CN116666459A - Punch-through type SiC-TVS device capable of realizing quick response and preparation method thereof - Google Patents
Punch-through type SiC-TVS device capable of realizing quick response and preparation method thereof Download PDFInfo
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- 230000004044 response Effects 0.000 title claims abstract description 61
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- 238000000137 annealing Methods 0.000 claims description 15
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- 238000005275 alloying Methods 0.000 claims description 8
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- 230000000694 effects Effects 0.000 abstract description 10
- 238000009825 accumulation Methods 0.000 abstract description 6
- 238000002513 implantation Methods 0.000 abstract description 4
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 55
- 229910010271 silicon carbide Inorganic materials 0.000 description 55
- 238000010586 diagram Methods 0.000 description 26
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
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- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a 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
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- H01L29/66053—Multistep manufacturing processes of devices having a semiconductor body comprising crystalline silicon carbide
- H01L29/6606—Multistep manufacturing processes of devices having a semiconductor body comprising crystalline silicon carbide the devices being controllable only by variation of the electric current supplied or the electric potential applied, to one or more of the electrodes carrying the current to be rectified, amplified, oscillated or switched, e.g. two-terminal devices
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Abstract
The invention discloses a punch-through type SiC-TVS device capable of realizing quick response and a preparation method thereof, wherein the device comprises a SiC substrate, a SiC epitaxial layer, a first electrode and a second electrode, wherein the SiC epitaxial layer comprises a base region positioned on the upper surface of the SiC substrate and a plurality of emitter regions embedded on the upper surface of the base region and spaced from each other, the emitter regions and the SiC substrate have the same doping type, and the emitter regions and the base regions have opposite doping types; the first electrode is arranged on the upper surface of the SiC epitaxial layer and consists of a plurality of emitters positioned on the upper surface of the emitter region and a plurality of base shorts positioned on the upper surface of the base region, wherein the emitters and the bases are alternately contacted; the second electrode is located on the lower surface of the SiC substrate. According to the invention, a plurality of evenly distributed emitter regions are formed on the surface of the base region through ion implantation, and the base electrode and the emitter electrode are in short circuit, so that the minority carrier accumulation effect of the forward bias PN junction on one side of the base region caused by minority carrier implantation is effectively weakened, and the clamping response speed of the device is greatly improved.
Description
Technical Field
The invention belongs to the technical field of microelectronics, and particularly relates to a punch-through SiC-TVS device capable of realizing quick response and a preparation method thereof.
Background
Transient high energy surge impacts such as lightning, electromagnetic pulse (EMP) and the like can cause failure or even damage of electronic components and downstream electronic systems. The transient voltage suppression diode (Transient Voltage Suppressor, TVS) has the advantages of high absorption power, high response speed, stable clamping voltage and the like, is a protective device commonly used at present, and is widely applied to the circuit miniaturization and integration application fields of aerospace, rail transit, high-voltage power grids, advanced weapon systems and the like. When the transient surge impacts the circuit system, the TVSs connected in parallel with the two ends of the circuit system are conducted in a short time to absorb surge power, and terminal voltage is clamped to a preset value to realize the clamping protection function, so that the electronic components/electronic system is prevented from being damaged by overvoltage or overcurrent impact.
Currently commonly used TVS devices are fabricated from silicon (Si) based semiconductor materials. Compared with Si materials, silicon carbide (SiC) materials have the advantages of wide forbidden band, high critical breakdown electric field intensity, high electron saturation drift velocity, high thermal conductivity and the like, and TVS devices prepared by the silicon carbide (SiC) materials can show the potential advantages of low electric leakage, quick response, high temperature resistance, strong robustness brought by intensive size and the like compared with Si-TVS, and are paid more attention to extremely complex working environments such as high temperature, strong radiation electromagnetic interference and the like.
In EMP protection applications, the rising edge time of the EMP signal is typically in the order of nanoseconds or hundred picoseconds, thus requiring a corresponding fast response time for the TVS device. For an NPN punch-through SiC-TVS device, when the reverse bias N+/P-junction is connected with the forward bias P-/N+ junction so that the intermediate P-base region is fully depleted, the TVS is conducted. However, due to the minority carrier injection-induced minority carrier accumulation effect of the forward bias P-/n+ junction at the P-region side, depletion promotion of the reverse bias n+/P-junction at the P-region is hindered, so that the clamp response speed of the device is slow (the response time is microsecond), and nanosecond fast response cannot be realized, so that the device is limited in EMP protection application.
Disclosure of Invention
In order to solve the problems in the prior art, the present invention provides a punch-through SiC-TVS device capable of achieving a rapid response and a method of fabricating the same. The technical problems to be solved by the invention are realized by the following technical scheme:
one aspect of the present invention provides a through-type SiC-TVS device capable of achieving a fast response, comprising a SiC substrate, a SiC epitaxial layer, a first electrode, and a second electrode, wherein,
the SiC epitaxial layer comprises a base region positioned on the upper surface of the SiC substrate and a plurality of emitter regions embedded in the upper surface of the base region and spaced from each other, wherein the emitter regions and the SiC substrate have the same doping type, and the emitter regions and the base region have opposite doping types;
the first electrode is arranged on the upper surface of the SiC epitaxial layer and consists of a plurality of emitters positioned on the upper surface of the emitter region and a plurality of base shorts positioned on the upper surface of the base region, wherein the emitters and the bases are alternately contacted;
the second electrode is positioned on the lower surface of the SiC substrate.
In one embodiment of the invention, the emitter region forms an ohmic contact with the emitter, the base region forms a schottky contact with the base, and the second electrode forms an ohmic contact with the SiC substrate.
In one embodiment of the invention, the emitter regions are uniformly arranged on the upper surface of the base region and the number n of the emitter regions is equal to or greater than 3.
In one embodiment of the invention, the doping concentration of both the emitter region and the SiC substrate is greater than the doping concentration of the base region.
In one embodiment of the present invention, the emission area width W has a value ranging from 0.5 μm to 5 μm, and the interval distance S between two adjacent emission areas has a value ranging from (S 1 ,S 2 ) Wherein S is 1 ＝W，S 2 ＝4×W。
In one embodiment of the present invention, the emission area width W has a value ranging from 0.5 μm to 2 μm, and the interval distance S between two adjacent emission areas has a value ranging from (S 1 ,S 2 ) Wherein S is 1 ＝W，S 2 ＝2×W。
Another aspect of the present invention is a method for manufacturing a through-type SiC-TVS device capable of achieving a rapid response, characterized by being used for manufacturing the through-type SiC-TVS device according to any one of the above embodiments, the method comprising:
s1: epitaxially growing a SiC epitaxial layer on the SiC substrate;
s2: forming a plurality of mutually-spaced emitting areas on the upper surface of the SiC epitaxial layer by utilizing an ion implantation method, and performing activation annealing;
s3: preparing a first electrode on the upper surface of the SiC epitaxial layer, wherein the first motor comprises an emitter and a base which are alternately arranged;
s4: and preparing a second electrode on the lower surface of the SiC substrate.
In one embodiment of the present invention, the S2 includes:
depositing a SiO layer with the thickness of 2 mu m on the upper surface of the SiC epitaxial layer 2 Layer, spin-on photoresist etch mask, dry etching SiO by ion 2 Forming an ion implantation mask layer so that an ion implantation window is positioned above a preset emission region;
removing the photoresist and performing ion implantation to form an ion implantation region on the upper surface of the SiC epitaxial layer;
and removing the ion implantation mask, cleaning the device and performing activation annealing to form a base region and a plurality of emitter regions which are embedded in the upper surface of the base region and are spaced from each other.
In one embodiment of the present invention, the S3 includes:
one or more metals in Ti, ni, al, W are integrally deposited on the surfaces of an emitter region and a base region of the SiC epitaxial layer, and the emitter region and the metal on the upper surface of the emitter region form ohmic contact through alloying annealing at the temperature of 800-1100 ℃, so that an emitter is formed on the upper surface of the emitter region; and simultaneously, the base region and the metal on the upper surface of the base region form Schottky contact, so that a base electrode is formed on the upper surface of the base region.
In one embodiment of the present invention, the S3 includes:
depositing metal Ni on the emitter region, and forming ohmic contact with the emitter region through alloying annealing at the temperature of 800-1100 ℃ so as to form an emitter positioned on the upper surface of the emitter region;
one or more metals in Ti, ni, al, W are deposited on the upper surfaces of the SiC epitaxial layer and the emitter so that the metals form Schottky contact with the base region, thereby forming a base electrode on the upper surface of the base region.
Compared with the prior art, the invention has the beneficial effects that:
compared with the traditional NPN punch-through type SiC-TVS device, the invention designs the punch-through type SiC-TVS device capable of realizing quick response, and a plurality of evenly distributed emitter regions are formed by ion implantation on the surface of the base region, and the base electrode is in short circuit with the emitter electrode, so that the minority carrier accumulation effect of a forward bias PN junction on one side of the base region due to minority carrier implantation is effectively weakened, the clamping response speed of the device is greatly improved, and the response time reaches nanosecond level; by designing structural parameters (width, spacing, etc.), particularly the number of emitter regions, a balance between fast response and high reliability large through-flow (avoiding local heat concentration) can be achieved; the metallization scheme can be flexibly selected, and the contact preparation of the base electrode and the emitter electrode can be realized.
The present invention will be described in further detail with reference to the accompanying drawings and examples.
Drawings
Fig. 1 is a schematic structural diagram of a through-type SiC-TVS device capable of achieving a fast response according to an embodiment of the present invention;
fig. 2 is a schematic diagram of a cell unit structure of a through-type SiC-TVS device capable of realizing a fast response according to an embodiment of the present invention;
FIG. 3 is a block diagram, electric field profile, and current density profile of a conventional open base NPN punch-through SiC-TVS device;
fig. 4 is a 3-cell structure diagram, an electric field distribution diagram, and a current density distribution diagram of a punch-through SiC-TVS device capable of achieving a fast response according to an embodiment of the present invention;
fig. 5a is a 10-cell structure diagram of a punch-through SiC-TVS device capable of achieving a fast response provided by an embodiment of the present invention;
FIG. 5b is a 10-cell current density distribution diagram of a punch-through SiC-TVS device capable of achieving a fast response according to an embodiment of the invention;
FIG. 6 is a graph comparing clamping characteristics of a 3-cell of a conventional open-base NPN punch-through SiC-TVS device with a punch-through SiC-TVS device according to an embodiment of the invention;
fig. 7 is a graph comparing the SRH recombination rate peak value at the forward P-/n+ junction with time for a conventional open base NPN pass-through SiC-TVS device and a pass-through SiC-TVS device 3 cell capable of achieving a fast response in accordance with an embodiment of the present invention.
Fig. 8 is a flowchart of a method for manufacturing a through-type SiC-TVS device capable of achieving a fast response according to an embodiment of the present invention;
fig. 9a is a schematic diagram of a through SiC-TVS device provided by an embodiment of the present invention in which the same metallization scheme is used to fabricate the first electrode;
fig. 9b is a schematic diagram of a through-type SiC-TVS device employing different metallization schemes for fabricating a first electrode according to an embodiment of the present invention.
Reference numerals illustrate:
a 10-SiC substrate; a 20-SiC epitaxial layer; 201-base region; 202-an emission region; 30-a first electrode; 301-emitter; 302-base; 40-a second electrode;
Detailed Description
In order to further illustrate the technical means and effects adopted by the invention to achieve the preset aim, the following describes the through type SiC-TVS device capable of realizing the fast response according to the present invention in detail with reference to the accompanying drawings and the detailed description.
The foregoing and other features, aspects, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments when taken in conjunction with the accompanying drawings. The technical means and effects adopted by the present invention to achieve the intended purpose can be more deeply and specifically understood through the description of the specific embodiments, however, the attached drawings are provided for reference and description only, and are not intended to limit the technical scheme of the present invention.
It should be noted that in this document relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that an article or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in an article or apparatus that comprises the element.
Example 1
Referring to fig. 1, fig. 1 is a schematic structural diagram of a through-type SiC-TVS device capable of realizing fast response according to an embodiment of the present invention. The through type SiC-TVS device comprises a SiC substrate 10, a SiC epitaxial layer 20, a first electrode 30 and a second electrode 40, wherein the SiC epitaxial layer 20 comprises a base region 201 positioned on the upper surface of the SiC substrate 10 and a plurality of emitter regions 202 embedded on the upper surface of the base region 201 and spaced from each other. In this embodiment, the plurality of emitter regions 202 are formed by ion implantation, the emitter regions 202 and the SiC substrate 10 have the same doping type, and the emitter regions 202 and the base regions 201 have opposite doping types. That is, when emitter region 202 and SiC substrate 10 are P-type doped, base region 201 is N-type doped, and when emitter region 202 and SiC substrate 10 are N-type doped, base region 201 is P-type doped. The region of SiC epitaxial layer 20 other than emitter region 202 is base region 201, and the effective thickness H of base region 201 is the thickness of the epitaxial layer below emitter region 202.
The first electrode 30 is disposed on the upper surface of the SiC epitaxial layer 20, and is composed of a plurality of emitters 301 disposed on the upper surface of the emitter region 202 and a plurality of bases 302 disposed on the upper surface of the base region 201 in short circuit, where the plurality of emitters 301 and the plurality of bases 302 are disposed in alternating contact. The emitter 301 and the base 302 may be formed simultaneously using the same metallization scheme or may be formed separately using different metallization schemes, the specific fabrication process being described in detail in example two below. In this embodiment, emitter region 202 forms an ohmic contact with emitter 301, base region 201 forms a schottky contact with base 302, and second electrode 40 forms an ohmic contact with SiC substrate 10. The second electrode 40 is located on the lower surface of the SiC substrate 10.
In this embodiment, the emitter regions 202 are uniformly disposed on the upper surface of the base region 201, and the number n of the emitter regions 202 is greater than or equal to 3. The width W of the emitter region 202 is in the range of 0.5-5 μm, and the spacing distance S between two adjacent emitter regions 202 is in the range of S 1 ,S 2 Wherein S is 1 ＝W，S 2 =4×w. The depth of the emitter region 202 is D, which ranges from 0.5 to 1.2 μm.
In another embodiment of the present invention, the width W of the emitter region 202 is in the range of 0.5-2 μm, and the spacing distance S between two adjacent emitter regions 202 is in the range of S 1 ,S 2 Wherein S is 1 ＝W，S 2 ＝2×W。
Further, in the present embodiment, the ion doping type of the SiC substrate layer 10 and the emitter region 202 is N-type, and the ion doping type of the base region 201 is P-type. And, the doping concentrations of both the emitter region 202 and the SiC substrate 10 are greater than the doping concentration of the base region 201. That is, at this time, siC substrate layer 10 is an n+ substrate, base region 201 is a P-base region, and emitter region 202 is an n+ emitter region. At this time, the first electrode 30 is a negative electrode, and the second electrode 40 is a positive electrode.
In another embodiment of the present invention, the ion doping type of SiC substrate layer 10 and emitter region 202 is P-type and the ion doping type of base region 201 is N-type. That is, at this time, siC substrate layer 10 is a p+ substrate, base region 201 is an N-base region, and emitter region 202 is a p+ emitter region. At this time, the first electrode 30 is a positive electrode, and the second electrode 40 is a negative electrode.
Referring to fig. 2, fig. 2 is a schematic diagram of a cell unit of a through-type SiC-TVS device capable of realizing fast response according to the present invention, and referring to fig. 1 and fig. 2, it can be seen that the through-type SiC-TVS device having a complete structure in fig. 1 is obtained by repeatedly arranging a plurality of cell unit structures.
Based on the through type SiC-TVS device of the embodiment, simulation verification is carried out by adopting Sentaurus TCAD software. The signal source used for dynamic characteristic simulation is a pulse signal with a peak voltage of 1000V and 10/1000 mu s. Referring to fig. 3, fig. 3 (a) is a structural diagram, an electric field distribution diagram and a current density distribution diagram of a conventional base-open NPN through SiC-TVS device, where fig. 3 (a) is a structural diagram of a conventional base-open NPN through SiC-TVS device, which sequentially includes, from bottom to top, a SiC substrate, a base epitaxial layer and a SiC emitter epitaxial layer, and basic parameters of a device structure include: the doping type of the SiC substrate is N type, and the doping concentration is 5 multiplied by 10 18 cm -3 . The thickness of the base region epitaxial layer is 6 mu m, the doping type is P type, and the doping concentration is 1 multiplied by 10 16 cm -3 . Depth H of epitaxial layer of SiC emitter N+ 0.8 μm, N type doping, 1×10 doping concentration 19 cm -3 . The positive electrode is positioned in the lower region of the substrate, the negative electrode is positioned in the upper region of the emission region, and the base electrode is in an open circuit state.
FIG. 3 (b) is an electric field distribution diagram of a conventional open base NPN punch-through SiC-TVS device with a maximum peak electric field mainly concentrated on the P-base side of the P-/N+ junction biased by lower Fang FanxiangValue E BM =1.106 MV/cm. FIG. 3 (c) is a graph showing the current density distribution of a conventional open-base punch-through SiC-TVS device, the entire device being a through-current region with a smaller current density having a peak current density of 154A/cm 2 。
Referring to fig. 4, fig. 4 is a 3-cell structure diagram, an electric field distribution diagram and a current density distribution diagram of a through-type SiC-TVS device capable of realizing a fast response according to an embodiment of the present invention, where fig. 4 (a) is a 3-cell structure diagram of a through-type SiC-TVS device capable of realizing a fast response, and basic parameters of a device structure include: the SiC substrate 10 has a doping type of N type and a doping concentration of 5×10 18 cm -3 . The thickness of the SiC epitaxial layer 20 is 6.8 μm, wherein the SiC epitaxial layer 20 includes 3 emitter regions 202 (i.e., composed of 3 unit cells, for example) formed by ion implantation, the effective thickness H of the base region 201 is 6 μm, the depth D of the emitter regions 202 is 0.8 μm, the width w=1 μm, the distance s=2 μm between adjacent emitter regions, the doping type of the base region 201 is P-type, and the doping concentration is 1×10 16 cm -3 The emitter region 202 is doped N-type with a doping concentration of 1×10 19 cm -3 . The positive electrode is located in the lower region of the substrate, and the negative electrode is formed by the short circuit of the emitter and the base on the upper side.
FIG. 4 (b) is a graph showing the distribution of the 3-cell electric field of a punch-through SiC-TVS device capable of achieving a fast response, with the maximum peak electric field mainly concentrated on the P-base side of the P-/N+ junction biased by Fang Fanxiang, the maximum peak electric field value E BM =1.134 MV/cm, which is not very different from the conventional base-open NPN punch-through SiC-TVS device. The schottky barrier region and the N+ emission region on the surface of the base region have no high electric field concentration at the edges.
FIG. 4 (c) is a 3-cell current density distribution diagram of a punch-through SiC-TVS device capable of achieving a fast response, with the current-through region being located mainly in the base region at the lower side of the emitter region, with a peak current density of 993A/cm 2 The current density is relatively large, local thermal effect is easy to generate, and the reliability of the device is reduced.
Further, referring to fig. 5a, fig. 5a is a schematic diagram of a through-type SiC-TVS device capable of realizing fast response according to an embodiment of the present invention10-cell structure of the device, the basic parameters of the device structure include: the SiC substrate 10 has a doping type of N type and a doping concentration of 5×10 18 cm -3 . The thickness of the SiC epitaxial layer 20 is 6.8 μm, wherein the SiC epitaxial layer 20 includes 10 emitter regions 202 (i.e., 10 unit cells are formed by ion implantation, for example), the effective thickness H of the base region 201 is 6 μm, the depth D of the emitter regions 202 is 0.8 μm, the width w=1 μm, the distance s=2 μm between adjacent emitter regions, the doping type of the base region 201 is P-type, and the doping concentration is 1×10 16 cm -3 The emitter region 202 is doped N-type with a doping concentration of 1×10 19 cm -3 . The positive electrode is located in the lower region of the substrate, and the negative electrode is formed by shorting the upper emitter electrode to the base electrode.
Referring to FIG. 5b, FIG. 5b shows a 10-cell current density distribution diagram of a through-type SiC-TVS device with a peak current density of 373A/cm for a fast response according to an embodiment of the present invention 2 The peak current density is reduced by about 70% compared to a 3-cell structure, i.e., as the number of emitter regions n increases, the peak current density within the TVS device decreases, which is beneficial for reducing heat concentration and improving device reliability.
Referring to fig. 6, fig. 6 is a graph showing a clamp characteristic curve of a conventional open-base NPN through SiC-TVS device and a through SiC-TVS device (3-cell) capable of realizing a fast response according to an embodiment of the present invention, wherein a vertical axis is Voltage (V); the abscissa is Time (Time), in s; the unsigned curve is an input voltage change curve, the solid square curve is a clamping voltage change curve of a traditional NPN (negative-positive-negative) through type SiC-TVS (dielectric constant-current-to-voltage) device with an open base, and the hollow round curve is a clamping voltage change curve of a through type SiC-TVS device structure (3-cell) capable of realizing quick response. It can be seen that the clamp response time of the conventional base open-circuited NPN through SiC-TVS device is relatively large, about 2 μs; the clamp response speed of the punch-through SiC-TVS device (3-cell) is obviously faster, and the response time can reach ns level.
Further, please refer to the drawingsFIG. 7 is a graph of the peak SRH (Shockley-Read-Hall) recombination rate over time for a conventional open-base NPN-type SiC-TVS device with a fast response of the 3-cell SRH (Shockley-Read-Hall) at the forward P-/N+ junction for a through-type SiC-TVS device according to an embodiment of the invention, where the vertical axis is the SRH recombination rate (SRH Combination Rate) in cm -3 S; the horizontal axis is Time (Time), in s; the solid square curve is the SRH composite rate change curve of the traditional NPN punching type SiC-TVS device with an open base, and the hollow round curve is the SRH composite rate change curve of the punching type SiC-TVS device structure (3-cell) capable of realizing quick response. As can be seen in connection with fig. 6, during a relatively long clamping time (10 -9 ～10 -5 s), the SRH composite rate peak value at the forward bias P-/N+ junction of the traditional base open NPN punch-through SiC-TVS device is always high and maintained at 10 20 cm -3 S; whereas the inventive through-type SiC-TVS device structure (3-cell) capable of achieving a fast response is only formed in a short time (10 -9 ～10 -8 s) the peak value of the SRH composite rate reaches 10 20 cm -3 And then fall back quickly, remaining at a small value (10 4 cm -3 S), the inhibition effect of the punch-through type SiC-TVS device structure capable of realizing quick response on minority carrier accumulation effect at the forward bias P-/N+ junction is obvious. Compared with the traditional NPN punching-through type SiC-TVS device with an open base electrode, the punching-through type SiC-TVS device provided by the embodiment of the invention has the advantages that a plurality of evenly distributed emitter regions are formed by ion implantation on the surface of the base region, and the base electrode is in short circuit with the emitter electrode, so that the minority carrier accumulation effect of a forward bias PN junction on one side of the base region of an epitaxial layer due to minority carrier implantation is effectively weakened, the clamping response speed of the device is greatly improved, and the response time reaches nanosecond level.
Example two
On the basis of the first embodiment, the present embodiment provides a method for preparing a through type SiC-TVS device capable of achieving a fast response, as shown in fig. 8, and fig. 8 is a flowchart of a method for preparing a through type SiC-TVS device capable of achieving a fast response, where the method for preparing a through type SiC-TVS device capable of achieving a fast response according to an embodiment of the present invention includes:
s1: an SiC epitaxial layer is epitaxially grown on the SiC substrate.
S2: and forming a plurality of mutually-spaced emitting areas on the upper surface of the SiC epitaxial layer by utilizing an ion implantation method and performing high-temperature activation annealing.
Specifically, a SiO layer with a thickness of 2 μm is deposited on the upper surface of the SiC epitaxial layer 2 Layer, spin-on Photoresist (PR) etch mask, dry etch SiO by ICP or RIE plasma 2 Forming an ion implantation mask, wherein the width of an implantation window is designed according to the preset emission area width W and the preset emission area interval S, so that the ion implantation window is positioned above the preset emission area; removing the photoresist and performing ion implantation to form an ion implantation region on the upper surface of the SiC epitaxial layer; the ion implantation mask is removed and the device is cleaned and annealed at a high temperature (annealing temperature 800-1100 ℃) to activate the implanted impurity atoms and eliminate lattice damage, thereby forming a base region and a plurality of emitter regions which are located at a distance from each other and are embedded in the upper surface of the base region.
S3: and preparing a first electrode on the upper surface of the SiC epitaxial layer, wherein the first motor comprises emitters and bases which are alternately arranged and short-circuited. The emitter and base can be prepared simultaneously using the same metallization scheme, or can be prepared separately using different metallization schemes.
Referring to fig. 9a, fig. 9a is a schematic diagram of a through-type SiC-TVS device for manufacturing a first electrode using the same metallization scheme according to an embodiment of the present invention. In this embodiment, the emitter and the base may be simultaneously fabricated using the same metallization scheme, specifically including the following steps: one or more metals in Ti, ni, al, W are integrally deposited on the surfaces of an emitter region and a base region of the SiC epitaxial layer, and the emitter region and the metal on the upper surface of the emitter region form ohmic contact through alloying annealing at the temperature of 800-1100 ℃, so that an emitter is formed on the upper surface of the emitter region; meanwhile, due to low doping of the base region, the base region and metal on the upper surface of the base region form Schottky contact, so that a base electrode is formed on the upper surface of the base region.
In another embodiment of the invention, the emitter and base may also be prepared separately using different metallization schemes. Referring to fig. 9b, fig. 9b is a schematic diagram of a through SiC-TVS device for manufacturing a first electrode by using different metallization schemes according to an embodiment of the present invention, where the manufacturing process specifically includes:
depositing metal Ni on the emitter region, and forming ohmic contact with the emitter region through alloying annealing at 800-1100 ℃ to form an emitter positioned on the upper surface of the emitter region; one or more metals of Ti, ni, al, W are deposited on the upper surfaces of the SiC epitaxial layer and the emitter so that the metal contacts the base region to form a Schottky contact, thereby forming a base electrode on the upper surface of the base region. Furthermore, the Schottky contact characteristic can be further improved through alloying annealing, and the annealing temperature is 350-700 ℃.
S4: and preparing a second electrode on the lower surface of the SiC substrate.
Specifically, metal Ni is deposited on the lower surface of the SiC substrate by an electron beam evaporation mode, and an ohmic contact second electrode is formed by alloying annealing at 950-1100 ℃.
According to the invention, by utilizing the material characteristic advantages of SiC and based on an NPN punch-through working principle, the emitter regions which are distributed at intervals are formed on the surface of the base region through an ion implantation selective region doping process, and finally, electrodes are integrally prepared on the surfaces of the base region and the emitter regions, so that the short circuit between the base and the emitter is realized. Therefore, minority carrier accumulation effect at the forward PN junction can be effectively weakened, the clamping response speed of the device is greatly improved, and the response time reaches nanosecond level. The balance between response time and current capacity can be further realized by optimally designing the structural parameters (such as the distance between adjacent emitter regions, the number of the emitter regions and the like) of the emitter regions distributed on the surface of the base region at intervals.
The foregoing is a further detailed description of the invention in connection with the preferred embodiments, and it is not intended that the invention be limited to the specific embodiments described. It will be apparent to those skilled in the art that several simple deductions or substitutions may be made without departing from the spirit of the invention, and these should be considered to be within the scope of the invention.
Claims (10)
1. A punch-through SiC-TVS device capable of achieving a rapid response is characterized by comprising a SiC substrate (10), a SiC epitaxial layer (20), a first electrode (30) and a second electrode (40), wherein,
the SiC epitaxial layer (20) comprises a base region (201) positioned on the upper surface of the SiC substrate (10) and a plurality of emitter regions (202) embedded on the upper surface of the base region (201) and spaced from each other, wherein the emitter regions (202) and the SiC substrate (10) have the same doping type, and the emitter regions (202) and the base region (201) have opposite doping types;
the first electrode (30) is arranged on the upper surface of the SiC epitaxial layer (20) and is formed by shorting a plurality of emitting electrodes (301) positioned on the upper surface of the emitting region (202) and a plurality of base electrodes (302) positioned on the upper surface of the base region (201), wherein the plurality of emitting electrodes (301) and the plurality of base electrodes (302) are alternately contacted;
the second electrode (40) is located on the lower surface of the SiC substrate (10).
2. The fast response capable punch-through SiC-TVS device of claim 1, wherein said emitter region (202) forms an ohmic contact with said emitter (301), said base region (201) forms a schottky contact with said base (302), and said second electrode (40) forms an ohmic contact with said SiC substrate (10).
3. The through-type SiC-TVS device capable of realizing a fast response according to claim 1, characterized in that said emitter regions (202) are uniformly disposed on the upper surface of said base region (201) and the number n of said emitter regions (202) is not less than 3.
4. The through-type SiC-TVS device capable of achieving a fast response according to claim 2, characterized in that the doping concentration of both said emitter region (202) and said SiC substrate (10) is greater than the doping concentration of said base region (201).
5. A punch-through SiC-TVS device capable of achieving fast response as recited in claim 1, whichCharacterized in that the width W of the emitting areas (202) is 0.5-5 mu m, and the interval distance S between two adjacent emitting areas (202) is (S) 1 ,S 2 ) Wherein S is 1 ＝W，S 2 ＝4×W。
6. The through-type SiC-TVS device capable of realizing a rapid response according to claim 1, wherein said emitter region (202) has a width W ranging from 0.5 to 2 μm and a spacing distance S between adjacent two emitter regions (202) ranging from (S 1 ,S 2 ) Wherein S is 1 ＝W，S 2 ＝2×W。
7. A method of manufacturing a punch-through SiC-TVS device capable of achieving a fast response, characterized by being used for manufacturing the punch-through SiC-TVS device of any one of claims 1 to 6, the method of manufacturing comprising:
s1: epitaxially growing a SiC epitaxial layer on the SiC substrate;
s2: forming a plurality of mutually-spaced emitting areas on the upper surface of the SiC epitaxial layer by utilizing an ion implantation method, and performing activation annealing;
s3: preparing a first electrode on the upper surface of the SiC epitaxial layer, wherein the first motor comprises an emitter and a base which are alternately arranged;
s4: and preparing a second electrode on the lower surface of the SiC substrate.
8. The method of fabricating a punch-through SiC-TVS device capable of achieving a fast response according to claim 7, wherein S2 comprises:
depositing a SiO layer with the thickness of 2 mu m on the upper surface of the SiC epitaxial layer 2 Layer, spin-on photoresist etch mask, dry etching SiO by ion 2 Forming an ion implantation mask layer so that an ion implantation window is positioned above a preset emission region;
removing the photoresist and performing ion implantation to form an ion implantation region on the upper surface of the SiC epitaxial layer;
and removing the ion implantation mask, cleaning the device and performing activation annealing to form a base region and a plurality of emitter regions which are embedded in the upper surface of the base region and are spaced from each other.
9. The method of fabricating a punch-through SiC-TVS device capable of achieving fast response according to claim 7, wherein S3 comprises:
one or more metals in Ti, ni, al, W are integrally deposited on the surfaces of an emitter region and a base region of the SiC epitaxial layer, and the emitter region and the metal on the upper surface of the emitter region form ohmic contact through alloying annealing at the temperature of 800-1100 ℃, so that an emitter is formed on the upper surface of the emitter region; and simultaneously, the base region and the metal on the upper surface of the base region form Schottky contact, so that a base electrode is formed on the upper surface of the base region.
10. The method of fabricating a punch-through SiC-TVS device capable of achieving fast response according to claim 7, wherein S3 comprises:
depositing metal Ni on the emitter region, and forming ohmic contact with the emitter region through alloying annealing at the temperature of 800-1100 ℃ so as to form an emitter positioned on the upper surface of the emitter region;
one or more metals in Ti, ni, al, W are deposited on the upper surfaces of the SiC epitaxial layer and the emitter so that the metals form Schottky contact with the base region, thereby forming a base electrode on the upper surface of the base region.
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