 140nm.

[0063] The heterojunction bipolar transistor provided by the present invention comprises an emitter region ohmic contact layer 90 disposed on the surface of the sub-emitter layer 80. In the present invention, the material of the emitter region ohmic contact layer 90 is preferably In 0.5 GaAs, the doping element is preferably Te, and the doping concentration is preferably 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 the present invention comprises the following steps:

[0065] The present invention sequentially grows a buffer layer, a collector region ohmic contact layer, a collector region corrosion stop layer, a collector region and a base region on the surface of the substrate. In the present invention, the buffer layer, the collector region ohmic contact layer, the collector region corrosion stop layer, the collector region and the base region are grown by metal organic chemical vapor deposition (MOCVD). In a specific embodiment of the present invention, the present invention preferably places the substrate 10 into a MOCVD system (Aixtron) to sequentially grow a buffer layer 20, a collector region ohmic contact layer 30, a collector region corrosion stop layer 40, a collector region 50 and a base region 60. The reaction chamber temperature is preferably 680°C when the buffer layer 20, the collector region ohmic contact layer 30, the collector region corrosion stop layer 40 and the collector region 50 are grown, the reaction chamber temperature is preferably 570°C when the base region 60 is grown, and the reaction chamber pressure is preferably 100 mbar. The present invention uses H2 as a carrier gas, trimethyl indium (TMIn), trimethyl gallium (TMGa), carbon tetrachloride (CCl4), silane (SiH4), trimethyl arsenic (TMAs), arsine (AsH3) and phosphine (PH3) as reaction source gases, continuously introduces trimethyl gallium (TMGa), uses silane (SiH4) as a doping gas for the buffer layer, the collector region ohmic contact layer, the collector region corrosion stop layer and the collector region, and uses carbon tetrachloride (CCl4) as a reaction source gas. Carbon (CCl4) is used as the doping gas of the base region, and the Source flow rate of TMGa is preferably set to 100sccm. AsH3 is introduced to grow the N-GaAs buffer layer and the N-GaAs collector region ohmic contact layer, and then AsH3 is switched to PH3, and then trimethylgallium (TMGa) and trimethylindium (TMIn) are introduced to grow the GaInP collector region etching stop layer, and the Source flow rate of TMGa is preferably set to 15sccm, and the Source flow rate of TMIn is preferably set to 600sccm, and then PH3 is switched to AsH3 to grow the GaAs collector region, and the Source flow rate of TMGa is preferably set to 100sccm. The temperature of the reaction chamber is rapidly cooled from 680℃ to 570℃, and then trimethylgallium (TMGa) and trimethylindium (TMIn) are introduced to grow the InGaAs base region, and the Source flow rate of TMGa is preferably set to 15sccm, and the Source flow rate of TMIn is preferably set to 600sccm.

[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. A transition layer is grown by linear temperature-varying staged pulse metalorganic chemical vapor deposition. The total growth time of the linear temperature-varying staged 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-varying staged pulse metalorganic chemical vapor deposition, PH3 is continuously introduced. Trimethylindium, trimethylgallium, and silane are introduced during the times of T1, T2, T3, …… TN-1, and TN, and trimethylindium, trimethylgallium, and silane are not introduced during the times of 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-varying staged 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, and 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 of the double-dilution pipeline introduced into the reaction chamber can be calculated by the following formula 1:

[0068]

[0069] In formula 1, S is the gas flow rate actually introduced into the reaction chamber, F Source 、F Dilute 、F Inject represent the flow rates of Source, Dilute, and Injetct 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.

[0070] In a specific embodiment of the present invention, the T1 time is preferably set to 2s, the T2 time is preferably set to 3s, the T3 time is preferably set to 4s, ..., and the TN time is preferably set to N+1s. The times t1, t2, t3, t4, t5, ... and tN-1 are preferably set to 1s. The reaction chamber temperature at the initial moment of T1 is preferably 570°C, and the reaction chamber temperature at the initial moment of TN is preferably 640°C. In the present invention, the total growth time of the pulse 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 in the middle (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 pulse metal organic chemical vapor deposition method is calculated from the starting time of T1 to the end time of TN.

[0071] In a specific embodiment of the present invention, Figure 1 The relationship between the temperature in the MOCVD reaction chamber, the gas pulse introduction method, the change of GaInP composition and the growth time during the transition layer growth process is given. When the temperature of the reaction chamber is 570°C, the pulse is turned on within T1=1 second and lasts for 2 seconds, TMGa, TMIn and SiH4 are introduced to grow a GaInP nucleation layer, and the temperature of the reaction chamber increases linearly at the same time; the pulse is turned off for t=1 second, so that the atoms in the nucleation layer have enough time to migrate to their lowest energy point; the pulse is turned on within T2=4 seconds and lasts for 3 seconds, and TMGa, TMIn and SiH4 are introduced again to grow an epitaxial layer of a certain thickness; the time of each pulse deposition growth is gradually increased by 1 second, and the pulse off time remains unchanged. A stable epitaxial layer is formed when the pulse is turned off. In the intermittent stage, the pulse time is TN, which lasts for N+1 second, and TMGa, TMIn and SiH4 are introduced again to grow an epitaxial layer of a certain thickness, and the temperature of the reaction chamber reaches 640°C, N≥3 and is an integer; in the pulse growth method, the high partial pressure ratio (400sccm) of PH3 is always protected, which is conducive to accelerating the mobility of surface atoms during the growth process and allowing the atoms to reach a stable state at the lowest energy point faster.

[0072] After obtaining the transition layer, the present invention sequentially grows an emission layer, a sub-emission layer and an ohmic contact layer in the emission region on the surface of the transition layer to obtain a heterojunction bipolar transistor. In the present invention, the growth of the emission layer 70, the sub-emission layer 80 and the ohmic contact layer 90 in the emission region is preferably carried out in an MOCVD system (Aixtron Company), and the reaction chamber temperature is preferably 640°C when the emission layer 70, the sub-emission layer 80 and the ohmic contact layer 90 in the emission region grow, and the reaction chamber pressure is 100mbar, with H2 as the carrier gas, and one or more of trimethyl indium (TMIn), trimethyl gallium (TMGa), silane (SiH4), trimethyl arsenic (TMAs), arsine (AsH3) and phosphine (PH3) as the reaction source gas, and sequentially grows the emission layer 70, the sub-emission layer 80 and the ohmic contact layer 90 in the emission region, wherein the doping reaction source of the ohmic contact layer 90 in the emission region is Te metal. The present invention has no special requirements for the specific growth method of the emission layer 70, the sub-emission layer 80 and the ohmic contact layer 90 in the emission region.

[0073] In a specific embodiment of the present invention, during the growth of the emitter layer 70: the PH3 flow rate 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 via a double dilution pipeline, and its Source / Dilute / inject flow rates are 50 sccm / 150 sccm / 50 sccm respectively. The gas concentration introduced into the reaction chamber via the double dilution pipeline can be calculated by the following formula 1:

[0074]

[0075] In formula 1, S is the actual gas flow rate entering the reaction chamber, F Source 、F Dilute 、F Inject 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 it can be calculated that the 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] The present invention provides a heterojunction bipolar transistor obtained by the MOCVD epitaxial growth method described in the technical solution above, wherein the heterojunction bipolar transistor comprises a substrate, a buffer layer, a collector region ohmic contact layer, a collector region corrosion cutoff layer, a collector region, a base region, an emitter layer, a sub-emitter layer and an emitter region ohmic contact layer sequentially arranged 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] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0079] Example 1

[0080] The schematic diagram of the HBT epitaxial structure provided by the embodiment of the present invention is as follows Figure 1 Table 1 is a table of information on the materials, thickness, doping elements, doping concentrations and corresponding functions of each layer of the HBT epitaxial structure provided in this embodiment. A junction bipolar transistor epitaxial wafer is prepared according to the structure shown in Table 1.

[0081] Table 1 HBT epitaxial structure information provided in Example 1

[0082] Serial number Epitaxial Materials thickness wavelength Doping Doping Remark 90 <![CDATA[In 0.5 GaAs]]> 110nm Te <![CDATA[2E19cm -3 ]]> Ohmic contact layer of emitter region 80 GaAs 140nm / Si <![CDATA[5E18cm -3 ]]> Sub-emission 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 Region 50 GaAs 1100nm / Si <![CDATA[0.5-5E17cm -3 ]]> Collector area 40 GaInP 80nm Si <![CDATA[5E18cm -3 ]]> Corrosion cut-off layer in collector area 30 GaAs 500nm / Si <![CDATA[5E18cm -3 ]]> Collector region ohmic contact layer 20 GaAs 100nm / Si <![CDATA[1E18cm -3 ]]> Buffer layer 10 SI-GaAs 675um / / Substrate

[0083] In this embodiment, the resistivity is 4×10 8 Ω·cm GaAs is used as the growth substrate and placed in the MOCVD system of Aixtron. The reaction chamber pressure is 100mbar, the growth temperature is 680℃, H2 is used as the carrier gas, trimethyl indium (TMIn), trimethyl gallium (TMGa), carbon tetrachloride (CCl4), silane (SiH4), trimethyl arsenic (TMAs), arsine (AsH3) and phosphine (PH3) are used as the reaction source gas, trimethyl gallium (TMGa) is continuously introduced, silane (SiH4) is used as the buffer layer, collector ohmic contact layer, collector etching stop layer, collector region doping gas, carbon tetrachloride (CCl4) is used as the base region doping gas, and the Source flow of TMGa is 2.5 times that of TMGa. The flow rate is set to 100sccm, AsH3 is introduced to grow the N-GaAs buffer layer and the N-GaAs collector ohmic contact layer, then AsH3 is switched to PH3, and then trimethylgallium (TMGa) and trimethylindium (TMIn) are introduced to grow the GaInP collector etching stop layer, the TMGa Source flow rate is set to 15sccm, the TMIn Source flow rate is 600sccm, then PH3 is switched to AsH3, the GaAs collector region is grown, and the TMGa Source flow rate is set to 100sccm. The reaction chamber is quickly cooled to 570℃, and then trimethylgallium (TMGa) and trimethylindium (TMIn) are introduced to grow the InGaAs base region, the TMGa Source flow rate is set to 15sccm, and the TMIn Source flow rate is 600sccm.

[0084] Then AsH3 is switched to PH3, and then under the protection of 400sccm PH3 gas, trimethyl indium (TMIn), trimethyl gallium (TMGa) and silane (SiH4) are introduced into the MOCVD reaction chamber in a pulsed manner to grow the GaInP transition layer, wherein the Source flow rate of TMIn is set to 200sccm, the Source flow rate of SiH4 is set to 30sccm, and TMGa is introduced into the reaction chamber through a double dilution pipeline, and its Source / Dilute / inject flow rates are 20sccm / 200sccm / 27sccm respectively. The gas concentration introduced into the reaction chamber through the double dilution pipeline can be calculated by the following formula 1:

[0085]

[0086] In formula 1, S is the actual gas flow rate entering the reaction chamber, F Source 、F Dilute 、F Inject Represent the flow rates of Source, Dilute, and Injection, respectively. Therefore, the TMGa flow rate 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 0.03nm / s. The total growth time is 132 seconds, and the growth thickness of the GaInP transition layer region is 3.6nm.

[0087] Figure 2 The relationship between the temperature in the MOCVD reaction chamber, the gas pulse introduction method, the GaInP composition change and the growth time is given. When the temperature of the reaction chamber is 570°C, the pulse is turned on within T1=1 second and lasts for 2 seconds, TMGa, TMIn and SiH4 are introduced to grow a GaInP nucleation layer, and the temperature of the reaction chamber increases linearly at the same time; the pulse is turned off for t=1 second, so that the atoms in the nucleation layer have enough time to migrate to their lowest energy point; the pulse is turned on within T2=4 seconds and lasts for 3 seconds, and TMGa, TMIn and SiH4 are introduced again to grow an epitaxial layer of a certain thickness; the time of each pulse deposition growth is gradually increased by 1 second, and the pulse off time remains unchanged. A stable epitaxial layer is formed when the pulse is turned off. In the intermittent stage, the pulse time is TN, which lasts for N+1 second, and TMGa, TMIn and SiH4 are introduced again to grow an epitaxial layer of a certain thickness, and the temperature of the reaction chamber reaches 640°C, N≥3 and is an integer; in the pulse growth method, the high partial pressure ratio (400sccm) of PH3 is always protected, which is conducive to accelerating the mobility of surface atoms during the growth process and allowing the atoms to reach a stable state at the lowest energy point faster.

[0088] Figure 3The band gap of the HBT of the present invention is compared with the band gap of the traditional HBT. In the traditional HBT, there is a fixed band gap difference between the two materials GaInP and InGaAs, which will cause a potential barrier peak to exist in the GaInP / InGaAs heterojunction. The present invention adopts a linear temperature-varying stage pulse deposition of a GaInP transition layer with a gradual band gap, and mainly regulates the growth temperature of the GaInP transition layer and the Ga Source to control the step change of the band gap. The band gap difference between the GaInP transition layer with a low Ga component and the base InGaAs layer is reduced, thereby effectively reducing the potential barrier peak at the GaInP / InGaAs heterojunction, which will reduce the turn-on voltage Von and improve the device performance. At the same time, the electrons in the emission region are more likely to tunnel into the base region, further improving the emission efficiency; due to the discontinuity of the step band gap of the GaInP transition layer, the reverse injection of holes in the base region is blocked. After growing a GaInP transition layer with a high Ga component, a GaInP epitaxial layer with a high-quality lattice-matched emission region is grown. The transition layer does not affect the components and doping of the base and emission regions, so a high-quality, high-gain HBT can be obtained. Among them, compared with the present invention, the conventional HBT process uses the same equipment and substrate, and the growth process of the buffer layer, collector ohmic contact layer, collector region corrosion barrier layer, collector region and base region on the substrate surface is the same as that in Example 1, except that: after the base region is grown, TMGa, TMIn and CCl4 are immediately closed, and then the temperature is set to rise to prepare for the growth of the emitter region. By increasing the set temperature, the temperature is quickly raised from 570°C to 640°C, and the temperature rise lasts for about 120 seconds, and then the TMAs valve is immediately closed, the PH3 valve is opened, and the Source flow rate of PH3 is 800sccm, and then TMGa, TMIn and SiH4 and other source gases are introduced to grow the GaInP epitaxial layer of the emitter region (the same as in Example 1). Then the GaAs sub-emission layer (also called the sub-emission region) and the InGaAs emitter region ohmic contact layer are grown, that is, the HBT epitaxial structure produced by the complete conventional HBT process is formed.

[0089] The present invention firstly introduces TMGa, TMIn and SiH4 in short pulses to form a very thin nucleation layer and make it stable, thereby reducing stacking faults and vacancies. Then, based on the nucleation layer, the single-cycle pulse gas flow is used to linearly increase the temperature of the reaction chamber from 570°C to 640°C, and the Ga source is adjusted to grow a GaInP epitaxial transition layer with a gradient band gap of different thicknesses. The total thickness is 3.6nm, the total time is 132 seconds, and the doping concentration is then grown to 4E17cm -3 The GaInP emission layer is then grown, and then the GaAs sub-emission layer and the InGaAs emission region ohmic contact layer are grown to form a complete HBT epitaxial structure.

[0090] The present invention optimizes the temperature transition process between the base region and the emitter region, and grows a GaInP transition layer with adjustable step bandgap, effectively reducing the potential barrier peak at the GaInP / InGaAs heterojunction, improving the emission efficiency and current gain, and not affecting the quality of the base epitaxial layer. After adopting the present invention, the gain beta of the HBT is significantly increased, such as Figure 4 At the same time, the GaInP transition layer matches the GaInP lattice, improving the quality of the epitaxial layer in the emitter region and avoiding the doping diffusion caused by the base region when waiting for temperature changes, so that the base region maintains uniform high doping, thus having lower square resistance and uniformity. After adopting this invention, the average square resistance of the HBT epitaxial wafer is 7.51ohm / sq, Std is 0.45%, as shown in FIG. Figure 5 shown.

[0091] From the above embodiments, it can be known that the present invention adopts a linear variable temperature stage pulse metal organic chemical vapor deposition method to grow a transition layer on the surface of the base region, and the linear variable temperature stage pulse metal organic chemical vapor deposition method continuously introduces PH3 during the total growth time, and introduces trimethyl indium, trimethyl gallium and silane in a single cycle stage pulse; from the initial time T1 to the initial time TN, the temperature of the reaction chamber increases linearly from the base region growth temperature to the emission layer growth temperature. The heterojunction bipolar transistor obtained by the method provided by the present invention has large gain, low square resistance and good reliability.

[0092] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for the MOCVD epitaxial growth of a heterojunction bipolar transistor, characterized in that: The heterojunction bipolar transistor includes a substrate, a buffer layer, a collector ohmic contact layer, a collector etch stop layer, a collector region, a base region, an emitter layer, a sub-emitter layer, and an emitter ohmic contact layer that are sequentially disposed on the surface of the substrate; The heterojunction bipolar transistor further includes: a transition layer disposed between the base region and the emitter layer; The MOCVD epitaxial growth method includes the following steps; (1) Grow a buffer layer, a collector ohmic contact layer, a collector etch stop layer, a collector region, and a base region on the surface of the substrate in sequence; (2) Grow a transition layer on the surface of the base region by linear temperature-varying stepwise pulsed metalorganic chemical vapor deposition. The total growth time of the linear temperature-varying stepwise 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 stepwise pulsed metalorganic 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; (3) Grow an emitter layer, a sub-emitter layer, and an emitter 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, characterized in that: 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.

3. The MOCVD epitaxial growth method according to claim 1, characterized in that: 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.

4. The MOCVD epitaxial growth method according to claim 1, characterized in that: 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.

5. The MOCVD epitaxial growth method according to claim 1, characterized in that: The times of t1, t2, t3, t4, t5,..., and tN-1 are all set to 1 s.

6. The MOCVD epitaxial growth method according to any one of claims 1 to 5, characterized in that: In step (2), the total growth time of the linear temperature-varying stepwise pulsed metalorganic chemical vapor deposition is 132 s; the thickness of the transition layer is 3.6 nm.

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

8. The MOCVD epitaxial growth method according to claim 1, characterized in that: The temperature of the reaction chamber during the growth of the buffer layer, the collector ohmic contact layer, the collector etch stop layer, and the collector region is 680 °C; The temperature of the reaction chamber during the growth of the base region is 570 °C; The temperature of the reaction chamber during the growth of the emitter layer, the sub-emitter layer, and the emitter ohmic contact layer is 640 °C.

9. The MOCVD epitaxial growth method according to claim 1 or 8, characterized in that: The material of the buffer layer is GaAs, the doping element is Si, and the doping concentration is 1E18cm -3 , the thickness of the buffer layer is 100 nm; The material of the collector region ohmic contact layer is GaAs, the doping element is Si, and the doping concentration is 5E18cm -3 , the thickness of the collector region ohmic contact layer is 500nm; The material of the collector region corrosion stop layer is GaInP, the doping element is Si, and the doping concentration is 5E18cm -3 , the thickness of the collector area corrosion cut-off layer is 80nm; The collector region is made of GaAs, doped with Si, and has a doping concentration of 0.5 to 5E17 cm -3 , the thickness of the collector region is 1100nm; The material of the base region is In 0.06 GaAs, doped with C, doping concentration 4E19m -3 , the thickness of the base region is 50nm; The material of the emission layer is GaInP, the doping element is Si, and the doping concentration is 4E17m -3 , the thickness of the emission layer is 30nm; The material of the sub-emitting layer is GaAs, the doping element is Si, and the doping concentration is 5E18m -3 , the thickness of the sub-emitting layer is 140nm; The material of the ohmic contact layer of the emitter region is In 0.5 GaAs, doped with Te, doping concentration 2E19m -3 , the thickness of the ohmic contact layer in the emission 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 in that: The heterojunction bipolar transistor includes a substrate, a buffer layer, a collector ohmic contact layer, a collector etch stop layer, a collector region, a base region, an emitter layer, a sub-emitter layer, and an emitter ohmic contact layer that are sequentially disposed on the surface of the substrate; The heterojunction bipolar transistor further includes: a transition layer disposed between the base region and the emitter layer.

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