CN104157703A - Trench floating junction silicon carbide SBD device with duplex metal - Google Patents

Abstract

The present invention relates to a kind of trench type floating junction silicon carbide SBD device with double metal, it is characterized in that, it comprises low potential barrier metal, high potential barrier metal, SiO ₂ isolation medium, trench, primary ^N- epitaxial layer, P ⁺ ion implantation area, secondary N ^- epitaxial layer, N ⁺ substrate area and ohmic contact area, the P + ion implantation area is on the surface of the secondary N ^- epitaxial layer, the groove is aligned up and down with the P ⁺ ion implantation area, and the shape same. The invention has a bimetal trench-type floating junction silicon carbide SBD device, which not only has the advantages of large bimetallic silicon carbide SBD Schottky contact area and low reverse leakage current, but also has the advantages of a floating junction silicon carbide SBD breakdown voltage Big plus.

Description

Trench floating junction silicon carbide SBD device with bimetal

technical field

The invention relates to the technical field of microelectronics, in particular to a trench type floating junction silicon carbide SBD device with double metals.

Background technique

Semiconductor materials have made great leaps in the past few decades. Wide bandgap semiconductor materials are the third-generation semiconductor materials represented by materials such as silicon carbide and gallium nitride. Among them, silicon carbide materials are especially famous. Silicon carbide materials In the 1980s and 1990s, it began to enter people's research sight, and it has developed rapidly in the past ten years. Silicon carbide technology has gradually matured and entered the market, and many silicon carbide technologies have been industrialized. Silicon carbide material has better electrical properties than Si, which makes it very suitable for high voltage, high power and high frequency fields. And its development pace has surpassed other wide bandgap semiconductors, and it has wider applications than other wide bandgap semiconductors.

The SiC material has a large band gap, which can reach more than 3eV. The critical breakdown electric field can reach more than 2MV/cm. SiC material has high thermal conductivity (about 4.9W/cm.K), and the device is resistant to high temperature, which is more suitable for high-current devices than Si. SiC carrier lifetime is short, only a few nanoseconds to hundreds of nanoseconds. The radiation resistance of SiC materials is also excellent, and the electron-holes introduced by radiation are much less than Si materials. Therefore, the excellent physical properties of SiC make SiC devices widely used in aerospace electronics, high-temperature radiation harsh environments, military electronic wireless communications, radar, automotive electronics, high-power phased array mines, radio frequency RF and other fields, and in the future The field of new energy has extremely good application prospects.

The floating junction structure can nearly double the breakdown voltage of devices under the same doping concentration. SiC floating junction devices have been successfully fabricated for the first time in the laboratory by T Hatakeyama et al. Schottky diodes are widely used in power devices due to their low voltage drop and high current. In order to achieve greater current, someone proposed a SiC trench Schottky diode (TSBD) in the 1990s. Trench Schottky diodes greatly increase the area of the Schottky contact, enabling lower voltage drop and higher current.

However, the floating junction silicon carbide Schottky diode (SiC FJ-SBD), the buried layer introduced in the epitaxial layer of the device, narrows the conductive channel of the forward conduction current, and the forward conduction current of the device becomes smaller. However, the trench corners of the trench SiC SBD lead to the introduction of a peak electric field under the action of the reverse voltage, which reduces the breakdown voltage of the device. The reverse leakage current of SiC SBD based on the field emission model mechanism increases, the lower the potential barrier, the larger the electric field, and the higher the reverse leakage current.

In view of the above-mentioned defects, the author of the present invention has finally obtained this creation through long-term research and practice.

Contents of the invention

The object of the present invention is to provide a trench-type floating junction silicon carbide SBD device with double metals to overcome the above-mentioned technical defects.

To achieve the above object, the present invention provides a trench type floating junction silicon carbide SBD device with double metal, which includes low barrier metal, high barrier metal, SiO ₂ isolation medium, trench, primary N ^- epitaxial layer, P ⁺ ion implantation area, secondary N ^- epitaxial layer, N ⁺ substrate area and ohmic contact area,

The P+ ion implantation region is on the surface of the secondary ^N- epitaxial layer, the groove is aligned up and down with the P ⁺ ion implantation region, and has the same shape, the high potential barrier metal is in the trench region on the device surface, and the low potential The barrier metal is in the non-trench region of the device surface.

Further, the groove has the same shape and area as the P ⁺ ion implantation region, and the groove is aligned with the edge of the bulk P ⁺ ion implantation region below the groove.

Further, the Schottky contact formed by the high barrier metal is located in the trench area on the device surface, and the Schottky contact formed by the low barrier metal is located in the non-trench area on the device surface.

Further, the depth of the groove is 1-3 μm.

Further, the doping concentration of the P ⁺ ion implantation region is 1×10 ¹⁷ cm ⁻³ to 1×10 ¹⁹ cm ⁻³ , and the thickness is 0.4˜0.6 μm.

Furthermore, the thickness of the uppermost end and the bottom of the ^N- epitaxial layer is 20 μm, the doping concentration thereof is 1×10 ¹⁵ cm ^-3 to 1×10 ¹⁶ cm ^-3 , and the thickness of the primary N ^- epitaxial layer is 5-15 μm.

Compared with the prior art, the beneficial effect of the present invention is that: the bimetallic trench type floating junction silicon carbide SBD device of the present invention has a large contact area of the trench type silicon carbide SBD Schottky and a large forward conduction current The advantages of the floating junction silicon carbide SBD have the advantages of a large breakdown voltage.

The device provided by the invention introduces a bimetallic structure, and under reverse bias, the peak electric field at the groove is borne by the high potential barrier Schottky contact, and the reverse leakage current is lower.

The device provided by the invention has the advantages of short switching time, high temperature resistance, strong radiation resistance, etc., and can be widely used in the field of power electronics.

Description of drawings

Figure 1a is a schematic cross-sectional view of a trench type floating junction silicon carbide SBD device with a bimetal in the present invention;

Fig. 1b is a top view of a trench type floating junction silicon carbide SBD device with a double metal in the present invention;

Fig. 2 is the top view of the primary N ^- epitaxial layer of the trench type floating junction silicon carbide SBD device with double metal in the present invention;

Detailed ways

The above and other technical features and advantages of the present invention will be described in more detail below in conjunction with the accompanying drawings.

Please refer to Fig. 1a, the device structure adopted by the trench type floating junction silicon carbide SBD device of the present invention includes: low barrier metal 1, high barrier metal 2, SiO ₂ isolation medium 3, trench 4, primary N ^- epitaxial layer 5, P ⁺ ion implantation area 6, secondary N ^- epitaxial layer 7, N ⁺ substrate area 8, ohmic contact area 9.

The N ⁺ substrate 8 is an N-type SiC substrate sheet, and the primary N ⁻ epitaxial layer 5 is located on the N + substrate 8 with a thickness of 5-15 μm, wherein the doping concentration of nitrogen ions is 1×10 ¹⁵ cm ^{− 3} ~ 1x10 ¹⁶ cm ^-3 .

The P ⁺ ion implantation region 6 is located on the surface of the primary N ^- epitaxial layer 5, the doping concentration is 1x10 ¹⁷ cm ^-3 ~ 1x10 ¹⁹ cm ^-3 , the ion implantation depth is 0.4 ~ 0.6 μm, and the secondary N ^- epitaxial layer 7 is located Above the primary N ^- epitaxy 5, the thickness is 5-15 μm and the doping concentration is 1x10 ¹⁵ cm ^-3 -1x10 ¹⁶ cm ^-3 . The total thickness of the primary N ^- epitaxial layer 5 and the secondary N ^- epitaxial layer 7 is 20 μm.

Referring to FIG. 1b , the low barrier metal 1 and the SiO ₂ isolation dielectric 3 are located above the secondary ^N- epitaxial layer 7 . The low-barrier metal 1 is adjacent to the SiO ₂ isolation dielectric 3 , and the metal and the SiO ₂ isolation dielectric 3 overlap 13 . The trench 4 has a depth of 1-3 μm and is located under the high barrier metal 1 . The trench 4 and the low barrier metal 1 are provided with an overlap 14 on the surface of the secondary N ⁻ epitaxial layer 7 .

Referring to Fig. 1a, Fig. 1b and Fig. 2, the trench 4 and the P ⁺ ion implantation region 6 have the same shape, are aligned up and down, and have the same area. When the device is under high reverse bias, the peak electric field at the corner of the trench 4 is aligned with the peak electric field at the corner of the P ⁺ ion implantation region 6, and the primary ^N- epitaxial layer 5 and the secondary N ^- epitaxial layer 7 effectively share the reverse With bias, the breakdown voltage of the device increases. At the same time, the peak electric field at the corner of the trench 4 is borne by the Schottky contact with a high potential barrier, and the reverse leakage current of the device can be effectively reduced. When the device is in the forward conduction state, the low barrier Schottky contact in the non-trench 4 region and the conductive channel in the non-P ⁺ ion implantation region 6 are aligned up and down, the turn-on voltage of the device is very small, and the forward current is effectively increased. big.

Embodiment one:

Referring to Fig. 1a, Fig. 1b and Fig. 2, the structure of the trench type floating junction silicon carbide SBD device with bimetal in the present invention is as follows:

The N ⁺ substrate is an N-type SiC substrate, the primary ^N- epitaxial layer is located on the N ⁺ substrate, the P ⁺ ion implantation area is located on the surface of the primary ^N- epitaxial layer, and the secondary ^N- epitaxial layer is located above the primary N ^- epitaxial layer .

The low barrier metal, the high barrier metal and the SiO ₂ isolation medium are located above the secondary N ^- epitaxial layer, the low barrier metal is adjacent to the SiO ₂ isolation medium, and the low barrier metal and the SiO ₂ isolation medium overlap place. The trench is located below the high barrier metal, secondary to the surface of the N ^- epi layer.

The thickness of the primary N ^- epitaxial layer is 15 μm, and the doping concentration of nitrogen ions is 1×10 ¹⁶ cm ^-3 . The doping concentration of the P ⁺ ion implantation region is 7×10 ¹⁷ cm ^-3 , and the ion implantation depth is 0.6 μm. The thickness of the secondary N ^- epitaxial layer is 5μm and the doping concentration is 1x10 ¹⁶ cm ^-3 .

The depth of the groove was 1 μm.

The trenches in the Schottky contact region have the same shape as the P ⁺ ion implantation region, aligned up and down.

Embodiment two:

Referring to Fig. 1a, Fig. 1b and Fig. 2, the structure of the trench type floating junction silicon carbide SBD device with bimetal in the present invention is as follows:

The N ⁺ substrate is an N-type SiC substrate, the primary ^N- epitaxial layer is located on the N ⁺ substrate, the P ⁺ ion implantation area is located on the surface of the primary ^N- epitaxial layer, and the secondary ^N- epitaxial layer is located above the primary N ^- epitaxial layer .

The low barrier metal, the high barrier metal and the SiO ₂ isolation medium are located above the secondary N ^- epitaxial layer, the low barrier metal is adjacent to the SiO ₂ isolation medium, and the low barrier metal and the SiO ₂ isolation medium overlap place. The trench is located below the high barrier metal, secondary to the surface of the N ^- epi layer.

The thickness of the primary N ^- epitaxial layer is 10 μm, and the doping concentration of nitrogen ions is 5x10 ¹⁵ cm ^-3 . The doping concentration of the P ⁺ ion implantation region is 3×10 ¹⁸ cm ^-3 , and the ion implantation depth is 0.5 μm. The thickness of the secondary N ^- epitaxial layer is 10μm and the doping concentration is 5x10 ¹⁵ cm ^-3 .

The depth of the groove is 2 μm.

The trenches in the Schottky contact region have the same shape as the P ⁺ ion implantation region, aligned up and down.

Embodiment three:

Referring to Fig. 1a, Fig. 1b and Fig. 2, the structure of the trench type floating junction silicon carbide SBD device with bimetal in the present invention is as follows:

The N ⁺ substrate is an N-type SiC substrate, the primary ^N- epitaxial layer is located on the N ⁺ substrate, the P ⁺ ion implantation area is located on the surface of the primary ^N- epitaxial layer, and the secondary ^N- epitaxial layer is located above the primary N ^- epitaxial layer .

The low barrier metal, the high barrier metal and the SiO ₂ isolation medium are located above the secondary N ^- epitaxy layer, the low barrier metal is adjacent to the SiO ₂ isolation medium, and the low barrier metal overlaps with the SiO ₂ isolation medium place. The trench is located below the high barrier metal, secondary to the surface of the N ^- epi layer.

The thickness of the primary N ^- epitaxial layer is 5 μm, and the doping concentration of nitrogen ions is 3x10 ¹⁵ cm ^-3 . The doping concentration of the P ⁺ ion implantation region is 1×10 ¹⁹ cm ^-3 , and the ion implantation depth is 0.4 μm. The thickness of the secondary N ^- epitaxial layer is 15μm and the doping concentration is 3x10 ¹⁵ cm ^-3 .

The depth of the groove was 3 μm.

The trenches in the Schottky contact region have the same shape as the P ⁺ ion implantation region, aligned up and down.

The above descriptions are only preferred embodiments of the present invention, and are only illustrative rather than restrictive to the present invention. Those skilled in the art understand that many changes, modifications, and even equivalents can be made within the spirit and scope defined by the claims of the invention, but all will fall within the protection scope of the present invention.

Claims (6)

1. have a bimetallic plough groove type floating junction carborundum SBD device, it is characterized in that, it comprises low barrier metal, high barrier metal, SiO ₂spacer medium, groove, a N ^-epitaxial loayer, P ⁺ion implanted region, secondary N ^-epitaxial loayer, N ⁺substrate zone and ohmic contact regions,

Described P+ ion implanted region is in secondary N ^-the surface of epitaxial loayer, groove and P ⁺ion implanted region consistency from top to bottom, shape is identical, the trench area of described high barrier metal in device surface, the non-trench area of described low barrier metal in device surface.

2. according to claim 1 have a bimetallic plough groove type floating junction carborundum SBD device, it is characterized in that described groove and P ⁺ion implanted region shape is identical, and area equates, and the groove P of beneath trenches therewith ⁺the justified margin of ion implanted region.

3. according to claim 1 have a bimetallic plough groove type floating junction carborundum SBD device, it is characterized in that, the trench area of the Schottky contacts that described high barrier metal forms in device surface, the non-trench area of the Schottky contacts that low barrier metal forms in device surface

4. according to claim 1 have a bimetallic plough groove type floating junction carborundum SBD device, it is characterized in that, the degree of depth of described groove is 1～3 μ m.

5. according to claim 1 have a bimetallic plough groove type floating junction carborundum SBD device, it is characterized in that P ⁺the doping content of ion implanted region is 1x10 ¹⁷cm ^-3～1x10 ¹⁹cm ^-3, thickness is 0.4～0.6 μ m.

6. according to claim 1 have a bimetallic plough groove type floating junction carborundum SBD device, it is characterized in that, described N-epitaxial loayer is topmost 20 μ m to the thickness of bottom surface, and wherein doping content is 1x10 ¹⁵cm ^-3～1x10 ¹⁶cm ^-3, a N ^-the thickness of epitaxial loayer is 5～15 μ m.