CN108735601B - HEMT fabricated by in-situ growth of patterned barrier layer and method thereof - Google Patents

Abstract

Translated fromChinese

本发明公开了一种利用原位生长图形化势垒层制备的HEMT及其方法，在生长势垒层时，利用高温条件下关断MO源时势垒层会从螺位错终止处开始分解，通过重复外延生长和高温分解过程可以获得带有随机分布开孔的图形化势垒子层，避免凹槽图形化势垒制备复杂性和重复性问题，简化器件制作工艺。得到的HEMT栅对二维电子气的控制能力强，同时部分保持栅极下的导电能力，减小源漏电极的接触电阻，提高器件高频特性。

The invention discloses a HEMT prepared by using an in-situ growth patterned potential barrier layer and a method thereof. When the potential barrier layer is grown, when the MO source is turned off under high temperature conditions, the potential barrier layer will start to decompose from the end of the screw dislocation, By repeating the epitaxial growth and high temperature decomposition process, a patterned barrier sublayer with randomly distributed openings can be obtained, so as to avoid the problems of complexity and repetition in the preparation of groove patterned barriers, and simplify the device fabrication process. The obtained HEMT gate has strong control ability for the two-dimensional electron gas, and meanwhile partially maintains the electrical conductivity under the gate, reduces the contact resistance of the source-drain electrodes, and improves the high-frequency characteristic of the device.

Description

HEMT prepared by in-situ growth of graphical barrier layer and method thereof

Technical Field

The invention relates to semiconductor material growth and epitaxial growth of a device structure layer, in particular to a HEMT prepared by using an in-situ growth graphical barrier layer and a method thereof.

Background

Currently, the main approach to improve the frequency performance of HEMT microwave devices is by shortening the gate length and using a thinner barrier. The prior art can realize a device with a gate length of 30-50nm, and the thickness of a barrier layer is about 20nm in general, and the short channel effect is more and more obvious in the dimension, so that the output power of the device is limited. In order to enhance the gate control capability of the device and inhibit the short channel effect, firstly, a groove gate process is adopted, namely, a dry etching method is adopted to thin the barrier layer of the gate region, and the distance from the gate to the two-dimensional electron gas channel is shortened, so that the control capability of the gate to the two-dimensional electron gas channel is enhanced. The other method is based on the structural design of a channel array, namely, the barrier layer in the partial area below the grid electrode is completely removed, and the grid metal covers the top and the side walls at the two sides of the channel to form a grid structure, so that the three-dimensional control of the grid electrode on the conductive channel is realized, and the modulation capability of the channel is enhanced. However, because the partial conductive area under the grid electrode is removed, the removed partial area can not participate in the conduction, the conductive capability of the device is reduced, and the output power of the device is influenced. In addition, the existing method has complex manufacturing process and higher process cost.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides an HEMT prepared by using an in-situ growth graphical barrier layer and a method thereof.

In order to achieve the above purpose, the technical scheme of the invention is as follows:

the method for preparing the HEMT by utilizing the in-situ growth graphical barrier layer comprises the following steps:

1) forming a buffer layer on a substrate;

2) forming a channel layer on the buffer layer;

3) forming a barrier layer on a channel layer, the channel layer and the barrier layer being a group III-V compound heterojunction material system; the barrier layer comprises a fixed component barrier sublayer and a graphical barrier sublayer, and the three-group growth source and the five-group growth source are controlled to be introduced with constant flow to grow the fixed component barrier sublayer; then controlling the five-group growth source gas to keep the introduction state, and periodically introducing and turning off the three-group growth source gas to grow the graphical barrier sublayer;

4) forming a source electrode and a drain electrode on the barrier layer;

5) forming a dielectric layer on the barrier layer between the source and the drain;

6) a gate is formed on the dielectric layer.

Optionally, the thickness of the fixed component barrier sublayer is 2-10 nm.

Optionally, the patterned barrier sublayer has a plurality of openings randomly distributed, and the width of the openings is 5-30nm, and the depth of the openings is 5-20 nm.

Optionally, the barrier/channel layer is an AlGaN/GaN heterojunction material system.

Optionally, the growth conditions of the fixed component barrier sublayer are as follows: TMAl flow rate of 150-₃The flow rate is 8000-10000sccm, the surface temperature of epitaxial growth is 1000-1100 ℃, the air pressure of the reaction chamber is 50-100mbar, and the growth time is 20-40 s.

Optionally, the periodic growth conditions of the patterned barrier sublayer are as follows: growing for 20-40s under the growth condition of the barrier sublayer with fixed components, then cutting off TMAl and TMGa, and only introducing NH₃Decomposing in situ for 20-40 s; repeating for 3-8 cycles.

Optionally, in step 1), the growth conditions of the buffer layer are as follows: adopting MOCVD process, the growth temperature is 1050-₃The flow rate is 2500-; then adopting TMGa flow of 150-250sccm and NH₃The flow rate is 11000-13000sccm, the growth surface temperature is 950-1000 ℃, the air pressure of the reaction chamber is 30-80mbar, and the growth time is 20-30 min.

Optionally, the growth conditions of the channel layer are as follows: TMGa flow rate of 150-₃The flow rate is 25000-35000sccm, the growth surface temperature is 1050-1100 ℃, the air pressure of the reaction chamber is 150-250mbar, and the thickness is 150-250 nm.

Optionally, in step 3), a step of growing a GaN cap layer on the patterned barrier sublayer is further included, where the growth conditions are: TMAl is turned off and TMGa and NH are introduced₃ 20-40s。

The HEMT prepared by utilizing the in-situ growth patterned barrier layer comprises a substrate, a buffer layer, a channel layer, the barrier layer, a dielectric layer, a source electrode, a drain electrode and a grid electrode, wherein the substrate, the buffer layer, the channel layer and the barrier layer are sequentially stacked, the dielectric layer, the source electrode and the drain electrode are arranged on the barrier layer, the grid electrode is arranged on the dielectric layer, the channel layer and the barrier layer are heterojunctions of three-five compounds, the barrier layer comprises a fixed component barrier sublayer and a patterned barrier sublayer which are sequentially stacked, the thickness of the fixed component barrier sublayer is 2-10nm, the patterned barrier sublayer is formed by repeating growth of a plurality of periods and in-situ decomposition through an MOCVD process to form a plurality of randomly arranged open holes.

The invention has the beneficial effects that:

1. the barrier layer starts to decompose from the stop position of the screw dislocation when the MO source is switched off under the high-temperature condition, and the graphical barrier layer with randomly distributed openings can be obtained by repeating epitaxial growth and the high-temperature decomposition process, so that the control capability of the grid on two-dimensional electron gas is enhanced, the conductive capability under the grid is partially maintained, the contact resistance of the source electrode and the drain electrode is reduced, and the high-frequency characteristic of a device is improved.

2. The problems of complexity and repeatability in preparing the groove graphical potential barrier are avoided, the manufacturing process of the device is simplified, and the manufacturing cost of the device is saved.

Drawings

FIG. 1 is a schematic overall structure diagram of an embodiment of the present invention;

FIG. 2 is a diagram of the position of electrodes relative to a patterned barrier layer;

FIG. 3 is a schematic diagram of a barrier layer structure;

fig. 4 is a schematic view of the growth conditions of the patterned barrier sublayer.

Detailed Description

The present invention is further explained with reference to the drawings and the specific embodiments, specifically, with reference to fig. 1 to 2, a GaN-based HEMT is exemplified, and the manufacturing method is as follows:

1) abuffer layer 2 was grown on a 500 μm 6-inch silicon carbide substrate 1 using MOCVD. Thebuffer layer 2 includes an AlN nucleation layer and a high-resistance GaN layer: firstly, desorbing at 1050 ℃ for 10min to remove oxides and impurities on the surface of SiC, exposing the step-shaped surface appearance, and then growing a nucleating layer at high temperature: the growth temperature is 1100 ℃, the TMAl flow is 250sccm, NH₃The flow rate is 3000sccm, the air pressure of the reaction chamber is 70mbar, the growth speed is about 0.3 mu m/h, and the growth time is 30 min; the high-resistance GaN layer is a GaN layer grown at low temperature and low pressure, the TMGa flow is 200sccm, and simultaneously NH is added₃The flow rate of the growth medium is 12000sccm, the growth surface temperature is 980 ℃, the air pressure of the reaction chamber is 50mbar, the growth rate is about 2.5 mu m/h, the growth time is 25min, and the thickness is 1000 nm.

2) Growing a GaNchannel layer 3 on the buffer layer, thechannel layer 3 being highWarm GaN layer, TMGa flow of 200sccm, NH₃The flow rate of the growth medium was 30000sccm, the growth surface temperature was 1060 ℃, the gas pressure in the reaction chamber was 200mbar, the growth rate was 2 μm/h, and the thickness was 200 nm.

3) Growing abarrier layer 4 on thechannel layer 3, referring to fig. 3, thebarrier layer 4 comprises a fixedcomponent barrier sublayer 41, a patternedbarrier sublayer 42 and a GaN cap layer 43, and firstly growing Al with a fixed Al component (25%) and a thickness of 5nm at a high temperature_xGa_1-xAnd N layers, wherein the specific growth conditions are as follows: TMAl flow rate is 200sccm, TMGa flow rate is 90sccm, NH in the growth process₃The flow rate of the reaction chamber is 9000sccm, the surface temperature of epitaxial growth is 1060 ℃, the air pressure of the reaction chamber is 75mbar, the barrier growth speed is about 0.6 mu m/h under the growth conditions of the MO flow rate, the V/III ratio and the surface temperature, and the growth time is 0.5 min; referring to fig. 4, the following growth process is then taken as one cycle: growing for 20-40s according to the growth conditions, then cutting off TMAl and TMGa, and only introducing NH₃Decomposing in situ for 20-40 s. Repeat for 5 cycles. When the MO source is turned off, the barrier layer starts to decompose from the stop position of the screw dislocation, and the patternedbarrier sublayer 42 with theopenings 421 distributed randomly can be obtained by repeating the epitaxial growth and the pyrolysis process, wherein the width of theopenings 421 is about 10nm-20nm, and the depth of theopenings 421 is about 10 nm-15 nm. Finally, TMAl is cut off and TMGa and NH are introduced₃The GaN cap layer 43 is grown for 30s at 3 nm.

4) Device isolation etching (Mesa isolation) comprises cleaning test piece, and etching epitaxial layer outside active region of device by dry etching (RIE or ICP) to etch depth of about 200 nm; after the completion of the cleaning, 20/150/50/100nm of Ti/Al/Ni/Au (Ti/Al/Ni/Au) was deposited by an electron beam deposition apparatus (E-gun). The substrate is placed in a rapid annealing machine and annealed at 830 degrees for 35 seconds to form ohmic contacts, and the Source electrode 5(Source) and the Drain electrode 6(Drain) are formed respectively. The ohmic contact herein can be any metal that can form an ohmic contact;

5) a dielectric layer 7 is deposited over thebarrier layer 4 between thesource 5 anddrain 6. The deposition method of the dielectric layer 7 can be PECVD, ALD, LPCVD, etc., and the material can be any oxide or insulating medium;

6) a gate metal is deposited as agate electrode 8 over the patterned barrier layer with the passivation layer. Thegate 8 may be any metal.

The obtained GaN-based HEMT comprises a substrate 1, abuffer layer 2, achannel layer 3, abarrier layer 4, a dielectric layer 7, asource electrode 5, adrain electrode 6 and agrid electrode 8, wherein the dielectric layer 7, thesource electrode 5, thedrain electrode 6 and thegrid electrode 8 are sequentially stacked, thedielectric layer 4 comprises a fixedcomponent barrier sublayer 41, apatterned barrier sublayer 42 and a GaN cap layer 43, the fixed component barrier sublayer, the patternedbarrier sublayer 42 and the GaN cap layer are sequentially stacked, the patternedbarrier sublayer 42 is grown and decomposed in situ for a plurality of periods through an MOCVD (metal organic chemical vapor deposition) process to form a plurality of randomly arrangedopen holes 421, the regulation and control capability of the grid electrode on the channel is enhanced.

In addition, the structure and method of the above embodiments are also applicable to other heterojunction material systems, such as AlGaAs/GaAs and the like.

The above embodiments are merely provided to further illustrate the HEMT and the method of the present invention using the in-situ grown patterned barrier layer, but the present invention is not limited to the embodiments, and any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical spirit of the present invention fall within the scope of the technical solution of the present invention.

Claims (10)

Translated fromChinese

1.利用原位生长图形化势垒层制备HEMT的方法，其特征在于包括以下步骤：1. Utilize the method for preparing HEMT by in-situ growth patterned barrier layer, it is characterized in that comprising the following steps:1)于一衬底上形成缓冲层；1) forming a buffer layer on a substrate;2)于缓冲层上形成沟道层；2) forming a channel layer on the buffer layer;3)于沟道层上形成势垒层，所述沟道层和势垒层是三五族化合物异质结材料系统；所述势垒层包括固定组分势垒子层和图形化势垒子层，首先控制三族生长源和五族生长源气体通入流量恒定，生长所述固定组分势垒子层；然后控制五族生长源气体保持通入状态，周期性的通入和关断三族生长源气体生长所述图形化势垒子层；3) forming a barrier layer on the channel layer, the channel layer and the barrier layer are three or five compound heterojunction material systems; the barrier layer includes a fixed composition barrier sublayer and a patterned barrier For the sublayer, first control the flow rate of the gas of the third group growth source and the fifth group growth source to be constant, and grow the fixed composition barrier sublayer; then control the fifth group growth source gas to keep the flow state, and periodically pass in and off. growing the patterned barrier sub-layer with off-group growth source gas;4)于势垒层上形成源极和漏极；4) forming a source electrode and a drain electrode on the barrier layer;5)于源极和漏极之间的势垒层上形成电介质层；5) forming a dielectric layer on the barrier layer between the source electrode and the drain electrode;6)于电介质层上形成栅极。6) A gate is formed on the dielectric layer.2.根据权利要求1所述的方法，其特征在于：所述固定组分势垒子层的厚度为2-10nm。2 . The method according to claim 1 , wherein the thickness of the fixed composition barrier sublayer is 2-10 nm. 3 .3.根据权利要求1所述的方法，其特征在于：所述图形化势垒子层具有随机分布的若干开孔，所述开孔的宽度为5-30nm，深度为5-20nm。3 . The method according to claim 1 , wherein the patterned barrier sublayer has a plurality of randomly distributed openings, the openings have a width of 5-30 nm and a depth of 5-20 nm. 4 .4.根据权利要求1所述的方法，其特征在于：所述势垒层/沟道层是AlGaN/GaN异质结材料系统。4. The method of claim 1, wherein the barrier layer/channel layer is an AlGaN/GaN heterojunction material system.5.根据权利要求4所述的方法，其特征在于：所述固定组分势垒子层的生长条件为：TMAl流量为150-250sccm，TMGa流量为60-120sccm，NH₃的流量为8000-10000sccm，外延生长的表面温度为1000-1100℃，反应室气压为50-100mbar，生长时间为20-40s。5. The method according to claim 4, wherein: the growth conditions of the fixed composition barrier sublayer are: the flow rate of TMAl is 150-250 sccm, the flow rate of TMGa is 60-120 sccm, and the flow rate of NH₃ is 8000- 10000sccm, the surface temperature of epitaxial growth is 1000-1100℃, the pressure of the reaction chamber is 50-100mbar, and the growth time is 20-40s.6.根据权利要求5所述的方法，其特征在于：所述图形化势垒子层的周期生长条件为：以固定组分势垒子层的生长条件生长20-40s，然后关断TMAl和TMGa，于只通入NH₃的条件下原位分解20-40s；重复3～8个周期。6 . The method according to claim 5 , wherein the periodic growth conditions of the patterned barrier sublayer are: growing for 20-40s under the growth conditions of the fixed composition barrier sublayer, and then turning off TMAl and TMGa was decomposed in situ for 20-40s under the condition that only NH₃ was introduced; repeat for 3-8 cycles.7.根据权利要求4所述的方法，其特征在于：步骤1)中，所述缓冲层的生长条件为：采用MOCVD工艺，生长温度为1050-1150℃，TMAl流量为200-300sccm，NH₃流量2500-3500sccm，反应室气压为50-100mbar，生长时间20-40min生长AlN成核层；然后采用TMGa流量为150-250sccm，同时NH₃的流量为11000-13000sccm，生长表面温度为950-1000℃，反应室气压为30-80mbar，生长时间20-30min生长高阻GaN层。7. The method according to claim 4, characterized in that: in step 1), the growth conditions of the buffer layer are: adopt MOCVD process, the growth temperature is 1050-1150 ℃, the flow rate of TMAl is 200-300sccm, NH₃ The flow rate is 2500-3500sccm, the pressure of the reaction chamber is 50-100mbar, and the growth time is 20-40min to grow the AlN nucleation layer; then the flow rate of TMGa is 150-250sccm, and the flow rate of_NH3 is 11000-13000sccm, and the growth surface temperature is 950-1000 ℃, the pressure of the reaction chamber is 30-80mbar, and the growth time is 20-30min to grow a high-resistance GaN layer.8.根据权利要求4所述的方法，其特征在于：所述沟道层的生长条件为：TMGa流量为150-250sccm，同时NH₃的流量为25000-35000sccm，生长表面温度为1050-1100℃，反应室气压为150-250mbar，厚度为150-250nm。8 . The method according to claim 4 , wherein the growth conditions of the channel layer are: the flow rate of TMGa is 150-250 sccm, the flow rate of NH₃ is 25000-35000 sccm, and the growth surface temperature is 1050-1100 ℃ , the pressure of the reaction chamber is 150-250mbar, and the thickness is 150-250nm.9.根据权利要求6所述的方法，其特征在于：步骤3)中，还包括于所述图形化势垒子层上生长GaN帽层的步骤，生长条件为：关断TMAl，通入TMGa和NH₃ 20-40s。9. The method according to claim 6, characterized in that: in step 3), further comprising the step of growing a GaN cap layer on the patterned barrier sublayer, and the growth conditions are: turning off TMAl, and feeding in TMGa and_NH3 for 20-40s.10.利用原位生长图形化势垒层制备的HEMT，包括依次叠设的衬底、缓冲层、沟道层、势垒层，设于势垒层之上的电介质层、源极、漏极以及设于电介质层上的栅极，所述沟道层和势垒层是三五族化合物的异质结，其特征在于：所述势垒层包括依次叠设的固定组分势垒子层和图形化势垒子层，其中所述固定组分势垒子层的厚度为2-10nm，图形化势垒子层通过MOCVD工艺重复若干个周期的生长和原位分解形成随机排布的若干开孔，所述开孔的宽度在5nm-30nm之间，深度在5-20nm之间。10. A HEMT prepared by in-situ growth of a patterned barrier layer, including a substrate, a buffer layer, a channel layer, and a barrier layer stacked in sequence, a dielectric layer, a source electrode, and a drain electrode disposed on the barrier layer and a gate disposed on the dielectric layer, the channel layer and the barrier layer are heterojunctions of three or five compounds, and it is characterized in that: the barrier layer includes fixed composition barrier sublayers stacked in sequence and a patterned barrier sub-layer, wherein the thickness of the fixed composition barrier sub-layer is 2-10 nm, and the patterned barrier sub-layer repeats several cycles of growth and in-situ decomposition through the MOCVD process to form a random arrangement of several Opening holes, the width of the openings is between 5nm-30nm and the depth is between 5-20nm.

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