A high-voltage silicon carbide photoconductive switch with opposite circular electrodes

Abstract

The present invention relates to the field of semiconductor device packaging, and in particular to a high-voltage silicon carbide photoconductive switch with eccentrically facing circular electrodes. The photoconductive switch provided by the present invention comprises a silicon carbide semi-insulating wafer, an input electrode and an output electrode. The input electrode and the output electrode are arranged eccentrically facing each other on both sides of the wafer, and a plurality of concentric circular annular grooves of different diameters are arranged around the electrodes, respectively, and a passivation layer is provided on the annular grooves. The present invention prolongs the edge distance between the input electrode and the output electrode on the wafer surface by setting the annular grooves, greatly reduces the risk of flashover breakdown along the wafer edge, reduces the field strength at the electrode edge, and improves the electric field uniformity by setting the electrodes facing each other, avoiding electric field distortion at the moment of conduction, thereby improving the voltage resistance and reliability of the photoconductive switch.

Description

Technical Field

[0001] The invention relates to the field of semiconductor device packaging, in particular to a high-voltage silicon carbide photoconductive switch with opposite circular electrodes. Background Art

[0002] Compared with traditional Si and GaAs materials, 4H-SiC has the advantages of large bandgap, high breakdown field strength, large dielectric constant and high thermal conductivity, and has a high saturated electron migration speed, making it the most suitable material for preparing ultrafast, high-power and high-temperature resistant devices. Photoconductive switches (PCSS) have the advantages of high repetition frequency, small jitter, fast switching speed, strong peak current tolerance and low loss, but conventional photoconductive switches are subject to surface flashover and high current density, and are prone to surface breakdown, resulting in performance degradation.

[0003] Chinese patent document CN200710045225.9 provides a high-voltage silicon carbide photoconductive switch, which adopts a relative surface design to multiply the voltage resistance of the switch. However, the technical solution adopted by the invention easily causes current density accumulation at the electrode, resulting in instantaneous metal semiconductor contact failure, and cannot meet the high repetition rate and long life working requirements of the device. Summary of the invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide a high-voltage silicon carbide photoconductive switch with eccentrically facing circular electrodes, specifically, comprising a semi-insulating silicon carbide chip, an input electrode and an output electrode, wherein the input electrode and the output electrode are located in opposite planes of the chip: the input electrode is located on the front side of the chip; the output electrode is located on the back side of the chip.

[0005] Furthermore, annular grooves with different diameters are arranged around the input electrode and the output electrode, and the centers of the annular grooves with different diameters are on the same axis as the centers of the input electrode and the output electrode. The circular rings with different diameters are concentric circular rings.

[0006] Furthermore, the input electrode and the output electrode are circular electrodes with the same diameter, and the centers of the input electrode, the output electrode and the center of the wafer are located on the same axis, that is, the input electrode and the output electrode are in a facing position.

[0007] Furthermore, a passivation layer is provided on the annular groove body.

[0008] Furthermore, the different diameters include inner diameters and outer diameters, the ring widths of the annular grooves of different diameters are equal, and adjacent concentric rings are arranged in an equidistant manner.

[0009] Furthermore, the ring widths of the annular grooves of different diameters are 0.3mm-0.5mm; they are arranged in an equidistant manner, specifically meaning that the shortest distance between adjacent concentric rings is 0.3mm-0.5mm.

[0010] Furthermore, the width of the annular groove body is equal to the shortest distance between adjacent concentric circular rings.

[0011] Furthermore, the size of the annular groove body is calculated by an electric field simulation optimization method.

[0012] Furthermore, the processing methods of the annular groove body include laser etching, wet etching and dry etching, and any one of them can be selected for processing and manufacturing.

[0013] Furthermore, both the input electrode and the output electrode have metal film layers on their surfaces, specifically including Ni / W film layers and alloy film layers.

[0014] Furthermore, the alloy film layer is Ta / Ti / Pd / Au, Ta / TiW / Pd / Au, Ta / TiW / Pt / Au, Ti / Pd / Au or TiW / Pt / Au.

[0015] Furthermore, the alloy film layer is Ta / Ti / Pd / Au.

[0016] Furthermore, the thickness of the Ni layer is 800-1000 Å, and the thickness of the W layer is 1500-1800 Å.

[0017] After adopting the above technical solution, compared with the prior art, the present invention is beneficial in that: by respectively setting a plurality of annular grooves of different diameters around the input electrode and the output electrode of the silicon carbide wafer, the edge distance of the input electrode and the output electrode on the wafer surface is extended, which greatly reduces the risk of flashover breakdown along the edge of the wafer, and through simulation optimization, the field strength at the edge of the wafer electrode can be effectively reduced, and the current density can be reduced. In addition, by setting the electrodes in a facing relationship, the uniformity of the electric field is improved, the electric field distortion at the moment of conduction is avoided, the withstand voltage and reliability of the photoconductive switch are improved, and the working requirements of high repetition rate and long life of the device are met. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the cross-sectional structure of the high-voltage silicon carbide photoconductive switch with opposite circular electrodes provided in the embodiment, 101 is a SiC semi-insulating wafer, S1 is an input electrode, S2 is an output electrode, 102 is a circular annular groove, 103 is a passivation layer, 104 is a Ni / W film layer, and 105 is a Ta / Ti / Pd / Au film layer;

[0019] Figure 2 A schematic diagram of a top view of the structure of a high withstand voltage silicon carbide photoconductive switch with opposite circular electrodes provided in an embodiment when a passivation layer is not sputtered;

[0020] Figure 3 This is a simulation diagram of the electrostatic field of the oppositely facing electrodes provided in the embodiment;

[0021] Figure 4 This is a simulation diagram of the electrostatic field of a conventional front electrode provided in an embodiment. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below through examples and drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Those skilled in the art should understand that the details and forms of the technical solutions of the present invention can be modified or replaced without departing from the structural ideas and scope of use of the present invention, but these modifications and replacements are within the protection scope of the present invention.

[0023] The present invention provides a high withstand voltage silicon carbide photoconductive switch with electrodes facing each other on opposite surfaces, the photoconductive switch comprises a silicon carbide semi-insulating wafer, an input electrode and an output electrode. The input electrode and the output electrode are located at the center of the wafer and are arranged facing each other on opposite surfaces. A plurality of annular grooves with different diameters are arranged around the input electrode and the output electrode, and a passivation layer is arranged on the annular grooves.

[0024] The high withstand voltage silicon carbide photoconductive switch with opposite electrodes provided in this embodiment is specifically Figure 1 As shown, it includes a silicon carbide semi-insulating wafer (101), an input electrode (S1) arranged on the front side of the wafer, and an output electrode (S2) arranged on the back side of the wafer. The input electrode (S1) and the output electrode (S2) are located at the center of the wafer and are arranged opposite to each other on the opposite side planes of the wafer. In addition, a plurality of circular grooves (102) with different diameters are arranged around the input electrode and the output electrode, and a passivation layer (103) is arranged on the circular grooves. A Ni / W film layer (104) and a Ta / Ti / Pd / Au film layer (105) are arranged on the surface of the input electrode (S1) and the output electrode (S2).

[0025] All circular grooves are concentric rings and are set at equal distances. For details, please refer to Figure 2 As shown, the geometric center of the annular groove body (102) and the centers of the input electrode (S1) and the output electrode (S2) are at the same point in the plane, and the ring width and the shortest distance between adjacent concentric rings are both 0.3mm-0.5mm.

[0026] The circular groove of the high-voltage silicon carbide photoconductive switch with opposite electrodes provided in this embodiment is made by laser etching. It should be noted that the laser etching method used here is not the only processing method, and other processing methods, such as wet etching and dry etching, can also complete the processing of the circular groove.

[0027] The high withstand voltage silicon carbide photoconductive switch with opposite electrodes provided in this embodiment has an annular groove size that is optimized based on electric field simulation. The electric field intensity distribution cloud diagram at the cross section can be obtained through electrostatic field simulation. For details, please refer to Figure 3 and Figure 4 As shown, in this group of simulation embodiments, the two peak field strength values ​​of the non-coplanar facing electrode and the conventional front electrode are approximately 12.8 kV / mm and 8.4 kV / mm, respectively. It can be seen that the photoconductive switch provided by the present invention can increase the peak field strength value by 52%;

[0028] The high withstand voltage silicon carbide photoconductive switch with opposite electrodes provided in this embodiment is specifically Figure 1 As shown, the film layers of the input electrode (S1) and the output electrode (S2) are both Ni / W film layers (104) and Ta / Ti / Pd / Au film layers (105). The Ni / W film layer is obtained based on experimental optimization. The film layer thickness varies within a certain range with the annealing temperature and annealing time. The Ni layer thickness is 800-1000, and the W layer thickness is 1500-1800. The specific contact resistivity obtained by this solution is the lowest. At this time, the specific contact resistivity can be reduced to 1×10 -5 Ωcm 2 the following.

[0029] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. The input electrodes and output electrodes in the present invention are not limited to skew-opposite circular electrodes, but can also be expanded to skew-opposite electrodes of other shapes. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A high-voltage silicon carbide photoconductive switch with opposite-plane circular electrodes, characterized in that: The invention comprises a semi-insulating silicon carbide wafer, an input electrode and an output electrode, wherein the input electrode and the output electrode are located in opposite side planes of the wafer. The input electrode is located on the front side of the wafer; The output electrode is located on the back side of the wafer; Circular ring-shaped grooves with different diameters are arranged around the input electrode and the output electrode, and the centers of the circular ring-shaped grooves with different diameters are on the same axis as the centers of the input electrode and the output electrode.

2. The silicon carbide photoconductive switch according to claim 1, characterized in that: The input electrode and the output electrode are circular electrodes with the same diameter, and the center of the input electrode, the center of the output electrode and the center of the wafer are located on the same axis.

3. The silicon carbide photoconductive switch according to claim 1, characterized in that: A passivation layer is arranged on the annular groove body.

4. The silicon carbide photoconductive switch according to claim 1, characterized in that: The annular groove bodies with different diameters have equal ring widths, and adjacent concentric rings are arranged in an equidistant manner.

5. The silicon carbide photoconductive switch according to claim 4, characterized in that: The ring widths of the annular grooves of different diameters are 0.3mm-0.5mm; the equidistant arrangement specifically refers to the shortest distance between adjacent concentric rings being 0.3mm-0.5mm.

6. The silicon carbide photoconductive switch according to claim 1, characterized in that: The dimensions of the annular groove body are calculated by an electric field simulation optimization method.

7. The silicon carbide photoconductive switch according to claim 1, characterized in that: The processing method of the annular groove body includes laser etching, wet etching and dry etching.

8. The silicon carbide photoconductive switch according to claim 1, characterized in that: The surfaces of the input electrode and the output electrode are both provided with metal film layers, specifically including Ni / W film layers and alloy film layers.

9. The silicon carbide photoconductive switch according to claim 8, characterized in that: The alloy film layer is Ta / Ti / Pd / Au, Ta / TiW / Pd / Au, Ta / TiW / Pt / Au, Ti / Pd / Au or TiW / Pt / Au.

10. The silicon carbide photoconductive switch according to claim 9, characterized in that: The Ni film layer in the Ni / W film layer has a thickness of 800Å-1000Å, and the W film layer has a thickness of 1500Å-1800Å.

Images