CN112151361B - Preparation method of high electron mobility transistor - Google Patents
Preparation method of high electron mobility transistor Download PDFInfo
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- CN112151361B CN112151361B CN202010846216.5A CN202010846216A CN112151361B CN 112151361 B CN112151361 B CN 112151361B CN 202010846216 A CN202010846216 A CN 202010846216A CN 112151361 B CN112151361 B CN 112151361B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/66007—Multistep manufacturing processes
- H01L29/66053—Multistep manufacturing processes of devices having a semiconductor body comprising crystalline silicon carbide
- H01L29/66068—Multistep manufacturing processes of devices having a semiconductor body comprising crystalline silicon carbide the devices being controllable only by the electric current supplied or the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched, e.g. three-terminal devices
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/66007—Multistep manufacturing processes
- H01L29/66969—Multistep manufacturing processes of devices having semiconductor bodies not comprising group 14 or group 13/15 materials
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/68—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by only the electric current supplied, or only the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched
- H01L29/76—Unipolar devices, e.g. field effect transistors
- H01L29/772—Field effect transistors
- H01L29/778—Field effect transistors with two-dimensional charge carrier gas channel, e.g. HEMT ; with two-dimensional charge-carrier layer formed at a heterojunction interface
Abstract
The disclosure provides a preparation method of a high electron mobility transistor, belonging to the technical field of semiconductors. The preparation method comprises the following steps: forming an AlGaN buffer layer on a substrate, and carrying out patterning treatment in the forming process of the AlGaN buffer layer; and sequentially growing a GaN channel layer and an AlGaN barrier layer on the AlGaN buffer layer. According to the method, the AlGaN buffer layer is formed on the substrate and is subjected to patterning processing in the forming process of the AlGaN buffer layer, the AlGaN buffer layer can form the protruding part and the recessed part after being subjected to patterning processing, the growth rate of the AlGaN buffer layer on the side wall of the protruding part is higher than that of the AlGaN buffer layer on the recessed part directly, the AlGaN buffer layer on the protruding part around the recessed part can be healed on the recessed part, and stress and defects generated by lattice mismatch between the substrate and the AlGaN buffer layer can be offset in the healing process.
Description
Technical Field
The present disclosure relates to the field of semiconductor technologies, and in particular, to a method for manufacturing a high electron mobility transistor.
Background
A HEMT (High Electron Mobility Transistor) is one of FETs (Field Effect transistors) that forms a heterojunction using two materials having different energy gaps to provide a channel for carriers. The GaN (gallium nitride) based material has the characteristics of wide band gap, high electron mobility, high voltage resistance, radiation resistance, easy formation of a heterostructure, large spontaneous polarization effect and the like, and is suitable for preparing semiconductor devices such as HEMT and the like.
In the related art, the GaN-based HEMT includes an epitaxial layer, and a source electrode, a drain electrode, and a gate electrode respectively disposed on the epitaxial layer, wherein ohmic contacts are formed between the source electrode and the drain electrode and the epitaxial layer, and a schottky contact is formed between the gate electrode and the epitaxial layer. The epitaxial layer comprises a substrate, and a channel layer and a barrier layer which are sequentially laminated on the substrate, wherein two-dimensional electron gas with high concentration and high mobility is formed at the heterojunction interface of the channel layer and the barrier layer.
The substrate is made of sapphire or silicon carbide, the channel layer is made of GaN, large lattice mismatch exists between the substrate and the channel layer, stress and defects generated by the lattice mismatch extend and accumulate in the epitaxial layer, the crystal quality of the epitaxial layer is poor, and the mobility of current carriers is influenced.
Disclosure of Invention
The embodiment of the disclosure provides a preparation method of a high electron mobility transistor, which can effectively avoid stress and defect extension caused by lattice mismatch in an epitaxial layer and improve the crystal quality at a heterojunction interface. The technical scheme is as follows:
the embodiment of the disclosure provides a preparation method of a high electron mobility transistor, which comprises the following steps:
forming an AlGaN buffer layer on a substrate, and carrying out patterning treatment in the forming process of the AlGaN buffer layer;
and sequentially growing a GaN channel layer and an AlGaN barrier layer on the AlGaN buffer layer.
Optionally, the forming an AlGaN buffer layer on the substrate, and performing patterning processing during the forming of the AlGaN buffer layer include:
firstly, growing a first AlGaN layer;
secondly, carrying out patterning treatment on the first AlGaN layer, and forming a plurality of convex parts and concave parts positioned among the convex parts on the surface of the first AlGaN layer;
thirdly, growing a second AlGaN layer on the concave part;
wherein the second AlGaN layer and the first AlGaN layer constitute an AlGaN buffer layer.
Optionally, each of the protrusions is conical or multi-pyramidal.
Optionally, the first step, the second step, and the third step are performed periodically a plurality of times.
Optionally, the number of times the first step, the second step, and the third step are periodically performed a plurality of times is less than or equal to 5 times.
Optionally, the second step is periodically performed a plurality of times to form the protruding portions, and a distance between two of the protruding portions adjacent in the longitudinal direction of the high electron mobility transistor is gradually decreased in a direction from the substrate to the GaN channel layer, the longitudinal direction of the high electron mobility transistor being parallel to the direction from the substrate to the GaN channel layer.
Optionally, a distance between two of the convex portions adjacent in the longitudinal direction of the high electron mobility transistor is reduced in a proportion of 10% to 40%.
Optionally, the second step is periodically performed a plurality of times in the bump formed, the size of the bump gradually decreasing in a direction from the substrate to the GaN channel layer.
Optionally, the size of the protrusions is reduced by a ratio of 15% to 60%.
Optionally, the second step is periodically performed a plurality of times to form the protruding portions, and a distance between two protruding portions adjacent in a lateral direction of the high electron mobility transistor is gradually decreased in a direction from the substrate to the GaN channel layer, the lateral direction of the high electron mobility transistor being perpendicular to the direction from the substrate to the GaN channel layer.
The technical scheme provided by the embodiment of the disclosure has the following beneficial effects:
before a GaN channel layer grows on a substrate, an AlGaN buffer layer is formed on the substrate, patterning processing is carried out in the forming process of the AlGaN buffer layer, the AlGaN buffer layer can be tiled on the substrate before patterning processing is carried out, a protruding part and a recessed part can be formed after the patterning processing is carried out, growth crystal faces provided by the protruding part and the recessed part are different, different crystal faces have different reaction adsorption energy to AlGaN, the growth rate of the AlGaN buffer layer on the side wall of the protruding part is higher than that of the AlGaN buffer layer on the recessed part directly, the AlGaN buffer layer on the protruding part around the recessed part can be healed on the recessed part, stress and defects generated by lattice mismatch between the substrate and the AlGaN buffer layer can be offset in the healing process, and therefore the stress and the defects extending to the GaN channel layer are effectively reduced. And the lattice matching between the AlGaN buffer layer and the GaN channel layer is high, and new stress and defects can be ignored. Therefore, stress and defects extending and accumulating in the epitaxial layer are reduced as a whole, the crystal quality of the epitaxial layer is improved, and the electron mobility of the high electron mobility transistor is high.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present disclosure, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
Fig. 1 is a flowchart of a method for manufacturing a high electron mobility transistor according to an embodiment of the present disclosure;
fig. 2 is a flowchart of a method for manufacturing a high electron mobility transistor according to an embodiment of the present disclosure;
fig. 3 is a schematic structural diagram of the hemt provided in the embodiment of the present disclosure after step 201 is performed;
fig. 4 is a schematic structural diagram of the hemt provided in the embodiment of the present disclosure after step 202 is performed;
fig. 5 is a schematic structural diagram of the hemt provided in the embodiment of the present disclosure after step 203 is performed;
fig. 6 is a schematic structural diagram of the hemt provided in the embodiment of the present disclosure after step 204 is performed;
fig. 7 is a schematic structural diagram of an AlGaN buffer layer provided in an embodiment of the present disclosure after multiple periodic executions;
fig. 8 is a schematic structural diagram of the hemt provided in the embodiment of the present disclosure after step 205 is performed.
Detailed Description
To make the objects, technical solutions and advantages of the present disclosure more apparent, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.
The embodiment of the disclosure provides a preparation method of a high electron mobility transistor. Fig. 1 is a flowchart of a method for manufacturing a high electron mobility transistor according to an embodiment of the present disclosure. Referring to fig. 1, the preparation method includes:
step 101: forming an AlGaN buffer layer on a substrate, and carrying out patterning treatment in the forming process of the AlGaN buffer layer.
Step 102: and sequentially growing a GaN channel layer and an AlGaN barrier layer on the AlGaN buffer layer.
According to the embodiment of the disclosure, before the GaN channel layer grows on the substrate, the AlGaN buffer layer is firstly formed on the substrate, and patterning processing is performed in the forming process of the AlGaN buffer layer, the AlGaN buffer layer can be tiled on the substrate before patterning processing, the protruding part and the recessed part can be formed after patterning processing, growth crystal faces provided by the protruding part and the recessed part are different, different crystal faces have different reaction adsorption energy to AlGaN, so that the growth rate of the AlGaN buffer layer on the side wall of the protruding part is higher than that of the AlGaN buffer layer on the side wall of the recessed part directly, the AlGaN buffer layer on the protruding part around the recessed part can be healed on the recessed part, stress and defects generated by lattice mismatch between the substrate and the AlGaN buffer layer can be offset in the healing process, and therefore the stress and the defects extending to the GaN channel layer are effectively reduced. And the lattice matching between the AlGaN buffer layer and the GaN channel layer is high, and new stress and defects can be ignored. Therefore, stress and defects extending and accumulating in the epitaxial layer are reduced as a whole, the crystal quality of the epitaxial layer is improved, and the electron mobility of the high electron mobility transistor is high.
The embodiment of the disclosure provides a preparation method of a high electron mobility transistor. Fig. 2 is a flowchart of a method for manufacturing a high electron mobility transistor according to an embodiment of the disclosure. Referring to fig. 2, the preparation method includes:
step 201: a GaN nucleation layer is grown on the substrate.
Fig. 3 is a schematic structural diagram of the hemt provided in the embodiment of the present disclosure after step 201 is performed. Referring to fig. 3, a GaN nucleation layer 20 is disposed on a substrate 10.
In the embodiment of the disclosure, in the growth process of the GaN nucleation layer, a layer of thinner gallium nitride is grown on the substrate, and the nucleation points are distributed on the substrate; then, performing longitudinal growth of gallium nitride at the nucleation point to form a plurality of mutually independent three-dimensional island-shaped structures; and then, transverse growth of gallium nitride is carried out on all the three-dimensional island-shaped structures and among the three-dimensional island-shaped structures, so that a two-dimensional plane structure is formed. In the process of filling and leveling the three-dimensional island-shaped structure by the transverse growth of gallium nitride, acting forces in different directions can be provided by two adjacent three-dimensional island-shaped structures, so that stress offset and defect annihilation in the epitaxial layer are facilitated, and the stress and defects extending and accumulating in the epitaxial layer are reduced.
And on the GaN nucleating layer, the AlGaN buffer layer is positioned between the GaN nucleating layer and the GaN channel layer, and the AlGaN buffer layer has a good blocking effect on the stress and defect extension in the GaN relative to the GaN buffer layer.
In practical applications, the growth process can be achieved by providing a growth surface on the substrate and controlling the growth conditions of the epitaxial material. Therefore, this step 201 is an optional step, and the growth process can also be implemented by an AlGaN buffer layer. However, the AlGaN buffer layer is equivalent to an Al-doped GaN layer, and impurities exist inside the AlGaN buffer layer, so that new defects may be generated, and the AlGaN buffer layer has no good implementation effect compared with a GaN nucleation layer.
Illustratively, the material of the substrate is sapphire (aluminum oxide is a main material) or silicon nitride (SiC), such as sapphire with a crystal orientation of [0001 ]. The thickness of the GaN nucleating layer is 10 nm-50 nm.
Optionally, step 201 includes:
growing a GaN nucleating layer on a substrate;
and carrying out in-situ annealing treatment on the GaN nucleating layer.
Illustratively, the growth temperature of the GaN nucleating layer is 600-950 ℃, and the growth pressure of the GaN nucleating layer is 100-300 mbar. The temperature of the in-situ annealing treatment is 1000-1200 ℃, the pressure of the in-situ annealing treatment is 100-300 mbar, and the time of the in-situ annealing treatment is 5-10 minutes.
Optionally, before step 201, the preparation method further comprises:
annealing the substrate in a hydrogen atmosphere;
the substrate is subjected to nitridation treatment.
Illustratively, the time of the annealing treatment is 8 minutes, and the temperature of the annealing treatment is 1000 ℃ to 1200 ℃.
The surface of the substrate is cleaned through the steps, so that impurities are prevented from being doped, and the growth quality is improved.
Step 202: a first AlGaN layer is grown.
Fig. 4 is a schematic structural diagram of the hemt provided in the embodiment of the present disclosure after step 202 is performed. Referring to fig. 4, a first AlGaN layer 31 is disposed on the GaN nucleation layer 20.
When the AlGaN buffer layer is formed, the first AlGaN layer is grown first, so that an action object can be provided for subsequent patterning treatment.
Illustratively, the content of the Al component in the first AlGaN layer is 0.25 to 0.35. The growth temperature of the first AlGaN layer is 1000-1200 ℃, and the growth pressure of the first AlGaN layer is 100-300 mbar.
Step 203: and patterning the first AlGaN layer to form a plurality of convex parts and concave parts positioned among the convex parts on the surface of the first AlGaN layer.
Fig. 5 is a schematic structural diagram of the hemt provided in the embodiment of the present disclosure after step 203 is performed. Referring to fig. 5, the surface of the first AlGaN layer 31 changes from a flat surface to a curved surface having projections 311 and recesses 312, and a plurality of projections 311 are spaced apart in the recesses 312.
Through carrying out the graphical processing to first AlGaN layer, form a plurality of bellyings and the depressed part that is located between a plurality of bellyings on the surface on first AlGaN layer, be equivalent to the three-dimensional island structure in the nucleation process of forming on the homogeneous substrate, compare with the three-dimensional island structure of control growth condition formation on the foreign substrate, neither can produce defect and stress because of the lattice mismatch that the heterogeneity exists, can utilize the process of filling up three-dimensional island structure again with epitaxial layer extension and the stress of accumulation and defect offset and annihilate, consequently, the improvement effect to epitaxial layer quality is better.
Optionally, each protrusion is conical or multi-pyramidal, such as a triangular pyramid.
Each protruding portion is conical or multi-pyramid, the inclination angle of the side wall of each protruding portion is kept unchanged, the deposition of the AlGaN layers is facilitated, defects and stress existing in the AlGaN layers on the two adjacent protruding portions can be kept consistent, and the defects and the stress can be just offset during healing.
Optionally, this step 203 comprises:
forming a patterned photoresist on the first AlGaN layer by adopting a photoetching technology;
dry etching the area which is not covered by the patterned photoresist on the first AlGaN layer, and forming a plurality of convex parts and concave parts positioned among the convex parts on the surface of the first AlGaN layer;
and removing the patterned photoresist.
In practical application, photoresist is formed on the first AlGaN layer, the photoresist is exposed through a through hole in a mask plate, the photoresist in a region corresponding to the edge of the through hole is partially exposed, and an inclined plane is formed after development, so that the side face of a protruding portion formed after dry etching of the first AlGaN layer is also an inclined plane. And when the first AlGaN layer is etched by a dry method, the etching degree of the upper part is larger than that of the lower part, so that the side surface of a convex part formed after the first AlGaN layer is etched by the dry method is also an inclined surface, and the convex part is conical or multi-pyramid.
Step 204: and growing a second AlGaN layer on the concave part.
Fig. 6 is a schematic structural diagram of the hemt provided in the embodiment of the present disclosure after step 204 is performed. Referring to fig. 6, the second AlGaN layer 32 is provided at least on the recess 312 of the first AlGaN layer 31.
And growing a second AlGaN layer on the concave part, wherein the AlGaN layers tend to grow on the side walls of the convex parts around the concave part, the AlGaN layers on the side walls of two adjacent convex parts are converged together, the stress extending and accumulating in the epitaxial layer is offset, and the quality of the epitaxial layer is improved.
In an embodiment of the present disclosure, the second AlGaN layer and the first AlGaN layer constitute an AlGaN buffer layer.
Illustratively, the AlGaN buffer layer has a thickness of 1 to 3 micrometers.
Illustratively, the content of the Al component in the second AlGaN layer is 0.25 to 0.35. The growth temperature of the second AlGaN layer is 1000-1200 ℃, and the growth pressure of the second AlGaN layer is 100-300 mbar.
Alternatively, steps 202 to 204 are performed periodically a plurality of times.
By carrying out patterning treatment for many times in the forming process of the AlGaN buffer layer, the stress and the defects in the epitaxial layer can be eliminated in the healing process for many times, the stress and the defects in the epitaxial layer are reduced to the greatest extent, and the crystal quality of the epitaxial layer is improved.
Illustratively, the number of times of periodically performing steps 202 to 204 is less than or equal to 5 times.
The realization cost of one-time graphic processing is high, the times of the graphic processing are limited within 5 times, and the realization cost can be effectively avoided from being too high. And with the increase of the times of the graphical processing, the improvement effect of the graphical processing on the stress and the defects can reach the limit, the times of the graphical processing is more than 5 times, the difference of the realization effect is not large, and the production effect can be reduced and the production cost can be increased.
Alternatively, the step 203 may be periodically performed a plurality of times to form the protruding portions, and a distance between two protruding portions adjacent in a longitudinal direction of the high electron mobility transistor may be gradually decreased in a direction from the substrate to the GaN channel layer, the longitudinal direction of the high electron mobility transistor being parallel to the direction from the substrate to the GaN channel layer.
Fig. 7 is a schematic structural diagram of an AlGaN buffer layer provided in an embodiment of the present disclosure after multiple periodic executions. Referring to fig. 7, of the three-time formed protrusions, a distance a between the first-time formed protrusion and the second-time formed protrusion is greater than a distance b between the second-time formed protrusion and the third-time formed protrusion.
In the initial stage of growth of the AlGaN buffer layer, the distance between the AlGaN buffer layer and the substrate is short, the stress and the defect in the AlGaN buffer layer are large, and the thicker AlGaN buffer layer is needed to be improved; in the later stage of the growth of the AlGaN buffer layer, the stress and the defects in the AlGaN buffer layer are reduced after improvement, and the thinner AlGaN buffer layer is improved.
Illustratively, the distance between two projections adjacent in the longitudinal direction of the high electron mobility transistor is reduced in a proportion of 10% to 40%.
Taking fig. 7 as an example, b ═ 1-k × a, k is 10% to 40%.
The distance between two adjacent convex parts in the longitudinal direction of the high electron mobility transistor is reduced according to the proportion of 10-40%, and the distance between the two convex parts has obvious change and small change amplitude, so that the stress and the defect in the epitaxial layer are improved gradually.
Alternatively, the step 203 may be periodically performed a plurality of times to form the protrusions, and the size of the protrusions may be gradually reduced in a direction from the substrate to the GaN channel layer.
Also by way of example in fig. 7, the size of the first formed boss is larger than the size of the second formed boss, and the size of the second formed boss is larger than the size of the third formed boss.
In the embodiment of the present disclosure, the size of the protruding portion includes at least one of a height of the protruding portion, which is a length of the protruding portion in a longitudinal direction of the high electron mobility transistor, and a width of the protruding portion, which is a length of the protruding portion in a lateral direction of the high electron mobility transistor.
In practical applications, the protrusions formed multiple times are similar shapes with different sizes, and the sizes of the protrusions include the height of the protrusions and the width of the protrusions.
In the initial stage of growth of the AlGaN buffer layer, the distance between the AlGaN buffer layer and the substrate is short, the stress and the defect in the AlGaN buffer layer are large, the healing effect of the AlGaN buffer layer on a bulge part with a large size is strong, and the improvement strength of the stress and the defect is large; in the later stage of the growth of the AlGaN buffer layer, the stress and the defects in the AlGaN buffer layer are reduced after improvement, and the stress and the defects can be improved by healing the AlGaN buffer layer on the bulge part with smaller size.
Illustratively, the size of the projections is reduced by a ratio of 15% to 60%.
Also taking fig. 7 as an example, the size of the convex part formed for the second time is reduced by 15% to 60% compared with the size of the convex part formed for the first time; the size of the protrusions formed in the third time is reduced by 15% to 60% compared to the size of the protrusions formed in the second time.
Illustratively, the height of the protrusions is 50nm to 250nm, and the width of the protrusions is 2.5 μm to 3.5 μm.
Alternatively, the step 203 is periodically performed a plurality of times to form the protruding portions, and the distance between two protruding portions adjacent in the lateral direction of the high electron mobility transistor is gradually reduced along the direction from the substrate to the GaN channel layer, and the lateral direction of the high electron mobility transistor is perpendicular to the direction from the substrate to the GaN channel layer.
Also taking fig. 7 as an example, a distance e between two adjacent ones of the first-formed protrusions is greater than a distance f between two adjacent ones of the second-formed protrusions; the distance f between two adjacent convex parts in the convex parts formed for the second time is larger than the distance g between two adjacent convex parts in the convex parts formed for the third time.
In the initial stage of growth of the AlGaN buffer layer, the distance between the AlGaN buffer layer and the substrate is short, the stress and the defect in the AlGaN buffer layer are large, the healing effect of the AlGaN buffer layer on the convex part which is far away is strong, and the improvement strength of the stress and the defect is large; at the later stage of the growth of the AlGaN buffer layer, the stress and the defects in the AlGaN buffer layer are reduced after improvement, and the stress and the defects can be improved by healing the AlGaN buffer layer on the boss part which is closer to the AlGaN buffer layer.
Illustratively, the distance between two projections adjacent in the lateral direction of the high electron mobility transistor is 100nm to 500 nm.
Optionally, when the step 202 to the step 204 are performed once, the thickness of the first AlGaN layer is greater than 1/5 of the thickness of the AlGaN buffer layer, and the thickness of the second AlGaN layer is greater than 1/5 of the thickness of the AlGaN buffer layer; when the steps 202 to 204 are performed for a plurality of times, the thickness of the first AlGaN layer formed for the first time is greater than 1/5 the thickness of the AlGaN buffer layer, and the thickness of the second AlGaN layer formed for the last time is greater than 1/5 the thickness of the AlGaN buffer layer.
By limiting the proportion of the first AlGaN layer which grows firstly and the second AlGaN layer which grows finally in the AlGaN buffer layer, the patterning treatment is effectively controlled in the AlGaN buffer layer, the healing of the epitaxial material in the homogeneous material is ensured, the stress and the defect in the epitaxial layer are effectively counteracted by utilizing the healing effect, and new stress and defect can not be generated due to the heterogeneous material.
Also in the example of fig. 7, the thickness of the first AlGaN layer formed for the first time is 20% of the thickness of the AlGaN buffer layer, and the thickness of the second AlGaN layer formed for the first time is 25% of the thickness of the AlGaN buffer layer; the thickness of the first AlGaN layer formed for the second time is 10% of that of the AlGaN buffer layer, and the thickness of the second AlGaN layer formed for the second time is 20% of that of the AlGaN buffer layer; the thickness of the first AlGaN layer formed for the third time is 5% of the thickness of the AlGaN buffer layer, and the thickness of the second AlGaN layer formed for the third time is 20% of the thickness of the AlGaN buffer layer.
The thickness of the first AlGaN layer formed for the first time is 20% of that of the AlGaN buffer layer, namely the thickness of the first AlGaN layer formed for the first time is greater than 1/5% of that of the AlGaN buffer layer; the thickness of the second AlGaN formed for the third time is 20% of the thickness of the AlGaN buffer layer, that is, the thickness of the second AlGaN layer formed for the last time is greater than 1/5% of the thickness of the AlGaN buffer layer.
The thickness of the first AlGaN layer formed for the first time is 20% of that of the AlGaN buffer layer, the thickness of the first AlGaN layer formed for the second time is 10% of that of the AlGaN buffer layer, the thickness of the first AlGaN layer formed for the third time is 5% of that of the AlGaN buffer layer, the thickness of the first AlGaN layer is gradually reduced along the direction from the substrate to the GaN channel layer, the size of the protruding part formed by the first AlGaN layer is correspondingly gradually reduced along the direction from the substrate to the GaN channel layer, and the distance between the protruding parts formed at the same time is also correspondingly gradually reduced along the direction from the substrate to the GaN channel layer.
The thickness of the second AlGaN formed for the first time is 25% of that of the AlGaN buffer layer, the thickness of the first AlGaN layer formed for the second time is 10% of that of the AlGaN buffer layer, and the distance between the boss formed for the first time and the boss formed for the second time is 35% of that of the AlGaN buffer layer; the thickness of the second AlGaN formed for the second time is 20% of the thickness of the AlGaN buffer layer, the thickness of the first AlGaN layer formed for the third time is 5% of the thickness of the AlGaN buffer layer, and the distance between the protruding portion formed for the second time and the protruding portion formed for the third time is 25% of the thickness of the AlGaN buffer layer, which is smaller than the distance between the protruding portion formed for the first time and the protruding portion formed for the second time.
Step 205: and sequentially growing a GaN channel layer and an AlGaN barrier layer on the AlGaN buffer layer.
Fig. 8 is a schematic structural diagram of the hemt provided in the embodiment of the present disclosure after step 205 is performed. Referring to fig. 8, a GaN channel layer 40 and an AlGaN barrier layer 50 are sequentially disposed on the AlGaN buffer layer 30.
Illustratively, the thickness of the GaN channel layer is 15nm to 100 nm; the growth temperature of the GaN channel layer is 900-1100 ℃, and the growth pressure of the GaN channel layer is 100-200 mbar.
Illustratively, the content of the Al component in the AlGaN barrier layer is 10% to 30%. The AlGaN barrier layer has a thickness of 10nm to 50 nm. The growth temperature of the AlGaN barrier layer is 900-1100 ℃. The growth pressure of the AlGaN barrier layer is 50mbar to 150 mbar.
Optionally, the preparation method further comprises:
a source, a drain and a gate are provided on the AlGaN barrier layer, respectively.
In an embodiment of the disclosure, the source and drain electrodes are in ohmic contact with the barrier layer, and the gate electrode is in schottky contact with the barrier layer.
Illustratively, the material of the source electrode, the drain electrode, and the gate electrode is a metal layer, such as one or more of a titanium (Ti) layer, an aluminum (Al) layer, a nickel (Ni) layer, a niobium (Nb) layer, and a gold (Au) layer.
In one implementation manner of the embodiment of the present disclosure, a source, a drain, and a gate are respectively disposed on an AlGaN barrier layer, and the method includes:
photoetching a source electrode area and a drain electrode area on the barrier layer;
evaporating a metal material on the source region and the drain region;
carrying out rapid thermal annealing on the metal material, forming ohmic contact between the metal material and the barrier layer, and forming a source electrode and a drain electrode;
photoetching a grid electrode area on the barrier layer;
and evaporating a metal material on the gate region, wherein the metal material and the barrier layer form Schottky contact to form a gate.
In another implementation manner of the embodiment of the present disclosure, a source, a drain, and a gate are respectively disposed on an AlGaN barrier layer, including:
photoetching a grid electrode area on the barrier layer;
evaporating a metal material on the gate region, wherein the metal material and the barrier layer form Schottky contact to form a gate;
photoetching a source electrode area and a drain electrode area on the barrier layer;
evaporating a metal material on the source region and the drain region;
and carrying out rapid thermal annealing on the metal material, forming ohmic contact between the metal material and the barrier layer, and forming a source electrode and a drain electrode.
The above description is intended only to illustrate the preferred embodiments of the present disclosure, and should not be taken as limiting the disclosure, as any modifications, equivalents, improvements and the like which are within the spirit and principle of the present disclosure should be included in the scope of the present disclosure.
Claims (7)
1. A preparation method of a high electron mobility transistor is characterized by comprising the following steps:
forming an AlGaN buffer layer on a substrate, and carrying out patterning treatment in the forming process of the AlGaN buffer layer;
growing a GaN channel layer and an AlGaN barrier layer on the AlGaN buffer layer in sequence;
the forming of the AlGaN buffer layer on the substrate and the patterning process in the forming process of the AlGaN buffer layer comprise:
firstly, growing a first AlGaN layer;
secondly, carrying out patterning treatment on the first AlGaN layer, and forming a plurality of convex parts and concave parts positioned among the convex parts on the surface of the first AlGaN layer;
thirdly, growing a second AlGaN layer on the concave part;
wherein the second AlGaN layer and the first AlGaN layer constitute an AlGaN buffer layer, the first step, the second step, and the third step are periodically performed a plurality of times, and in a protruding portion formed by periodically performing the second step a plurality of times, a distance between two protruding portions adjacent in a longitudinal direction of the high electron mobility transistor is gradually reduced in a direction from the substrate to the GaN channel layer, the longitudinal direction of the high electron mobility transistor being parallel to a direction from the substrate to the GaN channel layer.
2. The method of claim 1, wherein each of the protrusions has a conical shape or a polygonal pyramid shape.
3. The production method according to claim 2, wherein the first step, the second step, and the third step are periodically performed a plurality of times less than or equal to 5 times.
4. The production method according to claim 1, wherein a distance between two of the convex portions adjacent in a longitudinal direction of the high electron mobility transistor is reduced in a ratio of 10% to 40%.
5. The production method according to claim 1, wherein the second-step formation is periodically performed a plurality of times in the convex portion, and a size of the convex portion gradually decreases in a direction from the substrate to the GaN channel layer.
6. The method for manufacturing a composite material according to claim 5, wherein the size of the raised portion is reduced by a ratio of 15% to 60%.
7. The production method according to claim 5, wherein, of the convex portions formed by periodically performing the second step a plurality of times, a distance between two of the convex portions adjacent in a lateral direction of the high electron mobility transistor is gradually reduced in a direction from the substrate to the GaN channel layer, the lateral direction of the high electron mobility transistor being perpendicular to the direction from the substrate to the GaN channel layer.
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