CN104867818A - Method for reducing defects of silicon carbide epitaxial material - Google Patents

Abstract

The invention discloses a method for reducing defects in silicon carbide epitaxial materials, which relates to the technical field of semiconductor devices; it includes the following steps: (1) Substrate preparation: select a silicon carbide substrate and perform standard cleaning on it for use; (2) Preliminary Epitaxial growth: Preliminary epitaxial growth of a thinner epitaxial layer on a silicon carbide substrate by chemical vapor deposition; (3) In-situ annealing: cut off the epitaxial growth source, vacuumize the reaction chamber of the equipment, at 1650 ° C ~ 2000 ° C , performing annealing treatment on the sample after step (2) epitaxy; (4) re-epitaxy growth: performing re-epitaxial growth on the sample after step (3) annealing, to the required thickness. The invention can significantly reduce the residual stress in the epitaxial layer, effectively reduce the propagation of defects in the epitaxial layer by the substrate, and obtain high-quality silicon carbide epitaxial materials with low defect density.

Description

A method for reducing defects in silicon carbide epitaxial material

technical field

The invention relates to the technical field of semiconductor devices.

Background technique

Compared with traditional semiconductor materials represented by silicon and gallium arsenide, silicon carbide (SiC), as a wide bandgap semiconductor material, has outstanding advantages such as high thermal conductivity, high breakdown electric field, high saturation electron drift rate and high bonding energy. , its excellent performance can meet the requirements of modern electronic technology for high temperature, high frequency, high power and radiation resistance.

The quality and surface of silicon carbide bulk materials cannot meet the requirements of direct manufacturing devices, while the silicon carbide epitaxial layer grown epitaxially on the surface of SiC wafer has higher quality, its electrical performance is better than that of SiC wafer, and its concentration can be Better control and repeatability. There are many methods for epitaxial growth of silicon carbide, among which the chemical vapor deposition (CVD) growth technology has become a widely used method for mass production of SiC epitaxial films due to its advantages of good repeatability, good film quality and relatively high production efficiency. method. During the epitaxial process, some dislocation defects in the SiC substrate will extend to the epitaxial layer, so there are still several kinds of dislocation defects in the SiC epitaxial material. Crystalline defects in the material body can also lead to surface morphology defects on the surface of the SiC epitaxial layer, such as "triangle" defects, "carrot" defects, etc.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for reducing defects in silicon carbide epitaxial materials, which can significantly reduce the residual stress in the epitaxial layer, effectively reduce the propagation of defects in the epitaxial layer by the substrate, and obtain high-quality silicon carbide with low defect density epitaxial material.

In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is:

A method for reducing defects in silicon carbide epitaxial materials, comprising the steps of:

(1) Substrate preparation: select the silicon carbide substrate and perform standard cleaning on it for use;

(2) Preliminary epitaxial growth: Preliminary epitaxial growth of a thinner epitaxial layer on a silicon carbide substrate by chemical vapor deposition;

(3) In-situ annealing: cut off the epitaxial growth source, evacuate the reaction chamber of the equipment, and anneal the sample after the epitaxy in step (2) at 1650-2000 ° C;

(4) Re-epitaxial growth: Re-epitaxial growth is performed on the annealed sample in step (3) to the required thickness.

In a further technical solution, the thinner epitaxial layer initially grown in step (2) has a thickness of 1 μm to 10 μm.

In a further technical solution, the epitaxial growth temperature in the step (2) or step (4) is 1300°C-1650°C, the epitaxial growth pressure is 100mbar-900mbar, and the flow rate of hydrogen carrier gas is 5 slm-60slm.

A further technical solution, the annealing time in the step (3) is 0.5h-5h.

In a further technical solution, the epitaxial growth time in the step (2) is 1 min to 60 min.

As a further technical solution, in the step (4), when the epitaxy rate is high, different flow rates of HCl gas are added to reduce contamination of the epitaxial wafer by impurities.

In a further technical solution, the carbon growth source in the step (2) or step (4) is one or a combination of propane, ethylene, and methylene chloride.

In a further technical solution, the silicon growth source in step (2) or step (4) is one or a combination of silane, dichlorosilane, and trichlorosilane.

In a further technical solution, in the step (2) or step (4), the N-type doping source is nitrogen, and the P-type doping source is trimethylaluminum.

In a further technical solution, the P-type dopant source in the step (2) or step (4) is trimethylaluminum.

The beneficial effect produced by adopting the above-mentioned technical solution is that the present invention first performs preliminary epitaxial growth to grow a thinner epitaxial layer, and then heats the epitaxial film to a high temperature under vacuum conditions for annealing, and the atoms in it can be diffused and rearranged. As a result, the movement of dislocations is induced, thereby reducing the residual stress in the SiC material, and effectively reducing the defects in the epitaxial layer propagated by the substrate; after growing a thinner epitaxial layer and annealing treatment, re-epitaxy grows to the required thickness to avoid The defects in the bottom extend to the epitaxial layer, so as to obtain high-quality silicon carbide epitaxial materials with low defect density.

Description of drawings

Fig. 1 is a schematic diagram of the heating curve of the present invention.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Example 1:

(1) Substrate preparation, select a 4-inch (0001) silicon-surface silicon carbide substrate with a 4° deviation from the <11-20> direction, and perform standard cleaning on it for use.

(2) Put the silicon carbide substrate into the reaction chamber of the CVD equipment and evacuate to <5×10 ^-6 mbar.

(3) Preliminary epitaxial growth: under the conditions of carrier gas hydrogen flow rate of 60slm and pressure of 100mbar, the temperature was raised to 1600°C, the flow rate of silane growth source was 15 sccm, the flow rate of propane growth source was 5 sccm, the epitaxial growth time was 10 min, and the flow rate of doped nitrogen gas was 50 sccm.

(4) In-situ annealing: cut off the epitaxial growth source, vacuumize the chamber of the CVD equipment, raise the temperature to 1700°C and keep it for 1 hour, and anneal the sample after the epitaxy in step (2).

(5) Re-epitaxial growth: For the annealed sample in step (3), naturally cool down to the epitaxial growth temperature for re-epitaxial growth. The epitaxial growth temperature was 1600°C, the epitaxial growth pressure was 100 mbar, the carrier gas hydrogen flow rate was 60 slm, the silane flow rate was 30 sccm, the propane flow rate was 10 sccm, and the epitaxial growth time was 120 min to obtain thick SiC epitaxial materials.

Example 2:

(1) Substrate preparation, select a 4-inch (000-1) carbon-faced silicon carbide substrate with an angle of 8° to the <11-20> direction, and perform standard cleaning on it for use.

(2) Put the silicon carbide substrate into the reaction chamber of the CVD equipment and evacuate to <5×10 ^-6 mbar.

(3) Preliminary epitaxial growth: under the conditions of carrier gas hydrogen flow rate of 60slm and pressure of 100mbar, the temperature was raised to 1600°C, the flow rate of silane growth source was 30 sccm, the flow rate of propane growth source was 10 sccm, the epitaxial growth time was 20 min, and the flow rate of doped nitrogen gas was 200 sccm.

(4) In-situ annealing: cut off the epitaxial growth source, vacuumize the chamber of the CVD equipment, raise the temperature to 1800°C and keep it for 0.5h, and anneal the sample after the epitaxy in step (2).

(5) Re-epitaxial growth: the annealed sample in step (3) is naturally cooled to the epitaxial growth temperature, and then re-epitaxial growth is performed. The epitaxial growth temperature was 1600°C, the epitaxial growth pressure was 100 mbar, the flow rate of carrier gas hydrogen was 60 slm, the flow rate of silane was 90 sccm, the flow rate of propane was 30 sccm, the flow rate of HCl was 300 sccm, and the epitaxial growth time was 180 min to obtain a thick SiC epitaxial material.

Example 3:

(1) Substrate preparation, select a 4-inch (0001) silicon-surface silicon carbide substrate with a 4° deviation from the <11-20> direction, and perform standard cleaning on it for use.

(2) Put the silicon carbide substrate into the reaction chamber of the CVD equipment and evacuate to <5×10 ^-6 mbar.

(3) Preliminary epitaxial growth: under the conditions of carrier gas hydrogen flow rate of 5 slm and pressure of 100 mbar, the temperature was raised to 1300 °C, the flow rate of silane growth source was 15 sccm, the flow rate of propane growth source was 5 sccm, the epitaxial growth time was 60 min, and the flow rate of doped nitrogen gas was 50 sccm.

(4) In-situ annealing: Cut off the epitaxial growth source, vacuumize the chamber of the CVD equipment, raise the temperature to 1650°C and keep it for 0.5h, and anneal the sample after the epitaxy in step (2).

(5) Re-epitaxial growth: For the annealed sample in step (3), naturally cool down to the epitaxial growth temperature for re-epitaxial growth. The epitaxial growth temperature was 1300°C, the epitaxial growth pressure was 100 mbar, the flow rate of carrier gas hydrogen was 5 slm, the flow rate of silane was 30 sccm, the flow rate of propane was 10 sccm, and the epitaxial growth time was 120 min to obtain a thick SiC epitaxial material.

Example 4:

(1) Substrate preparation, select a 4-inch (0001) silicon-surface silicon carbide substrate with a 4° deviation from the <11-20> direction, and perform standard cleaning on it for use.

(2) Put the silicon carbide substrate into the reaction chamber of the CVD equipment and evacuate to <5×10 ^-6 mbar.

(3) Preliminary epitaxial growth: under the conditions of carrier gas hydrogen flow rate of 60slm and pressure of 100mbar, the temperature was raised to 1650°C, the flow rate of silane growth source was 15 sccm, the flow rate of propane growth source was 5 sccm, the epitaxial growth time was 60 min, and the flow rate of doped nitrogen gas was 50 sccm.

(4) In-situ annealing: Cut off the epitaxial growth source, evacuate the chamber of the CVD equipment, raise the temperature to 2000°C and keep it for 5 hours, and anneal the sample after the epitaxy in step (2).

(5) Re-epitaxial growth: For the annealed sample in step (3), naturally cool down to the epitaxial growth temperature for re-epitaxial growth. The epitaxial growth temperature was 1650°C, the epitaxial growth pressure was 100 mbar, the flow rate of carrier gas hydrogen was 60 slm, the flow rate of silane was 30 sccm, the flow rate of propane was 10 sccm, and the epitaxial growth time was 120 min to obtain a thick SiC epitaxial material.

As shown in Figure 1, a schematic diagram of the heating curve of a method for reducing defects in silicon carbide epitaxial materials. During epitaxial growth, the growth temperature is 1300°C to 1650°C, and after epitaxial growth, the temperature is raised to 1650°C to 2000°C for in-situ annealing , so that the atoms in the epitaxial layer are diffused and rearranged, causing the movement of dislocations, reducing the residual stress in the SiC material, and then re-epitaxial growth. The invention can effectively reduce the defects in the substrate propagation epitaxial layer, and obtain high-quality silicon carbide epitaxial materials with low defect density.

Claims (10)

1. reduce a method for silicon carbide epitaxy material defect, it is characterized in that comprising the steps:

(1) substrate prepares: choose silicon carbide substrates, carries out standard cleaning stand-by to it;

(2) preliminary epitaxial growth: carry out preliminary epitaxial growth comparatively thin epitaxial layer with chemical vapour deposition technique on silicon carbide substrates;

(3) in-situ annealing: cut off epitaxial growth source, equipment reaction chamber is vacuumized, under 1650 DEG C ~ 2000 DEG C conditions, annealing in process is carried out to the sample delayed outside step (2);

(4) epitaxial growth again: to the sample after step (3) annealing, carry out epitaxial growth again, to desired thickness.

2. a kind of method reducing silicon carbide epitaxy material defect according to claim 1, is characterized in that the thickness compared with thin epitaxial layer of preliminary growth in step (2) is 1 μm ~ 10 μm.

3. a kind of method reducing silicon carbide epitaxy material defect according to claim 1, it is characterized in that the epitaxial growth temperature in described step (2) or step (4) is 1300 DEG C ~ 1650 DEG C, epitaxial growth pressure is 100 mbar ~ 900mbar, and carrier gas throughput is 5 slm ~ 60slm.

4. a kind of method reducing silicon carbide epitaxy material defect according to claim 1, is characterized in that the annealing time in described step (3) is 0.5h ~ 5h.

5. a kind of method reducing silicon carbide epitaxy material defect according to claim 1, is characterized in that epitaxial growth time 1min ~ 60min in described step (2).

6. a kind of method reducing silicon carbide epitaxy material defect according to claim 1, is characterized in that the HCl gas adding different flow in described step (4) when extension speed is higher.

7. a kind of method reducing silicon carbide epitaxy material defect according to claim 1, is characterized in that carbon growth source in described step (2) or step (4) is propane, ethene, the one of monochloro methane or combination.

8. a kind of method reducing silicon carbide epitaxy material defect according to claim 1, is characterized in that silicon growth source in described step (2) or step (4) is silane, dichlorosilane, the one of trichlorosilane or combination.

9. a kind of method reducing silicon carbide epitaxy material defect according to claim 1, is characterized in that in described step (2) or step (4), N-type doped source is nitrogen.

10. a kind of method reducing silicon carbide epitaxy material defect according to claim 1, is characterized in that in described step (2) or step (4), P type doped source is trimethyl aluminium.