CN207868205U - A kind of silicon carbide diode device - Google Patents

Abstract

The utility model provides a silicon carbide diode device, the cell structure of which includes: an anode metal, a p-type epitaxial layer, an n-type drift layer, an n+ substrate and a cathode metal are arranged from top to bottom, and the p-type epitaxial The top of the layer is provided with a contact groove, and the bottom of the anode metal is provided with a protrusion, and the contact groove and the protrusion are matched to each other to solve the junction barrier. In the Schottky diode, due to the existence of the pn junction region, in the conduction state The effective conduction area of the device is small, leading to the problem of high on-resistance.

Description

A silicon carbide diode device

technical field

The utility model relates to a silicon carbide diode device.

Background technique

Silicon carbide is an emerging third-generation semiconductor material with good physical and electrical properties, and is widely used in the preparation of high-voltage, high-power and high-temperature radiation-resistant electronic devices. Silicon carbide Schottky diodes are the earliest commercialized silicon carbide semiconductor devices. Common commercial Schottky diodes are Schottky Barrier Diodes and Junction Barrier Schottky Diodes. .

The traditional junction barrier Schottky diode uses the space charge region of the reverse-biased PN junction to bear the reverse bias voltage for the SBD structure, so that the height of the Schottky barrier can be appropriately reduced to reduce the forward voltage while ensuring the blocking voltage. voltage drop while reducing diode reverse bias leakage. However, in the junction barrier Schottky diode, the ion-implanted junction region cannot conduct electricity, so the effective conduction area of the device is reduced, which limits the further improvement of the conduction current density of the JBS device.

Contents of the invention

The technical problem to be solved by the utility model is to provide a silicon carbide diode device to solve the problem that in the junction barrier Schottky diode, due to the existence of the pn junction region, the effective conduction area of the device in the conduction state is small, resulting in conduction High resistance problem.

The utility model is achieved in the following way: a silicon carbide diode device, the cell structure of which includes: an anode metal, a p-type epitaxial layer, an n-type drift layer, an n+ substrate and a cathode metal are arranged from top to bottom, and the The top of the p-type epitaxial layer is provided with a contact groove, and the bottom of the anode metal is provided with a protrusion, and the contact groove and the protrusion are matched with each other.

Further, the doping concentration of the n-type drift layer ranges from 2×10 ¹⁴ cm ^-3 to 1×10 ¹⁶ cm ^-3 , and the thickness of the n-type drift layer ranges from 5um to 200um.

Further, the doping concentration of the p-type epitaxial layer is greater than or equal to 1×10 ¹⁹ cm ^-3 .

Further, the thickness of the p-type epitaxial layer is 0.2um to 1um, the width of the contact groove is 4um to 16um, and the distance from the bottom of the contact groove to the top of the n-type drift layer is less than or equal to 5nm.

Further, the anode metal is Ni or Ti, and the cathode metal is Ni.

Further, the width of the anode metal is 14um to 46um.

The utility model has the advantages that: the utility model is a silicon carbide diode device, which can be applied to a wide voltage range and has good conduction characteristics and reverse recovery characteristics. The preparation process of this structure is compatible with conventional silicon carbide diode devices, because it has a larger current conduction area under the same device area;

Moreover, on the basis of conventional SBD devices, the utility model introduces a highly doped p-type anode region, so that when the device is conducting forward, the carriers can pass through the p-type region through the tunneling effect; in the reverse blocking state Next, the epitaxial pn junction is subjected to reverse bias voltage. Compared with SBD and JBS devices that use Schottky junction to withstand reverse bias voltage, the diode uses pn junction to withstand reverse bias voltage, which can reduce the leakage current in the blocking state.

Description of drawings

The utility model will be further described below in conjunction with the embodiments with reference to the accompanying drawings.

FIG. 1 is a schematic diagram of a cell structure of a silicon carbide diode device according to an embodiment of the present invention.

Fig. 2 is a flowchart of the steps of the embodiment of the utility model.

FIG. 3 is a first schematic diagram of forming a contact groove in a method for manufacturing a silicon carbide diode device provided by an embodiment of the present invention.

FIG. 4 is a second schematic diagram of forming a contact groove in a method for manufacturing a silicon carbide diode device provided by an embodiment of the present invention.

FIG. 5 is a third schematic diagram of forming a contact groove in a method for manufacturing a silicon carbide diode device provided by an embodiment of the present invention.

FIG. 6 is a fourth schematic diagram of forming contact grooves in a method for manufacturing a silicon carbide diode device provided by an embodiment of the present invention.

FIG. 7 is a flowchart of the steps of forming contact grooves in a method of manufacturing a silicon carbide diode device provided by an embodiment of the present invention.

Detailed ways

See also shown in Fig. 1, the silicon carbide diode device of the present invention, it is formed by the parallel connection of a plurality of cellular structures, and this cellular structure comprises: anode metal 4, p-type epitaxial layer 3, p-type epitaxial layer 3, n-type drift layer 2, n+ substrate 1 and cathode metal 5, the top of the p-type epitaxial layer 3 is provided with a contact groove, the bottom of the anode metal 4 is provided with a protrusion, and the contact groove and the protrusion are matched with each other , the doping concentration range of the n-type drift layer 2 is 2×10 ¹⁴ cm ^-3 to 1×10 ¹⁶ cm ^-3 , the thickness of the n-type drift layer 2 is 5um to 200um, and the p-type epitaxial layer The doping concentration of 3 is greater than or equal to 1×10 ¹⁹ cm ^-3 , the thickness of the p-type epitaxial layer 3 is 0.2um to 1um, the width of the contact groove is 4um to 16um, and the bottom of the contact groove reaches the n-type drift The distance between the top of layer 2 is less than or equal to 5nm, the anode metal 4 is Ni or Ti, the cathode metal 5 is Ni, and the width of the anode metal 4 is 14um to 46um; by changing the thickness of the p-type epitaxial layer 3, the doping concentration and the width and depth of the central contact groove can be optimized between on-resistance and blocking leakage.

The anode metal 4 is Ni/Ti, the purpose is to form an anode contact, and form a field plate structure while filling the contact groove. The length of the field plate is 5um to 15um, and the purpose is to reduce the electric field concentration at the edge of the device cell. Ni is selected as the cathode metal 5 in order to form a cathode ohmic contact.

As shown in Figure 2, the preparation method of the silicon carbide diode device of the present invention specifically comprises the following steps:

growing an n-type drift layer 2 by epitaxy on the n+ substrate 1;

growing a p-type epitaxial layer 3 on the n-type drift layer 2 by epitaxy;

forming contact grooves on the p-type epitaxial layer 3 by etching;

Deposit metal by electron beam evaporation or magnetron sputtering method, and perform contact annealing to form cathode metal 5;

The metal is deposited by electron beam evaporation or magnetron sputtering, and the anode metal 4 is formed by photolithography.

The formation of contact grooves by etching on the p-type epitaxial layer 3 is further specifically:

On the surface of the p-type epitaxial layer, by means of electron beam evaporation, a metal Ni with a thickness of 0.3um is evaporated as the etching mask layer material, and the mask layer material is photolithographically opened, and RIE etching removes the required openings. A metal Ni mask layer above the contact groove;

Prepare a companion sheet with the same thickness as the p-type epitaxial layer, and use ICP dry etching to vertically etch the companion sheet and the p-type epitaxial layer, and stop the etching until it is 50nm away from the top of the p-type epitaxial layer;

Use the concentrated sulfuric acid hydrogen peroxide mixture to remove the metal on the surface under heating conditions;

Conduct SEM observation on the companion sheet to determine the thickness of the remaining p-type epitaxial layer, and calculate the time required to oxidize the remaining 5nm thick p-type epitaxial layer in combination with the Deal–Grove model;

The p-type epitaxial layer is oxidized according to the time required for calculation to form an oxide layer, and the oxide layer is removed using BOE solution to finally form the contact groove.

Depositing the cathode metal 5 by electron beam evaporation or magnetron sputtering, and performing contact annealing is further specifically: depositing metal Ni on one side of the n+ substrate 1 by electron beam evaporation or magnetron sputtering deposition method, Under the protection of nitrogen, contact annealing is carried out, the annealing time is 2min, and the annealing temperature is 975°C. The thickness of the deposited metal can be controlled according to user requirements.

Depositing metal by means of electron beam evaporation or magnetron sputtering, forming the anode metal 4 by photolithography is further specifically: depositing 200nm metal Ni or Ti by means of electron beam evaporation or magnetron sputtering, and depositing 200nm metal Ni or Ti under the protection of nitrogen. Conduct contact annealing, the annealing time is 2min, and the annealing temperature is 500°C, the thickness of the deposited metal can be controlled according to user requirements.

Embodiment one of the utility model

The preparation method of the utility model silicon carbide diode device, described method comprises:

S1, growing an n-type drift layer 2 on an n+ substrate 1 by epitaxy;

S2, growing a highly doped p-type epitaxial layer 3 on the n-type drift layer 2 by epitaxy;

S3, on the p-type epitaxial layer 3, forming a contact groove by etching;

S4, on the back of the device, deposit the cathode metal 5 by electron beam evaporation or magnetron sputtering, and perform contact annealing;

S5. On the front side of the device, an anode metal 4 is deposited by electron beam evaporation or magnetron sputtering, and a field plate pattern is formed by photolithography.

In the step S3 shown in it, it is necessary to form a contact groove by an etching method, the bottom of which is less than 5nm from the top of the n-type drift layer 2, and the utility model provides a feasible method under the existing process conditions.

As shown in Figures 3 to 7, first, metal Ni with a thickness of 0.3um is evaporated on the surface of the wafer by electron beam evaporation as the etching mask layer material, and the mask layer material is photolithographically opened. RIE etching removes the metal Ni mask layer above the contact groove. Prepare the SiC accompanying sheet of same epitaxial structure afterwards, adopt ICP dry etching to main sheet (main sheet is the p-type epitaxial layer that the utility model makes) and accompanying sheet (being the same as p-type epitaxial layer structure and thickness) SiC used for process verification) to perform vertical etching, and the etching stops when the distance from the top of the p-type epitaxial layer 3 is about 50 nm. Then use concentrated sulfuric acid and hydrogen peroxide mixture to remove the metal on the surface under heating conditions. Next, SEM observation was carried out on the etching companion to determine the thickness of the remaining p-type epitaxial layer 3 , and the time required to oxidize the remaining 5 nmp-type epitaxial layer 3 was calculated in combination with the Deal-Grove model. Finally, the main sheet is oxidized according to the calculated conditions to form the SiO ₂ oxide layer 6, and the SiO ₂ oxide layer 6 is removed using a BOE solution to finally form the contact groove.

The step S4 uses metal Ni as the cathode ohmic contact material, and the process includes: flipping the wafer, and depositing 200nm metal Ni on the back of (1) n+ substrate 1 by electron beam evaporation, under the protection of N2 gas, Conduct contact annealing for 2 minutes at an annealing temperature of 975°C.

The step S5 needs to use the anode metal 4Ti/Ni to fill the contact groove, including: on the back of the wafer, spread the glue and harden the film to protect the formed ohmic contact on the back. Afterwards, the wafer is turned over, and the metal Ti/Ni is deposited by electron beam evaporation. After coating, photolithography, development and film hardening, metal is etched to form a field plate structure. Afterwards, under the protection of N2 gas, Schottky contact annealing was performed for 2 minutes, and the annealing temperature was 500°C.

Although the specific embodiments of the present utility model have been described above, those skilled in the art should understand that the specific embodiments we describe are only illustrative, rather than used to limit the scope of the present utility model. Equivalent modifications and changes made by those skilled in the art in accordance with the spirit of the present utility model shall fall within the protection scope of the claims of the present utility model.

Claims (6)

1. a kind of silicon carbide diode device, it is characterised in that：Its structure cell includes：Anode gold is arranged with this from top to bottom Category, p-type epitaxial layer, n-type drift layer, n+ substrates and cathodic metal, the p-type epitaxial layer top are equipped with contact groove, the sun Pole metal bottom is equipped with protrusion, and the contact groove is mutually matched with the protrusion.

2. a kind of silicon carbide diode device as described in claim 1, it is characterised in that：The doping of the n-type drift layer is dense Degree ranging from 2 × 10¹⁴cm^-3To 1 × 10¹⁶cm^-3, the thickness of the n-type drift layer is 5um to 200um.

3. a kind of silicon carbide diode device as described in claim 1, it is characterised in that：The doping of the p-type epitaxial layer is dense Degree is more than or equal to 1 × 10¹⁹cm^-3。

4. a kind of silicon carbide diode device as described in claim 1 or 3, it is characterised in that：The thickness of the p-type epitaxial layer Width for 0.2um to 1um, the contact groove is 4um to 16um, and the contact trench bottom is small to n-type drift layer distance from top In equal to 5nm.

5. a kind of silicon carbide diode device as described in claim 1, it is characterised in that：The anode metal is Ni or Ti, The cathodic metal is Ni.

6. a kind of silicon carbide diode device as described in claim 1, it is characterised in that：The width 14um of the anode metal To 46um.