CN104233461A - Method for preparing N-type heavily-doped silicon carbide thin film epitaxy by controlling hydrogen flow - Google Patents
Method for preparing N-type heavily-doped silicon carbide thin film epitaxy by controlling hydrogen flow Download PDFInfo
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- CN104233461A CN104233461A CN201410349230.9A CN201410349230A CN104233461A CN 104233461 A CN104233461 A CN 104233461A CN 201410349230 A CN201410349230 A CN 201410349230A CN 104233461 A CN104233461 A CN 104233461A
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Abstract
The invention relates to a method for preparing an N-type heavily-doped silicon carbide thin film epitaxy by controlling hydrogen flow. The preparation method comprises the following steps: (1) placing a silicon carbide substrate into a reaction chamber of silicon carbide CVD (Chemical Vapor Deposition) equipment, and vacuumizing the reaction chamber; (2) introducing H2 into the reaction chamber till the air pressure of the reaction chamber reaches 100 mbar, keeping the air pressure of the reaction chamber constant, then gradually increasing the H2 flow to 60 L/minute, and continuously introducing the H2 into the reaction chamber; (3) starting a high-frequency coil induction heater RF, greatly enhancing the power of the high-frequency coil induction heater RF, and etching in situ when the temperature of the reaction chamber is gradually increased to 1400 DEG C; and (4) when the temperature of the reaction chamber reaches 1580-1600 DEG C, keeping the temperature and pressure constant, introducing C3H8 and SiH4 into the reaction chamber, and introducing high-purity N2 used as an N-type doped source into the reaction chamber.
Description
Technical field
The invention belongs to semiconductor device processing technology field, particularly relate to one and utilize existing carbofrax material MOCVD growth technique, prepare the method for N-type gradient heavy doping silicon carbide epitaxial layers.
Background technology
Silicon carbide has the advantages such as broad-band gap, high thermal conductivity, high breakdown strength, high electronics saturation drift velocity, high hardness, also has very strong chemical stability.These excellent physics and electric property make silicon carbide have a lot of advantage in application.The wide silicon carbide intrinsic carrier that makes in forbidden band at high temperature still can keep lower concentration, under being thus operated in very high temperature.High breakdown field strength makes silicon carbide can bear high strength of electric field, and this makes silicon carbide may be used for making high pressure, high-power semiconducter device.High heat conductance makes silicon carbide have good thermal diffusivity, contribute to the power density and integrated level, the attached cooling infrastructure of minimizing that improve device, thus making that the volume and weight of system reduces widely, efficiency then improves widely, this is for the electron device very advantageous in development space field.The saturated electrons travelling speed of silicon carbide is very high, and this characteristic also makes it may be used for radio frequency or microwave device, thus improves devices function speed.
The carrier concentration of carbofrax material is the basic electricity parameter of materials and devices.This parameter is realized by material doped control.Therefore, the doping of silicon carbide epitaxy material is one of the critical process in device preparation.But because the bonding strength of silicon carbide is high, the doping in device making technics can not adopt diffusion technique, extension controlled doping and high temperature tension doping can only be utilized.High temperature tension can cause a large amount of character to damage, and forms a large amount of character defect, even if annealing is also difficult to eliminate completely, had a strong impact on the performance of device, and ion implantation efficiency is very low, is thus not suitable for doing big area doping.Meanwhile, when preparing the semiconducter device of some multilayered structures, need the gradient of the longitudinal doping content of epitaxial film controlled.Only have by Reasonable adjustment growth parameter(s), growing doping and reaching the epitaxial film of pre-provisioning request, just can produce the satisfactory device of performance, thus the grade doping of silicon carbide epitaxial layers controls to be the difficult point that during current device manufactures one is very large.
Summary of the invention
The object of the invention is to the deficiency for above-mentioned prior art, a kind of preparation method of N-type gradient heavy doping silicon carbide epitaxial layers is provided, utilize the CVD equipment of silicon carbide, prepare the silicon carbide epitaxial layers that longitudinal doping content gradient is controlled, meet the requirement of preparation gradient heavy doping epitaxial film.
For achieving the above object, preparation method of the present invention comprises the following steps.
(1) silicon carbide substrates is placed in the reaction chamber of silicon carbide CVD equipment, reaction chamber is evacuated;
(2) H is passed into reaction chamber
2until reaction chamber air pressure arrives 100mbar, keep reaction chamber air pressure constant, then by H
2flow increases to 60L/min gradually, continues to ventilate to reaction chamber;
(3) open radio-frequency coil induction heater RF, increase the power of this well heater gradually, carry out original position etching when reaction chamber temperature raises gradually to 1400 DEG C;
(4) when reaction chamber temperature reaches 1580 DEG C-1600 DEG C, keep temperature and invariablenes pressure of liquid, pass into C to reaction chamber
3h
8and SiH
4; By high-purity N
2pass in reaction chamber as N-type doped source.After the growth of the first layer N-type doped layer terminates, stop passing into SiH to reaction chamber
4, C
3h
8and high-purity N
2and keep 1min, therebetween by H
2flow is reduced to 40L/min by 60L/min.Continue afterwards to pass into SiH to reaction chamber
4, C
3h
8and high-purity N
2growth second layer N-type doped layer.After the growth of second layer N-type doped layer terminates, stop passing into SiH to reaction chamber
4, C
3h
8and high-purity N
2and keep 1min, therebetween by H
2flow is reduced to 20L/min by 40L/min.Continue afterwards to pass into SiH to reaction chamber
4, C
3h
8and high-purity N
2growth third layer N-type doped layer.
(5) when after the epitaxy time reaching setting, stop growing, continue to pass into hydrogen at reaction chamber, substrate slice is lowered the temperature in the hydrogen gas stream;
(6) when temperature is reduced to after below 700 DEG C, again reaction chamber is evacuated, is then slowly filled with argon gas, make substrate slice naturally cool to room temperature under ar gas environment.
Compared with prior art, tool has the following advantages in the present invention:
1. the present invention adopts high-purity N
2as doped source, C atom in carbofrax material effectively replaced by the aluminium nuclear power mixed, and form substitutional impurity, relative to ion implantation technology, the heavy doping carbofrax material character of preparation is complete, and defect is few, is conducive to improving device performance.
2. the present invention adopts the CVD epitaxial device of silicon carbide, extension is carried out at the carbonization substrate of silicon carbide substrates or existing epitaxial film, control longitudinal doping content by growth parameter(s), the N-type epitaxy layer of different heavy dopant concentration can be grown continuously, the preparation technology of device is simplified.
Accompanying drawing explanation
Describe exemplary embodiment of the present invention in more detail by referring to accompanying drawing, above and other aspect of the present invention and advantage will become and more be readily clear of, in the accompanying drawings:
Fig. 1 is the process flow sheet of technical solution of the present invention.
Embodiment
Hereinafter, more fully the present invention is described now with reference to accompanying drawing, various embodiment shown in the drawings.But the present invention can implement in many different forms, and should not be interpreted as being confined to embodiment set forth herein.On the contrary, provide these embodiments to make the disclosure will be thoroughly with completely, and scope of the present invention is conveyed to those skilled in the art fully.
Referring to accompanying drawing 1, technical scheme of the present invention is described in further detail, below provides two kinds of embodiments.
Embodiment 1
Step one, is placed into silicon carbide substrates in the reaction chamber of silicon carbide CVD equipment.
(1.1) deflection is chosen
the 4H silicon carbide substrates in 4 °, crystal orientation, is placed in the reaction chamber of silicon carbide CVD equipment;
(1.2) reaction chamber is vacuumized, until reaction chamber air pressure is lower than 1 × 10
-7mbar.
Step 2, in the hydrogen gas stream reacting by heating room.
(2.1) open the hydrogen switch leading to reaction chamber, control hydrogen flowing quantity and increase to 60L/min gradually;
(2.2) open the gas of vacuum pump abstraction reaction room, keep reaction chamber air pressure at 100mbar;
(2.3) tune up heating source power gradually, reaction chamber temperature is slowly raised.
Step 3, carries out original position etching to substrate.
(3.1) when reaction chamber temperature reaches after 1400 DEG C, the constant original position etching of carrying out 10 minutes of reaction chamber temperature is kept.
Step 4, arranges growth conditions, starts growing silicon carbide epitaxial film.
(4.1) at reaction chamber temperature reaches 1580 DEG C, reaction chamber temperature and invariablenes pressure of liquid is kept;
(4.2) C is opened
3h
8, SiH
4and high-purity N
2switch, in reaction chamber, pass into the C that flow is 7mL/min
3h
8, flow is the SiH of 21mL/min
4be the high-purity N of 2000mL/min with flow
2, start growing silicon carbide epitaxial film N1, growth time is 13min.Close C afterwards
3h
8, SiH
4and high-purity N
2switch 1min, therebetween by H
2flow is reduced to 40L/min.Open C
3h
8, SiH
4and high-purity N
2switch, in reaction chamber, pass into the C that flow is 7mL/min
3h
8, flow is the SiH of 21mL/min
4be the high-purity N of 2000mL/min with flow
2, start growing silicon carbide epitaxial film N2, growth time is 13min.After silicon carbide epitaxial layers N2 growth terminates, close C
3h
8, SiH
4and high-purity N
2switch 1min, therebetween by H
2flow is reduced to 20L/min.Open C
3h
8, SiH
4and high-purity N
2switch, in reaction chamber, pass into the C that flow is 7mL/min
3h
8, flow is the SiH of 21mL/min
4be the high-purity N of 2000mL/min with flow
2, start growing silicon carbide epitaxial film N3, growth time is 13min.
Step 5, cools substrate in the hydrogen gas stream.
(5.1) after epitaxial film N3 growth terminates, C is closed
3h
8, SiH
4and high-purity N
2switch, stop growing;
(5.2) arranging the hydrogen flowing quantity leading to reaction chamber is 20L/min, keeps reaction chamber air pressure to be 100mbar, makes length have the substrate of silicon carbide epitaxial layers to cool 25min in the hydrogen gas stream;
(5.3) reaction chamber air pressure is elevated to 700mbar, continues cooling in the hydrogen gas stream.
Step 6, cools substrate in argon gas.
(6.1) when reaction chamber temperature is reduced to after 700 DEG C, the hydrogen switch leading to reaction chamber is closed;
(6.2) reaction chamber is vacuumized, until air pressure is lower than 1 × 10
-7mbar;
(6.3) open argon gas switch, pass into reaction chamber the argon gas that flow is 12L/min, make length have the substrate of silicon carbide epitaxial layers to continue to cool 30min under ar gas environment;
(6.4) slowly improve reaction chamber air pressure to normal pressure, make substrate naturally cool to room temperature, take out silicon carbide epitaxial wafer.
Embodiment 2
Step one, is placed into silicon carbide substrates in the reaction chamber of silicon carbide CVD equipment.
(1.1) deflection is chosen
the 4H silicon carbide substrates in 8 °, crystal orientation, is placed in the reaction chamber of silicon carbide CVD equipment;
(1.2) reaction chamber is vacuumized, until reaction chamber air pressure is lower than 1 × 10
-7mbar.
Step 2, in the hydrogen gas stream reacting by heating room.
(2.1) open the hydrogen switch leading to reaction chamber, control hydrogen flowing quantity and increase to 60L/min gradually;
(2.2) open the gas of vacuum pump abstraction reaction room, keep reaction chamber air pressure at 100mbar;
(2.3) tune up heating source power gradually, reaction chamber temperature is slowly raised.
Step 3, carries out original position etching to substrate.
(3.1) when reaction chamber temperature reaches after 1400 DEG C, in reaction chamber, the C that flow is 7mlL/min is passed into
3h
8, keep the constant original position etching of carrying out 10 minutes of reaction chamber temperature.
Step 4, arranges growth conditions, starts growing silicon carbide epitaxial film.
(4.1) at reaction chamber temperature reaches 1580 DEG C, reaction chamber temperature and invariablenes pressure of liquid is kept;
(4.2) SiH is opened
4and high-purity N
2switch, in reaction chamber, pass into the C that flow is 7mL/min
3h
8, flow is the SiH of 21mL/min
4be the high-purity N of 2000mL/min with flow
2, start growing silicon carbide epitaxial film N1, growth time is 13min.Close C afterwards
3h
8, SiH
4and high-purity N
2switch 1min, therebetween by H
2flow is reduced to 40L/min.Open C
3h
8, SiH
4and high-purity N
2switch, in reaction chamber, pass into the C that flow is 7mL/min
3h
8, flow is the SiH of 21mL/min
4be the high-purity N of 2000mL/min with flow
2, start growing silicon carbide epitaxial film N2, growth time is 13min.After silicon carbide epitaxial layers N2 growth terminates, close C
3h
8, SiH
4and high-purity N
2switch 1min, therebetween by H
2flow is reduced to 20L/min.Open C
3h
8, SiH
4and high-purity N
2switch, in reaction chamber, pass into the C that flow is 7mL/min
3h
8, flow is the SiH of 21mL/min
4be the high-purity N of 2000mL/min with flow
2, start growing silicon carbide epitaxial film N3, growth time is 13min.
Step 5, cools substrate in the hydrogen gas stream.
(5.1) after epitaxial film N3 growth terminates, C is closed
3h
8, SiH
4and high-purity N
2switch, stop growing;
(5.2) arranging the hydrogen flowing quantity leading to reaction chamber is 20L/min, keeps reaction chamber air pressure to be 100mbar, makes length have the substrate of silicon carbide epitaxial layers to cool 25min in the hydrogen gas stream;
(5.3) reaction chamber air pressure is elevated to 700mbar, continues cooling in the hydrogen gas stream.
Step 6, cools substrate in argon gas.
(6.1) when reaction chamber temperature is reduced to after 700 DEG C, the hydrogen switch leading to reaction chamber is closed;
(6.2) reaction chamber is vacuumized, until air pressure is lower than 1 × 10
-7mbar;
(6.3) open argon gas switch, pass into reaction chamber the argon gas that flow is 12L/min, make length have the substrate of silicon carbide epitaxial layers to continue to cool 30min under ar gas environment;
(6.4) slowly improve reaction chamber air pressure to normal pressure, make substrate naturally cool to room temperature, take out silicon carbide epitaxial wafer.
The foregoing is only embodiments of the invention, be not limited to the present invention.The present invention can have various suitable change and change.All any amendments done within the spirit and principles in the present invention, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (1)
1. control a hydrogen flowing quantity N-type heavy doping carborundum films epitaxial preparation method, it is characterized in that:
Described preparation method comprises the following steps:
(1) silicon carbide substrates is placed in the reaction chamber of silicon carbide CVD equipment, reaction chamber is evacuated;
(2) H is passed into reaction chamber
2until reaction chamber air pressure arrives 100mbar, keep reaction chamber air pressure constant, then by H
2flow increases to 60L/min gradually, continues to ventilate to reaction chamber;
(3) open radio-frequency coil induction heater RF, increase the power of this well heater gradually, carry out original position etching when reaction chamber temperature raises gradually to 1400 DEG C;
(4) when reaction chamber temperature reaches 1580 DEG C-1600 DEG C, keep temperature and invariablenes pressure of liquid, pass into C to reaction chamber
3h
8and SiH
4; By high-purity N
2pass in reaction chamber as N-type doped source; After the growth of the first layer N-type doped layer terminates, stop passing into SiH to reaction chamber
4, C
3h
8and high-purity N
2and keep 1min, therebetween by H
2flow is reduced to 40l/min by 60l/min; Continue afterwards to pass into SiH to reaction chamber
4, C
3h
8and high-purity N
2growth second layer N-type doped layer; After the growth of second layer N-type doped layer terminates, stop passing into SiH to reaction chamber
4, C
3h
8and high-purity N
2and keep 1min, therebetween by H
2flow is reduced to 20L/min by 40L/min; Continue afterwards to pass into SiH to reaction chamber
4, C
3h
8and high-purity N
2growth third layer N-type doped layer;
(5) when after the epitaxy time reaching setting, stop growing, continue to pass into hydrogen at reaction chamber, substrate slice is lowered the temperature in the hydrogen gas stream;
(6) when temperature is reduced to after below 700 DEG C, again reaction chamber is evacuated, is then slowly filled with argon gas, make substrate slice naturally cool to room temperature under ar gas environment.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108166056A (en) * | 2018-01-16 | 2018-06-15 | 李哲洋 | A kind of growing method that can effectively reduce silicon carbide epitaxy surface defect |
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2014
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Patent Citations (7)
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| US20060008661A1 (en) * | 2003-08-01 | 2006-01-12 | Wijesundara Muthu B | Manufacturable low-temperature silicon carbide deposition technology |
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Application publication date: 20141224 |