CN104131335A - Doping source flow control N-type heavily-doped silicon carbide film epitaxial making method - Google Patents

Abstract

The invention relates to a doping source flow control N-type heavily-doped silicon carbide film epitaxial making method. The making method comprises the following steps: 1, placing a silicon carbide substrate in a reaction chamber of a silicon carbide CVD apparatus, and vacuumizing the reaction chamber; 2, introducing H2 to the reaction chamber until the pressure in the reaction chamber reaches 100mbar, maintaining the pressure in the reaction chamber unchanged, gradually increasing the H2 flow to 60L/min, and continuously introducing H2 to the reaction chamber; 3, starting a high frequency coil induction heater RF, gradually increasing the power of the heater, and carrying out in situ etching when the temperature of the reaction chamber gradually rises to 1400DEG C; and 4, maintaining the temperature and the pressure unchanged when the temperature of the reaction chamber reaches 1580-1600DEG C, introducing C3H8 and SiH4 to the reaction chamber, introducing highly pure N2 to the reaction chamber as an N-type doping source, stopping the introduction of SiH4, C3H8 and highly pure N2 to the reaction chamber and maintaining for 1min after a first-layer N-type doping layer grows, adjusting the flow of the highly pure N2, and continuously introducing SiH4, C3H8 and the highly pure N2 to the reaction chamber to grow a second-layer N-type doping layer.

Description

A kind of controlled doping source flux N-type heavy doping carborundum films epitaxial preparation method

Technical field

The invention belongs to semiconductor device processing technology field, relate in particular 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 disruptive strength, high electronics saturation drift velocity, high hardness, also has very strong chemical stability.The physics that these are good and electric property make silicon carbide have a lot of advantages in application.The wide silicon carbide intrinsic carrier that makes in forbidden band at high temperature still can keep lower concentration, thereby can be operated at very high temperature.High breaking down field strength makes silicon carbide can bear high strength of electric field, this make silicon carbide can for make high pressure, high-power semiconducter device.High heat conductance makes silicon carbide have good thermal diffusivity, contribute to improve the power density of device and integrated level, the attached cooling infrastructure of minimizing, thereby the volume and weight that makes system reduces widely, efficiency improves widely, and 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 can be for radio frequency or microwave device, thereby improves device working speed.

The carrier concentration of carbofrax material is the basic electricity parameter of materials and devices.This parameter realizes by material doped control.Therefore, the doping of silicon carbide epitaxy material is one of 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, can only utilize extension controlled doping and high temperature ion implantation doping.The membership of high temperature implantation causes a large amount of lattice damages, forms a large amount of lattice imperfections, 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, thereby is not suitable for doing big area doping.Meanwhile, in the time of the semiconducter device of some multilayered structures of preparation, need the gradient of the longitudinal doping content of epitaxial film controlled.Only have by reasonable adjustment growth parameter(s), growing adulterates reaches the epitaxial film of pre-provisioning request, just can produce the satisfactory device of performance, thereby the grade doping control of silicon carbide epitaxial layers is a very large difficult point during current device is manufactured.

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 controlled silicon carbide epitaxial layers of longitudinal doping content gradient, met 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) pass into H to 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 gradually the power of this well heater, carry out original position etching when reaction chamber temperature rising gradually to 1400 DEG C;

(4) in the time that 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 finishes, stop passing into SiH to reaction chamber ₄, C ₃h ₈and high-purity N ₂and keep 1min, adjust high-purity N therebetween ₂flow.Continue afterwards to pass into SiH to reaction chamber ₄, C ₃h ₈and high-purity N ₂growth second layer N-type doped layer.

(5) when reaching after the epitaxy time of setting, stop growing, continue to pass into hydrogen at reaction chamber, substrate slice is lowered the temperature in hydrogen stream;

(6) after temperature is reduced to 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, the aluminium nuclear power mixing is effectively replaced C atom in carbofrax material, forms substitutional impurity, with respect to ion implantation technology, and the heavy doping carbofrax material lattice perfection of preparation, defect is few, is conducive to improve device performance.

2. the present invention adopts the CVD epitaxial device of silicon carbide, carbonization substrate at silicon carbide substrates or existing epitaxial film carries out extension, by the longitudinal doping content of growth parameter(s) control, the N-type epitaxial film of the different heavy dopant concentration of can growing continuously, simplifies the preparation technology of device.

Brief description of the drawings

By describing in more detail exemplary embodiment of the present invention with reference to accompanying drawing, above and other aspect of the present invention and advantage will become more and be readily clear of, in the accompanying drawings:

Fig. 1 is the process flow sheet of technical solution of the present invention.

Embodiment

Hereinafter, now with reference to accompanying drawing, the present invention is described more fully, 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, it will be thorough with completely providing these embodiment to make the disclosure, 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 provide two kinds of embodiment.

Embodiment 1

Step 1, is placed into silicon carbide substrates in the reaction chamber of silicon carbide CVD equipment.

(1.1) choose deflection the 4H silicon carbide substrates that crystal orientation is 4 °, 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, reacting by heating chamber in hydrogen stream.

(2.1) open the hydrogen switch that leads to reaction chamber, control hydrogen flowing quantity and increase to gradually 60L/min;

(2.2) open the gas of vacuum pump abstraction reaction chamber, keep reaction chamber air pressure at 100mbar;

(2.3) tune up gradually heating source power, reaction chamber temperature is slowly raise.

Step 3, carries out original position etching to substrate.

(3.1), when reaction chamber temperature reaches after 1400 DEG C, 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), when reaction chamber temperature reaches at 1580 DEG C, keep reaction chamber temperature and invariablenes pressure of liquid;

(4.3) open C ₃h ₈, SiH ₄and high-purity N ₂switch, in reaction chamber, pass into the C that flow is 7mL/min ₃h ₈, the flow SiH that is 21mL/min ₄with the flow high-purity N that is 1000mL/min ₂, starting growing silicon carbide epitaxial film N1, growth time is 20min.Close afterwards C ₃h ₈, SiH ₄and high-purity N ₂switch 1min, therebetween by high-purity N ₂flow set is 2000mL/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, the flow SiH that is 21mL/min ₄with the flow high-purity N that is 2000mL/min ₂, starting growing silicon carbide epitaxial film N2, growth time is 20min.

Step 5, cooling substrate in hydrogen stream.

(5.1) after epitaxial film N2 growth finishes, close C ₃h ₈, SiH ₄and high-purity N ₂switch, stop growing;

(5.2) hydrogen flowing quantity that leads to reaction chamber being set is 20L/min, and keeping reaction chamber air pressure is 100mbar, makes the long substrate cooling 25min in hydrogen stream that has silicon carbide epitaxial layers;

(5.3) reaction chamber air pressure is elevated to 700mbar, in hydrogen stream, continues cooling.

Step 6, cooling substrate in argon gas.

(6.1) when reaction chamber temperature is reduced to after 700 DEG C, close the hydrogen switch that leads to reaction chamber;

(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 under ar gas environment, to continue cooling 30min;

(6.4) slowly improve reaction chamber air pressure to normal pressure, make substrate naturally cool to room temperature, take out silicon carbide epitaxy sheet.

Embodiment 2

Step 1, is placed into silicon carbide substrates in the reaction chamber of silicon carbide CVD equipment.

(1.1) choose deflection the 4H silicon carbide substrates that crystal orientation is 8 °, 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, reacting by heating chamber in hydrogen stream.

(2.1) open the hydrogen switch that leads to reaction chamber, control hydrogen flowing quantity and increase to gradually 60L/min;

(2.2) open the gas of vacuum pump abstraction reaction chamber, keep reaction chamber air pressure at 100mbar;

(2.3) tune up gradually heating source power, reaction chamber temperature is slowly raise.

Step 3, carries out original position etching to substrate.

(3.1) when reaction chamber temperature reaches after 1400 DEG C, in reaction chamber, pass into the C that flow is 7mlL/min 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), when reaction chamber temperature reaches at 1580 DEG C, keep reaction chamber temperature and invariablenes pressure of liquid;

(4.3) open SiH ₄and high-purity N ₂switch, in reaction chamber, pass into the SiH that flow is 21mL/min ₄with the flow high-purity N that is 1000mL/min ₂, starting growing silicon carbide epitaxial film N1, growth time is 20min.Close afterwards C ₃h ₈, SiH ₄and high-purity N ₂switch 1min, therebetween by high-purity N ₂flow set is 2000mL/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, the flow SiH that is 21mL/min ₄with the trimethyl aluminium that flow is 2000mL/min, start growing silicon carbide epitaxial film N2, growth time is 20min.

Step 5, cooling substrate in hydrogen stream.

(5.1) after epitaxial film N2 growth finishes, close C ₃h ₈, SiH ₄and high-purity N ₂switch, stop growing;

(5.2) hydrogen flowing quantity that leads to reaction chamber being set is 20L/min, and keeping reaction chamber air pressure is 100mbar, makes the long substrate cooling 25min in hydrogen stream that has silicon carbide epitaxial layers;

(5.3) reaction chamber air pressure is elevated to 700mbar, in hydrogen stream, continues cooling.

Step 6, cooling substrate in argon gas.

(6.1) when reaction chamber temperature is reduced to after 700 DEG C, close the hydrogen switch that leads to reaction chamber;

(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 under ar gas environment, to continue cooling 30min;

(6.4) slowly improve reaction chamber air pressure to normal pressure, make substrate naturally cool to room temperature, take out silicon carbide epitaxy sheet.

The foregoing is only embodiments of the invention, be not limited to the present invention.The present invention can have various suitable changes and variation.All any amendments of doing within the spirit and principles in the present invention, be equal to replacement, improvement etc., within protection scope of the present invention all should be included in.

Claims (1)

1. a controlled doping source flux N-type heavy doping carborundum films epitaxial preparation method, 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) pass into H to 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 gradually the power of this well heater, carry out original position etching when reaction chamber temperature rising gradually to 1400 DEG C;

(4) in the time that 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 finishes, stop passing into SiH to reaction chamber ₄, C ₃h ₈and high-purity N ₂and keep 1min, adjust high-purity N therebetween ₂flow; Continue afterwards to pass into SiH to reaction chamber ₄, C ₃h ₈and high-purity N ₂growth second layer N-type doped layer;

(5) when reaching after the epitaxy time of setting, stop growing, continue to pass into hydrogen at reaction chamber, substrate slice is lowered the temperature in hydrogen stream;

(6) after temperature is reduced to 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.