CN215834534U - Planar electrode type silicon carbide photoconductive semiconductor device based on back light incidence - Google Patents
Planar electrode type silicon carbide photoconductive semiconductor device based on back light incidence Download PDFInfo
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Abstract
The utility model provides a planar electrode type silicon carbide photoconductive semiconductor device based on back light incidence, which comprises a semi-insulating silicon carbide substrate and Al2O3The upper surface of the semi-insulating silicon carbide substrate is provided with two electrode grooves, and a positive electrode and a negative electrode are respectively arranged in the two electrode grooves; the other areas of the upper surface of the semi-insulating silicon carbide substrate except the positive electrode and the negative electrode are provided with a layer of Al2O3A film; the utility model can be triggered by adopting an ultraviolet surface light incidence mode and can be arranged on the light guide halfA current channel is formed in the conductor device, so that the photoelectric conversion efficiency is effectively improved; the embedded ohmic contact electrode is used, so that the voltage resistance of the device is improved; meanwhile, due to the adoption of a thinning process, the size and the on-resistance of the device are further reduced, and the thickness of the device can be ensured to be close to the penetration thickness, so that the concentration of photo-generated carriers during the incidence of back light is effectively improved, and the practical application of the photoconductive semiconductor device in a subnanosecond electromagnetic pulse generation system is realized.
Description
Technical Field
The present invention relates to a photoconductive semiconductor device, and more particularly, to a planar electrode type silicon carbide photoconductive semiconductor device based on back light incidence.
Background
Photoconductive semiconductor devices are important components of the field of electromagnetic pulse generation technology and can be used to generate high power ultrashort pulses. Photoconductive semiconductor devices have a number of outstanding advantages, such as fast turn-on times, high synchronization accuracy, low time jitter, low turn-on inductance, etc. Due to the unique advantages, the photoconductive semiconductor device is widely applied to the research fields of pulse power such as a solid compact pulse power source, a high-power ultra-wideband microwave radiation source, a dielectric wall accelerator, a trigger system of a large pulse power device, terahertz radiation and the like. With the further development of science and technology, people put higher and higher requirements on performance indexes of the optical semiconductor device, such as response speed, volume weight, working precision, power capacity, on-resistance and the like.
At present, the adoption of wide-bandgap photoconductive semiconductors to generate radio frequency and electromagnetic microwaves with adjustable parameters is a brand new technology and has important application prospects. In practical applications, a photoconductive semiconductor device made of silicon carbide material has many excellent characteristics, such as wide bandgap, high critical breakdown electric field, high carrier mobility, high electron saturation drift velocity, high thermal conductivity, and the like, and related research work is increasing day by day. Typically, a photoconductive semiconductor device is composed of a pair of electrodes and a photoconductive wafer substrate. A bias voltage is applied to the electrodes, and incident light irradiates the wafer substrate to generate photoconductive current between the two electrodes. The photoconductive semiconductor device can be classified into a coplanar type and a non-coplanar type according to the electrode position. For the non-coplanar electrode structure, the electrodes are respectively positioned on two planes of the wafer, the voltage resistance is better, but the triggering light incidence direction is parallel to the carrier movement direction, and the device is influenced by stray electric parameters, so that the higher response speed is difficult to achieve. The coplanar electrode structure has the advantages that the electrodes are positioned on the same surface of the wafer, the manufacturing is simple, the incident direction of the trigger light is vertical to the moving direction of the current carrier, and the response speed is high. However, since the electrodes are on the same surface of the wafer, local strong current on the surface is easily formed, which causes surface breakdown, and the insulation strength is low, so that it is difficult to achieve a high power capacity of the device.
There is a related research introducing a planar electrode structure based on back light incidence, and related results show that the structure can effectively improve the voltage endurance of a planar electrode type photoconductive device. Meanwhile, in order to further improve the photoelectric conversion efficiency, intrinsic light (h v is more than or equal to Eg) is adopted for optical triggering, 355nm ultraviolet laser is taken as an example (h v is 3.493eV, third harmonic oscillation Nd-YAG laser), the penetration depth is 47 microns, and new requirements are provided for the structure, the thickness and the preparation method of the photoconductive semiconductor device.
Disclosure of Invention
The utility model provides a planar electrode type silicon carbide photoconductive semiconductor device based on back light incidence, aiming at solving the problem that a planar electrode structure based on back light incidence is lacked in the prior art, improving photoelectric conversion efficiency and device voltage endurance capability, further reducing device size and on-resistance, and realizing practical application of the photoconductive semiconductor device in a subnanosecond electromagnetic pulse generation system.
The utility model provides a planar electrode type silicon carbide photoconductive semiconductor device based on back light incidence, which comprises: semi-insulating silicon carbide substrate, Al2O3A film and a pair of ohmic contact electrodesComprises a positive electrode and a negative electrode; the upper surface of the semi-insulating silicon carbide substrate is provided with two electrode grooves, and a positive electrode and a negative electrode are respectively arranged in the two electrode grooves; the other areas of the upper surface of the semi-insulating silicon carbide substrate except the positive electrode and the negative electrode are provided with a layer of Al2O3A film; the positive electrode and the negative electrode are both Ni/Ti/Au three-layer metal electrodes, and the Ni, Ti and Au three-layer metal layers are arranged from bottom to top.
The thickness of the semi-insulating silicon carbide substrate is 50-60 mu m, and Al2O3The thickness of the film is 50-60 nm.
The depth of the two electrode grooves is 50-60nm respectively.
In the three-layer metal electrode of Ni/Ti/Au, the thicknesses of the three-layer metal electrode layers of Ni, Ti and Au are respectively 120nm, 30nm and 100 nm.
The utility model has the beneficial effects that:
the planar electrode type silicon carbide photoconductive semiconductor device based on back light incidence can be triggered by adopting an ultraviolet light (lambda is 355nm) back light incidence mode, and a current channel can be formed in the photoconductive semiconductor device, so that the surface current between planar electrodes is reduced, and the photoelectric conversion efficiency is effectively improved; the embedded ohmic contact electrode is used, so that the phenomenon that the breakdown occurs in advance due to overlarge local electric field caused by accumulation of current carriers at the electrode can be avoided, and the voltage resistance of the device is improved; meanwhile, due to the adoption of a thinning process, the size and the on-resistance of the device are further reduced, and the thickness of the device can be ensured to be close to the penetration thickness, so that the concentration of photo-generated carriers during the incidence of back light is effectively improved, and the practical application of the photoconductive semiconductor device in a subnanosecond electromagnetic pulse generation system is realized.
Drawings
FIG. 1 is a schematic cross-sectional view of a photoconductive semiconductor device according to the present invention;
FIG. 2 is a schematic top view of a photoconductive semiconductor device in accordance with the present invention;
FIG. 3 is a schematic flow chart of the main manufacturing process of the photoconductive semiconductor device according to the present invention;
FIG. 4 is a schematic view of the surface electric field distribution of the photoconductive semiconductor device of the present invention;
fig. 5 is a schematic view of the internal current density distribution of the photoconductive semiconductor device of the present invention.
1. Semi-insulating silicon carbide substrate 2, Al2O3Membrane 3, ohmic contact electrode 4, positive electrode 5, negative electrode.
Detailed Description
As shown in FIG. 1, the planar electrode type silicon carbide photoconductive semiconductor device based on back light incidence comprises a semi-insulating silicon carbide substrate 1, Al2O3A membrane 2 and a pair of ohmic contact electrodes 3, said pair of ohmic contact electrodes 3 comprising a positive electrode 4 and a negative electrode 5; the upper surface of the semi-insulating silicon carbide substrate 1 is provided with two electrode grooves, and a positive electrode 4 and a negative electrode 5 are respectively arranged in the two electrode grooves; the upper surface of the semi-insulating silicon carbide substrate 1 is provided with a layer of Al in the regions except the positive electrode 4 and the negative electrode 52O3A membrane 2; the positive electrode 4 and the negative electrode 5 are both Ni/Ti/Au three-layer metal electrodes, and the Ni, Ti and Au three-layer metal layers are arranged from bottom to top.
The thickness of the semi-insulating silicon carbide substrate 1 is 50 mu m, and Al2O3The thickness of the film 2 was 50 nm.
As shown in fig. 2, the transverse width and the longitudinal width of each electrode groove are both l mm and w mm, the edge angles are both 1/4 circular arcs, the radius of the circular arc is R mm, the depth is 50nm, and the distance between the two electrode grooves is d mm; the shapes of the two ohmic contact electrodes 3 are the same as those of the electrode grooves, and the thicknesses of the three metal electrode layers of Ni, Ti and Au are respectively 120nm, 30nm and 100 nm.
The utility model provides a planar electrode type silicon carbide photoconductive semiconductor device based on back light incidence, which is prepared by the following method:
(1) cleaning:
cleaning a semi-insulating silicon carbide substrate wafer with the thickness of 500 mu m, and further cleaning the surface of the wafer by using plasma gas by using a BRANSON S4100 plasma degumming machine; the semi-insulating silicon carbide substrate is obtained by doping vanadium in a high-purity silicon carbide material, and vanadium atoms can be used as donor atoms and acceptor atoms in the semi-insulating silicon carbide substrate;
(2) film coating:
plating a layer of Al with the thickness of 50nm on the surface of the cleaned wafer by using Plasma Enhanced Atomic Layer Deposition (PEALD) equipment and adopting a magnetron sputtering method2O3Coating at 300 ℃ for 3 h; to improve the voltage endurance of the planar device, as shown in fig. 3 (a);
(3) glue homogenizing:
firstly, spraying HDMS particles on the surface of a wafer coating to enhance the adhesiveness of the photoresist, and baking the wafer coating at 120 ℃ for 13 min and 5 sec; then ROL-7133 photoresist (negative photoresist) is used for spin coating, after static photoresist dripping, the photoresist is rotated for 10 seconds at 600rpm, and then rotated for 30 seconds at 2000 rpm; finally, prebaking for 2 minutes and 30 seconds at 110 ℃ to obtain a photoresist layer;
(4) photoetching:
after the wafer is cooled to room temperature, photoetching the photoresist layer on the surface of the wafer by using a metal layer photoetching plate by using a figure semiconductor MA6 photoetching machine for 6 seconds, then baking for 3 minutes at 110 ℃, developing for 1 minute by using 3038 developing solution, washing and drying, and finally hardening for 4 minutes at 120 ℃, wherein a plurality of groove window areas obtained by photoetching the photoresist layer on the surface of the wafer are electrode patterns to be made into metal electrodes, as shown in figure 3 (b);
(5) etching:
after the wafer is cooled to room temperature, etching the obtained electrode pattern by using an ICP-180 plasma etching machine, and etching Al at first2O3Film, dry etching with Cl-Ar based gas for 7 min 30 sec, etching down Al2O3Film 50 nm; then etching the semi-insulating silicon carbide substrate wafer, performing dry etching for 2 minutes and 50 seconds by using Cl-Ar-based gas, and etching the semi-insulating silicon carbide substrate downwards to a depth of 50nm, so as to obtain a plurality of grooves with a depth of 50nm on the surface of the wafer, namely a region of the planar metal electrode, as shown in fig. 3 (c);
(6) plating metal electrodes:
after the wafer is cooled to room temperature, sequentially plating three metal layers of Ni, Ti and Au on the groove by adopting a magnetron sputtering method, wherein the thicknesses of the three metal layers are respectively 120nm, 30nm and 100nm, as shown in a figure 3 (d);
(7) stripping:
firstly, soaking the wafer for more than 30 minutes by using acetone, then soaking and ultrasonically stripping for 15 minutes by using the acetone, replacing the acetone after ultrasonically stripping, soaking and ultrasonically cleaning for 15 minutes again, finally washing and drying, cleaning and stripping the metal layers in other areas except the metal electrode area, and finally forming a Ni/Ti/Au metal electrode in the metal electrode area, as shown in a figure 3 (e);
(8) scribing:
adhering a wafer to a blue film, and carrying out scribing treatment to obtain single discrete light guide semiconductor devices, wherein each light guide semiconductor device comprises two Ni/Ti/Au metal electrodes to form a pair of ohmic contact multilayer electrodes;
(9) thinning:
the single discrete photoconductive semiconductor device was thinned from 500 μm to 50 μm from the electrode back side silicon carbide substrate, and subjected to polishing treatment, completing the fabrication of the planar electrode type silicon carbide photoconductive semiconductor device based on back side light incidence, as shown in fig. 3 (f).
When incident light enters from the back of the plane electrode type silicon carbide photoconductive semiconductor device, a large number of photon-generated carriers are generated in the semi-insulating silicon carbide substrate 1, a pair of ohmic contact electrodes 3 embedded in the two electrode grooves can collect a large number of generated photon-generated carriers, so that current is formed between the pair of ohmic contact electrodes 3, and the device can be conducted within the action time of light pulse. The electric field distribution of the photoconductive device at turn-on is shown in fig. 4, and the current distribution inside the device is shown in fig. 5.
Claims (4)
1. A planar electrode type silicon carbide photoconductive semiconductor device based on back light incidence, characterized in that: comprises a semi-insulating silicon carbide substrate and Al2O3A membrane and a pair of ohmic contact electrodes including a positive electrode and a negative electrode; the upper surface of the semi-insulating silicon carbide substrate is provided with two electrode grooves, and a positive electrode and a negative electrode are respectively arranged in the two electrode grooves; semi-insulating silicon carbide substrateThe upper surface of the anode is provided with a layer of Al except for the positive electrode and the negative electrode2O3A film; the positive electrode and the negative electrode are both Ni/Ti/Au three-layer metal electrodes, and the Ni, Ti and Au three-layer metal layers are arranged from bottom to top.
2. A planar electrode type silicon carbide photoconductive semiconductor device based on back surface light incidence according to claim 1, characterized in that: the thickness of the semi-insulating silicon carbide substrate is 50-60 mu m, and Al2O3The thickness of the film is 50-60 nm.
3. A planar electrode type silicon carbide photoconductive semiconductor device based on back surface light incidence according to claim 1, characterized in that: the depth of the two electrode grooves is 50-60nm respectively.
4. A planar electrode type silicon carbide photoconductive semiconductor device based on back surface light incidence according to claim 1, characterized in that: in the three-layer metal electrode of Ni/Ti/Au, the thicknesses of the three-layer metal electrode layers of Ni, Ti and Au are respectively 120nm, 30nm and 100 nm.
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| CN202122270027.0U CN215834534U (en) | 2021-09-18 | 2021-09-18 | Planar electrode type silicon carbide photoconductive semiconductor device based on back light incidence |
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| CN202122270027.0U CN215834534U (en) | 2021-09-18 | 2021-09-18 | Planar electrode type silicon carbide photoconductive semiconductor device based on back light incidence |
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